Electric and dielectric properties of pure and doped CaCu3Ti4O12 perovskite materials

AC impedance spectroscopy (IS) measurements were performed in the 15-700 K temperature range on pure and Ni, Fe and Co doped CaCu3Ti4O12 (CCTO) materials. Capacitance values were also confirmed by direct current measurements at room temperature. Thermoelectric power measurements showed that the electrons are involved in the conduction process of the semiconducting bulk region. The IS results evidenced a dielectric behaviour in the grain boundary region, giving a permittivity of about 3400 for the pure sample, so CCTO can be considered an internal barrier layer capacitance (IBLC) material. The giant permittivity of CCTO can be strongly increased to values of similar to 150 000 by Co doping on Ti site. The IBLC behaviour, together with the giant permittivity and the opportunity to combine capacitance and resistance values in an R//C circuit, evidence the applicability of this material as an integrated resonant element for the electronic industry. (C) 2004 Elsevier Ltd. All rights reserved.