In this paper, (Sm_0.5Yb_0.5)₃TaO₇ was prepared via solid-reaction method in order to develop a novel ceramic layer material with excellent performance for thermal barrier coating and explore the influence of Yb addition on thermophysical performances of Sm₃TaO₇. Its crystal structure, microstructure, element composition, thermophysical performances and phase-stability at high temperatures were investigated. The final results indicate that the synthesized (Sm_0.5Yb_0.5)₃TaO₇ is of single pyrochlore-type lattice-structure, and compact microstructure, no element loss is found in the synthesis procedure. Owing to phonon scattering caused by doping cations, the thermal conductivity of (Sm_0.5Yb_0.5)₃TaO₇ reduces. Its thermal conductivity at high-temperature is about 1.02 W/(m· K), which is less than that of Sm₃TaO₇ (1.31 W/(m·K)) and Yb₃TaO₇ (1.14 W/(m·K)). Because of low electronegativity of Yb³⁺, its thermal expansion coefficient at 1 300 ℃ is about 9.92×10^-6 K^-1. Its thermal expansion coefficient is higher than that of Sm₃TaO₇ and lies in the same order with that of YSZ and La₂Zr₂O₇. The thermal conductivity and expansion coefficient of synthesized (Sm_0.5Yb_0.5)₃TaO₇ meet the requirements for thermal barrier coatings. This oxide also shows excellent phase-stability up to 1 300 ℃.