THE MOLAR VOLUMES AND THE SURFACE TENSIONS OF MELTS IN THE SYSTEMS CAF2-LIF, CAF2-NAF, AND CAF2-MGF2, CAF2-SRF2, CAF2-BAF2

Surface tension and density of molten CaF2-based binary system were measured. From the measurement, the following results were obtained. (1)Molar volumes of the melts in the systems CaF2-NaF, and CaF2-BaF2 are deviated possitively from the additive rule, while for CaF2-LiF and CaF2-MgF2 melts negative deviation from the additive rule on volume is found, but CaF2-SrF2 melt behaves ideally on volume.(2)Surface tensions of the melts in the binary systems can be expressed by Guggenheim's equation for regular solution, if a suitable interaction energy co of each binary system is selected. (3)The interaction energy co, estimated from surface tension of binary fluoride systems, is related to the excess volume on mixing for CaF2-/WxF2 equi-molar composition (x=1 for divalent and x=2 for monovalent fluoride). (4)Liquidus lines for the systems, calculated from the interaction energy co in combination with the thermochemical data are fairly in good agreement with those reported, but that for CaF2-NaF system is exceptional. (5)Surface tentions of binary fluoride melts are strongly depended on packing density of fluorine ions on the surface. © 1990, The Iron and Steel Institute of Japan. All rights reserved.