This study explores the short- and medium-range structures of borate glasses with the composition 0.5xNa2O•0.5xBaO•(100-x)B2O3 (x = 15, 20, 25, 33.3, 40 mol%) and a constant Na2O/BaO ratio equal to 1 using vibrational spectroscopy methods (IR and Raman). Based on an extensive literature analysis of crystalline borates’ spectra and quantum-chemical modeling of borate superstructural units, a set of deconvolution bands was identified in the Raman spectra of the investigated glasses. These bands were used to calculate the distribution of superstructural units as a function of the glass composition. However, the accuracy of such calculations was limited due to overlapping deconvolution bands of units with different tetrahedron counts and the absence of distinct vibrational bands of metaborate rings in the studied spectral region. Using IR spectroscopy, the N4 ratio, which reflects the fraction of tetrahedral boron, was determined alongside related to the short-range structural characteristics of the glasses. A combined technique was proposed to calculate the absolute fractions of superstructural units by integrating Raman-derived data with IR-based insights into the short-range structure. This approach yielded superstructural unit fractions closely matching the independent thermodynamic predictions for binary borate glasses. The structural data enabled calculations of key glass properties (density, molar volume, and molar refractivity), which were compared with experimental values. Both stoichiometric model, assuming that the borate network comprises units identical to binary crystalline borates, and a mixed model, incorporating ternary compounds (e.g., Na2O-2BaO-9B2O3 and Na2O-2BaO-5B2O3), were employed. The mixed model was essential for phase diagram regions with ternary crystalline compounds, while the stoichiometric model performed better outside these regions. Combination of both models resulted in average deviations from experiment of less than 0.03 g/cm3 for density and 0.3 cm3/mol for molar volume. The proposed methodology for structural and property calculations based on vibrational spectroscopy data is valuable for studying underexplored borate systems lacking sufficient thermodynamic data.
Original languageEnglish
Pages (from-to)32451-32464
Number of pages14
JournalCeramics International
Volume51
Issue number20-B
Early online date2 May 2025
DOIs
StatePublished - 1 Aug 2025

    Research areas

  • Borate glass, DFT calculations, Modifiers, Short-range order, Spectroscopic data, Superstructural units

ID: 136079945