Oxygen permeability of gadolinium-doped ceria at high temperature

The oxygen permeability and the electrical conductivity of gadolinium-doped ceria, Ce0.8Gd0.2O2-δ (GDC20) was measured as a function of temperature (1400–1600 °C) and oxygen partial pressure (0.21–10−10 atm). The measured oxygen permeation was compared with that estimated from the electrical conductivity. The oxygen permeation driven by a oxygen potential gradient, in the absence of an applied electrical potential, was measured by an oxygen sensor. The results of electrical conductivity measurement show that the doped-ceria is a mixed electronic and oxygenionic conductor at high temperature, guaranteeing the high oxygen permeability. The oxygen permeability of this compound is more than two orders of magnitude higher than that of Ca-doped ZrO2 in high Po2 region. The comparison of oxygen permeation and electrical conductivity shows that the measured permeation is less than the expected value estimated from the electrical conductivity. The deviation was ascribed to the polarization effect.