Synthesis and luminescence enhancement of Eu3+/Sm3+ co-doped Ca9Bi(VO4)7 phosphor for white-light-emitting diodes
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A series of Ca9Bi(VO4)7:Eu3+ and Ca9Bi(VO4)7:Eu3+, Sm3+ red-emitting phosphors were prepared via a citric acid-assisted sol combustion method. X-Ray diffraction profiles illustrated that all the samples were well matched to the rhombohedral crystal structure of pure Ca9Bi(VO4)7 phase with the R3c space group. The excitation spectra showed two effective excitation peaks, which are located near-ultraviolet light (393 nm) and blue light (464 nm) respectively. It can be concluded from the emission spectrum that the strongest emission peak was located at 618 nm at the excitation of 464 nm, which is due to the 5D0→7F2 transition of Eu3+. The Eu3+/Sm3+ co-doped Ca9Bi(VO4)7 sample exhibited stronger emission intensity at 618 nm owing to the energy transfer between Sm3+ and Eu3+. By analyzing the energy level diagram, the energy transfer process between is Sm3+ and Eu3+ explained. Moreover, the chromaticity coordinates of Ca9Bi(VO4)7:0.07Eu3+, 0.08Sm3+ was located near the standard red light region, and it also exhibited higher color purity than the blue-light-excited commercial SrS:Eu2+. Under the excitation of blue light, the excellent luminescence properties of Ca9Bi(VO4)7:Eu3+, Sm3+ makes it a potential red phosphor which can be used in white-light-emitting diodes.
The authors acknowledge the financial support from the Key Scientific and Technological Research and Development Program (Grant No. 2017GZ0400), Sichuan Province, P.R. China and also acknowledge the project of CDUT innovation team (utilization of rare earth resource and new materials, Grant No. 10912-kytd201506).
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