Conductivity of cerium doped BaFeO3−δ and applications for the detection of oxygen

The effect of Ce doping on the structure and the conductivity of BaFeO3 perovskite materials is investigated and the resulting materials are applied as oxygen sensors. The new perovskite family, Ba1−xCexFeO3−δ (x = 0, 0.01, 0.03, and 0.05), was prepared via a sol-gel method. Powder XRD indicates a hexagonal structure for BaFeO3 with a change to a cubic perovskite upon cerium doping at the A site. The solubility limit of Ce at the A site was experimentally determined to be between 5 and 7 mol%. Bulk, electronic and ionic conductivities of BaFeO3−δ and Ba0.95Ce0.05FeO3−δ were measured in air at temperatures up to 1000 °C. Cerium doping increases the conductivity throughout the entire temperature range with a more pronounced effect at higher temperatures. At 800 °C the conductivity of Ba0.95Ce.05FeO3−δ reaches 3.3 S/cm. Pellets of Ba0.95Ce.05FeO3−δ were tested as gas sensors at 500 and 700 °C and show a linear, reproducible response to O2.