Preparation and thermal conductivities of Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 ceramics for thermal barrier coatings

Research highlights: → Single phase Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 with fluorite structures were synthesized by solid state reaction methods between Gd2O3, CeO2 and CaO powders at 1600 deg. C for 10 h. → The lower thermal conductivities of Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 can be attributed to the significantly higher concentration of oxygen vacancies and the significantly larger atomic weight of the solute cations in these two ceramic materials. → Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 can be explored as novel candidate ceramic materials for use in thermal barrier coatings. - Abstract: Two kinds of rare earth cerium oxides Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 were prepared by solid state reaction method at 1600 deg. C for 10 h. The phase compositions, microstructures, and their thermal conductivities of these materials were investigated. XRD results revealed that single phase Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 with fluorite structure were synthesized. Results of SEM and EDS showed that the microstructures of these materials were dense and no other phases existed among grains. Because of phonon scattering resulted by the oxygen vacancies and difference in atomic mass between substitutional atoms and host atoms, thermal conductivities of Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 are lower than that of 8YSZ at 800 deg. C, and thermal conductivity of (Gd0.9Ca0.1)2Ce2O6.9 is lower than that of Gd2Ce2O7. These results imply the Gd2Ce2O7 and (Gd0.9Ca0.1)2Ce2O6.9 can be used as novel candidate materials for thermal barrier coatings in the future.