LaB6.06 crystals were obtained by using the floating zone method. The thermionic emission properties were compared with those of the stoichiometric crystal cathodes. It was found that increasing the boron content decreased the evaporation rate which, in turn, determined the lifetime of the cathodes without affecting emission properties. Composition control was found to be very effective in extending the lifetime of the cathodes.

Thermionic Emission Properties of Boron-Rich LaB6 and CeB6 Crystal Cathodes. Otani, S., Ishizawa, Y.: Journal of Alloys and Compounds, 1996, 245[1-2], L18-20