Degradation of La0.6Sr0.4Fe0.8Co0.2O3-delta in carbon dioxide and water atmospheres

The mixed ionic-electronic conductor La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) is a candidate for use as the membrane material in the pressure-driven air se parator. However the long-term stability of these materials is a major conc ern for the commercial realization of these devices. In an attempt to asses s the stability of the material under realistic operating conditions for su ch a system, samples of LSCF were exposed to atmospheres of H2O/CO2/O-2 at 750 degrees C. Degradation of the material was studied using Raman spectros copy and X-ray diffraction. Oxygen isotope exchange combined with secondary ion mass spectrometry was used to observe the effect of the presence of CO 2 and H2O on the oxygen diffusivity and surface exchange. It was observed t hat oxygen surface exchange was actually enhanced in the presence of CO2 an d H2O during the duration of the study, although the oxygen diffusivity rem ained the same. The presence of volatile chromia species was found to signi ficantly increase the rate of degradation of the ceramic. (C) 1999 The Elec trochemical Society. S0013-4651(98)07-080-3. All rights reserved.