Improved CMAS corrosion resistance of rare earth niobates by high-entropy and composite design

This study reports the preparation of two single-phase high-entropy rare-earth niobates (RE1/5Ho1/5Er1/5Y1/5Yb1/5)3NbO7, (RE = Ce, Lu), and two composite-phase high-entropy rare-earth niobates (RE1/5Ho1/5Er1/5Y1/5Yb1/5)3NbO7:(RE1/5Ho1/5Er1/5Y1/5Yb1/5)NbO4 = 1:2, (RE = Ce, Lu) via solid-phase synthesis. The interactions of these samples with molten calcium-magnesium-aluminum-silicates (CMAS) were studied at 1300 °C to explore their performance and mechanism in CMAS corrosion. The results indicate that the corrosion process involves the phase transformation of RE3NbO7 and the formation of apatite products. The Ce-composition sample exhibits superior performance in terms of reaction layer thickness, remaining CMAS thickness, and RE3+ content in the remaining CMAS. These findings underscore the potential application of high-entropy rare-earth niobates in thermal barrier coatings (TBCs) and contribute to understanding niobate system resistance to CMAS corrosion.