A kinetic analysis of the transformation from akaganeite to hematite: An in situ time-resolved X-ray diffraction study

Peterson, Kristina M.; Heaney, Peter J.; Post, Jeffrey E.

doi:10.1016/j.chemgeo.2016.09.017

Cited by 21 publications

(21 citation statements)

References 66 publications

(105 reference statements)

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“…The scale factor of a phase is directly linked to the total amount of the corresponding phase. The scale factor can then be used to model the growth mechanism using Equation (1), with the normalized scale factor being the measure of the extent of the reaction [30]. Fits of Equation (1) to the scale factors are presented in Figure S5 and the refined values are summarized in Table 2.…”

Section: Kinetics Of the Reactionsmentioning

confidence: 99%

Facile Low Temperature Hydrothermal Synthesis of BaTiO3 Nanoparticles Studied by In Situ X-ray Diffraction

et al. 2018

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Ferroelectric materials are crucial for today's technological society and nanostructured ferroelectric materials are important for the downscaling of devices. Controlled and reproducible synthesis of these materials are, therefore, of immense importance. Hydrothermal synthesis is a well-established synthesis route, with a large parameter space for optimization, but a better understanding of nucleation and growth mechanisms is needed for full utilization and control. Here we use in situ X-ray diffraction to follow the nucleation and growth of BaTiO 3 formed by hydrothermal synthesis using two different titanium precursors, an amorphous titania precipitate slurry and a Ti-citric acid complex solution. Sequential Rietveld refinement was used to extract the time dependency of lattice parameters, crystallite size, strain, and atomic displacement parameters. Phase pure BaTiO 3 nanoparticles, 10-15 nm in size, were successfully synthesized at different temperatures (100, 125, and 150 • C) from both precursors after reaction times, ranging from a few seconds to several hours. The two precursors resulted in phase pure BaTiO 3 with similar final crystallite size. Finally, two different growth mechanisms were revealed, where the effect of surfactants present during hydrothermal synthesis is discussed as one of the key parameters.

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Section: Kinetics Of the Reactionsmentioning

confidence: 99%

Facile Low Temperature Hydrothermal Synthesis of BaTiO3 Nanoparticles Studied by In Situ X-ray Diffraction

et al. 2018

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“…In Peterson et al . (2016), we presented a kinetic analysis of the hydrothermal nucleation and growth of akaganeite and its transformation to hematite. In the present paper, we describe the changes in crystal structure that accompany these reactions using TR-XRD and Rietveld analysis.…”

Section: Introductionmentioning

confidence: 99%

“…We used synchrotron diffraction with a sealed autoclave cell to conduct TR-XRD experiments in situ . The data presented are part of a larger study of the transformation of akaganeite to hematite (Peterson et al ., 2016).…”

Section: Introductionmentioning

confidence: 99%

Evolution in the structure of akaganeite and hematite during hydrothermal growth: anin situsynchrotron X-ray diffraction analysis

2018

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Synchrotron X-ray diffraction was used to monitor the hydrothermal precipitation of akaganeite (β-FeOOH) and its transformation to hematite (Fe2O3) in situ. Akaganeite was the first phase to form and hematite was the final phase in our experiments with temperatures between 150 and 200 °C. Akaganeite was the only phase that formed at 100 °C. Rietveld analyses revealed that the akaganeite unit-cell volume contracted until the onset of dissolution, and subsequently expanded. This reversal at the onset of dissolution was associated with a substantial and rapid increase in occupancy of the Cl site, perhaps by OH− or Fe3+. Rietveld analyses supported the incipient formation of an OH-rich, Fe-deficient hematite phase in experiments between 150 and 200 °C. The inferred H concentrations of the first crystals were consistent with “hydrohematite.” With continued crystal growth, the Fe occupancies increased. Contraction in both a- and c-axes signaled the loss of hydroxyl groups and formation of a nearly stoichiometric hematite.

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“…The scale factor is directly linked to the total amount of the corresponding phase. The scale factor can then be used to model the growth mechanism using Equation 1, with the normalized scale factor being the measure of the extent of the reaction [29]. Fits of Equation 1 to the scale factors are presented in Figure S4, and the refined values are summarized in Table 2.…”

Section: Kinetics Of the Reactionsmentioning

confidence: 99%

Facile Low Temperature Hydrothermal Synthesis of BaTiO<sub>3</sub> Nanoparticles Studied by <em>In Situ</em> X-ray Diffraction

Grendal¹,

Blichfeld²,

Skjarvø³

et al. 2018

Preprint

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Ferroelectric materials are crucial for today’s technological society, and nanostructured ferroelectric materials are important for downscaling of devices. Controlled and reproducible synthesis of these materials are therefore of immense importance. Hydrothermal synthesis is a well-established synthesis route, with a large parameter space for optimization, but a better understanding of nucleation and growth mechanisms is needed for full utilization and control. Here we use in situ X-ray diffraction to follow the nucleation and growth of BaTiO3 formed by hydrothermal synthesis using two different titanium precursors, an amorphous titania precipitate slurry and a Ti-citric acid complex solution. Sequential Rietveld refinement was used to extract the time dependency of lattice parameters, crystallite size, strain and atomic displacement parameters. Phase pure BaTiO3 nanoparticles 10 - 15 nm in size were successfully synthesized at different temperatures (100, 125, and 150 °C) from both precursors after reaction times ranging from a few seconds, to several hours. The two precursors resulted in phase pure BaTiO3 with similar final crystallite size. Finally, two different growth mechanisms were revealed, where the effect of surfactants present during hydrothermal synthesis is discussed as one of the key parameters.

show abstract

A kinetic analysis of the transformation from akaganeite to hematite: An in situ time-resolved X-ray diffraction study

Cited by 21 publications

References 66 publications

Facile Low Temperature Hydrothermal Synthesis of BaTiO3 Nanoparticles Studied by In Situ X-ray Diffraction

Facile Low Temperature Hydrothermal Synthesis of BaTiO3 Nanoparticles Studied by In Situ X-ray Diffraction

Evolution in the structure of akaganeite and hematite during hydrothermal growth: anin situsynchrotron X-ray diffraction analysis

Facile Low Temperature Hydrothermal Synthesis of BaTiO<sub>3</sub> Nanoparticles Studied by <em>In Situ</em> X-ray Diffraction

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