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Open AccessArticle

(Bi,Sr) (Fe1−x,Mx)O3−δ (M = Co, Ni and Mn) Cathode Materials with Mixed Electro-Ionic Conductivity

Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan
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Author to whom correspondence should be addressed.
Academic Editor: Christof Schneider
Materials 2016, 9(11), 922; https://doi.org/10.3390/ma9110922
Received: 20 June 2016 / Revised: 17 October 2016 / Accepted: 24 October 2016 / Published: 14 November 2016
(This article belongs to the Section Energy Materials)
(Bi,Sr)FeO3−δ (BSF) cathode materials doped with either Co, Ni or Mn are synthesized by an ethylene diamine tetra-acetic acid (EDTA)-citrate complexing method, and the effects of the doping level on the mixed electronic-ionic conductivity at various temperatures are studied up to 800 °C. The phase purity and solid solution limit are investigated by X-ray diffraction (XRD). The ionic conductivity is measured by the four-probe direct current (DC) method, the valence state of Fe and Mn by X-ray photoelectron spectroscopy (XPS), and the oxygen non-stoichiometry by differential thermo-gravimetric analysis (TGA). The doped ferrites show interesting electronic conductivity dependent on the testing temperature, implying two conductive mechanisms, either controlled by double exchange at lower temperatures or small polaron (electron-oxygen vacancy) conduction at temperatures greater than 400 °C. The results of Co-doped BSF (S50C20) show the best mixed conductivity among the ferrites, and this is used to assemble cells. The cell with a S50C20 cathode in the region of 600–800 °C is improved by 15% in maximum power density greater than the cell with La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) due to the balanced contribution from oxygen ions, vacancies and electrons. View Full-Text
Keywords: bismuth ferrite; dopant; cathode; fuel cell; ionic; conductivity bismuth ferrite; dopant; cathode; fuel cell; ionic; conductivity
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MDPI and ACS Style

Wei, W.-C.J.; Huang, D.-R.; Wang, D. (Bi,Sr) (Fe1−x,Mx)O3−δ (M = Co, Ni and Mn) Cathode Materials with Mixed Electro-Ionic Conductivity. Materials 2016, 9, 922.

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