Observations of Temperature-Induced Material Transformations in Impregnated Scandate Cathode Samples During in situ Heating in the SEM

Dispenser cathodes operate in a high vacuum environment when used as thermionic emitters in vacuum electron devices. Although significant materials research has been performed on cathodes in recent years, limitations of techniques or instrumentation have made it difficult to obtain real-time observations of dispenser cathodes in a dynamic (heated) state using high-resolution techniques such as advanced scanning electron microscopy. In the present study, to observe and better understand how cathode materials and morphologies were created, the authors performed high temperature in situ heating experiments on impregnated cathode pellet pieces in an SEM, to monitor W faceting and impregnant behavior during heating, in real time.