Photoluminescence characteristics of energy transfer between Er3+ and Bi3+ in Gd2O3: Er3+, Bi3+

The phosphors, Bi3+- activated Gd2O3:Er3+, were prepared by sol–gel combustion method, and their photoluminescent properties were investigated under ultraviolet light excitation. The emission spectrum exhibited sharp peaks at about 520, 535, 545, 550 and 559 nm due to (2H11/2, 4S3/2)→4I15/2 transitions of Er3+ ions. The luminescent intensity was remarkably improved by the incorporation of Bi3+ ions under 340 nm light excitation, which suggested very efficient energy transfer from Bi3+ ions to Er3+ions. The introducing of Bi3+ ions broadened the excitation band of the phosphor, of which a new strong peak occurred ranging from 320 to 360 nm due to the 6s2→6s6p transition of Bi3+ ions. There is significant energy overlap between the emission band of Bi3+ ions and the excitation band of Er3+ ions. Under 340 nm light excitation, Bi3+ absorbed most of the energy and transferred it to Er3+. The energy transfer probability from Bi3+ to Er3+ is strongly dependent on the Bi3+ ion concentration. Also, the sensitization effectiveness was studied and discussed in this paper.