Thermodynamic modeling of the Li2O-Na2O-Al2O3-SiO2 system under atmospheric pressure

English Abstract:

The system Li₂O-Na₂O-Al₂O₃-SiO₂ contains numerous minerals of geological interest such as eucryptite (LiAlSiO₄), spodumene (LiAlSi₂O₆), petalite (LiAlSi₄O₁₀), nepheline (NaAlSiO₄), jadeite (NaAlSi₂O₆) and albite (NaAlSi₃O₈) which are present in alkali-rich granites and pegmatites, for example. A critical assessment of the Li₂O-Na₂O-Al₂O₃-SiO₂ system was conducted using all available literature data. All the thermodynamic properties (like enthalpy, entropy, heat capacity, heat content, etc.) and phase diagram data (e.g. LiAlO₂-SiO₂ in Fig. 1a) were thermodynamically optimized and compared with experimental data. The solubility of SiO₂ in NaAlO₂, LiAlO₂, eucryptite, spodumene, nepheline, jadeite and albite was successfully modelled (e.g. in Fig. 1a) by taking into account the complex crystallographic structure of all the polymorphs involved. A set of optimized model parameters was obtained for all the phases of the system which could reproduce all reliable thermodynamic and phase equilibria data within experimental error limits over the entire temperature and composition range. Our database can be used along with Gibbs energy minimization software to calculate unknown thermodynamic properties and any phase diagram (such as the Li₂O-Al₂O₃-SiO₂ ternary liquidus projection shown in Fig. 1b).