The authors have developed a spherical field-emission cathode based on carbon nanotube paste. The cathode was formed on a 2 mm stainless-steel ball with a silver paste sublayer which provide good adhesion between carbon nanotubes and the metal substrate. The emission current with a density of 300 mA/cm(2) was obtained and the current showed good stability. The cathode was assembled into a luminescent lightbulb with 8 kV anode voltage. The luminous efficiency was 26.4 lm/W on pulse mode. (C) 2008 American Vacuum Society.