Sonochemical synthesis of hierarchical SrWO4:Eu3+/Bi3+ superstructures and tunable luminescence

Hierarchical 3D SrWO4:Eu3+/Bi3+ superstructures were synthesized by the sonochemical process. The SrWO4:Eu3+/Bi3+ phosphors were characterized by XRD, FTIR, SEM, and fluorescence spectrophotometer. The XRD and FTIR results indicated that the samples have the pure tetragonal phase. The SEM images showed that the samples have hierarchical structure composing of lots of similar nanosheets with the thickness of about 20 nm and the width in the range of 0.3-1.5 mu m. Under the excitation of 266 nm, SrWO4:Eu3+/Bi3+ phosphors showed characteristic emission bands originating from the D-5(0) -> F-7(J) (J = 1, 2, 3 and 4) transitions of Eu3+ ions. The codoped Bi3+ ions highly enhanced the emission intensity of Eu3+, suggesting the efficient energy transfer between Bi3+ and Eu3+. The energy transfer from Bi3+ to Eu3+ was mainly through exchange interaction which is located at the nearest neighbour lattices.