纳米晶Y_2O_3:Eu~(3+)的反常拉曼散射(英文)

作者用燃烧法制备了8nm-50nm的系列纳米晶Y2O3:Eu3+,利用XRD谱确定了纳米晶的晶体结构及晶粒大小。利用两套由不同波长的激光所激发的拉曼光谱,指认了纳米晶Y2O3:Eu3+的拉曼振动模,研究其拉曼光谱。与传统的拉曼光谱学相比较,光谱呈现出明显的反常,其一,是斯托克斯与相对应的反斯托克斯谱峰波数不相等;其二,随晶粒的减小,拉曼谱有明显的变化,包括谱峰的微移、半高宽的增加,以及谱峰强度比的强烈变化;其三,随着激发波长的变化,光谱也呈现出峰位移动的明显变化。这些反常的散射光谱的变化源于纳米结构的本征缺陷。     

Synthesis and luminescence properties of nanocrystalline LiF:Mg,Cu,P phosphor

Nanocrystalline LiF:Mg,Cu,P phosphor material of different shapes and sizes (microcrystalline cubic shape, nanorod shape and nanocrystalline cubical shaped) have been prepared by the chemical co-precipitation method. Thermoluminescence (TL) and other dosimetric characteristics of the phosphor are studied and presented here. The formation of the materials was confirmed by the X-ray diffraction (XRD). Its shapes and sizes were also observed using scanning electron microscope (SEM). The TL glow curve of the microcrystalline powder shows a prominent single peak at 408 K along with another peak of lesser intensity at around 638 K. On the contrary, the nanocrystalline rod shaped particles show a peak of low intensity at 401 K and a prominent peak around 700 K while the nanocrystalline particles in cubical shapes again show two peaks, one at around 407 K and the other at around 617 K, of which the lower temperature (407 K) peak is more prominent. The glow curve structure changes at very high doses (100 kRad) and some new peaks appear at around 525 and 637 K also the first peak appearing at around 401 K becomes prominent. The observed changes in TL due to the change in the shape and sizes of the nanophosphor have been reported. The PL has also been studied and various excitation and emission peaks observed due to the presence of various impurities are explained. The observed results have been explained in the light of asymmetrical crystal field effects due to asymmetrical shapes of the nanocrystalline phosphor. The comparison of these properties with the microcrystalline material prepared by the same co-precipitation method is also done.     

An analytical model for the determination of crystallite size and?crystal lattice microstrain distributions in nanocrystalline materials from the variance of the X-ray diffraction peaks

An analytical model for the determination of crystallite size and crystal lattice microstrain distributions in nanocrystalline (nc) materials by X-ray diffractometry (XRD) is presented. It entails generalizing the variance method to establish analytically the connection between the variance coefficients of the physically broadened XRD peaks and the characteristic parameters of explicit distributions of crystallite sizes and crystal lattice microstrains, which results in a more detailed characterization of the nc-materials. The proposed model is generic in nature and has the potential to be used under the assumption of different mathematical functions for the two distributions, which suggests that it may have an important role to play in the characterization of nc-materials. Nevertheless, the specialization to the case of nc-materials with log-normal crystallite size distribution and three typical types of lattice microstrains is used as an illustration and to formulate explicit analytical expressions of interest. Finally, the usefulness of the proposed model is demonstrated on standard XRD profiles.     

纳米ZnO薄膜可见发射机制研究

利用溶胶－凝胶法 （Sol-Gel）制备了纳米ZnO薄膜,获得了高强的近紫外发射室温下测量了样品的光致发光谱(PL )、吸收谱(ABS)、X射线衍射谱(XRD).X射线衍射(XRD)的结果表明：纳米ZnO薄膜呈多晶态,具有六角纤锌矿结构和良好的C轴取向;发现随退火温度升高,（002）衍射峰强度显著增强,衍射峰的半高宽（FWHM）减小、纳米颗粒的粒径增大.由吸收谱(ABS)给出了样品室温下带隙宽度为3.30 eV.在PL谱中观察到二个荧光发射带,一个是中心波长位于392 nm附近强而尖的紫带,另一个是519 nm附近弱而宽的绿带研究了不同退火温度样品的光致发光峰值强度的变化关系,发现随退火温度升高,紫带峰值强度增强、绿带峰值强度减弱,均近似呈线性变化.证实了纳米ZnO薄膜绿光发射主要来自氧空位(Vo)形成的浅施主能级与锌空位(VZn)形成的浅受主能级之间的复合,或氧空位(Vo)形成的深施主能级上的电子至价带顶的跃迁;紫带来自于导带中的电子与价带中的空位形成的激子复合.     

Aging of a nanostructured Zn50Se50 alloy produced by mechanical alloying

The aging at room temperature of a nanocrystalline equiatomic ZnSe alloy produced by mechanical alloying was investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. The measured XRD patterns showed the presence of the peaks corresponding to the crystalline trigonal selenium (c-Se) phase. It is observed that the ZnSe phase is stable with aging. The appearance of the c-Se phase is attributed to the migration of Se atoms located at the interfacial component of the as-milled ZnSe nanostructure with aging.     

溶胶-凝胶法纳米ZnO薄膜的绿光发射

利用溶胶-凝胶法制备了纳米ZnO薄膜,室温下测量了样品的光致发光谱(PL)和X射线衍射谱(XRD),观测到中心波长在523 nm附近的绿色荧光发射,研究了纳米ZnO薄膜的绿光发射机制,证实了纳米ZnO薄膜绿光可见发射带来自氧空位(Vo)形成的浅施主能级和锌空位(Vzn)形成的浅受主能级之间的复合。     

Grain size reduction of copper subjected to repetitive uniaxial compression combined with accumulative fold

This paper reports a novel method of repetitive uniaxial compression combined with accumulative fold for preparing bulk submicron- to nanocrystalline copper starting with a coarse grained counterpart. Grain size reduction and microstrain variations of the high purity copper samples after different passes of compression and fold are investigated by scanning electron microscope and x-ray diffraction (XRD), respectively. Our results show that the average grain size of samples decreases from about 830nm to 127nm as the number of compression passes increases to 30. Microstrain in the compressed sample is found to increase for the first 20 passes, but to decrease at the last 10 passes. The variations of compressive yield strength and the shift of XRD peaks to larger diffraction angles are observed in the squeezed sample. Our experimental results demonstrate that the repetitive uniaxial compression combined with accumulative fold is an effective method to prepare bulk nanocrystalline metallic materials, in particular for soft metals such as Cu, Al and Pb.     

光电变色器件用纳米晶氧化钛薄膜的微结构与特性

纳米晶TiO2薄膜在光电变色器件中具有很重要的作用。它的微结构直接影响染料的吸附、光的散射以及电荷输运的特性。因此，探索TiO2薄膜的微结构(如粒径、表面形貌和厚度等)及光电性能是非常有意义的。采用电子束蒸发工艺制备了光电变色器件用纳晶TiO2薄膜，利用原子力显微镜、X射线衍射、俄歇电子能谱等手段对纳米晶TiO2薄膜的表面形貌、结晶状态及组分进行了分析。从理论上研究和讨论了纳米晶TiO2薄膜晶粒尺寸对光电性能的影响，并用量子限制效应解释了吸收光谱峰值波长随粒径减小而发生蓝移的现象。     

Synthesis and structural characterization of nanostructured copper

In this paper, we report on the preparation and characterization of nanocrystalline powder of copper by dc-magnetron sputtering. Liquid nitrogen cooled cold finger arrangement has been used to prepare nanocrystalline powder. The particle size, crystal structure, and morphology of the samples were characterized by in situ high temperature X-ray diffraction (XRD) and transmission electron microscope (TEM). Results of high temperature XRD showed that highly oriented (111) phase becomes randomly oriented at higher temperature with a systematic shift in peak positions toward lower 2θ values due to changes in lattice parameters. Temperature dependence of lattice constants under vacuum shows linear increase in their values. Diffraction patterns obtained from TEM are also in accordance with the XRD data.     

Thermoluminescence of nanocrystalline LiF:Mg, Cu, P

Nanocrystalline LiF:Mg, Cu, P of rod shape (about 30-40 nm in diameter and 0.3-0.5 μm in length) has been prepared by the chemical co-precipitation method. Thermoluminescence (TL) and dosimetric characteristics of the nanocrystalline phosphor are studied and presented here. The formation of the material was confirmed by the X-ray diffraction (XRD). Its shape and size were also observed by transmission electron microscope (TEM). The TL glow curve of the nanocrystalline powder shows a single peak at 410 K along with four overlapping peaks of lesser intensities at around 570, 609, 638 and 663 K. The observed TL sensitivity of the prepared nanocrystalline powder is less than that of the commercially available “Harshaw TLD-700H hot-pressed chips” at low doses but it still around three times more than that of LiF:Mg, Ti (TLD-100) phosphor. The 410 K peak of the nanomaterial phosphor shows a very linear response with exposures increasing up to very high values (as high as 10 kGy), where all the other thermoluminesent dosimeters (TLD) phosphors show saturation. This linear response over a large span of exposures (0.1 Gy-10 kGy) along with negligible fading and its insensitivity to heating treatments makes the nanocrystalline phosphor useful for its application to estimate high exposures of γ-rays. The ‘tissue equivalence’ property of this material also makes it useful over a wide range of high-energy radiation.     

纳米ZnO薄膜的光致发光性质

利用溶胶－凝胶法制备了纳米ZnO薄膜,室温下测量了样品的光致发光谱(PL)、吸收谱(ABS)、X射线衍射谱(XRD)．X射线衍射(XRD)的结果表明：纳米ZnO薄膜呈多晶状态,具有六角纤锌矿晶体结构和良好的C轴取向．观察到二个荧光发射带,中心波长分别位于395 nm的紫带、524 nm的绿带和450 nm附近的蓝带．证实了纳米ZnO薄膜绿光可见发射带来自氧空位(VO)形成的浅施主能级和锌空位(VZn)形成的浅受主能级之间的复合;450 nm附近的蓝带来自电子从VO的浅施主能级到价带顶或锌填隙(Zni) 到价带顶或导带底到VZn的浅受主能级的复合．     

56Fe13+离子引起GaP晶体的微结构损伤

利用X射线衍射（XRD）技术、傅里叶变换红外光谱（FTIR）和Raman光谱对经不同剂量的56Fe13+离子辐照的GaP晶体的微结构进行了表征。结果表明:随着辐照离子剂量的增加,GaP晶体中产生了局部的无序与缺陷。随着56Fe13+离子剂量的增加,Raman光谱展示出振动峰强度逐渐减弱而且一些逐渐消失,但其峰位几乎没有发生变化;XRD显示出GaP晶体的衍射峰的强度逐渐减小;FTIR主要表现为宽化及其强度增加。这表明重离子56Fe13+的辐照使得GaP晶体中的缺陷与无序性增加,导致晶体产生了局部的非晶化。The Misconstructural damage of GaP irradiated with 56Fe13+ to fluences ranging from 1×107 ions/cm2~1×1010 ions/cm2 were analyzed by X-ray diffraction (XRD) techniques, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The result shows that, with the increase of irradiation ion fluences, local disorder and defects were produced in GaP crystal. With the increase of ion fluence, Raman spectra reveal the intensity of scattering peaks gradually weakens and some scattering peaks gradually disappear, however no changes in the peak position were found. XRD measurement displays that the intensity of diffraction peaks gradually decreases with an increase in ions fluences. Result from FTIR spectra exhibits that the intensity of reflection peaks gradually increases and the FWHM of reflection peaks broadens. These phenomena indicate that, the irradiation of heavy-ion Fe produces defects and disorder in GaP crystal, leading to a local amorphization.     

金属间化合物Cu4Al纳米微粉的热稳定性研究

 对采用自悬浮定向流法制备的Cu4Al纳米微粉进行了差热分析(DTA)，发现在258,423和537 ℃存在不同量值的吸热峰。参照DTA曲线上吸热峰所对应的温度，分别对粉末样品进行了模拟退火实验，热处理后样品的X射线衍射（XRD）分析证实258和423 ℃处无结构相变发生，537 ℃处的吸热峰则对应于从Cu4Al向Cu₃Al的相转变，并且伴随着Cu₃Al晶粒的长大。对比实验结果表明，Cu₄Al纳米微粉在440 ℃以下具有非常好的热稳定性，超过537 ℃将发生结构相变。     

BaClxBr2-x∶Eu2+材料光激励光谱及色心研究

采用高温固相法制备了BaClxBr2-x∶Eu2+光激励发光材料,利用XRD、激发、发射以及激励光谱研究了所制备材料的结构和光学性能。XRD图像表明所制备的材料为单一纯相,随X值增大,衍射角向大角度偏移。发射光谱中位于405nm的窄带谱峰,由Eu2+的4f65d→4f7能级跃迁所引起,监测405nm发射峰,所得激发光谱是位于250～380nm之间的宽带,谱峰位于303nm;光激励波段位于480～800nm,激励峰位于575nm。通过光谱曲线拟合,发现激励光谱由550,610和685nm左右的光谱叠加而成,分别对应F(Cl-),F(Cl-Br),F(Br-)色心,激励峰随Cl/Br比值增加而蓝移。     

Solid–solid transformation route to nanocrystalline sodalite from Al-PILC at room temperature

The present study describes a solid–solid transformation of nanocrystalline sodalite from the solid gel mixture of Al₂O₃-pillared montmorillonite (Al-PILC) with sodium hydroxide at room temperature (25 °C) under an ambient atmosphere. Powder X-ray diffraction (XRD) analysis confirms that the X-ray crystalline sodalite products are crystallized after 12 days, whereas infrared absorption (IR) spectra reveal that diagnostic IR absorption peaks due to single four-membered ring of sodalite framework is observed even after 1 day. Scanning electron microscopy (SEM) shows that Al-PILC is transformed into discrete nano-sized sodalite particles (∼50 nm). Although the induction period, the time elapsing before nucleation, for the solid–solid transformation takes much longer (12 days), the nanocrystalline sodalite is successfully obtained at this extremely mild synthetic condition through solid–solid transformation.     

La0.55Ca0.45MnO3的电子密度分布变温X射线衍射测量

运用X射线衍射(XRD)分析技术,对钙钛矿型La_0.55Ca_0.45MnO₃化合物的空间结构进行了变温测量,用Rietveld方法对XRD实验数据进行了精修拟合.随着温度的降低,实验上观测到衍射峰的劈裂,暗示该化合物内部晶体结构发生了相变.磁化曲线测量表明,对应晶体结构相变的温度,化合物的磁性也发生由铁磁性向反铁磁性的转变.运用Rietica软件对化合物的XRD数据进行了处理,得到了La_0.55Ca_{0.45< 关键词： 锰氧化物 相变 电子密度分布 磁结构}     

稀土Tb3+掺杂纳米ZnO的发光性质

ZnO是一种优良的直接宽带隙半导体发光材料(Eg=3.4 eV),具有优异的晶格、光学和电学性质,稀土离子掺杂浓度和热处理温度对ZnO∶Re3 纳米晶发光强度、峰位变化等光学性质具有重要影响.利用溶胶-凝胶法(Sol-Gel),在不同退火温度下,制备了不同浓度的ZnO∶Tb3 纳米晶.室温下,测量了样品的X射线衍射谱(XRD)、光致发光谱(PL)和激发谱(PLE).观察到纳米ZnO基质在520 nm附近宽的绿光可见发射和稀土Tb3 在485,544,584和620 nm附近的特征发射.通过ZnO基质可见发射强度和稀土Tb3 特征发射强度随Tb3 掺杂浓度、退火温度的变化关系,获得了5D4→7F5跃迁的绿色主发射峰最强的样品制备工艺参数,其退火温度为600℃、掺杂浓度为4 at%;给出了稀土Tb3 的激发态5D4→7F6(485 nm),5D4→7F5(544 nm)和5D4→7F4(584 nm)的发射机制;证实了稀土Tb3 与纳米ZnO基质之间存在双向能量传递.     

发光材料BaSrMg(PO_4)_2∶Eu~(3+)的水热法制备及发光性能研究

采用水热法制备了可用于白光LED的红色发光材料BaSrMg(PO_4)_2∶Eu~(3+)。通过X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)对其结构和形貌进行测试表征,研究了不同pH值(5,6,7和8)和不同反应温度(120,140,160,180和200℃)对荧光粉的晶体结构和形貌的影响。从XRD的结果可以看到,当pH6时合成的样品的衍射峰为较高强度的锐锋,FESEM扫描图像也显示该制备条件下获得了立方体形状的规则晶体。在pH值分别为5,7,8时所制备的样品XRD图谱中大多是强度很弱的宽峰叠加了极少的锐锋,表明样品为固熔体或者含有混合相,这与FESEM扫描图像所显示的无定形态颗粒的结果相一致。荧光光谱测试结果表明,该荧光粉在394nm波长光的激发下产生的发射谱包含了以下6组发射峰536nm(~5 D1→~7 F_1),578nm(~5 D_0→~7 F_0),590nm(~5 D_0→~7 F_1),613nm(~5 D_0→~7 F_2),646nm(~5 D_0→~7 F_3)和696nm(~5 D_0→~7 F_4)。荧光粉的激发光谱分别由361nm(~7 F_0→~5 D_4),380nm(~7 F_0→~5 L_8),394nm(~7 F_0→~5 L_6)和464nm(~7 F_0→~5 D_2)四组激发峰组成。经过条件优化后制备的荧光粉的主要激发峰在394nm(~7 F_0→~5 L_6),该荧光粉在394nm波长光激发下产生的发射峰主峰在613nm(~5 D_0→~7 F_2)。发射峰的劈裂随着pH值和温度的变化而改变,这一现象说明了荧光粉的发光性质与它的晶体结构和颗粒形貌存在着密切的联系。     

Red luminescence in ZnO films prepared by a glycol-based Pechini method

ZnO thin films on fused quartz substrates were prepared by a glycol-based Pechini method. The structural and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical transmittance spectrum, and photoluminescence (PL) spectrum. A red emission around 700 nm was found in PL spectrum, and its peak intensity gained a strong enhancement (140%) while annealing temperature increased from 700 °C to 800 °C. The red emission was ascribed to the possible high defect density in boundary layers of nanocrystalline grains.     

BaMoO4:Eu3+发光材料的制备及光谱特性研究

利用高温固相法制备了BAMoO4:Eu3+发光材料,采用X射线衍射(XRD)和荧光光谱仪对样品进行测试.结果表明,在800℃时得到BaMoO4纯相,属四方晶系.激发光谱由一个宽带和处在350nm后的若干个线状谱组成,宽带归属于Eu3+-O2-电荷迁移吸收带(CT),线状谱属于Eu3+的f--f激发跃迁吸收.发射光谱由5D0-7F1(591 nm),5D0-7F2(615 nn),5D0-7F3(654 nm)和5D0-7F4(702 nm)四组峰组成,其红光5D0-7F2辐射跃迁发射最强,对应EU3+的电偶极跃迁.