Average Thermionic Constants of Polycrystalline Tungsten Wires

Abstract

Because of its property of producing large crystals, the "doped" variety of tungsten wire is used in the study of the thermionic properties of single crystal surfaces of tungsten. In order to determine the effect of the impurities added to produce this property, the average high field thermionic constants of polycrystalline doped tungsten wire and undoped tungsten wire were measured. The thermionic constants from the doped wire are somewhat lower than those from the undoped wire which agree well with previously published values. Chemical and spectroscopic analyses before and after heat treatment are included. It is concluded that the differences in thermionic properties between the two types of wire are probably due to different distributions of the types of crystal surfaces exposed.