Enhancing the thermodynamic performance of rare‐earth tantalate materials by high‐entropy design

Abstract Rare earth tantalates (RE 3 TaO 7 ) demonstrate considerable potential for next‐generation thermal barrier coatings (TBCs) owing to their exceptionally high‐temperature phase stability and ultralow thermal conductivity. Nevertheless, their practical deployment is constrained by inherent challenges, including a mismatch in the coefficient of thermal expansion (CTE) with substrate materials and relatively low fracture toughness. To overcome these limitations, this study adopts a high‐entropy design approach by introducing equimolar six‐component doping at the A‐site of A 3 BO 7 ‐type rare earth tantalates. As a result, three novel high‐entropy tantalate materials with single‐phase structures and excellent high‐temperature stability were successfully synthesized: HE‐1((La 1/6 Lu 1/6 Nd 1/6 Sm 1/6 Eu 1/6 Dy 1/6 ) 3 TaO 7 ), HE‐2((La 1/6 Tm 1/6 Nd 1/6 Sm 1/6 Eu 1/6 Dy 1/6 ) 3 TaO 7 ), and HE‐3((La 1/6 Ce 1/6 Nd 1/6 Lu 1/6 Eu 1/6 Dy 1/6 ) 3 TaO 7 ). The experimental results demonstrate that all three high‐entropy materials meet critical performance requirements for TBCs: HE‐2 has the lowest lattice thermal conductivity (1.36 W·m −1 ·K −1 at 1000°C), which is attributed to enhanced phonon scattering effects caused by atomic mass/radius disparities and grain size inhomogeneity induced by high‐entropy doping. HE‐3 exhibits the highest coefficient of CTE, reaching 10.5 × 10 −6 K −1 at 1200°C. This enhancement is attributed to increased lattice disorder, arising from pronounced distortions of [TaO 6 ] polyhedra within short‐range ordered domains, which amplify atomic anharmonic vibrations and net atomic displacements. Mechanical testing indicates that all high‐entropy compositions display overall mechanical properties that surpass those of conventional single‐component rare‐earth tantalates. In summary, this study effectively optimizes the thermophysical and mechanical performance of rare‐earth tantalates through a high‐entropy design approach, offering valuable experimental insights and novel strategies for the development of next‐generation TBC materials.