B2O3对Eu2+,Dy3+共激活铝酸锶发光材料发光性能的影响

文章借助于材料的发射光谱和结晶相组成分析研究了B2O3对Eu2+,Dy3+共激活铝酸锶发光材料发光性能的影响.B2O3在Eu2+,Dy3+共激活铝酸锶发光材料的合成过程中,一方面作为助熔剂,降低发光材料的合成温度;另一方面,硼酸盐的存在促进Eu3+离子转化为Eu2+离子的还原过程.但是,B2O3加入量的变化并不引起发光材料发射光谱峰值的变化.     

合成工艺对2SrO·3A12O3:EW2+,Df3+磷光粉性能的影响

本文研究了B2O3的摩尔含量和合成温度两个因素对名义组成为2SrO.3A12O3:Eu2+,Dy3+长余辉发光材料性能的影响,实验表明,当B2O3加入量较少且合成温度适当时,可以观察到一个新物相的X射线衍射峰,此时EU2+的发射峰在460nm附近;当B2O3加入量较多或合成温度较高时,合成样品的主要物相是Sr4Al14O25:Eu2+,Dy3+,此时Eu2+的发射主峰在490hm附近.当合成温度为1250℃,B2O3加入量为15;摩尔分数时,样品的发光亮度较高,仪器可测的余辉时间达16h以上,肉眼可见的余辉时间达到24h,具有一定的实用价值.     

SrAl2O4:Eu2+,RE3+长余辉发光材料的微波合成及其发光特性

用微波法合成了SrAl2O4:Eu2 ,RE3 (RE3 =Er3 ,Dy3 ,Ho3 ,Nd3 ,Sm3 ,Ce3 ,Gd3 )系列长余辉发光材料.XRD结果表明:所得发光材料为α-Srnl2O4.激发光谱、发射光谱结果表明:RE3 的掺杂不改变材料的主发射峰位置,在室温下观察到了SrAl2O4:Eu2 ,RE3 (RE3 =Er3 ,By3 ,Ho3 ,Nd3 )的绿色上转换发光.余辉衰减曲线和热释光谱结果显示:余辉的初始亮度最高,时间最长,热释峰的温度最接近室温的是SrAl2O4:Eu2 ,Nd3 .     

荧光标记用Sr2MgSi2O7∶Eu2+,Dy3+纳米发光材料的研究

通过水热共沉淀法制备了Sr2MgSi2O7∶Eu2+,Dy3+纳米发光材料并对其进行表面修饰,研究了添加不同金属络合剂对样品粒径、分散性、发光性能的影响及表面修饰后样品的性能.通过X射线衍射分析,激发发射光谱及余辉性能测试研究了不同金属络合剂对Sr2MgSi2O7∶Eu2+,Dy3+结晶性能、发光性能的影响,通过SEM和TEM图分析研究了不同金属络合剂对颗粒粒径、分散性的影响,结果表明添加EDTA时样品结晶与发光性能良好且粒径为50～ 200 nm,为制备Sr2 MgSi2O7∶Eu2+,Dy3+纳米发光颗粒的最佳添加剂.此外,将样品进行表面修饰后,通过红外光谱、Zeta电势分析研究了其官能团的连接情况和电势大小,通过纳米粒度分析、SEM和TEM图谱分析研究了表面修饰后样品的粒径分布、形貌以及核壳结构,结果表明样品表面修饰后成功包裹了SiO2壳层,并通过悬浮测试证明了SiO2包覆后的长余辉纳米粒子悬浮性能良好.     

合成工艺对2SrO·3Al_2O_3:Eu~(2 ),Dy~(3 )磷光粉性能的影响

本文研究了B2O3的摩尔含量和合成温度两个因素对名义组成为2SrO.3Al2O3:Eu2 ,Dy3 长余辉发光材料性能的影响,实验表明,当B2O3加入量较少且合成温度适当时,可以观察到一个新物相的X射线衍射峰,此时Eu2 的发射峰在460nm附近;当B2O3加入量较多或合成温度较高时,合成样品的主要物相是Sr4Al14O25:Eu2 ,Dy3 ,此时Eu2 的发射主峰在490nm附近。当合成温度为1250℃,B2O3加入量为15%摩尔分数时,样品的发光亮度较高,仪器可测的余辉时间达16h以上,肉眼可见的余辉时间达到24h,具有一定的实用价值。     

烧结温度对蓝色长余辉材料Sr_2Al_6O_(11):Eu~(2+),Dy~(3+)发光性能的影响

采用传统的高温固相法合成了蓝色长余辉发光材料Sr_2Al_6O_(11)∶Eu~(2+),Dy~(3+),系统研究了烧结温度对Eu~(2+)和Dy~(3+)共掺杂蓝色铝酸锶长余辉材料物相及发光性能的影响.用X射线衍射仪对所合成的材料进行物相分析,用荧光分光光度计记录了样品的激发光谱和发射光谱,用亮度计记录其余辉衰减曲线.结果表明:随着烧结温度从1100 ℃升高到1300 ℃,材料的物相由富锶相逐渐向富铝相转变,其中1200 ℃条件下合成的样品主相为Sr_2Al_6O_(11);发射光谱首先发生蓝移,随后又发生红移,其中1200 ℃条件下合成的样品发射光谱峰值波长最短(468 nm);主相为Sr_2Al_6O_(11)的蓝色铝酸锶长余辉材料的余辉时间(≥1 mcd/m2)可达240 min以上.     

新型铝硅酸盐磷光体的结构及性能研究

以凝胶燃烧法在相对较低温度下合成了长石型的蓝白色长余辉材料Sr0.94Al2Si2O8:Eu2+0.02,Dy3+0.04,并用X射线粉末衍射(XRD)、荧光分光光度计(FL)以及扫描电子显微镜(SEM)等技术对样品的物相结构、光谱性质、微观形貌及粒度等进行了分析表征.结果发现:尿素用量、点火温度、还原温度及时间、冷却方式等工艺条件均直接影响样品的晶体结构,进而影响其发光性质.长余辉性能最佳时产物属于六方晶系及单斜晶系的混晶;其激发峰是位于290～400nm处的宽带峰;发射峰是位于380～520nm处的宽带峰,由两个发光中心构成,390nm处的发射峰归属于Dy3+的 4H21/2→6H15/2跃迁,440nm处的发射峰归属于Eu2+的4f65d1→4f7跃迁.结合XRD分析,我们认为两种发光中心是由于样品中包含两种晶型,且两种晶型的发射中心不同,六方晶系的发射中心以Dy3+为主,而单斜晶系的发射中心以Eu2+为主.1200℃还原1h后强制冷却所得样品的颗粒较细,一次粒径大约为0.5μm.     

宽带发射Ca2KMg2V3O12:Eu3+荧光粉的制备及其发光性能研究

本文通过高温固相法合成了新型的宽带发射Ca2KMg2V3O12:Eu3+荧光粉,并利用X射线粉末衍射仪,荧光光谱仪等表征手段对荧光粉的晶体结构及其发光性能进行了分析;探讨了Ca2KMg2V3O12荧光粉的自激活发光机理和Eu3+掺杂浓度对发光性能的影响.结果表明:所制备的样品为立方晶系Ca2KMg2V3O12晶体.在紫外光的激发下,Ca2KMg2V3O12:Eu3+既表现出[VO4]基团的宽带发射,又表现出Eu3+的特征发射,同时两者之间存在能量传递.Ca2KMg2V3O12:Eu3+荧光粉是一种良好的自激活发光材料,在紫外光激发的白光LED上具有潜在的应用前景.     

Eu3+对Ba3La(PO4)3∶Dy3+白光荧光粉发光性能的影响及发光机理的研究

采用高温固相法制备了Ba3La1-x-y(PO4)3∶ xDy3+,yEu3+白光荧光粉,并通过XRD和荧光光谱性能分析手段对样品的物相组成、发光性能和发光机理进行了研究.结果表明:由于Eu3+的掺杂影响了Ba3La(PO4)3∶ Dy3+荧光粉的晶体场环境,在Dy3+的6F9/2能级与Eu3+的5D0能级间发生交叉弛豫,并通过能量共振转移,Dy3向Eu3+传递能量,Ba3La1-x-y(PO4)3∶xDy3+,yEu3+荧光粉在350 nm紫外光激发下同时出现了Dy3+和Eu3+的特征发射,发射光谱中增加了红光成分,改善了色温.实验得出Dy3+和Eu3+掺杂浓度分别为0.08和0.06时,荧光粉的发射光最接近于理想白光.     

793nm光激发下GdVO4∶Eu3+上转换发光性能的研究

用水热法制备出GdVO4:Eu3上转换发光材料.对合成样品的发光性能进行研究,探讨了Eu3+掺杂量、pH值及乙二胺四乙酸二钠掺杂量对样品上转换发光性能的影响.结果表明:样品的结构为四方晶系,在793 nm近红外光的激发下,Eu3浓度为12;、pH值为3、乙二胺四乙酸二钠与稀土离子Eu3+掺杂比例为1:1时,GdVO4:Eu3+样品的上转换发光性能最好;且样品的发射光谱由四个发射峰组成,分别位于596 nm、619 nm、650 nm和698 nm处,归属于Eu3的5D0→7(J=1,2,3,4)电子跃迁.     

新型超细蓝色荧光粉Sr_2MgSi_3O_9: Eu~(2+)的合成及发光性质

采用凝胶-燃烧法在活性炭弱还原气氛下成功合成了新型蓝色发光材料Sr_2MgSi_3O_9∶ Eu~(2+).用X射线粉末衍射仪(XRD)、扫描电镜(SEM)、荧光分光光度计等对样品的物相结构、微观形貌及发光性质进行了分析和表征.结果表明:Sr_(2-x)MgSi_3O_9∶ Eu_x~(2+)系列样品的衍射峰数据与Sr_2MgSi_2O_7的JCPDS卡片(卡号:75-1736)衍射峰数据基本一致,属四方晶系.其一次颗粒近似球形,粒径在100 nm左右.激发光谱分布在250～450 nm的波长范围,主激发峰位于424 nm处,次激发峰位于400 nm处,可以被InGaN管芯产生的紫外辐射有效激发.发射光谱也为一宽带,最大发射峰位于470 nm附近,是典型的Eu~(2+)的4f 5d-4f跃迁导致的.Sr_2MgSi_3O_9∶ Eu~(2+)是一种很有前途用于白光LED的蓝色荧光粉.     

Strahlende und nichtstrahlende Rekombination am neutralen Silizium-Akzeptor in n-Ga0,2-Al0,8As

In cathodoluminescence of Si-doped n Ga_1-xAl_xAs (x ∼0,8) the most efficient near band transition is the recombination of a free hole with a bound electron at T = 80 K. This free-to-bound luminescence is observed competing with a 300 meV lower lying luminesccence band due to donor-acceptor-pair recombination. At high excitation density the pair radiation intensity is quenched in favour of the free-to-bound emission intensity. Both peaks shift to the short wavelength range; the pair band approximately by 45 meV and the free-to-bound transition peak by 3 meV. These effects are explained on the basis of a nonradiative threecenter-Auger-process involving the trapped holes on the acceptor states.     

Photoluminescence dynamics in chalcogenide glasses and crystals

Time-resolved photoluminescence studies reveal distinct differences between the recombination processes in a chalcogenide glass and in its crystalline counterpart. Here the three luminescence bands of a-As₂S₃ are interpreted in terms of the recombination of an excition, a self-trapped exciton and a pair of electron- and hole-like small polarons. The two luminescence bands observed in the crystal are attributed to the recombination of two types of excitons composed respectively of a hole bound to a self-trapped electron, and a hole which is induced to self-trap in the presence of a self-trapped electron.     

ZnS晶体中浅电子陷阱对光电子衰减过程的影响

本文采用微波吸收法,测量了ZnS:Mn,Cu:I,Br粉末材料受到超短激光脉冲激发后,其光生电子和浅束缚电子的衰减过程.发现制备过程中Mn2+、Cu1、I-、Br-的掺杂量对光生导带电子的衰减过程有明显的影响.光生电子寿命是I-、Br-形成的浅施主能级和Cu+受主能级、Mn2+发光中心共同作用的结果.本文还测量了材料的热释光曲线,Cu+受主能级、Mn2+发光中心会影响热释光强度,证实I-、Br-形成电子陷阱对光生电子和浅陷阱中的电子寿命有延长作用,而Mn2+发光中心会起到缩短寿命的作用.     

High performance visible light responsive photocatalysts for environmental cleanup via solution processing

Fabrication of nitrogen-doped titania and/or strontium titanate nanoparticles via soft chemical reactions and their performance for environmental cleanup under visible light irradiation were introduced. Nitrogen-doped anatase, brookite and rutile with high specific surface area can be selectively prepared by the solvothermal reactions in mixed aqueous solution of titanium trichloride-hexamethylenetetramine. Nitrogen-doped strontium titanate can be prepared by mechanochemical reaction of strontium carbonate, titania and hexamethylenetetramine using a planetary ball-mill. Nitrogen-doped titania shows excellent photocatalytic activity for the nitrogen monoxide destruction under visible light irradiation. The photocatalytic activity of nitrogen-doped titania is in the order anatase > brookite > rutile. The photocatalytic activity of nitrogen-doped titania and strontium titanate can be improved by co-doping with higher valence metal ions to reduce oxygen vacancy and/or coupling with Fe₂O₃ and Pt to retard quick recombination of photo-induced electron and hole by the heterogeneous electron transfer.     

Bi_4Si_3O_(12):Sm~(3+)荧光粉的制备及发光性能的研究

采用溶胶凝胶法制备了Bi_4Si_3O_(12):Sm~(3+)荧光粉体,并用X射线衍射(XRD)、扫描电镜(SEM)和荧光光谱(PL)对Bi_4Si_3O_(12):Sm~(3+)荧光粉的结构和发光性能进行表征。研究发现:在850℃煅烧下得到Bi_4Si_3O_(12)纯相;PL谱表明该粉体从近紫外到蓝光范围内都可以得到有效激发。在紫外光激发下,产物有4个发射峰,分别位于468 nm和563 nm,600 nm,649 nm,归属于Bi~(3+)的3P1→1S0跃迁和Sm~(3+)的~4G_(5/2)→~6H_J(J=5/2,7/2,9/2)能级跃迁,并对Bi~(3+)和Sm~(3+)之间的能量传递机制进行讨论。在467 nm的蓝光激发下粉体呈现橙黄色发光,发射峰来源于Sm~(3+)的~4G_(5/2)→~6H_J特征辐射跃迁,且最强发射峰位于563 nm处,Sm~(3+)的最佳掺杂浓度为3mol%。     

Ce3+激活NaSr4(BO3)3荧光粉的格位占据和发光性质研究

采用高温固相法制备了一系列可被紫外光有效激发的Na_1+xSr_4-2x(BO₃)₃∶xCe³⁺荧光粉,并通过X射线衍射、扫描电镜、荧光光谱等测试方法对样品的物相结构、形貌和发光特性进行了表征及分析。X 射线衍射结果显示,Ce³⁺成功掺入到基质NaSr₄(BO₃)₃中;利用高斯峰拟合、多光谱对比等手段,分析并验证了发光中心Ce³⁺占据了NaSr₄(BO₃)₃中Sr²⁺(1)和Sr²⁺(2)两个格位;研究了不同浓度Ce³⁺的掺杂对发光位置和发光强度的影响,随着Ce³⁺掺杂浓度的提高,发射光谱出现红移,发光强度出现增强→减弱→再增强的趋势;将荧光粉的发射光谱与植物光合色素吸收光谱进行对比,发现它不仅可以吸收300~350 nm的紫外光,发射光谱还很好地覆盖了植物光合色素所需的蓝光区吸收波段,证明其在农业生产的转光剂方面有潜在应用价值。     

Radiation-induced trapping centers in thin silicon dioxide films

In this paper the technological and scientific aspects of radiation-related charge trapping in thin SiO₂ films are reviewed. These films are amorphous in nature and are thermally grown on single crystal silicon substrates serving as the insulating layer in metal-oxide-semiconductor (MOS) capacitors and transistors. The structure and operation of these devices are reviewed with special emphasis on the effect of charges trapped in the oxide. The technical importance of understanding the interaction of ionizing radiation with thin SiO₂ films is illustrated with two practical examples. The first involves the operation of MOS transistors in environments where ionizing radiation is present, leading to an accumulation of positive space charge in the oxide. The second deals with process-induced defects generated by radiation encountered during the fabrication of devices by processes such as electron beam lithography or electron gun metallization. Unannealed traps of this type capture hot electrons producedin the substrate during the operation of the MOS transistor. In both these examples, the charging of the oxide results in instabilities which degrade operation.

Its sensitivity to charge trapped in the insulator makes the MOS system an ideal vehicle for scientific study of these phenomena. The basic techniques for characterizing the density, capture cross-sections, and location are briefly discussed and applied to the problem of radiation-induced defects in thin SiO₂ films. Ionizing radiation is shown to interact with the SiO₂ in two modes. In the first it supplies carriers to fill pre-existing hole traps at the interfaces. In the second it creates electron and hole traps in the bulk of the thin film. These latter defects are in a neutral state after irradiation and are detectable only when either electrons or holes are subsequently injected into the oxide. The capture cross-sections, trap densities and location of these centers in the film are presented. The annealing treatments required to remove these traps from aluminium and polysilicon gate devices are also discussed. The number traps produced by an incident 25 KV electron beam is found to depend weakly on the dosage. A dipolar defect, produced by the ionizing radiation, seems to explain the behavior of the neutral centers.