Investigation about thermophysical properties of Ln2Ce2O7 (Ln = Sm, Er and Yb) oxides for thermal barrier coatings

Three kinds of rare earth cerium oxides – Ln2Ce2O7 (Ln = Sm, Er and Yb) were prepared by solid state reaction method. Their phase compositions, microstructures and thermophysical properties were investigated. Results of X-ray diffraction reveal that pure Ln2Ce2O7 (Ln = Sm, Er and Yb) oxides with fluorite structure are successfully synthesized in the current research. Scanning electrical microscopy results show that their microstructures are dense and no other un-reacted oxides or inter-phases exist in the interfaces between grains. Their thermal expansion coefficients are higher than those of YSZ, while their thermal conductivities are lower than those of YSZ. The decreasing ionic radius from Sm3+ to Yb3+ results in the descending thermal expansion coefficients from Sm2Ce2O7 to Yb2Ce2O7. The effective phonon scattering by atomic weight difference contributes to the decreasing thermal conductivities from Sm2Ce2O7 to Yb2Ce2O7. These results imply that synthesized rare earth cerium oxides have potentials to be used as novel candidate materials for thermal barrier coatings in the future.