Recent development of ceramic basic science in Japan

Some topics on the basic science on ceramics are presented, limiting to the recent works carried out in Japan on densification and its concerns. The significant factors contributing to densification are considered to be: 1) effect of preparation of starting materials, 2) influence of atmosphere, 3) special treatment of powder, 4) sintering mechanism under vacuum, atmosphere and high pressure, and 5) others. As to the preparation of specially modified starting powder materials for the purpose of densification, there are two ways; one is the hysteresis of preparation from mother salt, and the other is the effect of minor additions. The studies on the easily sinterable powder of UO2 prepared by sol-gel process, the effects of Cl- and F- on MgO, very fast shrinkage at the initial stage of sintering of Al2O3, ZrO2 and BeO derived from sulfates, the densification effect of Li2O and B2O3, the effect of valency of metallic ions using NiO as a sintering sample, and others are described. As to the influence of atmosphere, the study on the effect of vapor pressure on the sintering of MgO is reviewed. This work was applied to the work of activation hot pressing of MgO. As to the special treatment of powder, two reports are introduced. The one was done with explosive, and the other is powder treatment by electro-discharge. As to studies on sintering mechanism, models for sintering under atmospheric pressure are reviewed. (Iwakiri, K.)