Zn2+掺杂诱导Eu3+激活BiOCl层状半导体的反常发光性能研究

采用固相法在500℃下成功制备Zn²⁺掺杂BiOCl:Eu³⁺层状半导体, 并研究了Zn²⁺ (0~20mol%)掺杂对Eu³⁺激活BiOCl层状半导体发光性能的影响。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、激发-发射光谱、荧光寿命衰减曲线对样品的结构和性能进行表征。研究发现, 随Zn²⁺掺杂浓度增大, BiOCl晶体结构不变, Eu³⁺荧光寿命延长, 但发光强度却出现先减后增的反常现象。综合分析表明这可能与BiOCl特殊的层状结构有关。通过XRD和XPS的表征可以推断: 当Zn²⁺掺杂浓度≤10mol%, Zn²⁺在BiOCl中掺杂方式以晶胞层间隙掺杂为主; 当Zn²⁺掺杂浓度>10mol%后, 掺杂方式逐渐向取代掺杂转变。两种掺杂机制对Eu³⁺荧光寿命的改变以及形成缺陷对基质能量传递效率的影响可能是形成上述反常现象的主要原因。研究结果有助于认识稀土掺杂层状半导体的发光性能及影响规律, 并对Eu³⁺掺杂BiOCl这类新型发光材料的开发设计具有指导意义。     

Eu2+和Dy3+掺杂浓度对Sr2MgSi2O7材料的荧光和长余辉性能的影响

采用高温固相法制备得到Sr₂MgSi₂O₇: Eu²⁺和Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺发光粉, 并详细研究了Eu²⁺和Dy³⁺的掺杂浓度对Sr₂MgSi₂O₇材料的荧光和长余辉性能的影响。所有样品都在470 nm附近呈现较宽的发光峰, 这可归因于Eu²⁺离子的4f⁶5d→4f⁷电子能级跃迁。当Eu²⁺掺杂浓度超过淬灭浓度, 其浓度淬灭效应导致发光粉的荧光强度下降和余辉时间减短。同时, 发射峰的峰位随Eu²⁺浓度的增加而发生红移, 这主要由于晶体场分裂能和斯托克斯位移变化造成的, 而电子云扩大效应变化所产生的影响相对较弱。Dy³⁺离子会抑制荧光, 但有助于延长余辉时间。当其掺杂浓度超过10mol%时, Eu²⁺\Dy³⁺离子通过隧道复合机制发生浓度淬灭, 从而使材料的长余辉寿命减少。     

Sr2Si5N8:Eu2+荧光粉的制备及其发光性能研究

以Sr₂CO₃、Si₃N₄和Eu₂O₃为原料, 以C为主要还原剂, 采用碳热还原氮化工艺合成Sr₂Si₅N₈:Eu²⁺荧光粉, 着重研究了C、Sr₂CO₃添加量及Eu²⁺浓度对产物物相及发光性能的影响。研究结果表明: 当C与Si₃N₄的摩尔比 n_c/=9/5时,合成出Sr₂Si₅N₈:Eu²⁺单相荧光粉, 添加适当过量的Sr₂CO₃可提高合成产物的N含量, 且荧光粉的发光强度与其N含量呈现正相关关系。在450 nm蓝光激发下, 受Eu²⁺的4f⁶5d¹ → 4f⁷跃迁作用, Sr₂Si₅N₈:Eu²⁺荧光粉在550~700 nm波段范围产生非对称宽带发射。随着Eu²⁺掺杂浓度由1.5mol%增加到20mol%, 荧光粉的发光强度先增强后减弱, 达到2mol%时发生浓度淬灭现象; 发射主峰由608 nm逐步红移至641 nm; CIE色坐标从(0.606, 0.393)位移至(0.656, 0.343), 是一种可用于白光LED的优质红色荧光粉。     

Nanosized strontium aluminate phosphors prepared via a reverse microemulsion route

Nanosized strontium aluminate phosphors co-activated by Eu²⁺ and Dy³⁺ were prepared via a novel reverse microemulsion process. This new synthesis technique lowered the synthesis temperature of SrAl₂O₄: Eu²⁺, Dy³⁺ phosphors to as low as 900 °C, and also reduced the particle size to the nanometer scale (around 40 nm). In the microemulsion process, the constituent cations were trapped by numerous nano-scaled micelles, leading to a shortening of the inter-diffusion length and enhancement of the precursor reactivity. The excitation intensity and emission peaks of nanosized SrAl₂O₄: Eu²⁺, Dy³⁺ phosphors significantly increased with increasing heating temperatures.     

Sensitized luminescence and energy transfer in Ce and Eu codoped calcium magnesium chlorosilicate

Ce³⁺ and Eu²⁺ ions codoped calcium magnesium chlorosilicate [Ca₈Mg(SiO₄)₄Cl₂] phosphors have been synthesized and characterized. Intense bluish-green light was observed under ultraviolet and blue light excitations. The diffuse reflection, excitation and emission spectra of Ca₈Mg(SiO₄)₄Cl₂:Ce³⁺,Eu²⁺ were measured at room temperature, and enhancement of Eu²⁺ emission was confirmed. The fluorescence lifetimes of Ce³⁺ were measured, and the mechanism of nonradiative energy transfer from Ce³⁺ to Eu²⁺ is found to be electric dipole–dipole interaction. The probabilities and efficiencies of nonradiative energy transfer were also calculated, and the results indicate that the efficiency can be as high as 86% in this material system.     

Improved optical photoluminescence by charge compensation in the phosphor system CaMoO4:Eu

It has been found that charge compensated CaMoO₄:Eu³⁺ phosphors show greatly enhanced red emission under 393 and 467 nm-excitation, compared with CaMoO₄:Eu³⁺ without charge compensation. Two approaches to charge compensation, (a) 2Ca²⁺ → Eu³⁺ + M⁺, where M⁺ is a monovalent cation like Li⁺, Na⁺ and K⁺ acting as a charge compensator; (b) 3Ca²⁺ → 2Eu³⁺ + vacancy, are investigated. The influence of sintering temperature and Eu³⁺ concentration on the luminescent property of phosphor samples is also discussed.     

Eu2+/Tb3+掺杂的Sr2Si5N8基荧光粉的制备与发光性能

采用碳热还原氮化法合成了Eu²⁺/Tb³⁺掺杂的Sr₂Si₅N₈基荧光粉, 并重点研究了Tb³⁺-Eu²⁺共掺时Sr₂Si₅N₈基荧光粉的发光性能。研究结果表明: 由于Tb³⁺的f → d间的跃迁是自旋允许的, Sr₂Si₅N₈:Tb³⁺在330 nm激发光下, 在490、543、585和623 nm四处各有一发射峰, 它们分别来源于Tb³⁺的⁵D₄ → ⁷F_j (j = 6、5、4、3)能级跃迁; 掺入Tb³⁺对Sr_1.96Si₅N₈:0.04Eu²⁺的激发谱和发射谱的形状及峰位无明显影响, 当共掺离子Tb³⁺浓度为x = 0.01时, 样品发射强度比未共掺的Sr_1.96Si₅N₈:0.04Eu²⁺提高了约20%, Tb³⁺主要通过电多极能量传递的方式转向Eu²⁺。     

Long lasting phosphorescence of Sr4Al14O25:Eu,Dy thin films by magnetron sputtering

This paper reports the preparation process and the long lasting phosphorescence of the Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ thin films obtained by magnetron sputtering. Phosphorescence was achieved by annealing the films in reducing atmosphere. Sr₄Al₁₄O₂₅ thin film was obtained when the films were treated at 1200 °C, while SrAl₂O₄ was generated as the intermediate phase during the annealing process. Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ film generated an emission at 485 nm, and SrAl₂O₄:Eu²⁺,Dy³⁺ film showed an emission peaking at 515 nm. Afterglow characteristics were observed for both films, and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ film showed a better afterglow property than the SrAl₂O₄:Eu²⁺,Dy³⁺ film due to a deeper trap level and a higher trap concentration formed in the thin films.     

Preparation of Eu: YVO4 red and Ce, Tb: LaPO4 green phosphors by hydrolyzed colloid reaction (HCR) technique

Eu³⁺: YVO₄ red and Ce³⁺, Tb³⁺: LaPO₄ green phosphors were prepared by newly discovered hydrolized colloid reaction (HCR) technique at low temperature (< 100 °C) and atmospheric pressure utilizing subsequent calcining and reductive treatments, respectively. The incorporation of activators (Eu³⁺ and Ce³⁺, Tb³⁺) in these very porous powders was checked by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence investigations.     

Ba3Gd(PO4)3:Eu3+荧光粉的合成及发光性质

采用高温固相反应法合成了不同Eu³⁺掺杂浓度的Ba₃Gd(PO₄)₃荧光粉。利用X射线衍射对产生的晶体结构进行了分析, 证实产物为纯相, Eu³⁺的引入没有导致晶体结构的改变。利用Van Uitert模型对⁵D₀能级荧光的浓度猝灭行为进行了研究, 发现浓度猝灭是由于Eu³⁺间交换相互作用所导致。分析了⁵D₀荧光发射的温度依赖, 给出了荧光温度猝灭行为符合横向穿越模型, 并通过非线性拟合获得了激活能。利用Eu³⁺的发射光谱和荧光衰减数据, 计算了⁵D₀→⁷F_J辐射跃迁速率及荧光分支比, 同时得到了光学跃迁强度参数。     

助溶剂对Ba3Si6O12N2:Eu2+氮氧化物荧光粉制备及光学性能的影响

采用微波法制备了Eu²⁺ 掺杂的Ba₃Si₆O₁₂N₂绿色氮氧化物荧光粉, 着重研究了不同助熔剂: BaCl₂、H₃BO₃、KF和NH₄F对Ba₃Si₆O₁₂N₂:Eu²⁺发光性能的影响。利用X射线衍射(XRD)、荧光光谱仪、扫描电子显微镜(SEM)和量子效率(QE)等检测方法研究了不同助溶剂的作用机理。研究结果表明: 添加助溶剂能够显著提高荧光粉的发光强度, 添加不同助溶剂制备荧光粉的发光强度大小依次为H₃BO₃ > KF > BaCl₂ >无助溶剂 > NH₄F。当添加1.0wt%的H₃BO₃时, 所制备的荧光粉粒径分布比较均匀, 形貌较好, 荧光粉的发光强度最大, 且与不添加助溶剂制备的荧光粉相比, 有较高的量子效率和吸收效率, 不同温度下的发射光谱表明其热淬灭性低, 荧光寿命较短。     

Preparation, patterning and luminescent properties of nanocrystalline Gd2O3:A (A=Eu, Dy, Sm, Er) phosphor films via Pechini sol–gel soft lithography

Nanocrystalline Gd₂O₃:A (A=Eu³⁺, Dy³⁺, Sm³⁺, Er³⁺) phosphor films and their patterning were fabricated by a Pechini sol–gel process combined with a soft lithography. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 °C and that the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained by optimizing the composition of the coating sol, which mainly consisted of grains with an average size of 70 nm and a thickness of 550 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 μm). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline Gd₂O₃ phosphor films due to an efficient energy transfer from Gd₂O₃ host to them. Both the lifetimes and PL intensity of the rare earth ions increased with increasing the annealing temperature from 500 to 900 °C, and the optimum concentrations for Eu³⁺, Dy³⁺, Sm³⁺, Er³⁺ were determined to be 5, 0.25, 1 and 1.5 mol% of Gd³⁺ in Gd₂O₃ films, respectively.     

Synthesis and the luminescent properties of europium-activated Ca2SnO4 phosphors

The synthesis and photoluminescent (PL) properties of calcium stannate crystals doped with europium grown by mechanically activated in a high energy vibro-mill have been investigated. The characteristics of Ca₂SnO₄:Eu³⁺ phosphors were found to depend on the amounts of europium ions. The XRD profiles revealed that the system, (Ca_1−xEu_x)₂SnO₄, could form stable solid solutions in the composition range of x = 0–7% after being calcined at 1200 °C. The calcined powders emit bright red luminescence centered at 618 nm due to ⁵D₀ → ⁷F₂ electric dipole transition. Both XRD data and the emission ratio of (⁵D₀ → ⁷F₂)/(⁵D₀ → ⁷F₁) reveal that the site symmetry of Eu³⁺ ions decreases with increasing doping concentration. The maximum PL intensity has been obtained for 7 mol% concentration of Eu³⁺ in Ca₂SnO₄.     

紫外激发蓝色荧光粉Sr2-x-yB5O9Cl:xEu2+,yTb3+的合成和发光性能

采用高温固相反应法合成Sr_2-x-yB₅O₉Cl:xEu²⁺,yTb³⁺蓝色荧光粉。用X射线衍射表征材料的晶体结构、用荧光光谱仪测定Eu²⁺和Tb³⁺的掺杂浓度,研究了助溶剂H₃BO₃过量浓度和反应温度对荧光粉发光性质的影响。结果表明,单掺杂Eu²⁺时,其浓度猝灭机理为电偶极-电偶极交互作用机制,浓度猝灭临界距离为R_C=1.71 nm。在紫外（230-410 nm）波段有强而宽的吸收带,表明此粉是一种近紫外白光LED用的蓝色荧光粉。     

Effects of rare-earth concentration and heat-treatment on the structural and luminescence properties of europium-doped zirconia sol–gel planar waveguides

Sol–gel zirconia films doped with Eu³⁺ concentrations ranging from 0.2% to 10%, were prepared by dip-coating a solution of the starting precursor, zirconium n-propoxide, ethanol, methanol, water, acetic acid and europium nitrate on glass and SiO₂/Si wafer substrates. The ZrO₂sol thus synthesized remains stable for several months. Structural characterization of the zirconia films was performed using Waveguide Raman Spectroscopy. These films present an amorphous phase up to an annealing temperature of 400 °C. Above 400 °C the matrix evolves towards a metastable tetragonal phase. This transformation was found to depend on the concentration of Eu³⁺ ions. Indeed, while for samples doped with 0.2% Eu³⁺ this transformation occurs around 450 °C, in the case of 10% of Eu³⁺ ions, the transition is pushed off to 500 °C. The optical losses of these waveguides were found to be about 0.3 dB cm⁻¹ for samples annealed at 400 °C. The surfaces of the films were characterized using Atomic Force Microscopy and the roughness was measured. The Eu-doped films were investigated using Waveguide Photoluminescence Spectroscopy. The dynamical behaviour of the Eu³⁺ emissions indicated that concentration quenching effect is not observed even when the matrix is doped up to 10%.     

YVO4∶Eu3+,Bi3+红色荧光粉的水热合成及其荧光性能

以Y₂O₃、Eu₂O₃、Bi(NO₃)₃·H₂O、浓HNO₃、偏钒酸铵、氨水、无水乙醇和一缩二乙二醇为原料,采用聚乙烯吡咯烷酮(PVP)辅助水热法合成YVO₄: Eu³⁺, Bi³⁺纳米颗粒。使用X射线衍射(XRD)、扫描电镜(SEM)、红外光谱(IR)和荧光光谱(FL)等手段对产品进行了表征和分析。结果表明：合成的样品为YVO₄: Eu³⁺, Bi³⁺纳米颗粒,均具有四方晶相结构,其微结构随反应溶液的的pH值变化。YVO₄: Eu³⁺, Bi³⁺纳米颗粒在619 nm处有较强的红光发射(电偶极跃迁⁵D₀→⁷F₂),在594 nm有较弱的橙光发射(磁偶极跃迁⁵D₀→⁷F₁)。随着Eu/Bi比值的增大材料的荧光先增强后减弱,在Eu/Bi比值为5时样品的红光发射最强。溶液的pH值影响YVO₄: Eu³⁺, Bi³⁺纳米晶的发光强度,其中pH值为10时的样品其红光发射最强。并探讨了YVO₄: Eu³⁺, Bi³⁺纳米晶的发光机理。     

Effect of heat treatment on photoluminescence behavior of BaMgAl10O17:Eu phosphors

The blue phosphor of BaMgAl₁₀O₁₇:Eu²⁺ (BAM) powders were prepared by solid-state reaction. The thermal degradation of BAM phosphor significantly reduces the intensity of the blue emission. BAM is reduced by an amount of 50% after heating at around 800 °C for 1 h. Photoluminescence (PL) excitation and emission spectra showed that the blue emission of 450 nm peak decreased with increasing annealing temperature. The ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transition of Eu³⁺ were observed at 590 and 615 nm emission lines over 1100 °C. Electron paramagnetic resonance (EPR) spectrum also detected two signals of Eu²⁺, corresponding to g=3.7156(9) for 88 mT, and g=2.9507(9) for 133 mT. X-ray absorption near edge structure (XANES) spectrum decreased the intensity of Eu²⁺ for 6977 eV with increasing annealing temperature, while high-energy peak of Eu³⁺ for 6984 eV was increased. The combined use of X-ray and neutron data by the Rietveld refinement appears to support that the secondary phase of EuMgAl₁₁O₁₉ magnetoplumbite structure in BAM may be formed by heat treatment.     

Preparation and photoluminescence properties of Eu-doped Ga2O3 nanorods

GaOOH:Eu³⁺ nanorods with different aspect ratios were prepared by hydrothermal method at 140 °C. - and β-Ga₂O₃:Eu³⁺ were converted from as-prepared GaOOH:Eu³⁺ particles by calcination at 500 and 850 °C, respectively. The products were characterized with X-ray diffraction (XRD), transmission electron microscope (TEM) and photoluminescence (PL). Results show that solution pH values play a key role in the formation of the GaOOH:Eu³⁺ powders with different morphologies and - and β-Ga₂:Eu³⁺ inherit the morphology of GaOOH:Eu³⁺ exactly. The photoluminescence characteristics of β-Ga₂O₃:Eu³⁺ were also investigated. Experimental results reveal that the color purity of β-Ga₂O₃:Eu³⁺ nanorods with high aspect ratio is enhanced in comparison with β-Ga₂O₃:Eu³⁺ nanorods with low aspect ratio.     

柔性Eu3+掺杂SiO2纳米纤维薄膜的制备及其发光性能

采用溶胶-凝胶法结合静电纺丝技术制备了柔性Eu³⁺掺杂SiO₂纤维薄膜, 采用SEM、XRD、FT-IR、TG和PL等测试方法对材料进行表征。Eu³⁺掺杂SiO₂纤维薄膜在热处理后纤维直径变小, 纤维表面平滑无粘连。通过控制升温速度, 纤维薄膜经热处理后仍具有较高的力学强度, 750℃热处理后其拉伸强度可达4.31 MPa, 经过多次弯曲仍能保持原样。在392.6 nm光源激发下, Eu³⁺掺杂SiO₂纤维薄膜在570~670 nm附近呈现出来自于⁵D₀→⁷F_J的发射峰。当Eu³⁺掺杂浓度为8mol%时, 经过750℃热处理后Eu³⁺掺杂SiO₂纤维薄膜的发光强度达到最大值。     

Eu3+掺杂硼酸盐玻璃的发光性质及其热稳定性研究

荧光玻璃具有发光中心分布均匀和热稳定好等优点, 成为LED领域研究的热点。本研究采用传统的高温熔融淬火法合成了一系列Eu³⁺掺杂的硼酸盐玻璃, 通过荧光光谱手段对其发光性质及热稳定性进行了表征; 利用Van Uitert模型对样品中Eu³⁺的浓度猝灭行为进行了研究。结果表明: 样品中Eu³⁺的浓度猝灭机理为Eu³⁺离子间的交换作用导致的无辐射能量传递; 利用Arrhenius公式对荧光玻璃样品的温度猝灭行为进行了分析。结果表明: 样品中Eu³⁺的发光温度猝灭属于Crossover过程; 最后分析了Eu³⁺与荧光玻璃基质之间的相互作用。