Abstract:

Yttrium aluminum perovskite (YAlO₃) is a promising candidate material for environmental barrier coatings (EBCs) to protect Al₂O_3f/Al₂O₃ ceramic matrix composites (CMCs) from the corrosion of high-temperature water vapor in combustion environments. Nevertheless, the relatively high thermal conductivity is a notable drawback of YAlO₃ for environmental barrier coating application. Herein, in order to make REAlO₃ more thermal insulating, a novel high-entropy rare-earth aluminate ceramic (Y_0.2Nd_0.2Sm_0.2Eu_0.2Er_0.2)AlO₃ was designed and synthesized. The as-prepared (Y_0.2Nd_0.2Sm_0.2Eu_0.2Er_0.2)AlO₃ ceramic possesses close thermal expansion coefficient (9.02 × 10^―6 /^oC measured from room temperature to 1200 °C) to that of Al₂O₃. The thermal conductivity of (Y_0.2Nd_0.2Sm_0.2Eu_0.2Er_0.2) AlO₃ at room temperature is 4.1 W·m^-1 K^-1, which is almost one third of the value of YAlO₃. Furthermore, to effectively prevent the penetration of water vapor from possible pores/cracks of coating layer, which are often observed in T/EBCs, a tri-layer EBC system REAlO₃/RE₃Al₅O₁₂/(Al₂O_3f/Al₂O₃ CMCs) is designed. Close thermal expansion coefficient to Al₂O₃ and low thermal conductivity of (Y_0.2Nd_0.2Sm_0.2Eu_0.2Er_0.2)AlO₃, as well as the formation of dense garnet layer at (Y_0.2Nd_0.2Sm_0.2Eu_0.2Er_0.2)AlO₃/Al₂O₃ interface, indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al₂O_3f/Al₂O₃ CMCs.

Key words: High-entropy ceramics, (Y_0.2Nd_0.2Sm_0.2Eu_0.2Er_0.2)AlO₃, Tri-layer EBC system, Low thermal conductivity, Al₂O_3f/Al₂O₃ CMCs