Study of crystallization of PbO–WO3–P2O5 glasses by thermoanalytical and spectroscopic methods

• Crystallization of lead phosphate glasses modified with tungsten oxide was investigated.
• Annealed crystallized glasses were characterized by XRD and Raman spectroscopy.
• Thermal stability of glasses and formation of glass-crystalline phases were assessed.
• New compound Pb(WO2)2(PO4)2 was found and its crystal parameters were determined.

The crystallization of PbO–WO3–P2O5 ternary glasses was studied in three compositional series of (100 − x)[0.5PbO–0.5P2O5]–xWO3 glasses (A series), 50PbO–(50 − y)P2O5–yWO3 glasses (B series) and (50 − z)PbO–50P2O5–zWO3 glasses (C series) beginning with Pb(PO3)2. The crystallization products of the annealed glass powders were evaluated using X-ray diffraction and Raman spectroscopy. The results of the X-ray diffraction analysis of the crystallized glasses revealed the formation of several crystalline phosphate compounds and in the samples with a high WO3 content also the formation of a new crystalline compound of Pb(WO2)2(PO4)2 in series A and B. From the obtained diffraction pattern, the hexagonal cell parameters were calculated as a = 11.3531(1) Å and c = 6.3168(1) Å. The surface mechanism of crystallization dominates the crystallization process of the glass into the Pb(WO2)2(PO4)2 compound as evaluated using Day's method. Raman spectra of the crystallized samples confirmed the results of the X-ray diffraction measurements and provided information on the thermal stability of the glasses and formation of the glass-crystalline phases by the annealing of glass samples.