Ellen Dr Ivers-Tiffee

Investigations on stoichiometric and substoichiometric La1-x-γSrxMnO3-δ used as cathode material in the sold oxide fuel cellused as cathode material in the sold oxide fuel cell

The influence of A-site deficiency in perovskite materials of the system La0.8-γSr0.2MnO3-δ on the rate of oxygen reduction at the cathode of the SOFC were investigated. Cathode layers with the compositions La0.8Sr0.2MnO3-δ and La0.75Sr0.2MnO3-δ were prepared by screenprinting and were sintered onto thin sheets of cubic Y-stabilized zirconia. The time dependent response of the cell voltage to changes in current density was found to be different for these two cathode composititons. During cell operation the performance of the La0.8Sr0.2MnO3-δ layer improved slowly and eventually attained values identical to those of the La0.75Sr0.2MnO3-δ layer which reached its final performance comparatively fast. Furthermore, for the La0.8Sr0.2MnO3-δ layer, degradation in the performance was observed, if subsequently the applied current density was lowered, i.e. the improvement is reversible. Similar effects were seen for the A-site deficient composition, but to a much smaller degree. The difference in electrochemical performance of these two compositions is attributed to a different reactivity between the electrolyte and the cathode material, a change of the morphology of the La0.8Sr0.2MnO3-δ layer during operation and/or a change of the electrochemically effective area in the vicinity of the three phase boundary.