We evaluated the electrochemical performances of LaNi0.6Fe0.4O3 (LNFO) and LaNi0.6Co0.4O3 (LNCO) perovskites as cathodes in La0.8Sr0.2Ga0.83Mg0.17O2.(815) (LSGM) electrolyte-supported solid oxide fuel cell. Both samples show excellent chemical compatibility with the LSGM electrolyte up to 900 degrees C, and exhibit small-polaron type electrical conduction with a high conductivity sigma approximate to 510 (430) S.cm(-1) at 800 degrees C and a small activation energy E-e(a) = 54.9 (44.4) meV for LNFO (LNCO). The oxygen-reduction reaction evaluated in a symmetric LNFO(LNCO)|LSGM|LNFO(LNCO) cell gives a polarization resistance R-p approximate to 0.51 (0.34) Omega.cm(2) at 800 degrees C in air and an activation energy E-a(O) = 1.61 (1.87) eV. For a single cell composed of LNFO (LNCO) cathode, 300-mu m-thick LSGM electrolyte, and a composite Ni + Gd-doped ceria anode, the maximum power densities reach P-max = 490 (650) and 850 (1015) mW.cm(-2) at 800 and 850 degrees C, respectively. These results demonstrated that LNFO and LNCO are promising cathode materials for the IT-SOFCs. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.