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) e lectrode with zirconia-yttria electrolyte has been investigated as a functi on of the A-site non-stoichiometry. In addition the effect of cathodic curr ent treatment on the electrode resistance and the mechanism of oxygen reduc tion have been carefully studied. The LSM/electrolyte interface region was examined by SEM/EDS and XRD. The adhesion of porous LSM electrode coating i s critically dependent on free La activity near the interface region and th e formation of a pyrochlore phase, La2Zr2O7. A slight A-site deficiency (si milar to 0.1) is effective in inhibiting the formation of such a pyrochlore phase and it greatly improves the adhesion to the electrolyte. The cathodi c current treatment significantly enhances the electrochemical activity of LSM and also modifies the reaction mechanism for oxygen reduction. This eff ect appears to be associated with the surface composition of LSM, near the electrode/electrolyte interface, which changes with prevailing oxygen parti al pressure near the three-phase boundary region under the condition of cur rent flow. (C) 1999 Published by Elsevier Science B.V. All rights reserved.