The spread of the total energy distribution of thermal field-emitted electrons from LaB6 was calculated and compared with that from W. The results showed that the energy spread of electrons emitted from LaB6 had a maximum at a certain temperature, and that the spread of those from W was smaller than those from LaB6. This suggested that a low work-function material did not necessarily imply good performance of a temperature field-emitted electron source.

Spread of Total Energy Distribution of Thermal Field-Emitted Electrons from LaB6. Adachi, H., Shibuya, Y., Hariu, T., Shibata, Y.: Journal of Physics D, 1977, 10[8], L113-5