Structural study of BaO-MoO3-P2O5 glasses by Raman and NMR spectroscopy (original) (raw)

Glasses in the BaO-MoO 3-P 2 O 5 ternary system were prepared, their basic physical properties measured and their structure studied by Raman and 31 P NMR spectroscopies. A modified glass-forming region in this system under slow cooling of the melt was determined. Four compositional series, namely (50-x/2)BaO-xMoO 3-(50-x/2)P 2 O 5 (A), 50BaO-yMoO 3-(50-y)P 2 O 5 (B), 20BaO-zMoO 3-(80-z)P 2 O 5 (C) and (70-u)BaO-uMoO 3-30P 2 O 5 (D) were chosen for a discussion on changes of the structure and properties of the studied glasses. The glass transition temperature revealed a maximum in series A at x = 40 mol% MoO 3 and in series C at z = 50 mol% MoO 3 , whereas monotonous increase of T g in the series B and monotonous decrease in the series D was observed. 31 P MAS NMR spectra of the glasses revealed depolymerization of the phosphate network, due to the incorporation of molybdate units, and isolated PO 4 groups were identified in glasses with high MoO 3 content. Fitting the NMR spectra provided compositional dependences of phosphate units Q n. On the Raman spectra of glasses with low MoO 3 content, a strong vibrational band at 940-944 cm − 1 , with a shoulder at~910 cm − 1 , dominated the spectra, which was assigned to the vibration of terminal oxygen atoms in molybdate structural units (MeOand M]O). In glasses with high MoO 3 content, a broad band at~854 cm − 1 , ascribed to MoeOeMo bonds, showed on the formation of octahedral clusters composed of MoO 6 units in the structure of these glasses.