Electrochemical behaviour of the surface treated composite-electrolyte/electrode interface

Abstract

The effect of surface treatment of the solid electrolyte 50 wt% (4.7 mol% Sc2O3+95.3 mol % ZrO2)+ 50 wt % Al2O3 (used in the SIRO2 low temperature oxygen sensor) on its electrochemical behaviour has been studied by complex impedance spectroscopy. Two techniques, namely, preferential etching of alumina from the surface by a suitable etchant and cosintering of a thin layer of an alumina free electrolyte composition were used. The electrode/electrolyte interfaces prepared by using surface treated electrolyte samples had much lower electrode resistance (by a factor of 3–6) compared with the untreated surfaces. The decrease in the interfacial impedance is attributed mainly to the absence of alumina at the interface (an insulator phase) at which no oxygen exchange reactions could take place.