The electrochemical performance of LSM/zirconia-yttria interface as a function of a-site non-stoichiometry and cathodic current treatment

The adhesion and the electrochemical performance of Sr doped LaMnO3 (LSM) electrode with zirconia-yttria electrolyte has been investigated as a function of the A-site non-stoichiometry. In addition the effect of cathodic current treatment on the electrode resistance and the mechanism of oxygen reduction have been carefully studied. The LSM/electrolyte interface region was examined by SEM/EDS and XRD. The adhesion of porous LSM electrode coating is critically dependent on free La activity near the interface region and the formation of a pyrochlore phase, La2Zr2O7. A slight A-site deficiency (similar to 0.1) is effective in inhibiting the formation of such a pyrochlore phase and it greatly improves the adhesion to the electrolyte. The cathodic current treatment significantly enhances the electrochemical activity of LSM and also modifies the reaction mechanism for oxygen reduction. This effect appears to be associated with the surface composition of LSM, near the electrode/electrolyte interface, which changes with prevailing oxygen partial pressure near the three-phase boundary region under the condition of current flow. (C) 1999 Published by Elsevier Science B.V. All rights reserved.