Distribution of species in Na2O-CaO-B2O3 glasses as probed by FTIR

The article presents a simple method that can be used to get the concentration of various species in mixed-modifier borate glasses. By using the fraction of four coordinated boron in xCaO (30-x)Na(2)O(center dot)70B(2)O(3) (0 <= x <= 27.5 mol%) and xCaO(center dot)(40-x)Na(2)O(center dot)60B(2)O(3) glasses (10 <= x <= 40 mol%), the concentration of BO4- and asymmetric BO3 units related to each modifier oxide could be determined. CaO has a greater tendency to form asymmetric BO3 units in the first glass series, while Na2O has the ability to form BO4 units to a greater extent. In xCaO(center dot)(40-x)Na(2)O(center dot)60B(2)O(3) glasses, BO4- and asymmetric BO3 units are formed at the same rate from Na2O and CaO. The fraction of four coordinated boron, can be predicted by treating the studied glasses as if they are mixtures of Na2O-B2O3 and CaO-B2O3 matrices. The change in N-4 is due to change in the relative concentration of these matrices. (C) 2013 Elsevier B.V. All rights reserved.