Effects of Sr2Nb2O7 additive on microstructure and mechanical properties of 3Y–TZP/Al2O3 ceramics

The effects of Sr2Nb2O7 additive on microstructure and mechanical properties of 3Y–TZP/Al2O3 ceramics were investigated. Sr2Nb2O7 reacted with Al2O3 to form SrAl12O19 platelets, which could contribute to the fracture toughness due to the elongated grains. The fraction of transformable tetragonal zirconia phase increased firstly with the Sr2Nb2O7 content and then decreased when the additive content is beyond a critical value. Also, the fracture toughness increased firstly to a maximum value (10.2 MPa.m1/2) with the additive content and then decreased for composites sintered at 1600 °C for 6 h, while it increased linearly with additive content for composites sintered at 1575 °C for 6 h. However, the Vickers hardness decreased linearly with the Sr2Nb2O7 content for composites sintered under any condition investigated here. The fracture toughness was affected by the fraction of transformable tetragonal zirconia phase and Sr2Nb2O7 content, and the toughening effects should be the integrated result of stress-induced transformation toughening and elongated grain toughening.