ZTA ceramics with optimized zirconia content for outstanding high-temperature mechanical properties

This study presents the first systematic investigation into the effect of ZrO₂ content on the Vickers hardness and fracture toughness of zirconia-toughened alumina (ZTA) ceramics over a temperature range from room temperature to 800 °C. The results reveal that the ZrO₂ content has a limited influence on the hardness of ZTA ceramics, with values converging to approximately 9.45 GPa at 800 °C, a level comparable to that of pure Al₂O₃. This confirms that high-temperature deformation is predominantly governed by the softening behavior of the Al₂O₃ matrix. Regarding fracture toughness, the 15ZTA (Al₂O₃-15 wt% ZrO₂) composition exhibits outstanding performance across both room and elevated temperatures. At room temperature, it achieves a fracture toughness of 4.27±0.28 MPa·m^1/2, primarily attributed to the synergistic effects of ZrO₂ particle transformation toughening, crack deflection, and bridging. At 800 °C, 15ZTA retains a fracture toughness of 3.02±0.32 MPa·m^1/2, which is approximately 1.8 times that of pure Al₂O₃ (1.67±0.02 MPa·m^1/2) and 2.0 times that of pure 3 mol% yttria-stabilized zirconia (3YSZ) (1.49±0.05 MPa·m^1/2). Microstructural analysis demonstrates that the continuous and rigid Al₂O₃ skeleton in 15ZTA not only ensures high-temperature structural stability, as evidenced by an elastic modulus of 342 GPa at 800 °C comparable to that of pure Al₂O₃ but also, due to thermal mismatch, the residual stress exerted on the ZrO₂ particles continues to promote transformation toughening even at elevated temperatures. This study reveals the composition-temperature-property relationships in ZTA ceramics and provides a theoretical foundation for the design of high-temperature structural materials.