| 摘要 |
PROBLEM TO BE SOLVED: To reduce the lowering of emission current at the time of operating a device for a long time, and prolong the lifetime of the device by coating a base with the electronic emitting material formed of particles, which are mainly composed of the oxide of alkaline rare earth group metal and which include zirconium or the like. SOLUTION: A metal base 3 is provided in an opening part of one end of a cylindrical sleeve 2 provided with a built-in heater coil 1, and the base 3 is mainly composed of nickel and the base 3 includes reduction element such as magnesium. The base 3 is coated with the electron emitting material formed of particles of alkaline rare earth group oxide, which includes zirconium or the like. Namely the metal base 3, which is mainly composed of nickel, is coated with the electron emitting material formed of the particles, which include at least one of titanium, zirconium and hafnium. With this structure, lowering of the emission current at the time of operating a device for a long time can be reduced, and lifetime can be prolonged. |
