Ti4+ doped high-entropy fluorite oxide ceramics ((ZrHfCeYEr)(1-x)/5Tix)O2-δ: Thermal, mechanical and cyclic thermal shock resistance properties studies

High-entropy fluorite oxide ceramics are promising candidates for spacecraft applications due to their excellent high-temperature thermal-mechanical properties. In this work, four kinds of high-entropy fluorite oxide ceramics ((ZrHfCeYEr) (1-x)/5 Ti x )O 2-δ (HEFOs, x = 0, 0.025, 0.05, 0.075) with different Ti 4+ contents were successfully synthesized through solid-state reaction method with conventional sintering. They all exhibited phase stability when annealed at 1500 ℃ for 20 h. When the content of Ti 4+ was increased to x = 0.075, the thermal conductivity reduced to1.34 W·m −1 ·K −1 at 1100 ℃, and the hardness and elastic modulus increased to 14.01 GPa and 205.70 GPa, respectively. Furthermore, the cyclic thermal shock resistance of HEFOs at different temperatures was investigated. The initial flexural strength reached 219.03 MPa when the content of Ti 4+ was increased to x = 0.075. After 60 thermal shock cycles at 1200 ℃ and 1500 ℃, the residual strength ratios were 97.56 % and 83.36 %, respectively. The results of this study establish the foundation for future applications of high-entropy fluorite oxide ceramics in spacecraft hot-end components.