HR: 16:30h
AN: V32G-03 [PDF]
TI: Frontiers of High-Pressure Research: Next Generation Large Volume Gem Anvil Devices
AU: * Hemley, R J
EM: hemley@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 United States
AU: Yan, C
EM: c.yan@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 United States
AU: Xu, J
EM: j.xu@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 United States
AU: Mao, W
EM: wmao@uchicago.edu
AF: Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637 United States
AU: Mao, H
EM: mao@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 United States
AB:
By any measure, the diamond anvil cell has revolutionized static high-pressure research, and in particular experimental study
of Earth and planetary deep interiors. Despite the prowess of the technique, however, its range of applicability is in many
ways quite limited and its potential not yet fully realized. We have embarked on a program to develop the next generation
high-pressure devices that will allow new classes of in situ high {\it P-T} measurements critical to understanding the
structure, dynamics, and evolution of planetary bodies. A crucial component of this effort is the enlargement of sample
volume without sacrificing the unmatched pressure range and versatility of diamond anvil cells. In conventional studies,
pressures to several hundred GPa are generated on sample volumes down to the picoliter range. The small sample size is
determined by the availability of perfect diamonds as anvils, which are currently of order of 0.2-0.4 up to a few carats. The
small sample size has precluded, or greatly limited the accuracy of, certain classes of high pressure experiments. The
production of high-quality single-crystal diamond by microwave plasma chemical vapor deposition (CVD) at very high growth
rate of 50-150 $\mu$m/h has opened new opportunities for the creation of large perfect single crystal diamond as anvils.$^1$
This morphology, photoluminescence, Raman spectra, and mechanical properties of the CVD diamond have been examined in detail.
Of particular interest is our finding of very high strength and improved optical properties of CVD diamond annealed at high
pressures and temperatures.$^2$ In addition, hybrid conventional synthetic/CVD single crystals have been successfully used to
generate pressures in the multimegabar range ($>$200 GPa).$^3$ A parallel initiative involves the continued development of
moissanite anvils, which can already be produced as large, perfect crystals and can reach pressures above 60 GPa. Recent
advances include the design and fabrication of supported moissanite anvils for enhanced sample volumes.$^4$ These
developments will make possible new classes of high {\it P-T} experiments, including neutron diffraction, inelastic neutron
scattering, various inelastic x-ray scattering measurements, magnetic resonance and susceptibility, ultrasonics, and
rheological studies in the megabar range.
$^1$ C.S. Yan et al., {\it Proc. Nat. Acad. Sci.} {\bf 99}, 12523 (2002)
$^2$ C.S. Yan et al., to be published.
$^3$ W. Mao et al., to be published.
$^4$ J. Xu et al., to be published.
DE: 3994 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting