Influence of γ-Irradiation on Some Properties of NaCl:Eu++ Crystals (II). Colourability

The room temperature colouration process of NaCl:Eu++ crystals strongly depends on both the dopant concentration, represented by the absorption coefficient α(eg), and the dopant dispersion state as well. It has been found that within the UV spectral range either some V-type absorption bands appear or only the background absorption increases. For heavily irradiated crystals the clustering of halogen-interstitial results in the formation of dislocation loops. In dependence of the dopant concentration the colourability of as received crystals is either larger (α(eg) ⪅, or smaller (α(eg) ⪆ ⁻¹) of that characteristic of the solution treated ones. The difference in the effectiveness of the halogen-interstitials trapping-process has been explained in terms of the various structure and/or composition of the europium-related aggregates and/or precipitates.     

Influence of γ-Irradiation on Some Properties of NaCl:Eu++ Crystals (III). Strengthening Effects

Mechanical strength of europium-doped NaCl crystals was studied as function of dopant concentration and dopant dispersion state as well. It has been found that the yield stress of the solution-treated samples is determined by the Snoek-type reorientation of dipoles in the stress field of moving dislocations. For as received samples the precipitation strengthening mechanisms are postulated. Irrespective of the dispersion state of europium, the strength of all NaCl:Eu⁺⁺ crystals can be remarkably changed by the room temperature irradiation. Although the yield stress increments can be explained in frames of the precipitation-strengthening mechanisms, the radiation-induced processes depend on the primary disprsion e state of the dopant. As far as the solution-treated samples the clustering of I.V. dipoles is of main importance, it is necessary to assume that dispersion of precipitates is required to achieve the strength of irradiated as received samples.     

Optical and Luminescence Properties of YAlO3 ‐Tm Crystals

The results on optical absorption, photoluminescence and thermoluminescence of YAP‐Tm crystals of 1 at.% and 4 at.% of Tm are presented as well as influence of UV‐, γ‐radiation and thermal treatments on optical and luminescence properties of the crystals. The blue‐green luminescence of defect centers was observed in YAP‐Tm crystals at Ar⁺‐laser excitation. The possibility of energy transfer processes between defect centers and Tm³⁺ ions was shown.     

Effect of plastic deformation of the thermoluminescence of γ-irradiated NaCl and KCl Crystals

The overall thermoluminescence (TL) intensity of γ-irradiated NaCl crystals initially increases and then decreases with the number of newly-created dislocations. However, the overall TL intensity of γ-irradiated KCl crystals increases with the increasing number of newly created dislocations. The TL spectra are recorded for different plastic deformations at different temperatures. It is found that the plastic deformation has no considerable effect on the TL spectra of γ-irradiated NaCl and KCl crystals. Trap destruction model and trap competition model are discussed for the decrease in the TL intensity with deformation of the crystals. The physical ideas behind the increases in the relative intensity of glow peaks and the appearance of new glow peaks are explored.     

Growth and Optical Properties of NaY(WO4)2:Eu Crystals

NaY_0.99Eu_0.01(WO₄)₂ crystals were grown along <101> and <001> directions. Single crystals with high quality can be obtained when they were grown along <101> direction from a melt with a small deviation from stoichiometric composition. Eu ions exist in two valences in the as‐grown crystals, in one valence after annealing only. The fluorescence spectrum shows the Stark splitting of energy levels of Eu ions is in accordance with the site symmetry of S₄.     

Optical Properties of Bi2Se3‐xAsx Single Crystals

Bi₂Se_3‐xAs_x single crystals with the As content of c_As = 0 to 2.0x10¹⁹ atoms/cm³ prepared from the elements of 5N purity by means of a modified Bridgman method were characterized by measurements of infrared reflectance and transmittance. Values of the plasma resonance frequency omega_p, optical relaxation time tau, and high‐frequency permittivity were determined by fitting the Drude‐Zener formulas to the reflectance spectra. It was found that the substitution of As atoms for Se atoms in the Bi₂Se₃ crystal lattice leads to a decrease in the omega_p values. This effect is accounted for by a model of point defects in the crystal lattice of Bi₂Se_3‐xAs_x. The dependences of the absorption coefficient K on the energy of incident photons were determined from the transmittance spectra. The optical width of the energy gap is found to decrease with increasing As content. The values of the exponent b from the relation of K ∼ lamda^b for the long‐wavelength absorption edge range within the interval 2.0 to 2.3, i.e. the dominant scattering mechanism of free current carriers in Bi₂Se_3‐xAs_x crystals is the scattering by acoustic phonons.     

Effect of Fluoride and Sodium Ions on Structural and Thermal Properties of γ-Al2O3

The structural properties of alumina as well as its fluoride and sodium modifications were characterized by X-ray diffraction, infrared spectroscopy and differential thermal analysis. We have shown, that fluoride ions interact with hydroxyls type Ia of γ-Al₂O₃ forming Al–F species, which then react at 400 °C forming β-Al₂O₃. Morever, F/Al₂O₃ sample heated up to 400 °C contain two acidic hydroxyls type IIa and III, which are also represented on a differential thermal curve as endoeffect with minima at 470 and 500 °C. For Na/Al₂O₃ sample the same types of hydroxyls interact with Na⁺ ions leading to substitution of their protons. After heating at 400 °C this sample contains also hydroxyls type IIa and III, which are represented by two endothermal effects with minima at 450 and 520 °C. Differential thermal analysis shown to be a powerful and simple technique to characterize surface hydroxyl types of Na and F samples supported on γ-alumina.     

Ce3+单掺和Ce3+,Eu3+共掺杂CaF2晶体生长与光学特性研究

采用Bridgman方法在氩气氛保护的单晶炉内生长出了Ce3+掺杂的以及Ce3+和Eu3+共掺的CaF2晶体,利用Ce2O3和E2O3分别与氢氟酸反应合成了CeF3和EuF3掺杂试剂,对掺杂晶体生长的起始原料-特定组成的CaF2、CeF3、EuF3混合物进行了高温氟化处理,确定了掺杂晶体的物相,讨论了掺杂浓度对晶体紫外波段透过率的影响.此外,还初步分析了Ce3+和Eu3+共掺的CaF2晶体作为紫外滤光材料的可行性.     

Growth and Optical Properties of LiNbO3: MgO Single Crystals

The technological procedure of the manufacturing of the LiNbO₃^˙ single crystals doped with 5 mol.% MgO is described in this paper. The results of the investigation of the crystal optical properties, ESR spectra and optical homogeneity are presented. The refractive index dispersion in 300–700 nm region and their temperature dependencies in 20–500 °C range are measured. The dispersion curve is approximated by the two oscillator Sellmeier formula. The data on the LiNbO₃: MgO crystal optical resistance are presented.     

Influence of the Orientational Order on the Optical Properties of Cholesteric Liquid Crystals

An orientational order parameter for cholesteric liquid crystals is defined in analogy to nematic mesophases. The influence of this parameter on the selective reflexion and the optical rotatory dispersion is described. Its relative change with temperature is evaluated from ORD measurements for an induced cholesteric soIution and is found to be similar to that known for nematic liquid crystals.     

The Morphology of Some Hydrothermally Synthesized Li-Minerals: A-Zeolite, α-Eucryptite, β-Spodumene and β-Eucryptite

The hydrothermal treatment of glass with the composition 2 LiF, Al₂O₃, 3 SiO₂ at 1 kbar in the range of 150 °C to 850 °C gave rise to the formation of A-zeolite with orthorhombic unit cell with å = 10.31 Å/b̊ = 8.18 Å/c̊ = 5.0 Å (space group Pna2₁), α-eucryptite, trigonal, å = 13.4 Å/bº = 13.4/Å/cº = 9.0 Å (space group R 3 ), β-spodumene, pseudocubic/tetragonal, å = 7.53 Å/b̊ = 7.53 Å/c̊ = 9.15 Å (space group P4₃2₁2), β-eucryptite, monoclinic, å = 7.75 Å/b̊ = 5.2 Å/c̊ = 11.16 Å (space group P6₂22). The morphology and development of the mineral phases depend on the temperature of formation.     

Chemistry of organic eutectics (IV). α-Naphthol-β-naphthol eutectic system

The detailed methods of investigating the phase diagram, supercooling, crystallization velocity, microstructure, and diffusion coefficient for the α-naphthol-β-naphthol eutectic system have been discussed. The results are discussed in the light of existing theories describing morphology, nucleation, crystallization kinetics, and diffusion phenomena.     

煅烧制度对ZnTiO3∶2;Eu3+荧光粉的结构和发光性能的影响

采用溶胶-凝胶法制备了ZnTiO3:2; Eu3+荧光粉,研究了不同煅烧制度下ZnTiO3:2; Eu3+荧光粉的结构和发光性能.结果表明:在煅烧温度为600 ～ 900℃时,可以得到六方相ZnTiO3,1000℃分解为立方相,随着煅烧温度的升高,激发光谱中电荷迁移带的峰值逐渐发生红移;发射光谱中样品发射峰的位置基本保持不变,样品中Eu3+的红光发射强度(5D0→7R)在煅烧温度为700℃时达到最大.在保温时间为1～6 h的范围内,发光强度随着保温时间的增长先增强后减弱,在700℃、保温4h的煅烧处理下ZnTiO3:2; Eu3+荧光粉发光性能最好,且其色度坐标比目前商用红色荧光粉更接近国际照明协会的指定坐标.     

不同膜厚对SiO2光子晶体形貌及光学性能的影响

利用改良的St6ber法制成了粒径均一的SiO2胶体颗粒,胶体微球颗粒平均粒径为200 nm.保持SiO2悬浮液体积分数相同,对双基片自组装垂直沉积进行改造,改变夹层厚度,沉积得到厚度不同的SiO2光子晶体薄膜.利用扫描电子显微镜观察了膜厚不同的SiO2光子晶体薄膜样品的表面以及断面微观形貌,测试了样品的光反射性能,此外还讨论了光子晶体薄膜厚度对样品表面的形貌以及样品光反射性能带来的影响.     

Chemistry of organic eutectics (III). α-Naphthol-naphthalene system

Relative supercooling, linear velocity of crystallization and microstructure for the α-naphthol-naphthalene eutectic system have been investigated in order to understand the mechanism of eutectic solidification. Heat of fusion measurements indicate the possibility of molecular association in the liquid melt. The effective distribution coefficient, direction of solute transference, and separation efficiency have also been determined using zone melting technique.     

Crystal and Molecular Structures of Modified Progestagens (I). 17α-Cyanomethyl-17β-hydroxy-estr-4-en-3-one,C20H27NO2

17α-Cyanomethyl-17β-hydroxy-estr-4-en-3-one is the first member in a series of progestagens investigated systematically by X-ray structure analyses. It crystallizes in the orthorhombic space group P 2₁2₁2₁ with cell parameters α = 8.887(6), b = 11.814(7), and c = 16.263(2) A. The structure was solved by MULTAN-82 and refined to R = 0.045 for 1453 observed reflections. The steroid ring A has an 1β-sofa conformation, the rings B and C adopt chair forms, ring D is intermediate between 13β,14α-half chair and 13β-envelope. All rings are trans-fused. In the present structure, O H… N hydrogen bonds link the molecules into chains parallel to α.     

高能电子辐照和退火对磷锗锌晶体红外光学性质的影响

对采用改进的垂直布里奇曼法生长出的磷锗锌(ZnGeP2)单晶体样品,在300 K,10 MeV高能电子束下进行辐照实验,测试辐照前后其红外透过率.同时,对样品进行同成分粉末包裹退火处理,对比两种工艺对磷锗锌晶体红外透过率的影响.实验结果表明,退火和高能电子辐照都能对磷锗锌晶体的红外光学性质产生影响,提高其红外透过率.在本文的实验条件下,退火工艺对磷锗锌晶体红外透过率的提高更为明显.     

BiOIO3和Bi2(IO4)(IO3)3晶体电子结构和光学性质研究

采用基于密度泛函理论(DFT)的第一性原理方法对BiOIO3和Bi2(IO4)(IO3)3两种碘酸铋非线性光学晶体的电子结构及光学性质-折射率及双折射率进行了计算研究.结果表明:采用GGA-PBE计算两者的禁带宽度分别为2.385 eV和2.930 eV;选用optados计算BiOIO3和Bi2(IO4)(IO3)3化合物的折射率和双折射率,计算结果表明二者皆具有较大的双折射率.     

Epitaxial Overgrowth of LiKSO4 on β–K2SO4 Single Crystals

Nucleation of LiKSO₄ (LKS) crystals from non-equimolar solutions may occur epitaxially on the surface of previously nucleated β-K₂SO₄ (KS) crystals. Both compounds evince a profound hexagonal substructure, and have common topological features and similar coordination schemes. Moreover, they may be related by quantitative similarities between their translation parameters and by correspondence between their bond chains along the directions of epitaxy. The planes of epitaxy are (001)_KS, and (0001)_LKS' and on these planes [010]_KS is always parallel to [010]_LKS' with a misfit of 12.19%. Another pair of directions, [11 0]_KS and [100]_LKS' showing a small angular misfit (0.18°), exhibit an even lower linear misfit (3.09%).     

Influence of preliminary thermomagnetic treatment on the yield point of NaCl: Ni Crystals

The influence of preliminary annealing (3 h, 1000 K), subsequent quenching in liquid nitrogen, and short magnetization in a constant magnetic field (0.5 h, 0.48 T) prior to deformation on the yield point of NaCl: Ni crystals is discovered. The effect depends on the time of sample storage between quenching and magnetization and is maximal 40 h after quenching.