Roger M. Williams

Electrode, current collector, and electrolyte studies for AMTEC cells

Studies of components for AMTEC devices at JPL have focussed on electrode materials, materials and construction of the current collection network, and the [beta][double prime]-alumina solid electrolyte. Electrode materials include thin films of molybdenum metal and metal alloys such as PtW and RhW. Surface self-diffusion coefficients have been determined for Mo electrodes in the temperature range 1050--1200 K, and for RhW at 1125 K. The diffusion coefficients have been used in a grain growth model to predict electrode operating lifetimes at temperatures in this range. Current collection networks sputtered with a thin film of platinum have decreased total electrical resistance in an operating device by 35%. Electrolyte studies have found no mechanical stress or chemical degradation induced by long term operation. Further electrolyte studies have focussed on synthesis of both sodium and potassium [beta][double prime]-alumina ceramic. Potassium [beta][double prime]-alumina solid electrolyte has potential application in a potassium-based AMTEC device which operates at a hot side temperature of [similar to]1000 K.