Thermophysical properties and CMAS corrosion resistance of a novel high-entropy RE monosilicate as T/EBC materials

High-entropy design is an attractive strategy to improve the comprehensive performances of RE₂SiO₅ as next-generation thermal/environmental barrier coating (T/EBC) materials for protecting SiC-based ceramic composites (SiC-CMCs) in the hot section of gas turbine engines. Herein, we designed a novel high-entropy RE monosilicate ((6RE_1/6)₂SiO₅) by co-doping the Sc, Yb, Tm, Er, Y, and Dy elements to synergistically improve thermophysical properties and molten calcium–magnesium–alumina–silicate (CMAS) corrosion resistance. The results revealed that as-prepared (6RE_1/6)₂SiO₅ had an ultra-low thermal conductivity (1.22–1.74 W·m⁻¹·K⁻¹), and a matched coefficient of thermal expansion ((4.57–5.05) × 10⁻⁶ K⁻¹) with SiC-CMCs in the testing temperature range. Moreover, it showed an excellent ability against CMAS corrosion at 1300°C and 1500°C. The thicknesses of reaction product layer were about 44 and 102 µm after CMAS corrosion at 1300°C for 48 h and 1500°C for 24 h, respectively. All of the above results identify that as-prepared (6RE_1/6)₂SiO₅ will be a suitable candidate as next-generation T/EBC for protecting SiC-CMCs.