Preparation, microstructure and mechanical properties of ZrB2–ZrO2 ceramics

ZrB2–ZrO2 ceramics with ZrO2 content varied from 15 to 30 vol.% were prepared by hot pressing. The content of ZrO2 was found to have an evident effect on the preparation, phase constitution, microstructure as well as the mechanical properties of ZrB2–ZrO2 ceramics. ZrB2–30 vol.% ZrO2 provided the optimal combination of dense microstructure (2.6 μm, as the average grain size) and excellent properties, including the flexural strength of 803 MPa, and the hardness of 22.7 GPa tested under 9.8 N. The highest t-ZrO2 transformability of 35.2 vol.% during fracture for ZrB2–30 vol.% ZrO2 brought the best toughness of 6.5 MPa m1/2 compared with any other ceramic. In addition, the dependence of toughness on the test method as well as the hardness on the indentation load was also investigated.