Structural and Electrical Properties of Mechanothermally Synthesized NiFe2O4 Nanoceramics

NiFe2O4 nanoceramics were prepared by high-energy ball milling followed by a solid-state reaction technique. X-ray powder diffractometry, scanning electron microscopy, and impedance spectroscopy techniques were used to study preliminary structural, microstructural, and detailed electrical characteristics, respectively, of the nickel ferrite nanoceramics. The crystallite size of the fine (nanosize) powder of the compound was found to decrease after 30 h, 60 h, and 90 h of milling. It was also found that, at low temperatures and high frequencies, the relative permittivity and tangent loss of the material were size and milling time dependent. Detailed analysis of impedance spectroscopy data clearly showed the size dependence of the impedance characteristics and dielectric relaxation of the material. The temperature-frequency dependence of the alternating-current (ac) conductivity obeyed Jonscher's universal power law.