Dielectric dispersion of CaCu3Ti4O12 ceramics at high temperatures

CaCu3Ti4O12 ceramics has been prepared by the conventional solid-state reaction method under different sintering conditions. Dielectric properties have been investigated in the temperature range of 25-350 deg. C within the frequency range of 40 Hz-10 MHz. It has been found that both the dielectric constants and the grain sizes increase with the sintering time. A relaxation has been observed in the frequency range of 100 Hz-100 kHz, apart from the one already known in the frequency range higher than 100 kHz. High-temperature dielectric dispersion shows one large low-frequency response and two Debye-type relaxations. Activation energy values of these two relaxations are 0.084 and 0.678 eV, respectively. An equivalent circuit model is suggested, which well explains the dielectric dispersion