Synthesis and decomposition of ferrous oxalato hydrazinate precursors to obtain magnetic oxides

Abstract

The preparation of gamma-Fe2O3 from the thermal decomposition of ferrous oxalate dihydrate and ferrous oxalato hydrazinate precursors was studied employing differential thermal analysis (DTA), X-ray diffraction (XRD), infrared and magnetic susceptibility measurements. Ferrous oxalate dihydrate was precipitated from solution following the standard precipitation technique. The synthesis of ferrous oxalato hydrazinate was carried out by two methods. The wet chemical method reported in the literature was adopted to precipitate the compound from ferrous chloride solution. In the second method ferrous oxalate dihydrate was equilibrated with hydrazine hydrate vapour in a desiccator. The resultant product was found to be anhydrous ferrous oxalato hydrazinate. The decomposition end-products of these complexes were X-ray characterized and magnetic measurements were done. Ferrous oxalate dihydrate yielded mainly gamma-Fe2O3 upon controlling the atmosphere during decomposition. However, autocatalytic decomposition of hydrazinated complexes formed a mixture of gamma-Fe2O3 and alpha-Fe2O3. Efforts were made to increase the gamma-Fe2O3 content by controlling the atmosphere during decomposition of these complexes.