On the monoclinic distortion of β-anhydrite CaSO4

β-anhydrite, the stable form of CaSO4, is a common mineral and a key phase in gypsum's dehydration mechanism. An in-depth multi-scale investigation of its structure by powder X-ray diffraction revealed a very slight distortion of the crystal cell at room temperature (β = 90.092(9) °), that led...

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Veröffentlicht in:Solid state sciences Jg. 108; S. 106399
Hauptverfasser: Beaugnon, Florian, Quiligotti, Sara, Chevreux, Sylviane, Wallez, Gilles
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Elsevier Masson SAS 01.10.2020
Elsevier
Schlagworte:
Anhydrite
Chemical Sciences
Crystal structure
Gypsum
Phase transition
Rietveld method
X-ray diffraction
Gypsum
X-ray diffraction
Rietveld method
Anhydrite
Crystal structure
Phase transition
crystal structure
phase transition
gypsum
anhydrite
ISSN:1293-2558, 1873-3085
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Zusammenfassung:β-anhydrite, the stable form of CaSO4, is a common mineral and a key phase in gypsum's dehydration mechanism. An in-depth multi-scale investigation of its structure by powder X-ray diffraction revealed a very slight distortion of the crystal cell at room temperature (β = 90.092(9) °), that led to rule out the commonly admitted orthorhombic model (space group Cmcm) in favor of monoclinic C2/c subgroup. According to high-temperature XRD, the structure resumes however the orthorhombic symmetry around 400 °C. [Display omitted] •The first evidence of a lattice distortion in β-anhydrite.•A “pseudo tetragonal – pseudo orthorhombic” monoclinic symmetry.•A second-order phase transition is observed around 400 °C.
ISSN:1293-2558
1873-3085
DOI:10.1016/j.solidstatesciences.2020.106399