Application of Mössbauer spectroscopy in thermal decomposition studies of some metal ferricarboxylates

795-799The thermal decomposition of magnesium and calcium hexa(formato)ferrates(III), M₃[Fe(HCOO)₆]₂×H₂O, has been carried out in flowing air atmosphere from ambient temperature to 700ºC. Various physico-chemical techniques i.e. TG, DTG, DSC, XRD, IR, Mössbauer spectroscopy etc. have been employed to characterize the intermediates/end products. After dehydration, the anhydrous complexes undergo decomposition to yield an iron(II) oxalate intermediate in the temperature range 100-130ºC. A subsequent oxidative decomposition of iron(II) species leads to the formation of ⍺-Fe₂O₃ and respective alkaline earth metal carbonate/oxide in successive stages. Finally, nanosized ferrites of the stoichiometry, MgFe₂O₄ and Ca₂Fe₂O₅ have been obtained as a result of solid-state reaction between ⍺-Fe₂O₃ and a fraction of MO. The obtention of ferrites at a temperature much lower than possible in conventional ceramic method, is a special feature of the method used