INFRARED ABSORPTION AND STRUCTURAL INVESTIGATION OF FLUORINE PHOSPHATE AND PHOSPHATE GLASSES.

Infrared spectra obtained for various homologous series of fluorine phosphate and phosphate glasses are analyzed. Alterations in vibration frequencies of the fluorine phosphate tetrahedra as a function of chemical composition are interpreted and indicate that fluorine ions are present in the glass network as PO//nF//4//-//n units. P-F vibrations show that fluorine ions have a network forming character in phosphate coordination. Another remarkable influence of the fluorine ions is the delocalization of the P equals O double bonding which is typical and localized for pure phosphate glasses. This delocalization is associated with an increase in frequency of all remaining P-O vibrations (stronger P-O bondings), which prevents the phosphorus atoms from carrying a higher charge. Neighboring aluminum atoms get a chance for a four-fold coordination without the presence of alkali ions by charge transfer from P**5** plus to Al**3** plus via the p-orbital of oxygen. From other frequency shifts the network forming influence of Al**3** plus , Mg**3** plus and the network modifying character of Na** plus , Ca**2** plus and Ba**2** plus are evident.