Institution: | Aichi Institute of Technology, 1247 Yakusa Toyota, Aichi, Japan Government Industrial Research Institute of Osaka, 1-8-31 Midorigaoka Ikeda, Osaka, Japan Osaka Yogyo Co. Ltd., Wakinohama Kaizuka, Osaka, Japan |
Abstract: | Glasses of compositions 5ZrO2·5SiO2(ZS), 5ZrO2·Al2O3·4SiO2(ZAS) and 5 5ZrO2·0.5Al2O3·0.5Na2O·4SiO2(ZANS) were prepared by the sol-gel process from metal alkoxides and sintered to make glass-ceramics. Tetragonal ZrO2 was precipitated by heat treatment at 900 to 1300°C. The activation energy for tetragonal ZrO2 crystal growth was extremely high in Al2O3 containing glasses. ZAS and ZS were sintered to the near theoretical densities above 1200°C, at which the predominant phase was tetragonal ZrO2. On the other hand, for ZANS, high densification was not attained owing to the large pores enclosed by the glass phase. Strength and fracture toughness increased with the densification and the crystal growth of tetragonal ZrO2, reaching 450 MPa and 9 MN/m1.5, respectively. |