Thermodynamic modeling of the structure of alkali aluminophosphate glasses and their ionic conductivity

Abstract This study presents the structural and ionic conductivity thermodynamic modeling for glasses with compositions in the system 50M ₂ O‐xAl ₂ O ₃ ‐(50 − x)P ₂ O ₅ , with M = Li or K. The Shakhmatkin and Vedishcheva thermodynamic model (SVTDM), or associated solutions model, has been previously used in successfully predicting the structure of simple binary phosphate glasses and it has now been employed with the aim to discerning the model's capability to predict the structural changes induced in the phosphate network by the addition of alumina. The results have been furthermore validated through their comparison with literature experimental data on the structural characterization of the glasses by ³¹ P NMR measurements as well as on ionic conductivity determined by impedance spectroscopy. Although this methodology demonstrates good agreement with experimental data on the structure of aluminophosphate glasses, some disparities persist, potentially arising from experimental uncertainties. However, SVTDM faces limitations, including the need for comprehensive knowledge of stable phases and their formation energies. Predictions of ionic conductivity, though promising, exhibit deviations from experimental values, attributed to factors such as the influence of the chemical environment on dielectric properties. To enhance accuracy in conductivity prediction, a deeper understanding of additional variables such as dielectric constant and attempt frequency is imperative.