Dielectric relaxations and formation mechanism of giant dielectric constant step in CaCu3Ti4O12 ceramics

Abstract

The dielectric relaxation behaviors of CaCu3Ti4O12 ceramics were evaluated together with the mixed-valence structure, and the formation mechanism of a giant dielectric constant step was discussed. The giant dielectric constant step was bounded by two dielectric relaxations in low and high temperature ranges. The low-temperature dielectric relaxation was intrinsic, and it was very similar to the electronic ferroelectricity, while the high temperature relaxorlike dielectric peak was assigned to be the result of defect ordering since it could be suppressed by O2 annealing. Both the low and high temperature dielectric relaxations were the thermal activated relaxation process following the Arrhenius law. Moreover, it was supposed that the giant dielectric constant step resulted from the competing balance between the low and high temperature dielectric relaxations.