La0.8Y0.2PO4∶Bi3+ ，Sm3+ ，Eu3+ 荧光粉的合成,性能及其前驱体热分解动力学

相对于绿色和蓝色荧光粉,红色荧光粉因不能有效吸收近紫外光,致使发射的红光强度不能与蓝、绿两种荧光粉的发光强度同步,影响了其显色性,降低了发光效率.为获得能够被近紫外光高效激发的红色荧光粉,本文以硝酸铕、硝酸钐、氯化铋、氧化镧、氧化钇、磷酸三铵为原料,经高温固相反应合成得到Bi,Sm,Eu掺杂磷酸镧钇荧光粉,利用XRD,SEM,荧光光谱及TG/DTG对产物进行了表征,并采用非等温法研究前驱体的热分解过程,进而探究前驱体热分解反应过程的动力学及焙烧过程中荧光粉的形成机理.研究表明:Bi3+的最佳掺杂浓度为x=0.03,所得产物为以磁偶极(5D0→7F1)跃迁为主导发射的红色荧光粉;最佳产物与未掺杂产物相比,前者的荧光强度是后者的2.66倍;最佳产物前驱体的热分解过程只有一步失重,经计算获得了该过程对应的活化能、机理函数及指前因子.Bi,Sm,Eu掺杂磷酸镧钇荧光粉是一种发光效率高、具有广泛应用前景的近紫外激发白光LED用红色荧光粉.     

白光LED用YAG∶Ce~(3+)发光材料的性能增强研究

以硼酸和碱土氟化物作为助熔剂,调整助熔剂比例和组分,采用高温固相法合成一系列白光LED用YAG∶Ce3+发光材料。采用XRD、扫描电镜(SEM)和荧光光谱(PL)等对样品进行表征。研究表明,合适的助熔剂有助于降低样品的烧结温度,不会有杂相产生,加入不同浓度和成分的助熔剂对样品的发射、激发光谱形状和峰值波长位置无影响,但对发光强度影响较大;采用助熔剂质量分数为0.4%(0.2%H3BO3-0.2%BaF2)时,所合成样品的颗粒比较均匀,发光性能的增强最为有效。将其和蓝光Ga(In)N芯片封装成白光LED,光效也得到显著提高。封装后白光LED的色坐标为(0.3341,0.4190),色温为5470K,显色指数为67,光效可达到78.3lm/W,高于其它条件合成荧光粉封装的白光LED。     

Color tuning of Y3Al5O12:Ce phosphor and their blend for white LEDs

Gadolinium or lanthanum co-doped (0.5 mole) yttrium aluminum garnet doped with cerium phosphors were synthesized by a citric acid gel method and the effect of co-dopants on the structural and luminescent properties were studied. A significant peak shift in the photoluminescence spectra of yttrium aluminum garnet doped cerium was observed from 535 to 556 and 576 nm for gadolinium or lanthanum co-doped phosphors, respectively. The color tuned phosphor were blended with yttrium aluminum garnet doped cerium which showed a considerable improvement in the Commission International De Eclairage chromaticity co-ordinate values of gallium nitride based blue light emitting diode pumped white light. White light emitted from yttrium aluminum garnet doped cerium shows a Commission International De Eclairage value of (0.229, 0.182) whereas the yttrium aluminum garnet doped cerium phosphor blended with gadolinium or lanthanum co-doped phosphor shows (0.262, 0.243) and (0.295, 0.282), respectively. These results demonstrate the possibility to use these phosphor blends to enhance the white light generation in the field of white-light emitting diode solid-state lighting.     

Effect of monovalent charge compensators on the photoluminescence properties of Ca3(PO4)2∶Tb3+,A+(A=Li,Na,K)phosphors

Ca3-x(PO4)2 ∶xTb3+(0.2≤x≤0.4),Ca2.3(PO4)2∶0.35Tb3+,0.35A+(A=Li,Na,K),and Ca2.3(PO4)2∶0.35Tb3+,yLi+(0.35≤y≤0.455)phosphors were prepared by solid-state reaction.All the prepared phosphors formed a rhombohedral unit cell with the R3c space group.To improve the photoluminescence(PL)properties of the Ca2.65(PO4)2∶0.35Tb3+phosphor,monovalent charge compensators such as Li+,NA+,and K+were added to the Ca2.65(PO4)2∶0.35Tb3+phosphor.The charge compensators acted as fluxes,so they improved the crystallinity.The excitation and emission properties were significantly improved through the incor-poration of charge compensators.In particular,among the charge compensators,Li+ion substantially enhanced the emission intensity and color purity.Furthermore,considering the evaporation of Li2CO3 during the annealing process,we optimized the concentration of Li+charge compensator to enhance its PL performance.Impressively,the green emission intensity of the Ca2.3(PO4)2∶0.35Tb3+,0.385Li+phosphor was 260％higher than that of the Ca2.65(PO4)2∶0.35Tb3+phosphor.We believe that the effect of charge compensators on the PL properties and the optimum concentration of Li+charge compensator are useful for the design of phosphors in light-emitting diodes.     

白光LED用单一基质白光荧光粉的研究进展

白光LED以其独特优势被称为第四代光源,具有广阔的应用前景。单一基质白光荧光粉(SMWP)因颜色稳定、色彩还原性好,成为白光LED用光转换材料的研究热点。概述了由近紫外LED芯片激发的白光荧光粉的研究现状,指出了该荧光粉存在的问题并对其发展趋势做了展望。     

蓝光激发红色荧光粉的研究进展及其在白光LED中的应用

蓝光LED芯片激发黄色荧光粉是目前白光LED的主要实现方式,引入红色荧光粉对调整白光LED的显色指数及色温有重要意义。重点介绍和评述了可被蓝光激发且具有宽发射带的硫化物、氮化物、铝酸盐等几种体系红色荧光粉的发光性质、最新研究成果及在白光LED中的应用。对比发现,氮化物荧光粉可被从近紫外到可见绿光有效激发,随基质组成的不同,可发出峰值波长为600～650nm的红色荧光,且由于其优良的化学稳定性、热稳定性成为最有前途的一类红色荧光粉。采用两种以上的荧光粉代替单一黄色荧光粉,有利于调整白光LED的色温,提高显色指数。     

Effects of the mixing ratio of the CaAl12O19:mn and Zn2SiO4:mn color-conversion layer on the color tunable emissions of white organic light-emitting devices

The optical properties of white organic light-emitting devices (WOLEDs) fabricated utilizing a CaAl12O19:Mn and Zn2SiO4:Mn phosphor layer were investigated. X-ray diffraction patterns for CaAl12O19:Mn and Zn2SiO4:Mn phosphors showed that Mn ions in the CaAl12O19:Mn phosphors were completely substituted into Ca ions and that Mn ions in the Zn2SiO4:Mn phosphors were completely substituted into Zn ions. Field emission scanning electron microscopy images showed that the size of the CaAl12O19:Mn phosphor was approximately between 0.1 and 3 microm, and that the size of the Zn2SiO4:Mn phosphor was smaller than 7 microm. The color coordinates of the electroluminescence spectra for WOLEDs with phosphor thicknesses of 0.25 and 0.35 mm shifted to the white emission side because the generated blue light from the blue OLEDs combined with the red and green lights was converted by the CaAl12O19:Mn and the Zn2SiO4:Mn phosphor down-conversion layers.     

Effect of zinc metal addition on microstructural evolution of Zn0.22Cd0.78S$ phosphors studied by transmission electron microscopy

The effect of zinc powder addition on the microstructural evolution of fine Zn_0.22Cd_0.78S:Ag$, Cl phosphor particles was investigated in relation to the luminescent property of phosphors. The phosphor microstructures were analyzed by high-resolution transmission electron microscopy (HRTEM) using the ultramicrotome technique for specimen preparation. The phosphor baking process at 480 °C for 30 min in air results in significant damage to the surface structure of the phosphors due to the decomposition and oxidation of the phosphor itself. The addition of zinc metal powders into the Zn_0.22Cd_0.78S$ phosphors suppresses the oxidization and decomposition of phosphors by oxidizing zinc metal during the baking process in air. The oxidation of the zinc powders during baking provides the baking furnace with less oxidizing atmosphere for phosphor particles. The structure of phosphors, especially at the surface region, is much less degraded compared to the phosphors baked with no zinc metal addition. © 2000 Kluwer Academic Publishers     

新型白光LED用SrMg_2(PO_4)_2单-基质荧光粉

本文通过高温固相法合成了紫外光LED用SrMg2(PO4)2为基质Eu2+,Tb3+和Mn2+为激活剂的白色荧光粉。采用XRD对荧光粉的结构和相纯度进行分析,Eu2+、Tb3+及Mn2+的加入对其结构没有明显的影响,且无杂相生成;当用Ca部分取代Sr时Eu2+和Mn2+的发射带分别发生红移和蓝移且二者之间存在着明显的能量传递;当引入共激活剂Tb3+时对其荧光光谱进行了详细研究,发现Eu2+和Tb3+,Eu2+和Mn2+之间存在部分的能量传递,通过调整它们的相对掺杂浓度可以得到发白光的荧光粉。     

Engineering phosphors for improved brightness

Factors affecting the cathodoluminescent (CL) efficiency of phosphors include: morphology, size, stoichiometry, composition, and surface of the phosphors. In the design of phosphors for low-voltage operations, processes such as surface etching are used to enhance phosphor efficiency. In this study, zinc-activated ZnO phosphors were subjected to three processes: acid etching, ball milling, and/or ultrasonic vibration, and the effect of each process on the CL efficiency studied. It is found that the brightness of phosphors increases 40% after ultrasonic vibration followed by etching twice with 0.005 M HNO₃.     

等离子体显示板真空紫外荧光测试系统

设计等离子体显示板(PDP)真空紫外荧光测试系统来测评PDP荧光粉的特性。系统通过巧妙设计测试腔,模拟PDP放电单元,为激发PDP荧光粉发光提供所需要的较强真空紫外线,使系统能够分析出荧光粉的光谱功率分布、发光亮度、带宽、发射谱线主峰波长、色品坐标、颜色纯度和主波长等各种光学特性。实验结果数据表明,该系统的可重复性好、精度高,为研制高质量的等离子体显示板提供了依据。     

Measured conversion efficiencies of P45, paraterphenyl, tetraphenyl butadiene, and sodium salicylate phosphors in the soft-x-ray wavelength range

The measured conversion efficiencies at 9.89, 23.6, 44.7, and 160 ? of P45 phosphor screens, as well as those of paraterphenyl, tetraphenyl butadiene, and sodium salicylate at 9.89, 44.7, and 67.6 ?, are presented. The conversion efficiency is defined as the ratio of photoelectrons ejected from the photocathode of a visible detector, which are excited by the scintillated photons that are emitted from the phosphor in a solid angle of 2π, to the number of soft-x-ray photons incident on the phosphor. The effect of the phosphor's thickness on the conversion efficiency was studied. The P45 phosphor converts the soft-x-ray photon (10-200 ?) into an order of magnitude more visible photons than the low-Z phosphors. The P45 phosphor screen used in conjunction with a photomultiplier tube offers a soft-x-ray photodetector with a conversion efficiency that ranges from 0.5 at 160 ? to 12 at 9.89 ? and a high electronic gain.     

White organic light-emitting devices utilizing a mixed color-conversion phosphor layer consisting of CaAl12O19:Mn and Zn2SiO4:Mn

White organic light-emitting devices (WOLEDs) were fabricated utilizing a mixed color-conversion layer consisting of CaAl12O19:Mn and Zn2SiO4:Mn phosphors. The ratio between the CaAl12O19:Mn and the Zn2SiO4:Mn phosphor determined the rate of the red and the green lights. The color rendering index was improved by using a mixed color-conversion phosphor layer.     

M2Si5N8:Eu-based (M = Ca, Sr) red-emitting phosphors fabricated by nitrate reduction process

M₂Si₅N₈:Eu²⁺-based (M = Ca, Sr) red-emitting phosphors were fabricated at relatively low temperature (1200 °C) and atmospheric pressure using a simple solid-state reaction process. Several processing parameters were systematically investigated to optimize the phosphors structural characterization and photoluminescence performance, including the amount of europium and the properties of the precursor and activated materials. The as-prepared M₂Si₅N₈:Eu²⁺-based (M = Ca, Sr) phosphors were orange in color and emitted intensively in the red region of 580-670 nm under 465 nm excitation. This simple fabrication technique can be readily used for the optimization of phosphor microstructures and high-performance red-emitting phosphors since it eliminates many air-sensitive precursors.     

LED用绿色荧光粉的研究进展

白光LED被誉为第四代照明光源,有着显著的节能前景和庞大的应用市场。荧光粉光转换型是未来白光LED发展的主流方向。(近)紫外激发三基色荧光粉的研制具有十分重要的意义。综述了近年来半导体白色发光二极管(WLED)用绿色荧光粉的研究进展,重点推介了性能较好的绿色荧光粉,并展望了LED用绿色荧光粉发展趋势。     

Eu2+掺杂硅基氮氧化物荧光粉的制备与发光特性

为获得接近太阳光的自然发光效果,制备了Eu2+掺杂的硅基氮化物系列荧光粉,并对其发光特性及原理进行研究.采用碳热还原氮化法制备了Eu2+掺杂Sr Si O3-Sr2Si5N8-Sr Si2O2N2红色荧光粉.利用X射线衍射仪(XRD)、荧光分光光度计、MS-CASTEP对产物物相、发光光谱、电子结构进行了测试分析.结果发现:通过调节煅烧工艺参数,可同时获得2种主要物相或者单一物相的荧光粉;所制备的荧光粉,能够在350~400 nm范围内被UVLED很好地激发,根据主晶相的不同,产物的发射光谱可以在400~700 nm波段内调控.采用第一性原理分析了发射峰位于650 nm附近橙红色主晶相Sr2Si5N8∶Eu2+的电子结构和光物理性能,发现该物相为直接带隙半导体材料,Eu2+的4f轨道对费米面电子峰起主要作用.Eu2+掺杂Sr Si O3-Sr2Si5N8-Sr Si2O2N2是优良的、颜色可调控的红色荧光粉材料.     

PLA/PBS荧光复合材料的制备及性能研究

目的 聚乳酸(PLA)具有良好的加工性能和生物相容性,通过加入耐热性能好的聚丁二酸丁二醇酯(PBS)可改善其力学性能和热力学性能,再加入365 nm长波荧光粉和色母粒制得的复合材料使其获得荧光防伪性能与色彩性能。方法 以聚乳酸为基体,利用双螺杆挤出机将PLA、PBS、荧光粉、普通色母熔融共混后挤出,得到含不同比例PBS的PLA/PBS共混材料,含不同比例荧光粉的PLA/PBS荧光复合材料,以及含不同比例色母的彩色PLA/PBS荧光复合材料,并对复合材料进行力学性能分析、热力学性能分析、红外分析、色彩性能分析、微观形貌分析等。结果 通过实验得出,当PLA/PBS质量比为6/4、荧光粉质量分数为5%、色母质量分数为0.5%时综合性能最佳。结论 制备了有色PLA/PBS荧光复合材料,赋予复合材料防伪的荧光性能和美观性,并且得到热力学性能有所改善的环境友好型复合材料,拓宽了PLA在3D打印领域和现代工业领域的应用。     

Mn4+激活氧氟化物红光荧光粉的研究进展

稳定可靠的高光子能量发光(620~650 nm)红光荧光粉, 对于构建低色温、高显指荧光粉转换型白光发光二极管(WLED)至关重要。Mn ⁴⁺激活红光荧光粉是当前WLED用荧光粉研究热点之一。本文介绍了Mn ⁴⁺离子的能级跃迁与光致发光特性, 详细叙述了目前所报道的七种Mn ⁴⁺激活含d ⁰/d ¹⁰/s ⁰离子氧氟化物系列红色荧光粉(如Na₂WO₂F₄:Mn ⁴⁺等)的制备方法、晶体结构及其发光特性。目前Mn ⁴⁺在氧氟化物结构中得到强R线发光的情况少, 微观配位体仍是[MnF₆]或[MnO₆], 其化学稳定性和量子效率研究也很缺乏。最后对Mn ⁴⁺激活氧氟化物红光荧光粉的研究进行了展望。     

Photonic Crystal Phosphors Integrated on a Blue LED Chip for Efficient White Light Generation

Following the proof‐of‐concept experiment in the unit structure level, photonic crystal (PhC) phosphors—structurally engineered phosphor materials based on the nanophotonics principles—are integrated with a blue light‐emitting diode (LED) chip to demonstrate a compact and efficient white light source. Red‐ or green‐emitting CdSe‐based colloidal quantum dots (CQDs) are coated on a Si₃N₄ thin‐film grating to fabricate PhC phosphors. The underlying PhC structure is designed such that the photonic band‐edge modes at the zone center (k_∣∣ = 0) are tuned to the energy of the blue excitation photons. By progressively stacking the PhC phosphor plates on a blue LED chip, the blue, green, and red emission intensities can be tightly controlled to obtain white light with the desired properties. The chromaticity coordinates, (0.332, 0.341), and correlated color temperature, 5500 K, are obtained from a stack of 3 red and 11 green PhC phosphor plates; in contrast, a stack of 5 red and 16 green reference phosphor plates are required to generate a similar white light. Overall, the PhC phosphors produce 8% higher total emission intensity out of 33% less amount of CQDs than the reference phosphors.