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

• 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.

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.

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