Correlation between structural and electrochemical properties of potassium doped strontium silicates for electrolyte application in intermediate temperature solid oxide fuel cells

Abstract

Electrolyte is the heart of the solid oxide fuel cell (SOFC), which can determine the working temperature. Currently, Yttria stabilized zirconia is used as electrolyte in commercial SOFCs, due to its high conductivity. The high working temperature (1073 K–1273 K) causes severe problems during SOFC design and operation. To reduce the working temperature of SOFCs to intermediate temperature (873 K–1073 K), here Sr1−XKXSiO3−δ (X = 0.00–0.20) solid solutions are synthesized by solid state reactions, characterized by different techniques. XRD patterns of Sr1−XKXSiO3−δ solid solutions can be indexed to monoclinic c2/c space group (15) structure. 29Si solid state NMR spectra of SrSiO3 and Sr0.95K0.05O3−δ shows a sharp single peak at −83.5 ppm. In 10–20 mol% K-doped samples, the additional broad peak at −89.0 ppm, is due to the presence of amorphous K2Si2O5 phase. FE-SEM and WDS mapping of SrSiO3−δ and Sr0.80K0.20SiO3−δ shows the segregation of amorphous K2Si2O5 along the grain boundaries. High temperature impedance study of Sr0.80K0.20SiO3−δ exhibits the conductivity, which is comparable to other solid electrolytes in the literature, which makes it as promising solid electrolyte for intermediate temperature SOFCs.