ELECTROCHEMICAL-BEHAVIOR OF TIN SPECIES DISSOLVED IN CRYOLITE-ALUMINAMELTS

Cyclic voltammetry and potential step measurements were performed on p latinum, gold and glassy carbon electrodes in molten cryolite and cryo lite-alumina melts containing SnF2, SnO2 or SnO. The reactions involvi ng dissolved tin species were found to behave more reversibly using a gold electrode. The voltammograms showed peaks attributed to the prese nce of two oxidation states of tin in the melt, ie Sn(II) and Sn(IV). Some waves were accompanied by current oscillations due to the formati on of volatile species, probably SnF2 and SnF4. These oscillations wer e not observed in melts containing dissolved Al2O3, which presumably s tabilizes the tin compounds. Some of the voltammograms gave indication s of anodic precipitation of SnO2 on platinum. Such precipitation was confirmed using potential step measurements. Copyright (C) 1997 Elsevi er Science Ltd.