Thermionic Electron Emission Capacity of the Ba₃ScGa₂O₇.₅ Impregnated Cathode

The high content of Ba and Sc in Ba3ScGa2O7.5 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1300~^{\circ }$ </tex-math></inline-formula>C by a high-temperature solid-phase method with the stoichiometric mole ratio of BaCO3:Sc2O3:Ga2O<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{3}} =6$ </tex-math></inline-formula>: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/cm2 at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$850~^{\circ }$ </tex-math></inline-formula>C in the dc mode. The sintered mixture of the compound and tungsten powder reveals that the formation of Ba3Sc2WO9 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 Ba3ScGa2O7.5 compound has superior thermionic cathode properties and promising applications in vacuum electron devices.