Influence of ZnO on the electrical properties of YSZ

Impedance spectroscopy was performed on dense YSZ/ZnO composites with a ZnO content varying from 3 to 25 vol% and under different oxygen pressures. Raman spectroscopy contact with ZnO, under the selected sintering conditions (1300 degrees C, 2h). The impedance diagrams reveal a peculiar blocking effect associated with the ZnO grains. Its magnitude is independent of the large variations in conductivity ofZnO, associated with changes in the equilibrium oxygen pressure. Its relaxation frequency markedly depends on this parameter. These peculiar properties are interpreted in terms of a pseudo-capacitive behavior of the electronically conducting ZnO in contant with the YSZ ionic conductor. This contact forms an electrode, the potential ofwhich being determined by the predominant point defect concentration in ZnO.