Thermoluminescence studies of UV-irradiated Y2O3:Eu3+ doped phosphor

The present paper reports thermoluminescence (TL) glow curves of Eu³⁺-doped Y₂O₃ phosphor with different ultraviolet (UV) exposure times. The glow peak shows second-order kinetics of Eu³⁺-doped Y₂O₃, and corresponding kinetic parameters were evaluated using the peak shape method. Calculations of trap depth were carried out using different methods. The kinetics order, activation energy, and frequency factor were calculated. The recorded glow curve shifts towards higher intensity with longer UV exposure. The heating rate used for recording TL was 3.0 °C s^?1. Particle size and structure were verified by X-ray diffraction (XRD) pattern and morphology by scanning electron microscopy (SEM) imaging.     

Synthesis, characterization and photoluminescence properties of CaSiO3:Eu3+ red phosphor

CaSiO3:Eu3+ (1-5 mol%) red emitting phosphors have been synthesized by a low-temperature solution combustion method. The phosphors have been well characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical spectroscopy. PXRD patterns reveal monoclinic CaSiO3 phase can be obtained at 900°C. The SEM micrographs show the crystallites with irregular shape, mostly angular. Upon 254 nm excitation, the phosphor show characteristic fluorescence 5D0→7FJ (J=0, 1, 2, 3, 4) of the Eu3+ ions. The electronic transition located at 614 nm corresponding to 5D0→7F2 of Eu3+ ions, which is stronger than the magnetic dipole transition located at 593 nm corresponding to 5D0→7F1 of Eu3+ ions. Different pathways involved in emission process have been studied. Concentration quenching has been observed for Eu3+ concentration>4 mol%. UV-visible absorption shows an intense band at 240 nm in undoped and 270 nm in Eu3+ doped CaSiO3 which is attributed to oxygen to silicon (O-Si) ligand-to-metal charge-transfer (LMCT) band in the SiO3(2-) group. The optical energy band gap is widened with increase of Eu3+ ion dopant.     

白光LED用红色荧光粉CaMoO4：Eu^3＋的制备及发光性能研究

采用柠檬酸溶胶-凝胶法制备了CaMoO4: Eu3 荧光粉,对前驱体进行了差热(DSC)分析,对样品进行了X-射线衍射(XRD)、粒度分析和荧光光谱测定. DSC 和XRD结果表明,在700℃时可得到CaMoO4纯相.粒度分析结果表明随着烧结温度的升高,产物的粒径明显增大,700℃时约为 160 nm,而用固相法在800℃制备的CaMoO4: Eu3 荧光粉的平均粒径明显增大至3μm左右.分别以393 nm 的近紫外光和 464 nm 的可见光激发样品,CaMoO4: Eu3 荧光粉发出明亮的红光,对应于Eu3 的4f - 4f跃迁,当Eu3 的掺杂浓度约为30 mol %时,在616 nm处的发光强度最大.在393,464 nm的吸收分别与目前应用的紫外光和蓝光LED芯片相匹配.因此,这种荧光粉是一种可能应用在白光LED上的红色荧光材料.     

Preparation, characterization and photoluminescence properties of BaB2O4: Eu3+ red phosphor

A new red emitting BaB2O4: Eu3+ phosphor was synthesized by solid-state reaction method. X-ray powder diffraction (XRD) analysis confirmed the monoclinic formation of BaB2O4. Field-emission scanning electron-microscopy (FE-SEM) observation indicated that the microstructure of the phosphor consisted of irregular grains with heavy agglomerate phenomena. Upon excitation with 394 nm light, the BaB2O4: Eu3+ phosphor shows bright red emissions with the highest photoluminescence (PL) intensity at 611 nm due to 5D0→7F2 transitions of Eu3+ ions. The CIE chromaticity coordinates are calculated from the emission spectrum to be x=0.64, y=0.35. The effects of the Eu3+ concentration on the PL were investigated. The results showed that the optimum concentration of Eu3+ in BaB2O4 host is 6 mol% and the dipole-dipole interaction plays the major role in the mechanism of concentration quenching of Eu3+ in BaB2O4: Eu3+ phosphor. The effect of charge compensation on the emission intensity was also studied. The charge compensations of Li+, Na+ and K+ anions all increased the luminescent intensity of BaB2O4: Eu3+. K+ anion gave the best improvement to enhance the intensity of the emission, indicating K+ is the optimal charge compensator. All properties show that this phosphor could serve as a potential candidate for application as a red phosphor for NUV chip LED.     

Preparation of Y2O3:Eu3+ nanoparticles in reverse micellar systems and their photoluminescence properties

Y2O3:Eu3+ phosphor nanoparticles (4-8 nm in size) with spherical morphology and narrow size distribution were obtained by calcination of composite Y-Eu hydroxide nanoparticles, which were prepared in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane or polyethylene glycol mono-4-nonylphenyl ether (NP-5)/cyclohexane reverse micellar systems. This was achieved by the incorporation of the Y-Eu hydroxide nanoparticles into polyurea (PUA) via in situ polymerization of hexamethylene diisocyanate (HDI) in the reverse micellar solution and subsequent calcination of the resulting PUA materials. The emission intensity of the Y2O3:Eu3+ nanoparticles, prepared in the AOT/isooctane system, was significantly lower than that of the micrometer-size particles prepared in a homogeneous aqueous solution, since the calcined nanoparticles contained Na2SO4 impurity derived from the remaining AOT surfactant. The nanoparticles prepared in the NP-5/cyclohexane system, in contrast, showed higher emission intensity compared to the nanoparticles prepared in the AOT/isooctane system and longer luminescence lifetime compared to the micrometer-size particles prepared in the homogeneous aqueous solution. The photoluminescence intensity of Y2O3:Eu3+, prepared via the proposed process was found to decrease with decreasing the particle size.     

掺铕Y2O3发光薄膜的制备及发光性能

溶胶-凝胶法;荧光;掺铕Y2O3发光薄膜的制备及发光性能     

Preparation and photoluminescence properties of Y2SiO5:Eu3+ nanocrystals

The sol-emulsion-gel method is used for the preparation of about 5-7 nm size Eu2O3 doped and coated Y2SiO5 nanoparticles at 1300 degrees C. Here, we report the role of surface coating, dopant concentration and temperature of heating on the modification of crystal structure and the photoluminescence properties of Y2SiO5:Eu3+ nanocrystals. It is found that photoluminescence properties are sensitive to the crystal structure which is again controlled by surface coating, concentration and heating temperature. The decay times are 0.76, 1.14, 1.23 and 1.40 ms for 0.25, 0.5, 1.0 and 2.5 mol% Eu2O3 doped Y2SiO5 nanocrystals prepared at 1100 degrees C (X1-Y2SiO5). However, in X2-Y2SiO5 crystal phase (at 1300 degrees C) the average decay times are 1.05, 1.35, 1.55 and 1.60 ms for 0.25, 0.5, 1.0 and 2.5 mol% Eu2O3 doped Y2SiO5 nanocrystals, indicating the photoluminescence properties depend on both the crystal structure and the concentration of ions. The emission intensity of the peak at 612 nm (5D0-->7F2) of the Eu3+-ions is found to be sensitive to the doping and surface coating of Y2SiO5 nanocrystals. The decay times are 1.55 and 1.70 ms for 1300 degrees C heated 1.0 mol% Eu2O3 doped and coated Y2SiO5 nanocrystals, respectively. Our analysis suggests that the site symmetry of ions plays a most important role in the modification of radiative relaxation mechanisms and as a result on the overall photoluminescence properties.     

Fabrication and photoluminescent characteristics of La2O3:Eu3+ nanowires

One-dimensional La(2)O(3):Eu(3+) nanowires (NWs) and sub-micrometer samples (SMs) were fabricated by a hydrothermal method. Their photoluminescent characteristics were studied and compared. The results indicated that the exciton band in NWs blue-shifted in contrast to SMs. In comparison with the charge transfer (CT) band, the relative intensity of the exciton band in NWs was lower than that in SMs, which was attributed to the more energy transfer from the exciton band to surface defects. Frequency-selective-excitation spectra indicated that there existed three symmetry sites of Eu(3+) ions in NWs and two sites in SMs. The results of the temperature dependence of (5)D(1)-(7)F(2) lifetimes indicated that the electronic radiative rate of (5)D(1)-Sigma(7)F(J) in the two samples had hardly any variation and the nonradiative transition rate of (5)D(1)-(5)D(0) in NWs increased slightly.     

纳米晶Y_2O_3∶Eu~(3+)的合成及其热分析动力学

以Y(NO3)3、Eu2O3、CO(NH2)2为原料,使用超声波作用下的均匀沉淀法合成了纳米晶荧光粉Y2O3∶Eu3+。利用不同升温速率的热重及差热分析研究了纳米晶Y2O3∶Eu3+的合成动力学及晶粒生长动力学。研究表明,纳米晶Y2O3∶Eu3+的前驱体分解过程可分为3个步骤,利用Doyle-Ozawa法和Kissinger法分别计算了各个反应阶段的表观活化能,用Kissinger法确定每个反应阶段的反应级数和频率因子,并给出了各个阶段的动力学方程。根据晶粒生长动力学理论计算纳米荧光粉Y2O3∶Eu3+晶粒生长活化能为17.80kJ·mol-1,表明热处理过程中纳米晶粒的长大为扩散生长机制。     

静电纺丝技术制备Y2O3:Eu3+纳米带及其发光性质

采用静电纺丝技术制备了PVP/[Y(NO3)3+Eu(NO3)3]复合纳米带,将其进行热处理,获得了Y2O3:Eu3+纳米带.采用XRD、FTIR、SEM、TEM、荧光光谱等技术对焙烧后的样品进行了表征.结果表明:600℃焙烧即可获得Y2O3:Eu3+纳米带,800 ℃时结晶更为良好,产物属于立方晶系.纳米带表面光滑,由平均直径为30 nm的小颗粒紧密排列而成,为多品结构.随着温度升高,纳米带宽度减小.焙烧800 ℃获得的Y2O3:Eu3+纳米带的发光性质优于焙烧600℃的Y2O3:Eu3+纳米带.与体材料相比,该纳米带的激发光谱Eu3+-O2-电荷迁移态(CTB)发生红移,发射光谱发生蓝移.     

Y2O3:Eu3+纳米线阵列的制备与表征

Y2O3:Eu3+红色荧光粉由于色纯度高、化学性质稳定和量子效率接近100%而广泛用于荧光灯和投影电视等方面.近年来,Y2O3:Eu3+的大量研究工作主要集中于纳米粉末的制备方法及其与体相材料不同的发光特性[1～3].最近,有关Y2O3:Eu3+及其稀土化合物的纳米管、纳米线和纳米带一维材料的制备成为研究热点.Wu Changfeng等[4,5]利用表面活性剂合成了Y2O3 : Eu3+纳米管.激光格位选择激发测试结果表明,Eu3+在纳米管中占据3个不同的格位,其611 nm处的红色发光峰出现了宽化.He Yu等[6]采用水热法及退火处理制备出了Y2O3:Eu3+纳米带,发现Eu3+的发射峰不仅宽化,而且出现了625 nm的新峰.Li Yadong等[7～9]采用水热法制备了稀土氧化物、硫氧化物和氢氧化物等的纳米线和纳米管,并探索了其形成机理,同时发现Y2O3S : yb3+,Er3+具有上转换的性质.     

Synthesis and properties of europium-based phosphors on the nanometer scale: Eu2O3, Gd2O3:Eu, and Y2O3:Eu

Nanocrystals of oxides containing europium as the main constituent or as a doping element in RE2O3 ( RE=Y, Gd) have been prepared by direct oxide precipitation in high-boiling polyalcohol solutions and characterized by high-resolution TEM, absorption spectroscopy, and luminescence spectroscopy. The samples obtained consisted of concentrated and colloidally stable suspensions of luminescent oxide nanoparticles with an average grain diameter in the range 2-5 nm. The nanoparticles were found to be highly crystalline despite their ultrasmall size and the low temperature of 180 degrees C applied during the synthesis. Upon UV excitation, the red luminescence relative to the 5D0-->7Fn transition within the cubic form of RE2O3 exhibits some important differences from that usually found in bulk materials.     

水热法制备具有光滑表面的球形Y2O3∶Eu3+发光材料

The spherical Y₂O₃∶Eu³⁺ luminescent particles with size of 0.5～3 μm and smooth surface were synthesized by hydrothermal method. The resulted Y₂O₃∶Eu³⁺ precursors and the calcined particles were characterized by differential thermal analysis (DTA) and thermogravimetric (TG) analysis, X-ray diffraction (XRD), Fourier-transform IR spectroscopy (FTIR), scanning electron microscopy (SEM) and photoluminescence spectra (PL). FTIR, TG-DTA, XRD measurements show that the precursors are crystal with hydroxyl and carbonate group, and the pure cubic yttria is obtained after annealing above 700 ℃. The SEM images indicate that the Y₂O₃∶Eu³⁺ particles are in spherical shape and with smooth surface. PL analysis shows that the particles present characteristic red emission of Eu³⁺.     

热分解法制备Y_2O_2S∶Eu~(3+)纳米粒子(英文)

采用热分解法和硫熔法分别合成了纳米Y2O2S∶Eu3+和体相Y2O2S∶Eu3+。其中硫氧化钇纳米粒子的制备是以水热法合成的Y(OH)3为前驱体,随后在激活剂和硫的共同作用下焙烧得到的。结果表明,所得Y2O2S∶Eu3+为单一纯相纳米粒子,粒径分布集中,大小约80nm,而前驱体Y(OH)3为纳米棒状,形貌上的这一巨大变化是由激活剂和硫粉在高温煅烧过程所形成的熔融物的腐蚀作用造成的。荧光光谱分析表明,Eu3+能有效地掺入硫氧化钇基质中,并具有良好的发光性能。此外,还探讨了纳米粒子的形成机理。     

Ligand-passivated Eu:Y2O3 nanocrystals as a phosphor for white light emitting diodes

Eu(III)-doped Y(2)O(3) nanocrystals are prepared by microwave synthetic methods as spherical 6.4 ± 1.5 nm nanocrystals with a cubic crystal structure. The surface of the nanocrystal is passivated by acetylacetonate (acac) and HDA on the Y exposed facet of the nanocrystal. The presence of acac on the nanocrystal surface gives rise to a strong S(0) → S(1) (π → π*, acac) and acac → Ln(3+) ligand to metal charge transfer (LMCT) transitions at 270 and 370 nm, respectively, in the Eu:Y(2)O(3) nanocrystal. Excitation into the S(0) → S(1) (π → π*) or acac → Ln(3+) LMCT transition leads to the production of white light emission arising from efficient intramolecular energy transfer to the Y(2)O(3) oxygen vacancies and the Eu(III) Judd-Ofelt f-f transitions. The acac passivant is thermally stable below 400 °C, and its presence is evidenced by UV-vis absorption, FT-IR, and NMR measurements. The presence of the low-lying acac levels allows UV LED pumping of the solid phosphor, leading to high quantum efficiency (～19%) when pumped at 370 nm, high-quality white light color rendering (CIE coordinates 0.33 and 0.35), a high scotopic-to-photopic ratio (S/P = 2.21), and thermal stability. In a LED lighting package luminosities of 100 lm W(-1) were obtained, which are competitive with current commercial lighting technology. The use of the passivant to funnel energy to the lanthanide emitter via a molecular antenna effect represents a new paradigm for designing phosphors for LED-pumped white light.     

一维Y2O3∶Eu3+纳米发光材料的制备与表征

One-dimensional Y₂O₃∶Eu³⁺ luminescence nanomaterials were prepared by hydrothermal method without template, and their properties were characterized. XRD patterns show that the precursors are hexagonal phase Y(OH)₃ crystals, and the samples are cubic Y₂O₃ after heat-treatment. SEM images indicate that the one-dimensional material with a diameter of 100 nm and length of micrometer scale can be obtained by this hydrothermal method. Photoluminescence properties show that the position and intensity of the precursors are different with that of the heat-treated samples resulted from the different hosts.     

稀土配合物前驱体热分解法合成Y2O3:Eu3+纳米材料

Y2O3:Eu是一种重要的红色发光材料。国内外生产多采用高温固相法和液相合成法,产物粒径较大,在涂屏(管)前需球磨以减小粒径,这样会造成晶粒劣化而引起光衰以及易引入杂质,使发光材料的发光性能和稳定性下降。因此,围绕荧光粉的粒度及分布、分散性和结晶性的控制     

Synthesis and Photoluminescence Properties of Uniform Y2O3:Eu3+ Hollow Spheres with Tunable Shell Thickness

Y2O3:Eu3+ hollow spheres were successfully prepared with melamine formaldehyde(MF) spheres as template. The MF spheres played a significant role in directing the formation of the hollow shells which are composed of numerous primary nanoparticles. Furthermore, the shell thickness of these hollow spheres could be readily tailored by adjusting the dosage of MF template. Based on the photoluminescence(PL) investigation, the red emission intensities(613 nm) of these Y2O3:Eu3+ hollow spheres are greatly influenced by their shell thickness and it was found that hollow spheres with thin shell thickness and intact hollow structures permit a better PL performance.     

Fabrication and photoluminescence of chemically stable La2O3:Eu3+-La2Sn2O7 core-shell-structured nanoparticles

Core-shell-structured La2O3:Eu3+-La2Sn2O7 nanoparticles were fabricated through SnO2-coating of LaOF:Eu3+ in an aqueous solution and subsequent heat treatments at a higher temperature. The nanoparticles exhibited high chemical stability under an ambient atmosphere and intense red photoluminescence upon irradiation with ultraviolet light.     

聚苯乙烯包覆Y2O3:Eu3+颗粒及表征

表面修饰;聚苯乙烯包覆Y2O3:Eu3+颗粒及表征