白光LED用黄色荧光粉Ba(Y1-0.5x-yAly)2S4:xHo3+的合成和发光特性

采用高温固相法合成了Ba(Y1-0.5x-yAly)2S4:xHo3+系列荧光粉。在465 nm蓝光激发下,荧光粉的发射光谱呈多谱带发射,主峰位于492、543和661 nm处,分别对应于Ho3+的5F3→5I8,(5S2,5F4)→5I8和5F5→5I8跃迁发射。研究了Ho3+和Al3+掺杂量对BaY2S4:Ho3+发光性能的影响。结果表明,随着Ho3+掺杂量的逐渐增大,荧光粉的发光颜色由绿色逐渐向红色转变;适量Al3+取代Y3+可以提高BaY2S4:Ho3+荧光粉的发光强度。荧光粉Ba(Y0.665Al0.3)2S4:0.07Ho3+在蓝光(465 nm)激发下发射黄光,是一种潜在的白光LED用黄色荧光粉。     

Emission analysis of Sm(3+) and Dy(3+):MgLaLiSi(2)O(7) powder phosphors

This paper reports on the structural and emission properties of newly synthesized Sm(3+) and Dy(3+):MgLaLiSi(2)O(7) powder phosphors based on the measurement of their XRD, SEM, FTIR and photoluminescence spectra. Emission spectra of the Sm(3+):MgLaLiSi(2)O(7) phosphors with lambda(exci)=402 nm ((6)H(5/2)-->(4)F(7/2)) and Dy(3+):MgLaLiSi(2)O(7) phosphors with lambda(exci)=385 nm ((6)H(15/2)-->(4)I(13/2)) have been analyzed. Emission mechanisms of these phosphors have also been explained.     

Dy3+,Eu3+双掺单基质Ca9Y(PO4)7白色荧光粉的合成与发光性能

以具有多种格位的Ca9Y(PO4)7作为基质, 以Dy3+和Eu3+作为共激活剂, 利用高温固相法合成了一种单基质白光荧光粉. X射线衍射证实样品属于三方晶系菱面体结构, Dy3+和Eu3+在Ca9Y(PO4)7晶体中占据了Y3+ 的格位. 样品在365 nm紫外线激发下, 荧光光谱同时出现了Dy3+和Eu3+的特征发射, 且发光强度以及色度坐标随着Dy3+和Eu3+掺杂比率的变化而有规律变化, 所有样品的发射均处于白光区域. 利用近紫外芯片作为激发源, 单一基质白色荧光粉Ca9Y1-x-y(PO4)7: xDy3+, yEu3+可应用于白光发光二极管等领域.     

Recent Research Progress of Red Phosphors for PDPs Applications

The commercial vacuum ultraviolet (VUV) red phosphor (Y, Gd)BO₃:Eu³⁺ has low luminous efficiency and poor color purity. Our work aims to overcome this drawback and we mainly devote to investigating the luminescence mechanism, improving the commercial red phosphor, and seeking for new red emitting VUV materials with high efficiency. Based on the investigation of the photoluminescence mechanism of VUV phosphors, both the luminous efficiency and the color purity of (Y, Gd)BO₃:Eu³⁺ are improved. Additionally, a series of novel VUV red phosphors have been developed, such as (Gd,Y)Al₃(BO₃)₄:Eu³⁺ and (La,Gd)P₃O₉:Eu³⁺. This presentation is a review about the recent research progress of red phosphors for plasma displays (PDPs) applications in our group.     

Vacuum Ultraviolet Excited Photoluminescence Properties of Y2O2S：Eu^3＋,Bi^3＋ Phosphor

As an Hg-free lamp using phosphor, the Bi3+ and Eu3+ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet(VUV) excitation were investigated. The VUV photoluminescent intensity of Y2O2S:Eu3+ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S:Eu3+,Bi3+ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S:Eu3+,Bi3+ at 147 nm is mainly because the Bi3+ acts as a med...     

磷灰石结构荧光粉Ba10(PO4)6F2:Ce3+,Tb3+的合成、发光和能量传递

采用高温固相法合成了系列Ce~(3+)和Ce~(3+)/Tb~(3+)激活的具有磷灰石结构荧光粉Ba_(10)(PO_4)_6F_2。用X射线衍射(XRD)、扫描电镜(SEM)、激发和发射(PLE和PL)光谱对样品进行了表征分析。研究结果表明:所合成的荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)具有氟磷灰石结构,样品微观呈现不规则形貌。荧光粉Ba10-x(PO4)6F2∶x Ce~(3+)的相对发射强度随着x增加而增强,当x=0.09时,荧光强度达到最大。荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的激发光谱为240～330 nm的宽带,发射光谱呈现出Ce~(3+)的5d→4f跃迁紫外光(335和358 nm)发射和Tb~(3+)的4f→4f跃迁绿光(542 nm)发射。光谱特性表明,发光过程中存在Ce~(3+)→Tb~(3+)能量传递,能量传递效率可以达到60%。计算Ce~(3+)和Tb~(3+)的临界距离为0.79 nm,能量传递机理是偶极-偶极交互作用。此外,详细论述了Ce~(3+)和Tb~(3+)之间的能量传递和发光的过程。通过调节Tb~(3+)的掺杂浓度,对荧光粉发光色坐标与Tb~(3+)的掺杂浓度之间的关系也进行了研究,随着Tb~(3+)的掺杂量从0增加0.52,荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的发射光谱色坐标可以从(0.149 4,0.045 1)蓝色区变化到(0.280 1,0.585 3)绿色区。     

Synthesis, structure, and thermally stable luminescence of Eu(2+)-doped Ba2Ln(BO3)2Cl (Ln = Y, Gd and Lu) host compounds

A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction. The crystal structure and thermally stable luminescence of chloroborate phosphors Ba(2)Ln(BO(3))(2)Cl:Eu(2+) (Ln = Y, Gd, and Lu) have been reported in this paper. X-ray diffraction studies verify the successful isomorphic substitution for Ln(3+) sites in Ba(2)Ln(BO(3))(2)Cl by other smaller trivalent rare earth ions, such as Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. The detailed structure information for Ba(2)Ln(BO(3))(2)Cl (Ln = Y, Gd, and Lu) by Rietveld analysis reveals that they all crystallize in a monoclinic P2(1)/m space group. These compounds display interesting and tunable photoluminescence (PL) properties after Eu(2+)-doping. Ba(2)Ln(BO(3))(2)Cl:Eu(2+) phosphors exhibit bluish-green/greenish-yellow light with peak wavelengths at 526, 548, and 511 nm under 365 UV light excitation for Ba(2)Y(BO(3))(2)Cl:Eu(2+), Ba(2)Gd(BO(3))(2)Cl:Eu(2+), and Ba(2)Lu(BO(3))(2)Cl:Eu(2+), respectively. Furthermore, they possess a high thermal quenching temperature. With the increase of temperature, the emission bands show blue shifts with broadening bandwidths and slightly decreasing emission intensities. It is expected that this series of chloroborate phosphors can be used in white-light UV-LEDs as a good wavelength-conversion phosphor.     

The quantum cutting of Tb(3+) in Ca(6)Ln(2)Na(2)(PO(4))(6)F(2) (Ln = Gd, La) under VUV-UV excitation: with and without Gd(3+)

The VUV-vis spectroscopic properties of Tb(3+) activated fluoro-apatite phosphors Ca(6)Ln(2-x)Tb(x)Na(2)(PO(4))(6)F(2) (Ln = Gd, La) were studied. The results show that phosphors Ca(6)Gd(2-x)Tb(x)Na(2)(PO(4))(6)F(2) with Gd(3+) ions as sensitizers have intense absorption in the VUV range. The emission color of both phosphors can be tuned from blue to green by changing the doping concentration of Tb(3+) under 172 nm excitation. The visible quantum cutting (QC) via cross relaxation between Tb(3+) ions was observed in cases with and without Gd(3+). Though QC can be realized in phosphors Ca(6)La(2-x)Tb(x)Na(2)(PO(4))(6)F(2), we found that Gd(3+)-containg phosphors have a higher QC efficiency, confirming that the Gd(3+) ion indeed plays an important role during the quantum cutting process. In addition, the energy transfer process from Gd(3+) to Tb(3+) as well as (5)D(3)-(5)D(4) cross relaxation was investigated and discussed in terms of luminescence spectra and decay curves.     

Spectral Property and Thermal Quenching Behavior of Tb3+-Doped YAG∶Ce Phosphor

A series of YAG:Ce,Tb phosphors were synthesized by vacuum sintering method.Moreover,their spectral properties,thermal quenching behaviors and color rendering properties were investigated systematically.The photoluminescence emission spectra of YAG:Ce,Tb show a great red shift compared with that of YAG:Ce.Direct energy transfer from Tb~(3+) to Ce~(3+) ions is verified based on the analysis of different photoluminescence spectra.The quenching temperature for Tb~(3+)-doped YAG:Ce phosphors is about 490 K.The thermal activation energy is estimated to be 0.18 and 0.291 eV for Tb~(3+)-doped YAG:Ce and YAG:Ce phosphors,respectively.The smaller activation energy for Tb~(3+)-doped YAG:Ce means a more rapid nonradiative transition from 5d to 4f state,thus resulting in the lower quenching temperature.In addition,white LEDs with improved color rendering properties are achieved by using modified YAG:Ce,Tb phosphors.     

LED用Sr(1-1.5x)Mo0.8Si0.2O3.8:Eu3+x红色荧光粉的制备及其荧光性能

通过高温固相法合成了LED用红色荧光粉Sr(1-1.5x)Mo0.8Si0.2O3.8∶Eu3+x（x=0.1,0.2,0.3,0.4,0.5）。 通过XRD、激发光谱和发射光谱测试了材料的物相组成以及发光性能。 x=0.1样品的XRD谱与JCPDS 08-0482(SrMoO4)的标准卡片相同。 Eu3+代替晶格中Sr2+的位置成为发光中心。 随着Eu3+含量x的增加,593 nm处的5D0-7F1跃迁和614 nm处的5D0-7F2跃迁发射强度会相互转换：当x≤0.4时,以磁偶极5D0-7F1跃迁为主,发射橙色光;而当x=0.5时,以电偶极5D0-7F2跃迁发射为主,发射红光。 可能是过量掺杂的Eu3+离子,只能存在于晶格空位形成缺陷,无法占据SrMoO4中Sr2+的格位中,Eu3+在晶格中占据非对称中心的格位,导致电偶极跃迁变成允许跃迁,从而增加了5D0-7F2跃迁,减弱了5D0-7F1跃迁。 因此,可以通过调节激活剂的含量获得不同发光色的荧光粉。 Eu3+掺杂的硅钼酸锶体系,614 nm激发下,在368 nm处出现宽的基质吸收峰和467 nm处7F0-5D2的跃迁峰,且这2处的吸收峰在x=0.5时比x=0.4时强3倍左右。 材料能非常好的吸收368 nm波长的光,产生颜色可调的橙红色。 与近紫外光LED芯片匹配良好。     

Luminescence in Zinc Selenide Doped with Sn and (Sn,Dy) Phosphors

Zinc selenide doped with Sn and (Sn, Dy) phosphors has been prepared by firing the samples in an atmosphere of nitrogen gas. The voltage and frequency dependence of electrolyte brightness has been studied. Voltage dependence of electroluminescence (EL) brightness reveals an acceleration collision mechanism in the Schottky barrier at the metal–semiconductor interfaces. EL and photoluminescence (PL) spectra and thermoluminescence (TL) glow curves of these phosphors have also been recorded to understand the nature and mechanism involved in the luminescence process. The trapping parameters are calculated for the glow curves of these phosphors.     

Y(P,V)O4:Dy phosphors for white light generation: Emission dynamics and host effect

The structural characteristics and optical spectra of Y(P,V)O₄:Dy³⁺phosphors obtained by solid state reaction, sol-gel and hydrothermal routes have been investigated and compared. The luminescence features of these materials show a complicate dependence on the composition, synthetic method and excitation conditions. The emission performance depends on different effects: host luminescence, energy transfer to the doping ions and host dependence of the Dy³⁺ emission properties. These effects have been rationalized in order to provide useful information for the development of a suitable material for the white light emitting phosphors technology.     

Fluorescence spectra of Tb3+-doped dual lanthanide oxyhalide powder phosphors

This short note presents the chemical preparation and recording of the fluorescence spectra of a new series of Tb³⁺-doped (La, Gd)OF, (La, Gd)OCl, (La, Y)OF and (La, Y)OCl powder phosphors. These phosphors have displayed green colour emission when irradiated with UV light. The measured fluorescence levels have been characterized by determining their stimulated emission cross-sections.     

Combinatorial study of the optimization of Y2O3:Bi,Eu red phosphors

The present investigation aims at the synthesis of (Y2-xEuxBiy)O3 red phosphor materials using the combinatorial chemistry method. We developed square-type arrays consisting of 90 compositions to obtain the optimum composition of co-dopants in a Y2O3 host. The optimized composition was found to be (Y2-xEuxBiy)O3 (x = 0.16-0.18, y = 0.08-0.10). The screening of the compositions was investigated by analysis of the emission spectrum under 365 nm UV excitation arising from the energy transfer between Bi3+ and Eu3+ ions. The results of the photoluminescence excited by ultraviolet agree well with the conventional-scale synthesis results, indicating that the combinatorial screening method is fast, reliable, reproducible, and applicable to the study of powder materials with relatively quick calcinations at high synthesis temperatures.     

Photoluminescence of Eu-doped triple phosphate Ca8MgR(PO4)7 (R=La, Gd, Y)

Eu³⁺-doped triple phosphate Ca₈MgR(PO₄)₇ (R=La, Gd, Y) was synthesized by the general high-temperature solid-state reaction. Excitation and emission spectra as well as luminescence decay were used to characterize the phosphors. Photoluminescence excitation and emission spectra showed that the phosphor could be efficiently excited by UV-vis light from 260 to 450 nm to give bright red emission assigned to the transition (⁵D₀→⁷F₂) at 612 nm. The richness of the red color has been verified by determining their color coordinates (X, Y) from the CIE standard.     

SiO2凝胶中铕(铽)-间甲基苯甲酸-邻菲咯啉配合物的热稳定性及发光性能研究

采用溶胶 凝胶法 ,以掺杂方式制备了含有铕 (铽 ) 间甲基苯甲酸 邻菲咯啉配合物的SiO2凝胶复合发光体 ,研究了其热分解曲线、激发光谱和发射光谱 ,并与固体粉末进行了比较 ,讨论了将配合物引入该凝胶后对其热稳定性及发光的影响。     

Photoluminescence characterization of Ca10Na(PO4)7:Eu3+ red-emitting phosphor

Eu3+-doped Ca10Na(PO4)7 phosphors were successfully synthesized by solid-state reaction techniques. Their structures and photoluminescence characteristics were carefully studied. An efficient red emission under near-ultraviolet excitation is observed. The maximum intensity of luminescence was observed at the Eu3+ concentration around 9 mol%. The quadrupole-quadrupole interaction between Eu3+ ions is the dominant mechanism for concentration quenching of fluorescence emission from Eu3+ ions in Ca10-xNa(PO4)7:xEu3+. Due to the excitation spectrum is well coupled with near UV light, Ca10-xNa(PO4)7:xEu3+ phosphors have potential application as red phosphors in near UV chip-based white light emitting diodes.     

High temperature optical spectroscopy of cubic holmium doped zirconia, Zr(0.78)Y(0.21)Ho(0.01)O(1.90)

The electronic absorption spectra of a Zr(0.78)Y(0.21)Ho(0.01)O(1.90) single crystal have been measured in in situ conditions between room temperature and 1289 K. The evolution of the spectra with rising temperatures is characterised by an overall increase in intensity. Notably the intensities of the (5)I(8) --> (5)F(2), (5)I(8) --> (5)S(2) and (5)I(8) --> (5)G(6) transitions increase by factors of two to three. The evaluation of the spectral parameters favours the conclusion that the intensity increases are due to vibronic coupling associated with effective frequencies ranging between 1 x 10(13) and 5 x 10(13) s(-1) (330 cm(-1) and 1670 cm(-1)). The changes in the optical spectra are reversible and are not connected with structural changes in the material.     

Synthesis and cofluorescence of Eu(Y) complexes with salicylic acid and o-phenanthroline

A series of dinuclear complexes of salicylic acid (HSal) and o-phenanthroline (Phen) with different molar ratios of Eu3+ to Y3+ have been synthesized. Their compositions are Eu(x)Y(1-x) (Sal)3(Phen) (x = 0 to approximately 1). Their UV spectra, IR spectra, and fluorescence spectra were studied. The UV spectra of the complexes reflect essentially absorption of the ligands for the fact that no obvious change of wavelength and band shape is found between the spectra of the complexes and that of the ligands except slight red shift. The IR absorption spectra indicate that salicylic acid is coordinated to the rare earth ions and chemical bonds are formed between rare earth ions and nitrogen atoms of o-phenanthroline. The fluorescence spectra of the complexes indicate that the fluorescence emission intensity of europium ion was enhanced by the addition of Y3+, which is referred to as cofluorescence. These facts show that not only the ligands but also the yttrium complex can transfer the absorbed energy to Eu3+ ion in the complexes. Formation of polynuclear complexes appears to be responsible for cofluorescence.     

One-step low-temperature solid-state synthesis of lead-free cesium copper halide Cs3Cu2Br5 phosphors with bright blue emissions

The development of new efficient and environmental-friendly inorganic phosphors is highly important for phosphor-converted white light-emitting diodes and optoelectronic displays. In this paper, we report a novel and simple one-step solid-state reaction to synthesize lead-free cesium copper halide Cs₃Cu₂Br₅ powders with bright blue emission around 460 nm. The preparation process is performed at low calcination temperatures (290–320 °C) and requires no complex apparatus, reagents, or techniques, and thus it holds great potential for mass production of halide emitters. The Cs₃Cu₂Br₅ powder phosphors are characterized by X-ray diffraction, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, photoluminescence excitation and emission spectroscopy, CIE color coordinates, color purity, photoluminescence quantum yield, and temperature-dependent emission spectra. The effect of calcination temperature on the photoluminescence properties of the as-prepared Cs₃Cu₂Br₅ blue phosphors has been investigated and the air-stability property has also been discussed. Impressively, Cs₃Cu₂Br₅ blue phosphors show outstanding stability toward air exposure exceeding one month (30 days). Our work will open a new and simple approach to obtain excellent halide emitters for future solid-state lighting and displays.