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Twin formation in hematite during dehydration of goethite

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Title: Twin formation in hematite during dehydration of goethite
Authors: Saito, Genki Browse this author →KAKEN DB
Kunisada, Yuji Browse this author →KAKEN DB
Nomura, Takahiro Browse this author →KAKEN DB
Sakaguchi, Norihito Browse this author →KAKEN DB
Akiyama, Tomohiro Browse this author →KAKEN DB
Keywords: Dehydration
Thermal decomposition
Twin boundary
Issue Date: Nov-2016
Publisher: Springer
Journal Title: Physics and chemistry of minerals
Volume: 43
Issue: 10
Start Page: 749
End Page: 757
Publisher DOI: 10.1007/s00269-016-0831-8
Abstract: Twin formation in hematite during dehydration was investigated using X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy (TEM). When synthetic goethite was heated at different temperatures between 100 and 800 degrees C, a phase transformation occurred at temperatures above 250 degrees C. The electron diffraction patterns showed that the single-crystalline goethite with a growth direction of [001](G) was transformed into hematite with a growth direction of [100](H). Two non-equivalent structures emerged in hematite after dehydration, with twin boundaries at the interface between the two variants. As the temperature was increased, crystal growth occurred. At 800 degrees C, the majority of the twin boundaries disappeared; however, some hematite particles remained in the twinned variant. The electron diffraction patterns and high-resolution TEM observations indicated that the twin boundaries consisted of crystallographically equivalent prismatic (100) (010), and (10) planes. According to the total energy calculations based on spin-polarized density functional theory, the twin boundary of prismatic (100) screw had small interfacial energy (0.24 J/m(2)). Owing to this low interfacial energy, the prismatic (100) screw interface remained after higher-temperature treatment at 800 degrees C.
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Type: article (author version)
Appears in Collections:エネルギー・マテリアル融合領域研究センター (Center for Advanced Research of Energy and Material) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 齊藤 元貴

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