Network connectivity and properties of non-alkali aluminoborosilicate glasses

The effects of alkaline earth metal oxides (RO) concentrations on the network structure and properties of non-alkali aluminoborosilicate glasses were studied. With the increasing of RO concentrations from 10 to 20 mol%, the number of Q4 units decreased, while the number of Q3 units increased. The [AlO4] units always predominated in Al groups, and the fraction of [BO4] among B groups increased from 2% to 10%. Meantime, the value of NBO/T increased from 0.48 to 0.70, indicating the weak network connectivity. The depolymerization of T-O-T network resulted in higher coefficient of thermal expansion, lower temperature of transition point, weaker durability in HF acid. While, the increasing in R2 + cations and [BO4] units led to the higher elastic modulus of glasses. The increasing in RO also enhanced the density, dielectric constant and durability in NaOH solution of glasses.