Correlation of O (1s) and Fe (2p) near edge x-ray absorption fine structure spectra and electrical conductivity of La1−xSrxFe0.75Ni0.25O3−δ

Abstract

A -site substitution of La3+ by Sr2+ in polaron conducting ABO3-type perovskite La1−xSrxFe0.75Ni0.25O3−δ causes oxidation of Fe3+ toward Fe4+ and formation of conducting electron holes, as evidenced by Fe (2p) and O (1s) near edge x-ray absorption fine structure spectra. Hole doping is reflected by linear variation of the prepeak ratio eg(↑)/[t2g(↓)+eg(↓)] of oxygen spectra, along with increased conductivity. The significant increase in conductivity due to NiO doping in La1−xSrxFeO3−δ is caused by increased overlap between Fe (3d) and O (2p) and charge transfer from the O (2p) to the Ni (3d) states, as concluded from near edge x-ray absorption fine structure spectra and ligand field multiplet calculations.