Study of Nd deposition onto W and Mo Cathodes from Molten Oxide-Fluoride Electrolyte

Abstract

Electrochemical reduction processes of Nd(III) on tungsten and molybdenum electrodes in NdF3+LiF and NdF3+LiF+Nd2O3 were investigated by cyclic voltammetry, chronoamperometry and open circuit measurements. Electrolytes and electrodes were examined after neodymium electrodeposition by optical microscopy and XRD. It was found that tungsten and molybdenum working electrodes behave identically during neodymium complexed ion reduction processes. Their reversible potentials in the electrolytes used differed only by 10 mV, and so did the potentials of the neodymium ion reduction processes. The recorded results indicated that the Nd(III) ions in the melts were reduced in two steps: Nd(III) → Nd(II) and Nd(II) → Nd(0). These consecutive processes are predominantly mass transfer controlled. Electrolytically obtained metal appeared to accumulate on the cathode and no metal neodymium was recorded in the solidified electrolyte placed close to the cathode after completed electrodeposition process. However, it was found that NdF2 formed by the disproportionation reaction between Nd(III) and that deposited Nd(0) coexists with other complex components in the electrolytes used.