Theory of thermionic and secondary emission properties of palladium–barium cathodes of microwave electrovacuum devices

A model of the surface structure of a palladium–barium cathode is proposed and the Dionne secondary electron emission model is used to calculate the dependence of the secondary electron emission coefficient of barium oxide crystallites forming on the surface of a cathode during its thermal activation on the temperature and oxygen vacancy concentration in the oxide. It is shown that the emission properties of a palladium–barium cathode significantly depend on both the emission properties of barium oxide crystallites and the cathode relative surface area occupied by them. The theoretical nomograms are built that relate the measured surface-averaged work function to the secondary electron emission coefficient of a palladium–barium cathode; the nomogram parameters are the temperature, oxygen vacancy concentration in barium oxide crystallites, and the relative cathode surface area occupied by them.