Phase Equilibria and Structural Species in MgF2-MgO, MgF2-CaO, and MgF2-Al2O3 Systems |
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Authors: | RAM A SHARMA |
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Affiliation: | General Motors Research Laboratories, Warren, Michigan 48090–9055 |
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Abstract: | Partial equilibrium phase diagrams for the systems MgF2-MgO, MgF2-CaO, and MgF2-Al2O3 were determined by differential thermal analysis. Simple eutectics were observed at 8.5 mol% MgO and 1228°± 3°C in the MgF2-MgO system, at 7.5 mol% CaO and 1208°± 3°C in the MgF2-CaO system, and at 2.5 mol% Al2O3 and 1250°± 3°C in the MgF2-Al2O3 system. On the basis of agreements between the activities calculated by the Clausius-Clapeyron equation and Temkin's model using the present data, the eutectic melt consists of Mg2+, F-, and O2- ions in the MgF2-MgO system; Mg2+, Ca2+, F-, and O2- ions in the MgF2-CaO system; and Mg2+, Al3+, F-, and AlO2¯ ions in the MgF2-Al2O3 system. Well-defined long needles of MgO in the MgF2-MgO system, less defined needles of CaO in the MgF2-CaO system, and Al2O3 grains in the MgF2-Al2O3 system were observed by optical microscopy. |
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