A3M2Ge3O12石榴石体系中Cr3+离子的宽带发射光谱

首次报告在Ａ３Ｍ２Ｇｅ３Ｏ１２∶Ｃｒ（Ａ＝Ｃｄ２＋,Ｃａ２＋;Ｍ＝Ａｌ３＋,Ｇａ３＋,Ｓｃ３＋）锗酸盐石榴石体系中,Ｃｒ３＋离子室温下的红—近红外（Ｒ—ＮＩＲ）宽发射带光谱性质。随位于八面体格位上的Ａｌ３＋→Ｇａ３＋→Ｓｃ３＋和十二面体格位上的Ｃｄ２＋→Ｃａ２＋组成顺序变化,室温下,Ｃｒ３＋离子的４Ｔ２→４Ａ２能级跃迁的Ｒ－ＮＩＲ宽发射带,发射峰及光谱的长波和短波边逐渐向低能长波边移动。这是由于晶场强度减弱,阳离子的离子半径增大的结果。在镉（钙）铝和镉（钙）镓锗酸盐体系中,少量Ｓｃ３＋取代八面体上的Ａｌ３＋和Ｇａ３＋时,可使Ｃｒ３＋的Ｒ－ＮＩＲ荧光发射强度增强。     

A3M2GeO12石榴石体系中Cr^3＋离子的宽带发射光谱

首次报道在Ａ３Ｍ２Ｇｅ３Ｏ１２：Ｃｒ（Ａ＝Ｃｄ＾２＋,Ｍ＝Ａｌ＾３＋,Ｇａ＾３＋,Ｓｃ＾３＋）锗酸盐石榴石体系中,Ｃｒ＾３＋离子室温下的红－近红外宽发射带光谱性质。随位于八面体格位上的Ａｌ＾３＋→Ｇａ＾３＋→Ｓｃ＾３＋和十二面体格位上的Ｃｄ＾２＋→Ｃａ＾２＋组成顺序变化,室温下,Ｃｒ＾３＋离子的＾４Ｔ２→＾４Ａ２能级跃迁的Ｒ－ＮＩＲ宽发射带,发射峰及光谱的长波和短波边逐渐向低能长波边移动。     

M2SiO4：Re(M=Mg,Ca,Ba;Re=Ce3+,Tb3+)的发光性能

合成了系列M₂SiO₄:Re(M=Mg,Ca,Ba;Re=Ce³⁺,Tb³⁺)样品,研究了样品在真空紫外区域的激发光谱和发射光谱。从激发谱可以看出:M₂SiO₄:Re(M=Mg,Ca,Ba;Re=Ce³⁺,Tb³⁺)在147,172nm有很强的吸收带。用Mg,Ca完全取代Ba₂SiO₄:Tb³⁺中的Ba,相对应的晶体的晶格参数逐渐增大,晶场的能量逐渐减少,其激发光谱随着碱土离子半径的增加向长波方向移动。在172nm真空紫外光激发下,观察到M₂SiO₄:Re(M=Mg,Ca,Ba;Re=Tb³⁺和M₂SiO₄:Re(M=Mg,Ca,Ba;Re=Ce³⁺,Tb³⁺)特征发射;在真空紫外激发下,随着M₂SiO₄:Re(M=Mg,Ca,Ba;Re=Ce³⁺,Tb³⁺)中Ce³⁺含量的增加,M₂SiO₄:Re的特征发射明显减弱,并分析讨论了相关发光现象的成因。     

M2SiO4:Re(M=Mg,Ca,Ba;Re=Ce3+,Tb3+)的发光性能

合成了系列M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )样品,研究了样品在真空紫外区域的激发光谱和发射光谱.从激发谱可以看出:M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )在147,172 nm有很强的吸收带.用Mg,Ca完全取代Ba2SiO4∶Tb3 中的Ba ,相对应的晶体的晶格参数逐渐增大,晶场的能量逐渐减少,其激发光谱随着碱土离子半径的增加向长波方向移动.在172 nm真空紫外光激发下,观察到M2SiO4∶Re(M=Mg,Ca,Ba; Re=Tb3 和M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )特征发射;在真空紫外激发下,随着M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )中Ce3 含量的增加,M2SiO4∶Re的特征发射明显减弱,并分析讨论了相关发光现象的成因.     

Raman scattering study of reduced Er:LiNbO3 crystals

Raman spectra of as-grown and reduced (or annealed) Er:LiNbO₃ crystals, which have different cut orientations, varied Li/Nb ratio, and different Er-doping levels of 0.2, 0.4, 0.6, 1.0, and 2.0 mol%, were recorded at room temperature over a wavenumber range of 50–1000 cm^-1 by use of backward scattering geometries. The spectra are assigned on the basis of their Raman scattering features and previous relevant work. A weak but well-resolved peak around 633 cm^-1 appears in the E(TO) spectra that were recorded under the configuration of X(ZY)X̄(for an X-cut sample) or Y(ZX)Ȳ(for a Y-cut sample) for all crystals studied. The appearance of this peak in the E(TO) spectrum provides further evidence for a previous attribution of this peak to E(TO₉) mode. Some additional peaks distributed in the low wavenumber region ranging from 101–137 cm^-1 are attributed to Er³⁺ fluorescence with a wavelength range of 490.41–491.3 nm. The reduction effects include a significant drop of the Raman scattering intensity and a slight narrowing instead of a broadening in the linewidth. The reduction procedure hardly affects the spectral shape and the wavenumber of most of the phonons. The anneal effect is similar to the reduction effect and both effects are not as obvious as the vapor transport equilibration (VTE) effect. In addition, the present Raman scattering result provides evidence for our earlier reported individual result on light-induced diffraction from strongly reduced Er:LiNbO₃ crystals. PACS 42.70.Hj; 81.05.-t; 63.20.-e; 78.30.-j.     

Optical losses in YVO4: RE (RE = Nd3+, Er3+, Tm3+) laser crystals

The relevance of processes contributing to depletion of pump and upper laser levels has been assessed based on experimental data obtained during measurement of excited state absorption, steady state emission and dynamics of excited states as a function of excitation power and activator concentration. It has been concluded that the excited state absorption in YVO₄: Nd and YVO₄: Er is not significant except for that from the ⁴ I _11/2 level of Er³⁺. In these systems, the interionic processes are dominant. In particular, the reported decrease of the YVO₄: Er laser slope efficiency when the Er³⁺ concentration increased from 0.5 to 1 at % is due mainly to the up-conversion by energy transfer from the pump level and upper laser level. Excited state absorption cannot contribute to depletion of excited states involved in the ³ F ₄-³ H ₆ laser operation near 1800 nm in the YVO₄: Tm crystal. However, the heavy doping required to enhance the cross-relaxation process which feeds the upper laser level brings about the migration-accelerated energy transfer to energy sinks.     

铜铁镁三掺铌酸锂晶体的第一性原理研究

利用基于密度泛函理论的第一性原理,研究了Cu:Fe:Mg:LiNbO3晶体及对比组的电子结构和光学特性.研究显示,单掺铜或铁铌酸锂晶体的杂质能级分别由Cu 3d轨道或Fe 3d轨道贡献,禁带宽度分别为3.45和3.42 eV;铜、铁共掺铌酸锂晶体杂质能级由Cu和Fe的3d轨道共同贡献,禁带宽度为3.24 eV,吸收峰分别在3.01,2.53和1.36 eV处;Cu:Fe:Mg:LiNbO3晶体中Mg^2+浓度低于阈值或高于阈值(阈值约为6.0 mol%)的禁带宽度分别为2.89 eV或3.30 eV,吸收峰分别位于2.45 eV,1.89 eV或2.89 eV,2.59 eV,2.24 eV.Mg^2+浓度高于阈值,会使吸收边较低于阈值情况红移;并使得部分Fe^3+占Nb位,引起晶体场改变,从而改变吸收峰位置和强度.双光存储应用中可选取2.9 eV作为擦除光,2.5 eV作为读取和写入光,选取Mg^2+浓度达到阈值的三掺晶体在增加动态范围和灵敏度等参量以及优化再现图像的质量等方面更具优势.     

Photorefractive light scattering in lithium niobate crystals doped with Mg2+, B3+, Y3+, and Ta5+

We have investigated the photorefractive (photoinduced) light scattering in lithium niobate single crystals: LiNbO₃, LiNbO₃:B, LiNbO₃:Y(0.46 mas %), LiNbO₃:Y(0.24):Mg(0.63 mas %), and LiNbO₃:Ta(1.13):Mg(0.0109 mas %) that were grown from congruent melts. We have found that the shape of the speckle structure of this scattering and the kinetics of the development of its indicatrix depend substantially on the type of the impurity dopant in the lithium niobate crystal. We have observed that, upon laser irradiation of crystals doped with Y³⁺, Ta⁵⁺:Mg²⁺, and Y³⁺:Mg²⁺, the shape of their scattering indicatrix changes with time. At the same time, the LiNbO₃:B crystal is characterized by a complete absence of time changes in its speckle structure, which indicates that the photorefractive effect in this crystal is substantially lowered.     

[M(SS)(NN)](M=Zn2+,Cd2+)配合物分子内跃迁与结构的关系

报道了配合物[M(SS)(NN)](M=Zn2 ,Cd2 )(SS=mnt2-,1,2-二氰基乙烯-1,2-二硫醇离子,NN=5-NO2-phen,5-硝基-1,10-邻菲咯啉)的合成,探讨了Zn(SS)(NN)和Cd(SS)(NN)在二甲基亚砜(DM-SO)、二甲基甲酰胺(DMF)、丙酮(acetone)、吡啶(Py)等溶剂中的电子吸收光谱。研究发现配合物的紫外区的吸收带270～280nm,320～350nm,350～390nm本质上属于配体mnt2-,5-NO2-phen内部的πb→π*跃迁,可见光区400～500nm本质上属于配体mnt2-到配体5-NO2-phen的荷移跃迁(LL′CT)。确认了标题配合物的荷移跃迁光谱在相关分子轨道能级图中的对应关系。标题配合物的LL′CT吸收带与组成相似配合物M(SS)(NN)(M=Co2 ,Fe2 ,Ni2 ,Cu2 )的对应吸收带相比较弱一些,这是由于[M(SS)(NN)](M=Zn2 ,Cd2 )的LL′CT谱带(7b2→7b1)是部分解除轨道禁阻的跃迁。     

Photorefractive light scattering in LiNbO3: Cu crystals

The time dependence of the photorefractive light scattering in lithium niobate single crystals of the congruent composition (LiNbO₃) doped by “photorefractive” Cu cations (0.015 wt %) is studied for a radiation power of 160 mW. The data for the photorefractive scattering are confirmed by changes in Raman scattering spectra.     

Phase transitions of [M(H2O)6](MnO4)2 polycrystalline compounds,where M=Mg2+,Ni2+,Zn2+,Cd2+, studied by DSC

Phase transitions of [M(H₂O)₆](MnO₄)₂, where M=Mg, Ni, Zn and Cd, have been studied at 100–400 K by differential scanning calorimetry (DSC). One solid–solid phase transition for the compounds with M=Mg and Ni and two solid–solid phase transitions for these with M=Zn and Cd have been discovered. Additionally, three phase transitions, connected with three-stage melting process of these compounds, were also found. Thermodynamic parameters of the all detected phase transitions were calculated.     

Theoretical study of efficiency of metal cations (Mg+, Ca+, and Ag+) for effective hydrogen storage

The interaction between the metal cations and H₂ molecule has been investigated using dispersion-corrected and -uncorrected hybrid density functional and CCSD(T) methods in conjunction with the correlation consistent triple-ζ quality basis sets for the storage of the H₂ molecule. The molecular properties, potential energy surfaces, stability, binding energy and well-depth have been computed for the metal cation–dihydrogen (M⁺–H₂, M = Mg, Ca, and Ag) complexes in the gas phase. The results obtained by the dispersion-corrected hybrid density functional B2PLYP-D method agree very well with the earlier experimental and theoretical results wherever available. Different components of the interaction energy have been estimated by the symmetry adapted perturbation theory (SAPT) to get physical insight into the interaction energy. Among the three complexes, only Ag⁺–H₂ is the most stable complex and it accumulates more H₂ molecules as the interaction between the metal cation Ag⁺ and the H₂ molecule is the greatest.     

Photoluminescence investigations of Li2SiO3:Ln (Ln=Er3+, Eu3+, Dy3+, Sm3+) phosphors

In this study, we report a comprehensive structural and photoluminescence (PL) study on lithium metasilicate (Li₂SiO₃) phosphor ceramics doped with four rare earth (RE) ions. X-ray diffraction (XRD) patterns show a dominant phase, characteristic of the orthorhombic structure Li₂SiO₃ compound and the presence of dopants has no effect on the basic crystal structure of the material. The first excited state Er³⁺ luminescence at 1.54 μm arises from a sharp atomic-like radiative transition between the ⁴I_13/2 state and the ⁴I_15/2 state (ground level) under a 532 nm line of an Ar ion laser excitation. Sm doped samples showed Sm³⁺ emission characteristics corresponding to the some ⁴G_5/2→⁶H_j (j=5/2,9/2,11/2) transitions indicating a strong crystal-field effect. PL spectra of Eu doped material exhibited peaks corresponding to the ⁵D₀→⁷F_j (j=0,1,2,3 and 4) transitions under 405 nm excitation. The dominant red color emission at 612 nm from the hypersensitive (⁵D₀→⁷F₂) transition of Eu³⁺ indicates the inversion antisymmetry crystal field around Eu³⁺ ion, which is favorable to improve the red color purity. Dy doped samples showed the Dy³⁺ emission characteristic due to the ⁴F_9/2→⁶H_13/2 transition. Their relative intensity ratios also suggested the presence of a symmetric environment around the metal ion. We suggest that lithium metasilicate has enough potential candidates to be a phosphor material.     

LiNbO3:Fe晶体中光写入平面光波导的导光特性研究

从光折变效应的单中心模型和载流子的光伏迁移机理出发给出了高斯片光在LiNbO3:Fe晶 体中导致的折射率变化分布的解析表达式.利用片光以“三明治”辐照方式在LiNbO3:Fe晶 体中写入了平面光波导结构.用切片干涉法测量了波导区的折射率分布，并对波导进行了简 单的导光测试.根据射线方程以及波导的折射率分布对光写入波导的导光特性进行了模拟计 算分析.研究结果表明，在LiNbO3:Fe晶体中光写入光波导是可行的. 关键词： LiNbO3:Fe晶体 光辐照法 平面光波导 导光特性 高斯片光     

Spectroscopic properties, energy transfer and structural analysis of Sr2CeO4:M+ and Sr2CeO4:Eu3+, M+ (M+ = Li+, Na+, K+)

The room-temperature luminescent emission characteristics of Sr₂CeO₄:M⁺ and Sr₂CeO₄:Eu³⁺,M⁺ (M⁺ = Li⁺, Na⁺, K⁺) have been investigated under UV excitation. By introducing appropriate alkali metal cations dopants (Li⁺, Na⁺, K⁺) into the crystalline lattice, not only emission color of the blue-white-emitting Sr₂CeO₄ doped with low Eu³⁺ content can be tuned to green, but also the red emission intensity of Sr₂CeO₄ doped with high Eu³⁺ concentration is strengthened significantly. The relevant mechanisms have been elucidated in detail.     

Lattice site of Er in LiNbO3:Mg,Er crystals

Abstract

The lattice site of Er has been determined in LiNbO₃:Mg, Er crystals by the Rutherford backscattering channeling technique. It has been shown unambiguously that Er occupies Li site in the crystal lattice. OH absorption band has not been found in the 3500–3525 cm^?1 region. The RBS result confirms the assumption that OH^? ions may form defect complexes only with those trivalent impurities which replace niobium.     

M/Li+(M = Mg2+, Zn2+, and Mn2+) ion-exchange on lithium ion-conducting perovskite-type oxides and their properties

Lithium ions of perovskite-type lithium ion conductor La_0.55Li_0.35TiO₃ were replaced by divalent Mg²⁺, Zn²⁺, and Mn²⁺ ions in an ion-exchange reaction using molten chlorides. The polycrystalline Mg-exchanged and Zn-exchanged samples are solid electrolytes for divalent Mg²⁺ and Zn²⁺ ions, whose dc ionic conductivities (σ = 2.0 × 10^− 6 S cm^− 1 at 558 K for the Mg-exchanged sample, La_0.56(2)Li_0.02(1)Mg_0.16(1)TiO_3.01(2) and σ = 1.7 × 10^− 6 S cm^− 1 at 708 K for the Zn-exchanged samples, La_0.55(1)Li_0.0037(2)Zn_0.15(1)TiO_2.98(2)) were compared to those of the known highest Mg²⁺ and Zn²⁺ inorganic solid electrolytes. The Mn-exchanged sample, then, showed paramagnetic behavior in the temperature range of 2 to 300 K. The Mn ions in the exchanged sample are divalent and the spin configuration is in high spin state (S = 5/2).     

Lithium ion conductivity of the B-site substitution in Li3xLa0.67−xRE y III Ti1−2yPyO3 system (REIII=Sc3+, Y3+, Nd3+, Sm3+, Eu3+, Yb3+)

The B-site substituted perovskite solid solution systems Li_3xLa_0.67−xRE_yTi_1−2yP_yO₃ (RE=Sc, Y, Nd, Sm, Eu, Yb) have been investigated. Perovskite solid solutions formed in the range of x=0.10, y<0.10 for RE=Sc³⁺, Y³⁺, Yb³⁺, x=0.10, y≤0.05 for RE=Nd³⁺, Sm³⁺, Eu³⁺. Li_0.3La_0.57Nd_0.05Ti_0.9P_0.05O₃ has the highest bulk conductivity of 4.31×10⁻⁴ S·cm⁻¹ and the highest total conductivity of 2.52×10⁻⁴ S·cm⁻¹ at room temperature in all prepared compositions. The compositions have low activation energies of about 24–30 kJ/mol in the temperature ranges of 298–523 K. SEM studies showed that the sample made by solid-state reaction has a sphere-like morphology and a rough particle with particle size of about 50 μm. The research results also indicated that the reaction temperature decreases and the electrochemical stabilities of the titanate-based perovskite-type solid solutions are improved by using RE³⁺ and P⁵⁺ replaced Ti⁴⁺ on B-site in the Li_3xLa_0.67−xTiO₃ parent.     

Synthesis and Spectral Study of Several Solid M3[Eu(2,6-Pyridinedicarboxylate)3] Salts (M=Li+, Na+, K+, Rb+, Cs+, NH4 +, and Pyridinium+)

Abstract

Salts of the [Eu(2,6-pyridinedicarboxylate)₃]^3- complex anion and various monovalent inorganic and organic counterions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH₄ ⁺, and pyridinium⁺) have been synthesized and studied by emission spectroscopy. The Eu³⁺ ion emission spectra exhibited by these salts have been observed with high resolution (less than 1.0 cm^?1) and at low temperature (77 K). The emission spectra of these compounds indicate that changing the attached counterion does not affect the site symmetry observed by the europium ion beyond slight distortions indicated by small shifts in the energies of the Eu³⁺ electronic levels.