We fabricated electrolyte supported single cells with three types of cathodes that consisted of a Ce0.1Gd0.1O1.95 (GDC) buffer layer, a LaNi0.6Fe0.4O3 (LNF) cathode and an active layer. The only difference between the three cathodes was that each had a different active layer, namely a GDC-LNF composite active layer (our conventional cathode), a PrxCe1-xO2-delta (x = 0.1, 0.3, 1.0)-LNF composite active layer and a Pr6O11 (PrxCe1-xO2-delta (x = 1.0)) active layer. The interface resistance, R-inf, and overvoltage, eta(c), of the cathodes were investigated. At 800 degrees C, the R-inf of the cathode with the Pr6O11 active layer was reduced to 1/30 that of the cathode with the GDC-LNF composite active layer. The R-inf at 800 degrees C for the cathode with the Pr6O11-LNF composite active layer was reduced to 1/8 that of the cathode with the GDC-LNF composite active layer. The R-inf values of the cathode with an active layer between 650 and 750 degrees C were also much better than those of the cathode with the GDC-LNF composite active layer. By using the cathode with the Pr6O11 active layer, the operating temperature can be reduced to 700 degrees C while retaining the same performance (same overvoltage at 254 mA/cm(2)) as a cathode with a GDC-LNF composite active layer at 800 degrees C. We also investigated the reactions at the interfaces in the sintering process. X-ray diffraction (XRD) analysis revealed that the Pr6O11 reacted easily with zirconia, and Pr2Zr2O7 was produced at 1000 degrees C or above. It was suggested that the sintering temperature of the cathodes with the active layer could be increased to around 1000 degrees C without any reaction at the interface between Pr6O11 and other materials. (C) 2013 Published by Elsevier B.V.