Effect of Oxide Particle Size on Electron Emission and Vacuum Arc Characteristic of Mo-La2O3 Cathode

Abstract A nanocomposite Mo-4wt% La 2 O 3 cathode was prepared by a high-energy ball-milling and hot pressing technique. The sizes of lanthana particles in the nanocomposite Mo-La 2 O 3 cathode are less than 100 nm; in contrast, the sizes of thoria particles are about 1∼2 μm in a commercial W-4wt% ThO 2 cathode. The average vacuum arc-starting field intensity of the nanocomposite Mo-La 2 O 3 cathode is 2.97×10 7 V/m, which is 62.7% lower than that of the commercial W-ThO 2 . The nanocomposite Mo-La 2 O 3 cathode exhibits superior electron emission performances, and its distribution area and thickness of electron emission spots are remarkably larger, as compared to those of the commercial W-ThO 2 cathode. The size of oxide particles has a great effect on the electron emission performances and vacuum arc characteristics of cathode. The electron emission performance of Mo-La 2 O 3 cathode will be improved with decreasing of the lanthana particles size. When La 2 O 3 particle size decreases to less than 100 nm, the electron emission area and ability of the Mo-La 2 O 3 cathode significantly increase. The much enhanced electron emission performance of the nanocomposite Mo-La 2 O 3 cathode is attributed to the formation of a higher inter electric field and space-charge regions at the interphase boundaries between Mo and La 2 O 3 phases.