Strontium mediated modification of structure and ionic conductivity in samarium doped ceria/sodium carbonate nanocomposites as electrolytes for LTSOFC

The structural changes on the addition of strontium in samarium doped ceria/Na2CO3 nanocomposites were investigated with respect to sintering temperature. The nanocomposites prepared by a co-precipitation method in the presence (SrSDS) and absence (SDS) of strontium were sintered at 500, 600 and 700 degrees C. XRD results indicated an increase in crystallite size and lattice parameter with respect to sintering temperature in the presence of strontium. Raman, SEM and FT-IR studies confirmed the presence of Na2CO3 and CeO2 phases. The observed changes in crystallinity and oxygen vacancy concentrations indicate the beneficial role of strontium upon sintering up to 600 degrees C. The impedance spectral analysis clearly shows the beneficial effect of adding strontium to the composite. The lowest activation energy (0.61 eV) with the highest conductivity (3.8 x 10(-3) S cm(-1)) for SrSDS sintered at 600 degrees C arises due to the strong interaction between the Na2CO3 and CeO2 phase. However, sintering the composites at 700 degrees C indicated a negligible effect of strontium due to the decomposition of N2CO3, thereby limiting the operational temperature of the nanocomposites for potential fuel cell applications.