Sintering characteristics of microfine zirconia powder

Abstract

In this paper the sintering characteristics of yttria-doped zirconia microfine powder are investigated by measuring shrinkage and shrinkage rate curves of powder compacts. The experimental results show that there is a transition point in the shrinkage-temperature curves and two peaks appear in the shrinkage rate-temperature curves. These results provide further support for the idea that the sintering of microfine zirconia powders is a two-stage process. In the first stage, sintering of the powder compact is mainly dominated by inner-sintering in agglomerates and in the second stage, sintering will occur among densified agglomerates. The microstructure of agglomerates during sintering is also studied by TEM and provides evidence that the transition point in the shrinkage-temperature curve is the end of the first sintering stage. Furthermore, the relationships between sintering characteristics and powder parameters are investigated. It is found that the shrinkage rate in the first stage is related to the primary grain size of the powder, and in the second stage it is related to agglomerate size. The effect of agglomerates on the sinterability of microfine Zr02 powder can be directly evaluated by the difference of shrinkage rate between the two sintering stages. Experiments also show that the shrinkage rate can be influenced by heating rate. A rapid heating rate would result in difficulties in the second sintering stage.