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

Abstract

Electro-magnetic properties and microstructural characterization of MgFe2O4 synthesized by a ceramic technique at similar to 1000 degrees C from iron oxides, consisting of mainly gamma-Fe2O3 and traces of alpha-Fe2O3, prepared from iron ore rejects, are compared with the ferrite obtained from commercial alpha-Fe2O3. The sources of gamma-Fe2O3 are hydrazinated iron (II) carboxylates and iron oxyhydroxides which autocatalytically decompose giving mainly gamma-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 gamma-Fe2O3 gave a porosity of similar to 25 percent with grains ranging from 0-3 mu m On the other hand, MgFe2O4 obtained from commercial alpha-Fe2O3 grains (of 1-2 mu m size) gave particles of 0-6 mu m with a porosity similar to 42 percent. Saturation magnetization values 922-1168 G are found for MgFe2O4 from gamma-Fe2O3 source while the alpha-Fe2O3 source gave the lowest value, similar to 609. The Curie temperature, T-c, from magnetic susceptibility, initial permeability and resistivity measurements indicated a highest T-c of similar to 737 K for MgFe2O4 from alpha-Fe2O3, while lower values are found for the ferrite prepared from gamma-Fe2O3.