Structural and electrical properties of nanocrystalline cobalt substituted nickel zinc ferrite

The structural and electrical properties of the spinel ferrite system Ni0.7-xCoxZn0.3Fe2O4 (x = 0.0-0.7) have been studied. Samples in the series were prepared through chemical route using sucrose as fuel and PVA as chelating agent. Structural characterization was done by X-ray diffraction technique and infrared absorption spectroscopy XRD patterns were analyzed to calculate lattice constant (a), X-ray density (d(x)) and pore fraction (f). Far infrared absorption spectra show two significant absorption bands, around 600 cm(-1) and 425 cm(-1), which are respectively attributed to tetrahedral (A) and octahedral (B) vibrations of the spinel. Scanning electron microscopy was used to study surface morphology. SEM images reveal particles in the nanosize range. DC resistivity (rho(DC)) measurements were carried out as function of temperature using two-probe method and activation energy (Delta E) was determined. It is found that conduction is due to formation of small polarons. The dielectric parameters such as dielectric constant, loss tangent were determined as a function of frequency in the range 100 Hz-1 MHz at room temperature. The compositions exhibit normal dielectric behavior, which is attributed to Maxwell-Wagner type interfacial polarization. AC conductivity was studied as a function of frequency at room temperature. The variation is found to be linear suggesting that conduction is due to small polaron hopping. (C) 2009 Published by Elsevier B.V.