Chair of Non-Ferrous Metals and Gold, National University of Science and Technology “MISiS”, Moscow, Russia:

A. P. Lysenko, Assistant Professor, e-mail: reikis@yandex.ru
V. P. Tarasov, Professor, Head of a Chair
A. Yu. Nalivayko, Engineer
R. S. Selnitsyn, Engineer

This article describes the modern view on mechanism of behavior of electrode processes during the obtaining of rare-earth metals by electrolysis of oxide-fluoride melts. More perfect model of process of neodymium oxide electrolysis was offered due to the analysis of fusibility diagrams of double systems of fluorides of alkaline metals and rare-earth metals. At the same time, there were made the necessary thermodynamic calculations. Participation of rare-earth metals in electrode processes with high current density is possible due to the relatively high dissolubility of these metals` oxides in fluoride melts. This participation makes electrolysis profitable. Low value of Gibbs energy of the considered reactions shows the weakness of rare-earth metals` oxides. As a consequence, this value shows the possibility of decomposition of these oxides with low voltage, which is economically profitable. That`s why, nowadays, metallothermy is practically replaced by electrolyte obtaining of Nd, Tb and Dy.

1. Baymakov Yu. V., Vetyukov M. M. Elektroliz rasplavlennykh soley (Electrolysis of fused salts). Metallurgiya — Metallurgy. 1966. p. 558.
2. Diagrammy plavkosti solevykh sistem. Chast 2 : spravochnik (Diagrams of fusibility of salt systems. Part 2 : reference book). Moscow : Metallurgiya, 1977. p. 199.
3. Zakharova B. S., Reshetnikova L. P., Novoselova A. V. Vestnik MGU. Seriya 2, Khimiya — Moscow University Chemistry Bulletin. 1967. No. 3. pp. 102.
4. Ardashnikova E. I., Borzenkova E. I., Novoselova A. V. Izvestiya Akademii nauk SSSR. Neorganicheskie materialy — Bulletin of USSR Academy of Sciences. Inorganic materials. 1974. Vol. 10. p. 1632.
5. Thoma R. E. Rare-earth halides. 1965. Available at : http://energyfromthorium.com/pdf/ORNL-3804.pdf.
6. Kober V. I. et al. Termodinamicheskie svoystva splavov samariya s legkoplavkimi metallami (Thermodynamic properties of samarium alloys with casting metals). Tezisy dokladov V Kolskogo seminara po elektrokhimii redkikh i tsvetnykh metallov (Thesis of a report of the V Kola seminar on electrochemistry of rare and non-ferrous metals). Apatity, 1986. p. 51.
7. Lysenko A. P., Khayrullina R. T. Metallurgiya alyuminiya (Metallurgy of aluminium). Moscow : MISiS, 2012.
8. Grebnev V. A., Dmitrienko V. P. Poluchenie neodima elektrolizom iz rasplavov (Obtaining of neodymium from the metls by electrolysis). Izvestiya Tomskogo politekhnicheskogo universiteta — Bulletin of the Tomsk Polytechnic University. 2007. Vol. 311, No. 3.
9. Ruzinov L. P., Gulyanitskiy B. S. Ravnovesnye prevrashcheniya metallurgicheskikh reaktsiy (Equillibrium conversions of metallurgical reactions). Moscow : Metallurgiya, 1975. 416 p.
10. Lobanov V. I., Yasnikov G. P., Gordon Ya. M., Telegin A. S. Tekhnicheskaya termodinamika (Technical thermodynamics). Moscow : Metallurgiya, 1992.
11. Morachevskiy A. G., Sladkov I. B. Termodinamicheskie raschety v metallurgii : spravochnik (Thermodynamic calculations in metallurgy : reference book). Moscow : Metallurgiya, 1985.