東北大学研究者紹介

顔写真

フジワラ　タクミ

藤原　巧

Takumi Fujiwara

所属

大学院工学研究科　応用物理学専攻　応用物性物理学講座（光物性学分野）

職名

教授

学位

工学博士（筑波大学）
工学修士（筑波大学）

researchmap

https://researchmap.jp/read0210514

J-GLOBAL ID

200901005521548916

学歴 4

筑波大学　理工学研究科　物理工学

～ 1984年
筑波大学

～ 1984年
筑波大学

～ 1982年
筑波大学　第三学群　基礎工学類物理工学専攻

～ 1982年

委員歴 36

日本セラミックス協会・ガラス部会　事務局長

2012年4月～継続中
日本セラミックス協会・ガラス部会　事務局長

2012年4月～継続中
応用物理学会・ランダム系フォトエレクトロニクス研究会　委員長

2010年4月～継続中
日本セラミックス協会・フォトニクス分科会　幹事長

2010年4月～継続中
応用物理学会・ランダム系フォトエレクトロニクス研究会　委員長

2010年4月～継続中
日本セラミックス協会・フォトニクス分科会　幹事長

2010年4月～継続中
ニューガラスフォーラム　特別会員

2009年4月～継続中
ニューガラスフォーラム　特別会員

2009年4月～継続中
応用物理学会・プログラム委員会　講演分科会世話人

2008年4月～継続中
応用物理学会・プログラム委員会　講演分科会世話人

2008年4月～継続中
応用物理学会・東北支部　役員

2006年4月～継続中
応用物理学会・東北支部　役員

2006年4月～継続中
日本セラミックス協会・フォトニクス分科会　幹事

1998年4月～継続中
日本セラミックス協会・フォトニクス分科会　幹事

1998年4月～継続中
（社）ニューガラスフォーラム・評価技術研究会　主査

2011年4月～ 2012年3月
（社）ニューガラスフォーラム・評価技術研究会　主査

2011年4月～ 2012年3月
日本セラミックス協会・ガラス部会　副事務局長

2010年4月～ 2012年3月
日本セラミックス協会・ガラス部会　副事務局長

2010年4月～ 2012年3月
京都大学化学研究所　客員教授

2010年4月～ 2011年3月
神戸大学　非常勤講師

2010年4月～ 2011年3月
京都大学化学研究所　客員教授

2010年4月～ 2011年3月
神戸大学　非常勤講師

2010年4月～ 2011年3月
応用物理学会・会誌編集委員会　編集委員

2008年4月～ 2010年3月
応用物理学会・会誌編集委員会　編集委員

2008年4月～ 2010年3月
応用物理学会・ランダム系フォトエレクトロニクス研究会　副委員長

2003年4月～ 2010年3月
応用物理学会・ランダム系フォトエレクトロニクス研究会　副委員長

2003年4月～ 2010年3月
応用物理学会・教育公益事業委員会　委員

2008年4月～ 2009年3月
応用物理学会・教育公益事業委員会　委員

2008年4月～ 2009年3月
日本セラミックス協会・学術論文誌編集委員会　編集委員

2005年4月～ 2008年3月
日本セラミックス協会・学術論文誌編集委員会　編集委員

2005年4月～ 2008年3月
日本光学会　幹事

2004年4月～ 2006年3月
日本光学会　幹事

2004年4月～ 2006年3月
レーザー学会　先端光学材料専門委員

2000年9月～ 2002年3月
レーザー学会　先端光学材料専門委員

2000年9月～ 2002年3月
日本光学会　幹事

1999年4月～ 2001年3月
日本光学会　幹事

1999年4月～ 2001年3月

︎全件表示 ︎最初の5件までを表示

所属学協会 3

日本物理学会
日本セラミックス協会
応用物理学会

研究キーワード 5

応用光学・量了光工学
Semiconductor and Dielectrics)
固体物性I(光物体・半導体・誘電体)
Solid-State Physics I (Optical Properties
Applied Optics and Quantum Optics

研究分野 3

ナノテク・材料 / 光工学、光量子科学 /
自然科学一般 / 半導体、光物性、原子物理 /
ナノテク・材料 / 無機材料、物性 /

受賞 10

The Best Presentation Award

2015年10月　11th International Symposiumon Crystallization in Glasses and Liquids
第38回（2015年春季）応用物理学会講演奨励賞

2015年9月13日　応用物理学会
第28回秋季シンポジウム講演奨励賞

2015年9月　日本セラミックス協会
The Stevanato Award for the best poster presentation with 1,000 Euros

2015年9月　ICG
第35回（2013年秋季）応用物理学会講演奨励賞

2013年11月19日　応用物理学会
第32回（2012年春季）応用物理学会講演奨励賞

2012年9月11日　応用物理学会
第33回（2011年度）応用物理学会論文賞（奨励賞）

2011年7月11日　応用物理学会
日本セラミックス協会学術写真賞優秀賞

2010年3月23日　日本セラミックス協会
日本セラミックス協会賞（学術賞）

2010年2月1日　社団法人日本セラミックス協会　光非線形ガラス材料の開発と光制御デバイスへの応用
日本セラミックス協会学術論文誌JCerSJ優秀論文賞

2003年5月　日本セラミックス協会

︎全件表示 ︎最初の5件までを表示

論文 224

Nonconventional Li2O–SrO–Al2O3 glass preparable through melt-quenching: A preliminary study

Yuta Hayashibara, Yudai Yokochi, Yoshihiro Takahashi, Nobuaki Terakado, Takumi Fujiwara

Journal of the Ceramic Society of Japan　2024年
出版者・発行元：Ceramic Society of Japan
DOI： 10.2109/jcersj2.24008 　

ISSN：1882-0743

eISSN：1348-6535
Diversely phased glass-ceramics in Bi2O3–SiO2 system for heterostructure formation: A demonstration via visible-light-sensitive photocatalytic reaction

OhHyeok Kwon, Yoshihiro Takahashi, Nobuaki Terakado, Takamichi Miyazaki, Takumi Fujiwara

Ceramics International　2024年1月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.ceramint.2024.01.188 　

ISSN：0272-8842
Optical modulation in nonlinear-optical glass-ceramic fiber driven by Pockels effect

Takuma Nakamura, Yoshihiro Takahashi, Nobuaki Terakado, Takamichi Miyazaki, Takumi Fujiwara

Journal of the Ceramic Society of Japan　132　(1)　11-15　2024年1月1日
出版者・発行元：Ceramic Society of Japan
DOI： 10.2109/jcersj2.23139 　

ISSN：1882-0743

eISSN：1348-6535
Silicate glass-ceramic fibers with nonlinear optical crystals: Evaluation of propagation loss and comparison to optical materials

Takuma Nakamura, Yoshihiro Takahashi, Nobuaki Terakado, Takamichi Miyazaki, Takumi Fujiwara

Ceramics International　2023年6月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.ceramint.2023.06.217 　

ISSN：0272-8842
Nanosheet fabrication from magnon thermal conductivity cuprates for the advanced thermal management

Hiroya Kinoshita, Nobuaki Terakado, Yoshihiro Takahashi, Takamichi Miyazaki, Chitose Ishikawa, Koki Naruse, Takayuki Kawamata, Takumi Fujiwara

npj 2D Materials and Applications　6　(1)　2022年10月13日
出版者・発行元：Springer Science and Business Media LLC
DOI： 10.1038/s41699-022-00344-2 　

eISSN：2397-7132

詳細を見る詳細を閉じる

Abstract Spin-chain–spin-ladder cuprates, such as La5Ca9Cu24O41, have notable electronic and thermal properties because of their unique electron spin arrangement. Among them, magnon thermal conductivity, which originates from the excitation of paired electron spins, is promising for the advanced thermal management applications that enable dynamic control of heat flow. This is because of its high, anisotropic thermal conductivity at room temperature and its dynamic controllability. In this study, we report nanosheet fabrications from polycrystalline La5Ca9Cu24O41 to enhance the control width. We obtained that the nanosheets with a thickness of about 3 nm are obtained via immersion of the polycrystals in a NaOH aqueous solution. We propose the exfoliation model based on the chemical reaction between the (La/Ca)2Cu2O3 subsystem and NaOH solution. The nanosheet fabrications can also lead to new research development on spin-ladder system and other strongly correlated cuprates.
Potential of afterglow zirconia as a sensitive biological temperature probe

Aoni Sato, Yoshihiro Takahashi, Nobuaki Terakado, Takamichi Miyazaki, Noriko Onoue, Tsuyoshi Shinozaki, Takumi Fujiwara

Ceramics International　48　(17)　25587-25591　2022年9月1日

DOI： 10.1016/j.ceramint.2022.05.238 　

ISSN：0272-8842

詳細を見る詳細を閉じる

Noninvasive and site-selective temperature sensing is required in biology and advanced medicine. Recently, we proposed a new concept for temperature sensing, which is based on afterglow and optically-stimulated luminescence [Sci. Rep. 10, 2242 (2020)]. Here we assessed the thermal sensitivity of afterglow zirconia and clarified the potential of this material as probe phosphor by thermoluminescence measurements. The evaluated sensitivity value of the zirconia was 10 %/K, which was higher than typical materials used in luminescent thermometers. Therefore, the prepared zirconia is a great candidate as a harmless and biocompatible sensing probe.
Face-on orientation of spin ladders in La5Ca9Cu24O41 films deposited by radio-frequency magnetron sputtering on heated SiO2 and Si substrates

Shota Watanabe, Nobuaki Terakado, Yoshihiro Takahashi, Takamichi Miyazaki, Koki Naruse, Takayuki Kawamata, Takumi Fujiwara

Applied Surface Science　154444-154444　2022年8月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.apsusc.2022.154444 　

ISSN：0169-4332
Repetitive afterglow in zirconia by pulsed near-infrared irradiation toward biological temperature sensing. 国際誌

Masaharu Ohashi, Yoshihiro Takahashi, Nobuaki Terakado, Noriko Onoue, Tsuyoshi Shinozaki, Takumi Fujiwara

Scientific reports　12　(1)　8587-8587　2022年5月21日

DOI： 10.1038/s41598-022-12585-8 　

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Photoluminescence provides information about the surrounding environment. In this study, aiming to develop a non-invasive deep body-temperature sensing method, we investigated photoluminescence properties of afterglow zirconia (ZrO2) by pulsed near-infrared (NIR) light irradiation based on the biological temperature. Pulsed light irradiation produced optically stimulated luminescence, followed by afterglow, with the property of repeating 100 times or more. Furthermore, the basic principle of temperature measurement was demonstrated through afterglow decay curve measurements. The use of harmless ZrO2 as a sensing probe and NIR light, which is relatively permeable to living tissues, is expected to realize temperature measurements in the brain and may also facilitate optogenetic treatment.
Dynamic control of heat flow using a spin-chain ladder cuprate film and an ionic liquid

Nobuaki Terakado, Yoshinori Nara, Yuki Machida, Yoshihiro Takahashi, Takumi Fujiwara

Scientific Reports　10　(1)　2020年12月
出版者・発行元：Springer Science and Business Media LLC
DOI： 10.1038/s41598-020-70835-z 　

eISSN：2045-2322
Nanostructure and photocatalytic behavior of glass-ceramics in Bi2O3–Nb2O5–Li2O–B2O3–SiO2 system

OhHyeok KWON, Yoshihiro TAKAHASHI, Takamichi MIYAZAKI, Nobuaki TERAKADO, Takumi FUJIWARA

Journal of the Ceramic Society of Japan　128　(10)　839-842　2020年10月1日
出版者・発行元：Ceramic Society of Japan
DOI： 10.2109/jcersj2.20125 　

ISSN：1882-0743

eISSN：1348-6535
Fresnoite-type Ba2TiGe2O8 glass-ceramics toward electro-optic device: Crystallization structure and Pockels effect 査読有り

Haruki Okamoto, Yoshihiro Takahashi, Takuma Nakamura, Nobuaki Terakado, Takamichi Miyazaki, Takumi Fujiwara

Journal of the European Ceramic Society　2020年6月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.jeurceramsoc.2020.06.054 　

ISSN：0955-2219
Transparent glass-ceramics for thermal management application: achievement of optical transparency and high thermal conductivity 査読有り

Nobuaki Terakado, Toshikazu Yoshimine, Ryusei Kozawa, Yoshihiro Takahashi, Takumi Fujiwara

RSC Advances　10　(38)　22352-22360　2020年6月
出版者・発行元：Royal Society of Chemistry (RSC)
DOI： 10.1039/d0ra03026k 　

eISSN：2046-2069

詳細を見る詳細を閉じる

Oxide glass is an industrial material with advantages such as optical transparency and shaping ability of the melt, but at the same time, it is a bad conductor of heat due to its disordered structures.
Temperature dependence of afterglow in zirconia and its optically-stimulated luminescence by bone-through irradiation for biological temperature probe. 国際誌査読有り

Masaharu Ohashi, Yoshihiro Takahashi, Nobuaki Terakado, Noriko Onoue, Tsuyoshi Shinozaki, Takumi Fujiwara

Scientific Reports　10　(1)　2242-2242　2020年2月10日

DOI： 10.1038/s41598-020-58979-4 　

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Development of minimally invasive and site-selective biological temperature sensing is quite important in medical field. This study presents a novel temperature sensing technique based on afterglow and optically-stimulated luminescence (OSL). The dependence of afterglow photoluminescent intensity on the environmental temperature of zirconia (ZrO2) phosphor is examined to validate its use as a sensing probe. In addition, assuming the measurement in deep-part of human body, we have applied the information gathered from our validation to observe OSL from the ZrO2 by irradiation with near-infrared laser through a bone sample. This study demonstrates an alternative medical application of phosphor, and introduces an elemental-technology for the temperature sensing.
Fabrication of VO2-Dispersed Glass in B2O3-P2O5-V2O5 System and Its Thermal Property 査読有り

Kei Muramoto, Yoshihiro Takahashi, Nobuaki Terakado, Yoshiki Yamazaki, Shigeru Suzuki, Takumi Fujiwara

FRONTIERS IN MATERIALS　7　2020年2月
出版者・発行元：FRONTIERS MEDIA SA
DOI： 10.3389/fmats.2020.00005 　

ISSN：2296-8016

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Phase change material (PCM), which enables heat storage based on phase transition, plays an important role for efficient energy utilization. This paper briefly describes our recent study about all-solid PCM by combination of vanadium dioxide (VO2) with latent heat storage capacity and multicomponent glass, i.e., VO2-dispersed glass. A B2O3-P2O5-V2O5 glass system is used as a matrix for the VO2-dispersed glass. An attempt to describe its latent heat storage function is given. Endothermic behavior due to structural phase transition of the VO2 crystals was observed in the VO2-dispersed sample, and the transition enthalpy corresponding to latent heat storage capacity was estimated to be Delta H similar to 9.5 J/g. The value of the studied sample was larger than the value of dispersed glass in the BaO-TeO2-V2O5 system that was previously reported. Potential for PCM was considered in the studied sample.
A novel method for stress evaluation in chemically strengthened glass based on micro-Raman spectroscopy 査読有り

Nobuaki Terakado, Ryusei Sasaki, Yoshihiro Takahashi, Takumi Fujiwara, Shuji Orihara, Yoshio Orihara

COMMUNICATIONS PHYSICS　3　(1)　2020年2月
出版者・発行元：NATURE PUBLISHING GROUP
DOI： 10.1038/s42005-020-0305-7 　

ISSN：2399-3650

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Chemically strengthened glass is widely used for screen protection in mobile devices, and its strengthening processes and application fields have rapidly diversified. The origin of the strength is residual compressive stress induced by ion exchange, and the stress evaluation has been performed via the photoelastic effect. However, for a deep understanding of the nature of the strength and development of stronger glasses, we need a method directly connected to atomic-scale glass structures. Here, we propose a method based on the "stuffing" effect, where we can determine the residual stress non-contactively and non-destructively with a high spatial resolution using Boson, D-1, D-2, and A(1) peaks in micro-Raman spectra. Finally, we show a plausible depth dependence of the residual stress.The strength of glass can be increased post-production by treatment with chemical processes, and such materials are used in everyday devices such as mobile phones. Here, the authors report a non-invasive method based on micro-Raman spectroscopy to analyse the compressive stress responsible for the increased strength of the treated glass.
Photoluminescence and afterglow in samarium-doped zirconia toward biological temperature sensor 査読有り

Satoshi Goto, Yoshihiro Takahashi, Nobuaki Terakado, Yasushi Nakajima, Noriko Onoue, Tsuyoshi Shinozaki, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　127　(10)　696-699　2019年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.19082 　

ISSN：1882-0743

eISSN：1348-6535

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This study describes the investigation of photoluminescence (PL) and afterglow properties of samarium ion (Sm3+)-doped zirconia and the comparison with those of pure zirconia. The pure sample exhibits bluish PL and afterglow upon excitation by ultraviolet light, whereas white-to-reddish PL and white afterglow are detected by means of visual observation and spectroscopic measurement in the doped samples. It is therefore suggested that the Sm3+-doped zirconia is applicable to a temperature-sensing probe for the human body because it shows afterglow PL in the near-infrared "biological window" region. (C) 2019 The Ceramic Society of Japan. All rights reserved.
Journal of the Ceramic Society of Japan The 57th Symposium on Basic Science of Ceramics Preface 査読有り

Nanba Tokuro, Nakajima Akira, Kakihana Masato, Fuji Masayoshi, Shimizu Youichi, Kirihara Soshu, Fujiwara Takumi

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　127　(10)　2019年10月
出版者・発行元：None
DOI： 10.2109/jcersj2.127.P10-1 　

ISSN：1882-0743

eISSN：1348-6535
Improvement of Pockels effect by crystallization-process control in nonlinear-optical glass-ceramics 査読有り

Tomoki Otsuki, Yoshihiro Takahashi, Nobuaki Terakado, Takumi Fujiwara

CERAMICS INTERNATIONAL　45　(13)　16713-16716　2019年9月
出版者・発行元：ELSEVIER SCI LTD
DOI： 10.1016/j.ceramint.2019.05.170 　

ISSN：0272-8842

eISSN：1873-3956

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We have fabricated perfectly-surface-crystallized glass-ceramics (PSC-GCs) consisting of polar frenoite-type Sr2TiSi2O8 by different crystallization-process conditions, i.e., isothermal treatment at 880 degrees C for 72 h and 960 degrees C for 1 h, and have examined their Pockets effect in this study. The PSC-GCs obtained by the lower-temperature process exhibited the Pockels coefficients, i.e., r(13) similar to 3.0 pm/V and r(33) similar to 2.4 pm/V, and the coefficients exceeded the reported values of the PSC-GCs with Sr2TiSi2O8 phase. The improvement of Pockels effect is attributed to the higher crystal-orientation, which is provided by the lower-temperature condition.
Crystallization of nanostructured ZrO2 phase in borosilicate glass: Impact of Al2O3 on tetragonal-to-monoclinic phase transformation 査読有り

Yasuhiro Nobuta, Yoshihiro Takahashi, Takamichi Miyazaki, Nobuaki Terakado, Noriko Onoue, Tsuyoshi Shinozaki, Takumi Fujiwara

JOURNAL OF NON-CRYSTALLINE SOLIDS　501　49-54　2018年12月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.jnoncrysol.2017.12.052 　

ISSN：0022-3093

eISSN：1873-4812

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Recently, we have developed the borosilicate glass, in which ZrO2 phase is singly crystallizable, and has found an emissive monoclinic ZrO2 dendrites in the resulting GCs. In order to promote the formation of monoclinic phase, we have examined the effect of substitution of alumina Al2O3 for ZrO2 in the precursor glass composition, i.e., 15Na(2)O-(15 - x)ZrO2-xAl(2)O(3)-30B(2)O(3)-40SiO(2). It was found that the substitution of small amount of Al2O3 (x = 1) gave a positive effect, i.e., increase in the amount of monoclinic phase and decrease in the crystal size. Furthermore, the substitution improved the internal quantum-yield. On the other hand, the further substitution (x >= 2) provided the decrease in amount of the monoclinic phase.
Contribution of spinons to thermal properties of glass-ceramics containing spin-chain compound SrCuO2 査読有り

Nobuaki Terakado, Yuudai Yokochi, Kouki Watanabe, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　126　(12)　1019-1021　2018年12月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.18116 　

ISSN：1882-0743

eISSN：1348-6535

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Materials with high thermal conductivity have attracted considerable attention for thermal management of electronic devices. Therefore, focusing on formability and anisotropic heat transfer, we fabricated glass-ceramics containing the spin-chain compound SrCuO2 and demonstrated its high thermal conductivity in the previous work, where SrCuO2 is known to exhibit high thermal conductivity owing to the presence of quasiparticles, i.e., spinons. In this study, we attempt to confirm the presence of spinons by analyzing temperature dependence of specific heat and investigate relationship between spinons and thermal properties. (C) 2018 The Ceramic Society of Japan. All rights reserved.
Attempt to fabricate a high thermal conductivity, transparent oxide glass by dispersing MgO crystals and refractive index matching 査読有り

Nobuaki Terakado, Ryusei Kozawa, Toshikazu Yoshimine, Yoshihiro Takahashi, Takumi Fujiwara

AIP ADVANCES　8　(11)　2018年11月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.5054339 　

ISSN：2158-3226

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Oxide glasses generally have low thermal conductivity due to their disordered structures. Here, a fabrication method to provide them with high thermal conductivity while retaining their optical transparency is proposed. It consists of dispersing similar to 20 mu m MgO crystals in a glass matrix and matching their refractive indexes to prevent the decrease of the oxide glass optical transparency due to light scattering. The dispersion of the MgO crystals increased the thermal conductivity of the original glass by similar to 50% and the new glass still exhibited optical transparency. Such MgO-dispersed glass could be successfully used in thermal management applications requiring both transparency and formability. (C) 2018 Author(s).
Prominent long-lasting photoluminescence in defect-activated zirconia: A rare-earth free and accessible phosphor 査読有り

Kenichiro Iwasaki, Yoshihiro Takahashi, Nobuaki Terakado, Noriko Onoue, Tsuyoshi Shinozaki, Takumi Fujiwara

CERAMICS INTERNATIONAL　44　(11)　12929-12933　2018年8月
出版者・発行元：ELSEVIER SCI LTD
DOI： 10.1016/j.ceramint.2018.04.105 　

ISSN：0272-8842

eISSN：1873-3956

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We investigated the long-lasting photoluminescence (LLP) properties in a commercial zirconia powder with a monoclinic system after thermal treatment at different temperatures. Clear-blue photoluminescence and LLP were observed in the zirconia without emissive dopants subjected to thermal treatment at 1400 degrees C. Decay curve measurements revealed a pronounced, visually observable bluish LLP that lasted for similar to 10 h at moderate temperature. Based on spectroscopic observation and electron spin resonance results, a possible origin of the LLP is discussed.
VO2-dispersed glass: A new class of phase change material 査読有り

Kei Muramoto, Yoshihiro Takahashi, Nobuaki Terakado, Yoshiki Yamazaki, Shigeru Suzuki, Takumi Fujiwara

SCIENTIFIC REPORTS　8　2018年2月
出版者・発行元：NATURE PUBLISHING GROUP
DOI： 10.1038/s41598-018-20519-6 　

ISSN：2045-2322

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Energy storage technology is crucial for a sustainable society, and its realisation strongly depends on the development of materials. Oxide glass exhibits high durability. Moreover, the amorphous structure of the glass without periodic ordering demonstrates excellent formability and controllability, thus enabling a large-scale production. These factors provide impetus for the development of new materials for thermal management applications. As vanadium dioxide (VO2) with a strongly correlated electron system exhibits a structural phase transition, leading to a large heat of transition. Therefore, VO2 demonstrates immense potential as a phase change material (PCM). This study reports the fabrication of VO2-dispersed glass and examines its potential as a new latent heat storage material, which can be applied for massive PCM heat storage applications.
CO2 laser-induced weakening in chemically strengthened glass: Improvement in processability and its visualization by Raman mapping 査読有り

Nobuaki Terakado, Shohei Uchida, Ryusei Sasaki, Yoshihiro Takahashi, Takumi Fujiwara

CERAMICS INTERNATIONAL　44　(3)　2843-2846　2018年2月
出版者・発行元：ELSEVIER SCI LTD
DOI： 10.1016/j.ceramint.2017.11.030 　

ISSN：0272-8842

eISSN：1873-3956

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Chemically strengthened glass has become essential in our daily lives and the demand is rapidly increasing in a variety of fields. However, the conventional cutting process is not applicable because of its tough layer with the compressive stress. To achieve higher-throughput production of the glass, we report spatially selective weakening of the compression layer by CO2 laser scanning and provide its visualization by Raman mapping. We demonstrate cutting the scanned glass without shattering using a typical scribing wheel. Finally, we discuss the improvement in processability from the viewpoint of microscopic structures by means of thermal analysis and Raman spectroscopy.
Variation in Pockels constants of silicate glass-ceramics prepared by perfect surface crystallization 査読有り

Kazuya Takano, Yoshihiro Takahashi, Takamichi Miyazaki, Nobuaki Terakado, Takumi Fujiwara

APPLIED PHYSICS LETTERS　112　(2)　2018年1月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.5017671 　

ISSN：0003-6951

eISSN：1077-3118

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We investigated the Pockels effect in polycrystalline materials consisting of highly oriented polar fresnoite-type Sr2TiSi2O8 fabricated using perfectly surface-crystallized glass-ceramics (PSC-GCs). The chemical composition of the precursor glass was shown to significantly affect the crystallized texture, e.g., the crystal orientation and appearance of amorphous nanoparasites in the domains, resulting in variations in the Pockels constants. Single crystals exhibiting spontaneous polarization possessed large structural anisotropy, leading to a strong dependence of the nonlinear-optical properties on the direction of polarized light. This study suggests that variations in the Pockels constants (r(13) and r(33)) and tuning of the r(13)/r(33) ratio can be realized in PSC-GC materials. Published by AIP Publishing.
Multicolor emission based on amorphous-to-crystalline phase transitions in nanostructured Mn-doped glass 査読有り

Yoshinobu Hoshino, Yoshihiro Takahashi, Nobuaki Terakado, Takumi Fujiwara

JAPANESE JOURNAL OF APPLIED PHYSICS　56　(12)　2017年12月
出版者・発行元：IOP PUBLISHING LTD
DOI： 10.7567/JJAP.56.120302 　

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We fabricated glass-ceramics composed of emissive nanocrystals that show variation in photoluminescence coloration. The change in emission color is based on the amorphous-to-crystalline phase transformation in a Mn-containing zincogermanate glass. The transformation occurred at a 50 degrees C temperature range (538-588 degrees C), resulting in a change in photoluminescence color from orange to white to green. The color change is attributed to the co-crystallization of emissive nanophases and a change in the coordination state of Mn2+. Using laser-induced crystallization, we also achieved the space-selective arrangement of the different photoluminescence colors, indicating that photoluminescence coloration can be tuned in this Mn-doped glass. (C) 2017 The Japan Society of Applied Physics
Line patterning of anisotropic spin chains by polarized laser for application in micro-thermal management 査読有り

Nobuaki Terakado, Ryosuke Takahashi, Yoshihiro Takahashi, Takumi Fujiwara

APPLIED PHYSICS LETTERS　110　(19)　2017年5月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4983369 　

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The control of heat flow has become increasingly important in energy saving and harvesting. Among various thermal management materials, spinon thermal conductivity materials are promising for heat flow control at microscales because they exhibit high, anisotropic thermal conductivity resulting from spin chains. However, there has been only little development of the materials for controlling heat flow. Here, we present the line patterning of the spin chain structure on a SrCuO2 nanocrystalline film by laser scanning. When the polarization direction of laser light was orthogonal to the scanning direction, we found that the spin-chain structure anisotropically grew on the patterned line. Published by AIP Publishing.
Post-annealing effects in two-dimensional spin system SrCuO2 sputtered on glass substrate 査読有り

Ryosuke Takahashi, Nobuaki Terakado, Yoshiki Yamazaki, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　125　(5)　423-426　2017年5月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.16328 　

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We prepared SrCuO2 thin film by radio-frequency magnetron sputtering on glass substrate and have investigated its post-annealing effects on structure and thermal conductivity. The as-sputtered film belongs to two-dimensional spin system SrCuO2, namely, layer-type SrCuO2, which has a possibility of exhibiting high, anisotropic thermal conductivity by magnetic excitation of the spins. It was found that the as-sputtered film has (001)-orientation in which the spin layers are parallel to the surface of substrate and that post-annealing results in enhancement of crystallinity of the film such as disappearance of grain boundaries, which can cause an increase in thermal conductivity. (C) 2017 The Ceramic Society of Japan. All rights reserved.
Synthesis of nanocrystals from glass-ceramics by YAG-laser irradiation: Mn4+ -doped Li2Ge4O9 deep-red nanophosphor 査読有り

Yuto Odawara, Yoshihiro Takahashi, Yoshiki Yamazaki, Nobuaki Terakado, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　125　(4)　378-381　2017年4月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.17002 　

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Functional nanocrystals have received considerable attention because of their various applications. Although glass-ceramic (GC) processing is recognized as promising for preparation of nanostructured material, it is difficult to use the materials as nanocrystals as in. This study provides a possible way to obtain nanocrystals by irradiation of fundamental wave of Q-switched Nd: YAG laser to nanocrystallized GCs in liquid. In this study, we employed Mn4+: Li2Ge4O9 nanocrystallized GCs as the target, and succeeded in fabricating deep-red emissive nanocrystals with a size of similar to 100 nm. (c) 2017 The Ceramic Society of Japan. All rights reserved.
Formation and photoluminescence of zirconia dendrites in borosilicate glass-ceramics 査読有り

Yasuhiro Nobuta, Yoshihiro Takahashi, Takamichi Miyazaki, Nobuaki Terakado, Noriko Onoue, Tsuyoshi Shinozaki, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　125　(4)　343-347　2017年4月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.17001 　

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We prepared a borosilicate glass, in which the ZrO2 phase is singly crystallizable, i.e., 15Na(2)O-15ZrO(2)-30B(2)O(3)-40SiO(2) glass, and investigated the texture and morphology of the resulting glass-ceramics. ZrO2 dendrites with a tetragonal system (high-temperature phase) were developed as initial phase, and the tetragonal phase was transformed to the monoclinic phase (lowtemperature phase) by elongation of the heat-treatment time, and finally the needle-/rod-like crystals on a scale of few hundred nanometers were obtained. The glass-ceramics with monoclinic ZrO2 showed photoluminescence around 480nm by excitation in the ultraviolet region. The effect of TiO2-addition on the photoluminescent property was also considered. (C) 2017 The Ceramic Society of Japan. All rights reserved.
結晶化ガラス法によるナノ結晶合成と臨床医学応用に向けた光機能性発現招待有り査読有り

高橋儀宏, 寺門信明, 尾上紀子, 篠崎毅, 藤原巧

Journal of the Society of Inorganic Materials, Japan　24　(391)　415-421　2017年
出版者・発行元：無機マテリアル学会
ISSN：1345-3769
Observation of visible light-driven water splitting by TiO2 crystallized glass 査読有り

Kazuki Yoshida, Hiroshi Takahashi, Hirokazu Masai, Nobuaki Terakado, Yoshihiro Takahashi, Takumi Fujiwara, Hideki Kato, Masato Kakihana

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY　41　(47)　22055-22058　2016年12月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.ijhydene.2016.10.016 　

ISSN：0360-3199

eISSN：1879-3487

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Study on visible light response of photocatalytic materials is very important research area for future energy society. Generally, in conventional photocatalysts, visible light response is provided by defect introduction. This phenomenon is based on formation of trap level between valence and conduction band. In our previous report, we have already succeeded in observing the photocatalytic activity of TiO2 crystallized glass. Since glass-based material is suitable for industrial use, crystallized glass is expected to be a novel bulk photocatalyst with high productivity if we provide visible light response ability to TiO2 crystallized glass. In this study, we tried the defect introduction to TiO2 crystallized glass and investigated the photocatalytic activity under visible light irradiation. As a result, we have demonstrated water splitting by TiO2 crystallized glass with Ti3+ defect under visible light irradiation for the first time. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Depth analysis of a compression layer in chemically strengthened glass using depth-resolved micro-Raman spectroscopy 査読有り

Nobuaki Terakado, Shohei Uchida, Yoshihiro Takahashi, Takumi Fujiwara, Mototaka Arakawa

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　124　(10)　1164-1166　2016年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.16138 　

ISSN：1882-0743

eISSN：1348-6535

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We performed depth analysis of a compression layer in Corning Gorilla Glass 3, one of commercialized chemically-strengthened glasses, using depth-resolved micro-Raman spectroscopy. We obtained a depth variation of Raman spectra and an ion-exchange rate of Na for K was determined by energy dispersive X-ray spectroscopy. We found that a peak position around 1100 cm(-1) in the Raman spectra is shifted to higher wavenumber and the ion-exchange rate of Na for K increases with a decreasing depth when shallower than similar to 30 mu m. This correlation can be qualitatively explained as follows: compression of a TO2 tetrahedra network (T = Si or Al) induced by the ion exchange gives rise to an increase in frequency of vibrational modes of the TO4 tetrahedra. (C) 2016 The Ceramic Society of Japan. All rights reserved.
Syntheses of Spinon Thermal Conductivity Materials in Sr-Cu-O System by Glass-Ceramics Technique 査読有り

Nobuaki Terakado, Yuudai Yokochi, Kouki Watanabe, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF THE AMERICAN CERAMIC SOCIETY　99　(5)　1565-1572　2016年5月
出版者・発行元：WILEY-BLACKWELL
DOI： 10.1111/jace.14096 　

ISSN：0002-7820

eISSN：1551-2916

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We have synthesized spinon thermal conductivity materials in Sr-Cu-O system by glass-ceramics technique. The materials are promising for active control of thermal energy in microelectronic devices because of high and anisotropic thermal conduction, its controllability, and electric insulation. Nevertheless, research on these materials has been limited to that concerning theoretical perspectives and investigation of physical properties using large single crystals. In this study, we adopt glass-ceramics technique to synthesize these materials: We prepared melt-quenched multicomponent oxides including SrO and CuO, and checked its glass-forming ability and crystallization behaviors by heating. As a result, we have found that SrCuO2 and Sr14Cu24O41, known as the spinon thermal conductivity materials, are synthesized using SrO-CuO-Li2O-Al2O3-Ga2O3 system. This synthesis process for the system will provide practical application of the spinon thermal conductivity materials.
Synthesis of chain-type SrCuO2 by laser irradiation on sputtered layer-type SrCuO2 film 査読有り

Nobuaki Terakado, Ryosuke Takahashi, Yoshihiro Takahashi, Takumi Fujiwara

THIN SOLID FILMS　603　303-306　2016年3月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.tsf.2016.02.035 　

ISSN：0040-6090

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We prepared SrCuO2 film by radio-frequency magnetron sputtering on silica glass and have investigated structure change induced by super-band-gap light. An X-ray diffraction pattern shows that the as-sputtered film is composed of (001)-oriented SrCuO2 nanothick crystals belonging to tetragonal system, i.e., the layer-type SrCuO2. Raman-scattering spectra show that irradiation of high-power super-band-gap laser light onto the film gives rise to structure change into orthorhombic system, i.e., the chain type SrCuO2, which is known to exhibit high, anisotropic thermal conductivity due to spin interaction. A mechanism of the structure change is discussed in terms of photoexcitation and heating process. (C) 2016 Elsevier B.V. All rights reserved.
Mn-doped LiNaGe4O9 as a rare-earth free phosphor: impact of Na-substitution on emission in tetragermanate phase 査読有り

Rie Suzuki, Jun Kunitomo, Yoshihiro Takahashi, Kensaku Nakamura, Minoru Osada, Nobuaki Terakado, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　123　(1441)　888-891　2015年9月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.123.888 　

ISSN：1882-0743

eISSN：1348-6535

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We have synthesized Mn4+-doped mixed tetragermanate phases in the Li2Ge4O9-LiNaGe4O9 system, i.e., Li(Li,Na)Ge4O9, by a glass-ceramic technique using stoichiometric precursor glasses, and have examined the effect of substitution of Na on their photoluminescence properties. The tetragermanate phases indicated clear red emission based on a E-2 <-(4)A(2) transition, and the entire substitution resulting in an LiNaGe4O9 phase provided an improvement of quenching temperature for the emission. Furthermore, the LiNaGe4O9 phase synthesized by solid-state reaction showed a high internal quantum yield and red color purity, demonstrating it to be a possible candidate as a rare-earth-free red phosphor. (C) 2015 The Ceramic Society of Japan. All rights reserved.
Spectroscopically and thermometrically observed boson peaks in oxide glass system 査読有り

Kensaku Nakamura, Yoshihiro Takahashi, Nobuaki Terakado, Minoru Osada, Takumi Fujiwara

JAPANESE JOURNAL OF APPLIED PHYSICS　54　(8)　088003/1-088003/4　2015年8月
出版者・発行元：IOP PUBLISHING LTD
DOI： 10.7567/JJAP.54.088003 　

ISSN：0021-4922

eISSN：1347-4065

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We compare the boson peaks (BPs) observed in low-frequency Raman scattering with the BPs observed in low-temperature specific heat in many oxide glasses. We find a linear correlation of the maximum positions between the Raman BP and specific-heat BP regardless of the constituents. In addition, we show that several chalcogenide and molecular glasses also exhibit the same correlation. The linearity enables us to convert the BPs between different observation techniques, which is expected to provide significant insight into the features of the BP. (C) 2015 The Japan Society of Applied Physics
Affects of supercooled liquid state on the properties of the crystallized phase: Microscopic and spectroscopic observations in ZnO-crystallized glass-ceramics 査読有り

Yoshihiro Takahashi, Mikio Kinoshita, Takamichi Miyazaki, Minoru Osada, Nobuaki Terakado, Takumi Fujiwara

APPLIED PHYSICS LETTERS　107　(6)　061902/1-061902/4　2015年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4928538 　

ISSN：0003-6951

eISSN：1077-3118

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We examined the crystallization and crystal growth of ZnO in the viscoelastic supercooled liquid (SCL) phase based on microscopic and spectroscopic observations. The resulting glass-ceramics exhibits complex ZnO dendrites that precede the formation of Zn-rich regions because of phase separation. Compressive stresses are concentrated at the interface of ZnO crystals and SCL phase, suggesting that the domains are subject to a resistance during ZnO crystal growth. Defects were detected in the crystallized ZnO and attributed to the suppression of smooth ordering of the Zn-rich regions in the SCL phase. (C) 2015 AIP Publishing LLC.
Nano-phase separation and the effect of SnO addition in TiO2-precipitated glass-ceramics 査読有り

Hirokazu Masai, Takamichi Miyazaki, Ko Mibu, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY　35　(7)　2139-2144　2015年7月
出版者・発行元：ELSEVIER SCI LTD
DOI： 10.1016/j.jeurceramsoc.2015.01.013 　

ISSN：0955-2219

eISSN：1873-619X

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We have investigated the nano-structure of TiO2-precipitated CaO-B2O3-Bi2O3-Al2O3-TiO2 (CaBBAT) glass-ceramics, and discussed the effect of the addition of SnO. Sn-119 Mossbauer spectra of the Sn-doped glass suggest that most of the SnO was oxidized during melting. Selective crystallization of TiO2 occurred independently of SnO addition in the homogeneous glass. However, EDX analysis of the glass-ceramics revealed that the Ti cation is partially localized and that the addition of SnO promotes the nano-phase separation. It can be concluded, therefore, that the addition of SnO influenced the formation of secondary particles of TiO2 nano-crystallites and thereby improved the photocatalytic activity. (C) 2015 Elsevier Ltd. All rights reserved.
Controllable photoluminescence by melting-process temperature in SnO-containing glass 査読有り

Mikio Kinoshita, Yoshihiro Takahashi, Nobuaki Terakado, Hirokazu Masai, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　123　(1439)　611-614　2015年7月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.123.611 　

ISSN：1882-0743

eISSN：1348-6535

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We prepared SnO-ZnO-B2O3 system glasses by means of melt-quenching technique with different melting-process temperatures in range of 1100-1500 degrees C, and examined the impact of the process temperature on photoluminescent (PL) property. The glass obtained at 1100 degrees C showed clear PL band at similar to 2.8 eV at room temperature. As elevating the process temperature, a shoulder appeared at lower-energy side of the PL band, and eventually broad band with peak at similar to 2.2 eV developed, resulting the clear orange PL. We demonstrated that the PL-color is controllable from blue to orange via white by change in the process temperature. (C) 2015 The Ceramic Society of Japan. All rights reserved.
High thermal stability of red emission in Mn-doped benitoite-type strontium silicogermanate 査読有り

Rie Suzuki, Yoshihiro Takahashi, Kenichiro Iwasaki, Nobuaki Terakado, Takumi Fujiwara

APPLIED PHYSICS EXPRESS　8　(7)　072603/1-072603/4　2015年7月
出版者・発行元：IOP PUBLISHING LTD
DOI： 10.7567/APEX.8.072603 　

ISSN：1882-0778

eISSN：1882-0786

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We assessed the photoluminescence performance characteristics of Mn4+-doped tetragermanate and silicogermanate phases with a benitoite-type structure. We observed a visible red emission based on the E-2 ->(4)A(2) transition in the doped benitoite-type tetragermanate. The partial substitution of Si for Ge, resulting in SrGe3.495Mn0.005Si0.5O9, improved the internal quantum efficiency and thermal stability of the red emission. A possible explanation of the substitution effect was reasonably presented on the basis of the connectivity of luminescent polyhedral units and the decrease in the Franck-Condon off-set value in the benitoite structure. (C) 2015 The Japan Society of Applied Physics
Pockels effect of silicate glass-ceramics: Observation of optical modulation in Mach-Zehnder system 査読有り

Kazuki Yamaoka, Yoshihiro Takahashi, Yoshiki Yamazaki, Nobuaki Terakado, Takamichi Miyazaki, Takumi Fujiwara

SCIENTIFIC REPORTS　5　12176/1-12176/5　2015年7月
出版者・発行元：NATURE PUBLISHING GROUP
DOI： 10.1038/srep12176 　

ISSN：2045-2322

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Silicate glass has been used for long time because of its advantages from material's viewpoint. In this paper, we report the observation of Pockels effect by Mach-Zehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network.
Fabrication of glass-ceramics containing spin-chain compound SrCuO2 and its high thermal conductivity 査読有り

Nobuaki Terakado, Kouki Watanabe, Takayuki Kawamata, Yuudai Yokochi, Yoshihiro Takahashi, Yoji Koike, Takumi Fujiwara

APPLIED PHYSICS LETTERS　106　(14)　141902/1-141902/4　2015年4月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4917035 　

ISSN：0003-6951

eISSN：1077-3118

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High thermal conductivity materials are in great demand for heat-flow control and heat dissipation in electronic devices. In this study, we have produced a glass-ceramics that contains spin-chain compound SrCuO2 and have found that the glass-ceramics yields high thermal conductivity of similar to 5W K-1 m(-1) even at room temperature. The glass-ceramics is fabricated through crystallization of inhomogeneous melt-quenched oxides made from SrCO3, CuO, Li2CO3, Ga2O3, and Al2O3. Transmission electron microscopy and X-ray and electron diffraction reveal that SrCuO2 crystallites with a size of 100-200 nm are precipitated in the glass-ceramics. The highness of the thermal conductivity is attributable to two sources: one is elongation of phonon mean free path due to the crystallization of the inhomogeneous structure or structural ordering. The other is emergence of the heat carriers, spinons, in the SrCuO2. This highly thermal conductive glass-ceramics is expected to be utilized as base materials for heat-flow control devices. (C) 2015 AIP Publishing LLC.
Microstructure of Transparent Strontium Fresnoite Glass-Ceramics 査読有り

Wolfgang Wisniewski, Kazuya Takano, Yoshihiro Takahashi, Takumi Fujiwara, Christian Ruessel

SCIENTIFIC REPORTS　5　9096/1-9096/5　2015年3月
出版者・発行元：NATURE PUBLISHING GROUP
DOI： 10.1038/srep09069 　

ISSN：2045-2322

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Glass-ceramics grown from a glass of the composition Sr2TiSi2.45O8.9 (STS 45) are analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Oriented nucleation with the c-axes preferably perpendicular to the surface is detected. A very strong 001-texture is observed after only 10 mu m of growth into the bulk, making this the first system in which an orientation preferred during nucleation prevails during growth into the bulk in glass-ceramics. Piezoelectric measurements are performed and d(33)-values presented and discussed. The obtained results are critically viewed with respect to the two growth models describing Sr2TiSi2O8 growth in glasses.
Photo- and Radioluminescence of ZnO-Precipitated Glass-Ceramics 査読有り

Hirokazu Masai, Takayuki Yanagida, Takumi Fujiwara

SENSORS AND MATERIALS　27　(3)　237-245　2015年
出版者・発行元：MYU, SCIENTIFIC PUBLISHING DIVISION
ISSN：0914-4935

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The photoluminescence (PL) and radioluminescence (RL) of ZnO-precipitated CaO-B2O3-ZnO-Al2O3-K2O-SiO2 (CaBZAKS) glass-ceramics were examined. Surface crystallization with a certain crystal orientation was observed after heat treatment. A broad emission was observed in both the CaBZAKS glass and the glass-ceramics. The PL decay curves of the glass-ceramics indicate that decay constants are increased by the crystallization of ZnO. Because the scintillation and scintillation decay spectra obtained by X-ray irradiation are independent of the heat treatment conditions, scintillation mainly depends on the host matrix, whose emission decays consist of at least three components. On the other hand, an optically stimulated luminescence (OSL) with a stimulation of 1.97 eV shows that the OSL intensity, whose emission energy is the same as that of scintillation, increases with heat treatment temperature.
Low-Temperature Excess Specific Heat in Oxide Glasses: Comprehensive Study of Thermometrically Observed Boson Peak 査読有り

Kensaku Nakamura, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN　83　(11)　114603-1-114603-4　2014年11月
出版者・発行元：PHYSICAL SOC JAPAN
DOI： 10.7566/JPSJ.83.114603 　

ISSN：0031-9015

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We present the results of low-temperature (similar to 5 to 20 K) specific-heat measurements performed in numerous oxide glass systems. These results allow us to elucidate the impact of the system or component on the excess specific heat, which when plotted on C-p/T-3 vs T appears as a broad band known as the boson peak (BP). By integrating our experimental results with the data of Richet [Physica B 404, 3799 (2009); J. Chem. Phys. 136, 034703 (2012)], we demonstrate a strong negative correlation between the BP amplitude and its maximum temperature. We also describe the BP characteristics of multicomponent systems based on different binary systems in silicate glasses.
Large enhancement of photocatalytic activity by chemical etching of TiO2 crystallized glass 査読有り

Kazuki Yoshida, Yoshihiro Takahashi, Rie Ihara, Nobuaki Terakado, Takumi Fujiwara, Hideki Kato, Masato Kakihana

APL MATERIALS　2　(10)　106103/1-106103/6　2014年10月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4897961 　

ISSN：2166-532X

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The authors aim to report the largest enhancement of photocatalytic activity by chemical etching in anatase-type TiO2 crystallized glass. Optimization of several conditions for crystallization behavior and chemical etching to realize the nano-structured ceramics (NSC) has been performed in the crystallized glass. NSC-fabrication by chemical etching in the crystallized glass is one of the most effective solutions to provide bulk materials with high specific surface area. We have found that the best condition for the NSC fabrication as a novel bulk photocatalyst in our glass system, and have obtained 16 times higher catalytic activity than that of non-etched one. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Low-temperature excess heat capacity in fresnoite glass and crystal 査読有り

Kensaku Nakamura, Yoshihiro Takahashi, Takumi Fujiwara

SCIENTIFIC REPORTS　4　6523/1-6523/4　2014年10月
出版者・発行元：NATURE PUBLISHING GROUP
DOI： 10.1038/srep06523 　

ISSN：2045-2322

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The effect of thermal annealing on low-temperature excess heat capacity was investigated in fresnoite (Ba2TiSi2O8) glass. The amplitudes of the excess heat capacity decreased, and their positions shifted to a higher temperature by relaxation or crystallization. In particular, we revealed that the change in the excess heat capacity during transition from the glassy state to the crystalline state is relatively small compared with that of other oxides. Therefore, it is suggested that distribution of the excess vibrational density of states of the glass is similar to that of the corresponding crystal.
Red-emissive Mn-doped Li2Ge4O9 phase synthesized via glass-ceramic route 査読有り

Jun Kunitomo, Rie Suzuki, Yoshihiro Takahashi, Takamichi Miyazaki, Nobuaki Terakado, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　122　(1428)　725-727　2014年8月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.122.725 　

ISSN：1882-0743

eISSN：1348-6535

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We synthesized the lithium-tetragermanate (Li2Ge4O9) phase doped with Mn4+ by glass-ceramics technique using the stoichiometric glass-precursor with different MnO2 concentrations, i.e., 20Li(2)O-80GeO(2)-xMnO(2) (x = 0.1-0.7), and examined their photoluminescent property. The doped phase showed clear red-emission at room temperature, and the internal quantum-yield was found to be approximately 40% in the samples with x = 0.1-0.3. (c) 2014 The Ceramic Society of Japan. All rights reserved.
Multiferroic BiFeO3 glass-ceramics: Phase formation and physical property 査読有り

Yoshihiro Takahashi, Kousuke Meguro, Hiroshi Naganuma, Nobuaki Terakado, Takumi Fujiwara

APPLIED PHYSICS LETTERS　104　(22)　221901/1-221901/4　2014年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4881138 　

ISSN：0003-6951

eISSN：1077-3118

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A production of polycrystalline phase with glassy precursor, i.e., glass-ceramics processing, has a great potential to fabricate the sophisticated materials. In this study, we have prepared the Bi2O3-Fe2O3-BaO-B2O3 system precursor, in which BiFeO3 phase is crystallizable, and examined the phase formation and physical properties in resulting glass-ceramics. We found both ferroelectricity and ferromagnetism in the glass-ceramics consisting of BiFeO3 phase, i.e., multiferroic glass-ceramics. This study has demonstrated an alternative method for synthesis of polycrystalline BiFeO3 material. (C) 2014 AIP Publishing LLC.
Fabrication of multilayer-type Mn-Si thermoelectric device 査読有り

T. Kajitani, T. Ueno, Y. Miyazaki, K. Hayashi, T. Fujiwara, R. Ihara, T. Nakamura, M. Takakura

Journal of Electronic Materials　43　(6)　1993-1999　2014年

DOI： 10.1007/s11664-013-2933-0 　
Ultra-low propagation losses in fresnoite-type precipitated crystallized glasses 査読有り

Yoshiki Yamazaki, Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara

APPLIED PHYSICS LETTERS　104　(3)　031901/1-031901/4　2014年1月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4862888 　

ISSN：0003-6951

eISSN：1077-3118

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The propagation losses for fresnoite-phase crystallized glasses fabricated from 35BaO-15TiO(2)-50GeO(2), 28BaO-18TiO(2)-54SiO(2), and 35SrO-20TiO(2)-45SiO(2) (STS45) glasses using a cut-back technique are reported. The values are comparable with those for LiNbO3 waveguide single crystals and transparent Y3Al5O12 ceramics. In addition, the propagation loss data indicate that the losses depend on the relationship between the polarization direction and crystal growth direction. The lowest propagation loss value (0.6 dB/cm) was measured for the STS45 crystallized glass; this value is the lowest value ever reported for an oriented crystallized glass. (C) 2014 AIP Publishing LLC.
Emission property of Sn2+-doped ZnO-P2O5 glass 査読有り

Hirokazu Masai, Takumi Fujiwara, Syuji Matsumoto, Yomei Tokuda, Toshinobu Yoko

JOURNAL OF NON-CRYSTALLINE SOLIDS　383　184-187　2014年1月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.jnoncrysol.2013.04.017 　

ISSN：0022-3093

eISSN：1873-4812

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Photoluminescent properties of amorphous zinc phosphate glass, containing Sn2+ as an emission center, were investigated. Varying the chemical composition changed both the excitation and emission properties. The redox reaction that occurred during melting was found to affect both valences of transition metal and Sn cations to change the emission property of the Sn2+-containing glass. We have also examined the emission property of substituted SnO-ZnO-P2O5 glass, and demonstrated that the emission color can be tailored by chemical composition to obtain blue, white, and red. It is notable that the quantum efficiency value of the present RE-free glass is comparable to that of crystal phosphor such as MgWO4. We have, therefore, emphasized that transparent inorganic glass phosphor will be one of the fascinating emitting materials adoptable to future strong LED light source. (C) 2013 Elsevier B.V. All rights reserved.
Selective crystallization of anatase and rutile by control of heat-treatment conditions and SiO2 addition in TiO2-crystallized glass 査読有り

Kazuki Yoshida, Hirokazu Masai, Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　121　(1420)　999-1003　2013年12月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.121.999 　

ISSN：1882-0743

eISSN：1348-6535

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In this study, we have investigated the effects of heat-treatment condition and SiO2 addition on the crystallization behavior and chemical durability of TiO2-ZnO-B2O3-Al2O3 (TZBA) glass. Systematic analysis indicated that not only the precipitated phases (rutile, anatase, and brookite) after crystallization but also the chemical durability of TZBA glass-ceramics were affected by heat-treatment condition and SiO2 addition. In a specific glass composition, we have found that etching resulted in TiO2 grains of several dozen nanometers and asperity of several hundred nanometers at the sample surface. The present method, in which the increase of specific surface area and formation of nanoparticles at the surface is achieved by chemical etching, will become an important technique for the fabrication of novel bulk photocatalysts with high catalytic activity. (C) 2013 The Ceramic Society of Japan. All rights reserved.
Fabrication of Sr0.5Ba0.5Nb2O6 Nanocrystallite-Precipitated Transparent Phosphate Glass-Ceramics 査読有り

Hirokazu Masai, Ryota Shirai, Takamichi Miyazaki, Kazuki Yoshida, Takumi Fujiwara, Yomei Tokuda, Toshinobu Yoko

JOURNAL OF THE AMERICAN CERAMIC SOCIETY　96　(11)　3576-3583　2013年11月
出版者・発行元：WILEY-BLACKWELL
DOI： 10.1111/jace.12547 　

ISSN：0002-7820

eISSN：1551-2916

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Transparent (Sr0.5Ba0.5)Nb2O6 (SBN50) nanocrystallite-precipitated phosphate glass-ceramics were prepared by a conventional glass-ceramic process. x(SrO-BaO-2Nb(2)O(5))-(100-4x)P2O5 (xSBNP) glasses with a refractive index of 1.9-2.0 exhibited high water resistance owing to the presence of Q(0) and Q(1) phosphate units. Both bulk and surface crystallization of the SBN50 phase were observed in 20SBNP and 21SBNP glass-ceramics. Although the nominal content of SBN50 crystals in the 21SBNP glass was larger than that in the 20SBNP glass, the latter exhibited better crystallinity of SBN50 and a higher number density of precipitated SBN nanocrystallites. By tuning the two-step heat-treatment and the chemical composition, transparent SBN50-precipitated glass-ceramics were successfully obtained. Given that no remarkable increase of the relative dielectric constants was observed after crystallization of the SBN50 nanocrystallites, it is postulated that the relative dielectric constant of the bulk is mainly governed by the amorphous phosphate region, and that the contribution of precipitation of the SBN50 nanocrystallites to the dielectric constant is not very significant in this system.
P-31 NMR and IR Study of Highly Water-stable SrO-BaO-Nb2O5-P2O5 Glass and Glass-ceramics 査読有り

Hirokazu Masai, Ryota Shirai, Kazuki Yoshida, Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara, Yomei Tokuda, Toshinobu Yoko

CHEMISTRY LETTERS　42　(10)　1305-1307　2013年10月
出版者・発行元：CHEMICAL SOC JAPAN
DOI： 10.1246/cl.130477 　

ISSN：0366-7022

eISSN：1348-0715

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We describe the preparation of [(100 - gamma)/(4)](SrO-BaO-2Nb(2)O(5))-gamma P2O5 (SBNP gamma) glasses and glass-ceramics with the Sr0.5Ba0.5Nb2O6 (SBN50) phase, using a conventional process, and the analysis of the chemical stability of the materials in water. The SBNP gamma glasses and glass-ceramics consist of orthophosphate (Q(0)) and pyrophosphate (Q(1)) units with strongly delocalized P=O bonds. Because of the presence of these phosphate units, the glasses and glass-ceramics obtained in this study show no weight changes, even after exposure to water at 70 degrees C for 100 h. We hypothesize that the lack of phosphate chains within the glass network is responsible for the superior water stability.
Crystal domain growth driven by nanometric phase separation in perfect surface crystallization 査読有り

Yoshihiro Takahashi, Kazuki Yamaoka, Yoshiki Yamazaki, Takamichi Miyazaki, Takumi Fujiwara

APPLIED PHYSICS LETTERS　103　(7)　071909/1-071909/4　2013年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4818674 　

ISSN：0003-6951

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Phase separation often makes glass structure inhomogeneous. Nevertheless, a uniform texture consisting of single-crystal domains has been found by crystallization in nonstoichiometric glass, i.e., perfect surface-crystallization (PSC). Although the PSC is probably caused by evolution of SiO2-rich amorphous nanoparasites on the domain, its mechanism has not been understood yet. In this study, we examined an early-stage of PSC in a strontium-titanosilicate glass by means of nanoscopic observations. It was demonstrated that the binodal-like nanometric phase-separation and crystal-growth of fresnoite-type phase occur simultaneously at the crystal interface. It was strongly suggested that the PSC process is driven by the phase separation. (C) 2013 AIP Publishing LLC.
Successive phase transformation in stoichiometric glassy Li2Ge4O9: Isothermal and nonisothermal study 査読有り

Yoshihiro Takahashi, Jun Kunitomo, Takamichi Miyazaki, Minoru Osada, Takumi Fujiwara

JOURNAL OF APPLIED PHYSICS　114　(3)　033512/1-033512/5　2013年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4813783 　

ISSN：0021-8979

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Stoichiometric glassy germanate is an important material in geophysics and materials science. Despite the binary Li2O-GeO2 system being primitive, its crystallization mechanism remains undetermined. In this study, we investigated crystallization and structural ordering in glassy ferroelectric Li2Ge4O9. Using isothermally and nonisothermally prepared samples, we demonstrated that the glassy Li2Ge4O9 shows no direct structural change to the stoichiometric phase; it rather forms alpha-GeO2 nanocrystals, i.e., it undergoes successive phase transformation. The results suggest that the metastable immiscibility is related to the ordering that occurs prior to crystallization of the stoichiometric phase. (C) 2013 AIP Publishing LLC.
Perfect surface crystallization and parasitic structures in nonstoichiometric glass-ceramics: Micro-/nanoscopic aspects 査読有り

Yoshihiro Takahashi, Yoshiki Yamazaki, Rie Ihara, Takumi Fujiwara

APPLIED PHYSICS LETTERS　102　(19)　191903/1-191903/4　2013年5月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4805028 　

ISSN：0003-6951

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Uniform and highly oriented crystalline layers with submillimeter thickness have been demonstrated recently by crystallization in nonstoichiometric precursor glass, i.e., perfectly surface-crystallized glass-ceramics (PSC-GCs). Although the origin of PSC in the SrO-TiO2-SiO2 system was interpreted by the presence of SiO2-rich amorphous nanoparasites on the crystalline domains [Takahashi et al., Sci. Rep. 3, 1147 (2013)], an essential question arose: Is the parasitic structure in PSC-GCs special or natural? To answer it, we prepared PSC samples from other ternary titanosilicate systems and conducted micro-and nanoscopic observations. We found the conditions necessary for PSC by combining our results with previous PSC studies. (C) 2013 AIP Publishing LLC.
Localized Sn2+ Emission Center Independent of the Optical Basicity of Zinc Phosphate Glass 査読有り

Hirokazu Masai, Toshiro Tanimoto, Takumi Fujiwara, Syuji Matsumoto, Yomei Tokuda, Toshinobu Yoko

CHEMISTRY LETTERS　42　(2)　132-134　2013年2月
出版者・発行元：CHEMICAL SOC JAPAN
DOI： 10.1246/cl.2013.132 　

ISSN：0366-7022

eISSN：1348-0715

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We report the emission and optical properties of RO-substituted (R = Mg, Ca, Sr, and Ba) 2.5SnO-57.5ZnO-40P(2)O(5) glasses. Although the optical basicity of the host glass is changed by substitution of RO for ZnO, the optical band edge and the peak positions of the photoluminescence (PL) and PL excitation (PLE) spectra show no significant changes. Considering the characteristics of ns(2)-type emission centers, the properties of which are strongly affected by the coordination field, it can be concluded that the localized Sn2+ state affects both the optical absorption edge and the emission.
Parasitic amorphous on single-domain crystal: Structural observations of silicate glass-ceramics 査読有り

Yoshihiro Takahashi, Yoshiki Yamazaki, Rie Ihara, Takumi Fujiwara

SCIENTIFIC REPORTS　3　1147/1-1147/5　2013年1月
出版者・発行元：NATURE PUBLISHING GROUP
DOI： 10.1038/srep01147 　

ISSN：2045-2322

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Glass-ceramics (GCs) are materials obtained from the crystallisation of functional phases in glass, and have a structure that the crystallised phase embedded in the glass matrix. Glass-forming oxides are commonly added to the functional phases to improve the stability of precursor glass; however, the issue of glass-ceramics permitting the presence of residual phases resulting from addition is required to be clarified. To elucidate this issue, we prepared 'perfectly surface-crystallised' GC consisting of fresnoite-type Sr2TiSi2O8 from a non-stoichiometric glass and performed texture/morphology observations. Numerous SiO2-rich binodal-like nanospheres (similar to 10 nm) were parasitic on the fresnoite single-crystal domains. The parasitic texture is considered to form via the following process: (i) binodal-type phase separation into stoichiometric fresnoite (crystalline matrix) and SiO2-rich phases (amorphous nanoparticles) and (ii) single-domain formation by surface crystallisation in the matrix. Furthermore, in terms of texture, the resulting GC differs from the GCs reported to date, i.e., inverse GC.
Crystallization of Tungstenbronze Phase and its Inelastic Light Scattering in Niobiophosphate-System Glass 査読有り

Yoshihiro Takahashi, Nobuhiro Fujie, Minoru Osada, Rie Ihara, Takumi Fujiwara

ELECTROCERAMICS IN JAPAN XV　566　306-309　2013年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM.566.306 　

ISSN：1013-9826

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We prepared a niobiophosphate-glass-crystallizing tungstenbronze-type Ba2NaNb5O15 and measured elastic light scattering spectra in situ in the glass-ceramics fabrication regime. We found that the studied glass possesses a strong tendency for phase separation into Al2O3-P2O5 and Nb-rich regions prior to crystallization. It is suggested that the tungstenbronze phase crystallizes in the Nb-rich region separated from the supercooled liquid phase. This study demonstrated that in situ Raman spectroscopy is also useful for observing the phase-separation dynamics in glass.
Impact of Nd-doping on crystallization and phase separation in glassy ferroelectric La BSixGe1-xO5 (x=0, 0.4) 査読有り

Yoshihiro Takahashi, Tomomichi Yasuoka, Takumi Fujiwara

Journal of the Ceramic Society of Japan　121　(1420)　984-987　2013年
出版者・発行元：Ceramic Society of Japan
DOI： 10.2109/jcersj2.121.984 　

ISSN：1348-6535 1882-0743

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Since stillwellite-type ferroelectric La BGeO5 shows the intriguing physical properties by the doping/substituting-modification, the stillwellite-type glass-ceramics has been studied extensively from viewpoint of material engineering. In this study, we examined how the Nd-doping affects the glassy ferroelectric La BGeO5 and its modified sample, La BSi0.4Ge0.6O5. We experimentally demonstrated that small amount of the doping gives a significant effect on the crystallization and phase-separation trends. © 2013 The Ceramic Society of Japan. All rights reserved.
Low-frequency Raman scattering in binary silicate glass: Boson peak frequency and its general expression 査読有り

Kensaku Nakamura, Yoshihiro Takahashi, Minoru Osada, Takumi Fujiwara

Journal of the Ceramic Society of Japan　121　(1420)　1012-1014　2013年
出版者・発行元：Ceramic Society of Japan
DOI： 10.2109/jcersj2.121.1012 　

ISSN：1348-6535 1882-0743

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Low-frequency Raman measurement was performed in alkali and alkaline-earth silicate glasses to elucidate the effect of introduction of network modifiers on boson peak nature. Our study illustrated that introduction of small/medium ions tended to increase in the boson peak frequency (ωBP), whereas the introduction of large ions tended to decrease the frequency. Although ωBP has been suggested to be proportional to the shear modulus, no linear relationship was obtained in these binary systems. Instead, we experimentally demonstrated that mean atomic volume can explain variations in ωBP regardless of the trend of boson peaks. © 2013 The Ceramic Society of Japan. All rights reserved.
Correlation between emission property and concentration of Sn2+ center in the SnO-ZnO-P2O5 glass 査読有り

Hirokazu Masai, Toshiro Tanimoto, Takumi Fujiwara, Syuji Matsumoto, Yomei Tokuda, Toshinobu Yoko

OPTICS EXPRESS　20　(25)　27319-27326　2012年12月
出版者・発行元：OPTICAL SOC AMER
DOI： 10.1364/OE.20.027319 　

ISSN：1094-4087

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The authors report on the correlation between the photoluminescence (PL) property and the SnO amount in SnO-ZnO-P2O5 (SZP) glass. In the PL excitation (PLE) spectra of the SZP glass containing Sn2+ emission center, two S-1 states, one of which is strongly affected by SnO amount, are assumed to exist. The PLE band closely correlates with the optical band edge originating from Sn2+ species, and they both largely red-shifts with increasing amount of SnO. The emission decay time of the SZP glass decreased with increasing amount of SnO and the internal quantum efficiencies of the SZP glasses containing 1 similar to 5 mol% of SnO are comparable to that of MgWO4. It is expected that the composition-dependent S-1 state (the lower energy excitation band) governs the quantum efficiency of the SZP glasses. (c) 2012 Optical Society of America
Effect of melt temperature on the structure of BaO-TiO2-GeO2 glass 査読有り

Hirokazu Masai, Katsumi Hamaguchi, Kenichiro Iwasaki, Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara

MATERIALS RESEARCH BULLETIN　47　(12)　4065-4070　2012年12月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.materresbull.2012.08.058 　

ISSN：0025-5408

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We have examined the dependence of the structure of BaO-TiO2-GeO2(BTG) glass on the temperature at which the BTG glass melt is held in the molten state (called the "melt temperature" in the present paper). The absorption coefficient and refractive index of the BTG glass increase with increasing melt temperature because of the reductive conditions. During melting at 1550 degrees C, Ti3+ and GeE' centers are generated together with the formation of TiO5 units. We conclude that the yellow coloration observed in the BTG glass prepared at higher melt temperatures is due to the generated Ge2+. It is expected that the local structures of the glass generated at high melt temperatures will affect the crystallization behavior to increase the second-order optical nonlinearity of the glass-ceramic material. (C) 2012 Elsevier Ltd. All rights reserved.
Formation of TiO2 Nanocrystallites in the TiO2–ZnO–B2O3–Al2O3 Glass-Ceramics 査読有り

H. Masai, K. Hirakawa, K. Yoshida, T. Miyazaki, Y. Takahashi, R. Ihara, T. Fujiwara

Journal of the American Ceramics Society　95　(10)　3138-3143　2012年10月
出版者・発行元：None
DOI： 10.1111/j.1551-2916.2012.05397.x 　

ISSN：0002-7820
Structural relaxation and quasi-elastic light scattering in glass: Approach by ferroelectric and ion-conducting phases 査読有り

Yoshihiro Takahashi, Kensaku Nakamura, Minoru Osada, Takumi Fujiwara

SCIENTIFIC REPORTS　2　714/1-714/6　2012年10月
出版者・発行元：NATURE PUBLISHING GROUP
DOI： 10.1038/srep00714 　

ISSN：2045-2322

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Inelastic light scattering has been utilized for examining the structure of glass and its relaxation. However, the quasi-elastic-light-scattering (QLS) phenomenon has not been addressed in much detail. In this study, we observed pronounced QLS-intensity variations in two temperature domains-supercooled liquid (SCL) state (alpha-relaxation regime) and below the glass-transition temperature (beta-relaxation regime)-in niobium-oxide (Nb2O5)-rich glass. These variations may be interpreted on the basis of the concept of ferroelectric and ion-conducting phases. It was suggested that the observed QLS originates as a result of the polarization fluctuation of NbO6 units, which is due to the dynamics of the nanometric phase separation in the SCL phase (alpha-regime), and the fluctuation due to the migration/hopping of conductible ions that are localized in the vicinity of the NbO6 units (beta-regime).
希土類フリー酸化物ガラス蛍光体の創製招待有り査読有り

正井博和, 藤原巧, 松本修治, 横尾俊信

化学工業　63　753-757　2012年9月
New photoluminescent semiconductive Zn2GeO4 nanostructured in glass 招待有り

Y. Takahashi, T. Fujiwara

Proceedings of "The 12th International Meeting on Information Display" (IMID 2012)　168-169　2012年8月29日

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The 12th International Meeting on Information Display (IMID 2012)/ August 28-31, 2012/EXCO, Daegu, Korea (ISSN 1738-1558)
NANOCRYSTALLIZATION AND OPTICAL PROPERTY OF WILLEMITE-TYPE SEMICONDUCTIVE Zn2GeO4 IN GLASS 査読有り

Yoshihiro Takahashi, Masataka Ando, Rie Ihara, Takumi Fujiwara, Minoru Osada

FUNCTIONAL MATERIALS LETTERS　5　(2)　2012年6月
出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD
DOI： 10.1142/S1793604712600089 　

ISSN：1793-6047

eISSN：1793-7213

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A wide band-gap semiconductive oxide Zn2GeO4 has recently attracted considerable interest because it is a multifunctional material; excellent photoluminescent (PL) and photocatalytic property, high-capacity anode for lithium batteries, and so on. Recently, present authors' group have fabricated transparent Zn2GeO4-nanocrystallized glass from a lithium zincogermanate glass. This article briefly describes a series of our studies on the nanocrystallized glass. Particularly, the phase-formation dynamics in supercooled-liquid phase and PL property of nanocrystallized glasses are presented.
Precipitation of Pt nanocrystallites from BaO-TiO2-GeO2 remelted glass 査読有り

Hirokazu Masai, Katsumi Hamaguchi, Yoshiyuki Suzuki, Kenichiro Iwasaki, Rie Ihara, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF APPLIED PHYSICS　111　(12)　123513/1-123513/5　2012年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4729488 　

ISSN：0021-8979

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We have examined the correlation between the thermal and optical properties of 30BaO-15TiO(2)-55GeO(2) glass and its mode of preparation, i.e., the different temperatures at which the glass melts were held in a molten state (melt temperature). The changes in the absorption coefficients and the refractive indices, which increased with the increasing melt temperature, were reversible, and temperature-dependent structures were formed in the glass. In the remelted glass with short remelting duration, a black coloration and the precipitation of Pt nanocrystallites were observed. The precipitated Pt nanocrystallites acted as nucleation sites to induce crystallization by heat treatment at 10 degrees C below the glass transition temperature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729488]
Effect of annealing at maximum nucleation temperature on boson peak in lithium-disilicate glass 査読有り

Kensaku Nakamura, Yoshihiro Takahashi, Minoru Osada, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　120　(1402)　256-258　2012年6月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.120.256 　

ISSN：1882-0743

eISSN：1348-6535

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Low-frequency Raman scattering and TEM observations were conducted in 1Li(2)O-2SiO(2) glass subjected to annealing at maximum homogeneous nucleation temperature (similar to 460 degrees C) to elucidate the annealing effect on Boson-peak behavior and its relation to the structural evolution in nanoscale. It is suggested that the 1Li(2)O-2SiO(2) glass possesses a successive medium-range ordering through phase separation, and the Boson-peak frequency was largely affected by the ordering/phase-separation. (C) 2012 The Ceramic Society of Japan. All rights reserved.
Nano-sized Ba2NaNb5O15–NaNbO3 co-crystallized glass-ceramics in phosphoniobate system 査読有り

Y. Takahashi, N. Fujie, T. Fujiwara

Applied Physics Letters　100　(20)　201907/1-201907/3　2012年5月
出版者・発行元：None
DOI： 10.1063/1.4719034 　

ISSN：0003-6951

eISSN：1077-3118
Photoluminescent Properties of Sb-Doped Phosphate Glass 査読有り

Hirokazu Masai, Syuji Matsumoto, Takumi Fujiwara, Yomei Tokuda, Toshinobu Yoko

JOURNAL OF THE AMERICAN CERAMIC SOCIETY　95　(3)　862-865　2012年3月
出版者・発行元：WILEY-BLACKWELL
DOI： 10.1111/j.1551-2916.2011.05055.x 　

ISSN：0002-7820

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The authors report on the UV-excited photoluminescence measured in Sb2O3ZnOP2O5 glass. Pre-heat treatment performed before melting effectively prevented the discoloration caused by precipitation of Sb nanoparticles. Although both Sb3+ and Sn2+ belong to the ns2-type emission center, the Sb3+-doped 60ZnO40P2O5 glass showed an emission with a weaker intensity and a broader band than Sn2+-doped 60ZnO40P2O5 glass. The emission decay of 1.0SbO3/260ZnO40P2O5 glass was about 2.5 similar to mu s, which was shorter than that of 1.0SnO60ZnO40P2O5 glass. The obtained results suggest that the emission properties of ns2-type emission centers depend on several factors, such as element of emission center, chemical composition, and preparation scheme, which are easily and widely tuned in random amorphous materials.
Soft-phonon mode observation in Li2Ge4O9 phase above room temperature 査読有り

Yoshihiro Takahashi, Jun Kunitomo, Kensaku Nakamura, Minoru Osada, Takumi Fujiwara

APPLIED PHYSICS LETTERS　100　(9)　091902/1-091902/3　2012年2月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3688603 　

ISSN：0003-6951

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Li2Ge4O9 is known to be a ferroelectric phase with Curie temperature at T-c similar to -93 degrees C. In this study, we found both the lowest-frequency phonon and heat-capacity anomalies around 100 degrees C in the Li2Ge4O9 phase, demonstrating their presence in the structural phase-transition. The phase transition is probably triggered by regularization of distorted GeO6 octahedra in the paraelectric phase, resulting in another phase consisting of the regular octahedral GeO6 unit, which was supported by in situ measurement of emission of E-2 -> (4)A(2) transition in the Mn4+-doped phase. It is deduced that the phase transition is more dynamic than ferroelectric phase-transition originating in ordering of the Li ions. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3688603]
Fabrication of Sn-doped zinc phosphate glass using a platinum crucible 査読有り

Hirokazu Masai, Toshiro Tanimoto, Takumi Fujiwara, Syuji Matsumoto, Yoshihiro Takahashi, Yomei Tokuda, Toshinobu Yoko

JOURNAL OF NON-CRYSTALLINE SOLIDS　358　(2)　265-269　2012年1月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.jnoncrysol.2011.09.025 　

ISSN：0022-3093

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The authors investigate the structural change of a ZnO-P(2)O(5) sintered matrix for the preparation of SnO-doped zinc phosphate (SZP) glass using a platinum crucible. Heat treatment of zinc oxide and ammonium phosphate at 800 degrees C causes the formation of a Zn(2)P(2)O(7)-like species, which is effective in preventing damage to the platinum crucible. Although the thermal property of the glass was affected by added Al(2)O(3), Al(2)O(3) hardly affects the quantum efficiency of the SZP glass phosphor. This process is important for the fabrication of contamination-free phosphate glass using ammonium phosphate as a starting material. (C) 2011 Elsevier B.V. All rights reserved.
Fabrication of Sn-doped zinc phosphate glass using a platinum crucible 査読有り

Hirokazu Masai, Toshiro Tanimoto, Takumi Fujiwara, Syuji Matsumoto, Yoshihiro Takahashi, Yomei Tokuda, Toshinobu Yoko

JOURNAL OF NON-CRYSTALLINE SOLIDS　358　(2)　265-269　2012年1月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.jnoncrysol.2011.09.025 　

ISSN：0022-3093

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The authors investigate the structural change of a ZnO-P(2)O(5) sintered matrix for the preparation of SnO-doped zinc phosphate (SZP) glass using a platinum crucible. Heat treatment of zinc oxide and ammonium phosphate at 800 degrees C causes the formation of a Zn(2)P(2)O(7)-like species, which is effective in preventing damage to the platinum crucible. Although the thermal property of the glass was affected by added Al(2)O(3), Al(2)O(3) hardly affects the quantum efficiency of the SZP glass phosphor. This process is important for the fabrication of contamination-free phosphate glass using ammonium phosphate as a starting material. (C) 2011 Elsevier B.V. All rights reserved.
Photoluminescence in mineral-derived titanosilicates with various Ti-polyhedral types for rare-earth free phosphor 査読有り

Yoshihiro Takahashi, Kenichiro Iwasaki, Takumi Fujiwara

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 12　9　(12)　2336-2339　2012年
出版者・発行元：WILEY-V C H VERLAG GMBH
DOI： 10.1002/pssc.201200270 　

ISSN：1862-6351

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Usually, phosphor is composed by host crystal and doped rare-earth ion which is an efficient luminescent centre. However, rare-earth elements have considerably small Clarke number and are produced from specific area. Since titanate and silicate minerals are relatively deposited in the earth's crust, we focused on titanosilicate mineral with excellent phololuminescent activity, e. g., benitoite and fresnoite. In this article, our recent results about synthesis of mineral-related Ti-including silicates and their PL property are introduced as a brief review. The origin and mechanism of the phololuminescent properties are also described. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Precipitation of ZnO in Al2O3-doped zinc borate glass ceramics 査読有り

Hirokazu Masai, Takahiro Ueno, Yoshihiro Takahashi, Takumi Fujiwara

OPTICAL MATERIALS　33　(12)　1980-1983　2011年10月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.optmat.2011.03.051 　

ISSN：0925-3467

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Crystallization behavior of the oxide semiconductor ZnO in zinc borate glass was investigated. The precipitated crystalline phase of glass ceramics containing a small amount of Al2O3 was alpha-Zn3B2O6 whereas that of the glass ceramics containing a large amount of Al2O3 was ZnO. It was found that the c-oriented precipitation of ZnO in a glass ceramic was brought about by the in-plane crystal growth of needle-like ZnO crystallites along the a-axis. Amount of Al2O3 that can make glass network affected the coordination state of B2O3 in the glass, and a three-coordinated BO3 unit was preferentially formed in the glass containing a higher amount of Al2O3. The present results suggest that crystallization of ZnO from multi-component glass is dominated by the local coordination state of the mother glass. (C) 2011 Elsevier B.V. All rights reserved.
High efficient white light emission of rare earth-free MnO-SnO-ZnO-P2O5 glass 査読有り

Hirokazu Masai, Takumi Fujiwara, Syuji Matsumoto, Yoshihiro Takahashi, Kenichiro Iwasaki, Yomei Tokuda, Toshinobu Yoko

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　119　(1394)　726-730　2011年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.119.726 　

ISSN：1882-0743

eISSN：1348-6535

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White light emission of rare earth (RE)-free Mn-doped SnO-ZnO-P2O5 glass is demonstrated. Glass transition temperature of the obtained glass is below 440 degrees C, which assures the application to sealant of solid state light emitting devices. The RE-free transparent glass shows white light emission with a high value of quantum efficiency (QE) comparable to conventional crystalline phosphor by excitation of deep UV light. The broad emission of RE-free transparent glass can be continuously tuned by both the amount of activator and the composition of the glass without decrease of the QE value. (C)2011 The Ceramic Society of Japan. All rights reserved.
Fabrication of Sr0.5Ba0.5Nb2O6-precipitated microstructured ceramics for photocatalytic application 査読有り

Kazuki Yoshida, Hirokazu Masai, Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　119　(1394)　731-735　2011年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.119.731 　

ISSN：1882-0743

eISSN：1348-6535

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We have succeeded in preparing Sr0.5Ba0.5Nb2O6 (SBN50)-precipitated ceramics by acid etching via a glass-ceramic process using SrO-BaO-Nb2O5-B2O3-ZnO-SiO2 glasses. Although the mother glass has good resistance to acid etching, the phase separated glass-ceramic, obtained by crystallization was easily etched. This phase separation process was favorable for removing the amorphous B2O3-ZnO phase and a superfluous crystalline phase. Addition of SiO2, substituted for B2O3, was effective for maintaining the bulk structure of the SBN50-etched ceramic because of its ability to form a strong and chemically stable network. We have found that the SBN50-precipitated ceramic demonstrates photocatalytic activity, which is the first report on the activity of SBN50. (C)2011 The Ceramic Society of Japan. All rights reserved.
Surface crystallization of Fresnoite-type crystallized glasses with large thickness 査読有り

Yoshiki Yamazaki, Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　119　(1394)　757-762　2011年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.119.757 　

ISSN：1882-0743

eISSN：1348-6535

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Transparent crystallized glass with a surface crystallization layer of sub-millimeter thickness was found in the glass compositions of 35BaO-15TiO(2)-50GeO(2) (BTG50), 28BaO-18TiO(2)-54SiO(2) (BTS54), and 35SrO-20TiO(2)-45SiO(2) (STS45), and the precipitated fresnoite-type crystalline phase showed nonlinear optical properties. XRD measurements confirmed that BTS54 and STS45 crystallized glasses precipitate as a single phase of the fresnoite-type crystallites Ba2TiSi2O8 and Sr2TiSi2O8, respectively. On the other hand, BTG50 crystallized glass precipitated two phases with mainly fresnoite-type BTG, Ba2TiGe2O8 and BaGe4O9. The results of the OD analysis of STS45 crystallized glass demonstrated high crystal orientation in the (002) direction from the glass surface. (C)2011 The Ceramic Society of Japan. All rights reserved.
High-Energy Shift of Boson Peak and Its Broadening in Crystallization Regime: A Qualitative Aspect 査読有り

Yoshihiro Takahashi, Minoru Osada, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN　80　(9)　095003/1-095003/2　2011年9月
出版者・発行元：PHYSICAL SOC JAPAN
DOI： 10.1143/JPSJ.80.095003 　

ISSN：0031-9015
White light emission of Mn-doped SnO-ZnO-P2O5 glass containing no rare earth cation 査読有り

Hirokazu Masai, Takumi Fujiwara, Syuji Matsumoto, Yoshihiro Takahashi, Kenichiro Iwasaki, Yomei Tokuda, Toshinobu Yoko

OPTICS LETTERS　36　(15)　2868-2870　2011年8月
出版者・発行元：OPTICAL SOC AMER
DOI： 10.1364/OL.36.002868 　

ISSN：0146-9592

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The authors have demonstrated white light emission of rare earth (RE)-free Mn-doped SnO-ZnO-P2O5 glass. The RE-free glass shows white light emission with a high value of quantum efficiency (QE) comparable to conventional crystalline phosphor. It is notable that the high QE value is attained for RE-free transparent glass, and the broad emission can be continuously tuned by both the amount of activator and the composition of the glass. Since this glass possesses low-melting property, we emphasize that the glass phosphor will lead to the development of a novel inorganic white-light-emitting device in combination with a solid state UV light-emitting source. (C) 2011 Optical Society of America
Correlation between Surface-Crystallized ZnO and the Amount of Al2O3 in Borate-Based Glass-Ceramics 査読有り

Hirokazu Masai, Takahiro Ueno, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF THE AMERICAN CERAMIC SOCIETY　94　(8)　2452-2457　2011年8月
出版者・発行元：WILEY-BLACKWELL
DOI： 10.1111/j.1551-2916.2011.04604.x 　

ISSN：0002-7820

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The correlation between the Al2O3 content and the crystallization behavior of the oxide semiconductor ZnO in 5CaO-25B(2)O(3)-45ZnO-xAl(2)O(3)-10K(2)O-15SiO(2) (CaBZAKSx) glass-ceramics was investigated, with a particular focus on the c-oriented crystallization behavior of ZnO. C-oriented precipitation of ZnO crystallites in glass-ceramics is brought about by the in-plane crystal growth of ZnO along the a-axis. Addition of Al2O3 promotes the formation of ZnO4 rather than ZnO6 in the mother glass, and the ZnO4 unit affects the nucleation and selective crystallization of ZnO that also takes the four-coordination state of Zn. The present results suggest that crystallization of ZnO from multi-component glass is also dominated by the local coordination state of the mother glass.
Green-emissive Mn-activated nanocrystallized glass with willemite-type Zn2GeO4 査読有り

Yoshihiro Takahashi, Masataka Ando, Rie Ihara, Takumi Fujiwara

Optical Materials Express　1　(3)　372-378　2011年7月1日

DOI： 10.1364/OME.1.000372 　

ISSN：2159-3930

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We fabricated Mn2+-activated nanocrystallized glasses (NCG) with willemite-type Zn2GeO4 from a zincogermanate system glass added by various MnO-concentrations, and examined their photoluminescence (PL) properties. The Mn2+-activated NCGs indicated bright green-emission based on the 4T1→6A1 transition of the Mn2+, indicating exclusive Mn2+-occupation of Zn site in the Zn2GeO4 nanocrystals. In addition, green long-lasting photoluminescence (LLP) was also observed in the NCGs with low MnO-concentration. Relation between the MnO-concentration and the LLP property was also considered. © 2011 Optical Society of America.
In situ Observation of Supercooled Liquid–Crystal Phase Transition in Glassy Ferroelectric LaBGeO5 査読有り

Y. Takahashi, T. Yasuoka, M. Osada, R. Ihara, T. Fujiwara

Japanese Journal of Applied Physics　50　(6)　068002/1-068002/2　2011年6月
出版者・発行元：None
DOI： 10.1143/JJAP.50.068002 　

ISSN：0021-4922
Low-frequency inelastic light scattering of zincogermanate glass in supercooledliquid regime 査読有り

Yoshihiro Takahashi, Minoru Osada, Masataka Ando, Rie Ihara, Takumi Fujiwara

JOURNAL OF APPLIED PHYSICS　109　(12)　126105/1-126105/3　2011年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3602085 　

ISSN：0021-8979

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We performed in situ observation of low-frequency inelastic light scattering in a zincogermanate glass showing nanocrystallization of semiconductive Zn(2)GeO(4) to elucidate the crystallization and phase transformation dynamics. In supercooledliquid state, an anomalous damping behavior of Boson peak was observed as the elastic softening happened. Combination of Boson and TEM studies revealed that the Boson damping is due to the liquid-liquid phase separation, which occurs prior to nanocrystallization, suggesting possibility of in situ spectroscopic observation of phase separation. (C) 2011 American Institute of Physics. [doi:10.1063/1.3602085]
Formation of Zn defects in willemite-type Zn2GeO4 during supercooled liquid-crystal phase transition 査読有り

Yoshihiro Takahashi, Masataka Ando, Rie Ihara, Takumi Fujiwara

APPLIED PHYSICS LETTERS　98　(22)　221907/1-221907/3　2011年5月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3597300 　

ISSN：0003-6951

eISSN：1077-3118

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This letter elucidates the formation mechanism of interstitial Zn defects in wide band-gap semiconductive willemite-type Zn2GeO4 via nanocrystallization in a zincogermanate glass. The results of time-development structural observations suggest that Zn2GeO4 nanocrystals precipitate in the nanometric Zn-condensed region, which occurs prior to nanocrystallization. The Zn-condensed environment probably promotes the capture of Zn ions in the interstitial sites of the Zn2GeO4 structure during the structural ordering of the supercooled liquid phase. The Zn-condensation mechanism is also discussed. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3597300]
Crystallization and Morphology of Glassy Sanbornite 査読有り

Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara, Minoru Osada

ELECTROCERAMICS IN JAPAN XIV　485　301-+　2011年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM.485.301 　

ISSN：1013-9826

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We investigated the crystallization and resulting morphology of a stoichiometric barium-silicate glass 1BaO-2SiO(2) (glassy sanbornite) by using transmission electron microscope and Raman spectroscopy. A crystalline aggregate structure consisting of a Ba5Si8O21 phase (trunk) and a beta-BaSi2O5 phase (branch) was observed in the heat-treated glassy sanbornite. The Ba-richer phase of Ba5Si8O21 precipitated prior to the formation of the stoichiometric beta-BaSi2O5 phase, suggesting the presence of the region in which the Ba ions are enriched or cohesively distributed. A considerable structural similarity between the glassy sanbornite and the Ba5Si8O21 phase was also suggested in this study.
Chemical compositions and crystallization behavior of BaO-TiO2-GeO2 Glass 査読有り

Yoshiki Yamazaki, Yoshihiro Takahashi, Rie Ihara, Takumi Fujiwara

ELECTROCERAMICS IN JAPAN XIV　485　317-320　2011年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM.485.317 　

ISSN：1013-9826

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We prepared glasses in 30BaO-(15+x)TiO2-(55-x)GeO2 composition (x=0, 10, 20, 35) and examined their crystallization behavior. Relation of crystallizing-phase to optical transparency in the resulting crystallized sample was also considered. Although the glass samples with x=0-20, which precipitate fresnoite-type Ba2TiGe2O8 as main phase, lost transparency after crystallization, the glass with x=30, which precipitates BaTi4O9 phase, kept good transparency. Dependence of transparency on the x is also discussed.
Fabrication and photoluminescent property of transparent nanocrystallized-glass in Li2O-ZnO-GeO2 system 査読有り

M. Ando, Y. Takahashi, K. Iwasaki, H. Masai, R. Ihara, T. Fujiwara

IOP Conference Series: Materials Science and Engineering　18　(8)　112002/1-112002/4　2011年

DOI： 10.1088/1757-899X/18/11/112002 　

ISSN：1757-8981 1757-899X

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We investigated crystallization behaviour of several glasses in ternary Li2O-ZnO-GeO2 system in order to fabricate the glass-ceramics consisting of Zn-related compound showing photoluminescent property. Nanocrystallized glass with willemite-type Zn2GeO 4 could be prepared from the 15Li2O-15ZnO-70GeO 2 glass, and revealed a long-lasting photoluminescence (LLP). Origin of the LLP in the nanocrystallized glass is also discussed. © 2011 Ceramic Society of Japan.
Nucleation and nanometric inhomogeneity in niobiogermanate glass: In-situ inelastic light scattering and tem studies 査読有り

Y. Takahashi, M. Osada, H. Masai, R. Ihara, T. Fujiwara

IOP Conference Series: Materials Science and Engineering　18　(8)　112009/1-112009/4　2011年

DOI： 10.1088/1757-899X/18/11/112009 　

ISSN：1757-8981 1757-899X

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We performed in-situ inelastic light scattering measurement in KNbGeO 5 glass with a high nucleation ability during heating in order to elucidate nanocrystallization dynamics. The results of the in-situ measurement and TEM observation revealed that nanometric heterogeneous region (∼1-2 nm) consisting of the Nb-richer phase develops, i.e., K3Nb 7O19, at the temperature, in which glassy-supercooled- liquid (SCL) phase-transition occurs, i.e., precursive stage of nanocrystallization. This strongly suggests that evolution of the nanometric Nb-richer phase in the SCL phase corresponds to nucleation in the KNbGeO 5 glass. © 2011 Ceramic Society of Japan.
Surface crystallization of CaO–Bi2O3–B2O3–Al2O3–TiO2 glass using IR furnace 査読有り

H. Masai, E. Kanamori, Y. Takahashi, T. Fujiwara

Journal of Non-Crystalline Solids　356　(52-54)　2977-2979　2010年12月
出版者・発行元：None
DOI： 10.1016/j.jnoncrysol.2010.03.046 　

ISSN：0022-3093
TEM and in situ Raman studies in glassy sanbornite: An insight intonucleation trend and its relation to structural variation 査読有り

Y. Takahashi, M. Osada, H. Masai, T. Fujiwara

Journal of Applied Physics　108　063507/1-063507/5　2010年11月
Crystallization of tungstenbronze-type Ba2NaNb5O15 in high-Nb2O5-content glass: An inelastic light scattering study 査読有り

Yoshihiro Takahashi, Nobuhiro Fujie, Minoru Osada, Hirokazu Masai, Rie Ihara, Takumi Fujiwara

JOURNAL OF APPLIED PHYSICS　108　(10)　103519/1-103519/5　2010年11月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3512909 　

ISSN：0021-8979

eISSN：1089-7550

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In situ observations of phonon Raman and Boson scattering were performed in high-Nb2O5-content barium-sodium aluminophosphate glass, which crystallizes tungstenbronze-type Ba2NaNb5O15 (BNN), during heating and subsequent cooling processes in order to examine the BNN crystallization dynamics and phase transitions. It is suggested that NbO6 clusters/cohesive regions are present and are subjected to stress by the surrounding aluminophosphate network prior to crystallization of the BNN phase. Furthermore, in the cooling period, a successive phase transition (4/mmm -> 4mm -> mm2) of the BNN phase was observed in the glass-ceramics, implying the possibility of producing functional glass-ceramics with ferroelastic properties. (C) 2010 American Institute of Physics. [doi:10.1063/1.3512909]
Fabrication of Bi-free TiO2 nano-crystallized glass 査読有り

Hirokazu Masai, Tatsuya Toda, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF NON-CRYSTALLINE SOLIDS　356　(44-49)　2674-2676　2010年10月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.jnoncrysol.2010.04.047 　

ISSN：0022-3093

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Fabrication of Bi-free transparent TiO2 glass-ceramics was attained by substitution a mixture of alkaline earth oxide and ZnO for Bi2O3. It is suggested that ZnO, which can play a role of both intermediate and network modifier, is important for the substitution. Observed particle size of precipitated anatase in the glass-ceramics was several nanometers enough to possess high transparency. It was found that diffraction intensity of metastable anatase in XRD patterns of glass-ceramics increases with increasing ZnO-concentration with heat-treatment at T-g + 50 K. The obtained results show that substitution of Bi2O3 by thermodynamic approach is effective for glass materials as well as glass-ceramics. (C) 2010 Elsevier B.V. All rights reserved.
Fabrication of surface crystallized glasses with α-Zn3B2O6 and their optical property 査読有り

H. Masai, T. Ueno, Y. Takahashi, T. Fujiwara

Journal of Non-Crystalline Solids　356　(44-49)　2689-2692　2010年10月
出版者・発行元：None
DOI： 10.1016/j.jnoncrysol.2010.04.046 　

ISSN：0022-3093
Formation of spherulite and metastable phase in stoichiometric Ba2Si3O8 glass 査読有り

Yoshihiro Takahashi, Hirokazu Masai, Minoru Osada, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　118　(1382)　955-958　2010年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.118.955 　

ISSN：1882-0743

eISSN：1348-6535

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We investigated the crystallization and resulting morphology of a stoichiometric barium-silicate glass Ba2Si3O8 (B2S3) using TEM observation and Raman spectroscopy. Spherical crystal growth (i.e., spherulite) of stoichiometric B2S3 phase was observed in the heat-treated glass samples, and the size of the spherulites drastically increased as the temperature increased during the heat-treatment process. It was also found that an initial precipitating phase in the precursive stage of crystallization is neither the B2S3 phase nor other crystalline phases in the BaO-SiO2 system. It was deduced that a metastable phase precipitates prior to the formation of spherulite and acts as nucleation site for the spherulite. (C) 2010 The Ceramic Society of Japan. All rights reserved
Inelastic light scattering from nanocrystallizing niobiotellurite glass: an insight into the metastable phase and phase-transformation dynamics 査読有り

Yoshihiro Takahashi, Naoki Iwafuchi, Minoru Osada, Hirokazu Masai, Rie Ihara, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　118　(1381)　814-818　2010年9月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.118.814 　

ISSN：1882-0743

eISSN：1348-6535

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In situ observations of inelastic light scattering of Raman and Boson regions were performed in nanocrystallized 15K(2)O-15Nb(2)O(5)-70TeO(2) glass to investigate nanocrystallization dynamics during the heating process. These in situ observations revealed a drastic structural rearrangement during the evolution of metastable K[Nb1/3Te2/3](2)O-4.8 nanocrystals. It is suggested that the distortion of the octahedral NbO6 unit being released in the glassy phase is the key to nanocrystallization. (C) 2010 The Ceramic Society of Japan. All rights reserved.
High Photoluminescent Property of Low-Melting Sn-Doped Phosphate Glass 査読有り

Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Syuji Matsumoto, Toshinobu Yoko

APPLIED PHYSICS EXPRESS　3　(8)　082102/1-082102/3　2010年8月
出版者・発行元：JAPAN SOC APPLIED PHYSICS
DOI： 10.1143/APEX.3.082102 　

ISSN：1882-0778

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The authors report on the quantum efficiency (QE) of UV-excited photoluminescence measured in SnO-ZnO-P(2)O(5) glass developed as rare earth (RE)-free material for light emitting diode (LED) applications, we report what is, to the best of our knowledge, the highest value of QE ever reported It is notable that the QE value of the present RE-free glass (similar to 90%) is comparable to that of RE-doped glass For future LED applications, we have emphasized that the low-melting glass will be one of the most industrially favorable inorganic materials to replace organic sealants that suffer degradation by strong LED irradiation (C) 2010 The Japan Society of Applied Physics
Defect activation in willemite-type Zn2GeO4 by nanocrystallization 査読有り

Yoshihiro Takahashi, Masataka Ando, Kenichiro Iwasaki, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS LETTERS　97　(7)　071906/1-071906/3　2010年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3481081 　

ISSN：0003-6951

eISSN：1077-3118

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We demonstrated the selective introduction of interstitial Zn defects (Zn-i(center dot)) into willemite-type semiconductive Zn2GeO4 by nanocrystallization of 15Li(2)O-15ZnO-70GeO(2) glass. The resulting nanocrystallized glass consisting of Zn2GeO4 exhibited a long-lasting photoluminescence (LLP). It is suggested that the Zn-i(center dot) is produced by capturing a zinc ion through six-membered rings of the Zn2GeO4 phase during nanocrystallization and the excess Zn-i(center dot) acts as an electron trap for the LLP. This defect activation through nanocrystallization is a promising new approach to functionalization. (C) 2010 American Institute of Physics. [doi:10.1063/1.3481081]
Precipitation of heterogeneous nanostructures: Metal nanoparticles and dielectric nanocrystallites 査読有り

Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Yomei Tokuda, Toshinobu Yoko

JOURNAL OF APPLIED PHYSICS　108　(2)　023503/1-023503/4　2010年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3457790 　

ISSN：0021-8979

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Heterogeneous precipitation of nanocrystallites of metallic Bi and anatase was observed in CaO-Bi(2)O(3)-B(2)O(3)-Al(2)O(3)-TiO(2) glass-ceramics. Addition of AlN reduced the Bi(2)O(3) to Bi metal nanoparticles, which were uniformly dispersed in the glass. After heat-treatment of the Bi-precipitated glass around the glass transition temperature, nanocrystalline anatase precipitated out without aggregation of the Bi metal particles. It was found that the anatase nanocrystal size was affected by the distance between a nanocrystal and a precipitated Bi nanoparticle. The glass-ceramic produced is a functional material containing a random dispersion of different types of nanoparticles with different dielectric constants. (C) 2010 American Institute of Physics. [doi:10.1063/1.3457790]
Second harmonic generation in periodically polarity-inverted zinc oxide 査読有り

Jinsub Park, Yayo Yamazaki, Masanobu Iwanaga, Heonsu Jeon, Takumi Fujiwara, Takafumi Yao

OPTICS EXPRESS　18　(8)　7851-7856　2010年4月
出版者・発行元：OPTICAL SOC AMER
DOI： 10.1364/OE.18.007851 　

ISSN：1094-4087

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We report on the second harmonic generation (SHG) in 2D periodically polarity-inverted (PPI) ZnO heterostructures. The grating structures with nanometer-scale periodicity are fabricated on (0001) Al2O3 substrates by using the in situ polarity inversion method. The achievements of SHG with grating in fabricated PPI ZnO structures are demonstrated under consideration of quasi phase matching conditions. In general, grating formation using the this periodical array of differnet polar surface can be extended to the other heteroepitaxial systems with polarity characteristics. (C) 2010 Optical Society of America
Crystal polarity control of ZnO films and nonlinear optical response 査読有り

J. Park, Y. Yamazaki, Y. Takahashi, T. Minegishi, S. H. Park, S. K. Hong, J. H. Chang, T. Fujiwara, T. Yao

Materials Research Society Symposium Proceedings　1201　185-195　2010年3月
Processing and photoluminescence properties of surface crystallized ZnO glass-ceramics 査読有り

H. Masai, T. Ueno, T. Toda, Y. Takahashi, T. Fujiwara

Journal of Non-Crystalline Solids　356　(52-54)　3080-3084　2010年

DOI： 10.1016/j.jnoncrysol.2010.04.055 　
Crystallization and Raman Spectra of Langasite-Type Na2CaGe6O14, Na2SrGe6O14 and Pb3Ga2Ge4O14 in Corresponding Glasses 査読有り

Yoshihiro Takahashi, Takumi Fujiwara, Yasuhiko Benino, Takayuki Komatsu

ASIAN CERAMIC SCIENCE FOR ELECTRONICS III AND ELECTROCERAMICS IN JAPAN XII　421-422　213-+　2010年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM.421-422.213 　

ISSN：1013-9826

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We investigated the crystallization behavior of langasite-type phases in the stoichiometric corresponding glasses, i.e., Na2CaGe6O14, Na2SrGe6O14 and Pb3Ga2Ge4O14. The langasite-type phases singly were formed by heat-treatment in the glasses. Raman spectroscopy revealed the structural similarity on the Scale of short-/medium-range order between the langasite-type phases and the corresponding glasses. Furthermore, we also examined the temperature dependence of second-harmonic (SH) intensity of the langasite-type phases. The SH-temperature curves exhibited an anomalous behavior, implying a structural change, e.g., isomorphous phase transition.
Electro-optic measurement in glass ceramics with highly oriented crystalline layers 査読有り

N. Iwafuchi, M. Hirokazu, Y. Takahashi, T. Fujiwara

ELECTRONICS LETTERS　46　(1)　69-70　2010年1月
出版者・発行元：INST ENGINEERING TECHNOLOGY-IET
DOI： 10.1049/el.2010.1386 　

ISSN：0013-5194

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Liner electro-optic (EO) constants r(13) and r(33), have been investigated in 30BaO-20TiO(2)-50SiO(2) glass ceramics with oriented crystalline layers using a Mach-Zehnder interferometer at 0.633 mm wavelength. The EO constants have been measured at 10-1000 Hz frequency of the applied voltage, and typical values of r(13) and r(33) at 100 Hz are 3.15+/-0.04 and 1.00+/-0.02 pm/V, respectively. It has been found that these values are approximately 58-64% in r(13) and 59% in r(33) compared with those in fresnoite single crystals.
Thermal property of BaO-TiO2-GeO2 glass and the crystallization behavior 査読有り

Yoshiki Yamazaki, Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara

ELECTROCERAMICS IN JAPAN XIII　445　179-182　2010年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM.445.179 　

ISSN：1013-9826

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Correlation between surface crystallization behavior of BaO-TiO2-GeO2 (BTG) glass and the thermal stability parameter measured by Differential Thermal Analysis (DTA) was examined. We have proposed normalized thermal stability Delta T-norm of the BTG glass using crystallization temperature (Tx), glass transition temperature (Tg), and melting temperature (Tm). It was found that surface crystallization occurred in the BTG glass possessing Delta T-norm (= (Tx-Tg)/Tm) value larger than 0.08. Compared Delta T-norm value of bulk state with that of powdered state, it has been revealed that Ba2TiGe2O8 was precipitated independently of thermal stabilities whereas BaTiGe3O9 or BaGe4O9 was precipitated in precursor glasses possessing high surface stability.
Photoluminescence in Bazirite Crystal by Addition of Impurity Ions 査読有り

Kenichiro Iwasaki, Yoshihiro Takahashi, Hirokazu Masai, Takumi Fujiwara

ELECTROCERAMICS IN JAPAN XIII　445　221-224　2010年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM445.221 　

ISSN：1013-9826

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We examined photoluminescent (PL) and afterglow properties in bazirite (BaZrSi3O9) phases with Sr2+-, Sn4+-, Ge4+-, and Ti4+-impurities, in order to elucidate effect of the impurity-addition on these properties. The bazirite phases studied showed blue PL and afterglow regardless of sort of the impurities. Origin of PL and afterglow emission in the bazirite phase is also discussed.
Low-Frequency Inelastic Light Scattering of Glassy Ba2TiGe2O8 During Heating Process 査読有り

Yoshihiro Takahashi, Hirokazu Masai, Takumi Fujiwara, Minoru Osada

ELECTROCERAMICS IN JAPAN XIII　445　225-+　2010年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM445.225 　

ISSN：1013-9826

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In-situ observation of inelastic light scattering of boson region in glassy Ba2TiGe2O8 (BTG) was performed during heating process. The in-situ boson observation revealed structural relaxation below glass-transition temperature in the as-quenched sample, suggesting the nanometric structural heterogeneity. Relation of the boson behavior to crystallization tendency is also discussed.
Correlation between near infrared emission and bismuth radical species of Bi2O3-containing aluminoborate glass 査読有り

Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Takenobu Suzuki, Yasutake Ohishi

JOURNAL OF APPLIED PHYSICS　106　(10)　103523/1-103523/5　2009年11月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3264631 　

ISSN：0021-8979

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A strong correlation between bismuth radical species and emission in the near infrared (NIR) region of SnO-doped bismuth-containing aluminoborate glass, (CaO-B2O3-Bi2O3-Al2O3-TiO2) (CaBBAT), was observed. Since the activation energy of the NIR emission was similar to that of electron spin resonance signal, it is expected that bismuth radical species in the CaBBAT glass is an origin of the NIR emission. Compared to the observed emission spectra with energy diagram of previous data, we have confirmed that bismuth ion possessing low valence is the origin of broad emission in the NIR region. (C) 2009 American Institute of Physics. [doi:10.1063/1.3264631]
Blue photoluminescence, greenish-blue afterglow and their Ti-concentration dependence in rare earth-free bazirite-type BaZr1-xTixSi3O9 査読有り

Kenichiro Iwasaki, Yoshihiro Takahashi, Hirokazu Masai, Takumi Fujiwara

Optics Express　17　18054-18062　2009年10月
Pulsed laser induced nanostructure and thermal properties of bismuth borate glass 査読有り

Hirotoshi Yasunaga, Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Takayuki Komatsu

GLASS TECHNOLOGY-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART A　50　(5)　288-292　2009年10月
出版者・発行元：SOC GLASS TECHNOLOGY
ISSN：1753-3546

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We have investigated the formation of nanostructure at the surface of 50Bi(2)O(3 center dot)50B(2)O(3) glass using XeCl pulsed laser irradiation with a heated support. The growth of a protuberant nanostructure was enhanced by either increasing the support temperature or the laser pulse repetition rate. It was found that the surface protuberances were amorphous with the same composition as the original glass, In order to discuss the relation between the temperature and the structural change, the Urbach rule was applied to analyse the optical absorption. As a result, we found that the effect of temperature was insufficient for crystallisation in the 50Bi(2)O(3 center dot)50B(2)O(3) glass. Considering the characteristics of the glass, it appears that dynamic randomness is independent of the morphology and only affects the phase change.
Influence of Sm2O3 doping on formation and structure of SrBi2Nb2O9 nanocrystals in lithium borate glasses 査読有り

B. Harihara Venkataraman, T. Fujiwara, K. B. R. Varma, T. Komatsu

MATERIALS CHEMISTRY AND PHYSICS　117　(1)　244-249　2009年9月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.matchemphys.2009.05.055 　

ISSN：0254-0584

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New glasses of 16.66SrO-16.66[(1-x)Bi2O3-xSm(2)O(3)]-16.66Nb(2)O(5)-50Li(2)B(4)O(7) (0 <= x <= 0.5, in molar ratio), i.e., the pseudo-binary Sm2O3-doped SrBi2Nb2O9-Li2B4O7 glass system, giving the crystallization of Sm3+-doped SrBi2Nb2O9 nanocrystals are developed. It is found that the thermal stability of the glasses against the crystallization and the optical band gap energy increases with increasing Sm2O3 content. The formation of fluorite-type Sm3+-doped SrBi2Nb2O9 nanocrystals (diameters: 13-37 nm) with a cubic structure is confirmed in the crystallized (530 degrees C, 3 h) samples from X-ray powder diffraction analyses, Raman scattering spectrum measurements, and transmission electron microscope observations. The effect of Sm3+-doping on the microstructure, Raman scattering peak positions, and dielectric properties of composites comprising of fluorite-type SrBi2Nb2O9 nanocrystals and the Li2B4O7 glassy phase is clarified. It is found that fluorite-type SrBi2Nb2O9 nanocrystals transform to stable perovskite-type SrBi2Nb2O9 crystals with an orthorhombic structure by heat treatments at around 630 degrees C. (c) 2009 Elsevier B.V. All rights reserved.
Nucleation tendency and crystallizing phase in silicate glasses: A structural aspect 査読有り

Yoshihiro Takahashi, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS LETTERS　95　(7)　071904/1-071904/3　2009年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3206931 　

ISSN：0003-6951

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We consider the relationship of nucleation tendency with crystallizing-phase structures in silicate glasses using glassy sanbornite (1BaO-2SiO(2)) that shows homogeneous nucleation resulting crystallization of Ba(5)Si(8)O(21) and beta-BaSi(2)O(5) phases with a layered structure of a network modifier and a network former. This trend is also confirmed in other silicate glasses with homogeneous nucleation tendency, which has been assessed by Zanotto and other researchers. It is suggested that the structural dimension of the crystallizing phase governs the nucleation tendency in silicate glasses.
Precursive stage of nanocrystallization in niobium oxide-containing glass 査読有り

Yoshihiro Takahashi, Hirokazu Masai, Minoru Osada, Takumi Fujiwara

APPLIED PHYSICS LETTERS　95　(7)　071909/1-071909/3　2009年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3211989 　

ISSN：0003-6951

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In situ observation of inelastic light scattering in Raman and Boson regions was performed in a niobiogermanate glass with a high nucleation ability during heating in order to examine its nanocrystallization dynamics. The relation of structural heterogeneity to the precursive stage of crystallization is also discussed. It is suggested that evolution of nuclei occurs in a nanometric niobate-rich region due to density fluctuation in the supercooled liquid phase prior to nanocrystallization.
Synthesis and characterization of rare-earth doped SrBi2Nb2O9 phase in lithium borate based nanocrystallized glasses 査読有り

B. Harihara Venkataraman, Takumi Fujiwara, Takayuki Komatsu

JOURNAL OF SOLID STATE CHEMISTRY　182　(6)　1538-1544　2009年6月
出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI： 10.1016/j.jssc.2009.04.004 　

ISSN：0022-4596

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Glass composites comprising of un-doped and samarium-doped SrBi2Nb2O9 nanocrystallites are fabricated in the glass system 16.66SrO-16.66[(1-x)Bi2O3-xSm(2)O(3)]-16.66Nb(2)O(5)-50Li(2)B(4)O(7) (0 <= x <= 0.5, in mol%) via the melt quenching technique. The glassy nature of the as-quenched samples is established by differential thermal analyses. Transmission electron microscopic studies reveal the presence of about 15 nm sized spherical crystallites of the fluorite-like SrBi1.9Sm0.1Nb2O9 phase in the samples heat treated at 530 degrees C. The formation of layered perovskite-type un-doped and samarium-doped SrBi2Nb2O9 nanocrystallites with an orthorhombic structure through the intermediate fluorite phase is confirmed by X-ray powder diffraction and micro-Raman spectroscopic studies. The influence of samarium doping on the lattice parameters, lattice distortions, and the Raman peak positions of SrBi2Nb2O9 perovskite phase is clarified. The dielectric constants of the perovskite SrBi2Nb2O9 and SrBi1.9Sm0.1Nb2O9 nanocrystals are relatively larger than those of the corresponding fluorite-like phase and the precursor glass. (C) 2009 Elsevier Inc. All rights reserved.
Origin of second-order nonlinear optical response of polarity-controlled ZnO films 査読有り

J. S. Park, Y. Yamazaki, Y. Takahashi, S. K. Hong, J. H. Chang, T. Fujiwara, T. Yao

APPLIED PHYSICS LETTERS　94　(23)　231118/1-231118/3　2009年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3152773 　

ISSN：0003-6951

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Polarity-controlled ZnO thin films grown on different buffer layers were investigated as nonlinear optical materials for second harmonic generation. The effective nonlinear optical coefficient (d(eff)) of ZnO grown on Cr-compound buffer layers showed a higher value than that of ZnO grown on MgO buffer layers. The correlations among the grain size and surface roughness with the values of d(eff) were found to be strong. The d(eff) of the ZnO film increased with decrease in the grain size and surface roughness. This relationship could be explained by the increase in reaction interface and the decrease in scattering probability at the surface as decrease in grain size and surface roughness, respectively.
Softer region at boundary of supercooled liquid–crystal in glassy fresnoite 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

Applied Physics Letters　94　(24)　241909/1-241909/3　2009年6月
出版者・発行元：None
DOI： 10.1063/1.3156025 　

ISSN：0003-6951
Crystallization and nanometric heterogeneity in glass: In situ observation of the boson peak during crystallization 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

PHYSICAL REVIEW B　79　(21)　214204/1-214204/5　2009年6月
出版者・発行元：AMER PHYSICAL SOC
DOI： 10.1103/PhysRevB.79.214204 　

ISSN：1098-0121

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In situ measurement of boson peak in several glasses was performed during the crystallization process to elucidate crystallization dynamics. In this study, it was experimentally illustrated that a drastic decrease in elasticity and damping of the boson peak occurred during the crystallization process when T/T(g)similar to 1.1-1.2. A possible mechanism for the crystallization precursive stage is also discussed, which integrates our boson peak observation results, Hikima's description [J. Mol. Struct. 479, 245 (1999)], Cabral's thermodynamic data [J. Non-Cryst. Solids 343, 85 (2004)], and other works.
Structural heterogeneity and homogeneous nucleation of 1BaO-2SiO(2) glass 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS LETTERS　94　(21)　211907/1-211907/3　2009年5月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3142394 　

ISSN：0003-6951

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Structural relaxation was examined by in situ Boson peak observation in 1BaO-2SiO(2) glass with homogeneous nucleation tendency, in order to clarify the structural heterogeneity. The relation between the glass structure in the medium-range scale and nucleation feature is also discussed. From the results, it is predicted that a sheet-like structure with a network modifier in the resulting crystal is an essential condition for homogeneous nucleation.
Correlation between the temperature of molten state and the SH intensity of 30BaO center dot 15TiO(2)center dot 55GeO(2) crystallized glass 査読有り

Hirokazu Masai, Yoshiyuki Suzuki, Yoshihiro Takahashi, Hiroshi Mori, Takumi Fujiwara, Takayuki Komatsu

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　117　(1365)　671-674　2009年5月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.117.671 　

ISSN：1882-0743

eISSN：1348-6535

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We have examined the dependence of the optical nonlinearity of the 30BaO center dot 15TiO(2)center dot 55GeO(2) (BTG55) crystallized glass on the temperature at which the BTG55 glass melts are held in a molten state (called the "melt temperature" in the present paper). The absorption coefficient and the refractive index of the BTG55 precursor glass, and the second harmonic efficiency of its crystallized glass increased with increasing melt temperature of the precursor glass. We have defined the local structure similar to that of a crystal, "embryos of crystallites", and the embryos are envisioned as the origin of precipitated Ba2TiGe2O8 crystallites. The second harmonic generation efficiency of the BTG55 crystallized glass increased with increasing melt temperature. This is explained as due to an increase of the number of embryos of Ba2TiGe2O8 crystallites with increasing melt temperature. (C) 2009 The Ceramic Society of Japan. All rights reserved.
Space-selectively crystallized fiber with second-order optical nonlinearity for variable optical attenuation 査読有り

Seiki Ohara, Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Yuki Kondo, Naoki Sugimoto

Optics Letters　34　(7)　1027-1029　2009年4月1日
出版者・発行元：Optical Society of America (OSA)
DOI： 10.1364/OL.34.001027 　

ISSN：1539-4794 0146-9592

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We have fabricated BaO-TiO2-GeO2-SiO 2-based glass fibers with the oriented space-selectively crystallized structure by laser irradiation and also demonstrated variable optical attenuation induced by electro- optical birefringence change based on second-order optical nonlinearity. The transmittance of a polarized signal is controlled by an electric field applied to the fiber, and the electro-optic fiber devices are operated with extremely low nanowatt electric power dissipation. © 2009 Optical Society of America.
Addition effect of SnO in optical property of Bi2O3-containing aluminoborate glass 査読有り

Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF APPLIED PHYSICS　105　(8)　083538/1-083538/4　2009年4月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3115472 　

ISSN：0021-8979

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We have found that an addition of SnO in a bismuth-containing aluminoborate glass, (CaO-B2O3-Bi2O3-Al2O3-TiO2) (CaBBAT), decreases both the optical absorption coefficient in the visible region and the relative intensity of x-ray photoelectron spectroscopy (XPS) signal at 157 eV. Since signal intensity of electron spin resonance (ESR) at g=1.95 also decreased with increasing amount of SnO, it is suggested that bismuth radical-like species exist in the glass and that SnO reacts with the bismuth species. Concentration dependence of SnO in the XPS and in the ESR spectra shows that we can assign the observed signal to bismuth radical species in the glass. We, therefore, conclude that there is qualitative correlation between the optical absorption in the visible region and bismuth radical species in the CaBBAT glass.
ZnO glass-ceramics: An alternative way to produce semiconductor materials 査読有り

Hirokazu Masai, Tatsuya Toda, Takahiro Ueno, Yoshihiro Takahashi, Takumi Fujiwara

APPLIED PHYSICS LETTERS　94　(15)　151908/1-151908/3　2009年4月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3120282 　

ISSN：0003-6951

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Fabrication of transparent glass-ceramics containing ZnO nanocrystallites has been reported. The obtained material shows UV-excited photoluminescence consisting of both broad emission in the visible region and the free exciton emission at 3.28 eV. Since the observed emission depends on the precipitated state of ZnO in the glass matrix, the glass-ceramics obtained by this way will give an alternative selection of semiconductor material with unique optical and electronic functions.
Fabrication of anatase precipitated glass-ceramics possessing high transparency 査読有り

Hirokazu Masai, Tatsuya Toda, Yoshihiro Takahashi, Takumi Fujiwara

APPLIED PHYSICS LETTERS　94　(15)　151910/1-151910/3　2009年4月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3117238 　

ISSN：0003-6951

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Transparent anatase precipitated glass-ceramics were fabricated using ZnO as a component. The particle size of precipitated anatase is several nanometers enough to possess high transparency. The preparation of the Bi-free transparent TiO(2) glass-ceramic was attained by substitution of two different kinds of oxides for bismuth oxide. It is also noteworthy that we have demonstrated the crystallization of metastable anatase in the glass-ceramics as a main phase. The present bulk anatase glass-ceramics will open up an application field for a TiO(2)-containing photocatalyst.
Optical characteristics of nanocrystallized glass fiber with second-order optical nonlinearity 査読有り

Naoki Iwafuchi, Takumi Fujiwara, Yasuhiko Benino, Takayuki Komatsu

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　117　(1362)　143-146　2009年2月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.117.143 　

ISSN：1882-0743

eISSN：1348-6535

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Second harmonic generation (SHG) and propagation loss have been measured on nanocrystallized optical fibers of tellurite-based glass, 15K(2)O center dot 15Nb(2)O(5)center dot 70TcO(2). The result of the angular dependence of the SHG intensity is discussed based on the difference in the transmission factor varying with the polarization direction. Propagation-loss measurements on the fiber samples by a cut-back method showed low loss compared with that of a typical LiNbO3 waveguide. (C) 2009 The Ceramic Society of Japan. All rights reserved.
Preparation of crystallized glass for application in fiber-type devices 査読有り

Hirokazu Masai, Naoki Iwafuchi, Yoshihiro Takahashi, Takumi Fujiwara, Seiki Ohara, Yuki Kondo, Naoki Sugimoto

JOURNAL OF MATERIALS RESEARCH　24　(1)　288-294　2009年1月
出版者・発行元：MATERIALS RESEARCH SOC
DOI： 10.1557/JMR.2009.0021 　

ISSN：0884-2914

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We have demonstrated that 30BaO-15TiO(2)-30GeO(2)-25SiO(2) (BTGS25) glass is it candidate for fiber-type nonlinear optical devices using crystallization of glass matrix. We determined the glass composition is suitable for crystallized fiber using partial substitution of Ge in 30BaO-15TiO(2)-55GeO(2) (BTG55) by Si. The BTGS25 satisfied both thermal stability for fiber drawing and electronic polarizability for nonlinear optical property. After crystallization, the BTGS25 bulk crystallized glass showed surface crystallization behavior with the polar c-orientation of fresnoite phase, which was favorable for large second-order optical susceptibility. Following the results of the bulk ass, we prepared the BTGS25 glass fiber without precipitation of fresnoite crystallites. The BTGS25 crystallized fiber also showed c-oriented surface crystallization of fresnoite and second harmonic generation, which shows that the crystallized fiber is a promising material for fiber-type optical active devices.
Crystallization Behavior of BaO-TiO2-GeO2 Glass Thin Film 査読有り

Ryoh Ogawa, Hirokazu Masai, Yoshihiro Takahashi, Hiroshi Mori, Takumi Fujiwara, Takayuki Komatsu

ELECTROCERAMICS IN JAPAN XI　388　149-+　2009年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/0-87849-359-x.149 　

ISSN：1013-9826

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Crystallization behavior of the fresnoite-type Ba2TiGe2O8 (BTG) with a large optical nonlinearity has been examined in the BaO-TiO2-GeO2 glass thin film fabricated by a RF sputtering technique and the corresponding glass (same composition of thin film, i.e., 28BaO-22TiO(2)-50GeO(2)). Both the glass thin film and the corresponding glass were crystallized by the heat-treatment, keeping a good transparency. Initial formation of BTG phase followed by the BaGe4O9 phase was confirmed in the both glass samples. In addition, the BTG crystallites in the both glass samples indicated the preferential (211) orientation. Crystallization behavior confirmed in this study was quite different from the previous study about the 30BaO-15TiO(2)-55GeO(2) glass.
Anomalous Boson Behavior and Nanometric Heterogeneity in Glassy Fresnoite 査読有り

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, Takumi Fujiwara

APPLIED PHYSICS EXPRESS　1　(12)　121901/1-121901/3　2008年12月
出版者・発行元：JAPAN SOCIETY APPLIED PHYSICS
DOI： 10.1143/APEX.1.121901 　

ISSN：1882-0778

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In-situ observation of the boson peak, omega(BP), Of as-quenched and annealed glassy Ba(2)TiGe(2)O(8) (BTG) and Ba(2)TiSi(2)O(8) (BTS) was performed during a heating process. Although annealed glassy BTG and BTS indicated a monotonous decrease in omega(BP) with temperature, the asquenched varieties, which included internal stress, revealed anomalous boson behavior at similar to 600 degrees C, lower than each one's glass-transition temperature. It was suggested that the omega(BP) anomaly was caused by beta-relaxation. This experimental result also supports the inhomogeneous structure (or cluster) model of glass. (C) 2008 The Japan Society of Applied Physics
Fabrication of BaO-TiO2-GeO2-SiO2 based glass fiber 査読有り

Seiki Ohara, Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Yuki Kondo, Naoki Sugimoto

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1358)　1083-1086　2008年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.1083 　

ISSN：1882-0743

eISSN：1348-6535

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The thermal properties of BaO-TiO2-GeO2-SiO2 based glasses have been investigated. The temperature differences, AT, between the crystallization onset temperature and glass transition temperature were over 95 degrees C. The wide range of AT enables the fabrication of practical fibers with a core/clad structure including partial crystallization. The rod-in-tube method was used for fabricating fiber preform, and the fiber drawing was successfully achieved. The double clad fiber with the core diameter of 6.5 mu m, the 1st clad diameter of 24.5 mu m, and the 2nd clad diameter of 125 mu m was obtained over 100 m in length. The propagation loss of the fiber was 1.8 dB/cm. The crystallization onset temperature of the 1st cladding is lower than other glasses, so that only the 1st cladding is selectively crystallized by post-heating for active devices. Furthermore, the 1st cladding contains CuO to assist heating by absorbing the energy of laser irradiation. Fusion splicing to the conventional silica fiber was also achieved, in spite of the different thermal properties of BTGS glass and silica glass, by precisely controlling the heating power and heating position of the fiber. The splicing loss with less than 1.5 dB per point was achieved. (C)2008 The Ceramic Society of Japan. All rights reserved.
Origin of photoluminescence in suzukiite-type BaTiSi2O7 査読有り

Yoshihiro Takahashi, Tomoya Konishi, Kohei Soga, Takumi Funwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1358)　1104-1107　2008年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.1104 　

ISSN：1882-0743

eISSN：1348-6535

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A barium titanosilicate, BaTiSi2O7, with suzukiite (BaVSi2O7)-type structure has a unique Ti-O unit, which consists of mirror-symmetrical TiO5 pyramids pair, and possesses a visible orange photoluminescence (PL) by an ultraviolet excitation at room temperature. However, the origin of orange PL has not been fully understood. Therefore, the purpose of this study is to elucidate the origin and mechanism of orange PL in suzukiite-type BaTiSi2O7. It has been proposed that two types of oxygen-defect in the pyramidal TiO5 unit pair contribute to the efficient orange PL, i.e., the extrinsic oxygen-vacancy due to the lack of oxygen in the TiO5 unit, and the intrinsic oxygen-vacancy, which exists in the TiO5 unit pair due to its structural peculiarity. (C)2008 The Ceramic Society of Japan. All rights reserved.
Comprehensive study of crystallization and phase formation in (La,Gd)BGeO5 glass 査読有り

Yoshihiro Takahashi, Yasuhiko Benino, Takutni Fujiwara, Takayttki Komatsu

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1358)　1108-1114　2008年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.1108 　

ISSN：1882-0743

eISSN：1348-6535

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The glasses with (25-x)La2O3 center dot xGd(2)O(3)center dot 25B(2)O(3)center dot 50GeO(2) composition corresponding to the (La,Gd)BGeO5 were prepared, and the substitution effect of gadolinium ions (Gd3+) on crystallization behavior and phase formation was examined by DTA, XRD and Raman techniques in detail. Ferroelectric (La,Gd)BGeO5 phase with hexagonal stillwellite structure were crystallized in the composition range of x = 0-15. Although no significant change in physical properties was observed in the whole composition range, crystallization behavior was drastically changed as the progressive substitution of Gd 3, was carried out (i.e., crystallization of monoclinic phase of (La,Gd)BGeO5 and high-pressure phase of Gd2Ge2O7 with a triclinic structure). Structure of the glasses and crystallized phases, and the phase formation mechanism were also discussed. (C)2008 The Ceramic Society of Japan. All rights reserved.
Crystallization behavior of optical fibers with multi layered structure for nonlinear optical devices 査読有り

Naoki Iwafuchi, Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Seiki Ohara, Yuki Kondo, Naoki Sugimoto

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1358)　1115-1120　2008年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.1115 　

ISSN：1882-0743

eISSN：1348-6535

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We examined the crystallization behavior of double clad fiber composed by BaO-TiO2-GeO2-SiO2 based glasses in detail. Formation of needle-like fresnoite-type Ba2Ti(Ge,Si)(2)O-8 were observed at the interface between the first and second clad. In addition, we employed the two-step heat-treatment (i.e., 728 degrees C, 20 h + 749 degrees C, 1 h) in fabrication of the crystallized fiber in order to obtain the highly-oriented fresnoite phase in the fiber structure. The first treating temperature, 728 degrees C, which gives the maximum nucleation rate, was determined by differential thermal analysis. It was demonstrated that the two-step heat-treatment was effective for improvement of the orientation of fresnoite-type phase in the first clad of the double clad fiber. (C)2008 The Ceramic Society of Japan. All rights reserved.
Formation of fresnoite-type BaO-TiO2-GeO2 glass thin Ba2TiGe2O8 crystallites in film and its optical nonlinearity 査読有り

Ryoh Ogawa, Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1358)　1130-1133　2008年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.1130 　

ISSN：1882-0743

eISSN：1348-6535

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We report on fabrication of the BaO-TiO2-GeO2 glass thin films on a fused silica substrate by RF sputtering, and investigation of the crystallization behavior, surface texture and the optical non-linearity in the glass thin film by means of AFM, XRD, Raman and Maker fringe techniques. Although the Ba2TiGe2O8, hereafter abbreviated to BTG, phase with second-order optical nonlinearity was mainly crystallized, the precipitation of the sub-phase of BaGe4O9 was also confirmed in the heat-treated glass thin films. In the glass thin film heat-treated at heat-treatment temperature (T-HT) = 730-750 degrees C, the (211) preferential orientation of BTG phase and an upheaval about 300-400 nm were confirmed at the surface. These transparent crystallized glass thin films indicated a clearly Maker fringe patterns, demonstrating a second-order optical nonlinearity, and the effective second-order nonlinear optical constant, d(eff), was estimated to be similar to 0.8 pm/V. (C)2008 The Ceramic Society of Japan. All rights reserved.
Raman spectroscopic study of benitoite-type compounds 査読有り

Yoshihiro Takahashi, Kettichiro Iwasaki, Hirokazu Masai, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1358)　1139-1142　2008年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.1139 　

ISSN：1882-0743

eISSN：1348-6535

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Raman scattering measurements were performed in the benitoite-type BaTiSi3O9, BaZrSi3O9, BaSnSi3O9 and tetragermanate-type BaGe4O9 phases in order to elucidate the spectroscopic and structural features of D(2/v)G(T3O9)-type compounds (expressed by Smith's notation) with the GO(6) octahedral unit isolated by the T3O9 ring. The Raman band assignments in middle and high wavenumber region wes also carried out. In addition, the wavenumber of antisymmetric stretching vibration mode, v(as), for Si-O-G bond was calculated by means of combination of the simple molecular model and Badger's rule, and compared with the experimental results. It was suggested that the v(as) was governed by the force constant of T-O-ax bond, which was connected with the G(4+). (C)2008 The Ceramic Society of Japan. All rights reserved.
Blue photoluminescence of germania-stabilized benitoite 査読有り

Yoshihiro Takahashi, Kenji Kitamura, Nobuo Iyi, Satoru Inoue, Takumi Fujiwara

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1358)　1143-1146　2008年10月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.1143 　

ISSN：1882-0743

eISSN：1348-6535

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Benitoite (BaTiSi3O9) phases, which were partially-substituted by germania (GeO2) in order to stabilize the phase, were synthesized, and their optical properties were examined. The benitoite phase was crystallized by a small quantity of Ge-introduction into the benitoite composition. Clear blue emission with the peak at similar to 430 nm, due to the transition of T-3(1) -> (1)A(1) in the TiO6 octahedra, was observed at room temperature during the ultraviolet excitation, being sufficient for a visual confirmation. On the other hand, the reduction in blue emission intensity by the Ge-introduction was confirmed. This was qualitatively explained on the basis of configurational-coordinate mode without discrepancy. (C)2008 The Ceramic Society of Japan. All rights reserved.
Effect of SnO addition on optical absorption of bismuth borate glass and photocatalytic property of the crystallized glass 査読有り

Hirokazu Masai, Takumi Fujiwara, Hiroshi Mori

APPLIED PHYSICS LETTERS　92　(14)　141902/1-141902/3　2008年4月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2903151 　

ISSN：0003-6951

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We have found that an addition of SnO in a bismuth-borate glass, CaO-B(2)O(3)-Bi(2)O(3)-Al(2)O(3)-TiO(2), decreases the optical absorption coefficient in the visible region, in which selective crystallization of TiO(2) was observed after heat treatment. Since selective crystallization of TiO(2) was also attained in the SnO-containing glass, the transparency of TiO(2) crystallized glass can be improved independently of selective crystallization of TiO(2). We have also demonstrated that the rutile-nanocrystallized glass with SnO addition shows a higher photocatalytic activity than the glass without SnO, indicating that this crystallized glass has a large potential for application as transparent photocatalytic materials. (C) 2008 American Institute of Physics.
Transparent nonlinear optical crystallized glass fibers with highly oriented Ba2TiGe2O8 crystals 査読有り

Yosuke Hane, Takayuki Komatsu, Yasuhiko Benino, Takumi Fujiwara

JOURNAL OF APPLIED PHYSICS　103　(6)　063512/1-063512/7　2008年3月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2890144 　

ISSN：0021-8979

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Glass fibers with a diameter of 100-200 mu m are drawn by just pulling up melts of 30BaO-15TiO(2)-55GeO(2) glass, and transparent crystallized glass fibers consisting of nonlinear optical Ba2TiGe2O8 crystals are fabricated by crystallization of glass fibers. It is clarified from linearly polarized micro-Raman scattering spectra that fibers show the surface crystallization and Ba2TiGe2O8 crystals grow from the surface to the interior, giving c-axis orientations. It is found that holes are formed frequently in the center of fully crystallized glass fibers, and transparent hollow crystallized glass fibers are fabricated through careful heat treatments, e. g., fibers with phi = 200 mu m show hollows (capillary-type holes) with phi= 40 mu m. By adding a small amount of Sb2O3 in glass fiber preparations, transparent crystallized glass fibers with no holes are developed and second harmonic generations (SHGs) are clearly observed from such fibers. The present study proposes that transparent crystallized glass fibers showing strong SHGs would have a potential for fiber-type light control optical devices. (c) 2008 American Institute of Physics.
Afterglow in synthetic bazirite, BaZrSi3O9 査読有り

Yoshihiro Takahashi, Hirokazu Masai, Takurni Fujiwara, Kenji Kitamura, Satoru Inoue

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　116　(1350)　357-360　2008年2月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj2.116.357 　

ISSN：1882-0743

eISSN：1348-6535

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A blue afterglow was observed in the bazirite-type BaZrSi3O9 synthesized by a solid-state reaction for the first time. The synthetic bazirite phase showed a clear blue long-lasting luminescence at room temperature after the exposure of UV light, in spite of the free from any lanthanide-doping. It was proposed that the afterglow in the BaZrSi3O9 phase was originated from the occupation of Ti4+ as an impurity in the distorted octahedral site.
Fabrication of metal nanocluster and nanoparticles in the CaO-Bi2O3-B2O3-Al2O3-TiO2 glass by irradiation of XeCl pulsed laser 査読有り

Hirokazu Masai, Shintaro Mizuno, Takumi Fujiwara, Hiroshi Mori, Takayuki Komatsu

OPTICS EXPRESS　16　(4)　2614-2620　2008年2月
出版者・発行元：OPTICAL SOC AMER
DOI： 10.1364/OE.16.002614 　

ISSN：1094-4087

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We report the fabrication of nanoparticles that contain metal nanoclusters at the surface of the CaO-B2O3-Bi2O3-Al2O3-TiO2 glass using XeCl laser irradiation. We have demonstrated that the surface morphology such as that containing nanoparticles or a smooth flat surface can be controlled by laser irradiation conditions; the laser fluence, repetition rate, and temperature of the glass. The transmission electron microscope (TEM) images of the cross section of the nanoparticles show that the metal nanoclusters were formed inside the nanoparticle by XeCl pulsed laser irradiation, a unique phenomenon different from TiO2-crystallization achieved by conventional heat-treatment of the glass. Since formation of nanoparticles containing metal nanocluster is a phenomenon different from previous papers about XeCl laser irradiation of oxide glasses, the combined process of pulsed laser irradiation and heat-treatment will open a wide variety of optical glass devices. (C) 2008 Optical Society of America.
Writing of crystal line patterns in glass by laser irradiation 査読有り

Tsuyoshi Honma, Rie Ihara, Yasuhiko Benino, Ryuji Sato, Takumi Fujiwara, Takayuki Komatsu

Journal of Non-Crystalline Solids　354　(43140)　468-471　2008年1月15日
出版者・発行元：Elsevier B.V.
DOI： 10.1016/j.jnoncrysol.2007.07.081 　
Variable Optical Attenuation using space-selectively crystallized fiber with second-order optical nonlinearity 査読有り

Seiki Ohara, Hirokazu Masai, Yoshihiro Takahashi, Takumi Fujiwara, Yuki Kondo, Naoki Sugimoto

2008 34TH EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC)　34　(PDP)　Th.3.C.5-1-Th.3.C.5-2　2008年
出版者・発行元：IEEE
DOI： 10.1109/ECOC.2008.4729561 　

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We have fabricated glass fibers with nonlinear crystalline phase in clad area by laser irradiation, and demonstrated variable optical attenuation by electro-optic effect using the space-selectively crystallized fiber.
Fabrication of Ba2TiGe2O8 thin film with optical nonlinearity 査読有り

Ryoh Ogawa, Hirokazu Masai, Yoshihiro Takahashi, Hiroshi Mori, Takumi Fujlwara, Takayuki Komatsu

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS　46　(10B)　7145-7147　2007年10月
出版者・発行元：INST PURE APPLIED PHYSICS
DOI： 10.1143/JJAP.46.7145 　

ISSN：0021-4922

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We have successfully fabricated a glass thin film in the BaO-TiO2-GeO2 system and a fresnoite-type Ba2TiGe2O8 (BTG) crystalline thin film with second-order optical nonlinearity for the first time. An as-deposited glass thin film showing good transparency and homogeneity could be formed on a fused silica substrate by RF sputtering with a 30BaO-15TiO(2)-55GeO(2) glass target. Subsequently, a transparent BTG-crystallized thin film could be obtained using proper heat-treatment conditions. Furthermore, a clear second-harmonic generation has been observed by the Maker fringe technique in the transparent BTGcrystallized thin films obtained by heat treatment at 730-750 degrees C for 3 h.
Structure and non-linear optical properties of BaO-TiO2-SiO2 glass containing Ba2TiSi2O8 crystal 査読有り

Hirokazu Masai, Shinji Tsuji, Takumi Fujiwara, Yasuhiko Benino, Takayuki Komatsu

JOURNAL OF NON-CRYSTALLINE SOLIDS　353　(22-23)　2258-2262　2007年7月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.jnoncrysol.2007.03.005 　

ISSN：0022-3093

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The BaO TiO2-Sio(2) crystallized glass containing Ba2TiSi2O8 crystal phase was examined using X-ray diffraction (XRD) measurement and Maker fringe technique. It has been found that the crystallized glasses with a composition of close to the stoichiometric Ba2TiSi2O8 showed bulk crystallization, whereas other crystallized glasses with non-stoichiometric composition of Ba2TiSi2O8 showed surface crystallization. The parameter AT, the difference in temperature between the crystallization onset and the glass transition temperature, strongly affects the crystallization behaviors of the present BTS glasses. The 30BaO-20TiO(2)-50SiO(2) transparent surface crystallized glass with strong c-oriented BaTiSi2O8 phase showed its second-order non-linear optical constant, d(33) = 6.1 pm/V. (c) 2007 Published by Elsevier B.V.
Dual layered surface crystallization of 30BaO-15TiO(2)-55GeO(2) glass by stepwise heat treatment 査読有り

Hirokazu Masai, Takumi Fujiwara, Hiroshi Mori, Yasuhiko Benino, Takayuki Komatsu

JOURNAL OF APPLIED PHYSICS　101　(12)　123505/1-123505/6　2007年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2743827 　

ISSN：0021-8979

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In the crystallization process of 30BaO-15TiO(2)-55GeO(2) (BTG55), we demonstrated by an x-ray diffraction analysis that a stepwise heat treatment enables a selective crystallization of fresnoite and benitoite, two crystalline phases obtained from the BTG55 mother glass and that these two phases form a dual surface layer. The result indicates that the stepwise heat treatment generates a compositional heterogeneity inside the glass matrix, which facilitates the nucleation of the fresnoite phase. The mechanism for the generation of the dual surface layer is discussed. Due to a marked difference in optical nonlinearity of the two phases, the selective crystallization may open the possibility of an optimized heat-treatment condition to achieve a large optical nonlinearity in crystallized glass. Also, two types of fresnoite, tetragonal and orthorhombic, were observed in the crystallized phase after a stepwise heat treatment of 690/720 degrees C. (c) 2007 American Institute of Physics.
Chemically etched sharpened tip of transparent crystallized glass fibers with Nonlinear optical Ba2TiSi2O8 nanocrystals 査読有り

Itaru Enomoto, Yasuhiko Benino, Takurni Fujiwara, Takayuki Komatsu

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　115　(1342)　374-378　2007年6月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj.115.374 　

ISSN：1882-0743

eISSN：1348-6535

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Glass fibers with a diameter of similar to 100 mu m are drawn by just pulling up melts of 40BaO center dot 20TiO(2)center dot 40SiO(2) glass, and transparent crystallized glass fibers consisting of nonlinear optical fresnoite Ba2TiSi2O8 nanocrystals (particle size: similar to 100-200 nm) are fabricated by crystallization of glass fibers. Precursor glass fibers and nanocrystallized glass fibers are etched chemically using a meniscus method, in which an etching solution of 0.1 wt%-HF/hexane is used. Glass fibers with sharpened tips (e.g., the taper length is similar to L = 200,mu m and the tip angle is similar to theta = 23 degrees) are obtained. It is found that etched nanocrystallized glass fibers also have sharpened tips (L = 50 mu m, theta = 80 degrees). Compared with precursor glass fibers, nanocrystallized glass fibers show a high resistance against chemical etching in a 0.1 wt%HF solution. Although sharpened tips in nanocrystallized glass fibers do not have nanoscaled apertures, the present study suggests that nanocrystallized glass fibers showing second harmonic generations would have a potential for fiber-type light control optical devices.
Creation of locally selective mirror surface on 40BaO-40TiO(2)-20B(2)O(3) glass by XeCl pulse laser irradiation 査読有り

Hirokazu Masai, Shintaro Mizuno, Takumi Fujiwara, Yasuhiko Benino, Takayuki Komatsu, Hiroshi Mori

JOURNAL OF MATERIALS RESEARCH　22　(5)　1270-1274　2007年5月
出版者・発行元：MATERIALS RESEARCH SOCIETY
DOI： 10.1557/JMR.2007.0175 　

ISSN：0884-2914

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Creation of mirror dots, localized areas of smooth surface with a shape of laser beam on a glass material, using a XeCl laser irradiation is reported. Laser irradiation of a 40BaO-40TiO(2)-20B(2)O(3) sample heated to 300 degrees C induced a smooth and flat surface, where no scratches caused by a mechanical polishing were observed. The present finding indicates that the melting of the surface occurred by the combined effect of the heat-assistance and the increased absorption coefficient of TiO2. In the present system, the absorption coefficient in the ultraviolet region, which originates from TiO2, was found to increase with increasing temperature. The presented technique will open new possibilities in integrated optics; the surface of a small protruded or hollow area can be made smooth, which cannot be achieved by conventional mechanical polishing.
Patterning of non-linear optical crystals in glass by laser-induced crystallization 招待有り査読有り

T. Komatsu, R. Ihara, T. Honma, Y. Benino, R. Sato, H. G. Kim, T. Fujiwara

JOURNAL OF THE AMERICAN CERAMIC SOCIETY　90　(3)　699-705　2007年3月
出版者・発行元：WILEY-BLACKWELL
DOI： 10.1111/j.1551-2916.2006.01441.x 　

ISSN：0002-7820

eISSN：1551-2916

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This paper reports recent progress in the patterning of non-linear optical crystals on the glass surface by laser irradiation. Two techniques for the writing of crystal lines have been developed, i.e., rare-earth (samarium) atom heat processing and transition metal atom heat processing, in which a continuous wave Nd:YAG laser (wavelength: lambda=1064 nm) is irradiated to the glasses containing rare-earth (RE: Sm3+, Dy3+) ions or transition metal (TM: Ni2+, Fe2+, V4+) ions. The writing of crystal lines such as beta-BaB2O4, SmxBi1-xBO3, and Ba2TiGe2O8 showing second harmonic generations has been successful. It is clarified from the azimuthal dependence of second harmonic intensity and polarized micro-Raman scattering spectra that crystal lines consist of highly oriented crystals along the crystal line growth direction. It is also possible to write two-dimensional crystal bending or curved lines by just changing the laser scanning direction. The mechanism of the laser-induced crystallization has been proposed.
Selective surface crystallization of nonstoichiometric 30BaO-15TiO(2)-55GeO(2) glass 査読有り

Hirokazu Masai, Takumi Fujiwara, Yasuhiko Benino, Takayuki Komatsu, Hiroshi Mori

JOURNAL OF APPLIED PHYSICS　101　(3)　033530/1-033530/4　2007年2月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2433992 　

ISSN：0021-8979

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The correlation between heat-treatment temperature for crystallization and orientation of surface crystalline phase, which should correspond to the intensity of second-order optical nonlinear susceptibility, in 30BaO-15TiO(2)-55GeO(2) (BTG55) crystallized glass was examined by measurements of x-ray diffraction (XRD) and second harmonic generation. A highly oriented fresnoite (Ba2TiGe2O8) or benitoite (BaTiGe3O9) phase was found to nucleate from the same mother BTG55 glass depending on the heat-treatment temperature, and both the fresnoite and benitoite phases showed XRD patterns of surface crystallization. It was found that the crystallization behavior of the two phases was strongly affected by the heat-treatment temperature. Based on this finding, the nonlinear optical property has also been tailored using the heat-treatment procedures. (c) 2007 American Institute of Physics.
Fabrication of TiO2 nanocrystallized glass 査読有り

Hirokazu Masai, Takumi Fujiwara, Hiroshi Mori, Takayuki Komatsu

APPLIED PHYSICS LETTERS　90　(8)　081907/1-081907/3　2007年2月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2679044 　

ISSN：0003-6951

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Nanocrystallization of rutile and anatase was observed in a CaO-B2O3-Bi2O3-Al2O3-TiO2 crystallized glass. The color of the present crystallized glass was changed by the heat-treatment temperature, and x-ray diffraction (XRD) patterns of the crystallized glass show that the apparent color change is correlated with the formation of titania nanocrystallites. The particle size of crystallites observed in the transmission electron microscope image is comparable to that measured by XRD pattern. In addition, a large change of refractive index between the rutile particles and glass matrix, 0.8 or larger, was obtained. The present titania crystallized glass will be not only a photocatalytic material but also a promising candidate for random lasing devices. (c) 2007 American Institute of Physics.
Molecular orbital approach to the optical nonlinearities of fresnoite-type crystals 査読有り

Nozomu Uchida, Satoshi Tanaka, Keizo Uematsu, Takumi Fujiwara, Takayuki Komatsu

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY　27　(2-3)　531-533　2007年
出版者・発行元：ELSEVIER SCI LTD
DOI： 10.1016/j.jeurceramsoc.2006.04.105 　

ISSN：0955-2219

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Hyperpolarizability (P) values have been evaluated by means of molecular orbital calculation for the clusters which simulate the fresnoit type crystals, Ba2TiGe2O8(BTG), Ba2TiSi2O8 (BTS), and Sr2TiSi2O8 (STS). The experimental results have suggested that the second order optical nonlinearity of the crystals were strongly affected by the distortion of the crystal structure. In this study, beta values were calculated for distorted clusters of BTG, BTS, and STS crystals. The obtained values increase both with axial (c-axis direction) and equatorial (in c-plane) expansions of the unit cell. Especially, beta the value of BTG cluster increased significantly with axial expansion. (c) 2006 Elsevier Ltd. All rights reserved.
Laser-induced crystallization of beta '-RE2(MoO4)(3) ferroelectrics (RE : Sm, Gd, Dy) in glasses and their surface morphologies 査読有り

R. Nakajima, M. Abe, Y. Benino, T. Fujiwara, H. G. Kim, T. Komatsu

JOURNAL OF NON-CRYSTALLINE SOLIDS　353　(1)　85-93　2007年1月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.jnoncrysol.2006.08.050 　

ISSN：0022-3093

eISSN：1873-4812

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The glasses with the compositions of 21.25RE(2)O(3)-63.75MoO(3)-15B(2)O(3) (RE: Sm, Gd, Dy) were prepared and the formation of beta'RE2(MoO4)(3) ferroelectrics was confirmed in the crystallized glasses obtained through a conventional crystallization in an electric furnace. The features of the glass structure and crystallization behavior were clarified from measurements of Raman scattering spectra. Continuous-wave Nd:YAG laser with a wavelength of 1064 nm (laser power: 0.6-0.9 W, laser scanning speed: S = 1-16 mu m/s) was irradiated to 10.625Sm(2)O(3)-10.625Gd(2)O(3) (or DY2O3)-63.75MoO(3)-15B(2)O(3) glasses, and the structural modification was induced at the glass surface. At the scanning speed of S = 10 mu m/s, crystal lines consisting of beta'-Gd2-xSmx(MoO4)(3) or beta'-Dy2-x,Sm-x(MoO4)(3) crystals were patterned on the glass surface. It was found that those crystal lines have the surface morphology with periodic bumps. At S = 1 mu m/s, it was found that crystal lines consist of the mixture of paraclectric alpha-Gd2-xSmx(MoO4)(3) and ferroelectric beta'-Gd2-xSmx(MoO4)(3) crystals, indicating the phase transformation from the beta' phase to the alpha phase during laser irradiation. Homogeneous crystal lines with beta'-RE2MoO4)(3) ferroelectrics have not been written in this study, but further research is continuing. (c) 2006 Elsevier B.V. All rights reserved.
Electronic polarizability and crystallization of K2O-TiO2-GeO2 glasses with high TiO2 contents 査読有り

T. Fukushima, Y. Benino, T. Fujiwara, V. Dimitrov, T. Komatsu

JOURNAL OF SOLID STATE CHEMISTRY　179　(12)　3949-3957　2006年12月
出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI： 10.1016/j.jssc.2006.08.035 　

ISSN：0022-4596

eISSN：1095-726X

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Some K2O-TiO2-GeO2 glasses with a large amount of TiO2 contents (15-25 mol%) such as 25K(2)O-25TiO(2)-50GeO(2) have been prepared. and their electronic polarizability, Raman scattering spectra, and crystallization behavior are examined to clarify thermal properties and structure of the glasses and to develop new nonlinear optical crystallized glasses. It is proposed that the glasses consist of the network of TiO6 and GeO4 polyhedra. The glasses show large optical basicities of Lambda = 0.88-0.92, indicating the high polarizabity of TiOn (n = 4-6) polyhedra in the glasses. K2TiGe3O9 crystals are formed through crystallization in all glasses prepared in the present study. In particular, 20K(2)O-20TiO(2)-60GeO(2) glass shows bulk crystallization and 18K(2)O-18TiO(2)-64GeO(2), glass exhibits surface crystallization giving the c-axis orientation. The crystallized glasses show second harmonic generations (SHGs), and it is suggested that the distortion of TiO6 octahedra in K2TiGe3O9 crystals induces SHGs. (c) 2006 Elsevier Inc. All rights reserved.
Novel technique for fabrication of nanoparticle structures in KNbO3-TeO2 glass for photonic integrated circuits 査読有り

Shintaro Mizuno, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS　45　(8A)　6121-6125　2006年8月
出版者・発行元：INST PURE APPLIED PHYSICS
DOI： 10.1143/JJAP.45.6121 　

ISSN：0021-4922

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We succeeded in fabricating novel nanoparticle structures on KNbO3-TeO2 glass induced by ultraviolet (UV) laser irradiation and found that the size and size distribution could be controlled by the conditions of laser irradiation, such as fluence, pulse repetition rate, and the temperature of the glass specimen by heat assistance (HA). Nano-sized particles are an interesting new material, because they will be able to open the door to the invention of photonic circuits of extremely small size, which transfer optical signals through optical near-field energy operating by a completely different principle. The particle diameters may be controlled from approximately 200 nm up to 500 nm by modifications of UV laser fluence and the repetition rate of pulses. When using HA with a glass specimen during laser irradiation, it has been found that nanoparticle formation is activated and particle size increased as the temperature of the glass increased, and the uniformity of particle size is markedly improved by HA treatment. The standard deviation of particle size is 20 nm at 100 degrees C. A 60% improvement in the size variation of particles is possible in comparison with laser irradiation without HA. These results suggest that heat is involved in, nanoparticle formation during UV laser irradiation, which means that the overall history of heating with pulsed laser irradiation is critically important to control the form of the particles. Furthermore, periodic structures with an 800 nm pitch constructed by lines of ordered nanoparticles with diameters of approximately 150-300 nm were successfully fabricated by laser irradiation through a phase mask. This is a significant advancement towards the realization of nanophotonic circuits.
Crystallization of langasite-type phases in gallium germinate glasses and optical properties of crystallized glasses 査読有り

S. Kosaka, Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Optical Materials　28　(10)　1129-1135　2006年7月

DOI： 10.1016/j.optmat.2005.05.018 　
Large second-order optical nonlinearity in 30BaO-15TiO(2)-55GeO(2) surface crystallized glass with strong orientation 査読有り

Hirokazu Masai, Takumi Fujiwara, Yasuhiko Benino, Takayuki Komatsu

JOURNAL OF APPLIED PHYSICS　100　(2)　023526/1-023526/4　2006年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2210173 　

ISSN：0021-8979

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The correlation between the orientation degree of surface crystalline phase and the second-order optical susceptibility, d coefficient for second-harmonic generation, in 30BaO-15TiO(2)-55GeO(2) (BTG55) crystallized glass was investigated using x-ray diffraction measurements and a Maker fringe technique. The d coefficient in BTG55 crystallized glass was confirmed to depend on the orientation degree of the surface crystalline phase. An oriented fresnoite (Ba2TiGe2O8) phase was observed in transparent BTG55 crystallized glass which had been heat treated at 720 degrees C for 3 h. The orientation degree along the polar c axis in the fresnoite phase increased with increasing removal thickness by polishing from the surface up to several microns. A d coefficient in transparent BTG55 crystallized glass of 24 +/- 3 pm/V has been obtained, which is the largest value in crystallized glass ever reported.
Transition metal atom heat processing for writing of crystal lines in glass 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu

APPLIED PHYSICS LETTERS　88　(23)　231105-1-231105-3　2006年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2212272 　

ISSN：0003-6951

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A technique for the writing of crystal line in glass has been developed, in which a continuous-wave Nd:YAG laser (wavelength: lambda = 1064 nm) is irradiated to the glasses containing transition metal (TM) ions such as Fe2+, Ni2+, and V4+. Laser energies are absorbed through d-d transitions of TM ions and dissipated to the lattice surrounding TM ions by nonradiative relaxation process, giving the increase in temperature in the laser irradiated region and inducing crystallization. This technique has been demonstrated for the writing of crystal lines consisting of nonlinear optical fresnoite-type Ba2TiGe2O8 and Ba2TiSi2O8 crystals in NiO Fe2O3-, and V2O5-doped (0.3-1 mol %) BaO-TiO2-GcO(2) and BaO-TiO2-SiO2 glasses. It is confirmed that crystals in the crystal lines are highly oriented-along the laser scanning direction. The technique developed in this study is proposed to be called "transition metal atom heat processing." (c) 2006 American Institute of Physics.
Formation of nano-particle structures induced by ultraviolet laser irradiations in KNbO3-TeO2 glass 査読有り

S Mizuno, Y Benino, T Fujiwara, T Komatsu

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN　114　(1327)　293-295　2006年3月
出版者・発行元：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
DOI： 10.2109/jcersj.114.293 　

ISSN：1882-0743

eISSN：1348-6535

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We report on a novel technique for formation of nano-particle structures in KNbO3-TeO2, glasses induced by ultraviolet (UV) XeCl excimer laser irradiations operating at 308 nm wavelength. The glasses with a composition of 0.5Er(2)O(3)-15K(2)O-15Nb(2)O(5)-70TeO(2) (mol%), which are known to exhibit a nano-crystallization behavior by heat treatments, have been used in this experiment. It has been found that the morphological properties of nanoparticles, such as diameter, height, and distribution density of nano-particles, can be tailored by the pulsed UV laser conditions. The nature of these nano-structures on glass surface induced by laser processing has been clarified that laser-induced nano-particles are consisting of the same composition as that in glass substrate.
Enhancement and depression in second-order optical nonlinearity of Ba2TiGe2O8 in crystallized glass prepared in a high magnetic field 査読有り

N Toyohara, Y Benino, T Fujiwara, S Tanaka, K Uematsu, T Komatsu, Y Takahashi

JOURNAL OF APPLIED PHYSICS　99　(4)　043515-1-043515-4　2006年2月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2170412 　

ISSN：0021-8979

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A magnetic field of H=10 T was applied perpendicularly or parallel to the surface of the 30BaO.15TiO(2).55GeO(2) (BTG) glass during its crystallization, and the effect of the magnetic field on the crystal orientation and second-order optical nonlinearity of the Ba2TiGe2O8 crystals formed at the glass surface was examined. Compared with the sample prepared by conventional crystallization in zero magnetic field, the c-axis (polarization axis) orientation and second-harmonic intensity of the Ba2TiGe2O8 crystals at the surface were enhanced in the sample fabricated with the field perpendicular to the surface and, by contrast, were depressed in the sample fabricated with the field parallel to the surface. The present study indicates that the application of high magnetic fields during crystallization is a technique to control the crystal orientations and optical properties of BTG crystallized glasses. (c) 2006 American Institute of Physics.
Order/disorder hybrid structures in photonic glass materials 招待有り査読有り

T. Fujiwara, T. Honma, S. Mizuno, N. Iwafuchi, Y. Benino, T. Komatsu

AICAM 2005　11-12　53-+　2006年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
ISSN：1022-6680

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Investigations for space-selected structure ordering from nano-particles to single-crystal patterning in glasses will be described. Transparent crystallization in glass must be the best material solution to obtain novel functional glasses with a permanent second-order optical nonlinearity. We focus on the new functions created by structure ordering in glass by means of laser micro-fabrication for space-selected crystallization. Two topics in our recent experimental results of space-selected structure ordering in glass will be presented as follows: 1) Single crystalline patterning by atom heat laser processing in Sm-doped glasses for optical waveguides with second-order optical nonlinearity, 2) structure ordering of domains in crystallized glass fibers for possible photonic fiber-type devices with active signal processing.
Improvement of second-order optical nonlinearity in transparent Ba2TiGe2O8 crystallized glasses prepared in high magnetic field 査読有り

Nozomu Toyohara, Yasuhiko Benino, Takumi Fujiwara, Satoshi Tanaka, Keizo Uematsu, Yoshihiro Takahashi, Takayuki Komatsu

AICAM 2005　11-12　193-196　2006年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
ISSN：1022-6680

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A high magnetic field of H = 10 T was applied to 30BaO-15TiO(2)-55GeO(2) glass through its crystallization process. It was found that the c-axis of Ba2TiGe2O8 optical nonlinear/ferroelectric crystals oriented along the magnetic field. The second harmonic intensity of crystallized glass which the high magnetic field was applied perpendicular to the surface of glass was enhanced compared with a conventional crystallization in no magnetic field. Transparencies, photorefractive indices and thicknesses were also measured. As a result, crystal orientation of Ba2TiGe2O8 in glass matrix induced by a high magnetic field causes improvement of transparency and low value of photorefractive index.
Fabrication of optical waveguide in glass by laser-induced crystallization 査読有り

R. Ihara, Y. Benino, T. Fujiwara, T. Komatsu

AICAM 2005　11-12　197-+　2006年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
ISSN：1022-6680

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Homogeneous crystal lines were fabricated at the surface of 8Sm(2)O(3).37Bi(2)O(3).55B(2)O(3) glass by irradiations of cw Nd: YAG laser (lambda = 1064 nm) with laser powers of 0.7-0.9 W and laser scanning speeds of 3-5 mu m/s. It was confirmed from micro-Raman scattering spectra that the lines consist of nonlinear optical SmxBi1-xBO3 crystals showing second harmonic generations. The curved crystal lines with bending angles of 0 similar to 90 degrees were successfully written by just changing laser scanning directions. The light (lambda = 632.8 nm) transmission was confirmed for a crystal line (length: 850 mu m) with two bending angles of +/- 30 degrees, where significant light scattering losses were not observed at the bending points. We propose that the curved crystal lines written by YAG laser irradiations have a high potential for applications in optical waveguides.
Nano-crystallized glass fibers with second-order optical nonlinearity 査読有り

N. Iwafuchi, S. Mizuno, Y. Benino, T. Fujiwara, T. Komatsu, M. Koide, K. Matsushita

AICAM 2005　11-12　209-+　2006年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
ISSN：1022-6680

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Transparent nano-crystallized glass fibers with 300 mu m diameter were successfully fabricated in tellurite (TeO2) based glass systems. Structure of crystallized glass fibers and orientation of nano-size crystals were quantitatively investigated by microscopic Raman spectroscopy and X-ray diffraction. Second harmonic generation was measured in the nano-crystallized optical fibers.
Development of new crystallized glasses with nanocrystals and Nonlinear optical properties 査読有り

Y. Benino, T. Fujiwara, T. Komatsu

AICAM 2005　11-12　189-+　2006年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
ISSN：1022-6680

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New crystallized glasses with nonlinear optical properties are developed by various thermal processes for glassy materials which involve the precisely controlled heat-treatment and the novel crystallization patterning using laser spot heating technique. The nonlinear optical functions and their applications are discussed based on the morphologies of the precipitated crystalline phases. The enhancement of the nonlinear optical properties can be expected by introduction of internal stress during the thermal process.
Synthesis of Sm3+-doped strontium barium niobate crystals in glass by samarium atom heat processing 査読有り

Nakon Chayapiwut, Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu

Journal of Solid State Chemistry　178　(11)　3507-3513　2005年10月3日
出版者・発行元：None
DOI： 10.1016/j.jssc.2005.09.002 　
Temperature dependence of second-harmonic intensity and Raman shift in langasite-type phases 査読有り

Y. Takahashi, K. Kitamura, S. Inoue, R. Ihara, Y. Benino, T. Fujiwara, T. Komatsu

Journal of the Ceramic Society of Japan　113　(1322)　692-695　2005年10月
出版者・発行元：公益社団法人日本セラミックス協会
DOI： 10.2109/jcersj.113.692 　

ISSN：1882-1022

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In this study, we examined the temperature dependence of the second-harmonic (SH) intensity and Raman shift in the langasite-type Ba_3Ga_2Ge_4O_<14> (BGG) and Na_2CaGe_6O_<14> (NCG) crystalline phases. The SH intensity curves revealed an anomalous temperature behavior around 370℃ and 270℃ in the BGG and NCG phases, respectively. Furthermore, as a result from the Raman spectral measurement, it was suggested that the anomaly observed in the lagasite-type phases originated in the A-site.
Crystallization and Raman spectra of langasite-type phases in glasses of La3Ga5GeO14-Ba3Ga2Ge4O14 system 査読有り

Y. Takahashi, K. Kitamura, S. Inoue, Y. Benino, T. Fujiwara, T. Komatsu

Japanese Journal of Applied Physics　44　(9B)　7177-7181　2005年9月
出版者・発行元：Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics
DOI： 10.1143/JJAP.44.7177 　

ISSN：0021-4922

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Crystallization of the langasite-type La3Ga5GeO14–Ba3Ga2Ge4O14 mixed crystals in the stoichiometric corresponding glasses was studied by differential thermal and X-ray diffraction analyses, and by Raman spectroscopy. Although the glasses used in this study were multicomponent systems (BaO–La2O3–Ga2O3–GeO2), the langasite-type phases were singly crystallized in the corresponding glasses. The Raman spectroscopic study revealed the structural similarity on the scale of short-range order between the langasite-type phase and the corresponding glasses. This also strongly suggested the coexistence of Ga and Ge with six-coordination in the gallogermanate glasses.
Writing of two-dimensional crystal curved lines at the surface of Sm2O3-Bi2O3-B2O3 glass by samarium atom heat processing 査読有り

Rie Ihara, Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Ryuji Sato, Takayuki Komatsu

Solid State Communications　136　(5)　273-277　2005年8月18日
出版者・発行元：None
DOI： 10.1016/j.ssc.2005.08.004 　
LaBGeO5 single crystals in glass and second-harmonic generation 査読有り

Y. Takahashi, K. Kitamura, Y. Benino, T. Fujiwara, T. Komatsu

Materials Science and Engineering B　120　(1-3)　155-160　2005年7月15日

DOI： 10.1016/j.mseb.2005.02.010 　
Effect of heat-treatment temperature on optical properties of Ba2TiSi2O8 nanocrystrallized glasses 査読有り

Y. Takahashi, K. Kitamura, S. Inoue, Y. Benino, T. Fujiwara, T. Komatsu

Journal of the Ceramic Society of Japan　113　(1318)　419-423　2005年6月
出版者・発行元：公益社団法人日本セラミックス協会
DOI： 10.2109/jcersj.113.419 　

ISSN：1882-1022

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Nanocrystallized glasses with the composition of 40BaO・20TiO_2・40SiO_2, stoichiometric to fresnoite (Ba_2TiSi_2O_8), have been prepared by heat-treatment at various temperatures, and their optical properties, second-harmonic generation (SHG) and photoluminescence (PL), have been examined. The glass subjected to the heat-treatment at 760℃ for 1h showed a dense formation of Ba_2TiSi_2O_8 crystals with the dimension of 200-300nm, and maintained a visual transparency. Visible green light corresponding to SHG at 532nm was confirmed in the transparent Ba_2TiSi_2O_8 nanocrystallized glasses. The maximum second-harmonic intensity in the nanocrystallized samples was on the order of 1/100 when compared to that of an α-quartz single crystal. Furthermore, the bluish white PL with a peak at the wavelength of about 470nm was also visually observed in samples heat-treated at 750-800℃.
Line patterning with large refractive index changes in the deep inside of glass by nanosecond pulsed YAG laser irradiation 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu

Solid State Communications　135　(3)　193-196　2005年4月21日
出版者・発行元：None
DOI： 10.1016/j.ssc.2005.04.005 　
Crystal Orientation in Bi-based Superconducting Glass-Ceramics Prepared in High Magnetic Field 査読有り

Nozomu Toyohara, Yasuhiko Benino, Takumi Fujiwara, Satoshi Tanaka, Keizo Uematsu, Takayuki Komatsu

Physica C　420　(3-4)　88-94　2005年4月1日
出版者・発行元：Elsevior
DOI： 10.1016/j.physc.2005.01.012 　
Crystalline phases and YAG laser-induced crystallization in Sm2O3-Bi2O3-B2O3 glasses 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu, Ryuji Sato

Journal of the American Ceramic Society　88　(4)　989-992　2005年3月23日
出版者・発行元：None
DOI： 10.1111/j.1551-2916.2005.00166.x 　

ISSN：1551-2916
Second-order optical nonlinear and luminescent properties of Ba2TiSi2O8 nanocrystalized glass 査読有り

Y. Takahashi, K. Kitamura, Y. Benino, T. Fujiwara, T. Komatsu

Applied Physics Letters　86　(9)　091110-1-091110-3　2005年2月28日

DOI： 10.1063/1.1879114 　
Nonlinear optic behavior of transparent surface crystallized glasses in the BaO-B2O3-TeO2 system 査読有り

GS Murugan, T Suzuki, Y Ohishi, Y Takahashi, Y Benino, T Fujiwara, T Komatsu

2005 PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS　501-502　2005年
出版者・発行元：IEEE

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Second order nonlinear optic behavior of a transparent glass-ceramic containing borate crystallites in tellurite glass is reported. Controlled heat-treatment resulted in surface crystallization of BaB4O7 in the BaO-B2O3-TeO2 glass system.
Second harmonic generation in transparent surface crystallized glasses in the system BaO-B2O3-TeO2 査読有り

G. S. Murugan, T. Suzuki, Y. Ohishi, Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Applied Physics Letters　85　(16)　3405-3407　2004年10月18日
出版者・発行元：None
DOI： 10.1063/1.1808873 　

ISSN：0003-6951

eISSN：1077-3118
Formation of Ba2TiGe2O8 phase in BaO-TiO2-GeO2 glasses and their optical nonlinearities 査読有り

Y. Takahashi, K. Saitoh, Y. Benino, T. Fujiwara, T. Komatsu

Journal of Non-Crystalline Solids　345　412-416　2004年10月15日

DOI： 10.1016/j.jnoncrysol.2004.08.054 　
Second order optical nonlinearity of transparent glass-ceramic materials induced by alternating field 査読有り

Y. Benino, Y. Takahashi, T. Fujiwara, T. Komatsu

Journal of Non-Crystalline Solids　345　422-427　2004年10月15日

DOI： 10.1016/j.jnoncrysol.2004.08.056 　
Spatially selected crystallization in glass by YAG laser irradiation 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Ryuji Sato, Takayuki Komatsu

Journal of Non-Crystalline Solids　345-346　127-131　2004年9月11日

DOI： 10.1016/j.jnoncrysol.2004.08.009 　
Second-order optical nonlinearities of metastable BiBO3 phases in crystallized glasses 査読有り

Rie Ihara, Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu

Optical Materials　27　(3)　403-408　2004年9月11日
出版者・発行元：None
DOI： 10.1016/j.optmat.2004.07.002 　
Micro-Raman and photoluminescence spectra of Sm3+-doped β-BaB2O4 crystal lines written by YAG laser irradiation in glass 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Ryuji Sato, Takayuki Komatsu

Journal of Physics and Chemistry of Solids　65　(10)　1705-1710　2004年7月3日
出版者・発行元：None
DOI： 10.1016/j.jpcs.2004.04.010 　
Formation of nonlinear optical KSm(PO3)4 crystals in phosphate glasses by YAG laser irradiation 査読有り

Maiko Saito, Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu

Solid State Sciences　6　(9)　1013-1018　2004年6月17日
出版者・発行元：None
DOI： 10.1016/j.solidstatesciences.2004.04.012 　
Stoichiometric crystallized glasses with large second-order optical nonlinearities 査読有り

Y. Takahashi, K. Saitoh, Y. Benino, T. Fujiwara, T. Komatsu

Journal of the Ceramic Society of Japan　112-1　(1305)　S1168-S1172　2004年5月

DOI： 10.14852/jcersjsuppl.112.0.S1168.0 　
Unique crystallization and formation of nonlinear optical (Na,K)NbO3 phases in (Na,K)NbGeO5 glasses 査読有り

K. Narita, Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Optical Materials　25　(4)　393-400　2004年5月

DOI： 10.1016/j.optmat.2003.10.003 　
Temperature dependence of second-order optical nonlinearity in crystallized (Sr,Ba)2TiGe2O8 glasses 査読有り

K. Saitoh, Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Journal of the Ceramic Society of Japan　112-1　(1305)　S1262-S1264　2004年5月

DOI： 10.14852/jcersjsuppl.112.0.S1262.0 　
Photonic crystallized structures in glass 査読有り

T. Fujiwara, T. Honma, Y. Takahashi, Y. Benino, R. Satoh, T. Komatsu

Journal of the Ceramic Society of Japan　112-1　S1257-S1261　2004年5月

DOI： 10.14852/jcersjsuppl.112.0.S1161.0 　
Large second-order optical nonlinearities of fresnoite-type crystals in transparent surface-crystallized glasses 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Journal of Applied Physics　95　(7)　3503-3508　2004年4月1日

DOI： 10.1063/1.1664022 　
Writing of crystalline dots and lines in Sm2O3 doped borate and tellurite glasses by YAG laser irradiation and their optical properties 査読有り

Takayuki Komatsu, Shingo Kawasaki, Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Ryuji Sato

Physics and Chemistry of Glasses　45　(2)　75-78　2004年4月1日
出版者・発行元：None
Effectiveness of broadcasting guidelines for photosensitive seizure prevention 査読有り

Y Takahashi, T Fujiwara

NEUROLOGY　62　(6)　990-993　2004年3月
出版者・発行元：LIPPINCOTT WILLIAMS & WILKINS
ISSN：0028-3878

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Emissions from TV programs are a dangerous light source for photosensitive individuals, because 48.9% of patients have photosensitive seizures caused by TV programs. The authors used a national survey to verify the effectiveness of current Japanese guidelines, which are based on neurophysiologic principles of photosensitivity. They show that the guidelines successfully control TV images to protect many photosensitive persons from harmful TV emissions.
Photo-induced structure ordering in catallized glass from nano-particles to single-crystal patterning 査読有り

T Fujiwara, S Mizuno, T Honma, Y Benino, T Komatsu, R Sato

FIFTH INTERNATIONAL SYMPOSIUM ON LASER PRECISION MICROFABRICATION　5662　24-29　2004年
出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING
DOI： 10.1117/12.595719 　

ISSN：0277-786X

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Challenges for laser-induced structure ordering from nano-particles to single-crystal patterning in glasses are described. Transparent crystallization in glass must be the best material solution to obtain novel functional glasses with a permanent second-order optical nonlinearity. We focus on the new functions created by structure ordering in glass by means of laser micro-fabrication for space-selected crystallization. Two topics in our recent experimental results of laser-induced structure ordering in glass will be presented as follows: 1) UV-laser induced structure ordering of nano-particles in tellurite-based glasses and possible photonic integrated circuits with innovative minute scale. 2) Single crystalline patterning by atom heat laser processing in Sm-doped glasses for optical waveguides with second-order nonlinearity.
Development of new transparent nonlinear optical crystallized glasses

T. Komatsu, Y. Takahashi, T. Honma, Y. Benino, T. Fujiwara

Proceedings of the XX ICG in Kyoto　1 (O-08-015)-4　2004年
Formation of langasite-type crystals in corresponding glasses and their second-order optical nonlinearities 査読有り

Y. Takahashi, K. Saitoh, Y. Benino, T. Fujiwara, T. Komatsu

Journal of the Ceramic Society of Japan　112　(1301)　61-64　2004年1月
出版者・発行元：公益社団法人日本セラミックス協会
DOI： 10.2109/jcersj.112.61 　

ISSN：1882-1022

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Second-order optical nonlinearities for the langasite-type phases obtained by crystallization of corresponding glasses are clarified for the first time. It is confirmed that most of langasite-type crystalline phases can be formed by crystallization in the corresponding glasses without introducting of any impurity phases, e.g., the glasses with the stoichiometric composition of Ba_3Ga_2Ge_4O_<14>, BaGa_4La_2Ge_2O_<14>, Pb_3Ga_2Ge_4O_<14>, etc. We find that Pb_3Ga_2Ge_4O_<14> and Pb_3AlGaGe_4O_<14> phases exhibited strong second-harmonic intensities of approximately 100 times as large as α-quartz by means of a powder technique, demonstrating that those langasite-type crystals are excellent nonlinear optical materials. It is also suggested that the octahedral site is one of keys for second-order optical nonlinearity in langasite-type crystals.
Prominent nanocrystallization of 25K2O-25Nb2O5-50GeO2 glass 査読有り

K. Narita, Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Journal of The American Ceramic Society　87　(1)　113-118　2004年1月

DOI： 10.1111/j.1551-2916.2004.00113.x 　
Writing of Nonlinear Optical Single Crystal-Lines in Glass by YAG Laser Scanning 査読有り

T. Honma, Y. Benino, T. Fujiwara, R. Sato, T. Komatsu

Journal of the Ceramic Society of Japan, Supplement 112-1, PacRim5 Special Issue　112　(5)　S1161-S1167　2003年12月11日
出版者・発行元：None
DOI： 10.14852/jcersjsuppl.112.0.S1189.0 　
Origin of Intrinsic Second-Harmonic Generation in Crystallized GeO2-SiO2 Glass Films 査読有り

Takumi Fujiwara, Takashi Sawada, Tsuyoshi Honma, Yasuhiko Benino, Takayuki Komatsu, Masahide Takahashi, Toshinobu Yoko, jyunji Nishii

Japanese Journal of Applied Physics, Part 1： Regular Papers and Short Notes and Review Papers　42　(12)　7326-7330　2003年12月10日
出版者・発行元：Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics
DOI： 10.1143/jjap.42.7326 　

ISSN：0021-4922

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The origin and properties of second-harmonic generation (SHG) from crystalline particles and their crystalline phases in GeO2–SiO2 glass films were investigated. GeO2–SiO2 glass films with a thickness of approximately 5 μm were fabricated by the chemical vapor-phase deposition (CVD) method. Heat treatments in the temperature range of 1100–1260°C for durations of 2–8 h have been performed to crystallize the glass films. X-ray diffraction (XRD) peaks at around $2\theta=22$° in the crystallized GeO2–SiO2 films were observed, and the obtained XRD patterns in the glass films are exactly the same as those in ultraviolet (UV) poled GeO2–SiO2 glasses with a large second-order optical nonlinearity comparable to that in LiNbO3 crystals. Using a SHG microscopic technique, it has been found that the intensity of SHG emission from crystalline particles is clearly dependent on stress-induced optical retardation which is accompanied by the formation of crystalline particles of the \textit{pseudo-$\beta$-cristobalite} containing GeO2. In addition, a new technique for enhancing the intrinsic SHG by means of modification of defect states is demonstrated.
Refractive index change induced by ultraviolet laser irradiations in erbium-doped tellurite glasses 査読有り

Takumi Fujiwara, Takahiro Nakamoto, Tsuyoshi Honma, Yasuhiko Benino, Takayuki Komatsu

Electronics Letters　39　(22)　1576-1577　2003年11月10日
出版者・発行元：None
DOI： 10.1049/el：20031031 　
Technique for writing of nonlinear optical single-crystal lines in glass 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu, Ryuji Sato

Applied Physics Letters　83　(14)　2796-2798　2003年10月6日
出版者・発行元：None
DOI： 10.1063/1.1615833 　
Writing of crystal-dots and lines by YAG laser irradiation and their morphologies in samarium tellurite glasses 査読有り

Shingo Kawasaki, Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Ryuji Sato, Takayuki Komatsu

Journal of Non-Crystalline Solids　325　(1-3)　61-69　2003年7月16日
出版者・発行元：Elsevier
DOI： 10.1016/S0022-3093(03)00365-X 　

ISSN：0022-3093
Direct observation of second-harmonic generation from crystalline particles in Ge-doped SiO2 glass films 査読有り

T Fujiwara, T Sawada, Y Benino, T Komatsu, M Takahashi, T Yoko, J Nishii

OPTICS EXPRESS　11　(14)　1598-1606　2003年7月
出版者・発行元：OPTICAL SOC AMER
DOI： 10.1364/OE.11.001598 　

ISSN：1094-4087

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The authors report what is, to our best knowledge, the first observation of second-harmonic generation (SHG) directly from the crystalline particles in Ge-doped SiO2 (Ge:SiO2) glass films. Ge:SiO2 glass films with approximately 5 mum thickness were fabricated by chemical vapor-phase deposition. X-ray diffraction ( XRD) peaks at around 2theta=22degrees in thermally crystallized Ge:SiO2 films were observed, and obtained XRD patterns are exactly the same as those in ultraviolet-laser-poled Ge: SiO2 glasses. Using SHG microscopic technique with a Nd:YAG laser, it has been successfully found that SH emitting with 532 nm wavelength is observed directly from the crystalline particles induced in the crystallized films. (C) 2003 Optical Society of America.
Evolution and characterization of fluorite-like nano-SrBi2Nb2O9 phase in the SrO-Bi2O3-Nb2O5-Li2B4O7 glass system 査読有り

N. S. Prasad, K. B. R. Varma, Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Journal of Solid State Chemistry　173　(1)　209-215　2003年6月

DOI： 10.1016/S0022-4596(03)00026-4 　
Role of benitoite phase on formation of fresnoite-type Ba2TiGe2O8 with large optical nonlinearities in glasses 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Advances in Technology of Materials and Materials Processing Journal　5　(2)　64-69　2003年5月
YAG laser-induced β-BaB2O4 crystalline dot formation in Sm2O3-BaO-B2O3 glasses 査読有り

Hitoshi Tanaka, Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu

Journal of Physics and Chemistry of Solids　64　(7)　1179-1184　2003年4月23日
出版者・発行元：None
DOI： 10.1016/S0022-3697(03)00047-7 　

ISSN：0022-3697
Crystalline phases and second harmonic intensities in potassium niobium silicate crystallized glasses 査読有り

H. Tanaka, M. Yamamoto, Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Optical Materials　22　(1)　71-79　2003年3月

DOI： 10.1016/S0925-3467(02)00242-2 　
Formation mechanism of ferroelastic Ba2TiGe2O8 and second order optical nonlinearity in transparent crystallized glasses 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komastu

Journal of Non-Crystalline Solids　316　(2-3)　320-330　2003年2月

DOI： 10.1016/S0022-3093(02)01638-1 　
Nonlinear optical crystal-line writing in glass by yttrium aluminum garnet laser irradiation 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu, Ryuji Sato

Applied Physics Letters　82　(6)　892-894　2002年12月16日
出版者・発行元：None
DOI： 10.1063/1.1544059 　
Second order optical nonlinearity of LaBGeO5, LiBGeO4 and Ba2TiGe2O8 crystals in corresponding crystallized glasses 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Japanese Journal of Applied Physics PART 2-LETTERS　41　(12B)　L1455-L1458　2002年12月15日
出版者・発行元：社団法人応用物理学会
DOI： 10.1143/JJAP.41.L1455 　

ISSN：0021-4922

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Second-order optical nonlinearities, $d_{33}$, of LaBGeO5, LiBGeO4 and Ba2TiGe2O8 crystals in transparent crystallized glasses were estimated by means of the Maker fringe technique. Transparent surface crystallized glasses were fabricated by crystallization of a glass with the exact or close stoichiometric composition of each crystal. The $d_{33}$ values of ${\sim}\,0.13$ pm/V for LaBGeO5, ${\sim}\,0.7$ pm/V for LiBGeO4 and ${\sim}\,7$ pm/V for Ba2TiGe2O8 crystals were obtained. The crystallized glass consisting of Ba2TiGe2O8 crystals with pyramidal TiO5 units has the largest $d_{33}$ value of the crystallized glasses reported so far, and its value is comparable to the $d_{22}$ value of LiNbO3 single crystal. It is proposed that LiBGeO4 and Ba2TiGe2O8 crystals can be considered as new candidates for optical nonlinear crystals.
レーザー照射によるガラスの高機能化と光導波路パターニング

藤原巧, 本間剛, 高橋儀宏, 紅野安彦, 小松高行

レーザー学会第303回研究会報告／レーザープロセッシング　RTM-02-34　27-31　2002年11月
Photochemical reaction of divalent-germanium center in germanosilicate glasses under intense near-ultraviolet laser excitation: Origin of 5.7 eV band and site selective excitation of divalent-germanium center 査読有り

Masahide Takahashi, Kentaro Ichii, Yomei Tokuda, Takashi Uchino, Toshinobu Yoko, Junji Nishii, Takumi Fujiwara

Journal of Applied Physics　92　(7)　3442-3446　2002年10月1日

DOI： 10.1063/1.1505979 　

ISSN：0021-8979

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The photochemical reaction of Ge 2+ in 10GeO 2- 90SiO 2 optical fiber preform and the origin of the 5.7 eV optical absorption band induced by intense ultraviolet laser excitation have been investigated using a near-ultraviolet XeF excimer laser (3.7 eV) as the main excitation source. Based on the previous and present experimental results, it is concluded that the 5.7 eV optical absorption band does not originate from the Ge(2) electron trapped center. In place of this model, we have proposed an alternative structural model for the origin of the 5.7 eV band taking into account the experimental fact that the corresponding center is diamagnetic. In addition, it is found that the site selective excitation of the Ge 2+ center can be achieved by using laser sources with different photon energies. © 2002 American Institute of Physics.
Optical second order nonlinearity of transparent Ba2TiGe2O8 crystallized glasses 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Applied Physics Letters　81　(2)　223-225　2002年7月8日

DOI： 10.1063/1.1493667 　
Ferroelectric properties and second harmonic intensities of stillwellite-type (La,Ln)BGeO5 crystallized glasses 査読有り

Y. Takahashi, A. Iwasaki, Y. Benino, T. Fujiwara, T. Komatsu

Japanese Journal of Applied Physics PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS　41　(6A)　3771-3777　2002年6月
出版者・発行元：社団法人応用物理学会
DOI： 10.1143/JJAP.41.3771 　

ISSN：0021-4922

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Glasses with compositions corresponding to stillwellite-type (La,Ln)BGeO5 (Ln: Nd, Gd, Eu and Tm) crystalline phases have been prepared, and the effect of lanthanide substitutions on ferroelectric properties and second harmonic (SH) intensities of stillwellite-type crystalline phases formed by crystallization of glasses has been examined. The substitution of $\textit{Ln}^{3+}$ for La3+ ions in the LaBGeO5 phase has been confirmed from the results of X-ray diffraction (XRD) analysis and fluorescence spectra of Eu3+ ions. The substitution of $\textit{Ln}^{3+}$ for La3+ ions causes a decrease not only in the lattice constants but also in the $a/c$ axis ratio. The amount of substitutions depends on the $\textit{Ln}^{3+}$ ionic radius. The Curie temperature of crystallized glasses increases almost linearly with decreasing mean ionic radius of lanthanides estimated from the composition of base glasses. A similar trend is observed in the SH intensity for crystallized glasses (powdered form), indicating the presence of a close relationship between Curie temperature and SH intensity. It is proposed from Raman spectra that the enhancement of SH intensities is caused by the change in the arrangements of BO4 and GeO4 tetrahedra in the (La,Ln)BGeO5 crystals due to the substitution of $\textit{Ln}^{3+}$ ions having stronger $\textit{Ln}^{3+}$–O bonds. A clear second harmonic generation is observed in transparent surface crystallized glasses of the Nd2O3- or Gd2O3-substituted system.
Optical nonlinear crystalline dot and line patterning in samarium bismuth borate glasses by YAG laser irradiation 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Ryuji Sato, Takayuki Komatsu

Journal of the Ceramic Society of Japan　110　(1281)　398-402　2002年5月1日
出版者・発行元：公益社団法人日本セラミックス協会
DOI： 10.2109/jcersj.110.398 　

ISSN：1882-1022

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New transparent surface crystallized glasses in the system of Sm_2O_3-Bi_2O_3-B_2O_3 have been successfully fabricated. The second harmonic generation (SHG) from the crystalline phase at the surface layers has been confirmed from Maker fringe measurements. The chemical composition of optical nonlinear crystals in the crystallized glass of 12.5Sm2_O3 30Bi_2O_3 57.5B_2O_3 is determined to be Bi_<0.7>Sm_<0.3>BO_3. The irradiation of a continuous-wave YAG laser with a wavelength of 1064 nm induces sharp refractive-index changes or crystalline dot formation, depending on Sm_2O_3 content in the glasses and laser irradiation condition. In 10Sm_2O_3 30Bi_2O_3 60B_2O_3 glass, refractive-index changes (not crystallites) are induced by laser irradiations (power:1 W, time: 1-250 s), and spherical spots with 2-45 μm are formed. In 12.5Sm_2O_3・30Bi_2O_3・57.5B_2O_3 and 16.5Sm_2O_3 26Bi_2O_3 57.5B_2O_3 glasses, crystalline dots with diameters of 5-65 μm are formed by laser irradia-tions (power: 0.5-0.7 W, times: 1-250 s). The lines consisting of refractive-index changes and crystallites are fabricated by scanning laser spots with the speeds of 5-25 μms・s^<-1> It is found that the crystalline phase formed by laser irradiation is the same as that precipitated by usual heat treatment in an electric furnace and thus the crystalline dots and lines generate optical second harmonic waves.
New optical nonlinear crystallized glasses and YAG laser-induced crystalline dot formation in rare-earth bismuth borate system 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Ryuji Sato, Takayuki Komatsu

Optical Materials　20　(1)　27-33　2002年3月26日
出版者・発行元：None
DOI： 10.1016/S0925-3467(02)00027-7 　

ISSN：0925-3467
Electronic polarizability, optical basicity, and interaction parameter of La2O3 and related glasses 査読有り

Tsuyoshi Honma, Yasuhiko Benino, Takumi Fujiwara, Takayuki Komatsu, Ryuji Sato, Vesselin Dimitrov

Journal of Applied Physics　91　(5)　2942-2950　2002年2月25日
出版者・発行元：None
DOI： 10.1063/1.1436292 　
YAG laser-induced nonlinear optical crystalline dot and line patterning in glasses 査読有り

T Komatsu, T Honma, H Tanaka, Y Benino, T Fujiwara

GLASS SCIENCE AND TECHNOLOGY　75　13-18　2002年
出版者・発行元：VERLAG DEUTSCHEN GLASTECHNISCHEN
ISSN：0946-7475

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A continuous wave (CW) Nd: YAG laser with a wavelength of 1064 nm was irradiated to Sm2O3-Bi2O3-B2O3 glasses and crystalline dots (diameter: similar to5mum) and lines (width: similar to3mum) consisting of the Bi0.7Sm0.3BO3 crystalline phase were formed. A second harmonic generation (SHG) was observed from each crystalline dot or line. It is suggested from polarized optical microscope observations and Maker fringe SHG measurements that each crystalline line is a single crystal line. It was confirmed that a nonlinear optical crystalline line works as an optical waveguide. Nonlinear optical beta-BaB2O4 crystalline dots were also fabricated in 11.1Sm(2)O(3)-44.4BaO-44.4B(2)O(3) glass by YAG laser irradiations. CW YAG laser irradiation to glass with Sm3+ is a nice technique for spatially controlled crystalline dot and line patterning.
Second-harmonic generation of transparent crystallized glasses with ferroelectric LaBGeO5 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Physics and Chemistry of Glasses　43C　217-220　2002年
UV-laser induced photonic periodic structure in tellurite glass 査読有り

T. Fujiwara, R. Ogawa, Y. Takahashi, Y. Benino, T. Komatsu, J. Nishii

Physics and Chemistry of Glasses　43C　213-216　2002年
Fabrication and optical second order nonlinearity of transparent Ba2TiGe2O8 crystallized glasses

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komastu

Proceedings of Nonlinear Optics　256-258　2002年
New transparent crystallized glasses with optical nonlinear LiBGeO4 crystals 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, K. B. R. Varma, T. Komatsu

Journal of the Ceramic Society of Japan　110　(1)　22-26　2002年1月
出版者・発行元：公益社団法人日本セラミックス協会
DOI： 10.2109/jcersj.110.22 　

ISSN：1882-1022

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Crystallization behaviors of the glass with a composition of 25Li_2O・25B_2O_3・50GeO_2 corresponding to lithium borogermanate LiBGeO_4 have been examined. It has been confirmed that the LiBGeO_4 crystalline phase is formed at the surface of heat-treated glasses. The second harmonic(SH)generation is found from transparent surface crystallized glasses, demonstrating for the first time that the LiBGeO_4 phase shows optical nonlinearity. The SH intensity of LiBGeO_4 crystallites(powdered state)prepared through crystallization is about ten times as large as that of pulverized α-quartz. The SH intensity of transparent crystallized glasses(bulk state)with crystalline layers of 3-4.5 μm thickness increases with increasing heat treatment temperature(540-560℃)and time(1-6 h), and the maximum SH intensity among the samples studied is in the order of 1/10 in comparison with that of α-quartz single crystal. The transparent crystallized glass obtained by heat treatment at 550℃ for 3 h exhibits a clear and fine Maker fringe pattern, indicating a highly orientation of LiBGeO_4 crystals at the surface.
Second harmonic generation in transparent surface crystallized glasses with stillwellite-type LaBGeO5 査読有り

Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu

Journal of Applied Physics　89　(10)　5282-5287　2001年5月15日

DOI： 10.1063/1.1360699 　
Second-harmonic generation in UV-poled germanosilicate glass 査読有り

T Fujiwara, M Takahashi, AJ Ikushima

IOOC-ECOC 97 - 11TH INTERNATIONAL CONFERENCE ON INTEGRATED OPTICS AND OPTICAL FIBRE COMMUNICATIONS / 23RD EUROPEAN CONFERENCE ON OPTICAL COMMUNICATIONS, VOL 2　(448)　119-122　1997年
出版者・発行元：INST ELECTRICAL ENGINEERS INSPEC INC
ISSN：0537-9989

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Large second-harmonic generation (SHG) in a germanosilicate glass, induced by electrical poling with UV-irradiation at 193nm, is reported. Obtained SHG coefficient d, in a UV-poled glass was found to exceed d(22) of LiNbO3.
Preparation and Superconducting Properties of Pb2Sr2(Ho1-xCax)n-1Cun+1O2n+4 (n = 2 and 3) Thin Films 査読有り

T. Fujiwara, Y. Koike, M. Inaba, T. Noji, M. Kato, Y. Saito

Physica B　194-196　2299-2300　1994年

DOI： 10.1016/0921-4526(94)91649-7

︎全件表示 ︎最初の5件までを表示

MISC 115

マグノン熱伝導を利用した熱流の電気的制御

寺門信明, 高橋儀宏, 藤原巧

クリーンエネルギー　30　(1)　2021年

ISSN：0918-7510
アクティブファイバ応用に向けた結晶化ガラスの低損失化

藤原巧, 高橋儀宏, 寺門信明

レーザー研究　48　(7)　2020年

ISSN：0387-0200
結晶化ガラス法による光触媒材料の創製およびヘテロ接合形成の試み

KWON O., 寺門信明, 高橋儀宏, 藤原巧

日本セラミックス協会年会講演予稿集(CD-ROM)　2020　2020年
光非線形結晶化ガラスファイバーのPockels効果に基づく光変調

中村拓真, 大槻智貴, 寺門信明, 高橋儀宏, 藤原巧

日本セラミックス協会年会講演予稿集(CD-ROM)　2020　2020年
偏光顕微ラマン散乱を用いた1段階及び2段階イオン交換強化ガラスの構造調査

江袋信悟, 寺門信明, 高橋儀宏, 藤原巧

日本セラミックス協会年会講演予稿集(CD-ROM)　2020　2020年
チタノジャーマネート系完全表面結晶化ガラス:Fresnoite相の組織構造とPockels係数

岡本晴樹, 高橋儀宏, 大槻智貴, 寺門信明, 藤原巧

日本セラミックス協会年会講演予稿集(CD-ROM)　2020　2020年
マグノン熱伝導性La-Ca-Cu-O薄膜における熱キャリアの電界制御

奈良由紀, 寺門信明, 寺門信明, 渡辺祥太, 藤原巧

応用物理学会春季学術講演会講演予稿集(CD-ROM)　67th　2020年
透明性と3W/(m・K)超の熱伝導率を有するMgO析出ガラスの作製

吉嶺季和, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会春季学術講演会講演予稿集(CD-ROM)　67th　2020年
材料の特徴を知る-計測技術の開発と展開ラマンスペクトルに基づく化学強化ガラスの局所応力評価式の構築

寺門信明, 高橋儀宏, 藤原巧, 折原秀治, 折原芳男

機能材料　40　(12)　2020年

ISSN：0286-4835
シリケート系非線形結晶化ガラスファイバーのPockels効果

中村拓真, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会東北支部学術講演会(CD-ROM)　75th　2020年
熱流の電界制御に向けたLa-Ca-Cu-O系スピン熱伝導性ナノシートの創製

木下大也, 寺門信明, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会春季学術講演会講演予稿集(CD-ROM)　67th　2020年
マグノン熱伝導結晶のナノシート化とその形成機構

木下大也, 寺門信明, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会東北支部学術講演会(CD-ROM)　75th　2020年
蓄熱技術の最前線と社会実装への挑戦「全固体型潜熱蓄熱材料を指向した二酸化バナジウム分散ガラス」

高橋儀宏, 寺門信明, 藤原巧

化学工学　83　(9)　510-512　2019年9月
BaO-TiO2-GeO2系完全表面結晶化ガラスの作製と電気光学効果

岡本晴樹, 大槻智貴, 林原佑太, 寺門信明, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会春季学術講演会講演予稿集(CD-ROM)　66th　2019年
化学強化ガラスにおける残留応力と短距離構造の関係

寺門信明, 佐々木隆成, 江袋信悟, 高橋儀宏, 藤原巧, 折原秀治, 折原芳男

応用物理学会秋季学術講演会講演予稿集(CD-ROM)　80th　2019年
顕微ラマン分光を用いた化学強化ガラスの局所応力評価法の開発

佐々木隆成, 寺門信明, 高橋儀宏, 藤原巧, 折原秀治, 折原芳男

日本セラミックス協会年会講演予稿集(CD-ROM)　2019　2019年
完全表面結晶化ガラスにおける結晶配向性向上とPockels効果

大槻智貴, 高橋儀宏, 寺門信明, 藤原巧

日本セラミックス協会年会講演予稿集(CD-ROM)　2019　2019年
残光体を用いた生体温度センシングにおける測定精度向上

佐藤碧丹, 後藤聡敏, 大橋昌立, 寺門信明, 高橋儀宏, 尾上紀子, 篠崎毅, 藤原巧

日本セラミックス協会年会講演予稿集(CD-ROM)　2019　2019年
スピン熱伝導性La-Ca-Cu-O薄膜における電界誘起構造変化

寺門信明, 寺門信明, 町田雄気, 高橋儀宏, 藤原巧

応用物理学会春季学術講演会講演予稿集(CD-ROM)　66th　2019年
光触媒材料を指向したBi2Ti2O7ナノ結晶化ガラスの作製

KWON O. H., KWON O. H., BAEK C. G., 寺門信明, 高橋儀宏, 藤原巧, YANG Y. S.

日本セラミックス協会年会講演予稿集(CD-ROM)　2019　2019年
完全表面結晶化ガラスのPockels定数および二次非線形光学定数

高野和也, 舟嶋康祐, 高橋儀宏, 山崎芳樹, 寺門信明, 藤原巧

日本セラミックス協会年会講演予稿集(CD-ROM)　2019　2019年
Fresnoite型Ba2TiGe2O8結晶化ガラス:前駆体組成が与える微細組織とPockels効果への影響

岡本晴樹, 大槻智貴, 寺門信明, 高橋儀宏, 藤原巧

ガラスおよびフォトニクス材料討論会講演要旨集　60th　2019年
温度センシングに向けた残光性ジルコニアにおける熱処理温度と測定精度の関係

佐藤碧丹, 寺門信明, 高橋儀宏, 尾上紀子, 篠崎毅, 藤原巧

応用物理学会東北支部学術講演会(CD-ROM)　74th　2019年
核磁気共鳴法を用いたMgO飽和析出ガラスの構造調査と熱伝導性の向上

吉嶺季和, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会東北支部学術講演会(CD-ROM)　74th　2019年
生体温度センシングを指向したSmドープZrO2残光体の開発

後藤聡敏, 大橋昌立, 寺門信明, 高橋儀宏, 中島靖, 尾上紀子, 篠崎毅, 藤原巧

セラミックス基礎科学討論会講演要旨集　57th　2019年
熱のアクティブ制御に向けたスピン熱伝導性薄膜の配向制御

渡辺祥太, 寺門信明, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会春季学術講演会講演予稿集(CD-ROM)　66th　2019年
La-Ca-Cu-O系スピン熱伝導薄膜における粒径と物性値の関係

奈良由紀, 寺門信明, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会春季学術講演会講演予稿集(CD-ROM)　66th　2019年
b軸配向したスピン梯子系Sr14Cu24O41スパッタ膜の形成機構とその熱伝導率

渡辺祥太, 奈良由紀, 寺門信明, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会秋季学術講演会講演予稿集(CD-ROM)　80th　2019年
透明かつ高熱伝導なMgO飽和析出ガラスの開発と評価

吉嶺季和, 小澤龍成, 寺門信明, 高橋儀宏, 藤原巧

セラミックス基礎科学討論会講演要旨集　57th　2019年
熱の電界制御に向けたLa-Ca-Cu-O系スピン熱伝導性薄膜の作製と周波数領域サーモリフレクタンス法による熱伝導性評価

奈良由紀, 寺門信明, 高橋儀宏, 藤原巧

セラミックス基礎科学討論会講演要旨集　57th　2019年
Science As Art

舟嶋康祐, 高橋儀宏, 寺門信明, 藤原巧

応用物理　87　(11)　805-805　2018年11月
光と色に関わるフォトセラミックスの最先端「生体温度センシングのためのZrO2の残光および輝尽発光」

高橋儀宏, 寺門信明, 尾上紀子, 篠崎毅, 藤原巧

セラミックス　53　(7)　500-502　2018年7月
レーザー照射によるシリケート系ガラスへの局所結晶化およびドメイン制御

林原佑太, 舟嶋康祐, 寺門信明, 高橋儀宏, 藤原巧

電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018年

ISSN：0913-5685
放射状分極構造を有する結晶化ガラスファイバーの創製と非線形光学効果

林原佑太, 舟嶋康祐, 寺門信明, 高橋儀宏, 小澤祐市, 佐藤俊一, 長能重博, 藤原巧

電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018年

ISSN：0913-5685
MgO飽和析出によるガラス複合材料の開発及び光透過率・熱伝導率評価

吉嶺季和, 小澤龍成, 寺門信明, 高橋儀宏, 藤原巧

電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018年

ISSN：0913-5685
生体温度センシングのプローブのための残光体開発-ZrO2へのSmドーピング効果-

後藤聡敏, 大橋昌立, 寺門信明, 高橋儀宏, 中島靖, 尾上紀子, 篠崎毅, 藤原巧

電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018年

ISSN：0913-5685
MgO飽和析出による透明かつ高熱伝導なガラス複合材料の開発

吉嶺季和, 小澤龍成, 寺門信明, 高橋儀宏, 藤原巧

日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)　31st　2018年
La-Ca-Cu-O系スピン熱伝導性薄膜の電圧印加下における熱伝導率評価

奈良由紀, 寺門信明, 高橋儀宏, 藤原巧

電子情報通信学会技術研究報告　118　(238(OFT2018 13-51)(Web))　2018年

ISSN：0913-5685
La-Ca-Cu-O系スピン熱伝導性薄膜の熱伝導率評価と電界効果

奈良由紀, 寺門信明, 高橋儀宏, 藤原巧

日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)　31st　2018年
熱流の電気制御に向けたLa-Ca-Cu-O系スピン熱伝導性薄膜の作製と非弾性光散乱

町田雄気, 寺門信明, 高橋儀宏, 藤原巧

応用物理学会東北支部学術講演会(CD-ROM)　73rd　2018年
スピン・フォノン熱伝導性薄膜の作製とパターニングによる人工熱物性の開拓 (特集ガラス転移を超えて,ランダム系構造・物性の進展)

寺門信明, 山崎芳樹, 高橋儀宏, 藤原巧

New glass　31　(3)　21-24　2016年11月
出版者・発行元：ニューガラスフォーラム
ISSN：0914-6563
スピン・フォノン熱伝導性薄膜の作製とパターニングによる人工熱物性の開拓

寺門信明, 山崎芳樹, 高橋儀宏, 藤原巧

NEW GLASS　31　219-222　2016年6月
ガラスの不均一性によるナノ結晶化と機能性発現

高橋儀宏, 寺門信明, 藤原巧

セラミックス　51　234-236　2016年4月
結晶化ガラス，材料としての可能性と限界～結晶化の因果律からの検証～

藤原巧

セラミックス　50　29-33　2015年11月
出版者・発行元：日本セラミックス協会
Science As Art

星野愛信, 高橋儀宏, 寺門信明, 藤原巧

応用物理　84　(5)　381-381　2015年5月10日
完全表面結晶化による透明結晶化ガラスの創製

高橋儀宏, 山崎芳樹, 藤原巧

応用物理　83　(7)　560-564　2014年7月
出版者・発行元：応用物理学会
ISSN：0369-8009
不均質ガラスによる光学応用の新展開～アクティブ光ファイバーと光学的ストイキオメトリ―～

藤原巧, 山崎芳樹, 高橋儀宏, 井原梨恵, 寺門信明

セラミックス　49　604-607　2014年7月
電子顕微鏡による結晶化ガラスの微細組織観察

宮崎孝道, 高橋儀宏, 藤原巧, 正井博和

NEW GLASS　29　14-19　2014年6月
Science as art

星野愛信, 高橋儀宏, 寺門信明, 藤原巧

応用物理　29　(3)　67-69　2014年
シリケート結晶化ガラスにおける単結晶ドメイン中への非晶質粒子の寄生

高橋儀宏, 山崎芳樹, 井原梨恵, 藤原巧

NEW GLASS　28　(1)　29-33　2013年3月
出版者・発行元：ニューガラスフォーラム
ISSN：0914-6563
IMID2012参加報告 : 蛍光体材料分野における : 最新研究と大邱(テグ)紀行 (情報ディスプレイ・IMID2012報告会)

高橋儀宏, 藤原巧

映像情報メディア学会技術報告　36　(45)　17-19　2012年11月
出版者・発行元：映像情報メディア学会
ISSN：1342-6893
IMID 2012参加報告－蛍光体材料分野における : 最新研究と大邸(テグ)紀行

高橋儀宏, 藤原巧

電子情報通信学会技術研究報告. EID, 電子ディスプレイ　112　(278)　17-19　2012年10月31日
出版者・発行元：一般社団法人電子情報通信学会
ISSN：0913-5685

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韓国のテグで開催された国際学会IMID 2012に参加した際の注目研究発表の内容をメインに報告する.
ゾル-ゲル法によるBa2TiSi2O8薄膜の結晶化挙動の評

佐藤恵斗, 井原梨恵, 高橋儀宏, 藤原巧, 正井博和

日本セラミックス協会第25会秋季シンポジウム ,名古屋　2012年9月20日
Photocatalytic Activity and Chemical Durability in Sr0.5Ba0.5Nb2O6 (SBN50) Crystallized Glass

Yoshida, K, Masai, H, Takahashi, Y, Ihara, R, Fujiwara, T

XIII International Conference on the Physics of Non-Crystalline Solids ,Yichang, China　2012年9月19日
BaO-TiO2-GeO2再溶融ガラスにおけるPtナノ結晶析出

正井博和, 浜口克己, 岩崎謙一郎, 井原梨恵, 高橋儀宏, 藤原巧

2012年秋季第73回応用物理学会学術講演会 ,松山　2012年9月12日
Sr0.5Ba0.5Nb2O6結晶化ガラスの構造解析

吉田和貴, 正井博和, 高橋儀宏, 井原梨恵, 藤原巧

2012年秋季第73回応用物理学会学術講演会 ,松山　2012年9月12日
BI-6-2 結晶化ガラスによるアクティブ光ファイバー型デバイスの開発(BI-6.特殊光ファイバの産業・医療応用 -画像伝送・パワー伝送を中心に-,依頼シンポジウム,ソサイエティ企画)

大原盛輝, 藤原巧

電子情報通信学会ソサイエティ大会講演論文集　2012　(2)　"SS-96"-"SS-97"　2012年8月28日
出版者・発行元：一般社団法人電子情報通信学会
Sn2+発光中心を有するリン酸塩ガラス蛍光体における発光特性

正井博和, 山田泰裕, 徳田陽明, 横尾俊信, 藤原巧

第7回日本セラミックス協会関西支部学術講演会 ,神戸　2012年7月13日
SBN50結晶化ガラスの構造と化学的耐久性との相関

吉田和貴, 高橋儀宏, 井原梨恵, 藤原巧, 正井博和

日本セラミックス協会2012年年会 ,京都　2012年3月20日

DOI： 10.14853/pcersj.2012S.0.481.0 　
SnO-ZnO-P2O5-SiO2系ガラスの熱的特性とガラス構造

井原梨恵, 黒江礼奈, 高橋儀宏, 正井博和, 藤原巧

第59回応用物理学関係連合講演会 ,東京　2012年3月17日
Sn2+含有ホウ酸塩ガラス蛍光体の発光特性

正井博和, 鈴木優斗, 山田泰裕, 藤原巧, 徳田陽明, 横尾俊信

第59回応用物理学関係連合講演会 ,東京　2012年3月16日
エッチングを施したSBN50結晶化ガラスの光触媒反応による水分解の測定

吉田和貴, 正井博和, 高橋儀宏, 井原梨恵, 藤原巧

第59回応用物理学関係連合講演会 ,東京　2012年3月16日
多様な配位多面体を有するチタン酸塩の発光―希土類フリー蛍光体として

高橋儀宏, 藤原巧

NEW GLASS　27　(104)　8-13　2012年3月
出版者・発行元：ニューガラスフォーラム
Sn含有ホウ酸塩ガラスにおける発光特性の評価

正井博和, 鈴木優斗, 山田泰裕, 藤原巧, 徳田陽明, 横尾俊信

The 22st Meeting on Glasses for Photonics ,東京　2012年2月7日
SnO-SrO-B2O3ガラス蛍光体におけるSnO含有量と発光特性との相関

鈴木優斗, 正井博和, 山田泰裕, 徳田陽明, 横尾俊信, 藤原巧

日本セラミックス協会年会講演予稿集　2012　2012年
Sn含有リン酸塩ガラスの組成と発光特性との相関

谷本俊朗, 正井博和, 藤原巧, 松本修治, 徳田陽明, 横尾俊信

第52回ガラスおよびフォトニクス材料討論会 ,姫路　2011年11月25日
Glass-Ceramics Containing Nano-Crystallites of Oxide Semiconductor

Masai, H, Fujiwara, T

BIT's 1st Annual World Congress of Nano-S&T 2011 ,Dalian, China　2011年10月26日
Sb3+含有ガラス蛍光体の開発

正井博和, 藤原巧, 松本修治, 高橋儀宏, 徳田陽明, 横尾俊信

日本セラミックス協会第24会秋季シンポジウム ,北海道　2011年9月8日

DOI： 10.14853/pcersj.2011F.0.370.0 　
Sn2+含有酸化物ガラス蛍光体における発光特性

正井博和, 藤原巧, 山田泰裕, 高橋儀宏, 徳田陽明, 横尾俊信

2011年秋季第72回応用物理学会学術講演会 ,山形　2011年8月31日
Sb3+発光中心を有する酸化物ガラス蛍光体の作製

正井博和, 藤原巧, 松本修治, 徳田陽明, 横尾俊信

2011年秋季第72回応用物理学会学術講演会 ,山形　2011年8月31日
希土類フリーガラス蛍光体の開発

正井博和, 横尾俊信, 藤原巧, 松本修治

マテリアルステージ　11　5-7　2011年6月10日
出版者・発行元：技術情報教会
希土類フリーガラス蛍光体の開発と応用

正井博和, 藤原巧, 松本修治, 横尾俊信

ＮＥＷＧＬＡＳＳ　26　(2)　20-25　2011年6月
出版者・発行元：ニューガラスフォーラム
Sn含有ガラス蛍光体の組成と発光特性との相関

正井博和, 谷本俊朗, 藤原巧, 松本修治, 高橋儀宏, 徳田陽明, 横尾俊信

第58回応用物理学関係連合講演会 ,神奈川　2011年3月25日
SnO-ZnO-P2O5ガラス蛍光体におけるSnO含有量と発光特性との相関

谷本俊朗, 正井博和, 藤原巧, 松本修治, 高橋儀宏, 徳田陽明, 横尾俊信

日本セラミックス協会2011年年会 ,浜松　2011年3月18日
白色発光を呈する新規希土類フリーガラス蛍光体の開発

正井博和, 藤原巧, 松本修治, 高橋儀宏, 徳田陽明, 横尾俊信

応用物理学関係連合講演会講演予稿集(CD-ROM)　58th　ROMBUNNO.25P-BJ-8　2011年3月9日
Sn含有希土類フリーガラス蛍光体の開発

松本修治, 正井博和, 藤原巧, 松本修治, 高橋儀宏, 徳田陽明, 横尾俊信

豊田工業大学ハイテク・リサーチ・センター先端フォトンテクノロジー研究センター第12回シンポジウム ,名古屋　2011年3月4日
新規希土類フリーガラス蛍光体の創製

正井博和, 藤原巧, 松本修治, 高橋儀宏, 徳田陽明, 横尾俊信

The 21st Meeting on Glasses for Photonics ,東京　2011年2月9日

DOI： 10.14853/pcersj.2011S.0.330.0 　
ガラスの結晶化と非線形フォトニクス応用

高橋儀宏, 井原梨恵, 藤原巧

MICROOPTICS NEWS　28　(4)　55-60　2010年12月
出版者・発行元：微小光学研究グループ機関紙
ボソンピークから見たガラス構造と結晶化過程

高橋儀宏, 藤原巧

New Glass　25　(4)　38-42　2010年10月
出版者・発行元：ニューガラスフォーラム
進展続けるガラス－構造制御と光・電気機能性－

藤原巧, 後藤民浩, 鍋谷暢一, 沼田秀昭, 和田健司

応用物理　78　(7)　624-624　2009年7月1日
出版者・発行元：応用物理学会
ISSN：0369-8009
光結晶化ファイバの創製と電気光学デバイス開発

大原盛輝, 正井博和, 高橋儀宏, 藤原巧, 近藤裕己, 杉本直樹

ＮＥＷＧＬＡＳＳ　24　(2)　49-55　2009年6月
出版者・発行元：ニューガラスフォーラム
Electro-Optic Fiber Devices in Crystallized Glass

Takumi Fujiwara, Seiki Ohara

New Breeze　21　(2)　18-19　2009年5月
出版者・発行元：日本ＩＴＵ協会
Low-frequency inelastic light scattering of glassy fresnoite: A nanocrystallization scenario 査読有り

Y. Takahashi, M. Osada, H. Masai, T. Fujiwara

IEEE International Symposium on Applications of Ferroelectrics　2009年

DOI： 10.1109/ISAF.2009.5307528 　
ガラスの結晶化／光結晶化と非線形光学応用

藤原巧, 高橋儀宏, 正井博和

セラミックス　43　(12)　1036-1041　2008年12月
出版者・発行元：日本セラミックス協会
ISSN：0009-031X
時空間レーザー結晶化法によるガラスの異相構造形成とナノ・フォトニクス回路

藤原巧, 水野真太郎

ＮＥＷＧＬＡＳＳ　23　(2)　21-27　2008年6月
出版者・発行元：（社）ニューガラスフォーラム
ISSN：0914-6563
酸化チタン透明ナノ結晶化ガラスの創製

藤原巧, 正井博和

未来材料　8　(3)　22-28　2008年3月
出版者・発行元：(株）エヌ・ティー・エス
酸化チタン透明ナノ結晶化ガラス

藤原巧

ＯＨＭ　94　(8)　10-11　2007年8月
出版者・発行元：オーム社
ナノ結晶化ガラスを用いた新規光学デバイスへの展開

正井博和, 藤原巧

ＮＥＷＧＬＡＳＳ　22　(2)　33-39　2007年6月
出版者・発行元：(社）ニューガラスフォーラム
ISSN：0914-6563
希土類原子加熱法によるガラス表面への光導波路形成

小松高行, 井原梨恵, 本間剛, 紅野安彦, 藤原巧

希土類 = Rare earths　(48)　32-33　2006年5月23日

ISSN：0910-2205
レーザーによるガラス中への周期構造の形成と非線形光学現象の発現

小松高行, 藤原巧, 紅野安彦

応用物理　75　(5)　553-559　2006年5月
光機能結晶化ガラス

小松高行, 紅野安彦, 藤原巧

光学　35　(3)　133-138　2006年3月
出版者・発行元：日本光学会（応用物理学会）
Thermal poling of transparent TeO2-based nanocrystallized glasses and enhanced second harmonic generation

N Tamagawa, Y Benino, T Fujiwara, T Komatsu

OPTICS COMMUNICATIONS　217　(1-6)　387-394　2003年3月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/S0030-4018(02)02356-8 　

ISSN：0030-4018

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A transparent TeO2-based nanocrystallized (crystalline particle size: similar to40 nm) glass (composition: 15K(2)O . 15Nb(2)O(5). 68TeO(2) . 2MoO(3)) showing a second harmonic generation (SHG) has been prepared, and a thermal poling has been applied to examine whether a poling technique is effective in enhancing the SH intensity of nanocrystallized glass. In the poling condition of 2.0 kV (DC voltage), 210 degreesC and 40 min, the SH intensity of nanocrystallized glass is enhanced, demonstrating that a combination of nanocrystallization and thermal poling is an useful technique to induce a SHG in glass. As similar to the case of glass, a prominent SHG is observed at the anode side in the thermal poling, suggesting the increase in polarization in nanocrystals. (C) 2003 Elsevier Science B.V. All rights reserved.
レーザー誘起ナノ結晶化によるフォトニック・ガラスの創製

藤原巧, 本間剛, 高橋儀宏, 紅野安彦, 小松高行, 佐藤隆士

光アライアンス　14　(4)　12-17　2003年
出版者・発行元：日本工業出版
ISSN：0917-026X
YAG laser-induced crystalline dot patterning in samarium tellurite glasses

R Sato, Y Benino, T Fujiwara, T Komatsu

JOURNAL OF NON-CRYSTALLINE SOLIDS　289　(1-3)　228-232　2001年8月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/S0022-3093(01)00736-0 　

ISSN：0022-3093

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CW YAG laser with a wavelength of 1064 mn and with a power of 1 W has been used to irradiate samarium. tellurite glasses with the compositions of 10RO (.) 10SM(2)O(3) (.) 80TeO(2) (R= Mg, Ba) at room temperature for 30-60 s. It is found from polarized optical microscopy and from X-ray diffraction (XRD) analyses that crystalline dot patterns with sharp refractive index changes are formed by laser irradiation. The diameters of the spherical dots in the glasses with BaO and MgO are about 50 and 150 tm, respectively. It has been proposed that the crystallization of a nanocrystalline Sm2Te6O15 phase is induced through the absorption of irradiated YAG laser by the Sm3+ ions. This is the first finding of crystalline dot patterning induced by infrared CW YAG laser irradiation in glass. (C) 2001 Published by Elsevier Science B.V.
紫外光ポーリングによる2次光非線形性-規則化構造制御と機能性発現-

藤原巧

セラミックス　36　(2)　76-79　2001年2月1日
出版者・発行元：日本セラミックス協会
ISSN：0009-031X
Silica glass: A material for photonics

AJ Ikushima, T Fujiwara, K Saito

JOURNAL OF APPLIED PHYSICS　88　(3)　1201-1213　2000年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.373805 　

ISSN：0021-8979

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Recent studies on two aspects of silica glass as a photonic material will be described. Part A of this review will be focused on structural disorder and structural relaxations in silica glass. With regard to the structural disorder, investigations have been made to improve transparency and to shift the optical absorption edge in the ultraviolet towards shorter wavelengths. Remarkable advances have been achieved in the understanding of both light scattering, which is a dominant factor in the optical losses in silica fibers, and the absorption edge. Freezing of the structural disorder was observed, and structural relaxations are found to be important for improving the transparency, whereas for the absorption edge thermal vibration effects seem to be more predominant than the structural disorder. From the results, the present authors have tried to control the structural relaxation for developing silica glass with an ultimate optical transparency, finding that a very tiny amount of the proper impurity species gives rise to structural subrelaxations, which are effective in reducing the Rayleigh scattering. The scattering was reduced by 13% by addition of only 10 wt ppm Na2O, for example. In part B of this review the second-order optical nonlinearity induced in Ge-doped silica glass will be described based on recent experiments carried out by the group of present authors. A large second-order optical nonlinearity has been successfully induced in the glass by simultaneous applications of a high dc electric field and ultraviolet (UV) irradiation, so-called UV poling. The nonlinearity induced by UV poling in bulk and film samples has achieved a magnitude of chi((2)), comparable to or even larger than those of LiNbO3 and other crystals. Surprisingly enough, the nonlinearity induced by this method then decays after the UV poling as an exact single-exponential function of time, very much unlike the usual decay processes observed in glasses. Evidence is presented associating the nonlinearity with GeE' defect centers created from oxygen deficient vacancies through photochemical reactions. The decay or degradation can be made much slower with the addition of proper impurities which work as electron scavengers. In addition, we have found that crystallites are generated in the glass by the UV poling, which leads to an increase in the third-order nonlinearity, chi((3)), approximately 15 times larger than before the treatment. As a whole, the evidence strongly suggests that a major origin of the second-order nonlinearity induced in the glass is a combined effect of a large third-order nonlinearity associated with the crystallites and an internal space-charge field, where the charges to build up the field are produced during the formation of GeE' centers. (C) 2000 American Institute of Physics. [S0021-8979(00)04815-5].
Origin and properties of second-order optical non-linearity in ultraviolet-poled GeO2-SiO2 glass

T Fujiwara, S Matsumoto, M Ohama, AJ Ikushima

JOURNAL OF NON-CRYSTALLINE SOLIDS　273　(1-3)　203-208　2000年8月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/S0022-3093(00)00168-X 　

ISSN：0022-3093

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Progress in establishing larger second-order optical non-linearity in Ge-doped silica glass (15.7 GeO2-84.3 SiO2 in mol%) induced by simultaneous applications of a direct current (DC) electric field (less than or equal to 10(5) V/cm) and ultraviolet laser irradiation (193 nm), the so-called the ultraviolet (UV)-poling method, is reported. The non-linearity thus induced has been shown to be affected by the GeE' centers created from oxygen deficient vacancies through photo-chemical reactions. In addition, we have found for the first time, to our knowledge, that crystallization in the glass is induced by the UV-poling, which leads to increase of third-order non-linearity, chi((3)), approximately 15 times larger than that before W-poling. Based on these results we suggest that origin of the second-order non-linearity in the glass induced by UV-poling is a combined effect of the third-order non-linearity possessed by the crystallites and an internal space-charge field where the charges are assumed to be produced during the formation of GeE' centers. (C) 2000 Elsevier Science B.V. All rights reserved.
Generation of second harmonics in Ge-doped SiO2 thin films by ultraviolet irradiation under poling electric field

J Khaled, T Fujiwara, M Ohama, AJ Ikushima

JOURNAL OF APPLIED PHYSICS　87　(5)　2137-2141　2000年3月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.372152 　

ISSN：0021-8979

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Thin films of Ge-doped silica were prepared by radio-frequency sputtering in a controlled atmosphere of Ar and O-2 and then subjected to ultraviolet irradiation under poling electric field (UV poling). Effects of oxygen mass flow content during the sputtering on the second-order nonlinearity of the films were investigated. Second harmonic generation (SHG) was observed and its intensity was found to depend greatly on the oxygen mass flow content with an optimum at 1 cm(3)/min. The annealing in a vacuum enhanced SHG intensity and values as high as 12.5 +/- 0.6 pm/V have been achieved with films containing 50 mole % of GeO2. This is on one hand, and we also found that loading thin films with hydrogen prior to UV poling largely improved the decay of SHG. A decay time as long as 7 years has been obtained. The change in second-order optical nonlinear properties of the films is discussed based on structural defects. (C) 2000 American Institute of Physics. [S0021-8979(00)01705-9].
Induced defects and increase of second-order nonlinearity in ultraviolet-poled GeO2SiO2 glass

M Ohama, T Fujiwara, AJ Ikushima

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS　38　(11)　6359-6361　1999年11月
出版者・発行元：JAPAN J APPLIED PHYSICS
DOI： 10.1143/JJAP.38.6359 　

ISSN：0021-4922

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We report on enhancement by thermal defects control of the second-order optical nonlinearity in GeO2-SiO2 glass induced by ultraviolet (UV) poling. The present work is based on the previous results which suggest GeE' centers as the most relevant ingredient to produce the induced nonlinearity, and heat treatment in a vacuum before UV poling has been found to increase the induced second-harmonic generation (SHG). The result is thought to be related to an increase of oxygen deficient defects, which function as precursors of the photoinduced GeE' centers. To obtain larger d coefficient, optimization of pre-heat treatment conditions, temperature and time duration, have been investigated. The largest value of d(33) coefficient thus far obtained is 5.1 +/- 0.2 pm/V in UV-poled GeO2-SiO2 glass of 15 mole % GeO2 content with the pre-heat treatment at 1200 degrees C for 5 h, which exceeds d(13), the second largest coefficient of LiNbO3.
Crystallization of GeO2-SiO2 glass by poling with ArF-laser excitation

S Matsumoto, T Fujiwara, M Ohama, AJ Ikushima

OPTICS LETTERS　24　(20)　1404-1406　1999年10月
出版者・発行元：OPTICAL SOC AMER
DOI： 10.1364/OL.24.001404 　

ISSN：0146-9592

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We report on crystallization of 15.7GeO(2).84.3SiO(2) (in mol.%) glass by poling with ArF-laser excitation. The UV intensity was 100 (mJ/cm(2))/pulse, and the number of shots was 10(4). The crystallites that were observed in the glass were approximately 15-20 mu m in diameter. The crystallization feature was dependent on the poling electric field, showing a threshold field of similar to 0.5 x 10(5) V/cm, beyond which crystallization occurred. (C) 1999 Optical Society of America OCIS codes: 160.2750, 160.4330, 060.4510.
Comparison of electro-optic effect between stoichiometric and congruent LiNbO3

T Fujiwara, M Takahashi, M Ohama, AJ Ikushima, Y Furukawa, K Kitamura

ELECTRONICS LETTERS　35　(6)　499-501　1999年3月
出版者・発行元：IEE-INST ELEC ENG
DOI： 10.1049/el:19990320 　

ISSN：0013-5194

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Comparison of the electro-optic (EO) effect between stoichiometric and congruent lithium niobate (LiNbO3) crystals has been investigated using the Mach-Zehnder interferometer at 0.633 mu m wavelength. Anisotropic changes of EO coefficients, r(33) and r(13), have been found between the stoichiometric and congruent LiNbO3 crystals. The measured r(33) value in the stoichiometric LiNbO3 is at least 20% larger than that of LiNbO3 with congruent composition, whereas the r(13) coefficient of stoichiometric LiNbO3 is the same as that of congruent LiNbO3.
Decay of ultraviolet-induced optical absorption in Ge-doped SiO2 glass

M Ohama, T Fujiwara, AJ Ikushima

APPLIED PHYSICS LETTERS　73　(11)　1481-1483　1998年9月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.122179 　

ISSN：0003-6951

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We report quantitative measurements on the decay of optical absorption at various elevated temperatures in ultraviolet (UV)-irradiated SiO2 glasses doped with Ge. From the Arrhenius plots of decay time constants, the activation energy of the Ge E' center in the UV-irradiated glasses has been determined to be 2.4 +/- 0.3 eV, while the reported activation energy of Ge E' decay in UV-poled glasses is 0.4 +/- 0.1 eV. The present experimental results strongly suggest that the decay process of the Ge E' center induced in UV-irradiated glasses is quite different from that in UV-poled glasses. (C) 1998 American Institute of Physics.
Thermal equilibrium of Ge-related defects in a GeO2-SiO2 glass

M Takahashi, T Fujiwara, T Kawachi, AJ Ikushima

APPLIED PHYSICS LETTERS　72　(11)　1287-1289　1998年3月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.121052 　

ISSN：0003-6951

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In a 15.7 GeO2 . 84.3 SiO2 glass prepared by a vapor axial deposition method, optical absorptions at 4.92 and 5.08 eV were observed from 300 to 600 K. The results were then compared with electron spin resonance (ESR) measurement using the same samples. The absorption at 4.92 eV was found to increase with increasing temperature, while the optical absorption at 5.08 eV decreased with increasing temperature. These changes of optical absorption indicate that the concentration of neutral oxygen monovacancy is reduced at higher temperatures. The changes were quite reversible with the temperature. Concentration of Ge E' center, estimated from ESR, increased with increasing temperature, which is in contrast with the decrease of neutral oxygen monovacancy. The present result strongly suggests the thermal equilibrium reaction between neutral oxygen monovacancy and Ge E' center. (C) 1998 American Institute of Physics.
Second-order nonlinearity and structural change in UV-poled glass

T Fujiwara, M Ohama, S Matsumoto, AJ Ikushima

DOPED FIBER DEVICES II　3542　94-101　1998年
出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING
ISSN：0277-786X

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A large second-order nonlinearity in Ge-doped silica glass induced by simultaneous applications of a high DC electric field and ultraviolet irradiation (W-poling) is reported. The nonlinearity thus induced has been found to be quite relevant to the GeE' center. The d coefficient so far obtained exceeds the second biggest d-tensor component of LiNbO3.
Second-harmonic generation in UV-poled glass

T Fujiwara, M Takahashi, AJ Ikushima

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS　37　15-18　1998年
出版者・発行元：JAPAN J APPLIED PHYSICS
ISSN：0021-4922

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A remarkably large second-harmonic generation (SHG) in a germanosilicate glass (15.7 GeO2-84.3 SiO2 in mol.%), which was induced by poling with ArF laser irradiation at the wavelength of 193 nm is reported Using the Maker-Fringe technique, the induced SHG coefficient, d, was measured at various poling electric-field strengths. The measured d coefficient value increases with increasing poling field and then saturates around 1.5x10(5) V/cm. The largest d coefficient value obtained in this experiment, which is 3.4+/-0.3 pm/V, seems to exceed d(22) of LiNbO3. Furthermore, polarization dependence of the induced SHG indicates an anisotropy of the refractive index.
A large second-order optical nonlinearity in glass

Photonics Science News　4　30　1998年
Second-harmonic generation in germanosilicate glass poled with ArF laser irradiation

T Fujiwara, M Takahashi, AJ Ikushima

APPLIED PHYSICS LETTERS　71　(8)　1032-1034　1997年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.119718 　

ISSN：0003-6951

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We report on a remarkably large second-harmonic generation (SHG) in a germanosilicate glass 15.7 GeO2-84.3 SiO2 in mol %), which was induced by poling while the sample was irradiated with the ArF laser at the wavelength of 193 nm. The SHG coefficient, d, thus induced was measured at various poling electric-field strengths using the Maker-fringe technique. The value of d increases with increasing poling field and then saturates around 1.5x10(5) V/cm. The largest d coefficient value obtained in this work, which is 3.4+/-0.3 pm/V, seems to exceed d(22) of LiNbO3. Furthermore, polarization dependence of the induced SHG shows an anisotropy of the refractive index. (C) 1997 American Institute of Physics.
Defect formation in GeO2-SiO2 glass by poling with ArF laser excitation

M Takahashi, T Fujiwara, T Kawachi, AJ Ikushima

APPLIED PHYSICS LETTERS　71　(8)　993-995　1997年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.119749 　

ISSN：0003-6951

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We have investigated formation of Ge-related defects in a GeO2-SiO2 glass fiber preformed by poling with ArF laser excitation. Electric field dependence of the induced-defect concentrations was measured by means of the optical absorption. Several color centers such as the germanium electron-trapped centers and the Ge E' center were induced. Concentrations of the induced germanium electron-trapped centers and Ge E' center increase with increasing the electric field. Conversion efficiency from the germanium electron-trapped centers to the Ge E' center was found to be independent of the electric field. The present result strongly suggests that the poling with ArF laser excitation is effective in the present GeO2-SiO2 glass for the formation of germanium electron-trapped centers. (C) 1997 American Institute of Physics.
Decay behaviour of second-order nonlinearity in GeO2-SiO2 glass poled with UV-irradiation

T. Fujiwara, M. Takahashi, A. J. Ikushima

Electronics Letters　33　(11)　980-982　1997年5月22日
出版者・発行元：Institution of Engineering and Technology
DOI： 10.1049/el:19970622 　

ISSN：0013-5194

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Quantitative decay measurement of the second-harmonic generation (SHG) at various elevated temperatures is reported for a GeO2-SiO2 glass with 15.7 GeO2 mole %, poled with UV-irradiation. It has been observed that the decay behaviour of the induced SHG is a single-exponential process in the temperature range 200-500°C. From the Arrhenius plot of the decay timeconstant, the activation energy of the induced SHG is 0.41 ± 0.05eV, and the decay time-constant at 15°C is ∼280 days.
Polarization dependent loss in a Ti:LiNbO3 polarization scrambler controller

T Fujiwara, A Watanabe, H Mori

IEEE PHOTONICS TECHNOLOGY LETTERS　8　(4)　542-544　1996年4月
出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI： 10.1109/68.491220 　

ISSN：1041-1135

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We have investigated the polarization dependent loss (PDL) of a waveguide-type polarization scrambler/controller consisting of a half-wave plate (HWP) and a quarter-wave plate (QWP) in series fabricated in x-cut/z-propagating Ti-diffused LiNbO3 optical waveguides, Based on the polarization dependences of both the propagation loss coefficient and mode-mismatch loss with fiber at 1.55 mu m combined with a numerical analysis, the PDL of the fabricated device is estimated to be 0.063 dB, It is shown that the low PDL is a direct consequence of a special anisotropy relation between the propagation loss and waveguide-fiber mode-mismatch loss.
LARGE ELECTROOPTIC MODULATION IN A THERMALLY-POLED GERMANOSILICATE FIBER

T FUJIWARA, D WONG, S FLEMING

IEEE PHOTONICS TECHNOLOGY LETTERS　7　(10)　1177-1179　1995年10月
出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI： 10.1109/68.466582 　

ISSN：1041-1135

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A large linear electro-optic phase shift observed in a germanosilicate fiber has been induced by thermal poling at about 250 degrees C for 20-60 min with an electric field of > 8 x 10(5) V/cm and a 3.3-cm electrode length. Polarization dependence of the V(pi)L product in a birefringent germanosilicate fiber has been found, and the lowest V(pi)L product has been measured for TE-polarization of 224 V/cm at 633 nm. Furthermore, it has been found that the electrical resistance between the electrodes is reduced by thermal poling.
ELECTROOPTIC MODULATION IN GERMANOSILICATE FIBER WITH UV-EXCITED POLING

T FUJIWARA, D WONG, Y ZHAO, S FLEMING, S POOLE, M SCEATS

ELECTRONICS LETTERS　31　(7)　573-575　1995年3月
出版者・発行元：IEE-INST ELEC ENG
DOI： 10.1049/el:19950384 　

ISSN：0013-5194

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The authors report what is, to their knowledge, the highest electro-optic effect measured in a germanosilicate fibre ever reported. The electro-optic effect based on a permanent second-order nonlinearity has been induced by UV-excited poling at 193 nm with an electric field > 8 x 10(5) V/cm. Polarisation dependence of the V(pi)L product in a birefringent fibre has been observed, and the lowest V(pi)L product obtained for the TE mode of 32 Vcm, comparable to that based on r(22) of LiNbO3, has been measured at 633 nm with a phase modulation at frequencies up to 5 MHz.
UV-Excited Poling and Electrically tunable Bragg Gratings in a germanosilicate fiber

Optical Fiber Conference　1995年
UV excited poling of germanosilicate fibre

Photosensitivity and Quadratic Nonlinearity in Glass Waveguides　1995年
Defect formation in GeO2-SiO2 glass by UV-excited poling

Japanese Journal of Applied Physics　37　71

︎全件表示 ︎最初の5件までを表示

書籍等出版物 6

化学便覧

藤原巧

丸善　2012年12月
Ceramic Materials

H. Masai, Y. Takahashi, T. Fujiwara

In Tech Publishing　2011年2月
無機材料必須３００

藤原巧

三共出版　2008年6月15日
ガラスの百科事典

藤原巧

（株）朝倉書店　2007年10月20日
ナノマテリアル工学大系

藤原巧, 水野真太郎, 紅野安彦, 小松高行

（株）フジ・テクノシステム　2005年10月17日
非晶質SiO2材料応用ハンドブック

リアライズ社　1999年

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講演・口頭発表等 24

Synthesis of spinon thermal conductivity materials by ordering process in Sr-Cu-O inhomogeneous system for thermal management materials 国際会議

N. Terakado, Y. Takahashi, T. Fujiwara

40th International Conference and Exposition on Advanced Ceramics and Composites　2016年1月24日
Pockels effect in glass-ceramics with polar phase: A new class of photonic material 国際会議

Y. Takahashi, Y. Yamazaki, N. Terakado, T. Fujiwara

Third International Workshop on Advanced Functional Nanomaterials　2015年12月16日
Perfect surface crystallization of fresnoite phase: Morphology and physical properties 国際会議

Y. Takahashi, N. Terakado, T. Fujiwara

Eighth French Research Organizations Tohoku University Joint Workshop on Frontier Materials　2015年11月29日
Preparation of layer-type SrCuO2 by rf-magnetron sputtering and its laser-induced structure change to chain-type 国際会議

N. Terakado, R. Takahashi, Y. Takahashi, T. Fujiwara

International Conference on Small Science　2015年11月5日
Crystallization in Glass for Advanced Photonic Application 国際会議

T. Fujiwara, Y. Takahashi, N. Terakado

The 9th International Conference on the Science and Technology for Advanced Ceramics　2015年10月20日
Crystallization in glass with transition-metal oxide: Comprehensive aspects of glass-ceramics for advanced functional material 国際会議

Y. Takahashi, N. Terakado, T. Fujiwara

11th International Symposium on Crystallization in Glasses and Liquids　2015年10月11日
New Glass-Ceramics toward Advanced Functional Material: Conception and Creation 国際会議

Y. Takahashi, N. Terakado, T. Fujiwara

The 8th Symposium on China Functional Glasses and International Forum on New Photoelectric Materials　2015年9月5日
Crystallization in Glass: Novel Functional Materials for Photonic Application 国際会議

The Sixth Symposium on Function Glasses and International Forum on Novel Optoelectoronic Materials　2012年11月19日
White Light Emission of Rare Earth-Free Phosphate Glass 国際会議

Hirokazu Masai

1st International Conference on Emerging Advanced Nanomaterials　2012年10月22日
White Light Emission of Rare Earth-Free Phosphate Glass 国際会議

Masai Hirokazu

Fifth International Conference on Optical, Optoelectronic and Photonic Materials and Applications　2012年6月3日
ガラスの光機能結晶化、レーザ加工とファイバ型素子への応用

ニューガラスフォーラム・ガラス科学技術研究会　2011年12月16日
Nano-Power Active Fiber Devices in Electro-Optic Crystallized Glass 国際会議

French Research Organizations-Tohoku University Joint Workshop on Frontier Materials　2011年12月4日
White Light Emission of Rare Earth-Free Phosphate Glass 国際会議

正井博和

International Symposium for Phosphor Materials 2011　2011年11月21日
光非線形ガラス材料の開発と光制御デバイスへの応用

日本セラミックス協会２０１１年年会　2011年3月16日
結晶化ガラスの光学評価と非線形フォトニクス応用

最近の結晶化ガラスとその評価技術　2011年3月9日
Nano Watt Active Fiber Devices in Electro-Optic Crystallized Glass 国際会議

2011 Photonic West　2011年1月22日
ガラスの結晶化と非線形光学応用

高橋儀宏, 井原梨恵

日本光学会第１８回微小光学研究会　2010年12月3日
ガラスの光学的性質

ニューガラス大学院　2010年10月7日
Active Fiber Devices with Nano-Watt Operations in Electr-Optic Crystallized Glass 国際会議

4th International Conference on Optical, Optoelectronic and Photonic Materials and Applications　2010年8月15日
Electro-Optic Fiber Devices with Nano-Watt Operations in Crystallized Glasses 国際会議

The 17th International Symposium on Non-Oxide and New Optical Glasses　2010年6月13日
Functional Crystallization in Glass for Photonic Application 国際会議

AEARU Advanced Materials Science Workshop　2009年11月11日
機能性結晶化ファイバの開発とその応用

大原盛輝, 正井博和, 高橋儀宏, 杉本直樹

日本化学会第８９春季年会　2009年3月27日
酸化物ガラスの光結晶化・光形態制御と最近の応用展開

第６９回応用物理学会学術講演会シンポジウム　2008年9月2日
レーザー結晶化法による光非線形ガラスの創製とフォトニクス応用

藤原巧

第１７回ナノオプティクス研究会・第６回プラズモニクスシンポジウム　2008年6月26日

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産業財産権 1

ガラス、結晶化ガラス、結晶化ガラスの製造方法及び光触媒部材

藤原巧, 正井博和, 森宏

産業財産権の種類: 特許権

共同研究・競争的資金等の研究課題 19

低エネルギーフォトン励起による近赤外エンジニアリングと非侵襲デバイス応用

高橋儀宏, 藤原巧, 寺門信明

2023年4月1日～ 2026年3月31日
ナノ結晶化ガラスの欠陥構造制御と蓄光特性

藤原巧

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Challenging Exploratory Research

研究機関：Tohoku University

2011年～ 2013年

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本研究では、「環境調和」、「安価・低コスト」、「省エネ」という環境調和型の持続社会を構築するために必要な社会要請に応えるため、ガラスにおけるナノ結晶化や熱処理により誘起される欠陥構造制御を活用する発光特性の発現と蓄光材料開発を進めた。これは、太陽光エネルギーの中で、従来は効率的に活用されていない波長の短い光エネルギーを、時間かつ周波数（波長）の観点から高効率利用が可能な形態へと変換させる画期的な技術である。具体的には、元素戦略的な観点から、希土類フリー酸化物発光体やガラス結晶化により誘起される欠陥構造が起源となり、発光の時間制御による蓄光効果が高効率に発現する新機能材料の開発に成功した。
時空間レーザー結晶化制御によるナノ構造ガラスの創製

藤原巧, 高橋儀宏, 井原梨恵, 正井博和

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (B)

研究機関：Tohoku University

2009年～ 2011年

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結晶化ガラスを機能材料として用いる場合、透明かつ高配向性を有するナノ結晶構造を実現することは極めて重要である。独自に開発したレーザーによるパルス的な時間制御加熱などの方法により、酸化チタン・ナノ結晶子がガラス表面に緻密に形成され新規機能構造の創製に成功した。レーザー結晶化の還元効果に着目し、白金などの金属微粒子が核となる結晶化ガラスを見出し、金属-誘電体複合ナノ結晶化ガラス構造を実現する成果を得た。
次元性を制御したナローギャップ半導体の機能デバイス化

梶谷剛, 藤原巧, 宮崎譲, 林慶, 湯蓋邦夫

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (A)

研究機関：Tohoku University

2007年～ 2010年

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熱流を直接電流に変換可能な熱電半導体の高性能化に向けた研究である。熱電半導体を2次元化することにより、Seebeck係数が向上することが理論的に予想され、先行研究によると、最適条件では、3次元状態のデバイスよりも性能が2. 5倍まで向上する。本研究では、蒸着薄膜、結晶方位制御バルク材、および人工層状化合物半導体について、次元性と熱電特性について調査した。
ナノ結晶の空間的な外場制御によるマルチ機能ガラス材料の創製

藤原巧

2007年～ 2009年

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最終年度である平成21年度の目標を、「ガラス等をベースとするマルチ機能材料の創製と革新機能性の評価」として実施し、次に示す成果を得ることが出来た。 (1)特異な配向構造と発光特性を有する酸化亜鉛を含有するナノ結晶化ガラスの開発:多様な電子・光機能性を示す酸化亜鉛(ZnO)について、ガラス中にナノ結晶として析出させることで、ガラス-結晶の界面準位や非平衡酸素欠陥などの可変的な導入が期待される。これは、例えばナローギャップ化による発光特性の拡幅など、さらなる高機能性化の実現につながる。この目的の元に、ある種のガラス系を前駆体とし、結晶化処理条件を最適化することによってZnOが単相で析出し、かつ50%以上の体積分率を有する従来にはない半導体含有結晶化ガラスを得ることに成功した。この結晶化ガラスは、熱処理条件や局所的なレーザー加熱、さらには外部印加電場による結晶化処理に依存して高い結晶配向性を示し、また単結晶等に比べて長波長領域にブロードな発光特性を示す。これらは局所的な外場制御により発現した特異な形態や光物性であることが示唆され、新規なガラスベースのマルチ機能材料につながる基盤的な成果が得られたといえる。 (2)酸化亜鉛薄膜の極性制御による1D/2D分極反転構造の形成と第二高調波発生:従来例に比して波長領域が格段に広い非線形光学素子への応用を目指して、分極反転構造を有するZnO薄膜を用いて、非線形光学特性の評価を実施した。1次元および2次元分極反転構造に特有の入射光角度成分に対して位相整合により振幅増幅された高調波発生を確認した。特に2次元分極反転構造は、これまで報告されている誘電体結晶の場合と比較して、およそ一桁以上の微細化が可能となり、より高機能・多機能な素子展開が期待される。
革新機能ガラスフォトニック素子の創製競争的資金

制度名：Special Coordination Funds for Promoting Science and Technology

2005年7月～ 2008年3月
希土類原子加熱法によるパノスコピック形態制御光学機能ガラスの創製と光波制御

小松高行, 本間剛, 藤原巧, 紅野安彦

2004年～ 2007年

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本研究は、光非線形性を示す単結晶ラインをガラス表面にレーザー誘起原子加熱法(希土類/遷移金属原子加熱法)で書き込み、形態や光機能を明らかにすると共に次世代光波制御デバイスへと展開することを目的とするものである。今年度の研究で得られた成果を以下に示す。 ○レーザー誘起原子加熱法の適用によって、Li_2O-Nb_2O_3-SiO_2系ガラスにおいて強誘電性LiNbO_3結晶ラインのパターニング(Yb:YVO_4ファイバーレーザー:波長1080nm、パワー:1.3W、走査速度:7μm/s)を行い、偏光マイクロラマン散乱スペクトルおよび第二高調波強度の方位依存性(Azimuthal法)から、LiNbO_3結晶は単結晶に近い高配向(レーザー走査方向に沿ってc-軸配向)で成長していることを明らかにした。光導波(波長:632.8nm)実験の結果、LiNbO_3結晶ラインに有効に光が閉じ込められることを実証した。また、前駆体ガラスにEr_2O_3を添加することにより、結晶ラインから、Er^<3+>イオンに起因する蛍光が観測されたことから、LiNbO_3結晶にEr^<3+>が固溶することを明らかにした。光制御デバイス創製に大きく前進した。 ○レーザー誘起原子加熱法によって、Gd_2O_3-MoO_3-B_2O_3系ガラスにおいて強弾性/強誘電性を示すβ'-Gd_2(MoO_4)_3結晶ラインは、屈折率の周期的構造およびそれに伴う第二高調波強度の周期的変化を示し、レーザー誘起結晶化において極めて特異な結晶成長をすることを発見した。また、前駆体ガラスを通常の電気炉で熱処理を行うと、結晶化に伴って、電気炉内(結晶化後の冷却過程ではなく)で自ら微粉化する現象を発見した。この現象を、我々は自己微粉化現象と命名した。自己微粉化したβ'-Gd_2(MoO_4)_3結晶片においても、屈折率の周期的構造およびそれに伴う第二高調波強度の周期的変化が観測された。これらの現象はいずれも、β'-Gd_2(MoO_4)_3結晶の強弾性に基づくものと結論した。新規光制御デバイスとしての可能性が高い。
レーザによるガラスのナノ局所構造制御と光子伝達型フォトニック回路の創製

藤原巧, 紅野安彦

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (B)

2004年～ 2006年

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これまでに、ナノ結晶化を呈するガラス系において、紫外レーザー光照射により2次光非線形性を有するナノサイズの結晶/粒子が生成されることを初めて明らかにし、さらにそれらナノ結晶/粒子を極めて簡便・低コストな方法により、ナノ結晶子の緻密化・均一化や規則周期的に1次元/2次元配列構造として形成する新しいレーザプロセス法を開発してきた。このナノ結晶粒子の緻密および規則構造を、光触媒用の比表面積増大やランダムレーザーの形成、さらにはナノ粒子間における近接場光の伝搬を基本原理として、信号を伝達する光子伝達型の光回路として利用することが可能となる。 KNbO_3-TeO_2という、熱処理によりナノ結晶化を示し、かつ結晶化により本来は結晶に固有の高機能性(2次光非線形性)を発現するガラス系を選択し、波長308nmを有するXeC1エキシマレーザにより局所加熱処理を実施し、次の成果を得た。1.パルスレーザの照射パルス数の増大に伴い、ナノ粒子の直径は漸増し、およそ30J/cm^2以上のエネルギーにおいて直径が飽和する変化傾向を見出した。2.基板に対して加熱補助を施すことにより、レーザ照射による加熱をより安定に実施することが可能となり、基板加熱のない場合に比べて、ナノ粒子直径のばらつき(偏差)を約1/5に低減することが出来た。ナノフォトニクス回路を実現する、新しい均一ナノ粒子形成法として実用的な手法の開発に成功した。さらに特筆すべき成果として、酸化チタンを選択的に形成するナノ結晶化ガラスの開発に成功した点を挙げることができる。我々が偶然見出した新しいガラス系においては、熱処理条件によって酸化チタン(ルチルおよびアナターゼ)のみが選択的に結晶化されることを発見した。この酸化チタンは、粒径約10nm程度のナノ結晶子としてガラス中に分布していることが電子顕微鏡観察によって確認され、酸化チタン・ナノ結晶化ガラスの開発に世界で初めて成功した。
2次光非線形性を有するガラス材料の基盤研究とそのフォトニクスへの応用

生嶋明, KHALED JABRI, 斉藤和也, 藤原巧

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (B).

研究機関：TOYOTA TECHNOLOGICAL INSTITUTE

1999年～ 2000年

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本研究は、紫外光ポーリング(紫外光照射+高電場印加)という独自の方法により、ガラス材料に結晶レベルの2次光非線形性を発現させ、ガラス本来の高機能特性(高透明度、広い透過波長域、賦形性など)とアクティブな特性を併せ持つ新フォトニクス材料及びそれを用いた新機能デバイスを創製することを目的として行ったものである。得られた研究成果の要点を以下に記す。 (1)紫外光ポーリングにより発現する大きな2次光非線形性の起因が、結晶化生成に伴う3次光非線形性の増大と、GeE'と呼ばれる欠陥生成に伴う空間電場形成の複合効果(χ^<(2)>=3Escχ^<(3)>)により説明できることを明らかにした。 (2)薄膜ガラスにおいて発現する2次光非線形性の最適化を行ない、今までで最も大きな2次光非線形性(d定数=12.5pm/V)を得ることに成功している。 (3)光誘起ESRスペクトルおよびVUV分光スペクトルの解析により、バンド間遷移による電子励起からの欠陥生成とアンダーソン局在の関係を明らかにしつつある。 (4)Bath大学提案のフォトニック・クリスタルへの本技術の適用を進めている。これらの成果は、フォトニクス応用において必須となる光スイッチなど、ガラスをベースとした全く新しいアクティブなデバイス創製に繋がることが期待されるものである。
紫外光ポーリングによるX^<(2)>周期構造の形成と新機能デバイスの研究

藤原巧

1997年～ 1998年

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1 紫外光ポーリングによりガラスに発現する2次光非線形性の起源究明・紫外光ポーリングにより、Ge添加SiO_2ガラスにある種の規則化構造が誘起されることを、X線回折法や透過電子顕微鏡観察、さらにはラマン分光法などの手法を用いて発見した。 (豊田中央研究所、ミクロ解析研究室広瀬室長、妹尾研究員らとの共同研究による) ・紫外光ポーリングにより発現する2次光非線形性の大きさが、熱ポーリングなど従来法に比べて約1桁以上増大すること、また単一指数関数型の緩和挙動を示すことは、上述の規則化構造に起因することを明らかにした。・第三高調波発生(THG)の測定から、紫外光ポーリングにより3次の光非線形性(χ^<(3)>)が約15倍に増大することを見出した。・以上の結果は、2次光非線形性の発現及び緩和が空間電場モデル(χ^<(2)>=3E_<sc>χ^<(3)>)により説明出来ることを強く示唆しており、機構解明に決定的となる実験事実を明らかにしつつある。 2光集積回路用の薄膜ガラスの2次光非線形性・フォトニクス分野において必須となる光集積回路として用いられる薄膜光導波路の基盤研究について、スパッタ法により精製したガラス薄膜に紫外光ポーリングを行ない2次光非線形性の発現を確認した。・ガラス薄膜のGe濃度やスパッタ中のAr/O_2のガス流量比、さらには成膜後の熱処理条件などについて、最大の2次光非線形性を得るための最適化を行なっている。現時点で得られた最も大きな値は、d=12.5pm/V(パルク:d=5.1pm/V)である。
ガラス中の凍結した密度揺らぎの構造緩和過程の研究

生嶋明, 斉藤和也, 藤原巧

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (C)

研究機関：Toyota Technological Institute

1997年～ 1998年

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シリカガラスはフォトニクスの主要な材料であり、その緩和機構を解明することはシリカガラスの高機能化に必要である。また、単純なガラス構造をもつシリカガラスは、ガラス転移を研究するにも格好の舞台となる。本研究では、これまでシリカガラスのガラス転移点近傍の物性研究を妨げてきた高温(1000℃〜2000℃)での物性測定の困難を克服し、その構造緩和過程及びその不純物効果を明らかにした。具体的には、光散乱、FTIRおよび誘電緩和測定を用いて以下のことを明らかにした。 1. OHやClなどの不純物は、粘性流動に支配されたa緩和を促進する。さらにこれらの不純物により副緩和過程が生ずる 2. この副緩和は、不純物の拡散による局所的な構造緩和に起因する。 3. Alは、OHやClと異なり、a緩和を抑制する。以上の結果を踏まえ、不純物を利用した緩和過程制御法を開発し、以下の高機能シリカガラスの開発を行った。 1. Na添加による超低損失光ファイバ用ガラス 2. Al添加による超耐熱ガラス 3. OH添加+紫外線照射+熱処理による耐紫外線ファイバ
密度揺らぎの制御による超低損失ファイバ用ガラスの開発

生嶋明, 藤岡一彦, 松山豊和, 伊藤忠, 斉藤和也, 藤原巧

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (A)

研究機関：Toyota Technological Institute

1997年～ 1998年

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マルチメディア時代を迎えるにあたって、中継距離の増大による通信コストの低減や、通信網の拡大のために、現在実用化されている石英ファイバを凌ぐ低損失性を有するファイバの開発が必須である。従来、ファイバの伝送損失の主要因であるレーリー散乱を低減化させるために、ガラス組成探索が活発に行われてきた。本研究グループでは、これらの研究とは一線を画し、ガラスが本来有する究極の伝送特性を得ることを目的として、石英ガラスの液体ガラス状態での諸物性の研究を進めてきた。本研究では、レーリー散乱の原因である密度揺らぎを制御するためにガラス転移近傍の構造緩和過程を詳しく調べ、以下の結果を得た。 1。凍結した密度揺らぎの構造緩和過程及びその不純物効果 OHやCl、Naなどの不純物は、粘性流動に支配されたa緩和を促進する。さらにこれらの不純物により副緩和過程が生ずることを光散乱およびFTIR測定より明らかにした。 2。副構造緩和の過程における不純物の役割副緩和は、不純物の拡散による局所的な構造緩和に起因することを誘電緩和測定より明らかにした。これらの知見をもとに、不純物を利用した構造緩和制御法を確立した。この制御法は、超低散乱ガラスの開発に直結する基盤技術であると同時に、耐紫外ファイバや超耐熱ガラスの開発に有用であることが明らかとなった。
X^<(2)>周期構造を持つガラス導波路/ファイバの研究

藤原巧

1996年～ 1996年

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紫外光ポーリング(紫外光照射+高電場印加)によりガラス材料に誘起される2次光非線形性に関して、材料科学に基づく微視的な観点に立脚した基礎からのアプローチを研究の基本方針とし、構造または物性変化を決定する因子、光非線形性を決定する因子などについて、それらの機構解明を行った結果、多くの重要な新しい知見を得た。以下に主な研究成果を示す。 ◎ゲルマニウム添加シリカ・ガラス材料の紫外光ポーリングによって、波長変換のために求められる光非線形性が、LiNbO_3結晶でのd_<22>係数を越える大きさまで誘起されることを初めて見い出した。 ◎紫外光ポーリング電場の増大による光非線形性の増大と、ポーリングの際に生じる吸収スペクトル変化の間に強い相関が認められることを初めて見い出した。光非線形性の発現に、欠陥が大きな寄与を及ぼすことを示しており、さらに、主要な欠陥を示唆する極めて重要な最初の実験例である。 ◎紫外光ポーリングにより誘起される光非線形性と光吸収の両者の緩和過程を調べ、次に示す重要な結果を得た。 1)紫外光ポーリングにより誘起される光非線形性の緩和過程が単一指数関数型に良く合致しており、非線形性の起源が単一の起因によることを明確に示している。 2)緩和過程の温度依存性について測定を行い、光非線形性の活性化エネルギーが、光吸収から求められるGeE'と呼ばれている欠陥の活性化エネルギーと極めてよく一致することを見い出した。これは、ガラスに誘起される2次光非線形性の発現に主要な寄与を及ぼす欠陥構造がGeE'であることを明確に示唆している。 ◎非線形性の周期構造形成のために用いる光学干渉系を設計・構築し基本測定を行った。発現する光非線形性により干渉縞のシフトが観測され動作電圧の定量的評価が可能となった。
光非線形フォトニック結晶競争的資金
LiNbO3結晶の非線形光学特性競争的資金
Optical Nonlinear Photonic Crystals 競争的資金
ガラス材料の光非線形性に関する研究競争的資金
Optical Nonlinearity in Glass Materials 競争的資金
Optical Nonlinear Properties in LiNbO3 Crystals 競争的資金

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社会貢献活動 5

出前講義

2010年12月11日～

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東北大説明会として、６０分の出前講義を２コマ担当
出前講義

2010年10月13日～

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東北地域の各大学説明会の一貫として、７０分講義を２コマ担当
ガラスに光触媒粒子分散効果は半永久的東北大

2007年4月23日～

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東北大学の藤原巧教授らの研究グループは、酸化チタンのナノサイズの結晶粒子を分散させたガラスを作製した。（抜粋、先端マテリアル欄に掲載、合計５９０字）
光触媒機能を半永久化

2007年4月16日～

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東北大と長岡技科大透明ナノ結晶化ガラス作製東北大学の藤原巧教授、正井博和助教、長岡技術科学大学の小松高行教授らは酸化チタンのナノ結晶粒子をガラス全体に分散させた「透明酸化チタンナノ結晶化ガラス」を作製した。（抜粋、科学技術・大学欄に掲載、合計７８０字）
酸化チタン、ガラス中に析出

2007年3月6日～

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東北大光触媒機能の劣化防ぐ東北大学の藤原巧電気情報・物理工学科教授らのグループは、光触媒機能を有する結晶化ガラスを開発した。（抜粋、合計７６０字）

メディア報道 3

白色発光のガラス蛍光体、希土類使わず高効率

化学工業日報

2011年3月9日

メディア報道種別: 新聞・雑誌
東北大、ガラス結晶化の仕組みを解明光ファイバ制御技術

日経産業新聞

2009年7月23日

メディア報道種別: 新聞・雑誌
光通信網を省電力化旭硝子と東北大

日経産業新聞

2008年11月4日

メディア報道種別: 新聞・雑誌

その他 9

光学整合法による超透明結晶化ガラスの創製

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結晶化ガラスの異相構造において、光学的な整合を実現する独自の材料デザインを開発し、これまでにはない高い透明性を実現し、結晶ドメインサイズに依存しない簡便で実用的な透明結晶化ガラスを得るプロセス開発を行う。
先進的光ファイバおよび発光材料の研究

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韓国POSTEC・J.Heo教授との共同研究であり、韓国側から２名の研究者（教員１名、博士院生１名）が来訪し（２０１１年２月、短期滞在）、当研究室にて表記テーマに関わる実験と解析を行った。
透明光機能材料の開発

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ガラスをベースとするナノ構造創製と結晶化による光触媒・高誘電体機能の発現に向けた新規材料開発
半導体を含有する新規ナノ結晶化ガラスの開発

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酸化亜鉛や酸化チタンなど、高機能半導体を含有するナノ結晶化ガラスを開発し、それらの形態制御や機能性開拓を行う。
新機能創製に向けた無機透明材料の研究

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ガラスファイバ中に選択的に２次光非線形性を発現する結晶を析出させ、アクティブな光波制御機能を有する結晶化ガラス材料の開発を行う。
光触媒機能を有する透明ナノ結晶化ガラスの開発

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ガラスと同等の透明性と酸化チタン結晶による光触媒能を示す、基板と触媒活性層が一体となった、耐久性の高い酸化チタン・ナノ結晶化ガラスを開発を目指す。
酸化チタン・ナノ結晶化ガラスを用いた透明光触媒材料の開発

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結晶とガラスの双方の特徴を併せ持つ新規ナノ結晶化ガラスとして、これまでにはない酸化チタンを単相で析出する透明な結晶化ガラスを開発し、その光触媒効果を明らかにする。
革新機能ガラスフォトニック素子の創製

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産学官共同研究の効果的な推進プロジェクトとして、企業（旭硝子）と共同研究体制を構築し、次世代光情報通信に必須とされる革新的な機能性を有するガラスベース光コンポーネントの研究開発を推進する。
レーザーによるガラスの微細加工法を用いた光学部材の開発

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独自に見出された「レーザー原子加熱法」の手法を活用し、ガラスの空間選択的な局所加熱によって、透明な結晶パターニング法を開発し、結晶機能を有するガラスベース材料とデバイス開発を行う。

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