The magnetic structure and hyperfine field of goethite ($\alpha$-FeOOH)

Forsyth, J. B.; Hedley, Ian; Johnson, C. E.

doi:10.1088/0022-3719/1/1/321

Cited by 174 publications

(113 citation statements)

References 13 publications

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“…These trends were observed also for goethites synthesized at 40~ where HRTGA showed a greater contribution of surface hydroxyls to the overall dehydration-dehydroxylation for samples aged at pH 11 (e.g., see Figure 2). These findings are consistent with Forsyth et al (1968) and Goss (1987) where water in excess of stoichiometric predictions was measured for goethite dehydroxylation.…”

Section: Morphology and Surface Dehydrationdehydroxylationsupporting

confidence: 90%

Distinguishing Between Surface and Bulk Dehydration-Dehydroxylation Reactions in Synthetic Goethites by High-Resolution Thermogravimetric Analysis

Ford

Bertsch

1999

Clays and clay miner.

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Abstract--Synthetic goethites studied by high-resolution thermogravimetry (HRTGA) show variability in surface characteristics and structural stability as a function of aging conditions. Goethites were synthesized at either pH 6 or 11, at temperatures of 40 or 70~ and in the presence or absence of sorbed Mn or Pb. Data from HRTGA analysis revealed at least four distinct weight-loss events near goethite dehydroxylation that relate to 1) three events involving the evolution of water associated with surface Fe-O functional groups and 2) bulk dehydroxylation of goethite during transformation to hematite. The relative mass of evolved surface and bulk structural water was related to the predominant particle morphology as determined by transmission electron microscopy (TEM). Differentiation of surface and bulk decomposition reactions allowed the identification of bulk structural dehydroxylation. Goethite crystallinity, estimated by the bulk dehydroxylation temperature, appeared to depend on the kinetics of crystallization. This trend was most evident for systems aged at pH 11 and 40~ Greater concentrations of coprecipitated Mn or Pb dramatically improved goethite crystallinity as indicated by higher dehydroxylation temperatures and smaller widths of the (110) Bragg reflection. Comparison of bulk dehydroxylation temperatures for these samples to other preparations suggests that structural defects predominated over the effects of particle size and Mn/Pb substitution in determining goethite thermal stability. A conceptual model is proposed to account for the disparate dehydroxylation profiles displayed by goethites of varying crystallinity.

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Section: Morphology and Surface Dehydrationdehydroxylationsupporting

confidence: 90%

Distinguishing Between Surface and Bulk Dehydration-Dehydroxylation Reactions in Synthetic Goethites by High-Resolution Thermogravimetric Analysis

Ford

Bertsch

1999

Clays and clay miner.

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“…The crystal structure of goethite is orthorhombic with space group Pnma. The magnetic properties of goethite have been studied extensively by Mössbauer spectroscopy, [1][2][3][4][5][6][7][8][9][10][11] magnetization measurements [9,11,12] and neutron scattering. [1,11,13,14] The magnetic properties of nanocrystalline goethite samples often differ from those of non-interacting nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

“…In goethite nanoparticles the dependence of magnetic fluctuations on particle volume and the temperature is usually not in accordance with Eq. (1). The reason for the anomalous behavior of goethite can be explained by inter-particle interactions and by magnetic fluctuations in interacting grains in the interior of the particles.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Particle Size Dependence of Magnetic Relaxation Phenomena in Goethite Nanoparticles

Frandsen¹,

Madsen²,

Boothroyd³

et al. 2015

Croat. Chem. Acta

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By use of Mössbauer spectroscopy we have studied the magnetic properties of samples of goethite nanoparticles with different particle size. The spectra are influenced by fluctuations of the magnetization directions, but the size dependence is not in accordance with the Néel-Brown expression for superparamagnetic relaxation of the magnetization vectors of the particles as a whole. The data suggest that the magnetic fluctuations can be explained by fluctuations of the magnetization directions of small interacting grains within the particles.

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“…It should be noted that ␣-GaO(OH) is also a structural analogue of a group of previously studied oxidic hydrates, such as ␣-ScO(OH), 30 groutite (␣-MnO(OH)), 31 and goethite (␣-FeO(OH)). [32][33][34][35] Avivi et al 36 produced so-called rolled-up tubular particles of ␣-GaO(OH) after exposing a 0.114M aqueous solution of GaCl 3 to ultrasonic irradiation for 6 h, by inserting the titanium horn of an ultrasonic finger into this solution. The same authors repeated the above procedure for InCl 3 solutions (0.68M), but this time 37 to form rodlike In(OH) 3 particles.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Gallium Oxide Hydroxide Crystals in Aqueous Solutions with or without Urea and Their Calcination Behavior

Taş

Majewski

Aldinger

2002

Journal of the American Ceramic Society

159

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Gallium oxide hydroxide (GaOOH⅐xH 2 O) single crystals were synthesized in aqueous solutions by using two different precipitation techniques: homogeneous decomposition of urea and forced hydrolysis in pure water. Precipitation of crystals started at exactly the same pH value (i.e., 2.05 at 85°C) in both cases. The morphology of crystals turned out to be quite different (zeppelin-like with urea, rodlike without urea) in each of the above methods. Calcination of these gallium oxide hydroxide crystals in air at temperatures >500°C transformed them into Ga 2 O 3 . Characterization of the samples was performed by X-ray diffractometry, scanning electron microscopy, thermogravimetry/differential thermal analysis, Fourier transform infrared spectroscopy, and ICP, carbon, and nitrogen analyses.

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The magnetic structure and hyperfine field of goethite ($\alpha$-FeOOH)

Cited by 174 publications

References 13 publications

Distinguishing Between Surface and Bulk Dehydration-Dehydroxylation Reactions in Synthetic Goethites by High-Resolution Thermogravimetric Analysis

Distinguishing Between Surface and Bulk Dehydration-Dehydroxylation Reactions in Synthetic Goethites by High-Resolution Thermogravimetric Analysis

Anomalous Particle Size Dependence of Magnetic Relaxation Phenomena in Goethite Nanoparticles

Synthesis of Gallium Oxide Hydroxide Crystals in Aqueous Solutions with or without Urea and Their Calcination Behavior

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