Composition engineering of high-entropy rare-earth monosilicates enables remarkable CMAS corrosion resistance

Exploring superior calcium-magnesium-aluminosilicate (CMAS) corrosion resistance is crucial for high-entropy rare-earth monosilicates (HEREMs) as the next-generation environmental barrier coating (EBC) materials. However, related studies are rarely reported. This work presents the exploration of HEREMs with remarkable CMAS corrosion resistance by engineering their compositions. The equimolar 3-to-9 cation high-entropy rare-earth monosilicate (3-9HEREM) specimens were initially prepared using a pressure-less sintering technique; subsequently, their resistance to CMAS corrosion was evaluated at temperatures up to 1600 °C. The results demonstrate that the 5HEREM specimens possess the best CMAS corrosion resistance among all the as-fabricated specimens, surpassing other reported EBC materials. Such remarkable CMAS corrosion resistance results from the generation of a dense apatite protective layer originating from its low dissolution rate at elevated temperatures. • 5HEREM samples show remarkable CMAS corrosion resistance up to 1600 °C. • Such CMAS corrosion resistance is due to the formation of a dense apatite layer. • Such a dense apatite layer originates from its low dissolution rate in the CMAS melt.