الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
A Raman scattering study of B203 has been performed from room temperature to 1273 K to study structural changes on the intermediate range scale as the glass transforms into the melt via the supercooled regime. Several striking anomalies in the dynamics are observed. The strongest vibrational mode at 808 cm-1 is attributed to the breathing mode of the boroxol rings. The 1210 and 1260 cm-1 modes are assigned to the vibrations of oxygens bridging two boroxol rings, respectively, bridging a boroxol ring to the network of B03 units. The intensities of the 808, 1210, and 1260 cm- 1 components decrease as the temperature increases, which all indicate a decrease of the amount of boroxol rings as temperature increases. The mode at 1325 cm- 1 is rapidly increasing in intensity as the temperature is raised, which is the reverse of the behavior of the 808 cm-1 component. The 1325 cm-1 mode is assigned to B-O vibrations of B03 units which are released as the boroxol rings open. The mode observed at 1475 cm-1 is in all respects temperature independent. It may therefore represent the unaffected network of B03 units The observed effects are consistent with a gradual breakup of the boroxol rings, which change into chains of B03 triangles as the temperature increases above T g. from a detailed analysis of the temperature dependence of the spectra, the structure is estimated to consist of about half of the number of atoms in boroxol rings at T g. Heating the glass to the melting temperature leads to breaking of about 113 of the boroxol rings.The dynamical and structural properties of B203 on the intermediate range scale are affected by the glass transition.