Electronic Transport in Molten Salt Rich Na — NaX Solutions (X = Br, I)

The electronic conductivity of liquid Na—Nal and Na—NaBr has been measured over a wide concentration range from dilute to concentrated nonmetallic solutions at different temperatures between 700 and 900°C. Two methods have been applied, the Wagner polarization technique at low metal activities and an ac‐technique at high activities where the concentration has been varied by coulometric titration. A thermodynamic defect model previously used for solids is developed and extended to liquid solutions. It quantitatively describes the concentration and temperature dependence of the thermodynamic properties as well as the charge carrier concentration in these nonmetallic systems. The electronic mobility has been determined and the transport mechanism approaching the nonmetal‐metal transition is discussed.