PURPOSE: A red fluorescent substance excitable with electron beams that is obtained by activating Y2O3:Eu with Tb or Pr at a specific ratio, thus showing good current-brightness saturation properties.

CONSTITUTION: The objective fluorescent substance is obtained by activating Y2O3:Eu with less than 500×10-6mol of Tb or Pr (where 0mol is excluded). The objective fluorescent substance is obtained by subjecting a starting mixture containing Y2O3 and others to first calcination in air at 1,500°C for 2hr, then second calcination in a gas atmosphere containing 4% H2 and 96% Ar at 1,000°C for 4hr. Then, they are a little loosened and washed with 3% HNO3 aqueous solution to remove remaining flux and rinsed with water.