Effect of mixing process on the luminescent properties of SrAl_2O_4:Eu~(2+),Dy~(3+) long afterglow phosphors

A new mixing method was developed for solid-state reaction synthesis of SrAl2O4:Eu2+,Dy3+ long afterglow phosphors.The morphology and crystal structure of the phosphors were analyzed with scanning electron microscope(SEM) and X-ray diffractometer(XRD).The excitation and emission spectra of the long afterglow phosphors were measured,and the main emission band was around 514 nm.The decay time of the product was measured and compared with the phosphors prepared using dry-mixing method and wet-mixing method.It ...     

SrAl_2O_4:Eu~(2+),Dy~(3+)的发光性质及机理

研究了Eu2＋、Dy3＋共激活的SrAl2O4体系的发光性能和能量传输。结果表明，Dy3＋、Eu2＋共存时，Eu2＋的发光强度远远大于无Dy3＋时的发光强度，证明Dy3＋对Eu2＋的发光有敏化作用。Dy→Eu2＋能量传输的方式为籍助于载流子的能量输运。     

Optical performance study of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) ternary luminous fiber

In this study, down-conversion fluorescent powder of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+), which were the common three primary colors materials with long afterglow, were synthesized by high temperature solid state method. The blends of rare earth(RE) luminescent materials have been of interest to reinvest the luminescent characteristics of polyethylene terephtahalate(PET) luminous fiber. The scanning electron microscopy(SEM) and an inversion fluorescence microscope were used to characterize the surface morphology and the dispersion of inclusion. Through analysis of microcosmic morphology, three typical dispersions of luminescent particles were summarized. The X-ray diffraction indicated that the phase structure of fiber samples and crystal structure of luminescence materials kept complete after prilling and spinning. From the fluorescence spectra and CIE 1931 coordinates, it could be found that different combinations of luminous fibers were desired to obtain divers colors emission luminous fiber. And the fiber samples were a light sensation which could induct different excitation wavelengths and convert it down to different colors. The afterglow decay curve and its differential curve were summarized indicating the three decay stages. The decay curve and decay rate curve showed that the contents of Sr_2ZnSi_2O_7:Eu~(2+),Dy~(3+), SrAl_2O_4:Eu~(2+),Dy~(3+) and Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) had obvious influence on the afterglow of fiber samples.     

Blue-green BaAl_2O_4：Eu~（2＋）,Dy~（3＋） phosphors synthesized via combustion synthesis method assisted by microwave irradiation

Blue-green luminescent BaAl2O4:Eu2+,Dy3+ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The XRD results revealed that when the concentration of urea was over 3 times higher than theoretical quantities, a BaAl2O4 single hexagonal phase was obtained. The SEM results revealed that the surface of the BaAl2O4:Eu2+,Dy3+ pow...     

Preparation and luminescence properties of rare-earth doped fiber with spectral blue-shift: SrAl_2O_4: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 SrAl_2O_4: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 SrAl_2O_4: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 SrAl_2O_4:Eu~(2+),Dy~(3+) phosphors.     

Enhanced afterglow performance of CaAl_2O_4:Eu~(2+),Nd~(3+) phosphors by co-doping Gd~(3+)

In order to effectively improve the afterglow properties of CaAl_2 O_4:Eu~(2+),Nd~(3+) phosphors,a series of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)(x=0,0.012,0.024,0.036,0.048,0.060 mol) phosphors were prepared by a high-temperature solid-phase approach.Crystalline composition and microstructure were characterized by XRD,TEM,HRTEM,and XPS,luminescence properties were systematically analyzed by fluorescence spectra,afterglow decay curves and TL glow curve.Results show that all of Ca_(0.982-x)Al_2 O_4:0.012 Eu~(2+),0.006 Nd~(3+),xGd~(3+)phosphors belong to monoclinic CaAl_2 O_4,without other cystalline phase.The blue emission at 442 nm is observed,which is assigned to the 4 f~65 d→4 f~7 transition of Eu~(2+) ions.Doping with appropriate amount of Gd~(3+) ions(x=0.036 mol) significantly improves the afterglow properties of phosphors,but the excessive doping of Gd~(3+) induces the fluorescent quenching.The doping of moderate Gd3+changes the traps states,the trap depth varies from 0.598 to 0.644 eV and the trap concentration is also greatly improved,thus significantly improving afterglow performance.     

Effect of light conversion agent on luminous properties of a new down-converting material SrAl_2O_4:Eu~(2+),Dy~(3+)/light conversion agent

A new luminous material SrAl_2O_4:Eu~(2+),Dy~(3+)/light conversion agent that can emit red light in the darkness after being excited was fabricated by combining light conversion agent on to SrAl_2O_4:Eu~(2+),Dy~(3+) particles through YsiX3.The morphology of the luminous materials was analyzed by scan electron microscopy(SEM).The emission behavior was evaluated by fluorescence spectrophotometric analysis and the results demonstrated that the emission spectra of samples had a redshift compared to SrAl_2O_4:Eu~(2+),Dy~(3+) and the emission intensity rose dramatically at first and then decreased when the ratio of light conversion agent doping was over 1.4 wt.%.And the emission color of SrAl_2O_4:Eu~(2+),Dy~(3+)/light conversion agent was tuned from green(SrAl_2O_4:Eu~(2+),Dy~(3+))to orange-red.Furthermore,the afterglow property was also investigated,and the results indicated that the afterglow brightness reached 6.5 cd/m~2,and as the light conversion agent concentration increased the brightness intensity decreased.     

Structure and luminescent properties of luminous polypropylene fiber based on Sr_2MgSi_2O_7:Eu~(2+),Dy~(3+)

The luminous polypropylene fiber based on long afterglow luminescent material Sr2MgSi2O7:Eu2+,Dy3+ was prepared by melt-spinning process. Micro-morphology, phase composition, crystal structure, spectral features and afterglow properties of the luminescent fiber were tested and analyzed. The results indicated that the fiber had independent superposition phase features of both Sr2MgSi2O7:Eu2+,Dy3+ and polypropylene. The range of its excitation wavelength was located between 250–450 nm; therefore, the luminescent fiber could be excited by ultraviolet or visible light. It could emit blue light of 460 nm wavelength after excitation, which was caused by the 5d-4f transition of Eu2+ ions within the host lattice. The initial luminescent intensity was more than 0.8 cd/m2, and afterglow life lasted 7 h. The afterglow decay was composed of rapid-decaying and slow-decaying processes, and the decay characteristics depended on the depth and concentration of trap level in the Sr2MgSi2O7:Eu2+,Dy3+.     

Luminescent properties and energy transfer mechanism from Tb~(3+) to Eu~(3+) in CaMoO_4:Tb~(3+),Eu~(3+) phosphors

A series of CaMoO_4:Tb~(3+),Eu~(3+) phosphors were prepared by the method of precipitation. The structure and morphology of the phosphors were characterized by the X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM). The photoluminescence properties of the prepared products were researched, and the energy transfer from Tb~(3+) to Eu~(3+) in CaMoO_4 phosphors was studied. By adjusting the doping concentration of Eu~(3+) ions in CaMoO_4:Tb~(3+),Eu~(3+) phosphors, the emitting color of the phosphors could be easily tuned from green to red. With Tb~(3+) doped in the phosphors, the red luminescence of Eu~(3+) by near UV excitation was significantly enhanced. The energy transfer efficiency, rate and average distance between Tb~(3+) and Eu~(3+) in CaMoO_4:5%Tb~(3+),x%Eu~(3+)(mole percent) phosphors(x=0.3–10) were calculated. It was found that the interaction type between Tb~(3+) and Eu~(3+) was electric dipole-dipole interaction in the phosphors.     

Structural characterization and optical properties of long-lasting CaAl_2O_4:Eu~(2+),Nd~(3+) phosphors synthesized by microwave-assisted chemical co-precipitation

The present paper reported the structural and luminescent properties of Eu~(2+) and Nd~(3+) doped CaAl_2O_4 phosphor. The samples were prepared by microwave-assisted chemical co-precipitation(MA-CCP), a synthesis technique which is suitable for small and uniform particle that could be used directly without grinding. The effects of different microwave temperatures on structure and photoluminescence behavior were studied. Formation of a phosphor and phase purity were confirmed by X-ray diffraction technique(XRD) with variable microwave temperatures. XRD analysis showed that the phosphors prepared by MA-CCP method at the temperature of 750, 900oC, respectively and solid-state reaction(SSR) method at 1300oC consisted of impurities. Commission Internationale de L'Eclairage(CIE) color coordinates of CaAl_2O_4:Eu~(2+),Nd~(3+) were suitable as blue light emitting phosphor. Excitation and emission peaks of the samples prepared by different methods in this study were almost the same. The images of SEM showed that the size of the phosphors prepared by MA-CCP method reached a submicrometer.     

Luminescence and energy transfer of color-tunable Lu_2MgAl_4SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+) phosphors

Energy transfer among the co-doped activators is an efficient route to achieve color-tunable emission in inorganic phosphors.Herein,photoluminescence tuning from blue to cyan has been achieved in the Lu_2MgAl_4 SiO_(12);Eu~(2+),Ce~(3+)phosphors by varying the Ce~(3+) concentration with a fixed Eu~(2+)content.With the further introduction of a Mn~(2+)-Si4+couple into the host lattice,the emission color can be tuned to red through the energy transfer of Eu~(2+)and Mn~(2+).The luminescence properties and the energy transfer mechanism were studied in detail.The energy transfer from Eu~(2+)to Ce~(3+)is certified as a dipolequadrupole interaction with the energy transfer efficiency of 41.4% and Eu~(2+)to Mn~(2+)belongs to a dipole-dipole interaction with the energy transfer efficiency of 94.3%.The results imply that this singlephased Lu_2MgAl4 SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+)phosphor has a potential prospect for application in near-UV chip pumped white light emitting diodes.     

Novel phosphors of Eu~(3+), Tb~(3+) or Tm~(3+) activated LaBGeO_5

Rare earth borogermanates as a group of stable compounds provided various potential properties important for modern sciences. Among the properties of interests, luminescence was manifested due to the variability of rare earth elements and the compounds constituted an important group of potential candidate. In this work, novel phosphors of Eu3+, Tb3+ or Tm3+ doped LaBGeO5 with the stillwellite type structure were synthesized by the solid state reaction method. Their X-ray and UV excitation luminescent proper...     

Synthesis and characterization of Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) nanorods via a solvothermal routine

Y2O2S:Eu3+,Mg2+,Ti4+ nanorods were prepared by a solvothermal procedure.Rod-like Y(OH)3 was firstly synthesized by hydrothermal method to serve as the precursor.Y2O2S:Eu3+,Mg2+,Ti4+ powders were obtained by calcinating the precursor at CS2 atmosphere.The Y2O2S:Eu3+,Mg2+,Ti4+ phosphor with diameters of 30-50 nm and lengths up to 200-400 nm inherited the rod-like shape from the precursor after calcined at CS2 atmosphere.The Y2O2S:Eu3+,Mg2+,Ti4+ nanorods showed hexagonal pure phase,good dispersion and exhibite...     

Significant enhancement of blue photoluminescence intensity of Dy~(3+) modified Sr_6Ca_4(PO_4)_6F_2:Eu~(2+) phosphors

Blue-emitting phosphors Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+)(SCPF:Eu~(2+)),Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+),Dy~(3+)(SCPF:Eu~(2+),Dy~(3+))and Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+),Dy~(3+),Si~(4+)(SCPF:Eu~(2+),Dy~(3+),Si~(4+)) with apatite structure were successfully synthesized by traditional solid-state reaction under reducing atmosphere.Eu~(2+),Dy~(3+) and Si4+ions occupy the corresponding sites of Sr~(2+),Ca~(2+) and P~(5+).Strong broad blue photo luminescence band is exhibited in SCPF:Eu~(2+),Dy~(3+) phosphor ranging from 400 to 550 nm centered at 455 nm and Dy~(3+) ions are vital in creating traps.Emission intensity of Eu~(2+),Dy~(3+) co-doped SCPF:0.02 Eu~(2+),0.02 Dy~(3+) is about 1.8 times that of SCPF:0.02 Eu~(2+) and electron trap centers serve as energy transporting media.To further elucidate the formation and effect of the specific defect on the luminescence of SCPF:0.02 Eu~(2+),0.02 Dy~(3+) phosphor,the thermoluminescence properties,decay curves and thermal stability studies were performed while the Si~(4+)-P~(5+) charge compensated pho sphor SCPF:0.02 Eu~(2+),0.02 Dy~(3+),0.02 Si~(4+) was prepared as a contrast.All the results of present work indicate that Dy~(3+) co-doping can obviously enhance photoluminescence intensity of SCPF:0.02 Eu~(2+) by the electron traps generated by non-equivalence replacement of Dy~(3+)-Ca~(2+).     

Synthesis and photoluminescent properties of Eu~(3+)/Dy~(3+) doped SrO-Al_2O_3-SiO_2 glass-ceramics

Eu~(3+)/Dy~(3+) single-doped and co-doped 6SrO-3Al_2O_3-91SiO_2 and 12SrO-6Al_2O_3-82SiO_2 glass and glass-ceramics were synthesized successfully by a sol-gel method. The prepared samples were characterized by the X-ray diffraction, high-resolution transmission electron microscopy, photoluminescent spectra and X-ray photoelectron spectroscopy. The effect of annealing temperature, doped ions and matrix component on the structure and the photoluminescent characteristics was systematically studied. The higher temperature was helpful to form nanocrystals and the amount of SrO and Al_2O_3 could better disperse the rare earth ions in matrix at suitable temperature, and both of them could improve the luminescent intensity. Meanwhile, the doped ions could change the luminescent color by single, codoped and energy transfer. The Sr_2SiO_4 nanocrystals were observed in silicates glasses and became larger with the increase of the annealing temperature and the luminous efficiency of rare-earth(RE) ions could be enhanced when the samples changed from glass state to glass-ceramic state. The results indicated that the photoluminescent properties could be changed through controlling the doped ions, annealing temperature and matrix component.     

Effect of alkaline metal ions on the photoluminescence properties of Eu~(3+)-doped Ca_3Al_2O_6 phosphors

Ca_3–xAl_2O_6:x Eu~(3+)(0.02≤x≤0.10) and Ca_(2.92)Al_2O_6:0.04Eu~(3+),0.04M~+(M~+=Li~+, Na~+, and K~+) phosphors were prepared by sol-gel method and their photoluminescence properties were investigated. The crystal structure of the annealed Ca_3–xAl_2O_6:x Eu~(3+) and Ca_(2.92)Al_2O_6:0.04Eu~(3+),0.04M~+ phosphors was analyzed with X-ray diffraction(XRD). The size and morphological characteristics of the annealed phosphors were investigated with a field emission scanning electron microscope(FE-SEM). The photoluminescence properties were evaluated with a spectrofluorometer. The phosphors were effectively excited by the light of 396 nm and showed intense red emission at 616 nm, which originated from the 5D_0→7F_2 transition of Eu~(3+). Among the prepared phosphors, the Ca_(2.96)Al_2O_6:0.04Eu~(3+) phosphor showed the strongest emission intensity and the highest color purity. The addition of alkaline metal ions(Li~+, Na~+, and K~+) to Ca_(2.96)Al_2O_6:0.04Eu~(3+) phosphor degraded the emission intensity and color purity.     

Superhydrophobic and luminescent cotton fabrics prepared by dip-coating of APTMS modified SrAl-_2O_4:Eu~(2+),Dy~(3+) particles in the presence of SU8 and fluorinated alkyl silane

An organic-inorganic composite dip-coating method was adopted in order to obtain ideal water repellent cotton fabrics. To be specific, a dual-functional coating with both superhydrophobic and luminescent properties was prepared on cotton fabric by using a dip-coating solution comprising(3-aminopropyl) trimethoxysilane(APTMS) modified SrAl_2O_4:Eu~(2+),Dy~(3+) particles, SU8, and fluorinated alkyl silane(FAS). The micro/nano-scale roughness generated by SrAl_2O_4:Eu~(2+),Dy~(3+) particles, together with low-surface-energy FAS, rendered the cotton fabric superhydrophobic with a water contact angle of about 160° and a sliding angle as small as 2°. The coated fabric could withstand at least 100 cycles of standard laundry. The emission spectra of the coated fabric showed two emission peaks at 440 and 520 nm, which belonged to the blue and yellow-green color areas, respectively. The afterglow duration of the coated fabric was mainly influenced by the different depths of the trap levels in the SrAl_2O_4:Eu~(2+),Dy~(3+).     

Tunable luminescence and energy transfer in Y_2BaAl_4SiO_(12):Tb~(3+),Eu~(3+)phosphors for solid-state lighting

Single-phase Y₂BaAl₄SiO₁₂:Tb³⁺,Eu³⁺phosphors with adjustable luminescence were successfully prepared by high-temperature solid-state reaction method.The structural,luminescent properties and ene rgy transfer(ET) process of Y₂BaAl₄SiO₁₂:Tb^(³⁺),Eu³⁺phosphors were syste matically analyzed with the help of X-ray diffraction(XRD),scanning electron microscopy(SEM),excitation spectra,emission spectra and photoluminescence decay curves.Tunable luminescence ranging from green through yellow and definitively to red can be achieved by elevating amounts of Eu³⁺ions in Tb³⁺,Eu³⁺co-doped samples.Besides,the ET mechanism and efficiency were also analyzed and the maximum ET efficiency is 67%.All the results show that Y₂BaAl₄SiO₁₂:Tb³⁺,Eu³⁺phosphors can be used in solid-state lighting.     

复合熔盐法合成Y2O3.Eu3+红色荧光粉

以草酸钇铕(Y2(C2O4)3:Eu3+)为前驱体,采用复合熔盐(NaCl+S+Na2CO3)协助焙烧法合成Y2O3:E.u3+红色荧光粉.利用XRD、SEM、光谱分析等测试和分析荧光粉粒径、颗粒形貌以及发光性能.主要考察复合熔盐配比、用量以及焙烧温度和时间对Y2O3:Eu3+荧光粉发光性能的影响.结果表明,NaCl在...     

Preparation and luminescent properties of CaAl_2O_4:Eu~(3+),R~+(R=Li,Na,K) phosphors

CaAl2O4:Eu3+,R+(R=Li+,Na+,K+) red phosphors were synthesized by solid state reaction method.X-ray diffraction(XRD) and photoluminescence(PL) were employed to characterize their structural and luminescent properties.It was found that the optimal sintering temperature and sintering time were 1200 °C and 4 h,respectively.The optimal concentration of doped Eu3+ was 3 mol.%.Furthermore,under ultraviolet excitation with a wavelength of 254 nm,these samples showed red luminescence which were probably attributed to the transitions from 5D0 excited state to 7FJ(J=0-4) ground states of Eu3+ ions.The feature and the high intensity of hypersensitive transition from 5D0→7F2 indicated that Eu3+ preferred to occupy a low symmetry site.The incorporation of alkali metal ions greatly enhanced the luminescence intensity probably due to the influence of charge compensation of alkali metal ions.