Significantly improved giant dielectric properties and enhanced nonlinear coefficient of Ni(2+) doped CaCu(3)Ti(4)O(12)/CaTiO(3) composites

CaCu(3-x)Ni(x)Ti(4)O(12)/CaTiO(3) ceramic composites were fabricated using initial Ca(2)Cu(2-x)Ni(x)Ti(4)O(12) compositions (x = 0, 0.05, 0.10, and 0.20) to improve the dielectric properties (DPs) of the CaCu(3)Ti(4)O(12) ceramics. CaCu(3)Ti(4)O(12) and CaTiO(3) phases were confirmed. Microstructural analysis and Rietveld refinement showed that the Ni(2+) dopant might substitute the Cu(2+) sites of the CaCu(3)Ti(4)O(12) structure. The average grain sizes of CaCu(3)Ti(4)O(12) (4.1–5.6 μm) and CaTiO(3) (1.2–1.4 μm) changed slightly with the Ni(2+) doping concentration. The best DPs were obtained for the CaCu(3-x)Ni(x)Ti(4)O(12)/CaTiO(3) with x = 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(3) to ∼4.0 × 10(3). Furthermore, the temperature dependence of ε′ could be improved by doping with Ni(2+). 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 CaCu(3-x)Ni(x)Ti(4)O(12)/CaTiO(3) with x = 0.05. Impedance spectroscopy showed that the CaCu(3-x)Ni(x)Ti(4)O(12)/CaTiO(3) composites consisted of semiconducting and insulating components. The DPs of CaCu(3-x)Ni(x)Ti(4)O(12)/CaTiO(3) were explained based on the space−charge polarization at the active−interfaces.