Work function distribution for W–Ir mixed metal matrix cathodes

Mixed metal matrix cathodes have inherent non-uniformity and patchiness of emission due to the presence of two-alloy phase structure on the surface. I–V characteristics of cathode studied in a close spaced diode configuration is one of the easy and cost effective methods to estimate the variation of work function on the cathode surface. Tungsten iridium mixed metal matrix dispenser cathodes of Ø1.4 mm (80 wt.% W–20 wt.% Ir) have been fabricated in the laboratory and their I–V characteristics have been investigated in diode configuration. In this paper the model suggested by Tonnerre et al. has been used to find out the work function distribution of W–Ir cathodes from I–V characteristics. An attempt has been made to correlate the microstructure with the work function values