HR: 0800h
AN: MR11A-0913    [Abstracts]
TI: X-ray Fluorescent Phosphors as {\it in Situ} Markers of X-ray Position for High-Pressure X-ray Techniques: Equation of State and X-ray Fluorescence Spectra to 40 GPa
AU: * Benedetti, L R
EM: benedetti@esrf.fr
AF: European Synchrotron Radiation Facility, Experiments Division, S-30 6 Rue Jules Horowitz, BP220, Grenoble, 38000 France
AU: Crichton, W A
EM: crichton@esrf.fr
AF: European Synchrotron Radiation Facility, Experiments Division, S-30 6 Rue Jules Horowitz, BP220, Grenoble, 38000 France
AU: Mezouar, M
EM: mezouar@esrf.fr
AF: European Synchrotron Radiation Facility, Experiments Division, S-30 6 Rue Jules Horowitz, BP220, Grenoble, 38000 France
AB: Their small size and heterogeneity make high-pressure samples in the diamond-anvil cell difficult to place perfectly in an x-ray beam to perform any of several analytical techniques (diffraction, scattering, etc.). X-ray fluorescent materials may help to solve this problem by providing a visual marker of the precise location of the x-ray beam or probe. In order to assess the utility of x-ray fluorescent markers for x-ray beam location at high-pressure conditions, we have characterized the high-pressure behavior of common x-ray fluorescent materials, particularly paying attention to structural stability at 300 K and high temperature, adequate fluorescence brightness, and potential use as an {\it in situ} pressure calibrant. We present x-ray diffraction and x-ray fluorescence (excited by x-rays, fluorescent in the visible range) data for two common x-ray phosphors: "red phosphor," Y$_{2}$O$_{3}$ doped with Eu, and "green phosphor," Gd$_{2}$O$_{2}$S doped with Tb. Red phosphor yttrium oxide undergoes two phase transitions from its initial cubic structure at 8 $\pm$ 2 GPa and 18 $\pm$ 2 GPa, and a third phase transformation occurs at high temperature during laser heating. In contrast Gd$_{2}$O$_{2}$S:Tb retains its hexagonal crystal structure with only slight modification to 40 GPa and during laser heating, and its volume and fluorescence peaks may be followed with increasing pressure making it a good material for {\it in situ} calibration of pressure as well as x-ray position. High pressure and temperature crystal structures, fluorescence spectra, and equation of state information will be presented for these two materials.
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3934 Optical, infrared, and Raman spectroscopy
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