Characteristics of Ag-doped LaMnO3 perovskite oxide and its application as a solid oxide fuel cell cathode†

Abstract

Ag-doped LaMnO₃ perovskite oxides were synthesized as new cathode materials for solid oxide fuel cells (SOFCs), and their phase stability, reactivity with yttria-stabilized zirconia (YSZ), electronic state of Mn, electrical conductivity, and power generation properties were investigated. La_0.9Ag_0.1MnO_3±δ (LAM01) showed no evidence of Ag metal deposition, whereas La_0.9Ag_0.2MnO_3±δ (LAM02) showed Ag metal deposition, suggesting that Ag dissolved in a perovskite-type structure and its solid solution limit for the La-site was 10%. LAM01 did not react with the YSZ electrolyte at 975 °C for 100 h. The electronic state of Mn was between that of the trivalent and tetravalent states at room temperature, suggesting that the Ag acceptor dopant was charge-compensated by the oxidation of Mn. Electrical conductivity and Seebeck coefficient measurements indicated that the main charge carrier was electron–hole. Stable power generation properties were obtained using the LAM01 cathode and indicated that the Ag acceptor was stable and was compatible with the YSZ electrolyte. Therefore, Ag-doped LaMnO₃ is promising as a novel SOFC cathode.