Effect of lattice distortion on thermal conduction behavior in a novel high-entropy rare-earth tantalates

In this study, seven types of thermal protection coating materials (high-entropy rare-earth tantalates 5RETaO4, RE= Nd, Sm, Eu, Gd, Dy, Ho, Y, Eu, Tm, and Y) were synthesized by solid-phase reaction and high-throughput experiment. Results showed that 5RETaO4 exhibits excellent thermophysical properties owing to its unique highentropy and lattice distortion effects. Namely, (Nd0.2Dy0.2Ho0.2Y0.2Eu0.2)TaO4 ceramics perform low thermal conductivity and suitable thermal expansion coefficient. The low thermal conductivity of 5RETaO4 is mainly due to the difference of RE3+-O2- bond caused by different rare-earth cation radius, which further changes the length of an ionic bond between O2- and Ta5+, resulting in severe lattice distortion and increased phonon scattering coefficient. These excellent properties indicate that (Nd0.2Dy0.2Ho0.2Y0.2Eu0.2)TaO4 can be used as a new generation of thermal protection coating material.