Defect chemistry and high-temperature transport in SrFe1−xSnxO3–δ

• The conductivity and oxygen nonstoichiometry in SrFe1−xSnxO3−δ were measured.
• Tin substitution was found to affect insignificantly defect formation reactions.
• The hole mobility was found to increase linearly with the oxygen content.
• The hole mobility was found to be much higher than the electron mobility.

The electrical conductivity of SrFe1–xSnxO3–δ (x=0.05, 0.10, 017) was measured by a four-probe dc technique in the partial oxygen pressure range of 10–18–0.5 atm at temperatures between 800 °С and 950 °С. The oxygen content in these oxides was measured under the same ambient conditions by means of coulometric titration. The thermodynamic analysis of oxygen nonstoichiometry data was carried out to determine the equilibrium constants for defect-formation reactions and to calculate the concentrations of ion and electron charge carriers. The partial contributions of oxygen ions, electrons and holes to charge transport were assessed, and the mobility of respective carriers was evaluated by an integral examination of the electrical conductivity and oxygen nonstoichiometry data. It has been found that the mobility of holes in SrFe1−xSnxO3−δ varies in the range of ~0.005–0.04 cm2 V−1 s−1, linearly increasing with the oxygen content and decreasing with increased tin concentration. The mobility of electron carriers was shown to be independent of the oxygen content. The average migration energy of an electron was estimated to be ~0.45 eV, with that of a hole being ~0.3 eV.

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