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-dope d titania ceramics that have been subjected to a constant field. The r esult of thermally stimulated current analysis shows a peak at a tempe rature of 170 degrees-180 degrees C, which increases because of the de polarization of oxygen vacancies. X-ray photoemission spectroscopy ind icates that an electrical stress results in an electrochemical reducti on inside the specimen, particularly on the cathodic side. These resul ts reinforce the viewpoint that the space charge that is responsible f or the anomalous current results from a blockage of the O-2(g)/O2-(s) ion transfer at the cathode.