Electrochemical processes occurring at the interface Pt/BICUVOX.10 were investigated by cyclic voltammetry and potentiostatic current-potential curves, taken under steady-state conditions, in different mixtures of nitrogen and oxygen at temperatures between 300 and 600 degrees C. Similar experiments were carried out for comparison at the Pt/YSZ interface. Point or paste electrodes were used. The equilibrium of the oxygen electrode is not established below 500 degrees C at both interfaces any more. Reasons for this behavior are presented. It is concluded on the basis of a comparison of the shape of voltammograms at different interfaces that BICUVOX.10 is reduced and oxidised electrochemically. Simultaneously a reoxidation of the solid elctrolyte by O-2 from the gas phase occurs. At temperatures below 500 degrees C the reoxidation is not fast enough to avoid a hysteresis at cathodic currents of the voltammograms. At higher temperatures and larger partial pressures of O-2 the hysteresis disappears.