Photo-luminescence properties and thermo-luminescence curve analysis of a new white long-lasting phosphor: Ca_2MgSi_2O_7:Dy^(3+)

A white long-lasting phosphor Ca2MgSi2O7:Dy3+ was prepared by the solid-state reaction. A strong band peaked at 260 nm was shown in the excitation spectrum of 578 nm emission, which might be attributed to the oxygen deficiency of the host. After irradiated with 254 nm for 4 min, the white afterglow of the sample could be seen for 3 h. Moreover, the depths and frequency factors of trap centers were calculated from the thermo-luminescence curve of the sample, which indicated that the trap centers corresponding to the 414 K band were more helpful to the long-lasting phosphorescence.

A white long-lasting phosphor Y_2O_2S:Tb^(3+), Sm^(3+): an improvement of Y_2O_2S:Tb^(3+)

As an improvement of reported Y2O2S：Tb^3＋, a white-light long-lasting phosphor： Y2O2S：Tb^3＋, Sm^3＋ was prepared by the solid-state reaction. The photo-luminescence spectra showed that the position and shape of Tb^3＋ and Sm^3＋ emissions under UV excitation were similar in this host, which ensured a stable white emission color （daylight standard of IEC） under different excitations. The decay curves of co-doped samples indicated that the decay times of emissions of the two ions were close. The thermo-luminescence measurement suggested that the traps created by the doped Sm^3＋ ions were helpful to postpone the white afterglow of co-doped samples. Therefore, the function of co-doped Sm^3＋ ions was confirmed as improving the white emission colors of samples and acting as new trap centers.

Novel Dy^(3+)-doped Gd(PO_3)_3 white-light phosphors under VUV excitation for Hg-free lamps application

Novel Dy^3＋-doped Gd（PO3）3 white light phosphors each with an orthorhombic system are successfully synthesized by solid-state reaction.The luminescence properties of white-light Gd1-x（PO3）3：xDy^3＋（0 〈 x ≤ 0.25） under vacuum ultraviolet（VUV） excitation are investigated.The strong absorption at around 147 nm in excitation spectrum energy can be transferred to the energy levels of Dy^3＋ ion from the host absorption.Additionally,the white light phosphor is activated by a single Dy^3＋ ion.Therefore,the luminescence of Gd1-x（PO3）3：xDy（0 〈 x ≤ 0.25） under VUV excitation is effective,and it has the promise of being applied to mercury-free lamps.

A Novel White Light Emitting Long-lasting Phosphor

A novel white light emitting long-lasting phosphor Cd1-xDyxSiO3 is reported in this letter. The Dy3+ doped CdSiO3 phosphor emits white light. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254 nm UV irradiation have been removed for about 30 min. In the emission spectrum of 5% Dy3+ doped CdSiO3 phosphor, there are two emission peaks of Dy3+, 580 nm (4F9/26H13/2) and 486 nm (4F9/26H15/2), as well as a broad band emission located at about 410 nm. All the three emissions form a white light with CIE chromaticity coordinates x=0.3874, y=0.3760 and the color temperature is 4000 K under 254 nm excitation. It indicated that this phosphor is a promising new luminescent material for practice application.

Phosphor Converted White Led with Improved CRI

Most of the commercial white LED lamps use blue chip coated with yellow emitting phosphor. YAG:Ce3+ phosphor is coated on blue chip to obtain white light. Though this is commercially successful, there are several drawbacks such as “halo effect”, poor colour rendition, etc. In recent years several efforts have been made to improve LED lamp performance. In this paper modifica-tion of YAG:Ce phosphor for improving CRI, by introducing Gd3+, Pr3+ or Tb3+ at Ce3+ site is reported.

Phosphor-free white light-emitting diodes

The multiple color-matching schemes that could improve the color rendering index for phosphor-free white LEDs are discussed. Then we review a few of the recent research directions for phosphor-free white LEDs, which include the development of monolithic GaN-based white LEDs and hybrid integrated GaN-based and A1GalnP-based white LEDs. These development paths will pave the way toward commercial application of phosphor-free white LEDs in the coming years.

Color-converted remote phosphor prototype of a multiwavelength excitable borosilicate glass for white light-emitting diodes

We report a unique red light-emitting Eu-doped borosilicate glass to convert color for warm white light-emitting diodes. This glass can be excited from 394 nm-peaked near ultraviolet light, 466 nm-peaked blue light, to 534 nm- peaked green light to emit the desired red light with an excellent transmission in the wavelength range of 400-700 nm which makes this glass suitable for color conversion without a great cost of luminous power loss. In particular, when assembling this glass for commercial white light-emitting diodes, the tested results show that the color rendering index is improved to 84 with a loss of luminous power by 12 percent at average, making this variety of glass promising for inorganic ＂remote-phosphor＂ color conversion.

白光LED用Phosphor-in-Glass荧光材料的研究进展

荧光粉/玻璃复合材料(Phosphor-in-Glass,PiG)具有优异的发光性能、导热性和化学稳定性,将有望替代传统白光LED产品中的有机树脂基荧光转换层,同时解决散热、发光效率、品质、眩光、使用寿命等多项技术性难题,具有广阔的市场应用前景。本文从发光性能、透明度、机械强度及批量化生产等方面分析了PiG材料研究过程中出现的关键科学问题,并综述了解决上述问题所采取的针对性措施,包括制备方法(压片烧结法、熔体急冷法、涂膜烧结法)、材料组分设计和荧光粉层结构优化等,从而全面阐述了高性能PiG材料的最新研究现状,最后展望了其未来的研究趋势。

Gd_(2)MgTiO_(6):Dy^(3+)荧光粉的制备与发光性能研究

采用高温固相法制备出一系列Dy^(3+)掺杂双钙钛矿Gd_(2)MgTiO_(6)白色荧光粉样品,通过X射线衍射仪和荧光光谱仪对荧光粉样品的晶体结构及荧光性能进行分析和表征。结果表明:在355 nm近紫外光激发下,样品发出极强的蓝光(484 nm)和黄光(575 nm)。通过调节Dy^(3+)的浓度可以使样品发光颜色向白光区移动,因此Gd_(2)MgTiO_(6):Dy^(3+)是一种可调荧光粉。当Dy^(3+)掺杂浓度为3%时可以发出色坐标为(0.3598,0.3946)的白光。Gd_(2)MgTiO_(6)合成方法简便、组份易调控,是一种具有潜在应用价值荧光材料。

NaYSiO_(4)∶Ce^(3+)蓝色荧光粉的发光性质及其在白光发光二极管上的应用

采用高温固相法合成了NaYSiO_(4)∶xCe^(3+)(0.01≤x≤0.05)系列蓝色荧光粉。NaYSiO_(4)∶xCe^(3+)荧光粉在250~360 nm之间的宽带吸收能与紫外LED芯片很好地匹配。NaYSiO_(4)∶xCe^(3+)荧光粉中存在多个Ce^(3+)离子荧光中心,且在紫外光激发下表现出峰值波长位于414 nm附近的宽带蓝光发射。NaYSiO_(4)∶0.02Ce^(3+)荧光粉在300~350 nm紫外光激发下量子效率在25%以上。NaYSiO_(4)∶0.02Ce^(3+)荧光粉表现出优良的化学稳定性,在水中浸泡14 d后荧光强度和量子效率几乎不变。将NaYSiO_(4)∶0.02Ce^(3+)蓝色荧光粉、商用(Sr,Ba)_2SiO_(4)∶Eu^(2+)绿色荧光粉和商用(Ca,Sr)AlSiN_(3)∶Eu^(2+)红色荧光粉涂覆于310 nm紫外LED芯片上制备得到了显色指数高达95的LED器件。当驱动电流从50 mA逐渐增大到300 mA时,制备的LED器件表现出稳定的暖白光发射,其色坐标几乎不变。上述结果说明,本研究报道的NaYSiO_(4)∶0.02Ce^(3+)蓝色荧光粉在紫外LED芯片驱动的白光发光二极管照明上有着潜在应用价值。

NaCa_(2)Mg_(2)(VO_(4))_(3)∶Eu^(3+)颜色可调荧光粉的熔盐法合成及其发光性能研究

以廉价的NaCl为熔盐,采用熔盐法合成了NaCa_(2-x)Mg_(2)(VO_(4))_(3)∶xEu^(3+)(0≤x≤0.10)系列颜色可调荧光粉,系统研究了合成条件、Eu^(3+)掺杂对样品结构及发光性能的影响。结果表明,反应温度为800℃、反应时间为0.5 h、原料与熔盐的质量比为1∶3是合成NaCa_(2)Mg_(2)(VO4)_(3)的适宜反应条件,所得样品为NaCa_(2)Mg_(2)(VO_(4))_(3)纯相,且结晶度高。样品微观形貌随着反应温度的升高由珊瑚状演变为表面光滑的不规则多面体。Eu^(3+)掺杂对NaCa_(2)Mg_(2)(VO_(4))_(3)的晶体结构影响较小,但对其发光性能影响较大。随着Eu^(3+)浓度(x)的增加,VO_(4)^(3-)的特征发射带强度逐渐减弱;而Eu^(3+)的特征发射峰强度先增大后减小,当x=0.06时,达到最大。故通过改变Eu^(3+)浓度,可对样品的发光颜色进行调制,从绿色可调制为黄绿色、黄色、黄白色、橙红色。荧光光谱与荧光寿命分析表明,NaCa_(2)Mg_(2)(VO_(4))_(3)∶Eu^(3+)体系中存在VO43-到Eu^(3+)的能量转移过程,能量转移效率约为23%;热稳定性分析结果表明,当温度从室温(298.15 K)升高到398.15 K时,NaCa_(1.94)Mg_(2)(VO_(4))_(3)∶0.06Eu^(3+)荧光粉在614 nm处的主发射峰强度可保留起始值的68.4%,表现出良好的热稳定性。

二价阳离子掺杂对钛酸盐基红色荧光粉性能的影响

白光LED以其所具备的环保、省电、效率高、寿命长等优点被广泛使用,而红色荧光粉是其发光所必需的。本文使用高温固相法,在1200℃下烧结4小时,制备了二价阳离子掺杂的CaTiO_(3):Eu^(3+)(CTE)红色荧光粉,研究二价阳离子(Mg^(2+),Zn^(2+))掺杂浓度对钛酸盐基红色荧光粉发光性能的影响。结构分析表明XRD图谱与CaTiO_(3)的标准PDF卡片符合得很好,表明烧结荧光粉为纯度较高的单相物质,具有较好的结晶性。经过一系列分析,结果表明,Mg^(2+)对CaTiO_(3):Eu^(3+)进行掺杂可以改善其发光性能,特别当掺杂浓度为4%时,其发光强度增强了约1.5倍。表明合适的二价阳离子掺杂有利于钛酸盐基红色荧光粉发光性能的提升,对CTE荧光粉的应用具有一定的参考意义。

低蓝光的白光LED制备与评价指标修正

基于GaN基蓝光LED激发荧光粉制备的白光LED已取得广泛应用,然而,照明光源中蓝光成分对人体健康、昼夜节律的影响逐渐受到关注。针对蓝光伤害问题,提出了修正后的蓝光危害占比指数(B_(mr)),以更合理地评估白光光源的蓝光危害指标;针对夜间照明用白光LED对人体昼夜节律的影响,使用商用蓝/紫光LED系统研究了激发波长、以及荧光粉种类和配比对暖白光LED的健康、护眼指标的影响。研究发现,基于410 nm波长紫光LED制备的暖白光LED光源的B_(mr)和褪黑素敏感区间光功率占比指数(M_(r))分别仅为4.2%和9.2%,接近于卤素灯的水平,显著优于商用高品质暖白光LED,为夜间低蓝光舒适护眼、低褪黑素干扰的健康照明提供了新选择。

Y_(0.97)Zr_(1-x)Ti_(x)O_(2):Eu_(0.03)荧光粉的制备及发光特性研究

采用高温固相法成功制备了一系列红色荧光粉Y_(0.97)Zr_(1-x)Ti_(x)O_(2):Eu_(0.03)(x=0.2,04,0.6,0.8,1).并且使用X射线衍射仪对荧光粉进行了物相分析,确定了荧光粉的物相结构.在室温下研究了荧光粉的发射光谱和激发光谱.荧光粉在394 nm近紫外光激发条件下产生了3个强发射峰,峰值全部位于580~620 nm范围内.通过在611 nm监测条件下获得的激发光谱,可以知道荧光粉在280~330 nm范围内以及394 nm和467 nm处具有很强的激发强度,与近紫外白光LED激发范围匹配.研究表明,该荧光粉可用作近紫外白光LED的红色荧光材料,在防伪、太阳能发电及照明等领域具有潜在的应用前景.

白光LED用Phosphor-on-Glass(PoG)材料的制备与表征

采用商业Ce^3+∶YAG荧光粉包埋钇铝硅酸盐玻璃并在该体系玻璃转变温度附近进行烧结的方法,成功制备了荧光粉粘附在玻璃表面上的复合材料(Phosphor-on-Glass,PoG)。利用XRD、SEM和荧光光谱仪等研究了PoG材料的物相、显微结构和变温发光性能。研究结果表明:PoG材料结构为荧光粉/玻璃/荧光粉复合体,Ce^3+∶YAG荧光粉粘附在玻璃上下表面且均匀分布,其形貌与颗粒大小未发生明显变化。固定烧结时间为10h,PoG材料的荧光强度随着烧结温度的增加先增强后减弱;PoG材料的发光抗热淬灭性能较好(热激活能为0.22eV),这说明Ce^3+∶YAG荧光粉的优良发光性能在PoG材料中得到了很好地保存。以PoG材料封装的白光LED样品在100mA电流驱动下,获得白光输出,其中最接近纯白光(0.33,0.33)的LED光效为69.8lm/W,相关色温为5873K,显色指数72.3。由于Ce^3+∶YAG荧光粉缺乏红色发光,尝试在钇铝硅酸盐玻璃基质中掺杂Eu3+以增加红色发光部分,获得光效为52.1lm/W,相关色温为3910K,显色指数75.8的暖白光输出。

Synthesis and luminescent properties of low oxygen contained Eu^(2+)-doped Ca-α-SiAlON phosphor from calcium cyanamide reduction

A new convenient calcium cyanamide （CaCN2） reduction route was developed to synthesize the Eu^2＋ activated Ca-α-SiAION phosphors containing low oxygen content. The luminescence properties of the obtained products were investigated for white LEDs application. The critical Eu^2＋ concentration in various hosts and its effect on the photoluminescence properties were studied. The optimized sample （10at.% Eu^2＋ vs. Ca^2＋） could be efficiently excited by the current GaN/InGaN blue LED chips and provided emission intensity competitive with that of YAG：Ce^3＋ （P46-Y3） standard, revealing that this phosphor was a potential candidate for phosphor-converted white LEDs.

Spherical YAG∶Ce^(3+) Phosphor Particles Prepared by Spray Pyrolysis

Spherical YAG：Ce^3＋ phosphor particles with narrow size distribution were prepared by spray pyrolysis. The effects of the concentration of solution, the flow rate of cartier gas and the annexing temperature on the phosphor morphology were studied. The productivity of precursor particles shows a trend of drop after rising with the increase of concentration Raising the flow rate of nitrogen can improve the productivity of the precursor particles. Phosphor prepared by spray pyrolysis has obviously higher emission intensity than that synthesized by solid state reaction, spray pyrolysis makes Ce^3＋ ions well distributed in the crystal lattice as the luminescent centers, and phosphor particles have regular sphericity and narrow size distribution.

Effect of fluxes on structure and luminescence properties of Y_3Al_5O_(12):Ce^(3+) phosphors

Ce3＋-activated yttrium aluminum garnet （YAG） was prepared by the solid-state reaction, in which H3BO3, LiF, NaF, KF and BaF2 were used as the fluxes. The effect of fluxes on optical properties of phosphors was studied in detail, especially the fluxes of alkali fluorides, which could enhance the emission intensity and change the wavelength of emission peaks. Among these YAG：Ce phosphors, the phosphor sintered with H3BO3 and NaF exhibited the strongest emission. The emission peaks of phosphors prepared with fluxes from LiF to KF were shifted to long wavelength. The effect of NaF concentration on the emission intensity of YAG：Ce was also investigated. The value of emission intensity reached the maximum when the concentration of NaF was 0.5%.

Photoluminescence Characteristics of Gd_2Mo_3O_9:Eu Phosphor Particles by Solid State Reaction Method

Eu^3＋-doped Gd2Mo3O9 was prepared by solid-state reaction method using Na2CO3 as flux and characterized by powder X-ray diffractometry. According to X-ray diffraction, this material belonged to a tetragonal system with space group I41/α. The effects of flux content and sintering temperature on the luminescent properties were investigated with the emission and excitation spectra. The results showed that flux content and sintering temperature had effects on the luminescent properties, the optimized flux content and the best temperature was 3 % and 800 ℃ respectively. The excitation and emission spectra also showed that this phosphor could be effectively excited by C-T band （280 nm）, ultraviolet light 395 nm and blue light 465 nm. The wavelengths at 395 and 465 nm were nicely fitting in with the widely applied output wavelengths of ultraviolet or blue LED chips. Integrated emission intensity of Gd2Mo3O9 ： Eu was twice higher than that of Y2O2S ： Eu^3 ＋ under 395 nm excitation. The Eu^3＋ doped Gd2Mo309 phosphor may be a better candidate in solid-state lighting applications.