ELECTROCHEMISTRY OF BORON OXYFLUORIDE COMPLEXES IN FLUORIDE MELTS

The electrochemical behavior of boron oxyfluoride complexes synthesize d directly in the LiF-NaF-KF melt (FLINAK) and those introduced into i t with the aid of the Na3B3O3F6 compound is studied by voltammetry in the temperature range 570-750 degrees C. At lower temperatures in this range, reduction of BOF:! complexes is shown to occur via the ECE mec hanism. The electrode processes become simplified with the growing mel t temperature, so that at 700 degrees C boron reduces to an elementary state via a single irreversible stage. The temperature dependence of the diffusion coefficients for boron oxyfluoride complexes is describe d by the equation log D = -1.66 - 3219/T, and the activation energy fo r diffusion is 61.6 kJ mol(-1). Studying thermal stability of oxyfluor ide electrolytes containing boron showed that the O : B ratio in the m elt undergoes a change due to volatilization of boron trifluoride. Thi s leads to emergence of berate complexes in addition to oxyfluoride co mplexes.