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Thermionic Electron Emission Capacity of the Ba $_{\text{3}}$ ScGa $_{\text{2}}$ O $_{\text{7.5}}$ Impregnated Cathode

Chenning Wang,Xiaoyu Zhou,Tianqi Jiang,Zhenrui Xu,Esmond A. Balfour,Hao Fu

The high content of Ba and Sc in Ba $_{\text{3}}$ ScGa $_{\text{2}}$ O $_{\text{7.5}}$ and its suitable melting point suggest that it is a candidate for thermionic emission in vacuum electron devices. To study its electron emission capacity, this compound was synthesized at 1300 $^{\circ}$ C by a high-temperature solid-phase method with the stoichiometric mole ratio of BaCO $_{\text{3}}$ :Sc $_{\text{2}}$ O $_{\text{3}}$ :Ga $_{\text{2}}$ O $_{\text{3}}$ $=$ 6:1:2. The test cathode impregnated with this material had a high emission capacity with the full-space charge current density of 10.2 A/cm $^{\text{2}}$ at 850 $^{\circ}$ C in the dc mode. The sintered mixture of the compound and tungsten powder reveals that the formation of Ba $_{\text{3}}$ Sc $_{\text{2}}$ WO $_{\text{9}}$ on the cathode surface leads to reduced work function and thus enhanced emission performance. The titled compound is environmentally stable with a low weight gain percentage (4.51%) and a steady phase in the air for 288 h. Coupled with the high emission current density at low temperatures, the cathode impregnated with Ba $_{\text{3}}$ ScGa $_{\text{2}}$ O $_{\text{7.5}}$ compound has superior thermionic cathode properties and promising applications in vacuum electron devices.