Abstract
Two ferrite ceramic materials, MgFe2O4 and MnFe2O4, were successfully fabricated by a conventional sintering of nanosized powders (at 1373 K for 2 h) synthesized by soft mechanochemical route. The particle size and morphology of powders were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis was carried out for the determination of phase purity, crystal structure and average crystallite size of sintered ferrites. Both mechanosynthesized ferrite samples show mean crystallite sizes in the nm-range. Over the frequency range of 100 Hz to 1 MHz, impedance spectra of prepared ferrite ceramics are investigated at and above room temperature. Changes in the impedance plane plots with temperature have been discussed and correlated to the microstructure of materials. An equivalent circuit model is applied to explore the electrical parameters (resistance and capacitance) associated with grains and grain boundaries. Complex impedance analysis indicates the dominance of grain boundary effects which control the overall electrical behaviour of studied ferrites. The decrease in grain boundary resistance with temperature suggests a thermally activated conduction mechanism.
Highlights
Spinel ferrites MFe2O4, where M2+ is a divalent metal cation, are an important class of magnetic materials, which have been intensively investigated over the last few decades due to good combination of electrical and magnetic properties
We have reported the electrical properties of MgFe2O4 and MnFe2O4 ferrites prepared by a conventional sintering of nanosized powders synthesized by soft mechanochemical processing that is environmentally friendly, does not require expensive starting materials or extremely high temperature [12]
The X–ray diffraction analysis confirmed the cubic spinel structure of sintered samples and the average crystallite sizes in the nm–range were determined on the basis of X– ray diffraction (XRD) data
Summary
Spinel ferrites MFe2O4, where M2+ is a divalent metal cation, are an important class of magnetic materials, which have been intensively investigated over the last few decades due to good combination of electrical and magnetic properties. It has been reported that the spinel structure of MgFe2O4 bulk material is nearly inverse with 90% of Mg2+ cations distributed over [B] sites, and that inversion factor decreases to about 70% for the magnesium ferrite nanoparticles [5]. Electrical as well as magnetic properties of spinel ferrites strongly depend on the cation distribution at the different sites as well as method of preparation, sintering temperature, particle size, doping of additives etc. In order to understand the conduction mechanism, electrical properties associated with grains and grain boundaries in these synthetized nanocrystalline ceramic materials were studied as a function of frequency and temperature using complex impedance spectroscopy technique
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