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Investigation of Crystalline Phases in the alpha-Fe2O3/alpha-Al2O3 System

Ristić, Mira; Popović, Stanko; Musić, Svetozar (2009) Investigation of Crystalline Phases in the alpha-Fe2O3/alpha-Al2O3 System. Croatica Chemica Acta, 82 (2). pp. 397-404. ISSN 0011-1643

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Abstract

Mixtures containing the desired weight ratios of alpha-Fe2O3 and gamma-AlOOH were homogenized in the planetary mill, then pressed into tablets and heated up to 1200 degrees C. All samples were characterized by X-ray diffraction, Mossbauer spectroscopy, Field emission scanning electron microscopy and Energy dispersive X-ray analysis. Two types of solid solutions of general formula alpha-(AlxFe1-x)(2)O-3 were found; one solid solution was closely related to alpha-Fe2O3, the other to alpha-Al2O3. The terminal solid solubility limits, r = 27.0 +/- 0.5 mole ratio of alpha-Al2O3 in alpha-Fe2O3 and r = 9.0 +/- 0.5 of alpha-Fe2O3 in alpha-Al2O3, were determined. The Mossbauer spectra showed a broadening of spectral lines and a decrease in the hyperfine magnetic field of alpha-Fe2O3 with incorporation of Al3+ ions in the alpha-Fe2O3 structure. For mole fractions between x = 0.40 and 0.70, the Mossbauer spectra were considered as the superposition of a sextet and quadrupole doublet(s). In this concentration range the samples showed an almost constant value of hyperfine magnetic field. For x = 0.90 and 0.93, the Mossbauer spectra were considered as a superposition of two quadrupole doublets, whereas for x = 0.95 the superposition of two quadrupole doublets and one singlet was considered. The origin of this singlet with the isomer shift close to zero is not clearly understood. FE-SEM showed a strong sintering effect on the particles in all samples in the alpha-(AlxFe1-x)(2)O-3 system.

Item Type: Article
Uncontrolled Keywords: solid solutions; alpha-Fe2O3; alpha-Al2O3; XRD; Fe-57 Mossbauer; FE-SEM; EDS; x-ray-diffraction; microstructural changes; lattice-parameters; mossbauer-spectra; monoclinic zro2; solid-solutions; alpha-al2o3; precursors
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Division of Materials Chemistry
Projects:
Project titleProject leaderProject codeProject type
Struktura i svojstva posebnih nanomaterijala dobivenih suvremenim tehnikama[50132] Antun Tonejc119-0982886-1009MZOS
Sinteza i mikrostruktura metalnih oksida i oksidnih stakala[85111] Mira Ristić098-0982904-2952MZOS
Depositing User: Mira Ristić
Date Deposited: 18 Oct 2013 08:52
Last Modified: 12 Feb 2014 11:24
URI: http://fulir.irb.hr/id/eprint/812

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