NdBa0.5Sr0.5CO2-xMnxO5+delta (x=0, 0.25, and 0.5) specimens are synthesized and investigated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The interaction between two different transition metals, Mn and Co, may affect the electronic conducting properties and electrochemical performance. The substitution of Mn for Co lowers the thermal expansion coefficient (TEC) of Co-based materials by suppression of the spin state transition of Co3+ which might consequently improve the mechanical compatibility with the electrolyte. The electrochemical performance, however, could be slightly degraded by trapping of the effective mobile charge with increasing Mn content. Such a substitution of Co by Mn would provide a tradeoff relationship between TEC and electrochemical performance in IT-SOFCs. In this paper, the tradeoff between electrochemical and thermal expansion is explored. (C) 2013 Elsevier Ltd. All rights reserved.