Electrochemical formation and thermodynamic evaluation of Pr-Zn intermetallic compounds in LiCl-KCl eutectic melts

Abstract

The electrochemistry of praseodymium was studied on liquid Zn film electrode in LiCl-KCl eutectic melts by transient electrochemical techniques. Cyclic voltammogram and square wave voltammogram showed that eight reduction peaks, corresponding to the formation of eight Pr-Zn intermetallic compounds, were observed at less negative potential values, which indicated the underpotential deposition of praseodymium occurs on liquid Zn film electrode. Thermodynamic properties on the formation for Pr-Zn intermetallic compounds, such as activities and relative partial molar Gibbs free energies of Pr in two-phase coexisting states as well as the standard Gibbs free energies of formation for Pr-Zn intermetallic compounds, were estimated using electromotive force (emf) measurement in the temperature range from 723 to 873K. Electrochemical preparation of Pr-Zn alloys was executed by potentiostatic and galvanostatic electrolysis on Zn film electrode and liquid Zn pool electrode, respectively. X-ray diffraction (XRD) indicated that Pr-Zn alloy were comprised of different Pr-Zn intermetallics. The surface microstructures and micro-zone chemical analyses of Pr-Zn alloys were also characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results of SEM-EDS displayed that the distribution of Pr is non-homogeneous in Pr-Zn alloys.