Fracture toughness,strength and Vickers hardness of yttria-ceria-doped tetragonal zirconia/alumina composites fabricated by hot isostatic pressing

Yttria-ceria-doped tetragonal zirconia ((Y, Ce)-TZP)/alumina (Al₂O₃) composites were fabricated by hot isostatic pressing (HIP) at 1400–1600 °C and 147 MPa for 30 min in Ar gas using fine powders prepared by hydrolysis of ZrOCl₂ solution. The mechanical properties of these ceramic composites were evaluated. The fracture toughness and bending strength of the composites consisting of 25 wt% Al₂O₃ and tetragonal zirconia with compositions 4 mol% YO_1.5-4 mol% CeO₂-ZrO₂, 2.5 mol% YO_1.5-4 mol% CeO₂-ZrO₂ and 2.5 mol% YO_1.5-5.5 mol% CeO₂-ZrO₂ fabricated by HIP at 1400 °C were 6–7 MPa m^1/2 and 1700–1800 MPa. Fracture toughness, strength and hardness of (Y, Ce)-TZP/Al₂O₃ composites were strongly dependent on HIP temperature. The fracture strength and hardness were increased, and grain growth of zirconia grains and phase transformation from the tetragonal to the monoclinic structure of (Y, Ce)-TZP during HIP in Ar at high temperature (1600 °C) were suppressed by the dispersion of Al₂O₃ into (Y, Ce)-TZP.