Oxide ion diffusion mechanism related to Co and Fe ions in (Ba0.5Sr0.5)(Co0.8Fe0.2)O3−δ using in-situ X–ray absorption spectroscopy

Abstract

The time changes of the white line and pre–edge intensities of Co and Fe K–edge in (Ba0.5Sr0.5)(Co0.8Fe0.2)O3−δ (BSCF) were observed to estimate the oxide ion diffusion related to Co and Fe ions by using in−situ X–ray absorption spectroscopy (XAS) during oxidation. The 20μm self–standing BSCF film was prepared for in−situ XAS measurements. The time changes of absorption were fitted to the exponential decay function with two terms. The longer relaxation time (τ), related to the oxide ion diffusion during the oxidation of BSCF, is dependent on temperature. The oxide ion diffusion coefficients (D) were calculated from the τ s estimated by in−situ XAS. The values of the activation energy (Ea) for D related to Co K–edge white line, Co pre–edge, and Fe pre–edge were 1.8–2.0eV. The value of Ea for D related to Fe K–edge white line, however, was higher than other absorption values at approximately 2.3eV. We discussed the oxide ion diffusion mechanism related to Co and Fe ions in BSCF using in−situ XAS.