Thermionic Studies of Various Uranium Compounds

The thermionic constants of UO2, UN, USi2, USi3, UB2, UB4, UC, UC–ZrC, and evaporated films of U on W have been determined using a pulsed strong-field Schottky method within the temperature range of 1200° to 2400°K. The results are consistent with the hypothesis that a film of uranium on the surface activates all of these compounds. This surface film can be provided by a natural excess of uranium in the compound, from a chemical reduction by the base metal, or by evaporation from an external source. The resulting active state for all of the compounds can be described within a factor of 2 or 3 by the empirical Richardson constants Φ=3.0 eV, A = 10 A/cm2deg2.