The electrical conductivity and Seebeck coefficient of sintered BSCF ceramics (Ba0.5Sr0.5CoxFe1 - xO3 - delta, 0 <= x <= 0.8) were simultaneously measured as a function of pO(2) (10(-5) <= pO(2) <= 1 atm) at 500 degrees C, 700 degrees C and 900 degrees C. All samples exhibited a positive Seebeck coefficient over the range of pO(2) and temperature examined, which indicates the predominance of p-type conduction. In all cases, conductivity increased with increasing PO2, ranging from a minimum of similar to 0.6 S/cm (x = 0, pO(2)= 10(-5) atm, T = 900 degrees C) to a maximum of similar to 36 S/cm (x = 0.8, pO(2) = 1 atm, and T = 900 degrees C). At low temperatures and high pO(2), conductivity was approximately proportional to pO(2)(1/4), which was attributed to the reduction of B-site cations from their tetravalent to trivalent state. At low pO(2) and high temperature, the conductivity exhibited positive deviations from the pO(2)(1/4) dependence. At 500 degrees C and x <= 0.6, the Seebeck coefficient (Q) decreased linearly with increasing log pO(2). At 700 and 900 degrees C, Q vs. log pO(2) curves exhibited maxima at 10(-3)

Keywords:BSCF;Barium strontium cobalt iron oxide;Perovskite;Solid oxide fuel cell;Cathode;Mixed ionic-electronic conductor;Defect chemistry;Seebeck coefficient;Jonker plot