Study on the dielectric properties and dielectric relaxation of Fe-doped CaCu3Ti4O12 ceramics

Abstract

The CaCu3Ti4-xFexO12 (0≤x≤0.2) ceramics have been prepared by a standard solid-state reaction method, and the influence of Fe doping on the microstructure and dielectric properties of CaCu3Ti4-xFexO12 ceramics were investigated by the X-ray diffraction, scanning electron microscopy, dielectric spectroscopy and impedance spectroscopy. It has been found that complete solid solutions are formed for all of the compositions x. With the increase of Fe content, the semiconductivity of grain vanishes gradually and the dielectric constant decreases. For specimens with x≤0.04, the two dielectric relaxation process Ⅰ and Ⅱappeared in the frequency ranges of 106—108 and 103—104 Hz, respectively. These two dielectric relaxation process were considered to be associated with grain boundaries and interfacial polarization between the electrode and ceramic surface, respectively. In addition, the third dielectric relaxation Ⅲ was detected in the high-temperature dielectric spectroscopy of CaCu3Ti3.99Fe0.01O12 ceramic, which was caused by a hopping process of localized charge carriers. The activation energy of this thermally excited relaxation is 0.78 eV, as obtained by using the Arrhenius formula.