Mg-doped CaCu3Ti4O12 nanocrystalline powders prepared by a modified sol-gel method: Preparation, characterization, and their giant dielectric response

Nanocrystalline Mg-doped CaCu3Ti4O12 powders were prepared by a modified sol-gel method. The effects of Mg2+ doping on the dielectric response and electrical properties of CaCu3Ti4O12 ceramics were systematically investigated. The dielectric properties of CaCu3Ti4O12 ceramics can be improved by doping Mg2+ ions with suitable concentrations. A high dielectric permittivity (epsilon' approximate to 7621.5) and a low loss tangent (tan delta) of about 0.02 at 1 kHz were obtained in the CaCu2.9Mg0.1Ti4O12 ceramic sintered at 1070 degrees C for 6 h. By using impedance spectroscopy analysis at different temperatures, it was found that the grain boundary resistance and the activation energy for conduction at the grain boundary of CaCu3Ti4O12 ceramics were significantly increased by doping Mg2+ ions, whereas the electrical properties of the grains slightly changed. These resulted in the reduction in tan delta and the enhancement of the nonlinear electrical properties of CaCu3Ti4O12 ceramics. (C) 2015 The Japan Society of Applied Physics