NdBa1 - xCo2O5 + delta (NB1 - x Co, x= 0.00, 0.02, 0.04, and 0.06) have been synthesized and evaluated as cathode materials for use in intermediate temperature solid oxide fuel cells (IT-SOFCs). The effect of Ba deficiency on the structure, thermal and electrochemical properties of NB1 - xCO is systematically investigated. NB1 - xCO have a tetragonal layered-perovskite structure. Iodometric titration indicates that the oxygen content decreases and the concentration of oxygen vacancy increases with increasing Ba deficiency. The thermal expansion coefficient decreases with increasing Ba deficiency. An inflection occurs on the slope approximately 300 degrees C for NBCO that changes to 250 degrees C for NB1 - xCO. The results suggest that introduction of Ba deficiency is beneficial for the release of lattice oxygen. Among all of the samples, NB0.96CO exhibits the lowest polarization resistances. Increasing oxygen vacancy by introduction Ba deficiency promotes the area conductivity of the oxygen ion transfer at the interface between the cathode and the electrolyte and the area conductivity of the reduction reaction of atom adsorbed oxygen into adsorbed oxygen ion. Our results demonstrate that the NB0.96CO electrode is a potential cathode material for IT-SOFCs. (C) 2016 Elsevier B.V. All rights reserved.