Research Progress on LaB₆ Cathode Material and Its Applications in Electric Propulsion

Lanthanum hexaboride (LaB₆), with its low work function, high melting point, high electrical conductivity, low evaporation rate, resistance to ion bombardment, and stable physicochemical properties, has become a widely studied electronic emission material. It has been extensively applied in fields such as high-resolution electron microscopes and electric propulsion systems. LaB₆ has a simple cubic crystal structure, with La atoms located in the B₆ octahedral framework. Each La atom has three valence electrons, two of which form chemical bonds with B atoms, while the remaining valence electron is relatively free and can move freely within the framework. This unique structure gives LaB₆ excellent stability and outstanding electron emission capability. This paper provides a detailed introduction to the preparation methods of both polycrystalline and single-crystal LaB₆, as well as optimization strategies for its electron emission and mechanical properties. In terms of LaB₆ applications, the paper focuses on its progress in the field of electric propulsion, particularly summarizing recent research and applications of LaB₆ hollow cathodes in electric thrusters, both domestically and internationally. Based on this, the paper also analyzes and looks forward to the technical challenges in the development of LaB₆ electronic emission materials and explores future research and application directions.