白光LED用Sr3SiO5-Eu2 荧光粉的合成及发光特性--外文翻译中英对照.doc

附录 附录 英文文献原文 Synthesis and luminescence property of Sr3SiO5:Eu2+ phosphors for white LED CHENG Guang 程 光, LIU Quansheng 刘全生, CHENG Liqun 程利群, LU Liping 卢利平, SUN Haiying 孙海鹰, WU Yiqing 吴移清, BAI Zhaohui 柏朝晖, ZHANG Xiyan 张希艳, QIU Guanming 邱关明 School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, China Received 29 September 2009; revised 23 March 2010 Abstract: Sr3SiO5:Eu2+ yellow phosphors for white LEDs were synthesized by high temperature solid state reaction method under a reductive atmosphere. The crystalline phases were examined with X-ray diffraction XRD. Luminescence properties were studied, and effects of various fluxing agents BaCl2, MgF2, CaF2 and BaF2 on the emission spectra were also studied. The optimal Eu2+ concentration and flux were determined. Sr3SiO5: Eu2+ was obtained by firing the sample on optimal composition and fabrication process. The sample showed a broad excitation band from 300 to 500 nm and a broad band emission peaking at 561 nm. Keywords: phosphor; Sr3SiO5:Eu2+; fluxing agents; rare earths White LEDs have been widely applied in many fields for their merits such as energy saving, high efficiency, long life and reliability etcUp to now white LEDs fabricated by using GaN based blue LED as the excitation source and coating with Y3Al5O12:Ce3+ phosphors have attracted much attention due to the easy fabrication, low cost, and high brightness1?4. Since the LEDs with Y3Al5O12:Ce3+ phosphors generate cool white, phosphors emitting longer wavelength have been extensively studied. Silicate system is an excellent luminescent host with a stable crystal structure and high thermal stability. Many studies on phosphors with silicate as a host have been conducted5?9. The Eu2+-doped M2SiO4 MCa, Sr, Ba was investigated by Kim et al.10 The emission peak of the phosphor is centered at 540 nm, showing shorter emission wavelength than Y3Al5O12:Ce3+. Warm white LED could not be obtained with this phosphors11. Park et al.12 reported Sr3SiO5:Eu2+ phosphors and proved that warm white could be generated from the phosphors. The Sr3SiO5:Eu2+ phosphor has recently attracted much attention and has become a leading project13,14. However, the influence of fluxing agents on the luminescence properties of the Sr3SiO5:Eu2+ has not been reported to our knowledge. In this paper, we reported the fabrication of Sr3SiO5:Eu2+ phosphors and the effects of various fluxing agents on luminescence properties of the phosphors. 1 Experimental Sample preparation The samples were prepared by the high temperature solid-state reaction method. The raw materials used in the preparation of the phosphors were SrCO3 AR, ultrafine SiO2 AR, BaF2 AR, CaF2 AR, MgF2 AR, BaCl2 AR and Eu2O3 99.99% powders. Stoichiometric amounts of the raw materials were weighed and thoroughly mixed in an agate mortar and successively pre-sintered at 1100 oC for 2 h in an ambient atmosphere. The pre-fired products were then ground and calcined at 1400 oC for 6 h with some amounts of fluxing agents in a reductive atmosphere 95%N2/5%H2. The Sr3SiO5:Eu2+ phosphors with various fluxing agents and Eu2+ ion contents were obtained. Sample characterization XRD measurement was performed using a D/-IIB Rotating Anode X-ray diffractometer with Cu K radiation voltage40 kV, current20 mA, scanning speed4 /min, step length0.02. A Shimadzu RF-5301 fluorescence spectrophotometer was used to detect the excitation and emission spectra of the products 150 W Xenon lamp. All measurements were carried out at room temperature. 2 Results and discussion XRD analysis of the sample Fig. 1 shows the XRD pattern of the Sr3SiO5:Eu2+ sample fired at 1400 oC for 6 h. The flux BaF2 and Eu2+ concentration in the sample were 5 wt.% and 1 mol.%, respectively. Main diffraction peaks marked with “o” in the pattern agree with the standard card No.26-0984, indicating that main crystal phase Sr3SiO5 with lattice parameters values a0.6948 nm, b0.6948 nm, c1.0753 nm was obtained. Those peaks marked with “x” were assigned to the impurity phase Sr2SiO4. CHENG Guang et al., Synthesis and luminescence property of Sr3SiO5:Eu2+ phosphors for white LED Fig. 1 XRD pattern of Sr3SiO5:Eu2+ with 5 wt.% BaF2 fired at 1400 oC for 6 h Excitation and emission spectra Fig. 2 gives the excitation 1 and emission spectra 2 of the Sr3SiO5:Eu2+ sample with 1 mol.% Eu2+ and 5 wt.% BaF2. It is found that the excitation spectrum is a broad band ranging from 300 to 500 nm. It is obvious that there are two peaks in the excitation spectrum peaking at 373 and 419 nm respectively, indicating that there are two luminescence centers in the Sr3SiO5:Eu2+ sample10. These excitations are caused by 4f -5d transition of Eu2+ ion. The tail of the excitation band is extended to longer wavelength 500 nm, making an efficient excitation under 460 nm possible. Curve 2 in Fig. 2 shows the emission spectrum of the Sr3SiO5:Eu2+ sample under 460 nm excitation. The emission spectrum also exhibits a broad band peaking at 561 nm. It is well-known that the emission peak of Eu2+ is greatly influenced by the surrounding crystal field. Because of the presence of Sr2SiO4 phase in the sample the emission peak of the sample is different from that in other reports11,12. Fig. 2 Excitation 1 and emission 2 spectra of Sr3SiO5:Eu2+ 2.3 Effects of Eu2+ concentrations on emission spectrum of Sr3SiO5:Eu2+ The emission spectra of samples Sr3SiO5:xEu2+ with various Eu2+ concentrations x0.005?0.07 mol under 460 nm excitation are presented in Fig. 3. All samples show broad band emissions. Both the emission peak and intensity change with increasing Eu2+ concentrations. Sr3SiO5:0.01Eu2+ displays the strongest emission at 561 nm, whereas Sr3SiO5: 0.05Eu2+ exhibits the longest emission at 565 nm. The crystal field strengthened by the substitution of Sr2+ with smaller Eu2+ may contribute to the emission red-shift with increasing Eu2+ concentrations. Eu2+ occupies Sr2+ sites in the Sr3SiO5 lattice. Because the radius of Eu2+ is smaller than that of Sr2+ the crystal field strength is increased with increasing Eu2+ concentrations. The lowest 5d excitated state edge decreased and the emissions of the samples shift to longer wavelength. Fig. 3 Emission spectra of Sr3SiO5:Eu2+ with various Eu2+ concentrations 2.4 Effects of Eu2+concentrations on excitation spectra of Sr3SiO5:Eu2+ Fig. 4 exhibits the excitation spectra of Sr3SiO5:Eu2+ phosphor with various Eu2+ ion concentrations on emission at 561 nm. The intensity of the excitation increases with increasing Eu2+ ion concentration from 0.5 mol.% to 1 mol.%. Whereas the intensity decreases with increasing Eu2+ ions concentration further. The imum excitation intensity is found at Eu2+ ions 1 mol.% and the same optimal concentration with emission spectrum. The excitation peak shape showing broad band does not change with changing the Eu2+ concentrations. Fig. 4 Excitation spectra of Sr3SiO5:Eu2+ with various Eu2+ concentrations 2.5 Effects of flux on emission of Sr3SiO5:Eu2+ Effects of various fluxing agents BaCl2, BaF2, MgF2 and CaF2 on the emission were studied. Fig. 5 gives the emission spectra of Sr3SiO5:Eu2+ samples doped with various fluxing agents at 5 wt.%. An interesting result is found that samples with various fluxing agents show different emission property on both emission intensity and peak position. The samples with BaCl2 and BaF2 as fluxing agents have emission peaks at 564 and 561 nm, respectively. Whereas the samples with MgF2 and CaF2 as flux give longer wavelength emission peaking at 588 and 591 nm with less luminous intensity. The sample with BaF2 as fluxing agent exhibits the strongest emission peaking at 561 nm. The reason for these results, i.e., the role of fluxing agents in the silicate phosphors, will be further studied. Fig. 5 Effects of various fluxing agents on emission spectra of Sr3SiO5:Eu2+ The dependence of emission intensity of Sr3SiO5:Eu2+ on BaF2 concentrations 1wt.%?7 wt.% was investigated. The results are shown in Fig. 6. With an increase of BaF2 content, the luminescent intensity was enhanced gradually from 1 wt.%?5 wt.%, whereas the luminous intensity was decreased with increasing the flux more than 5 wt.%. The optimal BaF2 content was found to be 5 wt.%. Fig. 6 Dependence of emission intensity of Sr3SiO5:Eu2+ on BaF2 Contents Conclusions Sr3SiO5:Eu2+ yellow phosphors for white LEDs were synthesized. Main phase Sr3SiO5:Eu2+ was produced by firing the sample at 1400 oC for 6 h with BaF2 5 wt.% as fluxing agents. The sample showed a broad excitation band from 300 to 500 nm. A strong yellow emission at 561 nm was obtained for 0.01 mol Eu2+ under excitation of 460 nm. The phosphors are favorable for fabricating warm white LED pumping with GaN blue LEDs. References: 1 Pan Y X, Wu M M, Su Q. Tailored photoluminescence of YAG:Ce phosphor through various methods. J. Phys. Sol., 2004, 65: 845. 2 Li X, Yang Z P, Guan L, Guo Q L, Huai S F, Li P L. Synthesis and properties of Eu3+ activated strontium phosphor. J. Rare Earths, 2007, 25: 706. 3 Tokumatsu T, Masaru Y, Ken H, Takayasu I, Osamu Y. Novel synthesis of Y3Al5O12YAG leading to transparent ceramics. Solid State Communications, 2001, 119: 603. 4 Mihail N, Chulsoo Y. Controlled peak wavelength shift of Ca1?xSrxSySe1?y:Eu2+ phosphor for LED application. J. Solid State Chem., 2006, 179: 2529. 5 Kim S H, Lee H J, Kim K P, Yoo J S. Spectral dependency of Eu-activated silicate phosphors on the composition for LED application. Korean J. Chem. Eng., 2006, 23: 669. 6 Wang J L, Wang D J, Li L, Meng Y S, Zhang N, Li G M. Preparation of single host silicate phosphors for white LEDS and its photoluminescence properties. Chinese J. Lumin. in Chin., 2006, 27: 463. 7 Soon D, Jeejoung K, Park S H L. Photoluminescence properties of Eu2+-activated Sr3SiO5 phosphors. J. Mater. Sci., 2006, 41: 3139. 8 Yang Z P, Xiong Z J, Liu Y F, Xu X L. Synthesis of nanosized phosphor Ca3SiO5:Eu2+ by sol-gel method. J. Chin. Ceram. Soc. in Chin., 2007, 35: 546. 9 Luo X X, Cao W H, Sun F. The development of silicate matrix phosphors with broad excitation band for phosphor-converted white LED. Chin. Sci. Bull., 2008, 53: 2923. 10 Kim J S, Lim K T, Jeong Y J, Pyung E, Choi J C, Park H L. Full-color Ba3MgSi2O8:Eu2+ Mn2+ phosphors for whitelight- emitting diodes. Solid State Commun., 2005, 135: 21. 11 Li P L, Yang Z P, Wang Z J, Guo Q L, Li X. Preparation and luminescence characteristics of Sr3SiO5:Eu2+ phosphor forwhite LED. Chin. Sci. Bull., 2008, 53: 974. 12 Park J K, Choi K J, Yeon J H, Yeon J H, Lee S J, Kim C H. Embodiment of the warm white-light-emitting diodes by using a Ba2+ codoped Sr3SiO5:Eu phosphor. Appl. Phys. Lett., 2006, 88: 043511. 13 Jang H S, Jeon D Y. White light emission from blue and near ultraviolet light-emitting diodes precoated with a Sr3SiO5:Ce3+, Li+ phosphor. Opt. Lett., 2007, 32: 3444. 14 Joung K P, Chang H K, Seung H P, Hee D P, Se Y C. Application of strontium silicate yellow phosphor for white lightemitting diodes. Appl. Phys. Lett., 2004, 84: 1647. 附录 英文翻译 白光LED用Sr3SiO5:Eu2+荧光粉的合成及发光特性 程光,刘全生,程利群,卢利平,孙海鹰,吴移清,柏朝晖,张希艳,邱关明 ( 中国,长春130022,长春科技大学,材料科学与工程学院) 2009年9月29日收到,2010年3月23日修订 摘要:采用高温固相反应方法在还原气氛中合成了白光LED用黄色荧光粉Sr3SiO5:Eu2+。用x射线衍射(XRD)测定晶相。发光性质的研究表明,不同助熔试剂BaCl2,MgF2,CaF2和BaF2对发射光谱有影响。测定了最理想的Eu2+浓度及助熔剂。Sr3SiO5Eu2+是在理想的组成和制造工艺下灼烧样品得到的。样品显示了一个300到500nm的宽激发带以及发射峰值位于561nm的宽带。 关键词:荧光粉,SrSiO5:Eu2+,助熔剂,稀土元素 由于它们的优点如节能,高效,寿命长和稳定性等,白色LED已经广泛应用于许多领域。 目前白光LED是由氮化镓制造的,此氮化镓基于蓝色LED作为激发源及表面涂用Y3Al5O12:Ce3+荧光粉,由于其制造简单、低成本和高亮度已经备受关注。由于加了Y3Al5O12: Ce3+荧光粉的LED产生冷白光,荧光粉发光波长更长,其已经被广泛研究。硅酸盐体系是一个良好的发光基质,拥有稳定的晶体结构和高的热稳定性。对硅酸盐作为基质的荧光粉的很多研究已经进行了。Eu2+掺杂M2SiO4MCa,Sr,Ba的荧光粉的研究已经被金姆研究了。 这个荧光粉的发射峰位于540nm处,显示发射波长较Y3Al5O12:Ce3+短。暖白光LED不能利用该荧光粉。Park et al报导了Sr3SiO5:Eu荧光粉并证明了此荧光粉可形成暖白光。Sr3SiO5:Eu荧光粉最近吸引了大量的关注,已经成为一个主要项目。然而,助熔剂对Sr3SiO5:Eu荧光粉的发光性质的影响我们还未知。在本文中,我们报告了制作Sr3SiO5:Eu荧光粉以及各种不同助熔剂对荧光粉发光性能的影响。 1.实验 1.1 样品准备 样品是通过高温固态反应法制备的。荧光粉的准备中用的原材料是SrCO3AR,非常细微的SiO2 AR, BaF2 AR, CaF2 AR, MgF2 AR, BaCl2 AR和99.99%Eu2O3粉末。称重化学计量数量的原料并把它们放于玛瑙研钵中充分混合均匀,相继在1100环境中2小时。研磨之前烧过的产品并加入一些助熔剂放于还原气氛95%N2/5%H2中1400焙烧6小时。得到各种助熔剂的Sr3SiO5:Eu2+和Eu2+离子成分的荧光粉。 1.2 样品特性描述 XRD测量是通过使用一个D/-IIB旋转阳极X射线和Cu K辐射的衍射仪(电压40Kv,电流20Ma,扫描速度4()/min,步长0.02)。使用日本岛津公司的RF-5301荧光分光光度计来检测产品的激发和发射光谱(150W氙灯)。所以测量均在室温下进行。 2.结果与讨论 2.1 XRD样品分析 图1显示了Sr3SiO5:Eu样品在1400灼烧6小时的XRD谱图。熔剂BaF2和Eu2+在样品中的浓度分别是5 wt.%和1 mol.%。主要衍射峰(标有“”)的谱图与标准卡(No.26-0984)相吻合,标明了Sr3SiO5,其晶格参数值是a0.6948nm,b0.6948nm,c1.0753nm的主要晶体相已获得。这些标有“x”的峰标明了Sr2SiO4不纯净相。 Fig. 1 XRD pattern of Sr3SiO5:Eu2+ with 5 wt.% BaF2 fired at 1400 oC for 6 h CHENG Guang et al., Sr3SiO5:Eu白色LED荧光粉的合成和发光性质 2.2 激发和发射光谱 图2给出了1mol.% Eu2+和5wt.%BaF2的Sr3SiO5:Eu2+样品的激发光谱(1)和发射光谱(2)。可发现激发光谱是一条范围从300到500nm的宽频带。明显可见在激发光谱峰中有两个峰分别位于373和419nm处,显示了在Sr3SiO5:Eu2+样品中有两个发光中心。这些激发是由Eu2+离子从4f过度到5d引起的。发射谱带的尾部扩展到更长的波长(500nm),展示了有效发射低于460nm成为可能。图表2中的曲线(2)说明了Sr3SiO5:Eu2+样品的发射光谱低于460nm激发。这个发射光谱同样展示了561nm峰值的宽带。众所周知Eu2+的发射峰是非常容易被周围的晶体场影响的。由于Sr2O4相在样品中的存在,这个样品与其他报告中的发射峰是不同的。 Fig. 2 Excitation 1 and emission 2 spectra of Sr3Si