Study Of CaCu₃Ti₄O₁₂ Oxide Ceramics With Giant Dielectric Permittivity By Impedance Spectroscopy

CaCu₃Ti₄O₁₂(CCTO)ceramics were prepared by the conventional solid-state reaction method,the effects of sintering atmosphere and doping on phase compositions and impedance spectroscopy characteristics of CCTO ceramics have been studied. Compared with the CCTO ceramics sintered in air, the domain resistivity of the CCTO ceramics sintered in O₂ increases from 70?.cm to 120?.cm, and both are in the same order, which indicating the semi-conductivity in CCTO grain or domain is not caused by oxygen loss. With the increasing of Al³⁺ doping level, the resistivity of CCTO ceramics grain and grain boundary increase to a peak and then decrease. At low doping level, Al³⁺ substitutes Ti⁴⁺ and acts as acceptor; at high doping level, Al³⁺ substitutes Cu²⁺ and acts as donor. The resistivity of grain boundary and domain boundary of Nb-doped CCTO ceramics were decreased gradually with the increase of Nb doping level. The giant dielectric permittivity of CCTO ceramics either sintering in various atmospheres or using different doped states was attributed to internal barrier layer capacitance effect.