BaTiO₃ powders were synthesized by glycine-nitrate process, using BaCO₃ and Ti[OCH(CH₃)₂]₄ as starting materials. Nitric acid was used as a solvent for the starting materials as well as an oxidant for self-combustion. The physical and chemical properties of as-prepared and calcined powders were characterized by helium pycnometer, X-ray diffraction, BET method and SEM. Single cubic phase of BaTiO₃ was obtained at 1000°C. When the glycine/cation molar ratio was 1.2, the reactivity of self-combustion was the highest and the degree of aggregates after calcination was very low. Relative density of 95% was obtained at 1400°C when the molar ratio of 1.2 for glycine/cation was applied. The dielectric constant of the sintered body was about 2000 at 1400°C.

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Thermoelectric properties of Chevrel-type sulfides AMo₆S₈ (A=Fe, Ni, Ag, Zn, Sn, Pb, Cu) were investigated with respect to many advantageous characteristics of the Chevrel compounds for thermoelectric applications. The electrical conductivity, σ, was 10^2.5S·cm^-1<σ<10³S·cm^-1 for most of the samples from room temperature to 1000°C; AgMo₆S₈ gave the largest σ up to 250°C. The Seebeck coefficient, S, was positive for all the samples, indicating the p-type conduction. All the S values were 10μV·K^-1<S<80μV·K^-1, and AgMo₆S₈ showed the smallest S, probably owing to the higher hole concentration for A=Ag compared to other samples. The maximum S²σ value was attained by SnMo₆S₈, reaching ca. 1.7×10^-4W·m^-1·K^-2 at 800°C. All the κ values were 1W·m^-1·K^-1<κ<3W·m^-1·K^-1 from room temperature to 1000°C. The maximum Z value was ca. 0.07×10^-3K^-1 attained by SnMo₆S₈ at 800°C.

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As-received calcium titanate and neodymium aluminate of median sizes 4.0 and 1.2μm, respectively, showed fast sedimentation within 10min because of the formation of hard agglomerates about 1-10μm. When ball-milling time became longer, the larger particles were selectively ground and the particle size distributions became narrow. The dispersibility of 96h-milled powders was greatly improved by addition of polyacrylic ammonium (PAA) of 2mass%. The viscosity of suspension depended on the amount of PAA adsorbed and was lower for CaTiO₃ suspension than NdAlO₃ suspension. Consolidation of the suspensions and sintering behavior of the CaTiO₃-NdAlO₃ system were also studied.

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Samarium-doped aluminosilicate thin films were prepared by rf magnetron sputtering in both pure argon and in a mixture of argon and hydrogen at the substrate temperatures of 25, 200 and 300°C. A hot-pressed ceramic disk was used as a target with a nominal composition of Sm₂O₃⋅5Al₂O₃⋅88SiO₂. X-ray photoelectron spectroscopy revealed that the samarium and aluminum contents in the films deposited in both sputtering gases increased with increasing substrate temperature at the expense of silicon. The photoluminescence intensity of Sm²⁺ ions increased with increasing substrate temperature and with decreasing sputtering pressure, due to the increase in activated Sm²⁺ ions. Hydrogen gas mixed with argon enhanced the reduction of Sm³⁺ to Sm²⁺ at the substrate temperatures of 25 and 200°C. The addition of an aluminum chip on the ceramic target during deposition increased the absorbance of the films and the photoluminescence intensity of Sm²⁺, whereas that of aluminum oxide did not. These results are attributed to the shifts in the UV edge of the films.

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In this study, self-propagating high temperature synthesis (SHS) reaction was utilized for the production of Sm-Fe alloys which are precursor for Sm-Fe-N system hard magnetic materials. A main goal was to shorten the processing time required for the alloy production. Furthermore, super high pressure by explosive shock compaction method was applied to the alloys obtained by SHS reaction for very short time. The effect of the high pressure on the crystal structures was also investigated. Samarium and iron powders were used as raw materials. Mixture molar ratios of theses powders were varied from Sm:Fe=2:7 to 2:17 in order to find the optimum condition. The SHS reaction was initiated by a tungsten heating coil. Although variation in temperature, resulting from the synthesis reaction, was significantly abrupt at the initial stage (i.e., for 15s), the temperature gradually decreased from the maximum temperature. Specimens showed a similar tendency for the variation in synthesis temperature, and attained a maximum at about 1200°C, except for the specimen with a composition of Sm:Fe=2:17. From the results of X-ray diffraction (XRD), an expected Sm₂Fe₁₇ phase, and small amounts of SmFe₂, SmN, and α-Fe phases were detected. The magnetic properties were also studied on as-SHSed, explosively hot-compacted, and cold-compacted specimens. Pulverized SmFe alloys, obtained by SHS reaction, were used as raw materials for the cold compaction. The cold-compacted specimen had relatively good magnetic properties. It was considered that the lattice defects introduced by the shock processing, which made a crystal lattice distorted, improved the coercive force.

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The plasticity of kaolinitic Kentucky-Tennessee clay (KT), before and after an ion-exchange with 1N-CH₃COONH₄ solution was studied by a uniaxial compression test. Kaolinitic clay of the weathering-origin clay showed a large amount of dissolution of Ca²⁺ and Mg²⁺ ions after the ion-exchange, while kaolinitic clay of the hydrothermal origin kaolinitic clay showed a very small amount of divalent cations dissolved. Large amount of divalent cations predominantly dissolved from the montmorillonite contained in the weathering-origin clays and partly from the surface of kaolinitic clay particle. The zeta potential of the Kentucky-Tennessee clays showed a large negative charge with increasing the pH after the ion-exchange. According to an analysis of uniaxial compression test performed on green bodies, the plasticity of Kentucky-Tennessee clays degraded extensively after the ion-exchange. A clear relationship between the plasticity of kaolinitic clay and the zeta potential was found.

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Influence of a silica layer on oxidation of free carbon in Si-Ti-C-O fiber-bonded ceramics has been investigated. The rate of oxidation of the Si-Ti-C-O fibers has been measured by thermogravimetric analysis at temperatures ranging between 773 and 1573K. The relative mass of the fibers increased parabolically and the kinetics of the oxidation followed the parabolic rate characteristic of diffusion controlled processes. The thickness of the silica layer, calculated according to a simple equation, well agreed well with the experimentally observed one. Pores created by the oxidation of free carbon were observed inside the fibers after etching the surface of a heat-treated Si-Ti-C-O fiber-bonded ceramics at 773K. Using the parabolic rate constant and the volume expansion coefficient of the fiber, the time required to close the pores by the formation of silica layer was calculated. The thickness of the free carbon layer and the oxidation rate of the fibers were the key parameters for the analysis of the oxidation behavior of the materials.

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Molecular dynamics (MD) simulations were employed to study the properties of Al₂O₃ grain boundaries (near Σ11 tilt) in presence of Mg, Ca and Si dopants. Three initial configuration of boundaries were considered. The excess energies and excess volumes strongly depend on the initial configuration. In addition, the Mg-doped grain boundaries showed a relatively lower distortion and more stable structures, with a tendency toward decreasing excess energy and excess volume, or compared to pure boundaries or those doped with different ions. The diffusion coefficients of each atom type at grain boundary increased in the order Mg>Al>Si>Ca>O. The coordination numbers of atoms at grain boundary were found to be 5 for Al, 4 for Si, 5 for Mg and more than 6 for Ca, against the value of 6 for Al in the bulk. The MD simulation of Mg doped grain boundaries is discussed in terms of the effect of Mg segregation on the grain growth of Al₂O₃.

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The relationship between crystallized phases and dielectric properties of crystallized glasses in the (Ca, Sr, Ba)O-Al₂O₃-SiO₂-TiO₂ system was investigated. Powder sample of 0.386(Ca_0.189, Sr_0.518, Ba_0.293)O⋅0.094Al₂O₃⋅0.520SiO₂⋅0.121TiO₂ glass (sample Ti-G) was used for this study and powder samples of 0.386(Ca_0.189, Sr_0.518, Ba_0.293)O⋅0.094Al₂O₃⋅0.520SiO₂ glass (sample G) and mixture of sample G with 0.121TiO₂ (sample G/Ti) were used to obtain reference data. These powders were pressed in disks and sintered at 850, 900 and 950°C for 2h. Crystalline phases of (Ca, Sr, Ba)Al₂Si₂O₈ (AS) and (Ca, Sr, Ba)₂TiSi₂O₈ (TS) precipitated in sample Ti-G and only AS phase precipitated in sample G at 950°C. Dielectric constant and temperature coefficient of capacitance (TCC) were measured for each sintered sample. The TCC values of the samples Ti-G and G (sintered at 950°C) were negative and positive values, respectively. These experimental results clearly show that the negative TCC value of sintered Ti-G samples is mainly due to the presence of TS phase. The dielectric constant and the TCC of the TS phase, estimated by empirical equations involving the rule of mixture, were 13.2 and -241ppm/°C, respectively.

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Phase stability of Y-Ba-Cu-O superconducting phases was evaluated as a function of temperature, oxygen partial pressure and total gas pressure by the hot isostatic pressing method using argon and oxygen mixtures as a surrounding atmosphere. The phase transformation temperature from Y₂Ba₄Cu₇O_y to YBa₂Cu₄O₈ increased with increasing the total gas pressure, even if the oxygen partial pressure was kept constant. It indicates that the equilibrium partial pressure of a gas involving the chemical reaction changes if a solid-gas reaction is progressed under high total gas pressure. Dependence of chemical potential of the reactant gas on the inert gas pressure was thermodynamically discussed on the basis of Lewis-Randall's empirical scaling law and Ishizaki's approximation. These two approximations resembled each other at pressures less than the usual HIPing pressure.

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Fatigue tests of ceramics are usually performed under cyclic stress. However, piezoelectric materials are used under an applied electric field and stresses are caused by the displacement. It is very important to understand the relation between the fatigue behavior and the compositional conditions. S-N curves of fatigue test in an applied electric field were composed of two curves having different gradients, acceleration was observed in the range of many time cycles. Fatigue behavior of piezoelectric ceramics considers accumulative fatigue which shows markedly decrease of strength caused by internal-crack with domain switching.

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Highly resistant, high-transmittance woodceramic thin films were prepared using rf magnetron sputtering of a woodceramic disk in argon plasma. A film series was deposited based on substrate temperature, which was varied from 50 to 500°C. The film's electrical and optical properties depended on substrate temperature. Films deposited below 300°C were insulative, ρ>10¹⁰Ω·cm. Films deposited at 50°C had a density of 1.9-2.2g/cm³ comparable to that of single crystal graphite. Below 200°C, films had higher transmittance than typical DLC films in the visible and infrared region. Infrared C-H absorption spectrum was observed by FT-IR and there exist two types of bonding corresponding to sp² or sp³.

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Material characteristics of powder compact are closely related to the packing arrangement of particles. In this paper, the effect of particle shape was investigated on the non-uniform packing structure. In the experiments, the shape of stainless steel particles was modified by changing the operational conditions of rotational impact blending and differently shaped particles were consolidated under piston press. The packing structure of the powder bed was expressed by void-size distribution. As a result, it has been clarified that the void-size distribution becomes narrow as the particle shape gets elongated, and the local voidage decreases. Thus, a uniform packing structure is apparently attained.

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Electrical properties were investigated for nitrogen-doped SiC, prepared by pressureless sintering (by adding boron and carbon as the sintering additives). A nitrogen doping process compensated the acceptor level that was formed by solid-dissolved boron, one of the sintering additives. Thus, it was confirmed that the donor level was formed by solid-dissolved nitrogen. The specific electrical resistance of nitrogen-doped pressureless sintered SiC was clearly separated into two groupings. One grouping of electrical properties strongly depended on the temperature, while the other grouping of electrical properties was less dependent. Microscopy, electron diffraction, and X-ray diffraction analyses suggested that the electrical conduction through a dominant 6H α-SiC crystal phase, where a nitrogen-doped donor level is deep, the temperature dependency is strong. On the other hand, the electrical conduction through a dominant 3C β-SiC crystal phase, where a nitrogen-doped donor level is shallow, the dependency on temperature is less pronounced. Two sintered SiC samples were prepared by using the recrystallizing technique. One only consisted of a 6H α-SiC crystal phase, and the other only of a 3C β-SiC crystal phase. The experimentally measured electrical properties showed agreement with the above stated theory interpretation.

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Synthesis and fabrication of pollucite glass-ceramics was investigated. The mixture which was measured to be the stoichiometric ratio of pollucite was melted by using an arc melting technique to synthesize the material in glass state. Milled powder of the glass was mold pressed and CIPed to obtain green compacts. Dense pollucite glass-ceramics were obtained by heat-treating the compact at 1400°C for 4h in air. Enhanced densification of the present material was ascribed to the viscous deformation of the glass phase. Fracture strength and the Young's modulus of the resultant pollucite glass-ceramics were 102MPa and 100GPa at room temperature, respectively. Average fracture strength exhibited 128MPa for specimens measured at 1000°C. Thermal expansion coefficient of the sample was 2.7×10^-6/°C between room temperature and 1000°C.

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A monoclinic hollandite type barium-titanium oxide Ba_1.1Ti₈O_15.6 (I-centered monoclinic (I2/m), a=1.0297(3)nm, b=0.2966(2)nm, c=0.9966(4)nm, β=91.38(4)°) was synthesized in H₂ atmosphere at 1500°C. The mean value of valence of Ti in the new phase is +3.62.

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Effect on α-alumina formation from gibbsite powder by heating was investigated for dry-grinding of gibbsite powder and the gibbsite powder added α-alumina fine powder as a seed. Two powder samples were prepared so as to adjust α-alumina formation temperature to nearly the same temperature at 1100°C. The transformation of intermediate alumina to α-alumina in the ground sample proceeded more homogeneous than that in the seeded sample. The particle size distribution of α-alumina powder calcined from the ground sample become narrower than that from the seeded sample, leading to the formation of sintered body with homogeneous grain size. This may be due to both the formation of much more fine α-alumina particles as nuclei of transformation and to a good dispersion in the intermediate alumina powder by the grinding in comparison with seeding.

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The chemical stability and photoreactivity of zirconium precursor was successfully improved by the additions of N-phenyldiethanolamine and diethanolamine. The prepared solution has strong absorptions at 256 and 302nm, leading to the effective absorption of ultra-violet light. Photolithographic patterning of zirconium precursor film could be obtained by the UV irradiation. It is reported that the metal alkoxide solutions chemically modified with alkanolamines, such as diethanolamine and triethanolamine, can be used for the patterning of the metal oxide films. However, the procedure possesses a weak points in how to make a precursor with little absorptions in the regions of the emission of a convenient mercury lamp. The present modification has solved this problem by the chemical modification of zirconium iso-propoxide upon additions of N-phenyldiethanolamine and diethanolamine.

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