共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
白光LED用新型红色荧光粉的组成与发光性能的关系 总被引:5,自引:0,他引:5
白光LED有望发展成为新一代绿色照明光源.荧光粉作为配套材料,其性能优劣直接影响白光LED的发光效率、亮度以及显色性等.高效红色荧光粉已经成为白光LED发展的瓶颈.概述了Eu3+激活的钨/钼酸盐、氧化钇铋和钛酸盐,Sm3+激活的锌酸锶,Pr3+和Bi3+共激活的钛酸钙,Eu2+激活的氮化物,Ce3+激活的硅锗酸盐石榴石以及Mn4+激活的多铝酸钙和Mn2+激活的硫氧化锌钙等白光LED用新型红色荧光粉的发光性能的研究进展;着重分析了它们的组成变化对荧光性能的影响;并对今后的研究提出了一些设想. 相似文献
3.
(Ce0.001Y0.999)3Al5O12 and (Ce0.001Y0.999)3(CrxAl1−x)5O12 (x=0.001−0.005) transparent ceramics were synthesized by the solid state reaction and vacuum sintering and their optical properties were measured. High quality white light was obtained when the Ce:YAG/Ce,Cr:YAG dual-layered composite ceramic was directly combined with commercial blue LED chip. A maximum luminous efficacy exceeding 76 lm/W at a low correlated color temperature of 4905 K was obtained. The color temperature can be controlled by variations of Cr3+ concentration and the ceramic thickness. Hence, the Ce:YAG/Ce,Cr:YAG dual-layered composite phosphor ceramic may be a promising candidate for white LEDs. 相似文献
4.
《Journal of the European Ceramic Society》2020,40(10):3673-3678
This paper describes the laser sintering and luminescence properties of Y3Al5O12 (YAG) phosphors doped with different concentrations of Ce3+ and synthesized using the polymeric precursor method. The ceramics were sintered by a new laser sintering technique in which a CO2 laser is employed as the heating source. The resultant ceramics exhibited a homogeneous microstructure with narrow grain size distribution and high relative density. The introduction of Ce3+ ions led to luminescence quenching at a concentration above 0.5 mol% and a redshift of the emission spectrum band with increasing cerium concentration. The excitation spectrum showed two characteristic bands centered at 340 nm and 460 nm and a relative change in their intensity by change the Ce3+ concentration. The presence of a single valence (Ce3+) of cerium was determined by X-ray absorption near edge structure measurements. 相似文献
5.
6.
根据目前LED实现白光的两种主流方式:近紫光LED芯片+红/绿/蓝三基色荧光粉和蓝光LED芯片+黄色荧光粉(或+绿色/红色荧光粉),本文重点从黄色荧光粉、绿色荧光粉、红色荧光粉及蓝色荧光粉四个方面综述了利用阳离子置换实现对白光LED灯用荧光粉发光性能改善的研究进展,并对利用该方法对荧光粉的发光性能改善的研究趋势进行了展望。 相似文献
7.
To develop warm‐white light‐emitting diodes via conversion phosphors, blue light‐emitting diodes are generally combined with mixtures of green and red‐emitting phosphor powders. Generally, the phosphors are provided by resin embedded particle dispersions. Such resin‐based solutions cause several drawbacks with respect to LED lifetime and quality. Therefore, it has been investigated whether the red‐emitting nitride phosphor CaAlSiN3:Eu and the green‐emitting oxidic phosphor YAG:Ce can be cofired to layered ceramic composites. The shrinkage behavior and the composition of the interface in dependence of sintering temperature and the effect of interdiffusion processes at the interface on the luminescence properties were investigated. The formation of secondary phases at the interface in the cofired structures was found to limit the phosphor functionality for the nitride‐based CaAlSiN3:Eu in such composite ceramics. To counteract this, sacrificial interlayers were introduced to produce multilayered ceramics comprising CaAlSiN3:Eu and YAG:Ce for LED lighting applications. It is shown for the first time, that it is possible to sinter layered CaAlSiN3:Eu and YAG:Ce composite ceramics in a pressureless process at moderate sintering temperatures if one uses thin‐film passivated interfaces to reduce luminescence‐disturbing diffusion phenomena. These results demonstrate that diffusion barriers can be suitable means to obtain layered ceramic composites comprising CaAlSiN3:Eu and YAG:Ce in a pressureless sintering process with good optical properties. 相似文献
8.
9.
Yun‐Fang Wu Ya‐Han Chan Yung‐Tang Nien In‐Gann Chen 《Journal of the American Ceramic Society》2013,96(1):234-240
Ca3Sc2Si3O12:Ce3+ (CSS:Ce) green phosphors used for white light‐emitting diodes (LEDs) are synthesized and codoped with Al3+ via a solid‐state reaction method. The crystal structure and vibrational modes are analyzed by X‐ray diffraction, Fourier transform infrared spectroscopy, and Raman scattering spectroscopy. The energy transfer behavior and optical performance are characterized by photoluminescence and excitation spectra, quantum efficiency, and time‐resolved photoluminescence. The incorporation of Al3+ into CSS:Ce can inhibit the formation of the impurity phases Sc2O3 and CeO2, improve crystallinity, and enhance the photoluminescence intensity as well as quantum efficiency. The substitution of Sc3+ with Al3+ increased the crystal field splitting of Ce3+ and resulted in the red shift of photoluminescence. The results show that Ca3Sc2?xAlxSi3O12:Ce3+ has high quantum efficiency, making it a promising green phosphor that can be collocated with a commercial 450 nm blue LED and a red phosphor for solid‐state lighting applications. 相似文献
10.
Lihong Liu Rong‐Jun Xie Wanyuan Li Naoto Hirosaki Yoshinobu Yamamoto Xudong Sun 《Journal of the American Ceramic Society》2013,96(6):1688-1690
A novel Y3?xSi6N11: xCe3+ yellow phosphor was synthesized using the carbothermal reduction and nitridition method at 1550°C for 16 h in this letter. Photoluminescence spectra indicated that the phosphor showed broad excitation spectrum and had strong absorption in range of 350–450 nm. It also gave a broad emission band (Full width at half maximum = 153 nm) centered at 575 nm under 425‐nm excitation. With increasing Ce3+ concentration, the strongest emission intensity was obtained at 5 mol% Ce3+ doping amount and a systematic redshift was observed as the Ce3+ concentration increased. The results indicate that this novel yellow phosphor is a promising candidate for using in blue‐chip‐excited white light–emitting diodes (LEDs). 相似文献
11.
选用了10、20、30、40、50 μm 5种粒径的天然鳞片石墨(NG)作为添加剂,通过热压成型工艺制备了聚酰亚胺(PI)/NG复合材料,对其动态热力学性能、摩擦性能及断面、磨痕形貌进行测试与表征。结果表明,NG能够提高PI的储能模量及损耗模量,但是NG的粒径对其影响较小;随着NG粒径的降低,PI/NG复合材料的摩擦因数(f)和磨损率(ω)依次减小,添加粒径10 μm的NG之后,PI/NG复合材料的f为0.088 2,ω为6.19×10-7 mm3/N·m,并且具备比纯PI更平滑的磨损面,以及更连续致密的转移膜。 相似文献
12.
基于填料粒度对离合器摩擦材料性能影响的研究 总被引:4,自引:1,他引:3
本文提出采用丁腈乳胶改性酚醛树脂作粘结剂、采用玻璃纤维和复合包芯纱作为增强纤维、丁腈橡胶复合填料制备离合器摩擦材料的工艺方法。试验表,在相同配方和工艺条件下,复合填料的粒度对离合器摩擦材料的性能有很大影响。当复合填料粒度为20-60目左右时,摩擦材料具有较好的物理机械性能和良好的摩擦磨损性能。 相似文献
13.
14.
15.
通过界定不同的石粉粒径,改变石粉的掺量,研究不同粒径石粉对混凝土工作性能的影响,并最终确定对机制砂混凝土性能有显著影响的石粉粒径,即石粉中的关键粒径。在此基础上研究了关键粒径石粉含量与机制砂混凝土性能的关联性,提出相应的经验公式。研究表明,45μm为石粉的关键粒径,45μm以下石粉含量以及石粉的颗粒分布对于机制砂混凝土性能影响都十分显著;通过不同石粉含量与机制砂混凝土性能的关联分析,提出了机制砂混凝土用水量调整经验公式。 相似文献
16.
Junrong Ling Wentao Xu Jian Yang Tinghai Mu Ye Zhang Youfu Zhou Maochun Hong 《Journal of the European Ceramic Society》2021,41(12):5967-5976
Intense green emission is extremely significant to the color rendering index (CRI) of white LEDs. Various green-emitting YLuAG:Ce phosphor ceramics were successfully prepared by vacuum sintering. The effects of Lu3+ doping on structure and luminescence property were investigated in detail. In comparison with YAG:Ce, YLuAG:Ce ceramics own smaller grain size, better luminescence performance and higher thermal stability. The photoluminescence (PL) intensity of YLuAG:Ce ceramics increases by 23.6 % due to the “light scattering enhanced effect”. Furthermore, the Ce3+ emission is obviously blue-shifting from 533 nm to 519 nm, and the intensity of YLuAG:Ce ceramics reduces only about 8.9 % at 250 °C, showing better thermal stability (vs 11.1 % of YAG:Ce). The LE of LED packaged by YLuAG:Ce ceramic is up to 148.88 lm/W when the doping Lu3+ y is 2.1. The above results show that tailored YLuAG:Ce phosphor ceramic is a potential green-emitting color converter for high-power LEDs (hp-LEDs). 相似文献
17.
WaldemarA. Trzciski Stanisaw Cudzio Jzef Paszula James Callaway 《Propellants, Explosives, Pyrotechnics》2008,33(3):227-235
Detonation performance of non‐ideal RDX‐based compositions was studied. Charges of phlegmatised RDX containing 30% of two types of aluminium powders, coarse aluminium oxide or fine lithium fluoride particles were tested. The research concerning influence of inert and reactive additives on the detonation velocity and quasi‐static pressure was carried out. To estimate the degree of afterburning of the detonation products and reactive particles, closed explosions were performed in a chamber filled with different atmospheres. Explosion residues were also analysed. Gasdynamical and thermochemical calculations were also performed for the tested explosive compositions. 相似文献
18.
采用高速搅拌和快速膜乳化法制备鸡新流二联白油佐剂疫苗,考察了疫苗粒径均一性与疫苗引起的炎症反应和免疫学效应的关系. 结果表明,2种疫苗粒径约为1.0 mm,快速膜乳化疫苗(ME vaccine)的多分散系数(PDI)为0.036,高速搅拌疫苗(HS vaccine)的PDI值为0.279,前者粒径分布更均一. 两种疫苗的HI抗体和IgG抗体水平无显著差异. HS vaccine注射部位炎症因子IL-1b, IL-6, IL-17, TNF-a表达量最高分别为45, 7, 25和80 pg/mL,显著高于ME vaccine(均低于5 pg/mL). 均一白油佐剂疫苗在诱导有效免疫应答的同时,引起的炎症反应更轻. 相似文献
19.
20.
The influence of the particle shape on the results of different measuring techniques was investigated. Considered were single‐frequency ultrasound technique, 3D optical reflectance measurement (advanced particle analyzing system with multi capture signal technology), and focused‐beam reflectance measurement probes as techniques which are usable inline and in suspension density ranges usually present in industrial crystallization processes. Advantages and shortcomings of these techniques are compared and discussed. 相似文献