Mid-entropy ceramic (Y 0.3 Gd 0.3 Yb 0.4 ) 7 (Hf 0.5 Ta 0.5 ) 6 O 24: A potential novel thermal barrier ceramic prepared by ultrafast high-temperature sintering

To meet the demanding service requirements of aero-engines, a mid-entropy thermal barrier ceramic (Y0.3Gd0.3Yb0.4)7(Hf0.5Ta0.5)6O24 (YGYbHT) was designed and successfully prepared by the ultrafast hightemperature sintering, and its performances were systematically characterized and analyzed. After hightemperature annealing at 1500 degrees C, it exhibited excellent high-temperature phase stability and an extremely sluggish grain growth rate (13 nm/h). Furthermore, the coefficient of thermal expansion(14.85 x 10-6/K) approximated that of nickel-based superalloy, and the thermal conductivity of 2.27 W m- 1 K- 1 was obtained. Finally, YGYbHT possessed an elastic modulus (155.9 GPa) inferior to traditional YSZ and high hardness (11.83 GPa). The excellent performances are mainly attributed to the entropy-stabilized effect, lattice distortions resulting from the size disorder, and sluggish diffusion effect within the entropy-stabilized material. In conclusion, YGYbHT has the potential to be further developed to replace traditional YSZ as a next-generation thermal barrier coating material.