Black and electrically insulating coatings provide touch panel displays with a classic appearance. In this study, black and electrically insulating Ag–Fe2O3-based coatings were prepared using reactive magnetron sputtering, stainless steel and silver foil. The thin films prepared with oxygen introduction and no Ag foil showed blue light absorption and high electrical resistance, which are comparable to those of Fe2O3 single crystals. The optimal Ag foil size for maintaining a high electrical resistivity of 108 Ω·sq−1 was determined to be 54 mol%Ag in the film samples. Black and electrically insulating thin films composed of metallic Ag, amorphous Ag–Fe–O, and slightly crystallized Fe2O3 were prepared using 3.4 or 3.9 %O2. Metallic Ag segregated randomly in the high-refractive-index Fe2O3-based matrix, resulting in plasmonic absorption over a wide range of wavelengths centered in the red-wavelength region. At 3.9 %O2, a high sheet resistance of 108 Ω·sq−1 and strong visible absorption of 35.2 μm−1 (on average), slightly deviating by 2.4 μm−1 were simultaneously achieved by clear phase separation of the Ag grains and Fe2O3-based matrix. A clear phase separation mechanism based on thermodynamic nonequilibrium oxidation of the metallic Ag phase is proposed.

Layered bismuth oxyhalides with bilayered (Bi2O2) fluorite (FL) slabs are promising visible-light photocatalysts because of their excellent stability and the ability to adjust band levels depending on the layers combined. It is interesting to manipulate the Bi2O2 slab itself, but only trilayered FL blocks (e.g., Bi3O4) are reported so far. Here, a structurally uncharacterized Bi12O17Cl2, which is extensively studied as a photocatalyst for a variety of reactions, has a sextuple Bi6O8.5 block separated by Cl is shown. Unlike double and triple layered cases, the inner region of the Bi6O8.5 block contains 1D rock-salt (RS) units in the FL matrix along the a-axis, causing in-plane corrugation. A topochemical reaction involving anion-exchange gives Bi12O17-0.5xFxCl2 (x <= 6) with alternate FL and RS slabs along the c-axis. The elimination of the structural corrugation increases higher photo-conductivity and improves photocatalytic activity against acetic acid decomposition under visible light irradiation. This study paves new opportunities of controlling the properties of layered bismuth oxyhalides by the thickness of Bi-O block, FL/RS configuration, and structural modulation.

Ce_0.5Zr_0.5O₂ is a well-known oxygen storage material used in a three-way catalyst for automobiles to maintain the air–fuel ratio during operation. The ordered structure emerges at lower temperatures in the presence of iron oxides.

Ultrafast optical control of phase change materials is of great importance from fundamental and practical points of view. Transition-metal dichalcogenides are of significant interest in this research field because of the photoinduced phase transition originating from the nonthermal melting of their charge density wave (CDW) orders. In this work, we investigated the ultrafast optical response of VTe2 by using broadband coherent optical phonon spectroscopy with subpicosecond time resolution. With an increase of laser-excitation fluence, a characteristic oscillation around 4.4 THz appeared in the transient reflectivity change. This suggests photoinduction of the high-temperature phase, i.e., a CDW-melt state, of VTe2 within a picosecond. Such an ultrafast transition would be induced by a purely electronic effect, but as with thermodynamic melting, it is strongly suggested that the phase transition dynamics induced spatially by laser irradiation proceeds inhomogeneously via a nucleation mode.

Black antireflective (AR) coatings with electric insulative properties are required to improve the visibility of touch panel displays in the turned-on state and their appearance in the turned-off state. In this study, multilayer black AR stacks comprised of black insulative Ag-Fe-O, high-n TiO2, and low-n SiOxNy were constructed by optical simulation and prepared using RF magnetron sputtering and pulsed laser deposition. For the stacking model with five layers, the calculations show an excellent low reflectance of below 0.15% over the whole visible range with a transmittance of 0.002%. A simulation of the three-layered model indicated that the average reflectance can be reduced from over 43% for a monolayer to 3% with a reasonable average transmittance of 15% for display applications. RF magnetron sputtering, an industrial friendly method, was used to prepare the black insulative Ag-Fe-O in the AR stack for the first time. The Ag-Fe-O thin films deposited at 200-300 °C show both a large and constant absorption coefficient over the whole visible range and an acceptable high sheet resistance. The black AR stack was comprised of the black insulative Ag-Fe-O prepared at 250 °C by RF magnetron sputtering. The observed reflectance is in good agreement with the simulated model. These results indicate the high potential of the black Ag-Fe-O films for use in AR black coatings in touch panel displays for a visually attractive turn-off appearance.

The refractory nature of oxide-ion conducting Sm-doped CeO2 (SDC) has hindered the development of SDC devices. Lithium has been found to be an excellent sintering aid that enables sintering at temperatures as low as 900 °C and also increases grain boundary conductivity. Even though Li–Si oxides melt only above the sintering temperature in reality, it is generally believed that these benefits are given by virtue of a formation of liquid phases with silicon contaminants. In this study, the key element for low-temperature sintering was revealed to be aluminum, which is spontaneously introduced into SDC by a covert but intense chemical reaction between the mixed lithium and the alumina crucible. The results show that 1 wt% lithium addition is responsible for the unintended introduction of 32 mol% aluminum. Computational thermodynamic calculations for a Li–Si–Al oxide system clarified that aluminum introduction is essential to reduce the melting point below the sintering temperature. A nano-scale analysis clearly indicates the segregation of aluminum at SDC grain-boundary triple junctions, like LiAlO2, while silicon appears to migrate towards the SDC-SDC grain boundaries as amorphous SiO2. This suggests that the decomposition of the Li–Si–Al liquid oxide filling the grain boundaries is associated with the reflow of silicon and the loss of lithium as sintering proceeds. It was shown that zirconium is also introduced into SDC due to ball-mill processing, and that it potentially forms Li–Si–Zr oxides which remain in their solid state during sintering. The results of this study highlight the importance of taking the impact of unintended aluminum introduction into consideration for a variety of ceramics mixed with even minute quantities of lithium.

A new mixed proton-hole conducting material is developed by doping the proton conductor, BaZr1-xScxO3-δ with cobalt, which is known for yielding high hole conductivity in oxides. The phases present, proton incorporation, and electrical conductivity of BaCoxZr0.9-xSc0.1O3-δ are investigated in this study. XRD analysis reveals that the doping of Sc, which has a larger ionic radius than Co and Zr, increases the cobalt solubility limit for BaZrO3 from 0.13 to 0.2. It is found that the conductive protons are incorporated in the bulk portion of Co, Sc-doped BaZrO3. The proton concentration of BaCoxZr0.9-xSc0.1O3-δ is shown to decrease as the Co content increases up to x = 0.1; however, at higher Co content (x = 0.15 and 0.2), the proton concentration increases again. In addition, it is found that the conductivity of BaCoxZr0.9-xSc0.1O3-δ is higher than that of Fe or Pr doped BaMxZr1-x-yYyO3-δ for the same dopant concentration. The maximum conductivity of the single phase samples in both the wet oxidizing (PH2O = 0.012 atm, PO2 = 0.21 atm) and dry oxidizing atmosphere (PO2 = 0.21 atm) is 0.1 S cm−1 for BaCo0·2Zr0.7Sc0.1O3-δ.

Multilayer antireflection (AR) coatings require a material with a large and constant absorption coefficient over the whole visible range and thermal stability. Coatings for use in touch panel displays are also required to be electrically insulative. In this study, 60 mol % Ag-40 mol % (Fe1-xAlx)-O (x = 0, 0.25, 0.50, 0.75, and 1.0) thin films are prepared by pulsed laser deposition, and their optical properties, electric resistance, and thermal stability are clarified by combining the experimental data and density functional theory (DFT) calculations. Over the visible range, large and constant absorption coefficients are obtained for all compositions. The standard deviations of the absorption coefficients of the x = 0.75 and 1.0 samples are found to be smaller than those of conventional materials like graphite and CrOx. High sheet resistance (Rsheet > 107 ω·sq-1) is also confirmed. It is determined that nanometer-sized Ag dispersed into a matrix, which was confirmed to be ionic Ag in the matrix phase, is responsible for the absorption at a shorter visible light range and insulative nature even at high Ag content. The films with high Al content are stable up to 500 °C. The potential of these black insulative Ag-Al-Fe-O thin films for use as black AR coatings is confirmed by optical simulations with multilayer stacks.

Metal-supported SOFC consists of metallic and ceramic multilayers. Since the cell has to be flat, interaction between the layers that results in a flat sintered layer needs to be studied. The method used here was changing the starting materials through several experiments. Here, we highlight the effects of pore former in metal slurry on the sintered half-cell multilayer of a 430L metallic support, an NiO-8YSZ anode, and an 8YSZ electrolyte. The results show that by changing the amount of pore former in the 430L metal slurry changed the sinterability of the metal layer. This change of the sinterability of the metal support affected the final warpage state of the cell. This study aid in explaining the sintering phenomena between layers of metal-supported SOFCs.

<title>Abstract</title>Most solid-state materials are composed of p-block anions, only in recent years the introduction of hydride anions (1s²) in oxides (e.g., SrVO₂H, BaTi(O,H)₃) has allowed the discovery of various interesting properties. Here we exploit the large polarizability of hydride anions (H^–) together with chalcogenide (Ch^2–) anions to construct a family of antiperovskites with soft anionic sublattices. The M₃HCh antiperovskites (M = Li, Na) adopt the ideal cubic structure except orthorhombic Na₃HS, despite the large variation in sizes of M and Ch. This unconventional robustness of cubic phase mainly originates from the large size-flexibility of the H^– anion. Theoretical and experimental studies reveal low migration barriers for Li⁺/Na⁺ transport and high ionic conductivity, possibly promoted by a soft phonon mode associated with the rotational motion of HM₆ octahedra in their cubic forms. Aliovalent substitution to create vacancies has further enhanced ionic conductivities of this series of antiperovskites, resulting in Na_2.9H(Se_0.9I_0.1) achieving a high conductivity of ~1 × 10^–4 S/cm (100 °C).

© 2020 Elsevier B.V. Preference for a classy black turn-off appearance and for distinct dark colors on flat-panel displays has led to a high demand for optically black materials. Titanium oxynitrides and tungsten-doped oxynitrides were prepared using nitrogen plasma assisted pulsed laser deposition, and their optical absorption properties were investigated. A selection of Ti-O-N films were prepared with different compositions by controlling the emission current (Ie) and discharge voltage (Vd) of the ion source. It was found that the nitrogen content of the Ti(O,N)x could be adjusted by controlling the Ie. The large, flat absorption coefficient of approximately 40 μm−1 in the visible range (400–700 nm) attained for the samples deposited at high Vd was attributed to tungsten doping from a W filament in the ion source. The 4.1 mol%W-doped Ti(O,N)x, which had a rock-salt-type structure, was optically jet-black. The origin of the flat wavelength dispersion in the W-doped Ti(O,N)x was attributed to the coexistence of semiconducting absorption and metallic absorption mechanisms. DFT calculations suggest that the 5d states achieved when using doped tungsten provide high absorption in the mid-wavelength range, whereas undoped-Ti(O,N)x was characterized by weak absorption.

© The Royal Society of Chemistry. Improving the oxygen surface exchange reaction rate in the intermediate temperature range is one of the most important challenges in the effort to facilitate the widespread use of high temperature electrochemical devices such as solid oxide fuel cells. While the fast surface exchange kinetics of Co-based mixed ionic conductors is well known, it is also believed that Co-based oxides which have negligible oxygen incorporation reactions, such as Co3O4, are superior catalysts for surface-exchange reactions. In this investigation, a modified pulse isotopic exchange technique was used to quantitatively evaluate the dissociative adsorption rate of Co-Fe-based spinel-type and Co-Mg-based rock salt-type oxides. Catalytic activity increased exponentially as the Co concentration increased regardless of the crystal structure. This trend can be explained by site percolation probability, indicating the importance of Co clusters in catalytic activity. The dissociative adsorption rate of Co3O4 was found to be comparable with the overall surface exchange rate of mixed oxide-ion and electronic conductors. This journal is

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Apart from transparent conductors, the demand for nontransparent black insulators in the electronic display industry is significant. The development of these dark insulators requires sophisticated material designs. This study shows that narrow-gap-oxide-based nanoscale cermets with nonequilibrium phases which decompose into metal and oxide phases have both the insulative character and a stronger and less-dispersive absorption than graphite throughout the visible range. Herein, the cases of pulsed-laser-deposition-derived Ag–Fe2O3 and Cu–Bi2O3 systems are shown. The combination of the interband absorption of the narrow-gap oxides and the plasmonic absorption of the metals provides strong optical absorption throughout the visible range. Because they create diffusion at the edge of the interband absorption and the peaks of the plasmonic absorption, the nonequilibrium phases make the absorption less dispersive. By preventing the mutual contact of the metal grains, they also make the cermets electrically insulative. This new approach has the potential to produce excellent black and insulating optical coatings using a variety of combinations of metals and ceramics for touch panel displays.

© 2019 American Physical Society. Bi1-xSrxFeO3-δ (BSFs) are well known not only as multiferroic materials but also as mixed oxide-ion and electronic conductors. BSFs show remarkable ionic conductivity despite their limited electrochemical activity due to their low electronic conductivity. In this study, the discontinuous change in the electrical conductivity of Bi0.7Sr0.3FeO3-δ (BSF30) at around 770 °C was investigated in the context of their unique defect order-disorder transition. Based on the electrical conductivity and the Seebeck coefficient of BSF30, both functions of temperature and oxygen partial pressure, the discontinuous change in both hole and oxide-ion conductivities was the result of a reduction in their mobility but unrelated to their concentration term. High-temperature x-ray diffraction and scanning transmission electron microscopy revealed that periodic oxygen-deficient planes with fivefold d-spacing of {001} emerge in an ordered low-temperature phase while the ordered defect structure disappears in a high-temperature phase. The discontinuous change of electrical conductivity of BSF30 was then found to be the result of the order-disorder transition of its oxygen sublattice, i.e., oxygen vacancies. Because there was no such transition in the cation sublattice, the cation did not affect the electrical conductivity of BSF30. This study suggests that BSFs with the desired electrochemical and multiferroic functionalities can be designed by controlling their order-disorder transition.

© 2019 The Authors Optically black anti-reflective coatings that absorb light are potentially useful for color isolation in the flat panel display industries and stray light reduction in imaging technologies. Here we report the design and fabrication of high performance multilayered black anti-reflective coatings. Thin film suboxides NbxTi1−xO2, NbO2 and TiO2−x were prepared using pulsed laser deposition (PLD). Their optical constants were then used to design a six layer coating which has less than 2% reflectivity across the visible range (400–700 nm) even at moderate incidence angles. Furthermore, this six layer coating displays large and constant absorbance across the visible range making it optically black. This optical behavior is due largely to the use of the suboxide NbxTi1−xO2 which is unique because of its spectrally constant absorption coefficient.

© 2019 Author(s). To develop resistive switches using TiO2, the control of their switching voltage is a crucial issue. This study shows how acceptor and compensating oxygen vacancies modify the resistive switching behavior from both the experimental and theoretical points of view. Nonequilibrium TiO2 thin films doped with acceptor Al with oxygen vacancies were prepared by pulsed laser deposition. Al doping results in a clear reduction in the switching voltage when the TiO2 thin films are operated as a unipolar-type switch but not when they are operated as bipolar-type switches. Density functional theory calculations revealed that the doped Al and compensating oxygen vacancies ([A l ′ Ti] = 2 [V O]) promote the formation of oxygen vacancies compensated by electrons (2 [V O] = n) due to the defects association of 2 A l ′ Ti - 2 V O - 2 e ′. This defect cluster functions like the formation center of conductive nanofilaments for the electrochemical reduction. It was concluded that by promoting the formation of oxygen vacancies compensated by electrons, Al doping results in a decrease in energy consumption of the unipolar-type resistive switching.

© 2019 American Chemical Society. Multiple hydrogen occupation in Ba-Ti oxyhydride is demonstrated by a negative Knight shift in the 1H magic-angle spinning (MAS) NMR spectra combined with hydrogen concentration and X-ray photoelectron spectroscopic analysis. A negative Knight shift, an indicator of the interaction between conduction band electrons and a probe nucleus, is observed in the 1H MAS NMR signal of Ba-Ti oxyhydrides at room temperature for the first time. This Knight shift indicates multiple hydrogen occupation. This was confirmed by the X-ray photoelectron spectra of Ba-Ti oxyhydrides and the hydrogen concentrations. The presence of hydrogen species with different bonding characteristics indicates a flexible hydrogen configuration in Ba-Ti oxyhydrides, from an ionic-state hydride ion with single occupation to partially anionic state hydrogen atoms with multiple occupation. It also indicates the potential to modify the electronic structure and physical properties of Ba-Ti oxyhydrides by manipulating their hydrogen configuration.

© 2019 American Chemical Society. Surface oxygen reduction reaction (ORR) rates at n-type oxide-based mixed ionic-electronic conducting (MIEC) solid oxide fuel cell (SOFC) cathodes can be expected to be enhanced relative to that at p-type MIEC cathodes due to the greater availability of electrons at higher energies in the band structure needed for the charge transfer reaction. However, given the difficulty of achieving coexisting oxygen vacancies and electrons in the conduction band under oxidizing cathode conditions, no stable n-type MIEC cathodes have been reported to date. In this study, a predominantly n-type MIEC conductivity is confirmed in a Ba-In-based oxide (BNIM) co-doped with Nd and Mn at high temperature and high PO 2 confirmed by the PO 2 dependence of the electrical conductivity and negative Seebeck coefficients, combined with readily measurable oxide ion transference numbers. This coexistence of n-type electronic and oxide ion conductivities is discussed based on the electrical behavior of BNIM with different Mn levels and is attributed to the significant change in the degree of anion Frenkel ordering and the band structure associated with heavy donor doping of Ba 2 In 2 O 5 . This novel n-type MIEC has the potential for enhancing the ORR at SOFC cathodes at reduced temperatures and thereby identifying new potential candidate cathode materials for next-generation SOFCs.

© The Electrochemical Society. In this study, first, power densities by using SOFC system for APU of regional jets were estimated based on metal supported SOFC system and compared with those in gas turbine APU. As the second, based on the results of power density analysis in the SOFC system, all materials making up the cell stacks are examined and developed for the weight reduction. Such material development strategy is the first trial without precedent in SOFC development history.

© The Electrochemical Society. Ti alloys were evaluated as new candidates for interconnects of a lightweight SOFC which is to be mounted on aircrafts. Oxygen permeation test was performed by flowing air and He gas. No notable oxygen leak was observed. Area specific resistance (ASR) of oxide-scales formed between the alloy the electrode contacts was investigated by impedance spectroscopy. Two different electrodes, Pt and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), attached on the surface of Ti alloys were tested with time in air at 873 K. Although ASR at the contact with Pt electrode was small, the oxide scale grown under LSCF showed a large ASR increasing with time. After the ASR measurement, cross section between the alloy and the electrode contacts were observed by scanning electron microscope and analyzed by energy-dispersive X-ray spectroscopy. Growth of the oxide scale was found to be promoted by LSCF.

© 2018 Elsevier B.V. We investigated the optical absorption properties of NbxTi1−xO2 thin films, a solid solution combining the reduced titanium and niobium oxide phases TiO2 and NbO2. The optical absorption properties of NbxTi1−xO2 thin films prepared by pulsed laser deposition at 600 °C were shown to be large in magnitude at an almost constant value of ≈17 µm−1. Because this large absorption coefficient is nearly independent of incident photon energy in the visible range (400–700 nm), the NbxTi1−xO2 thin films appear optically black. Flat and homogenous, optically black coatings like these are desirable for color isolation in flat panel displays. The origin of flat wavelength dispersion in NbxTi1−xO2 is the coexistence of semiconducting absorption and metallic light absorption mechanisms. Localized Nb-Nb dimers in the metallic NbxTi1−xO2 phase open an optical band gap which gives rise to semiconducting behavior. We show here that reduction results in strong visible light sensitization in normally transparent Nb-Ti oxides.

Ceramic sheet of Na+ ion-conducting solid electrolyte, Na3Zr2Si2PO12 (NASICON), has been prepared by tape-casting method. Addition of 60Na2O-10Nb2O5-30P2O5 glass as a sintering aid is crucial for fabrication of fully-densified impermeable sheet. Otherwise the gas tightness is not achieved even sintered at 1200 °C. The best preparation condition is 5 or 10 wt% grass-addition with respect to NASICON and sintering at 1000–1100 °C, which is lower by 100–200 °C than the typical densification temperature of NASICON without the additive. A sample with a thickness of 35 μm and total conductivity of 4.4 × 10−4 S cm−1 is obtained by 5 wt% glass addition and sintering at 1100 °C for 4 h.

It is necessary to elucidate the correlation between hydration properties and proton distributions in electrolytes as proton conductors to allow for further improvements in solid oxide fuel cells. In this study, the hydration properties of Sc-doped BaZrO3 (BZO) were investigated by means of density functional theory calculations capable of taking both the local structural configurations and the hydration levels into account. At a low hydration level, Sc-doped BZOs gained a negatively larger hydration energy, that is, more exothermic reaction, by incorporating an H2O molecule with unstable oxygen vacancies adjacent to Zr. At a high hydration level, the configuration of ScO4(OH)2, which has a positive net charge as a local structure, was formed with a smaller but negative hydration energy by the reaction of H2O with oxygen vacancies adjacent to Sc. This indicates that the stability of the whole system, and not only the local electrostatic interactions of point defects, needs to be taken into account when considering the hydration energy. The characteristic local structure of ScO4(OH)2 was identified using 45Sc nuclear magnetic resonance (NMR) chemical shift calculations. It is proposed that the resolution of current 45Sc NMR spectroscopy techniques does not allow for the detection of ScO4(OH)2 in Sc-doped BZOs and that a higher resolution 45Sc NMR technique will likely reveal the existence of ScO4(OH)2.

The preparation of a transparent and smooth rutile-type TiO2 thin film without the use of the crystallographical effect of the substrate is a challenge for the advanced utilization of TiO2 in the fields of optics and solid state ionics. Because acceptor doping leads to the formation of oxygen vacancies, this method has promise as a new approach to promote the formation of rutile-type TiO2. Mg2+-doped TiO2 thin films were prepared by pulsed laser deposition, and the effects of Mg2+ doping on the phases present, the microstructure, the optical properties, and the surface roughness of the films were investigated. Particular attention was paid to the Mg2+ distribution in the prepared films. The formation of the rutile phase was promoted by 2.7 mol% and 5.5 mol%Mg2+ doping. The negligible segregation of Mg2+ and absence of change in the extinction coefficient by Mg2+ doping indicate that Mg2+ worked as the acceptor and induced oxygen vacancies for charge compensation, which promoted the formation of the rutile phase. Given that Mg2+ is a doubly charged acceptor, Mg2+ doping is a more effective method for promoting the formation of the rutile phase than trivalence doping. Besides the excellent optical properties (n 3.03 and k &lt 0.02 at = 400 nm) of the 2.7%Mg2+-doped rutile-type TiO2 thin film deposited at 350°C, the films were smooth, with a roughness index of only approximately 0.8 nm. This method of preparing smooth rutile-type TiO2 thin films has potential for the further development of TiO2-based resistive memory devices.

A rutile-type TiO2 thin film with a high refractive index (n), a low extinction coefficient (k) and small surface roughness (R-a) is required for use in a variety of optical coatings to improve the controllability of the reflection spectrum. In this study, Al-doped TiO2 thin films were prepared by pulsed laser deposition, and the effects of Al doping on their phases, optical properties, surface roughness and nanoscale microstructure, including Al distribution, were investigated. By doping 5 and 10 mol%Al, rutile-type TiO2 was successfully prepared under a P-02 of 0.5 Pa at 350-600 degrees C. The nanoscale phase separation in the Al doped TiO2 thin films plays an important role in the formation of the rutile phase. The 10 mol%Al-doped rutile-type TiO2 thin film deposited at 350 degrees C showed excellent optical properties of n approximate to 3.05,k approximate to 0.01 (at lambda = 400 nm) and negligible surface roughness, at R-a approximate to 0.8 nm. The advantages of the superior optical properties and small surface roughness of the 10 mol%Al-doped TiO2 thin film were confirmed by fabricating a ten-layered dielectric mirror. (C) 2017 Elsevier B.V. All rights reserved.

The fundamental factors that influence the hydration of BaZrO3 (BZO) doped with trivalent cation M3+ Sc, Ga, Y, In, and Lu) for proton conductors were investigated by means of density functional theory calculations which take the configuration of complex defects into account. The creation of oxygen vacancies is favored for Al-and Ga-doped BZOs and leads to small hydration energies with stable proton sites at the nearest neighbor (INN). Meanwhile, Y-, In-, and Lu-doped BZOs prefer protons at the second nearest neighbor (2NN). The stability of those defects can be formulated in the context of the energies of oxygen vacancy formation and hydration. BZOs with larger dopants gain more hydration energy by structural relaxation with protons located at 2NN. By isolating the associated complex defects, it is possible to increase the negative hydration energy, which in effect improves the degree of hydration of BZOs.

The effect of Ca doping on the Li-ion conductivity and phase stability of the rock-salt-type LiBH4 phase emerging under high pressures in the range of gigapascals has been investigated. In situ electrochemical measurements under high pressure were performed using a cubic-anvil-type apparatus. Ca doping drastically enhanced the ionic conductivity of the rock-salt-type phase: the ionic conductivity of undoped and 5 mol %Ca-doped LiBH4 was 2.2 x 10(-4) and 1.4 x 10(-2) S.cm(-1) under 4.0 GPa at 220 degrees C, respectively. The activation volume of LiBH4-5 mol %Ca(BH4)(2), at 3.2 cm(3).mol(-1), was comparable to that of other fast ionic conductors, such as lithium titanate and NASICONs. Moreover, Ca-doped LiBH4 showed lithium plating-stripping behavior in a cyclic voltammogram. These results indicate that the conductivity enhancement by Ca doping can be attributed to the formation of a LiBH4-Ca(BH4)(2) solid solution; however, the solid solution decomposed into the orthorhombic LiBH4 phase and the orthorhombic Ca(BH4)2 phase after unloading the high pressure.

Lithium borohydride (LiBH4) is a candidate material for a solid electrolyte of all-solid-state lithium secondary batteries. In this study, the hydration behavior and influences of hydration on the ionic conductivity of LiBH4 were investigated. LiBH4 was found to become hydrated without decomposing; structural water can dehydrate at 55 degrees C and then rehydrate at around 35 degrees C. Hydrated LiBH4 has a high lithium-ion conductivity of 4.89 x 10(-4) S . cm(-1) at 45 degrees C. The temperature dependence of conductivity and motional narrowing of the Li-7 NMR spectra at around dehydration temperature suggest that the enhanced lithium-ion conductivity is attributed to the motion of structural water molecules. (C) 2015 Elsevier B.V. All rights reserved.

The distribution of protons and oxygen vacancies at room temperature at different proton concentrations in 10 mol % Sc-doped BaZrO3 was investigated to clarify the influence of proton concentration and oxygen vacancies in the trapping of protons caused by the acceptor dopant. To enhance proton conductivity for practical use, it is essential to understand this phenomenon known to limit the long-range transport of protons. In this study, Sc-45 nuclear magnetic resonance (NMR) spectroscopy combined with thermogravimetric analysis (TGA) and NMR is used to elucidate the protonic defects and oxygen vacancies formed around Sc and Zr. The results reveal that the high protonic defect concentration around Sc with a 9-10 mol % proton concentration is a clear indication for proton trapping and that the high protonic defect concentration around Zr at an intermediate proton concentration of 4 mol % suggests that the protons are residing in the nontrapping sites. The oxygen vacancies that tend to be located around Sc apparently prevent the formation of protonic defects due to the repulsive interaction between the protonic defect and the association of Sc and an oxygen vacancy, both of which have a positive net charge. This study suggests that the formation of oxygen vacancies around the acceptor may inhibit proton trapping and therefore have a positive effect on the long-range transport of protons.

Single-phase rutile-type TiO2 thin films with a high refractive index (n) and a low extinction coefficient(k) prepared on glass are expected to improve the performance of anti-reflection coatings. In this study, TiO2 thin films were prepared by the pulsed laser deposition (PLD) method at temperatures ranging from room temperature to 600 degrees C under an oxygen partial pressure of 1-9 Pa or a 10(-5) Pa vacuum, and their crystal structure, microstructure and optical properties were investigated. A single-phase rutile-type TiO2 thin film was successfully prepared on a glass substrate by depositing at room temperature in a vacuum followed by post-annealing at 450 degrees C in air. A nanocrystalline oxygen-deficient phase in the as-deposited films plays an important role in the formation of the single rutile phase during post-annealing. The single-phase rutile-type TiO2 thin films showed excellent optical properties, with n = 3.14 and k &lt; 0.05 at lambda = 400 nm. (C) 2015 Elsevier B.V. All rights reserved.

Nanograined 25 mol% Sc-doped BaZrO3, BaZr0.75Sc0.25O3 (-) (delta), well-known as a proton conductor, has been successfully synthesized at low processing temperature with average grain sizes of 8.9 nm, 15.9 nm, and 68.5 nm, and the effect of grain size on the conductivity has been examined. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns for these samples suggest a simple cubic perovskite type structure. The total DC conductivity, bulk and grain boundary contributions, of BaZr0.75Sc0.25O3 (-) (delta) as-pressed at room temperature (non-sintered) is 553 x 10(-6) S/cm (8.9 nm grains) at 500 degrees C, while values of 2.68 x 10(-6) S/cm and 127 x 10(-3) S/cm are observed at 500 degrees C for those samples post-annealed at 800 C and 1250 degrees C with average grain sizes of 15.9 and 685 nm, respectively. The observed total DC conductivity for 68.5 nm grain size is almost comparable to that reported for benchmark Y-doped BaZrO3 with nanometer and micrometer grains. (C) 2014 Elsevier B.V. All rights reserved.

All-solid-state lithium batteries using LiBH4 electrolyte and LiCoO2 cathode were prepared, and the effect of the intermediate layers between LiBH4 and LiCoO2 was demonstrated by electrochemical measurement. Li3PO4, LiNbO3 and Al2O3 thin films with smooth surfaces deposited by PLD were utilized for the intermediate layer. With the intermediate layer, the interfacial resistance between LiBH4 and LiCoO2 decreased by as much as 3 orders of magnitude by suppressing the interfacial reaction between LiBH4 and LiCoO2. A 10-25 nm-thick Li3PO4 intermediate layer was found to be the most effective to suppress the interfacial resistance. (C) 2013 Elsevier B.V. All rights reserved.

The high energy density and excellent cycle performance of lithium ion batteries makes them superior to all other secondary batteries and explains why they are widely used in portable devices. However, because organic liquid electrolytes have a higher operating voltage than aqueous solution, they are used in lithium ion batteries. This comes with the risk of fire due to their flammability. Solid electrolytes are being investigated to find an alternative to organic liquid. However, the nature of the solid-solid point contact at the interface between the electrolyte and electrode or between the electrolyte grains is such that high power density has proven difficult to attain. We develop a new method for the fabrication of a solid electrolyte using LiBH4, known for its super Li+ ion conduction without any grain boundary contribution. The modifications to the conduction pathway achieved by stabilizing the high pressure form of this material provided a new structure with some LiBH4, more suitable to the high rate condition. We synthesized the H. P. form of LiBH4 under ambient pressure by doping LiBH4 with the KI lattice by sintering. The formation of a KI LiBH4 solid solution was confirmed both macroscopically and microscopically. The obtained sample was shown to be a pure Li+ conductor despite its small Li+ content. This conduction mechanism, where the light doping cation played a major role in ion conduction, was termed the "Parasitic Conduction Mechanism." This mechanism made it possible to synthesize a new ion conductor and is expected to have enormous potential in the search for new battery materials. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

The correlation between the local structure and the electric-field gradient at the Sc site in ScO6 polyhedra in Sc2O3, Ba3Sc4O9 and BaSc2O4 was investigated by means of Sc-45 NMR spectroscopy and DFT calculations. The electric-field gradient at the nucleus as determined experimentally and by calculations is compared using the quadrupolar coupling constant, C-Q, around chemically and crystallographically distinct Sc sites in Sc-containing compounds. With C-Q as the NMR parameter, the results obtained from the DFT calculation were in good agreement with the NMR measurements. The increase in the C-Q values with the standard deviation of the O-O bond length surrounding Sc indicates that C-Q is affected by the distribution of the six nearest neighboring O atoms around Sc. This study suggests that C-Q plays an important role as an indicator of the local structure around ions, and that a combined complementary approach using both NMR spectroscopy and DFT calculation can be used along with diffraction techniques to provide a detailed understanding of crystal structures.

Impedance measurements indicate that Na2B12H12 exhibits dramatic Na+ conductivity (on the order of 0.1 S cm(-1)) above its order-disorder phase-transition at approximate to 529 K, rivaling that of current, solid-state, ceramic-based, Na-battery electrolytes. Superionicity may be aided by the large size, quasispherical shape, and high rotational mobility of the B12H122- anions.

Sodium and magnesium ionic conduction in complex hydrides as a new category of solid-state fast ionic conductors is presented. We first investigated experimentally the sodium ionic conductivities of the representative Na-based complex hydrides NaBH4, NaNH2, NaAlH4, and Na3AlH6, all of which have single complex anion [BH4](-), [NH2I-, [AlH4](-) and [AIH(6)](3-), respectively. Na3AlH6 showed much higher ionic conductivity of 5 x 10(-7) S/cm at 300 K than NaBH4, NaNH2, and NaAlH4 (their ionic conductivities were around 10(-10) S/cm). We obtained the sodium fast-ionic conductor Na-2(BH4)(NH2) with the [BH4](-) and [NH2](-) complex anions by combining NaBH4 and NaNH2 with a molar ratio of 1:1. It exhibited the most superior sodium ionic conductivity of 3 x 10(-6) S/cm at 300 K because of the specific antiperovskite-type structure with vacancies in the Na+ site. Furthermore, first-principles molecular dynamics simulations suggested the possible magnesium ionic conduction in the high-temperature phase of Mg(BH4)(2) by substituting partly [BH4](-) with [AlH4](-). (C) 2013 Elsevier B.V. All rights reserved.

Cu-Ag core-shell particles with 5 mu m-diameter Cu core and 260 nm-thick Ag shell were prepared by an electroless plating method in an aqueous system. The obtained core-shell particles were investigated for their thermal oxidation behavior during baking in air ambient. Thermogravimetric analysis indicated that the oxidation was started at about 200 degrees C. This oxidation temperature was a little higher than that (150 degrees C) of Cu particles without Ag shell. Microstructure observation of the core-shell particles baked in Ar ambient revealed the agglomeration of Ag shell on the Cu core surface after heating the sample above 200 degrees C, which resulted in direct exposure of the Cu core to ambient. Thus in air ambient, the exposed Cu core was destined to be oxidized. The temperature dependent growth of the agglomerated Ag shell was characterized with an activation energy of 37.56 kJ/mol, which could be assigned to a surface- diffusion-controlled mechanism. This characteristic of the Ag shell would limit the applications of the Cu-Ag core-shell particles to conductive paste for solar cells, wherein baking temperature beyond 200 degrees C in air ambient is generally required to promote good sintering of the paste particles as well as to obtain good electrical contact between metal and silicon. (C) 2013 Elsevier B.V. All rights reserved.

Electrochemical properties of all-solid-state lithium batteries using lithium borohydride (LiBH4) as a solid electrolyte are presented for the first time. Despite its high conductivity and good compatibility with a lithium electrode, LiBH4 has not been considered suitable for practical applications partly due to its high reducing capability when used with metal oxides. In our investigation, it was confirmed that contact between this hydride solid lithium ion conductor and LiCoO2 results in a large interfacial resistance, and therefore significant capacity loss. In an attempt to minimize this effect, an intermediate Li3PO4 layer was employed. Our results indicate a significant improvement in both the:rate and the cycle performance of LiBH4 solid electrolyte batteries, suggesting that LiBH4 can be used in practical applications as an electrolyte in all-solid-state lithium batteries. (C) 2012 Elsevier B.V. All rights reserved.

Ti-doped La-Sr-Co-Fe-based oxides (LSTCFs) were prepared as cathode material for co-sintering with electrolyte at high temperatures. LSTCFs have relatively high solid solubility limits of Ti up to 80mol%. Before reaching the solubility limits, LSTCFs were well densified and single phase with a rhombohedral structure (R-3c). Meanwhile, after exceeding the solubility limits, a Ti-rich secondary phase appeared and microstructures tend to be porous. Electrical conductivity and thermal expansion coefficient (TEC) for LSTCF decreased with increasing Ti content. Ti4+ appears to work as a donor and suppress electronic spin state transition of Co3+ ions and formation of oxygen vacancies. The composition, such as La0.6Sr0.4Ti0.4(Co0.2Fe0.8)(0.6)O3-delta (LSTCF28) with 40 mol% Ti and La0.6Sr0.4Ti0.6(Co0.8Fe0.2)(0.4)O3-delta (LSTCF82) with 60 mol% Ti, showed low sinterability and sufficient thermomechanical compatibility with GDC electrolyte. Those, however, possess more than two order of magnitude lower electrical conductivity than those of typical cathode materials.

The Fe-site of Bi0.7Sr0.3FeO3 - δ (BSF) was doped with manganese to determine any changes in the charged defects and understand how this change affects the electrode properties of this material. The electrical conductivity and oxygen permeability results suggest that Mn-doping effectively improves the electronic compensation of BSF, which is energetically favored by ionic compensation. In terms of electrode properties, 50 mol% Mn-doped BSF (BSFM55) showed more than one order of magnitude greater electrode resistance than BSF, suggesting that kinetics related to ionic defects plays a more important role than electronic defects in determining the properties of Bi-Sr-Fe based perovskite oxides. © 2013 Published by Elsevier B.V.

In situ proton nuclear magnetic resonance (NMR) was employed to study the hydrogenation and dehydrogenation kinetics of ZrCr2. The powder samples prepared by arc melting followed by homogenizing heat treatment and grinding were put inside a boron nitride (BN) crucible, which was placed inside a quartz tube attached to a high pressure assembly specially designed for in situ NMR measurements. The samples were activated at 573 K under vacuum inside the high temperature probe and then exposed to the required hydrogen gas pressure at room temperature for hydrogenation. Gradual hydrogenation of the samples was recorded through in situ NMR. Before activation of the sample, the exposure to high pressure showed two peaks with NMR shifts of 8.5 and -3.3 ppm, which were assigned to hydrogen gas and physisorbed hydrogen, respectively. After activation, the sample showed absorption manifested through the appearance of a broad peak with an NMR shift of -141 ppm. The NMR shift of absorption peak increased to higher magnetic fields as the hydrogen absorption proceeded. It was also accompanied by a change in NMR shift of physisorbed hydrogen peak in the same direction. Both the shifts, i.e., of absorbed hydrogen as well as of physisorbed hydrogen were linearly related with the degree of hydrogenation. This change in NMR shift of physisorbed hydrogen was explained on the basis of increase in density of d-electronic states at Fermi level with an increase in the absorbed hydrogen. (C) 2012 Elsevier B.V. All rights reserved.

Al-doped Mg0.5(1+x)AlxTi2-x(PO4)(3) has been prepared by a sol-gel method and the conductivity has been evaluated by an ac impedance method to determine the optimum lattice volume for Mg-ion conduction. Instead of using Ti in the samples, 10-15 mol%Al was used, resulting in lattice contraction in the c-axis direction. The samples, sintered at 500-80 degrees 0C for 12 h by a reaction sintering method, had a relative density of 70-80% and their grain size was 2-3 mu m. The ionic conductivity calculated from the grain and grain boundary resistance at 600 degrees C was 7.1 x 10(-5) and 1.3 x 10(-5) S/cm, respectively. The activation energy of the grain conductivity was 128 kJ/mol in the temperature range of 300 to 600 degrees C. By comparing ionic conductivity of various-doped titanium phosphates, optimum lattice volume was estimated to be 1.304 nm(3). [doi:10.2320/matertrans.MBW201111]

We report the experimental results of structural and sodium ionic conductive properties of the Na(BH4)-Na(NH2)-NaI system. Na(BH4)(0.5)(NH2)(0.5) with [BH4](-) and [NH2](-) complex anions formed by combining Na(BH4) and Na(NH2) complex hydrides shows the most superior sodium ionic conductivity of 2 x 10(-6) S/cm at 300K because of the specific antiperovskite-type structure with vacancies in the Na+ site Furthermore, Na(BH4)(0.5)(NH2)(0.5) shows a high electrochemical stability of at least 6 V (vs Na+/Na). The result suggests that Na(BH4)(0.5)(NH2)(0.5) could be a potential candidate for solid electrolyte. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4716021]

New Magnesium-Ion Conductors, TM-Doped Mg_0.5Ti₂(PO₄)₃ (TM = Fe, Mn, Co and Nb), Have Been Prepared by Sol-Gel Method. In Addition, their Crystal Structure Has Been Refined by Rietveld Technique and the Conductivity Has Been Evaluated by Ac Impedance Method. The Samples Were Sintered at 1150°C for 2 H (Fe, Mn and Co) or 1200°C for 10 H (Nb). For All Samples, Three Resistance Components Attributed to Grain, Grain Boundary and the Interface of Electrolyte-Electrode Were Successfully Separated as a Result of Sintering Accompanied by Grain Growth Reaching to 5 to 10 µm. The Change of Ionic Conductivity Will Be Discussed in Relation to the Dopants and their Crystal Structures.

The high-pressure effects on lithium ion conduction in LiBH(4) have been investigated. The high-pressure ac-impedance measurement was performed by using a cubic anvil-type apparatus under 2 to 6 GPa at various temperatures. For the hexagonal structure (Phase I), the activation volume for lithium ion conduction was found to be around 3 cm(3)/mol (approximate to 0.09V(m), where V(m) means its molar volume). This activation volume is almost comparable to that for other fast-ion conductors such as NASICONs. The lithium ion conductivities of orthorhombic (Phase Ill) and cubic (Phase V) structures were also measured. Regardless of crystal structures, the activation energies of Phases 1,111, and V were almost identical at around 50 to 60 kJ/mol; on the other hand, the pre-exponential terms of Phases III and V were smaller than those of Phase! by one to two orders of magnitude. (C) 2010 Elsevier B.V. All rights reserved.

In the present work, we focus attention on the effect of LiI addition to newly discovered pure lithium ion conductor, LiBH4. Solid solution of the composition LiBH4-LiI (LiI: 6.25-33.3 mol%) was synthesized by solid state reaction. Electrical conductivity was measured from room temperature to 140 degrees C by ac impedance method, which revealed the fast-ion conduction phase of LiBH4 can be stabilized to lower temperature, below the room temperature. Solid solution with LiI showed higher conductivities and lower activation energies in comparison with LiBH4. Powder XRD measurement was carried out at 120 degrees C (just above the transition temperature of LiBH4). The lattice constants of the solid solution were determined. DSC measurement showed a systematic compositional dependence on the transition temperature. The stabilization mechanism was discussed. (C) 2010 Elsevier B.V. All rights reserved.

The electrical conductivities of complex hydrides Li-2(BH4)(NH2) and Li-4(BH4)(NH2)(3) consisting of (BH4)(-) and (NH2)(-) anions are investigated focusing on their low melting temperatures (365 K for Li-2(BH4)(NH2) and 490 K for Li-4(BH4)(NH2)(3)). The two hydrides show lithium fast-ion conductivities of about 1 x 10(-4) S.cm(-1) at room temperature. After melting, the total ion conductivities of Li-2(BH4)(NH2) and Li-4(BH4)(NH2)(3) reach 6 x 10(-2) S.cm(-1) (378 K) and 2 x 10(-1) S.cm(-1) (513 K), respectively. The crystal structure and local atomistic structures closely correlated with the lithium ion conduction before and after melting are also discussed. [doi:10.2320/matertrans.MA201003]

A NMR system for in situ analysis of hydrogen storage materials under high pressure and temperature conditions was developed. The system consists of a gas pressure and flow rate controlling unit, a temperature controller, a high temperature NMR probe tunable for both (1)H and other nuclei, and a sample tube holder. Sample temperature can be controlled up to 623 K by heated N(2) gas flow. Sample tube atmosphere can be substituted by either H(2) or Ar and can be pressurized up to 1 MPa under constant flow rate up to 100 ml/min. During the NMR measurement, the pressure can be adjusted easily by just handle a back pressure valve. On the blank NMR measurement, (1)H background noise was confirmed to be very low. (1)H and (11)B NMR spectrum of LiBH(4) were successfully observed at high temperature for the demonstration of the system. The intensity of the (1)H NMR spectra of H(2) gas was also confirmed to be proportional to the applied pressure. (C) 2010 American Institute of Physics. [doi:10.1063/1.3484282]

Lithium-ion conduction in complex hydrides LiAlH(4) and Li(3)AlH(6) was investigated using ac complex impedance measurements. The conductivities at room temperature were 8.7 x 10(-9) S/cm in the case of LiAlH(4) and 1.4 x 10(-7) S/cm in the case of Li(3)AlH(6). To enhance the conductivity of Li(3)AlH(6) having good thermal stability in heating/cooling cycles, mechanical milling, and addition of lithium halides (LiCl, LiI) were implemented. The maximum value of 2.5 x 10(-4) S/cm at 393 K was observed when 0.33 M ratio of LiI was added to Li(3)AlH(6). This study demonstrated two research directions to enhance the lithium-ion conductivity in a variety of complex hydrides. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3356981]

This paper describes the water adsorption behavior and electrical conductivity of Sm-doped ceria nanoparticles under humidified atmosphere. Single nano-sized 6 mol% Sm-doped ceria was prepared by either homogeneous precipitation using hexamethylenetetramine (HMTA) or ultraviolet (UV) laser irradiation. For the ceria nanoparticles prepared by HMTA, weakly-bundled agglomerates with pores were formed; as a result, approximately 3 mass% of water adsorption and capillary condensation were observed at room temperature. On the other hand, those prepared by UV laser irradiation formed tightly-bundled agglomerates without such pores; only 0.12 mass% of water was adsorbed under the same condition. For electrical conductivity measurements, dense samples having a relative density of 85 to 93% were prepared at 300 degrees C under 6 GPa by using a high-pressure apparatus. The proton conductivity of dense nanocrystalline ceria was on the order of 10(-7) to 10(-8) S/cm at around 50 degrees C under humidified atmosphere. As temperature increased, the proton conductivity decreased. (C) 2009 Elsevier ay. All rights reserved.

The perovskite oxides in the system Bi-1 (-) xSrxFeO3-delta (x = 0.05, 0.15, 0.3. 0.6, and 0.8) were characterized in the intermediate temperature range (650 to 800 degrees C) by oxygen permeation and electrical conductivity measurements. The samples exhibited a single phase perovskite structure with a decreasing lattice constant with increasing Sr concentration and a structural change from rhombohedral to cubic at x &gt;= 0.3. Mixed conductivity was confirmed in all samples with maximum flux levels on the order of 0.11 mu mol/cm(2) s at 800 degrees C for the x = 0.8 composition. Materials studied displayed p-type conductivity over the oxygen partial pressure range present in permeation measurements (0.21 to 10(-6) atm). A local maximum of oxygen flux and ionic conductivity was found near x = 0.3. (C) 2009 Elsevier B.V. All rights reserved.

The measurement of oxygen flux across nanocrystalline cerium oxide (CeO2) thin films at intermediate temperature (650-800 degrees C) is presented. Porous ceria support substrates were fabricated by sintering with carbon additions. The final dense film was deposited from an optimized sol-gel solution resulting in a mean grain size of 50 nm, which displayed oxygen flux values of up to 0.014 mu mol/cm(2) s over the oxygen partial pressure range from air to helium gas used in the measurement at 800 degrees C. The oxygen flux characteristics confirm mixed ionic and electronic conductivities in nanocrystalline ceria films and demonstrate the role of size dependent materials properties as a design parameter in functional membranes for oxygen separation. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3503519] All rights reserved.

An electrode design with no use of three-phase boundary was investigated using palladium electrode. The hydrogen evolution rate of the palladium electrode cell using SrZr(0.9)Y(0.1)O(3 -aEuro parts per thousand alpha) electrolyte followed Faraday&apos;s law up to 180 mA cm(-2), and the anode and cathode overpotentials were significantly lower than those of a platinum electrode cell, suggesting that the palladium electrode is effective to improve the performance of the hydrogen-pumping cell using SrZrO(3)-based electrolyte. The rate-determining step (RDS) for electrode reaction was also investigated by changing the electrode morphology and hydrogen partial pressure, and it was suggested that the RDS of the anode is a reaction at electrode/electrolyte interface.

Some of the authors have reported that a complex hydride, Li(BH4), with the (BH4)(-) anion exhibits lithium fast-ion conduction (more than 1 x 10(-3) S/cm) accompanied by the structural transition at similar to 390 K for the first time in 30 years since the conduction in Li-2(NH) was reported in 1979. Here we report another conceptual study and remarkable results of Li-2(BH4)(NH2) and Li-4(BH4)(NH2)(3) combined with the (BH4)(-) and (NH2)(-) anions showing ion conductivities 4 orders of magnitude higher than that for Li(BH4) at RT, due to being provided with new occupation sites for Li+ ions. Both Li-2(BH4)(NH2) and Li-4(BH4)(NH2)(3) exhibit a lithium fast-ion conductivity of 2 x 10(-4) S/cm at RT, and the activation energy for conduction in Li-4(BH4)(NH2)(3) is evaluated to be 0.26 eV, less than half those in Li-2(BH4)(NH2) and Li(BH4). This study not only demonstrates an important direction in which to search for higher ion conductivity in complex hydrides but also greatly increases the material variations of solid electrolytes.

High-pressure synthesis has been widely used for exploration of novel materials. In this study. Li-Y hydrides were explored under GPa-order pressure by using a cubic-anvil-type apparatus. Unfortunately, a novel hydride in Li-Y system was not synthesizedin this study, but it is found that 10at% addition of Li can stabilize FCC-YH3 high pressure phase even under ambient pressure. The Li added FCC-YH3 have a CeH3-type structure judging from the results of XRD and raman spectrometry and its lattice constant was estimated to be 0.52666(1) run. Total hydrogen content of the hydride was estimated to be 3.52 mass%. This hydride was partially dehydrogenated at 575 K with decreasing its lattice constant down to 0.5206(1)nm. Then, the sample could absorb hydrogen again under 5 MPa-H-2 at 623 K. Hydrogenation enthalpy of the hydride was estimated from endothermic peak to vertical bar Delta H vertical bar = 29.2 kJ/mol-H and this Value is lower than that of YH3 ambient pressure phase. [doi: 10.2320/matertrans.M2009011]

The effect of variation of LiOH content on hydrogen desorption properties in LiH-(30-60) mol%LiOH composites was investigated. The addition of LiOH destabilized LiH in desorbing hydrogen below 300 degrees C for all composites while pure LiH desorbs hydrogen above 650 degrees C. The hydrogen desorption temperature of these composites decreased with decreasing the content of LiOH. The onset temperature of hydrogen desorption lowered to 262 degrees C for the sample of LiH-30 mol%LiOH. In the TDS measurement, the generation of water was observed around 420 degrees C for the samples of LiH-(40-60)mol%LiOH due to decomposition of unreacted LiOH. The intensity of the water peak from these composites in TDS decreases with decreasing the content of LiOH. The water generation was unobserved from LiH-30 mol%LiOH composite. These results indicate that LiH-(30 and 40) mol%LiOH is a suitable composition for hydrogen desorption in this study. [doi: 10.2320/matertrans.M2009055]

We prepared ultrafine Fe-Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe-Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5-3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe-Pt nanoparticles and UV-visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe-Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.

In our previous papers, we have reported the hydrogenation of MgNi2 with C36-type structure under GPa-order hydrogen pressure. In this paper, the effect of Cu substitution in MgNi2 was studied on the crystal structures, thermal stabilities and hydrogen contents of Mg(Ni1-xCux)(2) hydrides (x = 0-0.2). The hydrides were obtained by high pressure synthesis using cubic-anvil-type apparatus at 973 K for 8 h under 5 GPa. The hydrides were found to have primitive orthorhombic (Pmmm, x = 0.0-0.1) and body-centered tetragonal structures (14/mmm, x = 0.15-0.2). Their hydrogen contents were estimated to be 2.23-2.32 mass%. Dehydrogenation temperature decreased from 460 K (x 0,0) to 429 K (x = 0.20) with increasing amount of Cu Substitution. After dehydrogenation, the C36-type phase was observed by X-ray diffraction (XRD). Consequently, it is noteworthy that Mg(Ni1-xCux)(2) could be hydrogenated reversibly without disproportionation under high pressure of the order of gigapascals. [doi:10.2320/matertrans.MRA2008451]

Structural transition properties of the LiBH4+xLiI (x=0-1.00) pseudobinary system were examined by powder x-ray diffraction and differential scanning calorimetry combined with periodic density functional theory calculations. We experimentally and computationally confirmed the stabilization of the high-temperature [hexagonal, lithium super(fast-)ionic conduction] phase of LiBH4 with x=0.33 and 1.00, and the results also imply the existence of intermediate phases with x=0.07-0.20. The studies are of importance for further development of LiBH4 and the derived hydrides as solid-state electrolytes.

The present paper describes the grain size refinements of Cu-3 mass%Ti alloys by hydrogen heat-treatment of so-called Hydrogenation-Disproportionation-Desorption-Recombination (HDDR) process. During hydrogenation process, the disproportionation reaction occurred with forming of T hydrides in the alloy. With decomposition of Ti hydrides by the subsequent desorption process, Ti resolved into Cu matrix. In consequence, the original solid solution phase of the alloys formed. This means that the HDDR phenomena could take place ill the Cu-3 mass%Ti alloy. The grain size of the alloy is found to be about 20-50 nm after HDDR treatments such as hydrogenation treatment at 350 degrees C under hydrogen pressure of 7.5 MPa for 48 h, followed by the hydrogen desorption treatment at 530 degrees C for 4 h in vacuum. On the other hand, it is found that remarkable simultaneous improvements of mechanical strength of 1100 MPa and electrical properties of 21%IACS are obtained in the hydrogenated alloy. [doi: 10.2320/matertrans.MBW200807]

An oxygen permeable membrane based on mixed oxide-ion and electronic conduction is a promising material for hydrogen production from methane at high temperatures. To increase an oxygen permeation flux, decreasing in thickness is required. In this study, integrated oxygen permeable membranes supported on a porous layer was prepared by partial reduction of dense composite materials. The dense samples of (ZrO2- 3 mol%Y2O3)-x vol%NiFe2O4 (x = 33,40,50) were prepared by sintering at 1400 degrees C under air for 5 h. The one side of the sample was reduced at a temperature range of 800 to 1000 degrees C under Ar-5%H-2. The microstructure and oxygen flux density were analyzed by using a scanning electron microscopy and a quadrupole mass spectroscopy, respectively. An integrated oxygen permeable membrane of (ZrO2-3 mol%Y2O3)-50vol%NiFe2O4 having a dense layer of 200 mu m and a porous layer of 300 mu m was successfully prepared. The oxygen flux density of the membrane was found to be 4.3-7.4 x 10(-7) mol.cm(-2).s(-1). [doi: 10.2320/matertrans.MBW200802]

LiBH4 exhibits lithium superionic conduction accompanied by structural transition at around 390 K. Addition of LiCl to LiBH4 drastically affects both the transition and electrical conductivity: Transition from low-temperature (LT) to high-temperature (HT) phases in LiBH4 is observed at 370 K upon heating and the HT phase can be retained at 350-330 K upon cooling. Further, the conductivity in the LT phase is more than one or two orders of magnitude higher than that of pure LiBH4. These properties could be attributed to the dissolution of LiCl into LiBH4, suggested by in situ x-ray diffraction measurement.

This paper describes the electrical conductivity of ceria nanoparticles under high pressure ranging from 2 to 6 GPa. The samples used were pure and acceptor-doped ceria nanoparticles with a grain size of approximately 2 nm prepared by mixing hexamethylenetramine and metal nitrate solutions. The size of ceria nanoparticles was controlled to be 2 to 15 nm by varying heat-treatment conditions. The in-situ electrical conductivity measurements under high pressure were conducted by using an ac-impedance spectroscopy. By applying a pressure of 6 GPa at 300 A degrees C, the green compact of 6 mol % Sm-doped ceria nanoparticles was densified; a relative density of 93% was achieved. The sample showed an electrical conductivity of 3 x 10 (-aEuro parts per thousand 3) S/cm at 300 A degrees C under 6 GPa. The enhancement of electrical conductivity under high pressure seems to be related to ionic conduction in the vicinity of grain boundaries.

This paper describes the fabrication of a novel hydrogen production system based on an oxygen permeable membrane and its methane reforming properties. The planar-type membrane reformer module with dimensions of 6 cm x 6 cm was developed by using the composite-type membrane of (Ce(0.85)Sm(0.15))O(2)-15vo1%MnFe(2)O(4) and ferric stainless-steel separators. For the reformer module, high CH(4) conversion and H(2) selectivity of 96% and 89% were achieved, respectively. Based on energy analysis, it can be found that Delta G of partial oxidation of methane was effectively used for oxygen separation and heat compensation. The durability of the membrane was confirmed for 450 h.

Solid state lithium conductors are attracting much attention for their potential applications to solid-state batteries and supercapacitors of high energy density to overcome safety issues and irreversible capacity loss of the currently commercialized ones. Recently, we discovered a new class of lithium super ionic conductors based on lithium borohydride (LiBH4)center dot LiBH4 was found to have conductivity as high as 10(-2) Scm(-1) accompanied by orthorhombic to hexagonal phase transition above 115 degrees C. Polarization to the lithium metal electrode was shown to be extremely low, providing a versatile anode interface for the battery application. However, the high transition temperature of the superionic phase has limited its applications. Here we show that a chemical modification of LiBH4 can stabilize the superionic phase even below room temperature. By doping of lithium halides, high conductivity can be obtained at room temperature. Both XRD and NMR confirmed room - temperature stabilization of superionic phase for Lil-doped LiBH4. The electrochemical measurements showed a great advantage of this material as an extremely lightweight lithium electrolyte for batteries of high energy density. This material will open alternative opportunities for the development of solid ionic conductors other than previously known lithium conductors.

This paper describes the fabrication of a planar-type methane reformer based on a composite-type oxygen permeable membrane and its reforming properties. The membrane reformer module comprising Of (Ce0.85Sm0.15)O-2-15 vol.%MnFe2O4 and a ferric stainless steel separator with a same thermal expansion coefficient was successfully developed. For the reformer module, high CH4 conversion, CO and H-2 Selectivity of 96%, 84%, and 89% were achieved, respectively. Based on an electrical conductivity isotherm, joule heat caused by oxygen permeation in the module was estimated to be approximately 8.4 W. In addition, the effect of ZrO2-doping on the mechanical properties and oxygen permeability of the composite material was investigated. The highest Zr-content sample, (Ce0.85SM0.15)(0.2)Zr0.8O2-15 vol.% MnFe2O4, showed a tetragonal structure. As a result of the crystal structural change, superior mechanical properties of Young's modulus of 337 GPa and fracture toughness of 2.8 MPa m(1/2) were obtained. (c) 2008 Elsevier B.V. All rights reserved.

Mixed oxide-ion and electronic conductive thin films with the composition of (Ce0.85Sm0.15)O2-delta-15 vol%MnFe2O4 (CSO-MFO) were prepared on porous yttria stabrized zirconia substrates by a spin coating process, and their oxygen permeation flux densities were measured. The porous substrates were prepared from ZrO2-3 mol%Y2O3 (3YSZ)-33 vol%carbon and NiFe2O4. 3YSZ porous substrates were obtained from 3YSZ-33 vol%carbon by sintering at 1350 degrees C under At for 5 h and following oxidation at 800 degrees C under air for 2 h. For 3YSZ-33 vol%NiFe2O4, the optimum condition was sintering at 1400 degrees C under air for 5 h and following reduction at 800 degrees C under H-2 for 2 h. A CSO-MFO film was prepared by a spin coating process on the substrate. The thickness of the CSO-MFO was approximately 150 nm. Oxygen flux density of the CSO-MFO sample was found to be 8.9 x 10(-8) mol.cm(-2).s(-1).

High-pressure works are attractive techniques to obtain new compounds, such as alkali or alkaline earth metal-based systems. The atomic radius of Mg under GPa pressure is considerably smaller compared with transition metals; as such, it may be preferable to synthesize novel intermetallic compounds and hydrides by using high-pressure techniques. In this study, novel compounds were synthesized in an Mg-Ni system by a high-pressure technique using a cubic-anvil-type apparatus. A novel Mg6Ni intermetallic compound was obtained by exposing a mixture of Mg and Ni to 6 GPa at 900 degrees C for 2 h. The crystal structure of the compound is a tetragonal F-43m structure with a lattice parameter of a = 1.9987(1) nm. This compound decomposed to Mg and Mg2Ni phases at 278 degrees C with exothermic reaction. As is well known, MgNi2 does not form hydrides under conventional hydrogenation conditions, hence we investigated the reactivity of MgNi2 with highly pressurized hydrogen. It was found that the MgNi2 was able to form MgNi2H3.2 by treatment at 700 degrees C for 2 It under 5 GPa with a hydrogen source, leading to a hydrogen capacity of 2.23 mass%. This novel hydride was found to be a tetragonal MoSi2-type structure (14/mmm) with lattice parameters of a = 0.327(3) nm and c = 0.878(9) nm. The dehydrogenation of this hydride occurred at 187 degrees C with endothermic reaction, and caused decomposition into C36-type MgNi2. This hydride had solubility of Ni content and its thermal stability decreased with increasing Ni content. (C) 2007 Elsevier Ltd. All rights reserved.

The electrical conductivity of lithium borohydride (LiBH4) measured by the ac complex impedance method jumped by three orders of magnitude due to structural transition from orthorhombic to hexagonal at approximately 390 K. The hexagonal phase exhibited a high electrical conductivity of the order of 10(-3) S cm(-1). Furthermore, the conductivity calculated from the Nernst-Einstein equation using the correlation time obtained from Li-7 nuclear magnetic resonance was in good agreement with the measured electrical conductivity. It was concluded that the electrical conductivity in the hexagonal phase is due to the Li superionic conduction. (C) 2007 American Institute of Physics.

High-pressure synthesis has been widely used for exploration of novel materials. In this study, new Mg-based ternary hydrides in Mg-TM-H systems (TM = Zr, Nb, Hf and Ta) have been prepared under a pressure of 5 GPa by using a cubic-anvil-type apparatus. In TM = Zr, Nb and Hf. MgTM2Hy with a monoclinic-type structure were synthesized at 923 K under 5 GPa. Lattice parameters of MgTM2Hy were a = 5.816 angstrom, b = 3.3569 angstrom, c = 8.519 angstrom, beta = 103.06 degrees (for TM = Zr); a = 5.70 angstrom, b = 3.2888 angstrom, c = 7.927 angstrom, beta = 103.06 degrees(for TM = Nb); a = 5.782 A, b = 3.317 angstrom, c = 8.507 angstrom, beta = 103.06 degrees (for TM = HF). Results from fusion extraction analysis for MgTM2Hy (TM = Zr, Nb and Hf) showed their hydrogen contents., giving chemical formula of MgTM2H5.9. In TM = Nb and Ta, ternary hydrides with an FCC-type structure were synthesized under 5 GPa. These FCC hydrides had lattice parameters of a = 9.5526 angstrom (TM = Nb) and 9.5376 angstrom (TM = Ta). For TM = Nb, hydrogen content was determined from the fusion extraction analysis to be 5.8 mass%, corresponding to Mg6.2NbH14. Among the newly found hydrides, Mg6.2NbH14 showed the lowest dehydrogenation temperature of 595 K with endothermic reaction. Crystal structures and thermal stabilities of these hydrides were also investigated. (C) 2007 Published by Elsevier B.V.

Novel hydrides were synthesized in Mg-Ni-H and Mg-Ni-Cu-H systems by high-pressure technique using a cubic-anvil-type apparatus. Crystal structure and thermal stability of the hydrides were studied. The novel hydride with a composition of MgNi2H gamma was synthesized at 973 K for 2 h under the pressure of over 2 GPa. This hydride could be synthesized from each starting material, such as MgNi2(C36) and mixture of MgH2-x mol% Ni (x = 65-70). From fusion analysis, hydrogen content of the sample of MgH2-67 at.% Ni prepared with hydrogen source at 973 K for 2 It under 5 GPa was estimated to be 2.23 mass% and chemical formula was corresponding to be MgNi2-H-3.2. The novel hydride was found to exhibit the body-centered tetragonal structure (space group 14/mmm, No. 139) with lattice parameters of a = 0.327(3) nm, c = 0.878(9) nm. Moreover, crystal structure of novel hydride was distorted with varying Ni content, then it was found to exhibit C-faced based-centered orthorhombic structure (space group Pmmm, No. 47) with lattice parameters of a = 0.460(l) nm, b = 0.468(l) nm, c = 0.893(l) nm. In Mg-Ni-Cu-H system, crystal structure and thermal stability of Mg(Ni1-xCUx)(2)H-y (x = 0.05, 0.10, 0.15 0.20) were investigated. The sample of Mg(Ni0.95CU0.05)(2) prepared with hydrogen source at 973 K for 8 h under 5 GPa was dehydrogenated at 446 K, which is 15 K lower than that of MgNi2H3.2. Moreover, Mg(Ni0.95CU0.05)(2) prepared with hydrogen source at 973 K for 2 h under 5 GPa,which did not react hydrogen sufficiently, was decomposed at 409 K. (C) 2007 Elsevier B.V. All rights reserved.

A new intermediate temperature mixed conducting material has been fabricated based on acceptor doping of bismuth ferrite (BiFeO3). Acceptor doping at levels of 5 mol % with either Ca or Sr was found to increase the maximum operating temperature of ceramics by more than 100 degrees C as well as eliminate secondary phase formation often reported in the pure BiFeO3 system. Mixed ionic and electronic conductivity was confirmed by measuring the oxygen permeation properties of doped ceramics which exhibited flux's on the order of 0.018 mu mol/(cm(2)s) at 800 degrees C over the oxygen partial pressure range 0.21 atm (air) to 10(-6) atm (He). Ceramic membranes showed an increase in oxygen flux with decreasing sample thickness indicating good surface catalysis properties of the system.

Hydrogen storage materials are attracting much attention as media of storing hydrogen. High-pressure synthesis has been widely used for exploration of novel materials. We have reported that many new Mg-based hydrides or alloys have been synthesized by anvil-type apparatus under the pressure of GPa-order. In Mg - TM (TM = Nb, Ta) - H systems, it was reported that novel FCC-type hydride which is similar in crystal structure and composition to Mg7TiH13-16 was synthesized under 8 GPa. On the other hand, there is few reports of novel Ca-based hydrides to be synthesized under high pressure. However, the compressibility of calcium is higher than that of magnesium. Thus, there is a tendency for Ca compounds to be synthesized by lower pressure than Mg ones. This study describes the synthesis of new Ca-based hydrides by this high-pressure techniques. In Ca - TM (TM = Ti, Hf, V, Nb and Ta) systems, the influence of applied pressure on present phases were investigated. For the composition of CaH2 - 14.3 mol%ZrH2 in Ca - Zr - H system, novel hydride was synthesized at 1073 K for 2 h under 5 GPa. Crystal structure of the novel hydride was found to be FCC-type with a lattice parameter of a = 0.531 nm. In addition, the thermal stability and hydrogen contents of this novel hydride were investigated. In Ca - Hf - H system, the unknown phase was observed in the sample of CaH2 - 12.5 mol%HfH2 prepared 1073 K for 2 h under 5 GPa. This unknown phase is FCC structure with lattice parameter of a = 0.528(2) nm.

Electronic and oxygen ionic conductive (mixed-conductive) oxides allow oxygen permeation under oxygen partial pressure differences at elevated temperatures of typically 800-1000 degrees C. The oxygen permeation performance decreases abruptly at lower temperatures as a result of the high activation energy required for solid-state transport of O2- ions and electrons. This study is intended to improve the oxygen permeation flux of a mixed-conductive solid oxide at lower temperatures. Dense nanocrystalline Ge0.8Gd0.2O1.9 (CGO)-CoFe2O4 (CFO) mixed-conductive films were prepared on porous Ce0.8Gd0.2O1.9 substrates using a chemical solution spin-coating technique. The oxygen permeation flux and morphology of the CGO-CFO films were investigated along with the crystallinity of the CGO-CFO powder samples. The oxygen permeation flux of the CGO-CFO films was improved through the use of a reduced preparation firing temperature, suggesting that the membrane's oxygen permeation properties are correlated closely with the material's nanocrystalline structure. This result is important for developing oxygen permeable devices with enhanced performance at lower temperatures of approximately 600 degrees C. (c) 2006 Elsevier B.V. All rights reserved.

The preparation and oxygen permeation properties of the (Ce0.8Pr0.2)O2-delta - x vol% MnFe2O4 composites, where x = 0 to 35, have been investigated. The samples were prepared by the Pechini method. In the case of Ce0.8Pr0.2O2-delta, an oxygen flux density of 6 mu mol(.)cm(-2.)s(-1) (L = 0.0247 cm) and the maximum methane conversion of 50% were attained at 1000 degrees C. Unlike composites consisting of Gd-doped CeO2 and MnFe2O4, the oxygen permeability of the (Ce0.8Pr0.2)O2-delta - x vol% MnFe2O4 composites was almost constant regardless of the volume fraction of MnFe2O4; however, the optimum volume fraction of MnFe2O4 was determined to be 5 to 25 in the context of the chemical and mechanical stabilities under methane conversion atmosphere. In addition, the surface modification of the (Ce0.8Gd0.2)O2-delta - 15 vol% MnFe2O4 composite was performed by using the FePt nanoparticles. The catalyst loading of 2.8 mg/cm(2) on the both side of the 0.3 mm-thick (Ce0.8Gd0.2)O2-delta - 15vol% MnFe2O4 composite increased the oxygen flux density from 0.30 to 0.76 mu mol(.)cm(-2.)s(-1) in the case of He/air gradients; however, the effect seems to be reduced in the case of high oxygen flux density caused by a large pO(2) gradient. Moreover, the Langmuir-Blodgett film of the FePt nanoparticles were successfully prepared on the tape-cast (Ce0.8Gd0.2)O2-delta - 15vol% MnFe2O4 composite. Hydrophobic treatments for the surface of the composite were crucial to achieve high transfer ratio for the deposition of the LB film.

A partial oxidation test was performed using a La0.6Sr0.4Fe0.8CO0.2O3 (LSFCO6482) membrane in the surface limited conditions at a temperature range of 800-920 degrees C and in a syngas side atmosphere of CH4 diluted with Ar (100%, 25.6% and 1%) in order to investigate chemical stability and oxygen permeation properties. On the surface, deposited carbon was observed in the test and it was revealed to be graphite by an insitu Raman measurement. It was combusted by oxygen fed through the membrane. Segregation of the membrane on both surfaces was observed in all specimens after the test. Moreover, significant decomposition occurred on Air side surface of the membrane which tested in a syngas side atmosphere of 25.6% and 100%. However, the significant decomposition did not affect to be oxygen permeation properties, but it did affect its mechanical strength. (c) 2006 Elsevier B.V. All rights reserved.

This paper describes the electrode and oxygen permeation properties of Sm-doped CeO2-MFe2O4 composites prepared on a Sm-doped CeO2 electrolyte, where M = Co and Mn. The porous and thin-film samples were prepared by means of citrate-based liquid-mix and chemical solution deposition techniques, respectively. For Cole-Cole plots of porous and thin-film electrodes, two semi-circles corresponding to interface and chemical impedances were observed. The thin-film electrode of 1-mu m-thick (Ce0.9Sm0.1)O-2-30 vol.%CoFe2O4 (30CFO) composites showed a current density of 509 mA/cm(2) at 900 degrees C under a cathodic overpotential of 159 mV The 30CFO thin film exhibited an oxygen flux density of 1.3 mu mol/cm(2) s at 900 degrees C under PO2 of 1.2 x 10(-20) atm. (c) 2006 Elsevier B.V All rights reserved.

A novel hydride was synthesized in Mg-Ni-H system by high pressure technique using a cubic-anvil-type apparatus. Crystal structure, thermal stability and hydrogen content of the hydride were studied. The novel hydride with a composition of MgNi2Hy was synthesized at 973 K for 2 h under the pressure of more than 2 GPa, and was found to exhibit the body-centered tetragonal structure (space group I4/mmm, No. 139) with lattice parameters of a = 0.327(3) mn, c = 0.878(9) nm. Moreover, this hydride could be synthesized from each starting material, such as MgNi2 high pressure phase, MgNi2 (C36) and mixture of MgH2-x mol% Ni (x = 65-70). Its hydrogen content was estimated to be 2.23 mass% from fusion analysis and corresponding chemical formula was found to be MgNi2H3.2. This hydride was decomposed into MgNi2 (C36) over 460 K, and has solubility of Ni content and thermal stability of the novel hydride was decreased with increasing Ni content.

Oxygen permeable ceramics based on mixed conductors are attracting much attention for use in partial oxidation of hydrocarbons as a novel technique for syngas and pure hydrogen production. This paper describes the preparation and oxygen permeation properties including the methane reforming property of a novel member of oxygen permeable ceramics. The materials used are solid solutions of (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta. The single phase of perovskite-type (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta is obtained in the range of x=0.4 to 0.9. The highest oxygen flux densities of 2.2 and 11 mol/cm(2) s (membrane thickness, L=0.2 mm) are attained for (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta (x=0.6) at 1000 degrees C under He/air and CH4/air gradients, respectively. The electrical conductivity of (La0.5Ba0.3Sr0.2)(Fe0.6In0.4)O3-delta is dominated by p-type conduction having a slope of 1/4 under the high P(02) region. The oxide-ion conductivity of the same sample is estimated to be 0.05 S/cm at 800 degrees C. Even though the oxygen flux density slightly decreases with increasing time, high CO selectivity of 90% is kept for 100 h. The oxygen flux density of the solid solution is also discussed in the context of surface exchange kinetics.

The high-pressure synthesis of new hydrides of Mg-RE-H systems, where RE = Y, La, Ce, Pr, Sm, Gd, Tb and Dy, were conducted by using a cubic-anvil-type apparatus, and their crystal structure, thermal stabilities and hydrogen contents were investigated. In Mg-Y-H system, newly found MgY2Hy with a FCC-type structure has been prepared. In MgH2-x mol% REH (REH = LaH3, CeH2.5 and PrH3), new hydrides with primitive tetragonal structure were synthesized around x = 25-33 under GPa-order high pressures. The lattice constants were a = 0.8193 nm, c = 0.5028 nm, a = 0.8118 nm, c = 0.4979 nm and a = 0.8058 nm, c = 0.4970 nm at x = 25 in Mg-La, Ce and Pr systems, respectively. The hydrogen contents of the novel compounds were 4.1, 3.7 and 3.9 mass% in Mg-La, Ce and Pr systems, respectively, and the chemical formulae were found to correspond to Mg3LaH9, Mg3CeH8.1 and Mg3PrH9. The new hydrides decomposed into Mg and rare-earth hydride at about 600 K (Mg3LaH9: 614 K, Mg3CeH8.1: 609 K, Mg3PrH9: 630 K) with an endothermic reaction. In M-H-2-x mol% hREH (hREH = GdH3, TbH3 and DyH3), new hydrides with FCC-type structure were synthesized around x = 67. (c) 2005 Elsevier B.V. All rights reserved.

The preparation and oxygen permeation properties of novel composites of Ce0.9Sm0.1O1.95-xvol% Mn(1.5-0.5y)Co(1+0.5y)Ni0.5O4 (CSO-xMCNO; 5 &lt;= x &lt;= 25; 0 &lt;= y &lt;= 1.0) have been investigated. The composites were prepared by the Pechini process to obtain fine microstructures. The composites fired at 1300 degrees C for 2 h were found to consist of Ce0.9Sm0.1O1.95 and two different spinel-type oxides. The oxygen flux density of 0.3 mm-thick CSO-15MCNO with y = 1.0 was found to be 1.1 and 7.5 mu mol cm(-2) s(-1) at 1000 degrees C under He (20 sccm)/air and Ar-10%CH4 (100 scm)/air gradients, respectively. CSO-25MCNO with a larger amount of spinel-type phases exhibited a high oxygen flux density of 6.2 mu mol cm(-2) s(-1) and CO selectivity of 72% at 1000 degrees C without a conventional reforming catalyst. In addition, Ce0.9Sm0.1O1.95-15 vol% MnFe2O4 (CSO-15MFO) membranes were prepared by means of tape-casting technique. As a result of the optimization of slurry composition, a crack-free dense membrane with dimensions of 5 cm x 5 cm was successfully prepared after sintering at 1300 degrees C for 2 h. For the tape-cast 133 mu m-thick membrane, an oxygen flux density of 9.5 mu mol cm(-2) s(-1) was attained at 1000 degrees C. Laminated membranes has been also successfully prepared. (c) 2005 Elsevier B.V. All rights reserved.

The appearance of ferromagnetism in (Sc0.85Ca0.15)Co-2 Laves phase synthesized under high pressure of 6 GPa was confirmed. A magnetically homogeneous state was achieved by applying pressure of 6 GPa in 1373 K for 48 h. This is the first study that confirmed a stable ferromagnetic state in exchange-enhanced Pauli paramagnet ScCo2-based compound system. The quantities of pressure P and magnetization M dependence of the Curie temperature T-C, dIn T-C/dP and (dln T-C/dP)/(dln M/dP) = dln T-C/dln M for (Sc0.85Ca0.15)Co-2 are smaller than those for Lu(Co1-xAlx)(2) compounds, and accordingly the magnetic moment of (Sc0.85Ca0.15)Co-2 is stiffer against pressure. The ratio of the spin wave stiffness constant D-S to T-C, D-S/T-C, in (Sc0.85Ca0.15)Co-2 is smaller than that of Lu(Co1-xAlx)(2), implying that the spin wave in (Sc0.85Ca0.15)Co-2 spread over wider wavevector space. (c) 2005 Elsevier B.V. All rights reserved.

Nano-particles of Pr and Mn-doped ceria have been prepared by mixing nitrate solutions and hexamethylenetetramine as an oxidizing agent, and their thermal stability has been investigated. The particle size was evaluated by means of XRD, BET and dynamic light scattering techniques. The particle size of Pr and Mn-doped ceria was found to be approximately 3 nm as prepared. Even though the particle size of doped ceria increases with increasing annealing temperature, the size of less than 15 nm was kept after annealing at 600 degrees C for 10 h. On the other hand, the lattice constant of nano-sized ceria, for example 0.544 run for 3 nm-size particles, decreases and reaches to the value of bulk material (0.541 nm) as annealing temperature increases. This suggests that the valence state of cerium and the amount of oxygen vacancies strongly depend-on the particle size.

This paper describes preparation and methane reforming characteristics of a proto-type reformer based on a composite-type oxygen permeable membrane. The tape-cast membrane of Sm-doped CeO2 - 15 vol% MnFe2O4 composite was combined with a ferric stainless steel separator with a same thermal expansion coefficient. For the reformer module, high CH4 conversion, CO and H-2 selectivity of 96%, 84%, and 89% were achieved, respectively. Based on C, H, and O balances, oxygen permeation flux was found to be 5.7 pmol/cm(2)s. Joule heat caused by oxygen permeation was estimated to be approximately 17.5 W, and this covered most part of heat required for reforming reactions.

Present paper describes the effects of the Mg content on the occurrence of HDDR phenomena as well as the microstructural evolution in Al-(3-7.8mass%)Mg alloys. It was found that the HDDR phenomena take place in all those alloys, and grain size of the alloy turned into a several 10 run after HDDR treatments such as heat-treatment at 350°C under hydrogen pressure of 7.5 MPa for 72 h, in following by the hydrogen desorption treatment at 350°C for 4 h in vacuum. The refined grain size of Al-3.0mass% Mg alloy was observed to be largest among there alloys. However, it should be emphasized that small content of Mg (3 mass%) is able to induce the HDDR phenomena associated with the nano-order grain refinements in Al-Mg alloys. This could be the first observation of HDDR phenomena which occur in Al-3 and 5mass%Mg alloys, and are effective for yielding the nano-order fine grain size.

Phases present and thermal stability of synthesized new compounds in the Mg-Li-H and Mg-Pd systems by preparing under a high pressure were studied. In the Mg-Li-H system, a new hydride with a tentative composition Mg2LiH5 is synthesized by exposing a mixture of MgH2 and LiH to pressures of 2-5 GPa at 973 K for 4 It. The hydride has a cubic structure with the lattice parameter of 0.4219 nm. In the Mg-Pd system, a new intermetallic compound Mg-20 at.% Pd was synthesized at 1073 K and a pressure exceeding 2 GPa. This phase had a bcc structure with a = 1.4053(l) nm and it transformed into a low-symmetry phase on heating above 663 K. Moreover, hydrogenation of the compound at 650 K for 3 days under hydrogen pressure of 9 MPa, changed into MgH2 and new hydride Mg2PdHx with fcc structure similar to that Of Mg2PdCx [D. Noreus, B. Bogdanovic, U. Wilczok, J. Less-Common Met. 169 (1991) 369-373]. The new hydride dehydrogenated at 586 K that is about 100 K lower than MgH2. (c) 2005 Elsevier B.V. All rights reserved.

The novel intermetallic compound of MgCu with a CsCl-type structure has been prepared under high pressure, and its energetics including the enthalpy of formation has been discussed by means of density functional calculations. The MgCu phase with a lattice constant of a = 0.3161 nm was prepared by using cubic anvil-type apparatus at 800 degrees C under 6 GPa. For the first-principles calculation, a full potential linearized augmented plane wave (FPLAPW) technique was used. The lattice constant obtained as a result of volume optimization showed a good agreement with the observed value with an accuracy of less than 0.3%. From the calculation of the total energy, the enthalpy of formation of the novel MgCu phase was estimated to be - 18.4 kJ/mol. In addition, the MgCu phase decomposed into Mg2Cu and MgCu2 phases at around 520 K with A H = -2.2 kJ/mol (exothermic). The calculated Delta H (-6.4 kJ/mol) also showed a fairly good agreement with the observed value. (c) 2005 Elsevier B.V. All rights reserved.

The present paper describes the grain size refinements of an Al-7.8 mass%Mg alloy by hydrogen heat-treatment of so-called Hydrogenation-Disproportionation-Desorption-Recombination (HDDR) process. Upon hydrogenation of the alloys, a disproportionation reaction occurred in forming of MgH2 embedded in AI matrix phases. In the subsequent hydrogen-desorption of the alloys, MgH2 was decomposed and was resolved into AI matrix phase, in resulting in the original solid solution of the alloys. This means that the HDDR phenomena take place in the Al-7.8 mass%Mg alloy. It is rather surprising that the grain size of the alloy turned into a several 10 nm after HDDR treatments such as heat-treatment at 350 degrees C under hydrogen pressure of 7.5 MPa for 7211, in following by the hydrogen desorption treatment at 350 degrees C for 4 h in vacuum. This could be the first report that I-IDDR treatments are effective in producing the fine grain size of the order of nm in Al-based alloys.

New hydrides of Mg-TM-H systems, where TM = Zr, Nb and Mo, have been prepared by using cubic-anvil-type apparatus, and their crystal structure and hydrogen content have been investigated. The high-pressure synthesis was performed at 1073-1173 K under 2-5 GPa. In the Mg-Zr-H system, a new hydride Mg2Zr3Hy with a monoclinic structure (a = 0.8591(1) nm, b = 0.33539(5) nm, c = 0.5816(1) nm, beta = 103.06(3)degrees) was obtained by exposing a mixture of MgH2 and ZrH2 to pressure of 2 to 5 GPa at 1073 K for 2 h. In the Mg-Mo system, a new hydride Mg3MoH6 was synthesized by exposing a mixture of MgH2 and Mo to 5 GPa at 1173 K for 2 h. The hydride was found to have a hexagonal structure (a = 0.49958(6) nm, c = 0.8840(2) nm). In the Mg-Nb-H system, a new hydride Mg4NbHy was also synthesized by exposing a mixture of MgH2 and Nb to 5 GPa at 1073 K for 2 h.

oxygen permeable ceramics based on mixed conductors are attracting much attention for use in partial oxidation of hydrocarbons as a novel technique for syngas and pure hydrogen production. This paper describes the preparation and oxygen permeation properties including methane reforming property of a novel member of oxygen permeable ceramics. The materials used are solid solutions of (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta. The single phase of perovskite-type (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta is obtained in the range of x = 0.4 to 0.9. The highest oxygen flux densities of 2.2 and 11 mu mol/cm(2) s are attained for (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta (x = 0.6) at 1000 degrees C under He / air and CH4 / air gradients, respectively. The electrical conductivity of (La0.5Ba0.3Sr0.2)(FC0.6In0.4)O3-delta is dominated by p-type conduction having a slope of 1/4 under the high P(02) region. The oxide-ion conductivity of the same sample is estimated to be 0.05 S/cm at 800 degrees C. Even though the oxygen flux density slightly decreases with increasing time, high CO selectivity of 90 % is kept for 100 h. The oxygen flux density of the solid solution is also discussed in the context of surface exchange kinetics.

The oxide-ion conduction of gadolinium zirconate - titanates, Gd-2(Ti1-xZrx)(2)O-7 (GTZ), has been investigated under high pressure in the range of 2 to 6 GPa with the aid of a cubic-anvil-type apparatus. For these pyrochlore compounds, the oxide-ion conductivity at elevated temperatures in the range of 750 to 960 degrees C decreased with increasing pressure, indicating the presence of a positive activation volume, Delta V. The activation volumes Delta V of GZ (x = 1.0) and GTZ (x = 0.95) were 2.0 and 1.3 cm(3)/mol, respectively, at 750 degrees C and decreased with increasing temperature.

Ce0.8Gd0.2O1.9 (CGO) - MFe2O4 (M=divalent cation) is a composite-type oxygen-ionic and electronic mixed conductor. Dense nanocrysalline CGO-CoFe2O4 thin films with a thickness of approximately 1 mu m were prepared on CGO porous substrates by a chemical solution spin-coating method. The oxygen permeable flux of the thin film was investigated in temperature range of 700 degrees C - 800 degrees C without physical leak of N-2 gas. The permeable flux depends on the measuring time, when the measuring temperature was kept at 750 degrees C before increasing to 800 degrees C. This fact suggests that the O-2 permeable properties were affected by a slight change of the film morphology and the crystallinity.

The high-pressure synthesis of new hydrides of Mg-RE-H systems, where RE = La, Ce and Pr, were conducted by using a cubic-anvil-type apparatus, and their crystal structure, thermal stabilities and hydrogen contents were investigated. In MgH2-xmol%REH (REH = LaH3, CeH2.5 and PrH3) new hydrides with primitive tetragonal structure were synthesized around x = 25 - 33 under GPa-order high pressures. The lattice constants were a = 0.8193 nm, c = 0.5028 nm, a = 0.8118 nm, c = 0.4979 nm and a = 0.8058 nm, c= 0.4970 nm at x = 25 in Mg-La, Ce and Pr systems, respectively. The hydrogen contents of the novel compounds were 4.1 mass%, 3.7 mass% and 3.9 mass% in Mg-La, Ce and Pr systems, respectively, and the chemical formulas were found to correspond to Mg3LaH9, Mg3CeH8.1 and Mg3PrH9. The new hydrides decomposed into Mg and rare-earth hydride at about 600 K (Mg3LaH9: 614 K, Mg3CeH8.1: 609 K, Mg3PrH9: 630 K) with an endothermic reaction.

We propose the use of porous substrates and thin films of oxygen permeable ceramics as a method for separating oxygen from air. The porosity and pore size of various Ce0.8Gd0.2O1.9 (CGO) porous substrates were modified in an attempt to optimize the oxygen permeable flux of CGO-CoFe2O4 thin films. The oxygen permeable flux density of the CGO-CoFe2O4 thin film coated on the porous CGO substrate was found to be 4.7 mu mol cm(-2) s(-1) under a O-2 partial pressure difference (-log(P-OII/ P-OI)) of 4.5 at 1000 degrees C. This value is about 20 times higher than that of the 1 mm thick bulk material. (C) 2004 The Electrochemical Society.

oxygen permeable ceramics based on mixed conductors are attracting much attention for use in partial oxidation of hydrocarbons as a novel technique for syngas and pure hydrogen production. This paper describes the preparation and oxygen permeation properties including methane reforming property of a novel member of oxygen permeable ceramics. The materials used are solid solutions of (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta. The single phase of perovskite-type (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta is obtained in the range of x = 0.4 to 0.9. The highest oxygen flux densities of 2.2 and 11 mu mol/cm(2) s are attained for (La0.5Ba0.3Sr0.2)(FexIn1-x)O3-delta (x = 0.6) at 1000 degrees C under He / air and CH4 / air gradients, respectively. The electrical conductivity of (La0.5Ba0.3Sr0.2)(FC0.6In0.4)O3-delta is dominated by p-type conduction having a slope of 1/4 under the high P(02) region. The oxide-ion conductivity of the same sample is estimated to be 0.05 S/cm at 800 degrees C. Even though the oxygen flux density slightly decreases with increasing time, high CO selectivity of 90 % is kept for 100 h. The oxygen flux density of the solid solution is also discussed in the context of surface exchange kinetics.

The preparation and oxygen permeability of Pr(0.9)AE(0.1)Al(1-x)M(x)O(3) system, where AE=Ca or Sr; M=Co or Fe, have been studied. For Pr0.9Ca0.1Al1-xFexO3 solid solution having an orthogonal structure, an oxygen flux density of 4.6 x 10(-6) mol cm(-2) s(-1) was attained for x=0.8 in a methane conversion test at 1000 degreesC, by virtue of the enhancement of p-type conductivity by Fe-doping. In addition, Pr0.9Sr0.1Al0.2Fe0.8O3 with a membrane thickness of 160 mum exhibited an oxygen flux density of 8.2 x 10(-6) mol cm(-2) s(-1) at 1000 degreesC with the CH4 conversion and CO selectivity of 12% and 93%, respectively. (C) 2004 Elsevier B.V. All rights reserved.

The oxygen flux density of Ce0.8Gd0.2O1.9-x vol% MnFe2O4 (CGO-xMFO) composite-type ceramics membranes has been investigated. The samples and reforming catalysts were prepared by the Pechini process. For the CGO-xMFO composites, oxygen permeation was observed even at x = 3 vol%, presumably due to the presence of grain boundary phases. For CGO- 15MFO, the n-type electronic conductivity was found to be dominant at 900degreesC or higher. The thickness dependence Of jO(2) revealed that surface exchange kinetics was significantly involved in the case of the membrane thickness of L &lt; 0.5 mm. The highest oxygen flux density of 10 &mu;mol&BULL;cm(-2) &BULL; s(-1) was achieved for CGO- 15MFO with the 10 mass% Ni-Pr:CeO2 catalyst (L = 0.25 mm) at 1000&DEG;C and a flow rate of 270 sccm.

Ti-Cr-V alloys are known to absorb protium (hydrogen atom) up to H/M = 2. However, the Cr-rich alloys, e.g. Ti-Cr-20 at%V alloys containing more than 56 at%Cr. absorb up to H/M = 1 because of the formation of the mono-protides (mono-hydrides). The appearance region of the mono-dueteride was found to be more Cr-rich compositions than that of the in mono-protides. For example, Ti-Cr-20 at%V alloys containing more than 60 at%Cr absorb deuterium up to D/M = 1. Therefore, Ti-56 at%Cr-20 at%V alloy absorbs protium up to H/M = 1 but deuterium up to D/M = 2. As higher protium desorption capacity is achieved by increasing the Cr content in the region of the di-protide, there is some possibility of increasing the protium desorption capacity in Ti-Cr-V alloys using the isotope effects on absorption-desorption properties of the Ti-56at%Cr-20at%V alloy. This paper aims to clarify the isotope effects on protium and deuterium absorption propel-ties in the Ti-56at%Ci-20at%V alloy. It was found that the memory effect for the absorption plateau pressure appears only once when deuterium was absorbed after desorbing protium. and the memory effect for the absorption capacity appears when protium was absorbed after desorbing deuterium. The protium desorption capacity after deuterium treatment, namely, after desorbing deuterium showed twice as high as that without deuterium treatment in the Ti-56 at%Cr-20at%V alloy. Increasing protium desorption capacity for deuterium treatment was caused by increasing di-protide formation and decreasing mono-protide formation.

The present paper describes the grain size refinements of Mg alloys (AZ61, AZ91, ZK60) by HDDR treatment. As a result of the HDDR treatment at 350degreesC under a hydrogen pressure of 7 MPa for 24 h, following by evacuation at 350degreesC for 3 It, the grain size of AZ61 alloys was reduced from 10similar to20 mum to 100similar to200 nm. At the hydrogenation stage for the AZ91 alloys, the disproportionation reaction occurred with forming MgH2, Mg2Al3 and Al phases. At the following desorption stage, the three phases were recombined and the Mg-AI-Zn solid-solution alloy was reformed. After the HDDR treatment, the grain size of AZ91 alloys was reduced to 100similar to200 mn. For the ZK60 alloy without Al, the grain size was reduced from 2similar to20 mum to about 300 nm by the HDDR treatment.

Ti-Cr-V alloys with a BCC structure have high protium (hydrogen atom) capacities. In considering practical use, protium absorption-desorption cyclic properties become an important problem. In this paper, the cyclic properties in high-low hydrogen pressure regions are investigated in order to clarify the change of the crystal structure and the protium capacities of appeared phases of the beta,gamma protides in the Ti-Cr-V alloys and Ti-Cr-Mo, Ti-Cr-Al alloys. As a result, it was found that the crystal structure of the beta protide phase changed from a BCC structure to a BCT structure by increasing the cycle number in the Ti-Cr-Mo, Ti-Cr-Al alloys similar to the Ti-Cr-V alloys. This result suggests that the lattice will be hard to be contracted gradually along the a-axis direction of the absorbing process with an increasing cycle number. It was also found that beta protide phase in the alloys which have bad cyclic properties became stable with an increasing cycle number because the low hydrogen pressure region P-C-isotherm curves shifted to the low pressure side with an increasing cycle number. The major reason of this result is considered to be the accumulation of the lattice defects in the alloys with an increasing cycle number.

We have investigated the protium absorption-desorption properties of Ti-Cr-Mo alloys of varying composition, including cycling-induced effects. The capacity of alloys with less than 10 at% Mo has an H/M ratio of 1.8 at 10 MPa hydrogen pressure, and remains almost unchanged regardless of Mo content. The 40Ti-Cr-2.5Mo alloy has the widest plateau region observed in this study. The amount of protium desorption and the mean particle size vary inversely with the logarithm of cycle number up to 300 cycles. The capacity of the alloy is drastically affected by the conditions of cycling. With longer evacuation times the capacity decreases significantly. The lattice parameter of the P protide increases with increasing cycles, and the reflection peaks in XRD studies are broadened. The reduction in capacity after several absorption-desorption cycles is somewhat restored by annealing at 673 K for 2 h under vacuum. The absorption pressure of the plateau for the 101st cycle, after annealing following the 100th cycle, recovers to that of the plateau for the first cycle, but then decreases with additional cycling. (C) 2002 Elsevier B.V. All rights reserved.

The effects of additional elements to the Ti-Cr alloys on their protium absorption-desorption properties were investigated. Although Ti-Cr alloys with a b.c.c. structure is expected to exhibit a high protium content, it is difficult to obtain single b.c.c. phase quenching from the high temperature. The effects of additional elements such as V, Mo, W, Nb, Ta, Ru, Rh, Re, Os, Ir etc. on stabilizing b.c.c. phase in the alloys were investigated. Then, it was found that the additions of V, Mo, W, Ru, Rh, Re, Os, Ir effectively stabilized b.c.c. phases. But the addition of Nb and Ta preferentially formed Laves phases. Specially, the addition of Mo and Ru is effective to stabilize the b.c.c. phases with high protium content. The Ti-Cr-(1similar to2.5%)Mo alloys show almost same capacity of protium as that reported in Ti-Cr-(5-7.5)V alloys. The addition of Ru to Ti-Cr alloys also shows the capacity of 3.0 mass% protium. These V-ree Ti-Cr alloys will be also suitable for the future applications. (C) 2002 Elsevier B.V. All rights reserved.

The present paper describes the grain size refinement of AZ31 alloys by means of the HDDR process. Hydrogenation was carried out at 250similar to450 degreesC under a hydrogen pressure of 7 Wa for 24similar to36 h. Upon hydrogenation, the disproportionation reaction occurred, leading to the formation of MgH2, Mg-0.42 Al-0.58, and Al phases. In the subsequent desorption process, the three phases were recombined, and the AZ31 alloy was recovered. As a result of the HDDR process, the grain size of the AZ31 alloy powders was reduced from 50similar to300 mum to about 100 nm in the case of the heat treatment at 350 degreesC under a hydrogen pressure of 7 Wa for 24 h. The grain size tended to be increased with increasing process temperatures. In addition, the HDDR process was also applied to AZ31 alloy plates. By means of the HDDR process at 450 degreesC, the grain size was reduced to less than 500 nm, while the layer thickness being treated was limited to the range of about 20 mum from the surface after 36 h at 7 Wa pressure of H, (C) 2003 Elsevier B.V. All rights reserved.

Ti-Cr-V alloys are known to absorb about 3.8 mass% (H/M=2) of protium (hydrogen atom), but to desorb about 2.4 mass%. This paper aims to clarify protium absorption properties and protide formations of Ti-Cr-V alloys. It was found that higher protium desorption capacity was achieved by increasing Cr content and controlling measurement temperature in order to control the desorption plateau pressure near atmospheric pressure for the alloys with less than 40 at% V content. However, Cr-rich alloys were found to absorb up to H/M =1 because of the formation of the mono-protides. The region with higher protium desorption capacity was obtained. The lattice parameters of the alloys and the enthalpy changes for di-protide formation were estimated from the compositions of the alloys. Moreover, estimated enthalpy changes for di-protide fort-nation and the lattice parameters of the alloys were found to be generally constant on the limited line between appearance of regions of mono- and di-protides. (C) 2002 Elsevier B.V. All rights reserved.

High-pressure synthesis of the hydrides in Mg-M(M = Mn, Y) systems and the influence of applied pressures during synthesis on present phases and their crystal structures have been studied. In Mg-Mn system, it was found that the crystal structure of Mg3MnHy changed from hexagonal structure (a = 0.47107(4) nm and c = 1.0297(1) nm) to monoclinic structure (a = 0.8819(8) nm, b = 0.4658(4) nm, c = 0.4678(5) nm and beta = 105.6(1)degrees) in a pressure range of 3-3.5 GPa. This crystal structural change was reversible with respect to pressure. The Mg3MnHy synthesized under 5 GPa was stable up to around 620 K. From thermogravimetric and fusion extraction analyses, the hydrogen content was determined as Mg3MnH5.0-5.6. In Mg-Y system, the high-pressure hydride (MgY2Hy) with yellowish color was synthesized at 1073 K for 2 h under 3 GPa or higher. This phase exhibited an FCC-type structure with a cell parameter of a = 0.516 nm. Its hydrogen content was determined to be about 3.7 mass%, corresponding to a chemical formula of MgY2H7.8. The hydride was partially dehydrogenated at around 600 K, and the amount of hydrogen partially desorbed was 1.4 mass%. The FCC-type structure was stable even after the partial dehydrogenation. (C) 2003 Published by Elsevier Ltd.

The present study, investigates the effect of Mo addition to the TiFe alloys on a stabilization of bee phase and their protium absorption and desorption properties. Ti0.5Fe0.5 alloys with more than 10mol% Mo had CsCl phase and bcc phase, which show single plateaus in the PCT curves and were easily hydrogenated without homogenization. The bcc phase has larger lattice parameter than that of the CsCl phase. TiFe-10mol% Mo annealed alloys with the Ti/Fe ratio of more than 2 had a bee phase as a main phase and CsCl as a minor one. The alloys had 3 mass% of the maximum protium capacity and desorbed protium only I mass%. The phases of the hydrogenated alloy were fcc and orthorhombic structure. which may be caused by di-hydrides of bcc solid solution and mono-hydrides of CsCl phase, respectively. It is found that the Mo addition to TiFe alloys could stabilize bee phase and enhances the hydrogenation reaction of the disordered bcc Ti-Fe-Mo phase similar to Ti-Cr-X bcc alloys.

Ti-Cr-V alloys are known to absorb protium (hydrogen atom) up to H/M = 2, while Cr-rich alloys absorb up to H/M = I because of the, formation of mono-protides (mono-hydrides). However, few hydrogen isotope effects of the Ti-Cr-V alloys have been reported. This paper aims to clarify the hydrogen isotope effects on the absorption properties of the Ti-Cr-V alloys in a composition range near the boundary between the appearance regions of mono- and di-protides. It was found that the appearance region of the mono-dueteride was Cr-richer composition than that of the mono-protides. The absorption plateau pressure for deuterium was lower than that for protium in the appearance region of the di-protide and the di-deuteride, but higher in the appearance region of the mono-protides and the mono-deuteride. The hydrogen isotope effects on the plateau pressure were found to cause the difference in the appearance regions of the protides and the deuterides.

The electrical conductivity and oxygen permeability of transition-metal-doped (Ba0.3Sr0.2La0.5)(2) (In1-xTMx)(2)O5+delta (TM = Fe, Co, Mn and Sn; 0 less than or equal to x less than or equal to 0.5) have been investigated. The X-ray diffraction analysis revealed that all the samples had a cubic perovskite-type structure due to La3+ doping on the alkaline earth site. For Fe-doped specimens, the lattice parameter of 0.414 nm for (Ba0.3Sr0.2La0.5)(2)In2O5+delta linearly decreased with increasing the Fe content, suggesting the incorporation of Fe into the matrix phase. Fe-doping for the In site enhanced the p-type conduction under a wide P(O-2) range, and the p-type conductivity increased with increasing the Fe content without decreasing the ionic conductivity. The oxygen permeability was measured under the P(O-2) difference between helium and air in the temperature range of 800 similar to1000degreesC. For the Fe-doped specimens, the oxygen flux density of j(O-2) increased with increasing the Fe content, and a maximum value of 0.5 mumol.cm(-2).s(-1) was attained at 1000 degreesC for the membrane thickness of 1.0 mm.

Oxygen-ionic and electronic conductive thin films with the composition of La0.6Sr0.4Co0.5Fe0.5O3-alpha (LSCF) were prepared on a porous alumina substrate by a chemical solution deposition (CSD) process and their oxygen permeating flux densities were measured. Thickness of the LSCF layer on the substrate was about 0.4 mum. Oxygen flux density of the LSCF sample was found to be 0.6 mumol.cm(-2).s(-1) , however, time-dependent degradation of oxygen flux was observed. The CeO2 barrier layer between the LSCF layer and the substrate was effective in order to improve time-dependent degradation of oxygen flux.

The preparation and oxygen permeability of composites of Ce0.8Gd0.2O2-delta (GDC) and spinel-type ferrites, MFe2O4 (M = Co and Mn) have been investigated. The composites of GDC x vol% MFe2O4, where x ranged from 5 to 65, were prepared by a citrate-based liquid-mix technique. The composites were found to be almost fully densified by sintering at 1300 degreesC for 2 h. From TEM observations, the grain size of GDC and spinel-type phases was found to be less than 0.5 mum. In the case of M = Co, GDC - 25 vol% CoFe2O4 with a membrane thickness of 1.0 mm exhibited an oxygen flux density of 0.21 mumol.cm(-2).s(-1) under the P(O-2) difference between He (20 sccm) and air at 1000 degreesC. Under reducing atmosphere of Ar-5%H-2, the oxygen flux density of this composite increased up to 1.3 mumol.cm(-2).s(-1). Moreover, under Ar-10%CH4 gas flow, GDC - 15 vol% MnFe2O4 with a membrane thickness of 0.24 mm exhibited the oxygen flux density of 2 and 7 mumol.cm(-2).s(-1) at 800 and 1000 degreesC, respectively.

New high-pressure hydrides in the MgH2-REH3 systems, where RE = Y and La, have been prepared by using a cubic-anvil-type apparatus, and their detailed crystal structure and hydrogen content have been investigated. The high-pressure synthesis was performed at 800 degreesC under 5 GPa for 2 h. In the Mg-Y system, MgY2H7.8 (H/M approximate to 2.6) with an FCC structure (a = 0,51657(2) nm) have been prepared. Based on the hydrogen content and crystallographic consideration, it was suggested that octahedral sites were partially (approximate to 60%) occupied by H atoms in addition to tetrahedral sites. For this hydride, H atoms on the tetrahedral sites seem to play a role to hold the FCC unit cell. For MgH2 - x mol% LaH3, the new high-pressure hydride was obtained in the range of 25 less than or equal to x less than or equal to 33. Mg3LaH9 was found to have a primitive tetragonal unit cell (a = 0.8172 nm, c = 0.5015 nm).

The present paper describes the development of ultra-fine grains on the surface of AZ31 alloys caused by hydrogenation and dehydrogenation treatment, so-called HDDR process. Upon hydrogenation process, disproportionation reaction occurred in forming of MgH2, Mg0.42Al0.58, and Al phases. In the following desorption process, the three phases were re-solved into the AZ31 alloy. As a result of the HDDR phenomena, the grain size of AZ31 alloy powders was reduced down to about 100 nm after the heat treatment at 350 degreesC under a hydrogen pressure of 7 MPa for 24 h. The grain size tended to be increased with increasing process temperatures. In addition, the HDDR process was also applied to AZ31 alloy plates. By the HDDR process at 450 degreesC, the grain size was reduced to less than 500 nm, where hydrogenated layer thickness was limited to be in the range of about 20 gm from the surface. The Vickers hardness of AZ31 alloy plates was increased from 51.9 to 59.4 by HDDR-treatment.

The preparation and oxygen permeability of Pr0.9Ca0.1Al1-xMxO3 system, where M = Co and Fe, have been investigated. For Pr0.9Ca0.1Al1-xFexO3 solid solution with an orthogonal structure, an oxygen flux density of 4.6x10(-6) mol(.)cm(-2.)s(-1) was attained for x = 0.8 under a methane conversion test at 1000 degreesC, as a result of the enhancement of p-type conductivity by Fe-doping. For Pr0.9Ca0.1Al0.2Fe0.8O3, the surface exchange kinetics seemed to be involved in oxygen permeation process when the membrane thickness was less than 0.03 cm.

The electrical conductivity of layered-perovskite-type La2Ti2O7 and Sr-doped La2Ti2O7 has been studied. La2Ti2O7 and (La0.9Sr0.1)(2)Ti2O7 with a layered-perovskite structure were successfully prepared by the Pechini process. The grain size of La2Ti2O7 was found to be 41, 57, and 70 nm for a firing temperature of 700, 1000, and 1300 degreesC, respectively. A single phase of (La0.9Sr0.1)(2)Ti2O7 was also obtained by firing at 1000 degreesC for only 2 h. The electrical conductivity of the layered compounds was measured as a function of partial oxygen pressures and temperatures by a complex impedance technique. La2Ti2O7 fired at 700 degreesC showed an ionic conductivity of 3.4 x 10(-6) S/cm at 700 degreesC, due to the Frenkel defects incorporated by low-temperature synthesis. As a result of the grain size refinement, the enhancement of electronic conductivity was also observed for La2Ti2O7. The ionic conductivity of (La0.9Sr0.1)(2)Ti2O7 was less than that of La2Ti2O7. (C) 2002 Elsevier Science B.V. All rights reserved.

Ti-Cr-V alloys have a higher protium (hydrogen atom) desorption capacity, but a larger hysteresis in the absorption and desorption processes than AB(2) and AB(5) type protium absorption alloys. It is desirable that the alloys have a smaller hysteresis for the use of hydrogen storage tanks. This paper aims to clarify the effects of protide (hydride) structures on the hysteresis in Ti-Cr-V protium absorption alloys. It was found that the beta phases observed after desorbing at the desorption plateau region had the BCC structure for the alloys (Ti:Cr = 2:3) containing less than 70 at%V, but the BCT structure for the alloys (Ti:Cr = 2:3) containing more than 70 at%V. A major reason for the large hysteresis in the Ti-Cr-V alloys appears to be the a-axial contraction in the absorbing process and the a-axial expansion in the desorbing process as opposed to the c-axial changes.

A new hydride in the MgH2-YH3 system was found by using a high pressure of 5 GPa, and their crystal structure, thermal stability and hydrogen content were studied. The high-pressure synthesis was carried out at 1073 K for 2 h under 5 GPa by using an anvil-type apparatus. In the MgH2-xat%YH3 system (x = 33-100), novel hydride was synthesized near x = 67 (MgY2Hy). This phase exhibited a FCC-type structure with a cell parameter of a = 0.516 nm. This high-pressure phase was dehydrogenated at about 600 K under an At atmosphere of 0.05 MPa, and the FCC structure was maintained after dehydrogenation. The amount of hydrogen desorbed at about 600 K was 1.4 mass%.

Ti-Cr-V alloys with a BCC structure have high protium capacities, but it is known that the cyclic properties for the alloys change with varying V content. In this paper, the cyclic properties of the Ti-Cr-V alloys are investigated in view of the crystal structure of the beta protide phase. which was measured at the point after desorbing at the plateau region and the thermal stability of the gamma protide phase, which was Measured at the point immediately before desorbing at the desorption region. It was found that the crystal structure of the beta phase was changed from BCC phase to BCT phase and the c/a increased with increasing the cycle number. This difference of the crystal structure of the phase suggests that the lattice can't gradually contract to a-axis direction at absorbing process with increasing the cycle number. Furthermore, it was found that the absorption-desorption cycle process causes the declined slope of the DeltaH plots due to existence of the different gamma protides of different thermal stabilities. Namely, this result suggests that site energies of protium in the lattice have a distribution after absorption-desorption cycles.

Many intermetallics such as AB, AB, A,B show the excellent hydrogen absorbing properties. Specially, LaNi5 compound has been extensively studied for the negative electrode of Ni-MH batteries. In today's use for the negative electrode of Ni-MH batteries, alloys must be single phase. But it is well known that it is difficult to make non-stoichiometric LaNi5 alloys as single phase because of its limited solid-solution range. The present study describes the rapid quenching effects on the solid-solution range of La(Ni, M)(x) (x = 3-5) alloys prepared by melt spinning in discussing their hydrogen absorption properties. It is found that the single phase with CaCu5 crystal structure extends to LaNi4.65 compositional alloys. For fuel cell automobile, the alloys with high content of hydrogen must be developed. Strong candidates for this will be Vanadium based BCC alloys, which would be hard to be activated. Since it is well known that the Laves phases undergo easy activation treatment, it may be possible that the BCC phases will be easily activated if the alloys contain such Laves phases. The present study also found that Zr addition is effective on forming Laves phase as grain boundary phases in BCC phases in V-Ti-Zr-Ni alloys, and on improving the hydrogen absorbing properties. The study will be also extended to future hydrogen absorbing alloys with high capacity. (C) 2002 Elsevier Science B.V. All rights reserved.

The effects of At addition on structures and protium absorption-desorption properties of Ti-Cr alloys were investigated. It was found that 1 at% Atl addition is effective for improvement of protium storage capacity. The BCC phase increases with increasing Al content in TiCr-Al alloys. It is generally well known that plateau pressure of the protium storage alloys, e.g. Ti-Cr-V and Ti-Fe-V alloys, increases with decreasing lattice constants, however, the plateau pressure of the Ti-Cr-Al alloys increases with increasing lattice constants, namely increasing Al content.

The cyclic properties of protium storage in Ti-Cr-V alloys with a BCC structure were investigated in order to develop the alloys with good cyclic properties. It was found that the hysteresis factor of pure V was almost unchanged but the hysteresis factor of Ti-Cr-V heat-treated alloys decreased with increasing cycle number. The plateau pressure of Ti-Cr-V heat-treated alloy in absorbing process dropped significantly with increasing cycle number up to the 20th cycle. In contrast to this, there was not any change in PCT curves of pure V metal. This could be originated from the difference in mechanical properties between V metal and Ti-Cr-V alloys.

The present study aims to investigate the effects of addition of Mn to Ti-Cr-V alloys on their protium absorption properties and to find the design criteria for increasing effective protium capacity. The effects of V and Mn content of the alloys on the protium absorption properties of heat-treated Ti-Cr-V-Mn alloys in low pressure regions were studied at various temperatures, and it was found that increasing Mn content and decreasing, V content unstabilize protoride in low pressure region. The PCT curves from low pressure plateau region (10(-1)-10(5)Pa) to high pressure plateau region (10(5)-10(7) Pa) shifted to the side of low protium concentration. It was found that the addition of Mn or decreasing V content in the alloys is effective for increasing effective protium capacity.

Vapor grown carbon nano-fibers (VGCFs) were synthesized by using Fe ingots, Fe powders, nanocrystalline Fe91Zr7B2 and Fe75Si15B10 alloy catalysts with fine bcc-Fe grains (similar to20 nm). The Fe particles worked as catalysts were formed by fracturing original Fe ingots, Fe powders, and nanocrystalline alloys before the formation of VGCFs. TEM and HREM observations indicated that VGCFs' structures turned out to be platelet type grown from Fe powders and Fe91Zr7B2, and the tubular type grown from nanocrystalline Fe75Si15B10 alloy. In addition to these structures, VGCFs grown from Fe ingots exhibited herringbone and coil type structures. Diameter of VGCFs prepared from nanocrystalline Fe75Si15B10 alloy was smaller than that of grown from Fe91Zr7B2 alloy. This could be originated from the difference of fracturing process between nanocrystalline Fe91Zr7B2 and Fe75Si15B10 alloys. Protium absorbing properties of VGCFs were evaluated by a Siverts-type apparatus and electrochemical method. It turned out that VGCFs had little protium absorbing capacity.

This paper aims to develop the vanadium free Ti-Cr-X BCC solid solution alloys with high protium content. The effects of additional elements such as Mo, W, Nb and Ta to the phase formation on the Ti-Cr alloys were studied. It was found that Mo-added heat-treated alloys had the flattened plateau regions with the capacity of more than 2.2 mass% protium with maximum of 3.6 mass% protium content. which is equal to that of Ti-Cr-V alloys, It was found that the Ti-Cr-Mo alloys A with BCC structure transformed to protide phase with BCC or FCC structure, The plateau pressure of the Ti-Cr-Mo alloys increased with increasing Mo content. but the lattice parameters decreased. The HIM ratio of the alloy with less than 10 at%Mo was 1.8 at 10 MPa hydrogen pressure and was almost unchanged with Mo content.

Ti-Cr-V alloys are known to absorb protium up to H/M = 2. However, Ti-Cr-20 at%V alloys with more than 56 at%Cr content were found to absorb up to HIM = 1. This paper aims to make clear the effects of compositions on formations of 1. 2 protorides in Ti-Cr-V alloys, and the structure of the mono-protorides. It was found that the mono-protorides with fcc and hcp structures exist. The mono-protoride with the fcc structure was different from the di-protoride with the FCC structure in the lattice constants. Some relationship between appearance of the mono-protorides and disappearance of the plateau regions in low hydrogen pressure regions was considered to exist. As a result, the appearance regions of 1, 2 protorides in Ti-Cr-V alloys were derived.

The protium absorption-desorption properties of Ti-V-Cr-Mn alloys were studied by varying the contents of Mn, Ti and V in the alloys. It was found that Mn addition of &lt;10 at% was effective in improving the slope of the plateau region without any reduction of the protium absorption-desorption capacity. For Ti-V-Cr-Mn alloys, the alpha-Ti phase, which does not contribute to the protium storage capacity, appeared along grain boundaries during heat treatment. The formation of the alpha-Ti phase was found to be suppressed by reducing the Ti content and increasing the V content. By inhibiting the appearance of the alpha-Ti phase along the grain boundary, the protium absorption-desorption capacity of Ti-xV-Cr-Mn (x=45, 55; Ti/Cr/Mn=24:31:10) heat-treated alloys exhibited 2.7 mass% H, the highest value reported so far. (C) 2002 Elsevier Science B.V. All rights reserved.

The effects of composition and heat-treatment on the protium absorption-desorption properties of Ti-V-Cr alloys were investigated. It was found that the Ti-35V-40Cr alloy shows a 2.6 mass% protium capacity. The plateau pressure of the Ti-35V-xCr alloys increased with decreasing lattice constants associated with increasing Cr content. The main phase of the as-cast Ti-xV-Cr (Cr/Ti=40/25) alloys containing more than 15%V was a b.c.c. phase. These b.c.c. alloys exhibited a 2.4 mass% protium capacity. Heat-treatment over 1673 K was effective on stabilizing the b.c.c. structure for the Ti-xV-Cr (Cr/Ti=2/3) alloys with low V content. The Ti-5V-57.5Cr alloy heat-treated at 1673 K for I h yields a high capacity of 2.8 mass% protium, which is the highest value at 313 K reported so far. The alloy is economically promising since it contains low amounts of expensive V metal. (C) 2002 Elsevier Science BY All rights reserved.

The crystal structure of novel hydrides in the Mg-Ni-H system has been studied using a powder X-ray diffraction and transmission electron microscopy. A cubic-anvil-type apparatus was utilized to prepare samples. The new hydride with a chemical composition of around MgH2-60 at% Ni was synthesized at 1073 K for 2 h under a pressure as high as 5 GPa. From TGA analysis, the new hydride was found to be Mg2Ni3H3.4. Orthorhombic and monoclinic crystal systems with a primitive cell were proposed as possible symmetries of the new hydride. X-ray and electron diffraction patterns of the new hydride were indexed in an orthorhombic structure with a=0.8859(4), b=1.3740(5), c=0.4694(2) nm. Moreover, decomposition of the hydride into Mg2Ni was observed by the transmission electron microscopy. (C) 2002 Elsevier Science B.V. All rights reserved.

The electrical conductivity of Bi3Zn2Sb3O14 pyrochlore was studied as a function of temperature and partial pressure of oxygen. Conductivity measurements by ac complex impedance analysis and ionic transference number measurements show this pyrochlore to be a mixed ionic-electronic conductor with an energy band gap of 3.15 +/- 0.9 eV. A defect model in which Frenkel defects on the oxygen lattice are dominant is confirmed. Enthalpies of reduction, oxidation and the sum of oxygen vacancy formation and migration were found to be 4.82 +/- 0.8 eV, 1.48 +/- 1.0 eV and 1.67 +/- 1.0 eV respectively.

Phases and thermal stability of new hydrides synthesized by using under a high pressure of 5 GPa in Ca-Mg-Ni-H systems were studied The high-pressure synthesis was carried out at 1073 K-1223 K for 2 h under 5 GPa by using an anvil-type apparatus. A series of (Ca1-xMgx)(2)NiHdelta was found to form solid solution in the range of x = 0-0.4. This hydride decomposed around 646 K regardless of Mg content. In CaH2-X%MgH2 systems, hydrides with BCC structure were obtained in the range of X = 50-67. Lattice constant of the BCC phase decreased from 0.4032(9) nm (X = 50) to 0.3988(3) mn (X = 67) with increasing Mg content. The decomposed temperature of the BCC phase increased from 650 K (X = 50) to 673 K (X = 67) with increasing Mg content, in other words, with decreasing the lattice constant of BCC phase.

Ti-Cr-V alloys are known to absorb about 3.8 mass% of protium, but to desorb about 2 mass% because of the formation of stable protorides in low hydrogen pressure regions. However, few protium storage properties of the alloys in low hydrogen pressure regions were reported. This paper aims to clarify the protium absorption properties of Ti-Cr-V alloys in low hydrogen pressure regions. It was found that first low pressure plateau regions were coexistence regions of two different BCC phases for 20 at% V alloys. Decreasing V content and increasing Cr content turned out to shift the beginning of the second high pressure plateau regions to low protium concentration in unstabilizing the protorides in the first plateau regions. As a result, the Ti-52 at%Cr-20 at%V alloy was designed and found to have about 2.4 mass% protium desorption capacity in the width of the second plateau region at 273 K.

The high-pressure synthesis of new hydrides of the Ca-Mg-Ni system and crystal structural and thermal analyses have been conducted. The high-pressure synthesis was carried out at 1073 K for 2 h at 5 GPa using a cubic-anvil-type apparatus. An additional hydrogen source was used to stabilize the hydride phases. A series of (Ca1-xMgx)(2)NiHdelta was found to form solid solutions in the range of x = 0-0.4. The crystal structure of the (Ca1-xMgx)(2)NiHdelta solid solutions was of the CsCl-type. The lattice constant of the CsCl-type phase decreased from 0.35542(2) nm (x = 0) to 0.35478(2) nm (x = 0.4) with increasing Mg content. For the samples with a Ni-rich composition, in addition to the CsCl-type phase, a Mg2Ni3H3.4 phase was also present at high pressures. The CsCl-type phases were thermally stable at less than 646 +/- 2 K, regardless of Mg content.

synthesis of vapor-grown carbon fibers (VGCFs) using the nanocrystalline Fe75Si15B10 alloy as a novel catalyst has been investigated. and the growth process of VGCFs was discussed. The nanocrystalline Fe75Si15B10 alloy with fine bcc-Fe grains less than about 20 nm was prepared by the melt spinning technique followed by annealing. VGCFs with a diameter of less than about 40 nm were successfully prepared using the nanocrystalline Fe75Si15B10 catalyst at 773 K under 80%CO-20%H-2 atmosphere. High-resolution transmission electron microscopic characterization indicated that the VGCFs catalytically generated over the Fe75Si15B10 nanocrystal surfaces at both 773 K and 873 K most likely have a tubular-type structure, in which the graphite sheets were stacked parallel to the fiber axis. The Fe75Si15B10 catalyst particles appear to be made of the single-phase Fe3C grains, which is in contrast to the Fe91Zr7B2 catalyst particles previously studied by us. The formation of Fe3C leads to the brittleness of catalyst particles and results in a growth of filamentous carbon.

New hydrides of Ca-TM-H systems (TM = Mn, Fe, Co and Ni) have been explored by using a high-pressure technique. The high-pressure of up to 5 Gpa was yielded by cubic-anvil-type apparatus. All the samples of Ca-TM-H systems (TM = Mn, Fe and Co) prepared at 1073 K under 5 GPa were found to be mixtures of the raw materials. However, for the Ca-Ni-H system. a new hydride with a chemical composition of CaH2-33 at%Ni was prepared at 1223 K under 5 GPa. The color of the hydride was reddish brown. As an additional hydrogen source was used during the synthesis, the color changed into black. The new hydride prepared with additional hydrogen was found to have the CsCl-type structure. The lattice parameter was a = 0.35542(2) nm.

This paper aims to study the relationship between the protium absorption properties and alloy composition of Ti-V-Cr alloys. We studied the effects of composition of the alloys and the heat-treatment on the protium absorption-desorption properties of Ti-V-Cr alloys, and found that Ti-35V-40Cr alloys show 2.6 mass% protium capacity. The plateau pressure of the alloys increased with decreasing lattice constants, resulting from increasing Cr content. The main phase of the samples containing more than 15%V was a BCC phase in the cast state. These BCC phase alloys exhibited 2.4, mass% protium. It was also found that the heat-treatment was effective in stabilizing a BCC structure in Ti-V-Cr alloys with low V content. The alloy yields the high capacity of 3.0 mass% protium capacity, which will be the highest value at 313 K reported so far. The alloy will be promising since it contains a low amount of the expensive V element.

Nb-doped barium titanate (BaTiO3) thin films have been prepared by pulsed laser deposition. Nd:YAG laser with a wavelength of 266 nm was used to ablate sintered BaTiO3 targets, and films were deposited on pure Pt substrates at 600 or 700degreesC. The amount of the addition of niobium to BaTiO3 affected the electrical properties of the thin films. The samples showed high dielectric constant, and polarization hysteresis. Films deposited on pure Pt substrates heated at 700degreesC exhibited (001) oriented structures and high remanent polarization (similar to8 mu C/cm(2)). Annealing in air was found to be effective to increase electrical resistivity of these films.

La2Ti2O7 and Ca-doped La2Ti2O7 were prepared by citrate process. In the La2Ti2O7, it was confirmed that citrate process gave the good compositional homogeneity and fine particle size of 40-70mn. La2Ti2O7 synthesized at low temperature of 700degreesC exhibited higher ionic conductivity by an order of magnitude than one synthesized at high temperature of 1300degreesC. This increase in ionic conductivity seems to be due to the incorporation of structural disorder. And each conductivity isotherm showed a different behavior due to the different type of defects. Frenkel defects were considered to be incorporated into one fired at 700degreesC while titanium interstitial could be formed in one fired at 1300degreesC. Ca-doped La2Ti2O7 showed a lower electrical conductivity than that of La2Ti2O7. This decrease in ionic conductivity might be attributed to the defect association.

A new pyrochlore solid solution family, Gd2GaSbO7-Gd2Zr2O7 (Gd-2(GaSb)(1-x)Zr2xO7; GGSZ) exhibiting oxygen ion conduction due to structural disorder, has been investigated. In this study, the ionic conductivity and structural disorder of GGSZ were analyzed by fitting the electrical conductivity as functions of PO2 and temperature to a defect chemical model based on oxygen Frenkel disorder. GGSZ with x = 0.8 exhibited an ionic conductivity of 2.14 x 10(-3) S/cm at 1000 degreesC, and an activation energy of 0.51+/-0.003 eV. The Frenkel disorder enthalpy was found to decrease rapidly with increasing x, dropping to approximate to0 eV at x = 0.8. The oxygen vacancy mobility was found to increase with x which, together with the increase in carrier density, led to a very sharp increase in ionic conductivity at higher values of x. The GGSZ system is compared with the Gd2Ti2O7-Gd2Zr2O7 and Gd2Sn2O7-Gd2Zr2O7 systems also known to exhibit a structural disorder Correlated ionic conductivity. (C) 2000 Elsevier Science B.V. All rights reserved.

The protium absorption properties of Mg-AI-Cu, Mg-Al-Ni, and Mg-Al-Si alloys have been investigated in conjunction with microstructures and the phases present. The alloys were prepared by a flux-melting technique. Mg-Al-Cu as-cast alloys were found to consist of Mg, MgAlCu, and Mg17Al12 phases. In addition to the Mg phase, the Mg17Al12 phase also contributed to the protium absorption by undergoing a disproportionation reaction. The protium absorption capacity of these Mg-AI-Cu alloys ranged from 2.2 to 4.6 mass% at 623 K, and was found to be controlled by the amount of Mg and Mg17Al12 phases present. For the Mg-25Al-5Ni and Mg-25Al-5Si as-cast alloys, Me and Mg17Al12 phases were found to be present. In addition. a Mg2Si phase was observed in the Mg-25Al-5Si alloy. The protium absorption capacities of the Mg-25Al-5Ni and Mg-25Al-5Si alloys were 3.6 and 3.9 mass%: respectively. Unlike the Mg-Al-Cu alloys, the Mg17Al12 phase in Mg-Al-Ni and Mg-Al-Si alloys partially remained even after protium absorption. This difference in disproportionation behavior seems to be due to the small amount of solute elements in the Mg17Al12 phase, and/or to the microstructure.

The synthesis of vapor-grown carbon fibers (VGCFs) using the nanocrystalline Fe91Zr7B2 alloy as a novel catalyst, and the growth process of these VGCFs, have been investigated. We selected the nanocrystalline Fe91Zr7B2 alloy as a novel catalyst for VGCF synthesis. The nanocrystalline Fe91Zr7B2 alloy with fine bcc-Fe grains (similar to 20nm) was prepared by a melt-spinning technique followed by annealing at 873 K for 5 min. VGCFS with a width ranging from 50 to 300 nm and a maximum length of about 6 mu m were successfully prepared, by using a nanocrystalline Fe91Zr7B2 alloy annealed at 873 K under a 80%CO-20%H-2 mixture. From HREM observation, it was found that the catalyst particle was made of fine bcc-Fe grains, and the VGCF consisted of graphite platelets with the spacing 0.396 nm, that were stacked in a direction parallel to the base of the catalyst particle and perpendicular to the fiber axis. The growth process of the VGCF using the nanocrystalline Fe91Zr7B2 alloy can be described by two major stages, i.e., "the separation of catalyst particles" and "fiber growth."

The protium absorption-desorption properties of Ti-V-Cr-(Mn, Ni) alloys were investigated in conjunction with Mn, Ni and V contents and heat-treatment conditions. The compositions studied were (1) Ti-35V-(37-x)Cr-xM (M=Mn and Ni; 0 less than or equal to x less than or equal to 15), and (2) Ti-xV-Cr-M (M=Mn and Ni; 15 less than or equal to x less than or equal to 45) in which the content of Ti, Cr, and M was fixed at a ratio of 28 : 32 : 5. The addition of Ni reduced the protium storage capacity and increased the plateau pressure due to the formation of a Ti2Ni secondary phase, and to the incorporation of Mn into the BCC matrix phase. Increasing the V content was found to be an effective way of stabilizing the BCC phase, and thereby increasing the protium storage capacity. For Ti-V-Cr-Ni alloys, the slope of the plateau region was also improved by increasing the V content. In addition, the Mn-added alloy after annealing at 1573 K exhibited an almost uniform BCC solid solution and a storage capacity as high as 2.6 mass%; however, the Ni-added alloy still contained the Ti2Ni phase. The addition of Mn was found to be an effective way of decreasing the slope of the plateau region.

The preparation of Nb-doped PbZrO3 thin films by pulsed laser deposition and the effects of the Nb-doping on the dielectric properties of PbZrO3 thin films have been investigated. By optimizing film deposition conditions and annealing temperatures, the 3 mol% Nb-doped PbZrO3 thin films was successfully prepared under the partial oxygen pressure of 2 or 5 Pa followed by the rapid thermal annealing at 873 K for 1 min. From X-ray diffractometry, the PbZrO3 phase was found to be crystallized without any preferred orientation. The 3 mol% Nb-doped PbZrO3 film exhibited a double hysteresis loop with a transition field (antiferroelecric to ferroelectric phase) of 208 x 10(5) V/m and saturation polarization of 20 x 10(-2) C/m(2). It was found that the Nb-doping might contribute to reduce the transition field and polarization of PbZrO3 thin films. In addition, the Nb-doped PbZrO3 film with a thickness of 185 nm showed a ferroelectric hysteresis loop with the parameters of Ps = 22 x 10(-2) C/m(2), Pr = 17 x 10(-2) C/m(2), and Ec = 320 x 10(5) V/m.

Phases present and thermal stability of synthesized hydrides of Mg - TM - H systems (TM Co and Ni) by preparing under a high pressure of 5 Cpa using an anvil-type apparatus were studied. The MgNi2 phase with a novel crystal structure was formed at 1073 K under 5 Cpa. In addition, for MgH2 - Ni system, two novel phases with a new composition of Mg - 64 at% Ni, and Mg - 55 at% Ni were formed. Using an additional hydrogen source to supply enough hydrogen, the volume fraction of the new phase with a composition of Mg - 55 at%Ni increased, and the other phase vanished. This MgNi-H compound was thermally stable up to 498K under an Ar atmosphere of 0.5 MPa.

The protium absorbing properties of Mg-Y-Ni, Mg-Y-Cu, and Mg-Al-Cu ternary alloys have been investigated in conjunction with phases present and microstructures. The alloys with a Mg-rich composition (approximate to 80 at%Mg) were prepared by a flux-melting technique. It was found that the Mg-10Y-10Ni alloy with Mg, Mg-24 Y-5, Mg2Ni, and MgNi2 (C15-type Laves structure) phases formed hydrides of Mg,Ni and Mg at 373 and 473 K, respectively. The decrease in the reaction temperature can be attributed to a morphological improvement, where Mg and Mg-24 Y-5 main phases with a needle-like shape surrounded by the Mg2Ni and MgNi2 phases, and/or the effect of Y incorporated into these phases. The Mg-10Y-10Ni alloy absorbed 4.0 and 4.5 mass% of protium at 473 and 573 K, respectively. For the Mg-10Y-10Cu alloy, a two-step plateau regime was observed due to the disproportionation of the Mg2Cu phase. The Mg-6Y-24Cu alloys exhibited a protium storage capacity of 3.4 mass%, and its plateau pressure for the desorption process was about 0.08 MPa at 523 K. The Mg-10Al-10Cu alloy absorbed 4.5 mass% of protium. However, a temperature as high as 573 K was needed for observing the protium absorption - desorption process.

The effect of microstructure on the diffusion of protium (hydrogen) in La-Ni alloys was studied by the desorption method. Five alloys were prepared; one was the well known protium absorbing alloy LaNi5 with the stoichiometric composition, and the others were the two phase alloys LaNix (x=5.5-8.1) consisting of the LaNi5 phase and the Ni phase. By the analysis of the desorption curves for the temperature range 353-573 K, the diffusion coefficient of protium in the alloys was determined under the assumption that the sample particles were spheres. The Arrhenius plots of the diffusion coefficients, D, for all the alloys show linear relationships. The value of D in LaNix (x=6.0, 6.5, 8.1) increases with increasing the value of x, and they are larger than that in LaNi5, although the value of D in LaNi5.5 is the smallest in the temperature range examined. The literature value of D in LaNi5 obtained by the quasielastic neutron scattering (QNS) method is in the middle of the coefficients of the five alloys. This suggests that the effective surface area of the LaNi5 specimen for the desorption is reduced by the formation of oxide layer and that in the two phase alloys the protium diffusion is enhanced via a net work of the Ni phase deformed by the expansion of the LaNi5 phase due to the absorption of protium, although the Ni phase in LaNi5.5 is insufficient to form the network. (C) 1999 Elsevier Science S.A. All rights reserved.

The present study describes the rapid quenching effects on the solid-solution range of La(Ni, M)(x) (x=3-4.7) (M=Al, Co, Mn, Si) alloys prepared by melt-spinning and discusses their protium (hydrogen atom) absorption properties. It is found that the single phase with CaCu5 crystal structure extends to LaNi4.65 compositional alloys. When x in LaNi5-x becomes smaller, the alloy acquires better protium absorption properties including easier activation, better flatness of plateau region and a good hydrogen storage capacity comparable to those of LaNi5 homogenized sample. On adopting a melt-spinning technique it is easy to form single phase of CaCu5 type-structure for La-rich non-stoichiometric La-Ni-M alloys such as La(Ni, M)(x) (x=3-4.7) (M=Al, Mn, Si) alloys. The readiness of forming a single phase CaCu5 type-structure in melt-spun La-Ni-M alloys is in order of Al greater than or equal to Si&gt;Mn&gt;Co. The phases formed and protium absorption properties of La-rich LaNi4.5M0.2 melt-spun alloys are studied. It was found that LaNi4.5M0.2 alloys had better protium absorption properties such as easier activation than the LaNi4.65 binary alloy and as good hydrogen storage capacity as that of homogenized LaNi3. (C) 1999 Elsevier Science S.A. All rights reserved.

The hydrogen absorption properties of V-Zr-Ti-M(M=Fe, Mn, Ni) alloys were examined in order to develop the alloys with high hydrogen capacity. It was found that the best composition among the studied alloys is the V-Zr-Ti-Ni system. A suitable amount of the vanadium in the V-Zr-Ti-Ni system was studied in correlation with its hydrogen, absorption properties, and turned out to be around 75 at.%V. Substitution with Zr improved the hydrogen absorption properties in forming the grain boundary network phases of C14 Laves phase. Heat treating the alloys (homogenize and quench) drastically improves the plateau region of PCT curves. Zr addition also improves the properties for V-Zr-Ti-Cr alloys. (C) 1999 Elsevier Science S.A. All rights reserved.

ZnO-Pr<SUB>6</SUB>O<SUB>11</SUB> varistors exhibit non-ohmic current-voltage characteristics due to the double Schottky barrier formed at the interface between ZnO grains and intergranular phases of Pr<SUB>6</SUB>O<SUB>11</SUB>. In this paper, the I-V characteristic of ZnO/Pr<SUB>6</SUB>O<SUB>11</SUB> multilayerd films with different thickness fabricated by pulsed laser ablation method are studied. In spite of decreasing the film thickness, the films with 5000-500&Aring; thickness exhibit nonlinear I-V characteristic. The values of breakdown voltage (V<SUB>b</SUB>) and non-linear coefficient (a) are estimated as V<SUB>b</SUB>=0.19-0.30V, &alpha;=2.5-4.1. Therefore, thin ZnO/Pr<SUB>6</SUB>O<SUB>11</SUB> multilayered films prepared by PLD method show lower breakdown voltage.

It is reported that the Bi metal/ceramics composites can show PTCR properties at the melting point of Bi metal of about 270&deg;C. This materials have a few advantages such as low resistivity and high PTCR properties, but there is the problem that the resistivity doesn't coincide with the original value after the cycle measurement. This will be originated from Bi metal rearrangement during melting. Further densifications of ceramic matrix phase will overcome this problem. The purpose of the present study is to prepare high-density sample by hot-pressing, and to clarify the relationship between resistivity-temperature characteristics and microstuructures in obtaining the optimum conditions of hot-pressing.<BR>The relative density of hot-pressed 0.55Bi-0.45SrBi<SUB>4</SUB>(Ti<SUB>0.95</SUB>Nb<SUB>0.05</SUB>)<SUB>4</SUB>O<SUB>15</SUB> with using fine Bi metal reached more than 99% and its resistivity of nearly 10<SUP>-1</SUP>&Omega;m at room temperature remains unchanged after cycle measurement. In addition, the magnitudes of PTCR effect reaches 7 order of magnitude, and resistivity-temperature curve also remains unchanged even after 3rd measurements.

Bismuth metal dispersed in insulating or semiconducting matrix shows PTCR properties at the melting point of bismuth metal of about 270 degrees C. In this study, the optimum sintering conditions of bismuth metal/strontium-bismuthtitanate ceramics composites were investigated and quantitative analysis of the resistivity of the composites was performed by General Effective Media (GEM) equation. A sample of 0.73Bi-0.27SrBi(4)(Ti0.95Nb0.05)(4)O-15 sintered at 1398 K for 2 h in Ar atmosphere shows PTCR property of about 5 orders of magnitudes and good cycle property. A relation between the resistivity of composite and the volume fraction of Bi metal particles in a series of xBi-(1-x) SrBi4(Ti0.95Nb0.05)(4)O-15 was explained by percolation theory. But calculated PTCR properties from the shrinkage of Bi metal of 3.35% at the melting point are less than one order of magnitude, and therefore, the PTCR properties in this study can not be explained simply by decrease of the volume fraction of Bi metal because of the shrinkage at the melting point.

Vanadium or V-based solid solution type alloys with a BCC crystal structure are known to absorb the high capacity of protium but not to desorb completely. This paper tried to find new compositional V-based high density protium storage alloys, with the starting composition of V2.5M1 (M=Al, Co, Fe, Mn, Ni, Ti, Zr). It was found that the best composition among studied alloys is V-3.5 (Zr1/3Ti1/3Ni1/3) where the alloys consist of the BCC phase with the C14 type Lavas phase along the grain boundary. The V-3.5(Zr1/3Ti1/3Ni1/3) heat-treated alloys have about 2.0 mass% protium storage capacity of the 3rd cycle and have the Bat plateau region in the PCT curves. The V70Zr1Ti12Cr17 alloys show higher protium capacity of nearly 2.5 mass% protium as well as flat plateau region. In the present investigations, it was found that the Zr substitution was very effective for easier activation, better plateau region and higher protium capacity, by forming the C14 Laves phase as minor phases in the BCC major matrix phase for various V-based alloys such as V-Ti-Ni (Cr) alloys.

When hydrogen storage alloy is used as a negative electrode of nickel-metal hydride batteries, protium absorbing properties at a negative electrode is different from those at a gas phase because of the formation of oxide layers and a nickel-rich layer on the surface of the alloy due to charge and discharge. This paper investigates the effect of surface chemical etching on protium absorbing properties and electrochemical characteristics of LaNi<SUB>5</SUB> alloys. Dilute HCI solution under 1% was used as etchants for the formation of a nickel-rich layer which works as a protection surface of the alloy against the KOH electrolyte. Protium absorbing properties of annealed LaNi<SUB>5</SUB> samples which were etched shortly with 0.2N HCl or 0.02N HCl were better protium storage capacity than those of unetched annealed LaNi<SUB>5</SUB> samples. Electrochemical characteristics of annealed LaNi<SUB>5</SUB> samples which were etched for 60min with 0.02N HCl were better cycle stability than those of unetched annealed LaNi<SUB>5</SUB> samples.

It has been interesting that high performance SrFe₂-W type ferrite can be produced using a carbon powder as a reducing agent. This paper describes the possibility of adopting new reducing agent such as silicon powder and colloidal carbon. These additions broaden the formativre condition of the SrFe₂-W phase and improve the magnetic properties. Especially, the addition of colloidal carbon yields high volume fraction of the SrFe₂-W phase in comparison with the addition of carbon and silicon powder.

The synthesis and electrical conductivity of a novel solid solution pyrochlore Gd2GaSbO7-Gd2Zr2O7 were studied as a function of x in Gd-2(GaSb)(1-x)Zr2xO7 (0 less than or equal to x less than or equal to 1). In this study, single phases with the pyrochlore structure were obtained in the range of x less than or equal to 0.2, while a garnet phase appeared as a minor second phase for x greater than or equal to 0.3. In the x = 0.2 sample, evidence of the displacement of 48f oxygens towards the normally empty 8b site was suggested by Rietveld analysis. The total electrical conductivity of the pyrochlores was 2.6x10(-2) S/m for x = 0.0 and 6.0x10(-3) S/m for x = 0.2 at 1273 K, respectively. In addition, evidence for n-type semiconductivity was obtained for x = 0.2 under reducing conditions. Further studies are underway to identify the dominant carriers under oxidizing conditions.

The crystal structure and electric and magnetic properties of newly synthesized spinel manganites were investigated. CuNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> had cubic spinel structure, and magnetoresistance effect like CMR in perovskite manganites was observed in this system for the first time. Judging from the calculation of effective-valency according to the result of Rietveld analysis, it was estimated that both of Mn<SUB>3+</SUB> and Mn<SUB>4+</SUB> are in octahedral site. This fact may be related with the reason why magnetoresistance effect appealed in this system.

The protium-absorbing characteristics such as the amount of absorbing protium and the hydrogen reaction have been studied for the LaTMSi, LaTMSi, and LaTM2Si2 (TM = Co, Mi) ternary intermetallic compounds. For these compounds, it is found from DSC measurements that only the LaCoSi and LaNiSi compounds show hydride reactions at elevated temperatures. The LaCoSi alloy has a disproportionation reaction at 457 K, whereas the LaNiSi alloy reversibly absorbs and desorbs protium near 425 K. The maximum absorbed amount of protium is 0.52 mass% for the LaNiSi alloy.

The magnetic properties of Sm-Co-Cu films and Sm-Co-Cu/Co multilayered films prepared by rf-sputtering were investigated. The addition of Cu to Sm-Co film had the effect of decrement of crystallization temperature. The Sm28Co59Cu13 film annealed for 1 h at 623 K showed a reversible demagnetization curve with 82% springback ratio of [Mr'-M(H)]/[Mr-M(H)] and a high coercivity of 2480 kA.m(-1). This film was found to be an exchange-spring magnet film composed of the hard magnetic phase such as SmCo5 and Sm2Co7 phases and a soft magnetic phase of Co. Sm28Co59Cu13/Co(x nm) multilayered him whose Co thickness was from 0 to 15 nm was also found to be an exchange-spring magnet film.

The W-type hexagonal ferrite, with the chemical formula of Sr(Ba)Fe<SUP>2</SUP>+Fe<SUP>3</SUP>+<SUB>16</SUB>O<SUB>27</SUB>, is the future candidate ferrite because of its 10% higher saturation magnetization in comparing with that of M-type ferrites. A complicated atmosphere control during sintering process is, however, required in manufacturing of W-type ferrites, which will be unsuitable for industrial production. Recently, it is reported that a high performance SrFe<SUB>2</SUB>-W type ferrite can be produced with using a carbon powder as a solid reducing agent and controlling the drying temperature of green compacts. The energy product (BH)max of this SrFe2-W type ferrite is reported to be 5.3MGOe. The purpose of this study is to clarify the effects of drying treatment of green compacts, and addition of Si as a new solid reducing agent on the formative condition of SrFe<SUB>2</SUB>-W type ferrite.<BR>The drying treatment at 373K and following by firing at 1473K for 10 hours in Po<SUB>2</SUB>=250 Pa are the suitable formative conditions for silicon addition to achieve high volume fraction of SrFe<SUB>2</SUB>-W phase and this sample has the(BH)max of 10.3kJ.m<SUP>-3</SUP>.

A new type of PTC material based on Bi metal/ceramics composites has been developed. Bi/SrBi4(Ti0.95Nb0.05)(4)O-15 composites with various Bi contents were fabricated by powder metallurgical process. It was found that the samples of x=0.73 similar to 0.80 in xBi-(1 - x)SrBi4(Ti0.95Nb0.05)(4)O-15 composites fired at 1075 degrees C for 2 h in Ar atmosphere can show the PTCR properties at the melting point of Bi metal of about 270 degrees C. The composites consisted of the microstructures where Bi metal phases were dispersed in the SrBi4(Ti0.95Nb0.05)(4)O-15 ceramics matrix. The same techniques were applied to other ceramics matrix. Both of Bi/TiO2 and Bi/Al2O3 composites were confirmed to show PTCR properties at the same temperature. Since the resistivity-temperature characteristics at higher temperatures were determined by the ceramic matrix, the resistivity of composites and the magnitudes of PTCR effect could be controlled by choosing the different resistivity of the ceramic matrix.

The crystal structure and magnetic properties of Zn-stabilized La M-type ferrite with magnetoplumbite structure were studied. The single phase of M-type ferrite was obtained by using conventional ceramic techniques with nominal composition of LaZn<SUB>0.5</SUB>Fe<SUB>11.3</SUB> O<SUB>19</SUB>. It was confirmed that the Zn-stabilized La M-type ferrite had a hexagonal symmetry (P6<SUB>3</SUB>/mmc) with lattice constants of a=0.5890, c=2.2926nm. The c-axis length was smaller than that of Sr or Ba M-type ferrite. The magnetization of this ferrite is 81.4&mu;Wb&sdot;m&sdot;kg<SUP>-1</SUP> at room temperature at the applied field of 1200kA&sdot;m<SUP>-1</SUP>, and the Curie temperature is 649K.

The structure and magnetic properties of Sm-Co films and Sm-Co/M (M=Co, Fe) multilayered films prepared by rf sputtering were investigated. The results show that a hard magnetic phase as Sm<SUB>2</SUB>Co<SUB>17</SUB> and SmCo<SUB>5</SUB> phase and a soft magnetic phase were formed by annealing Sm-Co and Sm-Co/M films. Sm<SUB>16</SUB>Co<SUB>84</SUB> film annealed for 1.8 ks at 773 K had the springback ratio of [Mr-M(H)]/[Mr-M(H)]=0.72. This film was found to behave as a exchange-spring magnet composed of a hard magnetic phase and a soft magnetic phase. Sm<SUB>16</SUB>Co<SUB>84</SUB>/Fe multilayered film was also found to be a exchange-spring magnet.

Polycrystalline isotropic perovskite-like La(5/6)AM(1/6)MnO(3) (AM=Na, K, Rb, Cs) partially substituted trivalent La3+ for monovalent cations were fabricated by conventional ceramics techniques and their magnetoresistance effects in addition to magnetic/electrical properties were studied. The all studied samples show magnetization as large as about 100-110 mu Wb . m . kg .(-1) at 77 K and high electrical conductivity of 10(-3) Omega . m order at 300 K. At room temperature polycrystalline isotropic La5/6K1/6MnO3 shows large negative magnetoresistance effect Delta rho/rho(0) approximate to -20% when magnetic field of 1.5 T is applied. This value is larger than the previously reported values for La(1-x)Me(x)MnO(3) (Me=divalent cations) polycrystalline ceramics.

The possibility of formation of amorphous phase in La-Ni-B system by melt-spun technique has been investigated. It is found that the amorphous phase was formed in a relatively wide compositional range and composition forming amorphous phase nearest LaNi5 compound is LaNi6.4B1.2. The PCT curves of the amorphous ribbons neither have plateau pressure nor almost absorb hydrogen. In addition LaNi6.4B1.2 ribbons start to absorb hydrogens after crystallizing at 1073K. The amount of absorbed hydrogen is about 0.7mass% at 2.0MPa, which is almost half of that of the LaNi5 compound. However, after 30 hydride-dehydride cycle rest, crystallized LaNi6.4B1.2 ribbons show less degradation in comparison with LaNi5 alloys.

The apparent phases and magnetic properties of ferrites of the RE₂O₃-AM₂O-Fe₂O₃ system (RE=Y, La, Ce, Pr, Nd, Sm, Gd, and AM=Na, K, Rb) were studied. The observed phases were classified according to the combination of rare earth metal and alkaline metal. M-type ferrites, which have a magnetoplumbite structure, were obtained in the La₂O₃AM₂O-Fe₂O₃system (AM=Na, K, Rb). M-type ferrites were synthesized at over 1473 K for the La-Na system, 1573 K for the La-K system, and 1673 K for the La-Rb system. A single phase of M-type ferrite was prepared in (La_1-<i>x</i>K_<i>x</i>)O&middot;6Fe ₂O₃ at <i>x</i>=0.2. The magnetization of (La_0.8K_0.2)O&middot;6Fe₂O₃ is 86&mu;Wb&middot;m&middot;kg^-1,and the Curie temperature is 708 K.

Bulk samples of RE(1-x)Sr(x)Mn(1-y)TM(y)O(3) (RE = La, Pr, Nd, Sm;TM = 3d transition metal) ceramics were prepared by using conventional ceramic techniques, and the magnetic/electric properties and the magnetoresistance effects defined as Delta rho/rho(o) = (rho(H) - rho(0))/rho(0) where rho(0) is the ten, field resistivity and rho(H) is the resistivity in applied magnetic field, were systematically investigated. AU studied samples (x = 1/3) showed perovskite-like structure. For examples, Pr-2/3 Sr-1/3 MnO3 sample sintered at 1573K showed MR ratio of -10% at room temperature, and Sm-2/3 Sr-1/3 MnO3 sample showed MR ratio of -80% at 77K. Then MR ratio tends to have a maximum around the Curie temperature of the sample. The MR values of the samples for substituting Mn of B-site ions by the other 3d transition metals, such as LaMn4/5 V-1/5 O-3 and LaMn4/5 Cr-1/5 O-3 are -24% at 120K and -15% at 140K respectively.

(Bi0.85Sr0.15)(4)(Ti0.95Nb0.05)(3)O-12 shows a large positive temperature coefficient of resistivity (PTCR) properties of almost 4 orders of magnitude at about 543K. This temperature does not correspond to the Curie point of Bi4Ti3O12, but to the melting point of Bi metal. The microstructure of samples with or without showing PTCR properties observed by optical microscopy, showd the presence of Bi metal distributed in matrix. The various resistivity-temperature characteristics were obtained by controlling the distribution Bi metals in the matrix. Therefore, the new appearance of PTCR properties in Bi-Sr-Ti-O system would be related with the melting and solidification of Bi metal which is finely distributed in samples and isolated for each other. The equivalent electrical circuit for the samples were determind by complex impedance and modulus analysis. A model of this appearance of PTCR properties is proposed from these results as follows; Electrical current would now in Di metal at lower temperatures, but would not flow at higher temperatures. The resistivity of the sample at higher temperatures would be determined by matrix. Another RC component which acts only in the vicinity of PTCR temperature was also observed. This component may be due to the interface of Bi metals and the matrix.

The appeared phases and magnetic properties of Sr<SUB>1-x</SUB>(La, AM)<SUB>x</SUB> ferrites (AM=Na, K) were studied. The prepared samples having the nominal composition of (Sr<SUB>1-x</SUB>⋅(La, AM)<SUB>x</SUB>)O⋅6Fe<SUB>2</SUB>O<SUB>3</SUB>, contain α-Fe<SUB>2</SUB>O<SUB>3</SUB> phase and M-type ferrite phase. However the single phase of M-type ferrites with nominal compositions of (Sr<SUB>1-x</SUB>(La<SUB>0.5</SUB>Na<SUB>0.5</SUB>)<SUB>x</SUB>)O⋅(6-2x)Fe<SUB>2</SUB>O<SUB>3</SUB> and (Sr<SUB>1-x</SUB>(La<SUB>0.7</SUB>K<SUB>0.3</SUB>)<SUB>x</SUB>)O⋅6-x)Fe<SUB>2</SUB>O<SUB>3</SUB>, where x=0.2 -0.8, was obtained by the selection of a tie-line composition. The c-axis of M-type ferrites became shoter with increasing x. Their magnetizations, Curie temperatures and anisotropy fields decreased with increasing the amount of substitution of La-AM for Sr.

Many metals show the steep increase of their specific resistivity on melting. This phenomenon was applied for producing new PTCR materials in the Pb Ti0_2 and Sn Ti0_2 systems. The xPb (100-x) Ti_<0.99>Nb_<0.01>0_2 samples with x> 15 showed the steep increase of resistivity (PTCR properties) around 327℃, and it was noted that the temperature coefficient of resistivity below the PTCR temperature changes from negative to positive with increasing Pb content. The xSn (100 x) Ti_<0.99>Nb_<0.01>0_2 samples showed PTCR properties around the melting point of Sn (232℃), but PTCR properties are less significant than those observed in the Pb Ti0_2 system.