IMPEDANCE SPECTROSCOPIC INVESTIGATION OF THE REDUCTION-MECHANISM OF TANTALUMHALIDES DURING ELECTRODEPOSITION IN MOLTEN-SALTS

The mechanism of electrochemical reduction of TaCl5 dissolved in molte n alkalihalides or their mixtures has been investigated by impedance s pectroscopy in the frequency range 10 mHz less-than-or-equal-to omega less-than-or-equal-to 100 kHz at various cathodic and anodic potential s and temperatures up to 1100 K. From a quantitative interpretation of the diffusion controlled impedance various reduction steps are resolv ed to better than +/- 10 mV. This is demonstrated here for a few selec ted examples. Besides this, the most important observation reported he re for the first time is that electronic contributions can become domi nant. Only with appropriate consideration of the electronic conduction a quantitative description of the impedance spectra over the whole po tential range is found.