Jiancan Yang

Scandia-doped tungsten bodies for Sc-type cathodes

Abstract We systematically investigated scandium oxide-doped (and with small amount of rhenium-doped) tungsten bodies for Scandate-type cathodes. Homogeneous microstructure and uniform distribution of scandia were found in these bodies. Sub-micron granular porous bodies with greatly uniformly dispersed scandia are obtained by sintering Sc 2 O 3 and Re doped tungsten powder. Such bodies are thought to be beneficial for emission uniformity. For Scandate-type cathodes with such bodies, a slight decrease of scandia was observed by “in situ” AES analysis after ion sputtering, but it recovers completely on reheating. It is assumed that film-like Sc 2 O 3 coating over tungsten grains but leaving porous areas for diffusion of barium to the surface leads to good emission properties and high resistance to ion bombardment. Reprocucibility has been proved for the body manufactering process. This offers the possibility of improving the performance of these cathodes in applications such as CRT’s.

A Compact Cathode Performance Test System

To meet the requirement for cathode performance investigation, a testing system has been developed. This multi-functional system includes cathode I-U character testing; automatic measurement of Miram curve and conversion into PFWD plot as well as cathode emission uniformity investigation by anode-hole principle (Gibson and Thomas, 1985)

La-Mo film cathode preparation and analysis in situ

Summary form only given. Lanthanum-containing cathodes are an attractive alternative to thorium tungsten cathodes because of their low work function and their comparatively low operating temperatures. The function of La element in La-Mo cathode material was studied by using a set of equipment specially designed to cathode research. A La-Mo film cathode was prepared with pulsed laser deposition (PLD) in diverse vacuum condition. For the first time, the electron emission properties have been measured without exposing to the atmosphere. By means of Auger electron spectroscopy, we investigated the surface composition of the cathode in situ. We find out obviously that the cathode emission properties have relation to the surface La/O ratio. As the La/O ratios get higher, the emission properties show better. The excess La element is contributed to thermionic emission. On the basis of experiment result, the emission mechanism of La-Mo cathode has been discussed.

Study on preparation and thermionic emission of nanometer rare-earth tungsten emission materials

As one of the alternatives Th-W materials, La-W thermionic emission materials appeared in recent years. Although this emission material has good emissivity, it has not been used commercially because of its poor emission stability. Properties of a material depend on composition and microstructure. In this paper, a fine grain tungsten emission material, activated with nanoscale oxide, was fabricated by freeze-drying and spark plasma sintering, which differs completely compared to the conventional process. Emphasis has been concentrated on the relationship between surface composition and electron emission performance.