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

Abstract

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 °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 °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 × 10⁻³ S cm⁻¹) for SrSDS sintered at 600 °C arises due to the strong interaction between the Na₂CO₃ and CeO₂ phase. However, sintering the composites at 700 °C indicated a negligible effect of strontium due to the decomposition of Na₂CO₃, thereby limiting the operational temperature of the nanocomposites for potential fuel cell applications.