Regulation in CMAS corrosion behavior of high entropy RE monosilicates by component design of doped RE

High entropy design is an attractive strategy to improve CMAS corrosion resistance of rare earth monosilicates (RE₂SiO₅) as next-generation thermal/environmental barrier coating materials for protecting SiC-based ceramic composites in the hot section of gas turbine engines. In this paper, five kinds of high entropy (5RE_xi)₂SiO₅ with the non-equivalent molar ratios were prepared in order to investigate the effect of equivalent ion radius of RE³⁺ on CMAS corrosion behavior at low and high temperatures. For CMAS corrosion at 1300 °C, the CMAS corrosion behavior was controlled by the competitive balance between reaction thermodynamics and kinetics of (5RE_xi)₂SiO₅ and CMAS, and the thicknesses of apatite product layer decreased and then increased with the increasing equivalent ionic radius of RE³⁺. However, for CMAS corrosion at 1500 °C, the CMAS corrosion behavior mainly resulted from the dissolution-precipitation controlled by thermodynamics. With the increase of equivalent ionic radius of RE³⁺, the forming ability of apatite product will be enhanced, and the compact apatite product layer can be rapidly formed at the corrosion front to suppress CMAS attack on substrate, so the thicknesses of apatite product layer decreased gradually with increasing equivalent ionic radius of RE³⁺. The results of the study will provide theoretical guidance for the microstructural design of high entropy RE monosilicates in the future.