Two distinct dielectric relaxation mechanisms in the low-frequency range in Bi5TiNbWO15 ceramics

The ac data in terms of impedance and dielectric loss (tan delta) were exploited simultaneously to probe the dielectric relaxation mechanisms in Bi5TiNbWO15 ceramics. It was found that two distinct relaxation mechanisms exist in the low-frequency range (10 Hz-5 MHz). One is attributed to the grain boundary relaxation and the other is associated with oxygen ion diffusion. Furthermore, the temperature dependence of the oxygen vacancy relaxation strength is analogous to the Curie-Weiss law and follows the traditional point defect relaxation theory. These results could be helpful to understand the phenomena related to ferroelectric fatigue, oxygen ion conductivity, etc. (c) 2006 American Institute of Physics.