In AsO_3/2-BO_3/2 glass system molar volume (V), molar refractivity (R) and thermal expansion coefficient (α) increased linearly with AsO_3/2 content (Fig. 1, 2, 3). Infrared spectra of these glasses showed good agreement with the summed curves for As₂O₃ and B₂O₃ glasses with the mole percents of the components taken into account (Fig. 7). These facts reveal that the structure of these glasses consists of As₄O₆ molecules and boroxol rings randomly distributed each other without forming As-O-B bonds. The increase in transformation temperature (T_g) of the glasses containing more than 70mol% BO_3/2, shown in Fig. 5, is due to the structural change into a layer network of boroxol rings interlaced with As₄O₆ molecules.
The change in ratio of infrared absorption intensities of the BO₄ band at 930cm^-1 and BO₃ band at about 1300cm^-1, shown in Fig. 10, revealed that the fraction of four-coordinated B³⁺(N₄) increased rapidly up to 25mol% BiO_3/2 and reduced to zero at 65-70mol% BiO_3/2. This change of boron coordination estimated from infrared spectra corresponds fairly to the changes of the other properties, that is, the maxima in T_g and Vickers microhardness (H_v), and the minima in V and α at 20-25mol% BiO_3/2 (Fig. 5, 6, 3, 4), and a maxima in α and breaks of T_g- and H_v- composition curves at 65-70mol% BiO_3/2 (Fig. 4, 5, 6).
In binary SbO_3/2-BO_3/2 glasses, α decreased slightly, and T_g and H_v increased with SbO_3/2 content, dangling in a minimum in α, a maximum in T_g and a break of H_v-composition curve at about 30mol% SbO_3/2 (Fig. 4, 5, 6). Introducing SbO_3/2 into B₂O₃ glass weak absorption peaks due to BO₄ groups appeared at 850-1050cm^-1 (Fig. 11). These are obviously due to the change of coordination number of B³⁺ from 3 to 4, but N₄ in these glasses is much smaller than that in BiO_3/2-BO_3/2 glasses.
The difference in the tendency of the coordination number change of boron in three binary borate glasses was interpreted as follows. As³⁺ and Sb³⁺ are coordinated trigonal-pyramidally because of stronger covalent characters of As-O and Sb-O bonds. In the region rich in BO_3/2 content owing to stronger ionic character of Sb-O bond compared to As-O bond, a small amount of Sb³⁺ behaves as NWM, resulting in the coordination number change of a small portion of B³⁺. As Bi-O bond is stronger in ionic character than Sb-O bond, Bi³⁺ behaves as NWM in the same region, resulting in the coordination number change of B³⁺. The coordination number of Bi³⁺, however, decreases with increasing BiO_3/2 content because of increase in the covalent character of Bi-O bond.

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Translucent aluminum oxide-to-niobium metal seals were formed by using an oxide solder and interfaces between the materials were examined by an optical microscope and an electron probe microanalyzer.
The oxide solder used for this experiment was a crystalline solder and was composed of crystals of CaO, Al₂O₃, MgO and B₂O₃, and contained no alkali.
The results were as follows:
(1) Vacuum tight seals were formed by this technique.
(2) The solder which turned into a glass-ceramic composite by sealing operation contained 3CaO⋅Al₂O₃, CaO⋅Al₂O₃ and MgO⋅Al₂O₃ as main constituent phases.
(3) B₂O₃ in the solder was very useful in improving adhesion.
(4) The intermediate layer about 10μ thick was formed at translucent aluminum oxidesolder interface.
(5) Thickness of the intermediate layer at niobium metal-solder interface was less than 1μ. This was in contrast to the case of solder containing Na₂O and K₂O which had formed intermediate layer 10μ thick in the author's previous experiment.
(6) Transition layers with concentration gradients of Al and Nb were formed in the solder at the ceramic-solder and metal-solder interfaces, respectively. These layers were expected to be useful in reducing sealing stress and in improving adhesion.

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With DTA, TGA and X-ray diffraction analysis of the phases obtained in a closed vessel in the temperature range 300-600°C, it was postulated that the dissociation sequence of chromium trioxide into intermediate chromium oxides was CrO₃→Cr₃O₈→X-phase→Cr₂O₅→CrO₂→Cr₂O₃. Although the X-phase was not characterized enough, it was considered to be a new intermediate phase (Cr:O=1:2.49) different from Cr₂O₅.
Seed crystal (HCrO₂), water and oxygen pressure had effects on the reaction. With water, phase of Cr₂O₅ was stabilized At elevated oxygen pressure beforehand (up to 10kg/cm²), phase of Cr₃O₈ was stabilized and formation of Cr₂O₃ was retarded.
Adding HCrO₂ for seed crystals gave rise to change in the reaction sequence, the sequence being CrO₃→Cr₂O₅→CrO₂→Cr₂O₃. Further, seed crystals decreased the effects of water and oxygen pressure on the reaction.

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The effects of V₂O₅ addition on the magnetic properties of Li-Zn ferrites have been studied. Samples were fired at 1050-1150°C for 2 hours in air. The squareness ratio, sintered density, saturation magnetization, Curie temperature, and order-disorder transition of Li-Zn ferrites were determined as functions of V₂O₅ addition.
The results obtained are summarized as follows.
(1) The maximum squareness ratio (B_r/B_m) were obtained by the addition of 0.1 wt% V₂O₅, but further increase in V₂O₅ content decreased B_r/B_m.
(2) The improvement of squareness ratio was due to the combination of small grain size and homogeneous grain size distribution.
(3) It was found from saturation magnetization, Curie temperature and lattice constant that a portion of V₂O₅ dissolved into ferrite. The result support the B-site ordering which decreased with increasing V₂O₅ content. It was shown that the decrease in octahedral site ordering by the addition of V₂O₅ is attributed to the incorporation of V ions in the spinel lattice and also to the separation of α-Fe₂O₃.

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Up to date, refractive index of optical glasses has been discussed in the Drude-Voigt dispersion formula in terms of the inherent wavelength of absorption λ₀ and the number of molecules in unit volume N₁ on the assumption that the oscillator strength f₀ is constant. In this study, the influence of oscillator strength on the refractive index was investigated. It was found that the Drude-Voigt equation in which only a single oscillator is considered,
n_λ²-1=(e²/πmc²)N₁f₀/(1/λ₀²-1/λ²),
is applied very well to the measured dispersions of almost all optical glasses. λ₀, N₁ and f₀ of about two hundred kinds of optical glasses were calculated from above equation, and the following conclusions were obtained;
1) As N₁f₀λ₀ of crystals of the same structure are constant, those of each series of optical glasses such as SK-, La-series etc. are also found to be roughly constant.
2) Refractive index n_d is approximately expressed as a linear function of N₁f₀λ₀². While Abbe's number ν_d is approximately expressed as a linear function of 1/λ₀² but is independent of N₁ and f₀.
3) Refractive index was surely affected by oscillator strength values f₀ as seen in those glasses which have nearly equal λ₀ and N₁ but different f₀ values.
4) Oscillator strength f₀ are small in F-series glasses, while they are large in BK-, SK-, La- and Ta-series glasses. In La- and Ta-series glasses, N₁ are also large.

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The nature of Al-O bonds in K₂O-Al₂O₃-B₂O₃ glasses has been studied by using the optical absorption spectra of VO²⁺ ions dissolved in the glasses. It has been found that the Al-O bonds in the glasses involve a double-bond character found only in the Al-O bonds in a structure unit containing a four-coordinated Al atom. The bonding mode of Al atoms in the glasses has been discussed in the light of the information obtained from the X-ray emission spectra for some aluminoborate glasses. Two modes have been suggested to be considered. In a mode, the only K⁺AlO₄- group is formed independently of the glass composition and, in the other, the K⁺(K⁺AlO₆^-)^- group, together with an AlO₄, is formed in the low K₂O region and the K⁺AlO₄^- group is dominantly formed at the high K₂O content.

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[in Japanese]

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Cobalt-aluminum spinel (CoO⋅Al₂O₃) was synthesized by sintering the equimolar mixture of Co(OH)₂ and γ-Al₂O₃ in at temperature range from 1000 to 1500°C under different atmosphere. When heating the sample in air, the grain size of the spinel was 0.07μ at 1000°C, 11μ at 1500°C. The color of the products was changed from light to violet blue with raising temperature which results larger grain size. Under O₂ atmosphere, a defect spinels (CoO)_1-x⋅Al₂O₃ were formed below 1200°C, and the stoichiometric spinel above 1200°C. Lattice constants of the spinels synthesized below 1200°C under O₂ atmosphere were smaller than those of the samples synthesized at the corresponding temperature in air.
In air, the solid solutions between CoO⋅Al₂O₃ and Al₂O₃ were formed above 1200°C. The amount of dissolved Al₂O₃ in spinel increases with increasing temperature.

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