Multiscale Defect-Mediated Thermophysical Properties of High-Entropy Ferroelastic Rare-Earth Tantalates

The foremost objective of this work is to employ an entropy strategy to optimize the thermophysical properties of rare-earth (RE) tantalates. The stabilizing single-phase structure of seven-component rare-earth tantalates is verified by density functional theory calculations, and entropy-stabilized (7RE1/7)TaO4 with a defective structure is successfully synthesized via spark plasma sintering. (7RE1/7)TaO4 exhibits lower intrinsic thermal conductivity over the entire temperature range from 100 to 1200 degrees C. Furthermore, its intrinsic thermal conductivity (0.83-0.90 W m ? 1 & sdot;K- 1) is 39-51% and 68-71% lower compared to those of single-RE RETaO4 and 8YSZ at 1200 degrees C, respectively, and is even close to the limited thermal conductivity from the Cahill model. This is the result of multiscale phonon scattering by Umklapp phonon-phonon, point defect, dislocation, ferroelastic domain and distorted structures. Moreover, (7RE1/7)TaO4 exhibits superior high-temperature phase stability and excellent mechanical properties. Therefore, entropy-stabilized (7RE1/7)TaO4 compounds with ultralow thermal conductivity can be used as promising thermal insulating materials.