白光LED用红色荧光粉Sr0.7Ca0.3－2xMoO4:Eux3+Nax+的制备及发光性能研究

采用高温固相法合成白光LED用红色荧光粉Sr0.7Ca0.3-2 xMoO4Eux3+Nax+,对样品分别进行X射线衍射(XRD)分析和荧光光谱的测定,讨论了不同掺杂量下合成的荧光粉的发光性质。XRD图谱分析表明,在1 000℃下灼烧9h得到的样品为纯相的SrMoO4。研究结果表明,制备的Sr0.7Ca0.3-2 xMoO4:Eux3+Nax+荧光粉可以被近紫外光(393nm)和蓝光(464nm)有效激发;发射光谱中,在波长在611nm和615nm处有很强的发射峰,其中最强发射峰位于615nm左右,与Eu3+的5D0→7F2跃迁对应。进一步探讨Na+和Eu3+掺杂浓度对发光强度的影响,得出Sr0.7Ca0.3-2 x MoO4:Eux3+Nax+样品的发光强度比SrMoO4:Eu3+Na+增强,当掺杂量x=0.07时,Sr0.7Ca0.3-2 x MoO4:Eux3+Nax+样品在波长614nm处发光强度最强。最后测试计算样品在393nm紫外激发下的色坐标,当Eu3+和Na+的掺杂量x=0.02时,样品红色显示最强。研究结果表明,所合成的红色荧光粉Sr0.7Ca0.3-2 xMoO4:Eux3+Nax+新型红色荧光粉适合在白光LED中应用。     

一种白光LED用绿色荧光粉Ba_3Si_6O_(12)N_2:Eu~(2+)的制备及研究

采用传统高温固相反应法,合成了Ba3-x Si6O12N2:xEu2+系列荧光粉。X射线衍射(XRD)图谱分析表明,所有的样品均生成了Ba3Si6O12N2纯相。激发光谱表明,样品在紫外到蓝光(250~470nm)范围内都可以被有效激发,当激发波长为358nm时,发射光谱是Eu2+典型的宽带发射,发射峰在495nm附近,属于4 f7→4 f65 d1能级之间的跃迁,半峰宽覆盖青绿光范围(480~557nm)。研究了Eu2+掺杂浓度对发光性能的影响。结果表明,随着Eu2+掺杂量的逐渐增加,发光强度逐渐增大,当x=0.15时,发射强度达到最大,所对应的发射光谱波峰的波长最小(492nm);当Eu2+的掺杂量继续增加时,发光强度开始减弱,这是由于Eu2+间距逐渐减小,非辐射跃迁几率增加而发生浓度猝灭现象;不同浓度的样品的发光强度与波长呈相反变化趋势,这与斯托克斯(Stokes)定律是相符合的。研究结果表明,所合成的Ba3Si6O12N2:Eu2+新型绿色荧光粉适合在白光LED中应用。     

LiCaPO4:Eu3+材料制备白光LED及其发光特性

采用高温固相法制备了LiCaPO4:Eu3+红色发光材料,研究了Eu3+掺杂浓度、R+或Cl-等对材料发光性质的影响.结果显示,在399 nm近紫外光激发下,材料呈多峰发射,分别由Eu3+的5DO→7FJ(J=0,1,2,3,4)能级跃迁产生,主峰为612 nm;监测612 nm发射峰,所得激发光谱由O2-→Eu3+电...     

KSrPO_4:Eu~(3+)红色发光材料的制备及性能研究

采用高温固相合成工艺制备了KSrPO4:x Eu3+红色发光材料,通过X射线衍射、荧光光谱、量子效率仪、封装对发光材料的晶体结构及发光特性进行了研究。XRD表明KSrPO4晶体结构并没有随着Eu3+的掺入而发生变化;荧光光谱表明KSrPO4:Eu3+在394 nm处存在最强激发峰,发射光谱最强发射峰为612nm;量子效率研究表明随着Eu3+掺杂量的增加,量子效率先增后降,在Eu3+掺杂量x=0.04时,量子效率存在最大值51%;封装光源的显色指数为83,色温3497 K,并且随着电流的变化色坐标(X,Y)基本保持不变,因此,KSrPO4:Eu3+红色发光材料作为近紫外激发的红色发光材料具有一定的潜力。     

利用“纳米反应器”一步合成YF3:Yb3+,Er3+纳米粒子及光谱特性

采用微乳液法在室温下快速合成出YF3:Yb3+,Er3+纳米粒子,X射线衍射图(XRD)与YF3标准卡片PDF#74-911非常吻合,经扫描电镜( SEM)分析表明所制备的纳米粒子为球形,粒径约为32 nm.同时研究了YF3:Yb3,Er3+的下转换光谱和上转换光谱,实验发现,下转换光谱最强发射峰位于1544 nm;在...     

Bi3+共掺和能量传递对BaY2Si3O10: Eu3+发光的调制和影响

荧光粉BaY2Si3O10: Bi3+, Eu3+经高温固相法制备并由X-ray衍射谱仪分析其物相结构。实验结果显示Bi3+共掺下BaY2Si3O10: Eu3+的激发光谱呈现一个有明显增强的宽电荷转移带和系列Eu3+的 f – f 窄吸收峰,发射谱为Eu3+的5D0-7FJ橙-红光发射。当用285 nm 紫外光激发时,Bi3+到Eu3+间存在有效的能量传递,导致Bi3+的宽带紫外发射(中心345 nm)强度减弱,而Eu3+的橙-红光发射显著增强;随着Eu3+浓度的增加,能量传递效率也随之提高。最佳Eu3+浓度为0.4摩尔百分比,此后荧光粉发射强度发生浓度猝灭。结果表明Bi3+共掺时明显改善和提升荧光粉在电荷转移带(200 – 350 nm)的激发效率。Bi3+到Eu3+间主要的能量传递机制是通过四极–四极相互作用实现,并且能量传递的临界作用距离是1.604 nm     

纳米SiO2基质中Eu3+的发光特性

采用溶胶凝胶法(sol-gel)制备了Eu3+掺杂SiO2基质发光材料,分别用荧光(PL)光谱、原子力显微镜(AFM)、扫描电镜(SEM)等分析手段对样品进行了表征,研究了退火温度以及掺杂浓度对发射光谱的影响,并对其发光机制进行了分析.薄膜样品在258 nm光激发下,在620 nm,667 nm处出现了比较少见的双峰红光发射,而620 nm处的光发射最强,说明Eu3+离子处在对称性较低的配位环境中.退火处理温度对样品的发射光谱影响很大,经900 ℃退火处理的样品发射强度最强.随着掺杂浓度的变化,改变了Eu3+ -O2-间的距离,在相同紫外光激发下O2-外层的电子迁移到Eu3+ 4f轨道上的能量变化,使得谱线位置出现了移动.     

天然方钠石的近红外发光特性

采用高温固相法制备了天然方钠石近红外发光材料.测定了荧光粉的X射线衍射(X Ray Diffraction,XRD)谱以及室温下的光致近红外发射光谱和激发光谱.在600nm可见光的激发下,天然方钠石粉末中的Mn5+离子(3A2-1E跃迁)发射了主发射峰位于1200 nm的近红外光谱.在500 nm可见光的激发下,该粉末中的Fe2+离子(3T1-5E)发射了主发射峰位于1000 nm的近红外光谱.这种现象对于提高硅太阳能电池的效率可能具有积极意义.     

ZnS∶Er纳米晶的水热合成及其性能研究

该文以硫代乙酰胺为硫源,采用水热法合成了ZnS∶Er纳米晶。并用X线衍射(XRD)、透射电子显微镜(TEM)、X线光电子能谱仪(XPS)、荧光光谱仪对其物相、形貌、组成及光学性能进行了表征。结果表明,ZnS∶Er纳米晶为立方闪锌矿结构,粒径约为5nm。由XPS图谱可知,ZnS∶Er纳米晶中存在Zn、S、C、O、Er等元素。ZnS∶Er纳米晶荧光光谱中出现了2个主要发射峰,分别位于469nm和583nm处。两发射峰的发光强度随着pH的升高而增强且发光峰的位置存在微弱的蓝移,pH=12时,两发射峰的荧光强度最强;随着Er3+掺杂量的增加,469nm处发射峰的强度先增强后减弱,583nm处发射峰的强度随之减弱。     

基于PLD法制备ZnO:Eu3+,Li+薄膜的发光性质研究

采用脉冲激光沉积(PLD)技术在Si(111)衬底上生长了Eu3+、Li+共掺杂的ZnO薄膜。分别对样品进行了X射线衍射(XRD)谱测试和光致发光(PL)谱分析,重点研究了退火处理对样品结构和发射光谱的影响。XRD谱测试表明,样品具有很好的C轴择优取向。PL谱研究表明,当用325nm光激发样品时,样品的发射光谱仅由ZnO基质的紫外发射和蓝光发射组成,并没有发现稀土Eu3+的特征发光峰;样品的蓝光发射源于电子从Zn填隙形成的浅施主能级到Zn空位形成的浅受主能级跃迁;和真空中退火的样品相比,O2中制备的样品的蓝光发射减弱,紫外发光增强。用395nm的光激发时,退火前样品分别在594nm和613nm处存在两个明显的Eu3+特征发光峰,退火后的样品仅发现Eu3+位于594nm的特征发光峰,这表明,退火处理不利于稀土离子的特征发射,但O2中退火的样品ZnO基质红绿波段发射光谱明显增强。     

YAlO3∶Eu3+发光纳米纤维的制备与表征

采用静电纺丝技术制备了聚乙烯吡咯烷酮PVP/[Y(NO3)3+Al(NO3)3+Eu(NO3)3]复合纤维,将其进行热处理,得到了YAlO3:Eu3+发光纳米纤维。采用X射线衍射(XRD)、扫描电镜(SEM)、荧光光谱等技术对样品进行了表征。PVP/[Y(NO3)3+Al(NO3)3+Eu(NO3)3]复合纤维经1200℃焙烧2h后,获得了YAlO3:Eu3+纳米纤维,属于正交晶系,空间群为Pnma。用Shapiro-Wilk方法检验了纤维直径分布情况,在95%的置信度下,纤维直径属于正态分布。PVP/[Y(NO3)3+Al(NO3)3+Eu(NO3)3]复合纤维表面光滑,纤维分散性较好,有很好的长径比,尺寸均一,平均直径为(152.9±26.0)nm;YAlO3:Eu3+纳米纤维的平均直径为(106.7±20.2)nm。在234nm的紫外光激发下,YAlO3:Eu3+纳米纤维的主要发射峰位于590nm和609nm处,分别属于Eu3+的5 D0→7F1跃迁和5 D0→7F2跃迁,Eu3+掺杂离子浓度对YAlO3:Eu3+发射峰的峰型与位置均没有影响,当Eu3+掺杂离子浓度为5%时,YAlO3:Eu3+纳米纤维发光最强。     

电纺丝方法制备GaN：Eu2+ 纳米纤维与发光特征

通过结合静电纺丝和氨化技术方法合成了Eu2 掺杂的GaN（GaN：Eu2 ）纳米纤维。SEM和TEM图像显示纳米纤维由尺寸均匀分布的GaN纳米颗粒组成。XRD测试结果表明GaN：Eu2 样品主要为六方相GaN（h-GaN）,其平均粒径为7.3 nm。进一步的拉曼测试结果显示出现了两个额外的GaN拉曼位移,波数分别位于252和422 cm-1。室温光致发光谱表明GaN基质中的Eu 2 在407 nm处产生了强烈的特征蓝色发光峰。     

Effect of strontium nitride on the properties of Sr2Si5N8∶Eu2+ red phosphor

The nitride phosphor Sr2Si5Ng:Eu2+ was synthesized by the high temperature solid-state method. The properties of Sr2Si5N8:Eu2+ were discussed by X-ray diffraction (XRD) scanning electron microscope (SEM) and spectra analysis. The XRD pattern shows that the single phase produces when strontium nitride is a bit excessive. The SEM photo implies that the excessive strontium nitride works as a flux in the reaction system. The position of emission peak is also located at about 612 nm as strontium nitride is excessive. The luminescent intensity of the phosphor adding excessive strontium nitride is higher than that of the phosphor introducing stoichiometric strontium nitride. The optimized content of nitride strontium was 2.05 mol/mol for the obtained phosphor with excellent properties.     

长余辉蓝色荧光粉SrSiO3:Eu2+,Dy3+的制备与发光性能研究

采用高温固相法,在碳粉还原条件下制备了SrSiO<,3>:Eu<'2+>,Dy<'3+>长余辉蓝光发光材料.研究了Eu<'2+>的掺杂浓度对样品发光性质的影响.用X射线衍射仪(XRD)、扫描电镜(SEM)和荧光光谱等手段对样品进行物相、形貌和光谱等性能的表征.研究结果表明,样品为单斜晶体,样品颗粒呈花束形;该荧光粉激发...     

硅酸盐橙色荧光粉的发光性能研究

采用高温固相反应法制备了高效橙色荧光粉Sr3–xSiO5:xEu2+。通过X射线粉末衍射仪(XRD)、扫描电镜(SEM)及荧光分光光度计研究了Eu2+含量和不同助熔剂对荧光粉发光性能的影响,并分析了所制荧光粉的封装性能。研究表明,荧光粉Sr3–xSiO5:xEu2+的晶体结构属正方晶系。当Eu2+的摩尔分数为4%,并用质量分数为3%的NH4Cl作助熔剂时,制得的Sr3–xSiO5:xEu2+的发射光谱强度最大。荧光粉封装后可以有效降低白光LED的色温并提高其显色指数,这表明该荧光粉是一种适用于白光LED的光转化材料。     

Effect of Co2+ ions on structural,morphological and optical properties of ZnO nanoparticles synthesized by sol–gel auto combustion method

Undoped and Co²⁺ doped ZnO nanoparticles have been successfully synthesized by sol–gel auto combustion method. The ratio of metal nitrates to citric acid was taken at 1:1.11. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared and Uv–visible spectroscopy techniques. The X-ray powder diffraction analysis revealed the formation of single phase having hexagonal wurtzite structure. The lattice constant ‘a’ increases while ‘c’ decreases as Co²⁺ concentration ‘x’ increases. The average crystallite size obtained from XRD data is in the range of 19–15 nm. The X-ray density, atomic packing factor, strain, surface area to volume ratio, etc was obtained using XRD data. SEM analysis showed that the prepared nanoparticles are in nano regime, nearly spherical and loosely agglomerates. EDAX analysis showed that composition obtained is near stoichiometries. In order to understand functional group and vibrational frequency band position of synthesized nanoparticles FTIR technique was used. FTIR analysis results observed that vibrational frequency band position of Zn–O shifted to higher frequency band with Co²⁺ ion increasing host semiconductor nanoparticles. Uv–visible absorption spectra showed that absorption edge shifted to higher wavelength with increasing Co²⁺ concentration while corresponding energy band gap of semiconductor nanoparticles decreases with increasing Co²⁺ concentration.     

超声分散技术在制备小颗粒(Y,Gd)BO_3∶Eu~(3+)粉体中的应用

采用共沉淀法结合超声分散技术制备亚微米级红色荧光粉(Y,Gd)BO3∶Eu3+,研究了超声时间对离子混合及沉淀过程的影响,以及进而对粉体性能的影响。采用红外光谱(IR)、扫描电子显微镜(SEM)、粉末X射线衍射(XRD)、PDP真空紫外荧光粉测试系统对荧光粉的组成、结构与光学性能等进行表征,结果表明:(Y,Gd)BO3∶Eu3+中[BO3]基团中B原子以四配位为主,同时混有三配位,主体基质YBO3以六方碳钙石结构存在,空间群为P63/mmc(194),晶胞参数a=3.778,c=8.814;在离子混合和沉淀过程中经过超声分散制备的粉体与未经超声分散制备的粉体相比较,相对发光强度提高,色坐标红移(x=0.6392,y=0.3604→x=0.6422,y=0.3575),红橙比(626nm/592nm)提高12%,粒径细小,颗粒形貌均匀,分散性良好。     

Tunable properties of cadmium substituted ZnS nanocrystals

Tailored Zn_1−xCd_xS (x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles, synthesized by co-precipitation method under ultrasonic irradiation, were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), UV–Vis and photoluminescence (PL) spectroscopy measurements. According to the XRD results, substitution of Zn²⁺ by Cd²⁺ ion leads to an increase in the lattice parameters and the average size of zinc blended nanoparticles are in the range of 3–4 nm. Transmission electron microscopy image revealed the formation of nano-sized particles with dimension of 5 nm confirming that the samples are quantum dots. The shift observed in the absorption edges by increasing Cd²⁺ ion substitution is ascribed by the alloying effect but the enhancement of band gap energy compared to that of the corresponding bulk value is attributed to the nanometric grain size and quantum confinement effects. The position and intensity of PL emission peaks are tuned with Cd²⁺/Zn²⁺ ion content.     

Synthesis and characterization of ball milled Fe-doped ZnO diluted magnetic semiconductor

Fe-doped ZnO (Zn0.99Fe0.01O) powders are successfully prepared by ball milling with different milling time, and are inves- tigated using X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet-visible (UV-VIS) spectroscopy, vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR) spectroscopy. The structural analysis using XRD reveals that the Fe-doped ZnO milled at different milling time can crystallize in a wurtzite structure, and in the XRD patterns, the secondary phase related to Fe cluster with the sensitivity of the XRD instrument can not be found. The SEM image of the sample milled for 24 h shows the presence of spherical nanoparticles. From the optical analysis, the optical band gap is found to decrease with increasing the milling time, which indicates the incorporation of Fe2+ ions into the ZnO lattice. The magnetization measurement using VSM reveals that the nanoparticles exhibit ferromagnetic behavior at room temperature, and the magnetization increases gradually with increasing the milling time. The conclusion is further confirmed by the electron paramagnetic resonance of the nanoparticles examined at room temperature, which shows an intense and broad ferromagnetic resonance signal related to Fe ions.     

Ultrasound-assisted preparation of CdSe nanocrystals in the presence of Polyvinyl alcohol as a capping agent

Nanosized Polyvinyl alcohol-capped CdSe particles were prepared via a simple and fast ultrasound-assisted technique through the reaction between aqueous solutions of cadmium acetate and sodium selenosulfate. The nanoparticles are characterized using X-ray diffraction (XRD), UV–Visible spectrophotometer, Scanning electron microscope (SEM), Energy dispersive X-ray (EDAX) analysis and Fourier transform infrared (FTIR) spectrometer. XRD pattern reveals that the nanoparticles are in well-crystalline cubic phase. The broadening of diffraction peaks indicated the formation of particles in the nanometer size regime. A shift in absorption peak is observed in the spectra near 544 nm due to quantum confinement effect. Particle sizes calculated from the X-ray diffraction studies agree fairly well with those estimated from optical absorption studies. The homogeneity of the sample could be controlled by adjusting the concentration of Polyvinyl alcohol. SEM images of a specific concentration of Polyvinyl alcohol for as-prepared CdSe nanocrystals show uniform particles distribution. The particle size is found to be less than 100 nm based on the observed SEM images and the reason of this mismatch is discussed. The calculated result from XRD and optical characterizations shows that the particles size is smaller than those observed in SEM images. The elemental analysis from EDAX shows that the average atomic percentage of Cd:Se was 50:50 showing that the prepared samples are exactly stoichiometric.