Synergistic effect of lithium and calcium for low temperature densification and grain boundary scavenging in samarium doped ceria electrolyte

A highly dense electrolyte with lower grain boundary resistance is desirable for improving the performance of solid oxide fuel cell. This paper studies the synergistic role of calcium and lithium on the densification and ionic conductivity of samarium doped ceria (SDC) electrolyte. Nanosized powders of compositions, CaxLiySm0.2Ce0.78O2-delta (CLSDC, x + y = 0.02) were prepared by citrate - nitrate combustion method and subsequently sintered at 900 degrees C. A single phase cubic fluorite structure of CeO2 was observed in X-ray diffraction analysis. The segregation of the co-dopants was identified from Raman spectroscopic analysis and FESEM-EDX analysis. The presence of lithium enhanced the densification at 900 degrees C while calcium improved the grain boundary scavenging. The synergistic effect of an increase in configurational entropy and density in 0.5 mol% Ca and 1.5 mol% Li (0.5CLSDC900) resulted in the highest conductivity of 5.3 x 10(-3) S/cm at 800 degrees C with a scavenging factor of 20.2. Thus the optimum ratio of Li+ and Ca2+ plays a key role in suppressing the ordering of oxygen vacancy and improve the ionic conductivity for its use as an electrolyte for solid oxide fuel cells.