Ionizing properties of some nonmetal emitters

A mass-spectrometer study is made of the ionizing properties of tungsten carbide, and emitters used to produce a lead-ion current: molten lead chromate on tungsten and a quaternary alumosilicate-based emitter. Work functions phi*, determined from the variation of silver-ion currents with ionizer surface temperature, are 6.7+-0.1, 6.7+-0.4 and 6.94+-0.02 ev, respectively. The lack of agreement of the ionization potentials of silver and lead on tungsten carbide with the phi* values (phi* approximately phisub(max)) is due to the difference in properties between the entire surface and the small ''active'' regions which constitute about 10-3 of the entire emitter area. The heat of vaporization of lead ions is 3.1+-0.6 ev for molten lead chromate and less than or equal to 1.0+-0.2 ev for the complex emitter. The values obtained for phi* explain the high ionizing capabilities of the emitters and provide the basis for a proposed emission mechanism