Study of the structure and properties of Pb-Zn borophosphate glasses

Multicomponent oxide glasses of composition 25PbO-25ZnO-xB(2)O(3)-(50 - x)P 2O5, series A, and yPbO-(50 - y) ZnO-20B(2)O(3)-30P(2)O(5), series B, are i nvestigated. The role of compositional changes on their density, chemical d urability, thermomechanical properties and Raman scattering is examined. St ructural changes are found to be more pronounced in the series A glasses af fecting most thermomechanical properties of the glasses. Raman spectra reve al a continuous shift in frequency of the main vibrational band from 1170 c m(-1) at x = 0, to 960 cm(-1) at x = 40, explained in terms of a successive transformation of metaphosphate (Q(2)) units into pyrophosphate (Q(1)) and orthophosphate (Q(0)) units. In the series B of glasses, results show that mixed Pb-Zn borophosphate glasses (y = 25) have better chemical durability than end point (y = 0, y = 50) composition single-cation glasses. With an increasing PbO content, T-g is found to slowly decrease and the thermal exp ansion coefficient to increase. The frequency shift of the main Raman band from 1092 cm(-1) (at y = 0) to 1011 cm(-1) (at y = 50) is ascribed to diffe rences in chemical bonding, coordination numbers and field strength of both cations. (C) 2001 Elsevier Science B.V. All rights reserved.