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2024
ACL
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Salomé Pannefieu, Charles Le Losq, Pierre Florian, Roberto Moretti, 'Effect of the Na/Mg mixing on the structure and properties of aluminosilicate melts', J. Non-Cryst. Solids 637 123056 (2024) doi:10.1016/j.jnoncrysol.2024.123056
This study documents the mixed modifier effect occurring between Na and Mg in aluminosilicate glasses. Rheological, thermodynamic, and structural data were acquired on compositions with 37.5 mol% Na2O+MgO, 12.5 mol% Al2O3 and 50 mol% SiO2. When Na substitutes Mg, melt viscosity decreases non-linearly, as does glass configurational entropy, showing large deviations from the ideal mixing law. This suggests ordering in the glass atomic structure upon Na/Mg mixing, as supported by structural data. Indeed, as Na2O/(MgO+Na2O) increases, Raman spectra reveal a shift of the 2Q3= Q2+Q4 equilibrium to the left-hand side, while 27Al MAS NMR spectra reveal that the Al coordination tends to 100 % Al[IV]. 23Na MAS NMR data further indicate that the network modifier/charge compensator role of metal cations also changes upon Na/Mg mixing. Those results therefore suggest important changes in melt/glass structure as alkali cations substitute calc-alkaline ones, with important rheological and thermodynamical impacts.
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