<p>According to the present invention, an impregnated cathode is provided wherein an alloy layer (19) of iridium and tungsten is formed on a surface of a porous pellet (11) impregnated with an oxide of an alkali earth metal, wherein a crystal structure of the alloy has an epsilon II phase comprising an hcp structure whose lattice constants a and c satisfy 2.76 </= a </= 2.78 and 4.44 </= c </= 4.46, respectively. The impregnated cathode of the present invention maintains stable electron emission characteristics from an early stage of operation.</p>
