(La0.2Dy0.2Nd0.2Sm0.2Eu0.2)2GdTaO7: a promising candidate oxides for high-temperature coating applications

In the paper, the (La0.2Dy0.2Nd0.2Sm0.2Eu0.2)2GdTaO7 oxide was prepared employing sol-gel and solid-reaction method. Its crystal-structure, microstructure, element-distribution, mechanical and thermophysical properties are investigated. The analytical conclusions reveal that this high-entropy oxide shows single pyrochlore structure, dense microstructure, and even element distribution. Owing to the strong phonon scattering originated from high-entropy effect and numerous oxygen vacancies, it has low thermal conductivity and ranges from 1.41 to1.27 W/m. K. Its coefficient of thermal expansion is less than those of rare-earth cerium oxides and greater than that of 7YSZ. The Young's modulus of this high-entropy oxide is in the same order with 7YSZ, its Vickers hardness and fracture-toughness are lower than those of 7YSZ. This high-entropy oxide is also of excellent lattice-stability up to 1200°C.