HR: 14:10h
AN: MR13A-03    [Abstracts]
TI: A New Technique for High-Pressure Angle-Dispersive Powder Diffraction Using an Energy-Dispersive Setup and White Synchrotron Radiation
AU: * Wang, Y
EM: wang@cars.uchicago.edu
AF: Center for Advanced Radiation Sources, Univ. Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 United States
AU: Uchida, T
EM: uchida@cars.uchicago.edu
AF: Center for Advanced Radiation Sources, Univ. Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 United States
AU: Von Dreele, R B
EM: vondreele@anl.gov
AF: Advanced Photon Source and Intense Pulse Neutron Source, 9700 S. Cass Ave., Argonne, IL 60439 United States
AU: Rivers, M L
EM: rivers@cars.uchicago.edu
AF: Center for Advanced Radiation Sources, Univ. Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 United States
AU: Nishiyama, N
EM: nishiyama@cars.uchicago.edu
AF: Center for Advanced Radiation Sources, Univ. Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 United States
AU: Funakoshi, K
EM: funakosi@spring8.or.jp
AF: Japan Synchrotron Radiation Research Institute, SPring-8, Koto 1-1-1, Mikazuki, Sayo, 679-5198 Japan
AU: Nozawa, A
EM: nozawa@spring8.or.jp
AF: Japan Synchrotron Radiation Research Institute, SPring-8, Koto 1-1-1, Mikazuki, Sayo, 679-5198 Japan
AU: Kaneko, H
EM: kaneko@spring8.or.jp
AF: Japan Atomic Energy Reesrach Institute, SPring-8, Koto 1-1-1, Mikazuki, Sayo, 679-5198 Japan
AB: We introduce a new step-scan diffraction technique, which collects angle-dispersive data using a solid-state detector (SSD) and white synchrotron radiation. By step-scanning a well-calibrated SSD over a limited 2$\theta$ range, a series of 1-dimensional energy dispersive data (intensity vs. energy) are obtained as a function of 2$\theta$. The entire intensity (Int) dataset consists of several thousand channels covering a range of photon energies, E, (up to ~150 keV) at each of the ~1000 2$\theta$ steps, forming a 2-4 mega-element two-dimensional array, Int(E, 2$\theta$). These intensity data are then regrouped according to photon energies, which are defined in the multichannel SSD as individual channels, yielding a large number of intensity versus 2$\theta$ (angle-dispersive) datasets, Int(E=const., 2$\theta$), each of which corresponds to a given photon energy or wavelength. The entire dataset, selected subsets or composite scans can be used for multiple dataset Rietveld refinement. Data collected on $\alpha$-Al2O3 (a NIST diffraction standard) at ambient conditions, from both the tapered undulator at 13-ID-D, APS and the bending magnet beamline BL04B1, SPring-8, were analyzed using the Rietveld technique, with varying schemes of data treatment. We demonstrate that data within certain energy bands ($\Delta$E/E=$\pm$10 percent) may be binned together to improve counting statistics in a composite angle dispersive scan, so that data can be collected with much coarser scan steps of 0.1$\deg$ or 0.2$\deg$. This technique has been used to collect high-pressure angle-dispersive data at the BL04 bending magnet beamline at SPring-8, with the multianvil apparatus SPEED-1500, up to 20 GPa and 1100 K. Data obtained on several materials will be shown to demonstrate the feasibility of simultaneous high pressure and temperature Rietveld refinement.
DE: 3620 Crystal chemistry
DE: 3694 Instruments and techniques
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
DE: 3994 Instruments and techniques
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting