Ba10(PO4)4(SiO4)2∶Eu2+荧光体的光谱特性

采用高温固相法合成了荧光体Ba₁₀（PO₄）₄（SiO₄）₂：Ce³⁺和Ba₁₀（PO₄）₄（SiO₄）₂：Eu²⁺,研究了两种荧光体的光谱特性。结果表明,两者都呈现较强的宽带激发特征。根据同种基质中Eu²⁺和Ce³⁺两种离子光谱特征的相关性,通过测得的Ba₁₀（PO₄）₂（SiO₄）₂基质中Ce³⁺的光谱数据估算了Ba₁₀（PO₄）₂（SiO₄）₂：Eu²⁺中Eu²⁺的斯托克斯位移（ΔS）和激发能量,估算结果与Ba₁₀（PO₄）₂（SiO₄）₂：Eu²⁺样品的光谱分析结果十分吻合。Ba₁₀（PO₄）₂（SiO₄）₂：Eu²⁺可以同时被紫光和蓝光激发,发出偏白的绿光,可用作白光LED的荧光粉。     

镱掺杂钼酸铅的光谱和EPR谱的理论研究

该文表达了一个研究Yb³⁺掺杂PbMoO₄晶体的光谱和电子顺磁共振谱(EPR)的理论方法. 采用晶体场理论,推导了有关光谱和电子顺磁共振谱的公式. 基于这些理论公式,构建了4f¹³电子组态在D_2d晶体对称下包括Zeeman磁相互作用的14阶能量矩阵. 通过对角化这一能量矩阵,研究了Yb³⁺掺杂PbMoO₄晶体的光谱和电子顺磁共振谱. 所得的理论结果与实验值很好符合. 而且,相关的晶体场参量也在研究中确定.     

中子探测晶体Li6Gd(BO3)3:Ce的光谱特性研究

文章用提拉法生长出Li₆Gd(BO₃)₃:Ce晶体,并对其光谱性能与发光过程进行了探索. 借助于真空紫外-紫外透过光谱测试,发现晶体的透过光谱中存在Ce³⁺离子和Gd³⁺的特征吸收峰,同时还存在与Ce⁴⁺离子相关的电荷迁移带. 对晶体的真空紫外-紫外激发发射光谱进行研究发现,在晶体存在着Ce³⁺离子的5d→4f辐射跃迁发光与Gd³⁺离子的4f→4f辐射跃迁发光,而且存在着Gd³⁺→Ce³⁺之间的能量传递. 对Li₆Gd(BO₃)₃:Ce晶体的X射线与γ射线激发发射光谱研究可知,晶体在高能射线激发下的闪烁光主要是Ce³⁺离子的发光. 关键词： 6Gd(BO₃)₃:Ce晶体')" href="#">Li₆Gd(BO₃)₃:Ce晶体 真空紫外-紫外透过光谱 真空紫外-紫外激发发射光谱 能量传递     

Cr3+掺杂的Cd3Al2Ge3O12光谱特性及晶场参数计算

采用高温固相法合成了Cd₃Al₂Ge₃O₁₂：Cr³⁺多晶材料,利用X射线衍射对其结构进行了分析,通过Cr³⁺的室温吸收光谱、室温和77K发射光谱分别对其光谱特性和晶场参数进行了分析和计算.结果表明：在450 nm的蓝光激发下,Cd₃Al₂Ge₃O₁₂：Cr³⁺室温发 关键词： 3Al₂Ge₃O₁₂：Cr³⁺')" href="#">Cd₃Al₂Ge₃O₁₂：Cr³⁺ 荧光光谱 晶场参数 可调谐激光     

Dy含量对红色长余辉发光材料Sr3Al2Ｏ6:Eu2＋,Dy3＋性能的影响

采用溶胶凝胶法制备了Sr₃Al₂Ｏ₆:Eu^2＋,Dy^3＋红色长余辉发光材料,利用X射线衍射仪对材料的物相进行了分析,结果表明,1200℃下制备的样品的物相为Sr₃Al₂Ｏ₆,少量的Eu和Dy掺杂没有影响样品的相组成.采用荧光分光光度计、照度计测定了样品的发光特性.结果表明Sr₃Al₂Ｏ关键词： 红色长余辉 3Al₂Ｏ₆')" href="#">Sr₃Al₂Ｏ₆ 溶胶凝胶法     

掺Gd3+钼酸盐AMoO4 (A=Ca,Sr, Ba,Pb)自旋哈密顿参量的理论计算

采用基于单电子晶体场机制的对角化能量矩阵方法, 计算了Gd³⁺在钼酸盐AMoO₄ (A=Ca, Sr, Ba, Pb)晶体中的自旋哈密顿参量(g因子g_//, g_⊥和零场分裂b₂⁰, b₄⁰, b₄⁴, b₆⁰, b₆⁴). 矩阵中的晶体场参量采用重叠模型计算. 计算结果显示, 应用三个合理的可调参量[即重叠模型中的内禀参量A₂ (R₀), A₄ (R₀)和A₆ (R₀)], 计算的七个自旋哈密顿参量与实验结果符合甚好, 表明该方法可用于计算或解释Gd³⁺在晶体中的自旋哈密顿参量. 关键词： AMoO₄ (A=Ca,Sr,Ba,Pb):Gd³⁺晶体')" href="#">AMoO₄ (A=Ca,Sr,Ba,Pb):Gd³⁺晶体 自旋哈密顿参量 晶体场理论 对角化能量矩阵     

Tm3+离子掺杂的钨酸钇钠晶体中浓度猝灭效应的研究

测量了Tm³⁺离子不同浓度(0.5at.%, 3 at.%, 5 at.%)掺杂的NaY(WO₄)₂晶体在800nm激光二极管激发下的上转换发射光谱.结合吸收谱、荧光谱和由Judd-Ofelt理论计算的光谱参数，详细分析了Tm³⁺:NaY(WO₄)₂晶体中上转换能量传递机理和离子浓度对上转换发射的影响.讨论了四种影响上转换发光效率的离子间相互作用机理：³H₅+¹G₄→³H₆+¹D₂，³H₅+³H₅→³H₆+³F₃，¹G₄+³H₆→³F₄+³F₃，¹G₄+³H₆→³F₃+³F₄，并根据Miyakawa-Dexter理论定量计算了各过程的发生概率.论证了交叉弛豫和共协上转换等浓度猝灭效应是影响Tm³⁺离子蓝色上转换荧光发射效率的主要因素. 关键词： 3+离子')" href="#">Tm³⁺离子 4)₂晶体')" href="#">NaY(WO₄)₂晶体 上转换 浓度猝灭     

KCdF3:Cr3+晶体EPR零场分裂参量与电荷补偿效应的研究

按照叠加模型与EPR零场分裂参量的三阶微扰理论,建立了KCdF₃:Cr³⁺晶体EPR零场分裂参量与四角对称Cr³⁺-Cd²⁺缺陷中心局域结构之间的定量关系.证实Cd²⁺空位与晶格畸变的存在,我们获得:围绕Cr³⁺离子的六个F^-配体分别向中心Cr³⁺移动Δ₁=0.00294nm,Δ₂=0.0010nm,Δ₃=0.0028nm (参见图2).EPR零场分裂参量与实验一致表明:Cd²⁺空位与晶格畸变的假设是合理的.尽管四角晶场主要来自Cd²⁺空位,但晶格畸变的贡献不可忽略.     

Sr3Gd0.5-xTb0.5(BO3)3∶xEu3+的发光性质及能量传递

采用高温固相法制备了Sr₃Gd_0.5-xTb_0.5(BO₃)₃∶xEu³⁺系列荧光粉,并研究了其发光性质与能量传递过程。Sr₃Gd_0.5-xTb_0.5(BO₃)₃∶xEu³⁺系列荧光粉在300~400 nm的近紫外光有效激发下产生489,544,594,614,624 nm的发射谱线,分别对应于Tb³⁺和Eu³⁺的特征跃迁。荧光寿命测试表明,随着Eu³⁺掺杂浓度的增大,Tb³⁺寿命逐渐缩短,证实该体系中存在Tb³⁺→Eu³⁺的能量传递过程,能量传递效率最大值为20.53%。在对Tb³⁺和Eu³⁺的能级结构进行分析的基础上,进一步探讨了Tb³⁺→Eu³⁺能量传递过程。Sr₃Gd_0.5-xTb_0.5-(BO₃)₃∶xEu³⁺系列荧光粉具有良好的红色发光性质,是潜在的可以应用于白光LED的光转换材料。     

Ce3+和Mn2+掺杂的Ba9(Y2-xScx)(SiO4)6光谱特性和温度特性研究

采用高温固相法制备了Ba₉(Y_2-xSc_x)(SiO₄)₆:Ce³⁺,Mn²⁺(x=0,0.5,1.0,1.5,2.0)样品。在该体系中,当Sc³⁺含量从x=0逐渐增加至x=2时,Ce³⁺的蓝光发射强度提高了1.7倍;同时,Mn²⁺的红光发射强度提高了1.9倍,显示了优良的红光特性。样品的发射光谱和漫反射光谱表明,Ce³⁺、Mn²⁺发射强度的增加与Ce³⁺吸收能力和Ce³⁺向Mn²⁺能量传递的提升有直接关系。研究了样品Ba₉Sc₂(SiO₄)₆:Ce³⁺,Mn²⁺的热稳定性。随着温度的升高,Mn²⁺的红光发射呈现先升后降的态势。当温度从室温升至488 K时,Mn²⁺发射强度仅下降至室温时的84%,表现出优良的热稳定性。高亮的红光发射和优良的热稳定性表明该荧光材料可为紫外基白光LED提供良好的红色光源。     

蓝宝石(α-Al_2O_3:Fe~(3+))体系基态分裂与局域晶格畸变的研究

2002年Scholz和Buzaré对蓝宝石晶体中Fe3+离子的基态分裂重新进行了EPR实验测量和研究,他们的初步分析表明在蓝宝石晶体中Fe3+离子的6A1基态分裂有可能同时与两个方向的畸变角(θ和φ)有关.本文采用对角化d5组态在C3点群对称下的252×252完全能量矩阵的方法,对蓝宝石晶体中Fe3+离子的光谱和EPR谱进行了系统的研究.计算结果表明蓝宝石体系中Fe3+离子的6A1基态分裂确实将明显依赖于两个方向的畸变角θ和φ,这一理论结果与Scholz和Buzaré等的实验相符合.同时,通过拟合Fe3+离子在蓝宝石体系中的实验光谱和EPR参量,确定了蓝宝石晶体中(FeO6)9团簇局域晶格畸变角θi的范围.     

Theoretical investigation of the optical spectra and local lattice structure for Mn5+ in a Sr10(VO4)6F2 crystal

In this paper, the relationships between the optical spectra and local lattice structure for Mn⁵⁺ in a Sr₁₀(VO₄)₆F₂ crystal are established by the crystal- and ligand-field theory. The effect of spin–orbital coupling between the central 3d² ions and ligand ions has been considered in the full energy matrix. Using the matrix and superposition model formula, we have calculated the optical spectra and local lattice structure parameters of Mn⁵⁺ in Sr₁₀(VO₄)₆F₂ with a C_3v system. The calculated results are in good agreement with the observed values. In addition, the trigonal compressed distortions of the (MnO₄)^3? centers in Sr₁₀(VO₄)₆F₂ crystals are also obtained from the calculations.     

Theoretical studies of the optical and EPR spectra for Fe ion in the MF3:Fe (M=Al, Ga) systems

By analyzing the EPR spectra of Fe³⁺ ion in the fluorinde glasses, the local lattice structures around impurity Fe³⁺ ion in MF₃:Fe³⁺ (M=Al, Ga) systems have been studied by means of diagonalizing the complete energy matrices of the electron-electron repulsion, the ligand-field and the spin-orbit coupling for a d⁵ configuration ion in a trigonal ligand-field. Both the second-order and fourth-order EPR parameters D and (a−F) are taken simultaneously in the structural investigation. The results indicate that the local lattice structure around octahedral Fe³⁺ center has an expansion distortion for Fe³⁺ in MF₃:Fe³⁺ (M=Al, Ga). The expansion distortion may be ascribed to the fact that the radius of Fe³⁺ ion is larger than that of Al³⁺ ion and Ga³⁺ ion, and the Fe³⁺ ion will push the fluoride ligands upwards and downwards, respectively. The local lattice structure parameters R=1.927 A, θ=55.538° for Fe³⁺ in AlF₃:Fe³⁺ and R=1.931 A, θ=56.09° for Fe³⁺ in GaF₃:Fe³⁺ are determined, respectively, and the EPR spectra of the MF₃:Fe³⁺ (M=Al, Ga) systems are satisfactorily explained.     

Research on the defect structure and g factors for the tetragonal (CrO4)3− impurity center in ZrSiO4: Cr5+ crystal

ABSTRACT

The EPR g factors g// and g⊥ for the tetragonal (CrO₄)^3? impurity center in ZrSiO4: Cr⁵⁺ crystal are studied from the high-order perturbation formulas based on the two-mechanism (the crystal field and charge-transfer mechanisms) model. The studies indicate that differing from the tetragonally-elongated host (SiO4)^4- tetrahedron, the dominant defect structure of the substitutional (CrO₄)^3? tetrahedron is tetragonally- compressed with the ground state |d_z² due to the Jahn-Teller distortion. Furthermore, the agreement of g factors between calculation and experiment requires a small admixture of the first excited state |d_x²_?y² to the ground state |d_z² due to the vibrational motion of ligands, which leads a compressed (CrO₄)^3? tetrahedron to become a twinkling elongated one, These results are discussed.     

Temperature and pressure dependences of EPR spectra of Gd ion doped in the EuAl3(BO3)4 monocrystal

The ground state of Gd³⁺ ions substituting for trivalent europium in the EuAl₃(BO₃)₄ single crystal was studied by electron paramagnetic resonance (EPR) over the temperature range of 300-4.2 K and at pressures up to 9 kbar. The EPR spectra were analysed using the spin Hamiltonian of axial symmetry. The following parameters are reported: g=1.981±0.002, b₂⁰=280.18±0.12, b₄⁰=−12.95±0.08 and b₆⁰=0.61±0.12 (at Т=298 K). The distortions of the nearest environment of Gd³⁺ ion were analysed within the framework of the superposition model of crystal field.     

Effect on the EPR and local lattice structure distortion of V3+ ion doping corundum crystal: three models studied

This paper reports on the application of conventional models (the displacement model and the elongation model) and the four-parameter model in detecting the local molecular structure of a coordination complex. By diagonalizing the complete energy matrices, the EPR parameters and optical spectra as well as the local distortion structure for V³⁺ ion in the Al₂O₃ : V³⁺ system have been studied using the three models. The four-parameter model is shown to provide a significant improvement over the conventional models. Based on these calculations, it was found that when V³⁺ is doped in Al₂O₃, the distance between upper and lower ligand oxygen plane increases by 0.16097 Å and the shifts of O^2? ions in the upper and lower ligand oxygen planes expand by 0.07076 Å and 0.004066 Å, respectively. To understand the detailed physical and chemical properties of the doped Al₂O₃, the contributions of the spin-orbit coupling to the zero-field splitting for V³⁺ ion are investigated.     

近化学计量组分掺铒铌酸锂晶体光学特性研究

用气相输运平衡技术成功地制备出了近化学计量组分的Er∶LiNbO₃晶体,系统 地研究了该 晶体的吸收边移动、可见—红外透射谱、荧光光谱的物理特性.与同成分Er∶LiNbO_{3晶体 相比, 近化学计量组分Er∶LiNbO3晶体的吸收边出现了“蓝移”;OH^{-吸收带明显减弱 ;在可见—近红外波段呈现出更高的透过率;同时Er3+离子的发光强度也明显 提高. 这些结果表明近化学组分的Er∶LiNbO关键词： 近化学组分掺铒铌酸锂晶体 -}吸收带')" href="#">OH^-吸收带 透射谱 荧光光谱}     

Charge-transfer transitions and optical spectra of chromites

Specific features of charge-transfer states and charge-transfer transitions of the O_2p → Cr_3d type in octahedral complexes (CrO₆)^9? have been considered in the cluster approximation. Reduced matrix elements of the electric-dipole moment operator on many-electron wave functions, which are the initial and final states for charge-transfer transitions, are calculated. The results are parameterized, and the relative intensities of different allowed charge-transfer transitions in the absence of mixing of different charge-transfer configurations with identical symmetry are calculated. This mixing is taken into account within the Tanabe-Sugano theory, and the true energies and intensities of many-electron charge-transfer transitions are obtained. The Coulomb interaction between 2p electrons of O^2? ligands and 3d electrons of the central Cr³⁺ ion in (CrO₆)^9? cluster is considered. The influence of this interaction on the optical spectra is found to be insignificant. Simulation of the optical spectra of chromium oxides has shown the presence of a band of complex charge-transfer transitions composed of 33 lines with a total width of about 8 eV. The model spectrum is in adequate agreement with the experimental data, which indicates limited applicability of the widespread view that charge-transfer transition spectra have a simple structure.