Study on the compositions of emission active materials and the emission properties of dispenser cathodes made from Scandia-doped powders

Abstract

Scandia-doped dispenser cathode provided significantly better performance compared to standard dispenser cathodes in the application of microwave devices. Emission active materials are the key to dispenser cathodes. Scandium doping can enhance the performance of dispenser cathodes. In this paper, active materials are fabricated by co-precipitation method. Comparison is made between the active materials undergoing different heat treatments. XRD and SEM methods are employed to analyze the compositions and microstructure of active material samples. The cathode matrix powders are prepared by the sol–gel method using different recipes of scandium content. The contents of scandium oxide are, respectively, 3.5wt%, 4wt% and 5wt%. Emission tests are carried out in dedicated test vehicles. The results show that there are different aluminates including Ba4Al2O7, CaAl2O4, Ba7Al2O10, Ba3CaAl2O7, and Ba3Al2O6 come into being after heating using different techniques. The cathode impregnated with self-developed emission materials which numbered LN4 can achieve an inflection point emission current density of 122A/cm2 at 1165°C. On the study of different cathode matrix powders, when impregnated with the conventional material (S), the cathode made from 3.5wt% Scandia-doped powders has the best emission performance. The 4wt% cathode sample performs better when the cathodes are impregnated with the self-developed emission materials.