X-ray Photoemission Spectroscopy (XPS) and Thermally Stimulated Current (TSC) Studies on the Resistance Degradation of Iron-Doped Titania Ceramics

An anomalous increase of current with time has been found in iron-doped titania ceramics that have been subjected to a constant field. The result of thermally stimulated current analysis shows a peak at a temperature of 170°–180°C, which increases because of the depolarization of oxygen vacancies. X-ray photoemission spectroscopy indicates that an electrical stress results in an electrochemical reduction inside the specimen, particularly on the cathodic side. These results reinforce the viewpoint that the space charge that is responsible for the anomalous current results from a blockage of the O₂( g )/O²⁻( s ) ion transfer at the cathode.