Abstract:

To prepare Al-Tb alloys from Tb₄O₇ assisted by AlF₃ in NaCl-KCl melts, we initially studied the effect of AlF₃ on the dissolution of Tb₄O₇ by analyzing the supernatant and bottom salts. X-ray diffraction (XRD) results revealed that Tb₄O₇ was fluorinated by AlF₃ to form TbF₃. The electrochemical behavior of the NaCl-KCl-AlF₃-Tb₄O₇ system was investigated using a Mo electrode at 1073 K. Cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP) and open circuit chronopotentiometry (OCP) analyses indicated that the under-potential deposition of Tb(III) occurred on pre-deposited Al. The co-deposition of Al-Tb alloys was investigated by galvanostatic electrolysis under different conditions. These samples were characterized by XRD and scanning electron microscopy and energy dispersive spectrometry (SEM-EDS). The Al-Tb alloy obtained by galvanostatic electrolysis at -2.5 A consisted of Al and Al₃Tb phases. The effects of the electrolysis conditions on the composition of the alloy and current efficiency were studied by analyzing the compositions of the Al-Tb alloys by inductively coupled plasma-atomic emission spectrometer (ICP-AES). The current efficiency could reach 76.5% under the conditions of galvanostatic electrolysis at -1.5 A for 2 h.

Key words: Electrochemical behavior, Tb₄O₇, Co-reduction, NaCl-KCl melt, Al-Tb alloy, Current efficiency