Ba1-xCo0.7Fe0.2Nb0.1O3-delta oxides (x = 0, 0.05 and 0.10) were optimized as potential cathodes on oxygen ionic conductor electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). The creation of additional oxygen vacancies in Ba0.9Co0.7Fe0.2Nb0.1O3-delta was confirmed. Low polarization resistances of 0.015, 0.029 and 0.089 Omega cm(2) were achieved at 700, 650 and 600 degrees C, respectively. By further optimizing the microstructure of the Ba0.9Co0.7Fe0.2Nb0.1O3-delta electrode by using polyvinyl butyral as a pore former and adjusting the sintering temperature, the maximum power density was improved from 682 to 955 mW cm(-2) at 650 degrees C. The operational stability of the Ba0.9Co0.7Fe0.2Nb0.1O3-delta electrode was also investigated. The CO2 in the surrounding air was detrimental to the oxygen reduction reaction; however, the performance of the cell was recovered after removing the CO2 in the air at 650 or 700 degrees C. In addition, the Ba0.9Co0.2Fe0.2Nb0.1O3-delta electrode in symmetrical cells exhibited a stable performance at 650 degrees C for 400 h and maintained a reliable performance after repeated thermal cycles from room temperature to 700 degrees C. The results showed that Ba0.9Co0.3Fe0.2Nb0.1O3-delta was a promising cathode material for practical application in IT-SOFCs. (c) 2013 Elsevier Ltd. All rights reserved.