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  • Author or Editor: B. S. Randhawa x
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Summary  

The thermal analysis of strontium and barium hexa(formato)ferrates(III), M3[Fe(HCOO)6]2 . xH2O, has been carried out from ambient temperature to 800 °C. 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 yielda-Fe2O3and metal oxalate in the temperature range of 275-290 °C. A subsequent oxidative decomposition of metal oxalate leads to the formation of respective alkaline earth metal carbonate in successive stages. Finally, nanosized ferrites of Sr2Fe2O5and BaFe2O4stoichiometry have been obtained as a result of a solid-state reaction betweena-Fe2O3and a fraction of MCO3. The temperature of ferrite formation is much lower than possible in the conventional ceramic method.

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Summary  

The thermal decomposition of manganese tris(malonato)ferrate(III) hexahydrate, Mn3[Fe(CH2C2O4)3]2 . 6H2O has been investigated from ambient temperature to 600 °C in static air atmosphere using various physico-chemical techniques, i.e., simultaneous TG-DTG-DSC, XRD, Mössbauer and IR spectroscopic techniques. Nano-particles of manganese ferrite, MnFe2O4, have been obtained as a result of solid-state reaction between a-Fe2O3 and MnO (intermediate species formed during thermolysis) at a temperature much lower than that for ceramic method. SEM analysis of final thermolysis product reveals the formation of monodisperse manganese ferrite nanoparticles with an average particle size of 35 nm. Magnetic studies show that these particles have a saturation magnetization of 1861G and Curie temperature of 300 °C. Lower magnitude of these parameters as compared to the bulk values is attributed to their smaller particle size.

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The thermal decomposition of iron(III) citrate pentahydrate, Fe(C6H5O7) · 5 H2O, has been investigated at different temperatures in air using Mössbauer spectroscopy, nonisothermal techniques (DTA-TG) and X-ray diffraction. The reduction of iron(III) to iron(II) takes place at 553 K. At higher temperature the formation of α-Fe2O3 and γ-Fe2O3 as the ultimate thermal decomposition products has been confirmed.

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