Electrical Conductivity of Oxide Cathode Coatings

Conductivity measurements on activated coatings give results similar to those of Vink and Loosjes. Their theory implies barium concentration of at least 10 19 atoms/cm 3 . Hall effect measurements indicate 10 14 electrons/cm 3 at 1 100° K, and free path 2 × 10 -5 cm. This result may not in fact be inconsistent with the Vink-Loosjes theory. P-type conductivity is not encountered in well activated coatings, and is a feature developing while drawing emission under non-activating conditions. It is due to oxidizable impurities in the coatings. Rapid poisoning or activating effects at low temperatures emphasize the importance of phenomena at surfaces, and it is suggested that these are associated with electron or hole movement rather than ion movement.