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0797–0808 (2014)

PACS numbers: 61.05.Qr, 75.50.Tt, 76.80.+y, 81.07.Wx, 81.16.Be, 81.40.Rs, 82.80.Ej

Fine-dispersed powders of magnetite are obtained by means of the two methods, which differ with each other by row productsreagents for its synthesis. Within the first method, a mixture of aqueous solutions of ferrous chloride (FeCl2) and ferric chloride (FeCl3) is precipitated using concentrated NH4OH to pH???8.010.0, and within the second method, a chemically-pure Mohrs salt (Fe(NH4)2(SO4)2?6H2O) and FeCl3 solutions are used, and the deposition is carried out similarly as within the first method. Fine-dispersed powders with particle sizes from 5 to 25 nm are obtained. Some portions of powders are subjected to heat treatment in air at temperatures of 473, 573 and 673 K. Such annealing leads to the formation of ?-Fe2O3. The annealing of fine-dispersed powder fabricated from the chloride solutions in a vacuum of 10?5 mmHg at 773 K for 20 hours leads to formation of single-phase Fe3O4 magnetite, for which phase transition is observed that was established within the recoilless nuclear resonance fluorescence measurements.

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