Electron emission distribution of (W-Sc_2 W_3 O_<12>)-coated impregnated cathodes is evaluated. The distribution is much larger than that of Os-coated impregnated cathode. The high electron emissive areas are correspond to the regions of the pore sections in which impregnants exist. The distribution is not changed by heating the cathode up to 950℃_b. It might be modeled that Sc_2W_3O_<12>, Sc_2O_3 or Sc prevents the surface diffusion of Ba, and then makes the high Ba concentration area where the work function is low.
