Dy3+ emission in M5(PO4)3F (M = Ca, Ba) phosphor

Ultrafine M₅(PO₄)₃F:Dy³⁺ (M = Ca, Ba) phosphors were prepared via combustion process using metal nitrates as precursors. The formation of crystalline phosphate was confirmed by X-ray diffraction pattern. The PL excitation spectra show the excitation peaks observed at 250 to 400 nm due to f → f transition of Dy³⁺ ion, which are useful for solid-state lighting purpose (mercury free excitation). The PL emission of Dy³⁺ ion by 348 nm excitation gave an emission at 489 nm (blue), 582 nm (yellow) and 675 nm (red). All the characteristics of BYR emissions like BGR indicate that Dy doped Ca₅(PO₄)₃F and Ba₅(PO₄)₃F phosphors are good candidates that can be applied in solid-state lighting phosphor (mercury free excited lamp phosphor) and white light LED.      

Photoluminescence and thermoluminescence characterization of Eu- and Dy -activated Ca3(PO4)2 phosphor

Rare-earth-doped polycrystalline Ca₃(PO₄)₂:Eu, Ca₃(PO₄)₂:Dy and Ca₃(PO₄)₂:Eu,Dy phosphors prepared by a modified solid-state synthesis has been studied for its X-ray diffraction, thermoluminescence (TL) and photoluminescence (PL) characteristics. The PL emission spectra of the phosphor suggest the presence of Eu³⁺ ion in Ca₃(PO₄)₂:Eu and Dy³⁺ ion in Ca₃(PO₄)₂:Dy lattice sites. The TL glow curve of the Ca₃(PO₄)₂:Eu compounds has a simple structure with a prominent peak at 228 °C, while Ca₃(PO₄)₂:Dy peaking at 146 and 230 °C. TL sensitivity of phosphors are compared with CaSO₄: Dy and found 1.52 and 1.20 times less in Ca₃(PO₄)₂:Eu and Ca₃(PO₄)₂:Dy phosphors, respectively. The Ca₃(PO₄)₂:Eu,Dy phosphors shows switching behavior under two different excitation wavelengths and enhancement in PL intensity of Dy³⁺ ions were reported. The paper discusses the photoluminescence and thermoluminescence behavior of Eu³⁺ and Dy³⁺ ion in Ca₃(PO₄)₂ hosts, it may be applicable to solid-state lighting as well as thermoluminescence dosimetry applications.     

A novel red-emitting phosphor Ca9Bi(PO4)7:Eu3+ for near ultraviolet white light-emitting diodes

Red phosphors Ca₉Bi_1-x(PO₄)₇:xEu³⁺ (x = 0.06, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80 and 1.00) were synthesized by a conventional solid-state reaction (SSR) route. The X-ray diffraction patterns, photoluminescence spectra, ultraviolet–visible reflection spectroscopy, decay time and the International Commission on Illumination (CIE) chromaticity coordinates of these compounds were characterized and analyzed. The Eu-doped Ca₉Bi(PO₄)₇ phosphors exhibited strong red luminescence which peaks located at 615 nm due to the ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺ ions after excitation at 393 nm. Ultraviolet–visible spectra indicated that the band-gap of Ca₉Bi_0.30(PO₄)₇:0.70Eu³⁺ is larger than that of Ca₉Bi(PO₄)₇. The results indicate that the phosphor Ca₉Bi_0.30(PO₄)₇:0.70Eu³⁺ can be a suitable red-emitting phosphor candidate for LEDs.     

VUV sensitisation of Eu emission by Tb in Ba3Tb(PO4)3-Eu

The luminescence properties of Ba₃Tb_0.9Eu_0.1(PO₄)₃ and Ba₃Gd_0.9Eu_0.1(PO₄)₃ phosphors were studied for excitation over the 120-300 nm wavelength range. It is found that Tb³⁺, which exhibits a strong vacuum-ultraviolet (VUV) absorption band, provides sensitisation of Eu³⁺ emission in this host. This effect can be used to develop phosphors with enhanced conversion efficiency of the VUV radiation into visible light.     

Luminescent properties of KGd1−x(WO4)2:Eux and KGd1−x(WO4)2−y(MoO4)y:Eux phosphors in UV-VUV regions

KGd_1−x(WO₄)_2−y(MoO₄)_y:Eu³⁺_x(0.1?x?0.75, y=0 and 0.2) phosphors are synthesized through traditional solid-state reaction and their luminescent properties in ultraviolet (UV) and vacuum ultraviolet (VUV) regions are investigated. Under 147 nm excitation, these phosphors show characteristic red emission with good color purity. In order to improve their emission intensity, the MoO₄²⁻ (20 wt%) is introduced into the anion of KGd_1−x(WO₄):Eu³⁺_x. The Mo⁶⁺ and Eu³⁺ co-doped KGd(WO₄)₂ phosphors show higher emission intensity in comparison with the singly Eu³⁺-doped KGd(WO₄)₂ in VUV region. The chromaticity coordination of KGd_0.45(WO₄):Eu³⁺_0.55 is (x=0.669, y=0.331), while that of KGd_0.45(WO₄)_1.8(MoO₄)_0.2:Eu³⁺_0.55 is (x=0.666, y=0.334) in VUV region.     

Photoluminescence of double-color-emitting phosphor Ca5(PO4)3Cl:Eu, Mn for near-UV LED

Eu²⁺ activated Ca₅(PO₄)₃Cl blue-emitting phosphors were prepared by the conventional solid state method using CaCl₂ as the chlorine source and H₃BO₃ as flux. The structure and luminescent properties of phosphors depend on the concentrations of Eu²⁺, the amount of CaCl₂ and the usage of the H₃BO₃ flux were investigated systematically. Eu²⁺ and Mn²⁺ Co-doped Ca₅(PO₄)₃Cl with blue and orange double-band emissions were also researched based on the optimal composition and synthesis conditions. The energy transfer between Eu²⁺ and Mn²⁺ was found in the phosphor Ca₅(PO₄)₃Cl:Eu²⁺, Mn²⁺, and the Co-doped phosphor can be efficiently excited by near-UV light, indicating that the phoshor is a potentional candidate for n-UV LED used phosphor.     

Synthesis, structure and luminescence properties of Y(V,P)O4:Eu,Bi phosphors

YVO₄:Eu³⁺-based red-emitting phosphors with the compositions of Y_0.95−xVO₄:0.05Eu³⁺,xBi³⁺ (x=0.01, 0.03, 0.05, 0.07 and 0.09) and Y_0.90(V_1−zP_z)O₄:0.05Eu³⁺,0.05Bi³⁺ (z=0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were synthesized by the high temperature solid-state method. The as-prepared phosphors have the similar tetragonal phase structure and their morphologies varied with the relative content ratio of V to P. The photoluminescence spectra for the as-synthesized phosphors show that a dominant red emission line at around 619 nm, which is due to the Eu³⁺ electric dipole transition of ⁵D₀-⁷F₂, is observed under different excitation wavelengths (254 and 365 nm). Further, the emission intensities of ⁵D₀-⁷F₂ transition upon 365 nm excitation increase sharply owing to the Bi³⁺ doping. Energy transfer process, luminescent lifetime and quantum efficiency for the selected Y_0.90(V_1−yP_y)O₄:0.05Eu³⁺,xBi³⁺phosphors were also studied in detail.     

Dy含量对红色长余辉发光材料Sr3Al2Ｏ6:Eu2＋,Dy3＋性能的影响

采用溶胶凝胶法制备了Sr₃Al₂Ｏ₆:Eu^2＋,Dy^3＋红色长余辉发光材料,利用X射线衍射仪对材料的物相进行了分析,结果表明,1200℃下制备的样品的物相为Sr₃Al₂Ｏ₆,少量的Eu和Dy掺杂没有影响样品的相组成.采用荧光分光光度计、照度计测定了样品的发光特性.结果表明Sr₃Al₂Ｏ关键词： 红色长余辉 3Al₂Ｏ₆')" href="#">Sr₃Al₂Ｏ₆ 溶胶凝胶法     

Synthesis and luminescence properties of red-emitting phosphors NaY0.87Eu0.13(WO4)1.2(MoO4)0.8

A series of NaY_1−yEu_y(WO₄)_2−x(MoO₄)_x (x=0−2 and y=0.06−0.15) phosphors have been prepared by a combustion route. X-ray powder diffraction, photoluminescence excitation and emission spectra were used to characterize the resulting samples. The excitation spectra of these phosphors show the strongest absorption at about 396 nm, which matches well with the commercially available n-UV-emitting GaN-based LED chip. Their emission spectra show an intense red emission at 616 nm due to the ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺. As the Mo content increases, the intensity of the ⁵D₀→⁷F₂ emission of Eu³⁺ activated at wavelength of 396 nm increases and reaches a maximum when the relative ratio of Mo/W is 2:3. The intense red-emission of the tungstomolybdate phosphors at near-UV excitation suggests that the material is a potential candidate for white light emitting diode (WLEDs).     

Synthesis and luminescence properties of Eu, Ce and Tb-activated Sr3La2(BO3)4 under UV excitation

The spectroscopic properties in UV-excitable range for the phosphors of Sr₃La₂(BO₃)₄:RE³⁺ (RE³⁺=Eu³⁺, Ce³⁺, Tb³⁺) were investigated. The phosphors were synthesized by conventional solid-state reactions. The photoluminescence (PL) spectra and commission international de I'Eclairage (CIE) coordinates of Sr₃La₂(BO₃)₄:RE³⁺ were investigated. The f-d transitions of Eu³⁺, Ce³⁺ and Tb³⁺ in the host lattices are assumed and corroborated. The PL and PL excitation (PLE) spectra indicate that the main emission wavelength of Sr₃La₂(BO₃)₄:Eu³⁺ is 611 nm, and Sr₃La₂(BO₃)₄:Ce³⁺ shows dominating emission peak at 425 nm, while Sr₃La₂(BO₃)₄:Tb³⁺ displays green emission at 487, 542, 582 and 620 nm. These phosphors were prepared by simple solid-state reaction at 1000 °C. There are lower reactive temperature and more convenient than commercial phosphors. The Sr₃La₂(BO₃)₄:Tb³⁺ applied to cold cathode fluorescent lamp was found to emit green light and have a major peak wavelength at around 542 nm. These phosphors may provide a new kind of luminescent materials under ultraviolet excitation.     

Emission analysis of RE3+ (Eu3+, Tb3+ & Ho3+): B2O3-BaO-LiF/AIF3 glasses

We report here the luminescence spectra of certain rare earth ions (Eu³⁺, Tb³⁺ & Ho³⁺) doped B₂O₃-BaO-LiF/AiF₃ based on the measurements of emission and decay curves of prominent emission transitions. For both the reference host glasses, FTIR, XRD, DTA-TG profiles have been recorded to understand their structural and thermal properties. Eu³⁺ doped glasses have shown five emission transitions of ⁵D₀ → ⁷F_{01,2,3 & 4} located at 580nm, 593nm, 615nm, 655nm and 704nm respectively with an excitation at λ_exci = 392 nm (⁷F₀ → ⁵L₆). Also under an UV source, these europium glasses have displayed a bright red emission from their surfaces. Tb³⁺ glasses have exhibited four emission bands of ⁵D₄ → ⁷F_6,5,4,3 at 491nm, 547nm, 588nm and 625nm respectively with an excitation at λ_exci = 376 nm (⁷F₆ → ⁵G₆). Intense green emission from the glass surfaces has been noticed upon exposure to the UV source. Prominently bluish-green emission has been noticed from the surfaces of the holmium glasses under an UV source and same emission transition (⁵F₄ → ⁵I₈) at 519 nm with an excitation at λ_exci = 389 nm (⁵I₈ − ⁵G₄) has also been obtained from their measured emission spectra. For all the prominent emissions of the rare earth glasses, decay curves have been measured to compute their lifetimes.     

Combustion synthesis and luminescent properties of a new material Li2(Ba0.99,Eu0.01)SiO4:B for ultraviolet light emitting diodes

Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and particle sizes of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ have been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a bluish green light with peak wavelength of 490 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li₂(Ba_0.99,Eu_0.01)SiO₄ and the optimum molar ratio of boric acid to barium nitrate was about 0.06. The optimized phosphors Li₂(Ba_0.99,Eu_0.01)SiO₄:B_0.06³⁺ showed 160% improved emission intensity compared with that of the Li₂(Ba_0.99,Eu_0.01)SiO₄ phosphors under UV (λ_ex=350 nm) excitation.     

Combustion synthesis and luminescent properties of green-emitting phosphor (Sr, Zn) Al2O4: Eu2+, B3+ for white light emitting diodes (WLED)

In this study, the phosphors (Sr_1−x , Zn _x )_0.9(Al_2−y , B _y )O₄ doped 10 mol % Eu²⁺, were prepared by combustion method as the fluorescent material for white light emitting diodes (WLEDs), performing as a light source. The luminescent properties were investigated by changing the combustion temperature, the boron concentration, and the ratio of Sr to Zn. The luminescence, crystallinity and particle morphology were investigated by using a luminescence spectrometer, X-ray diffractometer (XRD) and transmission electron microscopy (TEM), respectively. The highest intensity of Sr_0.9(Al_2−y , B _y )O₄: Eu_0.1²⁺ phosphor was achieved when the combustion temperature was 600° and the concentration of B³⁺ was 8 mol % of the aluminate. A new blue emission was observed when the high Zn concentration (x ⩾ 0.8), and this blue emission disappeared with the Zn concentration became lower than 0.8. The combustion method synthesized phosphor (Sr_0.6, Zn_0.4)_0.9(Al_1.92, B_0.08)O₄: Eu_0.1²⁺ showed 3.3 times improved emission intensity compared with that of the Sr_0.9(Al_1.92, B_0.08)O₄:Eu_0.1²⁺ phosphor under λ _ex = 390 nm.      

Photoluminescence properties of Eu in Y(PO3)3 under VUV excitation

The photoluminescence properties of Y_1−x(PO₃)₃:xEu³⁺ (0<x≤0.2) are investigated. The excitation spectrum of Y_0.85(PO₃)₃:0.15Eu₃⁺ shows that both the (PO₃)₃³⁻ groups and the CT bands of O²⁻-Y³⁺ can efficiently absorb the excitation energy in the region of 120-250 nm. Under 147 nm excitation, the optimal emissive intensity of Y_1−x(PO₃)₃:xEu³⁺ (0<x≤0.2) is about 36% of the commercial phosphor (Y,Gd)BO₃:Eu³⁺, which hints that the absorbed energy by the host matrix could be efficiently transferred to Eu³⁺. We try to study the concentration quenching mechanism of Y_1−x(PO₃)₃:xEu³⁺ (0<x≤0.2) under 147 and 172 nm excitation.     

Luminescence in Dy<Superscript>3+</Superscript> and Eu<Superscript>3+</Superscript> Activated K<Subscript>3</Subscript>Al<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The Dy³⁺ and Eu³⁺ activated K₃Al₂ (PO₄)₃ phosphors were prepared by a combustion synthesis. From a powder X-ray diffraction (XRD) analysis the formation of K₃Al₂ (PO₄)₃ was confirmed. In the photoluminescence emission spectra, the K₃Al₂(PO₄)₃:Dy³⁺ phosphor emits two distinctive colors: blue and yellow whereas K₃Al₂(PO₄)₃:Eu³⁺ emits red color. Thus the combination of colors gives BYR (blue–yellow–red) emissions can produce white light. These phosphors exhibit a strong absorption between 340 and 400 nm which suggest that present phosphor is a promising candidate for producing white light-emitting diodes (LED).     

Luminescent properties of HTP AgGd1−xW2O8:Eux and AgGd1−x(W1−yMoy)2O8:Eux phosphor for white LED

Intense red phosphors, AgGd_1−xEu_x(W_1−yMo_y)₂O₈ (x=0.0-1.0, y=0.0-1.0), have been synthesized through traditional solid-state reaction and characterized by X-ray diffraction (XRD) and photoluminescence (PL). XRD results reveal that AgGd_1−xEu_xW₂O₈ synthesized at 1000 °C has a tetragonal crystal structure, which is named as high temperature phase (HTP) AgGdW₂O₈. All phosphors compositions with Eu³⁺ show red and green emission on excitation either in the charge-transfer or Eu³⁺ levels. Analysis of the emission spectra with different Eu³⁺ concentrations reveal that the optimum dopant concentration for Eu³⁺ is x=0.6 in the HTP AgGd_1−xEu_xW₂O₈ (x=0.0-1.0). Studies on the AgGd_0.4Eu_0.6(W_1−yMo_y)₂O₈ (y=0.0-1.0) and AgGd_1−xEu_x(W_0.7Mo_0.3)₂O₈ (x=0.0-1.0) show that the emission intensity is maximum for compositions with y=0.3 and x=0.5, respectively, and a decrease in emission intensity is observed for higher y or x values. The Mo⁶⁺ and Eu³⁺ co-doped AgGd(WO₄)₂ phosphors show higher emission intensity in comparison with the singly Eu³⁺-doped AgGd(WO₄)₂ in UV region. The intense emission of the tungstate/molybdate phosphors under 394 and 465 nm excitations, respectively, suggests that these materials are promising candidates as red-emitting phosphors for near-UV/blue GaN-based white LED for white light generation.     

Luminescence and energy transfer in Y2O3 CO-doped with Bi3+ and Eu3+

The emission spectra and decay times of the Y₂O₃ CO-doped with Bi³⁺ and Eu³⁺ have been investigated using site-selective excitation and time-resolved spectroscopy in the temperature range 8–296 K. Evidence for an energy transfer from Eu³⁺(S₆) to Eu³⁺(C₂) is given. The critical transfer distance R₀ = 8.6 Å was found from the decay curve.     

用于白光LED的单一基质白光荧光粉Ca2SiO3Cl2:Eu2+，Mn2+的发光性质

用高温固相法合成了Eu²⁺，Mn²⁺共激活的Ca₂SiO₃Cl₂高亮度白色发光材料，并对其发光性质进行了研究. 该荧光粉在近紫外光激发下发出强的白色荧光，Eu^{2+中心形成峰值为419 nm和498 nm的特征宽带，通过Eu2+中心向Mn2+中心的能量传递导致了峰值为578 nm的发射，三个谱带叠加从而在单一基质中得到了白光. 激发光谱均分布在250—415 nm的波长范围，红绿蓝三个发射带的激发谱峰值分别位于385 nm，412 nm，370 nm和396 nm处，可以被InGaN管芯产生的紫外辐射有效激发. Ca₂SiO₃Cl₂:Eu2+，Mn2+是一种很有前途的单一基质白光LED荧光粉.}     

花状NaY(MoO4)2的合成和(MoO4)2:Eu3+的光学性质

用微波辅助水热-煅烧法成功合成了花状NaY(MoO₄)₂颗粒,用XRD、XPS、FESEM进行了表征,提出了花状NaY(MoO₄)₂颗粒可能的形成机理. 采用相同的方法合成了NaY(MoO₄)₂:Eu³⁺荧光体,该荧光材料在612 nm处有一个强的发射峰,可用作白色发光二极管的红色磷光剂. 此外,微波辅助水热-煅烧法可能发展成为制备其他花状稀土钼酸盐的有效途径.     

A novel Dy3+-doped Gd(PO3)3 white-light phosphors under VUV excitation for Hg-free lamps application

Novel Dy³⁺-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 Gd_1-x(PO₃)₃:xDy³⁺ (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 Dy³⁺ ion from the host absorption. Additionally, the white light phosphor is activated by a single Dy³⁺ ion. Therefore, the luminescence of Gd_1-x(PO₃)₃:xDy (0<x≤ 0.25) under VUV excitation is effective, and it has the promise of being applied to mercury-free lamp.