Phase transitions and equation of state of CsI under high pressure and the development of a focusing system for x-rays

Technical Report · Thu Nov 01 00:00:00 EST 1990

DOI:https://doi.org/10.2172/6299092· OSTI ID:6299092

Wu, Yan

The phase transitions and equation of state of ionic solid cesium iodide were studied under high pressure and room temperature in a diamond anvil cell. The studies were carried out using both energy dispersive and angular dispersive diffraction methods on synchrotron radiation sources over the pressure range from atmospheric pressure to over 300 gigapascals (3 million atmospheres). CsI undergoes a distinct phase transition at about 40 GPa, a pressure that is much lower than the reported insulator-metal transition at 110 GPa, from the atmospheric pressure B2(CsCl) structure to an orthorhombic structure. At higher pressures, a continuous distortion in the structure was observed with a final structure similar to a hcp lattice under ultra high pressure. No volume discontinuity was observed at the insulator-metal transition. The newly found transition sequence is different from the result of previous static compression studies. The current structure has a smaller unit cell volume than the previous assignment. This has resolved a long existing controversy among the previous static compression studies, the dynamic compression studies, and the theoretical studies. The current results also explain the apparent discrepancy between the present study and the previous static studies. We also present the development of a focusing system for high energy x-rays (> 12 keV) that is particularly suited for high pressure diffraction studies. This system uses a pair of multilayer coated spherical mirrors in a Kirkpatrick-Baez geometry. A focused beam size less than 10 micron in diameter can be readily achieved with sufficient intensity to perform diffraction studies. 93 refs., 46 figs., 15 tabs.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6299092
• Report Number(s): LBL-29844; ON: DE91007646; TRN: 91-004577
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CESIUM IODIDES
EQUATIONS OF STATE
PHASE TRANSFORMATIONS
X RADIATION
FOCUSING
CRYSTAL STRUCTURE
PRESSURE EFFECTS
VERY HIGH PRESSURE
X-RAY DIFFRACTION
ALKALI METAL COMPOUNDS
CESIUM COMPOUNDS
COHERENT SCATTERING
DIFFRACTION
ELECTROMAGNETIC RADIATION
EQUATIONS
HALIDES
HALOGEN COMPOUNDS
INORGANIC PHOSPHORS
IODIDES
IODINE COMPOUNDS
IONIZING RADIATIONS
PHOSPHORS
RADIATIONS
SCATTERING
360602* - Other Materials- Structure & Phase Studies
360603 - Materials- Properties