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KMID : 1059520070510030265
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Journal of the Korean Chemical Society
2007 Volume.51 No. 3 p.265 ~ p.269
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Variation of Band Gap Energy upon Structural Distortion for Nb-containing Oxyfluorides
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Kim Hyun-Jun
Kim Seung-Joo
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Abstract
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A comparative study on crystal structures and UV-visible diffuse reflectance spectra for Nb-containing oxyfluorides was performed to probe the relationship between energy band gap and local structure. The oxyfluorides, RbSrNb2O6F, RbCaNb2O6F and RbNb2O5F are commonly composed of the corner-sharing NbO5F octahedra as structural building units. The average Nb-O(F)-Nb bond angles, which can be a measure of the structural distortion, are 158.6° for RbSrNb2O6F, 149.6° for RbCaNb2O6F and 139.5° for RbNb2O5F. As the bond angle decreases, the band gap increases: 3.48eV for RbSrNb2O6F, 3.75eV for RbCaNb2O6F and 4.03 eV for RbNb2O5F. This experimental result implies that the band gap can be controlled with a range of 0.6 eV through a variation of local structure for the Nb-containing oxyfluorides.
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KEYWORD
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Transition-metal Oxyfluoride, Local Structure, Structural Distortion, Band Gap, Perovskite, Pyrochlore
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