Temperature-dependent complex impedance, electrical conductivity and dielectric studies of MFe<inf>2</inf>O<inf>4</inf> (M = Mn, Ni, Zn) ferrites prepared by sintering of mechanochemical synthesized nanopowders

Abstract

© 2015, Springer Science+Business Media New York. Effect of temperature on electrical and dielectric properties of MFe2O4 (M = Mn, Ni, Zn) ferrites has been investigated in a wide frequency range 100 Hz to 1 MHz. Ferrite ceramics under study were successfully fabricated by a conventional sintering of nanosized powders (1100 °C/2 h) synthesized by soft mechanochemical processing. The structural studies have been carried out using the transmission electron microscopy, X-ray diffraction and scanning electron microscopy. Direct current (DC) resistivity of all samples decreases with increasing temperature, while drift mobility increases, exhibiting the typical semiconductor-like behaviour. Activation energy is calculated by using Arrhenius type resistivity plots. The analysis of experimental data indicates that alternating current (AC) conductivity is mainly due to the hopping mechanism, which is discussed in terms of Maxwell–Wagner two-layer model. The dielectric behaviour is explained by using the mechanism of polarization process, which is correlated to that of electron exchange interaction. Ni-ferrite possesses the lowest value of conductivity of 10−7 (Ωcm)−1, whereas Zn-ferrite has the highest dielectric constant value of 2,641 at frequency of 1 kHz and room temperature. The complex impedance spectroscopy was used to study the effect of microstructures on the electrical properties of sintered ferrites using equivalent circuits. It was found that the electrical resistivity is predominantly controlled by the grain boundaries.