Sintering Kinetics at Constant Rates of Heating: Mechanism of Silica-Enhanced Sintering of Fine Zirconia Powder

The sintering behavior of 3 mol% Y₂O₃-doped ZrO₂ powders with and without a small amount of SiO₂ was investigated to clarify the effect of SiO₂ addition on the initial sintering stage. The shrinkage behavior of a powder compact was measured under constant rates of heating (CRH). The sintering rate increased remarkably with the addition of a small amount of SiO₂. The apparent activation energy ( nQ ) and apparent frequency factor     , where n is the order depending on the diffusion mechanism, were estimated at the initial sintering stage by applying the sintering-rate equation to the CRH data. The diffusion mechanism changed from grain-boundary diffusion (GBD) to volume diffusions (VD) on SiO₂ addition, and both nQ and     increased with the GBD→VD change. It is, therefore, concluded that the sintering rate increases by SiO₂ addition because the increase in     rather than nQ is predominant.