Ion transport in dual-phase SrFe1-xD cent D degrees O-x(3-delta) (x=0.03-aEuro parts per thousand 0.10): effects of redox cycling


The incorporation of tantalum cations in mixed-conducting SrFe1-xTaxO3-delta (x = 0.03 -aEuro parts per thousand 0.10) results in the formation of single cubic perovskite-like phases in oxidizing atmospheres while under reducing conditions phase separation is observed, accompanied with an appearance of brownmillerite-type nanodomains on the background of the perovskite-like matrix. For SrFe0.97Ta0.03O3-delta after reduction, the x-ray and electron diffraction studies combined with transmission electron microscopy evidence the formation of approximately 30 vol.% brownmillerite phase with an average domain size of 20-40 nm. The oxygen partial pressure dependencies of the total conductivity in the range from 10(-20) to 0.5 atm at 700-950 A degrees C show that the electron transport parameters remain virtually independent on the dopant content and domain structure. Contrary to the materials with higher dopant content, however, the ion conduction in SrFe0.97Ta0.03O3-delta tends to substantially increase on redox cycling. This behavior was attributed to the brownmillerite domain disintegration and rearrangement, induced by cyclic formation and disappearance of oxygen vacancies.






Shalaeva, EV; Patrakeev, MV; Markov, AA; Tyutyunnik, AP; Murzakaev, AM; Kharton, VV; Tsipis, EV; Waerenborgh, JC; Leonidov, IA; Kozhevnikov, VL

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The authors are grateful for the support of this work from the Russian Foundation for Basic Research (projects 13-03-00931 and 14-29-04042), the regional programs of the Ural Branch of RAS (12-Y-3-1005), the Ministry of Education and Science of the Russian Federation (project 14.B25.31.0018), and the FCT, Portugal (project PTDC/CTM-CER/114561/2009).

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