Towards thermal barrier coating application for rare earth silicates RE2SiO5 (RE = La, Nd, Sm, Eu, and Gd)

Rare earth (RE) silicates X1-RE2SiO5 (RE = La, Nd, Sm, Eu, and Gd) are comprehensively investigated as promising thermal barrier coating candidates. The mechanical, thermal, and corrosion resistance properties are evaluated by theoretical exploration and experimental measurement. Mechanical properties and corrosion resistance to calcium-magnesium alumino-silicates (CMAS) melts of X1-RE2SiO5 are linearly correlated with ionic radius of RE elements. Elastic moduli increase with the decrease of ionic radius of RE3+. X1-RE2SiO5 with larger RE3+ exhibits better resistance to molten melts corrosion. For thermal properties, they are not obviously sensitive to RE species. All X1-RE2SiO5 demonstrate low thermal conductivities and their magnitudes are significantly modified by concentration of defects. Thermal expansion coefficients of X1-RE2SiO5 are more or less close and are compatible with the value of superalloy. The results highlight X1-RE2SiO5 as potential thermal barrier coating candidates with overall properties.