Electrocoloration and oxygen vacancy mobility of BaTiO3

The electrical-insulation degradation of BaTiO3 is now of growing interest as the BaTiO3-based dielectric layers of multilayer ceramic capacitors are getting thinner to submicron thicknesses. The degradation is understood to be due to the electrotransport of oxygen vacancies and may be monitored by the colors emanating from the cathode and/or anode. In the case of single crystal BaTiO3, a brown color emanates from the anode and a blue color from the cathode. We will experimentally review the generation of the colors in BaTiO3 in electric fields, and discuss their origins and kinetics of color front migration. From the latter the oxygen vacancy mobility against temperature in the range of 150–500°C is subsequently determined and compared with all the literature data that have normally been estimated by other means at elevated temperatures.