| 摘要 |
PURPOSE:To substantially stabilize electron emission characteristic for a long period of time from the initial stage by specifying a crystal structure of an irridium and tungsten alloy of a coated layer to be formed on a porous substrate surface. CONSTITUTION:An irridium and tungsten alloy surface layer 15 is spread on a porous substrate 11 consisting of tungsten or the like made by melting and impregnating mixed oxides of alkaline earth metals such as barium oxide, calcium oxide and almunum oxide to form an impregnated cathode structure. By selecting a crystal structure of said layer so that it consists of epsilon phase to show a range of 2.76-2.78A for the lattice constant(a) and a range of 4.44-4.46A for the lattice constant C, the concentration composition of irridium and tungsten is fixed by epsilon alloy layer which is substantially stable from the initial stage, work function is maintained relatively at low value and electron emission characteristic is substantially stabilized for a long period of time from the initial stage. |
