Egorova, Y.; Scherb, T.; Schumacher, G.; Bouwmeester, H.; Filatova, E.: Soft X-ray absorption spectroscopy study of (Ba0.5Sr0.5)(Co0.8Fe0.2)1-xNbxO3-δ with different content of Nb (5%-20%). Journal of Alloys and Compounds 650 (2015), p. 848-852
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The mixed electronic ionic conducting materials (Ba0.5Sr0.5) (Co0.8Fe0.2)1−хNbхO3−δ with partial Nb substitution (x: 0.05, 0.10, 0.15, 0.20) for B cations (Co/Fe), synthesized using a solid state reaction method, have been studied by near edge X-ray absorption fine structure (NEXAFS). Co L2,3- absorption spectra of (Ba0.5Sr0.5) (Co0.8Fe0.2)1−хNbхO3−δ (BSCFN) powders were analyzed with the purpose to understand the influence of the Nb substitution on the atomic electronic structure of BSCFN. The joint analysis of the Co L2,3- absorption spectra reveals the presence of mixed oxidation states Co2+/Co3+ in all the studied BSCFN structures. It was established that the proportion of oxidation states Co2+/Co3+ and the corresponding coordinations of Co atoms depend on the content of Nb. In the 10% Nb substituted BSCF sample Co atoms mostly occur in the Co2+ oxidation state and are preferentially characterized by an octahedral coordination site. In all other structures Co atoms are rather characterized by Co2+/Co3+ oxidation states and occupy both octahedrally and tetrahedrally coordinated sites.