(Invited) Enhancing Phase Stability and CO2 Tolerance of Ba0.5Sr0.5Co0.8Fe0.2O3-δ

Abstract

The effect of B-site cation substitution on the phase stability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) in O2- and CO2-containing atmospheres has been studied thoroughly by our group. In particular, a doping concentration of 10 mol-% yttrium (Y) was found to strongly reduce or suppress secondary phase formation extending the stability of the cubic phase regime. Characterization by electrochemical impedance spectroscopy (EIS) of both, pure and Y-doped BSCF electrodes, is performed in oxygen-nitrogen mixtures as well as in CO2-containing atmospheres using symmetrical SOFC cells with Ce0.9Gd0.1O2-δ (CGO) as electrolyte from 600 to 900 °C. Analysis of the EIS data in combination with the distribution of relaxation times (DRT) reveals an enhanced tolerance of the Y-doped BSCF cathodes towards the adsorption of CO2 molecules. The enhanced stability of the cubic phase and reduced poisoning effect on the oxygen reduction reaction in CO2- containing atmospheres by doping, is further confirmed by scanning electron microscopy (SEM) and analytical (scanning) transmission electron microscopy ((S)TEM) combined with energy dispersive X-ray spectroscopy (EDXS).