Thermophysical properties of a novel high entropy hafnate ceramic

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, (La 0.2 Ce 0.2 Pr 0.2 Sm 0.2 Eu 0.2 ) 2 Hf 2 O 7 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 (La 0.2 Ce 0.2 Pr 0.2 Sm 0.2 Eu 0.2 ) 2 Hf 2 O 7 has pure single-phase ordered pyrochlore structure with highly homogeneous composition at both micrometer and nanometer scales. The synthesized (La 0.2 Ce 0.2 Pr 0.2 Sm 0.2 Eu 0.2 ) 2 Hf 2 O 7 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 (RE 2 Hf 2 O 7 , RE = La, Ce, Pr, Sm, Eu). Therefore, it provides a new perspective and potential to prompt the next generation TBC materials with better performance.