| 摘要 |
PURPOSE:To restrain deterioration of an electron irradiation property so as to aim at a long lifetime by forming, as a second layer, a film incorporating 0.5-5wt.% of at least one of nickel and cobalt into an alkaline earth metal oxide including barium on a first layer, and sticking, as a third layer, an alkaline earth metal oxide including barium on the second layer. CONSTITUTION:For example, a second layer 6 incorporating 1wt.% of nickel into a ternary oxide of barium, strontium and calcium is formed on a first layer 4 while a third layer 6 made of the ternary oxide of barium, strontium and calcium is stuck onto the second layer 5. On the first layer 4, free barium required for electron irradiation is formed so as to be stuck onto the third layer 6 at the outermost surface, thus contributing to the election irradiation. The existence of the second layer 5 increases conductivity so that a resistance of the whole electron irradiating layer decreases, thereby reducing generation of Joule heat so as to restrain evaporation of barium and further deterioration of an electron irradiation property. Therefore, a long lifetime can be achieved even in case of an operation in a high current density of 2A/cm<2>. |
