Synthesis and luminescence properties of lanthanide (III)-doped YF3 nanoparticles

Synthesis process and luminescence properties of trivalent lanthanide ions (Ln3+) doped YF3 nanoparticles have been investigated. To synthesis Ln(3+)-doped YF3 nanoparticles, the mixture of (YCl3 x nH2O + LnCl3 x nH2O), and NH4F was hydrothermal treated at 180 degrees C in a Teflon-liner auto-clave or heated at higher temperatures (400 degrees C - 600 degrees C) in a stove. The XRD patterns showed that the Ln(3+)-doped orthorhombic YF3 nanoparticles with no second phase have been prepared. The solid solution Y(1-x)Eu(x)F3 (x = 0 - 0.4) nanoparticles have been synthesized. The luminescence concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurred at higher Eu3+ concentrations (30 mol%). The upconversion luminescence of Er(3+)-Yb3+ codoped YF3 nanoparticles under 980 nm excitation has also been observed. With increase of heated temperature, the size of the Er(3+)-Yb3+ codoped YF3 nanoparticles increased gradually, and upconversion luminescence intensity increased significantly.     

Ln(Ln=Gd3+,Cu+,Sm3+,Dy3+)助激活的Ca8Mg（SiO4）4Cl2∶Eu2+荧光粉的光谱特性和Eu2+的格位计算

采用高温固相法合成了掺杂Ln(Ln=Gd3+,Cu+,Sm3+,Dy3+)作助激活离子的氯硅酸镁钙荧光粉。通过X射线衍射(XRD)对Ca8Mg(SiO4)4Cl2∶Eu2+,Ln进行了表征,结果表明Ln的共掺杂并没有影响基质晶体的面心立方结构。所合成的荧光粉发射峰值位于507nm的绿光区,激发光谱在330~430nm之间均有较强吸收,与紫光InGaN芯片(395nm)相匹配。掺杂Ln作助激活剂增强了荧光粉的发光强度。借助Uitert经验公式计算出Eu2+在Ca8Mg(SiO4)4Cl2基质中占据八配位Ca(Ⅱ)格位。     

Luminescence study on Eu(3+) doped Y(2)O(3) nanoparticles: particle size, concentration and core-shell formation effects

Nanoparticles of Eu(3+) doped Y(2)O(3) (core) and Eu(3+) doped Y(2)O(3) covered with Y(2)O(3) shell (core-shell) are prepared by urea hydrolysis for 3?h in ethylene glycol medium at a relatively low temperature of 140?°C, followed by heating at 500 and 900?°C. Particle sizes determined from x-ray diffraction and transmission electron microscopic studies are 11 and 18?nm for 500 and 900?°C heated samples respectively. Based on the luminescence studies of 500 and 900?°C heated samples, it is confirmed that there is no particle size effect on the peak positions of Eu(3+) emission, and optimum luminescence intensity is observed from the nanoparticles with a Eu(3+) concentration of 4-5?at.%. A luminescence study establishes that the Eu(3+) environment in amorphous Y (OH)(3) is different from that in crystalline Y(2)O(3). For a fixed concentration of Eu(3+) doping, there is a reduction in Eu(3+) emission intensity for core-shell nanoparticles compared to that of core nanoparticles, and this has been attributed to the concentration dilution effect. Energy transfer from the host to Eu(3+) increases with increase of crystallinity.     

Eu3+掺杂的硼酸锶系列荧光体的合成及其发光性能

采用溶胶-凝胶法和高温固相反应法合成了Eu^3 掺杂的SrB4O7、SrB2O4、Sr2B2O5、Sr3B2O6荧光体．荧光光谱测试结果表明在不同基质中Eu^3 的荧光发射是有区别的，Sr2B2O5：Eu^3 、Sr3B2O7：Eu^3 发射峰在610nm左右的红光区，SrB2O4：Eu^3 的发射峰在593nm的橙色区，而SrB4O7：Eu^3 则表现出了Eu^2 离子的特征峰，产生这种区别主要是由Eu^3 所处的配位环境不同造成的．荧光体SrB4O7：Eu^3 、SrB2O4：Eu^3 、Sr2B2O5：Eu^3 、Sr3B2O6：Eu^3 的最佳掺杂浓度为2％左右．     

Thermoluminescence of MgSO4 doped with Eu and P impurities

CaSO4:Eu, MgSO4:Eu and MgSO4:Eu,P phosphors have been prepared and their thermoluminescence (TL) characteristics were studied. A main glow peak due to Eu2+ ions is seen at approximately 146 degrees C and 440 nm and glow peaks at approximately 145 degrees C, approximately 190 degrees C, approximately 260 degrees C and approximately 360 degrees C for 590 nm and 625 nm wavelengths are identified as Eu3+ ion emissions in MgSO4:Eu. Emission spectra in MgSO4:Eu and the MgSO4:Eu,P show that the MgSO4:Eu3+ glow peak at 260 degrees C for 590 nm and 625 nm shifts to 280 degrees C with enhanced intensity while the Eu2+ ion glow peak at 146 degrees C remains but with reduced intensity. The main glow peak at approximately 146 degrees C and 440 nm from Eu2+ ions shows significant difference from the characteristic glow peaks of Eu3+ ions. It is observed that the wavelength of the Eu2+ ion glow peak is inversely proportional to the radius of the cation of the host sulphate in alkaline-earth sulphate phosphors. By contrast the wavelengths of the Eu3+ ion glow peaks remain unchanged in different sulphates. Besides, the glow curve at approximately 146 degrees C obtained using a conventional blue sensitive reader shows simply the first order kinetics. It is concluded that the luminescence centres and distribution of traps related to Eu2+ ions are different from that of Eu3+ ions in MgSO4:Eu and MgSO4:Eu,P phosphors.     

Fabrication of novel luminor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) with core/shell heteronanostructure

A novel polychromic phosphor with core-shell heteronanostructure has been prepared to improve the chromatic index of phosphors. As for the first example, Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+), its synthetic route, structure and optical properties are presented in this paper. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy-dispersive x-ray spectra (EDS) and photoluminescence (PL) were all employed to characterize the composite core-shell phosphors. The XRD, FE-SEM and HR-TEM results indicate that the SiO(2) and YVO(4):Eu(3+) layers have been successfully coated on Y(2)O(3):Eu(3+) nanoparticles and SiO(2) layer, respectively: these layers were further verified by the EDS. The PL showed that the red-emitting phosphor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) possessed the independent luminescent properties of both the core Y(2)O(3):Eu(3+) and the shell YVO(4):Eu(3+). The emissions were dominated by [Formula: see text] or [Formula: see text] transitions of Eu(3+) when excited with different wavelengths. Since this broad-band response to excitation in the range of 225-340?nm gave more red/dark red emissions found at 612, 616 and 620?nm, the novel phosphor Y(2)O(3):Eu(3+)@SiO(2)@YVO(4):Eu(3+) could have potential biological labeling applications with wide flexibility.     

Luminescence properties of nano-crystalline Ba3MgSi2O8:Eu2+, Mn2+ phosphors

Ba3MgSi2O8:Eu2+, Mn2+ phosphors were synthesized by the sol-gel method and high temperature solid-state reaction method, respectively. XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), PL (photoluminescence spectra), and PLE (photoluminescence excitation spectra) were measured to characterize the samples. Emission and excitation spectra of our Ba3MgSi2O8:Eu2+, Mn2+ phosphors monitored at 441, 515, and 614 nm are depicted in the paper. The emission intensities of 441 and 515 nm emission bands increase with increasing Eu2+ concentration, while the peak intensity of the 614 nm band increases with increasing Mn2+ concentration. We conclude that the 515 nm emission band is attributed to the 4f(6)5d transition of Eu2+ ions substituted by Ba2+ sites in Ba2SiO4. The 441 nm emission band originates from Eu2+ ions, while the 614 nm emission band originates from Mn2+ ions of Ba3MgSi2O8:Eu2+, Mn2+. Nano-crystalline Ba3MgSi2O8:Eu2+, Mn2+ phosphors prepared by the sol-gel method show higher color rendering and better color temperature in comparison with the samples prepared by high temperature solid-state reaction method.     

Preparation and luminescence properties of LaMgAl11O19:Eu3+ phosphor powder

LaMgAl11O19, is a kind of rare earth aluminate with the hexagonal structure, which has been used as a host material for the luminescence of various rare earth and magnet-like ions. LaMgAl11O19:Eu3+ phosphors have been prepared through the one-pot method. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicated that the phosphors crystallized completely at 1,400 degrees C. In LaMgAl11O19:Eu3+ phosphors, the Eu3+ shows its characteristic red emission at 615 nm (5D0-7F2) upon excitation into 404 nm, with an optimum doping concentration of 15 mol% of La3+ in the host lattices.     

Defect complexes in Re3+-doped magnesium sulphate phosphors

A series of magnesium sulphate phosphors MgSO4:RE3+,X ( RE = Dy, Tm, Eu and X = P, Mn) have been prepared and studied. Based on the experimental results of thermoluminescence (TL) emission spectra and dose responses studies, it is proposed that in these phosphors large defect complexes are formed, which include intrinsic imperfections and dopants. These defect complexes were formed in the course of preparation of phosphors and could be regarded as basic elements in the TL multi-stage processes. This defect model might be applicable to the most of TL materials.     

Fabrication of photoluminescent S doped Y2O3:Eu3+ nanobelts

We have successfully fabricated the S doped Y(OH)3 nanobelts with 15-30 microm in length and 50-300 nm in width and S doped Y(OH)3:Eu3+ nanobelts with 4-15 microm in length and 80-500 nm in width (most between 100 and 200 nm) via a similar process for preparation of Y(OH)3 nanotubes. Photoluminescent (PL) nanobelts of S doped Y2O3:Eu3+ were obtained through dehydration of the S doped Y(OH)3:Eu3+ nanobelts at 450 degrees C in N2. The PL properties of the S doped Y2O3:Eu3+ nanobelts have been studied and evidenced that we have successfully synthesized functional S doped Y2O3:Eu3+ nanobelts with interesting photoluminescence properties.     

Study on luminescent properties of Eu3+ doped new type yttrium tungsten oxide nanophosphors

In this paper, a novel nanophosphor, Y10W2O21:Eu, was synthesized through co-precipitation which is a simple and low-costing method. The structure and morphology of the nanocrystal samples were characterized by using XRD and FE-SEM. The emission spectra, excitation spectra and fluorescence decay curves were measured. J-O parameters, quantum efficiencies of Eu3+ 5D0 energy level, color coordinates and Huang-Rhys factor of Y10W2O21:Eu nanophosphors were calculated. The results indicate that EU3+ 5D0-7F2 red luminescence at 610 nm can be effectively excited by 394 nm near-UV light and 464 nm blue light in Y10W2O21 host, which is similar to the familiar Eu3+ doped tungstate phosphors (e.g., Gd2(WO4)3:Eu, CaWO4:Eu). Besides, compared with the other types of tungstate phosphors, a less expensive tungsten was used, which can effectively reduce cost. Therefore, the Y10W2O21:Eu red nanophosphors may have a potential application for white LED.     

Fabrication of nano-sized emitting phosphors for photoluminescence films via hydro-thermal synthesis

Nano-sized red and blue emitting phosphors for a photoluminescence film were fabricated via hydrothermal synthesis through the sol-gel process. The nano-sized phosphors had a spherical shape such as the 60-110 nm Y2O2S:Eu3+ phosphor and the 45-90 nm of Y2SiO5:Ce phosphor. Firing at 1000 degrees C for 2 hours resulted in an increase in their size to 90-190 nm for the Y2O2S:Eu3+ phosphor and 70-160 nm for the Y2SiO5:Ce phosphor. Heat treatment of the gel powders of the emitting phosphors above 730 degrees C was recommended because of their crystallization. The maximum excitation and emission intensities of the red and blue phosphors with Y2O2S:Eu3+ and Y2SiO5:Ce were at the wavelengths of 308 nm and 617 nm, and 254 nm and 464 nm, respectively. The photoluminescence of the films increased as increasing the content of the red and blue phosphor powder mixture in the plastic films. The 100 microm-thick PVB film with the nano-sized phosphors showed the maximum photoluminescence of 537 x 1000 counts/sec.     

Synthesis and luminescence properties of Sr2SiO4: Eu3+, Dy3+ phosphors by the sol-gel method

The Sr2SiO4:Eu3+, Dy3+ phosphors for white light emitting diodes (LEDs) were synthesized by the sol-gel method. The microstructure and luminescent properties of the obtained Sr2SiO4:Eu3+, Dy3+ particles were well characterized. The results demonstrate that the Sr2SiO4:Eu3+, Dy3+ particles, which have spherical morphology, emitted an intensive white light emission under excitation at 386 nm. The phosphors show three emission peaks: the blue emission at 486 nm corresponding to the 4F(9/2)-6H(15/2) transition of Dy3+, the yellow emission at 575 nm corresponding to the 4F(9/2)-6H(13/2) transition of Dy3+, and the red emission at 615 nm corresponding to the 5D0-7F2 transition of Eu3+. At the same time, the effect of Eu3+ concentration on the emission intensities of Sr2SiO4:Eu3+, Dy3+ was investigated in detail. The phosphors used for white LEDs were obtained by combining near ultraviolet (NUV) light (386 nm) with Sr2SiO4:0.04Dy3+, 0.01Eu3+ phosphors with the characteristic of Commission Internationale de l'Eclairage (CIE) chromaticity coordinate (x, y) of (0.33, 0.34), and color temperature Tc of 5,603 K. In addition, the effect of the charge compensators (Li+, Na+, and K+ ions) on the photoluminescence (PL) emission intensities were studied.     

Study on UV excitation properties of Y2O3:Ln3+ (Ln = Eu3+ or Tb3+) luminescent nanomaterials

Y2O3:Ln3+ (Ln = Eu or Tb) nanocrystals with different Ln3+ doping concentrations and average sizes were prepared by chemical self-combustion. The corresponding bulk materials with various doping concentrations were obtained by annealing the nanomaterials at high temperature. The emission spectra, excitation spectra, and X-ray diffraction spectra were used in this study. It was found that the charge transfer band of Y2O3:Eu3+ red-shifted as particle size decreased, and the charge transfer band in the 5-nm particles obviously broadened toward the long wavelength. It was also found that the profile of excitation spectra corresponding to the 4f5d (4f8 --> 4f(7)5d1) transition changed a lot with the variation of the particle size. The dependence of the excitation spectra of Y2O3:Ln3+ on particle size was investigated.     

Luminescent properties and characterization of one dimensional Gd(2)O(3):Eu(3+) phosphor nano-wire for field emission application

Gd(2)O(3):Eu(3+) nano-wire phosphors embedded in SBA-15 silica templates were synthesized using a combination of the sol-gel method and hydrothermal reactions followed by a sintering process at 1000?°C. The crystal structure of Gd(2)O(3):Eu(3+) was confirmed using x-ray diffraction. Observation using transmission electron microscopy shows that the nano-wire diameters were very uniform in the 7-9?nm range. In comparison with bulk Gd(2)O(3):Eu(3+) materials, we found that the photo-luminescent property of the nano-wire was different. The analysis shows that the main nano-wire emission peaks were at 585, 597, 613 and 620?nm. The CIE value (x = 0.62, y = 0.38) indicates that the nano-wire emitted a pink colour and not red as for the bulk material. The field emission experimental results agreed well with the photo-luminescent analysis results.     

Effect of structure, particle size and relative concentration of Eu(3+) and Tb(3+) ions on the luminescence properties of Eu(3+) co-doped Y(2)O(3):Tb nanoparticles

Eu(3+) co-doped Y(2)O(3):Tb nanoparticles were prepared by the combustion method and characterized for their structural and luminescence properties as a function of annealing temperatures and relative concentration of Eu(3+) and Tb(3+) ions. For Y(2)O(3):Eu,Tb nanoparticles annealed at 600 and 1200?°C, variation in the relative intensity of excitation transitions between the (7)F(6) ground state and low spin and high spin 4f(7)5d(1) excited states of Tb(3+) is explained due to the combined effect of distortion around Y(3+)/Tb(3+) in YO(6)/TbO(6) polyhedra and the size of the nanoparticles. Increase in relative intensity of the 285?nm peak (spin-allowed transition denoted as peak B) with respect to the 310?nm peak (spin-forbidden transition denoted as peak A) with decrease of Tb(3+) concentration in the Y(2)O(3):Eu,Tb nanoparticles heated at 1200?°C is explained based on two competing effects, namely energy transfer from Tb(3+) to Eu(3+) ions and quenching among the Tb(3+) ions. Back energy transfer from Tb(3+) to Eu(3+) in these nanoparticles is found to be very poor.     

Eu3+对Na3Gd2(BO3)3∶Tb3+发光性能的影响及其能量传递

采用高温固相法制备了Na_3Gd_2(BO_3)_3∶Tb~(3+),Eu~(3+)荧光粉,并对样品的物相组成、微观形貌、发光性能和能量传递进行了分析。结果表明,Na_3Gd_(2-x)(BO_3)_3∶xTb~(3+)荧光粉在紫外和近紫外区域有较强的激发峰,在368nm波长激发下,发射光呈绿色,Tb~(3+)最佳掺杂量为x=0.04。随着在Na_3Gd_(1.96)(BO_3)_3∶0.04Tb~(3+)中掺入Eu~(3+),Tb~(3+)对Eu~(3+)产生了以电偶极-电偶极相互作用为主的能量传递,且传递效率随Eu~(3+)掺杂量的增加而逐渐增大。发射光谱中Tb~(3+)的发射峰强度逐渐减弱,而Eu~(3+)的发射峰强度逐渐增强,导致Na_3Gd_(1.96-y)(BO_3)_3∶0.04Tb~(3+),yEu~(3+)荧光粉发光颜色由绿色向橙色变化。     

Hydrothermal synthesis and optical properties of Eu(3+)-doped CaSnO3 nanocrystals

In this paper, CaSnO3:Eu3+ nanocrystals were prepared by hydrothermal synthesis method. The influence of different molar ratio of Ca:Sn on structure of CaSnO3:Eu3+ was investigated by using X-ray powder diffraction (XRD). Well-crystallized and phase-pure CaSnO3:Eu3+ particles of approximately 90 nm in size can be readily obtained at 900 degrees C. Furthermore, photoluminescence characterization of the Eu(3+)-doped CaSnO3 nanocrystals was performed and discussed. The emission peak situated at 618 nm showing prominent and bright red light is due to the 5D0-7F2 electric dipole transition. The excellent luminescence properties make it possible as a good candidate for PDP application.     

Luminescence and energy transfer characteristics of Ce3+- and Tb3+-codoped nanoporous 12CaO 7Al2O3 phosphors

The novel green-emitting phosphors of 12CaO 7Al2O3:Ce3+ , Tb3+ (C12A7:Ce3+, Tb3+) were synthesized by a solid-state reaction. Upon the excitation of Ce3+ at 350 nm, the C12A7:Ce3+, Tb3+ phosphor shows intense green emissions located at 543 nm assigning to 5D4-7F5 transitions of Tb3+ ions, and weak blue emissions centered at 434 nm due to the transitions of Ce3+ 5d-4f. The photoluminescence (PL) intensity of Ce3+ decrease with increasing Tb3+ concentration, indicating the effective energy transfer (ET) occurred from Ce3+ to Tb3+ in C12A7:Ce3+, Tb3+. The ET efficiency between Ce3+ and Tb3+ in the optimum composition reaches to 99%. Based on Dexter's ET theory, we have demonstrated that the efficient ET is a resonant type via dipole-dipole mechanism with an energy transfer critical distance of 4.02 A. Our results suggested that C12A7:Ce3+, Tb3+ phosphor would be a promising green-emitting phosphor for UV-converting white light-emitting diodes.     

High-pressure synthesis, electrical and magnetic properties of new filled skutterudites LnOs4P12 (Ln = Eu, Gd, Tb, Dy, Ho, Y)

New filled skutteudites LnOs₄P₁₂ (Ln: Eu, Gd, Tb, Dy, Ho and Y) have been prepared at high temperatures and at high pressures. X-ray diffraction of these compounds is studied at room temperature. The relationship between lattice constants and atomic numbers of lanthanide (including Y) is obtained for LnOs₄P₁₂ (Ln: lanthanide). Electrical and magnetic properties of the new filled skutterudites with heavier lanthanide have been investigated at low temperatures. EuOs₄P₁₂ and GdOs₄P₁₂ show ferromagnetic transitions at around 15 and 22 K, respectively. The valence states of both compounds are +2 for the Eu compound and +3 for the Gd compound. DyOs₄P₁₂ does not show the magnetic transition down to 2 K. However, a small electrical anomaly is found at around 10 K. YOs₄P₁₂ exhibits a superconducting transition at around 3 K. This compound is a new superconductor. Electrical and magnetic anomalies of new filled skutterudites with heavier lanthanide LnOs₄P₁₂ (Ln: Eu, Gd, Dy and Y) are discussed. We have also found the electrical anomaly based on the magnetic transition at around 22 K for GdFe₄P₁₂.