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Phase Transition of Electrooxidized Fe_3O_4 to γ and α-Fe_2O_3 Nanoparticles Using Sintering Treatment

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Kazeminezhad I., Mosivand S.

vol. 125

issue 5

1210-1214

In this work, electrosynthesis of Fe_3O_4 nanoparticles was carried out potentiostatically in an aqueous solution of C_4H_{12}NCl which acts as supporting electrolyte and electrostatic stabilizer. γ-Fe_2O_3 nanoparticles were synthesized by controlling oxidation of the electrooxidized Fe_3O_4 nanoparticles at different temperature. Finally the phase transition to α-Fe_2O_3 nanoparticles was performed at high temperatures using sintering treatment. The synthesized particles were characterized using X-ray diffraction, Fourier transformation, infrared scanning electron microscopy with energy dispersive X-ray analysis, and vibrating sample magnetometry. Based on the X-ray diffraction results, the transition from Fe_3O_4 to cubic and tetragonal γ-Fe_2O_3 was performed at 200C and 650°C, respectively. Furthermore, phase transition from metastable γ-Fe_2O_3 to stable α-Fe_2O_3 with rhombohedral crystal structure was approved at 800°C. The existence of the stabilizer molecules at the surface of Fe_3O_4 nanoparticles was confirmed by Fourier transformation infrared spectroscopy. According to scanning electron microscopy images, the average particles size was observed around 50 nm for electrooxidized Fe_3O_4 and γ-Fe_2O_3 nanoparticles prepared at sintering temperature lower than 900°C, however by raising sintering temperature above 900C the mean particles size increases. Energy dispersive X-ray point analysis revealed that the nanoparticles are almost pure and composed of Fe and O elements. According to the vibrating sample magnetometry results, saturation magnetization, coercivity field, and remnant magnetization decrease by phase transition from Fe_3O_4 to Fe_2O_3.

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1 Acta Physica Polonica A

1 2014

1 Kazeminezhad I.

1 Mosivand S.

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Phase Transition of Electrooxidized Fe_3O_4 to γ and α-Fe_2O_3 Nanoparticles Using Sintering Treatment