Application of Mössbauer spectroscopy to the thermal decomposition of strontium and barium bis(CITRATO)Ferrates(III)

The thermal decomposition of M3[Fe(cit)2]2 4H2O (M = Sr, Ba) has been studied isothermally and non-isothermally employing simultaneous (TG–DTG–DSC), XRD, IR, SEM and Mössbauer spectroscopic techniques. The anhydrous complexes decompose at 140–220°C to yield α-Fe2O3 and MC5H4O5 (metal acetone-dicarboxylate) intermediates. The latter decomposes to respective carbonate at higher temperature. α-Fe2O3 and MCO3 undergo a solid state reaction in the temperature range 400–430°C to yield Sr2Fe2O5 and BaFe2O4 respectively. Finally above 600°C, a solid state reaction between these products and respective metal oxides leads to the formation of M3Fe2O7 − X showing simultaneous presence of Fe(III) and Fe(IV) species. These perovskite ferrites can exhibit electrical conductivity and dielectric properties. SEM analysis shows these ferrites to be nanosized with average particle diameter of 50–55 nm.