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BaTiO 3 ceramics doped with 0.40 mol% NaNbO 3 were prepared using a traditional approach by sintering at temperature of 1250°C to 1290°C. The prepared ceramics was characterized by very good dielectric properties, such as high dielectric constant (1.5 × 10 5 ), low dielectric loss (0.1), and good dielectric temperature stability in the −40°C to 100°C range for the sample sintered below 1270°C. The dielectric characteristics obtained with XPS confirmed that Ti 4+ ions remain in the state without any change. The huge increase in dielectric constant in NaNbO 3 doped BaTiO 3 samples occurs when large amount of Ba 2+ ions are excited to a high energy bound state of Ba 2+ − e or Ba + to create electron hopping conduction. For samples with the content of NaNbO 3 higher than 0.40 mol%, or sintering temperature higher than 1280°C, compensation effect is dominated by cation vacancies with sharply decreasing dielectric constant and increased dielectric loss. The polaron effect is used to explain the relevant mechanism of giant dielectric constant appearing in the ferroelectric phase.

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Sol–gel method has been employed to prepare Ni–Zn ferrite with chemical formula Ni[Formula: see text]ZnxFe2O4 where [Formula: see text] 0, 0.1, 0.2, 0.3, 0.4 and 0.5. The structural Ni–Zn ferrite was studied via the X-ray diffractometer (XRD) pattern. X-ray analysis showed that there is a small shift in peaks towards shorter angles which increases with the concentration of zinc. Experimental values of lattice constant was varied from 8.34 of Ni ferrite to 8.397[Formula: see text]nm for Ni–Zn ferrite. The crystallite size of Ni ferrite was 83[Formula: see text]nm which is decreasing with substituted Zn to it and became 43[Formula: see text]nm at [Formula: see text]. Therefore, the superparamagnetic behavior appears with substitution of Zn to Ni ferrite. The saturation magnetization, remiensis, coersivity, magnetic moment and anisotropy constant were calculated according to hysteresis loop using the result of vibrating sample magnetometer (VSM). The effect of cation distribution appeared clearly through the saturation magnetization value which was 46.8[Formula: see text]emu/gm for nickel ferrite and increased to an optimum value (59.64[Formula: see text]emu/gm) at [Formula: see text].