Perovskite-type oxides of Ln(0.4)Sr(0.6)Co(0.8)Fe(0.2)O(3-delta) (Ln = La, Pr, Nd, Sm, Gd) have been prepared by the solid state reaction of corresponding oxides. The electrical conductivity of the sintered samples showed semiconductor-like behavior at a lower temperature and metallic behavior at a higher temperature. Nd0.4Sr0.6Co0.8Fe0.2O3-delta exhibited the highest conductivity in Ln(0.4)Sr(0.6)Co(0.8)Fe(0.2)O(3-delta) in the temperature range of 25-1000 degrees C. The reactivity test of these oxides with 8 mol% Y2O3 doped zirconia (8YSZ) was carried out between 800 and 1000 degrees C for 96 h in air. The perovskite oxides reacted with 8YSZ to produce SrZrO3 at 900 degrees C and no reaction product was observed at 800 degrees C. The cathodic polarization of these oxide electrodes sputtered on the 8YSZ tablet was studied at 600-800 degrees C in air. Nd0.4Sr0.6Co0.8Fe0.2O3-delta showed the best catalytic activity for oxygen reduction. These perovskite oxides showed no degradation of the electrode performance by annealing between 600 and 800 degrees C.