Influence of dopant concentration on oxygen reduction for highly doped zirconias

Abstract

The ionic conductivity of the (ZrO 2) 1− x (Y 2O 3) x system, where x is equal to 9, 15 and 25 mol%, has been studi ed. The conductivity decreases as x increases for the investigated compositions in the 300–1000°C temperature range. The electrochemical behavior of Pt-paste electrodes on these solid electrolytes is also examined. At low polarizations, the oxygen reaction rate depends on the electrolyte composition and varies similarly to the ionic conductivity, indicating the active participation of the electrolyte in the rate-determining step. At cathodic overpotentials lower than about −100 mV/air, a sudden increase of the current is observed. The value of the overpotential beyond which this transition occurs decreases as x increases.