An electron hole doping and soft x-ray spectroscopy study on La1-xSrxFe0.75Ni0.25O3-δ

Abstract

The conductivity of the electron hole and polaron conductor La1-xSrxFe0.75Ni0.25O3-δ, a potential cathode material for intermediate temperature solid oxide fuel cells, was studied for 0 <x < 1 and for temperatures 300 K <T < 1250 K. In LaSrFe-oxide, an ABO3 type perovskite, A-site substitu-tion of the trivalent La3+ by the divalent Sr2+ causes oxidation of Fe3+ towards Fe4+, which forms conducting electron holes. Here we have in addition a B-site substitution by Ni. The compound for x = 0.5 is identified as the one with the highest conductivity (σ ~ 678 S/cm) and lowest activation energy for polaron conductivity (Ep = 39 meV). The evolution of the electronic structure was monitored by soft x-ray Fe and oxygen K-edge spectroscopy. Homogeneous trend for the oxida-tion state of the Fe was observed. The variation of the ambient temperature conductivity and activation energy with relative Sr content (x) shows a correlation with the ratio of (eg/eg+t2g) in Fe L3 edge up to x=0.5. The hole doping process is reflected by an almost linear trend by the variation of the pre-peaks of the oxygen K-edge soft x-ray absorption spectra.

References in corpus (3)

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• Electron hole - phonon interaction and structural changes in La0.9Sr0.1FeO3 by temperature dependent conductivity and valence band photoemission spectros-copy

Cited by in corpus (3)

• Entanglement of charge transfer, hole doping, exchange interaction and octahedron tilting angle and their influence on the conductivity of La1-xSrxFe0.75Ni0.25O3-δ: A combination of x-ray spectroscopy and diffraction
• Fe-resonant valence band photoemission and oxygen NEXAFS study on La1-xSrxFe0.75Ni0.25O3-δ
• Correlation of conductivity and angle integrated valence band photoemission characteristics in single crystal iron perovskites for 300 K < T < 800 K: Comparison of surface and bulk sensitive methods