Glass-forming ability and the structure of glasses in the BaO-WO3-P2O5 system

The purpose of this work was to prepare and study new glasses from the system BaO-WO3-P2O5 focusing on their basic physical properties and studying their structure by Raman and P-31 NMR spectroscopies in five compositional glass series. The glass transition temperature increases in all compositional series with increasing WO3 content. The P-31 MAS NMR spectra of the glasses revealed depolymerization of the phosphate network. In the Raman spectra of glasses with a low WO3 content, two strong vibrational bands at 885 and 945 cm(-1) were assigned to the vibration of W=O and W-O- bonds in tungstate structural units. In glasses with a high WO3 content, a broad band at 820-841 cm(-1), ascribed to W-O-W bonds, indicated the formation of clusters composed of WO6 units. Raman spectra also revealed partial transformation of WO6 units into WO4 units in glasses with a low P2O5 content.