Surface mechanical properties of advanced zirconia after hydrothermal exposure

The surface mechanical properties of different types of advanced zirconia ceramics have been assessed after being subjected to hydrothermal degradation. Three different types of zirconia were considered: standard tetragonal polycrystalline zirconia doped with 3 % molar yttria (3Y-TZP) produced by conventional sintering; 3Y-TZP produced by spark-plasma sintering (3Y-TZP(SPS)) and a Ce-TZP/Al₂O₃ nanocomposite. Hydrothermal ageing was assessed by using X-ray diffraction. Berkovich nanoindentation was performed before and after the materials being exposed to 131 °C water vapour in autoclave, in order to assess changes in the surface hardness and Young modulus. It is shown that, while standard 3Y-TZP suffers a substantial decay of the surface mechanical properties with hydrothermal exposure, this is not the case for 3Y-TZP(SPS) and the Ce-TZP/Al₂O₃ materials. On the contrary, the later maintained their surface integrity during hydrothermal exposure. The results are explained in terms of microstructure and chemical composition.