(La _0.25 Sm _0.25 Gd _0.25 Ho _0.25 )AlO ₃ : High‐entropy perovskite with harmonizing mechanical‒thermal properties for TBCs

Abstract Rare‐earth aluminate (REAlO 3 ) has emerged as a highly promising candidate material for thermal barrier coatings due to its remarkable properties such as high thermal stability and low thermal conductivity. In this study, a novel quaternary rare‐earth aluminate, (La 0.25 Sm 0.25 Gd 0.25 Ho 0.25 )AlO 3 , was synthesized via entropy‐driven design. Its phase composition and mechanical and thermal properties were systematically investigated. The findings indicate that this material exhibits enhanced ductility with a shear modulus of 114.63 GPa and a Pugh's ratio of 0.63, surpassing that of single‐principal element REAlO 3 ceramics. Furthermore, it demonstrates a reduced thermal conductivity of 4.11 W m −1 K −1 at room temperature and a coefficient of thermal expansion of 10.10 × 10 −6 K −1 from 25°C to 1300°C, which is well matched to superalloy substrates.