Structural design and CMAS corrosion resistance of high entropy RE silicate multiphase ceramics as next-generation thermal/environmental barrier coatings

Abstract

The advanced high entropy rare earth (RE) silicates achieving versatile property optimization as thermal/environmental barrier coatings (T/EBCs) is crucial to protect SiC-based ceramic composites as hot-section components in aero-engines. In this work, we simulated the structure of T/EBCs and designed high entropy (4RE_0.25)₂Si₂O₇/(4RE_0.25)₂SiO₅ (RE= Yb, Y, Er and Sc) multiphase ceramics, as so to explore the relationship of structural regulation of multiphase ceramics with thermal properties and molten calcium–magnesium–aluminosilicate (CMAS) corrosion resistance. The results showed that the interaction of (4RE_0.25)₂Si₂O₇ and (4RE_0.25)₂SiO₅ can not only influence the crystal structures such as the bond length and the lattice distortion, but also change the interface structure and produce the amorphous phase at the interface due to the interfacial stress, leading to reduction in thermal conductivity. Moreover, the coupling effect of different dissolution rates of (4RE_0.25)₂Si₂O₇ and (4RE_0.25)₂SiO₅ can significantly improve high temperature CMAS corrosion resistance, and the corrosive depth was only about 150μm after CMAS corroding at 1500 °C for 48 h. This work also illustrates an efficient and reliable theoretical basis and guidelines in accelerating the design of next-generation T/EBCs.