The Research On The Mixed Metal Matrix Cathodes

The cathode is very important in the field of vacuum electronic device. Becauseof the low working temperature, high current density and long life, the Mixed MetalMatrix cathodes have been researched widely. So my issue is devoted to investigatingsteady technology and modelling for Mixed Metal Matrix cathodes.Because the general mixed metal matrix cathode can't reach the emission perfor-mance we need, the research is focused on the W-Ir mixed metal-based cathode madewith Sol-Gel method successfully.The composition, microgram and granularity of the power and the surface andinner of the mixed metal-based cathode are studied by XRD, SEM and EDAX. Theemission performance of the mixed metal-based cathode has been measured. And thein?uence of activation temperature and time on the emission performance has beenresearched. The results show that the surface , inner structure and the emission perfor-mance of the mixed metal-based cathode made with Sol-Gel method are all better thanthe general mixed metal matrix cathode made with Solid-Liquid doping. The emissioncurrent density reaches more than 30A/cm2, when the work temperature is 1100 .The model has three parts: a BaO depletion model , a coverage model and aplasma model. The BaO depletion model comes from the knowledge of the BaO-CaO-Al203 system. And reduce the BaO evaporation to a single reaction. The lowwork function model includes deposition, thermal desorption and ion sputtering. theseparameters have been calculated and quantitative. The plasma characteristics is themost important in the evolution. If we have the temperature, the discharge current andthe plasma parameters we can predict the BaO depletion in everywhere of the insert.Because of the conservative estimate, the result is not accurate, but in the industrialapplications, this conservative estimate can increase the safety factor.