Eur. Phys. J. AP
Volume 12, Number 1, October 2000
|Page(s)||17 - 30|
|Published online||15 October 2000|
The roles of crystallographic orientation and crystal origin in ferrobielastic twinning of quartz under uniaxial stress
Universidade Federal de Pernambuco,
Centro de Tecnologia e Geociências, Departamento de Engenharia Mecânica, Cidade Universitária,
50740-530 Recife PE, Brasil
2 École Nationale Supérieure de Mécanique et des Microtechniques, Laboratoire de Chronométrie Électronique et Piézoélectricité, 26 chemin de l'Épitaphe, 25030 Besançon Cedex, France
Corresponding author: email@example.com
Revised: 22 August 2000
Accepted: 22 August 2000
Published online: 15 October 2000
Ferrobielastic twinning in quartz single crystals has been investigated in relation to crystallographic orientation and crystal origin. By means of uniaxial compressive stress experiments, complete volumetric transformation to the alternate Dauphiné twin state was performed in X- and AT-cut samples of natural and synthetic quartz. Either polarized light or synchrotron radiation X-ray topography was employed to observe the movement of twin boundaries. The dependence of the coercive stress and the preferential orientation of twin boundaries on the crystallographic orientation are explained in terms of the thermodynamic potential of the Gibbs free energy. In relation to natural crystals, the stress levels related to optical visualization and complete transformation to the alternate twin state were 50% and 30% lower for synthetic quartz. These results are qualitatively discussed by the pinning of Dauphiné twin boundaries at randomly distributed impurity-related point defects which were evaluated by infrared spectroscopy and ion coupled plasma spectrometry. The spontaneous irreversibility of ferrobielastic twinning on unloading is confirmed.
PACS: 62.20.-x – Mechanical properties of solids / 64.70.Kb – Solid–solid transitions / 61.72.-y – Defects and impurities in crystals; microstructure
© EDP Sciences, 2000
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