| 摘要 |
PURPOSE:To reduce the evaporation of Ba and restrain the occurrence of grid emission by providing a layer composed of oxide mainly containing either SrO or CaO in addition on a layer composed of alkaline earth metal oxide containing Ba. CONSTITUTION:In an oxide cathode which is made up of Ni base substance 1 containing small-amount active metal and a layer 2 composed of alkaline earth metal oxide containing at least Ba, formed thereon, a layer 3 composed of oxide mainly containing either SrO or CaO is provided in addition on the layer 2 composed of alkaline earth metal oxide containing Ba. In this way, by providing the layer (the second layer) composed oxide mainly containing either SrO or CaO in addition on the layer (the first layer) composed of alkaline earth metal oxide containing at least Ba, the evaporation of BaO is prevented during an activating process where the oxide cathode is heated at a high temper ature because of slow diffusion of BaO sourcing from the first layer through the second layer, thus to restrain the occurrence of grid emission. |
