Impedance Spectroscopic Investigation of the Reduction Mechanism of Tantalumhalides During Electrodeposition in Molten Salts

Abstract The mechanism of electrochemical reduction of TaCl 5 dissolved in molten alkalihalides or their mixtures has been investigated by impedance spectroscopy in the frequency range 10 mHz≤ ω ≤100 kHz at various cathodic and anodic potentials and temperatures up to 1100 K. From a quantitative interpretation of the diffusion controlled impedance various reduction steps are resolved to better than ±10 mV. This is demonstrated here for a few selected examples. Besides this, the most important observation reported here for the first time is that electronic contributions can become dominant. Only with appropriate consideration of the electronic conduction a quantitative description of the impedance spectra over the whole potential range is found.