Comprehensive Analysis of Ce_1−xSmxO_2−δ Solid Electrolytes: Structural, Microstructural, and Electrochemical Characterization for Intermediate Temperature Solid Oxide Fuel Cells

Samarium substituted ceria has been studied as a potential electrolyte material for intermediate temperature range solid oxide fuel cells. The structural, microstructural, morphological and electrochemical properties of the Ce_1−xSm_xO_2−δ solid electrolytes were analyzed, with different substitutions from 0.05 to 0.50. The difference in the ionic radii of Sm³⁺ and Ce⁴⁺ resulted in lattice strain and expansion, which was found to decrease the average size of crystallites. The ionic conductivity of ceria increases as Sm³⁺ concentration is increased upto a limit of 20%. This is due to the combination of vacancy-vacancy repulsion and vacancy trapping by the substitution at a higher level. However, the conductivity of Ce_0.80Sm_0.20O_2−δ was the highest, at 4.04 × 10⁻² S cm⁻¹ at 600 °C. The grain activation energy and grain boundary activation energy were also found to be ∼0.87 eV and ∼0.74 eV respectively. The low values of activation energies indicate that Ce_0.80Sm_0.20O_2−δ could be a suitable electrolyte material for intermediate-temperature solid oxide fuel cells.