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Advances in Molten Salts

ISSN:
1-56700-142-4 (Print)

Niobium - Oxygen interaction in halide melts

L.P. Polyakova
Institute of Chemistry KSC RAS, Apatity, Russia 14 Fersman Str., Apatity 184200, Murmansk region, Russia

E.G. Polyakov
Institute of Chemistry KSC RAS, Apatity, Russia 14 Fersman Str., Apatity 184200, Murmansk region, Russia

T. V. Stogova
Institute of Chemistry KSC RAS, Apatity, Russia 14 Fersman Str., Apatity 184200, Murmansk region, Russia

Abstract

The oxygen effect on niobium complexation in NaCl-KCl-K2NbF7 melts has been studied at 700-720°C by means of linear sweep voltammetry, potentiostatic electrolyses, X-ray diffraction, IR-spectroscopy and optic crystallography analyses. The NaCl-KCl-K2NbOF6, NaCl-KCl-K2Nb02F4 and NaCl-KCl- K2NbF7 melts with addition of Na02 and Nb205 as source of oxygen were investigated. It was shown that at a molar ratio O/Nb=l the predominating complexes in the melt is NbOF5Cl3-. The reduction of these oxo complexes occurred at potentials more cathodic than those for oxygenless complexes. Increase in the O/Nb molar ratio in excess of one leads to a decrease of niobium concentration in the melt. The mechanism of the solubility of K3Nb02F4 compound in NaCl-KCl melt was determined.