Extrinsic mechanism for colossal dielectric constant in CaCu3Ti4O12 ceramics evidenced by nanodomain

We studied the effect of various sintering temperature and dwell time on phase formation, microstructure and dielectric properties of CaCu3Ti4O12 ceramic synthesized by sol-gel method. The dielectric property was greatly influenced by sintering temperature and dwell time. We found colossal dielectric constant (similar to 153 816) with low dielectric loss (similar to 0.20) for 1100 degrees C/4 h sintered sample at room temperature and 1 kHz frequency. Impedance spectroscopy results support the grain boundary barrier layer capacitor model. Observation of nanostripe structure domains inside the grains of CaCu3Ti4O12 confirms the extrinsic mechanism for colossal dielectric response of this material.