The crystallization mechanism in the glasses of MnO-P₂O₅ series containing from 35 to 50 mol% MnO has been investigated by high temperature microscope, X-ray diffraction and Scanning electron microscopy (SEM) techniques. Each batch was melted for 30 minutes at 1150°C in air. Two kinds of specimens were prepared: (1) The melts were poured onto a stainless plate to form discs for specimens of 50mm diameter. After annealing, polished bulk specimens of 10mm thickness were prepared for the experiments of crystallization. (2) The blown-films (about 10μm thickness) were prepared from the melts for the experiments of high temperature microscope. Each bulk specimen was covered with a stainless cup and heated in an electric furnace, under the condition of uniform temperature distribution. Each crystallization temperature was determined by DTA method. The precipitated crystals were determined by X-ray diffraction analysis to be mainly manganese pyrophosphate (Mn₂P₂O₇). The specimens containing 35-45mol% MnO from SEM on the fractured surface showed a fiber-oriented structure due to one-dimensional crystal growth from the surface toward the interior. The rate of the crystal growth was about 1mm/h at 610°C for the bulk specimen containing 45mol% MnO. The blown-film containing 50mol% MnO was mainly composed of the spherulite and dendrite crystals due to three-dimensional crystal growth. Spherulites formed on the blown-film glass showed periodic extinction rings under a polarization microscope. The differences in the direction of crystal growth and the crystal form were related not only to the (MnO+H₂O)/P₂O₅ ratio but also to the water content in the glasses.

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Rutile type soild solutions in both SnO₂-ABO₄ (A=Ga, Cr; B=Nb, Ta, Sb⁵⁺) systems and SnO₂-AB₂O₆ (A=Mg, Zn; B=Sb⁵⁺) systems were synthesized and their lattice parameters were investigated in each system. A complete series of solid solutions were found in the SnO₂-GaSbO₄ system at 1200°C and in the SnO₂-CrNbO₄ system at 1350°C. CrSbO₄ was soluble in SnO₂ up to 80mol% as the form of A_0.5B_0.5O₂ at 1200°C. Similarly, GaNbO₄ and GaTaO₄ were soluble up to 50mol% and up to 85mol% at 1300°C, respectively. In all cases, lattice parameters decreased with decreasing SnO₂ content. Sb-oxides dissolved in SnO₂ in air at 1200°C up to 2.3 atomic% expressed with Sb/(Sn+Sb). The lattice parameters increased with Sb content, which was analysed by X-ray fluorescence method. The lattice parameters of the sample with 2.3 atomic% Sb were a=4.740±0.001Å and c=3.190±0.0005Å. ZnSb₂O₆ (trirutile structure) was soluble in SnO₂ up to 50mol% as the form of Zn_1/3Sb_2/3O₂ at 1200°C; whereas SnO₂ dissolved in Zn_1/3Sb_2/3O₂ up to 20mol% at the same temperature. The lattice parameters decreased with decreasing SnO₂ content. Similarly, MgSb₂O₆ dissolved in SnO₂ up to 50mol% at 1250°C but SnO₂ was little soluble in MgSb₂O₆.

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The longitudinal and transverse ultrasonic wave velocities have been measured for the glasses in the systems R₂O-SiO₂ (R=Li, Na, K and Cs) by the pulse transmission method. The velocities and densities measured by the Archimedes method provided the elastic constants of the glasses; the shear modulus G, the bulk modulus K and Young's modulus E. The log-log plot of the bulk moduli vs. the mean atom-pair volumes can be approximated by a line of slope -4/3 throughout the glasses investigated. The results are different from those of the glasses in the systems MO-SiO₂ reported by Soga et al. (J. Non-Cryst. Solids, 22, 67 (1976)). Based on the previous models of the alkali silicate glasses (Osaka and Takahashi, Yogyo-Kyokai-Shi, 90, 703-09 (1982)) the relations between the bulk moduli and the volumes have been explained qualitatively in terms of the packing effects of the alkali ions and of the formation of the non-bridging oxygens. The former results in increasing elastic constants and the latter the inverse effect.

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Three types of carbon-fiber/CVD-carbon composite, in which carbon matrix was isotropic (ISO), rough columnar (RC) or smooth columnar (SC), were prepared at 1300°C by chemical vapor deposition of propane-hydrogen mixtures. The electrical resistivities of the as-deposited composites were 2.1×10^-3, 1.0×10^-3 and 1.6×10^-3Ω·cm for ISO, RC and SC composites, respectively. The transverse magnetoresistances of all these composites showed negative values at 4.2K. The electrical resistivities of their 3000°C heat-treated products were 1.2×10^-3, 0.3×10^-3 and 0.6×10^-3Ω·cm, respectively. The value of the transverse magnetoresistances of the heat-treated RC and SC composites were positive at 77K, but that of ISO composite was negative. The results indicate that all the as-deposited CVD carbon are turbostratic in structure, and that ISO carbon is non-graphitizing, while the other two, especially RC carbon is easily graphitizing.

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An apatite-type chromate (V) Ca₁₀(CrO₄)₆CO₃ could be obtained by heating the mixture of 2CaCO₃+3CaCrO₄ at around 900°C in a stream of dry carbon dioxide. It belonged to hexagonal system (a₀=9.82Å, c₀=6.98Å) and corresponded to isomorphous replacement of (OH)₂ of Ca₁₀(CrO₄)₆(OH)₂ by CO₃. This paper is concerned with the disproportionation of Ca₁₀(CrO₄)₆CO₃ in a flow of carbon dioxide gas. Ca₁₀(CrO₄)₆(OH)₂ was also used for comparison. The reaction occurred in two steps, that is, disproportionation reaction and recombination reaction. In the temperature region between 400°C and 700°C, both apatitetype chromates decomposed disproportionately to give CaCrO₄, CaCO₃ and CaCr₂O₄ with an exothermal deflection accompanied by remarkable weight gain (Eqs. 1 and 2).
Ca₁₀(CrO₄)₆CO₃+4CO₂→4CaCrO₄+5CaCO₃+CaCr₂O₄ (1)
Ca₁₀(CrO₄)₆(OH)₂+5CO₂→4CaCrO₄+5CaCO₃+CaCr₂O₄+H₂O (2)
The resulting calcium chromite (CaCr₂O₄) was assumed to be a high temperature modification with reference to the color tone and the diffraction pattern. The subsequent reaction step was observed above 700°C with an endothermic change accompanied by a stoichiometric weight loss to reproduce Ca₁₀(CrO₄)₆CO₃ as was expressed by the Eq. 1 in the opposite direciton.

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The effect of the atmosphere of heat-treatment on the valence and the coordination state of the cobalt ions were investigated. Cobalt carbonate and α-alumina were mixed in the equimolar ratio, and the mixture was heat-treated at 1400°C or 1300°C under various partial pressure of oxygen (P_o2) from 2.1×10^-1 atm to 1.7×10^-7 atm for the heat-treatment at 1400°C, and from 2.1×10^-1 atm to 1.1×10^-8 atm at 1300°C. The lattice constants and the photoacoustic spectra (PAS) of the samples were measured. The lattice constants were scarcely changed with temperature and oxygen partial pressure of the heat-treatment (Table 1). In the PAS of the samples heat-treated in low P_o2 region, only the peak corresponding to the ⁴A₂(F)→⁴T₁(P) transition of Co²⁺ ions in the tetrahedral sites was observed. On the samples heat-treated in high P_o2 region, however, additional peaks were observed, correspoding to the ⁴T_1g(F)→⁴T_1g(P) transition of Co²⁺ ions in the octahedral sites and also to the ¹A_1g(D)→¹T_2g(D) and ¹A_1g(D)→¹T_1g(D) transitions of Co³⁺ ions in the octahedral sites (Figs. 1 and 2, and Tables 2, 3 and 4). Then the following conclusions were deduced. In low P_o2 region, the cobalt ions in the samples were all bivalent and occupied the tetrahedral sites (normal spinel). In high Po₂ region, the following four reactions were supposed to take place at the same time. (1) The Co³⁺ ions were formed by the oxidation of the Co²⁺ ions. (2) By the reaction (1), the quantity of the Co²⁺ ions was decreased. Then the quantity of Al₂O₃ exceeded the stoichiometric quantity of CoO, and the defective spinel was formed. (3) The Co³⁺ ions substituted for the Al³⁺ ions in the defective spinel. (4) A part of the Co²⁺ ions occupied the octahedral sites. The lattice constants were favored to decrease by the formation of the defective spinel (reaction (2)), but favored to increase by the substitution of the Co³⁺ ions for the Al³⁺ ions (reaction (3)). As the result of the competition of the above two reactions, the lattice constants were scarcely changed.

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Preparation of single crystals of SmB₆ (cubic system) and SmB₄ (tetragonal system) using molten aluminum flux method in an argon atmosphere have been investigated. As-grown SmB₆ and SmB₄ single crystals were both used for measurements of lattice constant, density and Knoop-microhardness, and also for the study of oxidation reaction and kinetics in air at temperature range between 700°C and 1250°C and time between 10 and 120min. Results obtained are as follows. The condition to obtain single crystals of SmB₆ as the single phase was found, but it was not found for SmB₄; single crystals of SmB₄ were formed accompanied by the formation of those of SmB₆ in any condition. The optimum preparation conditions to obtain cubical SmB₆ and polyhedral SmB₄ single crystals are summarized as follows. The mixing atomic ratios of B, Sm and Al: for SmB₆; B/Sm=5.7, Al/Sm=87, and for SmB₄; B/Sm=3.0, Al/Sm=87. For both of SmB₆ and SmB₄, the heating temperature (the temperature of molten flux) and time held at the temperature: 1500°C for 10h. SmB₆ and SmB₄ single cryatals of blue SmB₆ and grayish brown SmB₄, both of metallic appearances, were obtained. Cubical single crystals of SmB₆ composed of {100} face, and needle and thick-plate single crystals, each of which has well-developed (100) face, were obtained. In case of SmB₄, polyhedral single crystals and thin-plate single crystals having well-developed (001) faces were obtained, Lattice constants and densities (D) determind on single crystals at room temperature are as follows;
SmB₆: a₀=4.1335±0.0001Å, D=4.97±0.04g/cm³
SmB₄: a₀=7.1781±0.0005Å, c₀=4.0694±0.0003Å, D=6.09±0.03g/cm³
Values of Knoop-microhardness determined on (100) faces of SmB₆ single crystals and that on (001) and (211) faces of SmB₄ single crystals are as follows;
SmB₆: (100) 1630-1930kg/mm²
SmB₄: (001) 1560-1920kg/mm²
(211) 1460-2130kg/mm²
It was observed that the oxidation reaction of both of SmB₆ and SmB₄ single crystals began to proceed at 740°-750°C, and that, in case of SmB₆, the oxidation products were Sm(BO₂)₃ (monoclinic system) and noncrystalline B₂O₃, however, in case of SmB₄ the final oxidation products were the same as in case of SmB₆, but SmB₆ and SmBO₃ (hexagonal system) appeared intermediately. The oxidation rate of SmB₆ single crystals were able to be expressed by the general oxidation rate equation, (dw)ⁿ=kt, where n was 2.00±0.10. Based on the relation mentioned above, the calculated apparent activation energy of SmB₆ single crystal is 201.3±6.4kcal/mol. In case of SmB₄, it was unable for the oxidation rate to be expressed by the equation described above. The investigation into oxidation kinetics is left in future.

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