Characterization of Material Phases on the Surface and in the Near-Surface Region of Scandate Cathodes

The impressive electron emission capabilities of scandate cathodes continue to receive significant research attention, although there remain gaps in understanding the mechanistic reasons for their performance. This is partly due to lingering questions about the materials and microstructure of the cathode emitting surface. In the current study, scandate cathodes fabricated using related but distinct processes were emission-tested and then characterized using advanced electron microscopy and analytical spectroscopy techniques. The cathode surfaces were consistently observed to consist of faceted tungsten grains decorated with ~100 nm oxide (BaAl
2
O
4
and Sc
2
O
3
) particles and ~20 nm Ba-containing particles.