Effect of hydrogen reduction on composition,microstructure and magnetic properties of MgZn ferrites

Abstract

Magnesium–zinc ferrite (Mg_0·6Zn_0·4Fe₂O₄) powder was prepared through the ceramic route by the calcination of a stoichiometric mixture of magnesium, zinc and iron oxides. The ferrite powders (Mg_0·6Zn_0·4Fe₂O₄) were then sintered at 1300°C for 4 h. Both the ferrite powders and sintered pellets were subjected to isothermal reduction in pure hydrogen at 500–700°C. Based on thermogravimetric analyses, the reduction behaviour of magnesium–zinc ferrite was systematically studied. The initial ferrite powder, the sintered bodies and the various reduction products were characterised by X-ray diffraction analyses, scanning electron microscopy and vibrating sample magnetometer to reveal the effect of sintering and hydrogen reduction on composition, microstructure and magnetic properties of Mg_0·6Zn_0·4Fe₂O₄. It is found that the sintered pellets had enhanced magnetic properties, whereas the saturation magnetisation increased and the coercivity decreased sharply. Homogenous Fe/ZnO/MgO nanocrystalline composite of ∼62·1 nm in size was obtained after the reduction of initial Mg_0·6Zn_0·4Fe₂O₄ powder. The magnetic properties of these Fe/MgO/ZnO composites were found to be improved according to the reduction temperature, whereas the saturation magnetisation increased from to 34·18 to 109·7 emu g⁻¹ and the coercivity values decreased from 157·7 to 136·4 Oe.