Ultrasonic Study on the Role of Na2O on the Structure of Na2O-B2O3 and Na2O-B2O3- SiO2 Glasses

Quantitative analysis has been carried out in order to obtain more information about the structure of two glass systems (Na₂O-B₂O₃) and (Na₂O-B₂O₃-SiO₂). Makishima and Mackenzie model together with bond compression model were used to calculate the elastic parameters, bond compression bulk modulus, atomic ring size, number of bonds per unit volume, and average cross link density. The bond length B-O of B₂O₃ in all glass compositions was calculated according to a method described by Hager and his co-workers to calculate the bond compression bulk modulus. Results were then used to assess the elastic properties of the two glass systems showing that these glasses become more stable and compact when modified with alkali oxide modifier (Na₂O). As long as R<0.4 (R=Na₂0/B₂O₃), the alkali modifier associated with boron presumably is converted from 3-coordination state (B₃ state) to 4-coordination state (B₄ state) and creation of NBOs is mostly very weak.