Microstructure and property evolution of high‐entropy rare‐earth silicate T/EBCs during thermal aging

Abstract With the increasing service temperature of aeroengines, the development of thermal/environmental barrier coatings (T/EBCs) has been considered to be a great challenge, which requires high‐temperature stability and excellent thermal and mechanical properties. In this work, high‐entropy design was adopted to change the crystal structure of rare‐earth monosilicates used for T/EBCs. The microstructure evolution, thermal and mechanical properties of the plasma‐sprayed (Lu 0.25 Yb 0.25 Er 0.25 Y 0.25 ) 2 SiO 5 and (Lu 0.2 Yb 0.2 Er 0.2 Ho 0.2 Y 0.2 ) 2 SiO 5 coatings before and after thermal aging at 1350°C for 50 h were investigated. Results showed that the as‐sprayed coatings exhibited dense structure with amorphous and decomposed phases. The change of microstructure like amorphous crystallized and defect healing occurred after thermal aging, which had obvious influence on thermomechanical properties. Compared with single‐component RE 2 SiO 5 (RE = Yb, Er, Y) coatings, the thermal‐aged high‐entropy coatings exhibited lower thermal conductivity, similar thermal expansion coefficient, and better toughness. The work will provide a foundation for the design and application of T/EBCs materials.