The effect of mechanical activation on the synthesis of MgFe2O4 from mixtures of MgCO3·Mg(OH)2· xH2O and FeC2O4· 2H2O

The synthesis of MgFe2O4 has been attempted starting from mixtures of 4MgCO3 ·Mg(OH)2· xH2O and FeC2O4 · 2H2O by combining mechanical activtion of the mixtures (by high-energy
milling) with annealing at temperatures between 673 and 1073 K. TG measurements of mixtures of the precursors have been performed to assess the reaction mechanism, and to determine the minimum temperature where the two binary oxides (MgO and Fe2O3) are formed. X-Ray powder patterns of the milled / annealed mixtures have shown that MgFe2O4 is formed in an amorphous state already upon thermal treatment at 673 K, while annealing of the mixtures (not mechanically activated) at temperatures as high as 1473 K of the mixtures does not lead to the complete formation ofMgFe2O4. The molar specific heat and the Curie temperature of the milled / annealed mixtures have been determined by DSC: MgFe2O4 is obtained provided that the annealing of the milled mixture is performed at temperatures
as low as 873 K. The effect of the annealing temperature on the surface area of MgFe2O4 has been determined by BET measurements.