X-ray diffraction from stishovite under nonhydrostatic compression to 70 GPa: Strength and elasticity across the tetragonal - orthorhombic transition
IR@NAL: CSIR-National Aerospace Laboratories, Bangalore
View Archive Info| Field | Value | |
| Title |
X-ray diffraction from stishovite under nonhydrostatic compression to 70 GPa: Strength and elasticity across the tetragonal - orthorhombic transition
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| Creator |
Singh, AK
Andrault, Denis Bouvier, Pierre |
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| Subject |
Chemistry and Materials (General)
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| Description |
The tetragonal phase of silica (stishovite) was synthesized at high pressure and temperature in a laser heated diamond anvil cell. Nonhydrostatic pressure condition was produced by pressurizing the sample without any pressure transmitting medium. The tetragonal?orthorhombic transition could be detected from the X-ray diffraction patterns at �40 GPa. In contrast, the orthorhombic phase has been reported to occur only above �60 GPa in an earlier experiments under hydrostatic pressure. However, the transition pressures derived from the square of the symmetry-breaking strain versus pressure data in the two cases differ only marginally, the values being 44(8) GPa and 49(2) GPa under nonhydrostatic and hydrostatic compressions, respectively. We combine the d-spacings measured under nonhydrostatic and hydrostatic compressions to derive a parameter Q(hkl) that contains the information on differential stress t (a measure
of compressive strength) and single-crystal elasticity. The compressive strengths derived from the average value of Q(hkl) and line-width analysis agree well. It increases from �4 GPa at 20 GPa to �8 GPa at 40 GPa and decreases as the transition pressure is approached. In the orthorhombic phase, t increases with pressure monotonically. The mean crystallite size of the sample decreases from �5000 Å to �1000 Å as the pressure is increased from 20 GPa to 45 GPa and remains nearly unchanged between 45 GPa and 70 GPa. The single-crystal elastic moduli derived from the X-ray diffraction data indicate that ðC11 � C12Þ decreases rapidly as the transition pressure is approached. Line-width analysis of the diffraction lines suggests that near-hydrostatic pressure condition is achieved by laser annealing of the compressed sample.
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| Publisher |
Elsevier
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| Date |
2012
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| Type |
Journal Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://nal-ir.nal.res.in/10836/1/PEPI_2012.pdf
Singh, AK and Andrault, Denis and Bouvier, Pierre (2012) X-ray diffraction from stishovite under nonhydrostatic compression to 70 GPa: Strength and elasticity across the tetragonal - orthorhombic transition. Physics of the Earth and Planetary Interiors, 208-20 . pp. 1-10. |
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| Relation |
http://nal-ir.nal.res.in/10836/
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