Effect of grinding on the low temperature photoluminescence of certain inorganic crystals

The broadening as well as shift in the photoluminescence spectra of K₂[Pt(CN)₄] · 3 H₂O, Ba[Pt(CN)₄] · 4 H₂O, CdS:Te and Ru(C₁₅H₁₁N₃)₂I₂ · H₂O crystals take place with their grinding. The original vibronic peaks at 632 and 628 nm of CdS:Te and Ru(C₁₅H₁₁N₃)₂I₂ · H₂O crystals, respectively, disappear with the grinding. A new vibronic peak at 650 nm appears with grinding of Ru(C₁₅H₁₁N₃)₂I₂ · H₂O crystals. It is concluded that the change in the photoluminescence spectra is attributed to the creation of dislocations during the process of grinding.     

Nd:NaY(WO4)2激光晶体光谱性能研究

Nd:NaY(WO4)2 是一种性能优良的激光晶体.本文采用提拉法生长了Nd:NaY(WO4)2晶体,测试了该晶体的吸收光谱和光荧光光谱.结果表明,该晶体在804nm、752nm、586nm附近有较强、较宽的吸收峰,适合于LD泵浦.从光荧光光谱得到发射波长分别为1064nm和1350nm,并计算了晶体的吸收截面和发射截面.     

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.     

Growth and luminescence of CsBr:Cu crystals

Special features of the incorporation of a copper impurity into CsBr crystals are studied for different types of impurities (metallic copper, CuO, and CuBr₂) and crystal-growth techniques (the Bridgman method or the method of isothermal evaporation from solution). The optical characteristics of these crystals (absorption, photoluminescence, and photostimulated-luminescence spectra) are investigated. The copper impurity is shown to enter CsBr:Cu_met crystals in the monovalent state Cu⁺ and CsBr:CuO and CsBr:CuBr₂ crystals in the divalent state Cu²⁺. It is found that the CsBr crystals doped with Cu⁺ and Cu²⁺ ions exhibit intense photostimulated luminescence and can be used as storage phosphors for visualization of X-ray images.     

高掺镁铌酸锂晶体OH-吸收光谱的低温研究

本文测量了纯铌酸锂和高掺镁铌酸锂晶体的低温红外光谱,观察了OH-吸收峰的温度依赖特性.研究发现纯铌酸锂的OH-振动吸收峰基本不随温度而变化,而高掺镁铌酸锂晶体的OH-振动吸收峰的主峰峰位随温度的降低向高波数方向移动.通过分析两种晶体中不同的缺陷模型以及H+在晶格中的占位,我们提出高掺镁铌酸锂晶体中的H+紧邻高电性杂质缺陷(MgNb)3-分布,直接参与缺陷集团,完全不同于纯铌酸锂晶体中H+的分布情形,这造成了高掺镁铌酸锂晶体中OH-振动吸收峰随温度的变化.而集团内部缺陷之间相互作用随温度降低而增强的趋势是OH-振动吸收峰右移的主要原因.     

钨酸铅闪烁晶体的双掺杂性能研究

本文采用坩埚下降法生长出了PbWO4:(F,Er)晶体和PbWO4:(F,Nd)晶体,并且对此两种晶体透过性能和闪烁发光性能进行了测试分析.透过光谱结果显示,PbWO4:(F,Er)晶体和PbWO4∶(F,Nd)晶体在350 nm至700nm范围内的透过率比纯的钨酸铅均有较大的提高.紫外激发发射光谱测试结果表明,通过双掺杂可以提高钨酸铅晶体闪烁发光的强度,并且PbWO4:(F,Er)双掺杂晶体在波长为527 nm处和546 nm处均形成了较强的发光峰.通过对掺杂晶体进行XRD分析可知,阴阳离子的同时掺入并未引起钨酸铅晶体结构的明显改变.     

Growth of large doped Bi12SiO20 crystals

The conditions for growing Cr-, Mn-, Fe-, Co-, Ni-, and Cr + Al-doped BSO crystals from a stoichiometric melt by the Czochralski method have been the subject of research. A decrease of the absorption coefficient along the growth axis was observed in undoped crystals of 50 mm diameter and 150 mm long, which is indicative of melt stoichiometry change in the course of the growth run. The transmission and reflection spectra of different crystals were measured and the absorption coefficients was determined in the range 0.38–0.70 μm. When Fe dopant concentration exceeds a limit value, the absorption spectrum is blue-shifted relative to the undoped case and the absorption coefficient decreases. Co, Cr, Mn, and Cr + Al dopants produce a red shift and increase the absorption coefficient. Combined Cr + Al doping shift the absorption spectrum to the blue region as compared to Cr-only doping with the same Cr concentration.     

Preparation and Photoluminescent Properties of Hydrogen-bonded Discotic Liquid Crystals

Photoluminescent discotic liquid crystals (DLCs) have been prepared through intermolecular hydrogen bonding between core and peripheral units. 1,3,5-Trihydroxybenzene was employed as core molecule and peripheral stilbazole derivatives containing linearly conjugated moieties were complexed to form hydrogen-bonded DLCs. Their structures, mesophases, and optical properties were investigated. The complexation of core and peripherals made some discotic complexes form photoluminescent DLCs. The prepared luminescent DLCs exhibited columnar mesophases with strong blue or sea green photoluminescence. These findings may contribute to the development of luminescent supramolecular liquid crystals for emitting materials in light emitting devices.     

InSeI单晶的制备及其结构与性能研究

利用化学气相传输法(CVT)制备了InSeI单晶。该晶体为黄色的针状物,晶体较脆。在室温下进行X射线衍射分析发现,其属于四方晶系,晶胞参数为a=b=1.864 3(5) nm,c=1.012 0(3) nm,V=3.517 2 nm³,空间群为I4₁/a。紫外可见光吸收光谱、光致发光光谱等结果显示该晶体的禁带宽度是2.48 eV,在一定波段光的激发下,InSeI单晶在600 nm左右有较宽的发射峰,表明该晶体的发光方式为缺陷态发光。介电温谱表明InSeI单晶在440 K时其四方相的结构发生了相变。     

Deformation-induced After-Glow in [(C2H5)4N]2MnBr4 Crystals

The mechanoluminescence appears in [(C₂H₅)₄N]₂MnBr₄ crystals even after their mechanical deformation. During the excitation of mechanoluminescence by the impact of a piston on to the crystals, the peak corresponding to the mechanoluminescence intensity versus time curve and the total intensity of mechanoluminescence increase with the impact velocity and decrease with the temperature of the crystals. It seems that the electric field produced during the inpact of the piston on to the crystal may perturb the ground and excited states of the molecules comprising the crystals. Thus the mechanoluminescence may follow the rate of compression during the deformation of the crystal and it may decay with the decay rate of phosphorescence after the compression. The mechanoluminescence and high pressure photoluminescence spectra are also reported.     

Effect of reversible photostructural change on the polarization of photoluminescence in chalcogenide glasses

Optical absorption edge in annealed As₂S₃ films shifts to lower energy after band-gap illumination. In these photodarkened films, polarization memory of photoluminescence was found to increase. In the case of illumination with linearly polarized light, anisotropy is induced in the absorption edge. The polarization memory was larger for larger shift of absorption edge. In contrast with this trend, the memory was smaller in As-rich films, the absorption edge of which was located at lower energy. It is considered that the optical anisotropy of the luminescence centers increases accompanying the reversible photostructural change.     

Growth and characterization of near-band-edge transitions in β-In2S3 single crystals

Single crystals of β-In₂S₃ were grown by chemical vapor transport method using ICl₃ as a transport agent. The below and above band-edge transitions in β-In₂S₃ have been characterized using optical absorption and photoluminescence (PL) measurements in the temperature range 20–300 K. Thermoreflectance (TR) and photoconductivity (PC) measurements were carried out to verify the band-edge nature of the diindium trisulfide tetragonal crystals. Experimental analyses of the transmittance, PL, PC, and TR spectra of β-In₂S₃ confirmed that the chalcogenide compound is a direct semiconductor with a band gap of about 1.935 eV at 300 K. β-In₂S₃ is familiar with its defect nature. For the β-In₂S₃ crystals, two defect emissions and two above band-edge luminescences were simultaneously detected in the PL spectra at low temperatures. The energy variations of the defect emissions showed temperature-insensitive behavior with respect to the temperature change from 20 to 300 K. Temperature dependences of transition energies of the near-band-edge (NBE) transitions below and above band gap are analyzed. The origins for the NBE transitions in the β-In₂S₃ defect crystals are discussed.     

Optical properties of ZnNb2O6 single crystals prepared via the optical floating zone technology

By using an optical floating zone technology, orthorhombic columbit ZnNb₂O₆ single crystals are fabricated successfully. The as‐prepared sample are blue and transparent rods of Φ 4 to 6 mm ×L 48 mm and the biggest domain of Φ 4 mm× L 25 mm. After annealing, the sample fades to colorless. X‐ray diffractions indicates that the as‐perpared samples are ZnNb₂O₆ with orthorhombic columbite structure and grows along the a‐axis. The micropolariscopy in cross transmission arrangements analyzing give that the crystals are of low‐angle crystal boundary‐free and bubble‐free. Besides, the crystals have also been tested by Raman spectra, optical absorption and photoluminescence spectra before and after being annealed. The luminescence pattern has an emission peak located at 450 nm blue‐region.     

阴离子掺杂钨酸铅晶体的生长与发光性能研究

本文报道了阴离子F~-, Cl~-, I~- 和S~(2-)掺杂的PbWO_4晶体的生长与发光性能.通过对掺杂PbWO_4晶体的X射线粉末衍射、紫外可见区的透过光谱、光致激发、光产额和发光衰减特性进行了测试表征,结果表明:F~-掺杂能使PbWO_4晶体在短波方向的透过率明显提高,显著提高PbWO_4晶体的发光强度,但增加的发光强度主要来自于慢发光的贡献.而随着掺杂阴离子半径和电荷数的增加,PbWO_4晶体的发光强度逐渐降低,并且PbWO_4晶体吸收截止边逐渐向长波方向移动.     

Zur Ätzstruktur von Silizium-Einkristallen,besonders in versetzungsfreien Bereichen

In silicon crystals a real etching structure can be visualized by means of a suitable method of etching also in the domains free from dislocations. The shapes of etch pits are chiefly dependent on the orientation of the grinding faces. It may be that the etching structure comes from growth domains, bordered by faces {111}, at which impurities are segregated or adsorbed.     

固溶体半导体碲硫锌多晶薄膜的制备及发光特性研究

ZnS1-x Tex薄膜具有高效的发光特性.样品可观测到强烈的光致发光,随着Te含量x的不同,发射光的颜色从深蓝到黄变化,使其成为制作短波长光波段光电子器件和紫外探测器的理想材料.本文介绍了ZnS1-x Tex多晶薄膜真空蒸发制备的情况,并用X射线衍射仪对淀积在玻璃、石英玻璃和单晶硅衬底上的多晶薄膜进行结构分析,用紫外-可见分光光度计、荧光光谱分析仪对样品的光吸收和发光性质进行研究.分析表明,该薄膜的结构符合闪锌矿的特征.紫外-可见吸收光谱显示该样品在紫外光区有一个强烈的吸收峰,可见光区的吸收很微弱.光致发光光谱表明,样品在可见光区有一个以470nm为中心的发射峰,发射光肉眼可见.该多晶薄膜基本保持了单晶薄膜的紫外吸收、光致发光等良好特性.     

Influence of γ-Irradiation on Some Properties of NaCl: Eu++ Crystals (I). Optical and Dielectrical Characteristics of the Dopant Ions

The present work opens a series of papers describing a variety of properties of the same material, and deals with the effect of Eu⁺⁺ ions, and y–irradiation on the optical and dielectrical characteristics of NaCl crystals. For nonirradiated crystals four types of Eu⁺⁺-related absorption spectra have been identified and correlated with I.V. dipoles and three types of precipitates stable in the well aged crystals. For the solution—treated samples the effect of irradiation was to diminish the concentration of I.V. dipoles and to change the absorption spectrum in a remarkable way. These changes are explained in terms of the formation of some dopant—related clusters different of those obtainable thermally. No spectroscopic evidences have been obtained for the radiation—induced changes of the valence state of the dopant irrespective of its dispersion degree.     

Crystalloluminescence and Mechanoluminescence Spectra of Ba(ClO3)2 · H2O and 2 K2SO4 · Na2SO4 Crystals

Crystalloluminescence and mechanoluminescence of Ba(ClO₃)₂ · H₂O and 2 K₂SO₄ · Na₂SO₄ crystals are investigated. The crystalloluminescence spectra are almost similar to the photoluminescence spectra; however, they differ completely from the mechanoluminescence spectra. The crystalloluminescence excitations may take place due to the various processes: (i) the recombination of ions, (ii) from amorphous to crystalline transition, (iii) from the phase change during the crystallization, and (iv) from the dielectric breakdown by the electric field produced due to the creation of microfracture during the crystal growth. It is concluded that the crystalloluminescence excitation in Ba(ClO₃)₂ · H₂O and 2K₂SO₄ · Na₂SO₄ crystals may be chemical in origin.     

Advanced optical characterization of active micro-strips induced on Lithium Fluoride crystals by a monochromatic soft X-ray beam

Broad-band visible-emitting micro-strips were induced in Lithium Fluoride crystals by direct writing with a monochromatic soft X-ray beam. They were successfully characterized via fluorescence imaging, photoluminescence and optical transmittance. The irradiation gave rise to stable primary and aggregate color centers within a thin surface layer of the crystals. Their volume concentrations were evaluated together with the induced modification of the complex refractive index in the irradiated volume.     

Optical absorption spectra of LiNbO3, Fe:LiNbO3, and Zn:Fe:LiNbO3 single crystals grown by Bridgman method

The optical absorption spectra of LiNbO₃ (LN), Fe:LiNbO₃ (Fe:LN), and Zn:Fe:LiNbO₃ (Zn:Fe:LN) single crystals grown by Bridgman method were measured and compared. The absorption characteristics of the samples and the effects of growth process conditions on the absorption spectra were investigated. The Fe, Zn and Li concentrations in the crystals were analyzed by inductively coupled plasma (ICP) spectrometry. The results indicated that the overall Fe ion and Fe²⁺ concentration in Fe:LN and Zn:Fe:LN crystals increased along the growing direction. The incorporation of ZnO in Fe:LN crystal induced increase of Fe²⁺ in the crystal. Among Fe‐doped and Zn:Fe‐codoped LN single crystals, 3 mol% ZnO doped Fe:LN had a biggest change of Fe²⁺ ion concentration from bottom to top part of crystal. The effects of technical conditions (atmosphere and thermal history) on Fe²⁺ ion concentration were discussed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)