EFFECT OF Cu SUBSTITUTION ON THE STRUCTURE, ELECTRICAL AND DIELECTRIC PROPERTIES OF Co-Ni FERRITE MATERIALS

Abstract

Synthesis and characterization of nanoparticles, which is less than 100 nm ferrite materials have gained much attention in recent years because of their unique properties and potential for many applications such as magnetic storage systems, magnetic resonance imaging, spintronics etc. Cu substitute Co 0.7-x Ni0.3 Cux Fe2O4 for x = 0.05 and 0.1 ferrite materials are successfully synthesized by sol-gel method processing at pH value of 7. The synthesized ferrites are annealed at a temperature of 800 °C for 8 hrs. The structure, chemical composition, electrical and dielectric properties of both ferrites are characterized by the x-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FT-IR) spectroscopy and complex impedance spectroscopy (CIS). XRD analysis reveals that both ferrites show cubic spinel structure with space group Fd3m. The lattice parameter decreases from 8.447Å to 8.441 Å with increasing Cu content from x = 0.05 to x = 0.1. The average crystallite sizes of the synthesized samples are determined by using the X-ray analysis broadening of the (311) diffraction peak by using Debye-Scherrer’s formula and it is found in the values of 72 and 70.90 nm. The elemental analysis as obtained from the EDX measurement indicates the quantitative presence of Co, Ni, Cu, Fe and O in the synthesized samples. It also confirms the absence of impurities in Co 0.65 Ni0.3 Cu0.05 Fe2O4 and Co 0.6 Ni0.3 Cu0.1 Fe2O4 ferrite samples. The FT-IR spectra show the tetrahedral stretching vibration modes of Co0.65 Ni0.3 Cu0.05 Fe2O4 and Co0.6 Ni0.3 Cu0.1 Fe2O4 ferries. The two strong frequency bands appeared at wavenumber 569.02 and 572.90 cm −1 are responsible for the formation of Co 0.65 Ni0.3 Cu0.05 Fe2O4 and Co 0.6Ni0.3 Cu0.1 Fe2O4 ferrites, respectively. From the electrical and dielectric properties studies, it is found that the value of the dielectric constant as well as the real impendence of both samples decreases exponentially with an increasing frequency due to interfacial polarization. For the case of conductivity, the effect of the variation of frequency on the electrical conductivity of both synthesized sample are identified. Their conduction mechanism is explained on the basis of hopping of charge carriers between Fe 2+ - Fe 3+ ions on octahedral sites.