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- Title
Fe-bearing vanadium dioxide–paramontroseite: structural details and high-temperature transformation.
- Authors
Curetti, Nadia; Pavese, Alessandro
- Abstract
A natural sample of Fe-bearing paramontroseite (V 0.84 Fe 0.19 Al 0.03 O 2 ; a = 4.8960(14), b = 9.395(3), c = 2.9163(5) Å, V = 134.14(6) Å 3 ; space group Pbnm) from Prachovice mine (Czech Republic) was investigated to shed light on cation partitioning and behavior upon heating. XRD experiments showed that V and Fe are not vicariant of one another, as V occupies the octahedral site at (0.09, 0.14, 0.25), whereas Fe enters a tetrahedral site at (0.41, 0.06, 0.25), the latter expected to be empty in the ideal structure. Thermal expansion is anisotropic, leading to the following β coefficients: -2.0×10-5 , 3.0×10-5 , 0.8×10-5 and 1.8×10-5 ∘ C -1 for a , b , c and V , respectively. At T higher than 350 ∘ C, V undergoes oxidation, from [4 + ] to [5 + ], and paramontroseite decomposes into Fe-tetrapolyvanadate (Fe 2 V 4 O 13) and V-pentoxide (V 2 O 5). µ -Raman spectroscopy analyses confirmed that paramontroseite is sensitive to heating: the crystal surface invested by the laser beam degrades very quickly, leading to the phases revealed by diffraction measurements. There is no evidence for the formation at high T of a rutile-type phase, as we observed for iso-structural ramsdellite MnO 2.
- Subjects
CRYSTAL surfaces; LASER beams; SPACE groups; X-ray diffraction; THERMAL expansion; VANADIUM
- Publication
European Journal of Minerology, 2023, Vol 35, Issue 3, p373
- ISSN
0935-1221
- Publication type
Article
- DOI
10.5194/ejm-35-373-2023