Dielectric properties of giant permittivity NaCu3Ti3NbO12 ceramics

A series of NaCu3Ti3NbO12 ceramics was fabricated by the conventional solid-state reaction method, and their microstructures, phase structures, electric and dielectric properties were systematically investigated. Single phase of NaCu3Ti3NbO12 with body-centered cubic perovskite-related structure was confirmed by X-ray diffraction. Normal grain growth was observed, and the average size of grains was limited to less than 6 µm. Impedance spectroscopy analysis reveals that NaCu3Ti3NbO12 ceramics are electrically heterogeneous, consisting of semiconducting grains and insulating grain boundaries. The activation energy for the dc conduction process is comparable to that for conduction at the grain boundaries, indicating that the dc conduction process is associated with the electric response of grain boundaries in NaCu3Ti3NbO12 ceramics. The dielectric properties can be well described by the internal barrier layer capacitor effect based on Maxwell-Wagner polarization at grain boundaries.