Sintered samples of Li_xV₂O₅ were prepared and the Li⁺ ion distribution in the β-phase was discussed. In the sample preparation by solid state reaction, LiVO₃ powder was used as the lithium source in place of Li₂O and Li₂CO₃ which had been used so far. The tablets made of mixed powders of LiVO₃, V₂O₅ and V₂O₃ were preheated at 560°C in nitrogen atmosphere. The samples thus obtained were ground, pressed into tablets and heated again at 560°C for 11h in nitrogen flow. The final products were identified to be β-phase by X-ray diffraction. The cell Li_xV₂O₅/LISICON/Li_0.25V₂O₅ was assembled to examine the sample of Li_xV₂O₅ physicochemically. The emf of the cell changed monotonously with the lithium content, which suggested that the one-phase β region was 0.22≤x>0.55 and the Li⁺ ions distributed at random on the possible cation sites, i.e. seven-coordinated, eight-coordinated and tetrahedral sites.

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The preparation of ZrC powder from ZrCl₄ and C with a stoichiometric amount of reducing metal has been investigated from 300° to 1100°C under an argon flow (150-200ml/min). Activated carbon was used as the carbon source and the influences of Al and Mg metals were examined. Zinc, as a reducing metal, was entirely ineffective in this reaction. In the ZrCl₄-Al-C system, the formation of Al₃Zr alloy was observed from 500° to 1000°C, and the carburization proceeded above 800°C, but the evaporation loss of ZrCl₄ was about 65% after 1100°C-1h heating. On the other hand, in the ZrCl₄-Mg-C system, ZrC was formed above 500°. In this reaction, the formation of Zr metal from 500° to 700°C and of MgCl₂ from 400° to 1000°C was observed. Due to some amount of oxygen contained in the raw material, MgO and ZrO₂ were obtained above 400°C and 800°C, respectively. At the Mg/ZrCl₄ molar ratio of 3 (1.5 times the stoichiometric ratio), ZrO₂ was not observed and an increase in ZrC and MgO was observed. MgO and MgCl₂ were removed by washing the product in 1N HCl solution, and the product obtained from the carburization of ZrCl₄ above 800°C was the single phase of ZrC. ZrC powder whose particle size ranged from 0.1 to 0.3μm with the lattice constant of a=4.686Å and the crystallite size of 159Å, was obtained by 1100°C-1h heating, and the evaporatio loss of ZrCl₄ was 0.2%. The results showed that Mg is effective as a reducing agent.

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Electrical conductivity of the sodium-borosilicate glasses in 2Na₂O⋅xB₂O₃⋅(8-x)SiO₂ system has been measured in the wide temperature range from solid to molten state. Self-diffusion coefficients for sodium ion were determined at 600°C using RI tracer. Results were discussed in relation to the glass composition using NMR data with the coordination number of oxygen to boron. In the molten state above T_g, the conductivity is inversely proportional to increasing ratio of [BO₄]^-Na⁺/∑Na₊, and took a constant value in the composition range of B/Na≥2, in which non-bridging oxygen disappeared, that is, the electrical conductivity had a singularity at the composition of B/Na=2. Substitution of [BO₄]^- unit for [SiO₄] one decreased the conductivity because bonding state of sodium ion is tightened by [BO₄]^- substitution. No significant effect of [BO₃] on the conductivity was observed. In the solid state below T_g, the composition dependence of conductivity and activation energy had no singularity over the composition range as was reported in the previous reports. The discrepancy of composition dependence on the electrical conductivity between solid and molten states is caused by the difference in frozen temperatures (≅T_g) from melt to glass. In these glasses with compositions of B/Na≥1, the activation energy for conduction increases by approximately 3.5kcal/mol per 100 degree lowering of T_g. It is concluded that the increments are assigned to the elastic term in the activation energy according to Anderson model.

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Optical absorption spectra of the X-ray irradiated alkali borate glasses containing various kinds of halide ions were obtained. Halide ions in glasses form V_k centers (X₂^- centers, X=F, Cl, Br and I) and showed sharp absorptions in the visible or ultra violet range. In the K₂O-B₂O₃-KCl glasses the intensity due to Cl₂^- center decreases with increasing concentration of potassium oxide and drops abruptly at about 20mol% potassium oxide. This behavior coincides with that observed in the previous study on Na₂O-B₂O₃-NaCl glasses and is related to the structural change in the borate network with glass composition. The addition of fluoride or bromide ion to the Na₂O-B₂O₃ glasses also generates F₂^- or Br₂^- center in the acidic range on X-ray irradiation. On the other hand, I₂^- center was created over the entire range of composition examined in this work. Thus it is expected that the iodide ion dissolves in the glasses in a distinguishable way owing to its large polarizing power. The absorption energies due to V_k centers in the glasses are larger than that seen in the corresponding alkali halides. By combining the above results with the Raman shift observed in the Cl₂^- center, it is concluded that the stability of V_k centers in glasses is larger than that in alkali halide crystals. Finally it is observed that halide ions in glasses also reduces the concentration of defect centers in mother glasses as scavenger ions.

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Electronic ceramics with the refractory metallization are fired in a reducing atmosphere to prevent oxidation of the metals. Firing and binder burn-out phenomena of 92% alumina ceramics (Al₂O₃-MgO-SiO₂) with polyvinyl butyral binder was discussed by the first to third reports. In this, the fourth report, a method to minimize the firing shrinkage dispersion was studied referring to moisture in the atmosphere, binder concentration, ambient gas pressure, gas charging rate and furnace structures. The increase in moisture in the reducing gas, and decrease in the binder concentration in the ceramic batch decreased the dispersion of the firing shrinkage (Figs. 6 and 9). When a sufficient amount of fresh gas was circulated on the sample surface in the furnace, the dispersion in the firing shrinkage decreased. The gas inlet structure, gas flow rate, and especially the stacked setter structure should be considerd for the gas circulation uniformity (Figs. 10 and 11). Increased ambient gas pressure in the furnace disturbed the gas-out from the ceramic body, greater dispersion of firing shrinkage (Fig. 12). Through the reports from the first to fourth, the interaction between the binder burn-out and firing shrinkage is indicated as the phenomena of Fig. 13 during heating up. Consequently, Fig. 14 was conducted as a method for the firing shinkage control.

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Mixtures of Si(OC₂H₅)₄ and Al(OC₃H₇ⁱ)₃ corresponding to 3Al₂O₃⋅2SiO₂ were hydrolyzed with ammoniated water of pH above 7.0 in the temperature range from 20° to 80°C. The chemical composition of the products was almost independent of pH or reaction temperature and close to 2Al₂O₃⋅SiO₂. Powders prepared with water of pH below 9.1 were amorphous and consisted of spherical particles smaller than about 0.1μm. Hydrolysis with water of pH above 10.0 gave aluminum hydroxide such as boehmite gel or nordstrandite to X-ray diffraction. From IR spectroscopic analysis of amorphous SiO₂-Al₂O₃ powders, the structure could be interpreted to be one where Si(Al)O₄-tetrahedron and AlO₆-octahedron are bonded at random by sharing oxygen atom. All as-produced powders showed an exothermic peak at 980°-1005°C on DTA associated with crystallization to Al-Si spinel phase. Lattice constant of Al-Si spinel phase produced by heating at 1100°C for 1h was 7.894±0.003Å, and no significant difference in preparation conditions of powders was recognized. Above 1200°C mullitization of Al-Si spinel proceeded rapidly with formation of θ- and α-alumina. Lattice constant a₀ of mullite decreased with increasing temperature. This result suggests that alumina content is higher in mullite produced at lower temperature and that elevation in heating temperature releases alumina component as θ- and α-type from mullite solid solution. The average particle size of SiO₂-Al₂O₃ powders decreased slightly from 0.08 to 0.05μm up to 1300°C but increased remarkably to 0.5μm at 1600°C owing to rapid grain growth.

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The creep behavior of normal sintered silicon carbide has been studied. The creep experiments were performed under compressive stress of 63-267MPa and at temperature of 1620°-1760°C. The silicon carbide showed a constant creep rate. The activation energy of creep was about 790kJ/mol, and the stress exponent was measured as 1.8-2.0. Creep behavior of silicon carbide was discussed from the viewpoint of diffusional process.

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The wetting of oxides (Al₂O₃, ZrO₂), nitrides (Si₃N₄, Sialon, BN, AlN) and carbides (SiC, ZrC, TiC, B4C) and carbon by Ni-Mo alloy (0-40wt%) were determined in N₂ atmosphere at 1500°C by sessile drop method. The following results were obtained.
1) In Al₂O₃/ZrO₂-Ni-Mo system, the metal did not wet these oxide plaques. There were no reaction and no bonding were observed.
2) In nitrides-Ni-Mo system, the metal did not wet nitride plaques. Reaction between nitride plaques and metal slightly occurred, but there was no bonding between them.
3) Contact angle of Ni-30 Mo on Si₃N₄ or sialon plaques in vacuum was≈0°.
4) Contact angle of Ni-Mo containing above 10wt% Mo on TiC and ZrC was≈0°.
Contact angle of Ni-Mo containing above 40wt% Mo on SiC was≈0°.
5) In ZrC-Ni/Ni-Mo system, the following reactions were observed.
ZrC+Ni→NiZr alloy+graphite
ZrC+Mo→MoZr₂+Mo₂C
ZrC+Mo₂C→(Zr, Mo) C
6) In SiC-Ni/Ni-Mo system, the observed reaction were
SiC+Ni→Ni silicide+graphite
SiC+Mo→MoSi₂+Mo₂C

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Absorption spectra of Mn³⁺ ions in PbO-SiO₂ and PbO-SiO₂-K₂O-Na₂O glasses and refractive indices of these glasses were measured, and the effect of chemical composition was studied. The peak wave numbers of Mn³⁺ ion shifted toward the lower wave numbers with increasing MnO₂ addition in PbO-SiO₂ glasses. The refractive indices of PbO-SiO₂ glasses were nearly constant. The peak wave numbers of Mn³⁺ ions in PbO-SiO₂-K₂O-Na₂O glasses shifted toward the lower wave numbers with increasing [K₂O]/[K₂O+Na₂O] ratio. The mixed alkali effect was not observed in the relation between peak wave number of Mn³⁺ and composition. The refractive indices shifted linearly toward the lower values with increasing [K₂O]/[K₂O+Na₂O] ratio. No mixed alkali effect was observed clearly in the refractive index.

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