Synthesis and characterization of YAG: Ce3+ fluorescence powders by co-precipitation method

YAG:Ce³⁺(Yttrium aluminum garnet) fluorescence powders were successfully prepared by co-precipitation method using aluminum nitrate, yttrium nitrate, cerous nitrate as the starting materials and ammonium carbonate as precipitant. The products were characterized by X-ray powder diffraction, luminescence spectrometer, transmission electron microscope (TEM). The XRD results showed that the obtained YAG:Ce³⁺ fluorescence powders had the crystalline structures of YAG at calcinations temperature of 900 °C and the TEM results showed that the grain diameters were about 100 nm. The YAG:Ce³⁺ fluorescence powders, synthesized by co-precipitation method, had the best luminescence property when the Ce doping amount was x=0.06 in the molecular formula of Y_3-xCe_xAl₅O₁₂, the calcinations time was 2 h and the calcinations temperature was 1000 °C.     

Citrate sol-gel combustion preparation and photoluminescence properties of YAG:Ce phosphors

Yellow-emitting YAG:Ce3+ nanocrystalline phosphors were prepared by citrate sol-gel combustion method using citric acid as the fuel and chelating agent. The influence of mole ratio of citric acid to metallic ions (MRCM), pH value of the solution, calcination temperature and Ce-doped concentration on the structures and properties of as-prepared powders were investigated in detail. Higher crystallinity and better luminescence performance powders were obtained at MRCM=2, pH=3 and the calcination temperature of 1200 °C. The phosphors exhibited the characteristic broadband visible luminescence of YAG:Ce. The optimum concentration of Ce3+ was 1.0 mol.%, and the concentration quenching was derived from the reciprocity between electric dipole and electric quadrupole (d-q). Especially, the pH value of the solution was a key factor to obtain a stable sol-gel system and then obtain pure and homogeneous rare earth ions doped YAG phosphors at a lower tem-perature. The Y3Al5O12:Ce0.03 phosphor with optimized synthesis-condition and composition had a similar luminescence intensity with the commercial phosphor YAG:Ce.     

Effects of aluminum co-doping on photoluminescence properties of Ce³⁺-doped SiO₂ glasses

SiO2 glasses co-doped with Al3+ ions were prepared by a sol-gel method by holding 0.5% of Ce3+ ions constant and varying the Al3+ ions concentrations.Thermal stability,the structural,chemical and the optical properties of the samples were studied by using differential scanning calorimetric(DSC),thermo gravimetric analysis(TGA),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),UV-vis spectroscopy and photoluminescence spectroscopy(PL).The DSC and TGA of samples depicted that the presence of dopant and co-dopant decreased the endothermic peak temperature and the yield respectively.SEM images showed that the particles were in the nano-range and spherical in shape.The XRD showed that all the samples were amorphous.The UV absorption measurements indicated that the presence of Al3+ ions significantly reduced the SiO2 absorption band,increased the absorbance intensity of SiO2 and decreased the transmittance as compared to the presence of the Ce3+ ions alone.The photoluminescence results displayed an optimum increase in luminescence intensity when the ratio of Al:Ce was 10:1 and further increase in aluminum content quenched the luminous intensity.     

Preparation and characterization of Y3Al5O12:Ln（Ln=Eu,Ce） phosphor powders by ultrasonic atomization and co-precipitation process

A novel technique for YAG:Ln(Ln=Eu,Ce) phosphor powder synthesis with a nanocrystalline structure was developed.Nanocrystalline YAG:Ln powder was prepared by an ultrasonic atomization and co-precipitation method using a mixture solution of ammonium hydroxide(NH3·H2O) and ammonium hydrogen carbonate(NH4HCO3) as precipitant.The as-prepared nano-powders were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),and fluorescence spectrometer.The obtained phosphor powders were homogenous and in size of 50-70 nm.The results demonstrated that by using ultrasonic atomization and co-precipitation process,we could synthesize a good quality YAG:Ln(Ln=Eu,Ce) phosphor powder that had many potential applications.     

Photoluminescence enhancement of YAG：Ce~（3＋） phosphor prepared by co-precipitation-rheological phase method

YAG:Ce3+ phosphor was prepared by a novel co-precipitation-rheological phase method.The resulting YAG:Ce3+ phosphor was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and photoluminescent emission spectra.By using acetic acid as solvent,YAG:Ce3+ powder with small particle size(≤2 μm) was obtained at a relatively lower sintering temperature of 1400 oC.With the content of acetic acid increasing,small particles dissolved and disappeared,but larger particles grew up and changed its shape from spherical to partially rectangular.Meanwhile,the emission intensity of the sample prepared by co-precipitation-rheological phase method was about 43% higher than that of the sample prepared by co-precipitation method.It was assumed that the significant improvement of luminescence was mainly because the rheological phase presented a better diffusion environment,and therefore,a better homogeneity of activators of Ce3+.     

Preparation and characterization of Y3Al5O12:Ln (Ln=Eu,Ce) phosphor powders by ultrasonic atomization and co-precipitation process

A novel technique for YAG:Ln (Ln=Eu, Ce) phosphor powder synthesis with a nanocrystalline structure was developed. Nanocrystalline YAG:Ln powder was prepared by an ultrasonic atomization and co-precipitation method using a mixture solution of ammonium hydroxide(NH₃·H₂O) and ammonium hydrogen carbonate(NH₄HCO₃) as precipitant. The as-prepared nano-powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fluorescence spectrometer. The obtained phosphor powders were homogenous and in size of 50-70 nm. The results demonstrated that by using ultrasonic atomization and co-precipitation process, we could synthesize a good quality YAG:Ln (Ln=Eu, Ce) phosphor powder that had many potential applications.     

白光LED用高效荧光转化材料钪硅酸盐的研究进展

由于目前LED用绿色荧光粉体系分别存在热稳定性差、显色指数低、制备复杂苛刻等问题,因此日本三菱化学开发出了一种新型LED用绿色Ca3Sc2Si3O12∶Ce3+钪硅酸盐荧光粉。在综述Ca3Sc2Si3O12∶Ce3+荧光性能的基础上,总结分析了Ca3Sc2Si3O12∶Ce3+荧光发光材料的晶体结构和发光机制,表明这种荧光粉兼备了硅酸盐和YAG∶Ce荧光粉的石榴石结构,使得晶体场能够与Ce3+配合展现出良好的匹配性,可以很好的与现行蓝光芯片匹配得到高品质的白光,并且类似YAG晶体的石榴石结构有着良好的发光性能和热稳定性;讨论了在电荷补偿作用和这种作用下基质改变后荧光粉的性能变化,以及激活剂改变、能量传递的影响,表明荧光粉光色可调幅度较大,能够根据不同变化产生不同的发光;然后分固相法和液相法总结了该荧光粉的制备方法,证明该荧光粉烧结温度低、合成工艺适应性广泛,并且高温固相法是工业化生产该系列荧光粉的最佳方法;最后展望了Ca3Sc2Si3O12∶Ce3+荧光转换材料的发展趋势和在白光LED中的应用前景,作为一种新型高效的白光LED用绿色荧光粉,需要进一步的研究和探索。     

Influence of ammonium sulfate on YAG nanopowders and Yb:YAG ceramics synthesized by a novel homogeneous co-precipitation method

Homogeneous and dispersed Y_3 Al_5 O_(12)(yttrium aluminum garnet,YAG) nanopowders were synthesized via a homogeneous co-precipitation method from the mixed solutions of yttrium nitrate,aluminum nitrate and a small amount of ammonium sulfate using hot urea as the precipitant.The method has the superiorities that co-precipitation of cations is ensured and continuous decomposition of the hot urea is achieved to obtain the narrow size distribution particles.The addition of small amount of ammonium sulfate surfactant,although has no influence on YAG garnet phase formation,has significant effect on dispersion,particles distribution and sinterability of the resultant YAG and Yb:YAG powders.Compared with the undoped sample,the green body of Yb:YAG doped with ammonium sulfate has higher total shrinkage,linear shrinkage rate and relative density through sintering at 1600 ℃.The resultant Yb:YAG powders can be sintered into transparent ceramics at 1700 ℃ through vacuum sintering.The influence of the sulfate ions on characteristics of the resultant powders was thoroughly studied.     

Luminescence properties of BaAl₁₂O₁₉:Tb,Ce and energy transfer between Ce³⁺,Tb³⁺

BaAl12O19:Tb,Ce phosphors were prepared by sol-gel technique,the crystalline structures of samples characterized by XRD,and the luminescence properties and energy transfer between Ce3+ and Tb3+ were investigated.The results indicated that the emission intensity and the excitation wavelength range of Tb3+ increased when Ce3+ was doped.It demonstrated that the Ce3+ added in the BaAl12O19:Tb could deliver energy to Tb3+,and Ce3+ was not luminous by itself.The relative emission intensity of Tb3+ at wavelength of 548 nm was the strongest by Tb3+/Ce3+ ratio of 2:1,when excited at 310 nm,which was the characteristic adsorption wavelength of Ce3+.     

Controlled synthesis and tunable luminescence of NaYF₄:Eu³⁺

High quality NaYF4:Eu3+ luminescent materials were successfully synthesized via a facile template technique by hydrothermal method.The samples were characterized by X-ray powder diffraction(XRD),transmission electron microscopy(TEM) and fluorescence spectroscopy(FS).The incorporating of Eu3+ ions into NaYF4 crystal lattice influenced the symmetry types of NaYF4 crystals,resulting in phase transformation of NaYF4 crystals between α and β phase.The pure hexagonal phase of branched NaYF4:Eu3+ was obtained as the Eu3+ concentration reached 15 mol.%.In addition,the luminescence color was tuned by changing the doping concentration of Eu3+ ions.     

Study of cerium ion in (Y0.95La0.05)2O3:Ce

(Y0.95La0.05)2O3: Ce3+ nano-powder was synthesized by co-precipitation method and sintered at 800 and 900 oC. All the samples were cubic phase characterized by X-ray diffraction (XRD) analysis. The samples sintered at the lower temperature exhibited luminescence. According to the distinguishable structure of Ce 3d peaks and the shift of O 1s lines in the X-ray photoelectron spectroscopy (XPS), luminescence was further confirmed to originate from Ce3+ ions. Effects of introducing La3+ into Y2O3 were discusse...     

沉淀温度对制备铈掺杂YAG粉体的影响

文中采用共沉淀法来制备铈掺杂YAG前驱体.为获得纯相YAG:Ce3+粉体,实验以CeO₂、Y₂O₃、Al(NO₃)₃·9H₂O和NH₄HCO₃为原料,在不同的沉淀温度下来制备YAG:Ce3+前驱体,将所制得的前驱体经高温煅烧还原得到YAG:Ce3+粉体,并通过TG/DTA、XRD及光谱分析等手段分析了沉淀温度对YAG:Ce3+粉体性能的影响.实验结果表明:沉淀温度为25 ℃时制备出来的YAG:Ce3+粉体发光强度好.      

Synthesis of Ce:YAG Phosphor via Homogeneous Precipitation under Microwave Irradiation

Ultra-fine Ce:YAG phosphors were prepared by homogeneous precipitation under microwave irradiation method. The formation of Ce:YAG was investigated by means of XRD and DTA/TG. The purified YAG crystallized phase was obtained at a lower temperature (1100 ℃). Basically spherical Ce:YAG powders were indicated from TEM images, and the size of the particles is about 80 nm. Two peaks of 436 and 473 nm can be seen from the excitation spectrum in the range of 402～510 nm. A broad emission band located at 480～630 nm shows the phosphors prepared by this method have good emission properties.     

溶胶-凝胶法制备YAG:Ho~(3+),Yb~(3+)纳米晶

以稀土氧化物和硝酸铝为原料,采用溶胶-凝胶法合成了YAG:1%Ho~(3+),1%Yb~(3+)纳米晶,并通过正交试验法确定其干凝胶的合成条件.采用DTA-TG、XRD及TEM对干凝胶的合成过程、纳米晶的晶相组成及形貌进行了研究,表明干凝胶经1 200 ℃煅烧后形成了结晶完全的YAG相,无中间相产生.吸收光谱和上转换发射光谱分析表明,Yb~(3+)在材料的发光过程中具有传递能量的作用,Ho~(3+)在跃迁过程中发射出中心波长为650 nm的红色上转换荧光及540 nm的绿色上转换荧光.     

Electrospinning synthesis and luminescent properties of Lu₂O₃:Eu³⁺ nanofibers

One-dimensional Lu2O3:Eu3+ nanofibers were prepared by electrospinning followed by high-temperature calcinations.Thermogravimetric and differential thermal analysis,X-ray powder diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,photoluminescent spectra and decay curves were used to characterize the samples.Results showed that samples began to crystallize at ～500 oC and crystallized completely around 1000 oC.The average diameter of nanofibers(1000 oC annealed) was about 55 nm and the particle size of Lu2O3:Eu3+ increased with increasing annealing temperature.Under ultraviolet excitation,nanofibers exhibited typical red emission of Eu3+ in Lu2O3.The effect of heat-treatment temperature on luminescent properties of nanofibers was also discussed.     

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.     

Preparation and properties of Nd:YAG ultra-fine powders

Ultra-fine Nd:YAG powders with different doping concentrations were synthesized by sol-gel combustion method.The pure Nd:YAG could be prepared at the low temperature of 900 oC.Ethanol could improve the dispersity of powders,and the average size of the ul-tra-fine powders was around 250 nm.The reflection spectrum showed that there were several apparent characteristic absorption peaks and the intensity of these peaks enhanced with the increasing concentration of Nd3+.The luminescence spectrum,which was excite...     

An impact of sintering temperature and doping level on structural and spectral properties of Eu-doped strontium aluminium oxide

In the present work,a sol-gel method was employed to prepare nanosized SrAl2O4 powders doped with Eu3+ ions.The raw nano-materials were thermally treated at 900 to 1100 oC for 3 h.The XRD analysis demonstrated that the powders were single-phase nanopowders with high crystallite dispersion.Our studies were focused on relating the luminescence properties of the Eu3+ dopant to the NC(nanocrystal-lites) size.This was achieved by varying the calcinations temperature between 900 and 1100 oC.The average NC size varied accordingly be-tween ～36 and ～75 nm.We found that size effect manifested mainly in the expansion of the cell volume and broadening of XRD peaks as in-dicated by Rietveld analysis.Moreover the emission and excitation spectra,although typical for Eu3+ ions,demonstrated some degree of variability with calcinations temperature and doping concentration.To explain these differences a detailed analysis of luminescence spectra by the Judd-Ofelt theory was performed.     

Nanostructured yttrium aluminum garnet powders synthesized by co-precipitation method using tetraethylenepentamine

Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray ...     

Synthesis and luminescent properties of Ce~(3+) doped LuAG nano-sized powders by mixed solvo-thermal method

Polycrystalline LuAG:Ce3+(cerium3+-doped lutetium aluminum garnet) powders were prepared by mixed solvo-thermal method.Fourier-transform IR spectroscopy(FTIR) and X-ray diffraction(XRD) measurements showed that the precursors were ethanol derivatives AlO(OH) crystal with hydroxyl and carbonate group.XRD results showed that phase of Lu2O3 disappeared with the precursors were annealed at 400 °C,cubic phase LuAG:Ce3+ appeared but only one diffraction peaks of LuAP(LuAlO3) at calcination temperature to 700 °C,and the purified crystalline phase of LuAG:Ce3+ was obtained at 1000 °C.The scanning electron microscopy(SEM) analysis revealed that the synthesized LuAG:Ce3+ powders were uniform and had good dispersivity with an average particle size about 100 nm.Excitation and emission spectra of Ce3+ doped LuAG phosphors were measured.Many factors of affecting the intensity of emission spectra were discussed.