ELECTRICAL-CONDUCTIVITY MEASUREMENTS OF BINARY-SOLUTIONS OF MOLTEN ALKALINE-EARTH FLUORIDES

The electrical conductivities of binary solutions of molten MgF2-CaF2, MgF2-SrF2, MgF2-BaF2, CAF2-SrF2, CaF2-BaF2, and SrF2-BaF2 were measured by electrochemical impedance spectroscopy in a conductance cell comprising twin capillaries of pyrolytic boron nitride, movable tungsten electrodes, and a molybdenum crucible. In three of the systems, MgF2-CaF2, CaF2-SrF2, and SrF2-BaF2, the specific electrical conductivity was found to vary linearly with composition at constant temperature, while in the other three systems, MgF2-SrF2, MgF2-BaF2, and CaF2-BaF2, there were pronounced negative deviations from additivity. In a given binary system, the relative excess specific conductivity was found to vary parabolically with composition at constant temperature. In a homologous sequence the parabolic constant was proportional to the relative polarizability of the cations comprising the binary system.