Thermodynamics of niobium chlorides and mixtures with alkali chlorides

摘要

Refractory metals and particularly niobium and tantalum are obtained by molten salt electrolysis. Several authors /1-6/investigated the electrochemical reduction of niobium ions in chloride or chloride + fluoride melts. However the current efficiency during electrolysis is trongly dependent on the "average" valence of the bath. Different reduction steps are proposed with niobium valences ranging from V to I. This is supported by the existence of many stoichiometric compounds. However, very few if not nothing is known on thermodynamics.