High-entropy (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3: A promising thermal/environmental barrier material for oxide/oxide composites

Yttrium aluminum perovskite (YAlO3) is a promising candidate material for environmental barrier coatings (EBCs) to protect Al(2)O(3)f/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 (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 was designed and synthesized. The as-prepared (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 ceramic possesses close thermal expansion coefficient (9.02 x 10(-6) /degrees C measured from room temperature to 1200 degrees C) to that of Al2O3. The thermal conductivity of (Y0.2Nd0.2Sm0.2Eu0.2Er0.2) 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/(Al(2)O(3)f/Al2O3 CMCs) is designed. Close thermal expansion coefficient to Al2O3 and low thermal conductivity of (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3, as well as the formation of dense garnet layer at (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3/Al2O3 interface, indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al(2)O(3)f/Al2O3 CMCs. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.