Abstract

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Samples of hematite (α-Fe2O3) nanoparticles (HTW) have been synthesized through a modified sol-gel method in Tween 20 (a polysorbate surfactant), separate portions of the powders were annealed at three different temperatures (400, 500 and 600 °C). The samples were characterized by X-ray diffraction (XRD), high-resolution electron microscopy (HRTEM), Mössbauer spectroscopy and by means of a vibrating sample magnetometer (VSM). In addition, all the characterization techniques used showed the formation of phases of hematite nanoparticles with improved purity and crystallinity after higher temperature annealing. The nanoparticle size range was between 16 and 27 nm indicating good size control for Tween 20. The BET specific surface area ranged between 17 and 37 m2 g -1 which is also good for synthesis via solution route. The saturation magnetization and and mӧssbauer analysis both support the presence in the sample at lower annealing temperature of the presence of impurities of maghemite (γ-Fe2O3). Of particular note was the ability of Tween 20 to control the growth of the particles so that grain sizes well below 15 nm were obtained. Thus, Tween 20, when used as a surfactant in the sol-gel route, can serve to improve the physical properties of synthesized hematite nanoparticles.

Keywords: hematite; nanoparticles; Mössbauer spectroscopy; magnetic properties; Tween 20;