Calculated Thermodynamic Data and Metastable Immiscibility in the System SiO2-Al2O3 |
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| Authors: | SUBHASH H RISBUD JOSEPH A PASK |
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| Affiliation: | Materials and Molecular Research Division, Lawrence Berkeley Laboratory and Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720 |
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| Abstract: | Thermodynamic data on activities, activity coefficients, and free energies of mixing in SiO2-Al2O3 solutions were calculated from the phase diagram. Positive deviations from ideal mixing in the thermodynamic data suggest a tendency for liquid immiscibility in both SiO2- and Al2O3-rich compositions. The calculated data were used to estimate regions of liquid-liquid immiscibility. A calculated metastable liquid miscibility gap with a consolute temperature of ～1540°C at a critical composition of ～36 mol% Al2O3 was considered to be thermodynamically most probable; the gap extended from ～11 to °49 mol% Al2O3 at 1100°C. SiO2-rich glass compositions showed evidence of glass-in-glass phase separation when examined by direct transmission electron microscopy. |
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