BaCe0.8Y0.2O3-delta and BaCe0.9-xYxNb0.1O3-delta (x=0.1, 0.15, 0.2, 0.25, 0.3, 0.35) were prepared by a solid-state reactions. It was found that the BaCe0.8Y0.2O3-delta samples decomposed into CeO2 and BaCO3 after being exposed in the atmosphere (3% CO2 + 3% H2O + 94% N-2) at 700 degrees C for 10 h. However, samples containing Nb remains unchanged in the same conditions, demonstrating a better stability in the presence of CO2 and H2O. The conductivity of BaCe0.9-xYxNb0.1O3-delta increased with the increase of Y content (x <= 0.30), and the highest value was observed at x = 0.30 where a significant decrease in conductivity took place at x = 0.35. The conductivity of BaCe0.9-xYxNb0.1O3-delta reaches 0.01 S/cm in humid hydrogen at 700 degrees C, slight lower than BaCe0.8Y0.2O3-delta, 0.012 S/cm in the same conditions. Fuel cell with BaCe0.6Y0.3Nb0.1O3-delta as-prepared was successfully prepared and humidified hydrogen was supplied as fuels in evaluating the fuel cell performance. The open circuit voltage, peak power density and interfacial resistance at 700 degrees C were 1.02 V, 345 mW/cm(2) and 0.27 Omega cm(2), respectively. (c) 2009 Elsevier Ltd. All rights reserved.