Improved wear resistance and low thermal radiative conductivity of a middle-entropy tantalate Y0.5Gd0.5Ta0.5Nb0.5O4

Ferroelastic YTaO 4 is a promising material for thermal barrier coatings (TBCs), and its thermal and mechanical properties can be further optimized by various methods. In this study, a ferroelastic middle-entropy ceramic Y 0.5 Gd 0.5 Ta 0.5 Nb 0.5 O 4 was synthesized by solid-phase sintering, and its microstructures and thermophysical properties were key points. We determined the contributions of phonons and photons to total thermal conductivity, and a low thermal conductivity was obtained by inhibiting high-temperature thermal radiation. The thermal expansion coefficients were improved by introducing of Nb atom into the lattice of the prepared middle-entropy ceramic, which meets the requirements of TBCs. The improved wear resistance originated from relatively high Young's modulus and the hardness of Y 0.5 Gd 0.5 Ta 0.5 Nb 0.5 O 4 , and it would contribute to the service performance of the corresponding coatings. This work motivates the engineering applications of ferroelastic RETaO 4 and RENbO 4 (RE is rare-earth element) as high-temperature TBCs.