Chemical bonding in the Bi1−xSrxFeO3±y system by X-ray photoelectron and Mössbauer spectroscopy

Ceramic samples Bi1−xSrxFeO3±y are synthesized with 0 ≤ x ≤ 1 by the solid state reaction method. X-ray diffraction study of the samples is performed. Chemical bonding and the valence state of the Fe ions in the Bi1−xSrxFeO3±y ceramics are studied using X-ray photoelectron Fe2p-, Sr3d-, Bi4f-, and O1s-spectra, and Mössbauer spectroscopy. Fe2p-spectra for various ionic states of Fe are calculated in an isolated ion approximation. Considerable deviations of actual elemental compositions from nominal ones are discovered. Both Fe3+ and Fe4+ ions are found to be present in the samples with x > 0. Relative Fe3+/Fe4+ contents are determined by comparing the parameters of experimental and theoretical Fe2p-spectra. Concentration of Fe4+ ions in the samples correlates with that of the Sr atoms.