Scandate cathode coated with Mo and Sc films

To obtain excellent emission characteristics for scandate cathodes, scandium atoms should be supplied at the cathode surface to make a monolayer with barium and oxygen. In conventional scandate cathodes coated with a thin film that includes scandium oxide, the scandium oxide must be reduced by chemical reactions that generate free-Sc to supply scandium atoms at the surface. The temperature for cathode activation and the emission recovery from degraded emission due to ion bombardment in CRT depend on the supply speed of scandium atoms. To supply scandium to the surface without chemical reactions usually needed, we fabricated a scandium metal layer as part of the thin film. The activation temperature of the new cathode is around 950°Cb. The electron emission after ion bombardment tends to recover at 1000°Cb. Both the temperatures are 100–150°Cb lower than those for conventional scandate cathodes.