Sequence of phases in the hydrothermal synthesis of zinc-doped magnetite system

Hydrothermal techniques have been used to synthesize samples of ZnxFe3−xO4 (x = 0.0–1.0) starting with ZnSO4·7H2O/FeSO4·7H2O aqueous solution. The sequence of phases, structural and magnetic properties were followed by X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). Refinement of the XRD spectra yielded the dependence of the lattice parameters of zinc-doped magnetite and zinc ferrite phase as function of the Zn molar concentration x. As well, the particle diameter was derived and represented as a function of Zn content x. As a function of Zn concentration, the phase content of hydrothermally synthesized samples was found to consist of zinc-doped magnetite, goethite and zinc ferrite. Consistent with the XRD results, Mössbauer spectroscopy data indicate the presence of magnetite and goethite at x ≤ 0.2, magnetite and zinc ferrite at x ≤ 0.9 and pure zinc ferrite only at high zinc concentrations. The presence of different magnetite phases was confirmed by TEM and particles with a size of 50 nm were identified. Our results show that zinc ferrite is formed at high zinc concentration by the hydrothermal method and an acicular component of goethite–magnetite is obtained at low zinc content.