Bismuth-doped Y2O3: Eu is used as red phosphors with very high efficiency and appropriate emission wavelength. These red phosphors have been synthesized by homogeneous coprecipitation and solid-state reaction without any flux, which may be used in the field of white LEDs (light-emitting diodes). The crystal structure of bismuth-doped Y2O3: Eu is cubic (space group: Ia (3) over bar) with C-2 and S-6 sites. Y2O3: Eu can be excited by charge transfer (254 nm) and direct excitation (about 350-420 nm). When incorporated in Y2O3:Eu phosphors, Bi3+ ions act as a sensitizer for Eu3+ ions under 350 nm radiation. The energy transferred from Bi3+ ions to Eu3+ ions by a nonradiation process resulted in the final emission from excited Eu3+ ions. The emission is observed at 610 nm, which is due to the electric dipole transition D-5(0) -> F-7(2) induced by the lack of inversion symmetry (C-2 site). Moreover, luminescence intensity of Y2O3:Eu, Bi increases with sintering temperature. Bismuth concentration dependence energy transfer rate and color purity have been observed in this investigation. (c) 2005 The Electrochemical Society. All rights reserved.