Electrical properties of Ce sub(0.85)Sm sub(0.15)O sub(1.925)-Fe sub(2)O sub(3) electrolytes for IT-SOFCs

Ce sub(0.85)Sm sub(0.15)O sub( 1.925)-x mol% Fe sub(2)O sub(3) (x = 0, 0.5, 1, 1.5) materials (named as SDC, SDC + 0.5Fe sub(2)O sub(3), SDC + 1Fe sub(2)O sub(3), and SDC + 1.5Fe sub(2)O sub(3)) were developed and used as the electrolytes for intermediate temperature fuel cells. Because of the scavenging effect of Fe sub(2)O sub(3) on SiO sub(2) impurity located at the grain boundary of SDC, SDC-Fe sub(2)O sub(3) electrolytes exhibited a significantly improved grain boundary conduction compared to that of SDC. In addition, we found that the grain boundary conductivity of SDC-Fe sub(2)O sub(3) decreased with the increase of the amount of Fe sub(2)O sub(3). The total conductivity of SDC-Fe sub(2)O sub(3) was higher than the pure SDC, indicating that the total conductivity was dominated by grain boundary conductivity. In our case, the optimal amount of Fe sub(2)O sub(3) additive was proved to be 0.5 mol%. The SDC + 0.5Fe sub(2)O sub(3) electrolyte had the highest conductivity ([sigma] sub(t) = 0.02 S cm super(-1), at 750 [degrees]C) and the fuel cell based on the SDC + 0.5Fe sub(2)O sub(3) showed the best performance (the maximum power density reached as high as 419 mw cm super(-2) at 750 [degrees]C). The encouraging results suggest that the SDC-Fe sub(2)O sub(3) materials are the very promising electrolyte materials for IT-SOFCs.