Dielectric responses and multirelaxation behaviors of pure and doped CaCu3Ti4O12 ceramics

Pure and Co/Fe doped CaCu3Ti4O12 (CCTO) ceramics were prepared by solid state reaction method. The electrical properties of ceramics were found to be dependent on the type of dopant materials. A multirelaxation mechanism should be considered for the common observed (50-200 K) dielectric relaxation of CCTO ceramic. In relatively high temperature range, this relaxation followed the Arrhenius behavior with activation energy of 68 meV, which was ascribed to the Maxwell-Wagner (MW)-type relaxation associated with grains. In lower temperature range, this relaxation exhibited variable-ranger-hopping behavior due to the dipolar effects. The dielectric relaxation mechanism of Co doped CCTO ceramic was similar to that of pure CCTO ceramic, while that of Fe doped CCTO ceramic was quite different. Two dielectric relaxations were identified in the temperature range from 4 to 300 K. A dielectric relaxation at room temperature with an activation energy of 390.3 meV was attributed to the MW-type relaxation associated with grain boundaries. Another dielectric relaxation at low temperatures (100-200 K) with an activation energy of 265 meV was originated from the carrier hopping process between Fe2+ and Fe3+. (c) 2008 American Institute of Physics.