الفهرس 
Abstract.
FerritesOnly 14 pages are availabe for public view
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Abstract
Ferrites in the nano-scale size have been studied extensively, because of their large-scale of technological application due to their interesting physical properties which differ from those of the corresponding bulk materials. A familiar Zn- and (Cu, Zn) - ferrites have been chosen here and synthesized by microwave combustion process in the nano size form. It is well known that bulk ZnFe2O4 is a normal spinel with paramagnetic properties at room temperature and antiferromagnetic below 10 k, while Cu–Zn ferrites show a ferromagnetic feature with high initial permeability, and low loss. Their magnetization and coercivity are strongly depending upon Cu content. Electrically Cu–Zn ferrites are behaving like n-type semiconductors with high resistivity and dielectric constant. Their electrical conductivity enhanced with copper substitution.
The present study focuses on the magnetic properties and catalytic activity of these ferrites in the reduced size system. To enhance the variations of these properties, a systematic calcination and high energy ball milling of selected Cu-ZnFe2O4 compositions were carried out and investigated by XRD, Mössbauer spectroscopy and VSM.
The composition, crystallinity and crystallite size of the as synthesized zinc ferrites sample are controlled by U/N ratios. The synthesized sample at U/N=1.5 has very low impurity ratio and nearly can be considered as monophase of zinc ferrite. Calcinations of the as synthesized sample led to monophase zinc ferrite with high crystallinity. Zn- ferrite nano-powders were synthesized as a monophase using glycine as a fuel. An impurity phases start to appear as Cu-substituted Zn ions with concentration greater than 0.2.The as-prepared Cu0.5Zn0.5Fe2O4 nanoparticles show low crystallinity and very small crystallite size. A minor α-Fe2O3 phase is also detected, whereas it is totally assimilated into the ferrite after milling for 330 min. contrasting with the bulk paramagnetic state at room temperature, our synthesized nano-size zinc ferrite exhibited a ferromagnetic state with magnetization measured approximately 47 emu/g. This behavior is indicative of Fe and Zn occupying both the A- and B- sites of the spinel structure in a metastable chemical configuration. The magnetic state, however, reversed to paramagnet with calcination which drove the chemical state toward equilibrium as in bulk. Substituting Zn by Cu has enhanced magnetization to 57.6 emu/g, remnant magnetization (Mr) to 8 emu/g, and coercive field (Hc) to 83 Oe. Upon milling, however, the coercivity and remanence fields.