Structure and Properties of Composite 6YSZ-Al₂O₃-HfO₂ Ceramics Depending on the Sintering Mode

The article presents the main results on the development of technology for the synthesis of ceramics based on zirconium oxide. The influence of the temperature factor on the structure and physical and mechanical properties of ceramic materials synthesized from 6YSZ-Al₂O₃-HfO₂ by semi-dry pressing followed by sintering in vacuum was established. The optimal mode of heat treatment of ceramic samples in vacuum was established to be 1600 °C. At this sintering temperature, the apparent density of the experimental sample was 5.8 g/cm³, which corresponds to 96% of the theoretical value, open porosity was 0.19%, water absorption was 0.07%, microhardness was 12.1 GPa, and crack resistance reached the value K_1C = 6.0 MPa·m^1/2. Sintering the 6YSZ-Al₂O₃-HfO₂ system resulted in the transformation of the monoclinic lattice into tetragonal depending on the temperature. The monoclinic crystal structure of Al₂O₃ transformed into hexagonal. Y₂O₃ and HfO₂ were represented by monoclinic phases and did not undergo phase transformations in the studied temperature range.