Electrical properties of Ce0.85Sm0.15O1.925-Fe2O3 electrolytes for IT-SOFCs

Ce0.85Sm0.15O1.925-x mol% Fe2O3 (x = 0, 0.5, 1, 1.5) materials (named as SDC, SDC + 0.5Fe2O3, SDC + 1Fe2O3, and SDC + 1.5Fe2O3) were developed and used as the electrolytes for intermediate temperature fuel cells. Because of the scavenging effect of Fe2O3 on SiO2 impurity located at the grain boundary of SDC, SDC-Fe2O3 electrolytes exhibited a significantly improved grain boundary conduction compared to that of SDC. In addition, we found that the grain boundary conductivity of SDC-Fe2O3 decreased with the increase of the amount of Fe2O3. The total conductivity of SDC-Fe2O3 was higher than the pure SDC, indicating that the total conductivity was dominated by grain boundary conductivity. In our case, the optimal amount of Fe2O3 additive was proved to be 0.5 mol%. The SDC + 0.5Fe2O3 electrolyte had the highest conductivity (σt = 0.02 S cm−1, at 750 °C) and the fuel cell based on the SDC + 0.5Fe2O3 showed the best performance (the maximum power density reached as high as 419 mw cm−2 at 750 °C). The encouraging results suggest that the SDC-Fe2O3 materials are the very promising electrolyte materials for IT-SOFCs.