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Phase Equilibria and Structural Species in MgF 2 ‐MgO, MgF 2 ‐CaO, and MgF 2 ‐Al 2 O 3 Systems
Author(s) -
SHARMA RAM A.
Publication year - 1988
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1988.tb05859.x
Subject(s) - eutectic system , ion , differential thermal analysis , phase diagram , phase (matter) , analytical chemistry (journal) , materials science , mineralogy , chemistry , crystallography , microstructure , diffraction , physics , optics , chromatography , organic chemistry
Partial equilibrium phase diagrams for the systems MgF 2 ‐MgO, MgF 2 ‐CaO, and MgF 2 ‐Al 2 O 3 were determined by differential thermal analysis. Simple eutectics were observed at 8.5 mol% MgO and 1228°± 3°C in the MgF 2 ‐MgO system, at 7.5 mol% CaO and 1208°± 3°C in the MgF 2 ‐CaO system, and at 2.5 mol% Al 2 O 3 and 1250°± 3°C in the MgF 2 ‐Al 2 O 3 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 Mg 2+ , F ‐ , and O 2‐ ions in the MgF 2 ‐MgO system; Mg 2+ , Ca 2+ , F ‐ , and O 2‐ ions in the MgF 2 ‐CaO system; and Mg 2+ , Al 3+ , F ‐ , and AlO 2¯ ions in the MgF 2 ‐Al 2 O 3 system. Well‐defined long needles of MgO in the MgF 2 ‐MgO system, less defined needles of CaO in the MgF 2 ‐CaO system, and Al 2 O 3 grains in the MgF 2 ‐Al 2 O 3 system were observed by optical microscopy.