Capacitance scaling of grain boundaries with colossal permittivity of CaCu3Ti4O12-based materials

Samples of copper-deficient CaCu3Ti4O12 (CCTO) compared to the nominal composition, all synthesized via organic gel-assisted citrate process, show huge change of grain boundaries capacitance as deduced from a fit of an RC element model to the impedance spectroscopic data. The grain boundary capacitance is found to scale with the permittivity measured at 1 kHz weighted by the size of the grains. This result is found consistent with the internal barrier layer capacitance (IBLC) model. [Display omitted] •Ceramics synthesized via organic gel assisted citrate process.•Mechanism of high dielectric constants in CaCu3Ti4O12 (CCTO) related materials.•Copper stoichiometry influence on microstructure and dielectric properties of CCTO.•Grain boundary capacitance scaling with material permittivity.•Results consistent with the internal barrier layer capacitance (IBLC) model.