Effect of TiO₂ and Ta₂O₅ co-doping on phase stability, fracture toughness, and sintering behavior of ZrO₂ stabilized by 10mol%(Y_0.4Gd_0.3Yb_0.3)₂O₃

The effect of TiO₂ and Ta₂O₅ co-doping on the phase structure, fracture toughness, and sintering behavior of 10mol%(Y_0.4Gd_0.3Yb_0.3)₂O₃-stabilized zirconia was investigated using X-ray diffraction, scanning electron microscopy, microindentation, and pressureless sintering. The results showed that 10mol%(Y_0.4Gd_0.3Yb_0.3)₂O₃–ZrO₂ had a single cubic phase structure, and an increase in the Ta₂O₅ (≥6 mol%) and TiO₂ doping concentrations resulted in a simultaneous increase in the content and stability of the tetragonal phase. The fracture toughness of TiO₂ and Ta₂O₅ co-doping 10mol%(Y_0.4Gd_0.3Yb_0.3)₂O₃–ZrO₂ decreased with an increase in the Ta₂O₅ content. On the other hand, the TiO₂ content had no significant effect on the fracture toughness of 10mol%(Y_0.4Gd_0.3Yb_0.3)₂O₃–ZrO₂. The sintering resistance of the specimens increased with an increasing in the Ta₂O₅ content; however, an increase in the TiO₂ content accelerated the densification of the specimens. When the Ta₂O₅ content was 10 mol% and the TiO₂ content was in the range of 4–8 mol%, a single non-transformable tetragonal phase structure with fracture toughness similar to that of 6–8 wt% Y₂O₃ stabilized ZrO₂ and excellent anti-sintering properties could be obtained. This structure can be explored as a thermal barrier coating material for high-temperature applications.