The diffused barium tungsten cathode is a cathode composed of a porous tungsten matrix and an active substance barium salt. Its working principle is based on thermal electron emission. When the cathode works at a certain temperature, the active substance (such as barium salt) filled inside it will react with the tungsten matrix to generate active barium atoms and gradually diffuse to the cathode surface. These barium atoms form a single atomic dipole layer on the cathode surface, reducing the surface work function, thereby increasing the number of thermal electrons emitted.
The diffused barium tungsten cathode has the advantages of simple preparation process, uniform emission surface temperature, and a working temperature zone that matches the hot end temperature of the concentrated solar energy system. Since a large amount of active substances are stored inside the barium tungsten cathode, it can continuously replenish the barium loss caused by evaporation, gas poisoning, etc., maintain a stable low work function state on the cathode surface, and thus achieve long-term stable thermal electron emission.
The internal pore characteristics of the porous tungsten matrix will have a direct impact on the electron emission performance of the barium tungsten cathode (current emission stability, uniformity, life, etc.). At the same time, the performance of the cathode is mainly determined by two aspects: the porous tungsten matrix and the active material filled in the pores of the matrix – salt. The salt currently used is aluminate mixed with BaO, CaO, and Al2O3 in a certain proportion.
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