Influence of DC degradation on the dielectric response of CaCu3Ti4O12 Ceramics

In this work, CaCu₃Ti₄O₁₂ ceramics were synthesized to investigate the influence of dc degradation on the dielectric response. Two dielectric relaxation processes related to grain and domain boundaries appearing at low temperature were fitted according to Debye theory. It was found that the dc conductance loss at low frequency was greatly increased after dc degradation. The relaxation behaviors of grain and grain boundaries were characterized in impedance plots. The results showed that the values of grain boundaries resistance were greatly decreased from 1.7 megohm to 15 megohm at 433 K with the dc degradation. And the corresponding activation energy of grain boundaries was decreased from 1.25 eV to 0.73 eV, while the activation energy of grain keep nearly a constant at about 0.11 eV. The results of current density-breakdown field (J-E) behavior revealed that the breakdown field and nonlinear coefficient of CaCu₃Ti₄O₁₂ ceramics were both dropped after the dc gradation processes. The barrier height were also decreased from 0.57 eV to 0.31 eV. Therefore, it was proposed that the relaxation processes of grain boundaries may be mainly related with electrical properties of CaCu₃Ti₄O₁₂ ceramics and influenced by the dc degradation.