Effect of Ta2O5 addition on the microstructure and mechanical properties of TiO2-added yttria-stabilized zirconia-toughened alumina (ZTA) composites

In this study, the effect of Ta 2 O 5 addition on the phase evolution and mechanical properties of sintered (1600 °C, 4 h) TiO 2 -added yttria-stabilized zirconia-toughened alumina (ZTA) ceramic composites was investigated. The scanning electron microscopy and X-ray diffraction results revealed the formation of a new tantalum zirconium oxide, TaZr 2.75 O 8 , with a block-like morphology at Ta 2 O 5 contents higher than 1 wt%. The grain sizes of both the Al 2 O 3 and yttria-stabilized zirconia phases first increased and then decreased with an increase in the Ta 2 O 5 content. The relative density, Vickers hardness , and fracture toughness of the composites were found to be strongly dependent on their grain sizes, relative densities, and the formation of the TaZr 2.75 O 8 secondary phases. The composite with 3 wt% Ta 2 O 5 showed the highest relative density (99.3%), Vickers hardness (1932 HV), and fracture toughness (8.21 MPa m 1/2 ).