Preparation of magnesium and calcium ferrites from the thermolysis of M3[Fe(cit)2]2 x xH2O precursors

Magnesium and calcium ferrites have been prepared from the thermolysis of M3[Fe(C6H5O7)2]2 x xH2O (M=Mg, Ca) precursors. Thermal decomposition of the precursors has been studied employing various physico-chemical techniques, i.e., TG-DSC, XRD, IR and Moessbauer spectroscopy. After dehydration the anhydrous precursors undergo an abrupt oxidative pyrolysis to yield α-Fe2O3 and a metastable acetone-dicarboxylate intermediate. A subsequent exothermic decomposition leads to the formation of MgO and CaCO3 from the respective intermediates. Finally ferrite is formed as a result of solid state reaction between MO/MCO3 and α-Fe2O3. Nanosized ferrites of the stoichiometry MgFe2O4 and Ca2Fe2O5 have been obtained from magnesium and calcium bis(citrato) ferrates(III). The temperature of ferrite formation is much lower than possible in conventional ceramic method. The results have been compared with the respective oxalate and maleate precursors. (author)