In this study, we have investigated the feasibility of forming a new ionic conducting electrolyte from a proton conducting phase, BaCe0.8Y0.2O3-delta (BCY), and an oxygen conducting phase, Ce0.8Gd0.2O1.9 (CDC). in order to decrease the reduction of Ce4+ ions to Ce3+ ions in reducing atmospheres at high temperatures. BCY-GDC composite powders (molar ratio 1:1) are synthesized via a one-step citric acid-nitrate gel combustion method. The reaction between the BCY and GDC in these composite powders at 1550 degrees C results in the formation of a new perovskite phase with a nominal composition of BaCe1.6Y0.2Gd0.2O4.9-alpha. The conductivity of the new perovskite phase is found to be substantially (similar to 150%) higher than that of the composite electrolyte made from the mixture of BCY and GDC with the same nominal composition as the new perovskite phase. The single fuel cells with the new perovskite electrolyte exhibit better electrochemical performance than the cells with the composite electrolyte made of the mixture of BCY and GDC. The maximum power density of single cells with the new perovskite electrolyte can reach 0.657 W cm(-2) at 700 degrees C using humidified hydrogen (3% H2O) as the fuel. This maximum power density is similar to 65% higher than that of the cells with the BCY+GDC composite electrolyte. (C) 2012 Elsevier B.V. All rights reserved.