Photoluminescence properties of a novel orange-red emitting Ba_2CaZn_2Si_6O_(17):Sm~(3+) phosphor

Novel orange-red emitting Ba_2Ca_(1–x)Zn_2Si_6O_(17):x Sm~(3+)(0.02≤x≤0.08) phosphors were synthesized using conventional solid-state reaction method under air atmosphere. The phase formation of the samples was characterized by powder X-ray diffraction patterns. Scanning electron microscopy(SEM) and photoluminescence properties were also investigated. The narrow excitation and emission spectra indicated the typical 4f-4f transitions of Sm~(3+). The dominant excitation line was around 405 nm attributed to ~6H_(5/2)→ ~4F_(7/2) and the emission spectrum consisted of four emission peaks at 562, 600, 647, and 708 nm corresponding to the various transitions ~4G_(5/2) to ~6HJ(J=5/2, 7/2, 9/2 and 11/2) of the Sm~(3+) ions in the same order. The strongest emission band located at 600 nm was attributed to ~4G_(5/2)→~6H_(7/2) transition of Sm~(3+), producing bright orange-red color emission. The optimal dopant concentration of Sm3+ ion in Ba_2CaZn_2Si_6O_(17):x Sm~(3+) phosphor was around 4 mol.% and the critical transfer distance(Rc) of Sm~(3+) was calculated to be 2.65 nm. Decay time varied with the Sm~(3+) concentrations in Ba_2 CaZn_2Si_6O_(17) phosphors. In addition, the Commission International del'Eclairagethe(CIE) chromaticity coordinates of Ba_2Ca_(0.96)Zn_2Si_6O_(17):0.04Sm~(3+) phosphor was located in the orange-red region(0.547, 0.450) and the correlated color temperature(CCT) was 2543 K. The present results indicated that Sm~(3+) activated Ba_2CaZn_2Si_6O_(17) phosphors may be used as an orange-red emitting phosphor for near-ultraviolet(n-UV) based white light emitting diodes(WLEDs) applications.     

Warm-white persistent luminescence of Lu_3Al_2Ga_3O_(12):Pr~(3+) phosphor

A warm-white emitting persistent luminescence phosphor Lu_3Al_2Ga_3O_(12):Pr~(3+) was synthesized by solid state method at 1600 °C in air. The refined crystal structure of Lu_3Al_2Ga_3O_(12) host was solved by X-ray diffraction(XRD). The photoluminescence spectra, decay curve and thermoluminescence were investigated. It was revealed that the persistent luminescence originated from the f-f transitions of Pr~(3+) emitters at Lu~(3+) sites in LuO_8 polyhedrons, and it showed white color due to the ~3P_0→~3H_4, ~3P_1→~3H_5, ~3P_0→~3H_5, ~3P_0→~3H_6, ~3P_0→~3F_2, ~3P_0→~3F_3 and ~3P_0→~3F_4 transitions of Pr~(3+) emitters in a wide range. The persistent luminescence of Pr~(3+) in this host could be promoted by f-d transition(278 nm) but f-f transitions, due to the different thermal activation energy. The persistent luminescence of the optimal sample could be actually recorded for 3 h by the definition of 0.32 mcd/m~2 and was visible for more than 7 h by dark-adapted vision in darkness. The initial depth of the dominant shallow traps was calculated to be about 0.56 eV, which is suitable for persistent luminescence. The different roles of the shallow and deep traps on the persistent decay process were investigated. Accordingly, the persistent luminescence processes and mechanism of the as-synthesized Lu_3Al_2Ga_3O_(12):Pr~(3+) phosphors were proposed.     

Single-phase full-color Ba_3Lu_2（SiO_4）_3：Eu~（2＋） phosphor for white-light emitting diodes

we developed a new silicate-based full-color phosphor Ba3Lu2(SiO4)3:Eu2+ through solid state reaction.The host crystal structure was isostructural with Ca3Y2(SiO4)3 instead of garnet-type.The phosphor absorbed near-ultraviolet light from 250 to 400 nm,which was very suitable for a color converter of white LED that used UV-LED as the primary light source.The photoluminescence peak wavelength of Ba3Lu2(SiO4)3:Eu2+ was about 461 nm and a shoulder peak was around 522 nm,which resulted from the 5d-4f transition ...     

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...     

Energy transfer mechanism of Sr_4Al_(14)O_(25):Eu~(2+) phosphor

Long lasting blue-green-emitting Sr4Al14O25:Eu2+ phosphors were synthesized by solid-state reactions.The phosphors were investigated by X-ray diffraction(XRD) and fluorescence spectrophotometer.A pure phase of Sr4Al14O25:Eu2+ phosphor was obtained at 1250 °C.There are two different types of Eu emission centers in Sr4Al14O25:Eu2+ phosphor.The effects of the Eu2+ concentration and the reducing temperature on the distribution of Eu2+ among different sites were investigated.The energy transfer mechanism between two different emission centers was elucidated via the investigation of thermal damage influence on the phosphorescence spectra,that is,the energy emitted from an Eu1 emission center could be reabsorbed by an Eu2 emission center.     

Sensitizing effect of Nd~(3+) on Tb~(3+) activated ZrP_2O_7 long persistent phosphor materials

The long persistent phosphors of Zr_(0.97)P_2 O_7:0.018 Tb~(3+),0.012 Nd3+with Nd~(3+)as sensitized ions and Tb~(3+)as emission centers were synthesized using high temperature solid state reaction.The crystal structure and defects,excitation and emission spectra,decay curves and thermoluminescence(TL) curves of the phosphors were investigated.The synthesized Zr_(0.97)P_2 O_7:0.018 Tb3+,0.012 Nd3+is essentially in line with the standard card PDF#49-1079.The emission band with main peak at 548 nm exhibits the characteristic transitions of ~5 D_3-~7 F_j(j=5,4) and ~5 D3-~7 F_j(j=6,5,4,3) of Tb~(3+).The analysis of excitation and emission spectra shows that there exists the overlap between the emission peaks of Nd~(3+)at 466 and 485 nm and the excitation of Tb3+at 443 and 485 nm,and the energy transfer from Nd3+to Tb3+plays an important role in the improvement of luminescence properties.The decay curves shows that Zr_(0.97)P_2 O_7:0.018 Tb3+,0.012 Nd3+has longer afterglow time than ZrP_2 O_7 and Zr_(0.982)P_2 O_7:0.018 Tb3+.Additionally,the TL curves indicate that the trap depth at 0.72 eV in Zr_(0.97)P_2 O_7:0.018 Tb~(3+),0.012 Nd3+is to the benefit of the afterglow time.The possible luminescence mechanism of ZrP_2 O_7:Tb~(3+),Nd3+is proposed on the basis of the XPS spectra,EPR spectra,excitation and emission spectra,decay curves,TL curves and the analysis of defect equations.     

Characterization and properties of a Sr_2Si_5N_8:Eu~(2+)-based light-conversion agricultural film

In this paper,the fracture surfaces of a light-conversion film were observed using a scanning electron microscope(SEM),and then,the fluorescence spectra and mechanical properties of the film were tested.The SEM results show that the average diameter of the light conversion agent is 500 nm.The results of the mechanical properties tests show that the tensile strengths of light-conversion film increase from9.86 to 12.16 MPa and that the strain at breakage increases from 2.37% to 2.75%.In addition,the application effects of the light-co nversion film were studied.The results indicate that plant height,length of the maximum leaf,width of the maximum leaf and breadth of the plants increase by 24.43%,15.30%,15.60% and 19.07%,respectively.The quality of Chinese flowering cabbages treated with the lightconversion film is superior,including a 9.09% increase in the soluble protein content,a 21.27% increase in the polyphenol content,and a 19.15% increase in the soluble sugar content.Based on these results,light-conversion films can be applied in agricultural production.     

High thermal stability and quantum yields of green-emitting Sr_3Gd_2(Si_3O_9)_2:Tb~(3+) phosphor by co-doping Ce~(3+)

A series of Tb~(3+) mono-doped and Ce~(3+)-Tb~(3+) co-doped Sr_3Gd_2(Si_3O_9)_2 phosphors with high thermal stability and quantum yields were successfully prepared via the solid state reaction. The as-prepared Sr_3Gd_2(Si_3O_9)_2:Tb~(3+) samples showed broad excitation spectrum from 250 to 400 nm and presented characteristic emission transitions ~5D_4→~7F_J(J=6, 5, 4, 3) of Tb~(3+) under 313 nm excitation, which were located at about 488, 541, 584 and 620 nm. The emission intensities of Tb~(3+) rose steadily in Sr_3Gd_2(Si_3O_9)_2 host with the increase of Tb~(3+) concentration even though Gd~(3+) ions were completely replaced by Tb~(3+) ions. The Ce~(3+) ion as a sensitizer could efficiently improve the performance of Tb~(3+) ion. First, with Ce~(3+) co-doping, the excitation spectrum of Tb~(3+) monitored at 541 nm showed a similar band that responds to the violet emission of Ce~(3+) monitored at 416 nm. Second, the quantum yields of Sr_3Gd_2(Si_3O_9)_2:Tb~(3+) phosphors could be enhanced from 26.6% to 80.2% by co-doping Ce~(3+). Finally, the co-doping of Ce~(3+) was also effective to improve the thermal stability of Sr_3Gd_2(Si_3O_9)_2:Tb~(3+). As the temperature rose to 150 oC, the emission intensity of Tb~(3+) remained at about 83.6% of that measured at room temperature, which was better than the commercial YAG:Ce phosphor in terms of their thermal quenching properties. These results indicated that the as-prepared Sr_3Gd_2(Si_3O_9)_2:Tb~(3+),Ce~(3+) samples could be used as green emission phosphors for possible applications in near ultraviolet based WLEDs.     

Luminescence investigation of Eu~(3+)-Bi~(3+) co-doped CaMoO_4 phosphor

A series of Eu3+-Bi3+ co-doped CaMoO4 red phosphors were synthesized via the solid-sate reaction method. The crystal structures of the obtained samples were identified by X-ray powder diffraction (XRD). The photoluminescence property was investigated, and the results showed that the intensity of excitation spectra and emission spectra could be changed with different doping ratios of Bi3+/Eu3+. The proposed explanation of these changes was from the energy transfer between Bi3+ and Eu3+ and the unbalanced cha...     

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.     

Reaction mechanism and luminescence properties of orange-red SrAlSi_4N_7:Eu~(2+) phosphor for white-LEDs

The well-crystalline SrAlSi_4N_7:Eu~(2+) phosphor could be synthesized by the solid-state reaction method using different types of Si_3N_4 raw material.The corresponding reaction mechanism was studied by means of X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectrometry(EDS) and fluorescence spectra.It was found that the structural difference between α-Si_3N_4 and β-Si_3N_4,and the rearrangement of Si_3N_4 microstructures at high temperature had an important influence on the formation of SrAlSi_4N_7 phase.Results showed that the α-β transformation of Si_3N_4 was included in the synthesis reaction of SrAlSi_4N_7.So the reaction mechanism of SrAlSi_4N_7:Eu~(2+) phosphor should be:α-Si_3N_4→β-Si_3N_4;β-Si_3N_4+AlN+Sr_2N→SrAlSi_4N_7.The β-Si_3N_4 seeds addition were actually helpful to the grain growth of α-β transformation of Si_3N_4 and then increased the synthesis reaction rate of SrAlSi_4N_7.Pure SrAlSi_4N_7:Eu~(2+) phosphor with higher luminous efficacy and better crystal morphology was finally obtained,indicating that the as-synthesized phosphor was an attractive candidate material as an orange-red component for warm white light LEDs.     

Luminescence of Eu~(2+) and Eu~(2+)-Mn~(2+) in sodium scandium diphosphate NaScP_2O_7 crystal

In this work, the photoluminescence(PL) of NaScP_2O_7:Eu~(2+) and NaScP_2O_7:Eu~(2+),Mn~(2+) was investigated. Phase purity was checked using X-ray powder diffractometry(XRD). PL excitation and emission spectra were recorded to elucidate the PL properties of NaScP_2O_7:Eu~(2+) and NaScP_2O_7:Eu~(2+),Mn~(2+). Furthermore, fluorescence lifetime measurements were performed. PL and lifetime measurements were carried out from 10 to 525 K. Moreover, the Eu~(2+) site occupation was discussed. It turned out that the incorporated Eu~(2+) ions substituted for Na+ site and occupied two different sites. Temperature dependent PL measurements indicated the emission intensity decreased with increasing temperature due to temperature quenching in NaScP_2O_7:Eu~(2+). Fluorescence lifetimes of Eu~(2+) in NaScP_2O_7:Eu~(2+) almost did not change with a decay constant τ=~0.53 μs in the temperature range of 10–280 K, and then shortened due to temperature quenching. The luminescent lifetime reached ~0.05 μs at T=525 K. Finally, it was found that energy transfer occurred from Eu~(2+) to Mn~(2+) in co-doped NaScP_2O_7:Eu~(2+),Mn~(2+).     

F~-掺杂对红色荧光粉NaGd(WMo)O_(8-x/2)F_x:Eu~(3+)的结构和发光特性的影响

采用高温固相法合成了NaGd(WMo)O_(8-x/2)F_x:Eu~(3+)(x=0、0.1、0.2、0.3、0.4、0.5)系列红色荧光粉。分别采用X射线衍射、荧光光谱测试手段对所得粉末的晶型及其发光性能进行了表征分析。结果表明,该系列红色荧光粉均为白钨矿四方晶系结构,空间点群结构为I41/a(88),可被近紫外光395 nm有效激发,其最强发射峰位于616 nm处,属于Eu~(3+)的~5D_0→~7F_2电偶极跃迁。F-离子掺杂量为0.2 mol时发光强度最强,与未掺杂F-相比其发光强度提高了41%,其色坐标为(0.653,0.336)。由此可见,NaGd(WMo)O_(7.9)F_(0.2):Eu~(3+)是一种具有潜在应用价值的白光LED红色荧光粉。     

Synthesis and luminescent properties of Ba_2V_2O_7:Sm~(3+)

Samarium doped pyrovanadate Ba_2V_2O_7:Sm~(3+) phosphors were synthesized by traditional high-temperature solid-state reaction method. The phase and the structure of the samples were characterized by powder X-ray diffraction(XRD), and the luminescent properties and the energy transfer mechanism of the material were investigated using quantitative photoluminescence(PL) spectroscopy. The excitation spectrum of the sample exhibited a broad ultraviolet(UV) band with maximum at around 341 nm due to V–O charge transfer transition of the host. The emission spectrum displayed a yellow-greenish broadband(peaking at around 498 nm) coming from the host Ba_2V_2O_7 and three narrow peaks(at 561, 599 and 646 nm) attributed to the dopant Sm~(3+) ions. The PL spectra revealed the energy transfer from the host to the Sm~(3+) ions. In addition, the color coordinates and the color temperature of the phosphor Ba_(1.95)V_2O_7:5%Sm~(3+) were(0.314, 0.365) and 6135 K, respectively, under 365 nm excitation, suggesting it to be a candidate of single-phase converting phosphors for white-light-emitting diodes(WLEDs) with near-UV chips.     

Electrophoretic deposition and an investigation of co-dopants effect on luminescence property of Mg_2SiO_4:Eu~(3+) phosphors

Forsterite particles doped with europium ions(Eu~(3+)) were synthesized via a solution combustion method. The effect of co-dopants on photoluminescence intensity was described. Different percentages of calcium(Ca~(2+)), zinc(Zn~(2+)), barium(Ba~(2+)) and strontium(Sr~(2+)) were added to the Mg_2SiO_4:Eu~(3+)host.The synthesized sample was characterized by X-ray diffraction, transmission electron microscopy,scanning electron microscopy, spectrofluorometer and the FTIR spectroscopy. X-ray diffraction(XRD)results revealed that dominant phase was forsterite in all samples. Additionally, a negligible amount of periclase phase was recognized in the samples. The average size of the synthesized particles was less than 200 nm. The presence of co-dopant led to an enhancement in the photoluminescent property of the synthesized samples. The maximum increase in photoluminescence intensity was obtained by Ba~(2+)ions as a co-dopant. Condensed films of photoluminescence particles were produced by utilizing electrophoresis technique to deposit particles. The results showed that polyvinyl pyrrolidone was the best surface modifier to raise the mass deposition of the samples on the substrate.     

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.     

Influence of dispersant on Y_2O_3:Eu~(3+) powders synthesized by combustion method

Y2O3:Eu3+ powders were synthesized by combustion method and the influence of dispersant was investigated.XRD analysis indicated that the particle size increased with a small amount of dispersant firstly and then decreased with a further increase of dispersant.The morphologies of the powders were studied by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy(HRTEM).SEM images revealed that an appropriate amount of dispersant could reduce the agglomeration significantly.Due ...     

Synthesis and luminescence properties of a novel red-emitting phosphor SrCaSiO_4：Eu~（3＋） for ultraviolet white light-emitting diodes

A novel red phosphor based on Eu3+-activated SrCaSiO4 was successfully synthesized by conventional solid state reaction method and the photoluminescence properties were investigated. X-ray diffraction (XRD) patterns indicated that SrCaSiO4:Eu3+ phosphors belong to orthorhombic crystal system (space group=Pmnb). The photoluminescence (PL) excitation spectrum showed broad-band absorption and the strongest excitation peak at 397 nm contributed to the 7F0→5L6 transition which matched well with the emission of a...     

红色荧光粉NaBaPO_4:Eu~(3+)的制备及其性能研究

采用高温固相法制备单一六方晶系红色荧光粉NaBaPO4:Eu3+。利用XRD、SEM和荧光光谱等对NaBaPO4:Eu3+粉末的理化特性进行表征,考察了激活剂Eu3+的浓度和助熔剂NH4F用量对粉末的晶体结构和发光性能的影响。结果表明:激活剂Eu3+最大掺入量为20%,助熔剂NH4F的最大掺入量为10%,采用该配比合成得到的荧光粉NaBa0.8PO4具有最好的发光性能。在最强激发波长的近紫外光(≈393nm)激发下,样品发射强的红光(≈613nm)和橙光(≈591nm)。     

Photoluminescence of Eu~(2+)-activated Na_(1-x)Al_(1-x)Si_(1+x)O_4 upon UV excitation

A convenient high temperature solid-state reaction method was developed to fabricate Na1-xAl1-xSi1+xO4:Eu2+ phosphors.The as-prepared products were characterized by X-ray diffraction(XRD),photoluminescence(PL),and photoluminescence excitation(PLE).The luminescence of Na1-xAl1-xSi1+xO4:Eu2+ phosphors were characterized by the two corresponding emission centers at 535 and 440 nm.The excitation spectrum extended from 250 to 400 nm.A white light was observed by naked eye upon ultraviolet excitation.The relative...