Maxwell-Wagner relaxations and their contributions to the high permittivity of calcium copper titanate ceramics

Calcium copper titanate ceramics were fabricated by cold isostatic pressing at various calcination and sintering conditions. Depending on fabrication condition, three electrical responses were observed in the combined modulus and impedance plots, indicating the presence of two Maxwell-Wagner relaxations. These electrical responses show different response to temperature and applied field. The activation energies, as well as the driving force factors, were calculated for these relations. The determined activation energy values are in the range of $0.57\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}0.65\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The contribution of Maxwell-Wagner relaxations to the high permittivity of CCTO and related materials is briefly discussed.