Synthesis and characterization of magnetite powders obtained by the solvothermal method: Influence of the Fe3+ concentration

Nonstoichiometric magnetite particles are prepared via a polyol process using ethylene glycol as a solvent and reducing agent. The powders are investigated by XRD, SEM, Mössbauer spectroscopy and SQUID magnetometry. The influence of the initial concentration of Fe3+ ions on both particle size and morphology is investigated. For 0.1 and 0.3 mol L−1 concentrations, the particles are spherical (with a diameter between 100 and 350 nm) and composed of nanocrystallites (sized between 20 and 43 nm). For 0.8 mol L−1 concentration, the particles are quasi-monocrystalline compact spheres with a diameter between 100 and 250 nm. XRD analysis and Mössbauer spectroscopy show that the smaller the crystallites are, the more oxidized the samples are. The saturation magnetization decreases when the particle size decreases and when the oxidation degree increases.

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► Ethylene glycol allows a partial reduction of Fe3+ ions by solvothermal process.
► Magnetite can be obtained by this way.
► Initial iron concentration change particles morphology.