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Fluorination and reduction of CaCrO3 by topochemical methods

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Title: Fluorination and reduction of CaCrO3 by topochemical methods
Authors: Juillerat, Christian A. Browse this author
Tsujimoto, Yoshihiro Browse this author
Chikamatsu, Akira Browse this author
Masubuchi, Yuji Browse this author →KAKEN DB
Hasegawa, Tetsuya Browse this author
Yamaura, Kazunari Browse this author
Issue Date: 14-Feb-2020
Publisher: Royal Society of Chemistry
Journal Title: Dalton transactions
Volume: 49
Issue: 6
Start Page: 1997
End Page: 2003
Publisher DOI: 10.1039/c9dt04321g
Abstract: Topochemical reactions between CaCrO3 and polyvinylidene difluoride yield the new fluorinated phase CaCrO2.5F0.5, which was characterized by powder synchrotron X-ray diffraction, X-ray photoemission spectroscopy, and magnetic susceptibility measurements. The reaction proceeds via reduced oxide intermediates, CaCrO2.67 and CaCrO2.5, in which CrO6 octahedral and CrO4 tetrahedral layers are stacked in a different manner along the c axis of CaCrO3. These two intermediate phases can be selectively synthesized by the carbothermal reduction with g-C3N4. Both CaCrO3 and CaCrO2.5F0.5 adopt the same orthorhombic space group, Pbnm; however, the fluorinated phase has decreased Cr-O-Cr bond angles as compared to the parent compound in both the ab plane and along the c-direction, which indicates an increased orthorhombic distortion due to the fluorination. While the oxygen vacancies are ordered in both intermediate phases, CaCrO2.67 and CaCrO2.5, a site preference for fluorine in the oxyfluoride phase cannot be confirmed. CaCrO3 and CaCrO2.5F0.5 undergo antiferromagnetic phase transitions involving spin canting, where the fluorination causes the transition temperature to increase from 90 K to 110 K, as a result of the competition between the increased octahedral tilting and the enhancement of superexchange interactions involving Cr3+ ions in the CaCrO2.5F0.5 structure.
Type: article (author version)
Appears in Collections:総合化学院 (Graduate School of Chemical Sciences and Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 辻本 吉廣

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