Electrical conductivity of polycrystalline (CeO2)0.80(LaO1.5)0.20 with a small amount of (LaF3)0.95(SrF2)0.05

Adding 1 wt.% of the fluorine-ion conducting (LaF3)0.95(SrF2)0.05 to polycrystalline oxygen-ion conducting (CeO2)0.80(LaO1.5)0.20 solid solution, the effect on the electrical conductivity is studied as a function of sintering temperature. Highly sinterable (CeO2)0.80(LaO1.5)0.20 starting powder was fabricated by co-precipitation using oxalate method and followed by a hydrothermal treatment. The oxide conductivity was measured by DC and AC four-probe techniques at high oxygen partial pressures between 0.21 and 1 bar. The polycrystalline microstructure of the sintered specimens was investigated by transmission electron microscopy (TEM). The oxide conductivity is slightly increased by the addition of 1 wt.% (LaF3)0.95(SrF2)0.05 to polycrystalline (CeO2)0.80(LaO1.5)0.20, provided the specimens were sintered above 1500 °C. At sintering temperatures above 1700 °C, (LaF3)0.95(SrF2)0.05 was detected at the grain boundaries of the polycrystalline (CeO2)0.80(LaO1.5)0.20. Obviously, the (LaF3)0.95(SrF2)0.05 generates ion-conducting pathways between the (CeO2)0.80(LaO1.5)0.20 grains causing a higher grain boundary conductivity.