Hydrazine method of synthesis of γ-Fe2O3 useful in ferrites preparation. Part IV – preparation and characterization of magnesium ferrite, MgFe2O4 from γ-Fe2O3 obtained from hydrazinated iron oxyhydroxides and iron (II) carboxylato-hydrazinates

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Abstract

Electro-magnetic properties and microstructural characterization of MgFe2O4 synthesized by a ceramic technique at ∼1000°C from iron oxides, consisting of mainly γ-Fe2O3 and traces of alpha-Fe2O3, prepared from iron ore rejects, are compared with the ferrite obtained from commercial alpha-Fe2O3. The sources of γ-Fe2O3 are hydrazinated iron (II) carboxylates and iron oxyhydroxides which autocatalytically decompose giving mainly γ-Fe2O3 of uniform particles of 10–30 nm (by scanning electron microscopy (SEM) studies) having high surface area. The ferrite synthesized from such nanoparticle size γ-Fe2O3 gave a porosity of ∼25% with grains ranging from 0–3 μm. On the other hand, MgFe2O4 obtained from commercial alpha-Fe2O3 grains (of 1–2 μm size) gave particles of 0–6 μm with a porosity ∼42%. Saturation magnetization values 922–1168 G are found for MgFe2O4 from γ-Fe2O3 source while the alpha-Fe2O3 source gave the lowest value, ∼609. The Curie temperature, Tc, from magnetic susceptibility, initial permeability and resistivity measurements indicated a highest Tc of ∼737 K for MgFe2O4 from alpha-Fe2O3, while lower values are found for the ferrite prepared from γ-Fe2O3.