Preparation and luminescence properties of rare-earth doped fiber with spectral blue-shift： SrAl2O4：Eu^(2＋),Dy^(3＋) phosphors/triarylsulfonium hexafluoroantimonate based on polypropylene substrate

The rare-earth doped fiber with spectral blue-shift based on long afterglow luminescent materials SrAl2O4：Eu^2＋,Dy^3＋ phosphors and an organic cationic photoinitiators-triarylsulfonium hexafluoroantimonate（TSHF） in the presence of polypropylene substrate（PP） was prepared by melt-spinning process. Scanning electron microscopy（SEM）, infrared spectroscopy（IR）, afterglow properties and luminescence properties were tested. The results of SEM and FTIR spectra showed that the fiber consisted of irregular particles and had independent structural constitution of SrAl2O4：Eu-（2＋）,Dy-（3＋） phosphors, TSHF and polypropylene. Furthermore, it was observed that there existed the highest afterglow initial intensity for the fiber with the TSHF concentration of 5 wt.%. More interestingly, the emission peak shifted to blue area gradually as the TSHF doping increased. The rare-earth doped fiber was distributed on blue light area in the CIE 1931 chromaticity diagram, which showed more obvious blue-shift phenomenon than the yellow-green light of SrAl2O4：Eu^2＋,Dy^3＋ phosphors.

Improved luminescent properties of SrZn_2(PO_4)_2:Sm^(3+) doped with Li^+, Na^+ and K^+ ions

SrZn2(PO4)2:Sm3+ phosphor was synthesized by a high temperature solid-state reaction in atmosphere. SrZn2(PO4)2:Sm3+ phosphor is efficiently excited by ultraviolet(UV) and blue light, and the emission peaks are assigned to the transitions of 4G5/2-6H5/2(563 nm), 4G5/2-6H7/2(597 nm and 605 nm) and 4G5/2-6H9/2(644 nm and 653 nm). The emission intensities of SrZn2(PO4)2:Sm3+ are influenced by Sm3+ concentration, and the concentration quenching effect of SrZn2(PO4)2:Sm3+ is also observed. When doping A+(A=Li, Na and K) ions, the emission intensity of SrZn2(PO4)2:Sm3+ can be obviously enhanced. The Commission Internationale de l'Eclairage(CIE) color coordinates of SrZn2(PO4)2:Sm3+ locate in the orange-red region. The results indicate that the phosphor has a potential application in white light emitting diodes(LEDs).

Growth and optical properties of Dy^(3+)/Eu^(3+) co-doped NaYF_4 single crystals with cubic lattice for white LED application

Dy3+/Eu3+ co-doped cubic lattice Na YF4 single crystal with high quality in the size of ~Φ1.0 cm×10.0 cm was grown by an improved Bridgman method using potassium fluoride(KF) as assistant flux. X-ray diffraction(XRD), absorption spectra, excitation spectra and emission spectra are measured to investigate the phase and luminescent properties of the crystal. The effects of excitation wavelength and concentrations of Dy3+ and Eu3+ ions on the luminescent characteristics are analyzed. The Na YF4 single crystal with the doping molar concentrations of 1.205% Dy3+ and 0.366% Eu3+ exhibits an excellent white light emission with chromaticity coordinates of x=0.321, y=0.332. It indicates that the Dy3+/Eu3+ co-doped cubic lattice Na YF4 single crystal can be a potential luminescent material for the ultraviolet(UV) light excited white light emitting diode(w-LED).