Study on the formation of Co1−xZnxFe2O4 system using two low-temperature synthesis methods

This paper deals with the synthesis of cobalt–zinc ferrite Co1−xZnxFe2O4 (x = 0.5), by two different synthesis methods: thermal decomposition of carboxylate complex, and co-precipitation. The effect of temperature on the characteristics of the obtained powders was investigated by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and magnetic measurements. Thermal analysis was used to investigate metal carboxylate complex formation and their thermal stability. The mixture of Co(II), Zn(II), and Fe(III) carboxylates (precursor) decomposed at 300 °C was annealed at 350, 500, and 1000 °C. The XRD patterns revealed that all powders consist of the spinel phase Co1−xZnxFe2O4. As the annealing temperature increased, the crystallite size, lattice parameter, and saturation magnetization were increased. Co-precipitation method was used to synthesize samples at different temperatures: 25, 40, 60, and 80 °C. X-ray diffractometry proved that cobalt–zinc ferrite was formed starting with 25 °C, while the ferritization process was almost completed at 80 °C. The precipitate obtained at 80 °C was annealed at 500 and 1000 °C. At 80 and 500 °C, the powders have similar crystallite size (~9 nm) and similar lattice parameter (a = 8.37 Å) and show a super-paramagnetic behavior. Powders obtained by both methods, at 1000 °C, have close values for the saturation magnetization σ (~60 emu g−1) and tend to have super-paramagnetic behavior (coercive field Hc = 0.08 kOe). The lattice parameter has also similar values, corresponding to the Co0.5Zn0.5Fe2O4 composition (a = 8.40 Å). Thermal decomposition of carboxylate complexes is a new method for the obtaining of Co0.5Zn0.5Fe2O4 ferrite. The results are comparable to those obtained by co-precipitation, starting from the same reagents (metal nitrates). The magnetic behavior makes this nanoferrite suitable for applications such as preparation of ferrofluids and hyperthermia for cancer treatment.