abstract
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.
keywords
CALCIUM LANTHANUM FERRITES; MIXED CONDUCTIVITY; TEMPERATURE; CAXLA1-XFEO3-Y
subject category
Electrochemistry
authors
Shalaeva, EV; Patrakeev, MV; Markov, AA; Tyutyunnik, AP; Murzakaev, AM; Kharton, VV; Tsipis, EV; Waerenborgh, JC; Leonidov, IA; Kozhevnikov, VL
our authors
Ekaterina Tsipis
Post-doc Fellowship
Vladislav Kharton
Invited Principal ResearcherGroups
acknowledgements
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).