Microwave sintering and fracture behavior of zirconia ceramics

Abstract Yttria and Lanthana co-stabilized zirconia ceramics were successfully prepared by microwave hybrid sintering with a multi-mode cavity at 2.45 GHz. Microhardness, bending strength, fracture toughness, and relative density were tested. The fracture behavior of 3Y–ZrO2 ceramics was studied after sintering. The results showed the average toughness values of 1550 °C microwave sintered and conventional sintered samples were 7.68 MPa m1/2 and 4.31 MPa m1/2 respectively. The average grain size of microwave sintered samples was 500 nm which was smaller than that (700 nm) of conventional sintered samples. The microstructure of fracture samples showed that the intergra1nular fractures were main features for microwave sintered samples, whereas the numerous transgranular fractures were observed in conventional sintered samples. The XRD results revealed that content of monoclinic phase gradually increase with the increasing of microwave sintering temperature in 3Y–ZrO2 samples. It was proposed that the grain boundary diffusion and induced phase transformation worked together weakening the grain boundary bonding strength under the effect of microwave field.