Characterization of Nd-Bi intermetallic compound formations by co-reduction of Nd(III) and Bi(III) in molten LiCl-KCl eutectic

Abstract

The co-reduction of Nd(III) and Bi(III) by forming intermetallics on an inert W electrode in LiCl-KCl at 773 K was investigated by using transient electrochemical techniques, including cyclic voltammetry, square wave voltammetry, and open circuit chronopotentiometry. It was shown that the formation of the intermetallic compounds was observed between -1.2 and -1.9 V, which is a range of more positive potentials than that of Nd(III)/Nd(0). Peak separation techniques allow determining corresponding I-V curves to five intermetallic compounds of NdBi2, NdBi, Nd4Bi3, Nd5Bi3, and Nd2Bi. For these intermetallic compounds, thermodynamics data including Gibbs free energies of formation, equilibrium potentials, and activity coefficients are obtained. The types and amounts of resulting intermetallic compounds on the inert electrode by co-reduction were dependent on the applied potential and the molar ratio of Bi(III) to Nd(III) ions, respectively. The Bi-rich intermetallic compound of Nd-Bi is mainly formed at a small molar ratio, whereas almost all intermetallic compounds between Nd and Bi are formed at a large molar ratio.