Evaluation of Work Function for Scandate Cathodes Produced from Nano-Scandia/Tungsten Composite

Scandate cathodes represent a next-generation performance enhancement over current state-of-the-art tungsten emitters (i.e., the M-type dispenser cathode). The improvement in performance of scandate cathodes is attributed to a lower work function, which yields longer lifetimes, higher power, and/or higher brightness. In this study, we report on a series of scandate cathode emitters fabricated from a novel nano-scandia/tungsten composite powder. The work functions of the cathode surfaces have been measured directly by contact potential difference using a Kelvin probe. These are the first reported work function values for scandate cathodes to be measured directly (in situ) at high temperatures rather than calculated from emission current density via the Richardson-Dushman equation. Several scandate cathodes were determined to have work function values less than that of standard M-type cathodes, with a difference up to ~ 0.4 eV.