Effect of Rare Earth Substitution on Physical Properties of Nano Crystalline Ferrites

Abstract

The thesis reports the systematic study of effects of rare earth substituent on the structural, magnetic and electrical properties of the nanocrystalline cobalt-zinc (Co-Zn) ferrites. The three rare earth elements selected are samarium (Sm), gadolinium (Gd) and lanthanum (La). Thus the thesis reports synthesis and the study of properties of three different ferrite systems viz. Sm substituted Co-Zn ferrites (CZS), Gd substituted Co-Zn ferrites (CZG) and La substituted Co-Zn ferrites (CZL). The ferrites were synthesized by using the sol gel auto-combustion method. The structural properties were studied by means of powder X-ray diffraction method. The morphology of the ferrite powders was analysed from the scanning electron microscopy (SEM) images. The elemental analysis was performed by the energy dispersive X-ray spectroscopy (EDS). The particle shape and size of the ferrite nanocrystals was studied by means of the transmission electron microscopy (TEM). The crystal phase in the ferrite was confirmed from the high resolution TEM and selected area electron diffraction (SAED) analysis. The phase characterization and the cation occupancy was analysed from the Fourier transform infra-red spectroscopy (FTIR). The magnetic property analysis performed from the hysteresis loops of the ferrites obtained from the vibration scanning magnetometer (VSM) and permeability measurements. The dielectric behaviour of the ferrites was analysed from the frequency variation of the dielectric constant (and#949;and#697;), dielectric loss (and#949;and#698;) and loss tangent (tanand#948;). newlineThe nanocrystalline samarium substituted Co-Zn ferrites with chemical formula Co0.7Zn0.3SmyFe2-yO4 (where y = 0, 0.01, 0.02, 0.03, 0.04) were synthesized by sol-gel auto combustion route. The analysis of X-ray diffractograms (XRD) revealed the formation of cubic spinel structure. The planes indexed from XRD analysis were confirmed in the selected area electron diffraction (SAED) image of the sample. Nanocrystalline nature of the particles in the ferrite samples were confirmed by TEM. The