Electrodeposition of Mg-Li-Al-La Alloys on Inert Cathode in Molten LiCl-KCl Eutectic Salt

Electrochemical preparation of Mg-Li-Al-La alloys on inert electrodes was investigated in LiCl-KCl melt at 853 K (580 °C). Cyclic voltammograms (CVs) and square wave voltammograms (SWVs) show that the existence of AlCl₃ or AlF₃ could promote La deposition on an active Al substrate, which is predeposited on inert electrodes. All electrochemical tests show that the reduction of La³⁺ is a one-step reduction process with three electrons exchanged. The reduction of La(III)→La(0) occurred at –2.04 V, and the underpotential deposition (UPD) of La was detected at –1.55 V (vs Ag/AgCl). The same phenomena concerning La UPD were observed on two inert cathodes, W and Mo. In addition, Mg-Li-Al-La alloys were obtained by galvanostatic electrolysis on the W cathode from La₂O₃ in LiCl-KCl-MgCl₂-KF melts with aluminum as the anode. X-ray diffraction (XRD) measurements indicated that various phases like the Al₂La, Al₁₂Mg₁₇, and βLi phase (LiMg/Li₃Mg₇) existed in the Mg-Li-Al-La alloys. The distribution of Mg, Al, and La in Mg–Li–Al-La alloys from the analysis of a scan electron micrograph (SEM) and energy dispersive spectrometry (EDS) indicated that the elements Mg, Al, and La distributed homogeneously in the alloys.