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

Abstract High‐entropy design is an attractive strategy to improve the comprehensive performances of RE ₂ SiO ₅ 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 ) ₂ SiO ₅ ) 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 ) ₂ SiO ₅ 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 ) ₂ SiO ₅ will be a suitable candidate as next‐generation T/EBC for protecting SiC‐CMCs.