Effect of Organic Solvent and Resin on Luminescent Capability of SrAl2O4:Eu2+, Dy3+ Phosphor

Organic substance such as solvent and resin's effect on luminescent capability of SrAl2O4:Eu2 , Dy3 phosphor was studied. Some organic solvents and resins were selected for experimentation. The results indicate that those organic solvents will not have negative effect on the applied capability of SrAl2O4:Eu2 , Dy3 phosphor. Adopting the organic resins and covering method, the afterglow luminance of SrAl2O4:Eu2 , Dy3 phosphor was increased by 85.01% and 82.51%.     

Synthesis of Long Afterglow SrAl2O4 :Eu2+, Dy3+ Phosphor by Microemulsion Method

Long afterglow SrAl2 O4: Eu2 , Dy3 phosphor was synthesized by microemulsion method. The synthesized phosphor was characterized by XRD. XRD pattern indicates that the phosphor has monoclinic SrAl2 O4 crystal structre.The microstructure of the phosphor was investigated by SEM and TEM. The excitation spectrum, emission spectrum and afterglow decay curve were measured, the wide range of excitation wavelength indicated that the luminescent material could be excited by the light from ultraviolet ray to visible light, and the emission maximum was found to peak mainly at λem of 525 nm. The sample excited by ultraviolet visible light could emit bright green light.     

SrAl2O4 :Eu2+, Dy3+ Long Afterglow Phosphors Prepared by Chemical Coprecipitation Method

SrAl2 O4: Eu2 , Dy3 long afterglow phosphors were prepared by chemical coprecipitation method. Ammonium carbonate and ammonium hydrogen carbonate were used as the precipitants. The preparation of the SrAl2 O4: Eu2 ,Dy3 precursor was completed at room temperature by controlling the concentration of the metal-salt solution, pH value of the system, etc. The phosphors were prepared by sintering the precursor at 1000 ～ 1200 ℃ in a weak reducing atmosphere for 2 h. The XRD, SEM, excitation spectra, emission spectra and afterglow decay of the samples were tested and the optimal synthesis conditions of the SrAl2O4: Eu2 , Dy3 long afterglow phosphors prepared by precipitation method were determined. The phosphor which had good luminescent properties is prepared and its persistent time can reach more than 1600 min. In the coprecipitation process, a small amount of glucose operates to refe the luminescent powders. The particle size of the phosphor can be less than 1 μm. The sintering temperature of the sample prepared by the coprecipitation method is much lower than that of the one prepared by the high temperature solid state method.Compared with the high temperature solid state method, a clear blue shift occurs in the excitation and emission spectra of the samples.     

Preparation and Luminescence of SrAi2O4:Eu2+, Dy3+ Nano-Particle

SrAl2O4: Eu2 , Dy3 nano-particle luminescence material was prepared by sol-gel method. Influences of synthesis conditions on the particle size and luminescence properties of SrAl2O4: Eu2 , Dy3 were studied. The synthesis process and the properties of the samples were analyzed by DTA, TGA, XRD, SEM. The result suggested that the formation of SrAl2O4: Eu2 , Dy3 sol is a slow heat release process beginning at 500 ℃ and peaking at 759 ℃.SrAl2O4: Eu2 ,Dy3 crystalline was formed at 1100 ℃. The luminescence properties of the SrAl2O4: Eu2 , Dy3 nanoparticle were compared with the conventional SrAl2O4: Eu2 , Dy3 particles. The average particle size of the product is about 30 nm. The excitation spectrum of the sample shows a broad band with peaks at 240, 330, 378 and 425 nm. The emission spectrum is a broadband spectrum with a peak at 523 nm.     

Adjustable Luminescence of SrAl2O4：Eu^2＋ , Dy^3＋ Assembled in Zeolite

Capsulating guest into the nanometer yoids of zeolites is a effective way to form novel host-guest material. In our work, stoichiometric SrAl2O4: Eu^2 , Dy^3 sol guest was prepared by sol-gel method and assembled into the nanometer channels of zeolite ZSM-5 host through mechanical mixing, hydrothermal reaction and microwave heating reaction, respectively. After being reduced and diffused in a microwave muffle, the fluorescence spectra of the host-guest materials exhibit remarkable blue shifts in comparison of that of SrAl2O4 : Eu^2 , Dy^3 . Some interesting phenomena in the assembled hostguest materials are that the after-glow emission spectra exist two bands at about 400 nm and 517 nm and the relative strengths of these two bands can be adjusted by changing the assembly methods and the assembly concentration. These are attributed to the fact that the phosphor was capsulated into the voids of zeolite ZSM-5 and generated the quantum size effect and the host-guest effect.     

SrAl2O4∶Eu2+,Dy3+磷光粉低成本制备工艺及发光性能研究

以工业铝酸钠溶液制备的氢氧化铝为铝基原料,采用高温固相反应法合成了SrAl2O4∶Eu2+,Dy3+磷光粉,考察了稀土掺杂量、烧结温度及硼酸加入量对其发光性能、激发光谱及发射光谱的影响,并通过XRD谱及余辉衰减曲线对最佳工艺条件下制备的样品进行表征。结果表明,当稀土掺杂量x(Eu)=3%、x(Dy)=3%,烧结温度为1 300℃,烧结时间为4h,硼酸加入量w(H3BO3)=9%时,所制备磷光粉样品仍保持SrAl2O4的晶体结构,其发光性能最好,发光强度最大,主激发波长在360nm左右,主发射波长在510nm左右;余辉为黄绿色,衰减时间长。     

Y2SiO5:Ce3+ particle growth during sol-gel preparation

The phosphor Y2SiO5:Ce3+ was prepared by a sol-gel method and the particle growth process was investigated by XRD, SEM and TEM. After heating at 400 °C, the as-dried gel became a powder composed of mixed phases of polycrystalline Y2O3 and amorphous SiO2. With an increase in temperature, the crystallinity of Y2O3 improved. The sample quickly changed to the pure Y2SiO5 phase when it was heated at 1400 °C for 10 min. SEM indicated that the as-dried gel consisted of large porous particles. At an annealing temperature of higher than 400 °C, the pores in the large particles gradually expanded and grains started to appear. Consequently, the large particles disintegrated into small particles. When the sample was heated at 1400 °C, we obtained fine phosphor particles (around 2 μm) with smooth surfaces. The optimized condition for the preparation of the Y2SiO5:Ce3+ phosphor was to heat at 1400 °C for 2 h.     

Citric Gel Synthesis and Luminescent Properties of Ce^3＋-Activated SrGa2O4 Phosphor

Ce^3＋-activated SrGa2O4 phosphor was synthesized by a method of citric gel,wherein citric acid served as a chelate agent,and the as-synthesized powder was calcined in a slightly reduced ambient.The crystallization characteristics of the sample varied with the calcining temperature.Compared with the phosphor prepared by the solid-state reaction,the phosphor synthesized by citric gel was calcined at a relatively lower temperature.Consequently,the volatilization of Ga2O3 during high-temperature calcining process was avoided.The typical double-peak emission of Ce^3＋ originated from 2D（5d）→4F5/2（4f）,and 2D（5d）→4F7/2（4f）was observed,and the intrinsic emission of SrGa2O4 host was much restricted.The emission intensity varied with the calcining temperature because the different crystallinity and the optimal concentration of Ce-dopant was determined at 3%.     

Investigations into thermoluminescence and afterglow characterization of strontium aluminates with boron-modification and reductions via sol-gel route

The effects of strontium aluminates of SrAl2O4:Eu2+,Dy3+(SAED) and boron-modified SAED (BSAED) phases synthesized from a sol-gel process on thermoluminescence (TL) along with their afterglow properties were systematically investigated with thermal activation in the different atmospheres. The result showed that the addition of boron and the reduction routes of Eu3+to Eu2+ in SrAl2O4:Dy3+were related to phosphorescent decay properties. The aid of Dy3+to induce the hole-trapping effect required both SAED and BSAED to be heated at 1300°C under the H2/N2(5%:95%) atmosphere. However, the trapping behavior of the reductions of SAED in nitrogen was similar to the compound without Dy3+co-doping SrAl2O4:Eu2+ (SAE) in H2/N2(5%:95%). BSAED showed deeper traps in situ compared to SAED which contained no boron, and this led to the better afterglow properties of BSAED than those of SAED. The afterglow spectrum of BSAED showed two peaks at 400±1 nm and 485±1 nm, which were two individuals composed and contributed from different depths of traps at 0.57 and 0.76eV, accordingly. The depth of the traps was calculated from the Hoogenstraaten’s plot of glow curves. The calculations for SAED and SAE were at around 0.43 and 0.18eV, respectively.     

SrAl2O4:Eu, Dy Nanometer Phosphors Synthesized by Combustion Method

SrAl2 O4: Eu, Dy nanometer phosphors were synthesized by combustion method at 500 ～ 900℃, followed by heating the combustion sample at 1150℃ at a weak reductive atmosphere and nanometer phosphor with much better luminescent properties was obtained. The influences of the initiating combustion temperature, H3BO3 quantity, the mass ratio of urea and nitrate on the luminescent intensity of nanometer phosphors were studied. The optimum synthetic conditions were determined. The analysis results by transmission electron microscopy (TEM) indicate that the particle size of the synthetic product is less than 75 nm. The luminescent materials do not need to be ground. Their coating can be refined. It supplies a new approach to the rapid preparation of the luminescent materials at low temperature. The excitation and emission spectra indicate that the main peaks in the excitation and emission spectrum of nanometer phosphor synthesized by combustion method shifted to the short wavelength compared with the phosphor obtained by the solidstate reaction synthesis method. The reason of blue shift was explained. The afterglow decay results indicate that the decay speed of the afterglow for nanometer phosphor is faster than that obtained by the solid-state reaction method.     

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。     

Fluorescence Effect of SrAl2O4:Eu and Diffuse Reflectivity of SrAl2O4:Eu Based Ceramics

SrAl2O4:Eu was adopted as main phase to prepare the ceramic pumping cavity material with ultraviolet(UV) converting function in order to match with laser absorption spectra. The relationship between SrAl2O4:Eu powder processing and fluorescence effect was studied. The glass material with lower refractive index was added to the SrAl2O4:Eu based ceramics. The diffusive reflectivity and the influence of fluorescence effect on reflection spectra of the ceramics were investigated. Some experimental results can be used for evaluating technical feasibility of the SrAl2O4:Eu based ceramics used for laser reflectors.     

Synthesis and Luminescence Properties of Ba2 MgSi2 O7 :Eu2+ under UV Excitation

Eu2 activated pyrosilicate phosphor were prepared under a reducing atmosphere by solid-state reaction.The crystal structure of Ba2 MgSi2 O7: Eu2 was analyzed by XRD method.The excitation spectrum of Ba2MgSi2 O7; Eu2 is composed of two broad bands centered at about 310 nm and 395 nm respectively.In the emission spectra, the peak wavelength is at about 507 nm under 380 nm UV excitation.It was found that the introduction of Zn2 into Ba2MgSi2O7: Eu2 Can effectively increase its emission intensity without changing the position of emission peak.And the Eu2 and Ce3 codoped pyrosilicate phosphor is the efficient bluish green phosphor under the excitation of long UV light and its emission intensity is stronger than Eu2 doped pyrosilicate phosphor.     

Preparation of Incompact Strontium Aluminate Phosphors

The incompact long afterglow pigment SrAl2O4: Eu, Dy was synthesized by ceramics technology.The agglomerated starting raw material had little effect on the synthesis of SrA12O4 matrix through solid-state reaction method,but the shrinkage and densification was retarded greatly by the agglomerated powder by the formation of large and extensive pore network.The sintering mechanism is surface diffusion ( without flux B2O3 ) and grain boundary diffusion (with B2O3 as flux)respectively, and the as-prepared long afterglow pigment glows in the dark for over 4000 min.     

Synthesis of Long Afterglow Phosphors MAl2O4:Eu2+, Dy3+(M=Ca, Sr, Ba) by Microemulsion Method and Their Luminescent Properties

Long afterglow phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) were synthesized by microemulsion method, and their crystal structure and luminescent properties were compared and investigated. XRD patterns of samples indicate that phosphors CaAl2O4:Eu2 , Dy3 and SrAl2O4:Eu2 , Dy3 are with monoclinic crystal structure and phosphor BaAl2O4:Eu2 , Dy3 is with hexagonal crystal structure. The wide range of excitation spectrum of phosphors MAl2O4:Eu2 , Dy3 (M=Ca,Sr,Ba) indicates that the luminescent materials can be excited by light from ultraviolet ray to visible light and the maximum emission wavelength of phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) is found mainly at λem of 440 nm (M=Ca), 520 nm (M=Sr) and 496 nm (M=Ba) respectively, the corresponding colors of emission light are blue, green and cyna-green respectively. The afterglow decay tendency of phosphors can be summarized as three processes: initial rapid decay, intermediate transitional decay and very long slow decay. Afterglow decay curves coincide with formula I=At-n, and the sequence of afterglow intensity and time is Sr＞Ca＞Ba.     

Quenching mechanism of Er~(3+) emissions in Er~(3+)-and Er~(3+)/Yb~(3+)-doped SrAl_(12)O_(19) nanophosphors

Nanoscaled SrAl12O19:Er3+ and SrAl12O19:Yb3+,Er3+ phosphors were synthesized by a combustion method.The emission intensities of every sample were compared by a new method with the emission of codoped Gd3+ ions as a reference.Compared with their bulk material prepared by the solid-state reaction method,a higher Er3+ quenching concentration,as high as 20%,was observed in the nanoscaled phosphors for both visible(VIS) and near infrared(NIR) emissions.The higher quenching concentration in both VIS and NIR regio...     

Preparation of Non-Grinding Long Afterglow SrAl2O4 ：Eu^2＋ , Dy^3＋ Material by Microwave Combustion Method

The non-grinding long afterglow material SrAl2O4：Eu^2＋ , Dy^3＋ was prepared by combustion method in home mierowave oven direetly, after dispersant, frother, eomburent, and mineralizer were added into the reacting system. XRD analysis showed that the powders were nearly pure SrAl2O4 phase with few other phases, and the size of the grain was 41.1 nm. Fluoreseenee speetrum results indieated that there were 2 exeitation peaks loeated at 345 and 400 nm, and the emission peak loeated at 516 nm, afterglow lasted up to 30 min or more. The mierowave eombustion method has advantages of less time, low temperature and no grinding process, and the material made by the method has good luminescent property.     

Combustion synthesis and luminescence properties of blue NaBaPO4:Eu2+ phosphor

The blue-emitting phosphor NaBaPO4:Eu2+ was prepared by the combustion method. The phase structure and microstructure of the as-prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Under the excita-tion wavelength of 360 nm, the emission spectrum exhibited only one blue band centering at 435 nm, which was ascribed to the 4f65d1→4f7 transition on Eu2+ ions. Compared with the phosphor obtained by solid-state reaction method, the relative emission intensity of sample ob-tained by combustion method increased slightly. The decay times and the temperature dependence luminescence intensities (25-300 oC) were discussed in order to further investigate the potential applications. Furthermore, Eu2+-doped NaBaPO4 phosphor showed higher thermally sta-ble luminescence comparable to commercially available Y3Al5O12:Ce3+ (YAG:Ce3+) phosphor. All the investigated suggestions that Na-BaPO4:Eu2+ is a good phosphor candidate applied in white light emitting diode.     

Synthesis of Long Afterglow Phosphor CaAl2Si2O8:Eu2+, Dy3+ via Sol-Gel Technique and Its Optical Properties

The long afterglow phosphor CaAl2Si2O8:Eu2 , Dy3 was prepared by a sol-gel method. The sol-gel process and the structure of the phosphor were investigated by means of X-ray diffraction analysis (XRD). It is found that the single anorthite phase formed at about 1000 ℃, which is 300 ℃ lower than that required for the conventional solid state reaction. The obtained phosphor powders are easier to grind than those of solid state method and the partical size of phosphor has a relative narrow distribution of 200 to 500 nm. The photoluminescence and afterglow properties of the phosphor were also characterized. An obvious blue shift occurs in the excitation and emission spectra of phosphors obtained by sol-gel and solid state reaction methods. The change of the fluorescence spectra can be attributed to the sharp decrease of the crystalline grain size of the phosphor resulted from the sol-gel technique.