Preparation of a Core-Shell Structured Al2O3/YAG:Ce Phosphor by a Spray Drying Method and Formation Mechanism

采用喷雾干燥法制备核壳结构的Al2O3/YAG:Ce荧光粉,所得样品为立方Y3Al5O12结构,球形颗粒的粒径为1~8μm,显示出比共沉淀法高的内部量子效率。核壳结构的Al2O3/YAG:Ce荧光粉的形成机理为,起始悬浮液包含微米级的Al2O3和Y3+、Al3+、Ce3+等形成的聚阳离子,经过雾化形成小液滴,在溶剂挥发过程中,由于聚阳离子比微米级的Al2O3的迁移速度大,在颗粒间的毛细管力的作用下,自组装成为聚阳离子包裹微米级的Al2O3的核壳型结构,在850~1250℃时焙烧2 h,就得到了核壳型的荧光粉。     

吲哚啉螺苯并吡喃表面包覆SrAl_2O_4:(Eu~(2+),Dy~(3+))发光粉

以吲哚啉螺苯并吡喃(indoline spiropyrans,SP)和SrAl2O4:(Eu2+,Dy3+)(SAO-ED)发光粉为原料,采用界面配位键合方法在SAO-ED发光粉的表面包覆SP制备了SP/SAO-ED复合发光粉。通过X射线衍射、X射线光电子能谱、Fourier红外光谱表征了SP/SAO-ED复合发光粉的晶体结构和表面涂层组成;用紫外光谱、激发和发射光谱分析了该复合发光粉的光致发光性能和光致变色性能。结果表明:SP/SAO-ED复合发光粉由SAO-ED表面的金属离子与SP杂环上的N原子配位结合而成;该复合发光粉不但具有SAO-ED发光粉的晶体结构和光致发光性能,还具有SP的光致变色性能。     

Enhanced luminescence properties of Eu3+ in La2MoO6 by nonsensitization of Bi3+

It was unusual for Bi³⁺ ions to enhance the emission intensity of phosphors via nonsensitization. Here, La₂MoO₆:Eu³⁺, Bi³⁺ phosphors were successfully synthesized by a high temperature solid-state reaction method in air atmosphere. As the increase of doping concentration of Bi³⁺, the emission spectra of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors had obvious shifts, splits and the enhancement of intensities, which indicated that the characteristics of the phosphors were modified. To analyze these phenomena, the crystal structure refinements, spectral characteristic analyze and Judd-Ofelt theoretical calculation were mainly performed. Bi³⁺ ions played the role of the nonsensitizer and affected the distortion of the crystal, the sites of Eu³⁺ ions, the field splitting energy and the internal quantum yield. Moreover the nephelauxetic effects of Bi³⁺ ions and the ET process caused synergistically the life times of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors to increase and then gradually decrease. The CIE coordinates of phosphors changed within a small range. This study might be instrumental in promoting the further application of Bi³⁺ ions in rare earth luminescent materials.     

Controllable hydrothermal synthesis and photoluminescence properties of CaGd2(WO4)4:Eu3+ red-emitting phosphor

CaGd₂(WO₄)₄:Eu³⁺ phosphors with controllable morphology were synthesized via the hydrothermal method. The influences of pH value, reaction time and Eu³⁺ concentration on the crystal structure, morphology, and photoluminescence properties of CaGd₂(WO₄)₄:Eu³⁺ were studied. The pure tetragonal structure CaGd₂(WO₄)₄ is obtained when the pH value is 8 and 9. Furthermore, by altering the pH value of the reaction solution, the morphologies of the CaGd₂(WO₄)₄:Eu³⁺ phosphors evolve from spindle-shaped grains to tetragonal plate-like grains and finally to aggregated bulk particles. Under the 394 nm excitation, the phosphors display a bright red emission corresponding to the characteristic 4f-4f transitions of Eu³⁺, and the intensity of emission peaks depends mainly on the pH value, the reaction time, and the Eu³⁺ concentration. The optimum photoluminescence performance is achieved for CaGd_2-x(WO₄)₄:xEu³⁺ (x = 1) phosphor synthesized at pH = 8 under the reaction time of 16 h. Finally, the thermal stability of the phosphors is analyzed at different ambient temperatures.     

低温下改良型ICEAS工艺处理生活污水

采用改良型ICEAS工艺进行低温污水处理,考察了低温条件下改良型ICEAS工艺去除有机物及脱氮除磷的效果。实验结果表明：在温度为5～13℃时,改良型ICEAS工艺对生活污水中的有机物、氨氮、总氮及总磷的平均去除率分别达到87％、64％、60％和78％,较常温下的去除率分别降低了4％、20％、28％和4％。低温时活性污泥中微生物种群有所减少,但污泥沉降性能良好,因此改良型ICEAS有利于防止污泥膨胀。     

Synthesis of SrAl2O4：Eu^2＋,Dy^3＋ phosphors by the coupling route of microemulsion with coprecipitation method

Nano-sized SrAl2O4：Eu^2＋,Dy^3＋ phosphors with good monodispersity and narrow size distribution were synthesized by the coupling of water-in-oil （W/O） microemulsion with coprecipitation method. The phase composition, morphology, crystallinity, excitation spectra, emission spectra, and afterglow decay of SrAl2O4：Eu^2＋,Dy^3＋ nanophosphors were measured. It was found that the amount of surfactant that was used had an important effect on the shape and average size of the phosphor particles. SrAl204 phase of the phosphors showed an increase with the increase in calcination temperature. When the calcination temperature reached 1150℃, the fine crystal of SrAl2O4 was formed and the long afterglow luminescence could be obviously observed. In comparison with the samples prepared by the high-temperature solid-state method, the calcination temperature showed an obvious decrease and a dear blue shift occurred in the excitation and emission spectra of the sample. The afterglow time could be more than 8 h.     

New projection tubes using spherical phosphors and an electron gun having an impregnated cathode

Today, demand for flat and large displays are increasing dramatically. One of the solutions is a projection CRT system, which has significant advantages of low cost and high picture quality.1 We have newly developed projection tubes that combine spherical phosphors and a new electron gun that uses an impregnated cathode, resulting in a 40% improvement in resolution as well as a 5% increase in brightness compared with conventional tubes. The new projection tubes are suitable for high‐resolution displays for DTV and HDTV applications.     

稀土灯粉的质量控制以及与制灯工艺的配合

本文叙述了稀土三基色荧光粉的质量对荧光灯质量影响的诸多因素,简述了荧光粉与制灯工艺的配合和存在的问题。