Characterization of osmium-ruthenium coatings for porous tungsten dispenser cathodes

Dispenser cathodes serve as electron sources in numerous vacuum devices, including traveling wave tubes and cathode ray tubes. These devices find use in commercial, military and space applications, requiring a long and reliable operating lifetime, especially for space-based operation. Semicon Associates, in Lexington, KY, leads this market, producing over 20,000 dispenser cathodes annually. The cathodes comprise several materials, including platinum group metal coatings that add significant production cost. It is not yet understood how the microstructure of these precious metal films affects cathode performance. Fundamental understanding of microstructure-property relationships in the coating could improve device performance and allow more economical use of the precious metals.