It is important to reveal the exact cause of poor diffractivity in protein crystals in order to determine the accurate structure of protein molecules. It is shown that there is a large amount of local strain in subgrains of glucose isomerase crystals even though the overall crystal quality is rather high, as shown by clear equal-thickness fringes in X-ray topography. Thus, a large stress is exerted on the subgrains of protein crystals, which could significantly lower the resistance of the crystals to radiation damage. It is also demonstrated that this local strain can be reduced through the introduction of dislocations in the crystal. This suggests that the introduction of dislocations in protein crystals can be effective in enhancing the crystal quality of subgrains of protein crystals. By exploiting this effect, the radiation damage in subgrains could be decreased, leading to the collection of X-ray diffraction data sets with high diffractivity.

We previously reported that giant crystal enantiomeric excess (CEE) can be obtained when sodium chlorate (NaClO3) chiral crystallization from a solution is induced by the excitation of localized surface plasmon resonance (LSPR) of a Au triangle trimer nanostructure by a circularly polarized laser. However, the role of the LSPR excitation in the giant CEE remains unclear. In this work, we showed, by finite-difference time-domain analysis of plasmonic near-field, that the magnitude of a chiral optical gradient force originating from the strong superchiral near-field at the Au trimer nanogap on a virtual NaClO3 chiral crystalline cluster is comparable to that of the electric-field gradient force in previous laser-trapping-induced crystallization from unsaturated solution. We revealed that the giant CEE resulted from a difference in the frequency of attachment of chiral crystalline clusters to crystal nuclei or in the local concentration due to chirally biased diffusion rather than enantioselective optical trapping.

Because ice surfaces catalyze various key chemical reactions impacting nature and human life, the structure and dynamics of interfacial layers between water vapor and ice have been extensively debated with attention to the quasi-liquid layer. Other interfaces between liquid water and ice remain relatively underexplored, despite their importance and abundance on the Earth and icy extraterrestrial bodies. By in situ optical microscopy, we found that a high-density liquid layer, distinguishable from bulk water, formed at the interface between water and high-pressure ice III or VI, when they were grown or melted in a sapphire anvil cell. The liquid layer showed a bicontinuous pattern, indicating that immiscible waters with distinct structures were separated on the interfaces in a similar manner to liquid-liquid phase separation through spinodal decomposition. Our observations not only provide a novel opportunity to explore ice surfaces but also give insight into the two kinds of structured water.

The control of crystallization not only impacts the production of functional crystalline materials or pharmaceuticals but also provides profit to investigate the fundamental mechanism of crystallization. Recently, we have revealed that plasmonic optical tweezers (POT) can "manipulate" the crystallization of a pharmaceutical compound from its aqueous solution by optically trapping molecular clusters, offering a novel strategy to control crystallization. Here we report a variety of unique crystallization phenomena by applying POT to sodium chlorate (NaClO3) chiral crystallization from an aqueous microdroplet loaded on a plasmonic substrate. Plasmon excitation significantly promotes crystallization intermediated by an achiral metastable crystal as a precursor. Also, the direction of the creeping of the resulting chiral crystal can be controlled. By utilizing this phenomenon, we achieved the directed chirality transfer from the chiral crystal to the achiral crystal via a forced contact-induced polymorphic transformation by intentionally making creeping chiral crystal contact with an achiral crystal. Moreover, we captured, by in situ optical microscopic observation, a liquid precursor that intermediates the NaClO3 achiral crystallization for the first time. Our results highlight the plasmonic manipulation of crystallization opening a new door not only to control crystallization but also to investigate the unprecedented fundamental process of crystallization.

Due to their tunable material properties, binary colloidal crystals (BCCs) are highly desired for many of the same applications as colloidal crystals. Here, we have investigated the detailed growth process of BCCs with attractive interparticle interactions in which depletion forces were induced between particles via added polymer. An AB(2) superlattice phase (A, large; B, small) was grown under various solution conditions, including various large-to-small particle ratios and polymer concentrations. The solution composition at which the AB(2) phase initially nucleated shifted toward an A-rich composition as the polymer concentration increased because the free energy curves of AB(2) and other phases displayed different trends. This indicates that interparticle interactions played an important role and depended on the particle structure. In situ observations revealed that BCCs typically grew via one-dimensional heteroepitaxy, which differs from conventional colloidal epitaxial growth, demonstrating a novel technique to control the growth of BCCs.

For the versatile potential applications of colloidal crystals, precisely controlling their growth is required to achieve properties such as high crystallinity and large-area crystals. Because colloidal crystallization is a self-assembly process of dispersed particles in a solution, solution flow directly and markedly changes the behavior of particles. Thus, the effects of solution flow on the growth of colloidal crystals were investigated in the present study. We found three different effects of solution flow on the growth of colloidal crystals: enlarging the first layer, facilitating the growth of superlattice structures, and forming a new circular packing structure. Specifically, in the single-component system, because the flow speed is lower closer to the bottom of the cell, the second and further layers dissolve owing to the large flow speed, whereas the first layer remains undissolved at the appropriate flow speed. The dissolved particles (particles that are detached from the crystals and returned back into the aqueous medium) are transported near the first layer, where they facilitate the growth of the first layer. In a binary system, when colloidal crystals with different particles are neighboring each other, the flow dissolves the surface of each crystal, which forms a dense, melt-like phase between crystals, from which a superlattice structure such as AB(2) grows. The flow often moves the second layer more than the first layer because the flow speed varies with the distance from the bottom. This causes the second layer to slide above the first layer of the neighboring crystals composed of different particle sizes, which transform from the initial face-centered cubic structure of the first layer into a circular pattern with strain. These findings contribute to establishing a sophisticated control method for growing colloidal crystals.

© 2020 Author(s). The phase relation between supercooled liquid silicon (l-Si) and amorphous silicon (a-Si) is discussed based on experimental results. Electrostatically levitated l-Si samples were supercooled down to low temperatures, 300 K below the melting temperature (Tcl: 1683 K), and solidified accompanied by the release of latent heat. It was found that solidified Si samples melted again at 1480 K caused by the latent heat. Also, it was found that the Si samples that rapidly quenched near the solidification temperature contained a large amount of a-Si with tetrahedral coordination. These two findings show that the supercooled l-Si samples solidified into a-Si and a-Si melted, confirming the idea of a first-order phase transition between two metastable phases proposed by Turnbull et al. [Metall. Mater. Trans. A 29, 1825 (1998)].

© 2019 American Chemical Society. The effect of a substrate on the heterogeneous two-dimensional (2D) nucleation of colloidal crystals has been investigated. Nucleation rates, J, of 2D colloidal crystals on uncoated cover glass, Pt-coated cover glass, and Au-coated cover glass are measured. Among the three substrates, the J of the uncoated cover glass is found to be the largest, while it is smallest for the Pt-coated cover glass under the same supersaturation conditions. The interfacial free energy change, ?σ, is obtained from the nucleation rate based on classical nucleation theory (CNT), indicating that uncoated cover glass possesses the smallest ?σ, while it is largest for the Pt-coated cover glass. Since ?σ originates from the bond energy in atomic crystals, we deduce that it is related to the interaction between colloidal particles and the substrate in a colloidal system. The interactions between a colloidal particle (polystyrene) and each substrate are determined with surface force measurements using atomic force microscopy (AFM). The results show that the adhesive force, which predominantly consists of the van der Waals force, between particles and uncoated cover glass, is the weakest, while that for the Pt-coated cover glass is the strongest. A larger attractive interaction between the colloidal particles and the substrate yields a higher ?σ, and thus a smaller J. The interaction between particles and substrate has a great influence on the heterogeneous nucleation rate of colloidal crystals.

© 1965-2012 IEEE. An in-field annealing-quenching furnace utilized for magnets with a 52 mm experimental bore was developed. The cooling rate from 663 to 473 K was 38 K/s under a magnetic field of 19 T. The phase boundary between the ferromagnetic MnBi and the paramagnetic Mn1.08Bi was examined using this furnace. The phase boundary was confirmed around 663 K. It was found that the MnBi grain became elongated during recrystallization under 19 T.

© 2018 Author(s). An investigation was carried out into the instability of the crystal/melt interface in Si-rich SiGe, and the effects of the Ge concentration and growth velocity on the periodicity of zigzag facets at the interface were determined. It was found that the periodicity at the onset of instability became shorter with the increasing growth velocity and Ge concentration.

The relationship between protein crystal quality and growth kinetics was assessed by measuring the normal growth rates vs supersaturation of the (110) and (101) faces of dislocation-free tetragonal hen egg white lysozyme crystals at three precipitant concentrations, with NaCl as the precipitant. Assuming a two-dimensional birth and spreading nucleation mechanism, an increase in the surface free energy of the step edges was realized with increasing NaCl concentration, as established by decreases in the full width at half maximum values of X-ray diffraction rocking curves obtained from crystals. These results demonstrate that controlling the surface free energy of the step edges is an important aspect of obtaining high-quality protein crystals. This work also proposes a mechanism for the observed improvements in the crystal quality, based on the reduced incorporation of impurities into the steps during crystal growth.

The heterogeneous nucleation of colloidal crystals with attractive interactions has been investigated via in situ observations. We have found two types of nucleation processes: a cluster that overcomes the critical size for nucleation with a monolayer, and a method that occurs with two layers. The Gibbs free energy changes (Delta G) for these two types of nucleation processes are evaluated by taking into account the effect of various interfacial energies. In contrast to homogeneous nucleation, the change in interfacial free energy, Delta sigma, is generated for colloidal nucleation on a foreign substrate such as a cover glass in the present study. The Delta sigma and step free energy of the first layer, gamma(1), are obtained experimentally based on the equation deduced from classical nucleation theory (CNT). It is concluded that the Delta G of q-2D nuclei is smaller than of monolayer nuclei, provided that the same number of particles are used, which explains the experimental result that the critical size in q-2D nuclei is smaller than that in monolayer nuclei.

Dislocation-free tetragonal hen egg white (HEW) lysozyme crystals were grown from a seed crystal in a cell. The rates of tetragonal HEW lysozyme crystal growth normal to the (110) and (101) faces with and without a 1-MHz external electric field were measured. A decrease in the typical growth rates of the crystal measured under an applied field at 1 MHz was observed, although the overall driving force increased. Assuming that the birth and spread mechanism of two-dimensional nucleation occurs, an increase in the effective surface energy of the step ends was realized in the presence of the electric field, which led to an improvement in the crystal quality of the tetragonal HEW lysozyme crystals. This article also discusses the increase in the effective surface energy of the step ends with respect to the change in the entropy of the solid.

Understanding nucleation dynamics is important both fundamentally and technologically in materials science and other scientific fields. Two-dimensional (2D) nucleation is the predominant growth mechanism in colloidal crystallization, in which the particle interaction is attractive, and has recently been regarded as a promising method to fabricate varieties of complex nanostructures possessing innovative functionality. Here, polymers are added to a colloidal suspension to generate a depletion attractive force, and the detailed 2D nucleation process on the terrace of the colloidal crystals is investigated. In the system, we first measured the nucleation rate at various area fractions of particles on the terrace, phi(area). In situ observations at single-particle resolution revealed that nucleation behavior follows the framework of classical nucleation theory (CNT), such as single-step nucleation pathway and existence of critical size. Characteristic nucleation behavior is observed in that the nucleation and growth stage are dearly differentiated. When many nuclei form in a small area of the terrace, a high density of kink sites of once formed islands makes growth more likely to occur than further nucleation because nucleation has a higher energy barrier than growth. The steady-state homogeneous 2D nucleation rate, J, and the critical size of nuclei, r*, are measured by in situ observations based on the CNT, which enable us to obtain the step free energy, gamma, which is an important parameter for characterizing the nucleation process. The gamma value is found to change according to the strength of attraction, which is tuned by the concentration of the polymer as a depletant.

The effect of point defects on the Curie temperature (T-c) of LiNbO3 (LN) was investigated by combining T-c measurements with an analysis of the defect structures of LN doped with impurities having various valences. The data show that T-c of congruent LN increases with the impurity concentration up to around 3 and 2 mol% for divalent and trivalent impurities, respectively, whereas it decreases continuously with increased concentrations of tetravalent impurities. These T-c variations were examined with respect to the defect structures of impurity-doped LN, which are expressed in the form chemical formulae using Kroger-Vink notation. The defect structures of divalent and trivalent impurity-doped LN are {[LiLix]1-5x-2y[NbLi....]x[MLi.]y[VLi]4x+y}[NbNbx][OOx]3 and {[LiLix]1-5x-3y[NbLi....]x[MLi..]y[VLi]4x+2y}[NbNbx][OOx]3, respectively (Nb-Li: Nb at Li sites; V-Li: vacancies at Li sites, M-Li: impurities at Li sites, and Li/Nb = the congruent ratio). The defect structure in the case of tetravalent impurities is {[LiLix]1-5x+y[NbLi....]x[VLi]4x-y}{[NbNbx]1-y[MNb]y}[OOx]3. Analyses of the defect structures indicated that the Nb-Li concentration decreases with divalent or trivalent impurity doping, which increases T-c. In contrast, the Nb-Li concentration increases with tetravalent impurity doping, which decreases T-c. In addition, the divalent or trivalent impurity concentrations at which the Nb-Li concentration becomes zero were found to correspond to the concentrations at which T-c is maximized, suggesting that T-c of LN depends on the Nb-Li concentration.

Microstructural analysis was performed for Mn-Bi prepared by in-field solid-phase reactive sintering, in order to investigate the origin of magnetic field effects on the reaction. The number of formed MnBi phase around Mn grain in 10 T was almost 3 times larger than that in a zero field. The results indicated that the magnetic field enhanced the phase formation rate of MnBi phase. Due to the enhancement of the phase formation rate, the fraction of MnBi phase was drastically increased by in-field annealing.

Although many studies have indicated that Ca3TaGa3Si2O14 (CTGS) grows congruently from a stoichiometric melt when using the Czochralski (Cz) technique, the occurrence of a secondary phase during growth when using the micro-pulling down (11 -PD) technique has been reported. We have examined the detailed growth mechanism of u-PD grown CTGS as well as its congruency. Differential thermal analysis (DTA) at an elevated temperature up to 1650 degrees C shows no peaks associated with the presence of a secondary phase, whereas a secondary phase related peak was detected at an elevated temperature up to 1490 degrees C with the same heating rate. Back-scattered electron images (BEls) revealed the occurrence of Ca3Ta2Ga4O14 (CTG) as a secondary phase. The secondary phase appears at the very early stage of growth, which is not possible to explain by a eutectic reaction. The experimental results suggest that liquid immiscibility was present in the melt at around 1490 degrees C during the growth of s-CTGS. Liquid immiscibility produces Si-rich and Si-poor melts, from which different phases with different compositions are solidified. The mu-PD technique poses a more static environment in the melt than that of Cz technique due to low melt convection and the lack of stirring, which enables liquid immiscibility to emerge. (C) 2016 Elsevier B.V. All rights reserved.

In this, study, we show using X-ray diffraction (XRD) rocking-curve measurements that 1 01 strain in tetragonal hen egg white (HEW) lysozyme crystals can be removed to a large degree by utilizing seed crystals cross-linked with glutaraldehyde. We, also find that misorientation between subgrains and subgrain size decrease when employing cross-linked seed crystals, which suggests that subgrain formation in tetragonal HEW lysozyme crystals can be controlled using this technique. The ideal mosaic structure of proteins that enables the: collection of accurate integrated intensities of the diffracted waves is also discussed using tetragonal HEW lysozyme crystals as a model protein.

We show that the extinction effect explained by the dynamical theory of diffraction must be considered even in the case of protein crystals. Equal-thickness fringes, which are attributed to the Pendellosung effect, were clearly observed in the region of a tapered glucose isomerase crystal with wedge-like edges using X-ray topography carried out with a beam of monochromatic synchrotron radiation. This indicates that the perfection of this glucose isomerase crystal is high enough to produce this dynamical theory-related effect: this surely leads to difficulty in the collection of accurate integrated intensities of diffraction spots for Xray structural analysis. Therefore, it is important to determine whether the crystal quality of a protein crystal under analysis is adequate to obtain accurate three-dimensional structures of protein molecules for X-ray structural analyses. We show that X-ray diffraction rocking-curve measurements can provide clues for this determination.

X-ray diffraction (XRD) rocking-curves were measured for tetragonal hen egg white (HEW) lysozyme crystals grown with and without application of an external electric field, and the crystal quality was assessed according to the full width at half-maximums (FWHMs) of each rocking-curve profile. The average FWHMs for tetragonal HEW lysozyme crystals grown with an external electric field at 1 MHz were smaller than those for crystals grown without, especially for the 12 12 0 reflection. The crystal homogeneity of the tetragonal HEW lysozyme crystals was also improved under application of an external electric field at 1 MHz, compared to that without. Improvement of the crystal quality of tetragonal HEW lysozyme crystals grown under an applied field is discussed with a focus on subgrain formation. In addition, the origin of subgrain misorientation is also discussed with respect to the incorporation of impurities into protein crystals.

Good model systems are required in order to understand crystal growth processes because, in many cases, precise incorporation processes of atoms or molecules cannot be visualized easily at the atomic or molecular level. Using a transmission-type optical microscope, we have successfully observed in situ adsorption, desorption, surface diffusion, lattice defect formation, and kink incorporation of particles on growth interfaces of colloidal crystals of polystyrene particles in aqueous sodium polyacrylate solutions. Precise surface transportation and kink incorporation processes of the particles into the colloidal crystals with attractive interactions were observed in situ at the particle level. In particular, contrary to the conventional expectations, the diffusion of particles along steps around a two-dimensional island of the growth interface was not the main route for kink incorporation. This is probably due to the number of bonds between adsorbed particles and particles in a crystal; the number exceeds the limit at which a particle easily exchanges its position to the adjacent one along the step. We also found novel desorption processes of particles from steps to terraces, attributing them to the assistance of attractive forces from additionally adsorbing particles to the particles on the steps.

Impurity accumulation at the grain boundaries in multicrystalline Si (mc-Si) was investigated by in situ observation of the crystal/melt interface, analysis of the grain boundary characteristics, and measurement of impurity concentrations. The impurity concentration was higher at grain boundaries that formed a groove at the crystal/melt interface than that at regions which did not form a groove at the crystal/melt interface. We conclude that groove formation at the crystal/melt interface is the cause of impurity accumulation at the grain boundary. (C) 2016 Elsevier Ltd. All rights reserved.

The effect of the solid-liquid interface morphology on grain boundary (GB) segregation during colloidal polycrystallization was investigated by in situ optical observations. The time evolution of the impurity distribution in the liquid in the vicinity of solid-liquid interface was directly Observed during crystal growth. Impurities were distributed homogeneously along the direction perpendicular to the growth orientation during the initial stage of the growth and were then gathered in the groove that formed at the solid liquid interface as crystallization proceeded. GBs were exposed to the liquid at the bottom of the groove, and a high impurity concentration at the GB (C-GB) was obtained when the area of the groove was large. The area of the groove changes depending on the crystallographic orientation of neighboring grains across GBs, which results in a difference in the interfacial energies.

Impurity partitioning during colloidal crystallization was investigated for grains with different orientations. Particles of various sizes were doped as impurities during the growth of colloidal polycrystals. The effective partition coefficient, k(eff), which is the impurity concentration in the solid (C-S) divided by that in initial solution (C-L), was measured for grains oriented in the [111] and [100] directions normal to the growth direction. The [111]-oriented grains were found to have a larger k(eff)-than [100] -oriented grains. This was analyzed by using the Thurmond and Struthers model. Though both [111]- and [100] -oriented grains were face centered cubic (fcc) structures, within several layers of crystals, the volume fraction of [111] -oriented grains was larger than that of [100] -oriented grains, yielding a larger driving force for nucleation, Delta G(Tr), and thus a larger equilibrium partition coefficient, k(0), for [111] -oriented grains. (C) 2016 Elsevier B.V. All rights reserved.

Impurity partitioning at grain boundaries (GBs) during polycrystalline colloidal crystallization has been investigated via direct observation. Polycrystalline grains have a partitioning behavior similar to that of single colloidal crystals, which follows the Burton, Prim, and Slichter (BPS) model. We have found that impurities segregate at GBs during colloidal crystal growth, and the impurity concentration at GBs (C-GB) for various misorientation angles (theta) between adjacent grains and growth rates (V) has been investigated. C-GB was found to increase with either increasing theta or V, and also when the size of the impurity is close to that of the host colloid particle. In situ observations reveal that impurities incorporated into GBs are supplied mostly from the impurities segregated at the solid liquid interface, and C-GB and the growth rate show a BPS-like relationship.

The effect of a 20 kHz external electric field on the quality of tetragonal hen egg white (HEW) lysozyme crystals was investigated using X-ray diffraction rocking-curve measurements. The full width at half-maximum was found to be larger for high-order reflections but smaller for low-order reflections. In particular, it was revealed that a large amount of local strain is accumulated in tetragonal HEW lysozyme crystals grown under an applied field at 20 kHz. Comparison with previous results obtained for crystals grown with an applied field at 1 MHz [Koizumi, Uda, Fujiwara, Tachibana, Kojima & Nozawa (2013). J. Appl. Cryst. 46, 25-29] indicated that improvement of the protein crystal quality could be achieved by selection of an appropriate frequency for the applied electric field, which has a significant effect on the growth of the solid.

The segregation of Ge in B and Ge codoped Czochralski (CZ)-Si crystal growth was investigated. The concentration of Ge in heavily Ge codoped CZ-Si was measured by electron probe micro analysis (EPMA) and X-ray fluorescence spectroscopy. The effective segregation coefficient of Ge (k(eff)) was calculated by fitting the EPMA data to the normal freezing equation, and by taking the logarithmic ratio of the Ge concentrations at the seed and tail of the ingots (top to bottom approach). The k(eff) of Ge increased from 0.30 to 0.55, when the initial Ge concentration in the Si melt (C-L(o)(Ge)) was increased from 3 x 10(19) to 3 x 10(21) cm (3). To avoid cellular growth, the crystal pulling rate was decreased for heavily Ge codoped crystal growth (C-L(o)(Ge) > 3 x 10(20) cm(-3)). The equilibrium segregation coefficient (k(0)) of Ge was calculated by partitioning theory, and was smaller than the experimentally estimated k(eff). The variation of k(eff) from k0 was discussed based on Ge clustering in the heavily Ge codoped crystal, which led to changes in the bonding and strain energies caused by the incorporation of Ge into Si. (C) 2015 Elsevier B.V. All rights reserved.

A lever rule was applied to data concerning the compositions and proportions of secondary phases coexisting with a Ca3TaGa3Si2O14 (CTGS) matrix to determine the boundary compositions of the solid-solution region for CTGS at 1320 degrees C, as a means of ascertaining the solid-solution for the langasite-type phase in the quaternary CaO-Ta2O5-Ga2O3-SiO2 system. The compositions and proportions of secondary phases were assessed by electron probe micro-analysis as well as through back-scattered electron images. The experimental results showed that the narrow solid-solution region for CTGS is located in a Ta-poor, Ga-poor and Si-rich region relative to its stoichiometric composition. (C) 2015 Elsevier B.V. All rights reserved.

© 2015 The Authors. Published by Elsevier B.V. For investigating in-field process of melting and solidification visually and quantitatively, in-situ observation system with differential thermal analysis (DTA) utilized in high temperature and in high magnetic field was developed. Decomposition processes of the bulk sample of ferromagnetic MnBi were directly observed with collecting DTA data under high magnetic field of 10 T for the 290-770 K temperature range. When the temperature was over decomposition point (ferromagnetic MnBi → paramagnetic Mn1.08Bi + liquid), liquid phase appeared on the sample surface. Furthermore, when the temperature was over peritectic temperature (∼ 700 K: paramagnetic Mn1.08Bi → Mn + liquid), the sample surface was broken and a large quantity of the liquid phase appeared from the sample. The in-situ observation also suggested that the decomposition temperature increased from 620 K for a zero field to 638 K for a magnetic field of 10 T.

For investigating in-field process of melting and solidification visually and quantitatively, in-situ observation system with differential thermal analysis (DTA) utilized in high temperature and in high magnetic field was developed. Decomposition processes of the bulk sample of ferromagnetic MnBi were directly observed with collecting DTA data under high magnetic field of 10 T for the 290-770 K temperature range. When the temperature was over decomposition point (ferromagnetic MnBi paramagnetic Mn1.08Bi + liquid), liquid phase appeared on the sample surface. Furthermore, when the temperature was over peritectic temperature (similar to 700 K: paramagnetic Mn1.08Bi -> Mn + liquid), the sample surface was broken and a large quantity of the liquid phase appeared from the sample. The in-situ observation also suggested that the decomposition temperature increased from 620 K for a zero field to 638 K for a magnetic field of 10 T.

The defect structures of impurity-doped congruent lithium niobates (c-LN) were determined for impurities with various valences, including divalent, trivalent, and tetravalent impurities, in a concentration range where antisite niobium (Nb-Li) exists. On the basis of the "Li site vacancy model," six kinds of defect structures in impurity-doped c-LN are possible. Using thermodynamic constraints, these can be narrowed down to two kinds. The first structure is that in which impurities, vacancies and Nb exist as defects in the Li site and no defects exist in the Nb site (structure A), described as {[Li-Li](1-5x-jy)[Nb-Li](x)[M-Li](y)[V-Li](4x+(j-1)y)}[Nb-Nb][O-O](3) (V: vacancy, M: impurity, j: valence of impurity, x, y: compositional variable (not equal 0), Li/Nb = congruent ratio). {[Li-Li(x)](1-5x-2y)[Nb-Li(center dot center dot center dot center dot)](x)[M-Li(center dot)](y)[V-Li'](4x-y)}[Nb-Nb(x)][O-O(x)](3) is an example by the Krooger-Vink notation for divalent M. In the second structure, vacancies and Nb exist as defects in the Li site and impurities exist as defects in the Nb site (structure B), described as {[Li-Li](1-5x-(j-5)y)[Nb-Li](x)[V-Li](4x+(j-5)y)}{[Nb-Nb](1-y)[M-Nb](y)}[O-O](3). {[Li-Li(x)](1-x+y)[Nb-Li(center dot center dot center dot center dot)](x)[V-Li'](4x-y)}{[Nb-Nb(x)](1-y)[M-Nb'](y)}[O-O(x)](3)is an example for tetravalent M. Since the relationship between impurity concentration and lattice constants for structures A and B differs, the defect structures can be differentiated by analyzing lattice constant variations as a function of impurity concentration. The results show that the defect structure of divalent and trivalent impurity-doped c-LN is structure A and that of tetravalent impurity-doped c-LN is structure B. The Nb-Li concentration increased with increasing tetravalent impurity concentration. In contrast, the Nb-Li concentration decreased with increasing divalent and trivalent impurities, leading to suppression of optical damage. The valence of an impurity determines whether the impurity is located in the Li site or Nb site in c-LN, consequently determining whether Nb-Li decreases or increases when the population of the impurity changes. (C) 2015 AIP Publishing LLC.

The essential concept of stoichiometry is discussed. The discussion is based on a simple consideration-whether the activities of the constituent elements of a material can be unity. A comparison with nonstoichiometry characterized by solute mixing reveals that the unity of activity for all constituent elements is an essential attribute of a stoichiometric material because it leads to a zero mixing term in the chemical potential. For the activity of an element to be unity, which results when the standard-state chemical potential is equal to the chemical potential itself, at least one degree of freedom is required in each crystal site containing an element. On the basis of the extended concept of stoichiometry, new LiNbO3 and LiTaO3 crystals have been developed by introducing Mg and vacancy, both of which are simultaneously congruent and stoichiometric. They are homogeneous in composition and show excellent nonlinear optical properties.

X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. Analysis of the full width at half-maximum (fwhm) of the rocking curves indicated that misorientation between subgrains, |theta - theta|, and local strain, <epsilon>, in the crystals contributed to the broadening of the experimentally determined rocking curves for the tetragonal HEW lysozyme crystals. In particular, the data suggested that imperfections in tetragonal HEW lysozyme crystals are predominantly caused by misorientation between subgrains. Moreover, it was determined that improvements in the quality of tetragonal HEW lysozyme crystals, as assessed by a decrease in the misorientation between subgrains, can be achieved by imposing a 1 MHz electric field during crystal growth. This paper also discusses the origin of subgrain misorientation in light of the incorporation of impurities into protein crystals.

MgO-doped lithium niobate that is simultaneously congruent and stoichiometric, denoted cs-MgO:LN (Li2O:Nb2O5MgO=45.3:50.0:4.7) Ill has a partition coefficient of unity for each of its constituent species, including ionic species. As such, this material exhibits no segregation of ions during crystal growth. However, a crystallization electromotive force (c-EMF) is observed during growth by the micropulling down (mu-PD) method, due to segregation of the cs-MgO:LN ionic species. This arises from a steep temperature gradient at the solid liquid interface that generates an electric field due to the Seebeck effect. In this case, the equilibrium partition coefficient, k(o), must be modified to km to take into account the effect of an electric field on the partitioning of ionic species. A coefficient of km rather than k(o) has a value of non unity and therefore can lead to generation of a c-EMF. An electric current was injected into the melt in such a way that the Seebeck effect was canceled, and this demonstrated that the value of k(o) is unity for all constituent ionic species of cs-MgO:LN. It has thus been confirmed that an injected electric current reduces the c-EMF. Only cs-MgO:LN attained a zero c-EME value at a specific current that was valid at all growth rates, whereas s-MgO(2.5 mol%):LN and ZnO-doped LN required velocity -dependent currents to reduce their c-EMEs to zero. The observation of a zero c-EMF at all growth rates upon removing the Seebeck field effect indicates that the value of k(o) is unity for all constituent species of cs-MgOIN in both the melt and crystal phases, including ionic species. Therefore, the activity of all components of cs-MgO:LN in both phases is unity and this compound is simultaneously stoichiometric and congruent. (C) 2014 Elsevier B.V. All rights reserved.

Conference date: 4-7 April 2014<br /> Location: Athens, Greece<br /> 10th International Conference of Computational Methods in Sciences and Engineering (ICCMSE 2014)

Glucose isomerase crystals with thicknesses of 0.5 mm were grown using seed crystals. The thickness required for better X-ray topographic images by kinematical theory is determined by the extinction distance, xi(g). The seed crystals were cross-linked with glutaraldehyde to maintain stability for a long period before the growth experiments. Dislocations that were produced during the growth of such thick glucose isomerase crystals were observed as clearly as those in inorganic crystals via X-ray topography with monochromatic-beam synchrotron radiation, which is attributed to the high quality of the glucose isomerase crystals. This also indicates that high-quality protein crystals can be grown using seed crystals. The dislocations extended from the interface with the cross-linked seed crystal to the surface of the grown crystal; however, no dislocations were generated if the seed crystal was not cross-linked. We discuss the effect of the chemical cross-linking of the seed on the generation of dislocations from seed crystals.

The crystal growth shape (CGS) and equilibrium crystal shape (ECS) of silicon in Si melt are observed using in situ observation. Fully faceted silicon CGSs, which are dominated by the {111} facets, are observed from the {112} and {110} orientation. Silicon CGS in three-dimensional in Si melt is octahedral in shape, bounded by {111} facets. Silicon ECSs in the melt are obtained by the relaxation from the CGSs and exhibit the {111} facets separated by curved interface. Copyright (c) 2012 John Wiley & Sons, Ltd.

The instability of crystal/melt interfaces including twin boundaries and no twin boundaries of silicon were studied using in situ observation technique. It was found that the instability is promoted at the twin boundaries on the flat crystal/melt interface. We showed that the Mullins and Sekerka theory cannot apply to an interface including twin boundaries, while it can apply to an interface including no twin boundaries. It was shown that the instability occurs even in a positive temperature gradient and the wavelength of the perturbation is determined by the twin spacing in the case of an interface including twin boundaries. (C) 2014 AIP Publishing LLC.

This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

The electrical conduction mechanism in La3Ta0.5Ga5.3Al0.2O14 (LTGA) single crystals was studied by nonstoichiometric defect formation during crystal growth. Since stoichiometric LTGA is not congruent, the single crystal grown from the stoichiometric melt was Ta-poor and Al-rich, where Al atoms were substituted not only in Ga sites but also in Ta sites. The population of the substitutional Al in Ta sites increased with increasing oxygen partial pressure during growth (growth-pO(2)) in the range from 0.01 to 1 atm. Below 600 degrees C, substitutional Al atoms in Ta sites were ionized to yield holes, and thus the electrical conductivity of the LTGA crystal depended on temperature and the growth-pO(2). The dependence of the electrical conductivity on the growth-pO(2) decreased as temperature increased. The temperature rise increases ionic conductivity, for which the dominant carriers are oxygen defects formed by the anion Frenkel reaction. (C) 2013 AIP Publishing LLC.

The minority carrier lifetime (MCL)/flow pattern defect of B and Ge co-doped Czochralski silicon (CZ-Si) was increased/decreased with the initial Ge concentration up to 3 x 10(20) cm(-3) and decreased/increased at higher Ge concentrations. Secco etch pit defects were increased in heavily (&gt;= 3 x 10(20) cm(-3)) Ge co-doped CZ-Si (grown at low growth rate), which resulted in a low MCL. The influence of Ge on microdefect variation was relatively lower than the crystal growth rate in heavily Ge co-doped CZ-Si. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Lithium tantalate (LT) is an oxide material whose congruent composition differs from its stoichiometric composition in the Li2O-Ta2O5 binary system. Ionic species in the LT melt are segregated during crystal growth, even at the congruent composition, which leads to crystallization electromotive force (C-EMF) at the solid-liquid. On the other hand, when a compound has a stoichiometric structure at the congruent composition, such segregation does not occur. By employing a new concept of stoichiometry of a material where the activity of any constituent element could be unity, we developed a new lithium tantalate with MgO doping, cs-MgO:LT (Li2O:Ta2O5:MgO=40.8:50.0:9.2), that is stoichiometric and coincident with the congruent composition. Because of this coincidence, cs-MgO:LT does not yield C-EMF and does not show segregation during growth even for ionic species. A bulk crystal was grown from the melt of the cs-MgO:LT composition via the Czochralski (CZ) method, and it showed excellent compositional homogeneity, proved by the constant distribution of the Curie temperature throughout the crystal. (C) 2013 Published by Elsevier B.V.

The effect of grain boundary characteristics on the crystal/melt interface morphology during the unidirectional solidification of multicrystalline Si was studied by in situ observations. It was shown that sharp and smooth grooves were formed at the crystal/melt interfaces at Σ27 and random grain boundaries, whereas no grooves were formed at Σ3 {1 1 1} twin boundaries. We explain the reasons why the grooves form at grain boundaries and discuss the impurity segregation at the grain boundary grooves on the crystal/melt interface. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A current-modulating four-point-probe method (CMR) is proposed as a method to determine the conversion efficiency of crystalline Si solar cells. This technique was implemented based on the comprehensive consideration of multiple problems or factors that are present in crystalline Si wafers and the subsequent thermal processes during solar cell fabrication, rather than employ conventional lifetime mapping or diffusion length mapping. A single parameter measurement of I-th-I-s from the CMR method reflects the effective resistivity or minority carriers of an entire wafer, to quickly characterize the quality or conversion efficiency of all kinds of crystalline Si. (C) 2013 AIP Publishing LLC.

X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white lysozyme (HEWL) crystals grown with and without application of an external alternating current (AC) electric field, and then the crystal quality was assessed by the FWHMs of each rocking-curve profile. The FWHMs for HEWL crystals grown with an external electric field were smaller than those for crystals grown without. In particular, the average FWHM for the 12 12 0 reflection with an external electric field (0.0034 degrees) was significantly smaller than that without (0.0061 degrees). This indicates that the crystal quality of HEWL crystals was improved by application of the external AC electric field. This crystallization technique can be expected to enhance the resolution of protein molecule structure analysis by X-ray diffraction.

We report an unconventional approach to produce a periodically twinned crystal of a non-ferroelectric material that can function as a quasi-phase matching (QPM) device. A twin boundary control method was developed based on the twin boundary formation mechanism during crystallization, and a periodically twinned QPM structure was realized in a non-ferroelectric lithium tetraborate (Li2B4O7; LB4) crystal. It was demonstrated that the periodically twinned LB4 crystal can function as a QPM device, and the second-harmonic generation (SHG) light of a Nd:YAG laser was observed. (C) 2013 The Japan Society of Applied Physics

The effect of Ge codoping on the light induced degradation (LID) of B doped Czochralski-silicon (CZ-Si) was investigated. The rate of degradation under illumination is relatively suppressed in B and Ge codoped Czochralski- silicon (CZ-Si) compared to B-doped CZ-Si. The O-i concentrations measured by FTIR spectroscopy was decreased as the Ge concentration increased in the Si crystal. The formation of Ge-VO complex in silicon lattice is considered as a possible reason for the variation in O-i. Moreover, the compressive strain field around the Ge-VO complex may increase the barrier for O diffusion which limits the formation of fast diffusing O dimmers. As a consequence, the B-O dimmer (O-2i) related defects were relatively suppressed, which causes the suppression of LID effect in B and Ge codoped CZ-Si. [GRAPHICS] (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

We investigated the effects of the Si crystal/crucible and Si melt/crucible interfacial energies on the orientation of the nucleus of multicrystalline Si during unidirectional growth. We calculated the Gibbs free energy upon nucleation on the crucible by considering the shape of the nucleus of the Si crystal and found that the nucleus with the &lt; 111i &gt; or &lt; 100 &gt; upper direction is stable. It was experimentally shown that {111} planes are dominant at the bottom of a multicrystalline Si ingot grown at a low rate, which was explained by the difference between the Si crystal/crucible and Si melt/crucible interfacial energies at nucleation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769742]

The nucleation rate of porcine insulin increased under application of an external AC electric field at 3 MHz. This is attributed to the electrostatic energy added to the chemical potentials of both the liquid and solid phases; the chemical potential of the solid was significantly changed compared with that of the liquid, which lead to an increase in the driving force for nucleation. Therefore, application of an external AC electric field can be a useful technique for protein crystallization. (c) 2012 Elsevier B.V. All rights reserved.

The crystal growth shape (CGS) and faceted dendrite growth of silicon near (1 0 0) are observed by in situ observation. The morphological transformations of the facets and curved orientations on the CGSs under different undercoolings (Delta T) are investigated, and the growth mechanism of the faceted dendrite is clarified. (1 10) facets with a low growth velocity and (1 0 0) curved interface with a relatively high growth velocity are observed on the crystal during the formation of silicon CGS, which shows a perfect foursquare shape dominated by (110) facets. At a relatively high Delta T, a faceted dendrite with a flat tip appears at the (1 1 0) facet of CGS. The (100) curved interface disappears with decreasing curvature. With increasing Delta T, both facet and curved interface growth velocities increase linearly, and the rate of curvature decrease increases. A two-dimensional image is developed to elucidate the growth mechanism of silicon &lt; 110 &gt; faceted dendrites near (100). (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The distribution of phases between bulk (tetragonal structure) and spherulitic crystals for hen egg white lysozyme was controlled under application of an external alternating current electric field. The distribution of phases differed depending on differences in the magnitude of the electrostatic energy contribution to the respective chemical potentials of the two solid phases. Therefore, the Gibbs free energy relationship between the two solid phases could be controlled by changing the frequency of the applied external electric field. Such a method of controlling the Gibbs free energy relationship among polymorphs would be adaptable to many kinds of protein.

Crystal-melt interface morphological transformation of differently oriented SiGe crystals with different Ge concentrations was observed, and the effect of Ge concentration on critical growth velocity (V-c) for the interface morphological transformation was investigated. A planar-to-faceted morphological transformation for the &lt; 110 &gt;, &lt; 112 &gt;, and &lt; 100 &gt; interfaces was observed. V-c for planar-to-faceted transformation of the &lt; 110 &gt;, &lt; 112 &gt;, and &lt; 100 &gt; interfaces decreases nonlinearly with increasing Ge concentration. SiGe faceted interfaces can be attributed to the fact that the perturbation induced in a planar interface was amplified when the constitutional undercooled zone was formed at high growth velocities. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698336]

The effect of Ge codoping on minority carrier lifetime in boron (B)-doped Czochralski-silicon (CZ-Si) crystals was investigated. The minority carrier lifetime increased from 110 to 176 mu s as Ge concentration was increased from zero to 1 x 10(20) cm(-3) in B/Ge codoped CZ-Si crystals. Light-induced degradation (LID) experiments showed that B-doped CZ-Si degrades rapidly, while B/Ge codoped CZ-Si degrades more slowly. Moreover, the flow pattern defect (FPD) density of grown-in micro-defects (GMD) in as-grown B/Ge codoped CZ-Si decreased with increasing Ge concentration. From the infrared (IR) absorption studies, it was observed that the interstitial oxygen (O-i) concentration decreased as Ge concentration increased in the crystal. The suppressed LID effect in the B/Ge codoped CZ-Si appears to be related to the low concentration of B-O associated defects, possibly because Ge doping retards the O-i diffusion in addition to the low O-i concentration present (evidenced from IR studies). The mechanism by which the Ge concentration influences the reduction of FPDs and O-i concentration is discussed in terms of Ge-vacancy defect formation during post-growth cooling of the ingots. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3687935]

The formation mechanism of a cellular structure during the growth of Si-rich SiGe crystals was studied by in situ observation. We directly observed the morphological transformation of the crystal-melt interface during the unidirectional growth of Si-rich SiGe. It was found that the morphology of the interface transformed from a planar to a zigzag facets to a faceted cellular interface with increasing growth rate. It is clarified that Ge segregation at valleys of zigzag facets leads to the formation of a cellular structure in Si-rich SiGe crystals. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3675860]

We study the boron-oxygen defect in Si co-doped with gallium and boron with the hole density 10 times higher than the boron concentration. Instead of the linear dependence of the defect density on the hole density observed in boron and phosphorus compensated silicon, we find a proportionality to the boron concentration. This indicates the participation of substitutional, rather than interstitial, boron in the defect complex. The measured defect formation rate constant is proportional to the hole density squared, which gives credit to latent defect models against defect reactions limited by the diffusion and trapping of oxygen dimers by boron atoms. (C) 2012 American Institute of Physics. [doi:10.1063/1.3680205]

Maximization of the quality factors Q of langasite (LGS) and langatate (LGT) is necessary for optimal performance of acoustic resonators of these materials in frequency-control and high-temperature sensing applications. In this report, measurements and least-squares analysis of Q(-1) as a function of ultrasonic frequency and temperature of undoped LGS (100 K to 750 K) and LGT (300 K to 760 K) reveal a superposition of physical effects, including point-defect relaxations and intrinsic phonon-phonon loss. In LGS, these effects are superimposed on a large temperature-dependent background with weak frequency dependence that is interpreted as arising from a relaxation process with a distribution of activation energies. This distributed relaxation is suggested to be a result of anelastic kink migration. No evidence for a significant background of this form is found in the LGT specimen, consistent with the lower measured dislocation etch-pit density of this crystal. The analysis of the dependence of Q(-1) of LGT on frequency and temperature indicates that, at near-ambient temperatures, the damping in this specimen is close to the intrinsic limit determined by phonon-phonon interactions. Piezoelectric/carrier relaxation, which must occur at sufficiently elevated temperatures, is found not to be a significant contribution to Q(-1), relative to defect-related contributions, in either LGS or LGT in the measured range of temperatures. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3672443]

We investigated the relationship between crystal growth direction and twin boundary orientation in lithium tetraborate. We found that there are two twin boundary orientations, {100} and {112}, and that the twin boundary orientation depends on the growth interface orientation. Using the micro-pulling-down method, the tilting angle of a seed crystal containing a (010) twin boundary has a critical effect on controlling the twin boundary orientation. Only a (010) twin boundary forms in a growing crystal for tilting angles between 0 degrees and 45 degrees, whereas both (010) and (100) twin boundaries form when the tilting angle is 45 degrees. Employing a periodic twin structure in a borate crystal may be useful for fabricating quasi-phase-matching structures since the twin boundary orientation could be controlled by selecting an appropriate growth direction. (C) 2011 Elsevier B.V. All rights reserved.

The effect of an external ac electric field on the nucleation rate of hen egg white lysozyme crystals increased with an increase in the concentration of the precipitant used, which enabled the design of an electric double layer (EDL) formed at the inner surface of the drop in the oil. This is attributed to the thickness of the EDL controlled by the ionic strength of the precipitant used. Control of the EDL formed at the interface between the two phases is important to establishing this novel technique for the crystallization of proteins under the application of an external ac electric field.

La3Ta0.5Ga5.5O14 (LTG) single crystals, which have no phase transition up to the melting point, were heat-treated in air at temperatures from 1000 degrees C to 1450 degrees C for 10 h. LaTaO4 (LT) and LaGaO3 (LG), which coexist with LTG in the three-phase region on the Ga-poor side, precipitated on the surface of the crystal for heat treatments above 1300 degrees C because of Ga evaporation during the heat treatment. The Ga-poor state near the surface of the 1450 degrees C heat-treated specimen was confirmed by electron probe micro-analysis measurements. The electrical resistivity of LTG single crystals decreased by heat treatment in the range of 1000 degrees C to 1200 degrees C for 10 h in air, where no precipitation was observed, whereas the resistivity increased with heat treatment over 1400 degrees C for 10 h in air. The electrical resistivity of the Ga-poor surface region was higher than that of the interior.

Si-faceted dendrites growth orientation as a function of twin spacing and undercooling were investigated by in situ observation, and the mechanisms of the growth behaviors were discussed and clarified. The growth orientation of Si-faceted dendrites strongly depends on the twin spacing and undercooling. For a given undercooling, a dendrite with twin spacing narrower than the critical twin spacing preferentially grows in the (110) direction, whereas growth in the (112) direction preferentially occurs for a dendrite with twin spacing wider than the critical twin spacing. The critical twin spacing for stable faceted dendrite growth increases as the undercooling increases. In the case of low undercooling (similar to 1.0 K &lt; Delta T less than or similar to 15K), dendrites dominantly grow in the &lt; 112 &gt;&gt; direction. For high undercooling (similar to 25 K&lt; Delta T less than or similar to 100 K), dendrites preferentially grow in the (110) direction. (110) and (112) growth directions occur with equal frequency for intermediate values of undercooling (similar to 15 K &lt; Delta T &lt;= 25 K).

The intensity of the infrared absorption band at 1107 cm(-1) related to interstitial oxygen (Os) concentration, decreased as the Ge concentration increased in Ga and Ge codoped CZ-Si crystals. In contrast, the number of precipitates observed on the etched surfaces of CZ-Si wafers increased as the Ge concentration increased. From an energy dispersive X-ray (EDX) analysis, O was observed to be one of the major components of the precipitates. Moreover, Ge was found as one of the components in the precipitate observed on the heavily Ge (&gt; 1 x 10(18) cm(-3)) codoped CZ-Si wafers. These results suggest that the grown-in O precipitates increase as the Of concentration decreases when the Ge concentration increases in the Si crystal. The Ge-vacancy (V) complex in the Si lattice probably acted as a heterogeneous nucleation center and may enhanced the grown-in O precipitates thereby reducing the dissolved O-i concentration in the Si lattice. (C) 2011 Elsevier B.V. All rights reserved.

Langasite (LGS), langatate (LGT), and similar piezoelectric crystals in the P321 crystal class have become an increasing focus of research during the past two decades, and much of the motivation for this research has been the application of these materials in high-temperature resonant acoustic sensing. The quality factor Q of these materials directly affects the resolution of sensors, and Q decreases dramatically at elevated temperatures. We present measurements and multi-frequency least-squares analysis of Q -1 of LGS and LGT bulk-acoustic resonators as a function of temperature that reveal a superposition of physical effects contributing to the damping, including point-defect relaxations and intrinsic phonon-phonon loss. In LGS, these effects are superimposed on a background that increases with increasing temperature. Parameters for this background obtained from least-squares analysis are found to be consistent with an anelastic dislocation mechanism with a distribution of activation energies. The absence of a significant background of this type in LGT, over the measured temperature range, and associated differences in the crystal growth and phase diagrams of LGS and LGT provide support for the view that LGT is a more attractive choice for high-temperature sensing applications. © 2011 IEEE.

Si faceted dendrites grown from the same parallel twins under different undercooling (Delta T) were observed by in situ observation, and the dependence of faceted dendrite growth velocity (V(d)) on undercooling was investigated. V(d) increase linearly as the increasing Delta T. The faceted dendrite growth velocity-undercooling relationship was analyzed using a model developed on the basis of theoretical dendrite growth velocity. The results obtained using the proposed model fit the experimental results well and indicate that the twin spacing markedly affects the dendrite growth velocity-undercooling relationship. (C) 2011 American Institute of Physics. [doi:10.1063/1.3543623]

Transport of ionic species in the melt and their partitioning at the solid-liquid Interface during growth of lithium mobate was studied under the influence of intrinsic and external electric fields A Mn-doped lithium mobate (Mn LiNbO3) single crystal was grown via the micro-pulling-down (mu-PD) method with electric current injection at the Interface Mn ions were accumulated or depleted at the interface depending on the sign of the injected current The electric current injection Induced an interface electric field as well as a Coulomb force between the Interface and Mn ions The electric field modified the transportation of Mn ions and their partitioning into the crystal while the Coulomb force led to adsorption or rejection of Mn ions at the interface in addition to Mn concentration change due to the electric field Effect of the Coulomb force was often observed to be larger on Mn concentration at the interface than that of the induced electric field and dominated the redistribution of Mn in the solid It has been experimentally and analytically shown that Mn concentration partitioned into the crystal can be obtained by multiplying Mn concentration at the interface by a field-modified partition coefficient k(E0) instead of the conventional equilibrium partition coefficient k(0) (C) 2010 Elsevier B V All rights reserved

Langatate (La3Ta0.5Ga5.5O14, LTG) single crystal has been one of the promising candidate piezoelectric materials in high temperature applications because of its structural stability at high temperature. However, it has been reported that compositions of LTG grown by the Czochralski method deviates from the ideal stoichiometry to Ta-poor and Ga-rich material. In this work, to elucidate the energetic stability of defects and their influences on electronic properties, defect formation energies, and electronic properties were calculated for perfect and defective LTG crystals by using first-principles calculations. The results with oxygen-rich assumption showed that Ga substitution on Ta site and Ta vacancy were the most energetically stable defects among various acceptor-like defects under low and high Fermi energy region, respectively. The most stable cation vacancy V&apos;&apos;&apos;&apos;&apos;(Ta) could affect the electronic and optical properties of the LTG crystal, as the band gap of a crystal with V&apos;&apos;&apos;&apos;&apos;(Ta) has a smaller gap than other defects. (C) 2010 American Institute of Physics. [doi:10.1063/1.3514008]

A new LiNbO3 bulk crystal has been grown by doping with MgO (cs-MgO:LN; Li2O:Nb2O5: MgO=45.30:50.00:4.70, (Li0.906Mg0.047V0.47Li)NbO3), which successfully has the congruent point coinciding with the stoichiometric point. Its second-harmonic-generation (SHG) properties were evaluated. It was found that cs-MgO:LN has a much more homogeneous composition leading to uniform in-plane distribution of the non-critical phase-matching wavelength than the conventional LiNbO3 crystals such as congruent LiNbO3 (c-LN), stoichiometric LiNbO3 (s-LN), and MgO-doped congruent LiNbO3 (5MgO:LN). This homogeneity arose from the observation that none of the solute components including ionic species were segregated at the interface during growth. The SHG conversion efficiency of cs-MgO:LN is comparable to those of s-LN and 5MgO:LN. (C) 2010 Elsevier B.V. All rights reserved.

It was observed that the effect of an external electric field on the nucleation rate of tetragonal hen egg-white lysozyme crystals varied depending on the precipitant used (NaCl, NiCl(2) or YbCl(3)) and that the electric double layer (EDL) played an important role in generating an external electric field of the necessary strength to control the nucleation rate. This phenomenon depended on the ionic strength of the precipitant used; that is, a precipitant of greater ionic strength resulted in a thinner EDL and increased the effect of the external electric field as the driving force for nucleation. The dependence of the nucleation rate on the precipitant was attributed to the magnitudes of the external electric fields generated in EDLs of varying thickness which were formed in the presence of different precipitants. (C) 2010 Elsevier B.V. All rights reserved.

The segregation of Ga during the growth of Czochralski-Si crystals with Ge codoping was investigated. The effective segregation coefficient of Ga in Ga/Ge-codoped Si crystal growth was nearly constant over a wide Ge concentration range, even at high Ge concentrations of about 10(21) cm(-3). In contrast, the effective segregation coefficient increased at high B concentrations in Ga/B-codoped CZ-Si crystal growth. The segregation behavior of Ga in Ga/Ge- and Ga/B-codoped CZ-Si crystal growth was theoretically compared. The difference in the segregation coefficients of Ga as a function of the codoped impurity (Ge or B) between the two Si crystals was attributed to a difference in the excess enthalpy due to impurity incorporation into the Si crystal between Ga-Ge pairs and Ga-B pairs The effect of Ge codoping on the minority carrier lifetime in Ga/Ge-codoped a-Si crystals was also investigated. The minority carrier lifetime increased with increasing Ge concentration. The higher minority carrier lifetime was associated with a decrease in interstitial oxygen related to D-defects in the Si crystal. (C) 2010 Elsevier B.V. All rights reserved.

The growth velocity of silicon &lt; 110 &gt; faceted dendrites as a function of the twin spacing was investigated by in situ observation. As the twin spacing increases, &lt; 110 &gt; dendrite growth velocity nonlinearly decreases. The theoretical &lt; 110 &gt; and &lt; 112 &gt; dendrite growth velocities were calculated on the basis of the modified re-entrant corner model, and the theoretical growth velocity of &lt; 110 &gt; dendrites was found to be slower than that of &lt; 110 &gt; dendrites under the same twin spacing. The theoretical &lt; 110 &gt; dendrite growth velocity fits quite well with the experimental results. (C) 2010 American Institute of Physics. [doi:10.1063/1.3501974]

The electrical conduction mechanism in La3Ta0.5Ga5.5O14 (LTG) was studied from the standpoint of defect formation during growth caused by the nonstoichiometry of the crystal. Since the stoichiometric composition of LTG does not coincide with the congruent composition, single crystals grown from the stoichiometric melt under an atmosphere of O-2/Ar in the oxygen partial pressure range from 0.005 to 1 atm was Ta-poor. Ta vacancies were formed during the growth, and their population was predominated by the growth-pO(2). With increasing temperature up to 600 degrees C, the Ta vacancies were ionized to yield holes, and thus the electrical conductivity of the LTG crystal varied with temperature and growth-pO(2). In contrast, Ga vacancies as a carrier source would form by Ga evaporation during growth under pO(2) below 0.005 atm. The growth-pO(2) dependence of the electrical conductivity was opposite to the case for Ta vacancies. For the case of sintered LTG with the exact stoichiometric composition, impurity defects dominated electrical conduction below 600 degrees C, where the impurity concentration was higher than the cation vacancies arising from the nonstoichiometry of the sintered LTG. Thus, electrical conductivity was almost independent of the sintering atmosphere of pO(2). Above 700 degrees C, the dominant carrier in both single crystal and sintered LTG was ions related to oxygen defects formed by the anion Frenkel reaction. (C) 2010 American Institute of Physics. [doi:10.1063/1.3478772]

The nucleation rate of tetragonal hen egg white (HEW) lysozyme crystals could be increased or decreased via application of an ac electric field, which modifies the chemical potential of the liquid and solid states. The strength of an external electric field necessary to control the nucleation rate was calculated to be 10(4)-10(5) V/cm, which was larger than that used experimentally by 2 or 3 orders of magnitude. This huge discrepancy could be understood by assuming the presence of a very large electric field sustained in the electric double layer (EDL) that forms at the interface between the dissimilar phases. By changing the frequency of an applied electric field of 800 V/cm in the range of 1-9 MHz, we were able to increase or decrease the nucleation rate. Specifically, the nucleation rate with an applied electric field increased with an increasing applied frequency up to 5 MHz and then significantly dropped above this value. The rapid decrease is considered to result from extinction of the EDL above 5 MHz.

The growth mechanism of the Si &lt; 110 &gt; faceted dendrite was studied using an in situ observation technique. We directly observed the growth process of Si faceted dendrites from Si melts. It was found that the shape of the &lt; 110 &gt; faceted dendrite during growth is markedly different from that of the &lt; 112 &gt; faceted dendrite; the tip of the &lt; 110 &gt; faceted dendrite is narrow while that of the &lt; 112 &gt; faceted dendrite is wide. We present a scheme for the growth shapes of the faceted dendrites based on the experimental evidences.

Dopant distribution in yttrium aluminum garnet (YAG:Y3Al5O12) shaped crystal grown via the micropulling-down method depends primarily on the distribution coefficient (k(0)). The solid-favoring dopants (k(0) &gt;1.0), Cr and Yb, concentrated in the central core of the crystal, while the liquid-favoring dopants (k(0)&lt;1.0), Nd and Ce, concentrated in the rim. Secondary rare-earth oxide phases were sometimes segregated and crystallized circumferentially with Nd and Ce dopant. The dopant distribution profile was also controlled by the position of the melt entrance hole in the crucible shaper, which was confirmed by SIMPLER calculation. Segregation/distribution coefficients for Cr, Yb, Nd, and Ce in YAG were found to be 1.5, 1.01, 0.1, and 0.01, respectively. (C) 2009 Elsevier B.V. All rights reserved.

The growth behavior of faceted Si crystals in grain boundary formation during crystallization was studied by the in situ observation technique. We directly observed the transition of the shape of the growing interface just before the impingement of two crystals. It is found that when a crystal with a zigzag-shaped faceted interface encounters another crystal, {111} facet facing on the growing interface gradually disappears with the transition of the interfacial shape from zigzag to linear. This shape transition of the growing interface determines the grain boundary shape and grain boundary character. (C) 2009 Elsevier B.V. All rights reserved.

The mechanism of polarization due to thermoelectric power and current-induced electric fields during the growth of LiNbO3 crystals was studied using a micro-pulling-down method. With no applied electric current, a +c single-domain crystal was grown regardless of the domain orientation of the seed crystal. This +c domain growth was consistent with the direction of the electric field caused by the thermoelectric power in the liquid, despite an opposing electric field in the solid due to the opposite sign of the Seebeck coefficient. Thus, it was the electric field in the liquid that determined the domain structure of the growing crystal. On the other hand, when a current was applied from the melt to the crystal, a -c domain crystal was grown. The electric current required for this domain inversion to occur became larger as the temperature gradient in the solid phase decreased. This shows that the electric field in the solid phase became large enough to induce domain inversion from +c to -c through a combination of the thermoelectric power in the solid phase and current-induced electric field. (C) 2009 Elsevier B.V. All rights reserved.

Several chemical components exist in the oxide melt, including ionic species. During crystal growth these are partitioned into the solid phase with their own equilibrium partitioning coefficients. Therefore, they are usually segregated, even at the congruent composition. However, when a compound has a stoichiometric structure at the congruent composition, the equilibrium partitioning coefficients of all chemical components become unity and segregation does not occur. Segregation of ionic species was observed at the binary congruent composition of LiNbO3 because of its non-stoichiometric structure. On the other hand, the segregation of ionic species did not occur at the ternary congruent composition of MgO-doped LiNbO3 (Li2O:Nb2O5:MgO = 45.5:50:4.5). This demonstrates that non-stoichiometry of congruent LiNbO3 was converted to the constitutional stoichiometry at the ternary congruent composition by MgO doping. (C) 2009 Elsevier B.V. All rights reserved.

We investigated the effects of B/Ge codoping on the minority carrier lifetime in gallium (Ga)-doped Czochralski-silicon (CZ-Si) crystals. Minority carrier lifetime decreased from 28 to 0.1 mu s when the B concentration was increased from 1x10(15) to 1x10(17) cm(-3) in Ga/B codoped CZ-Si crystals. The minority carrier lifetime increased from 30 to 76 mu s with increasing Ge concentration from 1x10(17) to 2x10(20) cm(-3) in Ga/Ge codoped CZ-Si crystals. Light-induced degradation experiments showed that Ga/B codoped CZ-Si degraded rapidly, while Ga/Ge codoped CZ-Si showed no degradation. Moreover, the flow pattern defect density related to grown-in microdefects in as-grown Ga/Ge codoped CZ-Si decreased with increasing Ge concentration. The experimental results are explained using a defect reaction model based on the formation of Ge-vacancy-oxygen dimer complexes in the CZ-Si crystal during postgrowth cooling.

Control of the nucleation rate is important for the growth of high quality protein crystals; therefore, the development of improved growth methods is required. Crystal growth with an external electric field is an attractive method for control of the nucleation rate. However, mainly a decrease in nucleation rate was observed when an external electric field was applied using DC voltage. By focusing on the chemical potential of the liquid and solid, control of both the increase and the decrease in nucleation rate was successfully achieved by applying an AC electric field. Control of nucleation rate in terms of enhancement and retardation is reported for hen-egg white lysozyme crystals by imposition of an electric field with varying frequencies, which was determined by the electrical permittivity of both the hen-egg white lysozyme solution and crystals.

The segregation of intrinsic ionic species of LiNbO3 during crystallization generates electromotive force (EMF) at the growth interface. The EMF was measured during the growth of LiNbO3 Crystal doped with MgO, ZnO, ZrO2 and MnO2 in the concentration range from 0 to 12 mol% using a micro-pulling-down growth system. The influence of these impurities on the partitioning of intrinsic ionic species of LiNbO3 was examined. in the case of MgO-, ZnO- and ZrO2-doping, crystallization EMF had a minimum value at the concentration where the impurity ion changed its partitioning site from the Li-site to the Nb-site, as confirmed by Raman scattering measurements. The crystallization EMF of MnO2-doped LiNbO3 showed no such minimum value because Mn4+ ion did not change its partitioning site. These results demonstrate that it is the segregation of the intrinsic ionic species that generates the crystallization EMF rather than that of impurities and that the partitioning behavior of intrinsic ionic species of LiNbO3 is greatly affected by the partitioning site of impurity ions. (C) 2008 Elsevier B.V. All rights reserved.

The temperature dependences of acceptor concentration n(A), conductivity mobility mu(C), and resistivity p of gallium (Ga)-doped Czochralski (CZ)-silicon (Si) crystals were studied in the temperature range from 220 to 360 K (-53 to 87 degrees C). Crystals with Ga concentration N(A) from 6.1 x 10(14) to 2.0 x 10(18) atoms/cm(3) were analyzed by Hall-effect measurements using the van der Pauw method in the temperature range from 80 to 360 K. The temperature dependences of n(A) and rho of crystals with less than 10(16) atoms/cm(3) showed the same trends as those of B-doped p-type Si crystals, while those of crystals with more than 10(16) atoms/cm(3) differed from those of B-doped crystals, mainly because the temperature dependence of n(A) is not in the saturation range and the degree of ionization n(A)/N(A) decreases with decreasing temperature from 360 to 220 K. (C) 2009 The Japan Society of Applied Physics M pill

Higher minority carrier lifetimes (76 mu s) were measured in Ga and Ge codoped Czochralski-silicon (CZ-Si) crystal compared to Ga-doped CZ-Si (28 mu s). The minority carrier lifetime increase was associated with a decrease in etch pit density related to grown-in microdefects (GMD) in as-grown CZ-Si with increasing Ge concentration. Furthermore, oxygen (O) precipitation was enhanced in CZ-Si by increased Ge concentration, but this had a lesser limiting influence on minority carrier lifetime. The mechanism by which Ga and Ge codoping affects GMD suppression and enhances O precipitation in CZ-Si is discussed on the basis of the behavior of Ge-vacancy-O related complexes.

The relationship between gallium (Ga) concentration and resistivity was studied in Ga-doped Czochralski (CZ) silicon (Si) single crystals in the dopant concentration range from 1 x 10(14) to 2 x 10(18) atoms/cm(3) by the four-point probe method, inductively Coupled plasma (ICP) analysis, and Hall-effect Measurement. The resistivity of Ga-doped Si was found to be larger than that of B-doped Si, because Ga is not fully ionized at Ga concentrations higher than 10(16) atoms/cm3 at 300 K. A conversion curve from resistivity to Ga concentration in the range from 1 x 10(14) to 1 x 10(17) atoms/cm(3) is proposed. [DOI: 10.1143/JJAP.47.8691]

Unidirectional benzophenone single crystals grown by vertical Bridgman (VB), microtube-Czochralski (mu T-CZ), uniaxially solution crystallization method of Sankaranarayanan-Ramasamy (SR) were characterized using X-ray diffraction (XRD), high-resolution XRD (HRXRD), laser damage threshold (LDT) studies and the results were compared. The XRD study exhibits the growth direction of the benzophenone crystal ingots. The HRXRD curves recorded by multicrystal X-ray diffractometer (MCD) revealed that the crystals grown by all the three methods contain internal structural grain boundaries. The SR grown sample shows relatively good crystalline nature with the full-width half-maximum (FWHM) of the main peak of 39 arcsec. While, the VB grown crystal contain multiple low-angle (alpha &gt;= 1 arcmin) grain boundaries, probably due to thermal stress during post-growth annealing caused by the difference in the lattice expansion coefficients of the crystal and the ampoule, whereas such thermal stress are absent in mu T-CZ grown sample due to the free standing nature of the grown crystal. Hence, the mu T-CZ grown crystals contain only one very low-angle (alpha&lt;1 arcmin) grain boundary. LDT study shows that the SR grown benzophenone crystal has higher LDT than the samples grown by other methods, probably due to relatively high-crystalline perfection of the SR grown crystals. (c) 2008 Elsevier BY. All rights reserved.

Most oxide melts consist of several constituent species, including ionic species, and they have their own equilibrium partition coefficients. They are not necessarily unity at the congruent point, although phase diagrams based on the oxide components show the partition coefficient to be unity for the oxide components simply because their concentrations are equal between the liquid and the solid at the congruent point. However, if the material has very little solid solution such as Li2B4O7 whose congruent point matches its stoichiometric point, all the partition coefficients of its constituents are unity at the congruent point. In contrast, a material with a distinct solid solution, whose congruent composition is different from its stoichiometric composition, such as LiNbO3, almost always shows segregation of ionic species in the liquid boundary layer even in the congruent melt and the partitioned ionic species in the solid do not make the charge neutrality. (C) 2008 Elsevier B.V. All rights reserved.

The melting temperatures of lithium niobate (LN:LiNbO3) sintered powders of varying composition were measured under an electric field by an in-house-made DTA capable of applying an electric field. For non-doped LN (X-Li = [Li]/[Li]+[Nb] = 0.460-0.500), the congruent point moved away from the stoichiometric composition under an external electric field, while the congruent point may have moved toward the stoichiometric composition when 6.0 mol% Mg was added to LN. The temperature change for 0-10 mol% Mg-doped c-LN is also shown and the maximum temperature change (similar to 3 degrees C) was observed at 6.0 mol% doping. (C) 2008 Elsevier B.V. All rights reserved.

Codoping of gallium (Ga) and boron (B) in a Czochralski-silicon (CZ-Si) crystal has been proposed to be an effective way to improve the homogeneity of resistivity over the length of a simply Ga-doped Si crystal, by increasing the very small equilibrium segregation coefficient of Ga (k(0) = 0.008). It was observed that the axial resistivity variation in a Ga- and B-codoped Si crystal was smaller than that in simply Ga-doped Si crystals. The segregation behavior of Ga and B in the codoped CZ-Si crystal growth has been investigated in the present study. The effective segregation coefficient of Ga was kept almost constant when the B concentrations were low, but it increased at higher B concentrations. On the other hand, the effective segregation coefficient of B was kept almost constant when the B concentrations were low; however, it decreased at higher B concentrations. It has been analytically demonstrated that there is strong interaction between Ga and B in a Si crystal, which leads to an increase in the segregation coefficient of Ga in Si crystal growth. (C) 2008 Elsevier B.V. All rights reserved.

The influence of growth atmosphere and Ir contamination on electrical resistivity of langatate (La(3)Ta(0.5)Ga(5.5)O(14); LTG) was studied. LTG single crystals were grown via the Czochralski method under different oxygen partial pressures with Ir contamination from the Ir crucible. In addition, LTG crystals were grown by the floating zone method and they were not contaminated by Ir. The electrical resistivity and ionic transport number of these crystals were measured in the temperature range 300-1000 degrees C. The conduction mechanism of LTG changed at about 720 degrees C. At T 720 degrees C, electronic conduction was dominant, and the resistivity was affected by growth atmosphere as well as Ir contamination. In contrast, at T 720 degrees C, ionic conduction was dominant, and the resistivity was affected only by Ir contamination. In both temperature regions, Ir contamination decreased the resistivity by an order of magnitude.

A control system with automatic power alterations to stabilize the temperature at the meniscus area was developed for crystal production by the micro-pulling-down technique. The system was successfully applied to the growth of Lu3Al5O12 and Al2O3 crystals with stable shape rod up to 110 mm in length. The developed system gives a possibility to prevent the crystal quality from degradation caused by the uncontrollable change of the meniscus height. Application of the developed system can help to minimize the number of preliminary experiments needed for the optimization of the growth conditions and to increase the crystal shape uniformity. (C) 2007 Elsevier B.V. All rights reserved.

Spherical Si single crystals for solar cell substrates have been grown successfully with a yield of almost 100%. Spherical Si multicrystals with diameters of approximately 400 mu m in a teardrop shape were initially fabricated by a dropping method. The as-dropped spherical Si multicrystals were melted into droplets on a silica plate in an oxygen atmosphere, and the Si droplets were then recrystallized to form single crystals by supercooling within a specific temperature range. It was found that the recrystallization process occurred unidirectionally in each Si droplet, and recrystallized spherical Si single crystals free of defects (dislocations and oxidation-induced stacking faults, OSF) were obtained at a supercooling in the range of 12-42 degrees C. For supercooling ranging from 42 to 87 degrees C, spherical Si single crystals could still be obtained; however, many defects such as dislocations and OSF were generated. When the supercooling was larger than 87 degrees C, the crystal growth showed a dendritic growth mode and only multicrystals were obtained. (c) 2007 Elsevier B.V. All rights reserved.

The crystal growth process of YBCO superconductive oxide under an external electric field has been investigated by means of in situ observations and differential thermal analysis. The effects of an external electric field on the growth processes via the peritectic reaction of 123 (YBa2Cu3O7-x) crystals from liquid +211 (Y2BaCuO5). including (1) dissolution of the 211 phase into solution, (2) transportation process of the solute, Y (Y2O3), in the liquid, and (3) kinetic attachment of the solute to the growth front, were analyzed in detail based on the coupling equation. An external electric field of 600 V/cm resulted in the generation of an electric double layer either at the interface between the solution and the ambient atmosphere or at the interface of the solution and the 211 grains; however, almost no electric field could be generated in the bulk liquid due to it being electrically conductive. The external electric field enhanced dissolution of the 211 gains slightly, but had almost no effective electric field operated on the transportation process of the solute, and little effect was observed on the attachment kinetics. On the other hand, the external electric field increased the Gibbs energy for the nucleation of the 123 grains, which retarded the nucleation of the 123 grains. (c) 2007 Elsevier B.V. All rights reserved.

Si multicrystals with several large grains have been grown by the Czochralski (CZ) method with multiple seeds using semiconductor-grade high-purity Si raw material in order to investigate the influence of defects such as dislocations and sub-grain-boundaries on the minority carrier lifetime. Two or three single-crystal Si seeds with [1 0 0], [1 1 0] and [1 1 0] orientations were used for the growth. It was found that the minority carrier lifetime in the Si multicrystals decreased considerably in the region of grains near the semicoherent interfaces with others, e.a., interfaces between [2 3 2] and [1 1 1] grains, [1 0 0] and [1 1 1] grains, and [1 1 0] and [1 1 1] grains. Numerous dislocations with densities as high as 10(6)/cm(2) in these grains moved to align and generate sub-grain boundaries by the shear stress caused by the semicoherence near the interfaces, which was determined to be responsible for the decrease in the minority carrier lifetime. (c) 2007 Elsevier B.V. All rights reserved.

The electric-field modified partitioning of Li ion species was studied for the growth of LiNbO3 fiber crystals via a micro-pulling down (mu-PD) method. DC power was applied between the platinum seed and the outlet of a capillary pipe attached to the bottom of the crucible so as to generate a constant electric current. The electric current, passing through the molten zone, the solid-liquid interface and the crystal, induced an electric field near the interface which influences the transport and segregation of ionic species in the melt. The compositional change in terms of mol% Li2O was examined by measuring the Curie temperature of crystals grown from melts with various compositions. The melt with Li2O concentration larger than the congruent-melting composition (k(0)(Li2O) &lt; 1) decreased its Li2O content near the interface by an electric current flowing from the crystal to the melt, while it did not change by the inverse current. In contrast, the melt with Li2O concentration smaller than the congruent composition (k(0)(Li2O) &gt; 1) increased its Li2O content by the electric current from the melt to the crystal, while it did not change by the inverse current. The above variation was peculiar to growth via a mu-PD method under an electric field induced by an imposed electric current, which confirmed that the major ionic species driven by the electric field was the Li ion species resulting in a change in the bulk Li2O concentration both in the melt near the interface and in the grown crystal. (c) 2007 Elsevier B.V. All rights reserved.

The dependence of the crystallization electromotive force (EMF) on the Li2O composition of the melt in the growth of LiNbO3 (LN) and Li2B4O7 (LB4) crystals was measured using a micro-pulling-down (mu-PD) method. The crystallization EMF developed during the growth of LN crystals continuously decreased with increase in Li2O composition. The eutectic compositions in the Li2O-Nb2O5 System were found to be peculiar compositions, at which the development of the crystallization EMF was prevented owing to no degree of freedom in the Gibbs phase rule. It was found that no segregation of the ionic species occurred in the LB4 growth from the melt with the stoichiometric composition, which suggested that the equilibrium partitioning coefficients for all the chemical species in the stoichiometric LB4 melt were unity. (c) 2007 Elsevier B.V. All rights reserved.

In order to elucidate the effects of Ba doping in a silica crucible used for growing Czochralski Si (CZ-Si) crystals, in situ observations and differential scanning calorimetry (DSC) measurements were employed for investigating the reaction at the interface between the Si melt and the Ba-doped silica glass. It was found that the generation of a so-called brownish ring was suppressed completely by Ba doping when the Ba concentration in the silica glass was higher than 30 ppm. Ba doping in the silica glass increased the formation rate of white cristobalite crystallized by phase transition directly from the silica glass, which counteracted the growth of the brownish rings and suppressed their amount. A decrease in the activation energy for the crystallization of cristobalite by Ba doping was verified by means of the DSC measurements, which caused an increase in the growth rate of the white cristobalite. (c) 2007 Elsevier B.V. All rights reserved.

Si multicrystals have been grown by the Czochralski (CZ) method using commercially available semiconductor grade Si raw material (11N) and high purity silica crucibles for investigating the influence of crystalline defects such as grain boundaries including sub-grain-boundaries, and high-density dislocations on the minority carrier lifetime. The minority carrier lifetime in the CZ-Si multicrystal was compared with that in a CZ-Si single crystal, both with and without intentional Fe doping. It was found that the minority carrier lifetime in regions with high density of crystalline defects in the CZ-Si multicrystal decreased drastically to I mu s from 8 mu s, which was the value in the CZ-Si single crystal. Fe doping with a concentration of 3 x 10(13) atoms/cm(3) decreased the minority carrier lifetime to 2 mu s in the CZ-Si single crystal. We therefore conclude that both crystalline defects and Fe doping play a very important role in the deterioration of the minority carrier lifetime, and the influence of the crystalline defects is more crucial by considering that the occurrence of crystalline defects in a multicrystal is an intrinsic problem whereas Fe contamination is an extrinsic one. (c) 2007 Elsevier B.V. All rights reserved.

We have investigated the crystallization electromotive force (EMF) during the growth of congruent LiNbO3 (LN) by exploiting the features of a micro-pulling-down (mu-PD) method. The electric potential distribution around the growth interface that was measured in the mu-PD system was attributed to the Seebeck effect and several mV of crystallization EMF. The mechanism of the crystallization EMF during the growth of congruent LN from the melt was explained using a model wherein segregation of the ionic species in the melt formed a net ionic charge at the growth interface resulting in the development of an EMF. Redistribution of the net ionic charge, which was analyzed on the basis of a one-dimensional differential equation that included electric-field-driven transport in the melt, well reproduced the experimental data of the nonlinear dependence of crystallization EMF on the growth rate. We concluded that the crystallization EMF occurred during crystal growth of the congruent LN owing to the ionic-charge accumulation at the growth interface. (c) 2006 Elsevier B.V. All rights reserved.

In situ observation of crystal growth process of YBCO superconductive oxide under an external electric field has been carried out. Nucleation and growth processes of Y123 (YBa2Cu3O7-x) crystals from liquid + Y211 (Y2BaCuO5) on MgO (100) substrate through a peritectic reaction were observed. A DTA system with in situ observation and external electric field imposition mechanism was specially designed for measuring the peritectic temperature. It was found that the equilibrium peritectic temperature was 10 12 +/- 0.5 degrees C, which was almost the same as reported in literature, and an external electric field did not affect the peritectic temperature. However, an external electric field retarded nucleation process of Y123 although it did not affect the growth kinetics. The retardation resulted from an increase of critical Gibbs energy for nucleation due to an external field. (c) 2006 Elsevier B.V. All rights reserved.

The phase relationship between langatate (LTG, La(3)Ta(0.5)Ga(5.5)O(14)) and associated phases was studied. Equilibrium solid phase tie lines were obtained for the ternary system La(2)O(3)-Ga(2)O(3)-Ta(2)O(5) by phase identification of sintered samples with various compositions through X-ray diffraction analysis. The solid solution range of LTG was determined in the temperature range of 1300-1350 degrees C. A new compound was identified that was stable above 1485 degrees C up to its melting point. Liquidus phases were investigated by in-situ observation of the crystallization process from melts having various compositions. Differential scanning calorimetry analysis was carried out to study the phase transitions associated with eutectic and peritectic reactions. On the basis of the results of these experiments, a primary phase diagram was established around LTG. It was concluded that LTG is an incongruent-melting compound and has a peritectic relation to LaGaO(3). (c) 2006 Elsevier B.V. All rights reserved.

The electric field required for the transformation of the melting state of langasite from incongruent into congruent was semi-quantitatively and quantitatively evaluated. Both evaluation methods demonstrated that the required electric field was on the order of 10(4)-10(5) V/cm. This was significantly higher than the external electric field of 600 V/cm, which was experimentally observed. This large difference was attributed to the possibility that nucleation occurred in the electric double layer, which could sustain a very large electric field. (c) 2006 Elsevier B.V. All rights reserved.

Segregation phenomenon of Ga in Czochralski (CZ)-Si crystal growth has been investigated. The effective segregation coefficient, k(eff), of Ga was obtained for different growth rates by assuming the simple relationship between the concentration of Ga in Si crystal and the bulk Ga concentration in. melt. Applying BPS theory to effective segregation coefficients which is valid for the melt-solidified fraction up to 0.38, an equilibrium segregation coefficient of Ga was obtained, k(0) = 0.0079. (c) 2006 Elsevier B.V. All rights reserved.

Raman backscattering measurements were carried out on Si crystals heavily doped with B and/or Ge over the temperature range from 123 to 573K. It was found that the frequency of the q approximate to 0 optical phonon in the Si crystals decreased almost linearly with increasing temperature, and the temperature coefficient depended on the B concentration. On the other hand, the change in frequency with temperature was relatively insensitive to Ge doping in comparison with B doping. However, heavy B and Ge codoping in Si resulted in a relatively larger temperature coefficient than B doping with the same B concentration. (c) 2006 Elsevier Ltd. All rights reserved.

The influence of applied loads and loading/unloading rates on pressure-induced phase transitions in lightly and heavily boron-doped silicon was systematically investigated. The resultant phases were plotted into two-dimensional maps with applied loads and loading/unloading rates as the coordinate axes. The formation region of the amorphous phase in the heavily boron-doped silicon was found to be much larger than that in the lightly boron-doped one, suggesting that heavy boron doping promotes the amorphization in silicon. (C) 2005 American Institute of Physics.

The imposition of an external electric field on a growth system affects the crystallization process in two manners: (i) the thermodynamic effect and (ii) the growth-dynamic effect. The former modifies the chemical potentials of associated phases in equilibrium which could convert the incongruent-melting state into congruent-melting state. Langasite (La3Ga5SiO14), an incongruent-melting material in the ternary system of La2O3-Ga2O3-SiO2, became congruent-melting under an external electric field of 600V/cm. This conversion was attributed to the inversion of the stability relationship in terms of the molar free energy between the primary phase in equilibrium with liquid and the liquid phase at the composition of langasite. Such a transformation is generally possible when the electrical permittivities of liquid, primary phase and incongruent-melting material increase toward the end component of the primary phase. (c) 2005 Elsevier B.V. All rights reserved.

A silica crucible with Ba doping at inner surface was used for growing a Czochralski Si (CZ-Si) crystal. Reaction at the interface between Si melt and a Ba-doped silica crucible was investigated. It was found that generation of brownish rings could be suppressed effectively by Ba doping with proper concentration. Almost no brownish rings formed at a silica crucible after Si crystal growth when Ba concentration was more than 100 ppm. Instead of the brownish rings, a white uniform cristobalite layer formed at the inner surface of the Ba-doped silica crucible. The surface of the cristobalite layer was very smooth and no traces of release of flakes or particles could be identified from the surface even after the Si crystal growth. (c) 2005 Elsevier B.V. All rights reserved.

Although langasite (La3Ga5SiO14) is an incongruent material, it can directly grow from the "pseudo-congruent melt" via the Czochralski method using a langasite seed crystal when the appropriate supercooling is provided. This may be explained by the extension of the univariant line of langasite+ liquid into the primary phase field of Ga-containing lanthanum silicate. Free energies serving to solute transport, growth kinetics, surface creation and defect generation are summed up to be the total supercooling necessary for growth which may be larger for the formation of Ga-containing lanthanurn silicate and smaller for langasite than the actual supercooling. The growth technology of 4-in-size crystal along [01 (1) over bar1] is optimized by understanding (i) the importance of the prior annealing of the melt to acquire the suitable supercooling for growth, (ii) the transform of the unstable growth interface, (01 (1) over bar1), into the complex of more stable principal planes, and (iii) the necessity of the accurate evaluation method to examine the homogeneity of the grown crystal. Issues of (i) and (ii) are interrelated. Physical crystal properties at high temperature are also demonstrated. (c) 2004 Elsevier B.V. All rights reserved.

Heavily B- and Ge-codoped Si wafers with and without swirl defects have been characterized in comparison with lightly B-doped and heavily B-doped Si wafers (with and without swirl defects) as references. It was found that only very few slip dislocations could be observed in the heavily B-and Ge-codoped (10(19) atoms/cm(3)) Si wafers whereas many slip dislocations were observed in both the heavily B-doped (10(19) atoms/cm(3)) and the lightly B-doped (10(15) atoms/cm(3)) reference wafers, after the same heat treatment had been carried out. On the other hand, much more slip dislocations occurred in the heavily B-doped Si wafers with swirl defects in comparison with that in the heavily B-doped Si wafers without swirl defects. The fact that almost no slip dislocations occurred in the heavily B-and Ge-codoped Si wafers in spite of swirl defects existingindicated that heavy B and Ge codoping in Si wafers had an effect on suppressing dislocation generation as well as suppressing generated dislocations propagating. This indicates that heavily B-and Ge-codoped Si wafers have the highest resistance to thermal stress, and are thus called robust Si wafers. (C) 2004 Elsevier B. V. All rights reserved.

The significance of an electric field on the crystallization process is differentiated into two consequences; (i) thermodynamic effect and (ii) growth-dynamic effect. The former modifies the chemical potential of the associated phases which changes the equilibrium phase relationship while the latter influences the solute transport, growth kinetics, surface creation and defect generation during growth. The intrinsic electric field generating during growth is attributed to the crystallization-related electromotive force and the thermoelectric power driven by the temperature gradient at the interface which influences the solute transport and solute partitioning. The external electric field was applied to the growth apparatus in the ternary system of La2O3-Ga2O3-SiO2 so that the chemical potential of both solid and liquid phases changed leading to the variation of the equilibrium phase relationship. Imposing a 500 V/cm electric field on the system moved the boundary of primary phase field of lanthanum gallate (LaGaO3) and Ga-bearing lanthanum silicate (La14GaxSi9-xO39-x/2) toward the SiO2 apex by 5 mol% which clearly demonstrated the change of the phase relationship by the external electric field. (C) 2004 Elsevier B. V. All rights reserved.

2-inch langasite (La3Ga5SiO14) single crystals were grown for the first time via a vertical Bridgman method, assisted by the accelerated crucible rotation technique (ACRT) along [0001] (Z-axis), [2 (1) over bar(1) over bar0] (X-axis) and [01 (1) over bar1] (54degrees-rotated Y-axis) for piezoelectric applications. Because of the possible liquid immiscibility, incongruency and segregation, secondary phases other than langasite are formed during growth. The mode of occurrence of these phases was closely related to the interface instability that was specific to the growth direction. The formation of inclusions consisting of lanthanum gallate (LaGaO3), aligned parallel to (01 (1) over bar0), was associated with the constitutional supercooling. The residual products during the terminal transient were the mixture of gallium oxide (Ga2O3) and lanthanum gallate (LaGaO3) or the mixture of gallium oxide and lanthanum silicate (La2Si2O7) reflecting the position of the initial melt, relative to the tie line connecting the langasite solid solution with gallium oxide in the system of La2O3-Ga2O3-SiO2. The homogeneity of the grown crystal was evaluated by the distribution of SAW velocities of the devices fabricated on the (01 (1) over bar0) wafer, as well as by the uniformity of d-spacing of 05 (5) over bar5. (C) 2004 Elsevier B.V. All rights reserved.

Three types of etch defects were observed on a (0 0 1) lithium tetraborate (Li2B4O7:LB4) single crystal wafer. Type I appeared all over the +c plane taking a four-sided pyramidal shape. The etch defects on the -c plane were differentiated into two types; Type II corresponded to dislocation arrays and presented a four-sided pyramidal shape while Type III was distributed all over the -c plane, forming a eight-sided hillock. After annealing the wafer at 850 degreesC in several different atmospheres, the density of Types I and II did not change while that of Type III was reduced by two order of magnitude in the oxygen atmosphere. This might suggest that the formation mechanism of each of these defects was different and they showed the various motions for the thermal treatment. (C) 2004 Elsevier B.V. All rights reserved.

A wireless surface acoustic wave (SAW) temperature sensor was produced using langsite single crystal as a piezoelectric substrate. The properties of both solid-electrode and split-electrode interdigital transducers (IDTs) were studied by fitting the admittance curves. A miniature antenna was used and the impedance matching technique between the antenna and the IDT was investigated. The temperature characteristic in the temperature range of 20-700degreesC was measured. The results showed that both the SAW chip and the antenna functioned in this temperature range.

This paper presents advanced techniques to determine all independent elastic-stiffness coefficients C-ij, the associated internal friction Q(ij)(-1), and piezoelectric coefficients e(ij) of monocrystal langasite (La3Ga5SiO14) using a single rectangular parallelepiped specimen. Langasite's crystal structure belongs to the trigonal system with point group 32, thus six independent Cij, two eij, and two dielectric coefficients epsilon(ij). All of the elastic and piezoelectric coefficients affect the mechanical resonance frequencies of the solid specimen, and measuring them very accurately permits one to determine the Cij and eij with known density, dimensions, and epsilon(ij). We developed a piezoelectric tripod to support the specimen upward and measured the free-vibration resonance frequencies with minimum load from its own weight. This weak and stable acoustic coupling ensures high accuracy of the frequency measurement better than 10(-5), being enough to determine the reliable coefficients. Our Cij fall in the range of results measured with previous (conventional) methods. Our ell is smaller than the reported values by 1.2-13%, and e(14) is larger than those by 44-97%. For the internal friction measurement, we used a solenoid coil to vibrate the specimen without any contact. The longitudinal-wave internal friction considerably exceeds the shear-wave internal friction, which can be interpreted as phonon-phonon interactions.

Phase relations around langasite (LGS, La(3)Ga(5)SiO](4)) were studied on the basis of phase assemblage observed during calcination and crystallization process of samples of various compositions in the ternary system La(2)O(3)-Ga(2)O(3)-SiO(2). A ternary compound of apatite structure, La(14)Ga(x)Si(9-x)O(39-x/2) was found for the first time. Crystallization of this compound was observed in the cooling process of molten samples of stoichiometric LGS as well as LGS single crystal, demonstrating that LGS is an incongruent-melting compound. A phase diagram was established primarily based on the crystallization sequence in the cooling process. (C) 2003 Elsevier Science B.V. All rights reserved.

Resonant ultrasonic loss Q(-1) in piano-convex unplated Y-cut disks of langasite and langanite was measured as a function of frequency and temperature with the aim of identifying dominant internal mechanisms that will degrade the performance of electronic oscillators. In both materials, the dependence on temperature is similar to that previously reported for langatate. An anelastic peak appears with maxima in the 150-280 K range at frequencies between 2 MHz and 14 MHz. The dependencies of this peak on temperature and frequency is consistent with a point-defect relaxation. The width of the peak is greater than that of a Debye peak, which indicates that the relaxation has a distribution of activation energies. The peak appears at higher temperatures in langasite than in langatate, and this may explain the lower room-temperature Q(-1) reported thus far in langatate. Additional anelastic peaks appear at elevated temperatures. The peaks are superimposed on a component of the loss that increases monotonically with temperature according to an approximate Arrhenius expression.

A macro defect-free langasite (La3Ga5SiO14) Crystal in 4" diameter was grown along [0 0 0 1] and [0 1 (1) over bar l] directions by the Czochralski technique. The interface during growth was a faceted plane of (0 0 0 1) for the [0 0 0 1] growth while (0 1 (1) over bar l) interface plane was decomposed into (0 0 0 1) and (0 1 (1) over bar l) making a rough interface for the [0 1 (1) over bar l] growth. For the latter growth, the interface was convex toward the melt and the degree of convex was determined by the mode of dissolution of these two planes which was controlled by the radial and axial temperature gradients in the melt near the interface. The volume defect that was initiated at secondary phases occurred when the melt was away from the congruent melt composition. The homogeneity in composition was discussed in association with the relationship between SAW velocity, d-spacing of a specific plane and chemical composition. The congruent melt composition is close to a stoichiometric composition and was found to be a slightly rich in Ga component by examining the compositional variation in both crystal and residual melt during growth. The simple and easy way by use of bulk wave was demonstrated for the measurement of the uniformity of wafers fabricated from grown crystals. (C) 2002 Elsevier Science B.V. All rights reserved.

0312Rev

In this study, we carried out experimental research on the directivity of surface acoustic wave (SAW) filters with Al, W and Ta electrodes formed on langasite single-crystal wafers, in order to find electrode materials that make the natural unidirectionality disappear. The results proved that by using W and Ta, the natural unidirectionality disappears at the normalized thickness (<I>h</I>/λ) of 0.033-0.037. This suggests a potential application of these metals as electrode materials for langasite-based SAW filters so that the design process of the single-phase unidirectional transducer (SPUDT) filter can be simplified by using tools for conventional SPUDT filters.

In this study, we carried out experimental research on the directivity of surface acoustic wave (SAW) filters with Al, W and Ta electrodes formed on langasite single-crystal wafers, in order to find electrode materials that make the natural unidirectionality disappear. The results proved that by using W and Ta, the natural unidirectionality disappears at the normalized thickness (h/,lambda) of 0.033-0.037. This suggests a potential application of these metals as electrode materials for langasite-based SAW filters so that the design process of the single-phase unidirectional transducer (SPUDT) filter can be simplified by using tools for conventional SPUDT filters.

A characterization technique for homogeneity of piezoelectric wafers utilizing bulk-wave measurement was established. and measurements were carried out on langasite (LGS: La3Ga5SiO14) wafers fabricated in our laboratory. The technique is capable of predicting the homogeneity of the phase velocity of a surface acoustic wave (SAW), which determines the deviation of the central frequencies of SAW devices, by measuring the distribution of the frequency constant of thickness-shear mode resonance. The frequency constant, measured by a combination of resonance frequency measurement and thickness measurement in a single wafer, yields a relative accuracy of about +/- 55 ppm. The distribution of the frequency constant is consistent with that of the phase velocity of SAW obtained by fabricating and measuring SAW devices. The method is both rapid and nondestructive. thus is suitable for routine characterization in the production of piezoelectric wafers. Characterization of langasite wafers using this technique correlated inhomogeneity to the growth conditions of the crystal.

Congruent-melting composition of langasite (La(3) Ga(5) SiO(14)) was studied by a combination of melting-point measurement, crystal growth and compositional characterizations. The melting points of sintered samples with various compositions within the solid solution range determined by X-ray diffraction (XRD) around the stoichiometric composition were measured by differential thermal analysis (DTA). Upon the growth of single crystals from the compositions with the highest melting point, the compositions of various parts of the crystals and residual melts were investigated by X-ray fluorescence spectrum (XFS). The congruent-melting composition was determined to be the composition from which a minimum deviation of composition of both the crystal and the residual melt was obtained. (C) 2000 Elsevier Science B.V. All rights reserved.

A new nondestructive evaluation method for surface acoustic wave (SAW) velocity on a piezoelectric wafer was proposed. Split electrodes were formed on a glass wafer and a nonconductive liquid was interposed between the piezoelectric wafer and the glass wafer. The mode of the SAW excited on the piezoelectric wafer surface was leaky (LSAW) and its velocity was evaluated using the electrical reflection characteristics of the split electrodes. The usefulness of the new method was experimentally proven by showing the high reproducibility of the measured velocity and the agreement between the measured and calculated values indicating the SAW characteristics on a rotated-Y langasite wafer.

A Macro defect-free langasite (La_3Ga_5SiO_<14>) crystal 3" in diameter was grown along its Z-axis by the conventional Czochralski technique. The grown crystal represents clear faceting on (0001) and (011^^-0) faces, forming a basal Z plane and hexagonal columnar Y plane, respectively. Holding melt at the temperature close to the equilibrium melting temperature makes the supercooling degree appropriate for the development of the (0001) facet plane. A good balance between convection and surface stability of (0001) plane leads to the uniform interface during growth. The homogeneity in composition was investigated two-dimensionally by the X-ray Bond diffraction method. The congruent melt composition for langasite is also discussed relative to the stoichiometric composition.

A macrodefect-free langasite (La3Ga5SiO14) crystal 3 " in diameter was growth along its Z-axis by the Czochralski technique. The grown crystal showed clear faceting on (0001) and (01 (1) over bar 0) faces, forming a hexagonal column shape, and it had minor faceting on (01 (1) over bar 1) in the conical part, making a stepped hexagonal pyramid. Thermal treatment of the melt and uniform interface shape are important to the growth of langasite with stable facet development. Interface instability occurred during the formation of the conical portion of the crystal under a high crystal rotation rate. The homogeneity in composition was investigated two dimensionally by the X-ray Bond diffraction method. The congruent melt composition for langasite is also discussed relative to the stoichiometric composition. (C) 2000 Elsevier Science B.V. All rights reserved.

Ti:LiNbO3 waveguide polarizers were obtained by an epitaxial growth of a Zn-doped LiNbO3 layer on the Ti:LiNbO3 waveguide. The film growth was carried out by a liquid-phase-epitaxy technique using a Li2O-V2O5 flux. Such an X-cut waveguide polarizer achieved a TE-mode (extraordinary ray) propagation with an extinction ratio over 30 dB at a light wavelength of 1.55 mu m. This technique can be easily applied to Z- and Y-cut waveguide polarizers with TM- and TE-mode propagation, respectively. (C) 2000 American Institute of Physics. [S0003-6951(00)02112-4].

The surface damage thresholds of Li2B4O7 crystals, nonlinear crystals used in ultraviolet (UV) solid-state lasers, were measured and found to be 8.4 GW/cm(2) at 1064 nm, 1.9 GW/cm(2) at 532 nm, and 0.83 GW/cm(2) at 266 nm. The damage threshold at 1064 nm was 1.5 times higher than that of fused silica. In addition, the direction dependence of the damage threshold was {1 1 0} &gt; {0 0 1} &gt; {1 0 0}. No color center was generated in the crystal after 20 W/cm(2), 10(7) shots irradiation of KrF and ArF excimer lasers. The excellent damage threshold and radiation resistance of Li2B4O7 were attributable to its wide band gap and relatively few defects in the crystal. (C) 1999 Elsevier Science B.V. All rights reserved.

Macro defect-free langasite (La3Ga5SiO14) of 3" diameter was grown by the Czochralski technique. Thermal treatment of the melt and a uniform interface shape are important for langasite growth with a clear habit of faceting. The homogeneity in composition was two-dimensionally investigated by X-ray diffraction analysis and SAW (surface acoustic wave) velocity distribution on the wafer fabricated from the crystal. The deviation was sufficiently small for the use of langasite as a suitable substrate in SAW device applications. SAW properties were calculated based on the available material constants.

The scatterers observed in the Li2B4O7 crystals grown in the optically useful direction showed Mie scattering. The polarization mode of the scattering light depends on the relative configuration of the incident beam and the crystal direction. The scattering sources were proven to be sub-micron bubbles which can be attributed to water in the melt. The scattering-free Li2B4O7 crystals 2 " in diameter and 70 mm in length were successfully grown in dry air. The formation mechanism of bubbles was discussed. (C) 1999 Published by Elsevier Science B.V. AU rights reserved.

A body-centered-cubic (BCC) lattice model with realistic many-body interactions is introduced and investigated by means of the Metropolis' Monte Carlo method to describe both crystalline and molten states of Si. Under the simplest assumption that atoms surrounded by tetrahedral first-neighbors only have an energy lower than the other atoms, a clear first-order phase transition including hysteresis is observed between a solid with diamond structure and a melt. Nucleation and domain growth are dynamically observed in certain range of the supercooling. In order to introduce more realistic and accurate lattice-gas models, the Tersoff potential is renormalized and the interactions are mapped onto a BCC lattice. Then, it is found that the phase transition temperature and other thermodynamic properties are dramatically improved compared with the case using the Tersoff potential directly in the lattice model without renormalization. (C) 1999 American Institute of Physics. [S0021-9606(99)51318-4].

A body-centered-cubic (BCC) lattice model with realistic many-body interactions is introduced and investigated by means of the Metropolis' Monte Carlo method to describe both crystalline and molten states of Si. Under the simplest assumption that atoms surrounded by tetrahedral first-neighbors only have an energy lower than the other atoms, a clear first-order phase transition including hysteresis is observed between a solid with diamond structure and a melt. Nucleation and domain growth are dynamically observed in certain range of the supercooling. In order to introduce more realistic and accurate lattice-gas models, the Tersoff potential is renormalized and the interactions are mapped onto a BCC lattice. Then, it is found that the phase transition temperature and other thermodynamic properties are dramatically improved compared with the case using the Tersoff potential directly in the lattice model without renormalization. (C) 1999 American Institute of Physics. [S0021-9606(99)51318-4].

The propagation characteristics of Rayleigh waves on a Y-rotated La3Ga5SiO14 (langasite) substrate are evaluated with the use of newly obtained material constants. The calculated phase velocity, the power flow angle (PFA), the coupling electromechanical coefficient (K-2), the temperature coefficient of delay (TCD) and the diffraction coefficient (gamma) are shown as contour maps. The revised numerical calculations were in much better agreement with the experimental results of the temperature characteristics on the langasite substrate with Euler angle (0 degrees, 140 degrees, phi). Moreover, the temperature characteristics as a function of the metal thickness were experimentally investigated. It was found that a thicker metal leads to a lower turnover temperature. Finally, an example of the frequency response of the transversal filter designed for IS95 is shown.

Lithium tetraborate Li2B4O7 (LB4) has proved to be very promising for the generation of the fourth and fifth harmonics of Nd:YAG lasers. The birefringence of LB4 is higher than that of LBO. LB4 is negative uniaxial and belongs to the 4 mm point group which means that its effective nonlinearity is maximized under the conditions of 90° phase-matching. The clear transmittance spans from 170 nm to 3300 nm. We demonstrate sum-frequency generation of tunable VUV femtosecond pulses with LB4 from 185 nm down to 170 nm (7.3 eV), the lower limit being set by the available fourth harmonic tunability. A comparison with an LBO reference sample reveals that LB4 has a superior performance in the VUV spectral region below 180 nm.

Conference Information: 1999 IEEE Ultrasonics Symposium. Proceedings. International Symposium<br /> Caesars Tahoe, NV, USA, 17-20 October 1999<br /> Ultrasonics, Ferroelectr., &amp; Frequency Control Soc

In spite of their superior laser and polarizer properties rare-earth orthovanadates (REVO4) single crystals have not been adopted yet into extensive industrial applications because of crystal growth difficulties. The main problems of CZ technique are compositional change and diameter instability. This work presents the first attempt to apply the edge-defined film-fed growth (EFG) technique by which well-shaped REVO4 crystals have been grown directly. The capillary properties of WO4 and GdVO4 melt have been measured. The applicability of shaped growth for rare-earth orthovanadate family was approved by successful EFG growth of transparent rod-like macro-defect-free single crystals of YVO4 and GdVO4. We address two main approaches to enhance the quality of EFG crystals: (i) meniscus and crystal shape stability dependence on die top shape and (ii) the strategy of effective operating control. Concave die top was found to be the best choice for high-quality EFG growth of REVO4 along [001] direction. The spectral analysis of weight signal from growing crystal was shown to be a useful feedforward clue to prevent crystallinity degradation at a very early stage. A reasonable stability of the EFG process was achieved using [211], [101], [001] and [100] pulling directions.

We investigate and characterize the newly grown crystal Li2B4O7 which is transparent down to 160 nm for nonlinear optical conversion into the vacuum ultraviolet using sum frequency mixing with femtosecond pulses. This material exhibits excellent properties below 180 nm and makes possible the generation of wavelengths down to 170 nm with an all solid state laser system. The most important advantage of Li2B4O7 in this spectral range turns out to be the possibility of utilizing noncritical phase matching with maximized effective nonlinearity. We demonstrate generation of nearly transform limited 100 fs pulses between 170 and 185 nm with conversion efficiency of 4%. Their peak powers range from 200 kW at 170 nm &gt;2 MW at 185 nm. (C) 1998 American Institute of Physics. [S0021-8979(98)07523-9]

Li2B4O7 crystals, nonlinear crystals used in ultraviolet solid-state lasers, were grown by the Czochralski method in appropriate directions for the low-cost production of devices for fourth- and fifth-harmonic generation of a Nd:YAG laser. The crystals were 2 " in diameter and 55-70 mm in length. The homogeneity of the refractive index in both crystals was good, and the refractive index variation did not depend on the pulling direction. However. significant scattering of the injected light beam was observed in a crystal grown in rite fifth HG direction, and the laser damage threshold of the crystal decreased. (C) 1998 Elsevier Science B.V. All rights reserved.

Theoretical analysis of the micro-pulling-down process for the growth of GexSi1-x single crystal fibers is conducted using a finite-volume/Newton's method. Steady-state heat and nondilute solute transfer, melt flow, the melt/crystal interface, and the free surface as well as the grown fiber diameter are solved simultaneously. The effects of process parameters including the melt height, the die temperature, and the growth rate on the grown fiber diameter and solute distribution are investigated. Good agreement is found for the calculated meniscus shape and the grown fiber diameter with the observed ones. In the melt zone, due to the small physical dimension and the damping effect by Ge, buoyancy convection is negligible. However, Marangoni convection is dominant there and the solute segregation is thus affected. As the melt zone becomes shorter with the decreasing die temperature, a secondary flow is induced by the Marangoni convection leading to an inversion on radial segregation and a large depletion of Ge in the fiber core, which are consistent with the measurements. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

A new type of monomorph actuator has been produced that uses twinned lithium tetraborate, a paraelectric piezo-crystal, to improve the hysteresis and creep in conventional actuators employing ferroelectric materials. Its characteristics have been examined in comparison with other actuators. The piezoelectric constant (d31) for this actuator is derived from measurements and compared with the calculated value. (C)1998 Scripta Technica.

The transparent rod-like macro-defect-free single crystals of YVO4 and GdVO4 have been successfully grown by EFG technique. Basic properties of EFG crystals have been investigated in connection with growth interface morphology. The origin of asymmetric radial growth phenomena for both EFG and CZ growth of REVO4 is discussed. Finally, the quality of EFG crystals is marked as comparable to CZ crystals. © 1998 Elsevier Science B.V. All rights reserved.

Platinum dendrites were found in lithium tetraborate crystals grown by the Czochralski method using a platinum crucible. The mode of occurrence and formation mechanism of platinum dendrite in lithium tetraborate were examined. It is revealed that platinum dendrites developed in the cellular structure that occurred during growth. The formation of platinum dendrite that is discussed is associated with the growth condition leading to cellular growth. The morphology of platinum dendrite is also explained by its specific crystallographic symmetry. (C) 1998 Elsevier Science Ltd.

The influence of the additive SO3 on the phase relationships in the quaternary system CaO-SiO2-Al2O3-Fe2O3 was investigated by observing the change of volume ratio of 3CaO . SiO2 (C3S) to 2CaO . SiO2 (C2S) + CaO (C) in the sintered material with the increase of SO3 content. The primary phase volume of C3S in the quaternary phase diagram shrank with the increase of SO3 and disappeared when the SO3 content exceeded 2.6 wt% in the sintered material, Changes in the peritectic reaction relationship between CaO (C), 2CaO . SiO2 (C2S), 3CaO . SiO2 (C3S), 3CaO . Al2O3 (C(3)A), 4CaO . Al2O3 . Fe2O3 (C(4)AF), and liquid were also observed and discussed.

The refractive indices of Li2B4O7 crystal were measured for both ordinary and extraordinary beams in the range of 184.887 nm-2325.42 nm, and the Sellmeier equations were derived from these results. Li2B4O7 crystal has a suitable phase-matching condition in the ultraviolet range and the shortest SHG output wavelength of 243.8 nm. Considering also its short-wavelength cutoff and low scattering, Li2B4O7 crystal is an excellent nonlinear optical crystal for an ultraviolet solid-state laser. (C) 1998 Elsevier Science Ltd. All rights reserved.

The influence of an interface electric field on the solute partitioning during LiNbO3 single crystal fiber by micro-pulling-down method has been studied. Thermoelectric power was a dominant cause of the electric field, and the Seebeck-effect-induced electric field was measured in the solid near the interface along the axial as well as radial directions. Solute partitioning was subject to these interface field effects. Mn was rich in the core of the Mn-doped LiNbO3 crystal fiber of small diameter, which was two dimensionally analyzed to predict the redistribution of the ionic solute by an interface electric field. The inversion of the radial temperature gradient in the molten zone was specific to the micro-pulling-down method and suppressed the radial thermoelectric power in the liquid, which consequently led to the rather homogeneous radial solute distribution in the solid.

Pseudobinary compounds of column III elements and nitrogen are semiconductors widely studied for optoelectronic applications. Ga1-xBxN compounds are considered to be prone to phase separation due to the large difference in bond length between B-N and Ga-N. However if a sufficient amount of boron can be incorporated to Ga1-xBxN compounds, lattice matching with substrates such as SiC, AlN and Ga1-xAlxN may be achieved. We used molecular beam epitaxy to grow Ga1-xBxN films on sapphire c faces with various values of x. Single-phase wurtzite Ga1-xBxN with x up to 4.56% has been obtained.

たわみモードアクチュエータは, 比較的低電圧で駆動でき, 大きな変位量が得られ, 構造が簡単であるため, 種々のデバイスに応用されている. 近年, このたわみモードアクチュエータに, クリープ更にはヒステリシスのないモノモルフ形が報告され, 注目されている. これらの材料は, 強誘電体の単結晶またはセラミックスである. 本研究では, 常誘電体結晶(四ホウ酸リチウム)の双晶を用いたモノモルフ形たわみモードアクチュエータを作製し, このアクチュエータの印加電圧と変位との線形性, 径時変化等を測定した.

信学技報<br /> OME97-88, OPE97-77

The parameters in the Sellmeier equation for langasite are accurately obtained on the basis of the measurement of the ordinary and extraordinary refractive indices in the region of 500 nm to 2500 nm, and the phase-matching of langasite is investigated. The second harmonic generation (SHG) of langasite is also examined by the Maker fringe method.

Lithium tetraborate (Li2B4O7) has attracted much attention as a surface acoustic wave substrate for high-frequency use and its excellent nonlinear optical properties have been recently found. In the present report, the main crystalline defects observed by X-ray topography in Li2B4O7 (110) wafers grown by the Bridgman method and by the Czochralski method are presented. The main trends observed are a majority of dislocations in {112} planes, a minority of dislocations in the {111} planes, and low-angle grain boundaries in both {111} and {112} planes.

The heteroepitaxial growth of hexagonal ErF3 onto CaF2(1 1 1) substrates using the molecular beam epitaxy (MBE) method is reported for the first time. Results of the X-ray rocking-curve (XRC) analyses showed the presence of the epitaxial relationship as (0 0 0 1)(ErF3)parallel to(1 1 1)(CaF2). Reflection high-energy electron diffraction (RHEED) investigation suggests the growth of hexagonal metastable ErF3 with the epitaxial relationship of (0 0 0 1)(ErF3)parallel to(1 1 1)(CaF2), (0 1 (1) over bar 0)(ErF3)parallel to(1 1 (2) over bar)(CaF2), ((2) over bar 1 1 0)(ErF3)parallel to(0 (1) over bar 1)(CaF2). Detailed analysis of RHEED pattern elucidates that the metastable ErF3 has the space group setting of P6(3)/mmc, and among the several models proposed for LaF3-type structure, this setting is the unique one which is consistent with the observation of RHEED patterns. The up-conversion property of ErF3 for green-light emission (lambda = 538 nm) pumped by an AlGaAs diode laser (lambda = 798 nm) is investigated.

A novel technique for single-crystal fibers cladding immediately in the course of the growth process based on the micro-pulling-down (mu-PD) method has been proposed and verified. The principle of the double-die-mu PD implies that the capillary nozzle provides capillary feeding to the growing fiber simultaneously from the inner pipe channel with undoped melt and from the outer surface with doped melt. The menisci shape, melt flow outside the nozzle, control of the doped/undoped melt ratio and process stability are discussed in terms of capillarity. Examples of practical crucible design are discussed in connection with radial dopant distribution. Mn-doped lithium niobate fiber, 0.5 and 0.7 mm in diameter, having 40-60 mu m doped outer area were grown successfully.

During the growth of Mn : LiNbO3 crystal fiber by the micro-pulling down method, the solute partitioning is greatly influenced by the interface electric field mainly caused by the large temperature gradient at the interface. This was experimentally and analytically studied for the initial transient, steady-state and terminal transient solute redistribution based on the concept of a field-modified partition coefficient, k(E0), and an effective growth velocity, V-Ei. The field-modified effective partition coefficient, k(E), becomes larger than unity in the steady state although its equilibrium partition coefficient, k(0) &lt; 1.0, which consequently leads to the Mn concentration deficiency in the solid during the terminal transient. There is a critical growth velocity, V-double dagger, below which the effective growth velocity, V-Ei, and the field-modified equilibrium partition coefficient, k(E0), take negative value in which cases the positive ions such as Mn4+ move away from the interface.

The heteroepitaxial growth of hexagonal ErF3 onto CaF2(1 1 1) substrates using the molecular beam epitaxy (MBE) method is reported for the first time. Results of the X-ray rocking-curve (XRC) analyses showed the presence of the epitaxial relationship as (0 0 0 1)(ErF3)parallel to(1 1 1)(CaF2). Reflection high-energy electron diffraction (RHEED) investigation suggests the growth of hexagonal metastable ErF3 with the epitaxial relationship of (0 0 0 1)(ErF3)parallel to(1 1 1)(CaF2), (0 1 (1) over bar 0)(ErF3)parallel to(1 1 (2) over bar)(CaF2), ((2) over bar 1 1 0)(ErF3)parallel to(0 (1) over bar 1)(CaF2). Detailed analysis of RHEED pattern elucidates that the metastable ErF3 has the space group setting of P6(3)/mmc, and among the several models proposed for LaF3-type structure, this setting is the unique one which is consistent with the observation of RHEED patterns. The up-conversion property of ErF3 for green-light emission (lambda = 538 nm) pumped by an AlGaAs diode laser (lambda = 798 nm) is investigated.

The problem of increasing yellow coloration of PbWO4 crystal grown from the melt has been analyzed using a micro-pulling down technique. The ratio of free surface area to melt volume in mu-PD growth is noticeably higher in comparison with CZ method. The incongruent vaporization of PWO melt generates changes in stoichiometry and subsequently causes difficulties for crystal growth from tungsten-excess melt.

We have successfully grown macro-step-free dysprosium vanadate (DyVO4) single crystals by a modified Czochralski technique in which a steep temperature gradient was maintained at the interface during growth. The crystals showed remarkable spiral bending. In order to suppress the spiral bending, we have investigated the growth of (Dy1-xGdx)VO4 crystals. Substitution of dysprosium with gadolinium was found to be effective for the suppression of spiral bending. The weight ratio of spiral-free portion of grown crystals increased depending on the gadolinium concentration. Grown(Dy1-xGdx)VO4 crystals were compositionally homogeneous.

A 2 in. diam single crystal of lithium tetraborate (Li2B4O7) was successfully grown by the Czochralski method. The crystal was free from macrodefects and had a dislocation density as low as 100/cm(2). It had an excellent homogeneity of the refractive index and a wide transparency down to 170 nm. The optical damage threshold was 40 GW/cm(2). Second-harmonic generation and sum frequency generation were investigated in association with the generation of the fourth and fifth harmonics of a e-switched Nd:YAG laser. The conversion efficiency of the second-harmonic generation from the green (532 nm) light was 20%. (C) 1997 American Institute of Physics.

Homogeneity of potassium lithium niobate single-crystal fibers grown by micro-pulling-down technique is examined via second-harmonic-generation measurement both in axial and radial directions, It is found that fluctuation of phase-matching wavelength along the growth axis is small and independent of growth rate. On the other hand, relatively large variation of phase-matching wavelength is found along the radial direction. The phase-matching wavelength shows its minimum around the center of the section of the fiber and increase toward the periphery. Compositional inhomogeneity and internal strain in the radial direction are investigated in association with variation of phase-matching wavelength. X-ray rocking-curve analysis, absorption measurement and polarized beam transmittance are also reported.

The problem of SiC precipitation during micro-pulling-down growth of Si-Ge mixed crystals has been analyzed as an important constraint of the technique. Three mechanisms of SiC microcrystal formation have been discussed. The solute transport in the melt and the dependence of the rate of Si-Ge melt evaporation on melt composition have been investigated. The troublesome influence of CO on SiC formation has been reduced by modification of the micro-pulling-down (mu-PD) growth assembly with optimization of argon flow. As a result the effective lifespan of the crucible was increased at least fivefold.

Comparison of the resonance frequency of surface acoustic wave (SAW) resonators fabricated on defect-free and highly defective lithium tetraborate wafers was attempted. The intrinsic variation of SAW velocity due to crystal defects, impurities and chemical compositional inhomogeneities for lithium tetraborate wafers is smaller than +/-0.011%. In addition, the variation of SAW velocity in a wafer is influenced by the device fabrication process rather than the lithium tetraborate substrate quality.

A new lattice model is proposed for Si crystallization from molten state, which is based on Monte Carlo (MC) simulation. In this model, each atom is allowed to move only on BCC lattice sites, and the potential energy of atom depends on the configuration in the Ist nearest neighbors. With the parameter that only the atoms constructing tetrahedron have lower energy than others, the Ist-order phase transition between diamond and random structures is observed, including a hysteresis behavior. On the other hand, with using a parameter set which is defined as a function of the number of the Ist nearest neighbors and the bond angles, which is determined by using genetic algorithm, the state is continuously changed with temperature.

The influence of cluster size on nucleation rate was discussed based on the cluster-size- dependent entropy of the melt of which derivation is precisely reviewed. The model is useful for the estimation of the free energy of thermally treated melts. The increase of the cluster radius in the melt by 3 % caused by the decrease of the melt soaking temperature from 1050 to 950 degrees C potentially leads to the 8 degrees C degree increase of the equilibrium melting temperature and 40 degrees C increase of the solidification temperature of melt provided that the melt quenched down close to the phase transition temperature holds its initial structure at the soaking temperature.

Congruent melt composition for Li2B4O7 single crystal growth was investigated by surveying the residual melt obtained after the quick growth of Li2B4O7 polycrystals under strong stirring in the melt. Residual products were examined by X-ray diffraction (XRD) and differential thermal analysis (DTA) to determine if there were phases formed other than Li2B4O7, which represents the crystallization from the off-congruent melt. This ''residual melt'' method confined the congruent composition within the range of 33.232-33.537 mol% Li2O in which the stoichiometric composition, 33.334 mol% Li2O, lies. Thus, the congruent melt composition is very close to the stoichiometric composition for Li2B4O7 within the error range of 0.2 mol% Li2O. The solid solution range of Li2B4O7 in the Li2O-rich side is constrained to be less than 0.35 mol% Li2O by investigating the solubility limit of Li2O into the Li2B4O7 phase.

Lasers and Electro-Optics, 1997. CLEO/Pacific Rim &#039;97., Pacific Rim Conference on<br /> 14-18 July 1997

Monocrystalline Er3+-doped LaF3 layers were heteroepitaxially grown on CaF2 (111) substrates with an Er3+ concentration of up to 38.7 mol% by molecular beam epitaxy. The hexagonal crystal structure of LaF3 was confirmed from the beginning of the layer formation by RHEED patterns. Green light emission at 538 nm was generated by upconversion employing near 800 nm pump wavelengths from a Ti:sapphire laser. The maximum emission intensity of green light was obtained at an Er3+ concentration of 11 mol%, which was several times higher than that obtained from an Er3+-doped CaF2 film on CaF2 (111). This is discussed in relation to the effect of the heavy mass of La on the emission mechanism.

The Ge distribution in both melt and crystal was analyzed for the growth of Si1-xGex (x = 0.05) single crystal fibers by the micro-pulling down (mu-PD) method. The solute accumulation volume in the vicinity of the interface comprises the molten zone (zone I) next to the interface and the capillary zone (zone II) leading to the bulk melt, A steady-state solution was given for each of these two zones and the initial transient analysis lead to the equilibrium partition coefficient, k(0) and diffusion constant, D, for Ge in the S1-xGex (x = 0.05) melt to be 0.43 and 5.6 x 10(-5) cm(2) s(-1), respectively. A sudden change of either the growth velocity or the molten zone volume size during steady-state growth yields an abrupt change of Ge distribution, and its change mode is interpreted in terms of the degree of imbalance of the Ge mass flow between zone I and zone II at the zone boundary. It is, therefore, suggested that the desired impurity distribution in a Si single crystal fiber can be designed by the manipulation of the imbalance of the impurity mass flow at the zone boundary.

Twinned Li2B4O7 crystals have been successfully grown by the Czochralski (CZ) method. Parameters necessary for the reproducible growth of twinned Li2B4O7 crystal have been also investigated. A piezoelectric bimorph actuator using twinned Li2B4O7 crystal has been produced. It is confirmed that this actuator shows an excellent linearity between the applied voltage and displacement.

信学技報<br /> US92-21, EMD96-16, CPM96-39

Silicon single crystal fibers with a constant diameter as small as 200 mu m have been successfully grown by the micro pulling down technique. Grown crystal fibers are uniform in shape and contain a large defect-free volume. Basic parameters for stable growth were discussed in association with the conservation of mass and heat as well as the meniscus stability of the molten zone.

It has been experimentally revealed that the variation of surface acoustic wave (SAW) velocity in lithium tetraborate crystals is smaller than that in other SAW crystals. This may relate to the small deviation of lattice constant due to the little change in chemical composition of the wafer. Such homogeneity can be explained by the specific compositional properties of Li2B4O7 crystal and its melt.

Monocrystalline Er3+-doped CaF2 layers are grown on CaF2 substrates by molecular beam epitaxy (MBE) with Er3+ concentration up to 31.2 wt%. The lattice parameter and the crystallinity of the epilayers are investigated by X-ray diffraction analysis, electron probe microanalysis, and scanning electron microscopy. Green light emission at 538 nm is generated by upconversion for the first time: using a 798 nm laser diode pump. Maximum emission intensity at this wavelength is obtained at an Er3+ concentration of 13.3 wt%.

The influence of the cluster size on the physical properties of the melt, i.e., homogeneous nucleation rate, critical radius, supercooling degree for crystallization, etc., has been studied by investigating the crystallization temperatures from the quenched glass made out of several Li_2B_4O_7 melts which were initially soaked at various temperatures. The theoretical modeling of the cluster-size-dependent entropy of the melt has been developed based on the classical homogeneous nucleation theory, which well explains the experimental relationship between the crystallization temperature and the melt soaking temperature, provided that the quenched glass retains the melt structure at the soaking temperature. The discussion made here is applicable to growth from solution as well as growth from gaseous phase.

We have successfully grown Nd3+-doped gadolinium vanadate (Nd:GdVO4) single crystals by a modified Czochralski method in which a high temperature gradient was maintained at the interface during growth. Step faceting occurred during crystal growth and the cause of the faceting is discussed in relation to the growth conditions. Laser diode (LD) pumped laser oscillations were demonstrated. The Nd:GdVO4 single crystal showed superior lasing properties to Nd:YVO4 and Nd:YAG single crystals.

Conference Information: OSA Trends in Optics and Photonics on Advanced Solid State Lasers. Vol. 1<br /> San Francisco, CA, USA, 31 January-2 February 1996<br /> Opt. Soc. America; IEEE/Laser &amp; Electro-Opt. Soc

During crystal growth from a stirred melt, partitioning of the intrinsic LiNbO3 melt species is significantly influenced by the interface electric field caused by the thermoelectric power and the charge separation effects (crystallization EMF) which are a function of growth parameters such as solute boundary layer thickness, delta(C), growth velocity, V and temperature gradient, G(L). Thus, combinations of delta(C)(g), V(g) and G(L)(g) were calculated as a function of solidified melt fraction, g, by using a nonlinear programming technique 'polytope method', which leads to the true dynamic congruent-state growth from a finite amount of melt, i.e. a growth with an almost constant composition throughout the crystal and very little amount of uncoupled ionic species contained in the crystal. The micro-pulling-down technique is the most suitable growth method which can meet the calculated growth conditions.

During crystal growth from a stirred melt, partitioning of the intrinsic LiNbO3 melt species is significantly influenced by the interface electric field caused by the thermoelectric power and the charge separation effects (crystallization EMF) which are a function of growth parameters such as solute boundary layer thickness, delta(C), growth velocity, V and temperature gradient, G(L). Thus, combinations of delta(C)(g), V(g) and G(L)(g) were calculated as a function of solidified melt fraction, g, by using a nonlinear programming technique 'polytope method', which leads to the true dynamic congruent-state growth from a finite amount of melt, i.e. a growth with an almost constant composition throughout the crystal and very little amount of uncoupled ionic species contained in the crystal. The micro-pulling-down technique is the most suitable growth method which can meet the calculated growth conditions.

Mode of occurrence and cause of twinning, which are occasionally observed in lithium tetraborate crystals growm pararell to [110], have been investigated. Twinning is related to the crystal symmetry, i.e., 4-fold screw axis along the c-axis. Relashionship between the cause of striations in crystals and the occurence of twinning during growth has also been examined in connection with temperature fluctuations near the interface.

Distribution coefficients of Nd3+, Tm3+ and Er3+ in calcium niobium gallium garnet (CNGG) single crystals have been investigated. The values of the equilibrium distribution coefficient, k(0), of Nd3+, Tm3+ and Er3+ in CNGG single crystals have been determined to be 0.55, 1.09 and 1.14, respectively. It is shown that the distribution coefficients of Nd3+ in CNGG single crystals are larger than those in other garnet crystals such as Y3Al5O12 and Gd3Ga5O12. The variation of the k(0) values is discussed in relation to the ionic radii of each of the cations.

Each ionic species of LiNbO3 melt has a particular field-modified equilibrium partition coefficient. k(EO), and effective partition coefficient, k(E), which are predominated by growth parameters, i.e., solute boundary laver thickness, delta(C), growth velocity, V and temperature gradient, G(L). Variations of these coefficients have been discussed in association with growth parameters and a combination of delta(C)(g), V(g) and G(L)(g) as a function of solidified melt fraction, g, was calculated for true dynamic congruent-state growth from a finite amount of melt when the interface electric field is taken into account.

Bubbles whose size ranged from sub-micron to similar to 1 mu m were observed along the interface in the interface liquid boundary layer of LiNbO3 melts when fiber-shaped LiNbO3 crystals were grown via laser-heated pedestal growth (LHPG). This method usually yields a very high temperature gradient near the solid-liquid interface leading to significant thermoelectric power which affects the distribution of LiNbO3 intrinsic species in the melt. Supersaturation of OLi- and/or O2- ions at the interface were calculated to have a large enough total supersaturation to nucleate bubbles due to a combination of both solute build up and a significant temperature difference between the interface and the far-field liquid.

The mode of occurrence and the origin of cracking of lithium tetraborate (Li2B4O7) during growth by CZ method have been investigated. It is considered that crystal cracking can be divided into two main modes of occurrence. Each origin of cracking have been examined; 3-inch-diameter crack-free Li2B4O7 have been successfully grown.

The growth of crack-free 3-inch-diameter lithium tetraborate (Li2B4O7) Single crystals by the Czochralski method has been studied. The relationships between crystal cracking rate during growth and the crystal rotation rate and the position of the work-coil have been examined. It is concluded that crystal cracking at a later stage of growth is related to the temperature fluctuation in melt.

Electric field effects at the interface influence the solute partitioning leading to an electric field-dependent equilibrium solute distribution cocfficient, k_<EO>. The causes of these electric fields, i.e., the thermoelectric power and the charge separation effects (crystallization EMF), are a function of growth velocity, V, temperature gradient, G_L, and solute boundary layer thickness, δ_c. Subsequently, the interface electric field becomes an extremely important variable for the crystallization process. Here, LiNbO_3 crystal growth from a stirred melt is discussed by considering the electric field-dependent solute partitioning for all of the seven intrinsic species. Additionally, the chemical conversion reactions in the melt are taken into account. The above considerations eventually lead us to discuss conditions for the dynamic congruent-state growth of LiNbO_3 from a finite amount of melt, 1-g via the Czochralski technique by finding an appropriate combination of δ_c(g), V(g) and G_L (g).

The effects of the cluster size on the physical properties of a L2B4O7 Melt have been studied via measuring the transition temperatures from liquid to crystal and from quenched glass to crystal by using differential thermal analysis (DTA). Theoretical modeling of the cluster-size dependent entropy of the melt has been developed, based on the classical homogeneous nucleation theory, and simulation of the homogeneous nucleation rate has been carried out for the melts soaked at different temperatures to match the experimental data. The calculation results show that a decrease of the soaking temperature from 1050 to 950-degrees-C yields 3% radial growth of the unit cluster leading to a 40-degrees-C increase of the crystallization temperature from the melt while leading to a 30-degrees-C decrease of the crystallization temperature from the quenched glass and an 8-degrees-C increase of the equilibrium melting temperature, provided that the melt retains the structure at the soaking temperature.

Meeting Date: 06/01/1994 - 06/03/1994<br /> Location: Boston, MA, USA

The mode of occurrence and the origin of cracking of lithium tetraborate (Li2B4O7) Single Crystals during growth have been investigated. The melt temperature dependence and the origin of crystal cracking have been explained in terms of activation enthalpy change for viscous flow in Li2B4O7 melt associated with temperature distribution in the melt.

Crystal growth from a stirred melt is discussed by considering the relationship of a phase diagram partition coefficient, k0j, and its effective partition coefficient, k(E)j, for all of the seven LiNbO3 intrinsic species. Here, the interface electric field becomes an extremely important variable for the crystallization process. The causes of these electric fields, i.e., the thermoelectric power and the charge separation effects (crystallization EMF), are a function of growth velocity, V, temperature gradient, G(L), and solute boundary layer thickness, delta(C). Additionally, the chemical conversion reactions in the melt are taken into account. The above considerations eventually lead us to discuss conditions for the dynamic congruent-state growth of LiNbO3 via the Czochralski technique and to set up the most appropriate congruent composition for each bulk crystal growth condition from a finite amount of melt, 1 - g. For the best congruent-state growth, one must find an appropriate combination of delta(C)(g), V(g) and G(L)(g) which satisfies the conditions that, as much as possible, lead to a crystal with approximately constant composition.

Phase diagram solute partition coefficients and partial liquidus slopes for the intrinsic chemical species comprising LiNbO3 are calculated over a 25-degrees-C range immediately below the congruent liquid liquidus point by using the population data of these intrinsic species in a LiNbO3 melt combined with the published phase diagram, ionic conductivity and diffusivity data for Li+ and O2-.

The role of thermoelectric Power and/or charge separation-generated electric fields upon Cr-doped LiNbO3 crystal growth is treated by investigating both steady-state and initial transient solute redistribution based on the concept of a field-modified partition coefficient and an effective growth velocity. The magnitude of these electric field effects is dominated not only by the strength of the field but also by the solute diffusion coefficient in the phase considered. The high diffusion coefficient of Cr3+ in the liquid and the very low diffusion coefficient of Cr3+ in the solid combined with the electric field operating in the liquid leads to a strong pulling force on the Cr3+ from the solid through the interface into the liquid. This generates a deep solute depletion region in the solid behind the interface. An analytical solution to this depletion phenomena is given for a specific case.

The thermodynamic and kinetic behavior of LiNbO3 melts has been studied experimentally by differential thermal analysis (DTA). Theoretical modeling has been carried out for three cases and the predicted results matched to the experimental data: (1) the melt contains only one species and no chemical reactions are present during heating and cooling, (2) the melt contains three species and a dissociation/recombination reaction occurs between LiNbO3 and Li2O + Nb2O5 and (3) the melt contains seven species with both dissociation and ionization reactions occurring to form the additional species Li+, LiO-, Nb2O4V(O)2+ ,and O2-. The best fit, using the linear programming technique LINDO, was for case 3 with seven active species in the melt. DELTA-G - values, DELTA-H - values and reaction rate constants (beta - values) were found for the dissociation/recombination reaction as well as for the two ionization reactions. These values allowed the species populations to be calculated for both the congruent liquid (mole ratio of Li2O to Nb2O5 = k = 0.942) and the Nb - rich (k = 0.724) and Li - rich (k = 1.222) liquid cases studied experimentally by DTA at 1275-degrees-C.

The effective solute partitioning of chromium was investigated on single crystals of LiNbO3 grown by the laser-heated pedestal growth (LHPG) technique. Electric field effects at the interface influence this solute partitioning, leading to an electric field-dependent effective solute distribution coefficient, k(E). The LHPG technique made it possible to explore these field effects by controllably changing the growth velocity (V) and the temperature gradient (G(s), G(L)) near the interface over a wide range. The electric field generated via the temperature gradient is associated with the thermoelectric power while an additional electric field is growth rate associated via a charge separation effect. By applying the Burton-Prim-Slichter (BPS) theory to our experimental data, we found the phase diagram solute partition coefficient to be k0 almost-equal-to 3.65, while the field-influenced solute partition coefficient (V = 0) was k(E0)' almost-equal-to 8.17 at G(L) almost-equal-to 11500-degrees-C/cm. It is theoretically shown that the same considerations can be applied to all ionic partitioning at a solid-liquid interface.