Studies of the Influence of ZrH2 Addition to the Impregnant on the Performance of Yttrium Oxide–Tungsten Matrix Ba Dispenser Cathodes

摘要

The cathode in the magnetron should have good secondary emission property and a certain thermionic property. In this article, ZrH ₂ was added as an activator to obtain rare earth-doped tungsten matrix impregnated cathode to improve the emission property. Cathodes with ZrH ₂ (Y15-411-Zr cathode) or without ZrH ₂ (Y15-411 cathode) were prepared by a spray drying method combined with high-temperature sintering in dry hydrogen atmosphere. The emission properties and emission mechanism have been studied. The results showed that thermionic emission performance and secondary emission performance of Y15-411-Zr cathode are 3.4 times and 1.2 times higher than those of Y15-411 cathode, respectively. With the addition of ZrH ₂ , yttrium was produced during activating process, which contributed to the better emission properties of Y15-411-Zr cathode. Furthermore, the work function of barium and oxygen adsorbed on yttrium oxide and yttrium surface was calculated using the first principle. The results showed that the lowest work function of Ba-O absorbed on Y ₂ O ₃ and Y is 1.9 and 1.6 eV, respectively.