Reactivity of single, equiatomic and non-equiatomic rare-earth disilicates with CMAS at high temperature

Multi-component RE2Si2O7 have gained scientific interest due to their combination of improved properties which can be used for T/EBC (thermal and environmental barrier coating) application. This work addresses the role of Sc3+, Lu3+, Yb3+, Er3+, Y3+, and Ho3+ cations in the reactivity with CMAS of single and multi-component rareearth silicates having either equiatomic or non-equiatomic RE contents. Thermochemical powder interactions were investigated at 1350 and 1400 ◦C through the reaction products. The reaction products include RE2Si2O7, apatite (Ca2RE8(SiO4)6O2) and pyroxene-type (Ca(Mg,Fe)[(Si,Al)2O6]) phases. The observed trends indicate that Sc3+, Lu3+, and Yb3+ are slowly dissolved in CMAS without causing any crystalline phase formation, meanwhile, Er3+, Y3+, and Ho3+ rapidly crystallized the apatite phase. Non-equiatomic multi-component materials can be designed to tune physical, mechanical, environmental, and other relevant properties depending on the con­ centration of RE elements.