Perovskite oxide Ba1.0Co0.7Fe0.2Nb0.1O3-delta has been reported as oxygen transport membrane and cathode material for solid oxide fuel cells (SOFCs). In this study, the effects of A-site cation deficiency and B-site iron doping concentration on the crystal structure, thermal expansion coefficient (TEC), electrical conductivity and electrochemical performance of Ba1-xCo0.9-yFeyNb0.1O3-delta (x = 0-0.15, y = 0-0.9) have been systematically evaluated. Ba1-xCo0.9-yFeyNb0.1O3-delta (x = 0-0.10, y = 0.2 and x = 0.10, y = 0.2-0.6) can be indexed to a cubic structure. Increased electrical conductivity and decreased cathode polarization resistance have been achieved by A-site deficiency. No obvious variation can be observed in TEC by A-site deficiency. The electrical conductivity and TEC of Ba0.9Co0.9-yFeyNb0.1O3-delta decrease while the cathode polarization resistance increases with the increase in iron doping concentration. The highest conductivity of 13.9 S cm(-1) and the lowest cathode polarization resistance of 0.07 Omega cm(2) have been achieved at 700 degrees C for Ba0.9Co0.7Fe0.2Nb0.1O3-delta. The composition Ba0.9Co0.3Fe0.6Nb0.1O3-delta shows the lowest TEC value of 13.2 x 10(-6) degrees C-1 at 600 degrees C and can be a potential cathode material for SOFCs. Copyright (c) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.