Thermophysical properties of a novel high entropy hafnate ceramic

Abstract High-entropy oxides (HEOs) are considered promising thermal barrier coating (TBC) materials due to their unique thermophysical performances induced by the entropy effects. In this work, (La0.2Ce0.2Pr0.2Sm0.2Eu0.2)2Hf2O7 high entropy hafnate, as a thermal barrier coating (TBC) material, was successfully synthesized by solution combustion method for the first time. From the X-ray diffraction, scanning electron microscopy, and transmission electron microscopy results, it is confirmed that (La0.2Ce0.2Pr0.2Sm0.2Eu0.2)2Hf2O7 has pure single-phase ordered pyrochlore structure with highly homogeneous composition at both micrometer and nanometer scales. The synthesized (La0.2Ce0.2Pr0.2Sm0.2Eu0.2)2Hf2O7 possesses excellent phase stability at 1600 °C and demonstrates a low thermal conductivity (1.0–1.24 W·m−1·K−1) which is lower than those of rare earth hafnates (RE2Hf2O7, RE = La, Ce, Pr, Sm, Eu). Therefore, it provides a new perspective and potential to prompt the next generation TBC materials with better performance.