| 摘要 |
PURPOSE:To increase the initial emission current and also to reduce the deterioration of the emission current after an operation for a long time by maintaining an electron emitting substance in which the weight ratio of barium oxide to a rare earth metal oxide is specified over the surface of a heat-resisting metal. CONSTITUTION:As a cathode, an electron emitting substance which consists of a mixture of 0.2-20 wt% of a rare earth metal oxide and an alkaline earth metal oxide including at least barium oxide in the remaining component, and the weight ratio of the barium oxide to the rare earth metal oxide is made 0.4-60 is used. As the rare earth metal oxide, Sc2O3, Y2O3, Gd2O3, or the like is used. And as the metal used for the linear hot cathode, a sort of heat-resisting metal selected from tungsten, molybdenum, and tantalum as the main component is used. |
