Thermophysical and mechanical properties of dual-phase medium- and high-entropy rare-earth zirconate ceramics

The medium-entropy ceramic (La 1/3 Nd 1/3 Gd 1/3 ) 2 (Zr 3/4 Ce 1/4 ) 2 O 7 and high-entropy ceramic (La 1/5 Nd 1/5 Sm 1/5 Eu 1/5 Gd 1/5 ) 2 (Zr 3/4 Ce 1/4 ) 2 O 7 were successfully synthesized. The two ceramics had a pyrochlore-fluorite dual-phase structure, and they exhibited excellent phase stability at elevated temperature. Grain refinement or solution strengthening improved the Vickers hardness , fracture toughness and elastic modulus of the dual-phase ceramics. Compared with the single-element ceramic La 2 Zr 2 O 7 , multicomponent doping resulted in a significant increase in the thermal expansion coefficient. Simultaneously, the thermal conductivity of the dual-phase ceramics was lower than that of single-phase ones. In addition, on account of the large size disorder parameter of the medium-entropy ceramic, the thermal conductivity could outperform its high-entropy counterpart. These results indicate that pyrochlore-fluorite dual-phase rare-earth zirconates have enormous potential in applications concerning next generation thermal barrier coatings .