High entropy engineering boosts thermo-mechanical properties of rare-earth tantalates: Influences of cocktail effects

High entropy engineering has been widely used to optimize properties of various materials, and we improve comprehensive performance of rare-earth tantalates RETaO 4 (RE is rare earth) by changing configurational entropy in this work. Four medium/high entropy RETaO 4 (M/HERT) are successfully prepared, and the variations of disorders and distortion degree of lattices with the increasing configurational entropy are described in detail. It is revealed that M/HERT with the highest configurational entropy does not correspond to the best comprehensive properties. Unexpected variations in properties of M/HERT compared to RETaO 4 are observed. By comparing with values obtained from rule of mixture (ROM), it is believed that the cocktail effect exists in M/HERT. The synergistic optimizations of thermo-mechanical properties are realized, including reducing thermal conductivity, increasing thermal expansion coefficients (TECs), and enhancing mechanical properties. M/HERT exhibit excellent high temperature stability and provide a good thermal insulation gradient, which is significant for high-temperature applications of RETaO 4 . This work serves as an important part for thermal barrier coatings materials with high working temperatures and low thermal conductivity. • Radiative thermal conductivity of M/HERT is 0.11 W K −1 m −1 at 900 °C. • Samples have high TECs (10.48 × 10 −6 K −1 ) and low modulus (119.1 GPa). • Sample with the highest configurational entropy does not show the best properties, and cocktail effects cause unpredictable changes.