Structural and electrical properties of nickel cadmium ferrites prepared through self-propagating auto combustion method

The ferrite compositions Ni1-x Cd-x Fe2O4 with x=0.2, 0.4, 0.6 were synthesized through the self-propagating auto combustion method. The powders were characterized using XRD for phase identification, crystallite size and lattice parameter calculation. It reveals the presence of cubic spinel structure of ferrites with crystallite size of 15-20 nm. SEM micrographs show uniform distribution of ferrite particles with some agglomeration. The lattice parameter is found to increase with increase in cadmium content. The IR absorption spectra show two bands corresponding to tetrahedral and octahedral vibrations. The dc electrical resistivity measured as a function of temperature from room temperature to 700 degrees C shows the semiconducting nature of the ferrites. The room temperature resistivity was found to be of the order of 10(8) Omega m. The drift mobility is found to decrease with increase in cadmium content. The linear variation of AC conductivity with frequency confirms small polaron type of conduction mechanism. The dielectric properties were studied in the frequency range 20 Hz to 1 MHz. Dielectric constant shows dispersion in the lower frequency region and remains almost constant at higher frequencies. The variation of loss tangent with frequency is similar to that of the variation of dielectric constant with frequency. The present ferrites are well suitable for the applications in multi layer chip inductor (MLCI) due to low temperature sinterability and low magnetic loss. (c) 2008 Published by Elsevier B.V.