Plasma-sprayed La₂Ce₂O₇ thermal barrier coatings against calcium-magnesium-alumina-silicate penetration

As one of promising thermal barrier coating (TBC) candidates, La₂Ce₂O₇ (LC) has attracted increasing attention because of its low thermal conductivity and potential capability to be operated above 1250°C. In this paper, the microstructure evolution and mechanical properties of the plasma-sprayed LC TBC with calcium-magnesium-alumina-silicate (CMAS) glassy deposits at 1250°C were investigated. Due to chemical reaction between the CMAS deposits and LC coating, a dense sealing layer, mainly composed of Ca₂(La_xCe_1-x)₈(SiO₄)₆O_6-4x and CeO₂, was formed on the coating after heat-treatment at 1250°C and effectively prevented CMAS from further penetration. The interaction layer had the micro-hardness of ~10-12GPa, relatively harder than the LC coating.