Shape effects on crystallite size distributions in synthetic hematites from X-ray line-profile analysis

Duvigneaud, Paul-Henri; Derie, René

doi:10.1016/0022-4596(80)90430-2

Cited by 45 publications

(23 citation statements)

References 12 publications

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“…TEM images reveal that the 57 hematite is a mixture of acicular crystals 200×20 nm and rounded hexagonal plates 100-200 nm in diameter. Hexagonal plates are more typical of this synthesis method (dehydration of ferrihydrite), and we suspect the acicular hematite formed from a topotactic dehydration of a precursor goethite [15], which also forms via dehydration of ferrihydrite [13].…”

Section: Resultsmentioning

confidence: 98%

Morin transition suppression in Polycrystalline 57Hematite (α-Fe2O3) exposed to 56Fe(II)

Larese-Casanova

Scherer

2007

Hyperfine Interact

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Section: Resultsmentioning

confidence: 98%

Morin transition suppression in Polycrystalline 57Hematite (α-Fe2O3) exposed to 56Fe(II)

Larese-Casanova

Scherer

2007

Hyperfine Interact

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“…Bars denote 500 nm and with dimensions of ~ 60 nm. None of the hematite particles contain macropores which commonly occur in hematites grown from thermal decomposition of goethites at moderate temperatures (Watari et al 1979;Duvigneaud and Derie 1980;Naono and Fujiwara 1980;Rendon et al 1983). …”

Section: Characterization Of the Samplesmentioning

confidence: 98%

Mössbauer effect study of the spin structure in natural hematites

Grave

Vandenberghe

1990

Phys Chem Minerals

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Abstract. Three natural hematites, ~-F%O3, from the region of Elba have been investigated by means of SVFe M6ssbauer spectroscopy at variable temperatures between 80 and 400K. The samples were selected on the basis of their different morphology as observed from powder X-ray diffraction and transmission electron microscopy. The mean crystallite diameters (MCD) along [104] are 1000, 280 and 40 nm respectively. Energy-dispersive analyses of X-rays revealed the presence of minor amounts of Si impurities in those two hematites having the largest MCD. All three hematites show the coexistence at low temperatures of antiferromagnetic-like (AF) and weakly-ferromagnetic-like (WF) spin states. The saturation values of the AF and WF magnetic hyperfine fields and quadrupole shifts have been determined, from which conclusions are drawn concerning the spin structure in relation to the crystallinity of the samples. The variations of the hyperfine parameters in the Morin-transition region indicate a gradual reorientation of both AF and WF spins towards the basal plane. As expected, the Morin transition itself is affected by the particle size. The two hematites exhibiting the largest particle dimensions still show an AF contribution for T > 270K. It is suggested, and argued that this unusual behaviour is due to the presence of Si 4+, and hence Fe 2+, in the lattice. The characteristic M6ssbauer temperatures and the intrinsic isomer shifts were evaluated from the temperature variation of the observed isomer shifts. Both parameters are not significantly affected by the morphology and are in excellent agreement with data obtained for synthetic hematites.

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“…Two hundred and seventy milligrams of 56 goethite were added to 5.4 ml of 8.0 M NaOH solution within a pressure-sealed Teflon container and heated to 250°C for 6 h. After cooling, the red-purple precipitate was centrifuged at 10,000g, washed in deionized water, centrifuged again, and dried for 3 days at 100°C. 56 Hematite needles were converted from acicular 56 goethite by heating to 450°C for 24 h (Duvigneaud and Derie, 1980). 56 Magnetite was synthesized according to a modified method of Fe(II)-Fe(III) coprecipitation (Cornell and Schwertmann, 2003).…”

Section: Reagentsmentioning

confidence: 99%

Heterogeneous oxidation of Fe(II) on iron oxides in aqueous systems: Identification and controls of Fe(III) product formation

Larese-Casanova

Kappler

Haderlein

2012

Geochimica et Cosmochimica Acta

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Shape effects on crystallite size distributions in synthetic hematites from X-ray line-profile analysis

Cited by 45 publications

References 12 publications

Morin transition suppression in Polycrystalline 57Hematite (α-Fe2O3) exposed to 56Fe(II)

Morin transition suppression in Polycrystalline 57Hematite (α-Fe2O3) exposed to 56Fe(II)

Mössbauer effect study of the spin structure in natural hematites

Heterogeneous oxidation of Fe(II) on iron oxides in aqueous systems: Identification and controls of Fe(III) product formation

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