Tb^3＋ concentration dependent optical properties and energy transfer in GdF3 nanocrystals

By controlling the concentration of Tb3＋, a series of GdF3 samples were synthesized by a hydrothermal method without any surfactant. The samples were characterized by X-ray diffraction （XRD） patterns, field emission scanning electron microscopy （FE-SEM） images, photoluminescence （PL） excitation and emission spectra as well as luminescent dynamic decay curves. The opti-cal properties of Tb3＋, the concentration quenching phenomenon of Tb3＋, and the energy transfer from host Gd3＋to Tb3＋were inves-tigated and discussed based on the concentration of Tb3＋in the GdF3 samples. The experimental results suggested that the optical properties of Tb3＋and the energy transfer from host Gd3＋to Tb3＋could be adjusted by the concentration of Tb3＋in the samples.     

Photoluminescent properties of Eu3＋ and Tb3＋ codoped Gd2O3 nanowires and bulk materials

In this paper, the Gd2O3：Eu3＋,Tb3＋phosphors with different doping concentrations of Eu3＋and Tb3＋ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3：Eu3＋,Tb3＋phosphors were analyzed by means of X-ray powder diffraction （XRD）, transmission electron mi-croscopy （TEM） and scanning electron microscopy （SEM）. The photoluminescence （PL） properties of Gd2O3：Eu3＋,Tb3＋phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3＋was fixed at 1 mol.%, the emis-sion intensity of Eu3＋ions was degenerating with Tb3＋content increasing, while when the Tb3＋content was fixed at 1 mol.%, the emission intensity of Tb3＋ions reached a maximum when the concentration of Eu3＋was 2 mol.%, implying that the energy transfer from Eu3＋to Tb3＋took place. In addition, Tb3＋could inspire blue-green light and the Eu3＋could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.     

Effects of Doping Trace Sm^3＋ and Gd^3＋ on Luminescent Character of Y2O2S：Eu^3＋

After trace Sm^3＋ ions and Gd^3＋ ions doping, the emission intensity of red phosphors Y2O2S： Eu^3 ＋ was enhanced and the voltage character （relation between emission intensity and excitation voltage） was improved while the other properties of physics and chemistry were not changed. The origins of enhancement and improvement are discussed. Probably the distortion and the defect of crystals are decreased by the substitution of Gd^3＋ for Y^3＋ instead of Eu^3＋ for Y^3＋ , and thus the Eu^3＋ crystal field is improved, and radiationless process and energy loss resulted from crystal defect are weakened, which leads to increased luminescence intensity and voltage character improvement. The overlapping fluorescent spectra of Y2O2S： Sm^3＋ emission and Y2O2S：Eu^3＋ excitation as well as Eu^3 ＋ excitation spectra transitions spectra lead to energy transfer from Sm^3 ＋ sensitization of Sm^3＋ ions fectively. containing Sm^3＋ excitation the possibility of resonance ions to Eu^3＋ ions, and the to Eu^3＋ ions is achieved effectively.     

Hydrothermal synthesis and luminescence properties of YW2O6（OH）3：Tb^3＋ green phosphors

YW2O6(OH)3:Tb3+ green phosphors were synthesized at different pH values via a facile hydrothermal method. The structure and optical properties of as-synthesized samples were studied by X-ray diffractometer (XRD), scanning electron microscopy (SEM), photolumi-nescence spectra and luminescence decay curve. The results showed that pure monoclinic YW2O6(OH)3:Tb3+ green phosphors could be ob-tained at pH 2-5. Uniform spherical micro-phosphors of ~5 μm in diameter with narrow size distribution could be prepared at pH 5. pH value had dramatic influence on morphologies, which could be ascribed to the various spatial configurations of different poly-tungstates existing at different pH values. The emission spectra under 261 nm excitation exhibited dominant green emission at 546 nm. The green emission inten-sity reached the maximum value at pH 5 due to the high packing density of the obtained phosphor.     

Photoluminescence characterization and energy transfer of NaBa1-x-yPO4：xCe3＋, yTb3＋ phosphors

A series of NaBa1-x-yPO4: xCe3+, yTb3+ phosphors were synthesized by solid-state reaction method. The crystal structure, photoluminescence emission and excitation spectra and decay times of the phosphors were carefully investigated. The results revealed that an efficient energy transfer occurred from Ce3+ to Tb3+ ions in NaBaPO4 host by means of dipole-dipole interactions and the critical distance of the energy transfer was about 0.638 nm. Moreover, the phosphor emitted strong green emission under UV excitation, indicating that the phosphors are potentially useful as a highly efficient, green-emitting phosphor.     

Solvothermal fabrication and luminescent properties of Eu2＋/Ce3＋ doped barium lithium fluoride

Phosphors of BaLiF3 doped with Eu or/and Ce were solvothermally prepared at 200°C for 5d and characterized by means of X-ray powder diffraction (XRD) and environment scanning electron microscopy (ESEM). The excitation and emission spectra of the rare earth ions doped BaLiF3 were measured by fluorescence spectroscopy and the effects of Ce3+ ions on the luminescence of Eu2+ ions were investigated. In the codoped Eu2+ and Ce3+ system, the emission intensity of Eu2+ ion gradually increased with the Ce3+ concentration increasing, and the enhancement of Eu2+ fluorescence was due to efficient energy transfer from Ce3+ to Eu2+ in the host.     

Synthesis and luminescence properties of CeF3：Tb3＋ nanodisks via ultrasound assisted ionic liquid method

CeF3 and CeF3：Tb3＋ nanocrystals were successfully synthesized by the ultrasound assisted ionic liquid （IL） method at room temperature. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, selected area electron diffraction （SAED）, high-resolution transmission electron micrographs （HRTEM） and photoluminescence （PL） spectra were employed to characterize the nanocrystals. The results of XRD indicated that the obtained samples crystallized well with a hexagonal phase crystal structure. SEM and TEM images demonstrated that the obtained CeF3：Tb3＋ nanocrystals had a discoid shapein the presence of ultrasound and IL, whereas only granular nanoparticles were obtained by magnetic stirring. The possible formation mechanisms of the crystal growth were proposed. The PL spectra of the CeF3：Tb3＋ nanodisks exhibited a strong green emission when excited at 254 nm. Furthermore, the photoluminescence intensity of CeF3：Tb3＋ of the discoid particles was largely improved com-pared with that of the granular nanoparticles.     

LiZnPO4：Tb^3＋,Ce^3＋ green phosphors with high efficiency

Tb3+ and Ce3+ co-activated LiZnPO4 phosphors with high luminescence efficiency were synthesized by a high temperature solid-state reaction at 1000 oC for 3 h. The XRD patterns, photoluminescence spectra and SEM were recorded and the effects of Tb3+ and Ce3+ concentration, sintering condition on the luminescent properties of as-synthesized phosphors were investigated. The emission spectra under ultraviolet (200-300 nm) radiation showed a dominant peak at 543 nm attributed to the 5D4→7F5 transition of Tb3+, which was greatly en-hanced by the co-doping of Ce3+, indicating that there occurred an efficient non-radiative energy transfer from Ce3+ to Tb3+. The optimal dop-ing concentrations of Tb3+ and Ce3+ were determined to be 9% and 10%, respectively.     

Synthesis and luminescence properties of Sr3-z（AlxSi1-x）O5-xFx：zCe^3＋phosphors

Sr3-z(Alx,Si1-x)O -5-xFx:zCe3+ phosphors were synthesized by high-temperature solid-state reaction.The structure and luminescence properties of phosphors with various Al/Si ratios and Ce3+ concentrations were characterized using various methods such as X-ray diffraction,photoluminescence excitation and photoluminescence spectra.XRD result displayed that a complete solid solution between Sr3AlO4F and Sr3SiO5 was formed.With the increasing of x value,a broader excitation band and stronger absorption appeared in the blue light region.Moreover,the emission band shifted to a shorter wavelength and the emission intensity reached a maximum at x=0.6.By adjusting the concentration of Ce3+,a widely tunable range of emission wavelength under the excitation of 460 nm was obtained from the green to yellow regions.In addition,the concentration and thermal quenching were also discussed.     

Combustion synthesis and luminescence properties of Ca4Y6（SiO4）60：Eu3＋ red phosphor for white LEDs

Eu3＋ activated Ca4Yt（SiO4）60 phosphors were prepared by combustion synthesis method, and their morphologies and lu- minescent properties were investigated. Field scanning electron microscopy （FSEM） confirmed that the crystallite sizes of nanoparti- cles with narrow diameter ranging from 30 to 60 rim. The excitation spectra of CaaY6（SiO4）60：Etl3＋ showed that there existed two strong excitation bands at around 399 nm （TFo----~SL6） and 469 nm （TF0---＊SD2）, which were consistent with the output wavelengths of near-UV and blue LEDs, respectively. The emission spectra of Ca4Y6（SiO4）60：Eu3＋ were dominant by a red peak located at 614 nm due to the 5Do→7TF2 transition of Eu3＋. With the increase of Eu3＋concentration, the luminescence intensity of the red phosphor reached maximum and then decreased. The optimum concentration for Eug＋in Ca4Y6（SiO4）60 was 21 mol.%.     

Photoluminescence of SrGdGa_3O_7∶RE (RE=Ce~(3 ), Pr~(3 ), Tb~(3 )) under VUV-UV Excitation

SrGdGa3 O7belongstothelargefamilieswhosegeneralchemicalformulaisAMM′3 O7(A =Ca ,Sr ,Ba ;M =La ,Gd ,Y ;M′ =Al,Ga) .Thesecom poundshavemelilitestructure .Structuralinvestiga tionsindicatethatSrGdGa3 O7formstetragonalcrystalswithspacegroupP 4 2 1m .Theunit…     

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+.     

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.     

Rare earth double activated phosphors for different applications

For the purpose of development of highly energy-efficient light sources,one needs to design highly efficient green,red and yellow phosphors,which are able to absorb excitation energy and generate emissions.In this contribution,we present our results on producing some efficient phosphors with improved luminescence properties.Using double activation,energy could be transferred from one luminescent activator to the other one,resulting in more efficient or brighter device operation.Co-activators could be added to a host material to change the color of the emitted light.The incorporation of Eu3+ or Tb3+ ions into the CaWO4 crystal lattice modified the luminescence spectrum due to the formation of the emission centers that generated the specific red and green light.Very efficient new red phosphors based on YNbO4 and doped by Eu3+,Ga3+,Al3+ allowed recommending these materials as good candidates for different applications including LED and X-ray intensifying screens.For double activated TAG with Ce3+ and Eu3+ and for different mole ratios of Ce/Eu,the color temperature changed from 5500 K(0.331,0.322) up to 4200 K(0.370,0.381) and the light became "warmer".Application of TAG:Ce,Eu in the light emitting device showed better chromaticity coordinates of luminescence and color rendering index of LEDs.     

溶胶-凝胶法制备Sr2SiO4:Tb3+绿色荧光粉及其发光性能

采用溶胶-凝胶法合成了一系列适合紫外-近紫外激发的(1-X)Sr₂SiO₄:XTb3+(X=0,0.01,0.02,0.03,0.04,0.05,0.06)绿色荧光粉,并采用X射线衍射(XRD)、扫描电子显微镜(SEM)和荧光光谱(PL)研究了样品的结构及发光性能.由XRD的检测结果可知,合成样品属于单斜晶系的β-Sr₂SiO₄相.由SEM图可知,所有样品都呈无规则块状结构.当监测波长为546 nm,样品的激发光谱的主峰位于370 nm处,属于Tb3+的4f-4f特征跃迁吸收.当激发波长分别为285 nm和250 nm,所有样品在488 nm,547 nm,586 nm,623 nm处都出现了1个强发射峰,分别对应Tb3+的5D₄→7F₆、5D₄→7F₅、5D₄→7F₄和5D₄→7F₃电子跃迁.最强发射峰位于547 nm处,呈现特征为绿光发射.随Tb3+掺杂量增大,发射强度呈现出先增大后减小的变化趋势,即存在浓度猝灭效应.当Tb3+掺杂量为X=0.03时,样品的发光强度最大.      

Effect of Li+ ions doping on structure and luminescence of (Y,Gd)BO3:Tb3+

The (Y,Gd)BO3:Tb3+ and Li+-doped (Y,Gd)BO3:Tb3+ phosphors were prepared by high temperature solid-state method. The inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the excitation and emission spectra were used to characterize the samples. The results of ICP-AES and XRD indicated that Li+ ions could enter the (Y,Gd)BO3:Tb3+ lattice and induce the lattice expansion. It could be seen from SEM that the particles were spherical a...     

表面活性剂对ZnWO4：Tb3+绿色荧光粉发光性能的影响

采用水热法合成应用于荧光灯的绿色荧光粉 ZnWO4：Tb3+。通过X 射线粉末衍射分析仪（XRD）,扫描电子显微镜（SEM）和荧光光谱仪,系统考察不同表面活性剂条件下合成的ZnWO4：Tb3+绿色荧光粉。结果表明,不同表面活性剂条件下,采用水热法合成的产品均为纯ZnWO4结构,Tb3+掺杂并不改变钨酸锌结构;荧光光谱仪对样品的激发和发射以及荧光衰减曲线测定表明,表面活性剂PEG-2000条件下合成的荧光粉,其发光强度增强最有效,采用PVP 为表面活性剂合成ZnWO4：Tb3+的荧光粉寿命较采用PEG-2000和CTAB 为表面活性剂合成的长。综合发光强度和荧光寿命的影响,选PVP为表面活性剂最佳。     

Influence of CeO2 on scintillating properties of Tb3+-doped silicate glasses

A series of Tb3+-,Ce3+-doped,and Tb3+/Ce3+-codoped silicate glasses were synthesized by melt-quenching technique.Some properties of the investigated glasses were characterized by X-ray photoelectron spectroscopy(XPS),photoluminescence(PL),X-ray excited luminescence(XEL) and thermoluminescence(TL) spectra.The result of XPS revealed that both Ce3+ and Ce4+ ions coexisted in these silicate glasses,and energy transfer from Ce3+ to Tb3+ ions was observed under UV excitation.However,under X-ray excitation the XEL...     

Luminescent properties of SrSi2N2O2:Ce3+,Tb3+-a potential phosphor for white light emitting diodes

Ce3+ and Tb3+ co-doped SrSi2N2O2 phosphors were prepared by solid-state reaction. The X-ray diffraction pattern exhibited that the phosphor consisted mainly of oxygen-rich SrSi2N2O2. The optical properties of SrSi2N2O2:Ce3+, SrSi2N2O2:Tb3+ and SrSi2N2O2:Ce3+,Tb3+ were studied, respectively. The emission intensity of Tb3+ at 541 nm was remarkably enhanced by Ce3+ in SrSi2N2O2:Ce3+,Tb3+ phosphor, which was attributed to the energy transfer from Ce3+ to Tb3+. The chromaticity coordinates of phosphors were investigated as a function of Tb3+ concentration. When the Ce3+ and Tb3+ concentrations were 0.02 and 0.18 mol per formula unit, respectively, the chromaticity coordinate was (0.257, 0.337) in the CIE 1931 chromaticity diagram. SrSi2N2O2Ce3+,Tb3+ phosphors could be used for white light emitting diodes.