Structural correlations in BaO-PbO-B2O3 glasses as inferred from FTIR spectra

Infrared spectra of xBaO·(30-x)PbO·70B2O3, xBaO·(40-x)PbO·60B2O3 and xBaO·(50-x)PbO·50B2O3 glasses have been quantitatively analyzed. The fraction of four coordinated boron atoms varies linearly, for each group, between the values of the corresponding binary borate glasses. The data could be used to calculate and follow the composition dependence of the concentration of structural units in all glasses. The results show a linear increase in the ratio of PbO forming BO4 units to the total content of PbO, with increasing B2O3 in binary PbO-B2O3 glasses. Similar behavior has been observed for the ratio of BaO forming BO4 units to the total content of BaO in binary BaO-B2O3 glasses. The ratio of PbO forming PbO4 units to the total PbO content, and that of BaO forming asymmetric BO3 units to the total BaO content, shows a reversed dependence. The linear change in fraction of four coordinated boron atoms and in density and molar volume suggests that the studied glasses can be treated as mixtures of binary PbO-B2O3 and BaO-B2O3 matrices.