ELECTROCHEMICAL INVESTIGATION ON THE REDOX CHEMISTRY OF NIOBIUM IN LICL-KCL-KF-NA2O MELTS

The system LiCl-KCl-KF-1 mole percent K2NbF7 (molar ration F-/Nb = 8) has been investigated in-the temperature range 370 to 725 degrees C by cyclic and square wave voltammetry. In the temperature range from 370 to 520 degrees C Nb(V) was reduced to Nb(III) in two reversible steps : Nb(V) --> Nb(IV) --> Nb(III). At these temperatures subvalent halide s of niobium were formed at more negative potentials. At temperatures above 660 degrees C metallic niobium was formed during reduction. When oxide (molar ratio O2-/Nb = 1.1) was introduced in the melt at 725 de grees C only minor changes were observed in the voltammograms. It is s uggested that oxide addition mainly leads to precipitation of oxide co ntaining compounds.