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  Filatova, E.; Egorova, Y.; Galdina, K.; Scherb, T.; Schumacher, G.; Bouwmeester, H.; Baumann, S.: Effect of Fe content on atomic and electronic structure of complex oxides Sr(Ti,Fe)O₃-δ. Solid State Ionics 308 (2017), p. 27-33

10.1016/j.ssi.2017.05.016
Open Access Version

Abstract:
Two series of SrTi1-xFexO3-δ (STFO) powders with different Fe content produced by two different methods, solid state reaction or modified Pechini synthesis, have been investigated by soft X-ray absorption spectroscopy. The O1s (K)- , Fe2p (L2,3)- and Ti2p (L2,3)- absorption spectra of STFO powders were analyzed. Partial substitution of Ti by Fe atoms in SrTiO3 were found to cause asymmetric distortion of TiO6 octahedrons which may violate the cubic symmetry of STFO. It was established that the distortion of TiO6 octahedrons increases with increasing Fe content. The joint analysis of the STFO spectra along with the reference compounds points to the presence mainly of Fe3+states in octahedral environment at small concentration of Fe atoms along with essentially smaller content of Fe4+ states in octahedral environment where the latter contribution increases with increasing Fe content. Also a presence of Fe3+states in tetrahedral environment with Fe content higher than 50% is traced. A certain amount of Fe2+ ions in an octahedral environment was also found in the STFO compound prepared by spray pyrolysis with Fe content higher than 75%. The O1s (K)- absorption spectra point to increase in oxygen vacancy concentration with increasing Fe content. The lowest degree of structure distortions was traced in STFO35. Hence, the STFO35 compound seems to be mostly appropriate for technical applications.