Interaction laws of RE2O3 and CMAS and rare earth selection criterions for RE-containing thermal barrier coatings against CMAS attack

Thermal barrier coatings (TBCs) with higher rare earth (RE) contents are more resistant to CaO-MgO-Al2O3-SiO2 (CMAS) attack due to their reaction to form apatite protective products. In this study, the reaction behavior between RE2O3 and CMAS was investigated and their interaction laws were clarified, based on which three criterions for selecting RE dopants for RE-containing TBC materials are proposed: 1) favorable reaction product types and strong protective products formation kinetics, 2) low RE3+ solubility in molten CMAS, and 3) low wettability of residual mixture. Sm2O3 and Gd2O3 are demonstrated as the most attractive dopants for RE-containing TBCs against CMAS attack.