We have fabricated the silicon-based films on the substrates with and without water-cooling and with various hydrogen gas flow rates in a plasma gas by means of a low-pressure-plasma spraying method. The obtained films were almost porous polycrystalline silicon, and contained a slight amount of microcrystalline silicon. The size of the microcrystals slightly decreased with increasing the hydrogen flow rate in the plasma gas, and with decreasing the substrate temperature. The existence of amorphous region was also suggested at higher hydrogen gas flow rate. The small change in the electric conductivity was observed, which corresponded to the structural changes. The present low-pressure-plasma spraying method is expected to be applied for other various materials, which will be used for the future electronic and optical devices.

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The initial stage sintering of a plate-like β-alumina powder compact was investigated by isothermal dilatometry between 1200°C and 1400°C, and microstructure observation by SEM. The initial stage sintering was divided into two stages. The shrinkage was proportional to time in the first stage and to time^1/3 in the second stage. It is considered that rearrangement is predominant in the first stage, and the mass transport from the grain boundaries to the grain surfaces through the necks is predominant in the second stage. This mass transport is caused probably by the strong anisotropy and idiomorphic habit of the plate-like grains.

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Crystal structure parameters including B thermal parameters of each constituent atom were determined for PbMg_1/3Nb_2/3O₃ (PMN) between 27 and 700°C by the single crystal high temperature X-ray diffraction technique. For lead, and magnesium and niobium atoms, the optimum shift directions from the special positions were not a single direction but “spherical” shifts were observed. For oxygen atom, it was confirmed that the optimum shift direction was not one ring on XY plane but two parallel rings away from XY plane. PMN began to decompose into polycrystalline pyrochlore type compound at 600°C. The mechanism of decomposition was discussed from the view point of crystal structure.

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Poly-crystalline β-SiC films have been deposited on Si (100) at 400°C by the microwave-plasma chemical vapor deposition using CH₃Cl and SiH₄ as source gases. A single crystal film was obtained at 725°C. The deposition rate increased with decreasing substrate temperature, and with increasing gas composition ratio [CH₃Cl]/[SiH₄], which is larger than 1. The crystal had a very few bonded-hydrogen, but contained a small amount of residual Cl. Si-rich films were obtained at low substrate temperatures and low [CH₃Cl]/[SiH₄] ratios. The obtained results indicate that the film deposition process is a CH₃Cl decomposition-limited.

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To examine formation of pores in the cordierite body consisting of kaolin, talc and alumina, melting behavior of talc particles in the body during firing and its relation to the pore formation were studied by means of SEM, XRD and EPMA. According to the phase diagram of MgO-Al₂O₃-SiO₂ system, it was considered that the melting temperature of talc is lowered by the addition of alumina. Two kinds of specimens of cordierite and alumina containing 5wt% coarse talc particles were fired in the range of 1250-1350°C. Results of experiments by XRD and SEM observations showed that the melting point of talc particles decreased with increase in alumina content in the matrix phase. Distribution of Mg and Al measured by EPMA showed that the eutectic melt of talc and alumina penetrated into the surrounding matrix phase and left pores behind them.

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MgO-C bricks containing 0 to 30 vol% flake graphite and expanded graphite were prepared and heat-treated at 800 and 1400°C. The dependence of mechanical properties of the MgO-C bricks on the graphite content was studied. The maximum values of bending strength, elastic modulus and fracture toughness were obtained at 2 to 3 vol% expanded graphite and at around 5 vol% flake graphite. The effective fracture energy increased with an increase in graphite content up to 30 vol% for expanded graphite. However, no slight increase in effective fracture energy was observed above 20 vol% flake graphite. Thermal shock resistance parameters R″″ and R_st were calculated based on the data obtained. R″″ was not correlated with graphite content. On the other hand, R_st remarkably increased above 7 vol% graphite and larger R_st was obtained with expanded graphite. Consequently, improvement of the spalling resistance of MgO-C brick was expected with expanded graphite.

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Effects of sub-grain-boundaries (SGB) formed in Al₂O₃ grains and residual stress caused by additions of SiC particles in Al₂O₃ phase on the strength of Al₂O₃/SiC composites were investigated. The number of the SGB and the residual tensile stress in Al₂O₃ were found to increase with increasing SiC content. The experimental results suggest that the strengthening in Al₂O₃/SiC composites is attributable not only to the formation of the SGB but also to the toughness increases which is possibly related with the residual stress. The strengthening by annealing in Ar was also investigated. The annealing resulted in the strength increase of more than 200MPa, whereas the annealed and subsequently ground specimens did not show the strength increase. It is therefore concluded that the strengthening due to the anneal is mainly caused by healing of surface defects.

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The subsolidus pseudo-ternary phase diagram in the system SrCO₃-Bi₂O₃-CuO was constructed by using prereacted binary compounds. The composition of superconducting Raveau (R) phase was determined to be Sr₅Bi₆Cu₃O₁₇ (563), and it melts at 920°C. Besides R-phase, two ternary compounds with composition of Sr₇Bi₆Cu₄O₂₀ (764) and Sr₂₈Bi₁₈CuO₅₆ (28-18-1) were found. The former phase was identified as the already-reported “collapsed 221” (C) phase, and it melted incongruently above 870°C. The latter showed a perovskite-type structure related to that of K₃MoF₆, and had a cubic symmetry with α₀=8.506Å.

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The internal friction of 16.3Na₂O⋅33.7MgO⋅50.0SiO₂ glass was measured with an inverted torsion pendulum in the frequency range 0.35-0.95Hz, and the tracer diffusion coefficients of oxygen and magnesium were measured at temperatures below the glass transition point by use of stable isotopes ¹⁸O and ²⁶Mg, respectively. The temperature dependence of the relaxation time of a high-temperature peak was represented by τ_H.P.(s)=(2.04±0.05)×10^-15×exp[{183.8±5.7 (kJ/mol)}/RT] The temperature dependence of the tracer diffusion coefficients for oxygen and magnesium was represented by the following equations: D_Oxy(m²⋅s^-1)=(1.22±0.06)×10^-10×exp[{-150.2±5.1(kJ/mol)}/RT] D_Mg(m²⋅s^-1)=(4.29_-1.15^+1.57)×10^-6×exp[{-195.3±19.9(kJ/mol)}/RT] The activation energy for the high-temperature peak (183.8kJ/mol) was smaller than that for magnesium diffusion (195.3kJ/mol) by about 7% but greater than that for oxygen diffusion (150.2kJ/mol). Comparison of the results of the present study with those obtained by Hino et al. led to the conclusion that the high-temperature peak was caused by the movement of magnesium ion under stress.

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Recently, sound and mechanical vibration are becoming important problems in our life. In order to absorb vibrations, the input vibration energy has to be transformed into other kind of energy which can be emitted out to the surrounding easily. Piezoelectric ceramics have a function of transforming mechanical energy into electric energy by changes in the direction of the spontaneous polarization. Mechanical input vibration of 1 kHz was produced continuously by the actuator. The electric charge produced by the piezoelectric effect was measured in open state (both electrodes are not connected to anywhere), short state (both electrodes are connected each other) and ground state (one or both electrodes are connected to the ground). Then, the vibration absorption characteristics were measured. They showed very large values at the ground state. The transformation of vibration energy into electric charge by the piezoelectric effect was identified by observing the maximum charge at the resonant frequency. The produced electric charge and vibration absorption increased with the increase in electromechanical coupling factor and piezoelectric coefficient. In case of the internal insertion of electrode such as multilayer ceramics, however, elastic and dielectric losses compensated the contribution of piezoelectric coefficient and electromechanical coupling factor to the production of electric charge and gave a low charge and a low vibration absorption efficiency.

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Influence of Y₂O₃ content on the thermal shock resistance of ZrO₂-Y₂O₃ ceramics including 12vol% of ZrO₂-Y₂O₃ fiber was investigated by varying the content of Y₂O₃ from 1.5 to 8.0mol%. After specimens were sintered at 1300, 1400 and 1500°C for 2h, bending strength, fracture toughness, thermal conductivity, and thermal expansion coefficient were measured. Thermal shock resistance was characterized by strength degradation before/after thermal shock experiment (quenching temperature difference; ΔT=600K), and it was increased as the Y₂O₃ content was decreased. It is considered that this is due to the decrease in thermal expansion coefficient caused by the increase in monoclinic phase in the matrix, and the increasing of fracture toughness.

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Unidirectional carbon fiber-reinforced hBN composites were fabricated by a filament winding technique, followed by hot-pressing at 1900°C, 30MPa for 1h in N₂ atmosphere. An hBN powder containing 8 wt% oxygen and a high-purity hBN powder admixed with 30 wt% Al₂O₃ were used as starting powders. The bending strength of hBN composites and monolithic hBN was evaluated by three-point bending test. The strength of hBN composites was twenty-five times and six times larger than that of monolithic hBN (B₂O₃) and hBN (Al₂O₃), respectively. The hBN composites exhibited typical fracture behavior of fiber-reinforced composites.

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Mechanical and electromechanical properties of monoclinic ZrO₂ fiber/PZT composites fabricated by slip casting and ordinary sintering were examined. Bending strength of the composites decreased by increasing the fiber content from 0 to 20vol%. However, the composite containing 5vol% ZrO₂ fibers yielded a fracture toughness K_IC of 1.4MPa⋅m^1/2, 75% higher than that of PZT matrix. The measurement of thermal expansion and observation of microstructure suggest that microcracking, crack bowing and crack deflection contribute to the increase in K_IC. Addition of ZrO₂ fibers reduced both permittivity and coupling factor K₃₁ of the composites. At 5vol% ZrO₂, the K₃₁ value of the composite was 25% lower than that of PZT matrix.

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Thermal-shock fracture behavior of low-thermal-expansion KZr₂(PO₄)₃ (KZP) ceramic was evaluated by the water-quenching test. KZP ceramic was prepared by sintering at 1200°C to 1400°C with MgO. The linear thermal expansion coefficient of the sintered ceramic changed from -1.0×10^-6/°C for the addition of 1wt% MgO to +3.0×10^-6/°C for the addition of 10wt% MgO. The critical quenching temperature difference decreased from ca. 1000°C to ca. 700°C with increasing thermal expansion coefficient. The strength of KZP ceramic sintered with 2wt% MgO did not decrease after quenching from 800°C into water was repeated 10 times.

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Pitch and resin are used as binders of carbon-containing refractories, because of their high degrees of carbonization. Carbons formed by decomposition of these binders during heating have different high temperature properties. In this paper, crystallization, oxidation, true density and microstructure of carbons obtained from pitch, resin and their mixtures were examined. As compared with carbon obtained from resin, carbon obtained from pitch was higher in degree of crystallization, true density and starting temperature of oxidation. In other words, similar oxidation properties of carbon from resin were obtained when resin was heated at temperatures above 500-600°C higher than that for pitch. Carbon obtained from mixtures of pitch and resin, especially, for 80wt% pitch and 20wt% resin, had the highest starting temperature of oxidation. The mixtures of pitch and resin thus binary binder seems to be better than pitch or resin as binders for carbon-containing refractories.

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In order to obtain corundum-free mullite ceramics from mixtures of kaolin and aluminous materials, effects of grinding of kaolin, particle size of alumina, and particles size, calcination and grinding of aluminum hydroxide on mullitization and densification were investigated. Grinding of kaolin, use of fine alumina and aluminum hydroxide, and calcination and grinding of aluminum hydroxide promoted the mullitization and densification. Firing these mixtures at temperatures higher than 1500°C yielded corundum-free, comparatively high strength mullite ceramics.

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Differential scanning calorimetric measurements were performed for the superionic glasses in the systems AgI-Ag₂O-M_xO_y (M_xO_y=B₂O₃, GeO₂, P₂O₅, MoO₃). Since the heat capacity change (ΔC_p) in glass transition was decreased with an increase in the AgI content in all of the systems, the fragility seemed superficially to be decreased with the AgI content from a viewpoint of ΔC_p. Transformation-range viscosities were also measured for the same glasses above by using a beambending method. The fragility was not changed with an increase in the AgI content from a viewpoint of E_η/T_g, where E_η and T_g are respectively the activation energy for viscous flow and the glass transition temperature. It is thus concluded that only network part in the glass structure contributes to the value of ΔC_p and thus the decrease of ΔC_p with increasing AgI content is caused by the fact that the portion of the glass network is decreased with increasing AgI content.

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A fibrous lead titanate (PbTiO₃) powder with light-yellow color has been prepared by hydrothermal synthesis. The influence of Pb/Ti (0.3 to 1.0) ratio in the mixture and reaction time on the formation of fibrous PbTiO₃ under hydrothermal conditions have been investigated. The preferable conditions for preparing fibrous perovskite-type PbTiO₃ from fibrous potassium titanate are that Pb/Ti ratio is 1.0, reaction temperature is 150°C, and time is 72h. The fibrous powder of perovskite-type is usually less than 2μm in diameter and more than 50μm in length. The morphology on the face of fibers is essentially unchanged up to 800°C, but it changed after heating at 900°C. But the fibrous morphology is unchanged at 1000°C.

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Ceramic composite was synthesized using an in-situ reaction between synthetic zircon and Al₂O₃. High-temperature strength did not decrease up to 1500°C for the sample having only mullite for matrix. While, the strength decreased above 1300°C for others. With increase of the Al₂O₃ precipitated in the mullite matrix phase, the mullite grains became isotropic and small, which may occur the creep deformation. On the contrary, the ceramic composite used in the in-situ reaction revealed excellent high-temperature strength. It was found that ZrO₂ and Al₂O₃ particles dispersed in the grains of mullite matrix, contributed to increase the room temperature strength, and to improve effectively the high-temperature strength. Remarkable difference of the microstructure was not observed in the composite obtained from the natural zircon instead of the synthetic zircon at same composition. However, high-temperature strength decreased markedly due to the increase of impurity content in the natural zircon. High-temperature strength of the ceramic composite obtained from synthetic mullite, ZrO₂ and Al₂O₃ powders by the mixing method, decreased significantly at 1300°C. This behavior can be explained by the shape and size of the mullite in matrix, or the quantities of ZrO₂ and Al₂O₃ precipitated at the grain boundary.

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Effect of quartz on the sintering and bending strength of the porcelain bodies in quartz-feldspar-kaolin system was investigated by the observation of bulk density, 3-point bending strength test, X-ray diffraction and the microstructures using a scanning electron microscope. Quartz and feldspar were jet-milled to mean particle sizes of 5μm and 4.5μm respectively, before the wet-mixing of the raw materials. Porcelain bodies containing 45% feldspar and 55% kaolin showed full densification in long firing range. A mean bending strength of the body increased from 15kg/mm² to 19kg/mm² with the increase of firing temperature from 1150°C to 1300°C. Quartz particles acted as inclusions before dissolution and restrained the sintering of the body to increase the maturing temperature. These particles hardly reacted on the eutectic melts, formed from decomposed kaolin and feldspar, and showed isolated microstructures. Therefore, the bending strength of the body containing quartz never exceeded 16kg/mm² in this experimental conditions. These results were discussed in a viewpoint of microstructural developments, utilizing a phase diagram in K₂O-Al₂O₃-SiO₂ system.

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Hexagonal BaTiO₃ was formed by doping only 2mol% of Mn. Investigation of this effect of Mn in terms of its valency state and size of Mn ion revealed that the small size of Mn⁴⁺ ion is a dominant factor favoring the formation of the hexagonal phase.

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