Colossal dielectric permittivity and relevant mechanism of Bi2/3Cu3Ti4O12 ceramics

Bi2/3Cu3Ti4O12 (BCTO) ceramics with pure perovskite phase were successfully prepared by traditional solid-state reaction technique. Uniformly distributed and dense grains with the grain size of 2–3 μm were observed by SEM. A giant low-frequency dielectric permittivity of ~3.3×105 was obtained. The analysis of complex impedance revealed that Bi2/3Cu3Ti4O12 ceramics are electrically heterogeneous. There are three kinds of dielectric response detected in Bi2/3Cu3Ti4O12 ceramics, which existed in the low-frequency range, middle-frequency range, and high-frequency range, respectively. Through the study of dielectric spectrum at different temperatures, the relatively low activation energy of 0.30 eV for middle-frequency dielectric response was calculated, which suggested that this Middle-frequency dielectric response can be ascribed to grain boundaries response. In view of the analysis of dielectric spectrum at low temperatures, the activation energy of 0.07 eV for high frequency dielectric response was found. This value illustrated that dielectric response at high frequencies was associated with grains polarization effect. The comparison of dielectric spectra of Bi2/3Cu3Ti4O12 ceramics with different types of electrodes revealed that giant low-frequency dielectric constant was attributed to the electrode polarization effect.