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An infrared spectroscopic and single-crystal X-ray study of malayaite, CaSnSiO5 |
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| Authors: | M Zhang H-W Meyer L A Groat U Bismayer E K H Salje G Adiwidjaja |
| Institution: | Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK, GB Mineralogisch-Petrographisches Institut, Universit?t Hamburg, D-20146 Hamburg, Germany, DE Department of Geological Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada Fax: (604) 822-6088, e-mail: lgroat@eos.ubc.ca, CA Mineralogisch-Petrographisches Institut, Universit?t Hamburg, D-20146 Hamburg, Germany, DE Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK, GB Mineralogisch-Petrographisches Institut, Universit?t Hamburg, D-20146 Hamburg, Germany, DE |
| Abstract: | Powder infrared spectroscopy and X-ray diffraction techniques on single crystals were used to study the thermal behaviour of malayaite, CaSnSiO5. Infrared spectra show a discontinuity in the temperature evolution of phonon frequencies and absorbance near 500 K. However, crystal structure data collected at 300, 450, 550, 670, and 750 K show no evidence of a symmetry-breaking phase transition and no split positions. The most obvious change with heating is a tumbling motion of the SnO6 octahedra and an increase of the anisotropic displacement factors of Ca. The thermal evolution of the mean-square vibrational amplitude of the Ca atom shows a pronounced change in slope near 500 K. The evidence suggests that the 500 K anomaly in malayaite is more similar in character to the 825 K (β-γ) transition as opposed to the 496 K (α-β) transition in synthetic titanite. Received: 26 March 1998 / Revised, accepted: 23 December 1998 |
| Keywords: | Malayaite Infrared spectroscopy Crystal structure |
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