Stability of the SOFC Cathode Material (Ba,Sr)(Co,Fe)O[sub 3−δ] in CO[sub 2]-Containing Atmospheres

The stability of the solid oxide fuel cell (SOFC) cathode material in -containing atmospheres is investigated by precision thermogravimetry (TG) and mass spectrometry (MS) as a function of temperature . The desorption of and from samples with different pretreatments is compared. Oxygen exchange at is significantly impaired by -containing atmospheres. At the kinetics of carbonate formation in -rich atmosphere is described by a linear-parabolic rate law. A pronounced dependence of the rate constant on the content is suggested. Temperature cycles at and bar, which show effects due to oxygen exchange of the perovskite and due to , are analyzed based on reference experiments in a -free atmosphere, and under consideration of the TG-MS results. The decomposition temperature of the carbonate in contact with an atmosphere of bar amounts to . Complementary, the impact of carbonate formation on the oxygen exchange kinetics is investigated by conductivity relaxation measurements. A severe degradation of the surface oxygen exchange coefficient is observed after of exposure to ambient air. Regeneration and activation of the oxygen exchange kinetics is demonstrated after treatment in a -free atmosphere at .