Oxygen nonstoichiometry of perovskite-type La _0.6Sr _0.4Co _1-yFe _yO _3-δ (y=0.2, 0.4, 0.5, 0.6, 0.8, 1) SOFC cathode materials

The oxygen nonstoichiometry of La _0.6Sr _0.4Co _1-yFe _yO _3-δ (LSCF) mixed-conducting perovskite-oxides can be classified into two groups: the cobalt-rich compounds (y=0, 0.2, 0.4) were previously reported to show a sharp decrease in oxygen content with reducing atmosphere, while the oxygen vacancy concentration increased more smoothly for the iron-rich compounds (y=0.6, 0.8, 1). Here we measured the oxygen content of LSCF with y=0.5 by thermogravimetry and coulometric titration as a function of oxygen partial pressure and temperature. No transitional behavior could be observed for La _0.6Sr _0.4Co _0.5Fe _0.5O _3-δ, the oxygen nonstoichiometry showed the same behavior as for the cobalt-rich compounds. Except for y=1, the thermochemical stability of LSCF was little affected by the iron dopant content; all compounds (y=0-0.8) decomposed at similar oxygen partial pressures.