Electrode Kinetics at the Silver-sputtered Electrode/ (Bi₂O₃)_07.7 (Y₂O₃)_0.23 Solid Electrolyte Interface

Abstract

The interface properties of the silver-sputtered electrode and (Bi₂O₃)_07.7 (Y₂O₃)_0.23 solid electrolyte were studied by means of d. c. and a. c. measurements in the temperature range from 400°C to 700°C and in the oxygen partial pressure region between 8.6 × 10^-6 atm and 1 atm using Ar + O₂ gas mixtures. In order to obtain the same surface conditions of the electrolyte, the electrolyte surface was presputtered before the silver electrode was prepared by the rf magnetron sputtering technique.
The electrode process is influenc ed by the oxygen partial pressure. The complex impedance results in a frequency dispersion between 2 Hz and 20 kHz composed of one or two depressed semicircular arcs attributed to a different polarization process. The differential capacitance obtained from the a. c. method varied with potential, temperature, and oxygen partial pressure. These results indicate the presence of the Ag-Bi(Y)-O matching area between the electrode and the electrolyte plays an important role in the electrode reaction. On the partial pressure of oxygen, the low frequency arcs in correspondence to the electrode process at, the Ag(gas)/matching area interface is revealed the dependence of P_O2^-0.35 by the analysis of the dependence. The migration of O₂^- along the matching area plays an important role in the electrode kinetics at the lower overpotential. On the other hand, the high frequency arc in correspondence to the behaviour of the matching area shows the dependence of about P_O2^-0.16 at the temperature below 450°C. The influence of the matching area on the electrode process increases with decreasing temperature and/or increasing overpotential at a given P_O2. Probably diffusion of Vo- and in the matching area is the essential process in the electrode kinetics.