PbTiO₃ single crystals containing Li₂O or Na₂O were grown by a flux method. Electrical measurements were carried out for as-grown crystals doped with 0.01wt% Li₂O or 0.10wt% Na₂O. (1) The addition of Li₂O and Na₂O increased the size of obtained crystals, and gave also the crystals with low defect concentration. (2) The grown PbTiO₃ crystals by the addition of Li₂O (0.7wt%) and Na₂O (0.7wt%) were highly transparent red-brown and brown single crystals, respectively, and had average size of 3.0×2.8×1.1mm and 3.6×2.8×1.0mm. (3) The content of Li₂O in all the Lidoped crystals was less than 0.01wt%, whereas the Na₂O content was more than 0.07wt% and increased with increasing addition of Na₂O. (4) Crystals doped with Li₂O showed no variations in the lattice constant, but the lattice constant of c-axis and axial ratio of crystals doped with Na₂O were smaller than those of undoped crystal. (5) Electrical properties of the crystals were affected by the addition of Li₂O or Na₂O. The electrical conductivity of crystals was very low (10^-10S⋅cm^-1) for Li₂O addition but that of crystals for Na₂O addition was high (10^-8S⋅cm^-1) at room temperature. At temperature above 300°C, the current-voltage characteristic curve of the crystal doped with Li₂O was composed of two parts, ohmic and non-ohmic ones. E_H decreased remarkably with increasing temperature.

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In order to investigate the formation process of titanium nitride (TiN) films by the plasma chemical vapor deposition (CVD) method utilizing d.c. glow discharge, a plasma diagnostic study by optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS) was carried out. The dependence of optical emission intensities or mass intensities of the observed plasma species on plasma CVD operating parameters was investigated, and their spatial distributions were observed. Plasma species which increase their densities in the cathode sheath region near the surface of the substrate were identified. From these results, Ti⁺ ions and NH radicals are proposed to be active plasma species which play important roles in the TiN film formation reaction. Formation processes of the plasma species are presumed.

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Homogeneous and highly dense insulating Yb₂BaCuO₅ substrates were successfully prepared by the PMQ (plasma arc melting and rapid quenching) method. The formation of a Yb₂BaCuO₅ single phase was identified by means of X-ray diffraction analysis. The relative density was 98% of the theoretical density. Furthermore, the formation of superconducting YbBa₂Cu₃O_x films on the insulating Yb₂BaCuO₅ substrate was attempted by RF magnetron sputtering. Superconducting YbBa₂Cu₃O_x films were grown with their c-axis preferentially perpendicular to the surface of the Yb₂BaCuO₅ substrate, and their T_c was observed at 88K. The current density J_c of the YbBa₂Cu₃O_x films on the Yb₂BaCuO₅ substrate measured at 77K under an absence of magnetic field was 1.2×10⁵A/cm².

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Machinability of alumina ceramics prepared by ratecontrolled sintering (RCS) has been evaluated as normal and tangential force (F_n and F_t) during grinding and compared with that prepared by temperature-controlled sintering (TCS) with a constant heating rate. The RCS alumina showed low F_n as the controlled shrinking rate [d(ΔL/L₀)/dt] decreased. The lowest F_n in RCS alumina at d(ΔL/L₀)/dt=0.1%⋅min^-1 was one/third times of that for the TCS alumina at 5K⋅min^-1. The grinding ratio and surface roughness were also improved for RCS materials. The microstructure influencing machinability was discussed in relation to the difference in shrinking behavior between RCS and TCS.

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High temperature oxidation of refractory-grade SiC was carried out in O₂ and Ar atmospheres mixed with various concentrations of water vapor, and its oxidation behavior was followed mainly by using a mass-spectrometer. The results were as follows,
(1) In the dry and wet O₂ atmospheres, main gaseous products in the temperature-raising process up to 1400°C were CO and CO₂ formed from the free carbon. Water vapor accelerated the oxidation of free carbon. On the other hand, in the successive soaking process at 1400°C, CO₂ formed from SiC was a dominant product. The evolution behavior of CO₂ during the soaking process was well fitted with the parabolic law and a positive tendency was observed between the parabolic rate constant and the water vapor content.
(2) In the wet Ar atmospheres, CO, CO₂ and H₂ were evolved due to oxidation of the free carbon by water vapor in the temperature-raising process. The oxidation behavior of SiC in the soaking process changed with the water vapor content. At high water vapor contents, the passive oxidation took place, obeying the parabolic law and the parabolic rate constant increased in proportion to the content of water vapor. At the water vapor content as low as 0.6vol% H₂O, however, the initial part of the reaction proceeded according to the active oxidation mechanism obeying the linear law. White spots observed on the surface of the sample after the active oxidation were composed of SiO₂ fiber, which was presumably formed by the vapor phase reaction among SiO, CO and H₂O.

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Ag-YBa₂Cu₃O_7-x composite superconductor was prepared by the mist-pyrolysis method. YBa₂Cu₃O_7-x and Ag particles were mixed with a mechanical mixer, and collected with electrostatic precipitator. The superconductive properties of sintered YBa₂Cu₃O_7-x and Ag-YBa₂Cu₃O_7-x were examined. Fine Ag particles were distributed uniformly in the matrix. The sintered Ag-YBa₂Cu₃O_7-x and their ground powder showed improved magnetic properties.

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Three kinds of heterometal assemblies, {Ln[Cr(ox)₃]⋅10H₂O}_x (Ln=La, Pr or Nd), were prepared by the reaction of K₃[Cr(ox)₃]⋅3H₂O with Ln(NO₃)₃⋅6H₂O in water. These compounds were regarded to have the oxalato-bridged three-dimensional lattice. The thermal decomposition behavior of these assemblies was investigated in an air stream. The behavior was similar to each other. The mixed oxides, LnCrO₄, and the perovskite-type oxides, LnCrO₃, were found to form in the temperature range of 823 to 973K and above 1023K, respectively. Specific surface areas of LaCrO₃, PrCrO₃, and NdCrO₃ obtained by calcining the corresponding complex assemblies at 1073K were 1.82, 1.85, and 1.91m²⋅g^-1, respectively. The effective magnetic moment per LaCr unit of LaCrO₃ increased from 1.98μ_B at 296K to 2.79μ_B at 285K, and then the moment decreased below 285K because of the phase transition. PrCrO₃ and NdCrO₃ showed ferrimagnetic behavior. That is, the magnetic moments per LnCr units of PrCrO₃ and NdCrO₃ increased drastically below 240 and 225K, respectively, also due to the phase transition. The moments of PrCrO₃ and NdCrO₃ were 9.79μ_B at 219K and 18.98μ_B at 223K, respectively, which were much larger than those expected from the respective total spin states, S_T=5/2 for PrCrO₃ and S_T=3 for NdCrO₃.

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Oxygen-ion conductive CeO₂ ceramics doped with Y₂O₃ and Gd₂O₃ were prepared by sintering pellets of these oxide mixture pressed at 150MPa under atmospheric pressure at upper 1500°C. Electrical property was investigated by measuring the d.c. electrical conductivity in air, as a function of temperature. Electrochemical property was also measured potential as a pH membrane electrode in buffer solution's with defferent pH's. The CeO₂ specimen doped with 5mol% Y₂O₃ sintered at 1700°C showed the highest ion conductivity at temperature lower than 100°C. The pH response of the membrane pH electrode with the CeO₂ specimen doped with 5mol% Y₂O₃ sintered at 1700°C was indicated Nernstian response. The specific potential was obtained in about 30s at 25°C and about 10s at 75°C in buffer solutions.

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A new type of bending device “monomorph” is composed of only a single plate made of semiconductive piezoelectric ceramics. This monomorph has been applied to the fabrication of speakers. In comparison with the conventional piezoelectric bimorph types, new monomorph speakers have advantages in massproduction and cost, and can be utilized commercially, though their acoustic characteristics are not satisfactory.

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The effect of sintering temperature on the electrical conductivity of recrystallized SiC was investigated. Recrystallized SiC specimens were prepared by sintering slip-cast compacts of SiC powders without any additives at 1800°-2200°C for 1h in a nitrogen atmosphere. Temperature dependence of specific resistance was studied in the temperature range from ambient temperature to 900°C. Two types of electrical conduction mechanisms are proposed. (1) At higher temperatures, the electric current above the potential barrier due to thermal excitation is dominant. (2) At lower temperatures, the current through the potential barrier due to tunnel conduction and bulk conduction is dominant. The barrier height was affected by impurity concentration and grain boundary energy. The barrier height increased with decrease in impurity concentration or increase in grain boundary energy. When the recrystallized SiC was sintered at higher temperatures, the impurity concentration decreased and grain boundary energy decreased. As a result, the barrier height depends on the sintering temperature, and the maximum barrier height was observed at the sintering temperature of 2000°-2100°C.

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Silicon nitride powder compacts without additives were produced by underwater-shock wave. The as-compacted specimens and sintered ones at various temperatures were characterized by relative density, micro Vickers hardness and fracture toughness. Microstructural characterization was also made by SEM and TEM. The relative density of an as-compacted specimen was about 75%, but hardness value was quite low about 2GPa. Mechanical properties were remarkably improved by sintering. Hardness and fracture toughness values of the specimen sintered at 1973K for 5h were about 24GPa and about 4MPa√m, respectively. TEM observation of the compact sintered at 1973K showed that there was no large glass pockets at grain boundary edges and that the glass phases at grain boundary surfaces were a few atoms thick.

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A method for estimating the grain-size and grain-aspect-ratio distributions in polycrystalline sintered bodies has been developed. We assume that grains are ellipsoids specified by three radii and that the radii distribution obeys to a probability-distribution function expressed with four distribution parameters. As a function of the four parameters, the area and the aspect-ratio histograms of the grain cross-sections of a sintered-body cross-section can be calculated by a Monte Carlo simulation method. The distribution parameter values are determined so that the calculated histograms conform to the observed ones by iterative calculation. We apply this analysis to the observed histograms about two kinds of alumina, obtained by using an image analyzer. The calculated histograms agree with the observed ones fairly well.

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The interface states at the grain boundaries in ZnO varistors are quantitatively investigated by Isothermal Capacitance Transient Spectroscopy (ICTS). At first we describe the formulation of ICTS signals caused by the interface states, and then analyze the observed results. They were characterized as monoenergetic interface states laid at 0.77eV below the conduction band. The density and the capture cross section of the interface states were calculated as 1.1×10¹²cm^-2 and 1.1×10^-16cm², respectively. The level of the interface states which capture electrons at zero-biased voltage was considered to be identical with that detected by ICTS measurements.

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The influence of compositions of coating solutions (SiO₂, 1Na₂O⋅99SiO₂) and of substrates (SiO₂ glass, Na₂O-CaO-SiO₂ glass) on the formation of sol-gel derived coating were evaluated by a scratch test, X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectroscopy (FT-IR), a porosity test, and ellipsometry measurements. Three types of samples were prepared; (a) SiO₂ film coated on Na₂O-CaO-SiO₂ substrate, (b) SiO₂ film coated on SiO₂ substrate, and (c) 1Na₂O⋅99SiO₂ film coated on SiO₂ substrate. The results of the scratch test showed that Na⁺ ions influenced strongly on the adhesion of the film to the substrates. The strength of the adhesion of (a) and (c) was larger than that of (b). The results of XPS analysis revealed that the Na⁺ ions contained in Na₂O-CaO-SiO₂ substrates diffused easily into the film below 200°C, and that those in 1Na₂O⋅99SiO₂ film did not diffuse into SiO₂ substrate. In the samples (a) and (c), a large amount of Na⁺ ions existed at the interface, which enhanced the adhesion of the film. The results of FT-IR and the porosity test indicated that the structure of sol-gel derived films were very porous and contained high content of residual -OH groups at the early stage of heat treatment. Na⁺ ions accelerated the dehydration of Si-OH and accompanying decrease of the porosity of films.

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A maximum likelihood method for estimating multimodal Weibull parameters from the data of strength and fracture origin for different types of specimens was studied. Three kinds of 4-point bending test and one kind of tensile test were carried out for Si₃N₄ ceramics and the fracture origin of each specimen was investigated. A set of multimodal Weibull parameters of the Si₃N₄ ceramics was estimated by the maximum likelihood method. In this method parameters can be determined so as to maximize the likelihood function which is the product of the individual likelihood functions of each type of specimen. The strength distributions calculated from those parameters were in good agreement with the experimental results. It is indicated that the probability of failure can be predicted by collecting the size effects for every kind of fracture origin. The probability of failure after eliminating a critical fracture origin was estimated for each type of specimen.

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Silicon nitride ceramics with different grain morphology and fracture toughness were prepared by sintering at 1900°C for 2 to 24h in a N₂ atmosphere of 0.9MPa. Two and three-dimensional (2-D and 3-D) distributions of grain size and aspect ratio were analyzed to clarify the relationship between microstructure and fracture toughness. The 2-D and 3-D grain size distributions were in good agreement. However, the 3-D aspect ratio distribution curve shifted toward the higher value with a broader distribution as compared with that of 2-D. The improvement in fracture toughness was attributable to the increase in the volume and number fractions of grains in a particular elongated grain group (grain size: 1 to 1.5μm, aspect ratio: 4 to 8) in the 3-D distribution. The increase in fracture toughness was also explained by the increase in the area and number fractions of grains in a particular grain group modified in the 2-D distribution.

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MgTiO₃ ceramics are used as capacitors because of the very small temperature coefficient of dielectric constant. MgTiO₃ ceramics were fired in reducing atmosphere and their phases were identified by X-ray diffraction method. The MgTiO₃ (illmenite) phase was decomposed into illmenite and spinel phases, and EDX analysis and lattice parameter measurement revealed that the illmenite phase was a solid solution of MgTiO₃ and Ti₂O₃ and that the spinel phase was a solid solution of Mg₂TiO₄ and MgTi₂O₄.

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The grain boundary structure of semiconductive BaTiO₃ and Bi₂O₃-diffused BaTiO₃ BL capacitor was studied using XRD, EDS, SEM, and AEM. Without SiO₂, Ba₆Ti₁₇O₄₀ (B6T17) phase was detected in the semiconductive BaTiO₃ sample, and Ba₄Ti₁₃O₃₀ (B4T13) and BaBi₄Ti₄O₁₅ (BBIT) phases were found in the BL capacitor sample. On addition of SiO₂, B6T17 and Ba₂TiSi₂O₈ were found at the grain boundaries of the semiconductor, and B6T17, BTS, BBIT in the BL capacitor were found at the grain boundary. The dihedral angle seen in the semiconductive sample was about 20°, but after the Bi₂O₃ was diffused, it changed to 0°. So it is suggested that the liquid phase containing bismuth has a very low viscosity compared with that of the liquid phase without bismuth, and it is easy to make microstructure of BL capacitor when bismuth oxide diffuses.

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Rheological behavior of alumina suspensions and properties of green sheets were investigated to find optimal conditions for preparation of aqueous green sheets. Acrylic binder and dispersants were used in this study. In an aqueous alumina /dispersant system, as the acid value of dispersant increased, the relative viscosity and sedimentation volume of the suspension decreased. This indicated that the suspension was well dispersed. In contrast, in an aqueous alumina/dispersant/binder system, the suspension showed high shear-thinning flow behavior. As the acid value of dispersant increased, the packing density, strength and extension of the green sheet decreased. The results indicated that the rheological behavior of suspension was affected by the compatibility between dispersant and binder.

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The temperature dependence of ionic conductivity in a Li-stabilized β′′-alumina ceramics has been investigated using complex impedance analysis to explore the behavior patterns of its bulk and grain boundary conductivities between 200° and 800°C. The bulk and grain boundary ionic conductivities with activation energies of 0.14eV and 0.25eV, respectively, were obtained for the material coated with Au sputtered films as electrodes in the temperature range 300° to 600°C. The grain boundary conduction behavior changed from multi-relaxation to single-relaxation with increasing temperature. It has been found that the complex impedance plots of the materials are considerably influenced by electrode materials used and their morphology. This naturally leads to wrong conclusions on the conduction behaviors of the materials. A material with Pt sputtered film electrodes had bulk and grain boundary conductivities about half as low as those for the same material with Au electrodes.

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