THERMAL-DECOMPOSITION OF ZINC-IRON CITRATE PRECURSOR

A citrate precursor technique has been used to synthesize ultrafine particles of zinc ferrite (ZnFe2O4). The precursor, Zn3Fe6(C6H5O7)(8) .(12 + n)H2O, was studied using thermoanalytical techniques. It was found that decomposition in air was suitable for obtaining ZnFe2O4. The thermal decomposition involved seven steps, with the citrate precursor first losing the adsorbed and coordinated water molecules. In subsequent steps, the citrate groups lost water molecules to form metal aconitates, which further decomposed in the temperature range 260-320 degrees C to give hydrozincite and FeO . OH, These intermediates decomposed further with the formation of ZnO and Fe2O3, along with the evolution of CO2 and H2O. A further step involved the formation of ZnFe2O4 in the temperature range 460-560 degrees C at the expense of the ZnO and Fe2O3 phases. The citrate precursor and decomposed products were analysed by IR and X-ray diffraction techniques.