Abstract
Thermionic coatings based on the hexaborides of rare-earth elements (ReB 6) were deposited onto molybdenum and tungsten substrates using DC magnetron sputtering from LaB 6, CeB 6, SmB 6 and YB 6 targets. Films were investigated by means of scanning electron microscopy, electron probe microanalysis and X-ray diffraction. The work function and electron emission characteristics of the coatings have been studied by the thermionic emission method using coated tungsten filaments. After optimization of the sputtering parameters, extremely fine-columnar coatings consisting of predominantly (100)-orientated LaB 6, CeB 6 and SmB 6 crystals were obtained. The Y-B films showed nearly amorphous film growth. All coatings were overstochiometric with B:Re atomic ratios ranging from 6.3 to 7.5. The work function was measured to be in the range 2.6–3.3 eV. Coated cathodes worked with comparable electron emission current at temperatures approximately 1000°C below the operating temperature of uncoated tungsten filaments. LaB 6 and CeB 6 were found to be the most promising electron emissive coating materials useful as low temperature emitters. However, satisfactory lifetimes may be only yielded at low operating temperatures and vacuum pressures.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
