Internal mobility of Ln3+ ions in the KCl-LnCl3 and NaCl-NdCl3 systems. A single coefficient correlation model

Literature data on internal mobility of cations in MCl-LnCl3 systems are available only for three KCl-LnCl3 systems (lanthanum, neodymium and dysprosium) and for one system with sodium chloride - NaCl-NdCl3. These data, as well as mobilities of Ln3+ cations in molten LnCl3, calculated on the basis of electrical conductivities and molar volumes of melts, have been critically reviewed. A simple equation was proposed to describe the dependence of internal mobility of Ln3+ cations on the LnCl3 equivalent fraction in the melt. The single coefficient in this equation is characteristic for specified system and represents a difference between internal mobility of Ln3+ cations in molten LnCl3 and mobility of this cations in infinitely diluted solution of LnCl3 in alkali metal (potassium) chloride. It has been assumed that this coefficient linearly depends on the Ln3+ radius, what enabled calculation of internal mobilities of Ln3+ ions for other KCl-LnCl3 systems, not investigated yet. Significant difference between mobility of Nd3+ cations in NaCl-NdCl3 and KCl-NdCl3 systems reveals that alkali metal cations distinctly affect migration properties of lanthanide ions in molten halide melts.