Thermal Conductivities and Thermal Expansion Coefficients of (Sm0.5Gd0.5)2(Ce1−x Zr x )2O7 Ceramics

The (Sm0.5Gd0.5)2(Ce1−x Zr x )2O7 oxides were prepared by solid-state reaction, and their phase compositions, microstructures, and thermophysical properties were investigated. Results of x-ray diffraction reveal that pure (Sm0.5Gd0.5)2(Ce1−x Zr x )2O7 oxides with fluorite structure are successfully synthesized in the current study. The thermal expansion coefficient decreases with increasing content of ZrO2, which is higher than that of 7 wt.% yttria-stabilized zirconia (YSZ). The substitution of Zr4+ for Ce4+ reduces the thermal conductivity of Sm2Ce2O7 oxide. The thermal conductivity decreases from 1.69 W/m K (x = 0) to 1.22 W/m K (x = 0.3) at 1000 °C. The composition with x = 0.3 exhibits the lowest thermal conductivity at all temperatures, and the thermal conductivity of (Sm0.5Gd0.5)2 (Ce1−x Zr x )2O7 ceramics was obviously lower than those of fully dense 7 wt.% YSZ. These results suggested promising potential applications of the (Sm0.5Gd0.5)2 (Ce1−x Zr x )2O7 ceramics for high-temperature thermal barrier coatings.