Thermionic Cathodes

P‐29: X‐Ray Absorption of Oxide Cathode Emission Materials

“…show the scanning electron micrographs of the binary and ternary oxides, respectively. The binary system is more porous than the ternary, consistent with the lower density of the binary (0.81g/cm 3 ) system than that of the ternary (0.95g/cm 3 ) system. This indicates that the binary system has larger surface area than the ternary system.…”

“…Scanning electron micrographs of (a) binary system and (b) ternary system. The binary system is more porous than the ternary, consistent with the lower density of the binary (0.81g/cm 3 ) system than that of the ternary (0.95g/cm 3…”

“…The oxide cathode based on BaO is still an attractive electron source for advanced cathode ray tubes (CRTs), although it was first introduced almost 70 years ago [1]. The main reasons for its success are low production costs and the low work function [1][2][3][4].…”

“…In oxide cathode emission materials used for cathode ray tubes (CRTs), the existence of free Ba on the surface is very important to produce the low work function surface of the oxide cathode [6][7][8][9]. However, there are few experimental evidences about the free Ba formation on the surface, even though it is generally accepted in the literature [1][2][3][4]. We used high resolution soft-X-ray absorption spectroscopy (XAS) to study the chemical structure of oxide cathode emission materials.…”

On the emission mechanism of oxide cathodes

“…So a staircase of energy level is formed in the trioxide allowing the electrons to be easily supplemented after emission. Facing his two storage cathodes towards each other, Zalm (1968) measured the conductivities of various systems of coating with different sources in the compartment to produce alkaline-earth' metallic atoms which could be adsorbed on the surface of grain coating, He found that the low-temperature activation energy might be as low as 0·06 eV and no larger than 0-30 eV. These low values of activation energy in conductivity, together with high values in evaporation, are compatible with the addition of Sr and Ca which may improve the overall performance of the cathode.…”