Elastic softening of metamict titanite CaTiSiO5: Radiation damage and annealing

Salje, Ekhard K. H. and Safarik, Douglas J. and Lashley, Jason C. and Groat, Lee A. and Bismayer, Ulli (2011) Elastic softening of metamict titanite CaTiSiO5: Radiation damage and annealing. American Mineralogist, 96 (8-9). 1254 -1261. DOI https://doi.org/10.2138/am.2011.3747

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We have measured the elastic response of radiation-damaged titanite, CaTiSiO5, as a function of thermal annealing. We estimate the bulk modulus of the damaged samples (~24% amorphous) to be 85 GPa, which is much softer than for undamaged crystalline titanite [131.4 GPa; Angel et al. (1999)]. Conversely, the lowest shear modulus of the radiation-damaged material is 52–58 GPa, which is harder that of the undamaged titanite, 46–52 GPa. The bulk and shear moduli of the radiation-damaged materials are close to those of thermal titanite glass, Bglass ≈ 75 GPa and Gglass ≈ 47 GPa, and are much smaller than expected based on other radiation-damaged materials such as zircon (ZrSiO4). Surprisingly, annealing of the damaged titanite in the range 600 < T < 1000 K leads to additional massive softening of the shear moduli. During annealing the shear modulus of titanite sample 1 softened from 58 to 29 GPa, and sample 2 softened from 52 to 19 GPa. The temperature range for the softening coincides with that found for crystallization of the amorphous regions, as measured previously by diffraction and spectroscopic methods. In contrast to the huge softening of the ultrasonically measured shear modulus, the calorimetrically measured Debye temperature

Item Type: Article
Uncontrolled Keywords: 2011AREP; IA63;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: American Mineralogist
Volume: 96
Page Range: 1254 -1261
Identification Number: https://doi.org/10.2138/am.2011.3747
Depositing User: Sarah Humbert
Date Deposited: 08 Feb 2012 10:41
Last Modified: 23 Jul 2013 10:03
URI: http://eprints.esc.cam.ac.uk/id/eprint/2370

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