Analysis of the Thermionic Emission from Barium Telluride

The thermionic emission from barium telluride in various states of activation has been measured using cathodes formed by the direct reaction of the elements and by the reduction of barium tellurate. The data are presented in the form of effective work function plots. A method of analyzing thermionic emission data by comparing effective work function plots with curves calculated from models of the electronic structure of the material is described. Using this technique, barium telluride was found to have an electron affinity of 1.5±0.2 eV, a donor at about 2.2 eV below the vacuum level and a second donor of lower density about 3.2 eV below the vacuum level.