| 摘要 |
PURPOSE:To maintain the electron discharging ability of an oxide cathode for a long time, and enable equalized electron discharge of the cathode by subjecting a metallic Ni base body material to heat treatment at a high temperature to make crystal grains of a given size to be grown, and subjecting the metallic Ni base body to work before it is decarburized in a wet atmosphere of hydrogen. CONSTITUTION:A metallic Ni base body material is subjected to a high-temperature heat treatment carried out in an atmosphere of hydrogen at 1,000 deg.C for one hour, thereby Ni crystal grains with a size of over 30mum being grown. Next, the metallic Ni base body is subjected to lathe work of the like, and is subjected to decarburization treatment carried out, for example, in a wet hydrogen atmosphere with a dew point of 20 deg.C at 950 deg.C for one hour. After that, an oxide of Ba, Sr, Ca or the like working as an electron discharge source is made to adhere to the former metallic Ni base body. By the means mentioned above, the electron discharging ability of an oxide cathode can be maintained for a long time, since almost no harmful effect of an intermediate layer exists. Besides, the cathodes can provide equalized electron discharge. |
