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High temperature X-ray study of single crystal stishovite synthesized with Li2WO4 as flux |
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| Authors: | S Endo T Akai Y Akahama M Wakatsuki T Nakamura Y Tomii K Koto Y Ito M Tokonami |
| Institution: | 1. High Pressure Research Laboratory, Faculty of Engineering Science, Osaka University, 560, Toyonaka, Osaka, Japan 2. Institute of Material Science, University of Tsukuba, Sakura, 305, Ibaraki, Japan 4. Department of Metal Science & Technology, Faculty of Engineering, Kyoto University, 606, Kyoto, Japan 5. Institute of Scientific and Industrial Research, Osaka University, 567, Ibaraki, Osaka, Japan 6. Mineralogical Institute, Faculty of Science, University of Tokyo, 113, Tokyo, Japan |
| Abstract: | Single crystal stishovite with a square prismatic habit and maximum length 0.8 mm was grown from α-quartz at 120 kbar and ～1,300° C. Li2WO4, chosen as a result of a previous experiment in growing coesite, was also successful as flux for stishovite. Single crystal X-ray structure analysis of the crystals thus obtained has been carried out at high temperatures under ambient pressure. Lattice constant measurements give a larger thermal expansion coefficient along the a-axis than along the c-axis. The bond distances and bond angles show a decreasing distortion of the SiO6 octahedron with increasing temperature. The increasing amplitude of thermal vibrations of oxygen atoms with increasing temperature results in increasing O-O repulsion in the basal plane, which explains the observed crystallographic changes. |
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