CMAS-induced corrosion behavior of high-entropy rare-earth disilicate at 1500 °C

High-entropy rare earth silicates have emerged as promising environmental barrier coatings (EBCs) materials for aircraft engines due to their superior corrosion resistance against calcium–magnesium–aluminum–silicate (CMAS). In this work, a high-entropy disilicate, (Yb 0.2 Y 0.2 Lu 0.2 Er 0.2 Dy 0.2 ) 2 Si 2 O 7 (abbreviated as (5RE 0.2 ) 2 Si 2 O 7 ), was synthesized by spark plasma sintering (SPS) and exposed to CMAS at 1500 °C for 1, 10, and 50 h. The resulting dissolution–reprecipitation process promoted the preferential formation of a continuous apatite (Ca 2 RE 8 (SiO 4 ) 6 O 2 ) layer, which was notably more effective at hindering CMAS infiltration than the layers formed in conventional Yb 2 Si 2 O 7 . This robust apatite interface suppressed further degradation by limiting interaction with the underlying pyrosilicate matrix. Furthermore, a correlation between the radii of rare earth cations and the kinetics of apatite formation provides insight into tailoring rare earth compositions to optimize CMAS corrosion resistance. These findings highlight the potential of high-entropy pyrosilicates as next-generation EBCs with enhanced durability in demanding engine environments.