Glass phase expelling during liquid phase sintering of YSZ

Expelling of the liquid phase during sintering of ZrO2-6.5 mol% Y2O3- 0.5 mol% Pr2O3 ceramic was observed as a result of grain coarsening. ZrO2- 7.0 mol% Y2O3 samples, without Pr2O3 addition, do not show this effect under the same sintering conditions. The expelling process is caused by surface tension forces and attracting van der Waals forces between the grains, coupled with the existence of two glass phases on the grain boundaries. The amount of expelled glass phase increases with grain growth, but saturates above 16 mm average grain size