Sr2Y8(SiO4)6O2:Bi3+/Eu3+: a single-component white-emitting phosphor via energy transfer for UV w-LEDs

A series of Bi3+,Eu3+-doped Sr2Y8(SiO4)(6)O-2 (SYSO) phosphors were synthesized by the Pechini-type sol-gel route. XRD patterns, Rietveld refinement, FT-IR spectra, photoluminescence spectra (PL), fluorescence decay time, and quantum yields (QYs) were utilized to characterize the as-prepared samples. Intense blue-green emission due to the P-3(1) -> S-1(0) transition of Bi3+ ions is produced under UV excitation in Bi3+ singly doped SYSO samples. Spectral analysis illustrates that two kinds of Bi3+ ions are generated by occupying the two kinds of sites (4f and 6h) available for Y in SYSO, denoted as Bi3+(1) and Bi3+(2), corresponding to the two main emission bands at around 413 and 493 nm, respectively. A wide spectral overlap between Bi3+ emission and Eu3+ excitation spectra results in the energy transfer from Bi3+ to Eu3+. This has been demonstrated via the excitation spectra monitored at Bi3+ and Eu3+ emission bands, and the PL emission spectra and decay time of Bi3+ in SYSO:Bi3+,Eu3+ phosphors. The energy transfer mechanism is determined to be dipole-quadrupole interaction. The critical distance of energy transfer from Bi3+ to Eu3+ ions is calculated to be 12.78 angstrom based on the concentration quenching method, which is in good agreement with that of the spectral overlap route (10.03-13.37 angstrom). Moreover, the QYs, CIE chromaticity and thermal quenching properties have also been investigated. White emission color can be realized with the CIE coordinates (0.325, 0.311) and QY 52% for SYSO:0.08Bi(3+),0.48Eu(3+). The above results suggest that SYSO:Bi3+,Eu3+ can be a potential single-component white-emitting phosphor for UV w-LEDs.