Enhanced dielectric response of GeO2-doped CaCu3Ti4O12 ceramics

CaCu3Ti4O12 ceramic samples were prepared by solid state conventional route using stoichiometric amounts of CuO, TiO2, and CaCO3. Afterward the material was doped with GeO2 with concentrations up to 6% by weight and sintered at 1050 deg. C for 12 h. The influence of doping on the microstructure, vibrational modes, and dielectric properties of the material was investigated by x-ray diffraction, scanning electron microscopy coupled with an energy dispersive spectrometer, and infrared and dielectric measurements between 100 Hz and 30 MHz. The materials presented huge dielectric response, which increases with doping level relative to undoped CaCu3Ti4O12. The main effect of doping on the microstructure is the segregation of Cu-rich phase in the ceramic grain boundaries. Cole-Cole modeling correlates well the effects of this segregation with the relaxation parameters obtained. The intrinsic phonon contributions for the dielectric response were obtained and discussed together with the structural evolution of the system