Spinel Frerrite Materials

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Nanocrystalline perovskite and spinel magnetic mixed oxides materials have gained immense importance due to their novel properties, which are significantly different from those of their bulk counterparts [1]. Nanocrystals of spinel ferrites, with general formula MFe2O4 (where M = Ni, Cu and Zn) are most interesting class of magnetic materials due to its facinating properties such as low melting point, high spectfic heat, large expansion coefficent and low magnetic transition temperature[2,3]. Because of these properties, ferrite materials are widely used in ferrofluid technology, information storage and magnetic pigments[4-6]. Especially, due to their peculiar magnetic properties and ability to respond at the molecular level, magnetic nanostructures are potential candidates for biomedicine such as targeted drug delivery [7], diagnostics [8], and magnetic separation [9]. These materials are also being explored as contrast agents in magnetic resonance image (MRI) [10], thermo responsive drug carriers [11] as well as in the thermal activation therapy of cancer [12]. The crystal structure of spinel ferrite compounds have a cubic close packing of O2- ions structure linked with two sub-lattice sites namely tetrahedral (A-sites) and octahedral (B-sites) [13]. The magnetic and other properties of spinel ferrite can be varied systematically by changing the identity of the ion, their charges and their distribution among the tetrahedral and octahedral sites [14]. Zinc ferrite (ZnFe2O4) and cobalt ferrite (CoFe2O4) have been most extensively studied system, because they exhibit the typically normal and inverse spinel ferrite respectively [15]. Nickel ferrite (NiFe2O4) is a well known inverse spinel structure ferrite with Ni2+ ions at octahed... ... middle of paper ... ... low temperature surfactant Tween80-assisted hydrothermal method to produce nanocrystaline nickel ferrite (NiFe2O4) and copper nickel ferrite (Cu1-xNixFe2O4, 0≤x≤0.5) using fine metal powders as raw materials. The formation of single spinel phase requires high calcination temperature. Therefore, in the present work, hydrothermal process was adopted because metal hydroxides were devoped after the hydrothermal reaction which were calcined at high temperature i.e.850oC to produce the desired spinel ferrite oxides.The thermal stability, phase development, microstructures, sintering characteristics and the distribution of cations in tetrahedral and octahedral sites of developed nanosized crystal structure ferrite materails were examined by TG-DTA, FTIR, XRD and SEM and Mössbauer spectroscopy. The impedance properties of sintered ferrite materials were also ascertained.

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