Optical Spectra of Synthetic Spinels in the System MgAl2O4–MgCr2O4 |
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Authors: | Ko Ikeda Yoshinori Nakamura Kiyoshi Masumoto Hiromi Shima |
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Affiliation: | Department of Advanced Materials Science and Engineering, Yamaguchi University, Ube 755, Japan;;Department of Chofu Seisakusho Company, Ltd., Shimonoseki 752, Japan |
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Abstract: | Unpolarized optical spectra were measured in the wavelength range 322–1666 nm by the diffuse reflection technique from spinel powders synthesized in the system MgAl2O4–MgCr2O4. The spectra were interpreted by the crystal-field theory on the basis of trigonally distorted spinel octahedra with D3d symmetry. For chromium-rich solid solutions, including the MgCr2O4 end-member, results after peak fittings showed octahedral D3d local symmetry around Cr3+ ions, identical to the crystallographic site symmetry. For chromium-poor solid solutions, however, octahedral C3v local symmetry was suggested around Cr3+ ions, different from the D3d crystallographically expected. |
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