کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1484055 | 1510519 | 2008 | 8 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Octahedral fluoride glasses: Raman spectra and structure of niobium pentafluoride Octahedral fluoride glasses: Raman spectra and structure of niobium pentafluoride](/preview/png/1484055.png)
Raman spectroscopy is used to characterize the NbF5 phases in the temperature range 80–500 K. A new clear glass is formed by quenching the melt to liquid nitrogen temperatures having a glass transition at ∼206 K and crystallization at ∼233 K. For all phases including the melt, the glass, the supercooled liquid, the crystalline solid and the gas, the Raman spectra show a rather common high frequency band at ∼760 cm−1 which is attributed to the Nb–F terminal frequency of partially bridged ‘NbF6’ octahedra. Based on the systematics of the Raman spectra for all phases and the literature physicochemical data a model is proposed for the glass and the liquid phases where ‘NbF6’ octahedral bridged in cis and/or trans configurations form a variety of cyclic and/or chain structures which intermix building up the overall structure. At exceptionally low energies (<11 cm−1) a rather weak in intensity Boson peak is observed in the glass which shifts to even lower energies with increasing temperature. Librational and/or tortional motions of the bridged octahedra participating in the glass structure are possible candidates for the origin of this peak.
Journal: Journal of Non-Crystalline Solids - Volume 354, Issues 52–54, 15 December 2008, Pages 5521–5528