Influence of Sr doping on structural and electrical properties of ceria and performance of a single solid oxide fuel cell

Abstract

Doped and undoped compositions of Ce_1-xSr_xO_2-δ (x = 0, 0.025, 0.05, 0.075, and 0.1) are synthesized using the sol–gel auto-combustion method. The calcined powders are sintered at 1450 °C for four hours (h). The sintered samples are characterized and tested by various experimental techniques to study their structural, microstructural, and electrical properties as electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFC). The X-ray diffraction results confirm the single-phase formation except for the x = 0.1 sample, which also exhibited a minor secondary phase, i.e., SrCeO₃. X-ray photoelectron spectroscopy (XPS) reveals the mixed oxidation state of cerium (Ce⁴⁺/Ce³⁺) in undoped and doped CeO_2. The presence of oxygen vacancies has also been verified using Raman spectroscopy. The Sr creates oxygen vacancies and acts as the sintering aid to densify the samples. The highest conductivity is 6.46 × 10^–3 S.cm⁻¹ for x = 0.075 sample at 600 °C. The power density of the sample is about 89 mW.cm⁻² at 600 °C. With a relative density of ~ 97%, the x = 0.075 sample can be used as a solid electrolyte in IT-SOFC.