Phase-structures, thermophysical properties of Sm3Ce7Ta2O23.5 and Gd3Ce7Ta2O23.5 oxides for thermal barrier coating applications

Two types of rare earth tantalite oxides, Sm3Ce7Ta2O23.5 and Gd3Ce7Ta2O23.5, were synthesised using a high-temperature sintering technique. The phase-structures, micro-morphologies, element compositions, thermal conductivities, and thermal expansion performances were investigated. The final conclusions show that these two ceramics are approximately composed of 2RETa(0.5)Ce(2.5)O(8.25) and RETaCe2O7. The relative densities are above 90%, and the interfaces between grains are clear. Owing to the relatively high total atomic weights, complicated element compositions, and many more oxygen vacancies, the obtained oxides exhibit lower thermal conductivities than RE2Zr2O7 and YSZ. The coefficients of thermal expansion for Sm3Ce7Ta2O23.5 and Gd3Ce7Ta2O23.5 above 1473 K are greater than those of La2Zr2O7 and YSZ. The thermal expansion coefficients and conductivities of the obtained oxides satisfy the requirements for thermal barrier coating applications.