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Ba x Sr 1− x Co 0.9 Sb 0.1 O 3− δ (BSCSbx, x = 0.0–0.8) are investigated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). BSCSbx oxides are crystallized in a tetragonal structure with s.g. P4/mmm . XPS analysis shows that Ba doping reduces valence state of Co ions: Co in SrCo 0.9 Sb 0.1 O 3− δ is prone to Co 4+ , while Co in Ba doped SrCo 0.9 Sb 0.1 O 3− δ becomes more prone to Co 3+ . Oxygen deficiency δ increases with Ba doping even at high temperatures. Conductivity is found to decrease with Ba doping. Thermal expansion coefficient (TEC) decreases from 20.6 × 10 −6 K −1 for x = 0.0 to 18.4 × 10 −6 K −1 for x = 0.6 at 30–1000 °C. With increasing x from 0.0 to 0.6, polarization resistance ( R p ) decreases monotonously, and then increases with further increasing x. The lowest R p of 0.081 Ω cm 2 at 700 °C is obtained for BSCSb0.6 cathode. At 700–850 °C, the R p of BSCSb0.6 is mainly contributed from electron charge transfer; however, below 700 °C, ion charge transfer plays a more important role in R p . Maximum power densities of the cell with BSCSb0.6 cathode on 300-μm thick La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ (LSGM) electrolyte attain 306–944 mW cm −2 at 700–850 °C. These results indicate that BSCSb0.6 is a promising cathode for application in IT-SOFC. [ABSTRACT FROM AUTHOR]

Ba0.6Sr0.4Co0.9Nb0.1O3−δ (BSCN)–xGd0.1Ce0.9O1.95 (GDC) composites with various GDC contents (x = 0–40, wt%) have been investigated for their potential application in IT-SOFCs. The effects of GDC addition on thermal expansion and electrochemical performances were studied. Thermal expansion measurement indicates that thermal expansion coefficients (TECs) decrease with increasing GDC content; in addition, GDC plays a catalytic role during the process of low-temperature thermal-driven reduction of Co4+ to Co3+. Polarization resistance (R p) measurement indicates that the proper addition of GDC improves electrochemical performance of BSCN cathode. The optimum GDC addition to BSCN cathode is 20 wt% with the lowest R p of 0.042 Ω cm2 at 700 °C. The maximum power density of a cell with BSCN–20GDC cathode on 300 μm-thick GDC electrolyte achieves 460–880 mW cm−2 at 700–800 °C. The excellent electrochemical performance of BSCN–20GDC composite cathode is ascribed to its much finer microstructure and larger cathode/electrolyte/gas triple phase boundary (TPB) areas. [ABSTRACT FROM AUTHOR]