Electrochemical properties of Li₃ N  dissolved in molten LiCl at 900 K

Abstract

Thermodynamic properties of Li₃ N dissolved in the molten LiCl salt at 900 K were explored using electrochemical methods. It was difficult to determine precisely the decomposition voltage of Li₃ N dissolved in the molten salt by cyclic voltammetry. The oxidation wave of N^3- ion could not be located with high accuracy. However, the lithium activity of the Pb-Li alloy in equilibrium with the molten salt containing dissolved Li₃ N under nitrogen atmosphere could be measured electrochemically with high accuracy using the Li/Li⁺ reference electrode. Under the conditions used in this study, the potential of the Li-Pb electrode is equal to the decomposition voltage of Li₃ N The activity of Li₃ N in molten LiCl was determined for anionic fractions of N^3- ranging from χ_N^3-=10^-4 to 0.028. The nitride ion concentration in the salt was determined by chemical titration. The activity coefficient of the Li₃ N at high dilution was found to be very low, around 10^-4 The activity coefficient increases sharply with composition and has a value of 0.25 at χ_N^3-=0.028.