Deep trap states relaxation in CaCu3Ti4O12

Abstract

The abnormal dielectric behaviors of the perovskite oxide CaCu3Ti4O12 (CCTO) ceramics were discussed. The hysteretic dc current – voltage (I–V) curves that change hysteresis degree with voltage sweeping rate suggest that there is a slow trap charge transfer process between deep trap sites, which at the same time involve a defect dipole movement, leading to hysteretic capacitance vs. dc voltage (C–V) curve that also change hysteresis degree with voltage sweeping rate. Then, the polarization of the defect dipoles in the deep trap sites is further proved by the frequency dependent C–V relation as well as capacitance-time (C-t) relation. At last, the dynamic processes for the trap charge transfer and the corresponding defect dipoles polarization in a specific boundary was provided. The model suggests that the permittivity (or capacitance) is dependent on the number of trap charges participating the transfer process, which was confined by the energy levels of trap sites.