The performance of a composite electrolyte composed of a samarium doped ceria (SDC) and a binary eutectic carbonate melt phase has been examined. This material shows higher ionic conductivity than pure SDC in intermediate temperature region. SDC with different morphologies is obtained by co-precipitation, sol-gel and glycine-nitrate combustion preparation techniques. A tri-layer single cell is prepared with a cost-effective co-pressing and co-sintering technique. It is found that the surface properties of SDC and the electrolyte thickness have a great influence on the fuel cell performance. When the co-precipitated SDC is used as the electrolyte component and CO2/O-2 gas mixture is adopted as the cathode oxidantgas, a fuel cell with an excellent performance is obtained,which has a peak power output of 1704 mW cm(-2) at a current density of 3000 mA cm(-2) at 650 degrees C. The influence of cathode atmosphere is examined with conductivity measurement and fuel cell performance test. The results support the concept of O2-/H*/CO32- ternary conduction. (C) 2009 Elsevier B.V. All rights reserved.