Various doping strategies with transition metals like, e.g., Y have shown beneficial effects with respect to stabilizing the cubic BSCF phase and preservation of the oxygen conductivity [3,4]. In this direction the effect of B-site partial substitution with Y, Ti or Nb has been studied thoroughly by our group using scanning electron microscopy (SEM) and analytical (scanning) transmission electron microscopy ((S)TEM) combined with energy dispersive X-ray spectroscopy (EDXS).
In addition, the oxygen reduction reaction of pure and doped BSCF electrodes is investigated in oxygen-nitrogen mixtures (pO2 = 0.02 to 0.4 atm) as well as in CO2-atmospheres (0.1…1 vol. % CO2) using symmetrical SOFC cells with Ce0.9Gd0.1O2-δ (CGO) as electrolyte from 600 to 800 °C. Characterization by electrochemical impedance spectroscopy (EIS) combined with the distribution of relaxation times (DRT) reveals an enhanced tolerance of doped BSCF cathodes, in particular Y-doped, towards the adsorption-desorption of CO2 molecules. Channeling enhanced microanalysis (ALCHEMI) investigations on Y-doped BSCF demonstrate the coexistence of Y ions on both cation lattice sites with up to 55 % of the Y-ions located on the unintended A-lattice site [5,6].
Overall this study shows that enhancing the phase stability and the CO2 tolerance of BSCF by a rational substitution of the B-site is plausible while the high performance and its excellent oxygen transport properties are kept.
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