A red cathode-ray phosphor, Y2OS:Eu3, shows a large decrease in luminescence efficiency at high excitation density at room temperature. The luminescence intensity is approximately proportional to the square root of the electron-beam current, indicating that a bimolecular-type nonradiative process competes with a radiative process. In undoped Y2OS, broad luminescence bands with peaks at around 35and 440nm are found at 80K. The defect levels involved in this luminescence can be a candidate of the nonradiative process at room temperature, because the luminescence is thermally quenched at room temperature.
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