白光LED用Ca0.5-xWO4∶Eu0.253+Li0.25+Srx2+红色荧光粉的合成及发光性能研究

采用溶胶-凝胶燃烧法合成了不同Sr2+掺杂浓度的Ca0.5-xWO4∶Eu0.253+Li0.25+Srx2+(x=0,0.05,0.10,0.15,0.20,0.25)红色荧光粉,分别采用X射线衍射(XRD)、扫描电镜(SEM)和荧光分光光度计对荧光粉的结构、微观形貌和发光特性进行表征.结果表明,在500℃低温下煅烧4h可得到纯白钨矿结构的Ca05WO4∶Eu0.253+Li0.25+荧光粉,且荧光粉的颗粒随着煅烧温度的升高而增大,800℃合成的晶粒尺寸比较均匀,平均粒径在1～2 μm左右.Ca0.5-xWO4∶Eu0.253+Li0.25+Srx2+系列荧光粉均可以被393 nm和464 nm有效激发,其发射主峰值位于615 nm,属于Eu3的5D0→7F2跃迁.同时还系统研究了Sr2+的不同掺杂浓度对荧光粉发光性能的影响.Ca05-xWO4∶Eu0.253+Li0.25+Srx2+荧光粉中Sr2+的最佳掺杂浓度为x取0.15.     

铕离子掺杂的钼酸镉红色荧光粉的合成与光谱性质

为了优化荧光粉合成工艺条件,本文以Cd(NO3)2.4H2O和Na2MoO4.2H2O为原料,采用沉淀法制备Eu3+掺杂的CdMoO4微纳米颗粒。在300℃下,分别对样品保温1 h,3 h,5 h,通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、红外光谱(IR)、荧光光谱分析(PL)对样品进行了表征。XRD分析结果表明产物为纯白钨矿型纯四方相CdMoO4。固定发射波长在615 nm,样品激发波长在333 nm左右出现最强锋,在534 nm、464 nm、394 nm处的锐激发谱线分别对应Eu3+的7F0→5D1、7F0→5D2、7F0→5L6的跃迁,在333 nm光激发时,主发射峰位于615 nm附近,归属于5D0→7F2能级跃迁发射,而位于589 nm附近的弱发射峰归属于5D0→7F1跃迁。     

CaCO3基红色荧光粉的合成及其光谱性能分析

采用水热法合成CaCO3: Eu3+和CaCO3: Eu3+, Li+红色荧光粉,研究了掺杂离子对样品的物相、晶粒形貌和光谱性质的影响.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、傅立叶红外光谱(FT-IR)、激光拉曼光谱(Raman)和荧光光谱(PL-PLE)等手段表征样品的性能.结果表明:样品均为三角晶系的方解石结构;Eu3+作为发光中心取代了基质CaCO3中Ca2+的位置;Li+作为电荷补偿剂有助于Eu3+更好的进入到基质的晶格中,提高样品的发光性能;样品CaCO3: Eu3+ 和CaCO3: Eu3+,Li+的最大激发峰分别位于254 nm(Eu3+-O2-的电荷迁移跃迁)和396 nm(7F0→5L6跃迁),其最强发射峰分别位于 616 nm和610 nm,均为电偶极跃迁5D0→7F2,属于红色发光.     

花状NaLa(MoO4)2∶Eu3+,M(M=Gd3+,Ti4+)红色荧光粉的水热合成及发光性能

以乙二醇和水的混合溶液为溶剂,采用水热法合成了花状的NaLa(MoO4)2∶Eu3+红色荧光粉.通过X射线衍射仪、扫描电子显微镜、荧光分光光度计等手段对产物进行了分析和表征.结果表明:产物NaLa(MoO4)2∶Eu3+属于四方晶系白钨矿结构.样品分散性好,粒度均匀,呈花状结构.样品的激发光谱分为两部分:位于250～350 nm的宽激发带归属于Eu-O,Mo-O之间的电荷迁移;350～500 nm的系列尖锐峰归属于Eu3+的f-f跃迁.样品的发射光谱中主发射峰位于615 nm处,归属于Eu3的5 Do→7R电偶极跃迁.此外,共掺杂适量的Gd3+或Ti4能够有效敏化Eu3+的发光,明显增强了615 nm的红光发射.     

MMoO4∶Pr3+(M=Sr,Ba,Ca)红色荧光粉的合成及其发光性能研究

采用水热法制备了Pr3+激活的MMoO4∶Pr3+(M=Sr,Ba,Ca)系列荧光粉,通过X射线衍射(XRD)、扫描电镜(SEM)及荧光光谱(PL)对该系列荧光粉的物相、形貌及发光性能进行了表征.结果表明:Pr3+的掺入没有改变荧光粉的主晶相,在450nm蓝光激发下,样品产生了红光发射,其中对应于Pr3+的特征跃迁3P0→3 F2位于647 nm的Ba9.98Pr0.02MoO4发射峰最强.MMoO4∶Pr3+ (M =Sr,Ba,Ca)红色荧光粉可以被蓝光LED有效激发产生红光,是一种优异的YAG∶ Ce3+黄色荧光粉的红光补偿粉.     

白光发光二极管用CaAl2B2O7:Eu3+微晶的发光性质

利用高温固相法合成了CaAl2B2O7:Eu3+微晶.X射线衍射分析表明我们得到了纯相的CaAl2B2O7基质.样品在近紫外光和蓝光激发下能发出红光.发射光谱的主峰位于614nm,对应于Eu3+的5D0→7F2跃迁.激发光谱中两个主峰位于401nm和471nm,分别与紫外和蓝光LED相匹配.并研究了电荷补偿剂和Eu3+的浓度对样品发光强度的影响.所有掺入电荷补偿剂(Li+,Na+和K+)样品的发光强度都比没有掺入电荷补偿剂的样品高.其中掺入Li+的样品的发光强度最高.Eu3+的最佳浓度为6;.CaAl2B2O7:Eu3+是一种有应用前景的白光LED用红色荧光粉.     

碱金属和三价Eu离子共掺杂的碱土钼酸盐荧光粉发光性能

采用固相法制备了用于白光LED的Eu3+和碱土离子(Li+,Na+,K+)共激活的钼酸盐荧光粉AMoO4(A=Ca,Sr).通过X射线衍射图片看出,Eu3+和Na+的掺入降低了晶格参数,同时衍射峰强度明显增加.本文研究了荧光粉的激发光谱和发射光谱.它的激发谱覆盖了从240nm到500nm的范围,在470nm处有一个激发峰,这说明它能够被GaN LED发出的蓝光有效激发.发射谱表明它能够发射峰值位于616nm和624nm的红光.实验研究了碱土离子的量(摩尔分数)对AMoO4:Eu3+发光性能的影响,0.25是最合适的掺杂量.反应时间和反应温度对发光性能也有很大的影响.搅拌均匀的反应物在800℃灼烧3h得到的样品发光强度最强.     

NaBaPO4∶Eu3+,Yb3+的近红外下转换机制

采用固相法制备了掺杂Eu3+,Yb3+的NaBaPO4下转换荧光粉.在394 nm紫外光激发Eu3+下,获得了对应于Yb3+∶2 F7/2→2F5/2发射的1004 nm的近红外光.测量了样品的可见和近红外荧光光谱以及Eu3+的衰减曲线,验证了Eu3+到Yb3+的能量传递.观测到了样品的下转换过程,并未观测到量子剪裁现象.研究表明:Yb3+的荧光强度和能量传递效率随着Yb3+掺杂浓度的变化而变化,当样品中Eu3+,Yb3+的掺杂浓度都为5;时,具有最强的近红外发光,Eu3+到Yb3+的能量传递效率为67.9;.     

Na+,Dy3+,Eu3+掺杂YAG荧光粉的光学性能

本文用高温固相法制备了Na+,Dy3+,Eu3+掺杂YAG系列荧光粉.通过改变掺杂的Dy3+浓度、激发波长、掺杂Na+,研究其对发光的影响.X射线衍射结果显示,硼酸、Na+、Dy3+、Eu3+掺入基本不影响YAG的立方晶相,且随Na+、Dy3+、Eu3+浓度增加,样品衍射峰位置向小角度偏移.用λem=590 nm监测D...     

CaGd2(MoO4)4:Sm3+,La3+荧光粉的 制备及发光性能研究

采用高温固相法合成了CaGd2-x(MoO4)4:xSm3+(x=0.1、0.3、0.5、0.7、0.9)橙红色荧光粉.研究了样品的X射线衍射谱(XRD)、激发光谱和发射光谱.从XRD图谱测试结果表明,在900℃下烧结6 h后得到的样品为纯CaMnO4晶相,样品CaGd2(MoO4)4:Sm3+的激发光谱由两部分组成:一部分(250～340)nm为属于O2--M6+O的电荷迁移带;另一部分(350～450)nm的系列线状峰是Sm3+的f-f跃迁特征激发峰.样品在405 nm(6H5/24F7/2)下激发得到的发射光谱,其主发射峰位于646 nm(6 G5/26 H7/2)处.当Sm3+掺杂浓度高于2;时,样品CaGd2-x(MoO4)4:xSm3+发生浓度猝灭现象,该现象是由于离子间的能量传递.在CaGd1.5(MoO4)4:0.5Sm3+样品中掺入一定浓度La3+,掺入La3+并没有改变CaGd2(MoO4)4:Sm3+光谱峰的形状和位置,当y=0.8时,荧光粉的发光强度最好.通过测量计算GIE在405 nm激发下的色坐标,显示色坐标均在橙红色区域移动,表明荧光粉的光色性较好.     

Crystal Structure Phase Transitions in the Perovskites A(Cu1−xMnx)Mn4O12(A = Na+, Ca2+, Y3+, La3+)

X-Ray diffraction and neutronographical studies on the crystal structure of the perovskitelike compounds A(Cu_1−xMn_x)Mn₄O₁₂ have been undertaken. It has been shown that the samples with 50% of Mn³⁺ in the octahedral sites have a cubic unit cell, while the samples with higher Mn³⁺ composition may have a monoclinic or rhombohedral unit cell. The temperature increase raises the symmetry to the cubic one. The concentration ranges with different symmetry type have been determined. The lowering of the symmetry of the unit cell is due to the cooperative Jahn-Teller effect.     

Determination of Concentration of Rare Earth Ions Yb3+, Er3+, Tb3+, Ho3+, Tm3+ in Monocrystals of Yttriumaluminum Garnets on Basis of Magnetic Susceptibility

Crystals of solid solutions (R_xY_1-x)₃Al₅O₁₂ (where R is rare earth ion Er³⁺, Yb³⁺, Tb³⁺, Ho³⁺, Tm³⁺) with garnet structure were grown. The temperature dependencies of magnetic susceptibility for these crystals were obtained. On the basis of measurement of magnetic susceptibility a non-destructive technique for determining the concentration of rare earth ions in yttrium-aluminum garnets was developed.     

Photoacoustic Spectra of Pr3+, Nd3+, Gd3+ Acetate Complexes

The crystals of the complexes Pr(Ac)₃ · 4 H₂O, Nd(Ac)₃ · 4 H₂O, Gd(Ac)₃ · 4 H₂O were synthesized and their Pa spectra determined firstly. Their PA spectra and absorption are interpreted. The fluorescence properties of Pr³⁺, Nd³⁺, Gd³⁺ and the relaxation process models were studied by their PA spectra.     

Crystal Growth and Spectroscopic Characterisation of BiB3O6:RE3+ (RE3+ = Pr3+, Nd3+, Gd3+, Er3+, Tm3+)

Large single crystals of optical quality of BiB₃O₆:RE³⁺ (RE³⁺ = Pr³⁺, Nd³⁺, Gd³⁺, Er³⁺, Tm³⁺) were grown from nearly stoichiometric melts using the top‐seeding growth technique to dimensions up to 12 x 12 x 18 mm³. Absorption spectra were measured in the wavelength range from 10000 cm^‐1 to 30000 cm^‐1 with an absorption spectrometer to estimate the doping concentration of RE³⁺. For the determination of the phonon energies and the quenching behaviour of the host lattice IR and Raman spectra were recorded.     

Photoluminescence of Sm3+, Dy3+, and Tm3+-doped transparent glass ceramics containing CaF2 nanocrystals

Photoluminescence properties of Sm³⁺, Dy³⁺, and Tm³⁺-doped transparent oxyfluoride silicate glass ceramics containing CaF₂ nanocrystals were reported. Emission bands of ⁴G_5/2 → ⁶H_5/2 (562 nm), ⁴G_5/2 → ⁶H_7/2 (598 nm), ⁴G_5/2 → ⁶H_9/2 (645 nm) and ⁴G_5/2 → ⁶H_11/2 (706 nm) for the Sm³⁺: glass and glass ceramic, with an excitation at ⁶H_5/2 → ⁴F_7/2 (402 nm) have been recorded. Of them, ⁴G_5/2 → ⁶H_7/2 (598 nm) has shown a bright orange emission. With regard to the Dy³⁺: glass, a bright fluorescent yellow emission at 575 nm (⁴F_9/2 → ⁶H_13/2) and blue emission at 481 nm (⁴F_9/2 → ⁶H_15/2) have been observed, apart from 662 nm (⁴F_9/2 → ⁶H_11/2) emission transition with an excitation at 386 nm (⁶H_15/2 → ⁴I_13/2 + ⁴F_7/2) wavelength. Emission bands of ¹G₄ → ³F₄ (650 nm) and ¹G₄ → ³H₅ (795 nm) transitions for the Tm³⁺: glass and glass ceramic, with an excitation at ³H₆ → ¹G₄ (467 nm) have been observed. Of them, ¹G₄ → ³F₄ (650 nm) has shown bright red emission. Decay lifetime measurements were also carried out for all the observed Sm³⁺, Dy³⁺, and Tm³⁺-doped glass and glass ceramic emission bands.     

Excited-state absorption spectroscopy of crystals doped with Cr3+, Ti3+, and Nd3+ ions. Review

Basic results of the investigations of the absorption and luminescence spectra of strongly pumped crystals doped with Cr³⁺, Ti³⁺, and Nd³⁺ ions are considered. These investigations have been systematically carried out since 1968 in the Laboratory of Physics of Optical Crystals and the Laboratory of Spectroscopy of Crystals of the Shubnikov Institute of Crystallography of the Russian Academy of Sciences. The results obtained are compared with the data in the literature.     

X‐ray diffraction and magnetization studies of BiFeO3 multiferroic compounds substituted by Sm3+, Gd3+, Ca2+

The multiferroic compounds Bi_0.9Sm_0.1FeO₃, Bi_0.9Gd_0.1FeO₃, Bi_0.9Ca_0.1FeO₃, Bi_0.9Sm_0.05Ca_0.05FeO₃, and Bi_0.9Gd_0.05Ca_0.05FeO₃ were prepared by the conventional ceramic method and were characterized by X‐ray diffraction, vibrating sample magnetometry, and differential scanning calorimetry. The compounds were found to have the rhombohedral perovskite‐like structure, accompanied by a small residual Bi₂Fe₄O₉ impurity phase. Magnetic hysteresis loops with enhanced remnant magnetization and coercive field were obtained for the Gd‐containing compounds. The improvement of magnetic behavior of the Gd‐containing compounds is thought to arise mainly from the partial suppression of the spiral spin structure and the stronger interaction between magnetic ions. The magnetic transition temperatures of the compounds were found to be in the range 300‐310 °C. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structures and magnetic properties ofA 2MnCl6 salts (A = NH4 +, K+ and Rb+)

The temperature dependence of the magnetic susceptibility ofA ₂MnCl₆ salts (A = NH₄ ⁺, K⁺, Rb⁺) has been measured, and their crystal structures determined using powder X-ray diffraction methods. The structures of these simple cubic salts are governed by thex coordinate of the halide ion. The magnetic and the structural data suggest the presence of antiferromagnetic interactions between adjacent MnCl ₆ ^2– octahedra across bridges of the type as were found in related iridium salts: the susceptibility and the structural data have been used to estimate separately the values of ratios of the exchange integrals between pairs of salts; the agreement is better than 6 %.Research performed under the auspices of the U.S. Atomic Energy Commission.     

In situ chemical co-precipitation synthesis of YVO4:RE (RE = Dy3+, Sm3+, Er3+) phosphors by assembling hybrid precursors

YVO₄:RE (RE = Dy³⁺, Sm³⁺, Er³⁺) were prepared via an in situ chemical co-precipitation technology, and the assembly process of hybrid precursors was as follows: using rare earth coordination polymers with salicylic acid as precursors and composing with the polyvinyl alcohol (PVA) as dispersing media. Their microstructure and micromorphology have been analyzed by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), which indicate that there exist some novel cobblestone-like microcrystalline particles. All the doped rare earth ions showed their characteristic emissions in YVO₄ hosts. The concentration quenching all appeared of the three dopant ions and the optimum concentrations for Dy³⁺, Er³⁺, Sm³⁺ were determined to be 2, 3, 1 mol% in yttrium vanadate particles, respectively.