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http://dx.doi.org/10.5012/jkcs.2007.51.3.265

Variation of Band Gap Energy upon Structural Distortion for Nb-containing Oxyfluorides  

Kim, Hyun-Jun (Division of Energy Systems Research, Ajou University)
Kim, Seung-Joo (Division of Energy Systems Research, Ajou University)
Publication Information
Journal of the Korean Chemical Society / v.51, no.3, 2007 , pp. 265-269 More about this Journal
Abstract
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.
Keywords
Transition-metal Oxyfluoride; Local Structure; Structural Distortion; Band Gap; Perovskite; Pyrochlore;
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