Tuning CMAS corrosion resistance in high-entropy zirconates via rare-earth ionic radius control

During high-temperature service of aero-engines, molten Calcium–magnesium–alumina–silicate (CMAS) deposits can infiltrate thermal barrier coatings, posing a severe threat to their long-term stability. This study investigates the CMAS corrosion behavior of two high-entropy rare-earth zirconate ceramics, (La 0.2 Nd 0.2 Sm 0.2 Gd 0.2 Ho 0.2 ) 2 Zr 2 O 7 (LNSGH) and (Nd 0.2 Sm 0.2 Gd 0.2 Ho 0.2 Er 0.2 ) 2 Zr 2 O 7 (NSGHE). CMAS corrosion tests were conducted at 1300 °C for 5, 10, and 20 h to evaluate their structural stability and corrosion product evolution. The results show that NSGHE exhibits superior resistance to CMAS attack compared to LNSGH. This improvement is attributed to its smaller average RE 3+ ionic radius and reduced optical basicity difference with CMAS, which lowers the chemical driving force for interfacial reactions and thus reduces the tendency for apatite formation. These findings offer theoretical insight into RE 3+ -dependent corrosion mechanisms and suggest a viable high-entropy design strategy for developing structural ceramics with improved chemical stability in high-temperature aerospace environments.