Ni doped CaCu3Ti4O12 ceramics (CaCu3−xNixTi4O12, x = 0, 0.05, 0.1, 0.2) were prepared by a sol–gel method and the influence on the microstructure, dielectric properties and impedance spectroscopy has been investigated.

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Nickel ferrite (NiFe 2 O 4) powders were synthesized via sol-gel auto-combustion method and the corresponding temperature dependence of microstructure, dielectric and magnetic properties have been investigated. Results of XRD and SEM indicate that the NiFe 2 O 4 samples exhibit a typical single phase spinel structure and a uniform particle distribution. The dielectric constant and dielectric loss measurements show strong frequency dependence of all the samples. The peak observed in frequency dependence of dielectric loss measurements shifts to higher frequency with the increasing sintering temperature, indicating a Debye-like dielectric relaxation. The remanent magnetization increases with the increasing grain size while the coercivity is just the opposite. The saturation magnetization can achieve 50 emu/g when the sintering temperature is more than 1000 o C, and the lowest coercivity (159.49 Oe) was observed in the NFO sample sintered at 1300 o C for 2 h.

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