Synthesis of Spherical （Y, Gd） BO3 ： Eu^3＋ Phosphor Using W/O Emulsion System

Spherical （Y, Gd）BO3：Eu^3＋ phosphor particles with a narrow size distribution（2 -4 μm） was obtained by firing the Y-Gd-Eu-BO3 precursor prepared in a W/O style emulsion system. In the W/O emulsion system, kerosene, used as oil phase, was mixed with Span 80 and Tween 80 compounds which were employed as the emulsifier with an HLB （hydrophile-lipophile balance） value of 5.2- 5.3. Both rare earths （Y, Gd and Eu） nitrate and boric acid solution or ammonia solution were used as aqueous phase. The synthesis conditions, such as emulsion composition, emulsifying style, precipitation reaction process, reaction temperature, morphology control, and so on, were investigated, and the optimum synthesis conditions for preparing spherical （Y, Gd）BO3：Eu^3＋ phosphor was obtained. The phosphor was characterized by XRD, SEM, laser particle size analysis, emission and excitation spectrum under vacuum ultraviolet （VUV）, and so on. The phosphor synthesized using the water-in-oil emulsion method with median diameter （D50） of 2 - 4 μm shows agreeable photoluminescence （PL） property and sphericity. The main emission peak appears at about 593 nm, which corresponds to ^5D0→^7F1 transition （magnetic-dipole transition） of the Eu^3＋ ion. The cell parameters and powder diffraction data were indexed. The structure of the phosphor belongs to the hexagonal system with space group P63/m.     

Influence of Molten Salt on Luminescent Intensity and Particle Size of Y2O3 ：Eu^3＋ Phosphor

The Y-Eu oxalate precursor was prepared with a homogeneous precipitation method. And the additives, Na2CO3, S, NaCl or their combination, were introduced into the precursor to prepare Y2O3 ：Eu^3＋ red phosphors at 1000 1300 ℃ for 2 h. The effect of molten salts on particle size and luminescent intensity was studied. The experimental results showed that the complex molten salt （Na：CO3 ＋ S ＋ NaCl） was conductive to enhance the luminescent intensity of Y2O3 ：Eu^3＋. The emission intensity of the phosphor prepared with these additives at 1300 ℃ was about 45% higher than that of the one prepared without molten salt, and about 11% higher than that of the corresponding commercial phosphor. Meanwhile, the particle size of Y2O3 ：Eu^3＋ phosphor was controlled effectively with the molten salt.     

Synthesis and Properties of Eu Activated Strontium Molybdate Phosphor

In order to prepare fluorescent material for white Light Emitting Diodes （LEDs）, a new Eu^3＋ activated molybdate phosphor SrMoO4 was fabricated with solid-state method. X-ray diffraction （XRD） showed that the doping of trivalent europium ion reduced the lattice parameters. The excitation and emission spectra indicated that this phosphor could be excited effectively by the visible light, and then emitted red light with the peaks located at 616 and 624 nm. The influence of Eu^3＋ concentration on the luminescent properties of Eu^3＋ doped SrMoO4 was investigated and the 25% （mole fraction） was the appropriate molar concentration. The reaction time and temperature had obvious effect on the luminescent properties. The luminescent intensity reached the strongest when it was sintered at 800 ℃ for 3 h.     

溶胶-凝胶法制备Sr2SiO4:Tb3+绿色荧光粉及其发光性能

采用溶胶-凝胶法合成了一系列适合紫外-近紫外激发的(1-X)Sr₂SiO₄:XTb3+(X=0,0.01,0.02,0.03,0.04,0.05,0.06)绿色荧光粉,并采用X射线衍射(XRD)、扫描电子显微镜(SEM)和荧光光谱(PL)研究了样品的结构及发光性能.由XRD的检测结果可知,合成样品属于单斜晶系的β-Sr₂SiO₄相.由SEM图可知,所有样品都呈无规则块状结构.当监测波长为546 nm,样品的激发光谱的主峰位于370 nm处,属于Tb3+的4f-4f特征跃迁吸收.当激发波长分别为285 nm和250 nm,所有样品在488 nm,547 nm,586 nm,623 nm处都出现了1个强发射峰,分别对应Tb3+的5D₄→7F₆、5D₄→7F₅、5D₄→7F₄和5D₄→7F₃电子跃迁.最强发射峰位于547 nm处,呈现特征为绿光发射.随Tb3+掺杂量增大,发射强度呈现出先增大后减小的变化趋势,即存在浓度猝灭效应.当Tb3+掺杂量为X=0.03时,样品的发光强度最大.      

钠离子对KNa4B2P3O13: Sm荧光粉发光性能的增强作用研究

通过高温固相法在硼磷酸盐KNa₄B₂P₃O₁₃基质中掺杂稀土Sm3+离子获得橘红色发光性能,研究了电荷补偿剂Na+对该荧光粉发光性能的影响,开展了粉末X射线衍射、红外光谱、紫外可见漫反射、荧光光谱、荧光寿命及量子效率等测试对材料的物相、形貌和发光性能进行了表征。研究结果表明,该荧光粉的荧光发射源于Sm3+的4G_5/2→6H_5/2（562 nm）、4G_5/2→6H_7/2（598 nm）和4G_5/2→6H_9/2（645 nm）跃迁,Na+的掺杂没有改变Sm3+特征发射峰的形状和位置,增强了其发光强度。Na+浓度为1%时,可使发光积分强度提高48%。此外,掺杂Na+对荧光粉的寿命和色坐标无明显影响,其色坐标均位于橘红色区域。      

阳离子引入对CsPF6:Mn4+红色荧光粉发光性能的影响

采用共沉淀法在室温条件下合成了CsPF₆:Mn4+荧光粉,研究了Li+、Na+、K+阳离子的引入对CsPF₆:Mn4+荧光粉发光强度的影响。所制备的系列荧光粉样品均为立方结构纯相。在蓝光激发下,呈现最强峰位于634 nm处的一系列窄带红色发射。加入K+和Li+后,发光强度增强,加入Na+后发光强度有所减弱,其中加入K+的CsPF₆:Mn4+荧光粉发光强度最强。CsPF₆:Mn4+, K+荧光粉的发射强度随着温度的上升先增强然后由于非辐射跃迁的增加而降低,在423 K时达到最大值,发射强度相较于未引入阳离子的荧光粉发射强度亦增强。阳离子的引入可以有效提升CsPF₆:Mn4+荧光粉的发光性能。      

Luminescence properties of Eu2＋ -doped Ba3Si6O12N2 green phosphor： concentration quenching and thermal stability

The efficient Eu2+ -doped Ba3 Si6O12N2 green phosphors were prepared by a traditional solid state reaction method under N2 /H2 atmosphere at a temperature up to 1350 oC for 12h. Photoluminescence (PL) properties showed a broad emission band with a peak of 525 nm and the full width of half-emission maximums (FWHM) of 70 nm under 460 nm light irradiation. The X-ray diffraction patterns (XRD) and scanning electron microscope (SEM) images of the synthesized powder demonstrated its pure phase and excellent crystallization. Quenching concentration in this phosphor was found to be 0.3. The mechanisms of concentration quenching and redshift of emission peak with increasing concentration of Eu2+ were studied. The temperature dependence measurement of this green phosphor revealed excellent thermal quenching property compared to silicate green phosphor. It is believed that Ba3 Si6O12N2 :Eu2+ is an excellent green phosphor for UV or blue chip based white LEDs.     

Preparation and Upconversion Luminescence of Y3Al5O12 ： Yb^3＋ , Er^3＋ Trapsparent Ceramics

YAG： 1% （atom fraction） Yb^3＋ , 0.5% （atom fraction） Er3＋ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of ^2H11/2→^4I15/2, ^4S3/2→^4I15/2, and ^4F9/2→^4I15/2 of Er^3＋ ions, respectively.     

作为白光LED用铕掺杂氟化镧红色荧光粉的制备与光谱性能研究

采用水热法制备具有单一相六方晶系的LaF₃:Eu3+纳米荧光粉.通过X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、光致发光光谱(PL)和荧光衰减曲线对LaF₃:Eu3+纳米荧光粉进行表征.LaF₃:Eu3+荧光粉的激发光谱主要由250 nm处的宽带(O2-→Eu3+的电荷转移跃迁)和一些尖峰(Eu3+ f-f跃迁)构成,其中位于近紫外区396 nm处有一较强的激发峰.通过发射光谱探测Eu3+在LaF₃晶体中的局部晶场环境.在298 K下激发光谱和发射光谱可知,在六方晶系的LaF₃纳米晶体中的Eu3+晶格位置从D_4h降至到C_2v,这是由于晶格变化所造成的.在396 nm激发下,观测到较优掺杂浓度为10%的LaF₃:Eu3+荧光粉在591 nm(5D₀→7F₁跃迁)处有强烈的红色发射峰.其发光性能表明,LaF₃:Eu3+红色荧光粉在近紫外发光二极管领域具有潜在的应用价值.      

Yb3+，Er3+掺杂Y2Ti2O7荧光粉的制备与上转换发光机理研究

采用溶胶-凝胶法制备合成了(Y_0.98-xYb_xEr_0.02)₂Ti₂O₇(x=0, 0.02, 0.04...0.10)荧光粉, 分别采用XRD和荧光光谱仪对样品的结构和上转换发光性能进行了表征.研究了Yb3+掺杂浓度对样品上转换发光性能的影响, 并对样品的发光机理进行了研究.结果表明, 所得样品为面心立方结构的烧绿石相.在980nm激发下, 样品展现出很强的上转换荧光发射并且发光颜色可以通过Yb3+掺杂浓度来调节.样品上转换绿光和红光发射均为双光子过程并且交叉弛豫过程在上转换红光发射过程中占据主导作用.      

Y2MgTiO6:Mn4+/Nd3+的制备及近红外发光性能

采用传统的高温固相反应制备了一系列Y₂MgTiO₆:Mn4+/Nd3+下转换材料。利用稳态激发发射光谱以及瞬态荧光寿命等进行了分析, 在Mn4+→Nd3+能量传递过程中, 在331 nm激发下Nd3+产生885 nm和1 085 nm的红外发射对应于4F_3/2→4I_11/2与4F_3/2→4I_9/2能级跃迁。研究结果证实, 双掺Mn4+/Nd3+的Y₂MgTiO₆在1 085 nm荧光强度比其单掺Nd3+的Y₂MgTiO₆增强了5倍。还进一步阐释了Mn4+→Nd3+能量传递主要是共振能量传递的偶极-偶极机制。近红外发光的下转换材料Y₂MgTiO₆:Mn4+/Nd3+对晶体硅太阳能电池的荧光转换层具有很好的应用价值。      

Investigations on Valence-Change Behaviors of Europium Ions in Eu-Doped Aluminate and Silicate Phosphors

Compounds of Sr3Al2O6∶Eu, Sr4Al14O25∶Eu, and BaZnSiO4∶Eu were synthesized by high-temperature solid state reactions. The doping Eu3 ions were partially reduced to Eu2 in Sr4Al14O25∶Eu and BaZnSiO4∶Eu prepared in an oxidizing atmosphere, N2 O2. However, such an abnormal reduction process could not be performed in Sr3Al2O6∶Eu, which was also prepared in an atmosphere of N2 O2. Moreover, even though Sr3Al2O6∶Eu was synthesized in a reducing condition CO, only part of the Eu3 ions was reduced to Eu2 . The existence of trivalent and divalent europium ions was confirmed by photoluminescent spectra. The different valence-change behaviors of europium ions in the hosts were attributed to the difference in host crystal structures. The higher the crystal structure stiffness, the easier the reduction process from Eu3 to Eu2 .     

白光LED用LaPO4:Eu3+红色荧光粉的合成与表征

利用水热法制备了性能稳定的红色荧光粉LaPO4:Eu3+,同时研究了不同的Eu3+浓度、煅烧温度对荧光粉发光性能的影响.通过X射线粉末衍射(XRD)和扫描电子显微镜(SEM)来表征荧光粉的晶体结构和颗粒大小及形貌;用激发光谱和发射光谱以及荧光衰减曲线来表征荧光粉的荧光性能.结果表明:未煅烧时前躯体主要是六方晶相LaPO4·0.5H2O,煅烧温度在900℃时,所制备样品为单斜相LaPO4:Eu3+;SEM图像显示5 at.%Eu3+掺杂LaPO4呈椭球形,颗粒长约为500 nm,宽约为300 nm.最大发射波长和激发波长分别为592 nm和393 nm,发射光谱中592 nm和612 nm的发射峰对应的是Eu3+离子的5D0→7F1和5D0→7F2跃迁.其荧光寿命为3.32 ms.     

微波辅助液相沉淀法合成Ca(MoO4)1-x(WO4)x:Eu3+红色荧光粉

以尿素为沉淀剂，采用微波辅助液相沉淀法合成了类球状双基质Ca(MoO₄)_1-x(WO₄)_x:Eu3+红色荧光粉，通过采用XRD、SEM、荧光光谱(PL)等现代分析技术对荧光粉的结构、形貌及发光性能进行了表征.结果表明，制备的Ca(MoO₄)_1-x(WO₄)_x:Eu3+红色荧光粉晶型完整，纯度高，为白钨矿结构；掺杂WO₄2-离子后，CaMoO₄:Eu3+红色荧光粉的发光性能明显增强，当WO₄2-离子的掺杂量x=0.4时，在395 nm激发下，在616 nm处的主发射峰的发光强度达到最大，掺杂浓度过高时会出现浓度淬灭现象.其较优的煅烧温度为1 000 ℃，煅烧时间为4 h.      

Luminescence Properties of Green-Emitting Phosphor （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ for White LEDS

The （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ green-emitting phosphors were synthesized by conventional solid-state reaction in a CO-reductive atmosphere, and their luminescent properties were investigated. The XRD data show that the Ba/Sr ratio not only affects the lattice parameters, but also influences the emission peak. The excitation spectra indicate that this phosphor can be effectively excited by UV light from 370 to 470 nm. The emission band is due to the 4f^65d^1→4f^7 transition of the Eu^2＋ ion. With an increase in x, the emission band shifts to longer wavelength and the reason was discussed. The emission spectra exhibit a satisfactory green performance under different excitation wavelength（380,398,412,420,460 nm）. （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ is a promising phosphor for green white-lighting-emission diode by ultraviolet chip.     

Preparation of BaMgAl10O17 ：Eu^2＋ and Its Phase Behavior in Microemulsion System

BaMgAl10O17 ： Eu^2＋ （BAM） was prepared in the microemulsion system and its phase behavior was studied. There exists a small region in the reverse microemulsion system where the dispersed particles are of spherical form. In this way, BAM blue phosphor with good dispersion can be synthesized. The microemulsion phase diagrams of the pseudo-ternary system （Triton X-100/cosuffactant-oil-BAM brine） were first established intuitively by the dilution method. The microstructure of microemulsions was determined through eyeballing, conductance technique, and polar optical microscopy. Its phase behavior is affected by various factors, such as temperature （room temperature, 30, 40 ℃）, oil, surfactants, and cosurfactants in microemulsions. According to the phase diagrams, the microemulsion system of Triton X-100/1-hexanol-hexane-BAM brine was chosen to prepare the precursor. The BAM phosphor can be obtained via sintering the precursor at a comparatively low temperature. The phosphors were characterized by XRD and vacuum ultraviolet （VUV） spectra.     

Combustion synthesis and luminescence properties of blue NaBaPO4:Eu2+ phosphor

The blue-emitting phosphor NaBaPO4:Eu2+ was prepared by the combustion method. The phase structure and microstructure of the as-prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Under the excita-tion wavelength of 360 nm, the emission spectrum exhibited only one blue band centering at 435 nm, which was ascribed to the 4f65d1→4f7 transition on Eu2+ ions. Compared with the phosphor obtained by solid-state reaction method, the relative emission intensity of sample ob-tained by combustion method increased slightly. The decay times and the temperature dependence luminescence intensities (25-300 oC) were discussed in order to further investigate the potential applications. Furthermore, Eu2+-doped NaBaPO4 phosphor showed higher thermally sta-ble luminescence comparable to commercially available Y3Al5O12:Ce3+ (YAG:Ce3+) phosphor. All the investigated suggestions that Na-BaPO4:Eu2+ is a good phosphor candidate applied in white light emitting diode.     

Luminescence properties of SrB4O7：Sm^2＋ for light conversion agent

A deep red-emitting SrB4O7:Sm2+ phosphor for light conversion agent was synthesized by the conventional solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the phase formation of SrB4O 7:Sm2+ materials. Results of luminescence properties showed that the phosphor could be efficiently excited by the UV-vis light region from 250-500 nm, and it exhibited deep red (685 nm) emission corresponding to 5D0 → 7F0 transition of Sm 2+ . The critical quenching concentration of Sm 2+ in SrB4O7 :Sm 2+ phosphor was about 0.05, and the corresponding concentration quenching mechanism was verified to be the dipole-dipole interaction according to the Dexter’s theory. The decay times had few alterations with different concentrations in SrB4O7:xSm 2+ phosphor.     

Luminescent characteristics of Ba3Y2（BO3）4：Eu^3＋ phosphor for white LED

The Ba3Y2（BO3）4：Eu^3＋ phosphor was synthesized using a high temperature solid-state reaction method and the luminescent characteristics were investigated. The emission spectrum exhibited one strong red emission at 613 nm, corresponding to the electric dipole 5D0-TF2 transition of Eu^3＋, under 365 nm excitation. The excitation spectrum of 613 nm indicated that the Ba3Y2（BO3）n：Eu^3＋ phosphor was effectively excited by ultraviolet （UV） （254, 365 and 400 nm） and blue （470 nm） light. The effect of Eu^3＋ concentration on the 613 nm emission of the Ba3Y2（BO3）n：Eu^3＋ phosphor was measured. The results showed that the emission intensity increased with increasing Eu^3＋ concentration, and then decreased. The CIE color coordinates of Ba3Y2（BO3）4：Eu^3＋ phosphor were x=0.641 and y=0.359 at 15 mol.% Eu^3＋.     

溶胶-凝胶法制备La2Ce2O7:Eu3+及其发光性能

采用溶胶-凝胶法（Sol-gel）合成La₂Ce₂O₇:Eu3+系列红色荧光粉,并研究煅烧温度、Eu3+掺杂浓度以及不同种类电荷补偿剂对样品发光性能的影响.通过XRD、SEM、荧光光谱对样品的晶体结构、形貌以及发光性能进行测量和表征.结果表明:实验所得样品主晶相为La₂Ce₂O₇,属于萤石结构. Eu3+及电荷补偿剂的掺杂没有改变其晶体结构.合成的样品在467 nm蓝光激发下发出612 nm的红光.样品的发光强度随煅烧温度以及Eu3+掺杂浓度的提高先增强后减弱,样品的较优的煅烧温度为1 100 ℃,Eu3+较优的掺杂浓度为10 %（摩尔百分比）.掺入电荷补偿剂可以有效增强样品的发光强度,其中掺入Li+后发光增强的效果最显著.