Influence of FeNb codoping on the dielectric and electrical properties of CaCu3Ti4O12 ceramics

Abstract

The CaCu3 (Ti1−xFex/2Nbx/2)4O12 (x = 0.00, 0.50, 0.53, 0.57, 0.60) ceramics were prepared by the solid-state reaction method via the pre-synthesis of the monoclinic precursor FeNbO4. The temperature dependence of dielectric properties showed that the dielectric permittivity of pure CaCu3Ti4O12 sample increased rapidly with the rising temperature, while a broad peak of dielectric permittivity of the FeNb codoped CaCu3Ti4O12 samples was observed in the temperature range. The frequency dependence of dielectric spectra was measured in frequency range from 20 Hz to 1 GHz for pure CaCu3Ti4O12 sample, two Debye-type relaxations were shown in low and high frequency, respectively, and the giant dielectric plateau of pure CaCu3Ti4O12 sample was attributed to the interfacial polarization at grain boundaries. A reduce of dielectric permittivity of the FeNb codoped CaCu3Ti4O12 samples occurred in low frequency, indicating the existence of a Debye-type relaxation related to the surface layer effect. By the complex impedance spectroscopy measurement, three semi-circle arcs of the FeNb codoped CaCu3Ti4O12 samples were revealed, which represented the responses of surface layer, grain boundary and grain, respectively. The nonlinear I–V characteristics revealed the existence of Schottky potential barrier and the heights of Schottky potential barrier of FeNb codoped CaCu3Ti4O12 were lower than that of pure CaCu3Ti4O12.