Simulation Studies of Low Work Function Hollow Cathode Emitter Materials

Low-work function materials are of special interest to plasma thrusters for space applications, solar cells in renewable energy and other electronic devices due to their thermionic emission characteristics. This paper deals with low-work function materials, modelling and simulation aspects to demonstrate the features of thermionic emission. The material properties of low work function are obtained from experimental values reported in the literature. The thermionic emission characteristics are addressed by modelling the hollow cathode emitter as a hot cathode in a vacuum diode using a COMSOL Multiphysics environment. The emitted electrons give rise to space charge, which helps in identifying the potential drop across the diode. The potential drop is compared with the Langmuir-Fry model. Furthermore, simulations are performed to obtain the saturation currents for the insert materials. Cerium hexaboride has shown higher saturation current in comparison to Lanthanum hexaboride, Tantalum, Tungsten and Molybdenum. Though Lanthanum hexaboride is widely used as a hollow cathode emitter, the results encourage the consideration of Cerium hexaboride as a promising alternative. Major Findings: The planar diode simulation studies helped rank emitter materials through developed electric potential and current saturation studies. Cerium hexaboride, Lanthanum hexaboride and Tantalum are recommended emitter materials.