Enhanced photoluminescence of Sm3+/Bi3+ co-doped Gd2O3 phosphors by combustion synthesis

Gd2O3:Sm3+ and Gd2O3:Sm3+,Bi3+ powders were prepared by a combustion method. Their structures were determined using X-ray diffraction. UV–visible absorption and photoluminescence spectra were investigated for Gd2O3:Sm3+ and Gd2O3:Sm3+,Bi3+ at different annealing temperatures and different doping concentrations. The emission spectra of all samples presented the characteristic emission narrow lines arising from the 4G5/2→6HJ transitions (J=5/2, 7/2, and 9/2) of Sm3+ ions upon excitation with UV irradiation. The emission intensity of Sm3+ ions was largely enhanced with introducing Bi3+ ions into Gd2O3:Sm3+ and the maximum occurred at a Bi3+ concentration of 0.5 mol%. The relevant mechanisms were discussed with the sensitization theory by Dexter and the aggregation behavior of Bi3+ ions.