Heating of the mixture of CaCO₃, SnO₂, SiO₂ and Cr₂O₃ developed reddish color simultaneously with the formation of tin-sphene (CaO⋅SnO₂⋅SiO₂). Characterization of chromium in tin-sphene by chemical analysis, ESCA and ESR revealed that the chromium was mostly tetravalent. ESR and chemical analyses of vanadium in tin-sphene showed that the vanadium was also mostly tetravalent, substituting for the Sn⁴⁺ in the tetragonally distorted octahedral symmetry. It was pointed out that the only one broad absorption band in the visible region observed in the reflectance spectra of a chrome-tin pink stain would be caused by Cr⁴⁺ in this distorted octahedral symmetry. Furthermore, chemical states of chromium and tin in glazes containing calcium were studied by ESR and ESCA in connection with the glaze colors.

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Glasses were prepared over a wide range of composition in the system Li₂O-B₂O₃ using a rapid quenching technique. The glass-forming region was extended up to the composition of 70mol% Li₂O. Raman spectra of the glasses were measured; drastic spectral changes were observed in the glasses containing more than 50mol% Li₂O whereas the spectra of the glasses with the smaller Li₂O content showed a close resemblance to each other. The spectra revealed that the main structural units were the six-membered borate rings with BO₄ units for the glasses with small Li₂O contents and the pyroborate and orthoborate groups for those with large Li₂O contents. Corrected Raman spectra were deconvoluted into six Gaussian lines ascribed to specific structural units and the relative amounts of the structural units were determined on the basis of each area of the Gaussian lines. The six-membered borate ring with BO₄ units and the pyroborate group were shown to have a maximum proportion at the compositions with 33 and 67mol% Li₂O, respectively. A large amount of orthoborate groups, completely discrete anions, was also shown to be present even in the compositions with such a small Li₂O content as 25mol%. The fraction N₄ of four coordination boron atoms present in the glasses was determined against the glass composition and compared with the results by NMR study. Although in both results a maximum of N₄ was observed in the composition region around 30 to 40mol% Li₂O, the maximum value in this study was only a half of that by NMR study. This would be caused by the fact that every structural unit was assumed to have the same Raman scattering efficiency.

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Pb(Zr_0.5Ti_0.5)O₃ (PZT) was prepared by calcining the oxalates which were co-precipitated from a reaction of metallic components in small amount of water with oxalic acid in large amount of ethanol. In the co-precipitation experiments, mixing procedures of two kinds of solutions and effects of additional titration with ammonia solution after oxalation were investigated. It was found that the addition of an aqueous solution containing metallic components to the ethanol solution of oxalic acid and subsequent addition of an ammonium solution were necessary in order to obtain highly dispersed fineparticulated PZT powders which have good crystallinity. These effects were confirmed by X-ray diffractometry, SEM observation, and measurements of particle size distribution. Calcination of thus obtained oxalate at 800°C for 2h produced a mixed phase of PZT's of rhombohedral and tetragonal symmetries. The particle size was around 0.2μm. On the other hand, the calcination at 1100°C produced the tetragonal phase, of which the c/a value was 1.029, and particle size was around 1μm.

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Fusion cast refractories for high temperature (>1400°C) glass melting are Al₂O₃-ZrO₂-SiO₂ system, Al₂O₃-ZrO₂-Cr₂O₃-SiO₂ system and ZrO₂ system. The corrosion resistance, stoning potential and bubble potential of fusion cast refractories has been studied in the temperature range over 1400°C. Five commercial glasses are used for testing. Glasses are soda-lime glass, panel glass, al-silicate glass, alkali-resistant glass and boro-silicate glass. Corrosion resistance of fusion cast refractories to five commercial glasses has different results by glass composition. ZrO₂ system refractory is the best corrosion resistance to al-silicate glass and boro-silicate glass. Al₂O₃-ZrO₂-SiO₂ system refractory is the best corrosion resistance to panel glass and alkali-resistant glass. Al₂O₃-ZrO₂-Cr₂O₃-SiO₂ system refractory is the best corrosion resistance to soda-lime glass. ZrO₂ system refractory is the best stoning and bubble potential.

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The SiO₂-Al₂O₃ powders containing 68 to 78wt% Al₂O₃ were synthesized by spray pyrolysis technique to study their sinterability at 1630°-1650°C. The prepared amorphous powders were transformed directly to crystalline mullite by calcination above 980°C. When heat-treated at temperatures above 1500°C, corundum was detected in the powder composed of 78wt% Al₂O₃. Densification of the silica-rich powder was accelerated by the formation of glassy phase, and the bulk density of alumina-rich powder also increased with the increase of alumina content. While, in the 3Al₂O₃⋅2SiO₂ region, poor densification was observed. The shape of mullite grain in the sintered body changed from needle-like to roundish in compliance with the increase in alumina content, and corundum particles were observed along the grain-boundary in the sintered specimen of 78wt% Al₂O₃ content. Glassy phase which consists merely of silicon and oxygen was observed along the grain-boundaries of the 70wt% Al₂O₃ sintered body.

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The electrolytic behavior of molten glass is important to understand its ionic behavior and is also essential to control an electric melting furnace. The present investigation was undertaken to obtain the fundamental electrolytic behavior of various glass melts composed of mined network-forming oxides such as borosilicate, phosphoaluminate, boroaluminate, phosphoborate and aluminosilicate. Besides the potential sweep voltammetry, decomposition voltages were determined from stationary current-potential curves. The elemental compositions of the Pt electrode-glass interface after polarization were analyzed by EPMA. Decomposition voltages at 900°C were determined as follows; 25Na₂O⋅25B₂O₃⋅50SiO₂: 1.46V, 40Na₂O⋅20Al₂O₃⋅40P₂O₅: 1.05V, 40Na₂O⋅30Al₂O₃⋅30B₂O₃: 1.19V, 40Na₂O⋅30B₂O₃⋅30P₂O₅: 1.02V, The value in 26Na₂O⋅19CaO⋅8Al₂O₃⋅47SiO₂ was 0.96V at 1200°C. The network-forming or conditional ions were reduced at different potentials and the order subject to reduction was confirmed to be (easy) P⁵⁺>Al³⁺>Si⁴⁺>B³⁺ (difficult). The decomposition potentials of these ions were tentatively estimated to be P⁵⁺: -0.7V, Al³⁺: -0.85V, Si⁴⁺: -1.1V, B³⁺: -1.2--1.4V with respect to the electrode potential of the Pt reference immersed in the respective molten sample glass. On the Pt anode, oxygen anions were oxidized resulting in oxygen gas evolution.

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Silicon powder compacts formed by slip casting were reaction-sintered at various heating rates in a mixed nitrogen-hydrogen atmosphere containing 0 to 80vol% hydrogen. The rate of gas consumption measured in the temperature from 1050° to 1400°C gave two peaks. With increasing hydrogen content the nitriding fraction increased a maximum value at 40vol% hydrogen. The hydrogen content also influenced the bending-rupture strength of sintered bodies, and the maximum bending rupture strength was obtained at about 25vol% hydrogen. The nitridation was almost independent of the heating rate.

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The effects of TiO₂ addition on the sintering process and microstructure of alumina ceramics were studied. In air, the solid solubility of TiO₂ in α-Al₂O₃ was too small to be determined by the lattice parameter shift of α-Al₂O₃. Then, the relative amounts of titanium compounds remaining in fired bodies were measured by X-ray diffractometry using a step-scanning technique which can detect less than 0.1wt% rutile or Al₂TiO₅ in α-Al₂O₃, and were compared with the amount of TiO₂. The solid solution of TiO₂ in α-Al₂O₃ was found above 1150°C, and the solubility was estimated to be 0.27wt% at the temperature range from 1300° to 1700°C. Beyond the solubility limit, excess TiO₂ coexisted with α-Al₂O₃ as rutile below 1350°C and as Al₂TiO₅ above 1450°C. The sintering of α-Al₂O₃ was markedly promoted when TiO₂ was added up to the solubility limit and the fired density higher than 97% of the theoretical was obtained at 1400°C. The addition of TiO₂ also promoted the grain growth of α-Al₂O₃. But beyond the solubility limit, the grain size decreased with an increase of Al₂TiO₅. Therefore it is inferred that Al₂TiO₅ existing as a second phase retards the grain growth of α-Al₂O₃. The lattice parameters of Al₂TiO₅ in fired bodies considerably differed from the those of a single crystal. It is explained as due to the difference of thermal expansion coefficient between Al₂TiO₅ and α-Al₂O₃.

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A dense β-SiC sintered body was fabricated using a new process, high-pressure self-combustion sintering (HPCS). By using this process, SiC can be simultaneously synthesized and sintered directly from mixed reactants of silicon and carbon without any sintering aids by initiating the exothermic reaction under high pressure. The conversion ratio to SiC was improved over 99% and the mean grain diameter in the compact could be reduced below 1μm when submicron fine powders of silicon and carbon were used as starting elements. The relative density, Vickers microhardness and fracture toughness were 92-93% of theoretical, 27GN/m² and 4.5MN/m^3/2 respectively.

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The effect of reaction conditions on the chemical composition and particle size of the powders was studied in the preparation of silicon carbide from the SiC₄-CH₄-H₂ system by using RF-plasma. Reaction product was β-SiC by X-ray diffraction. Under the condition of [SiCl₄]=0.1vol% and [CH₄]=0.13vol%, the C/Si ratio of the powders increased sharply with decreasing [H₂] below [H₂]/[CH₄]<15 and the increase in the C/Si ratio was remarkable at higher reaction temperature. When [H₂]/[CH₄]>15, the C/Si ratio was approximately unity and independent of [H₂]. On the other hand, the C/Si ratio increased moderately with increase of [CH₄], and thus the C/Si ratio could be controlled easily by the control of [CH₄]. The crystallite size, D₁₁₁ of SiC powders had a tendency to increase with increasing reaction temperature. This may be due to the decrease in supersaturation ratio at higher temperature.

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The initial alkali corrosion process of ZrO₂ containing glass was investigated. Alkali-resistant glass fiber which contains about 15wt% of zirconia was immersed in 1N NaOH and KOH solutions for 1 to 29 days at 50°C. Quantitative analysis of dissolved elements in the alkali solution and surface analysis by X-ray photoelectron spectroscopy (XPS) of corroded glass were performed. The amount of Si dissolved was approximately propotional to t^0.8, whereas the amount of Zr dissolved remained constant with increasing immersion time. Changes of Zr/Si, Na/Si, Si/O surface atomic ratios and binding energies of photoelectron peaks indicated that despite the difference in the reaction rate the initial corrosion mechanism was the same for NaOH and KOH and that the reaction process consisted of two stages. From the depth profile analysis of Zr/Si, Na/Si, (Si+Zr)/O atomic ratios, in the first stage Zr and Na are enriched at near surface region of 2-10nm depth and this region was inferred to be formed by reprecipitation of dissolved Zr. In the second stage, the Zr-rich layer grows by Si diffusion and its composition was expressed as (Si_1-xZr_x)O₂ (x=0.6-0.7). The first and second stages are reaction- and diffusion-controlled processes respectively. Apparent suppression of Si dissolution by this layer was not observed under these experimental conditions. Transition from the first to second stage occurred when the corrosion by dissolution of Si reached 40-60nm from the initial surface.

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A series of alkali tungsten bronzes are non-stoichiometric compounds having a general formula R_xWO₃, where R is Li, Na, K and Rb and x is less than unity. They are metallic conductors and some of them are reported to be superconductors. The present work has been done in order to obtain glass-ceramics which has high electric conductivity (logσ) by crystallization of glasses containing tungsten and sodium oxides. A series of glasses of a selected compositions in the systems 30-37.5Na₂O⋅57.5-65WO₃⋅2.5-7.5B₂O₃ (in mol%) were melted. The batches of about 70 grams corresponding to the nominal compositions were melted in a 100cc alumina crucible at 1000°C for 1h. The melts were quenched by pouring on a stainless steel plate and pressing with a pressing iron plate. Glasses were ground into a powder of particles less than 37μm. Theses powders were heated in hydrogen atmosphere between 350° and 650°C, and held for 2h. The precipitated crystal was found to contain only tungsten bronze in the range of 500° to 600°C by X-ray diffraction analysis. Pellets were made from the precipitated powder of tungsten bronze for the electric conductivity measurement. The glass-ceramics containing tungsten bronze had logσ_100°C=-0.98--1.50. The logσ of glass-ceramics was shown to be much higher, and their temperature coefficient was much lower than those of glasses with the same composition. The electrical carrier of glass-ceramics was confirmed to be electron from the analysis of thermal electromotive force. Thus conduction mechanism of glass-ceramics was considered to be electronic conduction due to the large polaron.

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The rotary bending test was carried out on sintered Si₃N₄ at room temperature within the range from 10⁴ to 10⁸ stress-cycles by using an Ono's rotary bending fatigue testing machine operating at 3400 cycles per minute. It was observed that fractured surfaces of tested specimen had regions like mirror which appeared in those after the static test. The size of mirrorlike region was also correlated with the stress amplitude and number of cycles to failure. Mirrorlike region seemed to be restricted to the subcritical crack growth under the cyclic stress.

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The tensile tests at elevated temperatures above 1200°C on HP-Si₃N₄ with Al₂O₃ and Y₂O₃ were conducted, and yield phenomena pretty similar to those of mild steel etc. could be observed in the load displacement diagrams. The behaviour of these was effected by cross-head speeds as well as temperatures. These phenomena were thought to be attributed to the cavitation caused by the fall of viscosity of the glassy phase on the grain-boundaries. In the case of reloading following unloading at the lower yield point, the above phenomena could not be seen.

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