Research of Three-Dimensional Fluorescence Spectra of RE^(3+)(RE=Eu,Tb) and Na_2WO_4 Co-doped Silica Luminescence Materials

In the preparation of this precursor tetraethlortho silicate (TEOS), sodium tungstate, ethyl alcohol, HCl and RECl3(RE=Eu,Tb) were mixed and then heated at 800 ℃ for 2 h, leading to a luminescent compound. The structure of the materials was characterized by TG-DTA and IR analysis, and the results indicate that the materials were in SiO2 network structure. Three-dimensional fluorescence spectra was used to characterize the luminescent properties of the materials. The luminescence property of doped and un-doped Eu3+or Tb3+ and Na2WO4 in silica materials were prepared and measured. The results show that good energy transfer from WO2-4 to Eu3+ ion, sensitized the luminescence intensity of Eu3+ remarkably. Tb3+ ion incorporated silica materials expressed the inverse energy transition from Tb3+ to WO2-4, however, we got the materials with homogeneous green blue fluorescent light. Finally, the energy transfer of WO2-4 and Eu3+, WO2-4 and Tb3+ were explained by energy levels diagram.

Crystal Structure and Luminescence Spectra of Ternary Europium（Ⅲ） Complex［Eu（DBM）_3（2，2＇－BIPY）］（HDBM）

The crystal structure of europium tri(dibenzoylmethanate) complex with 2.2'-bipyridyl,C70 H57 N2 O8 Eu, has been determined by X-ray diffraction. The complex crystallizes in the triclinic space group P1. The cell dimensions are a=1.3375(1) nm.b=1.8591(2) nm, c=1.1339(3) nm,α= 95.89(9) °,β=93.36(1)°,γ=85.48(1)° and Z=2. The total number of 5413 independent reflections with I>3σ(I) were used for the structure determination. The final calculated R value is 0.039. The central europium ion is octa-coordinated by six oxygen atoms and two nitrogen atoms forming a distorted square antipnsm (SAP) with the local symmetry C1. Using the Eu3+ ion as a luminescence probe. the high resolution excitation and emission spectra measured at 77 K indicate only one Eu3+ site existing in the complex. The emission spectra of 5D0→7Fj transition display the symmetry of the Eu3+ site is C1.

Study on Visible Photoluminescence and Absorption Spectra of Fergusonite Group Minerals

Visible photoluminescence and absorption spectra of the metamict and annealing-recrystallized fergusonite and brocenite, found in Bayun Obo ore deposit in China, were determined and discussed. The results show that the glow centers of the fergusonite group minerals are Er3+ and Eu3 + when 488.0 and 514.5 nm lasers are used as excitation sources. The luminescence of fergusonites results mainly from Er3+, whereas that of brocenites is produced by Er3+ and Eu3+. The absorption spectra indicate that Nd3 + may be an important sensitizer to the luminescence of Er3 + and Eu3+.

SYNTHESIS OF MeO-SiO_2:Eu^(3+),Bi^(3+)LUMINOPUORS BY THE SOL-GEL METHOD AND A STUDY OF THEIR LUMINESCENCE SPECTRA

The luminophors MeO-SiO_2:Eu^(3+),Bi^(3+)and MeO-SiO_2Bi^(3+)(Me=Mg.Sr)were synthesized at relatively lower temperature by the sol-gel method using the silica sol as a source of silica.The optimum composition and synthesis conditions were obtained by studying the excitation and emission spectra and the effects of energy transfer from the Bi^(3+)ions to the Eu^(3+)ions.

Resonance luminescence spectra of selenium （Ⅳ）—iodide—rhodamie B sy

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Study on Luminescence Properties and Crystal-Lattice Environment of Eu^(2+) in Sr_(4-x)Mg_x Si_3O_8Cl_4∶Eu^(2+) Phosphor

According to the Van Uitert experimental equation, crystal-lattice environment of Eu^(2+) in the Sr_4Si_3O_8Cl_4 crystal was discussed. By adding Mg^(2+) to the host lattice, Sr_(4- x )Mg_ x Si_3O_8Cl_4∶Eu^(2+) was synthesized and the emission peak shifted from blue-green (488 nm) to blue-violet (411 nm) with the increase of amount of the magnesium which replaced the strontium. By analyzing the spectra of Sr_(4- x )Mg_ x Si_3O_8Cl_4∶Eu^(2+) the two Eu^(2+) emission centers were found because of the change of crystal-lattice environment in the host and the crystal structure was obtained by X-ray diffraction data.

Luminescence and Defect Properties of Novel Bluish-Green Phosphor β-Zn_3(PO_4)_2∶Zr^(4+)

Luminescence and defect properties of novel phosphor β-Zn 3(PO 4) 2:Zr 4+ were systematically investigated. Corresponding to its lowest optical absorption transition at 240 nm, phosphor emits a bluish-green light at 485 nm, which yields the Stokes shift about 20000 cm -1. The unusual optical properties of Zr 4+ ion are ascribed to its uncommon coordination environment. In addition it shows intensive bluish-green long lasting phosphorescence (LLP) due to the existence of electron trap, which is generated by aliovalent substitution of Zr 4+ ion for the cation site in the matrix as shown in thermoluminescence (TL) spectrum.

Enhancement of Er^(3+) Luminescence in LiNbO_(3):Mg Crystals

The luminescent properties of Er^(3+) ions in LiNbO_(3):Er and LiNbO_(3):Mg, Er crystals at room temperature have been investigated by the emission spectra and the selective excitation spectra. The energy transition processes of Er3+ luminescence have been analysed. It has been found that the luminescent intensity of Er^(3+) ions in the LiNbO_(3):Mg, Er crystal increased up to 7.8 times compared with that in the LiNbO_(3):Er crystal. The decrease of the defect centre (NbLi) concentration due to doping with Mg^(2+) ions plays a key role in this phenomenon.

Luminescence of Eu(MBA)_2NO_3Phen Complexes

At 77 K excitation spectra,luminescence and time-resolved spectra of Eu(o-MBA)2NO3 Phen and Eu(m-MBA)2NO3 Phen (MBA:methylbenzoate,Phen 1,10-phenanthroline) complexes were measured. Spectral data show that because of steric effect of ortho-methyl substituent there occur two Eu3+ sites with slightly different chemical environment in the Eu(o-MBA)2NO3Phen complex.The local symmetnes for the central metal ions are C2v and C1,C2 or Cs,respectively.However,there is only one Eu3+ site in the Eut(m-MBA)2NO3Phen complex which is similar to the C2v Eu3+ site of the previous complex.This demonstrates that the Eu3+ ion can be used as a conformational probe in the solid state compounds.

Synthesis and Luminescence Properties of Gd_2O_3∶Eu^(3+) Phosphors

Gd 2O 3∶Eu 3+ phosphors were prepared by urea homogeneous precipitation with different surfactant and sol-gel method. XRD patterns show that all the obtained samples are in cubic Gd 2O 3, and the results of FTIR and fluorescent spectra conformed that OP is a good surfactant for preparing the Gd 2O 3∶Eu 3+ phosphors. The SEM photographs show that the particles prepared by urea homogeneous precipitation method are all spherical and well-dispersed, and grain morphology can be controlled by different surfactant. XRD and SEM indicate that the particle sizes prepared by sol-gel method are in the range of 5～30 nm, and the grain sizes increase with increasing of heated temperatures. Luminescence spectra indicat that the main emission peaks of all samples are at 610 nm, the intensities are different from samples prepared with different surfactant and the luminescence intensities increase with increasing of annealed temperatures.

Diffraction and luminescence analysis of extremely rapidly cooled molten system(LiF-CaF)-xLnF(Ln=Sm and Gd)

Samples of(LiF-CaF2)eut-x SmF3(-x GdF3)(x=0.03-0.50) were prepared by spontaneous cooling as well by very fast cooling(using the rapid solidification processing(RSP) method) which provide two types of sample morphology: riffle-like and sphere-like fragments. All types of samples were studied by XRD, optical absorption and fluorescence spectroscopy. The presence of LiF stabilises the cubic cell dimension, and the content of lanthanide fluorides presents influence on phases formed, as well as the crystallinity of the system, in both the spontaneously and rapidly-cooled systems. The photoluminescence properties of the investigated systems are dependent on the lanthanide fluoride content. The intensity of the emission bands, corresponding to the Sm3+ ion, reaches the maximum when the Sm content is x(SmF3)=0.03. An even stronger dependence is observed of optical properties on the morphology of the samples, i.e. whether the samples are spontaneously cooled or processed by the RSP method followed by mechanical grinding. Mechanical grinding enhances the luminescent properties and leads to higher emission intensities. It is also shown that the photoluminescent spectroscopy is suitable for detection/approval of lowered local symmetry via significant splitting of spectral bands.

Optics and Spectral Investigation in Dy^(3+)-Doped Borate Glasses

Dy^3＋-doped borate glasses （LBLB） with high effective visible fluorescence emission were synthesized. The absorption spectrum and fluorescence spectrum of this glass were measured and analyzed. By using J-O theory, the oscillator strengths for some absorption transitions were calculated according to the absorption spectra. The intensity parameters Ω1 （t = 2, 4, 6） of Dy^3＋ were determined by using a least-squares fitting approach, and the values are 4.04 × 10^-20, 1.30 × 10^-20 and 1.82 × 10^-20 cm, respectively. The root-mean-square deviation δrma was calculated. Under UV light excitation, Dy^3＋-doped borate glasses （LBLB） emit intense yellowish white lights. The excitation spectrum indicates that argon laser is the effective excitation source in Dy^3＋-doped LBLB glasses

Eu^（3＋） Ion as Luminescent Probe：Eu^（3＋） Sites in Eu（PBI）_3·phen and ［Eu（PBI）_3·C_2H_5OH·H_2O］·H_2O Complexes

The luminescence of Eu￣(3+) in Eu(PBI)_3 phen and [Eu (PBI)_3 ·C_2H_5OH ·H_2O] ·H_2O(PBI: 3-phenyl-4-benzoyl isoxazate ,phen: 1, 10-phenanthroline) is reported. It is shown that theEu￣(3+) ions in Eu(PBI)_3 phen are positioned on the two sites and the various lines are assigned to eachsite. However, Eu￣(3+) ions occupy a single site in [Eu(PBI)_3 ·C_2H_5OH ·H_2O] ·H_2O and the crystal field splittings of the￣7F_(1￣4) levels are much larger than those in Eu (PBI)_3phen.

Crystal structure and luminescence spectra of Eu_2(p-MAB)_6(PHEN)_2 complex

The title complex crystalizes in the space group P1 with a = 1.3349(7), b=1.9790(4), c= 1.2784 (7) nm, α = 97.67(1). β = 10636(1), γ=91.71(1)° ,Z = 2, Mr= 1475.19 and the final R = 0.051. Each asymmetric species in the crystal contains two crystallographically different Eu (p-CH3C6H4COO)3(C12H8N2) units. Two types of bmuclear molecules are formed by the combination of each of the units through inversion with corresponding units of (he closest asymmetric species. The former contains 4 bridged carboxylate groups bonded to the two central europium (III) ions, and the latter, only 2 bridged carboxylate anions Their Eu-Eu atomic distances are 0.4203 and 0.5298 nm respectively. In the 7F0→ 5D0, excitation spectrum of the complex, there are two sharp peaks al 580.07 and 580.73nm. This shows that the complex has two Eu(III) sites. Two different sets of 5D0→Fj (j= 1 - 4) luminescence spectra have been obtained at the selectively excited 5D0 levels of the complex, which indicates that Eu(III) ions in the complex have unequally chemical environments. This is in agreement with the results of the structure determination.

Sm^(3+) ions doped Sm_(2)Si_(2)O_(7)-based glass ceramics:Crystallization,luminescence and energy transfer process through heat treatment

Sm^(3+) ions incorporated Sm_(2)Si_(2)O_(7) crystalline phase formed in the aluminoborosilicate glass matrix synthesized via melting quenching technique followed by heat-treatment process is reported herewith.The preliminary confirmation on the obtained glass ceramics was made through X-ray diffration(XRD) studies.Formation of non-bridging oxygens(NBOs) in the glass network and the modes of vibrations of network units we re analyzed through Fourier transform infrared spectroscopy(FTIR) studies.Surface morphology of heat-treated samples at varying temperatures was determined via a field emission scanning electron microscope(FESEM).The absorption studies on heat-treated samples signify the low bandgap values and high Urbach energy values due to improved crystallinity in the glass network.Judd-Ofelt intensity parameters identified for visible absorption transitions follow the trend of Ω_(4)>Ω_(2)>Ω_(6).Excitation and emission studies on heat-treated samples show improvement in their intensities compared to the unheated base glass.The thermal quenching is observed at higher temperatures(540 and 580℃ for 3 h) of heat-treated samples.Calculations based on luminescence spectra including radiative transition probability,stimulated emission cross-section and branching ratio show good results for glass ceramics prior to precursor glass.Longer lifetimes of Sm^(3+) ions(milliseconds) in the level ^(4)G_(5/2) are seen for glass ceramics.Color coordinates suggest the reddish-orange emissions from prepared glass ceramics.Thus,Sm^(3+) doped Sm_(2)Si_(2)O_(7) glass ceramics are favorable materials for solid-state lighting and laser applications.

Observation of the hyperfine structure and anticrossings of hyperfine levels in the luminescence spectra of LiYF4:Ho3+

Resolved hyperfine structure and narrow inhomogeneously broadened lines in the optical spectra of a rare-earth-doped crystal are favorable for the implementation of various sensors.Here,a well-resolved hyperfine structure in the photoluminescence spectra of LiYF4:Ho single crystals and the anticrossings of hyperfine levels in a magnetic field are demonstrated using a self-made setup based on a Bruker 125HR high-resolution Fourier spectrometer.This is the first observation of the resolved hyperfine structure and anticrossing hyperfine levels in the luminescence spectra of a crystal.The narrowest spectral linewidth is only 0.0022 cm-1.This fact together with a large value of the magnetic g factor of several crystal-field states creates prerequisites for developing magnetic field sensors,which can be in demand in modern quantum information technology devices operating at low temperatures.Very small random lattice strains characterizing the quality of a crystal can be detected using anticrossing points.

Crystal structure and luminescence spectra of Eu(DBM)3 4,4'-BIPY complex

The title complex,C_(55)H_(41)O_6N_2Eu,M_r=979.91,crystallizes in the monoclinic space group C_(2/c) with a=2.0413(4),b=2.5556(5),c=0.8926(3)nm,β=104.64(2)°,μ=14.44cm^(-1),T=295K and the final R=0.043.The structure was solved by the heavy-atom method and refined by the full-matrix least-squares technique for 64 non-hydrogen atoms anisotropicaUy for 2180 reflections with I≥3σ(I).The title complex forms one-dimensional chains through C-C bonds between pyridine rings of 4,4'-bipyridine.The central Eu(Ⅲ)ion is coordinated to six oxygen atoms and two nitrogen atoms and its polyhedron is a distorted square antiprism.The high resolution laser excited excitation and luminescence spectra show that the complex pos- sesses two Eu(Ⅲ)sites with the energy difference 39 cm^(-1)of ~5D_0 levels in excited state.The radiationless energy transfer to a great extent between the two Eu(Ⅲ)sites and the dominant luminescence of Eu(Ⅲ)site with lower energy as the complex was excited have been supported by the selectively excited luminescence spectra, time-resolved luminescence spectra and selectively excited luminescence decay curves.

配合物Eu_xM_(1-x)(TTA)_3(H_2O)_2(M=La,Gd)光致发光特性

合成了一系列组成为Eu_xM_(1-x)(TTA)_3(H_2O)_2(M=La,Gd)的固体配合物,利用红外光谱和荧光光谱研究了配合物结构和发光性质随Eu^(3＋)浓度的变化规律.红外光谱的结果表明,配合物的成份为Eu_xM_(1-x)(TTA)_3(H_2O)_2和M(TTA)_3(H_2O)_2,没有新化合物生成.而荧光光谱的结果显示配合物的发光强度与Eu^(3＋)浓度不成线性关系,其中不发光的M(TTA)_3组分对发光有增益作用.对其可能的发光机制进行了探讨.

SrAl_2O_4：Eu^（2＋）的长余辉发光特性的研究

本文研究了ＳｒＡｌ２Ｏ４：Ｅｕ２＋材料的发光及长余辉特性．首次得到了这一材料的发光衰减由初始的快衰减和后期的慢衰减过程所组成，以及热释发光光谱出现两个热释发光峰值的实验结果．对所得结果进行了分析讨论，提出了这一材料的发光衰减是由两个足够深的电子陷阱所引起．

苯甲酸及其一氯代衍生物与邻菲罗啉或联吡啶的稀土铕三元配合物的荧光性质

本文报道合成了八种苯甲酸及其一氯代衍生物与邻菲罗啉或联吡啶的稀土铕三元配合物并测得了荧光光谱。通过改变第一和第二配体,研究了配合物发光峰强度、位置和分裂间隔等的变化情况,依据荧光发射峰的分裂推断出Eu^(3+)离子所处的局域环境对称性大致都是C_1,C_2或C_s。虽然配合物的局域对称性大致相同,但由于配体场作用和能级匹配等原因,发光峰位置和强度是不同的;讨论了第一配体分子结构的变化对荧光性能的影响,认为分子自身结构的对称性可能对提高配合物发光性能有较大影响;实验还观察到第二配体也参与配位且对发光性能影响较大。同时看到发光峰的分裂间隔大小变化和发光峰的相对强度的变化是一致的。