Single-phase rare-earth high-entropy zirconates with superior thermal and mechanical properties

Emerging of high-entropy ceramics has brought new opportunities for designing and optimizing materials with desired properties. In the present work, high-entropy rare-earth zirconates (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 and (Yb0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 are designed and synthesized. Both high-entropy ceramics exhibit a single pyrochlore structure with excellent phase stability at 1600 degrees C. In addition, the Yb-containing system possesses a high coefficient of thermal expansion (10.52 x 10-6 K-1, RT-1500 degrees C) and low thermal conductivity (1.003 W center dot m-1 K-1, 1500 degrees C), as well as excellent sintering resistance. Particularly, the Yb-containing system has significantly improved fracture toughness (1.80 MPa center dot mm1/2) when compared to that of lanthanum zirconate (1.38 MPa center dot mm1/2), making it a promising material for thermal barrier coatings (TBCs) applications. The present work indicates that the high-entropy design can be applied for further optimization of the comprehensive properties of the TBCs materials.