Nickel–iron and zinc–iron bimetal oxalates: preparation, characterization and thermal decomposition to spinel ferrites

A systematic investigation of Ni and Zn spinel ferrites preparation via oxalate route, involving a detailed characterization of synthesized precursors, in situ study of thermally induced decomposition reactions and analyses of the prepared ferrites is presented. Although the oxalate route in general is rather well known, the detailed investigations of the decomposition reactions of the well-characterized bimetal oxalate precursors have been mostly omitted by the authors. The formation of the solid solution, i.e., the incorporation of both metals into the single oxalate crystal structure, is essential for the subsequent decomposition reaction and synthesis of pure spinel ferrites. The optimally prepared precursor decomposes in a single reaction step at relatively low temperatures, evading the undesirable sintering, and allowing the preparation of microporous/mesoporous ferrites with relatively high BET areas.