燃烧法合成铕镝掺杂铝酸锶长余辉发光材料的研究

以尿素和硝酸盐溶液为反应介质 ,在 6 0 0℃下用燃烧法一次制备出了Eu2 ,Dy3 掺杂的铝酸锶 (SrAl2 O4 )磷光体。用SEM、XRD研究了所得磷光材料的形态、粒度和物相组成 ,用荧光分光光度计测定了磷光材料的发光性能。结果表明 ,SrAl2 O4 ∶Eu2 ,Dy3 磷光材料的晶体结构属于单斜晶系结构。制备产物在 5 2 0nm处有很强的发射峰 ,它的激发光谱是激发峰峰值 2 90nm的宽带激发。制备产物的形貌呈疏松多孔状 ,晶粒形状为针状 ,长度有 2 0 0nm左右 ,直径在 80nm以下。并探讨了该材料发光性能的影响因素     

Persistent luminescence of Eu2+ and Dy3+ doped barium aluminate (BaAl2O4:Eu2+,Dy3+) materials

Polycrystalline Eu²⁺ and Dy³⁺ doped barium aluminate materials, BaAl₂O₄:Eu²⁺,Dy³⁺, were prepared with solid state reactions at temperatures between 700 and 1500 °C. The influence of the thermal treatments on the stability, homogeneity and structure as well as to the UV-excited and persistent luminescence of the materials was investigated by X-ray powder diffraction, SEM imaging and infrared spectroscopies as well as by steady state luminescence spectroscopy and persistent luminescence decay curves, respectively. The IR spectra of the materials prepared at 250, 700, and 1500 °C follow the formation of BaAl₂O₄ composition whereas the X-ray powder diffraction of compounds revealed how the hexagonal structure was obtained. The morphology of the materials at high temperatures indicated important aggregation due to sintering. The luminescence decay of the quite narrow Eu²⁺ band at ca. 500 nm shows the presence of persistent luminescence after UV irradiation. The dopant (Eu²⁺) and co-dopant (Dy³⁺) concentrations affect the crystallinity and luminescence properties of the materials.     

Powder synthesis and white light-emitting properties of Eu3+ co-doped K2CaP2O7:Dy3+ phosphors with energy transfer between Dy3+ and Eu3+

A series of white-emitting K₂CaP₂O₇:Dy³⁺ and K₂CaP₂O₇:Dy³⁺, Eu³⁺ phosphors were synthesized via a solid-state method, and Eu³⁺ was co-doped in K₂CaP₂O₇:Dy³⁺ to improve its white light performance. The influences of preparation temperature and Dy³⁺/Eu³⁺ concentration on the crystal structure and photoluminescence characteristics were investigated. XRD results indicate that K₂CaP₂O₇:Dy³⁺ samples prepared above 700 °C matches the standard K₂CaP₂O₇ phase. Under excitation of 349 nm, K₂CaP₂O₇:Dy³⁺ phosphor exhibited characteristic emission peaks at 487 nm (blue) and 579 nm (yellow), and white emission was realized through combining these blue and yellow emissions. After co-doping Eu³⁺ ions, the co-luminescence of Dy³⁺/Eu³⁺ with energy transfer between Dy³⁺and Eu³⁺ were demonstrated. The chromaticity of white light was controlled by changing the ratio of Dy³⁺/Eu³⁺ concentrations, which lead to a warm white light. Therefore, the results indicate that K₂CaP₂O₇:Dy³⁺, Eu³⁺ powders have a potential application in w-LEDs as single-component white-emitting phosphor.     

Photoluminescence,trap states and thermoluminescence decay process study of Ca2MgSi2O7: Eu2+, Dy3+ phosphor

Europium and dysprosium-doped calcium magnesium silicate powder with different concentrations of dysprosium were synthesized using solid-state reaction. The Fourier transform infrared (FT-IR) spectra confirmed the proper preparation of the sample. The prepared phosphors were characterized using photoluminescence excitation and emission spectra. Prominent green colour emission was obtained under ultraviolet excitation. The thermoluminescence glow curves of the samples were measured at various delay times. With increased delay time, the intensity of the thermoluminescence peak decays and the position of the thermoluminescence peak shifts towards higher temperature, indicating the considerable retrapping associated with general order kinetics.     

Hydrothermal synthesis of Eu3+-doped Y2Sn2O7 nanocrystals

Fine powders of Y₂Sn₂O₇ nanocrystals with pyrochlore structure have been successfully synthesized by the hydrothermal method in an alkaline system. The samples were characterized by X-ray diffraction, Fourier transform infrared and Raman spectroscopy. Furthermore, photoluminescence characterization of the Y₂Sn₂O₇ nanocrystals doped with 5 mol% Eu³⁺ was carried out, and the results show that there were some intense and prevailing emission peaks located at 580–635 nm.     

White light emission of Dy3+-doped and Dy3+:Yb3+-codoped oxyfluoride glass ceramics under 388-nm excitation

Dy³⁺-doped and Dy³⁺:Yb³⁺-codoped oxyfluoride glass ceramics have been prepared by high-temperature solid phase sintering method. The micrographs of scanning electron microscope show that a lot of nanorods are formed on the surface of Dy³⁺:Yb³⁺-codoped sample. The excitation spectra and emission spectra are measured, respectively, and intense photoluminescence peaks at 482 and 575 nm corresponding to the transitions of Dy³⁺ ions are found in single-doped samples under 388-nm excitation. For Dy³⁺:Yb³⁺-codoped oxyfluoride glass ceramics, the intensities at blue and green bands become weaker whereas the intensity at 695 nm gets stronger. The indirect sensitization is detailedly discussed and Commission Internationale de l′E-clairage chromaticity coordinates exhibit that two kinds of oxyfluoride glass ceramics are available candidates for the solid-state white light emission.     

Fabrication and luminescent enhancement of Eu3+-doped Y2O3@YOF core-shell nanocrystals

In this paper, a two-step synthesis method for preparing Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals is introduced. Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals were prepared by combining an autocombustion process with a low temperature solid state reaction. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and fluorescence decay were employed to characterize the prepared samples. The results of XRD, TEM and EDS indicated that the products prepared by this method were not a mixture of Y2O3:Eu3+ and YOF:Eu3+ nanocrystals, but Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals. Compared with Y2O3:Eu3+ nanocrystals, a 20% increment in luminescence intensity was observed in the Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals, thus suggesting that coating with a YOF:Eu3+-shell can efficiently block the nonradiative relaxation channels that are induced by surface defect states.     

Fluorescence properties of Eu3+-doped alumino silicate glasses

Alumino silicate glasses of a very broad range of molar compositions doped with 1 ⋅ 10²⁰ Eu³⁺ cm⁻³ (about 0.2 mol% Eu₂O₃) were prepared. As network modifier oxides Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO, ZnO, PbO, Y₂O₃ and La₂O₃ have been used. All glasses show relatively broad fluorescence excitation and emission spectra. For most glasses only a weak effect of the glass composition on the excitation and emission spectra is observed. Although the glasses should be structurally similar, notable differences are found for the fluorescence lifetimes. These increase steadily with decreasing mean atomic weight, decreasing refractive index and decreasing optical basicity of the glasses, which may be explained by local field effects. An exception from this rule are the strontium, barium and potassium containing glasses, which show significantly increased fluorescence lifetimes despite of their high refractive index, optical basicity and molecular weight. The non mono-exponential fluorescence decay curves as well as the fluorescence spectra indicate a massive change in the local surroundings of the doped rare earth ions for these glasses.     

Luminescence properties of Eu3+ or Dy3+/Au co-doped SiO2 nanoparticles

Silica nanoparticles, prepared by the Stober method, have been doped with Eu³⁺, Dy³⁺, or processed to result in Au nanoparticles on the silica surface. The luminescence of the rare earth (RE)-doped SiO₂ particles has been studied as a function of the nature of the RE, their concentration and also of the presence of Au nanoparticles at the surface of the SiO₂ nanoparticles. We have shown that the Eu³⁺ emission is observable over the experimental conditions examined, whereas it was not possible to observe any emission for Dy³⁺ doped materials. No enhancement of the Eu³⁺ emission was observed following the adsorption of gold nanoparticles at the surface of the SiO₂ nanoparticle, however an excitation at 250 nm leads to both the emission of the matrix and Eu³⁺ showing an energy transfer from the SiO₂ matrix to Eu³⁺ ions.     

Luminescent properties of Ca2MgSi2O7 phosphor activated by Eu2+, Dy3+ and Nd3+

Long lasting alkaline earth silicates, Ca₂MgSi₂O₇:Eu,Dy,Nd was prepared under a reduction atmosphere through solid state reaction. The obtained phosphor was characterized by means of X-ray diffraction (XRD) and photoluminescence spectrum (PLS). The crystal structure of Ca₂MgSi₂O₇:Eu,Dy,Nd phosphor was refined by Rietveld analysis. The obtained Ca₂MgSi₂O₇:Eu,Dy,Nd phosphor showed a yellow–green emission peaking at 518 nm, which is ascribed to the luminescent emission of the Eu²⁺ that occupied the octa-coordinated Ca²⁺ sites in the Ca₂MgSi₂O₇ host. The electron affinity (ea) value for Eu²⁺ in [EuO₈] was calculated to 1.9 eV. The decay profile and the emission spectrum indicated that when the value of Dy/Eu is increasing, there is a concentration quenching of Eu²⁺.     

Monitoring of hydroxyapatite conversion by luminescence intensity of Eu3+ ions during mineralization of Eu3+-doped β-Ca2SiO4

β-Dicalcium silicate (β-Ca₂SiO₄) doped with Eu³⁺ was synthesized by sol–gel method. The luminescence intensity of the mineralization products formed during the hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA) conversion of Eu³⁺-doped β-Ca₂SiO₄, in 0.25 M K₂HPO₄ solution, were detected using luminescence spectroscopy. The results indicated that the luminescence intensity of Eu³⁺ ion gradually depressed with prolonged mineralization time, and it could hardly be detected with the complete transformation from β-Ca₂SiO₄:Eu³⁺ to hydroxyapatite. The change of Eu³⁺ ionic concentrations in the mineralization products and the final solutions after conversion reaction, were further examined using energy-dispersive X-ray and inductively-coupled plasma mass spectrometry, respectively. This suggested that the process of mineralization can be monitored with the luminescence intensity of Eu³⁺ ions in the mineralization products. The current study will open up a new and simple in vivo avenue for in situ monitoring hydroxyapatite conversion with a fiber luminescence spectrometer.     

Eu3+、Dy3+和Er3+对制备堇青石晶相转变的对比表征

以菱镁矿风化石、工业Al2O3和SiO2微粉为原料,固相反应烧结合成制备堇青石.通过在反应物中分别加入不同含量的Eu2O3、Dy2O3和Er2O3,研究分析和对比了Eu3+、Dy3+和Er3+对堇青石晶相组成、晶粒大小、晶胞常数、结晶度及显微结构的影响.采用XRD和SEM表征试样中的晶相和显微结构,利用X'Pert Plus 软件对结晶相的晶胞参数和结晶度进行分析,采用半定量法对试样晶相组成进行计算,利用Scherrer公式计算堇青石的晶粒大小.结果表明:由于Eu2O3、Dy2O3和Er2O3的加入,通过固相反应烧结所得堇青石试样中出现了莫来石相,Eu3+、Dy3+和Er3+对Mg2+的置换作用改变了堇青石相晶格常数和晶胞体积.随着添加剂含量的增加,堇青石结构中液相量增加,相对结晶度降低,常温致密度提高,堇青石晶粒粒径减小.综合对比分析,Eu2O3对堇青石晶相转变的影响程度最弱,Er2O3对堇青石晶相转变的影响程度最强,对提高合成堇青石的烧结性和热震稳定性效果最好.     

Photophysical properties of Eu3+ and Tb3+-doped ZnAl2O4 phosphors obtained by combustion reaction

Europium- and terbium-doped zinc aluminate oxide nanocrystals with a spinel structure were successfully prepared by a combustion method, using urea as fuel. The samples thus obtained were characterized by X-ray diffraction, scanning electron microscopy and luminescence spectroscopy. X-ray diffraction results confirmed the formation of ZnAl₂O₄ spinel phase and a minor amount of ZnO. Our SEM results revealed agglomerates in the shape of irregular plates composed of nanoparticles with dispersed points of second phase in the surface. Powders containing Eu³⁺ and Tb³⁺ ions displayed red and green photoluminescence, respectively.     

Structural and spectroscopic characteristics of Eu3+-doped tungsten phosphate glasses

Tungsten based phosphate glasses are interesting non-crystalline materials, commonly known for photochromic and electrochromic effects, but also promising hosts for luminescent trivalent rare earth ions. Despite very few reports in the literature, association of the host́s functionalities with the efficient emissions of the dopant ions in the visible and near-infrared spectra could lead to novel applications. This work reports the preparation and characterization of glasses with the new composition 4(Sb₂O₃)96−x(50WO₃ 50NaPO₃)xEu₂O₃ where x = 0, 0.1, 0.25, 0.5 and 1.0 mol%, obtained by the melt quenching technique. The glasses present large density (∼4.6 g cm⁻³), high glass transition temperature (∼480 °C) and high thermal stability against crystallization. Upon excitation at 464 nm, the characteristic emissions of Eu³⁺ ions in the red spectral region are observed with high intensity. The Judd–Ofelt intensity parameters Ω₂ = 6.86 × 10⁻²⁰, Ω₄ = 3.22 × 10⁻²⁰ and Ω₆ = 8.2 × 10⁻²⁰ cm² were calculated from the emission spectra and found to be higher than those reported for other phosphate glass compositions. An average excited state lifetime value of 1.2 ms, was determined by fitting the luminescence decay curves with single exponential functions and it is comparable or higher than those of other oxide glasses.     

Preparation and luminescent properties of Eu3+-doped zinc sulfide nanocrystals

The preparation and luminescent properties of Eu³⁺-doped zinc sulfide nanocrystal were investigated. The best reactive conditions were determined, such as the concentration of reactants, the kinds and amount of the surfactants, the reaction temperature and reaction time, the pH, the flowing speed and pressure of reactive gases. The crystal structure of the nanocrystal powders was tested by X-ray diffraction (XRD). The emission and excitation spectra of ZnS:Eu were characterized by fluorescent divide spectroscopy (FDS). The luminescent sites and their strength as a function of doping Eu³⁺ ions are discussed.     

Synthesis and afterglow properties of MgAl2O4:Eu2+, Dy3+ nanopowders

The MgAl2O4:Eu2+, Dy3+ nanophosphors with different particle sizes have been synthesized through a simple and inexpensive precipitate approach followed by a post-annealing process. The structure and morphology of the phosphor are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). According to XRD and TEM results, the particle size of MgAl2O4:Eu2+, Dy3+ could be controlled via changing the ratio of MgSO4/Al2O3, and the obtained samples possess regular morphology. The afterglow properties of MgAl2O4:Eu2+, Dy3+ nanophosphors as a function of particle sizes are investigated by afterglow decay curves. Compared with the bulk phosphor, the nanophosphors exhibit longer afterglow time and higher initial afterglow intensity. In nanophosphors, there exist numerous defects on their surfaces due to the large surface to volume ratio, which generally act as luminescent killers, while some of which, however, can probably act as traps beneficial for the generation of afterglow. In the nanosized MgAl2O4:Eu2+, Dy3+ phosphor, the thermoluminescence results indeed indicate the existence of more traps which are introduced due to the large surface to volume ratio of nanoparticles and that the high temperature sintering process contributes to the longer afterglow in the nanophosphors.     

SrAl2O4:Eu2+,Dy3+光致发光搪瓷涂层的制备

稀土Eu^2 激活的铝酸盐发光材料是近年来新发展起来的新型长余辉光致发光材料，由于其发光亮度和发光余辉比传统的硫化物高许多，且无毒，无放射性，因而引起广泛关注，采用高温固相反应法制备了SrAl2O4:Eu^2 ,Dy^3 发光材料，并利用SrAl2O4:Eu^2 ,Dy^3 发光材料，参考普通搪瓷的制备工艺，制得了性能稳定的光致发光搪瓷涂层，余辉时间长达12h以上，这种发光搪瓷涂层可用于制造广告牌，交通标牌和建筑物标识牌等，在许多领域有应用前景。