Initial sintering mechanism and additive effect in zirconia ceramics

Y₂O₃-stabilized ZrO₂ (YSZ) ceramics have been used for various engineering applications because of their excellent mechanical properties or oxide-ion conductivity applicable to solid-electrolyte. The performance of YSZ depends on the sintered texture that is directly determined by sinterability of raw powders. A new kinetic analysis method of diffusion mechanism based on an initial sintering theory (grain-boundary or volume diffusion) is theoretically derived, the initial sintering mechanism of hydrolytic YSZ powder is experimentally determined, and the effects of powder characteristics on sinterability are discussed. Furthermore, the additive-enhanced sintering is proposed. A small amount of Al₂O₃ significantly enhances the densification. Using the additive effect, the low-temperature degradation that is the fault of zirconia ceramics can be improved by decreasing the sintering temperature.