Electro-chemo-mechanical studies of perovskite-structured mixed ionic-electronic conducting SrSn[subscript 1-x]Fe[subscript x]O[subscript 3-x/2+δ] part II: Electrical conductivity and cathode performance

Abstract

The bulk electrical conductivity of the mixed ionic-electronic conducting perovskite-structured SrSn[subscript 1-x]Fe[subscript x]O[subscript 3-x/2+δ] (SSF) was measured to examine how changes in defect chemistry and electronic band structure associated with the substitution of Ti by Sn impact defect charge carrier density and ultimately electrode performance. These results complement a defect chemical model for SSF investigated and reported in Part I of this study. The electrical properties of SSF were found not to differ significantly from the corresponding composition in SrTi[subscript 1-x]Fe[subscript x]O[subscript 3-x/2+δ] (STF). It is believed that Fe dominates the character of the valence and conduction bands and thus governs the electronic properties in SSF. Though slightly shifted in energy due to the larger size of Sn, the defect equilibria and therefore the electrical conductivity of SSF were found to be largely dominated by Fe and thus differed only in a limited way from that in STF. Key kinetic parameters obtained include the migration enthalpy of oxygen vacancies (0.772 ± 0.204 eV), the activation energy of area-specific-resistance for oxygen exchange (1.65 ± 0.03 eV) and the magnitudes of electron (0.0002 ± 0.00005 cm2/V∙s) and hole (0.0037 ± 0.0015 cm[superscript 2]/V∙s) mobilities. Keywords: Mixed ionic electronic conductor, Cathode, Area specific resistance, Impedance spectroscopy, Perovskite oxide