Structure and properties of silver phosphate glasses with tungsten trioxide

• Glass-forming region in the system Ag 2 O-WO 3 -P 2 O 5 was determined. • Tungsten-phosphate glasses with only 10 mol% P 2 O 5 were prepared. • Glass color depends on the WO 3 content and optical basicity. • Raman and 31 P MAS NMR reflect transformation of phosphate network to tungstate phosphate network. • The shift of Raman band of W=O bonds vibration depends on the content of Ag + ions. Phosphate glasses from the ternary Ag 2 O–WO 3 –P 2 O 5 system were prepared and investigated. A total of 22 compositions were synthesized across five series, and their basic physical parameters were determined. The glass-forming region of the system was established, and glasses containing as little as 10 mol% P 2 O 5 were successfully obtained. The highest achievable Ag 2 O content in these ternary glasses was 60 mol%. The glass transition temperature (T g ) increased with WO 3 content, reaching a maximum of 500 °C for the 10Ag 2 O–50WO 3 –40P 2 O 5 composition. Structural characterization was performed using Raman spectroscopy and 31 P MAS NMR spectroscopy. In the series with constant P 2 O 5 content, 31 P MAS NMR spectra revealed that a reduction in Ag + concentration decreases the number of nonbridging oxygen atoms, while promoting the formation of W–O–P linkages. Both Raman and NMR data demonstrated that progressive incorporation of WO 3 induces depolymerization of the phosphate network and its transformation into a tungstate–phosphate framework, where isolated PO 4 units are incorporated into the disordered tungstate network via W–O–P bridges. Tungsten atoms are exclusively octahedrally coordinated, and with increasing WO 3 content, isolated WO 6 octahedra progressively connect into chains and clusters through W–O–W bridges.