(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 (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 was designed and successfully synthesized in this work. The as-synthesized (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 is phase-pure with homogeneous rare-earth element distribution. The thermal conductivity of as-synthesized (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 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 (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 only increases from 1.69 μm to 3.92 μm, while the average grain size of La2Zr2O7 increases from 1.96 μm to 8.89 μm. Low thermal conductivity and sluggish grain growth rate indicate that high-entropy (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 is suitable for application as a thermal barrier coating material and it may possess good thermal stress-induced cracking resistance.