| 摘要 |
PURPOSE:To increase the electrical conductivity of an electron-emission material layer as a whole to realize a long service life thereof under operation at a high current density of 2A/cm<2> or more, by causing first, second and third layers having specified compositions to adhere onto a substrate composed of nickel. CONSTITUTION:A layer, which consists of an alkalline earth metal oxide containing barium and 0.05 to 5wt.% of scandium oxide as measured with respect thereto, is formed as a first layer 4 on a substrate 1 having nickel as a main component. On the first layer 4, a layer, which consists of an alkalline earth metal oxide containing barium and 0.01 to 5wt.% of one element selected from the group consisting of respective metals and oxides of selenium and tellurium in the VIb group, is formed as a second layer 5. Further, on this second layer 5, an alkalline earth metal oxide containing barium is caused to adhere as a third layer 6. A free barium necessary for electron emission is produced through action of the first layer 4 and attaches onto the third layer 6, contributing to emission of electrons. Further, since the electrical conductivity is increased due to the presence of the second layer 5, generation of Joule heat is decreased, whereby vaporization of barium and hence deterioration of the electron emission characteristics are suppressed. |
