Dielectric properties and relaxor behavior of Ba0.67Sr0.33TiO3-CaBi4Ti4O15 ceramics

(1-x)Ba_0.67Sr_0.33TiO₃(BST)+xCaBi₄Ti₄O₁₅(CBT) (x=0, 2%, 4%, 6% and 8%) lead-free relaxor ferroelectric ceramics with submicro grain size of about 200nm were prepared by solidstate reactions. Structure and dielectric properties of BST-CBT have been investigated. X-ray diffraction patterns show a relative low degree of solubility as a result of coupled substitutions of Bi³⁺ and Ca²⁺ both on the A site and the specific structure of CBT. The temperature and frequency dependences of the dielectric constant indicate a crossover from a normal ferroelectric to relaxor behavior. The degrees of diffuseness and relaxor behavior are found to increase with the increasing amount of CBT. The frequency dependence of the temperature of dielectric peak Tm can be well described by Vogel-Fulcher relation. The activation energy Ea increases with x increasing, indicating the more and more energy for the polarization reversal of micropolar regions, which is associated with the enhanced interactions of polar domains.