Sample records for 2sesub 4sub 4sesub

  1. Thermodynamic Model for the Solubility of Ba(SeO4sub>, SO4sub>) Precipitates

    SciTech Connect

    Rai, D.; Felmy, Andrew R.; Moore, Dean A.; Kitamura, Akira; Yoshikawa, Hideki; Doi, Reisuke; Yoshida, Yasushi


    The solubility of Ba(SeO4sub>, SO4sub>) precipitates was determined as a function of the BaSeO4sub> mole fractions, ranging from 0.0015 to 0.3830, and time with an equilibration period extending to as long as 302 days. Equilibrium/steady state conditions in this system are reached in ≤ 65 days. Pitzer’s ion interaction model was used to calculate solid and aqueous phase activity coefficients. Thermodynamic analyses showed that the data do not satisfy Gibbs-Duhem equation, thereby demonstrating that a single-solid solution phase does not control both the selenate and sulfate concentrations. Our extensive data with log 10 [Ba] ranging from -3.6 to -5.9 mol kg-1, log 10 [SeO4sub>] rangingfrom-3.6 to -5.2 mol kg-1, and log 10 [SO4sub>] ranging from-4.0 to -5.3 mol kg-1 can be explained with the formation of an ideal BaSeO4sub> solid solution phase that controls the selenium concentrations and a slightly disordered/less-crystalline BaSO4sub>(s) (log 10Κ°sp = -9.5 instead of -10.05 for barite) that controls the sulfate concentrations. In these experiments the BaSO4sub> component of the solid solution phase never reaches thermodynamic equilibrium with the aqueous phase. Thermodynamic interpretations of the data show that both the ideal BaSeO4sub> solid solution phase and less-crystalline BaSO4sub> (s) phase are in equilibrium with each other in the entire range of BaSeO4sub> mole fractions investigated in this study.

  2. Solvate Structures and Computational/Spectroscopic Characterization of LiBF4sub> Electrolytes

    SciTech Connect

    Seo, D. M.; Boyle, Paul D.; Allen, Joshua L.; Han, Sang D.; Jonsson, Erlendur; Johansson, Patrik; Henderson, Wesley A.


    Crystal structures have been determined for both LiBF4sub> and HBF4sub> solvates—(acetonitrile)2:LiBF4sub>, (ethylene glycol diethyl ether)1:LiBF4sub>, (diethylene glycol diethyl ether)1:LiBF4sub>, (tetrahydrofuran)1:LiBF4, (methyl methoxyacetate)1:LiBF4sub>, (suc-cinonitrile)1:LiBF4sub>, (N,N,N',N",N"-pentamethyldiethylenetriamine)1:HBF4sub>, (N,N,N',N'-tetramethylethylenediamine)3/2:HBF4sub> and (phenanthroline)2:HBF4sub>. These, as well as other known LiBF4sub> solvate structures, have been characterized by Raman vibrational spectroscopy to unambiguously assign the anion Raman band positions to specific forms of BF4sub>-...Li+ cation coordination. In addition, complementary DFT calculations of BF4sub>-...Li+ cation complexes have provided additional insight into the challenges associated with accurately interpreting the anion interactions from experimental Raman spectra. This information provides a crucial tool for the characterization of the ionic association interactions within electrolytes.

  3. Solution-processable glass LiI-Li4sub>SnS4sub> superionic conductors for all-solid-state Li-ion batteries

    SciTech Connect

    Kern Ho Park; Oh, Dae Yang; Choi, Young Eun; Nam, Young Jin; Han, Lili; Kim, Ju -Young; Xin, Huolin; Lin, Feng; Oh, Seung M.; Jung, Yoon Seok


    The new, highly conductive (4.1 × 10–4 S cm–1 at 30 °C), highly deformable, and dry-air-stable glass 0.4LiI-0.6Li4sub>SnS4sub> is prepared using a homogeneous methanol solution. Furthermore, the solution process enables the wetting of any exposed surface of the active materials with highly conductive solidified electrolytes (0.4LiI-0.6Li4sub>SnS4sub>), resulting in considerable improvements in electrochemical performances of these electrodes over conventional mixture electrodes.

  4. U(v) in metal uranates: A combined experimental and theoretical study of MgUO4sub>, CrUO4sub>, and FeUO4sub>

    SciTech Connect

    Guo, Xiaofeng; Tiferet, Eitan; Qi, Liang; Solomon, Jonathan M.; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H.; Kukkadapu, Ravi K.; Wu, Di; Ilton, Eugene S.; Asta, Mark; Sutton, Stephen R.; Xu, Hongwu; Navrotsky, Alexandra


    Although pentavalent uranium can exist in aqueous solution, its presence in the solid state is uncommon. Metal monouranates, MgUO4sub>, CrUO4sub> and FeUO4sub> were synthesized for detailed structural and energetic investigations. Structural characteristics of these uranates used powder X-ray diffraction, synchrotron X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and 57Fe-Mossbauer spectroscopy. Enthalpies of formation were measured by high temperature oxide melt solution calorimetry. Density functional theory (DFT) calculations provided both structural and energetic information. The measured structural and thermodynamic properties show good consistency with those predicted from DFT. The presence of U5+ has been solidly confirmed in CrUO4sub> and FeUO4sub>, which are thermodynamically stable compounds, and the origin and stability of U5+ in the system was elaborated by DFT. Lastly, the structural and thermodynamic behaviour of U5+ elucidated in this work is relevant to fundamental actinide redox chemistry and to applications in the nuclear industry and radioactive waste disposal.

  5. The novel phase transition of NaBi(WO{sub 4}){sub 2} under high pressure

    SciTech Connect

    Ma, Chunli; Cui, Hang; Li, Fangfei; Wang, Jingshu; Wu, Xiaoxin; Zhang, Jian; Zhou, Qiang; Liu, Jinghe; Cui, Qiliang


    The Raman and synchrotron angle-dispersive X-ray diffraction studies have been performed on NaBi(WO{sub 4}){sub 2} under high pressure up to 30.7 and 36.2 GPa, respectively, at room temperature. With pressure increases to ∼7.0 GPa, the structure of NaBi(WO{sub 4}){sub 2} begins to transform from tetragonal (I4{sub 1}/a) into monoclinic (P2/m), and the phase transition completes around 13 GPa. With pressure higher than 29.0 GPa, the NaBi(WO{sub 4}){sub 2} turns into amorphous state. The random arrangement of Na{sup +} and Bi{sup 3+} in short-range ordered scheelite NaBi(WO{sub 4}){sub 2} results in the tetragonal to monoclinic phase transition, which is different from that observed in AWO{sub 4} tungstates and AMoO{sub 4} molybdates (A=Ca, Sr, Ba, Pb, Eu, Cd). - Graphical abstract: The NaBi(WO{sub 4}){sub 2} transforms from tetragonal into monoclinic, which starts around 7 GPa and completes at about 13 GPa. With pressure higher than 29 GPa, the NaBi(WO{sub 4}){sub 2} turns into amorphous state. Highlights: ► Raman and X-ray diffraction studies performed on NaBi(WO{sub 4}){sub 2} up to 30.7 and 36.2 GPa, respectively. ► The tetragonal (I4{sub 1}/a) into monoclinic (P2/m) phase transition is determined. ► With pressure higher than 29 GPa, the NaBi(WO{sub 4}){sub 2} ultimately turns into amorphous state. ► The ambient pressure bulk modulus and volume of tetragonal and monoclinic phases are obtained.

  6. Aqueous Sulfate Separation by Sequestration of [(SO4sub>)2(H2O)4sub>]4sub> Clusters within Highly Insoluble Imine-Linked Bis-Guanidinium Crystals

    SciTech Connect

    Custelcean, Radu; Williams, Neil J.; Seipp, Charles A.; Ivanov, Aleksandr; Bryantsev, Vyacheslav


    Quantitative removal of sulfate from seawater was achieved by selective crystallization of the anion with a bis(guanidinium) ligand self-assembled in situ through imine condensation of simple components. The resulting crystalline salt has an exceptionally low aqueous solubility, on a par with BaSO4sub>. Single-crystal X-ray diffraction analysis revealed pairs of sulfate anions clustered together with four water molecules within the crystals.

  7. Native defects in Tl6SI4sub>: Density functional calculations

    SciTech Connect

    Shi, Hongliang; Du, Mao -Hua


    In this study, Tl6SI4sub> is a promising room-temperature semiconductor radiation detection material. Here, we report density functional calculations of native defects and dielectric properties of Tl6SI4sub>. Formation energies and defect levels of native point defects and defect complexes are calculated. Donor-acceptor defect complexes are shown to be abundant in Tl6SI4sub>. High resistivity can be obtained by Fermi level pinning by native donor and acceptor defects. Deep donors that are detrimental to electron transport are identified and methods to mitigate such problem are discussed. Furthermore, we show that mixed ionic-covalent character of Tl6SI4sub> gives rise to enhanced Born effective charges and large static dielectric constant, which provides effective screening of charged defects and impurities.

  8. Origin of modulated phases and magnetic hysteresis in TmB4sub>

    SciTech Connect

    Wierschem, Keola; Sunku, Sai Swaroop; Kong, Tai; Ito, Toshimitsu; Canfield, Paul C.; Panagopoulos, Christos; Sengupta, Pinaki


    In this study, we investigate the low-temperature magnetic phases in TmB4sub>, a metallic quantum magnet on the geometrically frustrated Shastry-Sutherland lattice, using coordinated experimental and theoretical studies. Our results provide an explanation for the appearance of the intriguing fractional plateau in TmB4sub> and accompanying magnetic hysteresis. Together with observation of the bump in the half plateau, our results support the picture that the magnetization plateau structure in TmB4sub> is strongly influenced by the zero-field modulated phases. We present a phenomenological model to explain the appearance of the modulated phases and a microscopic Hamiltonian that captures the complete magnetic behavior of TmB4sub>.

  9. The hydrogen permeability of Pd4sub>S

    SciTech Connect

    O’Brien, Casey P.; Gellman, Andrew J.; Morreale, Bryan D.; Miller, James B.


    Hydrogen permeates rapidly through pure Pd membranes, but H2S, a common minor component in hydrogencontaining streams, produces a Pd4sub>S film on the Pd surface that severely retards hydrogen permeation. Hydrogen still permeates through the bi-layered Pd4sub>S/Pd structure, indicating that the Pd4sub>S surface is active for H2 dissociation; the low hydrogen permeability of the Pd4sub>S film is responsible for the decreased rate of hydrogen transport. In this work, the hydrogen permeability of Pd4sub>S was determined experimentally in the 623-773 K temperature range. Bi-layered Pd4sub>S/Pd foils were produced by exposing pure Pd foils to H2S. H2 fluxes through the bi-layered Pd4sub>S/Pd foils were measured during exposure to both pure H2 and a 1000 ppm H2S in H2 gas mixture. Our results show that H2S slows hydrogen permeation through Pd mainly by producing a Pd4S film on the Pd surface that is roughly an order-of-magnitude less permeable to hydrogen (kPd4S = 10-7.5 exp(-0.22 eV/kBT)molH2/m/s/Pa-1/2) than pure Pd. The presence of H2S in the gas stream results in greater inhibition of hydrogen transport than can be explained by the very low permeability of Pd4sub>S. H2S may block H2 dissociation sites at the Pd4sub>S surface.

  10. The role of carbonic anhydrase in C4sub> photosynthesis

    SciTech Connect

    Studer, Anthony


    Current pressures on the global food supply have accelerated the urgency for a second green revolution using novel and sustainable approaches to increase crop yield and efficiency. This proposal outlines experiments to address fundamental questions regarding the biology of C4sub> photosynthesis, the method of carbon fixation utilized by the most productive food, feed and bioenergy crops. Carbonic anhydrase (CA) has been implicated in multiple cellular functions including nitrogen metabolism, water use efficiency, and photosynthesis. CA catalyzes the first dedicated step in C4sub> photosynthesis, the hydration of CO2 into bicarbonate, and is potentially rate limiting in C4sub> grasses. Using insertional mutagenesis, we have generated CA mutants in maize, and propose the characterization of these mutants using phenotypic, physiological, and transcriptomic profiling to assay the plant’s response to altered CA activity. In addition, florescent protein tagging experiments will be employed to study the subcellular localization of CA paralogs, providing critical data for modeling carbon fixation in C4sub> plants. Finally, I propose parallel experiments in Setaria viridis to explore its relevance as model C4sub> grass. Using a multifaceted approach, this proposal addresses important questions in basic biology, as well as the need for translation research in response to looming global food challenges.

  11. Investigations On Stoichiometry And Melting Behavior Of NaY(WO{sub 4}){sub 2}

    SciTech Connect

    Salunke, R. G.; Gosavi, S. W.; Singh, S. G.; Singh, A. K.; Desai, D. G.; Chauhan, A. K.; Gadkari, S. C.


    Differential thermal analysis (DTA) and X-ray diffraction (XRD) studies were carried out to understand the melting behavior of the NaY(WO{sub 4}){sub 2}, an important functional material used for the laser production. It has been observed that the stoichiometric NaY(WO{sub 4}){sub 2} composition forms a solution with another phase of the Na{sub 2}WO{sub 4}-Y{sub 2}(WO{sub 4}){sub 3} pseudo-binary system. This is found to be detrimental for the growth of single crystals of the material. Therefore, molar fraction in the starting charge was suitably altered to successfully restrict the formation of the undesired phase in the melt. A composition is suggested for the favorable crystal growth of this material.

  12. Integrated Data Collection Analysis (IDCA) Program - KClO4sub>/Aluminum Mixture

    SciTech Connect

    Sandstrom, Mary M.; Brown, Geoffrey W.; Preston, Daniel N.; Pollard, Colin J.; Warner, Kirstin F.; Sorensen, Daniel N.; Remmers, Daniel L.; Whinnery, LeRoy L.; Shelley, Timothy J.; Reyes, Jose A.; Hsu, Peter C.; Reynolds, John G.


    The Integrated Data Collection Analysis (IDCA) program is conducting a Proficiency Test for Small-Scale Safety and Thermal (SSST) testing of homemade explosives (HMEs). Described here are the results for impact, friction, electrostatic discharge, and differential scanning calorimetry analysis of a mixture of KClO4sub> and aluminum—KClO4sub>/Al mixture. This material was selected because of the challenge of performing SSST testing of a mixture of two solids. The mixture was found to be: 1) much less sensitive to impact than RDX, (LLNL being the exception) and PETN, 2) more sensitive to friction than RDX and PETN, and 3) extremely sensitive to spark. The thermal analysis showed little or no exothermic character. One prominent endothermic feature was observed in the temperature range studied and identified as a phase transition of KClO4sub>.

  13. Magnetic moment of the 4/sub 1//sup +/ state in /sup 20/Ne

    SciTech Connect

    Bright, T.; Ballon, D.; Saxena, R.J.; Niv, Y.; Benczer-Koller, a.N.


    The magnetic moment of the 4/sub 1//sup +/ state in /sup 20/Ne was measured by the transient field technique, and the transient field was calibrated in a simultaneous measurement on the 2/sub 1//sup +/ state. The resulting g(4/sub 1//sup +/) = 0.49 +- 0.34 is in agreement with the shell model description of /sup 20/Ne. The magnitude of the transient field measured in previous experiments on O, Ne, and Mg ions traversing iron foils was reexamined and appears to be in good agreement with the results of this experiment.

  14. Novel Solution Process for Fabricating Ultra-Thin-Film Absorber Layers in Fe2SiS4sub> and Fe2GeS4sub> Photovoltaics

    SciTech Connect

    Orefuwa, Samuel A.; Lai, Cheng-Yu; Dobson, Kevin D.; Ni, Chaoying; Radu, Daniela R.


    Fe2SiS4sub> and Fe2GeS4sub> crystalline materials posses direct bandgaps of ~1.55 and ~1.4 eV respectively and an absorption coefficient larger than 10^5 cm–1; their theoretical potential as solar photovoltaic absorbers has been demonstrated. However, no solar devices that employ either Fe2SiS4sub> or Fe2GeS4sub> have been reported to date. In the presented work, nanoprecursors to Fe2SiS4sub> and Fe2GeS4sub> have been fabricated and employed to build ultra-thin-film layers via spray coating and rod coating methods. Temperature-dependent X-Ray diffraction analyses of nanoprecursors coatings show an unprecedented low temperature for forming crystalline Fe2SiS4sub> and Fe2GeS4sub>. Fabricating of ultra-thin-film photovoltaic devices utilizing Fe2SiS4sub> and Fe2GeS4sub> as solar absorber material is presented.

  15. Negative thermal expansion in Th{sub 2}O(PO{sub 4}){sub 2}

    SciTech Connect

    Wallez, Gilles; Clavier, Nicolas; Dacheux, Nicolas


    Highlights: {yields} Dithorium oxide phosphate shows a continuous negative thermal expansion over a 600 {sup o}C range. {yields} Negative expansion arises from oxygen rocking and cations repulsions. {yields} Big and high-charge thorium IV appears ideal for generating negative expansion. -- Abstract: High temperature X ray diffraction performed on recently discovered orthorhombic Th{sub 2}O(PO{sub 4}){sub 2} shows a continuous linear thermal contraction (-1.6 x 10{sup -6} {sup o}C{sup -1}) in 20-600 {sup o}C range and a near-zero expansion at higher temperatures resulting from a dual structural deformation involving oxygen oscillations and inter-cations repulsions. Although similar mechanisms were observed in isotypic Zr{sub 2}O(PO{sub 4}){sub 2} (+1.5 x 10{sup -6} {sup o}C{sup -1}) and U{sub 2}O(PO{sub 4}){sub 2} (-1.4 x 10{sup -6} {sup o}C{sup -1}), those observed in Th{sub 2}O(PO{sub 4}){sub 2} are particularly intense because of the high ionic radius of tetravalent thorium.

  16. The superionic phase transitions in (NH{sub 4}){sub 3}H(SeO{sub 4}){sub 2} under hydrostatic pressure up to 400 MPa

    SciTech Connect

    Lindner, Ł.; Zdanowska-Frączek, M. Pawłowski, A.; Frączek, Z. J.


    The effect of hydrostatic pressure on proton conductivity of (NH{sub 4}){sub 3}H(SeO{sub 4}){sub 2} superionic crystal was studied in a wide temperature range and different isobaric conditions by means of impedance spectroscopy method. The measurements were performed along the trigonal c axis of the crystal, i.e., along the direction perpendicular to the plane in which, in the superionic phases, a dynamically disordered H-bond network is formed. The obtained pressure-temperature phase diagram is linear with increasing pressure. The triple point, which is the point of coexistence of the three phases: ferroelastic phase IV, ferroelastic phase III, and superionic phase II was found at p = 116.3 MPa and T = 287.3 K. High pressure leads to increase in the temperature range of stability of both superionic phases and to a drastic decrease in the temperature width of the ferroelastic phase III. With increasing pressure, the range of the superionic phase II expands at the expense of the range of the ferroelastic phase III, which is unstable and vanishes at the triple point.

  17. The crystal structure of Yb{sub 2}(SO{sub 4}){sub 3}.3H{sub 2}O and its decomposition product, {beta}-Yb{sub 2}(SO{sub 4}){sub 3}

    SciTech Connect

    Mills, Stuart J.; Petricek, Vaclav; Kampf, Anthony R.; Herbst-Imer, Regine; Raudsepp, Mati


    Yb{sub 2}(SO{sub 4}){sub 3}.3H{sub 2}O, synthesised by hydrothermal methods at 220(2) deg. C, has been investigated by single crystal X-ray diffraction. Yb{sub 2}(SO{sub 4}){sub 3}.3H{sub 2}O crystallises in space group Cmc2{sub 1} and is isostructural with Lu{sub 2}(SO{sub 4}){sub 3}.3H{sub 2}O. The crystal structure has been refined to R{sub 1}=0.0145 for 3412 reflections [F{sub o}>3{sigma}(F)], and 0.0150 for all 3472 reflections. The structure of Yb{sub 2}(SO{sub 4}){sub 3}.3H{sub 2}O is a complex framework of YbO{sub 6} octahedra, YbO{sub 8} and YbO{sub 5}(H{sub 2}O){sub 3} polyhedra and SO{sub 4} tetrahedra. Thermal data shows that Yb{sub 2}(SO{sub 4}){sub 3}.3H{sub 2}O decomposes between 120 and 190 deg. C to form {beta}-Yb{sub 2}(SO{sub 4}){sub 3}. The structure of a twinned crystal of {beta}-Yb{sub 2}(SO{sub 4}){sub 3} was solved and refined using an amplimode refinement in R3c with an R{sub 1}=0.0755 for 8944 reflections [F{sub o}>3{sigma}(F)], and 0.1483 for all 16,361 reflections. {beta}-Yb{sub 2}(SO{sub 4}){sub 3} has a unique structural topology based on a 3D network of pinwheels. - Graphical abstract: Octahedral-tetrahedral linkages found in Y{sub 2}(SO{sub 4}){sub 3} [and Er{sub 2}(SO{sub 4}){sub 3}] and ss-Yb{sub 2}(SO{sub 4}){sub 3}. Highlights: > The crystal structure and decomposition reactions of Yb{sub 2}(SO{sub 4}){sub 3}.3H{sub 2}O. > The crystal structure of a twinned crystal of {beta}-Yb{sub 2}(SO{sub 4}){sub 3}. > Comparison of the structures of {beta}-Yb{sub 2}(SO{sub 4}){sub 3} and Y{sub 2}(SO{sub 4}){sub 3}.

  18. Shape resonances in the photoionization of CF4sub>

    SciTech Connect

    Stephens, J. A.; Dill, Dan; Dehmer, Joseph L.


    Calculations of photoionization cross sections and photoelectron angular distributions have been performed for all occupied orbitals of CF4sub> using the multiple-scattering model. Results are compared with very recent experiments which employ synchrotron radiation to measure these quantities, namely the measurements of Truesdale e t a l. for the carbonK shell, and measurements of Carlson e t a l. and Novak e t a l. for the five outermost valence levels. The calculations predict intense shape resonances below 3 eV in continua of a1 and t2 final state symmetry. Qualitative agreement is attained on comparing much of the theory with experiment, notably the five outer valence levels, which serves to establish a one-electron picture of the photoionization dynamics of CF4sub>.

  19. Sub-nanosecond Yb:KLu(WO4sub>)2 microchip laser.


    Loiko, P; Serres, J M; Mateos, X; Yumashev, K; Yasukevich, A; Petrov, V; Griebner, U; Aguiló, M; Díaz, F


    A diode-pumped Yb:KLu(WO4sub>)2 microchip laser passively Q-switched by a Cr4+:YAG saturable absorber generated a maximum average output power of 590 mW at 1031 nm with a slope efficiency of 55%. The pulse characteristics were 690 ps/47.6 μJ at a pulse repetition frequency of 12.4 kHz. The output beam had an excellent circular profile with M2<1.05. Yb:KLu(WO4sub>)2 is very promising for ultrathin sub-ns microchip lasers. PMID:27244429

  20. Thermal decomposition behavior of the rare-earth ammonium sulfate R{sub 2}(SO{sub 4}){sub 3}.(NH{sub 4}){sub 2}SO{sub 4}

    SciTech Connect

    Nagai, Tsukasa; Tamura, Shinji; Imanaka, Nobuhito


    Rare-earth ammonium sulfate octahydrates of R{sub 2}(SO{sub 4}){sub 3}.(NH{sub 4}){sub 2}SO{sub 4}.8H{sub 2}O (R=Pr, Nd, Sm, and Eu) were synthesized by a wet process, and the stable temperature region for the anhydrous R{sub 2}(SO{sub 4}){sub 3}.(NH{sub 4}){sub 2}SO{sub 4} form was clarified by thermogravimetry/differential thermal analysis, infrared, Raman, and electrical conductivity measurements. Detailed characterization of these double salts demonstrated that the thermal stability of anhydrous R{sub 2}(SO{sub 4}){sub 3}.(NH{sub 4}){sub 2}SO{sub 4} is different between the Pr, Nd salts and the Sm, Eu salts, and the thermal decomposition behavior of these salts was quite different from the previous reports. - Graphical abstract: Stable temperature range of anhydrous rare-earth ammonium sulfate R{sub 2}(SO{sub 4}){sub 3}.(NH{sub 4}){sub 2}SO{sub 4} was clarified by thermogravimetry/differential thermal analysis, infrared, Raman, and electrical conductivity measurements. Since the previous reports were based only on thermal analysis, the present work has more accurately determined the exact thermal stability of rare-earth ammonium sulfate solids.

  1. Crystal Chemistry of Electrochemically and Chemically Lithiated Layered αI-LiVOPO4sub>

    SciTech Connect

    He, Guang; Bridges, Craig A.; Manthiram, Arumugam


    LiVOPO4sub> is an attractive cathode for lithium-ion batteries with a high operating voltage and the potential to achieve the reversible insertion of two lithium ions between VOPO4sub> and Li2VOPO4sub>. Among the three known forms of LiVOPO4sub> (α, β, and αI), the αI-LiVOPO4sub> has a layered structure that could promote better ionic mobility and reversibility than others. However, a comprehensive study of its lithiated product is not available as αI-LiVOPO4sub> is metastable and difficult to prepare by conventional approaches. We present here a facile synthesis of highly crystalline αI-LiVOPO4sub> and αI-LiVOPO4sub>/rGO nanocomposite by a microwave-assisted solvothermal method and its electrochemical/chemical lithiation. The LiVOPO4sub>/rGO cathodes exhibit a high reversible capacity of 225 mAh g–1, indicating the insertion of more than one lithium into VOPO4sub>. Both electrochemical and chemical lithiation imply a solid-solution reaction mechanism on inserting the second lithium into αI-LiVOPO4sub>, but a two-phase reaction feature could also occur under certain conditions such as insufficient time for equilibration of Li+ diffusion in the structure. The fully lithiated new αI-Li2VOPO4sub> phase was characterized by combined Rietveld refinement of neutron diffraction and X-ray diffraction data and by bond-valence sum maps. The results suggest that αI-Li2VOPO4sub> retains the tetragonal P4/nmm symmetry of the parent αI-LiVOPO4sub> structure, where the second lithium ions are located in the lithium layers rather than in the VOPO4sub> layers

  2. Integrated Data Collection Analysis (IDCA) Program - KClO4sub>/Carbon Mixture

    SciTech Connect

    Sandstrom, Mary M.; Brown, Geoffrey W.; Preston, Daniel N.; Pollard, Colin J.; Warner, Kirstin F.; Sorensen, Daniel N.; Remmers, Daniel L.; Shelley, Timothy J.; Reyes, Jose A.; Hsu, Peter C.; Reynolds, John G.


    The Integrated Data Collection Analysis (IDCA) program is conducting a proficiency study for Small- Scale Safety and Thermal (SSST) testing of homemade explosives (HMEs). Described here are the results for impact, friction, electrostatic discharge, and differential scanning calorimetry analysis of a mixture of KClO4sub> and activated carbon—KClO4sub>/C mixture. This material was selected because of the challenge of performing SSST testing of a mixture of two solids. The mixture was found to be insensitive to impact, friction, and thermal stimulus, and somewhat sensitive to spark discharge. This effort, funded by the Department of Homeland Security (DHS), ultimately will put the issues of safe handling of these materials in perspective with standard military explosives. The study is adding SSST testing results for a broad suite of different HMEs to the literature. Ultimately the study has the potential to suggest new guidelines and methods and possibly establish the SSST testing accuracies needed to develop safe handling practices for HMEs. Each participating testing laboratory uses identical test materials and preparation methods wherever possible. Note, however, the test procedures differ among the laboratories. The results are compared among the laboratories and then compared to historical data from various sources. The testing performers involved for the KClO4sub>/carbon mixture are Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), Indian Head Division, Naval Surface Warfare Center, (NSWC IHD), and Air Force Research Laboratory (AFRL/RXQL). These tests are conducted as a proficiency study in order to establish some consistency in test protocols, procedures, and experiments and to understand how to compare results when these testing variables cannot be made consistent.

  3. Discovery of a metastable Al20Sm4sub> phase

    SciTech Connect

    Ye, Z.; Zhang, F.; Sun, Y.; Mendelev, M. I.; Ott, R. T.; Park, E.; Besser, M. F.; Kramer, M. J.; Ding, Z.; Wang, C. -Z.; Ho, K. -M.


    In this study, we present an efficient genetic algorithm, integrated with experimental diffraction data, to solve a nanoscale metastable Al20Sm4sub> phase that evolves during crystallization of an amorphous magnetron sputtered Al90Sm10 alloy. The excellent match between calculated and experimental X-ray diffraction patterns confirms an accurate description of this metastable phase. Molecular dynamic simulations of crystal growth from the liquid phase predict the formation of disordered defects in the devitrified crystal.

  4. SU(4){sub L}xU(1){sub X} models with little Higgs mechanism

    SciTech Connect

    Nam, Soo-hyeon; Lee, Kang Young; Keum, Yong-Yeon


    We study the aspects of the fermion and gauge boson sectors in SU(4){sub L}xU(1){sub X} models with a little Higgs mechanism. We introduce a new setup of fermions, which ensures the cancellation of gauge anomaly and the cancellation of one-loop quadratic divergence to the Higgs mass for all fermion multiplets and gauge bosons. We explicitly present the interactions between the standard model fermions and the heavy gauge bosons to discuss the phenomenological implications of extra Z{sup '} and Z{sup ''} gauge bosons based on recent experimental data.

  5. Integrated Data Collection Analysis (IDCA) program--KClO4sub>/Dodecane Mixture

    SciTech Connect

    Sandstrom, Mary M.; Brown, Geoffrey W.; Preston, Daniel N.; Pollard, Colin J.; Warner, Kirstin F.; Sorensen, Daniel N.; Remmers, Daniel L.; Shelley, Timothy J.; Reyes, Jose A.; Hsu, Peter C.; Reynolds, John G.


    The Integrated Data Collection Analysis (IDCA) program is conducting a proficiency study for Small- Scale Safety and Thermal (SSST) testing of homemade explosives (HMEs). Described here are the results for impact, friction, electrostatic discharge, and differential scanning calorimetry analysis of a mixture of KClO4sub> and dodecane—KClO4sub>/dodecane mixture. This material was selected because of the challenge of performing SSST testing of a mixture of solid and liquid materials. The mixture was found to: 1) be less sensitive to impact than RDX, and PETN, 2) less sensitive to friction than RDX and PETN, and 3) less sensitive to spark than RDX and PETN. The thermal analysis showed little or no exothermic features suggesting that the dodecane volatilized at low temperatures. A prominent endothermic feature was observed and assigned to a phase transition of KClO4sub>. This effort, funded by the Department of Homeland Security (DHS), ultimately will put the issues of safe handling of these materials in perspective with standard military explosives. The study is adding SSST testing results for a broad suite of different HMEs to the literature. Ultimately the study has the potential to suggest new guidelines and methods and possibly establish the SSST testing accuracies needed to develop safe handling practices for HMEs. Each participating testing laboratory uses identical test materials and preparation methods wherever possible. Note, however, the test procedures differ among the laboratories. The results are compared among the laboratories and then compared to historical data from various sources. The testing performers involved for the KClO4sub>/dodecane mixture are Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), Indian Head Division, Naval Surface Warfare Center, (NSWC IHD), and Air Force Research Laboratory (AFRL/RXQL). These tests are conducted as a proficiency study in order to establish some

  6. Neutrino masses in SU(4){sub L}⊗U(1){sub X} gauge models

    SciTech Connect

    Palcu, Adrian


    Neutrino masses are obtained within SU(4){sub L}⊗U(1){sub X} electroweak gauge models with spontaneous symmetry breaking by simply exploiting the tree level realization of certain dimension-five effective operators. The scalar sector needs not to be enlarged, since these operators are constructed as direct products among scalar multiplets already existing in the model. There is a unique generic matrix for Yukawa couplings in the neutrino sector, while the charged leptons are already in their diagonal basis. The experimentally observed phenomenology in the neutrino sector is obtained as a natural consequence of this particular approach.

  7. A dispersive treatment of Kl4sub> decays

    SciTech Connect

    Colangelo, Gilberto; Passemar, Emilie; Stoffer, Peter


    Kl4sub> decays offer several reasons of interest: they allow an accurate measurement of ππ-scattering lengths; they provide the best source for the determination of some low-energy constants of xPT; one form factor is directly related to the chiral anomaly, which can be measured here. We present a dispersive treatment of Kl4sub> decays that provides a resummation of ππ- and Kπ-rescattering effects. In addition, the free parameters of the dispersion relation are fitted to the data of the high-statistics experiments E865 and NA48/2. The matching toxPT at NLO and NNLO enables us to determine the LECs Lr1, Lr2 and Lr3. With recently published data from NA48/2, the LEC Lr9 can be determined as well. In contrast to a pure chiral treatment, the dispersion relation describes the observed curvature of one of the form factors, which we understand as a rescattering effect beyond NNLO.

  8. Synthesis, structure, and optical properties of CsU{sub 2}(PO{sub 4}){sub 3}

    SciTech Connect

    Oh, George N.; Ringe, Emilie; Van Duyne, Richard P.; Ibers, James A.


    CsU{sub 2}(PO{sub 4}){sub 3} was synthesized in highest yield by the reaction in a fused-silica tube of U, P, and Se in a CsCl flux at 1273 K. It crystallizes with four formula units in space group P2{sub 1}/n of the monoclinic system in a new structure type. The structure of CsU{sub 2}(PO{sub 4}){sub 3} is composed of U and Cs atoms coordinated by PO{sub 4}{sup 3-} units in distorted octahedral arrangements. Each U atom corner shares with six PO{sub 4}{sup 3-} units. Each Cs atom face shares with one, edge shares with two, and corner shares with three PO{sub 4}{sup 3-} units. The structure shares some features with the sodium zirconium phosphate structure type. X-ray powder diffraction results demonstrate that the present CsU{sub 2}(PO{sub 4}){sub 3} compound crystallizes in a structure different from the previously reported {beta} Prime - and {gamma}-CsU{sub 2}(PO{sub 4}){sub 3} compounds. CsU{sub 2}(PO{sub 4}){sub 3} is highly pleochroic, as demonstrated by single-crystal optical absorption measurements. - Graphical abstract: Stacking of the layers in CsU{sub 2}(PO{sub 4}){sub 3}, viewed along [100]. Highlights: Black-Right-Pointing-Pointer Compound CsU{sub 2}(PO{sub 4}){sub 3} crystallizes in a new structure type. Black-Right-Pointing-Pointer Structure shares some features with the sodium zirconium phosphate structure type. Black-Right-Pointing-Pointer CsU{sub 2}(PO{sub 4}){sub 3} is highly pleochroic, as demonstrated by single-crystal optical absorption measurements.

  9. Magnetic properties of the superconducting polymers (SN)/sub x/ and (SNBr/sub 0. 4/)/sub x/

    SciTech Connect

    Dee, R.H.; Carolan, J.F.; Turrell, B.G.; Greene, R.L.


    The magnetizations of the superconducting sulfur nitrogen polymer (SN)/sub x/ and its brominated modification, (SNBr/sub 0.4/)/sub x/, have been studied as a function of magnetic field and temperature. There is anisotropy in the magnetization observed in both materials. However, (SNBr/sub 0.4/)/sub x/ behaves more like a bulk superconductor than (SN)/sub x/ does, indicating stronger interfiber coupling in the former.

  10. Heat capacity and neutron diffraction studies on the frustrated magnetic Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [0{<=}x{<=}1] solid solution

    SciTech Connect

    Pedro, I. de; Rojo, J.M.; Rodriguez Fernandez, J.; Sanchez Marcos, J.; Fernandez-Diaz, M.T.; Rojo, T.


    The Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [0{<=}x{<=}1] solid solution exhibits a complex magnetic behaviour due to the bond-frustration in its magnetic structure. Heat capacity measurements of the (x=0.1-0.5) phases show a three-dimensional magnetic ordering ({lambda} anomaly) that shifts to lower temperatures and becomes broader as the AsO{sub 4}{sup 3-} content increases. For x=0.75, no significant feature was observed whereas for higher arsenate ion content, x=0.9 and 1, a small maximum was detected. The magnetic structures of solid solution are consistent with the existence of predominant antiferromagnetic superexchange interactions through the |OH| and |XO{sub 4}| (X=P and As) groups between the Co{sup +2} ions. The substitution of PO{sub 4}{sup 3-} by AsO{sub 4}{sup 3-} anions by more than 90% substantially modifies the magnetic exchange pathways in the solid solution, leading to an incommensurate antiferromagnetic structure in Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [x=0.9 and 1] phases. - Graphical abstract: Magnetic structures of Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [0{<=}x{<=}1]. The ordering of the magnetic moments of Co{sup 2+} is in c direction for the two crystallographic positions (dimers and chains) in all compounds. The unit cell is surrounded by a red line. Highlights: Black-Right-Pointing-Pointer Synthesis of a new adamite-type compounds, Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} (0.1, 0.25, 0.5, 0.75, 0.9) phases. Black-Right-Pointing-Pointer Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} (0-1) solid solution; magnetic frustrated system. Black-Right-Pointing-Pointer High resolution neutron powder diffraction to determine the crystal structures. Black-Right-Pointing-Pointer Incommensurate magnetic structures at low temperature. Black-Right-Pointing-Pointer Magnetostructural correlations in cobalt-based Co{sub 2}(OH)XO{sub 4} (X=P and As) insulation compounds.

  11. Pressure-induced phase transitions in multiferroic RbFe(MoO{sub 4}){sub 2}-Raman scattering study

    SciTech Connect

    Maczka, M.; Ptak, M.; Luz-Lima, C.; Freire, P.T.C.; Paraguassu, W.; Guerini, S.; Hanuza, J.


    High pressure Raman scattering experiments were performed on RbFe(MoO{sub 4}){sub 2}. These experiments revealed that two phase transitions take place in RbFe(MoO{sub 4}){sub 2} at very low pressures, i.e. between ambient pressure and 0.2 GPa and between 0.4 and 0.7 GPa. Raman results showed that at the first phase transition the room temperature P3-bar m1 phase transforms into the P3-bar phase, which is also observed at ambient pressure below 190 K. The second pressure-induced phase transition occurs into a low symmetry phase of unknown symmetry. The performed lattice dynamics calculations for the P3-bar m1 phase and ab initio calculation of the structural changes under hydrostatic pressure helped us to get better insights into the mechanism of the observed phase transitions. - Graphical abstract: Raman spectra of RbFe(MoO{sub 4}){sub 2} crystal in the high wavenumber region recorded at different pressures during compression experiment. Highlights: > RbFe(MoO{sub 4}){sub 2} exhibits two pressure-induced phase transitions below 0.7 GPa. > First phase transition is from the P3-bar m1 into P3-bar structure. > Phase transitions in RbFe(MoO{sub 4}){sub 2} are similar as in KFe(MoO{sub 4}){sub 2}. > Transitions' pressures are much lower for the rubidium compound.

  12. Second harmonic generation of diamond-blade diced KTiOPO4sub> ridge waveguides.


    Chen, Chen; Rüter, Christian E; Volk, Martin F; Chen, Cheng; Shang, Zhen; Lu, Qingming; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng; Kip, Detlef


    We report on the fabrication of ridge waveguides in KTiOPO4sub> nonlinear optical crystals through carbon ion irradiation followed by precise diamond blade dicing. The diced side-walls have low roughness, which allows for low propagation loss of ~1dB/cm in fabricated of ridges. The waveguide property investigation has been performed at 1064 nm as well as 532 nm, showing good guidance at both TE and TM polarizations. Based on type II phase matching configuration, efficient second harmonic generation of green light at room temperature has been realized. High conversion efficiencies of ~1.12%W-1 and ~12.4% have been obtained for frequency doubling under the pump of continuous-wave (CW) and pulsed fundamental waves at 1064 nm, respectively. PMID:27464095

  13. Preparation and crystal structure of Na sub 3 SbO(PO sub 4 ) sub 2

    SciTech Connect

    Guyomard, D.; Pagnoux, C.; Verbaere, A.; Piffard, Y. ); Zah Letho, J.J. )


    The single phase compound Na{sub 3}SbO(PO{sub 4}){sub 2} was prepared by a solid state reaction. It crystallizes in the orthorhombic system, space group P2{sub 1}2{sub 1}2{sub 1} with a = 6.964(1) {angstrom}, b = 9.284(2) {angstrom}, c = 12.425(2) {angstrom}, Z = 4. The structure was determined from 968 reflections collected on a Nonius CAD4 automatic diffractometer with MoK{alpha} radiation. The final R index and weighted R{sub w} index are 0.031 and 0.039, respectively. The structure is built up from strings of corner-sharing SbO{sub 6} octahedra to which phosphate groups are linked by two of their vertices. These chains, running parallel to the a-axis, are separated from each other by sodium atoms.

  14. Anomalous magnetic structure and spin dynamics in magnetoelectric LiFePO4sub>

    SciTech Connect

    Toft-Petersen, Rasmus; Reehuis, Manfred; Jensen, Thomas B. S.; Andersen, Niels H.; Li, Jiying; Le, Manh Duc; Laver, Mark; Niedermayer, Christof; Klemke, Bastian; Lefmann, Kim; Vaknin, David


    We report significant details of the magnetic structure and spin dynamics of LiFePO4sub> obtained by single-crystal neutron scattering. Our results confirm a previously reported collinear rotation of the spins away from the principal b axis, and they determine that the rotation is toward the a axis. In addition, we find a significant spin-canting component along c. Furthermore, the possible causes of these components are discussed, and their significance for the magnetoelectric effect is analyzed. Inelastic neutron scattering along the three principal directions reveals a highly anisotropic hard plane consistent with earlier susceptibility measurements. While using a spin Hamiltonian, we show that the spin dimensionality is intermediate between XY- and Ising-like, with an easy b axis and a hard c axis. As a result, it is shown that both next-nearest neighbor exchange couplings in the bc plane are in competition with the strongest nearest neighbor coupling.

  15. Predicted energies and structures of {beta}-Ca{sub 3}(PO{sub 4}){sub 2}

    SciTech Connect

    Jay, E.E.; Michie, E.M.; Parfitt, D.; Rushton, M.J.D.; Fong, S.K.; Mallinson, P.M.; Metcalfe, B.L.; Grimes, R.W.


    One of the 6a cation sites of the {beta}-Ca{sub 3}(PO{sub 4}){sub 2} structure has previously been described as half occupied. Here, classical static lattice techniques are used to model the different configurations that the Ca ions can exhibit over these Ca(4) 6a sites. All possible configurations in the single primitive unit cell and a hexagonal supercell 3{sub h}x1x1 have been generated, along with configurationally averaged structures, that exhibit the experimentally reported R 3c symmetry. The lowest energy configuration of the primitive cell exhibits R 3 symmetry. Conversely, the lowest energy configurations derived from the hexagonal supercell, which are considerably more stable, exhibit P 3{sub 1} and P 3{sub 2} symmetries, which are isomorphic supergroups of R 3c. The implication of these simulations are discussed in terms of refined structural models of the material. - Graphical Abstract: One of the 6a cation sites of the {beta}-Ca{sub 3}(PO{sub 4}){sub 2} structure has previously been described as half occupied. Here, classical static lattice techniques are used to model the different configurations that the Ca ions can exhibit over these Ca(4) 6a sites. All possible configurations in the single primitive unit cell and a hexagonal supercell (3{sub h}x1x1) have been generated, along with configurationally averaged structures, that exhibits experimentally reported R 3c symmetry. The lowest energy configuration of the primitive cell exhibits R 3 symmetry. Conversely, the lowest energy configurations derived from the hexagonal supercell cell, which are considerably more stable, exhibit P 3{sub 1} and P 3{sub 2} symmetries, which are isomorphic supergroups of R 3c. The implication of these simulations are discussed in terms of refined structural models of the material.

  16. Luminescence properties of phosphate phosphor Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+}

    SciTech Connect

    Yang, Fu; Liu, Yufeng; Tian, Xiaodong; Dong, Guoyi; Yu, Quanmao


    A series of reddish orange-emitting phosphate phosphors Ba{sub 3}Y{sub 1−x}(PO{sub 4}){sub 3}:xSm{sup 3+}(0.01≤x≤0.20) were synthesized by solid-state reaction. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of as-synthesized phosphors. The optimized phosphors Ba{sub 3}Y{sub 0.95}(PO{sub 4}){sub 3}:0.05Sm{sup 3+} present several excitation bands from 300 to 500 nm, and exhibit intense reddish orange-emitting properties. The energy transfer type between Sm{sup 3+} ions was confirmed as d–d interaction by using Van Uitert model. The chromatic properties of the typical sample Ba{sub 3}Y(PO{sub 4}){sub 3}:0.05Sm{sup 3+} phosphor have been found to have chromaticity coordinates of (0.583, 0.405), which are located in reddish orange region under the excitation of 401 nm. These results indicated that Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} phosphors have potential applications in the field of lighting and display due to their effective excitation in the near-ultraviolet range. - Graphical abstract: The color coordinates for 5 mol% Sm{sup 3+} doped Ba{sub 3}Y(PO{sub 4}){sub 3} phosphor were calculated to be (0.583, 0.405), which are located in reddish orange region under the excitation of 401 nm. The peaks of Ba{sub 3}Y{sub 0.95}(PO{sub 4}){sub 3}:0.05Sm{sup 3+} phosphor with the highest emission intensity at 600 nm are broader than those of Y{sub 2}O{sub 3}:Eu{sup 3+} and Y{sub 2}O{sub 2}S:Eu{sup 3+} phosphors. All these characteristics suggest that Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} phosphors are suitable for near-UV (370–410 nm) excitation and can be applicable to near UV-based WLEDs. ▪ - Highlights: • Different concentration Sm{sup 3+}-doped Ba{sub 3}Y(PO{sub 4}){sub 3} phosphors were fabricated by solid state method. • The optimized phosphors present the several excitation bands from 300 to 500 nm. • The Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} shows bright reddish orange

  17. New insight in the structure-luminescence relationships of Ca{sub 9}Eu(PO{sub 4}){sub 7}

    SciTech Connect

    Benhamou, Rajia Ait; Bessiere, Aurelie; Wallez, Gilles; Viana, Bruno; Elaatmani, Mohamed; Daoud, Mohamed; Zegzouti, Abdelwahed


    The double phosphate Ca{sub 9}Eu(PO{sub 4}){sub 7}, obtained by solid state reaction, was found to be isotypic with Ca{sub 3}(PO{sub 4}){sub 2}, with space group R3c and unit cell parameters a=10.4546(1) A, c=37.4050(3) A, V=3540.67(9) A{sup 3}, Z=6. The structure parameters refined using the Rietveld method showed that europium shares positions M1, M2 and M3 with calcium, contradicting previously published Moessbauer results. Low temperature luminescence under selective excitation of Eu{sup 3+} in Ca{sub 9}Y{sub 1-x}Eu{sub x}(PO{sub 4}){sub 7} and in Ca{sub 9}Eu(PO{sub 4}){sub 7} samples was studied, confirming the Eu{sup 3+} distribution into these sites. At 10 K, {sup 5}D{sub 0}->{sup 7}F{sub 0} emission lines of Eu{sup 3+} were observed at 578.5, 579.5, 580.1 nm for the M3, M1 and M2 sites, respectively. High temperature X-ray powder diffraction evidenced a second-order phase transition around 573 deg. C. - Graphical Abstract: Emission spectra of Ca{sub 9}Eu(PO{sub 4}){sub 7} recorded at 10 K evidencing the three different sites for Eu{sup 3+} dopant cation.

  18. Insights into the structure of mixed CO2/CH4sub> in gas hydrates

    SciTech Connect

    Everett, S. Michelle; Rawn, Claudia J.; Chakoumakos, Bryan C.; Keffer, David J.; Huq, Ashfia; Phelps, Tommy J.


    The exchange of carbon dioxide for methane in natural gas hydrates is an attractive approach to harvesting CH4sub> for energy production while simultaneously sequestering CO2. In addition to the energy and environmental implications, the solid solution of clathrate hydrate (CH4sub>)1-x(CO2)x·5.75H2O provides a model system to study how the distinct bonding and shapes of CH4sub> and CO2 influence the structure and properties of the compound. In this paper, high-resolution neutron diffraction was used to examine mixed CO2/CH4sub> gas hydrates. CO2-rich hydrates had smaller lattice parameters, which were attributed to the higher affinity of the CO2 molecule interacting with H2O molecules that form the surrounding cages, and resulted in a reduction in the unit-cell volume. Experimental nuclear scattering densities illustrate how the cage occupants and energy landscape change with composition. Finally, these results provide important insights on the impact and mechanisms for the structure of mixed CH4sub>/CO2 gas hydrate.

  19. Mechanisms for pressure-induced crystal-crystal transition, amorphization, and devitrification of Snl4sub>

    SciTech Connect

    Liu, Hanyu; Tse, John S.; Hu, Michael Y.; Bi, Wenli; Zhao, Jiyong; Alp, E. Ercan; Pasternak, Moshe; Taylor, R. Dean; Lashley, Jason C.


    The pressure-induced amorphization and subsequent recrystallization of SnI4sub> have been investigated using first principles molecular dynamics calculations together with high-pressure 119Sn nuclear resonant inelastic x-ray scattering measurements. Above ~8 GPa, we observe a transformation from an ambient crystalline phase to an intermediate crystal structure and a subsequent recrystallization into a cubic phase at ~64 GPa. The crystalline-to-amorphous transition was identified on the basis of elastic compatibility criteria. The measured tin vibrational density of states shows large amplitude librations of SnI4sub> under ambient conditions. Although high pressure structures of SnI4sub> were thought to be determined by random packing of equal-sized spheres, we detected electron charge transfer in each phase. As a result, this charge transfer results in a crystal structure packing determined by larger than expected iodine atoms. (C) 2015 AIP Publishing LLC.

  20. Crystal structure of the high-temperature modification of ytterbium perrhenate Yb(ReO{sub 4}){sub 3}

    SciTech Connect

    Khrustalev, V.N.; Varfolomeev, M.B.; Shamrai, N.B.; Struchkov, Yu.T.; Pisarevskii, A.P. |


    Yb(ReO{sub 4}){sub 3} obtained by the slow crystallization of its melt in air is investigated by X-ray diffraction (298 K, 329 reflections, R = 0.083, R{sub w} = 0.102). Crystals are hexagonal, a = 9.999(4) {angstrom}, c = 6.070(2) {angstrom}, Z = 2, space group P6{sub 3}/m. The structure is related to the CdTh(MoO{sub 4}){sub 3} type and consists of columns of Yb polyhedra (three-cap trigonal prisms) and of Re tetrahedra. The correlation of the structures of Yb(ReO{sub 4}){sub 3} and apatite is discussed.

  1. Spin Hall magnetoresistance in CoFe2O4sub>/Pt films

    SciTech Connect

    Wu, Hao; Qintong, Zhang; Caihua, Wan; Ali, Syed Shahbaz; Yuan, Zhonghui; You, Lu; Wang, Junling; Choi, Yongseong; Han, Xiufeng


    Pulse laser deposition and magnetron sputtering techniques have been employed to prepare MgO(001)//CoFe2O4sub>/Pt samples. Cross section transmission electron microscope results prove that the CoFe2O4sub> film epitaxially grew along (001) direction. X-ray magnetic circular dichroism results show that magnetic proximity effect in this sample is negligible. Magnetoresistance (MR) properties confirm that spin Hall MR (SMR) dominates in this system. Spin Hall effect-induced anomalous Hall voltage was also observed in this sample. Lastly, these results not only demonstrate the universality of SMR effect but also demonstrate the utility in spintronics of CoFe2O4sub> as a new type of magnetic insulator.

  2. Biodiesel production using lipase immobilized on epoxychloropropane-modified Fe3O4 sub-microspheres.


    Zhang, Qian; Zheng, Zhong; Liu, Changxia; Liu, Chunqiao; Tan, Tianwei


    Superparamagnetic Fe3O4 sub-microspheres with diameters of approximately 200 nm were prepared via a solvothermal method, and then modified with epoxychloropropane. Lipase was immobilized on the modified sub-microspheres. The immobilized lipase was used in the production of biodiesel fatty acid methyl esters (FAMEs) from acidified waste cooking oil (AWCO). The effects of the reaction conditions on the biodiesel yield were investigated using a combination of response surface methodology and three-level/three-factor Box-Behnken design (BBD). The optimum synthetic conditions, which were identified using Ridge max analysis, were as follows: immobilized lipase:AWCO mass ratio 0.02:1, fatty acid:methanol molar ratio 1:1.10, hexane:AWCO ratio 1.33:1 (mL/g), and temperature 40 °C. A 97.11% yield was obtained under these conditions. The BBD and experimental data showed that the immobilized lipase could generate biodiesel over a wide temperature range, from 0 to 40 °C. Consistently high FAME yields, in excess of 80%, were obtained when the immobilized lipase was reused in six replicate trials at 10 and 20 °C. PMID:26803008

  3. A high performance hybrid battery based on aluminum anode and LiFePO4sub> cathode

    SciTech Connect

    Sun, Xiao-Guang; Bi, Zhonghe; Liu, Hansan; Bridges, Craig A.; Paranthaman, Mariappan Parans; Dai, Sheng; Brown, Gilbert M.


    A unique battery hybrid utilizes an aluminum anode, a LiFePO4sub> cathode and an acidic ionic liquid electrolyte based on 1-ethyl-3-methylimidazolium chloride (EMImCl) and aluminum trichloride (AlCl 3) (EMImCl-AlCl 3, 1-1.1 in molar ratio) with or without LiAlCl4sub> is proposed. This hybrid ion battery delivers an initial high capacity of 160 mAh g-1 at a current rate of C/5. It also shows good rate capability and cycling performance.

  4. Theoretical Study of the Molecular and Electronic Structures of TiO4sub>H4sub>, Ti2O7H6, and Ti2O6H4sub>

    SciTech Connect

    Tsuchiya, Takashi; Whitten, Jerry L.


    State-of-the-art multistate configuration interaction (CI) calculations were performed for a series of titanium complexes, namely, TiO4sub>H4sub>, Ti2O7H6, and Ti2O6H4sub>, which were chosen to identify features present in titanium oxide nanoclusters and titanium dioxide surfaces. All electrons were included in the calculations, and transformation methods were employed to achieve high accuracy for the excitations of interest. The electronic structures of the ground and excited states are discussed, and excitation energies are reported for different molecular conformations. Of particular interest is the extent of localization of the electron-hole pair formed upon excitation from the oxygen 2p molecular orbitals. Singlet and triplet excited states were resolved, and energies of electronic states are reported as a function of molecular geometry.

  5. Solvothermal indium fluoride chemistry: Syntheses and crystal structures of K{sub 5}In{sub 3}F{sub 14}, beta-(NH{sub 4}){sub 3}InF{sub 6} and [NH{sub 4}]{sub 3}[C{sub 6}H{sub 21}N{sub 4}]{sub 2}[In{sub 4}F{sub 21}

    SciTech Connect

    Jayasundera, Anil C.A.; Goff, Richard J.; Li Yang; Finch, Adrian A.; Lightfoot, Philip


    The solvothermal syntheses and crystal structures of three indium fluorides are presented. K{sub 5}In{sub 3}F{sub 14} (1) and beta-(NH{sub 4}){sub 3}InF{sub 6} (2) are variants on known inorganic structure types chiolite and cryolite, respectively, with the latter exhibiting a complex and apparently novel structural distortion. [NH{sub 4}]{sub 3}[C{sub 6}H{sub 21}N{sub 4}]{sub 2}[In{sub 4}F{sub 21}] (3) represents a new hybrid composition displaying a unique trimeric metal fluoride building unit. - Graphical abstract: Solvothermal synthesis has been used to prepare three indium fluorides, including a novel hybrid material containing a unique [In{sub 3}F{sub 15}] trimer templated by tren.

  6. Structural and conductivity studies of CsK(SO{sub 4}){sub 0.32}(SeO{sub 4}){sub 0.68}Te(OH){sub 6}

    SciTech Connect

    Djemel, M.; Abdelhedi, M.; Dammak, M.; Kolsi, A.W.


    The compound CsK(SO{sub 4}){sub 0.32}(SeO{sub 4}){sub 0.68}Te(OH){sub 6} crystallizes in the monoclinic P2{sub 1}/n space group. It was analyzed, at room temperature, using X-ray diffractometer data. The main feature of these atomic arrangements is the coexistence of three and different anions (SO{sub 4}{sup 2-}, SeO{sub 4}{sup 2-} and TeO{sub 6}{sup 6-}groups) in the unit cell, connected by hydrogen bonds which make the building of the crystal. The thermal analysis of the title compound shows three distinct endothermal peaks at 435, 460 and 475 K. Complex impedance measurements are performed on this material as a function of both temperature and frequency. The electric conduction has been studied. The temperature dependence on the conductivity indicates that the sample became an ionic conductor at high temperature. - Graphical abstract: Projection of crystal structure CsK(SO{sub 4}){sub 0.32}(SeO{sub 4}){sub 0.68}Te(OH){sub 6} on the ab plane. Highlights: Black-Right-Pointing-Pointer We have studied the results of the crystal structure of the new mixed compound. Black-Right-Pointing-Pointer We have characterized the phase transition observed in DSC curve. Black-Right-Pointing-Pointer The protonic conduction in our material is probably due to a hopping mechanism.

  7. Electron paramagnetic resonance spectra and structures of Cu(C sub 2 H sub 4 ), Cu(C sub 2 H sub 4 ) sub 2 , and Cu(C sub 2 H sub 4 ) sub 3 in hydrocarbon matrices

    SciTech Connect

    Howard, J.A.; Joly, H.A.; Mile, B. )


    Two mononuclear {pi}-complexes, Cu(C{sub 2}H{sub 4}) and Cu(C{sub 2}H{sub 4}){sub 2}, have been positively identified by EPR spectroscopy from reaction of Cu atoms and ethylene at 77 K in inert hydrocarbon matrices on a rotating cryostat. The spectra of these copper(O) complexes are consistent with dative bonding for both species and with a C{sub 2v} structure for Cu(C{sub 2}H{sub 4}) and a D{sub 2h} structure for Cu(C{sub 2}H{sub 4}){sub 2}. Spectra of Cu({sup 13}CH{sub 2}CH{sub 2}) and Cu({sup 13}CH{sub 2}CH{sub 2}){sub 2} are consistent with these assignments. A third complex is formed in both adamantane and cyclohexane that could be Cu(C{sub 2}H{sub 4}){sub 2} with a structure other than D{sub 2h} but is more likely to be the mononuclear trisligand complex Cu(C{sub 2}H{sub 4}){sub 3} with a D{sub 3h} structure. In the absence of a well-resolved isotropic spectrum of Cu({sup 13}CH{sub 2}CH{sub 2}){sub 3}, this assignment must however be taken as tentative.

  8. A new three-dimensional cobalt phosphate: Co{sub 5}(OH{sub 2}){sub 4}(HPO{sub 4}){sub 2}(PO{sub 4}){sub 2}

    SciTech Connect

    Han Zhangang . E-mail:; Tian Aixiang; Peng Jun . E-mail:; Zhai Xueliang


    A three-dimensional (3D) cobalt phosphate: Co{sub 5}(OH{sub 2})PO{sub 4}){sub 2}(PO{sub 4}){sub 2} (1), has been synthesized by hydrothermal reaction and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic techniques. The title compound is a template free cobalt phosphate. Compound 1 exhibits a complex net architecture based on edge- and corner-sharing of CoO{sub 6} and PO{sub 4} polyhedra. The magnetic susceptibility measurements indicated that the title compound obeys Curie-Weiss behavior down to a temperature of 17 K at which an antiferromagnetic phase transition occurs. - Graphical abstract: A 3D cobalt phosphate with a neutral framework: Co{sub 5}(OH{sub 2}){sub 4}(HPO{sub 4}){sub 2}(PO{sub 4}){sub 2} (1), has been synthesized and characterized. Compound 1 exhibits a complex net architecture based on edge- and corner-sharing of CoO{sub 6} and PO{sub 4} polyhedra. Its magnetic property was researched.

  9. A facile solvothermal synthesis of octahedral Fe3O4sub> nanoparticles

    SciTech Connect

    DuChene, Joseph S.; Qiu, Jingjing; Graham, Jeremy O.; Engelhard, Mark H.; Cao, Guixin; Gai, Zheng; Wei, Wei David; Ooi, Frances


    Anisotropic Fe3O4sub> octahedrons are obtained via a simple solvothermal synthesis with appropriate sizes for various technological applications. Here, a complete suite of materials characterization methods confirms the magnetite phase for these structures, which exhibit substantial saturation magnetization and intriguing morphologies for a wide range of applications.

  10. New mixed-valence chromium structure type: NH{sub 4}Cr(CrO{sub 4}){sub 2}

    SciTech Connect

    Casari, Barbara M. . E-mail:; Wingstrand, Erica; Langer, Vratislav


    Synthesis and crystal structure of a new structure type of mixed Cr(III)/Cr(VI) chromates is reported. NH{sub 4}Cr(CrO{sub 4}){sub 2} was prepared from CrO{sub 3} in the presence of (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6}. Since this is the first preparation of mixed valence ternary chromium oxides from aqueous solution, a reaction pathway for this synthesis is suggested. The crystal structure of NH{sub 4}Cr(CrO{sub 4}){sub 2} has been determined from three-dimensional X-ray data collected at low temperature, 173K. The structure belongs to the orthorhombic space group Pnma, with a=14.5206(10), b=5.4826(4), c=8.7041(7)A and Z=4. The title compound consists of corner-sharing chromium(III) octahedra and chromium(VI) tetrahedra forming a three-dimensional network with the composition [Cr(CrO{sub 4}){sub 2}]{sub n}{sup n-}, containing channels in which zigzag rows of ammonium ions balance the net charge.


    SciTech Connect

    McCauley, Patrick I.; Mangum, Jeffrey G.; Wootten, Alwyn


    We present Green Bank Telescope observations of the 3{sub 12}-3{sub 13} (29 GHz) and 4{sub 13}-4{sub 14} (48 GHz) transitions of the H{sub 2}CO molecule toward a sample of 23 well-studied star-forming regions. Analysis of the relative intensities of these transitions can be used to reliably measure the densities of molecular cores. Adopting kinetic temperatures from the literature, we have employed a large velocity gradient (LVG) model to derive the average hydrogen number density (n(H{sub 2})) within a 16'' beam toward each source. Densities in the range of 10{sup 5.5}-10{sup 6.5} cm{sup -3} and ortho-formaldehyde column densities per unit line width between 10{sup 13.5} and 10{sup 14.5} cm{sup -2} (km s{sup -1}){sup -1} are found for most objects, in general agreement with existing measurements. A detailed analysis of the advantages and limitations to this densitometry technique is also presented. We find that H{sub 2}CO 3{sub 12}-3{sub 13}/4{sub 13}-4{sub 14} densitometry proves to be best suited to objects with T{sub K} {approx}> 100 K, above which the H{sub 2}CO LVG models become relatively independent of kinetic temperature. This study represents the first detection of these H{sub 2}CO K-doublet transitions in all but one object in our sample. The ease with which these transitions were detected, coupled with their unique sensitivity to spatial density, makes them excellent monitors of density in molecular clouds for future experiments. We also report the detection of the 9{sub 2}-8{sub 1} A {sup -} (29 GHz) transition of CH{sub 3}OH toward six sources.

  12. Synthesis and conductivities of sulfate/selenate phases related to nasicon: Na[sub x]M[prime](III)[sub 2[minus]x](SO[sub 4])[sub 3[minus]y](SeO[sub 4])[sub y

    SciTech Connect

    Slater, P.R.; Greaves, C. )


    The synthesis of Na containing Nasicon-type phases of the form Na[sub x]M[prime](II)[sub x]M[double prime](III)[sub 2[minus]x](SO[sub 4])[sub 3[minus]y](SeO[sub 4])[sub y] (M[prime] = Mg, Zn, Cd, Mn; M[double prime] = Al, Cr, Fe, In, Yb; 0 [le] x [le] 1.75; 0 [le] y [le] 3) is reported. The conductivities of a range of samples have been measured, with the highest value observed at 200[degrees]C being 2 x 10[sup [minus]4] [Omega][sup [minus]1] cm[sup [minus]1] for Na[sub 1.75]Mg[sub 1.75]Cr[sub 0.25](SO[sub 4])[sub 3]. The range of x for which single phase samples are observed depends on the nature of M[prime] and M[double prime], and on the value of y. Attempts to increase the Na content, and so increase the conductivity, by partially substituting the (S, Se)O[sub 4] groups by PO[sub 4] or SiO[sub 4] have proven unsuccessful.

  13. Magnetic structure of the antiferromagnetic Kondo lattice compounds CeRhAl4sub>Si2 and CeIrAl4sub>Si2

    SciTech Connect

    Ghimire, N. J.; Calder, S.; Janoschek, M.; Bauer, E. D.


    In this article, we have investigated the magnetic ground state of the antiferromagnetic Kondo-lattice compounds CeMAl4sub>Si2(M = Rh, Ir) using neutron powder diffraction. Although both of these compounds show two magnetic transitions TN1 and TN2 in the bulk properties measurements, evidence for magnetic long-range order was only found below the lower transition TN2. Analysis of the diffraction profiles reveals a commensurate antiferromagnetic structure with a propagation vector k = (0, 0, 1/2). The magnetic moment in the ordered state of CeRhAl4sub>Si2 and CeIrAl4sub>Si2 were determined to be 1.14(2) and 1.41(3) μB/Ce, respectively, and are parallel to the crystallographic c-axis in agreement with magnetic susceptibility measurements.

  14. Single crystal growth of Yb doped NaGd(WO{sub 4}){sub 2} and structural and spectroscopic studies

    SciTech Connect

    Singh, S. G.; Singh, A. K.; Desai, D. G.; Tiwari, B.; Tyagi, M.


    High quality single crystals of NaGd(WO{sub 4}){sub 2} doped with 5 mol % Yb and oriented along <001> have been grown by the Czochralski technique in Ar atmosphere. The tetragonal space group I41/a accounts for all the reflections observed in the powder X-ray diffraction analysis. Polarized optical spectroscopy at room temperature revealed a direction dependence of absorption at different wavelength. As a novel uniaxial laser host for Yb{sup 3+}, NaGd(WO{sub 4}){sub 2} is characterized with respect to its transparency and band-edge. The emission spectrum of Yb{sup 3+} (excitation: 980-990 nm diode laser) was also recorded.

  15. Investigation of room temperature ferromagnetic nanoparticles of Gd5Si4sub>

    SciTech Connect

    Hadimani, R. L.; Gupta, S.; Harstad, S. M.; Pecharsky, V. K.; Jiles, D. C.


    Gd5(SixGe1-x)4sub> compounds undergo first-order phase transitions close to room temperature when x ~ = 0.5, which are accompanied by extreme changes of properties. We report the fabrication of the nanoparticles of one of the parent compounds-Gd5Si4sub>-using high-energy ball milling. Crystal structure, microstructure, and magnetic properties have been investigated. Particles agglomerate at long milling times, and the particles that are milled >20 min lose crystallinity and no longer undergo magnetic phase transition close to 340 K, which is present in a bulk material. The samples milled for >20 min exhibit a slightly increased coercivity. As a result, magnetization at a high temperature of 275K decreases with the increase in the milling time.

  16. Effects of Nickel Doping on the Multiferroic and Magnetic Phases of MnWO 4sub>

    SciTech Connect

    Poudel, N.; Lorenz, B.; Lv, B.; Wang, Y. Q.; Ye, F.; Wang, Jinchen; Fernandez-baca, J. A.; Chu, C. W.


    There are various orders in multiferroic materials with a frustrated spiral spin modulation inducing a ferroelectric state are extremely sensitive to small perturbations such as magnetic and electric fields, external pressure, or chemical substitutions. A classical multiferroic, the mineral Hubnerite with chemical formula MnWO4sub>, shows three different magnetic phases at low temperature. The intermediate phase between 7.5K < T < 12.7K is multiferroic and ferroelectricity is induced by an inversion symmetry breaking spiral Mn-spin order and strong spin-lattice interactions. Furthermore, the substitution of Ni2+ (spin 1) for Mn2+ (spin 5/2) in MnWO4sub> and its effects on the magnetic and multiferroic phases are studied. The ferroelectric phase is stabilized for low Ni content (up to 10%). Upon further Ni doping, the polarization in the ferroelectric phase is quickly suppressed while a collinear and commensurate magnetic phase, characteristic of the magnetic structure in NiWO4sub>, appears first at higher temperature, gradually extends to lower temperature, and becomes the ground state above 30% doping. Between 10% and 30%, the multiferroic phase coexists with the collinear commensurate phase. In this concentration region, the spin spiral plane is close to the a-b plane which explains the drop of the ferroelectric polarization. Finally, the phase diagram of Mn1-xNixWO4sub> is derived by a combination of magnetic susceptibility, specific heat, electric polarization, and neutron scattering measurements.

  17. Fermions and gauge bosons in SU(4){sub L}xU(1){sub X} models with little Higgs

    SciTech Connect

    Nam, Soo-hyeon


    We discuss the aspects of the little Higgs model with the SU(4){sub L}xU(1){sub X} electroweak gauge group as an alternative solution to the naturalness and fine-tuning issues. We introduce anomaly-free fermion spectra, and present their interactions with the physical gauge bosons. We also discuss some phenomenological implications of these fermions and the extra gauge bosons based on recent experimental results.

  18. Crystal chemistry of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} double monophosphates

    SciTech Connect

    Bregiroux, Damien; Popa, Karin; Wallez, Gilles


    M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds have been extensively studied for several decades for their potential applications in the field of several domains such as matrices for actinides conditioning, phosphors etc. In this paper, the relationships between composition and crystal structure of these compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. M{sup II}M′{sup IV}(PO{sub 4}){sub 2} structures stem from two different archetypes: the cheralite and the yavapaiite structures, with some exceptions that are also described in this article. The ratio of the cations radii appears to be the most relevant parameter. The high ratio between the ionic radii of the divalent and tetravalent cations in yavapaiite derivates results in the ordering of these cations into well-differentiated polyhedra whereas cheralite is the only non-ordered structure encountered for M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds. - Graphical abstract: In this paper, the relationships between composition and crystal structure of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. - Highlights: • Crystal structure–composition relationships of MIIM′IV(PO4)2 compounds. • Review of the various processes used for the synthesis of these compounds. • Their most reported properties are described and discussed.

  19. High-temperature phase transformation and topochemical nature in ferroelastic (NH{sub 4}){sub 2}SO{sub 4}

    SciTech Connect

    Lee, Kwang-Sei; Oh, In-Hwan; Ko, Jae-Hyeon


    The electrical conductivity of ferroelastic ammonium sulfate (NH{sub 4}){sub 2}SO{sub 4} revealed an anomaly at around 130 °C (=403 K, T{sub P}) on heating with large and irreversible thermal hysteresis through thermal cycle. Ferroelastic domain walls and surface morphology of (NH{sub 4}){sub 2}SO{sub 4} were investigated by hot-stage polarizing microscopy. Structural phase transition from an orthorhombic ferroelastic phase to a hexagonal paraelastic phase was not identified at T{sub P} upon heating. On further heating above T{sub P}, microscopic spots appeared and grew on the crystal surface, suggesting that the high-temperature anomaly at T{sub P} was an indication of an onset of thermal decomposition controlled by topochemical factors. The increase of electrical conductivity above T{sub P} was attributed to proton migration. - Graphical abstract: Surface morphology of the (100) face of (NH{sub 4}){sub 2}SO{sub 4} on heating, showing chemical reaction at the surface. - Highlights: • We investigate the high-temperature phase transformation of ammonium sulfate. • The increasing conductivity upon heating is attributed to proton migration. • Structural phase transition from orthorhombic to hexagonal phase is not confirmed. • High-temperature anomaly is related to an onset of thermal decomposition. • The nature of the high-temperature anomaly is topochemical controlled by defects.

  20. Hydrothermal synthesis and luminescent properties of NaLa(MoO{sub 4}){sub 2}:Dy{sup 3+} phosphor

    SciTech Connect

    Li Linlin; Zi Wenwen; Li Guanghuan; Lan Shi; Ji Guijuan; Gan Shucai; Zou Haifeng; Xu Xuechun


    Pompon-like NaLa(MoO{sub 4}){sub 2}:Dy{sup 3+} phosphors have been successfully prepared via a hydrothermal method using ammonia as pH value regulator. The hydrothermal process was carried out under aqueous condition without the use of any organic solvent, surfactant, and catalyst. The experimental results demonstrate that the obtained NaLa(MoO{sub 4}){sub 2}:Dy{sup 3+} phosphor powders are single-phase scheelite structure with tetragonal symmetry. Moreover, the phosphor under the excitation of 390 and 456 nm exhibited blue emission (486 nm) and yellow emission (574 nm), corresponding to the {sup 4}F{sub 9/2}{yields}{sup 6}H{sub 15/2} transition and {sup 4}F{sub 9/2}{yields}{sup 6}H{sub 13/2} transition of Dy{sup 3+} ions, respectively. In addition, the yellow-to-blue emission intensity ratio (Y/B) can be changed with the doped concentration of Dy{sup 3+} ions. All chromaticity coordinates of the obtained NaLa(MoO{sub 4}){sub 2}:Dy{sup 3+} phosphors are located in the white-light region. The results indicate that this kind of phosphor may has potential applications in the fields of near UV-excited and blue-excited white LEDs. - Graphical abstract: It can be seen from the SEM images that a pompon-like shape was obtained with an average diameter of about 1 {mu}m, and it is composed of many nanoflakes. Highlights: Black-Right-Pointing-Pointer Pompon-like NaLa(MoO{sub 4}){sub 2}:Dy{sup 3+} phosphors have been successfully prepared via a hydrothermal method. Black-Right-Pointing-Pointer Blue emission at 486 nm and yellow emission at 574 nm were obtained from the samples. Black-Right-Pointing-Pointer The yellow-to-blue emission intensity ratio (Y/B) can be changed with the doped concentration of Dy{sup 3+} ions. Black-Right-Pointing-Pointer NaLa(MoO{sub 4}){sub 2}:Dy{sup 3+} can be efficiently excited by the blue light and the near ultraviolet light.

  1. 1.1 MW peak power in doubly QML composite Nd:YVO4sub>/Nd:YVO4sub>/Nd:YVO4sub>/KTP sub-nanosecond green laser with EO and Bi-GaAs.


    Li, Shixia; Li, Dechun; Zhao, Shengzhi; Li, Guiqiu; Li, Xiangyang; Qiao, Hui


    By simultaneously employing electro-optic (EO) modulator and Bi-doped GaAs, dual-loss-modulated Q-switched and mode-locked (QML) multi-segment composite Nd:YVO4sub>/Nd:YVO4sub>/Nd:YVO4sub>/KTP sub-nanosecond green laser is demonstrated with low repetition rate and high peak power. When the incident pump power is up to 6.93 W, only one mode-locking pulse underneath a Q-switching envelope is generated with sub-nanosecond pulse duration at one kilohertz repetition rate. An average output power of 445 mW and a pulse duration of 399 ps are obtained with the incident pump power of 11.13 W, corresponding to a peak power of 1.115 MW which is the highest one in doubly QML sub-nanosecond green laser by now. The laser characteristics are better than those obtained with EO and GaAs. The experimental results indicate that Bi-GaAs is a promising saturable absorber for dual-loss-modulated QML laser. PMID:26907054

  2. New open-framework in the uranyl vanadates A{sub 3}(UO{sub 2}){sub 7}(VO{sub 4}){sub 5}O (A=Li, Ag) with intergrowth structure between A(UO{sub 2}){sub 4}(VO{sub 4}){sub 3} and A{sub 2}(UO{sub 2}){sub 3}(VO{sub 4}){sub 2}O

    SciTech Connect

    Obbade, S. Renard, C.; Abraham, F.


    New uranyl vanadates A{sub 3}(UO{sub 2}){sub 7}(VO{sub 4}){sub 5}O (M=Li (1), Na (2), Ag (3)) have been synthesized by solid-state reaction and their structures determined from single-crystal X-ray diffraction data for 1 and 3. The tetragonal structure results of an alternation of two types of sheets denoted S for {sub {infinity}}{sup 2}[UO{sub 2}(VO{sub 4}){sub 2}]{sup 4-} and D for {sub {infinity}}{sup 2}[(UO{sub 2}){sub 2}(VO{sub 4}){sub 3}]{sup 5-} built from UO{sub 6} square bipyramids and connected through VO{sub 4} tetrahedra to {sub {infinity}}{sup 1}[U(3)O{sub 5}-U(4)O{sub 5}]{sup 8-} infinite chains of edge-shared U(3)O{sub 7} and U(4)O{sub 7} pentagonal bipyramids alternatively parallel to a- and b-axis to construct a three-dimensional uranyl vanadate arrangement. It is noticeable that similar {sub {infinity}}[UO{sub 5}]{sup 4-} chains are connected only by S-type sheets in A{sub 2}(UO{sub 2}){sub 3}(VO{sub 4}){sub 2}O and by D-type sheets in A(UO{sub 2}){sub 4}(VO{sub 4}){sub 3}, thus A{sub 3}(UO{sub 2}){sub 7}(VO{sub 4}){sub 5}O appears as an intergrowth structure between the two previously reported series. The mobility of the monovalent ion in the mutually perpendicular channels created in the three-dimensional arrangement is correlated to the occupation rate of the sites and by the geometry of the different sites occupied by either Na, Ag or Li. Crystallographic data: 293 K, Bruker X8-APEX2 X-ray diffractometer equipped with a 4 K CCD detector, MoK{alpha}, {lambda}=0.71073 A, tetragonal symmetry, space group P4-bar m2, Z=1, full-matrix least-squares refinement on the basis of F{sup 2}; 1,a=7.2794(9) A, c=14.514(4) A, R1=0.021 and wR2=0.048 for 62 parameters with 782 independent reflections with I{>=}2{sigma}(I); 3, a=7.2373(3) A, c=14.7973(15) A, R1=0.041 and wR2=0.085 for 60 parameters with 1066 independent reflections with I{>=}2{sigma}(I). - Abstract: A view of the three-dimensional structure of Li{sub 3}(UO{sub 2}){sub 7}(VO{sub 4}){sub 5}O

  3. Supramolecular Chemistry with Uranyl Tetrahalide ([UO2X4sub>]2-) Anions

    SciTech Connect

    Deifel, Nicholas P.; Cahill, Christopher L.


    Five compounds containing the uranyl tetrabromide anion ([UO2Br4sub>2-) have been synthesized through room temperature reactions of uranium (VI) oxyacetate with several pyridinium cations in highly acidic solutions containing Br- anions. The resulting compounds have been characterized via single-crystal X-ray diffraction and fluorescence spectroscopy. Three of these compounds exhibit both a bifurcated hydrogen bond NH-Br2U and an extended “ribbon motif” of alternating organic and inorganic species.

  4. Synthesis and photoluminescence characteristics of Dy{sup 3+} doped NaY(WO{sub 4}){sub 2} phosphors

    SciTech Connect

    Liu, Xiaohua; Xiang, Wendou; Chen, Fengming; Hu, Zhengfa; Zhang, Wei


    Graphical abstract: The phosphor powders of NaY(WO{sub 4}){sub 2}: Dy{sup 3+} were prepared by solid state reaction. For the different kinds of excitations, the dependence of luminescence intensity on the Tb{sup 3+} concentration was investigated. Display Omitted Highlights: ► We synthesize NaY(WO{sub 4}){sub 2}:Dy{sup 3+} phosphors by the solid-state reaction technique. ► We observe and explain the change of Y/B ratio with Dy{sup 3+} content. ► The I−x curve shows different behavior for different excitations. ► The concentration quenching mechanism is the d–d interaction. -- Abstract: The novel phosphor powders of NaY(WO{sub 4}){sub 2} doped with Dy{sup 3+} were synthesized by solid state reaction. X-ray diffraction analysis showed that the phosphors sintered at 900 °C for 6 h were a pure NaY(WO{sub 4}){sub 2} phase for all the Dy{sup 3+} doping concentrations. The room temperature excitation spectra of the phosphors vary with the Dy{sup 3+} concentration and consist of an intense charge transfer band of WO{sub 4}{sup 2−} groups and weak f–f transition absorption peaks of Dy{sup 3+}. The photoluminescence spectra, excited at the peak wavelength of charge transfer band, exhibit three bands centered at 488, 575 and 662 nm, which originate from the transitions of {sup 4}F{sub 9/2} → {sup 6}H{sub 15/2} (blue), {sup 4}F{sub 9/2} → {sup 6}H{sub 13/2} (yellow) and {sup 4}F{sub 9/2} → {sup 6}H{sub 11/2} (red) of Dy{sup 3+}, respectively. The effects of Dy{sup 3+} concentration on luminescence intensity and the yellow-to-blue intensity ratio of the phosphors were investigated. The different behaviors for the doping concentration dependence of luminescence intensity resulted from the different kinds of excitation was discussed.

  5. trans-K3[TcO2(CN)4sub>

    SciTech Connect

    Chatterjee, Sayandev; Del Negro, Andrew S; Edwards, Matthew K; Twamley, Brendan; Krause, Jeanette A; Bryan, Samuel A


    The dioxotetracyanotechnetate anion, [TcO2(CN)4sub>]3-, of the title complex has octahedral symmetry. The technetium is located on a center of inversion and is bound by two oxygen atoms and four cyano ligands. The Tc=O bond distance of 1.7721 (12) Å is consistent with double bond character. The potassium cations [located on special (1/2,0,1) and general positions] reside in octahedral or tetrahedral environments; interionic K···O and K···N interactions occur in the 2.7877 (19)-2.8598 (15) Å range.

  6. Infrared-to-visible upconversion in thin films of LaEr(MoO{sub 4}){sub 3}

    SciTech Connect

    Bubb, D.M.; Cohen, D.; Qadri, S.B.


    LaEr(MoO{sub 4}){sub 3} thin films have been grown by pulsed laser deposition. The films were characterized by x-ray diffraction, Rutherford backscattering, and fluorescence measurements. The results show that the deposited films were epitaxial with their c axis oriented along the surface normal. Films illuminated with 980 nm laser light show visible emission spectra. This visible emission arises as a result of the Er 4f-4f transitions and their lifetimes. Such so-called 'upconverting phosphors' are important to the development of new chemical and biological sensing applications.

  7. Morphology control of open-framework zinc phosphate Zn{sub 4}(H{sub 3}O)(NH{sub 4}){sub 3}(PO{sub 4}){sub 4} via microwave-assisted technique

    SciTech Connect

    Ding, Ling; Song, Yu; Yang, Wei; Xue, Run-Miao; Zhai, Shang-Ru; An, Qing-Da


    Open-framework zinc phosphates were synthesized by microwave-assisted technique, and it was shown that the morphology of as-prepared materials could be easily tailored by changing synthesis temperature, reaction time and pH value. During the synthesis, when the reaction temperature increases from 130 °C to 220 °C, the products transformed from hexagonal prisms to polyhedron along with the disappearance of the hexagonal prisms vertical plane. Simultaneously, both the reaction time and pH value could promote the nucleation and growth of crystal particles. More interestingly, the target products with different morphologies could be obtained by varying the usage of NaOH or NH{sub 3}·H{sub 2}O at 130 °C during the microwave synthesis process. - Graphical abstract: Zinc phosphates with variable morphologies can be obtained by simply tuning the microwave-heating temperatures. Display Omitted - Highlights: • Synthesis of open-framework Zn{sub 4} (H{sub 3}O) (NH{sub 4}){sub 3}(PO{sub 4}){sub 4} compounds employing microwave technique. • Dependence of morphology on the reaction conditions. • Morphology transformation from hexagonal prisms to polyhedron was observed.

  8. Tailoring the surface properties of LiNi0.4sub>Mn0.4sub>Co0.2O₂ by titanium substitution for improved high voltage cycling performance

    SciTech Connect

    Wolff-Goodrich, Silas; Xin, Huolin L.; Lin, Feng; Markus, Isaac M.; Nordlund, Dennis; Asta, Mark; Doeff, Marca M.


    The present research aims to provide insights into the behavior of LiNi0.4Mn0.4Co0.2O2 (NMC442) and LiNi0.4sub>Mn0.4sub>Co0.2O₂ (NMC442-Ti02) cathode materials under galvanostatic cycling to high potentials, in the context of previous work which predicted that Ti-substituted variants should deliver higher capacities and exhibit better cycling stability than the unsubstituted compounds. It is found that NMC cathodes containing Ti show equivalent capacity fading but greater specific capacity than those without Ti in the same potential range. When repeatedly charged to the same degree of delithiation, NMC cathodes containing Ti showed better capacity retention. Soft x-ray absorption spectroscopy (XAS) spectra for Mn and Co indicated increased reduction in these elements for NMC cathodes without Ti, indicating that the substitution of Ti for Co acts to suppress the formation of a high impedance rock salt phase at the surface of NMC cathode particles. The results of this study validate the adoption of a facile change to existing NMC chemistries to improve cathode capacity retention under high voltage cycling conditions.

  9. Heterogeneous Nature of Relaxation Dynamics of Room-Temperature Ionic Liquids (EMIm)2[Co(NCS)4sub>] and (BMIm)2[Co(NCS)4sub>

    SciTech Connect

    Hensel-Bielowka, Stella; Wojnarowska, Zaneta; Dzida, Marzena; Zorębski, Edward; Zorębski, Michał; Geppert-Rybczyńska, Monika; Peppel, Tim; Grzybowska, Katarzyna; Wang, Yangyang; Sokolov, Alexei P.; Paluch, Marian


    Dynamic crossover above Tg has been recognized as a characteristic feature of molecular dynamics of liquids approaching glass transition. Experimentally, it is manifested as a change in Vogel–Fulcher–Tammann dependence or a breakdown of the Stokes–Einstein and related relations. In this study, we report the exception from this rather general pattern of behavior. By means of dielectric, ultrasonic, rheological, and calorimetric methods, dynamics of two good ionic conductors (BMIm)2[Co(NCS)4sub>] and (EMIm)2[Co(NCS)4sub>] of less common stoichiometry (2:1) was studied in a very broad temperature range. However, none of the mentioned dynamic changes was observed in the entire studied temperature range. On the contrary, the single VFT and the same fractional Walden coefficient were found for conductivity and viscosity changes over 12 decades. Finally and moreover, ultrasonic studies revealed that the data at temperatures which cover the normal liquid region cannot be fitted by a single exponential decay, and the Cole–Cole function should be used instead.

  10. Study of calcium-containing orthophosphates of NaZr{sub 2}(PO{sub 4}){sub 3} structural type by high-temperature X-ray diffraction

    SciTech Connect

    Orlova, A. I.; Kanunov, A. E.; Samoilov, S. G.; Kazakova, A. Yu.; Kazantsev, G. N.


    Orthophosphates Ca{sub 0.5}Ti{sub 2}(PO{sub 4}){sub 3}, Ca{sub 0.5}Zr{sub 2}(PO{sub 4}){sub 3}, Ca{sub 0.75}Zr{sub 2}(SiO{sub 4}){sub 0.5}(PO{sub 4}){sub 2.5}, and CaMg{sub 0.5}Zr{sub 1.5}(PO{sub 4}){sub 3} (structural type NaZr{sub 2}(PO{sub 4}){sub 3}), having different occupancies of interframework positions by calcium, have been prepared by the sol-gel method with the subsequent thermal treatment of dried gels and investigated by IR spectroscopy and X-ray diffraction. The analytical indexing of X-ray diffraction patterns is performed within the sp. gr. R3{sup -}. High-temperature X-ray diffraction was used to investigate the behavior of the orthophosphates upon heating: thermal expansion in the temperature range of 20-610 Degree-Sign C (up to 500 Degree-Sign C for Ca{sub 0.5}Zr{sub 2}(PO{sub 4}){sub 3}). The coefficients of thermal expansion are calculated from the shift of diffraction peaks. The unit-cell parameters of crystals at different temperatures are determined. The dependences of thermal expansion and its anisotropy on the occupancy of cation M positions by calcium are revealed.

  11. M{sup II}Ge(PO{sub 4}){sub 2} (M=Ca, Sr, Ba): Crystal structure, phase transitions and thermal expansion

    SciTech Connect

    Popa, Karin; Wallez, Gilles; Bregiroux, Damien; Loiseau, Pascal


    Three earth alkali-germanium monophosphates M{sup II}Ge(PO{sub 4}){sub 2} (M=Ca, Sr, Ba) were prepared by solid state reaction and their structures, previously unknown, studied by Rietveld analysis. BaGe(PO{sub 4}){sub 2} and high-temperature {beta}-SrGe(PO{sub 4}){sub 2} (space group C2/m, Z=2) are fully isotypic with yavapaiite, whereas CaGe(PO{sub 4}){sub 2} and low-temperature {alpha}-SrGe(PO{sub 4}){sub 2} (C2/c, Z=4) are distorted derivatives. The phase transition between the two forms is observed for the first time. The thermal expansion, resulting from several structural mechanisms, is very anisotropic. - Graphical abstract: The superstructure of SrGe(PO{sub 4}){sub 2} at room temperature ({alpha}) results from the off-centering of cation Sr{sup II}. Highlights: > Crystal structures of yavapaiite-type M{sup II}Ge(PO{sub 4}){sub 2} (M=Ca, Sr, Ba) have been solved. > Distortion and superstructure result from Ca and Sr off-centering. > A global scheme for the polymorphism of yavapaiites is proposed.

  12. Nanocrystalline K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}: Eu for proton beam dosimetry

    SciTech Connect

    Bahl, Shaila; Lochab, S. P.; Pandey, A.; Aleynikov, V. E.; Molokanov, A.; Kumar, Pratik


    This paper investigates the Thermoluminescent response of nanocrystalline K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}: Eu, prepared by Co-precipitation technique to 150 MeV proton beam. The particle size was calculated to be 45 nm by the broadening of the XRD peaks using Scherrer's formula. Samples in the form of pellets were irradiated by 150 MeV proton beam with dose range of 0.1 Gy to 325 Gy. Thermoluminescence (TL) glow curves of the irradiated samples were recorded and studied. It has been found that the phosphor shows a characteristic single peak at around 420 K. The TL response is linear in the range upto 200 Gy and then saturates for higher doses. The wider linear TL response of nanocrystalline K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}: Eu and low fading makes it a superior candidate as a dosimeter to be used for detecting the doses of protons beams for its various applications in the field of space, therapy and research.

  13. First-principles predicted low-energy structures of NaSc(BH{sub 4}){sub 4}

    SciTech Connect

    Tran, Huan Doan Amsler, Maximilian; Goedecker, Stefan; Botti, Silvana; Marques, Miguel A. L.


    According to previous interpretations of experimental data, sodium-scandium double-cation borohydride NaSc(BH{sub 4}){sub 4} crystallizes in the crystallographic space group Cmcm where each sodium (scandium) atom is surrounded by six scandium (sodium) atoms. A careful investigation of this phase based on ab initio calculations indicates that the structure is dynamically unstable and gives rise to an energetically and dynamically more favorable phase with C222{sub 1} symmetry and nearly identical x-ray diffraction pattern. By additionally performing extensive structural searches with the minima-hopping method we discover a class of new low-energy structures exhibiting a novel structural motif in which each sodium (scandium) atom is surrounded by four scandium (sodium) atoms arranged at the corners of either a rectangle with nearly equal sides or a tetrahedron. These new phases are all predicted to be insulators with band gaps of 7.9–8.2 eV. Finally, we estimate the influence of these structures on the hydrogen-storage performance of NaSc(BH{sub 4}){sub 4}.

  14. Photoluminescence performance of thulium doped Li{sub 4}SrCa(SiO{sub 4}){sub 2} under irradiation of ultraviolet and vacuum ultraviolet lights

    SciTech Connect

    Wang, Zhaofeng; Li, Yezhou; Liu, Xiong; Wei, Xingmin; Chen, Yueling; Zhou, Fei; Wang, Yuhua


    Highlights: • A novel blue-emitting phosphor Li{sub 4}SrCa(SiO{sub 4}){sub 2}:Tm{sup 3+} was reported. • Li{sub 4}SrCa(SiO{sub 4}){sub 2}:Tm{sup 3+} exhibited excellent thermal and irradiation stability. • Li{sub 4}SrCa(SiO{sub 4}){sub 2}:Tm{sup 3+} was found to possess high color purity. - Abstract: In this work, we synthesized Tm{sup 3+} doped Li{sub 4}SrCa(SiO{sub 4}){sub 2} phosphors and investigated their photoluminescence properties under the excitation of ultraviolet and vacuum ultraviolet lights. The crystal structure analysis and variation of cell parameters confirm that Tm{sup 3+} ions have been successfully doped in the structure of Li{sub 4}SrCa(SiO{sub 4}){sub 2} host by occupying the sites of Ca{sup 2+} with the coordination number of 6. The luminescence results suggest that Li{sub 4}SrCa(SiO{sub 4}){sub 2}:Tm{sup 3+} is a good blue-emitting phosphor when excited by ultraviolet and vacuum ultraviolet irradiations. In addition, it is observed that there is nearly no degradation for Li{sub 4}SrCa(SiO{sub 4}){sub 2}:Tm{sup 3+} after undergoing thermal and irradiation treatments. Possible mechanisms for the luminescence processes are proposed on the basis of the discussion of excitation and emission spectra. In particular, the emission color of Li{sub 4}SrCa(SiO{sub 4}){sub 2}:Tm{sup 3+} by excitation of 147 and 172 nm irradiations is very close to the standard blue color, suggesting that it could be potentially applied in plasma display panels and mercury-free fluorescence lamps.

  15. Crystal structure, thermally stability and photoluminescence properties of novel Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors

    SciTech Connect

    Guo, Qingfeng; Liao, Libing Mei, Lefu; Liu, Haikun


    A series of novel luminescent phosphors Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} with apatite structure were synthesized via a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples, and the selected Sr{sub 9.97}(PO{sub 4}){sub 6}O:0.03Eu{sup 2+} phosphor exhibits strong thermal quenching resistance, retaining the luminance of 88.73% at 150 °C. The quenching concentration of Eu{sup 2+} in Sr{sub 10}(PO{sub 4}){sub 6}O was about 0.03 attributing to the dipole–quadrupole interaction. The Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphor exhibited a broad-band blue emission at 439 nm upon excitation at 346 nm. The results indicate that Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. - Graphical abstract: Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. - Highlights: • Sr{sub 9.97}(PO{sub 4}){sub 6}O:0.03Eu{sup 2+} phosphor exhibits strong thermal quenching resistance. • Two different Eu{sup 2+} emission centers exists in Sr{sub 10}(PO{sub 4}){sub 6}O. • The activation energy was also estimated for the Eu{sup 2+} luminescence center.

  16. Controlled synthesis, characterization and photoluminescence property of olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3}

    SciTech Connect

    Zhang, Youjin; Zheng, Ao; Yang, Xiaozhi; He, Hongmei; Fan, Yun


    Highlights: ► The olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was gained with EDTA assisted hydrothermal method. ► The product was characterized by XRD, XPS, FTIR, FESEM, and PL. ► The possible formation mechanism for olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was proposed. ► The PL in visible region of the olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was studied. -- Abstract: The olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was obtained by a convenient and facile complex agent assisted hydrothermal method. The product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM) and photoluminescence (PL). The possible formation mechanism of the olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was proposed. The photoluminescence property in visible region of the olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was studied.

  17. Investigation of the physical properties of the tetragonal CeMAl4sub>Si2 (M = Rh, Ir, Pt) compounds

    SciTech Connect

    Ghimire, N. J.; Ronning, F.; Williams, D. J.; Scott, B. L.; Luo, Yongkang; Thompson, J. D.; Bauer, E. D.


    The synthesis, crystal structure and physical properties studied by means of x-ray diffraction, magnetic, thermal and transport measurements of CeMAl4sub>Si2 (M = Rh, Ir, Pt) are reported, along with the electronic structure calculations for LaMAl4sub>Si2 (M = Rh, Ir, Pt). These materials adopt a tetragonal crystal structure (space group P4/mmm) comprised of BaAl4sub> blocks, separated by MAl2 units, stacked along the c-axis. Both CeRhAl4sub>Si2 and CeIrAl4sub>Si2 order antiferromagnetically below TN1 = 14 and 16 K, respectively, and undergo a second antiferromagnetic transitition at lower temperature (TN2 = 9 and 14 K, respectively). CePtAl4sub>Si2 orders ferromagnetically below TC = 3 K with an ordered moment of μsat = 0.8 μB for a magnetic field applied perpendicular to the c-axis. Electronic structure calculations reveal quasi-2D character of the Fermi surface.

  18. Gain change by adjusting the pumping wavelength in an end-pumped Nd:YVO4sub> amplifier.


    Nie, Mingming; Liu, Qiang; Ji, Encai; Fu, Xing; Gong, Mali


    In this paper, the performance of an end-pumped laser amplifier was experimentally studied by adjusting the pumping wavelength of a laser diode. An interesting phenomenon was observed: that the gain would decrease with an increase in absorbed pump power. The scaled output power of 0.3 at. % doped 20 mm long Nd:YVO4sub> crystal decreased from 0.48 to 0.2 W when the absorbed pump power increased from 17.5 to 17.8 W. Theoretical analysis was demonstrated according to our previous model. The long crystal length is the main reason for the observed phenomenon. This phenomenon could be utilized to enhance amplifier gain and improve thermal performance, including the maximal temperature and thermal stress of the crystal. PMID:27409123

  19. Morphologically Templated Growth of Aligned Spinel CoFe2O4sub> Nanorods

    SciTech Connect

    Zhang, Zongtao; Rondinone, Adam Justin; Ma, Jianxing; Shen, Jian; Dai, Sheng


    Uniaxially aligned CoFe{sub 2}O{sub 4} nanorods are obtained by coprecipitation of Co{sup 2+}, Fe{sub 2+}, and C{sub 2}O{sub 4}{sup 2-} ions in a microemulsion solution, and subsequent high-temperature decomposition of CoFe{sub 2}(C{sub 2}O{sub 4}){sub 3}. Each nanorod is made up of a 'tectonic' assembly of CoFe{sub 2}O{sub 4} nanocrystals. Magnetization of such SoFe{sub 2}O{sub 4} materials may lead to their use in high-density magnetic recording media and high-performance electromagnetic and spintronic devices.

  20. Megahertz-level, high-power picosecond Nd:LuVO4sub> regenerative amplifier free of period doubling.


    Gao, Peng; Lin, Hua; Li, Jinfeng; Guo, Jie; Yu, Haohai; Zhang, Huaijin; Liang, Xiaoyan


    We report on a high repetition rate, high-power picosecond Nd:LuVO4sub> regenerative amplifier. Period doubling caused energy instability was eliminated at megahertz-level repetition rate with the modified seeding source. A multi-pass cell was used to improve the seed pulse energy to achieve complete suppression of the onset of bifurcation. At a maximum repetition rate of 1.43 MHz, the system produced 7.0-ps-long pulses with an average output power of 25.1 W, corresponding to a pulse energy of 17.6 μJ. At 100 kHz, the pulse energy increased to 205 μJ with an average power of 20.5 W. Moreover, the injected pulses with pulse duration of 5.1 ps broadened to 8.9 ps because of gain narrowing in the amplifier. PMID:27410559

  1. New measurement of the {sup 68}Zn(4{sub 1}{sup +}) g factor combined with a reanalysis of previous data

    SciTech Connect

    Moschner, K.; Bernards, C.; Bettermann, L.; Speidel, K.-H.; Leske, J.; Bauer, C.; Moeller, T.; Honma, M.; Maier-Komor, P.; Muecher, D.


    We have remeasured and have redetermined the g factor for the 4{sub 1}{sup +} state in {sup 68}Zn following inconsistencies between earlier measurements and a recent result. We have reanalyzed several former measurements by applying an alternative analysis procedure, which allows for determining the precession effect separately for each gamma detector implying less uncertainties in the background subtraction for the relevant spectra. In addition, all measured g-factor and B(E2) data for the first 2{sup +} and 4{sup +} states in all stable even-A Zn isotopes and the radioactive {sup 62}Zn, are compared with new large-scale shell model calculations based on the most advanced effective interaction in the fpg-shell model space.

  2. Neutron diffraction study on the two-dimensional Ising system KEr(MoO{sub 4}){sub 2}

    SciTech Connect

    Mat'as, Slavomir; Dudzik, Esther; Feyerherm, Ralf; Gerischer, Sebastian; Klemke, Sebastian; Prokes, Karel; Orendacova, Alzbeta


    The magnetic properties of the two-dimensional Ising antiferromagnet KEr(MoO{sub 4}){sub 2} have been investigated below and above transition temperature T{sub N}{approx}0.95 K in zero field and in fields up to 6.5 T by means of elastic neutron-diffraction, heat-capacity, and magnetization measurements. The low-temperature signal recorded at 0.34 K by neutron diffraction is explained within a noncollinear magnetic structure model. However, additional contribution is also present when applying the external magnetic field along the c axis even at temperatures well above the magnetic transition temperature T{sub N}. Various explanations are discussed.

  3. Enhanced Thermoelectric Properties of Cu2ZnSnSe4sub> with Ga-doping

    SciTech Connect

    Wei, Kaya; Beauchemin, Laura; Wang, Hsin; Porter, Wallace D.; Martin, Joshua; Nolas, George S.


    Gallium doped Cu2ZnSnSe4sub> quaternary chalcogenides with and without excess Cu were synthesized by elemental reaction and densified using hot pressing in order to investigate their high temperature thermoelectric properties. The resistivity, , and Seebeck coefficient, S, for these materials decrease with increased Ga-doping while both mobility and effective mass increase with Ga doping. The power factor (S2/ρ) therefore increases with Ga-doping. The highest thermoelectric figure of merit (ZT = 0.39 at 700 K) was obtained for the composition that had the lowest thermal conductivity. Our results suggest an approach to achieving optimized thermoelectric properties and are part of the continuing effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.

  4. Ionic liquid assisted microwave synthesis route towards color-tunable luminescence of lanthanide- doped BiPO4sub>

    SciTech Connect

    Cybinska, Joanna; Lorbeer, Chantal; Mudring, Anja -Verena


    Ln3+-doped (Ln=Sm, Eu, Tb, Dy) nanoparticles of BiPO4sub> with a particle size below 10 nm were synthesized in a straightforward manner from the appropriate mixture of the respective metal acetates and the task-specific ionic liquids choline or butylammonium dihydrogen-phosphate by conversion in a laboratory microwave (120 °C, 10 min). The ionic liquid acts not only as a solvent and microwave susceptor, but also as the reaction partner and nanoparticle stabilizer. The materials were thoroughly characterized not only with respect to their optical properties but also by PXRD, FT-IR, TEM techniques. Furthermore, depending on the lanthanide, the nanomaterial shows intense luminescence of different colors such as: orange (Sm3+), red (Eu3+), green (Tb3+) or even white (Dy3+).

  5. Luminescent and lasing characteristics of heavily doped Yb{sup 3+}:KY(WO{sub 4}){sub 2} crystals

    SciTech Connect

    Kisel', V E; Troshin, A E; Shcherbitskii, V G; Kuleshov, N V; Pavlyuk, A A; Brunner, F; Paschotta, R; Morier-Genoud, F; Keller, U


    The luminescence decay times are measured taking into account reabsorption for KY(WO{sub 4}){sub 2}:Yb(KYW:Yb) crystals with atomic concentrations of active ions from 0.2% to 30%. The radiative lifetime of Yb{sup 3+} ions was measured to be 233 {mu}s. The cw output power of 1.46 and 1.62 W was achieved with the slope efficiency 52% and 47% for Yb:KYW lasers with the atomic concentration of Yb{sup 3+} ions equal to 10% and 30%, respectively. Using a semiconductor mirror with a saturable absorber (SESAM) in the passive mode-locking regime, pulses of duration 194 and 180 fs were obtained at wavelengths of 1042 and 1039 nm for crystals with Yb{sup 3+} concentrations equal to 10% and 30%, respectively, the average output power being 0.63 and 0.75 W. (lasers and amplifiers)

  6. Syntheses, crystal structures and vibrational spectra of KLn(SO{sub 4}){sub 2}.H{sub 2}O (Ln=La, Nd, Sm, Eu, Gd, Dy)

    SciTech Connect

    Kazmierczak, Karolina; Hoeppe, Henning A.


    The potassium lanthanide double sulphates KLn(SO{sub 4}){sub 2}.H{sub 2}O (Ln=La, Nd, Sm, Eu, Gd, Dy) were obtained by evaporation of aqueous reaction mixtures of rare earth (III) sulphates and potassium thiocyanate at 298 K. X-ray single-crystal investigations show that KLn(SO{sub 4}){sub 2}.H{sub 2}O (Ln=Nd, Sm, Eu, Gd, Dy) crystallise monoclinically (Ln=Sm: P2{sub 1}/c, Z=4, a=10.047(1), b=8.4555(1), c=10.349(1) A, wR2=0.060, R1=0.024, 945 reflections, 125 parameters) while KLa(SO{sub 4}){sub 2}.H{sub 2}O adopts space group P3{sub 2}21 (Z=3, a=7.1490(5), c=13.2439(12) A, wR2=0.038, R1=0.017, 695 reflections, 65 parameters). The coordination environment of the lanthanide ions in KLn(SO{sub 4}){sub 2}.H{sub 2}O is different in the case of the Nd/Sm/Gd and the Eu/Dy compounds, respectively. In the first case the Ln atoms are nine-fold coordinated in contrast to the latter where the Ln ions are eight-fold coordinated by oxygen atoms. The vibrational spectra of KLn(SO{sub 4}){sub 2}.H{sub 2}O and the UV-vis reflection spectra of KEu(SO{sub 4}){sub 2}.H{sub 2}O and KNd(SO{sub 4}){sub 2}.H{sub 2}O are also reported. - Graphical abstract: The lanthanide potassium double sulphates exhibit an unexpected change in the coordination mode by a simple rotation of sulphate tetrahedron 2.

  7. Synthesis, structural and spectroscopic properties of acentric triple molybdate Cs{sub 2}NaBi(MoO{sub 4}){sub 3}

    SciTech Connect

    Savina, A.A.; Atuchin, V.V.; Solodovnikov, S.F.; Solodovnikova, Z.A.; Krylov, A.S.; Maximovskiy, E.A.; Molokeev, M.S.; Oreshonkov, A.S; Pugachev, A.M.; and others


    New ternary molybdate Cs{sub 2}NaBi(MoO{sub 4}){sub 3} is synthesized in the system Na{sub 2}MoO{sub 4}–Cs{sub 2}MoO{sub 4}–Bi{sub 2}(MoO{sub 4}){sub 3}. The structure of Cs{sub 2}NaBi(MoO{sub 4}){sub 3} of a new type is determined in noncentrosymmetric space group R3c, a=10.6435(2), c=40.9524(7) Å, V=4017.71(13) Å{sup 3}, Z=12 in anisotropic approximation for all atoms taking into account racemic twinning. The structure is completely ordered, Mo atoms are tetrahedrally coordinated, Bi(1) and Bi(2) atoms are in octahedra, and Na(1) and Na(2) atoms have a distorted trigonal prismatic coordination. The Cs(1) and Cs(2) atoms are in the framework cavities with coordination numbers 12 and 10, respectively. No phase transitions were found in Cs{sub 2}NaBi(MoO{sub 4}){sub 3} up to the melting point at 826 K. The compound shows an SHG signal, I{sub 2w}/I{sub 2w}(SiO{sub 2})=5 estimated by the powder method. The vibrational properties are evaluated by Raman spectroscopy, and 26 narrow lines are measured. - Graphical abstract: - Highlights: • The crystal structure of Cs{sub 2}NaBi(MoO{sub 4}){sub 3} is defined. • The molybdate Cs{sub 2}NaBi(MoO{sub 4}){sub 3} is stable up to melting point at 826 K. • Vibrational properties of Cs{sub 2}NaBi(MoO{sub 4}){sub 3} are evaluated by Raman spectroscopy.

  8. Synthesis, structures and properties of the new lithium cobalt(II) phosphate Li{sub 4}Co(PO{sub 4}){sub 2}

    SciTech Connect

    Glaum, R.; Gerber, K.; Schulz-Dobrick, M.


    {alpha}-Li{sub 4}Co(PO{sub 4}){sub 2} has been synthesized and crystallized by solid-state reactions. The new phosphate crystallizes in the monoclinic system (P2{sub 1}/a, Z=4, a=8.117(3) Angstrom-Sign , b=10.303(8) Angstrom-Sign , c=8.118(8) Angstrom-Sign , {beta}=104.36(8) Angstrom-Sign ) and is isotypic to {alpha}-Li{sub 4}Zn(PO{sub 4}){sub 2}. The structure of {alpha}-Li{sub 4}Co(PO{sub 4}){sub 2} has been determined from single-crystal X-ray diffraction data {l_brace}R{sub 1}=0.040, wR{sub 2}=0.135, 2278 unique reflections with F{sub o}>4{sigma}(F{sub o}){r_brace}. The crystal structure, which might be regarded as a superstructure of the wurtzite structure type, is build of layers of regular CoO{sub 4}, PO{sub 4} and Li1O{sub 4} tetrahedra. Lithium atoms Li2, Li3 and Li4 are located between these layers. Thermal investigations by in-situ XRPD, DTA/TG and quenching experiments suggest decomposition followed by formation and phase transformation of Li{sub 4}Co(PO{sub 4}){sub 2}: {alpha}-Li{sub 4}Co(PO{sub 4}){sub 2} Long-Rightwards-Double-Arrow {sup 442 Degree-Sign C}{beta}-Li{sub 3}PO{sub 4}+LiCoPO{sub 4} Rightwards-Harpoon-Over-Leftwards-Harpoon {sup 773 Degree-Sign C}{beta}-Li{sub 4}Co(PO{sub 4}){sub 2} Long-Rightwards-Double-Arrow {sup quenchingto25 Degree-Sign C}{alpha}-Li{sub 4} Co(PO{sub 4}){sub 2} According to HT-XRPD at {theta}=850 Degree-Sign C{beta}-Li{sub 4}Co(PO{sub 4}){sub 2} (Pnma, Z=2, 10.3341(8) A, b=6.5829(5) A, c=5.0428(3) Angstrom-Sign ) is isostructural to {gamma}-Li{sub 3}PO{sub 4}. The powder reflectance spectrum of {alpha}-Li{sub 4}Co(PO{sub 4}){sub 2} shows the typical absorption bands for the tetrahedral chromophore [Co{sup II}O{sub 4}]. - Graphical abstract: The complex formation and decomposition behavior of Li{sub 4}Co(PO{sub 4}){sub 2} with temperature has been elucidated. The crystal structure of its {alpha}-phase was determined from single crystal data, HT-XRPD allowed derivation of a structure model for the {beta}-phase. Both

  9. Three-dimensional frameworks of cubic (NH{sub 4}){sub 5}Ga{sub 4}SbS{sub 10}, (NH{sub 4}){sub 4}Ga{sub 4}SbS{sub 9}(OH) {small _bullet} H{sub 2}O, and (NH{sub 4}){sub 3}Ga{sub 4}SbS{sub 9}(OH{sub 2}) {small_bullet} 2H{sub 2}O.

    SciTech Connect

    Mertz, J. L.; Ding, N.; Kanatzidis, M. G.


    Three new isostructural open-framework sulfides, (NH{sub 4}){sub 5}Ga{sub 4}SbS{sub 10} (1), (NH{sub 4}){sub 4}Ga{sub 4}SbS{sub 9}(OH) {sm_bullet} H{sub 2}O (2a), and (NH{sub 4}){sub 3}Ga{sub 4}SbS{sub 9}(H{sub 2}O) {sm_bullet} 2H{sub 2}O (2b), were synthesized under basic hydrothermal conditions using ammonium hydroxide as the structure-directing agent. The structures feature a three-dimensional open framework comprised of adamantane [Ga{sub 4}Q{sub 10}]{sup 8-} clusters linked with Sb{sup 3+} centers. The compounds are wide gap semiconductors, crystallize in the chiral space group P2{sub 1}3, and represent a new structure type. They exhibit nonlinear optical properties.

  10. Exchange bias effect in Au-Fe3O4sub> dumbbell nanoparticles induced by the charge transfer from gold

    SciTech Connect

    Feygenson, Mikhail; Bauer, John C; Gai, Zheng; Marques, Carlos; Aronson, Meigan C.; Teng, Xiaowei; Su, Dong; Stanic, Vesna; Urban, Volker S; Kevin, Beyer; Dai, Sheng


    We have studied the origin of the exchange bias effect in the Au-Fe3O4sub> dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe3O4sub> nanoparticles (9.8 nm). The magnetization, small-angle neutron scattering, synchrotron x-ray diffraction and scanning transmission electron microscope measurements determined the antiferromagnetic FeO wüstite phase within Fe3O4sub> nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe3O4sub> is giving rise to the exchange bias effect. The strength of the exchange bias fields depends on the interfacial area and lattice mismatch between both phases. We propose that the charge transfer from the Au nanoparticles is responsible for a partial reduction of the Fe3O4sub> into FeO phase at the interface with Au nanoparticles. The Au-O bonds are formed across the interface to accommodate an excess of oxygen released during the reduction of magnetite.

  11. CuCo2O4sub> ORR/OER Bi-functional catalyst: Influence of synthetic approach on performance

    SciTech Connect

    Serov, Alexey; Andersen, Nalin I.; Roy, Aaron J.; Matanovic, Ivana; Artyushkova, Kateryna; Atanassov, Plamen


    A series of CuCo2O4sub> catalysts were synthesized by pore forming, sol-gel, spray pyrolysis and sacrificial support methods. Catalysts were characterized by XRD, SEM, XPS and BET techniques. The electrochemical activity for the oxygen reduction and oxygen evolution reactions (ORR and OER) was evaluated in alkaline media by RRDE. Density Functional Theory was used to identify two different types of active sites responsible for ORR/OER activity of CuCo2O4sub> and it was found that CuCo2O4 sub>can activate the O-O bond by binding molecular oxygen in bridging positions between Co or Co and Cu atoms. It was found that the sacrificial support method (SSM) catalyst has the highest performance in both ORR and OER and has the highest content of phase-pure CuCo2O4sub>. It was shown that the presence of CuO significantly decreases the activity in oxygen reduction and oxygen evolution reactions. As a result, the half-wave potential (E1/2) of CuCo2O4sub>-SSM was found as 0.8 V, making this material a state-of-the-art, unsupported oxide catalyst.

  12. Microwave-assisted preparation of Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C composite with high-rate capacity

    SciTech Connect

    Yan, Ji; Mao, Wen-feng; Xie, Hui; Tang, Zhi-yuan; Yuan, Wei; Chen, Xue-cheng; Xu, Qiang; Ma, Li


    Highlights: ► High-rate Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C is firstly reported via a microwave-assisted method. ► The reduced particle size is responsible for the improved high-rate performance. ► A discharge capacity of 100 mAh g{sup −1} is obtained at 20 C charge–discharge rate. -- Abstract: A fast sol–gel assisted microwave heating approach has been developed for the synthesis of high-rate Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C cathode material. This approach can synthesize Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C particles with high purity and good crystallinity in 12 min at a low microwave power of 320 W. In the voltage range of 3.0–4.3 V, the obtained Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C delivers a reversible discharge capacity of 100 mAh g{sup −1} after 100 cycles at 20 °C, exhibiting excellent rate capability and cycling performance. The rate-recovery performance also suggests that the Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C material possesses excellent structure stability after high-rate cycles, presenting excellent application value in high-power lithium ion batteries.

  13. Structural features of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, and their catalytic activity in butan-2-ol conversion

    SciTech Connect

    Kacimi, Mohammed; Ziyad, Mahfoud; Hatert, Frederic . E-mail:


    AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, were synthesized by a solid state reaction in air at 750 deg. C. The X-ray powder diffraction pattern of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} indicates the presence of small amounts of (Ca, Mg){sub 3}(PO{sub 4}){sub 2} with the whitlockite structure, as impurity, whereas AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3} is constituted by pure alluaudite. The Rietveld refinements of the X-ray powder diffraction patterns indicate an ordered cationic distribution for AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, with Ag on A(2)', Cd on A(1) and M(1), and Mg on M(2), whereas a disordered distribution of Cd and Ca between the A(1) and M(1) sites is observed for AgCaCdMg{sub 2}(PO{sub 4}){sub 3}. The catalytic properties of these compounds has been measured in reaction of butan-2-ol dehydrogenation. In the absence of oxygen, both samples exhibit poor dehydrogenation activity. All samples displayed no dehydration activity. Introduction of oxygen into the feed changed totally the catalytic behavior of the catalysts. The production of methyl ethyl ketone increases with time on stream and the reaction temperature. AgCaCdMg{sub 2}(PO{sub 4}){sub 3} is more efficient than AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}.

  14. X-ray and Neutron Diffraction Studies of Rb{sub 4}LiH{sub 3}(XO{sub 4}){sub 4} (X = S, Se) Single Crystals

    SciTech Connect

    Troyanov, S.I.; Snigireva, E.M.; Ling, C.D.


    Rb{sub 4}LiH{sub 3}(SeO{sub 4}){sub 4} single crystals (1) are studied by the X-ray diffraction method at 180 K and Rb{sub 4}LiH{sub 3}(SO{sub 4}){sub 4} single crystals (2a-2c) are studied by the neutron diffraction method at 298 K (2a and 2b) and 480 K (2c). It is established that isostructural single crystals 1 and 2 (sp. gr. P4{sub 1}) have analogous systems of hydrogen bonds: chains of four XO{sub 4} tetrahedra linked by three H bonds with the central bond (2.49 A) being somewhat shorter than the terminal ones (2.52-2.54 A). In the high-temperature 2c phase, the amplitudes of atomic thermal vibrations and the degree of proton disorder in the central hydrogen bond have somewhat elevated values.

  15. Mechanism of the low thermal expansion in {alpha}-Hf{sub 2}O(PO{sub 4}){sub 2} and its zirconium analog

    SciTech Connect

    Wallez, Gilles Bregiroux, Damien; Quarton, Michel


    The thermal expansion of recently characterized {alpha}-Zr{sub 2}O(PO{sub 4}){sub 2} and {alpha}-Hf{sub 2}O(PO{sub 4}){sub 2} is found to be very low (respectively 2.6 and 2.9x10{sup -6} K{sup -1}, 20-900 deg. C). High-temperature X-ray diffraction and Rietveld analysis allowed to identify a dual contraction mechanism, involving a classical ring deformation and the rocking of bridging oxygens. - Graphical abstract: Compared to other zirconium phosphates, {alpha}-Zr{sub 2}O(PO{sub 4}){sub 2} shows a remarkable low thermal expansion of 2.6x10{sup -6} K{sup -1}.

  16. Nonperturbative tests for asymptotic freedom in the PT-symmetric (-{phi}{sup 4}){sub 3+1} theory

    SciTech Connect

    Shalaby, Abouzeid; Al-Thoyaib, Suleiman S.


    In the literature, the asymptotic freedom property of the (-{phi}{sup 4}) theory is always concluded from real-line calculations while the theory is known to be a non-real-line one. In this article, we test the existence of the asymptotic freedom in the (-{phi}{sup 4}){sub 3+1} theory using the mean field approach. In this approach and contrary to the original Hamiltonian, the obtained effective Hamiltonian is rather a real-line one. Accordingly, this work resembles the first reasonable analysis for the existence of the asymptotic freedom property in the PT-symmetric (-{phi}{sup 4}) theory. In this respect, we calculated three different amplitudes of different positive dimensions (in mass units) and find that all of them go to very small values at high energy scales (small coupling) in agreement with the spirit of the asymptotic freedom property of the theory. To test the validity of our calculations, we obtained the asymptotic behavior of the vacuum condensate in terms of the coupling, analytically, and found that the controlling factor {Lambda} has the value ((4{pi}){sup 2}/6)=26.319 compared to the result {Lambda}=26.3209 from the literature, which was obtained via numerical predictions. We assert that the nonblowup of the massive quantities at high energy scales predicted in this work strongly suggests the possibility of the solution of the famous hierarchy puzzle in a standard model with the PT-symmetric Higgs mechanism.

  17. Spectral properties of Tm{sup 3+}:NaGd(MoO{sub 4}){sub 2} crystal

    SciTech Connect

    Wang Zujian; Li Xiuzhi; Wei Qian; Long Xifa


    The Tm{sup 3+}:NaGd(MoO{sub 4}){sub 2} crystal with dimensions of {phi} 15 x 38 mm{sup 2} was grown by Czochralski method. Polarized absorption and fluorescence spectra at room temperature were investigated. The absorption bands attributed to {sup 3}H{sub 6} {yields} {sup 3}H{sub 4} transition have large absorption cross-sections, which are 3.99 x 10{sup -20} and 2.36 x 10{sup -20} cm{sup 2} for {sigma}- and {pi}-polarization, respectively. The emission bands corresponding to the {sup 3}H{sub 4} {yields} {sup 3}H{sub 6} transition are strong and broad with emission cross-sections of 1.33 x 10{sup -20} and 1.20 x 10{sup -20} cm{sup 2} for {sigma}- and {pi}-polarization, respectively. The correlative full widths at half maximum are 35 nm for {sigma}-polarization and 36 nm for {pi}-polarization. The fluorescence lifetime for the {sup 3}H{sub 4} {yields} {sup 3}F{sub 4} transition is 146 {mu}s and the luminescent quantum efficiency is 76.8%.

  18. SU(4){sub L} x U(1){sub X} three-family model for the electroweak interaction

    SciTech Connect

    Sanchez, Luis A.; Wills-Toro, Luis A.; Zuluaga, Jorge I.


    An extension of the gauge group SU(2){sub L} x U(1){sub Y} of the standard model to the symmetry group SU(4){sub L} x U(1){sub X} (3-4-1 for short) is presented. The model does not contain exotic electric charges and anomaly cancellation is achieved with a family of quarks transforming differently from the other two, thus leading to FCNC. By introducing a discrete Z{sub 2} symmetry we obtain a consistent fermion mass spectrum, and avoid unitarity violation of the Cabibbo-Kobayashi-Maskawa mixing matrix arising from the mixing of ordinary and exotic quarks. The neutral currents coupled to all neutral vector bosons are studied, and by using CERN LEP and SLAC Linear Collider data at Z-pole and atomic parity violation data, we bound parameters of the model related to tree-level Z-Z{sup '} mixing. These parameters are further constrained by using experimental input from neutral meson mixing in the analysis of sources of FCNC present in the model. Constraints coming from the contribution of exotic particles to the one-loop oblique electroweak parameters S, T and U are also briefly discussed. Finally, a comparison is done of the predictions of different classes of 3-4-1 models without exotic electric charges.

  19. Compact KGd(WO4sub>)2 picosecond pulse-train synchronously pumped broadband Raman laser.


    Gao, Xiao Qiang; Long, Ming Liang; Meng, Chen


    We demonstrate an efficient approach to realizing an extra-cavity, synchronously pumped, stimulated Raman cascaded process under low repetition frequency (1 kHz) pump conditions. We also construct a compact KGd(WO4sub>)2 (KGW) crystal picosecond Raman laser that has been configured as the developed method. A pulse-train green laser pumped the corresponding 70 mm long KGW crystal Raman cavity. The pulse train contains six pulses, about 800 ps separated, for every millisecond; thus, it can realize synchronous pumping between pump pulse and the pumped Raman cavity. The investigated system produced a collinear Raman laser output that includes six laser lines covering the 532 to 800 nm spectra. This is the first report on an all-solid-state, high-average-power picosecond collinear multi-wavelength (more than three laser components) laser to our knowledge. This method has never been reported on before in the synchronously pumped stimulated Raman scattering (SRS) realm. PMID:27556971

  20. Magnetic susceptibility, specific heat and magnetic structure of CuNi{sub 2}(PO{sub 4}){sub 2}

    SciTech Connect

    Escobal, Jaione; Pizarro, Jose L.; Mesa, Jose L. . E-mail:; Larranaga, Aitor; Fernandez, Jesus Rodriguez; Arriortua, Maria I.; Rojo, Teofilo


    CuNi{sub 2}(PO{sub 4}){sub 2} phosphate has been synthesized by the ceramic method at 800 deg. C in air. The crystal structure consists of a three-dimensional skeleton constructed from MO{sub 4} (M{sup II} =Cu and Ni) planar squares and M{sub 2}O{sub 8} dimers with square pyramidal geometry, which are interconnected by (PO{sub 4}){sup 3-} oxoanions with tetrahedral geometry. The magnetic behavior has been studied on powdered sample by using susceptibility, specific heat and neutron diffraction data. The bimetallic copper(II)-nickel(II) orthophosphate exhibits a three-dimensional magnetic ordering at, approximately, 29.8 K. However, its complex crystal structure hampers any parametrization of the J-exchange parameter. The specific heat measurements exhibit a three-dimensional magnetic ordering ({lambda}-type) peak at 29.5 K. The magnetic structure of this phosphate shows ferromagnetic interactions inside the Ni{sub 2}O{sub 8} dimers, whereas the sublattice of Cu(II) ions presents antiferromagnetic couplings along the y-axis. The change of the sign in the magnetic unit-cell, due to the [1/2, 0, 1/2] propagation vector determines a purely antiferromagnetic structure. - Graphical abstract: Magnetic structure of CuNi2(PO4)2.

  1. Controllable synthesis and down-conversion properties of flower-like NaY(MoO{sub 4}){sub 2} microcrystals via polyvinylpyrrolidone-mediated

    SciTech Connect

    Lin, Han; Yan, Xiaohong; Wang, Xiangfu


    Double alkaline rare-earth molybdates NaY(MoO{sub 4}){sub 2} with multilayered flower-like architectures have been successfully synthesized via hydrothermal method in polyvinylpyrrolidone (PVP)-modified processes. The crystal structure and morphology of the obtained products were characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that reaction time and the amount of PVP have crucial influences on the morphology of the resulting novel microstructures. Under 450 nm excitation, Ho{sup 3+}/Yb{sup 3+} co-doped NaY(MoO{sub 4}){sub 2} samples exhibit 539 nm green emission and 960–1200 nm broadband near-infrared emission, corresponding to the characteristic lines of Ho{sup 3+} and Yb{sup 3+}, respectively. Moreover, increasing Yb{sup 3+} doping enhances the energy transfer efficiency from Ho{sup 3+} to Yb{sup 3+}. - Graphical abstract: Low and high-magnification SEM images demonstrate the perfect flower-like NaY(MoO{sub 4}){sub 2} prepared in the presence of PVP; Detailed TEM and HRTEM images further manifest the single-crystalline feature. Highlights: • NaY(MoO{sub 4}){sub 2} flower-like microstructures were synthesized by hydrothermal method using polyvinylpyrrolidone. • Polyvinylpyrrolidone induces the growth of the NaY(MoO{sub 4}){sub 2} to form multilayered architectures. • Flowerlike NaY(MoO{sub 4}){sub 2}: Ho{sup 3+}, Yb{sup 3+} phosphors were investigated as a downconversion layer candidate.

  2. Oxygen trapped by rare earth tetrahedral clusters in Nd4sub>FeOS6: Crystal structure, electronic structure, and magnetic properties

    SciTech Connect

    Lin, Qisheng; Taufour, Valentin; Zhang, Yuemei; Wood, Max; Drtina, Thomas; Bud’ko, Sergey L.; Canfield, Paul C.; Miller, Gordon J.


    Single crystals of Nd4sub>FeOS6 were grown from an Fe-S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4sub>MnOSe6-type structure (P63mc, a = 9.2693(1) Å, c = 6.6650(1) Å, V = 495.94(1) Å3, Z = 2), featuring parallel chains of face-sharing [FeS6x1/2]4- trigonal antiprisms and interlinked [Nd4sub>OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4sub>MnOSe6-type Nd4sub>FeOS6 and the related La3CuSiS7- and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4sub>FeOS6 suggested the dominance of antiferromagnetic interactions at low temperature, but no magnetic ordering down to 2 K was observed. Spin-polarized electronic structure calculations revealed magnetic frustration with dominant antiferromagnetic interactions.

  3. High power, diffraction limited picosecond oscillator based on Nd:GdVO4sub> bulk crystal with σ polarized in-band pumping.


    Lin, Hua; Guo, Jie; Gao, Peng; Yu, Hai; Liang, Xiaoyan


    We report on a high power passively mode-locked picosecond oscillator based on Nd:GdVO4sub> crystal with σ polarized in-band pumping. Thermal gradient and thermal aberration was greatly decreased with proposed configuration. Maximum output power of 37 W at 81 MHz repetition rate with 19.3 ps pulse duration was achieved directly from Nd:GdVO4sub> oscillator, corresponding to 51% optical efficiency. The oscillator maintained diffraction limited beam quality of M2 < 1.05 at different output coupling with pulse duration between 11.2 ps to 19.3 ps. PMID:27410558

  4. Photoluminescence and thermoluminescence properties of Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor

    SciTech Connect

    Gupta, Palvi; Bedyal, A.K.; Kumar, Vinay; Khajuria, Y.; Lochab, S.P.; Pitale, S.S.; Ntwaeaborwa, O.M.; Swart, H.C.


    Energy level diagram of Tb{sup 3+} ion in the K{sub 3}Gd(PO{sub 4}){sub 2} host lattice. - Highlights: • First time, a detailed TL and PL study on undoped and Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor. • Combustion method was employed to synthesize the Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor. • Mechanism of excitation and emission in undoped and Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor was given. - Abstract: Tb{sup 3+} doped nanoparticulate K{sub 3}Gd(PO{sub 4}){sub 2} phosphor was prepared by combustion method using urea as a fuel. The structure, optical and luminescent properties of the phosphor were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and thermoluminescence (TL) spectroscopy. In undoped K{sub 3}Gd(PO{sub 4}){sub 2}, the excitation and emission peaks at 273 nm and 323 nm belongs to the {sup 8}S{sub 7/2} → {sup 6}I{sub J(J=7/2)} and {sup 6}P{sub J(J=7/2)} → {sup 8} S{sub 7/2} transitions of Gd{sup 3+} while green emission was observed in the Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2}. TL study was carried out after exposing the samples to γ-radiations (0.1–5 kGy) in the K{sub 3}Gd(PO{sub 4}){sub 2}:Tb{sup 3+} (1.5 mol%). The calculated kinetic parameters were compared with different methods. The band gap of the phosphor was estimated as 5.80 eV. The green shade of the Tb{sup 3+} ion with the CIE coordinates (x, y) as (0.29, 0.54) was in good agreement with the well known green phosphors.

  5. Calculation of enthalpies of formation of compounds of the type M/sub 5/R(EO/sub 4/)/sub 4/

    SciTech Connect

    Kaganyuk, D.S.; Perepelitsa, A.P.


    Enthalpies of formation were determined for compounds of the M/sub 5/R(EO/sub 4/)/sub 4/ type, where M = Li, Na, K, Rb, Cs, Fr, Tl, Ag, Cu; R = the rare earth elements, y, Bi; and E = Mo, W. Values of 0/, either experimentally determined or estimated by any quantum-chemical methods, are absent in the literature for these compounds. The obtained values of lambdaHf/sup 0/ for M/sub 5/R(EO/sub 4/)/sub 4/ are presented.

  6. Synthesis, crystal structure and spectroscopy properties of Na{sub 3} AZr(PO{sub 4}){sub 3} (A=Mg, Ni) and Li{sub 2.6}Na{sub 0.4}NiZr(PO{sub 4}){sub 3} phosphates

    SciTech Connect

    Chakir, M. . E-mail:; El Jazouli, A.; Waal, D. de


    Na{sub 3} AZr(PO{sub 4}){sub 3} (A=Mg, Ni) phosphates were prepared at 750 deg. C by coprecipitation route. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Li{sub 2.6}Na{sub 0.4}NiZr(PO{sub 4}){sub 3} was synthesized through ion exchange from the sodium analog. These materials belong to the Nasicon-type structure. Raman spectra of Na{sub 3} AZr(PO{sub 4}){sub 3} (A=Mg, Ni) phosphates present broad peaks in favor of the statistical distribution in the sites around PO{sub 4} tetrahedra. Diffuse reflectance spectra indicate the presence of octahedrally coordinated Ni{sup 2+} ions. - Graphical abstract: Structure of Na{sub 3} AZr(PO{sub 4}){sub 3} (A=Mg, Ni) phosphates. Display Omitted.

  7. Magnetic structures of R5Ni2In4sub> and R11Ni4sub>In9 ( R = Tb and Ho): Strong hierarchy in the temperature dependence of the magnetic ordering in the multiple rare-earth sublattices

    SciTech Connect

    Ritter, C.; Provino, A.; Manfrinetti, P.; Pecharsky, V. K.; Gschneidner, Jr., K. A.; Dhar, S. K.


    In this study, the magnetic properties and magnetic structures of the R5Ni2In4sub> and the microfibrous R 11Ni4sub>In9 compounds with R = Tb and Ho have been examined using magnetization, heat capacity, and neutron diffraction data. Rare earth atoms occupy three and five symmetrically inequivalent rare earth sites in R5Ni2In4sub> and R 11Ni4sub>In9 compounds, respectively. As a result of the intra- and inter-magnetic sublattice interactions, the magnetic exchange interactions are different for various rare earth sites; this leads to a cascade of magnetic transitions with a strong hierarchy in the temperature dependence of the magnetic orderings.

  8. Phase transition and multicolor luminescence of Eu{sup 2+}/Mn{sup 2+}-activated Ca{sub 3}(PO{sub 4}){sub 2} phosphors

    SciTech Connect

    Li, Kai; Chen, Daqin; Xu, Ju; Zhang, Rui; Yu, Yunlong; Wang, Yuansheng


    Graphical abstract: We have synthesized Eu{sup 2+} doped and Eu{sup 2+}/Mn{sup 2+} co-doped Ca{sub 3}(PO{sub 4}){sub 2} phosphors. The emitting color varies from blue to green with increasing of Eu{sup 2+} content for the Eu{sup 2+}-doped phosphor, and the quantum yield of the 0.05Eu{sup 2+}: Ca{sub 2.95}(PO{sub 4}){sub 2} sample reaches 56.7%. Interestingly, Mn{sup 2+} co-doping into Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi-color luminescence from green to red via Eu{sup 2+} → Mn{sup 2+} energy transfer. - Highlights: • A series of novel Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} phosphors were successfully synthesized. • Phase transition of Ca{sub 3}(PO{sub 4}){sub 2} from orthorhombic to rhombohedral occurred when Mn{sup 2+} ions were doped. • The phosphors exhibited tunable multi-color luminescence. • The quantum yield of 0.05Eu{sup 2+}: Ca{sub 2.95}(PO{sub 4}){sub 2} phosphor can reach 56.7%. • The analyses of phosphors were carried out by many measurements. - Abstract: Intense blue-green-emitting Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} and tunable multicolor-emitting Eu{sup 2+}/Mn{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} phosphors are prepared via a solid-state reaction route. Eu{sup 2+}-doped orthorhombic Ca{sub 3}(PO{sub 4}){sub 2} phosphor exhibits a broad emission band in the wavelength range of 400–700 nm with a maximum quantum yield of 56.7%, and the emission peak red-shifts gradually from 479 to 520 nm with increase of Eu{sup 2+} doping content. Broad excitation spectrum (250–420 nm) of Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} matches well with the near-ultraviolet LED chip, indicating its potential applications as tri-color phosphors in white LEDs. Interestingly, Mn{sup 2+} co-doping into Eu{sup 2+}: Ca{sub 3}(PO{sub 4}){sub 2} leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi

  9. Trivalent aluminum ion conducting characteristics in Al{sub 2}(WO{sub 4}){sub 3} single crystals

    SciTech Connect

    Imanaka, N.; Tamura, S.; Hiraiwa, M.; Adachi, G.; Dabkowska, H.; Dabkowski, A.; Greedan, J.E.


    Single crystals of the trivalent Al{sup 3+} ion conductor Al{sub 2}(WO{sub 4}){sub 3} were grown by the Czochralski (CZ) method. The ionic conductivity in the a-, b-, and c-axis directions was determined and Al{sup 3+} ion conduction in the direction of the b-axis was concluded to be the most suitable pathway for ion migration in the tungstate grains. The ionic conductivities in the a- and c-axis directions were 0.3 and 10{sup {minus}2} times lower than the conductivity in the b-axis. Consistent with this observation, the lowest activation energy (E{sub a}) for Al{sup 3+} ion migration was obtained for the b-axis direction. The E{sub a} of the conductivity in the direction of the c-axis was almost comparable to that of the polycrystalline samples and the E{sub a} of the Al{sup 3+} ionic conduction in the grains of this material was explicitly verified to be controlled by the Al{sup 3+} ionic migration in the c-axis direction. The Al{sup 3+} ion conductivity of the polycrystalline sample was higher in the higher temperature region, indicating that the conductivity in the grain boundaries enhances the total Al{sup 3+} ion conductivity to a considerable extent. From the oxygen pressure dependencies of the electrical conductivity and the polarization behavior, the single crystals were demonstrated to be pure Al{sup 3+} ionic conductors showing an anisotropic ion conducting behavior.

  10. Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO4sub>-

    SciTech Connect

    Chatterjee, Sayandev; Norton, Amie E.; Edwards, Matthew K.; Peterson, James M.; Taylor, Stephen D.; Bryan, Samuel A.; Andersen, Amity; Govind, Niranjan; Albrecht-Schmitt, Thomas E.; Connick, William; Levitskaia, Tatiana G.


    In an effort to address the need for a rapid, selective and economical detection technique for aqueous pertechnetate (TcO4sub>-) anion based on recognition at the molecular level, simple salts of transition metal complexes that undergo a distinct spectroscopic change upon exposure to aqueous anions were explored. The Pt(II) complex [Pt(tpy)Br]SbF6 (tpy=2,2';6',2"-terpyridine) undergoes a dramatic color change and intense luminescence response upon TcO4sub>- uptake due to concomitant enhancement of Pt•••Pt interactions. The spectroscopic response was highly selective and quantitative for aqueous TcO4sub>- among other competing anions. Complimentary Raman spectroscopy and microscopy techniques, structural determination and theoretical methods were employed to achieve molecular-level understanding of the mechanism of the response to aqueous TcO4sub>-.

  11. Low Temperature Propane Oxidation over Co3O4sub> based Nano-array Catalysts. Ni Dopant Effect, Reaction Mechanism and Structural Stability

    SciTech Connect

    Ren, Zheng; Wu, Zili; Gao, Puxian; Song, Wenqiao; Xiao, Wen; Guo, Yanbing; Ding, Jun; Suib, Steven L.; Gao, Pu-Xian


    Low temperature propane oxidation has been achieved by Co3O4sub>-based nano-array catalysts featuring low catalytic materials loading. The Ni doping into the Co3O4sub> lattice has led to enhanced reaction kinetics at low temperature by promoting the surface lattice oxygen activity. In situ DRIFTS investigation in tandem with isotopic oxygen exchange reveals that the propane oxidation proceeds via Mars-van Krevelen mechanism where surface lattice oxygen acts as the active site whereas O2 in the reaction feed does not directly participate in CO2 formation. The Ni doping promotes the formation of less stable carbonates on the surface to facilitate the CO2 desorption. The thermal stability of Ni doped Co3O4sub> decreases with increased Ni concentration while catalytic activity increases. A balance between enhanced activity and compromised thermal stability shall be considered in the Ni doped Co3O4sub> nano-array catalysts for low temperature hydrocarbon oxidation. This study provides useful and timely guidance for rational catalyst design toward low temperature catalytic oxidation.

  12. Ionic conductivity and the formation of cubic CaH{sub 2} in the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composite

    SciTech Connect

    Sveinbjörnsson, Dadi; Blanchard, Didier; Myrdal, Jon Steinar Gardarsson; Younesi, Reza; Viskinde, Rasmus; Riktor, Marit Dalseth; Norby, Poul; Vegge, Tejs


    LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites were prepared by ball milling. Their crystal structures and phase composition were investigated using synchrotron X-ray diffraction and Rietveld refinement, and their ionic conductivity was measured using impedance spectroscopy. The materials were found to form a physical mixture. The composites were composed of α-Ca(BH{sub 4}){sub 2}, γ-Ca(BH{sub 4}){sub 2} and orthorhombic LiBH{sub 4}, and the relative phase quantities of the Ca(BH{sub 4}){sub 2} polymorphs varied significantly with LiBH{sub 4} content. The formation of small amounts of orthorhombic CaH{sub 2} and cubic CaH{sub 2} in a CaF{sub 2}-like structure was observed upon heat treatment. Concurrent formation of elemental boron may also occur. The ionic conductivity of the composites was measured using impedance spectroscopy, and was found to be lower than that of ball milled LiBH{sub 4}. Electronic band structure calculations indicate that cubic CaH{sub 2} with hydrogen defects is electronically conducting. Its formation along with the possible precipitation of boron therefore has an effect on the measured conductivity of the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites and may increase the risk of an internal short-circuit in the cells. -- Graphical abstract: An Arrhenius plot of the ionic conductivity of the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites (red, blue, green). The ionic conductivity of ball milled (gray) and non-milled (black) LiBH{sub 4} is shown for comparison. The filled symbols are measured during heating runs and the empty symbols are measured during subsequent cooling runs. The conductivity of the composites is in all cases higher during cooling, most probably due to the formation of an electronically conducting layer containing defect-rich cubic CaH{sub 2}. Such layer formation could eventually lead to a short circuit in the cell and reveals a general issue of chemical stability that should be attended to in the development of solid

  13. A novel red long lasting phosphorescent (LLP) material {beta}-Zn{sub 3}(PO{sub 4}){sub 2}:Mn{sup 2+}, Sm{sup 3+}

    SciTech Connect

    Wang Jing; Su Qiang . E-mail:; Wang Shubin


    A novel red long lasting phosphorescent materials {beta}-Zn{sub 3}(PO{sub 4}){sub 2}:Mn{sup 2+},Sm{sup 3+} is firstly synthesized by high-temperature solid-state reaction. The influence of Sm{sup 3+} ions on luminescence and long lasting phosphorescence properties of Mn{sup 2+} in phosphor {beta}-Zn{sub 3}(PO{sub 4}){sub 2}:Mn{sup 2+},Sm{sup 3+} are systematically investigated. It is found that the red phosphorescence ({lambda} = 616 nm) performance of Mn{sup 2+} ion such as brightness and duration is largely improved when Sm{sup 3+} ion is co-doped into the matrix in which Mn{sup 2+} ion acts as luminescent center and Sm{sup 3+} ion plays an important role of electron trap. Thermoluminescence spectrums show that there exists one peak in {beta}-Zn{sub 3}(PO{sub 4}){sub 2}:Mn{sup 2+},Sm{sup 3+}, the depth of which is 0.33 eV, and that there are three peaks in {beta}-Zn{sub 3}(PO{sub 4}){sub 2}:Mn{sup 2+}, among which the depth of the lowest temperature peak in {beta}-Zn{sub 3}(PO{sub 4}){sub 2}:Mn{sup 2+} is 0.37 eV. Such differences in the trap depth result in the improvement of red long lasting phosphorescence of Mn{sup 2+} in present matrix.

  14. Syntheses, crystal structures and optical spectroscopy of Ln{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O (Ln=Ho, Tm) and Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O

    SciTech Connect

    Kazmierczak, Karolina; Hoeppe, Henning A.


    The lanthanide sulphate octahydrates Ln{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O (Ln=Ho, Tm) and the respective tetrahydrate Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O were obtained by evaporation of aqueous reaction mixtures of trivalent rare earth oxides and sulphuric acid at 300 K. Ln{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O (Ln=Ho, Tm) crystallise in space group C2/c (Z=4, a{sub Ho}=13.4421(4) A, b{sub Ho}=6.6745(2) A, c{sub Ho}=18.1642(5) A, {beta}{sub Ho}=102.006(1) A{sup 3} and a{sub Tm}=13.4118(14) A, b{sub Tm}=6.6402(6) A, c{sub Tm}=18.1040(16) A, {beta}{sub Tm}=101.980(8) A{sup 3}), Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O adopts space group P2{sub 1}/n (a=13.051(3) A, b=7.2047(14) A, c=13.316(3) A, {beta}=92.55(3) A{sup 3}). The vibrational and optical spectra of Ho{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O and Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O are also reported. -- Graphical abstract: In the lanthanide sulphate octahydrates the cations form slightly undulated layers. Between the layers are voids in which sulphate tetrahedra and water molecules are located. The holmium compound exhibits an Alexandrite effect. Display Omitted Highlights: {yields} Determination of the optimum conditions for the growth of single-crystals of Ln{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O (Ln=Ho, Tm) and Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O. {yields} Single-crystal structure elucidation of Ln{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O (Ln=Ho, Tm) including hydrogen bonds. {yields} Single-crystal structure determination of Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O including hydrogen bonds. {yields} UV-vis spectra of Ho{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O and Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O recorded and interpreted: Assignation of bands and clarification of the Alexandrite effect of the Ho compound. {yields} IR and Raman spectra of Ln{sub 2}(SO{sub 4}){sub 3}.8H{sub 2}O (Ln=Ho, Tm) and Pr{sub 2}(SO{sub 4}){sub 3}.4H{sub 2}O recorded and interpreted.

  15. Structural study and physical properties of a new phosphate KCuFe(PO{sub 4}){sub 2}

    SciTech Connect

    Badri, Abdessalem; Hidouri, Mourad; Lopez, Maria Luisa; Pico, Carlos; Wattiaux, Alain; Ben Amara, Mongi


    Single crystals of a new phosphate KCuFe(PO{sub 4}){sub 2} have been prepared by the flux method and its structural and physical properties have been investigated. This compound crystallizes in the monoclinic system with the space group P2{sub 1}/n and its parameters are: a=7.958(3) A, b=9.931(2) A, c=9.039(2) A, {beta}=115.59(3){sup o} and Z=4. Its structure consists of FeO{sub 6} octahedra sharing corners with Cu{sub 2}O{sub 8} units of edge-sharing CuO{sub 5} polyhedra to form undulating chains extending infinitely along the b-axis. These chains are connected by the phosphate tetrahedra giving rise to a 3D framework with six-sided tunnels parallel to the [101] direction, where the K{sup +} ions are located. The Moessbauer spectroscopy results confirm the exclusive presence of octahedral Fe{sup 3+} ions. The magnetic measurements show the compound to be antiferromagnetic with C{sub m}=5.71 emu K/mol and {theta}=-156.5 K. The derived experimental effective moment {mu}{sub ex}=6.76{mu}{sub B} is somewhat higher than the theoretical one of {mu}{sub th}=6.16{mu}{sub B}, calculated taking only into account the spin contribution for Fe{sup 3+} and Cu{sup 2+} cations. Electrical measurements allow us to obtain the activation energy (1.22 eV) and the conductivity measurements suggest that the charge carriers through the structure are the potassium cations. -- Graphical abstract: A projection along the [101] direction of the structure showing the six-edged tunnels, occupied by the K{sup +} ions. Display Omitted Highlights: {yields} The reported structure is of a new type. {yields} The structural model is supported by a Moessbauer spectroscopy study. {yields} The magnetic susceptibility results are reported. {yields} The electrical properties are discussed.

  16. Combustion synthesized nanocrystalline Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C cathode for lithium-ion batteries

    SciTech Connect

    Nathiya, K.; Bhuvaneswari, D.; Gangulibabu; Kalaiselvi, N.


    Graphical abstract: Nanocrystalline Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C compound has been synthesized using a novel corn assisted combustion (CAC) method, wherein the composite prepared at 850 °C is found to exhibit superior physical and electrochemical properties than the one synthesized at 800 °C (Fig. 1). Despite the charge disproportionation of V{sup 4+} and a possible solid solution behavior of Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} cathode upon insertion and de-insertion of Li{sup +} ions, the structural stability of the same is appreciable, even with the extraction of third lithium at 4.6 V (Fig. 2). An appreciable specific capacity of 174 mAh g{sup −1} with an excellent columbic efficiency (99%) and better capacity retention upon high rate applications have been exhibited by Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C cathode, thus demonstrating the feasibility of CAC method in preparing the title compound to best suit with the needs of lithium battery applications. Display Omitted Highlights: ► Novel corn assisted combustion method has been used to synthesize Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C. ► Corn is a cheap and eco benign combustible fuel to facilitate CAC synthesis. ► Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C exhibits an appreciable specific capacity of 174 mAh g{sup −1} (C/10 rate). ► Currently observed columbic efficiency of 99% is better than the reported behavior. ► Suitability of Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C cathode up to 10C rate is demonstrated. -- Abstract: Nanocrystalline Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C composite synthesized using a novel corn assisted combustion method at 850 °C exhibits superior physical and electrochemical properties than the one synthesized at 800 °C. Despite the charge disproportionation of V{sup 4+} and a possible solid solution behavior of Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} cathode upon insertion and extraction of Li{sup +} ions, the structural stability of the same is appreciable, even with

  17. Structural, energetic and thermodynamic analyses of Ca(BH{sub 4}){sub 2}{center_dot}2NH{sub 3} from first principles calculations

    SciTech Connect

    Yuan Pengfei; Wang Fei; Sun Qiang; Jia Yu; Guo Zhengxiao


    Ca(BH{sub 4}){sub 2}{center_dot}2NH{sub 3} is a relatively new compound with potential application in hydrogen storage. Here the fundamental properties of the compound, such as electronic structure, energetic and thermodynamic properties, were comprehensively studied using first-principles calculations. Results from electronic density of states (DOS) and electron localization function (ELF) indicate the covalent bond nature of the N-H bond and the B-H bond. Charge density analyses show weak ionic interactions between the Ca atom and the NH{sub 3} complexes or the (BH{sub 4}){sup -} complexes. The calculated vibration frequencies of B-H and N-H are in good agreement with other theoretical and experimental results. Furthermore, we calculated the reaction enthalpy and reaction Gibbs free energy at a range of temperature 0-700 K. Our results are in good agreement with experimental results in literature. Possible reaction mechanism of the decomposition reaction is proposed. - Graphical Abstract: The crystal structure of this compound and the calculated decomposition reaction free energy for two different reactions: Reac(2):Ca(BH{sub 4}){sub 2} Dot-Operator 2NH{sub 3} Long-Rightwards-Arrow {sup 162 Degree-Sign C}Ca(BH{sub 4}){sub 2} Dot-Operator NH{sub 3}+NH{sub 3} Long-Rightwards-Arrow {sup 230 Degree-Sign C}Ca(BH{sub 4}){sub 2}+2NH{sub 3} Reac(3):Ca(BH{sub 4}){sub 2} Dot-Operator 2NH{sub 3} Long-Rightwards-Arrow {sup 190 Degree-Sign C}1/4Ca(BH{sub 4}){sub 2}+1/4Ca{sub 3}(BN{sub 2}){sub 2}+BN+6H{sub 2}. Highlights: Black-Right-Pointing-Pointer Crystal structure of this compound was studied in detail. Black-Right-Pointing-Pointer Electronic properties were calculated for the first time. Black-Right-Pointing-Pointer Phonon density of states and reaction free energy at different temperatures were first calculated. Black-Right-Pointing-Pointer Possible decomposition mechanism was presented.

  18. Structure symmetry determination and magnetic evolution in Sr2Ir1–xRhxO4sub>

    SciTech Connect

    Ye, Feng; Wang, Xiaoping; Hoffmann, Christina; Wang, Jinchen; Chi, Songxue; Matsuda, Masaaki; Chakoumakos, Bryan C.; Fernandez-Baca, Jaime A.; Cao, Gang


    We use single-crystal neutron diffraction to determine the crystal structure symmetry and to study the magnetic evolution in the rhodium doped iridates Sr2Ir1–xRhxO4sub> (0 ≤ x ≤ 0.16). Throughout this doping range, the crystal structure retains a tetragonal symmetry (space group I4<sub>1/a) with two distinct magnetic Ir sites in the unit cell forming staggered IrO6 rotation. Upon Rh doping, the magnetic order is suppressed and the magnetic moment of Ir4+ is reduced from 0.21 μB/Ir for x = 0 to 0.18 μB/Ir for x = 0.12. As a result, the magnetic structure at x = 0.12 is different from that of the parent compound while the moments remain in the basal plane.

  19. Neutron scattering studies of the H2a-H2b and (H3-H4)/sub 2/ histone complexes

    SciTech Connect

    Carlson, R.D.


    Neutron scattering experiments have shown that both the (H3-H4)/sub 2/ and H2a-H2b histone complexes are quite asymmetric in solution. The (H3-H4)/sub 2/ tetramer is an oblate or flattened structure, with a radius of gyration almost as large as that of the core octamer. If the tetramer is primarily globular, it must have an axial ratio of about 1:5. It is more likely, however, that this asymmetry results in part from N-terminal arms that extend outward approximately within the major plane of the particle. If this is the case, less asymmetric models for the globular part of the tetramer, including a dislocated disk, can be made consistent with the scattering data. The H2a-H2b dimer, on the other hand, is an elongated structure. 48 references, 12 figures, 1 table.

  20. Stabilization of heterogeneous silicon lasers using Pound-Drever-Hall locking to Si3N4sub> ring resonators.


    Spencer, Daryl T; Davenport, Michael L; Komljenovic, Tin; Srinivasan, Sudharsanan; Bowers, John E


    Recent results on heterogeneous Si/III-V lasers and ultra-high Q Si3N4sub> resonators are implemented in a Pound-Drever-Hall frequency stabilization system to yield narrow linewidth characteristics for a stable on-chip laser reference. The high frequency filtering is performed with Si resonant mirrors in the laser cavity. To suppress close in noise and frequency walk off, the laser is locked to an ultra-high Q Si3N4sub> resonator with a 30 million quality factor. The laser shows high frequency noise levels of 60 × 103 Hz2/Hz corresponding to 160 kHz linewidth, and the low frequency noise is suppressed 33 dB to 103 Hz2/Hz with the PDH system. PMID:27410367

  1. Structurally induced magnetization in a La2/3Sr4/3MnO4sub> superlattice

    SciTech Connect

    Shah, Amish B.; Nelson-Cheeseman, Brittany B.; Subramanian, Ganesh; Bhattacharya, Anand; Spence, John C.H.


    A structural transition has been observed in a digital superlattice of La2/3Sr4/3MnO4sub>, which is correlated to a magnetization enhancement upon cooling the sample. The artificial superlattices were grown layer-by-layer using ozone-assisted molecular beam epitaxy (MBE). Electron diffraction experiments show a phase transition below 150K in nanopatches of the superlattice, which coincides with an enhanced magnetization starting below 110K. Furthermore, atomic scale electron energy loss spectroscopy (EELS) shows changes in the Mn L2,3 and O K edges, which are related to valence, strain, and the atomic coordination within nanopatches. Atomic resolution image and EELS showing variations of oxygen and lanthanum signature edges in a La2/3Sr4/3MnO4sub> supperlattice.

  2. Theoretical Assessment on the Phase Transformation Kinetic Pathways of Multi-component Ti Alloys: Application to Ti-6Al-4sub>V

    SciTech Connect

    Ji, Yanzhou; Heo, Tae Wook; Zhang, Fan; Chen, Long-Qing


    Here we present our theoretical assessment of the kinetic pathways during phase transformations of multi-component Ti alloys. Employing the graphical thermodynamic approach and an integrated free energy function based on the realistic thermodynamic database and assuming that a displacive structural transformation occurs much faster than long-range diffusional processes, we analyze the phase stabilities of Ti-6Al-4sub>V (Ti-6wt.%Al-4sub>wt.%V). Our systematic analyses predict a variety of possible kinetic pathways for β to (α + β) transformations leading to different types of microstructures under various heat treatment conditions. In addition, the possibility of unconventional kinetic pathways is discussed. Lastly, we also briefly discuss the application of our approach to general multicomponent/multiphase alloy systems.

  3. Magnetic properties of (FeIn{sub 2}S{sub 4}){sub 1-x}(In{sub 2}S{sub 3}){sub x} alloy single crystals

    SciTech Connect

    Bodnar, I. V. Novikova, M. A.; Trukhanov, S. V.


    (FeIn{sub 2}S{sub 4}){sub 1-x}(In{sub 2}S{sub 3}){sub x} alloy single crystals are grown by oriented crystallization in the entire range of component concentrations. For the single crystals, studies of the magnetic properties are carried out in the temperature range 4-300 K and the magnetic-field range 0-14 T. It is established that almost all of the alloys are paramagnetic materials at temperatures down to the lowest achievable temperatures ({approx}4 K). It is shown that the ground magnetic phase state of the alloys is the spin-glass state with the freezing temperature steadily increasing with increasing Fe{sup 2+} cation content. The most probable causes and mechanism of formation of the magnetic state of the (FeIn{sub 2}S{sub 4}){sub 1-x}(In{sub 2}S{sub 3}){sub x} crystals are discussed.

  4. Electric-field-induced linear birefringence in TmAl3(BO3)4sub>.


    Pashchenko, M I; Bedarev, V A; Merenkov, D N; Gnatchenko, S L; Bezmaternykh, L N; Sukhachev, A L; Temerov, V L


    The linear birefringence induced by the electric field was first detected in a TmAl3(BO3)4sub> single crystal. The electric field dependence of the birefringence was investigated. The estimation of the electro-optical coefficient of the material gives ≈1.5×10-10  cm/V for a wavelength 632.8 nm. PMID:27140114

  5. Phase-matching directions and refined Sellmeier equations of the monoclinic acentric crystal BaGa4sub>Se7.


    Boursier, Elodie; Segonds, Patricia; Ménaert, Bertrand; Badikov, Valeriy; Panyutin, Vladimir; Badikov, Dmitrii; Petrov, Valentin; Boulanger, Benoît


    We directly measured the phase-matching directions of second-harmonic and difference frequency generation in the principal planes of the biaxial BaGa4sub>Se7 (BGSe) crystal using the sphere method. The simultaneous fit of the data allowed us to refine the Sellmeier equations of the three principal refractive indices of BGSe, and to calculate the tuning curves for infrared optical parametric generation. PMID:27304275

  6. Multi-wavelength Yb:YAG/Nd3+:YVO4sub> continuous-wave microchip Raman laser.


    Wang, Xiao-Lei; Dong, Jun; Wang, Xiao-Jie; Xu, Jie; Ueda, Ken-Ichi; Kaminskii, Alexander A


    Multi-wavelength continuous-wave (CW) Raman lasers in a laser diode pumped Yb:YAG/Nd3+:YVO4sub> microchip Raman laser have been demonstrated for the first time to our best knowledge. The multi-wavelength laser of the first Stokes radiation around 1.08 μm has been achieved with a Raman shift of 261  cm-1 for a-cut Nd:YVO4sub> crystal corresponding to the fundamental wavelength at 1.05 μm. Multi-wavelength laser operation simultaneously around 1.05 and 1.08 μm has been achieved under the incident pump power between 1.5 and 1.7 W. Multi-wavelength Raman laser with frequency separation of 1 THz around 1.08 μm has been obtained when the incident pump power is higher than 1.7 W. The maximum Raman laser output power of 260 mW at 1.08 μm is obtained and the corresponding optical-to-optical conversion efficiency is 4.2%. Elliptically polarized fundamental laser and linearly polarized Raman laser were observed in an Yb:YAG/Nd:YVO4sub> CW microchip Raman laser. The experimental results of linearly polarized, multi-wavelength Yb:YAG/Nd:YVO4sub> CW microchip Raman laser with adjustable frequency separation provide a novel approach for developing potential compact laser sources for Terahertz generation. PMID:27472618

  7. New insulating antiferromagnetic quaternary iridates MLa10Ir4sub>O24 (M=Sr, Ba)

    SciTech Connect

    Zhao, Qingbiao; Han, Fei; Stoumpos, Constantinos C.; Han, Tian -Heng; Li, Hao; Mitchell, J. F.


    Recently, oxides of Ir4+ have received renewed attention in the condensed matter physics community, as it has been reported that certain iridates have a strongly spin-orbital coupled (SOC) electronic state, Jeff = ½, that defines the electronic and magnetic properties. The canonical example is the Ruddlesden-Popper compound Sr2IrO4sub>, which has been suggested as a potential route to a new class of high temperature superconductor due to the formal analogy between Jeff = ½ and the S = ½ state of the cuprate superconductors. The quest for other iridium oxides that present tests of the underlying SOC physics is underway. In this spirit, here we report the synthesis and physical properties of two new quaternary tetravalent iridates, MLa10Ir4sub>O24 (M = Sr, Ba). The crystal structure of both compounds features isolated IrO6 octahedra in which the electronic configuration of Ir is d5. As a result, both compounds order antiferromagnetically despite the lack of obvious superexchange pathways, and resistivity measurement shows that SrLa10Ir4sub>O24 is an insulator.

  8. Correlation of anisotropy and directional conduction in β-Li3PS4sub> fast Li+ conductor

    SciTech Connect

    Chen, Yan; Cai, Lu; Liu, Zengcai; dela Cruz, Clarina R.; Liang, Chengdu; An, Ke


    Our letter reports the correlation of anisotropy and directional conduction in the fast Li+ conductor β-Li3PS4sub>, one of the low-symmetry crystalline electrolyte candidates. The material has both high conductivity and good stability that serves well for the large-scale energy storage applications of all-solid-state lithium ion batteries. The anisotropic physical properties, demonstrated here by the thermal expansion coefficients, are crucial for compatibility in the solid-state system and battery performance. Neutron and X-ray powder diffraction measurements were done to determine the crystal structure and thermal stability. Moreover, the crystallographic b-axis was revealed as a fast expansion direction, while negligible thermal expansion was observed along the a-axis around the battery operating temperatures. The anisotropic behavior has its structural origin from the Li+ conduction channels with incomplete Li occupancy and a flexible connection of LiS4sub> and PS4sub> tetrahedra within the framework. This indicates a strong correlation in the direction of the ionic transport in the low-symmetry Li+ conductor.

  9. Synthesis, crystal growth, structural and magnetic characterization of NH4sub>MCl2(HCOO), M=(Fe, Co, Ni)

    SciTech Connect

    Greenfield, Joshua T.; Ovidiu Garlea, V.; Kamali, Saeed; Chen, Michael; Kovnir, Kirill


    In this paper, an ambient-pressure solution route and an improved solvothermal synthetic method have been developed to produce polycrystalline powders and large single crystals of NH4sub>MCl2(HCOO) (M=Fe, Co, Ni). The magnetic structure of the 1D linear chain compound NH4sub>FeCl2(HCOO) has been determined by low-temperature neutron powder diffraction, revealing ferromagnetic intra-chain interactions and antiferromagnetic inter-chain interactions. Finally, the newly-reported Co and Ni analogs are isostructural with NH4sub>FeCl2(HCOO), but there are significant differences in the magnetic properties of each compound; the Ni analog behaves similarly to the Fe compound but with stronger magnetic coupling, exhibiting antiferromagnetic ordering (TN=8.5 K) and a broad metamagnetic transition between 2 and 5 T, while the Co analog does not order magnetically above 2 K, despite strong antiferromagnetic nearest-neighbor interactions.

  10. Organogold oligomers: Exploiting iClick and aurophilic cluster formation to prepare solution stable Au4sub> repeating units

    SciTech Connect

    Yang, Xi; Wang, Shanshan; Ghiviriga, Ion; Abboud, Khalil A.; Veige, Adam S.


    A novel synthetic method to create gold based metallo–oligomers/polymers via the combination of inorganic click (iClick) with intermolecular aurophilic interactions is demonstrated. Complexes [PEt3Au]4sub>(μ-N3C2C6H5) (1) and [PPhMe2Au]4sub (μ-N3C2C6H5) (2) and {[PEt3Au]4sub>[(μ-N3C2)2-9,9-dihexyl-9H-fluorene]}n (8) have been synthesized via iClick. The tetranuclear structures of 1 and 2, induced by aurophilic bonding, are confirmed in the solid state through single crystal X-ray diffraction experiments and in solution via variable temperature NMR spectroscopy. The extended 1D structure of 8 is constructed by aurophilic induced self-assembly. 1H DOSY NMR analysis reveals that the aurophilic bonds in 1, 2, and 8 are retained in the solution phase. The degree of polymerization within complex 8 is temperature and concentration dependent, as determined by 1H DOSY NMR. The complex 8 is a rare example of a solution stable higher ordered structure linked by aurophilic interactions.

  11. Magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet Cs2CuBr4sub>

    SciTech Connect

    Zvyagin, S. A.; Ozerov, M.; Kamenskyi, D.; Wosnitza, J.; Krzystek, J.; Yoshizawa, D.; Hagiwara, M.; Hu, Rongwei; Ryu, Hyejin; Petrovic, C.; Zhitomirsky, M. E.


    We present on high- field electron spin resonance (ESR) studies of magnetic excitations in the spin- 1/2 triangular-lattice antiferromagnet Cs2CuBr4sub>. Frequency- field diagrams of ESR excitations are measured for different orientations of magnetic fields up to 25 T. We show that the substantial zero- field energy gap, Δ ≈ 9.5 K, observed in the low-temperature excitation spectrum of Cs2CuBr4sub> [Zvyagin et al:, Phys. Rev. Lett. 112, 077206 (2014)], is present well above TN. Noticeably, the transition into the long-range magnetically ordered phase does not significantly affect the size of the gap, suggesting that even below TN the high-energy spin dynamics in Cs2CuBr4sub> is determined by short-range-order spin correlations. The experimental data are compared with results of model spin-wave-theory calculations for spin-1/2 triangle-lattice antiferromagnet.

  12. Graphene oxide wrapped Ag{sub 3}PO{sub 4} sub-microparticles with highly enhanced photocatalytic activity and stability under visible light irradiation

    SciTech Connect

    Xiu, Zhiliang; Wu, Yongzhong; Hao, Xiaopeng; Lu, Qifang; Liu, Suwen


    Highlights: • Graphene oxide wrapped Ag{sub 3}PO{sub 4} sub-microparticles were prepared. • The photocatalytic activity of Ag{sub 3}PO{sub 4} is increased by 6 times by GO wrapping. • The hybrid photocatalysts exhibited excellent stability. - Abstract: Graphene oxide (GO) wrapped Ag{sub 3}PO{sub 4} sub-microparticles were prepared by in situ deposition–precipitation method. By hybridization of Ag{sub 3}PO{sub 4} with GO nanosheets, a 6-fold enhancement in the photodegradation rate toward orange methyl (MO) under visible light irradiation (λ ≥ 420 nm) was observed compared with the pure Ag{sub 3}PO{sub 4} sub-microsparticles. The hybrid photocatalysts also exhibited excellent stability in the successive MO degradation experiments. The highly enhanced photocatalytic activity and stability were mainly attributed to the quick transfer of the photogenerated electrons from Ag{sub 3}PO{sub 4} to GO nanosheets, which could effectively suppress the electron–hole pairs recombination and thus inhibit the photocorrosion of Ag{sub 3}PO{sub 4}. These high-efficient and stable hybrid photocatalysts were expected to show considerable potential applications in wastewater treatment and water splitting.

  13. Crystal structure, IR and Mössbauer spectroscopy and magnetic properties of KZnFe(PO{sub 4}){sub 2} related to the zeolite-ABW-like compounds

    SciTech Connect

    Badri, Abdessalem; Hidouri, Mourad; Wattiaux, Alain; López, María Luisa; Veiga, María Luisa; Amara, Mongi Ben


    Highlights: • The reported structure of KZnFe(PO{sub 4}){sub 2} is closely related to the zeolite ABW-type. • The structure is described in detail. • The IR and Mössbauer spectroscopy results are reported. • The magnetic properties are developed. - Abstract: The new iron phosphate KZnFe(PO{sub 4}){sub 2} has been synthesized by flux method and solid state reaction, and characterized by X-ray diffraction, IR, Mössbauer spectroscopy and magnetic susceptibility. This compound crystallizes in the monoclinic space group C2/c with the cell parameters: a = 13.514(4) Å, b = 13.273(6) Å, c = 8.742(3) Å and β = 100.07(2)°. It displays strong similarities with the phosphates KCoAl(PO{sub 4}){sub 2} and NaCoPO{sub 4} and features some analogies with the zeolite-ABW structural type. 3D framework is built up by a corner-sharing between MO{sub 4} (M = 0.5 Zn + 0.5 Fe) and PO{sub 4} tetrahedra. The K{sup +} ions are found within crossing tunnels perpendicular to the (1 0 0), (0 1 0) and (0 0 1) planes, delimited by this framework. A Mössbauer study confirmed the presence of Fe{sup 3+} ions in a tetrahedral environment. Magnetic measurements revealed an antiferromagnetic behavior with T{sub N} = 8.5 K.

  14. Color tunable and thermally stable luminescence of Tb{sup 3+} doped Li{sub 4}SrCa(SiO{sub 4}){sub 2} phosphors

    SciTech Connect

    Zhang, Xinmin; Seo, Hyo Jin


    Highlights: ► Lowest spin-allowed and spin-forbidden f–d transitions locate at 250 and 280 nm. ► Cross relaxation shortens lifetime of {sup 5}D{sub 3} level, while that of {sup 5}D{sub 4} are unaffected. ► Cross-relaxation can explain concentration quenching of the {sup 5}D{sub 3} emission. ► Dipole–quadrupole interaction is responsible for the non-radiative relaxation. ► Li{sub 4}SrCa(SiO{sub 4}){sub 2}:Tb{sup 3+} is thermally stable and color tunable phosphor. -- Abstract: Tb{sup 3+} ions activated Li{sub 4}SrCa(SiO{sub 4}){sub 2} phosphors were synthesized using a solid state reaction method. The phase impurity was checked by XRD. The photoluminescence (PL) excitation spectrum, emission spectra at room and high temperature, decay curves of samples with different Tb{sup 3+} ions concentration were studied in detail. Cross-relaxation and the Inokuti–Hirayama model were used to analyze the experimental results. Li{sub 4}SrCa(SiO{sub 4}){sub 2}:xTb{sup 3+} are thermally stable and color tunable phosphors.

  15. On the role of the VO(H{sub 2}PO{sub 4}){sub 2} precursor for n-butane oxidation into maleic anhydride

    SciTech Connect

    Sananes, M.T. |; Hutchings, G.J.; Volta, J.C.


    The catalytic role of VO(H{sub 2}PO{sub 4}){sub 2}, the precursor of the VO(PO{sub 3}){sub 2} phase, has been studied for N-butane oxidation to maleic anhydride. By comparison with the activated VPO catalyst, derived from the VOHPO{sub 4} {center_dot} 0.5H{sub 2}O precursor phase, VO(H{sub 2}PO{sub 4}){sub 2} gives a highly selective final catalyst. The total oxidation products CO and CO{sub 2} are not observed under any of the conditions examined, a result confirmed by extensive catalyst testing and carbon mass balances. The final catalyst derived from VO(H{sub 2}PO{sub 4}){sub 2} has a low surface area, ca. 1 m{sup 2}/g, and consequently demonstrates low specific activity on the basis of n-butane conversion per unit mass. However, the intrinsic activity (activity per unit surface area) is found to be higher than that for catalysts derived from VOHPO{sub 4}{center_dot}0.5H{sub 2}O. Since some VO(H{sub 2}PO{sub 4}){sub 2} is present in VOHPO{sub 4}{center_dot}0.5H{sub 2}O, which is the precursor of the industrial catalyst, the results of this study complicate the simple model in which the (VO){sub 2}O{sub 7} phase derived from VOHPO{sub 4} {center_dot}0.5H{sub 2}O is responsible for the selective oxidation of n-butane. The observation that the precursor VO(H{sub 2}PO{sub 4}){sub 2} can generate catalysts of high specific activity and of total selectivity to partial oxidation products might provide a useful insight into the design of a new series of high activity and high selectivity partial oxidation catalysts. 36 refs., 12 figs., 2 tabs.

  16. Structural, electronic and thermodynamic properties of britholites Ca{sub 10−x}La{sub x}(PO{sub 4}){sub 6−x}(SiO{sub 4}){sub x}F{sub 2} (0 ≤ x ≤ 6): Experiment and theory

    SciTech Connect

    Njema, H.; Debbichi, M.; Boughzala, K.; Said, M.; Bouzouita, K.


    Highlights: • The structural and electronic properties of apatites with the general formula Ca{sub 10−x}La{sub x}(PO{sub 4}){sub 6−x}(SiO{sub 4}){sub x}F{sub 2} (0 ≤ x ≤ 6) have been investigated by means of the density functional theory. • The calculated enthalpy of formation of the compounds increased with the substitution degree. • The decrease in stability is probably due to the disorder induced in the Ca/LaO{sub 6}F polyhedron, following the substitution. - Abstract: The apatite-type compounds Ca{sub 10−x}La{sub x}(PO{sub 4}){sub 6−x}(SiO{sub 4}){sub x}F{sub 2} with 0 ≤ x ≤ 6 were prepared using a high temperature solid state reaction and were characterized by X-ray diffraction. The crystal structure, chemical bonding, electronic structure and formation energy of all relaxed structures were analyzed by density functional theory (DFT). The calculated results show that the predicted geometry can well reproduce the structural parameters. The incorporation of La{sup 3+} into the fluorapatite (FA) structure induced especially at the level of the S(2) sites a certain disorder which is responsible for the weakening in the stability with x. Excellent agreement were obtained between the calculated and experimental results. Moreover, the band structure indicates that despite the reduction of the band gap with x content all materials remain insulating.

  17. Crystal structures of alkali-metal indium (III) phosphates of [M{sub 3}In(PO{sub 4}){sub 2}]{sub n} (M=K, n=10; M=Rb, n=2) compounds, and band structures and chemical bond properties of [Rb{sub 3}In(PO{sub 4}){sub 2}]{sub 2} crystal

    SciTech Connect

    Zhang Yongchun; Cheng Wendan . E-mail:; Wu Dongsheng


    Ternary indium (III) phosphates with three-dimensional frameworks, [M{sub 3}In(PO{sub 4}){sub 2}]{sub n} (M=K, n=10; M=Rb, n=2), are found and firstly reported in this paper. These compounds have been obtained by high temperature solid-state reactions and their crystal structures have been determined by single crystal X-ray diffraction analysis. The title compounds, which crystallize in monoclinic system, possess the same [In(PO{sub 4}){sub 2}]{sub n}{sup 3n-} anionic frameworks built up from interconnected InO{sub 6} octahedra and PO{sub 4} tetrahedra and have an interesting tunnel structure where M{sup +} cations are located. Optical and bonding properties of [Rb{sub 3}In(PO{sub 4}){sub 2}]{sub 2} are investigated in terms of measured absorption and emission spectra, and calculated band structures and density of states. The crystal band structures obtained by the DFT method show that the solid compound of [Rb{sub 3}In(PO{sub 4}){sub 2}]{sub 2} is an insulator with direct band gap, and the P-O covalent bond characters are larger than the In-O ones in this compound.

  18. Infrared and Raman spectra of Na{sub 2}Cu(SO{sub 4}){sub 2}{center_dot}2H{sub 2}O and (CH{sub 3}NH{sub 3}){sub 2}M(II)(SO{sub 4}){sub 2}{center_dot}6H{sub 2}O with M(II) = Cu, Zn, and Ni

    SciTech Connect

    Pillai, V.P.M.; Nayar, V.U.; Jordanovska, V.B.


    FTIR and Raman spectra of Na{sub 2}Cu(SO{sub 4}){sub 2}{center_dot}2H{sub 2}O and (CH{sub 3}NH{sub 3}){sub 2}M(II) (SO{sub 4}){sub 2}{center_dot}6H{sub 2}O with M(II) = Cu, Zn, and Ni are recorded and analyzed. Bands are assigned on the basis of SO{sub 4}{sup 2-}, CH{sub 3}NH{sub 3}{sup +}, and H{sub 2}O vibrations. The lifting of degeneracies of {nu}{sub 2}, {nu}{sub 3} and v{sub 4} modes and the appearance of {nu}{sub 1} and {nu}{sub 2} modes in the IR spectra confirm the lowering of symmetry of the SO{sub 4}{sup 2-} ion from T{sub d} to C{sub 1} in all of the title compounds. Bands obtained indicate that the distoration of the SO{sub 4}{sup 2-} ion in the four crystals are in the order, (CH{sub 3}NH{sub 3})Cu(SO{sub 4}){sub 2}{center_dot}6H{sub 2}O > (CH{sub 3}NH{sub 3}){sub 2}Ni(SO{sub 4}){sub 2}{center_dot}6H{sub 2}O > (CH{sub 3}NH{sub 3}){sub 2}Zn(SO{sub 4}){sub 2}{center_dot}6H{sub 2}O > Na{sub 2}Cu(SO{sub 4}){sub 2}{center_dot} 2H{sub 2}O. The appearance of NH{sub 3} stretching modes at wavenumbers lower than the values obtained for the free ion indicates the presence of hydrogen bonds between NH{sub 3} and SO{sub 4}{sup 2-} groups. The appearance of multiple bands in the blending and rocking mode regions and the broad nature of stretching modes show the existence of at least two symmetrically inequivalent water molecules in Na{sub 2}Cu(SO{sub 4}){sub 2}{center_dot}2H{sub 2}O. The shifting of stretching modes to lower wavenumbers and bending modes to higher wavenumbers of water molecules confirms the existence of strong hydrogen bonds in the crystal which is in agreement with the X-ray data. Bands indicate the presence of strong hydrogen bonds involving water molecules in (CH{sub 3}NH{sub 3}){sub 2}Cu(SO{sub 4}){sub 2}{center_dot}6H{sub 2}O and (CH{sub 3}NH{sub 3}){sub 2} Zn(SO{sub 4}){sub 2}{center_dot}6H{sub 2}O and of lesser strength in (CH{sub 3}NH{sub 3}){sub 2}Ni(SO{sub 4}){sub 2}{center_dot}6H{sub 2}O.

  19. Superconductivity in the presence of disorder in skutterudite-related La3Co4sub>Sn13 and La3Ru4sub>Sn13 compounds: Electrical transport and magnetic studies

    SciTech Connect

    Slebarski, A.; Maska, M. M.; Fijalkowski, M.; McElroy, C. A.; Maple, M. B.


    La3Co4sub>Sn13 and La3Ru4sub>Sn13 were categorized as BCS superconductors. In a plot of the critical field Hc2 vs T, La3Ru4sub>Sn13 displays a second superconducting phase at the higher critical temperature Tc*, characteristic of inhomogeneous superconductors, while La3Co4sub>Sn13 shows bulk superconductivity below Tc. We observe a decrease in critical temperatures with external pressure and magnetic field for both compounds. Additionally, for La3Ru4sub>Sn13 we find that Tc*/dP>dTc/dP. The pressure dependences of Tc are interpreted according to the McMillan theory and understood to be a consequence of lattice stiffening. The investigation of the superconducting state of La3CoxRu4–xSn13 shows a Tc* that is larger then Tc for x < 4. Furthermore, this unique and unexpected observation is discussed as a result of the local disorder and/or the effect of chemical pressure when Ru atoms are partially replaced by smaller Co atoms.

  20. Study of phase relationships in the Sr{sub 3}(PO{sub 4}){sub 2}–CePO{sub 4} system. Phase diagram and thermal characteristics of phases

    SciTech Connect

    Matraszek, Aleksandra


    A diagram representing phase relationships in the Sr{sub 3}(PO{sub 4}){sub 2}–CePO{sub 4} phosphate system has been developed on the basis of results obtained by thermal analysis (DTA/DSC/TGA) and X-ray diffraction (XRD) methods. One intermediate compound with the formula Sr{sub 3}Ce(PO{sub 4}){sub 3} occurs in the Sr{sub 3}(PO{sub 4}){sub 2}–CePO{sub 4} system at temperatures exceeding 1045 °C. The compound has a eulytite structure with the following structural parameters: a=b=c=10.1655(8) Å, α=β=γ=90.00°, V=1050.46(6) Å{sup 3}. It's melting point exceeds 1950 °C. A limited solid solution exists in the system, which possesses the structure of a low-temperature form of Sr{sub 3}(PO{sub 4}){sub 2}. At 1000 °C the maximal concentration of CePO{sub 4} in the solid solution is below 20 mol%. The solid solution phase field narrows with increased temperature. There is a eutectic point in the (Sr{sub 3}(PO{sub 4}){sub 2}+Sr{sub 3}Ce(PO{sub 4}){sub 3}) phase field at 1765 °C and 15 mol% of CePO{sub 4}. The melting temperature of Sr{sub 3}(PO{sub 4}){sub 2} is 1882±15 °C. - Graphical abstract: The phase diagram of Sr{sub 3}(PO{sub 4}){sub 2}–CePO{sub 4} system showing the stability ranges of limited solid solution and Sr{sub 3}Ce(PO{sub 4}){sub 3} phases. - Highlights: • Sr{sub 3}(PO{sub 4}){sub 2} melts at 1882 °C. • Phase diagram of Sr{sub 3}(PO{sub 4}){sub 2}–CePO{sub 4} system has been proposed. • Limited solid solution of CePO{sub 4} in Sr{sub 3}(PO{sub 4}){sub 2} forms in the system. • The Sr{sub 3}Ce(PO{sub 4}){sub 2} phosphate is stable at temperatures above 1045 °C.

  1. Crystal structures of lazulite-type oxidephosphates Ti{sup III}Ti{sup IV}{sub 3}O{sub 3}(PO{sub 4}){sub 3} and M{sup III}{sub 4}Ti{sup IV}{sub 27}O{sub 24}(PO{sub 4}){sub 24} (M{sup III}=Ti, Cr, Fe)

    SciTech Connect

    Schoeneborn, M.; Glaum, R. Reinauer, F.


    Single crystals of the oxidephosphates Ti{sup III}Ti{sup IV}{sub 3}O{sub 3}(PO{sub 4}){sub 3} (black), Cr{sup III}{sub 4}Ti{sup IV}{sub 27}O{sub 24}(PO{sub 4}){sub 24} (red-brown, transparent), and Fe{sup III}{sub 4}Ti{sup IV}{sub 27}O{sub 24}(PO{sub 4}){sub 24} (brown) with edge-lengths up to 0.3 mm were grown by chemical vapour transport. The crystal structures of these orthorhombic members (space group F2dd ) of the lazulite/lipscombite structure family were refined from single-crystal data [Ti{sup III}Ti{sup IV}{sub 3}O{sub 3}(PO{sub 4}){sub 3}: Z=24, a=7.3261(9) A, b=22.166(5) A, c=39.239(8) A, R{sub 1}=0.029, wR{sub 2}=0.084, 6055 independent reflections, 301 variables; Cr{sup III}{sub 4}Ti{sup IV}{sub 27}O{sub 24}(PO{sub 4}){sub 24}: Z=1, a=7.419(3) A, b=21.640(5) A, c=13.057(4) A, R{sub 1}=0.037, wR{sub 2}=0.097, 1524 independent reflections, 111 variables; Fe{sup III}{sub 4}Ti{sup IV}{sub 27}O{sub 24}(PO{sub 4}){sub 24}: Z=1, a=7.4001(9) A, b=21.7503(2) A, c=12.775(3) A, R{sub 1}=0.049, wR{sub 2}=0.140, 1240 independent reflections, 112 variables). For Ti{sup III}Ti{sup IV}O{sub 3}(PO{sub 4}){sub 3} a well-ordered structure built from dimers [Ti{sup III,IV}{sub 2}O{sub 9}] and [Ti{sup IV,IV}{sub 2}O{sub 9}] and phosphate tetrahedra is found. The metal sites in the crystal structures of Cr{sub 4}Ti{sub 27}O{sub 24}(PO{sub 4}){sub 24} and Fe{sub 4}Ti{sub 27}O{sub 24}(PO{sub 4}){sub 24}, consisting of dimers [M{sup III}Ti{sup IV}O{sub 9}] and [Ti{sup IV,IV}{sub 2}O{sub 9}], monomeric [Ti{sup IV}O{sub 6}] octahedra, and phosphate tetrahedra, are heavily disordered. Site disorder, leading to partial occupancy of all octahedral voids of the parent lipscombite/lazulite structure, as well as splitting of the metal positions is observed. According to Guinier photographs Ti{sup III}{sub 4}Ti{sup IV}{sub 27}O{sub 24}(PO{sub 4}){sub 24} (a=7.418(2) A, b=21.933(6) A, c=12.948(7) A) is isotypic to the oxidephosphates M{sup III}{sub 4}Ti{sup IV}{sub 27}O{sub 24}(PO{sub 4

  2. Preparation and crystal structure of a new bismuth vanadate, Bi{sub 3.33}(VO{sub 4}){sub 2}O{sub 2}

    SciTech Connect

    Kumada, N.; Takei, T.; Haramoto, R.; Yonesaki, Y.; Dong, Q.; Kinomura, N.; Nishimoto, S.; Kameshima, Y.; Miyake, M.


    Graphical abstract: Crystal structure of Bi{sub 3.33}(VO{sub 4}){sub 2}O{sub 2}. Solid lines indicate the unit cell. Highlights: {yields} We can prepare a new bismuth vanadate, Bi{sub 3.33}(VO{sub 4}){sub 2}O{sub 2} by hydrothermal reaction using a hydrated sodium bismuthate. {yields} We clarify that the crystal structure is composed by four bismuth atoms with the coordination number of 6 or 8 and two VO{sub 4} tetrahedra. {yields} This compound exhibited photocatalytic behavior for decomposition of phenol under visible light irradiation. -- Abstract: Single crystals of a new bismuth vanadate, Bi{sub 3.33}(VO{sub 4}){sub 2}O{sub 2} was prepared by hydrothermal reaction using a hydrated sodium bismuthate, NaBiO{sub 3}.nH{sub 2}O as one of the starting compounds. The crystal structure was determined by using single crystal X-ray diffraction data. This compound crystallizes in the triclinic space group P1{sup -bar} (no. 2) with a = 7.114(1), b = 7.844(2), c = 9.372(2) A, {alpha} = 106.090(7), {beta} = 94.468(7) and {gamma} = 112.506(8){sup o}, Z = 2 and the final R factors are R1 = 0.052 and wR2 = 0.14 for 2085 unique reflections. The crystal structure is composed by four bismuth atoms with the coordination number of 6 or 8 and two VO{sub 4} tetrahedra, and one of four bismuth atoms is statistically distributed in the splitting sites with the distance of 0.83 A. This compound exhibited photocatalytic behavior for decomposition of phenol under visible light irradiation and its activity was less than that of monoclinic BiVO{sub 4}.

  3. Writing of nonlinear optical Sm{sub 2}(MoO{sub 4}){sub 3} crystal lines at the surface of glass by samarium atom heat processing

    SciTech Connect

    Abe, M.; Benino, Y.; Fujiwara, T.; Komatsu, T.; Sato, R.


    Some glasses such as 21.25Sm{sub 2}O{sub 3}.63.75MoO{sub 3}.15B{sub 2}O{sub 3} (mol %) giving the formation of nonlinear optical Sm{sub 2}(MoO{sub 4}){sub 3} crystals through conventional crystallization in an electric furnace and through continuous-wave Nd: yttrium aluminum garnet (YAG) laser (wavelength: 1064 nm) irradiation (samarium atom heat processing) have been developed. It is proposed from x-ray diffraction analyses, micro-Raman-scattering spectra, and second-harmonic generation measurements that the crystal structure of Sm{sub 2}(MoO{sub 4}){sub 3} formed by the crystallization is the {beta}{sup '}-phase structure with an orthorhombic (noncentrosymmetric) symmetry. The lines consisting of nonlinear optical {beta}{sup '}-Sm{sub 2}(MoO{sub 4}){sub 3} crystals are written at the surface of glasses by YAG laser irradiation (laser power: P=0.4 W, laser scanning speed: S=1-10 {mu}m/s), and, in particular, homogeneous crystal lines are formed at the laser scanning speed of 1 {mu}m/s. Refractive index changes (not crystallization) are also induced by YAG laser irradiation of P=0.4 W and a high laser scanning speed of S=25 {mu}m/s. The crystallization mechanism in the laser-irradiated region has been proposed. The present study demonstrates that the samarium atom heat processing is a technique for the writing of rare earth containing optical nonlinear/ferroelectric crystal lines in glass.

  4. Vacuum ultraviolet spectroscopic properties of rare earth (RE=Ce,Tb,Eu,Tm,Sm)-doped hexagonal KCaGd(PO{sub 4}){sub 2} phosphate

    SciTech Connect

    Zhang, Z. J.; Yuan, J. L.; Duan, C. J.; Xiong, D. B.; Chen, H. H.; Zhao, J. T.; Zhang, G. B.; Shi, C. S.


    Hexagonal KCaGd(PO{sub 4}){sub 2}:RE{sup 3+} (RE=Ce,Tb,Eu,Tm,Sm) were synthesized by coprecipitation method and their vacuum ultraviolet-ultraviolet (VUV-UV) spectroscopic properties were investigated. The bands at about 165 nm in the VUV excitation spectra are attributed to the host lattice absorptions. For Ce{sup 3+}-doped samples, the bands at 207, 256, 275, and 320 nm are assigned to the 4f-5d transitions of Ce{sup 3+} in KCaGd(PO{sub 4}){sub 2}. For Tb{sup 3+}-doped sample, the bands at 203 and 222 nm are related to the 4f-5d spin-allowed transitions. For Eu{sup 3+}-doped sample, the O{sup 2-}-Eu{sup 3+} charge-transfer band (CTB) at 229 nm is observed, and the fine emission spectrum of Eu{sup 3+} indicates that Eu{sup 3+} ions prefer to occupy Gd{sup 3+} or Ca{sup 2+} sites in the host lattice. For Tm{sup 3+}- and Sm{sup 3+}-doped samples, the O{sup 2-}-Tm{sup 3+} and O{sup 2-}-Sm{sup 3+} CTBs are observed to be at 176 and 186 nm, respectively. From the standpoints of the absorption band, color purity, and luminescent intensity, Tb{sup 3+}-doped KCaGd(PO{sub 4}){sub 2} is a potential candidate for 172 nm excited green plasma display phosphors.

  5. Mixed tetrahedral anionic framework in the K{sub 3}Ga{sub 2}(PO{sub 4}){sub 3} crystal structure

    SciTech Connect

    Yakubovich, O. V.; Steele, I.; Kireev, V. V.


    The crystal structure of a new synthetic potassium gallophosphate K{sub 3}Ga{sub 2}(PO{sub 4}){sub 3} grown from a solution in the melt of a mixture of GaPO{sub 4} and K{sub 2}MoO{sub 4} is determined using X-ray diffraction (Bruker Smart diffractometer, 2{theta}{sub max}= 56.6{sup o}, R = 0.044 for 2931 reflections, T = 100 K). The main crystal data are as follows: a = 8.661(2) A, b = 17.002(4) A, c = 8.386(2) A, space group Pna2{sub 1}, Z= 4, and {rho}{sub calcd} = 2.91 g/cm{sup 3}. The synthesized crystals represent the third phase in the structure type previously established for the K{sub 3}Al{sub 2}[(As,P)O{sub 4}]{sub 3} compound. It is shown that the structure consists of a three-dimensional anionic microporous tetrahedral framework of the mixed type, which is formed by PO{sub 4} and GaO{sub 4} tetrahedra shared by vertices. Large-sized cations K{sup +} occupy channels of the zeolite-like framework. The crystal chemical features of the formation of structure types of compounds with mixed frameworks described by the general formula A{sub 3}{sup +}M{sub 2}{sup 3+}(TO{sub 4}){sub 3} (where A = K, Rb, (NH{sub 4}), Tl; M = Al, Ga, Fe, Sc, Yb; T = P, As) are analyzed.

  6. High efficiency passively mode-locked Nd:YVO4sub> laser with direct in-band pumping at 914 nm.


    Waritanant, Tanant; Major, Arkady


    We report on the performance of a semiconductor saturable absorber mirror passively mode-locked Nd:YVO4sub> laser with in-band pumping at 914 nm and with the highest slope efficiency to date among the mode-locked Nd-lasers. The laser produced 6.7 W of output power with repetition rate of 87 MHz and pulse duration of 16 ps. The slope efficiency of 77.1% and the optical-to-optical efficiency of 60.7% were achieved. PMID:27410304

  7. Improved synthesis and crystal structure of the flexible pillared layer porous coordination polymer: Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)4sub>

    SciTech Connect

    Wong-Ng, W.; Culp, J. T.; Chen, Y. S.; Zavalij, P.; Espinal, L.; Siderius, D. W.; Allen, A. J.; Scheins, S.; Matranga, C.


    This paper reports our synthesis of flexible coordination polymer, Ni(L)[Ni(CN)4sub>], (L = 1,2-bis(4-pyridyl)ethylene (nicknamed bpene)), and its structural characterization using synchrotron single crystal X-ray diffraction. The structure of the purplish crystals has been determined to be monoclinic, space group P21/m, a = 13.5941(12) Å, b = 14.3621(12) Å, c = 14.2561(12) Å, β = 96.141(2)°, V = 2767.4(4) Å3, Z = 4, Dc = 1.46 g cm-1. Ni(bpene)[Ni(CN)4sub>] assumes a pillared layer structure with layers defined by Ni[Ni(CN)4sub>]n nets and bpene ligands acting as pillars. With the present crystallization technique which involves the use of concentrated ammonium hydroxide solution and dimethyl sulfoxide (DMSO), disordered free bpene ligands and solvents of crystallization (DMSO and water molecules) occupy the pores, resulting in a formula of Ni(bpene)[Ni(CN)4sub>](1/2)bpene∙DMSO2H2O, or Ni2N7C24H25SO3. Without the inclusion of free bpene ligands and solvent molecules, the free volume is approximately 61% of the total volume; this free volume fraction is reduced to 50% with the free ligands present. Pores without the free ligands were found to have a local diameter of 5.7 Å and a main aperture of 3.5 Å. Based on the successful crystal synthesis, we also devised a new bulk synthetic technique which yielded a polycrystalline material with a significantly improved CO2 uptake as compared to the originally reported powder material. The improved synthetic technique yielded a polycrystalline material with 40% higher CO2 uptake compared to the previously reported powder material. An estimated 14.4 molecules of CO2 per unit cell was obtained.

  8. Quantum oscillations in a novel organic quasi-two-dimensional (BEDO-TTF){sub 5}[RbHg(SCN){sub 4}]{sub 2} metal

    SciTech Connect

    Lyubovskii, R. B.; Pesotskii, S. I. Perenboom, J. A. A. J.; Zhilyaeva, E. I.; Bogdanova, O. A.; Lyubovskaya, R. N.


    Quantum magnetization and magnetoresistance oscillations are detected in the quasi-two-dimensional organic metal (BEDO-TTF){sub 5}[RbHg(SCN){sub 4}]{sub 2} for the first time. The magnetization oscillation spectrum corresponds to a calculated Fermi surface provided that a magnetic breakdown is realized. The magnetoresistance oscillation spectrum contains additional frequencies, one of which can unambiguously be related to quantum interference. An analysis of the angular dependence of the magnetoresistance oscillation amplitude indicates that the many-body interactions in this metal are weak.

  9. Integrated chip-scale Si3N4sub> wavemeter with narrow free spectral range and high stability.


    Xiang, Chao; Tran, Minh A; Komljenovic, Tin; Hulme, Jared; Davenport, Michael; Baney, Doug; Szafraniec, Bogdan; Bowers, John E


    We designed, fabricated, and characterized an integrated chip-scale wavemeter based on an unbalanced Mach-Zehnder interferometer with 300 MHz free spectral range. The wavemeter is realized in the Si3N4sub> platform, allowing for low loss with ∼62  cm of on-chip delay. We also integrated an optical hybrid to provide phase information. The main benefit of a fully integrated wavemeter, beside its small dimensions, is increased robustness to vibrations and temperature variations and much improved stability over fiber-based solutions. PMID:27420522

  10. Widely tunable in the mid-IR BaGa4sub>Se7 optical parametric oscillator pumped at 1064  nm.


    Kostyukova, Nadezhda Y; Boyko, Andrey A; Badikov, Valeriy; Badikov, Dmitrii; Shevyrdyaeva, Galina; Panyutin, Vladimir; Marchev, Georgi M; Kolker, Dmitry B; Petrov, Valentin


    A BaGa4sub>Se7 nanosecond optical parametric oscillator (OPO) shows extremely wide idler tunability in the mid-IR (2.7-17 μm) under 1.064 μm pumping. The ∼10  ns pulses at ∼7.2  μm have an energy of 3.7 mJ at 10 Hz. The pump-to-idler conversion efficiency for this wavelength reaches 5.9% with a slope of 6.5% corresponding to a quantum conversion efficiency or pump depletion of 40%. PMID:27472645

  11. Unique edge-sharing sulfate-transition metal coordination in Na{sub 2}M(SO{sub 4}){sub 2} (M=Ni and Co)

    SciTech Connect

    Fry, Allyson M.; Sweeney, Owen T.; Adam Phelan, W.; Drichko, Natalia; Siegler, Maxime A.; McQueen, Tyrel M.


    Two compounds, Na{sub 2}Ni(SO{sub 4}){sub 2} and Na{sub 2}Co(SO{sub 4}){sub 2}, were synthesized and their structure and properties were characterized. They adopt a structure that contains a bidentate coordination of sulfate to the transition metal center, which was determined via single crystal X-ray diffraction combined with model refinements to both laboratory X-ray and time-of-flight neutron powder diffraction data. The compounds were both found to crystallize in the C2/c space group with Z=24 and a unit cell of a=23.3461(3) Å, b=10.3004(1) Å, c=17.4115(2) Å, β=98.8659(9)°, and V=4136.99(8) Å{sup 3} for the cobalt analog and a=23.2253(1) Å, b=10.26155(6) Å, c=17.3353(1) Å, β=99.0376(5)°, and V=4080.20(5) Å{sup 3} for the nickel analog. Magnetization measurements show that the transition metal centers have negligible interactions with neighboring sites. Infrared and Raman spectroscopies were used to further probe the unique sulfate-transition metal coordination, and confirm the bidentate binding motif. The resulting pseudo-trigonal bipyramidal coordination produces vivid violet, Na{sub 2}Co(SO{sub 4}){sub 2}, and yellow, Na{sub 2}Ni(SO{sub 4}){sub 2}, colors that were probed by diffuse reflectance. - Graphical abstract: Two blue distorted transition metal octahedra (oxygen in red) bridged by two sulfate tetrahedra are shown here. Each bridging sulfate tetrahedra shares an edge with one octahedron and a corner with the other. All of the remaining corners of the octahedra are corner sharing with four tetrahedra forming a polyhedral network. - Highlights: • Structure of Na2Ni(SO4)2 and Na2Co(SO4)2 is determined. • Unique sulfate-transition metal binding observed in the new structure. • Combined diffraction and spectroscopic techniques were used. • Magnetization measurements show negligible interactions between sites.

  12. Investigation of the structure of Cs{sub 3}(HSO{sub 4}){sub 2}(H{sub 2}PO{sub 4}) single crystals

    SciTech Connect

    Makarova, I. P. Grebenev, V. V.; Vasiliev, I. I.; Dmitricheva, E. V.; Komornikov, V. A.; Dolbinina, V. V.


    Cs{sub 3}(HSO{sub 4}){sub 2}(H{sub 2}PO{sub 4}) single crystals, obtained for the first time based on a systematic study of the phase diagram of the CsH{sub 2}PO{sub 4}–CsHSO{sub 4}–H{sub 2}O ternary system, have been studied by X-ray diffraction. The atomic structure of the crystals at room temperature is determined, and their structural features are analyzed.

  13. Reducing ultra-low thermal expansion of {beta}-Zr{sub 2}O(PO{sub 4}){sub 2} by substitutions?

    SciTech Connect

    Barreteau, Celine; Bregiroux, Damien; Laurent, Guillaume; Wallez, Gilles


    The ultra-low thermal expansion of {beta}-Zr{sub 2}O(PO{sub 4}){sub 2} could still be reduced by chemical modifications, according to previous works on uranium and thorium IV homologues that evidenced a contracting effect of big cations. However, the present study shows that the only isovalent cations likely to substitute for Zr{sup IV} or P{sup V} are either harmful, or unstable, chemically or thermally. Furthermore, aliovalent modifications seem to be forbidden by the crystal structure of the material, leaving probably very few perspectives of improvement. Vanadium however improves significantly the crystallinity of the material and lowers the {alpha}-{beta} transition temperature.

  14. Luminescent properties of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} and its luminescence improvement by incorporating A{sup +} (A=Li, Na, and K)

    SciTech Connect

    Li, Panlai Wang, Zhijun Yang, Zhiping; Guo, Qinglin


    A novel green phosphor SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} is synthesized by a high temperature solid-state method, and its luminescent property is investigated. X-ray diffraction patterns of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} indicate a similarity crystalline phase to SrZn{sub 2}(PO{sub 4}){sub 2}. SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} shows green emission under 369 nm excitation, and the prominent luminescence in green (544 nm) due to {sup 5}D{sub 4}–{sup 7}F{sub 5} transition of Tb{sup 3+}. For the 544 nm emission, excitation spectrum has several excitation band from 200 nm to 400 nm. Emission intensity of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} is influenced by Tb{sup 3+} concentration, and concentration quenching effect of Tb{sup 3+} in SrZn{sub 2}(PO{sub 4}){sub 2} is also observed. With incorporating A{sup +} (A=Li, Na, and K) as compensator charge, the emission intensity of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can be obviously enhanced. CIE color coordinates of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} locate in the green region. The results indicate this phosphor may be a potential application in white LEDs. - Graphical abstract: SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can produce green emission under near-UV excitation, and its luminescent properties can be improved by incorporating A{sup +} (A=Li, Na, and K). - Highlights: • SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can produce green emission under near-UV excitation. • Concentration quenching effect of Tb{sup 3+} in SrZn{sub 2}(PO{sub 4}){sub 2} is observed. • Emission intensities of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} are enhanced by codoped A{sup +} (A=Li, Na, K)

  15. Synthesis and crystal structure of a new open-framework iron phosphate (NH{sub 4}){sub 4}Fe{sub 3}(OH){sub 2}F{sub 2}[H{sub 3}(PO{sub 4}){sub 4}]: Novel linear trimer of corner-sharing Fe(III) octahedra

    SciTech Connect

    Mi, Jin-Xiao; Wang, Cheng-Xin; Chen, Ning; Li, Rong; Pan, Yuanming


    A new iron phosphate (NH{sub 4}){sub 4}Fe{sub 3}(OH){sub 2}F{sub 2}[H{sub 3}(PO{sub 4}){sub 4}] has been synthesized hydrothermally at HF concentrations from 0.5 to 1.2 mL. Single-crystal X-ray diffraction analysis reveals its three-dimensional open-framework structure (monoclinic, space group P2{sub 1}/n (No. 14), a=6.2614(13) A, b=9.844(2) A, c=14.271(3) A, {beta}=92.11(1){sup o}, V=879.0(3) A{sup 3}). This structure is built from isolated linear trimers of corner-sharing Fe(III) octahedra, which are linked by (PO{sub 4}) groups to form ten-membered-ring channels along [1 0 0]. This isolated, linear trimer of corner-sharing Fe(III) octahedra, [(FeO{sub 4}){sub 3}(OH){sub 2}F{sub 2}], is new and adds to the diverse linkages of Fe polyhedra as secondary building units in iron phosphates. The trivalent iron at octahedral sites for the title compound has been confirmed by synchrotron Fe K-edge XANES spectra and magnetic measurements. Magnetic measurements also show that this compound exhibit a strong antiferromagnetic exchange below T{sub N}=17 K, consistent with superexchange interactions expected for the linear trimer of ferric octahedra with the Fe-F-Fe angle of 132.5{sup o}. -- Graphical abstract: The three-dimensional open-framework structure of (NH{sub 4}){sub 4}Fe{sub 3}(OH){sub 2}F{sub 2}[H{sub 3}(PO{sub 4}){sub 4}] is built from a novel isolated, linear (FeO{sub 4}){sub 3}(OH){sub 2}F{sub 2} trimer of corner-sharing Fe(III) octahedra linked by PO{sub 4} tetrahedra. Display Omitted

  16. Magnetic excitations from an S=1/2 diamond-shaped tetramer compound Cu2PO4sub>OH

    SciTech Connect

    Matsuda, Masaaki; Dissanayake, Sachith E.; Abernathy, Douglas L.; Totsuka, K.; Belik, A. A.


    Inelastic neutron scattering experiments have been carried out on a powder sample of Cu2PO4sub>OH, which consists of diamond-shaped tetramer spin units with S=1/2. We have observed two nearly dispersionless magnetic excitations at E1 ~2 and E2 ~0 meV, whose energy width are broader than the instrumental resolution. The simplest square tetramer model with one dominant interaction, which predicts two sharp excitation peaks at E1 and E2(=2E1), does not explain the experimental result. We found that two diagonal intratetramer interactions compete with the main interaction and weak intertetramer interactions connect the tetramers. The main intratetramer interaction is found to split into two inequivalent ones due to a structural distortion below 160 K. Cu2PO4sub>OH is considered to be a good material to study the S=1/2 Heisenberg tetramer system.

  17. Metastability in the MgAl2O4sub>-Al2O3 System

    SciTech Connect

    Wilkerson, Kelley R.; Smith, Jeffrey D.; Hemrick, James G.


    Aluminum oxide must take a spinel form ( γ-Al2O3) at elevated temperatures in order for extensive solid solution to form between MgAl2O4sub> and α-Al2O3. The solvus line between MgAl2O4sub> and Al2O3 has been defined at 79.6 wt% Al2O3 at 1500°C, 83.0 wt% Al2O3 at 1600°C, and 86.5 wt% Al2O3 at 1700°C. A metastable region has been defined at temperatures up to 1700°C which could have significant implications for material processing and properties. Additionally, initial processing could have major implications on final chemistry. The spinel solid solution region has been extended to form an infinite solid solution with Al2O3 at elevated temperatures. A minimum in melting at 1975°C and a chemistry of 96 wt% Al2O3 rather than a eutectic is present, resulting in no eutectic crystal formation during solidification.

  18. Thermodynamic Properties of α-Fe2O3 and Fe3O4sub> Nanoparticles

    SciTech Connect

    Spencer, Elinor C.; Ross, Nancy L.; Olsen, Rebecca E.; Huang, Baiyu; Kolesnikov, Alexander I.; Woodfield, Brian F.


    Here we comprehansively assessed the thermodynamic properties of hydrated α-Fe2O3 (hematite) and Fe3O4sub> (magnetite) nanoparticles. In addition to 9 nm Fe3O4sub>, three α-e2O3nanoparticles samples of different sizes (11, 14, and 25 nm) and bulk α-e2O3 have been evaluated by inelastic neutron scattering methods. The contribution of the two-level magnetic spin flip transition to the heat capacity of the α-e2O3 particles has been determined. The isochoric heat capacity of the water confined on the surface of these two types of iron oxide particles have been calculated from their INS spectra, and is affected by the chemical composition of the underlying particle. Furthermore, the heat capacity and dynamics of the particle hydration layers appear to be influenced by a complex array of factors including particle size, water coverage, and possibly the magnetic state of the particle itself.

  19. Structural instability of the CoO4sub> tetrahedral chain in SrCoO3-δ thin films

    SciTech Connect

    Glamazda, A.; Choi, Kwang-yong; Lemmens, P.; Choi, Woo Seok; Jeen, Hyoungjeen; Meyer, Tricia L.; Lee, Ho Nyung


    Raman scattering experiments together with detailed lattice dynamic calculations are performed to elucidate crystallographic and electronic peculiarities of SrCoO3-δ films. We observe that the 85 cm-1 phonon mode involving the rotation of a CoO4sub> tetrahedron undergoes a hardening by 21 cm-1 when the temperature is decreased. In addition, new phonon modes appear at 651.5 and 697.6 cm-1 . The latter modes are attributed to the Jahn-Teller activated modes. Upon cooling from room temperature, all phonons exhibit an exponential-like increase of intensity with a characteristic energy of about 103–107 K. We attribute this phenomenon to an instability of the CoO4sub> tetrahedral chain structure, which constitutes a key ingredient to understand the electronic and structural properties of the brownmillerite SrCoO2.5.

  20. Disorder from order among anisotropic next-nearest-neighbor Ising spin chains in SrHo2O4sub>

    SciTech Connect

    Wen, J. -J.; Tian, W.; Garlea, V. O.; Koohpayeh, S. M.; McQueen, T. M.; Li, H. -F.; Yan, J. -Q.; Rodriguez-Rivera, J. A.; Vaknin, D.; Broholm, C. L.


    In this study, we describe why Ising spin chains with competing interactions in SrHo2O4sub> segregate into ordered and disordered ensembles at low temperatures (T). Using elastic neutron scattering, magnetization, and specific heat measurements, the two distinct spin chains are inferred to have Néel (↑↓↑↓) and double-Néel (↑↑↓↓) ground states, respectively. Below TN = 0.68(2)K, the Néel chains develop three-dimensional long range order (LRO), which arrests further thermal equilibration of the double-Néel chains so they remain in a disordered incommensurate state for T below TS = 0.52(2)K. SrHo2O4sub> distills an important feature of incommensurate low dimensional magnetism: kinetically trapped topological defects in a quasi–d–dimensional spin system can preclude order in d + 1 dimensions.

  1. Crystal structure and electrical properties of K/sub 3/Bi/sub 2/(VO/sub 4/)/sub 3/, a new potassium bismuth vanadate

    SciTech Connect

    Debreuille-Gresse, M.F.; Abraham, F.


    K/sub 3/Bi/sub 2/(VO/sub 4/)/sub 3/ crystallizes in the space group C2/c, a = 13.957(4), b = 13.858(4), c = 7.095(2) A, ..beta.. = 112.80(3)/sup 0/, Z = 4. The crystal structure was determined from single-crystal intensity data obtained by means of an automated four-circle diffractometer and refined to the conventional values R = 0.050 and R/sub w/ = 0.059 for 1498 observed reflections. The structure is characterized by a three-dimensional network of Bi/sub 2/O/sub 10/ units and VO/sub 4/ tetrahedra. A Bi/sub 2/O/sub 10/ unit is formed by two BiO/sub 6/ octahedra sharing an edge. K/sup +/ ions occupy three different crystallographic sites. One of them has a high thermal vibration which could reflect ionic mobility. The ionic conductivity highly increases at 790 K. DSC measurements show a reversible transition at this temperature. One K atom, and only one, can be substituted by one Na atom to give NaK/sub 2/Bi/sub 2/(VO/sub 4/)/sub 3/; this substitution improves the conductivity.

  2. Magnetic order in the S=1/2 two-dimensional molecular antiferromagnet, copper pyrazine perchlorate Cu(Pz){sub 2}(ClO{sub 4}){sub 2}.

    SciTech Connect

    Lancaster, T.; Blundell, S. J.; Brooks, M. L.; Baker, P. J.; Pratt, F. L.; Manson, J. L.; Connor, M. M.; Xiao, F.; Landee, C. P.; Chaves, F. A.; Soriano, S.; Novak, M. A.; Papageorgiou, T.; Bianchi, A.; Wosnitza, J.; Schlueter, J. A.; Materials Science Division; Oxford Univ.; Rutherford Appleton Lab.; Eastern Washington Univ.; Clark Univ.; Inst. de Fisica, UFRJ; Hochfeld-Magnetlabor Dresden


    We present an investigation of magnetic ordering in the two-dimensional S=1/2 quantum magnet Cu(Pz){sub 2}(ClO{sub 4}){sub 2} using specific heat and zero-field muon-spin relaxation ({mu}{sup +}SR). The magnetic contribution to the specific heat is consistent with an exchange strength of 17.7(3) K. We find unambiguous evidence for a transition to a state of three-dimensional long-range order below a critical temperature T{sub N} = 4.21(1) K using {mu}{sup +} SR even though there is no feature in the specific heat at that temperature. The absence of a specific heat anomaly at T{sub N} is consistent with recent theoretical predictions. The ratio of T{sub N}/J=0.24 corresponds to a ratio of intralayer to interlayer exchange constants of |J{prime}/J| = 6.8 x 10{sup -4}, indicative of excellent two-dimensional isolation. The scaled magnetic specific heat of [Cu(Pz){sub 2}(HF{sub 2})]BF{sub 4}, a compound with an analogous structure, is very similar to that of Cu(Pz){sub 2}(ClO{sub 4}){sub 2} although both differ slightly from the predicted value for an ideal 2D S=1/2 Heisenberg antiferromagnet.

  3. In situ studies of surface of NiFe2O4sub> catalyst during complete oxidation of methane

    SciTech Connect

    Zhang, Shiran; Shan, Junjun; Nie, Longhui; Nguyen, Luan; Wu, Zili; Tao, Franklin


    Here, NiFe2O4sub> with an inverse spinel structure exhibits high activity for a complete oxidation of methane at 400 °C–425 °C and a higher temperature. The surface of the catalyst and its adsorbates were well characterized with ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and in situ infrared spectroscopy (IR). In situ studies of the surface of NiFe2O4sub> using AP-XPS suggest the formation of methoxy-like and formate-like intermediates at a temperature lower than 200 °C, supported by the observed vibrational signatures in in situ IR studies. Evolutions of C1s photoemission features and the nominal atomic ratios of C/(Ni + Fe) of the catalyst surface suggest that the formate-like intermediate is transformed to product molecules CO2 and H2O in the temperature range of 250–300 °C. In situ studies suggest the formation of a spectator, – Olattice – CH2 – Olattice –. It strongly bonds to surface through C–O bonds and cannot be activated even at 400 °C.

  4. Monodispersed Li4sub>Ti5O12 with Controlled Morphology as High Power Lithium Ion Battery Anodes

    SciTech Connect

    Li, Yunchao; Fu, Guoyi; Watson, Mark; Harrison, Stephen; Paranthaman, M Parans


    Monodispersed Li4sub>Ti5O12 (LTO) nanoparticles with controlled microstructure were successfully synthesized by a combination of hydrolysis and hydrothermal method followed by a post-annealing process. The scanning electron microscopy images showed that particles with a size of 30-40 nm were precisely controlled throughout the synthesis process. The electrochemical tests of the as-prepared LTO electrodes in a half-cell proved its high rate performance and outstanding cyclability which benefits from the preserved well-controlled nanoparticle size and morphology. LTO electrodes were also tested in a full cell configuration in pairing with LiFePO4sub> cathodes, which demonstrated a capacity of 147.3 mAh g-1. In addition, we have also demonstrated that LTO materials prepared using lithium salts separated from geothermal brine solutions had good cyclability. These demonstrations provide a promising way for making low-cost, large-scale LTO electrode materials for energy storage applications.

  5. Conduction below 100 °C in nominal Li6ZnNb4sub>O14

    SciTech Connect

    Li, Yunchao; Paranthaman, Mariappan Parans; Gill, Lance W.; Edward W. Hagaman; Wang, Yangyang; Sokolov, Alexei P.; Dai, Sheng; Ma, Cheng; Chi, Miaofang; Veith, Gabriel M.; Manthiram, Arumugam; Goodenough, John B.


    The increasing demand for a safe rechargeable battery with a high energy density per cell is driving a search for a novel solid electrolyte with a high Li+ or Na+ conductivity that is chemically stable in a working Li-ion or Na-ion battery. Li6ZnNb4sub>O14 has been reported to exhibit a σ Li > 10-2 S cm-1 at 250 °C, but to disproportionate into multiple phases on cooling from 850 °C to room temperature. An investigation of the room-temperature Li-ion conductivity in a porous pellet of a multiphase product of a nominal Li6ZnNb4sub>O14 composition is shown to have bulk σ Li 3.3 x 10-5 S cm-1 at room temperature that increases to 1.4 x 10-4 S cm-1 by 50 °C. 7Li MAS NMR spectra were fitted to two Lorentzian lines, one of which showed a dramatic increase with increasing temperature. As a result, a test for water stability indicates that Li+ may move to the particle and grain surfaces to react with adsorbed water as occurs in the garnet Li+ conductors.

  6. Hydrothermal syntheses, structures, and properties of two new potassium vanadium phosphates: K[sub 3](VO)(V[sub 2]O[sub 3])(PO[sub 4])[sub 2](HPO[sub 4]) and K[sub 3](VO)(HV[sub 2]O[sub 3])(PO[sub 4])[sub 2](HPO[sub 4])

    SciTech Connect

    Vaughey, J.T.; Harrison, T.A.; Jacobson, A.J. )


    Two new potassium vanadium phosphates have been prepared and their structures have been determined from analysis of single crystal X-ray data. The two compounds, K[sub 3](VO)(V[sub 2]O[sub 3])(PO[sub 4])[sub 2](HPO[sub 4]) and K[sub 3](VO)(HV[sub 2]O[sub 3])(PO[sub 4])[sub 2](HPO[sub 4]), are isostructural, except for the incorporation of an extra hydrogen atom into the nearly identical frameworks. The structures consist of a three-dimensional network of [VO][sub n] chains connected through phosphate groups to a [V[sub 2]O[sub 3

  7. Electrochemically influenced cation inter-diffusion and Co3O4sub> formation on La0.6Sr0.4sub>CoO3 infiltrated into SOFC cathodes

    SciTech Connect

    Song, Xueyan; Lee, Shiwoo; Chen, Yun; Gerdes, Kirk


    Nanosized LSC electrocatalyst was infiltrated into a porous scaffold cathode composed of Sm2O3-doped CeO2 (SDC) and La0.6Sr0.4sub>Co0.2Fe0.8O3-δ (LSCF) in a commercial button solid oxide fuel cell (SOFC). To understand the stability of cathodes infiltrated with LSC, the infiltrated composite cells were subjected to both electrochemical operating and thermal aging states at 750 °C for 1500 h. Nanostructure and local chemistry evolution of La0.6Sr0.4sub>CoO3 (LSC) infiltrated cathodes upon operation and aging were investigated by transmission electron microscopy. After operation, the LSC remained a cubic perovskite, and the crystal grains exhibit comparable size to as-infiltrated LSC grains. Inter-diffusion of Fe from the LSCF to a Fe-incorporated LSC layer developed on the LSCF backbone. However, only sharp interfaces were observed between LSC and SDC backbone in the as-infiltrated cathode and such interfaces remain after operation. The infiltrated LSC on the SDC backbone also retains granular particle morphology. Furthermore, newly grown Co3O4sub> nanocrystals were found in the operated cathode. After thermal aging, on the other hand, cation inter-diffusion across the interfaces of the infiltrate particles and the cathode backbones is less than that from the operated cells. Lastly, the following hypothesis is proposed: Co3O4sub> forms on LSC arising from local charge balancing between cobalt and oxygen vacancies.

  8. Phosphorus-bridged ansa-metallocene complexes of titanium, zirconium, and hafnium: The syntheses and structures of [PhP(C{sub 5}Me{sub 4}){sub 2}]MX{sub 2} and [Ph(E)P(C{sub 5}Me{sub 4}){sub 2}]MX{sub 2} (E = O, S, Se) derivatives

    SciTech Connect

    Shin, J.H.; Hascall, T.; Parkin, G.


    A series of phosphorus-bridged ansa-metallocene complexes of titanium, zirconium, and hafnium, [PhP(XC{sub 5}Me{sub 4}){sub 2}]MX{sub 2} and [Ph(E)P(C{sub 5}Me{sub 4}){sub 2}]MX{sub 2} (X = Cl, Me, CO, (Se{sub 3}){sub 0.5}; E = O, S, Se), has been synthesized. Structural characterization by X-ray diffraction indicates that, in comparison to their non-ansa counterparts (C{sub 5}Me{sub 5}){sub 2}MX{sub 2}, the cyclopentadienyl groups in phosphorus-bridged complexes are displaced from symmetric {eta}{sup 5}-coordination toward {eta}{sup 3}-coordination. Such {eta}{sup 3},{eta}{sup 3}-coordination creates more electrophilic metal centers than those in their permethylcyclopentadienyl counterparts, as judged by the {nu}(CO) stretching frequencies of the zirconium dicarbonyl complexes Cp{sup *}{sub 2}Zr(CO){sub 2} (1946 and 1853 cm{sup {minus}1}) and [PhP(C{sub 5}Me{sub 4}){sub 2}]Zr(CO){sub 2} (1959 and 1874 cm{sup {minus}1}).

  9. Crystal structure and magnetic properties of NaCu{sup II}[(Cu{sup II}{sub 3}O)(PO{sub 4}){sub 2}Cl

    SciTech Connect

    Jin Tengteng; Liu Wei; Chen Shuang; Prots, Yurii; Schnelle, Walter; Zhao Jingtai; Kniep, Ruediger; Hoffmann, Stefan


    A new copper(II) oxide phosphate chloride, NaCu{sup II}[(Cu{sup II}{sub 3}O)(PO{sub 4}){sub 2}Cl], has been synthesized by flux synthesis. Single-crystal X-ray diffraction data show that the title compound crystallizes in the monoclinic system, space group P2{sub 1}/c (No. 14), with lattice parameters a=8.392(2) A, b=6.3960(10) A, c=16.670(2) A, {beta}=109.470(10) Degree-Sign , V=843.6(3) A{sup 3}, Z=4. The crystal structure is characterized by a complex chain of copper-centered polyhedra running along [0 1 0] which are connected by phosphate tetrahedra. The resulting three-dimensional polyhedra framework exhibits channels filled by additional copper and sodium atoms. Field and temperature dependent measurements of the specific heat and the magnetic susceptibility reveal low-dimensional magnetic behavior. The compound starts to decompose at 700 K under release of oxygen and evaporation of Cu{sup I}Cl as shown by simultaneous thermogravimetry and mass spectrometry. - Graphical abstract: The crystal structure of the new copper(II) phosphate chloride, NaCu{sup II}[(Cu{sup II}{sub 3}O)(PO{sub 4}){sub 2}Cl], exhibits linear chains of copper tetrahedra which show low-dimensional magnetic behavior proven by specific heat and magnetic susceptibility measurements. Highlights: Black-Right-Pointing-Pointer A new copper(II) oxide phosphate chloride, NaCu{sup II}[(Cu{sup II}{sub 3}O)(PO{sub 4}){sub 2}Cl], has been synthesized by flux synthesis. Black-Right-Pointing-Pointer The crystal structure comprises chains of Cu{sub 4}O tetrahedra. Black-Right-Pointing-Pointer Low-dimensional behavior has been proven by magnetic and specific heat measurements. Black-Right-Pointing-Pointer On heating, Cu{sup I}Cl and oxygen are released shown by simultaneous thermogravimetry and mass spectrometry.

  10. 119Sn-NMR investigations on superconducting Ca3Ir4sub>Sn13: Evidence for multigap superconductivity

    SciTech Connect

    Sarkar, R.; Petrovic, C.; Bruckner, F.; Gunther, M.; Wang, Kefeng; Biswas, P. K.; Luetkens, H.; Morenzoni, E.; Amato, A.; Klauss, H. -H.


    In this study, we report bulk superconductivity (SC) in Ca3Ir4sub>Sn13 by means of 119Sn nuclear magnetic resonance (NMR) experiments. Two classical signatures of BCS superconductivity in spin-lattice relaxation rate (1/T1), namely the Hebel–Slichter coherence peak just below the Tc, and the exponential decay in the superconducting phase, are evident. The noticeable decrease of 119Sn Knight shift below Tc indicates spin-singlet superconductivity. The temperature dependence of the spin-lattice relaxation rate 119(1/T1) is convincingly described by the multigap isotropic superconducting gap. NMR experiments do not witness any sign of enhanced spin fluctuations.

  11. Theoretical crystal chemistry of M{sub x}(TO{sub 4}){sub y} sulfates and selenates: Topological analysis and classification of suprapolyhedral invariants

    SciTech Connect

    Ilyushin, G. D. Blatov, V. A.


    A geometric topological analysis of orthotetrahedral phases M{sub x}(TO{sub 4}){sub y} (T = S or Se) is performed for 46 sulfates and 17 selenates with the TOPOS 3.2 software package. The values of coordination sequences {l_brace}N{sub k}{r_brace} of T atoms are used as classification parameters of topologically different MTO nets. The crystal structures are analyzed within 12 coordination spheres of T sites and assigned to 26 topological types. It is established that only 7 types are common for the structures of sulfates and selenates, 16 types include only sulfates, and 3 types include only selenates. The average values of the bond lengths are determined: = 1.48(2) A and = 1.63(2) A. The hierarchical ordering of the crystal structure is performed using the concept of a polyhedral microensemble of the structure.

  12. Multiband Te p Based Superconductivity of Ta4sub>Pd3Te16

    SciTech Connect

    Singh, David J.


    We recently discovered that Ta4sub>Pd3Te16 is a superconductor that has been suggested to be an unconventional superconductor near magnetism. Here, we report electronic structure calculations showing that despite the layered crystal structure the material is an anisotropic three-dimensional (3D) metal. The Fermi surface contains prominent one-dimensional (1D) and two-dimensional (2D) features, including nested 1D sheets, a 2D cylindrical section, and a 3D sheet. Moreover, the electronic states that make up the Fermi surface are mostly derived from Te p states with small Ta d and Pd d contributions. This places the compound far from magnetic instabilities. The results are discussed in terms of multiband superconductivity.

  13. Beam quality management by periodic reproduction of wavefront aberrations in end-pumped Nd:YVO4sub> laser amplifiers.


    Liu, Bin; Liu, Chong; Shen, Lifeng; Wang, Chunhua; Ye, Zhibin; Liu, Dong; Xiang, Zhen


    A method for beam quality management is presented in a master oscillator power amplifier (MOPA) using Nd:YVO4sub> as the gain medium by extra-cavity periodic reproduction of wavefront aberrations. The wavefront aberration evolution of the intra-cavity beams is investigated for both symmetrical and asymmetrical resonators. The wavefront aberration reproduction process is successfully realized outside the cavity in four-stage amplifiers. In the MOPA with a symmetrical oscillator, the laser power increases linearly and the beam quality hardly changes. In the MOPA with an asymmetrical oscillator, the beam quality is deteriorated after the odd-stage amplifier and is improved after the even-stage amplifier. The wavefront aberration reproduction during the extra-cavity beam propagation in the amplifiers is equivalent to that during the intra-cavity propagation. This solution helps to achieve the effective beam quality management in laser amplifier chains. PMID:27137329

  14. Optical modeling and optimizations of Cu2ZnSnSe4sub> solar cells using the modified transfer matrix method.


    Cozza, Dario; Ruiz, Carmen M; Duché, David; Giraldo, Sergio; Saucedo, Edgardo; Simon, Jean Jacques; Escoubas, Ludovic


    The fast and computationally inexpensive Modified Transfer Matrix Method (MTM) is employed to simulate the optical response of kesterite Cu2ZnSnSe4sub> solar cells. This method can partially take into account the scattering effects due to roughness at the interfaces between the layers of the stack. We analyzed the optical behavior of the whole cell structure by varying the thickness of the TCO layer (iZnO + ITO) between 50 and 1200 nm and the buffer CdS layer between 0 and 100 nm. We propose optimal combinations of the TCO/CdS thicknesses that can locally maximize the device photocurrent. We provide experimental data that qualitatively confirm our theoretical predictions. PMID:27607723

  15. New insights into the thermodynamic behavior of 2LiBH4sub>-MgH2 composite for hydrogen storage

    SciTech Connect

    Cova, Federico; Ronnebro, Ewa; Choi, Yong-Joon; Gennari, Fabiana; Larochette, Pierre


    The composite 2LiBH4sub>:MgH2 has been studied as a possible hydrogen storage material due to its high storage capacity. The present work is directed towards the clarification of the thermodynamic behavior of the system, especially in the temperature region above 400°C. We reveal different reaction paths during hydrogen absorption and desorption at various temperatures which has important implication for applications. At temperatures higher than 413°C, the observation of two different absorption pressure plateaus indicates that two different reactions occur, however, below this temperature there is only one plateau present in the system. During desorption, the double plateau can be observed at temperatures as low as 375°C.

  16. Nanoparticles of K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}:Eu as effective detectors for swift heavy ions

    SciTech Connect

    Salah, Numan; Lochab, S. P.; Kanjilal, D.; Ranjan, Ranju; Habib, Sami S.; Rupasov, A. A.; Aleynikov, V. E.


    The modification of thermoluminescence (TL) and photoluminescence (PL) properties of K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}:Eu nanoparticles by swift heavy ions (SHI), irradiation is studied. Pellets form of the nanomaterials were irradiated by 48 MeV Li{sup 3+}, 75 MeV C{sup 6+}, and 90 MeV O{sup 7+} ion beams. The fluence range is 1x10{sup 9}-1x10{sup 13} ions/cm{sup 2}. The modification in TL glow curves of the nanomaterials irradiated by Li{sup 3+}, C{sup 6+}, and O{sup 7+} ion beams are essentially similar to those induced by {gamma}-ray irradiation. These glow curves have single peaks at around 427 K with a small variation in their positions by around {+-}3 K. The TL intensity of the ion beams irradiated nanomaterials is found to decease, while going from low to high atomic number (Z) ions (i.e., Li{sup 3+}{yields}O{sup 7+}). The TL response curve of the pellets irradiated by Li{sup 3+} ions is linear in the whole range of studied fluences. The curves for C{sup 6+} and O{sup 7+} irradiated samples are linear at lower fluences (1x10{sup 9}-1x10{sup 12} ion/cm{sup 2}) and then saturate at higher fluence. These results for the nanomaterials are much better than that of the corresponding microcrystalline samples irradiated with a Li{sup 3+} ion. The curves were linear up to the fluence 1x10{sup 11} ion/cm{sup 2} and then become sublinear at higher fluences. The TL efficiency values of K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}:Eu nanoparticles irradiated by 48 MeV Li{sup 3+}, 75 MeV C{sup 6+}, and 90 MeV O{sup 7+} ion beams have been measured relative to {gamma} rays of {sup 60}Co and are found to be 0.515, 0.069, and 0.019, respectively. This value for the Li{sup 3+} ion (0.515) is much higher than that of the corresponding microcrystalline material (0.0014). These superiorities for the nanomaterials make K{sub 2}Ca{sub 2}(SO{sub 4}){sub 3}:Eu nanophosphor a suitable candidate for detecting the doses of swift heavy ions. PL studies on the ion beams irradiated and

  17. Thermal expansion of NaTi/sub 2/(PO/sub 4/)/sub 3/ studied by Rietveld method from x-ray diffraction data

    SciTech Connect

    Rodrigo, J.L.; Carrasco, P.; Alamo, J. )


    Previous disagreement about the thermal expansion of the rhombohedral compound, NZP-type, NaTi/sub 2/(PO/sub 4/)/sub 3/ is clarified. It is shown that thermal stresses affect the thermal expansion, but they relax after some time of storage. Its anisotropic thermal expansion, has been calculate from high temperature X-ray diffraction, and it is linear in the range from room temperature up to 800{sup 0}C. The predictability of thermal expansion and the tailoring of the composition of NZP ceramics require checking whether the thermal effect on the rotations and distortions of the atomic polyhedra in this structure is the responsible for the high anisotropy in the thermal expansion. This effect has been determined experimentally by solving the chemical structure at five different temperatures, applying the Rietveld method to deconvolute the powder X-ray diffraction profiles.

  18. Temperature, Oxygen, and Soot-Volume-Fraction Measurements in a Turbulent C2H4sub>-Fueled Jet Flame

    SciTech Connect

    Kearney, Sean P.; Guildenbecher, Daniel Robert; Winters, Caroline; Farias, Paul Abraham; Grasser, Thomas W.; Hewson, John C.


    We present a detailed set of measurements from a piloted, sooting, turbulent C 2 H 4 sub>- fueled diffusion flame. Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (CARS) is used to monitor temperature and oxygen, while laser-induced incandescence (LII) is applied for imaging of the soot volume fraction in the challenging jet-flame environment at Reynolds number, Re = 20,000. Single-laser shot results are used to map the mean and rms statistics, as well as probability densities. LII data from the soot-growth region of the flame are used to benchmark the soot source term for one-dimensional turbulence (ODT) modeling of this turbulent flame. The ODT code is then used to predict temperature and oxygen fluctuations higher in the soot oxidation region higher in the flame.

  19. Negative to positive magnetoresistance and magnetocaloric effect in Pr0.6Er0.4sub>Al2

    SciTech Connect

    Pathak, Arjun K.; Gschneidner, Jr., K. A.; Pecharsky, V. K.


    We report on the magnetic, magnetocaloric and magnetotransport properties of Pr0.6Er0.4sub>Al2. The title compound exhibits a large positive magnetoresistance (MR) for H ≥ 40 kOe and a small but non negligible negative MR for H ≤ 30 kOe. The maximum positive MR reaches 13% at H = 80 kOe. The magnetic entropy and adiabatic temperature changes as functions of temperature each show two anomalies: a broad dome-like maximum below 20 K and a relatively sharp peak at higher temperature. As a result, observed behaviors are unique among other binary and mixed lanthanide compounds.

  20. Calorimetric, spectroscopic and structural investigations of phase polymorphism in [Ru(NH{sub 3}){sub 6}](BF{sub 4}){sub 3}. Part I

    SciTech Connect

    Dolega, Diana; Mikuli, Edward; Inaba, Akira; Gorska, Natalia; Holderna-Natkaniec, Krystyna; Nitek, Wojciech


    Four crystalline phases of the coordination compound [Ru(NH{sub 3}){sub 6}](BF{sub 4}){sub 3} are identified by adiabatic calorimetry. Three phase transitions, one at T{sub C3}(IV{yields}III)=30.7 K, the second at T{sub C2}(III{yields}II)=91.7 K (both accompanied by comparable entropy changes 3.0 and 3.1 J K{sup -1} mol{sup -1}, respectively) and the third at T{sub C1}(II{yields}I)=241.6 K (accompanied by an entropy change of 8.1 J K{sup -1} mol{sup -1}) were discovered. X-ray single crystal diffraction (at 293 K) demonstrates that phase I is a highly dynamic disordered cubic phase (Fm3{sup Macron }m, No. 225) with two types of BF{sub 4}{sup -} anions differing in a degree of disorder. In phase II (at 170 K) the structure remains cubic (Ia3{sup Macron }, No. 206), with two different types of cations and four different types of anions. Splitting of certain IR bands connected with NH{sub 3} ligands at the observed phase transitions suggests a lowering of the symmetry of the [Ru(NH{sub 3}){sub 6}]{sup 3+} complex cation. Both NH{sub 3} ligands and BF{sub 4}{sup -} anions perform fast reorientations ({tau}{sub R} Almost-Equal-To 10{sup -12} s), which are significantly slowed down below the phase transition at T{sub C3}. {sup 1}H NMR studies led to estimate the values of the activation energy of NH{sub 3} ligands reorientation in the phases II and I as equal to {approx}8 kJ mol{sup -1}. In phase I the whole hexammineruthenium(III) cations reorientation as a tumbling process can be noticed. The activation energy value of this motion is {approx}24 kJ mol{sup -1}. {sup 19}F NMR studies give the values of the activation energy of BF{sub 4}{sup -} anions reorientation as {approx}6 kJ mol{sup -1}. Above the phase transition temperature half of BF{sub 4}{sup -} anions perform a tumbling motion with E{sub a} Almost-Equal-To 8 kJ mol{sup -1}. - Graphical abstract: A series of complementary methods, such as Adiabatic Calorimetry, Differential Scanning Calorimetry, Fourier

  1. One Dimensional(1D)-to-2D Crossover of Spin Correlations in the 3D Magnet ZnMn2O4sub>

    SciTech Connect

    Disseler, S. M.; Chen, Y.; Yeo, S.; Gasparovic, G.; Piccoli, P. M. B.; Schultz, A. J.; Qiu, Y.; Huang, Q.; Cheong, S. -W.; Ratcliff, W.


    In this paper we report on the intriguing evolution of the dynamical spin correlations of the frustrated spinel ZnMn2O4sub>. Inelastic neutron scattering and magnetization studies reveal that the dynamical correlations at high temperatures are 1D. At lower temperature, these dynamical correlations become 2D. Surprisingly, the dynamical correlations condense into a quasi 2D Ising-like ordered state, making this a rare observation of two dimensional order on the spinel lattice. Remarkably, 3D ordering is not observed down to temperatures as low as 300 mK. This unprecedented dimensional crossover stems from frustrated exchange couplings due to the huge Jahn-Teller distortions around Mn3+ ions on the spinel lattice.

  2. Generation of 30  fs pulses from a diode-pumped graphene mode-locked Yb:CaYAlO4sub> laser.


    Ma, Jie; Huang, Haitao; Ning, Kaijie; Xu, Xiaodong; Xie, Guoqiang; Qian, Liejia; Loh, Kian Ping; Tang, Dingyuan


    Stable 30 fs pulses centered at 1068 nm (less than 10 optical cycles) are demonstrated in a diode pumped Yb:CaYAlO4sub> laser by using high-quality chemical vapor deposited monolayer graphene as the saturable absorber. The mode-locked 8.43 optical-cycle pulses have a spectral bandwidth of ∼50  nm and a pulse repetition frequency of ∼113.5  MHz. To the best of our knowledge, this is the shortest pulse ever reported for graphene mode-locked lasers and mode-locked Yb-doped bulk lasers. Our experimental results demonstrate that graphene mode locking is a very promising practical technique for directly generating few-cycle optical pulses from a laser oscillator. PMID:26974072

  3. The behavior of thermal conductivity in the chaotic phase of [N(CH{sub 3}){sub 4}]{sub 2}ZnCl{sub 4} crystal

    SciTech Connect

    Sveleba, S. A. Karpa, I. V.; Kunyo, I. M.; Semotyuk, O. V.; Katerynchuk, I. M.; Phitsych, E. I.; Pankivskyi, Yu. I.


    A thermal investigation of the modulated structure dynamics at the transition between metastable states in the incommensurate phase of [N(CH{sub 3}){sub 4}]{sub 2}ZnCl{sub 4} crystal have been performed. It is established that the anomalous behavior of the thermal conductivity in the absence of a defect-density wave is due to the inelastic scattering of thermal phonons from critical phonons of the soft optical branch. In the presence of a defect-density wave, the anomalous increase in thermal conductivity is caused by the existence of a chaotic phase and is related to the contribution that soft optical phonons make to the heat transfer due to the increase in their group velocity.

  4. Enhanced ferromagnetic order in Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} featuring canted [MnO{sub 4}]{sub ∞} spin chains of mixed-valent Mn(III)/Mn(IV). Aliovalent substitution of the Sr{sub 4−x}Ln{sub x}Mn{sup III}{sub 2+x}Mn{sup IV}{sub 1−x}O{sub 3}(GeO{sub 4}){sub 3} solid-solution

    SciTech Connect

    West, J. Palmer; Sulejmanovic, Dino; Becht, Gregory; He, Jian; Hitchcock, Dale; Yan, Yonggao; Hwu, Shiou-Jyh


    Crystals of Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0; x∼0.15 for Ln=La, Pr, Nd, Sm. Eu, Gd, Dy; x∼0.3 for Ln=Gd) were isolated upon using high-temperature, solid-state methods in molten-salt media. These compounds are isostructural with the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} (Ln=La, Sm, Gd) series that contains the same [MnO{sub 4}]{sub ∞} spin chains. The synthesis of the Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0) phase was carried out by a double aliovalent substitution with respect to the Sr{sup 2+} and Ge{sup 4+} ions that replace Na{sup +}/Ln{sup 3+} and As{sup 5+} in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, respectively. The title series contains mixed-valent Mn(III)/Mn(IV) and shows a limited range of solid solution, both of which were not observed in the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series. To form the Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} solid solution, one of the Sr{sup 2+} sites, i.e., the original Ln-site in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, is partially substituted by Ln{sup 3+} in a statistical disorder of Sr{sub 1−x}/Ln{sub x}. Initial magnetic investigations of selected derivatives reveal higher ferromagnetic ordering temperatures than those reported for the Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series, presumably attributed to a lesser degree of canting as a result of introducing non-Jahn–Teller Mn{sup 4+} ions. Also intriguing is the observation of multiple anomalies at low temperatures which appear to be of electronic origins. - Graphical abstract: Sr{sub 4−x}Ln{sub x}Mn(III){sub 2+x}Mn(IV){sub 1−x}O{sub 3}(GeO{sub 4}){sub 3}. Display Omitted - Highlights: • Double aliovalent substitution: Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} with respect to Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}. • Solid solution with respect to statistical disorder of Sr{sub 1

  5. Decoupling of the antiferromagnetic and insulating states in Tb-doped Sr2IrO4sub>

    SciTech Connect

    Wang, J. C.; Aswartham, S.; Ye, Feng; Terzic, J.; Zheng, H.; Haskel, Daniel; Chikara, Shalinee; Choi, Yong; Schlottmann, P.; Custelcean, Radu; Yuan, S. J.; Cao, G.


    Sr2IrO4sub> is a spin-orbit coupled insulator with an antiferromagnetic (AFM) transition at TN = 240 K. We report results of a comprehensive study of single-crystal Sr2Ir1-xTbxO4sub> (0≤x≤0.03). This study found that mere 3% (x=0.03) tetravalent Tb4+(4f7) substituting for Ir4+ (rather than Sr2+) completely suppresses the long-range collinear AFM transition but retains the insulating state, leading to a phase diagram featuring a decoupling of magnetic interactions and charge gap. The insulating state at x = 0.03 is characterized by an unusually large specific heat at low temperatures and an incommensurate magnetic state having magnetic peaks at (0.95, 0, 0) and (0, 0.95, 0) in the neutron diffraction, suggesting a spiral or spin density wave order. It is apparent that Tb doping effectively changes the relative strength of the SOI and the tetragonal CEF and enhances the Hund’s rule coupling that competes with the SOI, and destabilizes the AFM state. However, the disappearance of the AFM accompanies no metallic state chiefly because an energy level mismatch for the Ir and Tb sites weakens charge carrier hopping and renders a persistent insulating state. Furthermore, this work highlights an unconventional correlation between the AFM and insulating states in which the magnetic transition plays no critical role in the formation of the charge gap in the iridate.

  6. Complex conductance of ultrathin La2-xSrxCuO4sub> films and heterostructures

    SciTech Connect

    V. A. Gasparov; Bozovic, I.


    We used atomic-layer molecular beam epitaxy to synthesize bilayers of a cuprate metal (La1.55Sr0.45CuO4sub>) and a cuprate insulator (La2CuO4sub>), in which each layer is just one unit cells thick. We have studied the magnetic field and temperature dependence of the complex sheet conductance, σ(ω), of these films. Experiments have been carried out at frequencies between 2 and 50 MHz using the single-spiral coil technique. We found that: (i) the inductive response starts at ΔT = 3 K lower temperatures than Re σ(T), which in turn is characterized by a peak close to the transition, (ii) this shift is almost constant with magnetic field up to 14 mT; (iii) ΔT increases sharply up to 4 K at larger fields and becomes constant up to 8 T; (iv) the vortexdiffusion constant D(T) is not linear with T at low temperatures as in the case of free vortices, but is rather exponential due to pinning of vortex cores, and (v) the dynamic Berezinski–Kosterlitz–Thouless (BKT) transition temperature occurs at the point where Y=(lω/ξ+)2 = 1. As a result, our experimental results can be described well by the extended dynamic theory of the BKT transition and dynamics of bound vortex–antivortex pairs with short separation lengths.

  7. Self-powdering and nonlinear optical domain structures in ferroelastic beta'-Gd{sub 2}(MoO{sub 4}){sub 3} crystals formed in glass

    SciTech Connect

    Tsukada, Y.; Honma, T.; Komatsu, T.


    Ferroelastic beta'-Gd{sub 2}(MoO{sub 4}){sub 3}, (GMO), crystals are formed through the crystallization of 21.25Gd{sub 2}O{sub 3}-63.75MoO{sub 3}-15B{sub 2}O{sub 3} glass (mol%), and two scientific curious phenomena are observed. (1) GMO crystals formed in the crystallization break into small pieces with a triangular prism or pyramid shape having a length of 50-500 {mu}m spontaneously during the crystallizations in the inside of an electric furnace, not during the cooling in air after the crystallization. This phenomenon is called 'self-powdering phenomenon during crystallization' in this paper. (2) Each self-powdered GMO crystal grain shows a periodic domain structure with different refractive indices, and a spatially periodic second harmonic generation (SHG) depending on the domain structure is observed. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of second harmonic intensities that GMO crystals are oriented in each crystal grain and the orientation of (MoO{sub 4}){sup 2-} tetrahedra in GMO crystals changes periodically due to spontaneous strains in ferroelastic GMO crystals. - Graphical abstract: This figure shows the polarized optical photograph at room temperature for a particle (piece) obtained by a heat treatment of the glass at 590 deg. C for 2 h in an electric furnace in air. This particle was obtained through the self-powdering behavior in the crystallization of glass. The periodic domain structure is observed. Ferroelastic beta'-Gd{sub 2}(MoO{sub 4}){sub 3} crystals are formed in the particle, and second harmonic generations are detected, depending on the domain structure.

  8. Lithium diffusion in Li4sub>Ti5O12 at high temperatures

    SciTech Connect

    Vijayakumar, M.; Kerisit, Sebastien; Rosso, Kevin M.; Burton, Sarah D.; Sears, Jesse A.; Yang, Zhenguo; Graff, Gordon L.; Liu, Jun; Hu, Jianzhi


    Synthesis of the spinel lithium titanate Li4sub>Ti5O12 by an alkoxide-free sol–gel method is described. This method yields highly pure and crystalline Li4sub>Ti5O12 samples at relatively low temperature (850 °C) and via short thermal treatment (2 h). 6Li magic angle spinning nuclear magnetic resonance (MAS NMR) measurements on these samples were carried out at high magnetic field (21.1 T) and over a wide temperature range (295–680 K). The temperature dependence of the chemical shifts and integral intensities of the three 6Li resonances demonstrates the migration of lithium ions from the tetrahedral 8a to the octahedral 16c sites and the progressive phase transition from a spinel to a defective NaCl-type structure. This defective structure has an increased number of vacancies at the 8a site, which facilitate lithium diffusion through 16c → 8a → 16c pathways, hence providing an explanation for the reported increase in conductivity at high temperatures. Molecular dynamics simulations of the spinel oxides Li4+xTi5O12, with 0 ≤ x ≤ 3, were also performed with a potential shell model in the temperature range 300–700 K. Finally, the simulations support the conclusions drawn from the NMR measurements and show a significant timescale separation between lithium diffusion through 8a and 16c sites and that out of the 16d sites.

  9. Enhanced thermoelectric performance driven by high-temperature phase transition in the phase change material Ge4sub>SbTe5

    SciTech Connect

    Williams, Jared B.; Lara-Curzio, Edgar; Cakmak, Ercan; Watkins, Thomas R.; Morelli, Donald T.


    Phase change materials are identified for their ability to rapidly alternate between amorphous and crystalline phases and have large contrast in the optical/electrical properties of the respective phases. The materials are primarily used in memory storage applications, but recently they have also been identified as potential thermoelectric materials. Many of the phase change materials researched today can be found on the pseudo-binary (GeTe)1-x(Sb2Te3)x tie-line. While many compounds on this tie-line have been recognized as thermoelectric materials, here we focus on Ge4sub>SbTe5, a single phase compound just off of the (GeTe)1-x(Sb2Te3)x tie-line, that forms in a stable rocksalt crystal structure at room temperature. We find that stoichiometric and undoped Ge4sub>SbTe5 exhibits a thermal conductivity of ~1.2 W/m-K at high temperature and a large Seebeck coefficient of ~250 μV/K. The resistivity decreases dramatically at 623 K due to a structural phase transition which lends to a large enhancement in both thermoelectric power factor and thermoelectric figure of merit at 823 K. In a more general sense the research presents evidence that phase change materials can potentially provide a new route to highly efficient thermoelectric materials for power generation at high temperature.

  10. Crystal chemistry of anhydrous Li uranyl phosphates and arsenates. II. Tubular fragments and cation-cation interactions in the 3D framework structures of Li{sub 6}[(UO{sub 2}){sub 12}(PO{sub 4}){sub 8}(P{sub 4}O{sub 13})], Li{sub 5}[(UO{sub 2}){sub 13}(AsO{sub 4}){sub 9}(As{sub 2}O{sub 7})], Li[(UO{sub 2}){sub 4}(AsO{sub 4}){sub 3}] and Li{sub 3}[(UO{sub 2}){sub 7}(AsO{sub 4}){sub 5}O

    SciTech Connect

    Alekseev, Evgeny V.; Krivovichev, Sergey V.; Depmeier, Wulf


    Single crystals of the new compounds Li{sub 6}[(UO{sub 2}){sub 12}(PO{sub 4}){sub 8}(P{sub 4}O{sub 13})] (1), Li{sub 5}[(UO{sub 2}){sub 13}(AsO{sub 4}){sub 9}(As{sub 2}O{sub 7})] (2), Li[(UO{sub 2}){sub 4}(AsO{sub 4}){sub 3}] (3) and Li{sub 3}[(UO{sub 2}){sub 7}(AsO{sub 4}){sub 5}O)] (4) have been prepared using high-temperature solid state reactions. The crystal structures have been solved by direct methods: 1-monoclinic, C2/m, a=26.963(3) A, b=7.063(1) A, c=19.639(1) A, beta=126.890(4){sup o}, V=2991.2(6) A{sup 3}, Z=2, R{sub 1}=0.0357 for 3248 unique reflections with |F{sub 0}|>=4sigma{sub F}; 2-triclinic, P1-bar, a=7.1410(8) A, b=13.959(1) A, c=31.925(1) A, alpha=82.850(2){sup o}, beta=88.691(2){sup o}, gamma=79.774(3){sup o}, V=3107.4(4) A{sup 3}, Z=2, R{sub 1}=0.0722 for 9161 unique reflections with |F{sub 0}|>=4sigma{sub F}; 3-tetragonal, I4{sub 1}/amd, a=7.160(3) A, c=33.775(9) A, V=1732(1) A{sup 3}, Z=4, R{sub 1}=0.0356 for 318 unique reflections with |F{sub 0}|>=4sigma{sub F}; 4-tetragonal, P4-bar, a=7.2160(5) A, c=14.6540(7) A, V=763.04(8) A{sup 3}, Z=1, R{sub 1}=0.0423 for 1600 unique reflections with |F{sub 0}|>=4sigma{sub F}. Structures of all the phases under consideration are based on complex 3D frameworks consisting of different types of uranium polyhedra (UO{sub 6} and UO{sub 7}) and different types of tetrahedral TO{sub 4} anions (T=P or As): PO{sub 4} and P{sub 4}O{sub 13} in 1, AsO{sub 4} and As{sub 2}O{sub 7} in 2, and single AsO{sub 4} tetrahedra in 3 and 4. In the structures of 1 and 2, UO{sub 7} pentagonal bipyramids share edges to form (UO{sub 5}){sub i}nfinity chains extended along the b axis in 1 and along the a axis in 2. The chains are linked via single TO{sub 4} tetrahedra into tubular units with external diameters of 11 A in 1 and 11.5 A in 2, and internal diameters of 4.1 A in 1 and 4.5 A in 2. The channels accommodate Li{sup +} cations. The tubular units are linked into 3D frameworks by intertubular complexes. Structures of 3 and 4

  11. Synthesis of MoS2/g-C3N4sub> nanocomposites with enhanced visible-light photocatalytic activity for the removal of nitric oxide (NO).


    Wen, M Q; Xiong, T; Zang, Z G; Wei, W; Tang, X S; Dong, F


    Molybdenum disulfide and graphitic carbon nitride (MoS2-g-C3N4sub>) nanocomposites with visible-light induced photocatalytic activity were successfully synthesized by a facile ultrasonic dispersion method. The crystalline structure and morphology of the MoS2-g-C3N4sub> nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microcopy (TEM), high-resolution TEM (HRTEM) and scanning electron microscopy (SEM). The optical property of the as-prepared nanocomposites was studied by ultraviolet visible diffusion reflection (UV-vis) and photoluminescence(PL) spectrum. It could be observed from the TEM image that the MoS2 nanosheets and g-C3N4sub> nanoparticles were well combined together. Moreover, the photocatalytic activity of MoS2-g-C3N4sub> composites was evaluated by the removal of nitric oxide under visible light irradiation (>400nm). The experimental results demonstrated that the nanocomposites with the MoS2 content of 1.5 wt% exhibited optimal photocatalytic activity and the corresponding removal rate of NO achieved 51.67%, higher than that of pure g-C3N4sub> nanoparticles. A possible photocatalytic mechanism for the MoS2-g-C3N4sub> nanocomposites with enhanced photocatalytic activity could be ascribed to the hetero-structure of MoS2 and g-C3N4sub>. PMID:27409846

  12. Electronic Structure and Optical Properties of Cu2ZnGeSe4sub>. First-Principles Calculations and Vacuum-Ultraviolet Spectroscopic Ellipsometric Studies

    SciTech Connect

    Choi, Sukgeun; Park, Ji-Sang; Donohue, Andrea; Christensen, Steven T.; To, Bobby; Beall, Carolyn; Wei, Su-Huai; Repins, Ingid L.


    Cu2ZnGeSe4sub> is of interest for the development of next-generation thin-film photovoltaic technologies. To understand its electronic structure and related fundamental optical properties, we perform first-principles calculations for three structural variations: kesterite, stannite, and primitive-mixed CuAu phases. The calculated data are compared with the room-temperature dielectric functionϵ=ϵ1+iϵ2 spectrum of polycrystalline Cu2ZnGeSe4sub> determined by vacuum-ultraviolet spectroscopic ellipsometry in the photon-energy range of 0.7 to 9.0 eV. Ellipsometric data are modeled with the sum of eight Tauc-Lorentz oscillators, and the best-fit model yields the band-gap and Tauc-gap energies of 1.25 and 1.19 eV, respectively. A comparison of overall peak shapes and relative intensities between experimental spectra and the calculated ϵ data for three structural variations suggests that the sample may not have a pure (ordered) kesterite phase. We found that the complex refractive index N=n+ik, normal-incidence reflectivity R, and absorption coefficients α are calculated from the modeled ϵ spectrum, which are also compared with those of Cu2ZnSnSe4sub> . The spectral features for Cu2ZnGeSe4sub> appear to be weaker and broader than those for Cu2ZnSnSe4sub> , which is possibly due to more structural imperfections presented in Cu2ZnGeSe4sub> than Cu2ZnSnSe4sub> .

  13. Crystal structure of Cs/sup +/((XeOF/sub 4/)/sub 3/F)/sup -/ and vibrational study of the /sup 18/O-enriched (XeOF/sub 5/)/sup -/ and ((XeOF/sub 4/)/sub 3/F)/sup -/ anions

    SciTech Connect

    Holloway, J.H.; Kaucic, V.; Martin-Rovet, D.; Russell, D.R.; Schrobilgen, G.J.; Selig, H.


    The cesium salts of the anions (XeOF/sub 5/)/sup -/ and ((XeOF/sub 4/)/sub 3/F)/sup -/ have been prepared and characterized. The Raman spectra of Xe/sup 16/OF/sub 5//sup -/ and Xe/sup 18/OF/sub 5//sup -/ are consistent with a stereochemically active lone pair in the xenon valence shell that results in a distorted octahedral arrangement of five fluorine and one oxygen around xenon to give C/sub s/ symmetry. The X-ray structure of Cs/sup +/((XeOF/sub 4/)/sub 3/F)/sup -/ has been obtained. Crystals are cubic, space group Pa3 with a = 13.993 (7) A and Z = 8. The structure was solved by means of Patterson and Fourier synthesis and refined by the least-squares method to R = 0.0969 and R/sub w/ = 0.0960 for 355 reflections. The anion possesses C/sub 3/ symmetry and consists of octahedra of O=XeF/sub 4/E (E = lone electron pair; mean XeF = 1.90 (3) A; Xe=O = 1.70 (5) A) linked through three fluorine bridges with the trigonally bonded fluorine positioned 0.49 A above the plane defined by the three xenon atoms. The Raman spectra of the /sup 16/O//sup 18/O isotopic isomers of (XeOF/sub 4/)/sub 3/F)/sup -/ and their associated coupling patterns have been interpreted on the basis of the X-ray structure. 33 references, 6 figures, 5 tables.

  14. Insight into the Atomic Structure of High-Voltage Spinel LiNi0.5Mn1.5O4sub> Cathode Material in the First Cycle

    SciTech Connect

    Huang, Xuejie; Yu, Xiqian; Lin, Mingxiang; Ben, Liubin; Sun, Yang; Wang, Hao; Yang, Zhenzhong; Gu, Lin; Yang, Xiao -Qing; Zhao, Haofei; Yu, Richeng; Armand, Michel


    Application of high-voltage spinel LiNi0.5Mn1.5O4sub> cathode material is the closest and the most realistic approach to meeting the midterm goal of lithium-ion batteries for electric vehicles (EVs) and plug-in hybrid electric vehicles (HEVs). However, this application has been hampered by long-standing issues, such as capacity degradation and poor first-cycle Coulombic efficiency of LiNi0.5Mn1.5O4sub> cathode material. Although it is well-known that the structure of LiNi0.5Mn1.5O4sub> into which Li ions are reversibly intercalated plays a critical role in the above issues, performance degradation related to structural changes, particularly in the first cycle, are not fully understood. Here, we report detailed investigations of local atomic-level and average structure of LiNi0.5Mn1.5O4sub> during first cycle (3.5–4.9 V) at room temperature. We observed two types of local atomic-level migration of transition metals (TM) ions in the cathode of a well-prepared LiNi0.5Mn1.5O4sub>//Li half-cell during first charge via an aberration-corrected scanning transmission electron microscopy (STEM). Surface regions (~2 nm) of the cycled LiNi0.5Mn1.5O4sub> particles show migration of TM ions into tetrahedral Li sites to form a Mn3O4sub>-like structure. However, subsurface regions of the cycled particles exhibit migration of TM ions into empty octahedral sites to form a rocksalt-like structure. The migration of these TM ions are closely related to dissolution of Ni/Mn ions and building-up of charge transfer impedance, which contribute significantly to the capacity degradation and the poor first-cycle Coulombic efficiency of spinel LiNi0.5Mn1.5O4sub> cathode material. Accordingly, we provide suggestions of effective stabilization of LiNi0.5

  15. Crystal structure and thermal expansion of the low- and high-temperature forms of BaM{sup IV}(PO{sub 4}){sub 2} compounds (M=Ti, Zr, Hf and Sn)

    SciTech Connect

    Bregiroux, D.; Popa, K.; Jardin, R.; Raison, P.E.; Wallez, G.; Quarton, M.; Brunelli, M.; Ferrero, C.; Caciuffo, R.


    The crystal structure of beta-BaZr(PO{sub 4}){sub 2}, archetype of the high-temperature forms of BaM(PO{sub 4}){sub 2} phosphates (with M=Ti, Zr, Hf and Sn), has been solved ab initio by Rietveld analysis from synchrotron X-ray powder diffraction data. The phase transition appears as a topotactic modification of the monoclinic (S.G. C2/m) lamellar alpha-structure into a trigonal one (S.G. P3-barm1) through a simple mechanism involving the unfolding of the [Zr(PO{sub 4}){sub 2}]{sub n}{sup 2-} layers. The thermal expansion is very anisotropic (e.g., -4.14}){sub 2}) and quite different in the two forms, as a consequence of symmetry. It stems from a complex combination of several mechanisms, involving bridging oxygen rocking in M-O-P linkages, and 'bond thermal expansion'. - Graphical abstract: The layered high-temperature form of BaM(PO{sub 4}){sub 2}, only expands along the c-axis.

  16. Temperature-dependent framework–template interaction of |Na{sub 6}(H{sub 2}O){sub 8}|[ZnPO{sub 4}]{sub 6} sodalite

    SciTech Connect

    Robben, Lars Gesing, Thorsten M.


    The partial dehydration followed by the decomposition of sodium-zincophosphate-hydrosodalite caused by the total water loss was examined by temperature-dependent X-ray powder diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy as well as thermogravimetry combined with difference thermoanalysis. The dehydration causing the decomposition of this sodalite could be described in a two step-process. Initially two water molecules per unit-cell were lost, changing the interaction between the zincophosphate framework and the remaining water molecules as well as sodium cations as non-framework constituents. In this stage a 3+3 coordination of water molecules and sodium cations in the sodalite cage is observed. Using the autocorrelation function (AC) for the evaluation of the temperature-dependent FTIR spectra of sodalites is reported here for the first time. Calculating the changes in the AC broadness, structural features could well be analyzed due to its correlation with respective structural parameters. Temperature dependent Raman data was used to give a band assignment of bands at Raman shifts below 300 cm{sup −1}. - Graphical abstract: The thermal decomposition of |Na{sub 6}(H{sub 2}O){sub 8}|[ZnPO{sub 4}]{sub 6} sodalite is a two-step process with an initial loss of two water molecules at 400 K, intermediately stabilizing the highly stressed framework. Further heating leads to a subsequent loss of the remaining six water molecules and a breakup of the sodalite framework. A beryllonite-type NaZnPO{sub 4} is the final product of this process. Display Omitted - Highlights: • The decomposition of |Na{sub 6}(H{sub 2}O){sub 8}|[ZnPO{sub 4}]{sub 6} sodalite is a two-step process. • Initial loss of two water molecule at 400 K stabilizes the sodalite (step 1). • Further heating leads to complete loss of water and structural breakdown. • Autocorrelation of temperature dependent FTIR-spectra gives structural information.

  17. Effects of quark family nonuniversality in SU(3){sub c} x SU(4){sub L} x U(1){sub X} models

    SciTech Connect

    Nisperuza, Jorge L.; Sanchez, Luis A.


    Flavor changing neutral currents arise in the SU(3){sub c} x SU(4){sub L} x U(1){sub X} extension of the standard model because anomaly cancellation among the fermion families requires one generation of quarks to transform differently from the other two under the gauge group. In the weak basis the distinction between quark families is meaningless. However, in the mass eigenstates basis, the Cabibbo-Kobayashi-Maskawa mixing matrix motivates us to classify left-handed quarks in families. In this sense there are, in principle, three different assignments of quark weak eigenstates into mass eigenstates. In this work, by using measurements at the Z pole, atomic parity violation data, and experimental input from neutral meson mixing, we examine two different models without exotic electric charges based on the 3-4-1 symmetry, and address the effects of quark family nonuniversality on the bounds on the mixing angle between two of the neutral currents present in the models and on the mass scales M{sub Z{sub 2}} and M{sub Z{sub 3}} of the new neutral gauge bosons predicted by the theory. The heaviest family of quarks must transform differently in order to keep lower bounds on M{sub Z{sub 2}} and M{sub Z{sub 3}} as low as possible without violating experimental constraints.

  18. Stable platinum nanoparticles on specific MgAl2O4sub> spinel facets at high temperatures in oxidizing atmospheres

    SciTech Connect

    Li, Wei-Zhen; Kovarik, Libor; Mei, Donghai; Liu, Jun; Wang, Yong; Peden, Charles H. F.


    The development of thermally stable, nanometer-sized precious metal-based catalysts remains a daunting challenge. Such materials, especially those based on the use of costly platinum metal, are essential and, to date, non-replaceable for a large number of industrially important catalytic processes. Here we report a well-defined cuboctahedral MgAl2O4sub> spinel support material that is capable of stabilizing platinum particles in the range of 1–3 nm on its relatively abundant {111} facets during extremely severe aging at 800 °C in air for 1 week. The aged catalysts retain platinum dispersions of 15.9% with catalytic activities for methanol oxidation being ~80% of that of fresh ones, whereas a conventional Pt/γ-Al2O3 catalyst is severely sintered and nearly inactive. Finally, we reveal the origin of the markedly superior ability of spinel {111} facets, resulting from strong interactions between spinel surface oxygens and epitaxial platinum {111} facets, inspiring the rational design of anti-sintering supported platinum group catalysts.

  19. Band alignment of atomic layer deposited (HfZrO{sub 4}){sub 1−x}(SiO{sub 2}){sub x} gate dielectrics on Si (100)

    SciTech Connect

    Heo, Sung; Tahir, Dahlang; Chung, Jae Gwan; Lee, Jae Cheol; Kim, KiHong; Lee, Junho; Lee, Hyung-Ik; Park, Gyeong Su; Oh, Suhk Kun; Kang, Hee Jae; Choi, Pyungho; Choi, Byoung-Deog


    The band alignment of atomic layer deposited (HfZrO{sub 4}){sub 1−x}(SiO{sub 2}){sub x} (x = 0, 0.10, 0.15, and 0.20) gate dielectric thin films grown on Si (100) was obtained by using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap, valence band offset, and conduction band offset values for HfZrO{sub 4} silicate increased from 5.4 eV to 5.8 eV, from 2.5 eV to 2.75 eV, and from 1.78 eV to 1.93 eV, respectively, as the mole fraction (x) of SiO{sub 2} increased from 0.1 to 0.2. This increase in the conduction band and valence band offsets, as a function of increasing SiO{sub 2} mole fraction, decreased the gate leakage current density. As a result, HfZrO{sub 4} silicate thin films were found to be better for advanced gate stack applications because they had adequate band gaps to ensure sufficient conduction band offsets and valence band offsets to Si.

  20. Structure and conductivity of the NASICON analog Na/sub 3/SC/sub 2/(PO/sub 4/)/sub 3/

    SciTech Connect

    Susman, S.; Delbecq, C.J.; Brun, T.O.; Prince, E.


    Neutron and x-ray diffraction data of Na/sub 3/SC/sub 2/(PO/sub 4/)/sub 3/ are presented that show the transition from an ordinary-conducting, high temperature phase to a still higher temperature, superionic conducting phase. There are at least four polymorphic modifications. At room temperature, the refined neutron diffraction data confirm the Cc space group reported by Efremov and Kalinin but with a = 16.0449(24), b = 8.9225(15), c = 9.0656(13)A, ..beta.. = 126.918(21), R/sub weighted pattern/ = 17.5%, and R/sub expected/ = 7%. Between 25/sup 0/C and 64/sup 0/C, a second polymorph appears. The structure is monoclinic but has not yet been refined. At 64/sup 0/C, a third polymorph C appears. It is rhombohedral R3c. Using hexagonal axes, a = 8.9273(2), c = 22.3668A, R/sub wp/ = 6.28% and R/sub e/ = 3.83% at 100/sup 0/C. At 166/sup 0/C, the high temperature polymorph D appears. It is the superconducting phase of NASICON(Sc). It, too, is rhombohedral R3c with a = 8.9274(1), c = 22.5493(6)A, R/sub wp/ = 5.81% and R/sub e/ = 3.87% at 225/sup 0/C. The diffraction data are correlated with ionic conductivity measurements as a function of temperature.

  1. New localized/delocalized emitting state of Eu2+ in orange-emitting hexagonal EuAl2O4sub>

    SciTech Connect

    Liu, Feng; Meltzer, Richard S.; Li, Xufan; Budai, John D.; Chen, Yu -Sheng; Pan, Zhengwei


    Eu2+-activated phosphors are being widely used in illuminations and displays. Some of these phosphors feature an extremely broad and red-shifted Eu2+ emission band; however, convincing explanation of this phenomenon is lacking. Here we report a new localized/delocalized emitting state of Eu2+ ions in a new hexagonal EuAl2O4sub> phosphor whose Eu2+ luminescence exhibits a very large bandwidth and an extremely large Stokes shift. At 77 K, two luminescent sites responsible for 550 nm and 645 nm broadband emissions are recognized, while at room temperature only the 645 nm emission band emits. The 645 nm emission exhibits a typical radiative lifetime of 1.27 μs and an unusually large Stokes shift of 0.92 eV. We identify the 645 nm emission as originating from a new type of emitting state whose composition is predominantly that of localized 4f65d character but which also contains a complementary component with delocalized conduction-band-like character. This investigation gives new insights into a unique type of Eu2+ luminescence in solids whose emission exhibits both a very large bandwidth and an extremely large Stokes shift.

  2. Anisotropic lattice thermal expansion of PbFeBO4sub>: A study by X-ray and neutron diffraction, Raman spectroscopy and DFT calculations

    SciTech Connect

    Murshed, M. Mangir; Mendive, Cecilia B.; Curti, Mariano; Nénert, Gwilherm; Kalita, Patricia E.; Lipinska, Kris; Cornelius, Andrew L.; Huq, Ashfia; Gesing, Thorsten M.


    We present the lattice thermal expansion of mullite-type PbFeBO4sub> in this study. The thermal expansion coefficients of the metric parameters were obtained from composite data collected from temperature-dependent neutron and X-ray powder diffraction between 10 K and 700 K. The volume thermal expansion was modeled using extended Grüneisen first-order approximation to the zero-pressure equation of state. The additive frame of the model includes harmonic, quasi-harmonic and intrinsic anharmonic potentials to describe the change of the internal energy as a function of temperature. Moreover, the unit-cell volume at zero-pressure and 0 K was optimized during the DFT simulations. Harmonic frequencies of the optical Raman modes at the Γ-point of the Brillouin zone at 0 K were also calculated by DFT, which help to assign and crosscheck the experimental frequencies. The low-temperature Raman spectra showed significant anomaly in the antiferromagnetic regions, leading to softening or hardening of some phonons. Selected modes were analyzed using a modified Klemens model. The shift of the frequencies and the broadening of the line-widths helped to understand the anharmonic vibrational behaviors of the PbO4, FeO6 and BO3 polyhedra as a function of temperature.

  3. X-ray absorption spectroscopy of LiBF 4sub> in propylene carbonate. A model lithium ion battery electrolyte

    SciTech Connect

    Smith, Jacob W.; Lam, Royce K.; Sheardy, Alex T.; Shih, Orion; Rizzuto, Anthony M.; Borodin, Oleg; Harris, Stephen J.; Prendergast, David; Saykally, Richard J.


    Since their introduction into the commercial marketplace in 1991, lithium ion batteries have become increasingly ubiquitous in portable technology. Nevertheless, improvements to existing battery technology are necessary to expand their utility for larger-scale applications, such as electric vehicles. Advances may be realized from improvements to the liquid electrolyte; however, current understanding of the liquid structure and properties remains incomplete. X-ray absorption spectroscopy of solutions of LiBF4sub> in propylene carbonate (PC), interpreted using first-principles electronic structure calculations within the eXcited electron and Core Hole (XCH) approximation, yields new insight into the solvation structure of the Li+ ion in this model electrolyte. By generating linear combinations of the computed spectra of Li+-associating and free PC molecules and comparing to the experimental spectrum, we find a Li+–solvent interaction number of 4.5. This result suggests that computational models of lithium ion battery electrolytes should move beyond tetrahedral coordination structures.

  4. Optical gain in capillary light guides filled with NaYF4sub>: Yb3+, Er3+ nanocolloids.


    Patel, Darayas N; Sarkisov, Sergey S; Darwish, Abdalla M; Ballato, John


    A capillary light guide optical amplifier using nanocolloids of Yb3+-Er3+ co-doped NaYF4sub> as a filler was successfully demonstrated. A 7-cm-long and 150-micron-inner-diameter capillary light guide was capable to amplify a pulsed optical signal at 1550 nm with a gain coefficient of 0.15 cm-1 at a pump power of 4 mW (980-nm wavelength). The nanocolloid gain medium was prepared by pulverizing the phosphor powder with a high-speed planetary ball mill. Ball milling of the powder in water produced nanoparticles with a size of approximately 130 nm that after drying were transferred to a liquid with high refractive index (1.551 at 1550 nm) required to maintain light confinement within the fused silica capillary light guide. The results show that RE-doped colloids of nanocrystals can be potentially used as liquid gain media fillers in capillary light guide lasers and amplifiers with high photostability and low toxicity. PMID:27607717

  5. Synthesis of nanostructured LiTi{sub 2}(PO{sub 4}){sub 3} powder by a Pechini-type polymerizable complex method

    SciTech Connect

    Mariappan, C.R.; Galven, C.; Crosnier-Lopez, M.-P.; Le Berre, F.; Bohnke, O. . E-mail:


    The nanostructured NASICON-type LiTi{sub 2}(PO{sub 4}){sub 3} (LTP) material has been synthesized by Pechini-type polymerizable complex method. The use of water-soluble ammonium citratoperoxotitanate (IV) metal complex instead of alkoxides as precursor allows to prepare monophase material. Thermal analyses have been carried out on the powder precursor to check the weight loss and synthesis temperature. X-ray powder diffraction analysis (XRD) has been performed on the LTP powder obtained after heating the powder precursor over a temperature range from 550 to 1050 deg. C for 2 h. By varying the molar ratio of citric acid to metal ion (CA/Ti) and citric acid to ethylene glycol (CA/EG), the grain size of the LTP powder could be modified. The formation of small and well-crystalline grains, in the order of 50-125 nm in size, has been determined from the XRD patterns and confirmed by transmission electron microscopy.

  6. An air-stable Na3SbS4sub> superionic conductor prepared by a rapid and economic synthetic procedure

    SciTech Connect

    Wang, Hui; Chen, Yan; Hood, Zachary D.; Samuthira Pandian, Amaresh; Keum, Jong Kahk; An, Ke; Sahu, Gayatri; Liang, Chengdu


    All-solid-state sodium batteries, using abundant sodium resources and solid electrolyte, hold much promise for safe, low cost, large-scale energy storage. To realize the practical applications of all solid Na-ion batteries at ambient temperature, the solid electrolytes are required to have high ionic conductivity, chemical stability, and ideally, easy preparation. Ceramic electrolytes show higher ionic conductivity than polymers, but they often require extremely stringent synthesis conditions, either high sintering temperature above 1000 C or long-time, low-energy ball milling. Herein, we report a new synthesis route for Na3SbS4sub>, a novel Na superionic conductor that needs much lower processing temperature below 200 C and easy operation. This new solid electrolyte exhibits a remarkable ionic conductivity of 1.05 mS cm-1 at 25 °C and is chemically stable under ambient atmosphere. In conclusion, this synthesis process provides unique insight into the current state-of-the-art solid electrolyte preparation and opens new possibilities for the design of similar materials.

  7. Passive Q-switching of a Tm,Ho:KLu(WO4sub>)2 microchip laser by a Cr:ZnS saturable absorber.


    Serres, J M; Loiko, P; Mateos, X; Jambunathan, V; Yasukevich, A S; Yumashev, K V; Petrov, V; Griebner, U; Aguiló, M; Díaz, F


    A diode-pumped Tm,Ho:KLu(WO4sub>)2 microchip laser passively Q-switched with a Cr:ZnS saturable absorber generated an average output power of 131 mW at 2063.6 nm with a slope efficiency of 11% and a Q-switching conversion efficiency of 58%. The pulse characteristics were 14  ns/9  μJ at a pulse repetition frequency of 14.5 kHz. With higher modulation depth of the saturable absorber, 9  ns/10.4  μJ/8.2  kHz pulses were generated at 2061.1 nm, corresponding to a record peak power extracted from a passively Q-switched Tm,Ho laser of 1.15 kW. A theoretical model is presented, predicting the pulse energy and duration. The simulations are in good agreement with the experimental results. PMID:27168288

  8. Hydrothermal synthesis, structural and physico-chemical characterizations of two Nasicon phosphates: M{sub 0.50}{sup II}Ti{sub 2}(PO{sub 4}){sub 3} (M = Mn, Co)

    SciTech Connect

    Essehli, Rachid; Bali, Brahim El; Benmokhtar, S.; Fejfarova, Karla; Dusek, Michal


    The family of titanium Nasicon-phosphates of generic formula M{sub 0.5}{sup II}Ti{sub 2}(PO{sub 4}){sub 3} has been revisited using hydrothermal techniques. Two phases have been synthesized: Mn{sub 0.5}{sup II}Ti{sub 2}(PO{sub 4}){sub 3} (MnTiP) and Co{sub 0.5}{sup II}Ti{sub 2}(PO{sub 4}){sub 3} (CoTiP). Single crystal diffraction studies show that they exhibit two different structural types. Mn{sub 0.5}{sup II}Ti{sub 2}(PO{sub 4}){sub 3} phosphate crystallizes in the R-3 space group, with the cell parameters a = 8.51300(10) A and c = 21.0083(3) A (V = 1318.52(3) A{sup 3} and Z = 6). The Co{sub 0.5}{sup II}Ti{sub 2}(PO{sub 4}){sub 3} phosphate crystallizes in the R-3c space group, with a = 8.4608(9) A and c = 21.174(2) A (V = 1312.7(2) A{sup 3} and Z = 6). These two compounds are clearly related to the parent Nasicon-type rhombohedral structure, which can be described using [Ti{sub 2}(PO{sub 4}){sub 3}] framework composed of two [TiO{sub 6}] octahedral interlinked via three [PO{sub 4}] tetrahedra. {sup 31}P magic-angle spinning nuclear magnetic resonance (MAS-NMR) data are presented as supporting data. Curie-Weiss-type behavior is observed in the magnetic susceptibility. The phases are also characterized by IR spectroscopy and UV-visible.

  9. Near-infrared quantum-cutting luminescence and energy transfer properties of Ca{sub 3}(PO{sub 4}){sub 2}:Tm{sup 3+},Ce{sup 3+} phosphors

    SciTech Connect

    Dong, S. L.; Lin, H. H. E-mail:; Yu, T.; Zhang, Q. Y. E-mail:


    The phosphors Ca{sub 3}(PO{sub 4}){sub 2}:Tm{sup 3+} by co-doping Ce{sup 3+} have been synthesized by conventional high-temperature solid-state reaction method. Their spectroscopic properties in the UV-VIS-NIR range have been investigated. The first 5d crystal field level location and stokes shift have been determined from the UV excitation and emission spectra of Ca{sub 3}(PO{sub 4}){sub 2}:Ce{sup 3+}. The three-photon NIR quantum-cutting luminescence of Tm{sup 3+} assigned to the electronic transitions of {sup 1}G{sub 4}→{sup 3}H{sub 4}, {sup 3}H{sub 4}→{sup 3}F{sub 4} and {sup 3}F{sub 4}→{sup 3}H{sub 6} is observed, whether in Ca{sub 3}(PO{sub 4}){sub 2}:Tm{sup 3+} or Ca{sub 3}(PO{sub 4}){sub 2}:Tm{sup 3+},Ce{sup 3+}. The energy transfer from Ce{sup 3+} to Tm{sup 3+} takes place with energy-transfer efficiency up to 34.5% for the Ca{sub 3}(PO{sub 4}){sub 2}:Tm{sup 3+},Ce{sup 3+}. A cross relaxation scheme using the 5d states of Ce{sup 3+} and f-f transition of Tm{sup 3+} is proposed. The mechanism is revealed from energy level and decay measurements. The results show that the broadband absorption of Ce{sup 3+} sensitizer not only extends the spectrum conversion in UV region but also greatly enhances the photoluminescence intensities of the three-photon quantum cutting luminescence of Tm{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2}.

  10. Synthesis and photoluminescence properties of Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} red phosphor for white light emitting diodes

    SciTech Connect

    Zhu, Ge; Ci, Zhipeng; Shi, Yurong; Wang, Yuhua


    Highlights: • A novel red phosphor Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} was synthesized and investigated firstly. • The structure and characteristic luminescence properties are discussed. • The excellent thermal stability was found and investigated. • It has good color saturation, the CIE is close to that of commercial Y{sub 2}O{sub 3}:Eu{sup 3+}. - Abstract: A series of Sm{sup 3+} doped Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14} red phosphors were successfully synthesized. X-ray diffraction analysis indicates that all the samples are single phased. The luminescence property is investigated in detail by measuring their photoluminescence excitation and emission spectra. Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} phosphors show strong absorption in 400–410 nm region, which is suitable for application in LEDs. When excited at 403 nm, Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} phosphor can emit red emission with CIE chromaticity coordinates (0.615, 0.384). The optimal doping concentration of Sm{sup 3+} doped Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14} is measured to be 0.02. The thermal quenching property is also measured and compared with the commercial red phosphor Y{sub 2}O{sub 3}:Eu{sup 3+} (Topstar, TXC-RIA). The results indicate Ca{sub 19}Mg{sub 2}(PO{sub 4}){sub 14}:Sm{sup 3+} phosphors have potential to serve as a red phosphor for white LEDs.

  11. Scintillation properties of Eu2+-doped KBa2I5 and K2BaI4sub>

    SciTech Connect

    Stand, L.; Zhuravleva, M.; Chakoumakos, Bryan C.; Johnson, J.; Lindsey, Adam; Melcher, Charles L.


    We report two new ternary metal halide scintillators, KBa2I5 and K2BaI4sub>, activated with divalent europium. Single crystal X-ray diffraction measurements confirmed that KBa2I5 has a monoclinic structure (P21/c) and that K2BaI4sub> has a rhombohedral structure (R3c). Differential scanning calorimetry showed singular melting and crystallization points, making these compounds viable candidates for melt growth. We grew 13 mm diameter single crystals of KBa2I5:Eu2+ and K2BaI4sub>:Eu2+ in evacuated quartz ampoules via the vertical Bridgman technique. The optimal Eu2+ concentration was 4% for KBa2I5 and 7% for K2BaI4sub>. The X-ray excited emissions at 444 nm for KBa2I5:Eu 4% and 448 nm for K2BaI4sub>:Eu 7% arise from the 5d-4f radiative transition in Eu2+. KBa2I5:Eu 4% has a light yield of 90,000 photons/MeV, with an energy resolution of 2.4% and K2BaI4sub>:Eu 7% has a light yield of 63,000 ph/MeV, with an energy resolution of 2.9% at 662 keV. Both crystals have an excellent proportional response to a wide range of gamma-ray energies.


    SciTech Connect

    Neufeld, David A.; Wu, Yuanwei; Kraus, Alex; Menten, Karl M.; Tolls, Volker; Melnick, Gary J.; Nagy, Zsofia


    Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have performed mapping observations of the 620.701 GHz 5{sub 32}-4{sub 41} transition of ortho-H{sub 2}O within a {approx}1.'5 Multiplication-Sign 1.'5 region encompassing the Kleinmann-Low nebula in Orion (Orion-KL), and pointed observations of that transition toward the Orion South condensation and the W49N region of high-mass star formation. Using the Effelsberg 100 m radio telescope, we obtained ancillary observations of the 22.23508 GHz 6{sub 16}-5{sub 23} water maser transition; in the case of Orion-KL, the 621 GHz and 22 GHz observations were carried out within 10 days of each other. The 621 GHz water line emission shows clear evidence for strong maser amplification in all three sources, exhibiting narrow ({approx}1 km s{sup -1} FWHM) emission features that are coincident (kinematically and/or spatially) with observed 22 GHz features. Moreover, in the case of W49N-for which observations were available at three epochs spanning a 2 yr period-the spectra exhibited variability. The observed 621 GHz/22 GHz line ratios are consistent with a maser pumping model in which the population inversions arise from the combined effects of collisional excitation and spontaneous radiative decay, and the inferred physical conditions can plausibly arise in gas heated by either dissociative or non-dissociative shocks. The collisional excitation model also predicts that the 22 GHz population inversion will be quenched at higher densities than that of the 621 GHz transition, providing a natural explanation for the observational fact that 22 GHz maser emission appears to be a necessary but insufficient condition for 621 GHz maser emission.

  13. Origin of Active Oxygen in a Ternary CuOx /Co3O4sub>–CeO 2 Catalyst for CO Oxidation

    SciTech Connect

    Liu, Zhigang; Wu, Zili; Peng, Xihong; Binder, Andrew; Chai, Songhai; Dai, Sheng


    In this paper, we have studied CO oxidation over a ternary CuOx/Co3O4sub>-CeO2 catalyst and employed the techniques of N2 adsorption/desporption, XRD, TPR, TEM, in situ DRIFTS and QMS (Quadrupole mass spectrometer) to explore the origin of active oxygen. DRIFTS-QMS results with labeled 18O2 indicate that the origin of active oxygens in CuOx/Co3O4sub>-CeO2 obeys a model, called as queue mechanism. Namely gas-phase molecular oxygens are dissociated to atomic oxygens and then incorporate in oxygen vacancies located at the interface of Co3O4sub>-CeO2 to form active crystalline oxygens, and these active oxygens diffuse to the CO-Cu+ sites thanks to the oxygen vacancy concentration magnitude and react with the activated CO to form CO2. This process, obeying a queue rule, provides active oxygens to form CO2 from gas-phase O2 via oxygen vacancies and crystalline oxygen at the interface of Co3O4sub>-CeO2.

  14. Syntheses and crystal structures of two novel alkaline uranyl chromates A{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2} (A=Rb, Cs) with bidentate coordination mode of uranyl ions by chromate anions

    SciTech Connect

    Siidra, Oleg I.


    Single crystals of Cs{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2} and Rb{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2} were prepared by solid state reactions. The structures are based upon the [(UO{sub 2})(CrO{sub 4}){sub 2}]{sup 2-} chains. Within the chains, UrO{sub 5} pentagonal bipyramids (Ur=uranyl) form Ur{sub 2}O{sub 8} dimers, which are linked via CrO{sub 4} tetrahedra into one-dimensional chains. The CrO{sub 4} tetrahedra coordinate uranyl ions in both mono- and bidentate fashion, which is unusual for uranyl chromates. The bidentate coordination has a strong influence upon geometrical parameters of both U and Cr coordination polyhedra. The conformation of the chains in 1 and 2 is different due to the different size of the Cs{sup +} and Rb{sup +} cations. - Graphical abstract: Uranyl chromate chain with monodentate and bidentate coordination mode of uranyl cations by CrO{sub 4} tetrahedra in Cs{sub 2}(UO{sub 2})(CrO{sub 4}){sub 2}. Highlights: Black-Right-Pointing-Pointer Single crystals of novel uranyl chromates were prepared by solid state reactions. Black-Right-Pointing-Pointer The CrO{sub 4} tetrahedra coordinate uranyl ions in both mono- and bidentate fashion. Black-Right-Pointing-Pointer The bidentate coordination has a strong influence upon geometrical parameters.

  15. Polyselenide chemistry of indium and thallium in dimethylformamide, acetonitrile, and water. Syntheses, structures, and properties of the new complexes [In[sub 2](Se[sub 4])[sub 4](Se[sub 5])][sup 4[minus

    SciTech Connect

    Dhingra, S.S.; Kanatzidis, M.G. )


    The reaction of InCl[sub 3] with Na[sub 2]Se[sub 5] in dimethylformamide (DMF) in the presence of Ph[sub 4]PCl gave (Ph[sub 4]P)[sub 4][In[sub 2](Se[sub 4])[sub 4](Se[sub 5])] (I) in 75% yield. Under the same conditions, InCl[sub 3] reacted with Na[sub 2]Se[sub 5] in the presence of Pr[sub 4]NBr or Et[sub 4]NBr and afforded (Pr[sub 4]N)[sub 4][In[sub 2](Se[sub 4])[sub 4](Se[sub 5])] (II) in 65% yield and (Et[sub 4]N)[sub 4][In[sub 2](Se[sub 4])[sub 4](Se[sub 5])] (III) in 72% yield, respectively. Single-crystal X-ray diffraction studies show that (I), (II), and (III) contain the same anion, [In[sub 2](Se[sub 4])[sub 4](Se[sub 5])][sup 4[minus

  16. Fundamental Understanding of Methane-Carbon Dioxide-Water (CH4sub>-CO2-H2O) Interactions in Shale Nanopores under Reservoir Conditions. Quarterly Report.

    SciTech Connect

    Wang, Yifeng


    This project focuses on the systematic study of CH4sub>-CO2-H2O interactions in shale nanopores under high-pressure and high temperature reservoir conditions. The proposed work will help to develop new stimulation strategies to enable efficient resource recovery from fewer and less environmentally impactful wells.

  17. In situ determination of the spinel-post-spinel transition in Fe3O4sub> at high pressure and temperature by synchrotron X-ray diffraction

    SciTech Connect

    Schollenbruch, K; Woodland, A B; Frost, D J; Wang, Y; Sanehira, T; Langenhorst, F


    The position of the spinel-post-spinel phase transition in Fe3O4sub> has been determined in pressure-temperature space by in situ measurements using a multi-anvil press combined with white synchrotron radiation. Pressure measurement using the equation of state for MgO permitted pressure changes to be monitored at high temperature. The phase boundary was determined by the first appearance of diffraction peaks of the high-pressure polymorph (h-Fe3O4sub>) during pressure increase and the disappearance of these peaks on pressure decrease along several isotherms. We intersected the phase boundary over the temperature interval of 700-1400 ºC. The boundary is linear and nearly isobaric, with a slightly positive slope. Post-experiment investigation by TEM confirms that the reverse reaction from h-Fe 3O4sub> to magnetite during decompression leads to the formation of microtwins on the (311) plane in the newly formed magnetite. Observations made during the phase transition suggest that the transition has a pseudomartensitic character, explaining in part why magnetite persists at conditions well within the stability field of h-Fe3O4sub>, even at high temperatures. This study emphasizes the utility of studying phase transitions in situ at simultaneously high temperatures and pressures since the reaction kinetics may not be favorable at room temperature.

  18. Photoelectron Spectroscopy of Anions at 118.2 nm. Observation of High Electron Binding Energies in Superhalogens MCI4sub>- (M=Sc, Y, La)

    SciTech Connect

    Yang, Jie; Wang, Xue B.; Xing, Xiaopeng; Wang, Lai S.


    High energy photon is needed for photoelectron spectroscopy (PES) of anions with high electron binding energies, such as superhalogens and O-rich metal oxide clusters. The highest energy photon used for anion PES in the laboratory has been 157 nm (7.866 eV) from F2 eximer lasers. Here, we report an anion PES experiment using coherent vacuum ultraviolet radiation at 118.2 nm (10.488 eV) by tripling the third harmonic output (355 nm) of a Nd:YAG laser in a Xe/Ar cell. Our study focuses on a set of superhalogen species, MCI4sub>- (M=Sc, Y, La), which were expected to possess very high electron binding energies. While the 157 nm photon can only access the ground state detachment features for these species, more transitions to the excited states at binding energies higher than 8 eV are observed at 118.2 nm. The adiabatic detachment energies are shown to be, 6.84, 7.02, and 7.03 eV for ScCl4sub>-, YCl4sub>-, and LaCl4sub>- eV, respectively, whereas their corresponding vertical detachment energies are measured to be 7.14, 7.31, and 7.38 eV.

  19. Magnetic field, frequency and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4sub>/La2CuO4sub> films and the organic superconductors κ-(BEDT-TTF)2Cu[N(CN)2]Br

    SciTech Connect

    V. A. Gasparov; Bozovic, I.; He, Xi; Dubuis, G.; Pavuna, D.; Kushch, N. D.; Yagubskii, E. B.; Schlueter, J. A.


    In this study, we used atomic-layer molecular beam epitaxy (ALL-MBE) to synthesize bilayer films of a cuprate metal (La1.65Sr0.45CuO4sub>) and a cuprate insulator (La2CuO4sub>), in which interface superconductivity occurs in a layer that is just one-half unit cell thick. We have studied the magnetic field and temperature dependence of the complex sheet conductance, σ(ω), of these films, and compared them to κκ-(BEDT-TTF)2Cu[N(CN)2]Br single crystals. The magnetic field H was applied both parallel and perpendicular to the 2D conducting layers. Experiments have been carried out at frequencies between 23 kHz and 50 MHz using either two-coil mutual inductance technique, or the LC resonators with spiral or rectangular coils. The real and the imaginary parts of the mutual-inductance M(T,ω) between the coil and the sample were measured and converted to complex conductivity. For H perpendicular to the conducting layers, we observed almost identical behavior in both films and κ-Br single crystals: (i) the transition onset in the inductive response, Lk–1(T) occurs at a temperature lower by 2 K than in Re σ(T), (ii) this shift is almost constant with magnetic field up to 8 T; (iii) the vortex diffusion constant D(T) is exponential due to pinning of vortex cores. These results can be described by the extended dynamic theory of the Berezinski–Kosterlitz–Thouless (BKT) transition and dynamics of bound vortex–antivortex pairs with short separation lengths.

  20. NaLa(MoO{sub 4}){sub 2}: RE{sup 3+} (RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}, Er{sup 3+}/Yb{sup 3+}) microspheres: the synthesis and optical properties

    SciTech Connect

    Gao, Zhiyi; Wang, Zhiying; Fu, Linlin; Yang, Xingxing; Fu, Zuoling; Wu, Zhijian; Jeong, Jung Hyun


    The strong green upconversion (UC) emission were observed in various Er{sup 3+}, Yb{sup 3+} co-doped NaLa(MoO{sub 4}){sub 2} samples synthesized via a hydrothermal route. The UC intensity depends on the dopant concentration, and the optimal UC emission was obtained in NaLa(MoO{sub 4}){sub 2}: 0.02Er{sup 3+}/0.10 Yb{sup 3+}. - Highlights: • The NaLa(MoO{sub 4}){sub 2} microspheres doped with Eu{sup 3+}, Sm{sup 3+} and Er{sup 3+}/Yb{sup 3+} were synthesized by a hydrothermal method. • The effects of the EDTA in the initial solution crystal phase and morphology were studied. • The down-conversion luminescence properties of NaLa(MoO{sub 4}){sub 2}: RE{sup 3+} (RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}) were investigated. • The UC luminescence properties and mechanism of Er{sup 3+}/Yb{sup 3+} co-doped NaLa(MoO{sub 4}){sub 2} was discussed. - Abstract: NaLa(MoO{sub 4}){sub 2}: RE{sup 3+} (RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}) microspheres have been synthesized at 180 °C via a facile EDTA-mediated hydrothermal route. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) spectra were employed to characterize the samples. It was found that the amount of EDTA in the initial solution was responsible for crystal phase and shape determination. The effect of Eu{sup 3+} and Sm{sup 3+} doping concentrations on the luminescent intensity was also investigated in details. Furthermore, the up-conversion (UC) emissions have been observed in a series of Er{sup 3+}/Yb{sup 3+} co-doped NaLa(MoO{sub 4}){sub 2} samples. Concentration dependent studies revealed that the optimal composition was realized for a 2% Er{sup 3+} and 10% Yb{sup 3+}-doping concentration.

  1. A study of room-temperature LixMn1.5Ni0.5O4sub> solid solutions

    SciTech Connect

    Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; Chen, Guoying


    Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4sub> solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4sub> (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4sub> (Phase I), Li0.5Mn1.5Ni0.5O4sub> (Phase II) and Mn1.5Ni0.5O4sub> (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. In conclusion, the work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance.

  2. NMR relaxation study of the phase transitions and relaxation mechanisms of the alums MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals

    SciTech Connect

    Lim, Ae Ran; Paik, Younkee; Lim, Kye-Young


    The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the {sup 87}Rb and {sup 133}Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T{sub 1} are related to variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}. We also compared these {sup 87}Rb and {sup 133}Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO{sub 4}){sub 2}.12H{sub 2}O and MAl(SO{sub 4}){sub 2}.12H{sub 2}O crystals. - Graphical Abstract: The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb, Cs, and NH{sub 4}) single crystals have been investigated. Highlights: > The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) crystals {yields} The NMR spectra and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals {yields} The variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}.

  3. Micro-Raman and Micro-Infrared Spectroscopic Studies of Pb- and Au-Irradiated ZrSiO4sub>. Optical Properties, Structural Damage and Amorphization

    SciTech Connect

    Zhang, Ming; Boatner, Lynn A.; Salje, Ekhard; Ewing, Rodney C.; Daniel, Philippe; Weber, William J; Zhang, Yanwen; Farnan, Ian E.


    The optical properties of damaged, periodic and aperiodic domains created by Pb+ (280 keV) and Au4+ (10 MeV) implantation of zircon were studied using micro-infrared (IR) and micro-Raman spectroscopy. The Pb+ and Au4+ irradiations caused a dramatic decrease in the IR reflectivity similar to that observed for metamict natural zircon. The irradiation with 10 MeV Au4+ ions (to fluences of 1x1015 Au4+ ions/cm2) also results in the formation of an amorphized phase similar to that observed in metamict zircon. These results show that high-energy, heavy-ion irradiations provide a good simulation of the ballistic effects of the recoil nucleus of an alpha-decay event, and in both cases, the result is the creation of aperiodic domains. Additional IR and Raman features were recorded in samples irradiated with 280 keV Pb+ ions (to fluences of 1x1014 and 1x1015 Pb+ ions/cm2), indicating the formation of an irradiation-induced new phase(s). The frequencies of the features are consistent with lead silicates, ZrO2 and SiO2. The results show that spectral features of the Au4+ and Pb+ irradiated zircon are different from those of quenched ZrSiO4sub> melts, and the finding further confirms that the amorphous state produced by high-energy ion irradiations is structurally different from the glassy state that results from quenching a high temperature melt. In contrast to significant changes in the frequency and width of the Raman v3 band observed in metamict zircon, the Pb+ and Au4+ irradiations do not cause similar variations, indicating that the remaining zircon crystalline domains in irradiated samples have a crystalline structure with fewer defects than those of metamict zircon.

  4. Thermal expansion of phosphates with the NaZr{sub 2}(PO{sub 4}){sub 3} structure containing lanthanides and zirconium: R{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} (R = Nd, Eu, Er) and Er{sub 0.33(1–x)} Zr{sub 0.25x}Zr{sub 2}(PO{sub 4}){sup 3}

    SciTech Connect

    Volgutov, V. Yu. Orlova, A. I.


    Phosphates R{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} (R = Nd, Eu, or Er) and Er{sub 0.33(1–x)}Zr{sub 0.25}Zr{sub 2}(PO{sub 4}){sub 3} (x = 0, 0.25, 0.5, 0.75, 1.0) of the NaZr{sub 2}(PO{sub 4}){sub 3} family have been synthesized and investigated by high-temperature X-ray diffraction. The crystallochemical approach is used to obtain compounds with expected small and controllable thermal-expansion parameters. Phosphates with close-to-zero thermal-expansion parameters, including those with low thermal-expansion anisotropy, have been obtained: Nd{sub 0.33}Zr{sub 2}(PO{sub 4}){sub 3} with α{sub a} =–2.21 × 10{sup −6} °C{sup −1}, α{sub c} = 0.81 × 10{sup −6} °C{sup −1}, and Δα = 3.02 × 10{sup −6} °C{sup –1} and Er{sub 0.08}Zr{sub 0.19}Zr{sub 2}(PO{sub 4}){sub 3} with α{sub a} =–1.86 × 10{sup −6} °C{sup −1}, α{sub c} = 1.73 × 10{sup −6} °C{sup −1}, and Δα = 3.58 × 10{sup −6} °C{sup −1}.

  5. From {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} to {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} infinite chains in A{sub 6}U{sub 2}Mo{sub 4}O{sub 21} (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure of Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})

    SciTech Connect

    Yagoubi, S.; Obbade, S.; Saad, S.; Abraham, F.


    A new caesium uranyl molybdate belonging to the M{sub 6}U{sub 2}Mo{sub 4}O{sub 21} family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A{sub 6}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}], the caesium compound Cs{sub 6}U{sub 2}Mo{sub 4}O{sub 21} should be written Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] crystallizes in the triclinic symmetry with space group P1-bar and a=10.4275(14) A, b=15.075(2) A, c=17.806(2) A, {alpha}=70.72(1){sup o}, {beta}=80.38(1){sup o} and {gamma}=86.39(1){sup o}, V=2604.7(6) A{sup 3}, Z=4, {rho}{sub mes}=5.02(2) g/cm{sup 3} and {rho}{sub cal}=5.08(3) g/cm{sup 3}. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R{sub 1}=0.0464 and wR{sub 2}=0.0950 for 596 parameters with 6964 independent reflections with I{>=}2{sigma}(I) collected on a BRUKER AXS diffractometer with Mo(K{alpha}) radiation and a CCD detector. The crystal structure of Cs compound is characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} parallels chains built from U{sub 2}O{sub 13} dimeric units, MoO{sub 4} tetrahedra and MoO{sub 5} square pyramids, whereas, Na, K and Rb compounds are characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} parallel chains formulated simply of U{sub 2}O{sub 13} units and MoO{sub 4} tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 610 {sup o

  6. Dual Phase Li4sub>Ti5O12–TiO2 Nanowire Arrays As Integrated Anodes For High-rate Lithium-ion Batteries

    SciTech Connect

    Liao, Jin; Chabot, Victor; Gu, Meng; Wang, Chong M.; Xiao, Xingcheng; Chen, Zhongwei


    Lithium titanate (Li4sub>Ti5O12) is well known as a zero strain material inherently, which provides excellent long cycle stability as a negative electrode for lithium ion batteries. However, the low specific capacity (175 mA h g-1) limits it to power batteries although the low electrical conductivity is another intrinsic issue need to be solved. In this work, we developed a facile hydrothermal and ion-exchange route to synthesize the self-supported dual-phase Li4sub>Ti5O12–TiO2 nanowire arrays to further improve its capacity as well as rate capability. The ratio of Li4sub>Ti5O12 to TiO2 in the dual phase Li4sub>Ti5O12–TiO2 nanowire is around 2:1. The introduction of TiO2 into Li4sub>Ti5O12 increases the specific capacity. More importantly, by interface design, it creates a dual-phase nanostructure with high grain boundary density that facilitates both electron and Li ion transport. Compared with phase-pure nanowire Li4sub>Ti5O12 and TiO2 nanaowire arrays, the dual-phase nanowire electrode yielded superior rate capability (135.5 at 5 C, 129.4 at 10 C, 120.2 at 20 C and 115.5 mA h g-1 at 30 C). In-situ transmission electron microscope clearly shows the near zero deformation of the dual phase structure, which explains its excellent cycle stability.

  7. Selective Metal Exsolution in BaFe2-yMy(PO4sub>)2 (M = Co2+, Ni2+) Solid Solutions

    SciTech Connect

    Alcover, Ignacio Blazquez; Daviero-Minaud, Sylvie; David, Rénald; Filimonov, Dmitry; Huvé, Marielle; Attfield, J. Paul; Kabbour, Houria; Mentré, Olivier


    The 2D-Ising ferromagnetic phase BaFe2+2(PO4sub>)2 shows exsolution of up to one-third of its iron content (giving BaFe3+1.33(PO4sub>)2) under mild oxidation conditions, leading to nanosized Fe2O3 exsolved clusters. Here we have prepared BaFe2–yMy(PO4sub>)2 (M = Co2+, Ni2+; y = 0, 0.5, 1, 1.5) solid solutions to investigate the feasibility and selectivity of metal exsolution in these mixed metallic systems. For all the compounds, after 600 °C thermal treatment in air, a complete oxidation of Fe2+ to Fe3+ leaves stable M2+ ions, as verified by 57Fe Mössbauer spectroscopy, TGA, TEM, microprobe, and XANES. Furthermore, the size of the nanometric α-Fe2O3clusters coating the main phase strongly depends on the yM metal concentration. For M-rich phases the iron diffusion is hampered so that a significant fraction of superparamagnetic α-Fe2O3 particles (100% for BaFe0.5–xCo1.5(PO4sub>)2) was detected even at 78 K. Although Ni2+and Co2+ ions tend to block Fe diffusion, the crystal structure of BaFe0.67Co1(PO4sub>)2demonstrates a fully ordered rearrangement of Fe3+ and Co2+ ions after Fe exsolution. We found that the magnetic behaviors of the Fe-depleted materials are mostly dominated by antiferromagnetic exchange, while Co2+-rich compounds show metamagnetic transitions reminiscent of the BaCo2(PO4sub>)2 soft helicoidal magnet.

  8. [H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3}]{sub 2}[Al{sub 4}(C{sub 2}O{sub 4})(H{sub 2}PO{sub 4}){sub 2}(PO{sub 4}){sub 4}].4[H{sub 2}O]: A new layered aluminum phosphate-oxalate

    SciTech Connect

    Peng Li; Li Jiyang; Yu Jihong . E-mail:; Li Guanghua; Fang Qianrong; Xu Ruren . E-mail:


    A new layered inorganic-organic hybrid aluminum phosphate-oxalate [H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3}]{sub 2}[Al{sub 4}(C{sub 2}O{sub 4})(H{sub 2}PO{sub 4}){sub 2}(PO{sub 4}){sub 4}].4[H{sub 2}O](AlPO-CJ25) has been synthesized hydrothermally, by using 1,4-diaminobutane (DAB) as structure-directing agent. The structure has been solved by single-crystal X-ray diffraction analysis and further characterized by IR, {sup 31}P MAS NMR, TG-DTA as well as compositional analyses. Crystal data: the triclinic space group P-1, a=8.0484(7) A, b=8.8608(8) A, c=13.2224(11) A, {alpha}=80.830(6) deg. , {beta}=74.965(5) deg. , {gamma}=78.782(6) deg. , Z=2, R {sub 1[} {sub I} {sub >2} {sub {sigma}} {sub (} {sub I} {sub )]}=0.0511 and wR {sub 2(alldata)}=0.1423. The alternation of AlO{sub 4} tetrahedra and PO{sub 4} tetrahedra gives rise to the four-membered corner-sharing chains, which are interconnected through AlO{sub 6} octahedra to form the layered structure with 4,6-net sheet. Interestingly, oxalate ions are bis-bidentately bonded by participating in the coordination of AlO{sub 6}, and bridging the adjacent AlO{sub 6} octahedra. The layers are held with each other through strong H-bondings between the terminal oxygens. The organic ammonium cations and water molecules are located in the large cavities between the interlayer regions. -- Graphical abstract: The alternation of AlO{sub 4} tetrahedra and PO{sub 4} tetrahedra gives rise to the four-membered corner-sharing chains, which are interconnected through AlO{sub 6} octahedra to form the layered structure with 4,6-net sheet. Oxalate ions are bis-bidentately boned by participating in the coordination of AlO{sub 6}, and bridging the adjacent AlO{sub 6} octahedra.

  9. Crystal structure of the binary complex of cobalt and zinc chlorides with carbamide [Co(OCN{sub 2}H{sub 4}){sub 5}(H{sub 2}O)][ZnCl{sub 4}

    SciTech Connect

    Furmanova, N. G. Chernaya, T. S.; Resnyanskii, V. F. Sulaimankulov, K. S.


    Mixed single crystals of [Co(OCN{sub 2}H{sub 4}){sub 5}(H{sub 2}O)][ZnCl{sub 4}] were grown by the isothermal evaporation of an aqueous solution. The crystal structure of this complex was established by X-ray diffraction (R = 0.052 based on 7003 reflections). The crystals consist of [Co(OCN{sub 2}H{sub 4}){sub 5}(H{sub 2}O)]{sup 2+} cations containing Co atoms in an octahedral coordination and [ZnCl{sub 4}]{sup 2-}] anions containing Zn atoms in a tetrahedral coordination. The carbamide molecules are involved in both intramolecular and interionic hydrogen bonds. The H{sub 2}O molecule forms hydrogen bonds with the anions.

  10. Phase-matching properties of yellow color HgGa2S4sub> for SHG and SFG in the 0.944-10.5910  μm range.


    Kato, Kiyoshi; Petrov, Valentin; Umemura, Nobuhiro


    We report new experimental results on the phase-matching properties of yellow color HgGa2S4sub> crystals for harmonic generation of an Nd:YAG laser-pumped KTiOPO4sub> (KTP) optical parametric oscillator (OPO) and CO2 lasers in the 0.944-10.5910 μm range. In addition, we present new Sellmeier equations that provide a good reproduction of the present experimental results as well as the published data points for second-harmonic generation of CO2 laser radiation at 9.2197-9.6392 μm and Nd:YAG laser-pumped OPOs at 1.205-1.725 μm and 2.77-9.10 μm that were achieved with the orange and yellow color crystals. PMID:27140080

  11. Synthesis of Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} through a reactive flux method and its visible-light photocatalytic performances

    SciTech Connect

    Zhu, Xianglin; Wang, Zeyan E-mail:; Huang, Baibiao E-mail:; Zhang, Xiaoyang; Qin, Xiaoyan; Wei, Wei; Dai, Ying


    Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} was prepared by a reactive flux method. The structures, morphologies, and light absorption properties were investigated. Owing to the polar crystal structure, an internal electric field can be formed inside the material, which can facilitate the photogenerated charge separation during the photocatalytic process. Based on both the wide light absorption spectra and high charge separation efficiency originated from the polarized internal electric field, Ag{sub 9}(SiO{sub 4}){sub 2}NO{sub 3} exhibit higher efficiency over Ag{sub 3}PO{sub 4} during the degradation of organic dyes under visible light irradiation, which is expected to be a potential material for solar energy harvest and conversion.

  12. Neutron-scattering evidence for a periodically modulated superconducting phase in the underdoped cuprate La1.905Ba0.095CuO4sub>

    SciTech Connect

    Xu, Zhijun; Stock, C.; Chi, Songxue; Kolesnikov, A. I.; Xu, Guangyong I.; Gu, Genda; Tranquada, J. M.


    The role of antiferromagnetic spin correlations in high-temperature superconductors remains a matter of debate. We present inelastic neutron-scattering evidence that gapless spin fluctuations coexist with superconductivity in La1.905Ba0.095CuO4sub>. Furthermore, we observe that both the low-energy magnetic spectral weight and the spin incommensurability are enhanced with the onset of superconducting correlations. We propose that the coexistence occurs through intertwining of spatial modulations of the pair wave function and the antiferromagnetic correlations. This proposal is also directly relevant to sufficiently underdoped La2-xSrxCuO4sub> and YBa2Cu3O6+x.

  13. Strain-relaxation and critical thickness of epitaxial La1.85Sr0.15CuO4sub> films

    SciTech Connect

    Meyer, Tricia L; Jiang, Lu; Park, Sungkyun; Egami, Takeshi; Lee, Ho Nyung


    We report the thickness-dependent strain-relaxation behavior and the associated impacts upon the superconductivity in epitaxial La1.85Sr0.15CuO4sub> films grown on different substrates, which provide a range of strain. We have found that the critical thickness for the onset of superconductivity in La1.85Sr0.15CuO4sub> films is associated with the finite thickness effect and epitaxial strain. In particular, thin films with tensile strain greater than ~0.25% revealed no superconductivity. We attribute this phenomenon to the inherent formation of oxygen vacancies that can be minimized via strain relaxation.

  14. Growth of the (In{sub 2}S{sub 3}){sub x}(FeIn{sub 2}S{sub 4}){sub 1-x} single crystals and properties of photoelectric structures on their basis

    SciTech Connect

    Bodnar, I. V.; Rud, V. Yu.; Rud, Yu. V.; Terukov, E. I.


    Complete mutual solubility in the (In{sub 2}S{sub 3}){sub x}(FeIn{sub 2}S{sub 4}){sub 1-x} system is established. The technology is developed, and single crystals of the continuous series of the (In{sub 2}S{sub 3}){sub x}(FeIn{sub 2}S{sub 4}){sub 1-x} solid solutions are grown for the first time. The linear dependence of the unit cell parameter of single crystals with a cubic spinel lattice on the solid solution composition is found. First, photosensitive Schottky barriers are fabricated, and then, based on studies of their photosensitivity, the character of band-to-band transition is discussed and the values of the band gap depending on the atomic composition are estimated. The possibility of using the obtained solid solutions as broadband photoconverters of optical radiation is revealed.

  15. Eye-safe 1.55  μm passively Q-switched Er,Yb:GdAl3(BO3)4sub> diode-pumped laser.


    Gorbachenya, K N; Kisel, V E; Yasukevich, A S; Maltsev, V V; Leonyuk, N I; Kuleshov, N V


    We report for the first time, to the best of our knowledge, on a diode-pumped passively Q-switched Er,Yb:GdAl3(BO3)4sub> laser. By using a Co2+:MgAl2O4sub> crystal as a saturable absorber, Q-switched laser pulses with a duration of 12 ns and a maximum energy of 18.7 μJ at a repetition rate of 32 kHz corresponding to an average output power of 0.6 W were obtained at 1550 nm under continuous-wave pumping. In the burst mode of operation, Q-switched laser pulses with the highest energy up to 44 μJ were realized with a pulse repetition rate of 6.5 kHz. PMID:26974080

  16. Structure electronic and ionic conductivity study versus Ca content in Ca{sub 10-x}Sr{sub x}(PO{sub 4}){sub 6}F{sub 2} apatites

    SciTech Connect

    Sghir, B.; Hlil, E.K.; Laghzizil, A.; Boujrhal, F.Z.; Cherkaoui El Moursli, R.; Fruchart, D.


    Substitution effect on the crystallographic structure in Ca{sub 10-x}Sr{sub x}(PO{sub 4}){sub 6}F{sub 2} solid solution are studied by X-ray diffraction patterns and Rietveld refinements. Full potential electronic structure calculations based on LCAO (linear combination atomic orbital) are also performed using the obtained crystallographic parameters. DOS modification and the charge transfer are estimated versus the calcium content. According to the complex impedance method, ionic conductivity changes are explained.

  17. Single-Step Synthesis of FeSO4sub>F1-yOHy (0 ≤ y ≤ 1) Positive Electrodes for Li-Based Batteries

    SciTech Connect

    Ati, M; Sougrati, M-T; Rousse, G; Recham, N; Doublet, M-L; Jumas, J-C; Tarascon, J-M


    The recent discovery of electrochemical activity at 3.6 V vs Li+/Li0 in LiFeSO4sub>F has generated widespread research activity in this new family of fluorosulfate electrode materials aiming at either increasing the Fe3+/Fe2+ redox potential, searching for new active members, or extending this family to hydroxyl-fluorosulfates. Here we present a new low temperature single step synthesis of FeSO4sub>F1-yOHy phases using FeF3 and Fe2(SO4sub>)3 ∙ nH2O as precursors. Using thorough chemical analytical techniques to test for F- content in conjunction with Moessbauer measurements, we demonstrate the existence of a limited solid solution (0.35 < y < 1) within this system. Members pertaining to this solid solution have a redox activity ranging from 3.2 to 3.6 V vs Li+/Li0 and show sustained reversible capacity retention of 130 mAh/g which makes them potentially interesting for Li-based polymer batteries. We demonstrate that the Li-insertion-deinsertion mechanism depends markedly on the sample F- content by using joint in situ XRD and Moessbauer spectroscopy. Moreover, we show the versatility of our synthetic approach by extending it to the elaboration of Fe1-zMzSO4sub>F1-yOHy phases with M = Ti and V.

  18. Synthetic and spectroscopic studies of vanadate glaserites II: Photoluminescence studies of Ln:K{sub 3}Y(VO{sub 4}){sub 2} (Ln=Eu, Er, Sm, Ho, or Tm)

    SciTech Connect

    Kimani, Martin M. McMillen, Colin D. Kolis, Joseph W.


    Glaserite-type potassium yttrium double vanadates (K{sub 3}Y(VO{sub 4}){sub 2}) doped with Eu{sup 3+}, Er{sup 3+}, Sm{sup 3+}, Ho{sup 3+}, or Tm{sup 3+} have been synthesized by solid state reactions at 1000 °C for 48 h and their photoluminescence properties investigated. Efficient energy transfer from the vanadate group to the rare earth ion has been established by photoluminescence investigation. Ultraviolet excitation into the metal to ligand charge transfer band of the vanadate groups results in orange-red, blue and green emissions from Eu{sup 3+} (592 nm), Sm{sup 3+} (602 nm), Tm{sup 3+} (475 nm), Er{sup 3+} (553 nm), and Ho{sup 3+} (541–551 nm) dopant ions. The emission intensities of the lanthanide-doped K{sub 3}Y(VO{sub 4}){sub 2} powders were studied as a function of dopant ion concentrations. Over the concentration ranges studied, no emission quenching was observed for Eu{sup 3+} or Ho{sup 3+} dopants, while Er{sup 3+}, Sm{sup 3+} and Tm{sup 3+} dopants did exhibit such effects for dopant ion concentrations greater than 5%, probably due to cross relaxation processes. - Graphical abstract: Synthesis and photoluminescence in vanadate glaserites. - Highlights: • K{sub 3}Y(VO{sub 4}){sub 2} doped with Eu, Er, Tm, Sm, or Ho were synthesized via solid-state reactions. • Photoluminescence properties are investigated. • The lanthanide doped K{sub 3}Y(VO{sub 4}){sub 2} compounds revealed efficient energy transfer from the vanadate group to the rare earth ions. • The presented compounds are promising materials for light display systems, lasers, and optoelectronic devices.

  19. A limited role for carbonic anhydrase in C4sub> photosynthesis as revealed by a ca1ca2 double mutant in maize.

    SciTech Connect

    Studer, Anthony J.; Gandin, Anthony; Kolbe, Allison R.; Wang, Lin; Cousins, Asaph B.; Brutnell, Thomas P.


    Carbonic anhydrase (CA) catalyzes the first biochemical step of the carbon concentrating mechanism of C4sub> plants, and in C4sub> monocots, it has been suggested that CA activity is near limiting for photosynthesis. Here, we test this hypothesis through the characterization of transposon induced mutant alleles of Ca1 and Ca2 in Zea mays. In addition, these two isoforms account for more than 85% of the CA transcript pool. A significant change in isotopic discrimination is observed in mutant plants, which have as little as 3% of wild-type CA activity, but surprisingly, photosynthesis is not reduced under current or elevated pCO2. However, growth and rates of photosynthesis under sub-ambient pCO2 are significantly impaired in the mutants. These findings suggest, that while CA is not limiting for C4sub> photosynthesis in Z. mays at current pCO2, it likely maintains high rates of photosynthesis when CO2 availability is reduced. Current atmospheric CO2 levels now exceed 400 ppm (~40.53 Pa) and contrast the low CO2 partial pressure (pCO2) conditions under which C4sub> plants expanded their range ~10 million years ago when the global atmospheric CO2 was below 300 ppm (~30.40 Pa). Thus, as CO2 levels continue to rise, selective pressures for high levels of CA may be limited to arid climates where stomatal closure reduces CO2 availability to the leaf.

  20. Temperature dependence of the luminescence of calcium-magnesium phosphate Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+}, a blue-emitting material for white light-emitting diodes

    SciTech Connect

    Zhang, Xinmin; Pan, Qi; Kim, Sun Il; Yu, Young Moon; Seo, Hyo Jin


    Graphical abstract: - Highlights: • Emission spectrum at 20 K confirms that Eu{sup 2+} ions occupy three sites. • Decay curves of three types of Eu{sup 2+} reflect the characteristics of energy transfer. • The Eu(I) emission is thermally quenched at 323 K. • Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} has good thermal stability. • Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} is a promising phosphor for near UV excited white LEDs. - Abstract: A blue-emitting phosphor Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} peaking at 450 nm was synthesized by a solid state reaction. The XRD patterns, luminescence properties, decay curves of samples as well as their thermal quenching and comparing the luminescence properties with that of commercial material were investigated. At 20 K, the emission spectrum exhibiting two distinct bands peaking at 437 and 473 nm with a shoulder peak at 510 nm can be attributed to the overlap of Eu(I), Eu(II) and Eu(III) emission bands. At 423 K the PL intensity decreases to 80% of the value at room temperature, and the emission wavelength shifts toward high energy. The derived activation energy indicates that the lowest energy level of the Eu{sup 2+} 4f{sup 6}5d{sup 1} state is well isolated from the host lattice conduction band. The PL spectra and chromaticity coordinates are close to those of BAM. Ca{sub 3}Mg{sub 3}(PO{sub 4}){sub 4}:Eu{sup 2+} could be a potential candidate for near-UV excited white LEDs.

  1. Electrical and physical characterization of the Al{sub 2}O{sub 3}/p-GaSb interface for 1%, 5%, 10%, and 22% (NH{sub 4}){sub 2}S surface treatments

    SciTech Connect

    Peralagu, Uthayasankaran Thayne, Iain G.; Povey, Ian M.; Carolan, Patrick; Lin, Jun; Hurley, Paul K.; Contreras-Guerrero, Rocio; Droopad, Ravi


    In this work, the impact of ammonium sulfide ((NH{sub 4}){sub 2}S) surface treatment on the electrical passivation of the Al{sub 2}O{sub 3}/p-GaSb interface is studied for varying sulfide concentrations. Prior to atomic layer deposition of Al{sub 2}O{sub 3}, GaSb surfaces were treated in 1%, 5%, 10%, and 22% (NH{sub 4}){sub 2}S solutions for 10 min at 295 K. The smallest stretch-out and flatband voltage shifts coupled with the largest capacitance swing, as indicated by capacitance-voltage (CV) measurements, were obtained for the 1% treatment. The resulting interface defect trap density (D{sub it}) distribution showed a minimum value of 4 × 10{sup 12 }cm{sup −2}eV{sup −1} at E{sub v} + 0.27 eV. Transmission electron microscopy and atomic force microscopy examination revealed the formation of interfacial layers and increased roughness at the Al{sub 2}O{sub 3}/p-GaSb interface of samples treated with 10% and 22% (NH{sub 4}){sub 2}S. In combination, these effects degrade the interface quality as reflected in the CV characteristics.

  2. Luminescence properties of Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8}:Eu{sup 2+} from various Eu{sup 2+} sites for white-light-emitting diodes

    SciTech Connect

    Zhang, Jia Jiang, Cheng


    Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8}:Eu{sup 2+} phosphors were synthesized by solid-state reaction method, and their luminescence properties were investigated. In the emission spectra, several overlapping emission bands originating from various Eu{sup 2+} sites were found. Eu{sup 2+} in Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8} exhibits green emission around 506 nm, and the sample doped with 0.1 mol% Eu{sup 2+} shows the strongest brightness under 365 nm excitation with the quantum efficiency of 63.6%. In the excitation spectra, strong and broad excitation bands from 250 to 450 nm were observed, which could well match with the emission wavelength of the light-emitting diode chip. The fabrication test on the InGaN chip indicates the Ca{sub 14}Mg{sub 2}(SiO{sub 4}){sub 8}:Eu{sup 2+} phosphor could be promising candidate for white light-emitting diodes.

  3. Temperature-induced changes in the single-crystal structure of K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O

    SciTech Connect

    Makarova, I. P. Grebenev, V. V.; Chernaya, T. S.; Verin, I. A.; Dolbinina, V. V.; Chernyshov, D. Yu.; Koval'chuk, M. V.


    Interest in superprotonic crystals of M{sub m}H{sub n}(XO{sub 4}){sub (m+n)/2} is associated with the solution to the fundamental problem of modern condensed matter physics: investigations of structural phase transitions and the stabilization of phases with high proton conductivity with the aim of designing new functional materials. The available data suggest that changes in the physical properties in these crystals can occur through different structural mechanisms. To reveal the structural conditionality for anomalies in the physical properties, the crystals of K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O were studied by X-ray diffraction in the temperature range of 25-463 K, and the crystal structure of the high-temperature phase was determined at 418 K (sp. gr. Pcan). The results of the study indicate that the occurrence of high conductivity in K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O crystals at high temperatures is associated with the diffusion of water of crystallization, the hydrogen-bond network rearrangement, and the motion of K ions. The hydrogen-bond rearrangement and the hindered back diffusion of water to the crystal stabilize the high-temperature phase and ensure its supercooling to low temperatures.

  4. Consequences of Optimal Bond Valence on Structural Rigidity and Improved Luminescence Properties in SrxBa2-xSiO4sub>:Eu2+ Orthosilicate Phosphors

    SciTech Connect

    Denault, Kristin A.; Brgoch, Jakoah; Gaultois, Michael W.; Mikhailovsky, Alexander; Petry, Ralf; Winkler, Holger; DenBaars, Steven P.; Seshadri, Ram


    The orthosilicate phosphors SrxBa2–xSiO4sub>:Eu2+ have now been known for over four decades and have found extensive recent use in solid-state white lighting. It is well-recognized in the literature and in practice that intermediate compositions in the solid-solutions between the orthosilicates Sr2SiO4sub> and Ba2SiO4sub> yield the best phosphor hosts when the thermal stability of luminescence is considered. We employ a combination of synchrotron X-ray diffraction, total scattering measurements, density functional theory calculations, and low-temperature heat capacity measurements, in conjunction with detailed temperature- and time-resolved studies of luminescence properties to understand the origins of the improved luminescence properties. We observe that in the intermediate compositions, the two cation sites in the crystal structure are optimally bonded as determined from bond valence sum calculations. Optimal bonding results in a more rigid lattice, as established by the intermediate compositions possessing the highest Debye temperature, which are determined experimentally from low-temperature heat capacity measurements. Greater rigidity in turn results in the highest luminescence efficiency for intermediate compositions at elevated temperatures.

  5. Influence of Ga-concentration on the electrical and magnetic properties of magnetoelectric CoGaxFe2–xO4sub>/BaTiO3 composite

    SciTech Connect

    Ni, Yan; Zhang, Zhen; Nlebedim, Cajetan I.; Jiles, David C.


    Multiferroic materials exhibit magnetoelectric (ME) coupling and promise new device applications including magnetic sensors, generators, and filters. An effective method for developing ME materials with enhanced ME effect is achieved by the coupling through the interfacial strain between piezoelectric and magnetostrictive materials. In this study, the electrical and magnetic properties of Ga doped magnetoelectric CoGaxFe2–xO4sub>/BaTiO3 composite are studied systematically. It is found that Ga doping improves the sensitivity of magnetoelastic response and stabilizes the magnetic phase of the composites. More importantly, Ga doping reduces the electrical conductivity of composite, as well as the dielectric loss. An enhancement of the electrostrain with doping Ga is also observed. Quantitative estimation indicates that magnetoelectric coupling is enhanced for Ga-doped CoGaxFe2–xO4sub>/BaTiO3 composites. As a result, the present work is beneficial to the practical application of composite CoFe2O4sub>/BaTiO3-based multiferroic materials.

  6. Site and local structure of activator Eu{sup 2+} in phosphor Ca{sub 10−x}(PO{sub 4}){sub 6}Cl{sub 2}:xEu{sup 2+}

    SciTech Connect

    Wang, Chun-Hai; Gui, Dong-Yun; Qin, Rui; Yang, Feng-Li; Jing, Xi-Ping; Tian, Guang-Shan; Zhu, Wenjun


    The site and local structure of activator Eu{sup 2+} in phosphor Ca{sub 10−x}(PO{sub 4}){sub 6}Cl{sub 2}:xEu{sup 2+} is investigated by experiment measurements, first-principle calculations and XAFS simulations. From first-principle calculations, the “local” structure [bond length L(M–O)≤R(M{sup 2+})+R(O{sup 2−})] of host shows a significant deformation (expansion) when Ca{sup 2+} is substituted by Eu{sup 2+}, and Eu{sup 2+} should prefer 6h site to 4f site in the host. The d→f emission of Eu{sup 2+} at 4f site should show a longer wavelength than that of Eu{sup 2+} at 6h site. The XAFS measurement and simulations suggest that the Eu{sup 2+} in our Ca{sub 9.9}(PO{sub 4}){sub 6}Cl{sub 2}:0.1Eu{sup 2+} sample mainly locates at 6h site. In the emission spectrum, two emission profiles of Ca{sub 9.9}(PO{sub 4}){sub 6}Cl{sub 2}:0.1Eu{sup 2+} sample are obtained and assigned. The major one (2.71 eV≈456 nm) should be the emission of Eu{sup 2+} at 6h site. The minor one (2.61 eV≈465 nm) should be that of Eu{sup 2+} at 4f site. - Graphical abstract: The d→f emission of Eu{sup 2+} in Ca{sub 9.9}(PO{sub 4}){sub 6}Cl{sub 2}:0.1Eu{sup 2+} can be assigned as: emission profile at 2.71 eV and 2.61 eV are Eu{sup 2+} at 6h and 4f site, respectively. Display Omitted - Highlights: • Eu{sup 2+} in Ca{sub 10−x}(PO{sub 4}){sub 6}Cl{sub 2}:xEu{sup 2+} causes deformation to “local” structure. • Eu{sup 2+} should prefer 6h site to 4f site in the host from energy aspect. • Emission at 2.71 eV and 2.61 eV should be Eu{sup 2+} at 6h and 4f site.

  7. Ground-based, integrated path differential absorption LIDAR measurement of CO2, CH4sub>, and H2O near 1.6  μm.


    Wagner, Gerd A; Plusquellic, David F


    A ground-based, integrated path, differential absorption light detection and ranging (IPDA LIDAR) system is described and characterized for a series of nighttime studies of CO2, CH4sub>, and H2O. The transmitter is based on an actively stabilized, continuous-wave, single-frequency external-cavity diode laser (ECDL) operating from 1.60 to 1.65 μm. The fixed frequency output of the ECDL is microwave sideband tuned using an electro-optical phase modulator driven by an arbitrary waveform generator and filtered using a confocal cavity to generate a sequence of 123 frequencies separated by 300 MHz. The scan sequence of single sideband frequencies of 600 ns duration covers a 37 GHz region at a spectral scan rate of 10 kHz (100 μs per scan). Simultaneously, an eye-safe backscatter LIDAR system at 1.064 μm is used to monitor the atmospheric boundary layer. IPDA LIDAR measurements of the CO2 and CH4sub> dry air mixing ratios are presented in comparison with those from a commercial cavity ring-down (CRD) instrument. Differences between the IPDA LIDAR and CRD concentrations in several cases appear to be well correlated with the atmospheric aerosol structure from the backscatter LIDAR measurements. IPDA LIDAR dry air mixing ratios of CO2 and CH4sub> are determined with fit uncertainties of 2.8 μmol/mol (ppm) for CO2 and 22 nmol/mol (ppb) for CH4sub> over 30 s measurement periods. For longer averaging times (up to 1200 s), improvements in these detection limits by up to 3-fold are estimated from Allan variance analyses. Two sources of systematic error are identified and methods to remove them are discussed, including speckle interference from wavelength decorrelation and the seed power dependence of amplified spontaneous emission. Accuracies in the dry air retrievals of CO2 and CH4sub> in a 30 s measurement period are estimated at 4 μmol/mol (1% of ambient levels) and 50

  8. Investigation of structural and luminescent properties of Ce{sup 3+}/Mn{sup 2+} ions-doped Ca{sub 5}(PO{sub 4}){sub 3}F

    SciTech Connect

    Zhang, Lei; Fu, Zuoling; Wu, Zhijian; Wang, Yuan; Fu, Xihong; Cui, Tian


    Graphical abstract: The structural and luminescent properties FAP: Ce{sup 3+} and FAP: Ce{sup 3+}, Mn{sup 2+} were investigated in detail by the spectral measurement and theoretical calculation. The emission of Ce{sup 3+} is fitted by two Gaussian functions dashed lines in wavenumber to further confirm the Ce{sup 3+} ion simultaneously occupy the 4f and 6h sites Ca{sub 5}(PO{sub 4})F host. - Highlights: • A simple hydrothermal method has been used to prepare Ca{sub 5}(PO{sub 4}){sub 3}F: Ce{sup 3+}, Mn{sup 2+} powders with structural and luminescent analysis. • The emission of Ce{sup 3+} is fitted by two Gaussian functions to confirm the Ce{sup 3+} ion simultaneously to occupy the 4f and 6h sites in Ca{sub 5}(PO{sub 4}){sub 3}F host. • Due to an efficient energy transfer, the existence of Ce{sup 3+} (sensitizer) can dramatically enhance the green emission of Mn{sup 2+} (activator) in co-doped samples. - Abstract: Ce{sup 3+}/Mn{sup 2+} ions-doped oxyapatite calcium fluorapatite [Ca{sub 5}(PO{sub 4}){sub 3}F, FAP] has been successfully synthesized by a facile one-step hydrothermal method. The luminescent properties of Ce{sup 3+}- and Ce{sup 3+}/Mn{sup 2+}- activated FAP phosphors were investigated using the photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The emission of Ce{sup 3+} was fitted by two Gaussian functions with dashed lines in wavenumber to confirm the Ce{sup 3+} ion simultaneously to occupy the 4f and 6h sites in Ca{sub 5}(PO{sub 4}){sub 3}F host, which was consistent with the calculated results of crystal field based on chemical bond theory. In addition, the existence of Ce{sup 3+} (sensitizer) can dramatically enhance the green emission of Mn{sup 2+} (activator) in Ce{sup 3+}/Mn{sup 2+} ions co-doped samples due to an efficient energy transfer from Ce{sup 3+} to Mn{sup 2+}. All of these results could help us understand the site assignments and optical properties of the rare earth ions doped in hexagonal Ca{sub 5}(PO{sub 4

  9. Synthesis, crystal structure and properties of alluaudite-like triple molybdate Na{sub 25}Cs{sub 8}Fe{sub 5}(MoO{sub 4}){sub 24}

    SciTech Connect

    Savina, Aleksandra A.; Solodovnikov, Sergey F.; Belov, Dmitry A.; Basovich, Olga M.; Solodovnikova, Zoya A.; Pokholok, Konstantin V.; Stefanovich, Sergey Yu.; Lazoryak, Bogdan I.; Khaikina, Elena G.


    A new triple molybdate Na{sub 25}Cs{sub 8}Fe{sub 5}(MoO{sub 4}){sub 24} was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, Mössbauer and dielectric impedance spectroscopy. Single crystals of Na{sub 25}Cs{sub 8}Fe{sub 5}(MoO{sub 4}){sub 24} were obtained and its structure was solved (the space group P1{sup ¯}, a=12.5814(5), b=13.8989(5), c=28.4386(9) Å, α=90.108(2), β=90.064(2), γ=90.020(2)°, V=4973.0(3) Å{sup 3}, Z=2, R=0.0440). Characteristic features of the structure are polyhedral layers composed of pairs of edge-shared FeO{sub 6} and (Fe, Na)O{sub 6} octahedra, which are connected by bridging MoO{sub 4} tetrahedra. The layers share common vertices with bridging MoO{sub 4} tetrahedra to form an open 3D framework with the cavities occupied by the Cs{sup +} and Na{sup +} cations. The compound undergoes first-order phase transformation at 642 K and above this phase transition, electrical conductivity reaches 10{sup −3}–10{sup −2} S cm{sup −1}. Thus, Na{sub 25}Cs{sub 8}Fe{sub 5}(MoO{sub 4}){sub 24} may be considered as a promising compound for developing new materials with high ionic conductivity. - Graphical abstract: A new triple molybdate Na{sub 25}Cs{sub 8}Fe{sub 5}(MoO{sub 4}){sub 24} was synthesized and structurally characterized, its physicochemical properties were studied. - Highlights: • New compound Na{sub 25}Cs{sub 8}Fe{sub 5}(MoO{sub 4}){sub 24} was synthesized. • Physicochemical properties of the compound were studied. • The first-order phase transformation is observed. • Electrical conductivity above 642 K is (10{sup −2}–10{sup −3}) S cm{sup −1}. • New compound may be considered as promising object with high ionic conductivity.

  10. Vacuum ultraviolet and near-infrared excited luminescence properties of Ca{sub 3}(PO{sub 4}){sub 2}:RE{sup 3+}, Na{sup +} (RE=Tb, Yb, Er, Tm, and Ho)

    SciTech Connect

    Zhang Jia; Wang Yuhua; Guo Linna; Zhang Feng; Wen Yan; Liu Bitao; Huang Yan


    Tb{sup 3+}, Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2} were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb{sup 3+}-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb{sup 3+} content is comparable with that of the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb{sup 3+}-Ho{sup 3+}, Yb{sup 3+}-Er{sup 3+}, and Yb{sup 3+}-Tm{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, in which the cross-relaxation process between Er{sup 3+} and Tm{sup 3+}, producing the {sup 1}D{sub 2}-{sup 3}F{sub 4} transition of Tm{sup 3+}, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams. - Graphical abstract: The CPO:0.25Tb{sup 3+}, 0.25Na{sup +} exhibits a comparable brightness to the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} upon 147 nm excitation. Good white light color is achieved in CPO:Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} under 980 nm excitation. Highlights: > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+},Na{sup +} exhibits a comparable brightness with commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+}. > Red, green and blue colors are achieved in Yb{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2}. > Good white emission is obtained in Yb{sup 3+}-Ho{sup 3+}-Er{sup 3+}-Tm{sup 3+} quadri-doped Ca{sub 3}(PO{sub 4}){sub 2}. > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+}, Yb{sup 3+}, Ho