Heat capacity studies of the iron oxyhydroxides akaganéite (β-FeOOH) and lepidocrocite (γ-FeOOH)

Claine L. Snow; Stacey J. Smith; Brian E. Lang; Quan Shi; Juliana Boerio-Goates; Brian F. Woodfield; Alexandra Navrotsky

doi:10.1016/j.jct.2010.08.022

Heat capacity studies of the iron oxyhydroxides akaganéite (β-FeOOH) and lepidocrocite (γ-FeOOH)

Claine L. Snow, Stacey J. Smith, Brian E. Lang, Quan Shi, Juliana Boerio-Goates, Brian F. Woodfield, Alexandra Navrotsky

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

Abstract

The iron oxides and iron oxyhydroxides exist as several different polymorphs, and a thermodynamic understanding of these polymorphs can provide us with an understanding of their relative stability and chemical reactivity. This study provides heat capacity measurements for lepidocrocite (γ-FeOOH) over the temperature range (0.8 to 38) K and akaganéite (β-FeOOH) over the range (0.7 to 302) K. Fits of the heat capacity of the two samples below T = 15 K showed similar behavior to previously published fits of goethite (α-FeOOH), which required a linear term and an anisotropic gap parameter to model accurately the antiferromagnetic spin-wave contributions. The akaganéite measurements were compared to previously reported measurements all of which showed significant disagreement. It is believed that the measurements reported here are the most reliable. Also, the presence of adsorbed water contributes significantly to the heat capacity of akaganéite, and the standard molar entropy at T = 298.15 K of the hydrated form was calculated to be (81.8 ± 2) J · mol^-1 · K^-1.

Original language	English (US)
Pages (from-to)	190-199
Number of pages	10
Journal	Journal of Chemical Thermodynamics
Volume	43
Issue number	2
DOIs	https://doi.org/10.1016/j.jct.2010.08.022
State	Published - Feb 2011
Externally published	Yes

Keywords

Antiferromagnetic
Entropy
Iron oxide
Thermodynamic

ASJC Scopus subject areas

Atomic and Molecular Physics, and Optics
Materials Science(all)
Physical and Theoretical Chemistry

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10.1016/j.jct.2010.08.022

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title = "Heat capacity studies of the iron oxyhydroxides akagan{\'e}ite (β-FeOOH) and lepidocrocite (γ-FeOOH)",

abstract = "The iron oxides and iron oxyhydroxides exist as several different polymorphs, and a thermodynamic understanding of these polymorphs can provide us with an understanding of their relative stability and chemical reactivity. This study provides heat capacity measurements for lepidocrocite (γ-FeOOH) over the temperature range (0.8 to 38) K and akagan{\'e}ite (β-FeOOH) over the range (0.7 to 302) K. Fits of the heat capacity of the two samples below T = 15 K showed similar behavior to previously published fits of goethite (α-FeOOH), which required a linear term and an anisotropic gap parameter to model accurately the antiferromagnetic spin-wave contributions. The akagan{\'e}ite measurements were compared to previously reported measurements all of which showed significant disagreement. It is believed that the measurements reported here are the most reliable. Also, the presence of adsorbed water contributes significantly to the heat capacity of akagan{\'e}ite, and the standard molar entropy at T = 298.15 K of the hydrated form was calculated to be (81.8 ± 2) J · mol-1 · K-1.",

keywords = "Antiferromagnetic, Entropy, Iron oxide, Thermodynamic",

author = "Snow, {Claine L.} and Smith, {Stacey J.} and Lang, {Brian E.} and Quan Shi and Juliana Boerio-Goates and Woodfield, {Brian F.} and Alexandra Navrotsky",

note = "Funding Information: We would like to thank Lena Mazeina for the preparation of the akagan{\'e}ite sample. This work was financially supported by a grant from the Department of Energy (USA) under contract numbered DE-FG02-05ER15666 . ",

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language = "English (US)",

volume = "43",

pages = "190--199",

journal = "Journal of Chemical Thermodynamics",

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T1 - Heat capacity studies of the iron oxyhydroxides akaganéite (β-FeOOH) and lepidocrocite (γ-FeOOH)

AU - Snow, Claine L.

AU - Smith, Stacey J.

AU - Lang, Brian E.

AU - Shi, Quan

AU - Boerio-Goates, Juliana

AU - Woodfield, Brian F.

AU - Navrotsky, Alexandra

N1 - Funding Information: We would like to thank Lena Mazeina for the preparation of the akaganéite sample. This work was financially supported by a grant from the Department of Energy (USA) under contract numbered DE-FG02-05ER15666 .

PY - 2011/2

Y1 - 2011/2

N2 - The iron oxides and iron oxyhydroxides exist as several different polymorphs, and a thermodynamic understanding of these polymorphs can provide us with an understanding of their relative stability and chemical reactivity. This study provides heat capacity measurements for lepidocrocite (γ-FeOOH) over the temperature range (0.8 to 38) K and akaganéite (β-FeOOH) over the range (0.7 to 302) K. Fits of the heat capacity of the two samples below T = 15 K showed similar behavior to previously published fits of goethite (α-FeOOH), which required a linear term and an anisotropic gap parameter to model accurately the antiferromagnetic spin-wave contributions. The akaganéite measurements were compared to previously reported measurements all of which showed significant disagreement. It is believed that the measurements reported here are the most reliable. Also, the presence of adsorbed water contributes significantly to the heat capacity of akaganéite, and the standard molar entropy at T = 298.15 K of the hydrated form was calculated to be (81.8 ± 2) J · mol-1 · K-1.

AB - The iron oxides and iron oxyhydroxides exist as several different polymorphs, and a thermodynamic understanding of these polymorphs can provide us with an understanding of their relative stability and chemical reactivity. This study provides heat capacity measurements for lepidocrocite (γ-FeOOH) over the temperature range (0.8 to 38) K and akaganéite (β-FeOOH) over the range (0.7 to 302) K. Fits of the heat capacity of the two samples below T = 15 K showed similar behavior to previously published fits of goethite (α-FeOOH), which required a linear term and an anisotropic gap parameter to model accurately the antiferromagnetic spin-wave contributions. The akaganéite measurements were compared to previously reported measurements all of which showed significant disagreement. It is believed that the measurements reported here are the most reliable. Also, the presence of adsorbed water contributes significantly to the heat capacity of akaganéite, and the standard molar entropy at T = 298.15 K of the hydrated form was calculated to be (81.8 ± 2) J · mol-1 · K-1.

KW - Antiferromagnetic

KW - Entropy

KW - Iron oxide

KW - Thermodynamic

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Heat capacity studies of the iron oxyhydroxides akaganéite (β-FeOOH) and lepidocrocite (γ-FeOOH)

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