Enhanced ionic conductivity of Sm0.2Ce0.8O2-δ electrolyte for solid oxide fuel cells through doping transition metals

Ceria-based electrolytes are considered as candidate electrolyte materials for intermediate temperature solid oxide fuel cells due to the high oxygen-ion conductivity. Lowing sintering temperature for ceria-based electrolyte is favorable for co-firing process as well as the reduction of fabrication cost. Transition metals (Fe, Co, Ni) were added to Sm-doped ceria (SDC) and the crystal structure, sintering performance and ionic conductivity were investigated by X-ray diffraction, SEM and AC impedance spectroscopy. The transition metal elements added to SDC as sintering aids reduced the sintering temperature of SDC electrolyte by 100-150 A degrees C and the grain size decreased with increased doping amount of transition metals. The ionic conductivity, especially the grain-boundary conductivity was significantly improved by a small addition of transition metals. Among Fe, Co, Ni doped SDC electrolytes, the 0.01 mol Fe3+ doped SDC sintered at 1350 A degrees C exhibited the highest ionic conductivity about 0.063 S cm(-1) at 800 A degrees C and the lowest activation energy of 0.73 eV.