Initial Sintering Mechanism of Fine Zirconia Particles with Added Alumina

Abstract

The sinterabilities of fine zirconia powders including 5mass% Y₂O₃ were investigated with emphasis on the effect of Al₂O₃ addition on densification at the initial stage. The powders were pressed into disks and sintered at 1100-1500°C. When a small amount of Al₂O₃ was added, high-density sintered bodies were obtained at a low temperature. The shrinkage of powder compact in the course of heating was measured by a dilatometric method, indicating that the addition of Al₂O₃ increased the densification rate with elevating temperature. The activation energies of sintering were determined by analyzing the densification curves. The activation energy at the initial sintering stage decreased by Al₂O₃ addition. The analysis of isothermal shrinkage curves exhibited that the diffusion mechanism changed from grain-boundary to volume diffusions by addition of Al₂O₃. It is concluded that the Al₂O₃ addition enhanced the densification because of decreasing the activation energy of volume diffusion at the initial sintering stage.