WorldWideScience

Sample records for vi doped crystals

  1. Ultratough single crystal boron-doped diamond

    Science.gov (United States)

    Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

    2015-05-05

    The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

  2. Nanoparticles Doped, Photorefractive Liquid Crystals

    National Research Council Canada - National Science Library

    Kaczmarek, Malgosia

    2005-01-01

    ...: The main objectives of this exploratory, short project will concern the study of the quality of liquid crystal cells with diluted suspensions of ferroelectric nanoparticles and their photorefractive properties...

  3. A first-principles study of group IV and VI atoms doped blue phosphorene

    Science.gov (United States)

    Bai, Ruimin; Chen, Zheng; Gou, Manman; Zhang, Yixin

    2018-02-01

    Using first-principles calculations, we have systematically investigated the structural, electronic and magnetic properties of blue phosphorene doped by group IV and VI atoms, including C, Si, Ge, Sn, O, S, Se and Te. All the doped systems are energetically stable. Only C, Si, Ge and O-substituted systems show the characteristics of spin polarization and the magnetic moments are all 1.0 μB. Moreover, we found that C, Si, Ge and O doped systems are indirect bandgap semiconductors, while Sn, S, Se and Te doped systems present metallic property. These results show that blue phosphorene can be used prospectively in optoelectronic and spintronic devices.

  4. Study on the Low Temperature Photoluminescence Spectra of II-VI Group Telluride Bulk Crystals.

    Science.gov (United States)

    Xu, Ya-dong; Liu, Hang; He, Yi-hui; Zhou, Yan; Jie, Wan-qi

    2015-03-01

    The dominant point defects in II-VI group telluride bulk crystals grown from melt usually varied due to different growth conditions and cooling history, in turn affect the electrical and optical behaviors of corresponding single crystals and devices. Low temperature photoluminescence (PL) spectra acts as a contact-less and non-destructive technique, can be used to evaluate the behaviors of point defects and impurities in the as-grown telluride bulk crystals. With the purpose of comparing the defect structures in un-doped ZnTe and CdTe crystals grown under Te-rich condition, 8. 6 K PL spectra were obtained. The conductivity type and resistivity were investigated by Hall-effect measurements at room temperature (RT). For p-type low resistivity ZnTe crystal, the intensity of. free electron to neutral acceptor (e, A(0)) transition is higher than the donor-acceptor pair (DAP) transition, which predominates in the PL spectra. However, in the contrary, DAP peak dominates the PL emissions for n-type high resistivity CdTe. This difference is mainly attributed to the distinct properties of the grown-in point defects due to different growth. velocities and cooling processes. In terms of the un-doped CdZnTe crystal grown under stoichiometry, neutral donor bound exciton (D(0), X) emission is predominated in the 9.2 K PL spectra, with the intensity of (e, A(0)) peak is higher than DAP peak, which then overlaps to each other when the temperature higher then 15 K. In the case of In-doped CdZnTe crystal grown by Te-rich situation, A-center emission is clearly observed, which introduces an energy level approximately of 0.15 eV, with the intensity proportional to the concentration of indium dopant. This defect is seemingly related to the complex of [In(Cd)+V(Cd)2-]- formed by a shallow donor In(Cd) and Cd vacancy.

  5. Transition-metal doped sulfide, selenide, and telluride laser crystal and lasers

    Science.gov (United States)

    Krupke, William F.; Page, Ralph H.; DeLoach, Laura D.; Payne, Stephen A.

    1996-01-01

    A new class of solid state laser crystals and lasers are formed of transition metal doped sulfide, selenide, and telluride host crystals which have four fold coordinated substitutional sites. The host crystals include II-VI compounds. The host crystal is doped with a transition metal laser ion, e.g., chromium, cobalt or iron. In particular, Cr.sup.2+ -doped ZnS and ZnSe generate laser action near 2.3 .mu.m. Oxide, chloride, fluoride, bromide and iodide crystals with similar structures can also be used. Important aspects of these laser materials are the tetrahedral site symmetry of the host crystal, low excited state absorption losses and high luminescence efficiency, and the d.sup.4 and d.sup.6 electronic configurations of the transition metal ions. The same materials are also useful as saturable absorbers for passive Q-switching applications. The laser materials can be used as gain media in amplifiers and oscillators; these gain media can be incorporated into waveguides and semiconductor lasers.

  6. Transition-metal doped sulfide, selenide, and telluride laser crystal and lasers

    Energy Technology Data Exchange (ETDEWEB)

    Krupke, W.F.; Page, R.H.; DeLoach, L.D.; Payne, S.A.

    1996-07-30

    A new class of solid state laser crystals and lasers are formed of transition metal doped sulfide, selenide, and telluride host crystals which have four fold coordinated substitutional sites. The host crystals include II-VI compounds. The host crystal is doped with a transition metal laser ion, e.g., chromium, cobalt or iron. In particular, Cr{sup 2+}-doped ZnS and ZnSe generate laser action near 2.3 {micro}m. Oxide, chloride, fluoride, bromide and iodide crystals with similar structures can also be used. Important aspects of these laser materials are the tetrahedral site symmetry of the host crystal, low excited state absorption losses and high luminescence efficiency, and the d{sup 4} and d{sup 6} electronic configurations of the transition metal ions. The same materials are also useful as saturable absorbers for passive Q-switching applications. The laser materials can be used as gain media in amplifiers and oscillators; these gain media can be incorporated into waveguides and semiconductor lasers. 18 figs.

  7. Systematic hardness measurements on mixed and doped crystals of ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Efforts are made to improve the hardness of rubidium halide crystals by (i) solid solution harden- ing and (ii) impurity hardening. Systematic microhardness measurements have been made on rubidium halide mixed crystals (RbBr–RbI and KI–RbI) and rubidium halide crystals doped with Sr2+ ions. The composition.

  8. Systematic hardness measurements on mixed and doped crystals of ...

    Indian Academy of Sciences (India)

    Efforts are made to improve the hardness of rubidium halide crystals by. solid solution hardening and; impurity hardening. Systematic microhardness measurements have been made on rubidium halide mixed crystals (RbBr–RbI and KI–RbI) and rubidium halide crystals doped with Sr2+ ions. The composition dependence ...

  9. Spectroscopic properties of Pr 3-doped erbium oxalate crystals

    Indian Academy of Sciences (India)

    Spectroscopic properties of praseodymium ions-doped erbium oxalate ( E r 2 ( C 2 O 4 ) 3 ⋅ n H 2 O ) crystals have been investigated. The crystals were grown by hydro silica gel method under suitable pH conditions and by single diffusion method. The well-grown crystals are bright and transparent. The dark green colour ...

  10. Spectroscopic properties of Pr -doped erbium oxalate crystals

    Indian Academy of Sciences (India)

    The crystals were grown by hydro silica gel method under suitable pH conditions and .... Chemical composition of the grown crystal (21% Pr3+-doped erbium oxalate crystals) was confirmed with the EDAX ... Spectroscopic parameters can be evaluated from both absorption and emission spectra. The absorption spectra of ...

  11. Stability of uranium(VI) doped CSH phases in high saline water

    Energy Technology Data Exchange (ETDEWEB)

    Wolter, Jan-Martin; Schmeide, Katja [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

    2017-06-01

    To evaluate the long-term stability of U(VI) doped calcium silicate hydrate (CSH) phases at high saline conditions, leaching experiments with NaCl, NaCl/Na{sub 2}SO{sub 4} and NaCl/NaHCO{sub 3} containing solutions were performed. Time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR) and X-ray powder diffraction (XRD) were applied to study the U(VI) binding onto the CSH phases and to get a deeper understanding of structural changes due to leaching. Results indicate that neither NaCl nor Na{sub 2}SO{sub 4} affect the structural stability of CSH phases and their retention potential for U(VI). However, carbonate containing solutions lead to a decomposition of CSH phases and thus, to a release of incorporated uranium.

  12. Negative Refraction in Rare-Earth Doped Crystals

    Science.gov (United States)

    2016-06-09

    AFRL-AFOSR-VA-TR-2016-0221 NEGATIVE REFRACTION IN RARE-EARTH DOPED CRYSTALS Deniz Yavuz UNIVERSITY OF WISCONSIN SYSTEM MADISON WI Final Report 06/09...DATES COVERED (From - To) March 2013-February 2016 4. TITLE AND SUBTITLE NEGATIVE REFRACTION IN RARE-EARTH DOPED CRYSTALS 5a. CONTRACT NUMBER...ABSTRACT In this project, our long-term goal is to demonstrate the first negative refraction in atomic systems. Although the concept of negative

  13. Zr doping on lithium niobate crystals: Raman spectroscopy and chemometrics

    Science.gov (United States)

    Kokanyan, Ninel; Chapron, David; Kokanyan, Edvard; Fontana, Marc D.

    2017-03-01

    Raman measurements were investigated on Zr-doped lithium niobate LiNbO3 crystals with different concentrations. Spectra were treated by fitting procedure and principal component analysis which both provide results consistent with each other. The concentration dependence of the frequency on the main low-frequency optical phonons provides an insight of site incorporation of Zr ions in the host lattice. The threshold concentration of about 2% is evidenced, confirming the interest of Zr doping as an alternative to Mg doping for the reduction of the optical damage in lithium niobate.

  14. Characterization of pure and copper-doped iron tartrate crystals ...

    Indian Academy of Sciences (India)

    Single crystal growth of pure and copper-doped iron tartrate crystals bearing composition Cu Fe(1−) C4H4O6 · H2O, where = 0, 0.07, 0.06, 0.05, 0.04, 0.03, is achieved using gel technique. The elemental analysis has been done using energy-dispersive X-ray analysis (EDAX) spectrum. The characterization studies ...

  15. Sectioned Core Doping Effect on Higher-Order Mode Amplification in Yb-Doped Rod-Type Photonic Crystal Fibers

    DEFF Research Database (Denmark)

    Poli, F.; Lægsgaard, Jesper; Passaro, D.

    2009-01-01

    The amplification properties of guided modes in Yb-doped rod-type photonic crystal fibers with sectioned core doping have been investigated, evaluating the doped-area radius which provides the effective suppression of both LP 11- and LP02-like modes.......The amplification properties of guided modes in Yb-doped rod-type photonic crystal fibers with sectioned core doping have been investigated, evaluating the doped-area radius which provides the effective suppression of both LP 11- and LP02-like modes....

  16. Optical tuning of photonic bandgaps in dye-doped nematic liquid crystal photonic crystal fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard; Hermann, David Sparre

    2005-01-01

    An all-optical modulator is demonstrated, which utilizes a pulsed 532 nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid crystal. In order to investigate the time response of the LCPBG fiber device, a low-power CW probe...

  17. Single mode dye-doped polymer photonic crystal lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Buss, Thomas; Smith, Cameron

    2010-01-01

    Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode...

  18. Growth and characterization of pure and doped bis(thiourea) cadmium acetate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Selvakumar, S. [Department of Physics, Sathyabama University, Chennai 600119 (India); Kumar, S.M. Ravi [Department of Physics, Loyola College, Chennai 600034 (India); Joseph, Ginson P. [Department of Physics, Loyola College, Chennai 600034 (India); Rajarajan, K. [Department of Physics, Loyola College, Chennai 600034 (India); Madhavan, J. [Department of Physics, Loyola College, Chennai 600034 (India); Rajasekar, S.A. [Department of Physics, Vellore Institute of Technology, Vellore 632014 (India); Sagayaraj, P. [Department of Physics, Loyola College, Chennai 600034 (India)]. E-mail: psagayaraj@hotmail.com

    2007-05-15

    Single crystals of pure and Zn{sup 2+} doped bis(thiourea) cadmium acetate (BTCA) were grown by slow solvent evaporation technique. The grown crystals were confirmed by single crystal XRD. The metal coordination with thiourea through sulphur in both pure and doped BTCA was ascertained by FTIR studies. The optical transmission spectra of pure and doped BTCA crystals were recorded and the results are discussed. The thermal decomposition of pure and doped BTCA crystals was investigated by means of thermogravimetric analysis (TGA). The dielectric response and photoconducting nature of the crystals were also investigated and reported.

  19. Synthesis, Characterization, and Crystal Structure of a Triazine Anion Pentafluoroosmium(VI Complex

    Directory of Open Access Journals (Sweden)

    Monther A. Khanfar

    2018-01-01

    Full Text Available The synthesis and characterization of a novel triazine anion pentafluoroosmium(VI complex are presented. The single crystal determination of the title compound (hereafter denoted 1 was carried out at −140 °C. Compound 1, C3F4N3OsF5, crystallizes in the monoclinic space group, P21/n, with unit cell dimensions: a = 8.6809(17 Å, b = 7.6848(15 Å, c = 12.415(3 Å, β = 102.633(4°, V = 808.2(3 Å3, and Z = 4. Synthesis, characterization, X-ray diffraction study along with the crystal supramolecular analysis of the title complex were carried out. The complex contains the anionic triazine unit C3N3F4− acting as a mono dentate ligand to osmium(VI with five fluoro ligands in a slightly distorted octahedral geometry around osmium(VI ion (osmium is denoted as Os. The C3N3F4−, triazine anion ring deviates from planarity, only with the C1 being tetrahedral. The crystal lattice of the title compound displays significant intermolecular X···X interactions, namly F···F, F···N and F···C. All types of X···X bonding consolidate to form a three-dimensional network.

  20. Ultraviolet photorefraction at 325 nm in doped lithium niobate crystals

    Science.gov (United States)

    Xin, Feifei; Zhang, Guoquan; Bo, Fang; Sun, Haifeng; Kong, Yongfa; Xu, Jingjun; Volk, Tatyana; Rubinina, Natalia M.

    2010-02-01

    We studied the photorefractive effect of lithium niobate (LiNbO3) doped with Mg, Zn, In, Hf, or codoped with Mg and Fe at an ultraviolet (UV) wavelength down to 325 nm. It is found that the UV photorefraction of LiNbO3 doped with Mg, Zn, In, or Hf was enhanced significantly as compared to that of the nominally pure LiNbO3. Our results show that the property of resistance against photorefraction in highly Mg, Zn, In, or Hf doped LiNbO3 is true only in the visible and near-infrared wavelength range. By contrast, these crystals exhibit excellent photorefractive characteristics at UV wavelength of 325 nm, even better than those at 351 nm. For example, the photorefractive two-wave coupling gain coefficient Γ and the photorefractive recording sensitivity at 325 nm were measured to be ˜38 cm-1 and 37.7 cm/J, respectively, in a LiNbO3 crystal doped with 9 mol % Zn. The photorefractive response time of a Mg:LiNbO3 with a 9 mol % Mg was measured to be 73 ms with a total recording intensity of 614 mW/cm2 at 325 nm. In highly Mg, Zn, In, or Hf doped LiNbO3 crystals, diffusion dominates over photovoltaic effect and electrons are the dominant charge carriers in UV photorefraction at 325 nm. The results are also of interest to the study on the defect structure of LiNbO3 near to the absorption edge.

  1. Optical switching in nonlinear photonic crystals lightly doped with nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Lipson, R H [Department of Chemistry, University of Western Ontario, London, ON N6A 5B7 (Canada)

    2008-01-14

    A possible switching mechanism has been investigated for nonlinear photonic crystals doped with an ensemble of non-interacting three-level nanoparticles. In this scheme, an intense pump laser field is used to change the refractive index of the nonlinear photonic crystal while a weaker probe field monitors an absorption transition in the nanoparticles. In the absence of the strong laser field the system transmits the probe field when the resonance energy of the nanoparticles lies near the edge of the photonic band gap due to strong coupling between the photonic crystal and the nanoparticles. However, upon application of an intense pump laser field the system becomes absorbing due to a band edge frequency shift that arises due to a nonlinear Kerr effect which changes the refractive index of the crystal. It is anticipated that the optical switching mechanism described in this work can be used to make new types of photonic devices.

  2. Hydrothermal derived nitrogen doped SrTiO3 for efficient visible light driven photocatalytic reduction of chromium(VI).

    Science.gov (United States)

    Xing, Guanjie; Zhao, Lanxiao; Sun, Tao; Su, Yiguo; Wang, Xiaojing

    2016-01-01

    In this work, we report on the synthesis of nitrogen doped SrTiO3 nanoparticles with efficient visible light driven photocatalytic activity toward Cr(VI) by the solvothermal method. The samples are carefully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and photocatalytic test. It is found that nitrogen doping in SrTiO3 lattice led to an apparent lattice expansion, particle size reduction as well as subsequent increase of Brunner-Emmet-Teller surface area. The visible light absorption edge and intensity can be modulated by nitrogen doping content, which absorption edge extends to about 600 nm. Moreover, nitrogen doping can not only modulate the visible light absorption feature, but also have consequence on the enhancement of charge separation efficiency, which can promote the photocatalytic activity. With well controlled particle size, Brunner-Emmet-Teller surface area, and electronic structure via nitrogen doping, the photocatalytic performance toward Cr(VI) reduction of nitrogen doped SrTiO3 was optimized at initial hexamethylenetetramine content of 2.

  3. Fabrication of ZnO Bi-crystals with twist boundaries using Co doped ZnO single crystals

    CERN Document Server

    Ohashi, N; Ohgaki, T; Tsurumi, T; Fukunaga, O; Haneda, H; Tanaka, J

    1999-01-01

    Zn O single crystals doped with Co were grown by using a flux method and their electrical properties were investigated by Hall effect. Then, these crystals were polished with diamond paste and bonded to form bi-crystal by hot pressing under a pressure of 10 MPa at 1000 .deg. C. The bi-crystals showed nonlinear I-V curves, and the curvature of I-V relation agreed with that for Co-doped polycrystalline ZnO.

  4. Nanoparticle-doped isotropic liquid crystals

    Science.gov (United States)

    Parfenov, Alexander; Xia, Xiaowei; Shapoury, Alireza; DeHoog, Edward A.; Zhang, Fang; Pradhan, Shilpa; Aye, Tin M.; Shih, Min-Yi; Hall, Arlynn Z.; Cooper, Thomas M.

    2011-10-01

    We demonstrate a new material composed of isotropic liquid crystal (ILC) blended with semiconductor nanoparticles, which could result in a novel high-speed, multiple-notch broadband passive optical switch to selectively discriminate bands of electromagnetic radiation in intelligence, surveillance, or reconnaissance systems. The new material has been demonstrated high nonlinear 3rd order optical Kerr coefficients (light-induced refractive index change, n2) exceeding 100 times of classic nonlinear material CS2 with n2 = 1.2E-11 esu. Details of fabrication and experimental results are presented.

  5. Influence of microgravity on Ce-doped Bi12 SiO20 crystal defect

    Indian Academy of Sciences (India)

    Space grown BSO crystal doped with Ce was characterized by means of X-ray fluorescence spectra, X-ray topography, dislocation density etc. Influence of microgravity on Ce-doped BSO crystal defect was studied by comparing space grown BSO crystal with ground grown one. These results show that compositional ...

  6. Lasing from dye-doped planar cholesteric liquid crystal devices

    Science.gov (United States)

    Wu, Ri-na; Dai, Qin; Yan, Bin; Liu, Yan-juan; Xu, Song-ning; Quan, Wei

    2011-06-01

    The lasing action of dye doped cholesteric liquid crystal (CLC) cell was investigated in this work. A planar state was prepared by antiparallel rubbing process ITO glasses with polymide layer coating. The dye doped cholesteric liquid crystal mixture was used by mixing a laser dye DCM, a chiral agent CB15 and a nematic liquid crystal TEB30A. A second harmonic Q-switched Nd:YAG pulsed laser (λ=532nm) was used as the pumping source. A sharp peak was measured at 611 nm in the cell-normal direction and cell-plane direction after reaching threshold pump energy. The least full width of half maximum (FWHM) were about 10 nm and 12 nm. The optical structure of the device was investigated upon applied voltage. The results show that planar state of the CLCs is a prerequisite for the generation of lasing emission. So laser emission attributed to the photonic band gap (Bragg mode) in the cell-normal direction in which the helical axis exists. Due to the waveguide structure formed by the liquid crystal sandwiched between glass substrates (ne=1.522, no=1.692>ng=1.50), quasi-in-plane leaky lasing modes exist in the cell-plane direction.

  7. Growth, Optical and Dielectric Studies on Pure and L-Lysine Doped KDP Crystals

    Directory of Open Access Journals (Sweden)

    N. Kanagathara

    2012-01-01

    Full Text Available Optically good quality single crystals of pure and L-lysine monohydrochloride-doped KDP crystals have been grown by a slow evaporation method. The grown crystals have been subjected to optical and dielectric studies. The UV-Vis spectrum shows the transmitting ability of the crystals in the entire visible region and transmittance percentage is increased for the doped KDP crystals. From the dielectric study, it is found that the dielectric constant and the dielectric loss of L-lysine-doped KDP crystals were lower than the pure KDP crystals. Hence L-lysine-doped KDP crystals are found to be more beneficial from an application point of view as compared to pure KDP crystals.

  8. Potential Advantage of Multiple Alkali Metal Doped KNbO3 Single Crystals

    Directory of Open Access Journals (Sweden)

    Hideo Kimura

    2014-06-01

    Full Text Available Potassium niobate crystal KNbO3 (KN is a well-known crystal for lead free piezoelectric or nonlinear optical applications. The KN crystal has been studied in both single crystal form and in thin film form which has resulted in many review articles being published. In order to exceed the KN crystal, it is important to study KN phase forming and doping effects on the K site. This article summarizes the authors’ study towards a multiple alkali metal doped KN crystal and related single crystals briefly from the viewpoint of crystal growth.

  9. Study of nonlinear effects in photonic crystals doped with nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, N6A 3K7 Ontario (Canada)

    2008-07-14

    A theory of nonlinear phenomena has been developed for a photonic crystal in the presence of a pump and a coupling laser field. The crystal is doped with an ensemble of four-level nanoparticle impurities. It is considered that the impurity particles are not only interacting with the photonic crystal but also with each other via dipole-dipole interaction. An expression for the susceptibility has been obtained using the density matrix method. The nonlinear effects due to the coupling and the pump fields have been included in the formulation. The absorption spectrum has been calculated in the presence of the strong coupling and pump fields for an isotropic photonic crystal made from dielectric spheres. The photonic crystal has a gap to midgap ratio of about 21%. It is predicted that the absorption spectrum in the photonic crystal can have zero, one, two or three absorptionless states by tuning one of the transition energies within the bands. This is an interesting phenomenon which can be used to make photonic switching devices. We have also calculated the absorption spectrum in the presence of the dipole-dipole interaction. It is found that a symmetric absorption spectrum changes to an asymmetric one due to this interaction. It is also found that there is a large enhancement in the absorption and the dispersion simultaneously for certain values of the detuning and concentration.

  10. Crystal Structure-Ionic Conductivity Relationships in Doped Ceria Systems

    DEFF Research Database (Denmark)

    Omar, Shobit; Wachsman, Eric D.; Jones, Jacob L.

    2009-01-01

    lattice strain of 10 mol% trivalent cation-doped ceria systems at the same temperatures. A consistent set of ionic conductivity data is developed, where the samples are synthesized under similar experimental conditions. On comparing the grain ionic conductivity, Nd0.10Ce0.90O2−δ exhibits the highest ionic...... conductivity among other doped ceria systems. The grain ionic conductivity is around 17% higher than that of Gd0.10Ce0.90O2−δ at 500°C, in air. X-ray diffraction profiles are collected on the sintered powder of all the compositions, from room temperature to 600°C, in air. From the lattice expansion data...... crystal structure–ionic conductivity relationship based on minimum elastic strain is not sufficient to explain the ionic conductivity behavior in ceria-based system....

  11. Crystallization behavior of rare-earth doped fluorochlorozirconate glasses.

    Science.gov (United States)

    Paßlick, C; Ahrens, B; Henke, B; Johnson, J A; Schweizer, S

    2011-06-01

    A series of fluorochlorozirconate (FCZ) glasses, each doped with a different rare-earth, was prepared and examined to determine thermal stability and activation energy, Ea , of the dopant dependent BaCl2 crystallization. Non-isothermal differential scanning calorimetry (DSC) measurements were done to investigate the endothermic and exothermic reactions upon heat treatment of the glass samples. In comparison to the rare-earth free FCZ glass, significant changes in the Hruby constant, Hr , and Ea were found due to the addition of a rare-earth and also between the individual dopants.

  12. Optical, thermal and electrical properties of pure and doped bis-thiourea cadmium formate (BTCF) crystal

    Science.gov (United States)

    Shejwal, N. N.; Anis, Mohd; Hussaini, S. S.; Shirsat, M. D.

    2014-12-01

    A glycine doped bis-thiourea cadmium formate (BTCF) crystal has been grown by a slow solution evaporation technique. The shifts in vibrational frequencies of different functional groups of BTCF were identified by Fourier transform infrared (FT-IR) spectral analysis. UV-visible studies were employed to assess the optical transparency of pure and doped BTCF crystals. The optical band gap of doped BTCF is found to be 5.16 eV. The optical constants, refractive index, reflectance, and optical conductivity have been evaluated, using the transmission data. The dielectric characteristics of pure and doped BTCF were investigated by employing dielectric studies. The decomposition temperature of pure and doped BTCF crystals was determined by using thermogravimetric analysis. The encouraging third-order nonlinear optical properties of pure and doped BTCF crystals were examined by employing the Z-scan technique at 632.8 nm.

  13. Sulfur-Doped Carbon Nitride Polymers for Photocatalytic Degradation of Organic Pollutant and Reduction of Cr(VI).

    Science.gov (United States)

    Zheng, Yun; Yu, Zihao; Lin, Feng; Guo, Fangsong; Alamry, Khalid A; Taib, Layla A; Asiri, Abdullah M; Wang, Xinchen

    2017-04-01

    As a promising conjugated polymer, binary carbon nitride has attracted extensive attention as a metal-free and visible-light-responsive photocatalyst in the area of photon-involving purification of water and air. Herein, we report sulfur-doped polymeric carbon nitride microrods that are synthesized through thermal polymerization based on trithiocyanuric acid and melamine (TM) supramolecular aggregates. By tuning the polymerization temperature, a series of sulfur-doped carbon nitride microrods are prepared. The degradation of Rhodamine B (RhB) and the reduction of hexavalent chromium Cr(VI) are selected as probe reactions to evaluate the photocatalytic activities. Results show that increasing pyrolysis temperature leads to a large specific surface area, strong visible-light absorption, and accelerated electron-hole separation. Compared to bulk carbon nitride, the highly porous sulfur-doped carbon nitride microrods fabricated at 650 °C exhibit remarkably higher photocatalytic activity for degradation of RhB and reduction of Cr(VI). This work highlights the importance of self-assembly approach and temperature-control strategy in the synthesis of photoactive materials for environmental remediation.

  14. Soft memory in a ferroelectric nanoparticle-doped liquid crystal

    Science.gov (United States)

    Basu, Rajratan

    2014-02-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC + FNP hybrid was found to exhibit a nonvolatile electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range pseudonematic domains surrounding the FNPs. The FNP-induced short-range orders become more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with an external electric field, exhibiting a Fréedericksz-type transition. When the field is turned off, these domains stay oriented, showing a hysteresis effect due to the absence of any long-range order and restoring forces in the isotropic phase. The hysteresis graph for this memory effect shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase.

  15. Electrically tunable Yb-doped fiber laser based on a liquid crystal photonic bandgap fiber device

    DEFF Research Database (Denmark)

    Olausson, Christina Bjarnal Thulin; Scolari, Lara; Wei, Lei

    2010-01-01

    We demonstrate electrical tunability of a fiber laser using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a tunable liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate...

  16. Elastico-mechanoluminescence and crystal-structure relationships in persistent luminescent materials and II–VI semiconductor phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, B.P., E-mail: bpchandra4@yahoo.co.in [School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur 492010, Chattisgarh (India); Chandra, V.K. [Department of Electrical and Electronics Engineering, Chhatrapati Shivaji Institute of Technology, Shivaji Nagar, Kolihapuri, Durg 491001, Chattisgarh (India); Jha, Piyush [Department of Applied Physics, Raipur Institute of Technology, Chhatauna, Mandir Hasuad, Raipur 492101, Chattisgarh (India)

    2015-04-15

    Elastico-mechanoluminescence (EML) has recently attracted the attention of a large number of researchers because of its potential in different types of mechano-optical devices. For understanding the mechanism of EML the relationships between elastico-mechanoluminescence (EML) and crystal-structure of a large number of persistent luminescent materials and II–VI semiconductor phosphors known to date are investigated. It is found that, although most of the non-centrosymmetric crystals exhibit EML, certain non-centrosymmetric crystals do not show EML. Whereas, many centrosymmetric crystals do not exhibit EML, certain centrosymmetric crystals exhibit EML. Piezoelectric ZnS:Cu,Cl single crystals do not show EML, but piezoelectric ZnS:Cu,Cl microcrystalline phosphors show very intense EML. Piezoelectric single crystals of undoped ZnS do not show EML. It seems that EML is related to local piezoelectrification near the impurities in crystals where piezoelectric constant is high. Suitable piezoelectric field near the local piezoelectric region and stable charge carriers in traps are required for appearance of EML. The EML of persistent luminescent materials and II–VI semiconductor phosphors can be understood on the basis of piezoelectrically-induced trap-depth reduction model of EML. Using suitable dopants both in non-centrosymmetric and centrosymmetric crystals intense elastico-mechanoluminescent materials emitting desired colours can be tailored, which may find applications in several mechano-optical devices.

  17. Elastico-mechanoluminescence and crystal-structure relationships in persistent luminescent materials and II-VI semiconductor phosphors

    Science.gov (United States)

    Chandra, B. P.; Chandra, V. K.; Jha, Piyush

    2015-04-01

    Elastico-mechanoluminescence (EML) has recently attracted the attention of a large number of researchers because of its potential in different types of mechano-optical devices. For understanding the mechanism of EML the relationships between elastico-mechanoluminescence (EML) and crystal-structure of a large number of persistent luminescent materials and II-VI semiconductor phosphors known to date are investigated. It is found that, although most of the non-centrosymmetric crystals exhibit EML, certain non-centrosymmetric crystals do not show EML. Whereas, many centrosymmetric crystals do not exhibit EML, certain centrosymmetric crystals exhibit EML. Piezoelectric ZnS:Cu,Cl single crystals do not show EML, but piezoelectric ZnS:Cu,Cl microcrystalline phosphors show very intense EML. Piezoelectric single crystals of undoped ZnS do not show EML. It seems that EML is related to local piezoelectrification near the impurities in crystals where piezoelectric constant is high. Suitable piezoelectric field near the local piezoelectric region and stable charge carriers in traps are required for appearance of EML. The EML of persistent luminescent materials and II-VI semiconductor phosphors can be understood on the basis of piezoelectrically-induced trap-depth reduction model of EML. Using suitable dopants both in non-centrosymmetric and centrosymmetric crystals intense elastico-mechanoluminescent materials emitting desired colours can be tailored, which may find applications in several mechano-optical devices.

  18. Protons and deuterons in magnesium-doped sapphire crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, R.; Gonzalez, R.; Colera, I. [Univ. Carlos III de Madrid, Leganes (Spain). Dept. de Fisica; Vila, R. [CIEMAT, Madrid (Spain). Inst. de Investigacion Basica

    1997-04-01

    Of great importance to the use of ceramics in fusion reactors are the problems associated with the presence of a high level of transmutation products induced by high-energy neutrons. For aluminum oxide, the four major products are magnesium, hydrogen, carbon, and helium. The solubility and diffusivity of hydrogen isotopes strongly depend on the concentration of specific impurities, which results in a change in the position and full-width-at-half-maximum of the OH{sup {minus}} and OD{sup {minus}} bands. The OH{sup {minus}} and OD{sup {minus}} stretching frequencies in magnesium-doped aluminum oxide crystals were determined by infrared absorption measurements. Two very broad bands centered at {approximately}3,005 and 2,228 cm{sup {minus}1} were observed for OH{sup {minus}} and OD{sup {minus}}, respectively. Polarization experiment results were compatible with OH{sup {minus}} (OD{sup {minus}}) ions lying in the basal plane, as is the case in undoped crystals. The threshold temperature for the in-diffusion of deuterons was obtained by annealing the samples in flowing D{sub 2}O vapor; the resulting value was {approximately}1,050 K. At 1223 K, the diffusion coefficient was {approximately}3 {times} 10{sup {minus}7} cm{sup 2}/s, and the activation energy was 1.6 eV.

  19. Hydrothermal growth and characterization of aluminum-doped ZnO bulk crystals

    Science.gov (United States)

    Wang, Buguo; Mann, Matthew; Claflin, Bruce; Snure, Michael; Look, David C.

    2013-03-01

    Bulk ZnO crystals were grown by the hydrothermal technique with Al2O3 added to the solution in an attempt to obtain Al-doped ZnO crystals. Aluminum and indium co-doped ZnO were also grown by the same technique. Adding Al2O3 to the growth solution has a significant impact on the ZnO growth ⎯ either preventing overgrowth and dissolving the seed growth or degrading the crystalline quality; nevertheless, the resulting crystals of both Al:ZnO and Al/In:ZnO are highly conductive, similar to In and Ga doped ZnO crystals, with a resistivity approaching 0.01 Ω cm, as revealed by temperature-dependent Hall-effect measurements. Photoluminescence spectra at 18 K show Al0-bound-exciton peak energies of 3.3604 eV on the Zn face and 3.3609 eV on the O face for the Al-doped ZnO crystals. Similarly both an Al0- bound-exciton peak at 3.3604 eV and an In0-bound-exciton peak at 3.3575 eV were found on the Al/In-co-doped crystals. The electrical properties of all group III doped ZnO crystals grown hydrothermally are compared with each other and with Al:ZnO obtained by other growth methods.

  20. Microstructural, optical and electrical properties of Cl-doped CdTe single crystals

    Directory of Open Access Journals (Sweden)

    Choi Hyojeong

    2016-09-01

    Full Text Available Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm−3, 9.94 × 1019 cm−3 and 1.99 × 1020 cm−3 and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot. It was shown that Cl dopant suppressed the unwanted secondary (5 1 1 crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm−3 was above 1010 Ω.cm.

  1. Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid

    Science.gov (United States)

    Jiang, Hong-Chen; Devereaux, T.; Kivelson, S. A.

    2017-08-01

    We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t -J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ =0 ) spin-1 /2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole per unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. Our results may be relevant to kagome lattice herbertsmithite upon doping.

  2. Crystallization of II-VI semiconductor compounds forming long microcrystalline linear assemblies

    Directory of Open Access Journals (Sweden)

    Marcelino Becerril

    2013-04-01

    Full Text Available In this work we report the formation of long microcrystalline linear self-assemblies observed during the thin film growth of several II-VI compounds. Polycrystalline CdTe, CdS, CdCO3, and nanocrystalline CdTe:Al thin films were prepared on glass substrates by different deposition techniques. In order to observe these crystalline formations in the polycrystalline materials, the thin film growth was suspended before the grains reached to form a continuous layer. The chains of semiconductor crystals were observed among many isolated and randomly distributed grains. Since CdTe, CdTe:Al, CdS and CdCO3 are not ferroelectric and/or ferromagnetic materials, the relevant problem would be to explain what is the mechanism through which the grains are held together to form linear chains. It is well known that some nanocrystalline materials form rods and wires by means of electrostatic forces. This occurs in polar semiconductors, where it is assumed that the attraction forces between surface polar faces of the small crystals are the responsible for the chains formation. Since there are not too many mechanisms responsible for the attraction we assume that a dipolar interaction is the force that originates the formation of chain-like grain clusters. The study of this property can be useful for the understanding of nucleation processes in the growth of semiconductor thin films.

  3. Crystal and electronic structure study of Mn doped wurtzite ZnO nanoparticles

    Directory of Open Access Journals (Sweden)

    O.M. Ozkendir

    2016-08-01

    Full Text Available The change in the crystal and electronic structure properties of wurtzite ZnO nanoparticles was studied according to Mn doping in the powder samples. The investigations were conducted by X-ray Absorption Fine Structure Spectroscopy (XAFS technique for the samples prepared with different heating and doping processes. Electronic analysis was carried out by the collected data from the X-ray Absorption Near-Edge Structure Spectroscopy (XANES measurements. Additional crystal structure properties were studied by Extended-XAFS (EXAFS analysis. Longer heating periods for the undoped wurtzite ZnO samples were determined to own stable crystal geometries. However, for some doped samples, the distortions in the crystal were observed as a result of the low doping amounts of Mn which was treated as an impurity. Besides, the changes in oxygen locations were determined to create defects and distortions in the samples.

  4. Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang [Columbia Univ., New York, NY (United States); Frisbie, Daniel [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-03-31

    The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

  5. Doping colloidal bcc crystals - interstitial solids and meta-stable clusters

    NARCIS (Netherlands)

    Higler, Ruben; Sprakel, Joris

    2017-01-01

    The addition of a small amount of dopant impurities to crystals is a common method to tune the properties of materials. Usually the doping grade is restricted by the low solubility of the dopants; increasing the doping concentration beyond this solubility limit leads to supersaturated solutions

  6. Flicker noise in degenerately doped Si single crystals near the metal ...

    Indian Academy of Sciences (India)

    Abstract. In this paper we report some of the important results of experimental investigations of the flicker noise near the metal–insulator (MI) transition in doped silicon single crystals. This is the first comprehensive work to study low-frequency noise in heavily doped Si over an extensive temperature range (2 K T. 500 K).

  7. Enhanced optical, thermal and piezoelectric behavior in dye doped potassium acid phthalate (KAP) single crystal

    Science.gov (United States)

    Rao, G. Babu; Rajesh, P.; Ramasamy, P.

    2017-06-01

    Dye inclusion crystals have attracted researchers in the context of crystal growth for applications in solid state lasers. Pure and 0.1 mol% amaranth doped KAP single crystals, were grown from aqueous solutions by slow evaporation technique at room temperature. The grown crystals are up to the dimension of 12×10×3 mm3. Attempt is made to improve the growth rate, optical, piezoelectric and photoconductive properties of pure KAP single crystal with addition of amaranth dye as a dopant. Various characterization studies were made for both pure and dye doped KAP. Thermal stability of the crystals is tested from thermogravimetric and differential thermal analysis (TG/DTA). There is only one endothermic peak indicating decomposition point. Higher optical transparency for dye doped KAP crystal was identified from the UV-vis spectrum. Etching studies showed an improvement in the optical quality of the KAP crystal after doping with amaranth dye. The positive photoconductive nature is observed from both pure and amaranth doped KAP.

  8. Microscopic Mechanism of Doping-Induced Kinetically Constrained Crystallization in Phase-Change Materials.

    Science.gov (United States)

    Lee, Tae Hoon; Loke, Desmond; Elliott, Stephen R

    2015-10-07

    A comprehensive microscopic mechanism of doping-induced kinetically constrained crystallization in phase-change materials is provided by investigating structural and dynamical dopant characteristics via ab initio molecular dynamics simulations. The information gained from this study may provide a basis for a fast screening of dopant species for electronic memory devices, or for understanding the general physics involved in the crystallization of doped glasses. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Structural and optical properties of europium doped zirconia single crystals fibers grown by laser floating zone

    OpenAIRE

    Soares, M.R.N.; Nico, C.; Peres, M.; Ferreira, N.; Fernandes, A.J.S.; Monteiro, T.; COSTA, F.M.

    2011-01-01

    Yttria stabilized zirconia single crystal fibers doped with europium ions were developed envisaging optical applications. The laser floating zone technique was used in order to grow millimetric high quality single crystal fibers. The as-grown fibers are completely transparent and inclusion free, exhibiting a cubic structure. Under ultraviolet (UV) excitation, a broad emission band appears at 551 nm. The europium doped fibers are translucent with a tetragonal structure and exhibit an intense r...

  10. The temperature dependent fracture strength of doped single crystal alumina fibers

    Energy Technology Data Exchange (ETDEWEB)

    Sayir, H.; Farmer, S.C.; Lagerlof, P. [NASA Lewis Research Center, Cleveland, OH (United States)] [and others

    1994-12-31

    The tensile strength of impurity doped, laser heated float zone (LHFZ) grown, single crystal sapphire ({alpha}-Al{sub 2}O{sub 3}) fibers were measured at elevated temperatures, 1100 and 1450{degrees}C. The effects of MgO doping, TiO{sub 2} doping and TiO{sub 2}/MgO co-doping were examined. MgO doping significantly enhanced the high temperature strength. At 1450{degrees}C, tensile strengths of MgO doped sapphire ({approximately}1760 MPa) are almost twice the strength of undoped fibers. In contrast, the effect of TiO{sub 2} doping and TiO{sub 2}/MgO-codoping on the tensile strength of sapphire fibers was not statistically significant at either 1100 or 1450{degrees}C. The relationship between strength distributions and temperature is examined and possible strengthening mechanisms are discussed.

  11. Crystal growth, electronic structure and luminescence properties of Nb/Yb co-doped RbTiOPO4 crystals

    Science.gov (United States)

    Liu, Jian; Li, Ziqing; Zhu, Pengfei; Duan, Xiulan

    2018-01-01

    Nb/Yb co-doped RbTiOPO4 (RTP) crystals were successfully grown by a top-seeded solution growth method from two different kinds of flux systems. 5%Nb/3%Yb: RTP crystal with more transparency was obtained from the mixed solvent containing MoO3. The chemical composition was analyzed by Electron Probe Microanalyzer (EPMA), and the result indicated that co-doping of Nb and Yb into RTP can greatly increase the concentration of Yb in RTP crystal. The addition of MoO3 into self-flux system can improve the quality of as-grown crystals, but it is not helpful to introduce Yb into crystal. The electronic structures of Nb/Yb: RTP crystals were analyzed using X-ray photoelectron spectra (XPS). The results show that the binding energy difference between O 1s and P 2p levels (ΔBE (O-P)) increases firstly with the increase of Yb content, and then decreases with Nb content increasing, which is associated with the covalency change of O-P bonds in crystals. However, the doping has little influence on the chemical bond properties of O-Ti. The FL spectra of Nb/Yb: RbTiOPO4 crystals were also analyzed, and five emission peaks characteristic of Yb3+ ions were observed.

  12. Two-photon photoluminescence and second-harmonic generation from unintentionally doped and semi-insulating GaN crystals

    Science.gov (United States)

    Godiksen, R. H.; Aunsborg, T. S.; Kristensen, P. K.; Pedersen, K.

    2017-11-01

    Unintentionally doped and semi-insulating Fe-doped GaN crystals grown by hydride vapor phase epitaxy have been investigated with two-photon photoluminescence and second-harmonic generation spectroscopy to reveal doping effects on the nonlinear optical properties and thus indirectly on crystal properties. Like for linear luminescence, it is found that Fe doping strongly reduces nonlinear luminescence. Recording of second-harmonic generation spectra in transmission probing bulk properties shows no significant difference between doped and un-doped crystals. Reflected second-harmonic generation probing 50-100 nm at the surface, on the other hand, shows significantly lower signal from the doped sample. Secondary ion mass spectroscopy shows that the Fe concentration is higher at the surface than in the bulk of the doped crystal. It is suggested that this causes higher defect density and degraded order in the surface region, thus reducing the second-harmonic signal.

  13. An “on-off-on” fluorescent nanoprobe for recognition of chromium(VI) and ascorbic acid based on phosphorus/nitrogen dual-doped carbon quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Xiaojuan, E-mail: gxj1124@sxu.edu.cn [Institute of Environmental Science, School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006 (China); Liu, Yang; Yang, Zhenhua; Shuang, Shaomin [Institute of Environmental Science, School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006 (China); Zhang, Zeyu [Faculty of Science, Beijing University of Chemical Technology, Beijing, 100029 (China); Dong, Chuan, E-mail: dc@sxu.edu.cn [Institute of Environmental Science, School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006 (China)

    2017-05-22

    Chromium (VI) [Cr(VI)] is a harsh environmental contaminates and has been proved to be highly toxic, carcinogenic and mutagenic. Therefore, developing an inexpensive, good selective and highly sensitive nanoprobe for the detection of Cr(VI) is in urgent demand. Recently, the highly fluorescent carbon quantum dots (CQDs) have been successfully utilized as efficient fluorescent nanoprobes for the detection of ions, pH and molecular substances. In this work, an “on-off” fluorescence phosphorus/nitrogen dual-doped CQDs (PNCQDs) probe was developed for the determination of Cr(VI) based on inner filter effect (IFE). The proposed PNCQDs nanoprobe shows its distinct merits of simplicity, convenience, fast implementation, good selectivity and high sensitivity towards Cr(VI), allowing its potential application in the determination of Cr(VI) in environment and biosystem. In addition, the chelation effect of the functional groups in reductant and Cr(VI), and the easy-conversion of Cr(VI) to reduced states (i.e. Cr(III) and Cr(0)) by reductants makes the minimization of IFE with a concomitant recovery of PNCQDs fluorescence possible. Hence, the PNCQDs/Cr(VI) hybrid was used as an “off-on” fluorescence probe for sensing ascorbic acid (AA), which is a model reductant. For the detection of Cr(VI), the linear range and the limit of detection achieved were 1.5–30 μmol/L and 23 nmol/L, respectively. For the detection of AA, the linear range and the limit of detection obtained were 5.0–200 μmol/L and 1.35 μmol/L, respectively. The as-constructed “on-off-on” PNCQDs fluorescent nanoprobe was successfully applied for detecting Cr(VI) and AA in biosystem. Furthermore, the as-constructed fluorescent sensing system was successfully applied to the analyses of AA in fresh fruits and in commercial fruit juices with satisfactory results. - Highlights: • Fast synthesis of phosphorus/nitrogen dual-doped CQDs (PNCQDs) by acid-base neutralization carbonization method.

  14. Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals

    Science.gov (United States)

    Sinha, Nidhi; Goel, Neeti; Singh, B. K.; Gupta, M. K.; Kumar, Binay

    2012-06-01

    Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (Tc) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications.

  15. Preparation and characterization of Ag-doped TiO{sub 2} nanomaterials and their photocatalytic reduction of Cr(VI) under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Lei, X.F., E-mail: leixuefei69@163.com [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization Technology and Boron Materials, Shenyang 110819 (China); Xue, X.X.; Yang, H. [Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization Technology and Boron Materials, Shenyang 110819 (China)

    2014-12-01

    Graphical abstract: - Highlights: • Ag-doping in TiO{sub 2} can preserve the anatase form to higher temperature. • Ag-doped TiO{sub 2} samples can absorb both UV and visible light. • The band gap energy of the sample significantly reduced after Ag-doping. • Ag-doped TiO{sub 2} samples effective for visible light-induced reduction of Cr(VI). - Abstract: Ag-doped TiO{sub 2} nanomaterials (Ag–TiO{sub 2}) were prepared by a sol–gel method. The structures of Ag–TiO{sub 2} nanomaterials were characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), X-ray photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The photocatalytic activities were checked through the photocatalytic reduction of Cr(VI) as a model compound under visible light irradiation. The results showed that the Ag doping and the calcination temperature played an important role on the microstructure and photocatalytic activity of the samples. Ag-doped TiO{sub 2} samples calcinated at 400 °C exhibits higher photocatalytic activity than that of the other samples under visible light irradiation.

  16. High efficient removal of chromium (VI) using glycine doped polypyrrole adsorbent from aqueous solution

    CSIR Research Space (South Africa)

    Ballav, N

    2012-08-01

    Full Text Available confirmed by ATR-FTIR and XRD, respectively. Field emission scanning electron microscopic imaging of PPy-gly revealed the formation of nearly spherical agglomerated particles. The adsorption of Cr(VI) onto the PPy-gly adsorbent was highly pH dependent...

  17. Crystal Structure of Hcp from Acinetobacter baumannii: A Component of the Type VI Secretion System.

    Directory of Open Access Journals (Sweden)

    Federico M Ruiz

    Full Text Available The type VI secretion system (T6SS is a bacterial macromolecular machine widely distributed in Gram-negative bacteria, which transports effector proteins into eukaryotic host cells or other bacteria. Membrane complexes and a central tubular structure, which resembles the tail of contractile bacteriophages, compose the T6SS. One of the proteins forming this tube is the hemolysin co-regulated protein (Hcp, which acts as virulence factor, as transporter of effectors and as a chaperone. In this study, we present the structure of Hcp from Acinetobacter baumannii, together with functional and oligomerization studies. The structure of this protein exhibits a tight β barrel formed by two β sheets and flanked at one side by a short α-helix. Six Hcp molecules associate to form a donut-shaped hexamer, as observed in both the crystal structure and solution. These results emphasize the importance of this oligomerization state in this family of proteins, despite the low similarity of sequence among them. The structure presented in this study is the first one for a protein forming part of a functional T6SS from A. baumannii. These results will help us to understand the mechanism and function of this secretion system in this opportunistic nosocomial pathogen.

  18. Improved critical current density in Zn doped YBCO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Manzoor, E-mail: manzoorhuss98@yahoo.co [Department of Electrical and Electronic Engineering, University Technology PETRONAS, 31750 Tronoh, Perak (Malaysia); Takita, Koki [Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan)

    2010-02-15

    Magnetic measurements were made using pure YBCO and Zn doped YBa{sub 2}(Cu{sub 1-x}Zn{sub x}){sub 3}O{sub 7-s}igma. Single crystals with Zn concentration of 0.5%, 1.5%, 3.0% and 4.3%. The magnetic hysteresis loops for these samples were measured in the temperature range 0.1 <= T/T{sub c} <= 0.96 under magnetic fields of 5 T using SQUID. It was found that the critical current density J{sub c} increased for low Zn content samples up to 3% Zn concentration compared to pure YBCO sample and decreased for the higher Zn content samples. These values varied consistently when compared at magnetic fields of 1 T and 3 T. Moreover Zn doped samples showed significant values of J{sub c} in the temperature range of 0.7-0.9T{sub c}, close to critical temperature compared to pure YBCO sample. The irreversibility field H{sub irr} was also enhanced in this temperature range showing consistent decrease with increase of Zn concentration. The peak field H{sub p} above H{sub c1} and irreversibility field H{sub irr}, both show power law dependence of the form H = m{sub 1}(1 - T/T{sub c}){sup m2} in the temperature range of 0.75-0.96T{sub c}. The values of parameter m{sub 2} increased from 1.44 to 1.95 for the samples up to 3% Zn content and decreased to 1.37 for higher Zn contents. The ratio H{sub irr}/H{sub p} was found to be 3-4 for the lower Zn content samples and was 7-8 for the sample with high Zn content indicating more disorder for higher Zn content samples. The region between peak field H{sub p} and irreversibility field H{sub irr} was broadened with the increase of Zn concentration. The strong effect of Zn substitution in modifying behavior of these samples even at elevated temperatures is possibly due to the changes in the anisotropy of our samples with the increase of Zn concentration and also due to the locally induced changes in magnetic moments by Zn substitution.

  19. [Study of scintillating luminescence spectra of lead tungstate scintillation crystal doped with ions].

    Science.gov (United States)

    Wan, You-bao; Wu, Yu-rong; Zhang, Jian-xin; Yang, Pei-zhi; Xiao, Lin-rong; Yang, Hui

    2009-09-01

    The light yield of the as-grown PbWO4, annealed PbWO4 and BaF2:PbWO4 crystals were raised by utilizing our improved crystal growth instrument and technique. Their scintillating properties including transmittance, decay time and light yield were studied. Results reveal that the scintillating performances of the crystals were improved evidently by using the crystal annealing technique and the ions doping technique, especially the negative ions doping technique. The influence results of the two techniques are different. The ions doping technique raises their transmittance intensity in the whole measuring wavelength range. But the influence of annealing PbWO4 crystal on their transmittance is complicated. It improves its transmittance intensity at the wavelength above 360 nm, but weakens the transmittance intensity of the annealed PbWO4 crystal in the wavelength range from 320 to 360 nm. These phenomena should be related to the crystal defects which have absorption peaks in this wavelength range, especially for V(Pb)3+ defect which has characterized absorption peaks in this wavelength range. Also, the absorption of the defects influences the character of the decay time of these crystals. The big defect concentration relates to the short decay time. It should be mentioned that the ions doping technique reduces the defect content in the crystal, which is beneficial to the high transmittance intensity but induces slightly longer decay time than that of as-grown crystal and well annealed PbWO4 crystal. Also, the ions doping technique of the F- ion doped crystal leads to high light yield. The annealing technique and ions doping technique improve the light yield of crystals. The light yield of BaF2:PbWO4 reaches 65 p.e./MeV, which is near to the requirement of PET. The good result is related to the degeneration of the [WO4]2- tetrahedron induced by the F- occupying the O2- site in the crystal cell.

  20. Luminescence characteristics of Tl + ions co-doped RbCl:Eu 2+ crystals

    Science.gov (United States)

    Nagarajan, S.; Sudarkodi, R.

    2008-08-01

    RbCl:Eu 2+ single crystals which are co-doped with thallium display characteristic Eu 2+ emission around 420 nm and additional emission band at 312 nm with a weak shoulder around 390 nm attributable to centers involving Tl + ions. Additional excitation and emission bands observed in Tl + doped RbCl:Eu 2+ single crystals are attributed to the presence of Eu 2+ aggregates and complex centres involving both Eu 2+ and Tl + ions. Inclusion of Tl + ions in RbCl:Eu 2+ crystals is found to enhance the intensity of Eu 2+ emission at 420 nm due to an energy transfer from Tl + → Eu 2+ ions.

  1. Enhanced amplified spontaneous emission in a quantum dot-doped polymer-dispersed liquid crystal

    Science.gov (United States)

    Cao, Mingxuan; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yan, Chao; Dai, Haitao; Liu, Guang; Zhang, Guizhong; Yao, Jianquan

    2016-07-01

    Quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared by photoinitiated polymerization and sealed in capillary tubes. The concentration of QDs in the PDLC was 1 wt%. Amplified spontaneous emission (ASE) of the quantum dot-doped polymer-dispersed liquid crystals was observed with 532 nm wavelength laser excitation. The threshold for ASE was 6 mJ cm-2, which is much lower than that for homogeneous quantum dot-doped polymer (25 mJ cm-2). The threshold for ASE was dramatically enhanced when the working temperature exceeded the clearing point of the liquid crystal; this result demonstrates that multi-scattering caused by the liquid crystals effectively improved the path length or dwell time of light in the gain region, which played a key role in decreasing the threshold for ASE.

  2. Synthesis and characterization of pure, urea and thiourea doped organic NLO L-arginine trifluoroacetate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Prasanyaa, T. [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Haris, M., E-mail: mharis8@yahoo.com [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Mathivanan, V. [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Department of Physics, United Institute of Technology, Coimbatore (India); Senthilkumar, M. [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Mahalingam, T. [Department of Electrical and Computer Engineering, Ajou University, Suwon 443-749 (Korea, Republic of); Jayaramakrishnan, V. [Department of Physics, P.S.G. College of Arts and Science, Coimbatore 641 014, Tamilnadu (India)

    2014-10-15

    Optically transparent L-arginine trifluoroacetate (LATF) single crystals by doping with organic materials urea and thiourea were grown by slow solvent evaporation technique. Powder X-ray diffraction confirms improvement in the crystalline quality for urea doped crystals. Urea doping in LATF also improves the percentage of transmittance. The vibrational frequencies of the grown crystals were assigned by Fourier Transform infrared spectroscopy. The thermal analysis (TG/DTA) indicated the better thermal stability for urea doped LATF crystals. EDAX analysis was carried out to calculate the percentage of elements present in doped and pure LATF. The hardness has been remarkably improved on urea and thiourea doped LATF crystals. The second harmonic generation (SHG) analysis showed 2.5 times than standard KDP for pure LATF and 2.2, 2.07 times than KDP for urea and thiourea doped LATF. - Highlights: • Urea doped LATF crystals enhances the structural and crystalline quality. • Urea doping enhances optical transparency and thermal stability. • Urea and thiourea doping in LATF improves the hardness. • SHG efficiency of urea, thiourea doped LATF are 2.2 and 2.07 times greater than KDP.

  3. Doping properties of cadmium-rich arsenic-doped CdTe single crystals: Evidence of metastable AX behavior

    Energy Technology Data Exchange (ETDEWEB)

    Nagaoka, Akira [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan; Materials Science and Engineering and Electrical and Computer Engineering Departments, University of Utah, Salt Lake City, Utah 84112, USA; Kuciauskas, Darius [National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA; Scarpulla, Michael A. [Materials Science and Engineering and Electrical and Computer Engineering Departments, University of Utah, Salt Lake City, Utah 84112, USA

    2017-12-04

    Cd-rich composition and group-V element doping are of interest for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe, but the critical details concerning point defects are not yet fully established. Herein, we report on the properties of arsenic doped CdTe single crystals grown from Cd solvent by the travelling heater method. The photoluminescence spectra and activation energy of 74 +/- 2 meV derived from the temperature-dependent Hall effect are consistent with AsTe as the dominant acceptor. Doping in the 10^16 to 10^17/cm^3 range is achieved for measured As concentrations between 10^16 and 10^20/cm^3 with the highest doping efficiency of 40% occurring near 10^17 As/cm^3. We observe persistent photoconductivity, a hallmark of light-induced metastable configuration changes consistent with AX behavior. Additionally, quenching experiments reveal at least two mechanisms of increased p-type doping in the dark, one decaying over 2-3 weeks and the other persisting for at least 2 months. These results provide essential insights for the application of As-doped CdTe in thin film solar cells.

  4. Study of pure and L-tartaric acid doped ammonium dihydrogen phosphate single crystals: A novel nonlinear optical non-centrosymmetric crystal

    Energy Technology Data Exchange (ETDEWEB)

    Hasmuddin, Mohd, E-mail: mhasmu@gmail.com [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Singh, Preeti [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Shkir, Mohd [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Department of Physics, School of Science, King Khalid University, P.O. Box. 9004, Abha 61413 (Saudi Arabia); Abdullah, M.M. [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India); Promising Centre for Sensors and Electronic Devices (PCSED), Department of Physics, College of Science and Arts, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Vijayan, N. [CSIR – National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110 012 (India); Ganesh, V. [Department of Physics, Kakatiya University, Warangal, Andhra Pradesh 506009 (India); Wahab, M.A., E-mail: mwahab@jmi.ac.in [Crystal Growth Laboratory, Dept. of Physics, Jamia Millia Islamia, New Delhi 110 025 (India)

    2014-04-01

    Single crystals of pure and L-tartaric acid (LTA) C{sub 4}H{sub 6}O{sub 6} doped ammonium dihydrogen phosphate (ADP) (NH{sub 4}) H{sub 2}PO{sub 4} were grown by slow evaporation solution technique (SEST) at ambient conditions. Powder X-ray diffraction (PXRD) analysis was carried out to confirm the crystal structure and no additional phase was observed due to doping except a systematic variation in peak intensities. Fourier transform infrared spectral analysis was done to examine the presence of various functional groups in the grown crystals. UV–VIS–NIR spectroscopic analysis was carried out to see the change in optical transparency of pure ADP and crystals due to LTA with different doping concentrations. Second harmonic generation (SHG) efficiency measurement was done to examine the enhancement in the nonlinear optical characteristics of the grown crystals. The effect of LTA dopant on crystal morphology, thermal and mechanical properties of ADP have also been presented in this paper. The above studies reveal the effect of incorporation of LTA into the lattice of ADP crystals. - Highlights: • LTA doped ADP crystals were grown for the first time. • Optical transmission was found to be higher at 1 mol% LTA doping. • SHG was found to be enhanced nonlinearly due to doping. • Thermal stability was found to higher at 1 mol% LTA doping. • Hardness was found to be increases with doping.

  5. Luminescence of devitrificated non-doped and Eu,Dy and Tm doped wollastonite crystal in glass; Luminescence de cristaux de devitrivication de wollastonite dans des verres non dopes et dopes en Eu,Dy et Tm

    Energy Technology Data Exchange (ETDEWEB)

    El Marraki, A.; Schvoerer, M.; Bechtel, F. [Univ. Michel de Montaigne-Bordeaux 3, Pessac (France). Centre de Recherche en Phys. Appliquee a l' Archeologie

    2000-10-16

    Wollastonite crystals (CaSiO{sub 3}), ''pure'' or doped with rare earth ions, were grown by a devitrification process of a ternary SiO{sub 2}-Na{sub 2}O-CaO glass. The nature of point defects in these crystals was studied. Concerning the non-doped crystals, two trap centers were revealed by thermoluminescence (TL) and identified by electron spin resonance (ESR) using preheating experiments: one is a hole center HC{sub 1} and the other one an electron center whose main characteristic feature is g = 2.0020. Cathodoluminescence (CL) studies showed an important emission band considered as intrinsic. As for the doped crystals (Eu, Dy, Tm), most CL emission bands were identified. With TL, it is shown that Eu acts in wollastonite crystals as an electron trap and also as an emission centre. (orig.)

  6. Efficient removal of Cr(VI) from wastewater under sunlight by Fe(II)-doped TiO{sub 2} spherical shell

    Energy Technology Data Exchange (ETDEWEB)

    Xu, S.C., E-mail: scxu@issp.ac.cn [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Pan, S.S.; Xu, Y.; Luo, Y.Y.; Zhang, Y.X. [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Li, G.H., E-mail: ghli@issp.ac.cn [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China)

    2015-02-11

    Graphical abstract: - Highlights: • Fe(II)/TiO{sub 2} spherical shell catalyst was synthesized by hydrothermal method. • Cr(VI) removal effectiveness reaches to 99.99% with 102.3 ppm initial content. • TiO{sub 2}, Fe(II) and Fe{sup 0} atom synergistically contribute to Cr(VI) reduction. • Bulk Fe(II) doping enhance electron transference between TiO{sub 2} and Fe(II) ions. • Special spherical shell structure enhances the utilization of sunlight. - Abstract: Fe(II)-doped TiO{sub 2} spherical shell catalyst was synthesized by one-pot hydrothermal method. The photocatalytic removal of Cr(VI) from plating wastewater under sunlight of the catalyst was demonstrated. It was found that the removal effectiveness of about 99.99% for initial Cr(VI) concentration of 102.3 ppm and 99.01% for 153.4 ppm under 3 h sunlight irradiation is realized. The Fe(II) ions serve not only as reducing agents for reducing the Cr(VI) to Cr(III) but also as an intermedium of a two-step reduction, in which the TiO{sub 2} photoreduces the Fe(II) ions to Fe atoms firstly, and then the Fe atoms reduce the Cr(VI) to Cr(III). The improved photocatalytic activity of the catalyst is considered due to the synergistic effect of a multi reducing process by Fe(II) doping. The extended optical response and effectively utilization of sunlight of the special spherical-shell-like morphology also contribute to the enhanced photocatalytic activity.

  7. Synthesis and properties of zirconium-doped RbTiOPO{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Agapova, E. I.; Voronkova, V. I., E-mail: voronk@polly.phys.msu.ru; Kharitonova, E. P.; Leont' eva, I. N.; Stefanovich, S. Yu. [Moscow State University (Russian Federation); Sorokina, N. I.; Dudka, A. P. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Alekseeva, O. A. [Moscow State University (Russian Federation); Kononkova, N. N. [Russian Academy of Sciences, Vernadsky Institute of Geochemistry and Analytical Chemistry (Russian Federation)

    2008-03-15

    Single crystals of the solid solutions RbTi{sub 1-x}Zr{sub x}OPO{sub 4} (0.015 < x < 0.034) were grown and their physical properties were studied. In the presence of zirconium in the crystals with the maximum content x = 0.034, the ferroelectric phase transition and the high-temperature transition from the orthorhombic to the cubic phase are shifted to lower temperatures by 100 and 50 Degree-Sign C, respectively. In the temperature range from 700 Degree-Sign C to room temperature, the conductivity of doped crystals decreases compared to that of the undoped crystals. It is of particular interest that the intensity of the second-harmonic generation of the doped crystals is substantially higher than that of RbTiOPO{sub 4}.

  8. Electrically tunable Yb-doped fiber laser based on a liquid crystal photonic bandgap fiber device.

    Science.gov (United States)

    Olausson, Christina B; Scolari, Lara; Wei, Lei; Noordegraaf, Danny; Weirich, Johannes; Alkeskjold, Thomas T; Hansen, Kim P; Bjarklev, Anders

    2010-04-12

    We demonstrate electrical tunability of a fiber laser using a liquid crystal photonic bandgap fiber. Tuning of the laser is achieved by combining the wavelength filtering effect of a tunable liquid crystal photonic bandgap fiber device with an ytterbium-doped photonic crystal fiber. We fabricate an all-spliced laser cavity based on the liquid crystal photonic bandgap fiber mounted on a silicon assembly, a pump/signal combiner with single-mode signal feed-through and an ytterbium-doped photonic crystal fiber. The laser cavity produces a single-mode output and is tuned in the range 1040-1065 nm by applying an electric field to the silicon assembly.

  9. Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Nidhi [Department of Electronics, SGTB Khalsa College, University of Delhi, Delhi-110007 (India); Goel, Neeti; Singh, B.K.; Gupta, M.K. [Crystal Lab, Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Kumar, Binay, E-mail: bkumar@physics.du.ac.in [Crystal Lab, Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

    2012-06-15

    Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (T{sub c}) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications. - Graphical abstract: Dye doping in TGS crystal resulted in hourglass morphology, increased hyper-luminescence intensity, improved T{sub c} and figure of merit. Highlights: Black-Right-Pointing-Pointer Amaranth dye doping in TGS crystals resulted in hourglass morphology. Black-Right-Pointing-Pointer Doping resulted in enhancement of Curie temperature from 49 to 53 Degree-Sign C. Black-Right-Pointing-Pointer Low cut off (230 nm) and wider transmittance window observed. Black-Right-Pointing-Pointer Strong hyper-luminescent emission bands at 350 and 375 nm were observed. Black-Right-Pointing-Pointer High and uniform figure of merit in ferroelectric phase was obtained.

  10. Electron Spin Resonance investigation of undoped and Li-doped CdWO_4 scintillator crystals

    OpenAIRE

    Laguta, V. V.; Nikl, M.; Buryi, M.

    2009-01-01

    Electron spin resonance (ESR) spectra of Fe3+ and Mn2+ ions have been studied in the nominally pure and 0.05% Li-doped single crystals of CdWO4. The zero-field splitting parameters are determined with a high precision for both of the impurities. The result suggest that the Li-doping leads to the increase of the ionic charge of iron from 3+ to 4+ and of manganese, from 1+ to 2+.

  11. Anomalous doping of a molecular crystal monitored with confocal fluorescence microscopy: Terrylene in a p-terphenyl crystal

    Science.gov (United States)

    Białkowska, Magda; Deperasińska, Irena; Makarewicz, Artur; Kozankiewicz, Bolesław

    2017-09-01

    Highly terrylene doped single crystals of p-terphenyl, obtained by co-sublimation of both components, showed bright spots in the confocal fluorescence images. Polarization of the fluorescence excitation spectra, blinking and bleaching, and saturation behavior allowed us to attribute them to single molecules of terrylene anomalously embedded between two neighbor layers of the host crystal, in the (a,b) plane. Such an orientation of terrylene molecules results in much more efficient absorption and collection of the fluorescence photons than in the case of previously investigated molecules embedded in the substitution sites. The above conclusion was supported by quantum chemistry calculations. We postulate that the kind of doping considered in this work should be possible in other molecular crystals where the host molecules are organized in a herringbone pattern.

  12. Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wen, E-mail: wzl0025@auburn.edu [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871 (China); Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); Sun, Weiling [The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871 (China); Borthwick, Alistair G.L. [School of Engineering, The University of Edinburgh, The King’s Buildings, Edinburgh EH9 3JL (United Kingdom); Wang, Ting [The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871 (China); Li, Fan [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); Guan, Yidong, E-mail: yidongguan@nuist.edu.cn [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States)

    2016-11-05

    Highlights: • TNS composed of anatase and titanate synthesized via a facile one-step method. • Cr(VI) and 4-CP can be simultaneously removed by TNS through photocatalysis. • Photocatalytic efficiencies of Cr(VI) and 4-CP greatly enhanced when coexisting. • Synergetic promotion effect occurs due to separation of electron-hole pairs. • Autosynchronous doping after Cr(III) adsorption leads to narrowed energy gap. - Abstract: Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k{sub 1}) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120 min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment.

  13. Enhanced carrier mobility in Si nano-crystals via nanoscale phosphorus doping

    Science.gov (United States)

    Shan, Dan; Ji, Yang; Li, Dongke; Xu, Jun; Qian, Mingqing; Xu, Ling; Chen, Kunji

    2017-12-01

    Usually, the conductivity of semiconductor can be increased after phosphorus (P) doping but the electron mobility will be obviously reduced due to the strong impurity scattering. Here, we report a novel phenomenon that the carrier mobility in Si nano-crystals is significantly enhanced after nanoscale P doping. It is found that the electron mobility reaches to 30.3 cm2/V s, which is improved by one order of magnitude compared with that of un-doped one (1.6 cm2/V s), while the room temperature conductivity is as high as 1.5 × 103 S/cm by appropriately P doping. The clear experimental evidences are present to demonstrate that both the reduction of barrier height of grain boundaries and the surface defects states due to P doping improve the corresponding electron mobility in nano-crystalline Si films.

  14. Fabrication of Microcapsules for Dye-Doped Polymer-Dispersed Liquid Crystal-Based Smart Windows.

    Science.gov (United States)

    Kim, Mingyun; Park, Kyun Joo; Seok, Seunghwan; Ok, Jong Min; Jung, Hee-Tae; Choe, Jaehoon; Kim, Do Hyun

    2015-08-19

    A dye-doped polymer-dispersed liquid crystal (PDLC) is an attractive material for application in smart windows. Smart windows using a PDLC can be operated simply and have a high contrast ratio compared to those of other devices that employed photochromic or thermochromic material. However, in conventional dye-doped PDLC methods, dye contamination can cause problems and has a limited degree of commercialization of electric smart windows. Here, we report on an approach to resolve dye-related problems by encapsulating the dye in monodispersed capsules. By encapsulation, a fabricated dye-doped PDLC had a contrast ratio of >120 at 600 nm. This fabrication method of encapsulating the dye in a core-shell structured microcapsule in a dye-doped PDLC device provides a practical platform for dye-doped PDLC-based smart windows.

  15. Superconductivity in Sm-doped CaFe2As2 single crystals

    Science.gov (United States)

    Dong-Yun, Chen; Bin-Bin, Ruan; Jia, Yu; Qi, Guo; Xiao-Chuan, Wang; Qing-Ge, Mu; Bo-Jin, Pan; Tong, Liu; Gen-Fu, Chen; Zhi-An, Ren

    2016-06-01

    In this article, the Sm-doping single crystals Ca1 - x Sm x Fe2As2 (x = 0 ˜ 0.2) were prepared by the CaAs flux method, and followed by a rapid quenching treatment after the high temperature growth. The samples were characterized by structural, resistive, and magnetic measurements. The successful Sm-substitution was revealed by the reduction of the lattice parameter c, due to the smaller ionic radius of Sm3+ than Ca2+. Superconductivity was observed in all samples with onset T c varying from 27 K to 44 K upon Sm-doping. The coexistence of a collapsed phase transition and the superconducting transition was found for the lower Sm-doping samples. Zero resistivity and substantial superconducting volume fraction only happen in higher Sm-doping crystals with the nominal x > 0.10. The doping dependences of the c-axis length and onset T c were summarized. The high-T c observed in these quenched crystals may be attributed to simultaneous tuning of electron carriers doping and strain effect caused by lattice reduction of Sm-substitution. Project supported by the National Natural Science Foundation of China (Grant No. 11474339), the National Basic Research Program of China (Grant Nos. 2010CB923000 and 2011CBA00100), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07020100).

  16. Electrical Properties of Zn-Phthalocyanine and Poly (3-hexylthiophene Doped Nematic Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Y. Karakuş

    2011-01-01

    Full Text Available An E7 coded nematic liquid crystal was doped with zinc phthalocyanine and poly (3-hexylthiophene. A variety of properties including relaxation time, absorption coefficient, and critical frequency of this doped system were investigated using impedance spectroscopy. The doped systems displayed increased absorption coefficients in the range 0.22–0.55 and relaxation times from 5.05×10−7 s to 3.59×10−6 s with a decrease in the critical frequency from 3.54 MHz to 2.048 MHz.

  17. Ferromagnetism in CVT Grown Tungsten Diselenide Single Crystals with Nickel Doping.

    Science.gov (United States)

    Habib, Muhammad; Muhammad, Zahir; Khan, Rashid; Wu, Chuan Qiang; Rehman, Zia Ur; Zhou, Yu; Liu, Hengjie; Song, Li

    2018-01-09

    Two dimensional (2D) single crystal layered transition materials have got extensive considerations owing to their interesting magnetic properties originated from their lattices and strong spin-orbit coupling, which make them of vital importance for spintronic application. Herein, we present synthesis of a highly crystalline tungsten diselenide layered single crystals grown by chemical vapor transport technique and doped with nickel (Ni) to tailor its magnetic properties. The pristine WSe2 single crystal and Ni doped one were characterized and analyzed for magnetic properties from both experimental and computational aspects. It is found that the magnetic behavior of 2D layered WSe2crystal changes from diamagnetic to ferromagnetic after Ni doping at all tested temperatures. Moreover, first principle density functional theory (DFT) calculations further confirmed the origin of room temperature ferromagnetism of Ni doped WSe2, where d-orbitals of doped Ni atom promotes the spin moment and thus largely contributes the magnetism change in the 2D layered material. © 2018 IOP Publishing Ltd.

  18. Interfacing superconducting qubits and telecom photons via a rare-earth-doped crystal.

    Science.gov (United States)

    O'Brien, Christopher; Lauk, Nikolai; Blum, Susanne; Morigi, Giovanna; Fleischhauer, Michael

    2014-08-08

    We propose a scheme to couple short single photon pulses to superconducting qubits. An optical photon is first absorbed into an inhomogeneously broadened rare-earth doped crystal using controlled reversible inhomogeneous broadening. The optical excitation is then mapped into a spin state using a series of π pulses and subsequently transferred to a superconducting qubit via a microwave cavity. To overcome the intrinsic and engineered inhomogeneous broadening of the optical and spin transitions in rare-earth doped crystals, we make use of a special transfer protocol using staggered π pulses. We predict total transfer efficiencies on the order of 90%.

  19. Optical bistability in erbium-doped yttrium aluminum garnet crystal combined with a laser diode.

    Science.gov (United States)

    Maeda, Y

    1994-01-10

    Optical bistability was observed in a simple structure of an injection laser diode combined with an erbium-doped yttrium aluminum garnet crystal. Since a hysteresis characteristic exists in the relationship between the wavelength and the injection current of a laser diode, an optical memory function capable of holding the output status is confirmed. In addition, an optical signal inversion was caused by the decrease of transmission of the erbium-doped yttrium aluminum garnet crystal against the red shift (principally mode hopping) of the laser diode. It is suggested that the switching time of this phenomenon is the time necessary for a mode hopping by current injection.

  20. The r22 electro-optic coefficients in indium-doped congruent lithium-niobate crystals

    Science.gov (United States)

    Abarkan, Mustapha; Danielyan, Anush; Sewastianow, Sasha; Aillerie, Michel; Théofanous, Nicéphore; Kostritskii, Sergey; Kokanyan, Edvard

    2017-07-01

    The high- and low- frequency electro-optic coefficients r222 of In-doped lithium niobate (LN) and the corresponding dielectric permittivity as well, have been experimentally determined and compared with the results obtained in undoped congruent LN crystals. Compared to pure congruent lithium niobate, a low acoustic contribution of the electro-optic and dielectric properties are originally found in indium (In)-doped congruent lithium niobate (LN:In) crystals in the low indium concentration range [0.12-1.7 mol%]. All reported results confirm that the LN:In is a very promising candidate for several non-linear devices as Pockels cells for laser Q-switching.

  1. PHOTOCATALYTIC ACTIVITIES of Ag+ DOPED ZIF-8 and ZIF-L CRYSTALS

    Directory of Open Access Journals (Sweden)

    Berna Topuz

    2016-09-01

    Full Text Available Photocatalysis is expected to contribute to the solution of environmental problems such as water and air pollution in the near future. The design of photocatalysts with high electron-hole generation rates, high surface areas and high light absorption capacities is crucial in producing sustainable and cost-effective photocatalytic processes. Titania, zirconia, copper oxide, zinc oxide, iron oxide are widely used photocatalysts which have good light absorption capacities with moderate surface areas depending on the synthesis conditions. In the last decade metal organic frameworks (MOFs have been used in photocatalytic applications due to their very high surface areas up to 1000s of m2/g and adequate light absorption capacities. In this study zeolitic imidazolate framework (ZIF based MOF photocatalytsts were prepared and the effect of silver (Ag doping on the photocatalytic activity of ZIF-8 and ZIF-L crystals was investigated. Ag doped ZIF-8 and ZIF-L crystals were prepared and their activities in the photocatalytic removal of methylene blue (MB dye under UV irradiation were determined for the first time in the literature. Doped ZIF-8 and ZIF-L crystals showed better photocatalytic activities compared to the undoped crystals. 100% of MB was removed with 5 mole% Ag+ doped ZIF-8 in 40 min. The photocatalytic activity decreased beyond 5% doping level since Ag+ ions may have segregated due to a possible solid state solubility limit of Ag+ ions in the crystal lattice of ZIF-8. ZIF-L crystals possessed lower photocatalytic activities compared to ZIF-8 crystals.

  2. Improvement of several properties of lead tungstate crystals with different doping ions

    CERN Document Server

    Auffray, Etiennette; Baccaro, Stefania; Cecilia, Angelica; Dafinei, Ioan; Diemoz, Marcella; Jarolímek, O; Korzhik, Mikhail; Lecoq, Paul; Nikl, M

    1998-01-01

    A very good radiation resistance of Lead Tungstate crystals is mandatory for their use in the high precision electromagnetic calorimeter of the CMS experiment at LHC. Since the beginning of 1996 we have organised systematic investigations of the parameters influencing the radiation hardness of this crystal. Two classes of parameters have been particularly studied, the first one related to the control of the stoichiometry and structure associated defects, the second one connected with the suppression and the charge compensation of existing defects with different kinds of doping ions. This paper reports about the second part of this study and complements a first paper where the role of the stoichiometry was already discussed. Results of tests are given on a significant statistical sample of full size crystals ( 23cm) which show a considerable improvement in the optical properties and the radiation resistance of appropriately doped crystals.

  3. Measurement of helical twisting power based on axially symmetrical photo-aligned dye-doped liquid crystal film.

    Science.gov (United States)

    Ko, Shih-Wei; Huang, Shu-Hao; Fuh, Andy Y-G; Lin, Tsung-Hsien

    2009-08-31

    This investigation demonstrates a simple but accurate method for measuring the helical twisting power of chiral doped liquid crystals using axially symmetrical photo-alignment in azo dye-doped liquid crystal films. As reported in our previous paper, a reversed twist effect produces a disclination line in photo-aligned axially symmetrical liquid crystal films. The pitch and helical twisting power can be obtained by measuring the rotation angle of the disclination line in chrial doped liquid crystal. This method is independent of cell gap and provide an error below 0.5%.

  4. Optical vibronic spectra of aggregates in Eu sup 2 sup + -doped KCl and KBr crystals

    CERN Document Server

    Pérez, S R; Aceves, R; Rodríguez, R; Barboza, M

    2003-01-01

    The vibronic structure on the optical absorption, emission, and excitation spectra of aggregates in Eu sup 2 sup + -doped KCl and KBr crystals has been obtained. The crystals were annealed at 435 K. During the aggregation process, four groups of narrow bands were found in KCl: Eu sup 2 sup + and two in KBr: Eu sup 2 sup + ,which were considered as the signature of different Eu sup 2 sup + -ion aggregated phases. The vibration frequency for each group is very similar. (Author)

  5. Two-dimensional coherent random laser in photonic crystal fiber with dye-doped nematic liquid crystal.

    Science.gov (United States)

    Nagai, Yusuke; Shao-Chieh, Chen; Kajikawa, Kotaro

    2017-11-10

    A random laser of a photonic crystal fiber (PCF) with holes filled with laser dye-doped nematic liquid crystal (NLC) is reported. When the excitation polarization was along the PCF axis, the measured laser threshold was 80  μJ/mm(2) per pulse, which is much lower than the previously reported random laser of PCF filled with laser dye-doped organic solvent. This low threshold is due to the high refractive index of the NLC, which produces a greater scattering efficiency. In contrast, when the excitation polarization is perpendicular to the PCF axis, the threshold was much higher or the laser oscillation was absent. This is because of the lower refractive index of the NLC for the perpendicular polarization. The laser oscillation was absent in the isotropic phase because of a low fluorescence efficiency at high temperatures.

  6. Highly Nd3+-doped Y3Al5O12 crystal fiber tip for laser thermotherapy

    Science.gov (United States)

    Tong, Limin; Lou, Jingyi; Xu, Yunfei; Luo, Qingming; Shen, Nan; Mazur, Eric

    2002-07-01

    Based on phonon relaxation, a 12-at. % neodymium-doped YAG (Y3Al5O12) crystal fiber tip has been developed for photothermal conversion. The near-cylindrical tip, with an average diameter of 0.68 mm and a length of 1.8 mm, is fabricated on a 0.65-mm-thick 220-mm-long pure YAG single-crystal fiber by laser-heated growth. Pumped by an 810-nm wavelength diode laser with a pump power of less than 2 W, the temperatures of the tip reach 725 degC in air, 78 degC in egg white, and 79 degC in porcine liver, with acceptable reproducibilities and thermal response times. The photothermal conversion efficiency of the doped tip is approximately 89%, and the high stability of the tip is also proved. Experimental results show that the doped fiber tip is promising for laser thermotherapy applications.

  7. Guiding and amplification properties of rod-type photonic crystal fibers with sectioned core doping

    DEFF Research Database (Denmark)

    Selleri, Stefano; Poli, Federica; Passaro, Davide

    2009-01-01

    Rod-type photonic crystal fibers are large mode area double-cladding fibers with an outer diameter of few millimeters which can provide important advantages for high-power lasers and amplifiers. Numerical studies have recently demonstrated the guidance of higher-order modes in these fibers, which...... can worsen the output beam quality of lasers and amplifiers. In the present analysis a sectioned core doping has been proposed for Yb-doped rod-type photonic crystal fibers, with the aim to improve the higher-order mode suppression. A full-vector modal solver based on the finite element method has...... been applied to properly design the low refractive index ring in the fiber core, which can provide an increase of the differential overlap between the fundamental and the higher-order mode. Then, the gain competition among the guided modes along the Yb-doped rod-type fibers has been investigated...

  8. Ion transport in Au doped/undoped KDP crystals with KI/NaI as ...

    Indian Academy of Sciences (India)

    Unknown

    meter (Hewlett–Packard) was used to measure capaci- tance (C) of the sample as a function of frequency. 2.2 Conductivity measurement. Both undoped and Au+ doped crystals were subjected to γ-irradiation using 60Co source to a dosage 5 Mrads. The conductivity measurements were carried out for both irradiated and ...

  9. Single crystal EPR studies of Mn (II) doped into zinc ammonium ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 62; Issue 1. Single crystal EPR studies of Mn(II) doped into zinc ammonium phosphate hexahydrate (ZnNH4PO4⋅6H2O): A case of interstitial site for bio-mineral analogue. H Anandalakshmi K Velavan I Sougandi Venkatesan P Sambasiva Rao. Research Articles ...

  10. single crystal EPR studies of Mn(II) doped into zinc ammonium ...

    Indian Academy of Sciences (India)

    -sulphato-aquotris(imidazole) cadmium(II), the paramagnetic ion enters substi- tutionally into the host lattice giving rise to two magnetically inequivalent sites. [9]. single crystal EPR study of Mn(II)-doped magnesium bis(hydrogen maleate) hexahydrate confirms that the impurity ion not only occupies the magnesium site.

  11. Single crystal EPR study of VO (II)-doped cadmium potassium ...

    Indian Academy of Sciences (India)

    Single crystal EPR studies of VO(II)-doped cadmium potassium phosphate hexahydrate (CPPH) have been carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice only substitutionally in place of Cd(II). Spin Hamiltonian ...

  12. Growth and characterization of air annealing Mn-doped YAG:Ce single crystal for LED

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Zhong, Jiasong [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Zhao, Yinsheng [Pan Asia Technical Automotive Center Co. Ltd., Shanghai 201201 (China); Zhao, Binyu [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); Dong, Yongjun [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China); Zhang, Zhimin; Chen, Zhaoping; Liu, Bingfeng [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China)

    2012-11-25

    Highlights: Black-Right-Pointing-Pointer The YAG:Ce,Mn single crystal was well synthesized by the Czochralski (CZ) method. Black-Right-Pointing-Pointer The emission intensity of the sample has been influenced after annealing. Black-Right-Pointing-Pointer Annealed in the air at 1200 Degree-Sign C was the most optimal annealing condition. Black-Right-Pointing-Pointer The single crystal could be used in the white light LED which emitted by blue light. - Abstract: The growth of Mn-doped YAG:Ce (yttrium aluminum garnet doped cerium) single crystal by the Czochralski (CZ) method and the characterization of its spectroscopy and color-electric parameters are presented. The absorption spectra indicate that the crystal absorbed highly in the 300-500 nm wavelength range. The emission spectrum of the crystal consists of a peak around 538 nm when excited by 460 nm blue light, which prove the YAG:Ce,Mn single crystal could be used in the white light emitting doides (LED). The different charges of Mn ions have different luminescence properties, and the air annealing process for the single crystal would change the concentration of Mn ions with different charges, which could influence the emission intensity of the single crystal.

  13. Growth and characterization of Sm3+ doped cerium oxalate single crystals

    Directory of Open Access Journals (Sweden)

    Minu Mary C

    2016-07-01

    Full Text Available Single crystals of Sm3+ doped cerium oxalate decahydrate were synthesized using single diffusion gel technique and the conditions influencing the size, morphology, nucleation density and quality of the crystals were optimized. Highly transparent single crystals of average size 3 mm × 2 mm × 1 mm with well-defined hexagonal morphology were grown during a time period of two weeks. X-ray powder diffraction analysis revealed that the grown crystals crystallize in the monoclinic system with space group P21/c as identical with the pure cerium oxalate. The various functional groups of the oxalate ligand and the water of crystallization were identified by Fourier transform infrared spectroscopy. The photoluminescence spectrum of the Sm3+ doped cerium oxalate indicated that the Sm3+ ions are optically active in the cerium oxalate matrix. The crystal has a strong and efficient orange red emission with a wavelength peak at 595 nm and hence can be effectively used for optical amplification. Microhardness measurements of the crystal revealed that they belong to the soft material category.

  14. Growth and characterization of pure and KCl doped zinc thiourea chloride (ZTC) single crystals.

    Science.gov (United States)

    Ruby Nirmala, L; Thomas Joseph Prakash, J

    2013-02-01

    Potassium Chloride (KCl) as an additive is added into zinc thiourea chloride solution in a small amount (1M%) by the method of slow evaporation solution growth technique at room temperature to get a new crystal. Due to the doping of the impurities on the crystals, remarkable changes in the physical properties were obtained. The grown crystals have been subjected to different instrumentation methods. The incorporation of the amount of potassium and zinc in the crystal lattices has been determined by AAS method. The lattice dimensions have been identified from single crystal X-ray diffraction measurements. The presence of functional group for the grown crystals has been identified by FTIR analysis. The optical, thermal and mechanical behaviors have been assessed by UV-Vis, TG/DTA and Vickers hardness methods respectively. The presence of dislocations of atoms has been identified by etching studies. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. An "on-off-on" fluorescent nanoprobe for recognition of chromium(VI) and ascorbic acid based on phosphorus/nitrogen dual-doped carbon quantum dot.

    Science.gov (United States)

    Gong, Xiaojuan; Liu, Yang; Yang, Zhenhua; Shuang, Shaomin; Zhang, Zeyu; Dong, Chuan

    2017-05-22

    Chromium (VI) [Cr(VI)] is a harsh environmental contaminates and has been proved to be highly toxic, carcinogenic and mutagenic. Therefore, developing an inexpensive, good selective and highly sensitive nanoprobe for the detection of Cr(VI) is in urgent demand. Recently, the highly fluorescent carbon quantum dots (CQDs) have been successfully utilized as efficient fluorescent nanoprobes for the detection of ions, pH and molecular substances. In this work, an "on-off" fluorescence phosphorus/nitrogen dual-doped CQDs (PNCQDs) probe was developed for the determination of Cr(VI) based on inner filter effect (IFE). The proposed PNCQDs nanoprobe shows its distinct merits of simplicity, convenience, fast implementation, good selectivity and high sensitivity towards Cr(VI), allowing its potential application in the determination of Cr(VI) in environment and biosystem. In addition, the chelation effect of the functional groups in reductant and Cr(VI), and the easy-conversion of Cr(VI) to reduced states (i.e. Cr(III) and Cr(0)) by reductants makes the minimization of IFE with a concomitant recovery of PNCQDs fluorescence possible. Hence, the PNCQDs/Cr(VI) hybrid was used as an "off-on" fluorescence probe for sensing ascorbic acid (AA), which is a model reductant. For the detection of Cr(VI), the linear range and the limit of detection achieved were 1.5-30 μmol/L and 23 nmol/L, respectively. For the detection of AA, the linear range and the limit of detection obtained were 5.0-200 μmol/L and 1.35 μmol/L, respectively. The as-constructed "on-off-on" PNCQDs fluorescent nanoprobe was successfully applied for detecting Cr(VI) and AA in biosystem. Furthermore, the as-constructed fluorescent sensing system was successfully applied to the analyses of AA in fresh fruits and in commercial fruit juices with satisfactory results. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Growth and characterization of undoped and Mn doped lead-free piezoelectric NBT–KBT single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Babu, G. Anandha, E-mail: anandcgc@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Subramaniyan, Raja R. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Bhaumik, Indranil [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Ganesamoorthy, S. [X-ray Scattering and Crystal Growth Section, Condensed Matter Physics Division, Materials Science Group, IGCAR, Kalpakkam 603102 (India); Ramasamy, P. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Gupta, P.K. [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

    2014-05-01

    Highlights: • Single crystals of undoped and Mn doped NKBT crystals are grown by spontaneous nucleation. • Temperature and frequency dependent dielectric constant and loss are measured. • Dielectric constant has increased and the loss has reduced on Mn doped NKBT. • Concentration of oxygen vacancies has been reduced in Mn doped NKBT. • The activation energy for undoped and Mn doped NKBT are calculated. - Abstract: Lead-free piezoelectric single crystals of undoped and 1 wt% Mn doped 0.80 Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}–0.20 K{sub 0.5}Bi{sub 0.5}TiO{sub 3} (NKBT) was grown using self-flux. Powder X-ray diffraction analysis revealed that the grown crystals belong to tetragonal system at room temperature. The lattice strain was calculated from Williamson Hall relation for undoped and Mn doped NKBT crystals. A significant change is observed in dielectric behavior of Mn doped NKBT when compared to undoped sample. The diffuseness increased substantially on Mn doped NKBT which masked the ferroelectric to antiferroelectric transition in the dielectric constant plot. The AC impedance study revealed that the conduction is governed by the singly ionized oxygen vacancy. Further, the decrease in the conductivity on Mn doping suggests that Mn replaces the Bi vacancy, which reduces the oxygen vacancy.

  17. Thermoluminescence characteristics of Sm doped NaYF4 crystals

    Indian Academy of Sciences (India)

    2006-06-28

    Jun 28, 2006 ... temperature peaks also vary in relation to the Sm3+ con- centration in NaYF4. This indicates a probable change in the trap structure of NaYF4 with the doping concentration of samarium impurity. This observation is in conformity with the earlier studies (Narasimha Reddy et al 1987;. Gopal Reddy et al 1988; ...

  18. Hole conduction in pure and doped lead bromide crystals

    NARCIS (Netherlands)

    Schoonman, J.

    The conductivity of pure and doped lead bromide was measured in a bromine atmosphere in the temperature region 25–200°C. The defect chemistry of nonstoichiometric lead bromide is presented. The hole mobility was derived from the time dependent change in the conductivity after admission/removal of

  19. Radiation defects in oxide crystals doped with rare earth ions

    NARCIS (Netherlands)

    Matkovskii, A; Durygin, A; Suchocki, A; Sugak, D; Wallrafen, F; Vakiv, M

    1999-01-01

    The nature of stable and transient color centers in Y3Al5O12, Gd3Ca5O12, YAlO3 and LiNbO3 crystals is studied. The color centers are created by various types of irradiation. The effect of irradiation on crystal optical properties in visible and ultraviolet range is presented.

  20. Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping.

    Science.gov (United States)

    Liu, Wen; Sun, Weiling; Borthwick, Alistair G L; Wang, Ting; Li, Fan; Guan, Yidong

    2016-11-05

    Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k1) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Nonmechanical Infrared Beam Steering Using Blue Addressed Quantum Dot Doped Liquid Crystal Grating

    Science.gov (United States)

    Wang, Xiangru; Huang, Xiaoping; Huang, Ziqiang; Wu, Liang; Shang, Jiyang; Qiu, Qi; Wu, Shuanghong

    2017-01-01

    We present a scheme of nonmechanical laser beam steering using ZnS/InP quantum dots doping nematic liquid crystal as the optical recording film. Because of its internal electric field generated by blue laser-induced charge carrier distribution, liquid crystal molecules are reoriented to form a phase grating which make the incident angle steer to the angle as we desire. Being a nonmechanical programmable laser beam steering, the anisotropy of the relative permittivity tensor and blue laser-induced electric carriers play a significant effect in determining the reorientable liquid crystal molecule and reconfigurable phase modulation of the gratings, that determines the steering angle and steering efficiency.

  2. Rare-Earth Doped Photonic Crystal Fibre Lasers and Amplifiers

    DEFF Research Database (Denmark)

    Hougaard, Kristian G.

    2005-01-01

    In this thesis, a theoretical and numerical study of the use of rare-earthdoped photonic crystal fibres as optical amplifiers and lasers, has been performed. Photonic crystal fibres or microstructured optical fibres is a new kind of optical fibre in which the cladding region typically consist....... Their novel properties allow for design of optical fibre amplifiers and fibre lasers with superior performance, compared to solutions based on conventional fibres. The primary applications considered are high efficiency fibre amplifiers based on index guiding photonic crystal fibres, and cladding pumped...

  3. Efficient crystal radiation detectors based on Tb{sup 3+}-doped fluorides for radioluminescence dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Marcazzo, J [IFAS, Facultad de Ciencias Exactas, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, 7000 Tandil (Argentina); Henniger, J [Institut fur Kern- und Teilchenphysik, Zellescher Weg 19, 01069 Dresden (Germany); Khaidukov, N M [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 31 Leninsky Prospect, 119991 Moscow (Russian Federation); Makhov, V N [Lebedev Physical Institute, Russian Academy of Sciences, Leninsky Prospect 53, 119991 Moscow (Russian Federation); Caselli, E [IFAS, Facultad de Ciencias Exactas, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, 7000 Tandil (Argentina); Santiago, M [IFAS, Facultad de Ciencias Exactas, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, 7000 Tandil (Argentina)

    2007-09-07

    The luminescence properties of Tb{sup 3+}-doped fluoride crystals under excitation with ionizing irradiation have been studied in order to assess the feasibility of using them as crystal detectors for in vivo radiotherapy dosimetry. In particular, it has been found that the radioluminescence intensity from both CsY{sub 2}F{sub 7} and CsGd{sub 2}F{sub 7} doped with 15 at% Tb{sup 3+} is almost six times that from the commercial Al{sub 2}O{sub 3} : C detector. The spectral composition of emitted light has been analysed in order to determine the function of the Tb{sup 3+} activator ion during ionizing radiation-induced luminescence. The thermally stimulated luminescence of the crystals has also been investigated.

  4. Crystallization Mechanism and Phase Transition Properties of W-doped VO2 Synthesized by Hydrothermal Method

    Directory of Open Access Journals (Sweden)

    LI Yao

    2017-11-01

    Full Text Available VO2 sol was firstly prepared using vanadyl sulfate as a vanadium source by precipitation-peptization method. Then tungsten(W doping vanadium dioxide(W-VO2 was prepared by hydrothermal crystallization of prepared sol with the presence of ammonium metatungstate. The morphologies, crystal structure of the as-prepared samples and phase transition properties were studied by X-ray diffraction(XRD, field emission scanning electron microscope(FESEMand differential scanning calorimetry(DSC analysis. The results indicate that rod-like W-VO2(B crystal with length of 1-2μm and radius of 100-200nm is firstly formed during hydrothermal treatment for 4-48h at 280℃, then the rod-like crystal dissolves gradually and sheet-like or snowflake-like crystal is formed with the phase transition from W-VO2(B to W-VO2(M and eventually, the W-VO2(M crystals can further grow up while the W-VO2(B gradually dissolves; the phase transition temperature of VO2 decreases with the increase in W doping content, and the phase transition temperature of W-VO2(M reduces to about 28℃ when the nominal dopant concentration is 6.0%(atom fraction.The "nucleation-growth-transformation-ripening" mechanism is proposed as the formation mechanism based on the hydrothermal crystallization and morphological evolution process of W-VO2(M.

  5. Quartz crystal microbalance and spectroscopy measurements for acid doping in polyaniline films

    Directory of Open Access Journals (Sweden)

    Mohamad M Ayad and Eman A Zaki

    2008-01-01

    Full Text Available We investigated the doping of thin polyaniline (PANI films, prepared by the chemical oxidation of aniline, with different acids. The initial step in the investigation is the preparation of PANI films from aqueous hydrochloric acid solution. This is followed by dedoping with ammonia to obtain a PANI base, which is subsequently doped with strong acids (e.g. hydrochloric, sulfuric, phosphoric and trichloroacetic acids and with a weak acid (acetic acid. The dopant weight fraction (w, which is connected with the gain of mass during the doping of PANI, was determined in situ using a quartz crystal microbalance (QCM. The behavior of PANI upon doping with different anions derived from strong acids indicates that both proton and the anion uptake into the polymer chains occur sharply, rapidly, completely, and reversibly. However the uptake in the case in acetic acid is characterized by slow diffusion. The doping was studied at different concentrations of acetic acid. A second cycle of dedoping–redoping was also performed. The kinetics of the doping reaction is dominated by Fickian diffusion kinetics. The diffusion coefficients (D of the dopant ions into the PANI chains were determined using the QCM and by UV–Vis absorption spectroscopy in the range of (0.076–1.64× 10−15 cm2 s−1. It was found that D in the second cycle of doping is larger than that evaluated from the first cycle of doping for high concentrations of acetic acid. D for the diffusion and for the dopant ion expulsion from the PANI chains was also determined during the redoping process. It was found that D for acetic acid ions in the doping process is larger than that calculated for the dedoping process.

  6. Visible light-responded C, N and S co-doped anatase TiO{sub 2} for photocatalytic reduction of Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Lei, X.F., E-mail: leixuefei69@163.com [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive, Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization, Technology and Boron Materials, Shenyang 110819 (China); Xue, X.X.; Yang, H. [Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive, Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization, Technology and Boron Materials, Shenyang 110819 (China); Chen, C.; Li, X.; Pei, J.X.; Niu, M.C.; Yang, Y.T.; Gao, X.Y. [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China)

    2015-10-15

    The (C, N and S) co-doped TiO{sub 2} (TH-TiO{sub 2}) samples were synthesized by a sol-gel method calcined at 500 °C, employing butyl titanate as the titanium source and thiourea as the dopant. The structures of TH-TiO{sub 2} samples were characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectroscopy, Thermo gravimetry and differential thermal analysis (TG-DTA), Scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The photocatalytic activities were checked through the photocatalytic reduction of Cr(VI) as a model compound under visible light irradiation. The results showed that the thiourea content played an important role on the microstructure and photocatalytic activity of the samples. According to XPS results, (C, N and S) atoms were successfully co-doped into the nanostructures of TH-TiO{sub 2} samples. TH-TiO{sub 2} samples with thiourea: Ti molar ratio of 1.5 exhibits higher photocatalytic activity than that of the other samples under visible light irradiation, which can be attributed to the synergic effect of the pure anatase structure, the higher light absorption characteristics in visible regions, separation efficiency of electron–hole pairs, the specific surface area and the optimum (C, N and S) content. - Graphical abstract: (C, N and S) co-doped TiO{sub 2} samples show good photocatalytic activity for Cr (VI) reduction under visible light irradiation. - Highlights: • (C, N and S) co-doping in TH-TiO{sub 2} samples can promote the formation of the pure anatase structure. • (C, N and S) atoms were successfully co-doped into the nanostructures of TH-TiO{sub 2} samples. • The band gap energy of TH-TiO{sub 2} samples reduced after (C, N and S) co-doping. • (C, N and S) co-doped TiO{sub 2} samples were effective for the photocatalytic reduction of Cr(VI) under visible light

  7. Enhanced and Stable Upconverted White-light Emission in Ho3+/Yb3+/Tm3+-doped LiNbO3Single Crystal via Mg2+Ion Doping.

    Science.gov (United States)

    Xing, Lili; Yang, Weiqi; Lin, Jincheng; Huang, Mei; Xue, Yuqi

    2017-11-07

    A strategy to enhance the upconversion white-light intensity via Mg 2+ ion doping was demonstrated in Ho 3+ /Yb 3+ /Tm 3+ /LiNbO 3 single crystal. It is found Mg 2+ ion doping affects the crystal field symmetry around RE 3+ ions and enhance the upconversion emission intensity. Bright white-light is obtained when the Mg 2+ ion concentration is 0.5 mol% in the melt. And the CIE coordinates are hardly changed with Mg 2+ ion doping. In addition, the upconversion mechanism is discussed in detail. It is observed the longer lifetimes of intermediate levels result in the lower upconversion photon numbers, which are beneficial to the upconversion process. Therefore, Mg 2+ ion doped Ho 3+ /Yb 3+ /Tm 3+ /LiNbO 3 single crystals would have potential applications in stable white-light devices and photoelectric instruments.

  8. Electro-optical characteristics of holographic polymer dispersed liquid crystal gratings doped with nanosilver.

    Science.gov (United States)

    Zhang, Menghua; Zheng, Jihong; Gui, Kun; Wang, Kangni; Guo, Caihong; Wei, Xiaopeng; Zhuang, Songlin

    2013-11-01

    We report on the synthesis and characteristics of a holographic polymer dispersed liquid crystal (H-PDLC) switchable grating based on nano-Ag particles. The influence of doping different concentrations of nano-Ag on the diffraction efficiency, driving voltage, and response time of the H-PDLC grating is investigated. The best grating characteristics were achieved with 0.05% nano-Ag doping. Calculated and experimental results reveal that the improvement of the characteristics is likely due to the surface plasmon effect of nano-Ag.

  9. Optical Study of Liquid Crystal Lens Doped with Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Hui LI

    2016-05-01

    Full Text Available In this paper, a new kind of electrically controlled liquid crystal lens, which respond in a relatively fast time, is presented. The multiwalled carbon nanotubes are doped into liquid crystal to fabricate the liquid crystal lens. As 0.02 % concentration of multiwalled carbon nanotubes is uniformly distributed in the liquid crystal, the optical features of the liquid crystal lens are obviously improved. The liquid crystal lens with a diameter of 2.0 mm was fabricated with about 0.2 s response time and less than 5 Vrms applied voltage. The focal length can vary from 16 to 510 mm, and the operation voltage changes from 1.0 to 5.5 Vrms. This liquid crystal lens has the very attractive feature of submillisecond response time, which is a much faster response time in comparison with conventional liquid crystal lens. Thus, this kind of liquid crystal lens has high potential for implementation in many practical imaging applications and imaging commercialisation.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12911

  10. Thiourea-doped ammonium dihydrogen phosphate: A single crystal ...

    Indian Academy of Sciences (India)

    A single crystal neutron diffraction investigation. A JAYARAMA1, M R SURESH KUMAR1, S M DHARMAPRAKASH1,. R CHITRA2,∗ and R R CHOUDHURY2. 1Department of Physics, Mangalore University, Mangalagangotri 574 199, India. 2Solid State Physics Division, Bhabha Atomic Research Centre, Trombay,. Mumbai ...

  11. Growth and superconducting properties of Cd-doped La(O,F)BiS2 single crystals

    Science.gov (United States)

    Nagao, Masanori; Tanaka, Masashi; Watauchi, Satoshi; Takano, Yoshihiko; Tanaka, Isao

    2017-08-01

    Cd-doped La(O,F)BiS2 single crystals were grown using a CsCl/KCl flux. The grown crystals have a plate-like shape with 1-2 mm square size in a well-developed ab-plane. The Cd doping in the crystals was successfully characterized by single crystal X-ray diffraction and electron probe microanalysis techniques. The superconductivity of La(O,F)BiS2 was gradually suppressed with Cd doping. The superconducting transition temperature with zero resistivity of La(O0.54F0.46)(Bi0.92Cd0.08)S2 was 2.3 K. The Cd doping does not change the superconducting anisotropy so much, albeit the considerable suppression of Tc.

  12. cis-Dioxomolybdenum(VI) complexes of a new ONN chelating thiosemicarbazidato ligand; Synthesis, characterization, crystal, molecular structures and antioxidant activities

    Science.gov (United States)

    İlhan Ceylan, Berat; Deniz, Nahide Gulsah; Kahraman, Sibel; Ulkuseven, Bahri

    2015-04-01

    5-Chloro-4-methyl-2-hydroxybenzophenone S-propyl-4-phenyl-thiosemicarbazone (H2L) and its cis-dioxomolybdenum(VI) complexes, in the general formula [MoO2(L)R-OH)] (R: methyl, 1; ethyl, 2; n-propyl, 3; n-butyl, 4; n-pentyl, 5), were synthesized and characterized by micro analysis, electronic, infrared and 1H and 13C NMR spectra. The crystal structures of complexes, 1 and 3, have been solved by direct methods (SIR92) and refined to the residual indexes R1 = 0.098 and R1 = 0.052 respectively. Complexes 1 and 3 are crystallized in the triclinic space group P-1 with Z = 2. The crystal study of complex 1 showed the first example of intermolecular hydrogen bond for this type of molybdenum-thiosemicarbazone complexes. The hydrogen bond is between the hydroxyl proton of attached alcohol and an oxo oxygen (in MoO22+ unit) of another complex molecule, and its bond distance (1.767(1) Å) is shorter than from the σ-coordination bonds in complex 1. Antioxidant activities of the compounds were determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Ligand showed 23.61% DPPH radical scavenging activity at 250 mg/L concentration. Cupric Reducing Antioxidant Capacity (CUPRAC) was also evaluated and trolox-equivalent antioxidant capacity (TEAC) values were found for ligand, 1 and 3 as 0.51, 0.33 and 0.30 respectively.

  13. Exploiting the natural doping gradient of Nd:YLF crystals for high-power end pumped lasers

    CSIR Research Space (South Africa)

    Bollig, C

    2008-01-01

    Full Text Available decided to use crystals of a doping concentration below the 0.5% previously used. In addition, researchers decided to exploit the natural doping gradient along the length of the boule, which is especially pronounced at low concentrations but commonly...

  14. The Insulator to Superconductor Transition in Ga-Doped Semiconductor Ge Single Crystal Induced by the Annealing Temperature

    Directory of Open Access Journals (Sweden)

    Y. B. Sun

    2015-01-01

    Full Text Available We have fabricated the heavily Ga-doped layer in Ge single crystal by the implantation and rapid thermal annealing method. The samples show a crossover from the insulating to the superconducting behavior as the annealing temperature increases. Transport measurements suggest that the superconductivity is from the heavily Ga-doped layer in Ge.

  15. Growth, structural, spectral, mechanical and dielectric characterization of RbCl-doped L-alanine hydrogen chloride monohydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lucia Rose, A.S.J., E-mail: luciarose_osm@yahoo.co.i [Department of Physics, St. Mary' s College, Thoothukudi 628 001 (India); Selvarajan, P. [Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628216 (India); Perumal, S. [Physics Research Centre, S.T. Hindu College, Nagercoil 629003 (India)

    2011-02-01

    Pure (undoped) and RbCl-doped LAHC single crystals were grown successfully by the solution method with the slow evaporation technique at room temperature. The grown crystals were colourless and transparent. The solubility of the grown samples were found out at various temperatures. The lattice parameters of the grown crystals were determined by the single crystal X-ray diffraction technique and the diffracting planes were indentified by recording the powder X-ray diffraction pattern. UV-visible transmittance studies were carried out for the grown samples. Chemical analysis and atomic absorption studies indicate the presence of rubidium in the doped LAHC crystals. Nonlinear optical studies reveal that the SHG efficiency increases when the LAHC crystal is doped with rubidium chloride (RbCl). From microhardness studies, it is observed that the RbCl-doped LAHC crystal is harder than the pure sample. It is observed that the dielectric properties of the LAHC crystal are altered when it is doped with rubidium chloride.

  16. Antimicrobial activity and second harmonic studies on organic non-centrosymmetric pure and doped ninhydrin single crystals

    Science.gov (United States)

    Prasanyaa, T.; Jayaramakrishnan, V.; Haris, M.

    2013-03-01

    In this paper, we report the successful growth of pure, Cu2+ ions and Cd2+ ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu2+ and Cd2+ ions in the specimen of ninhydrin single crystal has been determined by atomic absorption spectroscopy. The powder X-ray diffraction analysis was done to calculate the lattice parameters of the pure and doped crystals. The percentage of transmittance of the crystal was recorded using the UV-Vis Spectrophotometer. Thermal behaviors of the grown crystals have been examined by the thermal gravimetric/differential thermal analysis. The hardness of the grown crystals was assessed and the results show the minor variation in the hardness value for the pure and doped ninhydrin samples. The value of the work hardening coefficient n was found to be 2.0, 1.0 and 1.06 for pure, copper and cadmium doped ninhydrin crystals respectively. The second harmonic generation efficiency of Cd2+ and Cu2+ doped ninhydrin is 8.3 and 6.3 times greater than well known nonlinear crystal of potassium dihydrogen phosphate respectively. The antibacterial and antifungal activities of the title compound were performed by disk diffusion method against the standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillis niger and Aspergillus flavus.

  17. Crystallization studies on rare-earth co-doped fluorozirconate-based glasses.

    Science.gov (United States)

    Paßlick, C; Johnson, J A; Schweizer, S

    2013-07-01

    This work focuses on the structural changes of barium chloride (BaCl2) nanoparticles in fluorochlorozirconate-based glass ceramics when doped with two different luminescent activators, in this case rare-earth (RE) ions, and thermally processed using a differential scanning calorimeter. In a first step, only europium in its divalent and trivalent oxidation states, Eu(2+) and Eu(3+), is investigated, which shows no significant influence on the crystallization of hexagonal phase BaCl2. However, higher amounts of Eu(2+) increase the activation energy of the phase transition to an orthorhombic crystal structure. In a second step, nucleation and nanocrystal growth are influenced by changing the structural environment of the glasses by co-doping with Eu(2+) and trivalent Gd(3+), Nd(3+), Yb(3+), or Tb(3+), due to the different atomic radii and electro-negativity of the co-dopants.

  18. Scintillation and dosimetric properties of Tb-doped LiCaAlF6 single crystals

    Science.gov (United States)

    Kawaguchi, Noriaki; Nakauchi, Daisuke; Hirano, Shotaro; Kawano, Naoki; Okada, Go; Fukuda, Kentaro; Yanagida, Takayuki

    2018-02-01

    We have investigated the scintillation and dosimetric properties of Tb-doped LiCaAlF6 single crystals. The X-ray-induced emission spectrum consisted of several sharp peaks due to the 4f–4f transitions of the Tb3+ ion. The thermoluminescence (TL) spectrum showed similar emission peaks as in those of the X-ray-induced luminescence. The TL intensity monotonically increased as a function of X-ray irradiation dose, and the dose response was demonstrated from 0.01 to 10 mGy. These results suggest that the Tb-doped LiCaAlF6 single crystal is a good candidate TL dosimeter material for low-dose applications.

  19. All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper; Bjarklev, Anders Overgaard

    2004-01-01

    Photonic crystal fibers (PCFs) have attracted significant attention during the last years and much research has been devoted to develop fiber designs for various applications, hereunder tunable fiber devices. Recently, thermally and electrically tunable PCF devices based on liquid crystals (LCs......) have been demonstrated. However, optical tuning of the LC PCF has until now not been demonstrated. Here we demonstrate an all-optical modulator, which utilizes a pulsed 532nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid...... crystal. We demonstrate a modulation frequency of 2kHz for a moderate pump power of 2-3mW and describe two pump pulse regimes in which there is an order of magnitude difference between the decay times....

  20. Photonic manipulation of topological defects in liquid-crystal emulsions doped with azobenzene derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Takahiro [Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568, Ibaraki (Japan) and Liquid-Crystal Nano-System Project, ERATO/SORST, Japan Science and Technology, Agency, 5-9-9 Tokodai, Tsukuba 300-2635, Ibaraki (Japan)]. E-mail: takahiro.yamamoto@aist.go.jp; Tabe, Yuka [Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568, Ibaraki (Japan); Liquid-Crystal Nano-System Project, ERATO/SORST, Japan Science and Technology, Agency, 5-9-9 Tokodai, Tsukuba 300-2635, Ibaraki (Japan); Department of Applied Physics, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjyuku, 169-8555, Tokyo (Japan); Yokoyama, Hiroshi [Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568, Ibaraki (Japan); Liquid-Crystal Nano-System Project, ERATO/SORST, Japan Science and Technology, Agency, 5-9-9 Tokodai, Tsukuba 300-2635, Ibaraki (Japan)

    2006-06-19

    By modulating liquid-crystal alignment on a colloidal sphere, we successfully manipulated topological defects in glycerol-droplet/liquid-crystal emulsions doped with amphiphilic azobenzene derivatives. At an initial state, a disclination loop (Saturn ring) could be observed around the droplet, in which the azobenzene molecules should adsorb onto the droplet and liquid crystal molecules align normally to the surface of the droplet. On irradiation with ultra-violet light ({lambda} = 365 nm), the disclination loop was unfastened and transformed into two point defects called boojums. This should be attributed to the alignment change of the liquid crystal molecules from normal to planar arrangement triggered by trans-to-cis photoisomerization of the adsorbed azo-dyes. On irradiation with visible light causing cis-to-trans photoisomerization ({lambda} = 435 nm), the boojums went back to the Saturn ring reversibly.

  1. The study of nonlinear two-photon phenomenon in photonic crystals doped with nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, N6A 3K7 (Canada)

    2007-02-28

    A theory of the nonlinear two-photon absorption has been developed in a photonic crystal doped with an ensemble of four-level nanoparticles. We have considered that the nanoparticles are interacting with the photonic crystal. An expression of two-photon absorption has been obtained by using the density matrix method. The effect of the dipole-dipole interaction has also been included in the formulation. Interesting new phenomena have been predicted. For example, it is found that the inhibition of two-photon absorption can be turned on and off when the decay resonance energies of the four-level nanoparticles are moved within the energy band.

  2. Effect of Partial Crystallization on the Structural and Luminescence Properties of Er(3+)-Doped Phosphate Glasses.

    Science.gov (United States)

    Lopez-Iscoa, Pablo; Salminen, Turkka; Hakkarainen, Teemu; Petit, Laeticia; Janner, Davide; Boetti, Nadia G; Lastusaari, Mika; Pugliese, Diego; Paturi, Petriina; Milanese, Daniel

    2017-04-28

    Er-doped phosphate glass ceramics were fabricated by melt-quenching technique followed by a heat treatment. The effect of the crystallization on the structural and luminescence properties of phosphate glasses containing Al₂O₃, TiO₂, and ZnO was investigated. The morphological and structural properties of the glass ceramics were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), and micro-Raman spectroscopy. Additionally, the luminescence spectra and the lifetime values were measured in order to study the influence of the crystallization on the spectroscopic properties of the glasses. The volume ratio between the crystal and the glassy phases increased along with the duration of the heat treatment. The crystallization of the glass ceramics was confirmed by the presence of sharp peaks in the XRD patterns and different crystal phases were identified depending on the glass composition. Sr(PO₃)₂ crystals were found to precipitate in all the investigated glasses. As evidenced by the spectroscopic properties, the site of the Er(3+) ions was not strongly affected by the heat treatment except for the fully crystallized glass ceramic which does not contain Al₂O₃, TiO₂, and ZnO. An increase of the lifetime was also observed after the heat treatment of this glass. Therefore, we suspect that the Er(3+) ions are incorporated in the precipitated crystals only in this glass ceramic.

  3. Synthesis, properties, and structure of potassium titanyl phosphate single crystals doped with hafnium

    Energy Technology Data Exchange (ETDEWEB)

    Orlova, E. I.; Kharitonova, E. P. [Moscow State University, Faculty of Physics (Russian Federation); Novikova, N. E., E-mail: natnov@ns.crys.ras.ru; Verin, I. A.; Alekseeva, O. A.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Voronkova, V. I. [Moscow State University, Faculty of Physics (Russian Federation)

    2010-05-15

    Single crystals of potassium titanyl phosphate doped with hafnium are grown by spontaneous flux crystallization. Their physical properties are studied, and the structure of three KTi{sub 1-x}Hf{sub x}OPO{sub 4} crystals (x = 0.01, 0.03, and 0.12) is determined. In the crystals studied, hafnium mostly occupies the second titanium position. The doping of KTP crystals with hafnium results in an elongation of K-O bonds in the potassium polyhedra and, as a consequence, in a considerable (by approximately 180 deg. C) decrease in the temperature of ferroelectric phase transition. The magnitude of anomalous permittivity substantially decreases. The electrical conduction in the specimens studied decreases by approximately half an order of magnitude in the low-temperature region but remains almost unchanged in the high-temperature region. Even at minor concentrations, the presence of a hafnium additive in the specimens considerably (by 35%) enhances the intensity of the second harmonic generation of laser radiation.

  4. Very High Quality Crystals of Wide-Gap II-VI Semiconductors: What for?

    Science.gov (United States)

    2001-01-01

    The second modification was the use of a Cd reservoir outside the crucible made of pyrolytic boron nitride , in which the crystal was growing. Both the...of very high quality. In particular, the density of dislocations measured as etch pit density ( EPD ) was of 2000 cmŖ. In the crystals grown from the...the reciprocal space mapping, by the etch pit density ( EPD ) measurements (to determine the density of dislocations) and by the measurement of the width

  5. Electronic properties of C60 and alkali metal doped C60 thin films or single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Maruyama, Yusei; Inabe, Tamotsu; Ogata, Hironori; Hoshi, Hajime; Nakamura, Naoki; Mori, Yoshihisa (Inst. for Molecular Science, Okazaki (Japan)); Achiba, Yohji; Suzuki, Shinzo; Kikuchi, Koichi; Ikemoto, Isao (Dept. of Chemistry, Tokyo Metropolitan Univ. (Japan))

    1991-12-01

    Molecular beam epitaxy technique has been applied to prepare ultra-thin films of C{sub 60} (fullerite) and some optical properties, absorption spectra and nonlinear optical activities, have been studied. Morphological studies on the sub-mono-molecular layers have been carried out with TEM and STM technique. Electrical conductivities of alkali metal doped C{sub 60} (fulleride) have been measured for single crystals as well as thin films including the detection of their superconductivity. (orig.).

  6. Self-focusing in chromium-doped potassium niobate single ceramic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Castillo T, J.; Gonzalez M, S.; Aguirre L, A.; Hernandez, M.B.; Aguilar M, J.A. [Instituto de Fisica y Matematicas, Universidad Tecnologica de la Mixteca, 69000, Huajuapan de Leon, Oaxaca (Mexico); Hernandez A, J. [lFUNAM, PO Box 20-364, 01000 Mexico, DF (Mexico)]. e-mail: jaimec@mixteco.utm.mx

    2006-07-01

    The self-focusing and nonlinear optical absorption in a chromium-doped potassium niobate single ceramic crystal have been investigated. The third-order electric susceptibility X{sup (3)} at continuous 532 nm radiation is estimated based on a band transport model describing photo refractive properties for this electro-optic material. An anisotropic behavior on its nonlinear optical absorption properties has also been observed due to the presence of chromium ions. (Author)

  7. Single crystal growth and nonlinear optical properties of Nd3+ doped STGS crystal for self-frequency-doubling application

    Science.gov (United States)

    Chen, Feifei; Wang, Lijuan; Wang, Xinle; Cheng, Xiufeng; Yu, Fapeng; Wang, Zhengping; Zhao, Xian

    2017-11-01

    The self-frequency-doubling crystal is an important kind of multi-functional crystal materials. In this work, Nd3+ doped Sr3TaGa3Si2O14 (Nd:STGS) single crystals were successfully grown by using Czochralski pulling method, in addition, the nonlinear and laser-frequency-doubling properties of Nd:STGS crystals were studied. The continuous-wave laser at 1064 nm was demonstrated along different physical axes, where the maximum output power was obtained to be 295 mW for the Z-cut samples, much higher than the Y-cut (242 mW) and X-cut (217 mW) samples. Based on the measured refractive indexes, the phase matching directions were discussed and determined for type I (42.5°, 30°) and type II (69.5°, 0°) crystal cuts. As expected, self-frequency-doubling green laser at 529 nm was achieved with output powers being around 16 mW and 12 mW for type I and type II configurations, respectively.

  8. Effect of heat treatment on the crystal structure and FTIR spectra of Sm doped cerium dioxide film

    Science.gov (United States)

    Liu, Xiaozhou; Liu, Xiaozhou; Xia, Letian; Chen, Jie; Wang, Xiaoyu

    2017-04-01

    The Sm doped cerium dioxide films were prepared with cerium foils as raw materials by anodization in Sm(NO3)3-Na2C2O4-NH3·H2O-H2O-(CH2OH)2 electrolyte. The anodic Sm doped cerium oxide films were heat treated in 100°C ~ 400°C. The heat treated anodic Sm doped cerium oxide films were characterized with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques respectively. The heat treated anodic Sm doped cerium oxide film at 100°C is the semi crystalline film. As heat treatment temperatures being in 200°C ~ 400°C, the heat treated anodic Sm doped cerium oxide films have a structure of cubic fluorite respectively. The doping of Sm can be achieved well by anodization method and be recognized as replacement doping or caulking doping. The crystal structure of Sm doped cerium dioxide films become more complete with the increase of heat treatment temperature in 200 ~ 400 °C. The doping of Sm can improve the crystallinity of the cerium dioxide film. The presence of adsorbing water, ethylene glycol and CO2 in the heat treated anodic Sm doped cerium oxide film at 100°C. The adsorbing ethylene glycols and water, CO2 in the anodic Sm doped cerium oxide film are removed at 200°C and 300°C respectively.

  9. Effects in B-doped KDP crystals irradiated with neutrons of large spectra energy

    Energy Technology Data Exchange (ETDEWEB)

    Fischfeld, G.; Affranchino, A.; Di Loreto, A. [Lab. Electrooptica, Reactor Nuclear RA-4, FCEIA - CUR, Universidad Nacional de Rosario, Av. Pellegrini 250 - CP 2000 - Rosario - Santa Fe (Argentina); Rocco, C. [Ciclotron, Centro Atomico Ezeiza, Comision Nacional de Energia Atomica, Av. Libertador 8250 - CP 1428 - Capital Federal (Argentina)

    2004-10-01

    The results obtained for the r{sub 63} electro-optic coefficient of B-doped and undoped KDP (KH{sub 2}PO{sub 4}) crystals irradiated with neutrons (including thermalized neutrons) produced by scattering of 30 Mev cyclotron protons on a target of Ta{sup 201}, are presented and compared to those obtained for non-irradiated doped and undoped crystals. The B-doped (H{sub 3}BO{sub 3}, Na{sub 2}B{sub 4}O {sub 7} and Li{sub 2}B{sub 4}O {sub 7}) crystals were obtained by the conventional growth method by temperature decrease with 1 wt % dopant concentration in solution. The thermal neutron flux was around {phi}=1. 10{sup 10} n/cm{sup 2}s. Pulses of {proportional_to}15 {mu}s long, in damped oscillatory mode (V=8 kV, {tau}=1.95 {mu}s) were used for the electro-optic measurements. A Pockels cell, a photomultiplier, a He-Ne laser ({lambda}=632.8 nm, 5 mW, linearly polarized) and a Tk 720 A oscilloscope complete the experimental setup. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Growth and characterization of Tm-doped Y 2O 3 single crystals

    Science.gov (United States)

    Mun, J. H.; Jouini, A.; Novoselov, A.; Guyot, Y.; Yoshikawa, A.; Ohta, H.; Shibata, H.; Waseda, Y.; Boulon, G.; Fukuda, T.

    2007-07-01

    The rare-earth sesquioxides (RE2O3, RE = Lu, Y and Sc) are promising host materials for solid-state lasers due to their low phonon energy and high thermal conductivity. On the other hand, Tm3+ and Yb3+ are preferable activators for advanced laser diode pumped solid-state lasers. In addition to that, Tm-doped materials can be used for eye-safe lasers application. Tm-doped Y2O3 single crystals were grown using the micro-pulling-down method. Crystals were transparent with gray and blue colors of 4.2 mm in diameter and 13-20 mm in length. The crystallinity was characterized using X-ray rocking curve analysis. Tm-doped Y2O3 single crystals have a good compositional homogeneity along the growth axis and their thermal conductivity was calculated from the measurements of thermal diffusivity, heat capacity and density. We have also recorded absorption, fluorescence spectra and measured fluorescence lifetimes as a function of the Tm content, we have found a very attractive fluorescence around the eye-safe wavelength of 1.9 mm which corresponds to a 3F4 → 3H6 transition of Tm3+.

  11. Electrical response of liquid crystal cells doped with multi-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Amanda García-García

    2015-02-01

    Full Text Available The inclusion of nanoparticles modifies a number of fundamental properties of many materials. Doping of nanoparticles in self-organized materials such as liquid crystals may be of interest for the reciprocal interaction between the matrix and the nanoparticles. Elongated nanoparticles and nanotubes can be aligned and reoriented by the liquid crystal, inducing noticeable changes in their optical and electrical properties. In this work, cells of liquid crystal doped with high aspect ratio multi-walled carbon nanotubes have been prepared, and their characteristic impedance has been studied at different frequencies and excitation voltages. The results demonstrate alterations in the anisotropic conductivity of the samples with the applied electric field, which can be followed by monitoring the impedance evolution with the excitation voltage. Results are consistent with a possible electric contact between the coated substrates of the LC cell caused by the reorientation of the nanotubes. The reversibility of the doped system upon removal of the electric field is quite low.

  12. Random lasing in dye-doped polymer dispersed liquid crystal film

    Science.gov (United States)

    Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

    2016-09-01

    A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

  13. Optical homogeneity, defects, and photorefractive properties of stoichiometric, congruent, and zinc-doped lithium niobate crystals

    Science.gov (United States)

    Sidorov, N. V.; Yanichev, A. A.; Palatnikov, M. N.; Gabain, A. A.; Pikoul, O. Yu.

    2014-07-01

    Using the laser-conoscopy method, the photorefractive light-scattering method, and the Raman light-scattering method, we have studied the structural and optical homogeneities and photorefractive properties of (i) stoichiometric lithium niobate crystals (LiNbO3(stoich)), which were grown from a melt with 58.6 mol % of Li2O; (ii) congruent crystals (LiNbO3(congr)); and (iii) congruent crystals that were doped with Zn2+ cations (LiNbO3:Zn; [Zn] = 0.03-1.59 mol %). We have shown that the speckle-structure of the photorefractive light scattering in all the crystals is three-layer. The shapes of the second and third layers repeat in general the shape of the first layer. We have shown that the differences that are observed between the Raman spectra, the photorefractive light scattering, and the conoscopic patterns of the examined crystals are caused by the fact that defects are distributed inhomogeneously over the volume of these crystals and that Zn2+ cations are incorporated inhomogeneously into the lattice. This leads to the appearance of local changes in the elastic characteristics of the crystal and to the appearance of mechanical stresses, which locally change the optical indicatrix and, correspondingly, the conoscopic pattern and the Raman spectrum.

  14. Ultralow Self-Doping in 2D Hybrid Perovskite Single Crystals

    KAUST Repository

    Peng, Wei

    2017-06-28

    Unintentional self-doping in semiconductors through shallow defects is detrimental to optoelectronic device performance. It adversely affects junction properties and it introduces electronic noise. This is especially acute for solution-processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1 (n=1, 2, and 3)—over three orders of magnitude lower than those of typical three-dimensional hybrid perovskites—by analyzing their conductivity behavior. We propose that crystallization of hybrid perovskites containing large organic cations suppresses defect formation and thus favors a low self-doping level. To exemplify the benefits of this effect, we demonstrate extraordinarily high light-detectivity (1013 Jones) in (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1 photoconductors due to the reduced electronic noise, which makes them particularly attractive for the detection of weak light signals. Furthermore, the low self-doping concentration reduces the equilibrium charge carrier concentration in (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1, advantageous in the design of p-i-n heterojunction solar cells by optimizing band alignment and promoting carrier depletion in the intrinsic perovskite layer, thereby enhancing charge extraction.

  15. Co2+-doped diopside: crystal structure and optical properties

    Science.gov (United States)

    Gori, C.; Tribaudino, M.; Mezzadri, F.; Skogby, H.; Hålenius, U.

    2017-12-01

    Synthetic clinopyroxenes along the CaMgSi2O6-CaCoSi2O6 join were investigated by a combined chemical-structural-spectroscopic approach. Single crystals were synthesized by flux growth methods, both from Ca-saturated and Ca-deficient starting compositions. Single crystal structure refinements show that the incorporation of Co2+ at the octahedrally coordinated cation sites of diopside, increases the unit-cell as well as the M1 and the M2 polyhedral volumes. Spectroscopic investigations (UV-VIS-NIR) of the Ca-rich samples reveal three main optical absorption bands, i.e. 4 T 1g → 4 T 2g(F), 4 T 1g → 4 A 2g(F) and 4 T 1g → 4 T 1g(P) as expected for Co2+ at a six-coordinated site. The bands arising from the 4 T 1g → 4 T 2g(F) and the 4 T 1g → 4 T 1g(P) electronic transitions, are each split into two components, due to the distortions of the M1 polyhedron from ideal Oh-symmetry. In spectra of both types, a band in the NIR range at ca 5000 cm-1 is caused by the 4 A 2g → 4 T 1g(F) electronic transition in Co2+ in a cubic field in the M2 site. Furthermore, an additional component to a band system at 14,000 cm-1, due to electronic transitions in Co2+ at the M2 site, is recorded in absorption spectra of Ca-deficient samples. No variations in Dq and Racah B parameters for Co2+ at the M1 site in response to compositional changes, were demonstrated, suggesting complete relaxation of the M1 polyhedron within the CaMgSi2O6-CaCoSi2O6 solid solution.

  16. Luminescent Properties of Cerium Doped Potassium Iodide Single Crystals in Response to γ-irradiation.

    Science.gov (United States)

    Bangaru, S; Saradha, K; Muralidharan, G

    2015-05-01

    Potassium iodide doped with cerium ions were prepared by Bridgemann Stockbarger technique and investigated by optical absorption, Photoluminescence(PL), Thermoluminescence(TL), Photostimulated Luminescence(PSL) and TL emission. The optical absorption measurement indicates that F and V centers are formed in the crystals during the γ-ray irradiation process. Optical absorption and Photoluminescence studies confirm the presence of cerium ions in the trivalent state. Spectral distribution under the Thermoluminescence Emission(TLE) and Optically Stimulated Luminescence(OSL) support the idea that the defect annihilation process to be due to thermal release of F-electron in KI:Ce(3+) crystals. Both Ce(3+) and Ce(2+) emissions were observed in the Thermoluminescence emission of the crystals. Thermoluminescence(TL) has been identified to be due to thermal release of electron produced during colouration process.

  17. Vapor Phase Growth of ZnO Single Crystals/Thin Films and Attempts for p-type Doping

    OpenAIRE

    Zhang, Xi

    2014-01-01

    The growth of ZnO single crystals and ZnO thin films on Si substrates by an open-system vapor phase method was studied in this thesis. The as-grown ZnO single crystals were investigated by means of photoluminescence (PL). Two unique emissions were observed in virgin and hydrogenated crystals. The up-to-now attempts for the p-type doping of ZnO were summarized and our doping studies were performed using nitrogen and antimony. The seed-free and open-system vapor phase method is a simple and...

  18. Growth and photorefractive properties of an Fe-doped near-stoichiometric LiNbO3 crystal

    Science.gov (United States)

    Zhang, Tao; Wang, Biao; Fang, Shuangquan; Ma, Decai

    2005-06-01

    A near-stoichiometric LiNbO3 crystal with 0.02 wt% Fe2O3 doping was grown from a Li-rich melt (Li/Nb = 1.38, atomic ratio) by the Czochralski method in air atmosphere. The OH- absorption band was characterized by infrared transmittance spectra. The appearance of the 3466 cm-1 absorption band (2.89 µm) manifests that the composition of the grown crystal is close to the stoichiometric ratio. The photorefractive properties were measured by a two-wave coupling experiment. The measured results show that the Fe-doped near-stoichiometric LiNbO3 crystal has a larger exponential gain coefficient than the Fe-doped congruent LiNbO3 crystal. The remarkable gain can be attributed to the photovoltaic field being comparable with the effective limiting space-charge field.

  19. Structural and electrical properties of single crystal indium doped ZnO films synthesized by low temperature solution method

    Science.gov (United States)

    Quang, Le Hong; Swee Kuan, Lim; Kia Liang, Gregory Goh

    2010-01-01

    The indium doping effects on single crystal ZnO film using low temperature hydrothermal synthesis were investigated. Indium was incorporated into the film by adding indium chloride into the growth solution. From the Hall measurement results, indium dopants significantly increase the electron concentration, making the film heavily n type. However, with higher indium doping content, the crystallinity and surface roughness of the films degraded and the carrier mobility decreased due to the formation of smaller grain size. From the structural and electrical measurement results, the best electrical properties have been obtained for 2 at% indium doped ZnO film. This single-crystal film with high crystal quality exhibits the electron concentration of 3×10 19 cm -3 and mobility of 8 cm 2V -1 s -1. These n type single crystal ZnO films can be considered for light emitting diode applications.

  20. Rare-earth-doped photonic crystals for the development of solid-state optical cryocoolers

    Science.gov (United States)

    Garcia-Adeva, Angel J.; Balda, Rolindes; Fernández, Joaquín

    2009-02-01

    Optical cryocoolers made of luminescent solids are very promising for many applications in the fields of optical telecommunications, aerospace industry, bioimaging, and phototherapy. To the present day, researchers have employed a number of crystal and glass host materials doped with rare-earth ions (Yb3+, Tm3+, and Er3+) to yield anti-Stokes optical refrigeration. In these host materials, the attainable minimum temperature is limited by the average phonon energy of the lattice and the impurity concentration. However, recently Ruan and Kaviany have theoretically demonstrated that the cooling efficiency can be dramatically enhanced when the host material doped with rare-earth ions is ground into a powder made of sub-micron size grains. This is due to two facts: firstly, the phonon spectrum is modified due to finite size of the grains and, secondly, light localization effects increase the photon density, leading to an enhanced absorptivity. In the present work, we propose that using a photonic crystal doped with rare earth ions offers many advantages with regards to getting a larger cooling efficiency at room temperature when compared to standard bulk materials or nano-powders. Indeed, apart to analogous phenomena to the ones predicted in nano-crystalline powders, there is the possibility of directly controlling the spontaneous emission rate of the ions embedded in the structure and, also, the absorption rate in the Stokes side of the absorption band by adequately tuning the density of photonic states, thus obtaining a large improvement in the cooling efficiency.

  1. Optical investigations and control of spindynamics in Mn doped II-VI quantum dots; Optische Untersuchung und Kontrolle der Spindynamik in Mn dotierten II-VI Quantenpunkten

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Thomas

    2009-05-13

    The present thesis deals with the spin of charge carriers confined in CdSe/ZnSe quantum dots (QDs) closely linked to the polarization of emitted photons. II-VI material systems can be adequately mixed with the B-group element manganese. Such semimagnetic nanostructures offer a number of characteristic optical and electronic features. This is caused by an exchange interaction between the spin of optically excited carriers and the 3d electrons of the Mn ions. Within the framework of this thesis addressing of well defined spin states was realized by optical excitation of charge carriers. The occupation of different spin states was detected by the degree of polarization of the emitted photoluminescence (PL) light. For that purpose different optical methods of time-resolved and time-integrated spectroscopy as well as investigations in magnetic fields were applied. (orig.)

  2. Influence of MgSO{sub 4} doping on the properties of zinc tris–thiourea sulphate (ZTS) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Selvapandiyan, M., E-mail: mselvapandiyan@rediffmail.com [Department of Physics, Sri Vidya Mandir Arts and Science College, Uthangarai 635 207 (India); Arumugam, J. [Department of Physics, Sri Vidya Mandir Arts and Science College, Uthangarai 635 207 (India); Sundaramoorthi, P. [Department of Physics, Thiruvalluvar Government Arts College, Rasipuram 637 401 (India); Sudhakar, S. [CSIR–National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110 012 (India)

    2013-12-15

    Highlights: •The influence of MgSO{sub 4} doping on the properties of ZTS single crystals grown at room temperature. •Thermal stability of the crystals increased with incorporation of Mg atom. •Energy band gap was estimated from UV–vis spectra. •ZTS is a potential material for frequency conversion. •Both pure and doped ZTS crystals are belonging to category of typical insulating materials. -- Abstract: The influence of MgSO{sub 4} doping on the properties of zinc tris–thiourea sulphate single crystals grown at room temperature by slow evaporation solution growth technique was studied. Powder XRD analysis confirmed the orthorhombic crystal structure with noncentrosymmetric space group Pca2{sub 1}. The mechanical properties of the grown crystals were analysed by Vicker’s microhardness method. Functional groups present in the materials were identified by FTIR spectral analysis in the range between 4000 and 400 cm{sup −1}. The UV–Vis spectrum indicates that the UV cut-off wavelength of the crystals has less than 297 nm. The thermal stability of the grown crystals was determined with the aid of thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Second order nonlinear optical behaviour of the grown crystals have been confirmed by Kurtz powder second harmonic generation (SHG) test.

  3. The Study of Quantum Interference in Metallic Photonic Crystals Doped with Four-Level Quantum Dots

    Directory of Open Access Journals (Sweden)

    Hatef Ali

    2010-01-01

    Full Text Available Abstract In this work, the absorption coefficient of a metallic photonic crystal doped with nanoparticles has been obtained using numerical simulation techniques. The effects of quantum interference and the concentration of doped particles on the absorption coefficient of the system have been investigated. The nanoparticles have been considered as semiconductor quantum dots which behave as a four-level quantum system and are driven by a single coherent laser field. The results show that changing the position of the photonic band gap about the resonant energy of the two lower levels directly affects the decay rate, and the system can be switched between transparent and opaque states if the probe laser field is tuned to the resonance frequency. These results provide an application for metallic nanostructures in the fabrication of new optical switches and photonic devices.

  4. Superconductivity of the surface layers of the doped PbTe:Eu crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zayachuk, D.M., E-mail: zayachuk@polynet.lviv.ua [Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv (Ukraine); Mikityuk, V.I.; Shlemkevych, V.V. [Yuriy Fedkovych Chernivtsy National University, 2 Kotsyubynsky St., 58012 Chernivtsy (Ukraine); Kaczorowski, D. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw 2 (Poland); Ilyina, O.S. [Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv (Ukraine)

    2012-12-14

    We present evidence of superconductivity of the surface layers of PbTe crystals grown from melt and doped with Eu during growth. We have studied two different type of the powder samples made out of the surface layer and from bulk of the PbTe:Eu ingots. The magnetization in the range of magnetic field 0-5 T and the magnetic susceptibility (MS) in the temperature range 1.7-400 K were investigated. At low temperatures, a strong diamagnetism of the surface layers of the PbTe:Eu ingot is observed whereas at high temperatures a transition to strong paramagnetism takes place. This effect is attributed to the transition of the PbTe:Eu surface layers to state of superconductivity at low temperature. The superconductivity of the doped surface layers is explained by formation of the Pb-based inclusions within the ingot surface.

  5. Erbium-doped amplification in circular photonic crystal fiber supporting orbital angular momentum modes.

    Science.gov (United States)

    Deng, Yifan; Zhang, Hu; Li, Hui; Tang, Xianfeng; Xi, Lixia; Zhang, Wenbo; Zhang, Xiaoguang

    2017-02-20

    We propose a new orbital angular momentum (OAM) erbium-doped fiber amplifier based on a circular photonic crystal fiber, which can support a total of 18 modes (14 OAM modes) over C-band. A correction factor is proposed to modify the overlap factor, with the aim of evaluating the performance of the amplifier more accurately. We found that the confined doping profile can help optimize the differential model gain (DMG). Numerical simulations suggest that the proposed OAM fiber amplifier can provide a gain larger than 20 dB for all 14 OAM modes, with the small DMG less than 0.2 dB and the noise figure lower than 3.5 dB across the C-band.

  6. Polarization-Independent Electrically Tunable Holographic Polymer Dispersed Liquid Crystals Grating Doped with Chiral Molecules

    Directory of Open Access Journals (Sweden)

    Hui LI

    2017-08-01

    Full Text Available This study proposes a holographic grating made of polymer dispersed liquid crystal (PDLC, with a small amount of chiral molecules doped into PDLC material. The major advantage of this grating is that it is independent of light polarization. This characteristic was verified by applying the interference beam intensity of a He-Cd laser at 150 mW/cm2, with an incidence angle between the two interference beams of 24°, for an irradiation curing duration of 120 s. The observed periodic structure of the grating is consistent with the theoretical value. As chiral molecules are doped, nematic-LC experiences a phase-change in the grating. However, the electro-optical features are only slightly affected. This proposed grating has greatly potential in 3D imaging because of its polarization-independent feature.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16312

  7. High Performance Large Mode-Area Ytterbium-doped Photonic Crystal Fiber for Fiber Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Chen Wei; Lu Peixiang [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074 (China); Li Shiyu; Wang Dongxiang, E-mail: chenwei@fiberhome.com.cn [State Key Laboratory of Optical Communication Technologies and Networks, Fiberhome Telecommunication Technologies Co. Ltd, 430074 (China)

    2011-02-01

    In this letter, large-mode-area double-cladding ytterbium-doped photonic crystal fiber was designed in theory and fabricated in practice. This fiber we have fabricated successfully has endless single mode operation performance and large inner-cladding numerical aperture of more than 0.75. The struts width between large air-holes in the outer-cladding is about 0.22 {mu}m. The photonic crystal fiber has a mode-area about 1465.7{mu}m{sup 2}. Due to the material being pure silica and air, such structures have excellent capacity to with-stand high temperature. The laser light can have very good beam quality, even diffraction-limited beam quality because of the single-mode core. This fabrication technical breakthrough of novelty high performance double-cladding ytterbium-doped photonic crystal fibers will give contributions to the high power fiber lasers and promote the progress of technology in the fields of high power lasers.

  8. Hot Carrier Trapping in High-Purity and Doped Germanium Crystals at Millikelvin Temperatures

    Science.gov (United States)

    Piro, M.-C.; Broniatowski, A.; Marnieros, S.; Dumoulin, L.; Olivieri, E.

    2014-09-01

    A new set of experimental data is presented for the mean drift lengths and the drift velocities of hot electrons and holes as a function of the electric field in ultra-pure and in lightly doped (n- and p-type) germanium single crystals at mK temperatures. Measurements are made in the field range between 0.1 and 15 V/cm, typical for the operation of cryogenic germanium detectors for dark matter search. The analysis of the experimental data strongly suggests that the dominant trapping centers are the dopant species in the neutral state.

  9. Variation of nonlinear refractive index in dye-doped liquid crystals by local and nonlocal mechanisms

    Science.gov (United States)

    Rodríguez-Rosales, Antonio A.; Morales-Saavedra, Omar G.; Román-Moreno, Carlos J.; Ortega-Martínez, Roberto

    2008-10-01

    We report in this work on the simultaneous presence of both positive and negative nonlinear optical (NLO) refractive indexes measured in methyl-red dye doped 5CB liquid crystal (LC). Characterization of these materials was performed according to the Z-Scan technique under cw He-Ne laser irradiation, taking into account the polarization and temperature dependence of the NLO-refractive index, and how these parameters are related to local and nonlocal mechanisms. The experimental conditions and a possible explanation for the simultaneous presence of positive and negative nonlinear refractive indexes are carefully discussed.

  10. Gelator-doped liquid-crystal phase grating with multistable and dynamic modes

    Science.gov (United States)

    Lin, Hui-Chi; Yang, Meng-Ru; Tsai, Sheng-Feng; Yan, Shih-Chiang

    2014-01-01

    We demonstrate a gelator-doped nematic liquid-crystal (LC) phase grating, which can be operated in both the multistable mode and the dynamic mode. Thermoreversible association and dissociation of the gelator molecules can vary and fix the multistable diffraction efficiencies of the gratings. A voltage (V) can also be applied to modulate dynamically the diffraction efficiencies of the grating, which behaves as a conventional LC grating. Experimental results show that the variations of the diffraction efficiencies in the multistable and dynamic modes are similar. The maximum diffraction efficiency is approximately 30% at V = 2 V.

  11. Gelator-doped liquid-crystal phase grating with multistable and dynamic modes

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Hui-Chi, E-mail: huichilin@nfu.edu.tw; Yang, Meng-Ru; Tsai, Sheng-Feng; Yan, Shih-Chiang [Department of Electro-Optical Engineering, National Formosa University, Yunlin 632, Taiwan (China)

    2014-01-06

    We demonstrate a gelator-doped nematic liquid-crystal (LC) phase grating, which can be operated in both the multistable mode and the dynamic mode. Thermoreversible association and dissociation of the gelator molecules can vary and fix the multistable diffraction efficiencies of the gratings. A voltage (V) can also be applied to modulate dynamically the diffraction efficiencies of the grating, which behaves as a conventional LC grating. Experimental results show that the variations of the diffraction efficiencies in the multistable and dynamic modes are similar. The maximum diffraction efficiency is approximately 30% at V = 2 V.

  12. Multistable Phase-Retardation Plate Based on Gelator-Doped Liquid Crystals

    Science.gov (United States)

    Ying-Guey Fuh, Andy; Chiang, Jou-Ting; Chien, Yu-Shein; Chang, Chih-Juang; Lin, Hui-Chi

    2012-07-01

    This work demonstrates a multistable, large phase-retardation plate using gelator-doped liquid crystals (LCs). Multistability is achieved by forming a rubbery LC gel at room temperature. Experimentally, the phase retardation (PR) of an LC-gel film can be varied and fixed by the thermoreversible association and dissociation of the gelator molecules. The PR of the LC plate ranging from 0.3-3.7π can be electrically controllable within 10 V. Half-wave and quarter-wave LC plates were also produced at applied voltages of 3.5 and 6.3 V, respectively. Their properties were examined and found to be stable.

  13. Optical multistability in 1D photonic crystal doped with carbon-nanotube quantum dot nanostructures

    Science.gov (United States)

    Solookinejad, Gh; Payravi, M.; Jabbari, M.; Nafar, M.; Ahmadi Sangachin, E.

    2017-12-01

    The optical bistability (OB) and multistability (OM) in one-dimensional photonic crystals doped with carbon-nanotube quantum dots (CNT QDs) is theoretically investigated. Our investigations show that due to spin–orbit coupling in CNT QDs the threshold of optical bistability can be adjusted. Also, the switching from OB to OM, or vice versa, can be achieved by controlling the transverse magnetic field. Our proposed model can be used as a suitable structure based on CNT QDs for realizing all-optical switching devices. Moreover, we realize that the controlling of OB and OM can be done without changing the thickness of the layers.

  14. Ultraslow Light Propagation in an Inhomogeneously Broadened Rare-Earth Ion-Doped Crystal

    Science.gov (United States)

    Baldit, E.; Bencheikh, K.; Monnier, P.; Levenson, J. A.; Rouget, V.

    2005-09-01

    We show that coherent population oscillations effect allows us to burn a narrow spectral hole (26 Hz) within the homogeneous absorption line of the optical transition of an erbium ion-doped crystal. The large dispersion of the index of refraction associated with this hole permits us to achieve a group velocity as low as 2.7m/s with a transmission of 40%. We especially benefit from the inhomogeneous absorption broadening of the ions to tune both the transmission coefficient, from 40% to 90%, and the light group velocity from 2.7m/s to 100m/s.

  15. Smart windows using polymer-networked liquid crystals doped with push-pull azobenzene

    Science.gov (United States)

    Oh, Seung-Won; Baek, Jong-Min; Kim, Sang-Hyeok; Yoon, Tae-Hoon

    2017-02-01

    We propose a smart window using polymer-networked liquid crystals doped with push-pull azobenzene. Azobenzene is used to provide phase transition from the nematic to isotropic state through the trans-cis isomerization of azobenzene. When exposed to sunlight, the device switches from the opaque nematic phase to the transparent isotropic phase. Switching from the transparent to opaque state can be obtained through rapid cis-trans isomerization of push-pull azobenzene without sunlight exposure. The proposed device can reduce the transmittance of the incident sunlight during daytime, whereas it can scatter the incident light during the night for privacy.

  16. High transmittance optical films based on quantum dot doped nanoscale polymer dispersed liquid crystals

    Science.gov (United States)

    Gandhi, Sahil Sandesh; Chien, Liang-Chy

    2016-04-01

    We propose a simple way to fabricate highly transparent nanoscale polymer dispersed liquid crystal (nano-PDLC) films between glass substrates and investigate their incident angle dependent optical transmittance properties with both collimated and Lambertian intensity distribution light sources. We also demonstrate that doping nano-PDLC films with 0.1% InP/ZnS core/shell quantum dots (QD) results in a higher optical transmittance. This work lays the foundation for such nanostructured composites to potentially serve as roll-to-roll coatable light extraction or brightness enhancement films in emissive display applications, superior to complex nanocorrugation techniques proposed in the past.

  17. Rewritable Optical Storage with a Spiropyran Doped Liquid Crystal Polymer Film.

    Science.gov (United States)

    Petriashvili, Gia; De Santo, Maria Penelope; Devadze, Lali; Zurabishvili, Tsisana; Sepashvili, Nino; Gary, Ramla; Barberi, Riccardo

    2016-03-01

    Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real-time image recording feature. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Raman scattering in heavily boron-doped single-crystal diamond

    Directory of Open Access Journals (Sweden)

    G. Faggio

    2011-09-01

    Full Text Available A series of boron-doped homoepitaxial diamond films grown by Microwave Plasma Enhanced Chemical Vapor Deposition at the University of Rome "Tor Vergata" have been investigated with Raman spectroscopy. As the boron content increases, we observed systematic modifications in the Raman spectra of single-crystal diamonds. A significant change in the lineshape of the first-order Raman peak as well as a wide and structured signal at lower wavenumbers appeared simultaneously in samples grown at higher boron content.

  19. Growth and optical properties of ZnWO4 single crystals pure and doped with Ca and Eu

    Science.gov (United States)

    Kowalski, Z.; Kaczmarek, S. M.; Berkowski, M.; Głowacki, M.; Zhydachevskii, Y. A.; Suchocki, A.

    2017-01-01

    In frames of this work a series of ZnWO4 single crystals, pure and doped with either Ca (5 at%) or Ca (4 at%) and Eu (1 at%), has been grown by the Czochralski method. Phase analysis and structural refinement was performed X-ray powder diffraction and the powder diffraction and the patterns were analyzed by the Rietveld refinement method to analyze the lattice parameters of the crystal structure. Additionally, the absorbance, photoluminescence emission (PL) and photoluminescence excitation (PLE) and EPR spectra were measured and compared to investigate influence of Ca and Eu co-doping on optical properties of the obtained crystals. Furthermore the optical band-gap of the crystals has been calculated. The crystal structure of all mentioned ZnWO4 samples has also discussed in the scope of environment symmetry and possible sites of dopant ions.

  20. Facile synthesis of efficient visible active C-doped TiO{sub 2} nanomaterials with high surface area for the simultaneous removal of phenol and Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Mani, A.Daya; Reddy, P.Manoj Kumar; Srinivaas, M. [Department of Chemistry, IIT Hyderabad, Yeddumailaram 502 205 (India); Ghosal, P., E-mail: csubbu@iith.ac.in [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India); Xanthopoulos, N. [Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland); Subrahmanyam, Ch. [Department of Chemistry, IIT Hyderabad, Yeddumailaram 502 205 (India)

    2015-01-15

    Highlights: • Facile synthesis of C-doped TiO{sub 2} nanomaterials with high surface area. • Utilization of citric acid and ascorbic acid as fuels based on evolution of gases. • Enhanced visible activity for the oxidation of phenol and reduction of Cr(VI). • Study of simultaneous oxidation of phenol and reduction of Cr(VI) for the first time. • Proposed plausible mechanism for the simultaneous removal of phenol and Cr(VI). - Abstract: A single step synthesis of carbon doped TiO{sub 2} (anatase) nanomaterials have been reported by using combustion synthesis using ascorbic acid and citric acid fuels. X-ray diffraction studies indicated the formation of nanosized anatase titania, whereas, transmission electron microscopy confirmed the formation of nanosized TiO{sub 2} anatase. The carbon doping into TiO{sub 2} matrix was identified by X-ray photoelectron spectroscopy, whereas, thermogravimetric study quantified the carbon doping. Diffuse reflectance UV–vis spectra indicated the band gap of less than 3 eV, a prerequisite for the photocatalytic activity under visible light irradiation. The N{sub 2} adsorption studies revealed the high surface area (upto 290 m{sup 2}/g) of the synthesized photocatalysts. Typical photocatalytic activity data indicated that the simultaneous removal of Cr(VI) and phenol is advantageous than degradation of the individual pollutants.

  1. Effect of S doping on the critical current density and vortex dynamics in FeSe single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yue, E-mail: sunyue.seu@gmail.com; Pyon, Sunseng; Tamegai, Tsuyoshi

    2016-11-15

    Highlights: • J{sub c} and vortex pinning in S-doped FeSe single crystals are reported for the first time. • The value of J{sub c} for FeSe is found to be enhanced from 4 × 10{sup 4} A/cm{sup 2} at 2 K under self-field to 6 × 10{sup 4} A/cm{sup 2} after S doping. • Strong point-like pinning from nanometer-sized defects or imperfections are dominant in both pure and S-doped FeSe, while S doping reduces the size of flux bundle and enhances the effective pinning energy. - Abstract: We report a detailed study of the S doping effect on the critical current density, J{sub c}, and vortex pinning in FeSe single crystal. The value of J{sub c} for FeSe is found to be enhanced from ∼4 × 10{sup 4} A/cm{sup 2} at 2 K under self-field to ∼6 × 10{sup 4} A/cm{sup 2} after S doping. Similar field decaying rates of J{sub c} and the absence of fishtail effect in both FeSe and FeSe{sub 0.86}S{sub 0.14} single crystals indicate the similar pinning mechanism for both crystals, i.e., the dominance of strong point-like pinning from nanometer-sized defects or imperfections. On the other hand, vortex dynamics study manifests that the S doping reduces the size of flux bundle and enhances the effective pinning energy, which may come from the lattice distortion caused by S doping.

  2. Crystal growth, optical spectroscopy and laser action of Tm3+-doped monoclinic magnesium tungstate.

    Science.gov (United States)

    Zhang, Lizhen; Lin, Haifeng; Zhang, Ge; Mateos, Xavier; Serres, Josep Maria; Aguiló, Magdalena; Díaz, Francesc; Griebner, Uwe; Petrov, Valentin; Wang, Yicheng; Loiko, Pavel; Vilejshikova, Elena; Yumashev, Konstantin; Lin, Zhoubin; Chen, Weidong

    2017-02-20

    We report on the crystal growth, spectroscopic investigation and laser performance of Tm3+-doped monoclinic magnesium tungstate (Tm:MgWO4), for the first time, to the best of our knowledge. A high-quality crystal has been grown by the top seeded solution growth method. The relevant spectroscopic properties are characterized in terms of absorption, luminescence and Raman spectroscopy. Judd-Ofelt (J-O) analysis is performed to evaluate the spontaneous emission probabilities and the radiative lifetimes. The absorption, stimulated-emission and gain cross-section spectra are determined for the principal light polarizations. The first laser action in the 2 μm spectral range is demonstrated in the regime of continuous-wave operation with a maximum output power of 775 mW and a slope efficiency of 39%.

  3. Optical properties of D-serine doped TGS crystals for pyroelectric sensors*

    Directory of Open Access Journals (Sweden)

    Kurlyak V.Yu.

    2015-12-01

    Full Text Available Refractive and birefringence indices in the range of transparency of 300 to 700 nm for triglycine sulphate crystals doped with D-serine molecules have been measured in the temperature range of 290 K to 340 K. The obtained optical properties are discussed together with characteristic electrical features of these materials used as pyroelectric sensors for measurement of temperature. The experimental results obtained in this study will be necessary as the reference data for comparison with the calculated refractive indices of TGS + D-serine on the basis of density functional theory. Determination of the proper position of D-serine, will reveal the features of TGS + D-serine crystal structure necessary to achieve stable unipolarity.

  4. High quality factor nanophotonic resonators in bulk rare-earth doped crystals

    CERN Document Server

    Zhong, Tian; Kindem, Jonathan M; Miyazono, Evan; Faraon, Andrei

    2015-01-01

    Numerous bulk crystalline materials exhibit attractive nonlinear and luminescent properties for classical and quantum optical applications. A chip-scale platform for high quality factor optical nanocavities in these materials will enable new optoelectronic devices and quantum light-matter interfaces. In this article, photonic crystal nanobeam resonators fabricated using focused ion beam milling in bulk insulators, such as rare-earth doped yttrium orthosilicate and yttrium vanadate, are demonstrated. Operation in the visible, near infrared, and telecom wavelengths with quality factors up to 27,000 and optical mode volumes close to one cubic wavelength is measured. These devices enable new nanolasers, on-chip quantum optical memories, single photon sources, and non-linear devices at low photon numbers based on rare-earth ions. The techniques are also applicable to other luminescent centers and crystals.

  5. Radiation-induced color centers in La-doped PbWO sub 4 crystals

    CERN Document Server

    Deng, Q; Zhu, R Y

    1999-01-01

    This report presents the result of a study on radiation-induced color center densities in La-doped lead tungstate (PbWO sub 4) crystals. The creation and annihilation constants of radiation-induced color centers were determined by using transmittance data measured for a PbWO sub 4 sample before and during sup 6 sup 0 Co gamma-ray irradiation at a dose rate of 15 rad/h. Following a model of color center kinetics, these constants were used to calculate color center densities under irradiations at 100 rad/h. The result was found to be in good agreement with experimental data, indicating that the behaviour of PbWO sub 4 crystals under irradiation can be predicted according to this model.

  6. Co-doped sodium chloride crystals exposed to different irradiation temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz-Morales, A. [Unidad Profesional Interdisciplinaria de Ingenieria y Tecnologias Avanzadas, IPN, Av. Instituto Politecnico Nacional 2580, Col. La Laguna Ticoman, 07340 Mexico D.F., Mexico and Unidad de Irradiacion y Segurid (Mexico); Cruz-Zaragoza, E.; Furetta, C. [Unidad de Irradiacion y Seguridad Radiologica, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, A.P. 70-543, 04510 Mexico D.F (Mexico); Kitis, G. [Nuclear Physics Laboratory, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Flores J, C.; Hernandez A, J.; Murrieta S, H. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP. 20-364, 01000 Mexico D.F (Mexico)

    2013-07-03

    Monocrystals of NaCl:XCl{sub 2}:MnCl{sub 2}(X = Ca,Cd) at four different concentrations have been analyzed. The crystals were exposed to different irradiation temperature, such as at room temperature (RT), solid water (SW), dry ice (DI) and liquid nitrogen (LN). The samples were irradiated with photon from {sup 60}Co irradiators. The co-doped sodium chloride crystals show a complex structure of glow curves that can be related to different distribution of traps. The linearity response was analyzed with the F(D) index. The F(D) value was less than unity indicating a sub-linear response was obtained from the TL response on the function of the dose. The glow curves were deconvoluted by using the CGCD program based on the first, second and general order kinetics.

  7. Crystal-field investigations of rare-earth-doped wide band gap semiconductors

    CERN Multimedia

    Muller, S; Wahl, U

    Crystal field investigations play a central role in the studies of rare earth doped semiconductors. Optical stark level spectroscopy and lattice location studies of radioactive rare earth isotopes implanted at ISOLDE have provided important insight into these systems during the last years. It has been shown that despite a major site preference of the probe atoms in the lattice, several defect configurations do exist. These sites are visible in the optical spectra but their origin and nature aren't deducible from these spectra alone. Hyperfine measurements on the other hand should reveal these defect configurations and yield the parameters necessary for a description of the optical properties at the atomic scale. In order to study the crystal field with this alternative approach, we propose a new concept for perturbed $\\gamma\\gamma$-angular correlation (PAC) experiments at ISOLDE based on digital signal processing in contrast to earlier analog setups. The general functionality of the spectrometer is explained ...

  8. Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

    KAUST Repository

    Abutaha, Anas I.

    2013-02-06

    We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature of the laser deposition process on LaAlO3 (100) substrates. The change in surface termination of the LaAlO3 substrate with temperature induces a change in AZO film orientation. The anisotropic nature of electrical conductivity and Seebeck coefficient of the AZO films showed a favored thermoelectric performance in c-axis oriented films. These films gave the highest power factor of 0.26 W m−1 K−1 at 740 K.

  9. Studies of absorption coefficient cum electro-optic performance of polymer dispersed liquid crystal doped with CNT and dichroic dye

    Science.gov (United States)

    Sharma, Vandna; Kumar, Pankaj

    2017-11-01

    Absorption coefficient of doped polymer dispersed liquid crystals (PDLCs) is a critical factor for their device performance and depends on dopants parameters like solubility, order parameter and extinction coefficients, in addition to configuration and orientation of the droplets. In this study, a fixed amount (0.125% wt/wt) of multiwall carbon nanotubes (CNTs) and orange azo dichroic dye was doped in PDLC and measured the OFF state absorption coefficient. Considering the theory based on Beer's law and followed by extinction coefficients of CNT and dye, the OFF state transmission for dye doped PDLC was found lower compared to CNT doped PDLC. As a result, absorption coefficient for dye doped PDLC was higher and resulted in the superior contrast ratio. The experimental results were found be consistent with the theoretical results.

  10. Spatial angle dependent lasing from a dye-doped two-dimensional hexagonal photonic crystal made of holographic polymer-dispersed liquid crystals.

    Science.gov (United States)

    Luo, D; Dai, H T; Demir, H V; Sun, X W; Yang, H Z; Ji, W

    2012-04-09

    The observation of spatial angle dependent lasing from a dye-doped two-dimensional photonic crystal (2D PC) holographic polymer dispersed liquid crystals made of hexagonal lattice structure is reported. With the increasing output angle of the laser beam in the plane perpendicular to the 2D PC, the lasing wavelength is red-shifted. By analyzing the lasing oscillation trace, we found that the effective lattice constant changes with the output angle, causing the spatial angle dependent lasing.

  11. Crystal growth, characterization and theoretical studies of alkaline earth metal-doped tetrakis(thiourea)nickel(II) chloride

    Science.gov (United States)

    Agilandeshwari, R.; Muthu, K.; Meenatchi, V.; Meena, K.; Rajasekar, M.; Aditya Prasad, A.; Meenakshisundaram, SP.

    2015-02-01

    The influence of Sr(II)-doping on the properties of tetrakis(thiourea)nickel(II) chloride (TTNC) has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies of doped specimens confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the Sr(II) are observed by scanning electron microscopy. The incorporation of metal into the host crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The nonlinear optical properties of the doped and undoped specimens were studied. Theoretical calculations were performed using the Density functional theory (DFT) method with B3LYP/LANL2DZ as the basis set. The molecular geometry and vibrational frequencies of TTNC in the ground state were calculated and the observed structural parameters of TTNC are compared with parameters obtained from single crystal X-ray studies. The atomic charge distributions are obtained by Mulliken charge population analysis. The first-order molecular hyperpolarizability, polarizability and dipole moment were derived.

  12. Doping dependence of the vortex dynamics in single-crystal superconducting NaFe{}_{1-x}Co x As

    Science.gov (United States)

    Ahmad, D.; Choi, W. J.; Seo, Y. I.; Jung, S.-G.; Kim, Y. C.; Salem-Sugui, S., Jr.; Park, T.; Kwon, Y. S.

    2017-10-01

    We investigate the doping dependence of flux pinning in superconducting NaFe{}1-xCo x As (x = 0.01, 0.03, 0.05 and 0.07) single crystals grown by the Bridgman method. The electronic specific heat displays a pronounced anomaly in a sample series at superconducting transition temperature, which hardly shows any residual part at low temperature. We found that Co doping plays an important role in signifying the secondary peak in the magnetic hysteresis of optimally doped (x = 0.03) and heavily doped (x = 0.05, 0.07) crystals. Furthermore, the dependence of the relaxation rate S = ∣d ln M/d ln t∣ on magnetic field and temperature exhibits a decreasing trend within a certain range corresponding to the secondary peak effect in the optimally and heavily doped samples. The magnetic relaxation rate combined with the Maley analysis of the current-dependent creep energy shows a single-vortex pinning in the lightly doped sample dominant at low applied fields, and plastic pinning at high applied fields, without showing a secondary peak. However, in the optimally and heavily doped samples, the magnetic relaxation rate and U(J) isothermal analysis show that the collective pinning that dominates below H peak crosses over to plastic pinning for fields above H peak.

  13. Growth and characterization of pure and potassium iodide-doped zinc tris-thiourea sulphate (ZTS) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, C. [Department of Physics, Arignar Anna College, Aralvoymoli 629301, Tamil Nadu (India)], E-mail: ckrishnan_phy@yahoo.co.in; Selvarajan, P. [Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628216, Tamil Nadu (India); Freeda, T.H.; Mahadevan, C.K. [Physics Research Centre, S.T. Hindu College, Nagercoil 629003, Tamil Nadu (India)

    2009-02-28

    Single crystals of pure and potassium iodide (KI)-doped zinc tris-thiourea sulphate (ZTS) were grown from aqueous solutions by the slow evaporation method. The grown crystals were transparent. The lattice parameters of the grown crystals were determined by the single-crystal X-ray diffraction technique. The grown crystals were also characterized by recording the powder X-ray diffraction pattern and by identifying the diffracting planes. The FT-IR spectrum was recorded in the range 400-4500 cm{sup -1}. Second harmonic generation (SHG) was confirmed by the Kurtz powder method. The thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) studies reveal that the materials have good thermal stability. Atomic absorption studies confirm the presence of dopant in ZTS crystals. The electrical measurements were made in the frequency range 10{sup 2}-10{sup 6} Hz and in the temperature range 40-130 deg. C along a-, b- and c-directions of the grown crystals. The present study shows that the electrical parameters viz. dc conductivity, dielectric constant, dielectric loss factor and ac conductivity increase with increase in temperature. Activation energy values were also determined for the ac conduction process in grown crystals. The dc conductivity, dielectric constant, dielectric loss factor and ac conductivity of KI-doped ZTS crystal were found to be more than those of pure ZTS crystals.

  14. Nature of inhomogeneities and luminescence centers in low-resistance Al-doped ZnS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Morosova, N.K.; Filipova, V.A.; Galstyan, V.G.; Malyshev, A.A.; Muratova, V.I.

    1985-12-01

    The authors study low-resistance Al-doped ZnS single crytals and find that they exhibit a banding nonuniformity, which is explained by the nonuniform distribution of aluminum and oxygen impurities in them. The intense blue emission of the crystals is caused by the high-resistance layer, in which oxygen concentrates, while aluminum is completely bound to the oxygen. The emission is caused by the annihilation of localized excitons. The low-resistance layers with the weak blue luminescence are intercalations of oxygen-depleted Al-doped ZnS. ZnS crystals containing Al and O in equal concentrations are stable.

  15. Solid solutions of gadolinium doped zinc oxide nanorods by combined microwave-ultrasonic irradiation assisted crystallization

    Science.gov (United States)

    Kiani, Armin; Dastafkan, Kamran; Obeydavi, Ali; Rahimi, Mohammad

    2017-12-01

    Nanocrystalline solid solutions consisting of un-doped and gadolinium doped zinc oxide nanorods were fabricated by a modified sol-gel process utilizing combined ultrasonic-microwave irradiations. Polyvinylpyrrolidone, diethylene glycol, and triethylenetetramine respectively as capping, structure directing, and complexing agents were used under ultrasound dynamic aging and microwave heating to obtain crystalline nanorods. Crystalline phase monitoring, lattice parameters and variation, morphology and shape, elemental analysis, functional groups, reducibility, and the oxidation state of emerged species were examined by PXRD, FESEM, TEM, EDX, FTIR, micro Raman, H2-TPR, and EPR techniques. Results have verified that irradiation mechanism of gelation and crystallization reduces the reaction time, augments the crystal quality, and formation of hexagonal close pack structure of Wurtzite morphology. Besides, dissolution of gadolinium within host lattice involves lattice deformation, unit cell distortion, and angular position variation. Structure related shape and growth along with compositional purity were observed through microscopic and spectroscopic surveys. Furthermore, TPR and EPR studies elucidated more detailed behavior upon exposure to the exerted irradiations and subsequent air-annealing including the formed oxidation states and electron trapping centers, presence of gadolinium, zinc, and oxygen disarrays and defects, as well as alteration in the host unit cell via gadolinium addition.

  16. Physical and chemical properties of a Ga-doped ZnO crystal

    Energy Technology Data Exchange (ETDEWEB)

    Stashans, Arvids; Olivos, Katia; Rivera, Richard, E-mail: arvids@utpl.edu.e [Grupo de FisicoquImica de Materiales, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

    2011-06-01

    First-principles calculations based on density functional theory and strengthened by Hartree-Fock computations have been performed to study a Ga-doped wurtzite-type ZnO crystal. The large 108-atom supercell used throughout this work allows one to model a single point defect within the periodic supercell model. Thus, the Ga impurity produced purely local effects on the properties of the material. The electronic band structure was obtained for both pure and impurity-doped materials. The occurrence of free electrons in the conduction band was observed after the incorporation of Ga, implying the Ga dopant's contribution to n-type electrical conductivity in the ZnO crystal, in agreement with known experimental data. An analysis of the charges on atoms and obtained atomic displacements in the region surrounding the defect showed that there is some alteration in the chemical bonding because of the presence of Ga atoms. In particular, the ionic bonding is strengthened in the defect's neighbourhood.

  17. Electrical, optical, and analytical characterization of bulk hydrothermal ZnO crystals doped with indium

    Science.gov (United States)

    Witkowska-Baran, M.; Mycielski, A.; Kochanowska, D.; Witkowska, B.; Kaliszek, W.; JakieŁa, R.; łusakowska, E.; Domukhovski, V.; Weģrzycki, M.

    2011-04-01

    The communication describes our research on a technique of making electrical contacts to semi-insulating (Cd,Mn)Te crystals for radiation detector applications. Since the electrical contacts made by deposition of Au directly onto the (Cd,Mn)Te surface turned out to be unreproducible, and the contacts made by deposition of monocrystalline layers of heavily doped semiconductors were unpractical for applications, our investigations were focused on the amorphous contact layers. The amorphous layers of heavily doped ZnTe:Sb or CdTe:In were evaporated on the "epi-ready" surfaces of good-quality, high-resistivity (108-1010 Ω cm) single crystals of (Cd,Mn)Te. The evaporation was carried out in the medium-high vacuum of about 10 -7 Torr. For electrical connections the amorphous contact layers were covered by an evaporated Au top layer. We investigated, the effect of thickness of the amorphous layer on the functioning of the contact. At the moment 1 μm thickness seems to be satisfactory.

  18. Optical and X-ray absorption spectroscopy in lead doped lithium fluoride crystals

    Energy Technology Data Exchange (ETDEWEB)

    Somma, F; Aloe, P; D' Acapito, F; Montereali, R M; Polosan, S; Secu, M; Vincenti, M A, E-mail: somma@fis.uniroma3.it

    2010-11-15

    LiF:Pb doped crystals were successfully grown by Kyropoulos method, starting with drying powders. The presence of Pb{sup 2+} ions in the LiF crystals were evidenced by the absorption band at 278 nm and by 375 nm photoluminescence. The presence of some other Pb structures with oxygen compounds in the as made samples was evidenced, decreasing after some annealing procedures. The local environment and valence state of Pb in LiF were studied by X-ray Absorption Spectroscopy at the Pb L{sub III} and L{sub I} edges. XANES data reveal that Pb is present as Pb{sup 2+} whereas EXAFS data show that it is incorporated in the crystal and not forming PbF{sub 2} precipitates. Identical spectra are obtained for samples as prepared and after thermal annealing up to 650 deg. C demonstrating the stability of the incorporation site. Also the concentration of Pb in the crystal has no effect on the location site of the metal as the same spectrum is obtained for specimens with different dopant concentrations.

  19. EPR and optical absorption study of Mn 2+-doped zinc ammonium phosphate hexahydrate single crystals

    Science.gov (United States)

    Kripal, Ram; Govind, Har; Gupta, S. K.; Arora, Manju

    2007-04-01

    EPR study of Mn 2+-doped zinc ammonium phosphate hexahydrate (ZAPH) is done at room temperature. The Mn 2+ spin Hamiltonian parameters are evaluated employing a large number of resonant line positions observed for different orientations of the external magnetic field. The evaluated value of g-factor is 1.9527±0.0002 and the values of other parameters D, E, a, A and B (in 10 -4 cm -1) are, 175±2, 58±2, 10±1, 92±2 and 86±2, respectively. The optical absorption study of the crystal is also done. The observed bands are assigned as transitions from the 6A 1g(S) ground state to various excited quartet levels of Mn 2+ ion in a cubic crystal field. These bands are fitted with four parameters: inter-electronic repulsion parameters ( B and C), cubic crystal field splitting parameter ( Dq), and Tree's correction ( α). The values obtained for the parameters are B=917, C=2254, Dq=756 and α=76 cm -1. From the data obtained the surrounding crystal field and the nature of metal-ligand bonding are discussed. The considerable decrease in the values of B and C from their free ion values indicates the existence of a fair amount of covalent bonding between the central metal ion and the ligand. On the basis of the deviations Δ g= g-2.0023, the transfer of electrons to or from the central metal ion for bond formation is ascertained.

  20. Growth of congruent-melting lithium tantalate crystal with stoichiometric structure by MgO doping

    Science.gov (United States)

    Fujii, Shunsuke; Uda, Satoshi; Maeda, Kensaku; Nozawa, Jun; Koizumi, Haruhiko; Fujiwara, Kozo; Kajigaya, Tomio

    2013-11-01

    Lithium tantalate (LT) is an oxide material whose congruent composition differs from its stoichiometric composition in the Li2O-Ta2O5 binary system. Ionic species in the LT melt are segregated during crystal growth, even at the congruent composition, which leads to crystallization electromotive force (C-EMF) at the solid-liquid. On the other hand, when a compound has a stoichiometric structure at the congruent composition, such segregation does not occur. By employing a new concept of stoichiometry of a material where the activity of any constituent element could be unity, we developed a new lithium tantalate with MgO doping, cs-MgO:LT (Li2O:Ta2O5:MgO=40.8:50.0:9.2), that is stoichiometric and coincident with the congruent composition. Because of this coincidence, cs-MgO:LT does not yield C-EMF and does not show segregation during growth even for ionic species. A bulk crystal was grown from the melt of the cs-MgO:LT composition via the Czochralski (CZ) method, and it showed excellent compositional homogeneity, proved by the constant distribution of the Curie temperature throughout the crystal.

  1. Polarization tunable circular Dammann grating generated from azo-dye doped nematic liquid crystals

    Science.gov (United States)

    Luo, D.; Dai, H. T.; Sun, X. W.

    2011-03-01

    A polarization tunable circular Dammann grating (CDG) was generated from an azo-dye (Methyl Red from Aldrich) doped liquid crystal (LC, E7 from Merck) cell. A simple multi-exposure photo-aligned process, based on cell assembled with non-rubbing glass substrates, was used to fabricate the binary phase liquid crystal CDG zone plane consisted of even zone with homogenous LC structure and odd zone with TN LC structure. Different twist angle of fabricated TN structure for odd zone can be obtained by adjusting photo exposure intensity or time. CDG with equal-intensity rings was produced through a Fourier-transform and then captured by a charge-coupled-device in our experiment. The maximum 0th and 1st diffraction orders of obtained CDG can be separated achieved by rotating the analyzer's polarization direction. If the chosen analyzer's direction leads to a zero phase difference of output light from even and odd zones, the maximum 0th diffraction order will be achieved, in contrast, if the chosen analyzer's direction leads to a π phase difference of output light from even and odd zones, the maximum 1st diffraction order will be produced. The TN structure of azo-dye doped liquid crystal cell fabricated by photo alignment technique provides a new method to generate CDG with polarization-dependent property. A broad wavelength band of lasers used to generate CDG, if far away from MR azo-dye absorption peak, expands the device's application range and shows a great advantage comparing to previously reported CDG fabricated by fixed materials, where only one fixed working wavelength is allowed.

  2. Crystal structure and self-interaction of the type VI secretion tail-tube protein from enteroaggregative Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Badreddine Douzi

    Full Text Available The type VI secretion system (T6SS is a widespread machine used by bacteria to control their environment and kill or disable bacterial species or eukaryotes through toxin injection. The T6SS comprises a central tube formed of stacked hexamers of hemolysin co-regulated proteins (Hcp and terminated by a trimeric valine-glycine repeat protein G (VgrG component, the cell puncturing device. A contractile tail sheath, formed by the TssB and TssC proteins, surrounds this tube. This syringe-like machine has been compared to an inverted phage, as both Hcp and VgrG share structural homology with tail components of Caudovirales. Here we solved the crystal structure of a tryptophan-substituted double mutant of Hcp1 from enteroaggregative Escherichia coli and compared it to the structures of other Hcps. Interestingly, we observed that the purified Hcp native protein is unable to form tubes in vitro. To better understand the rationale for observation, we measured the affinity of Hcp1 hexamers with themselves by surface plasmon resonance. The intra-hexamer interaction is weak, with a KD value of 7.2 µM. However, by engineering double cysteine mutants at defined positions, tubes of Hcp1 gathering up to 15 stacked hexamers formed in oxidative conditions. These results, together with those available in the literature regarding TssB and TssC, suggest that assembly of the T6SS tube differs significantly from that of Sipho- or Myoviridae.

  3. Optical properties of pure and Ce{sup 3+} doped gadolinium gallium garnet crystals and epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Syvorotka, I.I. [Scientific Research Company “Carat”, 202 Stryjska Street, Lviv 79031 (Ukraine); Sugak, D. [Scientific Research Company “Carat”, 202 Stryjska Street, Lviv 79031 (Ukraine); Lviv Polytechnic National University, 12, S. Bandera Street, Lviv, 79013 (Ukraine); Wierzbicka, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Wittlin, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Cardinal Stefan Wyszyński University in Warsaw, ul. Dewajtis 5, 01-815 Warsaw (Poland); Przybylińska, H. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Barzowska, J. [Institute of Experimental Physics, Gdańsk University, ul. Wita Stwosza 57, Gdańsk (Poland); Barcz, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw (Poland); Berkowski, M.; Domagała, J. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Mahlik, S.; Grinberg, M. [Institute of Experimental Physics, Gdańsk University, ul. Wita Stwosza 57, Gdańsk (Poland); Ma, Chong-Geng [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); and others

    2015-08-15

    Results of X-ray diffraction and low temperature optical absorption measurements of cerium doped gadolinium gallium garnet single crystals and epitaxial layers are reported. In the region of intra-configurational 4f–4f transitions the spectra of the bulk crystals exhibit the signatures of several different Ce{sup 3+} related centers. Apart from the dominant center, associated with Ce substituting gadolinium, at least three other centers are found, some of them attributed to the so-called antisite locations of rare-earth ions in the garnet host, i.e., in the Ga positions. X-ray diffraction data prove lattice expansion of bulk GGG crystals due to the presence of rare-earth antisites. The concentration of the additional Ce-related centers in epitaxial layers is much lower than in the bulk crystals. However, the Ce-doped layers incorporate a large amount of Pb from flux, which is the most probable source of nonradiative quenching of Ce luminescence, not observed in crystals grown by the Czochralski method. - Highlights: • Ce{sup 3+} multicenters found in Gadolinium Gallium Garnet crystals and epitaxial layers. • High quality epitaxial layers of pure and Ce-doped GGG were grown. • Luminescence quenching of Ce{sup 3+} by Pb ions from flux detected in GGG epitaxial layers. • X-ray diffraction allows measuring the amount of the rare-earth antisites in GGG.

  4. Microwave-assisted self-doping of TiO2 photonic crystals for efficient photoelectrochemical water splitting

    KAUST Repository

    Zhang, Zhonghai

    2014-01-08

    In this article, we report that the combination of microwave heating and ethylene glycol, a mild reducing agent, can induce Ti3+ self-doping in TiO2. A hierarchical TiO2 nanotube array with the top layer serving as TiO2 photonic crystals (TiO2 NTPCs) was selected as the base photoelectrode. The self-doped TiO2 NTPCs demonstrated a 10-fold increase in visible-light photocurrent density compared to the nondoped one, and the optimized saturation photocurrent density under simulated AM 1.5G illumination was identified to be 2.5 mA cm-2 at 1.23 V versus reversible hydrogen electrode, which is comparable to the highest values ever reported for TiO2-based photoelectrodes. The significant enhancement of photoelectrochemical performance can be ascribed to the rational coupling of morphological and electronic features of the self-doped TiO 2 NTPCs: (1) the periodically morphological structure of the photonic crystal layer traps broadband visible light, (2) the electronic interband state induced from self-doping of Ti3+ can be excited in the visible-light region, and (3) the captured light by the photonic crystal layer is absorbed by the self-doped interbands. © 2013 American Chemical Society.

  5. A study of the ac Stark effect in doped photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Haque, I; Singh, Mahi R [Department of Physics and Astronomy, University of Western Ontario, London, ON, N6A 3K7 (Canada)

    2007-04-16

    In this paper we present calculations of level populations and susceptibility for an ensemble of five-level atoms doped in a photonic crystal, using the master equation method. The atoms in the ensemble interact with the crystal which acts as a reservoir and are coupled with two strong pump fields and a weak probe field. It is found that, by manipulating the resonance energy associated with one of the decay channels of the atom, the system can be switched between an inverted and a non-inverted state. We have also observed the ac Stark effect in these atoms and have shown that due to the role played by the band structure of the photonic crystal, it is possible to switch between an absorption state and a non-absorption state of the atomic system. This is a very important finding as techniques of rendering material systems transparent to resonant laser radiation are very desirable in the fabrication of novel optical and photonic devices.

  6. Doping controlled spin reorientation in dysprosium-samarium orthoferrite single crystals

    Science.gov (United States)

    Cao, Shixun; Zhao, Weiyao; Kang, Baojuan; Zhang, Jincang; Ren, Wei

    2015-03-01

    As one of the most important phase transitions, spin reorientation (SR) in rare earth transition metal oxides draws much attention of emerging materials technologies. The origin of SR is the competition between different spin configurations which possess different free energy. We report the control of spin reorientation (SR) transition in perovskite rare earth orthoferrite Dy1-xSmxFeO3, a whole family of single crystals grown by optical floating zone method from x =0 to 1. Temperature dependence of the magnetizations under zero-field-cooling (ZFC) and field-cooling (FC) processes are studied. We have found a remarkable linear change of SR transition temperature in Sm-rich samples for x>0.2, which covers an extremely wide temperature range including room temperature. The a-axis magnetization curves under FCC process bifurcate from and then jump down to that of warming process (ZFC and FCW curves) in single crystals when x =0.5-0.9, suggesting complicated 4f-3d electron interactions among Dy3+-Sm3+, Dy3+-Fe3+, and Sm3+-Fe3+ sublattices of diverse magnetic configurations for materials physics and design. The magnetic properties and the doping effect on SR transition temperature in these single crystals might be useful in the spintronics device application. This work is supported by the National Key Basic Research Program of China (Grant No. 2015CB921600), and the National Natural Science Foundation of China (NSFC, Nos. 51372149, 50932003, 11274222).

  7. Visualization of the magnetic flux structure in phosphorus-doped EuFe2As2 single crystals

    NARCIS (Netherlands)

    Veshchunov, I. S.; Vinnikov, L. Ya; Stolyarov, V.S.; Yu-shan zhou, N.; Shi, Z. X.; Xu, X. F.; Grebenchuk, S. Yu; Baranov, D. S.; Golovchanskiy, I.A.; Pyon, S.; Sun, Hong-yue; Jiao, Wenhe; Cao, Guanghan; Tamegai, T.; Golubov, A. A.

    2017-01-01

    Magnetic flux structure on the surface of EuFe2(As1-xPx)2 single crystals with nearly optimal phosphorus doping levels x = 0.20 and x = 0.21 is studied by low-temperature magnetic force microscopy and decoration with ferromagnetic nanoparticles. The studies are performed in a broad temperature

  8. Theoretical investigation of the formation of basal plane stacking faults in heavily nitrogen-doped 4H-SiC crystals

    Energy Technology Data Exchange (ETDEWEB)

    Taniguchi, Chisato; Ichimura, Aiko [School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 (Japan); Ohtani, Noboru, E-mail: ohtani.noboru@kwansei.ac.jp [School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 (Japan); Research and Development Center for SiC Materials and Processes, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 (Japan); Katsuno, Masakazu; Fujimoto, Tatsuo; Sato, Shinya; Tsuge, Hiroshi; Yano, Takayuki [Advanced Technology Research Laboratories, Nippon Steel & Sumitomo Metal Corporation, 20-1 Shintomi, Futtsu, Chiba 293-8511 (Japan)

    2016-04-14

    The formation of basal plane stacking faults in heavily nitrogen-doped 4H-SiC crystals was theoretically investigated. A novel theoretical model based on the so-called quantum well action mechanism was proposed; the model considers several factors, which were overlooked in a previously proposed model, and provides a detailed explanation of the annealing-induced formation of double layer Shockley-type stacking faults in heavily nitrogen-doped 4H-SiC crystals. We further revised the model to consider the carrier distribution in the depletion regions adjacent to the stacking fault and successfully explained the shrinkage of stacking faults during annealing at even higher temperatures. The model also succeeded in accounting for the aluminum co-doping effect in heavily nitrogen-doped 4H-SiC crystals, in that the stacking fault formation is suppressed when aluminum acceptors are co-doped in the crystals.

  9. Nanostructured anatase TiO2 microtubes doped by Zr(IV), Hf(IV) and Mo(VI)

    Science.gov (United States)

    Sokolov, A. A.; Opra, D. P.; Gnedenkov, S. V.; Sinebryukhov, S. L.; Voit, E. I.; Suschkov, Y. V.; Modin, E. B.; Sarin, S. A.; Mayorov, V. Y.; Zheleznov, V. V.

    2017-09-01

    The nanostructured Zr-, Hf-, and Mo-doped anatase TiO2 microtubes has been synthesized via a template solgel method on a carbon fiber. The correlation between synthesis conditions of materials and their structure and morphology was investigated in detail by means of scanning electron microscopy, small-angle X-ray scattering, transmission electron microscopy, and Raman spectroscopy. Electrochemical behaviour of the materials as Li-ion batteries anodes was investigated by galvanostatic charge/discharge cycling.

  10. Deterministic coupling of delta-doped nitrogen vacancy centers to a nanobeam photonic crystal cavity

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jonathan C.; Cui, Shanying; Zhang, Xingyu; Russell, Kasey J.; Magyar, Andrew P.; Hu, Evelyn L., E-mail: ehu@seas.harvard.edu [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Bracher, David O. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Ohno, Kenichi; McLellan, Claire A.; Alemán, Benjamin; Bleszynski Jayich, Ania [Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106 (United States); Andrich, Paolo; Awschalom, David [Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106 (United States); Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Aharonovich, Igor [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); School of Physics and Advanced Materials, University of Technology Sydney, Ultimo, New South Wales 2007 (Australia)

    2014-12-29

    The negatively charged nitrogen vacancy center (NV) in diamond has generated significant interest as a platform for quantum information processing and sensing in the solid state. For most applications, high quality optical cavities are required to enhance the NV zero-phonon line (ZPL) emission. An outstanding challenge in maximizing the degree of NV-cavity coupling is the deterministic placement of NVs within the cavity. Here, we report photonic crystal nanobeam cavities coupled to NVs incorporated by a delta-doping technique that allows nanometer-scale vertical positioning of the emitters. We demonstrate cavities with Q up to ∼24 000 and mode volume V ∼ 0.47(λ/n){sup 3} as well as resonant enhancement of the ZPL of an NV ensemble with Purcell factor of ∼20. Our fabrication technique provides a first step towards deterministic NV-cavity coupling using spatial control of the emitters.

  11. Local vibration modes of shallow thermal donors in nitrogen-doped CZ silicon crystals

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, N. [RIAST, Osaka Prefecture University, Sakai, 599-8570 (Japan) and Nitrogen Measurement WG, JEITA, Tokyo, 101-0062 (Japan)]. E-mail: inouen@riast.osakafu-u.ac.jp; Nakatsu, M. [RIAST, Osaka Prefecture University, Sakai, 599-8570 (Japan); Ono, H. [Japan Fine Ceramics Center, Tokyo, 105-0003 (Japan); Nitrogen Measurement WG, JEITA, Tokyo, 101-0062 (Japan)

    2006-04-01

    Local vibration mode (LVM) infrared absorption from shallow thermal donors (STD) composed of nitrogen-oxygen complexes in nitrogen-doped CZ silicon crystals was examined. The samples whose STD concentration had been determined were measured. The sample dependence of the peaks at 810 and 1018cm{sup -1} was similar to that of STD but the estimated concentration was slightly higher. New LVM peaks were found at 855, 973, 982, 1002cm{sup -1} and so on. Their magnitude and sample dependence agreed well with those of STD. Annealing temperature dependence of other samples supported the results. Annealing time dependence of STD concentration at 650 deg. C was examined. STD peaks at 250, 242 and those at 240, 234 and 238cm{sup -1} behaved differently, suggesting the presence of two kinds of STD origin.

  12. Polarization reversal induced by heating-cooling cycles in MgO doped lithium niobate crystals

    Science.gov (United States)

    Shur, V. Ya.; Mingaliev, E. A.; Lebedev, V. A.; Kuznetsov, D. K.; Fursov, D. V.

    2013-05-01

    Polarization reversal during heating-cooling cycles was investigated in MgO doped lithium niobate (MgO:LN) crystal using piezoresponse force microscopy. The essential dependence of the domain structure evolution scenario on the maximal temperature in the cycle has been revealed experimentally. It has been shown that the heating of the engineered domain matrix from room temperature to 85 °C leads to light size reduction of the isolated domains at the matrix edges, whereas the heating to 170 °C leads to essential reduction of the domain size. The opposite strong effect of the domain formation and growth during cooling after pulse heating have been revealed in single domain MgO:LN. The simulation of the time dependence of the pyroelectric field during heating-cooling cycle allowed to reveal the temperature hysteresis and to explain all observed effects taking into account the temperature dependence of the bulk conductivity.

  13. Magnetic and luminescent properties of nickel-doped ZnSe crystals

    Science.gov (United States)

    Sirkeli, Vadim; Radevici, Ivan; Sushkevich, Konstantin; Huhtinen, Hannu; Nedeoglo, Natalia; Nedeoglo, Dmitrii; Paturi, Petriina

    2015-12-01

    Magnetic and photoluminescent properties of nickel-doped ZnSe crystals with impurity concentrations varied by changing the Ni amount in the source material from 0.001 to 0.50 at.% are studied in 5-300 K temperature range. Investigation of magnetic properties shows that Ni impurity in ZnSe forms isolated paramagnetic centers and probability of Ni-Ni pairs formation is negligible due to low Ni concentration in the samples. The contribution of Ni impurity to edge emission and its influence on infra-red emission are discussed. It is found that complete concentration quenching of luminescence within all studied spectral range is observed starting with Ni concentration of 0.50 at.%.

  14. Enhanced photorefractive performance of bulk cu-doped KNSBN crystals through surface electrostatic modification

    Science.gov (United States)

    Li, Liang; Zhang, Jingwen; Zhao, Hua

    2017-01-01

    The remarkable photorefractivity enhancement was observed and investigated in copper-doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 (Cu:KNSBN) crystals due to charge accumulation on the surface, stemming from electrostrictive effect. This electrostatic modification to the surface was studied with conventional two beam coupling experiment and over 17 high diffraction orders were observed. To estimate the amount of charge accumulation, the surface charge density was measured through direct current measurement using a close loop circuit. It was believed that a thin phase grating was responsible for the diffraction pattern, which was confirmed by the related reading experiment. Corresponding calculation and analysis were given to highlight the strong refractive index modulation of the gratings.

  15. Radiation tests on erbium-doped garnet crystals for spaceborne CH4-Lidar applications

    Science.gov (United States)

    Meissner, Ansgar; Kreitler, Martin; Cubera, Miroslaw; Kucirek, Philipp; Gronloh, Bastian; Esser, Dominik; Höfer, Marco; Hoffmann, Hans-Dieter

    2015-02-01

    A test campaign for assessing the radiation hardness of different Erbium-doped garnet crystals including Er:YAG and a compositionally tuned Er:YAG/Er:LuAG mixed garnet is reported. Tests with proton and gamma radiation have been performed with parameters mimicking a 3-year low-earth-orbit satellite mission like MERLIN or ADM-Aeolus. For each test sample broadband transmission spectra in the wavelength range of 500 nm - 1700 nm and characteristic laser curves from a test laser oscillator have been measured. Radiation-induced losses have been calculated from the obtained data. The results indicate that gamma radiation is the dominant loss source with about 0.5 %/cm radiation-induced losses for the nominal dose of the chosen mission scenario.

  16. Anomalous decrease in the creep rate of Zn doped YBCO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Manzoor [Department of Electrical and Electronic Engineering, University Technology PETRONAS, 31750 Tronoh, Perak (Malaysia)], E-mail: manzoorhuss98@yahoo.com; Takita, Koki [Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan)

    2007-12-01

    The magnetic relaxation measurements were made using Zn doped YBCO single crystals YBa{sub 2}(Cu{sub 1-x}Zn{sub x}){sub 3}O{sub 7-{sigma}}. The decay of magnetization showed a linear dependence with the logarithm of time in wide temperature range of 0.1 < T/T{sub c} < 0.8, which indicates a strong flux pinning in these samples effective up to higher temperatures of 0.8T{sub c}. The temperature dependence of the normalized creep rate S(T) for applied fields of 1 T shows a non-monotonic behavior in the whole temperature range, with a peak at lower temperature and a dip at intermediate temperatures which is contrary to the predicted plateau in this region and indicates a strong change in the pinning mechanism of these samples at these temperatures and fields. The dip in creep rate S(T) of these samples up to 3% Zn concentration was found to be as large as 0.008, compared to 0.025-0.045 observed in the similar strong pinning systems. The weak temperature dependence of the pinning potential for these Zn doped samples at low temperatures shows drastic and systematic changes in U{sub 0} at higher temperatures which indicates that the Zn impurity contributes effectively to modify the pinning properties up to higher temperatures.

  17. Correlation between modulation structure and electronic inhomogeneity on Pb-doped Bi-2212 single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, A. [Low Temperature Physics Group, Nano-electronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan)]. E-mail: a.sugimoto@aist.go.jp; Kashiwaya, S. [Low Temperature Physics Group, Nano-electronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan); Eisaki, H. [Low Temperature Physics Group, Nano-electronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan); Yamaguchi, H. [Low Temperature Physics Group, Nano-electronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan); Oka, K. [Low Temperature Physics Group, Nano-electronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan); Kashiwaya, H. [Low Temperature Physics Group, Nano-electronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan); Tsuchiura, H. [Department of Applied Physics, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Tanaka, Y. [Department of Applied Physics, Nagoya University, Furo-cho Chikusa-ku Nagoya 464-8603 (Japan)

    2005-10-01

    The correlation between nanometer-size electronic states and surface structure is investigated by scanning tunneling microscopy/spectroscopy (STM/S) on Pb-doped Bi{sub 2-x}Pb {sub x}Sr{sub 2}CaCu2O{sub 8+y} (Pb-Bi-2212) single crystals. The advantage of the Pb-Bi-2212 samples is that the modulation structure can be totally or locally suppressed depending on the Pb contents and annealing conditions. The superconducting gap ({delta}) distribution on modulated Pb-Bi-2212 samples showed the lack of correlation with modulation structure except a slight reduction of superconducting island size for the b-axis direction. On the other hand, the optimal doped Pb-Bi-2212 (x = 0.6) samples obtained by reduced-annealing showed totally non-modulated structure in topography, however, the spatial distribution of {delta} still showed inhomogeneity of which features were quite similar to those of modulated samples. These results suggest that the modulation structure is not the dominant origin of inhomogeneity although it modifies the streaky {delta} structure sub-dominantly. From the gap structure variation around the border of narrow gap and broad gap regions, a trend of the coexistence of two separated phases i.e., superconducting phase and pseudogap like phase, is detected.

  18. Yb(3+) heavily doped photonic crystal fiber lasers prepared by the glass phase-separation technology.

    Science.gov (United States)

    Chu, Yingbo; Yang, Yu; Hu, Xiongwei; Chen, Zhangru; Ma, Yunxiu; Liu, Yongguang; Wang, Yibo; Liao, Lei; Xing, Yinbin; Li, Haiqing; Peng, Jinggagn; Dai, Nengli; Li, Jinyan; Yang, Luyun

    2017-10-02

    We report a Yb(3+) heavily doped photonic crystal fiber with 30 μm core diameter manufactured for the first time by an alternative technique. Silica core rods with a diameter of 3 mm and a length of 280 mm were prepared by the sodium-borosilicate glass phase-separation technology. The measurements show that the fiber has an Yb(3+) concentration of 22810 ppm by weight, and a resultant absorption of approximately 8.5 dB/m at 976 nm. The Yb(3+) ions are distributed throughout the fiber core with an excellent homogeneity. The laser performance demonstrates a high slope efficiency of 64.5% for laser emission at 1033.4 nm and a low power threshold of 3 W within a short fiber length of 1 m. This novel approach provides an alternative means of preparing large active silica rods with high doping levels and excellent material homogeneity for large mode area fibers with complex designs.

  19. Crystal structure of La{sub 2}Mo{sub 2}O{sub 9} single crystals doped with bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Alekseeva, O. A., E-mail: olalex@ns.crys.ras.ru; Verin, I. A.; Sorokina, N. I.; Krasil' nikova, A. E. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Voronkova, V. I. [Moscow State University, Faculty of Physics (Russian Federation)

    2010-07-15

    Precision X-ray diffraction studies of La{sub 2-x}Bi{sub x}Mo{sub 2}O{sub 9} (x = 0.04, 0.06, and 0.18) single crystals are performed. It is found that in the compounds doped with bismuth, analogously with the structure of the metastable {beta}{sub ms} phase of pure La{sub 2}Mo{sub 2}O{sub 9} (LM), the La, Mo1, and O1 atoms deviate from the threefold axis on which they are located in the high-temperature {beta} phase. It is shown that bismuth atoms substitute for part of lanthanum atoms and occupy a position at the threefold axis in the neighborhood of the split lanthanum position. The implantation of bismuth atoms in the LM structure results in the return of a part of the molybdenum atoms to the position at the threefold axis. The occupancy of this position is equal to the occupancy of the bismuth atomic position.

  20. Optical and magnetic resonance studies of Be-doped GaN bulk crystals

    Science.gov (United States)

    Glaser, E. R.; Freitas, J. A.; Storm, D. F.; Teisseyre, Henryk; Boćkowski, Michal

    2014-10-01

    Low temperature photoluminescence (PL) and optically-detected magnetic resonance (ODMR) at 24 GHz have been performed on a set of Be-doped GaN bulk crystals grown by the high pressure nitrogen solution method. Most notably, these crystals exhibit an intense 2.25 eV “yellow” PL band that is currently of high interest for use as a converter in white light-emitting-diode applications. In addition, the samples investigated in this work are found to emit a broad “violet” PL band of varying intensity with peak energy near 3.16 eV that is shown to be associated with a high concentration of residual Mg acceptor impurities as supported by secondary ion mass spectroscopy measurements. ODMR angular rotation studies obtained on the “yellow” and “violet” emission bands revealed two strong signals in each case and helped to provide information on the nature of these recombination processes. One feature, common to the ODMR of each PL band, has Zeeman splitting g-values of ~1.95 and is ascribed to residual Si and O shallow donor impurities. The second ODMR signal observed on the 2.25 eV “yellow” PL exhibits nearly isotropic g-values of ~2.0 characteristic of deep centers in GaN and is tentatively associated with Be-related deep acceptors. In contrast, the second ODMR feature found on the 3.16 eV “violet” PL has a larger degree of anisotropy with g║~2.1 and g⊥~2.0 and are similar to the g-values assigned previously to Mg shallow acceptors from ODMR studies of highly Mg-doped GaN heteroepitaxial layers with large degree (≥10%) of compensation.

  1. Bulk growth of undoped and Nd3+ doped zinc thiourea chloride (ZTC) monocrystal: Exploring the remarkably enhanced structural, optical, electrical and mechanical performance of Nd3+ doped ZTC crystal for NLO device applications

    Science.gov (United States)

    Anis, Mohd; Muley, Gajanan. G.

    2017-05-01

    In current scenario good quality crystals are demanded for NLO device application hence present communication is aimed to grow bulk crystal and investigate the doping effect of rare earth element Nd3+ on structural, linear-nonlinear optical, luminescence, mechanical and dielectric properties of zinc thiourea chloride (ZTC) crystal. The ZTC crystal of dimension 21×10×8 mm3 and the Nd3+ doped ZTC crystal of dimension 27×17×5 mm3 have been grown from aqueous solution by slow evaporation technique. The elemental analysis of Nd3+ doped ZTC single crystal has been performed by means of energy dispersive spectroscopic technique. The powder X-ray diffraction technique has been employed to confirm the crystalline phase and identify the effect of Nd3+ doping on structural dimensions of ZTC crystal. The grown crystals have been characterized by UV-Vis-NIR study in the range of 190-1100 nm to ascertain the enhancement in optical transparency of ZTC crystal facilitated by dopant Nd3+. The recorded transmittance data has been utilized to investigate the vital optical constants of grown crystals. The second order nonlinear optical behavior of grown crystals has been evaluated by means of Kurtz-Perry test and the second harmonic generation efficiency of Nd3+ doped ZTC crystal is found to be 1.24 times higher than ZTC crystal. The luminescence analysis has been performed to examine the electronic purity and the color centered photoluminescence emission nature of pure and Nd3+ doped ZTC crystals. The influence of Nd3+ ion on mechanical behavior of ZTC crystal has been investigated by means of microhardness studies. The nature of dielectric constant and dielectric loss of pure and Nd3+ doped ZTC crystal has been examined in the range of 40-100 °C under dielectric study. The Z-scan technique has been employed using the He-Ne laser to investigate the third order nonlinear optical (TONLO) nature of Nd3+ doped ZTC single crystal. The magnitude of TONLO susceptibility, absorption

  2. Luminescence of Er3+ doped double lead halide crystals under X-ray, UV, VIS and IR excitation

    Science.gov (United States)

    Serazetdinov, A. R.; Smirnov, A. A.; Pustovarov, V. A.; Isaenko, L. I.

    2017-09-01

    Er3+ doped double lead halide crystals incorporate a number of properties making them interesting for practical use in light conducting materials. X-ray excited luminescence (XRL) spectra, photoluminescence (PL) spectra in region of 1.5-3.5 eV, photoluminescence excitation (PLE) spectra (2.75-5 eV) and anti-stokes luminescence (ASL) spectra were measured at room temperature in KPb2Cl5 (KPC) and RbPb2Br5 (RPB) matrices doped with Er3+ (1%) ions and in KPC doped with Er3++ Yb3+ ions(1:3 ratio concentration). Intraconfigurational f→f transitions are observed in Er3+ ions in most of the cases. The concrete spectrum form is strongly dependent on the excitation energy. Under 980 nm excitation upper Er3+ levels are excited, showing upconversional processes. In case of 313 nm (UV) and 365 nm (VIS) excitation self trapped exciton luminescence was detected in RPB crystal. Additional Yb3+ doping ions strongly increase quantum yield under 980 nm excitation and this doping cause insignificant influence on quantum yield under VIS or UV excitation.

  3. Bistable light shutter using dye-doped liquid crystals for a see-through display

    Science.gov (United States)

    Huh, Jae-Won; Heo, Joon; Yu, Byeong-Huh; Yoon, Tae-Hoon

    2016-03-01

    See-through displays have got high attention as one of the next generation display devices. Especially, see-through displays that use organic light-emitting diodes (OLEDs) and liquid crystal displays (LCDs) have been actively studied. However, a see-through display using OLEDs cannot provide black color because of their see-through area. Although a see-through display using LCDs can provide black color with crossed polarizers, it cannot block the background. This inevitable problem can be solved by placing a light shutter at the back of a see-through display. To maintain the transparent or opaque state, an electric field must be applied to a light shutter. To achieve low power consumption, a bistable light shutter using polymer-stabilized cholesteric liquid crystals (CLC) has been proposed. It is switchable between the translucent and transparent states only. Therefore, it cannot provide black color. Moreover, it cannot block the background perfectly because of poor performance in the translucent state. In this work we will introduce a bistable light shutter using dye-doped CLCs. To improve the electro-optic characteristics in the opaque state, we employed a crossed electrode structure instead of a parallel one. We will demonstrate that the light shutter can exhibit stable bistable operation between the transparent homeotropic and opaque focal-conic states thanks to polymer stabilization.

  4. Nanophotonic coherent light-matter interfaces based on rare-earth-doped crystals

    Science.gov (United States)

    Zhong, Tian; Kindem, Jonathan M.; Miyazono, Evan; Faraon, Andrei

    2015-09-01

    Quantum light-matter interfaces connecting stationary qubits to photons will enable optical networks for quantum communications, precise global time keeping, photon switching and studies of fundamental physics. Rare-earth-ion-doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical photons, microwave photons and spin waves. Here we demonstrate coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal. Cavity quantum electrodynamics effects including Purcell enhancement (F=42) and dipole-induced transparency are observed on the highly coherent 4I9/2-4F3/2 optical transition. Fluctuations in the cavity transmission due to statistical fine structure of the atomic density are measured, indicating operation at the quantum level. Coherent optical control of cavity-coupled rare-earth ions is performed via photon echoes. Long optical coherence times (T2~100 μs) and small inhomogeneous broadening are measured for the cavity-coupled rare-earth ions, thus demonstrating their potential for on-chip scalable quantum light-matter interfaces.

  5. Synthetic strategy of porous ZnO and CdS nanostructures doped ferroelectric liquid crystal and its optical behavior

    Science.gov (United States)

    Pal, Kaushik; Maiti, Uday Narayan; Majumder, Tapas Pal; Debnath, Subhas Chandra; Bennis, Noureddine; Otón, Jose Manuel

    2013-03-01

    A simple and scalable chemical approach has been proposed for the generation of 1-dimensional nanostructures of two most important inorganic materials such as zinc oxide and cadmium sulfide. By controlling the growth habit of the nanostructures with manipulated reaction conditions, the diameter and uniformity of the nanowires/nanorods were tailored. We studied extensively optical behavior and structural growth of CdS NWs and ZnO NRs doped ferroelectric liquid crystal Felix-017/100. Due to doping band gap has been changed and several blue shifts occurred in photoluminescence spectra because of nanoconfinement effect and mobility of charges.

  6. Effect of L-Cysteine doping on growth and some characteristics of potassium dihydrogen phosphate single crystals

    Science.gov (United States)

    Mahadik, Ashwini; Soni, P. H.; Desai, C. F.

    2017-12-01

    Among quite a number of technologically important NLO materials, Potassium Dihydrogen Phosphate (KDP) is one of the most favourable ones for second harmonic generation applications, such as in electro-optic modulators, parametric oscillators and harmonic generators. The authors report here their studies on KDP crystals doped with L-Cysteine (1 mol% and 2 mol%). The dopant inclusion in the crystals was confirmed using Fourier transform infrared (FT-IR) spectroscopy and Powder X-Ray Diffraction (XRD). The XRD results also confirm the tetragonal structure with lattice parameters a = b = 7.45 Å and c = 6.98 Å. The presence of functional groups of crystals was analyzed using the FTIR spectra. For band gap evaluation, UV-Vis spectra were used and it was found to be 3.41 eV, 4.40eVand 4.50 eV, respectively in the cases of pure KDP, 1 mol% and 2 mol% L-Cysteine dopings. The spectra quality indicates good transparency of the doped crystals in the visible region, a feature quite desirable for applications in optoelectronics.

  7. Optical and structural properties of Eu 2 + doped BaBrI and BaClI crystals

    Science.gov (United States)

    Shendrik, R.; Shalaev, A. A.; Myasnikova, A. S.; Bogdanov, A.; Kaneva, E.; Rusakov, A.; Vasilkovskyi, A.

    2017-12-01

    The work is necessitated by search for new materials to detect ionizing radiation. The rare-earth ions doped with ternary alkali earth-halide systems are promising scintillators showing high efficiency and energy resolution. Some aspects of crystal growth and data on the structural and luminescence properties of BaBrI and BaClI doped with low concentrations of $\\mathrm{Eu^{2+}}$ ions are reported. The crystals are grown by the vertical Bridgman method in sealed quartz ampoule. New crystallography data for BaClI single crystal obtained by single crystal X-ray diffraction method are presented in this paper. Emission, excitation and optical absorption spectra as well as luminescence decay kinetics are studied under excitation by X-ray, vacuum ultraviolet and ultraviolet radiation. The energies of the first 4f-5d transition in $\\mathrm{Eu^{2+}}$ and band gap of the crystals have been obtained. We have calculated the electronic band structure of the crystals using density functional theory as implemented in the \\latin{Ab Initio}. Calculated band gap energies are in accord with the experimental estimates. The energy of gaps between the occupied Eu$^{2+}$ 4f level and the valence band top are predicted. In addition, positions of lanthanide energy levels in relation to valence band have been constructed using the chemical shift model.

  8. Polarization dependence of two-photon transition intensities in rare-earth doped crystals

    Energy Technology Data Exchange (ETDEWEB)

    Le Nguyen, An-Dien [Univ. of California, Berkeley, CA (United States)

    1996-05-01

    A polarization dependence technique has been developed as a tool to investigate phonon scattering (PS), electronic Raman scattering (ERS), and two-photon absorption (TPA) transition intensities in vanadate and phosphate crystals. A general theory for the polarization dependence (PD) of two-photon transition intensities has been given. Expressions for the polarization dependent behavior of two-photon transition intensities have been tabulated for the 32 crystallographic point groups. When the wavefunctions for the initial and final states of a rare-earth doped in crystals are known, explicit PD expressions with no unknown parameters can be obtained. A spectroscopic method for measuring and interpreting phonon and ERS intensities has been developed to study PrVO4, NdVO4, ErVO4, and TmVO4 crystals. Relative phonon intensities with the polarization of the incident and scattered light arbitrarily varied were accurately predicted and subsequently used for alignment and calibration in ERS measurements in these systems for the first time. Since ERS and PS intensities generally follow different polarization curves as a function of polar angles, the two can be uniquely identified by comparing their respective polarization behavior. The most crucial application of the technique in ERS spectroscopy is the establishment of a stringent test for the Axe theory. For the first time, the F1/F2 ratio extracted from the experimental fits of the ERS intensities were compared with those predicted by theories which include both the second- and third-order contributions. Relatively good agreement between the fitted values of F1/F2 and the predicted values using the second-order theory has been found.

  9. Effect of doping of KDP crystal with amino acid L-arginine on the strength properties and character of laser damage

    Science.gov (United States)

    Dolzhenkova, E. F.; Kostenyukova, E. I.; Bezkrovnaya, O. N.; Pritula, I. M.

    2017-11-01

    Studied were the strength characteristics of KDP crystals doped with L-arginine under a concentrated load and irradiation of the first harmonic YAG:Nd3+ laser. The crystals were obtained by means of the temperature reduction method on a point seed, the content of L-arginine in the aqueous solution being 0.3, 0.4, 1.0 and 1.4 wt%. The character of the dependence of KDP microhardness versus the concentration of amino acid in the crystal was investigated. The regularities of brittle damage of the doped KDP crystal at mechanical testing and laser irradiation were shown to be similar. As confirmed in the study, the planes of easy crack extension in the crystal are {2 2 1}, (1 0 0), and (0 0 1) planes, the cracks mainly propagate parallel to {2 2 1} planes. The mechanical and laser strength values of doped KDP crystals were evaluated.

  10. Light-induced charge-transport properties of photorefractive barium-calcium-titanate crystals doped with iron

    Science.gov (United States)

    Veenhuis, H.; Börger, T.; Buse, K.; Kuper, C.; Hesse, H.; Krätzig, E.

    2000-07-01

    Nominally pure and iron doped, as-grown, and thermally annealed photorefractive barium-calcium-titanate crystals of the congruently melting composition Ba0.23Ca0.77TiO3 (BCT) are investigated by holographic and conventional electrical techniques. Refractive-index changes, two-beam-coupling gains, photoconductivities, dark conductivities, and bulk-photovoltaic current densities are measured. As-grown and oxidized crystals are hole conductive and at usual illumination conditions (light wavelength 514.5 nm, light intensity between 0.1 and 1 W/cm2) all measured properties are excellently described by an one-center charge-transport model. The effective electrooptic coefficient r333 is only about 30 pm/V and thus much smaller than the value obtained from interferometric measurements. Two-beam-coupling gains as high as 7 cm-1 are achieved. Doping with iron increases considerably the effective trap density, and bulk-photovoltaic fields of the order of some kilovolts per centimeter are observed in iron-doped crystals. Typical response times of iron-doped, as-grown, or oxidized crystals are about 0.5 s at 1 W/cm2. Reduction yields electron-conductive BCT. The dark storage time increases from 6 min in the as-grown state to 3 h upon a slight reduction treatment, but decreases for strongly reduced samples. The investigation reveals that BCT will become a very promising alternative to barium-titanate crystals (BaTiO3) for many applications.

  11. Effect of Mg$^{2+}$ ions co-doping on timing performance and radiation tolerance of Cerium doped Gd$_{3}$Al$_{2}$Ga$_{3}$O$_{12}$ crystals

    CERN Document Server

    Lucchini, M.T.; Bohacek, P.; Gundacker, S.; Kamada, K.; Nikl, M.; Petrosyan, A.; Yoshikawa, A.; Auffray, E.

    2016-01-01

    Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd3Al2Ga3O12 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd3Al2Ga3O12 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd3Al2Ga3O12 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233 ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments.

  12. Photoredox degradation of different water pollutants (MO, RhB, MB, and Cr(VI)) using Fe–N–S-tri-doped TiO{sub 2} nanophotocatalyst prepared by novel chemical method

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xuyao; Zhou, Xiaosong, E-mail: zxs801213@163.com; Zhang, Lingling; Xu, Limei; Ma, Lin; Luo, Jin; Li, Mengjia; Zeng, Lihua

    2015-10-15

    Highlights: • TiO{sub 2} was synthesized through simple one-step hydrothermal method. • Photocatalytic activity for degradation of organic dyes and Cr(VI) are investigated. • The synergistic effect is shown in coexistence of MB and Cr(VI). - Abstract: Fe–N–S-tri-doped TiO{sub 2} (FeNS-TiO{sub 2}) was synthesized by a simple one-step hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of as-synthesized samples were tested by the oxidation of methyl orange (MO), rhodamine B (RhB), methylene blue (MB) and the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation, and compared with N-dope P25 (N-P25) and the undoped TiO{sub 2}. Besides, the effects of the coexistence of MO, RhB, and MB on FeNS-TiO{sub 2}-mediated photocatalytic reduction of aqueous Cr(VI) were also studied. The results indicated FeNS-TiO{sub 2} displayed higher visible-light-activated photocatalytic activity than N-P25 and the undoped TiO{sub 2}. Otherwise, FeNS-TiO{sub 2} showed the coexistence of MB enhanced the photocatalytic reduction of Cr(VI), whereas the coexistence of MO and RhB retarded the photocatalytic reduction of Cr(VI) over FeNS-TiO{sub 2}. Moreover, a possible photocatalytic mechanism is discussed.

  13. C atom endohedral doping effect on the bond lengths in the crystal structure of fcc-C60

    Directory of Open Access Journals (Sweden)

    S Javanbakht

    2011-03-01

    Full Text Available Single and double equilibrium bond lengths of the fcc-C60 crystal were calculated in the absence and presence of the endohedral C atom as an impurity doped into each C60 cluster, i.e., fcc-C@C60, by means of fully-relaxed self-consistent calculations within the density functtional theory (DFT employing the full potential-augmented plane waves plus local orbital (FP-APW+lo method. The result shows that the single and double bond lengths were decreased for the doped case of fcc-C@C60 when compared with the pure fcc-C60. The reduction in the bond lengths by the carbon impurity doping is attributed to the bond alternation effect and reduction of the symmetry in the C60 molecule. The result shows that the impurity injection gives rise to change in the electron charge distribution and as a result to change in electronic properties.

  14. Synthesis, characterization and anti-microbial activity of pure, Cu2+ and Cd2+ doped organic NLO l-arginine trifluoroacetate single crystals

    Science.gov (United States)

    Prasanyaa, T.; Haris, M.; Jayaramakrishnan, V.; Amgalan, M.; Mathivanan, V.

    2013-10-01

    Optically transparent Cu2+ and Cd2+ doped l-arginine trifluoroacetate (LATF) single crystals were grown from its aqueous solution using the slow solvent evaporation technique. The grown crystals were characterized by powder x-ray diffraction to confirm the monoclinic crystal structure. The percentage of transmittance measured using the ultraviolet-visible-near infrared spectrophotometer was found to be more than 80% for doped crystals. The functional group analysis of the grown crystals has been made by Fourier transform infrared spectroscopy. Thermogravimetric/differential thermal analysis was performed for the grown crystals. An atomic absorption study was carried out to determine the presence of Cu2+ and Cd2+. The hardness of the grown crystals was assessed and the results show a significant variation in the hardness value between the pure and doped LATF crystals. The second harmonic generation measurements show that Cu2+ doped LATF is 2.8 times greater and Cd2+ doped is 2.6 times greater than KDP. The anti-bacterial and anti-fungal activities of the title compound were performed using the disc diffusion method against standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillus niger and Aspergillus flavus.

  15. Electrical properties of lead-free Fe-doped niobium-rich potassium lithium tantalate niobate single crystals

    Science.gov (United States)

    Li, Yang; Li, Jun; Zhou, Zhongxiang; Guo, Ruyan; Bhalla, Amar S.

    2013-12-01

    Lead-free, 0.025 wt% Fe-doped niobium-rich potassium lithium tantalate niobate Fe: K0.95Li0.05Ta1-xNbxO3 single crystals have been grown by the top-seeded melt growth method. All the transition temperatures have been determined by the dielectric constant and loss-dependent temperature. The spontaneous polarizations computed by the integration of pyroelectric coefficients over all the temperatures are consistent with the results of the P-E hysteresis loops. The piezoelectric constants and electromechanical coupling factors are attractive among lead-free piezoelectric materials. With suitable Fe-doping, the electrical properties of KLTN single crystals have been improved overall and can be compared to those of the current important lead-based piezoelectric materials.

  16. Gamma-radiation-induced absorption in doubly doped PbWO sub 4 :Mo,Y crystals

    CERN Document Server

    Sulc, M; Bohácek, P; Nejezchleb, K; Jarolímek, O; Vognar, M

    2002-01-01

    The set of Mo and (Mo,Y) doped PbWO sub 4 scintillating crystals was irradiated 30 min by a homogeneous gamma-radiation field, produced in the irradiation of tungsten target by 21 MeV electron beam from the microtrone accelerator. The induced absorption spectra were measured on-line, i.e. during the irradiation and after switching-off the machine with a sampling rate of 10 s for the dose rates of about 0.17 Gy/min. The results show a clear effect of the doped ions in PWO crystals on the spectra and kinetics of both colour centres formation and recovery processes. The induced absorption build-up and recovery time dependences at fixed wavelength are approximated by a simple model and quantitative parameters are extracted and discussed.

  17. Holographic recording in a doubly doped lithium niobate crystal with two wavelengths: a blue laser diode and a green laser

    Science.gov (United States)

    Komori, Yuichi; Ishii, Yukihiro

    2010-08-01

    A doubly-doped LiNbO3 (LN) crystal has been well used as a nonvolatile two-wavelength recording material. By using two levels of the crystal, two-kind holograms can be recorded on one crystal; a hologram is recorded with a 405-nm blue laser diode (LD) for a deep Mn level, and another hologram is with a 532-nm green laser for a shallow Fe level. The recording capacity doubles. A 780-nm LD is non-volatile reconstructing source since the LD line is insensitive to both levels. Multiplexed reconstructed images are demonstrated by using a sharp angular selectivity of a volume LN crystal keeping Bragg condition with spherical reconstructions.

  18. Spectroscopic and neutron detection properties of rare earth and titanium doped LiAlO 2 single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dickens, Peter T.; Marcial, José; McCloy, John; McDonald, Benjamin S.; Lynn, Kelvin G.

    2017-10-01

    In this study, LiAlO2 crystals doped with rare-earth elements and Ti were produced by the CZ method and spectroscopic and neutron detection properties were investigated. Photoluminescence revealed no clear luminescent activation of LiAlO2 by the rare-earth dopants though some interesting luminescence was observed from secondary phases within the crystal. Gamma-ray pulse height spectra collected using a 137Cs source exhibited only a Compton edge for the crystals. Neutron modeling using Monte Carlo N-Particle Transport Code revealed most neutrons used in the detection setup are thermalized, and while using natural lithium in the crystal growth, which contains 7.6 % 6Li, a 10 mm Ø by 10 mm sample of LiAlO2 has a 70.7 % intrinsic thermal neutron capture efficiency. Furthermore, the pulse height spectra collected using a 241Am-Be neutron source demonstrated a distinct neutron peak.

  19. Improvement of Image Sticking in Liquid Crystal Display Doped with γ-Fe2O3 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Wenjiang Ye

    2017-12-01

    Full Text Available Image sticking in thin film transistor-liquid crystal displays (TFT-LCD is related to the dielectric property of liquid crystal (LC material. Low threshold value TFT LC materials have a weak stability and the free ions in them will be increased because of their own decomposition. In this study, the property of TFT LC material MAT-09-1284 doped with γ-Fe2O3 nanoparticles was investigated. The capacitances of parallel-aligned nematic LC cells and vertically aligned nematic LC cells with different doping concentrations were measured at different temperatures and frequencies. The dielectric constants perpendicular and parallel to long axis of the LC molecules ε⊥ and ε//, as well as the dielectric anisotropy Δε, were obtained. The dynamic responses and the direct current threshold voltages in parallel-aligned nematic LC cells for different doping concentrations were also measured. Although the dielectric anisotropy Δε decreased gradually with increasing temperature and frequency at the certain frequency and temperature in LC state for each concentration, the doping concentration of γ-Fe2O3 nanoparticles less than or equal to 0.145 wt % should be selected for maintaining dynamic response and decreasing free ions. This study has some guiding significance for improving the image sticking in TFT-LCD.

  20. Decolorization of crystal violet over TiO2 and TiO2 doped with zirconia photocatalysts

    Directory of Open Access Journals (Sweden)

    Vasic Marija B.

    2017-01-01

    Full Text Available Titania based catalyst and TiO2 doped with zirconia were prepared by modified sol–gel method. The synthesized catalysts samples were characterized by BET, XRD, SEM and FTIR techniques. Photocatalytic activity was tested in the reaction of crystal violet (CV dye decolorization/decomposition under UV light irradiation. The effect of several operational parameters, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment and number of reaction cycles were also considered. The obtained results indicated faster dye decolorization with the increase of the catalyst amount and a decrease of initial CV concentrations. An influence of doping with zirconia on the physico-chemical properties of bare titania was studied. The doping procedure had affected photocatalytic properties of the final catalytic material, and had improved photocatalytic performances of doped catalyst on crystal violet decolorization/degradation in comparison to bare titania. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 1612008, Grant no. 45012 and Grant no. 172061

  1. Electro-optical effects of oxidized multi-walled carbon nanotube doping on holographic polymer dispersed liquid crystal films

    Science.gov (United States)

    Shriyan, Sameet K.; Fontecchio, Adam K.

    2009-08-01

    In this work we demonstrate an improved electro-optic response and quantify the effect on transmitted wavefront properties of thiolene based reflection mode holographic polymer dispersed liquid crystals (HPDLC) gratings doped with oxidized multi-walled carbon nanotubes (MWNT). Effect of various doping levels on the reflection efficiencies is evaluated and optical spectrometry results indicate a reduction in the reflection efficiency and an anomalous electrooptic behavior at higher doping levels of MWNT especially in gratings with longer pitch where the diffusion length for liquid crystal (LC) is long. Wavefront analysis based on Shack-Hartmann wavefront sensor show an increase in the transmitted RMS wavefront error in a 633nm wavefront after a critical level of MWNT doping. Polarized optical microscopy results indicate that the MWNT do not participate in the photo polymerization induced phase separation hence acting as physical barriers for the counter diffusing LC at high MWNT concentrations. Reduction in overall size of the LC droplets in the LC rich planes, observed using scanning electron microscopy imaging, leads to faster rise and fall times hence quicker relaxation time. Observation of reduced switching voltage is attributed to the modification of dielectric properties of the medium manifested by an increase in capacitance and decrease in resistivity in presence of MWNT.

  2. Photo- and electro-isomerization of azobenzenes based on polymer-dispersed liquid crystals doped with azobenzenes and their applications.

    Science.gov (United States)

    Liu, Yen-Chen; Cheng, Ko-Ting; Chen, Hsin-Fu; Fuh, Andy Ying-Guey

    2014-02-24

    We report the photo-isomerization and electro-isomerization effects in azobenzenes-doped polymer-dispersed liquid crystals during the switching of the liquid crystal (LC) device between transparent (cis-isomers dominant) and scattering states (trans-isomers dominant). The isothermal phase transition, which is a result of the illumination of UV light and the application of DC voltage, was the main mechanism to switch the LC device between transparency, scattering, and gray scales. This study discusses in detail the variations in the population of cis-isomers as functions of the period and the amplitude of the applied DC voltage.

  3. Intense luminescence emission from rare-earth-doped MoO3 nanoplates and lamellar crystals for optoelectronic applications

    Science.gov (United States)

    Vila, M.; Díaz-Guerra, C.; Jerez, D.; Lorenz, K.; Piqueras, J.; Alves, E.

    2014-09-01

    Strong and stable room-temperature photoluminescence (PL) emission is achieved in MoO3 nanoplates and lamellar crystals doped with Er and Eu by ion implantation and subsequent annealing. Micro-Raman and PL spectroscopy reveal that optical activation of the rare earth ions and recovery of the original MoO3 structure are achieved for shorter annealing treatments and for lower temperatures in nanoplates, as compared with lamellar crystals. Er seems to be more readily incorporated into optically active sites in the oxide lattice than Eu. The influence of the dimensionality of the host sample on the characteristics of the PL emission of both rare earth dopants is addressed.

  4. Investigation on nonlinear optical and dielectric properties of L-arginine doped ZTC crystal to explore photonic device applications

    Directory of Open Access Journals (Sweden)

    Anis Mohd

    2016-09-01

    Full Text Available The present study is focused to explore the photonic device applications of L-arginine doped ZTC (LA-ZTC crystals using nonlinear optical (NLO and dielectric studies. The LA-ZTC crystals have been grown by slow evaporation solution technique. The chemical composition and surface of LA-ZTC crystal have been analyzed by means of energy dispersive spectroscopy (EDS and surface scanning electron microscopy (SEM techniques. The Vicker’s microhardness study has been carried out to determine the hardness, work hardening index, yield strength and elastic stiffness of LA-ZTC crystal. The enhanced SHG efficiency of LA-ZTC crystal has been ascertained using the Kurtz-Perry powder SHG test. The closed-and-open aperture Z-scan technique has been employed to confirm the third order nonlinear optical nature of LA-ZTC crystal. The Z-scan transmittance data has been utilized to calculate the superior cubic susceptibility, nonlinear refractive index, nonlinear absorption coefficient and figure of merit of LA-ZTC crystal. The behavior of dielectric constant and dielectric loss of LA-ZTC crystal at different temperatures has been investigated using the dielectric analysis.

  5. The effect of Nd and Mg doping on the micro-Raman spectra of LiNbO{sub 3} single-crystals

    Energy Technology Data Exchange (ETDEWEB)

    Quispe-Siccha, R; Villagran-Muniz, M [Laboratorio de FotofIsica, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, AP 70-186, DF (Mexico); MejIa-Uriarte, E V [Laboratorio de Fotonica de Microondas, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, AP 70-186, DF (Mexico); Jaque, D; GarcIa Sole, J; Jaque, F [Laboratorio de Espectroscopia Laser, Departamentode Fisica de Materiales, Universidad Autonoma de Madrid, Madrid 28049 (Spain); Sato-Berru, R Y [Laboratorio de Materiales y NanotecnologIa, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, AP 70-186, DF (Mexico); Camarillo, E; Hernandez A, J; Murrieta S, H [Laboratorio Propiedades Opticas, Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP 20-364 (Mexico)], E-mail: rosa.quispe@gmail.com, E-mail: elsi.mejia@ccadet.unam.mx, E-mail: mayo.villagran@ccadet.unam.mx, E-mail: dani.jaque@uam.es, E-mail: jose.garcia_sole@uam.es, E-mail: francisco.jaque@uam.es, E-mail: roberto.sato@ccadet.unam.mx, E-mail: cgarcia@fisica.unam.mx, E-mail: josemh@fisica.unam.mx, E-mail: murrieta@fisica.unam.mx

    2009-04-08

    The LiNbO{sub 3} congruent crystals doped with small Nd concentrations, <1 mol% Nd, and co-doped with Mg ions, 0-9 mol% Mg, were systematically investigated by means of micro-Raman spectroscopy in the Y and Z crystal directions. Results obtained from an undoped congruent crystal, an Nd-doped crystal, a Mg-doped crystal and Nd, Mg-co-doped crystals are compared. From the analyses of the results obtained in the Y direction, the Nd and Mg content dependence of the two lowest-Raman A{sub 1}(TO{sub 1}) and A{sub 1}(TO{sub 2}) modes, the half-width composition and the area ratio of the A{sub 1}(TO{sub 4}) and E(TO{sub 8}) bands, we reached several conclusions about the incorporation mechanism of the Nd and Mg ions into the LiNbO{sub 3} lattice. Likewise the Raman shift and half-width of the E(TO{sub 1}) and E(TO{sub 7}) modes were investigated in the Z direction. Results indicate that Mg and Nd ions are located in the Li site for low doping concentrations and for larger concentrations there is a replacement in both Li and Nb ion sites.

  6. Micro-Holograms in a Methyl Red-Doped Polymer-Dispersed Liquid Crystal (E48:PVP

    Directory of Open Access Journals (Sweden)

    N. P. Hermosa II

    2003-06-01

    Full Text Available Feasibility of a holographic point-by-point storage in a methyl red-doped Polymer-Dispersed LiquidCrystal (PDLC is determined. Micro-holograms (gratings are recorded next to each other. Smallestgrating diameter obtained is 69.9 mm, with minimum grating distance of 80 mm. Recording of adjacentgrating reduces the diffraction efficiency of existing grating by 17% (average.

  7. Enhanced photorefractive properties in Hf, Ce and Cu co-doped LiNbO{sub 3} crystals for holographic application

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tao, E-mail: tzhang_hit02@yahoo.com [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China); Wang, Xin; Geng, Tao; Tong, Chengguo [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Kang, Chong [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China)

    2015-04-25

    Graphical abstract: Correlation spots of 200 holograms in a Hf, Ce and Cu co-doped LiNbO{sub 3}. - Highlights: • Several doped LiNbO{sub 3} crystals with various level of Hf doping were grown by Cz method. • IR peak shift is attributed to the complex defect change at different level of Hf. • Enhanced photorefractive properties have been got with higher Hf-doping level. • Reduced defect and increased photoconductivity are responsible for optical properties. • 200 holograms’ experiment is realized in a coherent volume 0.073 cm{sup 3}. - Abstract: Hf, Ce and Cu co-doped LiNbO{sub 3} crystals with various level of Hf doping were grown in air by a conventional Cz method. The infrared spectra were measured to discuss the defect structures and the mechanism of the absorption peak shift in these crystals. The light-induced scattering of the crystals was evaluated by the transmitted light method. The influence of the Hf-doping level on the photorefractive properties of Hf, Ce and Cu co-doped LiNbO{sub 3} crystals was studied via two-beam coupling. It is found that proper doping Hf is an efficient method to enhance the comprehensive photorefractive properties of the LiNbO{sub 3}. Using one of these crystals as medium, 200 holograms storage and correlation experiments based on angle fractal multiplexing have been realized in a coherent volume 0.073 cm{sup 3}. Moreover the diffraction efficiency is uniform and the storage density has reached 2.2 Gb/cm{sup 3}.

  8. Optical and dielectric studies on pure and Ni{sup 2+}, Co{sup 2+} doped single crystals of bis thiourea cadmium chloride

    Energy Technology Data Exchange (ETDEWEB)

    Uthrakumar, R.; Vesta, C.; Raj, C.J.; Dinakaran, S. [Department of Physics, Loyola College, Chennai (India); Dhas, Rani C. [Department of Physics, Ethiraj College, Chennai (India); Das, S.J.

    2008-04-15

    Good quality single crystals of Ni{sup 2+}, Co{sup 2+} ions doped Bisthiourea Cadmium Chloride (BTCC) are some of the excellent and efficient non-linear optical materials grown from aqueous solution by slow evaporation method. The lattice parameters of the grown crystals are determined by single crystal X-ray analysis. UV spectral analyses on these samples reveal the improved transparency of the doped crystals ascertaining the inclusion of metal ion in the lattice. FTIR spectral analysis carried out on the materials confirm the presence of functional groups. Dielectric measurements reveal that the dielectric constant of pure and doped crystals decreases with increase of frequency. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Experimental evidence of a nonlinear loss mechanism in highly doped Yb:LuAG crystal.

    Science.gov (United States)

    Pirri, Angela; Toci, Guido; Nikl, Martin; Babin, Vladimir; Vannini, Matteo

    2014-02-24

    We report a rigorous study of the spectroscopic, laser and thermal properties of a 10at.% and a 15at.% Yb:LuAG crystals. A loss mechanism is observed in the medium with the highest doping, pumped at 936 nm and 968 nm, as a sharp and dramatic decrease of the laser output power is measured at higher excitation densities. The nonlinearity of the loss mechanism is confirmed by the fluorescence data and by the thermal lens. In particular, the dioptric power of the thermal lens acquired at different pumping levels shows a strong deviation of the expected linear trend. Here we report the influence of both the concentration and the ion excitation density of Yb3+ on the output powers, the slope efficiencies and the thresholds. Conversely excellent results are achieved with the 10at.%, which does not show any loss mechanism as at 1046 nm it delivers 11.8 W with a slope efficiency of η(s) = 82%, which is, to the best of our knowledge, the highest value reported in literature for this material.

  10. Simultaneous EPR and optical spectroscopy of pure and Rh-doped barium calcium titanate crystals

    Science.gov (United States)

    Grachev, Valentin; Malovichko, Galina; Schirmer, Ortwin

    2003-03-01

    The large electro-optic coefficients and high holographic sensitivity of barium calcium titanate (Ba0.77Ca0.23TiO3, BCT) make it promising candidate for various applications, since it has no drawback related to the phase transition at 280 K like barium titanate. The nominally pure and Rh doped BCT crystals were investigated with the help of optical absorption spectroscopy, light induced absorption change measurements and electron paramagnetic resonance (EPR) in the temperature range between 4.2 and 300 K. Analyzing angular dependencies of the EPR lines we succeed to identify low-symmetry and nearly cubic centers of iron trace impurity. Four other paramagnetic defects were found after illumination: Ti3+, Rh2+, O- and Pt3+. All these defects are participants of charge transfer processes. At the light energy E about 1.3 eV the holes abandon Ti4+ creating the paramagnetic electronic Ti3+. At E > 2.3 eV O2- ions capture the holes and create hole O- centers and simultaneously Ti3+ concentration increases. Nearly located non-controlled or intentionally introduced impurities (Sr, K, Na, Ca...) may serve as pins for the fixation of the electrons and holes. Additional correlated changes were found at E > 3.2 eV (band-band transition), when EPR lines of Rh2+, Pt3+ appear and intensities of Ti3+, O- and Fe3+ essentially increase. Models of defects involved in these light induced processes are proposed.

  11. Tunable amplified spontaneous emission in graphene quantum dots doped cholesteric liquid crystals

    Science.gov (United States)

    Cao, Mingxuan; Yang, Siwei; Zhang, Yating; Song, Xiaoxian; Che, Yongli; Zhang, Haiting; Yu, Yu; Ding, Guqiao; Zhang, Guizhong; Yao, Jianquan

    2017-06-01

    Graphene quantum dots (GQDs) have received much research attention, because of their useful structure and optical absorption/emission. We report the tunable amplified spontaneous emission (ASE) in GQD-doped cholesteric liquid crystal (CLC), which to the best of our knowledge has not been previously observed. The GQDs are uniformly dispersed with a weight ratio of 0.5 wt.% in CLC. Under optical excitation, typical ASE is triggered in the system at pump energies greater than 1.25 mJ cm-2. The emission peak at the long wavelength edge of the photonic bandgap shifts from 662 to 669 nm, as the working temperature is increased from 50 to 90 °C. The preparation of the combined GQDs and CLC is simple and low-cost, and the resulting material is photostable and non-toxic. Combining the GQD gain material with the self-assembled CLC resonator has potential in the fabrication of ASE source and laser devices.

  12. Significance of Al doping for antiferromagnetic AFII ordering in YBa2Cu3-xAlxO6+#delta# materials: A single-crystal neutron-diffraction study

    DEFF Research Database (Denmark)

    Brecht, E.; Schmahl, W.W.; Fuess, H.

    1995-01-01

    the antiferromagnetic ordering pattern is different for the AFI and AFII phase, the ordered moments on the Cu sites are within the experimental error ([S](Cu(2)) approximate to 0.56 mu(B), [S](Cu(1)) approximate to 0 mu(B)) identical in the two phases. Comparison of Al-doped crystals with pure crystals of the same...

  13. Infrared absorption, laser excitation and crystal-field analyses of the C-4v symmetry centre in KY3F10 doped with Pr3+

    NARCIS (Netherlands)

    Wells, J. P. R.; Yamaga, M.; Han, T. P. J.; Gallagher, H. G.

    2000-01-01

    We report a comprehensive spectroscopic study of KY3F10 doped with trivalent praseodymium. Employing both infrared absorption and laser excited fluorescence spectroscopy, we have constructed an energy level scheme of 39 crystal-field states. A C-4v symmetry, conventional crystal-field analysis can

  14. Evidence for interface superconductivity in rare-earth doped CaFe2As2 single crystals

    Science.gov (United States)

    Lv, Bing; Deng, L. Z.; Wei, F. Y.; Xue, Y. Y.; Chu, C. W.

    2014-03-01

    To unravel to the mysterious non-bulk superconductivity up to 49K observed in rare-earth (R =La, Ce, Pr and Nd) doped CaFe2As2 single-crystals whose Tc is higher than that of any known compounds consisting of one or more of its constituent elements of R, Ca, Fe, and As at ambient or under pressures, systematic magnetic, compositional and structural have carried out on different rare-earth-doped (Ca1-xRx) Fe2As2 samples. We have detected extremely large magnetic anisotropy, doping-level independent Tc, unexpected superparamagnetic clusters associated with As vacancies and their close correlation with the superconducting volume fraction, the existence of mesoscopic-2D structures and Josephson-junction arrays in this system. These observations lead us to conjecture that the Tc enhancement may be associated with naturally occurring chemical interfaces and thus provided evidence for the possible interface-enhanced Tc in naturally-grown single crystals of Fe-based superconductors.

  15. Tuning crystal structures and thermoelectric properties through Al doping in ReSi{sub 1.75}

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fei; Lidin, Sven [Division of Polymer and Materials Chemistry, CAS, Lund University, Getingevaegen 60, 22241, Lund (Sweden); Veremchuk, Igor [Department Chemical Metals Science, Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, 01187, Dresden (Germany)

    2017-01-03

    Binary rhenium silicide, ReSi{sub 1.75}, and its aluminium-doped variants have been synthesized. Their crystal structures were characterized by X-ray diffraction, solved and refined through the use of superspace group models. The binary undoped ReSi{sub 1.75} is a commensurate (supercell) structure of the previously well-known MoSi{sub 2}-type structure. Al doping renders an incommensurate structure that was solved and refined, and reported for the first time. The thermoelectric properties of these compounds were also measured, including their electrical resistivities, thermal conductivities, and Seebeck coefficients. Compared with the commensurate structure of binary ReSi{sub 1.75}, the Al-doped incommensurate phase exhibits lower lattice thermal conductivity, lower electrical resistivity, a higher Seebeck coefficient, and ultimately a much higher figure of merit (ZT). The cause of the structural incommensuration by Al doping was studied through the use of first-principle calculations. The relationship between the incommensurability and the improved thermoelectric properties is also discussed. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Crystal structures and magnetic properties of strontium and copper doped lanthanum ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Sora, Isabella Natali, E-mail: isabella.natali-sora@unibg.it [INSTM R.U. and Department of Industrial Engineering, University of Bergamo, Dalmine, BG, I-24044 (Italy); Caronna, Tullio; Fontana, Francesca [INSTM R.U. and Department of Industrial Engineering, University of Bergamo, Dalmine, BG, I-24044 (Italy); Julian Fernandez, Cesar de [INSTM R.U. Firenze and Department of Chemistry, University of Florence, I-50019 Sesto Fiorentino (Italy); CNR-Istituto di Scienze e Tecnologie Molecolari (ISTM), 20133 Milano (Italy); Caneschi, Andrea [INSTM R.U. Firenze and Department of Chemistry, University of Florence, I-50019 Sesto Fiorentino (Italy); Green, Mark [Center for Neutron Research, NIST, Gaithersburg, MD (United States); Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742-2115 (United States)

    2012-07-15

    The crystal and magnetic structures of La{sub 0.8}Sr{sub 0.2}Fe{sub 1-x}Cu{sub x}O{sub 3-w} compounds, which exhibit coercive fields larger than any others reported for iron-based perovskites, have been analyzed at room temperature with the neutron powder diffraction technique and the Rietveld method of profile fitting. For x in the range 0.05-0.10 the material is monophasic with orthorhombic symmetry (space group Pnma), and crystallizes in the perovskite-like cell of LaFeO{sub 3}, Fe/Cu cations occupy octahedral sites, La/Sr cations are twelve-fold coordinated. For x=0.20 the material is biphasic, with a main orthorhombic phase (space group Pnma) and a secondary rhombohedral phase with space group R-3c (hexagonal setting). The structural transition from the orthorhombic to the rhombohedral phase reduces the structural distortion of the (Fe/Cu)O{sub 6} octahedron. The average bond distance (Fe/Cu)-O and the pseudo-cubic unit cell volume decrease with increasing Cu content in accordance with the presence of higher valence states of the transition metals. The magnetic structure was modeled for the monophasic samples (x=0.05 and 0.10) assuming an antiferromagnetic interaction between Fe/Cu neighboring cations (G-type): the magnetic moments order antiferromagnetically along the b-axis, with the spin direction along a-axis. The magnetic moments of the Fe/Cu atoms are {mu}{sub x}=2.66(3){mu}{sub B} and 2.43(3){mu}{sub B} for the compositions x=0.05 and 0.10, respectively. By measuring the first magnetization curve and the hysteresis loops, coexisting antiferromagnetic and weak ferromagnetic interactions were observed for all samples. - Graphical abstract: Hysteresis loops measured at room temperature of the sample with x=0.05. Highlights: Black-Right-Pointing-Pointer Iron based perovskites with the largest coercive fields. Black-Right-Pointing-Pointer Sr and Cu lanthanum ferrites as magnetic materials. Black-Right-Pointing-Pointer Doped lanthanum ferrites show

  17. Remarkable effect of Ni{sup 2+}doping on structural, second harmonic generation, optical, mechanical and dielectric properties of KDP single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ganesh, V. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Shkir, Mohd, E-mail: shkirphysics@gmail.com [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); AlFaify, S.; Algarni, H. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Abutalib, M.M. [Faculty of Science-AL Faisaliah, Campus, King Abdulaziz University, P.O. Box 80200, Jeddah 21589 (Saudi Arabia); Yahia, I.S. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Nano-Science & Semiconductor Labs., Thin Film Lab., Department of Physics, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt)

    2016-06-15

    The nonlinear optical single crystals of pure and Ni{sup 2+} doped potassium dihydrogen phosphate (KDP) were successfully grown by slow evaporation solution growth technique. The effects of the addition of Ni{sup 2+} with different molar concentration have been studied by powder X-ray diffraction, FT-Raman, second harmonic generation, microscopic and dielectric studies. Its crystallinity was assessed by the FT-Raman technique and its surface, structural imperfections were recorded using high resolution microscope, which clearly reveals that the doping is showing considerable effect on the samples. The SHG measurements also carried out on pure and doped samples, which reveal the relative SHG efficiency has been enhanced due to doping. The optical activities were studied by UV–vis-NIR technique and reveals high optical transparency in doped samples. The remarkable enhancement in mechanical strength was observed due to doping. The enhanced dielectric constant and low dielectric loss confirms that the grown crystals with doping are superior to pure crystals and may be used in optoelectronic devices.

  18. Optical spectroscopy and crystal-field analysis of YAl sub 3 (BO sub 3) sub 4 single crystals doped with dysprosium

    CERN Document Server

    Cavalli, E; Magnani, N; Ramirez, M O; Speghini, A; Bettinelli, M

    2003-01-01

    YAl sub 3 (BO sub 3) sub 4 crystals doped with Dy sup 3 sup + were grown from a potassium trimolybdate flux. Their absorption and visible emission spectra and decay curves were measured at temperatures ranging from 10 to 298 K. The complete energy level scheme has been deduced from the low temperature measurements and reproduced by theoretical calculations based on a parametric Hamiltonian including coulombic, spin-orbit and crystal-field terms. The Judd-Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra. The calculated radiative lifetime of the sup 4 F sub 9 sub / sub 2 state is 344 mu s; this value is reasonably consistent with the experimental data.

  19. Development of n- and p-type Doped Perovskite Single Crystals Using Solid-State Single Crystal Growth (SSCG) Technique

    Science.gov (United States)

    2017-10-09

    develop a new single crystal growth method which is suitable to grow chemically uniform and large “n- and p-type doped” perovskite single crystals...boundary are also fabricated using diffusion bonding process of two single crystal plates. These results demonstrate that the SSCG (solid-state...that can be used to develop new non-linear dielectrics for high-voltage and high-power applications. A major need is to better understand their

  20. Single-mode amplification in Yb-doped rod-type photonic crystal fibers for high brilliance lasers

    DEFF Research Database (Denmark)

    Poli, F.; Lægsgaard, Jesper; Passaro, D.

    2009-01-01

    This paper presents the effect of a low refractive index ring in the Yb-doped rod-type photonic crystal fibre core on the guided mode propagation and analyzed through a spatial and spectral amplifier model. The ring provides a higher differential overlap between the fundamental mode (FM......) and the higher-order mode (HOM), stressing the difference between their spatial distributions, with respect to the uniform refractive index core. In the present analysis a rod-type PCF with a 19-missing air-hole core, whose radius is 30 mum, has been considered. Initially, a PCF step-index model has been applied...... to identify a proper ring characteristic that is width, position and refractive index. Then rod-type PCF designs have been optimized with a full-vector modal solver based on the finite-element method. Then, the amplification properties of the Yb-doped rod-type PCFs have been investigated by assuming a forward...

  1. Optical and structural characterization of GaSb and Te-doped GaSb single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Tirado-Mejia, L. [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Villada, J.A. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Qro (Mexico); Rios, M. de los [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Penafiel, J.A. [Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro (Mexico); Posgrado en Ciencia e Ingenieria Materiales, Universidad Nacional Autonoma de Mexico, Mexico (Mexico); Fonthal, G. [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Espinosa-Arbelaez, D.G. [Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro (Mexico); Posgrado en Ciencia e Ingenieria Materiales, Universidad Nacional Autonoma de Mexico, Mexico (Mexico); Ariza-Calderon, H. [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Rodriguez-Garcia, M.E. [Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro (Mexico)], E-mail: marioga@fata.unam.mx

    2008-11-30

    Optical and structural properties of GaSb and Te-doped GaSb single crystals are reported herein. Utilizing the photoreflectance technique, the band gap energy for doped samples was obtained at 0.814 eV. Photoluminescence (PL) spectra showed a peak at 0.748 eV that according to this research, belongs to electronic states of pure GaSb and not to the longitudinal optical (LO) phonon replica as has been reported by other authors. Analysis of the full width at half maximum (FWHM) values of X-ray diffraction, as well as micro-Raman peaks showed that the inclusion of Te decreases the crystalline quality.

  2. Effect of Ni2+ Doping on the Growth and Properties of Mn-L-Histidine Hydrochloride Monohydrate Crystals

    Directory of Open Access Journals (Sweden)

    J. Sai Chandra

    2013-01-01

    Full Text Available The main focus of this work had been to grow good quality crystals from amino acids and amino acid-based materials for nonlinear optics (NLO applications. For the first time, a series of amino acid complexes doped with transition metal ions were grown in our laboratory from aqueous solutions by slow evaporation technique. Ni(II ion doped Manganese L-Histidine hydrochloride monohydrate (Ni(II-MnLHICl crystals were grown on the same lines and were characterized by powder X-ray diffraction (XRD, optical absorption, electron paramagnetic resonance, and infrared absorption studies. From Powder XRD, the unit cell lattice parameters were calculated as a=1.5301 nm, b=0.8928 nm and c=0.6851 nm. From electron paramagnetic resonance (EPR spectra, isotropic “g” factor and spin hamiltonian parameter A all were calculated as 2.0439 and 20×10−4, respectively. From optical absorption studies, crystal field splitting value (Dq and the interelectron repulsion parameters B and C were calculated for Ni2+ and Mn2+ as Dq=850 cm−1, B=725 cm−1, C=2640 cm−1 and Dq=915 cm−1, B=810 cm−1, C=2780 cm−1, respectively. The presence of various functional groups and the modes of vibrations were confirmed by FTIR studies.

  3. Spin-glass-like behaviour in tin doped ZnCr{sub 2}Se{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Jendrzejewska, Izabela, E-mail: izabela.jendrzejewska@us.edu.pl [University of Silesia, Institute of Chemistry, Szkolna 9, 40-006 Katowice (Poland); Groń, Tadeusz; Kusz, Joachim [University of Silesia, Institute of Physics, Uniwersytecka 4, 40-007 Katowice (Poland); Żelechower, Michał [Silesian University of Technology, Krasińskiego 8, 40-019 Katowice (Poland); Maciążek, Ewa [University of Silesia, Institute of Chemistry, Szkolna 9, 40-006 Katowice (Poland); Ślebarski, Andrzej; Fijałkowski, Marcin [University of Silesia, Institute of Physics, Uniwersytecka 4, 40-007 Katowice (Poland)

    2015-06-25

    Highlights: • The new single crystals ZnCr{sub 2}Se{sub 4} doped by tin were successfully synthesized. • ZFC and FC splitting for all investigated crystals was observed. • Spin-glass-like behaviour for a large Sn content was discovered. - Abstract: The single crystals of ZnCr{sub 2}Se{sub 4} doped with tin ions having contents of 0.92, 1.01 and 1.26 located in the octahedral sites of the spinel structure were successfully synthesized. The ac and dc magnetic measurements, and as well as the specific heat studies showed the spin-glass-like behaviour for all compositions below the freezing temperatures T{sub f} = 13–15 K. Both high positive values of the paramagnetic Curie–Weiss temperature, decreasing from 112 K to 58 K as the Sn-content increases, and the lack of a metamagnetic transition (characteristic for the ZnCr{sub 2}Se{sub 4} matrix) suggest a strong ferromagnetic exchange in the (0 0 1) planes which is randomly frozen below T{sub f} between the spins in adjacent (0 0 1) planes. These effects are interpreted in terms of the exchange integral of the spin-glass system including non-stoichiometry, spin and structural defects.

  4. DC-field-assisted grating formation and nonlinear diffractions in methyl-red dye-doped blue phase liquid crystals.

    Science.gov (United States)

    Khoo, Iam Choon

    2015-01-01

    We report the observation of enhanced nonlinear optical responses of methyl-red-doped blue-phase liquid crystals by application of a DC field. We have observed strong multi-order nonlinear grating diffractions characterized by a nonlinear index coefficient n(2)∼0.5  cm(2)/W using unfocused CW laser power of ∼1  mW and a DC field of a few V/μm. The underlying mechanisms are crystalline lattice and director axis reorientations by torques exerted by the DC field and photo-excited dye molecules.

  5. Role of space charges on light-induced effects in nematic liquid crystals doped by methyl red.

    Science.gov (United States)

    Lucchetti, L; Simoni, F

    2014-03-01

    We show that both the extraordinarily large nonlinear response and the light-induced permanent reorientation in liquid crystals doped by the azo dye methyl red originates from the same phenomenon of modification of the charge density on the irradiated surface. The demonstration is done by applying ac voltage to the samples, showing that in this case no permanent anchoring is possible. The measurements confirm the role of photoisomerization that gives a transient contribution to the actual reorientation process only in the high dose regime. This result allows us to draw a picture for light-induced effects that might be applied to a large class of compounds.

  6. Higher-order mode suppression in rod-type photonic crystal fibers with sectioned doping and enlarged core

    DEFF Research Database (Denmark)

    Poli, F.; Coscelli, E.; Passaro, D.

    2010-01-01

    Yb-doped rod-type photonic crystal fibers are double-cladding large-mode-area fibers with the outer dimension of few millimeters. The higher-order mode suppression through gain filtering has been demonstrated in these fibers, by enlarging the core radius from 30 μm to 40 μm, while keeping fixed...... analyzed with a spatial and spectral amplifier model, showing the positive effect of the gain filtering in improving the fundamental mode amplification, to the detriment of the higher-order mode one. Comparisons have been made with the properties of rod-type fibers with 30 μm core radius, both with uniform...

  7. All-optical switchable holographic Fresnel lens based on azo-dye-doped polymer-dispersed liquid crystals.

    Science.gov (United States)

    Jashnsaz, Hossein; Nataj, Nahid Hosain; Mohajerani, Ezeddin; Khabbazi, Amir

    2011-08-01

    Fabrication of an all-optical switchable holographic liquid crystal (LC) Fresnel lens based on azo-dye-doped polymer-dispersed LCs is reported using a Michelson interferometer. It is found that, upon circularly polarized photoirradiation, the diffraction efficiency of the fabricated Fresnel lens was increased significantly in a reversible manner. We believe this is due to the anisotropy induced by reorientation of the LC molecules coupled with azo-dye molecule orientation due to trans-cis-trans photoisomerization, which modulates the refractive index of the LC-rich regions. We also studied the effect of azo dye on the polarization dependency of the fabricated lens.

  8. Photo-driven directional motion of droplets on the surface of a liquid crystal doped with photochromic azobenzene: theory

    Energy Technology Data Exchange (ETDEWEB)

    Seki, Kazuhiko; Tachiya, M [National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, Higashi 1-1-1, Tsukuba, Ibaraki 305-8565 (Japan)

    2005-12-14

    Recently, photo-driven directional motion of glycerol droplets on the surface of a liquid crystal doped with photochromic azobenzene derivatives has been reported. We present a theoretical model for this phenomenon. The motion of droplets is induced by a gradient in surface tension, which is produced by the combined effect of photo-isomerization and diffusion of surface azobenzenes. The theoretical relation between the surface tension and the surface concentration of cis isomers is proposed. The experimentally observed depletion zone of droplets can be reasonably well explained in terms of diffusion of droplets in the presence of the gradient in the surface tension.

  9. Phosphate ytterbium-doped single-mode all-solid photonic crystal fiber with output power of 13.8 W

    Science.gov (United States)

    Wang, Longfei; He, Dongbing; Feng, Suya; Yu, Chunlei; Hu, Lili; Qiu, Jianrong; Chen, Danping

    2015-01-01

    Single-mode ytterbium-doped phosphate all-solid photonic crystal fiber (AS-PCF) with 13.8 W output power and 32% slope efficiency was reported. By altering the diameter of the rods around the doped core and thus breaking the symmetry of the fiber, a polarization-maintaining AS-PCF with degree of polarization of >85% was also achieved, for the first time to knowledge, in a phosphate PCF. PMID:25684731

  10. Growth and spectral-luminescent study of SrMoO4 crystals doped with Tm3+ ions

    Science.gov (United States)

    Dunaeva, E. E.; Zverev, P. G.; Doroshenko, M. E.; Nekhoroshikh, A. V.; Ivleva, L. I.; Osiko, V. V.

    2016-03-01

    SrMoO4 crystals doped with Tm3+ ions have been produced from a melt using the Czochralski method; their spectral-luminescent characteristics have been studied, and laser radiation has been generated at the wavelength of 1.94 μm using laser-diode excitation. The high absorption section at the wavelength of 795 nm, the fairly high luminescence section, the long lifetime at the upper laser level 3F4 of 1.5 ms, and a wide luminescence band allow one to hope for developing efficient tunable Tm3+: SrMoO4 crystal lasers with diode pumping in the range of 1.7-2.0 μm, which are capable of implementing SRS self-transformation of radiation into the middle IR band.

  11. High-power single-frequency pulsed laser based on a Yb-doped large-pitch photonic crystal fiber

    Science.gov (United States)

    Cha, Yong-Ho; Kim, Yonghee; Park, Hyunmin; Lim, Gwon; Ko, Kwang-Hoon; Kim, Taek Soo; Jeong, Do-Young

    2017-06-01

    We have developed a high-power single-frequency pulsed fiber laser system utilizing a Yb-doped rod-type large-pitch photonic crystal fiber. The maximal peak power is 33 kW with a 0.4-mJ pulse energy and a 70-MHz linewidth, and the average power is 60 W at a 150-kHz repetition rate. At a higher repetition rate, the average power can be increased to 190 W, which is limited by the onset of transverse-mode instability in the large-pitch photonic crystal fiber. The output beam is linearly polarized and shows a good beam quality with a M2 value of 1.2.

  12. Polarization-independent holographic gratings based on azo-dye-doped polymer-dispersed liquid-crystal films.

    Science.gov (United States)

    Fuh, Andy Ying-Guey; Chen, Che-Chang; Cheng, Ko-Ting; Liu, Cheng-Kai; Chen, Wei-Ko

    2010-01-10

    We demonstrate polarization-independent holographic gratings (PIHGs) based on azo-dye-doped polymer-dispersed liquid crystal films. The PIHGs are recorded by irradiation under an intensity-modulated interference field, generated by two linearly polarized green optical beams, and by simultaneously applying a suitable AC voltage to the sample. The photoexcited azo dyes are adsorbed onto the UV-cured polymer film with their long axes parallel to the normal of the substrate. When the applied voltage is switched off, the PIHGs are generated with periodic modulation of liquid-crystal structures with transparently homeotropic and randomly scattered alignments. Additionally, the generated PIHGs can be completely switched off by an applied voltage.

  13. Spectroscopic signature of phosphate crystallization in Erbium-doped optical fibre preforms

    CERN Document Server

    Peretti, Romain; Jacquier, Bernard; Blanc, Wilfried; Dussardier, Bernard; 10.1016/j.optmat.2011.01.005

    2011-01-01

    In rare-earth-doped silica optical fibres, the homogeneous distribution of amplifying ions and part of their spectroscopic properties are usually improved by adding selected elements, such as phosphorus or aluminum, as structural modifier. In erbium ion (Er3+) doped fibres, phosphorus preferentially coordinates to Er3+ ions to form regular cages around it. However, the crystalline structures described in literature never gave particular spectroscopic signature. In this article, we report emission and excitation spectra of Er3+ in a transparent phosphorus-doped silica fibre preform. The observed line features observed at room and low temperature are attributed to ErPO4 crystallites.

  14. Thermoluminescence and F centers of manganese doped NaCl and NaCl-CKl crystals exposed to gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Somera, L.; Cruz Z, E.; Roman L, J. [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Hernandez A, J. M.; Murrieta S, H., E-mail: ecruz@nucleares.unam.mx [UNAM, Instituto de Fisica, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

    2015-10-15

    Alkali halides crystals doped with rare earths or transition metals have been widely studied due to the luminescence properties. In particular, NaCl and KCl single crystals present thermally stimulated luminescence (Tl) after gamma irradiation. The NaCl and the NaCl KCl mixed crystal doped with manganese (MnCl{sub 2}) impurity were grown by using the Czochralski method. The emission characteristic of Mn{sup 2+} was observed at 543 nm. The crystals were exposed between 0.02 and 10 kGy gamma dose from {sup 60}Co irradiator. Optical absorption at room temperature shows the peaked band at 452 nm corresponding to the manganese impurity. The F bands, was ascribed to the electron trapped in the anion vacancy in the lattice, were obtained at 452 nm and 455 nm belonging to NaCl:Mn and NaCl KCl:Mn, respectively. The F band increases as the doses increase and it was bleaching by the UV light at 470 nm. The glow curves of the samples show the first glow peak between 92-103 degrees C, while the second main peak was observed at 183 degrees C for the undoped NaCl and at 148 and 165 degrees C for the NaCl:Mn and NaCl-KCl:Mn, respectively. The main peak was slowly bleaching when the irradiated sample was illuminated with F (470 nm) light. Optical bleaching confirms that the F center has an important participation in the thermoluminescent response. The glow curves structure from the thermal bleaching suggests the participation of different kind of traps. Also, the kinetics parameters such as activation energy (E), frequency factor (s) and the kinetic order (b) were investigated. (Author)

  15. Thermoluminescence Response of Ge-Doped Cylindrical-, Flat- and Photonic Crystal Silica-Fibres to Electron and Photon Radiation.

    Science.gov (United States)

    Entezam, A; Khandaker, M U; Amin, Y M; Ung, N M; Bradley, D A; Maah, J; Safari, M J; Moradi, F

    2016-01-01

    Study has been made of the thermoluminescence (TL) response of silica-based Ge-doped cylindrical, flat and photonic crystal fibres (referred to herein as PCF-collapsed) to electron (6, 12 and 20 MeV) and photon (6, 10 MV) irradiation and 1.25 MeV γ-rays, for doses from 0.1 Gy to 100 Gy. The electron and photon irradiations were delivered through use of a Varian Model 2100C linear accelerator located at the University of Malaya Medical Centre and γ-rays delivered from a 60Co irradiator located at the Secondary Standard Dosimetry Laboratory (SSDL), Malaysian Nuclear Agency. Tailor-made to be of various dimensions and dopant concentrations (6-10% Ge), the fibres were observed to provide TL yield linear with radiation dose, reproducibility being within 1-5%, with insensitivity to energy and angular variation. The sensitivity dependency of both detectors with respect to field size follows the dependency of the output factors. For flat fibres exposed to 6 MV X-rays, the 6% Ge-doped fibre provided the greatest TL yield while PCF-collapsed showed a response 2.4 times greater than that of the 6% Ge-doped flat fibres. The response of cylindrical fibres increased with core size. The fibres offer uniform response, high spatial resolution and sensitivity, providing the basis of promising TL systems for radiotherapy applications.

  16. Photoalignment control: self-focusing effect in hybrid- and homeotropic-aligned dye-doped polymer-stabilized liquid crystals

    Science.gov (United States)

    Wang, J.; Shishido, A.

    2015-09-01

    Nonlinear optics has drawn much attention for its great potential in applications, such as frequency conversion, multiple-photon absorption, self-focusing, and so on. However, such optical nonlinearities are generally observed at very high light intensities. In this study, we designed hybrid-aligned dye-doped polymer-stabilized liquid crystals (PSLC), in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. In such film, the threshold intensity required to form self-focusing effect was markedly reduced by a factor of 8.5 compared to that in a conventional homeotropic cell, which enabled the generation of the self-focusing effect using a handheld 1-mW laser pointer. In addition, we investigated the structural effect of dye molecules: azo-dye methyl red (MR, photoisomerizable)-doped PSLC was prepared and its NLO response was evaluated. It turned out that such MR-based LC system was not effective for self-focusing effect compared to oligothiophene-doped systems.

  17. A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber

    OpenAIRE

    Soltanian, M. R. K.; Ahmad, H; A. Khodaie; Amiri, I. S.; M.F. Ismail; Harun, S. W.

    2015-01-01

    A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio.

  18. A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber.

    Science.gov (United States)

    Soltanian, M R K; Ahmad, H; Khodaie, A; Amiri, I S; Ismail, M F; Harun, S W

    2015-10-12

    A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio.

  19. Bulk- and electrode-limited conduction mechanisms in different phases of Mn{sup 2+}-doped potassium tetrachlorozincate crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gaffar, M A [Physics Department, School of Science and Engineering, American University in Cairo, Cairo 11511 (Egypt); Abousehly, A M [Physics Department, Faculty of Science, Al-Azhar University, 71524 Assiut (Egypt); El-Fadl, A Abu [Physics Department, Faculty of Science, Assiut University, 71516 Assiut (Egypt); Mostafa, M M [Physics Department, Faculty of Science, Al-Azhar University, 71524 Assiut (Egypt)

    2005-02-21

    The current density-electric field intensity relationship of pre-heated potassium tetrachlorozincate (KZC) crystals (undoped and doped with Mn{sup 2+} in different concentrations) has been measured along the polar a-axis. The dependence was studied at selected temperatures covering the three high-temperature phases of KZC in order to investigate the type of conduction mechanism dominating in each phase. The original Richardson-Schottky (R-S) equation shows disagreement between calculated and experimental values of the Richardson and optical dielectric constants. The modified R-S equation fits the data well and facilitated the calculation of the barrier height, electronic mobility and high-frequency dielectric constant of KZC. The calculated parameters are in good agreement with the corresponding experimental values. The results indicated that the bulk- and electrode-limited mechanisms contribute to conduction in different phases of KZC. The temperature dependence of the dc conductivity along the polar axis of undoped and Mn{sup 2+}-doped KZC shows anomalous behaviour in the region of the phase transitions. The dc conductivity and the activation energy of conduction (w) changed significantly due to doping. As indicated by the extremely high w values, superionic conduction is the dominating mechanism in the high-temperature part of the incommensurate (IC) and normal phases of KZC. Suppression of the superionic conduction by Mn{sup 2+}-doping is observed. The effect of discommensurate pinning by Mn{sup 2+} ions and the possibility of dislocation formation on the dc conduction in the IC phase is also discussed.

  20. Optical and crystallization behavior in Dy3+ doped 40GeSe2-25Ga2Se3-35CsI glass.

    Science.gov (United States)

    Shen, Xiang; Nie, Qiuhua; Xu, Tiefeng; Dai, Shixun; Wang, Xunsi; Chen, Feifei; Yang, Gaobo

    2009-09-15

    Dy(3+) doped 40GeSe(2)-25Ga(2)Se(3)-35CsI (GGC) glass was synthesized, and optical spectrum, such as infrared transmission and Vis-Nir absorption was measured. Base on the Judd-Ofelt theory, the three Judd-Ofelt parameters Omega(t) (t=2, 4, 6) were calculated and the results were compared with other chalcogenide glasses. The small Omega(2) in GGC glass is ascribed to the weak covalency of Se-Dy bond. The theory of crystallization kinetics under non-isothermal condition was developed, and was applied to analyze this Dy(3+) doped GGC glass. From the heating-rate dependence of crystallization temperature, the activation energy for crystallization E=148 kJ/mol is obtained, and this value is much smaller than that of the undoped glass host, indicating the introduction of Dy(3+) ions into the GGC glass will get the host crystallized easily.

  1. Liquid crystal tunable photonic crystal dye laser

    DEFF Research Database (Denmark)

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium.......We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium....

  2. Crystal structure of 1,4-bis(3-ammoniopropylpiperazine-1,4-diium bis[dichromate(VI

    Directory of Open Access Journals (Sweden)

    S. Vetrivel

    2016-05-01

    Full Text Available The asymmetric unit of the organic–inorganic title salt, (C10H28N4[Cr2O7]2, comprises one half of an 1,4-bis(3-ammoniopropylpiperazinediium cation (the other half being generated by the application of inversion symmetry and a dichromate anion. The piperazine ring of the cation adopts a chair conformation, and the two CrO4 tetrahedra of the anion are in an almost eclipsed conformation. In the crystal, the cations and anions form a layered arrangement parallel to (001. N—H...O hydrogen bonds between the cations and anions and additional C—H...O interactions lead to the formation of a three-dimensional network structure.

  3. Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi{sub 2}Te{sub 2}Se

    Energy Technology Data Exchange (ETDEWEB)

    Kushwaha, S. K., E-mail: kushwaha@princeton.edu; Gibson, Q. D.; Cava, R. J. [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States); Xiong, J.; Ong, N. P. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Pletikosic, I. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Condensed Matter Physics and Materials Science Department, Brookhaven National Lab, Upton, New York 11973 (United States); Weber, A. P. [National Synchrotron Light Source, Brookhaven National Lab, Upton, New York 11973 (United States); Fedorov, A. V. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Valla, T. [Condensed Matter Physics and Materials Science Department, Brookhaven National Lab, Upton, New York 11973 (United States)

    2014-04-14

    A comparative study of the properties of topological insulator Bi{sub 2}Te{sub 2}Se (BTS) crystals grown by the vertical Bridgeman method is described. Two defect mechanisms that create acceptor impurities to compensate for the native n-type carriers are compared: Bi excess, and light Sn doping. Both methods yield low carrier concentrations and an n-p crossover over the length of the grown crystal boules, but lower carrier concentrations and higher resistivities are obtained for the Sn-doped crystals, which reach carrier concentrations as low as 8 × 10{sup 14} cm{sup −3}. Further, the temperature dependent resistivities for the Sn-doped crystals display strongly activated behavior at high temperatures, with a characteristic energy of half the bulk band gap. The (001) cleaved Sn-doped BTS crystals display high quality Shubnikov de Haas (SdH) quantum oscillations due to the topological surface state electrons. Angle resolved photoelectron spectroscopy (ARPES) characterization shows that the Fermi energy (E{sub F}) for the Sn-doped crystals falls cleanly in the surface states with no interference from the bulk bands, which the Dirac point for the surface states lies approximately 60 meV below the top of the bulk valence band maximum, and allows for a determination of the bulk and surface state carrier concentrations as a function of Energy near E{sub F}. Electronic structure calculations that compare Bi excess and Sn dopants in BTS demonstrate that Sn acts as a special impurity, with a localized impurity band that acts as a charge buffer occurring inside the bulk band gap. We propose that the special resonant level character of Sn in BTS gives rise to the exceptionally low carrier concentrations and activated resistivities observed.

  4. Security devices based on liquid crystals doped with a colour dye

    OpenAIRE

    Carrasco Vela, Carlos; Quintana Arregui, Patxi Xabier; Otón, E.; Geday, Morten Andreas; Otón Sánchez, José Manuel

    2011-01-01

    Liquid crystal properties make them useful for the development of security devices in applications of authentication and detection of fakes. Induced orientation of liquid crystal molecules and birefringence are the two main properties used in security devices. Employing liquid crystal and dichroic colorants, we have developed devices that show, with the aid of a polarizer, multiple images on each side of the device. Rubbed polyimide is used as alignment layer on each substrate of the LC ce...

  5. Growth of High Quality Al-Doped CsLiB6O10 Crystals Using Cs2O-Li2O-MoO3 Fluxes

    Directory of Open Access Journals (Sweden)

    Xianchao Zhu

    2017-03-01

    Full Text Available Abstract: High quality and large size Al-doped CsLiB6O10 (CLBO single crystals have been successfully grown by top-seeded solution growth (TSSG technique using Cs2O–Li2O–MoO3 fluxes. The advantages of this newly developed flux system were investigated by viscosity measurements and growth experiments. Al-doped CLBO presents a very high transmittance in the visible region and the weak absorption values at 1064 nm along a and c axes are only 140 and 50 ppm/cm, respectively. The measured LIDT of Al-doped CLBO at λ = 1064 nm and τ = 5.0 ns is 5.10 GW/cm2. Moreover, Al-doped CLBO exhibits an apparent enhancement of the hygroscopic nature in contrast with the undoped crystal as determined by the humidity experiments. Finally, a high fourth harmonic generation (FHG conversion efficiency of 63% utilizing Al-doped CLBO has been achieved by a picosecond mode-locked Nd:YAG laser, the results also reveal that Al doping has no obvious impact on the FHG conversion efficiency.

  6. Structural, electronic and optical properties of pure and Ni{sup 2+}-doped CdI{sub 2} layered crystals as explored by ab initio and crystal field calculations

    Energy Technology Data Exchange (ETDEWEB)

    Brik, M.G., E-mail: brik@fi.tartu.e [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Kityk, I.V. [Electrical Engineering Department, Czestochowa University of Technology, Al. Armii Krajowej 17/19, 42-200 Czestochowa (Poland); Ozga, K.; Slezak, A. [Chair of Public Health, Czestochowa University of Technology, Al. Armii Krajowej 36B, 42-200 Czestochowa (Poland)

    2011-01-15

    Influence of impurity Ni{sup 2+} ions on optical absorption spectra of layered CdI{sub 2} single crystals has been considered for localized level of doping. Optical properties of CdI{sub 2}:Ni{sup 2+} crystals were modeled using two independent approaches: (i) DFT-based ab initio calculations and (ii) semi-empirical crystal field theory. The former method allowed for locating the Ni{sup 2+} 3d states with respect to the host's band structure, providing a link between the properties of impurity and host itself. The latter method allowed for calculations of crystal field splitting of the Ni{sup 2+} LS terms, giving an opportunity to assign the main bands in the absorption spectrum of the doped crystal. To increase accuracy in calculating the point charge contribution to the crystal field parameters (CFP), contributions of all crystal lattice ions located at a distance of up to 72.999 A from the Ni ion were included into the crystal lattice sums. The crystal field Hamiltonian was diagonalized in the space of 25 wave functions of the spin-triplet terms {sup 3}F, {sup 3}P and the spin-singlet terms {sup 1}S, {sup 1}D, {sup 1}G of the 3d{sup 8} electron configuration of Ni{sup 2+} ion. Additional calculations of the band structure and optical functions were performed to reveal the structure of the energy bands, their role in the formation of optical properties of this system in the overlapping impurity-ligand effects. Electron density distribution in the space between atoms before and after doping was compared; hybridization of the Ni 3d states with iodine 5p states was demonstrated. The role of the crystal anisotropy in the observed effects is discussed.

  7. Accurate X-ray diffraction studies of KTiOPO{sub 4} single crystals doped with niobium

    Energy Technology Data Exchange (ETDEWEB)

    Novikova, N. E., E-mail: natnov@ns.crys.ras.ru; Sorokina, N. I.; Alekseeva, O. A.; Verin, I. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Crystallography and Photonics Federal Scientific Research Center (Russian Federation); Kharitonova, E. P.; Orlova, E. I.; Voronkova, V. I. [Moscow State University, Faculty of Physics (Russian Federation)

    2017-01-15

    Single crystals of potassium titanyl phosphate doped with 4% of niobium (КТР:4%Nb) and 6% of niobium (KTP:6%Nb) are studied by accurate X-ray diffraction at room temperature. The niobium atoms are localized near the Ti1 and Ti2 atomic positions, and their positions are for the first time refined independent of the titanium atomic positions. Maps of difference electron density in the vicinity of K1 and K2 atomic positions are analyzed. It is found that in the structure of crystal КТР:4%Nb, additional positions of K atoms are located farther from the main positions and from each other than in КТР and KTP:6%Nb crystals. The nonuniform distribution of electron density found in the channels of the КТР:4%Nb structure is responsible for ~20% increase in the signal of second harmonic generation.

  8. One-pot synthesis of Mn-doped TiO{sub 2} grown on graphene and the mechanism for removal of Cr(VI) and Cr(III)

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zengping; Li, Yaru; Guo, Meng; Xu, Fengyun; Wang, Peng [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Du, Yu [China Tobacco Yunnan Industrial Co., Ltd., Yunnan 651600 (China); Na, Ping, E-mail: naping@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2016-06-05

    Highlights: • rGO-Mn-TiO{sub 2} is synthesized through one-pot hydrothermal method. • Cr(total) removal effectiveness reaches to 97.32% in 30 min under visible light, as the initial concentration of Cr(VI) is 20 mg/L. • Mn-TiO{sub 2} and rGO synergistically contribute to the adsorption and photocatalytic reduction of Cr. • Cr(III) being adsorbed by rGO helps to the release of abundant photocatalytic sites of Mn-TiO{sub 2}. - Abstract: Mn-doped TiO{sub 2} grown on reduced graphene oxide(rGO) was synthesized by one-pot hydrothermal method and the photocatalytic removal of Cr by the material was investigated under sunlight. The materials were characterized by a combination of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller method, UV–vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Cr(total) removal efficiency of the material is 97.32% in 30 min and 99.02% in 60 min under sunlight irradiation, as the initial concentration of Cr(VI) is 20 mg/L. The high photocatalytic activity under visible light is considered mainly due to the Mn-doping, and rGO plays an important role in the synergetic effect of adsorption and photocatalysis to sustain the high efficient removal of Cr(VI) and Cr(III). Cr(VI) adsorbed on the surface of rGO is reduced to Cr(III) by photo electrons which are transported through rGO, and the reaction product Cr(III) continues to be adsorbed. The process contributes to the release of abundant photocatalytic sites of Mn-TiO{sub 2} and improves photocatalytic efficiency. The excellent adsorption and photocatalytic effect with the explanation of the synergetic mechanism are very useful not only for fundamental research but also for the potential practical applications.

  9. Flicker noise in degenerately doped Si single crystals near the metal ...

    Indian Academy of Sciences (India)

    In this paper we report some of the important results of experimental investigations of the flicker noise near the metal–insulator (MI) transition in doped silicon ... Department of Physics, Indian Institute of Science, Bangalore 560 012, India; Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, UK ...

  10. Impact of carrier doping on electrical properties of laser-induced liquid-phase-crystallized silicon thin films for solar cell application

    Science.gov (United States)

    Umishio, Hiroshi; Matsui, Takuya; Sai, Hitoshi; Sakurai, Takeaki; Matsubara, Koji

    2018-02-01

    Large-grain-size (>1 mm) liquid-phase-crystallized silicon (LPC-Si) films with a wide range of carrier doping levels (1016–1018 cm‑3 either of the n- or p-type) were prepared by irradiating amorphous silicon with a line-shaped 804 nm laser, and characterized for solar cell applications. The LPC-Si films show high electron and hole mobilities with maximum values of ∼800 and ∼200 cm2 V‑1 s‑1, respectively, at a doping level of ∼(2–4) × 1016 cm‑3, while their carrier lifetime monotonically increases with decreasing carrier doping level. A grain-boundary charge-trapping model provides good fits to the measured mobility–carrier density relations, indicating that the potential barrier at the grain boundaries limits the carrier transport in the lowly doped films. The open-circuit voltage and short-circuit current density of test LPC-Si solar cells depend strongly on the doping level, peaking at (2–5) × 1016 cm‑3. These results indicate that the solar cell performance is governed by the minority carrier diffusion length for the highly doped films, while it is limited by majority carrier transport as well as by device design for the lowly doped films.

  11. Dynamical studies of the mechanisms for optical nonlinearities of methyl-red dye doped blue phase liquid crystals.

    Science.gov (United States)

    Chen, Chun-Wei; Lin, Tsung-Hsien; Khoo, Iam Choon

    2015-08-24

    Dynamical grating diffraction experiments and reflection/transmission polarization spectroscopy have been conducted on azo-dye doped Blue-Phase Liquid Crystal (BPLC) to investigate the mechanisms responsible for laser induced refractive index changes. The underlying mechanisms for the transient grating diffraction components are attributed to thermal indexing and lattice distortion, whereas the persistent component is due to lattice distortion/expansion caused by laser excited dye molecule isomerization. These mechanisms were distinguishable by their response dynamics and gave rise to the observed reflection spectra and photonic bandgap shift, polarization dependency and optical activity. Some preliminary studies have demonstrated the feasibility of using these mechanisms for coherent holographic and direct image writing operations.

  12. Ce-doped LuAG single-crystal fibers grown from the melt for high-energy physics

    CERN Document Server

    Xu, X; Moretti, F; Pauwels, K; Lecoq, P; Auffray, E; Dujardin, C

    2014-01-01

    Under a stationary stable regime undoped and Ce-doped LuAG (Lu3Al5O12) single-crystal fibers were grown by a micro-pulling-down technique. The meniscus length corresponding to the equilibrium state was <200 mu m. Fluctuations in the fiber composition and pulling rate were found to have a significant effect on the properties of the fibers grown. A great improvement in the performance was found in samples containing low Ce concentrations (<= 0.1 at.\\%) and produced using pulling rates <0.5 mm min(-1). Under such conditions a good lateral surface fiber quality was obtained and light propagation was significantly improved. Conversely, a high Ce concentration and a high pulling rate resulted in a strong degradation of the fiber surface quality causing defects to appear and a decrease in light output. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  13. The clamped and unclamped effective electro-optic coefficients of zirconium-doped congruent lithium niobate crystals

    Science.gov (United States)

    Abarkan, Mustapha; Danielyan, Anush; Kokanyan, Ninel; Aillerie, Michel; Kostritskii, Sergey; Kokanyan, Edvard

    2017-07-01

    All coefficients of the unclamped and clamped electro-optic tensor of zirconium-doped congruent LiNbO3 single crystals are determined as function of the dopant concentration at room temperature. With a distribution coefficient of zirconium closer to one in the considered range, the dopant concentration is in the range up to 2.5 mol% of ZrO2. The electro-optic coefficients are measured by direct techniques based on interferometric and Sénarmont optical arrangements at the wavelength of 633 nm. It is found that all the unclamped and clamped effective electro-optic coefficients are relatively constant, except for the sample grown with 2 mol% of zirconium. The electro-optic behavior of LN:Zr as function of the dopant concentration was confirmed by dielectric characterizations. The concentration equal 2 mol% of ZrO2 can be considered to a threshold concentration for various physical and optical properties.

  14. Low driving voltage ITO doped polymer-dispersed liquid crystal film and reverse voltage pulse driving method.

    Science.gov (United States)

    Wu, Qinqin; Wang, Yuanqing

    2017-10-10

    This paper investigates the effects of indium tin oxide (ITO) powders on the driving voltage of polymer-dispersed liquid crystal (PDLC). The threshold voltage (V th ) and driving voltage (V d ) can be reduced through doping the ITO powders; in particular, the V d is 5.8 V when the weight ratio of ITO is 1.5 wt. %. The relationship between the applied voltage and off-time of PDLC has been investigated; the lower the applied voltage, the shorter the off-time. On this basis, the reverse voltage pulse driving method was proposed; this driving method uses the driving signal to reduce the off-time of PDLC.

  15. Intrinsic Enhancement of Dielectric Permittivity in (Nb + In) co-doped TiO2 single crystals.

    Science.gov (United States)

    Kawarasaki, Masaru; Tanabe, Kenji; Terasaki, Ichiro; Fujii, Yasuhiro; Taniguchi, Hiroki

    2017-07-13

    The development of dielectric materials with colossal permittivity is important for the miniaturization of electronic devices and fabrication of high-density energy-storage devices. The electron-pinned defect-dipoles has been recently proposed to boost the permittivity of (Nb + In) co-doped TiO2 to 105. However, the follow-up studies suggest an extrinsic contribution to the colossal permittivity from thermally excited carriers. Herein, we demonstrate a marked enhancement in the permittivity of (Nb + In) co-doped TiO2 single crystals at sufficiently low temperatures such that the thermally excited carriers are frozen out and exert no influence on the dielectric response. The results indicate that the permittivity attains quadruple of that for pure TiO2. This finding suggests that the electron-pinned defect-dipoles add an extra dielectric response to that of the TiO2 host matrix. The results offer a novel approach for the development of functional dielectric materials with large permittivity by engineering complex defects into bulk materials.

  16. Crystal structure and electrical parameters of In-doped PbTe/Si films prepared by modified HWE technique

    Science.gov (United States)

    Samoylov, A. M.; Khoviv, A. M.; Buchnev, S. A.; Synorov, Yu. V.; Dolgopolova, E. A.

    2003-06-01

    The chemical quantitative composition, crystal structure, and electrical properties, of In-doped PbTe/Si and PbTe/SiO 2/Si films have been studied in this work. The modified hot wall technique has been used to prepare the PbTe/Si heterostructures, which were doped with In during the condensation process directly. In this way, the Pb 1- xIn x (0.05⩽ xIn⩽0.50) liquid alloys have been employed as the sources of indium and lead vapours coincidentally. By electron probe microanalysis and atomic absorption measurements, it has been established that the concentration of In atoms yIn varied from 0.0011 to 0.045 in these Pb 1- yIn yTe films. The comparison of microstructural observations and XRD measurements allows to determine that phase constitution and real-crystal structure of these Pb 1- yIn yTe films depend upon the indium content yIn and the presence of intermediate SiO 2 buffer layers. It has been found that formation of In solid solutions in lead telluride matrix revealed the PbTe-InTe and PbTe-In 2Te 3 pseudobinary systems. The results of X-ray diffraction show that the lattice parameter aPbTe of PbTe/Si and PbTe/SiO 2/Si heterostructures is described by the non-monotone function and does not obey Vegard's law within the concentration interval 0.0011⩽ yIn⩽0.045. It has been detected that at 77 K, the high values of charge carrier density of about 10 18-10 19 cm -3 appeared in p-type Pb 1- yIn yTe/Si films within concentration interval 0.0022 < yIn<0.0064.

  17. P-type poly-Si prepared by low-temperature aluminum-induced crystallization and doping for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Yasuhiro; Yu, Zhenrui; Morales-Acevedo, Arturo [CINVESTAV-IPN, Mexico, D.F. (Mexico)

    2000-07-01

    P-type poly-Si thin films prepared by low temperature aluminum-induced crystallization and doping are reported. The starting material was boron-doped a-Si:H prepared by PECVD on glass substrates. Aluminum layers with different thickness were evaporated on a-Si:H surface and conventional thermal annealing was performed at temperatures ranging from 300 to 550 Celsius degrees. XRD, SIMS, and Hall effect measurements were carried out to characterize the annealed Al could be crystallized at temperature as low as 300 Celsius degrees in 60 minutes. This material has high carrier concentration as well as high Hall mobility and can be used as a p-layer of seed layer for thin film poly-Si solar cells. The technique reported here is compatible with PECVD process. [Spanish] Se informa sobre la preparacion de peliculas delgadas tipo P y Poli-Si mediante la cristalizacion inducida de aluminio a baja temperatura y el dopado. El material inicial era de boro dopado y a-Si:H preparado PECVD sobre substratos de vidrio. Se evaporaron capas de aluminio de diferente espesor sobre una superficie de a-Si:H y se llevo a cabo un destemplado termico convencional a temperaturas que varian entre 300 y 500 grados Celsius. Se llevaron a cabo mediciones de XRB, SIMS y del efecto Hall para caracterizar el aluminio destemplado para que pudiera ser cristalizado a temperaturas tan bajas como 300 grados Celsius en 60 minutos. Este material tiene una alta concentracion portadora asi como una alta movilidad Hall y puede usarse como una capa de semilla para celdas solares de pelicula delgada Poli-Si. La tecnica reportada aqui es compatible con el proceso PECVD.

  18. A systematic analysis of the spectra of the lanthanides doped into single crystal LaF/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Carnall, W.T.; Goodman, G.L.; Rajnak, K.; Rana, R.S.

    1988-02-01

    The optical spectra of the lanthanides doped into single crystal LaF/sub 3/ have been interpreted in terms of transitions within 4f/sup N/ configurations. Energy-level calculations were based on a simultaneous diagonalization of the free-ion and crystal-field matrices using an approximate model with C/sub 2v/ site symmetry instead of the actual C/sub 2/ symmetry. Excellent correlations between experimental transition energies and the computed level structures were obtained; predicted levels are given for Pm/sup 3 +/. Previously unpublished experimental results for Nd/sup 3 +/ and Sm/sup 3 +/:LaF/sub 3/ are included in the tabulations. The spectroscopic data for each ion were analyzed independently, then the parameters of the effective-operator model were intercompared and systematic trends were identified. Since many of the 4f/sup N/ configurations extend well into the vacuum ultraviolet region, and thus beyond any presently available experimental observations, some of the free-ion (atomic) parameters were found to be only approximately defined by the accessible levels. However, the crystal-field parameters seem for the most part to be well established by fits to data at low energies. A new chart of the lanthanide ion 4f/sup N/ configuration energy level structures is presented. It was generated by including all of the computed crystal-field levels in the 0-50000 cm/sup -1/ range. In most cases, experimental analyses of individual ions extended to /approximately/40000 cm/sup /minus/1/. 94 refs., 23 figs., 10 tabs.

  19. Floating zone growth of Ni-doped MgGa2O4 single crystal for near-infrared tunable laser

    Science.gov (United States)

    Suzuki, Takenobu; Arai, Yusuke; Ohishi, Yasutake

    2008-08-01

    Crystal growth and spectroscopic characterization of Ni-doped MgGa2O4 belonging to inverse-spinel structure crystal family are described. Single crystals of this material were grown by floating zone method for the first time. Oxygen gas flow was essential to minimize evaporation of Ga2O3 during the floating zone crystal growth process. Bubble and inclusion-free crystals were obtained for the growth rate less than 5 mm/hour. Ni:MgGa2O4 single crystal was characterized by broadband fluorescence in 1100-1600 nm wavelength range and 1.6 msec room-temperature lifetime. It could be attributed to the transition of 3T2(3F)-->3A(2F) transition of the octahedrally coordinated Ni2+. The internal quantum efficiency of the near-infrared fluorescence was about 82 % for 1 mol% Ni-doped MgGa2O4 single crystal at room temperature. The new material is to be very promising for tunable laser applications covering the important optical communication, eye safe, 1100-1600 nm wavelength.

  20. Doping effect of L-cystine on structural, UV-visible, SHG efficiency, third order nonlinear optical, laser damage threshold and surface properties of cadmium thiourea acetate single crystal

    Science.gov (United States)

    Azhar, S. M.; Anis, Mohd; Hussaini, S. S.; Kalainathan, S.; Shirsat, M. D.; Rabbani, G.

    2017-01-01

    The present article is focused to investigate the influence of L-cystine (LC) on linear-non-linear optical and laser damage threshold of cadmium thiourea acetate (CTA) crystal. The structural parameters of pure and LC doped CTA crystals have been determined using the single crystal X-ray diffraction technique. The functional groups of grown crystals have been identified by means of fourier transform infrared (FT-IR) analysis. The UV-visible spectral analysis has been done in the range of 200-900 nm to ascertain the uplifting influence of LC on optical properties of CTA crystal. The second harmonic generation (SHG) efficiency of LC doped CTA crystal is found to be higher than CTA and KDP crystal. The Z-scan technique has been employed to determine the third order nonlinear optical (TONLO) nature of LC doped CTA crystal at 632.8 nm. The self focusing tendency confirmed the strong kerr lensing ability of LC doped CTA crystal. The TONLO susceptibility (χ3), refraction (n2) and absorption coefficient (β) has been calculated using the Z-scan data. The laser damage threshold of pure and LC doped CTA crystals has been measured using the Q-switched Nd:YAG laser and its is found to be in range of GW/cm2. The surface analysis has been done by means of etching studies.

  1. Thermal behavior of nano cellulose doped polymer dispersed liquid crystal (PDLC)

    Science.gov (United States)

    Kashyap, Swati; Saxena, S. K.; Gupta, S. J.; Mahajan, Jyoti

    2016-05-01

    Nano cellulose or cellulose nanofibers (CNF) material is composed of Nano sized cellulose fibrils with a high aspect ratio and typical lateral dimensions are 20-50 nm. Its pseudo-plastic characteristics exhibit the property of certain gels or fluids (viscous) and over a period of time, becomes, Thixotropic. The ability of CNFs to go into a PDLC ultrasonically with a helical arrangement results in dried CNF films. The films thus acquire attractive thermal properties, creating possibilities for their use in various applications. In this presentation, we discuss the thermal behavior of Nano cellulose doped in PDLC that governs the formation of the desired helical structure. By comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes particles, we outline in the present paper the variation in the number of mesogen phases in varying compositions of Nano Cellulose doped PDLCs.

  2. Structural Characterization of Doped GaSb Single Crystals by X-ray Topography

    Energy Technology Data Exchange (ETDEWEB)

    Honnicke, M.G.; Mazzaro, I.; Manica, J.; Benine, E.; M da Costa, E.; Dedavid, B. A.; Cusatis, C.; Huang, X. R.

    2009-09-13

    We characterized GaSb single crystals containing different dopants (Al, Cd and Te), grown by the Czochralski method, by x-ray topography and high angular resolution x-ray diffraction. Lang topography revealed dislocations parallel and perpendicular to the crystal's surface. Double-crystal GaSb 333 x-ray topography shows dislocations and vertical stripes than can be associated with circular growth bands. We compared our high-angular resolution x-ray diffraction measurements (rocking curves) with the findings predicted by the dynamical theory of x-ray diffraction. These measurements show that our GaSb single crystals have a relative variation in the lattice parameter ({Delta}d/d) on the order of 10{sup -5}. This means that they can be used as electronic devices (detectors, for example) and as x-ray monochromators.

  3. Control of the visible emission in the SrZrO3 nano-crystals with the rare earth ion doping.

    Science.gov (United States)

    Kim, Dong Hwan; Kim, Ji Hyun; Chung, Jin Seok; Lee, Yunsang

    2013-11-01

    We investigated the emission property of SrZrO3 nano-crystals (NCs) with the doping of rare earth (RE) ions, Eu3+ and Tm3+, by using 325 nm photo-excitation. SrZrO3 NCs show a sizable violet-blue emission, while the Eu3+ and Tm3+ ions are well known to be good red and blue phosphors, respectively. Combined emissions of the host and the RE ion dopant might suggest a new white luminescent source. The RE ion doped SrZrO3 NCs were initially synthesized by using the combustion method, and then the as-synthesized crystals were annealed at different temperatures from 650 degrees C to 1450 degrees C. The Eu3+-doped SrZrO3 NCs showed the sharp red emission near 600 nm, in addition to a violet-blue emission of the host material in itself. While the red emission is enhanced in the high temperature post-annealing, the blue emission is suppressed in an opposite way. This close relation between the emissions of the host and dopant was observed similarly in the Tm3+-doped NCs. We could control the emission property in the SrZrO3:Eu3+/Tm3+ NCs from blue to red by thermal annealing and RE ion doping.

  4. Crystal structure, electrical conductivity and thermal expansion of Ni and Nb co-doped LaCoO3.

    Science.gov (United States)

    Øygarden, Vegar; Grande, Tor

    2013-02-28

    The effect of co-doping LaCoO(3) with Ni and Nb has been investigated in the two solid solution series (1 - x)LaCoO(3)-xLaNi(2/3)Nb(1/3)O(3) and (1 - y)LaCo(2/3)Ni(1/3)O(3)-yLaNi(2/3)Nb(1/3)O(3). The materials were shown to be stoichiometric with respect to oxygen. The compositional effect on the evolution of the crystal structure, thermal expansion and electrical conductivity is reported. The chemical stability of LaCoO(3) in a reducing atmosphere was improved and the thermal expansion was suppressed at higher levels of Nb-substitution. The materials with mixed oxidation states on the B-site possessed superior electrical transport properties compared to solid solutions with cations in mainly isovalent oxidation states. The evolution of the electronic conductivity, thermal expansion and crystal structural is discussed with emphasis on the oxidation states of Ni and Co, and the spin transitions of Co.

  5. Single-crystal structure of vanadium-doped La{sub 2}Mo{sub 2}O{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Alekseeva, O. A., E-mail: olalex@ns.crys.ras.ru; Antipin, A. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Gagor, A.; Pietraszko, A. [Polish Academy of Sciences, Trzebiatowski Institute of Low Temperature and Structure Research (Poland); Novikova, N. E.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Kharitonova, E. P.; Voronkova, V. I. [Moscow State University (Russian Federation)

    2013-11-15

    A high-precision X-ray diffraction study of single crystals of two compositions-La{sub 2}Mo{sub 1.78}V{sub 0.22}O{sub 8.89} and La{sub 2}Mo{sub 1.64}V{sub 0.36}O{sub 8.82}-was performed. In the vanadium-doped compounds, as in the structure of the metastable {beta}{sub ms} phase of pure La{sub 2}Mo{sub 2}O{sub 9}, the La and Mo atoms and one of the three oxygen atoms are displaced from the threefold axis, on which they are located in the high-temperature {beta} phase. The structure contains two partially occupied oxygen sites. It was shown that molybdenum atoms are partially replaced by vanadium atoms, which are not involved in the disordering, are located on the threefold axis, and are shifted toward one of the oxygen atoms. This is consistent with the temperature-induced changes in the structure of La{sub 2}Mo{sub 2}O{sub 9} and the changes in the properties of these crystals caused by the introduction of vanadium atoms into the structure.

  6. Photoinduced nonlinear optical effects in Nd-doped δ-BiB{sub 3}O{sub 6} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Majchrowski, A. [Institute of Applied Physics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); Wojciechowski, A. [Faculty of Electrical Engineering, Czestochowa University Technology, Armii Krajowej 17 (Poland); Kityk, I.V., E-mail: ikityk@el.pcz.czest.pl [Faculty of Electrical Engineering, Czestochowa University Technology, Armii Krajowej 17 (Poland); Chrunik, M.; Jaroszewicz, L.R. [Institute of Applied Physics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); Michalski, E. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

    2014-10-15

    Highlights: • New type of optically operated rare earth doped borates is proposed. • Principal role of the phonon subsystem in photoinduced electrooptics, SHG and piezooptics is shown. • The possibility to create the laser operated materials is shown for the such kind of sold state alloys. - Abstract: The studies of the second harmonic generation, Pockels effect and piezoelectricity were performed for the new synthesized δ-BiB{sub 3}O{sub 6} single crystals. The incorporation of Nd{sup 3+} ions into these crystals plays an important role for the increasing of the photoinduced nonlinear optical properties. Temperature dependences of the optical and piezoelectric features showed existence of some anomalies in the vicinity of 160 K and 220 K. This may confirm a principal role of the photopolarization and of the localized impurity states which give additional contribution into the observed effect. It is crucial that the effect is dependent on the number of the photoinducing pulses. The effect is completely reversible after switching off of the photoinducing laser beam.

  7. Photoluminescence and crystal-field analysis of Pr{sup 3+}-doped SrMoO{sub 4} phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Wenlin [Chongqing University of Technology (China). Dept. of Applied Physics; Lin, Huaping [McGill Univ., Montreal, QC (Canada). Dept. of Chemistry and Centre for Self-Assembled Chemical Structures; Institut National de la Recherche Scientifique, Varennes, QC (Canada). Centre Energie, Materiaux et Telecommunications; Liu, Honggang [Sichuan Univ., Chengdu (China). Dept. of Material Science

    2015-07-01

    The phosphor SrMoO{sub 4}:Pr{sup 3+} was successfully prepared by high-temperature solid-state reaction process, and characterised by X-ray diffraction (XRD), scanning electron microscope (SEM), and fluorescence spectrometer. The results show that the prepared SrMoO{sub 4}:Pr{sup 3+} has a scheelite structure with pure phase and represents leaf-like shapes with good dispersity. The strong electron absorbabilities are located at 220-300 nm (charge transfer band), 448, 474, and 487 nm, respectively. The emission spectrum of the SrMoO{sub 4}:Pr{sup 3+} phosphor was characterised, which peaked at 529, 545, 554, 600, 619, and 645 nm, corresponding to the f-f transitions of Pr{sup 3+}. The average International Commission on Illumination (CIE) chromaticity coordinates of the phosphors are x ∼ 0.455, and y ∼ 0.520, and the optimum doping mole fraction of Pr{sup 3+} is 0.2 mol.%. To better understand the fluorescent behavior of as-prepared phosphors, a complete 91 x 91 energy matrix was built by an effective Hamiltonian operator, including free ion and crystal-field interactions. The fluorescent spectra of Pr{sup 3+} ion at the tetragonal (S{sub 4}) Sr{sup 2+} site of SrMoO{sub 4} crystal were firstly calculated from a full diagonalisation (of energy matrix) method. The fitting values are in good agreement with the experimental data.

  8. A comparison between size dependent paraelectric and ferroelectric BaTiO3 nanoparticle doped nematic and ferroelectric liquid crystals

    Science.gov (United States)

    Al-Zangana, S.; Turner, M.; Dierking, I.

    2017-02-01

    The electro-optic and dielectric properties of barium titanate, BaTiO3, and nanoparticle (NP) doped nematic and ferroelectric liquid crystal materials were examined with respect to different size and concentrations of the NPs. Smaller size paraelectric NPs (≈80 nm) are compared to larger, ferroelectric NPs (≈240 nm). It is found that for concentrations larger than 0.5 vol. %, the ferroelectric NPs exhibit an increasing effect on the electro-optic response of the nematic liquid crystal, which is demonstrated by the enhancement of the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the SmC* phase, such as the tilt angle Θ, switching time τ s , and spontaneous polarisation P s , are found to be independent of the concentration and size of the NPs. The rotational viscosity η calculated from response times, polarization reversal current, and dielectric properties is comparable for all three methods employed and practically independent of particle concentration and size. The relaxation frequency f R of the Goldstone mode is higher in the ferroelectric NPs suspensions of 2.0 vol. % as compared to the smaller paraelectric NPs.

  9. Gigahertz-repetition-rate Tm-doped fiber laser passively mode-locked by optoacoustic effects in nanobore photonic crystal fiber.

    Science.gov (United States)

    Pang, M; He, W; St J Russell, P

    2016-10-01

    We report a Tm-doped soliton fiber laser passively mode-locked by intense optoacoustic interactions in a short length of solid-core silica photonic crystal fiber (PCF) with a nanobore in core-center. A repetition rate of 1.446 GHz pulse is achieved, corresponding to the 52nd harmonic of the 27.8 MHz cavity round-trip frequency. Strong optoacoustic interactions in this PCF-based, Tm-doped fiber laser ensure stable and repeatable gigahertz-rate pulse train generation at 1.85 μm wavelength, with a high supermode noise suppression ratio and low pulse timing jitter.

  10. GROWTH AND CHARACTERIZATION OF Eu DOPED GaSe SINGLE CRYSTALS BY X-RAY DIFFRACTION AND RAMAN SPECTROSCOPY

    Directory of Open Access Journals (Sweden)

    Dumitru UNTILA

    2017-08-01

    Full Text Available GaSe single crystals doped with Eu (0.025, 0.05, 0.5, 1.0 and 3.0 at% were grown by Bridgman method using Ga, Se and Eu elementary components. The crystalline structure and vibration modes of the GaSe: Eu crystals lattice were studied by X-ray diffraction and Raman spectroscopy. Eu atoms arranged in the van der Waals space of GaSe: Eu crystals form Eu-Se valence bonds and restructure hexagonal lattice of GaSe leading to EuGa2Se4 crystallites formation. Defects generated by EuGa2Se4 crystallites lead to broadening and shifting of single phonon peaks present in Raman spectra towards shorter wavenumbers, and at the same time, activate the longitudinal optical vibrations of EuSe sublattice.Keywords: GaSe, doping, Eu, XRD, Raman. CREȘTEREA ȘI CARACTERIZAREA MONOCRISTALELOR DE GaSe: Eu PRIN DIFRACȚIA RAZELOR X ȘI SPECTROSCOPIA RAMANMonocristalele de GaSe nedopate și dopate cu Eu în cantități de 0.025, 0.05, 0.5, 1.0 și 3.0% at. au fost crescute prin metoda Bridgman din componente elementare Ga, Se și Eu. Structura cristalină și modelele de vibrație a rețelei crista­lelor de GaSe:Eu au fost studiate prin difracția razelor X și spectroscopia Raman. Atomii de Eu localizați în spaţiul van der Waals al cristalelor de GaSe:Eu creează legături de valență Eu-Se și restructurează rețeaua hexagonală a compusului GaSe, conducând la formarea cristalitelor de EuGa2Se4. Defectele generate de cristalitele de EuGa2Se4 duc la lărgirea și deplasarea benzilor monofononice de difuzie Raman spre numere de undă mici și, totodată, activează vibraţiile optice longitudinale ale subreţelei EuSe.Cuvinte-cheie: GaSe, dopare, Eu, XRD, Raman.

  11. Synthesis and optical properties of Tb{sup 3+} doped CdF{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boubekri, H. [Laser Department, Nuclear Technique Division, Nuclear Research Center of Algiers, 02 Bd Frantz Fanon, 16000 Algiers (Algeria); Laboratory of Laser Physics, Optical Spectroscopy and Optoelectronics (LAPLASO), Badji Mokhtar Annaba University, PO Box 12, 23000 Annaba (Algeria); Diaf, M., E-mail: diafma@yahoo.fr [Laboratory of Laser Physics, Optical Spectroscopy and Optoelectronics (LAPLASO), Badji Mokhtar Annaba University, PO Box 12, 23000 Annaba (Algeria); Labbaci, K. [Laboratory of Laser Physics, Optical Spectroscopy and Optoelectronics (LAPLASO), Badji Mokhtar Annaba University, PO Box 12, 23000 Annaba (Algeria); Guerbous, L. [Laser Department, Nuclear Technique Division, Nuclear Research Center of Algiers, 02 Bd Frantz Fanon, 16000 Algiers (Algeria); Duvaut, T.; Jouart, J.P. [ECATHERM/GRESPI, Reims Champagne-Ardenne University (France)

    2013-10-25

    Highlights: •Terbium doped CdF{sub 2} single crystals grown by Bridgman technique. •Absorption, excitation and emission spectra recorded at room temperature. •Spectroscopic properties investigated by use of the Judd–Ofelt theory. •Transition probability, radiative lifetimes, quantum efficiency and branching ratios are calculated. •Emission cross-section is measured by use of Füchtbauer–Ladenburg theory. -- Abstract: This paper reports the optical analysis of Tb{sup 3+} doped CdF{sub 2} single crystals. The pulled crystals were prepared by use of the Bridgman technique from a vacuum furnace in fluoride atmosphere. Absorption, photoluminescence excitation and emission spectra were recorded at room temperature. The Judd–Ofelt (JO) intensity parameters Ω{sub 2}, Ω{sub 4} and Ω{sub 6} for 4f–4f transitions of Tb{sup 3+} ions were computed from the optical absorption spectra using UV, visible and near infrared transitions. These parameters were then used to calculate the radiative transition probabilities (A{sub JJ′}), branching ratios (β{sub JJ′}) and radiative lifetimes of the two main laser emitting levels {sup 5}D{sub 3} and {sup 5}D{sub 4} of Tb{sup 3+} ions. The obtained spectroscopic properties are compared to those of Tb{sup 3+} transitions in other hosts. The excitation spectrum in the UV–Visible spectral range is very close to the absorption spectrum indicating that all observed absorption levels can excite the green emission of Tb{sup 3+} corresponding to {sup 5}D{sub 4} → {sup 7}F{sub 5} transition. The emission spectra exhibit a weak blue emission and a strong green emission in the spectral range 370–460 nm and 478–612 nm which are assigned to {sup 5}D{sub 3} → {sup 7}F{sub J} (J = 6, 5, 4, 3, 2) and {sup 5}D{sub 4} → {sup 7}F{sub J} (J = 6, 5, 4, 3) transitions of Tb{sup 3+}, respectively. The green emission {sup 5}D{sub 4} → {sup 7}F{sub 5} at 532 nm having an emission cross-section equal to 8 × 10{sup −22} cm

  12. Creation of domains by direct electron beam writing in magnesium-doped LiNbO{sub 3} and LiNbO{sub 3}:Fe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Palatnikov, M.N. [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation); Kokhanchik, L.S.; Emelin, E.V. [Institute of Microelectronics Technology and High Purity Materials of Russian Academy of Sciences, 6 Academician Ossipyan st, Chernogolovka, Moscow 142432 (Russian Federation); Sidorov, N.V. [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation); Manukovskaya, D.V., E-mail: deenka@yandex.ru [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation)

    2016-03-01

    Highlights: • The periodic domains are created in crystal LiNbO{sub 3}:Mg by direct electron beam writing. • Periodic domains appear only at equilibrium between switching and screening times. • Equilibrium exists in crystal co-doped by Fe. • Shape and appearance of domains depend on the conductivity type. - Abstract: Domain structures in the Z-cut of highly doped LiNbO{sub 3}:Mg and LiNbO{sub 3}:Mg,Fe single crystals were created by direct electron beam writing (DEBW). It was found that the value and type of electron conductivity influence the shape and number of domains thus created. Controlled electron beam regular domains were created only in samples of the crystal LiNbO{sub 3}:Mg,Fe [MgO] = 5.16 mol.%, [Fe] = 0.007 mol.%. In highly doped LiNbO{sub 3}:Mg ([MgO] = 5.19 mol.%) crystal, the domains were formed chaotically and controlled creation of domains did not occur. The domain shapes were analyzed in the framework of the theory of screening of domain nuclei depolarizing electric fields and the influence of screening on the final shape of domains. It was found that screening of intrinsic electric fields is faster in the LiNbO{sub 3}:Mg,Fe crystal. This crystal has a high electronic conductivity of hopping type with a high mobility of charge carriers. Thus, a small amount of Fe provides equilibrium between the ferroelectric switching velocity and screening of the depolarizing electric field velocity. The results are discussed considering differences in the electron conductivity mechanisms, which control the screening of depolarizing electric field velocity and spatial charge area formed under an electron beam.

  13. Thermal, defects, mechanical and spectral properties of Nd-doped GdNbO{sub 4} laser crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Shoujun [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China); University of Science and Technology of China, Hefei (China); Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Wang, Xiaofei; Sun, Guihua; Li, Xiuli; Sun, Dunlu [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China)

    2017-05-15

    A Nd-doped GdNbO{sub 4} crystal was grown successfully by Czochralski method. Its monoclinic structure was determined by X-ray diffraction; the unit-cell parameters are a = 5.38 Aa, b = 11.09 Aa, c = 5.11 Aa, and β = 94.56 . The morphological defects of Nd:GdNbO{sub 4} crystal were investigated using the chemical etching with the phosphoric acid etchant. For a new crystal, the physical properties are of great importance. The hardness and density of Nd:GdNbO{sub 4} were investigated first. Thermal properties of Nd:GdNbO{sub 4}, including thermal expansion coefficient and specific heat, were measured along a-, b-, and c-crystalline axes. Thermal properties indicate that the Nd:GdNbO{sub 4} pumped along c-axis can reduce the thermal lensing effect effectively. The specific heat is 0.53 J g{sup -1} K{sup -1} at 300 K, indicating a relatively high damage threshold of Nd:GdNbO{sub 4}. The transmission and emission spectrum of Nd:GdNbO{sub 4} were measured, and the absorption peaks were assigned. The strongest emission peak of Nd:GdNbO{sub 4} is located at 1065.3 nm in the spectral range of 850-1420 nm excited by 808 nm laser. The refractive index of Nd:GdNbO{sub 4} was calculated with the transmission spectrum and fitted with Sellmeier equation. All these obtained results is of great significance for the further research of Nd:GdNbO{sub 4}. (orig.)

  14. Synchrotron X-ray diffraction imaging studies of dislocations in Kyropoulos grown Ti doped sapphire crystal

    Science.gov (United States)

    Sen, Gourav; Tran Caliste, Thu Nhi; Stelian, Carmen; Baruchel, José; Barthalay, Nicolas; Duffar, Thierry

    2017-06-01

    In this study, X-ray diffraction and X-ray topography, using synchrotron radiation source, were used to analyse the nature of defects in a sapphire single crystal sample grown by Kyropoulos method. Qualitative and quantitative analysis were carried out on the results of the topography experiments. The dislocation density was found to be around 103-104 dislocations/cm2 indicating a crystal of good crystalline quality. Also, the variation of dislocation density with respect to the position on the sample was observed and discussed.

  15. Structure and crystallization of SiO2 and B2O3 doped lithium disilicate glasses from theory and experiment.

    Science.gov (United States)

    Erlebach, Andreas; Thieme, Katrin; Sierka, Marek; Rüssel, Christian

    2017-09-27

    Solid solutions of SiO2 and B2O3 in Li2O·2SiO2 are synthesized and characterized for the first time. Their structure and crystallization mechanisms are investigated employing a combination of simulations at the density functional theory level and experiments on the crystallization of SiO2 and B2O3 doped lithium disilicate glasses. The remarkable agreement of calculated and experimentally determined cell parameters reveals the preferential, kinetically controlled incorporation of [SiO4] and [BO4] at the Li+ lattice sites of the Li2O·2SiO2 crystal structure. While the addition of SiO2 increases the glass viscosity resulting in lower crystal growth velocities, glasses containing B2O3 show a reduction of both viscosities and crystal growth velocities. These observations could be rationalized by a change of the chemical composition of the glass matrix surrounding the precipitated crystal phase during the course of crystallization, which leads to a deceleration of the attachment of building units required for further crystal growth at the liquid-crystal interface.

  16. Growth of doped Pb S:Co{sup 2+} nano crystals by chemical bath

    Energy Technology Data Exchange (ETDEWEB)

    Portillo M, O.; Gutierrez P, R.; Chavez P, M.; Marquez S, M. N.; Hernandez T, G.; Lazcano H, M.; Moreno R, A. [Universidad Autonoma de Puebla, Facultad de Ciencias Quimicas, Laboratorio de Ciencia de Materiales, Apdo. Postal 1067, 72001 Puebla, Pue. (Mexico); Palomino M, R. [Universidad Autonoma de Puebla, Facultad de Ciencias Fisico-Matematicas, Posgrado en Fisica Aplicada, 72001 Puebla, Pue. (Mexico); Rubio R, E., E-mail: osporti@yahoo.com.mx [Universidad Autonoma de Puebla, Centro Universitario de Vinculacion y Transferencia de Tecnologia, 72001 Puebla, Pue. (Mexico)

    2016-11-01

    Nanocrystalline Pb S films grown by chemical bath at T = 40 ± 2 degrees Celsius onto glass slides were modified by in situ Co{sup 2+} -doping and their structural and optical properties were examined. By Ft-IR spectra, a sharp stretching mode can be seen at ∼1384 cm{sup -1} due to the vibration mode of CO{sup 2/3} ions. X-ray diffraction patterns shown the growth on the zinc blende crystalline face. The grain size was determined by using X-rays diffractograms and was found at ∼28 nm and ∼13 - 25 nm for undoped and doped samples, respectively. Optical absorption spectra was used for calculating the energy band gap, and displayed a shift in the ∼1.21 - 2.21 eV range, associated with quantum confinement effect. Raman peaks at ∼210, 271 and 451 cm{sup -1}, corresponding to a 1LO phonon mode, a two-phonon process, and a 2LO phonon mode respectively were also recorded. The surface and grain size of the films were measured by atomic force microscopy studies. (Author)

  17. Photoinduced reorganization of motor-doped chiral liquid crystals: bridging molecular isomerization and texture rotation.

    Science.gov (United States)

    Bosco, Alessandro; Jongejan, Mahthild G M; Eelkema, Rienk; Katsonis, Nathalie; Lacaze, Emmanuelle; Ferrarini, Alberta; Feringa, Ben L

    2008-11-05

    We recently reported that the photoisomerization of molecular motors used as chiral dopants in a cholesteric liquid crystal film induces a rotational reorganization which can be observed by optical microscopy and produces the motion of microscopic objects placed on top of the film (Feringa, B. L.; et al. Nature 2006, 440, 163; J. Am. Chem. Soc. 2006, 128, 14397). The mechanism underlying the mesoscopic manifestation of the molecular process was not fully understood, and here we present a joint theoretical and experimental investigation, which provides a detailed insight into the mechanism of texture rotation. This description allows us to identify the interplay between the chemical structure of the chiral dopant and the material properties of the liquid crystal host, and to quantify their role in the observed dynamic phenomenon. We have found that a crucial role is played by the hybrid anchoring of the liquid crystal, with the director parallel to the substrate and perpendicular to the interface with air; in this configuration an almost unperturbed cholesteric helix, with its axis normal to the substrate, is present in most of the film, with strong deformations only close to the free interface. The texture rotation observed in the experiment reflects the rotation of the director during the unwinding of the cholesteric helix, produced by the change in shape of the chiral dopant under photoisomerization. The rotational reorganization is controlled by the photochemical process, via the coupling between the chirality of the dopant and the elastic properties of the liquid crystal host.

  18. X-Ray diffraction study of KTiOPO{sub 4} single crystals doped with hafnium

    Energy Technology Data Exchange (ETDEWEB)

    Novikova, N. E., E-mail: natnov@ns.crys.ras.ru; Verin, I. A.; Sorokina, N. I.; Alekseeva, O. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Orlova, E. I.; Voronkova, V. I. [Moscow State University, Faculty of Physics (Russian Federation)

    2011-05-15

    Single crystals of KTi{sub 1-x}Hf{sub x}OPO{sub 4} (x = 0.015(2), 0.035(1), and 0.128(1) are reinvestigated by precision X-ray diffraction at room temperature. It is found that the implantation of hafnium atoms in the crystal structure of KTiOPO{sub 4} does not lead to significant changes in the framework and affects only the positions of the potassium atoms in the channel. Our studies reveal the displacements of the potassium atoms from their main and additional positions in the structure of pure KTP in all three structures studied. The largest displacements from the K1 Prime and K1 Double-Prime additional positions are observed in the structure with x = 0.035. At this hafnium concentration, the occupancy of the main positions of potassium atoms decreases and the occupancy of the additional positions increases in relation to those in KTP. This redistribution of potassium atoms enhances the nonuniformity of distribution of the electron density in the vicinity of their positions, which is probably responsible for the increase in the nonlinear susceptibility of KTP crystals that contain 3.5% hafnium in relation to crystals of pure KTP.

  19. Optical absorption and Faraday rotation in spin doped Cd1-xHgxSe : Mn crystals

    NARCIS (Netherlands)

    Savchuk, AI; Paranchich, SY; Paranchich, LD; Romanyuk, OS; Andriychuk, MD; Nikitin, PI; Tomlinson, RD; Hill, AE; Pilkington, RD

    1998-01-01

    Optical absorption spectra and the Faraday effect in crystals of Cd1-xHgxSe : Mn have been studied. The studied samples have been characterized abrupt absorption edge and transparency region with high transmission coefficient. The measured values of Verdet constant were considerably larger than in

  20. Photocatalytic degradation of crystal violet by thiourea-doped TiO2 ...

    African Journals Online (AJOL)

    In this study, optimisation of the photocatalytic behaviour of crystal violet (CV) by thiourea (Tu)-codoped TiO2 thin film in fixed bed photoreactor was investigated by central composite designs (CCDs). The effective variables were pH, the concentration of CV dye, flow rate and reaction time. The results of the CCD model ...

  1. Geometry VI

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 1; Issue 8. Geometry VI - Space-the Final Frontier. Kapil H Paranjape. Series Article Volume 1 Issue 8 August 1996 pp 28-33. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/001/08/0028-0033 ...

  2. VI KA’

    DEFF Research Database (Denmark)

    Sprogøe, Jonas

    2012-01-01

    Artiklen handler om hvordan man kan bruge et spil til at udvikle og måle kompetencer. Artiklen diskuterer forskellige forståelser kompetencebegrebet og diskuterer hvordan Vi Ka'-spillet bidrager til at indfange den mere aktive forståelse af kompetence, som noget du gør i en bestemt kontekst....

  3. Influence of strontium doping on the indirect band gap and optical constants of ammonium zinc chloride crystals

    Energy Technology Data Exchange (ETDEWEB)

    Gaffar, M.A.; El-Fadl, A. Abu; Anooz, S. Bin

    2003-03-01

    Optical transmittance measurements near the absorption edge in the energy range 3.4-6.4 eV have been carried out on (NH{sub 4}){sub 2}ZnCl{sub 4}:xSr{sup 2+} single crystals with x=0.000%, 0.020%, 0.039%, 0.087% or 0.144%. The introduction of Sr{sup 2+} in low concentration, x=0.02% or 0.039%, little bleach the intense charge transfer band observed for the undoped sample with a maximum at 5.30 eV. Doping with Sr{sup 2+} in a little bit higher concentration, x=0.087% or 0.144%, led to the disappearance of this band. While doping with Sr{sup 2+} has no effect on the indirect allowed type of optical transition in AZC, the optical energy gap decreased with increasing Sr{sup 2+} concentration. Measuring reflectance of AZC permitted the calculation of the refractive index n, the extinction coefficient K and both the real {epsilon}{sub r} and imaginary {epsilon}{sub i} components of the dielectric permittivity as functions of photon energy. The validity of Cauchy-Sellimaier equation was checked in the wavelength range 5.45-5.8 eV and its parameters were calculated. Applying the single-effective-oscillator model, the moments of {epsilon}(E) could be estimated. Electric susceptibility, as a measure of intraband transition, was calculated and its dependence on photon energy was considered.

  4. Toward the realization of erbium-doped GaN bulk crystals as a gain medium for high energy lasers

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Z. Y.; Li, J.; Zhao, W. P.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2016-08-01

    Er-doped GaN (Er:GaN) is a promising candidate as a gain medium for solid-state high energy lasers (HELs) at the technologically important and eye-safe 1.54 μm wavelength window, as GaN has superior thermal properties over traditional laser gain materials such as Nd:YAG. However, the attainment of wafer-scale Er:GaN bulk or quasi-bulk crystals is a prerequisite to realize the full potential of Er:GaN as a gain medium for HELs. We report the realization of freestanding Er:GaN wafers of 2-in. in diameter with a thickness on the millimeter scale. These freestanding wafers were obtained via growth by hydride vapor phase epitaxy in conjunction with a laser-lift-off process. An Er doping level of 1.4 × 10{sup 20} atoms/cm{sup 3} has been confirmed by secondary ion mass spectrometry measurements. The freestanding Er:GaN wafers exhibit strong photoluminescent emission at 1.54 μm with its emission intensity increasing dramatically with wafer thickness under 980 nm resonant excitation. A low thermal quenching of 10% was measured for the 1.54 μm emission intensity between 10 K and 300 K. This work represents a significant step in providing a practical approach for producing Er:GaN materials with sufficient thicknesses and dimensions to enable the design of gain media in various geometries, allowing for the production of HELs with improved lasing efficiency, atmosphere transmission, and eye-safety.

  5. Zero-charged catanionic lamellar liquid crystals doped with fullerene C60 for potential applications in tribology.

    Science.gov (United States)

    Chen, Mengjun; Liu, Baoyong; Wang, Xiaolin; Fu, Yanxu; Hao, Jingcheng; Li, Hongguang

    2017-09-20

    The formation of lamellar liquid crystals (LLCs) has been demonstrated in a few salt-free catanionic surfactant systems and their properties have been well documented. However, examples of their combination with other materials are relatively rare. Herein, a salt-free zero-charged catanionic surfactant with low chain melting temperature was prepared by mixing equimolar tetradecyltrimethylammonium oxide (TTAOH) and oleic acid (OA) in water, and its concentration-dependent aggregate transition was investigated. In the dilute region (cTTAO ≤ 5 wt%), fluorescence microscopy observations revealed the formation of vesicles (the Lαv phase). Further increasing cTTAO induced a transition from the Lαv phase to LLCs via a region where vesicles and lamellae coexist. With ordered hydrophobic domains, the LLCs can be used as hosts for the doping of fullerene C60 (refers to C60 hereafter) with the highest C60/TTAO weight ratio of 0.04. The doping of C60 effectively improves the viscoelasticity of the LLCs confirmed by rheological characterization while only slight modifications on their matrixes have been detected using small angle X-ray scattering measurements. The LLC/C60 hybrids with cTTAO = 80 wt% were then subjected to tribological measurements, and an obvious reduction in their friction coefficients and wear volumes was observed. The C60/TTAO weight ratio at which the best tribological performance appears was determined to be 0.01. Our results indicate that the combination of C60 and catanionic LLCs could lead to the appearance of a new generation of environmentally-benign lubricants.

  6. New optical tools used for characterization of phase transitions in nonlinear nano-crystals. Example of Yb{sup 3+}-doped BaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Amami, Jaouher [Physical Chemistry of Luminescent Materials, Claude Bernard Lyon 1 University, UMR 5620 CNRS, Batiment Kastler, La Doua, 69622 Villeurbanne (France); Hreniak, Dariusz [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Guyot, Yannick [Physical Chemistry of Luminescent Materials, Claude Bernard Lyon 1 University, UMR 5620 CNRS, Batiment Kastler, La Doua, 69622 Villeurbanne (France); Pazik, Robert [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Strek, Wieslaw [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Goutaudier, Christelle [Physical Chemistry of Luminescent Materials, Claude Bernard Lyon 1 University, UMR 5620 CNRS, Batiment Kastler, La Doua, 69622 Villeurbanne (France); Boulon, Georges [Physical Chemistry of Luminescent Materials, Claude Bernard Lyon 1 University, UMR 5620 CNRS, Batiment Kastler, La Doua, 69622 Villeurbanne (France)

    2007-03-07

    The main objective of this paper is to focus on the use of new techniques to specifically characterize BaTiO{sub 3} nonlinear nano-crystals as a test case. We use the second harmonic generation (SHG) of an IR YAG:Nd pump laser and detection of the Yb{sup 3+} ion pairs to investigate effect of doping and synthesis route (sol-gel between 700 and 1200 deg. C) on both crystallite sizes (25-60 nm) and different phase symmetries (tetragonal, cubic, hexagonal) in Yb{sup 3+}-doped BaTiO{sub 3}. In nano-crystals, a higher intensity of SHG was observed in the acentric tetragonal phase, whereas the isotropic cubic phase was detected by the absence of a SHG signal. Cooperative emission, indicating the presence of Yb{sup 3+} ion pairs, was easily detected in the cubic phase and not seen in the ferroelectric tetragonal structure.

  7. Nano crystals of Ni doped Zn O semiconductor by Sol-Gel combustion method

    Energy Technology Data Exchange (ETDEWEB)

    Carrero, A.; Sagredo, V. [Universidad de Los Andes, Departamento de Fisica, Laboratorio de Magnetismo, 5101 Merida (Venezuela, Bolivarian Republic of); Larionova, J., E-mail: aneelyc@gmail.com [Universite Montpellier II, 2 Place Eugene Bataillon, 34090 Montpellier (France)

    2016-11-01

    Nanoparticles of the system Zn{sub 0.95}O were prepared by sol-gel self - combustion method and a study of their structural, optical and magnetic properties were conducted. X-ray diffraction study shows a hexagonal wurtzite structure for the nano compound. The formation of the wurtzite structure in Ni doped Zn O was further confirmed by Fourier transform infra-red spectrometry. Transmission electron microscopy revealed an average size of 31 nm for the particles. Optical absorption spectra shows that the band energy of Zn{sub 0.95}Ni{sub 0.}9{sub 5}O powders is about 2.54 eV at room temperature. A study of the magnetic properties of the nano powders of Zn O: Ni, reveals paramagnetic behavior, with interaction ferromagnetic between particles. (Author)

  8. Thermoelectric thermal detectors based on ultra-thin heavily doped single-crystal silicon membranes

    Science.gov (United States)

    Varpula, Aapo; Timofeev, Andrey V.; Shchepetov, Andrey; Grigoras, Kestutis; Hassel, Juha; Ahopelto, Jouni; Ylilammi, Markku; Prunnila, Mika

    2017-06-01

    We present thermal detectors based on 40 nm-thick strain tuned single crystalline silicon membranes shaped into a heater area supported by narrow n- and p-doped beams, which also operate as a thermocouple. The electro-thermal characterization of the devices reveals a noise equivalent power of 13 pW/Hz1/2 and a thermal time constant of 2.5 ms. The high sensitivity of the devices is due to the high Seebeck coefficient of 0.39 mV/K and reduction of thermal conductivity of the Si beams from the bulk value. The performance enables fast and sensitive detection of low levels of thermal power and infrared radiation at room temperature. The devices operate in the Johnson-Nyquist noise limit of the thermocouple, and the performance improvement towards the operation close to the temperature fluctuation limit is discussed.

  9. Thermal radiation of Er doped dielectric crystals: Probing the range of applicability of the Kirchhoff law

    CERN Document Server

    Tanyi, Ekembu K; Narimanov, Evgenii E; Noginov, M A

    2016-01-01

    The Kirchhoff law of thermal radiation, relating emissivity {\\epsilon} and absorptance {\\alpha}, has been originally formulated for opaque bodies in thermodynamic equilibrium with the environment. However, in many systems of practical importance, both assumptions are often not satisfied. In this work, we revisit the century-old law and examine the limits of its applicability in an example of Er:YAG and Er:YLF dielectric crystals, potential radiation converters for thermophotovoltaic applications. In our experiments, the (80 at.%) Er:YAG crystal was opaque between 1.45 {\\mu}m and 1.64 {\\mu}m. In this spectral range, its absorptance {\\alpha}({\\lambda}) is spectrally flat and differentiates from unity only by a small amount of reflection. The shape of the emissivity spectrum {\\epsilon}({\\lambda}) closely matches that of absorptance {\\alpha}({\\lambda}), suggesting that the Kirchhoff law can adequately describe thermal radiation of opaque bodies, even if the requirement of thermodynamic equilibrium is not satisfie...

  10. Optically stimulated luminescence of Tb{sup 3+}/Sm{sup 3+} doubly doped K{sub 2}YF{sub 5} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Camargo, L.; Marcazzo, J.; Santiago, M.; Caselli, E. [Universidad Nacional del Centro de la Provincia de Buenos Aires, Instituto de Fisica Arroyo Seco, Gral. Pinto 399, B7000GHG, Tandil (Argentina); Khaidukov, N. M., E-mail: jmarcass@exa.unicen.edu.ar [Kurnakov Institute of General and Inorganic Chemistry, RAS, Leninskii Prospekt 31, 119991 Moscow (Russian Federation)

    2014-08-15

    In this work optically stimulated luminescence (OSL) properties of K{sub 2}YF{sub 5} crystals doubly doped with Tb{sup 3+} and Sm{sup 3+} ions have been investigated for the first time. OSL responses for different dopant concentration and for optical stimulation with different wavelengths have been analyzed for each compound. Dosimetric properties of the most efficient composition, namely, K{sub 2}YF{sub 5}:1.0 at.% Tb{sup 3+}; 1.0 at.% Sm{sup 3+}, have been studied. Finally, the possible application of this single crystal as OSL dosimeter has been evaluated. (Author)

  11. Crystallization behavior of Nd-doped SrBi{sub 2}Ta{sub 2}O{sub 9} thin films prepared by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Li Yibin [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Zhang, Sam [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)], E-mail: msyzhang@ntu.edu.sg; Fei Weidong [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001 (China); Wang Huili [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2008-06-30

    Nd-doped SrBi{sub 2}Ta{sub 2}O{sub 9} thin films are magnetron-sputtered on Pt/Ta/SiO{sub 2}/Si substrates. The effect of heating rate on crystallization behavior is investigated with conventional furnace annealing (CFA) and rapid thermal annealing (RTA). Grazing incidence X-ray diffraction and field emission scanning electron microscopy reveal that the crystallization goes through three stages (phases): amorphous, fluorite and finally Aurivillius. Under RTA, the fluorite-to-Aurivillius transformation starts around 100 {sup o}C lower than that under CFA. The reasons behind the transformation temperature drop are also discussed.

  12. Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping

    OpenAIRE

    Borthwick, Alistair; Liu, Wen; Sun, Weiling; Wang, Ting; Li, Fan; Guan, Yidong

    2016-01-01

    Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and...

  13. Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

    Science.gov (United States)

    Parmar, Narendra S.; Yim, Haena; Choi, Ji-Won

    2017-03-01

    Stable p-type conduction in ZnO has been a long time obstacle in utilizing its full potential such as in opto-electronic devices. We designed a unique experimental set-up in the laboratory for high Na-doping by thermal diffusion in the bulk ZnO single crystals. SIMS measurement shows that Na concentration increases by 3 orders of magnitude, to ~3 × 1020 cm-3 as doping temperature increases to 1200 °C. Electronic infrared absorption was measured for Na-acceptors. Absorption bands were observed near (0.20-0.24) eV. Absorption bands blue shifted by 0.04 eV when doped at 1200 °C giving rise to shallow acceptor level. NaZn band movements as a function of doping temperature are also seen in Photoluminescence emission (PL), Photoluminescence excitation (PLE) and UV-Vis transmission measurements. Variable temperature Hall measurements show stable p-type conduction with hole binding energy ~0.18 eV in ZnO samples that were Na-doped at 1200 °C.

  14. In situ hydrothermal crystallization of hexagonal hydroxyapatite tubes from yttrium ion-doped hydroxyapatite by the Kirkendall effect

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chengfeng, E-mail: cfli@sdut.edu.cn [School of Materials Science and Engineering, Shandong University of Technology, 255049 Shandong (China); Ge, Xiaolu [School of Science, Shandong University of Technology, 255049 Shandong (China); Li, Guochang; Lu, Hao; Ding, Rui [School of Materials Science and Engineering, Shandong University of Technology, 255049 Shandong (China)

    2014-12-01

    An in situ hydrothermal crystallization method with presence of glutamic acid, urea and yttrium ions was employed to fabricate hexagonal hydroxyapatite (HAp, Ca{sub 5}(PO{sub 4}){sub 3}(OH)) tubes with length of 200 nm–1 μm. Firstly, yttrium ion-doped HAp (Y-HAp, Ca{sub 5−x}Y{sub x}(PO{sub 4}){sub 3}(OH)) was synthesized after hydrolysis of urea and HPO{sub 4}{sup 2−} ions at 100 °C with a dwell time of 24 h. The shift of X-ray diffraction peaks of HAp to high angle was caused the substitution of Ca{sup 2+} ions by small-sized Y{sup 3+} ions. At 160 °C, further hydrolysis reactions of urea and HPO{sub 4}{sup 2−} ions resulted in the generation of ample OH{sup −} and PO{sub 4}{sup 3−} ions, which provided a high chemical potential for the dissolution of Y-HAp and recrystallization of HAp and YPO{sub 4}. Finally, HAp tubes were formed in situ on Y-HAp according to the Kirkendall effect as a result of the difference of diffusion rate of cations (Ca{sup 2+} ions, outward and slow) and anions (OH{sup −} and PO{sub 4}{sup 3−} ions, inward and fast). The formation process of HAp tube was simulated by the encapsulation of fluorescein molecules in precipitates. Photoluminescence properties were enhanced for HAp tubes with thick and dense walls. This novel tubular material could find wide applications as carriers of drugs, dyes and catalysts. - Highlights: • Hexagonal HAp tubes with adjustable sizes are prepared by a hydrothermal method. • A dissolution-recrystallization process occurs during hydrothermal treatment. • The formation mechanism is explained by the Kirkendall effect. • The crystallization is simulated by the encapsulation and release of fluorescein.

  15. Magnetization and FMR studies of crystal-ion-sliced narrow linewidth gallium-doped yttrium iron garnet

    Science.gov (United States)

    Rachford, F. J.; Levy, M.; Osgood, R. M.; Kumar, A.; Bakhru, H.

    2000-05-01

    Recent interest in employing single-crystal yttrium iron garnet (YIG) films for miniaturized microwave integrated circuit applications has prompted us to study detaching liquid phase epitaxy (LPE) grown YIG films from their gadolinium gallium garnet (GGG) substrates via crystal ion slicing (CIS). We report studies of magnetization and ferromagnetic resonance (FMR) of narrow linewidth gallium-doped YIG (GaYIG) films in various stages of separation from their oriented GGG substrates. All samples were diced from the same three-inch wafer of Y3Fe4.6Ga0.4O12 with 4πMeff of 1070 G and 9.45 GHz FMR linewidth of 0.4±0.1 Oe. The CIS separation process involved (1) implantation with helium ions, (2) flash annealing to remove surface damage, and (3) chemical etching to detach the YIG at the implantation damaged layer. The starting films were 10.8-μm thick. Separation occurred 7 to 8 μm from the front surface in the YIG. The implantation (5×1016cm-2 dosage, 3.8 MeV bias) increased the uniaxial anisotropy of these films. A small cubic anisotropy (˜5 G 60° in-plane periodicity) persisted in both implanted and unimplanted samples. Upon implantation the FMR linewidth increased from 0.4 to 3±0.5 Oe. The detached samples have linewidths ranging from 1.7 to 2.5 Oe. The temperature dependence of the linewidths is roughly exponential decreasing as the temperature is lowered for the unprocessed sample, increasing with reduced temperature for all processed samples. Post-detachment annealing restores the FMR linewidth to 0.55±0.5 Oe.

  16. Spatially selective Er/Yb-doped CaF{sub 2} crystal formation by CO{sub 2} laser exposure

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong-Seon; Lee, Jin-Ho; Lim, Ki-Soo, E-mail: kslim@chungbuk.ac.kr

    2014-10-30

    Highlights: • Oxyfluoride glass–ceramics containing CaF{sub 2} nanocrystals doped with Er{sup 3+} and Yb{sup 3+} ions were formed on the glass surface by CO{sub 2} laser and a heat gun exposure. • Most of Er and Yb ions were distributed inside CaF{sub 2} nanocrystals and fluorine loss was observed in the EDS element maps. • IR-to-VIS upconversion emission efficiency of laser annealed glass ceramics was much increased and compared with that of the furnace-annealed glass ceramics. • Distributed volume of the glass ceramics were estimated by a confocal fluorescence microscope imaging. - Abstract: We report the glass–ceramic precipitation on the oxyfluoride glass surface by spatially selective annealing with a CO{sub 2} laser and a heat gun exposure. X-ray diffraction analysis showed the formation of major CaF{sub 2} and miner Ca{sub 2}SiO{sub 4} nanoparticles. We observed ∼100 nm nanoparticle aggregation by tunneling electron microscopy and element distribution in glass and crystal phases. Spatial distribution of glass ceramics near the glass surface was probed by confocal fluorescence microscope by using much enhanced emission from the Er ions in the laser-treated area. Strong emissions at 365 nm excitation and visible up-conversion emissions at 980 nm excitation also indicated well incorporation of Er and Yb ions into a crystalline environment.

  17. Spatially selective Er/Yb-doped CaF{sub 2} crystal formation by CO{sub 2} laser exposure

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong-Seon; Lee, Jin-Ho; Lim, Ki-Soo, E-mail: kslim@chungbuk.ac.kr

    2015-04-15

    Highlights: • Oxyfluoride glass–ceramics containing CaF{sub 2} nanocrystals doped with Er{sup 3+} and Yb{sup 3+} ions were formed on the glass surface by CO{sub 2} laser and a heat gun exposure. • Most of Er and Yb ions were distributed inside CaF{sub 2} nanocrystals and fluorine loss was observed in the EDS element maps. • IR-to-VIS upconversion emission efficiency of laser annealed glass ceramics was much increased and compared with that of the furnace-annealed glass ceramics. • Distributed volume of the glass ceramics were estimated by a confocal fluorescence microscope imaging. - Abstract: We report the glass–ceramic precipitation on the oxyfluoride glass surface by spatially selective annealing with a CO{sub 2} laser and a heat gun exposure. X-ray diffraction analysis showed the formation of major CaF{sub 2} and miner Ca{sub 2}SiO{sub 4} nanoparticles. We observed ∼100 nm nanoparticle aggregation by tunneling electron microscopy and element distribution in glass and crystal phases. Spatial distribution of glass ceramics near the glass surface was probed by confocal fluorescence microscope by using much enhanced emission from the Er ions in the laser-treated area. Strong emissions at 365 nm excitation and visible up-conversion emissions at 980 nm excitation also indicated well incorporation of Er and Yb ions into a crystalline environment.

  18. Realization of compatible stealth material for infrared, laser and radar based on one-dimensional doping-structure photonic crystals

    Science.gov (United States)

    Zhang, Ji-Kui; Shi, Jia-Ming; Zhao, Da-Peng; Wang, Qi-Chao; Wang, Cheng-Ming

    2017-09-01

    To inhibit the radiant infrared energy between 8 and 14 μm, which is the infrared atmospheric window, and decrease the echo power of detecting laser and radar, to achieve compatible stealth, a doping structural one-dimensional photonic crystal (1-D PC) with Ge, ZnSe and Si was fabricated; and then combine it with radar absorbing material (RAM) to make a compound. After that, the reflection spectra of this compound was tested, and the result shows a high average reflectance (89.5%) in 8-14 μm waveband, and a reflective valley (39.8%) in the wavelength of 10.6 μm, which is the wavelength of CO2 laser; and the reflectance in radar band shows that at high frequency, especially between 7.8 and 18 GHz, the radar power is strongly absorbed by this material and the reflected energy attenuate over 10 dB within the range from 11.1 GHz to 18.3 GHz, even 24.5 dB to the most in the frequency of 14.6 GHz.

  19. Silica nanoparticle doped organic ionic plastic crystal electrolytes for highly efficient solid-state dye-sensitized solar cells.

    Science.gov (United States)

    Shi, Chengzhen; Qiu, Lihua; Chen, Xiaojian; Zhang, Haigang; Wang, Lei; Yan, Feng

    2013-02-01

    Organic ionic plastic crystal, 1-propyl-1-methylpyrrolidinium iodide (P₁₃I), which possesses a broad plastic phase from -36 to 135 °C, was doped with silica nanoparticles (SiO₂ NPs) and 1-ethyl-3-methylimidazolium iodide (EMII), for the preparation of SiO₂/EMII/P₁₃I solid-state electrolytes for dye-sensitized solar cells (DSSCs). The thermal properties of all the electrolytes, including solid-solid phase transitions and melting temperatures, were investigated by differential scanning calorimetry (DSC). The effect of silica particles on the ionic conductivity, diffusion of I⁻/I₃⁻ redox couple in electrolytes, and photovoltaic performance for solid-state DSSCs were investigated. The fabricated solid-state DSSCs yielded a high power conversion efficiency of 5.25% under simulated air mass 1.5 solar spectrum illuminations at 50 mW cm⁻². Furthermore, the DSSCs based on SiO₂/EMII/P₁₃I solid-state electrolytes show good stability after an accelerating aging test, demonstrating potential practical applications.

  20. Magnetic susceptibility of the rare earth element impurities in the IV-VI semiconductors and Curie-Weiss law

    Energy Technology Data Exchange (ETDEWEB)

    Zayachuk, D.M., E-mail: zayachuk@polynet.lviv.u [Lviv Polytechnic National University, 12 Bandera Street, 79013 Lviv (Ukraine)

    2010-01-15

    Peculiarities of applying the Curie-Weiss law to the analysis of the magnetic susceptibility of the impurities of the rare earth elements in the IV-VI crystals are examined. It is shown that the traditional approach to the determination of the paramagnetic Curie temperature of ferromagnets and antiferromagnets applied to the impurities of ferromagnetic and antiferromagnetic elements in the doped crystal may lead to fundamental mistakes. The results of this examination are used to analyze the high temperature magnetic susceptibility of Eu and Gd impurities in the PbTe doped crystals grown from the melt using the Bridgman method. It is established that the doping of PbTe with Eu leads to the formation of ferromagnetic inclusions and the same doping with Gd leads to the formation of antiferromagnetic inclusions in the crystal. It is shown that these inclusions are most likely the complexes based on the europium or gadolinium oxides EuO and Gd{sub 2}O{sub 3}, respectively.

  1. Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

    Directory of Open Access Journals (Sweden)

    Alberta Ferrarini

    2009-10-01

    Full Text Available The addition of a chiral non-racemic dopant to a nematic liquid crystal (LC has the effect of transferring the molecular chirality to the phase organization and a chiral nematic phase is formed. This molecular chirality amplification in the LC provides a unique possibility for investigating the relationship between molecular structure, intermolecular interactions, and mesoscale organization. It is known that axially chiral or helical-shaped molecules with reduced conformational disorder are good candidates for high helical twisting power derivatives. In particular, biaryl derivatives are known to be efficient chiral inducers in biaryl nematic mesophases. In this paper, we focus on a new series of helicene-like molecules of known absolute configuration. We have integrated cholesteric pitch measurements with geometry optimization by DFT calculations and analysis of the twisting ability by the Surface Chirality model to shed light on the structural features responsible for the analogies and differences exhibited by these derivatives. The investigation of these dopants with well-defined geometry, by virtue of the low conformational freedom, and the substituents variously distributed around the core, allows us to extend our knowledge of the molecular origin of the chirality amplification in liquid crystals and to confirm the simple relationship “molecular P-helicity” → “cholesteric P-handedness” for helical-shaped helicene-like derivatives.

  2. Phase transformation and intense 2.7 μm emission from Er3+ doped YF3/YOF submicron-crystals.

    Science.gov (United States)

    Chai, Guanqi; Dong, Guoping; Qiu, Jianrong; Zhang, Qinyuan; Yang, Zhongmin

    2013-01-01

    Yttrium fluoride YF3:Er(3+) and yttrium oxyfluoride YOF:Er(3+) submicron-crystals with mid-infrared fluorescent emissions were synthesized for the first time. The rhombohedral phase YOF submicron-crystals were synthesized by the crystalline phase transformation from pure orthorhombic YF3 submicron-crystals, which were prepared by co-precipitation method. The composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM), which showed that submicron-crystals were quasi-spherical with the particle size of ~400 nm. A novel formation mechanism of YOF submicron-crystals was proposed. Photoluminescence (PL) spectra indicated the 2.7 μm emission of Er(3+) has remarkably enhanced with the increase of Er(3+) doping concentration, and a novel dynamic circulatory energy transfer mechanism was proposed. Fourier transform infrared spectra (FTIR) were used to demonstrate the change of hydroxyl content. These oxyfluoride submicron-crystals provide a new material for nano/submicron-crystals-glass composites, and open a brand new field for the realization of mid-infrared micro/nano-lasers.

  3. Crystal structure of dioxidobis(pentane-2,4-dionato-κ2 O,O′)[1-phenyl-3-(pyridin-4-yl)propane-κN]uranium(VI)

    Science.gov (United States)

    Kawasaki, Takeshi; Kitazawa, Takafumi

    2015-01-01

    In the title compound, [UO2(C5H7O2)2(C14H15N)], the uran­yl(VI) unit ([O=U=O]2+) is coordinated to two acetyl­acetonate (acac) anions and one 1-phenyl-3-(pyridin-4-yl)propane (ppp) mol­ecule. The geometry around the U atom is UNO6 penta­gonal–bipyramidal; two uran­yl(VI) O atoms are located at the axial positions, whereas four O atoms from two chelating bidentate acac ligands and one N atom of a ppp ligand form the equatorial plane. PMID:25705446

  4. Crystal structure of dioxidobis(pentane-2,4-dionato-κ(2) O,O')[1-phenyl-3-(pyridin-4-yl)propane-κN]uranium(VI).

    Science.gov (United States)

    Kawasaki, Takeshi; Kitazawa, Takafumi

    2015-01-01

    In the title compound, [UO2(C5H7O2)2(C14H15N)], the uran-yl(VI) unit ([O=U=O](2+)) is coordinated to two acetyl-acetonate (acac) anions and one 1-phenyl-3-(pyridin-4-yl)propane (ppp) mol-ecule. The geometry around the U atom is UNO6 penta-gonal-bipyramidal; two uran-yl(VI) O atoms are located at the axial positions, whereas four O atoms from two chelating bidentate acac ligands and one N atom of a ppp ligand form the equatorial plane.

  5. Crystal growth and characterization of undoped and Dy-doped TlPb2Br5 for infrared lasers and nuclear radiation detection

    Science.gov (United States)

    Hömmerich, U.; Brown, E.; Kabir, A.; Hart, D.; Trivedi, S. B.; Jin, F.; Chen, H.

    2017-12-01

    We report results of the crystal growth and characterization of undoped and Dy-doped TlPb2Br5 for applications in infrared (IR) lasers and nuclear radiation detection. TlPb2Br5 (TPB) was synthesized from commercial starting materials of PbBr2 and TlBr and further purified through a combination of zone-refinement and directional solidification. For doping experiments, 2 wt% of DyBr3 was added to the purified TPB material. Crystal growth of TPB and Dy: TPB was carried out in a two-zone tube furnace by a vertical Bridgman method. Following optical excitation at ∼1.36 μm, the Dy: TPB crystal exhibited efficient mid-IR emission bands centered at 2.87 μm and 4.35 μm with room-temperature lifetimes of 9.5 ms and 5.2 ms, respectively. The peak emission cross-sections were determined to be ∼0.8 × 10-20 cm2 and ∼0.5 × 10-20 cm2, respectively, which makes Dy: TPB a promising candidate for mid-IR laser applications. Besides its potential as a solid-state laser host, an undoped TPB crystal was also tested for gamma-ray detection. Using Cs-137 and Am-241 sources resulted in energy resolutions for gamma-rays as good as 1-2% (FWHM) at room-temperature under non-optimized conditions.

  6. Crystal-field level inversion in lightly Mn-doped Sr3Ru2O7

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, M. A.; Hu, Z.; Haverkort, M. W.; Burnus, T.; Chang, C. F.; Klein, S.; Denlinger, J. D.; Lin, H.-J.; Chen, C. T.; Mathieu, R.; Kaneko, Y.; Tokura, Y.; Satow, S.; Yoshida, Y.; Takagi, H.; Tanaka, A.; Elfimov, I. S.; Sawatzky, G. A.; Tjeng, L. H.; Damascelli, A.

    2008-01-15

    Sr3(Ru1-xMnx)2O7, in which 4d-Ru is substituted by the more localized 3d-Mn, is studied by x-ray dichroism and spin-resolved density functional theory. We find that Mn impurities do not exhibit the same 4+ valence of Ru, but act as 3+ acceptors; the extra eg electron occupies the in-plane 3dx2-y2 orbital instead of the expected out-of-plane 3d3z2-r2. We propose that the 3d-4d interplay, via the ligand oxygen orbitals, is responsible for this crystal-field level inversion and the material's transition to an antiferromagnetic, possibly orbitally ordered, low-temperature state.

  7. Optically defined modal sensors incorporating spiropyran-doped liquid crystals with piezoelectric sensors.

    Science.gov (United States)

    Chen, Kuan-Ting; Chang, Chin-Kai; Kuo, Hui-Lung; Lee, Chih-Kung

    2011-01-01

    We integrated a piezoelectric sensing layer lamina containing liquid crystals (LC) and spiropyran (SP) in a LC/SP mixture to create an optically reconfigurable modal sensor for a cantilever beam. The impedance of this LC/SP lamina was decreased by UV irradiation which constituted the underlying mechanism to modulate the voltage externally applied to the piezoelectric actuating layer. Illuminating a specific pattern onto the LC/SP lamina provided us with a way to spatially modulate the piezoelectric vibration signal. We showed that if an UV illuminated pattern matches the strain distribution of a specific mode, a piezoelectric modal sensor can be created. Since UV illumination can be changed in situ in real-time, our results confirm for the first time since the inception of smart sensors, that an optically tailored modal sensor can be created. Some potential applications of this type of sensor include energy harvesting devices, bio-chips, vibration sensing and actuating devices.

  8. NMR molecular dynamics study of chromonic liquid crystals Edicol Sunset Yellow doped with salts.

    Science.gov (United States)

    de Almeida Martins, João P; Chávez, Fabián Vaca; Sebastião, Pedro J

    2014-10-01

    We investigate the effect of monoatomic salts on the molecular dynamics in the nematic and isotropic phases formed by the chromonic liquid crystal Edicol Sunset Yellow. The study was carried out using proton nuclear magnetic resonance relaxometry. To analyse the effect of incorporation of additional sodium chloride or lithium chloride on the solutions' molecular dynamics, the spin-lattice relaxation time was measured for Larmor frequencies between 10 kHz and 100 MHz. In the nematic phase, the presence of additional sodium or lithium ions seems to contribute to an increase of the rotations/reorientations corr elation times in comparison with the mixture without extra ions. The collective motions detected by proton NMR relaxometry are associated with collective fluctuations of molecules within the stacks in the nematic phase and with order parameter fluctuations in the isotropic phase. Copyright © 2014 John Wiley & Sons, Ltd.

  9. Optically Defined Modal Sensors Incorporating Spiropyran-Doped Liquid Crystals with Piezoelectric Sensors

    Directory of Open Access Journals (Sweden)

    Hui-Lung Kuo

    2011-01-01

    Full Text Available We integrated a piezoelectric sensing layer lamina containing liquid crystals (LC and spiropyran (SP in a LC/SP mixture to create an optically reconfigurable modal sensor for a cantilever beam. The impedance of this LC/SP lamina was decreased by UV irradiation which constituted the underlying mechanism to modulate the voltage externally applied to the piezoelectric actuating layer. Illuminating a specific pattern onto the LC/SP lamina provided us with a way to spatially modulate the piezoelectric vibration signal. We showed that if an UV illuminated pattern matches the strain distribution of a specific mode, a piezoelectric modal sensor can be created. Since UV illumination can be changed in situ in real-time, our results confirm for the first time since the inception of smart sensors, that an optically tailored modal sensor can be created. Some potential applications of this type of sensor include energy harvesting devices, bio-chips, vibration sensing and actuating devices.

  10. Thermoluminescence of LaAlO{sub 3} crystals doped with Eu and Ce - Dy ions exposed to ultraviolet and gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Vitor H.; Faria, Luiz O., E-mail: farialo@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Silva, Edna S. [Universidade Federal de Minas Gerais (DEN/UFMG), Belo Horizonte, MG (Brazil). Dept. de Energia Nuclear; Khaidukov, Nicholas M. [Kurnakov Institute of General and Inorganic Chemistry, IGIC, Moscow (Russian Federation)

    2011-07-01

    Due to environmental problems such as degradation of the ozone layer and control of radiation levels in units of radiation, new dosimetric materials with high sensitivity for ultraviolet (UV) and gamma radiation are of great interest for applications in environmental dosimetry. In this context, this paper presents the results of a systematic investigation of the thermoluminescent (TL) response of LaAlO{sub 3} crystals doped with different concentrations of trivalent optically active ions exposed to UV and gamma radiation doses. The work has been performed under a direct cooperation between the Institute of Inorganic Chemistry in Moscow (IGIC), responsible for crystal growth, and the Center for Development of Nuclear Technology (CDTN), responsible for the study of its luminescent properties. In this context, samples doped with 1% of Eu{sup 3+}, 1% Ce{sup 3+}, 5% of Ce{sup 3+} and also co-doped with 5% Ce{sup 3+} and 1% Dy{sup 3+} were grown under hydrothermal conditions. The investigation was divided into two fronts, one for gamma radiation and the other for UV radiation. In the investigation with gamma radiation the best TL response has been obtained from LaAlO{sub 3}:Eu. This crystal has shown good sensitivity and excellent linearity between TL output and the delivered gamma doses ranging from 0.1 to 10.0 mGy. In addition, its TL curve is quite similar to the Al{sub 2}O{sub 3}:C, a commercial TL phosphor with high sensitivity to gamma radiation. In the investigation with UV radiation the best response has been achieved for co-doped LaAlO{sub 3}:Ce,Dy. They have excellent sensitivity and good linearity for spectral irradiances ranging from 0.042 to 1.2 mJ.cm{sup -2}. (author)

  11. Single crystal EPR studies of paramagnetic ions doped zinc potassium phosphate hexahydrate. Part III: Mn(II)—a case of rhombic distortion

    Science.gov (United States)

    Anandalakshmi, H.; Sougandi, I.; Velavan, K.; Venkatesan, R.; Rao, P. S.

    2004-09-01

    Single crystal electron paramagnetic resonance (EPR) studies of Mn(II) doped zinc potassium phosphate hexahydrate have been carried out at room temperature. Single crystal rotations along the three orthogonal axes indicate orthorhombic symmetry with spin-Hamiltonian parameters as: gxx=1.9997; gyy=1.9538; gzz=1.9524, Dxx=15.49 mT; Dyy=0.22 mT; Dzz=-15.71 mT, Axx=11.70 mT; Ayy=10.53 mT; Azz=10.42 mT and a=0.8×10 -4 cm -1. A large E term indicates considerable distortion from axial symmetry. The impurity is found to enter the lattice substitutionally. The distortion axis for the impurity has been identified along one of the ZnO bond directions in the crystal.

  12. Single crystal EPR studies of paramagnetic ions doped zinc potassium phosphate hexahydrate; Part III: Mn(II)-a case of rhombic distortion.

    Science.gov (United States)

    Anandalakshmi, H; Sougandi, I; Velavan, K; Venkatesan, R; Rao, P S

    2004-09-01

    Single crystal electron paramagnetic resonance (EPR) studies of Mn(II) doped zinc potassium phosphate hexahydrate have been carried out at room temperature. Single crystal rotations along the three orthogonal axes indicate orthorhombic symmetry with spin-Hamiltonian parameters as: g(xx) = 1.9997; g(yy) = 1.9538; g(zz) = 1.9524, D(xx) = 15.49 mT; D(yy) = 0.22 mT; D(zz) = -15.71 mT, A(xx) = 11.70 mT; A(yy) = 10.53 mT; A(zz) = 10.42 mT and a = 0.8 x 10(-4) cm(-1). A large E term indicates considerable distortion from axial symmetry. The impurity is found to enter the lattice substitutionally. The distortion axis for the impurity has been identified along one of the Zn-O bond directions in the crystal.

  13. Comparative studies for Cr4+:YAG crystal and AlGaInAs semiconductor used as a saturable absorber in Q-switched Yb-doped fiber lasers.

    Science.gov (United States)

    Huang, J Y; Zhuang, W Z; Huang, W C; Su, K W; Hu, C; Huang, K F; Chen, Y F

    2009-11-09

    We demonstrate comparative studies for Cr(4+):YAG crystal and AlGaInAs quantum-well (QW) used as a saturable absorbers in passively Q-switched Yb-doped fiber lasers. Both saturable absorbers were designed to be possessed of nearly the same initial transmission. Under a pump power of 24 W, the average output powers were up to 14.4 W and 13.8 W obtained with the AlGaInAs QWs and with the Cr(4+):YAG crystal, respectively. The maximum pulse energies obtained with the Cr(4+):YAG crystal and with the AlGaInAs QWs were found to be 0.35 mJ and 0.45 mJ, respectively.

  14. Manipulating refractive index, homogeneity and spectroscopy of Yb3+-doped silica-core glass towards high-power large mode area photonic crystal fiber lasers.

    Science.gov (United States)

    Wang, Fan; Hu, Lili; Xu, Wenbin; Wang, Meng; Feng, Suya; Ren, Jinjun; Zhang, Lei; Chen, Danping; Ollier, Nadège; Gao, Guojun; Yu, Chunlei; Wang, Shikai

    2017-10-16

    Output power scaling of single mode large mode area (LMA) photonic crystal fiber (PCF) amplifiers urgently requires the low refractive index of Yb3+-doped silica glasses whilst maintaining high optical homogeneity. In this paper, we report on a promising alternative Yb3+/Al3+/F-/P5+-co-doped silica core-glass (YAFP), which is prepared by modified sol-gel method developed by our group and highly suitable for fabricating high power LMA PCF amplifiers. By controlling the doping combinations of Al3+/F-/P5+ in Yb3+-doped silica glass,it not only ensures low refractive index (RI) but also maintains the excellent optical homogeneity and spectroscopic properties of Yb3+. The spectroscopic properties of Yb3+ ions have not deteriorated by the co-doping of F- and P5+ in YAFP glass compared with that of Yb3+/Al3+ co-doped silica glass. A large-size (⌀5 mm × 90 mm) YAFP silica-core glass rod with low average RI difference of 2.6 × 10-4 (with respect to pure silica glass), and low radial and axial RI fluctuations of ~2 × 10-4, was prepared. A LMA PCF with 50 µm core diameter was obtained by stack-capillary-draw techniques using YAFP core glass. Its core NA is 0.027. An average amplified power of 97 W peaking at 1030 nm and light-light efficiency of 54% are achieved from a 6.5 m long PCF in the pulse amplification laser experiment. Meanwhile, quasi-single-mode transmission is obtained with laser beam quality factor M2 of 1.4.

  15. The crystal chemistry of novel thorium and uranium compounds with oxo-anions from group VI of periodic table (S, Se, Te, Cr, Mo and W)

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Bin

    2016-01-26

    This dissertation focus on the synthesis, phase studies and physicochemical properties of novel thorium and uranium compounds with the Group VI (S, Se, Te, Cr, Mo, W) of the Periodic Table. All the studied compounds are listed in Table 2.2 from the page 15. I subdivided all the newly synthesized compounds into several chapters according to their structural and topological differences. First, for thorium molybdates and tungstates, almost all of these compounds are based on corner-sharing of ThO{sub x} (x = 6, 8 and 9) and MoO{sub 4} or WO{sub x} (x = 4, 5, 6) polyhedra. Interestingly, all these compounds can be seen as derived from a pure thorium molybdate compound (ThMo{sub 2}O{sub 8}) which was isolated from high-temperature solid-state synthesis method. Therefore, the polymorphs of this most basic ThMo{sub 2}O{sub 8} compound is firstly introduced (see Chapter 3.1 from page 18). The thermodynamic, electronic and vibrational properties of all investigated ThMo{sub 2}O{sub 8} polymorphs were studied using ab initio calculations. Then, two subfamilies of thorium molybdates, that is, rubidium thorium molybdate and cesium thorium molybdate and their thermal and vibrational behaviors were discussed in details in Chapter 4.1 from page 37 and Chapter 4.2 from page 50, respectively. Moreover, some new insights about the complexity of thorium tungstates were also discussed (Chapter 4.3 from page 59). Some novel thorium molybdate and chromate compounds synthesized from aqueous condition are discussed in Chapter 5 from page 71. In the Chapter 8.2.4, the stereochemistry for thorium and uranium compounds are introduced, especially thorium selinites and uranyl tellurites (see Chapter 6.1 from page 82), thorium tellurites (Chapter 6.2 from page 93), and uranyl tellurites (Chapter 6.3 from page 99 for sodium uranyl tellurium and Chapter 6.4 from page 110 for potassium uranyl tellurium, respectively). In the actinide tellurium systems, additional MoO{sub 3}/WO{sub 3} were also

  16. Investigation of crystal structure, dielectric and magnetic properties in La and Nd co-doped BiFeO{sub 3} multiferroics

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ompal [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Agarwal, Ashish, E-mail: aagju@yahoo.com [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Sanghi, Sujata [Department of Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Das, Amitabh [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Anju [Department of Physics, Chaudhary Devi Lal University, Sirsa 125025, Haryana (India)

    2017-03-15

    For the investigation of the crystal structure, dielectric properties and magnetic properties of La and Nd co-doped BiFeO{sub 3} multiferroics; Bi{sub 0.8}La{sub 0.2−x}Nd{sub x}FeO{sub 3} (x=0.075, 0.1, 0.125) samples were prepared through solid state reaction method. Rietveld refinement of the obtained XRD patterns shows that there is change in crystal structure in these samples. At higher concentration of La (at x=0.075), the crystal structure was found to have mixed symmetry with rhombohedral and triclinic phases, while with equal concentration of both the dopants (at x=0.1), the structure changes to mixed symmetry having rhombohedral and orthorhombic phases. At higher concentration of Nd (at x=0.125), again mixed symmetry was established having both phases of the previous composition but approximately in reverse fraction. In dielectric analysis, x=0.1 sample showed the highest values of dielectric constant (ε′) and dielectric loss (tan δ). For x=0.125 sample, it was observed that the dielectric constant and dielectric loss response are improved. The magnetic characterization (M–H loops) indicates the significant enhancement in magnetisation with increasing concentration of Nd. Nd doping leads to the destruction of spiral modulation, forming the antiferromagnets, and visualisation of improved magnetisation via canting of spins. - Highlights: • La and Nd co-doped BiFeO{sub 3} were synthesized. • Change in crystal structure is observed. • Significant enhancement in magnetisation is observed.

  17. Impacts of thermal stress and doping on intrinsic point defect properties and clustering during single crystal silicon and germanium growth from a melt

    Science.gov (United States)

    Vanhellemont, Jan; Kamiyama, Eiji; Nakamura, Kozo; Śpiewak, Piotr; Sueoka, Koji

    2017-09-01

    This paper reviews recent considerable progress made in the last few years in understanding the behavior and properties of intrinsic point defects close to moving melt/solid Si interfaces during single crystal Si growth from a melt. The so called Voronkov criterion allows to determine whether the grown Si crystal is interstitial I- or vacancy V-rich. This criterion is written as the ratio Γ of the pulling rate v over the thermal gradient G at the interface. Crystals pulled with Γ above a critical value Γcrit are vacancy-rich while below Γcrit, they are interstitial-rich. Various expressions based on the intrinsic point defect thermal equilibrium concentration and diffusivity have been proposed to calculate Γcrit and are briefly discussed in this paper. Recently it was shown that the thermal stress at the interface and heavy doping with neutral and/or electrically active impurities, have a considerable impact on the intrinsic point defect balance and thus also on Γcrit. Furthermore, high energy barriers of formation energies of I and V around three or four atom layers from (001) free surface support a model in which the boundary conditions of the point defect concentrations at the surface in simulations can be set at fixed values. The situation is quite different for Ge single crystal pulling where the vacancy is always the dominant intrinsic point defect so that the Voronkov criterion cannot be applied. Prediction of vacancy cluster concentration/size distributions as a function of the pulling conditions is however still possible. The possibility of reaching Voronkov criterion conditions for Ge by doping with specific impurities is also discussed. Finally, impacts of stress and doping on self-diffusion in Si and Ge are evaluated with comparing the previous experimental results.

  18. Unconventional High-Performance Laser Protection System Based on Dichroic Dye-Doped Cholesteric Liquid Crystals

    Science.gov (United States)

    Zhang, Wanshu; Zhang, Lanying; Liang, Xiao; Le Zhou; Xiao, Jiumei; Yu, Li; Li, Fasheng; Cao, Hui; Li, Kexuan; Yang, Zhou; Yang, Huai

    2017-02-01

    High-performance and cost-effective laser protection system is of crucial importance for the rapid advance of lasers in military and civilian fields leading to severe damages of human eyes and sensitive optical devices. However, it is crucially hindered by the angle-dependent protective effect and the complex preparation process. Here we demonstrate that angle-independence, good processibility, wavelength tunability, high optical density and good visibility can be effectuated simultaneously, by embedding dichroic anthraquinone dyes in a cholesteric liquid crystal matrix. More significantly, unconventional two-dimensional parabolic protection behavior is reported for the first time that in stark contrast to the existing protection systems, the overall parabolic protection behavior enables protective effect to increase with incident angles, hence providing omnibearing high-performance protection. The protective effect is controllable by dye concentration, LC cell thickness and CLC reflection efficiency, and the system can be made flexible enabling applications in flexible and even wearable protection devices. This research creates a promising avenue for the high-performance and cost-effective laser protection, and may foster the development of optical applications such as solar concentrators, car explosion-proof membrane, smart windows and polarizers.

  19. Crystal structure, carrier concentration and IR-sensitivity of PbTe thin films doped with Ga by two different methods

    Science.gov (United States)

    Samoylov, A. M.; Sharov, M. K.; Buchnev, S. A.; Khoviv, A. M.; Dolgopolova, E. A.

    2002-05-01

    The comparison of the results of chemical composition, crystal structure, electronic properties and infrared photoconductivity investigations of PbTe/Si and PbTe/SiO 2/Si heterostructures doped with Ga atoms by two different techniques is presented in this work. One of these techniques is principally based on the vapour-phase doping procedure of PbTe/Si and PbTe/SiO 2/Si heterostructures, which were previously formed by the modified "hot wall" technique. The second method of PbTe(Ga)/Si and PbTe(Ga)/SiO 2/Si heterostructure preparation is based upon the fabrication of lead telluride films, which have been doped with Ga atoms in the layer condensation process directly. The lattice parameter and charge carrier density evolutions with the Ga impurity concentration show principally the different character of PbTe(Ga)/Si films prepared by these techniques. It has been proposed that complicated amphoteric (donor or acceptor) behaviour of Ga atoms may be explained by different mechanisms of substitution or implantation of impurity atoms in the crystal structure of lead telluride.

  20. Growth of Ca, Zr co-doped BaTiO3 lead-free ferroelectric single crystal and its room-temperature piezoelectricity

    Science.gov (United States)

    Liu, Donglin; Shim, Jaeshik; Sun, Yue; Li, Qiang; Yan, Qingfen

    2017-09-01

    Lead-free Ca, Zr co-doped BaTiO3 (BCZT) single crystal with a dimension up to 2mm×2mm×2mm was grown by a spontaneous nucleation technique using KF as the flux. The composition of the studied single crystal was defined to be Ba0.798Ca0.202Zr0.006Ti0.994O3, corresponding to a tetragonal phase at room temperature. The oriented single crystal exhibited a quasi-static piezoelectric constant of approximately 232 pC/N. The effective piezoelectric coefficient d33* of the single domain crystal obtained under a unipolar electric field of 35 kV/cm was 179 pm/V. Rayleigh analysis was used to identify the intrinsic and extrinsic contributions to the room-temperature piezoelectricity of BCZT single crystal. The extrinsic contribution was estimated up to 40% due to the irreversible domain wall movement. Furthermore a sixth-order polynomial of Landau expansion was employed to analyze the intrinsic contribution to piezoelectricity of BCZT single crystal. The large energy barriers inhibited polarization rotations, leading to the relatively low piezoelectricity.

  1. Mucopolysaccharidosis VI

    Science.gov (United States)

    2010-01-01

    Mucopolysaccharidosis VI (MPS VI) is a lysosomal storage disease with progressive multisystem involvement, associated with a deficiency of arylsulfatase B leading to the accumulation of dermatan sulfate. Birth prevalence is between 1 in 43,261 and 1 in 1,505,160 live births. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The characteristic skeletal dysplasia includes short stature, dysostosis multiplex and degenerative joint disease. Rapidly progressing forms may have onset from birth, elevated urinary glycosaminoglycans (generally >100 μg/mg creatinine), severe dysostosis multiplex, short stature, and death before the 2nd or 3rd decades. A more slowly progressing form has been described as having later onset, mildly elevated glycosaminoglycans (generally sialidosis and mucolipidosis. Before enzyme replacement therapy (ERT) with galsulfase (Naglazyme®), clinical management was limited to supportive care and hematopoietic stem cell transplantation. Galsulfase is now widely available and is a specific therapy providing improved endurance with an acceptable safety profile. Prognosis is variable depending on the age of onset, rate of disease progression, age at initiation of ERT and on the quality of the medical care provided. PMID:20385007

  2. Mucopolysaccharidosis VI

    Directory of Open Access Journals (Sweden)

    Harmatz Paul

    2010-04-01

    Full Text Available Abstract Mucopolysaccharidosis VI (MPS VI is a lysosomal storage disease with progressive multisystem involvement, associated with a deficiency of arylsulfatase B leading to the accumulation of dermatan sulfate. Birth prevalence is between 1 in 43,261 and 1 in 1,505,160 live births. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The characteristic skeletal dysplasia includes short stature, dysostosis multiplex and degenerative joint disease. Rapidly progressing forms may have onset from birth, elevated urinary glycosaminoglycans (generally >100 μg/mg creatinine, severe dysostosis multiplex, short stature, and death before the 2nd or 3rd decades. A more slowly progressing form has been described as having later onset, mildly elevated glycosaminoglycans (generally ARSB gene, located in chromosome 5 (5q13-5q14. Over 130 ARSB mutations have been reported, causing absent or reduced arylsulfatase B (N-acetylgalactosamine 4-sulfatase activity and interrupted dermatan sulfate and chondroitin sulfate degradation. Diagnosis generally requires evidence of clinical phenotype, arylsulfatase B enzyme activity ®, clinical management was limited to supportive care and hematopoietic stem cell transplantation. Galsulfase is now widely available and is a specific therapy providing improved endurance with an acceptable safety profile. Prognosis is variable depending on the age of onset, rate of disease progression, age at initiation of ERT and on the quality of the medical care provided.

  3. Nucleation and crystallization of Ca doped basaltic glass for the production of a glass-ceramic material

    Science.gov (United States)

    Tarrago, Mariona; Royo, Irene; Garcia-Valles, Maite; Martínez, Salvador

    2016-04-01

    Sewage sludge from wastewater treatment plants is a waste with a composition roughly similar to that of a basalt. It may contain potentially toxic elements that can be inertized by vitrification. Using a glass-ceramic process, these elements will be emplaced in newly formed mineral phases. Glass-ceramic production requires an accurate knowledge of the temperatures of nucleation (TN) and crystal growth of the corresponding minerals. This work arises from the study of the addition of ions to a basaltic matrix in order to establish a model of vitrification of sewage sludge. In this case a glass-ceramic is obtained from a glass made with a basalt that has been doped with 16% CaO. Two glasses which underwent different cooling processes have been produced and compared. The first was annealed at 650oC (AG) and the second was quenched (QG). The chemical composition of the glasses is SiO2 36.11 wt%, Al2O312.19 wt%, CaO 24.44 wt%, FeO 10.06 wt%, MgO 9.19 wt%, Na2O 2.28 wt%, TiO2 2.02 wt%, K2O 1.12 wt%, P2O5 0.46 wt%. Glass transition temperature obtained by dilatometry varies from 640 oC (AG) to 700 oC (QG). The temperatures of nucleation and crystal growth of the glass have been determined by Differential Thermal Analysis (DTA). The phases formed after these treatments were identified by X-Ray Diffraction. The temperatures of exothermic and endothermic peaks measured in the quenched glass are, in average, 10 oC higher than those found for the annealed glass. The exothermic peaks provide crystallization temperatures for different phases: a first event at 857 oC corresponds to the growth of magnetite, pyroxene and nepheline, whereas a second event at 1030 oC is due to the crystallization of melilite from the reaction between previous minerals and a remaining amorphous phase. The complete melting of this system occurs at 1201 oC. This glass has been nucleated inside the DTA furnace (500-850° C/3 hours) and then heated up to 1300 oC using the fraction between 400-500μm. TN

  4. In situ hydrothermal crystallization of hexagonal hydroxyapatite tubes from yttrium ion-doped hydroxyapatite by the Kirkendall effect.

    Science.gov (United States)

    Li, Chengfeng; Ge, Xiaolu; Li, Guochang; Lu, Hao; Ding, Rui

    2014-12-01

    An in situ hydrothermal crystallization method with presence of glutamic acid, urea and yttrium ions was employed to fabricate hexagonal hydroxyapatite (HAp, Ca5(PO4)3(OH)) tubes with length of 200 nm-1 μm. Firstly, yttrium ion-doped HAp (Y-HAp, Ca(5-x)Y(x)(PO4)3(OH)) was synthesized after hydrolysis of urea and HPO4(2-) ions at 100°C with a dwell time of 24h. The shift of X-ray diffraction peaks of HAp to high angle was caused the substitution of Ca(2+) ions by small-sized Y(3+) ions. At 160°C, further hydrolysis reactions of urea and HPO4(2-) ions resulted in the generation of ample OH(-) and PO4(3-) ions, which provided a high chemical potential for the dissolution of Y-HAp and recrystallization of HAp and YPO4. Finally, HAp tubes were formed in situ on Y-HAp according to the Kirkendall effect as a result of the difference of diffusion rate of cations (Ca(2+) ions, outward and slow) and anions (OH(-) and PO4(3-) ions, inward and fast). The formation process of HAp tube was simulated by the encapsulation of fluorescein molecules in precipitates. Photoluminescence properties were enhanced for HAp tubes with thick and dense walls. This novel tubular material could find wide applications as carriers of drugs, dyes and catalysts. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Thermal equilibrium concentration of intrinsic point defects in heavily doped silicon crystals - Theoretical study of formation energy and formation entropy in area of influence of dopant atoms-

    Science.gov (United States)

    Kobayashi, K.; Yamaoka, S.; Sueoka, K.; Vanhellemont, J.

    2017-09-01

    It is well known that p-type, neutral and n-type dopants affect the intrinsic point defect (vacancy V and self-interstitial I) behavior in single crystal Si. By the interaction with V and/or I, (1) growing Si crystals become more V- or I-rich, (2) oxygen precipitation is enhanced or retarded, and (3) dopant diffusion is enhanced or retarded, depending on the type and concentration of dopant atoms. Since these interactions affect a wide range of Si properties ranging from as-grown crystal quality to LSI performance, numerical simulations are used to predict and to control the behavior of both dopant atoms and intrinsic point defects. In most cases, the thermal equilibrium concentrations of dopant-point defect pairs are evaluated using the mass action law by taking only the binding energy of closest pair to each other into account. The impacts of dopant atoms on the formation of V and I more distant than 1st neighbor and on the change of formation entropy are usually neglected. In this study, we have evaluated the thermal equilibrium concentrations of intrinsic point defects in heavily doped Si crystals. Density functional theory (DFT) calculations were performed to obtain the formation energy (Ef) of the uncharged V and I at all sites in a 64-atom supercell around a substitutional p-type (B, Ga, In, and Tl), neutral (C, Ge, and Sn) and n-type (P, As, and Sb) dopant atom. The formation (vibration) entropies (Sf) of free I, V and I, V at 1st neighboring site from B, C, Sn, P and As atoms were also calculated with the linear response method. The dependences of the thermal equilibrium concentrations of trapped and total intrinsic point defects (sum of free I or V and I or V trapped with dopant atoms) on the concentrations of B, C, Sn, P and As in Si were obtained. Furthermore, the present evaluations well explain the experimental results of the so-called ;Voronkov criterion; in B and C doped Si, and also the observed dopant dependent void sizes in P and As doped Si

  6. Analysis of broadband near-infrared emission in ABCO4 and ABC3O7 crystals (A=Sr, Ba; B=La, Gd; C=Al, Ga) doped with rare earth and transition metals

    Science.gov (United States)

    Ryba-Romanowski, Witold

    1997-11-01

    Overview of basic spectroscopic properties of several crystals belonging to two wide families of compounds is presented. Both the families form tetragonal crystals with layered structure and show certain structural disorder resulting from random distribution of divalent A atoms and trivalent B atoms. After presenting some details concerning the crystal growth and structural investigation, the nature of activator sites in the matrices is discussed. Then, the emission spectra as well as relaxation dynamics of Nd3+, Yb3+, and Tm3+ are analyzed. After that, the basic spectroscopic features of chromium doped crystals are given. In conclusion, suitability of the crystals for the design of tunable lasers is discussed.

  7. Low power consumption and high-contrast light scattering based on polymer-dispersed liquid crystals doped with silver-coated polystyrene microspheres.

    Science.gov (United States)

    Chan, Chia-Hua; Wu, Ting-Yun; Yen, Meng-Hua; Lin, Chu-En; Cheng, Ko-Ting; Chen, Chii-Chang

    2016-12-26

    Polymer-dispersed liquid crystals (PDLCs) have attracted considerable attention for optical device applications in recent years. However, the high operating voltage of PDLCs limits their applications. This study reports a simple approach used for the first time to decrease the operating voltage of PDLCs by means of doping 3 μm-diameter silver-coated polystyrene microspheres (Ag-coated PSMSs) into PDLCs. Ag-coated PSMSs construct an induced electric field between each other when an external electric field is applied. This induced electric field can enhance the effective electric field so the operating voltage can be actively reduced from 77 V to 40 V. Such PDLCs also possess a high contrast ratio of >50 and a high on-state transmittance of ~73%. Therefore, PDLCs doped with Ag-coated PSMSs maintain a high contrast ratio and improve their electro-optical properties.

  8. Fast response in-line gas sensor using C-type fiber and Ge-doped ring defect photonic crystal fiber.

    Science.gov (United States)

    Kassani, Sahar Hosseinzadeh; Park, Jiyoung; Jung, Yongmin; Kobelke, Jens; Oh, Kyunghwan

    2013-06-17

    An in-line chemical gas sensor was proposed and experimentally demonstrated using a new C-type fiber and a Ge-doped ring defect photonic crystal fiber (PCF). The C-type fiber segment served as a compact gas inlet/outlet directly spliced to PCF, which overcame previous limitations in packaging and dynamic responses. C-type fiber was prepared by optimizing drawing process for a silica tube with an open slot. Splicing conditions for SMF/C-type fiber and PCF/C-type fiber were experimentally established to provide an all-fiber sensor unit. To enhance the sensitivity and light coupling efficiency we used a special PCF with Ge-doped ring defect to further enhance the sensitivity and gas flow rate. Sensing capability of the proposed sensor was investigated experimentally by detecting acetylene absorption lines.

  9. Spontaneous and stimulated emission in Sm{sup 3+}-doped YAl{sub 3}(BO{sub 3}){sub 4} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ryba-Romanowski, Witold [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Lisiecki, Radosław, E-mail: R.Lisiecki@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Beregi, Elena [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest (Hungary); Martín, I.R. [Departamento de Física, Instituto de Materiales y Nanotecnología (IMN), Universidad de La Laguna, 38206 S/C de Tenerife, Laguna (Spain)

    2015-11-15

    Single crystals of YAl{sub 3}(BO{sub 3}){sub 4} doped with trivalent samarium were grown by the top-seeded high temperature solution method and their absorption and emission spectra were investigated. Optical pumping into prominent absorption band around 405 nm feeds the {sup 4}G{sub 5/2} metastable level giving rise to intense visible luminescence distributed in several spectral lines with the most intense line around 600 nm characterized by a branching ratio of 0.42 and peak emission cross section of 0.25×10{sup −20} cm{sup 2}. Optical amplification at 600 nm with a gain coefficient of 2.9 cm{sup −1} was achieved during a pump-and-probe experiment. - Highlights: • YAB:Sm crystal grown by the top-seeded high temperature solution method. • Spectroscopic qualities relevant for visible laser operation. • YAB:Sm single crystal used in a pump-and-probe experiment. • Optical amplification properties of samarium doped YAl{sub 3}(BO{sub 3}){sub 4}.

  10. Magnetic, electric and electron magnetic resonance properties of orthorhombic self-doped La sub 1 sub - sub x MnO sub 3 single crystals

    CERN Document Server

    Markovich, V; Shames, A I; Puzniak, R; Rozenberg, E; Yuzhelevski, Y; Mogilyansky, D; Wisniewski, A; Mukovskii, Y M; Gorodetsky, G

    2003-01-01

    The effect of lanthanum deficiency on structural, magnetic, transport, and electron magnetic resonance (EMR) properties has been studied in a series of La sub 1 sub - sub x MnO sub 3 (x = 0.01, 0.05, 0.11, 0.13) single crystals. The x-ray diffraction study results for the crystals were found to be compatible with a single phase of orthorhombic symmetry. The magnetization curves exhibit weak ferromagnetism for all samples below 138 K. It was found that both the spontaneous magnetization and the coercive field increase linearly with x. The pressure coefficient dT sub N /dP decreases linearly with self-doping, from a value of 0.68 K kbar sup - sup 1 for La sub 0 sub . sub 9 sub 9 MnO sub 3 to 0.33 K kbar sup - sup 1 for La sub 0 sub . sub 8 sub 7 MnO sub 3. The resistivity of low-doped La sub 0 sub . sub 9 sub 9 MnO sub 3 crystal is of semiconducting character, while that of La sub 0 sub . sub 8 sub 7 MnO sub 3 depends weakly on temperature between 180 and 210 K. It was found that the magnetic and transport prop...

  11. One dimensional graphene based photonic crystals: Graphene stacks with sequentially-modulated doping for photonic band gap tailoring

    Science.gov (United States)

    Fuentecilla-Carcamo, I.; Palomino-Ovando, M.; Ramos-Mendieta, F.

    2017-12-01

    In a periodic arrangement of equally-doped graphene monolayers the electromagnetic wave propagation is described by band theory. We have found that the photonic response of this system enriches when the doping level is sequentially-modulated acquiring periodic, quasi-periodic or harmonic profiles along the superlattice axis. Because the dielectric background that supports the graphene layers is homogeneous, it is the doping modulation superimposed on the graphene layers that produces a particular photonic band structure. We report that the fixed separation between the layers generates a persistent structural band gap which is tunable by gating. We also demonstrate that doping modulations following continuous cosine or semi-continuous square envelope functions give place to frequency mini-bands. In our calculations the doping levels correspond to chemical potentials within the range 0.2 eV eV and the model for the graphene conductivity is valid in the limit of low temperatures in the THz spectrum.

  12. Room-temperature annealing effects on the basal-plane resistivity of optimally doped YBa2Cu3O7-δ single crystals

    Science.gov (United States)

    Khadzhai, G. Ya.; Vovk, R. V.; Vovk, N. R.; Kamchatnaya, S. N.; Dobrovolskiy, O. V.

    2018-02-01

    We reveal that the temperature dependence of the basal-plane normal-state electrical resistance of optimally doped YBa2Cu3O7-δ single crystals can be with great accuracy approximated within the framework of the model of s-d electron-phonon scattering. This requires taking into account the fluctuation conductivity whose contribution exponentially increases with decreasing temperature and decreases with an increase of oxygen deficiency. Room-temperature annealing improves the sample and, thus, increases the superconducting transition temperature. The temperature of the 2D-3D crossover decreases during annealing.

  13. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe{sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T., E-mail: 8781303601@mail.ecc.u-tokyo.ac.jp; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-15

    Highlights: • Post-annealing at 400 °C killed superconductivity for Co-free sample. • Pr,Co co-doped samples maintained superconductivity even after annealing. • Two-step superconducting transition was observed via magnetization measurement. • Bulk superconductivity of low-T{sub c} component was confirmed. • Superconducting volume fraction of high-T{sub c} component was always small. - Abstract: In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe{sub 2}As{sub 2} system, Pr doped and Pr,Co co-doped CaFe{sub 2}As{sub 2} single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with T{sub c1} = 25–42 K, and T{sub c2} < 16 K, suggesting that (Ca,RE)Fe{sub 2}As{sub 2} system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below T{sub c2} and high J{sub c} values of 10{sup 4}–10{sup 5} A cm{sup −2} at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe{sub 2}As{sub 2} phase occurred below T{sub c2}. On the contrary, the superconducting volume fraction above T{sub c2} was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  14. Electro-opto-thermal addressing bistable and re-addressable display device based on gelator-doped liquid crystals in a poly(N-vinylcarbazole) film-coated liquid crystal cell.

    Science.gov (United States)

    Cheng, Ko-Ting; Tang, Yi; Liu, Cheng-Kai

    2016-10-03

    This paper reports an electro-opto-thermal addressing bistable and re-addressable display device based on gelator-doped liquid crystals (LCs) in a poly(N-vinylcarbazole) film-coated LC cell. The bistability and re-addressability of the devices were achieved through the formation of a rubbery LC/gel mixture at room temperature. The desired patterns were addressed, erased, and re-addressed by controlling the temperature, applied voltage, and UV light illumination. Moreover, grayscales were obtained by adjusting UV light intensity. The initiation, relaxation, rise, and fall times of photoconductive poly(N-vinylcarbazole) via UV light illumination of various intensities were also examined.

  15. Superlattice structure of Ce{sup 3+}-doped BaMgF{sub 4} fluoride crystals - x-ray diffraction, electron spin-resonance, and optical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Yamaga, M.; Hattori, K. [Department of Electrical and Electronic Engineering, Faculty of Engineering, Gifu University, Gifu (Japan); Kodama, N. [Department of Materials Science and Engineering, Faculty of Engineering and Resource Science, Akita University, Akita (Japan); Ishizawa, N. [Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama (Japan); Honda, M. [Faculty of Science, Naruto University of Education, Naruto (Japan); Shimamura, K.; Fukuda, T. [Institute for Materials Research, Tohoku University, Sendai (Japan)

    2001-09-14

    The x-ray diffraction patterns for Ce{sup 3+}-doped BaMgF{sub 4} (BMF) crystals suggest the existence of superlattice structure. The superlattice model is consistent with the characterization of the 4f{sup 1} ground state of Ce{sup 3+} as a probe ion using the electron spin-resonance (ESR) technique. The distinct Ce{sup 3+} luminescence spectra with different peak energies and lifetimes also support the superlattice model. Although the detailed superlattice structure could not be analysed using the diffraction spots, a model has been proposed, taking into account the eight Ce{sup 3+} polyhedra with different anion coordinations in the unit cell of the BMF crystal obtained from the ESR experiments. (author)

  16. Preparation of NdMn1-xFexO3+δ single crystals-Effect of preparation atmosphere and iron doping

    Science.gov (United States)

    Mihalik, Matúš; Mat'aš, S.; Vavra, M.; Briančin, J.; Mihalik, Marián; Fitta, M.; Kavečanský, V.; Kopeček, J.

    2014-09-01

    We present the study of the effect of crystal growth atmosphere (argon or air) and chemical doping (iron) on the quality and oxygen nonstoichiometry of the single crystals with the general formula NdMn1-xFexO3+δ, which were grown by the optical floating zone method. The analysis of the grown ingots showed that in the Ar atmosphere the losses of the oxygen lead to MnO impurities, but in the air atmosphere some Mn3+ ions are replaced by Mn4+ ions (thence we have observed positive δ). The X-ray Laue diffraction and polarized light microscopy revealed that the twinning of the grown ingots is the common phenomenon. This twinning can be explained by the fact that a / c 1. Neutron diffraction experiment revealed that the preferential growing directions of the compound are (101) and (010).

  17. Extreme anisotropy and anomalous transport properties of heavily electron doped Lix(NH3)yFe2Se2 single crystals

    Science.gov (United States)

    Sun, Shanshan; Wang, Shaohua; Yu, Rong; Lei, Hechang

    2017-08-01

    We report the growth of heavily electron doped Li-NH3 intercalated FeSe single crystals that are free of material complexities and allow access to the intrinsic superconducting properties. Lix(NH3)yFe2Se2 single crystals show extremely large electronic anisotropy in both normal and superconducting states. They also exhibit anomalous transport properties in the normal state, which are believed to possibly be related to the anisotropy of relaxation time and/or temperature-dependent electron carrier concentration. Taking into account the great chemical flexibility of intercalants in the system, our findings provide a platform to understanding the origin of superconductivity in FeSe-related superconductors.

  18. Spectral properties and laser performances of Yb{sup 3+}:LaCa{sub 4}O(BO{sub 3}){sub 3} crystal with high concentration doping

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yuexia, E-mail: tcy@fjirsm.ac.cn [Key Laboratory of Photoelectric Materials Chemistry and Physics of CAS, Fujian Institute of Research on the Structure of Matter, University of Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); University of Chinese Academy of Sciences, Beijing City 100039 (China); Cao, Jiafeng; Xu, Jinlong; You, Zhenyu; Zhu, Zhaojie; Li, Jianfu; Wang, Yan; Tu, Chaoyang [Key Laboratory of Photoelectric Materials Chemistry and Physics of CAS, Fujian Institute of Research on the Structure of Matter, University of Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

    2013-11-05

    Highlights: •Yb{sup 3+}:LaCa{sub 4}O(BO{sub 3}){sub 3} single crystal was grown with high concentration doping. •Laser potentiality was evaluated based on the spectral and laser parameters. •Continuous wave laser operation was realized. •An output power of 0.77 W and a slope efficiency of 15.71% at 1077 nm were obtained. •The spectra and laser properties of Yb{sup 3+}:LaCa{sub 4}O(BO{sub 3}){sub 3} crystal were firstly reported. -- Abstract: High concentration of 15 at.% Yb{sup 3+} doped LaCa{sub 4}O(BO{sub 3}){sub 3} (LaCOB) crystal was grown by Czochralski technique. The absorption cross section was conclulated to be 0.63 × 10{sup −20} cm{sup 2} at 977 nm and the emission cross section to be 0.39 × 10{sup −20} cm{sup 2} at 1030 nm, with the FWHM of 6.15 and 33 nm respectively. Laser potentiality was evaluated based on the gain cross section σ{sub g}, the minimum inversion fraction β{sub min} and the minimum pump intensity I{sub min}, which were calculated to be 0.18 × 10{sup −20} cm{sup 2}, 0.05 and 0.47 kw/cm{sup 2}, respectively. Continuous wave laser operation was realized with an output power of 0.77 W and a slope efficiency of 15.71%. The laser emitted around 1077 nm. The radiation trapping and continuous pump mode are contributed to the lasing wavelength for present crystal.

  19. Magnetic evolution of itinerant ferromagnetism and interlayer antiferromagnetism in cerium doped LaCo{sub 2}P{sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Yong; Kong, Yixiu; Liu, Kai; Zhang, Anmin [Department of Physics, Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872 (China); He, Rui [Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614 (United States); Zhang, Qingming, E-mail: qmzhang@ruc.edu.cn [Department of Physics, Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872 (China)

    2017-05-01

    ThCr{sub 2}Si{sub 2}-type phosphide ACo{sub 2}P{sub 2} (A=Eu, La, Pr, Nd, Ce) has the same structure as iron arsenides, but their magnetic behaviors are quite distinct. In this paper, we grew a series of La{sub 1−x}Ce{sub x}Co{sub 2}P{sub 2} single crystals (x=0.0 to1.0), made structural and magnetic characterizations. We found the introduction of cerium induces a rapid decrease of c-axis and a change from ferromagnetic to antiferromagnetic states. Compared to other trivalent doped compounds, the enhancement of ferromagnetism with doping is suppressed and the transition from ferromagnetism to antiferromagnetism appear earlier. By employing first-principles band-structure calculations, we identify the increase of Ce valence suppress the itinerant ferromagnetism and leading to formation of P-P bonding with the shortening of c-axis. The bonding effectively drives an increase of interlayer antiferromagnetic interaction, eventually leads to antiferromagnetic ordering of cobalt in high-doping region.

  20. Infrared optical characterization and energy transfer of Na5Lu9F32 single crystals co-doped with Er3+/Tm3+ grown by Bridgman method

    Science.gov (United States)

    Tang, Qingyang; Xia, Haiping; He, Shinan; Sheng, Qiguo; Chen, Baojiu

    2017-11-01

    This paper reported on successful preparation of Na5Lu9F32 single crystals co-doped with ∼2 mol% Er3+ and various Tm3+ concentrations from 0.7 mol% to 3.2 mol% by Bridgman method. The J-O intensity parameters of Er3+ were calculated and analyzed according to the absorption spectra. The fluorescence decay curve at Er3+:4I13/2 level was measured to investigate the luminescent properties of the Er3+/Tm3+ co-doped Na5Lu9F32, and the energy transfer process between Er3+ and Tm3+. An intense 2.7 μm emission was achieved with Tm3+ ions sensitizing Er3+ ions under the 800 nm LD pumping. The maximum emission intensity at 2.7 μm was obtained at about 3.2 mol% doping concentration of Tm3+ when the concentration of Er3+ ions was fixed at ∼2 mol% in the current research. The calculated maximum value of emission cross section at 2.7 μm was 2.22 × 10-20 cm2, and energy transfer efficiency from Er3+:4I13/2 to Tm3+:3F4 was 78%. The electric dipole-dipole interaction was dominant for the energy transfer from Er3+ to Tm3+ ions by using Inokuti-Hirayama's model.

  1. In situ observation of thermally activated domain memory and polarization memory in an aged K{sup +}-doped (Ba, Sr)TiO{sub 3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Xue Dezhen; Gao Jinghui; Bao Huixin; Zhou Yumei; Zhang Lixue; Ren Xiaobing, E-mail: Xuedezhen@gmail.com [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

    2011-07-13

    Different ferroelectric domains are degenerate states of the same ferroelectric phase; thus they are energetically equivalent and, in principle there exists no preference for a particular domain pattern. However, the existence of point defects is considered to stabilize certain preferential domain states. In order to study the temperature violation on such stabilized domains, we performed in situ observation on an aged K{sup +}-doped (Ba, Sr)TiO{sub 3} single crystal and found that both the domain configuration and polarization state can be memorized after experiencing a thermally activated ferro-para-ferro transition cycle, as manifested by a reappearance of the same domain pattern and double P-E hysteresis loop. In contrast, after the sample was aged in the paraelectric state (>10 min), these memory effects disappeared. The above memory effects are considered to originate from the interaction between point defects and the crystal symmetry driven by a symmetry-conforming tendency of point defects. Such a mechanism suggests that the memory effects are relevant to the existence of acceptor dopant and associated mobile oxygen vacancies, and they are not restricted to a particular dopant. Thus similar memory effects are expected to exist in a wide range of ferroelectric materials with acceptor doping.

  2. Study on the low-temperature annealing-induced color center in Y{sup 3+}-doped PbWO{sub 4} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Li Weifeng, E-mail: liweifeng@suda.edu.c [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Long Yumei [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Feng Xiqi [Shanghai Institute of Ceramics, CAS, Shanghai 200050 (China)

    2009-11-11

    The optical transmittance spectrum of the as-grown Y-doped PbWO{sub 4} (PWO:Y) crystal exhibits annealing-induced absorption band peaking at 420 nm at low-temperature range (<400 deg. C). The annealing-induced 420 nm absorption coefficient gets to maximum at 400 deg. C and it can be effectively 'bleached' by irradiating with UV light. On the other hand, high-temperature (here is 850 deg. C) treatment strengthens the 420 nm absorption band but exerts little influence on the induced absorption band. Due to the smaller ionic radii of Y{sup 3+}, the substitution of Y{sup 3+} for Pb{sup 2+} results in large lattice relaxation, which is confirmed by FT-IR measurements. It is proposed that interstitial yttrium is an alternative doping way in PWO:Y and forms large defect aggregation of [(Y{sub Pb}{sup 3+}){sup c}entre dot-2V{sub Pb}{sup ''}-Y{sub i}{sup 3+}]. [(Y{sub Pb}{sup 3+}){sup c}entre dot-2V{sub Pb}{sup ''}-Y{sub i}{sup 3+}] is not stable and hence is considered as the origin of anomaly observed in PWO:Y crystal.

  3. Excited-state intramolecular proton transfer and conformational relaxation in 4'-N,N-dimethylamino-3-hydroxyflavone doped in acetonitrile crystals.

    Science.gov (United States)

    Furukawa, Kazuki; Yamamoto, Norifumi; Hino, Kazuyuki; Sekiya, Hiroshi

    2016-10-19

    The effect of intermolecular interactions on excited-state intramolecular proton transfer (ESIPT) in 4'-N,N-dimethylamino-3-hydroxyflavone (DMHF) doped in acetonitrile crystals was investigated by measuring its temperature dependence of steady-state fluorescence excitation and fluorescence spectra and picosecond time-resolved spectra. The relative intensity of emission from the excited state of the normal form (N*) to that from the excited state of the tautomer form (T*) and spectral features changed markedly with temperature. Unusual changes in the spectral shift and spectral features were observed in the fluorescence spectra measured between 200 and 218 K, indicating that a solid-solid phase transition of DMHF-doped acetonitrile crystals occurred. Time-resolved fluorescence spectra suggested conformational relaxation of the N* state competed with ESIPT after photoexcitation and the ESIPT rate increased with temperature in the low-temperature phase of acetonitrile. However, the intermolecular interaction of N* with acetonitrile in the high-temperature phase markedly stabilized the potential minimum of the fluorescent N* state and slowed the ESIPT. This stabilization can be explained by reorganization of acetonitrile originating from the strong electric dipole-dipole interaction between DMHF and acetonitrile molecules.

  4. Growth and scintillation characterization of Ce{sup 3+}-doped Rb{sub 2}LiGdBr{sub 6} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Rooh, Gul [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); Kim, H.J., E-mail: hongjoo@knu.ac.kr [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Sunghwan [Department of Radiological Science, Cheongju University, Cheongju 360-764 (Korea, Republic of); Khan, Sajid [Department of Physics, Kohat University of Science & Technology, 26000 (Pakistan)

    2016-10-01

    Growth and scintillation characterizations of the newly developed cerium doped Rb{sub 2}LiGdBr{sub 6} (RLGB) single crystals were investigated. RLGB, which belongs to bromo-elpasolite crystal family, was grown by the vertical Bridgman technique with nominally 1%, 5%, and 10% Ce{sup 3+}-concentration (mole%). X-ray excited luminescence spectra show typical Ce{sup 3+} bands between 350 to 460 nm wavelength regions. A good energy resolution of 5.5% (FWHM) and light yield of 25,500±2600 ph/MeV for 662 keV γ-rays were observed at 5% Ce{sup 3+}-concentration. Under γ-ray excitation, RLGB:Ce{sup 3+} crystals display multi-exponential decays with Ce{sup 3+} like decay components at 23 ns and 29 ns for 1% and 5% Ce-concentrations, respectively. From the results, it is expected that this scintillator could be used as a thermal neutron detector because of Li and Gd ions in the host lattice. Also, like other inorganic halide scintillators, it is very hygroscopic. - Highlights: • Scintillation properties of new Rb{sub 2}LiGdBr{sub 6}:Ce{sup 3+} were presented. • Single crystals of Rb{sub 2}LiGdBr{sub 6} were grown by two zone vertical Bridgman technique. • The grown material was highly hygroscopic and belongs to elpasolite crystal family. • Good energy resolution of 5.5% (FWHM) and light yield of 25,500±2600 ph/MeV were obtained under γ-ray excitation. • This material displayed multiexponential decays with Ce{sup 3+} like decay components.

  5. Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions

    Science.gov (United States)

    Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

    2016-07-01

    Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er3+ into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the 4I11/2 → 4I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er3+ around 2.7 μm is more than 1.2 × 10-20 cm2, which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers.

  6. Investigation of energy shift of 4f3 and 4f5d levels in Nd-doped YLF and LLF crystals

    Directory of Open Access Journals (Sweden)

    André Felipe Henriques Librantz

    2006-01-01

    Full Text Available We observed ultraviolet (UV luminescence from 4f25d and 4f3 configuration in Nd-doped YLiF4 (YLF and LuLiF4 (LLF crystals induced by multiphotonic excitation of the three photons (532 nanometers [nm]. The LLF lattice is more compact than the YLF crystal and favours an absorption and emission shift of the main peaks due to crystal field strength. The red and blue shifts of the emission bands towards to lower (and higher energy are different for the transitions from 4f3 and 4f25d levels. The 4f3 transitions have smaller shift (~5 times smaller than the shift of the 4f25d due to 5s25p6 closed-shell shielding effect. On the other hand the 4f25d transitions are more susceptible to lattice change. The effect of the crystalline field was compared for both lattice. The result shows that these emission bands from 4f25d configuration always shift to lower energy when substituting the Y3+ by Lu3+ (i.e., the last one has the ionic radius 5% smaller than Y3+.

  7. Dielectric and conductivity behavior of Mn-doped K0.5Na0.5NbO3 single crystal

    Science.gov (United States)

    Yan, Tianxiang; Sun, Xiaojun; Deng, Jianming; Liu, Saisai; Han, Feifei; Liu, Xiaoqi; Fang, Liang; Lin, Dabing; Peng, Biaolin; Liu, Laijun

    2017-09-01

    Dielectric and conduction behaviors of [001]-oriented K0.5Na0.5Nb0.5O3 single crystal (KNN) and 0.5 at% Mn-doped KNN single crystal (KNN-Mn) have been investigated in a broad temperature range. At low temperatures (330-400 K), an observed slight decrease of conductivity could be connected with the decreases of hole carrier concentration and mobility for the KNN-Mn. At high temperatures (723-773 K) above Cure temperature, the dielectric relaxation and conduction behavior of the samples were analyzed by measurements of impedance spectroscopy and universal dielectric response law. The activation energy values for relaxation frequency and conduction were 0.97 eV and 0.60 eV for the KNN-Mn, respectively. They could be attributed to the thermal motion of double ionized oxygen vacancies and the formation of defect dipoles. The defect compensation mechanism was proposed based on Mn4+ ion substitution. The KNN-Mn promoted a higher concentration of oxygen vacancies compared with KNN crystal, which gave rise to smaller domain size and higher piezoelectric properties.

  8. Photo-assisted Kelvin probe force microscopy investigation of three dimensional GaN structures with various crystal facets, doping types, and wavelengths of illumination

    Science.gov (United States)

    Ali Deeb, Manal; Ledig, Johannes; Wei, Jiandong; Wang, Xue; Wehmann, Hergo-Heinrich; Waag, Andreas

    2017-08-01

    Three dimensional GaN structures with different crystal facets and doping types have been investigated employing the surface photo-voltage (SPV) method to monitor illumination-induced surface charge behavior using Kelvin probe force microscopy. Various photon energies near and below the GaN bandgap were used to modify the generation of electron-hole pairs and their motion under the influence of the electric field near the GaN surface. Fast and slow processes for Ga-polar c-planes on both Si-doped n-type as well as Mg-doped p-type GaN truncated pyramid micro-structures were found and their origin is discussed. The immediate positive (for n-type) and negative (for p-type) SPV response dominates at band-to-band and near-bandgap excitation, while only the slow process is present at sub-bandgap excitation. The SPV behavior for the semi-polar facets of the p-type GaN truncated pyramids has a similar characteristic to that on its c-plane, which indicates that it has a comparable band bending and no strong influence of the polarity-induced charges is detectable. The SPV behavior of the non-polar m-facets of the Si-doped n-type part of a transferred GaN column is similar to that of a clean c-plane GaN surface during illumination. However, the SPV is smaller in magnitude, which is attributed to intrinsic surface states of m-plane surfaces and their influence on the band bending. The SPV behavior of the non-polar m-facet of the slightly Mg-doped part of this GaN column is found to behave differently. Compared to c- and r-facets of p-type surfaces of GaN-light-emitting diode micro-structures, the m-plane is more chemically stable.

  9. Influences of Silver-Doping on the Crystal Structure, Morphology and Photocatalytic Activity of TiO2 Nanofibers

    DEFF Research Database (Denmark)

    Barakat, Nasser A. M.; Kanjwal, Muzafar Ahmed; Al-Deyab, Salem S.

    2011-01-01

    morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. Study of the photocatalytic degradation of methylene blue dye clarified that in-crease the silver content...

  10. Cranial mononeuropathy VI

    Science.gov (United States)

    ... Abducens palsy; Lateral rectus palsy; VIth nerve palsy; Cranial nerve VI palsy; Sixth nerve palsy; Neuropathy - sixth nerve ... Cranial mononeuropathy VI is damage to the sixth cranial nerve. This nerve is also called the abducens nerve. ...

  11. Evaluation of the 4I11/2 terminal level lifetime for several neodymium-doped laser crystals and glasses

    Energy Technology Data Exchange (ETDEWEB)

    Bibeau, Camille [Univ. of California, Davis, CA (United States)

    1995-04-25

    All models of lasing action require knowledge of the physical parameters involved, of which many can be measured or estimated. The value of the terminal level lifetime is an important parameter in modeling many high power laser systems since the terminal level lifetime can have a substantial impact on the extraction efficiency of the system. However, the values of the terminal level lifetimes for a number of important laser materials such as ND:YAG and ND:YLF are not well known. The terminal level lifetime, a measure of the time it takes for the population to drain out of the terminal (lower) lasing level, has values that can range from picoseconds to microseconds depending on the host medium, thus making it difficult to construct one definitive experiment for all materials. Until recently, many of the direct measurements of the terminal level lifetime employed complex energy extraction or gain recovery methods coupled with a numerical model which often resulted in large uncertainties in the measured lifetimes. In this report we demonstrate a novel and more accurate approach which employs a pump-probe technique to measure the terminal level lifetime of 16 neodymium-doped materials. An alternative yet indirect method, which is based on the ``Energy Gap Law,`` is to measure the nonradiative lifetime of another transition which has the same energy gap as the transition of the terminal level lifetime. Employing this simpler approach, we measured the lifetime for 30 neodymium-doped materials. We show for the first time a direct comparison between the two methods and determine that the indirect method can be used to infer the terminal level lifetime within a factor of two for most neodymium-doped glasses and crystals.

  12. ZnO nanowires array grown on Ga-doped ZnO single crystal for dye-sensitized solar cells.

    Science.gov (United States)

    Hu, Qichang; Li, Yafeng; Huang, Feng; Zhang, Zhaojun; Ding, Kai; Wei, Mingdeng; Lin, Zhang

    2015-06-23

    High quality ZnO nanowires arrays were homoepitaxial grown on Ga-doped ZnO single crystal (GZOSC), which have the advantages of high conductivity, high carrier mobility and high thermal stability. When it was employed as a photoanode in the DSSCs, the cell exhibited a 1.44% power-conversion efficiency under the illumination of one sun (AM 1.5G). The performance is superior to our ZnO nanowires/FTO based DSSCs under the same condition. This enhanced performance is mainly attributed to the perfect interface between the ZnO nanowires and the GZOSC substrate that contributes to lower carrier scattering and recombination rates compared with that grown on traditional FTO substrate.

  13. All-optically controllable random laser based on a dye-doped polymer-dispersed liquid crystal with nano-sized droplets.

    Science.gov (United States)

    Lee, C-R; Lin, S-H; Guo, C-H; Chang, S-H; Mo, T-S; Chu, S-C

    2010-02-01

    This study elucidates for the first time an all-optically controllable random laser in a dye-doped polymer-dispersed liquid crystal (DDPDLC) with nano-sized LC droplets. Experimental results demonstrate that the lasing intensity of the random laser can be controlled to decrease by increasing irradiation time/intensity of one green beam, and increase by increasing the irradiation time of one red beam. The all-optical controllability of the random laser is attributed to the green (red)-beaminduced isothermal nematic-->isotropic (isotropic-->nematic) phase transition in LC droplets by trans-->cis (cis-->trans back) isomerization of azo dyes. This isomerization may decrease (increase) the difference between the refractive indices of the LC droplets and the polymer, thereby increasing (decreasing) the diffusion constant (or transport mean free path), subsequently decreasing the scattering strength and, thus, random lasing intensity.

  14. First-principles calculation study of electronic structures and magnetic properties of Mn-doped perovskite crystals for solar cell applications

    Science.gov (United States)

    Suzuki, Atsushi; Oku, Takeo

    2018-02-01

    The electronic structures and magnetic properties of manganese (Mn)-doped formamidinium lead halide perovskite compounds (FAPbI3, where FA = NH2CHNH2 +) were investigated for solar cell application. The effects of Mn doping into FAPbI3 crystals on electronic structures, chemical shifts in nuclear magnetic resonance, and optical absorption spectra were studied by first-principles calculation on the basis of the density functional theory. The electron density distribution of the 6p orbital was delocalized on an iodine atom at the highest occupied molecular orbital, and that of the 3d orbital was localized on a Mn atom at the lowest unoccupied molecular orbital. The absorption properties in the near-infrared region originated from the first excitation process of ligand-metal charge transfer (LMCT). The chemical shifts of I-NMR and the g-tensor of Mn ions were associated with nuclear quadrupole interactions based on an electron field gradient and asymmetry parameters. The combination of LMCT with magnetic interactions is important for developing photovoltaic solar cells with a broad-band optical absorption spectrum in the near-infrared region.

  15. High-performance p-channel thin-film transistors with lightly doped n-type excimer-laser-crystallized germanium films

    Science.gov (United States)

    Liao, Chan-Yu; Huang, Ching-Yu; Huang, Ming-Hui; Huang, Wen-Hsien; Shen, Chang-Hong; Shieh, Jia-Min; Cheng, Huang-Chung

    2017-06-01

    High-performance polycrystalline-germanium (poly-Ge) thin-film transistors (TFTs) fabricated with lightly doped Ge thin films by excimer laser crystallization (ELC) and counter doping (CD) have been demonstrated. High-quality n-type Ge thin films with a grain size as large as 1 µm were fabricated by ELC in the super lateral-growth regime and CD at a dose of 1 × 1013 cm-2 or higher. Consequently, a superior field-effect mobility of 271 cm2 V-1 s-1 and a high on/off current ratio of 2.7 × 103 have been obtained for p-channel Ge TFTs with the channel width and length of both 0.5 µm fabricated by ELC at 300 mJ/cm2 and CD at a dose of 1 × 1013 cm-2. The effects of ELC conditions and CD dose on the electrical characteristics of p-channel Ge TFTs were also investigated.

  16. Synthesis, crystal structure, and properties of Bi{sub 3}TeBO{sub 9} or Bi{sub 3}(TeO{sub 6})(BO{sub 3}): a non-centrosymmetric borate-tellurate(VI) of bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Daub, Michael; Krummer, Michael; Hoffmann, Anke [Institut fuer Anorganische und Analytische Chemie, Albert-Ludwigs-Universitaet, Albertstrasse 21, 79104, Freiburg (Germany); Bayarjargal, Lkhamsuren [Institut fuer Geowissenschaften, Abt. Kristallographie, Goethe-Universitaet, Altenhoeferallee 1, 60438, Frankfurt am Main (Germany); Hillebrecht, Harald [Institut fuer Anorganische und Analytische Chemie, Albert-Ludwigs-Universitaet, Albertstrasse 21, 79104, Freiburg (Germany); Freiburger Materialforschungszentrum FMF, Albert-Ludwigs-Universitaet, Stefan-Meier-Strasse 25, 79104, Freiburg (Germany)

    2017-01-26

    Pale-yellow single crystals of the new borate tellurate(VI) Bi{sub 3}TeBO{sub 9} were obtained by reaction of stoichiometric amounts of Bi{sub 2}O{sub 3}, B{sub 2}O{sub 3}, and Te(OH){sub 6} at 780 C. The non-centrosymmetric crystal structure (P6{sub 3}, Z=2, a=8.7454(16), c=5.8911(11) Aa, 738 refl., 43 param, R1=0.037, wR2=0.093) contains isolated trigonal-planar BO{sub 3} units and nearly undistorted TeO{sub 6} octahedra. The Bi{sup 3+} cations are located in between in octahedral voids. The BiO{sub 6} octahedra are significantly distorted to a [3+3] pattern (2.25/2.50 Aa) due to the ns{sup 2} configuration. According to the structural features, the formula can be written as Bi{sub 3}(TeO{sub 6})(BO{sub 3}). Alternatively, the structure can also be described as hcp of oxygen with Te{sup VI} and Bi{sup III} in octahedral voids and B{sup III} in trigonal- planar voids. The vibrational spectra show the typical features of BO{sub 3} and TeO{sub 6} units with a significant {sup 10}B/{sup 11}B isotopic splitting of the IR-active B-O valence mode (1248 and 1282 cm{sup -1}). The UV/Vis spectrum shows an optical band edge with an onset around 480 nm (2.6 eV). MAS-NMR spectra of {sup 11}B show an anisotropic signal with a quadrupole coupling constant of C{sub Q}=2.55 MHz. and a very small deviation from rotational symmetry (η=0.2). The isotropic chemical shift is 20.1 ppm. The second harmonic generation (SHG) test was positive with an activity comparable to potassium dihydrogen phosphate (KDP). Bi{sub 3}TeBO{sub 9} decomposes in air at 825 C to Bi{sub 2}TeO{sub 5}. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Crystal structure of octakis(N,N-dimethylformamide-κOeuropium(III tetracosa-μ2-oxido-dodecaoxido-μ12-phosphato-dodecamolybdate(VI

    Directory of Open Access Journals (Sweden)

    Yassine Ghandour

    2016-04-01

    Full Text Available In the title salt, [Eu(C3H7NO8][PMo12O40], the asymmetric unit comprises one α-Keggin-type [PMo12O40]3− polyoxidometalate anion and one distorted dodecahedral [Eu(C3H7NO8]3+ complex cation. In the crystal, the isolated polyoxidometalate anions are packed into hexagonally arranged rows extending parallel to [001]. The complex cations are situated between the rows and are linked to the neighbouring anions through weak C—H...O hydrogen-bonding interactions, leading to the formation of a three-dimensional network structure.

  18. Crystal structure of aqua-(nitrato-κO)dioxido{2-[3-(pyridin-2-yl-κN)-1H-1,2,4-triazol-5-yl-κN (4)]phenolato-κO}uranium(VI) aceto-nitrile monosolvate monohydrate.

    Science.gov (United States)

    Vashchenko, Oleksandr; Raspertova, Ilona; Dyakonenko, Viktoriya; Shishkina, Svitlana; Khomenko, Dmytro; Doroschuk, Roman; Lampeka, Rostislav

    2016-02-01

    In the title compound, [U(C13H9N4O)(NO3)O2(H2O)]·CH3CN·H2O, the U(VI) atom is seven-coordinated in a distorted penta-gonal-bipyramidal N2O5 manner by one tridentate triazole ligand, one monodentate nitrate anion and one water mol-ecule in the equatorial plane and by two uran-yl(VI) O atoms in the axial positions. In the crystal, the U(VI) complex mol-ecule is linked to the water and aceto-nitrile solvent mol-ecules through N-H⋯N, O-H⋯O and O-H⋯N hydrogen bonds, forming a sheet structure parallel to the bc plane. The sheets are further linked by an additional O-H⋯O hydrogen bond, forming a three-dimensional network.

  19. Anomalous behaviour of periodic domain structure in Gd-doped LiNbO{sub 3} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Palatnikov, M [Institute of Chemistry, Kola Science Centre RAS, Apatity, Murmansk Region (Russian Federation); Sidorov, N [Institute of Chemistry, Kola Science Centre RAS, Apatity, Murmansk Region (Russian Federation); Bormanis, K [Institute of Solid State Physics, University of Latvia, Riga (Latvia); Smith, P G R [University of Southampton, Optoelectronic Research Centre (United Kingdom)

    2007-12-15

    Atomic force microscopy studies of etching patterns, stability of regular domain structure, and anomalies of electrical characteristics in the 300-385 K range of a series of Gddoped lithium niobate single crystals grown under equal conditions are reported.

  20. Tunable Solid-State Quantum Memory Using Rare-Earth-Ion-Doped Crystal, Nd3(+):GaN

    Science.gov (United States)

    2017-04-26

    than the desired c-plane), which posses differing growth rates and lead to the observed structuring of the periodic sample. Fig. 26 TEM images...interaction between light and the ions in a semiconductor. We investigated the energy level structure of the neodymium (Nd) ions embedded into the...provide a tunable memory. To vary the applied field, we designed and grew a series of Nd-doped GaN p-i-n structures , strain-balanced superlattice

  1. Comparison of photoinduced reorientation of ortho-, meta-, and para-methyl red-doped nematic liquid crystals on rubbed polyimide.

    Science.gov (United States)

    Statman, David; Statman, Ariel T; Wozniak, Kaitlin; Brennan, Christopher

    2015-08-01

    We compare the photoinduced reorientation of the easy axis on rubbed polyimide surfaces for the nematic E7 doped with three isomers of methyl red; ortho, meta, and para. Using optical techniques, the angle and the pitch of the director at the polymer surface were measured before, during, and after photoexcitation of the dye. Optical absorbances were also measured before and after photoexcitation. Extrapolation lengths, hence anchoring energies, were determined with the on/off application of a magnetic field for meta- and para-methyl red-doped nematics. Because of an elastic reorientation of the easy axis in the presence of the magnetic field, we could not determine the extrapolation length of the ortho-methyl red-doped nematic. Our results confirm that photoinduced reorientation is facilitated by desorption of all dyes from the polymer surface. While there is little evidence of weak photoinduced adsorption of meta- and para-methyl red to the surface during photoexcitation, there is strong evidence of photoinduced adsorption of ortho-methyl red, which is long lasting.

  2. Formation of basal plane stacking faults on the (0 0 0 1 bar) facet of heavily nitrogen-doped 4H-SiC single crystals during physical vapor transport growth

    Science.gov (United States)

    Ohtomo, Kohei; Matsumoto, Nana; Ashida, Koji; Kaneko, Tadaaki; Ohtani, Noboru; Katsuno, Masakazu; Sato, Shinya; Tsuge, Hiroshi; Fujimoto, Tatsuo

    2017-11-01

    The formation of stacking faults in heavily nitrogen-doped (mid-1019 cm-3) 4H-SiC boules grown by the physical vapor transport (PVT) growth method was investigated by studying surface morphologies on the (0 0 0 1 bar) facet of the boules. Low-voltage scanning electron microscopy (LVSEM) observations detected stacking faults on the (0 0 0 1 bar) facet of heavily nitrogen-doped 4H-SiC crystals. LVSEM and atomic force microscopy (AFM) studies revealed that the stacking faults showed characteristic morphologies, which stemmed from the interaction between stacking faults and surface steps. These observations also revealed that heavy nitrogen doping resulted in the nucleation of a number of surface hillocks on the (0 0 0 1 bar) facet; the hillocks were never observed on the facet of conventionally doped (nitrogen concentration: mid-1018 cm-3) 4H-SiC boules. Furthermore, the hillocks were nucleated only on the facet and never observed on the outer regions of the facet. Based on these results, the stacking fault formation mechanism in heavily nitrogen-doped 4H-SiC crystals is discussed.

  3. Crystal structure of YwpF from Staphylococcus aureus reveals its architecture comprised of a β-barrel core domain resembling type VI secretion system proteins and a two-helix pair.

    Science.gov (United States)

    Lee, Sang Jae; Lee, Kyu-Yeon; Lee, Ki-Young; Kim, Dong-Gyun; Kim, Soon-Jong; Lee, Bong-Jin

    2015-04-01

    The ywpF gene (SAV2097) of the Staphylococcus aureus strain Mu50 encodes the YwpF protein, which may play a role in antibiotic resistance. Here, we report the first crystal structure of the YwpF superfamily from S. aureus at 2.5-Å resolution. The YwpF structure consists of two regions: an N-terminal core β-barrel domain that shows structural similarity to type VI secretion system (T6SS) proteins (e.g., Hcp1, Hcp3, and EvpC) and a C-terminal two-helix pair. Although the monomer structure of S. aureus YwpF resembles those of T6SS proteins, the dimer/tetramer model of S. aureus YwpF is distinct from the functionally important hexameric ring of T6SS proteins. We therefore suggest that the S. aureus YwpF may have a different function compared to T6SS proteins. © 2015 Wiley Periodicals, Inc.

  4. Energy scaling and extended tunability of terahertz wave parametric oscillator with MgO-doped near-stoichiometric LiNbO3 crystal.

    Science.gov (United States)

    Wang, Yuye; Tang, Longhuang; Xu, Degang; Yan, Chao; He, Yixin; Shi, Jia; Yan, Dexian; Liu, Hongxiang; Nie, Meitong; Feng, Jiachen; Yao, Jianquan

    2017-04-17

    A widely tunable, high-energy terahertz wave parametric oscillator based on 1 mol. % MgO-doped near-stoichiometric LiNbO3 crystal has been demonstrated with 1064 nm nanosecond pulsed laser pumping. The tunable range of 1.16 to 4.64 THz was achieved. The maximum THz wave output energy of 17.49 μJ was obtained at 1.88 THz under the pump energy of 165 mJ/pulse, corresponding to the THz wave conversion efficiency of 1.06 × 10-4 and the photon conversion efficiency of 1.59%, respectively. Moreover, under the same experimental conditions, the THz output energy of TPO with MgO:SLN crystal was about 2.75 times larger than that obtained from the MgO:CLN TPO at 1.60 THz. Based on the theoretical analysis, the THz energy enhancement mechanism in the MgO:SLN TPO was clarified to originate from its larger Raman scattering cross section and smaller absorption coefficient.

  5. The simultaneous enhancement of photorefraction and optical damage resistance in MgO and Bi2O3 co-doped LiNbO3 crystals

    Science.gov (United States)

    Zheng, Dahuai; Kong, Yongfa; Liu, Shiguo; Chen, Muling; Chen, Shaolin; Zhang, Ling; Rupp, Romano; Xu, Jingjun

    2016-02-01

    For a long time that optical damage was renamed as photorefraction, here we find that the optical damage resistance and photorefraction can be simultaneously enhanced in MgO and Bi2O3 co-doped LiNbO3 (LN:Bi,Mg). The photorefractive response time of LN:Bi,Mg was shortened to 170 ms while the photorefractive sensitivity reached up to 21 cm2/J. Meanwhile, LN:Bi,Mg crystals could withstand a light intensity higher than 106  W/cm2 without apparent optical damage. Our experimental results indicate that photorefraction doesn’t equal to optical damage. The underground mechanism was analyzed and attributed to that diffusion dominates the transport process of charge carriers, that is to say photorefraction causes only slight optical damage under diffusion mechanism, which is very important for the practical applications of photorefractive crystals, such as in holographic storage, integrated optics and 3D display.

  6. On the induction of homogeneous bulk crystallization in Eu-doped calcium aluminosilicate glass by applying simultaneous high pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Muniz, R. F., E-mail: robsonfmuniz@yahoo.com.br [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Ligny, D. de [Department of Materials Science, Glass and Ceramics, University of Erlangen Nürnberg, Martensstr. 5, 91058 Erlangen (Germany); Le Floch, S.; Martinet, C.; Guyot, Y. [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Rohling, J. H.; Medina, A. N.; Sandrini, M.; Baesso, M. L. [Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Andrade, L. H. C.; Lima, S. M. [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul, C.P. 351, Dourados, MS (Brazil)

    2016-06-28

    From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca{sub 3}Mg(SiO{sub 4}){sub 2}] and diopside [CaMgSi{sub 2}O{sub 6}]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f{sup 6}5d{sup 1} → 4f{sup 7} transition of Eu{sup 2+} was studied in both host systems. Additionally, the {sup 5}D{sub 0} → {sup 7}F{sub J} transition of Eu{sup 3+} was used as an environment probe in the pristine glass and the glass-ceramic.

  7. Influence of pH, layer charge location and crystal thickness distribution on U(VI) sorption onto heterogeneous dioctahedral smectite

    Energy Technology Data Exchange (ETDEWEB)

    Guimarães, Vanessa [Instituto de Ciências da Terra – Porto, DGAOT, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Geobiotec. Departamento de Geociências da Universidade de Aveiro, Campo Universitário de Santiago, 3810-193 Aveiro (Portugal); Rodríguez-Castellón, Enrique; Algarra, Manuel [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Málaga. Campus de Teatino s/n, 29071 Málaga (Spain); Rocha, Fernando [Geobiotec. Departamento de Geociências da Universidade de Aveiro, Campo Universitário de Santiago, 3810-193 Aveiro (Portugal); Bobos, Iuliu, E-mail: ibobos@fc.up.pt [Instituto de Ciências da Terra – Porto, DGAOT, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal)

    2016-11-05

    Highlights: • The UO{sub 2}{sup 2+} sorption at pH 4 and 6 on heterogeneous smectite structure. • The cation exchange process is affected by layer charge distribution. • Surface complexation and cation exchange modelling. • New binding energy components identified by X-ray photoelectron spectroscopy. - Abstract: The UO{sub 2}{sup 2+} adsorption on smectite (samples BA1, PS2 and PS3) with a heterogeneous structure was investigated at pH 4 (I = 0.02 M) and pH 6 (I = 0.2 M) in batch experiments, with the aim to evaluate the influence of pH, layer charge location and crystal thickness distribution. Mean crystal thickness distribution of smectite crystallite used in sorption experiments range from 4.8 nm (sample PS2), to 5.1 nm (sample PS3) and, to 7.4 nm (sample BA1). Smaller crystallites have higher total surface area and sorption capacity. Octahedral charge location favor higher sorption capacity. The sorption isotherms of Freundlich, Langmuir and SIPS were used to model the sorption experiments. The surface complexation and cation exchange reactions were modeled using PHREEQC-code to describe the UO{sub 2}{sup 2+} sorption on smectite. The amount of UO{sub 2}{sup 2+} adsorbed on smectite samples decreased significantly at pH 6 and higher ionic strength, where the sorption mechanism was restricted to the edge sites of smectite. Two binding energy components at 380.8 ± 0.3 and 382.2 ± 0.3 eV, assigned to hydrated UO{sub 2}{sup 2+} adsorbed by cation exchange and by inner-sphere complexation on the external sites at pH 4, were identified after the U4f{sub 7/2} peak deconvolution by X-photoelectron spectroscopy. Also, two new binding energy components at 380.3 ± 0.3 and 381.8 ± 0.3 eV assigned to ≡AlOUO{sub 2}{sup +} and ≡SiOUO{sub 2}{sup +} surface species were observed at pH 6.

  8. In situ optical absorption and reflection spectroscopy of doping CsCl crystal with Pb{sup 2+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, S.; Amaya, K.; Saito, T. [Research Center for Development of Far-Infrared Region, Fukui University, Bunkyo, Fukui (Japan); Higuchi, S.; Asada, H.; Ishikane, M. [Department of Applied Physics, Faculty of Engineering, Fukui University, Bunkyo, Fukui (Japan)

    2001-12-03

    Behaviours of Pb{sup 2+} ions during thermal treatments of PbCl{sub 2}-deposited CsCl crystals have been observed in situ by optical absorption and reflection spectroscopy. In the early stages of the treatments, the Pb{sup 2+} ions take part in the formation of Cs{sub 4}PbCl{sub 6} crystallites near the surface of the CsCl crystals. The crystallites exhibit a novel absorption spectrum suggesting that the 6s and 6p states of the Pb{sup 2+} ions are strongly localized. On heavy annealing at a high temperature (673 K) followed by a rapid cooling to room temperature, the Pb{sup 2+} ions are uniformly dispersed throughout the CsCl crystals, exhibiting the absorption spectrum attributable to isolated Pb{sup 2+}-ion centres. (author)

  9. [Comparisons of spectral properties of CsI:T1 crystals with various Tl(+)-doped concentrations].

    Science.gov (United States)

    Wu, Zheng-Long

    2011-08-01

    Absorption Spectra and Photoluminescence (PL) spectra of CsI: T1 crystals with various T1+-concentrations were measured for absorption and luminescent research in CsI: T1. Their UV absorption spectra contained three peaks at 297, 273 and 247 nm. The experiments were demonstrated that the peaks in the high T(1+)-concentration CsI: T1 crystals are broader than ones in the low T(1+)-concentration crystals and their absorption A-peak shift by 20 nm, but their PL with UV excitations are similar. It was suggested that lattice distortions in the high T1+-concentration CsI: T1 lead to the changes in absorption or fluorescence excitation peaks, but no changes in the fluorescence band widths and locations at room temperature.

  10. Characteristic properties of Raman scattering and photoluminescence on ZnO crystals doped through phosphorous-ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, T. S.; Yu, J. H.; Mo, H. S.; Kim, T. S.; Lim, K. Y.; Youn, C. J., E-mail: cjyoun@chonbuk.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center (SPRC), Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Hong, K. J. [Department of Physics, Chosun University, Gwangju 501-759 (Korea, Republic of)

    2014-02-07

    P-doped ZnO was fabricated by means of the ion-implantation method. At the Raman measurement, the blue shift of the E{sub 2}{sup high} mode and A{sub 1}(LO) phonon of the inactive mode were observed after the P-ion implantation. It suggested to be caused by the compressive stress. Thus, Hall effect measurement indicates that the acceptor levels exists in P-doped ZnO while still maintaining n-type ZnO. From the X-ray photoelectron spectroscopy, the chemical bond formation of the P2p{sub 3/2} spectrum consisted of 2(P{sub 2}O{sub 5}) molecules. Therefore, the implanted P ions were substituted to the Zn site in ZnO. From the photoluminescence (PL) spectra, P-related PL peaks were observed in the energy ranges of 3.1 and 3.5 eV, and its origin was analyzed at P{sub Zn}-2V{sub Zn} complexes, acting as a shallow acceptor. With increasing temperatures, the neutral-acceptor bound-exciton emission, (A{sup 0}, X), shows a tendency to quench the intensity and extend the emission linewidth. From the relations of the intensity and the linewidth as a function of temperature, the broadening of linewidth was believed to the result that the vibration mode of E{sub 2}{sup high} participates in the broadening process of (A{sup 0}, X) and the change of luminescent intensity was attributed to the partial dissociation of (A{sup 0}, X). Consequently, these facts indicate that the acceptor levels existed in P-doped ZnO layer by the ion implantation.

  11. Ultraviolet laser-induced poling inhibition produces bulk domains in MgO-doped lithium niobate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boes, Andreas, E-mail: s3363819@student.rmit.edu.au; Steigerwald, Hendrik; Sivan, Vijay; Mitchell, Arnan [School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3001 (Australia); ARC Center for Ultra-high Bandwidth Devices for Optical Systems (CUDOS), RMIT University, Melbourne, Victoria 3001 (Australia); Yudistira, Didit [School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3001 (Australia); Wade, Scott [Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Mailis, Sakellaris [Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Soergel, Elisabeth [Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn (Germany)

    2014-09-01

    We report the realization of high-resolution bulk domains achieved using a shallow, structured, domain inverted surface template obtained by UV laser-induced poling inhibition in MgO-doped lithium niobate. The quality of the obtained bulk domains is compared to those of the template and their application for second harmonic generation is demonstrated. The present method enables domain structures with a period length as small as 3 μm to be achieved. Furthermore, we propose a potential physical mechanism that leads to the transformation of the surface template into bulk domains.

  12. Ultraviolet laser-induced poling inhibition produces bulk domains in MgO-doped lithium niobate crystals

    Science.gov (United States)

    Boes, Andreas; Steigerwald, Hendrik; Yudistira, Didit; Sivan, Vijay; Wade, Scott; Mailis, Sakellaris; Soergel, Elisabeth; Mitchell, Arnan

    2014-09-01

    We report the realization of high-resolution bulk domains achieved using a shallow, structured, domain inverted surface template obtained by UV laser-induced poling inhibition in MgO-doped lithium niobate. The quality of the obtained bulk domains is compared to those of the template and their application for second harmonic generation is demonstrated. The present method enables domain structures with a period length as small as 3 μm to be achieved. Furthermore, we propose a potential physical mechanism that leads to the transformation of the surface template into bulk domains.

  13. Growth rate determination through automated TEM image analysis: crystallization studies of doped SbTe phase-change thin films

    NARCIS (Netherlands)

    Oosthoek, Jasper L.M.; Kooi, B.J.; de Hosson, Jeff T.M.; Wolters, Robertus A.M.; Gravesteijn, Dirk J; Gravesteijn, Dirk J.; Attenborough, Karen

    2010-01-01

    A computer-controlled procedure is outlined here that first determines the position of the amorphous-crystalline interface in an image. Subsequently, from a time series of these images, the velocity of the crystal growth front is quantified. The procedure presented here can be useful for a wide

  14. Growth Rate Determination through Automated TEM Image Analysis : Crystallization Studies of Doped SbTe Phase-Change Thin Films

    NARCIS (Netherlands)

    Oosthoek, Jasper L. M.; Kooi, Bart J.; De Hosson, Jeff T. M.; Wolters, Rob A. M.; Gravesteijn, Dirk J.; Attenborough, Karen

    A computer-controlled procedure is outlined here that first determines the position of the amorphous-crystalline interface in an image. Subsequently, from a time series of these images, the velocity of the crystal growth front is quantified. The procedure presented here can be useful for a wide

  15. Ab initio electronic structure and correlations in pristine and potassium-doped molecular crystals of copper phthalocyanine

    NARCIS (Netherlands)

    Giovannetti, G.; Brocks, G.; van den Brink, J.

    2008-01-01

    We investigate the effect that potassium intercalation has on the electronic structure of copper phthalocyanine (CuPc) molecular crystals by means of ab initio density functional calculations. Pristine CuPc (in its alpha and beta structures) is found to be an insulator containing local magnetic

  16. Synthesis of SnO2 versus Sn crystals within N-doped porous carbon nanofibers via electrospinning towards high-performance lithium ion batteries.

    Science.gov (United States)

    Wang, Hongkang; Lu, Xuan; Li, Longchao; Li, Beibei; Cao, Daxian; Wu, Qizhen; Li, Zhihui; Yang, Guang; Guo, Baolin; Niu, Chunming

    2016-04-14

    The design of tin-based anode materials (SnO2 or Sn) has become a major concern for lithium ion batteries (LIBs) owing to their different inherent characteristics. Herein, particulate SnO2 or Sn crystals coupled with porous N-doped carbon nanofibers (denoted as SnO2/PCNFs and Sn/PCNFs, respectively) are fabricated via the electrospinning method. The electrochemical behaviors of both SnO2/PCNFs and Sn/PCNFs are systematically investigated as anodes for LIBs. When coupled with porous carbon nanofibers, both SnO2 nanoparticles and Sn micro/nanoparticles display superior cycling and rate performances. SnO2/PCNFs and Sn/PCNFs deliver discharge capacities of 998 and 710 mA h g(-1) after 140 cycles (at 100, 200, 500 and 1000 mA g(-1) each for 10 cycles and then 100 cycles at 100 mA g(-1)), respectively. However, the Sn/PCNF electrodes show better cycling stability at higher current densities, delivering higher discharge capacities of 700 and 550 mA h g(-1) than that of SnO2/PCNFs (685 and 424 mA h g(-1)) after 160 cycles at 200 and 500 mA g(-1), respectively. The different superior electrochemical performance is attributed to the introduction of porous N-doped carbon nanofibers and their self-constructed networks, which, on the one hand, greatly decrease the charge-transfer resistance due to the high conductivity of N-doped carbon fibers; on the other hand, the porous carbon nanofibers with numerous voids and flexible one-dimensional (1D) structures efficiently alleviate the volume changes of SnO2 and Sn during the Li-Sn alloying-dealloying processes. Moreover, the discussion of the electrochemical behaviors of SnO2vs. Sn would provide new insights into the design of tin-based anode materials for practical applications, and the current strategy demonstrates great potential in the rational design of metallic tin-based anode materials.

  17. Development and measurement of luminescence properties of Ce-doped Cs2LiGdBr6 crystals irradiated with X-ray, γ-ray and proton beam

    Science.gov (United States)

    Jang, Jonghun; Kim, H. J.; Rooh, Gul; Kim, Sunghwan

    2017-12-01

    The effect of higher Ce-concentration on the luminescence and scintillation properties of Cs2LiGdBr6 single crystals are studied. We used the Bridgman method for the growth of Ce-doped Cs2LiGdBr6 single crystals. Luminescence properties of the grown crystals are measured by X-ray and proton excitations. We measured the pulse height and fluorescence decay time spectra of Cs2LiGdBr6:Ce3+ with a bi-alkali photo multiplier tube (PMT) under γ-ray excitation from 137Cs source. Improvements in the scintillation properties are observed with the increase of Ce-concentration in the lattice. Detailed procedure of the crystal growth is also discussed.

  18. Luminescence and photo-thermally stimulated defects creation processes in PbWO{sub 4} crystals doped with trivalent rare-earth ions

    Energy Technology Data Exchange (ETDEWEB)

    Fabeni, P. [Institute of Applied Physics “N.Carrara” (IFAC) of CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Firenze) (Italy); Krasnikov, A.; Kärner, T. [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Laguta, V.V.; Nikl, M. [Institute of Physics AS CR, Cukrovarnicka 10, 16253 Prague (Czech Republic); Pazzi, G.P. [Institute of Applied Physics “N.Carrara” (IFAC) of CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Firenze) (Italy); Zazubovich, S., E-mail: svet@fi.tartu.ee [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia)

    2013-04-15

    In PbWO{sub 4} crystals, doped with various trivalent rare-earth A{sup 3+} ions (A{sup 3+}: La{sup 3+}, Lu{sup 3+}, Y{sup 3+}, Ce{sup 3+}, Gd{sup 3+}), electron (WO{sub 4}){sup 3−} and {(WO_4)"3"−–A"3"+} centers can be created under UV irradiation not only in the host absorption region but also in the energy range around 3.85 eV (Böhm et al., 1999; Krasnikov et al., 2010). Under excitation in the same energy range, the UV emission peak at 3.05–3.20 eV is observed. In the present work, the origin of this emission is investigated in detail by low-temperature time-resolved luminescence methods. Photo-thermally stimulated creation of (WO{sub 4}){sup 3−} and {(WO_4)"3"−–A"3"+} centers is studied also in PbWO{sub 4}:Mo,A{sup 3+} crystals. Various processes, which could explain both the appearance of the UV emission and the creation of the {(WO_4)"3"−–A"3"+}-type centers under irradiation of PbWO{sub 4}: A{sup 3+} crystals in the 3.85±0.35 eV energy range, are discussed. The radiative and non-radiative decay of the excitons localized near A{sup 3+} ions is considered as the most probable mechanism to explain the observed features. -- Highlights: ► UV emission of PbWO{sub 4}: A{sup 3+} (A{sup 3+}: La{sup 3+}, Lu{sup 3+}, Y{sup 3+}, Ce{sup 3+}, and Gd{sup 3+}) crystals is studied. ► The emission is ascribed to the radiative decay of excitons localized near A{sup 3+} ions. ► The excitons are created at 3.85 eV excitation by a two-step process. ► Non-radiative decay of the excitons leads to the creation of (WO{sub 4}){sup 3−}–A{sup 3+} centers.

  19. Enhancing blue luminescence from Ce-doped ZnO nanophosphor by Li doping

    National Research Council Canada - National Science Library

    Shi, Qiang; Wang, Changzheng; Li, Shuhong; Wang, Qingru; Zhang, Bingyuan; Wang, Wenjun; Zhang, Junying; Zhu, Hailing

    2014-01-01

    .... The effects of the additional doping with Li ions on the crystal structure, particle morphology, and luminescence properties of Ce-doped ZnO were investigated by X-ray diffraction, scanning electron...

  20. Influence of sputtering power on crystal quality and electrical properties of Sc-doped AlN film prepared by DC magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jian-cang, E-mail: jcyang58@163.com; Meng, Xiang-qin; Yang, Cheng-tao; Zhang, Yao

    2013-12-15

    Scandium-doped aluminum nitride alloy (ScAlN) thin films were deposited on (1 0 0) silicon substrates by DC reactive magnetron sputtering method using a scandium aluminum alloy (Sc{sub 0.06}Al{sub 0.94}) target. The influence of sputtering power on the crystalline structure, surface morphology and electrical properties of ScAlN thin films were investigated. The XRD patterns indicated all the films showed a single pronounced hexagonal (0 0 2) peak. According to the peak intensities in θ/2θ scans and rocking curve FWHM measurements of the (0 0 2) peaks, the crystalline quality of ScAlN thin film first increased and then decreased, reaching the best crystalline state at a sputtering power of 130 W. The best surface morphology of ScAlN thin film was obtained at 130 W and the surface roughness reached a minimum of 2.612 nm. Then the piezoelectric response of ScAlN thin films was measured and the highest value, 8.9 pC/N, was achieved at the sample with the best crystal quality. The resistivity and dielectric constant change in the same rule as the crystal quality, first increasing to a maximum value of 3.35 × 10{sup 12} Ω cm and 13.6, and then decreasing with the sputtering power increasing. In addition, when the sputtering power was 130 W, the highest breakdown field strength and lowest leakage current were obtained, with values 1.12 MV/cm and 3 × 10{sup −8} A, respectively.

  1. Centers of near-IR luminescence in bismuth-doped TlCl and CsI crystals.

    Science.gov (United States)

    Sokolov, V O; Plotnichenko, V G; Dianov, E M

    2013-04-22

    A comparative first-principles study of possible bismuth-related centers in TlCl and CsI crystals is performed and the results of computer modeling are compared with the experimental data. The calculated spectral properties of the bismuth centers suggest that the IR luminescence in TlCl:Bi is most likely caused by Bi(+)···V(Cl)(-) centers (Bi(+) ion in thallium site and a negatively charged chlorine vacancy in the nearest anion site). On the contrary, Bi(+) substitutional ions and Bi(2)(+) dimers are most likely responsible for the IR luminescence in CsI:Bi.

  2. Collective vortex pinning and merging of the irreversibility line and second peak effect in optimally doped Ba1-xKxBiO3 single crystals

    Science.gov (United States)

    Jiao, Yanjing; Cheng, Wang; Deng, Qiang; Yang, Huan; Wen, Hai-Hu

    2018-02-01

    Measurements on magnetization and relaxation have been carried out on an optimally doped Ba1-xKxBiO3+δ single crystal with Tc = 31.3 K. Detailed analysis is undertaken on the data. Both the dynamical relaxation and conventional relaxation have been measured leading to the self-consistent determination of the magnetization relaxation rate. It is found that the data are well described by the collective pinning model leading to the glassy exponent of about μ ≈ 1.64-1.68 with the magnetic fields of 1 and 3 T. The analysis based on Maley's method combining with the conventional relaxation data allows us to determine the current dependent activation energy U which yields a μ value of about 1.23-1.29 for the magnetic fields of 1 and 3 T. The second magnetization peaks appear in wide temperature region from 2 K to 24 K. The separation between the second peak field and the irreversibility field becomes narrow when temperature is increased. When the two fields are close to each other, we find that the second peak evolves into a step-like transition of magnetization. Finally, we present a vortex phase diagram and demonstrate that the vortex dynamics in Ba1-xKxBiO3 can be used as a model system for studying the collective vortex pining.

  3. Characterization of the lasing properties of a 5%Yb doped Lu₂SiO₅ crystal along its three principal dielectric axes.

    Science.gov (United States)

    Toci, Guido; Pirri, Angela; Beitlerova, Alena; Shoji, Yasuhiro; Yoshikawa, Akira; Hybler, Jiri; Nikl, Martin; Vannini, Matteo

    2015-05-18

    The laser performance of a 5% Yb doped Lu2SiO5 (Yb:LSO) has been investigated in quasi continuous-wave pumping regime along the three principal dielectric axes of the crystal, to obtain a complete characterization of its laser properties. The comparison among the obtained results for differently polarized lasers, in term of relative slope efficiency and absolute efficiency, allows the exploitability of different orientations of the material in order to be determined to obtain efficient laser sources. The laser slope efficiency and the energy conversion efficiency were similar for emission polarized along the three indicatrix axes, with noticeable maximum values of slope efficiency around 90% for polarization along the Y and Z axes. Tunable laser action has been obtained in the range 990 nm - 1084 nm, with sizeable differences in the shape of the tuning curve for polarization along the X, Y and Z axes. In particular, the tuning for polarization along the Z axis is relatively flat and uniform in the range 1023 nm - 1083 nm.

  4. Erbium-doped fiber ring laser with wavelength selective filter based on non-linear photonic crystal fiber Mach-Zehnder interferometer

    Science.gov (United States)

    Khaleel, W. A.; Al-Janabi, A. H.

    2017-10-01

    A high output power, stable wavelength spacing and switchable multi-wavelength erbium-doped fiber laser has been demonstrated experimentally using a combination of non-linear photonic crystal fiber Mach-Zehnder (MZI) interferometer with polarization dependent loss effect. This MZI functions together with a polarization controller (PC) as a wave selecting filter (WSF). Adjusting the PC within the WSF part gives rise to three emissions as single, dual and triple wavelengths. Multi-wavelength laser with maximum spacing of 1.6 nm was achieved by controlling the polarization state in a ring cavity. Such stable wavelength spacing aroused interest in wavelength-division-multiplexer systems. Output power around  -3 dB at 1550 nm wavelength, with small power fluctuation for each line, was recorded at room temperature. The measured 3-dB laser line-width was 0.03 nm, with a high side-mode suppression ratio of 48 dB.

  5. All-optically controllable distributed feedback laser in a dye-doped holographic polymer-dispersed liquid crystal grating with a photoisomerizable dye.

    Science.gov (United States)

    Tong, Huai-Pei; Li, Yu-Ren; Lin, Jia-De; Lee, Chia-Rong

    2010-02-01

    This work demonstrates, for the first time, an all-optically controllable distributed feedback (DFB) laser based on a dye-doped holographic polymer-dispersed liquid crystal (DDHPDLC) grating with a photoisomerizable dye. Intensity of the lasing emission can be reduced and increased by raising the irradiation intensity of one CW circularly-polarized green beam and the irradiation time of one CW circularly-polarized red beam, respectively. The all-optical controllability of the lasing emission is owing to the green-beam-induced isothermal nematic-->isotropic and red-beam-induced isothermal isotropic-->nematic phase transitions of the LCs via trans-->cis and cis-->trans back isomerizations of the azo-dye, respectively, in the LC-droplet-rich regions of the grating. The former (latter) mechanism can reduce (increase) the index modulation and thereby the coupling strength in the DFB grating, resulting in the decay (rise) of the lasing emission. Thermal effect is excluded from possible mechanisms causing such an optical controllability of the lasing emission.

  6. Picosecond laser with 11 W output power at 1342 nm based on composite multiple doping level Nd:YVO4 crystal

    Science.gov (United States)

    Rodin, Aleksej M.; Grishin, Mikhail; Michailovas, Andrejus

    2016-01-01

    We report results of design and optimization of high average output power picosecond and nanosecond laser operating at 1342 nm wavelength. Developed for selective micromachining, this DPSS laser is comprised of master oscillator, regenerative amplifier and output pulse control module. Passively mode-locked by means of semiconductor saturable absorber mirror and pumped with 808 nm wavelength Nd:YVO4 master oscillator emits 12.5 ps pulses at repetition rate of 55 MHz with average output power of ∼100 mW. The four-pass confocal delay line forms a longest part of the oscillator cavity in order to suppress thermo-mechanical misalignment. Picked from the train seed pulses were injected to the cavity of regenerative amplifier based on composite Nd:YVO4 crystal with diffusion-bonded segments of multiple Nd doping concentration end-pumped at 880 nm wavelength. Laser produces pulses of ∼13 ps duration at 300 kHz repetition rate with average output power of 11 W and nearly diffraction limited beam quality of M2∼1.03. Attained high peak power ∼2.8 MW facilitates conversion to the 2nd, 3rd and 6th harmonics at 671 nm, 447 nm and 224 nm wavelengths with 80%, 50% and 15% efficiency respectively. Without seeding the regenerative amplifier transforms to electro-optically cavity-dumped Q-switched laser providing 10 ns output pulses at high repetition rates with beam propagation factor of M2∼1.06.

  7. Doping Liquid Crystal Cells with Photocurable Monomer via Holographic Exposure to Realize Optical-Scattering-Free Infrared Phase Modulators with Fast Response Time

    Directory of Open Access Journals (Sweden)

    Chun-Yu Chien

    2017-07-01

    Full Text Available Photocurable monomer-doped liquid crystal (LC cells were processed via holographic exposure using a low-power He–Ne laser to generate holographic polymer networks. The polymer network LC (PNLC cells are used to fabricate infrared phase modulators at 1550 nm wavelength possessing favorable electro-optical performance. Compared with our previous work, the percentages of ingredients in the LC mixture filled in PNLC cells underwent a slight change. The 2 wt% concentration of anisotropic monomer RM257 were in place of isotropic monomer N–vinyl–2–pyrrolidinone (NVP. As a result, the fabricated phase modulators also maintained well homogeneous LC alignments and optical-scattering-free characteristics. Furthermore, NVP dopant successfully reduced the operating voltages from 95 Vrms to 79 Vrms to prevent polymer network deformation when electrically operating with higher voltages. The fabricated infrared phase modulators had a good average response time (i.e., rising time of 0.88 ms and falling time of 0.40 ms.

  8. Influence of the artificial surface dielectric layer on domain patterning by ion beam in MgO-doped lithium niobate single crystals

    Science.gov (United States)

    Chezganov, D. S.; Shur, V. Ya.; Vlasov, E. O.; Gimadeeva, L. V.; Alikin, D. O.; Akhmatkhanov, A. R.; Chuvakova, M. A.; Mikhailovskii, V. Yu.

    2017-02-01

    We experimentally compared the shapes and sizes of isolated domains created by the focused ion beam irradiation in the lithium niobate crystals doped by MgO with polar surface covered by dielectric (resist) layer and those with free surface. We attributed the larger sizes of isolated domains in the samples covered by the resist layer to ion localization in the resist. We revealed a change in the domain shape as a function of increasing dose and explained it in terms of kinetic approach taking into account the modification of the surface layers by ion irradiation. We applied the obtained knowledge for 1D and 2D periodical poling using ion beam. Finally, we created the 2D square 1-μm-period array of isolated domains with radius about 300 nm and maximal depth of all domains in the array up to 100 μm as well as the 1D pattern of through stripe domains with 2-μm-period in 1-mm-thick wafer.

  9. EPR and optical absorption studies of VO{sup 2+} ion doped magnesium citrate decahydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, Prashant [Department of Physics, Kali Charan Nigam Institute of Technology, Banda 210001, UP (India); Kripal, Ram, E-mail: ram_kripal2001@rediffmail.co, E-mail: prashant_kcnit@rediffmail.co [EPR Laboratory, Department of Physics, University of Allahabad, Allahabad 211002 (India)

    2010-10-15

    An X-band electron paramagnetic resonance (EPR) study of VO{sup 2+} ions in magnesium citrate decahydrate single crystals was done at room temperature. Detailed EPR analysis indicated the presence of two magnetically inequivalent VO{sup 2+} sites. Both the vanadyl complexes were found to take up substitutional positions. The angular variation of the EPR spectra in three planes a{sup *}b, bc and ca{sup *} were used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are site I: g{sub x}=2.0976, g{sub y}=1.9093, g{sub z}=1.9505, |A{sub x}|=73, |A{sub y}|=115, |A{sub z}|=237x10{sup -4} cm{sup -1}; site II: g{sub x}=2.0735, g{sub y}=1.9235, g{sub z}=1.9699, |A{sub x}|=72, |A{sub y}|=111, |A{sub z}|=233x10{sup -4} cm{sup -1}. An optical absorption study was also performed at room temperature, and absorption bands were assigned to various transitions. The theoretical band positions were estimated using energy expressions, and good agreement with experimental values was found. By correlating EPR and optical data, different molecular orbital coefficients were evaluated; the nature of the bonding in the crystal is discussed.

  10. UV durable colour pigment doped SmA liquid crystal composites for outdoor trans-reflective bi-stable displays

    Science.gov (United States)

    Xu, H.; Davey, A. B.; Crossland, W. A.; Chu, D. P.

    2012-10-01

    High brightness trans-reflective bi-stable displays based on smectic A (SmA) liquid crystals (LCs) can have nearly perfect transparency in the clear state and very high reflection in the scattered state. Because the LC material in use is stable under UV radiation, this kind of displays can stand for strong day-light and therefore be ideal for outdoor applications from e-books to public signage and advertisement. However, the colour application has been limited because the traditional colourants in use are conventional dyes which are lack of UV stability and that their colours are easily photo bleached. Here we present a colour SmA display demonstrator using pigments as colourant. Mixing pigments with SmA LCs and maintain the desirable optical switching performance is not straightforward. We show here how it can be done, including how to obtain fine sized pigment nano-particles, the effects of particle size and size distribution on the display performance. Our optimized pigments/SmA compositions can be driven by a low frequency waveform (~101Hz) to a scattered state to exhibit colour while by a high frequency waveform (~103Hz) to a cleared state showing no colour. Finally, we will present its excellent UV life-time (at least performances are still to be fully understood. We hope this work will not only demonstrate a new and practical approach for outdoor reflective colour displays but also provide a new material system for fundamental liquid crystal colloid research work.

  11. Site-selective measurement of relaxation properties at 980 nm in Er^{3+}-doped congruent and stoichiometric lithium niobate crystals

    Science.gov (United States)

    Mandula, Gabor; Kis, Zsolt; Kovacs, Laszlo; Szaller, Zsuzsanna; Krampf, Andreas

    2016-04-01

    A pump-probe-type saturation spectroscopic experiment has been performed at 980 nm to measure the homogeneous linewidth of the ^4I_{11/2}-^4I_{15/2} transition and the lifetime of the ^4I_{11/2} state of erbium embedded into lithium niobate single crystals. There are several non-equivalent Er^{3+}_{Li^+}-V_{Li^+} sites with differently oriented defect structure for charge compensation. These non-equivalent centers differ in their transition energies. Hence, our measurements have been done at two nearby frequencies, addressing groups of erbium ions located at non-equivalent sites. The results are compared with lifetime calculations and measurements found in the literature and with the predictions of our simple model calculation.

  12. Enormous enhancements of the Kerr nonlinearity at C-band telecommunication wavelength in an Er3+-doped YAG crystal

    Science.gov (United States)

    Hamedi, Hamid Reza

    2014-06-01

    A novel solid configuration is proposed to achieve a giant Kerr nonlinearity with reduced absorption under conditions of slow light levels. It is shown that an enhanced Kerr nonlinearity accompanied with negligible absorption can be obtained just through the proper tuning of intensity of coherent driving field at C-band telecommunication wavelength which is practical for communication applications. Moreover, the impact of incoherent pump field as well as frequency detuning of coherent field on manipulating the linear and nonlinear optical properties of the yttrium-aluminum-garnet (YAG) crystal medium is discussed. The presented results may be of interest to researchers in the field of all-optical signal processing and solid-state quantum information science.

  13. Enhanced Cherenkov phase matching terahertz wave generation via a magnesium oxide doped lithium niobate ridged waveguide crystal

    Science.gov (United States)

    Takeya, K.; Minami, T.; Okano, H.; Tripathi, S. R.; Kawase, K.

    2017-01-01

    When combined with a nonlinear waveguide crystal, Cherenkov phase matching allows for highly effective generation of high power and broadband terahertz (THz) waves. Using a ridged Lithium Niobate (LiNbO3) waveguide coupled with a specially designed silicon lens, we successfully generated THz waves with intensity of approximately three orders of magnitude stronger than those from conventional photoconductive antenna. The broadband spectrum was from 0.1 THz to 7 THz with a maximum dynamic range of 80 dB. The temporal shape of time domain pulse is a regular single cycle which could be used for high depth resolution time of flight tomography. The generated THz wave can also be easily monitored by compact room-temperature THz camera, enabling us to determine the spatial characteristics of the THz propagation.

  14. Enhanced Cherenkov phase matching terahertz wave generation via a magnesium oxide doped lithium niobate ridged waveguide crystal

    Directory of Open Access Journals (Sweden)

    K. Takeya

    2017-01-01

    Full Text Available When combined with a nonlinear waveguide crystal, Cherenkov phase matching allows for highly effective generation of high power and broadband terahertz (THz waves. Using a ridged Lithium Niobate (LiNbO3 waveguide coupled with a specially designed silicon lens, we successfully generated THz waves with intensity of approximately three orders of magnitude stronger than those from conventional photoconductive antenna. The broadband spectrum was from 0.1 THz to 7 THz with a maximum dynamic range of 80 dB. The temporal shape of time domain pulse is a regular single cycle which could be used for high depth resolution time of flight tomography. The generated THz wave can also be easily monitored by compact room-temperature THz camera, enabling us to determine the spatial characteristics of the THz propagation.

  15. Synthesis of novel perovskite crystal structure phase of strontium doped rare earth manganites using sol gel method

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Latif, I.A. [Physics Department, College of Science, Najran University, P.O. 1988, Najran (Saudi Arabia); Reactor Physics Department, NRC, Atomic Energy Authority, Abou Zabaal, P.O. 13759, Cairo (Egypt); Ismail, Adel A., E-mail: adelali141@yahoo.com [Advanced Materials and Nano-Research Centre, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Central Metallurgical Research & Development Institute (CMRDI), Helwan 11421, Cairo (Egypt); Bouzid, Houcine [Advanced Materials and Nano-Research Centre, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Al-Hajry, A. [Physics Department, College of Science, Najran University, P.O. 1988, Najran (Saudi Arabia); Advanced Materials and Nano-Research Centre, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia)

    2015-11-01

    In the present work, polycrystalline perovskites of R{sub 0.6}Sr{sub 0.4}MnO{sub 3} nanocomposites (R=La, Nd, or Sm) were synthesized using the sol–gel method in the presence of citric acid and polyethylene glycol as chelating and structure directing agents respectively. The synthesized gel was calcined at 800 °C for 5 h. The XRD revealed that the obtained nanocrystalline R{sub 0.6}Sr{sub 0.4}MnO{sub 3} is monoclinic crystal structure of space group (I2/a). TEM images showed that the prepared perovskites are homogeneous and uniform with particle sizes in a range 20–40 nm and the HR-TEM images and lattice fringes displayed the monoclinic structure. IV measurements showed that Nd{sub 0.6}Sr{sub 0.4}MnO{sub 3} has semiconducting properties at room temperature. With applying low magnetic field, a transition from semiconductor behavior to Ohmic resistivity was observed. The static resistance of Nd{sub 0.6}Sr{sub 0.4}MnO{sub 3} was calculated to be ~2.985 TΩ for semiconductor phase and the resistance increased 1000 times that gives rise to negative magnetoresistance (MR). The value of MR of Nd{sub 0.6}Sr{sub 0.4}MnO{sub 3} equals to 99.84%, which leads to the use of these materials in fabrication of magnetic devices in the industrial scale. - Highlights: • Polycrystalline perovskites of R{sub 0.6}Sr{sub 0.4}MnO{sub 3} were synthesized using the sol–gel method. • The XRD analysis showed the prepared perovskites are monoclinic crystal structure. • The prepared perovskites are homogeneous and uniform with particles size (20–40 nm). • IV measurements displayed that Nd{sub 0.6}Sr{sub 0.4}MnO{sub 3} has semiconducting properties. • The value of MR equals to 99.84% in Nd{sub 0.6}Sr{sub 0.4}MnO{sub 3}.

  16. Vi, de civiliserede

    DEFF Research Database (Denmark)

    Nyemann, Dorthe

    2016-01-01

    Vi har i årtier troet på, at mennesker under de rette omstændigheder kan lykkes med at leve i fred og fordragelighed med hinanden. Skal vi til at erkende, at også vores samfundsstrukturer kun er en tynd fernis ovenpå et utæmmeligt voldspotentiale og egoisme?......Vi har i årtier troet på, at mennesker under de rette omstændigheder kan lykkes med at leve i fred og fordragelighed med hinanden. Skal vi til at erkende, at også vores samfundsstrukturer kun er en tynd fernis ovenpå et utæmmeligt voldspotentiale og egoisme?...

  17. Synthesis of novel perovskite crystal structure phase of strontium doped rare earth manganites using sol gel method

    Science.gov (United States)

    Abdel-Latif, I. A.; Ismail, Adel A.; Bouzid, Houcine; Al-Hajry, A.

    2015-11-01

    In the present work, polycrystalline perovskites of R0.6Sr0.4MnO3 nanocomposites (R=La, Nd, or Sm) were synthesized using the sol-gel method in the presence of citric acid and polyethylene glycol as chelating and structure directing agents respectively. The synthesized gel was calcined at 800 °C for 5 h. The XRD revealed that the obtained nanocrystalline R0.6Sr0.4MnO3 is monoclinic crystal structure of space group (I2/a). TEM images showed that the prepared perovskites are homogeneous and uniform with particle sizes in a range 20-40 nm and the HR-TEM images and lattice fringes displayed the monoclinic structure. IV measurements showed that Nd0.6Sr0.4MnO3 has semiconducting properties at room temperature. With applying low magnetic field, a transition from semiconductor behavior to Ohmic resistivity was observed. The static resistance of Nd0.6Sr0.4MnO3 was calculated to be 2.985 TΩ for semiconductor phase and the resistance increased 1000 times that gives rise to negative magnetoresistance (MR). The value of MR of Nd0.6Sr0.4MnO3 equals to 99.84%, which leads to the use of these materials in fabrication of magnetic devices in the industrial scale.

  18. EPR and optical absorption studies of Cu{sup 2+} ions doped magnesium citrate decahydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, Prashant, E-mail: prashant_kcnit@rediffmail.co [Department of Physics, Kali Charan Nigam Institute of Technology, Banda (U.P.) 210001 (India); Kripal, Ram, E-mail: ram_kripal2001@rediffmail.co [EPR Laboratory, Department of Physics, University of Allahabad, 22/5A Katra Road, Allahabad, 211002 (India); Misra, Madan Gopal [EPR Laboratory, Department of Physics, University of Allahabad, 22/5A Katra Road, Allahabad, 211002 (India)

    2010-06-04

    X-band electron paramagnetic resonance (EPR) studies of Cu{sup 2+} ions in magnesium citrate decahydrate single crystals are done at room temperature. Detailed EPR analysis indicates the presence of only one Cu{sup 2+} site. Cu{sup 2+} is found to take up substitutional position at Mg site. The angular variation of the EPR spectra in three planes a*b, bc and ca* are used to determine principal g and A tensors. The spin Hamiltonian parameters are: g{sub x} = 2.0346, g{sub y} = 2.1400, g{sub z} = 2.3874, A{sub x} = 57, A{sub y} = 76, A{sub z} = 99 (x10{sup -4}) cm{sup -1}. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are estimated using energy expressions and a good agreement is obtained with the experimental values. By correlating EPR and optical data, different molecular orbital coefficients are evaluated and the nature of bonding in the complex is discussed.

  19. Crystal structure and relaxor-type transition in SrBi(2)Ta(2)O(9) doped with praseodymium.

    Science.gov (United States)

    Mata, J; Durán, A; Martínez, E; Escamilla, R; Heiras, J; Siqueiros, J M

    2006-11-22

    The effects of Pr substitution in the structure and ferroelectric response for the Sr(1-x)Pr(x)Bi(2)Ta(2)O(9) (SBT-Pr) compound have been studied. Rietveld refinement of the x-ray diffraction patterns indicates that the Pr ion progressively replaces the Sr site in the A 2(1)am space group structure. The solubility of Pr in solid solution is around 15%. The replacement induces a change in the crystal structure and, as a consequence, the dielectric properties are affected. The ferroelectric transition at T(m)∼558 K is shifted to lower temperatures, T(m)∼413 K for x = 0.15 composition. Apparently, the tilt angle (α) associated with the c-axis does not play an important role since it remains essentially constant. However, the rotation in the ab-plane (β) as well as the octahedral distortion observed are strongly related to the coupling between T(m) and x. A relaxor-type transition is observed as Pr is increased, leading to polar microregions above the nominal ferroelectric transition. The local disorder induced by the Pr ion is confirmed by the continuous increase in the diffuseness coefficient according to Isupov's model. These facts hinder the displacement of the TaO(6) octahedra with respect to Bi(2)O(2) along the polarization axis, decreasing the polarization values.

  20. Crystal structures and phase transitions in Sr doped Ba{sub 2}InTaO{sub 6} perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Qingdi; Tan, Teck-Yee [School of Chemistry, The University of Sydney, Sydney, NSW 2006 Australia (Australia); Kennedy, Brendan J., E-mail: kennedyb@chem.usyd.edu.au [School of Chemistry, The University of Sydney, Sydney, NSW 2006 Australia (Australia); Hester, James R. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia)

    2013-10-15

    The crystal structures of the double perovskites of the type Ba{sub 2−x}Sr{sub x}InTaO{sub 6} have been studied by synchrotron X-ray and neutron powder diffraction methods. The structures are based on ordered array of the tilted InO{sub 6} and TaO{sub 6} octahedra, with the Ba/Sr cations being completely disordered. The structure evolves from cubic to monoclinic Fm3{sup ¯}m→{sup x∼0.6}I4/m→{sup x∼1.2}I2/m→{sup x∼1.6}P2{sub 1}/n. The changes in the symmetry induced by replacing the Ba with Sr have been identified by a symmetry-mode analysis. Variable temperature S-XRD studies of selected examples have shown that heating the samples induces the same sequence of transitions observed in the composition dependent studies. - Graphical abstract: The evolution of the structure of the B-site ordered perovskites has been determined by high resolution powder diffraction. The nature of the transitions are probed by examination of the symmetry-adapted modes. Display Omitted - Highlights: • Synthesis of Ba{sub 2−x}Sr{sub x}InTaO{sub 6} cation ordered perovskites. • Synchrotron X-ray and neutron diffraction structural studies of Ba{sub 2−x}Sr{sub x}InTaO{sub 6}. • Phase transitions in Ba{sub 2−x}Sr{sub x}InTaO{sub 6}. • Symmetry-adapted mode analysis of phase transitions.

  1. Layered hydride CaNiGeH with a ZrCuSiAs-type structure: crystal structure, chemical bonding, and magnetism induced by Mn doping.

    Science.gov (United States)

    Liu, Xiaofeng; Matsuishi, Satoru; Fujitsu, Satoru; Ishigaki, Toru; Kamiyama, Takashi; Hosono, Hideo

    2012-07-18

    Stimulated by the discovery of the iron oxypnictide superconductor with ZrCuSiAs-type structure in 2008, extensive exploration of its isostructural and isoelectronic compounds has started. These compounds, including oxides, fluorides, and hydrides, can all be simply recognized as valence compounds for which the octet rule is valid. We report herein the first example of a ZrCuSiAs-type hydride, CaNiGeH, which violates the octet rule. This hydride was synthesized by hydrogenation of the CeFeSi-type compound CaNiGe under pressurized hydrogen. Powder diffraction and theoretical simulation confirm that H enters into the interstitial position of the Ca(4) tetrahedron, leading to notable anisotropic expansion of the unit cell along the c axis. Density functional theory calculations indicate the modification of the chemical bonding and formation of ionic Ca-H bond as a result of hydrogen insertion. Furthermore, CaNiGeH shows Pauli paramagnetism and metallic conduction similar to that of CaNiGe, but its carrier type changes to hole and the carrier density is drastically reduced as compared to CaNiGe. Mn-doping at the Ni site introduces magnetism to both the parent compound and the hydride. The measurement demonstrates that hydrogenation of CaNi(1-x)Mn(x)Ge reduces ferromagnetic ordering of Mn ions and induces huge magnetic hysteresis, whereas the spin glass state observed for the parent compound is preserved in the hydride. The hydrogenation-induced changes in the electric and magnetic properties are interpreted in terms of development of two-dimensionality in crystal structure as well as electronic state.

  2. Structure and crystallization behavior of La{sub 2}O{sub 3}⋅3B{sub 2}O{sub 3} metaborate glasses doped with Nd{sup 3+} or Eu{sup 3+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Pytalev, D.S., E-mail: pytalev@isan.troitsk.ru [Institute of Spectroscopy, Russian Academy of Sciences, 5 Fizicheskaya St., 142190 Troitsk, Moscow (Russian Federation); Caurant, D.; Majérus, O.; Trégouët, H. [Institut de Recherche de Chimie Paris, CNRS – Chimie ParisTech, 11 Rue Pierre et Marie Curie, 75005 Paris (France); Charpentier, T. [CEA, IRAMIS, NIMBE, CEA-CNRS UMR 3299, Laboratoire de Structure et Dynamique par Résonance Magnétique, 91191 Gif-sur-Yvette (France); Mavrin, B.N. [Institute of Spectroscopy, Russian Academy of Sciences, 5 Fizicheskaya St., 142190 Troitsk, Moscow (Russian Federation)

    2015-08-25

    Highlights: • The structure and crystallization behavior of the La{sub 2}O{sub 3}⋅3B{sub 2}O{sub 3} glass are studied. • LaB{sub 3}O{sub 6} crystallizes congruently without intermediate but only from glass surface. • The structure of the amorphous and the crystalline phases differ significantly. • The activation energy of LaB{sub 3}O{sub 6} crystal growth is determined. - Abstract: The local structure and crystallization behavior of the stoichiometric La{sub 2}O{sub 3}⋅3B{sub 2}O{sub 3} (LaMB) metaborate glass doped with Nd{sup 3+} or Eu{sup 3+} ions are studied using differential thermal analysis (DTA), X-ray diffraction (XRD), Raman scattering and {sup 11}B magic-angle spinning nuclear magnetic resonance (MAS NMR), optical absorbance and luminescence techniques. In the crystallized samples, XRD, NMR and Raman spectroscopy have detected the formation of only one crystalline phase (congruent crystallization of LaB{sub 3}O{sub 6}). No intermediate metastable crystalline phase has been detected before LaB{sub 3}O{sub 6} crystals formation (single stage crystallization process). The observation of heat treated glass samples by scanning electron microscopy (SEM) and optical microscopy coupled with the study of the effect of varying the glass particle size on the DTA curves have both revealed that LaB{sub 3}O{sub 6} crystallization only occurs by a heterogeneous nucleation mechanism (needle-shape crystals) from glass surface. The activation energy E{sub c} of crystal growth has been determined by performing DTA experiments at different heating rates with the Kissinger (784 kJ/mol) and Ozawa (801 kJ/mol) equations than can be used for surface crystallization processes. The heterogeneous crystallization behavior and the spectroscopic results obtained in this work by comparing the LaMB glass with the LaB{sub 3}O{sub 6} crystalline phase suggest the existence of significant structural differences between the amorphous and the crystalline phases contrary to what

  3. Crystal electric field splitting of R{sup 3+}-ions in pure and Co- and Cu-doped RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm)

    Energy Technology Data Exchange (ETDEWEB)

    Gasser, U.; Allenspach, P.; Henggeler, W.; Zolliker, M.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    From the crystal-electric-field (CEF) splitting of the R{sup 3+}-ions, the CEF parameters of RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm) were deduced. In order to get information about the influence of the variation of the density of states (DOS) at the Fermi level (E{sub F}), CEF spectroscopy measurements with Co- and Cu-doped ErNi{sub 2}B{sub 2}C-samples were performed. (author) 1 fig., 1 tab., 1 ref.

  4. Role of the Yb{sup 3+} concentration in the high efficient UV-blue up-conversion emission from hydrothermally grown Yb{sup 3+}/Er{sup 3+}-doped K{sub 2}YF{sub 5} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Méndez-Ramos, J., E-mail: jmendezr@ull.es [Departamento de Física Fundamental y Experimental, Electrónica y Sistemas, Universidad de La Laguna, 38206 La Laguna, Tenerife (Spain); Acosta-Mora, P. [Departamento de Física Fundamental y Experimental, Electrónica y Sistemas, Universidad de La Laguna, 38206 La Laguna, Tenerife (Spain); Ruiz-Morales, J.C., E-mail: jcruiz@ull.es [Departamento de Química Inorgánica, Universidad de La Laguna, 38206 La Laguna, Tenerife (Spain); Khaidukov, N.M., E-mail: khaiduk2@gmail.com [N.S. Kurnakov Institute of General and Inorganic Chemistry, 31 Leninskii Prospect, Moscow 119991 (Russian Federation)

    2013-10-25

    Highlights: •Yb{sup 3+}/Er{sup 3+} doped K{sub 2}YF{sub 5} crystals were synthesized under hydrothermal conditions. •Intense up-conversion to enhance TiO{sub 2} and Fe{sub 2}O{sub 3} spectral response for water-splitting. •Total infrared to UV-VIS up-conversion efficiency was calculated to be around 66%. •Use of less common heavy RE versus light RE for equilibrating the balance problem. -- Abstract: High intense UV–VIS up-conversion luminescence from orthorhombic K{sub 2}YF{sub 5} fluoride crystals doubly doped with Yb{sup 3+} and Er{sup 3+} has been obtained under near-infrared excitation at 980 nm. Fluoride crystals containing high Yb{sup 3+} concentrations, namely 20; 40 and 99 at.%, and low Er{sup 3+} concentrations have been synthesized under hydrothermal conditions. The role of the Yb{sup 3+} ions in the mechanism of the up-conversion process is clearly disclosed with absorption and up-conversion luminescence spectra from which one can see that high intense green (520–545 nm) and outstanding UV-blue (380–410 nm) emissions are greatly enhanced by increasing the concentration of Yb{sup 3+} ions whose aggregate acts as an infrared collector harvesting long wavelength infrared photons. Outstanding total infrared to UV–VIS up-conversion efficiency of 66% has been calculated for the sample with the highest Yb{sup 3+} doping level, i.e. 99 at.%. These strong UV-blue up-conversion emissions would have the potential use in enhancing spectral response of main semiconductor electrodes (such as TiO{sub 2} and Fe{sub 2}O{sub 3}), and these K{sub 2}YbF{sub 5} crystals doped with Er{sup 3+} could be used in photo-electrochemical devices for sustainable production of hydrogen via photolysis of water, as a promising photonic approach which is currently discussed in the literature.

  5. The sensitivity of the electron transport within bulk zinc-blende gallium nitride to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqua, Poppy; O' Leary, Stephen K., E-mail: stephen.oleary@ubc.ca [School of Engineering, The University of British Columbia, 3333 University Way, Kelowna, British Columbia V1V 1V7 (Canada)

    2016-09-07

    Within the framework of a semi-classical three-valley Monte Carlo simulation approach, we analyze the steady-state and transient electron transport that occurs within bulk zinc-blende gallium nitride. In particular, we examine how the steady-state and transient electron transport that occurs within this material changes in response to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley. These results are then contrasted with those corresponding to a number of other compound semiconductors of interest.

  6. Doping effect on the physical properties of Ca10Pt3As8(Fe2As2)5 single crystals

    Science.gov (United States)

    Pan, Jiayun; Karki, Amar; Plummer, E. W.; Jin, Rongying

    2017-12-01

    Ca10Pt3As8(Fe2As2)5 is a unique parent compound for superconductivity, which consists of both semiconducting Pt3As8 and metallic FeAs layers. We report the observation of superconductivity induced via chemical doping in either Ca site using rare-earth (RE) elements (RE  =  La, Gd) or Fe site using Pt. The interlayer distance and the normal-state physical properties of the doped system change correspondingly. The coupled changes include (1) superconducting transition temperature T c increases with increasing both doping concentration and interlayer distance, (2) our T c value is higher than previously reported maximum value for Pt doping in the Fe site, (3) both the normal-state in-plane resistivity and out-of-plane resistivity change from non-metallic to metallic behavior with increasing doping concentration and T c, and (4) the transverse in-plane magnetoresistance (MRab) changes from linear-field dependence to quadratic behavior upon increasing T c. For La-doped compound with the highest T c (~35 K), upper critical fields (Hc2ab , Hc2c ), coherence lengths (ξ ab, ξ c), and in-plane penetration depth (λ ab) are estimated. We discuss the relationship between chemical doping, interlayer distance, and physical properties in this system.

  7. A crystal chemistry approach for high-power ytterbium doped solid-state lasers: diffusion-bonded crystals and new crystalline hosts; Relations structures-proprietes dans les lasers solides de puissance a l'ytterbium: elaboration et caracterisation de nouveaux materiaux et de cristaux composites soudes par diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Gaume, R

    2002-11-15

    This work deals with ytterbium based crystals for high-power laser applications. In particular, we focus our interest in reducing crystal heating and its consequences during laser operation following two different ways. First, we review the specific properties of ytterbium doped solid-state lasers in order to define a figure-of-merit which gives the evaluation of laser performances, thermo-mechanical and thermo-optical properties. Bearing in mind this analysis, we propose a set of theoretical tools, based on the crystallographic structure of the crystal and its chemical composition, to predict thermo-mechanical and optical potentials. This approach, used for the seek of new Yb{sup 3+}-doped materials for high-power laser applications, shows that simple oxides containing rare-earths are favorable. Therefore, the spectroscopic properties of six new materials Yb{sup 3+}:GdVO{sub 4}, Yb{sup 3+}:GdAlO{sub 3}, Yb{sup 3+}:Gd{sub 2}O{sub 3}, Yb{sup 3+}:Sc{sub 2}SiO{sub 5}, Yb{sup 3+}:CaSc{sub 2}O{sub 4} and Yb{sup 3+}:SrSc{sub 2}O{sub 4} are described. The second aspect developed in this work deals with thermal properties enhancement of already well characterized laser materials. Two different ways are explored: a) elaboration by diffusion bonding of end-caps lasers with undoped crystals (composite crystals). Thus, different composites were obtained and a fairly lowering of thermal lensing effect was observed during laser operation. b) strengthening of crystalline structures by ionic substitution of one of its constituents. We demonstrate how crystal growth ability can be improved by a cationic substitution in the case of Yb{sup 3+}:BOYS, a largely-tunable laser material which is of great interest for femtosecond pulses generation. (author)

  8. Optical absorption spectra of Pr{sup 3+} doped in yttrium pyrogermanate (Y{sub 2}Ge{sub 2}O{sub 7}) crystal

    Energy Technology Data Exchange (ETDEWEB)

    Das, K.; Ghosh, D. [Solid State Physics Department, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700032 (India); Wanklyn, B.M. [Clarendon Laboratory, University of Oxford (United Kingdom)

    1999-02-22

    This paper reports the low temperature absorption and Zeeman spectra of Pr{sup 3+} doped in yttrium pyrogermanate (YPG), which were studied for the first time. In this compound the site symmetry of Pr{sup 3+}, or the crystal field (CF) symmetry, was found to be D{sub 5h}, as present in other rare earth pyrogermanates, and not C{sub 1}. The spectral results were analysed by diagonalizing the total Hamiltonian consisting of the atomic (electrostatic, spin-orbit and configuration interactions) and the CF interactions, in a basis of 91 vertical bar SLJM{sub J}> states spanning the entire 4f{sup 2} ground configuration of Pr{sup 3+} in the intermediate coupling formalism, including J-mixing under CF. The best fitted free ion and CF parameters obtained were E{sup 1}=4335.0, E{sup 2}=23.1, E{sup 3}=464.0, {zeta}=775.0 {alpha}=22.9, {beta}=-674.0, {gamma}=1520.0, B{sub 20}=-100, B{sub 40}=1650, B{sub 60}=-1600 and B{sub 65}=-1000 (all in cm{sup -1}). Using these parameters the thermal characteristics of molar magnetic susceptibilities (K{sub parallel}, K{sub perpendicular}), their anisotropy {delta}K={+-}(K{sub parallel}-K{sub perpendicular}) and the Schottky specific heat (C{sub Sch}) of Pr{sup 3+} in YPG were calculated. It was found that the calculated values of K{sub parallel} >K{sub perpendicular} between 300 and 152 K (T{sub i}) but on cooling further K{sub perpendicular} >K{sub parallel} was observed, i.e. the sign of {delta}K was reversed below T{sub i}. The calculated values of C{sub Sch} exhibited a sharp peak at 24 K and a broad maximum at 156 K. These characteristics were similar to other Pr{sup 3+} compounds studied earlier. (author)

  9. and dioxouranium(vi)

    African Journals Online (AJOL)

    a

    Thorium(IV) and uranium(VI) with atomic radii of 1.65 and .... to ν(NH) vibrations. Practically no effect on these frequencies after complexation precludes the possibility of metal-coordination at this group. The absorptions at 1600 ... observation suggests involvement of unsaturated nitrogen atoms of the two azomethine groups.

  10. Thulium-doped fiber laser utilizing a photonic crystal fiber-based optical low-pass filter with application in 1.7 μm and 1.8 μm band.

    Science.gov (United States)

    Emami, Siamak Dawazdah; Khodaei, Amin; Gandan, Shumithira; Penny, Richard; Lim, Kok Sing; Abdul-Rashid, Hairul Azhar; Ahmad, Harith

    2015-07-27

    This paper describes a low pass filter based on photonics crystal fiber (PCF) partial ASE suppression, and its application within a 1.7 µm to 1.8 µm band thulium-doped fiber amplifier (TDFA) and a thulium-doped fiber laser (TDFL). The enlargement of air holes around the doped core region of the PCF resulted in a low-pass filter device that was able to attenuate wavelengths above the conventional long cut-off wavelength. These ensuing long cut-off wavelengths were 1.85 μm and 1.75 μm, and enabled a transmission mechanism that possessed a number of desirable characteristics. The proposed optical low-pass filter was applied within a TDFA and TDFL system. Peak spectrum was observed at around 1.9 μm for conventional TDF lasers, while the proposed TDF laser with PCF setup had fiber laser peak wavelengths measured at downshifted values of 1.74 μm and 1.81 μm.

  11. ACTIVE MEDIA: BaY2F8 single crystals doped with rare-earth ions as promising up-conversion media for UV and VUV lasers

    Science.gov (United States)

    Pushkar', A. A.; Uvarova, T. V.; Molchanov, V. N.

    2008-04-01

    BaY2F8 crystals are studied as promising active media for UV and VUV lasers. The up-conversion pumping of rare-earth activators is proposed to solve problems related to the solarisation of the medium and the selection of pump sources. The technology of growing oriented BaY2F8 single crystals is developed and the influence of the crystal orientation on the growth rate and quality of single crystals is determined.

  12. Influences of glycerol as an efficient doping agent on crystal structure and antibacterial activity of B-TiO2 nano-materials.

    Science.gov (United States)

    Yang, He; Wang, Yuzheng; Xue, Xiangxin

    2014-10-01

    In this study, highly effective boron acid and glycerol co-doped TiO2 nano-materials were directly synthesized via a sol-gel method. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrum (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron (PL) spectroscopy. The results indicate that boron dopant is partially embedded into the interstitial TiO2 structure or incorporated into the TiO2 lattice through occupying the position of the oxygen atom, and others is present in the form of B2O3. Boron acid and glycerol co-doping TiO2 materials show obvious red shift in their absorption edges and efficient electron-hole separation because of the glycerol doping. The study on the antibacterial activities demonstrate that co-doped TiO2 nano-materials could effectively inactivate the bacteria under visible light irradiation. Co-doped TiO2 nano-materials exhibit more excellent antibacterial performance than B-doped TiO2 nano-materials. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. First-Principles Calculations of Thermoelectric Properties of IV–VI Chalcogenides 2D Materials

    Directory of Open Access Journals (Sweden)

    J. O. Morales-Ferreiro

    2017-12-01

    Full Text Available A first-principles study using density functional theory and Boltzmann transport theory has been performed to evaluate the thermoelectric (TE properties of a series of single-layer 2D materials. The compounds studied are SnSe, SnS, GeS, GeSe, SnSe2, and SnS2, all of which belong to the IV–VI chalcogenides family. The first four compounds have orthorhombic crystal structures, and the last two have hexagonal crystal structures. Solving a semi-empirical Boltzmann transport model through the BoltzTraP software, we compute the electrical properties, including Seebeck coefficient, electrical conductivity, power factor, and the electronic thermal conductivity, at three doping levels corresponding to 300 K carrier concentrations of 1018, 1019, and 1020 cm−3. The spin orbit coupling effect on these properties is evaluated and is found not to influence the results significantly. First-principles lattice dynamics combined with the iterative solution of phonon Boltzmann transport equations are used to compute the lattice thermal conductivity of these materials. It is found that these materials have narrow band gaps in the range of 0.75–1.58 eV. Based on the highest values of figure-of-merit ZT of all the materials studied, we notice that the best TE material at the temperature range studied here (300–800 K is SnSe.

  14. II-VI semiconductor compounds

    CERN Document Server

    1993-01-01

    For condensed matter physicists and electronic engineers, this volume deals with aspects of II-VI semiconductor compounds. Areas covered include devices and applications of II-VI compounds; Co-based II-IV semi-magnetic semiconductors; and electronic structure of strained II-VI superlattices.

  15. Visible light absorbance enhanced by nitrogen embedded in the surface layer of Mn-doped sodium niobate crystals, detected by ultra violet - visible spectroscopy, x-ray photoelectron spectroscopy, and electric conductivity tests

    Science.gov (United States)

    Molak, A.; Pilch, M.

    2016-05-01

    Sodium niobate crystals doped with manganese ions, Na(NbMn)O3, were annealed in a nitrogen N2 flow at 600, 670, and 930 K. It was verified that simultaneous doping with Mn ions and annealing in nitrogen enhanced the photocatalytic features of sodium niobate. The transmission in the ultraviolet-visible range was measured at room temperature. The absorbance edge is in the range from 3.4 to 2.3 eV. The optical band gap Egap = 1.2-1.3 eV was evaluated using the Tauc relation. Crystals annealed at 670 K and 930 K exhibited an additional shift of the absorption edge of ˜20-40 nm toward longer wavelengths. The optical energy gap narrowed as a result of the superimposed effect of Mn and N co-doping. The x-ray photoelectron spectroscopy test showed that N ions incorporated into the surface layer. The valence band consisted of O 2p states hybridized with Nb 4d, Mn 3d, and N 2s states. The disorder detected in the surroundings of Nb and O ions decreased due to annealing. The binding energy of oxygen ions situated within the surface layer was EB ≈ 531 eV. The other contributions were assigned to molecular contamination. The contribution centered at 535.5 eV vanished after annealing at 600 K and 670 K. The contribution centered at 534 eV vanished after annealing at 930 K. The N2 annealing partly removed carbonates from the surfaces of the samples. In the 480-950 K range, the electric conductivity activation energy, Ea = 0.7-1.2 eV, was comparable with the optical Egap. The electric permittivity showed dispersion in the 0.1-800 kHz range that corresponds to the occurrence of defects.

  16. Dielectric constant, loss factor and ac conductivity of Ni{sup 2+}-doped K{sub 2}ZnCl{sub 4} crystals in the ferroelectric-commensurate, incommensurate and normal phases

    Energy Technology Data Exchange (ETDEWEB)

    Gaffar, M.A. [Physics Department, School of Science and Engineering, American University in Cairo, Cairo 11511 (Egypt); Abousehly, A.M.; Mostafa, M.M. [Physics Department, Faculty of Science, Al-Azhar University, 71524 Assiut (Egypt); Abu El-Fadl, A. [Physics Department, Faculty of Science, Assiut University, 71516 Assiut (Egypt)

    2006-11-15

    The dielectric constant ({epsilon}), dielectric loss (tan{delta}) and ac conductivity ({sigma}{sub ac}) of virgin and thermally cycled undoped and Ni{sup 2+}-doped K{sub 2}ZnCl{sub 4}(KZC) crystals in the ferroelectric-commensurate (FC), incommensurate (IC) and normal phases (N) have been studied. Anomalous behaviour at the two-phase transition points was observed while measuring {epsilon} along the polar a-axis for the undoped sample. With increasing Ni {sup 2+}concentration a systematic shift of the phase transition temperature towards lower values and a continuous inhibition of the peak height were detected. {epsilon} changed linearly with lnf up to f=10{sup 5} Hz. tan {delta} along the a-axis declared the phase transitions by peak changes. After Ni {sup 2+}-doping this behaviour was preserved at the FC-IC phase transition point while the IC-N phase transition was manifested by a change in the slope of the straight line representing the tan {delta}-T dependence. The ac conductivity changed lineally with frequency according to a relation of the form {sigma}{sub ac}={sigma}{sub o} f{sup {beta}} where 0>{beta}>1.9{sigma}{sub ac} increased monotonically with increasing temperature and doping concentration in the low-temperature phases tending to merge in one straight-line with high activation energy that might be due to superionic dc conduction in the high temperature N-phase. Doping with Ni{sup 2+} pinned stripples, decreased the soliton-soliton interaction, weakened discommensuration effects, shortened the IC-phase and strongly affected the 'chaotic' behaviour at the T{sub C-IC}. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Effect of different element doping on the structure and magnetic properties of composite crystal Sr{sub 14}(Cu{sub 1−x}M{sub x}){sub 24}O{sub 41} (M=Zn, Ni, Co)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun, E-mail: JohnKing2001@hotmail.com [Key Laboratory of Acoustic and Photonic Material and Device, Ministry of Education, Department of Physics, Wuhan University, Wuhan 430072 (China); Centre for Electron Microscopy, Wuhan University, Wuhan 430072 (China); Three Gorges Vocational College of Electric Power, Yichang 443000 (China); Zou, Huamin; Li, Yang [Key Laboratory of Acoustic and Photonic Material and Device, Ministry of Education, Department of Physics, Wuhan University, Wuhan 430072 (China); Centre for Electron Microscopy, Wuhan University, Wuhan 430072 (China); Xie, Hui; Hu, Ni; Wang, Lili; Shi, Jing [Key Laboratory of Acoustic and Photonic Material and Device, Ministry of Education, Department of Physics, Wuhan University, Wuhan 430072 (China)

    2014-05-15

    The Zn{sup 2+}, Ni{sup 2+} and Co{sup 3+} doped Sr{sub 14}(Cu{sub 1−x}M{sub x}){sub 24}O{sub 41} composite crystals were synthesized by a standard solid state reaction method. The temperature dependence of magnetic properties was measured for every sample. The Curie coefficient, Weiss temperature, number of dimers in CuO{sub 2} chain per formula unit (f.u.) and dimer coupling constant are obtained by fitting the temperature dependence of the magnetic susceptibility. Meantime, selected area electron diffraction patterns (EDPs) show that the diffraction spots corresponding to the CuO{sub 2} chain substructure are extended to streaks along a{sup ⁎} and b{sup ⁎} directions for all the samples, while the diffraction spots produced merely by the Cu{sub 2}O{sub 3} ladder substructure are still very sharp. This means that the periodicities of chains in a{sup ⁎} and b{sup ⁎} directions are partially destroyed upon doping of Zn, Ni and Co due to that the initial phase of each chain becomes a random variable. Considering the effect of different ions substitution for Cu on the magnetic susceptibility, it is found that the degree of initial phase disorder is related to the order degree of magnetic sequence in CuO{sub 2} chain. For the un-doped sample, the decoupling of dimers is weak, the magnetic sequence is slightly destroyed, and the streaks in EDP are also very weak, which implies the degree of initial phase disorder in CuO{sub 2} chain is very low. When Zn{sup 2+} and Ni{sup 2+} ions are doped, the number of dimers per f.u. decreases, and the intensity of diffraction streaks increases. Furthermore, when the high spin magnetic ions Co{sup 3+} are doped, the number of holes in Sr{sub 14}(Cu{sub 1−x}Co{sub x}){sub 24}O{sub 41} decreases, the magnetic sequence is destroyed very seriously, and the spots in EDP are extended to streaks almost completely. The phenomenon that the diffraction spots of CuO{sub 2} chain extend to streaks in EDP appears as evidence that the

  18. VI Nukitsa konkurss

    Index Scriptorium Estoniae

    2002-01-01

    VI Nukitsa konkursi auhinnad: Kirjanikud: I - Henno Käo ("Kusagil mujal"); II - Aidi Vallik ("Kuidas elad, Ann?"); III - Artur Jurin ("Piletijaht: uued segadused Kilulibeda teel"). Kunstnikud: I - Karel Korp (Leelo Tungla ja Karel Korbi "Tema amet"); II - Edgar Valter ("Kuidas õppida vaatama?"); III - Artur Jurin - ("Piletijaht: uued segadused Kilulibeda teel"). Täiskasvanute küsitluse võitis nii teksti kui piltidega Ene-Maris Tali ja Tarmo Tali "Tähtraamat. Aastaring Maarjamaal"

  19. Effect of calcination temperature on the structure and visible-light photocatalytic activities of (N, S and C) co-doped TiO{sub 2} nano-materials

    Energy Technology Data Exchange (ETDEWEB)

    Lei, X.F., E-mail: leixuefei69@163.com [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization Technology and Boron Materials, Shenyang 110819 (China); Xue, X.X.; Yang, H. [Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization Technology and Boron Materials, Shenyang 110819 (China); Chen, C.; Li, X.; Niu, M.C.; Gao, X.Y.; Yang, Y.T. [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China)

    2015-03-30

    Graphical abstract: (N, S and C) co-doped TiO{sub 2} samples show good photocatalytic activity for Cr(VI) reduction under visible light irradiation. - Highlights: • (N, S and C) co-doping in TiO{sub 2} can preserve the anatase form to higher temperature. • (N, S and C) co-doped TiO{sub 2} samples can absorb both UV and visible light. • The band gap energy of the sample significantly reduced after (N, S and C) co-doping. • (N, S and C) co-doped TiO{sub 2} samples effective for visible light induced reduction of Cr(VI). - Abstract: The (N, S and C) co-doped TiO{sub 2} samples (NSC-TiO{sub 2}) were synthesized by the sol–gel method combining with the high energy ball milling method calcined at the different temperature (400–700 °C), employing butyl titanate as the titanium source and thiourea as the doping agent. The structures of NSC-TiO{sub 2} samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), X-ray photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The photocatalytic activities were checked through the photocatalytic reduction of Cr(VI) as a model compound under visible light irradiation. The results showed that the (N, S and C) co-doping and the calcination temperature played important role on the microstructure and photocatalytic activity of the samples. According to XPS spectra, sulfur was mainly attributed to the Ti−O−S bond; nitrogen was ascribed to the Ti−O−N and Ti−N bonds; carbon was assigned to the Ti−O−C bond in the NSC-TiO{sub 2} samples. (N, S and C) co-doped TiO{sub 2} samples calcinated at 500 °C exhibits higher photocatalytic activity than that of the other samples under visible light irradiation, which can be

  20. Development of a new photorefractive and photovoltaic potassium niobate crystal

    Science.gov (United States)

    Evans, D. R.; Basun, S. A.; Seim, J. M.

    2005-03-01

    Photovoltaic measurements have been made on a new doped potassium niobate crystal that yields significantly larger photovoltaic fields than other doped potassium niobate crystals. Contra-directional two-beam coupling efficiencies and Raman spectroscopy measurements have also been conducted, which show major differences with respect to the published results for other doped potassium niobate materials.

  1. Role of metal d states in II-VI semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Wei, S.; Zunger, A.

    1988-05-15

    All-electron band-structure calculations and photoemission experiments on II-VI semiconductors both exhibit a metal d subband inside the main valence band. It has nevertheless been customary in pseudopotential and tight-binding approaches to neglect the metal d band by choosing Hamiltonian parameters which place this band inside the chemically inert atomic cores. Using all-electron self-consistent electronic-structure techniques (which treat the outermost d electrons on the same footing as other valence electrons) and comparing the results to those obtained by methods which remove the d band from the valence spectrum, we study their effects on valence properties. For II-VI semiconductors we find that p-d repulsion and hybridization (i) lower the band gaps, (ii) reduce the cohesive energy, (iii) increase the equilibrium lattice parameters, (iv) reduce the spin-orbit splitting, (v) alter the sign of the crystal-field splitting, (vi) increase the valence-band offset between common-anion II-VI semiconductors, and (vii) modify the charge distributions of various II-VI systems and their alloys. p-d repulsion is also shown to be responsible for the occurrence of deep Cu acceptor levels in II-VI semiconductors (compared with shallow acceptors of Zn in III-V), for the anomalously small band gaps in chalcopyrites, and for the negative exchange splitting in ferromagnetic MnTe.

  2. A variable temperature EPR study of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) single crystal at 170 GHz: zero-field splitting parameter and its absolute sign.

    Science.gov (United States)

    Misra, Sushil K; Andronenko, Serguei I; Chand, Prem; Earle, Keith A; Paschenko, Sergei V; Freed, Jack H

    2005-06-01

    EPR measurements have been carried out on a single crystal of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) at 170-GHz in the temperature range of 312-4.2K. The spectra have been analyzed (i) to estimate the spin-Hamiltonian parameters; (ii) to study the temperature variation of the zero-field splitting (ZFS) parameter; (iii) to confirm the negative absolute sign of the ZFS parameter unequivocally from the temperature-dependent relative intensities of hyperfine sextets at temperatures below 10K; and (iv) to detect the occurrence of a structural phase transition at 4.35K from the change in the structure of the EPR lines with temperature below 10K.

  3. Optical transmission damage of undoped and Ce doped Y{sub 3}Al{sub 5}O{sub 12} scintillation crystals under 24 GeV protons high fluence

    Energy Technology Data Exchange (ETDEWEB)

    Auffray, E. [CERN, Geneva (Switzerland); Fedorov, A. [Research Institute for Nuclear Problems, Minsk (Belarus); Dormenev, V. [Justus Liebig University, Giessen (Germany); Houžvička, J. [CRYTUR, spol. s r.o., Palackého 175, 51101 Turnov (Czech Republic); Korjik, M., E-mail: Mikhail.Korjik@cern.ch [Research Institute for Nuclear Problems, Minsk (Belarus); Lucchini, M.T. [CERN, Geneva (Switzerland); Mechinsky, V. [Research Institute for Nuclear Problems, Minsk (Belarus); Ochesanu, S. [CRYTUR, spol. s r.o., Palackého 175, 51101 Turnov (Czech Republic)

    2017-06-01

    This report presents results on the optical transmission damage of undoped and Ce doped Y{sub 3}Al{sub 5}O{sub 12} scintillation crystals under high fluence of 24 GeV protons. We observed that, similarly to other middle heavy scintillators, it possesses the unique radiation hardness at fluence values as high as 5×10{sup 14} p/cm{sup 2} and it is thus promising for the application in the detectors at High Luminosity LHC. The crystalline structure of the garnet scintillator allows to control and further optimize its scintillation parameters, such as scintillation decay time and emission wavelength, and shows a limited set of the radioisotopes after the irradiation with protons.

  4. Commendable Eu2+-Doped Oxide-Matrix-Based LiBa12(BO3)7F4Red Broad Emission Phosphor Excited by NUV Light: Electronic and Crystal Structures, Luminescence Properties.

    Science.gov (United States)

    Ding, Xin; Wang, Yuhua

    2017-07-19

    In this work, we synthesized a new Eu 2+ -doped oxide-matrix-based LiBa 12 (BO 3 ) 7 F 4 broad red emission phosphor. It can emit red light peaking at ∼644 nm under NUV excitation with the coordinate at (0.6350, 0.3586) and a sensitive color gamut for eyes. This phosphor with a special kind of tunnel crystal structure and layered distribution of Ba 2+ is contributed to longer wavelength emission. By theoretical calculation and analysis using local state density energy band structure simulation of Eu 2+ doped in different site, the origin of the observed emission center was distinguished. Furthermore, decay curves analysis also indicated there are three possible Ba 2+ sites for Eu 2+ to occupy. Temperature-dependent PL spectra appeared anomalous phenomena that the intensity increases first and then decreases, which is due to the traps energy level's contribution of electron's transition. The phosphor also has cathodoluminescence (CL) property which the spectra take on typical current saturation phenomenon. The CL curves indicated that this phosphor has a very good stability under much electron beam bombardment time. After fabricated combining with BAM, (Sr, Ba) 2 SiO 4 and our red phosphor excited under 405-nm NUV chips, warm light LED was obtained. Its CIE coordinate is (0.3475, 0.3416) and the CCT, Ra, and luminous efficiency are 4856 K, 84.1, and 72.6 lm/W, respectively.

  5. Effects of Bi doping on dielectric and ferroelectric properties of ...

    Indian Academy of Sciences (India)

    Effects of Bi doping on structure, dielectric and ferroelectric properties of PLBZT were investigated. Bi doping is useful in crystallization of PLBZT films and promoting grain growth. When the Bi-doping content is not more than 0.4, an obvious improvement in dielectric properties and leakage current of PLBZT was confirmed ...

  6. Vi tror, vi forstår hinanden, men det gør vi ikke

    DEFF Research Database (Denmark)

    Boysen, Mikkel Snorre Wilms

    2016-01-01

    Vores verdensbillede er baseret på en tro på, at vi forstår hinanden. Men meget tyder på, at denne tro snarere er en illusion. Derfor må vi indstille os på, at der skal en særlig indsats til, hvis vi skal kunne forstå vores omverden og menneskene i den......Vores verdensbillede er baseret på en tro på, at vi forstår hinanden. Men meget tyder på, at denne tro snarere er en illusion. Derfor må vi indstille os på, at der skal en særlig indsats til, hvis vi skal kunne forstå vores omverden og menneskene i den...

  7. Luminescence rise time in self-activated PbWO4 and Ce-doped Gd3Al2Ga3O12 scintillation crystals

    CERN Document Server

    E. Auffray; A. Borisevich; V. Gulbinas; A. Fedorov; M. Korjik; M.T. Lucchini; V. Mechinsky; S. Nargelas; E. Songaila; G. Tamulaitis; A. Vaitkevičius; S. Zazubovich

    2016-01-01

    The time resolution of scintillation detectors of ionizing radiation is one of the key parameters sought for in the current and future high-energy physics experiments. This study is encouraged by the necessity to find novel detection methods enabling a sub-10-ps time resolution in scintillation detectors and is focused on the exploitation of fast luminescence rise front. Time-resolved photoluminescence (PL) spectroscopy and thermally stimulated luminescence techniques have been used to study two promising scintillators: self-activated lead tungstate (PWO, PbWO4) and Ce-doped gadolinium aluminum gallium garnet (GAGG, Gd3Al2Ga3O12). A sub-picosecond PL rise time is observed in PWO, while longer processes in the PL response in GAGG:Ce are detected and studied. The mechanisms responsible for the PL rise time in self-activated and doped scintillators are under discussion.

  8. Stereospecific ligands and their complexes. VI. The crystal structure of (S,S-ethylenediamine-N,N’-di-2-propanoic acid hydrochloride, (S,S-H2eddp•HCl

    Directory of Open Access Journals (Sweden)

    VERICA V. GLODJOVIĆ

    2011-07-01

    Full Text Available (S,S-Ethylenediamine-N,N’-di-2-propanoic acid hydrochloride, (S,S-H2eddp·HCl, was prepared and its crystal structure determined. The compound was characterized by infrared and 1H- and 13C-NMR spectroscopy. It forms P1 in the space group of a triclinic crystal system with a = 5.3902(2 Å, b = 5.8967(2 Å, c = 10.3319(2 Å, a = 99.625(2°, b = 91.645(2°, g = 109.995(2° and Z = 1.

  9. The solely motif-doped Au36-xAgx(SPh-tBu)24 (x = 1-8) nanoclusters: X-ray crystal structure and optical properties.

    Science.gov (United States)

    Fan, Jiqiang; Song, Yongbo; Chai, Jinsong; Yang, Sha; Chen, Tao; Rao, Bo; Yu, Haizhu; Zhu, Manzhou

    2016-08-18

    We report the observation of new doping behavior in Au36-xAgx(SR)24 nanoclusters (NCs) with x = 1 to 8. The atomic arrangements of Au and Ag atoms are determined by X-ray crystallography. The new gold-silver bimetallic NCs share the same framework as that of the homogold counterpart, i.e. possessing an fcc-type Au28 kernel, four dimeric AuAg(SR)3 staple motifs and twelve simple bridging SR ligands. Interestingly, all the Ag dopants in the Au36-xAgx(SR)24 NCs are selectively incorporated into the surface motifs, which is in contrast to the previously reported Au-Ag alloy structures with the Ag dopants preferentially displacing the core gold atoms. This distinct doping behavior implies that the previous assignments of an fcc Au28 core with four dimers and 12 bridging thiolates for Au36(SR)24 are more justified than other assignments of core vs. surface motifs. The UV-Vis adsorption spectrum of Au36-xAgx(SR)24 is almost the same as that of Au36(SR)24, indicating that the Ag dopants in the motifs do not change the optical properties. The similar UV-Vis spectra are further confirmed by TD-DFT calculations. DFT also reveals that the energies of the HOMO and LUMO of the motif-doped AuAg alloy NC are comparable to those of the homogold Au36 NC, indicating that the electronic structure is not disturbed by the motif Ag dopants. Overall, this study reveals a new silver-doping mode in alloy NCs.

  10. Novel chromium doped perovskites A{sub 2}ZnTiO{sub 6} (A = Pr, Gd): Synthesis, crystal structure and photocatalytic activity under simulated solar light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Hekai [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Fang, Minghao, E-mail: fmh@cugb.edu.cn [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Huang, Zhaohui, E-mail: huang118@cugb.edu.cn [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Liu, Yan’gai [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Chen, Kai [National Engineering Research Center for Rare Earth Materials, General Research Institute For Nonferrous Metals, Grirem Advanced Materials Co.,Ltd., Beijing 100088 (China); Guan, Ming; Tang, Chao; Zhang, Lina; Wang, Meng [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China)

    2017-01-30

    Highlights: • Novel Cr doped A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) photocatalysts were successfully synthesized. • The light absorbance and photocatalytic activity are enhanced through Cr doping. • The photocatalytic reaction mechanism of these photocatalyst was investigated. - Abstract: Double perovskite related oxides A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) have been successfully synthesized by solid state reaction and investigated as photocatalysts for the first time. The two layered titanates mainly demonstrate absorbances under UV irradiation, except for several sharp absorption bands above 400 nm for Pr{sub 2}ZnTiO{sub 6}. Therefore, a series of photocatalysts by doping A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) with Cr have been developed in the hope to improve their absorption in the visible light region. The successful incorporation of Cr was detected by XRD and XPS, and the prepared samples have also been characteriazed by SEM, UV–vis DRS and PL. The characterization results suggested that Cr was present mainly in the form of Cr3+, with only a small amount of Cr6+ species. It served as an efficient dopant for the extension of visible light absorbance and improved photocatalytic activities under solar light irradiation. For both Pr{sub 2}ZnTiO{sub 6} and Gd{sub 2}ZnTiO{sub 6}, the valence band (VB) was composed of hybridized states of the Zn 3d, O 2p and the conduction band (CB) has major contribution from Zn 4s, Ti 3d orbitals. For Cr doped samples, the newly formed spin-polarized valence band in the middle of the band gap that primarily arises from Cr 3d orbitals was responsible for the improved optical and photocatalytic properties.

  11. Microstructural analyses of Cr(VI) speciation in chromite ore processing Residue (COPR)

    Energy Technology Data Exchange (ETDEWEB)

    CHRYSOCHOOU, MARIA; FAKRA, SIRINE C .; Marcus, Matthew A.; Moon, Deok Hyun; Dermatas, Dimitris

    2010-03-01

    The speciation and distribution of Cr(VI) in the solid phase was investigated for two types of chromite ore processing residue (COPR) found at two deposition sites in the United States: gray-black (GB) granular and hard brown (HB) cemented COPR. COPR chemistry and mineralogy were investigated using micro-X-ray absorption spectroscopy and micro-X-ray diffraction, complemented by laboratory analyses. GB COPR contained 30percent of its total Cr(VI) (6000 mg/kg) as large crystals(>20 ?m diameter) of a previously unreported Na-rich analog of calcium aluminum chromate hydrates. These Cr(VI)-rich phases are thought to be vulnerable to reductive and pH treatments. More than 50percent of the Cr(VI) was located within nodules, not easily accessible to dissolved reductants, and bound to Fe-rich hydrogarnet, hydrotalcite, and possibly brucite. These phases are stable over a large pH range, thus harder to dissolve. Brownmilleritewasalso likely associated with physical entrapment of Cr(VI) in the interior of nodules. HB COPR contained no Cr(VI)-rich phases; all Cr(VI) was diffuse within the nodules and absent from the cementing matrix, with hydrogarnet and hydrotalcite being the main Cr(VI) binding phases. Treatment ofHBCOPRis challenging in terms of dissolving the acidity-resistant, inaccessible Cr(VI) compounds; the same applies to ~;;50percent of Cr(VI) in GB COPR.

  12. A{sup I}B{sup III}C{sup VI}{sub 2} (A = Cu, Ag; B = Ga, In; C = S, Se, Te) based photonic crystal superlattices: Optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Simsek, Sevket [Faculty of Engineering, Department of Material Science and Engineering, Hakkari University, 3000, Hakkari (Turkey); Palaz, Selami [Faculty of Science and Letters, Department of Physics, Harran University, 63000, Sanliurfa (Turkey); Akhundov, Chingiz [International Scientific Center, Baku State University, Baku (Azerbaijan); Mamedov, Amirullah M. [International Scientific Center, Baku State University, Baku (Azerbaijan); Nanotechnology Research Center, Bilkent University, 06800, Ankara (Turkey); Ozbay, Ekmel [Nanotechnology Research Center, Bilkent University, 06800, Ankara (Turkey)

    2017-06-15

    In this study, we present an investigation of the optical properties and band structures for the photonic structures based on A{sup I}B{sup III}C{sup VI}{sub 2} with a Fibonacci sequence that can act as a multi-wavelength birefringent filter. The filtering wavelengths are analyzed by the indices concerning the quasi-periodicity of a Fibonacci sequence and the average lattice parameter. The transmittances of filtering wavelengths can be tuned by varying structure parameters such as the lengths of poled domains, filling factor, and dispersion relation. In our simulation, we employed the finite-difference time domain (FDTD) technique, which implies a solution from Maxwell equation. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Visible light absorbance enhanced by nitrogen embedded in the surface layer of Mn-doped sodium niobate crystals, detected by ultra violet - visible spectroscopy, x-ray photoelectron spectroscopy, and electric conductivity tests

    Energy Technology Data Exchange (ETDEWEB)

    Molak, A., E-mail: andrzej.molak@us.edu.pl; Pilch, M. [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland)

    2016-05-28

    Sodium niobate crystals doped with manganese ions, Na(NbMn)O{sub 3}, were annealed in a nitrogen N{sub 2} flow at 600, 670, and 930 K. It was verified that simultaneous doping with Mn ions and annealing in nitrogen enhanced the photocatalytic features of sodium niobate. The transmission in the ultraviolet-visible range was measured at room temperature. The absorbance edge is in the range from 3.4 to 2.3 eV. The optical band gap E{sub gap} = 1.2–1.3 eV was evaluated using the Tauc relation. Crystals annealed at 670 K and 930 K exhibited an additional shift of the absorption edge of ∼20–40 nm toward longer wavelengths. The optical energy gap narrowed as a result of the superimposed effect of Mn and N co-doping. The x-ray photoelectron spectroscopy test showed that N ions incorporated into the surface layer. The valence band consisted of O 2p states hybridized with Nb 4d, Mn 3d, and N 2s states. The disorder detected in the surroundings of Nb and O ions decreased due to annealing. The binding energy of oxygen ions situated within the surface layer was E{sub B} ≈ 531 eV. The other contributions were assigned to molecular contamination. The contribution centered at 535.5 eV vanished after annealing at 600 K and 670 K. The contribution centered at 534 eV vanished after annealing at 930 K. The N{sub 2} annealing partly removed carbonates from the surfaces of the samples. In the 480–950 K range, the electric conductivity activation energy, E{sub a} = 0.7–1.2 eV, was comparable with the optical E{sub gap}. The electric permittivity showed dispersion in the 0.1–800 kHz range that corresponds to the occurrence of defects.

  14. Crystal structure of μ-peroxido-κ(4) O (1),O (2):O (1'),O (2')-bis-[(nitrato-κO)(2,2':6',2''-terpyridine-κ(3) N,N',N'')dioxidouranium(VI)].

    Science.gov (United States)

    Kawasaki, Takeshi; Kitazawa, Takafumi

    2015-05-01

    In the title dimeric complex, [{UO2(NO3)(C15H11N3)}2O2], a peroxide ion bridges the two uran-yl(VI) [O=U=O](2+) ions. The O-O bond length of the peroxide is 1.485 (6) Å and the mid-point of this bond is located at the inversion centre of the dimer. The U atom exhibits a distorted hexa-gonal-bipyramidal coordination geometry with two uran-yl(VI) O atoms occupying the axial positions and one O atom of the monodentate nitrate ion, both O atoms of the peroxide ion and the three N atoms of the chelating tridentate 2,2':6',2''-terpyridine (terpy) ligand in the equatorial positions. Two of the N atoms of the terpy ligand lie above and below the mean plane containing the equatorial ligand atoms and the U atom [deviations from the mean plane: maximum 0.500 (2), minimum -0.472 (2) and r.m.s. = 0.2910 Å]. The dihedral angle between the terpy ligand and the mean plane is 35.61 (7)°. The bond lengths around the U atom decrease in the order U-N > U-Onitrate > U-Operoxo > U=O. The dimeric complexes pack in a three-dimensional network held together by weak π-π inter-actions [centroid-centroid distance = 3.659 (3) Å] between pyridyl rings of the terpy ligands in neighbouring dimers, together with inter-molecular C-H⋯O and C-H⋯π inter-actions. Weak intra-molecular C-H⋯O inter-actions are also observed.

  15. Spectroscopic characteristics of praseodymium-doped cubic double sodium-yttrium fluoride crystals Na0.4Y0.6F2.2:Pr3+. Intensities of optical transitions and luminescence kinetics

    Science.gov (United States)

    Tkachuk, A. M.; Ivanova, S. E.; Mirzaeva, A. A.; Joubert, M.-F.; Guyot, Y.

    2014-03-01

    Using the Bridgman-Stockbarger technique, we have grown a series of cubic crystals Na0.4Y0.6F2.2:Pr3+ (NYF:Pr3+) with a content of praseodymium in the range of 0.04-9 at %. We have determined the composition of crystals, evaluated their optical quality, and found the incorporation coefficient of Pr3+ ions into the Na0.4Y0.6F2.2 matrix ( K Pr ˜ 0.9). We have examined optical spectra of NaYF:Pr3+ crystals at room and low (7 K) temperatures in the range of 200-2500 nm. The low-temperature absorption spectra of NYF:Pr3+ crystals have been shown to consist of broad weakly structured bands. Based on the analysis of low-temperature absorption spectra, the structure of the Stark splitting of praseodymium levels has been represented in terms of a model of "quasi-centers," which are characterized by an inhomogeneous broadening of Stark components. From experimental absorption cross-section spectra at T = 300 K, we have calculated oscillator strengths for transitions from the ground state 3 H 4 to excited multiplets 3 H 5, 3 H 6, 3 F j ( j = 2, 3, 4), 1 G 4, 1 D 2, and (3 P j ,1 I 6) ( j = 0, 1, 2). Using the Judd-Ofelt method, we have determined intensity parameters Ω t and found that Ω2 = 0, Ω4 = 4.4 × 10-20, and Ω6 = 2.28 × 10-20 cm2. With these values, we have calculated the probabilities of radiative transitions, the branching coefficients, and the lifetimes of the radiative levels 1 D 2 and 3 P 0. The probabilities of multiphonon nonradiative transitions in NYF:Pr3+ crystals have been estimated. Using the method of kinetic spectroscopy with selective excitation, we have investigated the luminescence decay kinetics of praseodymium from the 3 P 0 and 1 D 2 levels upon their selective resonant excitation by nanosecond laser pulses. The inference has been made that Na0.4Y0.6F2.2:Pr3+ crystals are processable; admit doping by praseodymium in high concentrations; and, with respect to all their radiative characteristics, can be potentially considered as active media for

  16. 1.8 μm luminescent properties and energy transfer of Yb{sup 3+}/Tm{sup 3+} co-doped α-NaYF{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhigang [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Xia, Haiping, E-mail: hpxcm@nbu.edu.cn [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Wang, Cheng; Zhang, Zhixiong; Jiang, Dongsheng; Zhang, Jian; He, Shinan; Tang, Qingyang; Sheng, Qiguo; Gu, Xuemei; Zhang, Yuepin [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Chen, Baojiu [Department of Physics, Dalian Maritime University, Dalian, Liaoning Province, 116026 (China); Jiang, Haochuan, E-mail: jianghaochuan@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, The Chinese Academy of Sciences, Ningbo, Zhejiang, 315211 (China)

    2016-09-25

    This paper reports on successful preparation of α-NaYF{sub 4} single crystals co-doped with ∼1.9 mol% Tm{sup 3+} and various concentrations (3.85 mol%, 7.69 mol%, 11.54 mol%, 15.38 mol%) of Yb{sup 3+} by using a flux-Bridgman method. The fluorescence decay curve was measured to investigate the luminescent properties of the Yb{sup 3+}/Tm{sup 3+} co-doped α-NaYF{sub 4}, and the energy transfer process from Yb{sup 3+} to Tm{sup 3+}; the J-O intensity parameters of Tm{sup 3+} were further calculated and analyzed according to the absorption spectra. Results show that, an intense 1.8 μm emission was achieved with Yb{sup 3+} as sensitizer for Tm{sup 3+} in the α-NaYF{sub 4} single crystal under the excitation of 980 nm LD (Laser Diode) because of the strong energy transfer from Yb{sup 3+} to Tm{sup 3+}. The maximum emission intensity at 1.8 μm is obtained at about 15.38 mol% doping concentration of Yb{sup 3+} when the concentration of Tm{sup 3+} ions is fixed at ∼1.90 mol% in the current research. Moreover, the calculated maximum value of emission cross section at 1.8 μm is 1.63 × 10{sup −20} cm{sup 2} for 3.85 mol% Yb{sup 3+}/1.9 mol% Tm{sup 3+} sample, and the obtained energy transfer rate (W{sub ET}) and energy transfer efficiency (η) are 1543 s{sup −1} and 83.8%, respectively. Our analysis of the fluorescence dynamics indicates that electric dipole-dipole interaction is dominant for the energy transfer from Yb{sup 3+} ions to Tm{sup 3+} ions by using Inokuti-Hirayama’s model. - Highlights: • The Tm{sup 3+}/Yb{sup 3+} co-doped α-NaYF{sub 4} single crystals were grown by Bridgman method. • The 1.8 μm emission intensity is obtained at 15.38 mol% Yb{sup 3+}/1.90 mol% Tm{sup 3+} sample. • The maximum value of emission cross section at 1.8 μm is 1.63 × 10{sup −20} cm{sup 2}. • The energy transfer rate is 1543 s{sup −1} and energy transfer efficiency is 83.8%. • The physical mechanism for energy transfer from Yb{sup 3+} to Tm{sup 3+} ions

  17. Growth, structural and spectroscopic properties of Yb{sup 3+}-doped Li{sub 0.75}Gd{sub 0.75}Ba{sub 0.5}(MoO{sub 4}){sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Cortes, A. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, c/ Sor Juana Ines de la Cruz, 3, Cantoblanco, 28049 Madrid (Spain); Cascales, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, c/ Sor Juana Ines de la Cruz, 3, Cantoblanco, 28049 Madrid (Spain)], E-mail: ccascales@icmm.csic.es; Zaldo, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, c/ Sor Juana Ines de la Cruz, 3, Cantoblanco, 28049 Madrid (Spain)], E-mail: cezaldo@icmm.csic.es

    2008-01-15

    Yb-doped Li{sub 0.75}Gd{sub 0.75}Ba{sub 0.5}(MoO{sub 4}){sub 2} crystals were grown in air by the Top Seeded Solution Growth slow cooling method in a Li{sub 2}Mo{sub 2}O{sub 7} flux. The single crystal X-ray diffraction analysis indicates the symmetry of monoclinic space group C2/c (No. 15), with lattice parameters a = 5.2355(3) A, b = 12.7396(8) A, c = 19.1626(11) A, {beta} = 91.170(1) deg., V = 1277.84(13) A{sup 3}, and Z = 8, with one 8f site shared (0.725:0.06:0.215) by Gd{sup 3+}, Yb{sup 3+} and Li{sup +} ions, respectively. The optical absorption and photoluminescence properties are described consistently with the anisotropic character of the monoclinic phase. The relative energies of the Yb{sup 3+} Stark levels have been determined, and in order to make a preliminary evaluation of its laser properties, values of the 300 K absorption and emission cross-sections have been derived.

  18. Airplane dopes and doping

    Science.gov (United States)

    Smith, W H

    1919-01-01

    Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

  19. Growth and spectroscopic properties of Nd{sup 3+}-doped Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Wang [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Department of Physics, Huainan Normal University, Huainan, Anhui 232001 (China); Lin Zhoubin; Zhang Lizhen [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Wang Guofu, E-mail: wgf@ms.fjirsm.ac.cn [Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

    2011-02-10

    Research highlights: > In this paper we grow Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystals by the Czochralski method and study spectroscopic properties of Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal. > We find that Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal has high fluorescence quantum efficiency. > Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal can be considered as a new potential laser gain medium for the diode laser pumping. - Abstract: This paper reports the growth and spectral properties of Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystals. An Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal with dimensions of O20 x 25 mm{sup 3} has been grown by the Czochralski method. The spectroscopic properties of Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The polarized absorption cross-sections of Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal are 4.25 x 10{sup -20} cm{sup 2} with full width at half maximum (FWHM) of 14.6 nm for the {pi}-polarization and 2.87 x 10{sup -20} cm{sup 2} with FWHM of 16.2 nm for the {sigma}-polarization, respectively. The emission cross-sections are 10.0 x 10{sup -20} cm{sup 2} at 1060 nm for {pi}-polarization and 13.6 x 10{sup -20} cm{sup 2} at 1067 nm for {sigma}-polarization, respectively. The fluorescence quantum efficiency has been estimated to be 90.0%. Nd{sup 3+}:Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} crystal may be considered as a potential laser gain medium for the diode laser pumping.

  20. Rose-like I-doped Bi{sub 2}O{sub 2}CO{sub 3} microspheres with enhanced visible light response: DFT calculation, synthesis and photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Zai, Jiantao; Cao, Fenglei; Liang, Na; Yu, Ke; Tian, Yuan; Sun, Huai; Qian, Xuefeng, E-mail: xfqian@sjtu.edu.cn

    2017-01-05

    Highlights: • DFT reveals I{sup −} can partially substitute CO{sub 3}{sup 2−}to narrow the bandgap of Bi{sub 2}O{sub 2}CO{sub 3}. • Sodium citrate play a key role on the formation of rose-like I-doped Bi{sub 2}O{sub 2}CO{sub 3}. • Rose-like I-doped Bi{sub 2}O{sub 2}CO{sub 3} show enhanced visible light response. • The catalyst has enhanced photocatalytic activity to organic and Cr(VI) pollutes. - Abstract: Based on the crystal structure and the DFT calculation of Bi{sub 2}O{sub 2}CO{sub 3}, I{sup −} can partly replace the CO{sub 3}{sup 2−}in Bi{sub 2}O{sub 2}CO{sub 3} to narrow its bandgap and to enhance its visible light absorption. With this in mind, rose-like I-doped Bi{sub 2}O{sub 2}CO{sub 3} microspheres were prepared via a hydrothermal process. This method can also be extended to synthesize rose-like Cl- or Br-doped Bi{sub 2}O{sub 2}CO{sub 3} microspheres. Photoelectrochemical test supports the DFT calculation result that I- doping narrows the bandgap of Bi{sub 2}O{sub 2}CO{sub 3} by forming two intermediate levels in its forbidden band. Further study reveals that I-doped Bi{sub 2}O{sub 2}CO{sub 3} microspheres with optimized composition exhibit the best photocatalytic activity. Rhodamine B can be completely degraded within 6 min and about 90% of Cr(VI) can be reduced after 25 min under the irradiation of visible light (λ > 400 nm).

  1. Luminescence properties of Er3+/Nd3+ co-doped Na5Lu9F32 single crystals for 2.7 μm mid-infrared laser

    Science.gov (United States)

    Tang, Qingyang; Xia, Haiping; Sheng, Qiguo; He, Shinan; Zhang, Jianli; Chen, Baojiu

    2017-10-01

    The enhanced 2.7 μm mid-infrared emission from the Er3+:4I11/2 → 4I13/2 transition with Nd3+ ions as the sensitizer was achieved in the Na5Lu9F32 single crystal which was successfully grown by a Bridgman method. The transmission spectrum was tested and almost no absorption of 2.7 μm band was observed. It was indicated that the content of OH- ion was very low in the crystal and it was beneficial to the 2.7 μm mid-infrared laser output. Intense 2.7 μm emissions were achieved with Nd3+ ions sensitizing Er3+ ions under the 800 nm LD pumping and the energy transfer processes between Er3+ and Nd3+ ions were analyzed. Meanwhile, the greatly decreased near infrared emission at 1.5 μm and green up-conversion emission were obtained. Additionally, the optimized concentration ratio of Er3+ to Nd3+ for efficient 2.7 μm emission was investigated in this work and the maximum emission cross section at 2.7 μm was calculated. The decay curve of 1.5 μm emission could be well fitted by Inokuti-Hirayama expression, which was strongly indicated the dipole-dipole energy transfer from Er3+ to Nd3+ ions. The results showed that Er3+/Nd3+ co-doped Na5Lu9F32 single crystal had potential applications in 2.7 μm mid-infrared laser.

  2. Doped Nanocrystals

    National Research Council Canada - National Science Library

    David J. Norris; Alexander L. Efros; Steven C. Erwin

    2008-01-01

    The critical role that dopants play in semiconductor devices has stimulated research on the properties and the potential applications of semiconductor nanocrystals, or colloidal quantum dots, doped...

  3. Doped to Rare Earth Ions

    African Journals Online (AJOL)

    In the present work, we are interested by studying the spectroscopic properties for optical applications, mainly laser amplification, of MF2 crystals, where M is an alkaline earth (Ba, Sr) or Cadmium (Cd) doped with rare earth ions (Tb3+, Er3+, Ho3+. So far, we present the absorption and emission properties and also the ...

  4. Novel chromium doped perovskites A2ZnTiO6 (A = Pr, Gd): Synthesis, crystal structure and photocatalytic activity under simulated solar light irradiation

    Science.gov (United States)

    Zhu, Hekai; Fang, Minghao; Huang, Zhaohui; Liu, Yan'gai; Chen, Kai; Guan, Ming; Tang, Chao; Zhang, Lina; Wang, Meng

    2017-01-01

    Double perovskite related oxides A2ZnTiO6 (A = Pr, Gd) have been successfully synthesized by solid state reaction and investigated as photocatalysts for the first time. The two layered titanates mainly demonstrate absorbances under UV irradiation, except for several sharp absorption bands above 400 nm for Pr2ZnTiO6. Therefore, a series of photocatalysts by doping A2ZnTiO6 (A = Pr, Gd) with Cr have been developed in the hope to improve their absorption in the visible light region. The successful incorporation of Cr was detected by XRD and XPS, and the prepared samples have also been characteriazed by SEM, UV-vis DRS and PL. The characterization results suggested that Cr was present mainly in the form of Cr3+, with only a small amount of Cr6+ species. It served as an efficient dopant for the extension of visible light absorbance and improved photocatalytic activities under solar light irradiation. For both Pr2ZnTiO6 and Gd2ZnTiO6, the valence band (VB) was composed of hybridized states of the Zn 3d, O 2p and the conduction band (CB) has major contribution from Zn 4s, Ti 3d orbitals. For Cr doped samples, the newly formed spin-polarized valence band in the middle of the band gap that primarily arises from Cr 3d orbitals was responsible for the improved optical and photocatalytic properties.

  5. Two-step two-color recording in a photorefractive praseodymium-doped La3Ga5SiO14 crystal

    DEFF Research Database (Denmark)

    Nikolajsen, T.; Johansen, P.M.; Yue, X.

    1999-01-01

    Two-step two-color recording is demonstrated in a photorefractive La3Ga5SiO14:Pr3+ crystal using cw laser radiation. The 488 nm line from an Ar-ion laser is used for gating and gratings are written using a Ti:sapphire laser operating in the range from 788 to 840 nm. The dependence of holographic ...

  6. Nanocrystal doped matrixes

    Science.gov (United States)

    Parce, J. Wallace; Bernatis, Paul; Dubrow, Robert; Freeman, William P.; Gamoras, Joel; Kan, Shihai; Meisel, Andreas; Qian, Baixin; Whiteford, Jeffery A.; Ziebarth, Jonathan

    2010-01-12

    Matrixes doped with semiconductor nanocrystals are provided. In certain embodiments, the semiconductor nanocrystals have a size and composition such that they absorb or emit light at particular wavelengths. The nanocrystals can comprise ligands that allow for mixing with various matrix materials, including polymers, such that a minimal portion of light is scattered by the matrixes. The matrixes of the present invention can also be utilized in refractive index matching applications. In other embodiments, semiconductor nanocrystals are embedded within matrixes to form a nanocrystal density gradient, thereby creating an effective refractive index gradient. The matrixes of the present invention can also be used as filters and antireflective coatings on optical devices and as down-converting layers. Processes for producing matrixes comprising semiconductor nanocrystals are also provided. Nanostructures having high quantum efficiency, small size, and/or a narrow size distribution are also described, as are methods of producing indium phosphide nanostructures and core-shell nanostructures with Group II-VI shells.

  7. ViFiLite Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ViFiLite is a wireless infrastructure that utilizes the advantages of a V-band technology in supporting data gathering for structural health monitoring as well as...

  8. Skal vi have flere krondyr?

    DEFF Research Database (Denmark)

    Pedersen, Jens Christian

    2008-01-01

    Vi kunne have væsentligt flere krondyr i den danske natur end vi har i øjeblikket. Den primære årsag er jagt. Det viser en ny undersøgelse fra Danmarks Miljøundersøgelser ved Aarhus Universitet. Bestanden af krondyr er ganske vist steget meget siden 1970, men der er både plads og føde til mange...

  9. Rose-like I-doped Bi2O2CO3 microspheres with enhanced visible light response: DFT calculation, synthesis and photocatalytic performance.

    Science.gov (United States)

    Zai, Jiantao; Cao, Fenglei; Liang, Na; Yu, Ke; Tian, Yuan; Sun, Huai; Qian, Xuefeng

    2017-01-05

    Based on the crystal structure and the DFT calculation of Bi2O2CO3, I- can partly replace the CO32-in Bi2O2CO3 to narrow its bandgap and to enhance its visible light absorption. With this in mind, rose-like I-doped Bi2O2CO3 microspheres were prepared via a hydrothermal process. This method can also be extended to synthesize rose-like Cl- or Br-doped Bi2O2CO3 microspheres. Photoelectrochemical test supports the DFT calculation result that I- doping narrows the bandgap of Bi2O2CO3 by forming two intermediate levels in its forbidden band. Further study reveals that I-doped Bi2O2CO3 microspheres with optimized composition exhibit the best photocatalytic activity. Rhodamine B can be completely degraded within 6min and about 90% of Cr(VI) can be reduced after 25min under the irradiation of visible light (λ>400nm). Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Low temperature EPR investigation of Co{sup 2+} ion doped into rutile TiO{sub 2} single crystal: Experiments and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zerentürk, A. [Department of Physics, Marmara University, 34722 Kadıköy, Istanbul (Turkey); Açıkgöz, M., E-mail: muhammed.acikgoz@eng.bau.edu.tr [Bahcesehir University, Faculty of Engineering and Natural Sciences, Besiktas Campus, 34349 Besiktas, Istanbul (Turkey); Kazan, S.; Yıldız, F.; Aktaş, B. [Department of Physics, Gebze Technical University, 41400 Gebze, Kocaeli (Turkey)

    2017-02-01

    In this paper, we present the results of X-band EPR spectra of Co{sup 2+} ion doped rutile (TiO{sub 2}) which is one of the most promising memristor material. We obtained the angular variation of spectra in three mutually perpendicular planes at liquid helium (7–13 K) temperatures. Since the impurity ions have ½ effective spin and 7/2 nuclear spin, a relatively simple spin Hamiltonian containing only electronic Zeeman and hyperfine terms was utilized. Two different methods were used in theoretical analysis. Firstly, a linear regression analysis of spectra based on perturbation theory was studied. However, this approach is not sufficient for analyzing Co{sup +2} spectra and leads to complex eigenvectors for G and A tensors due to large anisotropy of eigenvalues. Therefore, all spectra were analyzed again with exact diagonalization of spin Hamiltonian and the high accuracy eigenvalues and eigenvectors of G and A tensors were obtained by taking into account the effect of small sample misalignment from the exact crystallographic planes due to experimental conditions. Our results show that eigen-axes of g and A tensors are parallel to crystallographic directions. Hence, our EPR experiments proves that Co{sup 2+} ions substitute for Ti{sup 4+} ions in lattice. The obtained principal values of g tensor are g{sub x}=2.110(6), g{sub y}=5.890(2), g{sub z}=3.725(7) and principal values of hyperfine tensor are A{sub x}=42.4, A{sub y}=152.7, A{sub z}=26 (in 10{sup −4}/cm). - Highlights: • X-band EPR spectra of Co{sup 2+} ion doped rutile (TiO{sub 2}) investigated at 7–13 K. • Two different methods were used in theoretical analysis. • The presence of two structurally equivalent centers for Co{sup 2+} ions observed. • It is concluded that impurity ions substitute for Ti{sup 4+} ion.

  11. Conoscopic evidence of the UV light-induced flexoelectric effect in homeotropic layers of nematic liquid crystal doped with azobenzene derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Marinov, Y G; Hadjichristov, G B; Petrov, A G; Sridevi, S; Hiremath, U S; Yelamaggad, C V; Prasad, S K, E-mail: ymarinov@issp.bas.b

    2010-11-01

    A digitalized version of the standard method of conoscopy was employed to register the bend deformation of molecular orientation in homeotropic nematic layers caused by an in-plane applied DC electric field, and influenced by UV light illumination. Two guest-host systems prepared by mixing of a nematic liquid crystal and an azobenzene-containing photochromic liquid crystalline material featuring a longitudinal molecular asymmetry, were studied. Upon continuous UV irradiation, a photo-isomerization of the photochromic molecules occurs resulting in an enhanced flexoelectric response of the guest-host mixtures. The dependence of the photoflexoeffect on the field strength and UV light intensity was also examined.

  12. Bismuth doping effect on the phase-change characteristics of nitrogen-doped GeTe films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ki-Hong [AE group, Corporate Technology Operations SAIT, Samsung Electronics Co. Ltd., Yong-In, 446-712 (Korea, Republic of); Choi, Sang-Jun, E-mail: sangjun5545.choi@samsung.co [System LSI, Samsung Electronics Co. Ltd., Yong-In, 446-712 (Korea, Republic of); Park, Ju-Cheol [Research Institute for Advanced Materials, Seoul National University, Seoul, 151-744 (Korea, Republic of)

    2010-11-01

    The microstructures and electrical properties of 8.4% nitrogen-doped GeTe and GeBi(6 at.%)Te films thermally annealed in N{sub 2} atmosphere were investigated. With the addition of Bi to N-doped GeTe films, the initial crystallization temperature was reduced and crystallization speed slowed. The N-doped GeBiTe films showed a rapid increase in crystallite size compared to the N-doped GeTe films. The formation energy of the nucleus may be lower due to the Bi atoms and the growth speed may be slower.

  13. Giant magneto-optical Kerr rotation, quality factor and figure of merit in cobalt-ferrite magnetic nanoparticles doped in silica matrix as the only defect layer embedded in magnetophotonic crystals

    Science.gov (United States)

    Zamani, Mehdi; Hocini, Abdesselam

    2018-03-01

    In this work, we report on the theoretical study of one-dimensional magnetophotonic crystals (MPC) comprising of periodic dielectric structure Si/SiO and of silica matrix doped with cobalt-ferrite (CoFe2O4) magnetic nanoparticles as the only magnetic defect layer. Such structure can be prepared by sol-gel dip coating method that controls the thickness of each layer with nanometer level, hence, can overcome the problem of integration of the magneto-optical (MO) devices. We have studied the influence of the volume fraction (concentration of magnetic nanoparticles VF%) on the optical (reflectance, transmittance and absorption) and MO (Kerr rotation) responses in reflection-type one-dimensional MPCs. During investigation of the influence of magnetic nanoparticle's concentration, we found that giant Kerr rotations (even ≈135° for VF = 39%) can be obtained accompanied by large reflectance and low amounts for transmittance and absorption. We report on the demonstration of large MO quality factor and figure of merit in cobalt-ferrite magnetic nanoparticles in the infrared regime. Given the large Kerr rotation, high reflectance accompanied by low absorption and nearly zero transmittance of the 1D MPC containing cobalt-ferrite magnetic nanoparticles, large MO Q factor and figure of merit are obtained.

  14. Doping droops.

    Science.gov (United States)

    Chaturvedi, Aditi; Chaturvedi, Harish; Kalra, Juhi; Kalra, Sudhanshu

    2007-01-01

    Drug abuse is a major concern in the athletic world. The misconception among athletes and their coaches is that when an athlete breaks a record it is due to some "magic ingredient" and not because of training, hard work, mental attitude and championship performance. The personal motivation to win in competitive sports has been intensified by national, political, professional and economic incentives. Under this increased pressure athletes have turned to finding this "magic ingredient". Athlete turns to mechanical (exercise, massage), nutritional (vitamins, minerals), pharmacological (medicines) or gene therapies to have an edge over other players. The World Anti-Doping Agency (WADA) has already asked scientists to help find ways to prevent gene therapy from becoming the newest form of doping. The safety of the life of athletes is compromised with all forms of doping techniques, be it a side effect of a drug or a new technique of gene doping.

  15. Multi-minimum adiabatic potential in the single crystal normal spinel ZnAl{sub 2}O{sub 4}, doped by Cu{sup 2+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Shapovalov, V A; Zhitlukhina, E S; Lamonova, K V; Orel, S M; Pashkevich, Yu G [A A Galkin Donetsk Institute for Physics and Engineering of NASU, 83114, Donetsk (Ukraine); Shapovalov, V V; Rafailovich, M [Garcia Center for Polymers at Engineered Interfaces, Department of Materials Science and Engineering, SUNY Stony Brook, NY 11794 (United States); Schwarz, S A [Department of Physics, Queens College of the City University of New York, NY 11367 (United States); Jahoda, R; Reidy, V J, E-mail: lamonova@fti.dn.u [Bronx High School of Science, NY 10468 (United States)

    2010-06-23

    Spectroscopic investigations of a ZnAl{sub 2}O{sub 4} spinel doped with bivalent copper ions of 0.05% concentration have been carried out in the temperature range 4.2-290 K using a 3 cm{sup -1} range electron paramagnetic resonance (EPR) spectrometer having an operational frequency f = (9.241 {+-} 0.001) GHz. The spectrum can be represented as a superposition of two components: a low-temperature (LT) and a high-temperature (HT) one. Redistribution of integrated intensity between HT and LT components of the spectra occurs with temperature change that is typical of systems with multi-minimum adiabatic potential. Spectra observed are explained within the modified theory of crystalline field (MTCF). The electron levels of a Cu{sup 2+} ion placed in an octahedral coordination center with trigonal distortion [CuO{sub 6}]{sup 10-} have been calculated. The influence of possible types of oxygen octahedron distortions and possible displacement of copper ions from the symmetry center on the electron spectrum, as well as the shape of the adiabatic potential, has been analyzed. It is shown that in the low-temperature phase the multiple minima of the adiabatic potential occur due to tetragonal distortions while the depth of a minimum is determined by the degree of trigonal octahedron distortions. Tetragonal distortion values and multi-minimum potential barrier heights have been determined.

  16. Effect of crystallization annealing under loading on the magnetic properties and the structure of a soft magnetic FeSiNbCuB alloy doped with chromium

    Science.gov (United States)

    Ershov, N. V.; Fedorov, V. I.; Chernenkov, Yu. P.; Lukshina, V. A.; Shishkin, D. A.

    2017-09-01

    The changes of quasi-static magnetic hysteresis loops and X-ray diffraction patterns of the Fe73.5Si13.5B9Nb3Cu1 doped to 10 at % chromium instead of iron have been studied to elucidate the influence of the thermomechanical treatment consisting of annealing and cooling of the alloy under the tensile stress (tensile-stress annealing (TSA)) on the magnetic properties and the structure of these alloys. It is shown that the treatment results in the induction of the magnetic anisotropy of the hard axis type at which the magnetization reversal along the direction of applying the external stress during annealing is hampered. The energy of the induced magnetic anisotropy decreases as the chromium content increases. During TSA, the nanocrystal lattices are deformed, and the deformation is retained after cooling. The interplanar spacings increase along the extension direction and decrease in the transverse direction. The deformation anisotropy is observed for crystallographic directions. The anisotropic deformation of the bcc lattice of nanocrystals with high content of the ordered Fe3Si phase characterized by a negative magnetoelastic interaction is the cause of formation of the state with the transverse magnetic anisotropy of the hard axis type.

  17. High frequency transducer for vessel imaging based on lead-free Mn-doped (K0.44Na0.56)NbO3 single crystal

    Science.gov (United States)

    Ma, Jinpeng; Xue, Saidong; Zhao, Xiangyong; Wang, Feifei; Tang, Yanxue; Duan, Zhihua; Wang, Tao; Shi, Wangzhou; Yue, Qingwen; Zhou, Huifang; Luo, Haosu; Fang, Bijun

    2017-08-01

    We report a high frequency ultrasonic transducer up to 50 MHz for vessel imaging based on a lead-free (K0.44Na0.56)NbO3-0.5 mol. % Mn (Mn-KNN) single crystal, which has a high electromechanical coupling coefficient kt of 0.64 and a large thickness frequency constant Nt of 3210 kHz . mm. The Krimholtz, Leedom, and Mattaei (KLM) equivalent circuit model was utilized to simulate and optimize the pulse-echo response combined with PiezoCAD software. Theoretically, a high -6 dB bandwidth of 74.94% was obtained at a center frequency of 50.47 MHz and optimized matching conditions. The experimental results showed a center frequency of 51.8 MHz with a -6 dB bandwidth of 70.2%. The excellent global performance makes this lead-free single-crystal transducer quite potential in an environmentally friendly vessel imaging transducer.

  18. Optical and magnetic spectroscopy of rare-earth-doped yttrium aluminium borate (YAl sub 3 (BO sub 3) sub 4) single crystals

    CERN Document Server

    Watterich, A; Borowiec, M T; Zayarnyuk, T; Szymczak, H; Beregi, E; Kovács, L G

    2003-01-01

    For Ce sup 3 sup + , Er sup 3 sup + and Yb sup 3 sup + ions, electron paramagnetic resonance (EPR) spectra typical for S' = 1/2 ions are measured for YAl sub 3 (BO sub 3) sub 4 (YAB) single crystal. The spectra show axial symmetry indicating that all three dopants replace Y sup 3 sup + at the given dopant concentration. Corresponding g-tilde - and hyperfine A-tilde -tensors are determined. The EPR linewidth of Ce broadens with increasing temperature due to an Orbach relaxation process. Fitting the curve with an exponential, the energy difference is found to be equal to 270 +- 16 cm sup - sup 1. The optical absorption and excitation spectra of Ce in YAB single crystal measured at 300 K are similar to those found for polycrystalline materials. High-resolution polarized emission from the lowest excited to the sup 2 F sub 5 sub / sub 2 ground state, measured at 4.2 K, indicates a splitting of the ground state into three levels. The second level is located 277 +- 18 cm sup - sup 1 above the first one, in excellent...

  19. Vanadium doped Sb{sub 2}Te{sub 3} material with modified crystallization mechanism for phase-change memory application

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Xinglong; Zheng, Yonghui; Zhou, Wangyang [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China); University of the Chinese Academy of Sciences, 100080 Beijing (China); Wu, Liangcai, E-mail: wuliangcai@mail.sim.ac.cn; Cao, Liangliang; Zhu, Min; Rao, Feng; Song, Zhitang; Feng, Songlin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China)

    2015-06-15

    In this paper, V{sub 0.21}Sb{sub 2}Te{sub 3} (VST) has been proposed for phase-change memory applications. With vanadium incorporating, VST has better thermal stability than Sb{sub 2}Te{sub 3} and can maintain in amorphous phase at room temperature. Two resistance steps were observed in temperature dependent resistance measurements. By real-time observing the temperature dependent lattice structure evolution, VST presents as a homogenous phase throughout the whole thermal process. Combining Hall measurement and transmission electron microscopy results, we can ascribe the two resistance steps to the unique crystallization mechanism of VST material. Then, the amorphous thermal stability enhancement can also be rooted in the suppression of the fast growth crystallization mechanism. Furthermore, the applicability of VST is demonstrated by resistance-voltage measurement, and the phase transition of VST can be triggered by a 15 ns electric pulse. In addition, endurance up to 2.7×10{sup 4} cycles makes VST a promising candidate for phase-change memory applications.

  20. Struvite recovery from solution containing phosphate(V and sulphate(VI ions

    Directory of Open Access Journals (Sweden)

    Hutnik Nina

    2015-07-01

    Full Text Available The research results concerning the application of magnesium and ammonium ions for continuous removal of phosphate(V ions from solution containing 1.0 or 0.20 mass% of PO43– and from 0.10 to 0.50 mass% of SO42– are presented. A continuous struvite MgNH4PO4 × 6H2O reaction crystallization process was carried out both under stoichiometric conditions and using 20% excess of magnesium ions. The research was conducted in a DT MSMPR type crystallizer with internal circulation of suspension driven by a propeller stirrer, in constant temperature 298 K. The pH varied from 9 to 11 and mean residence time of suspension in a crystallizer τ varied from 900 to 3600 s. It was concluded, that sulphate(VI ions influenced product quality disadvantageously. Depending on process parameter combinations struvite crystals of mean size from ca. 18 to ca. 44 μm and of moderate homogeneity: CV 7–95% were produced. Presence of sulphate(VI ions favored crystallization of struvite as prismatic crystals, but tubular forms were also identified. The best shaped struvite crystals were produced at relatively low concentration of sulphate(VI ions, pH 9 and for mean residence time of suspension in a crystallizer elongated up to 3600 s.

  1. SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURE ...

    African Journals Online (AJOL)

    Preferred Customer

    The Mo atom in the complex is in octahedral coordination. Thermal stability of the complex has also been studied. KEY WORDS: Molybdenum complex, Hydrazone ligand, Crystal structure, X-ray diffraction, Thermal property. INTRODUCTION. Coordination chemistry of molybdenum(VI) has attracted considerable attention ...

  2. Mild solution-processed metal-doped TiO2 compact layers for hysteresis-less and performance-enhanced perovskite solar cells

    Science.gov (United States)

    Liang, Chao; Li, Pengwei; Zhang, Yiqiang; Gu, Hao; Cai, Qingbin; Liu, Xiaotao; Wang, Jiefei; Wen, Hua; Shao, Guosheng

    2017-12-01

    TiO2 is extensively used as electron-transporting material on perovskite solar cells (PSCs). However, traditional TiO2 processing method needs high annealing temperature (>450 °C) and pure TiO2 suffers from low electrical mobility and poor conductivity. In this study, a general one-pot solution-processed method is devised to grow uniform crystallized metal-doped TiO2 thin film as large as 15 × 15 cm2. The doping process can be controlled effectively via a series of doping precursors from niobium (V), tin (IV), tantalum (V) to tungsten (VI) chloride. As far as we know, this is so far the lowest processing temperature for metal-doped TiO2 compact layers, as low as 70 °C. The overall performance of PSCs employing the metal-doped TiO2 layers is significantly improved in term of hysteresis effect, short circuit current, open-circuit voltage, fill factor, power conversion efficiency, and device stability. With the insertion of metal ions into TiO2 lattice, the corresponding CH3NH3PbI3 PSC leads to a ∼25% improved PCE of over 16% under irradiance of 100 mW cm-2 AM1.5G sunlight, compared with control device. The results indicate that this mild solution-processed metal-doped TiO2 is an effective industry-scale way for fabricating hysteresis-less and high-performance PSCs.

  3. Synthesis and characterization of bis(thiourea)zinc chloride doped with L-arginine

    Energy Technology Data Exchange (ETDEWEB)

    Moitra, Sweta [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Kar, Tanusree, E-mail: mstk@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2009-09-15

    Single crystals of bis(thiourea)zinc chloride (BTZC) doped with basic amino acid L-arginine were grown successfully by slow evaporation method at ambient temperature. The doped crystals are optically better and more transparent than the pure ones having wide transmission spectra lying between 280 and 2000 nm. The comparative study of solubility curve shows a slight reduction in the solubility of the doped crystals. There is a drastic change in morphology due to doping which is also reflected in the X-ray diffraction pattern. The Fourier transform infrared spectroscopy study confirms the incorporation of L-arginine into BTZC crystal, as there is a deepening of the absorption peak at around 3200 cm{sup -1}. The second harmonic generation efficiency of the pure and the doped samples are almost same, which is equivalent to potassium dihydrogen phosphate. The doped crystals are harder than the pure one.

  4. Yb3+-doped KLu(WO4)2, Nb:RbTiOPO4 and KGd(PO3)4 crystals. Growth, characterization and laser operation

    Science.gov (United States)

    Pujol, M. C.; Mateos, X.; Carvajal, J. J.; Solé, R.; Massons, J.; Aguiló, M.; Díaz, F.

    2017-01-01

    Macrodefect-free samples of Yb3+:KLu(WO4)2, Yb3+:Nb:RbTiOPO4 and Yb3+:KGd(PO3)4 laser crystals were grown using the Top Seeded Solution Growth - Slow Cooling technique. Structural and morphological studies related with the three materials were carried out and discussed. The dispersion of the refractive indices was measured and Sellmeier equations were constructed which are valid in the UV-Vis-IR range. The Stark splitting of the two electronic states of trivalent ytterbium was determined and the CW laser generation was demonstrated in these hosts. This paper shows a review of the main results achieved in FiCMA-FiCNA-URV laboratories in relation with these laser materials in the last years.

  5. Enormous enhancements of the Kerr nonlinearity at C-band telecommunication wavelength in an Er{sup 3+}-doped YAG crystal

    Energy Technology Data Exchange (ETDEWEB)

    Hamedi, Hamid Reza, E-mail: hamid.r.hamedi@gmail.com

    2014-06-01

    A novel solid configuration is proposed to achieve a giant Kerr nonlinearity with reduced absorption under conditions of slow light levels. It is shown that an enhanced Kerr nonlinearity accompanied with negligible absorption can be obtained just through the proper tuning of intensity of coherent driving field at C-band telecommunication wavelength which is practical for communication applications. Moreover, the impact of incoherent pump field as well as frequency detuning of coherent field on manipulating the linear and nonlinear optical properties of the yttrium–aluminum-garnet (YAG) crystal medium is discussed. The presented results may be of interest to researchers in the field of all-optical signal processing and solid-state quantum information science.

  6. Condensation of Self-Assembled Lyotropic Chromonic Liquid Crystal Sunset Yellow in Aqueous Solutions Crowded with Polyethylene Glycol and Doped with Salt

    Energy Technology Data Exchange (ETDEWEB)

    Park, Heung-Shik; Kang, Shin-Woong; Tortora, Luana; Kumar, Satyendra; Lavrentovich, Oleg D. (Chonbuk); (Kent)

    2012-10-10

    We use optical and fluorescence microscopy, densitometry, cryo-transmission electron microscopy (cryo-TEM), spectroscopy, and synchrotron X-ray scattering to study the phase behavior of the reversible self-assembled chromonic aggregates of an anionic dye Sunset Yellow (SSY) in aqueous solutions crowded with an electrically neutral polymer polyethylene glycol (PEG) and doped with the salt NaCl. PEG causes the isotropic SSY solutions to condense into a liquid-crystalline region with a high concentration of SSY aggregates, coexisting with a PEG-rich isotropic (I) region. PEG added to the homogeneous nematic (N) phase causes separation into the coexisting N and I domains; the SSY concentration in the N domains is higher than the original concentration of PEG-free N phase. Finally, addition of PEG to the highly concentrated homogeneous N phase causes separation into the coexisting columnar hexagonal (C) phase and I phase. This behavior can be qualitatively explained by the depletion (excluded volume) effects that act at two different levels: at the level of aggregate assembly from monomers and short aggregates and at the level of interaggregate packing. We also show a strong effect of a monovalent salt NaCl on phase diagrams that is different for high and low concentrations of SSY. Upon the addition of salt, dilute I solutions of SSY show appearance of the condensed N domains, but the highly concentrated C phase transforms into a coexisting I and N domains. We suggest that the salt-induced screening of electric charges at the surface of chromonic aggregates leads to two different effects: (a) increase of the scission energy and the contour length of aggregates and (b) decrease of the persistence length of SSY aggregates.

  7. Metal-to-metal charge transfer between dopant and host ions: Photoconductivity of Yb-doped CaF{sub 2} and SrF{sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Barandiarán, Zoila, E-mail: zoila.barandiaran@uam.es; Seijo, Luis [Departamento de Química, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Instituto Universitario de Ciencia de Materiales Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid (Spain)

    2015-10-14

    Dopant-to-host electron transfer is calculated using ab initio wavefunction-based embedded cluster methods for Yb/Ca pairs in CaF{sub 2} and Yb/Sr pairs in SrF{sub 2} crystals to investigate the mechanism of photoconductivity. The results show that, in these crystals, dopant-to-host electron transfer is a two-photon process mediated by the 4f{sup N−1}5d excited states of Y b{sup 2+}: these are reached by the first photon excitation; then, they absorb the second photon, which provokes the Y b{sup 2+} + Ca{sup 2+} (Sr{sup 2+}) → Y b{sup 3+} + Ca{sup +} (Sr{sup +}) electron phototransfer. This mechanism applies to all the observed Y b{sup 2+} 4f–5d absorption bands with the exception of the first one: Electron transfer cannot occur at the first band wavelengths in CaF{sub 2}:Y b{sup 2+} because the Y b{sup 3+}–Ca{sup +} states are not reached by the two-photon absorption. In contrast, Yb-to-host electron transfer is possible in SrF{sub 2}:Y b{sup 2+} at the wavelengths of the first 4f–5d absorption band, but the mechanism is different from that described above: first, the two-photon excitation process occurs within the Y b{sup 2+} active center, then, non-radiative Yb-to-Sr electron transfer can occur. All of these features allow to interpret consistently available photoconductivity experiments in these materials, including the modulation of the photoconductivity by the absorption spectrum, the differences in photoconductivity thresholds observed in both hosts, and the peculiar photosensitivity observed in the SrF{sub 2} host, associated with the lowest 4f–5d band.

  8. Ce-doped titania nanoparticles: The effects of doped amount and calcination temperature on photocatalytic activity

    Science.gov (United States)

    Shi, Jianwen; Zou, Yajun; Ma, Dandan

    2017-01-01

    A series of Ce-doped TiO2 nanoparticles with different doped amount and calcination temperature were prepared by sol-gel method. These obtained samples were characterized with X-ray diffraction (XRD), transmission electron microscope (TEM) and ultraviolet-visible diffuse reflectance spectra (DRS), and their photocatalytic activities were evaluated by the photocatalytic degradation of methyl orange. Results showed that Ce doping inhibits the growth of crystal size and the phase transformation from anatase to rutile, leads to lattice distortion and expansion of TiO2. Furthermore, Ce doping brings the red-shift of absorption profile and the increase of photons absorption in the range of 400-600 nm. Photocatalytic degradation of methyl orange shows that Ce doping improves the photocatalytic activity of TiO2. The optimal doped amount is 0.05 mol% and the optimal calcined temperature is 600 °C for the maximum photocatalytic degradation efficiency in our experiment.

  9. Mechanism of the emergence of the photo-EMF upon silicon liquid crystal-single crystal contact

    Science.gov (United States)

    Budagov, K. M.; Guseinov, A. G.; Pashaev, B. G.

    2017-03-01

    The effect light has on a silicon liquid crystal-single crystal contact at different temperatures of the surface doping of silicon, and when BaTiO3 nanoparticles are added to the composition of a liquid crystal, is studied. The mechanism of the emergence of the photo-EMF in the liquid crystal-silicon structure is explained.

  10. Metal-doped semiconductor nanoparticles and methods of synthesis thereof

    Science.gov (United States)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor); Wang, Wenzhong (Inventor); Dresselhaus, Mildred (Inventor)

    2009-01-01

    The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

  11. Protostars and Planets VI

    Science.gov (United States)

    Beuther, Henrik; Klessen, Ralf S.; Dullemond, Cornelis P.; Henning, Thomas

    star and planet formation. They are used by students to dive into new topics, and they are much valued by experienced researchers as a comprehensive overview of the field with all its interactions. We hope that you will enjoy reading (and learning from) this book as much as we do. The organization of the Protostars and Planets conference was carried out in close collaboration between the Max Planck Institute for Astronomy and the Center for Astronomy of the University Heidelberg, with generous support from the German Science Foundation. This volume is a product of effort and care by many people. First and foremost, we want to acknowledge the 250 contributing authors, as it is only due to their expertise and knowledge that such a comprehensive review compendium in all its depth and breadth is possible. The Protostars and Planets VI conference and this volume was a major undertaking, with support and contributions by many people and institutions. We like to thank the members of the Scientific Advisory Committee who selected the 38 teams and chapters out of more than 120 submitted proposals. Similarly, we are grateful to the reviewers, who provided valuable input and help to the chapter authors. The book would also not have been possible without the great support of Renée Dotson and other staff from USRA’s Lunar and Planetary Institute, who handled the detailed processing of all manuscripts and the production of the book, and of Allyson Carter and other staff from the University of Arizona Press. We are also grateful to Richard Binzel, the General Editor of the Space Science Series, for his constant support during the long process, from the original concept to this final product. Finally, we would like to express a very special thank you to the entire conference local organizing committee, and in particular, Carmen Cuevas and Natali Jurina, for their great commitment to the project and for a very fruitful and enjoyable collaboration.

  12. VI Tallinna arhitektuuritriennaal / Leonhard Lapin

    Index Scriptorium Estoniae

    Lapin, Leonhard, 1947-

    2005-01-01

    15.-17. IX Tallinnas Niguliste kirikus toimuval VI Tallinna arhitektuuritriennaalil esinevad inglise arhitektuurikriitik Peter Davey, šveitsi arhitekt Peter Zumthor, soome arhitekt Juha Leviskä, eesti arhitekt Vilen Künnapu, eesti kunstiajaloolane Juhan Maiste jt. Külastatakse KUMU, tutvutab autor Pekka Vapaavuori

  13. (VI) oxide in acetic acid

    African Journals Online (AJOL)

    The oxidation of cyclohexene by chromium (VI) oxide in aqueous and acetic media was studied. The reaction products were analysed using infra red (IR) and gas chromatography coupled with mass (GC/MS) spectroscopy. The major products of the oxidation reaction in acetic acid medium were cyclohexanol, ...

  14. Study of Crystal Formation and Nitric Oxide (NO) Release Mechanism fromS-Nitroso-N-acetylpenicillamine (SNAP)-Doped CarboSil Polymer Composites for Potential Antimicrobial Applications.

    Science.gov (United States)

    Wo, Yaqi; Li, Zi; Colletta, Alessandro; Wu, Jianfeng; Xi, Chuanwu; Matzger, Adam J; Brisbois, Elizabeth J; Bartlett, Robert H; Meyerhoff, Mark E

    2017-07-15

    Stable and long-term nitric oxide (NO) releasing polymeric materials have many potential biomedical applications. Herein, we report the real-time observation of the crystallization process of the NO donor, S -nitroso- N -acetylpenicillamine (SNAP), within a thermoplastic silicone-polycarbonate-urethane biomedical polymer, CarboSil 20 80A. It is demonstrated that the NO release rate from this composite material is directly correlated with the surface area that the CarboSil polymer film is exposed to when in contact with aqueous solution. The decomposition of SNAP in solution (e.g. PBS, ethanol, THF, etc.) is a pseudo-first-order reaction proportional to the SNAP concentration. Further, catheters fabricated with this novel NO releasing composite material are shown to exhibit significant effects on preventing biofilm formation on catheter surface by Pseudomonas aeruginosa and Proteus mirabilis grown in CDC bioreactor over 14 days, with a 2 and 3 log-unit reduction in number of live bacteria on their surfaces, respectively. Therefore, the SNAP-CarboSil composite is a promising new material to develop antimicrobial catheters, as well as other biomedical devices.

  15. MICROWAVE DIELECTRIC PROPERTIES AND CRYSTAL STRUCTURE OF CeO₂ DOPED (Na1/2Nd1/2TiO₃ CERAMICS

    Directory of Open Access Journals (Sweden)

    Bin Tang

    2017-09-01

    Full Text Available The crystal structures and microwave dielectric properties of (Na1/2Nd1/2TiO₃ (NNT ceramics with x wt. % CeO₂ dopants (x = 0, 0.15, 0.3, 0.45 were investigated in this paper. X-ray diffraction (XRD results showed that all the samples fitted well with a single perovskite structure phase in a Pm-3m space group. The lattice parameters increased because of the replacement of Ce4+ at the B-site. The change of dielectric constant (εr was similar to that of ionic polarizabilities. The temperature coefficient of resonant frequency (τf value of samples displayed a decreasing tendency with increasing x. The quality factor (Qxf was found to have a maximum value of 8287 GHz at x = 0.3. As a result, when x = 0.3, the (Na1/2Nd1/2TiO₃ ceramics sintered at 1300 °C for 2 h has good microwave dielectric properties of εr = 105.36, high Qxf = 8287 GHz, and τf = 246.3 ppm/ °C.

  16. Crystal structure, magnetic and magnetocaloric properties of aluminum-doped La{sub 0.6}Sr{sub 0.4}MnO{sub 3} perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Elhamza, Amal; Dhahri, J. [Universite de Monastir, Laboratoire de la Matiere Condensee et des Nanosciences, Monastir (Tunisia); Rhouma, F.I.H. [Centre de Recherche des Sciences et Technologies de l' Energie, Laboratoire de Photovoltaique de Semi-Conducteurs et de Nanostructures, Hammam-Lif (Tunisia); Hlil, E.K. [CNRS-Universite Joseph Fourier, Institut Neel, Grenoble (France)

    2017-05-15

    In this paper, we report on the structural, magnetic and magnetocaloric properties of a series of nanocrystallines La{sub 0.6}Sr{sub 0.4}Mn{sub 1-x}Al{sub x}O{sub 3} (0 ≤ x ≤ 0.2) which were prepared by the sol-gel method. The X-ray powder diffraction showed that all our synthesized samples were of a single phase and have crystallized in the hexagonal symmetry with R anti 3c space group. Magnetic measurements showed that the sample exhibits a ferromagnetic-to-paramagnetic phase transition at a Curie temperature close to 206 K. The maximum value of the magnetic entropy change vertical stroke ΔS{sub M}{sup max} vertical stroke was found to be 1.09 J kg{sup -1} K{sup -1} for an applied magnetic field of 5T. At this value of magnetic field, the relative cooling power was 141 J kg{sup -1}. Our result on magnetocaloric properties suggests that La{sub 0.6}Sr{sub 0.4}Mn{sub 1-x}Al{sub x}O{sub 3} nanopowder with (0 ≤ x ≤ 0.2) is attractive as a potential refrigerant for high-temperature magnetic refrigeration. (orig.)

  17. Six-fold Coordinated Carbon Dioxide VI

    Energy Technology Data Exchange (ETDEWEB)

    Iota, V; Yoo, C; Klepeis, J; Jenei, Z

    2006-03-01

    Under standard conditions, carbon dioxide (CO{sub 2}) is a simple molecular gas and an important atmospheric constituent while silicon dioxide (SiO{sub 2}) is a covalent solid, and represents one of the fundamental minerals of the planet. The remarkable dissimilarity between these two group IV oxides is diminished at higher pressures and temperatures as CO{sub 2} transforms to a series of solid phases, from simple molecular to a fully covalent extended-solid V, structurally analogous to SiO{sub 2} tridymite. Here, we present the discovery of a new extended-solid phase of carbon dioxide (CO{sub 2}): a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO{sub 2}-II above 50GPa at 530-650K. Together with the previously reported CO{sub 2}-V and a-carbonia, this new extended phase indicates a fundamental similarity between CO{sub 2}--a prototypical molecular solid, and SiO{sub 2}--one of Earth's fundamental building blocks. The phase diagram suggests a limited stability domain for molecular CO{sub 2}-I, and proposes that the conversion to extended-network solids above 40-50 GPa occurs via intermediate phases II, III, and IV. The crystal structure of phase VI suggests strong disorder along the caxis in stishovite-like P4{sub 2}/mnm, with carbon atoms manifesting an average six-fold coordination within the framework of sp{sup 3} hybridization.

  18. 29 CFR 1926.1126 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Chromium (VI). 1926.1126 Section 1926.1126 Labor... Chromium (VI). (a) Scope. (1) This standard applies to occupational exposures to chromium (VI) in all forms... objective data demonstrating that a material containing chromium or a specific process, operation, or...

  19. 29 CFR 1915.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false Chromium (VI). 1915.1026 Section 1915.1026 Labor... § 1915.1026 Chromium (VI). (a) Scope. (1) This standard applies to occupational exposures to chromium (VI... cement; or (4) Where the employer has objective data demonstrating that a material containing chromium or...

  20. Luminescence quenching and scintillation response in the Ce3+ doped GdxY3-xAl5O12 (x = 0.75, 1, 1.25, 1.5, 1.75, 2) single crystals

    Science.gov (United States)

    Bartosiewicz, K.; Babin, V.; Kamada, K.; Yoshikawa, A.; Mares, J. A.; Beitlerova, A.; Nikl, M.

    2017-01-01

    The luminescence and scintillation properties of the gadolinium yttrium aluminium garnets, (Gd,Y)3Al5O12 doped with Ce3+ are investigated as a function of the Gd/Y ratio with the aim of an improved understanding of the luminescence quenching, energy transfer and phase stability in these materials. An increase of both crystal field strength and instability of the garnet phase with increasing content of Gd3+ is observed. The instability of the garnet phase results in an appearance of the perovskite phase inclusions incorporated into the garnet phase. The luminescence features of Ce3+ in the perovskite phase inclusions and in the main garnet phase are studied separately. The thermal quenching of the 5 d → 4f emission of Ce3+ in the latter phase is determined by temperature dependence of the photoluminescence decay time. The results show that the onset of the thermal quenching is moved to lower temperatures with increasing gadolinium content. The measurements of temperature dependence of delayed radiative recombination do not reveal a clear evidence that the thermal quenching is caused by thermally induced ionization of the Ce3+ 5d1 excited state. Therefore, the main mechanism responsible for the luminescence quenching is due to the non-radiative relaxation from 5d1 excited state to 4f ground state of Ce3+. The energy transfer processes between Gd3+ and Ce3+ as well as between perovskite and garnet phases are evidenced by the photoluminescence excitation and emission spectra as well as decay kinetic measurements. Thermally stimulated luminescence (TSL) studies in the temperature range 77-497 K and scintillation decays under γ excitation complete the material characterization.