Preparation of spinel ferrites from citrate precursor route—A comparative study

Spinel ferrites MFe2O4 (M = Mn, Co, Ni, Cu) have been prepared from the thermolysis of transition metal bis(citrato)ferrates(III), M3[Fe(C6H5O7)2]2·xH2O. Various physico-chemical studies, i.e. TG–DTG–DSC, XRD and Mössbauer spectroscopy have been employed for the investigation of the mode of decomposition and characterization of intermediates/products formed. After dehydration the anhydrous precursor undergoes an oxidative decomposition to yield α-Fe2O3 and respective metal oxide. Finally spinel ferrites, MFe2O4, are formed as a result of a solid-state reaction between the oxides at a much lower temperature (310–440 °C) and in less time as compared to that of the conventional ceramic method. SEM studies show these ferrites to be of nanosized. Ferrites obtained from the thermolysis of transition metal ferricitrate precursors show higher values of saturation magnetization than those got from respective ferrimalonate precursors, thus designating the former as novel materials to operate at high frequencies.