THE ROLE OF AMPHOTERIC DOPANTS IN BARIUM TITANATE BASED DEVICES

Yoed Tsur and Clive A. Randall

Center for Dielectric Studies, Materials Research Laboratory The Pennsylvania State University University Park, PA 16802-4800 USA

Recently, multilayer ceramic capacitors based on BaTiO3 dielectrics have been processed at production scale with nickel electrodes. The properties in terms of dielectric constant, loss, dielectric breakdown strength and degradation are comparable to the more costly precious metal devices. In order to sinter the dielectric material without oxidizing the electrodes, the sintering is done in reducing atmosphere. The dielectric material is modified by various dopants, in order to maintain its electronic properties. In particular, it was found that some "magic" trivalent dopants are important to improve the dielectric breakdown strength of the devices. In this presentation we will first show (experimentally) that these "magic" dopants are amphoteric. The underlying point defect chemistry will be described. We will then present a hypothesis on the role of amphoteric defects in improving the lifetime of the devices, in connection with grain boundary segregation and diffusion of oxygen vacancies.