The optimum condition for the sample preparation in the measurement of glass homogeneity by Shelyubskii's method has been investigated to minimize the error arising from the unideality of the surface of glass particles to form a Christiansen cell. Both silica glass and optical glass particles were subjected to etching with HF or KOH solution to remove fine powder clinging to the surface of the particle or to remove the stressed layer which would be formed during pulverizing. The etching with 1% HF solution for 5min or 1N KOH solution for 60min at 40°C was most effective to minimize the error. The maximum transmission for the Christiansen cell prepared from optical glass powder (246-297μm) after this treatment was 94% which was close to theoretical value, 99%, calculated by assuming the standard deviation to be 1.0×10^-5. The chemical composition near the surface of an optical glass analyzed with ion microanalyzer was known to be unchanged with these etching.

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A Pt crucible having a pin hole at the center of its bottom was piled on another Pt crucible having no hole (Fig. 1 (A)), Polycrystalline aggregate of γ-6Bi₂O₃⋅SiO₂ or γ-6Bi₂O₃⋅GeO₂ was charged into the double crucibles. The top of the upper crucible was heated to 1250°-1280°C while the bottom of the lower crucible was cooled by water-cooled jacket in a SiC furnace so that the crystal aggregate melted leaving a thin crystal aggregate layer 1-2mm thick unmolten at the bottom of the lower crucible (Fig. 2). After 5h, the temperature of the top of the upper crucible was lowered at a rate of 5°C/h, so that the melt solidified at a rate of 0.4mm/h under a thermal gradient of 115°C/cm. The crystal aggregate left unmolten at the bottom of the lower crucible acted as seeds. Among numerous columnar crystals grown from the seeds, one having passed through the pin hole at the bottom of the upper crucible grew to its full size as a monocrystal of γ-6Bi₂O₃⋅SiO₂ or γ-6Bi₂O₃⋅GeO₂ in the upper crucible (Fig. 12). The crystallographic orientation of the monocrystal ingot could be adjusted by previously placing a small piece of γ-6Bi₂O₃⋅SiO₂ or γ-6Bi₂O₃⋅GeO₂ monocrystal with desired orientation at the center of the bottom of the lower crucible, i.e. just below the pin hole of the upper crucible (Fig. 1 (B)). Transparent crystal plates up to 30mm in diameter were obtained by cutting the ingot transversely and polishing their surfaces (Fig. 3). Although they showed a slight birefringence (Fig. 4) and some very weak diffraction peaks besides one strong peak, when X-rayed (Fig. 6 and 7), they were free from pore, inclusion and grainboundary. Their optical transmissions (Fig. 9), optical activities, photoconductions (Fig. 10) and electrooptic effects (Fig. 11) were almost comparable to those reported for the single crystal obtained by Czochralski technique (Ref. 1, 9 and 10).

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Iridescent phenomenon which is caused by the precipitation of very thin crystalline phases was studied in the glaze composition of 0.12K₂O⋅0.48PbO⋅0.40ZnO⋅0.15Al₂O₃⋅1.70SiO₂. The effect of TiO₂ and/or NH₄VO₃ additives on the precipitation behavior was examined. During slow cooling followed by heating the above mentioned primary glaze composition in the temperature range between 1150°C and 1250°C, Zn₂SiO₄ crystal was precipitated. Both Zn₂SiO₄ and Zn₂TiO₄ were precipitated when TiO₂ (5wt%) was added to the primary composition, while leaflet-shaped TiO₂ (rutile) crystals were precipitated with the addition of TiO₂ and NH₄VO₃. Clear iridescence was caused by precipitation of the leaflet-shaped TiO₂ (rutile) crystals, and was interfered by the precipitation of Zn₂TiO₄ and/or Zn₂SiO₄ crystals. The precipitates were examined by optical microscopy, scanning electron microscopy, analytical electron microscopy and X-ray diffractometry, and the origin of the iridescent phenomenon was discussed in detail.

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Iron content in kaolin minerals of Gairome clay (sedimentaly clay which is very important plastic fire clay for Japanese ceramic industries) was examined quantitatively by an analytical electron microscope equipped with energy dispersive X-ray spectrometer. It was confirmed that irregular shaped platy kaolinite showed definite iron content whereas the hexagonal and tubular particles did not show any iron content. Treatment with dilute hydrochloric acid could not reduce the iron content in Gairome clay, so it may suggest that the iron is contained in the crystal structure of kaolinite.

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As fundamentals for development of refractories composed of oxide and carbon, reactions between carbon and each oxide of Cr₂O₃, (Al_xCr_1-x)₂O₃ and Mg(Al_xCr_1-x)₂O₄ were studied. Compacts of the oxide powder only or mixing powder composed of carbon and each one of the oxides were heated in carbon powder at 1000°C to 1500°C. The following results were obtained.
(1) Their oxides hardly reacted with CO gas even at 1500°C, but reacted with carbon.
(2) Cr₂O₃ reacted with carbon to form Cr₃C₂ and/or Cr₇C₃ according to ratio of Cr₂O₃ and C in original compacts above 1100°C.
(3) (Al_xCr_1-x)₂O₃ reacted with carbon to give α-Al₂O₃ and Cr₃C₂ above 1300°C under existence of excess carbon.
(4) Mg(Al_xCr_1-x)₂O₄ reacted with carbon to form MgAl₂O₄, MgO and Cr₃C₂ above 1300°C, and MgO and Cr₃C₂ were formed owing to reaction of MgCr₂O₄ with carbon above 1200°C under existence of excess carbon.

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High efficiency infrared radiants similar to infrared radiation of black body were developed by ceramics made from mixture of several kinds of transitional element oxide. For example, in a mixture constituted by MnO₂ 60%, Fe₂O₃ 20%, CuO 10%, CoO 10% fired at 1150°C, good results as high efficiency infrared radiants were obtained using MnO₂ and Fe₂O₃ as main materials and addition of CuO and CoO ingredients as adjunct materials. But these ceramics have weak thermal shock due to high value of thermal expansion. However, this thermal expansion could be lowered by additiog of petalite and cordierite minerals. The efficiency of heating the object by high radiation infrared radiants were higher than metal surface radiants and the so-called far-infrared radiants.

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Growth of single crystals of PrB₆ and NdB₆ in molten aluminum flux in an argon atmosphere have been investigated. As-grown PrB₆ and NdB₆ single crystals were used for measurements of lattice constant, density and Knoop-microhardness, and also for the oxidation in air at temperatures between 700° and 1250°C. The optimum growth conditions to obtain cubical single crystals are summarized as follows. The mixing atomic ratios of B, Pr or Nd and Al: for PrB₆; (B/Pr)=5.7, (Al/Pr)=77, and for NdB₆; (B/Nd)=5.5, (Al/Nd)=78. For both of PrB₆ and NdB₆, the heating temperature (the temperature of molten flux) and time held at the temperature: 1500°C and 10h. Each of PrB₆ and NdB₆ single crystals exhibited blue color and metallic luster. In both cases, cubical single crystals composed of {100} faces, and needle and thick-plate single crystals, each of which has well-developed (100) face, were obtained. Lattice constants (a₀) and densities (D) determined on single crystals at room temperature are as follows, PrB₆; a₀=4.1327±0.0001(Å), D=4.76±0.03g/cm³ NdB₆; a₀=4.1266±0.0001(Å), D=4.89±0.02g/cm³
Values of Knoop-microhardness determined on (100) faces of single crystals are as follows,
PrB₆; ‹100›: 1890-2200kg/mm² ‹110›: 1520-1740kg/mm² NdB₆; ‹100›: 2010-2270kg/mm² ‹110›: 1645-1950kg/mm²
Oxidation of PrB₆ and NdB₆ single crystals began to proceed in the vicinity of 730°-750°C, and oxidation products of PrB₆ and NdB₆ were found to be Pr(BO₂)₃ (monoclinic system) and noncrystalline B₂O₃, and Nd(BO₂)₃ (monoclinic system) and noncrystalline B₂O₃, respectively. The oxidation rates of both of PrB₆ and NdB₆ single crystals were able to be expressed by the general oxidation rate equation, (dw)ⁿ=kt, where n was 2.02±0.10 for PrB₆, and 1.94±0.16 for NdB₆. Based on the relation, the estimated apparent activation energies of PrB₆ and NdB₆ single crystals were 148.5±3.8kcal/mol and 127.1±3.0kcal/mol, respectively.

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The heat capacities of leucite-type compounds, KAlSi₂O₆, RbAlSi₂O₆ and CsAlSi₂O₆ were measured by means of an adiabatic calorimeter at 77K to 300K, and differential scanning calorimeter at 300K to 970K. The entropy at 298.15K for KAlSi₂O₆, RbAlSi₂O₆ and CsAlSi₂O₆ based on our measurements were 166.5±2.0, 178.6±2.1 and 189.2±2.5J⋅mol^-1⋅K^-1, respectively. It was found that these values were related with the degree of the distorted structure in these compounds. At higher temperature, the heat capacities showed an anomaly at 893K and 638K for KAlSi₂O₆ and RbAlSi₂O₆, respectively. The corresponding entropy of transition for KAlSi₂O₆ and RbAlSi₂O₆ were 9.7J⋅K^-1mol^-1 and 8.2J⋅K^-1mol^-1, respectively. The results were interpreted the entropy change in α_??_β transition was a function of the degree of distortion in the framework structure obtained by X-ray analysis, together with the case of ferrisilicate compounds.

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Filtration method has been used for the quantitative determination of uncombined quartz in hydrothermal reaction system. Modifying this method, the authors tried a centrifugal method, and compared both methods in the student experiment in Tokyo Institute of Technology. The centrifugal method was found to be easier, and it was possible to measure in a short time. The standard deviation was within 0.5%, that was smaller than that of filtration method.
Several dissolution experiments were also carried out in order to obtain the basic informations related to this technique. The results of the treatment with 2N HCl only, showed bigger values because of the remaining of colloidal silica. When the ground quartz was treated with 5% Na₂CO₃ solution, only the amorphous silica, which was formed by grinding, was dissolved. And the amount of dissolution was constant even the time of treatment and the concentration of Na₂CO₃ solution were varied. It was clear that 195-280mg of absolute amount of silica gel could be dissolved in 30ml of 5% Na₂CO₃ solution in the condition of the given method of uncombined quartz determination.

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ESCA and IRA spectra of some mixed alkali glasses containing Li₂O and those of 10.7mol% Na₂OI-16.4mol% CaO-72.9mol% SiO₂ glass were measured.
O⁰1s and Si2p binding energies of mixed alkali glasses shifted toward low energy side from those of binary glasses containing the same amount of SiO₂. The shift size became maximum at about Me₂O/Me′₂O=1. It was observed that, although O^-1s binding energy also had tendency to shift toward low energy side even at Me₂O/Me′₂O=1 composition, the values were very close to those of binary glasses including cations of large atomic number. IRA spectra didn't show such an anomalous behavior as ESCA spectra. O⁰1s and Si2p binding energies of Na₂O-CaO-SiO₂ glasses had the same variation as those of mixed alkali glasses. However, O^-1s binding energy in this system shifted toward low energy side from those of binary system glasses. However, its IRA spectra showed a different pattern from those of binary system glasses.

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Five kinds of α-sialon were fabricated by hot-pressing. The composition of them is M_x(Si_9.3Al_2.7)(O_0.9N_15.1). Metal compound M which dissolves interstitially is Ca, Mg, Y, Nd or Er, and x is 0.9 in case of Ca and Mg, 0.6 in Y, Nd and Er. The bending strength and the fracture toughness of α-sialon were measured. The strength was 420-605MPa at room temperature, and degraded at 1200°C to 60-70% of that at room temperature. The fracture toughness was 3.58-3.90MN/m^3/2. A cluster of large grains was identified as a fracture origin.

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