Ceramic electrostatic chucks made of alumina ceramics were fabricated. Transition metal oxides (1wt% TiO₂, Cr₂O₃, MnO₂, CoO, CuO) were added to control the resistance of the dielectric insulation layer of the chuck. The electrical resistivity and electrostatic force at R. T. -200°C were measured, and it was revealed that the electrostatic force of the chuck depends on the electrical resistance of the ceramic. Among the additives examined, TiO₂ was found to be most effective for increasing the adhesion force of the alumina electrostatic chuck.

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Properties of α-alumina surface, dissociated fraction of polyacrylic acid, and the interaction between alumina surface and polyacrylic acid were investigated in aqueous suspensions in the pH range of 2.2 to 10.5. The isoelectric point of the colloidal α-alumina particles was pH 7.7, and the surface was charged positively and negatively at pH below and above 7.7, respectively. The dissociated fraction of polyacrylic acid changed with pH, close to 0% at pH below 3 and 100% at pH above 9. Polyacrylic acid was adsorbed on the alumina particles as neutral polymer at low pH and negatively charged polymer at high pH. The total amout of adsorbed polymer decreased with an increase in pH due to the repulsive interaction between the negative particle surface and negatively charged polymer.

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A high purity silica glass containing a large amount of OH-group was synthesized from high purity silicon tetrachloride by the oxy-hydrogen flame direct hydrolysis method, and the effects of heat-treatment at 900°C under ultrahigh pressure of 10kbar or 20kbar were examined. The glass so treated was optically isotropic and macroscopically amorphous because no birefringence was observed, but a substantial increase in the refractive index was noted. Structural analysis of the 10kbar-treated glass by the laser Raman scattering spectrometry revealed the occurrence of the Raman spectral shifts, indicating a decrease in the Si-O-Si bond angle even though it is basically of the amorphous silica structure. For the 20kbar-treated glass, on the other hand, the analysis revealed the presence of the Raman spectra that are characteristic of α-quartz in addition to those that are characteristic of silica glass.

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Porous glasses were prepared by phase separation and leaching of NaF, NaCl and NaBr containing sodium borosilicate glasses with low silica content. Each sodium halide was added to 10Na₂O⋅50B₂O₃⋅40SiO₂(wt%) glass and the effects of the additive on phase separation and leaching were investigated. The mean pore diameter, specific surface area and porosity were 300-2500Å, 20-60m²/g and 55-56%, respectively. The pore diameter increased and the specific surface area decreased with increasing temperature, time of heat treatment and halogen content. It was found that the halogen containing specimens were leached out in shorter soaking time than the halogen free specimen and that chlorine addition was most effective. The change in the leaching rate is probably caused by the dissolution of halogen containing sodium borate phase into hot water. For chlorine containing sample, leaching finished in a half time that of the halogen free sample.

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The annealing temperature dependences of the XRD pattern, Seebeck coefficient and electrical resistivity for Cr-doped and Co-doped FeSi₂ thin films were studied. The films were deposited by rf-sputtering method. Below 380°C, the films were amorphous and their Seebeck coefficient and electrical resistivity were relatively low. The crystallization of FeSi₂ occurred at 400° to 460°C. The Seebeck coefficient (in absolute value) and electrical resistivity steeply increased with increasing amount of FeSi₂ crystals in the amorphous matrix. Above 460°C, the electrical resistivity of the films gradually decreased with rising annealing temperature. The results of activation energy measurement explained the observed decrease of the electrical resistivity in Cr-doped thin films as due to both the increase of the carrier density and to the decrease of the activation energy.

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The internal friction of alkali aluminogermanate glasses containing no nonbridging oxygen ions was measured by the free torsional vibration method. The internal friction as a function of temperature revealed two peaks in mixed-alkali glasses with low alkali contents. Those peaks increased rapidly in magnitude and came close to overlapping with increasing alkali content. The results indicate that both peaks can be assigned as mixed-alkali peaks, and that the mixed-alkali peak was closely related to the low-temperature peak in single alkali glasses. The following explanation is proposed. (1) There are two kinds of mechanism responsible for the mixed-alkali peak. (2) The mixed-alkali peak is essentially caused by the individual and duplex movement of two species of alkali ions which are affected by the interaction between different kinds of alkali ions. (3) When two mixed-alkali peaks overlap, there is little difference between the two mechanisms since the two species of alkali ions move with almost the same activation energy. (4) The rapid increase in magnitude of the mixed-alkali peak with increasing alkali content is probably attributed to a considerable increase in the number of mobile alkali ions which contribute to the mechanism of the mixed-alkali peak, and at the same time is also attributed to the increase in energy consumption during alkali ion migration.

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Porous cordierite ceramics were prepared from the flyash exhaust of a power plant. Addition of the coal powder to the cordierite green bodies was effective for increasing the open pore volume. The size and the shape of pores were approximately the same as those of the original coal powder particles, and pore size could be controlled in the range from 50 to 1000μm by controlling the particle size of the coal powder. While, the intrinsic pore size of cordierite ceramics without coal additives was about 10μm. Thus, the porous ceramics showed bimodal pore size distributions. The observed correlation between the content of coal particle and the open pore volume percent well agreed with the calculation based on the density of the dried body and the coal. Pure water flux through the disc sample without coal powder addition was 2.08×10^-5m³/m²⋅s, but it increased 40 times when the volume percent of the large pores in the body became 45%. The increase in the pure water flux was well explained by a model in which pure water passes preferentially through the larger pores.

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Thermal Shock tests by arc-discharge heating were carried out on the notched disc specimens of artificial graphite electrodes, while monitoring the change of crack opening displacement (C. O. D.) with time by using a clip gage. The crack abruptly extended from the notch tip at a certain time and stayed at the arc spot in the center of the specimen. The slope θ of the line connecting the origin and C. O. D. just after abrupt extension of the crack, could be determined on each electrode sample within the accuracy of ±10%, independent of notch size. The θ-value thus determined was proposed to be used as a parameter for evaluating the thermal shock resistance of graphite electrode materials and to be named as “thermal shock energy dispersion rate”.

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Thermal decomposition of zinc 2-ethyl-hexanoate solution on glass substrates gave zinc oxide thin films. Zinc sulfide thin films were obtained by sulfidation of the zinc oxide films in a hydrogen sulfide atmosphere. The ZnS films were transparent, had a high degree of crystallinity with {111} preferred orientation, and the breakdown voltage of these films was about 28Vrms at a film thickness of 430nm (breakdown field was about 0.65MV/cm). The microstructure of the cross section of the ZnS thin films formed on a glass substrate was a particle-stacked structure, which is different from the columnar or conical grain structures obtainable by electron beam evaporation or sputtering. MIS (Metal/Insulator/Semiconductor)-type and sandwich (Metal/Insulator/Semiconductor/Insulator)-type thin film EL (electroluminescent) devices fabricated using the ZnS thin films showed EL emission above 100 ft-L at 130Vrms, 5kHz sine wave.

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Using two types of commercial Si-C-O fibers (Nicalon NL400 and NL200 produced by Nippon Carbon Co.), the pyrolysis mechanism of the fibers has been studied. The pyrolytic rate has been measured with a thermobalance in an argon atmosphere for 64.8ks at temperatures from 1473K to 1673K. The pyrolytic rate was strongly dependent on temperature. NL400 with the higher concentration of oxygen, in which the atomic arrangement was highly disordered, decomposed to β-SiC rapidly. Most of SiO evolved at the early stage of the pyrolysis, whereas CO continued to evolve constantly before the completion of the pyrolysis. The initial degradation in the tensile strength of the fiber was followed by a slower decrease. The pyrolytic rate was described by the Avrami-Erofeev equation. It is considered that the pyrolysis is controlled by the nucleation and growth of β-SiC crystallites.

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Na_1-xTi_2+xAl_5-xO₁₂ (NTAO) whiskers were effectively grown by the solid reactions in the presence of excess Na₂O. The excess Na₂O was evaluated by a y value in an experimental formula Na_1-x+yTi_2+xAl_5-xO_12+y/2. The best condition of whisker growth was obtained by heating for 3-5h with y=0.2-0.4 under the steady state of x=0.2 at 1350°C. The whiskers were 30-100μm in length and 5-10μm in diameter. The excess Na₂O played very important roles to promote following reactions through two stages. The first stage is the formation of freudenbergite by a reaction between rutile and Na-β''-alumina which was made with α-alumina and Na₂O. The second stage is the formation and growth of NTAO whiskers by a reaction between freudenbergite and Na-β''-alumina in the existence of Na₂O liquid phase.

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The electric field concentration and its singularity in the vicinity of the tip of a sharp crack-like electrode lying on the surface or interior of a solid dielectric are analysed theoretically. It is found that the local electric field in the vicinity of the tip of a sharp electrode is proportional to l to hte power of -1/2, where l is a distance from the tip of the electrode. A new concept, “the electric field intensity factor” is defined from above results. A similarity rule between the stress intensity factor and the electric field intensity factor is discovered. A new criterion for the dielectric breakdown is suggested using the electric field intensity factor. The dielectric breakdown tests on model materials are carried out, which show the validity of the new theory.

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Silver sheath process has been applied to the fabrication of oxide superconductor wires. In the present study, the possibilities of using the copper sheath are investigated from the view points of reactivities of YBa₂Cu₃O_7-x (YBC) with copper metals. After hot-pressing of YBC powders enclosed in a copper tube in the temperature range 400° to 800°C under 200kg/cm² for 1h, the reaction layers were examined by optical microscopy, SEM, XRD, EPMA, etc.. The reaction began above 600°C and the oxygen component in YBC oxidized the copper surface to produce Cu₂O. BaCu₂O₂ formed in the YBC side. YBC-Cu powder mixtures were hot-pressed in the same manner as the above. Cu₂O formed chiefly at 90-10wt% composition. For more than 30wt% of Cu, YCuO₂ and BaCu₂O₂ having monovalent Cu were produced by the reaction with Cu₂O. In order to prevent such reactions, gold or silver electroplating was applied to the inner surface of the copper tube. The electroplating of gold of 1μm or silver of 20μm prevented the reactions during hot-pressing at 700°C. The lower P_o2 in the copper tube led to the decomposition of YBC to give oxygen gas and the tetragonal phase. When the oxygen gas (1.5kg/cm²) was supplied to the copper tube, YBC kept the orthorhombic structure and its superconductivity after the hot-pressing at 700°C.

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Oxidation behavior of sintered AlN by oxygen and water vapor was studied at 1400°C for the purpose of surface treatment. The partial pressure of oxygen, P_o2 was controlled at 10^-10 and 10kPa, and that of water vapor, P_H2O was changed at 5.0×10^-2 to 8.5kPa. The oxidation product detected by XRD was α-Al₂O₃. Oxidation rate was increased with increasing P_H2O. The weight gain with time by oxygen was parabolic, and that by water vapor was linear. The Al₂O₃ layer formed by the oxidation of sintered AlN with oxygen was relatively dense, and coherent. The oxidation kinetics were discussed using the mixed-control rate equation on the basis of unreacted-core model.

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Electrophoretic coating was performed to form alumina insulation layers for the tungsten double helical filaments of a CRT heater. Alpha alumina particles an average diameter of about 4μm were dispersed in ethanol-water suspension containing with dehydrated Al(NO₃)₃ or dehydrated Al(NO₃)₃+Mg(NO₃)₂⋅6H₂O. Positively charged alumina particles in the suspension (43wt% solid) were deposited on tungsten double helical filaments by passing a direct current at 100V. Thickness of the alumina layer formed by dehydrated Al(NO₃)₃ suspension did not reach 30μm even for a long time current flow, and alumina particles were tightly packed within the spaces between the coils of the double helical filaments. On the other hand, that formed by the suspension with dehydrated Al(NO₃)₃+Mg(NO₃)₂⋅6H₂O increased with deposition time, but there was insufficient packing of alumina particles between the coils. A new electrophoretic deposition process for uniform packing of Al₂₃O₃ particles was proposed. The inner layer with closely packed Al₂O₃ particles was formed first by deposition from the dehydrated Al(NO₃)₃ suspension, and the outer layer was deposited successively from the suspension of mixed electrolytes of dehydrated Al(NO₃)₃ and Mg(NO₃)₂⋅6H₂O. The new deposition process (double step method) enables to pack Al₂O₃ particles closely, and the area ratio occupied by Al₂O₃ particles becomes higher than 50%.

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Corrosion behavior of gas-pressure sintered silicon nitride with the additions of yttria and alumina was investigated in boiling sulfuric acid. In the corrosion test ranging from 3 to 12N for 1h, the maximum weight loss was found at the concentration of 3N. The weight and strength of the specimens gradually decreased with time exposed for the corrosion test, although a rapid decrease in strength occurred in the initial stage of corrosion. A gradual decrease in strength with time could be attributed to the growth of corroded layer. The strength was approximately held constant when the corroded layer thickness, which was determined from the depth of the layer with a different color, was less than 100μm; the strength was strongly dependent on the thickness of the corroded layer beyond 100μm.

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A new bonding glass which can be worked at a low temperature (480°C) and is resistant to water has been prepared. The glass is composed of SiO₂-B₂O₃-PbO-ZnO-Al₂O₃-CdO with a low softening point (below 410°C) and a thermal expansion coefficient of (90-100)×10^-7/°C comparable with that of a ferrite substrate. The composition of the glass with a high durability against water is as follows: SiO₂=4wt%, B₂O₃=9wt%, PbO=75wt%, Al₂O₃=0-3wt%, ZnO=2-6wt%, CdO=5-12wt%.

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A new extracting method utilizing rubber pressing method has been developed; isostatically pressing and simultaneous heating of the green compacts. As a result, the extracting time was reduced to about 1/24, and it seemed that the binder extraction is possible without destroying the green compacts of any thickness in the case that the binder is water.

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Pollucite powders of single phase containing excess SiO₂ have been prepared from CsNO₃, Al₂O₃ sol and SiO₂ sol by a sol-gel processing. Behaviors of the thermal expansion of these powders have been also studied. As a result of the research for synthesis of the pollucite powders (Cs₂O:SiO₂:Al₂O₃ (molar ratio)=1:4.5-5:1), the two-stage heat treatment was the most effective: after the dried samples prepared by the solgel process were heated at 600°C for 24h and were subsequently heated at 750°C for 10h, then the powders were calcined at 1000°C for 50h. The synthesized pollucite powders of single phase containing excess SiO₂ showed a low thermal expansion from room temperature to 200°C. Furthermore, it is revealed that the range of temperature showing the thermal expansion less than 0.1% was extended up to 600°C.

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Spinel composite ceramics reinforced with 0-40vol% β-silicon carbide whiskers were prepared by hot-pressing at 1800°C under 30MPa for 30min. The mechanical properties (bending strength, hardness, modulus of elasticity, fracture toughness) of the hot-pressed bodies were measured. Fully dense composites were obtained in the whisker content up to 30vol%. The composite mixed with 30vol% whiskers showed the highest room temperature bending strength (about 440MPa), which was about two times as large as that of monolithic spinel. These composites had more excellent high temperature strengths than monolithic spinel. The hardness and modulus of elasticity of dense sintered bodies increased with an increase in whisker content. The fracture toughness increased monotonously with increasing whisker content and showed maximum values (3.5-4.0 MPa⋅m^1/2) at 40vol%, which were 2.1-2.7 times as large as those of monolithic spinel due to crack deflection and pull-out of whiskers.

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PTC (Positive Temperature Coefficient) effects of grain boundaries in a normal PTC thermistor and in a reduced and reoxidized one were directly measured by A. C. complex impedance analysis. The PTC effect and capacitance of a single grain boundary were different with each grain boundary and the PTC effect of the grain boundary with a smaller capacitance tended to be larger. It was considered that the difference in the thickness of the depletion layer of the Schottky barrier in the grain boundary caused the difference in the PTC effect and the capacitance of each grain boundary.

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Aluminum nitride (AlN) was formed by two-step pyrolysis of poly (isopropyliminoalane) in Ar. The product pyrolyzed at 1000°C was an amorphous material. Solidstate ²⁷Al-nuclear magnetic resonance spectroscopy (NMR) showed that an AlN-like structure was present in the product. Heat treatment of the pyrolyzed product at 1600°C yielded crystalline AlN from the amorphous material.

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Cu⁺ ion-conducting glasses were prepared in the pseudoternary system CuCl-Cu₂MoO₄-CuPO₃. These glasses showed high ion conductivities of the range of 10⁰ to 10^-4Sm^-1 at room temperature. The conductivities of these glasses increased with an increase in the CuCl content at a given composition parameter y, which denotes the ratio of the number of phosphorus atoms to the total number of phosphorus and molybdenum atoms in the glasses, y=[P]/([P]+[Mo]). For the glasses with a low and constant CuCl content the conductivities steeply decreased with an increase in y, while the conductivities gradually or almost independently changed with an increase in y for the glasses containing a constant and large amount of CuCl.

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