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⁺.     

Enhancement on the afterglow properties of Sr2MgSi2O7: Eu2+ by Er3+ codoping

The Sr_1.99MgSi₂O₇: Eu²⁺_0.01, and Sr_1.97MgSi₂O₇: Eu²⁺_0.01, R³⁺_0.02 (R: Dy, Er) are synthesized via high temperature solid-state reaction. The sample without codoping shows the highest luminescent efficiency, leading to the strongest emission intensity. Both Dy³⁺ and Er³⁺ enhance the afterglow properties. Compared with Dy³⁺, sample doped with Er³⁺ shows a longer afterglow duration because of a deeper trap and it may be the optimum codopant for Sr₂MgSi₂O₇: Eu²⁺ long afterglow phosphors.     

纳米Sr2MgSi2O7:Eu2+,Dy3+的长余辉发光行为

使用溶胶-凝胶技术合成纳米尺度的Sr2MgSi2O7：Eu^2 ，Dy^3 长余辉发光材料，比较了该方法与固相法获得的长余辉粉体的光致发光行为和长余辉性能．溶胶．凝胶获得的纯相Sr2MgSi2O7：Eu^2 ，Dy^3 长余辉粉体是由纳米尺度的微晶形成的团聚颗粒，具有光致发光行为和长余辉发光特性．其发射峰位于465nm．而固相合成的粉体具有两个发射峰，分别位于404nm和459nm．产生这些差别的原因在于Eu^2 抖在基质品格中的不同配位情况．固相合成的粉体的余辉发光性能高于溶胶-凝胶粉体，其原因在于高温固相合成在基质内部产生了更高浓度的电子陷阱．     

纳米Sr2MgSi2O7:Eu2+,Dy3+的长余辉发光行为

使用溶胶-凝胶技术合成纳米尺度的Sr2MgSi2O7Eu2+,Dy3+长余辉发光材料,比较了该方法与固相法获得的长余辉粉体的光致发光行为和长余辉性能.溶胶-凝胶获得的纯相Sr2MgSi2O7Eu2+,Dy3+长余辉粉体是由纳米尺度的微晶形成的团聚颗粒,具有光致发光行为和长余辉发光特性.其发射峰位于465nm.而固相合成的粉体具有两个发射峰,分别位于404nm和459nm.产生这些差别的原因在于Eu2+在基质晶格中的不同配位情况.固相合成的粉体的余辉发光性能高于溶胶-凝胶粉体,其原因在于高温固相合成在基质内部产生了更高浓度的电子陷阱.     

Preparation of Sr2MgSi2O7:Eu2+, Dy3+ nanofiber by electrospinning assisted solid-state reaction

Novel one-dimensional polyvinylpyrrolidone (PVP)/[Sr(NO₃)₂ + Mg(NO₃)₂ + TEOS + Eu(NO₃)₂ + Dy(NO₃)₂] composite fibers were prepared via electrospinning, and then it was calcined at high temperature to fabricate the long-persistent luminescence Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ nanofiber by solid-state reaction under a reducing atmosphere. X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy and fluorescence spectrophotometer as well as afterglow brightness tester were used to characterize the resulting samples. The results revealed that diameter of the composite nanofibers decreased firstly and then increased with the increasing of the calcination temperature. FTIR analysis manifested that there was two new absorption peaks around 660 and 834 cm^?1, which corresponded to Mg–O stretching and Sr–O stretching, when PVP/[Sr(NO₃)₂ + Mg(NO₃)₂ + TEOS + Eu(NO₃)₂ + Dy(NO₃)₂] composite nanofibers was calcined at the temperature of 1,100 °C, indicating that the crystalline Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ had formed. Furthermore, its luminescence properties were tested. Upon excitation in the UV region, the emission spectra consisted of broad emission band, and the emission peak was located at the wavelength of 468 nm. Decay process contained both rapid-decaying and the slow-decaying processes, which due to the short survival time of the electro in Eu²⁺ and the deep trap energy center of Dy³⁺.     

长余辉发光材料Sr4Al14O25:Eu2+,Dy3+的制备

采用化学沉淀法制备了Sr4Al14O25:Eu2 ,Dy3 蓝绿色长余辉发光粉.通过XRD分析表明:经1100℃和1200℃煅烧制得的发光粉均为单一的Sr4Al14O25晶相,不含其它任何杂相,同时研究了硼酸的加入量对发光粉的物相变化和发射光谱的影响,通过场发射扫描电子显微镜分析了粉体的形貌和粒径.     

Ce掺杂Sr2MgSi2O7的溶胶-凝胶法制备及性能研究

采用溶胶－凝胶（sol-gel）法制备稀土离子Ce掺杂的Sr2MgSi2O7硅酸盐基发光材料,通过X射线衍射仪（XRD）、透射电子显微镜（TEM）、荧光分光光度计（PL）对样品的晶体结构、形貌及光学性能进行测试。XRD测试结果表明,在较低的热处理温度下可获得Sr2MgSi2O7相,但样品中也存在少量的其它杂质相。荧光光谱测试结果表明,经1000℃氢气处理1％Ce离子掺杂Sr2MgSi2O7样品中存在两套不同的光致发光带,一个为321nm光激发产生的371nm紫外发光,另一个为350nm激发产生的400—450hm的宽带可见发光,通过分析表明两个发光带分别起源于不同基体中的Ce^3＋离子。     

BaAl2O4:Eu2+,Dy3+长余辉发光材料的燃烧合成及其发光特性

以金属硝酸盐和尿素为原料,采用燃烧法合成了发青绿光的BaAl2O4:Eu2+,Dy3+长余辉发光材料。采用XRD、SEM、荧光分光光度计等手段对其进行分析表征。研究结果表明:随着燃烧温度升高,燃烧反应加剧,副产物BaCO3的含量减少,BaAl2O4的结晶程度增加,晶粒尺寸增大。Ba-Al2O4:Eu2+,Dy3+的激发光谱和发射光谱峰值分别为310nm和500nm,均呈宽谱带特征,其发光是由Eu2+的4f65d1→4f7跃迁引起,长余辉特性主要基于Dy3+的电子陷阱作用。     

Eu2+和Dy3+掺杂浓度对Sr2MgSi2O7材料的荧光和长余辉性能的影响

采用高温固相法制备得到Sr₂MgSi₂O₇: Eu²⁺和Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺发光粉, 并详细研究了Eu²⁺和Dy³⁺的掺杂浓度对Sr₂MgSi₂O₇材料的荧光和长余辉性能的影响。所有样品都在470 nm附近呈现较宽的发光峰, 这可归因于Eu²⁺离子的4f⁶5d→4f⁷电子能级跃迁。当Eu²⁺掺杂浓度超过淬灭浓度, 其浓度淬灭效应导致发光粉的荧光强度下降和余辉时间减短。同时, 发射峰的峰位随Eu²⁺浓度的增加而发生红移, 这主要由于晶体场分裂能和斯托克斯位移变化造成的, 而电子云扩大效应变化所产生的影响相对较弱。Dy³⁺离子会抑制荧光, 但有助于延长余辉时间。当其掺杂浓度超过10mol%时, Eu²⁺\Dy³⁺离子通过隧道复合机制发生浓度淬灭, 从而使材料的长余辉寿命减少。     

蓝色长余辉发光材料Sr2MgSi2O7:Eu2+,Ln3+的合成和性质

采用凝胶-燃烧法合成了系列稀土掺杂的Sr2MgSi2O7:Eu2 0.02,Ln3 0.04(Ln=La,Ce,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm)蓝色长余辉发光材料,用X射线粉末衍射(XRD)、扫描电镜(SEM)、荧光分光光度计等对合成产物进行了分析和表征.结果表明:掺杂了不同稀土离子的Sr2MgSi2O7:Eu2 ,Ln3 的晶体结构均为四方晶系结构;其激发、发射光谱的峰形、峰位基本无变化,激发光谱为一宽带,最大激发峰位于402nm处,次激发峰位于415nm处,与高温固相法制得的样品相比,激发峰发生了明显的红移;发射光谱也为一宽带,最大发射峰位于468nm附近,是由典型的Eu2 的4f5d-4f跃迁导致的,不同之处在于其激发光谱、发射光谱强度与余辉性质有所差别,其中Dy3 是最理想的共掺杂稀土离子,Sr2MgSi2O7:Eu2 ,Dy3 的亮度最高、余辉时间最长,可达5h以上;而Sr2MgSi2O7:Eu2 ,Sm3 的发光强度最低,余辉时间最短.     

Study on the optical performance of red-emitting phosphor: SrAl2O4: Eu2+, Dy3+/Sr2MgSi2O7: Eu2+, Dy3+/light conversion agent for long-lasting luminous fibers

Journal of Materials Science: Materials in Electronics - A novel luminous phosphor SrAl2O4: Eu2+, Dy3+/Sr2MgSi2O7:Eu2+, Dy3+/light conversion agent with both red luminescence characteristics and...     

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.     

Characterization and luminescence of Eu3+ ions doped 12CaO 7Al2O3 nanopowders

Eu3+ ions doped 12CaO 7Al2O3 (C12A7) powders with different Eu3+ concentrations were prepared by sol-gel combined with solid state reaction method. The results of XRD and Raman spectra showed that single cubic phase polycrystalline C12A7:Eu3+ powders were prepared. The absorption peaks attributed to f-f transition of Eu3+ ion can be observed, indicating that Eu3+ had been incorporated into C12A7 lattice site. Visible PL peaks around 578, 588, 614 nm were ascribed to 5D0 --> 7FJ (J = 0, 1, 2) transitions of Eu3+ under the excitation of 488 nm line. The PL of C12A7:Eu3+ showed the strongest emission intensity at Eu3+ concentration of 0.5 at%. Two different types of Eu3+ centers were identified by the two lines from 5D0 --> 7F0 transition emission. The doping mechanism of C12A7:Eu3+ might be attributed to Eu3+ ions substitution for two types of Ca2+ lattice sites in C12A7. The temperature dependent PL spectra of Eu-doped C12A7 were measured in the range from 100 to 300 K under the excitation of 488 nm laser line. The PL intensities as a function of temperature were well fitted by using a unified theoretical model, considering thermal activation and nonradiative energy transfer processes.     

Preparation and luminescence properties of yellow long-lasting phosphor Ca2ZnSi2O7:Eu2+, Dy3+

Long-lasting phosphors Ca₂ZnSi₂O₇:Eu²⁺, Dy³⁺ are prepared by solid-state reaction method assisted with different fluxes. Broadband emission, peaked at 580 nm and originating from 4f to 5d transition of Eu²⁺, is observed. The emission intensities of the phosphors can be enhanced by 4.84 and 7.73 times with the introduction of H₃BO₃ and CaF₂, respectively. Moreover, their afterglow times are also respectively prolonged to 11 h and 12 h. The yellow afterglow can be excited by both ultraviolet and visible light, thus permitting its application in both room and outdoor environment. In terms of the crystal structure and trap feature of the phosphors added with different fluxes, the mechanism for the improved luminescence and afterglow properties is discussed.     

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.     

Enhanced long persistence of Sr2SnO4:Sm red phosphor by co-doping with Dy

We report the observation of long lasting red phosphorescence in Sr₂SnO₄:Sm³⁺ and Sr₂SnO₄:Sm³⁺, Dy³⁺ phosphors. The decay patterns of afterglow curves demonstrate that the afterglow time of Sr₂SnO₄:Sm³⁺ could be prolonged by the incorporation of Dy³⁺. The remarkable changes in the thermoluminescence glow curve exhibited that the first band responsible for the origin of the afterglow becomes the most prominent feature when Dy³⁺ added. In other words, the enhancement of the red afterglow in Sr₂SnO₄:Sm³⁺, Dy³⁺ compared with Sr₂SnO₄:Sm³⁺ could be ascribed to more appropriate traps (the hole-traps V^″Sr) created by the incorporation of Dy³⁺.     

Hydrothermally-mediated preparation and photoluminescent properties of Sr3Al2O6:Eu3+ phosphor

Hydrogarnet Sr₃Al₂(OH)₁₂ (SAH) has been obtained from hydrothermal systems with a wide range of pH values under mild conditions. The influence of reaction conditions on the formation of various phases has been considered. The addition of sodium hydroxide can favor the yield of pure SAH phase. Stoichiometric Sr₃Al₂O₆ (SAO) has been prepared from SAH through thermal decomposition over 600 °C for 4 h. SAO can act as a red phosphor host with doping of Eu³⁺ ions. The Eu³⁺ ions as activators can be introduced directly under hydrothermal conditions before thermal decomposition.     

煅烧温度对红色长余辉发光材料Sr3Al2O6:Eu2+,Dy3+性能的影响

采用溶胶凝胶法合成了Sr3Al2O6:Eu2+,Dy3+长余辉发光材料,利用X射线衍射仪(XRD)对材料的物相进行了分析,采用荧光分光光度计、照度计测定了样品的发光特性。XRD结果表明:随着煅烧温度的升高,SrCO3杂相的衍射峰越来越弱,Sr3Al2O6相的衍射峰越来越强,1200℃时发光基质为纯的Sr3Al2O6相,1250℃时出现新的SrAl2O4杂相。激发光谱和发射光谱结果表明:长余辉发光材料的激发峰位于473nm,发射峰位于612nm,归属于Eu2+的4f65d1→4f7特征发光。温度升至1250℃时,Eu2+的发射峰为612nm和520nm,后者归属于Eu2+在发光基质SrAl2O4中的发光。综合分析得制备Sr3Al2O6:Eu2+,Dy3+发光材料合适的煅烧温度为1200℃,在此温度下,材料具有较好的初始亮度和余辉时间。     

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.