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.     

Judd-Ofelt intensity parameters and spectral properties of Gd2O3:Eu3+ nanocrystals

Three nonequivalent centers of Cs (A, B, and C) in monoclinic phase and C2 and S6 centers in cubic phase were identified in the Gd2O3:Eu3+ nanocrystals with spectral techniques. Size dependence in the spectra indicated that the excitations from both host and charge-transfer band (CTB) for the 5D0 --> 7F2 transition of Eu3+ ions were nearly equal for a larger size of 135 nm of the cubic phase; however, with decreasing the size to or less than 23 nm, the excitations by the CTB dominated. The variation of excitation leading to the symmetry and energy change in the C2 and S6 sites was also observed for larger particle sizes. The Judd-Ofelt intensity parameters Omega(lambda) (lambda = 2, 4) for Gd2O3:Eu3+ nanoparticles were experimentally determined. The parameters Omega(lambda) were found to significantly change with the sizes of Gd2O3:Eu3+ from nanoparticles to bulk material. With decreasing the size from 135 to 15 nm, the quantum efficiencies for 5D0 reduced from 23.6% to 4.6% due to the increasing ratio of surface to volume.     

Novel dumbbell-like LaVO4:Eu3+ nanocrystals and effect of Ba2+ codoping on luminescence properties of LaVO4:Eu3+ nanocrystals

Journal of Sol-Gel Science and Technology - LaVO4:Eu3+ nanocrystals with different morphologies were synthesized via a simple hydrothermal method in a wide pH range. The as-synthesized samples were...     

溶剂热合成纳米球状La2O2S:Eu3+荧光粉

Eu3+离子激活的硫氧化物荧光粉是目前国内外广泛使用的CRT红色发光材料[1]. 它具有色纯度高、色彩不失真、亮度-电流饱和度特性好和稳定性高等特性, 已成为CRT不可替代的红色荧光粉. 此外, 掺杂或不掺杂Eu3+的硫氧化镧是还原SO2有害气体为S单质的优良催化剂[2,3]. 近年来兴起的纳米材料是有可能在本世纪得到广泛应用的材料; 掺杂稀土离子的硫氧化物有望应用于各种显示技术及催化剂中. 最近, 吴长峰等[4]在Y2O3∶Eu3+纳米管中观察到发射峰展宽等特性. 因而, 研究Eu3+离子激活的硫氧化镧纳米荧光粉是很有意义的.     

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.     

Li+,Zn2+共掺杂对Gd2O3:Eu3+纳米粉结构和发光性能的影响

采用燃烧法制备出Li^＋,Zn^2＋掺杂的Gd2O3：Eu^3＋纳米荧光粉,研究了掺杂离子对Gd2O3：Eu^3＋的结晶性能、晶粒形貌和光致发光特性的影响.以X射线衍射（XRD）、透射电子显微镜（TEM）、发射光谱和衰减时间谱等手段表征材料性能.结果表明,Li^＋,Zn^2＋掺杂可显著提高Gd2O3：Eu^3＋纳米粉在611 nm处的发光强度,最大可达到未掺杂时的2.5倍.发光增强的主要原因可归结为3个方面： （1）使晶粒由单斜相向更利于发光的立方相转变; （2）氧空位的敏化剂作用; （3）掺杂离子的助熔剂效应,使晶粒的结晶性能提高、粒径增大,从而降低表面态引起的发光猝灭.     

Thermal annealing of LaF3:Eu3+ nanocrystals synthesized by a solvothermal method and their luminescence properties

In this work, we used a low temperature solvothermal method to synthesize Eu³⁺-doped LaF₃ (LaF₃:Eu³⁺) nanocrystals. The effect of thermal annealing on their phase structures and luminescence properties was studied. Transformation from LaF₃ to LaOF was observed after the annealing, and the initial transformation process was studied using a rapid thermal annealing technique. It was found that a sufficiently high annealing temperature is required for the transformation of LaF₃ to LaOF. LaOF phase started to be formed after annealing at 500 °C for as short as 5 min, and higher annealing temperatures and longer annealing time led to a larger amount of LaOF formed. With the increase of the formation of LaOF, the luminescence was greatly enhanced. Strong O^2? → Eu³⁺ charge transfer band was present in these samples annealed at 500 °C and higher temperatures, and greatly enhanced ⁷F₀ → ⁵D₂ transition of Eu³⁺ was also observed.     

La2CaB10O19∶Eu3+的VUV-VIS范围光谱的研究

研究了La2CaB10O19∶Eu3+红色发光材料的高分辨发射光谱和UV-VUV激发光谱. 根据发射光谱和荧光寿命, 认为进入晶格的Eu3+占据了两种格位, 一种Eu3+占据了与O2-离子十配位的La3+的格位, 另一种Eu3+则占据了与O2-离子八配位的Ca2+的格位. 又从激发光谱的分析中, 得到Eu3+的电荷迁移带(CTB)是峰值位于244 nm的宽带, 而位于130～170 nm之间的成份复杂的宽带包括硼酸盐基质的吸收带和Eu3+的f-d跃迁的结论.     

Eu3+ und Eu2+ in Oxometallaten der Zusammensetzung MBeLn2O5: SrBeEu2O5 und EuBeNd2O5

Eu³⁺ and Eu²⁺ in Oxides of the Composition MBeLn₂O₅: SrBeEu₂O₅ and EuBeNd₂O₅ Single crystals of (I): SrBeEu₂O₅ and (II): EuBeNd₂O₅ were prepared by CO₂-LASER (I) in air and plasma torch (II) technique in H₂ atmosphere. X-ray investigations led to orthorhombic symmetry, space group D-Pnma; (I): a = 9.488, b = 7.156, c = 6.495 Å; (II): a = 9.534, b = 7.225, c = 6.544 Å, Z = 4. Sr²⁺ and Eu³⁺ as well as Eu²⁺ and Nd³⁺ are in statistical distribution within a Kagomé framework. Both compounds are discussed with respect to the monoclinic form of MBeLn₂O₅.     

Role of surface coating in ZrO2/Eu3+ nanocrystals

The sol-emulsion-gel method is used for the preparation of Eu3+ ion-doped and coated ZrO2 nanocrystals. Here, we report the role of surface coating, dopant concentration, and temperature of heating in the modification of their crystal structure and photoluminescence properties. It is found that the volume fraction of the tetragonal phase increases from 28.08 to 91.56% because of surface coating. This is a significant modification of the crystal phase in ZrO2 nanocrystals due to surface coating by Eu2O3. It is found that the photoluminescence properties are sensitive to the crystal structure, which is again controlled by surface coating, concentration, and heating temperature. It is found that the decay time (tau) of Eu-doped ZrO2 nanocrystals increases with increasing the concentration of dopant and with increasing the temperature of heating because of changes in their crystal phase. The emission intensity of the peak at 611-617 nm (5D0 --> 7F2) of the Eu3+ ion-activated ZrO2 nanocrystals (doped and coated) is also found to be sensitive to the nanoenvironment. The average decay times are 770 and 488 mus for 1100 degrees C-heated 1.0 mol % Eu2O3-doped and coated ZrO2 nanocrystals, respectively. Our analysis suggests that the site symmetry of the ions plays the most important role in the modifications of the radiative and nonradiative relaxation mechanisms as a result of the overall photoluminescence properties.     

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.     

球形La2O3∶Eu纳米晶的制备及其发光特性

The spheric La₂O₃∶Eu nanocrystals were prepared using NH₃·H₂O-NH₄HCO₃ mixture as precipitant. The material was characterized by FTIR, XRD and TEM techniques. The luminescence properties of Eu³⁺ in spheric La₂O₃ were measured by three dimension spectra, emission and excitation spectra. The results indicate that the La₂O₃∶Eu nanocrystals are in hexagonal phase by annealing at 800 ℃, the crystal size is about 30 nm. The maximum emission and excitation wavelength were determined by three dimensional spectroscopy to be at 591 nm and 394 nm, respectively. In emission spectrum the band at 591 nm and 612 nm are corresponding to ⁵D₀-⁷F₁ and ⁵D₀-⁷F₂ transition of Eu³⁺ ions. With increasing in annealing temperature the differences of intensity of the two transitions are increased. This phenomenon shows that the luminescence intensity of La₂O₃∶Eu nanocrystals can be tuned by changing annealing temperature.     

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     

Ca2+、La3+及Eu3+对NaDC胶团的作用

在水溶液中将脱氧胆酸钠（ＮａＤＣ）分别与ＣａＣＬ２、ＥｕＣｌ３及ＬａＣｌ３反应,改变反应物浓度和配比,合成了系列脱氧胆酸络全物。利用红外光谱（ＦＴＩＲ）、元素分析、ＩＣＰ分析及Ｘ身材线粉末衍射谱,对它们的组成和结构进行了研究。结果表明：水溶液中ＣａＣｌ２与ＮａＤＣ的反应不是简单离子间的反应,改变其反应物浓度和配比,生成组成和结构不同的络合物;而ＬｎＣｌ３与ＮａＤＣ反应时,反应物浓度和配比的改变不影     

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.     

Eu3+/Tb3+-doped La2O2CO3/La2O3 nano/microcrystals with multiform morphologies: facile synthesis, growth mechanism, and luminescence properties

LaCO(3)OH nano/microcrystals with a variety of morphologies/sizes including nanoflakes, microflowers, nano/microrhombuses, two-double microhexagrams sandwichlike microspindles, and peach-nucleus-shaped microcrystals have been synthesized via a facile homogeneous precipitation route under mild conditions. A series of controlled experiments indicate that the pH values in the initial reaction systems, carbon sources, and simple ions (NH(4)(+) and Na(+)) were responsible for the shape determination of the LaCO(3)OH products. A possible formation mechanism for these products with diverse architectures has been presented. After annealing at suitable temperatures, LaCO(3)OH was easily converted to La(2)O(2)CO(3) and La(2)O(3) with the initial morphologies. A systematic study on the photoluminescence and cathodoluminescence properties of Eu(3+)- or Tb(3+)-doped La(2)O(2)CO(3)/La(2)O(3) samples has been performed in detail. The excitation and site-selective emission spectra were recorded to investigate the microstructure, site symmetry, and difference in the (5)D(0) → (7)F(2) transition of Eu(3+) ions in La(2)O(2)CO(3) and La(2)O(3) host lattices. In addition, the dependence of the luminescent intensity on the morphology for the as-prepared La(2)O(2)CO(3)/La(2)O(3):Ln(3+) (Ln = Eu, Tb) samples has been investigated. The ability of generating diverse morphologies and multiemitting colors for different rare-earth activator ion (Ln = Eu, Tb) doped La(2)O(2)CO(3)/La(2)O(3) nano/microstructures provides a great opportunity for the systematic evaluation of morphology-dependent luminescence properties, as well as the full exploration of their application in many types of color display fields.     

若干物理处理方法对稀土荧光粉Y2O3:Eu3+发光性能的影响

采用物理法对商品化稀土荧光粉Y2O3：Eu^3＋进行改性，考察了真空干燥温度、焙烧温度对其发光性能的影响。SEM和TEM观测结果表明，经过200℃真空干燥后，随着焙烧温度的增加，荧光粉的分散性得到改善，且以纳米颗粒为主（5～85nm）。XRD测量结果表明，随着焙烧温度的增加，Y203：Eu^3＋的结晶度逐渐增加。发射光谱测试结果表明，真空干燥温度为200℃，焙烧温度为1200℃时得到的样品的发光性能较好。     

Thermal study in Eu3+-doped boehmite nanofibers and luminescence properties of the corresponding Eu3+:Al2O3

Eu³⁺-doped boehmite nanofiber materials with different Eu³⁺ concentrations were synthesized without any surfactant, and followed by a series of characterizations. It was found that the boehmite nanofibers became coarser with the increase of Eu³⁺ concentration, which resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by thermogravimetry–differential scanning calorimetry. All materials showed the phase transition from γ-Al₂O₃ to other forms. Yet the transition temperature was increased with the increase of Eu³⁺ concentration. The Eu³⁺-doped boehmite nanofibers with the maximum Eu³⁺ concentrations showed the best thermal stability. Photoluminescence spectra showed that the 2 mol% of doping concentration of Eu³⁺ ions in Eu³⁺:Al₂O₃ nanofiber was optimum.     

Ga~(3+)对Eu~(2+)掺杂钡长石结构和发光特性的影响

在弱还原气氛下采用高温固相法制备Ba0.955A l2-xGaxS i2O8:Eu2+(x=0~1.0)系列荧光粉,研究Ga3+置换A l3+对晶体结构和光谱特性的影响。Ga3+与A l3+以类质同相替代进入BaA l2S i2O8晶格形成连续固溶体,晶胞参数a,b,c,β和晶胞体积V均随Ga3+置换量呈线性增加。宽带激发光谱,覆盖范围为230~400 nm,可拟合成4个峰,表观峰值位于330 nm,基本不随Ga3+置换量变化;随着Ga3+置换量的增加,半高宽从93 nm减小至83 nm。发射光谱位于375~560 nm,可由422和456 nm两峰拟合而成,表观峰值位于434 nm,两拟合峰峰位均随Ga3+置换量呈线性红移,且拟合峰强度比呈线性递减。