In order to meet the requirement of THz vacuum devices for high-current density and small-size electron beam

a kind of miniature thermionic cathode is prepared in this paper by depositing an anti-emission Zr coating on impregnated scandate cathode surface via dual ion-beam-assisted deposition (Dual IBAD) and then etching in the center of the anti-emission coating a mini electron emission zone with a diameter of 100

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m via focus ion beam (FIB). Experimental results show that the electron emission has been effectively suppressed in the anti-emission zone within 370 h

and that the average current density of the cathode reach 43 A/cm

2

at 950 ℃ and 58 A/cm

2

at 1 000 ℃. The Ba-Sc-O-W and Zr-Ba-Sc-O-W atomic structural models are established by employing ab initio density functional theory (DFT) calculation. It is found that the surface work function of Ba-Sc-O-W is 1.497 eV when O is absorbed at top site

closing to the experimental result (1.41 eV)

and that the increase of working temperature contributed to the increase of cathode emission

whilst it also results in the formation of Zr-Ba-Sc-O-W atomic structure and the decrease of anti-emission performance (the work function of Zr and Zr-Ba-Sc-O-W are 4.05 eV and 3.348 eV respectively).