Ab initio investigation of the surface properties of dispenser B-type and scandate thermionic emission cathodes

作者：Vlahos Vasilios^*; Lee Yueh Lin; Booske John H; Morgan Dane; Turek Ladislav; Kirshner Mark; Kowalczyk Richard; Wilsen Craig

来源：Applied Physics Letters, 2009, 94(18): 184102.

DOI：10.1063/1.3129193

• ab initio calculations
• barium compounds
• density functional theory
• surface states
• surface structure
• thermionic cathodes
• thermionic electron emission
• work function

Scandate cathodes (BaxScyOz on W) are important thermionic electron emission materials whose emission mechanism remains unclear. Ab initio modeling is used to investigate the surface properties of both scandate and traditional B-type (Ba-O on W) cathodes. We demonstrate that the Ba-O dipole surface structure believed to be present in active B-type cathodes is not thermodynamically stable, suggesting that a nonequilibrium steady state dominates the active cathode's surface structure. We identify a stable, low work function BaxScyOz surface structure, which may be responsible for some scandate cathode properties and demonstrate that multicomponent surface coatings can lower cathode work functions.

• 出版日期2009-5-4