Initial Sintering Mechanism of 3 mol% Yttria-doped Zirconia Powder: Effect of Alumina

摘要

The sintering behavior of 3 mol% Y_2O_3-doped ZrO_2 powders with and without a small amount of Al_2O_3 was investigated to clarify the effect of Al_2O_3 on the initial sintering mechanism. The shrinkage behavior of a powder compact was measured under constant rates of heating (CRH). The shrinkage rate of a powder compact was remarkably increased by a small amount of Al_2O_3. The activation energies of diffusion at the initial sintering stage were determined by analyzing the shrinkage curves. The activation energy of a powder compact with Al_2O_3 was lower than that of a powder compact without Al_2O_3. The diffusion paths of material transport at the initial sintering stage were determined using the analytical equation that is applicable to the CRH data. This analytical result showed that Al_2O_3 changed the diffusion path from grain boundary (GBD) to volume diffusions (VD). It is, therefore, concluded that Al_2O_3 enhances the sintering rate because of a decrease in the activation energy with the GBD → VD change at the initial sintering stage. This enhanced sintering mechanism is reasonably explained by the segregated dissolution of Al_2O_3 at Y-TZP grain boundaries.