Role of Rare Earth (Gd3+) on Structural and Dielectric Properties of Cobalt Ferrite

Abstract

Nano ferrites are area of research focused due to their potential applications in various fields such as high-density magnetic recording, magnetic fluid and microwave devices etc. Usually substitution of metal ions in cobalt ferrite has led to enhancement in structural and electrical properties. These structural and electrical properties of the ferrites are influenced by their chemical composition, synthesis techniques, doping materials and environmental conditions. In the present investigation Gadolinium (Gd) substituted cobalt ferrites (CoFe2-xGdxO4) with variable Gd content (x = 0.0, 0.1, 0.3, 0.5) have been synthesized by sol-gel auto combustion method using glycine as a fuel and nitrates as oxidants. The crystal structure, electrical conduction and dielectric properties of the series of synthesised compound has been evaluated. X-ray diffraction spectra indicates that CoFe2-xGdxO4 crystallizes in the inverse spinel phase with a lattice constant of 8.373Å. It is evident from the FESEM (Field Emission Scanning Electron Microscope) and TEM (Transmission Electron Microscopy) study that substituiting Gd results in a smoother microstructure which may be attributed to the higher ionic radius of Gd3+ ions as compared to that of Fe, responsible for the increase in lattice constant. The EDS (Energy-Dispersive Spectroscopy) measurements show that the specimens are homogeneous with a uniform distribution. From the dielectric studies, it is observed that the specimens show Debye type of behaviour with a shift in dielectric maxima with increase in frequency at higher temperature. The temperature dependent dielectric constant, energy loss, ac electrical resistivity and conductivity studies indicates the existence of correlation and microstructural effect. Notably the effect of Gd-substitution in cobalt ferrite is significant on the resistivity which increases with increasing Gd content. The structural and dielectric studies can be tailored with the doping content of Gd in cobalt ferrite which can find applications in EMI shielding.