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Phase transitions in hydroxide perovskites: a Raman spectroscopic study of stottite, FeGe(OH)(6), to 21 GPa

DOI: 10.1180/minmag.2012.076.4.11 DOI Help

Authors: Annette Kleppe (Diamond Light Source) , Mark Welch (Natural History Museum) , W. A. Crichton (ESRF, France) , A.P. Jephcoat (University of Oxford, U.K.)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Mineralogical Magazine , VOL 76 (4) , PAGES 949-962

State: Published (Approved)
Published: August 2012

Abstract: The effect of pressure on the naturally occurring hydroxide-perovskite stottite, FeGe(OH)(6), has been studied in situ by micro-Raman spectroscopy to 21 GPa at 300 K. The ambient spectrum contains six OH-stretching bands in the range 3064-3352 cm(-1). The presence of six non-equivalent OH groups is inconsistent with space group P4(2)/n. In view of this inconsistency a new ambient structure determination of stottite from Tsumeb was carried out, but this did not allow the clear rejection of P4(2)/n symmetry. However, a successful refinement was also carried out in space group P2/n, a subgroup of P4(2)/n, which allows for six non-equivalent 0 atoms. The two refinements are of comparable quality and do not allow a choice to be made based purely on the X-ray data. However, taken with the ambient and 150 K Raman spectra, a good case can be made for stottite having P2/n symmetry at ambient conditions. On this basis, the pressure induced spectroscopic changes are interpreted in terms of a reversible phase transition P2/n <-> P4(2)/n.

Journal Keywords: Stottite; Hydroxide Perovskites; High-Pressure; Diamond-Anvil Cell; Raman Spectroscopy ; X-Ray Diffraction

Subject Areas: Chemistry

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