Influence of the precursors on the formation and the properties of ZnFe2O4

The phase ZnFe2O4, franklinite, with spinel structure, has been synthesised using solid-state reactions from the mechanically mixed powders of several precursor salts. However, this method requires a high-temperature treatment for some hours to homogenise the whole composition to obtain a single phase. In this paper ZnFe2O4 has been prepared by the ceramic method using different precursors of Fe and Zn. The spinel has also been prepared by a citrate route that allows to prepare a homogeneous single phase at lower temperature and shorter annealing time. The citrate method has let to obtain single phase of ZnFe2O4 at 600 degrees C/2h. In addition, this processing increases the inversion grade with respect to the ceramic ones obtained with the same precursor salts. The samples have been studied and characterised by means of differential thermal analysis (DTA), thermal gravimetric analysis (TGA), powder X-ray diffraction (XRD), Rietveld refinement method, Mossbauer spectroscopy, scanning electron microscopy (SEM), energy dispersion of X-ray spectrometry (EDX) and magnetic measurements. The inversion grade has been detected by means of Rietveld analyses and corroborated by magnetic measurements. (C) 1999 Published by Elsevier Science Limited. All rights reserved.