A novel high-entropy (Sc0.2La0.2Sm0.2Er0.2Yb0.2)2Zr2O7 ceramics with excellent thermophysical properties designed by thermal properties tailoring theory

The outstanding thermophysical properties and mechanical properties are crucial for the application of RE2Zr2O7 in thermal barrier coatings (TBCs). To simultaneously optimize the thermal conductivity, thermal expansion behaviour and mechanical properties of rare-earth zirconate ceramics, in this work a novel highentropy (Sc0.2La0.2Sm0.2Er0.2Yb0.2)2Zr2O7 (REZO) ceramics was designed with significant mass and size differences based on the thermal properties tailoring theory. Structural analysis revealed that the REZO ceramics prepared by conventional solid-state reaction exhibits a dual-phase structure with coexisting pyrochlore and fluorite phases, and the five rare-earth cations were uniformly distributed throughout REZO without compositional segregation. In terms of thermophysical properties, compared to La2Zr2O7 and Gd2Zr2O7, the REZO exhibits a glass-like thermal conductivity (1.31˙W•m−1•K−1, at room temperature) and a high thermal expansion coefficient (11.054 × 10−6/K, 1200°C). Additionally, the REZO demonstrates excellent high-temperature phase stability from room temperature to 1600°C. In terms of mechanical properties, the REZO exhibits a lower Young’s modulus, higher Vickers hardness and higher fracture toughness compared to La2Zr2O7 and Gd2Zr2O7. In summary, the thermal properties tailoring theory employed in this work provides a novel design approach for developing RE2Zr2O7 ceramics with tunable thermophysical and mechanical properties, enhancing the application prospects of RE2Zr2O7 in advanced TBCs.