Submicron powders of α-SiC obtained from commercial green (GC) and black (BC) carbide abrasives were treated with HF (-F powder) or a mixed acid of HF and HNO₃ (-FN powder). Linear shrinkage of these compacts containing 1wt% of boron and 1wt% of carbon were measured as a function of temperature. Then, polytypes in the sintered pellets were identified and the microstructures were observed.
The results obtained were summarized as follows:
(1) By mixed acid treatment, specific surface areas of GC-F and BC-F powders increased by a factor of about 2.
(2) These acid-treated powders could be sintered to 96-98%TD by heating for 1h at 2030°C under the atmosphere of pure helium gas.
(3) The initiation temperature of shrinkage in GC-FN and BC-FN compacts was lower by 100°-150°C than that in GC-F and BC-F compacts.
(4) The specimen GC-F which was sintered at 2030°C consisted of almost equiaxed grains of 2μm in average size.
(5) In contrast to the microstructure of GC-F compact, that of GC-FN compact contained a number of elongated grains.
(6) The microstructure of specimens BC-F and BC-FN which were sintered at 2030°C was similar to that of specimen GC-FN, whereas specimens which were sintered at 2130°C consisted of elongated grains only.
(7) The phenomena of (3) to (6) might be interpreted in terms of material transport through the boundary phase.

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The optical absorption spectra of VO²⁺ ions dissolved in R₂O-MgO-B₂O₃ glasses (R=Li, Na and K) have been measured in order to examine the behavior of π-electrons in the glass network. In the light of informations obtained from NMR measurements of four-coordinated boron atoms in Na₂O-MgO-B₂O₃ glasses, the discussion has been made on the formation of four-coordinated boron atoms and bonding mode of magnesium atoms in R₂O-MgO-B₂O₃ glasses by using the data of optical absorption spectra. Judging from the dependence by the peak position for B₂*-E_π* transition on the glass composition, it has been indicated that both MgO and R₂O behave as network modifiers in R₂O-MgO-B₂O₃ glasses and some of the MgO contribute to the formation of glass network, presumably in the form of planar MgO₄. Moreover, it has been also suggested that the formation of four-coordinated boron atoms in the glasses is controlled by the ratio of the electric charge to the ionic radii of Mg²⁺ and R⁺ ions and by the molar fraction of MgO and R₂O.

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Non-stoichiometric TiO sintered bodies were produced by sintering at the temperature of 1350°C in vacuum (10^-4Torr), starting from the mixed powder of titanium oxide and titanium as raw materials. Some physical properties (mechanical, electrical and optical) and some factors (mean particle size, lattice strain and apparent density) governing the microstructure of the sintered bodies were measured.
The following results were obtained. (1) The TiO phase obtained is mainly cubic, but it contains complex ordered lattice structure phase only a little between TiO_0.94 and TiO_1.02. (2) As the oxygen content in TiO phase decreases, the crystal size, the apparent density and the lattice strain increase. (3) As the oxygen content in TiO phase decreases, the hardness and the bending strength of the sintered bodies increase. The facts are assumed to be the effect of the lattice strain. (4) The electrical resistances of the sintered bodies are almost constant for TiO_0.94-TiO_1.02, whereas as the oxygen content in TiO phase increases, it increases for the composition of O/Ti>1.02. (5) According to the color analysis of the polished surface of the sintered bodies, as the oxygen content in TiO phase increases, the lightness of Munsell value decreases, whereas the hue is almost constant (2.5Y).

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Single crystal of lithium triborate, Li₂O⋅3B₂O₃, was prepared by heating B₂O₃ glass covered with LiF powder in a platinum cruicible at 750°C for 10h. Its crystal structure was studied by single crystal X-ray analysis. Weissenberg exposures were obtained for the zero to the 3rd layers, rotating the crystal around the c-axis and using Cu K_α radiation. The systematic extinctions of the reciprocal lattice points corresponded to those of the space group Pna2₁ or Pnam in orthorhombic system. Intensity data were collected with an on-line Picker single crystal automatic diffractometer by using Cu K_α radiation. Unit-cell dimensions and standard errors, a=8.4473±0.0007Å, b=7.3788±0.0006Å and c=5.1395±0.0005Å, were obtained by the method of least squares from phase angle data recorded for high angle reflexions. For the structure with two formula units of Li₂O⋅3B₂O₃ in the cell, the calculated density is 2.48g/cm³. An experimental test showed the material to have a density of 2.40g/cm³. Since this crystal has similar crystallographic parameters to those of cesium triborate, it is presumed that in this compound the anion structure consists of triborate anion groups (TAGs), as is the case with the Cs-salt. Moving a TAG in the unit cell, a self-consistent position of the TAG was found, from which a network structure of TAGs sharing corners was constructed by the symmetry operations of the space group Pna 2₁. The structure was then determined by a trial and error method, starting from this triborate model. Using the phase calculated from the triborate model, electron density sections were calculated. From these sections, positions of lithium atoms were found, and a crude model of the structure was constructed. The structure was refined by the method of least squares, which led to a structure of reliability index R=0.145. Examination of structure factors at this stage of refinement showed that stronger reflections were affected by the secondary extinction. The correction for the extinction was made on the structure factors, using an approximate linear equation. On the basis of modified structure factors, the structure was refined to a final R value of 0.097. Positional parameters of atoms are given. The borate polyanion in this phase is built up from the triborate groups. The groups share corners with each other and are connected to form endless spiral chains which run parallel to c-axis. These chains are then interlinked each other by B-O bonds, forming three dimensional networks.

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Sintering of pure Cr₂O₃ powder compact in carbon powder at 1000° to 1500°C was investigated.
When the compacts of fine particles (about 0.5μm in average) were fired, rapid shrinkage occurred in the early stage of the sintering. At temperature below 1350°C, the initial sintering could be described as a volume-diffusion process. However, after 70 to 90min, an evaporation-condensation mechanism became predominant and the shrinkage virtually stopped at a certain final value depending on the temperature. The logarithm of values of the final shrinkage increased linearly with temperature. At above 1400°C and after 20 to 35min, the grains grew abnormally and then closed-pores were left in the sintered body. A small amount of Cr₂(C, N) crystals was segregated on the grain boundary.
When the particle size was large, the rate of shrinkage decreased and the amount of Cr₂(C, N) increased. Moreover the abnormal grain growth did not occur and closed-pores were not observed. As a result, the pore-free body having almost theoreical density was obtained in this case. The grain growth seemed to be controlled by the segregated Cr₂(C, N). When the particle size was above 4.5μm in average, however, the compact hardly shrinked even heating at 1500°C.

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The optical absorption of high index glass in the near ultra-violet region has been studied on the glasses of PbO-B₂O₃, PbO-GeO₂ and PbO-SiO₂ systems. In order to separate the absorption due to impurities from the intrinsic absorption, ultra pure glasses, as well as ordinary glasses, were prepared from the raw materials for optical waveguide glass in a clean room. The results on the measurement of some optical properties and ultra-violet absorption edge for the glasses were as follows.
(1) Ultra-violet absorption edge of the ultra pure glasses were at the shorter wavelength than that of ordinary glass of the same composition. The difference in the absorption edge between two glasses of the same composition was larger for the composition containing larger amount of PbO.
(2) The ultra-violet absorption edge of the ultra pure glasses shifted toward longer wavelength with increasing amount of PbO content. For the glass of the same PbO content, the absorption edge was observed at longer wavelengh in the order germanate, silicate and borate glasses.
(3) The higher the refractive index of the glass, the longer the wavelength for ultraviolet absorption edge.
(4) For an ultra pure glass, the effect of impurity on the absorbance at the skirt of intrinsic absorption band was negligibly small. The wavelength corresponding to a given absorbance of a glass was dependent on the intrinsic absorption wavelength. From this relation, the limiting value toward the shortest wavelengh, where the transmittance of a high lead containing glass of 1cm thick was 80%, could be shown using the intrinsic absorption wavelengh of the glass.

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In X-ray diffraction patterns of calcium sulfite hemihydrate, CaSO₃⋅1/2H₂O, formed by passing a stream of SO₂ through the suspension of Ca(OH)₂ were paid attention to appear many unknown peaks besides peaks belonging to CaSO₃⋅1/2H₂O of orthorhombic system as generally known. Then, synthetic conditions, crystallographic forms and various properties of CaSO₃⋅1/2H₂O containing new phases were investigated in detail.
Unknown peaks were able to divide two phases (called for phases I or II) by synthetic conditions such as the temperature of Ca(OH)₂ suspension and the flow speed of SO₂ gas. Two phases as compound could be considered to result the formations of solid solution or double salt of CaSO₃-CaSO₄ systems, calcium compounds besides CaSO₃⋅1/2H₂O and new phases on polymorphism of CaSO₃⋅ 1/2H₂O. However, the chemical composition of CaSO₃⋅1/2H₂O containing phases I or II composed in the range of 0.6-0.8% as SO₃, 6.8-7.0% as H₂O and without finding calcium compounds corresponding to X-ray diffraction patterns of new phases. Accordingly, it was suggested that new phases were attributable to the formation of new polymorphism of CaSO₃⋅1/2H₂O.
Moreover, the crystal systems of phases I or II belonged to hexagonal systems by using Hull-Davey's graph from X-ray diffraction data. The unit cell dimensions of new phases were: phase I (rhombohedral lattice), a=17.08Å, c=15.46Å; phase II (simple triangular lattice), a=6.773Å, c=12.94Å, so that the crystal structure of two phases were essentially different. Also, phase I was formed by adding an aqueous CaCl₂ solution to an aqueous Na₂SO₃ solution and phase II was not formed. These facts supported existence of two forms as new phases.
In addition, the properties of CaSO₃⋅1/2H₂O containing new phases were confirmed from thermal analysis (TG-DTA), infrared spectra and scanning electron microscopic observation. In the case of CaSO₃⋅1/2H₂O containing phases I or II in comparison with individual CaSO₃⋅ 1/2H₂O, the endothermic peak on DTA curves due to the dehydration of CaSO₃⋅1/2H₂O shifted to low temperature side and also the stretching frequencies for O-H vibration of IR curves shifted to high wave number side. New absorption due to O-H and S-O vibration appeared to 3525cm^-1, 990-998cm^-1, 590cm^-1 and 405cm^-1 respectively. Finally, CaSO₃⋅1/2H₂O containing phases I or II after immersion in water (pH 8-12) at two months disappeared phase II in new phases so that phase II was proved a unstable in new phases.

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Synthesis of solid solutions was attempted in the fluor-tetrasilicic mica system [(Na_xK_1-x)Mg_2.5Si₄O₁₀F₂] and in the fluor-hectorite system [(Na_xK_1-x)1/3Mg_8/3Li_1/3Si₄O₁₀F₂] (0≤x≤1). And solid solubilities of interlayer (Na, K) ions in mica structures and thermal stabilities, crystallization processes and swelling characteristics of these solutions were studied by using X-ray diffraction and DTA method together with SEM. Moreover, discussions were made on the basis of the comparisons of these data with those of previously reported taeniolite system [(Na_xK_1-x)Mg₂LiSi₄O₁₀F₂] (0≤x≤1).
These systems, as well as the taeniolite system, show limited solubility. There form two types of solid solutions, i.e., K-type and Na-type solid solutions, and these two solid solutions coexist in the middle compositional range of each system. This range for each system extends to the side of K-type end member in the order; the fluor-tetrasilicic mica, the taeniolite and the fluor-hectorite system. In each Na-type solid solution, maximum amount of sodium ions which can be replaced with potassium ions is about 15mol%.
The crystallization processes in these system are different from those in the taeniolite system. Na-type solid solution in the fluor-tetrasilicic mica system is considered to be a metastable phase and decomposes into K-type solid solution, fluor-magnesio-richterite and α-cristobalite by prolonged heat treatment. On the other hand, in the fluor-hectorite system, fluor-magnesio-richterite is observed primarily and then changes into Na-type solid solution as the equilibrium phase.
All of the Na-type end members and Na-type solid solutions exhibit swelling properties, but the capacity of swelling decreases with increasing of potassium content. This tendency for each system decreases in the order; the fluor-hectorite, the tetrasilicic mica and the taeniolite system. The difference of swelling characteristics can be ascribed not only to the interlayer cation species, but also the content of interlayer cation and the octahedral cation species. These factors also influence the thermal stabilities and crystallization processes of Na-type solid solutions.

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A DTA curve for the powder prepared by the reaction of NH₃ gas and AlCl₃ solution (G-L method) had a sharp exothermic peak at 360°C and a following endothermic peak which could not be observed on the curve for the powder prepared by the reaction of AlCl₃ solution with NH₄OH solution (L-L method). The exothermic peak corresponds to the heat of crystallization of NH₄Cl included as an impurity and the endothermic peak does to a sublimation of NH₄Cl. The remarkable weight loss on a TG curve was observed corresponding to the endothermic peak.
Very small peaks at 710° and 800°C on the DTA curve for the powder by the G-L method could not observed on the curve from L-L method.
The X-ray diffraction peaks for the powder prepared by the G-L method and heated at 800°C were broader than those prepared by L-L method. These broadnesses are due to the smaller particle size.

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The vapor pressures of ZnO over the spinel solid solutions in the ZnO-CoO-Al₂O₃ and ZnO-NiO-Al₂O₃ systems were measured by Knudsen effusion method at 1330° to 1530°C.
The equation combining the vapor pressure of ZnO with the concentrations of Zn²⁺ ions and cation vacancies and their distribution over the two kinds of crystallographically equivalent cation sites in the spinel lattice was derived according to the method proposed by Nakano for inoic solids. The dependence of the vapor pressure of ZnO over the spinel solid solutions on the concentration of cation vacancies was explained satisfactorily by the equation.
The further experimental results for the relationship between the vapor pressure of ZnO and its concentration were not easily understood by the present derived equation, and it was proposed that the efforts should be made to relate the enthalpy term in the equation with the crystal structure of a solid.
The possible mechanisms for the vaporization of ZnO were also discussed on the basis of the enthalpy data.

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