Structural phase transition in titanite,CaTiSiO5: A ramanspectroscopic study |
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Authors: | Ekhard Salje Claudia Schmidt Ulrich Bismayer |
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Institution: | 1. Department of Earth Sciences, University of Cambridge, Downing Street, CB2 3EQ, Cambridge, UK 2. Institut für Mineralogie und SFB 173, Universit?t Hannover, Welfengarten 1, W-3000, Hannover 1, Germany
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Abstract: | The structural phase transition in titanite is correlated with a strong temperature dependence of Raman scattering cross sections and, to a somewhat lesser extent, with shifts of the phonon frequencies. Their quantitative temperature evolution in the low-symmetry phase (P21/a) is compatible with a nearly 2D Ising behaviour with β≈0.12 and T c = 497 K. At temperatures above 860 K, the phonon signals agree with A 2/a symmetry but not in the temperature interval between 497 K and 860 K. In this temperature range new structural states give rise to additional phonon signals. A model based on mobile APBs between slabs of P21/a material, first proposed by van Heurck et al. (1991), is in qualitative agreement with our experimental observations. |
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