HR: 11:50h
AN: V41E-07    [PDF]
TI: Elasticity, Equation of State, and Pressure Calibration Studies on MgO Using Ultrasonics in Conjunction with Synchrotron X-radiation
AU: * Woody, K
EM: kelsters99@yahoo.com
AF: Mineral Physics Institute, SUNY Stony Brook, Stony Brook, NY 11794 United States
AU: Li, B
EM: Baosheng.Li@sunysb.edu
AF: Mineral Physics Institute, SUNY Stony Brook, Stony Brook, NY 11794 United States
AB: Combined ultrasonic and synchrotron X-radiation techniques allow us to measure sound velocities, equation of state (unit cell parameters), and axial strain (sample length change) simultaneously at high pressure and temperature. It is feasible in the laboratory to conduct such measurements on millimeter-sized solids and liquids to P greater than 10 GPa and T around 1600K using a DIA-type apparatus (SAM85) installed at X-17B2, NSLS/BNL, and to P greater than 25 GPa and T greater than 1500K using the multi-anvil apparatus installed at GSECARS/Advanced Photon Source, University of Chicago. In this study, we report our progress in pressure calibration by simultaneously measuring acoustic velocities and P-V-T on pressure standard material MgO. These measurements not only allow redundant determination of elastic properties using equation of state and acoustic velocities, but also provide direct determination of sample pressure that can be compared with the NaCl pressure scale used in current high pressure experiments. Such experiments have been conducted up to 10 GPa and 1273K using hot-pressed polycrystalline sample. The MgO sample used in this study has P and S wave velocities within 0.2 percent of previously published data at ambient conditions. Travel times, X-ray images of sample, and X-ray diffraction spectra were collected in multiple heating/cooling cycles at various pressures during decompression. A third-order Birch-Murnaghan equation of state fit to the P-V data yielded results compatible with previous static compression data. The pressure derivatives of the elastic moduli (K and G) determined without using secondary pressure scale are compatible with previous acoustic data, but the sample pressures determined using current data are higher than those determined using equation of state of NaCl. This finding is consistent with that found in simultaneous velocity and X-ray diffraction measurements on other materials.
DE: 3900 MINERAL PHYSICS
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting