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

A-site substitution of La3+ by Sr2+ in polaron conducting ABO(3)-type perovskite La1-xSrxFe0.75Ni0.25O3-delta 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 e(g)(up arrow)/ [t(2g)(down arrow)+e(g)(down arrow)] of oxygen spectra, along with increased conductivity. The significant increase in conductivity due to NiO doping in La1-xSrxFe0.75Ni0.25O3-delta 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. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3246145]