石川 毅彦

The second flight of microgravity experiment system using a free fall capsule from a high altitude balloon was conducted in May 2007. Using a drag free control, around 10^-4G gravity conditions were obtained for 30 seconds. Results of a combustion experiment with Japanese sparker conducted inside the microgravity experimental unit were also reported.

Understanding the nature and behavior of liquid metals requires accurate values of their physical properties (e. g., density, surface tension, viscosity). However, maintaining samples of matter in their liquid phases, in particular under supercooled conditions, is a great challenge when dealing with refractory metals. This is due mainly to their high melting temperatures (e. g., 3,695 K for W), their high vapor pressure, and the risk of melt contamination with a support or crucibles. Electrostatic levitation, laser heating in vacuum, and non-contact characterization techniques circumvented these difficulties and allowed the determination of the properties of several metals in their liquid state, above their melting temperature as well as in their supercooled phase. In this work, several thermophysical properties were successfully measured with an electrostatic levitation furnace under vacuum conditions. For the first time, density and viscosity data of yttrium were reported over large temperature intervals in the liquid phase. Over the 1,560 to 2,100 K temperature span, the density can be expressed as rho(T) = 4.15 x 10(3) - 0.21 (T - T(m)) (kg.m(-3)) with T(m) = 1,796 K, yielding a volume expansion coefficient of 5.1 x 10(-5) K(-1). In addition, the surface tension can be expressed as sigma (T) = 8.04 x 10(2) - 0.05 (T - T(m)) (mN.m(-1)) and the viscosity as eta(T) = 0.00287 exp [1.1 x 10(5)/(RT)] mPa.s over the 1,830 to 2,070 K interval. The results, in particular those for viscosity, suggest that performing similar experiments in microgravity could improve the accuracy of the measurements.

Electrostatic levitators use strong electric fields to levitate and accurately position a sample against gravity. In this study, the effects of the electric field are investigated with regard to viscosity measurements conducted with the oscillating drop method. The effects of the external field on viscosity measurements are experimentally confirmed by changing the sample size. Moreover, a numerical simulation based on a simple mass-spring-damper system can reproduce the experimental observations. Based on the above results, measurement procedures are improved. These help to minimize the effect of the positioning force and to increase the accuracy of the viscosity measurements.

BaGe alloys with two compositions near their eutectic point form open framework structures called the clathrate structure. These BaGe compounds with the clathrate structure can be made by rapid solidification from their liquid state. However, the formation mechanism of the clathrate structure has not been clarified due to lack of information on their liquid-state structure and properties. Since BaGe alloy melts have very high reactivity, it is difficult to measure the thermophysical properties of them by ordinary methods using a container. Therefore, a containerless technique must be used to measure the thermophysical properties of BaGe melts. Using the electrostatic levitation (ESL) technique as a containerless technique, the thermophysical properties (density, surface tension, and viscosity) of BaGe melts around the eutectic composition were measured in order to clarify the formation mechanism of the clathrate structure, and also the structure of them was observed by using the high-energy X-ray diffraction method combined with ESL. From experimental results, it was observed that the short-range order based on the clathrate structure exists even in the liquid state at the clathrate-forming compositions.

Co-61.8 at.% Si (CoSi-CoSi(2)) eutectic alloys were solidified on an electromagnetic levitator (EML) and an electrostatic levitator (ESL) at different undercooling levels. The results indicated that there is only a single recalescence, event at low undercooling with the CoSi intermetallic compound as primary phase, which is independent of processing facilities, on either an EML or an ESL. The microstructure, however, is strongly dependent on the processing facility. The interior melt flow behavior in the sphere solidified at the EML differs substantially from that at the ESL, thus yielding different microstructures. On high undercooling, double recalescence takes place regardless of levitation condition. In situ X-ray diffraction of alloys solidified on the EML demonstrates that the CoSi(2) compound becomes the primary phase upon the first recalescence, and the CoSi intermetallic phase crystallises during the second recalescence. In addition to phase identification, real-time diffraction patterns can also provide additional evidence of the fragmentation of the primary phase and the ripening feature in the subsequent cooling process in the semisolid state. The phase competition between the CoSi and CoSi, compounds is discussed when considering the nucleation barrier. The low interfacial energy of the CoSi(2) phase favors a preferential nucleation event over the CoSi phase, which also plays a critical role in non-reciprocity nucleation and thus yields a double recalescence profile at high undercooling. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

ドラッグフリー技術に基づいた新しい自由落下カプセルを,2006年5月に高高度気球B200を用いて高度40km から投下し,微小重力実験が行われた。今回の最初の試験飛行により,三陸大気球観測所の制御室とカプセルとの間での無線通信,ドラッグフリー制御,そして飛行シーケンスを分析するための基本的データを得ることに成功した.

DECIGO (DECI-hertz interferometer Gravitational wave Observatory) is the future Japanese space gravitational wave antenna with observation band around 0.1 Hz. It aims at detecting gravitational waves from various kinds of sources, with sufficient sensitivity to establish the gravitational wave astronomy. In the pre-conceptual design, DECIGO is formed by three drag-free spacecraft, 1000 km apart from one another. The relative displacements between proof masses housed in these spacecraft are measured by Fabry-Perot interferometers. We plan to launch DECIGO in 2024 after research and development phase, including two milestone missions (DECIGO pathfinder and Pre-DECIGO) for verification of required technologies. © 2008 World Scientific Publishing Co. Pte. Ltd.

To counter residual accelerations, dedicated levitators or positioners are necessary to support a host of materials science experiments on the ground and in microgravity. All levitators (e.g., aerodynamic, acoustic, electromagnetic, electrostatic, optical) have their own merits and limitations but the electrostatic scheme offers the combined advantages of processing millimeter-size objects, independent heating, quasi-spherical shape of molten materials, handling of materials under extreme temperatures for hours, virtually convection-free samples, and wide view around the samples for diagnostic. These attributes provide unique research opportunities in materials science on the ground as well as under reduced gravity. In particular, electrostatic levitators are very attractive to measure the physical and structural properties of equilibrium and non-equilibrium liquids, to synthesize multi-function materials, and to understand metastable phase formation, vitrification, and diffusion. In this paper, research and development carried out by the Japan Aerospace Exploration Agency over the years in the field of electrostatic levitation are summarized and the main results obtained in materials science are presented. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

To understand the nature and behavior of rare earth metals in their liquid phases, accurate values of their physical properties are essential. However, to measure their physical properties, the samples should be maintained in liquid phases for prolonged time, and this raises a formidable challenge. This is mainly explained by their high melting temperatures (e.g., 1629 K for Tb), high vapor pressure, and the risk of melt contamination with a crucible or support. An electrostatic levitation furnace alleviated these difficulties and allowed the determination of density, surface tension, and viscosity of several metals above their melting temperature. Here, first, the levitation furnace facility and the noncontact diagnostic procedures were briefly discussed, followed by the explanation of their thermophysical property measurements over wide temperature ranges. The density was obtained using an ultraviolet-based imaging technique that allowed excellent illumination, even at elevated temperatures. Over the 1615 to 1880 K temperature span, the density measurements could be expressed as rho(T) = 7.84 x 10(3) - 0.47 (T - T-m) (kg center dot m (-3)) with Tm = 1629 K, yielding a volume expansion coefficient alpha(T) = 6.0 x 10(-5)(K-1). In addition, the surface tension and the viscosity could be determined by inducing a drop oscillation to a molten sample. Using this technique, the surface tension data could be expressed as sigma(T) = 8.93 x 10(2) - 0.10 (T - T-m) (mN center dot m (-3)) and those for viscosity as eta(T) =0.583 exp [4.1 x 10(4) /(RT)] (MPa center dot s) over the 1690 to 1980 K temperature range.

高温融体内の原子の運動に関する実験的な知見は,融体の熱物性と構造の関係を理解する上で極めて重要である.我々は,高温融液の原子ダイナミクスの観察を目的として非弾性X 線散乱用の小型の静電浮遊装置を開発し,融点および過冷却液体シリコンの動的構造因子を測定した.本装置を用いることにより液体シリコンのフォノンピークが明瞭に観察され,その分散関係が明らかになった.

We employed an electrostatic levitator (ESL) and an electromagnetic levitator (EML) to solidify Ni99B1 (at.%) alloys at various undercoolings. The microstructures and microtextures were revealed by using the electron backscatter diffraction pattern (EBSP) technique in a scanning electron microscope. It is found that that no significant refinement can be identified at the low and medium undercooling regimes for the primary trunk in the sample solidified on the ESL, while the fragmentation of the secondary and even tertiary branches may take place to generate equiaxed grains. Further investigation by the EBSP reveals that neighboring grains have small misorientation angles, which may be ascribed to the absence of mechanical stirring from electromagnetic eddy current. A sharp contrast is that the samples solidified on the EML at low and medium undercoolings have refined equiaxed microstructures. The EBSP mapping reveals that the equiaxed grains yielded on the EML have a random distribution in crystallographic orientations among neighboring grains, indicating that electromagnetic stirring (EMS) induced by the electromagnetic field in the EML plays a vital role in promoting fragmentation and thus generating refined grains and random distribution in orientation. Regarding to the refined microstructure at high undercoolings, no significant difference arises in the samples processed between the EML and ESL. (c) 2006 Published by Elsevier B.V.

High-energy synchrotron X-ray diffraction experiments were performed for clathrate-forming barium-germanium (Ba-Ge) alloys in the liquid state near the eutectic composition. The accurate structure information of highly reactive melts has been obtained by applying electrostatic levitation technique as a containerless method. The structure information obtained from the reverse Monte Carlo simulation suggests that the short-range ordering between the Ge atoms occurs with the addition of Ba atoms in the liquid Ba-Ge alloys. This can be associated with the formation of the cage-like structure composed of the Ge atoms in the liquid alloys near the eutectic composition.

A compact electrostatic levitator was developed for the structural analysis of high-temperature liquids by x-ray diffraction methods. The size of the levitator was 200 mm in diameter and 200 mm in height and can be set up on a two axis diffractometer with a laboratory x-ray source, which is very convenient in performing structural measurements of high-temperature liquids. In particular, since the laboratory x-ray source allows a great amount of user time, preliminary or challenging experiments can be performed with trial and error, which prepares and complements synchrotron x-ray experiments. The present small apparatus also provides the advantage of portability and facility of setting. To demonstrate the capability of this electrostatic levitator, the static structure factors of alumina and silicon samples in their liquid phases were successfully measured. (c) 2007 American Institute of Physics.

This paper proposes a new micro gravity experimental system called BOV (Balloon-based Operation Vehicle). BOV uses a free-fall capsule with double-shell structure to prevent influence of aerodynamic disturbance. Additionally, BOV is raised to 40km by a high altitude balloon to extend micro gravity duration to 30(or possibly 60) seconds. Thus we realize a medium duration micro gravity system with good micro gravity environment. In this system, the most characteristic point is double-shell structure. The inner shell can fall freely since the outer shell measures the relative position with laser displacement sensors and is controlled by gas-jet thrusters not to collide the inner shell. Therefore the inner shell can be uninfluenced of the dynamic pressure and other aerodynamic disturbances ideally. The BOVs project has run since 2004. The first flight to check the whole system was accomplished in 2006. The aim of this flight was test of a high altitude balloon, communication and data handling system, control system, onboard electronics and operation. The second flight expected to achieve 30 seconds micro gravity was also accomplished on May in 2007. This paper presents the development of BOV's control system and shows the experimental results of micro gravity and consideration for effectiveness of the proposed system. Copyright 2007 by the IAF or the IAA. All rights reserved.

The dynamic structure factor S(Q,.) of the melt of an icosahedral quasicrystal, Al72Pd20Mn8, was measured at 1223 K near the melting point, T-m = 1140 K, for momentum transfers, Q, from 1.5 to 27.15 nm(-1) by means of an inelastic x-ray scattering technique using synchrotron radiation at SPring-8. The composition of Al72Pd20Mn8 is a special one in AlPdMn ternary alloys, since an icosahedral AlPdMn quasicrystal is formed from the melt. The acoustic mode was observed in the low-Q region, and a substantial broadening of the longitudinal current current correlation function and the crossover of the effective sound velocity from hydrodynamic to viscoelastic regions were observed around 6 nm(-1), which hints at the existence of a cluster with a size of about 1 nm in the melt.

Ni99B1 alloys were solidified by containerless processing at various melt undercoolings on an electrostatic levitator (ESL) and an electromagnetic levitator (EML). A scanning electron microscope in combination with an electron backscatter diffraction pattern mapping technique was employed to reveal microstructures and microtextures formed on these two facilities. The microstructure consists of well-developed primary dendrites with coarse secondary arms in the alloys solidified on the ESL at low and medium undercooling levels, whereas equiaxed grains are yielded in alloys solidified on the EML at almost the same undercoolings. Further analysis indicates that the melt flow induced by the electromagnetic field in the EML may play a significant role in promoting fragmentation of primary dendrites in the mushy zone and thus resulting in equiaxed grains. In contrast, the primary dendrites in the alloy processed on the ESL can fully develop in the absence of melt flow. The fluid flow in the sample on the EML can rotate, move, and displace surviving fragments, yielding a random distribution of grain orientation and thus leading to a random microtexture at low and medium undercoolings. At high undercoolings, refined equiaxed grains can be obtained on both the ESL and the EML and the influence of melt flow on refinement seems negligible due to the enhanced driving force in capillarity and solute effects. A great number of coherent annealing twins are formed, making the pole figures more complex and random. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Containerless solidification and thermophysical properties of BaTiO3 were studied using a pressurized electrostatic levitation furnace and varying the heating temperature and the cooling rates of several samples. The solid and liquid densities of BaTiO3 over a range of 1220 to 2200 K were determined using containerless techniques. A single crystal of hexagonal BaTiO3 grown with this method exhibited a giant permittivity exceeding 100,000 at room temperature. (c) 2006 Elsevier B.V. All rights reserved.

In order to measure the surface tension and the viscosity of molten oxides, the oscillation drop technique has been applied on a pressurized hybrid electrostatic-aerodynamic levitator. To suppress the electrical discharge between the top and bottom electrodes, the drop excitation method which has been used with high vacuum electrostatic levitators has been modified. As a demonstration, the surface tension and viscosity of liquid BaTiO3 were measured using this new method. Over the 1500-2000 K interval, the surface tension was measured as gamma(T)=349-0.03 (T-T-m) (10(-3) N/m), where T-m=1893 K is the melting temperature. Similarly, the viscosity was determined as eta(T)=0.53 exp[5.35x10(4)/(RT)](10(-3) Pa s) over the same temperature interval. (c) 2006 American Institute of Physics.

A 2-mm-diameter glass sphere of ferroelectric BaTi2O5 was fabricated from melt using containerless processing. The glass structure was analyzed by high-energy X-ray diffraction using an incident photon energy of 113.5 keV, indicating that distorted Ti-O polyhedra, with average coordination number (NTi-o) of approximately 5, presented in the glass. Above the glass transition temperature (972 K), three successive phase transitions, from glass to a metastable a phase at 972 K, then to a metastable β phase at 1038 K, and finally to a stable monoclinic γ phase above 1100 K, were observed. At the crystallization temperature of the a phase, the permittivity jumped instantaneously by more than 1 order of magnitude, reaching a peak of 1.4 × 107. This interesting phenomenon, occurring near the crystallization temperature, has important technical implications for obtaining an excellent dielectric glass-ceramic through controlled crystallization of BaTi 2O5 glass. © 2006 American Chemical Society.

Thermophysical properties of equilibrium and supercooled liquid platinum were measured using non-contact diagnostic techniques with an electrostatic levitator. Over the 1691 to 2216 K temperature range, the density can be expressed as ρ(T) = 19.2 × 103 - 0.96(T - Tm) (kg·m-3) with Tm = 2041 K, yielding a volume expansion coefficient of 5.0 × 10-5 K-1. In addition, the surface tension can be expressed as γ(T)= 1.80 × 103 -0.14(T - Tm) (10-3N·m-1) and the viscosity as η(T) = 0.25 exp[4.99 × 104/(RT)] (10-3 Pa·s) over the 1743 to 2313 K temperature range. © 2006 The Japan Society of Applied Physics.

In the present work, the densities of a mould flux slag were measured as a function of temperature by electrostatic levitation (ESL) method. The density of a mould flux, as measured by ESL method decreased linearly with increasing temperature. The results obtained are compared with the value measured by the sessile drop method just above the melting point of the slag. The discrepancies are explained on the basis of the inherent merits and demerits of the two types of measurements. The experimental values of present work were also compared with the density data for other mould flux slags from Swedish plant practice, obtained by the sessile drop method as part of the present work as well as literature data. A thermodynamic model of molar volume, developed in the present group was used to predict the density of slags. The molar volume was described as a function of integral molar enthalpies of mixing. In the case of ternary systems corresponding to the mould flux slag, the calculated values are in reasonable agreement with the experimental values.

Thermophysical property measurements of molten refractory metals, which are very difficult and hardly conducted with conventional methods due to their high melting temperature and risk of reaction with container walls, have been conducted using noncontact diagnostic techniques in an electrostatic levitator. This paper first briefly summarizes the procedures and methods adopted by the Japan Aerospace Exploration Agency to enable the measurements of density, surface tension, and viscosity on molten refractory metals. Typical data of superheated and undercooled liquids that would have been impossible to obtain without the use of these techniques are then reported. Specifically, density, surface tension, and viscosity of Ti, Zr, Nb, Mo, Ta, and W were successfully measured over a wide temperature range, including the undercooled region.

Employing an electrostatic levitator (ESL) equipped with a CO2 laser heating setup, we solidified Ni99B1 bulk crystals through containerless processing at high undercoolings and observed grain-refined micro structures. The electron backscatter diffraction pattern (EBSP) and analysis of the twin directions were accomplished, from which the primary growth traces with a cellular-like structure were revealed on a macro-millimeter scale. In comparison with the strong mechanical electromagnetic stirring in a sample processed on an electromagnetic levitator, the ESL provides a quite quiescent state for the melt, which enables identification of the primary growth traces after solidification. The present observation supplied experimental evidence that the refined microstructure in the Ni99B1 alloys at the high undercooling regime was due to fragmentation of the primary growth crystal, rather than dynamic nucleation.

This paper reviews the past and present research and development activities in the field of electrostatic levitation at the Japan Aerospace Exploration Agency (JAXA). Particular emphasis is given on the important innovations of sub-millimeter sample handling, launch levitation initiation, aero-electrostatic hybrid levitation, multi-beam heating geometry, electrode design, and ultraviolet (UV) imaging. A summary of the thermophysical properties of refractory materials measured in their liquid states, above and below their melting point, as well as preliminary results of samples solidified from deep supercooled states are also reported. © 2005 Springer Science+Business Media, Inc.

Electrostatic levitation and multi-beam radiative heating overcame contamination and sample position instability problems associated with handling of liquid alumina. This allowed the measurements of the surface tension and viscosity in the superheated and undercooled states using the oscillation drop method. Over the 2190-2500 K interval, the surface tension of alumina was measured as sigma(T) = 0.64-8.2 x 10(-5) (T-T(m)) (N/m), where T(m), the melting temperature, is 2327 K. Similarly, on the same temperature range, the viscosity was determined as eta(T) = 3.2exp[43.2 x 10(3)/(RT)] (mPa.s). Both sets of data agree well with the literature values.

Thermophysical properties of equilibrium and supercooled liquid iridium were measured using noncontact diagnostic techniques in an electrostatic levitator. Over the 2300-3000 K temperature range, the density can be expressed as ρ (T)=19.5×103 - 0.85(T- T m) (kg•m -3) with T m=2719 K. The volume expansion coefficient is given by 4.4 × 10-5 K-1. In addition, the surface tension can be expressed as γ (T)=2.23 × 103 - 0.17(T-T m)(10-3N•m-1) over the 2373-2833 K span and the viscosity as η(T)=1.85 exp [3.0× 104/(RT)](10 -3Pa•s) over the same temperature range. © 2005 Springer Science+Business Media, Inc.

Knowledge of the viscosity and its temperature dependence is essential to improve metallurgical processes as well as to validate theoretical and empirical models of liquid metals. However, data for metals with melting points above 2504 K could not be determined yet due to contamination and containment problems. Here we report the viscosity of tungsten, the highest melting point metal (3695 K), measured by a levitation technique. Over the 3350-3700-K temperature range, which includes the undercooled region by 345 K, the viscosity data could be fitted as 77(T) = 0.108 exp[1.28 x 10(5)/ (RT)] (mPa s). At the melting point, the datum agrees with the proposed theoretical and empirical models of liquid metals but presents atypical temperature dependence, suggesting a basic change in the mechanism of momentum transfer. (c) 2005 American Institute Of Physics.

The use of a hybrid pressurized electrostatic-aerodynamic levitation furnace and procedures developed by the Japan Aerospace Exploration Agency overcame the contamination problems associated with the processing of ceramics under extreme temperature conditions. This made possible property measurements over wide temperature ranges, above the melting point as well as in the supercooled region. In this study, samples of various ceramics were levitated and their densities were found as a function of temperature by extracting the area from images of a UV backlit axi-symmetric sample of known mass. In addition, the work function of each molten material was estimated using the Richardson-Dushman equation.

The electrostatic levitation system, including its history and development, and techniques for non-contact thermophysical property measurements (density, ratio of isobaric heat capacity to hemispherical total emissivity, surface tension and viscosity) are reviewed. Thermophysical properties of refractory metals whose melting temperatures are over 2000 K have been measured with an electrostatic levitator. The experimental results for vanadium, zirconium, niobium, molybdenum, rhodium, ruthenium, iridium, tantalum and rhenium are presented. Comparison between theoretical calculations based on hard sphere model and measured data, as well as the necessity of microgravity conditions for this research is also discussed.

The microscopic orientations of Ni-18.7 at.% Sn eutectics solidified from undercooled states, in particular, within an indixidual eutectic colony and among neighboring eutectic colonies, have been measured with respect to the eutectic NI3Sn and Ni phase: this was done using a scanning electron microscope equipped with the electron backscatter diffraction pattern (EBSP) mapping technique. The EBSPs and inverse pole figures indicate that the Ni3Sn intermetallic compound is continuous and well oriented whereas the Ni solid solution is discontinuous and randomly oriented within an anomalous eutectic grain. Further examination reveals that although Ni particulates are random from an overall view, most neighboring Ni grains have small misorientations of less than 10degrees. The specific solidification sequence and the effect of released crystallization heat on subsequent crystallization are further considered, which enables the primary Ni phase to segment into individual grains whereas Ni3Sn does not due to higher entropy of fusion. A little rotation or floating within the constrained framework of the crystallizing Ni3Sn compound may yield small misorientation angles. The discontinuous Ni particulates and continuous Ni3Sn network are of great significance in revealing the anomalous euiectic formation. The orientation among independent eutectic colonies is random owing to the random appearance of nuclei throughout the volume of undercooled melts. The macrotextures of pole figures (PFs) of two euiectic phases are also mapped versus melt undercooling, which can be interpreted well when considering the nucleation frequency, variation of eutecic colony size. microtexture within a single eutectic colony, and the overall microstructure evolution as a function of melt undercooting. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A spheroid BaTiO3 with a diameter ca. 2 mm was synthesized using a pressurized electrostatic levitation furnace. Phase selection was controlled by varying the superheating and undercooling. A polycrystalline perovskite BaTiO3 was crystallized from a homogeneous melt superheated by 150 K and then undercooled by 750 K (∼0.4 Tm, whereas a single crystal of hexagonal BaTiO3 was grown from a melt superheated by 50 K and then undercooled by 100K. The polycrystalline perovskite BaTiO3 solidified from undercooled melt showed a high dielectric constant of 4000 at room temperature. © 2004 Elsevier B.V. All rights reserved.

Thermophysical properties of molten refractory metals have been measured using an electrostatic levitation furnace. The developed levitation furnace could stably levitate molten samples at temperatures exceeding 3,000 degrees C. In addition, non-contact thermophysical property measurement techniques have been implemented. Properties such as the density, the surface tension, and the viscosity have been measured over wide temperature ranges, including the undercooled region.

The influence of convection in a melt on the compositional uniformity and crystallinity of the TLZ-grown In_<0.3>Ga_<0.7> As crystals has been investigated by growing crystals with various shapes and dimensions on the ground. When the crystal diameter was reduced to 2mm, compositionally uniform single crystals have been grown, while no homogeneous nor single crystals were grown when a crystal diameter was increased to 10mm. These results suggested importance of suppressing convection in a melt during crystal growth by the TLZ method in the view points of maintaining concentration gradient and suppressing constitutional supercooling ahead of the growth interface. We then applied the TLZ method for substrate preparation by growing plate shaped crystals with suppressing convection by reducing the thickness of the plate. We report relationship between crystal quality and convection magnitude in the TLZ method.

過冷却状態を含むタングステン融体の熱物性値を静電浮遊炉を用いた無容器法により測定した。その結果、3125～3707K の温度範囲において測定された密度はρ(T) =16.7(±0.33)x10⊃3;-1.08(±0.08)(T-T_m) (kg⋅m^-3) （融点T_mは3695K ）となり、熱膨張率は6.6 x 10^-5 K^-1 となった。同様に3398～3695K の温度範囲において、表面張力はγ(T) =2.48x10⊃3;(±75)-0.31(±0.08)(T-T_m) (10^-3N⋅m^-1)、粘性係数はη(T) =0.11(±0.02)exp[12.8(±4.1)x10⁴/(RT)] (10^-3Pa⋅s)となった。

Three dielectric relaxations in hexagonal (h) -BaTi O3 single crystals exhibiting giant permittivity were detected in a frequency range of 100 Hz-3 GHz and analyzed by an equivalent circuit with three parallel RC elements. A best-fit result indicated that the three dielectric relaxations were the responses of bulk crystal with a capacitance of 1 pF, an interfacial layer with a capacitance of 1.4 nF, and a depletion layer with a capacitance of 1 nF. We confirmed that a giant permittivity exceeding 105 could be achieved by the interfacial layer in the h-BaTi O3 crystal. In addition, a Schottky barrier height at the contacting interface between Cu electrodes and the h-BaTi O3 surface was estimated as 1.56 eV from the voltage dependence of capacitance. © 2005 American Institute of Physics.