Fundamental Study on the Electrodes for Alkali Metal Thermoelectric Converter: (2nd Report, Impedance measurement and generating characteristics)

A. C. impedance measurement on the alkali metal thermoelectric converter (AMTEC) has been conducted under D. C. polarized conditions in the temperature range from 890-1 123 K. The obtained data have been analyzed in the complex impedance plane in terms of an equivalent circuit for the AMTEC system. The charge transfer resistance at the interface between the beta˝-alumina solid electrolyte (BASE) and porous molybdenum electrodes has been evaluated and approximated by the introduced electrochemical model. The calculated current-voltage curves including the effect of the charge transfer resistance show good agreement with the measured data. The generating characteristics of the AMTEC can be completely predicted by this method, which may be useful for further studies on more efficient AMTEC cells. The contributions of BASE ionic conduction, contact resistance and mass transport through the porous electrode are also discussed.