Double perovskites LnBaCoFeO(5+delta) (Ln = Pr and Nd, PBCF and NBCF) are comparatively investigated as potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). LnBaCoFeO(5+delta) materials are chemically compatible with La0.9Sr0.1Ga0.8Mg0.2O3-delta (LSGM) electrolyte at temperatures below 1000 degrees C. Fe and Co ions in LnBaCoFeO(5+delta) exist in two oxidation states, 3+ and 4+. Pr ions are found in PBCF mostly as Pr3+. Thermal expansion coefficients (TECs) of PBCF and NBCF are 21.0 x 10(-6) and 19.5 x 10(-6) K-1, respectively, between 30 and 1000 degrees C; these are lower than the TECs of undoped LnBaCo(2)O(5+delta). The best electrical conductivity for both materials is observed near 350 degrees C: 321 and 172 S cm(-1) for PBCF and NBCF, respectively. Polarization resistances of PBCF and NBCF cathodes on LSGM electrolyte are 0.049 and 0.062 Omega cm(2) at 800 degrees C, respectively. Maximum power densities of the single-cell with Ni/SDC as anode on a 0.3 mm-thick LSGM electrolyte reach 749 and 669 mW cm(-2) for PBCF and NBCF cathodes at 800 degrees C, respectively. As cathodes for application in IT-SOFCs, the performance of PBCF and NBCF double perovskites is promising. (c) 2013 Elsevier B.V. All rights reserved.