Studies on the metastable phase retention and hardness in zirconia ceramics

In the development of tough ceramic materials, partially stabilized zirconia (PSZ) has been considered as the analogue of steels which exhibit transformation-induced plasticity. The main reason for the high strength of the PSZ system appears to be the existence of a metastable tetragonal phase which is strongly dependent on several factors such as the percentage of stabilizer, the sintering temperature, the soak time and the nature of the ZrO 2 raw material. In the present work the influence of the percentage of YO 1.5 stabilizer and sintering temperature on the tetragonal phase retention and hardness was explored. ZrO 2YO 1.5 mixtures containing 0–15 mol.% YO 1.5 were prepared, pelletized and fired at various temperatures from 1100 to 1500°C. The tetragonal phase content, density, porosity and hardness of the pellets were evaluated. It was found that the percentage of tetragonal phase increases with YO 1.5 content and decreases as the sintering temperature is increased. The effect of partial stabilization in increasing the hardness was clearly demonstrated.