Significantly improved giant dielectric properties and enhanced nonlinear coefficient of Ni doped CaCuTiO/CaTiO composites.

CaCuNiTiO/CaTiO ceramic composites were fabricated using initial CaCuNiTiO compositions ( = 0, 0.05, 0.10, and 0.20) to improve the dielectric properties (DPs) of the CaCuTiO ceramics. CaCuTiO and CaTiO phases were confirmed. Microstructural analysis and Rietveld refinement showed that the Ni dopant might substitute the Cu sites of the CaCuTiO structure. The average grain sizes of CaCuTiO (4.1-5.6 μm) and CaTiO (1.2-1.4 μm) changed slightly with the Ni doping concentration. The best DPs were obtained for the CaCuNiTiO/CaTiO with  = 0.2. The loss tangent was significantly reduced by an order of magnitude compared to that of the undoped composite, from tanδ∼0.161 to ∼0.016 at 1 kHz, while the dielectric permittivity slightly decreased from ε'∼5.7 × 10 to ∼4.0 × 10. Furthermore, the temperature dependence of ε' could be improved by doping with Ni. The improved DPs were caused by the enhanced electrical responses of the internal interfaces, which resulted in enhanced non-Ohmic properties. The largest nonlinear coefficient (α∼7.6) was obtained for the CaCuNiTiO/CaTiO with  = 0.05. Impedance spectroscopy showed that the CaCuNiTiO/CaTiO composites consisted of semiconducting and insulating components. The DPs of CaCuNiTiO/CaTiO were explained based on the space-charge polarization at the active-interfaces.