Energy transfer in Tb~（3＋）,Yb~（3＋） codoped Lu_2O_3 near-infrared downconversion nanophosphors

Tb3+ and Yb3+ codoped Lu2O3 nanophosphors were synthesized by the reverse-strike co-precipitation method. The obtained Lu2O3:Tb3+,Yb3+ nanophosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectra. The XRD results showed that all the prepared nanophosphors could be readily indexed to pure cubic phase of Lu2O3 and indicated good crystallinity. The Tb3+→Yb3+ energy transfer mechanisms in the UV-blue region in Lu2O3 nanophosphors were investigated. The experimental results showed that the strong visible emission around 543 nm from Tb3+ (5D4→7F5) and near-infrared (NIR) emission around 973 nm from Yb3+ (2F5/2→2F7/2) of Lu2O3:Tb3+,Yb3+ nanophosphors were observed under ultraviolet light excitation, respectively. Tb3+ could be effectively excited up to its 4f75d1 state and relaxed down to the 5D4 level, from which the energy was transferred cooperatively to two neighboring Yb3+. The Yb3+ concentration dependent luminescent properties and lifetimes of both the visible and NIR emissions were also studied. The lifetime of the visible emission decreased with the increase of Yb3+ concentration, verifying the efficient energy transfer from the Tb3+ to the Yb3+. Cooperative energy transfer (CET) from Tb3+ to Yb3+ was discussed as a possible mechanism for the near-infrared emission. When doped concentrations were 1 mol.% Tb3+ and 2 mol.% Yb3+, the intensity of NIR emission was the strongest.     

Tunable color emission in K3Gd（PO4）2:Tb3+,Sm3+ phosphor for n-UV white light emitting diodes

A series of K3Gd(PO4)2:Tb3+,Sm3+ phosphors were synthesized through solid state reaction. By co-doping Tb3+ and Sm3+into K3Gd(PO4)2 host and singly varying the doping concentration of Sm3+, tunable colors from green to yellow and then to orange were obtained in K3Gd(PO4)2:Tb3+,Sm3+ phosphors under the excitation at 373 nm. The energy transfer process from Tb3+ to Sm3+ was verified through luminescence spectra and fluorescence decay curves. Moreover, the energy transfer mechanism was demonstrated to be the quadrupole-quadrupole interaction. The results indicated that K3Gd(PO4)2:Tb3+,Sm3+ phosphors could be a potential application for n-UV white light emitting diodes.     

Specific features of Eu^3＋ and Tb^3＋ magnetooptics in gadolinium-gallium garnet （Gd3Ga5O12）

We reported magnetooptical properties of Eu3+(4f(6)) and Tb3+(4f(8)) in single crystals of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG), and Eu3+(4f(6)) in Eu3Ga5O12 (EuGG) for both ions occupying sites of D2 symmetry in the garnet structure. Absorption, luminescence, and magnetic circular polarization of luminescence (MCPL) spectra of Tb3+ in GGG and YGG and absorption and magnetic circular dichroism (MCD) of Eu3+ in EuGG were studied. The data were obtained at 85 K and room temperature (RT). Magnetic susceptibility of Eu3+ in EuGG was also measured between 85 K and RT. The magnetooptical and magnetic susceptibility data were modeled using the wavefunctions of the crystal-field split energy (Stark) levels of Eu3+ and Tb3+ occupying D2 sites in the same garnets. The results reported gave a precise determination of these Stark level assignments and confirmed the symmetry labels (irreducible representations) of the closely-spaced Stark levels (quasi-doublets) found in the 5D1 (Eu3+) and 5D4 (Tb3+) multiplets. Ultraviolet (UV) excitation (<300 nm) of the 6PJ and 6IJ states of Gd3+ in the doped GGG crystals led to emission from 5D4 (Tb3+) and 5D1 and 5D0 (Eu3+) through radiationless energy transfer to the 4f(n-1)5d band of Tb3+ and to UV quintet states of Eu3+. The temperature-dependent emission line shapes and line shifts of the magnetooptical transitions excited by UV radiation suggested a novel way to explore energy transfer mechanisms in this rare-earth doped garnet system.     

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.     

Energy transfer from Tb³⁺ to Eu³⁺ in zinc lead borate glass

In order to sensitize the luminescence of Eu3+ ions in heavy metal glass,zinc lead borate glass samples containing various concentrations of Eu3+ and Tb3+ ions were prepared to study the Tb3+ to Eu3+ non-radiative energy transfer phenomena.Energy level structures of Tb3+ and Eu3+ ions were plotted to show the excitation and energy transfer routes.Efficient energy transfer from Tb3+ to Eu3+ was observed and studied qualitatively in terms of doping concentrations.The sensitization turned out to be less effective than expected.Further studies to characterize the oxidation of Tb3+ into tetravalent state and to examine the mechanism of energy transfer are proposed.     

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.     

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.     

Photoluminescence properties of Tb3+ and Ce3+ co-doped Sr2MgSi2O7 phosphors for solid-state lighting

Sr2Mg Si2O7:Tb3+,Ce3+ phosphors were synthesized by solid-state reaction and placed in a muffle furnace in a reducing atmosphere at 1300 oC for 3 h. Photoluminescence properties and energy transfer were investigated. The Ce3+/Tb3+ energy transfer was thoroughly investigated by their emission/excitation spectra and photoluminescence lifetime, there was shortened lifetime of Ce3+(from 51.31 to 50.06 ns) which could support evidence of energy transfer from Ce3+ to Tb3+ in the host. The varied emitted color of Sr1.97–yMg Si2O7:0.03Tb3+,y Ce3+ phosphors could be achieved by altering the concentration of Ce3+, the chromaticity coordinates(x, y) varied from(0.225, 0.376) to(0.172, 0.231). In Sr1.96 Mg Si2O7:0.03Tb3+,0.01 Ce3+ phosphors, the results indicated that Sr2 Mg Si2O7:Tb3+,Ce3+ might be useful as tunable phosphors for ultraviolet white-light-emitting diodes.     

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+.     

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.     

铽在硫氧化镧基质中的光致发光

采用高温固相反应法制备了La2O2S∶Tb3+、La2O2S∶Tb3+,RE3+(RE=Dy,Gd,Ce,Sm)荧光粉样品并进行了相关表征。结果表明,合成样品的晶体结构与La2O2S相同,为六方晶系;荧光粉颗粒的形貌多为长方形片状;发射光谱由494 nm、545 nm、587 nm、622 nm的一系列锐发射峰组成。研究发现Tb3+的掺杂浓度对样品主发射峰545 nm的发光强度影响很大,且在摩尔分数x(Tb3+)=0.02时达到最强。稀土离子Dy3+、Gd3+对La2O2S∶Tb3+荧光粉的发光有明显的敏化作用。     

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…     

Energy transfer from Ce~(3+) to Tb~(3+) and Eu~(3+) in zinc phosphate glasses

Ce3+,Eu3+ and Tb3+ singly doped and Ce3+/Eu3+ and Ce3+/Tb3+ co-doped zinc phosphate glasses were prepared by sintering P2O5,ZnO,Ce2(C2O4)3·10H2O and Eu2O3/Tb4O7 mixtures at 1200 °C in the air for 2 h and then annealing at 450 °C for 10 h.The obtained glasses were homogeneous and transparent.The glasses without Ce3+ were colorless and those with Ce3+ showed slightly yellow.The singly doped glasses showed strong emissions and excitations from doped trivalent rare earth ions.Strong energy transfer from Ce3+ to Tb3+ was observed for Ce3+/Tb3+ coped samples.There were also some very weak evidences for the energy transfer from Ce3+ to Eu3+.     

Hydrothermal Synthesis and Characterization of Pyrochlore Titanate R2Ti2O7(R=Gd3+, Tb3+, Dy3+)

Pyrochlore titanate oxides, R2Ti2O7(R=Gd3+, Tb3+, Dy3+), were synthesized under mild hydrothermal conditions. The crystal growth of pyrochlore titanate oxides and taking place of chemical reaction in the hydrothermal processing were sensitive to the alkalinity, temperature, reaction time, the nature of the rare earth ion and the composition of initial reaction mixture. The as-prepared samples were characterized by powder X-ray diffraction, scanning electron microscopy, Raman spectrum and variable temperature dc magnetic susceptibility(Superconductivity quantum interference device, SQUIDS). The magnetic studies gave 7.29×10-23 A·m2/Gd3+ and -8.28 K, 8.75×10-23 A·m2/Tb3+ and -19.7 K, and 8.85×10-23 A·m2/Dy3+ and 0.84 K effective moments and Weiss constants for Gd2Ti2O7,Tb2Ti2O7 and Dy2Ti2O7, respectively.     

Effect of trivalent rare earth ions doping on the fluorescence properties of electron trapping materials SrS：Eu~（2＋）

Trivalent rare-earth ions (La3+,Pr3+,Nd3+,Sm3+,Gd3+,Tb3+,Dy3+,Ho3+,Er3+,Tm3+,and Yb3+) were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS:Eu2+ in order to enhance the fluorescence properties.It was found that Sm3+ and Tb3+ had the best photoluminescence stimulated luminescence (PSL) effect among the selected trivalent rare-earth ions.All the SrS:Eu2+ samples doped by different trivalent rare-earth ions could be stimulated by 980 nm laser after being exposed to the conventional sunlight,and they emitted PSL with the peak located at 615 nm.The result also indicated that some co-doped rare earth ions could increase fluorescence intensities of the traditional electron trapping materials SrS:Eu2+.     

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...