The (100-x)Nd1.8Ce0.2CuO4+delta:Ce0.9Gd0.9Gd0.1O2-delta (x = 00, 10, 20 and 30 vol.%) composite systems are obtained by impregnating a stoichiometric solution of cerium and gadolinium nitrates followed by sintering at 900 degrees C for 4 h. Impregnating the Ce0.9Gd0.1O2-delta not only inhibits the growth of the host Nd1.8Ce0.2CuO4+delta grains during sintering but also enlarges the oxygen reduction reaction zone by introducing a nanosized phase that is ionically conductive, which significantly decreases the electrode polarization resistance of the composite cathode. A minimum polarization resistance value of 0.23 +/- 0.02 Omega cm(2) is obtained at 700 degrees C for a (80)Nd1.8Ce0.2CuO4+delta:(20)Ce0.9Gd0.9Gd0.1O2-delta Ce0.9Gd0.1O2-delta composite cathode, and this value is attributed to the optimal dispersion into the porous Nd1.8Ce0.2CuO4+delta matrix. The impedance spectra are modeled using an electrical equivalent model that consists of a mid-frequency ZRi cpE circuit (parallel combination of R1 and constant phase element (CPE)) and a low-frequency Gerischer impedance. The Gerischer impedance decreases significantly when Ce0.9Gd0.1O2-delta infiltrates the Nd1.8Ce0.2CuO4+delta matrix. The oxygen partial pressure-dependent polarization study suggests a medium-frequency response, which is due to charge transfer step; however, the low-frequency response corresponds to the non-charge transfer oxygen adsorption desorption and the diffusion process during the overall oxygen reduction reaction process. (C) 2014 Elsevier B.V. All rights reserved.