Coordination-Induced Shifts of Absorption and Binding Energies in the SrFe1−xZnxO3−δ System

The SrFe 1− x Zn x O 3−δ system (0 ≤ x ≤ 1) was synthesized and investigated by X-ray absorption near-edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS). These techniques were used to examine the effect of substitution on metal charge and coordination number (CN) and to study the influence of ground-state and final-state effects on spectral energies. As x increases, a greater oxygen deficiency lowers the transition-metal CN, as observed by examination of Fe K- and Zn K-edge XANES spectra. Substitution of Fe by Zn results in shifts in the (Fe 2p and Zn 2p) XPS binding energies and (Fe and Zn) K-edge XANES absorption energies that are much greater than the shifts observed in the corresponding Fe L- and Zn L-edge XANES absorption energies. These shifts are due to increasing final-state relaxation with decreasing metal CN. The O K-edge XANES absorption energies and O 1s binding energies were found to shift in a similar fashion because of ground-state effects owing to a greater screening of the O nuclear charge as Fe 3+/4+ is replaced by more electron rich Zn 2+ atoms.