Preparation of (La_1-xSr_x)₂Ce₂O_7-x by Sol-Gel method and its thermophysical properties

Series of Sr -doping La₂Ce₂O₇ samples, that is (La_1-xSr_x)₂Ce₂O_7-x, were synthesized with sol -gel method. It is shown that (La_1-xSr_x)₂Ce₂O_7-x crystallize in pure defect-fluorite structure when the Sr-doping amount (x) is less than 0.1. With increasing of temperature, the thermal expansion coefficients (TECs) of (La_1-xSr_x)₂Ce₂O_7-x increase, and the thermal conductivities (TCs) decrease. At a certain temperature, the TECs of (La_1-xSr_x)₂Ce₂O_7-x increase with x increasing; and the TCs decrease when x changes from 0 to 0.075, then increase obviously when x≥0.075.