High-entropy ferroelastic (10RE 0.1 )TaO 4 ceramics with oxygen vacancies and improved thermophysical properties

The primary purpose of this work is to optimize the thermophysical properties of rare-earth tantalate ceramics using the high-entropy effect. Here, the high-entropy rare-earth tantalate ceramic (Y 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Dy 0.1 Ho 0.1 Er 0.1 Tm 0.1 Yb 0.1 Lu 0.1 )TaO 4 ((10RE 0.1 )TaO 4 ) is synthesized successfully. The lattice distortion and oxygen vacancy concentration are characterized firstly in the rare-earth tantalates. Notably, compared with single rare-earth tantalates, the thermal conductivity of (10RE 0.1 )TaO 4 is reduced by 16%-45% at 100 degrees C and 22%-45% at 800 degrees C, and it also presents lower phonon thermal conductivity in the entire temperature range from 100 to 1200 degrees C. The phonon thermal conductivity (1.0-2.2 W m -1 K -1 , 10 0-120 0 degrees C) of (10RE 0.1 )TaO 4 is lower than that of the currently reported high-entropy four-, fiveand six-component rare-earth tantalates. This is the result of scattering by the ferroelastic domain, lattice distortion associated with size and mass disorder, and point defects, which target low-, mid- and highfrequency phonons. Furthermore, (10RE 0.1 )TaO 4 , as an improved candidate for thermal barrier coatings materials (TBCs), has a higher thermal expansion coefficient (10.5 x10 -6 K -1 at 1400 degrees C), lower Young's modulus (123 GPa) and better high-temperature phase stability than that of single rare-earth tantalates.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.