Jo Feb 15, 2024

Rare earth neodymium and neodymium-iron alloys are the main materials for production of Nd-Fe-B magnet.

The density, electric conductivity and melting point are the important properties of molten neodymium electrolyte. Knowledge of density is helpful for electrolyte selection with reasonable composition, which contributes to better separation of melts and metallic neodymium.

There have been some reports on the physical properties of neodymium fluoride electrolyte, where alkali fluorides were supposed to replace LiF and the changes of these physical properties with temperature and composition of the electrolyte were considered.

In an attempt to reduce the cost of producing metallic neodymium and neodymium-iron alloys by molten salt electrolysis, Jang Pok Nam, a section head at the Faculty of Metal Engineering, has investigated the melting point, density, electric conductivity and viscosity of ternary (NdF3-LiF-BaF2, NdF3-LiF-CaF2) and quaternary (NdF3-LiF-BaF2-CaF2) neodymium fluorides.

He drew the following conclusions.

The melting point of 90wt% (NdF3-LiF)-10wt% (BaF2-CaF2) melt is the lowest, about 702℃ and the density of molten salts linearly changes with the temperature. In ternary system, the melting points of 85wt%(NdF3-LiF)-15wt%BaF2 and 90wt%(NdF3-LiF)-10wt%CaF2 fall relatively, and in quaternary system, 90wt%(NdF3-LiF)-10wt%(BaF2-CaF2) has the lowest melting point among the considered samples. The relation between temperature and density is linear. Addition of BaF2 and CaF2 increased the viscosities of the considered molten salts. However, 90wt%(NdF3-LiF)-10wt%(BaF2-CaF2) melt has the lowest viscosity. Electrical conductivity of molten salts increases with the temperature and the content of LiF. At the same temperature, quaternary electrolyte has a greater value of electrical conductivity than ternary electrolyte. From the above measurements, it is concluded that 90wt%(NdF3-LiF)-10wt%(BaF2-CaF2) melt can reduce the cost of producing neodymium or neodymium iron alloys.