Transformation behaviour of tetragonal zirconia: role of dopant content and distribution

The goal of this paper is to investigate the influence of dopant content and distribution on the thermally induced transformation behaviour of yttria stabilised tetragonal zirconia polycrystals (Y-TZP). A range of TZPs with varying Y2O3 content (1.75–3 mol%) was fully densified by hot pressing at 1450 °C for 1 h in vacuum. Thermal length change of the hot pressed TZPs, as measured by the thermo-mechanical analysis (TMA) in air, has been obtained to evaluate the transformation behaviour of the tetragonal zirconia phase. The thermal hysteresis behaviour reveals the nature of the reversible tetragonal (t) to monoclinic (m) transformation and the low temperature degradation phenomenon. Furthermore, the obtained transformation data have been characterised in terms of the grain size, overall yttria content and distribution. While the yttria content remains important, overall yttria distribution has been identified as an additional key microstructural variable influencing the thermally induced transformation behaviour of Y-TZP ceramics. It is demonstrated in our research that the tetragonal zirconia transformation can be tuned by the controlled addition of the Y-free monoclinic zirconia particles to 3 mol% Y-ZrO2 powders in a simple “mixing route”.