Effects of Microwave Sintering and ZnO Addition on the Properties of Zirconia Toughened Alumina Ceramics for Artificial Joints

Brittleness remains one of the primary barrier limiting the clinical application of zirconia-toughened alumina (ZTA) ceramics in total hip arthroplasty (THA). To address this limitation, we developed a novel series of ZTA ceramics through an energy-efficient microwave sintering process, employing ZnO at concentrations of 0–2.5 wt% as a multifunctional sintering additive. We systematically investigated the effects of ZnO content on phase composition, microstructure, and mechanical performance enhancement were systematically elucidated. The results showed introducing ZnO into ZTA significantly enhanced its overall performance. At the optimal ZnO content of 0.5 wt%, the composite achieved a relative density of 98.41%, a Vickers microhardness of approximately 1903.2 HV, and a flexural strength of 882.34 MPa. The enhancement of these properties stems from the dual role of zinc oxide: promoting densification and grain refinement. The in situ formed plate-like ZnAl 2 O 4 spinel grains contribute to toughening through crack deflection and the pull-out effect. However, excessive introduction of spinel phases was found to compromise the overall material performance. Microwave sintering significantly improved the densification of ZTA ceramics at 1 500 °C compared to conventional sintering methods. Our findings demonstrate the potential of ZnO incorporation and microwave sintering in improving the properties of ZTA ceramics and provides a new strategy for the rapid preparation of high-performance ZTA ceramics.