Preparation and thermophysical properties of Sm2YbTaO7 and Sm2YTaO7

Sm2YbTaO7 and Sm2YTaO7 ceramics were synthesized by solid reaction method at 1600 °C for 10 h. Crystal phases have been identified by X-ray diffraction, and their thermal conductivities and thermal expansion coefficients were measured using a laser flash method and the pushing-rod technology, respectively. Results indicate that Sm2YbTaO7 and Sm2YTaO7 exhibit a typical defect fluorite-type crystal structure. Compared to Sm2YTaO7, Sm2YbTaO7 has lower thermal conductivity due to the higher atomic weight difference between the substituted and substituting atoms. The thermal expansion coefficient of Sm2YbTaO7 is greater than that of Sm2YTaO7 due to its elongated average interionic distance. Their thermal conductivities are much lower than that of YSZ, and their thermal expansion coefficients are very close to that of YSZ. The synthesized ceramics also exhibit excellent phase stability in the temperature range from ambient to 1200 °C.