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

Abstract 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·m1/2, 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·m1/2, which is approximately 1.8 times that of pure Al2O3 (1.67±0.02 MPa·m1/2) and 2.0 times that of pure 3 mol% yttria-stabilized zirconia (3YSZ) (1.49±0.05 MPa·m1/2). 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.