Oxygen-defects-related dielectric response in CaCu3Ti4O12 ceramics

A 10 mm thickness columned CaCu3Ti4O12 ceramic was fabricated by the conventional solid-state reaction method and the dielectric properties of different parts in ceramic had been investigated. For the sample close to the surface, only one Debye-type relaxation around 107 Hz was observed at room temperature. However, for the sample close to the core, another relaxation peak was observed at about 104 Hz. The results were explained in terms of the equivalent circuit model by showing in the impedance spectroscopy. Moreover, it was introduced that the low-frequency dielectric relaxation is associated with the electrode–sample contact effect based on varying sample thickness and an annealing treatment in the nitrogen atmospheres.