Rare-earth cerates with a high coefficient of thermal expansion and excellent CMAS corrosion resistance obtained through high-entropy designing

Abstract

As the demand for aero-engines with a high thrust-to-weight ratio has increased, the comprehensive performance requirements for thermal barrier coatings (TBCs) have become extremely challenging. Among them, the indicator that measures the service life of TBCs not only requires a high coefficient of thermal expansion (CTE) but also strong resistance to molten calcium-magnesium-aluminum-silicate (CMAS) corrosion. In this study, we used the solid-state method to prepare (La0.2Nd0.2Sm0.2Eu0.2Lu0.2)2Ce2O7 (5RLC), (La0.25Nd0.25Sm0.25Eu0.25)2Ce2O7 (4RLC), and Sm2Ce2O7 (SC) by sintering at 1700 °C for 10 h. By regulating the average radius and the variation of rare-earth ions through high-entropy designing, the lattice structure, micromorphology, element composition, CTE, and resistance to CMAS corrosion were systematically studied. The results showed that the bulk samples had defective fluorite structures, dense microstructures, and a uniform distribution of elements. At 1400 °C, the CTEs of 5RLC and 4RLC were 12.14 × 10−6 K−1 and 12.45 × 10−6 K−1, respectively. After 20 h of CMAS corrosion at 1300 °C, the thickness of the product layers was only 9.73 μm and 10.80 μm for 5RLC and 4RLC, respectively. In this study, we combined the high coefficient of thermal expansion and excellent CMAS corrosion resistance of 5RLC and 4RLC and found that they can maintain a good service life.