REACTION-ZONE EXPANSIONS AND MECHANISM OF THE O-2, AG YTTRIA-STABILIZED ZIRCONIA ELECTRODE-REACTION/

Experimental data obtained by impedance spectroscopy with silver dropl et electrodes of different radii have been reanalyzed in the medium-fr equency range under the assumption of rate-limiting oxygen diffusion t hrough a thin slab of the electrode material. The model, which is base d on Literature data and has no adjustable parameters, gives a good fi t. This demonstrates that in the medium-frequency range, oxygen diffus ion through the electrode material is evenly distributed over the whol e electrode interface. On the other hand, under de conditions it is co ncentrated along the electrode triple-phase perimeter. Therefore, the distribution of the transfer current over the interface varies with th e applied signal frequency. It follows that the electrode resistance a nd capacitance determined from the impedance diagram are related to an electrode reaction occurring over a reaction zone variable with the s ignal frequency.