(La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7: A novel high-entropy ceramic with low thermal conductivity and sluggish grain growth rate

Fine grains and slow grain growth rate are beneficial to preventing the thermal stress-induced cracking and thermal conductivity increase of thermal barrier coatings . Inspired by the sluggish diffusion effect of high-entropy materials, a novel high-entropy (HE) rare-earth zirconate solid solution (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 Zr 2 O 7 was designed and successfully synthesized in this work. The as-synthesized (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 Zr 2 O 7 is phase-pure with homogeneous rare-earth element distribution. The thermal conductivity of as-synthesized (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 Zr 2 O 7 at room temperature is as low as 0.76 W m-1 K-1. Moreover, after being heated at 1500 °C for 1–18 h, the average grain size of (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 Zr 2 O 7 only increases from 1.69 μm to 3.92 μm, while the average grain size of La 2 Zr 2 O 7 increases from 1.96 μm to 8.89 μm. Low thermal conductivity and sluggish grain growth rate indicate that high-entropy (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 Zr 2 O 7 is suitable for application as a thermal barrier coating material and it may possess good thermal stress-induced cracking resistance.