Addition of CeO₂ impurity and emission characteristics of M-type cathodes

The novel M-type cathode material has been successfully developed by mechanically adding CeO₂ impurity into the tungsten matrix. Its microstructures and its emission properties were characterized with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy(XPS), mercury intrusion poremeasurement (MIP) and water cooled anode diode. The results show that doping of rare-earth CeO₂ significantly improves the characteristics of the cathode, and in normal working temperature of 1050 °C, the CeO₂ doped cathode outperforms its counterpart-the conventional barium tungsten cathode. For instance, the CeO₂ doping results in a more uniform distribution of pores, with an average diameter of 2.08 μm. Its continuous and pulsed emission current densities are found to be 6.33 A·cm^-2and 17.48 A·cm^-2, respectively; and its effective work function is 1.86 eV. Besides, CeO₂ doping promotes the diffusion and surface absorption of Ba, leading to higher Ba3d peak.