Structural, Magnetic and DC Electrical Resistivity Studies of Ni-Zn-Cr Ferrites Prepared by the Citrate-Gel Auto-Combustion Method

摘要

Nanocrystalline chromium substituted Ni-Zn nanoferrites with composition Ni0.5Zn0.5CrxFe2-xO4(0 = x = 0.25, in steps of 0.05) have been synthesized using citrate-gel auto-combustion method. The as synthesized powder of the starting composition has been characterized by using TG-DTA in air atmosphere for the temperature up to 800 degrees C and X-ray diffraction for its structure. Upon confirming the spinel phase for the starting composition, the chromium substituted Ni-Zn ferrite nano powders were synthesized by the similar procedure. The as synthesized powders were pressed into pellets and toroids under uniaxial pressure followed with sintering in air atmosphere for 4 h at 1100 degrees C for electrical and magnetic characterizations. The X-ray diffraction studies revealed a decrease of the lattice constant and considerable modification in the structure of Ni-Zn ferrite with the substitution of Cr(3+)for Fe(3+)ions. The room temperature FT-IR spectra displayed three significant IR absorption bands in the wave number range of 350-600 cm(-1)which is a characteristic of the spinel structure. The band positions and intensities were found to vary with chromium substitution in Ni-Zn ferrite. The room temperature DC electrical resistivity and activation energy for conduction in the Ni-Zn-Cr ferrite samples were measured by using the two-probe method while the AC resistivity studies were carried out in the frequency range of 1 kHz to 13 MHz and the all the observations have been discussed in the light of existing understanding.