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Structure analysis on synthetic emerald crystals |
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| Authors: | Pei-Lun Lee Jiann-Shing Lee Eugene Huang Ju-Hsiou Liao |
| Institution: | 1. General Education Center, National Chiayi University, Chiayi, Taiwan, ROC 2. Department of Applied Physics, National Pingtung University of Education, Pingtung, Taiwan, ROC 3. Center for International Exchange, Chung-Chou University of Science and Technology, Yuanlin, Taiwan, ROC 4. Department of Chemistry and Biochemistry, National Chung Cheng University, Minxiong, Chiayi County, Taiwan, ROC |
| Abstract: | Single crystals of emerald synthesized by means of the flux method were adopted for crystallographic analyses. Emerald crystals with a wide range of Cr3+-doping content up to 3.16 wt% Cr2O3 were examined by X-ray single crystal diffraction refinement method. The crystal structures of the emerald crystals were refined to R 1 (all data) of 0.019–0.024 and wR 2 (all data) of 0.061–0.073. When Cr3+ substitutes for Al3+, the main adjustment takes place in the Al-octahedron and Be-tetrahedron. The effect of substitution of Cr3+ for Al3+ in the beryl structure results in progressively lengthening of the Al–O distance, while the length of the other bonds remains nearly unchanged. The substitution of Cr3+ for Al3+ may have caused the expansion of a axis, while keeping the c axis unchanged in the emerald lattice. As a consequence, the Al–O–Si and Al–O–Be bonding angles are found to decrease, while the angle of Si–O–Be increases as the Al–O distance increases during the Cr replacement. |
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