Concentration quenching of Eu2+ in SrO · 6Al2O3 : Eu2+ phosphor

In SrO · 6Al₂O₃ : Eu²⁺ phosphor, blue Eu²⁺ luminescence is observed from Eu²⁺ on the strontium site present in the lattice. The concentration quenching process between Eu²⁺ ions is determined and the corresponding concentration quenching mechanism is verified as dipole-dipole interaction. The value of the critical transfer distance is calculated as 25 Å and its reliability is confirmed by using Dexter's theory on energy transfer.     

Luminescent properties of Li2CaSiO4:Eu2+ phosphor

Li₂CaSiO₄:Eu²⁺ phosphors with single phase were successfully synthesized by the solid state reaction method and their photoluminescence properties were studied. The experimental results on Li₂CaSiO₄:Eu²⁺, summarized in effective absorption and excitation in the ultra-violet region, strong emission in the blue spectrum and the CIE Chromaticity coordinate (0.10, 0.20), indicate this phosphor has great potential in ultra-violet chip pumped white LEDs. A comparative investigation of the emission intensity suggests that Li₂CaSiO₄:Eu²⁺ has the best performance with Eu²⁺ concentration of 1% and excitation of 375 nm. Compound phosphors of Li₂CaSiO₄:Eu²⁺ and Li₂SrSiO₄:Eu²⁺ show two emission bands in the blue and yellow region. With the molar ratio of Li₂CaSiO₄:Eu²⁺ to Li₂SrSiO₄:Eu²⁺ being 1:1 and excitation of 390 nm, the CIE Chromaticity coordinate was tuned to be (0.32, 0.36), which is close to that of natural white light, indicating this may become blue phosphor candidate for ultra-violet chip pumped and multi-phosphors converted white LEDs.     

Optical properties of SrAl2O4: Eu2+ phosphor in glass

Phosphor-in-glass (PiG) typed robust color converters were fabricated using pb-free silicate glasses for luminescence materials applications. The PiG based on a SiO₂–B₂O₃–BaCO₃ ternary system and SrAl₂O₄: Eu²⁺ phosphor showed good transparency reached 99.50%, even if the GTP ratio is 25:1. By simply changing the mixing ratio of glass to SrAl₂O₄: Eu²⁺ phosphor, the emission color of PiG can be controlled from blue to bluish green. The results reveal that the luminescence properties of SrAl₂O₄: Eu²⁺ distinct from the phosphor in glass significantly. These suggest that PiG could provide potential application in a variety of luminescence materials.     

Composite phosphor films based on spherical Lu2O3:Eu3+ nanoparticles

A nanopowder of Lu₂O₃:Eu³⁺ (C _Eu = 5 at.%) was obtained by coprecipitation with urea (NH₂)₂CO from aqueous solutions. Using this nanopowder, compact Lu₂O₃:Eu³⁺ films with thicknesses within 20–200 μm and a relative density up to 65% of the theoretical limit were deposited using the spin-coating and painting techniques. The films were characterized by scanning electron microscopy, X-ray diffraction, and X-ray luminescence (XRL) measurements. It is established that the XRL intensity depends on the phosphor/organic binder ratio and thickness of the film. The most intense XRL and most homogeneous structure are observed for 20-μm-thick Lu₂O₃:Eu³⁺ films.     

Luminescence enhancement of Tb3+ in Sr3SiO5:Eu2+ phosphor

Sr₃SiO₅ phosphors co-doped with Eu²⁺ and Tb³⁺ were prepared by a conventional solid-state reaction method. The prepared Sr₃SiO₅:Eu²⁺,Tb³⁺,Li⁺ phosphors had characteristic luminescent spectra excited under near-UV excitation in which both the broadband spectrum assigned to Eu²⁺ and the line spectrum assigned to Tb³⁺ are observed, although Tb³⁺ is inactive with this photon energy in general. For Eu²⁺–Tb³⁺ codoped Sr₃SiO₅, energy transfer process takes place and the mechanism is ascribed to the overlap between the shorter Eu²⁺ luminescence band from the Sr₃SiO₅ crystal structure with two Sr sites and ₅D⁴ energy level of Tb³⁺ ion. Due to the energy transfer, PL intensity of Eu²⁺ emission increased about 26 %. We suggest that this enhancement mechanism could shed light on the potential applications in white light-emitting diodes excited by near-UV light. In addition, the emission peak position near the orange region indicates that our system is a step towards a new class of wavelength sources for artificial lighting with improved PL intensity and lower energy consumption.     

白光LED用BaMgAl_(10)O_(17):Eu~(2+)Mn~(2+)蓝绿荧光粉

采用高温固相法制备出一种Eu2+,Mn2+共掺的蓝绿色荧光粉BaMgAl10O17:Eu2+,Mn2+(BAM:Eu2+,Mn2+),对其进行了X射线衍射分析和光谱特性的测试.研究表明,它的发射光谱为双峰结构,峰值分别位于455 nm和525 nm处.455 nm发射峰归结为BAM中部分取代Ba2+离子的Eu2+离子的5d→4f的跃迁辐射;525 nm的发射峰源于部分Eu2+能量传递给Mn2+离子,Mn2+的4T1→6A1的跃迁辐射.采用近紫外LED芯片与该荧光粉以及一种红色荧光粉Ca(La0.5Eu0.5)4Si3O13封装,在20 mA前向电流驱动下,获得了显色指数为88的白光LED.     

BaMgAl10O17:Eu2+荧光粉表面包覆研究及展望

为改进稀土三基色荧光粉中蓝粉BaMgAl10O17:Eu2+(BAM)的光衰问题,目前,国内外解决这个问题的途径主要有:掺杂、调整化学组分、采用新合成工艺、表面包覆、寻找新蓝色荧光粉材料等,其中引起广泛注意的是在BAM表面包膜.在BAM荧光粉表面包膜可以解决由于电性和表面化学活性造成的荧光粉性能的下降,并可以提高其发光...     

Mechanism of energy transfer in Sr2CeO4:Eu3+ phosphor

Blue–white phosphor Sr₂CeO₄ belongs to a particular class of optical materials whose luminescence is governed by optical transitions associated with the electron charge transfer. The originality of its crystallographic structure, a chain-like sequence of luminescent centers, permits an effective transfer of the electronic excitation energy from the host to doped centers. Sr₂CeO₄, рure and doped with Eu³⁺-ions of different concentrations, was synthesized by the Pechini citrate-gel method. The luminescence spectra and luminescence decay curves of Sr₂CeO₄ and Sr₂CeO₄:Eu³⁺ at 300 and 80 K were investigated. The performed experiments revealed the Förster nonradiative energy transfer under the energy migration condition from the crystal host to the doped europium ions.     

Combustion synthesis of Eu2+-activated BaMgAl10O17 phosphor

The combustion synthesis of a Eu²⁺-doped BaMgAl₁₀O₁₇ phosphor was performed using urea and carbohydrazide (CH) as combustion fuel. The concentration of activator ion was fixed at 10 mol %, namely Ba_0.9Eu_0.1MgAl₁₀O₁₇. Powders with an excellent degree of crystallinity were obtained within a few minutes at 500 °C when urea was used as the fuel and at 400 °C for the case of CH. This as-synthesized phosphor obtained from using CH exhibited a larger surface area, a rougher surface and a higher PL brightness than that using urea. Particle characteristics and luminescent properties varied with the type of fuel and the amount of added NH₄NO₃ addition. However, the combustion reaction led to severe agglomeration of the particles, causing an irregular shape and a broad distribution of particle size regardless of the fuel used. Post-treatment such as ball milling and annealing was found to be beneficial to improving the crystallinity and morphology of the synthesized powder, but at the loss of PL brightness.     

Fabrication of SiO2@ZrO2@Y2O3:Eu3+ core-multi-shell structured phosphor

ZrO2 interface was designed to block the reaction between SiO2 and Y2O3 in SiO2@Y2O3:Eu coreshell structure phosphor. SiO2@ZrO2@Y2O3:Eu core-multi-shell phosphors were successfully synthesized by combing an LBL method with a Sol-gel process. Based on electron microscopy, X-ray diffraction, and spectroscopy experiments, compelling evidence for the formation of the Y2O3:Eu outer shell on ZrO2 were presented. The presence of ZrO2 layer on SiO2 core can block the reaction of SiO2 core and Y2O3 shell effectively. By this kind of structure, the reaction temperature of the SiO2 core and Y2O3 shell in the SiO2@Y2O3:Eu core-shell structure phosphor can be increased about 200-300 degrees C and the luminescent intensity of this structure phosphor can be improved obviously. Under the excitation of ultraviolet (254 nm), the Eu3+ ion mainly shows its characteristic red (611 nm, 5D0-7F2) emissions in the core-multi-shell particles from Y2O3:Eu3+ shells. The emission intensity of Eu3+ ions can be tuned by the annealing temperatures, the number of coating times, and the thickness of ZrO2 interface, respectively.     

Influence of Zn2+ and Si4+ codoping on luminescence properties of CaWO4:Eu3+ phosphor

The red afterglow phosphors of CaWO₄ doped with Eu³⁺, Zn²⁺ or (and) Si⁴⁺ were prepared by solid state reaction. All crystalline phases were identified by the X-ray powder diffraction (XRD). The photoluminescence spectra and decay curves as well as thermoluminecence (TL) curves of all samples were also investigated. In comparison to CaWO₄:Eu³⁺ phosphor, the luminescence and afterglow properties could be improved greatly after being doped with Zn²⁺ or (and) Si⁴⁺ ions.     

Ba2+离子对Sr2Al2SiO7:Eu2+荧光体微结构及发光性能的影响

采用复合胶体喷雾工艺制备了Ba2 离子掺杂的Sr2-xBaxAl2SiO7:Eu2 (x=0、0.1、0.2、0.4)荧光体.研究了Ba2 离子在基质Sr2Al2SiO7中的取代位置和机理,分析了Ba2 离子取代Sr2 离子对基质微结构及Sr2Al2SiO7:Eu2 荧光体发光性能的影响.XRD结果表明Ba2 离子取代Sr2 格位进入Sr2Al2SiO7晶格,导致晶胞体积增大.进入Sr2Al2SiO7晶格的Ba2 离子由于电负性较大,处在其周围的Eu2 离子外层电子受Ba2 离子影响,电子云膨胀,使发光波长发生红移.同时,掺入Ba2 离子后Sr2-xBaxAl2SiO7晶场强度增强,晶体场对Eu2 离子5d能级的劈裂程度增大,劈裂重心下降.Ba2 离子掺杂的Sr2-xBaxAl2SiO7:Eu2 (x=0、0.1、0.2、0.4)荧光体发射主峰位于520nm,与未掺杂Sr2Al2SiO7:Eu0.022 荧光体的发射峰相比出现红移.     

Photoluminescence properties of Eu2+-activated Ca2Y2Si2O9 phosphor

Eu²⁺-activated Ca₂Y₂Si₂O₉ phosphors with different Eu²⁺ concentrations have been prepared by a solid-state reaction method at high temperature and their photoluminescence (PL) properties were investigated. Photoluminescence results show that Eu²⁺-doped Ca₂Y₂Si₂O₉ can be efficiently excited by UV–visible light from 300 to 425 nm. Ca₂Y₂Si₂O₉: Eu²⁺ exhibits broad band emission in the wavelength range of 425–700 nm, due to the 4f⁶5d¹ → 4f⁷5d⁰ transition of the Eu²⁺ ions located at two different sites ((Ca/Y)1 and (Ca/Y)2) in Ca₂Y₂Si₂O₉. The effect of the Eu²⁺ concentration in Ca₂Y₂Si₂O₉ on the PL properties was investigated in detail. The results showed that the relative PL intensity reaches a maximum at 1 mol% of Eu²⁺, and a red-shift of the emission bands from these two different sites was observed with increasing Eu²⁺ concentration. Also there exists energy transfer between these two Eu²⁺ sites. The potential applications of Ca₂Y₂Si₂O₉: Eu²⁺ have been pointed out.     

红色蓄光材料Y2O2S:Eu3+的硫熔法制备及其发光性能

用硫熔法制备了系列红色蓄光材料Y2O2S ：Eux^3＋（0．01≤x≤0．10）的多晶粉末样品并系统研究了其发光特性。XRD结果表明,晶胞参数c随着Eu^3＋含量的逐渐增大而增大,而晶胞参数α没有明显的线性变化关系,这与Y2O2S ：Eu^3＋的晶体结构有关。Y2O2S ：Eux^3＋（0．01≤x≤0．10）的激发光谱相似,在626nm发射光监控下最大激发波长约在330nm附近。在330nm激发下,随着Eu^3＋含量逐渐增大,发射光谱最强发射峰位置从540nm右移至626nm,观察到红色特征发射峰626nm的强度逐渐增大,在Eu^3＋含量为0．09时,其强度达到最大。在最佳合成条件及最佳Eu^3＋含量下,正在进行掺杂Mg^2＋和Ti^4＋及其发光特性的研究。     

A promising red phosphor MgMoO4:Eu for white light emitting diodes

Motivated by the need for new red phosphors for solid-state lighting applications Eu³⁺-doped MgMoO₄ was prepared by solid-state reaction and its excitation and emission spectra were measured at room temperature. In addition, the effects of firing temperature and Eu³⁺ doping concentration on the PL intensities were also investigated. Compared with Y₂O₂S:0.05Eu³⁺, the obtained Mg_0.80MoO₄:Eu³⁺_0.20 phosphor shows a stronger excitation band near 400 nm and intensely red-emission lines at 616 nm correspond to the forced electric dipole ⁵D₀ → ⁷F₂ transitions on Eu³⁺ under 394 nm light excitation. The CIE chromaticity coordinates (x = 0.651, y = 0.348) of Mg_0.80MoO₄:Eu³⁺_0.20 close to the NTSC (National Television Standard Committee) standard values, and therefore may find application on near UV InGaN chip-based white light emitting diodes.     

The effects of Mn2+ doping on the luminescence properties of 12CaO 7Al2O:Eu2+ nanocrystal phosphor

The long lasting blue phosphorescence (LLP) and photostimulated luminescence (PSL) after ultraviolet light irradiation at room temperature in 12CaO 7Al2O3:xEu2+, yMn2+ (x = 0, 0.001; y = 0, 0.01) prepared by the chemical co-precipitation method were observed. It was shown that novel oxide 12CaO 7Al2O3:Eu2+, Mn2+ (C12A7:Eu2+, Mn2+) with unique nanocage structure can store energy when irradiated with 365 nm photons. And photon energy can be subsequently released by exposed to 980 nm light. The codopant Mn2+ enhances the intensity of the persistent phosphorescence and PSL due to the existence of more shallow and new deeper electron traps in C12A7: Eu2+, Mn2+. A model for energy storing and recovering and the detailed mechanism of PSL are presented through comparing with the luminescence properties of the co-doped C12A7:Eu2+, Mn2+ and C12A7:Eu2+.     

A novel green-emitting phosphor of Eu2+-doped Cs2MgSi5O12

A new phosphor of Eu²⁺-doped Cs₂MgSi₅O₁₂ was synthesized by conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurements. The photoluminescence excitation and emission spectra were measured. The phosphor presents bright yellowish-green-emitting luminescence. The site-occupancy of Eu²⁺ ions doped in Cs₂MgSi₅O₁₂ was discussed according to the crystal structure and the luminescence characteristics of Eu²⁺ ions. Two different Eu²⁺ centers were assigned in Cs₂MgSi₅O₁₂ lattices. The dependence of luminescence intensity on the heating temperatures was measured and discussed. The chromaticity coordinates and activation energy (ΔE) for the thermal quenching of Cs₂MgSi₅O₁₂:Eu²⁺ were reported.