Influence of Barium Incorporation on the Electrochemical Performance of Ln(0.58)Sr(0.4)Fe(0.8)Co(0.2)O(3-delta) (Ln=La, Pr, Sm) Perovskites for Oxygen Activation at Intermediate Temperatures

Highly active perovskite-based electrodes were obtained through partial substitution of lanthanides (La, Pr and Sm) by barium in the Ln(0.58)Sr(0.4)Fe(0.8)Co(0.2)O(3) system. These compositions were obtained as single phase crystalline compounds through a sol-gel synthetic route and tested by electrochemical impedance spectroscopy (EIS) as symmetrical cells on GDC-electrolyte samples in the temperature range 450-650 degrees C cooperative effects arose through the incorporation of a large divalent active cation (Ba-2) in the perovskite lattice of lanthanide-based strontium ferrites-cobaltites. Reduction in the electrode polarisation resistance with respect to non-substituted compositions is obtained irrespective of the amount of barium substitution and lanthanide nature. Barium additional also reduces the activation energy of these compositions, indicating changes in the oxygen activation processes. The specific effect of the barium incorporation on the electrode performance was dependent on the nature of the partially substituted lanthanide Lanthanum-barium-based compositions exhibited the lowest electrode polarisation resistance when the amount of the replaced barium was increased up to 50% molar On the other hand, for praseodymium- or samarium-barium-based compositions, the minimum in electrode polarisation resistance was achieved at barium substitutions close to 25% molar. The study of the effect of oxygen partial pressure on EIS data allowed in improving the understanding of the processes governing the electrode operation.