Hollow Cathode With Low Work Function Electride Insert Available to Purchase

Hollow cathodes are critical devices in the successful operation of electric propulsion thrusters. Cathodes featuring C12A7:electride as an ultra-low work function thermionic emitter are hypothesized to have faster start-up times and lower operating temperatures than conventional hollow cathodes. C12A7:electride is a crystalline ceramic in which electrons clathrated in sub-nanometer sized cages act as a conductive medium. Due to its unique atomic structure and large size, C12A7:electride has a predicted work function of 0.6 eV. As a result, C12A7:electride is an attractive option for a thermionic emission material in a hollow cathode. Calculations predict equivalent levels of current emission as LaB₆ or CeB₆, but at much lower temperature. C12A7:electride is stable at temperatures below its re-crystallization temperature (∼1000 °C) and is not consumed during operation. C12A7:electride has been fabricated at CSU using a simplified, one-step approach that results in a more conductive material than previously reported. The material has been integrated into a novel hollow cathode design that takes advantage of its unique properties to decrease start-up time and power consumption. Our paper will discuss preliminary results obtained with several cathode configurations. In addition, results from the experimental determination of basic material properties such as conductivity and work function will be presented. Strategies to further enhance electron emission through surface modifications will also be discussed.