Electrical Transport Properties and Defect Structure of SrFeCo0.5 O x

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Abstract
By using a gastight electrochemical cell with flowing air as the reference environment, we were able to achieve an oxygen partial pressure as low as atm inside the cell. The conductivity of has been studied as a function of and temperature. It was found that in the high‐ range, interstitial oxygen ions and electron holes are the dominant charge carriers, while in the low‐ range, oxygen vacancies and electrons (e′) are dominant. At 800°C in air, total conductivity and ionic conductivity of are 17 and , respectively, and the ionic transference number is 0.4. A semiconductor‐metal‐semiconductor transition is found in this system in a reduced‐oxygen environment. Defect dynamics in this system can be understood by means of the trivalence‐to‐divalence transition of Fe ions when is reduced. A defect model has been proposed. By using the conductivity results, we were able to estimate oxygen permeation through a ceramic membrane made of . The oxygen permeability we calculated is consistent with that measured at the conversion reactor. To confirm the ionic transference number measured by electron‐blocking method, electromotive force measurement was carried out and obtained consistent results.

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