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The Chemical Stability and Electrochemical Behavior of Dy2O3 in Molten CaCl2

Jianxun Song, Bart Blanpain and Jan Fransaer

Abstract The chemical stability of Dy2O3 in molten CaCl2 was studied by con- focal scanning laser microscopy. Results illustrate that Dy2O3 is relatively stable in molten CaCl2, and it is a good candidate for the extraction of dysprosium or dysprosium alloys through direct electrochemical reduction. The electrochemical behavior of dysprosium oxide in contact with either a solid molybdenum or a liquid tin cathode has been investigated by cyclic voltammetry in a CaCl2 melt at 1173 K (900 °C).

Keywords Dy2O3 • Molten CaCl2 • Direct reduction • CSLM • Liquid electrode


Dysprosium is produced by calciothermic reduction of DyF3, reduction distillation of Dy2O3 followed by master alloy distillation of Dy-Mg and electrochemical reduction of Dy from DyCl3 in molten salts [1-3].

Compared with calciothermic or magnesiothermic reduction method, molten salt electrolysis is widely used to prepare RE metals and alloys because of its simplicity and high processing rate. The cathodic electrochemical reduction of solid oxides, which is called the Fray-Farthing-Chen (FFC) Cambridge process, has been studied for the preparation of titanium from TiO2 since 2000 [4]. Actually, the method could be applied to produce many other metals, such as Nb, Ta, Zr, Cr, W and rare earth metals. Kim et al. [5] and Xie et al. [6] studied the direct electrochemical reduction of Dy2O3 in CaCl2 melts. It was reported that Dy2O3 could be reduced to metallic dysprosium and it is one step process from Dy(III) to Dy. So far, no other paper was published on the dysprosium extraction from Dy2O3 especially on a liquid electrode.

J. Song (H) • B. Blanpain • J. Fransaer

Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Heverlee, Belgium

e-mail: This email address is being protected from spam bots, you need Javascript enabled to view it ; This email address is being protected from spam bots, you need Javascript enabled to view it © The Minerals, Metals & Materials Society 2017

A. Allanore et al. (eds.), Materials Processing Fundamentals 2017,

The Minerals, Metals & Materials Series, DOI 10.1007/978-3-319-51580-9_3

Thus, in order to optimize the direct reduction process, the chemical stability and the electrochemistry of Dy2O3 in molten CaCl2 at 1173 K (900 °C) was studied using confocal scanning laser microscopy and cyclic voltammetry respectively.

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