Glass - Back to the Future!

Presenting Author:
Petr Mošner

article posted 20 April 2016

Petr Mošner is professor of chemistry and technology of inorganic materials at Faculty of chemical technology, University of Pardubice, Czech republic. His research is focused on the preparation and characterization of phosphate and borophosphate glassy and crystalline materials. He studies the relationships between the composition of these materials, their structure and their physicochemical properties. Experimentally, his work is oriented to application of the various thermoanalytical techniques to the study of thermal behaviour of glasses.

Structure and properties of La2O3 containing lead phosphate and borophosphate glasses

P. Mošner*, J. Chmelík & L. Koudelka
Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, 532 10 Pardubice, Czech Republic

La2O3 containing lead phosphate and borophosphate glasses were studied in the compositional series (40-x)PbO-xLa2O3-60P2O5 (x = 0, 5, 10, 15, 20 mol% La2O3; series A) and 20PbO-xLa2O3-(20-x)B2O3-60P2O5 (x = 0, 5, 10, 15 mol% La2O3; series B). The replacement of PbO by La2O3 (series A) or B2O3 by La2O3 (B) results in a substantial increase of glass density only in the series B, whereas molar volume substantially increased in both series of glasses. The refractive index decreases in the compositional series (40-x)PbO-xLa2O3-60P2O5 (A), whereas with the replacement of B2O3 by La2O3 (series B) the index of refraction gradually increases. Both parent lead phosphate glass 40PbO-60P2O5 and lead borophosphate glass 20PbO-20B2O3-60P2O5 reveals lower durability against water corrosion than the glasses containing La2O3, but with increasing La2O3 chemical durability of glasses slightly decreases in both compositional series. The DSC curves showed that all glasses crystallize on heating in the broad temperature range of 280-700°C. Major compounds formed by crystallization were Pb(PO3)2, Pb3P4O13, La(PO3)3 and BPO4. Most of studied glasses change in the course of the DSC curves corresponding to the glass transition temperature Tg insignificantly, nevertheless as emerged form TD curves the glass transition temperature and dilatometric softening temperature Td increases with La2O3 additions, both in the series (40-x)PbO-xLa2O3-60P2O5 (A) and (20PbO-xLa2O3-(20-x)B2O3-60P2O5 (B), whereas thermal expansion, α (150-250°C) with La2O3 content decreases within the range of 16.5-10.8 ppm/°C (A) and 12.5-10.8 ppm/°C (B). The Raman spectra show slight changes in the shape and position of main characteristic Raman bands with increasing La2O3 content. The structure of starting 40PbO-60P2O5 and 20PbO-20B2O3-60P2O5 glasses consists mostly by ultraphosphate (Q3) and metaphosphate (Q2) tetrahedral PO4 units. Increasing La2O3 content is accompanied by the gradual depolymerization of phosphate chains and transformation of three-connected branching units Q3 into two-connected middle Q2 units.