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

Published online by Cambridge University Press:  05 July 2018

A. K. Kleppe ,
M. D. Welch ,
W. A. Crichton  and
A. P. Jephcoat
A. K. Kleppe*
Affiliation:
Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
M. D. Welch
Affiliation:
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
W. A. Crichton
Affiliation:
European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP 220, Grenoble Cedex, F-38043, France
A. P. Jephcoat
Affiliation:
Department of Earth Sciences University of Oxford, South Parks Road, Oxford OX1 3AN, UK
*
*E-mail: [email protected]
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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 P42/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 P42/n symmetry. However, a successful refinement was also carried out in space group P2/n, a subgroup of P42/n, which allows for six non-equivalent O 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 ↔ P42/n.

Keywords

stottitehydroxide perovskiteshigh-pressurediamond-anvil cellRaman spectroscopyX-ray diffraction
Type
Research Article
Information
Mineralogical Magazine , Volume 76 , Issue 4 , August 2012 , pp. 949 - 962
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2012

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