Abstract
Microwave–hydrothermal (MH) route was employed to synthesize various iron oxide phases in ultra-fine crystalline powders by using ferrous sulphate and sodium hydroxide as starting chemicals. All chemical reactions were carried out under identical MH conditions, namely, at 190°C, 154 psi, 30 min, by varying the molar ratio (MR) of FeSO4/NaOH in the aqueous solutions. The variation of MR has a dramatic effect on the crystallization behavior of various phases of iron oxides under MH processing conditions. For example, spherical agglomerates of Fe3O4 powder were obtained if MR equal to 0.133 (pH > 10 sample A). On the other hand non-stoichiometric Fe3O4 powders (Sample B) were obtained for all higher MR of FeSO4/NaOH between 0.133 and 4.00 (6.6 < pH < 10). However, when MR was equal to 4.0 (pH ≅ 6.6) a varied distribution of shapes and sizes of agglomerates of -Fe2O3 powders (sample C) were produced. Fe57 Mössbauer spectra were recorded for all the three sets of samples at room temperature. In the case of sample B, temperature dependent Mössbauer spectra were recorded in the range of 77–300 K to understand the non-stoichiometric nature of Fe3O4 powders. All these results are discussed in the present paper.
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Bakare, P.P., Date, S.K., Khollam, Y.B. et al. Mössbauer effect studies on the formation of iron oxide phases synthesized via microwave–hydrothermal route. Hyperfine Interact 168, 1127–1132 (2006). https://doi.org/10.1007/s10751-006-9458-3
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DOI: https://doi.org/10.1007/s10751-006-9458-3