Influence of Thermal Cycling on Sintering and Stabilization of Zirconia

Abstract

The phase transformations in zirconia take place between 900°-1000° and 1200°c while heating, and between 1000° and 800°–600°C while cooling causing material movement. Hence, effect of amount of CaO and CaF2 additions and calcination temperature on densification and stabilization was studied by thermal cycling between 1200° and 700°C (lower range) and 1400° and 700°c (higher range) up to 25 thermal cycles.It was observed that higher densification can be obtained by thermal cycling at lower temperature compared to the temperature required in normal sintering process, particularly so, with CaO additions. High density was attained with CaO additions up to 2 % compared to equivalent amount of CaF2 additions in the lower temperature range. In general, uncalcined compositions attained high density which decreased with increasing calcination temperature. Thermal cycling promoted stabilization. The reaction was almost completed within 5 thermal cycles.