Microstructural, structural and dielectric analysis of Ni-doped CaCu3Ti4O12 ceramic with low dielectric loss

CaCu2.8Ni0.2Ti4O12 ceramics were elaborated using the solid-state reaction technic. The pellets were annealed at 1000 degrees C for 24 h. The X-ray diffraction (XRD) analysis proves the main phase formation of our sample crystallize in the cubic structure with Im (3) over bar space group. The diffuse reflectance analysis allow us to calculate the optical band gap energy which is equal to 3.172 eV. The dielectric properties of our compound were studied using complex impedance spectroscopy showing a lowering in dielectric loss (tan delta = 0.07) at 1 kHz and at room temperature. The impedance studies reveal the presence of temperature dependent dielectric relaxation. Thus, the electrical modulus studies show that the relaxation is associated with grain boundaries effects. The activation energy calculated from the electric modulus spectra, related to the electrical relaxation, is found to be 0.60 eV. This result suggests the hopping mechanism of oxygen vacancies produced at grain boundaries in relaxation processes.