This study was concerned with the formation and color development of the spinel solid solution in CoO-ZnO-Cr₂O₃-Fe₂O₃-TiO₂ system, and its application to colored glazes.
Specimens were prepared by calcining the oxide mixtures at 1400°C for 1h. The formation of spinel solid solution was examined by X-ray diffraction, the color was discussed by measuring the spectral reflectance, and the stability of the spinel in glazes was tested.
The results were summarized as follows:
(1) Formation of a continuous solid solution was comfirmed by X-ray analysis.
(2) As the amount of Cr³⁺ increased in ZnO-Cr₂O₃-TiO₂ system, the color changed from brownish white through grayish olive to pinkish beige, and absorption of Cr³⁺ shifted towards the short wavelength region.
(3) An increase of Fe³⁺ in ZnO-Fe₂O₃-TiO₂ system caused little change in color, the color being grayish brown.
(4) The color developed in ZnO-Cr₂O₃-Fe₂O₃-TiO₂ system ranged from light brown through grayish brown to reddish brown.
(5) As the amount of Cr³⁺ increased in CoO-ZnO-Cr₂O₃-TiO₂ system, the color change from light yellow brown through grayish olive to strong blue green, and absorption of Cr³⁺ and Co²⁺ shifted towards the short wavelength region.
(6) An increase of Fe³⁺ in CoO-ZnO-Fe₂O₃-TiO₂ system caused the color to change from grayish brown to dark reddish brown.
(7) The colors ranging from grayish brown through dark brownish gray to dark gray developed in CoO-ZnO-Cr₂O₃-Fe₂O₃-TiO₂ system.
(8) According to the results of the colored glaze test, formation of new spinels was observed, and the original Cr₂O₃ rich spinel was fairly stable in lime-zinc glaze and lime glaze. Speaking to shade of glazes in these two glazes, grayish brown was dominant concerning ZnO-Cr₂O₃-Fe₂O₃-TiO₂ system and dark bluish gray concerning CoO-ZnO-Cr₂O₃-Fe₂O₃-TiO₂ system, and magnesia-lime glaze produced generally lighter hue than lime glaze.

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Relation between infrared absorption in the range 800-700cm^-1 and glass structure of fluorine-containing alkalisilicate glasses was studied by comparing infrared spectra of F-containing alkalisilicate glasses with those of silica glass and alkalisilicate glasses.
Only one absorption maximum appeared in the range 800-700cm^-1 in the spectra of SiO₂, R₂O-SiO₂ (R=Li, Na, K, Rb or Cs) and RF-SiO₂ (R=Li or Na) glasses, and was interpreted as an absorption band corresponding to a symmetric stretching vibration of SiO₄ tetrahedron in glass structure. In the case of RF-SiO₂ (R=K, Rb or Cs) glasses, two absorption maximums appeared in the range 800-700cm^-1. The higher and lower frequency maximums were tentatively interpreted as absorption bands corresponding to symmetric stretching vibration of SiO₄ and SiO_4-αF_α (α<4) tetrahedra, respectively.
Owing to formation of SiO_4-αF_α tetrahedron in glass structure, glasses containing larger amount of fluorine were obtained in the KF-SiO₂, RbF-SiO₂ and CsF-SiO₂ systems in contrast to the LiF-SiO₂ and NaF-SiO₂ systems.

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9Al₂O₃⋅2B₂O₃ single crystals of prismatic shape, up to 1mm length, were grown by the slow cooling method of the melt of composition in CaO-B₂O₃-Al₂O₃ three component system. X-ray powder patterns and chemical analyses showed that this crystal was 9Al₂O₃⋅2B₂O₃ reported by Scholze. Its crystal structure was studied by single crystal X-ray analysis using Weissenberg camera. This crystal is orthorhombic, and has the space group C_2v¹²-Cmc2₁ with the following cell constants: a=5.682±0.013Å, b=14.973±0.034Å, c=7.692±0.017Å. The number of formular units of 9Al₂O₃⋅2B₂O₃ in an unit cell was calculated to be 1.09, using a measured density of 2.93±0.01g/cm³. Intensities were estimated visually from triple film packs by comparing Weissenberg spots with a standard scale. Since this crystal was presumed to have a similar structure as one of andalusite, mullite and sillimanite, some structure models of the boroaluminate were constructed based on structures of these crystals. An appropriate model of the structure was obtained by repetition of calculations of structure factors and electron density sections, starting from these model structures. The structure thus obtained was refined by the method of least squares, which led to a structure with a reliability index of R=10.3%. Positional parameters of atoms were obtained for this structure. When all equivalent postions of this structure are fully occupied without any atomic deficiency or atomic replacement, the calculated composition is 10Al₂O₃⋅2B₂O₃. This structure is therefore named 10Al₂O₃⋅2B₂O₃-type structure. This structure contains AlO₆-octahedra, AlO₄-tetrahedra, BO₃-triangles and five-oxygen-coordinated Al atoms. The linkage of these octahedra and tetrahedra runs parallel to a-axis. This structure is very similar to the andalusite structure. Thus X-ray study reveals 10Al₂O₃⋅2B₂O₃-type structure to this crystal. On the other hand, the composition of this crystal was determined as 9Al₂O₃⋅2B₂O₃ from the chemical analysis. In order to explain this discrepancy, it was not necessary to take a deficient structure which was similar to that of mullite as suggested by Scholze, in which some of the equivalent atomic positions were not filled with atoms, but to take a disordered structure of 10Al₂O₃⋅2B₂O₃-type structure in which only the replacement of atoms were noticed without any atomic deficiency. When in this type structure, 4/11 of Al atoms were replaced by B atoms, the composition became Al_20-4/11⋅B_4+4/11O₃₆, which was equal to 1.09 (9Al₂O₃⋅2B₂O₃), and z was calculated to be 1.002. Thus it was concluded that 9Al₂O₃⋅2B₂O₃ crystal had the structure of the 10Al₂O₃⋅2B₂O₃-type, in which less than 2% of Al atoms were replaced by B atoms statistically and 1.09 formular units of 9Al₂O₃⋅2B₂O₃ compounds were contained in an unit cell.

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By a new process, the potassium titanate “Fur-fibers” are easily formed than the KDC process. The new method is called Disk process; titanium dioxide and anhydrous potassium carbonate were well mixed (TiO₂:K₂O=3:1 in the molar ratio) and pressed into disks. The disks were calcined in a muffle furnace at the temperature between 900° to 1100°C for 3 to 10h.
In the reaction of titanium dioxide and potassium carbonate in the Disk process, a low-temperature-type potassium hexatitanate was found and two types of the potassium titanate “Fur-fibers” were observed. The reaction in the Disk Process was depended on the homogeneity of potassium carbonate in the mixture of titanium dioxide and potassium carbonate.
Addition of NH₄Cl, NH₄NO₃, KF and KCl to the mixture of titanium dioxide and potassium carbonate was effective in synthesizing and growing the potassium titanate “Fur-fibers”.

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Mass transport kinetics on surfaces of single crystalline alumim (1102), 1530°-1770°C and spinel MgO⋅2.4Al₂O₃, (100), 1730°-1770°C were measured by the multiple scratch smoothing method. The amplitude of the periodical surface corrugation decayed exponentially with time during annealing. For alumina, dependence of the decay rate on the periodicity of corrugation indicated that surface diffusion is the dominant mass transport mechanism. The surface diffusion coefficient were in a good agreement with the available data obtained on surfaces with different orientations. In the case of spinel, determination of the mechanism was prevented by the strong effect due to a surface anisotropy observed. But the results were compared with the available diffusion coefficients and it was suggested either volume diffusion or surface diffusion of oxygen ion was the dominant mechanism. The mass transport was faster on alumina than on spinel by about an order of magnitude.

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It was reported that the ultrafine particles of alumina was prepared by the neaction of NH₃ gas and AlCl₃ solution. A particle size decreased with decreasing NH₃ gas composition or AlCl₃ concentration. The particles of less than 50Å in size were prepared.
The formation mechanism was discussed as follows. While a mass of AlCl₃ solution falls from the top to the bottom of a stream in a flask, NH₃ gas is absorbed from the surface of a mass. The generation zone on the surface of solution defined in preceding paper shifts toward the innerpart of mother liquid during the very short exposure time for NH₃ gas, so that the ultrafine particles and excess OH^- ions remain in the stocking zone behind the generation zone. The particles and OH^- ions are carried into the mother liquid by the stream in the flask and the excess OH^- ions make the relatively large particles by inhomogeneous reaction with Al³⁺ ions there. The partcles exist in the mother liquid as a stable colloid for the very near equilibrium state of the mother liquid.

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