High-entropy (Y0.2Gd0.2Dy0.2Er0.2Yb0.2)2Hf2O7 ceramic: A promising thermal barrier coating material

Abstract Thermal barrier coating (TBC) materials perform an increasingly important role in the thermal or chemical protection of hot components in a gas turbine. In this study, a novel high entropy hafnate (Y0.2Gd0.2Dy0.2Er0.2Yb0.2)2Hf2O7 was synthesized by solution combustion method and investigated as a potential TBC layer. The as-synthesized (Y0.2Gd0.2Dy0.2Er0.2Yb0.2)2Hf2O7 possesses a pure single disordered fluorite phase with a highly homogeneous distribution of rare earth (RE) cations, exhibiting prominent phase stability and excellent chemical compatibility with Al2O3 even at 1300 °C. Moreover, (Y0.2Gd0.2Dy0.2Er0.2Yb0.2)2Hf2O7 demonstrates a more sluggish grain growth rate than Y2Hf2O7. The thermal conductivity of (Y0.2Gd0.2Dy0.2Er0.2Yb0.2)2Hf2O7 (0.73-0.93 W m−1 K−1) is smaller than those of components RE2Hf2O7 and many high entropy TBC materials. Beside, the calculated thermal expansion coefficient (TEC) of (Y0.2Gd0.2Dy0.2Er0.2Yb0.2)2Hf2O7 (10.68 × 10−6/K, 1100 °C) is smaller than that of yttria-stabilized zirconia (YSZ). Based on the results of this work, (Y0.2Gd0.2Dy0.2Er0.2Yb0.2)2Hf2O7 is suitable for the next generation TBC materials with outstanding properties.