Spectroscopic properties of Nd3+:(La,Sr)(Al,Ta)O-3 crystal

A new laser crystal Nd3+:(La, Sr)(Al, Ta)O-3 (abbreviated as Nd3+:LSAT) has been grown by the conventional Czochralski method. The absorption and luminescence spectra of trivalent neodymium in Nd3+:LSAT crystal were measured at room temperature. The value of absorption and emission cross-section was calculated. The Judd-Ofelt analysis was applied to the crystal to get the phenomenological parameters (Omega(i), i = 2,4,6), the line strengths, the radiative transition rates, the branching ratios and the radiative lifetime. (C) 2006 Elsevier B.V. All rights reserved.

掺Er3+玻璃上转换发光特性研究

采用高温熔制工艺制备了掺Er3+硅酸盐玻璃，应用Judd-Ofelt 理论计算了Er3+光谱参数， 发现玻璃中含有0.15 mol%Er2O3 时各参数取得最大值；分析了玻璃的吸收光谱随Er3+离子浓度的变 化关系；上转换光谱分析表明在522 nm、544 nm、658 nm 处有较强的绿光和红光，分别对应于 2H11/2→4I15/2、4 S3/2→4I15/2、4 F9/2→4I15/2 的跃迁，且522 nm 绿光强度和658nm 红光强度要远大于544 nm 绿光强度. 分析了上转换发光强度随泵浦功率和Er3+离子浓度的变化关系，揭示了上转换发光机制 主要是激发态吸收和能量转换，且均为双光子吸收过程.

铒镱共掺铅硅酸盐玻璃的光谱分析

采用传统的高温熔融工艺制备了铒镱共掺铅硅酸盐玻璃. 测量了样品的吸收光谱、荧光光谱和折射率， 利用McCumber 理论和Judd-Ofelt 理论计算了该玻璃系统中Er3+离子4I13/2→4I15/2 能级跃迁受激发射截面和荧 光寿命.该玻璃在1 536 nm 处受激发射截面σemi 为8.62×10-21 cm2；荧光寿命长达11.32 ms（实验测量值为9.26 ms）；在1536 nm 附近有很强的荧光发射，荧光有效线宽为46.5 nm；样品存在中心波长为580 nm 的4S3/2→4I15/2 跃迁的上转换荧光. 结果表明，该样品荧光寿命长，受激发射截面大，同时具有较弱的上转换发光等特性， 是制作高能脉冲光纤激光器的理想材料

稀土(Er, Nd, Yb, Pr, Ho, Sm)有机/无机杂化材料的制备及发光性能研究

目前，国内外对于铕和铽等稀土配合物的可见区发光和应用都有大量研究，但对具有近红外发光（800-1700 nm）性能的稀土配合物的研究还处于起步阶段。由于稀土的近红外发光在光纤通讯、激光系统及诊断学等方面应用具有特殊的优点，越来越引起人们的兴趣和重视。 稀土近红外发光配合物的致命弱点是其光、热和化学稳定性较差，从而限制了其在很多领域的实际应用。而溶胶－凝胶材料和介孔材料具有良好的光、热和化学稳定性，能改善客体分子的结构环境和化学微环境，从而能有效提高客体分子的发光性能。因此，本论文将具有优良近红外发光性能的稀土配合物分别与上述两种基质复合，从实验和理论研究稀土近红外发光杂化材料的性能和应用价值，制备出具有良好稳定性的高效稀土近红外发光杂化材料，以期为光纤通讯、激光等领域提供潜在的候选材料。围绕这一宗旨，开展了如下工作： 通过原位技术分别得到了掺杂和嫁接[Ln(dbm)3phen]化合物（Ln = Er, Nd, Yb）的杂化凝胶材料，Ln-D-P gel和Xerogel-Ln。通过对其近红外发光性能的研究，表明材料中配体能很好的保护稀土离子，并将能量有效的传递给稀土离子。采用Judd-Ofelt理论对所得部分材料进行了光谱分析，基于实验数据和理论分析表明其具有潜在的光放大和激光应用价值。 选择了两种含全氟化烷基链的β-二酮配体Hhfth和Htfnb，通过功能化的phen-Si配体，将三元配合物[Ln(hfth)3phen] (Ln = Er, Nd, Yb, Sm)和[Pr(tfnb)3phen]成功共价嫁接到介孔MCM-41和SBA-15杂化材料中，得到的衍生材料Ln(hfth)3phen–MCM-41、Pr(tfnb)3phen–MCM-41和Ln(hfth)3phen–SBA-15、Pr(tfnb)3phen–SBA-15都保持了高度有序的介孔p6mm结构，并展现出稀土离子特征的近红外发射。所得稀土配合物功能化的材料的发射光谱能完全覆盖对光通讯极具应用价值的1300-1600nm区域。 通过对Er(dbm)3phen–M41(X, Y) (X = 1~14, Y = 3, 6, 12, 18, 24 h)材料系统的比较研究，选择了X = 12, Y = 6作为合成目标材料的优化参数，通过功能化的phen-Si配体将[Ln(dbm)3phen]配合物共价嫁接于有序介孔MCM-41和SBA-15中(Ln = Er, Nd, Yb)，所得两类材料Ln(dbm)3phenM41和Ln(dbm)3phenS15都保持了很好的介孔有序性，并具有良好的近红外发光性能。通过对Ln(dbm)3phenM41和Ln(dbm)3phenS15两类材料发光行为的比较，以及两类材料中稀土离子的含量及孔结构的分析，推出以SBA-15为载体得到的材料在相对发光强度和荧光寿命上，均比以MCM-41为载体的材料有所提高。 通过对8－羟基喹啉配体进行改性，合成了具有双功能的配体Q-Si，继而合成了共价嫁接8－羟基喹啉衍生物的介孔杂化材料Q–SBA-15，其形貌均一，并具有高度有序的介孔p6mm结构。通过配体交换反应，得到了嫁接稀土喹啉配合物的具有近红外发光性能的介孔杂化材料LnQ3–SBA-15 (Ln = Er, Nd, Yb)，其仍然保持高度有序的介孔结构，且外形呈现与母体材料Q–SBA-15相似的弯曲圆柱状。激发配体的吸收，LnQ3–SBA-15材料都分别展现出相应稀土离子特征的近红外发射，并详细分析和讨论了所得介孔杂化材料的近红外发光性能。

吡唑酮衍生物的稀土配合物光致和电致发光性能研究

稀土配合物的发光具有发射带窄、色纯度高、峰发光位置不受配体环境变化的影响、发光不受温度影响等特点，而且发射峰覆盖400-1800纳米的可见区和近红外区，因此可以作为有机电致发光器件的发光层材料。现在的研究大多集中于铕、铽配合物的电致发光器件研究，对于近红外稀土配合物的电致发光以及发白光的镝配合物研究相对较少，但是近红外发光的稀土铒、钕、镱在光通讯、激光技术、生物医学、荧光探针等方面具有特殊的应用前景。在本论文中主要阐述了新型稀土配合物的设计与合成、在器件方面的应用以及器件结构机理的研究。 在本论文中，我们主要研究吡唑酮的衍生物配体对于稀土离子的敏化激发作用。通过配体基团的改性，得到发光更有效的新型稀土配合物。首先，合成了配体PM，并选择TP、Phen、Bipy、Bath做第二配体制备镝、铒、钕、镱、钐等的配合物。解析了配合物的晶体结构，测试得到了各种配合物的光致发光性能，系统分析了几种配合物中配体到中心稀土离子的能量传递过程，研究了配体对稀土的敏化机制。其中镝配合物显示近白光的发射，色坐标为x=0.35，y=0.40，以此配合物为发光层的器件显示明亮的白光，最大发光亮度为527cd/m2，是目前已经报道的镝配合物器件中，性能最突出的一个。 设计合成了配体PT、PC、PF，利用TP和Bath做中性配体与镱离子形成配合物YbPT3Bath、YbPT3TP、YbPC3Bath，它们都显示977纳米的近红外发射。经过分析发现，配体对镱离子的敏化过程是通过电子转移的机制来完成的。通过几种镱配合物发光强度对比发现YbPT3Bath、YbPC3Bath的发射最强。首先将YbPT3Bath用于电致发光器件中，发现其具有较好的电子传输特性，而且YbPM3TP2具有较好的空穴传输特性。因此，我们将这两种配合物结合制备了双发光层电致发光器件，得到的器件比单发光层器件的性能提升了若干倍。我们认为，双发光层器件结构改善了载流子的传输和最终的复合，使得激子在发光层内形成，提高激子激发发光层材料的效率。最后，利用这种双发光层器件结构得到了辐照度比较理想的镱配合物近红外器件。 对ErPM3TP2、NdPM3TP2配合物的发光性能做了系统研究。首先，分析了它们的晶体结构，得到了具体的晶体参数和结构组成。二者在紫外区的吸收光谱都显示为配体的吸收，在紫外区之后出现了稀土离子的特征吸收峰，由此我们利用Judd-Ofelt理论分析计算了Er3+、Nd3+离子在这个配位环境中的振子强度参数，最后得到Er3+、Nd3+离子从激发态能级到下能级的电偶极跃迁辐射几率以及相应的自然寿命值。利用这两种配合物做为发光层材料制备了系列近红外电致发光器件，得到理想的辐照度强度，证明它们在制备近红外器件方面具有潜在应用价值。

掺钕钙铝磷酸盐玻璃的光谱参数

掺钕钙铝磷酸盐玻璃的光谱参数于亚勤，张思远，王庆元，盛桂云（中国科学院长春应用化学研究所长春１３００２２）（长春冶金专科学校长春）关键词掺钕钙铝磷酸盐玻璃，光谱参数，Ｊｕｄｄ－Ｏｆｅｌｔ理论１９６０年第一台红宝石激光器问世后，１９６１年便出现了掺钕钡...

EFFECT OF THE CONCENTRATION OF THE ER3+ ION ON THE SPECTRAL INTENSITY PARAMETERS OF ER-YAG CRYSTALS

The absorption spectra of Er:YAG (YAG, yttrium-aluminium-garnet) crystals containing different concentrations of the trivalent erbium ion were measured and the spectral intensity parameters were calculated from these experimental spectra using the Judd-Ofelt model. The results indicate that the phenomenological intensity parameters, OMEGA(lambda) (lambda = 2, 4 and 6), vary as a function of the concentration of the Er3+ ion in the Er:YAG crystal, but no variation in the fluorescence-branching ratios as a function of the concentration of the Er3+ ion is found. An empirical formula is proposed to describe the relationship between the spectral intensity parameters and the Er3+ ion concentration in the Er:YAG crystal. The spectral intensity parameters exhibit a maximum in Er:YAG crystals containing about 1-1.5 at.% Er3+ ion. The effect of the Er3+ ion concentration on the spectral intensity parameters may be attributed to the inhomogeneous lattice distortion in the cell of the Er:YAG crystal caused by the dopant erbium ions.

Ho~(3+)离子及HoP_5O_(14)晶体的光谱性质

根据HoP_5O_(14)的吸收光谱和荧光光谱,用Judd-Ofelt理论计算了Ho~(3+)的强度参数.并计算了激发能级的辐射跃迁速率、辐射寿命、荧光分支比和积分发射截面等光谱参数.

Dislocation theory of the fracture criterion for anisotropic solids

A dislocation theory of fracture criterion for the mixed dislocation emission and cleavage process in an anisotropic solid is developed in this paper. The complicated cases involving mixed-mode loading are considered here. The explicit formula for dislocations interaction with a semi-infinite crack is obtained. The governing equation for the critical condition of crack cleavage in an anisotropic solid after a number dislocation emissions is established. The effects of elastic anisotropy, crack geometry and load phase angle on the critical energy release rate and the total number of the emitted dislocations at the onset of cleavage are analysed in detail. The analyses revealed that the critical energy release rates can increase to one or two magnitudes larger than the surface energy because of the dislocation emission. It is also found elastic anisotropy and crystal orientation have significant effects on the critical energy release rates. The anisotropic values can be several times the isotropic value in one crack orientation. The values may be as much as 40% less than the isotropic value in another crack orientation and another anisotropy parameter. Then the theory is applied to a fee single crystal. An edge dislocation can emit from the crack tip along the most highly shear stressed slip plane. Crack cleavage can occur along the most highly stressed slip plane after a number of dislocation emissions. Calculation is carried out step by step. Each step we should judge by which slip system is the most highly shear stressed slip system and which slip system has the largest energy release rate. The calculation clearly shows that the crack orientation and the load phase angle have significant effects on the crystal brittle-ductile behaviours.

Application of Similarity Theory to the Characterization of Non-Transferred Laminar Plasma Jet Generation

Laminar-flow non-transferred DC plasma jets were generated by a torch with an inter-electrode insert by which the arc column was limited to a length of about 20 mm. Current–voltage characteristics, thermal efficiency and jet length, a parameter which changes greatly with the generating parameters in contrast with the almost unchangeable jet length of the turbulent plasma, were investigated systematically, by using the similarity theory combined with the corresponding experimental examination. Formulae in non-dimensional forms were derived for predicting the characteristics of the laminar plasma jet generation, within the parameter ranges where no transfer to turbulent flow occurs. Mean arc temperature in the torch channel and mean jet-flow temperature at the torch exit were obtained, and the results indicate that the thermal conductivity feature of the working gas seems to be an important factor affecting thermal efficiency of laminar plasma generation.

Strain gradient theory with couple stress for crystalline solids

A new phenomenological strain gradient theory for crystalline solid is proposed. It fits within the framework of general couple stress theory and involves a single material length scale Ics. In the present theory three rotational degrees of freedom omega (i) are introduced, which denote part of the material angular displacement theta (i) and are induced accompanying the plastic deformation. omega (i) has no direct dependence upon u(i) while theta = (1 /2) curl u. The strain energy density omega is assumed to consist of two parts: one is a function of the strain tensor epsilon (ij) and the curvature tensor chi (ij), where chi (ij) = omega (i,j); the other is a function of the relative rotation tensor alpha (ij). alpha (ij) = e(ijk) (omega (k) - theta (k)) plays the role of elastic rotation reason The anti-symmetric part of Cauchy stress tau (ij) is only the function of alpha (ij) and alpha (ij) has no effect on the symmetric part of Cauchy stress sigma (ij) and the couple stress m(ij). A minimum potential principle is developed for the strain gradient deformation theory. In the limit of vanishing l(cs), it reduces to the conventional counterparts: J(2) deformation theory. Equilibrium equations, constitutive relations and boundary conditions are given in detail. For simplicity, the elastic relation between the anti-symmetric part of Cauchy stress tau (ij), and alpha (ij) is established and only one elastic constant exists between the two tensors. Combining the same hardening law as that used in previously by other groups, the present theory is used to investigate two typical examples, i.e., thin metallic wire torsion and ultra-thin metallic beam bend, the analytical results agree well with the experiment results. While considering the, stretching gradient, a new hardening law is presented and used to analyze the two typical problems. The flow theory version of the present theory is also given.

The Flow Theory of Mechanism-Based Strain Gradient Plasticity

The flow theory of mechanism-based strain gradient (MSG) plasticity is established in this paper following the same multiscale, hierarchical framework for the deformation theory of MSG plasticity in order to connect with the Taylor model in dislocation mechanics. We have used the flow theory of MSG plasticity to study micro-indentation hardness experiments. The difference between deformation and flow theories is vanishingly small, and both agree well with experimental hardness data. We have also used the flow theory of MSG plasticity to investigate stress fields around a stationary mode-I crack tip as well as around a steady state, quasi-statically growing crack tip. At a distance to crack tip much larger than dislocation spacings such that continuum plasticity still applies, the stress level around a stationary crack tip in MSG plasticity is significantly higher than that in classical plasticity. The same conclusion is also established for a steady state, quasi-statically growing crack tip, though only the flow theory can be used because of unloading during crack propagation. This significant stress increase due to strain gradient effect provides a means to explain the experimentally observed cleavage fracture in ductile materials [J. Mater. Res. 9 (1994) 1734, Scripta Metall. Mater. 31 (1994) 1037; Interface Sci. 3(1996) 169].

The Complete Proof of the Virial Theorem in the Refined TFD Theory for all Electrons of an Atom in a Solid

The complete proof of the virial theorem in refined Thomas-Fermi-Dirac theory for all electrons of an atom in a solid is given.

A micromechanical damage theory for brittle materials with small cracks

For brittle solids containing numerous small cracks, a micromechanical damage theory is presented which accounts for the interactions between different small cracks and the effect of the boundary of a finite solid, and includes growth of the pre-existing small cracks. The analysis is based on a superposition scheme and series expansions of the complex potentials. The small crack evolution process is simulated through the use of fracture mechanics incorporating appropriate failure criteria. The stress-strain relations are obtained from the micromechanics analysis. Typical examples are given to illustrate the potential capability of the proposed theory. These results show that the present method provides a direct and efficient approach to deal with brittle finite solids containing multiple small cracks. The stress-strain relation curves are evaluated for a rectangular plate containing small cracks.

Influences of strain rate and temperature variation on material intrinsic length of plasticity strain gradient theory

Cowper-Symonds and Johnson-Cook dynamic constitutive relations are used to study the influence of both strain rate effect and temperature variation on the material intrinsic length scale in strain gradient plasticity. The material intrinsic length scale decreases with increasing strain rates, and this length scale increases with temperature.