Simulation procedures for glass transition temperatures and thermal expansion coefficients of BaO-B2O3 glasses

In order to reflect the so-called boron anomaly, three types of B-O structural units, namely, BO3/2, BO4/2- and BO2/2O-, were considered for the BaO-B2O3 glass. Two chemical equilibrium equations were established among the three B-O structural units taking into account the so-called boron anomaly. Based on the chemical equilibrium equations and the conservation of mass equation, the fractions of the three B-O structural units can be calculated for BaO-B2O3 glasses. The required parameters and the contribution values of the three B-O structural units were obtained by fitting the equation with experimental data from the literature. Following this, the contributions of B2O3 to the glass transition temperature (T-g) or thermal expansion coefficient (TEC) are expressed in terms of the weighted average of the T-g or TEC contributions of the three B-O structural units. As a result, new simulation procedures for T-g and TEC based on the contributions of the three B-O structural units were established for BaO-B2O3 glasses. Comparisons were made between the calculation results for T-g/TEC obtained by the new simulation procedures with the experimental results from the available literature. It is shown that the predictions of the new simulation procedures are close to the experimental values.