Direct current electrical degradation of iron-doped titania ceramics

An anomalous increase of current was found in Fe-doped titania ceramics subjected to a constant field of 105 V/m. It is suggested that the space charge rises from blockage of O2(g) → O2−(s) ion transfer at the cathode. This leads to an increase of n-conductivity in the cathodic region and p-conductivity in the anodic region according to the specific defect equilibrium. This viewpoint was reinforced by two newly observed phenomena: (i) the I-V plot shows a linear feature at the initial stage, but it gradually becomes a rectifying feature with time; and (ii) an edge-located electrode shows lower current density and faster current saturation compared with a normal electrode.