In this paper paramagnetic centers primarily localized on a phosphorus ion in γ-irradiated glassy and polycrystalline metaphosphates were investigated with ESR. A P₄₊ having fourfold coordination was observed commonly in the asirradiated (77K) glassy and polycrystalline hosts, being considered to originate from a PO₄^2- group on trapping an electron. On thermal annealing of the as-irradiated glasses, the center was found to be converted into a P⁴⁺ with threefoldcoordination with C_3v symmetry, detaching an oxygen from its coordination sphere. The driving force of such a structural relaxation is considered to be electrostatic repulsion between an excess electron and lone pair electrons on the oxygens directly attached to the phosphorus.
The results obtained in this work are almost identical with those of arsenic (V) in glass (radiation-induced defects in reduced phosphate glasses are to be published in the subsequent paper). The formation of the fourfold-coordinated center observed for both phosphorus and arsenic has never been known for typical NWF such as Si, B and Al. It is suggested that this result is a common characteristic of radiationinduced centers primarily localized on an NWF whose valence is greater than the coordination number; these ions would provide a coulombic trapping potential for an electron.

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From a viewpoint of the treatment of high level radioactive liquid waste, the immobilization of divalent transition metal ions from aqueous solutions was studied by the use of the crystalline hydrated titania (H₂Ti₂O₅⋅nH₂O) fibers as an ion-adsorbent. The each metal ion was saturately adsorbed on the fibrous adsorbent from the aqueous solution of the divalent transition metal acetate. The adsorbed metal ions were immobilized in crystal lattices as main components of various titanate minerals after the sintering treatment. The copper ions were immobilized into the mineral assemblage of rutile, and Cu₂TiO₃ and Cu₃TiO₄ phases having a complex crystal structure. Zinc ions were fixed into the mineral assemblage of rutile and a Zn₂TiO₄ phase of the inverse spinel structure. Each metal ion of manganese, cobalt and nickel was immobilized into the same mineral assemblage of rutile and a MTiO₃ (M=Mn, Co, and Ni) phase of the ilmenite structure. Rutile in these immobilizers occurs as a matrix mineral in the largest amount. The leachability of each metal ion in the immobilizers was measured under normal atmospheric and hydrothermal conditions. The results of the former indicated to be very stable with high leach resistance of maximal 3.2×10^-9g·cm^-2·d^-1 of mangnese ion, and the results of the latter also indicated to be very stable with maximal 9.1×10^-9g·cm^-2·d^-1 of nickel ion.

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When dc voltage was applied to the fired ZnO specimens of low bulk densities, the current decreased with time for undoped specimens, whereas the current remained unchanged for Sm₂O₃-doped specimens. The resistivity increased remarkably with decreasing fired density. Using a model for initial sintering and Kaker's cubic model, neck radius between grains was calculated from relative density and grain size of fired specimens. The curve representing relation between resistivity and neck radius consists of two straight lines, and the radius at the cross point of these lines was thought to be equivalent to the Debye length. The Debye length was about 0.31μm and 0.53μm for undoped and Sm₂O₃-doped ZnO respectively.

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BaTiO₃-ceramics was prepared by the addition of Si₃N₄ or SiO₂ to the starting material and the resistivity was measured. For lower Si contents, and lower sintering temperatures, the room temperature resistivity of the Si₃N₄-doped specimens was lower than that of SiO₂-doped specimens. Observations of surface microstructure for specimens quenched during heating process revealed that marked grain growth took place in specimens doped with 1wt% Si₃N₄ at the eutectic point. No remarkable structural changes were observed in the specimen doped with 1wt% SiO₂. For 3wt% SiO₂ addition only heterogeneous grain growth was observed at the eutectic temperature. When heated in N₂ atmosphere, however, the specimen doped with 1wt% SiO₂ showed marked grain growth, and surface morphology suggested the presence of a liquid phase. Thermal analysis made in the temperature range 25°-1400°C suggested the formation of a larger amount of liquid phase in specimens doped with Si₃N₄ than those doped with SiO₂. These results indicate that nitrogen from Si₃N₄ enhances the grain growth. Resistivity vs. Si content relations may be explained in terms of the liquid phase formed at the eutectic point.

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Concerning the memory switching caused by the crystallization in CuO-V₂O₅-TeO₂ glasses, the crystallization and the change in conductivity were investigated. The glass formation region of the system was determined. The composition of the glass containing a maximum amount of transition metal oxides was 60CuO, 20V₂O₅, 20TeO₂ in mol% in the ternary system, though the glasses containing more than 55mol% of CuO or V₂O₅ were not found in the binary systems. The substitution of CuO for V₂O₅ with the same amount of TeO₂ (30, 40 and 50mol%) decreased the conductivity. The substitution of CuO for TeO₂ with the same V₂O₅ content (15, 25, 35 and 45mol%), however, increased the conductivity. The dependence of the conductivity on the average distance of vanadium was discussed. Four kinds of glasses of 30mol% TeO₂ with various CuO and V₂O₅ contents were crystallized by the heat-treatment from 300° to 460°C stepwise. The conductivity of 25CuO⋅45V₂O₅⋅30TeO₂ glass increased about two orders of magnitude from 10^-3 to 10^-0.5 ohm^-1·cm^-1 (150°C) by the crystallization. The activation energy for conduction of the crystallized glass was 0.1-0.2eV, which was nearly the same as that of the developed crystal V₂O₅, known as semiconductor. CuTeO₃ and phase A developed other than V₂O₅. However, the conductivity of 55CuO⋅15V₂O₅⋅30TeO₂ glass changed a little by the crystallization, which deposited the phase B and a little CuO and V₂O₅. Phases B, A and V₂O₅ developed in the 35CuO⋅35V₂O₅⋅30TeO₂ and 45CuO⋅25V₂O₅⋅30TeO₂ glasses by the crystallization. The phases which increased the conductivity were V₂O₅ and A. The conductivity changed a little by the deposition of CuTeO₃ and B. The composition of the new crystal phases A and B determined by EPMA analysis were 25CuO, 50V₂O₅, 25TeO₂ and 40-45CuO, 20-25V₂O₅, 35-40TeO₂ respectively.

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The hot pressing in the systems TiN-TiB₂, Ti(C_0.3N_0.7)-TiB₂ and Ti(C_0.5N_0.5)-TiB₂ was investigated concerning sintering conditions, mechanical properties, and the effects of solid solution of carbon in Ti(CN) complex powders. The results are as follows:
(1) Ti(C_0.5N_0.5)-TiB₂ compacts, which contained 30-50wt%TiB₂, have high density and high transverse rupture strength.
(2) Three systems TiN-30wt%TiB₂, Ti (C_0.3N_0.7)-30wt%TiB₂ and Ti (C_0.5N_0.5)-30wt%TiB₂ are compared. It is found that the mechanical properties such as the transverse rupture strength, hardness and the fracture toughness are all improved as the solution rate of carbon in Ti(CN) powders increased, and moreover, it is found that the sintering temperature can be lowered. The improvement is ascribed to the reinforcement of Ti(CN) due to the solid solution of carbon.
(3) Ti(C_0.5N_0.5)-30wt%TiB₂ compacts have the transverse rupture strength of 800MN/m², the porosity of 0.34vol%, the Vickers hardness of 2050kg/mm² at R. T. and the fracture toughness K_IC of 4MPa·m^1/2.

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The internal friction of crystallized Li₂O⋅2SiO₂ glass fibers was measured with torsional oscillations (frequency less than 1Hz) and longitudinal vibrations (about 40kHz). The low-and the high-temperature peaks decreased continuously in height with the increase of crystal content (lithium disilicate), but their positions did not shift. For glasses with crystal content over 50%, both peaks vanished and a new peak appeared in the higher-temperature range (305°C at 1Hz and 395°C at 40kHz). The activation energy for the relaxation mechanism of the new peak was estimated to be about 80kcal/mol. The decrease in the heights and the disappearance of the low and high-temperature peaks with crystallization were due to the decrease in “relaxing units” which were alkali ions and/or nonbridging oxygen ions within glass network matrix. The behavior that both peaks disappeared with about 50% crystal content was discussed on the basis of the following conception; crystallization will be initiated from the parts including unstable alkali ions and/or nonbridging oxygen ions which will most likely contribute to the relaxation mechanisms of the peaks. In other words, even if some stable alkali ions and/or nonbridging oxygen ions remain in glass phase, both peaks could disappear. The height of the new peak increased until crystallization fully proceeded. This result suggests that the relaxation mechanism of the new peak may be ascribed to slips between grain boundaries.

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The effects of several factors on the synthesis of monodispersed titania fine particles by hydrolysis of Ti(OC₂H₅)₄ as a method for synthesizing sinterable powders were studied. Submicron monodispersed titania fine particles were obtained from the neutral alcoholic solution of 0.1mol/l Ti(OC₂H₅)₄ and 0.3mol/l H₂O, respectively. From this result, the nucleation and growth of titania particles by hydrolysis of alkoxide were discussed. The titania particles were amorphous and hydrated and grew to 0.7μm in about 10min after hydrolysis reaction at room temperature. To prevent the particles from aggregation, it was effective to disperse the obtained particles ultrasonically in ammonia water of pH≅11.

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