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Sample records for 3sub 2ruchsub 2chsub

  1. Visible blind ultraviolet photodetector based on CH3sub>NH3sub>PbCl3sub> thin film.

    PubMed

    Wang, Wenzhen; Xu, Haitao; Cai, Jiang; Zhu, Jiabin; Ni, Chaowei; Hong, Feng; Fang, Zebo; Xu, Fuzong; Cui, Siwei; Xu, Run; Wang, Linjun; Xu, Fei; Huang, Jian

    2016-04-18

    We report a prototypical device of CH3sub>NH3sub>PbCl3sub> film ultraviolet photodetectors that were fabricated with a coplanar metal-semiconductor-metal Au interdigital electrode configuration. Pure phase CH3sub>NH3sub>PbCl3sub> films with a good crystallinity were formed by a hybrid sequential deposition process featured with inter-diffusion of PbCl2 and CH3sub>NH3sub>Cl upon annealing. The CH3sub>NH3sub>PbCl3sub> film photodetector exhibits a high responsivity of 7.56 A /W at 360 nm, a ultraviolet/visible rejection ratio (R360 nm/R500 nm) was about two orders of magnitude and fast response speed with a rising time of 170 μs and a decay time of 220 μs. All the above results demonstrate CH3sub>NH3sub>PbCl3sub> film photodetector as a competitive candidate in the application of visible blind UV detectors.

  2. Thermochemistry of Lewis Adducts of BH3sub> and Nucleophilic Substitution of Triethylamine on NH3sub>BH3sub> in Tetrahydrofuran

    SciTech Connect

    Potter, Robert G.; Camaioni, Donald M.; Vasiliu, Monica; Dixon, David A.

    2010-11-15

    The thermochemistry of the formation of Lewis base adducts of BH3sub> in tetrahydrofuran (THF) solution and the gas phase and the kinetics of substitution on ammonia borane by triethylamine are reported. The dative bond energy of Lewis adducts were predicted using density functional theory at the B3LYP/DZVP2 and B3LYP/6-311+G** levels and correlated ab initio molecular orbital theories, including MP2, G3(MP2), and G3(MP2)B3LYP, and compared with available experimental data and accurate CCSD(T)/CBS theory results. The analysis showed that the G3 methods using either the MP2 or the B3LYP geometries reproduce the benchmark results usually to within ~1 kcal/mol. Energies calculated at the MP2/aug-cc-pVTZ level for geometries optimized at the B3LYP/DZVP2 or B3LYP/6-311+G** levels give dative bond energies 2-4 kcal/mol larger than benchmark values. The enthalpies for forming adducts in THF were determined by calorimetry and compared with the calculated energies for the gas phase reaction: THFBH3sub> + L → LBH3sub> + THF. The formation of NH3sub>BH3sub> in THF was observed to yield significantly more heat than gas phase dative bond energies predict, consistent with strong solvation of NH3sub>BH3sub>. Substitution of NEt3sub> on NH3sub>BH3sub> is an equilibrium process in THF solution (K ≈ 0.2 at 25 °C). The reaction obeys a reversible bimolecular kinetic rate law with the Arrhenius parameters: log A = 14.7 ± 1.1 and Ea = 28.1 ± 1.5 kcal/mol. Finally, simulation of the mechanism using the SM8 continuum solvation model shows the reaction most likely proceeds primarily by a classical SN2 mechanism.

  3. Magnetic ordering-induced multiferroic behavior in [CH3sub>NH3sub>][Co(HCOO)3sub>] metal-organic framework.

    SciTech Connect

    Gomez-Aguirre, Lilian Claudia; Zapf, Vivien S.; Pato-Doldan, Breogan; Mira, Jorge; Castro-Garcia, Socorro; Senaris-Rodriguez, Maria Antonia; Sanchez-Andujara, Manuel; Singleton, John

    2015-12-30

    Here, we present the first example of magnetic ordering-induced multiferroic behavior in a metal–organic framework magnet. This compound is [CH3sub>NH3sub>][Co(HCOO)3sub>] with a perovskite-like structure. The A-site [CH3sub>NH3sub>]+ cation strongly distorts the framework, allowing anisotropic magnetic and electric behavior and coupling between them to occur. This material is a spin canted antiferromagnet below 15.9 K with a weak ferromagnetic component attributable to Dzyaloshinskii–Moriya (DM) interactions and experiences a discontinuous hysteretic magnetic-field-induced switching along [010] and a more continuous hysteresis along [101]. Coupling between the magnetic and electric order is resolved when the field is applied along this [101]: a spin rearrangement occurs at a critical magnetic field in the ac plane that induces a change in the electric polarization along [101] and [10-1]. The electric polarization exhibits an unusual memory effect, as it remembers the direction of the previous two magnetic-field pulses applied. The data are consistent with an inverse-DM mechanism for multiferroic behavior.

  4. Electronic structure evolution of fullerene on CH3sub>NH3sub>PbI3sub>

    SciTech Connect

    Wang, Chenggong; Wang, Congcong; Liu, Xiaoliang; Kauppi, John; Shao, Yuchuan; Xiao, Zhengguo; Bi, Cheng; Huang, Jinsong; Gao, Yongli

    2015-03-19

    The thickness dependence of fullerene on CH3sub>NH3sub>PbI3sub> perovskitefilm surface has been investigated by using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy(XPS), and inverse photoemission spectroscopy (IPES). The lowest unoccupied molecular orbital and highest occupied molecular orbital (HOMO) can be observed directly with IPES and UPS. It is observed that the HOMO level in fullerene shifts to lower binding energy. The XPS results show a strong initial shift of core levels to lower binding energy in the perovskite, which indicates that electrons transfer from the perovskitefilm to fullerene molecules. Further deposition of fullerene forms C60 solid, accompanied by the reduction of the electron transfer. As a result, the strongest electron transfer happened at 1/4 monolayer of fullerene.

  5. Optical characterization of voltage-accelerated degradation in CH3sub>NH3sub>PbI3sub> perovskite solar cells.

    PubMed

    Handa, Taketo; Tex, David M; Shimazaki, Ai; Aharen, Tomoko; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2016-05-16

    We investigate the performance degradation mechanism of CH3sub>NH3sub>PbI3sub> perovskite solar cells under bias voltage in air and nitrogen atmospheres using photoluminescence and electroluminescence techniques. When applying forward bias, the power conversion efficiency of the solar cells decreased significantly in air, but showed no degradation in nitrogen atmosphere. Time-resolved photoluminescence measurements on these devices revealed that the application of forward bias in air accelerates the generation of non-radiative recombination centers in the perovskite layer buried in the device. We found a negative correlation between the electroluminescence intensity and the injected current intensity in air. The irreversible change of the perovskite grain surface in air initiates the degradation of the perovskite solar cells. PMID:27409964

  6. Low Surface Recombination Velocity in Solution-Grown CH3sub>NH3sub>PbBr3sub> Perovskite Single Crystal

    SciTech Connect

    Yang, Ye; Yan, Yong; Yang, Mengjin; Choi, Sukgeun; Zhu, Kai; Luter, Joseph M.; Beard, Matthew C.

    2015-08-06

    Organic-inorganic hybrid perovskites are attracting intense research effort due to their impressive performance in solar cells. While the carrier transport parameters such as mobility and bulk carrier lifetime shows sufficient characteristics, the surface recombination, which can have major impact on the solar cell performance, has not been studied. Here we measure surface recombination dynamics in CH3sub>NH3sub>PbBr3sub> perovskite single crystals using broadband transient reflectance spectroscopy. The surface recombination velocity is found to be 3.4±0.1 103 cm s-1, B2–3 orders of magnitude lower than that in many important unpassivated semiconductors employed in solar cells. Our result suggests that the planar grain size for the perovskite thin films should be larger thanB30 mm to avoid the influence of surface recombination on the effective carrier lifetime.

  7. Synthesis, Crystal and Electronic Structures of the Pnictides AE3sub>TrPn3sub> (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

    SciTech Connect

    Stoyko, Stanislav; Voss, Leonard; He, Hua; Bobev, Svilen

    2015-09-24

    New ternary arsenides AE3sub>TrAs3sub> (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr3sub>GaP3sub> and Ba3sub>AlP3sub> have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr3sub>AlAs3sub> and Ba3sub>AlAs3sub> adopt the Ba3sub>AlSb3sub>-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr3sub>GaP3sub> and Ba3sub>AlP3sub>. Likewise, the compounds Sr3sub>GaAs3sub> and Ba3sub>GaAs3sub> crystallize with the Ba3sub>GaSb3sub>-type structure (Pearson symbol oP56, space group Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn4 and GaPn4 tetrahedra (Pn = pnictogen, i.e., P or As), separated by the alkaline-earth Sr2+ and Ba2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE2+]3sub>[Tr3+][Pn3-]3sub>, or rather [AE2+]6[Tr2Pn6]12-, i.e., as Zintl phases.

  8. Transparent Conducting Properties of SrSnO3sub> and ZnSnO3sub>

    SciTech Connect

    Ong, Khuong P.; Fan, Xiaofeng; Subedi, Alaska; Sullivan, Michael B.; Singh, David J.

    2015-04-29

    We report optical properties of doped n-type SrSnO3sub> and ZnSnO3sub> in relation to potential application as transparent conductors. We find that the orthorhombic distortion of the perovskite structure in SrSnO3sub> leads to absorption in the visible as the doping level is increased. This arises from interband transitions. We find that strain tuning could modify this absorption, but does not eliminate it. On the other hand, we find that ZnSnO3sub> although also having a non-cubic structure, can retain excellent transparency when doped, making it a good candidate transparent conductor.

  9. Electron attachment to Ni(PF{sub 3}){sub 4} and Pt(PF{sub 3}){sub 4}

    SciTech Connect

    Friedman, Jeffrey F.; Miller, Thomas M.; Friedman-Schaffer, Jessica K.; Rekha, G. K.; Stevens, Amy E.; Viggiano, A. A

    2008-03-14

    An experimental study has been made of thermal electron attachment to the transition-metal trifluorophosphine complexes Ni(PF{sub 3}){sub 4} and Pt(PF{sub 3}){sub 4} using a flowing-afterglow Langmuir-probe apparatus. Both complexes are efficient at electron attachment, although the rate constants are somewhat less than collisional. The rate constant for electron attachment to Ni(PF{sub 3}){sub 4} is 1.9x10{sup -7} cm{sup 3} s{sup -1} at room temperature, about a factor of 2 less than collisional. The activation energy is 39{+-}5 meV for the attachment reaction. The rate constant for electron attachment to Pt(PF{sub 3}){sub 4} is 5.4x10{sup -8} cm{sup 3} s{sup -1} at room temperature, and the activation energy is 84{+-}8 meV. For both complexes, a PF{sub 3} ligand is lost on electron attachment, and only the M(PF{sub 3}){sub 3}{sup -} ion is observed in the negative-ion mass spectrum. Density functional calculations were carried out on Ni(PF{sub 3}){sub 4} and various fragments in order to describe the thermochemistry of the attachment reaction.

  10. Mechanism of the H+O3sub> reaction

    SciTech Connect

    Chen, Maynard M. L.; Wetmore, Ross W.; Schaefer, III, Henry F.

    1981-03-01

    The H+O3sub> reaction has played an important role in the evolution of modern chemical kinetics. We investigate certain aspects of the HO3sub> potential energy hypersurface using nonempirical molecular electronic structure theory. For the qualitative purposes of the present study, most wave functions were of the self-consistent-field (SCF) variety, constructed from a double zeta basis set of contracted Gaussian functions. Two low energy pathways were established for the reaction. The first involves a coplanar transition state with a nearly linear H–O–O arrangement. The second possible mechanism allows the hydrogen atom to descend perpendicularly upon the ozone molecule. Finally, the two mechanisms are evaluated in light of the current experimental understanding of the H+O3sub>reaction.

  11. Oxygen octahedral distortions in LaMO3sub>/SrTiO3sub> superlattices

    SciTech Connect

    Sanchez-Santolino, Gabriel; Cabero, Mariona; Varela, Maria; Garcia-Barriocanal, Javier; Leon, Carlos; Pennycook, Stephen J.; Santamaria, Jacobo

    2014-04-24

    Here we study the interfaces between the Mott insulator LaMnO3sub> (LMO) and the band insulator SrTiO3sub> (STO) in epitaxially grown superlattices with different thickness ratios and different transport and magnetic behaviors. Using atomic resolution electron energy-loss spectrum imaging, we analyze simultaneously the structural and chemical properties of these interfaces. We find changes in the oxygen octahedral tilts within the LaMnO3sub> layers when the thickness ratio between the manganite and the titanate layers is varied. Superlattices with thick LMO and ultrathin STO layers present unexpected octahedral tilts in the STO, along with a small amount of oxygen vacancies. On the other hand, thick STO layers exhibit undistorted octahedra while the LMO layers present reduced O octahedral distortions near the interfaces. In conclusion, these findings will be discussed in view of the transport and magnetic differences found in previous studies.

  12. Neutrino masses in supersymmetric SU(3){sub c} x SU(3){sub L} x U(1){sub X} models

    SciTech Connect

    Rodriguez, J-Alexis; Duarte, J.

    2008-11-23

    The mass spectra and the superpotential of two different supersymetric models based on the gauge symmetry SU(3){sub C} x SU(3){sub L} x U(1){sub X}(331) without any exotic charges assigned to the fermionic spectra are studied. These two models have three families in different representations of the gauge group. In these kind of models, the diagonalization of the neutralino mass matrix allows that three light neutrinos get different mass values. Possible values for the neutrino masses are calculated covering the parameter space of the models. These values have to agree with the available data coming from the neutrino oscillations experiments. Therefore, a reduced space of parameters for the superpotential and the vacuum expectation values allowed in the framework of the 331 supersymetric models can be obtained.

  13. Electron-hole diffusion lengths >175 μm in solution-grown CH3sub>NH3sub>PbI3sub> single crystals

    SciTech Connect

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; Mulligan, Padhraic; Qiu, Jie; Cao, Lei; Huang, Jinsong

    2015-02-27

    Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3sub>NH3sub>PbI3sub> are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3sub>NH3sub>PbI3sub> single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm–2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals than in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH3sub>NH3sub>PbI3sub> in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.

  14. Synthesis and structure of In(IO{sub 3}){sub 3} and vibrational spectroscopy of M(IO{sub 3}){sub 3} (M=Al, Ga, In)

    SciTech Connect

    Ngo, Nhan; Kalachnikova, Katrina; Assefa, Zerihun; Haire, Richard G.; Sykora, Richard E. . E-mail: rsykora@jaguar1.usouthal.edu

    2006-12-15

    The reaction of Al, Ga, or In metals and H{sub 5}IO{sub 6} in aqueous media at 180{sup o}C leads to the formation of Al(IO{sub 3}){sub 3}, Ga(IO{sub 3}){sub 3,} or In(IO{sub 3}){sub 3}, respectively. Single-crystal X-ray diffraction experiments have shown In(IO{sub 3}){sub 3} contains the Te{sub 4}O{sub 9}-type structure, while both Al(IO{sub 3}){sub 3} and Ga(IO{sub 3}){sub 3} are known to exhibit the polar Fe(IO{sub 3}){sub 3}-type structure. Crystallographic data for In(IO{sub 3}){sub 3}, trigonal, space group R3-bar , a=9.7482(4)A, c=14.1374(6)A, V=1163.45(8) Z=6, R(F)=1.38% for 41 parameters with 644 reflections with I>2{sigma}(I). All three iodate structures contain group 13 metal cations in a distorted octahedral coordination environment. M(IO{sub 3}){sub 3} (M=Al, Ga) contain a three-dimensional network formed by the bridging of Al{sup 3+} or Ga{sup 3+} cations by iodate anions. With In(IO{sub 3}){sub 3}, iodate anions bridge In{sup 3+} cations in two-dimensional layers. Both materials contain distorted octahedral holes in their structures formed by terminal oxygen atoms from the iodate anions. The Raman spectra have been collected for these metal iodates; In(IO{sub 3}){sub 3} was found to display a distinctively different vibrational profile than Al(IO{sub 3}){sub 3} or Ga(IO{sub 3}){sub 3}. Hence, the Raman profile can be used as a rapid diagnostic tool to discern between the different structural motifs.

  15. Growth and characterization of acentric BaHf(BO{sub 3}){sub 2} and BaZr(BO{sub 3}){sub 2}

    SciTech Connect

    Mączka, Mirosław; Szymborska-Małek, Katarzyna; Gągor, Anna; Majchrowski, Andrzej

    2015-05-15

    Growth, single crystal X-ray diffraction, polarized Raman and infrared (IR) studies of BaHf(BO{sub 3}){sub 2} are presented. Raman and IR spectra of polycrystalline BaZr(BO{sub 3}){sub 2} are also reported to facilitate assignment of modes. BaHf(BO{sub 3}){sub 2} borate crystallizes in trigonal system, space group R3c, with lattice parameters: a=5.1540(4) Å, c=33.901(3) Å. It accommodates dolomite-like structure doubled in the c direction, which is built of alternating layers of HfO{sub 6} octahedra and BaO{sub 6} distorted trigonal prisms that are connected through borate groups. The obtained structural as well as spectroscopic data show that BaHf(BO{sub 3}){sub 2} is isostructural with BaZr(BO{sub 3}){sub 2} and the deviations from centrosymmetry is small. - Graphical abstract: Arrangement of BO{sub 3} groups in BaHf(BO{sub 3}){sub 2} along the c direction in one unit cell. Dark and light blue denote different borate groups. - Highlights: • BaHf(BO{sub 3}){sub 2} single crystals were grown. • X-ray diffraction showed that this borate crystallizes in the acentric R3c structure. • Raman and IR spectra were measured for BaHf(BO{sub 3}){sub 2} and BaZr(BO{sub 3}){sub 2}, respectively. • Assignment of modes is proposed.

  16. Octonary resistance states in La0.7Sr0.3sub>MnO3sub>/BaTiO3sub>/La0.7Sr0.3sub>MnO3sub> multiferroic tunnel junctions

    SciTech Connect

    Yue -Wei Yin; Tao, Jing; Huang, Wei -Chuan; Liu, Yu -Kuai; Yang, Sheng -Wei; Dong, Si -Ning; Zhu, Yi -Mei; Li, Qi; Li, Xiao -Guang

    2015-10-06

    General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La0.7Sr0.3sub>MnO3sub>/BaTiO3sub>/La0.7Sr0.3sub>MnO3sub> junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ shows at least two other stable noncollinear (45° and 90°) magnetic configurations. As a result, combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO3sub> barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.

  17. Gold-rich R3sub>Au7Sn3sub>: Establishing the interdependence between electronic features and physical properties

    SciTech Connect

    Provino, Alessia; Steinberg, Simon; Smetana, Volodymyr; Kulkarni, Ruta; Dhar, Sudesh K.; Manfrinetti, Pietro; Mudring, Anja -Verena

    2015-05-18

    Two new polar intermetallic compounds Y3sub>Au7Sn3sub> (I) and Gd3sub>Au7Sn3sub> (II) have been synthesized and their structures have been determined by single crystal X-ray diffraction (P63sub>/m; Z = 2, a = 8.148(1)/8.185(3), and c = 9.394(2)/9.415(3) for I/II, respectively). They can formally be assigned to the Cu10Sn3sub> type and consist of parallel slabs of Sn centered, edge-sharing trigonal Au6 antiprisms connected through R3sub> (R = Y, Gd) triangles. Additional Au atoms reside in the centres of trigonal Au6 prisms forming Au@Au6 clusters with Au–Au distances of 2.906–2.960 Å, while the R–R contacts in the R3sub> groups are considerably larger than the sums of their metallic radii. These exclusive structural arrangements provide alluring systems to study the synergism between strongly correlated systems, particularly, those in the structure of (II), and extensive polar intermetallic contacts, which has been inspected by measurements of the magnetic properties, heat capacities and electrical conductivities of both compounds. Gd3sub>Au7Sn3sub> shows an antiferromagnetic ordering at 13 K, while Y3sub>Au7Sn3sub> is a Pauli paramagnet and a downward curvature in its electrical resistivity at about 1.9 K points to a superconducting transition. DFT-based band structure calculations on R3sub>Au7Sn3sub> (R = Y, Gd) account for the results of the conductivity measurements and different spin ordering models of (II) provide conclusive hints about its magnetic structure. As a result, chemical bonding analyses of both compounds indicate that the vast majority of bonding originates from the heteroatomic Au–Gd and Au–Sn interactions, while homoatomic Au–Au bonding is evident within the Au@Au6 clusters.

  18. Structurally induced magnetization in a La2/3sub>Sr4/3sub>MnO4 superlattice

    SciTech Connect

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

    2012-03-16

    A structural transition has been observed in a digital superlattice of La2/3sub>Sr4/3sub>MnO4, 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 L2,3sub> 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 La2/3sub>Sr4/3sub>MnO4 supperlattice.

  19. Test results of a Nb3sub>Al/Nb3sub>Sn subscale magnet for accelerator application

    SciTech Connect

    Iio, Masami; Xu, Qingjin; Nakamoto, Tatsushi; Sasaki, Ken -ichi; Ogitsu, Toru; Yamamoto, Akira; Kimura, Nobuhiro; Tsuchiya, Kiyosumi; Sugano, Michinaka; Enomoto, Shun; Higashi, Norio; Terashima, Akio; Tanaka, Kenichi; Okada, Ryutaro; Takahashi, Naoto; Ikemoto, Yukiko; Kikuchi, Akihiro; Takeuchi, Takao; Sabbi, Gianluca; Zlobin, Alexander; Barzi, Emanuela

    2015-01-28

    The High Energy Accelerator Research Organization (KEK) has been developing a Nb3sub>Al and Nb3sub>Sn subscale magnet to establish the technology for a high-field accelerator magnet. The development goals are a feasibility demonstration for a Nb3sub>Al cable and the technology acquisition of magnet fabrication with Nb3sub>Al superconductors. KEK developed two double-pancake racetrack coils with Rutherford-type cables composed of 28 Nb3sub>Al wires processed by rapid heating, quenching, and transformation in collaboration with the National Institute for Materials Science and the Fermi National Accelerator Laboratory. The magnet was fabricated to efficiently generate a high magnetic field in a minimum-gap common-coil configuration with two Nb3sub>Al coils sandwiched between two Nb3sub>Sn coils produced by the Lawrence Berkeley National Laboratory. A shell-based structure and a “bladder and key” technique have been used for adjusting coil prestress during both the magnet assembly and the cool down. In the first excitation test of the magnet at 4.5 K performed in June 2014, the highest quench current of the Nb3sub>Sn coil, i.e., 9667 A, was reached at 40 A/s corresponding to 9.0 T in the Nb3sub>Sn coil and 8.2 T in the Nb3sub>Al coil. The quench characteristics of the magnet were studied.

  20. Gold-rich R3sub>Au7Sn3sub>: Establishing the interdependence between electronic features and physical properties

    SciTech Connect

    Provino, Alessia; Steinberg, Simon; Smetana, Volodymyr; Kulkarni, Ruta; Dhar, Sudesh K.; Manfrinetti, Pietro; Mudring, Anja -Verena

    2015-05-18

    Two new polar intermetallic compounds Y3sub>Au7Sn3sub> (I) and Gd3sub>Au7Sn3sub> (II) have been synthesized and their structures have been determined by single crystal X-ray diffraction (P63/m; Z = 2, a = 8.148(1)/8.185(3), and c = 9.394(2)/9.415(3) for I/II, respectively). They can formally be assigned to the Cu10Sn3sub> type and consist of parallel slabs of Sn centered, edge-sharing trigonal Au6 antiprisms connected through R3sub> (R = Y, Gd) triangles. Additional Au atoms reside in the centres of trigonal Au6 prisms forming Au@Au6 clusters with Au–Au distances of 2.906–2.960 Å, while the R–R contacts in the R3sub> groups are considerably larger than the sums of their metallic radii. These exclusive structural arrangements provide alluring systems to study the synergism between strongly correlated systems, particularly, those in the structure of (II), and extensive polar intermetallic contacts, which has been inspected by measurements of the magnetic properties, heat capacities and electrical conductivities of both compounds. Gd3sub>Au7Sn3sub> shows an antiferromagnetic ordering at 13 K, while Y3sub>Au7Sn3sub> is a Pauli paramagnet and a downward curvature in its electrical resistivity at about 1.9 K points to a superconducting transition. DFT-based band structure calculations on R3sub>Au7Sn3sub> (R = Y, Gd) account for the results of the conductivity measurements and different spin ordering models of (II) provide conclusive hints about its magnetic structure. As a result, chemical bonding analyses of both compounds indicate that the vast majority of bonding originates from the heteroatomic Au–Gd and Au–Sn interactions, while homoatomic Au–Au bonding is evident within the Au@Au6 clusters.

  1. Electronic structure, irreversibility line and magnetoresistance of Cu0.3sub>Bi2Se3sub> superconductor

    SciTech Connect

    Hemian, Yi; Gu, Genda; Chen, Chao -Yu; Sun, Xuan; Xie, Zhuo -Jin; Feng, Ya; Liang, Ai -Ji; Peng, Ying -Ying; He, Shao -Long; Zhao, Lin; Liu, Guo -Dong; Dong, Xiao -Li; Zhang, Jun; Chen, Chuang -Tian; Xu, Zu -Yan; Zhou, X. -J.

    2015-06-01

    CuxBi2Se3sub> is a superconductor that is a potential candidate for topological superconductors. We report our laser-based angle-resolved photoemission measurement on the electronic structure of the CuxBi2Se3sub> superconductor, and a detailed magneto-resistance measurement in both normal and superconducting states. We find that the topological surface state of the pristine Bi2Se3sub> topological insulator remains robust after the Cu-intercalation, while the Dirac cone location moves downward due to electron doping. Detailed measurements on the magnetic field-dependence of the resistance in the superconducting state establishes an irreversibility line and gives a value of the upper critical field at zero temperature of ~4000 Oe for the Cu0.3sub>Bi2Se3sub> superconductor with a middle point Tc of 1.9K. The relation between the upper critical field Hc2 and temperature T is different from the usual scaling relation found in cuprates and in other kinds of superconductors. Small positive magneto-resistance is observed in Cu0.3sub>Bi2Se3sub> superconductors up to room temperature. As a result, these observations provide useful information for further study of this possible candidate for topological superconductors.

  2. From thermoelectric bulk to nanomaterials: Current progress for Bi 2 Te 3sub> and CoSb 3sub>: From thermoelectric bulk to nanomaterials

    SciTech Connect

    Peranio, N.; Eibl, O.; Bäßler, S.; Nielsch, K.; Klobes, B.; Hermann, R. P.; Daniel, M.; Albrecht, M.; Görlitz, H.; Pacheco, V.; Bedoya-Martínez, N.; Hashibon, A.; Elsässer, C.

    2015-10-29

    We synthesized Bi2Te3sub> and CoSb3sub> based nanomaterials and their thermoelectric, structural, and vibrational properties analyzed to assess and reduce ZT-limiting mechanisms. The same preparation and/or characterization methods were applied in the different materials systems. Single-crystalline, ternary p-type Bi15Sb29Te56, and n-type Bi38Te55Se7 nanowires with power factors comparable to nanostructured bulkmaterialswere prepared by potential-pulsed electrochemical deposition in a nanostructured Al2O3sub> matrix. p-type Sb2Te3sub>, n-type Bi2Te3sub>, and n-type CoSb3sub> thin films were grown at room temperature using molecular beam epitaxy and were subsequently annealed at elevated temperatures. It yielded polycrystalline, single phase thin films with optimized charge carrier densities. In CoSb3sub> thin films the speed of sound could be reduced by filling the cage structure with Yb and alloying with Fe yielded p-type material. Bi2(Te0.91Se0.09)3sub>/SiC and (Bi0.26Sb0.74)2Te3sub>/SiC nanocomposites with low thermal conductivities and ZT values larger than 1 were prepared by spark plasma sintering. Nanostructure, texture, chemical composition, as well as electronic and phononic excitations were investigated by X-ray diffraction, nuclear resonance scattering, inelastic neutron scattering, M ossbauer spectroscopy, and transmission electron microscopy. Furthermore, for Bi2Te3sub> materials, ab-initio calculations together with equilibrium and non-equilibrium molecular dynamics simulations for point defects yielded their formation energies and their effect on lattice thermal conductivity, respectively. Current advances in thermoelectric Bi2Te3sub> and CoSb3sub> based nanomaterials are

  3. Electric-field-induced linear birefringence in TmAl3sub>(BO3sub>)4.

    PubMed

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

    2016-04-20

    The linear birefringence induced by the electric field was first detected in a TmAl3sub>(BO3sub>)4 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

  4. Thermodynamic Properties of α-Fe2O3sub> and Fe3sub>O4 Nanoparticles

    SciTech Connect

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

    2015-04-21

    Here we comprehansively assessed the thermodynamic properties of hydrated α-Fe2O3sub> (hematite) and Fe3sub>O4 (magnetite) nanoparticles. In addition to 9 nm Fe3sub>O4, three α-e2O3sub>nanoparticles samples of different sizes (11, 14, and 25 nm) and bulk α-e2O3sub> 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-e2O3sub> 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.

  5. Origin and elimination of photocurrent hysteresis by fullerene passivation in CH3sub>NH3sub>PbI3sub> planar heterojunction solar cells

    SciTech Connect

    Shao, Yuchuan; Xiao, Zhengguo; Bi, Cheng; Yuan, Yongbo; Huang, Jinsong

    2014-12-15

    The large photocurrent hysteresis observed in many organometal trihalide perovskite solar cells has become a major hindrance impairing the ultimate performance and stability of these devices, while its origin was unknown. Here we demonstrate the trap states on the surface and grain boundaries of the perovskite materials to be the origin of photocurrent hysteresis and that the fullerene layers deposited on perovskites can effectively passivate these charge trap states and eliminate the notorious photocurrent hysteresis. Fullerenes deposited on the top of the perovskites reduce the trap density by two orders of magnitude and double the power conversion efficiency of CH3sub>NH3sub>PbI3sub> solar cells. As a result, the elucidation of the origin of photocurrent hysteresis and its elimination by trap passivation in perovskite solar cells provides important directions for future enhancements to device efficiency.

  6. Method of preparing (CH.sub.3).sub.3 SiNSO and byproducts thereof

    DOEpatents

    Spicer, Leonard D.; Bennett, Dennis W.; Davis, Jon F.

    1984-01-01

    (CH.sub.3).sub.3 SiNSO is produced by the reaction of ((CH.sub.3).sub.3 Si).sub.2 NH with SO.sub.2. Also produced in the reaction are ((CH.sub.3).sub.3 Si).sub.2 O and a new solid compound [NH.sub.4 ][(CH.sub.3).sub.3 SiOSO.sub.2 ]. Both (CH.sub.3).sub.3 SiNSO and [NH.sub.4 ][(CH.sub.3).sub.3 SiOSO.sub.2 ] have fluorescent properties. The reaction of the subject invention is used in a method of measuring the concentration of SO.sub.2 pollutants in gases. By the method, a sample of gas is bubbled through a solution of ((CH.sub.3).sub.3 Si).sub.2 NH, whereby any SO.sub.2 present in the gas will react to produce the two fluorescent products. The measured fluorescence of these products can then be used to calculate the concentration of SO.sub.2 in the original gas sample. The solid product [NH.sub.4 ][(CH.sub.3).sub.3 SiOSO.sub.2 ] may be used as a standard in solid state NMR spectroscopy.

  7. Interfacial dislocations in (111) oriented (Ba0.7Sr0.3sub>)TiO3sub> films on SrTiO3sub> single crystal

    SciTech Connect

    Shen, Xuan; Yamada, Tomoaki; Lin, Ruoqian; Kamo, Takafumi; Funakubo, Hiroshi; Wu, Di; Xin, Huolin L.; Su, Dong

    2015-10-08

    In this study, we have investigated the interfacial structure of epitaxial (Ba,Sr)TiO3sub> films grown on (111)-oriented SrTiO3sub> single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a<110> comprised of a misfit dislocation along <112>, and threading dislocations along <110> or <100>. The misfit dislocation with Burgers vector of a <110> can dissociate into two ½ a <110> partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrieved the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba0.7Sr0.3sub>)TiO3sub> films.

  8. Synthesis and crystal structures of nitratocobaltates Na{sub 2}[Co(NO{sub 3}){sub 4}], K{sub 2}[Co(NO{sub 3}){sub 4}], and Ag[Co(NO{sub 3}){sub 3}] and potassium nitratonickelate K{sub 2}[Ni(NO{sub 3}){sub 4}

    SciTech Connect

    Morozov, I. V. Fedorova, A. A.; Albov, D. V.; Kuznetsova, N. R.; Romanov, I. A.; Rybakov, V. B.; Troyanov, S. I.

    2008-03-15

    The cobalt(II) and nickel(II) nitrate complexes with an island structure (Na{sub 2}[Co(NO{sub 3}){sub 4}] (I) and K{sub 2}[Co(NO{sub 3}){sub 4}] (II)] and a chain structure [Ag[Co(NO{sub 3}){sub 3}] (III) and K{sub 2}[Ni(NO{sub 3}){sub 4}] (IV)] are synthesized and investigated using X-ray diffraction. In the anionic complex [Co(NO{sub 3}){sub 4}]{sup 2-} of the crystal structure of compound I, the Co coordination polyhedron is a twisted tetragonal prism formed by the O atoms of four asymmetric bidentate nitrate groups. In the anion [Co(NO{sub 3}){sub 4}]{sup 2-} of the crystal structure of compound II, one of the four NO{sub 3} groups is monodentate and the other NO{sub 3} groups are bidentate (the coordination number of the cobalt atom is equal to seven, and the cobalt coordination polyhedron is a monocapped trigonal prism). The crystal structures of compounds III and IV contain infinite chains of the compositions [Co(NO{sub 3}){sub 2}(NO{sub 3}){sub 2/2}]{sup -} and [Ni(NO{sub 3}){sub 3}(NO{sub 3}){sub 2/2}]{sup 2-}, respectively. In the crystal structure of compound III, seven oxygen atoms of one monodentate and three bidentate nitrate groups form a dodecahedron with an unoccupied vertex of the A type around the Co atom. In the crystal structure of compound IV, the octahedral polyhedron of the Ni atom is formed by five nitrate groups, one of which is terminal bidentate. The data on the structure of Co(II) coordination polyhedra in the known nitratocobaltates are generalized.

  9. Advanced Nodal P3sub>/SP3sub> Axial Transport Solvers for the MPACT 2D/1D Scheme

    SciTech Connect

    Stimpson, Shane G; Collins, Benjamin S

    2015-01-01

    As part of its initiative to provide multiphysics simulations of nuclear reactor cores, the Consortium for Advanced Simulation of Light Water Reactors (CASL) is developing the Virtual Environment for Reactor Applications Core Simulator (VERA-CS). The MPACT code, which is the primary neutron transport solver of VERA-CS, employs the two-dimensional/one-dimensional (2D/1D) method to solve 3-dimensional neutron transport problems and provide sub-pin-level resolution of the power distribution. While 2D method of characteristics is used to solve for the transport effects within each plane, 1D-nodal methods are used axially. There have been extensive studies of the 2D/1D method with a variety nodal methods, and the P3sub>/SP3sub> solver has proved to be an effective method of providing higher-fidelity solutions while maintaining a low computational burden.The current implementation in MPACT wraps a one-node nodal expansion method (NEM) kernel for each moment, iterating between them and performing multiple sweeps to resolve flux distributions. However, it has been observed that this approach is more sensitive to convergence problems. This paper documents the theory and application two new nodal P3sub>/SP3sub> approaches to be used within the 2D/1D method in MPACT. These two approaches aim to provide enhanced stability compared with the pre-existing one-node approach. Results from the HY-NEM-SP3sub> solver show that the accuracy is consistent with the one-node formulations and provides improved convergence for some problems; but the solver has issues with cases in thin planes. Although the 2N-SENM-SP3sub> solver is still under development, it is intended to resolve the issues with HY-NEM-SP3sub> but it will incur some additional computational burden by necessitating an additional 1D-CMFD-P3sub> solver to generate the second moment cell-averaged scalar flux.

  10. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3sub> Fe3sub>Al, Co3sub>Al, and Ni3sub>Al based intermetallic phases

    SciTech Connect

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternary alloying additions in DO3sub> Fe3sub>Al, Co3sub>Al and Ni3sub>Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO3sub> lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe3sub>Al and Co3sub>Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.

  11. Pressure dependence of the monoclinic phase in (1–x)Pb(Mg1/3sub>Nb2/3sub>)O3sub>-xPbTiO₃ solid solutions

    SciTech Connect

    Ahart, Muhtar; Sinogeikin, Stanislav; Shebanova, Olga; Ikuta, Daijo; Ye, Zuo-Guang; Mao, Ho-kwang; Cohen, R. E.; Hemley, Russell J.

    2012-12-26

    We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopy to investigate a series of (1–x)Pb(Mg1/3sub>Nb2/3sub>)O3sub>-xPbTiO₃ (PMN-xPT) solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a peak centered at 380 cm⁻¹ starting above 6 GPa for all samples, in agreement with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition; we find that the triplet at the pseudocubic (220) Bragg peak merges into a doublet above 6 GPa. Our results indicate that the morphotropic phase boundary region (x=0.33–0.37) with the presence of monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed using a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappear at a modest pressure of 3 GPa. We propose a pressure-composition phase diagram for PMN-xPT solid solutions.

  12. Addition of CFCl3sub> to Aromatic Aldehydes via in Situ Grignard Reaction

    SciTech Connect

    Barkakaty, Balaka; Talukdar, Bandana; Lokitz, Bradley

    2015-08-18

    In the case of synthetic modification of trichlorofluoromethane (CFCl3sub>) to non-volatile and useful fluorinated precursors, we realized that it is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In our report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl3sub> for synthesis of dichlorofluoromethyl aromatic alcohols.

  13. Onset of metallic behavior in strained (LaNiO{sub 3}){sub + n}/(SrMnO{sub 3}){sub 2} superlattices.

    SciTech Connect

    May, S. J.; Santos, T. S.; Bhattacharya, A.

    2009-03-01

    (LaNiO{sub 3}){sub n}/(SrMnO{sub 3}){sub 2} superlattices were grown using ozone-assisted molecular beam epitaxy. In situ reflection high-energy electron diffraction and x-ray scattering has been used to characterize the structural properties of the superlattices, which are strained to the SrTiO{sub 3} substrates. The superlattices exhibit excellent crystallinity and interfacial roughness of less than 1 unit cell. A metal-insulator transition is observed as n is decreased from 4 to 1. Analysis of the transport data suggests an evolution from gapped insulator (n=1) to hopping conductor (n=2) to metal (n=4) with increasing LaNiO{sub 3} concentration.

  14. Structure determination and optical properties of CsSm(PO{sub 3}){sub 4}

    SciTech Connect

    Ben Hassen, N.; Ferhi, M. Horchani-Naifer, K.; Férid, M.

    2015-03-15

    Graphical abstract: Projection of the CsSm(PO{sub 3}){sub 4} structure viewing along the a axis. - Highlights: • Single crystal of a new polyphosphate CsSm(PO{sub 3}){sub 4} has been synthesized. • The obtained compound has been characterized by several techniques. • The crystal structure of CsSm(PO{sub 3}){sub 4} has been resolved. • Spectroscopic properties of Sm{sup 3+} in CsSm(PO{sub 3}){sub 4} have been performed. - Abstract: A new alkali metal-rare earth polyphosphate CsSm(PO{sub 3}){sub 4} has been synthesized by flux method. The obtained compound has been characterized by means of single crystal X-ray diffraction, Fourier transform infrared (FTIR) and Raman scattering spectroscopies. It crystallizes in the monoclinic space group P2{sub 1}/n with the following unit-cell parameters: a = 10.382(2), b = 8.978(6), c = 11.205(4) Å, β = 106.398(3)° and Z = 4. The structure of CsSm(PO{sub 3}){sub 4} is an infinite three-dimensional framework made up of double spiral (PO{sub 3}){sub n} chains linked with neighboring SmO{sub 8} and CsO{sub 11} polyhedra. Spectroscopic properties of Sm{sup 3+} in this new compound including excitation, emission, and kinetic measurement have been performed. The emission spectrum shows four transitions characteristics of Sm{sup 3+} in the orange–red region by excitation wavelength at 400 nm. The decay time curve of {sup 4}G{sub 5/2} → {sup 6}H{sub 7/2} transition has been also registered and fitted to a single exponential function.

  15. Induced Ferromagnetism at BiFeO3sub>/YBa2Cu3sub>O7 Interfaces

    SciTech Connect

    Zhu, Jian-Xin; Wen, Xiao-Dong; Haraldsen, J. T.; He, Mi; Panagopoulos, C.; Chia, Elbert E. M.

    2014-06-20

    We report that transition metal oxides (TMOs) exhibit many emergent phenomena ranging from high-temperature superconductivity and giant magnetoresistance to magnetism and ferroelectricity. In addition, when TMOs are interfaced with each other, new functionalities can arise, which are absent in individual components. Here, we report results from first-principles calculations on the magnetism at the BiFeO3sub>/YBa2Cu3sub>O7 interfaces. By comparing the total energy for various magnetic spin configurations inside BiFeO3sub>, we are able to show that a metallic ferromagnetism is induced near the interface. We further develop an interface exchange-coupling model and place the extracted exchange coupling interaction strengths, from the first-principles calculations, into a resultant generic phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the presence of a hysteresis loop in field-dependent magnetization data. Lastly, the emergence of interfacial ferromagnetism should have implications to electronic and transport properties.

  16. Electronic and Magnetic Properties of Epitaxial Perovskite SrCrO3sub>(001)

    SciTech Connect

    Zhang, K. H. L.; Du, Y.; Sushko, P. V.; Bowden, M. E.; Shutthanandan, V.; Qiao, L.; Cao, G. X.; Gai, Z.; Sallis, S.; Piper, L. F. J.; Chambers, S. A.

    2015-06-03

    We investigated the intrinsic properties of SrCrO3sub> epitaxial thin films synthesized by molecular beam epitaxy. We found compelling evidence that SrCrO3sub> is a correlated metal. X-ray photoemission valence band and O K-edge x-ray absorption spectra indicate a strongly hybridized Cr3sub>d–O2p state crossing the Fermi level, leading to metallic behavior. Furthermore, a comparison between valence band spectra near the Fermi level and the densities of states calculated using density functional theory (DFT) suggests the presence of coherent and incoherent states and points to strong electron correlation effects. The magnetic susceptibility can be described by Pauli paramagnetism at temperatures above 100 K, but reveals antiferromagnetic behavior at lower temperatures, possibly resulting from orbital ordering.

  17. Field-dependent magnetization of BiFeO3sub> in ultrathin La0.7Sr0.3sub>MnO3sub>/BiFeO3sub> superlattice

    SciTech Connect

    Fitzsimmons, Michael R.; Jia, Quanxi X.; Singh, Surendra; Chen, A. P.; Xiong, J.

    2015-12-02

    We report the observation of field-induced magnetization of BiFeO3sub> (BFO) in an ultrathin La0.7Sr0.3sub>MnO3sub> (LSMO)/BFO superlattice using polarized neutron reflectivity (PNR). The depth dependent structure and magnetic characterization of subnano layer thick (thickness ~ 0.7 nm each) LSMO/BFO hetrostructure is carried out using X-ray reflectivity and PNR techniques. Our PNR results indicate parallel alignment of magnetization as well as enhancement in magnetic moment across LSMO/BFO interfaces. The study showed an increase in average magnetization on increasing applied magnetic field at 10K. As a result, we observed a saturation magnetization of 110 ± 15 kA/m (~0.8 μB/Fe) for ultrathin BFO layer (~2 unit cell) sandwiched between ultrathin LSMO layers (~ 2 unit cell).

  18. Thermo-magnetic instabilities in Nb3sub>Sn superconducting accelerator magnets

    SciTech Connect

    Bordini, Bernardo

    2006-09-01

    The advance of High Energy Physics research using circulating accelerators strongly depends on increasing the magnetic bending field which accelerator magnets provide. To achieve high fields, the most powerful present-day accelerator magnets employ NbTi superconducting technology; however, with the start up of Large Hadron Collider (LHC) in 2007, NbTi magnets will have reached the maximum field allowed by the intrinsic properties of this superconductor. A further increase of the field strength necessarily requires a change in superconductor material; the best candidate is Nb3sub>Sn. Several laboratories in the US and Europe are currently working on developing Nb3sub>Sn accelerator magnets, and although these magnets have great potential, it is suspected that their performance may be fundamentally limited by conductor thermo-magnetic instabilities: an idea first proposed by the Fermilab High Field Magnet group early in 2003. This thesis presents a study of thermo-magnetic instability in high field Nb3sub>Sn accelerator magnets. In this chapter the following topics are described: the role of superconducting magnets in High Energy Physics; the main characteristics of superconductors for accelerator magnets; typical measurements of current capability in superconducting strands; the properties of Nb3sub>Sn; a description of the manufacturing process of Nb3sub>Sn strands; superconducting cables; a typical layout of superconducting accelerator magnets; the current state of the art of Nb3sub>Sn accelerator magnets; the High Field Magnet program at Fermilab; and the scope of the thesis.

  19. Epitaxial growth of high quality WO3sub> thin films

    SciTech Connect

    Leng, X.; Pereiro, J.; Strle, J.; Bollinger, A. T.; Bozovic, I.

    2015-09-09

    We have grown epitaxial WO3sub> films on various single-crystal substrates using radio-frequency (RF) magnetron sputtering. While pronounced surface roughness is observed in films grown on LaSrAlO4 substrates, films grown on YAlO3sub> substrates show atomically flat surfaces, as demonstrated by atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements. The crystalline structure has been confirmed to be monoclinic by symmetric and skew-symmetric XRD. Furthermore, the dependence of the growth modes and the surface morphology on the lattice mismatch is discussed.

  20. Investigation of Bismuth Triiodide (BiI3sub>) for Photovoltaic Applications

    SciTech Connect

    Brandt, Riley E.; Kurchin, Rachel C.; Hoye, Robert L. Z.; Poindexter, Jeremy R.; Wilson, Mark W. B.; Sulekar, Soumitra; Lenahan, Frances; Yen, Patricia; Stevanovic, Vladan; Nino, Juan C.; Bawendi, Moungi G.; Buonassisi, Tonio

    2015-10-12

    We investigate bismuth triiodide (BiI3sub>) as a candidate thin-film photovoltaic (PV) absorber. BiI3sub> was chosen for its optical properties and the potential for “defect-tolerant” charge transport properties, which we test experimentally by measuring optical absorption and recombination lifetimes. We synthesize phase-pure BiI3sub> thin films by physical vapor transport and solution processing and single-crystals by an electrodynamic gradient vertical Bridgman method. The bandgap of these materials is ~1.8 eV, and they demonstrate room-temperature band-edge photoluminescence. We measure monoexponential recombination lifetimes in the range of 180–240 ps for thin films, and longer, multiexponential dynamics for single crystals, with time constants up to 1.3 to 1.5 ns. We discuss the outstanding challenges to developing BiI3sub> PVs, including mechanical and electrical properties, which can also inform future selection of candidate PV absorbers.

  1. Fragile structural transition in Mo3sub>Sb7

    SciTech Connect

    Yan, Jiaqiang -Q.; McGuire, Michael A; May, Andrew F; Parker, David S.; Mandrus, D. G.; Sales, Brian C.

    2015-08-10

    Mo3sub>Sb7 single crystals lightly doped with Cr, Ru, or Te are studied in order to explore the interplay between superconductivity, magnetism, and the cubic-tetragonal structural transition. The structural transition at 53 K is extremely sensitive to Ru or Te substitution which introduces additional electrons, but robust against Cr substitution. We observed no sign of a structural transition in superconducting Mo2.91Ru0.09Sb7 and Mo3sub>Sb6.975Te0.025. In contrast, 3 at.% Cr doping only slightly suppresses the structural transition to 48 K while leaving no trace of superconductivity above 1.8 K. Analysis of magnetic properties suggests that the interdimer interaction in Mo3sub>Sb7 is near a critical value and essential for the structural transition. Futhermore, all dopants suppress the superconductivity of Mo3sub>Sb7. The tetragonal structure is not necessary for superconductivity.

  2. Ferromagnetism of Fe3sub>Sn and alloys

    SciTech Connect

    Sales, Brian C.; Saparov, Bayrammurad; McGuire, Michael A.; Singh, David J.; Parker, David S.

    2014-11-12

    Hexagonal Fe3sub>Sn has many of the desirable properties for a new permanent magnet phase with a Curie temperature of 725 K, a saturation moment of 1.18 MA/m. and anisotropy energy, K1 of 1.8 MJ/m3. However, contrary to earlier experimental reports, we found both experimentally and theoretically that the easy magnetic axis lies in the hexagonal plane, which is undesirable for a permanent magnet material. One possibility for changing the easy axis direction is through alloying. We used first principles calculations to investigate the effect of elemental substitutions. The calculations showed that substitution on the Sn site has the potential to switch the easy axis direction. Transition metal substitutions with Co or Mn do not have this effect. We attempted synthesis of a number of these alloys and found results in accord with the theoretical predictions for those that were formed. However, the alloys that could be readily made all showed an in-plane easy axis. The electronic structure of Fe3sub>Sn is reported, as are some are magnetic and structural properties for the Fe3sub>Sn2, and Fe5Sn3sub> compounds, which could be prepared as mm-sized single crystals.

  3. Search for compounds of the NaBaR(BO{sub 3}){sub 2} family (R = La, Nd, Gd, and Yb) and the new NaBaYb(BO{sub 3}){sub 2} orthoborate

    SciTech Connect

    Svetlyakova, T. N. Kokh, A. E.; Kononova, N. G.; Fedorov, P. P.; Rashchenko, S. V.; Maillard, A.

    2013-01-15

    A search for compounds of the NaBaR(BO{sub 3}){sub 2} composition (where R = La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, or Yb{sup 3+}) is performed by solid state synthesis and spontaneous crystallization. A new compound, NaBaYb(BO{sub 3}){sub 2}, is found in this series. It crystallizes in space group R3{sup -} and belongs to the family of sublayer complex orthoborates with isolated BO{sub 3} groups NaBaR(BO{sub 3}){sub 2} (R = Y, Sc, and Yb). Theoretical X-ray powder diffraction patterns of NaBaY(BO{sub 3}){sub 2}, NaBaSc(BO{sub 3}){sub 2}, and NaBaYb(BO{sub 3}){sub 2} are calculated based on single-crystal data.

  4. Synthesis of superconducting Nb3sub>Sn coatings on Nb substrates

    SciTech Connect

    Barzi, E.; Franz, S.; Reginato, F.; Turrioni, D.; Bestetti, M.

    2015-12-01

    In the present work the electrochemical and thermal syntheses of superconductive Nb3sub>Sn films are investigated. The Nb3sub>Sn phase is obtained by electrodeposition of Sn layers and Cu intermediate layers onto Nb substrates followed by high temperature diffusion in inert atmosphere. Electrodeposition was performed from aqueous solutions at current densities in the 20 to 50 mA/cm2 range and at temperatures between 40 and 50°C. Subsequent thermal treatments were realized to obtain the Nb3sub>Sn superconductive phase. Glow discharge optical emission spectrometry (GDOES) demonstrated that after thermal treatment interdiffusion of Nb and Sn occurred across a thickness of about 13 μm. Scanning Electron Microscopy (SEM) allowed accurately measuring the thickness of the Nb3sub>Sn phase, whose average for the various types of film samples was between 5.7 and 8.0 μm. X-ray diffraction (XRD) patterns confirmed the presence of a cubic Nb3sub>Sn phase (A15 structure) having (210) preferred orientation. The maximum obtained Tc was 17.68 K and the Bc20 ranged between 22.5 T and 23.8 T. With the procedure described in the present paper, coating complex shapes cost-effectively becomes possible, which is typical of electrochemical techniques. Furthermore, this approach can be implemented in classical wire processes such as "Jelly Roll" or "Rod in Tube", or directly used for producing superconducting surfaces. In conclusion, the potential of this method for Superconducting Radiofrequency (SRF) structures is also outlined.

  5. Structural and spectroscopic properties of pure and doped LiCe(PO{sub 3}){sub 4}

    SciTech Connect

    Abdelhedi, M.; Horchani-Naifer, K.; Dammak, M.; Ferid, M.

    2015-10-15

    Graphical abstract: Emission and excitation and spectra of Eu{sup 3+} doped LiCe(PO{sub 3}){sub 4} host lattice with 1, 2, 3 and 4 mol%. - Highlights: • Europium–doped LiCe(PO{sub 3}){sub 4} were prepared by flux method. • It was analyzed by infrared and Raman spectroscopy, and luminescence spectroscopy. • LiCe(PO{sub 3}){sub 4} doped with Eu{sup 3+} ions as luminophore host materials to produce an intense red. - Abstract: Single crystals of LiCe(PO{sub 3}){sub 4} polyphosphate have been synthesized by the flux method and its structural and luminescence properties have been investigated. This compound crystallizes in the space group C2/c with unit cell dimensions a = 16.52(7) Å, b = 7.09(4) Å, c = 9.83 (4)Å, β = 126.29(4)°, Z = 8 and V = 927.84(3) Å{sup 3}. The obtained polytetraphosphate exhibits very small crystals and the dopant Eu{sup 3+} ions were successfully incorporated into the sites of Ce{sup 3+} ions of the host lattice. The spectroscopy properties confirm the potentiality of present LiCe(PO{sub 3}){sub 4} doped with Eu{sup 3+} ions as luminophore host materials to produce an intense red luminescence at 628 nm corresponding to {sup 5}D{sub 0} → {sup 7}F{sub 2} emission level and have significant importance in the development of emission optical systems.

  6. New isoformula iodates In(IO{sub 3}){sub 3} and Sm(IO{sub 3}){sub 3} with different crystal structures: Specific structural features of I{sup 5+} compounds

    SciTech Connect

    Gurbanova, O. A. Ivanova, A. G.; Belokoneva, E. L.; Dimitrova, O. V.; Mochenova, N. N.

    2008-01-15

    New iodates, namely, In(IO{sub 3}){sub 3} (space group R3-bar) and Sm(IO{sub 3}){sub 3} (space group P2{sub 1}/a), are synthesized under hydrothermal conditions. The original crystal structure of the In(IO{sub 3}){sub 3} compound is determined without prior knowledge of the chemical formula. The Sm(IO{sub 3}){sub 3} compound is isostructural to the Gd(IO{sub 3}){sub 3} compound. The [IO{sub 4}]{sup 3-} tetrahedra with three short I-O bonds have an umbrella coordination, which is characteristic of pentavalent iodine, and form anionic radicals, such as a ring radical in the In(IO{sub 3}){sub 3} iodate, a triple helix in the isoformula compound Fe(IO{sub 3}){sub 3}, a complex chain in the Sm(IO{sub 3}){sub 3} iodate, and a linear triortho group in the Sm(IO{sub 3}){sub 3}.H{sub 2}O compound. All radicals contain triortho groups. The structural differences are determined by different ionic radii and shapes of the coordination polyhedra of the cations (indium and iron octahedra and an eight-vertex samarium polyhedron)

  7. Integrated Data Collection Analysis (IDCA) Program - NaClO3sub>/Icing Sugar

    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.

    2013-02-11

    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 NaClO3sub> and icing sugar—NaClO3sub>/icing sugar mixture. The mixture was found to: be more sensitive than RDX but less sensitive than PETN in impact testing (180-grit sandpaper); be more sensitive than RDX and about the same sensitivity as PETN in BAM fiction testing; be less sensitive than RDX and PETN except for one participant found the mixture more sensitive than PETN in ABL ESD testing; and to have one to three exothermic features with the lowest temperature event occurring at ~ 160°C always observed in thermal testing. Variations in testing parameters also affected the sensitivity.

  8. Electronic and magnetic properties of epitaxial perovskite SrCrO3sub>(001)

    SciTech Connect

    Zhang, K. H. L.; Du, Y.; Sushko, P. V.; Bowden, M. E.; Shutthanandan, V.; Cao, Guixin; Gai, Zheng; Sallis, S.; Piper, L. F. J.; Chambers, S. A.; Qiao, L.

    2015-06-03

    We have investigated the intrinsic properties of SrCrO3sub> epitaxial thin films synthesized by molecular beam epitaxy. We find compelling evidence that SrCrO3sub> is a correlated metal. X-ray photoemission valence band and O K-edge x-ray absorption spectra indicate a strongly hybridized Cr3d-O2p state crossing the Fermi level, leading to metallic behavior. Comparison between valence band spectra near the Fermi level and the densities of states calculated using density functional theory (DFT) suggests the presence of coherent and incoherent states and points to strong electron correlation effects. Here, the magnetic susceptibility can be described by Pauli paramagnetism at temperatures above 100 K, but reveals antiferromagnetic behavior at lower temperatures, possibly resulting from orbital ordering.

  9. The unusual magnetism of nanoparticle LaCoO3sub>

    SciTech Connect

    Durand, A. M.; Belanger, D. P.; Hamil, T. J.; Ye, F.; Chi, S.; Fernandez-Baca, J. A.; Booth, C. H.; Abdollahian, Y.; Bhat, M.

    2015-04-15

    Bulk and nanoparticle powders of LaCoO3sub> (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T≈85K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To ≈ 40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co3sub>O4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.

  10. Electronic and magnetic properties of Si substituted Fe3sub>Ge

    SciTech Connect

    Shanavas, Kavungal Veedu; McGuire, Michael A.; Parker, David S.

    2015-09-23

    Using first principles calculations we studied the effect of Si substitution in the hexagonal Fe3sub>Ge. We find the low temperature magnetic anisotropy in this system to be planar and originating mostly from the spin-orbit coupling in Fe-d states. Reduction of the unitcell volume reduces the in-plane magnetic anisotropy, eventually turning it positive which reorients the magnetic moments to the axial direction. We find that substituting Ge with the smaller Si ions also reduces the anisotropy, potentially enhancing the region of stability of the axial magnetization, which is beneficial for magnetic applications. Thus our experimental measurements on samples of Fe3sub>Ge1–xSix confirm these predictions and show that substitution of about 6% of the Ge with Si increases by approximately 35 K the temperature range over which anisotropy is uniaxial.

  11. Integrated Data Collection Analysis (IDCA) Program - KClO3sub>/Dodecane Mixture

    SciTech Connect

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

    2011-05-23

    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 KClO3sub> and dodecane—KClO3sub>/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 more sensitive to impact than RDX, and PETN, 2) less sensitive to friction than PETN, and 3) less sensitive to spark than RDX. The thermal analysis showed little or no exothermic features suggesting that the dodecane volatilized at low temperatures. A prominent endothermic feature was observed assigned to melting of KClO3sub>. 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 KClO3sub>/dodecane mixture are Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), and Indian Head Division, Naval Surface Warfare Center, (NSWC IHD). These tests are conducted as a proficiency study in order to establish some consistency in test protocols, procedures, and experiments and to understand

  12. Plentiful magnetic moments in oxygen deficient SrTiO3sub>.

    SciTech Connect

    Lopez Bezanilla, Alejandro; Ganesh, P.; Littlewood, Peter B.

    2015-10-01

    Correlated band theory is employed to investigate the magnetic and electronic properties of different arrangements of oxygen di- and tri-vacancy clusters in SrTiO3sub>. Hole and electron doping of oxygen deficient SrTiO3sub> yields various degrees of magnetization as a result of the interaction between localized magnetic moments at the defected sites. Different kinds of Ti atomic orbital hybridization are described as a function of the doping level and defect geometry. We find that magnetism in SrTiO3sub>-d is sensitive to the arrangement of neighbouring vacancy sites, charge carrier density, and vacancy-vacancy interaction. Permanent magnetic moments in the absence of vacancy doping electrons are observed. Our description of the charged clusters of oxygen vacancies widens the previous descriptions of mono and multi-vacancies and points out the importance of the controlled formation at the atomic level of defects for the realization of transition metal oxide based devices with a desirable magnetic performance.

  13. Collisions of electrons with trimethylphosphine [P(CH{sub 3}){sub 3}] molecules

    SciTech Connect

    Domaracka, Alicja; Mozejko, Pawel; Ptasinska-Denga, Elzbieta; Szmytkowski, Czeslaw

    2007-10-15

    We report on the absolute total electron-trimethylphosphine scattering cross section (TCS) measured from 0.4 to 400 eV using a linear electron-beam attenuation method. The experimental TCS energy function exhibits very pronounced asymmetric enhancement peaked near 5.5 eV. Calculations were also carried out to obtain the integral elastic and ionization cross sections at intermediate and high energies using the independent atom and the binary-encounter-Bethe approximations, respectively. Their sum, the computed total cross section, is for intermediate energies in a reasonable agreement with the present experimental TCS data. Furthermore, the measured TCS for P(CH{sub 3}){sub 3} is compared with the TCSs for some other phosphines [PH{sub 3}, PF{sub 3}] and other methides [B(CD{sub 3}){sub 3}, N(CH{sub 3}){sub 3}]. Analysis clearly shows that exterior atoms of a molecule influence the scattering process more significantly than the central atom.

  14. Superconductivity in strong spin orbital coupling compound Sb2Se3sub>

    SciTech Connect

    Kong, P. P.; Sun, F.; Xing, L. Y.; Zhu, J.; Zhang, S. J.; Li, W. M.; Liu, Q. Q.; Wang, X. C.; Feng, S. M.; Yu, X. H.; Zhu, J. L.; Yu, R. C.; Yang, W. G.; Shen, G. Y.; Zhao, Y. S.; Ahuja, R.; Mao, H. K.; Jin, C. Q.

    2014-10-20

    Recently, A2B3sub> type strong spin orbital coupling compounds such as Bi2Te3sub>, Bi2Se3sub> and Sb2Te3sub> were theoretically predicated to be topological insulators and demonstrated through experimental efforts. The counterpart compound Sb2Se3sub> on the other hand was found to be topological trivial, but theoretical studies indicated that the pressure might induce Sb2Se3sub> into a topological nontrivial state. We report on the discovery of superconductivity in Sb2Se3sub> single crystal induced via pressure. Our experiments indicated that Sb2Se3sub> became superconductive at high pressures above 10 GPa proceeded by a pressure induced insulator to metal like transition at ~3 GPa which should be related to the topological quantum transition. The superconducting transition temperature (TC) increased to around 8.0 K with pressure up to 40 GPa while it keeps ambient structure. As a result, high pressure Raman revealed that new modes appeared around 10 GPa and 20 GPa, respectively, which correspond to occurrence of superconductivity and to the change of TC slop as the function of high pressure in conjunction with the evolutions of structural parameters at high pressures.

  15. Beyond Yolk–Shell Nanoparticles: Fe 3sub> O 4 @Fe 3sub> C Core@Shell Nanoparticles as Yolks and Carbon Nanospindles as Shells for Efficient Lithium Ion Storage

    SciTech Connect

    Zhang, Jianan; Wang, Kaixi; Xu, Qun; Zhou, Yunchun; Cheng, Fangyi; Guo, Shaojun

    2015-02-25

    In order to well address the problems of large volume change and dissolution of Fe3sub>O4 nanomaterials during Li+ intercalation/extraction, herein we demonstrate a one-step in situ nanospace-confined pyrolysis strategy for robust yolk–shell nanospindles with very sufficient internal void space (VSIVS) for high-rate and long-term lithium ion batteries (LIBs), in which an Fe3sub>O4@Fe3sub>C core@shell nanoparticle is well confined in the compartment of a hollow carbon nanospindle. This structure can not only introduce VSIVS to accommodate volume change of Fe3sub>O4 but also afford a dual shell of Fe3sub>C and carbon to restrict Fe3sub>O4 dissolution, thus providing dual roles for greatly improving the capacity retention. Consequently, Fe3sub>O4@Fe3sub>C–C yolk–shell nanospindles deliver a high reversible capacity of 1128.3 mAh g–1 at even 500 mA g–1, excellent high rate capacity (604.8 mAh g–1 at 2000 mA g1), and prolonged cycling life (maintaining 1120.2 mAh g–1 at 500 mA g–1 for 100 cycles) for LIBs, which are much better than those of Fe3sub>O4@C core@shell nanospindles and Fe3sub>O4 nanoparticles. The present Fe3sub>O4@Fe3sub>C–C yolk–shell nanospindles are the most efficient Fe3sub>O4-based anode materials ever reported for LIBs.

  16. Magnetism and Raman spectroscopy of the dimeric lanthanide iodates Ln(IO{sub 3}){sub 3} (Ln=Gd, Er) and magnetism of Yb(IO{sub 3}){sub 3}

    SciTech Connect

    Sykora, Richard E. Khalifah, Peter; Assefa, Zerihun; Albrecht-Schmitt, Thomas E.; Haire, Richard G.

    2008-08-15

    Colorless single crystals of Gd(IO{sub 3}){sub 3} or pale pink single crystals of Er(IO{sub 3}){sub 3} have been formed from the reaction of Gd metal with H{sub 5}IO{sub 6} or Er metal with H{sub 5}IO{sub 6} under hydrothermal reaction conditions at 180 deg. C. The structures of both materials adopt the Bi(IO{sub 3}){sub 3} structure type. Crystallographic data are (MoK{alpha}, {lambda}=0.71073 A): Gd(IO{sub 3}){sub 3}, monoclinic, space group P2{sub 1}/n, a=8.7615(3) A, b=5.9081(2) A, c=15.1232(6) A, {beta}=96.980(1){sup o}, V=777.03(5) Z=4, R(F)=1.68% for 119 parameters with 1930 reflections with I>2{sigma}(I); Er(IO{sub 3}){sub 3}, monoclinic, space group P2{sub 1}/n, a=8.6885(7) A, b=5.9538(5) A, c=14.9664(12) A, {beta}=97.054(1){sup o}, V=768.4(1) Z=4, R(F)=2.26% for 119 parameters with 1894 reflections with I>2{sigma}(I). In addition to structural studies, Gd(IO{sub 3}){sub 3}, Er(IO{sub 3}){sub 3}, and the isostructural Yb(IO{sub 3}){sub 3} were also characterized by Raman spectroscopy and magnetic property measurements. The results of the Raman studies indicated that the vibrational profiles are adequately sensitive to distinguish between the structures of the iodates reported here and other lanthanide iodate systems. The magnetic measurements indicate that only in Gd(IO{sub 3}){sub 3} did the 3+ lanthanide ion exhibit its full 7.9 {mu}{sub B} Hund's rule moment; Er{sup 3+} and Yb{sup 3+} exhibited ground state moments and gap energy scales of 8.3 {mu}{sub B}/70 K and 3.8 {mu}{sub B}/160 K, respectively. Er(IO{sub 3}){sub 3} exhibited extremely weak ferromagnetic correlations (+0.4 K), while the magnetic ions in Gd(IO{sub 3}){sub 3} and Yb(IO{sub 3}){sub 3} were fully non-interacting within the resolution of our measurements ({approx}0.2 K). - Graphical abstract: Three f-element iodates Ln(IO{sub 3}){sub 3} (Ln=Gd, Er, Yb), all containing the Bi(IO{sub 3}){sub 3} structure type, were characterized by Raman spectroscopy and magnetic property measurements

  17. Strain tuning and strong enhancement of ionic conductivity in SrZrO3sub>-RE2O3sub> (RE = Sm, Eu, Gd, Dy, and Er) nanocomposite films

    SciTech Connect

    Lee, Shinbuhm; Zhang, Wenrui; Khatkhatay, Fauzia; Jia, Quanxi; Wang, Haiyan; MacManus-Driscoll, Judith L.

    2015-06-05

    Fast ion transport channels at interfaces in thin films have attracted great attention due to a range of potential applications for energy materials and devices, for, solid oxide fuel cells, sensors, and memories. Here, it is shown that in vertical nanocomposite heteroepitaxial films of SrZrO3sub>–RE2O3sub> (RE = Sm, Eu, Gd, Dy, and Er) the ionic conductivity of the composite can be tuned and strongly enhanced using embedded, stiff, and vertical nanopillars of RE2O3sub>. With increasing lattice constant of RE2O3sub> from Er2O3sub> to Sm2O3sub>, it is found that the tensile strain in the SrZrO3sub> increases proportionately, and the ionic conductivity of the composite increases accordingly, by an order of magnitude. Lastly, the results here conclusively show, for the first time, that strain in films can be effectively used to tune the ionic conductivity of the materials.

  18. Visible Light Assisted Photocatalytic Hydrogen Generation by Ta2O5/Bi2O3sub>, TaON/Bi2O3sub>, and Ta3sub>N5/Bi2O3sub> Composites

    SciTech Connect

    Adhikari, Shiba; Hood, Zachary D.; More, Karren Leslie; Ivanov, Ilia N.; Zhang, Lifeng; Gross, Michael; Lachgar, Abdou

    2015-06-15

    Composites comprised of two semiconducting materials with suitable band gaps and band positions have been reported to be effective at enhancing photocatalytic activity in the visible light region of the electromagnetic spectrum. Here, we report the synthesis, complete structural and physical characterizations, and photocatalytic performance of a series of semiconducting oxide composites. UV light active tantalum oxide (Ta2O5) and visible light active tantalum oxynitride (TaON) and tantalum nitride (Ta3sub>N5) were synthesized, and their composites with Bi2O3sub> were prepared in situ using benzyl alcohol as solvent. The composite prepared using equimolar amounts of Bi2O3sub> and Ta2O5 leads to the formation of the ternary oxide, bismuth tantalate (BiTaO4) upon calcination at 1000 °C. The composites and single phase bismuth tantalate formed were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy, and photoluminescence. The photocatalytic activities of the catalysts were evaluated for generation of hydrogen using aqueous methanol solution under visible light irradiation (λ ≥ 420 nm). The results show that as-prepared composite photocatalysts extend the light absorption range and restrict photogenerated charge-carrier recombination, resulting in enhanced photocatalytic activity compared to individual phases. The mechanism for the enhanced photocatalytic activity for the heterostructured composites is elucidated based on observed activity, band positions calculations, and photoluminescence data.

  19. Ultrafast Magnetization Dynamics of SrRuO3 sub>Thin Films

    SciTech Connect

    Langner, Matthew C.

    2009-05-19

    Itinerant ferromagnet SrRuO3sub> has drawn interest from physicists due to its unusual transport and magnetic properties as well as from engineers due to its low resistivity and good lattice-matching to other oxide materials. The exact electronic structure remains a mystery, as well as details of the interactions between magnetic and electron transport properties. This thesis describes the use of time-resolved magneto-optical Kerr spectroscopy to study the ferromagnetic resonance of SrRuO3sub> thin films, where the ferromagnetic resonance is initiated by a sudden change in the easy axis direction in response to a pump pulse. The rotation of the easy axis is induced by laser heating, taking advantage of a temperature-dependent easy axis direction in SrRuO3sub> thin films. By measuring the change in temperature of the magnetic system in response to the laser pulse, we find that the specific heat is dominated by magnons up to unusually high temperature, ~100 K, and thermal diffusion is limited by a boundary resistance between the film and the substrate that is not consistent with standard phonon reflection and scattering models. We observe a high FMR frequency, 250 GHz, and large Gilbert damping parameter, α ≈1, consistent with strong spin-orbit coupling. We observe a time-dependent change in the easy axis direction on a ps time-scale, and we find that parameters associated with the change in easy axis, as well as the damping parameter, have a non-monotonic temperature dependence similar to that observed in anomalous Hall measurements.

  20. Pressure-induced phase transitions in acentric BaHf(BO{sub 3}){sub 2}

    SciTech Connect

    Mączka, Mirosław; Szymborska-Małek, Katarzyna; Sousa Pinheiro, Gardenia de; Cavalcante Freire, Paulo Tarso; Majchrowski, Andrzej

    2015-08-15

    High-pressure Raman scattering studies revealed that BaHf(BO{sub 3}){sub 2} is more compressible than calcite-type orthoborates and calcite, aragonite or dolomite carbonates. It undergoes a first-order reversible pressure-induced phase transition in the 3.9–4.4 GPa pressure range. Second structural change is observed at 9.2 GPa. The intermediate phase is most likely trigonal. However, Raman results suggest increase in the number of distinct BO{sub 3} groups from two in the ambient pressure phase to at least three in the intermediate phase. This intermediate phase is also strongly compressible and strong pressure dependence of the lattice modes proves that the main changes under pressure occur within the layers built from BaO{sub 6} and HfO{sub 6} octahedra. The second phase transition leads most likely to lowering of the trigonal symmetry, as evidenced by significant increase of the number of observed bands. The pressure coefficients of the Raman bands of the high-pressure phase are relatively small, suggesting more dense arrangement of the metal–oxygen polyhedra and BO{sub 3} groups in this phase. It is worth noting that the high-pressure phase was not reached in the second compression experiment up to 10 GPa. This behavior can be most likely attributed to worse hydrostatic conditions of the first experiment. - Graphical abstract: Raman spectra of BaHf(BO{sub 3}){sub 2} recorded at different pressures during compression showing onset of pressure-induced phase transitions. - Highlights: • High-pressure Raman spectra were measured for BaHf(BO{sub 3}){sub 2.} • BaHf(BO{sub 3}){sub 2} undergoes a reversible first-order phase transition at 3.9–4.4 GPa into a trigonal phase. • The intermediate trigonal phase is strongly compressible second structural transformation is observed at 9.2 GPa under non-perfect hydrostatic conditions.

  1. YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB) high temperature vibration sensor

    SciTech Connect

    Kim, Kyungrim; Huang Wenbin; Jiang Xiaoning; Zhang Shujun; Yu Fapeng

    2011-06-15

    A shear-mode piezoelectric accelerometer using YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB) single crystal was designed, fabricated and successfully tested for high temperature vibration sensing applications. The prototyped sensor was tested at temperatures ranging from room temperature to 1000 deg. C and at frequencies ranging from 80 Hz to 1 kHz. The sensitivity of the sensor was found to be 5.7 pC/g throughout the tested frequency and temperature range. In addition, YCOB piezoelectric accelerometers remained the same sensitivity at 1000 deg. C for a dwell time of four hours, exhibiting high stability and reliability.

  2. Renormalizing (phi/sup 3/)/sub 6/ theory in curved space-time

    SciTech Connect

    Kodaira, J.; Okada, J.

    1986-05-15

    The renormalization of phi/sup 3/ theory in a six-dimensional conformally flat space-time is discussed at the two-loop level. The background-field method and the momentum-space representation of the Feynman propagator are used to calculate the ultraviolet divergences of the effective action. It is shown that (phi/sup 3/)/sub 6/ theory is renormalizable in a conformally flat space-time at the two-loop level. The counterterms are given to the two-loop order. The next-to-leading-order term in the ..beta.. function for the coupling constant of the Rphi/sup 2/ term is then obtained.

  3. Improved Electrochemical Performance of Carbon-Coated LiFeBO3sub> Nanoparticles for Lithium-Ion Batteries

    SciTech Connect

    Li, Zhaoping; Wang, Yiping; Hu, Querui; Yang, Ying; Wu, Zhuangchun; Ban, Chunmei

    2015-09-01

    Carbon-coated LiFeBO3 sub>nanoparticles have been successfully prepared by surfactant-assisted ball milling and a size selection process based on centrifugal separation. We observed monodispersed LiFeBO3sub> nanoparticles with dimensions of 10–20 nm by transmission electron microscope. The introduced surfactant acts as the dispersant as well as the carbon source for LiFeBO3sub> nanoparticles. Greatly improved discharge capacities of 190.4 mA h g–1 at 0.1 C and 106.6 mA h g–1 at 1 C rate have been achieved in the LiFeBO3sub> nanoparticles when cycling the cells between 1.0 V and 4.8 V. Meanwhile, the as-prepared micro-size LiFeBO3sub> electrodes show lower discharge capacities of 142 mA h g–1 and 93.3 mA h g–1 at 0.1 C and 1 C rates. Moreover, the post-treated LiFeBO3sub> nanostructure has drastically enhanced the electrochemical performance due to the short diffusion length and ameliorated electrical contract between LiFeBO3sub> nano particles.

  4. Synthesis, characterization and optical properties of NH{sub 4}Dy(PO{sub 3}){sub 4}

    SciTech Connect

    Chemingui, S.; Ferhi, M. Horchani-Naifer, K.; Férid, M.

    2014-09-15

    Polycrystalline powders of NH{sub 4}Dy(PO{sub 3}){sub 4} polyphosphate have been grown by the flux method. This compound was found to be isotopic with NH{sub 4}Ce(PO{sub 3}){sub 4} and RbHo(PO{sub 3}){sub 4}. It crystallizes in the monoclinic space group P2{sub 1/n} with unit cell parameters a=10.474(6) Å, b=9.011(4) Å, c=10.947(7) Å and β=106.64(3)°. The title compound has been transformed to triphosphate Dy(PO{sub 3}){sub 3} after calcination at 800 °C. Powder X-ray diffraction, infrared and Raman spectroscopies and the differential thermal analysis have been used to identify these materials. The spectroscopic properties have been investigated through absorption, excitation, emission spectra and decay curves of Dy{sup 3+} ion in both compounds at room temperature. The emission spectra show the characteristic emission bands of Dy{sup 3+} in the two compounds, before and after calcination. The integrated emission intensity ratios of the yellow to blue (I{sub Y}/I{sub B}) transitions and the chromaticity properties have been determined from emission spectra. The decay curves are found to be double-exponential. The non-exponential behavior of the decay rates was related to the resonant energy transfer as well as cross-relaxation between the donor and acceptor Dy{sup 3+} ions. The determined properties have been discussed as function of crystal structure of both compounds. They reveal that NH{sub 4}Dy(PO{sub 3}){sub 4} is promising for white light generation but Dy(PO{sub 3}){sub 3} is potential candidates in field emission display (FED) and plasma display panel (PDP) devices. - Graphical abstract: The CIE color coordinate diagrams showing the chromatic coordinates of Dy{sup 3+} luminescence in NH{sub 4}Dy(PO{sub 3}){sub 4} and Dy(PO{sub 3}){sub 3}. - Highlights: • The polycrystalline powders of NH{sub 4}Dy(PO{sub 3}){sub 4} and Dy(PO{sub 3}){sub 3} are synthesized. • The obtained powders are characterized. • The spectroscopic properties of Dy{sup 3+} ion

  5. Results from the first single cell Nb3sub>Sn cavity coatings at JLab

    SciTech Connect

    Eremeev, Grigory

    2015-09-01

    Nb3sub>Sn is a promising superconducting material for SRF applications and has the potential to exceed the limitations of niobium. We have used the recently commissioned Nb3sub>Sn coating system to investigate Nb3sub>Sn coatings on several single cell cavities by applying the same coating procedure on several different single cells with different history and pre-coating surface preparation. We report on our findings with four 1.5 GHz CEBAF-shape single cell and one 1.3 GHz ILC-shape single cavities that were coated, inspected, and tested.

  6. Coexistence of Weak Ferromagnetism and Polar Lattice Distortion in Epitaxial NiTiO3sub> thin films of the LiNbO3sub>-Type Structure

    SciTech Connect

    Varga, Tamas; Droubay, Timothy C.; Bowden, Mark E.; Colby, Robert J.; Manandhar, Sandeep; Shutthanandan, Vaithiyalingam; Hu, Dehong; Kabius, Bernd C.; Apra, Edoardo; Shelton, William A.; Chambers, Scott A.

    2013-04-15

    We report the magnetic and structural characteristics of epitaxial NiTiO3sub> films grown by pulsed laser deposition that are isostructural with acentric LiNbO3sub> (space group R3c). Optical second harmonic generation and magnetometry demonstrate lattice polarization at room temperature and weak ferromagnetism below 250 K, respectively. These results appear to be consistent with earlier predictions from first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LiNbO3 sub>structure. This acentric form of NiTiO3sub> is believed to be one of the rare examples of ferroelectrics exhibiting weak ferromagnetism generated by a Dzyaloshinskii-Moriya interaction.

  7. Strong spin-lattice coupling in CrSiTe3sub>

    SciTech Connect

    Casto, L. D.; Clune, A. J.; Yokosuk, M. O.; Musfeldt, J. L.; Williams, T. J.; Zhuang, H. L.; Lin, M. -W.; Xiao, K.; Hennig, R. G.; Sales, B. C.; Yan, J. -Q.; Mandrus, D.

    2015-03-19

    CrSiTe3sub> has attracted recent interest as a candidate single-layer ferromagnetic semiconductor, but relatively little is known about the bulk properties of this material. Here, we report single-crystal X-ray diffraction, magnetic properties, thermal conductivity, vibrational, and optical spectroscopies and compare our findings with complementary electronic structure and lattice dynamics principles calculations. The high temperature paramagnetic phase is characterized by strong spin-lattice interactions that give rise to glassy behavior, negative thermal expansion, and an optical response that reveals that CrSiTe3sub> is an indirect gap semiconductor with indirect and direct band gaps at 0.4 and 1.2 eV, respectively. Measurements of the phonons across the 33 K ferromagnetic transition provide additional evidence for strong coupling between the magnetic and lattice degrees of freedom. In conclusion, the Si-Te stretching and Te displacement modes are sensitive to the magnetic ordering transition, a finding that we discuss in terms of the superexchange mechanism. Lastly, spin-lattice coupling constants are also extracted.

  8. Collisions of electrons with trimethylamine N(CH{sub 3}){sub 3} molecules

    SciTech Connect

    Szmytkowski, Czeslaw; Domaracka, Alicja; Mozejko, Pawel; Ptasinska-Denga, Elzbieta

    2007-05-15

    Absolute total electron-trimethylamine scattering cross section (TCS) has been measured from 0.8 to 370 eV with a linear electron-transmission method. The experimental TCS energy function is dominated by very pronounced enhancement peaked near 9 eV. The present TCS agrees qualitatively with low-energy results of Schmieder [Z. Elektrochem. 36, 700 (1930)] but there are substantial differences in the position and peak values. Calculations were also carried out to obtain the integral elastic and ionization cross sections at intermediate and high energies using the independent atom (IAM) and the binary-encounter-Bethe (BEB) approximations, respectively. Their sum, the estimated total cross section, is for intermediate energies in a reasonable agreement with the present experimental TCS data. Furthermore, the measured TCS for N(CH{sub 3}){sub 3} is compared with the TCSs for other nitrous compounds: NH{sub 3} and NH{sub 2}CH{sub 3}. The variation of the TCS magnitude across the series of nitrogen-containing molecules [NH{sub 3}, NH{sub 2}CH{sub 3}, and N(CH{sub 3}){sub 3}] is explained in terms of their molecular size.

  9. Brønsted acid-base reactions with anhydrous sulfamates as a pathway to [SO3sub>N]3--containing compounds: Preparation of Li3sub>SO3sub>N

    SciTech Connect

    Kurzman, Joshua A.; Jouan, Gauthier; Courty, Matthieu; Palacín, M. Rosa; Armand, Michel; Recham, Nadir

    2013-09-26

    Li3sub>SO3sub>N has been prepared by the mechanochemical reaction between lithium sulfamate (LiSO3sub>NH2) and lithium amide or lithium hydride. This is the first example of an anhydrous compound containing the rare [SO3sub>N]3- polyanion. Li3sub>SO3sub>N adopts the low-temperature Pmn21β structure of isoelectronic Li3sub>PO4. Structural refinement from neutron powder diffraction data supports disordering of nitrogen over two of the three anion sites, although a fully disordered model cannot be conclusively refuted. While the compound is a poor ionic conductor, it is electrochemically stable to at least 5 V vs. Li+/Li0. This simple mechanochemical pathway should be suitable for preparing a host of other alkali-rich nitrogen-containing polyanionic compounds.

  10. Nuclear and magnetic supercells in the multiferroic candidate: Pb3sub>TeMn3sub>P2O14

    SciTech Connect

    Silverstein, Harlyn J.; Huq, Ashfia; Lee, Minseong; Choi, Eun Sang; Zhou, Haidong; Wiebe, Christopher R.

    2014-10-18

    Here we report that the dugganites, Te6+-containing members of the langasite series, have attracted recent interest due to their complex low-temperature magnetic unit cells, magnetodielectric, and potentially multiferroic properties. For Pb2+-containing dugganites, a large monoclinic supercell was reported and was found to have a profound effect on the low temperature magnetism and spin excitation spectra. Pb3sub>TeMn3sub>P2O14 is another dugganite previously shown to distort away from the canonical P321 langasite unit cell, although this supercell was never fully solved. We report the full crystal and magnetic structure solution of Pb3sub>TeMn3sub>P2O14 using synchrotron x-ray and neutron diffraction data: a large trigonal supercell is observed in this material, which is believed to be the first supercell of its kind in the langasite family. Here, the magnetic structure, high-magnetic field behavior, and dielectric properties of Pb3sub>TeMn3sub>P2O14 are presented. In addition to showing weak magnetoelectric behavior similar to other langasites, it was found that a phase transition occurs at 3 T near the antiferromagnetic transition temperature.

  11. An in-situ phosphorus source for the synthesis of Cu3sub>P and the subsequent conversion to Cu3sub>PS4 nanoparticle clusters

    SciTech Connect

    Sheets, Erik J.; Stach, Eric A.; Yang, Wei -Chang; Balow, Robert B.; Wang, Yunjie; Walker, Bryce C.; Agrawal, Rakesh

    2015-09-20

    The search for alternative earth abundant semiconducting nanocrystals for sustainable energy applications has brought forth the need for nanoscale syntheses beyond bulk synthesis routes. Of particular interest are metal phosphides and derivative I-V-VI chalcogenides including copper phosphide (Cu3sub>P) and copper thiophosphate (Cu3sub>PS4). Herein, we report a one-pot, solution-based synthesis of Cu3sub>P nanocrystals utilizing an in-situ phosphorus source: phosphorus pentasulfide (P2S5) in trioctylphosphine (TOP). By injecting this phosphorus source into a copper solution in oleylamine (OLA), uniform and size controlled Cu3sub>P nanocrystals with a phosphorous-rich surface are synthesized. The subsequent reaction of the Cu3sub>P nanocrystals with decomposing thiourea forms nanoscale Cu3sub>PS4 particles having p-type conductivity and an effective optical band gap of 2.36 eV.

  12. Crystal and molecular structure of the coordination compounds of Er{sup 3+} with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL{sub 2}{sup 1}(NO{sub 3}){sub 2}]{sub 2}[Er(NO{sub 3}){sub 2}(H{sub 2}O){sub 5}]{sub 0.333}(NO{sub 3}){sub 2.333} · 2.833H{sub 2}O and its ethyl substituted derivative [ErL{sub 2}{sup 2}(NO{sub 3}){sub 2}][Er(NO{sub 3}){sub 5}]{sub 0.5} · 0.5H{sub 2}O

    SciTech Connect

    Polyakova, I. N.; Baulin, V. E.; Ivanova, I. S.; Pyatova, E. N.; Sergienko, V. S.; Tsivadze, A. Yu.

    2015-01-15

    The coordination compounds of Er{sup 3+} with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL{sub 2}{sup 1}(NO{sub 3}){sub 2}]{sub 2}[Er(NO{sub 3}){sub 2}(H{sub 2}O){sub 5}]{sub 0.333}(NO{sub 3}){sub 2.333} · 2.833H{sub 2}O (I) and its ethyl substituted derivative [ErL{sub 2}{sup 2}(NO{sub 3}){sub 2}][Er(NO{sub 3}){sub 5}]{sub 0.5} · 0.5H{sub 2}O (II) are synthesized and their crystal structures are studied. I and II contain [ErL{sub 2}(NO{sub 3}){sub 2}]{sup +} complex cations of identical composition and close structure. The eight-vertex polyhedron of the Er atom in the shape of a distorted octahedron with two split trans vertices is formed by the O atoms of the phosphoryl groups of L ligands and nitrate anions. L ligands close nine-membered metallocycles. The structures contain spacious channels which are populated differently, namely, by disordered [Er(NO{sub 3}){sub 2}(H{sub 2}O){sub 5}]{sup +} complex cations, NO{sub 3}{sup −} anions, and crystallization water molecules in I and disordered [Er(NO{sub 3}){sub 5}]{sup 2−} complex anions and crystallization water molecules in II. The IR spectra of I and II are studied.

  13. Structural phase transitions in Bi2Se3sub> under high pressure

    SciTech Connect

    Yu, Zhenhai; Gu, Genda; Wang, Lin; Hu, Qingyang; Zhao, Jinggeng; Yan, Shuai; Yang, Ke; Sinogeikin, Stanislav; Mao, Ho -kwang

    2015-11-02

    Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi2Se3sub>) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi2Se3sub> crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint that the I4/mmm phase Bi2Se3sub> can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi2Se3sub> from this work (two independent runs) are still Raman active up to ~35 GPa. Furthermore, it is worthy to note that the disordered BCC phase at 27.8 GPa is not observed here. The remarkable difference in atomic radii of Bi and Se in Bi2Se3sub> may explain why Bi2Se3sub> shows different structural behavior than isocompounds Bi2Te3sub> and Sb2Te3sub>.

  14. Caffeine increases striatal dopamine D2/D3sub> receptor availability in the human brain

    SciTech Connect

    Volkow, N. D.; Wang, G. -J.; Logan, J.; Alexoff, D.; Fowler, J. S.; Thanos, P. K.; Wong, C.; Casado, V.; Ferre, S.; Tomasi, D.

    2015-04-14

    Caffeine, the most widely consumed psychoactive substance in the world, is used to promote wakefulness and enhance alertness. Like other wake-promoting drugs (stimulants and modafinil), caffeine enhances dopamine (DA) signaling in the brain, which it does predominantly by antagonizing adenosine A2A receptors (A2AR). However, it is unclear if caffeine, at the doses consumed by humans, increases DA release or whether it modulates the functions of postsynaptic DA receptors through its interaction with adenosine receptors, which modulate them. We used positron emission tomography and [11C]raclopride (DA D2/D3sub> receptor radioligand sensitive to endogenous DA) to assess if caffeine increased DA release in striatum in 20 healthy controls. Caffeine (300mg p.o.) significantly increased the availability of D2/D3sub> receptors in putamen and ventral striatum, but not in caudate, when compared with placebo. In addition, caffeine-induced increases in D2/D3sub> receptor availability in the ventral striatum were associated with caffeine-induced increases in alertness. Our findings indicate that in the human brain, caffeine, at doses typically consumed, increases the availability of DA D2/D3sub> receptors, which indicates that caffeine does not increase DA in the striatum for this would have decreased D2/D3sub> receptor availability. Instead, we interpret our findings to reflect an increase in D2/D3sub> receptor levels in striatum with caffeine (or changes in affinity). Furthermore, the association between increases in D2/D3sub> receptor availability in ventral striatum and alertness suggests that caffeine might enhance arousal, in part, by upregulating D2/D3sub> receptors.

  15. The signaling phospholipid PIP3sub> creates a new interaction surface on the nuclear receptor SF-1

    SciTech Connect

    Blind, Raymond D.; Sablin, Elena P.; Kuchenbecker, Kristopher M.; Chiu, Hsiu-Ju; Deacon, Ashley M.; Das, Debanu; Fletterick, Robert J.; Ingraham, Holly A.

    2014-10-06

    We previously reported that lipids PI(4,5)P2 (PIP2) and PI(3,4,5)P3sub> (PIP3sub>) bind NR5A nuclear receptors to regulate their activity. Here, the crystal structures of PIP2 and PIP3sub> bound to NR5A1 (SF-1) define a new interaction surface that is organized by the solvent-exposed PIPn headgroups. We find that stabilization by the PIP3sub> ligand propagates a signal that increases coactivator recruitment to SF-1, consistent with our earlier work showing that PIP3sub> increases SF-1 activity. This newly created surface harbors a cluster of human mutations that lead to endocrine disorders, thus explaining how these puzzling mutations cripple SF-1 activity. Finally, we propose that this new surface acts as a PIP3sub>-regulated interface between SF-1 and coregulatory proteins, analogous to the function of membrane-bound phosphoinositides.

  16. Ultrathin nanosheets of CrSiTe3sub>. A semiconducting two-dimensional ferromagnetic material

    SciTech Connect

    Lin, Ming -Wei; Zhung, Houlong L.; Yan, Jiaqiang; Ward, Thomas Zac; Puretzky, Alexander A.; Rouleau, Christopher M.; Gai, Zheng; Liang, Liangbo; Meunier, Vincent; Ganesh, Panchapakesan; Kent, Paul R. C.; Sumpter, Bobby G.; Mandrus, David G.; Geohegan, David B.; Xiao, Kai

    2015-11-27

    Finite range ferromagnetism and antiferromagnetism in two-dimensional (2D) systems within an isotropic Heisenberg model at non-zero temperature were originally proposed to be impossible. However, recent theoretical studies using an Ising model have recently shown that 2D magnetic crystals can exhibit magnetism. Experimental verification of existing 2D magnetic crystals in this system has remained elusive. In this work we for the first time exfoliate the CrSiTe3sub>, a bulk ferromagnetic semiconductor, to mono- and few-layer 2D crystals onto a Si/SiO2 substrate. The Raman spectra show the good stability and high quality of the exfoliated flakes, consistent with the computed phonon spectra of 2D CrSiTe3sub>, giving a strong evidence for the existence of 2D CrSiTe3sub> crystals. When the thickness of the CrSiTe3sub> crystals is reduced to few-layers, we observed a clear change in resistivity at 80~120 K, consistent with the theoretical calculations on the Curie temperature (Tc) of ~80 K for the magnetic ordering of 2D CrSiTe3sub> crystals. As a result, the ferromagnetic mono- and few-layer 2D CrSiTe3sub> indicated here should enable numerous applications in nano-spintronics.

  17. Syntheses, structures, and vibrational spectroscopy of the two-dimensional iodates Ln(IO{sub 3}){sub 3} and Ln(IO{sub 3}){sub 3}(H{sub 2}O) (Ln =Yb, Lu)

    SciTech Connect

    Assefa, Zerihun . E-mail: zassefa@ncat.edu; Ling Jie; Haire, Richard G.; Albrecht-Schmitt, Thomas E.; Sykora, Richard E. . E-mail: rsykora@jaguar1.usouthal.edu

    2006-12-15

    The reaction of Lu{sup 3+} or Yb{sup 3+} and H{sub 5}IO{sub 6} in aqueous media at 180 {sup o}C leads to the formation of Yb(IO{sub 3}){sub 3}(H{sub 2}O) or Lu(IO{sub 3}){sub 3}(H{sub 2}O), respectively, while the reaction of Yb metal with H{sub 5}IO{sub 6} under similar reaction conditions gives rise to the anhydrous iodate, Yb(IO{sub 3}){sub 3}. Under supercritical conditions Lu{sup 3+} reacts with HIO{sub 3} and KIO{sub 4} to yield the isostructural Lu(IO{sub 3}){sub 3}. The structures have been determined by single-crystal X-ray diffraction. Crystallographic data are (MoK{alpha}, {lambda}=0.71073 A): Yb(IO{sub 3}){sub 3}, monoclinic, space group P2{sub 1}/n, a=8.6664(9) A, b=5.9904(6) A, c=14.8826(15) A, {beta}=96.931(2){sup o}, V=766.99(13), Z=4, R(F)=4.23% for 114 parameters with 1880 reflections with I>2{sigma}(I); Lu(IO{sub 3}){sub 3}, monoclinic, space group P2{sub 1}/n, a=8.6410(9), b=5.9961(6), c=14.8782(16) A, {beta}=97.028(2){sup o}, V=765.08(14), Z=4, R(F)=2.65% for 119 parameters with 1756 reflections with I>2{sigma}(I); Yb(IO{sub 3}){sub 3}(H{sub 2}O), monoclinic, space group C2/c, a=27.2476(15), b=5.6296(3), c=12.0157(7) A, {beta}=98.636(1){sup o}, V=1822.2(2), Z=8, R(F)=1.51% for 128 parameters with 2250 reflections with I>2{sigma}(I); Lu(IO{sub 3}){sub 3}(H{sub 2}O), monoclinic, space group C2/c, a=27.258(4), b=5.6251(7), c=12.0006(16) A, {beta}=98.704(2){sup o}, V=1818.8(4), Z=8, R(F)=1.98% for 128 parameters with 2242 reflections with I>2{sigma}(I). The f elements in all of the compounds are found in seven-coordinate environments and bridged with monodentate, bidentate, or tridentate iodate anions. Both Lu(IO{sub 3}){sub 3}(H and Yb(IO{sub 3}){sub 3}(H{sub 2}O) display distinctively different vibrational profiles from their respective anhydrous analogs. Hence, the Raman profile can be used as a complementary diagnostic tool to discern the different structural motifs of the compounds. - Graphical abstract: Four new metal iodates, Yb(IO{sub 3

  18. Two-Dimensional Nb-Based M 4 C 3sub> Solid Solutions (MXenes)

    SciTech Connect

    Yang, Jian; Naguib, Michael; Ghidiu, Michael; Pan, Li-Mei; Gu, Jian; Nanda, Jagjit; Halim, Joseph; Gogotsi, Yury; Barsoum, Michel W.; Zhou, Y.

    2015-10-15

    Two new two-dimensional Nb4C3sub>-based solid solutions (MXenes), (Nb0.8,Ti0.2)4C3sub>Tx and (Nb0.8,Zr0.2)4C3sub>Tx (where T is a surface termination) were synthesizedas confirmed by X-ray diffractionfrom their corresponding MAX phase precursors (Nb0.8,Ti0.2)4AlC3sub> and (Nb0.8,Zr0.2)4AlC3sub>. In our report we discuss Zr-containing MXene. We also studied intercalation of Li ions into these two compositions, and Nb4C3sub>Tx in order to determine the potential of those materials for energy storage applications. Lithiation and delithiation peaks at 2.26 and 2.35 V, respectively, appeared in the case of Nb4C3sub>Tx, but were not present in Nb2CTx. After 20 cycles at a rate of C/4, the specific capacities of (Nb0.8,Ti0.2)4C3sub>Txand (Nb0.8,Ti0.2)4C3sub>Tx were 158 and 132 mAh/g, respectively, both slightly lower than the capacity of Nb4C3sub>Tx.

  19. New thallium iodates-Synthesis, characterization, and calculations of Tl(IO{sub 3}){sub 3} and Tl{sub 4}(IO{sub 3}){sub 6}, [Tl{sup +}{sub 3}Tl{sup 3+}(IO{sub 3}){sub 6}

    SciTech Connect

    Yeon, Jeongho; Kim, Sang-Hwan; Halasyamani, P. Shiv

    2009-12-15

    Two new thallium iodates have been synthesized, Tl(IO{sub 3}){sub 3} and Tl{sub 4}(IO{sub 3}){sub 6} [Tl{sup +}{sub 3}Tl{sup 3+}(IO{sub 3}){sub 6}], and characterized by single-crystal X-ray diffraction. Both materials were synthesized as phase-pure compounds through hydrothermal techniques using Tl{sub 2}CO{sub 3} and HIO{sub 3} as reagents. The materials crystallize in space groups R-3 (Tl(IO{sub 3}){sub 3}) and P-1 (Tl{sub 4}(IO{sub 3}){sub 6}). Although lone-pairs are observed for both I{sup 5+} and Tl{sup +}, electronic structure calculations indicate the lone-pair on I{sup 5+} is stereo-active, whereas the lone-pair on Tl{sup +} is inert. - Graphical abstract: Visualization of the stereo-active lone-pair (purple) through ELFs for Tl{sub 4}(IO{sub 3}){sub 6}. The spherical nature of the ELFs around the Tl{sup +} cation indicates the lone-pair is inert.

  20. Exchange-bias effect at La0.75Sr0.25MnO3sub>/LaNiO3sub> interfaces

    SciTech Connect

    Rojas Sánchez, J. C.; Nelson-Cheeseman, B.; Granada, M.; Arenholz, E.; Steren, L. B.

    2012-03-26

    In this paper, we show that ferromagnetic/paramagnetic La0.75Sr0.25MnO3sub>/LaNiO3sub> multilayers present an unexpected magnetic exchange-bias effect (EBE), observed in field-cooled magnetization loops. The exchange-bias field and the enhancement of the coercivity vanish around 50 K. We demonstrate that the oxidation state of the Ni and Mn cations changes from Mn3+-Ni3+ to Mn4+-Ni2+ in the layers close to the interface probed by x-ray absorption spectroscopy measurements. The variation of the valence states is accompanied by a change in the magnetic behavior of the cations at the La0.75Sr0.25MnO3sub>/LaNiO3sub> interface, possibly giving rise to the formation of magnetic or magnetically frustrated regions that may pin the ferromagnetic a0.75Sr0.25MnO3sub> layers and explain the EBE.

  1. Structure and optical properties of a noncentrosymmetric borate RbSr{sub 4}(BO{sub 3}){sub 3}

    SciTech Connect

    Xia, M.J.; Li, R.K.

    2013-01-15

    A new noncentrosymmetric borate, RbSr{sub 4}(BO{sub 3}){sub 3} (abbreviated as RSBO), has been grown from Rb{sub 2}O--B{sub 2}O{sub 3}--RbF flux and its crystal structure was determined by single crystal x-ray diffraction. It crystallizes in space group Ama2 with cell parameters of a=11.128(10) A, b=12.155(15) A, c=6.952(7) A, Z=4. The basic structural units are isolated planar BO{sub 3} groups. Second harmonic generation (SHG) test of the title compound by the Kurtz-Perry method shows that RSBO can be phase matchable with an effective SHG coefficient about two-thirds as large as that of KH{sub 2}PO{sub 4} (KDP). Finally, based on the anionic group approximation, the optical properties of the title compound are compared with those of the structure-related apatite-like compounds with the formula 'A{sub 5}(TO{sub n}){sub 3}X'. - Graphical abstract: RbSr{sub 4}(BO{sub 3}){sub 3} and some other borate NLO compounds, namely Ca{sub 5}(BO{sub 3}){sub 3}F RCa{sub 4}(BO{sub 3}){sub 3}O (R=Y or Gd) and Na{sub 3}La{sub 2}(BO{sub 3}){sub 3} can be viewed as the derivatives of apatite. They have similar formula composed of five cations and three anion groups (we call them 5/3 structures). The detailed SHG coefficients and optical properties of the apatite-like NLO crystals were compared and summarized. Highlights: Black-Right-Pointing-Pointer A new noncentrosymmetric borate RbSr{sub 4}(BO{sub 3}){sub 3} was grown from flux. Black-Right-Pointing-Pointer The RbSr{sub 4}(BO{sub 3}){sub 3} can be viewed as a derivative of the apatite-like structure. Black-Right-Pointing-Pointer The structure and its relationship to the optical properties of RbSr{sub 4}(BO{sub 3}){sub 3} are compared with other NLO crystals with apatite-like structures. Black-Right-Pointing-Pointer The basic structural units are the planar BO{sub 3} groups in the structure. Black-Right-Pointing-Pointer Second harmonic generation (SHG) test shows that RbSr{sub 4}(BO{sub 3}){sub 3} can be phase matchable with an

  2. Electrochemical Reduction of CO2 to CH3sub>OH at Copper Oxide Surfaces

    SciTech Connect

    Le, Minh; Ren, Maoming; Zhang, Ziyu; Sprunger, Phillip T.; Kurtz, Richard L.; Flake, John C.

    2011-03-05

    The direct reduction of CO2 to CH3sub>OH is known to occur at several types of electrocatalysts including oxidized Cu electrodes. In this work, we examine the yield behavior of an electrodeposited cuprous oxide thin film and explore relationships between surface chemistry and reaction behavior relative to air-oxidized and anodized Cu electrodes. CH3sub>OH yields (43 μmol cm-2 h-1) and Faradaic efficiencies (38%) observed at cuprous oxide electrodes were remarkably higher than air-oxidized or anodized Cu electrodes suggesting Cu(I) species may play a critical role in selectivity to CH3sub>OH. Experimental results also show CH3sub>OH yields are dynamic and the copper oxides are reduced to metallic Cu in a simultaneous process. Yield behavior is discussed in comparison with photoelectrochemical and hydrogenation reactions where the improved stability of Cu(I) species may allow continuous CH3sub>OH generation.

  3. Coupling of Crystal Structure and Magnetism in the Layered, Ferromagnetic Insulator CrI 3sub>

    SciTech Connect

    McGuire, Michael A.; Dixit, Hemant; Cooper, Valentino R.; Sales, Brian C.

    2014-12-23

    Here, we examine the crystallographic and magnetic properties of single crystals of CrI3sub>, an easily cleavable, layered and insulating ferromagnet with a Curie temperature of 61 K. Our X-ray diffraction studies reveal a first-order crystallographic phase transition occurring near 210–220 K upon warming, with significant thermal hysteresis. The low-temperature structure is rhombohedral (R$\\bar{3}$, BiI3sub>-type) and the high-temperature structure is monoclinic (C2/m, AlCl3sub>-type). Evidence for coupling between the crystallographic and magnetic degrees of freedom in CrI3sub> was found; we observed an anomaly in the interlayer spacing at the Curie temperature and an anomaly in the magnetic susceptibility at the structural transition. First-principles calculations reveal the importance of proper treatment of the long-ranged interlayer forces, and van der Waals density functional theory does an excellent job of predicting the crystal structures and their relative stability. Our calculations suggest that the ferromagnetic order found in the bulk material may persist into monolayer form, suggesting that CrI3sub> and other chromium trihalides may be promising materials for spintronic and magnetoelectronic research.

  4. Effects of Mg doping on the remarkably enhanced electrochemical performance of Na3sub>V2(PO4)3sub> cathode materials for sodium ion batteries

    SciTech Connect

    Li, Hui; Yu, Xiqian; Bai, Ying; Wu, Feng; Wu, Chuan; Liu, Liang-Yu; Yang, Xiao-Qing

    2015-01-01

    Na3sub>V2-xMgx(PO4)3sub>/C composites with different Mg2+ doping contents (x=0, 0.01, 0.03, 0.05, 0.07 and 0.1) were prepared by a facile sol-gel method. The doping effects on the crystal structure were investigated by XRD, XPS and EXAFS. The results show that low dose doping Mg2+ does not alter the structure of the material, and magnesium is successfully substituted for vanadium site. The Mg doped Na3sub>V2-xMgx(PO4)3sub>/C composites exhibit significant improvements on the electrochemistry performances in terms of the rate capability and cycle performance, especially for the Na3sub>V1.95Mg0.05(PO4)3sub>/C. For example, when the current density increased from 1 C to 30 C, the specific capacity only decreased from 112.5 mAh g-1 to 94.2 mAh g-1 showing very good rate capability. Moreover, even cycling at a high rate of 20 C, an excellent capacity retention of 81% is maintained from the initial value of 106.4 mAh g-1 to 86.2 mAh g-1 at the 50th cycle. Enhanced rate capability and cycle performance can be attributed to the optimized particle size, structural stability and enhanced ionic and electronic conductivity induced by Mg doping.

  5. Controlled Formation of Mixed Nanoscale Domains of High Capacity Fe2O3sub>–FeF3sub> Conversion Compounds by Direct Fluorination

    SciTech Connect

    Zhou, Hui; Ruther, Rose E.; Adcock, Jamie; Zhou, Wu; Dai, Sheng; Nanda, Jagjit

    2015-02-22

    In this paper, we report a direct fluorination method under fluorine gas atmosphere using a fluidized bed reactor for converting nanophase iron oxide (n-Fe2O3sub>) to an electrochemically stable and higher energy density iron oxyfluoride/fluoride phase. Interestingly, no noticeable bulk iron oxyfluoride phase (FeOF) phase was observed even at fluorination temperature close to 300 °C. Instead, at fluorination temperatures below 250 °C, scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM-EELS) and X-ray photoelectron spectroscopy (XPS) analysis showed surface fluorination with nominal composition, Fe2O3-xF2x (x < 1). At fluorination temperatures of 275 °C, STEM-EELS results showed porous interconnected nanodomains of FeF3sub> and Fe2O3sub> coexisting within the same particle, and overall the particles become less dense after fluorination. We performed potentiometric intermittent titration and electrochemical impedance spectroscopy studies to understand the lithium diffusion (or apparent diffusion) in both the oxyfluoride and mixed phase FeF3sub> + Fe2O3sub> composition, and correlate the results to their electrochemical performance. Finally and further, we analyze from a thermodynamical perspective, the observed formation of the majority fluoride phase (77% FeF3sub>) and the absence of the expected oxyfluoride phase based on the relative formation energies of oxide, fluoride, and oxyfluorides.

  6. Scalar-quark systems and chimera hadrons in SU(3){sub c} lattice QCD

    SciTech Connect

    Iida, H.; Takahashi, T. T.; Suganuma, H.

    2007-06-01

    In terms of mass generation in the strong interaction without chiral symmetry breaking, we perform the first study for light scalar-quarks {phi} (colored scalar particles with 3{sub c} or idealized diquarks) and their color-singlet hadronic states using quenched SU(3){sub c} lattice QCD with {beta}=5.70 (i.e., a{approx_equal}0.18 fm) and lattice size 16{sup 3}x32. We investigate ''scalar-quark mesons'' {phi}{sup {dagger}}{phi} and ''scalar-quark baryons'' {phi}{phi}{phi} as the bound states of scalar-quarks {phi}. We also investigate the color-singlet bound states of scalar-quarks {phi} and quarks {psi}, i.e., {phi}{sup {dagger}}{psi}, {psi}{psi}{phi}, and {phi}{phi}{psi}, which we name ''chimera hadrons.'' All the new-type hadrons including {phi} are found to have a large mass even for zero bare scalar-quark mass m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV. We find a ''constituent scalar-quark/quark picture'' for both scalar-quark hadrons and chimera hadrons. Namely, the mass of the new-type hadron composed of m {phi}'s and n {psi}'s, M{sub m{phi}}{sub +n{psi}}, approximately satisfies M{sub m{phi}}{sub +n{psi}}{approx_equal}mM{sub {phi}}+nM{sub {psi}}, where M{sub {phi}} and M{sub {psi}} are the constituent scalar-quark and quark masses, respectively. We estimate the constituent scalar-quark mass M{sub {phi}} for m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV as M{sub {phi}}{approx_equal}1.5-1.6 GeV, which is much larger than the constituent quark mass M{sub {psi}}{approx_equal}400 MeV in the chiral limit. Thus, scalar quarks acquire a large mass due to large quantum corrections by gluons in the systems including scalar quarks. Together with other evidences of mass generation of glueballs and charmonia, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluon effects. In addition, the large mass generation of pointlike colored scalar particles indicates that plausible diquarks used in effective hadron models cannot

  7. High-energy passively Q-switched laser operation of Yb:Ca3sub>La2(BO3sub>)4 disordered crystal.

    PubMed

    Wang, Lisha; Han, Wenjuan; Pan, Zhongben; Xu, Honghao; Chen, Xiaowen; Liu, Junhai; Yu, Haohai; Zhang, Huaijin

    2016-05-01

    Efficient high-energy passively Q-switched laser operation was demonstrated with Yb:Ca3sub>La2(BO3sub>)4 disordered crystal, producing an average output power of 3.0 W at 1018.7 nm, at a pulse repetition frequency of 5.0 kHz; the resulting pulse energy, duration, and peak power were 600 μJ, 5.3 ns, and 113.2 kW, respectively. PMID:27140354

  8. BF3sub>-promoted electrochemical properties of quinoxaline in propylene carbonate

    SciTech Connect

    Carino, Emily V.; Diesendruck, Charles E.; Moore, Jeffrey S.; Curtiss, Larry A.; Assary, Rajeev S.; Brushett, Fikile R.

    2015-02-04

    Electrochemical and density functional studies demonstrate that coordination of electrolyte constituents to quinoxalines modulates their electrochemical properties. Quinoxalines are shown to be electrochemically inactive in most electrolytes in propylene carbonate, yet the predicted reduction potential is shown to match computational estimates in acetonitrile. We find that in the presence of LiBF4 and trace water, an adduct is formed between quinoxaline and the Lewis acid BF3, which then displays electrochemical activity at 1–1.5 V higher than prior observations of quinoxaline electrochemistry in non-aqueous media. Direct synthesis and testing of a bis-BF3sub> quinoxaline complex further validates the assignment of the electrochemically active species, presenting up to a ~26-fold improvement in charging capacity, demonstrating the advantages of this adduct over unmodified quinoxaline in LiBF4-based electrolyte. The use of Lewis acids to effectively “turn on” the electrochemical activity of organic molecules may lead to the development of new active material classes for energy storage applications.

  9. Capturing ultrafast photoinduced local structural distortions of BiFeO3sub>

    SciTech Connect

    Wen, Haidan; Sassi, Michel JPC; Luo, Zhenlin; Adamo, Carolina; Schlom, Darrell; Rosso, Kevin M.; Zhang, Xiaoyi

    2015-10-14

    The interaction of light with materials is an intensively studied research forefront, in which the coupling of radiation energy to selective degrees of freedom offers contact-free tuning of functionalities on ultrafast time scales. Capturing the fundamental processes and understanding the mechanism of photoinduced structural rearrangement are essential to applications such as photo-active actuators and efficient photovoltaic devices. Using ultrafast x-ray absorption spectroscopy aided by density functional theory calculations, we reveal the local structural arrangement around the transition metal atom in a unit cell of the photoferroelectric archetype BiFeO3sub> film. The out-of-plane elongation of the unit cell is accompanied by the in-plane shrinkage with minimal change of interaxial lattice angles upon photoexcitation. This uniaxial elastic deformation of the unit cell is driven by localized electric field as a result of photoinduced charge separation, in contrast to a global lattice constant increase and lattice angle variations as a result of heating. The finding of a photoinduced elastic unit cell deformation elucidates a microscopic picture of photocarrier-mediated nonequilibrium processes in polar materials.

  10. Electric control of magnetism at the Fe/BaTiO3sub> interface

    SciTech Connect

    Radaelli, G.; Petti, D.; Plekhanov, E.; Fina, I.; Torelli, P.; Salles, B. R.; Cantoni, M.; Rinaldi, C.; Gutiérrez, D.; Panaccione, G.; Varela, M.; Picozzi, S.; Fontcuberta, J.; Bertacco, R.

    2014-03-03

    Interfacial magnetoelectric coupling (MEC) is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO3sub> (BTO) system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BTO dielectric polarization have been predicted so far. Here, by using X-ray magnetic circular dichroism in combination with high resolution electron microscopy and first principles calculations, we report on an undisclosed physical mechanism for interfacial MEC in the Fe/BTO system. At the Fe/BTO interface, an ultrathin FeOx layer exists, whose magnetization can be electrically and reversibly switched on-off at room-temperature by reversing the BTO polarization. The suppression / recovery of interfacial ferromagnetism results from the asymmetric effect that ionic displacements in BTO produces on the exchange coupling constants in the adjacent FeOx layer. The observed giant magnetoelectric response holds potential for optimizing interfacial MEC in view of efficient, low-power spintronic devices.

  11. Magnetism and Metal-Insulator Transition in Oxygen Deficient SrTiO3sub>

    SciTech Connect

    Lopez-Bezanilla, Alejandro; Ganesh, Panchapakesan; Littlewood, Peter B.

    2015-09-08

    First-principles calculations to study the electronic and magnetic properties of bulk, oxygen-deficient SrTiO3sub> (STO) under different doping conditions and densities have been conducted. The appearance of magnetism in oxygen-deficient STO is not determined solely by the presence of a single oxygen vacancy but by the density of free carriers and the relative proximity of the vacant sites. We find that while an isolated vacancy behaves as a nonmagnetic double donor, manipulation of the doping conditions allows the stability of a single-donor state, with emergent local moments coupled ferromagnetically by carriers in the conduction band. Strong local lattice distortions enhance the binding of this state. The energy of the in-gap local moment can be further tuned by orthorhombic strain. Consequently we find that the free-carrier density and strain are fundamental components to obtaining trapped spin-polarized electrons in oxygen-deficient STO, which may have important implications in the design of optical devices.

  12. Classification of AB O 3sub> perovskite solids: a machine learning study

    SciTech Connect

    Pilania, G.; Balachandran, P. V.; Gubernatis, J. E.; Lookman, T.

    2015-07-23

    Here we explored the use of machine learning methods for classifying whether a particularABO3sub>chemistry forms a perovskite or non-perovskite structured solid. Starting with three sets of feature pairs (the tolerance and octahedral factors, theAandBionic radii relative to the radius of O, and the bond valence distances between theAandBions from the O atoms), we used machine learning to create a hyper-dimensional partial dependency structure plot using all three feature pairs or any two of them. Doing so increased the accuracy of our predictions by 2–3 percentage points over using any one pair. We also included the Mendeleev numbers of theAandBatoms to this set of feature pairs. Moreover, doing this and using the capabilities of our machine learning algorithm, the gradient tree boosting classifier, enabled us to generate a new type of structure plot that has the simplicity of one based on using just the Mendeleev numbers, but with the added advantages of having a higher accuracy and providing a measure of likelihood of the predicted structure.

  13. Understanding strain-induced phase transformations in BiFeO3sub> thin films

    SciTech Connect

    Dixit, Hemant; Beekman, Christianne; Schlepütz, Christian M.; Siemons, Wolter; Yang, Yongsoo; Senabulya, Nancy; Clarke, Roy; Chi, Miaofang; Christen, Hans M.; Cooper, Valentino R.

    2015-05-01

    Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO₃ thin films, which comprises a tetragonal-like (T´) and an intermediate S´ polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniform T´ phase. This strain-induced phase transformation is investigated through a synergistic combination of first-principles theory and experiments. The results show that the S´ phase is energetically very close to the T´ phase, but is structurally similar to the bulk rhombohedral (R) phase. By fully characterizing the intermediate S´ polymorph, it is demonstrated that the flat energy landscape resulting in the absence of an energy barrier between the T´ and S´ phases fosters the above-mentioned reversible phase transformation. This ability to readily transform between the S´ and T´ polymorphs, which have very different octahedral rotation patterns and c/a ratios, is crucial to the enhanced piezoelectricity in strained BiFeO3sub> films. Additionally, a blueshift in the band gap when moving from R to S´ to T´ is observed. These results emphasize the importance of strain engineering for tuning electromechanical responses or, creating unique energy harvesting photonic structures, in oxide thin film architectures.

  14. Capturing ultrafast photoinduced local structural distortion of BiFeO3sub>

    SciTech Connect

    Wen, Haidan; Sassi, Michel; Luo, Zhenlin; Adamo, Carolina; Schlom, Darrell G.; Rosso, Kevin M.; Zhang, Xiaoyi

    2015-10-14

    The interaction of light with materials is an intensively studied research forefront, in which the coupling of radiation energy to selective degrees of freedom offers contact-free tuning of functionalities on ultrafast time scales. Capturing the fundamental processes and understanding the mechanism of photoinduced structural rearrangement are essential to applications such as photo-active actuators and efficient photovoltaic devices. Using ultrafast x-ray absorption spectroscopy aided by density functional theory calculations, we reveal the local structural arrangement around the transition metal atom in a unit cell of the photoferroelectric archetype BiFeO3sub> film. The out-of-plane elongation of the unit cell is accompanied by the in-plane shrinkage with minimal change of interaxial lattice angles upon photoexcitation. This anisotropic elastic deformation of the unit cell is driven by localized electric field as a result of photoinduced charge separation, in contrast to a global lattice constant increase and lattice angle variations as a result of heating. The finding of a photoinduced elastic unit cell deformation elucidates a microscopic picture of photocarrier-mediated non-equilibrium processes in polar materials.

  15. A SCR Model Calibration Approach with Spatially Resolved Measurements and NH3sub> Storage Distributions

    SciTech Connect

    Song, Xiaobo; Parker, Gordon G.; Johnson, John H.; Naber, Jeffrey D.; Pihl, Josh A.

    2014-11-27

    The selective catalytic reduction (SCR) is a technology used for reducing NO x emissions in the heavy-duty diesel (HDD) engine exhaust. In this study, the spatially resolved capillary inlet infrared spectroscopy (Spaci-IR) technique was used to study the gas concentration and NH3sub> storage distributions in a SCR catalyst, and to provide data for developing a SCR model to analyze the axial gaseous concentration and axial distributions of NH3sub> storage. A two-site SCR model is described for simulating the reaction mechanisms. The model equations and a calculation method was developed using the Spaci-IR measurements to determine the NH3sub> storage capacity and the relationships between certain kinetic parameters of the model. Moreover, a calibration approach was then applied for tuning the kinetic parameters using the spatial gaseous measurements and calculated NH3 storage as a function of axial position instead of inlet and outlet gaseous concentrations of NO, NO2, and NH3sub>. The equations and the approach for determining the NH3sub> storage capacity of the catalyst and a method of dividing the NH3sub> storage capacity between the two storage sites are presented. It was determined that the kinetic parameters of the adsorption and desorption reactions have to follow certain relationships for the model to simulate the experimental data. Finally, the modeling results served as a basis for developing full model calibrations to SCR lab reactor and engine data and state estimator development as described in the references (Song et al. 2013a, b; Surenahalli et al. 2013).

  16. Polymorphism in {kappa}-(BEDT-TTF){sub 2}M(CF{sub 3}){sub 4}(solvent) superconductors

    SciTech Connect

    Geiser, U.; Schlueter, J.A.; Williams, J.M.; Kini, A.M.; Dudek, J.D.; Kelly, M.E.; Naumann, D.; Roy, T.

    1996-09-01

    A new crystallographic modification ({Kappa}{sub L}{sup `}) was found in the BEDT-TTF:M(CF{sub 3}){sub 4}{sup -}: solvent (M=Cu, Ag, Au) system. The structure of monoclinic {Kappa}{sub L}{sup `}-(BEDT- TTF){sub 2}Cu(CF{sub 3}){sub 4}(1,2-dibromo-1-chloroethane = DCBE) is reported. It differs from the orthorhombic {Kappa}{sub L}{sup `}- phase by having all BEDT-TTF molecules tilted in the same direction with respect to the conducting phase normal, whereas in {Kappa}{sub L} the tilt direction alternates between layers.

  17. Strain tuning of electronic structure in Bi4Ti3sub>O12-LaCoO3sub> epitaxial thin films

    SciTech Connect

    Choi, Woo Seok; Lee, Ho Nyung

    2015-05-08

    In this study, we investigated the crystal and electronic structures of ferroelectric Bi4Ti3sub>O12 single-crystalline thin films site-specifically substituted with LaCoO3sub> (LCO). The epitaxial films were grown by pulsed laser epitaxy on NdGaO3sub> and SrTiO3sub> substrates to vary the degree of strain. With increasing the LCO substitution, we observed a systematic increase in the c-axis lattice constant of the Aurivillius phase related with the modification of pseudo-orthorhombic unit cells. These compositional and structural changes resulted in a systematic decrease in the band gap, i.e., the optical transition energy between the oxygen 2p and transition-metal 3d states, based on a spectroscopic ellipsometry study. In particular, the Co 3d state seems to largely overlap with the Ti t2g state, decreasing the band gap. Interestingly, the applied tensile strain facilitates the band-gap narrowing, demonstrating that epitaxial strain is a useful tool to tune the electronic structure of ferroelectric transition-metal oxides.

  18. Direct observation of oxygen-vacancy-enhanced polarization in a SrTiO3sub>-buffered ferroelectric BaTiO3sub> film on GaAs

    SciTech Connect

    Qiao, Q.; Zhang, Y.; Contreras-Guerrero, Rocio; Droopad, Ravi; Pantelides, S. T.; Pennycook, Stephen J.; Ogut, Serdar; Klie, Robert F.

    2015-11-16

    The integration of functional oxide thin-films on compound semiconductors can lead to a class of reconfigurable spin-based optoelectronic devices if defect-free, fully reversible active layers are stabilized. However, previous first-principles calculations predicted that SrTiO3sub> thin filmsgrown on Si exhibit pinned ferroelectric behavior that is not switchable, due to the presence of interfacial vacancies. Meanwhile, piezoresponse force microscopy measurements have demonstrated ferroelectricity in BaTiO3sub> grown on semiconductor substrates. The presence of interfacial oxygen vacancies in such complex-oxide/semiconductor systems remains unexplored, and their effect on ferroelectricity is controversial. We also use a combination of aberration-corrected scanning transmission electron microscopy and first-principles density functional theory modeling to examine the role of interfacial oxygen vacancies on the ferroelectricpolarization of a BaTiO3sub> thin filmgrown on GaAs. Moreover, we demonstrate that interfacial oxygen vacancies enhance the polar discontinuity (and thus the single domain, out-of-plane polarization pinning in BaTiO3sub>), and propose that the presence of surface charge screening allows the formation of switchable domains.

  19. Engineering two-dimensional superconductivity and Rashba spin–orbit coupling in LaAlO3sub>/SrTiO3sub> quantum wells by selective orbital occupancy

    SciTech Connect

    Herranz, Gervasi; Singh, Gyanendra; Bergeal, Nicolas; Jouan, Alexis; Lesueur, Jérôme; Gázquez, Jaume; Varela, María; Scigaj, Mateusz; Dix, Nico; Sánchez, Florencio; Fontcuberta, Josep

    2015-01-13

    We find the discovery of two-dimensional electron gases (2DEGs) at oxide interfaces—involving electrons in narrow d-bands—has broken new ground, enabling the access to correlated states that are unreachable in conventional semiconductors based on s- and p- electrons. There is a growing consensus that emerging properties at these novel quantum wells—such as 2D superconductivity and magnetism—are intimately connected to specific orbital symmetries in the 2DEG sub-band structure. Here we show that crystal orientation allows selective orbital occupancy, disclosing unprecedented ways to tailor the 2DEG properties. By carrying out electrostatic gating experiments in ​LaAlO3sub>/​SrTiO3sub> wells of different crystal orientations, we show that the spatial extension and anisotropy of the 2D superconductivity and the Rashba spin–orbit field can be largely modulated by controlling the 2DEG sub-band filling. Such an orientational tuning expands the possibilities for electronic engineering of 2DEGs at ​LaAlO3sub>/​SrTiO3sub> interfaces.

  20. Structural properties of Y2O3sub>–Al2O3sub> liquids and glasses: An overview

    SciTech Connect

    Wilding, Martin C.; Wilson, Mark; McMillan, Paul F.; Benmore, Chris J.; Weber, J. K. R.; Deschamps, Thierry; Champagnon, Bernard

    2015-01-01

    Liquids in the system Y2O3sub>–Al2O3sub> have been the subject of considerable study because of the reported occurrence of a first-order density and entropy-driven liquid-liquid phase transition (LLPT) in the supercooled liquid state. The observations have become controversial because of the presence of crystalline material that can be formed simultaneously and that can mask the nucleation and growth of the lower density liquid. The previous work is summarized here along with arguments for and against the different viewpoints. Also two studies have been undertaken to investigate the LLPT in this refractory system with emphasis on determining the structure of unequivocally amorphous materials. These include the in situ high energy X-ray diffraction (HEXRD) of supercooled Y2O3sub>–Al2O3sub> liquids and the low frequency vibrational dynamics of recovered glasses. Manybody molecular dynamics simulations are also used to interpret the results of both studies. The HEXRD measurements, combined with aerodynamic levitation and rapid data acquisition techniques, show that for the 20 mol% Y2O3sub> (i.e. AlY20) liquid there is a shift in the position of the first peak in the diffraction pattern over a narrow temperature range (2100-1800 K) prior to crystallization. Microbeam Raman spectroscopy measurements made on AlY20 glasses clearly show contrasting spectra in the low frequency part of the spectrum for low(LDA) and high-density (HDA) glassy regions. The molecular dynamics simulations identify contrasting coordination environments around oxygen anions for the high- (HDL) and low-density (LDL) liquids. (C) 2014 Elsevier B.V. All rights reserved.

  1. Complex doping of group 13 elements In and Ga in caged skutterudite CoSb3sub>

    SciTech Connect

    Xi, Lili; Qiu, Yting; Zheng, Shang; Shi, Xun; Yang, Jiong; Chen, Lidong; Singh, David J.; Yang, Jihui; Zhang, Wenqing

    2014-12-12

    The complex doping behavior of Ga and In in CoSb3sub> has been investigated using ab initio total-energy calculations and thermodynamics. The formation energies of void filling, Sb substitution and complex dual-site occupancy defects with different charge states, and their dependence on chemical potentials of species, were studied. Results show that Ga predominantly forms dual-site 2GaVF–GaSb defects and substitutes for Sb only at very high Fermi levels or electron concentrations. In, on the other hand, can play multiple roles in skutterudites, including filling in the crystalline voids, substituting for Sb atoms or forming dual-site occupancy, among which the fully charge-compensated dual-site defects (2InVF–InSb and 4InVF–2InSb) are dominant. The equilibrium concentration ratio of impurities at void-filling sites to those at Sb-substitution sites for Ga-doped CoSb3sub> is very close to be 2:1, while this value markedly deviates from 2:1 for In-doped CoSb3sub>. Furthermore, the 2:1 ratio of Ga doping in CoSb3sub> leads to low electron concentration (~2 × 1019 cm–3) and makes the doped system a semiconductor.

  2. Structure and luminescence properties of silver-doped NaY(PO{sub 3}){sub 4} crystal

    SciTech Connect

    El Masloumi, M.; Jubera, V.; Pechev, S.; Chaminade, J.P.; Videau, J.J. Mesnaoui, M.; Maazaz, M.; Moine, B.

    2008-11-15

    Single crystals of NaY(PO{sub 3}){sub 4} and Ag{sub 0.07}Na{sub 0.93}Y(PO{sub 3}){sub 4} have been synthesized by flux method. These new compounds turned out to be isostructural to NaLn(PO{sub 3}){sub 4}, with Ln=La, Nd, Gd and Er [monoclinic, P2{sub 1}/n, a=7.1615(2) A, b=13.0077(1) A, c=9.7032 (3) A, {beta}=90.55 (1){sup o}, V=903.86(14) A{sup 3} and Z=4]. The structure is based upon long polyphosphate chains running along the shortest unit-cell direction and made up of PO{sub 4} tetrahedra sharing two corners, linked to yttrium and sodium polyhedra. Infrared and Raman spectra at room temperature confirms this atomic arrangement. The luminescence of silver ions was reported in metaphosphate of composition Ag{sub 0.07}Na{sub 0.93}Y(PO{sub 3}){sub 4}. One luminescent centre was detected and assigned to single Ag{sup +} ions. - Graphical abstract: The presence of only one Ag{sup +} luminescence centre is the result from the perfect isolation (Ag{sup +}-Ag{sup +}=5.90 A) of each oxygenated silver site (AgO{sub 8} polyhedra) sharing two faces and one corner with three yttrium polyhedra.

  3. Atomic Layer Deposition of Fe2O3sub> Using Ferrocene and Ozone

    SciTech Connect

    Martinson, Alex B.F.; DeVries, Michael J.; Libera, J. A.; Christensen, S. T.; Hupp, Joseph T.; Pellin, Michael J.; Elam, Jeffrey W.

    2011-02-22

    Growing interest in Fe2O3sub> as a light harvesting layer in solar energy conversion devices stems from its unique combination of stability, nontoxicity, and exceptionally low material cost. Unfortunately, the known methods for conformally coating high aspect ratio structures with Fe2O3sub> leave a glaring gap in the technologically relevant temperature range of 170-350 °C. Here, we elucidate a self-limiting atomic layer deposition (ALD) process for the growth of hematite, α-Fe2O3sub>, over a moderate temperature window using ferrocene and ozone. At 200 °C, the self-limiting growth of Fe2O3sub> is observed at rates up to 1.4 Å/cycle. Dense and robust thin films grown on both fused quartz and silicon exhibit the expected optical bandgap (2.1 eV). In situ mass spectrometric analysis reveals the evolution of two distinct cyclic reaction products during the layer-by-layer growth. The readily available and relatively high vapor pressure iron precursor is utilized to uniformly coat a high surface area template with aspect ratio ~150.

  4. A facile solvothermal synthesis of octahedral Fe3sub>O4 nanoparticles

    SciTech Connect

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

    2015-01-26

    Anisotropic Fe3sub>O4 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.

  5. Quadruplexes of human telomere dG{sub 3}(TTAG{sub 3}){sub 3} sequences containing guanine abasic sites

    SciTech Connect

    Skolakova, Petra; Bednarova, Klara; Vorlickova, Michaela; Sagi, Janos

    2010-08-20

    Research highlights: {yields} Loss of a guanine base does not hinder the formation of G-quadruplex of human telomere sequence. {yields} Each depurination strongly destabilizes the quadruplex of dG{sub 3}(TTAG{sub 3}){sub 3} in NaCl and KCl. {yields} Conformational change of the abasic analogs of dG{sub 3}(TTAG{sub 3}){sub 3} is inhibited in KCl. {yields} The effects abasic sites may affect telomere-end structures in vivo. -- Abstract: This study was performed to evaluate how the loss of a guanine base affects the structure and stability of the three-tetrad G-quadruplex of 5'-dG{sub 3}(TTAG{sub 3}){sub 3}, the basic quadruplex-forming unit of the human telomere DNA. None of the 12 possible abasic sites hindered the formation of quadruplexes, but all reduced the thermodynamic stability of the parent quadruplex in both NaCl and KCl. The base loss did not change the Na{sup +}-stabilized intramolecular antiparallel architecture, based on CD spectra, but held up the conformational change induced in dG{sub 3}(TTAG{sub 3}){sub 3} in physiological concentration of KCl. The reduced stability and the inhibited conformational transitions observed here in vitro for the first time may predict that unrepaired abasic sites in G-quadruplexes could lead to changes in the chromosome's terminal protection in vivo.

  6. Composite WO3sub>/TiO2 nanostructures for high electrochromic activity

    SciTech Connect

    Reyes-Gil, Karla R.; Stephens, Zachary D.; Stavila, Vitalie; Robinson, David B.

    2015-01-06

    A composite material consisting of TiO2 nanotubes (NT) with WO3sub> electrodeposited on its surface has been fabricated, detached from its Ti substrate, and attached to a fluorine-doped tin oxide (FTO) film on glass for application to electrochromic (EC) reactions. Several adhesion layers were tested, finding that a paste of TiO2 made from commercially available TiO2 nanoparticles creates an interface for the TiO2 NT film to attach to the FTO glass, which is conductive and does not cause solution-phase ions in an electrolyte to bind irreversibly with the material. The effect of NT length and WO3sub> concentration on the EC performance were studied. As a result, the composite WO3sub>/TiO2 nanostructures showed higher ion storage capacity, better stability, enhanced EC contrast, and longer memory time compared with the pure WO3sub> and TiO2 materials

  7. Characterization of second-phase plates in a Gd5Ge3sub> intermetallic compound

    SciTech Connect

    Cao, Qing; Chumbley, Leonard S.

    2013-05-16

    Rare-earth compounds based on the stoichiometry R5(SixGe1-x)4 (R = rare-earth elements) exhibit many unusual features, including possessing R5(SixGe1-x)3sub> thin plates which always precipitate from the matrix despite efforts to suppress their formation. In an effort to better understand the unique relationship between these two intermetallic alloy systems, the bulk microstructure of the compound Gd5Ge3sub> was examined using scanning (SEM) and transmission electron microscopy (TEM) and optical microscopy. Surprisingly, SEM examination revealed a series of thin plates present in the Gd5Ge3sub> matrix similar to what is seen in Gd5Ge4. TEM observation revealed that a role reversal had occurred, with the thin plates possessing the orthorhombic structure and composition of Gd5Ge4. The orientation relationship between Gd5Ge4 thin plates and the Gd5Ge3sub> matrix was determined to be Graphic the same relationship reported for Gd5Ge3sub> plates precipitating from a Gd5Ge4 matrix. However, by exchanging the respective roles of the phases as regards matrix vs. precipitate, the total number of precipitation variants seen can be increased from two to six. The persistence with which these two intermetallic systems co-exist is truly unique. However, understanding exactly the kinetic and thermodynamic conditions that lead to their unique relationship is hampered by the high formation temperatures at which the observed reaction occurs.

  8. Observation on the Ion Association Equilibria in NaNO3sub> Droplets Using Micro-Raman Spectroscopy

    SciTech Connect

    Yu, Jun-Ying; Zhang, Yun; Tan, See-Hua; Liu, Yong; Zhang, Yun-Hong

    2012-10-18

    Ion association ratios as a function of concentration were estimated in single NaNO3sub> droplets (5–60 μm) on a polytetrafluoroethylene (PTFE) substrate with molar water-to-solute ratios (WSRs) of 0.8–28 and bulk NaNO3sub> solutions with WSRs of 35–200 by combining micro-Raman spectroscopy and component band analysis. Concentrations of the NaNO3sub> droplets were accurately controlled by adjusting relative humidity (RH) in a sample chamber. As the WSRs decreased from 200 to 0.8, symmetric stretching band (ν1-NO3sub>–) was observed to shift from 1047 to 1058 cm–1 along with a change in full width at half-maximum (fwhm) from ~10 to ~16 cm–1, indicative of formation of ion pairs with different structures. Through the component band analysis of the ν1-NO3sub>– band, five bands centered at 1040.0, 1042.9, 1048.5, 1053.5, and 1057.0 cm–1 were identified and assigned to coupled wagging modes of water molecules hydrated with nitrate ions, free hydrated nitrate anions, solvent-shared ion pairs (SIPs), contact ion pairs (CIPs), and the complex ion aggregates (CIAs), respectively. There were large amounts of SIPs and CIPs in dilute NaNO3sub> solution even at an extremely low concentration (WSR ~ 200), and each accounted for 50% and 20% of total nitrate species, respectively. This finding is in good agreement with earlier reported observations. In the dilute solutions (45 < WSR < 200), there is the same amount of free hydrated ions transformed into SIPs as that of SIPs transformed into CIPs. As a result, the overall amount of SIPs remained unchanged over the concentration range. With a decrease in WSR from 45 to 0.8, the amounts of SIPs and free solvated NO3sub>– ions kept decreasing, whereas the amount of CIPs rose to a maximum at WSR = 7 and then fell with a further decreasing WSR. Formation of CIAs started at WSR ~ 45, and its amount continuously

  9. Selective interlayer ferromagnetic coupling between the Cu spins in YBa2Cu3sub>O7–x grown on top of La0.7Ca0.3sub>MnO3sub>

    SciTech Connect

    Huang, S. W.; Wray, L. Andrew; Jeng, Horng -Tay; Tra, V. T.; Lee, J. M.; Langner, M. C.; Chen, J. M.; Roy, S.; Chu, Y. H.; Schoenlein, R. W.; Chuang, Y. -D.; Lin, J. -Y.

    2015-11-17

    Studies to date on ferromagnet/d-wave superconductor heterostructures focus mainly on the effects at or near the interfaces while the response of bulk properties to heterostructuring is overlooked. Here we use resonant soft x-ray scattering spectroscopy to reveal a novel c-axis ferromagnetic coupling between the in-plane Cu spins in YBa2Cu3sub>O7–x (YBCO) superconductor when it is grown on top of ferromagnetic La0.7Ca0.3sub>MnO3sub> (LCMO) manganite layer. This coupling, present in both normal and superconducting states of YBCO, is sensitive to the interfacial termination such that it is only observed in bilayers with MnO2 but not with La0.7Ca0.3sub>O interfacial termination. Thus, such contrasting behaviors, we propose, are due to distinct energetic of CuO chain and CuO2 plane at the La0.7Ca0.3sub>O and MnO2 terminated interfaces respectively, therefore influencing the transfer of spin-polarized electrons from manganite to cuprate differently. Our findings suggest that the superconducting/ferromagnetic bilayers with proper interfacial engineering can be good candidates for searching the theorized Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state in cuprates and studying the competing quantum orders in highly correlated electron systems.

  10. Sub-80 femtosecond pulses generation from a diode-pumped mode-locked Nd:Ca3sub>La2(BO3sub>)4 disordered crystal laser.

    PubMed

    Ma, Jie; Pan, Zhongben; Cai, Huaqiang; Yu, Haohai; Zhang, Huaijin; Shen, Deyuan; Tang, Dingyuan

    2016-04-01

    We experimentally demonstrated a diode-pumped sub-80 fs Nd:Ca3sub>La2(BO3sub>)4 disordered crystal laser. Pumping by an 808 nm fiber coupled laser diode, stable continuous-wave mode-locked pulses as short as 79 fs were achieved with a semiconductor saturable absorber mirror (SESAM). The ultrashort pulses had a repetition rate of ∼98.9  MHz at the central wavelength of about 1068 nm. To the best of our knowledge, this is the first demonstration of sub-100 fs pulses and the shortest mode-locked pulses generated from the Nd3+-doped crystal lasers. PMID:27192242

  11. Electron energy transfer effect in Au NS/CH3sub>NH3sub>PbI3-xClx heterostructures via localized surface plasmon resonance coupling.

    PubMed

    Cai, Chunfeng; Zhai, Jizhi; Bi, Gang; Wu, Huizhen

    2016-09-15

    Localized surface plasmon resonance coupling effects (LSPR) have attracted much attention due to their interesting properties. This Letter demonstrates significant photoluminescence (PL) enhancement in the Au NS/CH3sub>NH3sub>PbI3-xClx heterostructures via the LSPR coupling. The observed PL emission enhancement is mainly attributed to the hot electron energy transfer effect related to the LSPR coupling. For the energy transfer effect, photo-generated electrons will be directly extracted into Au SPs, rather than relaxed into exciton states. This energy transfer process is much faster than the diffusion and relaxation time of free electrons, and may provide new ideas on the design of high-efficiency solar cells and ultrafast response photodetectors. PMID:27628381

  12. Electron energy transfer effect in Au NS/CH3sub>NH3sub>PbI3-xClx heterostructures via localized surface plasmon resonance coupling.

    PubMed

    Cai, Chunfeng; Zhai, Jizhi; Bi, Gang; Wu, Huizhen

    2016-09-15

    Localized surface plasmon resonance coupling effects (LSPR) have attracted much attention due to their interesting properties. This Letter demonstrates significant photoluminescence (PL) enhancement in the Au NS/CH3sub>NH3sub>PbI3-xClx heterostructures via the LSPR coupling. The observed PL emission enhancement is mainly attributed to the hot electron energy transfer effect related to the LSPR coupling. For the energy transfer effect, photo-generated electrons will be directly extracted into Au SPs, rather than relaxed into exciton states. This energy transfer process is much faster than the diffusion and relaxation time of free electrons, and may provide new ideas on the design of high-efficiency solar cells and ultrafast response photodetectors.

  13. Tomography and High-Resolution Electron Microscopy Study of Surfaces and Porosity in a Plate-Like γ-Al2O3sub>

    SciTech Connect

    Kovarik, Libor; Genc, Arda; Wang, Chong M.; Qiu, Annie; Peden, Charles HF; Szanyi, Janos; Kwak, Ja Hun

    2012-12-10

    Morphological and surface characteristics of gamma-Al2O3sub> are topics of high relevance in the field of catalysis. Using tomography and high-resolution S/TEM imaging, we have studied the surface characteristics of a model gamma-Al2O3sub> synthesized in the shape of platelets and macroscopically defined by (110)Al2O3sub> and (111)Al2O3sub> surface facets. We show that the dominant (110)Al2O3sub> surface of the synthesized gamma-Al2O3sub> is not atomically flat but undergoes a significant reconstruction, forming nanoscale (111)Al2O3sub> terraces. In addition to high resolution imaging, tomographic analysis was carried out, enabling an examination of the pores/voids, which were found to be mostly enclosed within the bulk and inaccessible to gasses or metals. Tomographic analysis shows that the surfaces of the pores are defined exclusively by (100)Al2O3sub> and (111)Al2O3sub> facets. The importance of these findings is discussed in the context of relative surface energies of low index surfaces and ethanol desorption characteristics.

  14. Sonochemical synthesis of highly luminescent Ln2O3sub>:Eu3+ (Y, La, Gd) nanocrystals

    SciTech Connect

    Alammar, Tarek; Cybinska, Joanna; Campbell, Paul S.; Mudring, Anja -Verena

    2015-05-12

    In this study, sonication of Ln(CH3sub>COO)3sub>·H2O, Eu(CH3sub>COO)3sub>·H2O and NaOH dissolved in the ionic liquid-butyl-3-methylimidazolium bis(trifluoromethane)sulfonylamide lead to Ln(OH)3sub>:Eu (Ln: Gd, La, Y) nanoparticles. Subsequent calcination at 800 °C for 3 h allowed to obtain Ln2O3sub>:Eu nanopowders. Gd2O3sub> and Y2O3sub> were obtained in the C-type lanthanide sequioxide structure, whereas La2O3sub> crystallized in the A-type. Structure, morphology, and luminescent properties of the nano-oxides were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), dispersive X-ray (EDX), and photoluminescence (PL). SEM studies revealed that the synthesized Gd2O3sub>:Eu, La2O3sub>:Eu, and Y2O3sub>:Eu formed nano-spindle, -sheets, and -rods in shape, respectively. The nanoscale materials show very efficient red emission due to the intraconfigurational f–f transitions of Eu3+. The quantum yields for Ln2O3sub>:Eu (5%) were determined to be 4.2% for Ln=Gd, 13.8% for Ln=Y and 5.2% for Ln=La. The asymmetric ratio I02/I01 of Eu3+ varies from 5.3 for Gd2O3sub>, to 5.6 for Y2O3sub> to 6.5 for La2O3sub>, which increased the color chromaticity.

  15. Line positions and intensities of the phosphine (PH3sub>) Pentad near 4.5μm

    SciTech Connect

    Malathy Devi, V.; Kleiner, Isabelle; Sams, Robert L.; Brown, Linda R.; Benner, D. Chris; Fletcher, Leigh N.

    2014-04-01

    In order to improve the spectroscopic database for remote sensing of the giant planets, line positions and intensities are determined for the five bands (2ν2, ν2 + ν4, 2ν4, ν1 and ν3sub>) that comprise the Pentad of PH3sub> between 1950 and 2450 cm-1. Knowledge of PH3sub> spectral line parameters in this region is important for the exploration of dynamics and chemistry on Saturn, (using existing Cassini/VIMS observations) and future near-IR data of Jupiter from Juno and ESA’s Jupiter Icy Moons Explorer (JUICE). For this study, spectra of pure PH3sub> from two Fourier transform spectrometers were obtained: (a) five high-resolution (0.00223 cm-1), high signal-to-noise (~1800) spectra recorded at room temperature (298.2 K) with the Bruker IFS 125HR Fourier transform spectrometer (FTS) at the Pacific Northwest National Laboratory (PNNL), Richland, Washington and (b) four high-resolution (at 0.0115 cm-1 resolution), high signal-to-noise (~700) spectra recorded at room temperature in the region 1800–5200 cm-1 using the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory (NSO) on Kitt Peak. Individual line parameters above 2150 cm-1 were retrieved by simultaneous multispectrum fittings of all five Bruker spectra, while retrievals with the four Kitt Peak spectra were done in the 1938–2168 cm-1 range spectrum by spectrum and averaged. In all, positions and intensities were obtained for more than 4400 lines. These included 53 A+A- split pairs of transitions (arising due to vibration–rotation interactions (Coriolis-type interaction) between the ν3sub> and ν1 fundamental bands) for K" = 3, 6, and 9. Over 3400 positions and 1750 intensities of these lines were ultimately identified as relatively unblended and modeled up to J = 14 and K = 12 with rms values of 0

  16. Effect of Particle Size and Operating Conditions on Pt3sub>Co PEMFC Cathode Catalyst Durability

    SciTech Connect

    Gummalla, Mallika; Ball, Sarah; Condit, David; Rasouli, Somaye; Yu, Kang; Ferreira, Paulo; Myers, Deborah; Yang, Zhiwei

    2015-05-29

    The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt3sub>Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes with the smallest Pt3sub>Co particle size was the highest and that of the largest Pt3sub>Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt3sub>Co over the 4.9 nm Pt3sub>Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt3sub>Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis

  17. Jahn-Teller versus quantum effects in the spin-orbital material LuVO3sub>

    SciTech Connect

    Skoulatos, M.; Toth, S.; Roessli, B.; Enderle, M.; Habicht, K.; Sheptyakov, D.; Cervellino, A.; Freeman, P. G.; Reehuis, M.; Stunault, A.; McIntyre, G. J.; Tung, L. D.; Marjerrison, C.; Pomjakushina, E.; Brown, P. J.; Khomskii, D. I.; Rüegg, Ch.; Kreyssig, A.; Goldman, A. I.; Goff, J. P.

    2015-04-13

    In this article, we report on combined neutron and resonant x-ray scattering results, identifying the nature of the spin-orbital ground state and magnetic excitations in LuVO3sub> as driven by the orbital parameter. In particular, we distinguish between models based on orbital-Peierls dimerization, taken as a signature of quantum effects in orbitals, and Jahn-Teller distortions, in favor of the latter. In order to solve this long-standing puzzle, polarized neutron beams were employed as a prerequisite in order to solve details of the magnetic structure, which allowed quantitative intensity analysis of extended magnetic-excitation data sets. The results of this detailed study enabled us to draw definite conclusions about the classical versus quantum behavior of orbitals in this system and to discard the previous claims about quantum effects dominating the orbital physics of LuVO3sub> and similar systems.

  18. Integrated Data Collection Analysis (IDCA) Program — KClO3sub>/Icing Sugar (-100 mesh) Mixture

    SciTech Connect

    Sandstrom, Mary M.; Brown, Geoffrey W.; Preston, Daniel N.; Pollard, Colin J.; Warner, Kirstin F.; Sorenson, Daniel N.; Remmers, Daniel L.; Moran, Jesse S.; Shelley, Timothy J.; Hsu, Peter C.; Whipple, Richard E.; Reynolds, John G.

    2011-05-02

    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 scanning calorimetry analysis of a mixture of KClO3sub> sized through a 100-mesh sieve mixed with icing sugar, also sized through a 100-mesh sieve—KClO3sub>/icing sugar (-100) mixture. This material was selected because of the challenge of performing SSST testing of a mixture of two solid materials. The mixture was found to be: 1) more sensitive to impact than RDX, with sensitivity similar to PETN, 2) the same or more sensitive to friction than PETN, and 3) less sensitive to spark than RDX. The analysis showed that the mixture has thermally stability similar to RDX and is perhaps more energetic upon decomposition but variable results indicate sampling issues.

  19. Size-dependent amorphization of nanoscale Y2O3sub> at high pressure

    SciTech Connect

    Wang, Lin; Yang, Wenge; Ding, Yang; Ren, Yang; Xiao, Siguo; Liu, Bingbing; Sinogeikin, Stanislav V.; Meng, Yue; Gosztola, David J.; Shen, Guoyin; Hemley, Russell J.; Mao, Wendy L.; Mao, Ho-kwang

    2010-08-24

    Y2 O3sub> with particle sizes ranging from 5 nm to 1 μm were studied at high pressure using x-ray diffraction and Raman spectroscopy techniques. Nanometer-sized Y2 O3sub> particles are shown to be more stable than their bulk counterparts, and a grain size-dependent crystalline-amorphous transition was discovered in these materials. High-energy atomic pair distribution function measurements reveal that the amorphization is associated with the breakdown of the long-rang order of the YO6 octahedra, while the nearest-neighbor edge-shared octahedral linkages are preserved.

  20. Amphoteric doping of praseodymium Pr3+ in SrTiO3sub> grain boundaries

    SciTech Connect

    Yang, H.; Lee, H. S.; Kotula, P. G.; Sato, Y.; Ikuhara, Y.; Browning, N. D.

    2015-03-26

    Charge Compensation in rare-earth Praseodymium (Pr3+) doped SrTiO3sub> plays an important role in determining the overall photoluminescence properties of the system. Here, the Pr3+ doping behavior in SrTiO3sub> grain boundaries (GBs) is analyzed using aberration corrected scanning transmission electron microscopy (STEM). The presence of Pr3+ induces structure variations and changes the statistical prevalence of GB structures. In contrast to the assumption that Pr3+ substitutes for A site as expected in the bulk, Pr3+ is found to substitute both Sr and Ti sites inside GBs with the highest concentration in the Ti sites. As a result, this amphoteric doping behavior in the boundary plane is further confirmed by first principles theoretical calculations.

  1. Fabrication tolerances in As2S3sub> negative-curvature antiresonant fibers.

    PubMed

    Weiblen, R Joseph; Menyuk, Curtis R; Gattass, Rafael R; Shaw, L Brandon; Sanghera, Jasbinder S

    2016-06-01

    We computationally investigate fabrication tolerances in As2S3sub> negative-curvature antiresonant tube-lattice fibers. Since the dominant loss mechanisms for silica in the mid-infrared (mid-IR) is material absorption, As2S3sub>, which offers a reduced loss over that wavelength range, is a natural candidate for mid-IR antiresonant fibers. However, any fiber fabrication technology, including for soft glasses, will have imperfections. Therefore, it is important to know how imperfect fabrication will affect the results of a fiber design. We study perturbations to the fiber, including a nonconstant tube-wall thickness, a single cladding tube with a different radius, a single cladding tube with a different tube-wall thickness, and "key" sections in the jacket. PMID:27244430

  2. Heat conductivity of LiF-NaF-Al(PO{sub 3}){sub 3} mixed-alkali glasses

    SciTech Connect

    Il`in, A.A.; Pronkin, A.A.

    1995-03-01

    Described is the heat conductivity of LiF-NaF-Al(PO{sub 3}){sub 3} mixed-alkali phosphate glasses. The percentage of NaF was varied to measure the density, mean sound velocity, Debye temperature, thermal oscillation frequency, and heat conductivity coefficient at different molar fractions. Correlation between the heat conductivity and the Debye temperature show the same regularity of variation in these parameters as for most crystalline substances.

  3. Integrated Data Collection Analysis (IDCA) Program — KClO3sub> (as received)/Icing Sugar

    SciTech Connect

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

    2011-05-23

    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 KClO3sub> as received from the manufacturer mixed with icing sugar, sized through a 100-mesh sieve—KClO3sub>/icing sugar (AR) mixture. This material was selected because of the challenge of performing SSST testing of a mixture of two solid materials. The mixture was found to: 1) be more sensitive to impact than RDX, similar to PETN, 2) be the same or less sensitive to friction than PETN, and 3) to be less sensitive to spark than RDX. The thermal analysis showed that the mixture has thermally stability similar to RDX and is perhaps more energetic upon decomposition but variable results indicate sampling issues. Compared to the 100-mesh sieved counter part, the KClO3sub>/icing sugar (-100) mixture, the AR mixture was found to be about the same sensitivity towards impact, friction and ESD.

  4. Commissioning results of Nb3sub>Sn cavity vapor diffusion deposition system at JLab

    SciTech Connect

    Eremeev, Grigory; Clemens, William A.; Macha, Kurt M.; Park, HyeKyoung; Williams, R.

    2015-09-01

    Nb3sub>Sn as a BCS superconductor with a superconducting critical temperature higher than that of niobium offers potential benefit for SRF cavities via a lower-than-niobium surface resistance at the same temperature and frequency. A Nb3sub>Sn vapor diffusion deposition system designed for coating of 1.5 and 1.3 GHz single-cell cavities was built and commissioned at JLab. As the part of the commissioning, RF performance at 2.0 K of a single-cell 1.5 GHz CEBAF-shaped cavity was measured before and after coating in the system. Before Nb3sub>Sn coating the cavity had a Q0 of about 1010 and was limited by the high field Q-slope at Eacc ≅ 27 MV/m. Coated cavity exhibited the superconducting transition at about 17.9 K. The low-field quality factor was about 5∙109 at 4.3 K and 7∙109 at 2.0 K decreasing with field to about 1∙109 at Eacc ≅ 8 MV/m at both temperatures. The highest field was limited by the available RF power.

  5. Hydrogen centers and the conductivity of In2O3sub> single crystals

    SciTech Connect

    Yin, Weikai; Smithe, Kirby; Weiser, Philip; Stavola, Michael; Fowler, W. Beall; Boatner, Lynn A.; Pearton, Stephen J.; Hays, David C.; Koch, Sandro G.

    2015-02-24

    A series of infrared absorption experiments and complementary theory have been performed in order to determine the properties of OH and OD centers in In2O3sub> single crystals. Annealing In2O3sub> samples in H2 or D2 at temperatures near 450°C produces an n-type layer ≈0.06mm thick with an n-type doping of 1.6×1019 cm-3. The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm-1 that we associate with interstitial H+. Additional O-H (O-D) vibrational lines are assigned to metastable configurations of the interstitial H+(D+) center and complexes of H (D) with In vacancies. In addition, unlike other oxides studied recently where H trapped at an oxygen vacancy is the dominant shallow donor (ZnO and SnO2, for example), interstitial H+ is found to be the dominant H-related shallow donor in In2O3sub>.

  6. Correlating Local Structure with Electrochemical Activity in Li2MnO3sub>

    SciTech Connect

    Nanda, Jagjit; Sacci, Robert L.; Veith, Gabriel M.; Dixit, Hemant M.; Cooper, Valentino R.; Pezeshki, Alan M.; Ruther, Rose E.

    2015-07-31

    Li2MnO3sub> is of interest as one component of the composite lithium-rich oxides, which are under development for high capacity, high voltage cathodes in lithium ion batteries. Despite such practical importance, the mechanism of electrochemical activity in Li2MnO3sub> is contested in the literature, as are the effects of long-term electrochemical cycling. Here, Raman spectroscopy and mapping are used to follow the chemical and structural changes that occur in Li2MnO3sub>. Both conventional slurry electrodes and thin films are studied as a function of the state of charge (voltage) and cycle number. Thin films have similar electrochemical properties as electrodes prepared from slurries, but allow for spectroscopic investigations on uniform samples without carbon additives. Spectral changes correlate well with electrochemical activity and support a mechanism whereby capacity is lost upon extended cycling due to the formation of new manganese oxide phases. Raman mapping of both thin film and slurry electrodes charged to different voltages reveals significant variation in the local structure. Poor conductivity and slow kinetics associated with a two-phase reaction mechanism contribute to the heterogeneity.

  7. Metastability in the MgAl2O4-Al2O3sub> System

    SciTech Connect

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

    2014-07-22

    Aluminum oxide must take a spinel form ( γ-Al2O3sub>) at elevated temperatures in order for extensive solid solution to form between MgAl2O4 and α-Al2O3sub>. The solvus line between MgAl2O4 and Al2O3sub> has been defined at 79.6 wt% Al2O3sub> at 1500°C, 83.0 wt% Al2O3sub> at 1600°C, and 86.5 wt% Al2O3sub> 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 Al2O3sub> at elevated temperatures. A minimum in melting at 1975°C and a chemistry of 96 wt% Al2O3sub> rather than a eutectic is present, resulting in no eutectic crystal formation during solidification.

  8. High thermal stability of piezoelectric properties in (Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}){sub x}-(BaTiO{sub 3}){sub y}-(Na{sub 0.5}K{sub 0.5}NbO{sub 3}){sub 1-x-y} ceramics

    SciTech Connect

    Gupta, Shashaank; Priya, Shashank

    2013-01-07

    We report the piezoelectric and ferroelectric properties of (Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}){sub x}-(BaTiO{sub 3}){sub y}-(Na{sub 0.5}K{sub 0.5}NbO{sub 3}){sub 1-x-y} ceramics for Na{sub 0.5}K{sub 0.5}NbO{sub 3} rich end of composition (x, y {<=} 0.04 mol. %). These compositions were found to exhibit significantly improved thermal stability of piezoresponse. Variation of dielectric constant as a function of temperature revealed that orthorhombic-tetragonal (T{sub o-t}) and tetragonal-cubic (T{sub c}) transition temperatures for these compositions were in the vicinity of 0 Degree-Sign C and 330 Degree-Sign C, respectively. Dynamic scaling and temperature dependent X-ray diffraction analysis were conducted. Results are discussed in terms of intrinsic and extrinsic contributions to the piezoelectric response explaining the temperature dependent behavior.

  9. Interfacial charge-mediated non-volatile magnetoelectric coupling in Co0.3sub>Fe0.7/Ba0.6Sr0.4TiO3sub>/Nb:SrTiO3sub> multiferroic heterostructures

    SciTech Connect

    Zhou, Ziyao; Howe, Brandon M.; Liu, Ming; Nan, Tianxiang; Chen, Xing; Mahalingam, Krishnamurthy; Sun, Nian X.; Brown, Gail J.

    2015-01-13

    The central challenge in realizing non-volatile, E-field manipulation of magnetism lies in finding an energy efficient means to switch between the distinct magnetic states in a stable and reversible manner. In this work, we demonstrate using electrical polarization-induced charge screening to change the ground state of magnetic ordering in order to non-volatilely tune magnetic properties in ultra-thin Co0.3sub>Fe0.7/Ba0.6Sr0.4TiO3sub>/Nb:SrTiO3sub> (001) multiferroic heterostructures. A robust, voltage-induced, non-volatile manipulation of out-of-plane magnetic anisotropy up to 40 Oe is demonstrated and confirmed by ferromagnetic resonance measurements. This discovery provides a framework for realizing charge-sensitive order parameter tuning in ultra-thin multiferroic heterostructures, demonstrating great potential for delivering compact, lightweight, reconfigurable, and energy-efficient electronic devices.

  10. Ordered and disordered polymorphs of Na(Ni2/3sub>Sb1/3sub>)O₂: Honeycomb-ordered cathodes for Na-ion batteries

    SciTech Connect

    Ma, Jeffrey; Wu, Lijun; Bo, Shou -Hang; Khalifah, Peter G.; Grey, Clare P.; Zhu, Yimei

    2015-04-14

    Na-ion batteries are appealing alternatives to Li-ion battery systems for large-scale energy storage applications in which elemental cost and abundance are important. Although it is difficult to find Na-ion batteries which achieve substantial specific capacities at voltages above 3 V (vs Na⁺/Na), the honeycomb-layered compound Na(Ni2/3sub>Sb1/3sub>)O₂ can deliver up to 130 mAh/g of capacity at voltages above 3 V with this capacity concentrated in plateaus at 3.27 and 3.64 V. Comprehensive crystallographic studies have been carried out in order to understand the role of disorder in this system which can be prepared in both “disordered” and “ordered” forms, depending on the synthesis conditions. The average structure of Na(Ni2/3sub>Sb1/3sub>)O₂ is always found to adopt an O3-type stacking sequence, though different structures for the disordered (R3¯m, #166, a = b = 3.06253(3) Å and c = 16.05192(7) Å) and ordered variants (C2/m, #12, a = 5.30458(1) Å, b = 9.18432(1) Å, c = 5.62742(1) Å and β = 108.2797(2)°) are demonstrated through the combined Rietveld refinement of synchrotron X-ray and time-of-flight neutron powder diffraction data. However, pair distribution function studies find that the local structure of disordered Na(Ni2/3sub>Sb1/3sub>)O₂ is more correctly described using the honeycomb-ordered structural model, and solid state NMR studies confirm that the well-developed honeycomb ordering of Ni and Sb cations within the transition metal layers is indistinguishable from that of the ordered phase. The disorder is instead found to mainly occur perpendicular to the honeycomb layers with an observed coherence length of not much more than 1 nm seen in electron diffraction studies. When the Na environment is probed through ²³Na solid state NMR, no evidence is found for prismatic Na environments, and a bulk diffraction analysis finds no evidence

  11. Enhanced electrocatalytic activity and stability of Pd3sub>V/C nanoparticles with a trace amount of Pt decoration for the oxygen reduction reaction

    SciTech Connect

    Liu, Sufen; Han, Lili; Zhu, Jing; Xiao, Weiping; Wang, Jie; Liu, Hongfang; Xin, Huolin; Wang, Deli

    2015-09-14

    In this study, carbon supported Pd3sub>V bimetallic alloy nanoparticles (Pd3sub>V/C) have been successfully synthesized via a simple impregnation–reduction method, followed by high temperature treatment under a H2 atmosphere. Electrochemical tests reveal that the half-wave potential of Pd3sub>V/C-500 shifts positively 40 mV compared with Pd/C. However, the catalytic activity of Pd3sub>V/C-500 suffers from serious degradation after 1k cycles. By a spontaneous displacement reaction or co-reduction method, a trace amount of Pt was decorated on the surface or inside of the Pd3sub>V/C nanoparticles. The catalytic activity and stability of the Pd3sub>V@Pt/C and Pt-Pd3sub>V/C catalysts for the oxygen reduction reaction (ORR) are enhanced significantly, and are comparable to commercial Pt/C. In addition, the Pt mass activity of Pd3sub>V@Pt/C and Pt-Pd3sub>V/C improves by factors of 10.9 and 6.5 at 0.80 V relative to Pt/C. Moreover, Pt-decorated Pd3sub>V/C nanoparticles show almost no obvious morphology change after durability tests, because the Pt-rich shell plays an important role in preventing degradation.

  12. Magnetization Plateaus of SrCu{sub 2}(BO{sub 3}){sub 2} from a Chern-Simons Theory

    SciTech Connect

    Misguich, G.; Jolicoeur, Th.; Girvin, S. M.

    2001-08-27

    The antiferromagnetic Heisenberg model on the frustrated Shastry-Sutherland lattice is studied by a mapping onto spinless fermions carrying one quantum of statistical flux. Using a mean-field approximation these fermions populate the bands of a generalized Hofstadter problem. Their filling leads to the magnetization curve. For SrCu{sub 2}(BO{sub 3}){sub 2} we reproduce plateaus at 1/3 and 1/4 of the saturation moment and predict a new one at 1/2 . Gaussian fluctuations of the gauge field are shown to be massive at these plateau values.

  13. Electroelastic fields in artificially created vortex cores in epitaxial BiFeO3sub> thin films

    SciTech Connect

    Winchester, Ben; Wisinger, Nina Balke; Cheng, X. X.; Morozovska, A. N.; Kalinin, Sergei; Chen, L. Q.

    2015-08-03

    Here we employ phase-field modeling to explore the elastic properties of artificially created 1-D domain walls in (001)p-oriented BiFeO3sub> thin films, composed of a junction of the four polarization variants, all with the same out-of-plane polarization. It was found that these junctions exhibit peculiarly high electroelastic fields induced by the neighboring ferroelastic/ferroelectric domains. The vortex core exhibits a volume expansion, while the anti-vortex core is more compressive. We also discuss possible ways to control the electroelastic field, such as varying material constant and applying transverse electric field.

  14. Hydrothermal synthesis, structure, Raman spectroscopy, and self-irradiation studies of {sup 248}Cm(IO{sub 3}){sub 3}

    SciTech Connect

    Sykora, Richard E.; Assefa, Zerihun; Haire, Richard G. . E-mail: hairerg@ornl.gov; Albrecht-Schmitt, Thomas E. . E-mail: albreth@auburn.edu

    2004-12-01

    The study of curium iodate, Cm(IO{sub 3}){sub 3}, was undertaken as part of a systematic investigation of the 4f- and 5f-elements' iodates. The reaction of {sup 248}CmCl{sub 3} with aqueous H{sub 5}IO{sub 6} under mild hydrothermal conditions results in the reduction of IO{sub 6}{sup 5-} to IO{sub 3}{sup -} anions, and the subsequent formation of Cm(IO{sub 3}){sub 3} single crystals. Crystallographic data are: (193K, MoK{alpha}, {lambda}=0.71073A): monoclinic, space group P2{sub 1}/c, a=7.2014(7)A, b=8.5062(9)A, c=13.4622(14)A, {beta}=100.142(2){sup o}, V=811.76(14), Z=4, R(F)=2.11%, Rw(Fo2)=4.43% for 119 parameters with 1917 reflections with I>2{sigma}(I). The structure consists of Cm{sup 3+} cations bound by iodate anions to form [Cm(IO{sub 3}){sub 8}] units, where the local coordination environment around the curium centers can be described as a distorted dodecahedron. There are three crystallographically unique iodate anions within the structure; two iodates bridge between three Cm centers, and one iodate bridges between two Cm centers and has a terminal oxygen atom. The bridging of the curium centers by the iodate anions creates a three-dimensional structure. Three strong Raman bands with comparable intensities were observed at 846, 804, and 760cm{sup -1} and correspond to the I-O symmetric stretching of the three crystallographically distinct iodate ions. The Raman profile suggests a lack of inter-ionic vibrational coupling of the I-O stretching, while intra-ionic coupling provides symmetric and asymmetric components that correspond to each iodate site. Repeated collection of X-ray diffraction data for a crystal of Cm(IO{sub 3}){sub 3} over a period of time revealed a gradual expansion of the unit cell from self-irradiation. After 71 days, the new parameters were: a=7.2132(7)A, b=8.5310(8)A, c=13.505(1)A, {beta}=100.021(2){sup o}, V=818.3(2)

  15. Charge transfer and orbital reconstruction in the (La{sub 2/3}Sr{sub 1/3}MnO{sub 3}){sub m}/(SrRuO{sub 3}){sub n} superlattices

    SciTech Connect

    Lv, Kai; Zhu, H. P.; Zou, W. Q.; Zhang, F. M.; Wu, X. S.

    2015-05-14

    The structural, electronic, and magnetic properties of (La{sub 2/3}Sr{sub 1/3}MnO{sub 3}){sub m}/(SrRuO{sub 3}){sub n} superlattices have been investigated based on the first principles calculations. An obvious Jahn-Teller distortion, which depends on m, n, appears in MnO{sub 6} octahedron in the superlattices. The stretch along c-axis of MnO{sub 6} octahedron at the interface lifts the Mn e{sub g} orbital degeneracy, with electrons preferring the lower energy 3z{sup 2}−r{sup 2} to the higher energy x{sup 2}−y{sup 2}. Benefitting from the charge transfer at the interface, the still occupied x{sup 2}−y{sup 2} orbital can mediate a robust in-plane double exchange interaction. La{sub 2/3}Sr{sub 1/3}MnO{sub 3} block is ferromagnetic and metallic, even for the superlattice with m = n = 1.

  16. Magnetization jumps and exchange bias induced by a partially disordered antiferromagnetic state in (FeTiO{sub 3}){sub 0.9}-(Fe{sub 2}O{sub 3}){sub 0.1}

    SciTech Connect

    Song, P.; Li, G. K.; Ma, L. Zhen, C. M.; Hou, D. L.; Wang, W. H.; Liu, E. K.; Chen, J. L.; Wu, G. H.

    2014-06-07

    Magnetization jumps (MJs) and the exchange bias (EB) effect are simultaneously observed in the mixed-spin oxide (FeTiO{sub 3}){sub 0.9}-(Fe{sub 2}O{sub 3}){sub 0.1} at 2.0 K. Dc and ac susceptibility measurements confirm a reentrant spin glass phase with a partially disordered antiferromagnetic (PDA) state below the irreversibility temperature (T{sub ir} = 60 K). Antiferromagnetic (AFM) Fe{sup 3+} clusters are nested in AFM Fe{sup 2+} lattices forming a triangular lattice, in which 2/3 of the magnetic moments order antiferromagnetically with each other leaving the remaining 1/3 “confused.” This geometric frustration in the triangular lattice leads to a PDA state that is the ground state of the AFM triangular configuration. The PDA state, in the presence of a critical trigger field, evolves into a ferromagnetic (FM) state, and induces the AFM spins of the Fe{sup 2+} ions to enter a FM state, resulting in the MJs. Meanwhile, the FM spins of Fe{sup 2+} can serve as the pinned phase, and the AFM spins of Fe{sup 3+} can serve as the pinning phase, resulting in the EB effect. Thus, we point out that the PDA state is very likely to be at the origin of the MJs and the EB effect.

  17. Structure tracking aided design and synthesis of Li3sub>V2(PO4)3sub> nanocrystals as high-power cathodes for lithium ion batteries

    SciTech Connect

    Wang, Liping; Bai, Jianming; Gao, Peng; Wang, Xiaoya; Looney, J. Patrick; Wang, Feng

    2015-07-30

    In this study, preparing new electrode materials with synthetic control of phases and electrochemical properties is desirable for battery applications but hardly achievable without knowing how the synthesis reaction proceeds. Herein, we report on structure tracking-aided design and synthesis of single-crystalline Li3sub>V2(PO4)3sub> (LVP) nanoparticles with extremely high rate capability. A comprehensive investigation was made to the local structural orderings of the involved phases and their evolution toward forming LVP phase using in situ/ex situ synchrotron X-ray and electron-beam diffraction, spectroscopy, and imaging techniques. The results shed light on the thermodynamics and kinetics of synthesis reactions and enabled the design of a cost-efficient synthesis protocol to make nanocrystalline LVP, wherein solvothermal treatment is a crucial step leading to an amorphous intermediate with local structural ordering resembling that of LVP, which, upon calcination at moderate temperatures, rapidly transforms into the desired LVP phase. The obtained LVP particles are about 50 nm, coated with a thin layer of amorphous carbon and featured with excellent cycling stability and rate capability – 95% capacity retention after 200 cycles and 66% theoretical capacity even at a current rate of 10 C. The structure tracking based method we developed in this work offers a new way of designing battery electrodes with synthetic control of material phases and properties.

  18. Anisotropic swelling and microcracking of neutron irradiated Ti3sub>AlC2-Ti5Al2C3sub> materials

    SciTech Connect

    Ang, Caen K.; Silva, Chinthaka M.; Shih, Chunghao Phillip; Koyanagi, Takaaki; Katoh, Yutai; Zinkle, Steven J.

    2015-12-17

    Mn + 1AXn (MAX) phase materials based on Ti–Al–C have been irradiated at 400 °C (673 K) with fission neutrons to a fluence of 2 × 1025 n/m2 (E > 0.1 MeV), corresponding to ~ 2 displacements per atom (dpa). We report preliminary results of microcracking in the Al-containing MAX phase, which contained the phases Ti3sub>AlC2 and Ti5Al2C3sub>. Equibiaxial ring-on-ring tests of irradiated coupons showed that samples retained 10% of pre-irradiated strength. Volumetric swelling of up to 4% was observed. Phase analysis and microscopy suggest that anisotropic lattice parameter swelling caused microcracking. Lastly, variants of titanium aluminum carbide may be unsuitable materials for irradiation at light water reactor-relevant temperatures.

  19. Structure of two new borates YCa{sub 3}(AlO){sub 3}(BO{sub 3}){sub 4} and YCa{sub 3}(GaO){sub 3}(BO{sub 3}){sub 4}

    SciTech Connect

    Yu Yi; Wu, Q.S.; Li, R.K. . E-mail: rkli@cl.cryo.ac.cn

    2006-02-15

    By replacing Mn in YCa{sub 3}(MnO){sub 3}(BO{sub 3}){sub 4} with trivalent Al and Ga, two new borates with the compositions of YCa{sub 3}(MO){sub 3}(BO{sub 3}){sub 4} (M=Al, Ga) were prepared by solid-state reaction. Structure refinements from X-ray powder diffraction data revealed that both of them are isostructural to gaudefroyite with a hexagonal space group P6{sub 3}/m. Cell parameters of a=10.38775(13)A, c=5.69198(10)A for the Al-containing compound and a=10.5167(3)A, c=5.8146(2)A for the Ga analog were obtained from the refinements. The structure is constituted of AlO{sub 6} or GaO{sub 6} octahedral chains interconnected by BO{sub 3} groups in the ab plane to form a Kagome-type lattice, leaving trigonal and apatite-like tunnels. It is found that most rare-earth and Cr, Mn ions can be substituted into the Y{sup 3+} and M{sup 3+} sites, respectively, and the preference of rare-earth ions to locate in the trigonal tunnel is correlated to the sizes of the M{sup 3+} ions.

  20. Directionally solidified fabrication in planar geometry of Al2O3sub>-Er3sub>Al5O12 eutectic composite for thermophotovoltaic devices.

    PubMed

    Sola, D; Oliete, P B; Peña, J I

    2016-05-16

    In this work Al2O3sub>-Er3sub>Al5O12 eutectic composite was manufactured in planar geometry departing from eutectic particles both produced by directional solidification using a CO2 laser system at rates of 180 and 720 mm/h. Microstructure and mechanical properties were investigated as a function of the growth rate. Homogeneous and interpenetrated microstructure was found with phase size strongly dependent on the growth rate, decreasing when the processing rate was increased. Thermal emission of eutectic composites was studied in function of thermal excitation by using CO2 laser radiation as a heating source. An intense narrow emission band at 1.55 µm matching with the sensitive region of the InGaAs photoconverter and a low emission band at 1 µm were obtained. Features of thermal emission bands were correlated with collecting angle, microstructure and laser power, and compared to those obtained from departing eutectic particles. PMID:27409955

  1. Investigation of SO3sub> absorption line for in situ gas detection inside combustion plants using a 4-μm-band laser source.

    PubMed

    Tokura, A; Tadanaga, O; Nishimiya, T; Muta, K; Kamiyama, N; Yonemura, M; Fujii, S; Tsumura, Y; Abe, M; Takenouchi, H; Kenmotsu, K; Sakai, Y

    2016-09-01

    We have investigated 4-μm-band SO3sub> absorption lines for in situSO3sub> detection using a mid-infrared laser source based on difference frequency generation in a quasi-phase-matched LiNbO3sub> waveguide. In the wavelength range of 4.09400-4.10600 μm, there were strong SO3sub> absorption lines. The maximum absorption coefficient at a concentration of 170 ppmv was estimated to be about 3.2×10-5  cm-1 at a gas temperature of 190°C. In coexistence with H2O, the reduction of the SO3sub> absorption peak height was observed, which was caused by sulfuric acid formation. We discuss a method of using an SO3sub> equilibrium curve to derive the total SO3sub> molecule concentration. PMID:27607263

  2. Negative Ion Photoelectron Spectroscopy Confirms the Prediction that D-3h Carbontrioxide (CO3sub>) Has a Singlet Ground State

    SciTech Connect

    Hrovat, David; Hou, Gao-Lei; Chen, Bo; Wang, Xue B.; Borden, Weston

    2015-11-13

    The CO3sub> radical anion (CO3sub>•–) has been formed by electrospraying carbonate dianion (CO3sub>2–) into the gas phase. The negative ion photoelectron (NIPE) spectrum of CO3sub>•– shows that, unlike trimethylenemethane [C(CH2)3sub>], carbontrioxide (CO3sub>) has a singlet ground state. From the NIPE spectrum, the electron affinity of CO3sub> was determined to be EA = 4.06 ± 0.03 eV, and the singlet-triplet energy difference was found to be ΔEST = - 17.8 ± 0.9 kcal/mol. B3LYP, CCSD(T), and CASPT2 calculations all find that the two lowest triplet states of CO3sub> are very close in energy, a prediction that is confirmed by the relative intensities of the bands in the NIPE spectrum of CO3sub>•–. The 560 cm-1 vibrational progression, seen in the low energy region of the triplet band, enables the identification of the lowest, Jahn-Teller-distorted, triplet state as 3A1, in which both unpaired electrons reside in σ MOs, rather than 3A2, in which one unpaired electron occupies the b2 σ MO, and the other occupies the b1 π MO.

  3. Giant Magneto-Resistance in Epitaxial (La0.7Sr0.3sub>MnO3sub>)0.5: (ZnO)0.5 Nanocomposites

    SciTech Connect

    Pan, Wei; Jiang, Y. X.; Ihlefeld, Jon; Lu, Ping; Lee, Stephen R.

    2015-12-01

    A great deal of research has been carried out in oxide material systems. Among them, ZnO and La0.7Sr0.3sub>MnO3sub> (LSMO) are of particular interest due to their superb optical properties and colossal magneto-resistive effect. Here, we report our recent results of magneto-transport studies in self-assembled, epitaxial (ZnO)0.5:(La0.7Sr0.3sub>MnO3sub>)0.5 nanocomposite films.

  4. Synthesis of tris(triphenylsiloxy)yttrium and derivatives: Crystal structure of (Y(OSiPh sub 3 ) sub 3 (THF sub 3 ))ter dot THF

    SciTech Connect

    McGeary, M.J.; Coan, P.S.; Folting, K.; Streib, W.E.; Caoulton, K.G. )

    1989-08-23

    The synthesis of (Y(OSiPh{sub 3}){sub 3}){sub n} (1) has been accomplished by the reaction of Y(N(SiMe{sub 3}){sub 2}){sub 3} with 3 equivalents of Ph{sub 3}SiOH in toluene. Two monomeric Lewis base adducts were also formed. The product 1 was formed as a colorless, feather-like solid, and {sup 1}H and {sup 13}C NMR spectra gave data consistent with the structure of this compound as an aggregate presumably involving bridging Ph{sub 3}SiO{sup {minus}} ligands. The x-ray structure of the compounds is also reported.

  5. Wetting of sodium on β''-Al2O3sub>/YSZ composites for low temperature planar sodium-metal halide batteries

    SciTech Connect

    Reed, David; Coffey, Greg; Mast, Eric; Canfield, Nathan; Mansurov, Jirgal; Lu, Xiaochuan; Sprenkle, Vince

    2013-04-01

    Wetting of Na on B”-Al2O3sub>/YSZ composites was investigated using the sessile drop technique. The effects of moisture and surface preparation were studied at low temperatures. Electrical conductivity of Na/B”-Al2O3sub>-YSZ/Na cells was also investigated at low temperatures and correlated to the wetting behavior. The use of planar B”-Al2O3sub> substrates at low temperature with low cost polymeric seals is realized due to improved wetting at low temperature and conductivity values consistent with the literature.

  6. Revisiting the Al/Al2O3sub> Interface: Coherent Interfaces and Misfit Accommodation

    SciTech Connect

    Pilania, Ghanshyam; Thijsse, Barend J.; Hoagland, Richard G.; Lazić, Ivan; Valone, Steven M.; Liu, Xiang-Yang

    2014-03-27

    We report the coherent and semi-coherent Al/α-Al2O3sub> interfaces using molecular dynamics simulations with a mixed, metallic-ionic atomistic model. For the coherent interfaces, both Al-terminated and O-terminated nonstoichiometric interfaces have been studied and their relative stability has been established. To understand the misfit accommodation at the semi-coherent interface, a 1-dimensional (1D) misfit dislocation model and a 2-dimensional (2D) dislocation network model have been studied. For the latter case, our analysis reveals an interface dislocation structure with a network of three sets of parallel dislocations, each with pure-edge character, giving rise to a pattern of coherent and stacking-fault-like regions at the interface. Structural relaxation at elevated temperatures leads to a further change of the dislocation pattern, which can be understood in terms of a competition between the stacking fault energy and the dislocation interaction energy at the interface. In conclusion, our results are expected to serve as an input for the subsequent dislocation dynamics models to understand and predict the macroscopic mechanical behavior of Al/α-Al2O3sub> composite heterostructures.

  7. Oxidation and Hydration of U 3sub> O 8 Materials Following Controlled Exposure to Temperature and Humidity

    SciTech Connect

    Tamasi, Alison L.; Boland, Kevin S.; Czerwinski, Kenneth; Ellis, Jason K.; Kozimor, Stosh A.; Martin, Richard L.; Pugmire, Alison L.; Reilly, Dallas; Scott, Brian L.; Sutton, Andrew D.; Wagner, Gregory L.; Walensky, Justin R.; Wilkerson, Marianne P.

    2015-03-18

    Chemical signatures correlated with uranium oxide processing are of interest to forensic science for inferring sample provenance. Identification of temporal changes in chemical structures of process uranium materials as a function of controlled temperatures and relative humidities may provide additional information regarding sample history. In our study, a high-purity α-U3sub>O8 sample and three other uranium oxide samples synthesized from reaction routes used in nuclear conversion processes were stored under controlled conditions over 2–3.5 years, and powder X-ray diffraction analysis and X-ray absorption spectroscopy were employed to characterize chemical speciation. We measured signatures from the α-U3sub>O8 sample indicated that the material oxidized and hydrated after storage under high humidity conditions over time. Impurities, such as uranyl fluoride or schoepites, were initially detectable in the other uranium oxide samples. After storage under controlled conditions, the analyses of the samples revealed oxidation over time, although the signature of the uranyl fluoride impurity diminished. The presence of schoepite phases in older uranium oxide material is likely indicative of storage under high humidity and should be taken into account for assessing sample history. Finally, the absence of a signature from a chemical impurity, such as uranyl fluoride hydrate, in an older material may not preclude its presence at the initial time of production. LA-UR-15-21495.

  8. Doping SrTiO3sub> supported FeSe by excess atoms and oxygen vacancies

    SciTech Connect

    Shanavas, Kavungal Veedu; Singh, David J.

    2015-07-24

    Photoemission studies of FeSe monolayer films on SrTiO3sub> substrate have shown electronic structures that deviate from pristine FeSe, consistent with heavy electron doping. With the help of first-principles calculations we studied the effect of excess Fe and Se atoms on the monolayer and oxygen vacancies in the substrate in order to understand the reported Fermi surface in this system. We find that both excess Fe and Se atoms prefer the same adsorption site above the bottom Se atoms on the monolayer. The adsorbed Fe is strongly magnetic and contributes electrons to the monolayer, while excess Se hybridizes with the monolayer Fe-d states and partially opens a gap just above the Fermi energy. We also find that the two-dimensional electron gas generated by the oxygen vacancies is partly transferred to the monolayer and can potentially suppress the hole pockets around the Γ point. Furthermore, both O vacancies in the SrTiO3sub> substrate and excess Fe over the monolayer can provide high levels of electron doping.

  9. Insights into the structure–photoreactivity relationships in well-defined perovskite ferroelectric KNbO 3sub> nanowires

    SciTech Connect

    Zhang, Tingting; Lei, Wanying; Liu, Ping; Rodriguez, José A.; Yu, Jiaguo; Qi, Yang; Liu, Gang; Liu, Minghua

    2015-04-23

    Structure–function correlations are a central theme in heterogeneous (photo)catalysis. In this study, the geometric and electronic structure of perovskite ferroelectric KNbO3sub> nanowires with respective orthorhombic and monoclinic polymorphs have been systematically addressed. By virtue of aberration-corrected scanning transmission electron microscopy, we directly visualize surface photocatalytic active sites, measure local atomic displacements at an accuracy of several picometers, and quantify ferroelectric polarization combined with first-principles calculations. The photoreactivity of the as-prepared KNbO3sub> nanowires is assessed toward aqueous rhodamine B degradation under UV light. A synergy between the ferroelectric polarization and electronic structure in photoreactivity enhancement is uncovered, which accounts for the prominent reactivity order: orthorhombic > monoclinic. Additionally, by identifying new photocatalytic products, rhodamine B degradation pathways involving N-deethylation and conjugated structure cleavage are proposed. The findings not only provide new insights into the structure–photoreactivity relationships in perovskite ferroelectric photocatalysts, but also have broad implications in perovskite-based water splitting and photovoltaics, among others.

  10. Giant elastic tunability in strained BiFeO3sub> near an electrically induced phase transition

    SciTech Connect

    Yu, Pu; Vasudevan, Rama K.; Tselev, Alexander; Xue, Fei; Chen, Long -Qing; Maksymovych, Petro; Kalinin, Sergei V.; Balke, Nina; Li, Q.; Cao, Y.; Laanait, N.

    2015-01-01

    Elastic anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation elastic/piezoresponse spectroscopy, we probed sub-MHz elastic dynamics of a tip bias-induced rhombohedral–tetragonal phase transition of strained (001)-BiFeO3sub> (rhombohedral) ferroelectric thin films from ~103 nm3 sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with 2-3 folds enhancement of local piezoresponse. Coupled with phase-field modeling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (e.g., domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary (MPB) in ferroelectrics. Moreover, the giant electrically tunable elastic stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3sub> in next-generation frequency-agile electroacoustic devices, based on utilization of the soft modes underlying successive ferroelectric phase transitions.

  11. Thickness-dependent coherent phonon frequency in ultrathin FeSe/SrTiO3sub> films

    SciTech Connect

    Yang, Shuolong; Sobota, Jonathan A.; Leuenberger, Dominik; Kemper, Alexander F.; Lee, James J.; Schmitt, Felix T.; Li, Wei; Moore, Rob G.; Kirchmann, Patrick S.; Shen, Zhi -Xun

    2015-06-01

    Ultrathin FeSe films grown on SrTiO3sub> substrates are a recent milestone in atomic material engineering due to their important role in understanding unconventional superconductivity in Fe-based materials. By using femtosecond time- and angle-resolved photoelectron spectroscopy, we study phonon frequencies in ultrathin FeSe/SrTiO3sub> films grown by molecular beam epitaxy. After optical excitation, we observe periodic modulations of the photoelectron spectrum as a function of pump–probe delay for 1-unit-cell, 3-unit-cell, and 60-unit-cell thick FeSe films. The frequencies of the coherent intensity oscillations increase from 5.00 ± 0.02 to 5.25 ± 0.02 THz with increasing film thickness. By comparing with previous works, we attribute this mode to the Se A1g phonon. The dominant mechanism for the phonon softening in 1-unit-cell thick FeSe films is a substrate-induced lattice strain. Results demonstrate an abrupt phonon renormalization due to a lattice mismatch between the ultrathin film and the substrate.

  12. Magnetic Correlations in the Quasi-Two-Dimensional Semiconducting Ferromagnet CrSiTe3sub>

    SciTech Connect

    Williams, Travis J.; Aczel, Adam A.; Lumsden, Mark D.; Nagler, Stephen E.; Stone, Matthew B.; Yan, Jiaqiang -Q.; Mandrus, D.

    2015-10-02

    Intrinsic, 2D ferromagnetic semiconductors are an important class of materials for overcoming dilute magnetic semiconductors’ limitations for spintronics. CrSiTe3sub> is a particularly interesting material of this class, since it can likely be exfoliated to single layers, for which Tc is predicted to increase dramatically. Establishing the nature of the bulk material’s magnetism is necessary for understanding the thin-film magnetic behavior and the material’s possible applications. In this work, we use elastic and inelastic neutron scattering to measure the magnetic properties of single crystalline CrSiTe3sub>. We find a very small single ion anisotropy that favors magnetic ordering along the c-axis and that the measured spin waves fit well to a model in which the moments are only weakly coupled along that direction. Then, we find that both static and dynamic correlations persist within the ab-plane up to at least 300 K, which is strong evidence of the material's 2D characteristics that are relevant for future studies on thin film and monolayer samples.

  13. Nature of the insulating ground state of the 5d postperovskite CaIrO3sub>

    SciTech Connect

    Kim, Sun -Woo; Liu, Chen; Kim, Hyun -Jung; Lee, Jun -Ho; Yao, Yongxin; Ho, Kai -Ming; Cho, Jun -Hyung

    2015-08-26

    In this study, the insulating ground state of the 5d transition metal oxide CaIrO3sub> has been classified as a Mott-type insulator. Based on a systematic density functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals, we reveal that the Ir t2g states exhibit large splittings and one-dimensional electronic states along the c axis due to a tetragonal crystal field. Our hybrid DFT calculation adequately describes the antiferromagnetic (AFM) order along the c direction via a superexchange interaction between Ir4+ spins. Furthermore, the spin-orbit coupling (SOC) hybridizes the t2g states to open an insulating gap. These results indicate that CaIrO3sub> can be represented as a spin-orbit Slater insulator, driven by the interplay between a long-range AFM order and the SOC. Such a Slater mechanism for the gap formation is also demonstrated by the DFT + dynamical mean field theory calculation, where the metal-insulator transition and the paramagnetic to AFM phase transition are concomitant with each other.

  14. CaCO3sub> Precipitation, Transport and Sensing in Porous Media with In Situ Generation of Reactants

    SciTech Connect

    George Redden; Don Fox; Chi Zhang; Yoshiko Fujita; Luanjing Guo; Hai Huang

    2014-01-01

    Ureolytically driven calcite precipitation is a promising approach for inducing subsurface mineral precipitation, but engineered application requires the ability to control and predict precipitate distribution. To study the coupling between reactant transport and precipitate distribution, columns with defined zones of immobilized urease were used to examine the distribution of calcium carbonate precipitation along the flow path, at two different initial flow rates. As expected, with slower flow precipitate was concentrated toward the upstream end of the enzyme zone and with higher flow the solid was more uniformly distributed over the enzyme zone. Under constant hydraulic head conditions the flow rate decreased as precipitates decreased porosity and permeability. The hydrolysis/precipitation zone was expected to become compressed in the upstream direction. However, apparent reductions in the urea hydrolysis rate and changes in the distribution of enzyme activity, possibly due to CaCO3sub>precipitate hindering urea transport to the enzyme, or enzyme mobilization, mitigated reaction zone compression. Co-injected strontium was expected to be sequestered by coprecipitation with CaCO3sub>, but the results suggested that coprecipitation was not an effective sequestration mechanism in this system. In addition, spectral induced polarization (SIP) was used to monitor the spatial and temporal evolution of the reaction zone.

  15. Oxidation behavior of amorphous metallic Ni{sub 3}(SbTe{sub 3}){sub 2} compound

    SciTech Connect

    Jun, Jong-Ho; Jung, Jin-Seung . E-mail: jjscm@kangnung.ac.kr; Oh, Seung-Lim; Kim, Yong-Rok; Lee, Sung-Han; O'Connor, Charles J.

    2006-03-09

    Amorphous Ni{sub 3}(SbTe{sub 3}){sub 2} compound was prepared from a metathesis between Zintl phase K{sub 3}SbTe{sub 3} and NiBr{sub 2} in solution and its oxidation behavior was investigated in the temperature range of 200-700 deg. C in air. To characterize the sample, thermogravimetry (TG), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis by X-ray (EDAX) analyses were performed and electrical conductivity was measured as a function of temperature in the range of 25-800 deg. C in air. The specimen showed a metallic conducting-like behavior below 585 deg. C while a semiconducting-like behavior above 585 deg. C. At a first oxidation step of Ni{sub 3}(SbTe{sub 3}){sub 2} below 500 deg. C, TeO{sub 2} phase is formed. Above 500 deg. C, NiO phase is formed, then some NiO reacts with TeO{sub 2} to form NiTeO{sub 3} and NiSb{sub 2}O{sub 6} is simultaneously formed. Above 700 deg. C, NiTeO{sub 3} is further reacted with TeO{sub 2} to form NiTe{sub 2}O{sub 5}. Both NiTeO{sub 3} and NiTe{sub 2}O{sub 5} are decomposed above 774 deg. C.

  16. Research Update: Magnetic phase diagram of EuTi1-xBxO3sub> (B = Zr, Nb)

    SciTech Connect

    Li, Ling; Zhou, Haidong; Yan, Jiaqiang; Mandrus, David; Keppens, Veerle

    2014-11-21

    Herein, we report the magnetic phase diagram of EuTi1-xBxO3sub> (B = Zr, Nb), determined from magnetization and heat capacity measurements. Upon Zr-doping, the antiferromagnetic ordering temperature TN of EuTi1-xZrxO3sub> gradually decreases from 5.6 K (x = 0) to 4.1 K (x = 1). Whereas a similar decrease in TN is observed for small amounts of Nb doping (x ≤ 0.05), ferromagnetism is induced in EuTi1-xNbxO3sub> with x > 0.05. Lastly, the ferromagnetic interaction between localized Eu 4f spins mediated by itinerant electrons introduced by Nb doping results in the ferromagnetism in EuTi1-xNbxO3sub>.

  17. Demonstration of High Current Density YBCO Coated Conductors on RE2O3sub>-Buffered Ni Substrates with Two New Alternative Architectures

    SciTech Connect

    Beach, D.B.; Chirayil, T.G.; Christen, D.K.; Cui, X.; Feenstra, R.; Goyal, A.; Kroeger, D.M.; Lee, D.F.; Martin, P.M.; Mathis, J.E.; Morrell, J.S.; Norton, D.P.; Paranthaman, M.; Specht, E.D.; Verebelyi, D.T.

    1999-07-12

    In continuation of our effort to develop single buffer layer architectures for YBCO (YBa2Cu3sub>O7-g) coated tape conductors, we have studied RE2O3sub> (RE = Y, and rare earths) as candidate materials. Three types of crystal structures including the preferred cubic phase are known for the rare earth oxides. High quality simple cubic RE2O3sub> buffer layers were grown epitaxiahy on {100}<001> textured Ni substrates using both reactive evaporation and sol-gel processing. Detailed X-ray studies have shown that the Y2O3sub>, Eu2O3sub>, Gd2O3sub>, and Yb2O3sub> were grown with a single epitaxial orientation. SEM micrographs indicated that both e-beam and sol-gel grown films were dense, continuous and crack free. High Jc YBCO films were grown on RE2O3sub>-buffered Ni substrates with sputtered cap layers. Two new alternative buffer layer architectures were developed. A high Jc of 1.8 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (pulsed laser deposition)/Yb2O3sub> (sputtered)/Y2O3sub> (e-beam)/Ni. Also, a high Jc of over 1 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (ex-situ BaF2 process)/CeO2 (sputtered)YSZ sputtered)/RE2O3sub> (sol-gel or e-beam)Ni. The performance of sol-gel grown buffers approached the quality of e-beam grown buffers.

  18. Constrained Surface Complexation Modeling: Rutile in RbCl, NaCl, and NaCF3sub>SO3sub> Media to 250 °C

    SciTech Connect

    Machesky, Michael L.; Předota, Milan; Ridley, Moira K.; Wesolowski, David J.

    2015-06-01

    In this paper, a comprehensive set of molecular-level results, primarily from classical molecular dynamics (CMD) simulations, are used to constrain CD-MUSIC surface complexation model (SCM) parameters describing rutile powder titrations conducted in RbCl, NaCl, and NaTr (Tr = triflate, CF3sub>SO3sub>) electrolyte media from 25 to 250 °C. Rb+ primarily occupies the innermost tetradentate binding site on the rutile (110) surface at all temperatures (25, 150, 250 °C) and negative charge conditions (-0.1 and -0.2 C/m2) probed via CMD simulations, reflecting the small hydration energy of this large, monovalent cation. Consequently, variable SCM parameters (Stern-layer capacitance values and intrinsic Rb+ binding constants) were adjusted relatively easily to satisfactorily match the CMD and titration data. The larger hydration energy of Na+ results in a more complex inner-sphere distribution, which shifts from bidentate to tetradentate binding with increasing negative charge and temperature, and this distribution was not matched well for both negative charge conditions, which may reflect limitations in the CMD and/or SCM approaches. Finally, in particular, the CMD axial density profiles for Rb+ and Na+ reveal that peak binding distances shift toward the surface with increasing negative charge, suggesting that the CD-MUSIC framework may be improved by incorporating CD or Stern-layer capacitance values that vary with charge.

  19. Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO3sub>

    SciTech Connect

    Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; Gehring, P. M.; Stock, C.; Matsuda, Masaaki; Winn, Barry L.; Gu, Genda; Shapiro, Stephen M.; Birgeneau, R. J.; Ushiyama, T.; Yanagisawa, Y.; Tomioka, Y.; Ito, T.; Xu, Guangyong

    2015-02-10

    In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3sub>. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010], and TA2 along [110]) and two low-energy optic phonon modes (LO and TO1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN=640 K. In conclusion, this suggests that the magnetic order and low-energy lattice dynamics in this multiferroic material are coupled.

  20. Characterization of tetragonal phases of SrRuO3sub> under epitaxial strain by density functional theory

    SciTech Connect

    Herklotz, Andreas; Dörr, Kathrin

    2015-03-11

    Using density functional theory calculations we research the effect of strain on the magnetic and structural properties of tetragonal SrRuO3sub>. All four different oxygen octahedra rotation patterns that are in agreement with tetragonal symmetry are considered and compared with the bulk-like orthorhombic structure. We find that among the tetragonal structures the phase with I4 /mcm symmetry is energetically most favorable. This structure is also lower in energy than the orthorhombic phase for compressive and tensile strain larger than -2.1% and +3.8%, respectively. The stability of the magnetic moment is found to be greatly dependent on the octahedra rotation pattern. Finally, the magnetic moment of the zero or one-tilt systems is quenched under tensile strain, while ferromagnetic order is preserved in the two or three-tilt systems.

  1. Direct and inverse magnetoelectric effects in HoAl{sub 3}(BO{sub 3}){sub 4} single crystal

    SciTech Connect

    Freydman, A. L.; Balaev, A. D.; Dubrovskiy, A. A.; Eremin, E. V.; Temerov, V. L.; Gudim, I. A.

    2014-05-07

    The direct (ME{sub H}-) and inverse (ME{sub E}-) magnetoelectric effects in the HoAl{sub 3}(BO{sub 3}){sub 4} single crystal are studied. Temperature and magnetic field dependences of permittivity of the crystal are investigated. A relation between the investigated effects was established. It was found that the magnetoelectric effect can exist in crystals without magnetic order or spontaneous polarization. It was shown that the phenomena investigated are due to magnetostriction or magnetoelastic effect. The thermodynamic potential was considered for describing magnetoelectric effect at low magnetic fields. The results obtained are explained within a proposed qualitative microscopic model, based on interplay of configuration of 4f- electron subshell of the rare-earth element and applied magnetic or electric field.

  2. Local structure study of Fe dopants in Ni-deficit Ni3sub>Al alloys

    SciTech Connect

    V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.; Lei, Hechang; Li, Lijun; Cekic, B.; Koteski, V.; Petrovic, C.

    2015-08-24

    We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3sub> Al. Moreover, the value of calculated electric field gradient tensor Vzz=1.6 1021Vm-2 matches well with the results of Mössbauer spectroscopy and indicates that the Fe atoms occupy Ni sites.

  3. Electron-Temperature Dependence of the Recombination of NH4(+)((NH3)(sub n) Ions with Electrons

    NASA Technical Reports Server (NTRS)

    Skrzypkowski, M. P.; Johnson, R.

    1997-01-01

    The two-body recombination of NH4(+)(NH3)(sub 2,3) cluster-ions with electrons has been studied in an afterglow experiment in which the electron temperature T, was elevated by radio-frequency heating from 300 K up to 900 K. The recombination coefficients for the n = 2 and n = 3 cluster ions were found to be equal, alpha(sub 2, sup(2)) = alpha(sub 3, sup(2)) = (4.8 +/- 0.5) x 10(exp - 6)cu cm/s, and to vary with electron temperature as T(sub c, sup -0.65) rather than to be nearly temperature-independent as had been inferred from measurements in microwave-heated plasmas.

  4. Crystal structure and lattice dynamics of Sr{sub 3}Y(BO{sub 3}){sub 3}

    SciTech Connect

    Maczka, M. Waskowska, A.; Majchrowski, A.; Kisielewski, J.; Szyrski, W.; Hanuza, J.

    2008-12-15

    X-ray, Raman and infrared (IR) studies of the Sr{sub 3}Y(BO{sub 3}){sub 3} (BOYS) single crystal grown by the Czochralski technique are presented. The crystal structure is trigonal, space group R3-bar (no. 148), and comprises six formula units in the unit cell with the hexagonal axes a=12.527(2) and c=9.280(2) A. The assignment of the observed vibrational modes is proposed on the basis of lattice dynamics calculations. The unusual large bandwidth of the internal modes and the enhancement of the principal mean square thermal displacements for BO{sub 3} and Y(1) indicate that some type of disorder is present in the studied crystal. - Graphical abstract: View of the crystal structure of BOYS along the c-axis.

  5. Anisotropy of acousto-optic figure of merit for LiNbO3sub> crystals: anisotropic diffraction.

    PubMed

    Mys, Oksana; Kostyrko, Myroslav; Vlokh, Rostyslav

    2016-03-20

    We have developed a method for the analysis of anisotropy of an acousto-optic figure of merit (AOFM), which is valid for the case of anisotropic diffraction in the trigonal crystals of the point symmetries 3m, 32, and 3¯m. The method is verified via the example of LiNbO3sub> crystals. The relations for the effective elasto-optic coefficients and the AOFM are obtained for the three types of acousto-optic (AO) interactions peculiar for the anisotropic AO diffraction: the interaction of a so-called type VII with a quasi-longitudinal acoustic wave and the interactions of types VIII and IX with two quasi-transverse acoustic waves. The AO diffraction geometries providing maximal AOFM values have been determined for each of the mentioned interaction types. We have found that the maximum AOFM proper for LiNbO3sub> is equal to 15.9×10-15  s3/kg. This value is achieved at the type IX of AO interactions in the interaction plane rotated by 60.0 deg around the principal X axis with respect to the principal X-Z plane. The type VIII of AO interactions is characterized by a comparable AOFM (15.1×10-15  s3/kg), which is realized in the Y-Z interaction plane. A close comparison of our results with the available experimental data demonstrates their fairly good agreement. PMID:27140586

  6. Crystal structure and magnetic properties of Na{sub 2}Ni{sup II}(HPO{sub 3}){sub 2}

    SciTech Connect

    Maalej, Wassim; Vilminot, Serge; Elaoud, Zakaria; Mhiri, Tahar; Kurmoo, Mohamedally

    2010-11-15

    Na{sub 2}Ni(HPO{sub 3}){sub 2}, obtained as light yellow-green crystals under mild hydrothermal conditions, crystallizes in the orthorhombic Pnma space-group with lattice parameters: a=11.9886(3), b=5.3671(2), c=9.0764(3) A, V=584.01 A{sup 3}, Z=4. The structure consists of zig-zag chains of NiO{sub 6} octahedra bridged by two HPO{sub 3}{sup 2-} and the chains are further connected through HPO{sub 3}{sup 2-} to four nearest chains to form a three dimensional framework, delimiting intersecting tunnels in which the sodium ions are located. The Na cations reside in the irregular Na(1)O{sub 5}, Na-O of 2.276-2.745 A, and Na(2)O{sub 9}, Na-O of 2.342-2.376 A, environments. The presence of the phosphite monoanion has been further confirmed by IR spectroscopy. Due to the 3D framework of Ni connected by O-P-O bridges, the magnetic susceptibility behaves as a paramagnet above 100 K (C=1.49(2) emu K mol{sup -1}, {mu}{sub eff}=3.45 {mu}{sub B}, {Theta}=-39(2) K) and below 6 K, it orders antiferromagnetically as confirmed the sharp drop and the non-Brillouin behavior of the isothermal magnetization at 2 K. - Graphical abstract: The structure of Na{sub 2}Ni(HPO{sub 3}){sub 2} consists of zig-zag chains of NiO{sub 6} octahedra bridged by two HPO{sub 3}{sup 2-} and the chains are further connected through HPO{sub 3}{sup 2-} to four nearest chains to form a three dimensional framework, delimiting intersecting tunnels in which the sodium ions are located. It orders antiferromagnetically at 6 K. Display Omitted

  7. Crystal structures and magnetic properties of lanthanide containing borates LnM(BO{sub 3}){sub 2} (Ln=Y, Ho–Lu; M=Sc, Cr)

    SciTech Connect

    Doi, Yoshihiro Satou, Tatsuya; Hinatsu, Yukio

    2013-10-15

    The synthesis, crystal structures and magnetic properties of LnM(BO{sub 3}){sub 2} (Ln=Y, Ho–Lu; M=Sc, Cr) were investigated. The LnCr(BO{sub 3}){sub 2} compounds crystallize in the dolomite-type structure with space group R3{sup ¯}, in which the Ln and Cr ions occupy two octahedral sites. From the result of structural analysis, it was found that there is an anti-site disorder between these two sites and its chemical formula is more exactly Ln{sub 1−r}Cr{sub r}[Cr{sub 1−r}Ln{sub r}](BO{sub 3}){sub 2}. On the other hand, the LnSc(BO{sub 3}){sub 2} adopt the calcite-type structure with space group R3{sup ¯}c. The Ln and Sc ions randomly occupy an octahedral site and the chemical formula is represented as (Ln{sub 0.5}Sc{sub 0.5})BO{sub 3}. From the magnetic susceptibility and specific heat measurements, we found that all the LnCr(BO{sub 3}){sub 2} show an antiferromagnetic transition at 6.1–8.1 K. This transition is mainly due to the ordering of Cr{sup 3+} magnetic moments. Among the compounds with magnetic Ln{sup 3+} ions, only YbCr(BO{sub 3}){sub 2} shows an antiferromagnetic ordering of Ln{sup 3+} ion at 2.1 K. - Graphical abstract: The lanthanide containing borates LnM(BO{sub 3}){sub 2} (Ln=Y, Ho–Lu; M=Sc, Cr) have the dolomite-type (Ln=Cr) and calcite-type (Ln=Sc) structures. Both structures are similar to each other except for the difference in the partially or fully disordered arrangements of octahedral sites. At low temperatures, the LnCr(BO{sub 3}){sub 2} compounds show an antiferromagnetic transition due to a long-range ordering of Cr{sup 3+} moments. Among them only YbCr(BO{sub 3}){sub 2} shows an antiferromagnetic ordering of Ln{sup 3+} ion at 2.1 K. Display Omitted - Highlights: • Lanthanide containing borates LnM(BO{sub 3}){sub 2} (Ln=Y, Ho–Lu; M=Sc, Cr) have been synthesized. • LnCr(BO{sub 3}){sub 2} has the dolomite-type structure with an anti-site disorder between Ln and Cr sites. • LnSc(BO{sub 3}){sub 2} has the calcite

  8. Luminescence improvement in Pr{sup 3+} and Gd{sup 3+} activated Sr{sub 2}Mg(BO{sub 3}){sub 2} inorganic phosphor

    SciTech Connect

    Gawande, A.B.; Sonekar, R.P.; Omanwar, S.K.

    2014-12-15

    Highlights: • Sr{sub 2}Mg(BO{sub 3}){sub 2} doped Gd{sup 3+} and Pr{sup 3+} have been synthesized by solution combustion synthesis technique. • Effect of doping concentration of Gd{sup 3+} and Pr{sup 3+} on the luminescence of synthesized material is discussed. • Effect of charge compensation by Li{sup +}, Na{sup +} and K{sup +} on emission intensity is studied in detail. • Efficient energy transfer from Pr{sup 3+} to Gd{sup 3+} in Sr{sub 2}Mg(BO{sub 3}){sub 2} was observed. • Optimum concentration and critical transfer distance for optimum concentration have been determined. - Abstract: The photoluminescence properties of (Sr{sub 1−x}Pr{sub x}){sub 2}Mg(BO{sub 3}){sub 2}; (Sr{sub 1−2x}Pr{sub x}M{sub x}){sub 2}Mg(BO{sub 3}){sub 2,} (M = Li, Na, K); (Sr{sub 1−x}Gd{sub x}){sub 2}Mg(BO{sub 3}){sub 2}; (Sr{sub 1−2x}Gd{sub x}M{sub x}){sub 2}Mg(BO{sub 3}){sub 2}, (M = Li, Na, K) and (Sr{sub 1−4x}Pr{sub x}Gd{sub x}Na{sub 2x}){sub 2}Mg(BO{sub 3}){sub 2} inorganic phosphors prepared by solution combustion synthesis technique are discussed. The structure of the prepared phosphor characterized using Thermogravimetric–differential thermal analysis, X-ray diffraction and fourier transform-infrared. Scanning electron microscopy images of the prepared materials show irregular grains with agglomerate phenomena. Photoluminescence properties were studied at room temperature. Optimum concentration and critical transfer distance of the synthesized phosphors were determined.

  9. Highly constrained ferroelectric [BaTiO{sub 3}]{sub (1−x)Λ}/[BaZrO{sub 3}]{sub xΛ} superlattices: X-ray diffraction and Raman spectroscopy

    SciTech Connect

    Belhadi, J.; El Marssi, M. Gagou, Y.; El Mendili, Y.; Bouyanfif, H.; Yuzyuk, Yu. I.; Raevski, I. P.; Wolfman, J.

    2014-07-21

    We report an x-ray diffraction (XRD) and a Raman-scattering investigation of ferroelectric/paraelectric superlattices [BaTiO{sub 3}] {sub (1−x)Λ}/[BaZrO{sub 3}]{sub xΛ} for which the composition varied, 0.15 ≤ x ≤ 0.85, while the superlattice (SL) modulation period Λ was kept constant at about 100 Å. The samples were epitaxially grown by pulsed laser deposition on MgO substrates buffered with La{sub 0.5}Sr{sub 0.5}CoO{sub 3}. Based on the XRD analysis and on polarized Raman spectra, we have showed that the large strain in SLs induced ferroelectricity in BaZrO{sub 3} (BZ) for all SLs, a material that is paraelectric in the bulk form at any temperature and in the single film. The induced polar axis in BZ layers is perpendicular to the plane of substrate while BaTiO{sub 3} (BT) layers exhibit in-plane polar orientation. Raman spectroscopy revealed a lattice ordering in SLs due to the misfit strain generated by the large lattice mismatch between the alternating BZ and BT layers. This strain induced a huge upward frequency of the lowest E(1TO) soft mode from 60 cm{sup −1} in the BT single film to 215 cm{sup −1} in the SL with x = 0.85. These results show that in spite of relatively large periodicity of SLs, they are highly constrained and the variation of BZ ratio allowed modifying strains between layers. The temperature dependence of the Raman spectra for BT{sub 0.3Λ}/BZ{sub 0.7Λ} and BT{sub 0.7Λ}/BZ{sub 0.3Λ} samples revealed giant shift of the ferroelectric phase transition. The phase transition temperature was found to be upshifted by about 300 °C with respect to BT single crystal.

  10. Nanocrystalline SiC and Ti3sub>SiC2 Alloys for Reactor Materials: Diffusion of Fission Product Surrogates

    SciTech Connect

    Henager, Charles H.; Jiang, Weilin

    2014-11-01

    MAX phases, such as titanium silicon carbide (Ti3sub>SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3sub>SiC2 has been suggested in the literature as a possible fuel cladding material. Prior to the application, it is necessary to investigate diffusivities of fission products in the ternary compound at elevated temperatures. This study attempts to obtain relevant data and make an initial assessment for Ti3sub>SiC2. Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti3sub>SiC2, SiC, and a dual-phase nanocomposite of Ti3sub>SiC2/SiC synthesized at PNNL. Thermal annealing and in-situ Rutherford backscattering spectrometry (RBS) were employed to study the diffusivity of the various implanted species in the materials. In-situ RBS study of Ti3sub>SiC2 implanted with Au ions at various temperatures was also performed. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti3sub>SiC2 occurs during ion implantation at 873 K. Cs in Ti3sub>SiC2 is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti3sub>SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Further studies of the related materials are recommended.

  11. Thermal Reactions of Uranium Metal, UO2, U3sub>O8, UF4, and UO2F2 with NF3sub> to Produce UF6

    SciTech Connect

    McNamara, Bruce K; Scheele, Randall D; Kozelisky, Anne E; Edwards, Matthew K

    2009-11-01

    The objective of this paper is to demonstrate that NF3sub> fluorinates uranium metal, UO2, UF4, UO3sub>, U3sub>O8, and UO2F2•2H2O to produce the volatile UF6 at temperatures between 100 and 500ºC. Thermogravimetric reaction profiles are described that reflect changes in the uranium oxidation state and discrete chemical speciation. Differences in the onset temperatures for each system indicate that NF3sub>-substrate interactions are important for the temperature at which NF3sub> reacts: U metal > UO3sub> > UO2 > UO2F2 > UF4 and in fact may indicate different fluorination mechanisms for these various substrates. These studies demonstrate that NF3sub> is a potential replacement fluorinating agent in the existing nuclear fuel cycle and in oft-proposed actinide volatility reprocessing.

  12. Exchange bias effect in Au-Fe3sub>O4 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

    2015-08-10

    We have studied the origin of the exchange bias effect in the Au-Fe3sub>O4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe3sub>O4 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 Fe3sub>O4 nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe3sub>O4 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 Fe3sub>O4 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.

  13. Fe2O3sub>–TiO2 core–shell nanorod arrays for visible light photocatalytic applications

    SciTech Connect

    Yao, Kun; Basnet, Pradip; Sessions, Henry; Larsen, George K.; Murph, Simona E. Hunyadi; Zhao, Yiping

    2015-11-11

    By using the glancing angle deposition technique and post-deposition annealing, Fe2O3sub>–TiO2 core-shell nanorod arrays with specific crystalline states can be designed and fabricated. The Fe2O3sub>–TiO2 core-shell samples annealed at temperatures greater than 450°C formed α-Fe2O3sub> and anatase TiO2, and showed higher catalytic efficiency for the degradation of methylene blue (MB) under visible light illumination when compared with pure anatase TiO2 or α-Fe2O3sub> nanorod arrays. Solar conversion of carbon dioxide and water vapor in the presence of Fe2O3sub>–TiO2 core-shell nanorod arrays was also investigated. Carbon monoxide, hydrogen, methane, and methanol along with other hydrocarbons were produced after only several hours’ exposure under ambient sunlight. It was determined that the core-shell structure showed greater efficiency for solar CO2 conversion than the pure TiO2 nanorod arrays.

  14. Interfacial mode coupling as the origin of the enhancement of Tc in FeSe films on SrTiO3sub>

    SciTech Connect

    Lee, J. J.; Schmitt, F. T.; Moore, R. G.; Johnston, S.; Cui, Y. -T.; Li, W.; Yi, M.; Liu, Z. K.; Hashimoto, M.; Zhang, Y.; Lu, D. H.; Devereaux, T. P.; Lee, D. -H.; Shen, Z. -X.; /SIMES, Stanford /SLAC /Stanford U., Geballe Lab.

    2014-11-12

    Films of iron selenide (FeSe) one unit cell thick grown on strontium titanate (SrTiO3sub> or STO) substrates have recently shown superconducting energy gaps opening at temperatures close to the boiling point of liquid nitrogen (77 K), which is a record for the iron-based superconductors. The gap opening temperature usually sets the superconducting transition temperature Tc, as the gap signals the formation of Cooper pairs, the bound electron states responsible for superconductivity. To understand why Cooper pairs form at such high temperatures, we examine the role of the SrTiO3sub> substrate. Here we report high-resolution angle-resolved photoemission spectroscopy results that reveal an unexpected characteristic of the single-unit-cell FeSe/SrTiO3sub> system: shake-off bands suggesting the presence of bosonic modes, most probably oxygen optical phonons in SrTiO3sub>, which couple to the FeSe electrons with only a small momentum transfer. Such interfacial coupling assists superconductivity in most channels, including those mediated by spin fluctuations. Our calculations suggest that this coupling is responsible for raising the superconducting gap opening temperature in single-unit-cell FeSe/SrTiO3sub>.

  15. Manganese carbonyl complexes as catalysts for the hydrosilation of ketones: Comparison with RhCl(PPh{sub 3}){sub 3}

    SciTech Connect

    Cavanaugh, M.D.; Gregg, B.T.; Cutler, A.R.

    1996-06-11

    Manganese carbonyl complexes catalyze the hydrosilation of ketones with PhMe{sub 2}SiH and Ph{sub 2}SiH{sub 2} in C{sub 6}D{sub 6} solutions. Efficacy of the manganese carbonyl precatalysts (2.4 mol %) toward acetone hydrosilation with 1.1 equiv of PhMe{sub 2}SiH to give (CH{sub 3}){sub 2}CH(OSiMe{sub 2}Ph) (3) varied: (PPh{sub 3})(CO){sub 4}MnC(O)CH{sub 3} (1) (<5 min) > (CO){sub 5}MnC(O)Ph > (CO){sub 5}MnC(O)CH{sub 3} > (CO){sub 5}MnCH{sub 3} > (CO){sub 5}MnBr (6.0 h) > Mn{sub 2}(CO){sub 10} = (PPh{sub 3})(CO){sub 4}MnBr = (CO){sub 5}MnSiMe{sub 2}Ph (2). A turnover frequency of 27 min{sub -1} was measured for catalysis using 1% 1; rapid catalysis was possible with 0.1% 1 in the absence of solvent. As a precatalyst, 1 is much more reactive than Rh(PPh{sub 3}){sub 3}Cl for the PhMe{sub 2}SiH hydrosilation of acetone, acetophenone, and cyclohexanone; both catalysts exhibit similar reactivity with Ph{sub 2}SiH{sub 2}. With 1 as the precatalyst, isolated yields of the alkoxydimethylphenylsilanes exceeded 90%, with no evidence of competing dehydrogenative silation to yield vinyl silyl ethers. Photochemical activation of (CO){sub 5}MnSiMe{sub 2}Ph (2) affords moderate hydrosilation catalytic activity in transforming acetone to 3. In contrast, (CO){sub 4}CoSiMe{sub 2}Ph (10) or Co{sub 2}(CO){sub 8} in the presence of the excess HSiMe{sub 2}Ph, with or without photochemical activation, were ineffective acetone hydrosilation catalysts. 32 refs., 2 tabs.

  16. Room temperature optical anisotropy of a LaMnO3sub> thin-film induced by ultra-short pulse laser

    SciTech Connect

    Munkhbaatar, Purevdorj; Marton, Zsolt; Tsermaa, Bataarchuluun; Choi, Woo Seok; Seo, Sung Seok A.; Kim, Jin Seung; Nakagawa, Naoyuki; Hwang, H. Y.; Lee, Ho Nyung; Myung-Whun, Kim

    2015-03-04

    Ultra-short laser pulse induced optical anisotropy of LaMnO3sub> thin films grown on SrTiO3sub> substrates were observed by irradiation with a femto-second laser pulse with the fluence of less than 0.1 mJ/cm2 at room temperature. The transmittance and reflectance showed different intensities for different polarization states of the probe pulse after pump pulse irradiation. The theoretical optical transmittance and re ectance that assumed an orbital ordering of the 3d eg electrons in Mn3+ ions resulted in an anisotropic time dependent changes similar to those obtained from the experimental results, suggesting that the photo-induced optical anisotropy of LaMnO3sub> is a result of photo-induced symmetry breaking of the orbital ordering for an optically excited state.

  17. Highly dispersed SiOx/Al2O3sub> catalysts illuminate the reactivity of isolated silanol sites

    SciTech Connect

    Mouat, Aidan R.; George, Cassandra; Kobayashi, Takeshi; Pruski, Marek; van Duyne, Richard P.; Marks, Tobin J.; Stair, Peter C.

    2015-09-23

    The reaction of γ-alumina with tetraethylorthosilicate (TEOS) vapor at low temperatures selectively yields monomeric SiOx species on the alumina surface. These isolated (-AlO)3sub>Si(OH) sites are characterized by PXRD, XPS, DRIFTS of adsorbed NH3sub>, CO, and pyridine, and 29Si and 27Al DNP-enhanced solid-state NMR spectroscopy. The formation of isolated sites suggests that TEOS reacts preferentially at strong Lewis acid sites on the γ-Al2O3sub> surface, functionalizing the surface with “mild” Brønsted acid sites. As a result, for liquid-phase catalytic cyclohexanol dehydration, these SiOx sites exhibit up to 3.5-fold higher specific activity than the parent alumina with identical selectivity.

  18. Observation of a periodic array of flux-closure quadrants in strained ferroelectric PbTiO3sub> films

    SciTech Connect

    Tang, Y. L.; Zhu, Y. L; Ma, Xiuliang; Borisevich, Albina Y; Morozovska, A. N.; Eliseev, Eugene; Wang, W. Y; Wang, Yujia; Xu, Y. B.; Zhang, Z. D.; Pennycook, Stephen J

    2015-05-01

    Nanoscale ferroelectrics are expected to exhibit various exotic domain configurations, such as the full flux-closure pattern that is well known in ferromagnetic materials. Here we observe not only the atomic morphology of the flux-closure quadrant but also a periodic array of flux closures in ferroelectric PbTiO3sub> films, mediated by tensile strain on a GdScO3sub> substrate. Using aberration-corrected scanning transmission electron microscopy, we directly visualize an alternating array of clockwise and counterclockwise flux closures, whose periodicity depends on the PbTiO3sub> film thickness. In the vicinity of the core, the strain is sufficient to rupture the lattice, with strain gradients up to 109 per meter. We found engineering strain at the nanoscale may facilitate the development of nanoscale ferroelectric devices.

  19. Synergy of elastic and inelastic energy loss on ion track formation in SrTiO3sub>

    SciTech Connect

    Weber, William J.; Zarkadoula, Eva; Pakarinen, Olli H.; Sachan, Ritesh; Chisholm, Matthew F.; Liu, Peng; Xue, Haizhou; Jin, Ke; Zhang, Yanwen

    2015-01-12

    While the interaction of energetic ions with solids is well known to result in inelastic energy loss to electrons and elastic energy loss to atomic nuclei in the solid, the coupled effects of these energy losses on defect production, nanostructure evolution and phase transformations in ionic and covalently bonded materials are complex and not well understood due to dependencies on electron-electron scattering processes, electron-phonon coupling, localized electronic excitations, diffusivity of charged defects, and solid-state radiolysis. Here we show that a colossal synergy occurs between inelastic energy loss and pre-existing atomic defects created by elastic energy loss in single crystal strontium titanate (SrTiO3sub>), resulting in the formation of nanometer-sized amorphous tracks, but only in the narrow region with pre-existing defects. These defects locally decrease the electronic and atomic thermal conductivities and increase electron-phonon coupling, which locally increase the intensity of the thermal spike for each ion. This work identifies a major gap in understanding on the role of defects in electronic energy dissipation and electron-phonon coupling; it also provides insights for creating novel interfaces and nanostructures to functionalize thin film structures, including tunable electronic, ionic, magnetic and optical properties.

  20. Tuning the metal-insulator crossover and magnetism in SrRuO3sub> by ionic gating

    SciTech Connect

    Yi, Hee Taek; Gao, Bin; Xie, Wei; Cheong, Sang -Wook; Podzorov, Vitaly

    2014-10-13

    Reversible control of charge transport and magnetic properties without degradation is a key for device applications of transition metal oxides. Chemical doping during the growth of transition metal oxides can result in large changes in physical properties, but in most of the cases irreversibility is an inevitable constraint. We report a reversible control of charge transport, metal-insulator crossover and magnetism in field-effect devices based on ionically gated archetypal oxide system - SrRuO3sub>. In these thin-film devices, the metal-insulator crossover temperature and the onset of magnetoresistance can be continuously and reversibly tuned in the range 90–250 K and 70–100 K, respectively, by application of a small gate voltage. We infer that a reversible diffusion of oxygen ions in the oxide lattice dominates the response of these materials to the gate electric field. These findings provide critical insights into both the understanding of ionically gated oxides and the development of novel applications.

  1. Growth, structural, IR and magnetic studies of a new gadolinium metaphosphate, Gd(PO{sub 3}){sub 3}

    SciTech Connect

    Naili, H. . E-mail: houcine_naili@yahoo.com; Ettis, H.; Yahyaoui, S.; Mhiri, T.

    2006-11-09

    The crystal structure of gadolinium metaphosphate Gd(PO{sub 3}){sub 3} has been established by X-ray diffraction. This compound crystallizes in the orthorhombic system (space group C222{sub 1}, Z=4) with cell parameters: a=8.4530 (3), b=11.0576 (4) and c=7.1952 (2)A. The structure was refined to R{sub 1}=0.0234 and wR{sub 2}=0.0502 using 2180 independent reflections (I>2{sigma}(I)). Phosphorus atoms are in slightly irregular tetrahedral oxygen coordination, gadolinium atoms are in considerably distorted dodecahedral oxygen coordination. Formally, the 3D framework in the structure can be described by the PO{sub 4} tetrahedra sharing corners to form helical chains and the GdO{sub 8} polyhedra sharing edges in a zigzag fashion. The shortest Gd-Gd distance is 4.174 (2)A. The infrared spectrum of the title compound recorded at room temperature in the frequency range of 400-4000cm{sup -1}, confirm the atomic arrangement within the structure. Below T{sub C}=25K, the magnetic susceptibility evolution is characteristic of a ferromagnetic order. In the high-temperature region above 100K, the susceptibility follows a Curie-Weiss law with C=7.91cm{sup 3}Kmol{sup -1} and {theta}=9.96K.

  2. Stabilization of weak ferromagnetism by strong magnetic response to epitaxial strain in multiferroic BiFeO3sub>

    SciTech Connect

    Cooper, Valentino R.; Lee, Jun Hee; Krogel, Jaron T.; Okamoto, Satoshi; Dixit, Hemant M.

    2015-08-06

    Multiferroic BiFeO3sub> exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption. Thus, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications. Here, we explore the stabilization and switchability of the weak ferromagnetic moments under applied epitaxial strain using a combination of first-principles calculations and group-theoretic analyses. We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [-110]) under compressive and tensile strains. A direct coupling between the anisotropic antiferrodistortive rotations and Dzyaloshinskii-Moria interactions drives the stabilization of weak ferromagnetism. Furthermore, energetically competing C- and G-type magnetic orderings are observed at high compressive strains, suggesting that it may be possible to switch the weak ferromagnetism on and off under application of strain. These findings emphasize the importance of strain and antiferrodistortive rotations as routes to enhancing induced weak ferromagnetism in multiferroic oxides.

  3. Thermoelectric properties of the unfilled skutterudite FeSb3sub> from first principles and Seebeck local probes

    SciTech Connect

    Lemal, Sébastien; Nguyen, Ngoc; de Boor, Johannes; Ghosez, Philippe; Varignon, Julien; Klobes, Benedikt; Hermann, Raphaël P.; Verstraete, Matthieu J.

    2015-11-16

    In this paper, using a combination of first-principles calculations and experimental transport measurements, we study the electronic and magnetic structure of the unfilled skutterudite FeSb3sub>. We employ the hybrid functional approach for exchange correlation. The ground state is determined to be antiferromagnetic with an atomic magnetic moment of 1.6μB/Fe. The Néel temperature TN is estimated at 6 K, in agreement with experiments which found a paramagnetic state down to 10 K. The ground state is semiconducting, with a small electronic gap of 33meV, also consistent with previous experiments on films. Charge carrier concentrations are estimated from Hall resistance measurements. The Seebeck coefficient is measured and mapped using a scanning probe at room temperature that yields an average value of 38.6μVK-1, slightly lower than the theoretical result. Finally, the theoretical conductivity is analyzed as a function of temperature and concentration of charge carriers.

  4. M5Si3sub>(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

    SciTech Connect

    Tang, Zhihong

    2007-01-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3sub>-based alloys was investigated. Oxidation behavior of Ti5Si3sub>-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3sub> by nucleation and growth of nitride subscale. Ti5Si3.2and Ti5Si3sub>C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo3sub>Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo3sub>Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} NbSS + NbB was determined to occur at 2104 ± 5 C by DTA.

  5. Improved Pharmacological and Structural Properties of HIV Fusion Inhibitor AP3sub> over Enfuvirtide: Highlighting Advantages of Artificial Peptide Strategy

    SciTech Connect

    Zhu, Xiaojie; Zhu, Yun; Ye, Sheng; Wang, Qian; Xu, Wei; Su, Shan; Sun, Zhiwu; Yu, Fei; Liu, Qi; Wang, Chao; Zhang, Tianhong; Zhang, Zhenqing; Zhang, Xiaoyan; Xu, Jianqing; Du, Lanying; Liu, Keliang; Lu, Lu; Zhang, Rongguang; Jiang, Shibo

    2015-08-19

    Enfuvirtide (T20), is the first HIV fusion inhibitor approved for treatment of HIV/AIDS patients who fail to respond to the current antiretroviral drugs. However, its clinical application is limited because of short half-life, drug resistance and cross-reactivity with the preexisting antibodies in HIV-infected patients. Using an artificial peptide strategy, we designed a peptide with non-native protein sequence, AP3sub>, which exhibited potent antiviral activity against a broad spectrum of HIV-1 strains, including those resistant to T20, and had remarkably longer in vivo half-life than T20. While the preexisting antibodies in HIV-infected patients significantly suppressed T20’s antiviral activity, these antibodies neither recognized AP3sub>, nor attenuated its anti-HIV-1 activity. Structurally different from T20, AP3sub> could fold into single-helix and interact with gp41 NHR. The two residues, Met and Thr, at the N-terminus of AP3sub> form a hook-like structure to stabilize interaction between AP3sub> and NHR helices. Therefore, AP3sub> has potential for further development as a new HIV fusion inhibitor with improved antiviral efficacy, resistance profile and pharmacological properties over enfuvirtide. Meanwhile, this study highlighted the advantages of artificially designed peptides, and confirmed that this strategy could be used in developing artificial peptide-based viral fusion inhibitors against HIV and other enveloped viruses.

  6. Effect of neutron irradiation on defect evolution in Ti3sub>SiC2 and Ti2AlC

    SciTech Connect

    Tallman, Darin J.; He, Lingfeng; Garcia-Diaz, Brenda L.; Hoffman, Elizabeth N.; Kohse, Gordon; Sindelar, Robert L.; Barsoum, Michel W.

    2015-10-23

    Here, we report on the characterization of defects formed in polycrystalline Ti3sub>SiC2 and Ti2AlC samples exposed to neutron irradiation – up to 0.1 displacements per atom (dpa) at 350 ± 40 °C or 695 ± 25 °C, and up to 0.4 dpa at 350 ± 40 °C. Black spots are observed in both Ti3sub>SiC2 and Ti2AlC after irradiation to both 0.1 and 0.4 dpa at 350 °C. After irradiation to 0.1 dpa at 695 °C, small basal dislocation loops, with a Burgers vector of b = 1/2 [0001] are observed in both materials. At 9 ± 3 and 10 ± 5 nm, the loop diameters in the Ti3sub>SiC2 and Ti2AlC samples, respectively, were comparable. At 1 × 1023 loops/m3, the dislocation loop density in Ti2AlC was ≈1.5 orders of magnitude greater than in Ti3sub>SiC2, at 3 x 1021 loops/m3. After irradiation at 350 °C, extensive microcracking was observed in Ti2AlC, but not in Ti3sub>SiC2. The room temperature electrical resistivities increased as a function of neutron dose for all samples tested, and appear to saturate in the case of Ti3sub>SiC2. The MAX phases are unequivocally more neutron radiation tolerant than the impurity phases TiC and Al2O3sub>. Based on these results, Ti3sub>SiC2 appears to be a more promising MAX phase candidate for high temperature nuclear applications than Ti2AlC.

  7. Optimized moth-eye anti-reflective structures for As2S3sub> chalcogenide optical fibers.

    PubMed

    Weiblen, R J; Menyuk, C R; Busse, L E; Shaw, L B; Sanghera, J S; Aggarwal, I D

    2016-05-16

    We computationally investigate moth-eye anti-reflective nanostructures imprinted on the endfaces of As2S3sub> chalcogenide optical fibers. With a goal of maximizing the transmission through the endfaces, we investigate the effect of changing the parameters of the structure, including the height, width, period, shape, and angle-of-incidence. Using these results, we design two different moth-eye structures that can theoretically achieve almost 99.9% average transmisison through an As2S3sub> surface. PMID:27409844

  8. Influence of Mg2+ on CaCO3sub> precipitation during subsurface reactive transport in a homogeneous silicon-etched pore network

    SciTech Connect

    Boyd, Victoria; Yoon, Hongkyu; Zhang, Changyong; Oostrom, Martinus; Hess, Nancy J.; Fouke, Bruce W.; Valocchi, Albert J.; Werth, Charles J.

    2014-04-04

    Calcium carbonate (CaCO3sub>) geochemical reactions exert a fundamental control on the evolution of porosity and permeability in shallow-to-deep subsurface siliciclastic and limestone rock reservoirs. As a result, these carbonate water-rock interactions play a critically important role in research on groundwater remediation, geological carbon sequestration, and hydrocarbon exploration. A study was undertaken to determine the effects of Mg2+ concentration on CaCO3sub> crystal morphology, precipitation rate, and porosity occlusion under flow and mixing conditions similar to those in subsurface aquifers.

  9. Enhanced electrical transparency by ultra-thin LaAlO3sub> insertion at oxide metal/semiconductor heterointerfaces

    SciTech Connect

    Yajima, Takeaki; Minohara, Makoto; Bell, Christopher; Kumigashira, Hiroshi; Oshima, Masaharu; Hwang, Harold Y.; Hikita, Yasuyuki

    2015-02-05

    We demonstrate that the electrical conductivity of metal/semiconductor oxide heterojunctions can be increased over 7 orders of magnitude by inserting an ultrathin layer of LaAlO3sub>. This counterintuitive result, that an interfacial barrier can be driven transparent by inserting a wide-gap insulator, arises from the large internal electric field between the two polar LaAlO3sub> surfaces. In conclusion, this field modifies the effective band offset in the device, highlighting the ability to design the electrostatic boundary conditions with atomic precision.

  10. Synthesis of the Stereoisomeric Clusters 1,2-Os3sub>(CO)10(trans-dpmn) and 1,2-Os3sub>(CO)10(cis-dpmn) [where dpmn = 2,3-bis(diphenylphosphinomethyl)-5-norbornene]: DFT Evaluation of the Isomeric Clusters 1,2-Os3sub>(CO)10(dpmn) and Isomer-Dependent Diphosphine Ligand Activation

    SciTech Connect

    Yang, Li; Nesterov, Vladimir N.; Wang, Xiaoping; Richmond, Michael G.

    2014-07-23

    The bicyclic diphosphines trans- and cis-2,3-bis(diphenylphosphinomethyl)-5-norbornene (dpmn) react with 1,2-Os3sub>(CO)10(MeCN)2 (1) to furnish the corresponding ligand-bridged clusters Os3sub>(CO)10(trans-dpmn) (2) and Os3sub>(CO)10(cis-dpmn) (3). Both new products have been isolated and the molecular structures established by X-ray diffraction analyses. The dihydroxyl-bridged cluster 1,2-Os3sub>(CO)8(μ-OH)2(cis-dpmn) (4), which accompanied the formation of 3 in one reaction, has been isolated and characterized by mass spectrometry and X-ray crystallography. Whereas cluster 2 is stable in toluene at 373 K, 3 is thermally sensitive under identical conditions and undergoes loss of CO (2 equiv), coupled with the activation of three norbornene C-H bonds and one P-C(phenyl) bond, to furnish the dihydride cluster H2Os3sub>(CO)83sub>-2-PhPC-3sub>-endo-Ph2PCH2(C7H7)] (5). The solid-state structure of 5 confirms the multiple activation of the cis-dpmn ligand and accompanying formation of the face-capping 2-PhPC-3-endo-Ph2PCH2(C7H7) moiety in the product. DFT calculations on 2 and 3 indicate that the former cluster is the thermodynamically more stable isomer, and the conversion of 3→ 5 + 2CO + benzene is computed to be exergonic by 12.7 kcal/mol and is entropically favored due to the release of the CO and benzene by-products.

  11. Synthesis of phase-pure U2N3sub> microspheres and its decomposition into UN

    SciTech Connect

    Silva, Chinthaka M.; Hunt, Rodney Dale; Snead, Lance Lewis; Terrani, Kurt A.

    2014-12-12

    Uranium mononitride (UN) is important as a nuclear fuel. Fabrication of UN in its microspherical form also has its own merits since the advent of the concept of accident-tolerant fuel, where UN is being considered as a potential fuel in the form of TRISO particles. But, not many processes have been well established to synthesize kernels of UN. Therefore, a process for synthesis of microspherical UN with a minimum amount of carbon is discussed herein. First, a series of single-phased microspheres of uranium sesquinitride (U2N3sub>) were synthesized by nitridation of UO2+C microspheres at a few different temperatures. Resulting microspheres were of low-density U2N3sub> and decomposed into low-density UN. The variation of density of the synthesized sesquinitrides as a function of its chemical composition indicated the presence of extra (interstitial) nitrogen atoms corresponding to its hyperstoichiometry, which is normally indicated as α-U2N3sub>. Average grain sizes of both U2N3sub> and UN varied in a range of 1–2.5 μm. In addition, these had a considerably large amount of pore spacing, indicating the potential sinterability of UN toward its use as a nuclear fuel.

  12. Damped spin waves in the intermediate ordered phases in Ni3sub>V2O8

    SciTech Connect

    Ehlers, Georg; Podlesnyak, Andrey A.; Frontzek, Matthias D.; Pushkarev, A. V.; Shiryaev, Sergie V.; Barilo, Sergie

    2015-06-09

    Here, spin dynamics in the intermediate ordered phases (between 4 and 9 K) in Ni3sub>V2O8 have been studied with inelastic neutron scattering. It is found that the spin waves are very diffuse, indicative of short lived correlations and the coexistence of paramagnetic moments with the long-range ordered state.

  13. Low Temperature Propane Oxidation over Co3sub>O4 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

    2015-06-09

    Low temperature propane oxidation has been achieved by Co3sub>O4-based nano-array catalysts featuring low catalytic materials loading. The Ni doping into the Co3sub>O4 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 Co3sub>O4 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 Co3sub>O4 nano-array catalysts for low temperature hydrocarbon oxidation. This study provides useful and timely guidance for rational catalyst design toward low temperature catalytic oxidation.

  14. Absence of Significant Structural Changes Near the Magnetic Ordering Temperature in Small-ion Rare Earth Perovskite RMnO3sub>

    SciTech Connect

    Yu, T.; Ty, T.; Chen, H.; Abeykoon, A. M. M.; Chen, Y. -S.; Ahn, K. H.

    2014-11-14

    The detailed structural measurements on multiple length scales were conducted on a new perovskite phase of ScMnO3sub>, and on orthorhombic LuMnO3sub> as a benchmark. Complementary density functional theory (DFT) calculations were carried out, and predict that ScMnO3sub> possesses E-phase magnetic order at low temperature with displacements of the Mn sites (relative to the high temperature state) of ~0.07 Å, compared to ~0.04 Å predicted for LuMnO3sub>. However, detailed local, intermediate and long-range structural measurements by x-ray pair distribution function analysis, single crystal x-ray diffraction and x-ray absorption spectroscopy, find no local or long-range distortions on crossing into the low temperature E-phase of the magnetically ordered state. Our measurements place upper limits on any structural changes to be at most one order of magnitude lower than DFT predictions and suggest that this theoretical approach does not properly account for the spin–lattice coupling in these oxides and may possibly predict the incorrect magnetic order at low temperatures. The results suggest that the electronic contribution to the electrical polarization dominates and should be more accurately treated in theoretical models.

  15. Equation of state of a high-pressure phase of Gd3sub>Ga5O12

    SciTech Connect

    Mao, Z. Q.; Dorfman, S. M.; Shieh, S.; Lin, Jung-Fu; Prakapenka, Vitali B.; Meng, Yue; Duffy, T. S.

    2011-02-24

    Gd3sub> Ga5 O12 (GGG), which crystallizes in the garnet structure at ambient conditions, was observed to transform to a high-pressure phase at 88 GPa after laser heating at 1500 K. This new phase is stable at least up to 180 GPa, and can be preserved on decompression to 50 GPa. This phase is cubic and consistent with a perovskite structure of stoichiometry (Gd0.75Ga0.25)GaO3sub>. The zero-pressure bulk modulus, K0, obtained from fitting to a Birch-Murnaghan equation of state is 373(5) GPa with a fixed pressure derivative K' 0 =4. At 170 GPa, the bulk modulus of perovskite-type GGG is 979(15) GPa, which is comparable to that of diamond at the same pressure [956(21) GPa] and consistent with recently reported shock-compression data for Gd3sub> Ga5 O12. The new high-pressure phase of Gd3sub> Ga5 O12 is thus highly incompressible.

  16. Selective electrosynthesis of (CH[sub 3])[sub 2]C[sub 60]: A novel method for the controlled functionalization of fullerenes

    SciTech Connect

    Caron, C.; Subramanian, R.; D'Souza, F.; Kim, J.; Kutner, W.; Jones, M.T.; Kadish, K.M. )

    1993-09-08

    We describe here the first selective synthesis of (CH[sub 3])[sub 2]C[sub 60], i.e., the simplest dialkylated derivative of C[sub 60]. The selectivity is achieved by electrochemical control of the charge, n, on C[sub 60][sup n[minus

  17. Fabrication of flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} and their electrochemical properties evaluation

    SciTech Connect

    Kong, Ling-Bin; Deng, Li; Li, Xiao-Ming; Liu, Mao-Cheng; Luo, Yong-Chun; Kang, Long

    2012-07-15

    Graphical abstract: Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} nano-flakes materials, which have a flower-like structure, were successfully synthesized by a facile solvothermal method without adding any surfactant. The as-prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} possesses a maximum specific capacitance of 2212.5 F g{sup −1} at the current density of 5 mA, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Highlights: ► Flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} materials were fabricated in a simple method. ► High specific capacitance of 2212.5 F g{sup −1} has been achieved. ► For the first time the effects of concentration and temperature on its specific capacitance has been studied. -- Abstract: Flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} was successfully synthesized by a facile solvothermal method. The microstructure and surface morphology of prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} were physically characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and transmission electron microscope (TEM). The electrochemical properties studies were carried out using cyclic voltammetry (CV), chronopotentiometry technology and AC impedance spectroscopy, respectively. The results indicate that the flower-like structure has a profound impact on electrode performance at high discharge capacitance. A maximum specific capacitance of 2212.5 F g{sup −1} at the current density of 5 mA could be achieved, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Furthermore, the effects of Ni(NO{sub 3}){sub 2}·6H{sub 2}O concentration and temperature on the microstructure and specific capacitance of prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} have also been systematically studied. The results show that flower-like structure can be formed when the concentration is appropriate, while the

  18. The crystal structure, thermal behaviour and ionic conductivity of a novel lithium gadolinium polyphosphate LiGd(PO{sub 3}){sub 4}

    SciTech Connect

    Ettis, Hasna; Naili, Houcine . E-mail: houcine_naili@yahoo.com; Mhiri, Tahar

    2006-10-15

    Crystal structure and ionic conductivity of lithium gadolinium polyphosphate, LiGd(PO{sub 3}){sub 4}, were investigated. Single crystals of the title compound have been grown by a flux technique. The structure of this novel phosphate was determined by single crystal X-ray diffraction techniques. LiGd(PO{sub 3}){sub 4} is isotypic with LiNd(PO{sub 3}){sub 4}. It crystallizes in the monoclinic space group C2/c with the unit cell parameters a=16.386(2), b=7.059(3), c=9.677(2) A, {beta}=126.12(1){sup o}, V=904.2(4) A{sup 3} and Z=4. The structure refined from 967 independent reflections leads to R {sub 1}=0.0167 and wR {sub 2}=0.0458. The lattice of LiGd(PO{sub 3}){sub 4} is built of twisted zig-zag chains running along with the b direction and make up of PO{sub 4} tetrahedra sharing two corners, connected to the GdO{sub 8} and LiO{sub 4} polyhedra by common oxygen atoms to form a three-dimensional framework. Differential and thermogravimetric thermal analysis are given. The thermal curve of this compound was recorded and interpreted in agreement with impedance measurements. The ionic conductivity has been measured on pellet of the polycrystalline powder and evaluated as a function of temperature. This phase showed the conductivity of 2x10{sup -6} and 2x10{sup -4} {omega}{sup -1} cm{sup -1} at 682 and 951 K, respectively. - Graphical abstract: The structural arrangement of LiGd(PO{sub 3}){sub 4} viewed in the (0 1 0) plane.

  19. Structure of complexes of nitrilo tris methylene phosphonic acid with copper, [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] and Na{sub 4}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O, as bactericides and inhibitors of scaling and corrosion

    SciTech Connect

    Somov, N. V.; Chausov, F. F.

    2015-03-15

    Nitrilotris methylene phosphonate triaqua copper and octasodium bis(nitrilotris methylene phosphonate cuprate(II)) nonadecahydrate have been synthesized and investigated. [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] is crystallized in the sp. gr. P2{sub 1}/c, Z = 4, a = 9.2506(2) Å, b = 15.9815(2) Å, c = 9.5474(2) Å, β = 113.697(2)°. The copper atom is coordinated by oxygen atoms in the configuration of elongated octahedron; the ligand (of bridge type) links neighboring copper atoms. Na{sub 8}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O is crystallized in the sp. gr. P2{sub 1}/c, Z = 2, a = 11.24550(10) Å, b = 17.38980(10) Å, c = 13.5852(2) Å, β = 127.8120(10)°. This complex is chelating; the copper atom closes three five-membered N-C-P-O-Cu cycles with a shared Cu-N bond. Copper is coordinated in a distorted trigonal-bipyramidal configuration.

  20. Domain wall motion and electromechanical strain in lead-free piezoelectrics: Insight from the model system (1 - x)Ba(Zr0.2Ti0.8)O3sub>-x(Ba0.7Ca0.3sub>)TiO3sub> using in situ high-energy X-ray diffraction during application of electric fields

    SciTech Connect

    Tutuncu, Goknur; Li, Binzhi; Bowman, Keith; Jones, Jacob L.

    2014-07-17

    The piezoelectric compositions (1 - x)Ba(Zr0.2Ti0.8)O3sub>–x(Ba0.7Ca0.3sub>)TiO3sub> (BZT-xBCT) span a model lead-free morphotropic phase boundary (MPB) between room temperature rhombohedral and tetragonal phases at approximately x = 0.5. In the present work, in situ X-ray diffraction measurements during electric field application are used to elucidate the origin of electromechanical strain in several compositions spanning the tetragonal compositional range 0.6 ≤ x ≤ 0.9. As BCT concentration decreases towards the MPB, the tetragonal distortion (given by c/a-1) decreases concomitantly with an increase in 90° domain wall motion. The increase in observed macroscopic strain is predominantly attributed to the increased contribution from 90° domain wall motion. The results demonstrate that domain wall motion is a significant factor in achieving high strain and piezoelectric coefficients in lead-free polycrystalline piezoelectrics.

  1. Intrinsic quantum anomalous Hall effect in the kagome lattice Cs2LiMn3sub>F12

    SciTech Connect

    Xu, Gang; Lian, Biao; Zhang, Shou -Cheng

    2015-10-27

    In a kagome lattice, the time reversal symmetry can be broken by a staggered magnetic flux emerging from ferromagnetic ordering and intrinsic spin-orbit coupling, leading to several well-separated nontrivial Chern bands and intrinsic quantum anomalous Hall effect. Based on this idea and ab initio calculations, we propose the realization of the intrinsic quantum anomalous Hall effect in the single layer Cs2Mn3sub>F12 kagome lattice and on the (001) surface of a Cs2LiMn3sub>F12 single crystal by modifying the carrier coverage on it, where the band gap is around 20 meV. Furthermore, a simplified tight binding model based on the in-plane ddσ antibonding states is constructed to understand the topological band structures of the system.

  2. Mixed-metal chloro sulfido cluster complex of molybdenum and platinum, (Mo sub 3 Pt sub 2 S sub 4 Cl sub 4 (PEt sub 3 ) sub 6 )

    SciTech Connect

    Saito, Taro; Tsuboi, Toshio; Kajitani, Yoshimichi; Yamagata, Tsuneaki; Imoto, Hideo )

    1991-09-04

    In the authors recent publication, syntheses of mixed-metal chloro sulfido and chloro selenido complexes of molybdenum and nickel were reported. They were prepared by the reaction of (Mo{sub 3}X{sub 4}Cl{sub 4}(PEt{sub 3}){sub 3}(MeOH){sub 2}) (X = S, Se){sup 2} with Ni(cod){sub 2} (cod = 1,5-cyclooctadiene). In the present study, another excellent building block compound, Pt(cot){sub 2}, was reacted with the same trinuclear molybdenum complex, and the mixed-metal cluster complex (Mo{sub 3}Pt{sub 2}S{sub 4}Cl{sub 4}(PEt{sub 3}){sub 6}) (1) with an unexpected structure was obtained.

  3. Equations of state and stability of MgSiO3sub> perovskite and post-perovskite phases from quantum Monte Carlo simulations

    SciTech Connect

    Lin, Yangzheng; Cohen, Ronald E.; Stackhouse, Stephen; Driver, Kevin P.; Militzer, Burkhard; Shulenburger, Luke; Kim, Jeongnim

    2014-11-10

    In this study, we have performed quantum Monte Carlo (QMC) simulations and density functional theory calculations to study the equations of state of MgSiO3sub> perovskite (Pv, bridgmanite) and post-perovskite (PPv) up to the pressure and temperature conditions of the base of Earth's lower mantle. The ground-state energies were derived using QMC simulations and the temperature-dependent Helmholtz free energies were calculated within the quasiharmonic approximation and density functional perturbation theory. The equations of state for both phases of MgSiO3sub> agree well with experiments, and better than those from generalized gradient approximation calculations. The Pv-PPv phase boundary calculated from our QMC equations of state is also consistent with experiments, and better than previous local density approximation calculations. Lastly, we discuss the implications for double crossing of the Pv-PPv boundary in the Earth.

  4. Sagnac interferometer hydrogen sensor based on panda fiber with Pt-loaded WO3sub>/SiO2 coating.

    PubMed

    Xu, Ben; Zhao, C L; Yang, Fan; Gong, Huaping; Wang, D N; Dai, JiXiang; Yang, Minghong

    2016-04-01

    A highly sensitive optical fiber Sagnac interferometer hydrogen sensor is proposed and demonstrated. The device is fabricated by inserting a segment of panda fiber coated with Pt-loaded WO3sub>/SiO2 into a Sagnac interferometer loop. When Pt/WO3sub> film is exposed to hydrogen, the exothermic reaction raises the temperature of the panda fiber, resulting in the resonant wavelength shift of the interferometer, and the resonant dip obtained has a large extinction ratio of ∼25  dB and a narrow linewidth of 2.5 nm. Such a device responds fast to hydrogen, exhibits a high sensitivity of -7.877  nm/% (vol. %) within the range of 0%-1.0% and is robust, low cost, and easy to fabricate. PMID:27192295

  5. Phase-matched frequency conversion below 150 nm in KBe2BO3sub>F2.

    PubMed

    Nakazato, Tomoharu; Ito, Isao; Kobayashi, Yohei; Wang, Xiaoyang; Chen, Chuangtian; Watanabe, Shuntaro

    2016-07-25

    Sum frequency mixing has been demonstrated below 150 nm in KBeBO3sub>F2 by using the fundamental with its fourth harmonic of a 6 kHz Ti: sapphire laser system. The wavelength of 149.8 nm is the shortest ever obtained to our knowledge by phase matching in nonlinear crystals. The output powers were 3.6 μW at 149.8 nm and 110 μW at 154.0 nm, respectively. The phase matching angles measured from 149.8 to 158.1 nm are larger by 3-4 degrees than those expected from the existing Sellmeier equation. The measured transmission spectra of KBeBO3sub>F2 crystals support the generation of coherent radiation below 150 nm. PMID:27464165

  6. 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.

    2013-05-15

    (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.

  7. Highly pure green light emission of perovskite CsPbBr3sub> quantum dots and their application for green light-emitting diodes.

    PubMed

    Li, Cunlong; Zang, Zhigang; Chen, Weiwei; Hu, Zhiping; Tang, Xiaosheng; Hu, Wei; Sun, Kuan; Liu, Xianming; Chen, Weimin

    2016-06-27

    All-inorganic perovskite CsPbBr3sub> quantum dots (QDs) with an emission peak of around 520 nm were synthesized by a hot-injection method, and were systematically studied as green phosphor for light-emitting diodes (LEDs). Highly pure green light with an emission peak of 534 nm and a full-width at half-maximum (FWHM) about 20 nm was achieved using CsPbBr3sub> QDs and GaN LEDs. Commission Internationale Ed I'Eclairage coordinate of the fabricated green LEDs was (0.203, 0.757). Compared to GaN LEDs, the current-voltage characteristic of the green LED did not show any degradation. Moreover, the green LEDs displayed a luminous efficiency of 31.92 lm/W under an injection current of 10 mA. PMID:27410658

  8. Stabilization of heterogeneous silicon lasers using Pound-Drever-Hall locking to Si3sub>N4 ring resonators.

    PubMed

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

    2016-06-13

    Recent results on heterogeneous Si/III-V lasers and ultra-high Q Si3sub>N4 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 Si3sub>N4 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

  9. Phase diagrams of the systems Mn(VO{sub 3}){sub 2}-M(VO{sub 3}){sub 2} and Mn{sub 2}V{sub 2}O{sub 7}-M{sub 2}V{sub 2}O{sub 7} (M = Sr, Ba)

    SciTech Connect

    Zhuravlev, V.D.; Surat, L.L.; Velikodnyi, Yu.A.

    1994-12-01

    In this paper, the authors report results on the phase relations in meta- and pyrovanadate binary systems containing manganese, strontium, or barium and their phase diagrams. Using powder X-ray diffraction and differential thermal analysis, we studied the phase diagrams of the systems Mn(VO{sub 3}){sub 2}-M(VO){sub 3}{sub 2} and Mn{sub 2}V{sub 2}-O{sub 7}-M{sub 2}V{sub 2}O{sub 7} (M=Sr,Ba) in air. Mn{sub 1-x}Sr{sub x}(VO{sub 3}){sub 2}solid solutions and three new compounds, BaMnV{sub 2}O{sub 7}, SrMnV{sub 2}O{sub 7}, and Sr{sub 3}Mn(V{sub 2}O{sub 7}){sub 2}, were found, and their thermal behavior was studied.

  10. Adventures on the C3sub>H5O potential energy surface: OH+propyne, OH+allene and related reactions

    SciTech Connect

    Zádor, Judit; Miller, James A.

    2014-06-25

    We mapped out the stationary points and the corresponding conformational space on the C3sub>H5O potential energy surface relevant for the OH + allene and OH + propyne reactions systematically and automatically using the KinBot software at the UCCSD(T)-F12b/cc-pVQZ-F12//M06-2X/6-311++G(d,p) level of theory. We used RRKM-based 1-D master equations to calculate pressure- and temperature-dependent, channel-specific phenomenological rate coefficients for the bimolecular reactions propyne + OH and allene + OH, and for the unimolecular decomposition of the CH3sub>CCHOH, CH3sub>C(OH)CH, CH2CCH2OH, CH2C(OH)CH2 primary adducts, and also for the related acetonyl, propionyl, 2-methylvinoxy, and 3-oxo-1-propyl radicals. The major channel of the bimolecular reactions at high temperatures is the formation propargyl + H2O, which makes the title reactions important players in soot formation at high temperatures. However, below ~1000 K the chemistry is more complex, involving the competition of stabilization, isomerization and dissociation processes. We found that the OH addition to the central carbon of allene has a particularly interesting and complex pressure dependence, caused by the low-lying exit channel to form ketene + CH3sub> bimolecular products. In this study, we compared our results to a wide range of experimental data and assessed possible uncertainties arising from certain aspects of the theoretical framework.

  11. Anionic ordering and thermal properties of FeF3sub>·3H2O

    SciTech Connect

    Burbano, Mario; Duttine, Mathieu; Borkiewicz, Olaf; Wattiaux, Alain; Demourgues, Alain; Salanne, Mathieu; Groult, Henri; Dambournet, Damien

    2015-09-17

    In this study, iron fluoride tri-hydrate can be used to prepare iron hydroxyfluoride with the Hexagonal-Tungsten-Bronze (HTB) type structure, a potential cathode material for batteries. To understand this phase transformation, a structural description of β-FeF3sub>·3H2O is first performed by means of DFT calculations and Mössbauer spectroscopy. The structure of this compound consists of infinite chains of [FeF6]n and [FeF2(H2O)4]n. The decomposition of FeF3sub>·3H2O induces a collapse and condensation of these chains, which lead to the stabilization, under specific conditions, of a hydroxyfluoride network FeF3-x(OH)x with the HTB structure. The release of H2O and HF was monitored by thermal analysis and physical characterizations during the decomposition of FeF3sub>·3H2O. An average distribution of FeF4(OH)2 distorted octahedra in HTB-FeF3-x(OH)x was obtained subsequent to the thermal hydrolysis/olation of equatorial anionic positions involving F- and H2O. This study provides a clear understanding of the structure and thermal properties of FeF3sub>·3H2O, a material that can potentially bridge the recycling of pickling sludge from the steel industry by preparing battery electrodes.

  12. Ultrafast terahertz gating of the polarization and giant nonlinear optical response in BiFeO3sub> thin films

    SciTech Connect

    Chen, Frank; Goodfellow, John; Liu, Shi; Grinberg, Ilya; Hoffman, Matthias; Damodaran, Anoop R.; Zhu, Yi; Zhang, Xiaohang; Takeuchi, Ichiro; Rappe, Andrew; Martin, Lane W.; Wen, Haidan; Lindenberg, Aaron M.

    2015-09-21

    In this article, terahertz pulses are applied as an all-optical bias to ferroelectric thin-film BiFeO3sub> while monitoring the time-dependent ferroelectric polarization through its nonlinear optical response. Modulations in the intensity of the second harmonic light generated by the film correspond to on–off ratios of 220 × gateable on femtosecond timescales. Polarization modulations comparable to the built-in static polarization are observed.

  13. Effects of core type, placement, and width on the estimated interstrand coupling properties of QXF-type Nb3sub>Sn Rutherford cables

    SciTech Connect

    Collings, E. W.; Sumption, M. D.; Majoros, M.; Wang, X.; Dietderich, D. R.

    2015-01-12

    The coupling magnetization of a Rutherford cable is inversely proportional to an effective interstrand contact resistance Reff , a function of the crossing-strand resistance Rc, and the adjacent strand resistance Ra. In cored cables, Reff continuously varies with W, the core width expressed as percent interstrand cover. For a series of un-heat-treated stabrite-coated NbTi LHC-inner cables with stainless-steel (SS, insulating) cores, Reff (W) decreased smoothly as W decreased from 100%, whereas for a set of research-wound SS-cored Nb3sub>Sn cables, Reff plummeted abruptly and remained low over most of the range. The difference is due to the controlling influence of Rc - 2.5 μΩ for the stabrite/NbTi and 0.26 μΩ for Nb3sub>Sn. The experimental behavior was replicated in the Reff (W)’s calculated by the program CUDI, which (using the basic parameters of the QXF cable) went on to show in terms of decreasing W that: 1) in QXF-type Nb3sub>Sn cables (Rc = 0.26 μΩ), Reff dropped even more suddenly when the SS core, instead of being centered, was offset to one edge of the cable; 2) Reff decreased more gradually in cables with higher Rc’s; and 3) a suitable Reff for a Nb3sub>Sn cable can be achieved by inserting a suitably resistive core rather than an insulating (SS) one.

  14. Synthesis of five- and six-coordinate alkylidene complexes of the type Mo(CHR)(NAr)[OCMe(CF[sub 3])[sub 2

    SciTech Connect

    Fox, H.H.; Lee, J.K.; Park, L.Y.; Schrock, R.R. )

    1993-03-01

    Addition of a slight excess of 4-methoxy-1-hexene to Mo(CHCMe[sub 2]Ph)(NAr)(OR[sub F6])[sub 2] (1a) or Mo(CHCMe[sub 3])(NAr)(OR[sub F6])[sub 2] (1b) in pentane (OR[sub F6] = OCMe(CF[sub 3])[sub 2]) yielded crystalline, red-orange anti-Mo[CHCH[sub 2]CH(OMe)CH[sub 2]CH[sub 3

  15. Nonlinear Luminescence Response of CaF2:Eu and YAlO3sub>:Ce to Single-Ion Excitation

    SciTech Connect

    Liu, Peng; Zhang, Yanwen; Xiao, Haiyan Y.; Xiang, Xia; Wang, Xuelin; Weber, William J.

    2014-01-17

    Understanding scintillation physics and nonproportionality is essential to accelerate materials discovery that has been restricted due to the difficulties inherent to large crystal growth and complex nature of gamma-solid interaction. Taking advantage of less restrictive growth and deposition techniques for smaller crystal sizes or thin films and better fundamental understanding of ion-solid interactions, a unique ion approach is demonstrated to effectively screen candidate scintillators with relatively small size and evaluate their nonlinear scintillation response. Response of CaF2:Eu and YAlO3sub>:Ce scintillators to single ions of Hþ, Heþ, and O3sub>þ are measured by the corresponding pulse height over a continuous energy range using a time-of-flight–scintillator–photoelectric multiplier tube apparatus. Nonlinear response of the scintillators under ionizing ion irradiation is quantitatively evaluated by considering the energy partitioning process. In a differential energy deposition region with negligible displacement damage, the low, medium and high excitation energy deposition density (Dexci) can be produced by energetic Hþ, Heþ and O3sub>þ ions, respectively, and significantly different impacts on the response characteristics of these two benchmark scintillators are observed. For CaF2:Eu, the scintillation efficiency under ion irradiation monotonically decreases with increasing excitation-energy density. In contrast, the response efficiency of YAlO3sub>:Ce scintillation initially increases with excitation-energy density at low excitation-energy densities, goes through a maximum, and then decreases with further increasing excitation-energy density. The fundamental mechanism causing these different response behaviours in the scintillators is based on the competition between the scintillation response and the nonradiative quenching process under different excitation densities, which is also the main

  16. Synthesis and structure of R{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (R = Rb or Cs)

    SciTech Connect

    Serezhkin, V. N.; Peresypkina, E. V.; Grigor’eva, V. A.; Virovets, A. V.; Serezhkina, L. B.

    2015-01-15

    Crystals Rb{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (I) and Cs{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (II) have been synthesized and studied by IR spectroscopy and X-ray diffraction. Crystals I are monoclinic, with the following parameters: a = 12.2118(5) Å, b = 10.2545(3) Å, c = 11.8754(4) Å, β = 110.287(1)°, sp. gr. C2/c, Z = 4, and R = 0.0523. Crystals II are orthorhombic, with a = 13.7309(3) Å, b = 10.5749(2) Å, c = 10.1891(2) Å, sp. gr. Pnma, Z = 4, and R = 0.0411. The basic structural units of crystals I and II are one-core complexes [UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}]{sup 2−}, which belong to the crystallochemical group cis-AB{sub 2}{sup 01}M{sub 2}{sup 1} (A = UO{sub 2}{sup 2+}, B{sup 01} = NO{sub 3}{sup −}, M{sup 1} = NCS{sup −}), which are combined into a framework via electrostatic interactions with ions of alkaline metals R (R = Rb or Cs). The structural features of crystals I and II, which condition the formation of [UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}]{sup 2−} complexes with a cis rather than a trans position of isothiocyanate ions in the coordination sphere of uranyl ions, are discussed.

  17. Superconductivity in the presence of disorder in skutterudite-related La3sub>Co4Sn13 and La3sub>Ru4Sn13 compounds: Electrical transport and magnetic studies

    SciTech Connect

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

    2015-06-25

    La3sub>Co4Sn13 and La3sub>Ru4Sn13 were categorized as BCS superconductors. In a plot of the critical field Hc2 vs T, La3sub>Ru4Sn13 displays a second superconducting phase at the higher critical temperature Tc*, characteristic of inhomogeneous superconductors, while La3sub>Co4Sn13 shows bulk superconductivity below Tc. We observe a decrease in critical temperatures with external pressure and magnetic field for both compounds. Additionally, for La3sub>Ru4Sn13 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 La3sub>CoxRu4–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.

  18. Solid-state graphene formation via a nickel carbide intermediate phase [Nickel carbide (Ni3sub>C) as an intermediate phase for graphene formation

    SciTech Connect

    Xiong, W; Zhou, Yunshen; Hou, Wenjia; Guillemet, Thomas; Silvain, Jean-François; Lahaye, Michel; Lebraud, Eric; Xu, Shen; Wang, Xinwei; Cullen, David A; More, Karren Leslie; Lu, Yong Feng

    2015-01-01

    Direct formation of graphene with controlled number of graphitic layers on dielectric surfaces is highly desired for practical applications. Despite significant progress achieved in understanding the formation of graphene on metallic surfaces through chemical vapor deposition (CVD) of hydrocarbons, very limited research is available elucidating the graphene formation process via rapid thermal processing (RTP) of solid-state amorphous carbon, through which graphene is formed directly on dielectric surfaces accompanied by autonomous nickel evaporation. It is suggested that a metastable hexagonal nickel carbide (Ni3sub>C) intermediate phase plays a critical role in transforming amorphous carbon to 2D crystalline graphene and contributing to the autonomous Ni evaporation. Temperature resolved carbon and nickel evolution in the RTP process is investigated using Auger electron spectroscopic (AES) depth profiling and glancing-angle X-ray diffraction (GAXRD). Formation, migration and decomposition of the hexagonal Ni3sub>C are confirmed to be responsible for the formation of graphene and the evaporation of Ni at 1100 °C. The Ni3sub>C-assisted graphene formation mechanism expands the understanding of Ni-catalyzed graphene formation, and provides insightful guidance for controlled growth of graphene through the solid-state transformation process.

  19. New coordination features; A bridging pyridine and the forced shortest non-covalent distance between two CO3sub>2- species

    SciTech Connect

    Velasco, V.; Aguilà, D.; Barrios, L. A.; Borilovic, I.; Roubeau, O.; Ribas-Ariño, J.; Fumanal, M.; Teat, S. J.; Aromí, G.

    2014-09-29

    The aerobic reaction of the multidentate ligand 2,6-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine, H4L, with Co(II) salts in strong basic conditions produces the clusters [Co4(L)2(OH)(py)7]NO3sub> (1) and [Co8Na4(L)4(OH)2(CO3sub>)2(py)10](BF4)2 (2). Analysis of their structure unveils unusual coordination features including a very rare bridging pyridine ligand or two trapped carbonate anions within one coordination cage, forced to stay at an extremely close distance (dO···O = 1.946 Å). This unprecedented non-bonding proximity represents a meeting point between long covalent interactions and “intermolecular” contacts. These original motifs have been analysed here through DFT calculations, which have yielded interaction energies and the reduced repulsion energy experimented by both CO3sub>2- anions when located in close proximity inside the coordination cage.

  20. Efficient laser operation based on transparent Nd:Lu2O3sub> ceramic fabricated by Spark Plasma Sintering.

    PubMed

    Xu, Changwen; Yang, Chengdong; Zhang, Han; Duan, Yanmin; Zhu, Haiyong; Tang, Dingyuan; Huang, Huihui; Zhang, Jian

    2016-09-01

    Efficient laser operation of Nd:Lu2O3sub> ceramic fabricated by Spark Plasma Sintering (SPS) was demonstrated. Transparent Nd:Lu2O3sub> ceramic was successfully fabricated by Spark Plasma Sintering and its laser experiment was done. On the 4F3/2 to 4I11/2 transition, the obtained maximum output is 1.25W at the absorbed pump power of 4.15W with a slope efficiency of 38% and two spectral lines at 1076.7nm and 1080.8nm oscillated simultaneously. The slope efficiency of 38% is near two times higher than the previously demonstrated SPSed Nd:Lu2O3sub> ceramic lasers. On the 4F3/2 to 4I13/2 transition, the laser operated at the wavelength of 1359.7nm and the maximum output of 200mW was obtained at the absorbed pump power of 2.7W. PMID:27607660

  1. Thermodynamic approach to the stability of multi-phase systems. Application to the Y2O3sub>–Fe system

    SciTech Connect

    Samolyuk, German D.; Osetskiy, Yury N.

    2015-07-07

    Oxide-metal systems (OMSs) are important in many practical applications, and therefore, are under extensive studies using a wide range of techniques. The most accurate theoretical approaches are based on density functional theory (DFT), which are limited to ~102 atoms. Multi-scale approaches, e.g., DFT+Monte Carlo, are often used to model OMSs at the atomic level. These approaches can describe qualitatively the kinetics of some processes but not the overall stability of OMSs. In this paper, we propose a thermodynamic approach to study equilibrium in multiphase systems, which can be sequentially enhanced by considering different defects and microstructures. We estimate the thermodynamic equilibrium by minimization the free energy of the whole multiphase system using a limited set of defects and microstructural objects for which the properties are calculated by DFT. As an example, we consider Y2O3sub>+bcc Fe with vacancies in both the Y2O3sub> and bcc Fe phases, Y substitutions and O interstitials in Fe, Fe impurities and antisite defects in Y2O3sub>. The output of these calculations is the thermal equilibrium concentration of all the defects for a particular temperature and composition. The results obtained confirmed the high temperature stability of yttria in iron. As a result, model development towards more accurate calculations is discussed.

  2. Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4}

    SciTech Connect

    Ben Bechir, M. Karoui, K.; Guidara, K.; Ben Rhaiem, A.; Tabellout, M.

    2014-05-28

    The [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} crystallizes at room temperature in the monoclinic system with P2{sub 1}/{sub C} space group. Three phase transitions at T{sub 1} = 226 K, T{sub 2} = 264 K, and T{sub 3} = 297 K have been evidenced by DSC measurements. The electrical technique was measured in the 10{sup −1}–10{sup 7} Hz frequency range and 203–313 K temperature intervals. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law (developed). The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} compound is studied by two processes which can be attributed to a hopping transport mechanism: the correlated barrier hopping model in phases I, II, and III, the non-overlapping small polaron tunneling model in phase IV. The conduction mechanism is interpreted with the help of Elliot's theory, and the Elliot's parameters are found.

  3. Melting of Pb Charge Glass and Simultaneous Pb-Cr Charge Transfer in PbCrO3sub> as the Origin of Volume Collapse

    SciTech Connect

    Yu, Runze; Hojo, Hajime; Watanuki, Tetsu; Mizumaki, Masaichiro; Mizokawa, Takashi; Okada, Kengo; Kim, Hyunjeong; Machida, Akihiko; Sakaki, Kouji; Nakamura, Yumiko; Agui, Akane; Mori, Daisuke; Inaguma, Yoshiyuki; Schlipf, Martin; Rushchanskii, Konstantin; Lezaic, Marjana; Matsuda, Masaaki; Ma, Jie; Calder, Stuart A.; Isobe, Masahiko; Ikuhara, Yuichi; Azuma, Masaki

    2015-09-15

    A metal to insulator transition in integer or half integer charge systems can be regarded as crystallization of charges. The insulating state tends to have a glassy nature when randomness or geometrical frustration exists. In this paper, we report that the charge glass state is realized in a perovskite compound PbCrO3sub>, which has been known for almost 50 years, without any obvious inhomogeneity or triangular arrangement in the charge system. PbCrO3sub> has a valence state of Pb2+0.5Pb4+0.5Cr3+O3sub> with Pb2+–Pb4+ correlation length of three lattice-spacings at ambient condition. A pressure induced melting of charge glass and simultaneous Pb–Cr charge transfer causes an insulator to metal transition and ~10% volume collapse.

  4. Spin-Induced Polarizations and Nonreciprocal Directional Dichroism of the Room-Temperature Multiferroic BiFeO3sub>

    SciTech Connect

    Fishman, Randy Scott; Lee, Jun Hee; Bordacs, Sandor; Kezsmarki, Istvan; Nagel, Urmas; Room, Toomas

    2015-09-14

    A microscopic model for the room-temperature multiferroic BiFeO3sub> that includes two Dzyaloshinskii-Moriya interactions and single-ion anisotropy along the ferroelectric polarization predicts both the zero-field spectroscopic modes as well as their splitting and evolution in a magnetic field. Due to simultaneously broken time-reversal and spatial-inversion symmetries, the absorption of light changes as the magnetic field or the direction of light propagation is reversed. We discuss three physical mechanisms that may contribute to this absorption asymmetry known as directional dichroism: the spin current, magnetostriction, and single-ion anisotropy. We conclude that the directional dichroism in BiFeO3sub> is dominated by the spin-current polarization and is insensitive to the magnetostriction and easy-axis anisotropy. With three independent spin-current parameters, our model accurately describes the directional dichroism observed for magnetic field along [1, -1, 0]. Since some modes are almost transparent to light traveling in one direction but opaque for light traveling in the opposite direction, BiFeO3sub> can be used as a room-temperature optical diode at certain frequencies in the GHz to THz range. This work demonstrates that an analysis of the directional dichroism spectra based on an effective spin model supplemented by first-principles calculations can produce a quantitative microscopic theory of the magnetoelectric couplings in multiferroic materials.

  5. Blending Cr2O3sub> into a NiO-Ni electrocatalyst for sustained water splitting

    SciTech Connect

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng -Chang; Wang, Di -Yan; Yang, Jiang; Hwang, Bing -Joe; Dai, Hongjie

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3sub>-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3sub> triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3sub> is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.

  6. Crystal chemistry and ion-exchange properties of the layered uranyl iodate K[UO{sub 2}(IO{sub 3}){sub 3}

    SciTech Connect

    Shvareva, Tatiana Y.; Almond, Philip M.; Albrecht-Schmitt, Thomas E. . E-mail: albreth@auburn.edu

    2005-02-15

    Single crystals of the potassium uranyl iodate, K[UO{sub 2}(IO{sub 3}){sub 3}] (1), have been grown under mild hydrothermal conditions. The structure of 1 contains two-dimensional {sub {infinity}}{sup 2}[UO{sub 2}(IO{sub 3}){sub 3}]{sup 1-} sheets extending in the [ab] plane that consist of approximately linear UO{sub 2}{sup 2+} cations bound by iodate anions to yield UO{sub 7} pentagonal bipyramids. There are three crystallographically unique iodate anions, two of which bridge between uranyl cations to create sheets, and one that is monodentate and protrudes in between the layers in cavities. K{sup +} cations form long ionic contacts with oxygen atoms from the layers forming an eight-coordinate distorted dodecahedral geometry. These cations join the {sub {infinity}}{sup 2}[UO{sub 2}(IO{sub 3}){sub 3}]{sup 1-} sheets together. Ion-exchange reactions have been carried out that indicate the selective uptake of Cs{sup +} over Na{sup +} or K{sup +} by 1. Crystallographic data (193K, MoK{alpha}, {lambda}=0.71073A): 1, orthorhombic, Pbca, a=11.495(1)A, b=7.2293(7)A, c=25.394(2)A, Z=8, R(F)=1.95% for 146 parameters with 2619 reflections with I>2{sigma}(I)

  7. Pressure-induced isostructural phase transition of a metal-organic framework Co2(4,4'-bpy)3sub>(NO3sub>)4·xH2O

    SciTech Connect

    Zhou, Mi; Wang, Kai; Men, Zhiwei; Sun, Chenglin; Li, Zhanlong; Liu, Bingbing; Zou, Guangtian; Zou, Bo

    2014-07-17

    Based on the 4,4'-bipyridine organic linker, metal–organic frameworks of Co2(4,4'-bpy)3sub>(NO3sub>)4·xH2O (CB-MOF) have been prepared. The pressure-dependent structure evolution of CB-MOF has been investigated up to 11 GPa. An isostructural phase transition was observed at about 6 GPa followed by negative compressibility along the b axis.

  8. Synthesis and nonlinear optical properties of BaTi(BO{sub 3}){sub 2} and Ba{sub 3}Ti{sub 3}O{sub 6}(BO{sub 3}){sub 2} crystals in glasses with high TiO{sub 2} contents

    SciTech Connect

    Kosaka, Shinji; Benino, Yasuhiko; Fujiwara, Takumi; Dimitrov, Vesselin; Komatsu, Takayuki . E-mail: komatsu@chem.nagaokaut.ac.jp

    2005-06-15

    The ternary BaO-TiO{sub 2}-B{sub 2}O{sub 3} glasses containing a large amount of TiO{sub 2} (20-40mol%) are prepared, and their optical basicities ({lambda}), the formation, structural features and second-order optical nonlinearities of BaTi(BO{sub 3}){sub 2} and Ba{sub 3}Ti{sub 3}O{sub 6}(BO{sub 3}){sub 2} crystals are examined to develop new nonlinear optical materials. It is found that the glasses with high TiO{sub 2} contents of 30-40mol% show large optical basicities of {lambda}=0.81-0.87, suggesting the high polarizabity of TiO{sub n} polyhedra (n=4-6) in the glasses. BaTi(BO{sub 3}){sub 2} and Ba{sub 3}Ti{sub 3}O{sub 6}(BO{sub 3}){sub 2} crystals are found to be formed as main crystalline phases in the glasses. It is found that BaTi(BO{sub 3}){sub 2} crystals tend to orient at the surface of crystallized glasses. The new XRD pattern for the Ba{sub 3}Ti{sub 3}O{sub 6}(BO{sub 3}){sub 2} phase is proposed through Rietvelt analysis. The second harmonic intensities of crystallized glasses were found to be 0.8 times as large as {alpha}-quartz powders, i.e., I{sup 2{omega}}(sample)/I{sup 2{omega}}({alpha}-quartz)=0.8, for the sample with BaTi(BO{sub 3}){sub 2} crystals and to be I{sup 2{omega}}(sample)/I{sup 2{omega}}({alpha}-quartz)=68 for the sample with Ba{sub 3}Ti{sub 3}O{sub 6}(BO{sub 3}){sub 2} crystals. The Raman scattering spectra for these two crystalline phases are measured for the first time and their structural features are discussed.

  9. Structures and Energetics of (MgCO3sub> )n Clusters ( n ≤ 16)

    SciTech Connect

    Chen, Mingyang; Jackson, Virgil E.; Felmy, Andrew R.; Dixon, David A.

    2015-03-13

    There is significant interest in the role of carbonate minerals for the storage of CO2 and the role of prenucleation dusters in their formation. Global minima for (MgCO3sub>)n (n ≤ 16) structures were optimized using a tree growth-hybrid genetic algorithm in conjunction with MNDO/MNDO/d semiempirical molecular orbital calculations followed by density functional theory geometry optimizations with the B3LYP functional. The most stable isomers for (MgCO3sub>)n (n < 5) are approximately 2-dimensional. Mg can be bonded to one or two 0 atoms of a CO3sub>2-, and the 1-O bonding scheme is more favored as the cluster becomes larger. The average C-Mg coordination number increases as the cluster size increases, and at n = 16, the average C-Mg coordination number was calculated to be 5.2. The normalized dissociation energy to form monomers increases as n increases. At n = 16, the normalized dissociation energy is calculated to be 116.2 kcal/mol, as compared to the bulk value of 153.9 kcal/mol. The adiabatic reaction energies for the recombination reactions of (MgO)nclusters and CO2 to form (MgCO3sub>)n were calculated. The exothermicity of the normalized recombination energy < RE >(CO2) decreases as n increases and converged to the experimental bulk limit rapidly. The normalized recombination energy < RE >(CO2) was calculated to be -52.2 kcal/mol for the monomer and -30.7 kcal/mol for n = 16, as compared to the experimental value of -27.9 kcal/mol for the solid phase reaction. Infrared spectra for the lowest energy isomers were calculated, and absorption bands in the previous experimental infrared studies were assigned with our density functional theory predictions. The 13C, 17O, and 25Mg NMR chemical shifts for the clusters were predicted. We found that the results provide insights into the structural and energetic

  10. Electronic structure and optical properties of the nonlinear optical crystal Pb{sub 4}O(BO{sub 3}){sub 2} by first-principles calculations

    SciTech Connect

    Yang, Zhihua; Pan, Shilie; Yu, Hongwei; Lee, Ming-Hsien

    2013-02-15

    Pb{sub 4}O(BO{sub 3}){sub 2} has a layered-type arrangement with optimally aligned BO{sub 3} triangles. The optical band gap is 3.317 eV obtained via the extrapolation method from the UV-vis-IR optical diffuse reflectance spectrum, consequently the absorption edge is about 374 nm. Density functional calculations using a generalized gradient approximation were utilized to investigate the electronic structures and optical properties of Pb{sub 4}O(BO{sub 3}){sub 2}. The calculated band structures show a direct gap of 2.608 eV, which is in agreement with the experimental optical band gap. A delocalized {pi} bonding of BO{sub 3} triangles and the stereo-effect of the lone pair 6s{sup 2} of lead cations are studied in electron densities. The birefringence is about 0.039-0.061 with the wavelength larger than about 375 nm. The calculated second-order susceptibility d{sub 24}=3.5 d{sub 36} (KDP) which is well consistent with the powder SHG intensity. - Graphical abstract: The density of state (DOS) show that the bottom of the valence bands is mainly derived from of the lone pair 6s{sup 2} of Pb{sup 2+}, and the top of the valence band is attributed to the hybridization orbitals from B-O groups. Calculated electronic structures indicate that the BO{sub 3} group with typical delocalization {pi} orbitals and strongly distorted lead oxygen polyhedra with highly asymmetric lobes on lead cations make a large SHG effect in Pb{sub 4}O(BO{sub 3}){sub 2}. Highlights: Black-Right-Pointing-Pointer Lone pair effect on Pb{sup 2+} and delocalization {pi} orbital in BO{sub 3} group is studied. Black-Right-Pointing-Pointer The combination of PbO{sub n} (n=3,4,5) and BO{sub 3} group makes Pb{sub 4}O(BO{sub 3}){sub 2} a large SHG effect. Black-Right-Pointing-Pointer Pb{sub 4}O(BO{sub 3}){sub 2} is a direct gap material with the gap 2.608 eV by the ab initio method. Black-Right-Pointing-Pointer The calculated birefringence is about 0.039-0.061 with the wavelength of about 375 nm. Black

  11. Mechanism of CO 2 Hydrogenation on Pd/Al 2 O 3sub> Catalysts: Kinetics and Transient DRIFTS-MS Studies

    SciTech Connect

    Wang, Xiang; Shi, Hui; Kwak, Ja Hun; Szanyi, János

    2015-09-17

    The hydrogenation of CO2 was investigated over a wide range of reaction conditions, using two Pd/γ-Al2O3sub> catalysts with different Pd loadings (5% and 0.5%) and dispersions (~11% and ~100%, respectively). Turnover rates for CO and CH4 formation were both higher over 5% Pd/Al2O3sub> with a larger average Pd particle size than those over 0.5% Pd/Al2O3sub> with a smaller average particle size. The selectivity to methane (22-40%) on 5% Pd/Al2O3sub> was higher by a factor of 2-3 than that on 0.5% Pd/Al2O3sub>. The drastically different rate expressions and apparent energies of activation for CO and CH4 formation lead us to conclude that reverse water gas shift and CO2 methanation do not share the same rate-limiting step on Pd, and that the two pathways are probably catalyzed at different surface sites. Measured reaction orders in CO2 and H2 pressures were similar over the two catalysts, suggesting that the reaction mechanism for each pathway does not change with particle size. In accordance, the DRIFTS results reveal that the prevalent surface species and their evolution patterns are comparable on the two catalysts during transient and steady-state experiments, switching feed gases among CO2, H2 and CO2+H2. The DRIFTS and MS results also demonstrate that no direct dissociation of CO2 takes place over the two catalysts, and that CO2 has to first react with surface hydroxyls on the oxide support. The thus-formed bicarbonates react with dissociatively adsorbed hydrogen on Pd particles to produce adsorbed formate species (bifunctional catalyst: CO2 activation on the oxide support, and H2 dissociation on the metal particles). Formates near the Pd particles (most likely at the metal/oxide interface) can react rapidly with adsorbed H

  12. Influence of holmium impurities on photoelectric properties of As{sub 2}Se{sub 3} and (As{sub 2}S{sub 3}){sub 0.3}(As{sub 2}Se{sub 3}){sub 0.7}

    SciTech Connect

    Burdiyan, I. I.; Senokosov, E. A.; Kosyuk, V. V. Pynzar', R. A.

    2006-10-15

    The influence of a holmium impurity on the photoelectric properties of bulk and film As{sub 2}Se{sub 3} and (As{sub 2}S{sub 3}){sub 0.3}(As{sub 2}Se{sub 3}){sub 0.7} samples is studied. Measurements of the relative photoconductivity of bulk samples and the spectral distribution of the persistent photoconductivity in film samples showed an increase in the photoconductivity of materials doped with holmium to concentrations equivalent to 0.010-0.015 at %. The spectral distribution of the persistent photoconductivity and optical absorption showed that the band gap monotonically decreases from 1.88 to 1.85 eV for As{sub 2}Se{sub 3} and from 2.05 to 2.00 eV for (As{sub 2}S{sub 3}){sub 0.3}(As{sub 2}Se{sub 3}){sub 0.7} as Ho concentration increases to 0.015 at %, and then weakly increases to the values in initial pure materials.

  13. Centrosymmetric [N(CH{sub 3}){sub 4}]{sub 2}TiF{sub 6} vs. noncentrosymmetric polar [C(NH{sub 2}){sub 3}]{sub 2}TiF{sub 6}: A hydrogen-bonding effect on the out-of-center distortion of TiF{sub 6} octahedra

    SciTech Connect

    Kim, Eun-ah; Lee, Dong Woo; Ok, Kang Min

    2012-11-15

    The syntheses, structures, and characterization of organically templated zero-dimensional titanium fluoride materials, A{sub 2}TiF{sub 6} (A=[N(CH{sub 3}){sub 4}] or [C(NH{sub 2}){sub 3}]), are reported. Phase pure samples of A{sub 2}TiF{sub 6} were synthesized by either solvothermal reaction method or a simple mixing method. While [N(CH{sub 3}){sub 4}]{sub 2}TiF{sub 6} crystallizes in a centrosymmetric space group, R-3, [C(NH{sub 2}){sub 3}]{sub 2}TiF{sub 6} crystallizes in a noncentrosymmetric polar space group, Cm. The asymmetric out-of-center distortion of TiF{sub 6} octahedra in polar [C(NH{sub 2}){sub 3}]{sub 2}TiF{sub 6} are attributable to the hydrogen-bonding interactions between the fluorine atoms in TiF{sub 6} octahedra and the nitrogen atoms in the [C(NH{sub 2}){sub 3}]{sup +} cation. Powder second-harmonic generation (SHG) measurements on the [C(NH{sub 2}){sub 3}]{sub 2}TiF{sub 6}, using 1064 nm radiation, indicate the material has SHG efficiency of 25 Multiplication-Sign that of {alpha}-SiO{sub 2}, which indicates an average nonlinear optical susceptibility, Left-Pointing-Angle-Bracket d{sub eff} Right-Pointing-Angle-Bracket {sub exp} of 2.8 pm/V. Additional SHG measurements reveal that the material is not phase-matchable (Type 1). The magnitudes of out-of-center distortions and dipole moment calculations for TiF{sub 6} octahedra will be also reported. - Graphical abstract: The out-of-center distortion of TiF{sub 6} octahedron in the polar noncentrosymmetric [C(NH{sub 2}){sub 3}]{sub 2}TiF{sub 6} is attributable to the hydrogen-bonding interactions between the F in TiF{sub 6} octahedron and the H-N in the [C(NH{sub 2}){sub 3}]{sup +}. Highlights: Black-Right-Pointing-Pointer Two titanium fluorides materials have been synthesized in high yields. Black-Right-Pointing-Pointer Hydrogen-bonds are crucial for the out-of-center distortion of TiF{sub 6} octahedra. Black-Right-Pointing-Pointer [C(NH{sub 2}){sub 3}]{sub 2}TiF{sub 6} has a SHG efficiency of 25

  14. Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4}

    SciTech Connect

    Ben Bechir, M. Karoui, K.; Guidara, K.; Ben Rhaiem, A.; Tabellout, M.

    2014-04-21

    [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} hybrid compound is crystallized at room temperature (T ≈ 300 K) in the orthorhombic system with Pnma space group. Five phase transitions (T{sub 1} = 255 K, T{sub 2} = 282 K, T{sub 3} = 302 K, T{sub 4} = 320 K, and T{sub 5} = 346 K) have been proved by DSC measurements. The electrical technique was measured in the 10{sup −1}-10{sup 7} Hz frequency range and 233–363 K temperature interval. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} is analyzed by different processes, which can be attributed to several models: the correlated barrier hopping model in phase I, the overlapping large polaron tunneling model in phase II, the quantum mechanical tunneling model in phase IV, and the non-overlapping small polaron tunneling model in phases III, V, and VI. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.

  15. High critical currents in heavily doped (Gd,Y)Ba2Cu3sub>Ox superconductor tapes

    SciTech Connect

    Selvamanickam, V.; Gharahcheshmeh, M. Heydari; Xu, A.; Galstyan, E.; Delgado, L.; Cantoni, C.

    2015-01-20

    REBa2Cu3sub>Ox superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (Jc) above 20 MA/cm2 at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba2Cu3sub>Ox superconductor tapes, which is more than three times higher than the Jc typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m3 have also been attained at 20 K. A composition map of lift factor in Jc (ratio of Jc at 30 K, 3 T to the Jc at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO3sub> (BZO) nanocolumn defect density of nearly 7 × 1011 cm–2 as well as 2–3nm sized particles rich in Cu and Zr have been found in the high Jc films.

  16. A new family of superconducting fullerides, Na{sub 3}(NH{sub 3}){sub x}C{sub 60}(x = 2--8)

    SciTech Connect

    Schlueter, J.A.; Smart, J.L.; Wang, H.H.

    1994-05-01

    A series of A{sub 3}C{sub 60} fulleride superconductors (A is an alkali metal) with superconducting transition temperatures ({Tc}s) between 2.5 and 33 K has been reported. The {Tc}s of these materials are closely correlated to their f.c.c. lattice parameters, with the higher {Tc} materials having larger unit cell lengths. Recently, the {Tc} of the superconducting Na{sub 2}CsC{sub 60} has been raised from 10.5 K to 29.6 K by ammonia intercalation. The resulting intercalated compound, NaCs[Na(NH{sub 3}){sub 4}]C{sub 60} has an expanded unit cell compared to the starting material, with a larger cation Na(NH{sub 3}){sub 4+}, occupying the octahedral site. The sodium-doped C{sub 60} with nominal composition Na{sub 3}C{sub 60} however, does not show superconductivity and was reported to undergo a disproportionation reaction into two f.c.c. phases, Na{sub 2}C{sub 60} and Na{sub 6}C{sub 60} below 250 K. Here we report on the ammonia intercalation of Na{sub 3}C{sub 60}. Up to four superconducting phases with {Tc}s occurring near 6.7, 11.5, 13.5 and 16.5 K were observed in the compounds Na{sub 3}(NH{sub 3}){sub x}C{sub 60} (x {approx}2 = 8). All these phases gave significant superconducting shielding fractions (between 15 and 80% at 5 K). These compounds were characterized by use of AC susceptibility and SQUID measurements, TGA and x-ray powder diffraction.

  17. Passively {ital Q}-switched 180-ps Nd:LaSc{sub 3}(BO{sub 3}){sub 4} microchip laser

    SciTech Connect

    Braun, B.; Kaertner, F.X.; Keller, U.; Meyn, J.; Huber, G.

    1996-03-01

    We passively {ital Q} switched a Nd:LaSc{sub 3}(BO{sub 3}){sub 4} microchip laser with an antiresonant Fabry{endash}Perot saturable absorber (A-FPSA) and achieved single-frequency, 180-ps pulses with 0.1 {mu}J of pulse energy at a repetition rate of 110 kHz. Because of the compactness and scaling possibilities offered by the A-FPSA, the pulse width can be varied from 180 ps to 30 ns and the repetition rate from 50 kHz to 7 MHz. {copyright} {ital 1996 Optical Society of America.}

  18. Tunable terahertz generation in the picosecond regime from the stimulated polariton scattering in a LiNbO3sub> crystal.

    PubMed

    Warrier, Aravindan M; Li, Ran; Lin, Jipeng; Lee, Andrew J; Pask, Helen M; Spence, David J

    2016-09-15

    We demonstrate narrowband tunable terahertz generation from a picosecond LiNbO3sub> polariton laser, pumped by a CW mode-locked Nd:YVO4 picosecond laser. We generated up to 5.4 μW of terahertz output in untuned mode. We tuned the terahertz output, using etalons in the cavity, from 0.51 to 2.12 THz. Terahertz output powers of 3.7 μW and 2.4 μW were achieved at terahertz frequencies of 1.6 THz and 0.9 THz, respectively. PMID:27628410

  19. 266  nm ultraviolet light generation in Ga-doped BaAlBO3sub>F2 crystals.

    PubMed

    Yang, Lei; Yue, Yinchao; Yang, Feng; Hu, Zhanggui; Xu, Zuyan

    2016-04-01

    BaAlBO3sub>F2 (BABF) crystals are a recently developed and promising nonlinear optical material, notably for the third harmonic generation of ultraviolet (UV) light at 355 nm. However, the fourth harmonic generation of UV light at 266 nm has never been obtained by using a BABF crystal due to its relatively small birefringence. We demonstrate that the birefringence of BABF can be effectively increased by doping it with Ga3+. The fourth harmonic generation of UV light at 266 nm was achieved for the first time in a Ga-doped BABF crystal. PMID:27192296

  20. Integrated chip-scale Si3sub>N4 wavemeter with narrow free spectral range and high stability.

    PubMed

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

    2016-07-15

    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 Si3sub>N4 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

  1. Tunable terahertz generation in the picosecond regime from the stimulated polariton scattering in a LiNbO3sub> crystal.

    PubMed

    Warrier, Aravindan M; Li, Ran; Lin, Jipeng; Lee, Andrew J; Pask, Helen M; Spence, David J

    2016-09-15

    We demonstrate narrowband tunable terahertz generation from a picosecond LiNbO3sub> polariton laser, pumped by a CW mode-locked Nd:YVO4 picosecond laser. We generated up to 5.4 μW of terahertz output in untuned mode. We tuned the terahertz output, using etalons in the cavity, from 0.51 to 2.12 THz. Terahertz output powers of 3.7 μW and 2.4 μW were achieved at terahertz frequencies of 1.6 THz and 0.9 THz, respectively.

  2. Optical properties of trigonal single crystals (Yb,Tm)Al{sub 3}(BO{sub 3}){sub 4} grown from fluxes based on the bismuth and lithium molybdates

    SciTech Connect

    Temerov, V. L. Sokolov, A. E.; Sukhachev, A. L.; Bovina, A. F.; Edel'man, I. S.; Malakhovskii, A. V.

    2008-12-15

    The conditions for synthesis of Yb{sub x}Tm{sub 1-x}Al{sub 3}(BO{sub 3}){sub 4} (x = 0, 0.1, 0.2, 1.0) single crystals from fluxes based on bismuth trimolybdate Bi{sub 2}Mo{sub 3}O{sub 12} and lithium molybdate Li{sub 2}MoO{sub 4} are investigated. It is proposed to grow them by the group method on seeds. The polarized optical absorption spectra are measured for two mutually orthogonal linear polarizations at temperatures of 100 and 300 K.

  3. Temperature-dependent adsorption of surfactant molecules and associated crystallization kinetics of noncentrosymmetric Fe(IO{sub 3}){sub 3} nanorods in microemulsions

    SciTech Connect

    El-Kass, Moustafa; Ladj, Rachid; Mugnier, Yannick; Le Dantec, Ronan; Hadji, Rachid; Marty, Jean-Christophe; Rouxel, Didier; Durand, Christiane; Fontvieille, Dominique; Rogalska, Ewa; and others

    2013-11-15

    Graphical abstract: - Highlights: • Crystallization of Fe(IO{sub 3}){sub 3} in microemulsions probed by hyper-Rayleigh scattering. • A faster growth and a better shape control of nanorods are obtained at 80 °C. • Different persistent cell deformations are related to the crystallization kinetics. • A temperature-dependent adsorption of surfactants on nanorods is suggested. - Abstract: Aggregation-induced crystallization of iron iodate nanorods within organic–inorganic aggregates of primary amorphous precursors is probed by time-dependent hyper-Rayleigh scattering measurements in Triton X-100 based-microemulsions. In the context of a growing interest of noncentrosymmetric oxide nanomaterials in multi-photon bioimaging, we demonstrate by a combination of X-ray diffraction and electron microscopy that an increase in the synthesis of temperature results in faster crystallization kinetics and in a better shape-control of the final Fe(IO{sub 3}){sub 3} nanorods. For initial microemulsions of fixed composition, room-temperature synthesis leads to bundles of 1–3 μm long nanorods, whereas shorter individual nanorods are obtained when the temperature is increased. Results are interpreted in terms of kinetically unfavorable mesoscale transformations due to the strong binding interactions with Triton molecules. The interplay between the nanorod crystallization kinetics and their corresponding unit cell deformation, evidenced by lattice parameter refinements, is attributed to a temperature-dependent adsorption of surfactants molecules at the organic–inorganic interface.

  4. Synthesis of hierarchical Ni{sub 11}(HPO{sub 3}){sub 8}(OH){sub 6} superstructures based on nanorods through a soft hydrothermal route

    SciTech Connect

    Liao, Kaiming; Ni, Yonghong

    2010-02-15

    In this paper, we reported the successful synthesis of hierarchical Ni{sub 11}(HPO{sub 3}){sub 8}(OH){sub 6} superstructures based on nanorods via a facile hydrothermal route, employing NiCl{sub 2}.6H{sub 2}O and NaH{sub 2}PO{sub 2}.H{sub 2}O as the reactants in the presences of polyvinylpyrrolidone (PVP) and CH{sub 3}COONa.3H{sub 2}O. The reaction was carried out at 170 {sup o}C for 10 h. HPO{sub 3}{sup 2-} ions were provided via the dismutation reaction of H{sub 2}PO{sub 2}{sup -} ions in a weak basic solution. The as-obtained products were characterized by X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), field emission scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). Some factors influencing the morphology of the hierarchical Ni{sub 11}(HPO{sub 3}){sub 8}(OH){sub 6} nanorods, such as the reaction temperature, time, the amounts of PVP and CH{sub 3}COONa, and the initial concentration of Ni{sup 2+} ions, were systematically investigated. A possible growth mechanism was proposed based on experimental results.

  5. Synthesis and Luminescence Characteristics of Cr3+ doped Y3sub>Al5O12 Phosphors

    SciTech Connect

    Smith, Brenda A.; Dabestani, Reza T.; Lewis, Linda A.; Thompson, Cyril V.; Collins, Case T.; Aytug, Tolga

    2015-10-01

    Luminescence performance of yttrium aluminum garnet (Y3sub>Al5O12) phosphors as a function of Cr3+ concentration has been investigated via two different wet-chemical synthesis techniques, direct- (DP) and hydrothermal-precipitation (HP). Using either of these methods, the red-emitting phosphor [Y3sub>Al5-xCrxO12 (YAG: Cr3+)] showed similar photoluminescence (PL) intensities once the dopant concentration was optimized. Specifically, the YAG: Cr3+ PL emission intensity reached a maximum at Cr3+ concentrations of x = 0.02 (0.4 at.%) and x = 0.13 (2.6 at.%) for DP and HP processed samples, respectively. The results indicated the strong influence of the processing method on the optimized YAG: Cr3+ performance, where a more effective energy transfer rate between a pair of Cr3+ activators at low concentration levels was observed by using the DP synthesis technique. Development of a highly efficient phosphor, using a facile synthesis approach, could significantly benefit consumer and industrial applications by improving the operational efficiency of a wide range of practical devices.

  6. Atomic layer epitaxy of Ruddlesden-Popper SrO(SrTiO{sub 3}){sub n} films by means of metalorganic aerosol deposition

    SciTech Connect

    Jungbauer, M.; Hühn, S.; Moshnyaga, V.; Egoavil, R.; Tan, H.; Verbeeck, J.; Van Tendeloo, G.

    2014-12-22

    We report an atomic layer epitaxial growth of Ruddlesden-Popper (RP) thin films of SrO(SrTiO{sub 3}){sub n} (n = ∞, 2, 3, 4) by means of metalorganic aerosol deposition (MAD). The films are grown on SrTiO{sub 3}(001) substrates by means of a sequential deposition of Sr-O/Ti-O{sub 2} atomic monolayers, monitored in-situ by optical ellipsometry. X-ray diffraction and transmission electron microscopy (TEM) reveal the RP structure with n = 2–4 in accordance with the growth recipe. RP defects, observed by TEM in a good correlation with the in-situ ellipsometry, mainly result from the excess of SrO. Being maximal at the film/substrate interface, the SrO excess rapidly decreases and saturates after 5–6 repetitions of the SrO(SrTiO{sub 3}){sub 4} block at the level of 2.4%. This identifies the SrTiO{sub 3} substrate surface as a source of RP defects under oxidizing conditions within MAD. Advantages and limitations of MAD as a solution-based and vacuum-free chemical deposition route were discussed in comparison with molecular beam epitaxy.

  7. Temperature-dependent excitonic photoluminescence excited by two-photon absorption in perovskite CsPbBr3sub> quantum dots.

    PubMed

    Wei, Ke; Xu, Zhongjie; Chen, Runze; Zheng, Xin; Cheng, Xiangai; Jiang, Tian

    2016-08-15

    Recently, lead halide perovskite quantum dots have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3sub> quantum dots (QDs) has been studied at a broad temperature range, from 80 to 380 K. Two-photon absorption has been investigated and the absorption coefficient is up to 0.085 cm/GW at room temperature. Moreover, the PL spectrum excited by two-photon absorption shows a linear blue-shift (0.32 meV/K) below the temperature of 220 K. However, for higher temperatures, the PL peak approaches a roughly constant value and shows temperature-independent chromaticity up to 380 K. This behavior is distinct from the general red-shift for semiconductors and can be attributed to the result of thermal expansion, electron-phonon interaction and structural phase transition around 360 K. The strong nonlinear absorption and temperature-independent chromaticity of CsPbBr3sub> QDs observed in temperature range from 220 to 380 K will offer new opportunities in nonlinear photonics, light-harvesting, and light-emitting devices. PMID:27519098

  8. Bond-bending isomerism of Au2I3sub>-: Competition between covalent bonding and aurophilicity

    SciTech Connect

    Li, Wan -Lu; Liu, Hong -Tao; Jian, Tian; Lopez, Gary V.; Piazza, Zachary A.; Huang, Dao -Ling; Chen, Teng -Teng; Su, Jing; Yang, Ping; Chen, Xin; Wang, Lai -Sheng; Li, Jun

    2015-10-13

    We report a joint photoelectron spectroscopy and theoretical investigation of the gaseous Au2I3sub> cluster, which is found to exhibit two types of isomers due to competition between Au–I covalent bonding and Au–Au aurophilic interactions. The covalent bonding favors a bent IAuIAuI structure with an obtuse Au–I–Au angle (100.7°), while aurophilic interactions pull the two Au atoms much closer, leading to an acutely bent structure (72.0°) with an Au–Au distance of 3.08 Å. The two isomers are separated by a small barrier and are nearly degenerate with the obtuse isomer being slightly more stable. At low temperature, only the obtuse isomer is observed; distinct experimental evidence is observed for the co-existence of a combination of isomers with both acute and obtuse bending angles at room temperature. As a result, the two bond-bending isomers of Au2I3sub> reveal a unique example of one molecule being able to oscillate between different structures as a result of two competing chemical forces.

  9. K 3sub> Fe(CN) 6 under External Pressure: Dimerization of CN Coupled with Electron Transfer to Fe(III)

    SciTech Connect

    Li, Kuo; Zheng, Haiyan; Wang, Lijuan; Tulk, Christopher A.; Molaison, Jamie J.; Feygenson, Mikhail; Yang, Wenge; Guthrie, Malcolm; Mao, Hokwang

    2015-09-14

    The addition polymerization of charged monomers like C≡C2– and C≡N– is scarcely seen at ambient conditions but can progress under external pressure with their conductivity significantly enhanced, which expands the research field of polymer science to inorganic salts. Moreover, the reaction pressures of transition metal cyanides like Prussian blue and K3sub>Fe(CN)6 are much lower than that of alkali cyanides. To figure out the effect of the transition metal on the reaction, the crystal structure and electronic structure of K3sub>Fe(CN)6 under external pressure are investigated by in situ neutron diffraction, in situ X-ray absorption fine structure (XAFS), and neutron pair distribution functions (PDF) up to ~15 GPa. The cyanide anions react following a sequence of approaching–bonding–stabilizing. The Fe(III) brings the cyanides closer which makes the bonding progress at a low pressure (2–4 GPa). At ~8 GPa, an electron transfers from the CN to Fe(III), reduces the charge density on cyanide ions, and stabilizes the reaction product of cyanide. Finally, from this study we can conclude that bringing the monomers closer and reducing their charge density are two effective routes to decrease the reaction pressure, which is important for designing novel pressure induced conductor and excellent electrode materials.

  10. Segregation and trapping of oxygen vacancies near the SrTiO3sub>Σ3 (112) [110] tilt grain boundary

    SciTech Connect

    Liu, Bin; Cooper, Valentino R.; Zhang, Yanwen; Weber, William J.

    2015-03-21

    In nanocrystalline materials, structural discontinuities at grain boundaries (GBs) and the segregation of point defects to these GBs play a key role in defining the structural stability of a material, as well as its macroscopic electrical/mechanical properties. In this study, the segregation of oxygen vacancies near the Σ3 (1 1 2) [¯110] tilt GB in SrTiO3sub> is explored using density functional theory. We find that oxygen vacancies segregate toward the GB, preferring to reside within the next nearest-neighbor layer. This oxygen vacancy segregation is found to be crucial for stabilizing this tilt GB. Furthermore, we find that the migration barriers of oxygen vacancies diffusing toward the first nearest-neighbor layer of the GB are low, while those away from this layer are very high. Furthermore, the segregation and trapping of the oxygen vacancies in the first nearest-neighbor layer of GBs are attributed to the large local distortions, which can now accommodate the preferred sixfold coordination of Ti. These results suggest that the electronic, transport, and capacitive properties of SrTiO3sub> can be engineered through the control of GB structure and grain size or layer thickness.

  11. Coherent phonon study of (GeTe){sub l}(Sb{sub 2}Te{sub 3}){sub m} interfacial phase change memory materials

    SciTech Connect

    Makino, Kotaro Saito, Yuta; Fons, Paul; Kolobov, Alexander V.; Nakano, Takashi; Tominaga, Junji; Hase, Muneaki

    2014-10-13

    The time-resolved reflectivity measurements were carried out on the interfacial phase change memory (iPCM) materials ([(GeTe){sub 2}(Sb{sub 2}Te{sub 3}){sub 4}]{sub 8} and [(GeTe){sub 2}(Sb{sub 2}Te{sub 3}){sub 1}]{sub 20}) as well as conventional Ge{sub 2}Sb{sub 2}Te{sub 5} alloy at room temperature and above the RESET-SET phase transition temperature. In the high-temperature phase, coherent phonons were clearly observed in the iPCM samples while drastic attenuation of coherent phonons was induced in the alloy. This difference strongly suggests the atomic rearrangement during the phase transition in iPCMs is much smaller than that in the alloy. These results are consistent with the unique phase transition model in which a quasi-one-dimensional displacement of Ge atoms occurs for iPCMs and a conventional amorphous-crystalline phase transition takes place for the alloy.

  12. Rapid microwave-assisted sol-gel preparation of Pd-substituted LnFeO3sub> (Ln = Y, La): phase formation and catalytic activity

    SciTech Connect

    Misch, Lauren M.; Birkel, Alexander; Figg, C. Adrian; Fors, Brett P.; Hawker, Craig J.; Stucky, Galen D.; Seshadri, Ram

    2014-02-13

    We present a rapid microwave-assisted sol–gel approach to Pd-substituted LnFeO3sub> (Ln = Y, La) for applications in C–C coupling reactions. These materials could be prepared in household microwave ovens in less than 15 minutes of reaction time with the final materials displaying well-defined structure and morphology. Phase evolution was studied using time-dependent microwave heatings and then compared with the results obtained from thermogravimetric analyses. Materials were confirmed to be phase pure by laboratory and synchrotron X-ray diffraction. Substituted Pd is ionic as shown by the binding energy shift from X-ray photoelectron spectroscopy. The short heating periods required for phase purity allow these materials less time for sintering as compared to conventional solid state preparation methods, making relatively high surface areas achievable. These materials have been successfully used as catalyst precursor materials for C–C coupling reactions in which the active species is Pd0. Pd-substituted LnFeO3sub> (Ln = Y, La) provides Pd0 in solution which can be complexed by the ligand SPhos, allowing for aryl chloride coupling.

  13. Synthesis, characterization, and energetics of solid solution along the dolomite-ankerite join, and implications for the stability of ordered CaFe(CO{sub 3}){sub 2}

    SciTech Connect

    Chai, L.; Navrotsky, A.

    1996-09-01

    Samples along the dolomite-ankerite join were synthesized using a piston-cylinder apparatus and the double-capsule method. Some of the ankerite samples may be disordered. Thermal analysis and X-ray diffraction showed that all samples can be completely decomposed to uniquely defined products under calorimetric conditions (770 {degrees}C, O{sub 2}), and a well-constrained thermodynamic cycle was developed to determine the enthalpy of formation. The energetics of ordered and disordered ankerite solid solutions were estimated using data from calorimetry, lattice-energy calculations, and phase equilibria. The enthalpies of formation of ordered dolomite and disordered end-member ankerite from binary carbonates, determined by calorimetry, are -9.29 {+-} 1.97 and 6.98 {+-} 2.08 kJ/mol, respectively. The enthalpy of formation of ordered ankerite appears to become more endothermic with increasing Fe content, whereas the enthalpy of formation of disordered ankerite becomes more exothermic with increasing Fe content, whereas the enthalpy of formation of disordered ankerite becomes more exothermic with increasing Fe content. The enthalpy of disordering in dolomite (approximately 25 kJ/mol) is much larger than that in pure ankerite, CaFe(CO{sub 3}){sub 2} (approximately 10 kJ/mol), which may explain the nonexistence of ordered CaFe(CO{sub 3}){sub 2}. 24 refs., 3 figs., 3 tabs.

  14. Carbonylation of hydrocarbons via C-H activation catalyzed by RhCl(CO)(PMe sub 3 ) sub 2 under irradiation

    SciTech Connect

    Sakakura, Toshiyasu; Sodeyama, Touru; Tanaka, Masato ); Sasaki, Koushi; Wada, Keisuke )

    1990-09-26

    C-H bonds in hydrocarbons are carbonylated into aldehydes by reaction with carbon monoxide in the presence of RhCl(CO)(PR{sub 3}){sub 2} under irradiation. The reaction proceeds at an ambient temperature under an atmospheric pressure of CO. The catalytic activity of RhCl(CO)(PR{sub 3}){sub 2} decreases in the order PMe{sub 3} {approx} 1,3,4-trimethylphospholane {approx} 1,3,4-trimethylphospholene > P(CH{sub 2}O){sub 3}CMe > PEt{sub 3} {approx} PBu{sub 3} > P(i-Pr){sub 3} {approx} P(OMe){sub 3} > dppe. The thiocyanato complex exhibits a similar catalytic activity to the chloro complex. The use of other complexes of Co, Ir, and Ru resulted in much lower catalytic activities. In the carbonylation of benzene, benzophenone and benzyl alcohol are formed as byproducts. The yield of benzaldehyde reached 3.3% on the basis of benzene. Monosubstituted benzenes are converted mainly to meta-substituted benzaldehydes. In the reaction of n-alkanes, a terminal methyl group is selectively carbonylated to give a linear aldehyde.

  15. Atomic and electronic structures of single-layer FeSe on SrTiO3sub>(001): The role of oxygen deficiency

    SciTech Connect

    Bang, Junhyeok; Li, Zhi; Sun, Y. Y.; Samanta, Amit; Zhang, Y. Y.; Zhang, Wenhao; Wang, Lili; Chen, X.; Ma, Xucun; Xue, Q.-K.; Zhang, S. B.

    2013-06-06

    Using first-principles calculation, we propose an interface structure for single triple-layer FeSe on the SrTiO3sub>(001) surface, a high-Tc superconductor found recently. The key component of this structure is the oxygen deficiency on the top layer of the SrTiO3sub> substrate, as a result of Se etching used in preparing the high-Tc samples. The O vacancies strongly bind the FeSe triple layer to the substrate giving rise to a (2×1) reconstruction, as observed by scanning tunneling microscopy. The enhanced binding correlates to the significant increase of Tc observed in experiment. The O vacancies also serve as the source of electron doping, which modifies the Fermi surface of the first FeSe layer by filling the hole pocket near the center of the surface Brillouin zone, as suggested from angle-resolved photoemission spectroscopy measurement.

  16. Structural distortions in the spin-gap regime of the quantum antiferromagnet SrCu{sub 2}(BO{sub 3}){sub 2}

    SciTech Connect

    Vecchini, C.; Adamopoulos, O.; Chapon, L.C.; Lappas, A.; Kageyama, H.; Ueda, Y.; Zorko, A.

    2009-12-15

    We report the first crystallographic study within the low-temperature (<40 K) spin-gap region of the two-dimensional frustrated antiferromagnet SrCu{sub 2}(BO{sub 3}){sub 2}. The crystal system does not deviate from the tetragonal I-42m space group symmetry. However, our high-resolution neutron powder diffraction measurements uncover subtle structural modifications below 34 K, concomitant to the formation of the dimer singlet ground state. Intimate spin-lattice coupling leads to negative thermal expansion of the tetragonal structure, which reflects into particular local lattice adjustments. The extracted structural parameters suggest the reduction of the buckling found in the copper-borate planes and the strengthening of the leading, in-plane intra-dimer superexchange interaction. The observed contraction along the c-axis, associated with the inter-dimer exchange in adjacent layers, indicates the involvement of weaker three-dimensional interactions in the magnetic properties. The rules posed by the crystal symmetry do not preclude Dzyaloshinsky-Moriya interactions, which therefore remain as an important source of spin anisotropy necessary to rationalise the ground state behaviour. - Abstract: We report the first crystallographic study within the low-temperature spin-gap region of the two-dimensional frustrated antiferromagnet SrCu{sub 2}(BO{sub 3}){sub 2}. Subtle spin-lattice coupling was unveiled in the low-temperature region. Display Omitted

  17. Vapor-liquid equilibrium of the Mg(NO/sub 3/)/sub 2/-HNO/sub 3/-H/sub 2/O system

    SciTech Connect

    Thompson, B.E.; Derby, J.J.; Stalzer, E.H.

    1983-06-01

    The vapor-liquid equilibrium of the Mg(NO/sub 3/)/sub 2/-HNO/sub 3/-H/sub 2/O system in concentrations of 0 to 70 wt % Mg(NO/sub 3/)/sub 2/ and 0 to 75 wt % HNO/sub 3/ at atmospheric pressure was correlated by two approaches. One was based on a dissociation equilibrium expression in which the activities of the reacting species (HNO/sub 3/, NO/sub 3//sup -/, and H/sup +/) were approximated with mole fractions. The activity coefficients of the undissociated HNO/sub 3/ and H/sub 2/O were correlated as functions of the concentrations of magnesium nitrate and nitric acid by second-order polynomials. The average absolute difference between predicted and experimental values was 8% for the mole fraction of acid in the vapor and 8/sup 0/K for the bubble-point temperature. The second approach was to correlate the mean ionic rational activity coefficient of water with a form of the excess Gibbs energy composed of two terms. One term, a function of the ionic strength, accounts for the coulombic (ionic) interactions; the other term accounts for the non-coulombic (molecular) interactions. The average absolute difference between predicted and experimental values was 9% for the mole fraction of acid in the vapor, and 10/sup 0/K for the bubble-point temperature.

  18. Band-Gap Reduction and Dopant Interaction in Epitaxial La,Cr Co-doped SrTiO3sub> Thin Films

    SciTech Connect

    Comes, Ryan B.; Sushko, Petr; Heald, Steve M.; Colby, Robert J.; Bowden, Mark E.; Chambers, Scott A.

    2014-12-03

    We show that by co-doping SrTiO3sub> (STO) epitaxial thin films with equal amounts of La and Cr it is possible to produce films with an optical band gap ~0.9 eV lower than that of undoped STO. Sr1-xLaxTi1-xCrxO3sub> thin films were deposited by molecular beam epitaxy and characterized using x-ray photoelectron spectroscopy and x-ray absorption near-edge spectroscopy to show that the Cr dopants are almost exclusively in the Cr3+ oxidation state. Extended x-ray absorption fine structure measurements and theoretical modeling suggest that it is thermodynamically preferred for La and Cr dopants to occupy nearest neighbor A- and B-sites in the lattice. Transport measurements show that the material exhibits variable-range hopping conductivity with high resistivity. These results create new opportunities for the use of doped STO films in photovoltaic and photocatalytic applications.

  19. 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

    2013-01-15

    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

  20. Measurements of reactive trace gases and variable O3sub> formation rates in some South Carolina biomass burning plumes

    SciTech Connect

    Akagi, S. K.; Yokelson, R. J.; Burling, I. R.; Meinardi, S.; Simpson, I.; Blake, D. R.; McMeeking, G. R.; Sullivan, A.; Lee, T.; Kreidenweis, S.; Urbanski, S.; Reardon, J.; Griffith, D. W. T.; Johnson, T. J.; Weise, D. R.

    2013-02-01

    In October-November 2011 we measured the trace gas emission factors from 7 prescribed fires in South Carolina, U.S. using two Fourier transform infrared spectrometer (FTIR) systems and whole air sampling (WAS) into canisters followed by gas-chromatographic analyses. The fires were intended to emulate high-intensity burns as they were lit during the dry season and in most cases represented stands that had not been treated with prescribed burns in 10+ years, if at all. A total of 97 trace gas species are reported here from both airborne and ground-based platforms making this one of the most detailed field studies of fire emissions to date. The measurements included the first data for a suite of monoterpene compounds emitted via distillation of plant tissues during real fires. The known chemistry of the monoterpenes and their measured abundance of ~0.40% of CO (molar basis), ~3.9% of NMOC (molar basis), and ~21% of organic aerosol (mass basis), suggests that they impacted post-emission formation of ozone, aerosol, and small organic trace gases such as methanol and formaldehyde in the sampled plumes. The variability in the terpene emissions in South Carolina (SC) fire plumes was high and, in general, the speciation of the emitted gas-phase non-methane organic compounds was surprisingly different from that observed in a similar study in nominally similar pine forests in North Carolina ~20 months earlier. It is likely that the slightly different ecosystems, time of year and the precursor variability all contributed to the variability in plume chemistry observed in this study and in the literature. The ΔHCN/ΔCO emission ratio, however, is fairly consistent at 0.9 ± 0.06 % for airborne fire measurements in coniferous-dominated ecosystems further confirming the value of HCN as a good biomass burning indicator/tracer. The SC results also support an earlier finding that C3sub>-C4 alkynes may be of use as biomass burning indicators on the time-scale of

  1. Crystal structure of 0.96(Na0.5Bi0.5TiO3sub>)-0.04(BaTiO3sub>) from combined refinement of x-ray and neutron diffraction patterns

    SciTech Connect

    Usher, T -M; Forrester, J S; dela Cruz, C R; Jones, J L

    2012-10-12

    High-resolution x-ray and neutron diffraction of (0.96)Na0.5Bi0.5TiO3sub>–(0.04)BaTiO3sub> (NBT-4BT) reveal subtle structural distortions that evidence lower symmetry than allowed in the R3c space group. The combined refinement that best models the diffraction patterns is a two phase mixture of a monoclinic Cc phase and a minor fraction of a metrically cubic Pm 3¯ m phase (13 wt. %). The cubic phase is utilized to account for nanometer-scale regions whose local deviations from the long-range symmetry are not observed, such as polar nano-regions or tetragonal platelets. This suggests that the low symmetry found in the NBT-rich phases extends from 0 at. % to at least 4 at. % BT.

  2. Electrochemically influenced cation inter-diffusion and Co3sub>O4 formation on La0.6Sr0.4CoO3sub> infiltrated into SOFC cathodes

    SciTech Connect

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

    2015-06-18

    Nanosized LSC electrocatalyst was infiltrated into a porous scaffold cathode composed of Sm2O3sub>-doped CeO2 (SDC) and La0.6Sr0.4Co0.2Fe0.8O3-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 La0.6Sr0.4CoO3sub> (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 Co3sub>O4 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: Co3sub>O4 forms on LSC arising from local charge balancing between cobalt and oxygen vacancies.

  3. Spin frustration in M{sup II}[C(CN){sub 3}]{sub 2} (M = V, Cr). A magnetism and neutron diffraction

    SciTech Connect

    Manson, J.L.; Ressouche, E.; Miller, J.S.

    2000-03-20

    Three-dimensional coordination network solids of M{sup II}[C(CN){sub 3}]{sub 2} (M = V, Cr) composition possess interpenetrating rutile-like network structures. Each [C(CN){sub 3}]{sup {minus}} bonds to three different metal ions in a triangular array, affording a geometrical topology akin to a Kagome lattice leading to competing spin exchange interactions and spin frustration. The crystal and magnetic structure of Cr{sup II}[C(CN){sub 3}] was determined by Rietveld refinement of the powder neutron diffraction data at 2 and 15 K and belongs to the orthorhombic space group Pmna [a = 7.313(1) {angstrom}, b = 5.453(1) {angstrom}, c = 10.640(1) {angstrom}, Z = 2, T = 15 K]. Each Cr{sup II} has a tetragonally elongated octahedral structure with four Cr-N(1) distances of 2.077(2) {angstrom} and two significantly longer axial Cr-N(2) distances of 2.452(2) {angstrom}. Magnetic susceptibility measurements between 1.7 and 300 K reveal strong antiferromagnetic interactions for both V- and Cr[C(CN){sub 3}]{sub 2} with {theta} = {minus}67 and {minus}46 K, respectively, from a fit to the Curie-Weiss law. Long-range magnetic ordering does not occur for M = V above 1.7 K, in contrast to M = Cr, which antiferromagnetically orders at low temperature. This is attributed to Jahn-Teller distorted Cr{sup II} sites relieving frustration in one dimension, leading to 2-D Ising antiferromagnetism, as observed by both magnetic susceptibility and specific heat studies. Neutron diffraction experiments at 2 K for Cr[C(CN){sub 3}]{sub 2} yielded additional Bragg reflections as a result of antiferromagnetic ordering with the moments on the Cr{sup II} atoms aligned parallel to c and 4.7(1) {micro}{sub B}. Fitting of the magnetic order parameter to a power law yielded T{sub N} = 6.12(4) K and {beta} = 0.18(1) consistent with 2-D Ising behavior. A T{sub N} of 6.13 K is also observed from the specific heat data.

  4. Influence of structural distortions upon photoluminescence properties of Eu{sup 3+} and Tb{sup 3+} activated Na{sub 3}Ln(BO{sub 3}){sub 2} (Ln=Y, Gd) borates

    SciTech Connect

    Asiri Naidu, S.; Boudin, S.; Varadaraju, U.V.; Raveau, B.

    2012-06-15

    The comparative study of the structure and photoluminescence (PL) properties of the Eu{sup 3+} and Tb{sup 3+} activated Na{sub 3}Ln(BO{sub 3}){sub 2}, with Ln=Y, Gd, showed the important role of the host lattice structure upon PL. Higher emission intensities of Eu{sup 3+} and Tb{sup 3+} are observed for Na{sub 3}Gd(BO{sub 3}){sub 2} than for Na{sub 3}Y(BO{sub 3}){sub 2}, through direct Eu{sup 3+} excitation at 395 nm for Eu{sup 3+} doped borates, and through Gd{sup 3+} excitation around 280 nm for Tb{sup 3+} doped borates. This higher performance for Na{sub 3}Gd(BO{sub 3}){sub 2} is due to the less regular environment of Eu{sup 3+} (Tb{sup 3+}) in the Gd sites than in the Y sites and to energy transfer from Gd{sup 3+} to Eu{sup 3+}(Tb{sup 3+}). The smaller critical concentration in Na{sub 3}Ln{sub 1-x}Tb{sub x}(BO{sub 3}){sub 2} observed for Ln=Gd, x=0.5, compared to x=0.6 for Ln=Y, is explained by shorter Ln-Ln distances (4.11 A for Gd-Gd vs. 4.59 A for Y-Y). Both Na{sub 3}Y{sub 0.4}Tb{sub 0.6}(BO{sub 3}){sub 2} and Na{sub 3}Gd{sub 0.5}Tb{sub 0.5}(BO{sub 3}){sub 2} show intense green emission under UV excitation. - Graphical abstract: The PL properties of Eu{sup 3+} and Tb{sup 3+} are studied in Na{sub 3}Ln(BO{sub 3}){sub 2} (Ln=Y, Gd) borates. Eu{sup 3+} and Tb{sup 3+}exhibits higher emission intensity in Na{sub 3}Gd(BO{sub 3}){sub 2} compared to Na{sub 3}Y(BO{sub 3}){sub 2} due to the less regular environment of the Gd{sup 3+} ion. Energy transfer from Gd{sup 3+} to Tb{sup 3+} is observed. Highlights: Black-Right-Pointing-Pointer Crystal structure of Na{sub 3}Gd(BO{sub 3}){sub 2} by X-ray powder diffraction. Black-Right-Pointing-Pointer Photoluminescence properties of Eu{sup 3+} and Tb{sup 3+} doped Na{sub 3}Ln(BO{sub 3}){sub 2} (Ln=Y, Gd). Black-Right-Pointing-Pointer Higher Eu{sup 3+} and Tb{sup 3+} emission for Na{sub 3}Gd(BO{sub 3}){sub 2} due to an irregular environment of Gd{sup 3+}. Black-Right-Pointing-Pointer Higher Eu{sup 3+} and Tb{sup 3+} emission

  5. Local Structure of Ba1-xSrxTiO3sub> and BaTi1-yZryO3sub> Nanocrystals Probed by X-ray Absorption and X-ray Total Scattering

    SciTech Connect

    Rabuffetti, Federico A.; Brutchey, Richard L.

    2014-02-18

    The effect of isovalent chemical substitution on the magnitude and coherence length of local ferroelectric distortions present in sub-20 nm Ba1–xSrxTiO3sub> (x = 0.0, 0.30, 0.50, 1.0) and BaTi1–yZryO3sub> (y = 0.0, 0.15, 0.50, 1.0) nanocrystals synthesized at room temperature is investigated using X-ray absorption near edge structure (XANES) and pair distribution function analysis of X-ray total scattering data (PDF). Although the average crystal structure of the nanocrystals is adequately described by a centrosymmetric, cubic Pm3¯m space group, local ferroelectric distortions due to the displacement of the titanium atom from the center of the perovskite lattice are observed for all compositions, except BaZrO3sub>. The symmetry of the ferroelectric distortions is adequately described by a tetragonal P4mm space group. The magnitude of the local displacements of the titanium atom in BaTiO3sub> nanocrystals is comparable to that observed in single crystals and bulk ceramics, but the coherence length of their ferroelectric coupling is much shorter (≤20 Å). Substitution of Sr2+ for Ba2+ and of Zr4+ for Ti4+ induces a tetragonal-to-cubic transition of the room temperature local crystal structure, analogous to that observed for single crystals and bulk ceramics at similar compositions. This transition is driven by a reduction of the magnitude of the local displacements of the titanium atom and/or of the coherence length of their ferroelectric coupling. Replacing 50% of Ba2+ with Sr2+ slightly reduces the magnitude of the titanium displacement, but the coherence length is not affected. In contrast, replacing 15% of the ferroelectrically active Ti4+ with Zr4+ leads to a significant reduction of the coherence length. Deviations from the ideal solid solution behavior are observed in BaTi1

  6. Impact of a Mixed Oxide’s Surface Composition and Structure on Its Adsorptive Properties: Case of the (Fe,Cr)3sub>O4(111) Termination of the α-(Fe,Cr)2O3sub>(0001) Surface

    SciTech Connect

    Henderson, Michael A.; Engelhard, Mark H.

    2014-06-10

    Characterization of an α-(Fe0.75,Cr0.25)2O3sub>(0001) mixed oxide single crystal surface was conducted using x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD). After sputter/anneal cleaning in ultra-high vacuum (UHV), the mixed oxide surface became terminated with a magnetite-(111) structure based on the presence of (2x2) spots in LEED and Fe2+ in XPS. The composition of the surface was close to that of M3sub>O4 based on XPS, with the metal (M) content of Fe2+/3+ and Cr3+ being close to 1.4:1, despite the fact that the film’s bulk was 3:1 with respect to the metal cations. The enrichment of the surface with Cr was not altered by high temperature oxidation in UHV, but could be returned to that of the bulk film composition by exposure to the ambient. Adsorption of various probe molecules (NO, O2, CO2 and H2O) was used to identify the active cation sites present in the (Fe,Cr)3sub>O4(111) terminated surface. Although XPS and SIMS both indicated that the near-surface region was enriched in Cr3+, no adsorption states typically associated with Cr3+ sites on α-Cr2O3sub> single crystal surfaces were detected. Instead, the TPD behaviors of O2 and CO2 pointed toward the main active sites being Fe2+ and Fe3+, with O2 preferentially adsorbing at the former and CO2 at the latter. NO was observed to bind at both Fe2+ and Fe3+ sites, and H2O TPD looked nearly identical to that for H2O on the Fe3sub>O4(111) surface. Competition for adsorption sites between coadsorbed combinations of CO2, O2, H2O and NO corroborated these

  7. Stripe-like nanoscale structural phase separation in superconducting BaPb1-xBixO3sub>

    SciTech Connect

    Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; Manoharan, H. C.; Beasley, M. R.; Geballe, T. H.; Kramer, M. J.; Fisher, I. R.

    2015-09-16

    The phase diagram of BaPb1-xBixO3sub> exhibits a superconducting dome in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high-resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare with the Ginzburg–Landau coherence length. We find that the maximum Tc occurs when the superconducting coherence length matches the width of the partially disordered stripes, implying a connection between the structural phase separation and the shape of the superconducting dome.

  8. Crystallization and preliminary X-ray diffraction study of phosphopantetheine adenylyltransferase from M. tuberculosis crystallizing in space group P3{sub 2}

    SciTech Connect

    Timofeev, V. I.; Chupova, L. A.; Esipov, R. S.; Kuranova, I. P.

    2015-09-15

    Crystals of M. tuberculosis phosphopantetheine adenylyltransferase were grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one crystal at the Spring-8 synchrotron facility to 2.00-Å resolution. The crystals belong to sp. gr. P3{sub 2} and have the following unit-cell parameters: a = b = 106.47 Å, c = 71.32 Å, α = γ = 90°, β = 120°. The structure was solved by the molecular-replacement method. There are six subunits of the enzyme comprising a hexamer per asymmetric unit. The hexamer is a biologically active form of phosphopantetheine adenylyltransferase from M. tuberculosis.

  9. Time-resolved terahertz dynamics in thin films of the topological insulator Bi2Se3sub>

    SciTech Connect

    Valdés Aguilar, R.; Qi, J.; Brahlek, M.; Bansal, N.; Azad, A.; Bowlan, J.; Oh, S.; Taylor, A. J.; Prasankumar, R. P.; Yarotski, D. A.

    2015-01-07

    We use optical pump–THz probe spectroscopy at low temperatures to study the hot carrier response in thin Bi2Se3sub> films of several thicknesses, allowing us to separate the bulk from the surface transient response. We find that for thinner films the photoexcitation changes the transport scattering rate and reduces the THz conductivity, which relaxes within 10 picoseconds (ps). For thicker films, the conductivity increases upon photoexcitation and scales with increasing both the film thickness and the optical fluence, with a decay time of approximately 5 ps as well as a much higher scattering rate. Furthermore, these different dynamics are attributed to the surface and bulk electrons, respectively, and demonstrate that long-lived mobile surface photo-carriers can be accessed independently below certain film thicknesses for possible optoelectronic applications.

  10. Generation of 0.19-mJ THz pulses in LiNbO3sub> driven by 800-nm femtosecond laser.

    PubMed

    Zhong, Sen-Cheng; Li, Jun; Zhai, Zhao-Hui; Zhu, Li-Guo; Li, Jiang; Zhou, Ping-Wei; Zhao, Jian-Heng; Li, Ze-Ren

    2016-06-27

    A cylindrical lens telescope tilted-pulse-front pumping scheme was proposed for high energy terahertz (THz) pulse generation. This scheme allows higher pump energy to be used with lower saturation effects under high pump fluence, and higher THz generation efficiency was achieved within large range of pump energy. The optimum pump pulse duration and crystal cooling temperature for THz generation in LiNbO3sub> (LN) crystal were also researched systematically. Excited by 800-nm laser, up to 0.19 mJ THz pulse energy and 0.27% conversion efficiency was demonstrated under 800-nm 400-fs laser excitation with ~100-mJ pulse energy and 150-K LN cooling temperature. PMID:27410634

  11. Electronic and thermoelectric analysis of phases in the In2O3sub>(ZnO)k system

    SciTech Connect

    Hopper, E. Mitchell; Zhu, Qimin; Song, Jung-Hwan; Peng, Haowei; Freeman, Arthur J.; Mason, Thomas O.

    2011-01-01

    The high-temperature electrical conductivity and thermopower of several compounds in the In2O3sub>(ZnO)k system (k = 3, 5, 7, and 9) were measured, and the band structures of the k = 1, 2, and 3 structures were predicted based on first-principles calculations. These phases exhibit highly dispersed conduction bands consistent with transparent conducting oxide behavior. Jonker plots (Seebeck coefficient vs. natural logarithm of conductivity) were used to obtain the product of the density of states and mobility for these phases, which were related to the maximum achievable power factor (thermopower squared times conductivity) for each phase by Ioffe analysis (maximum power factor vs. Jonker plot intercept). With the exception of the k = 9 phase, all other phases were found to have maximum predicted power factors comparable to other thermoelectric oxides if suitably doped.

  12. Crystal structure and electric properties of the organic–inorganic hybrid: [(CH{sub 2}){sub 6}(NH{sub 3}){sub 2}]ZnCl{sub 4}

    SciTech Connect

    Mostafa, M.F. El-khiyami, S.S.

    2014-01-15

    The new organic-inorganic hybrid [(CH{sub 2}){sub 6}(NH{sub 3}){sub 2}]ZnCl{sub 4}, M{sub r}=325.406 crystallized in a triclinic, P1¯, a=7.2816 (5) Å, b=10.0996 (7) Å, c=10.0972 (7) Å, α=74.368 (4)°, β=88.046 (4)°, γ=85.974 (3)°, V=713.24 (9) Å{sup 3} and Z=2, D{sub x}=1.486 Mg m{sup −3}. Differential thermal scanning and x-ray powder diffraction, permittivity and ac conductivity indicated three phase transitions. Conduction takes place via correlated barrier hopping. - Graphical abstract: Display Omitted.

  13. Stripe-like nanoscale structural phase separation in superconducting BaPb1-xBixO3sub>

    SciTech Connect

    Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; Manoharan, H. C.; Beasley, M. R.; Geballe, T. H.; Kramer, M. J.; Fisher, I. R.

    2015-09-16

    The phase diagram of BaPb1-xBixO3sub> exhibits a superconducting “dome” in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare to the Ginzburg-Landau coherence length. Thus, we find that the maximum Tc occurs when the superconducting coherence length matches the width of the partially disordered stripes, implying a connection between the structural phase separation and the shape of the superconducting dome.

  14. Validation of Finite-Element Models of Persistent-Current Effects in Nb3sub>Sn Accelerator Magnets

    SciTech Connect

    Wang, X.; Ambrosio, G.; Chlachidze, G.; Collings, E. W.; Dietderich, D. R.; DiMarco, J.; Felice, H.; Ghosh, A. K.; Godeke, A.; Gourlay, S. A.; Marchevsky, M.; Prestemon, S. O.; Sabbi, G.; Sumption, M. D.; Velev, G. V.; Xu, X.; Zlobin, A. V.

    2015-01-06

    Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, in particular at low field where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb3sub>Sn accelerator magnets. Here a finite-element method based on the measured strand magnetization is validated against three state-of-art Nb3Sn accelerator magnets featuring different subelement diameters, critical currents, magnet designs and measurement temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent current effects is discussed. The performance, limitations and possible improvements of the approach are also discussed.

  15. 119Sn-NMR investigations on superconducting Ca3sub>Ir4Sn13: 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.

    2015-09-25

    In this study, we report bulk superconductivity (SC) in Ca3sub>Ir4Sn13 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.

  16. Giant optical enhancement of strain gradient in ferroelectric BiFeO3sub> thin films and its physical origin

    SciTech Connect

    Li, Yuelin; Adamo, C.; Chen, Pice; Evans, Paul G.; Nakhmanson, Serge M.; Parker, William; Rowland, Clare E.; Schaller, Richard D.; Schlom, Darrell G.; Walko, Donald A.; Wen, Haidan; Zhang, Qingteng

    2015-11-20

    Through mapping of the spatiotemporal strain profile in ferroelectric BiFeO3sub> epitaxial thin films, we report an optically initiated dynamic enhancement of the strain gradient of 105–106 m-1 that lasts up to a few ns depending on the film thickness. Correlating with transient optical absorption measurements, the enhancement of the strain gradient is attributed to a piezoelectric effect driven by a transient screening field mediated by excitons. In conclusion, these findings not only demonstrate a new possible way of controlling the flexoelectric effect, but also reveal the important role of exciton dynamics in photostriction and photovoltaic effects in ferroelectrics.

  17. 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.

    2010-07-15

    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.

  18. Bi2Te3sub> based passively Q-switched fiber laser with cylindrical vector beam emission.

    PubMed

    Yan, Ke; Lin, Jian; Zhou, Yong; Gu, Chun; Xu, Lixin; Wang, Anting; Yao, Peijun; Zhan, Qiwen

    2016-04-10

    We report a passively Q-switched fiber laser with cylindrical vector beam output modes using a few-mode fiber Bragg grating as a polarization-selective output coupler and Bi2Te3sub> as the saturable absorber. Both radially and azimuthally polarized beams can be readily generated, and the output polarization can be switchable by tuning the polarization controllers inside the laser cavity. The repetition rate of the Q-switched laser can be tuned from 31.54 to 49.40 kHz when the pump power increases from 103.5 to 139.5 mW. The fiber laser operates at a single wavelength of 1557.5 nm with a 3 dB linewidth of <0.04  nm. PMID:27139870

  19. Optical diode effect at spin-wave excitations in the room-temperature multiferroic BiFeO3sub>.

    SciTech Connect

    Kezsmarki, I.; Nagel, U.; Bordacs, S.; Fishman, Randy Scott; Lee, Jun Hee; Yi, Hee Taek; Cheong, Sang-Wook; Room, T.

    2015-09-15

    The ability to read and write a magnetic state current-free by an electric voltage would provide a huge technological advantage. Dynamic or optical ME effects are equally interesting, because they give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. This phenomenon, if realized at room temperature, would allow the development of optical diodes which transmit unpolarized light in one, but not in the opposite, direction. Here, we report strong unidirectional transmission in the room-temperature multiferroic BiFeO3sub> over the gigahertz-terahertz frequency range. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. Our findings are an important step toward the realization of optical diodes, supplemented by the ability to switch the transmission direction with a magnetic or electric field.

  20. Synthesis, structure, and C-H bond activation chemistry of ([eta][sup 6]-arene)Ru(H)[sub 2](SiMe[sub 3])[sub 2] complexes

    SciTech Connect

    Djurovich, P.I.; Carroll, P.J.; Berry, D.H. )

    1994-07-01

    The ([eta][sup 6]-arene)Ru(H)[sub 2](SiMe[sub 3])[sub 2] arene = C[sub 6]-Me[sub 6] (1a), p-cymene (1b), C[sub 6]H[sub 6] (1c) complexes have been prepared and characterized. The complexes activate both aromatic and aliphatic C-H bonds and catalyze H/D exchange in alkylsilanes upon thermolysis in benzene-d[sub 6]. A mechanism based on oxidative-addition/reductive-elimination steps which utilizes a Ru(II)-Ru(IV) cycle is proposed to account for the C-H bond activation and H/D exchange reactions. It is further proposed that H/D exchange into sites adjacent to silicon in alkylsilanes is due to the intermediacy of an [eta][sup 2]-silene complex generated by [beta]-hydrogen elimination from the silyl group. 19 refs., 1 fig.

  1. Multiband Te p Based Superconductivity of Ta4Pd3sub>Te16

    SciTech Connect

    Singh, David J.

    2014-10-06

    We recently discovered that Ta4Pd3sub>Te16 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.

  2. Interpenetration as a Mechanism for Negative Thermal Expansion in the Metal-Organic Framework Cu3sub>(btb)2 (MOF-14)

    SciTech Connect

    Wu, Yue; Peterson, Vanessa K.; Luks, Emily; Darwish, Tamim A.; Kepert, Cameron J.

    2014-07-11

    Metal–organic framework materials (MOFs) have recently been shown in some cases to exhibit strong negative thermal expansion (NTE) behavior, while framework interpenetration has been found to reduce NTE in many materials. Using powder and single-crystal diffraction methods we investigate the thermal expansion behavior of interpenetrated Cu3sub>(btb)2 (MOF-14) and find that it exhibits an anomalously large NTE effect. Temperature-dependent structural analysis shows that, contrary to other interpenetrated materials, in MOF-14 the large positive thermal expansion of weak interactions that hold the interpenetrating networks together results in a low-energy contractive distortion of the overall framework structure, demonstrating a new mechanism for NTE.

  3. [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4}: Ferroelectric properties and characterization of phase transitions by Raman spectroscopy

    SciTech Connect

    Ben Bechir, M. Karoui, K.; Guidara, K.; Ben Rhaiem, A.; Bulou, A.; Tabellout, M.

    2014-12-07

    The X-ray powder diffraction pattern shows that at room temperature, [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} is crystallized in the orthorhombic system with Pnma space group. The phase transitions at T{sub 1} = 255 K, T{sub 2} = 282 K, T{sub 3} = 302 K, T{sub 4} = 320 K, and T{sub 5} = 346 K have been confirmed by the differential scanning calorimetry. The electrical technique was measured in the 10{sup −1}–10{sup 7 }Hz frequency range and 233–363 K temperature intervals. The temperature dependence of the dielectric constant at different temperatures proved that this compound is ferroelectric below 282 K. Besides, [N(CH{sub 3}){sub 3 }H]{sub 2}ZnCl{sub 4} shows classical ferroelectric behaviour near curie temperature. In order to characterize the phase transitions, Raman spectra have been recorded in the temperature range of 233–383 K and the frequency range related to the internal and external vibrations of the cations and anions (90–4000 cm{sup −1}). The temperature dependence of the Raman line shifts ν and the half-width Δν detects all phase transitions and confirms their nature, especially at 282 K that corresponds to the ferroelectric-paraelectric phase transition.

  4. Molecular weight growth in Titan's atmosphere: Branching pathways for the reaction of 1-propynyl radical (H3sub>CC≡C˙) with small alkenes and alkynes

    SciTech Connect

    Kirk, Benjamin B.; Savee, John D.; Trevitt, Adam J.; Osborn, David L.; Wilson, Kevin R.

    2015-07-16

    The reaction of small hydrocarbon radicals (i.e. ˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC≡C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (–H = 27%, –CH3sub> = 73%) and (–H = 14%, –CH3sub> = 86%), respectively. Altogether, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.

  5. DNA 3'sub> pp 5' G de-capping activity of aprataxin: effect of cap nucleoside analogs and structural basis for guanosine recognition

    SciTech Connect

    Chauleau, Mathieu; Jacewicz, Agata; Shuman, Stewart

    2015-05-24

    DNA3'sub> pp 5'G caps synthesized by the 3'-PO4/5'-OH ligase RtcB have a strong impact on enzymatic reactions at DNA 3'-OH ends. Aprataxin, an enzyme that repairs A5'pp5'DNA ends formed during abortive ligation by classic 3'-OH/5'-PO4 ligases, is also a DNA 3' de-capping enzyme, converting DNAppG to DNA3sub>'p and GMP. By taking advantage of RtcB's ability to utilize certain GTP analogs to synthesize DNAppN caps, we show that aprataxin hydrolyzes inosine and 6-O-methylguanosine caps, but is not adept at removing a deoxyguanosine cap. We report a 1.5 Å crystal structure of aprataxin in a complex with GMP, which reveals that: (i) GMP binds at the same position and in the same anti nucleoside conformation as AMP; and (ii) aprataxin makes more extensive nucleobase contacts with guanine than with adenine, via a hydrogen bonding network to the guanine O6, N1, N2 base edge. Alanine mutations of catalytic residues His147 and His149 abolish DNAppG de-capping activity, suggesting that the 3' de-guanylylation and 5' de-adenylylation reactions follow the same pathway of nucleotidyl transfer through a covalent aprataxin-(His147)–NMP intermediate. Alanine mutation of Asp63, which coordinates the guanosine ribose hydroxyls, impairs DNAppG de-capping.

  6. Crystal structure and properties of [OsO{sub 2}(NH{sub 3}){sub 4}]SO{sub 4} . H{sub 2}O

    SciTech Connect

    Burvikova, J. N. Lin'ko, I. V.; Venskovskiy, N. U.; Rybakov, V. B.

    2007-03-15

    The structure of a single crystal of tetraammindioxoosmium(VI) sulfate [OsO{sub 2}(NH{sub 3}){sub 4}]SO{sub 4} . H{sub 2}O, which is synthesized by the reaction of K{sub 2}[OsO{sub 2}(OH){sub 4}] with (NH{sub 4}){sub 2}SO{sub 4} in an aqueous solution, is investigated using X-ray diffraction analysis. The compound crystallizes in the monoclinic crystal system, space group P2{sub 1}/c, a = 13.102(2) A, b = 6.158(3) A, c = 11.866(2) A, {beta} = 98.13(2) deg., and Z = 4. The [OsO{sub 2}(NH{sub 3}){sub 4}]SO{sub 4} . H{sub 2}O compound has an island structure. Two crystallographically independent osmium atoms are situated at the centers of symmetry, and their octahedral coordination includes two oxygen atoms and four nitrogen atoms of the ammonia molecules. In both octahedra, the osmyl group is linear. The Os-O distances in the octahedra are identical within the standard deviations [Os(1)-O, 1.762(2) A; Os(2)-O, 1.769(2) A]. The Os-N bond lengths vary from 2.082(3) to 2.101(3) A. The cationic complexes, SO{sub 4} groups, and water molecules are linked via the system of hydrogen bonds. The assignment of the absorption bands in the IR spectrum of the compound synthesized is performed, and its thermal behavior in air is studied.

  7. Identification of Organic Nitrates in the NO3sub> Radical Initiated Oxidation of α-Pinene by Atmospheric Pressure Chemical Ionization Mass Spectrometry

    SciTech Connect

    Perraud, Veronique M.; Bruns, Emily A.; Ezell, Michael J.; Johnson, Stanley N.; Greaves, John; Finlayson-Pitts, Barbara J.

    2010-07-07

    The gas-phase reactions of nitrate radicals (NO3sub>) with biogenic organic compounds are a major sink for these organics during night-time. These reactions form secondary organic aerosols, including organic nitrates that can undergo long-range transport, releasing NOx downwind. We report here studies of the reaction of NO3sub> with R-pinene at 1 atm in dry synthetic air(relative humidity ~3%) and at 298K using atmospheric pressure chemical ionization triple quadrupole mass spectrometry (APCI-MS) to identify gaseous and particulate products. The emphasis is on the identification of individual organic nitrates in the particle phase that were obtained by passing the product mixture through a denuder to remove gas-phase reactants and products prior to entering the source region of the mass spectrometer. Filter extracts were also analyzed by GCMS and by APCI time-of-flight mass spectrometry (APCI-ToFMS) with methanol as the proton source. In addition to pinonaldehyde and pinonic acid, five organic nitrates were identified in the particles as well as in the gas phase: 3-oxopinane- 2-nitrate, 2-hydroxypinane-3-nitrate, pinonaldehyde-PAN, norpinonaldehyde-PAN, and (3-acetyl-2,2-dimethyl-3-nitrooxycyclobutyl) acetaldehyde. Furthermore, there was an additional first generation organic nitrate product tentatively identified as a carbonyl hydroxynitrate with a molecular mass of 229. These studies suggest that a variety of organic nitrates would partition between the gas phase and particles in the atmosphere, and serve as a reservoir for NOx.

  8. Synthesis of MoS2/g-C3sub>N4 nanocomposites with enhanced visible-light photocatalytic activity for the removal of nitric oxide (NO).

    PubMed

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

    2016-05-16

    Molybdenum disulfide and graphitic carbon nitride (MoS2-g-C3sub>N4) 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-C3sub>N4 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-C3sub>N4 nanoparticles were well combined together. Moreover, the photocatalytic activity of MoS2-g-C3sub>N4 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-C3sub>N4 nanoparticles. A possible photocatalytic mechanism for the MoS2-g-C3sub>N4 nanocomposites with enhanced photocatalytic activity could be ascribed to the hetero-structure of MoS2 and g-C3sub>N4. PMID:27409846

  9. Synthesis of MoS2/g-C3sub>N4 nanocomposites with enhanced visible-light photocatalytic activity for the removal of nitric oxide (NO).

    PubMed

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

    2016-05-16

    Molybdenum disulfide and graphitic carbon nitride (MoS2-g-C3sub>N4) 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-C3sub>N4 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-C3sub>N4 nanoparticles were well combined together. Moreover, the photocatalytic activity of MoS2-g-C3sub>N4 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-C3sub>N4 nanoparticles. A possible photocatalytic mechanism for the MoS2-g-C3sub>N4 nanocomposites with enhanced photocatalytic activity could be ascribed to the hetero-structure of MoS2 and g-C3sub>N4.

  10. Influence of crustal dust and sea spray supermicron particle concentrations and acidity on inorganic NO3sub> aerosol during the 2013 Southern Oxidant and Aerosol Study

    SciTech Connect

    Allen, H. M.; Draper, D. C.; Ayres, B. R.; Ault, A.; Bondy, A.; Takahama, S.; Modini, R. L.; Baumann, K.; Edgerton, E.; Knote, C.; Laskin, A.; Wang, B.; Fry, J. L.

    2015-09-25

    Inorganic aerosol composition was measured in the southeastern United States, a region that exhibits high aerosol mass loading during the summer, as part of the 2013 Southern Oxidant and Aerosol Study (SOAS) campaign. Measurements using a Monitor for AeRosols and GAses (MARGA) revealed two periods of high aerosol nitrate (NO3sub>) concentrations during the campaign. These periods of high nitrate were correlated with increased concentrations of supermicron crustal and sea spray aerosol species, particularly Na+ and Ca2+, and with a shift towards aerosol with larger (1 to 2.5 μm) diameters. We suggest this nitrate aerosol forms by multiphase reactions of HNO3sub> and particles, reactions that are facilitated by transport of crustal dust and sea spray aerosol from a source within the United States. The observed high aerosol acidity prevents the formation of NH4NO3sub>, the inorganic nitrogen species often dominant in fine-mode aerosol at higher pH. In addition, calculation of the rate of the heterogeneous uptake of HNO3sub> on mineral aerosol supports the conclusion that aerosol NO3sub> is produced primarily by this process, and is likely limited by the availability of mineral cation-containing aerosol surface area. Modeling of NO3sub> and HNO3sub> by thermodynamic equilibrium models (ISORROPIA II and E-AIM) reveals the importance of including mineral cations in the southeastern United States to accurately balance ion species and predict gas–aerosol phase partitioning.

  11. Electrochemical behavior of [(Mn(Bpy))(VO{sub 3}){sub 2}]≈(H{sub 2}O){sub 1.24} and [(Mn(Bpy){sub 0.5})(VO{sub 3}){sub 2}]≈(H{sub 2}O){sub 0.62} inorganic–organic Brannerites in lithium and sodium cells

    SciTech Connect

    Fernández de Luis, Roberto; Rosa Palacín, M.; Karmele Urtiaga, M.

    2014-04-01

    The performance of MnV{sub 2}O{sub 6} (MnV) and its [(Mn(Bpy))(VO{sub 3}){sub 2}]≈(H{sub 2}O){sub 1.16} (MnBpy) and [(Mn(Bpy){sub 0.5})(VO{sub 3}){sub 2}]≈(H{sub 2}O){sub 0.62}(MnBpy0.5) hybrid derivative compounds was investigated against sodium and lithium counter electrodes. For MnV{sub 2}O{sub 6} stable capacities of 850 mAh/g were achieved in lithium cells, the best value reported so far. The whole capacity is ascribed to a conversion reaction in which the amorphization of the compounds takes place. No significant differences in the capacities for the inorganic compound and the hybrid ones were observed. Interestingly, the potential hysteresis decreases in the hybrid compounds. The difference between Li and Na cell capacity most probably comes from the difference of standard potential of the two redox couples Li{sup +}/Li and Na{sup +}/Na of about ca. 0.3 V leading to an incomplete conversion reaction and thus lowers capacity in the case of Na cells. The Raman and IR ex-situ experiments after cycling indicate that the bipyridine organic ligands are completely decomposed during the electrochemical testing. The IR studies in MnV inorganic and MnBpy and MnBpy0.5 hybrid electrodes after the electrochemical cycling, suggest that the SEI formation and bipyridine degradation give rise to different aliphatic compounds. - Graphical abstract: The electrochemical performance of [(Mn(Bpy))(VO{sub 3}){sub 2}]≈(H{sub 2}O){sub 1.16} and [(Mn(Bpy){sub 0.5})(VO{sub 3}){sub 2}]≈(H{sub 2}O){sub 0.62} against sodium and lithium counter electrodes give rise to the structural collapse of the initial compounds. The IR and Raman studies show that the Bpy organic ligand is completely decomposed during the during the electrochemical testing. However, after the amorphization stable capacities as high as 850 mAh/g for lithium cells were achieved. - Highlights: • We test the lithium and sodium insertion in hybrid brannerites. • Capacities as large as 850 mAh/g were obtained

  12. On the Bonding Nature of Ozone (O3sub>) and Its Sulfur-Substituted Analogues SO2, OS2, and S3sub>: Correlation between Their Biradical Character and Molecular Properties

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2014-02-19

    We investigate the bonding mechanism in ozone (O3sub>) and its sulfur-substituted analogues, SO2, OS2, and S3sub>. By analyzing their ground-state multireference configuration interaction wave functions, we demonstrate that the bonding in these systems can be represented as a mixture of a closed-shell structure with one and a half bonds between the central and terminal atoms and an open-shell structure with a single bond and two lone electrons on each terminal atom (biradical). The biradical character (β) further emerges as a simple measure of the relative contribution of those two classical Lewis structures emanating from the interpretation of the respective wave functions. Our analysis yields a biradical character of 3.5% for OSO, 4.4% for SSO, 11% for S3sub>, 18% for O3sub>, 26% for SOO, and 35% for SOS. The size/electronegativity of the end atoms relative to the central one is the prevalent factor for determining the magnitude of β: smaller and more electronegative central atoms better accommodate a pair of electrons facilitating the localization of the remaining two lone π-electrons on each of the end atoms, therefore increasing the weight of the second picture in the mixed bonding scenario (larger β). The proposed mixture of these two bonding scenarios allows for the definition of the bond order of the covalent bonds being (3-β)/2, and this accounts for the different O–O, S–S, or S–O bond lengths in the triatomic series. The biradical character was furthermore found to be a useful concept for explaining several structural and energetic trends in the series: larger values of β mark a smaller singlet–triplet splitting, closer bond lengths in the ground 1A' and the first excited 3A' states, and larger bond dissociation and atomization energies in the ground state. Finally, the latter explains the relative energy difference between the OSS/SOS and OOS/OSO isomers due to their

  13. Electric-field-induced strain effects on the magnetization of a Pr0.67Sr0.33MnO3sub> film

    SciTech Connect

    Zhang, B.; Sun, C. -J.; Lu, W.; Venkatesan, T.; Han, M. -G.; Zhu, Y.; Chen, J.; Chow, G. M.

    2015-05-26

    The electric-field control of magnetic properties of Pr0.67Sr0.33MnO3sub> (PSMO) film on piezoelectric Pb(Mg1/3sub>Nb2/3sub>)O3sub>-PbTiO3sub> (PMNT) substrate was investigated. The piezoelectric response of the PMNT substrate to the electric field produced strain that was coupled to the PSMO film. The in-plane compressive (tensile) strain increased (decreased) the magnetization. The change of magnetic moment was associated with the Mn ions. First principle simulations showed that the strain-induced electronic redistribution of the two eg orbitals (3dz2 and 3dx2-y2) of Mn ions was responsible for the change of magnetic moment. This work demonstrates that the magnetoelectric effect in manganite/piezoelectric hetero-structures originates from the change in eg orbital occupancy of Mn ions induced by strain rather than the interfacial effect.

  14. Highly Stable and CO-Tolerant Pt/Ti0.7W0.3sub>O2 Electrocatalyst for Proton-Exchange Membrane Fuel Cells

    SciTech Connect

    Wang, Deli; Subban, Chinmayee V.; Wang, Hongsen; Rus, Eric; DiSalvo, Francis J.; Abruña, Héctor D.

    2010-07-12

    The current materials used in proton-exchange membrane fuel cells (PEMFCs) are not sufficiently durable for commercial deployment. One of the major challenges lies in the development of an inexpensive, efficient, and CO-tolerant anode catalyst. Here we report the unique CO-tolerant property of Pt nanoparticles supported on Ti0.7W0.3sub>O2. The Ti0.7W0.3sub>O2 nanoparticles (50 nm) were synthesized via a sol-gel process and platinized using an impregnation-reduction technique. Electrochemical studies of Pt/Ti0.7W0.3sub>O2 show unique CO-tolerant electrocatalytic activity for hydrogen oxidation compared to commercial E-TEK PtRu/C catalysts. Differential electrochemical mass spectrometry measurements show the onset potential for CO oxidation on Pt/Ti0.7W0.3sub>O2 to be below 0.1 V (vs RHE). Pt/Ti0.7W0.3sub>O2 is a promising new anode catalyst for PEMFC applications.

  15. Molecular metals based on 1,2,7,8-tetrahydrodicyclopenta[cd:lm]perylene and iodine, (CPP){sub 2}(I{sub 3}){sub 1-{delta}}

    SciTech Connect

    Morgado, J. |; Santos, I.C.; Henriques, R.T.; Almeida, M.; Fourmigue, M.; Matias, P.; Veiros, L.F.; Duarte, M.T.; Alcacer, L.; Calhorda, M.J. |

    1994-12-01

    The synthesis and characterization of molecular metals derived from 1,2,7,8-tetrahydrodicyclopenta[cd:lm]perylene (CPP) by partial oxidation with iodine and with general formula (CPP){sub 2}(I{sub 3}){sub 1-{delta}}, {delta} = 0-0.13, are reported. Single crystals, obtained either by electrocrystallization or by diffusion-controlled iodine oxidation of CPP, present two types of morphologies, elongated diamond or thinner needle-shaped crystals, both with a monoclinic cell, space group P2{sub 1}/a, a = 4.3757(9), b = 19.3681(11), c = 10.0860(11) {angstrom}, {beta} = 98.050(8){degrees}, V = 846.4(2) {angstrom}{sup 3}, Z = 2. The structure of the diamond-shaped crystal was solved by X-ray diffraction to a final R(F) = 0.096, R{sub w}(F) = 0.069. It consists of regular stacks of CPP molecules along a with a 3.41 {angstrom} spacing and uncorrected one-dimensional chains of I{sub 3}{sup {minus}} located in channels between four CPP stacks corresponding to (CPP){sub 2}(I{sub 3}){sub 0.892}. The thin needle crystals have the same unit cell but an unspecified and slightly different iodine content. Band structure calculations in this structure by the extended Hueckel method indicate a one-dimensional conduction band 0.55 eV wide. These thin needle crystals present, at room temperature, an electrical conductivity along the a axis {alpha}{sub a}(RT) = 200 S/cm and thermopower S{sub a}(RT) = 30 {mu}V/K, while for the diamond-shaped crystals {alpha}{sub a}(RT) = 2 S/cm and S{sub a}(RT) = -8 {mu}V/K. These transport coefficients for both types of crystals indicate a metallic behavior from room temperature down to {approx_equal}63 K, where a metal-to-insular (M-I) transition takes place. EPR studies in single crystals show an almost isotropic line at g = 2.0044 and with a width of {approx_equal}6 G in the range 80-300 K and without significant differences between the two types of crystals. 53 refs., 9 figs., 4 tabs.

  16. A search for temperature induced time-dependent structural transitions in 10mol%Sc2O3sub>–1mol%CeO2–ZrO2 and 8mol%Y2O3sub>–ZrO2 electrolyte ceramics

    SciTech Connect

    Chen, Yan; Orlovskaya, Nina; Payzant, E. Andrew; Graule, Thomas; Kuebler, Jakob

    2014-11-08

    Both Sc2O3sub>–CeO2-stabilized-ZrO2 (SCSZ) and Y2O3sub>-stabilized-ZrO2 (YSZ) show similar Young's modulus damping at 175–400 °C and 200–400 °C, respectively, by impulse excitation acoustic technique. The phase transition in SCSZ is considered responsible for the damping; however for YSZ, such a phase transition has never been reported. To clarify the relation of damping and structural transition in these two materials, the time-dependent high temperature stabilities are studied by in situ X-ray diffraction, neutron diffraction and Raman scattering during long-term annealing of SCSZ at 350 °C and YSZ at 275 °C. The cubic-to-rhombohedral transition in SCSZ is detected. However, the existence of t' phase in YSZ raw powders is confirmed without significant changes of the cubic structure during isothermal annealing. It is concluded that the phase transition contributes to the Young's modulus damping in SCSZ, while the structural transition is excluded from the reason for damping in YSZ.

  17. Structural transitions in Pb(In1/2Nb1/2)O 3sub> under pressure

    SciTech Connect

    Ahart, Muhtar; Somayazulu, Maddury; Kojima, Seiji; Yasuda, Naohiko; Prosandeev, Sergey; Hemley, Russell J.

    2015-12-01

    Room-temperature Raman scattering and x-ray diffraction measurements together with first-principles calculations were employed to investigate the behavior of disordered Pb(In1/2Nb1/2)O3sub> (PIN) under pressure up to 50GPa. Raman spectra show broad bands but a peak near the 380cm-1 increases its intensity with pressure. The linewidth of the band at 550cm-1 also increases with pressure, while two of the Raman peaks merge above 6GPa. Above 16GPa, we observe additional splitting of the band at 50cm-1. The pressure evolution of the diffraction patterns for PIN shows obvious Bragg peaks splitting above 16GPa; consistent with a symmetry lowering transition. The transition at 0.5GPa is identified as a pseudo-cubic to orthorhombic (Pbam) structural change whereas the transition at 16GPa is isostructure and associated with changes in linear compressibility and octahedral titling, and the transition at 30GPa is associated to an orthorhombic to monoclinic change. First-principles calculations indicate that the Pbam structure is ground state with antiferrodisdortion consistent with experiment.

  18. Synthesis, crystal structure and vibrational spectra characterization of M{sup I}La(PO{sub 3}){sub 4} (M{sup I}=Na, Ag)

    SciTech Connect

    El Masloumi, Mohamed; Imaz, Inhar . E-mail: imaz@icmcb-bordeaux.cnrs.fr; Chaminade, Jean-Pierre; Videau, Jean-Jacques; Couzi, Michel; Mesnaoui, Mohamed; Maazaz, Mohamed

    2005-11-15

    The single crystals of lanthanum metaphosphate MLa(PO{sub 3}){sub 4} (M=Na, Ag) have been synthesized and studied by a combination of X-ray crystal diffraction and vibrational spectroscopy. The sodium and silver compounds crystallize in the same monoclinic P2{sub 1}/n space group (C{sub 2}{sup 5}h factor group) with the following respective unit cell dimensions: a=7.255(2), b=13.186(3), c=10.076(2)A, {beta}=90.40(2){sup o}, V=963.0(4)A{sup 3}, Z=4 and a=7.300(5), b=13.211(9), c=10.079(7)A, {beta}=90.47(4){sup o}, V=972.09(12)A{sup 3}, Z=4. This three-dimensional framework is built of twisted zig-zag chains running along a direction and made up of PO{sub 4} tetrahedra sharing two corners, connected to the LaO{sub 8} and NaO{sub 7} or AgO{sub 7} polyhedra by common oxygen atoms to the chains. The infrared and Raman vibrational spectra have been investigated. A group factor analysis leads to the determination of internal modes of (PO{sub 3}){sup -} anion in the phosphate chain.

  19. Polarization-insensitive, shallow Ti-diffused near-stoichiometric LiTaO3sub> strip waveguide for integrated optics.

    PubMed

    Yang, Xiao-Fei; Zhang, Zi-Bo; Du, Wan-Ying; Zhang, Qun; Wong, Wing-Han; Yu, Dao-Yin; Pun, Edwin Yue-Bun; Zhang, De-Long

    2016-06-01

    We report on a Ti-diffused near-stoichiometric (NS) LiTaO3sub> strip waveguide fabricated by diffusion of an 8 μm wide, 160 nm thick Ti-strip followed by Li-rich vapor transport equilibration. It is found that the waveguide surface caves in ∼60  nm below the crystal surface. X-ray single-crystal diffraction shows that the indentation is due to Ti-induced lattice contraction. Optical studies show that the waveguide is in an NS composition environment, supports TE and TM single-mode propagation at 1.5 μm wavelength, is polarization insensitive, and has a shallow mode field profile and a loss of 0.2/0.3 dB/cm for the TE/TM mode. Secondary ion mass spectrometry analysis shows that the Ti profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of the waveguide. With the optimized fabrication condition, the waveguide is promising for developing an optical-damage-resistant device that requires a shallow mode field profile.

  20. Correlation of anisotropy and directional conduction in β-Li3sub>PS4 fast Li+ conductor

    SciTech Connect

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

    2015-07-06

    Our letter reports the correlation of anisotropy and directional conduction in the fast Li+ conductor β-Li3sub>PS4, 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 LiS4 and PS4 tetrahedra within the framework. This indicates a strong correlation in the direction of the ionic transport in the low-symmetry Li+ conductor.

  1. Synthesis, Structure, and Pressure-Induced Polymerization of Li 3sub> Fe(CN) 6 Accompanied with Enhanced Conductivity

    SciTech Connect

    Li, Kuo; Zheng, Haiyan; Hattori, Takanori; Sano-Furukawa, Asami; Tulk, Christopher A.; Molaison, Jamie; Feygenson, Mikhail; Ivanov, Ilia N.; Yang, Wenge; Mao, Ho-kwang

    2015-11-17

    By providing a new route to synthesize inorganic/organic conductors with tunable composition and properties, pressure-induced polymerization of charged triple-bond monomers like acetylide and cyanide could lead to formation of a conductive metal–carbon network composite. The industry application of this promising synthetic method is mainly limited by the reaction pressure needed, which is often too high to be reached for gram amounts of sample. Here we successfully synthesized highly conductive Li3sub>Fe(CN)6 at maximum pressure around 5 GPa and used in situ diagnostic tools to follow the structural and functional transformations of the sample, including in situ X-ray and neutron diffraction and Raman and impedance spectroscopy, along with the neutron pair distribution function measurement on the recovered sample. The cyanide anions start to react around 1 GPa and bond to each other irreversibly at around 5 GPa, which are the lowest reaction pressures in all known metal cyanides and within the technologically achievable pressure range for industrial production. Moreover, the conductivity of the polymer is above 10–3 S·cm–1, which reaches the range of conductive polymers. Our investigation suggests that the pressure-induced polymerization route is practicable for synthesizing some types of functional conductive materials for industrial use, and further research like doping and heating can hence be motivated to synthesize novel materials under lower pressure and with better performances.

  2. An air-stable Na3sub>SbS4 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

    2016-01-01

    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 Na3sub>SbS4, 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.

  3. The C(3P) + NH3sub> reaction in interstellar chemistry. I. Investigation of the product formation channels

    SciTech Connect

    Bourgalais, Jeremy; Capron, Michael; Kailasanathan, Ranjith Kumar Abhinavam; Osborn, David L.; Hickson, Kevin M.; Loison, Jean -Christophe; Wakelam, Valentine; Goulay, Fabien; Picard, Sebastien D. Le

    2015-10-13

    The product formation channels of ground state carbon atoms, C(3P), reacting with ammonia, NH3, have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable vacuum-ultraviolet (VUV) photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH3sub> reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence (LIF) from room temperature to 50 K in a supersonic gas flow generated by the Laval nozzle technique. Electronic structure calculations are performed to derive intermediates, transition states, and complexes formed along the reaction coordinate. The combination of photoionization and LIF experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H2CN production channel represents 100% of the product yield for this reaction. As a result, kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in Paper II.

  4. 57Fe Mössbauer study of Lu2Fe3sub>Si5 iron silicide superconductor

    SciTech Connect

    Ma, Xiaoming; Ran, Sheng; Pang, Hua; Li, Fashen; Canfield, Paul C.; Bud'ko, Sergey L.

    2015-08-01

    With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu2Fe3sub>Si5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc=6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. Furthermore, the value of Debye temperature was estimated from temperature dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed.

  5. Momentum-space structure of quasielastic spin fluctuations in Ce3sub>Pd20Si6

    SciTech Connect

    Portnichenko, P. Y.; Cameron, A. S.; Surmach, M. A.; Deen, Pascale P.; Paschen, S.; Prokofiev, A.; Mignot, Jean-Michel; Strydom, A. M.; Telling, Mark T. F.; Podlesnyak, Andrey A.; Inosov, D. S.

    2015-03-13

    Surrounded by heavy-fermion metals, Ce3sub>Pd20Si6 is one of the heaviest-electron systems known to date. Here we used high-resolution neutron spectroscopy to observe low-energy magnetic scattering from a single crystal of this compound in the paramagnetic state. We investigated its temperature dependence and distribution in momentum space, which was not accessible in earlier measurements on polycrystalline samples. At low temperatures, a quasielastic magnetic response with a half-width Γ ≈ 0.1 meV persists with varying intensity all over the Brillouin zone. It forms a broad hump centered at the (111) scattering vector, surrounded by minima of intensity at (002), (220), and equivalent wave vectors. The momentum-space structure distinguishes this signal from a simple crystal-field excitation at 0.31 meV, suggested previously, and rather lets us ascribe it to short-range dynamical correlations between the neighboring Ce ions, mediated by the itinerant heavy f electrons via the Ruderman-Kittel-Kasuya-Yosida mechanism. With increasing temperature, the energy width of the signal follows the conventional T1/2 law, Γ(T)=Γ0+A√T. Lastly, the momentum-space symmetry of the quasielastic response suggests that it stems from the simple-cubic Ce sublattice occupying the 8c Wyckoff site, whereas the crystallographically inequivalent 4a site remains magnetically silent in this material.

  6. Magnetic Properties of Sm{sub 0.7}Ho{sub 0.3}Fe{sub 3}(BO{sub 3}){sub 4}

    SciTech Connect

    Demidov, A. A.; Gudim, I. A.; Eremin, E. V.

    2012-11-15

    The magnetic properties of a ferroborate single crystal of substituted composition Sm{sub 0.7}H{sub 0.3}Fe{sub 3}(BO{sub 3}){sub 4} with competing Sm-Fe and Ho-Fe exchange interactions are studied. The measured properties and effects are interpreted in terms of a general theoretical approach based on the molecular field approximation and calculations using the crystal field model for a rare-earth ion. The experimental temperature dependences of the initial magnetic susceptibility in the temperature range 2-300 K, the anomalies in the magnetization curves for B Double-Vertical-Line c and B Up-Tack c in fields lower than 1.2 T, and the field and temperature dependences of magnetization in fields lower than 9 T are described. The crystal field parameters and the parameters of the R-Fe and Fe-Fe exchange interactions are determined during the interpretation of the experimental data.

  7. Separation of Am-Cm from Al(NO/sub 3/)/sub 3/ waste solutions by in-canyon-tank precipitation as oxalates

    SciTech Connect

    Gray, L.W.; Burney, G.A.; Wilson, T.W.; McKibben, J.M.; Bibler, N.E.; Holtzscheiter, E.W.; Campbell, T.G.

    1982-04-01

    A process for recovery of Am-Cm residues from high-activity waste concentrates has been developed specifically for application in Savannah River Plant (SRP) canyon tanks. The Am-Cm residues were collected from a campaign to produce plutonium containing high isotopic concentrations of /sup 242/Pu. The separation of Am-Cm from the high-activity waste stream, containing about 2M Al(NO/sub 3/)/sub 3/, is necessary to produce an acceptable feed solution for a later pressurized cation exchange chromatography separation and purification step. The new process includes formic acid denitration, adjustment of contaminating cations by evaporation and water dilution, and oxalate precipitation of the actinides and lanthanides. After washing, the precipitate was dissolved in 8M nitric acid and the oxalate was destroyed by nitric acid oxidation that was catalyzed by manganous ions. This new process generates about one-fourth the waste of the californium solvent extraction process, which it replaced. The new process also produces a cleaner feed solution for the pressurized cation exchange chromatography separation and purification step.

  8. Nanocrystalline SiC and Ti3sub>SiC2 Alloys for Reactor Materials: Thermal and Mechanical Properties

    SciTech Connect

    Henager, Charles H.; Alvine, Kyle J.; Roosendaal, Timothy J.; Shin, Yongsoon; Nguyen, Ba Nghiep; Borlaug, Brennan A.; Jiang, Weilin

    2014-04-01

    SiC-polymers (pure polycarbosilane and polycarbosilane filled with SiC-particles) are being combined with Si and TiC powders to create a new class of polymer-derived ceramics for consideration as advanced nuclear materials in a variety of applications. Compared to pure SiC these materials have increased fracture toughness with only slightly reduced thermal conductivity. Future work with carbon nanotube (CNT) mats will be introduced with the potential to increase the thermal conductivity and the fracture toughness. At present, this report documents the fabrication of a new class of monolithic polymer derived ceramics, SiC + SiC/Ti3sub>SiC2 dual phase materials. The fracture toughness of the dual phase material was measured to be significantly greater than Hexoloy SiC using indentation fracture toughness testing. However, thermal conductivity of the dual phase material was reduced compared to Hexoloy SiC, but was still appreciable, with conductivities in the range of 40 to 60 W/(m K). This report includes synthesis details, optical and scanning electron microscopy images, compositional data, fracture toughness, and thermal conductivity data.

  9. Nonequivalent Yb{sup 3+} centres in Y{sub 1-x}Yb{sub x}Al{sub 3}(BO{sub 3}){sub 4} laser crystals

    SciTech Connect

    Boldyrev, K N; Popova, Marina N; Bezmaternykh, L N; Betinelli, M

    2011-02-28

    The absorption spectra of nonlinear laser crystals Y{sub 1-x}Yb{sub x}Al{sub 3}(BO{sub 3}){sub 4} grown from bismuth-lithium-molybdate and potassium-molybdate solution-melts are comparatively studied by high-resolution Fourier spectroscopy. The differences observed in the fine structure of the absorption spectra are correlated with the variations in the solution-melt composition and in the concentrations of bismuth and molybdenum impurities in the crystals. It is shown that the concentration of the molybdenum impurity (the main factor hindering lasing in the UV spectral region) in the single crystals grown from the bismuth-lithium-molybdate solutions is more than an order of magnitude smaller than in the crystals grown using the potassium-molybdate solution-melt. The described method can be used for express analysis of the quality of UV laser crystals and for improving the solution-melt technologies of growth of laser crystals and crystals used for generation of the fourth harmonic of Nd:YAG laser radiation. (active media)

  10. Free-standing millimetre-long Bi2Te3 sub-micron belts catalyzed by TiO2 nanoparticles.

    PubMed

    Schönherr, Piet; Zhang, Fengyu; Kojda, Danny; Mitdank, Rüdiger; Albrecht, Martin; Fischer, Saskia F; Hesjedal, Thorsten

    2016-12-01

    Physical vapour deposition (PVD) is used to grow millimetre-long Bi2Te3 sub-micron belts catalysed by TiO2 nanoparticles. The catalytic efficiency of TiO2 nanoparticles for the nanostructure growth is compared with the catalyst-free growth employing scanning electron microscopy. The catalyst-coated and catalyst-free substrates are arranged side-by-side, and overgrown at the same time, to assure identical growth conditions in the PVD furnace. It is found that the catalyst enhances the yield of the belts. Very long belts were achieved with a growth rate of 28 nm/min. A ∼1-mm-long belt with a rectangular cross section was obtained after 8 h of growth. The thickness and width were determined by atomic force microscopy, and their ratio is ∼1:10. The chemical composition was determined to be stoichiometric Bi2Te3 using energy-dispersive X-ray spectroscopy. Temperature-dependent conductivity measurements show a characteristic increase of the conductivity at low temperatures. The room temperature conductivity of 0.20 × 10(5) S m (-1) indicates an excellent sample quality. PMID:27342602

  11. Part 1: Kinetic energy dependencies of selected ion-molecule reactions; Part 2: Photochemistry of (FSO sub 3 ) sub 2 , FSO sub 3 , and FNO

    SciTech Connect

    Burley, J.D.

    1991-07-01

    In Part 1, guided ion beam mass spectroscopy is used to study the ion-molecule reactions O{sup +}({sup 4}S) + H{sub 2}(D{sub 2}, HD), (O{sup +}{sup 4}S) + N{sub 2}, C{sup +}({sup 2}P) + O{sub 2} and C{sup +}(P) + N{sub 2}. Integral reaction cross sections are measured as a function of kinetic energy in the center-of-mass frame. Reaction mechanisms and dynamics are examined, and the results are compared to the predictions of phase space theory. In some cases, thermochemistry for neutral and ionic species is derived. In Part 2, photoabsorption cross sections are measured for peroxydisulfuryl difluoride, (FSO{sub 3}){sub 2}, and the fluorosulfate radical, FSO{sub 3}. Photoabsorption cross sections of nitrosyl fluoride, FNO, are also measured, and the FNO absorption spectrum is analyzed and assigned. Spectral results for FNO are compared to the predictions and ab initio calculations and to those obtained for the isoelectronic compound HONO. 259 refs., 34 figs., 9 tabs.

  12. Crystal structure and magnetic properties of the coupled spin dimer compound SrCu{sub 2}(TeO{sub 3}){sub 2}Cl{sub 2}

    SciTech Connect

    Takagi, Rie . E-mail: takagi@inorg.su.se; Johnsson, Mats . E-mail: matsj@inorg.su.se; Kremer, Reinhard K. . E-mail: rekre@fkf.mpg.de; Lemmens, Peter . E-mail: p.lemmens@tu-bs.de

    2006-12-15

    Single crystals of the strontium copper tellurium oxochloride SrCu{sub 2}(TeO{sub 3}){sub 2}Cl{sub 2} were synthesized via solid-gas reactions in sealed evacuated silica tubes. The compound crystallizes in the monoclinic system, space group P2{sub 1}, a=7.215(2), b=7.2759(15), c=8.239(2) A, {beta}=96.56(4){sup o}, Z=2. The building units are [SrO{sub 6}Cl{sub 2}] irregular polyhedra, [CuO{sub 4}] and [CuO{sub 3}Cl] square planes, [TeO{sub 3}E] tetrahedra and [TeO{sub 3+1}E] trigonal bipyramids; E being the 5s {sup 2} lone pair of Te(IV). The Cu atoms can be regarded as forming a chain of weakly connected dimers. The magnetic susceptibility of the compound shows a broad maximum typical for antiferromagnetic spin fluctuations with a non-magnetic ground state. A Heisenberg spin model with coupled s=1/2 dimers leads to a satisfactory fitting of the experimental data. - Graphical abstract: Corner sharing CuO{sub 3}Cl and CuO{sub 4} square-planes result in strongly coupled Cu-Cu dimers that are connected by weaker couplings to form a distorted honeycomb pattern of Cu atoms.

  13. Annealing influence on the magnetostructural transition in Gd5Si1.3sub>Ge2.7 thin films

    SciTech Connect

    Pires, A. L.; Belo, J. H.; Gomes, I. T.; Hadimani, R. L.; Jiles, D. C.; Fernandes, L.; Tavares, P. B.; Araújo, J. P.; Lopes, A. M. L.; Pereira, A. M.

    2015-05-19

    Due to the emerging cooling possibilities at the micro and nanoscale, such as the fast heat exchange rate, the effort to synthesize and optimize the magnetocaloric materials at these scales is rapidly growing. Here, we report the effect of different thermal treatments on Gd5Si1.3sub>Ge2.7 thin film in order to evaluate the correlation between the crystal structure, magnetic phase transition and magnetocaloric effect. For annealing temperatures higher than 500ºC, the samples showed a typical paramagnetic behavior. On the other hand, thermal treatments below 500ºC promoted the suppression of the magnetostructural transition at 190 K, while the magnetic transition around 249 K is not affected. This magnetostructural transition extinction was reflected in the magnetocaloric behavior and resulted in a drastic decrease in the entropy change peak value (of about 68%). An increase in TC was reported, proving that at the nanoscale, heat treatments may be a useful tool to optimize the magnetocaloric properties in Gd5(SixGe1-x)4 thin films.

  14. Kinetic studies of ligand substitution rates for the Ru(NH/sub 3/)/sub 5/(H/sub 2/O)/sup 2 +/ ion in Nafion films

    SciTech Connect

    Lieber, C.M.; Schmidt, M.H.; Lewis, N.S.

    1986-10-01

    Substitution rates have been measured for reaction of a number of pyridines with the Nafion-bound Ru(NH/sub 3/)/sub 5/(H/sub 2/O)/sup 2 +/ complex. Reaction activities have been determined by electrochemical techniques, which also allow for determination of site thermodynamics and heterogeneity during the course of the reaction. Diffusion-coefficient effects are investigated by variation in polymer film thickness, and partition coefficients have been determined under equilibrium conditions by optical absorbance techniques. The partition-coefficient corrected rate law is found to be first order in Nafion-bound (Ru/sup II/) and first order in ligand concentration in the polymer phase. The partition-coefficient corrected bimolecular rate constants for a variety of pyridine ligands are found to vary by a factor of 5, which contrasts with the relatively constant substitution rates observed in aqueous solution. Also, sterically hindered ligands, such as 2-propylpyridine, exhibit surprisingly high substitution rate constants on the Nafion-bound Ru/sup II/ ion. These rate data indicate that pronounced molecular reactivity changes can occur upon electrode modification and have implications with respect to the design of chemically modified electrodes for use in electrocatalysis.

  15. Free-standing millimetre-long Bi2Te3 sub-micron belts catalyzed by TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Schönherr, Piet; Zhang, Fengyu; Kojda, Danny; Mitdank, Rüdiger; Albrecht, Martin; Fischer, Saskia F.; Hesjedal, Thorsten

    2016-06-01

    Physical vapour deposition (PVD) is used to grow millimetre-long Bi2Te3 sub-micron belts catalysed by TiO2 nanoparticles. The catalytic efficiency of TiO2 nanoparticles for the nanostructure growth is compared with the catalyst-free growth employing scanning electron microscopy. The catalyst-coated and catalyst-free substrates are arranged side-by-side, and overgrown at the same time, to assure identical growth conditions in the PVD furnace. It is found that the catalyst enhances the yield of the belts. Very long belts were achieved with a growth rate of 28 nm/min. A ˜1-mm-long belt with a rectangular cross section was obtained after 8 h of growth. The thickness and width were determined by atomic force microscopy, and their ratio is ˜1:10. The chemical composition was determined to be stoichiometric Bi2Te3 using energy-dispersive X-ray spectroscopy. Temperature-dependent conductivity measurements show a characteristic increase of the conductivity at low temperatures. The room temperature conductivity of 0.20 × 105 S m -1 indicates an excellent sample quality.

  16. Magnetic phase transitions in Nd{sub 1-x}Dy{sub x}Fe{sub 3}(BO{sub 3}){sub 4} ferroborates

    SciTech Connect

    Demidov, A. A.; Gudim, I. A.; Eremin, E. V.

    2012-02-15

    The magnetic properties of ferroborate single crystals with substituted compositions Nd{sub 1-x}Dy{sub x}Fe{sub 3}(BO{sub 3}){sub 4} (x = 0.15, 0.25) with competing exchange Nd-Fe and Dy-Fe interactions are investigated. For each composition, we observed a spontaneous spin-reorientation transition from the easy-axis to the easy-plane state and step anomalies on the magnetization curves for the spin-flop transition induced by a magnetic field B vertical bar c. The measured parameters and effects are interpreted using a unified theoretical approach based on the molecular field approximation and on calculations performed in the crystal-field model for the rare-earth ion. The experimental temperature dependences of the initial magnetic susceptibility from T = 2 K to T = 300 K, anomalies on the magnetization curves for B vertical bar c in fields up to 1.8 T, and their evolution with temperature, as well as temperature and field dependences of magnetization in fields up to 9 T are described. In the interpretation of experimental data, the crystal-field parameters in trigonal symmetry for the rare-earth subsystem are determined, as well as the parameters of Nd-Fe and Dy-Fe exchange interactions.

  17. Electron-phonon coupling and thermal transport in the thermoelectric compound Mo3sub>Sb7–xTex

    SciTech Connect

    Bansal, Dipanshu; Li, Chen W.; Said, Ayman H.; Abernathy, Douglas L.; Yan, Jiaqiang; Delaire, Olivier A.

    2015-12-07

    Phonon properties of Mo3sub>Sb7–xTex (x = 0, 1.5, 1.7), a potential high-temperature thermoelectric material, have been studied with inelastic neutron and x-ray scattering, and with first-principles simulations. The substitution of Te for Sb leads to pronounced changes in the electronic struc- ture, local bonding, phonon density of states (DOS), dispersions, and phonon lifetimes. Alloying with tellurium shifts the Fermi level upward, near the top of the valence band, resulting in a strong suppression of electron-phonon screening, and a large overall stiffening of interatomic force- constants. The suppression in electron-phonon coupling concomitantly increases group velocities and suppresses phonon scattering rates, surpassing the effects of alloy-disorder scattering, and re- sulting in a surprising increased lattice thermal conductivity in the alloy. We also identify that the local bonding environment changes non-uniformly around different atoms, leading to variable perturbation strengths for different optical phonon branches. The respective roles of changes in phonon group velocities and phonon lifetimes on the lattice thermal conductivity are quantified. Lastly, our results highlight the importance of the electron-phonon coupling on phonon mean-free-paths in this compound, and also estimates the contributions from boundary scattering, umklapp scattering, and point-defect scattering.

  18. Polarization-insensitive, shallow Ti-diffused near-stoichiometric LiTaO3sub> strip waveguide for integrated optics.

    PubMed

    Yang, Xiao-Fei; Zhang, Zi-Bo; Du, Wan-Ying; Zhang, Qun; Wong, Wing-Han; Yu, Dao-Yin; Pun, Edwin Yue-Bun; Zhang, De-Long

    2016-06-01

    We report on a Ti-diffused near-stoichiometric (NS) LiTaO3sub> strip waveguide fabricated by diffusion of an 8 μm wide, 160 nm thick Ti-strip followed by Li-rich vapor transport equilibration. It is found that the waveguide surface caves in ∼60  nm below the crystal surface. X-ray single-crystal diffraction shows that the indentation is due to Ti-induced lattice contraction. Optical studies show that the waveguide is in an NS composition environment, supports TE and TM single-mode propagation at 1.5 μm wavelength, is polarization insensitive, and has a shallow mode field profile and a loss of 0.2/0.3 dB/cm for the TE/TM mode. Secondary ion mass spectrometry analysis shows that the Ti profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of the waveguide. With the optimized fabrication condition, the waveguide is promising for developing an optical-damage-resistant device that requires a shallow mode field profile. PMID:27244402

  19. Three-Dimensionally Mesostructured Fe2O3sub> Electrodes with Good Rate Performance and Reduced Voltage Hysteresi

    SciTech Connect

    Wang, Junjie; Braun, Paul V.; Zhou, Hui; Nanda, Jagjit

    2015-03-26

    Ni scaffolded mesostructured 3D Fe2O3sub> electrodes were fabricated by colloidal templating and pulsed elec-trodeposition. The scaffold provided short pathways for both lithium ions and electrons in the active phase, enabling fast kinetics and thus a high power density. The scaffold also resulted in a reduced voltage hysteresis. The electrode showed a reversible capacity of ~1000 mA h g-1 at 0.2 A g-1 (~0.2 C) for about 20 cycles, and at a current density of 20 A g-1 (~20 C) the deliverable capacity was about 450 mA h g-1. The room temperature voltage hysteresis at 0.1 A g-1 (~0.1 C) was 0.62 V, which is significantly smaller than that normally reported in the literature. And it could be further reduced to 0.42 V when cycling at 45 ºC. Potentiostatic electrochemical impedance spectroscopy (PEIS) studies indicated the small voltage hysteresis may be due to a reduction in the Li2O/Fe interfacial area in the electrode during cycling relative to convention-al conversion systems.

  20. Gamma and proton irradiation effects and thermal stability of electrical characteristics of metal-oxide-silicon capacitors with atomic layer deposited Al2O3sub> dielectric

    SciTech Connect

    J. M. Rafi; Lynn, D.; Pellegrini, G.; Fadeyev, V.; Galloway, Z.; Sadrozinski, H. F. -W.; Christophersen, M.; Philips, B. F.; Kierstead, J.; Hoeferkamp, M.; Gorelov, I.; Palni, P.; Wang, R.; Seidel, S.

    2015-12-11

    The radiation hardness and thermal stability of the electrical characteristics of atomic layer deposited Al2O3sub> layers to be used as passivation films for silicon radiation detectors with slim edges are investigated. To directly measure the interface charge and to evaluate its change with the ionizing dose, metal-oxide-silicon (MOS) capacitors implementing differently processed Al2O3sub> layers were fabricated on p-type silicon substrates. Qualitatively similar results are obtained for degradation of capacitance–voltage and current–voltage characteristics under gamma and proton irradiations up to equivalent doses of 30 Mrad and 21.07 Mrad, respectively. While similar negative charge densities are initially extracted for all non-irradiated capacitors, superior radiation hardness is obtained for MOS structures with alumina layers grown with H2O instead of O3sub> as oxidant precursor. Competing effects between radiation-induced positive charge trapping and hydrogen release from the H2O-grown Al2O3sub> layers may explain their higher radiation resistance. Finally, irradiated and non-irradiated MOS capacitors with differently processed Al2O3sub> layers have been subjected to thermal treatments in air at temperatures ranging between 100 °C and 200 °C and the thermal stability of their electrical characteristics has been evaluated. Partial recovery of the gamma-induced degradation has been noticed for O3sub>-grown MOS structures. Lastly, this can be explained by a trapped holes emission process, for which an activation energy of 1.38 ± 0.15 eV has been extracted.

  1. Variation with mass of B(E3;0{sub 1}{sup +}{yields}3{sub 1}{sup -}) transition rates in A=124-134 even-mass xenon nuclei

    SciTech Connect

    Mueller, W.F.; Gade, A.; Hu, Z.; Lisetskiy, A.F.; Carpenter, M.P.; Henderson, D.T.; Janssens, R.V.F.; Lister, C.J.; Moore, E.F.; Pennington, T.O.; Church, J.A.; Dinca, D.C.; Glasmacher, T.; Perry, B.C.; Yurkewicz, K.L.; Zelevinsky, V.G.; Zwahlen, H.; Wiedenhoever, I.

    2006-01-15

    B(E3;0{sub 1}{sup +}{yields}3{sub 1}{sup -}) transition matrix elements have been measured for even-mass {sup 124-134}Xe nuclei using subbarrier Coulomb excitation in inverse kinematics. The trends in energy E(3{sup -}) and B(E3;0{sub 1}{sup +}{yields}3{sub 1}{sup -}) excitation strengths are well reproduced using phenomenological models based on a strong coupling picture with a soft quadrupole mode and an increasing occupation of the intruder h{sub 11/2} orbital.

  2. ALD TiO2-Al2O3sub> Stack: An Improved Gate Dielectrics on Ga-polar GaN MOSCAPs

    SciTech Connect

    Wei, Daming; Edgar, James H.; Briggs, Dayrl P.; Srijanto, Bernadeta R.; Retterer, Scott T.; Meyer, III, Harry M.

    2014-10-15

    This research focuses on the benefits and properties of TiO2-Al2O3sub> nano-stack thin films deposited on Ga2O3sub>/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO2, 7.1 nm Al2O3sub> and 2 nm Ga2O3sub> as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectron spectroscopy (XPS) depth profile, was negligible for GaN pretreated by thermal oxidation in O2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO2-Al2O3sub> on Ga2O3/GaN was increased to 12.5 compared to that of pure Al2O3sub> (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 1011 cm-2. The gate leakage current density (J=2.81× 10-8 A/cm2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO2/Al2O3sub> for serving as the gate oxide on Ga2O3sub>/GaN based MOS devices.

  3. Bis(arene) actinide sandwich complexes, ({eta}{sup 6}-C{sub 6}H{sub 3}R{sub 3}){sub 2}An: Linear or bent?

    SciTech Connect

    Li, J.; Bursten, B.E.

    1999-11-03

    The syntheses of the sandwich complexes ferrocene, ({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}-Fe, in 1951 and uranocene, ({eta}{sup 8}-C{sub 8}H{sub 8}){sub 2}U, in 1968 ushered in the modern eras of organotransition metal and organoactinide chemistry, respectively. Ferrocene and uranocene are examples of linear sandwich complexes, that is, those in which the (ring centroid)-M-(ring centroid) angle (denoted {theta}) is 180{degree}. In the case of ({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}M chemistry, a number of bent ({theta} < 180{degree}) complexes are known when M is a main-group or rare-earth element. The explanation for the bent structures of these complexes has been the subject of some debate concerning the relative importance of covalent, electrostatic, and steric interactions. The authors report optimized geometries of Bz{sub 2}An (An = Th-Am) and ({eta}{sup 6}-C{sub 6}H{sub 3}R{sub 3}){sub 2}An (An = Th, U, Pu; R = Me, {sup t}Bu) obtained by using local density approximation (LDA) and Perdew-Wang (PW91) gradient-corrected relativistic density functional theory (DFT) methods. These DFT methods are found to be able to reproduce the experimental geometries and vibrational frequencies of organoactinide complexes with satisfactory accuracy. The (TTB){sub 2}An calculations that are reported here are, to date, the largest full geometry optimizations to be carried out on an actinide system.

  4. Structure and Stoichiometry in Supervalent Doped Li7La3sub> Zr2O12

    SciTech Connect

    Mukhopadhyay, Saikat; Thompson, Travis; Sakamoto, Jeff; Huq, Ashfia; Wolfenstine, Jeff; Allen, Jan L.; Bernstein, Noam; Stewart, Derek A.; Johannes, M. D.

    2015-04-20

    The oxide garnet material Li7La3sub> Zr2O12 shows remarkably high ionic conductivity when doped with supervalent ions that are charge compensated by Li vacancies and is currently one of the best candidates for development of a technologically relevant solid electrolyte. Determination of optimal dopant concentration, however, has remained a persistent problem due to the extreme difficulty of establishing the actual (as compared to nominal) stoichiometry of intentionally doped materials and by the fact that it is still not entirely clear what level of lattice expansion/contraction best promotes. ionic diffusion. By combining careful synthesis, neutron diffraction, high-resolution X-ray diffraction (XRD), Raman measurements, and density functional theory calculations, we show that structure and stoichiometry are intimately related such that the former can in many cases be used as a gauge of the latter. We show that different Li-vacancy creating supervalent ions (Al3+ vs Ta5+) affect the structure very differently, both in terms of the lattice constant, which is easily measurable, and hi terms of the local structure, which can be difficult or impossible to access experimentally but may have important ramifications for conduction. We carefully correlate the lattice constant to dopant type/concentration via Vegard's law and then further correlate these quantities to relevant local structural parameters. In conclusion, our work opens the possibility of developing a codopant scheme that optimizes the Li vacancy concentration and the lattice size simultaneously.

  5. Symmetry of piezoelectric (1–x)Pb(Mg1/3sub>Nb2/3sub>)O₃-xPbTiO₃ (x=0.31) single crystal at different length scales in the morphotropic phase boundary region

    SciTech Connect

    Kim, Kyou-Hyun; Payne, David A.; Zuo, Jian-Min

    2012-11-29

    We use probes of three different length scales to examine symmetry of (1–x)Pb(Mg1/3sub>Nb2/3sub>)O₃-xPbTiO₃ (PMN-xPT) single crystals in the morphotropic phase boundary (MPB) region at composition x = 0.31 (PMN-31% PT). On the macroscopic scale, x-ray diffraction (XRD) shows a mixture of strong and weak diffraction peaks of different widths. The closest match to XRD peak data is made with monoclinic Pm (MC) symmetry. On the local scale of a few nanometers, convergent beam electron diffraction (CBED) studies, with a 1.6-nm electron probe, reveal no obvious symmetry. These CBED experimental patterns can be approximately matched with simulations based on monoclinic symmetry, which suggests locally distorted monoclinic structure. A monoclinic Cm (MA or MB)-like symmetry could also be obtained from certain regions of the crystal by using a larger electron probe size of several tens of nanometers in diameter. Thus the monoclinic symmetry of single crystal PMN-31%PT is developed only in parts of the crystal by averaging over locally distorted structure on the scale of few tens of nanometers. The macroscopic symmetry observed by XRD is a result of averaging from the local structure in PMN-31%PT single crystal. The lack of local symmetry at a few nanometers scale suggests that the polarization switching results from a change in local displacements, which are not restricted to specific symmetry planes or directions.

  6. Accessing conjugated polymers with precisely controlled heterobisfunctional chain ends via post-polymerization modification of the OTf group and controlled Pd(0)/t-Bu3sub>P-catalyzed Suzuki cross-coupling polymerization

    SciTech Connect

    Hu, Qiao -Sheng; Hong, Kunlun; Zhang, Hong -Hai

    2015-08-12

    In this study, a general strategy toward the synthesis of well-defined conjugated polymers with controlled heterobisfunctional chain ends via combination of controlled Pd(0)/t-Bu3sub>P Suzuki cross-coupling polymerization with the post-polymerization modification of the triflate (OTf) group was disclosed.

  7. Reduction of aldehydes and ketones by transition-metal hydrides. 1. Reaction of trans,trans-WH(CO){sub 2}(NO)(PMe{sub 3}){sub 2} with simple and phenoxy-functionalized aldehydes and ketones

    SciTech Connect

    van der Zeijden, A.A.H.; Bosch, H.W.; Berke, H.

    1992-06-01

    The tungsten complex, trans, trans-WH(CO){sub 2}(NO)(PMe{sub 3}){sub 2} reacts with propanol, benzaldehyde, salicylaldehyde, 2-hydroxyacetophenone, methyl salicylate, and 4-hydroxybenzaldehyde to yield insertion products. The reactions and their products were studied by IR, mass spectrometry, and X-ray crystallography. Structures of selected products were discussed. 1 fig., 7 tabs.

  8. Origin of Active Oxygen in a Ternary CuOx /Co3sub>O4–CeO 2 Catalyst for CO Oxidation

    SciTech Connect

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

    2014-11-14

    In this paper, we have studied CO oxidation over a ternary CuOx/Co3sub>O4-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/Co3sub>O4-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 Co3sub>O4-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 Co3sub>O4-CeO2.

  9. Optical Absorption and Spectral Photoconductivity in α-(Fe1-xCrx)2O3sub> Solid-Solution Thin Films

    SciTech Connect

    Chamberlin, Sara E.; Wang, Yong; Lopata, Kenneth A.; Kaspar, Tiffany C.; Cohn, Alicia; Gamelin, Daniel R.; Govind, Niranjan; Sushko, Peter V.; Chambers, Scott A.

    2013-09-04

    Hematite, α-Fe2O3sub>, is an attractive narrow gap oxide for consideration as an efficient visible light photocatalyst, with significant potential for band gap engineering via doping. We examine optical absorption in α (Fe1-xCrx)2O3sub> epitaxial films and explain the observed excitations, and the nature of the band gap dependence on x, through first principles calculations. The calculated and measured optical band gap becomes smaller than that of the bulk α-Fe2O3sub> and reaches a minimum as the Cr mole fraction increases to 50%. The lowest energy transitions in the mixed-metal alloys involve electron excitation from occupied Cr 3d orbitals to unoccupied Fe 3d orbitals, and they result in a measureable photocurrent. The onset of α-Fe2O3sub> photoconductivity can be reduced by nearly ~0.5 eV through addition of Cr.

  10. Strain localization in thin films of Bi(Fe,Mn)O3sub> due to the formation of stepped Mn4+-rich antiphase boundaries

    SciTech Connect

    MacLaren, I.; Sala, B.; Andersson, S. M. L.; Pennycook, T. J.; Xiong, Jia; Jia, Q. X.; Choi, E. -M.; MacManus-Driscoll, J. L.

    2015-10-17

    Here, the atomic structure and chemistry of thin films of Bi(Fe,Mn)O3sub> (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3sub> are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn4+-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3sub> on the SrTiO3sub> substrate to minimise any Mn-Ti interactions.

  11. Preparation of silicon nitride-titanium nitride and titanium-titanium nitride composites from (CH{sub 3}){sub 3}SiNHTiCl{sub 3}-coated Si{sub 3}N{sub 4} and Ti particles

    SciTech Connect

    Narula, C.K.; Demczyk, B.G.; Czubarow, P.; Seyferth, D.

    1995-05-01

    [(Trimethylsilyl)amino]titanium trichloride, (CH{sub 3}){sub 3}-SiNHTiCl{sub 3}, was isolated as a red-orange crystalline solid in 58% Yield from the reaction of TiCl{sub 4} with [(CH{sub 3}){sub 3}Si]{sub 2} NH in 1:1 molar ratio in dichloromethane at {minus}78 C. Pyrolysis of (CH{sub 3}){sub 3}SiNHTiCl{sub 3} at 600 C furnished titanium nitride. This precursor is suitable for the preparation of composites and was employed to prepare Si{sub 3}N{sub 4}-TiN and Ti-TiN powders by adding Si{sub 3}N{sub 4} particles or titanium powders to a solution of (CH{sub 3}){sub 3} SiNHTiCl{sub 3} in dichloromethane, drying and pyrolyzing the resulting solid. This precursor also has been used as a binder to prepare Si{sub 3}N{sub 4}-TiN and Ti-TiN bodies. High-resolution transmission electron microscopic studies of the Si{sub 3}N{sub 4}-TiN composite showed that titanium nitride is concentrated on the surface of the Si{sub 3}N{sub 4} particles.

  12. In situ determination of the spinel-post-spinel transition in Fe3sub>O4 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

    2011-08-10

    The position of the spinel-post-spinel phase transition in Fe3sub>O4 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-Fe3sub>O4) 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 3sub>O4 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-Fe3sub>O4, 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.

  13. Line shape parameters of PH3sub> transitions in the Pentad near 4–5 μm: Self-broadened widths, shifts, line mixing and speed dependence

    SciTech Connect

    Malathy Devi, V.; Benner, D. C.; Kleiner, Isabelle; Sams, Robert L.; Fletcher, Leigh N.

    2014-08-01

    Accurate knowledge of spectroscopic line parameters of PH3sub> is important for remote sensing of the outer planets, especially Jupiter and Saturn. In a recent study, line positions and intensities for the Pentad bands of PH3sub> have been reported from analysis of high-resolution, high signal-to noise room-temperature spectra recorded with two Fourier transform spectrometers (2014) [1]. The results presented in this study were obtained during the analysis of positions and intensities, but here we focus on the measurements of spectral line shapes (e.g. widths, shifts, line mixing) for the 2ν4, ν2 + ν4, ν1 and ν3sub> bands. A multispectrum nonlinear least squares curve fitting technique employing a non-Voigt line shape to include line mixing and speed dependence of the Lorentz width was employed to fit the spectra simultaneously. The least squares fittings were performed on five room-temperature spectra recorded at various PH3sub> pressures (~2–50 Torr) with the Bruker IFS-125HR Fourier transform spectrometer (FTS) located at the Pacific Northwest National Laboratory (PNNL), in Richland, Washington. Over 840 Lorentz self-broadened half-width coefficients, 620 self-shift coefficients and 185 speed dependence parameters were measured. Line mixing was detected for transitions in the 2ν4, ν1 and ν3sub> bands, and their values were quantified for 10 A+A- pairs of transitions via off-diagonal relaxation matrix element formalism. The dependences of the measured half-width coefficients on the J and K rotational quanta of the transitions are discussed. The self-width coefficients for the ν1 and ν3sub> bands from this study are compared to the self-width coefficients for transitions with the same rotational quanta (J, K) reported for the Dyad (ν2 and ν4) bands. The measurements from present study should be useful for the

  14. High-pressure synthesis, crystal structure, and structural relationship of the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}

    SciTech Connect

    Haberer, Almut; Huppertz, Hubert

    2009-04-15

    Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C, representing the first known ytterbium fluoride borate. The compound exhibits isolated BO{sub 3}-groups next to ytterbium cations and fluoride anions, showing a structure closely related to the other known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}. Monoclinic Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} crystallizes in space group C2/c with the lattice parameters a=2028.2(4) pm, b=602.5(2) pm, c=820.4(2) pm, and beta=100.63(3){sup o} (Z=4). Three different ytterbium cations can be identified in the crystal structure, each coordinated by nine fluoride and oxygen anions. None of the five crystallographically independent fluoride ions is coordinated by boron atoms, solely by trigonally-planar arranged ytterbium cations. In close proximity to the above mentioned compounds RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}, Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} can be described via alternating layers with the formal compositions 'YbBO{sub 3}' and 'YbF{sub 3}' in the bc-plane. - Graphical abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}, built up from isolated BO{sub 3}-groups. The compound shows structural relations to the known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}.

  15. Structural phase transition causing anomalous photoluminescence behavior in perovskite (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}

    SciTech Connect

    Yangui, A.; Pillet, S.; Mlayah, A.; Lusson, A.; Bouchez, G.; Boukheddaden, K. E-mail: kbo@physique.uvsq.fr; Triki, S.; Abid, Y. E-mail: kbo@physique.uvsq.fr

    2015-12-14

    Optical and structural properties of the organic-inorganic hybrid perovskite-type (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] (abbreviated as C{sub 6}PbI{sub 4}) were investigated using optical absorption, photoluminescence (PL), and x-ray diffraction measurements. Room temperature, optical absorption measurements, performed on spin-coated films of C{sub 6}PbI{sub 4}, revealed two absorption bands at 2.44 and 3.21 eV. Upon 325 nm (3.815 eV) laser irradiation, strong green PL emission peaks were observed at 2.41 eV (P1) and 2.24 eV (P2) and assigned to free and localized excitons, respectively. The exciton binding energy was estimated at 356 meV. At low temperature, two additional emission bands were detected at 2.366 eV (P3) and a large band (LB) at 1.97 eV. The former appeared only below 40 K and the latter emerged below 130 K. The thermal dependence of the PL spectra revealed an abnormal behavior accompanied by singularities in the peak positions and intensities at 40 and 130 K. X-ray diffraction studies performed on powder and single crystals as a function of temperature evidenced significant changes of the interlayer spacing at 50 K and ∼138 K. Around 138 K, a commensurate to incommensurate structural phase transition occurred on cooling. It involves a symmetry breaking leading to a distortion of the PbI{sub 6} octahedron. The resulting incommensurate spatial modulation of the Pb–I distances (and Pb–I–Pb angles) causes a spatial modulation of the band gap, which is at the origin of the emergence of the LB below ∼130 K and the anomalous behavior of the position of P1 below 130 K. The change of the interlayer spacing in the 40-50 K range may in turn be related to the significant decrease of the intensity of P2 and the maximum emission of the LB. These results underline the intricate character of the structural and the PL properties of the hybrid perovskites; understanding such properties should benefit to the design of optoelectronic devices with

  16. Metathetical reactions of Re(VII) alkylidene-alkylidyne complexes of the type Re(CR[prime])(CHR[prime])[OCMe(CF[sub 3])[sub 2

    SciTech Connect

    Toreki, R.; Vaughan, G.A.; Schrock, R.R.; Davis, W.M. )

    1993-01-13

    1-Decene and methyl 9-decenoate react with syn- and anti-Re(C-t-Bu)(CH-t-Bu)(OR[sub F6]) to give syn- and anti-Re(C-t-Bu)[CH(CH[sub 2])[sub 7]Me](OR[sub F6])[sub 2] and syn- and anti-Re(C-t-Bu)[CH(CH[sub 2])[sub 7]CO[sub 2]Me](OR[sub F6])[sub 2], respectively (OR[sub F6] = OCMe(CF[sub 3])[sub 2]). The new alkylidene complexes are unstable in the presence of excess terminal olefin and decompose upon attempted isolation. However, vinylferrocene reacts relatively smoothly and reversibly with syn-Re(C-t-Bu)(CH-t-Bu)(OR[sub F6])[sub 2] in a noncoordinating solvent to yield tert-butylethylene and primarily anti-Re(C-t-Bu)(CHFc)(OR[sub F6])[sub 2] (Fe = ferrocenyl). anti-Re(C-t-Bu)(CHFc)(OR[sub F6])[sub 2]. In the presence of THF or dimethoxyethane, complexes of the type syn- or anti-Re(C-t-Bu)(CHR)(OR[sub F6])S[sub 2] (R = Me, Et, Ph; S = THF or 0.5DME) could be prepared in high yield from Re(C-t-Bu)(CH-t-Bu)(OR[sub F6])[sub 2] and CH[sub 2][double bond]CHR. Heteroatom-substituted (O, S, or N) terminal olefins react more rapidly than ordinary olefins with Re(C-t-Bu)(CH-t-Bu)(OR[sub F6])[sub 2] in the presence of THF to yield complexes of the type syn- or anti-Re(C-t-Bu)(CHX)(OR[sub F6])[sub 2](THF)[sub 2] (X = OR, SR, NR[sub 2], or p-dimethylaminophenyl). 2-Pentene or methyl oleate is metathesized in the presence of Re(C-t-Bu)(CH-t-Bu)(OR[sub F6])[sub 2], and intermediate alkylidene complexes can be observed in each case. Addition of 3-hexene to Re(C-t-Bu)(CH-t-Bu)(OR[sub F6])[sub 2] followed by TMEDA yields Re(C-t-Bu)(CHEt)(OR[sub F6])[sub 2](TMEDA). Internal olefins are metathesized only very slowly by Re(C-t-Bu)(CH-t-Bu)(OR[sub F6])[sub 2] in the presence of several equivalents of THF or DME or especially in neat THF or DME. 58 refs., 4 figs., 4 tabs.

  17. 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.

    2010-01-15

    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.

  18. Coherent octave-spanning mid-infrared supercontinuum generated in As2S3sub>-silica double-nanospike waveguide pumped by femtosecond Cr:ZnS laser.

    PubMed

    Xie, Shangran; Tolstik, Nikolai; Travers, John C; Sorokin, Evgeni; Caillaud, Celine; Troles, Johann; Russell, Philip St J; Sorokina, Irina T

    2016-05-30

    A more than 1.5 octave-spanning mid-infrared supercontinuum (1.2 to 3.6 μm) is generated by pumping a As2S3sub>-silica "double-nanospike" waveguide via a femtosecond Cr:ZnS laser at 2.35 μm. The combination of the optimized group velocity dispersion and extremely high nonlinearity provided by the As2S3sub>-silica hybrid waveguide enables a ~100 pJ level pump pulse energy threshold for octave-spanning spectral broadening at a repetition rate of 90 MHz. Numerical simulations show that the generated supercontinuum is highly coherent over the entire spanning wavelength range. The results are important for realization of a high repetition rate octave-spanning frequency comb in the mid-infrared spectral region. PMID:27410155

  19. Reactions of methyl groups on a non-reducible metal oxide: The reaction of iodomethane on stoichiometric α-Cr2O3sub>(0001)

    SciTech Connect

    Dong, Yujung; Brooks, John D.; Chen, Tsung-Liang; Mullins, David R.; Cox, David F.

    2015-06-10

    The reaction of iodomethane on the nearly stoichiometric α-Cr2O3(sub>0001) surface produces gas phase ethylene, methane, and surface iodine adatoms. The reaction is first initiated by the dissociation of iodomethane into surface methyl fragments, -CH3sub>, and iodine adatoms. Methyl fragments bound at surface Cr cation sites undergo a rate-limiting dehydrogenation reaction to methylene, =CH2. The methylene intermediates formed from methyl dehydrogenation can then undergo coupling reactions to produce ethylene via two principle reaction pathways: (1) direct coupling of methylene and (2) methylene insertion into the methyl surface bond to form surface ethyl groups which undergo β-H elimination to produce ethylene. The liberated hydrogen also combines with methyl groups to form methane. Iodine adatoms from the dissociation of iodomethane deactivate the surface by simple site blocking of the surface Cr3+ cations.

  20. Quantum phase transitions and decoupling of magnetic sublattices in the quasi-two-dimensional Ising magnet Co3sub>V2O8 in a transverse magnetic field

    SciTech Connect

    Fritsch, Katharina; Ehlers, G.; Rule, K. C.; Habicht, Klaus; Ramazanoglu, Mehmet K.; Dabkowska, H. A.; Gaulin, Bruce D.

    2015-11-05

    We study the application of a magnetic field transverse to the easy axis, Ising direction in the quasi-two-dimensional kagome staircase magnet, Co3sub>V2O8, induces three quantum phase transitions at low temperatures, ultimately producing a novel high field polarized state, with two distinct sublattices. New time-of-flight neutron scattering techniques, accompanied by large angular access, high magnetic field infrastructure allow the mapping of a sequence of ferromagnetic and incommensurate phases and their accompanying spin excitations. Also, at least one of the transitions to incommensurate phases at μ0Hc1~6.25 T and μ0Hc2~7 T is discontinuous, while the final quantum critical point at μ0Hc3sub>~13 T is continuous.

  1. Infrared resonance Raman, and excitation profile studies of Os/sub 2/(O/sub 2/CCH/sub 3/)/sub 4/Cl/sub 2/ and Os/sub 2/(O/sub 2/CCD/sub 3/)/sub 4/Cl/sub 2/. The assignment of the osmium-osmium stretching vibration for a complex involving an osmium-osmium multiple bond

    SciTech Connect

    Clark, R.J.H.; Hempleman, A.J.; Tocher, D.A.

    1988-08-31

    Extensive Raman studies (1525-40 cm/sup /minus/1/) of Os/sub 2/(O/sub 2/CCH/sub 3/)/sub 4/Cl/sub 2/ have led to the identification of the three strong bands, /nu//sub 1/, /nu//sub 2/, and /nu//sub 3/, at 229, 393, and 292 cm/sup /minus/1/ to the key skeletal stretching modes, /nu/(OsOs), /nu/(OsO), and /nu/(OsCl), respectively. Raman spectra of the complex at resonance with the intense electronic band at /lambda//sub max/ = 383 nm lead to the development of a six-membered overtone progression in /nu//sub 1/ as well as combination band progressions in /nu//sub 1/ based upon one quantum of either /nu//sub 2/ or /nu//sub 3/. This indicates that the principal structural change attendant upon excitation to the resonant state is along the OsOs coordinate. Fourier transform infrared spectra (3500-40 cm/sup /minus/1/) have also been obtained. Acetate deuteriation provides conclusive evidence for many of the infrared and Raman band assignments. The study provides the first firm identification of /nu/(OsOs) for a multiply bonded species.

  2. Oxidatively induced reductive eliminations. Kinetics and mechanism of the elimination of ethane from the 17-electron cation radical of Cp[sup *]Rh(PPh[sub 3])(CH[sub 3])[sub 2

    SciTech Connect

    Pedersen, A.; Tilset, M. )

    1993-01-01

    The dimethylrhodium compound Cp[sup *]Rh(PPh[sub 3])(CH[sub 3])[sub 2] (1; Cp[sup *] = [eta][sup 5]-C[sub 5]Me[sub 5]) undergoes an overall 2-electron oxidation at 0.04 V vs the ferrocene/ferrocenium (Fc) couple in 9:1 acetonitrile/dichloromethane, 0.1 M Bu[sub 4]N[sup +]PF[sub 6][sup [minus

  3. Mechanism of the C-C cleavage of acetone by the ruthenium benzyne complex (PMe sub 3 ) sub 4 Ru(. eta. sup 2 -C sub 6 H sub 4 ): Formation and reactivity of an oxametallacyclobutane complex

    SciTech Connect

    Hartwig, J.F.; Bergman, R.G.; Andersen, R.A. )

    1990-04-11

    The reaction of acetone with the ruthenium benzyne complex (PMe{sub 3}){sub 4}Ru({eta}{sup 2}-C{sub 6}H{sub 4}) (1) results in cleavage of a C-C bond in the ketone, leading to methane and 2, an ortho-metalated enolate complex of acetophenone (Scheme I). The authors now report the generation and spectroscopic characterization of a potential intermediate in this reaction: complex 3, a rare example of an oxametallacyclobutane.

  4. A fundamental study on the [(μ-Cl)3sub> Mg2 (THF)6 ]+ dimer electrolytes for rechargeable Mg batteries

    SciTech Connect

    Liu, Tianbiao; Cox, Jonathan T.; Hu, Dehong; Deng, Xuchu; Hu, Jianzhi; Hu, Mary Y.; Xiao, Jie; Shao, Yuyan; Tang, Keqi; Liu, Jun

    2015-01-05

    We present a fundamental study on [(μ-Cl)3sub> Mg2 (THF)6 ]+ dimer electrolytes using various physical methods including Subambient Pressure Ionization with Nanoelectrospray Mass spectrometry (SPIN-MS), Raman spectroscopy, 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis. For the first time, long time sought THF solvated [MgCl]+ species was experimentally characterized by SPIN mass spectrometry in the solution of the Mgdimer containing electrolyte, confirming the mono-Cl- abstraction reaction between MgCl2 and an Al Lewis acid. Solvated MgCl2 in the electrolyte was confirmed by Raman spectroscopy. The experimental results establish the previously proposed dimerization equilibrium of solvated [MgCl]+ and MgCl2 with [(μ-Cl)3sub>Mg2(THF)6]+. 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis on chloration reaction of [(μ-Cl)3sub>Mg2(THF)6]AlPh3sub>Cl with external Cl- led to further insights on the coordination chemistry of the dimer electrolyte. Finally, a comprehensive mechanism is proposed for the reversible electrochemical Mg deposition and stripping and Mg2+ and Cl- ion transports of the Mg dimer electrolytes in rechargeable Mg batteries.

  5. Record figure of merit values of highly stoichiometric Sb2Te3sub> porous bulk synthesized from tailor-made molecular precursors in ionic liquids

    SciTech Connect

    Heimann, Stefan; Schulz, Stephan; Schaumann, Julian; Mudring, Anja; Stötzel, Julia; Maculewicz, Franziska; Schierning, Gabi

    2015-08-06

    We report on the synthesis of Sb2Te3sub> nanoparticles with record-high figure of merit values of up to 1.5. The central thermoelectric parameters, electrical conductivity, thermal conductivity and Seebeck coefficient, were independently optimized. Critical influence of porosity for the fabrication of highly efficient thermoelectric materials is firstly demonstrated, giving a strong guidance for the optimization of other thermoelectric materials.

  6. The dominant factors affecting the memory characteristics of (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} high-k charge-trapping devices

    SciTech Connect

    Gong, Changjie; Lan, Xuexin; Yin, Qiaonan; Ou, Xin; Liu, Jinqiu; Sun, Chong; Wang, Laiguo; Lu, Wei; Yin, Jiang Xu, Bo; Xia, Yidong; Liu, Zhiguo; Li, Aidong

    2014-09-22

    The prototypical charge-trapping memory devices with the structure p-Si/Al{sub 2}O{sub 3}/(Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x}/Al{sub 2}O{sub 3}/Pt(x = 0.5, 0.3, and 0.1) were fabricated by using atomic layer deposition and RF magnetron sputtering techniques. A memory window of 7.39 V with a charge storage density of 1.97 × 10{sup 13 }cm{sup −2} at a gate voltage of ±11 V was obtained for the memory device with the composite charge trapping layer (Ta{sub 2}O{sub 5}){sub 0.5}(Al{sub 2}O{sub 3}){sub 0.5}. All memory devices show fast program/erase speed and excellent endurance and retention properties, although some differences in their memory performance exist, which was ascribed to the relative individual band alignments of the composite (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} with Si.

  7. Influence of Mn concentration on magnetic topological insulator MnxBi2−xTe3sub> thin-film Hall-effect sensor

    SciTech Connect

    Ni, Y.; Zhang, Z.; Nlebedim, I. C.; Hadimani, R. L.; Jiles, D. C.

    2015-06-11

    Hall-effect (HE) sensors based on high-quality Mn-doped Bi2Te3sub> topological insulator (TI) thin films have been systematically studied in this paper. Improvement of Hall sensitivity is found after doping the magnetic element Mn into Bi2Te3sub>. The sensors with low Mn concentrations, MnxBi2-xTe3sub>, x = 0.01 and 0.08 show the linear behavior of Hall resistance with sensitivity about 5 Ω/T. And their Hall sensitivity shows weak dependence on temperature. For sensors with high Mn concentration (x = 0.23), the Hall resistance with respect to magnetic field shows a hysteretic behavior. Moreover, its sensitivity shows almost eight times as high as that of the HE sensors with low Mn concentration. The highest sensitivity can reach 43 Ω/T at very low magnetic field. This increase of Hall sensitivity is caused by the occurrence of anomalous HE (AHE) after ferromagnetic phase transition. Our work indicates that the magnetic-element-doped TIs with AHE are good candidates for HE sensors.

  8. Influence of Ga-concentration on the electrical and magnetic properties of magnetoelectric CoGaxFe2–xO4/BaTiO3sub> composite

    SciTech Connect

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

    2015-03-20

    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–xO4/BaTiO3sub> 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–xO4/BaTiO3sub> composites. As a result, the present work is beneficial to the practical application of composite CoFe2O4/BaTiO3sub>-based multiferroic materials.

  9. Mid-infrared supercontinuum generation in step-index As2S3sub> fibers pumped by a nanosecond shortwave-infrared supercontinuum pump source.

    PubMed

    Yao, Jinmei; Zhang, Bin; Yin, Ke; Yang, Linyong; Hou, Jing; Lu, Qisheng

    2016-06-27

    A supercontinuum (SC) source spanning from 2 to 4 μm is demonstrated in As2S3sub>-chalcogenide fibers pumped by a nanosecond supercontinuum pump source in the normal dispersion region. In this experiment, two pieces of 3-m-long step-index As2S3sub> fiber with different core diameters of 7 μm and 9 μm are pumped by a 1.9-2.5 μm nanosecond supercontinuum source. The zero dispersion wavelengths are both beyond 6.6 μm, thus cascaded stimulated Raman scattering is believed to be the dominant mechanism responsible for spectral broadening. With a low peak pump power of ~2.9 kW, both of the output spectra have extended to 4 μm with enhanced power distribution in the MIR region. The maximum output power of the mid-infrared supercontinua is ~140 mW. To the best of our knowledge, it is the first supercontinuum extenting to 4 μm in an As2S3sub> fiber pumped by shortwave-infrared SC pluses in the normal dispersion region. PMID:27410660

  10. Exploration of R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd2AlGe2 and Analysis of the U3sub>Si2 and Zr3sub>Al2 Structure Types

    SciTech Connect

    McWhorter, Sean William

    2006-01-01

    In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd5(SixGe1-x)4 several new compounds were synthesized with different crystal structures, but similar structural features. In Gd5(SixGe1-x)4, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd5(SixGe1-x)4 can be thought of as being formed from two 32434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd2MgGe2 and Gd2InGe2 both possess the same 32434 nets of Gd atoms as Gd5(SixGe1-x)4, but these nets are connected differently, forming the Mo2FeB2 crystal structure. A search of the literature revealed that compounds with the composition R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo2FeB2, Zr3sub>Al2, Mn2AlB2 and W2CoB2 crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd2AlGe2 forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how

  11. Four-Electron Donor Hemilabile n3-PPh3sub> Ligand that Binds Through a C = C Bond Rather than an Agostic C-H Interaction, and Displacement of the C = C by Methyl Iodide or Water

    SciTech Connect

    Cheng, Tan-Yun; Szalda, David J.; Hanson, Jonathan C.; Muckerman, J. T.; Bullock, R. Morris

    2008-07-12

    Hydride transfer from Cp(CO)2(PPh3sub>)MoH to Ph3sub>C+ BAr'4 [Ar' = 3,5-bis(trifluoromethyl)phenyl] produces [Cp(CO)23 PPh3sub>)Mo]+[BAr'4] . Spectroscopic and crystallographic data indicate that one C=C of a Ph ring is weakly bound to the Mo, so that the PPh3sub> ligand is four-electron donor ligand. Computations (DFT/B3LYP and MP2 on [Cp(CO)23 PPh3sub>)Mo]+ and [Cp(CO)23 PH2Ph)Mo]+, and DFT/B3LYP on [Cp(CO)23 PHtBuPh)Mo]+ and [Cp(CO)23 PH2Ph)Nb]) provide further information on the bonding, and on the preference for bonding of the metal to the C=C bond rather than an agostic C H interaction found in many related complexes. The hemilabile C=C bond is readily displaced by CH3sub>I or H2O, and crystal structures are reported for [Cp(CO)2(PPh3sub>)Mo(ICH3sub>)]+ and [Cp(CO)2(PPh3sub>)Mo(OH2)]+. The equilibrium constant for [Cp(CO)23 PPh3sub>)Mo]+ + ICH3sub> to give [Cp(CO)2(PPh3sub>)Mo(ICH3sub>)]+ is Keq = 5.2 x 102 M -1 in CD2Cl2 at 22 °C.

  12. Structure–property relations of orthorhombic [(CH{sub 3}){sub 3}NCH{sub 2}COO]{sub 2}(CuCl{sub 2}){sub 3}·2H{sub 2}O

    SciTech Connect

    Haussühl, Eiken; Schreuer, Jürgen; Wiehl, Leonore; Paulsen, Natalia

    2014-04-01

    Large single crystals of orthorhombic [(CH{sub 3}){sub 3}NCH{sub 2}COO]{sub 2}(CuCl{sub 2}){sub 3}·2H{sub 2}O with dimensions up to 40×40×30 mm{sup 3} were grown from aqueous solutions. The elastic and piezoelastic coefficients were derived from ultrasonic resonance frequencies and their shifts upon variation of pressure, respectively, using the plate-resonance technique. Additionally, the coefficients of thermal expansion were determined between 95 K and 305 K by dilatometry. The elastic behaviour at ambient conditions is dominated by the 2-dimensional network of strong hydrogen bonds within the (001) plane leading to a corresponding pseudo-tetragonal anisotropy of the longitudinal elastic stiffness. The variation of elastic properties with pressure, however, as well as the thermal expansion shows strong deviations from the pseudo-tetragonal symmetry. These deviations are probably correlated with tilts of the elongated tri-nuclear betaine–CuCl{sub 2}–water complexes. Neither the thermal expansion nor the specific heat capacity gives any hint on a phase transition in the investigated temperature range. - Graphical abstract: Single crystal of orthorhombic [(CH{sub 3}){sub 3}NCH{sub 2}COO]{sub 2}(CuCl{sub 2}){sub 3}·2H{sub 2}O. - Highlights: • Large single crystals (40 ×40 ×30 mm{sup 3}) of [(CH{sub 3}){sub 3}NCH{sub 2}COO]{sub 2}(CuCl{sub 2}){sub 3}·2H{sub 2}O were grown. • The elastic and piezoelastic coefficients were derived from ultrasonic resonance frequencies. • Thermal expansion (95 K–305 K) and heat capacity (113 K–323 K) were determined. • The orthorhombic structure shows pseudo-tetragonal elastic anisotropy at ambient conditions. • The crystal structure is stable in the investigated range (1–1600 bar, 95–303 K)

  13. Zero Thermal Expansion and Ferromagnetism in Cubic Sc1-xMxF3sub> (M = Ga, Fe) over a Wide Temperature Range

    SciTech Connect

    Hu, Lei; Chen, Jun; Fan, Longlong; Ren, Yang; Rong, Yangchun; Pan, Zhao; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2014-09-18

    The rare physical property of zero thermal expansion (ZTE) is intriguing because neither expansion nor contraction occurs with temperature fluctuations. Most ZTE, however, occurs below room temperature. It is a great challenge to achieve isotropic ZTE at high temperatures. Here we report the unconventional isotropic ZTE in the cubic (Sc1-xMx)F3sub> (M = Ga, Fe) over a wide temperature range (linear coefficient of thermal expansion (CTE), αl = 2.34 × 10-7 K-1, 300-900 K). Such a broad temperature range with a considerably negligible CTE has rarely been documented. The present ZTE property has been designed using the introduction of local distortions in the macroscopic cubic lattice by heterogeneous cation substitution for the Sc site. Even though the macroscopic crystallographic structure of (Sc0.85Ga0.05Fe0.1)F3sub> adheres to the cubic system (Pm3-m) according to the results of Xray diffraction, the local structure exhibits a slight rhombohedral distortion. This is confirmed by pair distribution function analysis of synchrotron radiation Xray total scattering. This local distortion may weaken the contribution from the transverse thermal vibration of fluorine atoms to negative thermal expansion, and thus may presumably be responsible for the ZTE. In addition, the present ZTE compounds of (Sc1-xMx)F3sub> can be functionalized to exhibit high-Tc ferromagnetism and a narrow-gap semiconductor feature. The present study shows the possibility of obtaining ZTE materials with multifunctionality in future work.

  14. Low-Temperature X-ray Diffraction Studies of [(CH{sub 3}){sub 2}NH{sub 2}]{sub 5}Cd{sub 3}Cl{sub 11} Crystals

    SciTech Connect

    Sheleg, A.U.; Zub, E.M.; Yachkovskii, A.Ya.; Kirpichnikova, L.F.

    2004-11-01

    [(CH{sub 3}){sub 2}NH{sub 2}]{sub 5}Cd{sub 3}Cl{sub 11} crystals are grown by the method of isothermal evaporation from saturated aqueous solutions containing dimethylamine and cadmium chlorides, [(CH{sub 3})2NH{sub 2}]Cl and CdCl{sub 2.5}H{sub 2}O. The crystal grown are studied by the X-ray diffraction method. It is established that the crystals are orthorhombic with the unit-cell parameters at room temperature a = 18.115 {+-} 0.004 A, b = 11.432 {+-} 0.002 A, and c = 15.821 {+-} 0.003 A. The unit-cell parameters a, b, and c of the [(CH{sub 3}){sub 2}NH{sub 2}]{sub 5}Cd{sub 3}Cl{sub 11} crystals are measured as functions of temperature in the temperature range 100-320 K. The data obtained were used to determine the thermal expansion coefficients along the main crystallographic axes. The temperature curves of the unit-cell parameters and thermal expansion coefficients showed pronounced anomalies in the vicinity of the temperatures T{sub 1} = 120, T{sub 2} = 150, and T{sub 3} = 180 K corresponding to the phase transitions in the [(CH{sub 3}){sub 2}NH{sub 2}]{sub 5}Cd{sub 3}Cl{sub 11} crystals. The crystals are also characterized by a pronounced anisotropy of thermal expansion.

  15. Mid-infrared supercontinuum generation based on cascaded Raman scattering in a few-mode As2S3sub> fiber pumped by a thulium-doped fiber laser.

    PubMed

    Yao, Jinmei; Zhang, Bin; Yin, Ke; Yang, Linyong; Hou, Jing; Lu, Qisheng

    2016-06-27

    By pumping a 1.7-m-long As2S3sub> fiber at 2050 nm directly, a fiber-based mid-infrared supercontinuum (SC) source with an output power of 366 mW is demonstrated. This is the first experimental demonstration to obtain such a mid-infrared SC in a piece of chalcogenide fiber pumped at 2 μm directly. The cut-off wavelength of the As2S3sub> fiber is 3.5 μm, indicating that it could support several modes at around 2 μm. It is found that nonlinear spectral broadening mechanisms in the few-mode chalcogenide fiber could be affected through adjusting the butt-coupling position. That is because different positions will excite different modes that correspondingly possess different nonlinearity and dispersion characteristics. When stimulated Raman scattering (SRS) corresponding to the excitation of the fundamental mode becomes dominant in this few-mode fiber, an efficient cascaded SRS-based SC is obtained with five Stokes peaks ranging from 2 μm to 3.4 μm. Results from numerical simulation are in accord with the experimental results, showing that it is feasible to obtain an SRS based mid-infrared SC in a step-index As2S3sub> fiber by using a 2 μm high peak power picosecond laser to pump directly. PMID:27410625

  16. The first Fe-based Na+-ion cathode with two distinct types of polyanions: Fe3sub>P5SiO19

    SciTech Connect

    Kan, W. H.; Huq, A.; Manthiram, A.

    2015-05-15

    We report the synthesis, structure, and electrochemistry of the first Na+-ion cathode with two distinct types of polyanions: Fe3sub>P5SiO19. The Fe-based cathode has a reversible capacity of ca. 70 mAh g-1; ca. 1.7 Na+ ions per formula can be inserted/extracted at an average voltage of 2.5 V versus Na+/Na.

  17. Sr{sub 3}Bi{sub 2}(SeO{sub 3}){sub 6}·H{sub 2}O: A novel anionic layer consisting of second-order Jahn–Teller (SOJT) distortive cations

    SciTech Connect

    Ahn, Hyun Sun; Lee, Eun Pyo; Chang, Hong-Young; Lee, Dong Woo; Ok, Kang Min

    2015-01-15

    A new layered bismuth selenite hydrate material, Sr{sub 3}Bi{sub 2}(SeO{sub 3}){sub 6}·H{sub 2}O has been synthesized through a hydrothermal reaction using SrCO{sub 3}, Bi{sub 2}O{sub 3}, SeO{sub 2}, and water as reagents. The crystal structure of the reported material has been determined by single crystal X-ray diffraction analysis. The anionic layered framework of Sr{sub 3}Bi{sub 2}(SeO{sub 3}){sub 6}·H{sub 2}O consists of polyhedra of second-order Jahn–Teller (SOJT) distortive cations, Bi{sup 3+} and Se{sup 4+}. Attributable to the variable and asymmetric coordination geometry of the constituent cations, a rich structural chemistry including uni-dimensional bands and linkers is observed in the layer. The material is thermally stable up to about 390 °C and starts decomposing due to the sublimation of SeO{sub 2} above the temperature. The UV–vis diffuse reflectance spectrum suggests a band gap of 3.3 eV. Elemental analysis, infrared spectrum, local dipole moment calculations, and electronic structure calculations are also reported. - Graphical abstract: Ball-and-stick and polyhedral representation of Sr{sub 3}Bi{sub 2}(SeO{sub 3}){sub 6}·H{sub 2}O in the ab-plane. The stereoactive lone pairs are visualized around the Bi{sup 3+} and Se{sup 4+} as lobelike isosurfaces through ELF calculations with η=0.9. - Highlights: • A novel layered bismuth selenite, Sr{sub 3}Bi{sub 2}(SeO{sub 3}){sub 6}·H{sub 2}O has been hydrothermally synthesized. • The layer is only composed of second-order Jahn–Teller distortive cations in asymmetric environments. • The stereoactive lone pairs are visualized as lobelike isosurfaces through ELF calculations.

  18. Resolving the grain boundary and lattice impedance of hot-pressed Li7La3sub>Zr2O12 garnet electrolytes

    SciTech Connect

    Tenhaeff, Wyatt E.; Wang, Yangyang; Sokolov, Alexei P.; Wolfenstine, Jeff; Sakamoto, Jeffrey; Dudney, Nancy J.; Rangasamy, Ezhiyl

    2013-07-24

    Here, the cubic-stabilized garnet solid electrolyte with a nominal composition of Li6.28Al0.24La3sub>Zr2O12 is thoroughly characterized by impedance spectroscopy. By varying the frequency of the applied AC signal over 11 orders of magnitude for characterizations from –100 to +60 °C, the relative contributions of grain and grain boundary conduction are unambiguously resolved.

  19. Connecting thermoelectric performance and topological-insulator behavior: Bi2Te3sub> and Bi2Te2Se from first principles

    SciTech Connect

    Shi, Hongliang; Parker, David S.; Du, Mao-Hua; Singh, David J.

    2015-01-20

    Thermoelectric performance is of interest for numerous applications such as waste-heat recovery and solid-state energy conversion and will be seen to be closely connected to topological-insulator behavior. In this paper, we here report first-principles transport and defect calculations for Bi2Te2Se in relation to Bi2Te3sub>. The two compounds are found to contain remarkably different electronic structures in spite of being isostructural and isoelectronic. We also discuss these results in terms of the topological-insulator characteristics of these compounds.

  20. Multiple bonds between transition metals and main-group elements. 73. Synthetic routes to rhenium(V) alkyl and rhenium(VII) alkylidyne complexes. X-ray crystal structures of (. eta. sup 5 -C sub 5 Me sub 5 )Re( double bond O)(CH sub 3 )(CH sub 2 C(CH sub 3 ) sub 3 ) and (. eta. sup 5 -C sub 5 Me sub 5 )(Br) sub 3 Re triple bond CC(CH sub 3 ) sub 3

    SciTech Connect

    Herrmann, W.A.; Felixberger, J.K.; Anwander, R.; Herdtweck, E.; Kiprof, P.; Riede, J. )

    1990-05-01

    Dialkyloxo({eta}{sup 5}pentamethylcyclopentadienyl)rhenium(V) complexes ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(CH{sub 3})R{prime}(R{prime} = C{sub 2}H{sub 5}, CH{sub 2}Si(CH{sub 3}){sub 3}, CH{sub 2}C(CH{sub 3}){sub 3}), 1c-e, have become accessible through alkylation of ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(Cl)(CH{sub 3}) (7) with R{prime}MgCl. 1c-e are the first rhenium complexes containing different alkyl ligands. The neopentyl derivative 1e (R{prime} = CH{sub 2}C(CH{sub 3}){sub 3}) crystallizes in the orthorhombic space group Pbca with a = 960.7 (2), b = 2.844.5 (4), c = 1,260.7 (2) pm, and Z = 8. The X-ray crystal structure was refined to R{sub W} = 3.9%. The chiral molecule shows a distorted tetrahedral geometry around the rhenium center. The tribromide 3b has been structurally characterized. Brown crystals of 3b belong to space group P2{sub 1}/c with unit cell dimensions a = 1,311.5 (2), b = 723.0 (1), c = 1,901.6 (2) pm, {beta} = 92.68 (1){degree}, and Z = 4. The structure exhibits a four-legged piano stool geometry with no trans influence of the neopentylidyne ligand to the bromine atom.

  1. Experimental observations of the effects of shear rates and particle concentration on the viscosity of Fe2O3sub>-deionized water nanofluids

    SciTech Connect

    Phuoc, Tran X.; Massoudi, Mehrdad

    2009-07-01

    We report here some experimental observations on the effects of the shear rates and particle volume fractions on the shear stress and the viscosity of Fe2O3sub>-DW nanofluids with Polyvinylpyrrolidone (PVP) or Poly(ethylene oxide), PEO, as a dispersant. The measurements were performed using a Brookfield DV-II Pro Viscometer with a small sample adapter (SSA18/13RPY). The results reported here clearly demonstrate that these fluids had a yield stress and behaved as shear-thinning non-Newtonian fluids. The yield stress decreased to the Newtonian limit, as the particle volume fraction decreased and still existed even at very low particle volume fractions. It was observed that the prepared Fe2O3sub>-DW-0.2% PVP nanofluids with particle volume fraction Φ less than 0.02 still behaved as a Newtonian fluid. As the volume fraction was increased beyond 0.02, the fluid became non-Newtonian with shear-thinning behavior. Similar results were also observed when DW-0.2% PEO was used. The suspension, however, exhibited its non-Newtonian, shear-thinning behavior at Φ as low as 0.02.

  2. Tetrahedrally coordinated disordered Cu2SnS3sub>-Cu2ZnSnS4-ZnS alloys with tunable optical and electronic properties

    SciTech Connect

    Erslev, Peter T.; Young, Matthew R.; Li, Jian V.; Siah, Sin Cheng; Chakraborty, Rupak; Du, Hui; Lad, Robert J.; Buonassisi, Tonio; Teeter, Glenn

    2014-08-28

    A key requirement for large-scale deployment of photovoltaic technologies is the development of highly functional materials with controllable opto-electronic properties. In this work, we report on the room-temperature synthesis of disordered alloys of the Earth-abundant, tetrahedrally coordinated semiconductors Cu2SnS3sub>, Cu2ZnSnS4 (CZTS), and ZnS as (Cu2SnS3sub>)1-x(ZnS)x. The resulting disordered semiconductors are found to have continuously and independently tunable optical and electronic properties. Quasi-isovalent alloying on the cation sublattice allows the optical band gap to be varied continuously from 1.1 eV to 2.8 eV. Aliovalent alloying leads to independent control of carrier concentration over at least three orders of magnitude. A conceptual framework describing these disordered materials is presented, in which the structural disorder, constrained by local tetrahedral coordination of both anions and cations, leads to the observed high degree of tunability of the opto-electronic properties. These materials are not only independently interesting, but the developed framework also applies to the opto-electronic properties of kesterite CZTS materials as well as provides a basis for the development of new semiconductors.

  3. Methylene migration and coupling on a non-reducible metal oxide: The reaction of dichloromethane on stoichiometric α-Cr2O3sub>(0001)

    SciTech Connect

    Dong, Yujung; Brooks, John D.; Chen, Tsung-Liang; Mullins, David R.; Cox, David F.

    2014-09-17

    The reaction of CH2Cl2 over the nearly-stoichiometric α-Cr2O3sub>(0001) surface produces gas phase ethylene, methane and surface chlorine adatoms. The reaction is initiated by the decomposition of CH2Cl2 into surface methylene and chlorine. Photoemission indicates that surface cations are the preferred binding sites for both methylene and chlorine adatoms. Two reaction channels are observed for methylene coupling to ethylene in temperature-programmed desorption (TPD). A desorption-limited, low-temperature route is attributed to two methylenes bound at a single site. The majority of ethylene is produced by a reaction-limited process involving surface migration (diffusion) of methylene as the rate-limiting step. DFT calculations indicate the surface diffusion mechanism is mediated by surface oxygen anions. The source of hydrogen for methane formation is adsorbed background water. Chlorine adatoms produced by the dissociation of CH2Cl2 deactivate the surface by simple site-blocking of surface Cr3+ sites. Finally, a comparison of experiment and theory shows that DFT provides a better description of the surface chemistry of the carbene intermediate than DFT+U using reported parameters for a best representation of the bulk electronic properties of α-Cr2O3sub>.

  4. Evidence and detailed study of a second-order phase transition in the (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] organic-inorganic hybrid material

    SciTech Connect

    Yangui, A.; Pillet, S.; Garrot, D.; Boukheddaden, K.; Triki, S.; Abid, Y.

    2015-03-21

    The thermal properties of the organic-inorganic hybrid material (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] are investigated using diffuse reflectivity, spectroscopic ellipsometry, differential scanning calorimetry, Raman spectroscopy, and X-ray diffraction. The diffuse reflectivity, performed in heating mode, clearly evidences the presence of a singularity at 336 K. This is confirmed by the temperature dependence of the spectroscopic ellipsometry spectra, which points out a second-order phase transition at 336 K with a critical exponent ∼0.5. Differential scanning calorimetry measurements on a polycrystalline powder of (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] show a reversible phase transition detected at T{sub C} = 336 K without hysteresis. Raman spectroscopy data suggest that this transition arises from a change in the interactions between inorganic sheets (([PbI{sub 4}]{sup 2−}){sub ∞}) and organic protonated molecules ([C{sub 6}H{sub 11}NH{sub 3}]{sup +}). The structural analysis from power X-ray diffraction reveals an incomplete order-disorder transition of the cyclohexylammonium cation, causing a subtle contraction of the inter-plane distance. The transition results from repulsive close contacts between the organic molecules in the interlayer spacing.

  5. (CN{sub 3}H{sub 6}){sub 2} {center_dot} Zn(HPO{sub 3}){sub 2}: A Three-Dimensional Framework Zincophosphite Containing Polyhedral 12-Rings

    SciTech Connect

    HARRISON,WILLIAM T.A.; PHILLIPS,MARK L.F.; NENOFF,TINA M.

    2000-10-24

    The solution-mediated synthesis and single crystal structure of (CN{sub 3}H{sub 6}){sub 2} {center_dot} Zn(HPO{sub 3}){sub 2} are reported. This phase is built up from a three-dimensional framework of vertex-linked ZnO{sub 4} and HPO{sub 3} building units encapsulating the extra-framework guanidinium cations. The structure is stabilized by template-to-framework hydrogen bonding. The inorganic framework shows a surprising similarity to those of some known zinc phosphates. Crystal data: (CN{sub 3}H{sub 6}){sub 2} {center_dot} Zn(HPO{sub 3}){sub 2}, AI,= 345.50, orthorhombic, space group Fdd2 (No. 43), a = 15.2109 (6) {angstrom}, b = 11.7281 (5) {angstrom}, c = 14.1821 (6) {angstrom}, V = 2530.0 (4){angstrom}{sup 3}, Z = 8, T = 298 (2)K, R(F) = 0.020, wR(F) = 0.025.

  6. Growth Temperature Dependence of Si Doping Efficiency and Compensating Deep Level Defect Incorporation in Al0.7Ga0.3sub>N

    SciTech Connect

    Armstrong, Andrew; Moseley, Michael William; Allerman, Andrew A.; Crawford, Mary H.; Wierer, Jonathan

    2015-05-11

    The growth temperature dependence of Si doping efficiency and deep level defect formation was investigated for n-type Al0.7Ga0.3sub>N. It was observed that dopant compensation was greatly reduced with reduced growth temperature. Furthermore, deep level optical spectroscopy and lighted capacitance-voltage were used to understand the role of acceptor-like deep level defects on doping efficiency. Deep level defects were observed at 2.34 eV, 3.56 eV, and 4.74 eV below the conduction band minimum. The latter two deep levels were identified as the major compensators because the reduction in their concentrations at reduced growth temperature correlated closely with the concomitant increase in free electron concentration. Possible mechanisms for the strong growth temperature dependence of deep level formation are considered, which includes thermodynamically driven compensating defect formation that can arise for a semiconductor with very large band gap energy, such as Al0.7Ga0.3sub>N.

  7. The high temperature superconductor YBa2Cu3sub>O7-δ: symmetry of the order parameter, and gradiometers for biomagnetic applications

    SciTech Connect

    Kouznetsov, Konstantin Alexander

    1999-12-01

    The cuprate YBa2Cu3sub>O7-δ is the material that drives the majority of the technological applications of high transition temperature (Tc) superconductors, particularly in the area of superconducting electronics. Despite the widespread use of high-Tc superconducting materials in a variety of applications, the nature of the superconducting state in these materials remains unknown since their discovery more than a decade ago. Many properties of the high-Tc superconductors are determined by their order parameter, which is a wavefunction describing the superconducting condensate. The symmetry of the order parameter in cuprates has been the subject of intensive investigation, leading to conflicting sets of results. Some experiments supported conventional, s-wave symmetry of the order parameter, while others indicated an unconventional, d-wave symmetry. The first part of this thesis is an experimental study of the symmetry of the order parameter in YBa2Cu3sub>O7-δ. A new class of phase sensitive experiments is described that involve Josephson tunneling along the c-axis of twinned crystals of YBa2Cu3sub>O7-δ. These experiments showed that an s-wave component must reverse sign across the twin boundary, providing direct evidence for a mixed, s+d symmetry of the order parameter in YBa2Cu3sub>O7-δ, and thereby reconciling two conflicting sets of previous findings and establishing the dominant d-wave pairing symmetry. The second part of the thesis focuses on practical applications of YBa2Cu3sub>O7-δ in superconducting electronics. The authors introduce a novel Superconducting Quantum Interference Device (SQUID) gradiometer. The principle of operation of these long baseline high-T{sub c} SQUID gradiometers is based on the inductive coupling of the input coil of a planar flux transformer to the

  8. Electrocatalytic Oxidation of Formate by [Ni(PR2NR'2)2(CH3sub>CN)]2+ Complexes

    SciTech Connect

    Galan, Brandon R.; Schöffel, Julia; Linehan, John C.; Seu, Candace; Appel, Aaron M.; Roberts, John A. S.; Helm, Monte L.; Kilgore, Uriah J.; Yang, Jenny Y.; DuBois, Daniel L.; Kubiak, Clifford P.

    2011-08-17

    [Ni(PR2NR'2)2(CH3sub>CN)]2+ complexes with R = Ph, R' = 4-MeOPh or R = Cy, R' = Ph , and a mixed-ligand [Ni(PR2NR'2)(PR"2NR'2)(CH3sub>CN)]2+ with R = Cy, R' = Ph, R" = Ph, have been synthesized and characterized by single-crystal X-ray crystallography. These and previously reported complexes are shown to be electrocatalysts for the oxidation of formate in solution to produce CO2, protons, and electrons, with rates that are first-order in catalyst and formate at formate concentrations below ~0.04 M (34 equiv). At concentrations above ~0.06 M formate (52 equiv), catalytic rates become nearly independent of formate concentration. For the catalysts studied, maximum observed turnover frequencies vary from <1.1 to 15.8 s–1 at room temperature, which are the highest rates yet reported for formate oxidation by homogeneous catalysts. These catalysts are the only base-metal electrocatalysts as well as the only homogeneous electrocatalysts reported to date for the oxidation of formate. An acetate complex demonstrating an η1-OC(O)CH3sub> binding mode to nickel has also been synthesized and characterized by single-crystal X-ray crystallography. Based on this structure and the electrochemical and spectroscopic data, a mechanistic scheme for electrocatalytic formate oxidation is proposed which involves formate binding followed by a rate-limiting proton and two-electron transfer step accompanied by CO2 liberation. Finally, the pendant amines have been demonstrated to be essential for electrocatalysis, as no activity toward formate oxidation was observed for the similar [Ni(depe)2]2+ (depe = 1,2-bis(diethylphosphino)ethane) complex.

  9. Preparations of nano-particles, nano-composites and fibers of ZnO from an amide precursor: Photocatalytic decomposition of (CH{sub 3}){sub 2}S{sub 2} in a continuous flow reactor

    SciTech Connect

    Daniele, Stephane . E-mail: daniele@catalyse.cnrs.fr; Ghazzal, Mohamed N.; Hubert-Pfalzgraf, Liliane G.; Duchamp, Christian; Guillard, Chantal; Ledoux, Gilles

    2006-12-14

    High surface area hexagonal ZnO nano-particles were obtained at room temperature from hydrolysis of the amide derivative Zn[N(SiMe{sub 3}){sub 2}]{sub 2}. The same procedure applied on silica or cellulose substrates led to homogeneous crack-free hybrid materials for which micro- down to nano-meter replication into ZnO cloth was achieved by calcination at 700 deg. C. These materials were characterized by FT-IR, UV-vis, photoluminescence, X-ray diffraction (XRD) and transmission electron microscopy (TEM). They demonstrated enhanced photocatalytic degradation of a tough pollutant such as CH{sub 3}SSCH{sub 3} compared with commercial ZnO powder.

  10. On photo-expansion and microlens formation in (GeS{sub 2}){sub 0.74}(Sb{sub 2}S{sub 3}){sub 0.26} chalcogenide glass

    SciTech Connect

    Knotek, P.; Tichy, L.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Photo-expansion induced by sub-band-gap photons in GeSbS glass. ► One-step microlens formation. ► The topography of the microlenses detected by AFM and DHM. ► The good mechanical characteristics of the microlenses were obtained. ► Local light-induced overheating of the glass. -- Abstract: Photo-expansion of the bulk of (GeS{sub 2}){sub 0.74}(Sb{sub 2}S{sub 3}){sub 0.26} glass induced by sub-gap photons is studied employing specifically atomic force microscopy (AFM) namely an atomic force acoustic microscopy (AFAM) and a force spectroscopy and digital holographic microscopy. The results are discussed with respect to the possible role of light induced overheating in the process of photo-expansion.

  11. Low-temperature thermal conductivity of antiferromagnetic S = 1/2 chain material CuCl{sub 2}·2((CH{sub 3}){sub 2}SO)

    SciTech Connect

    Ke, W. P.; Zhang, F. B.; Zhao, Z. Y.; Fan, C.; Sun, X. F.; Shi, J.; Zhao, X.

    2014-05-07

    We study the heat transport of S = 1/2 chain compound CuCl{sub 2}·2((CH{sub 3}){sub 2}SO) along the b axis (vertical to the chain direction) at very low temperatures. The zero-field thermal conductivity (κ) shows a distinct kink at about 0.9 K, which is related to the long-range antiferromagnetic (AF) transition. With applying magnetic field along the c axis, κ(H) curves also show distinct changes at the phase boundaries between the AF and the high-field disordered states. These results indicate a strong spin-phonon interaction and the magnetic excitations play a role in the b-axis heat transport as phonon scatterers.

  12. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3sub> perovskite under high pressure

    SciTech Connect

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu -Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-12-16

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3sub> perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. We find, consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.

  13. Magnetic and Crystallographic Studies of Mg-Herbertsmithite, γ-Cu3sub>Mg(OH)6Cl2-A New S = 1/2 Kagome Magnet and Candidate Spin Liquid

    SciTech Connect

    Colman, R H; Sinclair, A; Wills, A S

    2011-09-06

    Studies are presented of the synthesis, crystal structure, and magnetic properties of the new quantum kagome magnet Mg-herbertsmithite, γ-Cu3sub>Mg(OH)6Cl2. The material features strong antiferromagnetic exchange characterized by a Weiss temperature of θw ≃ -284 K and a gradual buildup of short-ranged antiferromagnetic correlations upon cooling. No magnetic transition is observed until TC ≃ 4-5 K when a small ferromagnetic component orders; susceptibility measurements indicate that this transition is due to an impurity and that there is no evidence of a magnetic transition in the herbertsmithite phase whose spins appear to remain dynamic down to the lowest temperatures studied.

  14. Second harmonic generation and waveguide properties in perovskite Na0.5Bi0.5TiO3sub> nanowires.

    PubMed

    Zhou, Hong; Wang, Xiaoxia; Zhuang, Xiujuan; Pan, Anlian

    2016-08-15

    Nanowires with nonlinear optical properties such as second harmonic generation (SHG) are essential elements for an all-optical integrated photonic circuit. However, the existing materials face challenges for applications in a wide wavelength range. To cope with the challenges, ferroelectric nanowires are considered promising candidates, especially for SHG applications. In this Letter, we study SHG and waveguide properties in perovskite Na0.5Bi0.5TiO3sub> (NBT) nanowires. Strong SHG is observed in NBT nanowires illuminated by a 1064 nm laser radiation. For the waveguide studies, these NBT nanowires show a waveguide propagation loss as low as 0.01 dB/μm at 532 nm. This work suggests potential applications in future integrated optics with NBT nanowires. PMID:27519093

  15. Synthesis and crystal structure of bis(3-ammoniumphenyl) sulfone dinitrate [C{sub 12}H{sub 14}N{sub 2}O{sub 2}S](NO{sub 3}){sub 2}

    SciTech Connect

    Mahroug, A.; Belhouchet, M. Mhiri, T.

    2013-07-15

    A new organic nitrate with the formula [C{sub 12}H{sub 14}N{sub 2}O{sub 2}S](NO{sub 3}){sub 2}, has been prepared and analyzed by X-ray diffraction. This compound crystallizes in the orthorhombic system: a = 16.771 (3), b = 13.884(2), c = 13.884(2) A, V = 3232.7(7)A{sup 3}, Z = 8, space group Pna2{sub 1}. Crystal structure can be described as a succession of organic and inorganic layers parallel to b, c plane. H-bonds between the different species play an important role in the three-dimensional network cohesion.

  16. Second harmonic generation at 399 nm resonant on the 1S0-1P1 transition of ytterbium using a periodically poled LiNbO3sub> waveguide.

    PubMed

    Kobayashi, Takumi; Akamatsu, Daisuke; Nishida, Yoshiki; Tanabe, Takehiko; Yasuda, Masami; Hong, Feng-Lei; Hosaka, Kazumoto

    2016-05-30

    We demonstrate a compact and robust method for generating a 399-nm light resonant on the 1S0 - 1P1 transition in ytterbium using a single-pass periodically poled LiNbO3sub> waveguide for second harmonic generation (SHG). The obtained output power at 399 nm was 25 mW when a 798-nm fundamental power of 380 mW was coupled to the waveguide. We observed no degradation of the SHG power for 13 hours with a low power of 6 mW. The obtained SHG light has been used as a seed light for injection locking, which provides sufficient power for laser cooling ytterbium. PMID:27410134

  17. Fluorocarbon assisted atomic layer etching of SiO2 and Si using cyclic Ar/C4F8 and Ar/CHF3sub> plasma

    SciTech Connect

    Metzler, Dominik; Li, Chen; Engelmann, Sebastian; Bruce, Robert L.; Joseph, Eric A.; Oehrlein, Gottlieb S.

    2015-11-11

    The need for atomic layer etching (ALE) is steadily increasing as smaller critical dimensions and pitches are required in device patterning. A flux-control based cyclic Ar/C4F8 ALE based on steady-state Ar plasma in conjunction with periodic, precise C4F8 injection and synchronized plasma-based low energy Ar+ ion bombardment has been established for SiO2.1 In this work, the cyclic process is further characterized and extended to ALE of silicon under similar process conditions. The use of CHF3sub> as a precursor is examined and compared to C4F8. CHF3sub> is shown to enable selective SiO2/Si etching using a fluorocarbon (FC) film build up. Other critical process parameters investigated are the FC film thickness deposited per cycle, the ion energy, and the etch step length. Etching behavior and mechanisms are studied using in situ real time ellipsometry and X-ray photoelectron spectroscopy. Silicon ALE shows less self-limitation than silicon oxide due to higher physical sputtering rates for the maximum ion energies used in this work, ranged from 20 to 30 eV. The surface chemistry is found to contain fluorinated silicon oxide during the etching of silicon. As a result, plasma parameters during ALE are studied using a Langmuir probe and establish the impact of precursor addition on plasma properties.

  18. Organometallic complexes of bulky, optically active, C3sub>-symmetric tris(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate (ToP*)

    SciTech Connect

    Xu, Songchen; Magoon, Yitzhak; Reinig, Regina R.; Schmidt, Bradley M.; Ellern, Arkady; Sadow, Aaron D.

    2015-07-16

    A bulky, optically active monoanionic scorpionate ligand, tris(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate (ToP*), is synthesized from the naturally occurring amino acid l-valine as its lithium salt, Li[ToP*] (1). That compound is readily converted to the thallium complex Tl[ToP*] (2) and to the acid derivative H[ToP*] (3). Group 7 tricarbonyl complexes ToP*M(CO)3sub> (M = Mn (4), Re (5)) are synthesized by the reaction of MBr(CO)5 and Li[ToP*] and are crystallographically characterized. The νCO bands in their infrared spectra indicate that π back-donation in the rhenium compounds is greater with ToP* than with non-methylated tris(4S-isopropyl-2-oxazolinyl)phenylborate (ToP). The reaction of H[ToP*] and ZnEt2 gives ToP*ZnEt (6), while ToP*ZnCl (7) is synthesized from Li[ToP*] and ZnCl2. The reaction of ToP*ZnCl and KOtBu followed by addition of PhSiH3sub> provides the zinc hydride complex ToP*ZnH (8). In this study, compound 8 is the first example of a crystallographically characterized optically active zinc hydride. We tested its catalytic reactivity in the cross-dehydrocoupling of silanes and alcohols, which provided Si-chiral silanes with moderate enantioselectivity.

  19. Resolving the structure of Ti3sub>C2Tx MXenes through multilevel structural modeling of the atomic pair distribution function

    SciTech Connect

    Wesolowski, David J.; Wang, Hsiu -Wen; Page, Katharine L.; Naguib, Michael; Gogotsi, Yury

    2015-12-08

    MXenes are a recently discovered family of two-dimensional (2D) early transition metal carbides and carbonitrides, which have already shown many attractive properties and a great promise in energy storage and many other applications. However, a complex surface chemistry and small coherence length has been an obstacle in some applications of MXenes, also limiting accuracy of predictions of their properties. In this study, we describe and benchmark a novel way of modeling layered materials with real interfaces (diverse surface functional groups and stacking order between the adjacent monolayers) against experimental data. The structures of three kinds of Ti3sub>C2Tx MXenes (T stands for surface terminating species, including O, OH, and F) produced under different synthesis conditions were resolved for the first time using atomic pair distribution function obtained by high-quality neutron total scattering. The true nature of the material can be easily captured with the sensitivity of neutron scattering to the surface species of interest and the detailed third-generation structure model we present. The modeling approach leads to new understanding of MXene structural properties and can replace the currently used idealized models in predictions of a variety of physical, chemical and functional properties of Ti3sub>C2-based MXenes. Furthermore, the developed models can be employed to guide the design of new MXene materials with selected surface termination and controlled contact angle, catalytic, optical, electrochemical and other properties. We suggest that the multi-level structural modeling should form the basis for a generalized methodology on modeling diffraction and pair distribution function data for 2D and layered materials.

  20. Electrocatalytic Oxidation of Formate by [Ni(P R 2 N R' 2 ) 2 (CH 3sub> CN)] 2+ Complexes

    SciTech Connect

    Galan, Brandon R.; Schöffel, Julia; Linehan, John C.; Seu, Candace; Appel, Aaron M.; Roberts, John A. S.; Helm, Monte L.; Kilgore, Uriah J.; Yang, Jenny Y.; DuBois, Daniel L.; Kubiak, Clifford P.

    2011-08-17

    New [Ni(PR2NR`2)2+(CH3sub>CN)]2+ complexes with R = Ph, R` = 4-MeOPh; R = Cy, R` = Ph and a mixed ligand [Ni(PR2NR`2)(PR``2NR`2)]2+ with R = Cy, R` = Ph, R`` = Ph have been synthesized and characterized by single crystal X-ray crystallography. These complexes are shown to be electrocatalysts for the oxidation of formate in solution to produce CO2, protons, and electrons with rates which are first order in catalyst and in formate at formate concentrations below approximately 0.05 M. For the catalysts studied, maximum observed turnover frequencies vary from <1.1 s-1 to 12.5 s-1 at room temperature, which are the highest rates yet reported for formate oxidation by homogeneous catalysts. A mechanistic scheme is proposed which involves an initial nickel complex bound <1-OC(O)H followed by a rate limiting hydride transfer step. An acetate complex demonstrating the η1-OC(O)CH3sub> binding mode to nickel has also been synthesized and characterized by single crystal X-ray crystallography. The pendant amines have been demonstrated to be essential for this electrocatalytic activity as no activity toward formate was found for the similar [Ni(depe)2][BF4]2+ (depe = diethylphosphinoethane) complex. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  1. Extended networks, porous sheets, and chiral frameworks. Thorium materials containing mixed geometry anions: Structures and properties of Th(SeO{sub 3})(SeO{sub 4}), Th(IO{sub 3}){sub 2}(SeO{sub 4})(H{sub 2}O){sub 3}.H{sub 2}O, and Th(CrO{sub 4})(IO{sub 3}){sub 2}

    SciTech Connect

    Sullens, Tyler A.; Almond, Philip M.; Byrd, Jessica A.; Beitz, James V.; Bray, Travis H.; Albrecht-Schmitt, Thomas E. . E-mail: albreth@auburn.edu

    2006-04-15

    Three novel Th(IV) compounds containing heavy oxoanions, Th(SeO{sub 3})(SeO{sub 4}) (1), Th(IO{sub 3}){sub 2}(SeO{sub 4})(H{sub 2}O){sub 3}.H{sub 2}O (2), and Th(CrO{sub 4})(IO{sub 3}){sub 2} (3), have been synthesized under mild hydrothermal conditions. Each of these three distinct structures contain trigonal pyramidal and tetrahedral oxoanions. Compound 1 adopts a three-dimensional structure formed from ThO{sub 9} tricapped trigonal prisms, trigonal pyramidal selenite, SeO{sub 3}{sup 2-}, anions containing Se(IV), and tetrahedral selenate, SeO{sub 4}{sup 2-}, anions containing Se(VI). The structure of 2 contains two-dimensional porous sheets and occluded water molecules. The Th centers are found as isolated ThO{sub 9} tricapped trigonal prisms and are bound by four trigonal pyramidal iodate anions, two tetrahedral selenate anions, and three coordinating water molecules. In the structure of 3, the Th(IV) cations are found as ThO{sub 9} tricapped trigonal prisms. Each Th center is bound by six IO{sub 3}{sup 1-} anions and three CrO{sub 4}{sup 2-} anions forming a chiral three-dimensional structure. Second-harmonic generation of 532nm light from 1064nm radiation by a polycrystalline sample of 3 was observed. Crystallographic data (193K, MoK{alpha}, {lambda}=0.71073): 1; monoclinic, P2{sub 1}/c; a=7.0351(5)A, b=9.5259(7)A, c=9.0266(7)A, {beta}=103.128(1), Z=4, R(F)=2.47% for 91 parameters with 1462 reflections with I>2{sigma}(I); 2, monoclinic, P2{sub 1}/n, a=7.4889(9)A, b=8.002(1)A, c=20.165(3)A, {beta}=100.142(2), Z=4, R(F)=4.71% for 158 parameters with 2934 reflections with I>2{sigma}(I); 3, orthorhombic, P2{sub 1}2{sub 1}2{sub 1}, a=7.3672(5)A, b=9.3617(6)A, c=11.9201(7)A, Z=4, R(F)=2.04% for 129 parameters with 2035 reflections with I>2{sigma}(I)

  2. Magnetic and Magnetotransport Properties of (Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3}){sub 1-x}/NiO{sub x} Composites

    SciTech Connect

    Chand, Umesh; Yadav, Kamlesh; Varma, G. D.; Gaur, Anurag

    2011-07-15

    In this paper, we report the structural, magnetic and magnetotransport properties of (Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3}){sub 1-x}/NiO{sub x}(x = 0, 0.05, 0.10, 0.15 and 0.20) composites samples. The composite samples have been synthesized in such a manner so that there is no reaction between Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3}(PSMO) and NiO. This has been confirmed by XRD and FESEM results. The magnetic measurements show reduction in ferromagnetic ordering in the composite samples with increasing level of NiO. Furthermore, incorporation of NiO phase into Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3} matrix lowers the metal-insulator transition temperature (TIM) and increases the resistance of composites. An enhancement in magnetoresistance (MR) is observed at low temperature, below 140 K, for the composites with x = 0.05, 0.10 and 0.15 and at high temperature (298K) for all the composites at applied magnetic field H = 5 kOe. It is suggested that the higher value of MR at temperature below 140 K is low field magnetoresistance (LFMR) caused by spin polarized tunneling, whereas at around room temperature it is caused by magnetic disordering.

  3. Experimental determination of valence band maxima for SrTiO3sub>,TiO2, and SrO and the associated valence band offsets with Si(001)

    SciTech Connect

    Chambers, Scott A.; Droubay, Timothy C.; Kaspar, Tiffany C.; Gutowski, Maciej S.

    2004-08-20

    We address the issue of accurate determination of the valence band maximum (VBM) for SrTiO3sub>(001) single crystals and epitaxial films, as well as TiO2(001) anatase and SrO epitaxial films. These measurements are of critical importance in determining valence band offsets in heterojunctions of these oxides with Si. Three different methods are analyzed: (1) fitting a Gaussian broadened theoretical density of states to the x-ray photoelectron valence band spectrum; (2) finding the intersection of a regression line that spans the linear portion of the x-ray photoelectron valence band leading edge with the background between the valence band maximum and the Fermi level; and (3) determining the energy at which high-resolution ultraviolet photoemission intensity at the leading edge goes to zero. We find that method 1 yields physically unreasonable results when used in conjunction with density functional theory because the latter does not predict the detailed shape of the valence bands in these oxides with sufficient accuracy. In contrast, methods 2 and 3 give physically reasonable results that are in good mutual agreement. The difference in VBM between method 1 and methods 2 and 3 is 0.4–0.6 eV, depending on the oxide. Methods 2 and 3 yield the most reliable VBM, provided the experiments are carried out with adequate energy resolution.

  4. Band alignment of epitaxial SrTiO{sub 3} thin films with (LaAlO{sub 3}){sub 0.3}-(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (001)

    SciTech Connect

    Comes, Ryan B.; Chambers, Scott A.; Xu, Peng; Jalan, Bharat

    2015-09-28

    SrTiO{sub 3} (STO) epitaxial thin films and heterostructures are of considerable interest due to the wide range of functionalities they exhibit. The alloy perovskite (LaAlO{sub 3}){sub 0.3}-(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (LSAT) is commonly used as a substrate for these material structures due to its structural compatibility with STO and the strain-induced ferroelectric response in STO films grown on LSAT. However, surprisingly little is known about the electronic properties of the STO/LSAT interface despite its potentially important role in affecting the overall electronic structure of system. We examine the band alignment of STO/LSAT heterostructures using x-ray photoelectron spectroscopy for epitaxial STO films deposited using two different molecular beam epitaxy approaches. We find that the valence band offset ranges from +0.2(1) eV to −0.2(1) eV depending on the film surface termination. From these results, we extract a conduction band offset from −2.4(1) eV to −2.8(1) eV, indicating that the conduction band edge is more deeply bound in STO and that LSAT will not act as a sink or trap for electrons in the supported film or multilayer.

  5. In-situ luminescence monitoring of ion-induced damage evolution in SiO2 and Al2O3sub>

    SciTech Connect

    Crespillo, Miguel L.; Graham, Joseph T.; Zhang, Yanwen; Weber, William J.

    2015-12-17

    Real-time, in-situ ionoluminescence measurements provide information of evolution of emission bands with ion fluence, and thereby establish a correlation between point defect kinetics and phase stability. Using fast light ions (2 MeV H and 3.5 He MeV) and medium mass-high energy ions (8 MeV O, E=0.5 MeV/amu), scintillation materials of a-SiO2, crystalline quartz, and Al2O3sub> are comparatively investigated at room temperature with the aim of obtaining a further insight on the structural defects induced by ion irradiation and understand the role of electronic energy loss on the damage processes. For more energetic heavy ions, the electronic energy deposition pattern offers higher rates of excitation deeper into the material and allows to evaluate the competing mechanisms between the radiative and non-radiative de-excitation processes. Irradiations with 8 MeV O ions have been selected corresponding to the electronic stopping regime, where the electronic stopping power is dominant, and above the critical amorphization threshold for quartz. Lastly, the usefulness of IBIL and its specific capabilities as a sensitive tool to investigate the material characterization and evaluation of radiation effects are demonstrated.

  6. Characterizing the Li–Li7La3sub>Zr2O12 interface stability and kinetics as a function of temperature and current density

    SciTech Connect

    Sharafi, Asma; Meyer, Harry M.; Nanda, Jagjit; Wolfenstine, Jeff; Sakamoto, Jeff

    2015-10-27

    The stability and kinetics of the Li–Li7La3sub>Zr2O12 (LLZO) interface were characterized as a function of temperature and current density. Polycrystalline LLZO was densified using a rapid hot-pressing technique achieving 97 ± 1% relative density, and <10% grain boundary resistance; effectively consisting of an ensemble of single LLZO crystals. It was determined that by heating to 175 °C, the room temperature Li-LLZO interface resistance decreases dramatically from 5822 (as-assembled) to 514 Ω cm2; a > 10-fold decrease. In characterizing the maximum sustainable current density (or critical current density – CCD) of the Li-LLZO interface, several signs of degradation were observed. In DC cycling tests, significant deviation from Ohmic behavior was observed. In post-cycling tests, regions of metallic Li were observed; propagating parallel to the ionic current. For the cells cycled at 30, 70, 100, 130 and 160 °C, the CCD was determined to be 50, 200, 800, 3500, and 20000 μA cm–2, respectively. As a result, the relationships and phenomena observed in this work can be used to better understand the Li-LLZO interface stability, enabling the use of batteries employing Li metal anodes.

  7. Remarkable charge-trapping efficiency of the memory device with (TiO{sub 2}){sub 0.8}(Al{sub 2}O{sub 3}){sub 0.1} composite charge-storage dielectric

    SciTech Connect

    Jiang, K.; Ou, X.; Cao, Z. Y.; Liu, X. J.; Lu, W.; Xu, B.; Li, A. D.; Xia, Y. D.; Yin, J. Liu, Z. G.; Lan, X. X.; Gong, C. J.

    2014-06-30

    A memory device p-Si/SiO{sub 2}/(TiO{sub 2}){sub 0.8}(Al{sub 2}O{sub 3}){sub 0.1}(TAO-81)/Al{sub 2}O{sub 3}/Pt was fabricated, in which a composite of two high-k dielectrics with a thickness of 1 nm was employed as the charge-trapping layer to enhance the charge-trapping efficiency of the memory device. At an applied gate voltage of ±9 V, TAO-81 memory device shows a memory window of 8.83 V in its C-V curve. It also shows a fast response to a short voltage pulse of 10{sup −5} s. The charge-trapping capability, the endurance, and retention characteristics of TAO-81 memory device can be improved by introducing double TAO-81 charge-trapping layers intercalated by an Al{sub 2}O{sub 3} layer. The charge-trapping mechanism in the memory device is mainly ascribed to the generation of the electron-occupied defect level in the band gap of Al{sub 2}O{sub 3} induced by the inter-diffusion between TiO{sub 2} and Al{sub 2}O{sub 3}.

  8. Laser patterning of Y3sub>Al5O12:Ce3+ ceramic phosphor platelets for enhanced forward light extraction and angular color uniformity of white LEDs.

    PubMed

    Wang, Shuai; Li, Yufeng; Feng, Lungang; Zhang, Linzhao; Zhang, Ye; Su, Xilin; Ding, Wen; Yun, Feng

    2016-07-25

    We present a facile fabrication process to directly fabricate cone-shaped microwells arrays on single crystal Y3sub>Al5O12:Ce3+ (YAG:Ce) ceramic phosphor platelets (CPPs) by short-pulse laser direct patterning. Compared to unpatterned YAG:Ce CPP with smooth surface, the forward-to-total ratio of emission photons of patterned YAG:Ce CPPs was enhanced from 53.2% up to 78.2%, and the total emission within 4-π degree is 6% higher. The fabricated patterns are also beneficial in increasing the color conversion efficiency of YAG:Ce CPPs by 7.6%. The patterned YAG:Ce CPPs display much better correlated color temperature (CCT) uniformity under varied currents. The angular correlated color temperature uniformity (ACU) of patterned YAG:Ce CPPs reaches as high as 0.933 compared to 0.730 of the unpatterned one. These results suggest that laser patterning of YAG:Ce CPP could effectively manipulate its luminance, chromaticity and illumination pattern, which may lead to further technological advancements for diversified applications of film-type CPPs in highly efficient white LEDs. PMID:27464198

  9. Hydrothermal synthesis, crystal structure and spectroscopic and magnetic properties of (C{sub 2}H{sub 10}N{sub 2})[Mn{sub 2.09}Co{sub 0.91}(HPO{sub 3}){sub 4}

    SciTech Connect

    Fernandez-Armas, S.; Mesa, J.L.; Pizarro, J.L.; Pena, A.; Chapman, J.P.; Arriortua, M.I

    2004-09-01

    (C{sub 2}H{sub 10}N{sub 2})[Mn{sub 2.09}Co{sub 0.91}(HPO{sub 3}){sub 4}] has been synthesized using mild hydrothermal conditions under autogeneous pressure. The compound crystallizes in the triclinic P-1 space group. The unit-cell parameters are a = 5.4061(8), b = 5.4150(7), c = 14.136(2) A, {alpha} = 80.84(1), {beta} = 85.41(1), {gamma} = 60.00(1) and Z = 1. The compound shows a layered structure constructed from M{sub 3}O{sub 12} trimer units linked thorough the (HPO{sub 3}){sup 2-} phosphite oxoanions with the ethylenediammonium cations located between the sheets compensating the anionic charge of the inorganic framework. The IR and Raman spectra confirm the presence of the ethylenediammonium cation and phosphite anion. The diffuse reflectance spectrum is in accordance with the presence of Co(II) and Mn(II) high spin cations in slightly distorted octahedral symmetry. The calculated Dq and Racah parameters for the Co(II) cations are Dq = 710, B = 870 and C = 4100 cm{sup -1}. The magnetic measurements indicate the existence of antiferromagnetic interactions as the major interactions. Hysteresis observed at low temperature indicates a weak ferromagnetic component, due to a non-cancellation of spins, with coercitive field of 900 G and magnetization of 700 emu/mol.

  10. Acentric langanite La3sub>Ga5.5Nb0.5O14 crystal: a new nonlinear crystal for the generation of mid-infrared parametric light.

    PubMed

    Lu, Dazhi; Xu, Tianxiang; Yu, Haohai; Fu, Qiang; Zhang, Huaijin; Segonds, Patricia; Boulanger, Benoit; Zhang, Xingyu; Wang, Jiyang

    2016-08-01

    The mid-infrared spectral range extending from 2 to 6 μm is significant for scientific and technological applications. A promising nonlinear oxide crystal La3sub>Ga5.5Nb0.5O14 (LGN) is proposed and fully characterized for the first time to our knowledge. The transparency range extends between 0.28 and 7.4 μm. The two principal refractive indices were measured and we found that the nonlinear coefficient d11 = 3.0 ± 0.1 pm/V at 0.532 μm. The simultaneous fit of data allowed us to refine the Sellmeier equations of LGN and to calculate the tuning curves for optical parametric generation (OPG) pumped at 1.064 μm. Calculations are consistent with recorded data and also show the generation of a supercontinuum between 1.5 and 3.5 μm when pumped at 0.98 μm by a Ti:Sapphire laser. PMID:27505730

  11. The microscopic structure of charge density waves in underdoped YBa2Cu3sub>O6.54 revealed by x-ray diffraction

    SciTech Connect

    E. M. Forgan; Huecker, M.; Blackburn, E.; Holmes, A. T.; Briffa, A. K. R.; Chang, J.; Bouchenoire, L.; Brown, S. D.; Liang, Ruixing; Bonn, D.; Hardy, W. N.; Christensen, N. B.; von Zimmermann, M.; Hayden, S. M.

    2015-12-09

    Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa2Cu3sub>O6.54 at its superconducting transition temperature ~60 K. We find that the CDWs in this material break the mirror symmetry of the CuO2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO2 planes, and are out of phase with each other. The planar oxygen atoms have the largest displacements, perpendicular to the CuO2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For example, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.

  12. Synthesis, structure and properties of (CN{sub 3}H{sub 6}){sub 4}Zn{sub 3}(SeO{sub 3}){sub 5}, the first organically-templated selenite

    SciTech Connect

    HARRISON,W.T.A.; PHILLIPS,MARK L.F.; STANCHFIELD,JESSE L.; NENOFF,TINA M.

    2000-05-22

    An astonishing variety of inorganic networks templated by organic species have been reported over the last 10 years. A great deal of attention has been paid to the structure-directing role of the organic species, and the structural effect of variously coordinated cations, for example distorted octahedral vanadium and pyramidal tin. Less exploratory work has been carried out on the anionic part of the inorganic network, and most groups reported so far (phosphate, germanate, etc.) invariably adopt tetrahedral coordination. The possibilities of incorporating the pyramidal [HP0{sub 3}]{sup 2{minus}} hydrogen phosphite group into extended structures templated by inorganic, alkaline earth cations was explored a few years ago. In this paper the authors report the synthesis, crystal structure, and some properties of (CN{sub 3}H{sub 6}){sub 4}{center_dot}Zn{sub 3}(SeO{sub 3}){sub 5}, the first organically-templated phase to contain the pyramidal selenite [SeO{sub 3}]{sup 2{minus}} anion.

  13. Ga{sub 3}(HPO{sub 3}){sub 4}F{sub 4}(H{sub 3}DETA) (DETA=diethylenetriamine): A new open-framework fluorinated gallium phosphite with pentameric building unit

    SciTech Connect

    Wang Li; Song Tianyou; Fan Yong; Wang Ying; Xu Jianing; Shi Suhua . E-mail: shish@mail.jlu.edu.cn; Zhu Tao

    2006-03-15

    Ga{sub 3}(HPO{sub 3}){sub 4}F{sub 4}(H{sub 3}DETA) is a new open-framework fluorinated gallium phosphite obtained by mild hydrothermal synthesis using diethylenetriamine as templated agent and characterized by single crystal X-ray diffraction, the powder X-ray diffraction, IR spectroscopy, TGA, ICP and elemental analyses. It crystallizes in the monoclinic space group C2/c, a=12.741(6) A, b=12.068(6) A, c=11.988(5) A, {beta}=94.902(8){sup o}, V=1836.6(15) A{sup 3}, Z=4. The construction of 3D open-framework structure in the title compound may be viewed as the assembly of pentameric building units and HPO{sub 3} groups. The pentameric building unit is the first to be found, which lead to form the three types of channels along a-, b- and c-axes, respectively, in gallium phosphite. The triprotonated DETA cations are inserted within the 10-membered ring channels and interact with anions of the framework via hydrogen bonds.

  14. PbI{sub 4}Cu{sub 2}(PPh{sub 3}){sub 4}: A heterometallic iodide with unusual cis-divacant octahedral coordination sphere for lead: Synthesis, structure, red-infrared fluorescence and theoretical studies

    SciTech Connect

    Fan Leqing; Huang Yizhi; Wu Liming . E-mail: Liming_Wu@fjirsm.ac.cn; Chen Ling . E-mail: chenl@fjirsm.ac.cn; Li Junqian; Ma En

    2006-08-15

    A new heterometallic iodide, PbI{sub 4}Cu{sub 2}(PPh{sub 3}){sub 4}, was synthesized by reactions of PbI{sub 2}, CuI and triphenylphosphine (PPh{sub 3}) in DMF solution. The single-crystal X-ray diffraction analyses show that Pb(II) center adopts an unusual cis-divacant octahedral geometry. Crystal data: triclinic, space group P1-bar , a=12.3455(2)A, b=13.8673(1)A, c=21.3421(1)A, {alpha}=106.623(4){sup o}, {beta}=103.478(6){sup o}, {gamma}=93.574(5){sup o}, V=3371.83(6)A{sup 3} and Z=2. Density function theory (DFT) calculations and fragment orbital interaction analyses reveal the presence of a three-center four-electron (3c-4e) hypervalent bonding about lead; and the formation of the unusual cis-divacant [PbI{sub 4}]{sup 2-} octahedron is energetically favorable. The title yellow compound has an optical bandgap of 2.69eV and shows remarkable red-infrared fluorescence emission at 732nm with lifetime of 24{mu}s which is assigned as an iodine 5p-lead 6s to PPh{sub 3}-lead 6p charge transfer (XM-LM-CT)

  15. Ablation of (GeS{sub 2}){sub 0.3}(Sb{sub 2}S{sub 3}){sub 0.7} glass with an ultra-violet nano-second laser

    SciTech Connect

    Knotek, P.; Navesnik, J.; Cernohorsky, T.; Kincl, M.; Vlcek, M.; Tichy, L.

    2015-04-15

    Highlights: • The interaction of (GeS{sub 2}){sub 0.3}(Sb{sub 2}S{sub 3}){sub 0.7} bulk glass and film with UV nanosecond laser. • Ablation process, topography of crater and structure of the material were studied. • Ablation threshold fluencies changed with the spot diameter and number of pulses. • The photo-thermal expansion of the material occurred for low laser fluency. • Laser direct writing process applicable for fabrication of passive optical elements. - Abstract: The results of an experimental study of the laser ablation of bulk and thin films of a GeSbS chalcogenide glass using UV nanosecond pulses are reported. The response of the samples to illumination conditions was studied through the use of atomic force spectroscopy, digital holographic microscopy, Raman scattering and scanning electron microscopy. The multi-pulse ablation thresholds were determined for both the bulk and thin film samples for varying number of pulses and illuminated spot diameter. The possible application of direct laser writing into the bulk and thin films of this material is presented.

  16. Magnetic properties of the Nd{sub 0.95}Dy{sub 0.05}Fe{sub 3}(BO{sub 3}){sub 4} ferroborate with small substitution in the rare-earth element subsystem

    SciTech Connect

    Begunov, A. I.; Demidov, A. A.; Gudim, I. A.; Eremin, E. V.

    2013-11-15

    The magnetic properties of a substituted Nd{sub 0.95}Dy{sub 0.05}Fe{sub 3}(BO{sub 3}){sub 4} ferroborate single crystal with competing Nd-Fe and Dy-Fe exchange interactions are studied experimentally and theoretically. A spontaneous spin-reorientation transition is detected near T = 4.3 K, and anomalies are observed in the low-temperature magnetization curves along trigonal axis c and in basal plane ab. The measured properties and the detected effects are interpreted in terms of a general theoretical approach, which is based on the molecular field approximation and crystal field calculations for a rare-earth ion. The experimental temperature dependences of the initial magnetic susceptibility in the range 2–300 K, the anomalies in the magnetization curves for B ‖ c and B ⊥ c in fields up to 1.5 T, and the field and temperature dependences of magnetization in fields up to 9 T are described. The effect of small substitution in the rare-earth subsystem on the magnetic properties is analyzed. The crystal field parameters and the parameters of the R-Fe and Fe-Fe exchange interactions are determined from the experimental data.

  17. Resonant magneto-optic Kerr effect in the magnetic topological insulator Cr:(Sbx,Bi1–x)2Te3sub>

    SciTech Connect

    Patankar, Shreyas; Hinton, J. P.; Griesmar, Joel; Orenstein, J.; Dodge, J. S.; Kou, Xufeng; Pan, Lei; Wang, Kang L.; Bestwick, A. J.; Fox, E. J.; Goldhaber-Gordon, D.; Wang, Jing; Zhang, Shou -Cheng

    2015-12-31

    Here, we report measurements of the polar Kerr effect, proportional to the out-of-plane component of the magnetization, in thin films of the magnetically doped topological insulator (Cr0.12Bi0.26Sb0.62)2Te3sub>. Measurements of the complex Kerr angle ΘK were performed as a function of photon energy in the range 0.8eV < ℏω < 3.0eV. We observed a peak in the real part of ΘK(ω) and zero crossing in the imaginary part that we attribute to a resonant interaction with a spin-orbit avoided crossing located ≈ 1.6 eV above the Fermi energy. The resonant enhancement allows measurement of the temperature and magnetic field dependence of ΘK in the ultrathin film limit, d ≥ 2 quintuple layers (QL). We find a sharp transition to zero remanent magnetization at 6 K for d < 8 QL, consistent with theories of the dependence of impurity spin interactions on film thickness and their location relative to topological insulator surfaces.

  18. Synthesis and crystal structure of Pb{sub 3}[IO{sub 3}]{sub 2}Cl{sub 4}, a representative of a new iodate-chloride class of compounds

    SciTech Connect

    Belokoneva, E. L. Dimitrova, O. V.

    2010-01-15

    Compound Pb{sub 3}[IO{sub 3}]{sub 2}Cl{sub 4} (space group C12/c1), representing a new iodate-chloride class of compounds, is synthesized under hydrothermal conditions. Only two minerals, schwartzembergite Pb{sub 3}[IO{sub 3}]Cl{sub 2}O(OH) and seeligerite Pb{sub 3}[IO{sub 3}]Cl{sub 3}O, the structures of which are unknown, are close in composition to this compound. In the iodate-chloride studied, the pentavalent iodine atom has an umbrella-like coordination, which is typical of iodates and consists of three O atoms at short distances and the fourth O atom at a longer distance. [IO{sub 4}]{sup 3-} tetrahedra share edges to form pairs. Lead ions form layers parallel to the ab plane. Along the c axis, these layers alternate with layers of iodate groups. Pb atoms are coordinated by O atoms of iodate groups and Cl atoms. The coordination sphere of the Pb(1) atom contains a free sector which is directed to more distant halogen atoms and possibly accommodates the lone electron pair.

  19. Synthesis and characterization of a new monophosphate (5-Cl-2,4-(OCH{sub 3}){sub 2}C{sub 6}H{sub 2}NH{sub 3})H{sub 2}PO{sub 4}

    SciTech Connect

    Kefi, R.; Abid, S.; Nasr, C. Ben . E-mail: cherif.bennasr@fsb.rnu.tn; Rzaigui, M.

    2007-03-22

    Chemical preparation, crystal structure and NMR spectroscopy of a new organic cation 5-chloro(2,4-dimethoxy)anilinium monophosphate H{sub 2}PO{sub 4} are given. This new compound crystallizes in the monoclinic system, with the space group P2{sub 1}/c and the following parameters: a=5.524(2)A, b=9.303(2)A, c=23.388(2)A, {beta}=90.66(4), V=1201.8(2)A{sup 3}, Z=4 and D{sub x}=1.573gcm{sup -3}. Crystal structure has been determined and refined to R=0.031 and R{sub w}=0.080 using 1702 independent reflections. Structure can be described as an infinite (H{sub 2}PO{sub 4}){sub n}{sup n-} corrugated chains in the a-direction. The organic groups (5-Cl-2,4-(OCH{sub 3}){sub 2}C{sub 6}H{sub 2}NH{sub 3}){sup +} are anchored between adjacent polyanions through multiple hydrogen bonds. This compound is also investigated by IR, thermal, and solid-state, {sup 13}C, {sup 31}P MAS NMR spectroscopies.

  20. Three-dimensional charge density wave order in YBa2Cu3sub>O6.67 at high magnetic fields

    SciTech Connect

    Gerber, S.; Jang, H.; Nojiri, H.; Matsuzawa, S.; Yasumura, H.; Bonn, D. A.; Liang, R.; Hardy, W. N.; Islam, Z.; Mehta, A.; Song, S.; Sikorski, M.; Stefanescu, D.; Feng, Y.; Kivelson, S. A.; Devereaux, T. P.; Shen, Z. -. X.; Kao, C. -C.; Lee, W. -S.; Zhu, D.; Lee, J. -S.

    2015-11-20

    In this study, charge density wave (CDW) correlations have recently been shown to universally exist in cuprate superconductors. However, their nature at high fields inferred from nuclear magnetic resonance is distinct from that measured by x-ray scattering at zero and low fields. Here we combine a pulsed magnet with an x-ray free electron laser to characterize the CDW in YBa2Cu3sub>O6.67 via x-ray scattering in fields up to 28 Tesla. While the zero-field CDW order, which develops below T ~ 150 K, is essentially two-dimensional, at lower temperature and beyond 15 Tesla, another three-dimensionally ordered CDW emerges. The field-induced CDW onsets around the zero-field superconducting transition temperature, yet the incommensurate in-plane ordering vector is field-independent. This implies that the two forms of CDW and high-temperature superconductivity are intimately linked.

  1. Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb (Zr0.80Ti0. 20)O3sub> single crystal

    SciTech Connect

    Frantti, Johannes; Fujioka, Y.; Puretzky, Alexander A.; Xie, Y; Ye, Z. -G.; Parish, Chad M.; Glazer, A. M.

    2014-12-22

    Zirconium-rich lead-zirconate-titanate (PZT) Pb(Zr0.80Ti0.20)O3sub> single crystal is studied by polarized-Raman scattering experiments as a function of temperature. We show that the crystal possesses complex domain boundaries which show no sign of instability even 200 K above the ferroelectric-to-paraelectric phase transition. The boundary stabilized the domains which had the same orientation after cyclic heating and cooling up to 773 K. The domains transformed normally to the cubic paraelectric phase, but returned to their original state after cooling. Physical mechanism behind the reversible behavior is related to the strain between the boundary region and domain, which forces the domain to grow similarly after each heating and cooling cycle. Electron backscattering diffraction measurements show that macroscopic domains, lengths scale in hundreds of microns, are divided into regions whose Pb-displacements are not correlated. The results are notably interesting for non-volatile memory development as it implies that the original ferroelectric state can be restored after the material has been transformed to a paraelectric phase. Incoherent Pbdisplacements play a role for polarization switching.

  2. Oxygen atom transfer between rhenium, sulfur, and phosphorus. Characterization and reactivity of Re(O)Cl/sub 3/(Me/sub 2/S)(OPPh/sub 3/) and Re(O)Cl/sub 3/(CNCMe/sub 3/)/sub 2/

    SciTech Connect

    Bryan, J.C.; Stenkamp, R.E.; Tulip, T.H.; Mayer, J.M.

    1987-07-15

    Re(O)Cl/sub 3/(PPh/sub 3/)/sub 2/ (I) reacts with Me/sub 2/SO to form OPPh/sub 3/ and Re(O)Cl/sub 3/(Me/sub 2/S)(OPPh/sub 3/) (II), not Re(O)Cl/sub 3/(Me/sub 2/SO)(PPh/sub 3/) as had been previously reported. Compounds I and II are catalysts for oxygen atom transfer from Me/sub 2/SO to PPh/sub 3/. The mechanism of these oxygen atom transfer reactions has been studied with oxygen-18 labeling experiments. The rhenium oxo group does not appear to be involved; rather, the rhenium center acts as a Lewis acid activator for a Me/sub 2/SO ligand. The rhenium oxo group does, however, exchange oxygen atoms with Me/sub 2/S/sup 18/O, probably by a similar mechanism. Compound II is an excellent starting material for compounds of the form Re(O)Cl/sub 3/L/sub 2/, with L = isonitriles, phosphines, bipyridine, etc. The compounds Re(O)Cl/sub 3/-(CNR)/sub 2/ (R = CMe/sub 3/ (IV), CHMe/sub 2/, C/sub 6/H/sub 11/) are rare examples of high-valent isonitrile complexes. Data from an X-ray crystal structure of IV are reported. 36 references, 2 figures, 3 tables.

  3. Role of ytterbium-erbium co-doped gadolinium molybdate (Gd2(MoO4)3sub>:Yb/Er) nanophosphors in solar cells.

    PubMed

    Jin, Xiao; Li, Haiyang; Li, Dongyu; Zhang, Qin; Li, Feng; Sun, Weifu; Chen, Zihan; Li, Qinghua

    2016-09-01

    Insufficient harvest of solar light energy is one of the obstacles for current photovoltaic devices to achieve high performance. Especially, conventional organic/inorganic hybrid solar cells (HSCs) based on PTB7 as p-type semiconductor can only utilize 400-800 nm solar spectrum. One effective strategy to overcome this obstacle is the introduction of up-conversion nanophosphors (NPs), in the virtue of utilizing the near infrared region (NIR) of solar radiation. Up-conversion can convert low-energy photons to high-energy ones through multi-photon processes, by which the solar spectrum is tailored to well match the absorptive domain of the absorber. Herein we incorporate erbium-ytterbium co-doped gadolinium molybdate (Gd2(MoO4)3sub>, GMO), denoted as GMO:Yb/Er, into TiO2 acceptor film in HSCs to enhance the light harvest. Here Er3+ acts as activator while Yb-MoO4 2- is the joint sensitizer. Facts proved that the GMO:Yb/Er single crystal NPs are capable of turning NIR photons to visible photons that can be easily captured by PTB7. Studies on time-resolved photoluminescence demonstrate that electron transfer rate at the interface increases sharply from 0.65 to 1.42 × 109 s-1. As a result, the photoelectric conversion efficiency of the GMO:Yb/Er doped TiO2/PTB7 HSCs reach 3.67%, which is increased by around 25% compared to their neat PTB7/TiO2 counterparts (2.94%). This work may open a hopeful way to take the advantage of those conversional rare-earth ion doped oxides that function in tailoring solar light spectrum for optoelectronic applications. PMID:27607730

  4. Thermomechanical behavior and microstructural evolution of a Ni(Pd)-rich Ni24.3sub>Ti49.7Pd26 high temperature shape memory alloy

    SciTech Connect

    Benafan, O.; Garg, A.; Noebe, R. D.; Bigelow, G. S.; Padula, S. A.; Gaydosh, D. J.; Vaidyanathan, R.; Clausen, B.; Vogel, S. C.

    2015-04-20

    We investigated the effect of thermomechanical cycling on a slightly Ni(Pd)-rich Ni24.3sub>Ti49.7Pd26 (near stochiometric Ni–Ti basis with Pd replacing Ni) high temperature shape memory alloy. Furthermore, aged tensile specimens (400 °C/24 h/furnace cooled) were subjected to constant-stress thermal cycling in conjunction with microstructural assessment via in situ neutron diffraction and transmission electron microscopy (TEM), before and after testing. It was shown that in spite of the slightly Ni(Pd)-rich composition and heat treatment used to precipitation harden the alloy, the material exhibited dimensional instabilities with residual strain accumulation reaching 1.5% over 10 thermomechanical cycles. This was attributed to insufficient strengthening of the material (insufficient volume fraction of precipitate phase) to prevent plasticity from occurring concomitant with the martensitic transformation. In situ neutron diffraction revealed the presence of retained martensite while cycling under 300 MPa stress, which was also confirmed by transmission electron microscopy of post-cycled samples. Neutron diffraction analysis of the post-thermally-cycled samples under no-load revealed residual lattice strains in the martensite and austenite phases, remnant texture in the martensite phase, and peak broadening of the austenite phase. The texture we developed in the martensite phase was composed mainly of those martensitic tensile variants observed during thermomechanical cycling. Presence of a high density of dislocations, deformation twins, and retained martensite was revealed in the austenite state via in-situ TEM in the post-cycled material, providing an explanation for the observed peak broadening in the neutron diffraction spectra. Despite the dimensional instabilities, this alloy exhibited a biased transformation strain on the order of 3% and a two-way shape memory effect (TWSME) strain of ~2%, at relatively high actuation

  5. Magnetic structures of the {alpha}-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3-} {sub x} (AsO{sub 4}) {sub x} (x=1, 1.5, 2, 3) solid solution

    SciTech Connect

    Goni, Aintzane; Wattiaux, Alain; Olazcuaga, Roger; Isabel Arriortua, Maria . E-mail: teo.rojo@ehu.es

    2006-01-15

    Moessbauer spectroscopy and neutron diffraction studies have been carried out for the {alpha}-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3-} {sub x} (AsO{sub 4}) {sub x} (x=1, 1.5, 2, 3) solid solution, potential candidate for the cathode material of the lithium secondary batteries. The crystal and magnetic structures of all these phases are based on the structural and magnetic model corresponding to the {alpha}-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} phosphate parent, but with some differences promoted by the arsenate substitution. The PO{sub 4} and AsO{sub 4} groups have a random distribution in the structure. In all compounds the coupling of the magnetic moments takes place in the (001) plane, but the value of the angle between the moments and the x direction decreases from 38.3 deg. ({alpha}-Li{sub 3}Fe{sub 2}(AsO{sub 4}){sub 3}) to 4.7{sup o} ({alpha}-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 2}(AsO{sub 4}){sub 1}). This rotation arises from the change in the tilt angle between the Fe(1)O{sub 6} and Fe(2)O{sub 6} crystallographically and magnetically independent octahedra in the structures, and affects the effectiveness of the magnetic exchange pathways. The ordering temperature T{sub N} decreases with the increase of phosphate amount in the compounds. The existence of a phenomenon of canting and the evolution of the ferrimagnetic behavior in this solid solution is also discussed.

  6. Enhanced tunable magnetoresistance properties over a wide temperature range in epitaxial (La{sub 0.7}Sr{sub 0.3}MnO{sub 3}){sub 1−x}:(CeO{sub 2}){sub x} nanocomposites

    SciTech Connect

    Fan, Meng; Khatkhatay, Fauzia; Zhang, Wenrui; Li, Leigang; Wang, Haiyan

    2015-08-14

    Vertically aligned nanocomposite (VAN) (La{sub 0.7}Sr{sub 0.3}MnO{sub 3}){sub 1−x}:(CeO{sub 2}){sub x} (LSMO:CeO{sub 2}) thin films have been grown on SrTiO{sub 3} (001) substrates by pulsed laser deposition. Tunable magnetoresistance properties as well as microstructures are demonstrated in these VAN films by modulating the film composition (x = 0, 0.3, 0.4, 0.45, 0.5, and 0.55). The sample of x = 0.3 shows a large low-field magnetoresistance (LFMR) in a high temperature range, i.e., over 10% at the range of 280 K to 320 K under 1 T and with a peak value of ∼13.5% at 310 K. In addition, a vast enhancement of LFMR in a low temperature range of 20–150 K with peak of ≈34.3% at 45 K for 1 T could be achieved with x = 0.5. The enhanced LFMR properties can be attributed to both the phase boundary induced spin fluctuation and the magnetic tunneling effect through vertical ferromagnetic/insulator/ferromagnetic structures. The observed enhanced LFMR performance, especially at high temperatures, as well as its simple growth method, offers a great potential for LSMO:CeO{sub 2}nanocomposites to be used in spintronic devices in a large temperature range.

  7. Preparation and photoluminescence properties of RE:Na{sub 3}La{sub 9}O{sub 3}(BO{sub 3}){sub 8} (RE=Er, Yb) crystals

    SciTech Connect

    Liu Zuoliang; Zhang, Guochun; Zhang Jianxiu; Bai Xiaoyan; Fu Peizhen; Wu Yicheng

    2010-06-15

    Using Na{sub 2}CO{sub 3}-H{sub 3}BO{sub 3}-NaF as fluxes, transparent RE:Na{sub 3}La{sub 9}O{sub 3}(BO{sub 3}){sub 8} (abbr. RE:NLBO, RE=Er, Yb) crystals have been grown by the top seed solution growth (TSSG) method. The X-ray powder diffraction analysis shows that the RE:NLBO crystals have the same structure with NLBO. The element contents were determined by molar to be 0.64% Er{sup 3+} in Er:NLBO, 2.70% Yb{sup 3+} in Yb:NLBO, respectively. The polarized absorption spectra of RE:NLBO have been measured at room temperature and show that both Er:NLBO and Yb:NLBO have a strong absorption bands near 980 nm with wide FWHM (Full Wave at Half Maximum) (21 nm for Er:NLBO and 25 nm for Yb:NLBO). Fluorescence spectra have been recorded. Yb:NLBO has the emission peaks at 985 nm, 1028 nm and 1079 nm and the emission peak of Er:NLBO is at 1536 nm. Spectral parameters have been calculated by the Judd-Ofelt theory for Er:NLBO and the reciprocity method for Yb:NLBO, respectively. The calculated values show that Er:NLBO is a candidate of 1.55 {mu}m laser crystals and Yb:NLBO is a candidate for self-frequency doubling crystal. - Graphical abstract: Fluorescence spectra show the emission peaks at 985, 1028 and 1079 nm of Yb:NLBO and at 1536 nm of Er:NLBO.

  8. Role of ytterbium-erbium co-doped gadolinium molybdate (Gd2(MoO4)3sub>:Yb/Er) nanophosphors in solar cells.

    PubMed

    Jin, Xiao; Li, Haiyang; Li, Dongyu; Zhang, Qin; Li, Feng; Sun, Weifu; Chen, Zihan; Li, Qinghua

    2016-09-01

    Insufficient harvest of solar light energy is one of the obstacles for current photovoltaic devices to achieve high performance. Especially, conventional organic/inorganic hybrid solar cells (HSCs) based on PTB7 as p-type semiconductor can only utilize 400-800 nm solar spectrum. One effective strategy to overcome this obstacle is the introduction of up-conversion nanophosphors (NPs), in the virtue of utilizing the near infrared region (NIR) of solar radiation. Up-conversion can convert low-energy photons to high-energy ones through multi-photon processes, by which the solar spectrum is tailored to well match the absorptive domain of the absorber. Herein we incorporate erbium-ytterbium co-doped gadolinium molybdate (Gd2(MoO4)3sub>, GMO), denoted as GMO:Yb/Er, into TiO2 acceptor film in HSCs to enhance the light harvest. Here Er3+ acts as activator while Yb-MoO4 2- is the joint sensitizer. Facts proved that the GMO:Yb/Er single crystal NPs are capable of turning NIR photons to visible photons that can be easily captured by PTB7. Studies on time-resolved photoluminescence demonstrate that electron transfer rate at the interface increases sharply from 0.65 to 1.42 × 109 s-1. As a result, the photoelectric conversion efficiency of the GMO:Yb/Er doped TiO2/PTB7 HSCs reach 3.67%, which is increased by around 25% compared to their neat PTB7/TiO2 counterparts (2.94%). This work may open a hopeful way to take the advantage of those conversional rare-earth ion doped oxides that function in tailoring solar light spectrum for optoelectronic applications.

  9. Molecular hydrogen complexes of the transition metals. 2. Evidence for a new complex, Mo(CO) (dppe)/sub 2/(H/sub 2/), and for solution equilibrium between dihydrogen and dihydride forms, M-eta/sup 2/-H/sub 2/ in equilibrium H-M-H, in W(CO)/sub 3/(PR/sub 3/)/sub 2/(H/sub 2/)

    SciTech Connect

    Kubas, G.J.; Ryan, R.R.; Wrobleski, D.A.

    1986-03-19

    Coordination of molecular hydrogen to transition metals is now firmly established, initially in the stable, structurally characterized complexes M(CO)/sub 3/(PR/sub 3/)/sub 2/(eta/sup 2/-H/sub 2/) (M = Mo, W; R = Cy, i-Pr), then in low-temperature stable Cr(CO)/sub 5/(H/sub 2/), and recently in IrH(H/sub 2/)(PPh/sub 3/)/sub 2/(C/sub 13/H/sub 8/N))SbF/sub 6/, (IrH/sub 2/(H/sub 2/)/sub 2/L/sub 2/)/sup +/, and (FeH(H/sub 2/)(dppe)/sub 2/)BF/sub 4/. In order to better define the steric and electronic requirements for H/sub 2/ to bind in molecular fashion rather than being cleaved to hydride ligands, reported here is new stable H/sub 2/ complex, Mo(CO)(dppe)/sub 2/(H/sub 2/) (dppe = diphenylphosphinoethane). Also, NMR evidence is presented for a dynamic equilibrium between the H/sub 2/ complex W(CO)/sub 3/(P-i-Pr/sub 3/)/sub 2/(eta/sup 2/-H/sub 2/), and an apparent dihydride complex, WH/sub 2/(CO)/sub 3/)P-i-Pr/sub 3/)/sub 2/, derived by oxidative addition of the H/sub 2/ ligand. 16 references, 2 figures.

  10. AlF 3sub> Surface-Coated Li[Li 0.2 Ni 0.17 Co 0.07 Mn 0.56 ]O 2 Nanoparticles with Superior Electrochemical Performance for Lithium-Ion Batteries

    SciTech Connect

    Sun, Shuwei; Yin, Yanfeng; Wan, Ning; Wu, Qing; Zhang, Xiaoping; Pan, Du; Bai, Ying; Lu, Xia

    2015-06-24

    For Li-rich layered cathode materials considerable attention has been paid owing to their high capacity performance for Li-ion batteries (LIBs). In our work, layered Li-rich Li[Li0.2Ni0.17Co0.07Mn0.56]O2 nanoparticles are surface-modified with AlF3sub> through a facile chemical deposition method. The AlF3 sub>surface layers have little impact on the structure of the material and act as buffers to prevent the direct contact of the electrode with the electrolyte; thus, they enhance the electrochemical performance significantly. The 3 wt% AlF3sub>-coated Li-rich electrode exhibits the best cycling capability and has a considerably enhanced capacity retention of 83.1% after 50 cycles. Moreover, the rate performance and thermal stability of the 3 wt% AlF3-coated electrode are also clearly improved. Finally, surface analysis indicates that the AlF3sub> coating layer can largely suppress the undesirable growth of solid electrolyte interphase (SEI) film and, therefore, stabilizes the structure upon cycling.

  11. Solid-state synthesis, structure and properties of a novel open-framework cadmium selenite bromide: [Cd{sub 10}(SeO{sub 3}){sub 8}Br{sub 4}]·HBr·H{sub 2}O

    SciTech Connect

    Chen, Wen-Tong; Wang, Ming-Sheng; Wang, Guan-E; Chen, Hui-Fen; Guo, Guo-Cong

    2013-08-15

    A novel open-framework cadmium selenite bromide, [Cd{sub 10}(SeO{sub 3}){sub 8}Br{sub 4}]·HBr·H{sub 2}O (1), has been obtained by a solid-state reaction at 450 °C, and the structure has been determined by single-crystal X-ray diffraction analysis. Compound 1 crystallizes in Pbcm of the orthorhombic system: a=10.882(3), b=16.275(5), c=18.728(6) Å, V=3317(2) Å{sup 3}, R1/wR2=0.0411/0.0659. Compound 1 is characteristic of a novel 3-D open-framework structure, composing {sub ∞}{sup 2}[CdSeO{sub 3}] layers and the pillars of edge-shared CdO{sub 3}Br{sub 2} square pyramids. The lattice water molecules and the HBr molecules locate in the voids of the framework. Optical absorption spectrum of 1 reveals the presence of an optical gap of 1.65 eV. Solid-state photoluminescent study indicates that compound 1 exhibits strong violet emission. TG–DSC measurement shows that compound 1 is thermally stable up to 200 °C. - Graphical abstract: A metal selenite halide has been synthesized and features a 3-D open-framework structure, composing edge-shared CdO{sub 8} decahedra and pillars of edge-sharing pentahedra. UV–vis, TG–DSC and luminescent measurements are also reported. Highlights: • This paper reports a novel cadmium selenite bromide obtained by an intermediate-temperature solid-state reaction. • The title compound is characteristic of a novel 3-D open-framework structure, composing {sub ∞}{sup 2}[CdSeO{sub 3}] layers and the pillars of edge-shared CdO{sub 3}Br{sub 2} square pyramids. • The title compound is thermally stable up to 200 °C. • The title compound has an optical gap of 1.65 eV and exhibits strong violet emission.

  12. Structural investigation of oxygen non-stoichiometry and cation doping in misfit-layered thermoelectric (Ca{sub 2}CoO{sub 3-} {sub x} )(CoO{sub 2}) {sub {delta}} , {delta}{approx}1.61

    SciTech Connect

    Ling, Chris D. Aivazian, Karina; Schmid, Siegbert; Jensen, Paul

    2007-04-15

    The chemical and crystallographic natures of oxygen non-stoichiometry and cation doping in the 'misfit-layered' cobaltate [Ca{sub 2}CoO{sub 3-} {sub x} ][CoO{sub 2}] {sub {delta}} , {delta}{approx}1.61, were investigated. Single-phase polycrystalline samples were prepared with the help of a high-energy planetary ball mill, and single crystals grown from a K{sub 2}CO{sub 3}/KCl flux. Polycrystalline undoped, Ti{sup 4+}-doped, and Nd{sup 3+}-doped samples were annealed under both air and under argon in order to modify the oxygen non-stoichiometry. The incommensurately modulated composite crystal structures of undoped and Ti{sup 4+}-doped single crystals were refined against X-ray diffraction data using the superspace group X2/m(0,{delta},0)s0. For the as-made (air-annealed) undoped crystal, 14(2)% oxygen vacancies were found on the disordered O2 site in the central layer of the rock-salt-type subsystem, giving an overall stoichiometry [Ca{sub 2}CoO{sub 2.86}][CoO{sub 2}]{sub 1.61}. For the Ti{sup 4+}-doped crystal this site was found to be almost fully occupied, while Ti{sup 4+}-dopant cations were located on the disordered Co1 site in the central layer of the rock-salt-type subsystem, giving an overall formula [Ca{sub 2}Co{sub 0.74}Ti{sub 0.26}O{sub 2.98}][CoO{sub 2}]{sub 1.61}. In both cases, the average cobalt oxidation state is 3.13+. The single-crystal refinements, thermogravimetric analyses and variations in the lattice parameters of polycrystalline samples refined against synchrotron X-ray diffraction (XRD) data indicate that for both undoped and Ti{sup 4+}-doped samples, substantial numbers of additional oxygen vacancies (15-20%) can be introduced on this site by annealing under an inert atmosphere. Nd{sup 3+}-doped samples have a much lower tolerance (<5%) for oxygen vacancies. - Graphical abstract: The incommensurately modulated composite structure of [Ca{sub 2}CoO{sub 2.86}][CoO{sub 2}]{sub 1.61}.

  13. Hydrothermal synthesis, structure, and magnetic properties of the mixed-valent Np(IV)/Np(V) selenite, Np(NpO{sub 2}){sub 2}(SeO{sub 3}){sub 3}.

    SciTech Connect

    Almond, P. M.; Sykora, R. E.; Skanthakumar, S.; Soderholm, L.; Albrecht-Schmitt, T. E.; Chemistry; Auburn Univ.

    2004-02-09

    The reaction of NpO{sub 2} with SeO{sub 2} in the presence of CsCl at 180 {sup o}C results in the formation of Np(NpO{sub 2}){sub 2}(SeO{sub 3}){sub 3} (1). The structure of 1 consists of three crystallographically unique Np centers with three different coordination environments in two different oxidation states. Np(1) is found in a neptunyl(V), ONpO{sup +}, unit that is further ligated in the equatorial plane by three chelating SeO{sub 3}{sup 2-} anions to create a hexagonal bipyramidal NpO{sub 8} unit. A second neptunyl(V) cation also occurs for Np(2); it is bound by four bridging selenite anions and by the oxo atom from the Np(1) neptunyl cation to form a pentagonal bipyramidal, NpO{sub 7}, unit. The third neptunium center, Np(3), which contains Np(IV), is found in a distorted NpO{sub 8} dodecahedron. Np(3) is bound by five bridging selenite anions and by three neptunyl units via cation-cation interactions. The NpO{sub 7} pentagonal bipyramids and NpO{sub 8} hexagonal bipyramids share both corners and edges. Both of these polyhedra share corners via cation-cation interactions with the NpO{sub 8} dodecahedra creating a three-dimensional structure with small channels that house the stereochemically active lone pair of electrons on the selenite anions. Magnetic susceptibility data follow Curie-Weiss behavior over the entire temperature range measured (5 {<=} T {<=} 320 K). The effective moment, {mu}{sub eff} = 2.28 {mu}{sub B}, which represents an average over the three crystallographically inequivalent Np atoms, is within the expected range of values. There is no evidence of long-range ordering of the Np moments at temperatures down to 5 K, consistent with the negligible Weiss constant determined from fitting the susceptibility data. Crystallographic data: 1, orthorhombic, space group Pbca, a = 10.6216(5), b = 11.9695(6), and c = 17.8084(8) {angstrom} and Z = 8 (T = 193 K).

  14. Synthesis and crystal structures of the layered uranyl tellurites A{sub 2}[(UO{sub 2}){sub 3}(TeO{sub 3}){sub 2}O{sub 2}] (A=K, Rb, Cs)

    SciTech Connect

    Woodward, Jonathan D.; Almond, Philip M.; Albrecht-Schmitt, Thomas E. . E-mail: albreth@auburn.edu

    2004-11-01

    The reactions of UO{sub 3} and TeO{sub 3} with KCl, RbCl, or CsCl at 800{sup o}C for 5d yield single crystals of A{sub 2}[(UO{sub 2}){sub 3}(TeO{sub 3}){sub 2}O{sub 2}] (A=K (1), Rb (2), and Cs (3)). These compounds are isostructural with one another, and their structures consist of two-dimensional {sub {infinity}}{sup 2}[(UO2)3(TeO3)2O2]2- sheets arranged in a stair-like topology separated by alkali metal cations. These sheets are comprised of zigzagging uranium(VI) oxide chains bridged by corner-sharing trigonal pyramidal TeO{sub 3}{sup 2-} anions. The chains are composed of dimeric, edge-sharing, pentagonal bipyramidal UO{sub 7} moieties joined by edge-sharing tetragonal bipyramidal UO{sub 6} units. The lone-pair of electrons from the TeO{sub 3} groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet non-polar. The alkali metal cations form contacts with nearby tellurite oxygen atoms as well as with oxygen atoms from the uranyl moieties. Crystallographic data (193K, MoK{alpha}, {lambda}=0.7107A): 1, triclinic, space group P1-bar , a=6.7985(5)A, b=7.0123(5)A, c=7.8965(6)A, {alpha}=101.852(1){sup o}, {beta}=102.974(1){sup o}, {gamma}=100.081(1){sup o}, V=349.25(4)A3, Z=2, R(F)=2.70% for 98 parameters and 1697 reflections with I>2{sigma}(I); 2, triclinic, space group P1-bar , a=7.0101(6)A, b=7.0742(6)A, c=8.0848(7)A, {alpha}=105.590(2){sup o}, {beta}=101.760(2){sup o}, {gamma}=99.456(2){sup o}, V=367.91(5)A3, Z=2, R(F)=2.36% for 98 parameters and 1817 reflections with I>2{sigma}(I); 3, triclinic, space group P1-bar , a=7.0007(5)A, b=7.5195(6)A, c=8.4327(6)A, {alpha}=109.301(1){sup o}, {beta}=100.573(1){sup o}, {gamma}=99.504(1){sup o}, V=399.49(5)A3, Z=2, R(F)=2.61% for 98 parameters and 1965 reflections with I>2{sigma}(I)

  15. Electron-ion-ion triple-coincidence spectroscopic study of site-specific fragmentation caused by Si:2p core-level photoionization of F{sub 3}SiCH{sub 2}CH{sub 2}Si(CH{sub 3}){sub 3} vapor

    SciTech Connect

    Nagaoka, S.; Hino, M.; Takemoto, M.; Pruemper, G.; Fukuzawa, H.; Liu, X.-J.; Lischke, T.; Ueda, K.; Tamenori, Y.; Harries, J.; Suzuki, I. H.; Takahashi, O.; Okada, K.; Tabayashi, K.

    2007-02-15

    Site-specific fragmentation caused by Si:2p core-level photoionization of F{sub 3}SiCH{sub 2}CH{sub 2}Si(CH{sub 3}){sub 3} vapor was studied by means of high-resolution energy-selected-electron photoion-photoion triple-coincidence spectroscopy. The ab initio molecular orbital method was used for the theoretical description. F{sub 3}SiCH{sub 2}CH{sub 2}{sup +}-Si(CH{sub 3}){sub 3}{sup +} ion pairs were produced by the 2p photoionization of the Si atoms bonded to the three methyl groups, and SiF{sup +}-containing ion pairs were produced by the 2p photoionization of the Si atoms bonded to the three F atoms.

  16. Superconductivity versus structural phase transition in the closely related Bi2Rh3.5S2 and Bi2Rh3sub>S2

    SciTech Connect

    Kaluarachchi, Udhara S.; Xie, Weiwei; Lin, Qisheng; Taufour, Valentin; Bud'ko, Sergey L.; Miller, Gordon J.; Canfield, Paul C.

    2015-05-19

    Single crystals of Bi2Rh3sub>S2 and Bi2Rh3.5S2 were synthesized by solution growth, and the crystal structures and thermodynamic and transport properties of both compounds were studied. In the case of Bi2Rh3sub>S2, a structural first-order transition at around 165 K is identified by single-crystal diffraction experiments, with clear signatures visible in resistivity, magnetization, and specific heat data. No superconducting transition for Bi2Rh3sub>S2 was observed down to 0.5 K. In contrast, no structural phase transition at high temperature was observed for Bi2Rh3.5S2; however, bulk superconductivity with a critical temperature, Tc ≈ 1.7 K, was observed. The Sommerfeld coefficient γ and the Debye temperature (ΘD) were found to be 9.41 mJ mol–1K–2 and 209 K, respectively, for Bi2Rh3sub>S2, and 22 mJ mol–1K–2 and 196 K, respectively, for Bi2Rh3.5S2. As a result, the study of the specific heat in the superconducting state of Bi2Rh3.5S2 suggests that Bi2Rh3.5S2 is a weakly coupled, BCS superconductor.

  17. New polymorphs of Ru{sup III}P{sub 3}O{sub 9}: Cyclo-hexaphosphate Ru{sub 2}P{sub 6}O{sub 18} and metaphosphate Ru(PO{sub 3}){sub 3} with a novel structure

    SciTech Connect

    Fukuoka, Hiroshi; Imoto, Hideo; Saito, Taro

    1995-10-01

    Two new polymorphs of ruthenium phosphate with RuP{sub 3}O{sub 9} composition were prepared and their crystal structures were determined by single-crystal X-ray diffraction. They are cyclo-hexaphosphate Ru{sub 2}P{sub 6}O{sub 18} and metaphosphate Ru(PO{sub 3}){sub 3}. Ru{sub 2}P{sub 6}O{sub 18} crystallizes in the monoclinic space group P2{sub 1}/c with a = 6.292(2) {angstrom}, b = 15.276(2) {angstrom}, c = 8.365(2) {angstrom}, {beta} = 106.54(2){degrees}, contains cyclo-hexaphosphate rings stacking obliquely along the [100] direction and is isotypic with B-form cyclo-phosphates. Ru(PO{sub 3}){sub 3} has a novel structure and crystallizes in the triclinic space group P1 with a = 6.957(1) {angstrom}, b = 10.324(2) {angstrom},c = 5.030(1) {angstrom}, {alpha} = 92.45(2){degrees}, {beta} = 92.31(2){degrees}, {gamma} = 98.61(1){degrees}, V = 356.5(1) {angstrom}{sup 3}, [PO{sub 3}{sup -}]{sub {infinity}} chains is different from that in the C-form Ru(PO{sub 3}){sub 3}. While the chains in the C-form consisting of PO{sub 3}-O-PO{sub 3} units are condensed in nearly staggered configurations, the units in the new phosphate are eclipsed.

  18. New operation strategy for driving the selectivity of NOx reduction to N2, NH3sub> or N2O during lean/rich cycling of a lean NOx trap catalyst

    SciTech Connect

    Mráček, David; Koci, Petr; Choi, Jae -Soon; Partridge, Jr., William P.

    2015-09-08

    Periodical regeneration of NOx storage catalyst (also known as lean NOx trap) by short rich pulses of CO, H2 and hydrocarbons is necessary for the reduction of nitrogen oxides adsorbed on the catalyst surface. Ideally, the stored NOx is converted into N2, but N2O and NH3sub> by-products can be formed as well, particularly at low-intermediate temperatures. The N2 and N2O products are formed concurrently in two peaks. The primary peaks appear immediately after the rich-phase inception, and tail off with the breakthrough of the reductant front accompanied by NH3sub> product. In addition, the secondary N2 and N2O peaks then appear at the rich-to-lean transition as a result of reactions between surface-deposited reductants/intermediates (CO, HC, NH3sub>, — NCO) and residual stored NOx under increasingly lean conditions.

  19. High-pressure high-temperature synthesis and crystal structure of the isotypic rare earth (RE)-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu)

    SciTech Connect

    Borna, Marija; Hunger, Jens; Ormeci, Alim; Zahn, Dirk; Burkhardt, Ulrich; Carrillo-Cabrera, Wilder; Cardoso-Gil, Raul; Kniep, Ruediger

    2011-02-15

    Application of high-pressure high-temperature conditions (3.5 GPa at 1673 K for 5 h) to mixtures of the elements (RE:B:S=1:3:6) yielded crystalline samples of the isotypic rare earth-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu), which crystallize in space group P6{sub 3} (Z=2/3) and adopt the Ce{sub 6}Al{sub 3.33}S{sub 14} structure type. The crystal structures were refined from X-ray powder diffraction data by applying the Rietveld method. Dy: a=9.4044(2) A, c=5.8855(3) A; Ho: a=9.3703(1) A, c=5.8826(1) A; Er: a=9.3279(12) A, c=5.8793(8) A; Tm: a=9.2869(3) A, c=5.8781(3) A; Yb: a=9.2514(5) A, c=5.8805(6) A; Lu: a=9.2162(3) A, c=5.8911(3) A. The crystal structure is characterized by the presence of two isolated complex ions [BS{sub 3}]{sup 3-} and [BS{sub 4}]{sup 5-} as well as [{open_square}(S{sup 2-}){sub 3}] units. -- Graphical abstract: Isotypic rare earth-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu) were prepared by application of high-pressure high-temperature conditions to mixtures of the elements. Their crystal structures are characterized by presence of the two isolated complex ions [BS{sub 3}]{sup 3-} and [BS{sub 4}]{sup 5-} as well as [{open_square}(S{sup 2-}){sub 3}] units. Quantum mechanical calculations revealed the arrangement of the intrinsic vacancies. Display Omitted Research Highlights: {yields} Application of high-pressure high-temperature conditions to mixtures of the elements yields crystalline samples of the isotypic rare earth-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu). {yields} RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu) crystallize in space group P6{sub 3} (Z=2/3) and adopt the Ce{sub 6}Al{sub 3.33}S{sub 14} structure type. {yields} The crystal structure of RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu) is characterized by the presence of two isolated complex ions [BS{sub 3

  20. The first example of a ferrocenylgallane: Synthesis, properties, and X-ray crystal structure of the ((. eta. sup 5 -C sub 5 H sub 5 )Fe(. eta. sup 5 -C sub 5 H sub 4 )Ga(CH sub 3 ) sub 2 ) sub 2 dimer

    SciTech Connect

    Lee, Baosheng; Pennington, W.T.; Laske, J.A.; Robinson, G.H. )

    1990-11-01

    The first ferrocenylgallane, (({eta}{sup 5}-C{sub 5}H{sub 5})Fe({eta}{sup 5}-C{sub 5}H{sub 4})Ga(CH{sub 3}){sub 2}){sub 2}, has been prepared by reaction of (chloromercurio)ferrocene with trimethylgallium in toluene and characterized by {sup 1}H NMR, elemental analyses, and single-crystal X-ray diffraction. The Ga-C bond distance of 2.587 (5) {angstrom} in the Ga{sub 2}C{sub 2} ring is among the longest gallium-carbon bonds reported.

  1. Highly efficient 2  μm CW and Q-switched Tm3+:Lu2O3sub> ceramics lasers in-band pumped by a Raman-shifted erbium fiber laser at 1670  nm.

    PubMed

    Antipov, Oleg; Novikov, Anton; Larin, Sergey; Obronov, Ivan

    2016-05-15

    Highly efficient laser oscillations at 2 μm were investigated in Tm:Lu2O3sub> ceramics in-band pumped at 1670 nm by a Raman-shifted erbium fiber laser. Both 23 W CW and 15 W active Q-switched oscillations with 40 ns pulse duration and 15-30 kHz repetition rate were achieved in a high-quality beam. The evolution of two generated waves at 1966 and 2064 nm in dependence on pump power was studied. PMID:27176987

  2. Highly efficient 2  μm CW and Q-switched Tm3+:Lu2O3sub> ceramics lasers in-band pumped by a Raman-shifted erbium fiber laser at 1670  nm.

    PubMed

    Antipov, Oleg; Novikov, Anton; Larin, Sergey; Obronov, Ivan

    2016-05-15

    Highly efficient laser oscillations at 2 μm were investigated in Tm:Lu2O3sub> ceramics in-band pumped at 1670 nm by a Raman-shifted erbium fiber laser. Both 23 W CW and 15 W active Q-switched oscillations with 40 ns pulse duration and 15-30 kHz repetition rate were achieved in a high-quality beam. The evolution of two generated waves at 1966 and 2064 nm in dependence on pump power was studied.

  3. ([M(NH{sub 3}){sub 6}][Ag{sub 4}M{sub 4}Sn{sub 3}Se{sub 13}]){sub ∞} (M=Zn, Mn): Three-dimensional chalcogenide frameworks constructed from quaternary metal selenide clusters with two different transition metals

    SciTech Connect

    Xiong, Wei-Wei; Miao, Jianwei; Li, Pei-Zhou; Zhao, Yanli; Liu, Bin; Zhang, Qichun

    2014-10-15

    Herein we report solvothermal syntheses of two new three-dimensional chalcogenide frameworks ([M(NH{sub 3}){sub 6}][Ag{sub 4}M{sub 4}Sn{sub 3}Se{sub 13}]){sub n} (M=Zn (1), Mn (2)), which consist of quaternary metal selenide clusters with two different transition metals. The compounds represent the first Ag–Zn/Mn–Sn–Se based quaternary anionic frameworks. The optical studies show that the band gaps for 1 and 2 are 2.09 eV and 1.71 eV, respectively. Moreover, the photoelectrochemical study indicates that compound 1 displays n-type semiconducting behaviour and is photoactive under visible light illumination (λ>400 nm). - Graphical abstract: Two 3D framework selenides, [M(NH{sub 3}){sub 6}][Ag{sub 4}M{sub 4}Sn{sub 3}Se{sub 13}] (M=Zn (1), Mn (2)), constructed from quaternary metal selenide clusters, have been solvothermally synthesized and are photoactive under visible light illumination. - Highlights: • Two new three-dimensional selenide frameworks. • Quaternary metal selenide clusters with two different transition metals. • Photoelectrochemical study.

  4. A study of suppressed formation of low-conductivity phases in doped Li7La3sub>Zr2O12 garnets by in situ neutron diffraction

    SciTech Connect

    Chen, Yan; Rangasamy, Ezhiylmurugan; dela Cruz, Clarina R.; Liang, Chengdu; An, Ke

    2015-09-28

    Doped Li7La3sub>Zr2O12 garnets, oxide-based solids with good Li+ conductivity and compatibility, show great potential as leading electrolyte material candidates for all-solid-state lithium ion batteries. Still yet, the conductive bulk usually suffers from the presence of secondary phases and the transition towards a low-conductivity tetragonal phase during synthesis. Dopants are designed to stabilize the high-conductive cubic phase and suppress the formation of the low-conductivity phases. In situ neutron diffraction enables a direct observation of the doping effects by monitoring the phase evolutions during garnet synthesis. It reveals the reaction mechanism involving the temporary presence of intermediate phases. The off-stoichiometry due to the liquid Li2CO3sub> evaporation leads to the residual of the low-conductivity intermediate phase in the as-synthesized bulk. Appropriate doping of an active element may alter the component of the intermediate phases and promote the completion of the reaction. While the dopants aid to stabilize most of the cubic phase, a small amount of tetragonal phase tends to form under a diffusion process. Lastly, the in situ observations provide the guideline of process optimization to suppress the formation of unwanted low-conductivity phases.

  5. Layered ruthenium hexagonal perovskites: The new series [Ba{sub 2}Br{sub 2-2x}(CO{sub 3}){sub x}][Ba{sub n+1}Ru{sub n}O{sub 3n+3}] with n=2, 3, 4, 5

    SciTech Connect

    Kauffmann, Matthieu; Roussel, Pascal Abraham, Francis

    2007-07-15

    Single crystals of the title compounds were prepared by solid state reactions from barium carbonate and ruthenium metal using a BaBr{sub 2} flux and investigated by X-ray diffraction method using Mo(K{alpha}) radiation and a Charge Coupled Device (CCD) detector. A structural model for the term n=2, Ba{sub 5}Ru{sub 2}Br{sub 2}O{sub 9} (1) was established in the hexagonal symmetry, space group P6{sub 3}/mmc, a=5.8344(2)A, c=25.637(2)A, Z=2. Combined refinement and maximum-entropy method (MEM) unambiguously show the presence of CO{sub 3}{sup 2-} ions in the three other compounds (2, 3, 4). Their crystal structures were solved and refined in the trigonal symmetry, space group P3-barml, a=5.8381(1)A, c=15.3083(6)A for the term n=3, Ba{sub 6}Ru{sub 3}Br{sub 1.54}(CO{sub 3}){sub 0.23}O{sub 12} (2), and space group R3-barm, a=5.7992(1)A, c=52.866(2)A and a=5.7900(1)A, c=59.819(2)A for the terms n=4, Ba{sub 7}Ru{sub 4}Br{sub 1.46}(CO{sub 3}){sub 0.27}O{sub 15} (3), and n=5, Ba{sub 8}Ru{sub 5}Br{sub 1.64}(CO{sub 3}){sub 0.18}O{sub 18} (4), respectively. The structures are formed by the periodic stacking along [001] of (n+1) hexagonal close-packed [BaO{sub 3}] layers separated by a double layer of composition [Ba{sub 2}Br{sub 2-2x}(CO{sub 3}){sub x}]. The ruthenium atoms occupy the n octahedral interstices created in the hexagonal perovskite slabs and constitute isolated dimers Ru{sub 2}O{sub 9} of face-shared octahedra (FSO) in 1 and isolated trimers Ru{sub 3}O{sub 12} of FSO in 2. In 3 and 4, the Ru{sub 2}O{sub 9} units are connected by corners either directly (3) or through a slab of isolated RuO{sub 6} octahedra (4) to form a bidimensional arrangement of RuO{sub 6} octahedra. These four oxybromocarbonates belong to the family of compounds formulated [Ba{sub 2}Br{sub 2-2x}(CO{sub 3}){sub x}][Ba{sub n+1}Ru{sub n}O{sub 3n+3}] where n represents the thickness of the octahedral string in hexagonal perovskite slabs. These compounds are compared to the oxychloride series.

  6. Structural, thermal, spectroscopic and magnetic studies of the (C{sub 2}N{sub 2}H{sub 10}){sub 0.5}[Fe {sub x}V{sub 1-x}(HPO{sub 3}){sub 2}] (x = 0.26, 0.52, 0.74) solid solution

    SciTech Connect

    Cisneros, Jose L.; Fernandez-Armas, Sergio; Mesa, Jose L. . E-mail: joseluis.mesa@ehu.es; Pizarro, Jose L.; Arriortua, Maria I.; Rojo, Teofilo . E-mail: teo.rojo@ehu.es

    2006-11-09

    The (C{sub 2}N{sub 2}H{sub 10}){sub 0.5}[Fe {sub x}V{sub 1-x}(HPO{sub 3}){sub 2}] (x = 0.26, 0.52 0.74) compounds have been obtained by mild solvothermal conditions in the form of micro-crystalline powder with brown color. The crystal structures were refined by X-ray powder diffraction data using the Rietveld method. The compounds crystallize in the monoclinic system, space group P2/c with the unit-cell parameters, a = 9.262(5) A, b = 8.823(5) A, c = 9.714(6) A, {beta} = 120.84(3){sup o}; a = 9.245(1) A, b = 8.823(1) A, c = 9.698(1)A, {beta} = 120.80(1){sup o} and, a = 9.254(4)A, b = 8.822(4)A, c = 9.702(4)A, {beta} = 120.73(3){sup o} for (C{sub 2}N{sub 2}H{sub 10}){sub 0.5}[Fe{sub 0.26}V{sub 0.74} (HPO{sub 3}){sub 2}] (1) (C{sub 2}N{sub 2}H{sub 10}){sub 0.5}[Fe{sub 0.52}V{sub 0.48}(HPO{sub 3}){sub 2}] (2), and (C{sub 2}N{sub 2}H{sub 10}){sub 0.5}[Fe{sub 0.74}V{sub 0.26}(HPO{sub 3}){sub 2}] (3). The compounds show an open crystalline structure with three-dimensional character, whose formula for the anionic inorganic skeleton is [M(HPO{sub 3}){sub 2}]{sup 2-}. The inorganic framework is formed by [MO{sub 6}] octahedra inter-connected by phosphite groups. The structure of the compounds exhibits channels extended along the [1 0 0] and [0 0 1] directions and the ethylendiammonium cations are located inside these channels, linked through hydrogen bonds and ionic interactions. The infrared spectra show the bands corresponding to the stretching (P-H) vibration of the phosphite group and the band corresponding to the deformation mode of the ethylendiammonium cation, {delta}(NH{sub 3} {sup +}). The thermal and thermodiffractometric behavior show that the compounds are stable up to approximately 300 deg. C, at higher temperatures the decomposition of the crystal structure by calcination of the organic cation starts. The diffuse reflectance spectra show bands of the V{sup 3+} ion (d {sup 2}), and a band of the Fe{sup 3+} ion (d {sup 5}), in a slightly distorted octahedral

  7. Six novel transition-metal phosphite compounds, with structure related to yavapaiite: Crystal structures and magnetic and thermal properties of A{sup I}[M{sup III}(HPO{sub 3}){sub 2}] (A=K, NH{sub 4}, Rb and M=V, Fe)

    SciTech Connect

    Hamchaoui, Farida; Alonzo, Veronique; Venegas-Yazigi, Diego; Rebbah, Houria; Le Fur, Eric

    2013-02-15

    Six new transition metal(III) phosphites A{sup I}[V{sup III}(HPO{sub 3}){sub 2}], where A=K (1), NH{sub 4} (2) and Rb (3) and A{sup I}[Fe{sup III}(HPO{sub 3}){sub 2}] where A=K (4), NH{sub 4} (5) and Rb (6) have been synthesized under hydrothermal conditions and the solid-state structures were solved from single-crystal X-ray diffraction data. These compounds crystallize in the hexagonal system, space group P6{sub 3}mc (no. 186), with a=5.3294(2) A and c=12.3130(5) A for 1, a=5.3330(2) A and c=12.8760(4) A for 2, a=5.3459(2) A and c=12.6850(8) A for 3, a=5.3256(1) A and c=12.2362(3) A for 4, a=5.3229(2) A and c=12.8562(4) A for 5, a=5.3393(2) A and c=12.6913(5) A for 6, with Z=2 in the six phases. The crystal structures of these compounds are isotypic and exhibit a layered structure stacked along the c-axis with the A{sup +} cations located in the interlayer space. The [M{sup III}(HPO{sub 3}){sub 2}]{sup -} sheets are formed by MO{sub 6} octahedra interconnected by HPO{sub 3} tetrahedral phosphite oxoanions through sharing vertices. Thermal analysis shows a large range of stability for compounds containing potassium and rubidium cations with decomposition starting around 550 K for stable compounds and above 840 K for the most stable compounds leading in general to pyrophosphate compounds. Triangular nets of metallic centers are observed within the layers in which antiferromagnetic interactions are evidenced by magnetic susceptibility measurements suggesting magnetic frustration. - Graphical abstract: Six new transition metal(III) phosphites A{sup I}[M{sup III}(HPO{sub 3}){sub 2}], where A=K, NH{sub 4}, Rb and M=V, Fe, have been synthesized. The crystal structures of these compounds are isotypic and exhibit a lamellar structure related to Yavapaiite. The M(HPO{sub 3}){sub 2} layers separated by cationic species present the metallic centers in a triangular arrangement. Bulk antiferromagnetic behavior is observed for all the studied compounds. Highlights: Black

  8. High dielectric non-linear properties of the Pb[(Mg{sub 1/3}Nb{sub 2/3}){sub 0.8}(Sc{sub 1/2}Nb{sub 1/2}){sub 0.2}]O{sub 3} ceramics

    SciTech Connect

    Peng, Biaolin; Fan, Huiqing; Li, Qiang; Zhang, Qi

    2012-08-15

    Highlights: ► A Lorentz relation and a small polaron over the curie temperature range can describe the relaxation behaviors of the Pb[(Mg{sub 1/3}Nb{sub 2/3}){sub 0.8}(Sc{sub 1/2}Nb{sub 1/2}){sub 0.2}]O{sub 3} ceramics possessing 1:1 B-site partially ordered perovskite structure. ► High dielectric tunability, low dielectric loss and high figure of merit make the Pb[(Mg{sub 1/3}Nb{sub 2/3}){sub 0.8}(Sc{sub 1/2}Nb{sub 1/2}){sub 0.2}]O{sub 3} ceramics an attractive material for tunable device applications. ► The high dielectric non-linear behavior is related not only to the contribution of the ‘intrinsic’ lattice phonon polarization but also to the contribution of the re-orientation of the polar nanoclusters. -- Abstract: Pure perovskite Pb[(Mg{sub 1/3}Nb{sub 2/3}){sub 0.8}(Sc{sub 1/2}Nb{sub 1/2}){sub 0.2}]O{sub 3} (PMNSN) ceramics were prepared via a modified ‘columbite-type’ method. The 1:1 B-site ordered structure was detected by X-ray diffraction and transmission electron microscopy. The dielectric relaxation behavior was described by a Lorentz relation and a small polaron over the Curie temperature range. The dielectric tunability properties were investigated at 300 K and 10 kHz. A high dielectric tunability (∼ 75% at 30 kV/cm), low dielectric loss (∼ 0.003) and high figure of merit (∼ 250) of PMNSN, indicate that PMNSN is a promising dielectric tunable material. The high dielectric non-linear behavior of PMNSN was further discussed in terms of the Landau–Ginsberg–Devonshire thermodynamic theory completed with a Langevin term that describes the contribution of the re-orientation of the polar nanoclusters to the non-linear ε(E) dependences.

  9. NMR Studies of the Vanadium Spin Dynamics and Spin Structure in LiV2O4, CaV2O4, and (LixV1-x)3sub>BO5 (x ≈ 0.33, 0.40)

    SciTech Connect

    Zong, Xiaopeng

    2007-01-01

    Strong electron correlation is believed to be an essential and unifying factor in diverse properties of condensed matter systems. Ground states that can arise due to electron correlation effects include Mott insulators, heavy fermion, ferromagnetism and antiferromagnetism, spin glasses, and high-temperature superconductivity. The electronic systems in transition metal oxide compounds are often highly correlated. In this thesis, the author presents experimental studies on three strongly correlated vanadium oxide compounds: LiV2O4, (LixV1-x)3sub>BO5, and CaV2O4, which have completely different ground states.

  10. ESR studies of two new organic superconductors: {beta}``-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} and {kappa}{sub L}`-(BEDT-TTF){sub 2}Cu(CF{sub 3}){sub 4}(DBCE)

    SciTech Connect

    Wang, H.H.; VanZile, M.L.; Geiser, U.

    1996-10-01

    The normal-state ESR of two new organic superconductors, {beta}{double_prime}-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} and {kappa}{sub L}{prime}-(BEDT-TTF){sub 2}Cu(CF{sub 3}){sub 4}(DBCE) are reported. Both compounds showed metallic properties below 140 K. The former gave ESR line widths and g-values of 23-34 G and 2.004-2.012. The latter gave line widths and g-values of 45-58 G and 2.006-2.012. Orientation-dependent line widths and g-values of the {kappa}{sub L}{prime}-phase were found to be similar to that of the {kappa}-(ET){sub 4}Hg{sub 3}Br{sub 8} but not to the {kappa}{sub L}-phases in general.

  11. {[Ga(en){sub 3}]{sub 2}(Ge{sub 2}Te{sub 15})}n : a polymeric semiconducting polytelluride with boat-shaped Te{sub 8}{sup 4-} rings and cross-shaped Te{sub 5}{sup 6-} units.

    SciTech Connect

    Zhang, Q.; Malliakas, C. D.; Kanatzidis, M. G.

    2009-11-11

    The reaction of the Zintl compound K{sub 4}Ge{sub 9} with Te and Ga{sub 2}Te{sub 3} in ethylenediamine (en) at 190 C gave the germanium polytelluride {l_brace}[Ga(en){sub 3}]{sub 2}[(GeTe){sub 2}(Te{sub 5}){sup 6-}(Te{sub 8}){sup 4-}]{r_brace}n (1). The single-crystal structure analysis revealed that 1 has two different polytelluride fragments: cross-shaped 36-e- TeTe{sub 4}{sup 6-} anions and boat-shaped 52-e- Te{sup 8}{sup 4-} rings. The new material is a p-type semiconductor at room temperature and switches to n-type at 380 K.

  12. Second order phase transition temperature of single crystals of Gd5Si1.3sub>Ge2.7 and Gd5Si1.4Ge2.6

    SciTech Connect

    Hadimani, R. L.; Melikhov, Y.; Schlagel, D. L.; Lograsso, T. A.; Dennis, K. W.; McCallum, R. W.; Jiles, D. C.

    2015-01-30

    Gd5(SixGe1–x)4 has mixed phases in the composition range 0.32 < x < 0.41, which have not been widely studied. In this paper, we have synthesized and indexed single crystal samples of Gd5Si1.3sub>Ge2.7 and Gd5Si1.4Ge2.6. In this study, we have investigated the first order and second order phase transition temperatures of these samples using magnetic moment vs. temperature and magnetic moment vs. magnetic field at different temperatures. We have used a modified Arrott plot technique that was developed and reported by us previously to determine the “hidden” second order phase transition temperature of the orthorhombic II phase.

  13. Eu3sub>Ir2In15: A mixed-valent and vacancy-filled variant of the Sc5Co4Si10 structure type with anomalous magnetic properties

    SciTech Connect

    Sarkar, Sumanta; Jana, Rajkumar; Siva, Ramesh; Banerjee, Swastika; Pati, Swapan K.; Balasubramanian, Mahalingam; Peter, Sebastian C.

    2015-10-27

    Here, a new compound, Eu3sub>Ir2In15 has been synthesized using indium as an active metal flux. The compound crystallizes in tetragonal P4/mbm space group with lattice parameters, a = 14.8580(4) Å, b = 14.8580(4) Å, c = 4.3901(2) Å. It was further characterized by SEM-EDX studies. The temperature dependent magnetic susceptibility suggests that Eu in this compound is exclusively in divalent state. The effective magnetic moment (μeff) of this compound is 7.35 μB/Eu ion with paramagnetic Curie temperature (θp) of -28 K suggesting antiferromagnetic interaction. The mixed valent nature of Eu observed in magnetic measurements was confirmed by XANES measurements. The compound undergoes demagnetization at a low magnetic field (10 Oe), which is quite unusual for Eu based intermetallic compounds. Temperature dependent resistivity studies reveal that the compound is metallic in nature. A comparative study was made between Eu3sub>Ir2In15 and hypothetical vacancy variant Eu5Ir4In10 which also crystallizes in the same crystal structure However our computational studies along with control experiments suggest that the latter is thermodynamically less feasible compared to the former and hence we proposed that it is highly unlikely that a RE5T4X10 would exist with X as a group 13 elements.

  14. A new organically templated monodimensional mixed valence (Fe{sup II}/Fe{sup III}) phosphite: (C{sub 4}H{sub 12}N{sub 2})[Fe{sup II}Fe{sup III}(HPO{sub 3}){sub 2}F{sub 3}

    SciTech Connect

    Fernandez-Armas, Sergio

    2007-03-22

    The organically templated (C{sub 4}H{sub 12}N{sub 2})[Fe{sup II}Fe{sup III}(HPO{sub 3}){sub 2}F{sub 3}] compound has been synthesized under mild solvothermal conditions. The crystal structure has been determined from X-ray single-crystal diffraction data. The compound crystallizes in the P2{sub 1}/n monoclinic space group, with the unit-cell parameters a = 12.935(1), b = 6.4476(7), c = 15.693(2) A, {beta} = 105.630(9){sup o} and Z = 4. The crystal structure consists of [Fe{sup II}Fe{sup III}(HPO{sub 3}){sub 2}F{sub 3}]{sup 2-} chains formed by a central chain built of [Fe(2)O{sub 4}F{sub 2}] edge-sharing octahedra, and two side chains formed by alternating [Fe(1)O{sub 3}F{sub 3}] octahedra and [HP(1)O{sub 3}] tetrahedra. The piperazinium cations are placed between the chains linked by ionic and hydrogen interactions. The IR and Raman spectra show the existence of two phosphite crystallographically independent. From the diffuse reflectance spectrum the D {sub q} parameter for the iron(II) cations has been calculated (D {sub q} = 820 cm{sup -1}). The Moessbauer spectrum in the paramagnetic state shows the simultaneous presence of Fe{sup 2+} and Fe{sup 3+}. The magnetic measurements indicate the existence of antiferromagnetic interactions.

  15. Synthesis and Structure of In(IO3sub>)3sub> and Vibrational Spectroscopy of M(IO3sub>)3sub> (M = Al, Ga, In)

    SciTech Connect

    Ngo, Nhan; Kalachnikova, Katrina; Assefa, Zerihun; Haire, Richard {Dick} G; Sykora, Richard E.

    2006-01-01

    The reaction of Al, Ga, or In metals and H5IO6 in aqueous media at 180 C leads to the formation of Al(IO3)3, Ga(IO3)3, or In(IO3)3, respectively. Single-crystal X-ray diffraction experiments have shown In(IO3)3 contains the Te4O9-type structure, while both Al(IO3)3 and Ga(IO3)3 are known to exhibit the polar Fe(IO3)3-type structure. Crystallographic data for In(IO3)3, trigonal, space group View the MathML source, a=9.7482(4) {angstrom}, c=14.1374(6) {angstrom}, V=1163.45(8) Z=6, R(F)=1.38% for 41 parameters with 644 reflections with I>2s(I). All three iodate structures contain group 13 metal cations in a distorted octahedral coordination environment. M(IO3)3 (M=Al, Ga) contain a three-dimensional network formed by the bridging of Al3+ or Ga3+ cations by iodate anions. With In(IO3)3, iodate anions bridge In3+ cations in two-dimensional layers. Both materials contain distorted octahedral holes in their structures formed by terminal oxygen atoms from the iodate anions. The Raman spectra have been collected for these metal iodates; In(IO3)3 was found to display a distinctively different vibrational profile than Al(IO3)3 or Ga(IO3)3. Hence, the Raman profile can be used as a rapid diagnostic tool to discern between the different structural motifs.

  16. High temperature redox reactions with uranium: Synthesis and characterization of Cs(UO{sub 2})Cl(SeO{sub 3}), Rb{sub 2}(UO{sub 2}){sub 3}O{sub 2}(SeO{sub 3}){sub 2}, and RbNa{sub 5}U{sub 2}(SO{sub 4}){sub 7}

    SciTech Connect

    Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

    2013-10-15

    Cs(UO{sub 2})Cl(SeO{sub 3}) (1), Rb{sub 2}(UO{sub 2}){sub 3}O{sub 2}(SeO{sub 3}){sub 3} (2), and RbNa{sub 5}U{sub 2}(SO{sub 4}){sub 7} (3) single crystals were synthesized using CsCl, RbCl, and a CuCl/NaCl eutectic mixture as fluxes, respectively. Their lattice parameters and space groups are as follows: P2{sub 1}/n (a=6.548(1) Å, b=11.052(2) Å, c=10.666(2) Å and β=93.897(3)°), P1{sup ¯} (a=7.051(2) Å, b=7.198(2) Å, c=8.314(2) Å, α=107.897(3)°, β=102.687(3)° and γ=100.564(3)°) and C2/c (a=17.862(4) Å, b=6.931(1) Å, c=20.133(4) Å and β=109.737(6)°. The small anionic building units found in these compounds are SeO{sub 3}{sup 2−} and SO{sub 4}{sup 2−} tetrahedra, oxide, and chloride. The crystal structure of the first compound is composed of [(UO{sub 2}){sub 2}Cl{sub 2}(SeO{sub 3}){sub 2}]{sup 2−} chains separated by Cs{sup +} cations. The structure of (2) is constructed from [(UO{sub 2}){sub 3}O{sub 11}]{sup 16−} chains further connected through selenite units into layers stacked perpendicularly to the [0 1 0] direction, with Rb{sup +} cations intercalating between them. The structure of compound (3) is made of uranyl sulfate layers formed by edge and vertex connections between dimeric [U{sub 2}O{sub 16}] and [SO{sub 4}] polyhedra. These layers contain unusual sulfate–metal connectivity as well as large voids. - Graphical abstract: A new family of uranyl selenites and sulfates has been prepared by high-temperature redox reactions. This compounds display new bonding motifs. Display Omitted - Highlights: • Low-dimensional Uranyl Oxoanion compounds. • Conversion of U(IV) to U(VI) at high temperatures. • Dimensional reduction by both halides and stereochemically active lone-pairs.

  17. Examination of the mechanism for the reversible aging behavior at open circuit when changing the operating temperature of (La0.8Sr0.2)0.95 MnO3sub> electrodes

    SciTech Connect

    Abernathy, Harry; Finklea, Harry O.; Mebane, David S.; Song, Xueyan; Chen, Yun; Gerdes, Kirk

    2015-02-17

    The aging behavior of symmetrical cells, consisting of either (La0.8Sr0.2)0.95 MnO3sub> (LSM) or La0.6Sr0.4Co0.2Fe0.8O3sub> (LSCF) electrodes screen printed on either 8 mol% yttria-stabilized zirconia (YSZ) or Ce0.8Gd0.2O2 (GDC) electrolyte substrates, is reported as the symmetrical cell is thermally cycled between 700 °C and 800 °C. For LSM, between 700 °C and 850 °C, the polarization resistance exhibits slow increases or decreases with time (on the order of days) after a quick change in temperature. When increasing the temperature, the polarization resistance decreases with time, and when decreasing the temperature, the polarization resistance slowly increases with time. In a previous work, the authors had explained these results with LSM by connecting the testing conditions to literature reports of surface analysis of LSM thin films which demonstrated a change in the amount of surface cation segregation as a function of temperature. In this work, TEM/EDS/XPS analysis of dense LSM pellets thermally cycled under the same conditions as the symmetrical cells does not indicate any significant reversible change in the surface composition of the LSM pellet between 700 °C and 800 °C. An alternative hypothesis is proposed to explain the relationship between polarization resistance and the LSM cation/anion vacancy concentrations controlled by the Schottky reaction. The timescale of aging behavior is related to the time necessary for the cations to move to or from the LSM surface to adjust to the new equilibrium at each temperature. Furthermore, the relevance in understanding the mechanism behind the aging behavior is emphasized with respect to fuel cell sample/stack modeling as well as to proper testing procedures for reaching reliable conclusions when comparing different electrode samples.

  18. Crystal structure of britvinite [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]: A new layered silicate with an original type of silicon-oxygen networks

    SciTech Connect

    Yakubovich, O. V. Massa, W.; Chukanov, N. V.

    2008-03-15

    The crystal structure of a new mineral britvinite Pb{sub 7.1}Mg{sub 4.5}(Si{sub 4.8}Al{sub 0.2}O{sub 14})(BO{sub 3})(CO{sub 3})[(BO{sub 3}){sub 0.7}(SiO{sub 4}){sub 0.3}]= (OH, F){sub 6.7} from the Langban iron-manganese skarn deposit (Vaermland, Sweden) is determined at T = 173 K using X-ray diffraction (Stoe IPDS diffractometer, {lambda}MoK{alpha}, graphite monochromator, 2{theta}{sub max} = 58.43{sup o}, R = 0.052 for 6262 reflections). The main crystal data are as follows: a = 9.3409(8) A, b = 9.3579(7) A, c = 18.8333(14) A, {alpha} = 80.365(6) deg., {beta} = 75.816(6) deg., {gamma} = 59.870(5) deg., V = 1378.7(2) A{sup 3}, space group P1, Z = 2, and {rho}{sub calcd} = 5.42 g/cm{sup 3}. The idealized structural formula of the mineral is represented as [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]. It is demonstrated that the mineral britvinite is a new representative of the group of mica-like layered silicates with structures in which three-layer (2: 1) 'sandwiches' composed of tetrahedra and octahedra alternate with blocks of other compositions, such as oxide, oxide-carbonate, oxide-carbonate-sulfate, and other blocks. The tetrahedral networks (Si{sub 5}O{sub 14}){sub {infinity}}{sub {infinity}} consisting of twelve-membered rings are fragments of the britvinite structure. Similar networks also form crystal structures of the mineral zeophyllite and the synthetic phase Rb{sub 6}Si{sub 10}O{sub 23}. In the crystal structures under consideration, the tetrahedral networks differ in the rotation of tetrahedra with respect to the layer plane.

  19. Crystal structure of britvinite [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]: A new layered silicate with an original type of silicon-oxygen networks

    SciTech Connect

    Yakubovich, O. V.; Massa, W.; Chukanov, N. V.

    2008-03-15

    The crystal structure of a new mineral britvinite Pb{sub 7.1}Mg{sub 4.5}(Si{sub 4.8}Al{sub 0.2}O{sub 14})(BO{sub 3})(CO{sub 3})[(BO{sub 3}){sub 0.7}(SiO{sub 4}){sub 0.3}](OH, F){sub 6.7} from the Langban iron-manganese skarn deposit (Vaermland, Sweden) is determined at T = 173 K using X-ray diffraction (Stoe IPDS diffractometer, {lambda}MoK{alpha}, graphite monochromator, 2{theta}{sub max} = 58.43 Degree-Sign , R = 0.052 for 6262 reflections). The main crystal data are as follows: a = 9.3409(8) Angstrom-Sign , b = 9.3579(7) Angstrom-Sign , c = 18.8333(14) Angstrom-Sign , {alpha} = 80.365(6) Degree-Sign , {beta} = 75.816(6) Degree-Sign , {gamma} = 59.870(5) Degree-Sign , V = 1378.7(2) Angstrom-Sign {sup 3}, space group P1, Z = 2, and {rho}{sub calcd} = 5.42 g/cm{sup 3}. The idealized structural formula of the mineral is represented as [Pb{sub 7}(OH){sub 3}F(BO{sub 3}){sub 2}(CO{sub 3})][Mg{sub 4.5}(OH){sub 3}(Si{sub 5}O{sub 14})]. It is demonstrated that the mineral britvinite is a new representative of the group of mica-like layered silicates with structures in which three-layer (2: 1) 'sandwiches' composed of tetrahedra and octahedra alternate with blocks of other compositions, such as oxide, oxide-carbonate, oxide-carbonate-sulfate, and other blocks. The tetrahedral networks (Si{sub 5}O{sub 14}){sub {infinity}{infinity}} consisting of twelve-membered rings are fragments of the britvinite structure. Similar networks also form crystal structures of the mineral zeophyllite and the synthetic phase Rb{sub 6}Si{sub 10}O{sub 23}. In the crystal structures under consideration, the tetrahedral networks differ in the rotation of tetrahedra with respect to the layer plane.

  20. Preparation, solution behavior, and solid-state structures of (1,3-R{sub 2}C{sub 5}H{sub 3}){sub 2}UX{sub 2}, where R is CMe{sub 3} or SiMe{sub 3} and X is a one-electron ligand

    SciTech Connect

    Lukens, W.W. Jr.; Beshouri, S.M.; Blosch, L.L.; Stuart, A.L.; Andersen, R.A.

    1999-03-29

    High-yield preparations of the uranium metallocenes [1,3-(Me{sub 3}Si){sub 2}C{sub 5}H{sub 3}]{sub 2}UCL{sub 2}(Cp{double_prime}{sub 2}UCL{sub 2}) and [1,3-(Me{sub 3}C){sub 2}C{sub 5}H{sub 3}]{sub 2}UCL{sub 2} (Cp{sup {double_dagger}}{sub 2}UCL{sub 2}) have been developed from the reaction of UCl{sub 4} and the corresponding magnesocenes Cp{double_prime}{sub 2}Mg and Cp{sup {double_dagger}}{sub 2}Mg in diethyl ether. The chloride ligands can be exchanged with either Me{sub 3}SiBr or Me{sub 3}SiI to give the uranium metallocene bromides or iodides. The fluorides were prepared by the reaction of BF{sub 3}{center_dot}OEt{sub 2} with Cp{double_prime}{sub 2}U(NMe){sub 2}, Cp{sup {double_dagger}}{sub 2}U(OMe){sub 2}, or Cp{sup {double_dagger}}{sub 2}UMe{sub 2}. The crystal structures of Cp{double_prime}{sub 2}UCl{sub 2}, Cp{sup {double_dagger}}{sub 2}UCl{sub 2}, Cp{double_prime}{sub 2}UMe{sub 2}, Cp{sup {double_dagger}}{sub 2}UF{sub 2}, and dimeric (Cp{double_prime}{sub 2}UF{sub 2}){sub 2} are reported. The idealized symmetry of the monomers Cp{double_prime}{sub 2}UX{sub 2} and Cp{sup {double_dagger}}{sub 2}UCl{sub 2} is C{sub 2{nu}} when X is F, Cl, or Br and C{sub 2} when X is I or Me; in the dimer, the idealized symmetry is C{sub i}. This preference is rationalized by intramolecular and intermolecular steric effects. The solution ring conformations and intramolecular exchange processes have been studied by variable-temperature {sup 1}H NMR spectroscopy. In all cases, the low-temperature limiting spectra are consistent with the idealized symmetry observed in the solid state.

  1. Thermodynamic Model for the Solubility of NdF3sub>(cr) in the Na+-NH4+ – Nd3+–F-–H2O System at 25 °C

    SciTech Connect

    Rai, Dhanpat; Yui, Mikazu; Kitamura, Akira; Yoshikawa, Hideki; Felmy, A. R.

    2013-08-02

    The objectives of this study were to develop a reliable thermodynamic model for the Nd-F system based on critical review and experimental studies. The SIT model was used to convert concentration constants reported in the literature to constants at zero ionic strengths for cross comparison and selection of reliable values. The critically evaluated thermodynamic constants for the formation of NdF2+ and NdF2+ were then used to interpret the extensive NdF3(cr) solubility data in NaF and NH4F solutions, ranging in concentrations from extremely low values to as high as 1.0 mol.kg-1, equilibrated for different periods ranging up to as long as 72 days. These efforts have resulted in log βn0 for the reaction [Nd3+ + nF- = NdFn3-n] of (3.81 ± 0.10), (5.89 ± 0.77), and <12.48 for n of 1 through 3, respectively. The log10 Ksp0 for the solubility of NdF3sub>(cr) (NdF3(cr) = Nd3+ + 3F-) was determined to be -(20.49 ± 0.37). Because 1) Nd is an excellent analog for trivalent actinides -- An(III) (e.i., Pu(III), Am(III), and Cm(III)) -- and 2) the available data for the An(III)-F system, especially the solubility products of AnF3sub>(cr), are of extremely poor quality, the critical literature review in combination with the experimental Nd-F system data have been used to assign thermodynamic constants for the An(III)-F reactions until good quality specific data for them becomes available.

  2. Syntheses and reactions of polymer-bound molybdenum complexes and hydrogenolyses of an alkynyl cobalt carbonyl cluster. [Co/sub 3/(CO)/sub 9/CCH/sub 2/CCH/sub 2/C(CH/sub 3/)/sub 3/; cyclopentadienyl-(tricarbonyl) hydridomolybdenum

    SciTech Connect

    Frommer, J.E.

    1980-08-01

    Co/sub 3/(CO)/sub 9/CCH/sub 2/C(CH/sub 3/)/sub 3/ reacted with hydrogen in aromatic solvents to yield 3,3-dimethylbutene, 2,2-dimethylbutane, and 4,4-dimethylpentanal. First order decomposition of starting material and a hydrogen pressure dependence for the rate of appearance of total products were indicated. The hydrogenation was inhibited in the presence of carbon monoxide (CO:H/sub 2/, 3.7:3.7 atm, 60/sup 0/C), but at 85/sup 0/ under the same CO/H/sub 2/ atmosphere, aldehyde production became the predominant reaction pathway at the expense of earlier-formed olefin. Incorporation of independently added olefins in the hydrogenation suggested the intermediacy of olefin aldehyde ad alkane production. A polystyrene-attached n/sup 5/-cyclopentadienyl(tricarbonyl)-hydridomolybdenum complex was prepared and its reactions with several THF-soluble bases were investigated. Enolates of ..beta..-dicarbonyl compounds quantitatively deprotonated this complex, giving polymer-bound salts of the corresponding anion. Little change in pKa in THF was induced by binding the molybdenum hydride to the polymer. Even though the polymer-supported partners rendered the reactions heterogeneous, the systems adhered reasonably well to conventional equilibrium behavior. A polymer-bound carboxylic acid and its conjugate base also displayed essentially conventional equilibrium dynamics.

  3. Enhanced magnetic behavior, exchange bias effect, and dielectric property of BiFeO{sub 3} incorporated in (BiFeO{sub 3}){sub 0.50} (Co{sub 0.4}Zn{sub 0.4}Cu{sub 0.2} Fe{sub 2}O{sub 4}){sub 0.5} nanocomposite

    SciTech Connect

    Mukhopadhyay, K.; Mahapatra, A. S.; Sutradhar, S.; Chakrabarti, P. K.

    2014-03-15

    Nanoparticles of BiFeO{sub 3} (BFO) are incorporated in the nanocomposite of (BiFeO{sub 3}){sub 0.50} (Co{sub 0.4}Zn{sub 0.4}Cu{sub 0.2} Fe{sub 2}O{sub 4}){sub 0.5}, (BFO-CZCF) and these are prepared by chemical route. The formation of pure crystallographic phase of each component (BFO and CZCF) in the nanocomposite of BFO-CZCF has been confirmed by Rietveld analysis of the X-ray diffractograms using FULLPROF program. Morphology, average particle size and its distribution, crystallographic phase etc. are obtained from the high-resolution transmission electron microscopy of BFO-CZCF. Magnetic measurements of BFO-CZCF have been carried out to explore the modulation of magnetic behavior of BFO in BFO-CZCF. Interestingly, magnetization of BFO-CZCF has been drastically enhanced compared to that of the pristine BFO. An exchange bias effect is also observed in the M vs. H loops of BFO-CZCF recorded in field cooled and zero field cooled conditions, which suggest that nanoparticles of BFO (AFM) are encapsulated by nanoparticles of CZCF (FM) in BFO-CZCF. Thermal variation of dielectric constant of BFO-CZCF is recorded in the range of 300 to 1073 K and a ferroelectric to paraelectric transition is observed at ∼728 K. Enhanced magnetic property of BFO would quite interesting for this important multiferroic.

  4. Surface collective modes in the topological insulators Bi2Se3sub> and Bi0.5Sb1.5Te3-xSex

    SciTech Connect

    Kogar, A.; Gu, G.; Vig, S.; Thaler, A.; Wong, M. H.; Xiao, Y.; Reig-i-Plessis, D.; Cho, G. Y.; Valla, T.; Pan, Z.; Schneeloch, J.; Zhong, R.; Hughes, T. L.; MacDougall, G. J.; Chiang, T. -C.; Abbamonte, P.

    2015-12-15

    In this study, we used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi2Se3sub> and Bi0.5Sb1.5Te3-xSex. Our goal was to identify the “spin plasmon” predicted by Raghu and co-workers [Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carriers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface χ''(q,ω) at THz energy scales, and is the most likely origin of a quasiparticle dispersion kink observed in previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role.

  5. Effect of metal in M3sub>(btc)2 and M2(dobdc) MOFs for O2/N2 separations: A combined density functional theory and experimental study

    SciTech Connect

    Parkes, Marie V.; Sava Gallis, Dorina F.; Greathouse, Jeffery A.; Nenoff, Tina M.

    2015-03-02

    Computational screening of metal-organic framework (MOF) materials for selective oxygen adsorption from air could lead to new sorbents for the oxyfuel combustion process feedstock streams. A comprehensive study on the effect of MOF metal chemistry on gas binding energies in two common but structurally disparate metal-organic frameworks has been undertaken. Dispersion-corrected density functional theory methods were used to calculate the oxygen and nitrogen binding energies with each of fourteen metals, respectively, substituted into two MOF series, M2(dobdc) and M3sub>(btc)2. The accuracy of DFT methods was validated by comparing trends in binding energy with experimental gas sorption measurements. A periodic trend in oxygen binding energies was found, with greater oxygen binding energies for early transition-metal-substituted MOFs compared to late transition metal MOFs; this was independent of MOF structural type. The larger binding energies were associated with oxygen binding in a side-on configuration to the metal, with concomitant lengthening of the O-O bond. In contrast, nitrogen binding energies were similar across the transition metal series, regardless of both MOF structural type and metal identity. Altogether, these findings suggest that early transition metal MOFs are best suited to separating oxygen from nitrogen, and that the MOF structural type is less important than the metal identity.

  6. DFT Description of the Magnetic Structure of Polynuclear Transition-Metal Clusters: The Complexes [{l_brace}Cu(bpca){sub 2}(H{sub 2}O){sub 2}{r_brace} {l_brace}Cu(NO{sub 3}){sub 2}{r_brace}{sub 2}], (bpca = Bis(2-pyridylcarbonyl)amine), and [Cu(DBSQ)(C{sub 2}H{sub 5}O)]{sub 2}, (DBSQ = 3,5-di-tert-butyl-semiquinonato)

    SciTech Connect

    Bencini, Alessandro; Totti, Federico

    2005-02-20

    Broken symmetry B3LYP-DFT calculations on three- and four-spin systems, namely the complexes [{l_brace}Cu(bpca){sub 2}(H{sub 2}O){sub 2}{r_brace} {l_brace}Cu(NO{sub 3}){sub 2}{r_brace}{sub 2}], (bpca = Bis(2-pyridylcarbonyl)amine), 1, and [Cu(DBSQ)(C{sub 2}H{sub 5}O)]{sub 2}, (DBSQ = 3,5-di-tert-butyl-semiquinonato), 2, have been performed. A procedure to compute the exchange coupling constants through the use of a complete set of broken symmetry determinants is suggested.

  7. Crystal and molecular structure of Sr{sub 2}(Edta) . 5H{sub 2}O, Sr{sub 2}(H{sub 2}Edta)(HCO{sub 3}){sub 2} . 4H{sub 2}O, and Sr{sub 2}(H{sub 2}Edta)Cl{sub 2} . 5H{sub 2}O strontium ethylenediaminetetraacetates

    SciTech Connect

    Polyakova, I. N.; Poznyak, A. L.; Sergienko, V. S.

    2009-03-15

    Three Sr{sup 2+} compounds with the Edta{sup 4-} and H{sub 2}Edta{sup 2-} ligands-Sr{sub 2}(Edta) . 5H{sub 2}O (I), Sr{sub 2}(H{sub 2}Edta)(HCO{sub 3}){sub 2} . 4H{sub 2}O (II), and Sr{sub 2}(H{sub 2}Edta)Cl{sub 2} . 5H{sub 2}O (III)-are synthesized, and their crystal structures are studied. In I, the Sr(1) atom is coordinated by the hexadentate Edta{sup 4-} ligand following the 2N + 4O pattern and by two O atoms of the neighboring ligands, which affords the formation of zigzag chains. The Sr(2) atom forms bonds with O atoms of five water molecules and attaches itself to a chain via bonds with three O atoms of the Edta{sup 4-} ligands. The Sr(1)-O and Sr(2)-O bond lengths fall in the ranges 2.520(2)-2.656(3) and 2.527(3)-2.683(2) A, respectively. The Sr(1)-N bonds are 2.702(3) and 2.743(3) A long. In II and III, the H{sub 2}Edta{sup 2-} anions have a centrosymmetric structure with the trans configuration of the planar ethylenediamine fragment. The N atoms are blocked by acid protons. In II, the environment of the Sr atom is formed by six O atoms of three H{sub 2}Edta ligands, two O atoms of water molecules, and an O atom of the bicarbonate ion, which is disordered over two positions. In III, the environment of the Sr atom includes six O atoms of four H{sub 2}Edta{sup 2-} ligands and three O atoms of water molecules. The coordination number of the Sr atoms is equal to 8 + 1. In II and III, the main bonds fall in the ranges 2.534(3)-2.732(2) and 2.482(2)-2.746(3) A, whereas the ninth bond is elongated to 2.937(3) and 3.055(3) A, respectively. In II, all the structural elements are linked into wavy layers. The O-H-O interactions contribute to the stabilization of the layer and link neighboring layers. In III, hydrated Sr{sup 2+} cations and H{sub 2}Edta{sup -} anions form a three-dimensional [Sr{sub 2}(H{sub 2}Edta)(H{sub 2}O){sub 3}]{sub n}{sup 2n+} framework. The Cl{sup -} anions are fixed in channels of the framework by hydrogen bonds with four water molecules. In

  8. Effect of TiO2 content on the crystallization and the color of (ZrO2,TiO2)-doped Li2O-Al2O3sub>-SiO2 glasses

    SciTech Connect

    Chavoutier, M.; Caurant, D.; Majérus, O.; Boulesteix, R.; Loiseau, P.; Jousseaume, C.; Brunet, E.; Lecomte, E.

    2014-02-18

    Glass–ceramics formed by controlled crystallization of Li2O–Al2O3sub>–SiO2 (LAS) parent glasses are well-known for their low thermal expansion and transparency. In order to promote bulk crystallization, it is necessary to add nucleating agents like TiO2 and ZrO2 to the glass composition leading to ZrTiO4 nuclei during heating, followed by the crystallization of a β-quartz phase that transforms into β-spodumene at higher temperature. Generally, these glass–ceramics present a yellowish-brown coloration whose intensity increases with the crystallization rate and that is partly due to coloring elements like titanium. In this study, we investigated the origin of the evolution of the color of LAS glasses and glass–ceramics by varying the TiO2 concentration. To do this, several TiO2-bearing LAS glasses (with TiO2 ranging from 0 to 4 mol% and 1 mol% ZrO2) were prepared and heat treated at a given temperature (925 °C) to study the impact of the TiO2 concentration on their crystallization behavior and their color. The crystallization and microstructure of LAS glasses and glass–ceramics were studied by DTA, XRD and TEM whereas their structure was investigated by EPR, optical and X-ray absorption spectroscopies. From all the results obtained, the evolution of the optical absorption and coloration of LAS glasses and glass–ceramics was mainly explained by Ti4+–O2- charge transfer (glasses) and by gap absorption and Rayleigh scattering of nanocrystals (glass–ceramics).

  9. Spectroscopic and laser characterization of Yb0.15:(LuxY1-x)3sub>Al5O12 ceramics with different Lu/Y balance.

    PubMed

    Pirri, Angela; Toci, Guido; Li, Jiang; Xie, Tengfei; Pan, Yubai; Babin, Vladimir; Beitlerova, Alena; Nikl, Martin; Vannini, Matteo

    2016-08-01

    We report a broad comparative analysis of the spectroscopic and laser properties of solid solution Lutetium-Yttrium Aluminum Garnet (LuYAG, (LuxY1-x)3sub>Al5O12) ceramics doped with Yb. The investigation was mainly aimed to assess the impact of the Lu/Y ratio on the Yb optical and laser properties. Therefore we analyzed a set of samples with different Y/Lu balance, namely 25/75, 50/50 and 75/25, with 15% Yb doping. We found that the Yb absorption and emission spectra changed from YAG to LuAG when gradually increasing in Lu content. Regarding the laser emission, remarkable results were achieved with all samples. Maximum output power was 8.2 W, 7.3 W and 8.7 W for Y/Lu balance 25/75, 50/50 and 75/25 respectively, at 1030 nm; the slope efficiency and the optical-to-optical efficiencies approached or exceeded 60% and 50% respectively. The tuning range was investigated using an intracavity ZnSe prism. The broadest tuning range (998 nm to 1063 nm) was obtained with Y/Lu balance 75/25, whereas the emission of the other two samples extended from 1000 nm to 1058 nm. To the best of our knowledge, this is the first comparative analysis of Yb:LuYAG ceramics or crystals as laser host across such a broad range of Y/Lu ratios. PMID:27505750

  10. Hybrid Inorganic-Organic Materials with an Optoelectronically Active Aromatic Cation: (C7H7)2SnI6 and C7H7PbI3sub>

    SciTech Connect

    Maughan, Annalise E.; Kurzman, Joshua A.; Neilson, James R.

    2015-06-04

    Inorganic materials with organic constituents—hybrid materials—have shown incredible promise as chemically tunable functional materials with interesting optical and electronic properties. Here, the preparation and structure are reported of two hybrid materials containing the optoelectronically active tropylium ion within tin- and lead-iodide inorganic frameworks with distinct topologies. The crystal structures of tropylium tin iodide, (C7H7)2SnI6, and tropylium lead iodide, C7H7PbI3sub>, were solved using high-resolution synchrotron powder X-ray diffraction informed by X-ray pair distribution function data and high-resolution time-of-flight neutron diffraction. Tropylium tin iodide contains isolated tin(IV)-iodide octahedra and crystallizes as a deep black solid, while tropylium lead iodide presents one-dimensional chains of face-sharing lead(II)-iodide octahedra and crystallizes as a bright red-orange powder. Experimental diffuse reflectance spectra are in good agreement with density functional calculations of the electronic structure. Calculations of the band decomposed charge densities suggest that the deep black color of tropylium tin iodide is attributed to iodide ligand to tin metal charge transfer, while the bright red-orange color of tropylium lead iodide arises from charge transfer between iodine and tropylium states. Understanding the origins of the observed optoelectronic properties of these two compounds, with respect to their distinct topologies and organic–inorganic interactions, provides insight into the design of tropylium-containing compounds for potential optical and electronic applications.

  11. Reversible Exsolution of Nanometric Fe2O3 sub> Particles in BaFe2-x(PO4)2 (0 ≤ x ≤ 2/3):The Logic of Vacancy Ordering in Novel Metal-Depleted Two-Dimensional Lattices

    SciTech Connect

    Alcover, Ignacio Blazquez; David, Rénald; Daviero-Minaud, Sylvie; Filimonov, Dmitry; Huvé, Marielle; Roussel, Pascal; Kabbour, Houria; Mentré, Olivier

    2015-08-12

    We show here that the exsolution of Fe2+ ions out of two-dimensional (2D) honeycomb layers of BaFe2(PO4)2 into iron-deficient BaFe2–x(PO4)2 phases and nanometric α-Fe2O3sub> (typically 50 nm diameter at the grain surface) is efficient and reversible until x = 2/3 in mild oxidizing/reducing conditions. It corresponds to the renewable conversion of 12 wt % of the initial mass into iron oxide. After analyzing single crystal X-ray diffraction data of intermediate members x = 2/7, x = 1/3, x = 1/2 and the ultimate Fe-depleted x = 2/3 term, we then observed a systematic full ordering between Fe ions and vacancies (VFe) that denote unprecedented easy in-plane metal diffusion driven by the Fe2+/Fe3+ redox. Besides the discovery of a diversity of original depleted triangular {Fe2/3+2–xO6} topologies, we propose a unified model correlating the x Fe-removal and the experimental Fe/VFe ordering into periodic one-dimensional motifs paving the layers, gaining insights into predictive crystahemistry of complex low dimensional oxides. When we increased the x values it led to a progressive change of the materials from 2D ferromagnets (Fe2+) to 2D ferrimagnets (Fe2/3+) to antiferromagnets for x = 2/3 (Fe3+).

  12. Synthesis, characterization and magnetic property of a new 3D iron phosphite: |C{sub 4}N{sub 3}H{sub 14}|[Fe{sub 3}(HPO{sub 3}){sub 4}F{sub 2}(H{sub 2}O){sub 2}] with intersecting channels

    SciTech Connect

    Qiao Jian; Zhang Lirong; Yu Yang; Li Guanghua; Jiang Tianchan; Huo Qisheng; Liu Yunling

    2009-07-15

    A new open-framework iron (III) phosphite |C{sub 4}N{sub 3}H{sub 14}|[Fe{sub 3}(HPO{sub 3}){sub 4}F{sub 2}(H{sub 2}O){sub 2}] has been solvothermally synthesized by using diethylenetriamine (DETA) as the structure-directing agent. Single-crystal X-ray diffraction analysis reveals that the compound crystallizes in the monoclinic space group C2/c having unit cell parameters a=12.877(3) A, b=12.170(2) A, c=12.159(2) A, beta=93.99(3){sup o}, V=1900.9(7) A{sup 3}, and Z=4 with R{sub 1}=0.0447, wR{sub 2}=0.0958. The complex structure consists of HPO{sub 3} pseudo-tetrahedra and {l_brace}Fe{sub 3}O{sub 14}F{sub 2}{r_brace} trimer building units. The assembly of these building units generates 3D inorganic framework with intersecting 6-, 8-, and 10-ring channels. The DETA cations are located in the 10-ring channels linked by hydrogen bonds. The Moessbauer spectrum shows that there exhibit two crystallographically independent iron (III) atoms. And the magnetic investigation shows the presence of antiferromagnetic interactions. Further characterization of the title compound was performed using X-ray powder diffraction (XRD), infrared (IR) spectra, thermal gravimetric analyses (TGA), inductively coupled plasma (ICP) and elemental analyses. - Graphical abstract: A new three-dimensional iron phosphite with intersecting 6-, 8-, 10-ring channels has been solvothermally synthesized by using diethylenetriamine (DETA) as the structure-directing agent.

  13. Structural phase transition, narrow band gap, and room-temperature ferromagnetism in [KNbO{sub 3}]{sub 1−x}[BaNi{sub 1/2}Nb{sub 1/2}O{sub 3−δ}]{sub x} ferroelectrics

    SciTech Connect

    Zhou, Wenliang; Yang, Pingxiong Chu, Junhao; Deng, Hongmei

    2014-09-15

    Structural phase transition, narrow band gap (E{sub g}), and room-temperature ferromagnetism (RTFM) have been observed in the [KNbO{sub 3}]{sub 1−x}[BaNi{sub 1/2}Nb{sub 1/2}O{sub 3−δ}]{sub x} (KBNNO) ceramics. All the samples have single phase perovskite structure, but exhibit a gradual transition behaviour from the orthorhombic to a cubic structure with the increase of x. Raman spectroscopy analysis not only corroborates this doping-induced change in normal structure but also shows the local crystal symmetry for x ≥ 0.1 compositions to deviate from the idealized cubic perovskite structure. A possible mechanism for the observed specific changes in lattice structure is discussed. Moreover, it is noted that KBNNO with compositions x = 0.1–0.3 have quite narrow E{sub g} of below 1.5 eV, much smaller than the 3.2 eV band gap of parent KNbO{sub 3} (KNO), which is due to the increasing Ni 3d electronic states within the gap of KNO. Furthermore, the KBNNO materials present RTFM near a tetragonal to cubic phase boundary. With increasing x from 0 to 0.3, the magnetism of the samples develops from diamagnetism to ferromagnetism and paramagnetism, originating from the ferromagnetic–antiferromagnetic competition. These results are helpful in the deeper understanding of phase transitions, band gap tunability, and magnetism variations in perovskite oxides and show the potential role, such materials can play, in perovskite solar cells and multiferroic applications.

  14. Synthetic and structural studies of the cyclopentadienyl-free yttrium alkyl alkoxide and aryloxide complexes [(Me{sub 3}Si){sub 2}CH]{sub 2}Y({mu}-OCMe{sub 3}){sub 2}Li(THF) and [Me{sub 3}SiCH{sub 2}]{sub 2}Y(OC{sub 6}H{sub 3}{sup t}Bu{sub 2}-2,6)(THF){sub 2}

    SciTech Connect

    Evans, W.J.; Broomhall-Dillard, R.N.R.; Ziller, J.W.

    1996-03-05

    YCL{sub 3} reacts with 2 equiv of LiCH(SiMe{sub 3}){sub 2} and 2 equiv of LiOCMe{sub 3} in THF to form the dialkyl dialkoxide complex [(Me{sub 3}Si){sub 2}CH]{sub 2}Y({mu}-OCMe{sub 3}){sub 2}Li(THF), 1. The yttrium in 1 is surrounded by a distorted tetrahedral arrangement of two terminal alkyl groups and two bridging alkoxide groups, and the coordination around lithium is trigonal planar. The reaction of YCl{sub 3} with 2 equiv of LiCH{sub 2}SiMe{sub 3} and 1 equiv of LiOC{sub 6}H{sub 3}{sup t}Bu{sub 2}-2,6 in THF forms the neutral dialkyl aryloxide complex (Me{sub 3}SiCH{sub 2}){sub 2}Y(OC{sub 6}H{sub 3}{sup t}Bu{sub 2}-2,6)(THF){sub 2} 2. The coordination geometry around yttrium in 2 is a distorted trigonal dipyramid with the THF groups in the apical positions. 61 refs., 2 figs., 3 tabs.

  15. Two new zincophosphates, (H{sub 3}NCH{sub 2}CH{sub 2}NH{sub 3}){sub 2}[Zn({mu}-PO{sub 4}){sub 2}] and (NH{sub 4})[(H{sub 3}N)Zn{l_brace}({mu}-PO{sub 4})Zn{r_brace}{sub 3}]: Crystal structures and relationships to similar open framework zinco- and aluminophospates

    SciTech Connect

    Karanovic, Ljiljana; Poleti, Dejan; Dordevic, Tamara; Sutovic, Sabina

    2011-09-15

    Two new zincophosphates, bis(ethylenediammonim) catena-bis({mu}-phosphato)zincate, (H{sub 3}NCH{sub 2}CH{sub 2}NH{sub 3}){sub 2}[Zn({mu}-PO{sub 4}){sub 2}] (1), and ammonium ammine-tris({mu}-phosphato)tetrazincate, (NH{sub 4})[(H{sub 3}N)Zn{l_brace}({mu}-PO{sub 4})Zn{r_brace}{sub 3}] (2), were synthesized under hydrothermal conditions and their crystal structures were determined by single-crystal X-ray diffraction analysis. The crystal structure of 1 consists of infinite macroanionic ZnP{sub 2}O{sub 8}{sup 4-} chains, running along the [0 0 1] direction, and diprotonated ethylenediammonium cations, H{sub 2}en{sup 2+}. The crystal structure of 2 is built up from ZnO{sub 4}, Zn(NH{sub 3})O{sub 3} and PO{sub 4} vertex-sharing tetrahedra connected to form an open 3D framework. The ammonium groups, NH{sub 4}{sup +}, are located in the channels formed by 8M-rings extending along [1 0 0]. In order to study vibrational behavior of H{sub 2}en{sup 2+} and NH{sub 4}{sup +} cations, NH{sub 3} molecules in 1 and 2, single-crystal Raman spectra were obtained. Structural, chemical and topological similarities to the other open framework zinco- and aluminophosphates incorporating different guest species are discussed. - Graphical Abstract: Structure of 1 (left): polyhedral (a) and ORTEP-like (b) representation of the ZnP{sub 2}O{sub 8}{sup 4-} chain with two H{sub 2}en{sup 2+} cations. Structure of 2 (right): polyhedral structure of the layers I and II seen along [1 0 0] (c-axis is vertical). Highlights: > Synthesis under hydrothermal conditions and the crystal structures of two new zincophosphates. > Compound 1 is a new inorganic-organic hybrid compound. > Structure of 1 consists of infinite macroanionic ZnP{sub 2}O{sub 8}{sup 4-} chains and H{sub 2}en{sup 2+} (en=ethylenediamine) cations. > Structure of 2 is a novel 3D open framework structure with 8M channels. > Structure of 2 is the first 3D zincophosphate which incorporates both, the coordinated NH{sub 3} molecule and NH

  16. Doping-evolution of the superconducting gap in single crystals of (Ca 1-x La x ) 10 (Pt 3sub> As 8 )(Fe 2 As 2 ) 5 superconductor from London penetration depth measurements

    SciTech Connect

    Cho, K.; Tanatar, M. A.; Ni, N.; Prozorov, R.

    2014-09-19

    The doping-evolution of the superconducting gap structure in iron-based superconductor (Ca1-xLax)10(Pt3sub>As8)(Fe2As2)5(x = 0.04, 0.06, 0.09, 0.11, and 0.18) was probed by high-resolution measurements of the London penetration depth, λ(T). The samples spanned compositions from underdoped to slightly overdoped with superconducting critical temperatures, Tc, from 12.7 K (x = 0.04) through (optimal) 23.3 K (x = 0.11) to 21.9 K (x = 0.18). The low-temperature variation (up to 0.3 Tc ) of λ(T) was analysed using a power-law function, Δλ = ATn. For compositions close to the optimal doping, (x = 0.09, 0.11, and 0.18), characterized by Tc > 20K, Δλ(T) shows a tendency to saturation, indicative of a full gap on the Fermi surface. Fitting over the lowest temperature range (T < 0.1 Tc) gives n = 2.6. This value is well outside the range 1 ≤ n ≤ 2 expected for the line-nodal superconductor. The exponent n decreased to n ~ 2 in the two most underdoped compositions x = 0.04 (Tc = 12.7 K) and 0.06 (Tc = 18.2 K), implying the development of a notable gap anisotropy revealed by the enhanced influence of pair-breaking scattering. This decrease is accompanied by a significant increase of the total variation of the penetration depth Δλ in a fixed temperature interval (e.g., Tmin - 0.3Tc). Both the decrease of the exponent and the increase of the absolute value of Δλ in the underdoped regime are similar to the observations in other charge-doped iron-based superconductors, such as doped BaFe2As2 and NaFeAs, suggesting a universal behavior in iron-based superconductors.

  17. [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: jihong@mail.jlu.edu.cn; Li Guanghua; Fang Qianrong; Xu Ruren . E-mail: rrxu@mail.jlu.edu.cn

    2005-09-15

    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.

  18. Interfacial Electron Transfer Dynamics for [Ru(bpy)2((4,4'-PO3sub>H2)2bpy)]2+ Sensitized TiO2 in a Dye-Sensitized Photoelectrosynthesis Cell: Factors Influencing Efficiency and Dynamics

    SciTech Connect

    Song, Wenjing; Brennaman, Kyle M; Concepcion, Javier J; Jurss, Jonah W.; Hoertz, Paul G; Luo, Hanlin; Chen, Chuncheng; Hanson, Kenneth G.; Meyer, Thomas J.

    2011-04-14

    Nanosecond laser flash photolysis and photocurrent measurements have been used to investigate use of [Ru(bpy)2((4,4'-PO3sub>H2)2bpy)]2+ attached to TiO2 nanoparticle films, TiO2-RuII, in a dye-sensitized photoelectrosynthesis cell (DSPEC) configuration for H2 production. In these experiments, laser flash excitation of TiO2-RuII and rapid injection lead to TiO2(e-)-RuIII with subsequent TiO2(e-)-RuIII → TiO2-RuII back electron transfer monitored on the nsec time scale with and without added triethanolamine (TEOA) and deprotonated ethylenediaminetetraacetic tetra-anion (EDTA4-) as irreversible electron transfer donors. With added TEOA or EDTA4-, a competition exists between back electron transfer and scavenger oxidation with the latter leading to H2 production in the photoelectrosynthesis cell. Reduction of TiO2(e-)-RuIII by both TEOA and EDTA4- occurs with kD ~ 106 M-1 s-1. EDTA4- is a more efficient scavenger by a factor of ~3 because of a more favorable partition equilibrium between the film and the external solution. Its increased scavenger efficiency appears in incident photon-to-current conversion efficiency (IPCE) measurements, in electron collection efficiencies (ηcoll), and in photocurrent measurements with H2 production. Evaluation of electron collection efficiencies by transient current measurements gave ηcoll ~ 24% for TEOA and ~ 70% for EDTA4-. The dynamics of back electron transfer are minimized, and collection efficiencies, photocurrents, and hydrogen production are maximized by application of a positive applied bias consistent with the results of I-V measurements. A p

  19. Thermodynamic Model for BiPO 4(cr) and Bi(OH)3sub>(am) Solubility in the Aqueous Na+–H+–H2PO- 4 –HPO 2- 4 –PO 3- 4 –OH- –Cl- –H2O System

    SciTech Connect

    Rai, Dhanpat; Yui, Mikazu; Schaef, Herbert T; Kitamura, Akira

    2010-07-10

    Prior to this study no data for the solubility product of BiPO 4(cr) or the complexation constants of Bi with phosphate were available. The solubility of BiPO 4(cr) was studied at 23 ± 2 °C from both the over- and under-saturation directions as functions of a wide range in time (6–309 days), pH values (0–15), and phosphate concentrations (reaching as high as 1.0 mol·kg-1). HCl or NaOH were used to obtain a range in pH values. Steady state concentrations and equilibrium were reached in <6 days. The data were interpreted using the SIT model. These extensive data provided a solubility product value for BiPO 4(cr) and an upper limit value for the formation of BiPO 4(aq). Because the aqueous system in this study involved relatively high concentrations of chloride, reliable values for the complexation constants of Bi with chloride were required to accurately interpret the solubility data. Therefore as a part of this investigation, existing Bi–Cl data were critically reviewed and used to obtain values of equilibrium constants for various Bi–Cl complexes at zero ionic strength along with the values for various SIT ion interaction parameters. Predictions based on these thermodynamic quantities agreed closely with our experimental data, the chloride concentrations of which ranged as high as 0.7 mol·kg-1. The study showed that BiPO 4(cr) is stable at pH values <9.0. At pH values >9.0, Bi(OH)3sub>(am) is the solubility controlling phase. Reliable values for the Bi(OH)3(am) solubility reactions involving Bi(OH)3sub>(aq) and Bi(OH) - 4 and the formation constants of these aqueous species are also reported.

  20. Fast self-diffusion of ions in CH 3sub> NH 3sub> PbI 3sub> : the interstiticaly mechanism versus vacancy-assisted mechanism

    SciTech Connect

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Wei, Su-Huai

    2016-01-01

    The stability of organic-inorganic halide perovskites is a major challenge for their applications and has been extensively studied. Among the possible underlying reasons, ion self-diffusion has been inferred to play important roles. While theoretical studies congruously support that iodine is more mobile, experimental studies only observe the direct diffusion of the MA ion and possible diffusion of iodine. The discrepancy may result from the incomplete understanding of ion diffusion mechanisms. With the help of first-principles calculations, we studied ion diffusion in CH3NH3PbI3 (MAPbI3) through not only the vacancy-assisted mechanisms presumed in previous theoretical studies, but also the neglected interstiticaly mechanisms. We found that compared to the diffusion through the vacancy-assisted mechanism, MA ion diffusion through the interstiticaly mechanism has a much smaller barrier which could explain experimental observations. For iodine diffusion, both mechanisms can yield relatively small barriers. Depending on the growth conditions, defect densities of vacancies and interstitials can vary and so do the diffusion species as well as diffusion mechanisms. Our work thus supports that both MA and iodine ion diffusion could contribute to the performance instability of MAPbI3. While being congruous with experimental results, our work fills the research gap by providing a full understanding of ion diffusion in halide perovskites.

  1. Density Functional Calculations of Native Defects in CH 3sub> NH 3sub> PbI 3sub> : Effects of Spin–Orbit Coupling and Self-Interaction Error

    SciTech Connect

    Du, Mao-Hua

    2015-04-02

    We know that native point defects play an important role in carrier transport properties of CH3NH3PbI3. However, the nature of many important defects remains controversial due partly to the conflicting results reported by recent density functional theory (DFT) calculations. In this Letter, we show that self-interaction error and the neglect of spin–orbit coupling (SOC) in many previous DFT calculations resulted in incorrect positions of valence and conduction band edges, although their difference, which is the band gap, is in good agreement with the experimental value. Moreover, this problem has led to incorrect predictions of defect-level positions. Hybrid density functional calculations, which partially correct the self-interaction error and include the SOC, show that, among native point defects (including vacancies, interstitials, and antisites), only the iodine vacancy and its complexes induce deep electron and hole trapping levels inside of the band gap, acting as nonradiative recombination centers.

  2. Mild hydrothermal synthesis, crystal structure, spectroscopic and magnetic properties of the [M{sub x}{sup II}M{sub 2.5-x}{sup III}(H{sub 2}O){sub 2}(HP{sup III}O{sub 3}){sub y}(P{sup V}O{sub 4}){sub 2-y}F; M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds

    SciTech Connect

    Orive, Joseba

    2009-08-15

    The [M{sub x}{sup II}M{sub 2.5-x}{sup III}(H{sub 2}O){sub 2}(HP{sup III}O{sub 3}){sub y}(P{sup V}O{sub 4}){sub 2-y}F; M=Fe (1), x=2.08, y=1.58; M=Co (2), x=2.5, y=2; Ni (3), x=2.5, y=2] compounds have been synthesized using mild hydrothermal conditions at 170 deg. C during five days. Single-crystals of (1) and (2), and polycrystalline sample of (3) were obtained. These isostructural compounds crystallize in the orthorhombic system, space group Aba2, with a=9.9598(2), b=18.8149(4) and c=8.5751(2) A for (1), a=9.9142(7), b=18.570(1) and c=8.4920(5) A for (2) and a=9.8038(2), b=18.2453(2) and c=8.4106(1) A for (3), with Z=8 in the three phases. An X-ray diffraction study reveals that the crystal structure is composed of a three-dimensional skeleton formed by [MO{sub 5}F] and [MO{sub 4}F{sub 2}] (M=Fe, Co and Ni) octahedra and [HPO{sub 3}] tetrahedra, partially substituted by [PO{sub 4}] tetrahedra in phase (1). The IR spectra show the vibrational modes of the water molecules and those of the (HPO{sub 3}){sup 2-} tetrahedral oxoanions. The thermal study indicates that the limit of thermal stability of these phases is 195 deg. C for (1) and 315 deg. C for (2) and (3). The electronic absorption spectroscopy shows the characteristic bands of the Fe(II), Co(II) and Ni(II) high-spin cations in slightly distorted octahedral geometry. Magnetic measurements indicate the existence of global antiferromagnetic interactions between the metallic centers with a ferromagnetic transition in the three compounds at 28, 14 and 21 K for (1), (2) and (3), respectively. Compound (1) exhibits a hysteresis loop with remnant magnetization and coercive field values of 0.72 emu/mol and 880 Oe, respectively. - Abstract: Polyhedral view of the crystal structure of the [M{sub x}{sup II}M{sub 2.5-x}{sup III}(H{sub 2}O){sub 2}(HP{sup III}O{sub 3}){sub y}(P{sup IV}O{sub 4}){sub 2-y}F; M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds showing the sheets along the [001] direction.

  3. Built-In Potential in Fe 2 O 3sub> -Cr 2 O 3sub> Superlattices for Improved Photoexcited Carrier Separation

    SciTech Connect

    Kaspar, Tiffany C.; Schreiber, Daniel K.; Spurgeon, Steven R.; McBriarty, Martin E.; Carroll, Gerard M.; Gamelin, Daniel R.; Chambers, Scott A.

    2015-12-17

    We demonstrate that the different surface terminations exhibited by α-Fe2O3 (hematite) and α-Cr2O3 (eskolaite) in superlattices (SL) of these materials, synthesized with exquisite control by molecular beam epitaxy, determine the heterojunction interface structure and result in controllable, non-commutative band offset values. Precise atomic control of the interface structure allowed us to vary the valence band offset from 0.35 eV to 0.79 eV. This controllable band alignment can be harnessed to generate a built-in potential in Fe2O3-Cr2O3 SLs. For instance, in a 2.5-period SL, a built-in potential of 0.8 eV was realized as measured by x-ray photoelectron spectroscopy of Ti dopants as probe species. The high quality of the SL structure was confirmed by atom probe tomography and scanning transmission electron microscopy. Enhanced photocurrents were measured for a thick Fe2O3 epitaxial film capped with an (Fe2O3)3-(Cr2O3)3 SL; this enhancement was attributed to efficient electron-hole separation in the SL as a result of the band alignment. The Fe-O-Cr bonds at the SL interfaces also red-shifted the onset of photoconductivity to ~1.6 eV. Exploiting the band alignment and photoabsorption properties of Fe2O3-Cr2O3 SLs has the potential to increase the efficiency of hematite-based photoelectrochemical water splitting.

  4. Lattice dynamics in elemental modulated Sb 2 Te 3sub> films: Lattice dynamics in elemental modulated Sb 2 Te 3sub> films

    SciTech Connect

    Bessas, D.; Winkler, M.; Sergueev, I.; König, J. D.; Böttner, H.; Hermann, R. P.

    2015-09-03

    We investigate the crystallinity and the lattice dynamics in elemental modulated Sbinline imageTeinline image films microscopically using high energy synchrotron radiation diffraction combined with inline imageSb nuclear inelastic scattering. The correlation length is found to be finite but less than 100 . Moreover, the element specific density of phonon states is extracted. A comparison with the element specific density of phonon states in bulk Sbinline imageTeinline image confirms that the main features in the density of phonon states arise from the layered structure. The average speed of sound at inline image inline image, is almost the same compared to bulk Sbinline imageTeinline image at inline image, inline image. Similarly, the change in the acoustic cut-off energy is within the experimental detection limit. Therefore, we suggest that the lattice thermal conductivity in elemental modulated Sbinline imageTeinline image films should not be significantly changed from its bulk value.

  5. Frustration of Tilts and A-Site Driven Ferroelectricity in KNbO3sub>-LiNbO3sub> Alloys

    SciTech Connect

    Bilc, Daniel I; Singh, David J

    2006-01-01

    Density functional calculations for K0.5Li0.5NbO3 show strong a-site driven ferroelectricity, even though the average tolerance factor is significantly smaller than unity and there is no sterochemically active A-stie ion. This is due to the frustration of tilt instabilities by A-site disorder. There are very large off-centerings of the Li ions, which contribute strongly to the anisotropy between the tetragonal and rhombohedral ferroelectric states, yielding a tetragonal ground state even without strain coupling.

  6. Thermoelectric properties of bromine filled CoSb3sub> skutterudite

    SciTech Connect

    Ortiz, Brenden R.; Crawford, Caitlin M.; McKinney, Robert W.; Parilla, Philip A.; Toberer, Eric S.

    2016-01-01

    Historically, the improved thermoelectric performance of skutterudite compounds has largely been driven by the incorporation of electropositive donors on interstitial sites. These 'rattlers' serve to optimize both electronic and thermal properties by tuning the carrier concentration and scattering phonons. In this work, we show that interstitial bromine can be incorporated into CoSb3 and assess the impact on electronic and thermal transport. In contrast to prior high pressure syntheses with iodine, interstitial bromine incorporation is achieved at ambient pressure. Transport properties are stable up to at least 375 degrees C. Bromine serves as an electronegative acceptor and can induce degenerate (>5 x 1019 cm-3) hole densities. In contrast to other p-type skutterudite compositions, bromine preserves the intrinsically high hole mobility of CoSb3 while significantly reducing the lattice thermal conductivity. The development of a stable p-type dopant for the interstitial filler site enables the development of skutterudites with both donor and acceptor interstitials to maximize phonon scattering while maintaining the high mobility of CoSb3.

  7. Nucleation of metastable aragonite CaCO3sub> in seawater

    SciTech Connect

    Sun, Wenhao; Jayaraman, Saivenkataraman; Chen, Wei; Persson, Kristin A.; Ceder, Gerbrand

    2015-03-04

    Predicting the conditions in which a compound adopts a metastable structure when it crystallizes out of solution is an unsolved and fundamental problem in materials synthesis, and one which, if understood and harnessed, could enable the rational design of synthesis pathways toward or away from metastable structures. Crystallization of metastable phases is particularly accessible via low-temperature solution-based routes, such as chimie douce and hydrothermal synthesis, but although the chemistry of the solution plays a crucial role in governing which polymorph forms, how it does so is poorly understood. Here, we demonstrate an ab initio technique to quantify thermodynamic parameters of surfaces and bulks in equilibrium with an aqueous environment, enabling the calculation of nucleation barriers of competing polymorphs as a function of solution chemistry, thereby predicting the solution conditions governing polymorph selection. We apply this approach to resolve the long-standing “calcite–aragonite problem”––the observation that calcium carbonate precipitates as the metastable aragonite polymorph in marine environments, rather than the stable phase calcite––which is of tremendous relevance to biomineralization, carbon sequestration, paleogeochemistry, and the vulnerability of marine life to ocean acidification. We identify a direct relationship between the calcite surface energy and solution Mg–Ca ion concentrations, showing that the calcite nucleation barrier surpasses that of metastable aragonite in solutions with Mg:Ca ratios consistent with modern seawater, allowing aragonite to dominate the kinetics of nucleation. Our ability to quantify how solution parameters distinguish between polymorphs marks an important step toward the ab initio prediction of materials synthesis pathways in solution.

  8. Dynamics of Composite Haldane Spin Chains in IPA-CuCl3sub>

    SciTech Connect

    Masuda, Takatsugu; Zheludev, Andrey I; Manaka, H.; Regnault, L.-P.; Chung, J.-H.; Qiu, Y.

    2006-01-01

    Magnetic excitations in the quasi-one-dimensional antiferromagnet IPA-CuCl{sub 3} are studied by cold neutron inelastic scattering. Strongly dispersive gap excitations are observed. Contrary to previously proposed models, the system is best described as an asymmetric quantum spin ladder. The observed spectrum is interpreted in terms of composite Haldane spin chains. The key difference from actual S = 1 chains is a sharp cutoff of the single-magnon spectrum at a certain critical wave vector.

  9. Electron-Impact Dissociation of Ozone Cations O3sub>+

    SciTech Connect

    Deng, Shihu; Vane, C Randy; Bannister, Mark E; FogleJr, Michael R

    2010-01-01

    Absolute cross sections for electron-impact dissociation of O3+ ions yielding O+ and O2+ fragment ions have been measured using a crossed electron-ion beams method for energies from about 3 eV to 100 eV. While the O2+ channel dominates the dissociation cross section over the measured energy range, a strong enhancement is observed in the O+ channel at low energy.

  10. Unusual Mott transition in multiferroic PbCrO 3sub>

    SciTech Connect

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S.; Jin, Changqing; He, Duanwei; Xu, Jian; Zhao, Yusheng

    2015-11-24

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. When turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. We report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of similar to 3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at similar to 300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid-gas transition. Moreover, the anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking.

  11. Synthesis and oxygen content dependent properties of hexagonal DyMnO{sub 3 + sub delta}.

    SciTech Connect

    Remsen, S.; Dabrowski, B.; Chmaissem, O.; Mais, J.; Szewczyk, A.

    2011-07-01

    Oxygen deficient polycrystalline samples of hexagonal P6{sub 3}cm (space group No.185) DyMnO{sub 3+{delta}} ({delta} < 0) were synthesized in Ar by intentional decomposition of its perovskite phase obtained in air. The relative stability of these phases is in accord with our previous studies of the temperature and oxygen vacancy dependent tolerance factor. Thermogravimetric measurements have shown that hexagonal samples of DyMnO{sub 3+{delta}} (0 {<=} {delta} {<=} 0.4) exhibit unusually large excess oxygen content, which readily incorporates on heating near 300 C in various partial-pressures of oxygen atmospheres. Neutron and synchrotron diffraction data show the presence of two new structural phases at {delta} {approx} 0.25 (Hex{sub 2}) and {delta} {approx} 0.40 (Hex{sub 3}). Rietveld refinements of the Hex{sub 2} phase strongly suggest it is well modeled by the R3 space group (No.146). These phases were observed to transform back to P6{sub 3}cm above {approx}350 C when material becomes stoichiometric in oxygen content ({delta} = 0). Chemical expansion of the crystal lattice corresponding to these large changes of oxygen was found to be 3.48 x 10{sup -2} mol{sup -1}. Thermal expansion of stoichiometric phases were determined to be 11.6 x 10{sup -6} and 2.1 x 10{sup -6} K{sup -1} for the P6{sub 3}cm and Hex{sub 2} phases, respectively. Our measurements also indicate that the oxygen non-stoichiometry of hexagonal RMnO{sub 3+{delta}} materials may have important influence on their multiferroic properties.

  12. Intelligent Engine Systems Work Element 1.3: Sub System Health Management

    NASA Technical Reports Server (NTRS)

    Ashby, Malcolm; Simpson, Jeffrey; Singh, Anant; Ferguson, Emily; Frontera, mark

    2005-01-01

    The objectives of this program were to develop health monitoring systems and physics-based fault detection models for engine sub-systems including the start, lubrication, and fuel. These models will ultimately be used to provide more effective sub-system fault identification and isolation to reduce engine maintenance costs and engine down-time. Additionally, the bearing sub-system health is addressed in this program through identification of sensing requirements, a review of available technologies and a demonstration of a demonstration of a conceptual monitoring system for a differential roller bearing. This report is divided into four sections; one for each of the subtasks. The start system subtask is documented in section 2.0, the oil system is covered in section 3.0, bearing in section 4.0, and the fuel system is presented in section 5.0.

  13. A novel nanomolecular organic-inorganic hybrid compound: Na{sub 2}[NH(CH{sub 2}CH{sub 2}OH){sub 3}]{sub 4}{l_brace}Mo{sub 36}O{sub 112}(OH{sub 2}){sub 14}[OHCH{sub 2}CH{sub 2}NH(CH{sub 2}CH{sub 2}OH){sub 2}]{sub 2}{r_brace}.nH{sub 2}O (n{approx}72) exhibiting a supramolecular one-dimensional chainlike structure

    SciTech Connect

    Liang Dadong; Liu Shuxia Wang Chunling; Ren Yuanhang

    2007-02-15

    A novel nanomolecular organic-inorganic hybrid compound, Na{sub 2}[NH(CH{sub 2}CH{sub 2}OH){sub 3}]{sub 4}{l_brace}Mo{sub 36}O{sub 112}(OH{sub 2}){sub 14} [OHCH{sub 2}CH{sub 2}NH(CH{sub 2}CH{sub 2}OH){sub 2}]{sub 2}{r_brace}.nH{sub 2}O (n{approx}72) (1), was synthesized in aqueous acidic medium with a high yield (85%) and characterized by single crystal X-ray crystallography, IR spectroscopy, {sup 1}H NMR, XRD and TG analysis. Compound 1 exhibits a supramolecular one-dimensional chainlike structure which consists of nanosized {l_brace}[Mo{sub 36}O{sub 112}(H{sub 2}O){sub 14}(HOC{sub 2}H{sub 4}){sub 2}NHC{sub 2}H{sub 4}OH]{sub 2}{r_brace}{sup 6-} anions ({l_brace}Mo{sub 36}(TEAH{sup +}){sub 2}{r_brace} for short) and cage-like dimers of TEAH{sup +} cations (TEAH{sup +}=protonated triethanolamine). In the {l_brace}Mo{sub 36}(TEAH{sup +}){sub 2}{r_brace} anion, two TEAH{sup +} cations connect to one ring-like {l_brace}[Mo{sub 36}O{sub 112}(H{sub 2}O){sub 16}]{sup 8-} ({l_brace}Mo{sub 36}{r_brace} for short) anion by covalent bonds via replacing two water ligands by the alkoxy ligands. The {l_brace}Mo{sub 36}(TEAH{sup +}){sub 2}{r_brace} unit could be considered as nanosized chelating ligand with [2N, 4O] donor sets. Crystal Data: triclinic, P-1, a=16.019(9) A, b=17.372(4) A, c=18.287(2) A, {alpha}=101.410(0){sup o}, {beta}=95.904(0){sup o}, {gamma}=116.332(0){sup o}, Z=1. - Graphical abstract: A novel organic-inorganic hybrid material based on macroisopolyanion {l_brace}Mo{sub 36}{r_brace} has been synthesized and characterized by X-ray single-crystal crystallography, XRD, IR spectroscopy, and TG analysis. The material exhibits a supramolecular one-dimensional chainlike structure. The {l_brace}Mo{sub 36}(TEAH{sup +}){sub 2}{r_brace} unit could be considered as nanosized chelating ligand with [2N, 4O] donor sets.

  14. Abnormal crystal growth in CH3sub>NH3sub>PbI3-xClx using a multi-cycle solution coating process

    SciTech Connect

    Dong, Qingfeng; Yuan, Yongbo; Shao, Yuchuan; Fang, Yanjun; Wang, Qi; Huang, Jinsong

    2015-06-23

    Recently, the efficiency of organolead trihalide perovskite solar cells has improved greatly because of improved material qualities with longer carrier diffusion lengths. Mixing chlorine in the precursor for mixed halide films has been reported to dramatically enhance the diffusion lengths of mixed halide perovskite films, mainly as a result of a much longer carrier recombination lifetime. Here we report that adding Cl containing precursor for mixed halide perovskite formation can induce the abnormal grain growth behavior that yields well-oriented grains accompanied by the appearance of some very large size grains. The abnormal grain growth becomes prominent only after multi-cycle coating of MAI : MACl blend precursor. The large grain size is found mainly to contribute to a longer carrier charge recombination lifetime, and thus increases the device efficiency to 18.9%, but without significantly impacting the carrier transport property. As a result, the strong correlation identified between material process and morphology provides guidelines for future material optimization and device efficiency enhancement.

  15. Structural and Electronic Properties of Reduced Transition Metal Oxide Clusters, M 3sub> O 8 and M 3sub> O 8 - (M = Cr, W), from Photoelectron Spectroscopy and Quantum Chemical Calculations

    SciTech Connect

    Li, Shenggang; Zhai, Hua-Jin; Wang, Lai-Sheng; Dixon, David A.

    2009-09-28

    We report a comparative study of reduced transition metal oxide clusters, M₃O₈⁻ (M = Cr, W) anions and their neutrals, via anion photoelectron spectroscopy (PES) and density functional theory (DFT) and molecular orbital theory (CCSD(T)) calculations. Well-resolved PES spectra are obtained for M₃O₈⁻ (M = Cr, W) at 193 and 157 nm photon energies. Different PES spectra are observed for M = Cr versus M = W. ExtensiveDFT and CCSD(T) calculations are performed to locate the ground and low-lying excited states for the neutrals and anions. The ground states of Cr₃O₈ and Cr₃O₈⁻ are predicted to be the ³B₂ and ⁴B₂ states of a C₂v structure, respectively, revealing ferromagnetic spin coupling for Cr 3d electrons. In contrast, the ground states of W₃O₈ and W₃O₈⁻ are predicted to be the ¹A' state (Cs symmetry) and the ²A₁ state (C₂v symmetry), respectively, showing metal-metal d-d bonding in the anion. The current cluster geometries are in qualitative agreement with prior DFT studies at the PBE level for M = Cr and the B3LYP level for M = W. The BP86 and PW91 functionals significantly outperform the B3LYP functional for the Cr species, in terms of relative energies, electron detachment energies, and electronic excitation energies, whereas the B3LYP functional is better for the W species. Accurate heats of formation for the ground states of M₃O₈ are calculated from the clustering energies and the heats of formation of MO₂ and MO₃. The energetics have been used to predict redox reaction thermochemistry.

  16. Synthesis of Ternary Nitrides From Intermetallic Precursors: Modes of Nitridation in Model Cr3sub>Pt Alloys to Form Cr3sub>PtN Perovskite and Applications to Other Systems

    SciTech Connect

    Brady, Michael P; Wrobel, Sarah; Lograsso, Tom; Payzant, E Andrew; Hoelzer, David T; Horton Jr, Joe A; Walker, Larry R

    2004-01-01

    The use of intermetallic alloy precursors is explored as a new means to synthesize complex transition and refractory metal nitrides, carbides, and related phases. The conditions under which model single-phase Cr{sub 3}Pt and two-phase Cr{sub 3}Pt-dispersed Cr alloys form Cr{sub 3}PtN antiperovskite when thermally nitrided were studied. Phenomenological experiments suggest that the key variable to achieving single-phase Cr{sub 3}PtN surface layers is the Cr{sub 3}Pt phase composition. In two-phase {beta}-Cr-Cr{sub 3}Pt alloys, the formation of single-phase Cr{sub 3}PtN at Cr{sub 3}Pt precipitates by in-place internal nitridation was found to be a strong function of the size of the Cr{sub 3}Pt dispersion in the microstructure. Nanoscale Cr{sub 3}Pt dispersions were readily converted to near single-phase Cr{sub 3}PtN, whereas nitridation of coarse Cr{sub 3}Pt particles resulted in a cellular or discontinuous-type reaction to form a lath mixture of Cr{sub 3}PtN and a more Cr-rich Cr{sub 3}Pt or {beta}-Cr. The potential for using such external/internal oxidation phenomena as a synthesis approach to layered or composite surfaces of ternary ceramic phases (nitrides, carbides, borides, etc.) of technological interest such as the Ti{sub 3}AlC{sub 2} phase, bimetallic nitride, and carbide catalysts (Co{sub 3}Mo{sub 3}N and Co{sub 3}Mo{sub 3}C and related phases), and magnetic rare earth nitrides (Fe{sub 17}Sm{sub 2}N{sub x} or Fe{sub 17}Nd{sub 2}N{sub x}) is discussed.

  17. High damping NiTi/Ti3sub>Sn in situ composite with transformation-mediated plasticity

    SciTech Connect

    Zhang, Junsong; Liu, Yinong; Huan, Yong; Hao, Shijie; Jiang, Daqiang; Ren, Yang; Shao, Yang; Ru, Yadong; Wang, Zhongqiang; Cui, Lishan

    2014-11-01

    The concept of transformation-induced plasticity effect is introduced in this work to improve the plasticity of brittle intermetallic compound Ti3Sn, which is a potent high damping material. This concept is achieved in an in situ NiTi/Ti3Sn composite. The composite is composed of primary Ti3Sn phase and (NiTi + Ti3Sn) eutectic structure formed via hypereutectic solidification. The composite exhibits a high damping capacity of 0.075 (indexed by tan δ), a high ultimate compressive strength of 1350 MPa, and a large plasticity of 27.5%. In situ synchrotron high-energy X-ray diffraction measurements revealed clear evidence of the stress-induced martensitic transformation (B2 → B19) of the NiTi component during deformation. The strength of the composite mainly stems from the Ti3Sn, whereas the NiTi component is responsible for the excellent plasticity of the composite.

  18. trans-K3sub>[TcO2(CN)4

    SciTech Connect

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

    2010-07-14

    The dioxotetracyanotechnetate anion, [TcO2(CN)4]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.

  19. Catalysis of the carbonylation of phenylacetylene in the presence of RhCOC1 (PPh/sub 3/)/sub 2/

    SciTech Connect

    Bakalova, E.P.; Chenets, V.V.; Grilitskaya, A.D.; Shmidt, F.K.

    1986-03-01

    This paper studies the carbonylation of phenylacetylene in the presence of chlorocarbonylbis (triphenylphosphine) rhodium with an addition of HI. The optimum conditions of synthesis of methyl esters of cinnamic and atropic acids were found. An influence of the CO pressure on the selectivity of the process was detected. The reaction kinetics were investigated at 0.1 MPa; the orders with respect to the substrate, catalyst, and HI were equal to 1.

  20. Creep-Resistant, Al2O3sub>- Forming Austenitic Stainless Steels

    SciTech Connect

    Yamamoto, Yukinori; Brady, Michael P; Lu, Zhao Ping; Maziasz, Philip J; Liu, Chain T; Pint, Bruce A; More, Karren Leslie; Meyer III, Harry M; Payzant, E Andrew

    2007-01-01

    A family of inexpensive, Al2O3-forming, high creep strength austenitic stainless steels have been developed. The alloys are based on Fe-20Ni-14Cr-2.5 Al wt.%, with strengthening achieved via nanodispersions of NbC. These alloys offer the potential to significantly increase the operating temperatures of structural components, and can be used under the aggressive oxidizing conditions encountered in energy conversion systems. Protective Al2O3 scale formation was achieved at lower levels of Al in austenitic alloys than previously used, provided that the Ti and V alloying additions frequently used for strengthening were eliminated. The lower levels of Al permitted stabilization of the austenitic matrix structure, and made it possible to obtain excellent creep resistance. Creep rupture lifetime in excess of 2000 h at 750 aC and 100 MPa in air, and resistance to oxidation in air + 10% water vapor environments at 650 and 800 aC are demonstrated

  1. Critical Experiments With Aqueous Solutions of {sup 233}UO{sub 2}(NO{sub 3}){sub 2}

    SciTech Connect

    Thomas, J.T.

    2001-05-17

    This report provides the critical experimenter's interpretations and descriptions of informal critical experiment logbook notes and associated information (e.g., experimental equipment designs/sketches, chemical and isotopic analyses, etc.) for the purpose of formally documenting the results of critical experiments performed in the late 1960s at the Oak Ridge Critical Experiments Facility. The experiments were conducted with aqueous solutions of 97.6 wt % {sup 233}U uranyl nitrate having uranium densities varying between about 346 g U/l and 45 g U/l. Criticality was achieved with single simple units (e.g., cylinders and spheres) and with spaced subcritical simple cylindrical units arranged in unreflected, water-reflected, and polyethylene reflected critical arrays.

  2. Critical Experiments With Aqueous Solutions of {sup 233}UO{sub 2}(NO{sub ;3}){sub 2}

    SciTech Connect

    Thomas, J T

    2001-05-17

    This report provides the critical experimenter's interpretations and descriptions of informal critical experiment logbook notes and associated information (e.g., experimental equipment designs/sketches, chemical and isotopic analyses, etc.) for the purpose of formally documenting the results of critical experiments performed in the late 1960s at the Oak Ridge Critical Experiments Facility. The experiments were conducted with aqueous solutions of 97.6 wt % {sup 233}U uranyl nitrate having uranium densities varying between about 346 g U/l and 45 g U/l. Criticality was achieved with single simple units (e.g., cylinders and spheres) and with spaced subcritical simple cylindrical units arranged in unreflected, water-reflected, and polyethylene reflected critical arrays.

  3. Testing of TAMU3: a Nb3sub>Sn Block–Coil Dipole with Stress Management

    SciTech Connect

    McIntyre, Peter

    2015-09-20

    The Accelerator Research Lab (ARL) at Texas A&M has recently concluded the construction and testing of a superconducting block-coil dipole TAMU3. TAMU3 reached 85% of the resistive-onset short sample critical current (0.1 μV/cm criterion) that was measured on extracted strands at the National High Magnetic Field Lab. Peak magnet current was 6603 amps, and all with quenches originated in the vicinity of the hard-way chicane near the exit lead of the TAMU3c inner winding. Leading up to the testing we discovered that we had made two grievous mistakes in the fabrication (we mistakenly used the wrong superconducting wire for the cables of the inner windings) and the heat treatment (we used a heat treatment that was too hot and too long). We extracted strands from the leads of the inner and outer windings, and colleagues at NHMFL performed short-sample measurements upon them. The NHMFL measurements indicated RRR ~ 2-5, which gives very little stability against microquenches. The short-sample tests of the extracted strands exhibited a long resistive transition, in which there was a current Isc(B) beyond which it became resistive, then a higher current In(B) at which it went fully normal. Using the Isc(B) data we predicted a short-sample limit for the revised load line of TAMU3 of 7700 A (9 T) – a disappointing reduction from the 14 T objective. On those unhappy notes we undertook the testing of the dipole. The first quench occurred at 5695 A, and the dipole trained thereafter to a maximum quench current of 6600 A (7.6 T), 85% of the compromised short-sample limit. All quenches occurred at a single location, in the region of the S-bend transition and outer lead of one inner winding. Data was collected from stress transducers on the outer windings to evaluate stress management, and on the coil ends to evaluate capture of axial forces by staticfriction lock. The low field reached prevented us from extending those tests to the stress levels where they would have become most interesting, but the designed stress management appeared to be working at the level tested.

  4. Thermoelectric properties of Si/SiB3 sub-micro composite prepared by melt-spinning technique

    NASA Astrophysics Data System (ADS)

    Xie, Jun; Ohishi, Yuji; Miyazaki, Yoshinobu; Yusufu, Aikebaier; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke

    2015-08-01

    This study presents a new self-assembly process to form a fine structure in bulk Si. We fabricated a semiconducting composite material consisting of sub-micro-sized (100-500 nm) SiB3 precipitates distributed in a Si matrix whose grain size was on the order of microns. The sub-micro-sized SiB3 particles were precipitated during the spark plasma sintering process of a metastable Si-B (Si:B = 92:8) supersaturated solid solution prepared by the melt-spinning technique. The composite was a heavily doped (5 × 1020 cm-3) p-type semiconductor. The SiB3 precipitates did not affect the Seebeck coefficient, slightly reduced the carrier mobility, and greatly reduced the lattice thermal conductivity. Specifically, the lattice thermal conductivity was reduced by 44% compared with that of p-type Si without precipitates at room temperature. The SiB3 precipitates improved the thermoelectric figure of merit ZT from 0.17 to 0.23 at 1073 K, which indicates that the formation of small precipitates effectively improves the thermoelectric performance of Si-based thermoelectric materials.

  5. Thickness-dependent metal-insulator transition in epitaxial SrRuO3sub> ultrathin films

    SciTech Connect

    Shen, Xuan; Qiu, Xiangbiao; Su, Dong; Zhou, Shengqiang; Li, Aidong; Wu, Di

    2015-01-06

    Transport characteristics of ultrathin SrRuO₃ films, deposited epitaxially on TiO₂-terminated SrTiO₃ (001) single-crystal substrates, were studied as a function of film thickness. Evolution from a metallic to an insulating behavior is observed as the film thickness decreases from 20 to 4 unit cells. In films thicker than 4 unit cells, the transport behavior obeys the Drude low temperature conductivity with quantum corrections, which can be attributed to weak localization. Fitting the data with 2-dimensional localization model indicates that electron-phonon collisions are the main inelastic relaxation mechanism. In the film of 4 unit cells in thickness, the transport behavior follows variable range hopping model, indicating a strongly localized state. As a result, magnetoresistance measurements reveal a likely magnetic anisotropy with the magnetic easy axis along the out-of-plane direction.

  6. Heuristic modelling of laser written mid-infrared LiNbO3sub> stressed-cladding waveguides.

    PubMed

    Nguyen, Huu-Dat; Ródenas, Airán; Vázquez de Aldana, Javier R; Martínez, Javier; Chen, Feng; Aguiló, Magdalena; Pujol, Maria Cinta; Díaz, Francesc

    2016-04-01

    Mid-infrared lithium niobate cladding waveguides have great potential in low-loss on-chip non-linear optical instruments such as mid-infrared spectrometers and frequency converters, but their three-dimensional femtosecond-laser fabrication is currently not well understood due to the complex interplay between achievable depressed index values and the stress-optic refractive index changes arising as a function of both laser fabrication parameters, and cladding arrangement. Moreover, both the stress-field anisotropy and the asymmetric shape of low-index tracks yield highly birefringent waveguides not useful for most applications where controlling and manipulating the polarization state of a light beam is crucial. To achieve true high performance devices a fundamental understanding on how these waveguides behave and how they can be ultimately optimized is required. In this work we employ a heuristic modelling approach based on the use of standard optical characterization data along with standard computational numerical methods to obtain a satisfactory approximate solution to the problem of designing realistic laser-written circuit building-blocks, such as straight waveguides, bends and evanescent splitters. We infer basic waveguide design parameters such as the complex index of refraction of laser-written tracks at 3.68 µm mid-infrared wavelengths, as well as the cross-sectional stress-optic index maps, obtaining an overall waveguide simulation that closely matches the measured mid-infrared waveguide properties in terms of anisotropy, mode field distributions and propagation losses. We then explore experimentally feasible waveguide designs in the search of a single-mode low-loss behaviour for both ordinary and extraordinary polarizations. We evaluate the overall losses of s-bend components unveiling the expected radiation bend losses of this type of waveguides, and finally showcase a prototype design of a low-loss evanescent splitter. Developing a realistic waveguide model with which robust waveguide designs can be developed will be key for exploiting the potential of the technology.

  7. Specificity of proteinase K at P2 to P3' sub-sites and its comparison to other serine proteases.

    PubMed

    Qasim, Mohammad A

    2014-01-01

    Specificity of the commercially important serine protease, proteinase K, has been investigated by measuring free energies of association of proteinase K with turkey ovomucoid third domain inhibitor variants at contact positions P2, P1, P1', P2', and P3'. Correlations of these values were run with similar values that have been obtained for six other serine proteases. Among the six proteases, subtilisin Carlsberg shows a near perfect correlation (Pearson Product correlation coefficient = 0.93 to 0.99) with proteinase K at all of these positions. Proteinase K has only 35% sequence identity with subtilisin Carlsberg, yet, the two enzymes are nearly identical in their specificity at P2 to P3' positions. With other serine proteases such as bovine chymotrypsin, human leukocyte elastase, porcine pancreatic elastase, Streptomyces griseus protease A and B, proteinase K showed relatively poor or no correlation.

  8. Nanoparticles of gold on ?-A12O3sub> Produced by dc Magnetron Sputtering

    SciTech Connect

    Veith, Gabriel M; Lupini, Andrew R; Pennycook, Stephen J; Ownby, Gary Webb; Dudney, Nancy J

    2005-01-01

    This paper describes a one-step magnetron sputtering technique for the preparation of supported catalyst particles that has a number of advantages over existing methods. In order to demonstrate the effectiveness of this technique, a supported gold on {gamma}-Al{sub 2}O{sub 3} oxidation catalyst has been prepared. This catalyst is as active as catalysts prepared via traditional chemical methods for the oxidation of carbon monoxide (TOF 1.1 conversions/surface Au atom/second at 300 K and 16% CO/8% O{sub 2}/He). Aberration-corrected scanning transmission electron microscopy demonstrates that this technique produces gold nanoparticles in a size range that is claimed in the literature to be most active (about 2 nm).

  9. Heuristic modelling of laser written mid-infrared LiNbO3sub> stressed-cladding waveguides.

    PubMed

    Nguyen, Huu-Dat; Ródenas, Airán; Vázquez de Aldana, Javier R; Martínez, Javier; Chen, Feng; Aguiló, Magdalena; Pujol, Maria Cinta; Díaz, Francesc

    2016-04-01

    Mid-infrared lithium niobate cladding waveguides have great potential in low-loss on-chip non-linear optical instruments such as mid-infrared spectrometers and frequency converters, but their three-dimensional femtosecond-laser fabrication is currently not well understood due to the complex interplay between achievable depressed index values and the stress-optic refractive index changes arising as a function of both laser fabrication parameters, and cladding arrangement. Moreover, both the stress-field anisotropy and the asymmetric shape of low-index tracks yield highly birefringent waveguides not useful for most applications where controlling and manipulating the polarization state of a light beam is crucial. To achieve true high performance devices a fundamental understanding on how these waveguides behave and how they can be ultimately optimized is required. In this work we employ a heuristic modelling approach based on the use of standard optical characterization data along with standard computational numerical methods to obtain a satisfactory approximate solution to the problem of designing realistic laser-written circuit building-blocks, such as straight waveguides, bends and evanescent splitters. We infer basic waveguide design parameters such as the complex index of refraction of laser-written tracks at 3.68 µm mid-infrared wavelengths, as well as the cross-sectional stress-optic index maps, obtaining an overall waveguide simulation that closely matches the measured mid-infrared waveguide properties in terms of anisotropy, mode field distributions and propagation losses. We then explore experimentally feasible waveguide designs in the search of a single-mode low-loss behaviour for both ordinary and extraordinary polarizations. We evaluate the overall losses of s-bend components unveiling the expected radiation bend losses of this type of waveguides, and finally showcase a prototype design of a low-loss evanescent splitter. Developing a realistic waveguide model with which robust waveguide designs can be developed will be key for exploiting the potential of the technology. PMID:27137062

  10. Quantum oscillations in magnetothermopower measurements of topological insulator Bi2Te3sub>

    SciTech Connect

    Qu, Dong -Xia; Hor, Y. S.; Cava, R. J.

    2012-12-10

    We report the magnetothermopower measurements of the nonmetallic topological insulator Bi2Te3 in magnetic fields up to 35 T. Quantum oscillations arising from surface states are observed in both thermoelectric and conductivity tensors. The inferred surface thermopower has a peak magnitude ~1 mV/K possibly as a result of surface electron and bulk phonon interaction. At the n = 1 Landau level, we resolve additional quantum oscillations signaling Landau sublevels.

  11. Neutron Scattering Study of the Relaxor Ferroelectric (1-x)Pb(Zn1/3sub>Nb2/3sub>)O3-xPbTiO3sub>

    SciTech Connect

    La-Orauttapong, D.; Toulouse, J.; Ye, Z.-G.; Chen, W.; Erwin, R.; Robertson, Lee

    2003-01-01

    Neutron elastic diffuse scattering experiments performed on Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3} (PZN) and on its solid solution with PbTiO{sub 3}(PT), known as PZN-xPT, with x=4.5 and 9 % around many reflections show that diffuse scattering is observed around reflections with mixed indices in the transverse and diagonal directions only. From the width of the diffuse scattering peak a correlation length is extracted. In PZN, we have reported that the diffuse scattering is more extended in the transverse than in the diagonal directions [D. La-Orauttapong, J. Toulouse, J. L. Robertson, and Z.-G. Ye, Phys. Rev. B 64, 212101 (2001)]. In the present work, the results show that the addition of PT leads to a broadening of the diffuse scattering along the diagonal, relative to the transverse directions, indicating a change in the orientation of the polar regions. Also, with the addition of PT, the polar nanoregions condense at a higher temperature above the transition than in pure PZN (>40K), due to stronger correlations between the polar regions. Neutron inelastic scattering measurements have also been performed on PZN-xPT. The results show the broadening of the transverse acoustic phonon mode at a small momentum transfer q upon cooling. We attribute this broadening to the appearance of the polar nanoregions.

  12. Growth and Superconducting Properties of YBa2Cu3sub>O 7-d Films on Conductive SrRuO3sub> and LaNiO3sub> Multilayers for

    SciTech Connect

    Aytug, T.

    2000-02-07

    Conductive multilayers of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}/SrRuO{sub 3}/LaNiO{sub 3} (YBCO/SRO/LNO), YBCO/SRO, and YBCO/LNO were grown epitaxially on single-crystal LaAlO{sub 3} and SrTiO{sub 3} substrates. Property characterizations revealed that the YBCO films on SRO and SRO/LNO buffer structures have excellent structural and superconducting properties. The YBCO/LNO, however, suffers degradation in superconducting transition temperatures and critical current densities, despite a good crystalline structure. The SRO/LNO bilayer showed excellent electrical contact with BCO. These results have demonstrated the structural and chemical compatibility of SRO/LNO multilayers with YBCO and their potential use as conductive buffer layers for YBCO-based coated conductors as well as for other high-temperature superconducting applications.

  13. Synthesis, Structures, and Vibrational Spectroscopy of the Two-Dimensional Iodates Ln(IO)3sub> and Ln(IO3sub>)3sub>(H2O) (Ln-Yb,Lu)

    SciTech Connect

    Assefa, Zerihun; Ling, Jie; Haire, Richard {Dick} G; Albrecht-Schmitt, Thomas E.; Sykora, Richard E.

    2006-01-01

    The reaction of Lu3+ or Yb3+ and H5IO6 in aqueous media at 180 C leads to the formation of Yb(IO3)3(H2O) or Lu(IO3)3(H2O), respectively, while the reaction of Yb metal with H5IO6 under similar reaction conditions gives rise to the anhydrous iodate, Yb(IO3)3. Under supercritical conditions Lu3+ reacts with HIO3 and KIO4 to yield the isostructural Lu(IO3)3. The structures have been determined by single-crystal X-ray diffraction. Crystallographic data are (MoKa, {lambda}=0.71073 {angstrom}): Yb(IO3)3, monoclinic, space group P21/n, a=8.6664(9) {angstrom}, b=5.9904(6) {angstrom}, c=14.8826(15) {angstrom}, {beta}=96.931(2){sup o}, V=766.99(13), Z=4, R(F)=4.23% for 114 parameters with 1880 reflections with I>2s(I); Lu(IO3)3, monoclinic, space group P21/n, a=8.6410(9), b=5.9961(6), c=14.8782(16) {angstrom}, {beta}=97.028(2){sup o}, V=765.08(14), Z=4, R(F)=2.65% for 119 parameters with 1756 reflections with I>2s(I); Yb(IO3)3(H2O), monoclinic, space group C2/c, a=27.2476(15), b=5.6296(3), c=12.0157(7) {angstrom}, {beta}=98.636(1){sup o}, V=1822.2(2), Z=8, R(F)=1.51% for 128 parameters with 2250 reflections with I>2s(I); Lu(IO3)3(H2O), monoclinic, space group C2/c, a=27.258(4), b=5.6251(7), c=12.0006(16) {angstrom}, {beta}=98.704(2){sup o}, V=1818.8(4), Z=8, R(F)=1.98% for 128 parameters with 2242 reflections with I>2s(I). The f elements in all of the compounds are found in seven-coordinate environments and bridged with monodentate, bidentate, or tridentate iodate anions. Both Lu(IO3)3(H2O) and Yb(IO3)3(H2O) display distinctively different vibrational profiles from their respective anhydrous analogs. Hence, the Raman profile can be used as a complementary diagnostic tool to discern the different structural motifs of the compounds.

  14. 23327Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of flower-like Bi2S3:Eu3+ sub-microspheres

    NASA Astrophysics Data System (ADS)

    Xu, Bingyu; Wang, Guofeng; Fu, Honggang

    2016-03-01

    In this paper, TiO2-Bi2S3 and TiO2-Bi2S3:Eu3+ composite photoanodes were successfully designed, which can not only fully absorb visible light but also transfer the electron from Bi2S3 to TiO2 conduction band due to the narrow band gap and high conduction band of Bi2S3. Compared to pure TiO2 cell, the photoelectric conversion efficiencies of TiO2-Bi2S3 and TiO2-Bi2S3:Eu3+ composite cells were increased significantly. In addition, the efficiency of TiO2-Bi2S3:Eu3+ composite cells were higher than that of TiO2-Bi2S3 cell which could be attributed to the larger BET surface area of Bi2S3:Eu3+. The electron transport and interfacial recombination kinetics were investigated by the electrochemical impedance spectroscopy and intensity-modulated photocurrent/photovoltage spectroscopy. The results indicated that the interfacial resistance of the TiO2-dye|I3-/I- electrolyte interface of TiO2-Bi2S3:Eu3+ composite cell was much bigger than that of pure TiO2 cell. In addition, the TiO2-Bi2S3:Eu3+ cell has longer electron recombination time and longer electron transport time than pure TiO2 cell. The charge collection efficiency of TiO2-Bi2S3:Eu3+ composite cell was higher than that of pure TiO2 cell.

  15. 23327Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the incorporation of flower-like Bi2S3:Eu3+ sub-microspheres.

    PubMed

    Xu, Bingyu; Wang, Guofeng; Fu, Honggang

    2016-01-01

    In this paper, TiO2-Bi2S3 and TiO2-Bi2S3:Eu(3+) composite photoanodes were successfully designed, which can not only fully absorb visible light but also transfer the electron from Bi2S3 to TiO2 conduction band due to the narrow band gap and high conduction band of Bi2S3. Compared to pure TiO2 cell, the photoelectric conversion efficiencies of TiO2-Bi2S3 and TiO2-Bi2S3:Eu(3+) composite cells were increased significantly. In addition, the efficiency of TiO2-Bi2S3:Eu(3+) composite cells were higher than that of TiO2-Bi2S3 cell which could be attributed to the larger BET surface area of Bi2S3:Eu(3+). The electron transport and interfacial recombination kinetics were investigated by the electrochemical impedance spectroscopy and intensity-modulated photocurrent/photovoltage spectroscopy. The results indicated that the interfacial resistance of the TiO2-dye|I3(-)/I(-) electrolyte interface of TiO2-Bi2S3:Eu(3+) composite cell was much bigger than that of pure TiO2 cell. In addition, the TiO2-Bi2S3:Eu(3+) cell has longer electron recombination time and longer electron transport time than pure TiO2 cell. The charge collection efficiency of TiO2-Bi2S3:Eu(3+) composite cell was higher than that of pure TiO2 cell.

  16. Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe2O3sub> nanoparticles

    SciTech Connect

    Khurshid, Hafsa; Lampen-Kelley, Paula; Iglesias, Òscar; Alonso, Javier; Phan, Manh-Huong; Sun, Cheng-Jun; Saboungi, Marie-Louise; Srikanth, Hariharan

    2015-10-27

    Disorder among surface spins largely dominates the magnetic response of ultrafine magnetic particle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8±0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and becomes frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point to highly frustrated surface spins that rearrange much more slowly than interior spins with bulk coordination. Monte Carlo simulations of a hollow particle reproducing the experimental morphology corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Lastly, our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures.

  17. Partitioning of Eu(III) between acidic aqueous Al(NO{sub 3}){sub 3} and tri-n-octyl phosphine oxide

    SciTech Connect

    Shafer, J.C.; Harrington, R.C.; Nash, K.L.

    2008-07-01

    As the Hanford site undergoes remediation, significant economies could be realized if aluminum is kept from High-Level Waste glass. An acidic scrub of the Hanford sludge could enhance Al removal; however, a caveat is the potential mobilization of transuranic elements, which would require a secondary cleanup of the Al/Cr waste stream. Previous solvent extraction (SX) studies have shown that >99% of the Eu and U can be extracted from simulated acidic Al/Cr waste. This study examines the use of extraction chromatographic methods. Results indicate the systems behave comparably and either method could be considered for Hanford clean-up purposes. (authors)

  18. A-site stoichiometry and piezoelectric response in thin film PbZr1-xTixO3sub>

    SciTech Connect

    Marincel, Dan; Jesse, Stephen; Belianinov, Alex; Okatan, Mahmut Baris; Kalinin, Sergei V.; Jackson, T. N.; Randall, Clive; Trolier-McKinstry, Susan E

    2015-05-29

    Lead zirconate titanate (PZT) films with Zr/Ti ratios of 52/48 and 30/70 annealed at varying partial pressures of PbO within the perovskite phase field exhibited permittivities of 1150 and 600, respectively, with loss tangents of 0.02. Many of the functional properties, including the permittivity, piezoelectricity as indicated via the Rayleigh coefficients, and the aging rates were found to be weakly dependent of the lead content in the single phase field. Minor polarization electric field hysteresis loops and piezoelectric coefficient e31,f values after a hot poling process suggest that the point defect helps stabilize the aligned domain states. Measurements of the local nonlinear response show an increased low response cluster size with decreasing PbO content, indicating that PbO deficiency acts to reduce domain wall motion where it is already low

  19. Properties of Haldane Excitations and Multiparticle States in the Antiferromagnetic Spin-1 Chain Compound CsNiCl3sub>

    SciTech Connect

    Kenzelmann, M.; Cowley, R. A.; Buyers, W. J. L.; Tun, Z.; Coldea, Radu; Enderle, M.

    2002-01-01

    We report inelastic time-of-flight and triple-axis neutron scattering measurements of the excitation spectrum of the coupled antiferromagnetic spin-1 Heisenberg chain system CsNiCl{sub 3}. Measurements over a wide range of wave-vector transfers along the chain confirm that above T{sub N} CsNiCl{sub 3} is in a quantum-disordered phase with an energy gap in the excitation spectrum. The spin correlations fall of