The structure of barium phosphate glasses and its influence on their thermodynamic stability and viscous flow

The Shakhmatkin and Vedishcheva thermodynamic (SVTD) model of associated solutions has been developed in glasses of the system BaO–P2O5, with the aim of deriving their short range structure and predicting the volume properties. The applicability of the model was examined by comparing the structure obtained from thermodynamic modelling and by Nuclear Magnetic Resonance spectroscopy. The evaluation of the molar volume of the investigated glasses was carried out through comparison of the experimental values calculated by two approaches: i) with the glass molar volume obtained through a linear combination of the product of the molar fractions of system components and their respective crystalline volume; and ii) with the molar volumes calculated by a multilinear regression analysis of the experimental molar volume of each composition. Furthermore, the viscosity curves were determined at low and high temperature ranges by beam-bending and rotation methods from which the fragility and activation energy of the viscous flow have been calculated and correlated with the thermodynamic chemical structure of the glasses.