High-entropy rare-earth zirconate ceramics with low thermal conductivity for advanced thermal-barrier coatings

Abstract The high-entropy rare-earth zirconate ((La 0.2 Nd 0.2 Sm 0.2 Gd 0.2 Yb 0.2 ) 2 Zr 2 O 7 , 5RE 2 Zr 2 O 7 HEREZs) ceramics were successfully prepared by a new high-speed positive grinding strategy combined with solid-state reaction method. The microstructure, crystal structure, phase composition, and thermophysical and mechanical properties of the samples were systematically investigated through various methods. Results indicate that the samples have a single-phase defect fluorite-type crystal structure with excellent high-temperature thermal stability. The as-prepared samples also demonstrate low thermal conductivity (0.9–1.72 W·m −1 ·K −1 at 273–1273 K) and high coefficient of thermal expansion (CTE, 10.9 × 10 −6 K −1 at 1273 K), as well as outstanding mechanical properties including large Young’s modulus ( E = 186–257 GPa) and high fracture toughness ( K IC ). Furthermore, the formation possibility of the as-prepared samples was verified through the first-principles calculations, which suggested the feasibility to form the 5RE 2 Zr 2 O 7 HE-REZs in the thermodynamic direction. Therefore, in view of the excellent multifunctional properties exhibited by the as-prepared 5RE 2 Zr 2 O 7 HE-REZs, they have great potential applications in next-generation thermal-barrier coatings (TBCs).