Effect of the Alkaline Metal Cations on

This study investigates the electrical conductivity of molten K3AlF6, Rb3AlF6, Cs3AlF6, and CsF at various temperatures using a pyrolytic boron nitride tube, platinum−rhodium alloy electrode, and alternating current impedance method. The conductivity measurements reveal that the electrical conductivity for molten K3AlF6 is 2.64 S·cm−1 at 1273 K, while for Rb3AlF6, it is 2.06 S·cm−1 at the same temperature. Notably, the conductivity of molten Cs3AlF6 at 1273 K is measured at 1.36 S·cm−1, and that of CsF at the same temperature is 2.57 S·cm−1. The data indicates a consistent decline in electrical conductivity from lithium fluoride/fluoroaluminate solutions through sodium and potassium to cesium fluoride/fluoroaluminate systems. This decrease is attributed to the increasing size and mass of cations, which leads to higher activation energy and lower conductivity. The findings suggest significant implications for electrochemical and electrometallurgical processes relying on the properties of molten salts.