Y_2O_3∶Eu~(3+)纳米棒的微乳液-微波法制备、表征与发光性能

用简单的微乳液-微波法合成大小和形貌可控的Y2O3∶Eu3+纳米棒晶体。XRD结果表明,所制备样品为Y2O3∶Eu3+纯相,属于体心立方晶系。TEM结果表明,随着水乳比ω0从5变化到35时,粒子发光粉的形状由纳米颗粒状变为纳米棒,纳米棒的直径约为30～50 nm,纳米棒长约为200～300 nm。激发光谱和发射光谱分析表明,最大的激发带是位于254 nm的Eu3+-O2-电荷迁移带。最大发射峰位于611 nm,属于Eu3+的特征发射。Y2O3∶Eu3+纳米发光粉的发光强度随着ω0的增加而增强。发光寿命分析表明Y2O3∶Eu3+纳米棒中Eu3+的发光寿命为2.03 ms。在阴极射线发光真空装置中测得的I-V曲线表明Y2O3∶Eu3+纳米棒薄膜的启动电压仅1 300 V。同时,在2 000 V外加电压下可以清楚地观察到Y2O3∶Eu3+纳米棒的阴极射线发光为Eu3+离子的特征红光。     

纳米晶Y2O3:Eu3+红色荧光体的发光性质研究

研究了纳米晶Y2 O3:Eu3 红色荧光体的发光性质。结果表明 :该荧光体最大激发峰位于 2 5 2 6nm ,最大发射峰位于 6 13 4nm ,随着团聚尺寸的增加、煅烧温度的提高和助熔剂的加入 ,Y2 O3:Eu3 红色荧光体的发光强度增大 ;包膜工艺消除了纳米晶Y2 O3:Eu3 红色荧光体的表面缺陷和悬挂键 ,改善了其发光特性。     

静电纺丝技术制备Gd_2O_3:Eu~(3+)发光纳米纤维与表征

采用静电纺丝技术制备了PVA/[Gd(NO3)3+Eu(NO3)3]复合纳米纤维,并将其进行热处理,得到Gd2O3:Eu3+发光纳米纤维。X射线衍射分析表明,复合纤维为无定型,Gd2O3:Eu3+发光纳米纤维属于体心立方晶系,空间群为Ia 3。扫描电子显微镜(SEM)分析表明,复合纳米纤维的平均直径约为200 nm,经过800℃焙烧后,获得了直径约50 nm的Gd2O3:Eu3+发光纳米纤维。差热-热重分析表明,温度高于600℃时,复合纳米纤维中水份、有机物和硝酸盐分解挥发完毕,样品不再失重,总失重率为71.9%。傅里叶转换红外光谱(FTIR)分析表明,复合纳米纤维的红外光谱与纯聚乙烯醇的红外光谱基本一致,600℃以上生成了Gd2O3:Eu3+发光纳米纤维。荧光光谱分析表明,在251 nm紫外光激发下,Gd2O3:Eu3+发光纳米纤维发射出Eu3+离子特征的609 nm明亮红光。讨论了Gd2O3:Eu3+发光纳米纤维的形成机理,该技术可以推广用于制备其他稀土氧化物发光纳米纤维。     

(Y,G d)(P,V)O_4∶Eu~(3+)荧光粉的发光特性

采用高温固相方法合成了(Y,Gd)(P,V)O4∶Eu3 ,经X射线结构分析确定为四方晶系,体心结构,空间群为I41/amd[141]。研究了(Y,Gd)(P,V)O4∶Eu3 在VUV及UV激发下的光谱特性,讨论了激活剂Eu3 的浓度对发光亮度的影响。(Y,Gd)(P,V)O4∶Eu3 荧光粉的发射主峰在619 nm,证明Eu3 离子占据了非反演对称中心的位置。在(Y,Gd)(P,V)O4∶Eu3 (监控619 nm)的激发谱,有一个中心位于156 nm的吸收带,它属于基质的吸收带。将(Y,Gd)(P,V)O4∶Eu3 的发光性能与PDP商用红粉(Y,Gd)BO3∶Eu3 进行了比较。(Y,Gd)(P,V)O4∶Eu3 的发射主峰在619 nm,比发射主峰为593 nm的(Y,Gd)BO3∶Eu3 色纯度好,是一种很有应用前景的发光材料。     

超细Y2O3：Eu荧光粉的阴极射线发光和光致发光

本文首次报道由尿素溶胶法制备的球形、超细(120~250nm)高效Y2O3:Eu红色荧光粉的晶体结构及其阴极射线发光和光致发光性质.这种超细颗粒在254nm激发时的发光强度比商用的传统微米样品低.但在中等电压(≤10kV)的电子束激发下,其阴极射线发光强度超过商用微米样品.这种接近纳米的Y2O3:Eu超细颗粒已表现出较强的表面效应.对实验结果进行了分析和讨论.     

Eu3+激活的硼钒酸钇的光致发光

找出了合成Eu3+激活的硼钒酸钇铕发光粉的适宜条件和发光最佳化学组分,它是(Y0.94Eu0.06)(V0.69B0.31)O3.7.对其发光光谱的温度依赖关系的研究指出,发光最佳温度在350℃左右.发光的这种温度依赖关系与基质和Eu3+对能量的吸收,以及基质向Eu3+能量传递效率的提高有关.此外,试验结果还表明,在365nm激发下,少显Gd2O3、Zn2GeO4·GeO2:Mn2+等添加剂的加入提高了样品的发光亮度.     

纳米晶Gd2O3：Eu^3＋的制备与发光性质

利用共沉淀法制备了纳米晶Gd2O3:Eu3+发光粉体. 在不同掺杂浓度、不同煅烧温度的系列样品中,均观测到Eu3+离子的特征发射.样品的晶相与发射性质的研究表明:所制备的样品经800~1 300 ℃热处理后,晶相为立方相,1 400 ℃时开始向单斜相转变.荧光强度与Eu3+离子掺杂浓度关系研究表明:在不同掺杂浓度中,Eu3+离子浓度为4%时其相对发射强度最强.在三个不同的煅烧温度中,经800 ℃煅烧的样品其发光效果最好.此外还观察到电荷转移激发态以及基质、Gd3+与Eu3+之间的能量传递.激发谱包含三部分,即电荷转移带、Eu3+的4f内壳层电子跃迁和Gd3+的激发谱.     

Gd2O3:Eu3+纳米晶的燃烧合成及光致发光性质

采用柠檬酸作燃烧剂用燃烧合成法制备了Gd2O3:Eu3+纳米晶.用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)和荧光分光光度计等对Gd2O3:Eu3+纳米晶的结构、形貌和发光性能进行了分析.结果表明:不同柠檬酸与稀土离子配比(C/M)制备的样品经800℃退火1 h后,均得到了纯立方相的Gd2O3:Eu3+纳米晶,晶粒尺寸约为30 nm,尺寸分布较窄,其中以C/M=1.0时制备的纳米晶结晶性最好,发光强度最大.Gd2O3:Eu3+纳米晶主发射峰位置均在612 nm处(5D0→7F2跃迁),激发光谱中电荷迁移态发生红移,观察到Gd3+向Eu3+的有效能量传递.对柠檬酸与稀土离子配比(C/M)对结晶度、发光性质等的影响也进行了分析和讨论.     

Y2O3双掺杂Eu3+,Tb3+的光谱性能及能量传递过程

采用溶胶凝胶法制备不同配比的Y2O3∶Eu3+、Y2O3∶Tb3+和Y2O3∶Eu3+,Tb3+荧光粉.并通过XRD、SEM和激发、发射光谱对其结构和发光性能进行了研究,用能级图解释了激活剂之间的能量传递关系.结果表明,材料结晶良好,粒度分别为20、31nm和17nm左右,样品形貌类似片状结构.(Y110Eu)2kO3和(Y110Tb)2kO3配比时相对发光强度最高.而共掺杂时,存在着强烈的Eu3+向Tb3+的能量转移,导致红色发光强度的降低而敏化了绿光和蓝光的发射.分析可知,除了激活剂的含量对发光性能有强烈的影响之外,不同的激发波长对体系混合光的形成有很大的影响.当在305nm的激发波长下,可以得到红绿蓝混合光,实现了通过一种荧光粉的激发,发射出近白色的光.为改变灯用三基色荧光粉的组成并降低成本奠定了有利的实验基础.     

LiBaPO4:Eu3+材料的制备及发光特性

采用高温固相法制备了LiBaPO4:Eu3+红色发光材料,研究了Eu3+掺杂浓度、电荷补偿剂等对材料发光性质的影响.结果显示,在401nm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,主峰位于619 nm;监测619 nm发射峰,所得激发光谱由O2- →Eu3+电...     

The gas phase infrared band contours of s-triazine and s-triazine-d3: The fundamentals of C3N3H3 and C3N3D3 and some overtone and combination bands of C3N3H3

The systematic application of band contour techniques to account for most of the observed features of the ir spectra of s-triazine and s-triazine-d₃ have been made as well as a critique as to the limitations of such methods. The experimental and computer methods used to study the gas phase infrared band contours of s-triazine and s-triazine-d₃ are out-lined. Contours of the five E′ fundamentals of s-triazine have been recorded under moderate resolution and analyzed to give the Coriolis constants $\text{ζ}{}_{\mathrm{i}}{}^{\mathrm{z}}$, i = 6–10. The effects of l-resonance are very apparent for ν₈ and ν₉, in the form of holes in the Q branches of these bands. Under the highest resolution available, ν₆ and ν₁₀ also show l-resonance effects. Values of the l-doubling constants $\text{q}{}_{\mathrm{i}}{}^{\mathrm{(+)}}$ were obtained for these four fundamentals. One of the parallel A₂″ fundamentals of C₃H₃N₃ (ν₁₂) has also been studied. It lies close to ν₁₀(E′) and an A × E type of second-order Coriolis resonance may be the cause of the intensity enhancement observed in the inner wings of the ν₁₂ and ν₁₀ bands. Hot bands of the type (ν_i + nν₁₄ ? nν₁₄) have been observed in the contours of ν₈, ν₁₀, and ν₁₂. This is felt to be responsible for the large difference between our observed zeta sum (?1.30) and the theoretical sum (?1.00).The gas phase infrared band contours of the five E′ and 2A₂″ fundamentals of C₃N₃D₃ have also been recorded under moderate resolution. From P-R separations and by computer simulation of the contours, values of the Coriolis constants $\text{ζ}{}_{\mathrm{i}}{}^{\mathrm{z}}$ have been obtained for the E′ modes. The effects of l-resonance have been observed for ν₈(E′) and ν₁₀(E′) and values of the l-doubling constants $\text{q}{}_{\mathrm{i}}{}^{\mathrm{(+)}}$ have been estimated. An extensive series of hot bands of the type (ν₁₂ + nν₁₄ ? nν₁₄) has been observed in the contour of the ν₁₂ (A₂″) fundamental. The mass effect on the Coriolis constants has been discussed.Infrared band contours of the overtone 2ν₇ and seven degenerate E′ combination bands of C₃N₃H₃ have been recorded under moderate resolution. Analysis of these contours using the P-R separation method and computer simulation of the contours has given values of $\text{ζ}{}_{\mathrm{<mtext>eff</mtext>}}{}^{\mathrm{z}}$ for these bands. Fermi resonance between 2ν₇ and ν₆ has been analyzed. The importance of considering both the observed contour as well as the observed frequency when assigning higher tone bands is illustrated.     

Fine structure and isotope shift of the 3s4d 3 D-3s3p 3 P, 3s5d 3 D-3s3p 3 P and 3p 2 3 P-3s3p 3 P Transitions of MgI

Summary We report the measurements of the³ D(3s4d)-³ P(3s3p)³ D(3s5d)-³ P(3s3p), and³ P(3p ²)-³ P(3s3p) transition frequency of MgI, the fine-structure separation and isotope shift between²⁴Mg and²⁶Mg. The measurements have been performed in a metastable atomic beam; a good agreement is found for data already existing in the literature. The accuracy of the measurements reported in this paper is mainly limited by the Doppler broadening of theI ₂ transitions used as a reference and by the precision in the knowledge of the related wavelengths.     

Dielectric investigations of solid solutions SrTiO3-KTaO3 and SrTiO3-KNbO3

The temperature dependences of the dielectric constant and dielectric hysteresis loops in ceramic samples of (1 ? x)SrTiO_3?x KNbO₃ and (1 ? x)SrTiO_3?x KTaO₃ (0 ≤ x ≤ 0.3) solid solutions prepared using different heat treatments have been investigated. Phase diagrams of the studied solid solutions have been constructed in the T-x coordinates. It has been shown that, after quenching of samples (spontaneous cooling at room temperature after long-term heating at the sintering temperature of the ceramic samples), the temperature of the induced phase transition increases because of the weakening of random electric fields associated with nonisovalent impurities due to their “frozen” nonequilibrium redistribution. For small concentrations x, strong dielectric relaxation is observed in the temperature range of 150–250 K. A model of relaxing centers, which is based on the local charge compensation of heterovalent impurities, has been proposed.     

Modulated magnetic structures of ErPb3, HoPb3, ErTl3 and HoTl3

Neutron diffraction experiments have been carried out on the magnetically ordered phases of ErPb₃, HoPb₃, ErTl₃ and HoTl₃. The magnetic moments were found to be sinusoidally modulated with a propagation vector of (0, 0.2, 0.5) for the Pb-compounds and (0.38, 0.38, 0.16) for the Tl-compounds.Work supported by the Bundesministerium für Forschung und Technologie     

Scintillation properties of Ce3+-doped YCl3 and YBr3

The dependence of the scintillation properties of Ce³⁺-doped YCl₃ and YBr₃ on activator concentration (0.5, 1 and 2 mol%) has been studied. The radioluminescence spectra of both materials contain asymmetric bands with maxima located at 3.13 eV (383 nm) for YCl₃:Ce³⁺ and 2.84 eV (422 nm) for YBr₃:Ce³⁺. The scintillation pulse decay curves for both materials are described by two components with decay constants of 37 and 640 ns for YCl₃:Ce³⁺ and 36 and 450 ns for YBr₃:Ce³⁺, the fractions of the faster component being 86 and 79 per cent, respectively. The dependences of the light yield of the studied materials on Ce³⁺ concentration pass through a maximum near 1 mol% of the activator, and the maximum light yields (relative to NaI:Tl) are 8700 photons per MeV for YCl₃:Ce³⁺ and 20,600 photons per MeV for YBr₃:Ce³⁺.     

Far Infrared Spectra of Ammonia-Boron Trifluoride: NH3BF3 and ND3BF3

Abstract

Spectra of polycrystalline samples of NH₃BF₃ and ND₃BF₃ at 300 K and 98 K have been recorded in the frequency range 20-400 cm^?1. Isotopic frequency ratios are used to interpret the observed features in terms of the known molecular and crystal structures.