Theory of thermionic emission of scandate cathodes

The effect of microimpurities in barium oxide on the parameters of its electronic structure and, accordingly, on the work function is demonstrated experimentally and substantiated theoretically considering the decisive role of oxygen vacancies in the formation of thermoemission properties of barium oxide crystallites. It is found that depending on the crystallite size in the nanosize region, scandium microimpurities in barium oxide crystallites lead to the formation of various types of domains enriched in scandium atoms and characterized by a smaller work function on the crystallite surface. A physical model is proposed and the dependence of the work function of the domains on the temperature and concentration of oxygen vacancies in barium oxide crystallites doped with scandium atoms is calculated theoretically for different types of domains. The experimental technique permitting a correct physical determination of emission properties of scandate cathodes is formulated.