The glasses in the system SiO₂-Fe₂O₃-K₂O by heating turn into glass-ceramics by precipitating Fe-leucite (4SiO₂⋅Fe₂O₃⋅K₂O) crystals. Thermal expansion of the glass-ceramics is distinctly high compared to the original glasses. Detailed studies show that:
1) Fe-leucite crystals precipitate by the heat-treatment at 800°-1160°C of the glasses 4SiO₂⋅K₂O⋅xFe₂O₃ (x=0.65-1). The amount of the crystals increases as x approaches to 1.
2) Thermal expansion coefficients of glass-ceramics are higher the more the amounts of crystals are, and are almost equivalent to those expected for glass-crystal composite.
3) The Fe-leucite crystals are tetragonal at 30°C and invert to cubic symmetry at about 570°C.

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The heats of solution of alkali germanate glasses and crystals in the system R₂O-GeO₂ (R=Li, Na, K, Rb) were measured in 5% HF aqueous solution with an isothermal jacket calorimeter at 25°C. The relation between the heat of solution per mol of GeO₂ and composition expressed by the mol ratio R₂O/GeO₂ was investigated and was discussed with respect to the structure and bond energy of the glasses and the corresponding crystals. The results are summarized as follows:
1) The relation for glasses showed concave curvature in the composition range, R₂O/GeO₂<0.5 and showed linearity in the range, R₂O/GeO₂>0.5. The extrapolated values of the straight lines to the zero content of R₂O correspond to the heat of solution of hexagonal crystalline GeO₂, irrespective of alkali species.
The above results suggest that the change, GeO₄→GeO₆, proceeds with increasing amount of R₂O up to about the composition 0.33 R₂O/GeO₂, and the inverse change takes place by the further addition of R₂O.
These results for the glasses support the view of E. F. Riebling on structure of alkali germanate melts at 1300°C.
2) For the crystals, the heat of solution increases linearly with increasing R₂O content in the composition range from the pure GeO₂ to the congruent melting compounds: Li₂O⋅7GeO₂, 2Na₂O⋅9GeO₂ and 3K₂O⋅11GeO₂ for respective systems. The slope of the lines becomes steeper in the R₂O rich region beyond above compounds.
3) The calculated heat of crystallization showed maximum at the composition of congruent melting compound in each R₂O-GeO₂ system.
It is suggested from 1), 2) and 3) that the composition range in which GeO₆ octahedra exist is more extensive in glasses than in crystals.
4) From the heat of solution of glasses and the available thermodynamic data, the O-R bond energies in the glasses in the composition range, R₂O/GeO₂>0.5 were calculated on the basis of the method used on silicates in our previous work. The Ge-O bond energy in the glasses was also calculated as 82kcal/mol which is fairly smaller than 108 energy in the glasses was also calculated as 82kcal/mol which is fairly smaller than 108kcal/mol reported by K. H. Sun. The validity of the value obtained here was confirmed in comparison with the activation energy for viscous flow presented by previous investigators.

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In order to determine the specimen length in thermal conductivity measurement of solid materials by hot wire method, a critical time T_d was investigated (T_d is a time where the relationship between the logarithm of time and heat source temperature deviates from a straight line depending the specimen length).
The results were as follows:
1) The relation among critical time T_d, thermal conductivity λ, specimen length l, and hot wire diameter Φ was summerized in a formula experimentally, T_d=0.45l^2.2-Φ/λ^0.6.
2) In order to measure thermal conductivity within an error of ±3% when T_d=300 sec and Φ=0.3mm for an convenient condition of measurement, the specimen length had to be l=(675λ^0.6)^1/1.9.
From the experimental relationship, one can determine a suitable sample length for the measurement when the value of λ can be estimated roughly.

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In order to examine the conduction mechanism of Na-ion in polycrystalline β-Al₂O₃, the temperature dependence of the conductivity was investigated. The plot 1/T vs. σT for the polycrystal which was sintered well at a higher temperature, showed a bending point in the vicinity of a temperature of 250°C. The apparent activation energy of the conduction from the plot was 4-5kcal/mol in the higher temperature range, and 6-10kcal/mol in the lower temperature range. Consideration about the conduction paths of Na-ion in the polycrystal gives the conclusion that Na-ion diffusion within the easy conduction plane of β-Al₂O₃ single crystal controls the conduction in the higher temperature range, and Na-ion diffusion along grain boundary is the controlling process in the lower temperature range. On the other hand, the plot of 1/T vs. σT for the polycrystal which was sintered at a lower temperature, did not show the bending point. The apparent activation energy from the plot was almost the same as that in the lower temperature range for the well-sintered polycrystal. This means that the temperature range in which Na-ion diffusion along grain boundary is the controlling process extends to higher temperature side with decreasing the sintering temperature of the polycrystal.

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The characters and the crystallographical relations of K2O-rich compounds of K₂O-MgO-SiO₂ and K₂O-Al₂O₃-SiO₂ system have not been enough investigated.
K₂O-rich compounds in K₂O-MgO-SiO₂ system were K₂O⋅MgO⋅SiO₂ and K₂O⋅MgO⋅2SiO₂ which was elucidated in this paper. The latter compound was face-centered cubic with a lattice constant of 7.706±0.005Å and formed solid solution with K₂O⋅MgO⋅SiO₂, and further K₂O⋅MgO⋅2SiO₂-K₂O⋅MgO⋅SiO₂ s.s. formed also solid solution with K₂0⋅Al₂O₃⋅SiO₂-K₂O⋅Al₂O₃ s.s. which was a K₂O-rich compound in K₂O-Al₂O₃-SiO₂ system. As a result, the new quarternary compound in K₂O-MgO-Al₂O₃-SiO₂ system was found. This compound was cubic and was expressed by following formula;
K_2x(Mg_x, Si_1-x)O₂-K_y(Al_y, Si_1-y)O₂ s.s. (1/3≤x≤1/2, 2/3≤y≤1)
On the basis of the compound, reaction products of chrome ore with K₂O were identified. Furthermore, corrosion of chome-magnesite and magnesite-chrome refractories by K₂CO₃ vapor were elucidated.

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Aluminium substituted hematite crystals, (Fe, Al)₂O₃, were grown by cooling the SrO-B₂O₃-Fe₂O₃-Al₂O₃ melts with about twenty different compositions. The composition of the crystal with maximum aluminium content was Fe_1.68Al_0.32O₃. Values of atomic ratio Al/(Al+Fe) of the solid solution crystals grown in each batch were always much smaller than those of the melt from which the crystals were grown. In was found that to obtain crystals with high aluminium content, the SrO/Al₂O₃ molar ratio of the melt should be less than 2 and also B₂O₃/Al₂O₃ ratio less than 4. The reason for this limitations may partly concern bonding nature of aluminium ions in the melts, i.e. aluminium ions, when they constitute network forming ions in sufficiently basic melts, would have to overcome relatively high potential barrier to join the crystal lattice upon cooling. Melt of 26SrO-41B₂O₃-11Fe₂O₃-22Al₂O₃ in molar ratio is recommended to obtain crystals with high aluminium content.
Lattice parameters and N′eel temperature were also measured for crystals with different aluminium content. The latter decreases with increasing amount of aluminium down to 586°C for Fe_1.68Al_0.32O₃.

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The chemical reaction process during the vapor growth of magnesia was studied. When magnesium and water vapor are used as starting materials, whiskers seem to grow in the following process; Mg(g) or Mg(OH)₂(g) adsorbs itself on the lateral surface of a whisker, migrates to the tip, and there reacts preferentially. Bulk crystals. were predominantly observed through hydrolysis of MgCl₂ vapor. These crystals seem to grow from magnesium hydroxychloride fluid phase. In this case whiskers having globules at their tips were also observed and thought to grow by VLS mechanism.

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Bulk samples in the system Ge-Se-Te were prepared by quenching in air from the melt. The glass-forming region and the crystalline phases coexisting with the vitrified phases were investigated by X-ray diffraction method. For the glassy samples, hardness and density were measured, and observation under an electron microscope were carried out.
The glass-forming region of these glasses had two “island” structures because polycrystalline materials GeSe₂ and Te were formed in the samples comprising binary systems GeSe₂-Te. The one region consists of the glasses with low content of Ge, typified by such a system as Ge₁₀Se_90-xTe_x with x_??_45. The other region is formed around a Ge (Se_1-zTe_z)₂ system with 0.3_??_z_??_0.7.
From the present experiments, it can be considered that the structure of the glasses in the system Ge₁₀Se_90-xTe_x are constructed from partially cross-linked Se-Te chains with Ge, and that Se in the chain structures are progressively substituted by Te with increasing Te content. In the system Ge (Se_1-zTe_z)₂, the substitution of the Se in the structure of GeSe₂ by Te make possible to form the glasses, and then it is considered that the structure of these glasses can be described as distorted three-dimentional network structure in which the Se-Te chains are completely cross-linked with Ge. The glasses with high Te content in these systems, however, have a remarkable tendency towards phase-separation.

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