Synthesis of sodium ferrite by precursor and combustion methods: A comparative study

Thermal decomposition of sodium ferricarboxylate precursors, Na₃Fe(L)₆].xH₂O (L = formate, acetate, propionate, butyrate) has been carried out in flowing air atmosphere from ambient temperature to 850 °C. Various physico-chemical techniques i.e. TG, DTG, DSC, XRD, IR, Mössbauer spectroscopy, etc. have been employed to characterize the intermediates and end products. After dehydration, the anhydrous complexes undergo decomposition to yield various intermediates i.e. sodium propionate/oxalate/carbonate and α-Fe₂O₃ in the temperature range 260–285 °C. A subsequent decomposition of sodium carbonate leads to the formation of sodium oxide in the successive stages. Finally, nanosized ferrites of the stoichiometry, NaFeO₂ have been obtained above 760 °C as a result of solid-state reaction between α-Fe₂O₃ and Na₂O. The same ferrite has also been prepared by the combustion method at comparatively lower temperature (400 °C) and in less time than that of precursor/conventional ceramic methods.