白光LED用Ce:YAG晶体的下降法生长和光谱性能

采用真空坩埚下降法生长了白色发光二极管(LED)用Ce:YAG晶体,该生长方法所得晶体的Ce3+掺杂浓度较高,相对色温(3 751K)低于传统方法所生长的Ce:YAG晶体,其激发峰是位于460nm左右的宽峰,与蓝光LED的发射波长相匹配,有望代替黄色荧光粉用于白光LED.随驱动电流增加,白光LED的发光效率逐渐降低,相对色温几乎不变.在100mA时,白光LED显色指数达到最大值.     

YAG:Ce~(3+)荧光粉最佳配方及其烧结工艺的探究(英文)

由于YAG:Ce3+荧光粉在白光发光二极管中的广泛应用,使其受到越来越多的关注.但是出于商业利益,其最佳配方和烧结工艺却是保密的.利用固相法,通过控制所掺杂Ce3+的浓度及调节烧结温度制备一系列YAG:Ce3+荧光粉.测试结果表明:当激发光波长为460 nm时,该荧光粉的发射波长为540 nm;最佳掺杂Ce3+的浓度及烧结温度分别为2%和1 400℃;此外,发射波长有红移的现象,此更符合现代固态照明对色度的需要.     

白光LED用YAG:Ce3+荧光粉的增红

目前白光LED在红光波段发射较弱,导致其显色指数偏低,本文在最常用的白光LED荧光粉Y3Al5O12:Ce3 (YAG:Ce3 )中掺入Gd3 、Pr3和Sm3 ,来增强红光波段的发射,从而提高显色指数.用X射线衍射仪(XRD)、分光光度计、光谱分析仪及荧光粉相对亮度测试仪对样品进行表征,研究了Gd3 、Pr3 和Sm3 对荧光粉性能的影响,并对其增红机理进行了初步的探讨.结果表明:Gd3 、Sm3 及Pr3 的加入都增强了光谱的红区发射,Gd3 使光谱发生红移;Sm3 则在光谱上增加了峰值分别位于566、600和616nm的三个弱发射峰;Pr3 在光谱的红区发射区叠加了一个峰值在610nm的尖锐发射峰;Gd3 、Sm3 及Pr3 的加入,使样品相对亮度及发光强度都下降了一定程度.     

暖白光发光二极管用红色荧光粉K2TiF6∶Mn4+的绿色合成

Mn⁴⁺掺杂的氟化物荧光粉具有宽带吸收、窄带红光发射、合成工艺简单等特点,在照明及显示领域受到极大关注,但其制备需要用到强腐蚀性的氢氟酸。本研究采用共沉淀法,分别以盐酸、硝酸、磷酸、醋酸替代氢氟酸制备了K₂TiF₆∶Mn⁴⁺荧光粉,采用X射线衍射仪、扫描电子显微镜、荧光光谱仪等对荧光粉的结构、形貌、性能进行表征。结果表明：酸性越强,荧光粉的结晶越好、形貌越完整、发光强度也越高,用强酸制备的样品与用氢氟酸制备的样品发光强度接近。将荧光粉用于制备白光发光二极管(light-emitting diode, LED)器件并进行光色性能的测试,结果表明：红色荧光粉的加入,能显著降低色温、提高显色指数;强酸样品的LED器件与氢氟酸样品的LED器件性能相当。     

Ce~(3+)、Sm~(3+)共掺杂YAG的制备及其发光性能的研究

用共沉淀法合成YAG:(Ce3+-Sm3+)前驱体后,在N2还原气氛下用高温灼烧法制备YAG:(Ce3+-Sm3+)荧光粉,并对Sm3+的掺杂浓度、样品的晶相以及表面形貌进行研究。同时,也对Sm3+与Ce3+之间Sm3+→Ce3+的能量转移机理进行了讨论。当Sm3+掺杂浓度(Sm3+/Ce3+为10%)时,其发射光谱强度能增加约3倍,并伴有明显的红移;合成的荧光粉体粒径大小在2～4μm时,有望与不同波长的蓝光LED组合,以期获得不同性质的白光LED。     

喷雾热解制备YAG∶Ce荧光粉及其发光性质表征

采用喷雾干燥热解二步法制备Y3Al5O12∶Ce荧光粉.利用X射线衍射、分子荧光光度法等研究柠檬酸和NaF等助剂添加对荧光粉结构与发光性能影响规律.结果表明,热解温度为1 100℃时,荧光粉中已不含YAP等过渡相;NaF能够增加荧光粉的光致发光强度,浓度为0.30 g.L-1时其发光强度最大;加入柠檬酸能够改善荧光粉成型性能,且以与金属离子等摩尔加入时最佳;制备的荧光粉在467 nm处获得最大激发,相应的发射光谱为峰值波长530 nm处的宽带发射.     

喷雾热解制备YAG:Ce荧光粉及其发光性质表征

采用喷雾干燥热解二步法制备Y3Al5O12: Ce荧光粉.利用X射线衍射、分子荧光光度法等研究柠檬酸和NaF等助剂添加对荧光粉结构与发光性能影响规律.结果表明,热解温度为1 100 ℃时,荧光粉中已不含YAP等过渡相;NaF能够增加荧光粉的光致发光强度,浓度为0.30 g·L-1时其发光强度最大;加入柠檬酸能够改善荧光粉成型性能,且以与金属离子等摩尔加入时最佳;制备的荧光粉在467 nm处获得最大激发,相应的发射光谱为峰值波长530 nm处的宽带发射.     

Gd_2Mo_4O_(15):Eu~(3+)荧光材料的制备与发光性能研究

采用了高温固相法制备了稀土离子Eu3+掺杂的Gd2M04O15:Eu3+荧光粉,通过X-射线衍射(XRD)和荧光光谱的测定,分别讨论了烧结温度、烧结时间以及稀土离子Eu3+掺杂量对发光性能的影响.测试结果表明Gd2Mo4O15:Eu3+荧光粉在近紫外区(uv)(393 nm)和蓝光区(464 nm)可以被有效的激发,Gd2Mo4O15:Eu3+荧光粉发出明亮的红光,对应于Eu3+的4f-4f跃迁,当Eu3+的掺杂浓度约为40 mol%时,在616nm处的发光强度最大.在393,464 nm的吸收分别与目前应用的紫外光和蓝光LED芯片相匹配.因此,Gd2Mo4015:Eu3+是一种可能应用在白光LED上的红色荧光材料.     

基于太阳能切削硅粉制备Eu~(2+)激发的直接白光荧光粉及其发光特性研究

以单晶硅太阳能电池切削产生的硅泥为原料,通过氨氮化工艺高温烧结制备了Eu~(2+)激发的直接白光荧光粉,研究了Eu~(2+)掺杂浓度对荧光粉发光性能的影响.物相分析结果显示,所合成的荧光粉为混合物,主要晶相为Ca_2SiO_4、CaSiO_3和Ca_2Si_5N_8.通过分析荧光光谱,发现荧光粉的有效激发范围为300～450 nm.在370nm近紫外光激发下,荧光粉中主要存在两个发光中心,分别位于470 nm和570 nm,发光颜色趋近于白光,色坐标为(0.327 5,0.386 6),色温为5 705 K(5 431.85℃).通过改变Eu离子掺杂浓度发现:荧光粉发光强度先增大后减小,最佳Eu~(2+)掺杂量为10.0 mol%;超过最佳掺杂浓度,由于离子间的相互作用导致浓度淬灭.通过单一荧光粉配合紫外芯片激发可直接获得白光输出.     

Ce:YAG透明陶瓷及其在白光LED中的应用

采用反应烧结法成功制备了透过率可以达到10%以上、平均晶粒尺寸约为8μm的Ce:YAG透明陶瓷,通过XRD、SEM等手段分析了此种透明陶瓷的基本性能.后将加工好的Ce:YAG透明陶瓷片制备成白光LED,并测试了相应的性能.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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