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Sample records for prsub 3isub 3ru

  1. Magnetic behavior of metallic kagome lattices, Tb3Ru4Al12 and Er3Ru4Al12

    Science.gov (United States)

    Upadhyay, Sanjay Kumar; Iyer, Kartik K.; Sampathkumaran, E. V.

    2017-08-01

    We report the magnetic behavior of two intermetallic-based kagome lattices, Tb3Ru4Al12 and Er3Ru4Al12, crystallizing in the Gd3Ru4Al2-type hexagonal crystal structure, by measurements in the range 1.8-300 K with bulk experimental techniques (ac and dc magnetization, heat capacity, and magnetoresistance). The main finding is that the Tb compound, known to order antiferromagnetically below (T N =) 22 K, shows glassy characteristics at lower temperatures (\\ll 15 K), thus characterizing this compound as a re-entrant spin-glass. The data reveal that the glassy phase is quite complex and is of a cluster type. Since glassy behavior was not seen for the Gd analog in the past literature, this finding on the Tb compound emphasizes that this kagome family could provide an opportunity to explore the role of higher-order interactions (such as quadrupole) in bringing out magnetic frustration. Additional findings reported here for this compound are: (i) The plots of temperature dependence of magnetic susceptibility and electrical resistivity data in the range 12-20 K, just below T N , are found to be hysteretic leading to a magnetic phase in this intermediate temperature range, mimicking disorder-broadened first-order magnetic phase transitions; (ii) features attributable to an interesting magnetic phase co-existence phenomenon in the isothermal magnetoresistance in zero field, after travelling across metamagnetic transition fields, are observed. With respect to the Er compound, we do not find any evidence for long-range magnetic ordering down to 2 K, but this compound appears to be on the verge of magnetic order at 2 K.

  2. Magnetic behavior of new compounds, Gd3RuSn6 and Tb3RuSn6

    Science.gov (United States)

    Upadhyay, Sanjay K.; Iyer, Kartik K.; Sampathkumaran, E. V.

    2017-11-01

    We report temperature (T) dependence of dc magnetization, electrical resistivity (ρ) and heat-capacity of rare-earth (R) compounds, Gd3RuSn6 and Tb3RuSn6, which are found to crystallize in the Yb3CoSn6-type orthorhombic structure (space group: Cmcm). The results establish that there is an onset of antiferromagnetic ordering near (TN =) 19 and 25 K respectively. In addition, we find that there is another magnetic transition for both the cases around 14 and 17 K respectively. In the case of the Gd compound, the spin-scattering contribution to ρ is found to increase below about 75 K as the material is cooled towards TN, thereby resulting in a minimum in the plot of ρ(T) unexpected for Gd based systems. Isothermal magnetization at 1.8 K reveals an upward curvature around 50 kOe. Isothermal magnetoresistance plots also show interesting anomalies in the magnetically ordered state. There are sign reversals in the plot of isothermal entropy change versus T in the magnetically ordered state, indicating subtle changes in the spin-orientations with T. The results reveal that these compounds exhibit interesting transport properties.

  3. Evolution of the local electronic states in Mn-doped Sr3 Ru2 O7

    Science.gov (United States)

    Leshen, Justin; Petryk, Matthew; Giannakis, Ioannis; Trager, Michael; Kavai, Mariam; Singer, Noah; Kaneko, Yoshio; Tokura, Yoshi; Aynajian, Pegor

    2015-03-01

    Thermal and quantum phase transitions have been central to the study of the strongly correlated electron systems. The double layer Sr3Ru2O7 is a particularly interesting candidate for such studies where a few percent of Mn-doping, replacing the Ru atoms, drives the system towards an antiferromagnetic (AFM) Mott insulator. Using scanning tunneling microscopy and spectroscopy we will address the effect of individual Mn dopants on the local electronic density of states in lightly doped Sr3(Ru1-xMnx)2 O7 and investigate the evolution of its electronic states across the paramagnetic metal to AFM Mott insulating phase transition.

  4. Competing magnetic fluctuations in Sr3Ru2O7 probed by Ti doping

    DEFF Research Database (Denmark)

    Hooper, J.; Fang, M.H.; Zhou, M.

    2007-01-01

    We report the effect of nonmagnetic Ti4+ impurities on the electronic and magnetic properties of Sr3Ru2O7. Small amounts of Ti suppress the characteristic peak in magnetic susceptibility near 16 K and result in a sharp upturn in specific heat. The metamagnetic quantum phase transition and related...

  5. Quasi-Two-Dimensional Metallic Ground State of Ca3Ru2O7

    Science.gov (United States)

    Yoshida, Yoshiyuki

    2005-03-01

    Ca3Ru2O7 is a three-dimensional antiferromagnetic metal between a first-order metal to nonmetal transition at 48 K and the antiferromagnetic ordering temperature, TN=56 K[1]. The crystal structure is the double layered Ruddlesden-Popper type with the Bb21m space group, which has both the rotation and tiling of RuO6 octahedra. We have succeeded in growing single crystals of Ca3Ru2O7 using a floating-zone method for the first time. The temperature dependence of the electrical resistivity establishes that Ca3Ru2O7 develops a quasi-two-dimensional metallic ground state below 30 K, from which the observed quantum oscillation derives. The specific heat measurement reveals the electronic specific-heat coefficient γ to be as small as 1.7 mJ/Ru mol K^2[2]. From the results of powder neutron diffractions, we proposed the most possible magnetic structure with an antiferromagnetic ordering. The field dependence of the resistivity at the metamagnetic transition around 6 T can be explained by the tunneling magnetoresistance. This work was done in collaboration with S. I. Ikeda, N. Shirakawa, C. H. Lee, M. Kosaka, and S. Katano. [1] G. Cao et al., Phys. Rev. Lett. 78 (1997) 1751. [2] Y. Yoshida et al., Phys. Rev. B 69 (2004) R220411.

  6. Antiferromagnetic instability in Sr3Ru2O7: stabilized and revealed by dilute Mn impurities

    Science.gov (United States)

    Hossain, Muhammed; Bohnenbuck, B.; Chuang, Y.-D.; Cruz, E.; Wu, H.-H.; Tjeng, L. H.; Elfimov, I. S.; Hussain, Z.; Keimer, B.; Sawatzky, G. A.; Damascelli, A.

    2009-03-01

    X-ray Absorption Spectroscopy (XAS) and Resonant Elastic Soft X-ray Scattering (RESXS) studies have been performed on Mn-doped Sr3Ru2O7, both on the Ru and Mn L-edges, to investigate the origin of the metal insulator transition. Extensive simulations based on our experimental findings point toward an intrinsic antiferromagnetic instability in the parent Sr3Ru2O7 compound that is stabilized by the dilute Mn impurities. We show that the metal-insulator transition is a direct consequence of the antiferromagnetic order and we propose a phenomenological model that may be applicable also to metal-insulator transitions seen in other oxides. Moreover, a comparison of Ru and Mn L-edge data on 5% Mn doped system reveals that dilute Mn impurities are generating much more intense signal than Ru which is occupying 95% of the lattice sites. This suggests the embedding of dilute impurities as a powerful mean to probe weak and, possibly, spatially inhomogeneous order in solid-state systems. In collaboration with: Y. Yoshida (AIST), J. Geck, D.G. Hawthorn (UBC), M.W. Haverkort, Z. Hu, C. Sch"ußler-Langeheine (Cologne), R. Mathieu, Y. Tokura, S. Satow, H. Takagi (Tokyo), J.D. Denlinger (ALS).

  7. Fermi Surface and Van Hove Singularities in the Itinerant Metamagnet Sr(3)Ru(2)O(7)

    Energy Technology Data Exchange (ETDEWEB)

    Tamai, A.; Allan, M.P.; Mercure, J.F.; /Scottish U. Research Reactor Ctr. /St. Andrews U.; Meevasana, W.; Dunkel, R.; Lu, D.H.; /Physics Intl., San Leandro /Stanford U., Phys. Dept. /SLAC, SSRL; Perry, R.S.; /Scottish U. Research Reactor Ctr. /Edinburgh U.; Mackenzie, A.P.; /Scottish U. Research Reactor Ctr. /St. Andrews U.; Singh, D.J.; /Hong Kong, City U. /Oak Ridge; Shen, Z.-X.; /Physics Intl., San Leandro /Stanford U., Phys. Dept. /SLAC, SSRL; Baumberger, F.; /Scottish U. Research Reactor Ctr. /St. Andrews U.

    2011-01-04

    The low-energy electronic structure of the itinerant metamagnet Sr{sub 3}Ru{sub 2}O{sub 7} is investigated by angle resolved photoemission and density functional calculations. We find well-defined quasiparticle bands with resolution limited line widths and Fermi velocities up to an order of magnitude lower than in single layer Sr{sub 2}RuO{sub 4}. The complete topography, the cyclotron masses and the orbital character of the Fermi surface are determined, in agreement with bulk sensitive de Haas - van Alphen measurements. An analysis of the dxy band dispersion reveals a complex density of states with van Hove singularities (vHs) near the Fermi level; a situation which is favorable for magnetic instabilities.

  8. Crystal-field level inversion in lightly Mn-doped Sr3Ru2O7

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, M. A.; Hu, Z.; Haverkort, M. W.; Burnus, T.; Chang, C. F.; Klein, S.; Denlinger, J. D.; Lin, H.-J.; Chen, C. T.; Mathieu, R.; Kaneko, Y.; Tokura, Y.; Satow, S.; Yoshida, Y.; Takagi, H.; Tanaka, A.; Elfimov, I. S.; Sawatzky, G. A.; Tjeng, L. H.; Damascelli, A.

    2008-01-15

    Sr3(Ru1-xMnx)2O7, in which 4d-Ru is substituted by the more localized 3d-Mn, is studied by x-ray dichroism and spin-resolved density functional theory. We find that Mn impurities do not exhibit the same 4+ valence of Ru, but act as 3+ acceptors; the extra eg electron occupies the in-plane 3dx2-y2 orbital instead of the expected out-of-plane 3d3z2-r2. We propose that the 3d-4d interplay, via the ligand oxygen orbitals, is responsible for this crystal-field level inversion and the material's transition to an antiferromagnetic, possibly orbitally ordered, low-temperature state.

  9. Synthesis and photocatalytic properties of Ag[Li{sub 1/3}Ru{sub 2/3}]O{sub 2}: A new delafossite oxide

    Energy Technology Data Exchange (ETDEWEB)

    Ramesha, K.; Prakash, A.S.; Sathiya, M. [Central Electrochemical Research Institute-Madras Unit, CSIR-Madras Complex, Taramani, Chennai 600 113 (India); Madras, Giridhar [Solid State and Structural Chemistry Unit, Indian Institute of Science, Malleswaram, Bangalore, Karnataka 560012 (India); Shukla, A.K., E-mail: akshukla2006@gmail.com [Solid State and Structural Chemistry Unit, Indian Institute of Science, Malleswaram, Bangalore, Karnataka 560012 (India)

    2011-02-15

    A new delafossite oxide, Ag[Li{sub 1/3}Ru{sub 2/3}]O{sub 2}, synthesized by ion-exchanging interlayer-Li{sup +} with Ag{sup +} in layered Li{sub 2}RuO{sub 3}, is reported. The transformation of layered Li{sub 2}RuO{sub 3} (monoclinic, space group C2/c) to Ag[Li{sub 1/3}Ru{sub 2/3}]O{sub 2} possessing a delafossite structure (space group R3-barm) has been established with powder X-ray diffraction. The successful conversion of Li[Li{sub 1/3}Ru{sub 2/3}]O{sub 2} to Ag[Li{sub 1/3}Ru{sub 2/3}]O{sub 2} is further confirmed by EDAX analysis. The diffuse reflectance spectrum of Ag[Li{sub 1/3}Ru{sub 2/3}]O{sub 2} shows broad absorption in the UV-visible region suggesting its use as a photocatalyst. The photocatalytic activity of Ag[Li{sub 1/3}Ru{sub 2/3}]O{sub 2} has been investigated by degrading various dyes. It showed significant photocatalytic activity for dye degradation both under UV and solar radiation.

  10. Pr{sub 1.33}Pt{sub 4}Ga{sub 10}: Superstructure and magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Doan Nguyen, Sau; Ryan, Kevin [Department of Chemistry and Biochemistry, University of Northern Colorado, Greeley, CO 80639 (United States); Chai, Ping [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States); Shatruk, Michael [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States); National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Xin, Yan [National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Chapman, Karena W.; Chupas, Peter J. [X-Ray Science Division, The Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439 (United States); Fronczek, Frank R. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Macaluso, Robin T., E-mail: robin.macaluso@unco.edu [Department of Chemistry and Biochemistry, University of Northern Colorado, Greeley, CO 80639 (United States)

    2014-12-15

    Pr{sub 1.33}Pt{sub 4}Ga{sub 10} crystals were prepared by Ga-flux method. The superstructure of this compound was studied by single-crystal X-ray diffraction (XRD), transmission electron microscopy (TEM), and diffuse X-ray scattering. Pr{sub 1.33}Pt{sub 4}Ga{sub 10} adopts the P6{sub 3}/mmc space group with a=b=4.3227(5) Å, c=16.485(3) Å: the structure features Pr{sub 2}Ga{sub 3} layers alternating with Pt{sub 2}Ga{sub 4} layers along the c-axis. TEM studies and pair distribution function (PDF) analysis of X-ray total scattering data show that Pr{sub 2}Ga{sub 3} layers possess an ordered superstructure (of dimension a′=a√(3)) in which Pr vacancies and Ga atoms are ordered within the ab-plane but disordered along the c-direction. PDF analysis also shows temperature-dependent structural features local to the Pr{sup 3+} ion. Magnetic measurements reveal that Pr{sup 3+} ions order ferrimagnetically below 12.5(2) K. - Graphical abstract: Left: Crystal structure of Pr{sub 1.33}Pt{sub 4}Ga{sub 10} showing Pr and Ga vacancies in the Pr{sub 2}Ga{sub 3} plane. Right: Tunneling electron microscopy (TEM) image of Pr{sub 1.33}Pt{sub 4}Ga{sub 10}. These vacancies have been studied using TEM and pair distribution function analysis. Magnetic measurements reveal that Pr{sup 3+} ions order ferrimagnetically below 7.8(2) K. - Highlights: • TEM studies indicate a superstructure from Pr and Ga vacancies. • Pair distribution function analyses may point to structural relaxation of vacancies. • Pr{sub 1.33}Pt{sub 4}Ga{sub 10} behaves as a ferromagnet and exhibits a metamagnetic transition.

  11. Manipulating the ferromagnetism in narrow-bandwidth Pr{sub 1-x}Ca{sub x}MnO{sub 3} (0 ≤ x ≤ 0.6) by means of the Mn-Ru t{sub 2g} ferromagnetic super-exchanges

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y. L.; Liu, M. F.; Xie, Y. L.; Yan, Z. B. [Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Dong, S. [Department of Physics, Southeast University, Nanjing 211189 (China); Liu, J.-M. [Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Institute for Advanced Materials and Laboratory of Quantum Engineering and Materials, South China Normal University, Guangzhou 510006 (China)

    2015-09-28

    The concurrent ferromagnetic and metal-insulator transitions via the double-exchange route and electronic phase separation scenario represent the core ingredients of the physics of manganites. In this work, a Ca{sup 2+} and Ru{sup 4+} co-substitution of Pr{sup 3+} and Mn{sup 3+} in narrow-bandwidth and insulating PrMnO{sub 3}, namely, Pr{sub 1-x}Ca{sub x}Mn{sub 1-x}Ru{sub x}O{sub 3} (PCMRO, x ≤ 0.6), is carried out in order to investigate an alternative approach to effectively manipulate the ferromagnetism of PrMnO{sub 3}-based manganites. It is revealed that PCMRO over the whole substitution range is homogeneous solid solution with increased lattice distortion. The preference of Ru{sup 4+} valence state and the absence of Mn{sup 4+} valence state disable the Mn{sup 3+}-Mn{sup 4+} e{sub g}-orbital double-exchange, and the random occupation of Ru{sup 4+} in the lattice excludes the charge ordering and electronic phase separation. While all these consequences should favor antiferromagnetic insulating states, nevertheless, a high-temperature ferromagnetic transition is triggered by the co-substitution and the magnetization can reach up to ∼1.0 μ{sub B}/f.u. at x ∼ 0.2–0.3, much bigger than the moment (<0.1 μ{sub B}/f.u.) of Pr{sub 1−x}Ca{sub x}MnO{sub 3} in the weak ferromagnetic insulator state. It is suggested that this strong ferromagnetism is substantially ascribed to the Mn{sup 3+}-Ru{sup 4+} t{sub 2g}-orbital ferromagnetic super-exchange, and a simple geometric network illustration of the magnetism and electrical transport is presented.

  12. Synthesis and characterization of highly efficient and stable Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt ternary hybrid structure

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Jiatao; Liu, Lin; Niu, Tongjun; Sun, Xiaosong, E-mail: sunxs@scu.edu.cn

    2017-05-01

    Highlights: • Visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalysts were prepared. • Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt showed highly efficient and stable photocatalystic activity. • The photocatalytic mechanism of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was given. - Abstract: Ag{sub 3}PO{sub 4} is an excellent photocatalyst with high efficiency and quantum yield, but suffers from the fast recombination of photogenerated electron-hole pairs and photo-corrosion. Hereby, the highly efficient and stable visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalyst were prepared via a three-step wet chemical approach. The as-prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was characterized by X-ray diffraction, US-vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra and transient photocurrent as well. Comparing with single Pr{sub 6}O{sub 11} or Ag{sub 3}PO{sub 4}, the prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite exhibited much higher photocatalytic activity and stability for the degradation of Rhodamine B under visible light irradiation (>420 nm). The enhanced photocatalytic performance of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite has been attributed to the efficient separation of photo-generated electron-hole pairs through a scheme system composed of Pr{sub 6}O{sub 11,} Ag{sub 3}PO{sub 4} and Pt.

  13. Strain and vector magnetic field tuning of the anomalous phase in Sr3Ru2O7.

    Science.gov (United States)

    Brodsky, Daniel O; Barber, Mark E; Bruin, Jan A N; Borzi, Rodolfo A; Grigera, Santiago A; Perry, Robin S; Mackenzie, Andrew P; Hicks, Clifford W

    2017-02-01

    A major area of interest in condensed matter physics is the way electrons in correlated electron materials can self-organize into ordered states, and a particularly intriguing possibility is that they spontaneously choose a preferred direction of conduction. The correlated electron metal Sr3Ru2O7 has an anomalous phase at low temperatures that features strong susceptibility toward anisotropic transport. This susceptibility has been thought to indicate a spontaneous anisotropy, that is, electronic order that spontaneously breaks the point-group symmetry of the lattice, allowing weak external stimuli to select the orientation of the anisotropy. We investigate further by studying the response of Sr3Ru2O7 in the region of phase formation to two fields that lift the native tetragonal symmetry of the lattice: in-plane magnetic field and orthorhombic lattice distortion through uniaxial pressure. The response to uniaxial pressure is surprisingly strong: Compressing the lattice by ~0.1% induces an approximately 100% transport anisotropy. However, neither the in-plane field nor the pressure phase diagrams are qualitatively consistent with spontaneous symmetry reduction. Instead, both are consistent with a multicomponent order parameter that is likely to preserve the point-group symmetry of the lattice, but is highly susceptible to perturbation.

  14. Thermopower of double-layered ruthenate Ca{sub 3}Ru{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, K. [Faculty of Science, Saitama University, Saitama 338-8570 (Japan)]. E-mail: iwata@hp.phy.saitama-u.ac.jp; Kosaka, M. [Faculty of Science, Saitama University, Saitama 338-8570 (Japan); Katano, S. [Faculty of Science, Saitama University, Saitama 338-8570 (Japan); Mori, N. [Faculty of Science, Saitama University, Saitama 338-8570 (Japan); Yoshida, Y. [Nanoelectronics Research Institute, AIST, Tsukuba 305-8568 (Japan); Shirakawa, N. [Nanoelectronics Research Institute, AIST, Tsukuba 305-8568 (Japan)

    2007-03-15

    We measured temperature dependence of in-plane and inter-plane thermopower S{sub ab} and S{sub c} of single crystalline Ca{sub 3}Ru{sub 2}O{sub 7}. The thermopower measurements were carried out by the low-frequency (33mHz) AC heating method. Large anisotropy between S{sub ab} and S{sub c} was observed, and its ratio (S{sub ab}/S{sub c}) is about 15 at 300K. The sign of S{sub ab} changes from positive to negative value at the structural transition temperature of 48K, indicating a reconstruction of Fermi surface. The behavior of S{sub ab} can be explained by the results of the electrical resistivity and Hall coefficient. On the other hand, S{sub c} shows a rather complex behavior.

  15. Thermodynamics of phase formation and heavy quasiparticles in Sr{sub 3}Ru{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Rost, Andreas W.; Bruin, Jan A.N.; Tian, Demian; Mackenzie, Andrew P. [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY169SS (United Kingdom); Grigera, Santiago A. [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY169SS (United Kingdom); Instituto de Fisica de Liquidos y Sistemas Biologicos, UNLP-CONICET, La Plata 1900 (Argentina); Perry, Robin S. [SUPA, School of Physics, University of Edinburgh, Mayfield Road, Edinburgh EH93JZ (United Kingdom); Raghu, Sri [Department of Physics and Astronomy, Rice University, Houston, Texas, 77005 (United States); Kivelson, Steve A. [Department of Physics, Stanford University, Stanford, California, 94305 (United States)

    2012-07-01

    The itinerant metamagnet Sr{sub 3}Ru{sub 2}O{sub 7} has motivated a wide range of experimental and theoretical work in recent years because of the discovery of an unusual low temperature phase which is forming in the vicinity of a proposed quantum critical point. A major challenge is the investigation of the thermodynamic properties of both this unusual phase and the fluctuations associated with the quantum critical point. Here we report on new specific heat measurements extending previous work to the wider phase diagram. Our results shed light on two important aspects of the system. First we discuss the entropic details of the formation of heavy quasiparticles as a function of temperature in this compound relevant for a wide class of materials. Secondly we present thermodynamic evidence for the anomalous low temperature phase forming directly out of the critical high temperature phase.

  16. Magnetic characterization of Pr{sub 2}BaCuO{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Saez Puche, R [Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Climent-Pascual, E [Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Paz, J Romero de [Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Fernandez-Diaz, M T [Institut Laue-Langevin, BP 156X, F-38042 Grenoble Cedex (France); Cascales, C [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28094-Madrid (Spain)

    2008-01-30

    The magnetic behaviour of Pr{sub 2}BaCuO{sub 5} oxide has been studied by means of magnetic susceptibility, magnetization, specific heat and neutron powder diffraction at low temperatures. This oxide behaves as an antiferromagnetic with a Neel temperature of 13.7 K and the magnetic structure can be described on the basis of a wavevector k = [0,0,0]. The Cu{sup 2+} magnetic moments are aligned along the c-axis of the crystal structure, while the Pr{sup 3+} magnetic moments lie in the ab-plane with a small component along the c-axis. The experimental values of the ordered moments at 2 K are 0.9(3) and 0.8(3) {mu}{sub B} for copper and praseodymium ions, respectively. The obtained set of crystal field parameters reproduces the paramagnetic susceptibility measurements and justifies the low experimental ordered moment of the Pr{sup 3+} ion.

  17. Monoclinic superstructure of Pr{sub 3}Rh{sub 4}Ge{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Vosswinkel, Daniel; Hoffmann, Rolf-Dieter; Greiwe, Magnus; Eul, Matthias; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2016-07-01

    Pr{sub 3}Rh{sub 4}Ge{sub 4} was synthesized by melting of the elements in an arc-melting furnace followed by annealing in a sealed tantalum ampoule in a muffle furnace. Structure refinement was based on temperature dependent single-crystal X-ray diffractometer data. At ambient temperature Pr{sub 3}Rh{sub 4}Ge{sub 4} adopts the U{sub 3}Ni{sub 4}Si{sub 4} type structure with strongly enhanced anisotropic displacement parameters for Rh1. Below 230 K additional reflections start to appear and at 110 K the structure could be described with the (3+1)D superspace group I2/m(α0γ)00; α=1/2, γ=1/2; (Z=2). This commensurately modulated structure could be refined with 1448 F{sup 2} values, 39 variables and residuals of wR=0.0417 for the main reflections and wR=0.1520 for the satellites of 1{sup st} order, [a=408.36(2), b=421.12(3) and c=2504.4(2) pm]. The commensurate description could be transformed to a 3D supercell with space group A2/m and Z=4: a=816.72(2), b=421.12(3), c=2537.5(1) pm, β=99.26(1) , 1448 F{sup 2} values, 69 variables and wR=0.0499. The relation of the U{sub 3}Ni{sub 4}Si{sub 4} type structure, the (3+1)D modulated and the 3D supercell is discussed on the basis of a group-subgroup scheme. Temperature dependent magnetic susceptibility data reveal Curie-Weiss paramagnetism with an experimental moment of 3.72(2) μ{sub B}/Pr atom and a Weiss constant of -12.6(5) K. No magnetic ordering is evident down to 3 K.

  18. T3RU test

    Science.gov (United States)

    ... normal levels may indicate: Kidney failure Overactive thyroid (hyperthyroidism) Nephrotic syndrome Protein malnutrition Lower-than-normal levels may indicate: Acute hepatitis (liver disease) Pregnancy Hypothyroidism Use of estrogen Abnormal results may also ...

  19. Flat bands and enigma of metamagnetic quantum critical regime in Sr{sub 3}Ru{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Shaginyan, V.R., E-mail: vrshag@thd.pnpi.spb.ru [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation); Clark Atlanta University, Atlanta, GA 30314 (United States); Msezane, A.Z. [Clark Atlanta University, Atlanta, GA 30314 (United States); Popov, K.G. [Komi Science Center, Ural Division, RAS, Syktyvkar 167982 (Russian Federation); Clark, J.W. [McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States); Zverev, M.V. [Russian Research Centre Kurchatov Institute, Moscow 123182 (Russian Federation); Moscow Institute of Physics and Technology, Moscow 123098 (Russian Federation); Khodel, V.A. [Russian Research Centre Kurchatov Institute, Moscow 123182 (Russian Federation); McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States)

    2013-11-22

    Understanding the nature of field-tuned metamagnetic quantum criticality in the ruthenate Sr{sub 3}Ru{sub 2}O{sub 7} has presented a significant challenge within condensed matter physics. It is known from experiments that the entropy within the ordered phase forms a peak, and is unexpectedly higher than that outside, while the magnetoresistivity experiences steep jumps near the ordered phase. We find a challenging connection between Sr{sub 3}Ru{sub 2}O{sub 7} and heavy-fermion metals expressing universal physics that transcends microscopic details. Our construction of the T–B phase diagram of Sr{sub 3}Ru{sub 2}O{sub 7} permits us to explain main features of the experimental one, and unambiguously implies an interpretation of its extraordinary low-temperature thermodynamic in terms of fermion condensation quantum phase transition leading to the formation of a flat band at the restricted range of magnetic fields B. We show that it is the flat band that generates both the entropy peak and the resistivity jumps at the QCPs.

  20. Neutron spectroscopic study of the crystal field interaction in Pr{sub 1-x}La{sub x}NiO{sub 3} (0{<=}x{<=}0.7)

    Energy Technology Data Exchange (ETDEWEB)

    Rosenkranz, S.; Medarde, M.; Mesot, J.; Zolliker, M.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Lacorre, P. [LeMans, Univ. (France)

    1997-09-01

    The crystal field interaction at the rare earth site in Pr{sub 1-x}La{sub x}NiO{sub 3} has been studied using inelastic neutron scattering. A parametrization consistent over the whole series is obtained and discussed within the point-charge model. (author) 2 figs., 3 refs.

  1. Investigation of diphasic region in the Pr{sub 2}O{sub 3} + Sm{sub 2}O{sub 3} mixed oxide system at various temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Vijayalakshmi, D. [Department of Physics, Kanchi Mamunivar Centre for PG and Research Studies, Govt. of Pondicherry, Lawspet 605008, Pondicherry (India); High Pressure Physics Section, Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Chandra Shekar, N.V., E-mail: chandru@igcar.gov.i [High Pressure Physics Section, Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Ramya, S. [Corrosion Science and Technology Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Sahu, P.Ch. [High Pressure Physics Section, Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Meenakshi, G. [Department of Physics, Kanchi Mamunivar Centre for PG and Research Studies, Govt. of Pondicherry, Lawspet 605008, Pondicherry (India)

    2010-09-03

    X-ray diffraction studies on mixed rare-earth oxides Pr{sub 2}O{sub 3} and Sm{sub 2}O{sub 3} quenched at various temperatures were carried out and their phase relationship was analyzed. Mixtures of Pr{sub 2}O{sub 3} and Sm{sub 2}O{sub 3} at different compositions were heated at various temperatures in the range 500-1200 {sup o}C and then air quenched. The structures of these quenched samples were analyzed using X-ray diffraction and Raman spectroscopy. Pure Pr{sub 2}O{sub 3} and Sm{sub 2}O{sub 3} exhibit C-type cubic phase at NTP. While Pr{sub 2}O{sub 3} retains its cubic phase up to 1200 {sup o}C, the Sm{sub 2}O{sub 3} transformed to B-type monoclinic phase above 800 {sup o}C. However, their mixtures when heated at different temperatures showed interesting structural behaviour. For the mixture up to 40 wt.% of Sm{sub 2}O{sub 3} in Pr{sub 2}O{sub 3}, no significant change was observed at lower temperatures ({approx}800 {sup o}C), and the C-type cubic phase was observed. As the ratio was gradually increased above 40%, a diphasic region in the range 50-70% was observed, with a combination of both C-type cubic and B-type monoclinic phases. When the temperature was raised to 1200 {sup o}C, the 80% of Sm{sub 2}O{sub 3} shows a complete structural transition from cubic to monoclinic phase. Based on the analysis of our results various crystal structures and stability regimes of mixed oxide have been reported.

  2. Thermodynamic analyses of structural phase transition of Pr{sub 2}NiO{sub 4+δ} involving variation of oxygen content

    Energy Technology Data Exchange (ETDEWEB)

    Niwa, Eiki, E-mail: e-niwa@phys.chs.nihon-u.ac.jp [Department of Physics, College of Humanities and Sciences, Nihon University, 3-8-1 Sakurajousui, Setagaya-ku, Tokyo 156-8550 (Japan); Wakai, Kazuya [Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, 3-8-1 Sakurajousui, Setagaya-ku, Tokyo 156-8550 (Japan); Hori, Tetsuya; Yashiro, Keiji; Mizusaki, Junichiro [Institute of Multidisciplinary Research for Advance Materials, Tohoku University, Sendai 980-8577 (Japan); Hashimoto, Takuya [Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, 3-8-1 Sakurajousui, Setagaya-ku, Tokyo 156-8550 (Japan)

    2014-01-10

    Graphical abstract: - Highlights: • P(O{sub 2}) dependence of phase transition behavior of Pr{sub 2}NiO{sub 4+δ} was investigated. • The structural phase transition was measured by DSC and TG–DTA. • ΔH and ΔS of Pr{sub 2}NiO{sub 4+δ} were confirmed to be almost constant against P(O{sub 2}). • Variation of oxygen content at the phase transition, Δδ changed by P(O{sub 2}). • The origin of different Δδ by P(O{sub 2}) is valence change of Pr ion. - Abstract: Structural phase transition behavior of Pr{sub 2}NiO{sub 4+δ}, which attracts interest as new cathode material for solid oxide fuel cells, was investigated by DSC and TG–DTA under controlled oxygen partial pressure, P(O{sub 2}). It was revealed that the structural phase transition from orthorhombic phase to tetragonal phase involved discrete decrease of oxygen content in Pr{sub 2}NiO{sub 4+δ} and that the phase transition temperature, T{sub p}, decreased with decreasing P(O{sub 2}). Variation of enthalpy, ΔH, and entropy, ΔS, at the phase transition per one molar Pr{sub 2}NiO{sub 4+δ} were calculated from the peak area of DSC and they were independent on P(O{sub 2}) between 1.0 × 10{sup −1} bar and 2.25 × 10{sup −3} bar. From the linear relationships between T{sub p} and RT{sub p}ln P(O{sub 2}) and between 1/T{sub p} and Rln P(O{sub 2}), variation of standard enthalpy, ΔH°, and standard entropy, ΔS°, of the phase transition per one molar O{sub 2} were calculated, showing fair agreement with ΔH and ΔS. The variation of oxygen content at the phase transition, Δδ, increased with decreasing P(O{sub 2}), which can be attributed to valence variation of Pr in tetragonal Pr{sub 2}NiO{sub 4+δ} by P(O{sub 2})

  3. Growth of polycrystalline Pr{sub 2}NiO{sub 4+δ} coating on alumina substrate by RF magnetron co-sputtering from composite targets

    Energy Technology Data Exchange (ETDEWEB)

    Sediri, A., E-mail: amal.sediri@univ-tours.fr [Université François-Rabelais de Tours, GREMAN UMR 7347 CNRS, IUT de Blois 15 rue de la chocolaterie CS 2903, 41029 Blois Cedex (France); Zaghrioui, M.; Barichard, A.; Autret, C.; Negulescu, B. [Université François-Rabelais de Tours, GREMAN UMR 7347 CNRS, IUT de Blois 15 rue de la chocolaterie CS 2903, 41029 Blois Cedex (France); Del Campo, L.; Echegut, P. [CNRS, UPR 3079 CEMHTI, 45071 Orléans Cedex 2 (France); Laffez, P. [Université François-Rabelais de Tours, GREMAN UMR 7347 CNRS, IUT de Blois 15 rue de la chocolaterie CS 2903, 41029 Blois Cedex (France)

    2016-02-01

    Polycrystalline Pr{sub 2}NiO{sub 4+δ} coatings have been deposited on alumina substrates at room temperature by RF magnetron co-sputtering from Pr and Ni metallic composite target. The mixed target's area and the sputtering conditions were optimized to reach an atomic ratio Pr/Ni of 2. A subsequent annealing, at 1050–1100 °C, allowed obtaining Pr{sub 2}NiO{sub 4+δ} phase after in situ high temperature x-ray diffraction study performed on as-deposited film. Microstructural analyses (SEM and AFM) revealed dense and rough microstructure. Normal spectral emittance measurements performed at 794 °C in the spectral range 400–5000 cm{sup -1} showed an emissivity of ε ≈ 0.8. - Highlights: • Pr{sub 2}NiO{sub 4+δ} coatings deposited by RF magnetron co-sputtering • Crystallization kinetic studied by X-ray diffraction versus temperature • SEM and AFM observations showed dense and rough microstructure • Normal spectral emittance reaches to ε = 0.8 at 794 °C in the opaque zone.

  4. Nanoscopic characterization of Pr{sub 2}Zr{sub 2}O{sub 7} at Zr sites

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, J.A.; Caracoche, M.C.; Rodriguez, A.M. [Departamento de Fisica, IFLP, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Rivas, P.C. [Departamento de Fisica, IFLP, Facultad de Ciencias Exactas y Facultad de Ciencias Agronomicas y Forestales, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Bondioli, F.; Manfredini, T. [Dipartimento di Ingegneria dei Materiali e dell' Ambiente, Facolta di Ingegneria, Universita di Modena e Reggio Emilia, 41100 Modena (Italy); Ferrari, A.M. [Dipartimento di Scienze e Metodi dell' Ingegneria, Facolta di Ingegneria, Universita di Modena e Reggio Emilia, 42100 Reggio Emilia (Italy)

    2005-07-01

    By using Perturbed Angular Correlation Spectroscopy, a suitable technique to explore internal fields at nanoscopic scale, the electric field gradients at Zr{sup 4+} sites in the Pr{sub 2}Zr{sub 2}O{sub 7} compound have been determined as a function of temperature. Three nonequivalent nanoconfigurations are present, which have been interpreted with the aid of point charge model calculations. Two of them correspond to pyrochlore - oxygen defective and perfect structures -, and the third one to the pyrochlore-related defect fluorite structure. The most abundant interaction is a disordered and fluctuating electric field gradient, which describes the oxygen defective pyrochlore. As temperature increases, its gradual and reversible transformation towards the perfect form is observed. Below 750 C the oxygen vacancies movement, which exhibits an activation energy of 0.14 eV, is assumed to be due to vacancies jumping among 48f equivalent sites. At higher temperatures the movement is interpreted as the fast diffusion of oxygen vacancies involving 48f and 8b sites, thus giving place to anionic disorder. The activation energy for this movement has been determined to be of 0.85 eV. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Synthesis of Pt doped Bi2O3/RuO2 photocatalysts for hydrogen production from water splitting using visible light.

    Science.gov (United States)

    Hsieh, S H; Lee, G J; Chen, C Y; Chen, J H; Ma, S H; Horng, T L; Chen, K H; Wu, J J

    2012-07-01

    This study was focused on the preparation of modified bismuth oxide photocatalysts, including Ru and Pt doped Bi2O3, using sonochemically assisted method to enhance their photocatalytic activity. The crystalline phase composition and surface structure of Bi2O3 photocatalysts were examined using SEM, XRD, UV-visible spectroscopy, and XPS. Optical characterizations have indicated that the Bi2O3 presents the photoabsorption properties shifting from UV light region into visible light which is approaching towards the edge of 470 nm. According to the experimental results, visible-light-driven photocatalysis for water splitting with the addition of 0.3 M Na2SO3 and 0.03 M H2C2O4 as sacrificing agents demonstrates that Pt/Bi2O3-RuO2 catalyst could increase the amount of hydrogen evolution, which is around 11.6 and 14.5 micromol g(-1) h(-1), respectively. Plausible formation mechanisms of modified bismuth oxide and reaction mechanisms of photocatalytic water splitting have been proposed.

  6. Dielectric and ferroelectric characteristics of Ba{sub 4}Pr{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} tungsten bronze ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Ting Ting; Chen, Wang; Zhu, Xiao Na; Zhu, Xiao Li; Chen, Xiang Ming, E-mail: xmchen59@zju.edu.cn

    2016-09-15

    Ba{sub 4}Pr{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} tungsten bronze ceramics have been prepared by a standard solid-state sintering method, and the electrical, dielectric and ferroelectric properties have been determined together with the structure. The structure dependence of ferroelectricity has been investigated by comparing the as-sintered, N{sub 2}-annealed and O{sub 2}-annealed samples. The typical relaxor ferroelectric nature is generally indicated in the present ceramics, where the broaden dielectric constant and dielectric loss peaks with strong frequency dispersion feature are observed. The peak temperatures for both dielectric constant and dielectric loss are significantly increased together with the much stronger frequency dispersion by N{sub 2}-annealing, while the O{sub 2}-annealing results in the decreased peak temperatures and the suppressed frequency dispersion. These phenomena are closely related to the valences of Fe and Pr ions. The hopping between Fe{sup 2+} and Fe{sup 3+} inside the grains causes the dielectric relaxation in as-sintered and N{sub 2}-annealed samples. The enhanced ferroelectricity near room temperature is attributed to the increased ion radius difference between A1 and A2 ions because of the “substitution” Pr{sup 4+} for Pr{sup 3+} after N{sub 2}-annealing. - Highlights: • Dielectric and ferroelectric properties of Ba{sub 4}Pr{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} are investigated. • Ferroelectric hysteresis loop is observed in Ba{sub 4}Pr{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} ceramics. • The ferroelectric properties are closely related to the valences of Pr ions. • The ferroelectric transition temperature is dominated by the radius difference between A1-and A2-site.

  7. X-ray resonant scattering studies of charge and orbital ordering in Pr{sub 1{minus}z}, Ca{sub x}, MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    V.ZIMMERMANN,M.; NELSON,C.S.; HILL,J.P.; GIBBS,D.; BLUME,M.; CASA,D.; KEIMER,B.; MURAKAMI,Y.; KAO,C.C.; VENKATARAMAN,C.; GOG,T.; TOMIOKA,Y.; TOKURA,Y.

    2000-08-14

    We present the results of x-ray scattering studies of the charge and orbital ordering in the manganite series Pr{sub 1{minus}z}, Ca{sub x}, MnO{sub 3} with x = 0.25, 0.4 and 0.5. The polarization and azimuthal dependence of the charge and orbital ordering in these compounds is characterized both in the resonant and nonresonant limits, and compared with the predictions of current theories. The results are qualitatively consistent with both cluster and LDA+U calculations of the electronic structure.

  8. Structure of compound Pr{sub 5}Mo{sub 3}O{sub 16+δ} exhibiting mixed electronic—ionic conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Antipin, A. M., E-mail: antipin@physics.msu.ru; Alekseeva, O. A.; Sorokina, N. I.; Kuskova, A. N.; Artemov, V. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Murzin, V. Yu. [National Research Center “Kurchatov Institute” (Russian Federation); Kharitonava, E. P.; Orlova, E. A.; Voronkova, V. I. [Moscow State University, Faculty of Physics (Russian Federation)

    2015-09-15

    The structure of Pr{sub 5}Mo{sub 3}O{sub 16+δ} single crystals is studied by X-ray diffraction, EDXS microanalysis, transmission microscopy, and XANES spectroscopy. It is found that in the structure Pr and Mo cations mutually replace each other, atomic positions of oxygen are split into several additional positions, and structural voids accommodate interstitial oxygen atoms (which make the main contribution to the conductivity). The disorder of the oxygen sublattice is responsible for the continuity of the framework of the ways of migration of oxygen ions.

  9. Change of conduction mechanism in the impedance of grain boundaries in Pr{sub 0.4}Ca{sub 0.6}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Shah, Matiullah [EMMG, Physics Division, PINSTECH, PO Nilore, Islamabad (Pakistan); Department of Chemical and Material Engineering, PIEAS, Islamabad 45650 (Pakistan); Nadeem, M., E-mail: mnadeem@pinstech.org.pk [EMMG, Physics Division, PINSTECH, PO Nilore, Islamabad (Pakistan); Idrees, M. [EMMG, Physics Division, PINSTECH, PO Nilore, Islamabad (Pakistan); Physics Department, COMSATS Institue of Information Technology, Lahore (Pakistan); Atif, M. [Department of Physics, Air University, PAF Complex E-9, Islamabad (Pakistan); Akhtar, M.J. [EMMG, Physics Division, PINSTECH, PO Nilore, Islamabad (Pakistan)

    2013-04-15

    Freshly synthesized polycrystalline Pr{sub 0.4}Ca{sub 0.6}MnO{sub 3} sample has been analyzed by employing X-ray diffraction, magnetization and impedance spectroscopic techniques. Magnetization M(T) showed charge ordering (T{sub CO}) around 268 K and below this temperature variation of magnetic and electric field effects is discussed. With the decrease of temperature, the change in the size and shape of the impedance plane plot is explored in terms of modulation of different relaxation processes. An equivalent circuit model (RQ) is used to determine the electrical parameters of Pr{sub 0.4}Ca{sub 0.6}MnO{sub 3} sample at different temperatures. Impedance of grain boundaries derived from the fitting of experimental data using an equivalent circuit model shows a change in conduction mechanism from small polaron hopping (SPH) to the variable range hopping (VRH) model around 148 K. Activation energies calculated from the SPH model and relaxation frequencies of imaginary part of impedance are compared and discussed. Average normalized change (ANC) deduced from the impedance data illustrates a change in conduction mechanism around 148 K due to the superexchange networks of Mn{sup 3+} and Mn{sup 4+}. - Highlights: ► Different field effects originated below charge ordering temperature. ► A transition around 148 K is established across the grain boundaries. ► Conduction mechanism changes from SPH to the VRH model. ► The Relaxation frequency shows dependent as well as independent regions.

  10. Colossal elastoresistance, electroresistance and magnetoresistance in Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liping, E-mail: chenliping0003@163.com [Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Department of Physics, Hong Kong University, Hong Kong (China); Guo, Xuexiang [Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Gao, J. [Department of Physics, Hong Kong University, Hong Kong (China)

    2016-05-01

    Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} thin films on substrates of (001)-oriented LaAlO{sub 3} were epitaxially grown by pulsed laser deposition. It was found that a substrate-induced strain of ~1.3% brings a great resistivity change of ~98% at 25 K. We studied the dependence of resistivity on the applied electric current and magnetic field. In the greatly strained films of 60 nm thickness the electroresistance ER=[ρ(I{sub 1} {sub μA})−ρ(I{sub 1000} {sub μA})]/ρ(I{sub 1} {sub μA}) reaches ~70% at T=25 K, much higher than ER~7% in the strain-relaxed films of 400 nm thickness, implying the strain effect on ER. Also the magnetoresistance of the film falls with strain-relaxation. Therefore the electric properties of the film could be efficiently modified by strain, electric current and magnetic field. All of them may be explained by the effect on the percolative phase separation and competition in the half-doped manganite material. The manganite films located at phase boundary are expected to be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance due to the multiphase coexistence. - Highlights: • The electric current-induced electroresistance (ER) and magnetoresistance (MR)studies on PLD grown Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3}/(001) LaAlO{sub 3} films were found to be greatly sensitive to the film thickness arising from the strain. • It is shown that, 60 nm film exhibit compressive in-plane strain which leads to phase separation and hence colossal MR and ER. • Our results suggest that the manganites located at phase boundary may be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance.

  11. Magnetic and XMCD studies of Pr{sub 1−x}Sr{sub x}MnO{sub 3} manganite films

    Energy Technology Data Exchange (ETDEWEB)

    Samoshkina, Yu.E., E-mail: uliag@iph.krasn.ru [Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk 660036 (Russian Federation); Edelman, I.S. [Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk 660036 (Russian Federation); Stepanova, E.A.; Neznakhin, D.S. [Ural Federal University, Yekaterinburg 620000 (Russian Federation); Ollefs, K. [European Synchrotron Radiation Facility (ESRF), BP 220, 38043 Grenoble Cedex 9 (France); Andreev, N.V.; Chichkov, V.I. [National University of Science and Technology “MISiS”, Moscow 119049 (Russian Federation)

    2017-04-15

    Magnetic properties of the Pr{sub 0.8}Sr{sub 0.2}MnO{sub 3} and Pr{sub 0.6}Sr{sub 0.4}MnO{sub 3} polycrystalline films have been studied using temperature and magnetic field dependences of the static magnetization and X-ray magnetic circular dichroism (XMCD) spectroscopy. For the both compositions, the difference between the temperature dependences of magnetization obtained in the zero fields cooling (ZFC) and field cooling (FC) modes has been revealed. The ZFC curves demonstrate a pronounced maximum at temperature T{sub m}. It is shown that the T{sub m} value dependence on the magnetic field follows the Almeida-Thouless line typical for the classic spin glass, what allows us to assume the possible spin-glass behavior of the films. Effect of the disorder in a direction of the crystallites easy-axis on the difference between FC and ZFC curves has been discussed also. Magnetic field dependences of the sample magnetization are presented by the hysteresis loops with the shape changing upon temperature variation. This behavior has been attributed to the effect of crystallographic anisotropy and Pr ions. The spectra and magnetic field dependences of XMCD at the Pr L{sub 2}- and Mn K-edges have been studied at 90 K. The magnetic field dependences of the XMCD at the Pr L{sub 2}-edge had shown Van Vleck paramagnetism from Pr{sup 3+} ions. - Highlights: • M (T) magnetization behavior indicates the presence of spin glass behavior in the films. • Shape of the hysteresis loops depends on temperature. • Magnetic field dependences of XMCD at T=90 K reveal Van Vleck paramagnetism from Pr{sup 3+} ions.

  12. Crystal-field study of magnetization and specific heat properties of frustrated pyrochlore Pr{sub 2}Zr{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Alam, J.; Jana, Y.M., E-mail: yatramohan@yahoo.com; Biswas, A. Ali

    2016-10-15

    The experimental results of temperature dependent dc magnetic susceptibility, field dependent isothermal magnetization, magnetic specific heat and entropy of the pyrochlore Pr{sub 2}Zr{sub 2}O{sub 7} are simulated and analyzed using appropriate D{sub 3d} crystal-field (CF) and anisotropic molecular field tensors at Pr-sites in the self-consistent mean-field approach involving four magnetically non-equivalent rare-earth spins on the tetrahedral unit of the pyrochlore structure. CF level pattern and wave-functions of the ground {sup 3}H{sub 4} multiplet of the Pr{sup 3+} ions are obtained considering intermediate coupling between different Russell-Saunders terms of the 4f{sup 2} electronic configurations of Pr-ion and J-mixing effects. CF analysis shows that the CF ground-state of the Pr{sup 3+} ion in Pr{sub 2}Zr{sub 2}O{sub 7} is a well-isolated doublet, with significant admixtures of terms coming from |M{sub J}=±4〉 and |M{sub J}=±1〉, and the Pr-spins are effectively Ising-like along the local <111> axes. Magnetic specific heat in zero-field is simulated by considering a temperature dependence of the exchange splitting of the ground doublet. - Highlights: • Full CF diagonalization using intermediate coupling and J-mixing. • Pr-spins are Ising-like along local [111] axis. • Magnetic specific heat is due to temperature dependence exchange splitting of ground CF doublet.

  13. Solid state chemistry of rare earth oxides. Technical progress report, 1975--1976. [Pr/sub 7/O/sub 12/; Pr/sub 10/O/sub 18/; HfO/sub 2/. xEr/sub 2/O/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Eyring, L.; Skarnulis, A.J.; Tuenge, R.T.; Von Dreele, R.B.

    1976-04-15

    It has been demonstrated that electron microscope images obtained at about 3A resolution for Pr/sub 7/O/sub 12/ are in agreement with calculated images based upon known structures. This establishes the efficacy of crystal structure image interpretation in structural terms, including the defect structure and mechanism of phase reactions, for these types of related phases whose structures are as yet beyond conventional means to determine. Further work on the epsilon (Pr/sub 10/O/sub 18/) phase is reported both utilizing electron optical methods and single crystal X-ray techniques. The ternary ceramic system HfO/sub 2/.xEr/sub 2/O/sub 3/ is being examined using electron optical techniques and ordering not hitherto reported is being observed. An interactive crystal structure image calculation system is being developed which will permit the immediate comparison of enhanced images synthesized from trial structures (including defects) and displayed in juxtaposition on a graphics unit. 22 fig. (auth)

  14. Dispersion of CEF levels in Nd{sub 2}CuO{sub 4} and Pr{sub 0.86}Ce{sub 0.14}CuO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Henggeler, W.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Chattopadyay, T.; Roessli, B. [Institut Max von Laue - Paul Langevin, 75 - Paris (France)

    1997-09-01

    We performed inelastic scattering experiments to determine the dispersion of the {Gamma}{sub 6}{sup (1)}-{Gamma}{sub 6}{sup (2)}-Nd crystal field excitation in Nd{sub 2}CuO{sub 4} and of the {Gamma}{sub 4}-{Gamma}{sub 5} Pr CEF excitation in Pr{sub 1.86}Ce{sub 0.14}CuO{sub 4}. Our results can be described within the random phase approximation model. (author) 4 figs.

  15. Knight shift measurements in the superconducting state of Pr{sub 1-x}La{sub x}Os{sub 4}Sb{sub 12}(x=0.4) probed by {mu}SR

    Energy Technology Data Exchange (ETDEWEB)

    Higemoto, W. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: higemoto.wataru@jaea.go.jp; Aoki, Y. [Department of Physics, Tokyo Metropolitan University of Hachioji, Tokyo 192-0397 (Japan); Ohishi, K. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Ito, T.U. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Heffner, R.H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Saha, S.R. [Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801 (Japan); Koda, A. [Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801 (Japan); Satoh, K.H. [Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801 (Japan); Kadono, R. [Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801 (Japan); Kikuchi, D. [Department of Physics, Tokyo Metropolitan University of Hachioji, Tokyo 192-0397 (Japan); Sugawara, H. [Department of Mathematical and Natural Sciences, University of Tokushima, Tokushima 770-8502 (Japan); Sato, H. [Department of Physics, Tokyo Metropolitan University of Hachioji, Tokyo 192-0397 (Japan)

    2007-03-15

    We report a muon spin rotation study of a single crystalline sample of the heavy fermion superconductor Pr{sub 1-x}La{sub x}Os{sub 4}Sb{sub 1}2(x=0.4). The muon Knight shift is independent of temperature, passing through T{sub c} down to 20mK, suggesting that the local spin susceptibility does not decrease in the superconducting state.

  16. Temperature-induced spin reorientation and magnetization jump of rare-earth orthoferrite Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guohua; Zhao, Weiyao; Cao, Yiming; Kang, Baojuan [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Zhang, Jincang [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444 (China); Ren, Wei, E-mail: renwei@shu.edu.cn [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444 (China); Cao, Shixun, E-mail: sxcao@shu.edu.cn [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444 (China)

    2016-07-25

    We report temperature-induced spin reorientation and magnetization jump effects in the rare earth (RE) orthoferrite Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal. The single crystal of about 6 mm in diameter and 50 mm in length was successfully grown by optical floating zone method. Both X-ray diffraction and Laue photograph confirmed the homogeneity and high quality of the crystal. Magnetic properties of Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal are studied over a wide temperature range from 2 to 300 K. Spin reorientation transition from Γ{sub 2} to Γ{sub 4} phase is observed in the temperature range of 75–90 K. At lower temperature, the Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} shows an abrupt jump of magnetization along the a-axis, which occurs only in the field-cooling process, and is sensitive to external applied magnetic field. By analyzing the jump temperature and magnitude of the magnetization, we conclude that it is caused by the spin reversal of the rare earth ions. The isothermal magnetization versus field hysteresis loop measurements along a axis explain the spin configuration variation from 3 K to 60 K. - Highlights: • Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal was grown by optical floating zone method. • It shows an abrupt jump of magnetization along a axis at low temperature. • The jump height and temperature is sensitive to external applied magnetic field. • It is attributed to the spin reversal of the rare earth ions.

  17. Stark and Zeeman effects in Nd{sub 2}Fe{sub 14}B and Pr{sub 2}Fe{sub 14}B intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Radwanski, R.J. [Institute of Physics and Informatics, Pedagogical University, Cracow (Poland)]|[Center of Soil State Physics, Cracow (Poland); Franse, J.M. [Van der Waals-Zeeman Laboratory, University of Amsterdam, Amsterdam (Netherlands)

    1996-12-31

    The energy level scheme of the Nd{sup 3+} and Pr{sup 3+} ions in ferromagnetic Nd{sub 2}Fe{sub 14}B and Pr{sub 2}Fe{sub 14}B intermetallic compounds was evaluated on the basis of well known experiments. In calculations the effect of charge (Stark effect) and spin-dependent (Zeeman effect) interactions were taken into account by means of the crystal-field and Molecular-field approximation, respectively. The derived energy levels scheme is associated with the removal of the degeneracy of the lowest multiplet given by Hund`s rules, i.e. {sup 4}I{sub 9/2} (Nd{sup 3+}) and {sup 3}H{sub 4} (Pr{sup 3+}). The revealed low-energy electronic structure (< 25 meV = 200 cm{sup -1}) is associated with many electron states of RE{sup 3+} ions. Magnetic and electronic properties resulting from this fine structure are compared with all known experimental results. The localized crystal electric field levels exist also in Nd{sub 2}CuO{sub 4}, and ionic compounds which by doping with Ce becomes high-T{sub c} superconductor, indicating the formation of crystal electric field states independently on the metallic or ionic state. (author) 12 refs, 9 figs

  18. Magnetic properties of polycrystalline Pr{sub x}Y{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Stari, C. [Grupo de Materiais e Dispositivos-GMD, Departamento de Fisica-UFSCar, Caixa Postal 676, Sao Carlos (Brazil); Instituto de Fisica, Facultad de Ingenieria, UdelaR, Julio Herrera y Reissig 565, C.C. 30, 11000 Montevideo (Uruguay); Rivera, V.A.G. [Grupo de Materiais e Dispositivos-GMD, Departamento de Fisica-UFSCar, Caixa Postal 676, Sao Carlos (Brazil); Lanfredi, A.J.C. [LIEC, Departamento de Quimica, Centro Multidisciplinar para o Desenvolvimento deMateriais Ceramicos, UFSCar, Caixa Postal 676, Sao Carlos, SP (Brazil); Cardoso, C.A. [Grupo de Materiais e Dispositivos-GMD, Departamento de Fisica-UFSCar, Caixa Postal 676, Sao Carlos (Brazil); Leite, E.R. [LIEC, Departamento de Quimica, Centro Multidisciplinar para o Desenvolvimento deMateriais Ceramicos, UFSCar, Caixa Postal 676, Sao Carlos, SP (Brazil); Mombru, A.W. [Laboratorio de Cristalografia, Estado Solido y Materiales, DETEMA, Facultad de Quimica, UdelaR, Gral. Flores 2124, 11800 Montevideo (Uruguay); Araujo-Moreira, F.M. [Grupo de Materiais e Dispositivos-GMD, Departamento de Fisica-UFSCar, Caixa Postal 676, Sao Carlos (Brazil)], E-mail: faraujo@df.ufscar.br

    2008-07-15

    In this work, we report a part of a systematic study of the influence of the synthesis routes on the properties of polycrystalline samples of Pr{sub x}Y{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}. We have prepared high-quality samples of this material by following a sol-gel method, associated with heat treatment in both an inert argon and an oxygen atmospheres in order to compare their influence on the formation of the superconducting phase. Magnetic measurement (AC susceptibility) show that the superconducting transition temperature (T{sub C}) increases in samples prepared in argon when compared to those prepared in oxygen, for the same composition and Pr fraction less than 0.5. In addition to this, preliminary results of AC and DC magnetic susceptibility show superconductivity for samples with Pr fraction higher than 0.5 (and up to 0.9) prepared under argon flux, which may indicate the existence of stable superconductivity for all compositions, including pure Pr-123.

  19. Observation of semiconductor to metallic transition and polaron hopping in double perovskite Pr{sub 2}CoTiO{sub 6} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800005 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1, APC Road, Kolkata 700009 (India)

    2017-05-01

    This paper describes semiconductor to metal transition and polaron conduction in double perovskite Pr{sub 2}CoTiO{sub 6} (PCTO) ceramics. The XRD pattern recorded at room temperature confirmed the pure phase, single crystalline structure. The semicircle arc in the impedance plot at each temperature can be attributed to the grain boundary contribution, indicating one dominating response in the measurement frequency range. The semiconductor to metallic transition was also confirmed by the variation of grain boundary resistance (R{sub gb}) with temperature. The activation energy estimated from the imaginary part of electrical modulus and impedance are found to be the characteristic of polaron conduction in PCTO. Ac conductivity followed power law dependence σ{sub ac} = Bω{sup n}. The observed variation of the exponent ‘n’ with temperature suggests the typical of charge transport assisted by a hopping process. The observed minimum in the temperature dependence of frequency exponent ‘n’ strongly suggests that the large polaron tunneling is the dominant transport process.

  20. Effects of multi-modification of rare earth oxides Pr{sub x}O{sub y} and La{sub x}O{sub y} on microstructure and tensile properties of casting Al-Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Yumei; Bai, Zhihao; Qiu, Feng; Jin, Shenbao [Key Laboratory of Automobile Materials, Ministry of Education, Department of Materials Science and Engineering, Jilin University, Renmin Street no. 5988, Changchun, Jilin Province, 130025 (China); Jiang, Qichuan, E-mail: jqc@jlu.edu.cn [Key Laboratory of Automobile Materials, Ministry of Education, Department of Materials Science and Engineering, Jilin University, Renmin Street no. 5988, Changchun, Jilin Province, 130025 (China)

    2012-12-15

    Through multi-modification with Pr{sub x}O{sub y} and La{sub x}O{sub y}, the tensile strength and elongation of casting Al-Cu alloy can reach to 580 MPa and 10.5%, increased by 26% and 50% respectively than those of the unmodified alloy. Simultaneous increase in the tensile strength and elongation of the multi-modified alloys is suggested to be induced by the refined {alpha}-Al dendrites, the formation of Al-RE intermetallic compounds at the grain boundaries, and the most important, more homogeneously distributed nano-scale {theta} Prime precipitates with higher diameter/thickness ratio.

  1. Structural, electrical and magnetic properties of Sb-doped Pr{sub 2/3}Ba{sub 1/3}MnO{sub 3} perovskite manganites

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Vikram [Superconductivity Division, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India); Panwar, Neeraj [Superconductivity Division, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Bhalla, G.L. [Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India); Agarwal, S.K. [Superconductivity Division, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India)]. E-mail: agarwal@mail.nplindia.ernet.in

    2007-07-31

    We report here the electrical, magnetic and micro-structural features of the Sb-doped (nominally at Mn-sites) Pr{sub 2/3}Ba{sub 1/3}MnO{sub 3} perovskite manganites. Pristine material shows two insulator-metal (I-M) like transitions in the resistivity-temperature ({rho}-T) behaviour. While the higher temperature transition (T {sub P1}) at {approx}195 K is reminiscent of the usual metal-insulator transition, the lower temperature transition (T {sub P2}) at {approx}160 K has been ascribed to the grain boundary (GB) effects arising out of the ionic size mismatch between the ions present at the rare-earth site (Pr and Ba). With Sb doping at the Mn-site, both the resistivity peaks are seen to shift to lower temperatures. Room temperature resistivity and the peak values are also successively increasing with Sb doping. Scanning electron micrographs of the samples indicate a gradual increase in their grain sizes with Sb which indicates a gradual decrease in the GB density. The higher temperature insulator-metal transition (T {sub P1}) shift is explained on the basis of a competition between double-exchange and super-exchange mechanisms. The observed overall resistivity increase and the shift in the resistivity hump (T {sub P2}) with Sb are found related to the gradually decreasing GB density and the ensuing lattice strain increase at the grain boundaries. The intrinsic MR gets suppressed and the extrinsic MR gets enhanced with Sb doping. The observed low temperature resistivity upturn related to the localization of carriers, is also seen to increase with Sb.

  2. Colossal anisotropic resistivity and oriented magnetic domains in strained La{sub 0.325}Pr{sub 0.3}Ca{sub 0.375}MnO{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Tao; Yang, Shengwei; Liu, Yukuai; Zhao, Wenbo; Feng, Lei; Li, Xiaoguang, E-mail: lixg@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, University of Science and Technology of China, Hefei 230026 (China); Zhou, Haibiao; Lu, Qingyou [Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, University of Science and Technology of China, Hefei 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230031 (China); Hou, Yubin [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230031 (China)

    2014-05-19

    Magnetic and resistive anisotropies have been studied for the La{sub 0.325}Pr{sub 0.3}Ca{sub 0.375}MnO{sub 3} films with different thicknesses grown on low symmetric (011)-oriented (LaAlO{sub 3}){sub 0.3}(SrAl{sub 0.5}Ta{sub 0.5}O{sub 3}){sub 0.7} substrates. In the magnetic and electronic phase separation region, a colossal anisotropic resistivity (AR) of ∼10{sup 5}% and an anomalous large anisotropic magnetoresistance can be observed for 30 nm film. However, for 120 nm film, the maximum AR decreases significantly (∼2 × 10{sup 3}%) due to strain relaxation. The colossal AR is strongly associated with the oriented formation of magnetic domains, and the features of the strain effects are believed to be useful for the design of artificial materials and devices.

  3. Investigation of conduction mechanism in Pr{sub 0.67}Sr{sub 0.13}Ag{sub 0.20}MnO{sub 3} manganites

    Energy Technology Data Exchange (ETDEWEB)

    Modi, Anchit, E-mail: sehr.masroor1952@gmail.com; Bhat, Masroor Ahamad; Gaur, N. K. [Department of Physics, Barkatullah University, Bhopal-462026 (India)

    2016-05-23

    We report the electronic conduction mechanism in Pr{sub 0.67}Sr{sub 0.13}Ag{sub 0.20}MnO{sub 3} synthesized successfully by conventional solid state reaction method. The compound under investigation was subjected by X – Ray diffraction using Rietveld refinement which confirms the single phase nature of the sample. The resistivity behavior indicates the semiconducting behavior and reduction in resistivity on the application of magnetic fields. The electronic nature can further been evaluated by using variable range hopping (VRH) model and small polaron hopping model (SPH) showing that the double exchange interaction increases suppress the band gap and enhances carrier delocalization on the application of magnetic fields.

  4. Structural, ferroelectric and leakage current properties of Bi{sub 3.96}Pr{sub 0.04}Ti{sub 2.95}Nb{sub 0.05}O{sub 12} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kao, Ming-Cheng, E-mail: kmc@mail.hust.edu.tw [Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung 412, Taiwan (China); Chen, Hone-Zern, E-mail: hzc@mail.hust.edu.tw [Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung 412, Taiwan (China); Young, San-Lin [Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung 412, Taiwan (China); Kao, Ming-Hui [Department of Electronic Engineering, Chung Chou University of Science and Technology, Changhua 510, Taiwan (China)

    2014-11-03

    Praseodymium and niobium-substituted bismuth titanate (Bi{sub 3.96}Pr{sub 0.04}Ti{sub 2.95}Nb{sub 0.05}O{sub 12}, BPTNO) thin films were deposited on Pt(111)/Ti/SiO{sub 2}/Si(100) substrates by a sol–gel technology. The effects of annealing temperature (500 ∼ 800 °C) on microstructure and electric properties of thin films were investigated. X-ray diffraction analysis shows that the BPTNO thin films have a bismuth-layered perovskite structure with preferred (117) orientation. The intensities of (117) peak increases with increasing annealing temperature. With the increase of annealing temperature from 500 °C to 800 °C, the grain size of BPTNO thin films increases. The highly (117)-oriented BPTNO thin films exhibits a high remnant polarization (2P{sub r}) of 48 μC/cm{sup 2} and a low coercive field (2E{sub c}) of 110 kV/cm, fatigue free characteristics up to > 10{sup 8} switching cycles. A small leakage current density (J) was 6.23 × 10{sup −8} A/cm{sup 2} at 200 kV/cm. The leakage current mechanisms were controlled by Poole–Frenkel emission in the low electric field region and by Schottky emission in the high field region. - Highlights: • Bi{sub 3.96}Pr{sub 0.04}Ti{sub 2.95}Nb{sub 0.05}O{sub 12} thin films were prepared by sol–gel technology. • Films show preferred (117) orientation. • The Pr and Nb-doping decrease the oxygen vacancy concentration. • The Pr and Nb-doping improved the ferroelectric and leakage current properties.

  5. Small angle neutron scattering study of magnetic clustering in (Pr{sub 0.55}Ca{sub 0.45})(Mn{sub 1-y}Cr{sub y})O{sub 3} manganites

    Energy Technology Data Exchange (ETDEWEB)

    Castellano, C., E-mail: carlo.castellano@unimi.it [Universita degli Studi di Milano, Dipartimento di Chimica, Via Golgi 19, 20133 Milano (Italy); Martinelli, A. [CNR-SPIN, C.so Perrone 24, 16152 Genova (Italy); Ferretti, M. [CNR-SPIN, C.so Perrone 24, 16152 Genova (Italy); Universita degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, Via Dodecaneso 31, 16146 Genova (Italy); Cimberle, M.R. [CNR-IMEM, Via Dodecaneso 33, 16146 Genova (Italy); Mondelli, C. [CNR-IOM-OGG and TOF at Institut Laue-Langevin, 6 rue Jules Horowitz, 38042 Genoble Cedex 9 (France)

    2012-11-25

    Highlights: Black-Right-Pointing-Pointer Magnetic clusters formation in (Pr{sub 0.55}Ca{sub 0.45})(Mn{sub 1-y}Cr{sub y})O{sub 3} manganites is pointed out. Black-Right-Pointing-Pointer We indicate that magnetic clusters formation is favoured by Mn/Cr substitution. Black-Right-Pointing-Pointer The importance of magnetic polarons in manganites phase behaviour is thus emphasized. Black-Right-Pointing-Pointer We tune by chemical substitution the weight of the different phase components. Black-Right-Pointing-Pointer Magnetic clusters formation in Mn/Cr substituted manganites results to be softened. - Abstract: In the present paper we report a small angle neutron scattering (SANS) study of magnetic clusters formation in (Pr{sub 0.55}Ca{sub 0.45})(Mn{sub 1-y}Cr{sub y})O{sub 3} (y = 0.00, 0.03, 0.06) manganites which was performed by analyzing, above and below the magnetic phase transitions, the momentum transfer q dependence of the SANS intensity on temperature and on the applied magnetic field 0 < H < 5 T. Thermal scans between 5 and 300 K in zero field, 1 and 5 T as well as isothermal field-scans at three different temperatures were collected in the suitable q range on each sample. These measurements allowed us to determine the spatial dimensions, density and distribution of the non-overlapping ferromagnetic clusters before, during and after their formation, both in the insulating high temperature and in the percolating low temperature phases. Our results indicate that the magnetic clusters formation is favoured by Mn/Cr partial substitution, thus emphasizing the importance of magnetic polarons in the natural tendency of manganites to phase separation and the possibility to tune by chemical substitution the relative weight of one phase component with respect to the other one.

  6. Phase separation and magnetocaloric effect in Pr{sub 0.5−x}Gd{sub x} Sr{sub 0.5}MnO{sub 3} system

    Energy Technology Data Exchange (ETDEWEB)

    Bourouina, M. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Krichene, A., E-mail: akramkri@hotmail.fr [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Chniba Boudjada, N. [Institut Néel, B.P. 166, 38042 Grenoble Cedex 9 (France); Boujelben, W. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia)

    2016-09-25

    The magnetic properties and the magnetocaloric effect have been studied in Pr{sub 0.5−x}Gd{sub x}Sr{sub 0.5}MnO{sub 3} (x = 0, 0.05 and 0.1) manganites prepared by the solid state reaction method. Magnetic measurements versus temperature in an applied magnetic field of 0.05 T show that the all samples exhibit a paramagnetic to ferromagnetic transition when temperature decreases. The x = 0.1 sample shows a clear transition, from the ferromagnetic state to the antiferromagnetic one at T{sub N} = 125 K. The Curie temperature decreases gradually with increasing gadolinium content. The absolute values of the maximum of magnetic entropy change |ΔS{sub M}| for an applied magnetic field of 2 T are equal to1.26, 1.25 and 1.02 J kg{sup −1} K{sup −1} for x = 0, 0.05 and 0.1, respectively. The decrease of |ΔS{sub M}| with Gd doping can be attributed to the enhancement of phase separation phenomenon. The magnetic entropy curves follow the universal law corresponding to the second-ordered paramagnetic-ferromagnetic transition. - Highlights: • Gd doping in Pr{sub 0.5−x}Gd{sub x}Sr{sub 0.5}MnO{sub 3} (with x = 0, 0.05 and 0.1) enhances the antiferromagnetic interactions. • The studied samples are characterized by the phase separation phenomenon. • Magnetic properties are in agreement with electrical results.

  7. Cobalt-free perovskite Pr{sub 0.5}Sr{sub 0.5}Fe{sub 1−x}Cu{sub x}O{sub 3−δ} (PSFC) as a cathode material for intermediate temperature solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Moura, Caroline G., E-mail: caroline.materiais@gmail.com [Materials Science and Engineering Postgraduate Program, UFRN, 59078-970, Natal (Brazil); Grilo, João Paulo de F. [Materials Science and Engineering Postgraduate Program, UFRN, 59078-970, Natal (Brazil); Macedo, Daniel A., E-mail: damaced@gmail.com [Materials Science and Engineering Postgraduate Program, UFPB, 58051-900, João Pessoa (Brazil); Cesário, Moisés R.; Fagg, Duncan Paul [Department of Mechanical Engineering, University of Aveiro, 3810-193, Aveiro (Portugal); Nascimento, Rubens M. [Materials Science and Engineering Postgraduate Program, UFRN, 59078-970, Natal (Brazil)

    2016-09-01

    PSFC (Pr{sub 0.5}Sr{sub 0.5}Fe{sub 1−x}Cu{sub x}O{sub 3−δ}) is a new perovskite-type oxide that has gained considerable attention as cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs), due to its high mixed ionic-electronic conductivity below 800 °C. In this work, PSFC (Pr{sub 0.5}Sr{sub 0.5}Fe{sub 1−x}Cu{sub x}O{sub 3−δ}, x = 0.2 and 0.4) powders were synthesized by the citrate method and structurally characterized by X-ray diffractometry. Screen-printed cathodes were sintered at 1050 °C and electrochemically characterized by impedance spectroscopy at 600–800 °C in pure oxygen. The area specific resistances (ASR) of the Pr{sub 0.5}Sr{sub 0.5}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} material are shown to be competitive with typical values reported for cobalt-based cathodes in the measured temperature range, while, importantly, offering a significantly lower activation energy, 0.62 eV. The thermal expansion coefficients of these Co-free cathodes are in the range of 13–15 × 10{sup −6} °C{sup −1}, in a temperature range 200–650 °C, demonstrating a good thermal compatibility with gadolinia doped ceria (CGO) electrolytes. - Highlights: • Cobalt-free Pr{sub 0.5}Sr{sub 0.5}Fe{sub 1−x}Cu{sub x}O{sub 3−δ} (PSFC) cathodes successfully prepared by the citrate method. • PSFC cathodes are thermally compatible with CGO electrolytes. • Pr{sub 0.5}Sr{sub 0.5}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} presents competitive area specific resistances of low activation energy, 0.62 eV.

  8. Effect of hydrostatic pressure on magnetic and magnetocaloric properties in La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Thiyagarajan, R. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Esakki Muthu, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Univ. Grenoble Alpes and CEA, INAC-SPSMS, F-38000 Grenoble (France); Manikandan, K. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Arumugam, S., E-mail: sarumugam1963@yahoo.com [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India)

    2016-01-15

    Magnetization of polycrystalline La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3} sample has been measured as a function of temperature (T) and magnetic field (H) under various external hydrostatic pressures (P) up to ~1 GPa. At ambient P, the sample exhibits paramagnetic (PM)–ferromagnetic (FM) transition (T{sub C}) at 167 K and 173 K in cooling and warming cycles respectively under the magnetic field (µ{sub 0}.H) of 0.1 T. It also shows a hysteresis during both temperature- and field- dependence of magnetization measurements at ambient P, suggests the presence of a first-order transition. Moreover, the field dependence of magnetization shows S type field-induced metamagnetic transition (FIMMT) over a temperature range below T{sub C} in the FM state. The application of P in M(T) increases T{sub C} at a rate [dT{sub C}/dP] of 13.9 K/GPa, but the thermally-driven first-order transition is not affected by P. However, the applied P suppresses FIMMT and reduces field-driven first-order transition in the magnetization isotherms [M(H)]below T{sub C}. H increases both magnetic entropy change (∆S{sub m}) and Relative Cooling Power (RCP), whereas the P slightly increases ∆S{sub m}{sup max} and no appreciable change in RCP. These results suggest that H and P can be used as a tool to enhance magnetocaloric values in the phase separated manganites. - Highlights: • At ambient P, La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3} sample shows first-order PM–FM transition. • P increases the T{sub C} at a rate of 13.9 K/GPa, thermal hysteresis is not affected. • P diminishes the field-driven first-order PM–FM transition, suppresses FIMMMT. • H increases ∆S{sub m} and RCP. P slightly increases ∆S{sub m}{sup max}, but no change in RCP by P.

  9. Study of complex impedance spectroscopic properties of Na{sub 2}Pb{sub 2}Pr{sub 2}W{sub 2}Ti{sub 4}Nb{sub 4}O{sub 30} Ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Biswal, L.; Das, Piyush R.; Behera, Banarji [Department of Physics, SOT, KIIT University, Bhubaneswar-751 024, Odisha (India) and School of Physics, Sambalpur University, Jyoti Vihar, Burla-768 019, Odisha (India); Department of Physics, ITER, S. O. A. University, Odisha, Bhubaneswar-751 030 (India); School of Physics, Sambalpur University, Jyoti Vihar, Burla-768 019, Odisha (India)

    2012-07-23

    The polycrystalline sample of Na{sub 2}Pb{sub 2}Pr{sub 2}W{sub 2}Ti{sub 4}Nb{sub 4}O{sub 30} was prepared by high temperature solid state reaction technique. The formation of compounds with an orthorhombic structure was confirmed by X-ray diffraction technique. Surface morphology study showed homogenous distribution of plate and rod like grains over the entire surface with less porosity. The study of effect of temperature on impedance parameters in the frequency range 10{sup 2}-10{sup 6} Hz and temperature range 30-500 Degree-Sign C revealed the presence of both bulk and grain boundary effects above 275 Degree-Sign C. The bulk resistance of the material decreased with rise in temperature exhibiting a typical negative temperature coefficient of resistance (NTCR) behavior like a semiconductor. Both the complex impedance and modulus studies suggested the presence of non-Debye type of relaxation in the materials. The ac conductivity spectrum obeys Johnsche's universal power law.

  10. Electrical conductance and complex impedance analysis of La{sub 0.6}Pr{sub 0.1}Ba{sub 0.3}Mn{sub 1-x}Ni{sub x}O{sub 3} nanocrystalline manganites

    Energy Technology Data Exchange (ETDEWEB)

    Hcini, Sobhi; Oumezzine, Elaa; Baazaoui, Mohamed; Oumezzine, Mohamed [Universite de Monastir, Laboratoire de Physico-chimie des Materiaux, Departement de Physique, Faculte des Sciences de Monastir, Monastir (Tunisia); Rahmouni, Hedi; Khirouni, Kamel [Universite de Gabes, Laboratoire de Physique des Materiaux et des Nanomateriaux appliquee a l' Environnement, Faculte des Sciences de Gabes, cite Erriadh, Gabes (Tunisia); Hlil, E.K. [CNRS et Universite Joseph Fourier, Institut Neel, BP 166, Grenoble (France)

    2015-09-15

    We have investigated the electrical properties of La{sub 0.6}Pr{sub 0.1}Ba{sub 0.3}Mn{sub 1-x}Ni{sub x}O{sub 3} (x = 0 and x = 0.1) nanocrystalline manganites using complex impedance spectroscopy technique in 40Hz-10 kHz and 80-320 K, frequency and temperature ranges, respectively. The two samples exhibit a metal-semiconductor transition temperature T{sub MS} which decreases from 160 to 120 K when increasing Ni content from x = 0 to x = 0.1. The total conductance curves for samples are found to obey Jonscher power law G(ω) = G{sub DC} + Aω {sup n}. The Ni content affects the activation energy (E{sub a}) which increases from 37 meV for x = 0 to 48 meV for x = 0.1. The obtained n exponent values for x = 0 are higher than those obtained for x = 0.1. This can be related to the decrease in grain size when Ni content increases. Nyquist plots of impedance show semicircle arcs for samples, and an electrical equivalent circuit has been proposed to explain the impedance results. (orig.)

  11. Influence of electron beam irradiation on electrical, structural, magnetic and thermal properties of Pr{sub 0.8}Sr{sub 0.2}MnO{sub 3} manganites

    Energy Technology Data Exchange (ETDEWEB)

    Christopher, Benedict [Department of Physics, Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Rao, Ashok, E-mail: ashokanu_rao@rediffmail.com [Department of Physics, Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Petwal, Vikash Chandra; Verma, Vijay Pal; Dwivedi, Jishnu [Industrial Accelerator Section, PSIAD, Raja Ramanna Centre for Advanced Technology, Indore 452012, M.P. (India); Lin, W.J. [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Kuo, Y.-K., E-mail: ykkuo@mail.ndhu.edu.tw [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China)

    2016-12-01

    In this communication, the effect of electron beam (EB) irradiation on the structural, electrical transport and thermal properties of Pr{sub 0.8}Sr{sub 0.2}MnO{sub 3} manganites has been investigated. Rietveld refinement of XRD data reveals that all samples are single phased with orthorhombic distorted structure (Pbnm). It is observed that the orthorhombic deformation increases with EB dosage. The Mn–O–Mn bond angle is found to increase with increase in EB dosage, presumably due to strain induced by these irradiations. Analysis on the measured electrical resistivity data indicates that the small polaron hopping model is operative in the high temperature region for pristine as well as EB irradiated samples. The electrical resistivity in the entire temperature region has been successfully fitted with the phenomenological percolation model which is based on phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. The Seebeck coefficient (S) of the pristine as well as the irradiated samples exhibit positive values, indicating that holes is the dominant charge carriers. The analysis of Seebeck coefficient data confirms that the small polaron hopping mechanism governs the thermoelectric transport in the high temperature region. In addition, Seebeck coefficient data also is well fitted with the phenomenological percolation model. The behavior in thermal conductivity at the transition is ascribed to the local anharmonic distortions associated with small polarons. Specific heat measurement indicates that electron beam irradiation enhances the magnetic inhomogeneity of the system.

  12. Study of electrical and magnetic properties of Pr{sub 0.6−x}Bi{sub x}Sr{sub 0.4}MnO{sub 3} (x=0.20 and 0.25)

    Energy Technology Data Exchange (ETDEWEB)

    Daivajna, Mamatha D. [Department of Physics, Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Rao, Ashok, E-mail: ashokanu_rao@rediffmail.com [Department of Physics, Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Lin, W.J. [Department of Physics, National Dong-Hwa University, Hualien 974, Taiwan (China); Kuo, Y.K., E-mail: ykkuo@mail.ndhu.edu.tw [Department of Physics, National Dong-Hwa University, Hualien 974, Taiwan (China)

    2017-06-01

    We have investigated the electrical and magnetic properties of Pr{sub 0.6-x}Bi{sub x}Sr{sub 0.4}MnO{sub 3} (x=0.20 and 0.25) manganites. XRD data shows that the synthesized samples are single-phase and crystallize in the orthorhombic structure with Pnma space group. Resistivity measurements show that the sample with x=0.25 exhibits a thermally activated behavior for the entire temperature range. The magnetoresistance (MR) for the x=0.25 sample is as high as nearly 100% over a wide range of temperature, demonstrating its important technological application as a material for MR-based devices. From the magnetization measurements, two magnetic transitions viz. paramagnetic insulating to ferromagnetic metallic (PMI-FMM) transition at T{sub C} and the ferromagnetic metallic (FMM) to antiferromagnetic insulating (AFI) transition at Neel temperature T{sub N} were observe in both samples. The Curie temperature decreases with bismuth doping, while T{sub N} increases with Bi content. Most interestingly, the temperature variation of magnetization and resistivity shows hysteresis behavior across the transition for the x=0.20 sample.

  13. Study of magnetic, structural and magnetocaloric properties of La{sub 0.6}Pr{sub 0.4}Mn{sub 2}Si{sub 2} under high pressures and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kaštil, J., E-mail: kastil@fzu.cz [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Arnold, Z. [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Isnard, O. [Centre national de la recherche scientifique (CNRS), Institut Néel, 25 rus des martyrs, F-38042 Grenoble (France); Université Grenoble Alpes, Institut Néel, F-38042 Grenoble (France); Skourski, Y. [Hochfeld-Magnetlabor Dresden (HLD), HZ Dresden-Rossendorf, D-01314 Dresden (Germany); Kamarád, J. [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Itié, J.P. [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, 91192 Gif-sur-Yvette (France)

    2017-02-15

    The structural, magnetic and magnetocaloric properties of La{sub 0.6}Pr{sub 0.4}Mn{sub 2}Si{sub 2} compound were measured in wide range of temperature, magnetic field and hydrostatic pressure. The structural study up to 10 GPa confirmed the existence of critical Mn-Mn distance 0.2883 nm for the ferromagnetic to antiferromagnetic transition at room temperature. The results demonstrated the crucial role of the volume in the suppression of the ferromagnetic phase above the transition temperature T{sub 1}=168 K under pressure. The huge pressure shift of the transition temperature T{sub 1}, dT{sub 1}/dp=230 K/GPa, was observed. Based on our magnetization measurement the low temperature transition at T{sub 2}=30 K is connected with reorientation of Mn moment and the rare-earth sublattice is not ordered in this case. The direct magnetocaloric measurement showed moderate values of the adiabatic temperature change connected with the magnetic transition at T{sub c} and T{sub 1} and confirmed the first order character of the transition at T{sub 1} and second order character of the transition at T{sub c}. - Highlights: • The huge pressure shift of the transition temperature dT{sub 1}/dp=230 K/GPa was observed. • Ferromagnetic order is suppressed by applying pressure of 1 GPa. • The direct magnetocaloric effect showed moderate values of ΔT{sub ad}.

  14. The zero-field glassy ground state and field-induced ferromagnetic transition in (La{sub 0.4}Pr{sub 0.6}){sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Tackett, R; Lawes, G; Suryanarayanan, R [Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201 (United States); Apostu, M [Faculty of Chemistry, Physical, Theoretical and Materials Chemistry, Alexandru Cuza University, Iasi 700506 (Romania); Revcolevschi, A, E-mail: glawes@wayne.edu [Laboratoire de Physico-Chimie de l' Etat Solide, ICMMO, CNRS-UMR 8182, Universite Paris-Sud, 91405 Orsay (France)

    2011-04-20

    We have investigated glassy magnetic freezing in (La{sub 0.4}Pr{sub 0.6}){sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} single crystals together with the field-induced transition to a metastable ferromagnetic phase using ac magnetic susceptibility and heat capacity measurements. The magnetization measurements show evidence for the development of a zero-field glassy ground state below 45 K along with a hysteretic, field-induced change in susceptibility associated with the transition to the ferromagnetic phase above 5 T. The heat capacity develops a clear peak at higher temperatures with the application of large magnetic fields, consistent with the development of a ferromagnetic order, while at low temperatures the Sommerfeld coefficient is monotonically reduced by an applied field, suggesting suppression of spin fluctuations. The heat capacity shows hysteretic behaviour, accompanied by a sharp decrease at a critical field, when held at fixed temperature, which does not recover on reducing the field back to zero. These measurements suggest that the zero-field ground state for (La{sub 0.4}Pr{sub 0.6}){sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} consists of frozen disordered spin clusters, which develop into a metastable ferromagnetic state in modest magnetic fields.

  15. Electronic structure study of wide band gap magnetic semiconductor (La{sub 0.6}Pr{sub 0.4}){sub 0.65}Ca{sub 0.35}MnO{sub 3} nanocrystals in paramagnetic and ferromagnetic phases

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, G. D.; Chou, H.; Yang, K. S.; Jhong, D. J.; Chan, W. L. [Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Joshi, Amish G. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Kumar, Shiv; Ghosh, A. K. [Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Chatterjee, Sandip, E-mail: schatterji.app@iitbhu.ac.in [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2016-04-25

    X-ray circular magnetic dichroism (XMCD), X-ray photoemission spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS) techniques were used to study the electronic structure of nanocrystalline (La{sub 0.6}Pr{sub 0.4}){sub 0.65}Ca{sub 0.35}MnO{sub 3} near Fermi-level. XMCD results indicate that Mn{sup 3+} and Mn{sup 4+} spins are aligned parallel to each other at 20 K. The low M-H hysteresis curve measured at 5 K confirms ferromagnetic ordering in the (La{sub 0.6}Pr{sub 0.4}){sub 0.65}Ca{sub 0.35}MnO{sub 3} system. The low temperature valence band XPS indicates that coupling between Mn3d and O2p is enhanced and the electronic states near Fermi-level have been suppressed below T{sub C}. The valence band UPS also confirms the suppression of electronic states near Fermi-level below Curie temperature. UPS near Fermi-edge shows that the electronic states are almost absent below 0.5 eV (at 300 K) and 1 eV (at 115 K). This absence clearly demonstrates the existence of a wide band-gap in the system since, for hole-doped semiconductors, the Fermi-level resides just above the valence band maximum.

  16. Effect of small quantity of chromium on the electrical, magnetic and magnetocaloric properties of Pr{sub 0.7}Ca{sub 0.3}Mn{sub 0.98}Cr{sub 0.02}O{sub 3} manganite

    Energy Technology Data Exchange (ETDEWEB)

    Bettaibi, A.; Rahmouni, H. [Universite de Gabes, Laboratoire de Physique des Materiaux et des Nanomateriaux appliquee a l' Environnement, Faculte des Sciences de Gabes cite Erriadh, Gabes (Tunisia); M' nassri, R. [Kairouan University, Higher Institute of Applied Sciences and Technology of Kasserine, Kasserine (Tunisia); Universite de Monastir, Laboratoire de Physico-Chimie des Materiaux, Departement de Physique, Faculte des Sciences de Monastir, Monastir (Tunisia); Selmi, A.; Cheikhrouhou, A. [Sfax University, Laboratory of Physics of Materials, Faculty of Sciences of Sfax, Sfax (Tunisia); Khirouni, K. [Kairouan University, Higher Institute of Applied Sciences and Technology of Kasserine, Kasserine (Tunisia); Chniba Boudjada, N. [Institut NEEL, Grenoble Cedex 09 (France)

    2016-03-15

    Structural, electrical and thermomagnetic properties of Pr{sub 0.7}Ca{sub 0.3}Mn{sub 0.98}Cr{sub 0.02}O{sub 3} were investigated. Sample was prepared by solid-state reaction method. X-ray diffraction revealed that the sample crystallizes in the orthorhombic system with Pnma space group. Electrical conductivity and complex impedance studies of Pr{sub 0.7}Ca{sub 0.3}Mn{sub 0.98}Cr{sub 0.02}O{sub 3} system are analyzed. The investigated compound exhibits a semiconductor behavior in the whole explored temperature range. From 100 to 206 K, the increase in DC conductance is more than two decade. At higher temperatures, the conductance varies slowly and a saturation region appears. The conduction mechanism is found to be governed by small polaron hopping process which is explained by the short range thermally activated energy. Conductance spectrum is well described by Jonsher law, and the temperature dependence of the frequency exponent confirms that conduction mechanism is governed by hopping process of the localized carriers. Using complex impedance analysis, the compound is modeled by an electrical equivalent circuit. Also, such analysis confirms the contribution of grain boundary to the transport properties. The substitution of Mn by 2 % Cr destroyed the charge order state observed in the parent compound and induced a ferromagnetic phase at low temperatures. For a magnetic field change of 5 T, the material shows a maximum magnetic entropy change ∇S {sup max} = 2.69 J kg{sup -1} K{sup -1} with a full width at half maximum δ {sub TFWHM} = 145 K, and a relative cooling power RCP = 389 J kg{sup -1}. Pr{sub 0.7}Ca{sub 0.3}Mn{sub 0.98}Cr{sub 0.02}O{sub 3} material demonstrates potential proprieties to be used in electronic and thermal devices and as magnetic refrigerant. (orig.)

  17. Evolution and sign control of square-wave-like anisotropic magneto-resistance in spatially confined La{sub 0.3}Pr{sub 0.4}Ca{sub 0.3}MnO{sub 3}/LaAlO{sub 3}(001) manganite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Alagoz, H. S., E-mail: alagoz@ualberta.ca; Jeon, J.; Keating, S.; Chow, K. H., E-mail: khchow@ualberta.ca; Jung, J., E-mail: jjung@ualberta.ca [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)

    2016-04-14

    We investigated magneto-transport properties of a compressively strained spatially confined La{sub 0.3}Pr{sub 0.4}Ca{sub 0.3}MnO{sub 3} (LPCMO) thin film micro-bridge deposited on LaAlO{sub 3}. Angular dependence of the magneto-resistance R(θ) of this bridge, where θ is the angle between the magnetic field and the current directions in the film plane, exhibits sharp positive and negative percolation jumps near T{sub MIT}. The sign and the magnitude of these jumps can be tuned using the magnetic field. Such behavior has not been observed in LPCMO micro-bridges subjected to tensile strain, indicating a correlation between the type of the lattice strain, the distribution of electronic domains, and the anisotropic magneto-resistance in spatially confined manganite systems.

  18. Comparative study of perovskite Pr{sub (1-x)}Ca{sub x}CoO{sub 3} e Gd{sub (1-x)}Ca{sub x}CoO{sub 3} (x=0,2) synthesized by gelatin modified route for application in automotive catalysis; Estudo comparativo das perovsquitas Pr{sub (1-x)}Ca{sub x}CoO{sub 3} e Gd{sub (1-x)}Ca{sub x}CoO{sub 3} (x=0,2) sintetizadas pela rota modificada gelatina para aplicacao em catalise automotiva

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, E.M. de; Medeiros, M.R.A.; Paiva, A.K.O.; Borges, F.M.M., E-mail: eduardamedeirosdearaujo@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), RN (Brazil); Ruiz, J.A.C. [Centro de Tecnologia do Gas e Energias Renovaveis (CTGAS-ER), RN (Brazil)

    2016-07-01

    Increased air pollution intensified the search for materials that could convert pollutant gases into less harmful substances. Thus, mixed oxides with perovskite structure began to be developed for presenting important features for the automotive catalysis. In this study has been compared the chemical composition of the materials with Pr{sub (1-x)}Ca{sub x}CoO{sub 3} and Gd{sub (1-x)}Ca{sub x}CoO{sub 3} (x = 0.2) synthesized by the method gelatine. The samples were characterized by techniques: Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-Ray Diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence (XRF) and subjected to the catalytic test in methane combustion reaction. The evaluation of the catalytic activity showed that gadolinium catalyst is more efficient compared with the praseodymium catalyst, although they have similar maximum conversion of methane at high temperature, during the catalytic test the material with gadolinium showed higher catalytic activity and stability. (author)

  19. Critical behavior of resistivity in the pressure-induced first to second order transition in Pr{sub 0.6}Ca{sub 0.4}Mn{sub 0.96}B{sub 0.04}O{sub 3} (B = Co and Cr)

    Energy Technology Data Exchange (ETDEWEB)

    Thiyagarajan, R.; Esakki Muthu, S.; Kalai Selvan, G. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Mahendiran, R. [Department of Physics, 2 Science Drive 3, Faculty of Science, National University of Singapore, Singapore 117551 (Singapore); Arumugam, S., E-mail: sarumugam1963@yahoo.com [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

    2015-01-05

    Highlights: • 1st order PMI–FMM transition at T{sub IM} Pr{sub 0.6}Ca{sub 0.4}Mn{sub 0.96}B{sub 0.04}O{sub 3} (B = Co and Cr) samples. • Crossover from 1st to 2nd order is observed by the application of P on both the samples. • Critical exponents’ are close to the 3D Heisenberg model for the Co doped sample. • Critical exponents’ are close to the Mean field model for the Cr doped sample. - Abstract: We have investigated the hydrostatic pressure (P) dependence of the resistivity on Pr{sub 0.6}Ca{sub 0.4}Mn{sub 0.96}B{sub 0.04}O{sub 3} (B = Co and Cr) polycrystals. At ambient pressure, the temperature dependence of resistivity [ρ(T)] of both the samples show a first order paramagnetic insulator–ferromagnetic metallic transition at T = T{sub IM}. The application of P on both the samples increases the T{sub IM}, reduces the resistivity, and suppresses the hysteresis width, indicating a crossover from first to second order transition. The critical pressure, where the first–second order crossover takes place, are 2.02 and 2.40 GPa for Co and Cr doped samples respectively. The critical property of both systems around second order transition is investigated using Fisher–Langer relation and Suezaki–Mori method. The estimated critical exponents are close to the three-dimensional Heisenberg model for the Co doped sample suggesting short range interaction, and the exponents for the Cr doped sample follow the mean field theory suggesting long range ferromagnetic order. Further, the application of P suppresses the high temperature resistivity by reducing high temperature polarons in the case of the Cr doped sample, but it does not happen for the Co doped sample. The application of P helps to examine the stability of polarons in the high temperature regime.

  20. Absence of the impurity-induced magnetic order in the electron-doped high-T {sub c} cuprates Pr{sub 0.86}LaCe{sub 0.14}Cu{sub 1-y}(Zn, Ni) {sub y}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Risdiana [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05, Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)]. E-mail: risdiana@teion.apph.tohoku.ac.jp; Adachi, T. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05, Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Koike, Y. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05, Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Watanabe, I. [Advanced Meson Science Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198 (Japan); Nagamine, K. [Muon Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK-IMSS), 1-1 Oho, Tsukuba 305-0801 (Japan)

    2005-10-01

    Zero-field muon-spin-relaxation measurements have been carried out in order to investigate the Zn- and Ni-substitution effects on the Cu-spin dynamics in the electron-doped Pr{sub 0.86}LaCe{sub 0.14}Cu{sub 1-y}(Zn, Ni) {sub y}O{sub 4+{alpha}}{sub -{delta}} with y = 0, 0.01, 0.02, 0.05 and different values of the reduced oxygen content {delta} ({delta} {<=} 0.09). For the samples with y = 0 and very small {delta} values of {delta} < 0.01, a muon-spin precession due to the formation of a long-range antiferromagnetic order has been observed at low temperatures below {approx}5 K. For the moderately oxygen-reduced samples of 0.01 {<=} {delta} {<=} 0.09, on the contrary, no muon-spin precession has been observed and the temperature dependence of the spectra is similar to one another regardless of the y value. That is, no impurity-induced slowing down of the Cu-spin fluctuations has been detected, which is very different from the results of the hole-doped high-T{sub c} cuprates. The reason is discussed.

  1. Chemical insertion in the perovskite solid solutions Pr{sub 0.5+x-y}Li{sub 0.5-3x}Bi{sub y}{open_square}{sub 2x}TiO{sub 3}: Implications on the electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Sanchez, M.F., E-mail: rusonil@yahoo.com [Unidad Profesional Interdisciplinaria en Ingenieria y Tecnologias Avanzadas-Instituto Politecnico Nacional (IPN), C.P. 07340, Mexico D.F. (Mexico); Fernandez, N. [Departamento de Quimica Inorganica, Universidad de la Habana, 10400 Ciudad de la Habana (Cuba); Martinez-Sarrion, M.-L.; Mestres, L. [Departament de Quimica Inorganica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Santana, G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacan 04510, Mexico D.F. (Mexico); Lewis, D.W. [Department of Chemistry, University College London, 20 Gordon St., London WC1H 0AJ (United Kingdom); Ruiz-Salvador, A.R. [Instituto de Ciencia y Tecnologia de Materiales, Universidad de La Habana, 10400 Ciudad de la Habana (Cuba)

    2012-05-15

    Highlight: Black-Right-Pointing-Pointer Lithium insertion is related to the number of vacancies and bismuth concentration. Black-Right-Pointing-Pointer The use of Kramers-Kronig relations allows the separation of the electronic conductivities. Black-Right-Pointing-Pointer The insertion changes the samples from ionic conductors to mixed conductors. Black-Right-Pointing-Pointer Electronic conduction is via a polaron mechanism with activation energy of {approx}0.8 eV. - Abstract: Chemical insertion and de-insertion of lithium in pellet samples of the solid solutions Pr{sub 0.5+x-y}Li{sub 0.5-3x}Bi{sub y}{open_square}{sub 2x}TiO{sub 3} were studied. Two regions of the phase diagram are studied: one having constant composition of bismuth and the other of lithium. The amount of inserted lithium depends on both the number of vacancies and the amount of bismuth in the original samples. The conductivity of the samples is directly related to the amount of inserted lithium and the activation energy depends on the unit cell volume. An analysis of the electronic and ionic components of the conductivity reveals that the untreated materials are pure ionic conductors, while after Li-insertion an additional electronic conductivity (t < 10{sup -2}) occurs, due to a polaron mechanism, with an activation energy of 0.8 eV.

  2. A comparative study of magnetic field induced meta-magnetic transition in nanocrystalline and bulk Pr{sub 0.65}(Ca{sub 0.7}Sr{sub 0.3}){sub 0.35}MnO{sub 3} compound

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Suvayan [CMP Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064 (India); Center for Research in Nanoscience and Nanotechnology, University of Calcutta, JD-2, Salt Lake City, Kolkata 700098, West Bengal (India); Department of Physics, University of Calcutta, 92 A.P.C. Road, Kolkata 700009 (India); Das, Kalipada, E-mail: kalipadadasphysics@gmail.com [Department of Materials Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032 (India); Bandyopadhyay, Sudipta [Center for Research in Nanoscience and Nanotechnology, University of Calcutta, JD-2, Salt Lake City, Kolkata 700098, West Bengal (India); Department of Physics, University of Calcutta, 92 A.P.C. Road, Kolkata 700009 (India); Das, I. [CMP Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064 (India)

    2017-06-15

    Highlights: • Field induced sharp meta-magnetic transition appears even in nanocrystalline sample. • Magnetic field for the meta-magnetic transition enhances depending upon the cooling field. • This unusual behavior is addressed by the effect of the interfacial strains. - Abstract: In our present study we highlight the observations of external magnetic field induced sharp meta-magnetic transition in polycrystalline bulk as well as nanocrystalline form of Pr{sub 0.65}(Ca{sub 0.7}Sr{sub 0.7}){sub 0.35}MnO{sub 3} compound. Interestingly, such behavior persists in the nanoparticles regardless of the disorder broadened transition. However, higher magnetic field is required for nanoparticles having average particle size ∼40 nm for such meta-magnetic transition, which differs from the general trends of the pure charge ordered nano materials. The interfacial strain between the different magnetic domains plays the important role in magnetic isothermal properties of nanoparticles, when the samples are cooled down in different cooling field. Additionally, both the bulk and nanoparticle compounds exhibit spontaneous phase separation and significantly large magnetoresistance at the low temperature region due to the melting of charge ordered fraction.

  3. Effect of Ni-doping on critical behavior of La{sub 0.6}Pr{sub 0.1}Ba{sub 0.3}Mn{sub 1−x}Ni{sub x}O{sub 3} nanocrystalline manganites

    Energy Technology Data Exchange (ETDEWEB)

    Oumezzine, Elaa [Laboratoire de Physico-chimie des Matériaux, Faculté des Sciences de Monastir, Département de Physique, Université de Monastir, 5019 Monastir (Tunisia); Hcini, Sobhi, E-mail: hcini_sobhi@yahoo.fr [Laboratoire de Physico-chimie des Matériaux, Faculté des Sciences de Monastir, Département de Physique, Université de Monastir, 5019 Monastir (Tunisia); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, 38042 Gronoble (France); Dhahri, Essebti [Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, Université de Sfax, B.P. 1171, 3000 Sfax (Tunisia); Oumezzine, Mohamed [Laboratoire de Physico-chimie des Matériaux, Faculté des Sciences de Monastir, Département de Physique, Université de Monastir, 5019 Monastir (Tunisia)

    2015-11-15

    We used Banerjee's criteria, modified Arrott plots and the scaling hypothesis to analyze magnetic-field dependences of magnetization near the ferromagnetic–paramagnetic (FM–PM) phase-transition temperature (T{sub C}) of La{sub 0.6}Pr{sub 0.1}Ba{sub 0.3}Mn{sub 1−x}Ni{sub x}O{sub 3} (0≤x≤0.3) nanocrystalline manganites. Experimental results reveal that all samples undergo a second-order phase transition. The estimated critical exponents obtained for x=0 sample are close to the mean-field model (β=0.503±0.004, γ= 1.024±0.068 and δ=2.821 at T{sub C}=215 K). Whereas for a high amount of Ni, these exponents belong to a different universality class (β=0.599±0.014, γ=0.897±0.013 and δ=2.570 at T{sub C}=162 K for x=0.1 sample) and (β=0.733±0.012, γ=0.753±0.014 and δ=2.320 at T{sub C}=131 K for x=0.3 sample). This is due to the fact that the substitution of Ni ions into the Mn-site leads to the formation of a larger proportion of Mn{sup 4+} with respect to Mn{sup 3+} which reduces the ferromagnetic double exchange interaction of Mn{sup 3+}–Mn{sup 4+} couples. These exponents indicate that the exchange interaction J(r) decreases with distance r slower than r{sup −4.5} for x=0 sample, however it ranges from r{sup −5} and r{sup −4.5} for x=0.1 and 0.3 samples.

  4. Magnetic interactions in new fluorite-related rare earth oxides LnLn’{sub 2}RuO{sub 7} (Ln, Ln’=rare earths)

    Energy Technology Data Exchange (ETDEWEB)

    Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.jp; Doi, Yoshihiro

    2016-07-15

    New fluorite-related quaternary rare earth oxides Pr{sub 2}YRuO{sub 7} and La{sub 2}TbRuO{sub 7} have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space group Cmcm. Through magnetic susceptibility and specific heat measurements, Pr{sub 2}YRuO{sub 7} shows an antiferromagnetic transition at 27 K, which is considerably lowered compared with that for Pr{sub 3}RuO{sub 7}. Analysis of the magnetic specific heat indicates that the magnetic behavior observed at 27 K for Pr{sub 2}YRuO{sub 7} is predominantly due to the magnetic interactions between Ru ions, and that the interactions between the Pr{sup 3+} and Ru{sup 5+} ions are also important. La{sub 2}TbRuO{sub 7} shows magnetic ordering at 9.0 K, which is ascribed to the magnetic ordering between Ru{sup 5+} ions from the analysis of the magnetic specific heat data. - Graphical abstract: New fluorite-related quaternary rare earth oxides Pr{sub 2}YRuO{sub 7} and La{sub 2}TbRuO{sub 7} have been prepared. Through magnetic susceptibility and specific heat measurements, Pr{sub 2}YRuO{sub 7} and La{sub 2}TbRuO{sub 7} show an antiferromagnetic transition at 27 and 9.0 K, respectively. Display Omitted - Highlights: • New fluorite-related quaternary rare earth oxides LnLn’{sub 2}RuO{sub 7} have been prepared. • Pr{sub 2}YRuO{sub 7} shows an antiferromagnetic transition at 27 K. • La{sub 2}TbRuO{sub 7} shows magnetic ordering at 9.0 K. • Their magnetic exchange mechanism has been elucidated by the magnetic entropy change.

  5. Complexes of gastrin with In3+, Ru3+ or Ga3+ ions are not recognised by the cholecystokinin 2 receptor.

    Science.gov (United States)

    Laval, Marie; Marshall, Kathryn M; Sachinidis, John; Scott, Andrew; Eutick, Mal; Baldwin, Graham S

    2017-10-01

    The peptide hormone gastrin (Gamide) binds trivalent metal ions, including indium (In), ruthenium (Ru) and gallium (Ga), with high affinity. Complexes of gastrin with chelated isotopes of In and Ga have previously been used for the location of tumours expressing the cholecystokinin 2 receptor (CCK2R). The aim of the present study was to purify the complexes of Gamide with radioactive isotopes of In, Ru or Ga and to investigate their ability to bind to the CCK2R. The radioactive Gamide complexes were purified on Sep-Pak C18 cartridges or by anion exchange HPLC. Binding to the CCK2R was assessed with a stably transfected clone of the gastric carcinoma cell line AGS. The 106Ru-Gamide complex could be eluted from the C18 cartridge; the 111In-Gamide and 68Ga-Gamide complexes bound irreversibly. All three complexes were successfully purified by anion exchange HPLC. The failure to detect binding of the 111In-Gamide, 106Ru-Gamide and 68Ga-Gamide complexes to the CCK2R suggests that formation of these complexes will not be useful for the detection of tumours expressing this receptor, but may instead provide alternative ways to block the actions of Gamide as a growth factor or a stimulant of gastric acid secretion. The complexes between the hormone gastrin and radioactive 111In, 106Ru or 68Ga ions were purified by anion exchange HPLC using a NaCl gradient. The failure to detect binding of the complexes to the cholecystokinin 2 receptor suggests that metal ion treatment may provide novel approaches to block the biological actions of gastrin.

  6. Neutron scattering and μSR investigations of quasi-one-dimensional magnetism in the spin =3/2 compound Li3RuO4

    DEFF Research Database (Denmark)

    Manuel, P.; Adroja, D. T.; Lindgård, Per-Anker

    2011-01-01

    observed two well-defined magnetic excitations at 5.5 meV and 8.5 meV and a weak low-energy peak near ~2 meV. We interpret the 5.5 meV energy peak as a 1D zone-boundary mode and that at 8.5 meV as arising from a maximum away from the zone boundary in the dispersion curve for spin-wave modes along the chain...

  7. Synthesis, spectroscopic characterization, and x-ray structural determination of W(CO)/sub 4/(PR/sub 3/)CNC/sub 6/H/sub 4/(PR/sub 3/ (R = Ph, Et)

    Energy Technology Data Exchange (ETDEWEB)

    Rommel, J.S.; Weinrach, J.B.; Grubisha, D.S.; Bennett, D.W.

    1988-08-24

    Two bimetallic complexes containing 1,4-diisocyanobenzene as a bridging ligand have been prepared and examined by x-ray crystallography and /sup 13/C NMR, /sup 31/P NMR, and infrared spectroscopies. W(CO)/sub 4/(PEt/sub 3/)CNC/sub 6/H/sub 4/NCW(CO)/sub 4/(PEt/sub 3/) (1) and W(CO)/sub 4/(PPh/sub 3/)CNC/sub 6/H/sub 4/NCW(CO)/sub 4/(PPh/sub 3/) (2) both crystallized in the same space group in very similar packing environments. Crystal data: for 1, monoclinic space group P2/sub 1//n,a = 7.780 (2) /angstrom/, b = 15.930 (3) /angstrom/, c = 14.137 (6) /angstrom/, /beta/ = 99.56 (3)/degree/, Z = 2, R = 0.040; for 2, monoclinic space group P2/sub 1//n, a = 11.641 (2) /angstrom/, b = 16.970 (2) /angstrom/, c = 12.463 (2), /angstrom/, /beta/ = 101.24 (1)/degree/, Z = 2, R = 0.047; NMR chemical shifts and vibrational frequencies for CNC/sub 6/H/sub 4/NC experience significant changes upon coordination, and the presence of an organophosphine ligand in the metal coordination sphere causes the diisocyanide to experience in-plane bends of 10.8/degrees/ for 1 and 4.2/degree/ for 2. In spite of strong evidence for the M-CNR back-bonding, the C-N bond length varies only negligibly among 1, 2, and CNC/sub 6/H/sub 4/NC, the free ligand. 20 references, 2 figures, 8 tables.

  8. A chiral alkyltris(pyrazolyl)borate ligand: synthesis of [(Ipc)B(pz)3Mn(CO)3] and [(Ipc)B(pz)3Ru(p-cymene)]PF6 (Ipc = Isopinocampheyl).

    Science.gov (United States)

    Bailey, Philip J; Pinho, Pedro; Parsons, Simon

    2003-12-29

    The application of the reagent (Ipc)BCl(2) (Ipc = isopinocampheyl) in the synthesis of a new tris(pyrazolyl)borate ligand having an Ipc substituent on boron is described. The sodium salt is a convenient precursor for the preparation of the complexes [(Ipc)tris(pyrazolyl)borato]tricarbonylmanganese and [[(Ipc)tris(pyrazolyl)borato](p-cymene)ruthenium](+), whose X-ray crystal structures are reported. While little distortion of the B(pz)(3)M unit is observed in these complexes, steric interaction between the Ipc group and the 3-positions of the pyrazolyl rings is noted to lead to distortion of the angles around the B-C bond.

  9. Electronic structure of layered ferroelectric high-k titanate Pr>2Ti2O7

    DEFF Research Database (Denmark)

    Atuchin, V.V.; Gavrilova, T.A.; Grivel, Jean-Claude

    2012-01-01

    The spectroscopic parameters and electronic structure of binary titanate Pr2Ti2O7 have been studied by IR-, Raman and X-ray photoelectron spectroscopy (XPS) for the powder sample prepared by solid state synthesis. The spectral features of valence band and all constituent element core levels have ...... parameters in comparison with those of other titanium- and praseodymium-bearing oxides....

  10. Carbon Dioxide Gas Sensors and Method of Manufacturing and Using Same

    Science.gov (United States)

    Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor)

    2014-01-01

    A gas sensor comprises a substrate layer; a pair of interdigitated metal electrodes, said electrodes include upper surfaces, the electrodes selected from the group consisting of Pt, Pd, Au, Ir, Ag, Ru, Rh, In, Os, and their alloys. A first layer of solid electrolyte staying in between electrode fingers and partially on said upper surfaces of said electrodes, said first layer selected from NASICON, LISICON, KSICON and.beta.''-Alumina. A second layer of metal carbonate(s) as an auxiliary electrolyte engaging said upper surfaces of the electrodes and the first solid electrolyte. The metal carbonates selected from the group consisting of the following ions Na.sup.+, K.sup.+, Li.sup.+, Ag.sup.+, H.sup.+, Pb.sup.2+, Sr.sup.2+, Ba.sup.2+, and any combination thereof. An extra layer of metal oxide selected from the group consisting of SnO.sub.2, In.sub.2O.sub.3, TiO.sub.2, WO.sub.3, ZnO, Fe.sub.2O.sub.3, ITO, CdO, U.sub.3O.sub.8, Ta.sub.2O.sub.5, BaO, MoO.sub.2, MoO.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5, CuO, Cr.sub.2O.sub.3, La.sub.2O.sub.3, RuO.sub.3, RuO.sub.2, ReO.sub.2, ReO.sub.3, Ag.sub.2O, CoO, Cu.sub.2O, SnO, NiO, Pr.sub.2O.sub.3, BaO, PdO.sub.2, HfO.sub.3, HfO.sub.3 or other metal oxide and their mixtures residing above and in engagement with the second electrolyte to improve sensor performance and/or to reduce sensor heating power consumption.

  11. Effect of Flap Mutations on Structure of HIV-1 Protease and Inhibition by Sanquinavir and Darunavir

    Energy Technology Data Exchange (ETDEWEB)

    Liu, F.; Kovalevsky, A.; Tie, Y.; Ghosh, A.; Harrison, R.; Weber, I. (GSU); (Purdue)

    2008-08-25

    HIV-1 (human immunodeficiency virus type 1) protease (PR) and its mutants are important antiviral drug targets. The PR flap region is critical for binding substrates or inhibitors and catalytic activity. Hence, mutations of flap residues frequently contribute to reduced susceptibility to PR inhibitors in drug-resistant HIV. Structural and kinetic analyses were used to investigate the role of flap residues Gly48, Ile50, and Ile54 in the development of drug resistance. The crystal structure of flap mutants PR{sub I50V} (PR with I50V mutation), PR{sub I54V} (PR with I54V mutation), and PR{sub I54M} (PR with I54M mutation) complexed with saquinavir (SQV) as well as PR{sub G48V} (PR with G48V mutation), PR{sub I54V}, and PR{sub I54M} complexed with darunavir (DRV) were determined at resolutions of 1.05--1.40 {angstrom}. The PR mutants showed changes in flap conformation, interactions with adjacent residues, inhibitor binding, and the conformation of the 80s loop relative to the wild-type PR. The PR contacts with DRV were closer in PR{sub G48V}-DRV than in the wild-type PR-DRV, whereas they were longer in PR{sub I54M}-DRV. The relative inhibition of PR{sub I54V} and that of PR{sub I54M} were similar for SQV and DRV. PR{sub G48V} was about twofold less susceptible to SQV than to DRV, wheres the opposite was observed for PR{sub I50V}. The observed inhibition was in agreement with the association of G48V and I50V with clinical resistance to SQV and DRV, respectively. This analysis of structural and kinetic effects of the mutants will assist in the development of more effective inhibitors for drug-resistant HIV.

  12. Environmental TEM Study of Electron Beam Induced Electrochemistry of Pr>0.64Ca0.36MnO3 Catalysts for Oxygen Evolution

    DEFF Research Database (Denmark)

    Mildner, Stephanie; Beleggia, Marco; Mierwaldt, Daniel

    2015-01-01

    an ETEM study of a Pr0.64Ca0.36MnO3 (PCMO) thin filth electrocatalySt for water splitting and Oxygen evolution in contact with water vapor: We show by means of off-axis electron holography and electrostatic modeling that the electron beam gives rise to a positive electric sample potential due to secondary....... The first reaction is an anodic oxidation of oxygen depleted amorphous PCMO which results in recrystallization of the oxide. The Second reaction is oxygen evolution which can be detected by the oxidation of a silane additive and formation of SiO2-gamma at catalytically active surfaces. The quantification...

  13. The low-temperature magnetostructure and magnetic field response of Pr>0.9Ca0.1MnO3

    DEFF Research Database (Denmark)

    Tikkanen, J.; Frontzek, M.; Hergert, W.

    2016-01-01

    calculations. Particular emphasis was placed on determining the presence of nanoscale magnetic phase separation. Previously published results of a canted A-AFM average ground state were reproduced to a good precision both experimentally and theoretically, and complemented by investigating the effects...... phase separation model of manganites to the material under discussion despite its very low Ca doping level in the context of the model. In the light of the new data, we also conclude that the low temperature magnetic moment of Pr must be ca. 300% larger than previously thought in this material, close...

  14. Amprenavir complexes with HIV-1 protease and its drug-resistant mutants altering hydrophobic clusters

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chen-Hsiang; Wang, Yuan-Fang; Kovalevsky, Andrey Y.; Harrison, Robert W.; Weber, Irene T. (GSU)

    2010-10-22

    The structural and kinetic effects of amprenavir (APV), a clinical HIV protease (PR) inhibitor, were analyzed with wild-type enzyme and mutants with single substitutions of V32I, I50V, I54V, I54M, I84V and L90M that are common in drug resistance. Crystal structures of the APV complexes at resolutions of 1.02-1.85 {angstrom} reveal the structural changes due to the mutations. Substitution of the larger side chains in PR{sub V32I}, PR{sub I54M} and PR{sub L90M} resulted in the formation of new hydrophobic contacts with flap residues, residues 79 and 80, and Asp25, respectively. Mutation to smaller side chains eliminated hydrophobic interactions in the PR{sub I50V} and PR{sub I54V} structures. The PR{sub I84V}-APV complex had lost hydrophobic contacts with APV, the PR{sub V32I}-APV complex showed increased hydrophobic contacts within the hydrophobic cluster and the PR{sub I50V} complex had weaker polar and hydrophobic interactions with APV. The observed structural changes in PR{sub I84V}-APV, PR{sub V32I}-APV and PR{sub I50V}-APV were related to their reduced inhibition by APV of six-, 10- and 30-fold, respectively, relative to wild-type PR. The APV complexes were compared with the corresponding saquinavir complexes. The PR dimers had distinct rearrangements of the flaps and 80's loops that adapt to the different P1{prime} groups of the inhibitors, while maintaining contacts within the hydrophobic cluster. These small changes in the loops and weak internal interactions produce the different patterns of resistant mutations for the two drugs.

  15. Estudio comparativo de dos métodos de síntesis para la obtención de polvos cerámicos de ZnO - Pr>2O3 - CoO

    OpenAIRE

    Rodríguez-Páez, J. E.; Caballero, A. C.; Villegas, M.; Cruz, A M; Ávila, H.

    2004-01-01

    Zinc oxide containing rare earth metal and Cobalt oxide are utilized as raw material to make varistors. Some of systems were found to exhibit non-ohmic current-voltaje characteristics and they are applicable not only for low voltaje devices but also for hight voltaje electric power stations. The microstructure of ZnO varistor can be considered as a vehicle thorugh which all of these properties ara manifested. Therefore, a discussion of the microstructure cannot be separated from a discussion ...

  16. Electrical resistivity anomaly, valence shift of Pr ion, and magnetic behavior in epitaxial (Pr.sub.1-y./sub.Y.sub.y./sub.).sub.1-x./sub.Ca.sub.x./sub.CoO.sub.3./sub. thin films under compressive strain

    Czech Academy of Sciences Publication Activity Database

    Fujishiro, H.; Noda, Y.; Akuzawa, K.; Naito, T.; Ito, A.; Goto, T.; Maryško, Miroslav; Jirák, Zdeněk; Hejtmánek, Jiří; Nitta, K.

    2017-01-01

    Roč. 121, č. 11 (2017), s. 1-8, č. článku 115104. ISSN 0021-8979 R&D Projects: GA ČR GA17-04412S Institutional support: RVO:68378271 Keywords : perovskite cobaltites * spin state transition * variable valence * epitaxial strain * XANES Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.068, year: 2016

  17. A study of Pr>0.7Sr0.3Fe1-xNixO3 as a cathode material for SOFCs with intermediate operating temperature

    DEFF Research Database (Denmark)

    Hashimoto, S.I.; Kammer Hansen, K.; Larsen, P.H.

    2005-01-01

    Pr0.7Sr0.3Fe1-xNxO3-δ (PSFN; x=0.2-0.5) compounds were synthesized and characterized by powder X-ray diffraction (XRD), thermal expansion coefficient (TEC) measurements, electrical conductivity and electrochemical impedance spectroscopy on cone-shaped electrodes on a Ce0.9Gd0.1O1.95 (CGO10)...

  18. Synthesis and characterization of several molybdenum chloride cluster compounds

    Energy Technology Data Exchange (ETDEWEB)

    Beers, W.W.

    1983-06-01

    Investigation into the direct synthesis of Mo/sub 4/Cl/sub 8/(P(C/sub 2/H/sub 5/)/sub 3/)/sub 4/ from Mo/sub 2/(OAc)/sub 4/ led to a synthetic procedure that produces yields greater than 80%. The single-crystal structure disclosed a planar rectangular cluster of molybdenum atoms. Metal-metal bond distances suggest that the long edges of the rectangular cluster should be considered to be single bonds and the short metal-metal bonds to be triple bonds. This view is reinforced by an extended Hueckel calculation. Attempts to add a metal atom to Mo/sub 4/Cl/sub 8/(PR/sub 3/)/sub 4/ to form Mo/sub 5/Cl/sub 10/(PR/sub 3/)/sub 3/ led instead to a compound with the composition Mo/sub 8/Cl/sub 16/(PR/sub 3/)/sub 4/. Solution and reflectance uv-visible spectra and x-ray photoelectron spectra suggest that tetranuclear molybdenum units are present. The facile reaction between Mo/sub 8/Cl/sub 16/(PR/sub 3/)/sub 4/ and PR/sub 3/ imply that the linkage between tetrameric units is weak.

  19. A NOVEL APPROACH TO CATALYTIC DESULFURIZATION OF COAL

    Energy Technology Data Exchange (ETDEWEB)

    John G. Verkade

    1997-08-31

    Remarkably mild conditions have been discovered for quantitative sulfur removal from dibenzothiophene and other organosulfur systems using relatively cheap elemental sodium. The project objectives are: (1) Optimize the coal desulfurization reaction with respect to time, temperature, coal type and the R groups (including R = H), and also on extraction, impregnation and sonication conditions; (2) Optimize the conditions for the HDS reaction (which allows the PR{sub 3} to function as an HDS catalyst for coal) with respect to R group, temperature, pressure, H{sub 2} gas flow rate and inert solvent presence; (3) Determine the product(s) and the pathway of the novel redox reaction that appears to quantitatively remove sulfur from dibenzothiophene (DBT) when R = Bu when FeCl{sub 3} is used as a catalyst; (4) Impregnate sulfur-laden coals with Fe{sup 3+} to ascertain if the PR{sub 3} desulfurization rate increases; (5) Determine the nature of the presently unextractable phosphorus compounds formed in solid coals by PR{sub 3}; (6) Explore the efficacy of PR{sub 3}/Fe{sup 3+} in removing sulfur from petroleum feedstocks, heavy ends (whether solid or liquid), coal tar and discarded tire rubber; (7) Explore the possibility of using water-soluble PR{sub 3} compounds and Fe{sup 3+} to remove sulfur from petroleum feedstocks and heavy ends in order to remove the SPR{sub 3} (and Fe{sup 3+} catalyst) by water extraction (for subsequent HDS of the SPR{sub 3}); and (8) Explore the possibility of using solid-supported PR{sub 3} compounds (plus Fe{sup 3+} catalyst) to remove sulfur from petroleum feedstocks and heavy ends in order to keep the oil and the SPR{sub 3} (formed in the reaction) in easily separable phases.

  20. Study of the influence of the temperature in the magnetic properties and in microstructure in the permanent magnets Pr-Fe-B-Nb-Co based obtained by hydrogen; Estudo da influencia da temperatura nas propriedades magneticas e na microestrutura nos imas permanentes a base de Pr-Fe-B-Nb-Co obtidos com hidrogenio

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Suelanny Carvalho da

    2007-07-01

    Fine magnetic powders were produced using the hydrogenation disproportionation desorption and recombination (HDDR) process. The first stage in this work involved an investigation of the effect of the Co content and range of desorption/ recombination temperatures between 800 and 900 deg C with the purpose of optimizing the HDDR treatment for Pr{sub 14}Fe{sub 80}B{sub 6} and Pr{sub 14}Fe{sub bal}Co{sub x}B{sub 6}Nb{sub 0,1} (x= 0, 4, 8, 10, 12, 16) alloys. The cast alloys were annealed at 1100 deg C for 20 hours for homogenization. The processing temperature (desorption/ recombination) affected the microstructure and magnetic properties of the bonded magnets. The alloy with low cobalt content (4 at.%) required the highest reaction temperature (880 deg C) to yield anisotropic bonded magnets. The optimum temperature for alloys with 8 at.% Co and 10 at.% Co were 840 deg C and 820 deg C, respectively. Alloys with high cobalt content (12 at.% and 16 at.%) were processed at 840 deg C. The optimum desorption temperature for achieving high anisotropy for Pr{sub 14}Fe{sub 80}B{sub 6} and Pr{sub 14}Fe{sub 79,9}B{sub 6}Nb{sub 0,1} was 820 deg C. The best remanence (862 mT) was achieved with the Pr{sub 14}Fe{sub 67,9}B{sub 6}Co{sub 12}Nb{sub 0,1} magnet, processed at 840 deg C. Each alloy required an optimum reaction temperature and exhibited a particular microstructure according to the composition. The second stage of the work involved the characterization, for each temperature, of the Pr{sub 14}Fe{sub 80}B{sub 6} HDDR powder processed using X-ray diffraction analysis. The samples of the HDDR material were studied by synchrotron radiation powder diffraction using the Rietveld method for cell refinement, phase quantification and crystallite sizes determination. Scanning electron microscopy has also been employed to reveal the morphology of the HDDR powder. (author)

  1. Post annealing investigations of thin praseodymia films on Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Gevers, Sebastian; Bruns, Daniel; Weisemoeller, Thomas; Deiter, Carsten; Wollschlaeger, Joachim [Fachbereich Physik, Universitaet Osnabrueck (Germany)

    2008-07-01

    Due to its large oxygen capacity and oxygen mobility praseodymia is interesting for applications in modern heterogenous catalysis. For instance the selectivity of praseodymia for carbon compounds is advantageous in olefiant gas synthesis. The investigation of annealing processes leads to a better understanding of the oxygen transport in the praseodymia films. In this context thin PrO{sub 2} films were annealed at temperatures from 300 C up to 600 C under UHV conditions before they were analysed with spot analysis profile low electron energy diffraction (SPALEED). The diffraction pattern indicates a phase transition to Pr{sub 2}O{sub 3} at the surface. Furthermore X-ray diffraction experiments (XRD) show a partial subsurface phase transition from PrO{sub 2} into various oxidation states including Pr{sub 2}O{sub 3}.

  2. Excitonic transition in (Pr,Ca)CoO{sub 3} family

    Energy Technology Data Exchange (ETDEWEB)

    Kunes, Jan; Augustinsky, Pavel [Insitute of Physics, AS CR, Prague (Czech Republic)

    2016-07-01

    The members of (Pr{sub 1-y}Y{sub y}){sub 1-x}Ca{sub x}CoO{sub 3} family exhibit a continuous phase transition accompanied by disappearance of the fluctuating moment of Co and increase of resistivity by several decades. Most intriguing feature of the low temperature phase is breaking of the time reversal symmetry without presence of ordered atomic moments. We will argue that the experimental observations are explained by condensation of atomic size excitons, which gives rise to ordered magnetic multipoles. We will present model calculations performed with dynamical-mean field theory, which demonstrate general features of the excitonic condensation. In addition, we will present results of material specific LDA+U calculations which uncover the excitonic order in Pr{sub 0.5}YCa{sub 0.5}CoO{sub 3} and explain its low temperature behavior.

  3. High-field magnetisation measurements on R sub 2 Fe sub 14 B single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Verhoef, R.; Franse, J.J.M.; Menovsky, A.A.; Radwanski, R.J. (Amsterdam Univ. (NL). Natuurkundig Lab.); Song-quan, J.; Fu-ming, Y. (Academia Sinica, Beijing (CN). Inst. of Physics); Li, H.S.; Gavigan, J.P. (Trinity Coll. Dublin (IE). Dept. of Pure and Applied Physics)

    1988-12-01

    High-field magnetisation measurements on single crystalline samples of Pr{sub 2}Fe{sub 14}B, Nd{sub 2}Fe{sub 14}B and Dy{sub 2}Fe{sub 14}B are presented and discussed within a two-sublattice model. Special attention is given to the high-field part of the curves (B{sub o} > 20 T).

  4. Magnetic properties of (Pr, Gd) sub 2 Fe sub 14 B compounds

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Zhi-dong; Sun, X.K.; Chuang, Y.C. (Academia Sinica, Wenhua (CN). Inst. of Metal Research); Boer, F.R. de; Radwanski, R.J. (Amsterdam Univ. (NL). Natuurkundig Lab.)

    1988-12-01

    The magnetization of magnetically-aligned (Pr{sub 1-x}Gd{sub x}){sub 2}Fe{sub 14}B samples with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 has been measured at 4.2 K in fields up to 35 T and the anisotropy constants have been derived. The dependence of the first-order magnetization process (FOMP) upon Gd substitution has been determined.

  5. Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating

    Directory of Open Access Journals (Sweden)

    Wan Rafizah Wan Abdullah

    2012-04-01

    Full Text Available High demands on low-voltage electronics have increased the need for zinc oxide (ZnO varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr>6O11 based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr>6O11 addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr>6O11 from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr>6O11 content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary.

  6. Electrochemical characterization of praseodymia doped zircon. Catalytic effect on the electrochemical reduction of molecular oxygen in polar organic solvents

    Energy Technology Data Exchange (ETDEWEB)

    Domenech, Antonio, E-mail: antonio.domenech@uv.es [Departament de Quimica Analitica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain); Montoya, Noemi; Alarcon, Javier [Departament de Quimica Inorganica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain)

    2011-08-01

    Highlights: > Electrochemical characterization of Pr centers in praseodymia-doped zircon. > Study of the catalytic effect on the reduction of peroxide radical anion in nonaqueous solvents. > Assessment of non-uniform distribution of Pr centers in the zircon grains. - Abstract: The voltammetry of microparticles and scanning electrochemical microscopy methodologies are applied to characterize praseodymium centers in praseodymia-doped zircon (Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4}; y + z = x; 0.02 < x < 0.10) specimens prepared via sol-gel synthetic routes. In contact with aqueous electrolytes, two overlapping Pr-centered cathodic processes, attributable to the Pr (IV) to Pr (III) reduction of Pr centers in different sites are obtained. In water-containing, air-saturated acetone and DMSO solutions as solvent, Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} materials produce a significant catalytic effect on the electrochemical reduction of peroxide radical anion electrochemically generated. These electrochemical features denote that most of the Pr centers are originally in its 4+ oxidation state in the parent Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} specimens. The variation of the catalytic performance of such specimens with potential scan rate, water concentration and Pr loading suggests that Pr is not uniformly distributed within the zircon grains, being concentrated in the outer region of such grains.

  7. Promotion effect of cobalt-based catalyst with rare earth for the ethanol steam reforming

    Energy Technology Data Exchange (ETDEWEB)

    Chiou, Josh Y. Z.; Chen, Ya-Ping; Yu, Shen-Wei; Wang, Chen-Bin [Department of Chemical and Materials Engineering, Chung Cheng Institute of Technology, National Defense University, Tahsi, Taoyuan 33509, Taiwan (China)

    2013-12-16

    Catalytic performance of ethanol steam reforming (ESR) was investigated on praseodymium (Pr) modified ceria-supported cobalt oxide catalyst. The ceria-supported cobalt oxide (Ce-Co) catalyst was prepared by co-precipitation-oxidation (CPO) method, and the doped Pr (5 and 10 wt% loading) catalysts (Pr{sub 5}−Ce−Co and Pr{sub 10}−Ce−Co) were prepared by incipient wetness impregnation method. The reduction pretreatment under 250 and 400 °C (H250 and H400) was also studied. All samples were characterized by XRD, TPR and TEM. Catalytic performance of ESR was tested from 250 to 500 °C in a fixed-bed reactor. The doping of Pr into the ceria lattice has significantly promoted the activity and reduced the coke formation. The products distribution also can be influenced by the different reduction pretreatment. The Pr{sub 10}−Ce−Co−H400 sample is a preferential ESR catalyst, where the hydrogen distribution approaches 73% at 475 °C with less amounts (< 2%) of CO and CH{sub 4}.

  8. Chemical bonding of hydrogen molecules to transition metal complexes

    Energy Technology Data Exchange (ETDEWEB)

    Kubas, G.J.

    1990-01-01

    The complex W(CO){sub 3}(PR{sub 3}){sub 2}(H{sub 2}) (CO = carbonyl; PR{sub 3} = organophosphine) was prepared and was found to be a stable crystalline solid under ambient conditions from which the hydrogen can be reversibly removed in vacuum or under an inert atmosphere. The weakly bonded H{sub 2} exchanges easily with D{sub 2}. This complex represents the first stable compound containing intermolecular interaction of a sigma-bond (H-H) with a metal. The primary interaction is reported to be donation of electron density from the H{sub 2} bonding electron pair to a vacant metal d-orbital. A series of complexes of molybdenum of the type Mo(CO)(H{sub 2})(R{sub 2}PCH{sub 2}CH{sub 2}PR{sub 2}){sub 2} were prepared by varying the organophosphine substitutent to demonstrate that it is possible to bond either dihydrogen or dihydride by adjusting the electron-donating properties of the co-ligands. Results of infrared and NMR spectroscopic studies are reported. 20 refs., 5 fig.

  9. Training effects induced by cycling of magnetic field in ferromagnetic rich phase-separated nanocomposite manganites

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kalipada, E-mail: kalipada.das@saha.ac.in; Das, I.

    2015-12-01

    We have carried out an experimental investigation of magneto-transport and magnetic properties of charge-ordered Pr{sub 0.67}Ca{sub 0.33}MnO{sub 3} (PCMO) and ferromagnetic La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (LSMO) nanoparticles along with a nanocomposite consisting of those two types of nanoparticles. From the magneto-transport measurements, clear irreversibility is observed in the field dependence of resistance due to magnetic field cycling in the case of PCMO nanoparticles. The value of resistance increases during such a field cycling. However such an irreversibility is absent in the case of LSMO nanoparticles as well as nanocomposites. On the other hand, the magnetic measurements indicate the gradual growth of antiferromagnetic phases in all samples leading to a decrease in magnetization. These inconsistencies between magneto-transport and magnetic behaviors are attributed to the magnetic training effects. - Highlights: • The resistance value in Pr{sub 0.67}Ca{sub 0.33}MnO{sub 3} nanoparticles is found to increase owing to the magnetic field cycling. • No anomaly in resistance was found in Pr{sub 0.67}Ca{sub 0.33}MnO{sub 3}–La{sub 0.67}Sr{sub 0.33}MnO{sub 3} nanocomposite. • Magnetic measurements indicate the training effect in nanostructure compounds.

  10. Interconversion of η3-H2SiRR' σ-complexes and 16-electron silylene complexes via reversible H-H or C-H elimination.

    Science.gov (United States)

    Lipke, Mark C; Neumeyer, Felix; Tilley, T Don

    2014-04-23

    Solid samples of η(3)-silane complexes [PhBP(Ph)3]RuH(η(3)-H2SiRR') (R,R' = Et2, 1a; PhMe, 1b; Ph2, 1c, MeMes, 1d) decompose when exposed to dynamic vacuum. Gas-phase H2/D2 exchange between isolated, solid samples of 1c-d3 and 1c indicate that a reversible elimination of H2 is the first step in the irreversible decomposition. An efficient solution-phase trap for hydrogen, the 16-electron ruthenium benzyl complex [PhBP(Ph)3]Ru[η(3)-CH2(3,5-Me2C6H3)] (3) reacts quantitatively with H2 in benzene via elimination of mesitylene to form the η(5)-cyclohexadienyl complex [PhBP(Ph)3]Ru(η(5)-C6H7) (4). This H2 trapping reaction was utilized to drive forward and quantify the elimination of H2 from 1b,d in solution, which resulted in the decomposition of 1b,d to form 4 and several organosilicon products that could not be identified. Reaction of {[PhBP(Ph)3]Ru(μ-Cl)}2 (2) with (THF)2Li(SiHMes2) forms a new η(3)-H2Si species [PhBP(Ph)3]Ru[CH2(2-(η(3)-H2SiMes)-3,5-Me2C6H2)] (5) which reacts with H2 to form the η(3)-H2SiMes2 complex [PhBP(Ph)3]RuH(η(3)-H2SiMes2) (1e). Complex 1e was identified by NMR spectroscopy prior to its decomposition by elimination of Mes2SiH2 to form 4. DFT calculations indicate that an isomer of 5, the 16-electron silylene complex [PhBP(Ph)3]Ru(μ-H)(═SiMes2), is only 2 kcal/mol higher in energy than 5. Treatment of 5 with XylNC (Xyl = 2,6-dimethylphenyl) resulted in trapping of [PhBP(Ph)3]Ru(μ-H)(═SiMes2) to form the 18-electron silylene complex [PhBP(Ph)3]Ru(CNXyl)(μ-H)(═SiMes2) (6). A closely related germylene complex [PhBP(Ph)3]Ru[CN(2,6-diphenyl-4-MeC6H2)](H)(═GeH(t)Bu) (8) was prepared from reaction of (t)BuGeH3 with the benzyl complex [PhBP(Ph)3]Ru[CN(2,6-diphenyl-4-MeC6H2)][η(1)-CH2(3,5-Me2C6H3)] (7). Single crystal XRD analysis indicated that unlike for 6, the hydride ligand in 8 is a terminal hydride that does not engage in 3c-2e Ru-H → Ge bonding. Complex 1b is an effective precatalyst for the catalytic Ge-H dehydrocoupling

  11. Direct imaging of hexaamine-ruthenium(III) in domain boundaries in monolayers of single-stranded DNA

    DEFF Research Database (Denmark)

    Grubb, Mikala; Wackerbarth, Hainer; Wengel, J.

    2007-01-01

    We describe adsorption and identification of the binding sites of [Ru(NH3)(6)](3+) (RuHex) molecules in a closely packed monolayer of a 13-base ss-DNA on Au(111) electrodes by electrochemical in situ scanning tunneling microscopy (STM), cyclic voltammetry and interfacial capacitance data. In situ...

  12. Study of the influence of zirconium and gallium on the magnetic properties and microstructures of praseodymium-based permanent magnets; Estudo da influencia do zirconio e galio nas propriedades magneticas e na microestrutura dos imas permanentes a base de praseodimio

    Energy Technology Data Exchange (ETDEWEB)

    Fusco, Alexandre Giardini

    2006-07-01

    In this work was studied the influence of the addition of 0.5 at. % of zirconium and gallium on praseodymium-based HD sintered magnets obtained using a mixture of alloys. The alloys used in this study were: Pr{sub 12.6}Fe{sub 68.3}Co{sub 11.6}B{sub 6}Zr{sub 0.5}Ga{sub 1}, Pr{sub 16}Fe{sub 75.5}B{sub 8}Zr{sub 0.5}, Pr{sub 13}Fe{sub 80.5}B{sub 6}Zr{sub 0.5}. The investigation started by measuring the magnetic properties and observing the microstructure of the magnets. After that, the magnets were annealed at 1000 deg C for 2 hours followed by rapid cooling, in a total of 10 hours. This heat treatment was followed by 5 hours at the same temperature up to a total of 35 hours. Changes in the microstructure were compared to the change in the magnetic properties aiming at a proper understanding of the role of each added element in relation to the magnetically hard phase (phase {phi}). It has been shown that gallium and zirconium act as grain refiners of the matrix phase {phi}. Gallium acts in the grain and favoring of the shape stability and improvement of the magnetic properties. For the Pr{sub 14.3}Fe{sub 71.9}Co{sub 5.8}B{sub 7}Zr{sub 0.5}Ga{sub 0.5} sintered magnet the evolution of the magnetic properties after 15 hours heat treatment was: remanence from (1.25{+-}0.02) T to (1.30{+-}0.02) T, intrinsic coercivity from (1.11{+-}0.02) T to (0.87{+-}0.02) T, squareness factor from (0.68{+-}0.02) to (0.82{+-}0.02) and energy product from (285{+-}5) kJ/m{sup 3} to (317{+-}5) kJ/m{sup 3}. Zirconium has two effects on the sintered magnets. Firstly, avoiding random grain growth and enhancing anisotropy. However, by concentrating on the grain boundaries, yield reverse domains and is detrimental to the intrinsic coercivity. For the sintered Pr{sub 14.5}Fe{sub 78}B{sub 7}Zr{sub 0.5} magnet the evolution of the magnetic properties achieved after a heat treatment of 15 hours was: remanence from (1.19{+-}0.02) T to (1.25{+-}0.02) T, coercivity from (0.74{+-}0.02) T to (0

  13. High coercivity in rare-earth lean nanocomposite magnets by grain boundary infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Madugundo, Rajasekhar, E-mail: mraja@udel.edu [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Salazar-Jaramillo, Daniel [BCMaterials, Bizkaia Science and Technology Park, E-48160 Derio (Spain); Manuel Barandiaran, Jose [BCMaterials, Bizkaia Science and Technology Park, E-48160 Derio (Spain); Department of Electricity & Electronics, University of the Basque Country (UPV/EHU), E-48080 Bilbao (Spain); Hadjipanayis, George C., E-mail: hadji@udel.edu [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

    2016-02-15

    A significant enhancement in coercivity was achieved by grain boundary modification through low temperature infiltration of Pr{sub 75}(Cu{sub 0.25}Co{sub 0.75}){sub 25} eutectic alloy in rare-earth lean (Pr/Nd)–Fe–B/α-Fe nanocomposite magnets. The infiltration procedure was carried out on ribbons and hot-deformed magnets at 600–650 °C for different time durations. In Nd{sub 2}Fe{sub 14}B/α-Fe ribbons, the coercivity increased from 5.3 to 23.8 kOe on infiltration for 4 h. The Pr{sub 2}Fe{sub 14}B/α-Fe hot-deformed magnet shows an increase in coercivity from 5.4 to 22 kOe on infiltration for 6 h. The increase in the coercivity comes at the expense of remnant magnetization. X-ray diffraction studies confirm the presence of both the hard Nd{sub 2}Fe{sub 14}B and soft α-Fe phases. A decrease in the soft α-Fe phase content was observed after infiltration. - Highlights: • Enhancement in coercivity was achieved by grain boundary modification. • Coercivity increased from 5.3 to 23.8 kOe in Nd{sub 2}Fe{sub 14}B/α-Fe on infiltration. • Pr{sub 2}Fe{sub 14}B/α-Fe deformed magnet shows an increase in coercivity from 5.4 to 22 kOe. • The increase in the coercivity comes at the expense of remnant magnetization. • A decrease in the soft α-Fe phase content was observed after infiltration.

  14. Phase and structural behaviour of the PrAlO{sub 3}-LaAlO{sub 3} pseudo-binary system

    Energy Technology Data Exchange (ETDEWEB)

    Basyuk, T. [Semiconductor Electronics Department, Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv (Ukraine)], E-mail: tanya.basyuk@gmail.com; Vasylechko, L.; Fadeev, S. [Semiconductor Electronics Department, Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv (Ukraine); Syvorotka, I.I. [SRC ' Carat' , 202 Stryjska St., 79031 Lviv (Ukraine); Trots, D. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt (Germany); Niewa, R. [Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching (Germany)

    2009-10-15

    High-resolution in situ X-ray powder diffraction applying synchrotron radiation has been used to examine the occurring crystal structures and the thermal behaviour of the solid solution Pr{sub 1-x}La{sub x}AlO{sub 3} in a wide temperature range 12-1173 K. At room temperature all studied samples in the whole composition range of the pseudo-binary system PrAlO{sub 3}-LaAlO{sub 3} adopt a rhombohedral perovskite structure. The phases Pr{sub 1-x}La{sub x}AlO{sub 3} with x=0.56 and 0.66 undergo a sequence of three phase transitions I2/m{r_reversible}Imma{r_reversible}R3-bar c{r_reversible}Pm3-bar m. For the sample with x=0.24 a series of four (I4/mcm{r_reversible}I2/m{r_reversible}Imma{r_reversible}R3-bar c{r_reversible}Pm3-bar m) phase transitions has been observed and for x=0.86 two transformations were apparent (I2/m{r_reversible}R3-bar c{r_reversible}Pm3-bar m). Crystal structure parameters for all studied compositions Pr{sub 1-x}La{sub x}AlO{sub 3} have been determined. Based on in situ powder diffraction and DTA/DSC data, the phase diagram of the pseudo-binary system PrAlO{sub 3}-LaAlO{sub 3} has been constructed.

  15. TRANSITING THE SUN. II. THE IMPACT OF STELLAR ACTIVITY ON Lyα TRANSITS

    Energy Technology Data Exchange (ETDEWEB)

    Llama, J.; Shkolnik, E. L., E-mail: joe.llama@lowell.edu [Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States)

    2016-01-20

    High-energy observations of the Sun provide an opportunity to test the limits of our ability to accurately measure the properties of transiting exoplanets in the presence of stellar activity. Here we insert the transit of a hot Jupiter into continuous disk integrated data of the Sun in Lyα from NASA’s Solar Dynamics Observatory/EVE instrument to assess the impact of stellar activity on the measured planet-to-star radius ratio (R{sub p}/R{sub ⋆}). In 75% of our simulated light curves, we measure the correct radius ratio; however, incorrect values can be measured if there is significant short-term variability in the light curve. The maximum measured value of R{sub p}/R{sub ⋆} is 50% larger than the input value, which is much smaller than the large Lyα transit depths that have been reported in the literature, suggesting that for stars with activity levels comparable to the Sun, stellar activity alone cannot account for these deep transits. We ran simulations without a transit and found that stellar activity cannot mimic the Lyα transit of 55 Cancari b, strengthening the conclusion that this planet has a partially transiting exopshere. We were able to compare our simulations to more active stars by artificially increasing the variability in the Solar Lyα light curve. In the higher variability data, the largest value of R{sub p}/R{sub ⋆} we measured is <3× the input value, which again is not large enough to reproduce the Lyα transit depth reported for the more active stars HD 189733 and GJ 436, supporting the interpretation that these planets have extended atmospheres and possible cometary tails.

  16. Effect of chromium concentration on the structural, magnetic and electrical properties of praseodymium-calcium manganite

    Energy Technology Data Exchange (ETDEWEB)

    Bettaibi, A. [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Faculté des Sciences de Gabès cité Erriadh, Université de Gabès, 6079 Gabès (Tunisia); M' nassri, R., E-mail: rafik_mnassri@yahoo.fr [Higher Institute of Applied Sciences and Technology of Kasserine, Kairouan University, B.P. 471, 1200 Kasserine (Tunisia); Laboratoire de Physico-Chimie des Matériaux, Département de Physique, Faculté des Sciences de Monastir, Université de Monastir, 5019 Monastir (Tunisia); Selmi, A. [Laboratory of Physics of Materials, Faculty of Sciences of Sfax, Sfax University, B.P.1171, 3000 Sfax (Tunisia); Rahmouni, H. [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Faculté des Sciences de Gabès cité Erriadh, Université de Gabès, 6079 Gabès (Tunisia); Chniba-Boudjada, N. [Institut NEEL, B.P.166, 38042 Grenoble Cedex 09 (France); Faculté des Sciences de Gabès cité Erriadh, Université de Gabès, 6079 Gabès (Tunisia); and others

    2015-11-25

    The influence of Cr doping on magnetic, magnetocaloric and electrical properties in a polycrystalline sample of Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3} is investigated. Structural studies show that our samples are single phase. The magnetization shows that the Pr{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} ceramics exhibit a paramagnetic–ferromagnetic transition with a large magnetic entropy change. The relative cooling power (RCP) values are comparable to those of other manganite. DC conductance G{sub DC} measurements show that all samples are characterized by a semiconductor behavior. It is found that G{sub DC} decreases by two decades when increasing chromium concentrations. For the parent compound, dc-conductance is characterized by the appearance of a saturation region at a specific temperature (T{sub sat} = 200 K). For the doped compound, T{sub sat} go beyond room temperature. Conduction mechanism is found to be dominated by the small polaron hopping (SPH) process at high temperature and by variable range hopping one (VRH) at low temperature. AC conductance study confirms that the conductivity is governed by hopping process and obeys to the Jonscher universal power law. The exponent ‘n’ variation with temperature is in good agreement with Mott theory. Its variation as a function of chromium content indicates that the material turns from metallic to semi-insulating behavior when chromium composition increases. Impedance analysis proves the presence of electrical relaxation phenomenon in the material and confirms that grain boundaries played a main role in the conduction process. - Highlights: • Pr{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} manganites phases crystallize in an orthorhombic (Pnma) structure. • Pr{sub 0.7}Ca{sub 0.3}Mn{sub 0.95}Cr{sub 0.05}O{sub 3} has the highest relative cooling power. • DC conductivity measurement indicates that samples have a semiconductor character. • Conduction mechanism is well described by hopping

  17. Transient electronic structure of the photoinduced phase of Pr0.7Ca0.3MnO3 probed with soft x-ray pulses

    Energy Technology Data Exchange (ETDEWEB)

    Rini, M.; Zhu, Y.; Wall, S.; Tobey, R. I.; Ehrke, H.; Garl, T.; Freeland, J. W.; Tomioka, Y.; Tokura, Y.; Cavalleri, A.; Schoenlein, R. W.

    2009-04-01

    We use time-resolved x-ray absorption near-edge structure spectroscopy to investigate the electronic dynamics associated with the photoinduced insulator-to-metal phase transition in the colossal magnetoresistive manganite Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3}. Absorption changes at the O K and Mn L edges directly monitor the evolution of the density of unoccupied states in the transient photoinduced phase. We show that the electronic structure of the photoinduced phase is remarkably similar to that of the ferromagnetic metallic phase reached in related manganites upon cooling below the Curie temperature.

  18. Reactivity of Fe and Ru Complexes of Picolyl-Substituted N-Heterocyclic Carbene Ligand: Diverse Coordination Modes and Small Molecule Binding.

    Science.gov (United States)

    Liang, Qiuming; Song, Datong

    2017-10-02

    Complexes [MClCp*(HL)] (1[Fe]/1[Ru]) (where HL = 1-mesityl-3-(pyridin-2-ylmethyl)imidazol-2-ylidene) were synthesized from the reaction of in situ generated HL ligand and [FeClCp*(TMEDA)] (where TMEDA is N,N,N',N'-tetramethylethylenediamine) or [RuClCp*]4, respectively. The deprotonation of 1[Fe]/1[Ru] with 1 equiv of LiHMDS led to cyclometalation through the o-Me of the mesityl group, forming [MCp*(L-κC,κC',κN)] 2[Fe]/2[Ru]. The coordinatively unsaturated compounds [MCp*(HL)]BPh4 3[Fe]/3[Ru] were prepared from 1[Fe]/1[Ru] and halide scavenger NaBPh4. Complex 3[Ru] showed agostic interactions between the o-Me group of the mesityl moiety and the metal center in solution and the solid state. When the vacant coordination site of 3[Fe]/3[Ru] is occupied by CO, the resulting [MCp*(CO)(HL)]BPh4 4[Fe]/4[Ru] can be deprotonated with 1 equiv of KHMDS at the pyridylic position to afford complexes [MCp*L'(CO)] 5[Fe]/5[Ru], where the L'(-) ligand chelates to the metal center through the nitrogen donor atom of the dearomatized pyridine ring and the carbene carbon. Complex 2[Fe] reacted rapidly with CO to afford the simple ligand substitution product [FeCp*(L-κC,κC')(CO)] 6[Fe], where the L(-) acts as a bidentate chelating ligand through the carbene carbon and benzylic carbon. Under the same condition, the reaction of 2[Ru] with CO forms [RuCp*L″(CO)] 7[Ru], where the L″(-) ligand (an isomer of L(-) and L'(-)) chelates to the metal center through the carbene carbon and a pyridyl carbon. Complexes 3[Fe]/3[Ru] reversibly bind dinitrogen to form [MCp*(HL)(N2)]BPh4 8[Fe]/8[Ru]. 3[Ru] reversibly binds dihydrogen to give [MCp*(H2)(HL)]BPh4 9[Ru], while no reaction was observed between 3[Fe] and H2. The reaction of 3[Ru] with dioxygen led to the isolation of a stable side-on O2 complex [RuCp*(HL)(O2)]BPh4 10[Ru], while the reaction of 3[Fe] with dioxygen led to an intractable mixture of products.

  19. Rare earth-ruthenium-magnesium intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Sebastian; Kersting, Marcel; Heletta, Lukas; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2017-07-01

    Eight new intermetallic rare earth-ruthenium-magnesium compounds have been synthesized from the elements in sealed niobium ampoules using different annealing sequences in muffle furnaces. The compounds have been characterized by powder and single crystal X-ray diffraction. Sm{sub 9.2}Ru{sub 6}Mg{sub 17.8} (a=939.6(2), c=1779(1) pm), Gd{sub 11}Ru{sub 6}Mg{sub 16} (a=951.9(2), c=1756.8(8) pm), and Tb{sub 10.5}Ru{sub 6}Mg{sub 16.5} (a=942.5(1), c=1758.3(4) pm) crystallize with the tetragonal Nd{sub 9.34}Ru{sub 6}Mg{sub 17.66} type structure, space group I4/mmm. This structure exhibits a complex condensation pattern of square-prisms and square-antiprisms around the magnesium and ruthenium atoms, respectively. Y{sub 2}RuMg{sub 2} (a=344.0(1), c=2019(1) pm) and Tb{sub 2}RuMg{sub 2} (a=341.43(6), c=2054.2(7) pm) adopt the Er{sub 2}RuMg{sub 2} structure and Tm{sub 3}Ru{sub 2}Mg (a=337.72(9), c=1129.8(4) pm) is isotypic with Sc{sub 3}Ru{sub 2}Mg. Tm{sub 3}Ru{sub 2}Mg{sub 2} (a=337.35(9), c=2671(1) pm) and Lu{sub 3}Ru{sub 2}Mg{sub 2} (a=335.83(5), c=2652.2(5) pm) are the first ternary ordered variants of the Ti{sub 3}Cu{sub 4} type, space group I4/mmm. These five compounds belong to a large family of intermetallics which are completely ordered superstructures of the bcc subcell. The group-subgroup scheme for Lu{sub 3}Ru{sub 2}Mg{sub 2} is presented. The common structural motif of all three structure types are ruthenium-centered rare earth cubes reminicent of the CsCl type. Magnetic susceptibility measurements of Y{sub 2}RuMg{sub 2} and Lu{sub 3}Ru{sub 2}Mg{sub 2} samples revealed Pauli paramagnetism of the conduction electrons.

  20. Magnetism and the absence of superconductivity in the praseodymium–silicon system doped with carbon and boron

    Energy Technology Data Exchange (ETDEWEB)

    Venta, J. de la, E-mail: jdelaventa@physics.ucsd.edu [Department of Physics and Center for Advanced Nanoscience, University of California, La Jolla, San Diego, CA 92093 (United States); Basaran, Ali C. [Department of Physics and Center for Advanced Nanoscience, University of California, La Jolla, San Diego, CA 92093 (United States); Materials Science and Engineering, University of California, La Jolla, San Diego, CA 92093 (United States); Grant, T. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Gallardo-Amores, J.M. [Departamento de Quimica Inorganica I, Universidad Complutense, E-28040 Madrid (Spain); Ramirez, J.G. [Department of Physics and Center for Advanced Nanoscience, University of California, La Jolla, San Diego, CA 92093 (United States); Alario-Franco, M.A. [Departamento de Quimica Inorganica I, Universidad Complutense, E-28040 Madrid (Spain); Fisk, Z. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Schuller, Ivan K. [Department of Physics and Center for Advanced Nanoscience, University of California, La Jolla, San Diego, CA 92093 (United States)

    2013-08-15

    We searched for new structural, magnetic and superconductivity phases in the Pr–Si system using high-pressure high-temperature and arc melting syntheses. Both high and low Si concentration areas of the phase diagram were explored. Although a similar approach in the La–Si system produced new stable superconducting phases, in the Pr–Si system we did not find any new superconductors. At low Si concentrations, the arc-melted samples were doped with C or B. It was found that addition of C gave rise to multiple previously unknown ferromagnetic phases. Furthermore, X-ray refinement of the undoped samples confirmed the existence of the so far elusive Pr{sub 3}Si{sub 2} phase. - Highlights: • Study of the Pr–Si system using HP–HT or doping with C and B. • New magnetic phases in the Pr–Si system doped with C. • Confirmation of the existence of the Pr{sub 3}Si{sub 2} phase.

  1. Anomalous thermal expansion in rare-earth gallium perovskites: a comprehensive powder diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Senyshyn, A; Trots, D M; Engel, J M; Ehrenberg, H; Fuess, H [Institute for Materials Science, Darmstadt University of Technology, D-64287 Darmstadt (Germany); Vasylechko, L [Lviv Polytechnic National University, 12 Bandera Street, 79013 Lviv (Ukraine); Hansen, T [Institut Max von Laue-Paul Langevin, 38042 Grenoble Cedex 9 (France); Berkowski, M [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland)

    2009-04-08

    Crystal structures of rare-earth gallium perovskites LaGaO{sub 3}, PrGaO{sub 3}, NdGaO{sub 3} and Pr{sub 1-x}Nd{sub x}GaO{sub 3} (x = 0.25, 0.50, 0.75) solid solutions were investigated in the temperature range 12-300 K by high-resolution powder diffraction using synchrotron or neutron radiation. The previously reported negative thermal expansion in the b direction of the PrGaO{sub 3} lattice has been found to be persistent in Pr{sub 1-x}Nd{sub x}GaO{sub 3} solid solutions and its magnitude has been revealed as proportional to the amount of praseodymium. Evaluation of the obtained temperature evolution of cell dimensions indicated a weak anomalous behaviour of the b lattice parameter in NdGaO{sub 3}, and its origin is supposed to be the same as in PrGaO{sub 3}, i.e. a coupling of the crystal electric field levels with phonon excitations of about 23-25 meV energy. The performed bond length analysis revealed an anomalous behaviour of both LnO{sub 12} (Ln-rare-earth) and GaO{sub 6} coordination polyhedra, which can be a structural manifestation of anomalous thermal expansion in the considered compounds.

  2. Valence determination as a function of doping in $PrBa_{2} Cu_{3} O_{7}$

    CERN Document Server

    Staub, U; Wasserman, S R; Conner, A G O; Kramer, M J; Patterson, B D; Shi, M; Knapp, M P

    2000-01-01

    We present results of X-ray absorption near edge spectra (XANES), neutron powder diffraction, and resonant X-ray diffraction on samples of PrBa/sub 2/Cu/sub 3/O/sub 7- delta / and Pr/sub 1-x/Ca/sub x/Ba /sub 2/Cu/sub 3/O/sub 7/. The data are obtained as a function of the doping levels of oxygen and Ca. There are significant changes in the Pr L/sub 3/ XANES spectra with changes in oxygen or Ca concentrations, indicating that the Pr electronic properties are affected by doping. The resonant X-ray scattering experiments show that the changes observed occur on Pr ions incorporated in the PrBa /sub 2/Cu/sub 3/O/sub 7- delta / structure, and are not the result of changes to a Pr-containing impurity phase. A quantitative model, based on literature precedent, is used to extract Pr valences from the data, although the XANES cannot distinguish between models involving charge transfer and those involving hybridization. The results are compared with data obtained from Pb/sub 2/Sr/sub 2/Pr/sub 1-x/Ca/sub x/Cu/sub 3/O/sub ...

  3. X-ray absorption measurements of charge-ordered La{sub 0.5}Sr{sub 1.5}MnO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Saitoh, T.; Villella, P.M.; Dessau, D.S. [Univ. of Colorado, Boulder, CO (United States)] [and others

    1997-04-01

    Perovskite and {open_quotes}layered perovskite{close_quotes}-type manganese oxides show a variety of electronic and magnetic properties such as the colossal magnetoresistance (CMR) or the charge ordering. Among them, La{sub 0.5}Sr{sub 1.5}MnO{sub 4} (K{sub 2}NiF{sub 4} structure) which has 0.5 holes per Mn site (d{sup 3.5}) shows the charge-order transition at {approximately}220 K below which Mn{sup 3+} and Mn{sup 4+} sites are believed to order in the CE-type. Although the charge ordering phenomenon has also been observed in the perovskite manganites Pr{sub 0.5}Sr{sub 1.5}MnO{sub 3} or Pr{sub 0.5}Ca{sub 1.5}MnO{sub 3}, the present system has another advantage that it has a layered structure. This enables the authors to address the issue of the orbital symmetry which should be directly related to the charge ordering. In this report, they present the results of x-ray absorption spectroscopy (XAS) on La{sub 0.5}Sr{sub 1.5}MnO{sub 4}, for two polarization angles and two (above and below the transition temperature T{sub CO}) temperatures.

  4. Isolation and Molecular Structure of Hexacyanoruthenate(III)

    DEFF Research Database (Denmark)

    Bendix, J; Steenberg, P; Søtofte, Inger

    2003-01-01

    The [Ru(CN)(6)](3-) ion is synthesized in aqueous solution and isolated as [Ph(4)AS](3)[Ru(CN)(6)].2H(2)O (1). Compound 1 crystallizes as orange needles in the monoclinic space group P2(1)/n with cell parameters a = 11.346(2) Angstrom, b = 23.107(5) Angstrom, c = 25.015(5) Angstrom, beta = 99...

  5. Minor alterations in thyroid-function tests associated with diabetes mellitus and obesity in outpatients without known thyroid illness.

    Science.gov (United States)

    Proces, S; Delgrange, E; Vander Borght, T V; Jamart, J; Donckier, J E

    2001-01-01

    Thyroid function tests might be affected by diabetes and obesity. To evaluate the influence of these parameters in routine conditions, 72 diabetic and 53 non-diabetic outpatients without known thyroid diseases or severe chronic illness were recruited over a 7-month period. For each patient, dosages of thyrotropin (TSH), total and free thyroxine (TT4 and FT4, respectively), total and free triiodothyronine (TT3 and FT3) and T3 resin uptake (T3RU) were performed by radioimmunoassays. The simultaneous influence of various parameters known to affect thyroid-function tests was evaluated by multivariate linear regression. The studied variables included gender, age, glucosteroids, estrogens, tobacco habits, iodine contacts, body mass index (BMI) and diabetes mellitus. Tobacco habits and iodine contacts did not influence any tests. As expected, estrogens induced an increase in TT4 and TT3 values (p < 0.001 and 0.020, respectively) associated with a decrease in T3RU (p < 0.001). Consequently, females had lower T3RU than males (p < 0.0001). Corticotherapy was associated with decreased TSH values (p = 0.022). TT3 and FT3 decreased with age (p < 0.001), whereas T3RU and FT4 increased (p = 0.020 and 0.004, respectively). In contrast to an increase in TSH (p = 0.006), TT4 and FT4 decreased at higher BMI levels (p = 0.018 and 0.004, respectively), which is consistent with subclinical hypothyroidism. In diabetic patients, TSH was lower than in nondiabetic subjects (p = 0.039). Thus, the present study indicates that besides known parameters such as age and drugs, thyroid-function tests can also be altered by diabetes mellitus and obesity.

  6. Praseodymia on non-passivated and passivated Si(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Gevers, Sebastian

    2010-12-15

    In the presented thesis thin praseodymia films on non-passivated and passivated Si(111) substrates were investigated. The first part deals with PDA of praseodymia films with fluorite structure under UHV conditions in the temperature region from RT to 600 C. It is shown that the untreated films, which are oxidized in 1 atm oxygen to obtain fluorite structure, do not exhibit pure PrO{sub 2} stoichiometry as it was assumed before. Instead, they decompose into two laterally coexisting species exhibiting a PrO{sub 2} and a Pr{sub 6}O{sub 11}. oxide phase, respectively. These species are laterally pinned to the lattice parameter of bulk Pr{sub 6}O{sub 11}. Homogeneous oxide films with Pr{sub 6}O{sub 11} phase can be observed after annealing at 100 C and 150 C. If higher annealing temperatures are applied, the film decomposes again into two coexisting species. Finally, after annealing at 300 C, a mixed crystalline film with both Pr{sub 2}O{sub 3} and Pr{sub 2}O{sub 3+{delta}} oxide phases is formed. Again the lateral strain increases due to the tendency of praseodymia phases to increase their lattice parameters during oxygen loss combined with the lateral pinning. This is accompanied by a decrease of crystallite sizes. The increase of the amorphous Pr-silicate interface between Si substrate and oxide at the expense of the crystalline oxide can be observed after annealing at higher temperatures. Furthermore, an increased mosaic spread of the crystallites occurs, which reduces the lateral strain caused by the oxygen loss. Nevertheless, the crystalline structure is stable against further annealing up to temperatures of 600 C. The results obtained from praseodymia films annealed in 1 atm nitrogen show that these films are good candidates to form homogeneous oxide films with pure cub-Pr{sub 2}O{sub 3} structure by subsequent annealing in UHV. Here, a single oxide species is already observed after annealing at 300 C by SPA-LEED measurements. Investigations on oxygen plasma

  7. Metal complexes with 1,2-dithione ligands. 3. Dithiooxamides as strong donors or acceptors in molybdenum carbonyl complexes

    Energy Technology Data Exchange (ETDEWEB)

    Dieck, H.T.; Form, M. (Hamburg Univ. (Germany, F.R.))

    1984-08-01

    Starting from substitution labile molybdenum carbonyl complexes L/sub 2/Mo(CO)/sub 4/, L/sub 3/Mo(CO)/sub 3/ and L/sub 2/L'/sub 2/Mo(CO)/sub 2/ several new complex types with the C-C-twisted tetraalkyldithiooxamides (R/sub 4/dto) and the planar N,N'-dialkyldithiooxamide (R/sub 2/H/sub 2/dto) such as (R/sub 4/dto)Mo(CO)/sub 4/, (R/sub 2/H/sub 2/dto)Mo(CO)/sub 4/, (R/sub 2/R'/sub 2/dto)Mo(CO)/sub 3/(P(C/sub 6/H/sub 5/)/sub 3/), (R/sub 2/R'/sub 2/dto)Mo(CO)/sub 2/(PR/sub 3/)/sub 2/ are described and compared with complexes of a cyclic dithiooxamide and analogous complexes with thioamides R/sub 2/NC(S)R'. In Mo(CO)/sub 4/ complexes, dithiooxamides display a rather strong donor character and are thus similar to simple thioamides, but the blue colour of the R/sub 2/H/sub 2/dto complexes indicates already low-lying acceptor levels. When passing from the Mo(CO)/sub 4/ complexes via Mo(CO)/sub 3/(PR/sub 3/) complexes to the very electron rich Mo(CO)/sub 2/(PR/sub 3/)/sub 2/ complexes, the IR and electronic spectra indicate an unexpected and drastic change in ligand character. Dto ligands in the latter complex type turn out to be very strong acceptors, independent of the degree of N-alkylation. A conformational change, with twisted R/sub 2/N-C bonds and a planar S-C-C-S skeleton (as in the dithiolene complexes), can account for all the peculiarities of the (dto)-dicarbonylbis(phosphine) complexes as compared to the 'normal' thioamide complexes. Dithiooxamides can thus control the oxidation state of metals by a remote conformational change and possibly act as an electron reservoir in chemical reactions at the metal center.

  8. Ballistic Electron Emission Microscopy (BEEM) of Au/Pr{sub 2}O{sub 3}/Si structures; Ballistische Elektronen Emissions Mikroskopie (BEEM) an Au/Si und Au/Pr{sub 2}O{sub 3}/Si-Strukturen

    Energy Technology Data Exchange (ETDEWEB)

    Mauch, I.

    2007-05-15

    This thesis describes Ballistic Electron Emission Microscopy (BEEM) measurements of Au/Si(111) and Au/Pr{sub 2}O{sub 3}/Si(111) structures. This technique is based on Scanning Tunnelling Microscopy (STM). It measures the ballistic transport of hot electrons through parts of the sample and across an interface, which provides a potential barrier. One part of this work was to modify the BEEM apparatus and to implement a lock in method, which modulates the tunnel current with a small frequency. In this way it is possible to study samples with very low resistance (as low as 30 k{omega}), which widely enlarges the number of samples which are appropriate for BEEM measurement at room temperature. Both types of samples studied in this thesis had low resistance and were therefore studied using the lock in method. For the classical BEEM system Au/Si(111), we observed a pronounced dependence of the sample resistance of Au/Si(111)-7 x 7 on the preparation temperature. We developed a model for the resistance of thermal prepared Au/Si(111)-7 x 7 samples. The model identifies that the low resistance is due to the surface conductivity of the reconstructed silicon surface. If the surface is prepared at a lower temperature (but still high enough that the surface is cleaned and the silicon dioxide desorbed) rough areas remain on the surface, which reduce the surface conductivity. For BEEM measurements flat areas of the sample surface are selected. The low temperature prepared samples we were able to obtain BEEM spectra as well as images at room temperature using the lock in method. The sesquioxide of praseodymium (Pr{sub 2}O{sub 3}) is currently discussed as a possible candidate for a gate oxide in semiconductor devices, since it has some of the required material properties such as a high dielectric constant, low leakage current and epitaxial growth on Si(100). We have for the first time performed BEEM measurement of praseodymium oxide. Despite a low resistance of the structures we

  9. Absence of a polar phase in perovskite chromite RCrO{sub 3} (R=La and Pr)

    Energy Technology Data Exchange (ETDEWEB)

    Yoshii, Kenji, E-mail: yoshiike@spring8.or.jp [Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148 (Japan); Ikeda, Naoshi [Okayama University, Okayama 700-8530 (Japan); Shimojo, Yutaka; Ishii, Yoshinobu [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan)

    2017-04-01

    Magnetic and dielectric properties have been studied for LaCrO{sub 3}, PrCrO{sub 3}, and their solid solution La{sub 0.5}Pr{sub 0.5}CrO{sub 3}, which belong to a family of the ferroelectric orthochromite series RCrO{sub 3} (R: rare earths). The magnetic measurements confirm that the materials show canted antiferromagnetic ordering at 240–288 K. Neutron diffraction patterns could be fitted with the centrosymmetric Pnma, which is different from the non-centrosymmetric structure proposed for the ferroelectric phase of NdCrO{sub 3}. The large dielectric constants are likely due to the hopping of charge carriers as proposed previously for other chromites. - Highlights: • Magnetic and dielectric properties of the three perovskite chromites. • Neutron diffraction patterns fitted with centrosymmetric Pnma. • Large dielectric constants likely due to the hopping of charge carriers.

  10. Evolution of structural and magnetic properties due to nanocrystallization of mechanically milled amorphous Pr-Co-B powders

    Energy Technology Data Exchange (ETDEWEB)

    Ucar, Huseyin; Parans Paranthaman, M., E-mail: paranthamanm@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Nlebedim, Ikenna C.; William McCallum, R. [Ames Laboratory, Ames, Iowa 50011 (United States)

    2014-12-21

    Pr{sub 2}Co{sub 14}B permanent magnet powders were prepared by mechanical milling of an arc-melted ingot. X-ray diffraction analysis revealed the presence of the 2:14:1 phase after 1 h of milling which transformed into an amorphous phase with additional milling time. Increasing the milling time also lowered the intrinsic coercivity while the saturation magnetization increased up to 105 emu/g. Differential scanning calorimetry measurements revealed a crystallization temperature of around 560 °C. Upon annealing 30 h of as-milled amorphous powders between 500 and 900 °C, we observed the precipitation of the 2:14:1 phase. The optimum post-milling annealing temperature was 600 °C with an intrinsic coercivity of 7 kOe and maximum energy product of 6 MGOe.

  11. Magnetism and the absence of superconductivity in the praseodymium–silicon system doped with carbon and boron

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Basaran, Ali C.; Grant, T.; Gallardo-Amores, J. M.; Ramirez, J. G.; Alario-Franco, M. A.; Fisk, Z.; Schuller, Ivan K.

    2013-08-01

    We searched for new structural, magnetic and superconductivity phases in the Pr–Si system using high-pressure high-temperature and arc melting syntheses. Both high and low Si concentration areas of the phase diagram were explored. Although a similar approach in the La–Si system produced new stable superconducting phases, in the Pr–Si system we did not find any new superconductors. At low Si concentrations, the arc-melted samples were doped with C or B. It was found that addition of C gave rise to multiple previously unknown ferromagnetic phases. Furthermore, X-ray refinement of the undoped samples confirmed the existence of the so far elusive Pr>3Si2 phase.

  12. Time reversal symmetry breaking in superconducting(Pr,La)Os{sub 4}Sb{sub 12} and Pr(Os,Ru){sub 4}Sb{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Shu, L. [Department of Physics, University of California, Riverside, CA 92521 (United States)]. E-mail: lei.shu@email.ucr.edu; Higemoto, W. [Japan Atomic Energy Agency, Tokai-Mura, Ibaraki 319-1195 (Japan); Aoki, Y. [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Frederick, N.A. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Yuhasz, W.M. [Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093 (United States); Heffner, R.H. [Japan Atomic Energy Agency, Tokai-Mura, Ibaraki 319-1195 (Japan); Ohishi, K. [Japan Atomic Energy Agency, Tokai-Mura, Ibaraki 319-1195 (Japan); Ishida, K. [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Kadono, R. [Meson Science Laboratory, KEK, Tsukuba, Ibaraki 305-0801 (Japan); Koda, A. [Meson Science Laboratory, KEK, Tsukuba, Ibaraki 305-0801 (Japan); Kikuchi, D. [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Sato, H. [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Sugawara, H. [Faculty of the Integrated Arts and Sciences, University of Tokushima, Minami-jousanjima-machi 1-1, Tokushima 770-8502 (Japan); Ito, T.U. [Japan Atomic Energy Agency, Tokai-Mura, Ibaraki 319-1195 (Japan); Sanada, S. [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Tunashima, Y. [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Yonezawa, Y. [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Maple, M.B. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); MacLaughlin, D.E. [Department of Physics, University of California, Riverside, CA 92521 (United States)

    2007-03-15

    Zero-field muon spin relaxation ({mu}SR) experiments have been carried out in the Pr(Os{sub 1-x}Ru{sub x}){sub 4}Sb{sub 12} and Pr{sub 1-y}La{sub y}Os{sub 4}Sb{sub 12} alloy systems to investigate the time-reversal symmetry (TRS) breaking found in an earlier ZF-{mu}SR study of the end compound PrOs{sub 4}Sb{sub 12}. Our results suggest that Ru doping is considerably more efficient than La doping in suppressing TRS-breaking superconducting pairing in PrOs{sub 4}Sb{sub 12}.

  13. Crystal field interactions studied by high-field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Radwanski, R.J.; Franse, J.J.M. (Van der Waals-Zeeman Lab., Univ. Amsterdam (Netherlands))

    1992-03-01

    The effect of crystalline electric field (CEF) interactions of the 4f ions on the magnetization process is reviewed for some intermetallic compounds. Special emphasis is given to metamagnetic transitions. The transitions in Ho{sub 2}Co{sub 17} are exchange-driven transitions associated with the formation of a non-collinear magnetic structure in contrast to the transition found in DyCo{sub 2}Si{sub 2} that is of a level-crossing type. The transition found in Pr{sub 2}Fe{sub 14}B results from a competition between lower and higher order crystal field terms. The formation of the rare earth moment under the action of CEF and exchange interactions as well as of external fields is analyzed. (orig.).

  14. The effect of surfactant addition on high-energy milling upon the magnetic properties and microstructure of the Pr-Fe-B HDDR magnetic powders; Efeito da adicao de surfactantes nas propriedades e microestrutura de pos magneticos a base de Pr-Fe-B obtidos via HDDR e moagem de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Santos, P.B.; Silva, S.C.; Faria, R.N.; Takiishia, H., E-mail: pbsantos@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2010-07-01

    Nanomagnetic powders based on the composition Pr{sub 12}Fe{sub 65.9}Co{sub 16}B{sub 6}Nb{sub 0.1} have been obtained from using (a) the hydrogenation, disproportionation, desorption and recombination (HDDR) process; (b) by varying of milling time and (c) with the addition of an oleic acid as a surfactant. The latter has been used to enhance milling condition by preventing the agglomeration of particles and hence to improve the intrinsic coercivity of the material. High-energy mechanical milling has been used to yield magnetic nanoparticles. Powders were characterized magnetically using vibrating sample magnetometer (VSM) and microstructurally by Scanning Electron Microscopy (SEM), Field Emission Gun SEM (FEG-SEM) and X-ray diffraction. (author)

  15. Low temperature diffusion process using rare earth-Cu eutectic alloys for hot-deformed Nd-Fe-B bulk magnets

    Energy Technology Data Exchange (ETDEWEB)

    Akiya, T., E-mail: akiya.takahiro@nims.go.jp; Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Liu, J.; Hono, K. [Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8577 (Japan); Hioki, K.; Hattori, A. [Daido Steel Co., LTD, Nagoya 457-8545 (Japan)

    2014-05-07

    The low temperature grain boundary diffusion process using RE{sub 70}Cu{sub 30} (RE = Pr, Nd) eutectic alloy powders was applied to sintered and hot-deformed Nd-Fe-B bulk magnets. Although only marginal coercivity increase was observed in sintered magnets, a substantial enhancement in coercivity was observed when the process was applied to hot-deformed anisotropic bulk magnets. Using Pr{sub 70}Cu{sub 30} eutectic alloy as a diffusion source, the coercivity was enhanced from 1.65 T to 2.56 T. The hot-deformed sample expanded along c-axis direction only after the diffusion process as RE rich intergranular layers parallel to the broad surface of the Nd{sub 2}Fe{sub 14}B are thickened in the c-axis direction.

  16. Mechanisms controlling renal hemodynamics and electrolyte excretion during amino acids

    Energy Technology Data Exchange (ETDEWEB)

    Woods, L.L.; Mizelle, H.L.; Montani, J.P.; Hall, J.E.

    1986-08-01

    Our purpose was to investigate the mechanisms by which increased plasma amino acids elevate renal blood flow (RBF) and glomerular filtration rate (GFR). Since transport of amino acids and Na is linked in the proximal tubule, the authors hypothesized that increased amino acids might stimulate proximal tubular Na reabsorption (PR/sub Na/) and thus increase RBF and GFR by a macula densa feedback mechanism. A solution of four amino acids (Ala, Ser, Gly, Pro) was infused intravenously into anesthetized dogs with normal kidneys (NK) and with kidneys in which the tubuloglomerular feedback mechanism was blunted by lowering renal artery pressure (LPK) or blocked by making the kidneys nonfiltering (NFK). In NK, RBF and GFR increased by 35 +/- 4% and 30 +/- 7% after 90 min of amino acid infusion, while PR/sub Na/ (estimated from lithium clearance) and O2 consumption increased by 31 +/- 5% and 29 +/- 5% and distal Na delivery remained relatively constant. Autoregulation of RBF and GFR in response to step deceases in renal artery pressure was impaired during amino acids in NK. The hemodynamic responses to amino acids were abolished in LPK and NFK. Infusion of the nonmetabolized -aminoisobutyric acid into NK produced changes in renal hemodynamics that were similar to the responses observed with the four metabolizable amino acids. These data are consistent with the hypothesis that elevation of plasma amino acids increases RBF and GFR by a mechanism that requires an intact macula densa feedback. Metabolism of the amino acids does not appear to be necessary for these changes to occur.

  17. CVD growth of (001) and (111)3C-SiC epilayers and their interface reactivity with pradeodymium oxide dielectric layers

    Energy Technology Data Exchange (ETDEWEB)

    Sohal, R.

    2006-07-24

    In this work, growth and characterisation of 3C-SiC thin films, investigation of oxidation of thus prepared layers and Pr-silicate and AlON based interface with SiC have been studied. Chemical vapor deposition of 3C-SiC thin films on Si(001) and Si(111) substrates has been investigated. Prior to the actual SiC growth, preparation of initial buffer layers of SiC was done. Using such a buffer layer, epitaxial growth of 3C-SiC has been achieved on Si(111) and Si(001) substrates. The temperature of 1100 C and 1150 C has been determined to be the optimal temperature for 3C-SiC growth on Si (111) and Si(001) substrates respectively. The oxidation studies on SiC revealed that a slow oxidation process at moderate temperatures in steps was useful in reducing and suppressing the g-C at the SiO{sub 2}/SiC interface. Clean, graphite-free SiO{sub 2} has been successfully grown on 3C-SiC by silicon evaporation and UHV anneal. For the application of high-k Pr{sub 2}O{sub 3} on silicon carbide, plausible interlayer, Pr-Silicate and AlON, have been investigated. Praseodymium silicate has been prepared successfully completely consuming the SiO2 and simultaneously suppressing the graphitic carbon formation. A comparatively more stable interlayer using AlON has been achieved. This interlayer mainly consists of stable phases of AlN along with some amount of Pr-aluminates and CN. Such layers act as a reaction barrier between Pr{sub 2}O{sub 3} and SiC, and simultaneously provide higher band offsets. (orig.)

  18. Novel chromium doped perovskites A{sub 2}ZnTiO{sub 6} (A = Pr, Gd): Synthesis, crystal structure and photocatalytic activity under simulated solar light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Hekai [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Fang, Minghao, E-mail: fmh@cugb.edu.cn [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Huang, Zhaohui, E-mail: huang118@cugb.edu.cn [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Liu, Yan’gai [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Chen, Kai [National Engineering Research Center for Rare Earth Materials, General Research Institute For Nonferrous Metals, Grirem Advanced Materials Co.,Ltd., Beijing 100088 (China); Guan, Ming; Tang, Chao; Zhang, Lina; Wang, Meng [Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China)

    2017-01-30

    Highlights: • Novel Cr doped A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) photocatalysts were successfully synthesized. • The light absorbance and photocatalytic activity are enhanced through Cr doping. • The photocatalytic reaction mechanism of these photocatalyst was investigated. - Abstract: Double perovskite related oxides A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) have been successfully synthesized by solid state reaction and investigated as photocatalysts for the first time. The two layered titanates mainly demonstrate absorbances under UV irradiation, except for several sharp absorption bands above 400 nm for Pr{sub 2}ZnTiO{sub 6}. Therefore, a series of photocatalysts by doping A{sub 2}ZnTiO{sub 6} (A = Pr, Gd) with Cr have been developed in the hope to improve their absorption in the visible light region. The successful incorporation of Cr was detected by XRD and XPS, and the prepared samples have also been characteriazed by SEM, UV–vis DRS and PL. The characterization results suggested that Cr was present mainly in the form of Cr3+, with only a small amount of Cr6+ species. It served as an efficient dopant for the extension of visible light absorbance and improved photocatalytic activities under solar light irradiation. For both Pr{sub 2}ZnTiO{sub 6} and Gd{sub 2}ZnTiO{sub 6}, the valence band (VB) was composed of hybridized states of the Zn 3d, O 2p and the conduction band (CB) has major contribution from Zn 4s, Ti 3d orbitals. For Cr doped samples, the newly formed spin-polarized valence band in the middle of the band gap that primarily arises from Cr 3d orbitals was responsible for the improved optical and photocatalytic properties.

  19. Tris(β-diketonato) Ru(III) complexes as chiral dopants for nematic liquid crystals: the effect of the molecular structure on the helical twisting power.

    Science.gov (United States)

    Yoshida, Jun; Watanabe, Go; Kakizawa, Kaori; Kawabata, Yasuhiro; Yuge, Hidetaka

    2013-10-07

    Doping nematic liquid crystals with optically active compounds transforms them into chiral nematic phases with helical structures. In this phenomenon, the chirality of the dopant molecules is transferred or amplified to the bulk of the liquid crystals. Δ-[Ru(acac)3] (acac = acetylacetonato) is known to work as one of the dopants with a strong helical twisting power (HTP). In this study, we have systematically modified [Ru(acac)3] to clarify the correlation between the molecular structure and HTP; we have designed and synthesized five new Ru(III) complexes, [Ru(acac)2(acacC8)] (RuC8-1, acac = acetylacetonate, acacC8 = 3-(4'-octyloxy-phenylalkynyl)-pentane-2,4-dionato), [Ru(acac)(acacC8)2] (RuC8-2), [Ru(acacC8)3] (RuC8-3), [Ru(acacC0)3] (RuC0-3, acacC0 = 3-(phenylalkynyl)-pentane-2,4-dionato), and [Ru(acacC24)3] (RuC24-3, acacC24 = 3-(3',4',5'-tri(octyloxy)-phenylalkynyl)-pentane-2,4-dionato). All the complexes, except for RuC0-3, could be separated into Δ, Λ isomers by HPLC on a chiral column and were examined as chiral dopants for a nematic liquid crystal, N-(4-methoxybenzilidene)-4-butylaniline (MBBA). The Δ isomers of RuC8-1, RuC8-2, RuC8-3, and RuC24-3 induced a right-handed (P) helix and the magnitudes of the HTPs (/μm(-1)) were determined as follows: RuC8-1 (+60) RuC8-3 (+78) > RuC24-3 (+41). The HTPs of the ruthenium dopants were not simply proportional to their size. The highest HTP observed in biaxial RuC8-2 was attributed to the balance of the molecular helicity and high ordering in MBBA based on the surface chirality model.

  20. Surface and Bulk Nanostructuring of Insulators by Ultrashort Laser Pulses

    Science.gov (United States)

    2017-04-05

    theoretical investigations in the literature show that high harmonic generation HHG in wide band-gap semiconductors (insulators) may lead to brighter...their bandstructure dependence since recent experimental and theoretical investigations in the literature show that high harmonic generation HHG in wide...before the start of the pulse a(mk)nk (t → −∞) = δnm and the matrix representation of the momentum operator is pnn′(k) = kδnn′ − i 1 Ωu.c. ∫ Ωu.c. d3ru

  1. Mathematical theory of non-equilibrium quantum statistical mechanics

    CERN Document Server

    Jaksic, V

    2001-01-01

    We review and further develop a mathematical framework for non-equilibrium quantum statistical mechanics recently proposed in [JP4, JP5, JP6, Ru3, Ru4, Ru5, Ru6]. In the algebraic formalism of quantum statistical mechanics we introduce notions of non-equilibrium steady states, entropy production and heat fluxes, and study their properties. Our basic paradigm is a model of a small (finite) quantum system coupled to several independent thermal reservoirs. We exhibit examples of such systems which have strictly positive entropy production.

  2. Thermodynamic assessment of the Ru-Si system

    Energy Technology Data Exchange (ETDEWEB)

    Du Yong [State Key Lab. for Powder Metallurgy, Hunan, HN (China); Inst. fuer Physikalische Chemie, Wien (Austria); Chen, K.H.; Huang, B.Y.; Yuan, Z.H. [State Key Lab. for Powder Metallurgy, Hunan, HN (China); Schuster, J.C. [Inst. fuer Physikalische Chemie, Wien (Austria); Perring, L. [Nestle Research Center, Lausanne (Switzerland); Gachon, J.C. [Lab. de Chimie du Solide Mineral, Vandoeuvre-les-Nancy (France)

    2001-04-01

    A consistent thermodynamic data set for the Ru-Si system is obtained by a computer-aided least-squares method applied to the experimental phase diagram and thermodynamic data. The liquid phase is described by the Redlich-Kister formula. All of the compounds, Ru{sub 2}Si, Ru{sub 4}Si{sub 3}, RuSi, and Ru{sub 2}Si{sub 3}, are treated as stoichiometric phases. Comparisons between the calculated and measured phase diagram and thermodynamic quantities show that all of the accurate experimental information is well accounted for by the thermodynamic description. (orig.)

  3. Bis-mixed-carbene ruthenium-thiolate-alkylidene complexes: synthesis and olefin metathesis activity.

    Science.gov (United States)

    Dahcheh, Fatme; Stephan, Douglas W

    2015-01-28

    A series of bis-carbene Ru-hydride species, including (IMes)(Im(OMe)2)(PPh3)RuHCl (1) and (SIMes)(Me2Im(OMe)2)(PPh3)RuHCl (2) were prepared and subsequently shown to react with aryl-vinyl-sulfides to give the bis-carbene-alkylidene complexes: Im(OMe)2(SIMes)RuCl(SR)(=CHCH3) (R = p-FC6H4 (3), p-(NO2)C6H4 (4)), Im(OMe)2(IMes)RuCl(=CHCH3)(SPh) (5), Me2Im(OMe)2(SIMes)RuCl(=CHCH3)(SPh) (6), Im(OMe)2(SIMes)(F5C6S)RuCl(=CHR) (R = C4H9 (9), C5H11 (10)). The activity of these species in the standard Grubbs' tests for ring-opening metathesis polymerization, ring-closing and cross-metathesis are reported. Although these thiolate derivatives are shown to exhibit modest metathesis activities, the reactivity is enhanced in the presence of BCl3.

  4. Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

    Directory of Open Access Journals (Sweden)

    Yannick Borguet

    2010-12-01

    Full Text Available The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium–indenylidene complex [(p-cymeneRu(μ-Cl3RuCl(3-phenyl-1-indenylidene(PCy3] (1 to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic γ-lactams and lactones from α,ω-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by 1H and 31P NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II–Ru(III mixed-valence compound [(p-cymeneRu(μ-Cl3RuCl2(PCy3], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions.

  5. Heat flux measurements of Tb{sub 3}M series (M=Co, Rh and Ru): Specific heat and magnetocaloric properties

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, J.C.B., E-mail: jolmiui@gmail.com [Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin, Campinas, SP 13083-859 (Brazil); Lombardi, G.A. [Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin, Campinas, SP 13083-859 (Brazil); Reis, R.D. dos [Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden (Germany); Freitas, H.E.; Cardoso, L.P.; Mansanares, A.M.; Gandra, F.G. [Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin, Campinas, SP 13083-859 (Brazil)

    2016-12-15

    We report on the magnetic properties and magnetocaloric effect (MCE) for the Tb{sub 3}M series, with M=Co, Rh and Ru, obtained using a heat flux technique. The specific heat of Tb{sub 3}Co and Tb{sub 3}Rh are very similar, with a first order type transition occurring around 6 K below the magnetic ordering temperature without any corresponding feature on the magnetization. The slightly enhanced electronic specific heat, the Debye temperature around 150 K and the presence of the magnetic specific heat well above the ordering temperature are also characteristic of many other compounds of the R{sub 3}M family (R=Rare Earth). The specific heat for Tb{sub 3}Ru, however, presents two peaks at 37 K and 74 K. The magnetization shows that below the first peak the system presents an antiferromagnetic behavior and is paramagnetic above 74 K. We obtained a magnetocaloric effect for M=Co and Rh, −∆S=12 J/kg K, but for Tb{sub 3}Ru it is less than 3 J/kg K (μ{sub 0}∆H=5 T). We believe that the experimental results show that the MCE is directly related with the process of hybridization of the (R)5d-(M)d electrons that occurs in the R{sub 3}M materials.

  6. Spectroscopy features of Pr{sup 3+} and Er{sup 3+} ions in Li{sub 2}O-ZrO{sub 2}-SiO{sub 2} glass matrices mixed with some sesquioxides

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasa Rao, Ch. [Department of Physics, Acharya Nagarjuna University - Nuzvid Campus, Nuzvid-521201, A.P. (India); Kityk, I.V., E-mail: iwank74@gmail.com [Electrical Engineering Department, Technical University of Czestochowa, Aleja Armii, Krajowej 17/19, PL-42-201 Czestochowa (Poland); Srikumar, T.; Naga Raju, G.; Ravi Kumar, V.; Gandhi, Y.; Veeraiah, N. [Department of Physics, Acharya Nagarjuna University - Nuzvid Campus, Nuzvid-521201, A.P. (India)

    2011-09-15

    Highlights: > Optical spectra of Pr{sup 3+} and Er{sup 3+} ions in Li{sub 2}O-ZrO{sub 2}-SiO{sub 2}: Pr{sub 2}O{sub 3}/Er{sub 2}O{sub 3} with sesquioxides (viz., Al{sub 2}O{sub 3}, Sc{sub 2}O{sub 3}, Y{sub 2}O{sub 3}) studied. > The highest branching ratios {beta}{sub r} and quantum efficiencies of {sup 3}P{sub 0} {yields} {sup 3}H{sub 4} (Pr{sup 3+}) and {sup 4}S{sub 3/2} {yields} {sup 4}I{sub 15/2} (Er{sup 3+}) emissions have shown principal role of Y{sub 2}O{sub 3}. > Principal role of disorder around rare earth is established. - Abstract: The glasses of the composition Li{sub 2}O-ZrO{sub 2}-SiO{sub 2}: Pr{sub 2}O{sub 3}/Er{sub 2}O{sub 3} mixed with three interesting sesquioxides (viz., Al{sub 2}O{sub 3}, Sc{sub 2}O{sub 3}, Y{sub 2}O{sub 3}) were synthesized. Optical absorption and fluorescence spectra (in the spectral range 350-2100 nm were studied at ambient temperature. The Judd-Ofelt theory was applied to characterize the absorption and luminescence spectra of Pr{sup 3+} and Er{sup 3+} ions in these glasses. Following the luminescence spectra, various radiative properties like transition probability A, branching ratio {beta} and the radiative life time {tau} for different emission levels of two rare earth ions have been evaluated. The radiative life times for the upper levels {sup 3}P{sub 0} (Pr{sup 3+}) and {sup 4}S{sub 3/2} (Er{sup 3+}) have also been measured and quantum efficiencies were estimated. The variations observed in these parameters were discussed in the light of changing environment of rare earth ions due to mixing of different sesquioxides in the glass network.

  7. Structural, magnetic, and crystalline electric-field effects in single crystals of Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Uma, S.; Sarkar, T.; Sethupathi, K.; Seshasayee, M.; Rangarajan, G. [Department of Physics, Indian Institute of Technology, Madras 600036 (India); Changkang, C.; Yongle, H.; Wanklyn, B.M.; Hodby, J.W. [Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, 0X13PU (England)

    1996-03-01

    We report here structural and directional magnetic susceptibility measurements on single crystals of Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} ({ital x}=1.0, {delta}=1, 0.11; {ital x}=0.7, {delta}=0; and {ital x}=0.42, {delta}=0.22). The space group of PrBa{sub 2}Cu{sub 3}O{sub 6} (Pr-O6) and Y{sub 0.58}Pr{sub 0.42}Ba{sub 2}Cu{sub 3}O{sub 6.78} (Pr 0.42-O7) were found to be {ital P}4/{ital mmm} and that of PrBa{sub 2}Cu{sub 3}O{sub 6.89} (Pr-O7) was found to be {ital Pmmm}. Also, Pr-O7 was found to be weakly orthorhombic. Directional, magnetic susceptibility measurements in the temperature range 2{endash}300 K revealed a clear peaking in the paramagnetic anisotropy of Pr-O7 around 17 K, and {chi}{sub {ital c}}{approx_gt}{chi}{sub {ital a},{ital b}} at all temperatures. However for Y{sub 0.3}Pr{sub 0.7}Ba{sub 2}Cu{sub 3}O{sub 7} (Pr0.7-O7) and Pr0.42-O7, {chi}{sub {ital c}}{approx_gt}{chi}{sub {ital a},{ital b}} at room temperature and {chi}{sub {ital c}}{lt}{chi}{sub {ital a},{ital b}} for temperatures below 110 and 60 K, respectively. The magnetic susceptibilities have been analyzed in the light of crystalline electric-field effects considering {ital J} mixing of all the thirteen multiplets. Intermediate coupled wave functions have also been used in the calculations. Crystal-field interaction is found to be stronger in the case of Pr-O7 compared to Pr-O6 which is also evident from a shorter Pr-O bond length in the case of Pr-O7 than in Pr-O6. A best set of eigenvalues and eigenfunctions has been determined and these are discussed and compared with inelastic neutron scattering data. {copyright} {ital 1996 The American Physical Society.}

  8. Effects of surfactant addition and high-speed ball milling on magnetic powders based on Pr-Fe-B obtained by HDDR; Efeitos da adicao de surfactante e moagem de alta velocidade em pos magneticos a base de Pr-Fe-B obtidos via HDDR

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Patricia Brissi

    2011-07-01

    This work verified the effect caused by adding the surfactant in the high speed/energy milling in order to obtain Pr{sub 12}Fe{sub 65.9}Co{sub 16}B{sub 6}Nb{sub 0.1} magnetic nano powders. The first part of this work involved the magnetic powder obtainment through the process of hydrogenation, disproportionation, desorption and recombination (HDDR). The pressure of H2 during the hydrogenation and disproportion steps was 930 mbar and the temperature of desorption and recombination was 840 deg C. Initially, the HDDR powders were subjected a high speed milling process at 900 rpm, with quantity variations of the milling medium (cyclohexane) and without the addition of oleic acid. Then, the HDDR powders were subjected to the milling process with the addition of oleic acid and with milling time variations. After the milling process, heat treatments of the powder were carried out at 700 deg C or 800 deg C for 30 minutes in order to obtain the crystallization of the powder. By performing the procedures, it was verified that the milling efficiency improved with the addition of 6.6 ml of cyclohexane as the milling medium and with the addition of oleic acid. It was determined that for the surfactant additions of 0.02 ml to 0.05 ml, with a milling time of up to 360 minutes, powder agglomeration does not occur in the milling pot and the milling efficiency is higher than 90%. The second stage of this work involved the magnetic powder's characterization obtained by using vibrating sample magnetometer, scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Through the characterizations it was found that the powder's magnetic properties improved when the addition of oleic acid in a high-speed /energy milling occurred. It was also verified that the {alpha}-Fe phase, present in the powder, shows a crystallite size decrease (from 35 nm to {approx} 10 nm) when the time milling variation occurred; meanwhile, the crystallinity degree was lower in

  9. Structures and stabilities of trivalent and tetravalent rare earth ions in sevenfold and eightfold coordination in fluorite-related complex oxides

    Energy Technology Data Exchange (ETDEWEB)

    Morss, L.R.

    1991-12-31

    This paper reports the preparation and characterization of a series of oxides containing 3+ or 4+ lanthanide (M = Ce, Pr, or Tb) ions, with different ionic sizes and varying M{sup 4+}/M{sup 3+} reduction potentials, in nearly cubic coordination. The objective of the study was to demonstrate how oxidation-reduction characteristics and ionic size trends explain the properties of these oxides and to compare the oxidation-reduction stability of M{sup 3+} and M{sup 4+} lanthanide ions in high (CN 7 or 8) coordination in fluorite-related oxides versus low (CN 6) coordination in perovskite oxides. Efficient preparative methods are reported, as well as powder diffraction and thermogravimetric measurements for oxides CaMTi{sub 2}O{sub 7-x} and CaMZr{sub 2}O{sub 7-x}. These oxides were characterized by X-ray powder diffraction and by thermogravimetric analysis. CaCeTi{sub 2}O{sub 7} is a pyrochlore, a = 10.142(4) {Angstrom}, with Ce{sup 4+} much more easily reducible than in the perovskite BaCeO{sub 3}. By contrast, a preparation with the stoichiometry ``CaPbTi{sub 2}O{sub 7-x}`` is a two-phase mixture-of perovskite CaTiCo{sub 3} and a presumably Pr{sup 3+}-rich pyrochlore Pr{sub 2}Ti{sub 2}O{sub 7}(?). CaTbTi{sub 2}O{sub 7-x} appears to be a Tb{sup 3+} pyrochlore, a = 10.149(2) {Angstrom}. CaCeZr{sub 2}O{sub 7} is a pyrochlore, a = 10.524(1) {Angstrom}. A preparation of ``CaPbZr{sub 2}O{sub 7-x}`` also appeared to yield a two-phase mixture, perovskite CaZrO{sub 3} and pyrochlore Pr{sub 2}Zr{sub 2}O{sub 7}. In this paper, the structures, f-element ion sites, and M(4)-M(3) stability trends in the CaMTi{sub 2}O{sub 7-x} and CaMZr{sub 2}O{sub 7-x} oxides are compared with the structural and stability trends in the perovskites BaMO{sub 3} which have M{sup 4+} ions in sixfold (tilted octahedra) coordination.

  10. Transmission electron microscopic study of pyrochlore to defect-fluorite transition in rare-earth pyrohafnates

    Energy Technology Data Exchange (ETDEWEB)

    Karthik, Chinnathambi, E-mail: Karthikchinnathambi@boisestate.edu [Department of Materials Science and Engineering, Boise State University, 1910 University drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd, Idaho Falls, ID 83415 (United States); Anderson, Thomas J. [Department of Materials Science and Engineering, Boise State University, 1910 University drive, Boise, ID 83725 (United States); Gout, Delphine [Oak Ridge National Lab, Neutron Scattering Science Division, Oak Ridge, TN (United States); Ubic, Rick [Department of Materials Science and Engineering, Boise State University, 1910 University drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd, Idaho Falls, ID 83415 (United States)

    2012-10-15

    A structural transition in rare earth pyrohafnates, Ln{sub 2}Hf{sub 2}O{sub 7} (Ln=Y, La, Pr, Nd, Tb, Dy, Yb and Lu), has been identified. Neutron diffraction showed that the structure transforms from well-ordered pyrochloric to fully fluoritic through the lanthanide series from La to Lu with a corresponding increase in the position parameter x of the 48f (Fd3{sup Macron }m) oxygen site from 0.330 to 0.375. As evidenced by the selected area electron diffraction, La{sub 2}Hf{sub 2}O{sub 7}, Pr{sub 2}Hf{sub 2}O{sub 7} and Nd{sub 2}Hf{sub 2}O{sub 7} exhibited a well-ordered pyrocholoric structure with the presence of intense superlattice spots, which became weak and diffuse (in Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}) before disappearing completely as the series progressed towards the Lu end. High resolution electron microscopic studies showed the breakdown of the pyrochlore ordering in the form of antiphase domains resulting in diffused smoke-like superlattice spots in the case of Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}. - Graphical abstract: Transmission electron microscopic studies showed the ordered pyrochlore to defect fluorite transition in rare-earth pyrohafnates to occur via the formation of anti-phase domains to start with. Highlights: Black-Right-Pointing-Pointer Pyrochlore to fluorite structural transition in rare earth pyrohafnates. Black-Right-Pointing-Pointer La{sub 2}Hf{sub 2}O{sub 7}, Pr{sub 2}Hf{sub 2}O{sub 7} and Nd{sub 2}Hf{sub 2}O{sub 7} showed well ordered pyrochlore structure. Black-Right-Pointing-Pointer Short range ordering in Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}. Black-Right-Pointing-Pointer Break down of pyrochlore ordering due to antiphase boundaries. Black-Right-Pointing-Pointer Rest of the series showed fluoritic structure.

  11. Magnetism in layered Ruthenates

    Energy Technology Data Exchange (ETDEWEB)

    Steffens, Paul C.

    2008-07-01

    In this thesis, the magnetism of the layered Ruthenates has been studied by means of different neutron scattering techniques. Magnetic correlations in the single-layer Ruthenates of the series Ca{sub 2-x}Sr{sub x}RuO{sub 4} have been investigated as function of Sr-concentration (x=0.2 and 0.62), temperature and magnetic field. These inelastic neutron scattering studies demonstrate the coexistence of ferromagnetic paramagnon scattering with antiferromagnetic fluctuations at incommensurate wave vectors. The temperature dependence of the amplitudes and energies of both types of excitations indicate the proximity to magnetic instabilities; their competition seems to determine the complex behavior of these materials. In Ca{sub 1.8}Sr{sub 0.2}RuO{sub 4}, which shows a metamagnetic transition, the ferromagnetic fluctuations are strongly suppressed at low temperature, but appear at higher temperature or application of a magnetic field. In the high-field phase of Ca{sub 1.8}Sr{sub 0.2}RuO{sub 4} above the metamagnetic transition, a ferromagnetic magnon dominates the excitation spectrum. Polarized neutron scattering revealed the existence of a very broad signal around the zone centre, in addition to the well-known incommensurate excitations at Q=(0.3,0.3,0) in the unconventional superconductor Sr{sub 2}RuO{sub 4}. With this additional contribution, it is possible to set up a general model for the Q-dependent magnetic susceptibility, which is well consistent with the results of other measurement methods that do not resolve the Q-dependence. Upon doping with Ti, the incommensurate fluctuations are enhanced, in particular near the critical concentration for the onset of magnetic order, but no divergence down to very low temperature is observed. In the bilayer Ti-doped Ca{sub 3}Ru{sub 2}O{sub 7}, the existence of magnetic order with a propagation vector of about ((1)/(4),(1)/(4),0) has been discovered and characterized in detail. Above and below T{sub N}, excitations at this

  12. Magnetic and electrical properties of single crystalline Sr{sub 3-x}Ca{sub x}Ru{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, K. [Faculty of Science, Saitama University, Saitama 338-8570 (Japan)], E-mail: iwata@hp.phy.saitama-u.ac.jp; Yoshida, Y. [Nanoelectronics Research Institute, AIST, Tsukuba 305-8568 (Japan); Kosaka, M.; Katano, S. [Faculty of Science, Saitama University, Saitama 338-8570 (Japan)

    2008-04-01

    We have successfully grown single crystalline Sr{sub 3-x}Ca{sub x}Ru{sub 2}O{sub 7} with the range of 2.0{<=}x{<=}3.0 using the floating-zone method. All compounds show orthorhombic symmetry in this substitution range, but the difference between lattice constants a and b decreases with increasing Sr concentration and becomes almost zero at x=2.0. Characteristic temperatures, which correspond to antiferromagnetic ordering and structural transition, decrease with increasing Sr concentration. The value of the magnetic susceptibility below 30 K increases with increasing Sr concentration. The temperature dependence of the electrical resistivity revealed that Sr substitution significantly suppresses the highly anisotropic electric structure of Ca{sub 3}Ru{sub 2}O{sub 7}.

  13. Mono- and Bimetallic Ruthenium—Arene Catalysts for Olefin Metathesis: A Survey

    Science.gov (United States)

    Borguet, Yannick; Sauvage, Xavier; Demonceau, Albert; Delaude, Lionel

    In this chapter, we summarize the main achievements of our group toward the development of easily accessible, highly efficient ruthenium—arene catalyst precursors for olefin metathesis. Major advances in this field are presented chronologically, with an emphasis on catalyst design and mechanistic details. The first part of this survey focuses on monometallic complexes with the general formula RuCl2(p-cymene)(L), where L is a phosphine or N-heterocyclic carbene ancillary ligand. In the second part, we disclose recent developments in the synthesis and catalytic applications of homobimetallic ruthenium—arene complexes of generic formula (p-cymene)Ru(μ-Cl)3RuCl(η2-C2H4)(L) and their derivatives resulting from the substitution of the labile ethylene moiety with vinylidene, allenylidene, or indenylidene units

  14. [Antitumor enzyme L-lyzine-alpha-oxidase from Trichoderma harzianum Rifai F-180 and investigation of its action on L-lysine oxidation by capillar electrophoresis].

    Science.gov (United States)

    Smirnova, I P; Shkinev, V M; Rudnev, A V; Kuznetsova, O M; Karimova, E V; Orlova, V S

    2014-01-01

    Trichoderma harzianum Rifai F-180, an organism producing the antitumor enzyme L-lysine-alpha-oxidase was cultivated and the enzyme was isolated and purified under the manufacturing conditions. The effect of L-lysine-alpha-oxidase on oxidation of L-lysine was investigated for the first time by capillary electrophoresis and the procedure conditions were developed. The reaction of L-lysine oxidative deamination is described and location of the reaction components picks on the elecrophoregrams was identified. The average rate of the catalytic reaction of L-lysine oxidation equal to 0.46 RU/min (7.7 x 10(-3) RU/sec) was determined. The use of the antitumor enzyme L-lysine-alpha-oxidase is recommended as a drug for the treatment of superficial tumors and tissue relative oxygen excess.

  15. The influence of methanol on the chemical state of PtRu anodes in a high-temperature direct methanol fuel cell studied in situ by synchrotron-based near-ambient pressure x-ray photoelectron spectroscopy

    Science.gov (United States)

    Saveleva, Viktoriia A.; Daletou, Maria K.; Savinova, Elena R.

    2017-01-01

    Synchrotron radiation-based near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) has recently become a powerful tool for the investigation of interfacial phenomena in electrochemical power sources such as batteries and fuel cells. Here we present an in situ NAP-XPS study of the anode of a high-temperature direct methanol fuel cell with a phosphoric acid-doped hydrocarbon membrane, which reveals an enhanced flooding of the Pt3Ru anode with phosphoric acid in the presence of methanol. An analysis of the electrode surface composition depending on the cell voltage and on the presence of methanol reveals the strong influence of the latter on the extent of Pt oxidation and on the transformation of Ru into Ru (IV) hydroxide.

  16. Bulk modulus and specific heat of B-site doped (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B=Fe, Cr, Ru, Al, Ga)

    Science.gov (United States)

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2014-04-01

    Specific heat (Cp) thermal expansion (α) and Bulk modulus (BT) of lightly doped Rare Earth manganites (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B3+ = Fe3+,Cr3+,Ga3+,Al3+,Ru4+); (0.3specific heat (Cp)lat of (La0.3Pr0.7)0.65Ca0.35Mn0.97Fe0.03O3 as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

  17. Radiosensitivity of cultured insect cells: II. Diptera

    Energy Technology Data Exchange (ETDEWEB)

    Koval, T.M.

    1983-10-01

    The radiosensitivity of five dipteran cell lines representing three mosquito genera and one fruit fly genus were examined. These lines are: (1) ATC-10, Aedes aegypti; (2) RU-TAE-14, Toxorhynchites amboinensis; (3) RU-ASE-2A, Anopheles stephensi; (4) WR69-DM-1, Drosophila melanogaster; and (5) WR69-DM-2, Drosophila melanogaster. Population doubling times for these lines range from approximately 16 to 48 hr. Diploid chromosome numbers are six for the mosquito cells and eight for the fruit fly cells D/sub 0/ values are 5.1 and 6.5 Gy for the Drosophila cell lines and 3.6, 6.2, and 10.2 Gy for the mosquito cell lines. The results of this study demonstrate that dipteran insect cells are a few times more resistant to radiation than mammalian cells, but not nearly as radioresistant as lepidopteran cells.

  18. Optical conductivity of layered ruthenates. The role of spin-orbit coupling and Coulomb anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Sarvestani, Esmaeel; Zhang, Guoren; Gorelov, Evgeny; Pavarini, Eva [Institute for Advanced Simulation, Forschungszentrum Juelich (Germany)

    2016-07-01

    We use the combination of density functional theory and dynamical mean-field theory (LDA+DMFT) to calculate the optical conductivity of the layered ruthenates Sr{sub 2}RuO{sub 4} and Sr{sub 3}Ru{sub 2}O{sub 7}. The calculations are performed via linear response theory and Kubo's formalism. For Sr{sub 2}RuO{sub 4} two sets of interaction parameters, (U,J)=(2.3,0.4)eV and (3.1,0.7)eV, both commonly employed for ruthenates, are used. We show that including the spin-orbit coupling improves the agreement with experimental data. Finally, we analyze the effects of low-symmetry Coulomb interaction.

  19. Endocrinologic profile of patients with idiopathic melasma.

    Science.gov (United States)

    Pérez, M; Sánchez, J L; Aguiló, F

    1983-12-01

    Complete endocrinologic evaluation of 9 women (ages 24-41) with idiopathic melasma (melasma not associated with pregnancy nor ingestion of oral contraceptives) was performed and compared to age- and sex-matched normal controls. Serum cortisol, adrenocorticotropin, plasma immunoreactive alpha and beta melanocyte-stimulating hormones, luteinizing hormone, follicular-stimulating hormone, estradiol and progesterone levels were performed in the basal state. Additionally, total T4, T3RU, FTI, prolactin, 2-h postprandial blood sugar, and 24-h urine for 17-hydroxysteroids and 17-ketosteroids were done and found to be normal. The melasma patients presented statistically significant increased levels of LH (p less than 0.001) and lower levels of serum estradiol (p less than 0.025) than normal controls. It is proposed that these hormonal alterations may represent subclinical evidence of a mild ovarian dysfunction which may underlie the pathogenesis of some cases of idiopathic melasma.

  20. Ferromagnetic grain boundary signature in die-upset RE-Fe-B magnets

    Energy Technology Data Exchange (ETDEWEB)

    Henderson Lewis, L.; Zhu, Y.; Welch, D.O.

    1994-07-01

    Previous nanostructural and nanocompositional studies performed on the boundaries of deformed grains in two die-upset rare earth magnets with bulk compositions Nd{sub 13.75}Fe{sub 80.25}B{sub 6}, and Pr{sub 13.75}Fe{sub 80.25}B{sub 6} indicate that the intergranular phase in many grain boundaries is enriched in iron relative to the bulk. Preliminary magnetic data are presented that provide further evidence that this grain boundary phase is indeed iron-rich, and in fact appears to be ferromagnetic. Hysteresis loops were performed at 800 K on die-upset magnets with the above compositions. Each sample showed a clear hysteresis with coercivities between 34 and 40 Oe average remanence 4{pi}M{sub R} of 6.8 G for the Nd-based sample and 10.3 G for the Pr-based sample. The ferromagnetic signals measured at high temperature in these magnets are attributed to the iron-rich grain boundary phase. The implications of this conclusion with respect to coercivity are discussed.

  1. Pressure-induced polyamorphism in lanthanide-solute metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Li, Liangliang; Li, Renfeng; Liu, Haozhe [Harbin Institute of Technology, Harbin (China); Center for High Pressure Science Technology Advanced Research, Changchun (China); Wang, Luhong [Harbin Institute of Technology, Harbin (China); Qu, Dongdong [School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD (Australia); Zhao, Haiyan [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL (United States); Center for Advanced Energy Studies, University of Idaho, Idaho Falls, ID (United States); Chapman, Karena W.; Chupas, Peter J. [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL (United States)

    2017-06-15

    The electronic structure inheritance of lanthanide-solvent atoms in lanthanide-based metallic glasses has been proposed. Is a polyamorphism possible in lanthanide-solute metallic glasses? So far, polyamorphic phase transitions in metallic glass containing lanthanide have been observed only in lanthanide-solvent metallic glasses. Here, a pressure-induced transition between two distinct amorphous states, accompanied by a 7% volume collapse at ambient pressure, was observed in La{sub 43.4}Pr{sub 18.6}Al{sub 14}Cu{sub 24} metallic glass, with low lanthanide content, by using in situ X-ray total scattering method. The transformation also indicated by changes in short range and medium range order. Thus, it is proposed that the lanthanide-solute metallic glasses also inherit 4f electronic transition from pure lanthanide element in polyamorphic transition. This discovery offers a supplement to research on lanthanide-based metallic glasses, which further provides a new perspective of the polyamorphic transformation in metallic glasses containing lanthanide element. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. FURTHER CONSTRAINTS ON THE OPTICAL TRANSMISSION SPECTRUM OF HAT-P-1b

    Energy Technology Data Exchange (ETDEWEB)

    Montalto, M.; Santos, N. C.; Martins, J. H. C.; Figueira, P.; Alonso, R. [Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto (Portugal); Iro, N. [Theoretical Meteorology Group Klimacampus, University of Hamburg Grindelberg 5, D-20144, Hamburg (Germany); Desidera, S., E-mail: Marco.Montalto@astro.up.pt [INAF—Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, Padova, I-35122 (Italy)

    2015-09-20

    We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo. Our measurements imply an average planet to star radius ratio equal to R{sub p}/R{sub *} = (0.1159 ± 0.0005). This result is consistent with the value obtained from recent near-infrared measurements of this object, but differs from previously reported optical measurements, being lower by around 4.4 exoplanet scale heights. Analyzing the data over five different spectral bins of ∼600 Å wide, we observed a single peaked spectrum (3.7 σ level) with a blue cutoff corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in-between 6180 and 7400 Å. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.

  3. The single crystal structure determination of Ln{sub 6}MnSb{sub 15} (Ln=La, Ce), Ln{sub 6}Mn{sub 1-x}Zn{sub x}Sb{sub 15} (x∝0.5), and Ln{sub 6}ZnSb{sub 15} (Ln=La-Pr)

    Energy Technology Data Exchange (ETDEWEB)

    Benavides, Katherine A.; McCandless, Gregory T.; Chan, Julia Y. [Texas Univ., Dallas, Richardson, TX (United States). Dept. of Chemistry and Biochemistry

    2017-09-01

    Single crystals of Ln{sub 6}MnSb{sub 15} (Ln=La, Ce), Ln{sub 6}Mn{sub 1-x}Zn{sub x}Sb{sub 15} (x∝0.5), and Ln{sub 6}ZnSb{sub 15} (Ln=La-Pr) have been successfully grown and the compounds adopt the orthorhombic Ln{sub 6}MnSb{sub 15} structure type (space group Immm), with a∝4.3 Aa, b∝15 Aa, and c∝19 Aa. This structure is comprised of antimony nets and antimony ribbons which exhibit positional disorder at connecting points between antimony substructures, in addition to two partially occupied transition metal sites. The unit cell volumes of the La analogs displayed a systematic decrease upon Zn substitution. However, for the Ce{sub 6}Mn{sub 1-x}Zn{sub x}Sb{sub 15} and Pr{sub 6}Mn{sub 1-x}Zn{sub x}Sb{sub 15} (x∝0.5), the volumes deviate from linearity as observed in the parent compounds.

  4. Superconductivity in Zigzag CuO Chains

    Energy Technology Data Exchange (ETDEWEB)

    Berg, E.

    2010-04-06

    Superconductivity has recently been discovered in Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} with a maximum T{sub c} of about 15K. Since the CuO planes in this material are believed to be insulating, it has been proposed that the superconductivity occurs in the double (or zigzag) CuO chain layer. On phenomenological grounds we propose a theoretical interpretation of the experimental results in terms of a new phase for the zigzag chain, labelled by C{sub 1}S{sub 3/2}. This phase has a gap in the relative charge mode and a partial gap in the relative spin mode. It has gapless uniform charge and spin excitations and can have a divergent superconducting susceptibility, even for repulsive interactions. A microscopic model for the zigzag CuO chain is proposed, and on the basis of density matrix renormalization group (DMRG) and bosonization studies, we adduce evidence that supports our proposal.

  5. Structure and surface properties of praseodymium modified alumina

    Energy Technology Data Exchange (ETDEWEB)

    Tankov, I. [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Pawelec, B. [Instituto de Catalisis y Petroleoquimica, CSIC, Cantoblanco, 28049 Madrid (Spain); Arishtirova, K. [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Damyanova, S., E-mail: soniad@ic.bas.bg [Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)

    2011-10-15

    Mixed PrO{sub 2}-Al{sub 2}O{sub 3} oxides with different PrO{sub 2} content (1-20 wt.%) were prepared by wetness impregnation of {gamma}-alumina with aqueous solution of praseodymium nitrate. The samples were characterized by different techniques, using surface adsorption-desorption of N{sub 2} (S{sub BET}), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR) and temperature-programmed desorption of CO{sub 2} (TPD-CO{sub 2}). TGA and XRD showed the presence of small praseodymium oxide species on the alumina surface. XPS and DRS detected electron deficient interaction between deposited praseodymium oxide and alumina. It was observed a lower reduction temperature for supported Pr oxide species compared to that of the bulk Pr{sub 6}O{sub 11}. TPD-CO{sub 2} studies suggested that the deposition of Pr oxide on alumina leaded to increase of the basicity of mixed oxides.

  6. X-ray induced insulator-metal transitions in CMR manganites

    Energy Technology Data Exchange (ETDEWEB)

    Kiryukhin, V.; Casa, D.; Keimer, B. [Princeton Univ., NJ (United States). Dept. of Physics; Hill, J.P.; Vigliante, A. [Brookhaven National Lab., Upton, NY (United States). Dept. of Physics; Tomioka, Y. [Joint Research Center for Atom Technology, Tsukuba, Ibaraki (Japan); Tokura, Y. [Joint Research Center for Atom Technology, Tsukuba, Ibaraki (Japan)]|[Univ. of Tokyo (Japan). Dept. of Applied Physics

    1997-12-01

    In this work the authors report a study of the photoinduced insulator-to-metal transition in manganese oxide perovskites of the formula Pr{sub 1{minus}x}Ca{sub x}MnO{sub 3}. The transition is closely related to the magnetic field induced insulator-to-metal transition (CMR effect) observed in these materials. It is accompanied by a dramatic change in the magnetic properties and lattice structure: the material changes from an insulating charge-ordered canted antiferromagnet to a ferromagnetic metal. The authors present an investigation of the transport and structural properties of these materials over the course of the transition (which usually takes about an hour to complete). The current-voltage characteristics exhibited by the material during the transition are highly nonlinear, indicating a large inhomogeneity of the transitional state. Possible practical applications of this novel type of transition are briefly discussed. They also report a high resolution X-ray diffraction study of the charge ordering in these materials. The temperature dependent charge ordering structure observed in these compounds is more complex than previously reported.

  7. Analysis of electrical and microstructural characteristics of a ZnO-based varistor doped with rare earth oxide; Analise das caracteristicas microestruturais e eletricas de um varistor a base de ZnO dopado com oxidos de terras raras

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, J.M. de; Dias, R.; Furtado, J.G. de M. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Assuncao, F.C.R. [Pontificia Univ. Catolica do Rio de Janeiro (PUC/Rio), RJ (Brazil)

    2010-07-01

    Varistor is a semiconductor device, used in the protection of electrical systems, characterized to have a high no-linear electric resistance. Its properties are directly dependents of its chemical composition and microstructural characteristics. In this work were analyzed microstructural and electrical characteristics of a ZnO-based varistor doped with rare earth oxide, with chemical composition (mol%) 98,5.ZnO - 0,3.Pr{sub 6}O{sub 11} - 0,2.Dy{sub 2}O{sub 3} - 0,9.Co{sub 2}O{sub 3} - 0,1.Cr{sub 2}O{sub 3}. X-ray diffraction for phase characterization, scanning electron microscopy and energy dispersive X-ray spectroscopy were used for microstructural analysis. Measurement of average grain size and electrical and dielectric characteristics complete the characterization. The results show the formation of biphasic microstructure and with high densification, presenting relevant varistors characteristics but that would need improvements.(author)

  8. Measuring bandgap states in individual non-stoichiometric oxide nanoparticles using monochromated STEM EELS: The Praseodymium–ceria case

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, W.J. [School for the Engineering of Matter, Transport and Energy, Arizona State University, 501 E. Tyler Mall, Tempe, AZ 85287-6106 (United States); March, K. [Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR 8502, 91405 Orsay Cedex (France); Hernandez, C.A. [School for the Engineering of Matter, Transport and Energy, Arizona State University, 501 E. Tyler Mall, Tempe, AZ 85287-6106 (United States); Crozier, P.A., E-mail: crozier@asu.edu [School for the Engineering of Matter, Transport and Energy, Arizona State University, 501 E. Tyler Mall, Tempe, AZ 85287-6106 (United States)

    2016-08-15

    We describe a method to perform high spatial resolution measurement of the position and density of inter-band impurity states in non-stoichiometric oxides using ultra-high energy resolution electron energy-loss spectroscopy (EELS). This can be employed to study optical and electronic properties of atomic and nanoscale defects in electrically-conducting and optically-active oxides. We employ a monochromated scanning transmission electron microscope with subnanometer diameter electron probe, making this technique suitable for correlating spectroscopic information with high spatial resolution images from small objects such as nanoparticles, surfaces or interfaces. The specific experimental approach outlined here provides direct measurement of the Pr inter-band impurity states in Pr{sub 0.1}Ce{sub 0.9}O{sub 2−δ} via valence-loss EELS, which is interpreted with valence-loss spectral simulation based on density of states data to determine the energy level and character of the inter-band state. Additionally, observation of optical color change upon chemically-induced oxygen non-stoichiometry indicates that the population of the inter-band state is accompanied by an energy level shift within the bandgap. - Highlights: • Ultra-high energy resolution EELS used to study inter-band states in oxide. • Energy level and character of inter-band state determined from spectral model. • EELS coupled with optical color change indicates energy shift of inter-band state.

  9. Investigation of magnetic and transport properties of PrCa(MnCo)O prepared by solid state process

    Energy Technology Data Exchange (ETDEWEB)

    Khelifi, M. [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l’Environnement, Faculté des Sciences de Gabès cité Erriadh, Université de Gabès, 6079 Gabès (Tunisia); M’nassri, R. [Unité de recherche Matériaux Avancés et Nanotechnologies (URMAN), Institut Supérieur des Sciences Appliquées et de Technologie de Kasserine, Kairouan University, BP 471, Kasserine 1200 (Tunisia); Selmi, A. [Laboratory of Physics of Materials, Faculty of Sciences of Sfax, Sfax University, BP 1171, 3000 Sfax (Tunisia); Rahmouni, H., E-mail: rahmounihedi@yahoo.fr [Unité de recherche Matériaux Avancés et Nanotechnologies (URMAN), Institut Supérieur des Sciences Appliquées et de Technologie de Kasserine, Kairouan University, BP 471, Kasserine 1200 (Tunisia); Khirouni, K. [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l’Environnement, Faculté des Sciences de Gabès cité Erriadh, Université de Gabès, 6079 Gabès (Tunisia); and others

    2017-02-01

    Magnetic, magnetocaloric and electrical properties in distorted orthorhombic system Pr{sub 0.7}Ca{sub 0.3}Mn{sub 0.98}Co{sub 0.02}O{sub 3} has been studied. Complex impedance analysis confirms the contribution of grain boundary on the conduction process. The latter is dominated by thermally activated hopping mechanism. The sample exhibits two relaxations phenomena. Only one process persists at higher temperatures. Conductivity analysis indicates that the investigated compound exhibits a semiconductor behavior. The material reveals a dielectric transition and the experimental results are well fitted by Curie-Weiss law. The magnetic measurements show a clear paramagnetic–ferromagnetic transition with a large magnetic entropy change over a wide range of temperature. Furthermore, Banerjee's criteria and Landau theory of phase transitions are also studied to access magnetic ordering in the sample. A maximum magnetic entropy change increases from 0.5 to 2.18 J kg{sup −1} K{sup −1} when magnetic field rises from 1 T to 5 T. For the higher applied magnetic field, the material exhibits a high relative cooling power RCP=268.14 J/kg with a large temperature full-width at half maximum δ{sub TFWHM}=123 K.

  10. A reactive distillation process for the treatment of LiCl-KCl eutectic waste salt containing rare earth chlorides

    Energy Technology Data Exchange (ETDEWEB)

    Eun, H.C., E-mail: ehc2004@kaeri.re.kr; Choi, J.H.; Kim, N.Y.; Lee, T.K.; Han, S.Y.; Lee, K.R.; Park, H.S.; Ahn, D.H.

    2016-11-15

    The pyrochemical process, which recovers useful resources (U/TRU metals) from used nuclear fuel using an electrochemical method, generates LiCl-KCl eutectic waste salt containing radioactive rare earth chlorides (RECl{sub 3}). It is necessary to develop a simple process for the treatment of LiCl-KCl eutectic waste salt in a hot-cell facility. For this reason, a reactive distillation process using a chemical agent was achieved as a method to separate rare earths from the LiCl-KCl waste salt. Before conducting the reactive distillation, thermodynamic equilibrium behaviors of the reactions between rare earth (Nd, La, Ce, Pr) chlorides and the chemical agent (K{sub 2}CO{sub 3}) were predicted using software. The addition of the chemical agent was determined to separate the rare earth chlorides into an oxide form using these equilibrium results. In the reactive distillation test, the rare earth chlorides in LiCl-KCl eutectic salt were decontaminated at a decontamination factor (DF) of more than 5000, and were mainly converted into oxide (Nd{sub 2}O{sub 3}, CeO{sub 2}, La{sub 2}O{sub 3}, Pr{sub 2}O{sub 3}) or oxychloride (LaOCl, PrOCl) forms. The LiCl-KCl was purified into a form with a very low concentration (<1 ppm) for the rare earth chlorides.

  11. RE{sub 2}B{sub 8}O{sub 15} (RE = La, Pr, Nd). Syntheses of three new rare earth borates isotypic to Ce{sub 2}B{sub 8}O{sub 15}

    Energy Technology Data Exchange (ETDEWEB)

    Glaetzle, Matthias; Hoerder, Gregor J.; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie

    2016-08-01

    The rare earth borates RE{sub 2}B{sub 8}O{sub 15} (RE = La, Pr, Nd) were synthesized in a Walker-type multianvil apparatus under conditions of 5.5 GPa and 1100 C. Starting from the corresponding rare earth oxides and boron oxide, the syntheses yielded crystalline products of all new compounds that allowed crystal structure analyses based on single-crystal X-ray diffraction data for La{sub 2}B{sub 8}O{sub 15} and Nd{sub 2}B{sub 8}O{sub 15}. The compound Pr{sub 2}B{sub 8}O{sub 15} could be characterized via X-ray powder diffractometry. The results show that the new compounds crystallize isotypically to Ce{sub 2}B{sub 8}O{sub 15} in the monoclinic space group P2/c. The infrared spectra of RE{sub 2}B{sub 8}O{sub 15} (RE = La, Pr, Nd) have also been studied.

  12. Thermodynamics of spin ice in staggered and direct (along the [111] axis) fields in the cluster approximation

    Energy Technology Data Exchange (ETDEWEB)

    Zinenko, V. I., E-mail: zvi@iph.krasn.ru; Pavlovskii, M. S. [Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation)

    2017-02-15

    We have analyzed the low-temperature thermodynamic properties of spin ice in the staggered and direct (acting along the [111] axis) fields for rare-earth oxides with the chalcolamprite structure and general formula Re{sub 2}{sup 3+}Me{sub 2}{sup 4+}O{sub 7}{sup 2-}. Calculations have been performed in the cluster approximation. The results have been compared with experimental temperature dependences of heat capacity and entropy for Dy{sub 2}Ti{sub 2}O{sub 7} compound for different values of the external field in the [111] direction. The experimental data and calculated results have also been compared for the Pr{sub 2}Ru{sub 2}O{sub 7} compound with the antiferromagnetic ordering of magnetic moments of ruthenium ions, which gives rise to the staggered field acting on the system of rare-earth ions. The calculated temperature dependences of heat capacity and entropy are in good agreement with experimental data.

  13. Structural and electrical properties of T′-type Ln{sub 2}CuO{sub 4} (Ln = Pr, Nd, Sm, Eu and Gd) ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Salame, Paresh Hiralal [Department of Applied Physics, Laxminarayan Institute of Technology, RTM Nagpur University, Nagpur, INDIA paresh.salame@gmail.com (India)

    2016-05-23

    T′-type Ln{sub 2}CuO{sub 4} (Ln = Pr, Nd, Sm, Eu and Gd) were successfully synthesized in phase pure form using conventional solid state reaction and sintering route. For all the Ln{sub 2}CuO{sub 4} samples, the solid state reaction temperature was found to be 950 °C and pure phase was realized only after 2-3 intermediate milling and solid state reaction cycles, irrespective of the lanthanide ion radius. Effect of lanthanide ion contraction on the structural properties was clearly revealed by the powder X-ray diffraction, with the XRD peaks observed to be shifting towards higher 2θ values with the decrease in Ln ionic radii. The optimum sintering temperature of these solid state reacted Ln{sub 2}CuO{sub 4} powder was found to be 1100 °C except for Pr{sub 2}CuO{sub 4} powder. The conductivity of these samples were tested over a wide temperature range (−100 to 150 °C), an anomaly was observed in the conductivity of all the Ln{sub 2}CuO{sub 4} samples near the antiferromagnetic ordering temperature of Cu (~ 30 °C), thus suggesting the bearing of ordering of magnetic moments on the electrical properties.

  14. Dynamic and Thermal Turbulent Time Scale Modelling for Homogeneous Shear Flows

    Science.gov (United States)

    Schwab, John R.; Lakshminarayana, Budugur

    1994-01-01

    A new turbulence model, based upon dynamic and thermal turbulent time scale transport equations, is developed and applied to homogeneous shear flows with constant velocity and temperature gradients. The new model comprises transport equations for k, the turbulent kinetic energy; tau, the dynamic time scale; k(sub theta), the fluctuating temperature variance; and tau(sub theta), the thermal time scale. It offers conceptually parallel modeling of the dynamic and thermal turbulence at the two equation level, and eliminates the customary prescription of an empirical turbulent Prandtl number, Pr(sub t), thus permitting a more generalized prediction capability for turbulent heat transfer in complex flows and geometries. The new model also incorporates constitutive relations, based upon invariant theory, that allow the effects of nonequilibrium to modify the primary coefficients for the turbulent shear stress and heat flux. Predictions of the new model, along with those from two other similar models, are compared with experimental data for decaying homogeneous dynamic and thermal turbulence, homogeneous turbulence with constant temperature gradient, and homogeneous turbulence with constant temperature gradient and constant velocity gradient. The new model offers improvement in agreement with the data for most cases considered in this work, although it was no better than the other models for several cases where all the models performed poorly.

  15. Feasibility Test of Commercial CFD Code for Thermal-Hydraulic Analysis of Wire-wrapped Fuel Pin Bundle in SFR

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Chiwoong; Ha, Kwiseok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Haeyong, Jeong [Sejong Univ., Daejeon (Korea, Republic of)

    2014-05-15

    acceptable values with certain ranges. However, the heat transfer is highly over-estimated especially higher Pe. It is not avoidable to simplify the interface between wire and fuel rod, because this geometrical complexity results in huge computational load. Thus, different wire configurations and a no-wire case were selected as the test geometries to estimate the sensitivity of the wire geometry. Compared to a no-wire case, a wire creates a higher pressure drop and heat transfer due to a swirling flow. However, there is no existing heat transfer correlation with wire design parameters. By reducing the wire contact area, the pressure drop slightly increased, but the heat transfer was reduced. Since a reduced contact area increases the frictional area, the thermal resistance is increased. The wire configuration is more sensitive during the heat transfer. The turbulent Prandtl number (Pr{sub t}) was considered in this study, and existing Pr{sub t} correlations were compared with the numerical results.

  16. Magnetic, ferroelectric and leakage current properties of gadolinium doped bismuth ferrite thin films by sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hone-Zern, E-mail: hzc@hust.edu.tw [Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung, Taiwan (China); Kao, Ming-Cheng, E-mail: kmc@hust.edu.tw [Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung, Taiwan (China); Young, San-Lin [Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung, Taiwan (China); Hwang, Jun-Dar [Department of Electrophysics, National Chiayi University, Chiayi, Taiwan (China); Chiang, Jung-Lung [Department of Mobile Technology, Toko University, Chiayi, Taiwan (China); Chen, Po-Yen [Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung, Taiwan (China)

    2015-05-01

    Bi{sub 0.9}Gd{sub 0.1}FeO{sub 3} (BGFO) thin films were fabricated on Pt(111)/Ti/SiO{sub 2}/Si(100) substrates by using the sol–gel technology. The effects of annealing temperature (400–700 °C) on microstructure and multiferroic properties of thin films were investigated. The X-ray diffraction analysis showed that the BGFO thin films had an orthorhombic structure. The thin films showed ferroelectric and ferromagnetic properties with remanent polarization (2P{sub r}) of 10 μC/cm{sup 2}, remnant magnetization (2M{sub r}) of 2.4 emu/g and saturation magnetization (M{sub s}) of 5.3 emu/g. A small leakage current density (J) was 4.64×10{sup −8} A/cm{sup 2} under applied field 100 kV/cm. It was found that more than one conduction mechanism is involved in the electric field range used in these experiments. The leakage current mechanisms were controlled by Poole–Frenkel emission in the low electric field region and by Schottky emission from the Pt electrode in the high field region. - Highlights: • Bi{sub 3.96}Pr{sub 0.04}Ti{sub 2.95}Nb{sub 0.05}O{sub 12} thin films were prepared by sol–gel technology. • Thin films showed 2P{sub r} of 10 μC/cm{sup 2}, 2M{sub r} of 2.4 emu/g and M{sub s} of 5.3 emu/g. • Leakage current mechanisms were controlled by Poole–Frenkel and Schottky emission.

  17. Thermal and spectroscopic study to investigate p-aminobenzoic acid, sodium p-aminobenzoate and its compounds with some lighter trivalent lanthanides

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, J.A.; Nunes, W.D.G.; Colman, T.A.D.; Nascimento, A.L.C.S do [Instituto de Química, UNESP—Universidade Estadual Paulista, Campus Araraquara, Departamento de Química Analítica, Araraquara 14801-970, SP (Brazil); Caires, F.J. [Faculdade de Ciências, UNESP—Universidade Estadual Paulista, Campus Bauru, Departamento de Química, Bauru 17033-260, SP (Brazil); Campos, F.X. [Instituto de Química, UNESP—Universidade Estadual Paulista, Campus Araraquara, Departamento de Química Analítica, Araraquara 14801-970, SP (Brazil); Instituto Federal de Educação, Ciência e Tecnologia de Mato Grosso, Primavera do Leste 78850-000, MT (Brazil); Gálico, D.A. [Instituto de Química, UNICAMP—Universidade Estadual de Campinas, Campinas 13083-970, SP (Brazil); Ionashiro, M., E-mail: massaoi@yahoo.com.br [Instituto de Química, UNESP—Universidade Estadual Paulista, Campus Araraquara, Departamento de Química Analítica, Araraquara 14801-970, SP (Brazil)

    2016-01-20

    Highlights: • The p-aminobenzoic acid melts followed partial evaporation. • The stoichiometry of compounds was established by TG, EA and complexometry. • The TG–DTA curves provided previously unreported information about thermal behavior. - Abstract: The characterization, thermal stability and thermal decomposition of some lighter trivalent lanthanide p-aminobenzoates, Ln(C{sub 7}H{sub 6}NO{sub 2}){sub 3}·H{sub 2}O (Ln = La, Ce, Pr, Nd, Sm), as well as the thermal behavior and spectroscopic study of p-aminobenzoic acid C{sub 7}H{sub 7}NO{sub 2} and its sodium salt were investigated. The following methods were utilized: simultaneous thermogravimetry and differential thermal analysis (TG–DTA) in dynamic dry air and nitrogen atmospheres; differential scanning calorimetry (DSC); middle (MIR) and near (NIR) infrared region spectroscopy; evolved gas analysis (EGA); elemental analysis; complexometry; X-ray diffraction (XRD); and diffuse reflectance spectroscopy (DR) in the ultraviolet and visible regions. All the compounds were obtained monohydrated and the thermal decomposition occurred in two, three or four steps in an air atmosphere, and three or four steps in N{sub 2} atmosphere. In both atmospheres (air and N{sub 2}) the final residues were CeO{sub 2}, Pr{sub 6}O{sub 11}, Ln{sub 2}O{sub 3} (Ln = La, Nd, Sm). The results also provided information concerning the coordination mode and thermal behavior, as well as the identification of the gaseous products which evolved during the thermal decomposition of these compounds. The DR and NIR spectra provided information about the ligand absorption bands and the f–f transitions of the Nd{sup 3+}, Pr{sup 3+} and Sm{sup 3+} ions.

  18. Active groups for oxidative activation of C-H bond in C{sub 2}-C{sub 5} paraffins on V-P-O catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Zazhigalov, V.A. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fizicheskoj Khimii

    1998-12-31

    For the first time in scientific literature, in our joint work with Dr. G. Ladwig in 1978 it was established phase portraite of the oxide vanadium-phosphorus system within wide range of P/V ratios from 0.5 to 3.2. Some later those data were confirmed. By investigation of the properties of individual vanadium-phosphorus phases it was also shown that the active component of such catalysts in n-butane oxidation was vanadyl pyrophosphate phase (VO){sub 2}Pr{sub 2}O{sub 7}. From then the conclusion has been evidenced by numerous publications and at present it has been out of doubt practically all over the world. It was hypothized that the unique properties of (VO){sub 2}P{sub 2}O{sub 7} in the reaction of n-butane oxidation could be explained by the presence of paired vanadyl groups and nearness of the distances between neighbouring vanadyl pairs and that between the first and fourth carbon atoms in n-butane molecule. The molecule activation occured at the latter atoms by proton abstraction. A comparison of the results on n-butane and butenes oxidation over vanadyl pyrophosphate allowed to conclude that the paraffin oxidation did not take place due to the molecule dehydrogenation process at the first stage of its conversion. Up to now, more than 100 papers related to paraffins oxidation over vanadyl pyrophosphate and the physico-chemical properties of the catalyst have been published. The process of n-butane oxidation is realized in practice. But still, the question about the nature of active sites of the catalyst and the reaction mechanism remains open and provokes further investigations. The present paper deals with our opinion about the problem and the experimental results supporting it. (orig.)

  19. DFT and time-resolved IR investigation of electron transfer between photogenerated 17- and 19-electron organometallic radicals

    Energy Technology Data Exchange (ETDEWEB)

    Cahoon, James B.; Kling, Matthias F.; Sawyer, Karma R.; Andersen, Lars K.; Harris, Charles B.

    2008-04-30

    The photochemical disproportionation mechanism of [CpW(CO){sub 3}]{sub 2} in the presence of Lewis bases PR{sub 3} was investigated on the nano- and microsecond time-scales with Step-Scan FTIR time-resolved infrared spectroscopy. 532 nm laser excitation was used to homolytically cleave the W-W bond, forming the 17-electron radicals CpW(CO){sub 3} and initiating the reaction. With the Lewis base PPh{sub 3}, disproportionation to form the ionic products CpW(CO){sub 3}PPh{sub 3}{sup +} and CpW(CO){sub 3}{sup -} was directly monitored on the microsecond time-scale. Detailed examination of the kinetics and concentration dependence of this reaction indicates that disproportionation proceeds by electron transfer from the 19-electron species CpW(CO){sub 3}PPh{sub 3} to the 17-electron species CpW(CO){sub 3}. This result is contrary to the currently accepted disproportionation mechanism which predicts electron transfer from the 19-electron species to the dimer [CpW(CO){sub 3}]{sub 2}. With the Lewis base P(OMe){sub 3} on the other hand, ligand substitution to form the product [CpW(CO){sub 2}P(OMe){sub 3}]{sub 2} is the primary reaction on the microsecond time-scale. Density Functional Theory (DFT) calculations support the experimental results and suggest that the differences in the reactivity between P(OMe){sub 3} and PPh{sub 3} are due to steric effects. The results indicate that radical-to-radical electron transfer is a previously unknown but important process for the formation of ionic products with the organometallic dimer [CpW(CO){sub 3}]{sub 2} and may also be applicable to the entire class of organometallic dimers containing a single metal-metal bond.

  20. Synthesis, crystal structure and optical property of three coordination polymer constructed from m-phenylenediacrylate acid

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, YiFan; Wang, TingTing; Zeng, HePing, E-mail: hpzeng@scut.edu.cn

    2015-01-15

    Three new complexes of the wholly deprotonated flexible ligand m-phenylenediacrylate acid (H{sub 2}mpda), namely, [Zn (mpda) (H{sub 2}O)] [1], [Pr{sub 2}(mpda){sub 2}(H{sub 2}O){sub 2}(CHOO){sub 2}] [2], and [Mn{sub 2}(mpda){sub 2} (H{sub 2}O){sub 4}] [3], were synthesized by the solvothermal reaction. The complexes were characterized by IR spectroscopy, thermogravimetric analysis, and X-ray single-crystal diffraction. A mixed sample [Nd(mpda)(H{sub 2}O)(CHOO)·Pr(mpda)(H{sub 2}O)(CHOO)] [2{sup ]} was also synthesized and studied. Compounds [1] and [2] exhibit a selective sensing function with respect to acetone, and they are a potential luminescent sensory material for the selective detection of Zn{sup 2+} and Ni{sup 2+} ions, respectively. Furthermore, the fluorescent changes of compound [1] upon the addition of cations (Fe{sup 3+} and Zn{sup 2+}, Bi{sup 2+} and Zn{sup 2+}) are utilized to construct two logic gates at the molecular level. - Graphical abstract: Three new complexes of flexible ligand m-phenylenedicarboxylic acid were synthesized by solvothermal reaction. Three metal−organic frameworks exhibiting 1D, 2D, 3D structures, respectively. - Highlights: • Three new complexes of m-phenylenedicarboxylic acid were synthesized. • Three metal−organic frameworks exhibiting 1D, 2D, 3D structures, respectively. • [1] and [2] exhibits a very high quenching effect with acetone. • [1] and [2] are a potential luminescent sensory material for Zn{sup 2+}, Ni{sup 2+} ions. • Two logic gates have been constructed using compound [1].

  1. Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data

    Energy Technology Data Exchange (ETDEWEB)

    Batalha, Natalie M.; /San Jose State U.; Rowe, Jason F.; /NASA, Ames; Bryson, Stephen T.; /NASA, Ames; Barclay, Thomas; /NASA, Ames; Burke, Christopher J.; /NASA, Ames; Caldwell, Douglas A.; /NASA, Ames; Christiansen, Jessie L.; /NASA, Ames; Mullally, Fergal; /NASA, Ames; Thompson, Susan E.; /NASA, Ames; Brown, Timothy M.; /Las Cumbres Observ.; Dupree, Andrea K.; /Harvard-Smithsonian Ctr. Astrophys. /UC, Santa Cruz

    2012-02-01

    New transiting planet candidates are identified in sixteen months (May 2009 - September 2010) of data from the Kepler spacecraft. Nearly five thousand periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1091 viable new planet candidates, bringing the total count up to over 2,300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multiquarter photo-center offsets derived from difference image analysis which identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the new candidates. Ephemerides (transit epoch, T{sub 0}, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (R{sub P}/R{sub {star}}), reduced semi-major axis (d/R{sub {star}}), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (197% for candidates smaller than 2R{sub {circle_plus}} compared to 52% for candidates larger than 2R{sub {circle_plus}}) and those at longer orbital periods (123% for candidates outside of 50 day orbits versus 85% for candidates inside of 50 day orbits). The gains are larger than expected from increasing the observing window from thirteen months (Quarter 1 - Quarter 5) to sixteen months (Quarter 1 - Quarter 6). This demonstrates the benefit of continued development of pipeline analysis software. The fraction of all host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant.

  2. Synthesis and properties of Pr-substituted MgZn ferrites for core materials and high frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Mukhtar, Muhammad Waqas; Irfan, Muhammad [Department of Physics, Federal Urdu University of Arts, Science and Technology, Islamabad 44000 (Pakistan); Ahmad, Ishtiaq; Ali, Ihsan [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan); Khan, Muhammad Azhar [Department of Physics, Islamia University, Bahawalpur (Pakistan); Abbas, Ghazanfar [Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan); Rana, M.U. [Center of Excellence in Solid State Physics, University of the Punjab, Lahore (Pakistan); Ali, Akbar [Department of Basic Sciences, Riphah International University, Islamabad-44000 (Pakistan); Ahmad, Mukhtar, E-mail: ahmadmr25@yahoo.com [Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan)

    2015-05-01

    A series of single phase spinel ferrites having chemical formula Mg{sub 0.5}Zn{sub 0.5}Pr{sub x}Fe{sub 2−x}O{sub 4} (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared using the sol–gel technique after sintering at 700 °C. The thermal decomposition behavior of an as prepared powder was investigated by means of DTA/TGA analyses. The sintered powders were then characterized by Fourier transform infrared spectroscope, X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscope and vibrating sample magnetometer. X-ray diffraction patterns confirm the single phase spinel structure of prepared ferrites without the presence of any impurity phase. The value of lattice parameter (a) increases with the increase of Pr contents (x) into the spinel lattice. The grain size estimated from electron microscope images is in the range of 2.75–5.4 µm which confirms the spinel crystalline nature of the investigated samples. The saturation magnetization (M{sub s}) decreases whereas coercivity (H{sub c}) increases with the increase of Pr contents (x). The measured parameters suggest that these materials are favorable for high frequency applications and as core materials. - Highlights: • Pr-substituted spinel ferrites synthesized by autocombustion route have been investigated. • The average grain size was in the range of 2.75–5.4 µm estimated by SEM technique. • The (M{sub s}) decreases whereas (H{sub c}) increases with the increase of Pr contents (x). • These parameters are favorable for high frequency applications and as core materials.

  3. Synthesis, structure, and reactivity of (eta/sup 5/-indenyl)tetracarbonylvanadium(I)

    Energy Technology Data Exchange (ETDEWEB)

    Kowaleski, R.M.; Kipp, D.O.; Stauffer, K.J.; Swepston, P.N.; Basolo, F.

    1985-11-06

    The compound (eta/sup 5/-C/sub 9/H/sub 7/)V(CO)/sub 4/ was prepared for the first time and its structure determined by X-ray crystallography. The structure closely resembles that of (eta/sup 5/-C/sub 5/H/sub 5/)V(CO)/sub 4/, with the V(CO)/sub 4/ moiety forming a square pyramid, and a planar indenyl group coordinating to the vanadium through the five-membered ring. The compound crystallizes in the space group Pna2/sub 1/ with a = 22.722 (6) A, b = 6.814 (1) A, c = 7.449 (2) A, and Z = 4. The reaction of (eta/sup 5/-C/sub 9/H/sub 7/)V(CO)/sub 4/ with P(n-Bu)/sub 3/ and with P(OEt)/sub 3/ to form (eta/sup 5/-C/sub 9/H/sub 7/)V(CO)/sub 3/PR/sub 3/ takes place by a dissociative (S/sub N/1) process with kinetic parameters of k(100/sup 0/C) = 3.7 x 10..sqrt../sub 4/ s/sup -1/, ..delta..H = 31.9 +/- 0.3 kcal/mol, and ..delta..S = 10.5 +/- 0.9 cal/(mol K). Again the indenyl effect on dissociative reactions is shown to be much smaller than on associative reactions when compared with the effect for corresponding cyclopentadienyl compounds. 18 references, 1 figure, 4 tables.

  4. Identification and development of nanoscintillators for biotechnology applications

    Energy Technology Data Exchange (ETDEWEB)

    Jung, J.Y. [Materials Science and Engineering Program, University of California—San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (United States); Hirata, G.A. [Centro de Nanociencias y Nanotecnologia UNAM, Km 107 Carretera Tijuana-Ensenada, Ensenada 22860, B.C. (Mexico); Gundiah, G.; Derenzo, S. [Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720 (United States); Wrasidlo, W.; Kesari, S.; Makale, M.T. [Translational Neuro-Oncology Laboratories and Department of Neurosciences, University of California, San Diego Moores Cancer Center, 3855 Health Sciences Dr., La Jolla, CA 92093 (United States); McKittrick, J., E-mail: jmckittrick@ucsd.edu [Materials Science and Engineering Program, University of California—San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (United States); Department of Mechanical and Aerospace Engineering, University of California—San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (United States)

    2014-10-15

    The purpose of this work is to investigate the radioluminescence emission properties in the range 300–400 nm of 15 nanoscintillators for potential application in radiation-triggered photodynamic therapy, and compare to those reported for single crystals with same composition. Garnet structures, silicates and an oxide activated with Pr{sup 3+} or Ce{sup 3+} were prepared by combustion synthesis and subsequently annealed at 1200 °C. The (Y{sub 1−x}Pr{sub x}){sub 3}Al{sub 5}O{sub 12} (x=0.0075, 0.01, 0.0125, 0.015, 0.0175) compositions have the highest luminosity, showing concentration behavior for x>0.01. The average particle size of (Y{sub 0.99}Pr{sub 0.01}){sub 3}Al{sub 5}O{sub 12} is 80 nm, which was obtained by post-annealing high power ultrasonic processing. These results demonstrate that (Y{sub 1−x}Pr{sub x}){sub 3}Al{sub 5}O{sub 12} is an excellent candidate for nanoscintillators-based biomedical applications. Comparisons to single crystal data indicate a general trend cannot be established between the radioluminescence emission intensity of nanoscintillators and single crystals with the same composition. - Highlights: • Nanoscintillators were synthesized by combustion reaction with high power ultrasonic processing. • Nanocrystalline (Y{sub 1−x}Pr{sub x}){sub 3}Al{sub 5}O{sub 12} has potential in radiation-triggered photodynamic therapy. • Nanocrystalline scintillators do not follow the same general trend as single crystal scintillators.

  5. The thermochemical of cerias in anodic conditions of fuel cell; A termoquimica de cerias nas condicoes anodicas de pilha a combustivel

    Energy Technology Data Exchange (ETDEWEB)

    Caffarena, Valeska da Rocha; Malta, Luiz Fernando Brum; Ogasawara, Tsuneharu [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia. Programa de Engenharia Metalurgica e de Materiais]. E-mail: valeska@metalmat.ufrj.br; Santos, Jorge Gomes dos [Instituto de Engenharia Nuclear (IEN), Rio de Janeiro, RJ (Brazil)]. E-mail: jg@ien.gov.br

    2003-07-01

    Gibbs' free energies of cerias doped with rare earths estimated from experimental data on hydrothermal synthesis allowed to calculate and construct diagrams of log{sub 10} pH{sub 2}O/pH{sub 2} versus temperature and log{sub 10} pCO{sub 2}/pCO versus temperature, for x = 0.1 and x = 0.01 (where x = fraction of the original ceria converted to Ce{sub 2}O{sub 3}). These diagrams show that cerias doped with rare-earths are more stable than pure ceria, under contact with hydrogen gas or hydrogen-carbon monoxide gaseous mixture which is found in anode region of solid oxide fuel cells operated with pure hydrogen or in situ reformed hydrocarbons. Among doped cerias, the chemical stability increases in the order:: Ce{sub 1.7}Eu{sub .0.}3O{sub 3.85} , Ce{sub 7.47}Sm{sub 1.53}TbO{sub 18.735} , Ce{sub 0.8}La{sub 0.2}O{sub 1.9} e Ce{sub 0.8}Pr{sub 0.4}O{sub 1.8}. In the case of fuel cell operation with CO +H{sub 2} mixture, the Boudouard's equilibrium determines the operational conditions in log{sub 10} pCO{sub 2}/pCO versus temperature domain. (author)

  6. Development of novel CO{sub 2}-stable oxygen permeable dual phase membranes for CO{sub 2} capture in an oxy-fuel process

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Huixia

    2012-07-19

    the cubic perovskite structure, which then becomes unstable. Chapter 3 demonstrated the development of the CO{sub 2}-stable alkaline-earth metals-free dual phase membranes. There novel dual phase membranes ofthe compositions: 40 wt.% NiFe{sub 2}O{sub 4-{delta}} - 60 wt.% Ce{sub 0.9}Gd{sub 0.1}O{sub 2-{delta}} (40NFO-60CGO), 40 wt.% Fe{sub 2}O{sub 3-{delta}} - 60 wt.% Ce{sub 0.9}Gd{sub 0.1}O{sub 2-{delta}} (40FO-60CGO), 40 wt.% Mn{sub 1.5}Co{sub 1.5}O{sub 4-{delta}} - 60 wt.% Ce{sub 0.9}Pr{sub 0.1}O{sub 2-{delta}} (40MCO-60CPO) were developed using different methods, including mixing powder by hand, mixing powder by ball-milling, one-pot single-step sol-gel method. The structures of the dual phase membranes were studied in detail by various analytical techniques such as in-situ XRD, SEM, back-scattered SEM (BSEM), EDXS, STEM and selected-area electron diffraction (SAED). lt was found that all these dual phase membranes show two weil separated phases. Moreover, the in-situ one-pot single-step sol-gel method was found to be the best way to prepare well-distribution dual phase membranes. On the other hand, since our dual phase membranes do not contain alkaline-earth metals, it can be expected that they are C02-stable. The oxygen permeation flux measurements were performed for a few days and no decrease of the oxygen permeation flux was observed, which confirms that these dual phase membranes are CO{sub 2}-stable. However, it is shown that all these materials are not stable in reducing atmosphere, since they contain easily reducible metals oxides of Co, Ni in their compositions. Chapter 4 demonstrated the development of a novel cobalt-free noble metal-free oxygen-permeable 40 wt.% Pr{sub 0.6}Sr{sub 0.4}FeO{sub 3-{delta}} - 60 wt.% Ce{sub 0.9}Pr{sub 0.1}O{sub 2-{delta}} (40PSFO-60CPO) dual phase membrane. The structures of the dual phase membranes were investigated in detail by various analytical techniques such as in-situ XRD, SEM, BSEM and EDXS. ln-situ XRD measurements

  7. Magnetic properties of Sr{sub 3-x}Ca{sub x}Ru{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, Kotaro; Kosaka, Masashi; Katano, Susumu [Graduate School of Science and Engineering, Saitama University, Saitama 338-8570 (Japan); Yoshida, Yoshiyuki, E-mail: iwata@hp.phy.saitama-u.ac.j [Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568 (Japan)

    2009-03-01

    We report the magnetization data of single crystalline Sr{sub 3-x}Ca{sub x}Ru{sub 2}O{sub 7} (x = 1.5, 2.0, 3.0) grown by a floating-zone method. In the magnetic phase diagram of this system, a phase with a ferromagnetic correlation (0.5 <=x <= 1.2) adjoins a two-dimensional (2D) metallic and antiferromagnetic phase (1.2 <= x <= 3). In the antiferromagnetic and 2D-metallic phase, the magnetic susceptibilities indicate that the magnetic easy axis changes continuously from the ab-plane to c-axis with increasing Sr content. Our results exhibit that the metamagnetic transition of Ca{sub 3}Ru{sub 2}O{sub 7}, which is on the basis of a tunneling magnetoresistance, shifts to lower field and the transition becomes broad with increasing Sr content. Moreover, the magnetization data at T = 5 K for x = 1.5, 2.0 show a hysteresis, which suggests that the magnetic ground state is a canted antiferromagnetic one in this phase.

  8. Homobimetallic Ruthenium-N-Heterocyclic Carbene Complexes For Olefin Metathesis

    Science.gov (United States)

    Sauvage, Xavier; Demonceau, Albert; Delaude, Lionel

    In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene (NHC) ligands are reviewed. Emphasis is placed on the last category of bimetallic compounds. Three representatives of this new type of molecular scaffold were investigated. Thus, [(p-cymene)Ru(m-Cl)3RuCl (h2-C2H4)(L)] complexes with L = PCy3 (15a), IMes (16a), or IMesCl2 (16b) were prepared. They served as catalyst precursors for cross-metathesis (CM) of various styrene derivatives. These experiments revealed the outstanding aptitude of complex 16a (and to a lesser extent of 16b) to catalyze olefin metathesis reactions. Contrary to monometallic Ru-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addition of a diazo compound nor visible light illumination to initiate the ring-opening metathesis of norbornene or cyclooctene. When diethyl 2,2-diallylmalonate and N,N-diallyltosylamide were exposed to 16a,b, a mixture of cycloisomerization and ring-closing metathesis (RCM) products was obtained in a nonselective way. Addition of phenylacetylene enhanced the metathetical activity while completely repressing the cycloisomerization process.

  9. Mechanism of RuO2 crystallization in borosilicate glass: an original in situ ESEM approach.

    Science.gov (United States)

    Boucetta, Hassiba; Podor, Renaud; Stievano, Lorenzo; Ravaux, Johann; Carrier, Xavier; Casale, Sandra; Gossé, Stéphane; Monteiro, Amélie; Schuller, Sophie

    2012-03-19

    Ruthenium, a fission product arising from the reprocessing of spent uranium oxide (UOX) fuel, crystallizes in the form of acicular RuO(2) particles in high-level waste containment glass matrices. These particles are responsible for significant modifications in the physicochemical behavior of the glass in the liquid state, and their formation mechanisms are a subject of investigation. The chemical reactions responsible for the crystallization of RuO(2) particles with acicular or polyhedral shape in simplified radioactive waste containment glass are described. In situ high-temperature environmental scanning electron microscopy (ESEM) is used to follow changes in morphology and composition of the ruthenium compounds formed by reactions at high temperature between a simplified RuO(2)-NaNO(3) precursor and a sodium borosilicate glass (SiO(2)-B(2)O(3)-Na(2)O). The key parameter in the formation of acicular or polyhedral RuO(2) crystals is the chemistry of the ruthenium compound under oxidized conditions (Ru(IV), Ru(V)). The precipitation of needle-shaped RuO(2) crystals in the melt might be associated with the formation of an intermediate Ru compound (Na(3)Ru(V)O(4)) before dissolution in the melt, allowing Ru concentration gradients. The formation of polyhedral crystals is the result of the direct incorporation of RuO(2) crystals in the melt followed by an Ostwald ripening mechanism. © 2012 American Chemical Society

  10. Spontaneous adsorption of 3,5-bis(3,5-dinitrobenzoylamino) benzoic acid onto carbon

    Energy Technology Data Exchange (ETDEWEB)

    Paez, Julieta I.; Strumia, Miriam C. [Departamento de Quimica Organica (IMBIV-CONICET), Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Cordoba (5000) (Argentina); Passeggi, Mario C.G. [Laboratorio de Superficies e Interfaces (INTEC-CONICET), Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santa Fe (3000) (Argentina); Ferron, Julio [Laboratorio de Superficies e Interfaces (INTEC-CONICET), Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santa Fe (3000) (Argentina); Departamento de Materiales, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santa Fe (3000) (Argentina); Baruzzi, Ana M. [Departamento de Fisicoquimica (INFIQC-CONICET), Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Cordoba (5000) (Argentina); Brunetti, Veronica [Departamento de Fisicoquimica (INFIQC-CONICET), Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Cordoba (5000) (Argentina)], E-mail: brunetti@fcq.unc.edu.ar

    2009-07-01

    Dendritic molecules contain multifunctional groups that can be used to efficiently control the properties of an electrode surface. We are developing strategies to generate a highly functionalized surface using multifunctional and rigid dendrons immobilized onto different substrates. In the present work, we explore the immobilization of a dendritic molecule: 3,5-bis(3,5-dinitrobenzoylamino) benzoic acid (D-NO{sub 2}) onto carbon surfaces showing a simple and rapid way to produce conductive surfaces with electroactive chemical functions. The immobilized D-NO{sub 2} layer has been characterized using atomic force microscopy and cyclic voltammetry. D-NO{sub 2} adsorbs onto carbon surfaces spontaneously by dipping the electrode in dendron solutions. Reduction of this layer generates the hydroxylamine product. The resulting redox-active layer exhibits a well-behaved redox response for the adsorbed nitroso/hydroxylamine couple. The film permeability of the derivatized surface has been analyzed employing the electrochemical response of redox probes: Ru(NH{sub 3}){sub 6}{sup 3+}/Ru(NH{sub 3}){sub 6}{sup 2+} and Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-}. Electrocatalytic oxidation of nicotinamide adenine dinucleotide onto a modified carbon surface was also observed.

  11. A novel technique for hydrogen production from hog-manure in supercritical partial oxidation (SCWPO)

    Energy Technology Data Exchange (ETDEWEB)

    Youssef, Emhemmed A.; Charpentier, Paul [Western Ontario Univ., London, ON (Canada). Dept. of Chemical and Biochemical Engineering; Nakhla, George [Western Ontario Univ., London, ON (Canada). Dept. of Chemical and Biochemical Engineering; Western Ontario Univ., London, ON (Canada). Dept. of Civil and Environmental Engineering; Elbeshbishy, Elsayed; Hafez, Hisham [Western Ontario Univ., London, ON (Canada). Dept. of Civil and Environmental Engineering

    2010-07-01

    In this study, the catalytic hydrogen production from hog manure using supercritical water partial oxidation was investigated in a batch reactor at a temperature of 500 C, and pressure of 28 MPa using several metallic catalysts. Hog manure was characterized by a total and soluble chemical oxygen demand (TCOD, SCOD) of 57000 and 28000 mg/L, total and volatile suspended solids (TSS, VSS) of 25000, 19000, and ammonia of 2400 mg/L, respectively. The order of H{sub 2} production was the following: Pd/AC > Ru/Al{sub 2}O{sub 3} > Ru/AC > AC > NaOH. The order of COD reduction efficiency was as follows: NaOH > Ru/AC > AC > Ru/Al{sub 2}O{sub 3} > Pd/AC. The behaviour of the volatile fatty acids (VFA's), ethanol, methanol, ammonia, H{sub 2}S, and Sulfate was investigated experimentally and discussed. A 35 % reduction in the H{sub 2} and CH{sub 4} yields was observed in the sequential gasification partial oxidation (oxidant at an 80 % of theoretical requirement) experiments compared to the gasification experiments (catalyst only). Moreover, this reduction in gas yields was coincided with a 45 % reduction in the liquid effluent chemical oxygen demand (COD), 60 % reduction of the ammonia concentration in the liquid effluent, and 20 % reduction in the H{sub 2}S concentration in the effluent gas. (orig.)

  12. The Uranian system - an overview

    Science.gov (United States)

    Bergstralh, Jay T.; Miner, Ellis D.

    Results of many years of observations from the ground and from the Voyager encounter with Venus are presented which clarify a number of issues that were subjects of speculation or partial information. The new issues that the encounter brought to light are outlined. The encounter revealed additional rings, extensive dust associated with them, and complexities, including azimuthal asymmetries. Uranus possesses a strong (about 1 gauss) magnetic field with a bizarre geometry that can be described as a dipole offset 0.3 RU from the center of the planet and tilted approximately 60 deg with respect to the axis of rotation. It is argued that it is produced by a magnetohydrodynamic dynamo at about 0.4 RU from the planet's center. It is inferred from this that at least part of the interior is a convective fluid, indicating an adiabatic temperature profile and a warm interior. The magnetic field produces a magnetosphere with some peculiar characteristics, owing to the unique orientation of the dipole axis with respect to the direction of the solar wind flow.

  13. Ruthenium and iron complexes with benzotriazole and benzimidazole derivatives as simple models for proton-coupled electron transfer systems

    Directory of Open Access Journals (Sweden)

    Rocha Reginaldo C.

    2001-01-01

    Full Text Available Iron and ruthenium complexes of the type [M-LH]n (where M = RuII,III(NH35(2+,3+, RuII,III(edta2-,- [edta = ethylenedinitrilotetraacetate], or FeII,III(CN5(3-,2- and LH = benzotriazole or benzimidazole were prepared and characterized in aqueous solutions by means of electrochemical and spectroelectrochemical methods. Special emphasis was given to the pH-dependent redox processes, exhibited by all the investigated complexes. From their related Pourbaix diagrams, which displayed a typically Nernstian behavior, the pKa and formal reduction potential values were extracted. In addition, these E1/2 versus pH curves were also used to illustrate the partitioning relationship concerning the redox and acid-base species, and their interconversion equilibria. The active area in which the dependence of the M III/M II couple on the pH takes place, as delimited by pKaIII and pKaII, was taken into account in order to evaluate the usefulness of such simple complexes as models for proton-coupled electron transfer (PCET. The results were interpreted in terms of the acceptor/donor electronic character of the ligands and sigma,pi-metal-ligand interactions in both redox states of the metal ion.

  14. Distribution and incorporation mode of the herbicide MCPA in soil derived organo-clay complexes.

    Science.gov (United States)

    Riefer, Patrick; Klausmeyer, Timm; Schmidt, Burkhard; Schäffer, Andreas; Schwarzbauer, Jan

    2017-08-03

    The incorporation of xenobiotics into soil, especially via covalent bonds or sequestration has a major influence on the environmental behavior including toxicity, mobility, and bioavailability. The incorporation mode of 4-chloro-2-methylphenoxyacetic acid (MCPA) into organo-clay complexes has been investigated under a low (8.5 mg MCPA/kg soil) and high (1000 mg MCPA/kg soil) applied concentration, during an incubation period of up to 120 days. Emphasis was laid on the elucidation of distinct covalent linkages between non-extractable MCPA residues and humic sub-fractions (humic acids, fulvic acids, and humin). The cleavage of compounds by a sequential chemical degradation procedure (OH-, BBr3, RuO4, TMAH thermochemolysis) revealed for both concentration levels ester/amide bonds as the predominate incorporation modes followed by ether linkages. A possible influence of the soil microbial activity on the mode of incorporation could be observed in case of the high level samples. Structure elucidation identified MCPA as the only nonextractable substance, whereas the metabolite 4-chloro-2-methylphenol was additionally found as bioavailable and bioaccessible compound.

  15. Nitric Oxide and Brazilian Propolis Combined Accelerates Tissue Repair by Modulating Cell Migration, Cytokine Production and Collagen Deposition in Experimental Leishmaniasis

    Science.gov (United States)

    Miranda, Milena Menegazzo; Panis, Carolina; Cataneo, Allan Henrique Depieri; da Silva, Suelen Santos; Kawakami, Natalia Yoshie; Lopes, Luiz Gonzaga de França; Morey, Alexandre Tadachi; Yamauchi, Lucy Megumi; Andrade, Célia Guadalupe Tardelli de Jesus; Cecchini, Rubens; da Silva, Jean Jerley Nogueira; Sforcin, José Maurício; Conchon-Costa, Ivete; Pavanelli, Wander Rogério

    2015-01-01

    The fact that drugs currently used in the treatment of Leishmania are highly toxic and associated with acquired resistance has promoted the search for new therapies for treating American tegumentary leishmaniasis (ATL). In this study, BALB/c mice were injected in the hind paw with Leishmania (Leishmania) amazonensis and subsequently treated with a combination of nitric oxide (NO) donor (cis-[Ru(bpy) 2imN(NO)](PF6)3) (Ru-NO), given by intraperitoneal injection, and oral Brazilian propolis for 30 days. Ru-NO reached the center of the lesion and increased the NO level in the injured hind paw without lesion exacerbation. Histological and immunological parameters of chronic inflammation showed that this combined treatment increased the efficacy of macrophages, determined by the decrease in the number of parasitized cells, leading to reduced expression of proinflammatory and tissue damage markers. In addition, these drugs in combination fostered wound healing, enhanced the number of fibroblasts, pro-healing cytokines and induced collagen synthesis at the lesion site. Overall, our findings suggest that the combination of the NO donor Ru-NO and Brazilian propolis alleviates experimental ATL lesions, highlighting a new therapeutic option that can be considered for further in vivo investigations as a candidate for the treatment of cutaneous leishmaniasis. PMID:25973801

  16. Influence of the Belousov–Zhabotinsky substrate concentration on the lifetime and self-oscillating behavior of a polymer solution

    Directory of Open Access Journals (Sweden)

    Nakazumi Tomoka

    2017-01-01

    Full Text Available In this study, we synthesized a self-oscillating polymer chain with N-ethylacrylamide (NEAAm as the main-chain. This exhibits a higher lower critical solution temperature than an N-isopropylacrylamide main chain. We subsequently measured the transmittance self-oscillation of poly[NEAAm-co-Ru(bpy3] [Ru(bpy3 = 4-vinyl-4’-methyl-2,2’-bipyridinebis(2,2’ bipyridinebis(hexafluorophosphate ruthenium] solutions comprising three Belousov-Zhabotinsky (BZ substrates (malonic acid, sodium bromate, and sulfuric acid, under stirring at constant temperature. The soluble-insoluble self-oscillation of the polymer solution originated from the different solubility of the Ru(bpy3 moiety as a catalyst of the BZ reaction in the reduced and oxidized states. We demonstrated that the self-oscillating behavior was significantly affected by the initial concentration of the sodium bromate. Moreover, we clarified that the lifetime of the transmittance self-oscillation can be predicted from the initial concentration of malonic acid.

  17. Investigation of structural, electronic and anisotropic elastic properties of Ru-doped WB{sub 2} compound by increased valence electron concentration

    Energy Technology Data Exchange (ETDEWEB)

    Surucu, Gokhan, E-mail: g_surucu@yahoo.com [Ahi Evran University, Department of Electric and Energy, 40100, Kirsehir (Turkey); Gazi University, Photonics Application and Research Center, 06500, Ankara (Turkey); Kaderoglu, Cagil [Ankara University, Department of Engineering Physics, 06100, Ankara (Turkey); Deligoz, Engin; Ozisik, Haci [Aksaray University, Department of Physics, 68100, Aksaray (Turkey)

    2017-03-01

    First principles density functional theory (DFT) calculations have been used to investigate the structural, anisotropic elastic and electronic properties of ruthenium doped tungsten-diboride ternary compounds (W{sub 1−x}Ru{sub x}B{sub 2}) for an increasing molar fraction of Ru atom from 0.1 to 0.9 by 0.1. Among the nine different compositions, W{sub 0.3}Ru{sub 0.7}B{sub 2} has been found as the most stable one due to the formation energy and band filling theory calculations. Moreover, the band structures and partial density of states (PDOS) have been computed for each x composition. After obtaining the elastic constants for all x compositions, the secondary results such as Bulk modulus, Young’s modulus, Poisson’s ratio, Shear modulus, and Vickers Hardness of polycrystalline aggregates have been derived and the relevant mechanical properties have been discussed. In addition, the elastic anisotropy has been visualized in detail by plotting the directional dependence of compressibility, Poisson ratio, Young’s and Shear moduli. - Highlights: • Effects of Ru substitution in WB{sub 2} using increased valence electron concentration. • Structural, electronic, mechanic and elastic properties for increasing Ru content. • Considered alloys are incompressible, brittle, stiffer and high hard materials.

  18. The relationship between iron status and thyroid hormone concentration in iron-deficient adolescent Iranian girls.

    Science.gov (United States)

    Eftekhari, Mohammad Hassan; Keshavarz, Seyed Ali; Jalali, Mahmood; Elguero, Eric; Eshraghian, Mohammad R; Simondon, Kirsten B

    2006-01-01

    Extensive data from animal and human studies indicate that iron deficiency impairs thyroid metabolism. The aim of this study was to determine thyroid hormone status in iron-deficient adolescent girls. By stepwise random sampling from among all public high schools for girls in Lar and its vicinity in southern Iran, 103 out of 431 iron deficient subjects were selected. Urine and serum samples were collected and assayed for urinary iodine and serum ferritin, iron, total iron binding capacity (TIBC), thyroid stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3), free thyroid hormones (fT4 and fT3), triiodothyronine resin uptake (T3RU), reverse triiodothyronine (rT3), selenium and albumin concentrations. Hematological indices for iron status confirmed that all subjects were iron-deficient. There was a significant correlation between T4 and ferritin (r = 0.52, P < 0.001) and between TSH and ferritin (r = -0.3, P < 0.05). Subjects with low serum ferritin had a higher ratio of T3/T4 (r = -0.42, P < 0.01). Using stepwise regression analysis, only ferritin contributed significantly to the rT3 concentration (r = -0.35, P < 0.01). The results indicate that the degree of iron deficiency may affect thyroid hormone status in iron-deficient adolescent girls.

  19. CFD modelling of supercritical water flow and heat transfer in a 2 × 2 fuel rod bundle

    Energy Technology Data Exchange (ETDEWEB)

    Podila, Krishna, E-mail: krishna.podila@cnl.ca; Rao, Yanfei, E-mail: yanfei.rao@cnl.ca

    2016-05-15

    Highlights: • Bare and wire wrapped 2 × 2 fuel rod bundles were modelled with CFD. • Sensitivity of predictions to SST k–ω, v{sup 2}–f and turbulent Prandtl number was tested. • CFD predictions were assessed with experimentally reported fuel wall temperatures. - Abstract: In the present assessment of the CFD code, two heat transfer experiments using water at supercritical pressures were selected: a 2 × 2 rod bare bundle; and a 2 × 2 rod wire-wrapped bundle. A systematic 3D CFD study of the fluid flow and heat transfer at supercritical pressures for the rod bundle geometries was performed with the key parameter being the fuel rod wall temperature. The sensitivity of the prediction to the steady RANS turbulence models of SST k–ω, v{sup 2}–f and turbulent Prandtl number (Pr{sub t}) was tested to ensure the reliability of the predicted wall temperature obtained for the current analysis. Using the appropriate turbulence model based on the sensitivity analysis, the mesh refinement, or the grid convergence, was performed for the two geometries. Following the above sensitivity analyses and mesh refinements, the recommended CFD model was then assessed against the measurements from the two experiments. It was found that the CFD model adopted in the current work was able to qualitatively capture the trends reported by the experiments but the degree of temperature rise along the heated length was underpredicted. Moreover, the applicability of turbulence models varied case-by-case and the performance evaluation of the turbulence models was primarily based on its ability to predict the experimentally reported fuel wall temperatures. Of the two turbulence models tested, the SST k–ω was found to be better at capturing the measurements at pseudo-critical and supercritical test conditions, whereas the v{sup 2}–f performed better at sub-critical test conditions. Along with the appropriate turbulence model, CFD results were found to be particularly sensitive to

  20. Redox behavior of a low-doped Pr-CeO{sub 2}(111) surface. A DFT+U study

    Energy Technology Data Exchange (ETDEWEB)

    Milberg, Brian [ITHES, UBA-CONICET, Departamento de Ingeniería Química, Pabellón de Industrias, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Juan, Alfredo [Departamento de Física & IFISUR, UNS-CONICET, Avda. Alem 1253, 8000 Bahía Blanca (Argentina); Irigoyen, Beatriz, E-mail: beatriz@di.fcen.uba.ar [ITHES, UBA-CONICET, Departamento de Ingeniería Química, Pabellón de Industrias, Ciudad Universitaria, 1428 Buenos Aires (Argentina)

    2017-04-15

    Highlights: • Pr doping facilitates oxygen donation due to the easy formation of Pr{sup 3+}/Pr{sup 4+} and Ce{sup 3+}/Ce{sup 4+} redox couples. • Pr doping also favors the formation of superoxide (O{sub 2}{sup −}) radicals on surface O-holes. • CO can be oxidized by superoxide radical forming a CO{sub 2} molecule floating on the surface. • CO can also interact on the (O{sub 2}{sup −})/Pr{sup 3+} interphase and forms weakly adsorbed carbonate-type intermediates. - Abstract: In this work, we investigated the redox behavior (donation and replenishing of oxygen) of a low praseodymium (Pr)-doped CeO{sub 2}(111) surface. We considered a 3.7 at.% Pr doping and performed density functional calculations using the GGA formalism with the ‘U’ correction on Ce(4f) and Pr(4f) orbitals. Our results indicate that Pr doping promotes oxygen donation by lowering the energy necessary to form surface anionic vacancies. When the Ce{sub 0.963}Pr{sub 0.037}O{sub 2}(111) surface donates one oxygen, the two excess electrons locate on Pr and Ce cations and reduce them to Pr{sup 3+} and Ce{sup 3+} ones. Praseodymium doping also favors the activation of O{sub 2} molecule on surface O-holes, leading to formation of a superoxide (O{sub 2}{sup −}) radical as well as to reoxidation of the Ce{sup 3+} cation to Ce{sup 4+} one. Additionally, we used the CO molecular adsorption for testing the reactivity of those superoxide species. The calculations expose the ability of these radicals to oxidize CO forming a CO{sub 2} molecule floating on the surface. However, when the superoxide is in the immediate vicinity of Pr dopant a carbonate-type species is formed. Our theoretical results may help to gain insight into redox properties and improved catalytic performance of low-doped Pr-CeO{sub 2} solids.

  1. A NOVEL APPROACH TO CATALYTIC DESULFURIZATION OF COAL

    Energy Technology Data Exchange (ETDEWEB)

    John G. Verkade

    2001-11-01

    Column chromatographic separation of the S=PBu{sub 3}/PBu{sub 3} product mixture followed by weighing the S=PBu{sub 3}, and by vacuum distillation of S=PBu{sub 3}/PBu{sub 3}mixture followed by gas chromatographic analysis are described. Effects of coal mesh size, pre-treatment with methanol Coal (S) + excess PR{sub 3} {yields} Coal + S=PR{sub 3}/PBu{sub 3} and sonication on sulfur removal by PBu{sub 3} revealed that particle size was not observed to affect desulfurization efficiency in a consistent manner. Coal pretreatment with methanol to induce swelling or the addition of a filter aid such as Celite reduced desulfurization efficiency of the PBu{sub 3} and sonication was no more effective than heating. A rationale is put forth for the lack of efficacy of methanol pretreatment of the coal in desulfurization runs with PBu{sub 3}. Coal desulfurization with PBu{sub 3} was not improved in the presence of miniscule beads of molten lithium or sodium as a desulfurizing reagent for SPBu{sub 3} in a strategy aimed at regenerating PBu{sub 3} inside coal pores. Although desulfurization of coals did occur in sodium solutions in liquid ammonia, substantial loss of coal mass was also observed. Of particular concern is the mass balance in the above reaction, a problem which is described in some detail. In an effort to solve this difficulty, a specially designed apparatus is described which we believe can solve this problem reasonably effectively. Elemental sodium was found to remove sulfur quantitatively from a variety of polycyclic organosulfur compounds including dibenzothiophene and benzothiophene under relatively mild conditions (150 C) in a hydrocarbon solvent without requiring the addition of a hydrogen donor. Lithium facilitates the same reaction at a higher temperature (254 C). Mechanistic pathways are proposed for these transformations. Curiously, dibenzothiophene and its corresponding sulfone was virtually quantitatively desulfurized in sodium solutions in liquid

  2. Determination of trace elements in high pure rare earth oxide by double focusing inductively coupled plasma mass spectrometry (HR ICP-MS) and high performance liquid chromatography (HPLC) techniques; Determinacao de impurezas metalicas em oxidos de terras raras de alta pureza pela espectrometria de massa (setor magnetico) com fonte de plasma induzida por argonio (HR ICP-MS) e cromatografia liquida de alto desempenho (HPLC)

    Energy Technology Data Exchange (ETDEWEB)

    Pedreira Filho, Walter dos Reis

    2000-07-01

    Rare earth oxides are used in several technological fields whose applications can be observed in several areas of modern technology, among which are included: lasers, semiconductors semi, high purity materials and metallic alloys. The field of applications of the rare earth elements is quite wide. Several important industrial applications are ceramics, catalysts and metallurgical as well as research areas and high technology sectors. Such applications have been presenting an accentuated growth in the last years. Chemical characterization of rare earth oxides of high purity has been constituting one of the major challenges of analytical chemistry. Several analytical techniques were used for chemical characterization of high purity rare earth the oxides. Even so, those techniques present limitations when one needs to characterize materials of a high level of purity, as in the case of rare earth oxides. Some of those limitations are associated, for example, to spectral interference. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a powerful analytical tool for quantitative analysis of metal impurities in high purity materials. The Instituto de Pesquisas Energeticas e Nucleares (IPEN) has an unit of production and purification of rare earth oxides, with above 99,9% level of purity. In this work, the rare earth impurities were characterized in samples (La{sub 2}O{sub 3}; CeO{sub 2}; Pr{sub 6}O{sub 11}; Nd{sub 2}O{sub 3}; Sm{sub 2}O{sub 3}; Gd{sub 2}O{sub 3}; Y{sub 2}O{sub 3}) produced at the IPEN and certified standard materials produced by Johnson Matthey Chemical (JMC). The technique of high performance liquid chromatography (HPLC) was used in the separation of the impurities. Quantification of metallic impurities was carried out as inductively coupled plasma mass spectrometer (HR-ICP MS). In this work it is presented a new analytical methodology in the chemical characterization of metallic impurities in rare earth oxides of high purity (> 99,9%) with and

  3. Degradation of surfactant-modified montmorillonites in HCl

    Energy Technology Data Exchange (ETDEWEB)

    Madejova, Jana, E-mail: jana.madejova@savba.sk [Institute of Inorganic Chemistry, SAS, Dubravska cesta 9, SK-845 36 Bratislava (Slovakia); Palkova, Helena, E-mail: helena.palkova@savba.sk [Institute of Inorganic Chemistry, SAS, Dubravska cesta 9, SK-845 36 Bratislava (Slovakia); Jankovic, Lubos, E-mail: lubos.jankovic@savba.sk [Institute of Inorganic Chemistry, SAS, Dubravska cesta 9, SK-845 36 Bratislava (Slovakia)

    2012-06-15

    The effect of surfactant size on the extent of montmorillonites decomposition in HCl was investigated. Na-SAz montmorillonite and tetraalkylammonium salts of alkyl-chains length increasing from methyl- Me{sub 4}N to pentyl- Pe{sub 4}N were used for organo-montmorillonites preparation. Decreasing intensity of d{sub 001} diffraction proved destruction of montmorillonite structure connected with gradual surfactant release. A shift of the SiO stretching band to 1097 cm{sup -1} confirmed formation of amorphous silica phase. A new band near 7315 cm{sup -1} corresponding to SiOH overtone revealed creation of protonated silica. This band was observed in the spectra of all acid-treated samples, also in those with minor decomposition of the structure. The size of the cations significantly affected decomposition of montmorillonites in HCl. The less stable were Na-SAz and Me{sub 4}N-SAz in which the content of octahedral atoms dropped to {approx}5% of their original values upon 8 h treatments. Et{sub 4}N-SAz and Pr{sub 4}N-SAz were slightly more resistant mainly at short times. Bu{sub 4}N-SAz and Pe{sub 4}N-SAz showed the least structural modifications, only 50% and 35% of octahedral atoms, respectively, were released into solution within 8 h treatments. This observation proves that bulky alkylammonium cations covering the inner and outer surfaces of montmorillonite prevent effectively the access of protons to the layers protecting the mineral from degradation in the acid. - Highlights: Black-Right-Pointing-Pointer Hybrid materials were prepared from montmorillonite and alkylammonium cations with short alkyl chains. Black-Right-Pointing-Pointer The effect of surfactant on organo-montmorillonites dissolution in HCl was studied. Black-Right-Pointing-Pointer With increasing size of cation the extent of montmorillonite decomposition decreased. Black-Right-Pointing-Pointer Bulky surfactants prevent the access of protons to the layers and thus protect montmorillonite from

  4. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    Energy Technology Data Exchange (ETDEWEB)

    Harlan U. Anderson; Fatih Dogan; Vladimir Petrovsky

    2002-03-31

    This project has three main goals: Thin Films Studies, Preparation of Graded Porous Substrates and Basic Electrical Characterization and testing of Planar Single Cells. This period has continued to address the problem of making dense 1/2 to 5 {micro}m thick dense layers on porous substrates (the cathode LSM). Our current status is that we are making structures of 2-5 cm{sup 2} in area, which consist of either dense YSZ or CGO infiltrated into a 2-5 {micro}m thick 50% porous layer made of either nanoncrystalline CGO or YSZ powder. This composite structure coats a macroporous cathode or anode; which serves as the structural element of the bi-layer structure. These structures are being tested as SOFC elements. A number of structures have been evaluated both as symmetrical and as button cell configuration. Results of this testing indicates that the cathodes contribute the most to cell losses for temperatures below 750 C. In this investigation different cathode materials were studied using impedance spectroscopy of symmetric cells and IV characteristics of anode supported fuel cells. Cathode materials studied included La{sub 0.8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (LSCF), La{sub 0.7}Sr{sub 0.2}MnO{sub 3} (LSM), Pr{sub 0.8}Sr{sub 0.2}Fe{sub 0.8}O{sub 3} (PSCF), Sm{sub 0.8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (SSCF), and Yb{sub .8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (SSCF). A new technique for filtering the Fourier transform of impedance data was used to increase the sensitivity of impedance analysis. By creating a filter specifically for impedance spectroscopy the resolution was increased. The filter was tailored to look for specific circuit elements like R//C, Warburg, or constant phase elements. As many as four peaks can be resolved using the filtering technique on symmetric cells. It may be possible to relate the different peaks to material parameters, like the oxygen exchange coefficient. The cathode grouped in order from lowest to highest ASR is

  5. Electronic band structure effects in monolayer, bilayer, and hybrid graphene structures

    Science.gov (United States)

    Puls, Conor

    Since its discovery in 2005, graphene has been the focus of intense theoretical and experimental study owing to its unique two-dimensional band structure and related electronic properties. In this thesis, we explore the electronic properties of graphene structures from several perspectives including the magnetoelectrical transport properties of monolayer graphene, gap engineering and measurements in bilayer graphene, and anomalous quantum oscillation in the monolayer-bilayer graphene hybrids. We also explored the device implications of our findings, and the application of some experimental techniques developed for the graphene work to the study of a complex oxide, Ca3Ru2O7, exhibiting properties of strongly correlated electrons. Graphene's high mobility and ballistic transport over device length scales, make it suitable for numerous applications. However, two big challenges remain in the way: maintaining high mobility in fabricated devices, and engineering a band gap to make graphene compatible with logical electronics and various optical devices. We address the first challenge by experimentally evaluating mobilities in scalable monolayer graphene-based field effect transistors (FETs) and dielectric-covered Hall bars. We find that the mobility is limited in these devices, and is roughly inversely proportional to doping. By considering interaction of graphene's Dirac fermions with local charged impurities at the interface between graphene and the top-gate dielectric, we find that Coulomb scattering is responsible for degraded mobility. Even in the cleanest devices, a band gap is still desirable for electronic applications of graphene. We address this challenge by probing the band structure of bilayer graphene, in which a field-tunable energy band gap has been theoretically proposed. We use planar tunneling spectroscopy of exfoliated bilayer graphene flakes demonstrate both measurement and control of the energy band gap. We find that both the Fermi level and

  6. New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Allan J. Jacobson

    2006-09-30

    the perovskite compositions that were being investigated at PNNL, in order to assess the relative importance of the intrinsic properties such as oxygen ion diffusion and surface exchange rates as predictors of performance in cell tests. We then used these measurements to select new materials for scaled up synthesis and performance evaluation in single cell tests. The results of the single cell tests than provided feedback to the materials synthesis and selection steps. In this summary, the following studies are reported: (1) Synthesis, characterization, and DC conductivity measurements of the P1 compositions La{sub 0.8}Sr{sub 0.2}FeO{sub 3-x} and La{sub 0.7}Sr{sub 0.3}FeO{sub 3-x} were completed. A combinational approach for preparing a range P1 (La,Sr)FeO{sub 3} compositions as thin films was investigated. Synthesis and heat treatment of amorphous SrFeO{sub 3-x} and LaFeO{sub 3-x} films prepared by pulsed laser deposition are described. (2) Oxygen transport properties of K1 compositions La{sub x}Pr{sub 2-x}NiO{sub 4+d} (x =2.0, 1.9, 1.2, 1.0 and 0) measured by electrical conductivity relaxation are presented in this report. Area specific resistances determined by ac impedance measurements for La{sub 2}NiO{sub 4+{delta}} and Pr{sub 2}NiO{sub 4+{delta}} on CGO are encouraging and suggest that further optimization of the electrode microstructure will enable the target to be reached. (3) The oxygen exchange kinetics of the oxygen deficient double perovskite LnBaCo{sub 2}O{sub 5.5+{delta}} (Ln=Pr and Nd) were determined by electrical conductivity relaxation. The high electronic conductivity and rapid diffusion and surface exchange kinetics of PBCO suggest its application as cathode material in intermediate temperature solid oxide fuel cells. The first complete cell measurements were performed on Ni/CGO/CGO/PBCO/CGO cells. (4) The oxygen exchange kinetics of highly epitaxial thin films of PrBaCo{sub 2}O{sub 5.5+{delta}} (PBCO) has been determined by electrical conductivity

  7. Rapid Solidification of AB{sub 5} Hydrogen Storage Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gulbrandsen-Dahl, Sverre

    2002-01-01

    thesis the changes of the crystal structure and the grain structure of La{sub 0.60}Ce{sub 0.29}Pr{sub 0.04}Nd{sub 0.07}Ni{sub 3.37}Co{sub 0.79}Mn{sub 0.25}Al{sub 0.7}= cooling rate during chill-block melt spinning are described. Totally, the material was rapidly solidified at 9 different cooling rates. The grain structure, crystallographic texture and the lattice parameters were studied by means of electron microscopy and powder X-ray diffraction. Additionally, the density of the rapidly solidified materials was measured by a gas pycnometer. All these properties were found to change with increasing cooling rate. The grain size decreased continuously with increasing cooling rate and was in the range of 1-5 {mu}m. The strength of the crystallographic texture first increased and then decreased with increasing cooling rate. Transmission electron microscopy studies revealed that the grains contained a large amount of crystallographic twins and that the solidification morphology changed from cellular to plane front at a cooling rate during solidification of approximately 6*10{sup 4} Ks{sup -1}. The unit cell volume and the density followed the same pattern with increasing cooling rate and decreased within each solidification morphology, but at the cooling rate from which the morphology changed, both these parameters suddenly increased. The identical variations in the unit cell volume and the density is explained by formation of excess lattice vacancies during rapid solidification. In Part IV of the thesis rapid solidification of the materials La{sub 0.60}Ce{sub 0.27}Pr{sub 0.04}Nd{sub 0.09}Ni{sub 4.76}Sn{sub 0.24} and LaNi{sub 4.76}Sn different cooling rates are described. The materials were analysed by means of electron microscopy and powder X-ray diffraction. The grain structures of both alloys were found to be in the nanometer range, and the grain sizes were almost invariant with increasing cooling rate. Furthermore, the lattice parameters of these materials were almost

  8. Ruthenium Water Oxidation Catalysts based on Pentapyridyl Ligands.

    Science.gov (United States)

    Gil-Sepulcre, Marcos; Böhler, Michael; Schilling, Mauro; Bozoglian, Fernando; Bachmann, Cyril; Scherrer, Dominik; Fox, Thomas; Spingler, Bernhard; Gimbert-Suriñach, Carolina; Alberto, Roger; Bofill, Roger; Sala, Xavier; Luber, Sandra; Richmond, Craig J; Llobet, Antoni

    2017-11-23

    Ruthenium complexes containing the pentapyridyl ligand 6,6''-(methoxy(pyridin-2-yl)methylene)di-2,2'-bipyridine (L-OMe) of general formula trans-[Ru II (X)(L-OMe-κ-N 5 )] n+ (X=Cl, n=1, trans-1 + ; X=H 2 O, n=2, trans-2 2+ ) have been isolated and characterized in solution (by NMR and UV/Vis spectroscopy) and in the solid state by XRD. Both complexes undergo a series of substitution reactions at oxidation state Ru II and Ru III when dissolved in aqueous triflic acid-trifluoroethanol solutions as monitored by UV/Vis spectroscopy, and the corresponding rate constants were determined. In particular, aqueous solutions of the Ru III -Cl complex trans-[Ru III (Cl)(L-OMe-κ-N 5 )] 2+ (trans-1 2+ ) generates a family of Ru aquo complexes, namely trans-[Ru III (H 2 O)(L-OMe-κ-N 5 )] 3+ (trans-2 3+ ), [Ru III (H 2 O) 2 (L-OMe-κ-N 4 )] 3+ (trans-3 3+ ), and [Ru III (Cl)(H 2 O)(L-OMe-κ-N 4 )] 2+ (trans-4 2+ ). Although complex trans-4 2+ is a powerful water oxidation catalyst, complex trans-2 3+ has only a moderate activity and trans-3 3+ shows no activity. A parallel study with related complexes containing the methyl-substituted ligand 6,6''-(1-pyridin-2-yl)ethane-1,1-diyl)di-2,2'-bipyridine (L-Me) was carried out. The behavior of all of these catalysts has been rationalized based on substitution kinetics, oxygen evolution kinetics, electrochemical properties, and density functional theory calculations. The best catalyst, trans-4 2+ , reaches turnover frequencies of 0.71 s -1 using Ce IV as a sacrificial oxidant, with oxidative efficiencies above 95 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Cytotoxicity and anti-tumor effects of new ruthenium complexes on triple negative breast cancer cells.

    Directory of Open Access Journals (Sweden)

    Cecília P Popolin

    Full Text Available Triple-negative breast cancer (TNBC is a highly aggressive breast cancer subtype. The high rate of metastasis associated to the fact that these cells frequently display multidrug resistance, make the treatment of metastatic disease difficult. Development of antitumor metal-based drugs was started with the discovery of cisplatin, however, the severe side effects represent a limitation for its clinical use. Ruthenium (Ru complexes with different ligands have been successfully studied as prospective antitumor drugs. In this work, we demonstrated the activity of a series of biphosphine bipyridine Ru complexes (1 [Ru(SO4(dppb(bipy], (2 [Ru(CO3(dppb(bipy], (3 [Ru(C2O4(dppb(bipy] and (4 [Ru(CH3CO2(dppb(bipy]PF6 [where dppb = 1,4-bis(diphenylphosphinobutane and bipy = 2,2'-bipyridine], on proliferation of TNBC (MDA-MB-231, estrogen-dependent breast tumor cells (MCF-7 and a non-tumor breast cell line (MCF-10A. Complex (4 was most effective among the complexes and was selected to be further investigated on effects on tumor cell adhesion, migration, invasion and in apoptosis. Moreover, DNA and HSA binding properties of this complex were also investigated. Results show that complex (4 was more efficient inhibiting proliferation of MDA-MB-231 cells over non-tumor cells. In addition, complex (4 was able to inhibit MDA-MB231 cells adhesion, migration and invasion and to induce apoptosis and inhibit MMP-9 secretion in TNBC cells. Complex (4 should be further investigated in vivo in order to stablish its potential to improve breast cancer treatment.

  10. Post Partum Depression and Thyroid Function

    Directory of Open Access Journals (Sweden)

    Farahnaz Keshavarzi MD

    2011-09-01

    Full Text Available Objective: Risk of depression is particularly high for women during the prenatal period. Various investigators have attempted to establish a link between thyroid function and post partum depression. This study aimed to investigate whether thyroid function differs in women with postpartum depression compared to a control group.Methods: In this case-control study, subjects were selected from Obstetrics & Gynecology and Psychiatric clinics of Kermanshah University of Medical Sciences. Forty eight patients suffering from postpartum depression according to Diagnostic and Statistical Manual of Mental Disorders, fourth edition totally revised (DSM-IV-TR, and 65 normal controls underwent diagnostic evaluation by one trained psychiatrist using Structured Clinical Interview for DSM-IV-TR. Then, the demographic questionnaire and the Persian version of Edinburgh Postnatal Depression Scale (EPDS were completed by the participants. Finally, their thyroid functions were assessed. Data analyses were done using the SPSS program 13.Results: No statistically significant differences were observed between thyroid function tests and postpartum depression. According to multiple regression analysis with stepwise method, subjects with lower serum TSH, T3RU, T3 levels, younger age and longer period after delivery tended to have higher EPDS scores (P-value=0.008. Conclusion:The present study reports that those women with postpartum depression had a no greater prevalence of thyroid dysfunction than the control subjects. It seems that thyroid dysfunction should be considered in women with postpartum depression individually, but the role of thyroid as an important cause of this condition is not yet established. This suggests that future studies should concentrate on this concept in postpartum depression.

  11. Thermal fragmentation of acyl thiolato complexes to reactive metal sulfido intermediates. Structure of Ru([eta][sup 6]-SC[sub 3]Me[sub 3]COMe)(PPh[sub 3])[sub 2

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Q.; Krautscheid, H.; Rauchfuss, T.B.; Skaugset, A.E.; Venturelli, A. (Univ. of Illinois, Urbana, IL (United States))

    1995-01-01

    In this study we have examined the thermal fragmentation of acyl thiolate complexes of the type (ring)M(SC[sub 3]Me[sub 3]COMe). While the (cymene)Ru derivative only gave insoluble materials, the thermolysis of the corresponding osmium compound, (cymene)Os(SC[sub 3]Me[sub 3]COMe) (2), proved very informative. Here it was established that the tetramethylfuran is indeed released prior to formation of the free cymene. Furthermore, two intermediates were observed, the second of which was identified as (cymene)[sub 3]Os[sub 3]S[sub 2]. This species is more stable with respect to loss of cymene than the corresponding (cymene)[sub 3]Ru[sub 3]S[sub 2]. Attempts were made to intercept intermediates in these fragmentation processes by employing PPh[sub 3] as a trapping agent. For the Ru case, PPh[sub 3] completely changed the course of the reaction and no tetramethylfuran was generated. Instead we obtained the structurally unusual [eta][sup 6]-acyl thiolate complex (5). We propose that this unimolecular step involves the formation of ([eta][sup 4]-cymene)Ru([eta][sup 6]-SC[sub 3]Me[sub 3]COMe). The forward rate for this equilibration is far slower than the rate of isomerization of the acyl thiolate and far faster than that for the unassisted thermal decomposition of (cymene)Ru(SC[sub 3]MesCOMe). This result leads to a more global assessment of the reactivity of the acyl thiolates: the orientation of the carbonyl center determines the decomposition pathway. 21 refs., 7 figs., 1 tab.

  12. Ru/Fe bimetallic complexes: Synthesis, characterization, cytotoxicity and study of their interactions with DNA/HSA and human topoisomerase IB.

    Science.gov (United States)

    Takarada, Jessica E; Guedes, Adriana P M; Correa, Rodrigo S; Silveira-Lacerda, Elisângela de P; Castelli, Silvia; Iacovelli, Federico; Deflon, Victor Marcelo; Batista, Alzir Azevedo; Desideri, Alessandro

    2017-12-15

    Three ruthenium/iron-based compounds, 1: [Ru(MIm)(bipy)(dppf)]PF 6 (MIm = 2-mercapto-1-methylimidazole anion), 2: [RuCl(Im)(bipy)(dppf)]PF 6 (Im = imidazole), and 3: [Ru(tzdt)(bipy)(dppf)]PF 6 (tzdt = 1,3-thiazolidine-2-thione anion) (dppf = 1,1'-bis(diphenylphosphine)ferrocene and bipy = 2,2'-bipyridine), were synthesized, and characterized by elemental analyses, conductivity, UV/Vis, IR, 1 H, 13 C and 31 P{1H} NMR spectroscopies, and by electrochemical technique. The complex 3 was also characterized by single-crystal X-ray. The three ruthenium(II) complexes show cytotoxicity against DU-145 (prostate carcinoma cells) and A549 (lung carcinoma cells) tumor cells. The free ligands do not exhibit any cytotoxic activity, such as evident by the IC 50 values higher than 200 μM. UV/Vis and viscosity experiments showed that the complexes interact weakly with the DNA molecule, via electrostatic forces. The interaction of the complexes 1-3 with the HSA is moderate, with K b values in range of 10 5 -10 7  M -1 , presenting a static mechanism of interaction stabilized by hydrophobic. Complexes 2 and 3 showed high affinity for the FA7 HSA site as evidenced by fluorescence spectroscopy and molecular docking. Complexes 1-3 were tested as potential human Topoisomerase IB inhibitors by analysing the different steps of the enzyme catalytic cycle. The results indicate that all compounds efficiently inhibit the DNA relaxation and the cleavage reaction, in which the effect increases upon pre-incubation. Complexes 1 and 2 are also able to slow down the religation reaction. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Microkinetic interpretation of HDS/HYDO selectivity of the transformation of a model FCC gasoline over transition metal sulfides

    Energy Technology Data Exchange (ETDEWEB)

    Daudin, A. [UMR CNRS 6503, Catalyse en Chimie Organique, Universite de Poitiers, Faculte des Sciences Fondamentales et Appliquees, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex (France); IFP-Lyon, Direction Catalyse et Separation, BP 3, 69390 Vernaison (France); Lamic, A.F.; Perot, G.; Brunet, S. [UMR CNRS 6503, Catalyse en Chimie Organique, Universite de Poitiers, Faculte des Sciences Fondamentales et Appliquees, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex (France); Raybaud, P. [IFP, Direction Chimie et Physico-Chimie Appliquees, 1-4 Av. de Bois Preau, 92858 Rueil Malmaison (France); IFP-Lyon, Direction Catalyse et Separation, BP 3, 69390 Vernaison (France); Bouchy, C. [IFP-Lyon, Direction Catalyse et Separation, BP 3, 69390 Vernaison (France)

    2008-01-15

    The conversion of a model FCC gasoline (composed of 2-methylthiophene (2MT), 2,3-dimethylbut-2-ene (23DMDB2N) and orthoxylene in n-heptane) under realistic hydrodesulfurization (HDS) conditions was investigated over a series of transition monometallic sulfides (Ni{sub 3}S{sub 2}, PdS, Co{sub 9}S{sub 8}, Rh{sub 2}S{sub 3}, RuS{sub 2}, PtS and MoS{sub 2}) and unsupported transition bimetallic sulfide catalysts (NiMoS and CoMoS). The results reveal for the first time that a volcano curve relationship exists between the ab initio calculated sulfur-metal bond energy, E(MS), descriptor of bulk TMS and their activities in olefin hydrogenation and in alkylthiophene desulfurization measured simultaneously. In particular, Rh{sub 2}S{sub 3} with an intermediate sulfur-metal bond energy of 119 kJ/mol is the most active catalyst in both case hydrogenation of the olefin and in HDS of a sulfur compound. Furthermore, the HDS/HYDO selectivity which is the most important parameter in the deep HDS of gasoline, presents a maximum for the NiMoS catalyst with E(MS) of 128 kJ/mol. A microkinetic model based on Broensted-Evans-Polanyi relationships and the competitive adsorption of the sulfur molecule and alkene on the catalytic site is proposed to give a rational interpretation of the experimental catalytic results. (author)

  14. Enhanced Method for Molybdenum Separation and Isotopic Determination in Geological Samples and Uranium-Rich Materials

    Science.gov (United States)

    Migeon, V.; Bourdon, B.; Pili, E.

    2014-12-01

    Molybdenum (Mo) shares analogous geochemical properties with uranium. Mo ispresent as a minor or a trace element in uranium ores under two main oxidation states: +IVand +VI. Mo has seven stable isotopes (92, 94, 95, 96, 97, 98 and 100). In natural systems,Mo and Mo isotopes were shown to fractionate during redox reactions. Because Morepresents an impurity difficult to separate in the nuclear fuel cycle, it has the potential to beused as an indicator of the origins of uranium concentrates, in the framework of nuclearforensics. This work focuses on developing an enhanced separation method for Mo from auranium-rich matrix (uranium ore, uranium concentrate) in order to analyze the massfractionation induced by processes typical of the nuclear fuel cycle. Purification of Mo forisotope ratio measurements is performed with a three-step separation on ion-exchange resins,with yields between 45 and 82%. Matrix and isobaric interferences (Zr, Ru) were reduced ingeological and uranium standards, such as U/Mo ≤ 2*10-4, Zr/Mo ≤ 1*10-3, Ru/Mo ≤ 6*10-4and Fe/Mo ≤ 4*10-3. Mo isotopic compositions were measured on a Neptune Plus MC-ICPMSequipped with Jet cones, for a concentration of 30 ng/ml. The achieved sensitivity is~1200-1800 V/ppm with interferences below 10 mV and an overall reproducibility of 0.02 ‰on the δ98Mo values. A double spike, with 97Mo and 100Mo, was added to the samples beforethe purification. It allows for correction of the chemical and instrumental mass fractionations,without requiring a quantitative yield. For igneous rocks, δ98Mo values range between -0.55and -0.03 ‰, relative to the NIST-SRM 3134 molybdenum standard. Fractionation amonguranium ore concentrates is higher, with δ98Mo ranging between 0.02 and -2.84 ‰.

  15. Chemical bonding and optoelectrical properties of ruthenium doped yttrium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Lei; Han, Jiecai [Harbin Institute of Technology, Harbin 150080 (China); Zhu, Jiaqi, E-mail: zhujq@hit.edu.cn [Harbin Institute of Technology, Harbin 150080 (China); Zhu, Yuankun [Harbin Institute of Technology, Harbin 150080 (China); Schlaberg, H.Inaki [North China Electric Power University, Beijing 102206 (China)

    2013-11-15

    Graphical abstract: IR transmittance of various transparent conductive materials (RYO films grown under RT, 400 °C and 600 °C, ITO films [2], Carbon Nano tube films [11], metal/dielectric multilayers [12]). - Highlights: • Y{sub 2}O{sub 3}:Ru (RYO) films were prepared on ZnS substrates by reactive magnetron sputtering. • Ru doping significantly decreases the resistivity and extends the transparent range. • Optical and electrical properties of RYO films can be tuned by substrate temperatures. • The RYO films exhibit excellent far-IR transmittance and electrical property. - Abstract: Highly infrared transparent conductive ruthenium doped yttrium oxide (RYO) films were deposited on zinc sulfide and glass substrates by reactive magnetron sputtering. The structural, optical, and electrical properties of the films as a function of growth temperature were studied. It is shown that the sputtered RYO thin films are amorphous and smooth surface is obtained. The infrared transmittance of the films increases with increasing the growth temperature. RYO films maintain greater than ∼65% transmittance over a wide wavelength range from 2.5 μm to 12 μm and the highest transmittance value reaches 73.3% at ∼10 μm. With increasing growth temperature, the resistivity changed in a wide range and lowest resistivity of about 3.36 × 10{sup −3} Ω cm is obtained at room temperature. The RYO thin films with high conductivity and transparency in IR spectral range would be suitable for infrared optical and electromagnetic shielding devices.

  16. Copper(II)-lanthanide(III) coordination polymers constructed from pyridine-2,5-dicarboxylic acid: Preparation, crystal structure and photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Xia Zhengqiang; Wei Qing [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); Chen Sanping, E-mail: sanpingchen@126.com [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); Feng Xinming; Xie Gang [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); Qiao Chengfang [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); Department of Chemistry and Chemical Engineering, Shangluo University, Shangluo 726000 (China); Zhang Guochun [Department of Chemistry and Chemical Engineering, Shangluo University, Shangluo 726000 (China); Gao Shengli [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China)

    2013-01-15

    A series of 3d-4f heterometallic coordination polymers, formulated as {l_brace} [Cu{sub 3}Ln{sub 2}(pydc){sub 6}(H{sub 2}O){sub 12}]{center_dot}4H{sub 2}O{r_brace} {sub n} [Ln=Tb (1), Eu (2), Dy (3), Ho (4), Lu (5)], {l_brace} [CuNd{sub 2}(pydc){sub 4}(H{sub 2}O){sub 3}]{center_dot}H{sub 2}O{r_brace} {sub n} (6) and {l_brace} [Cu{sub 3}Pr{sub 2}(pydc){sub 6}(H{sub 2}O){sub 13}]{center_dot}4H{sub 2}O{r_brace} {sub n} (7) (where H{sub 2}pydc=pyridine-2,5-dicarboxylic acid), have been hydrothermally prepared by reactions of H{sub 2}pydc ligand with lanthanide ions in the presence of Cu(II) ion. X-ray crystal structure analysis reveals that these compounds exhibit rich structural chemistry. 1-5 are isomorphous and present a two-dimensional network constructed from Ln{sub 2}Cu{sub 2}L{sub 2}(H{sub 2}O){sub 2} SBU rings and CuL{sub 2}(H{sub 2}O) building blocks. In 6, two-dimensional ladder-like layers based on Nd(III) belts and CuL{sub 2}O{sub 2} units are assembled by H{sub 2}pydc ligands into a three-dimensional open framework. Polymer 7 displays a two-dimensional wave-like layer structure containing two distinct ring units, in which a new coordination mode of the pydc{sup 2-} ligand is observed. The results indicate that the coordination flexibility of the pydc{sup 2-} ligand and lanthanide contraction effect play cooperative roles in the formation of coordination polymers with different polymeric architectures. Compounds 1-2 exhibit intense green and red luminescence emission characteristics of Tb(III) and Eu(III), respectively. Furthermore, elemental analyses (EA), infrared spectra (IR) and thermogravimetric analyses (TGA) of these compounds were also studied. - Graphical abstract: Seven 3d-4f heterometallic coordination polymers were synthesized by reactions of H{sub 2}pydc with lanthanide metal ions in the presence of Cu{sup 2+}, the effects of Cu{sup 2+} on the structures and photoluminescent properties of Ln-pydc{sup 2-} systems were investigated. Highlights

  17. Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E.Vanden; Anderson, Scott F.; Bahcall, Neta A.; /KIPAC, Menlo Park

    2006-11-30

    We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 {approx} 50 Myr for quasars with 2.9 {le} z {le} 3.5; and 30 {approx} 600 Myr for quasars with z {ge} 3.5. The corresponding duty cycles are 0.004 {approx} 0.05 for the lower redshift bin and 0.03 {approx} 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with 2.9 {le} z {le} 3.5 and 4-6 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with z {ge} 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b

  18. Oxygen permeation and thermo-chemical stability of oxygen separation membrane materials for the oxyfuel process

    Energy Technology Data Exchange (ETDEWEB)

    Ellett, Anna Judith

    2009-07-01

    The reduction of CO{sub 2} emissions, generally held to be one of the most significant contributors to global warming, is a major technological issue. CO{sub 2} Capture and Storage (CCS) techniques applied to large stationary sources such as coal-fired power plants could efficiently contribute to the global carbon mitigation effort. The oxyfuel process, which consists in the burning of coal in an oxygen-rich atmosphere to produce a flue gas highly concentrated in CO{sub 2}, is a technology considered for zero CO{sub 2} emission coal-fired power plants. The production of this O{sub 2}-rich combustion gas from air can be carried out using high purity oxygen separation membranes. Some of the most promising materials for this application are mixed ionic-electronic conducting (MIEC) materials with perovskite and K{sub 2}NiF{sub 4} perovskite-related structures. The present work examines the selection of La{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF58), La{sub 2}NiO{sub 4+{delta}}, Pr{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (PSCF58) and Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (BSCF50) as membrane materials for the separation of O{sub 2} and N{sub 2} in the framework of the oxyfuel process with flue gas recycling. Annealing experiments were carried out on pellets exposed to CO{sub 2}, water vapour, O{sub 2} and Cr{sub 2}O{sub 3} in order to determine the thermo-chemical resistance to the atmospheres and the high temperature conditions present during membrane operation in a coal-fired power plant. The degradation of their microstructure was investigated using Scanning Electron Microscopy (SEM) in combination with electron dispersive spectroscopy (EDS) as well as X-Ray Diffraction (XRD). Also, the oxygen permeation fluxes of selected membranes were investigated as a function of temperature. The membrane materials selected were characterised using thermo-analytical techniques such as precision thermogravimetric

  19. Chemical and structural changes in Ln{sub 2}NiO{sub 4+δ} (Ln=La, Pr or Nd) lanthanide nickelates as a function of oxygen partial pressure at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Flura, Aurélien; Dru, Sophie; Nicollet, Clément; Vibhu, Vaibhav; Fourcade, Sébastien; Lebraud, Eric; Rougier, Aline; Bassat, Jean-Marc; Grenier, Jean-Claude, E-mail: grenier@icmcb-bordeaux.cnrs.fr

    2015-08-15

    The chemical stability of lanthanide nickelates Ln{sub 2}NiO{sub 4+δ} (Ln=La, Pr or Nd) has been studied in the temperature range 25–1300 °C, either in air or at low pO{sub 2} (down to 10{sup −4} atm). Thermal gravimetry analysis (TGA) measurements coupled with X-ray diffraction (XRD) characterization have shown that all compounds retain their K{sub 2}NiF{sub 4}-type structure in these conditions, while remaining over-stoichiometric in oxygen up to 1000 °C. Only Nd{sub 2}NiO{sub 4+δ} starts to decompose into Nd{sub 2}O{sub 3} and NiO above 1000 °C, at pO{sub 2}=10{sup −4} atm. In addition, a careful analysis of the lanthanide nickelates structural features has been performed by in situ XRD, as a function of temperature and pO{sub 2}. For all compounds, a structural transition has been always observed in the temperature range 200–400 °C, in air or at pO{sub 2}=10{sup −4} atm. In addition, their cell volume did not vary upon the variation of the oxygen partial pressure. Therefore, these materials do not exhibit a chemical expansion in these conditions, which is beneficial for a fuel cell application as cathode layers. Additional dilatometry measurements have revealed that a temperature as high as 950 °C for Pr{sub 2}NiO{sub 4+δ} or 1100 °C for La{sub 2}NiO{sub 4+δ} and Nd{sub 2}NiO{sub 4+δ} has to be reached in order to begin the sintering of the material particles, which is of primary importance to obtain an efficient electronic/ionic conduction in the corresponding designed cathode layers. Besides, excellent matching was found between the thermal expansion coefficients of lanthanide nickelates and SOFC electrolytes such as 8wt% yttria stabilized zirconia (8YSZ) or Ce{sub 0.8}Gd{sub 0.2}O{sub 2−δ} (GDC), at least from 400 °C up to 1400 °C in air or up to 1200 °C at pO{sub 2}=10{sup −4} atm. - Graphical abstract: This study reports the good chemical stability of oxygen overstoichiometric Ln2NiO4+δ(Ln = La, Pr or Nd) at high temperatures

  20. Antibodies against gonadotropin-releasing hormone (GnRH) in patients with diabetes mellitus is associated with lower body weight and autonomic neuropathy.

    Science.gov (United States)

    Berntorp, Kerstin; Frid, Anders; Alm, Ragnar; Fredrikson, Gunilla Nordin; Sjöberg, Klas; Ohlsson, Bodil

    2013-08-17

    Esophageal dysmotility and gastroparesis are common secondary complications in patients with diabetes mellitus. Patients with dysmotility express antibodies against gonadotropin-releasing hormone (GnRH) in serum. The aim of the present study was to scrutinize patients with diabetes mellitus with regard to the presence of GnRH antibodies, and to examine associations between antibodies and clinical findings. Thirty-nine consecutive patients with diabetes mellitus were included in the study after clinical examination and examination by esophageal manometry and gastric emptying scintigraphy. Serum was analyzed for the presence of antibodies against GnRH using an ELISA, and values are expressed as relative units (RU). Two age- and gender-matched healthy subjects per each patient served as controls. The prevalence of IgM GnRH antibodies in patients was 33% compared to 14% in controls (p = 0.027), with a higher antibody titer; 1.2 (0.6-5.0) and 0.2 (0.1-0.3) RU, respectively (p = 0.000). The expression of IgG antibodies was 15% in patients and none in controls (p = 0.000). Lower body mass index was associated with the presence of IgM antibodies (OR = 0.835, 95% CI = 0.699-0.998), and autonomic neuropathy with the presence IgG antibodies (OR = 9.000, 95% CI = 1.327-61.025). Esophageal dysmotility (69%) or gastroparesis (18%) were not associated with the presence of IgM antibodies (OR = 0.589, 95% CI = 0.143-2.424 and OR = 3.407, 95% CI = 0.633-18.350, respectively). Neither was esophageal dysmotility associated with IgG antibodies (OR = 2.500, 95% CI = 0.259-24.096). Antibodies against GnRH are more common in patients with diabetes mellitus compared with healthy controls. IgM antibodies are associated with lower body mass index and IgG antibodies are associated with autonomic neuropathy.

  1. Rolling cycle amplification based single-color quantum dots–ruthenium complex assembling dyads for homogeneous and highly selective detection of DNA

    Energy Technology Data Exchange (ETDEWEB)

    Su, Chen; Liu, Yufei; Ye, Tai; Xiang, Xia; Ji, Xinghu; He, Zhike, E-mail: zhkhe@whu.edu.cn

    2015-01-01

    Graphical abstract: A universal, label-free, homogeneous, highly sensitive, and selective fluorescent biosensor for DNA detection is developed by using rolling-circle amplification (RCA) based single-color quantum dots–ruthenium complex (QDs–Ru) assembling dyads. - Highlights: • The single-color QDs–Ru assembling dyads were applied in homogeneous DNA assay. • This biosensor exhibited high selectivity against base mismatched sequences. • This biosensor could be severed as universal platform for the detection of ssDNA. • This sensor could be used to detect the target in human serum samples. • This DNA sensor had a good selectivity under the interference of other dsDNA. - Abstract: In this work, a new, label-free, homogeneous, highly sensitive, and selective fluorescent biosensor for DNA detection is developed by using rolling-circle amplification (RCA) based single-color quantum dots–ruthenium complex (QDs–Ru) assembling dyads. This strategy includes three steps: (1) the target DNA initiates RCA reaction and generates linear RCA products; (2) the complementary DNA hybridizes with the RCA products to form long double-strand DNA (dsDNA); (3) [Ru(phen){sub 2}(dppx)]{sup 2+} (dppx = 7,8-dimethyldipyrido [3,2-a:2′,3′-c] phenanthroline) intercalates into the long dsDNA with strong fluorescence emission. Due to its strong binding propensity with the long dsDNA, [Ru(phen){sub 2}(dppx)]{sup 2+} is removed from the surface of the QDs, resulting in restoring the fluorescence of the QDs, which has been quenched by [Ru(phen){sub 2}(dppx)]{sup 2+} through a photoinduced electron transfer process and is overlaid with the fluorescence of dsDNA bonded Ru(II) polypyridyl complex (Ru-dsDNA). Thus, high fluorescence intensity is observed, and is related to the concentration of target. This sensor exhibits not only high sensitivity for hepatitis B virus (HBV) ssDNA with a low detection limit (0.5 pM), but also excellent selectivity in the complex matrix. Moreover

  2. Minimum-Light Spectral Types for Four Mira Variables

    Science.gov (United States)

    Wing, R. F.; Yuan, Y.; Benfer, S. R.

    1997-12-01

    Spectral types for four little-studied Mira variables have been derived from narrow-band classification photometry obtained within three weeks of minimum light. The observations were made on May 24, 1997, with the CTIO 1.5-m telescope and ASCAP photometer when targets of a primary program were not accessible. The following stars were selected for observation based on AAVSO predicted times of minimum light. Star P V Sp.T.(pub) Phase I(104) Sp.T.(8c) RR Aqr 182.5 9.1--14.4 M2e--M4e 0.52 7.63 M7.5 RS Aqr 214.6 9.5--14.4 Me 0.62 6.63 M7.5 Z Aql 129.2 8.2--14.8 M3 0.67 7.07 M8.3 RU Cap 347.4 9.2--15.2 M9e 0.68 5.49 M8.8 The first four columns give data from the GCVS: the star's name, mean period in days, observed range in visual magnitude, and published spectral type. The last three columns refer to our own observations: the phase on 1997 May 24 (according to the AAVSO predictions), the apparent magnitude in a narrow band centered at 10400 Angstroms, and our spectral classification on the eight-color system, which is based on measurements of TiO at 7120 Angstroms and VO at 10540 Angstroms. The very late published spectral type of RU Cap (which appears to have been observed only at minimum) is confirmed. The three other stars, which had not previously been observed later than M4, all showed very strong TiO and significant absorption by VO, indicative of types M7.5 or later. These and earlier observations show that published spectral types of Mira variables --- even those that are brighter than V = 10 at maximum --- are often very incomplete and can be misleading. Indeed, it is difficult to find Miras that do not attain types of at least M7 at minimum.

  3. The new cerium-rich intermetallic phase Ce{sub 13}Ru{sub 2}Sn{sub 5}: Crystal structure and physical properties

    Energy Technology Data Exchange (ETDEWEB)

    Gribanova, V., E-mail: veragriban@gmail.com [Chemistry Department of Moscow Lomonosov State University, 119991 Moscow (Russian Federation); Sorokina, N. [Shubnikov Institute of Crystallography RAS, Leninsky pr., 59, Moscow 119333 (Russian Federation); Murashova, E. [Chemistry Department of Moscow Lomonosov State University, 119991 Moscow (Russian Federation); Slabon, A. [Department of Chemistry, University of California, Berkeley, Hildebrand Hall 315, CA 94720 (United States); Daou, R.; Maignan, A.; Lebedev, O. [CRISMAT, UMR 6508, CNRS-ENSICAEN-UCBN, 6 Bd Maréchal Juin, 14050 Caen (France); Gribanov, A. [Chemistry Department of Moscow Lomonosov State University, 119991 Moscow (Russian Federation)

    2015-02-15

    Highlights: • Intermetallic Ce{sub 13}Ru{sub 2}Sn{sub 5} with the high cerium content crystallizes with is a new type of structure. • The atomic order of the new stannide Ce{sub 13}Ru{sub 2}Sn{sub 5} is similar to the structure packing of the Ce{sub 9}Ru{sub 4}In{sub 11} intermetallic. • Three interatomic Ce-Ru distances in the Ce{sub 13}Ru{sub 2}Sn{sub 5} structure are less than the sum of the covalent Ce and Ru radii. • Two low temperature phases below 16 K and 6.5 K compatible with antiferro- and/or ferrimagnetic ordering were revealed. • The 6 K phase is very quickly suppressed by magnetic field, although the 16 K phase appears to be more robust. - Abstract: A new intermetallic compound with a high content of cerium, Ce{sub 13}Ru{sub 2}Sn{sub 5}, was found during the systematic investigation of the Ce-Ru-Sn ternary system. The crystal structure has been studied by a single crystal X-ray diffraction experiment and was found to be a new structure type of the intermetallic compounds: space group I4/mcm, the lattice parameters a = 22.8999(2) Å, c = 9.1668(1) Å, Z = 8. Ce{sub 13}Ru{sub 2}Sn{sub 5} structure is characterized by eight independent crystallographic Ce sites and some shortened Ce-Ru contacts: d{sub Ce1-Ru1} = 2.7693(3) Å, d{sub Ce2-Ru1} = 2.7925(12) Å and d{sub Ce3-Ru1} = 2.7612(12) Å. The low temperature measurements of electrical resistivity and magnetization of Ce{sub 13}Ru{sub 2}Sn{sub 5} reveal the complex behavior of the magnetoresistance occurring below 20 K but with an additional positive component below 7.5 K. This behavior is discussed in light of the magnetic measurements showing two transitions at ∼16 K and ∼6 K together with hysteretic loops in the M(H) below 20 K.

  4. Thyroid Function Test in Thyroid Diseases and Pregnancy - The diagnostic value of free thyroxine by RIA -

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, M. H.; Yoon, H. J.; Shin, Y. T.; Lee, J. C.; Chung, S. I.; Cho, B. Y.; Lee, M. H. [Seoul National University College of Medicine, Seoul (Korea, Republic of); Lee, M. C. [Capotal Armed Forces General Hospital, Seoul (Korea, Republic of)

    1981-03-15

    To evaluate the diagnostic accuracy of the measurement of free thyroxine(FT4) by radioimmunoassay, we measured free T{sub 4} and T{sub 4}, T{sub 3}, T{sub 3}RU, TSH and TBG serum levels by radioimmunoassay in 18 healthy persons and 52 patients with various thyroid diseases and 11 normal pregnant women. The results are as follows. 1) In 19 cases of overt hyperthyroidism, T{sub 3}, free T{sub 4} and FTI, T{sub 4}/TBG ratio reflect hyperfunction in all cases. T{sub 4} is increased in 94%(18/19) and TBG and TSH are decreased in 79%(15/19). 2) In 8 patients with overt hypothyroidism, TSH is increased in all cases and free T{sub 4} and FTI is decreased in all cases. T{sub 4} is decreased in 87.5%(7/8), T{sub 3} is decreased in 75%(6/8) and T{sub 4}/TBG ratio is decreased in 62.5%(5/8). 3) In 5 patients who are clinically in euthyroid state after treatment of hyperthyroidism, T{sub ,}4 free T{sub 4}, FTI and TSH are in the normal range in all cases and T{sub 3} is normal in 60%(3/5) and slightly increased in 40%(2/5). 4) In 10 patients who showed clinically borderline hypothyroidism after treatment of hyperthyroidism, TSH is increased in all cases and free T{sub 4} and FTI are decreased in all cases, but T{sub 4} and T{sub 3}, T{sub 4}/TBG ratio are in the normal limit in all cases. So after treatment of hyperthyroidism, TSH, free T{sub 4} or FTI are recommended as optimal function test. 5) In normal pregnancy, free T{sub 4}, FTI and T{sub 4}/TBG ratio reflect normal function, but the other parameters unreliable due to the influence of increased TBG. Also TBG and TSH level in pregnancy is increased significantly compared with normal healthy control group. 6) The coefficients of correlation between T{sub 4} and FTI were 0.862(p<0.001) and 0.685(p<0.001) between free T{sub 4} and T{sub 4}/TBG ratio. In most patients, diagnostic value of free T{sub 4} was comparable and even superior to FTI, so free T{sub 4} measurement can be used routinely with thyrotropin assay in the

  5. RuO2 supported NaY zeolite catalysts: Effect of preparation methods on catalytic performance during aerobic oxidation of benzyl alcohol

    Science.gov (United States)

    Jung, Dasom; Lee, Sunwoo; Na, Kyungsu

    2017-10-01

    The effects of preparation method for RuO2 supported zeolite catalysts on the catalytic consequences during the aerobic oxidation of benzyl alcohol to benzaldehyde were investigated. Three preparation methods, i.e., (i) simultaneous crystallization of the zeolite framework in the presence of RuCl3 (Ru(SC)/NaY), (ii) post ion-exchange with RuCl3 on the zeolite framework (Ru(IE)/NaY), and (iii) post support of preformed Ru metal nanoparticles on the zeolite surface (Ru(PS)/NaY), were used to construct three different RuO2 supported NaY zeolite catalysts. The catalyst performance was investigated as functions of the reaction time and temperature, in correlation with the structural changes of the catalysts, as analyzed by X-ray diffraction (XRD). The results revealed that the catalytic consequences were dramatically affected by the preparation methods. Although similar conversion was achieved with all three catalysts, the turnover frequency (TOF) differed. The Ru(PS)/NaY catalyst exhibited the highest TOF (33-48 h-1), whereas the other catalysts produced much lower TOFs (9-12 h-1). The Ru(PS)/NaY catalyst also had the highest activation energy (Ea) of 48.39 kJ mol-1, whereas the Ru(SC)/NaY and Ru(IE)/NaY catalysts had Ea values of 18.58 and 24.11 kJ mol-1, respectively. Notably, the Ru(PS)/NaY catalyst yielded a significantly higher pre-exponential factor of 5.22 × 105 h-1, which is about 5 orders of magnitude larger than that of the Ru(SC)/NaY catalyst (7.15 × 100 h-1). This suggests that collision between benzyl alcohol and molecular oxygen was very intensive on the Ru(PS)/NaY catalyst, which explains the higher TOF of the Ru(PS)/NaY catalyst relative to the others in spite of the higher Ea value of the former. In terms of recyclability, the pristine crystallinity of the zeolite framework was maintained in the Ru(SC)/NaY catalyst and the RuO2 phase exhibited an insignificant loss of the initial activity up to three catalytic cycles, whereas Ru(PS)/NaY showed slight

  6. Influence of physicochemical-electronic properties of transition metal ion doped polycrystalline titania on the photocatalytic degradation of Indigo Carmine and 4-nitrophenol under UV/solar light

    Energy Technology Data Exchange (ETDEWEB)

    Devi, L. Gomathi, E-mail: gomatidevi_naik@yahoo.co.in [Department of Post Graduate Studies in Chemistry, Central College City Campus, Dr. Ambedkar street, Bangalore University, Bangalore 560001 (India); Kumar, S. Girish [Department of Post Graduate Studies in Chemistry, Central College City Campus, Dr. Ambedkar street, Bangalore University, Bangalore 560001 (India)

    2011-01-15

    To understand the role of dopant inside TiO{sub 2} matrix, anatase TiO{sub 2} was doped with transition metal ions like Mn{sup 2+}, Fe{sup 3+}, Ru{sup 3+} and Os{sup 3+} having unique half filled electronic configuration and their photocatalytic activity was probed in the degradation of Indigo Carmine (IC) and 4-nitrophenol (NP) under UV/solar light. For comparison, TiO{sub 2} was also doped with V{sup 5+}, Ni{sup 2+} and Zn{sup 2+} metal ions having d{sup 0}, d{sup 8} and d{sup 10} electronic configuration respectively. Irrespective of excitation source UV/solar light and nature of the organic pollutant, photocatalytic activities of doped photocatalysts followed the order: Mn{sup 2+}-TiO{sub 2} > Fe{sup 3+}-TiO{sub 2} > Ru{sup 3+}-TiO{sub 2} {>=} Os{sup 3+}-TiO{sub 2} > Zn{sup 2+}-TiO{sub 2} > V{sup 5+}-TiO{sub 2} > Ni{sup 2+}-TiO{sub 2} at an optimum concentration of dopant. Based on the experimental results obtained, it is proposed that the existence of dopant with half filled electronic configuration in TiO{sub 2} matrix which is known to enhance the photocatalytic activity is not universal{exclamation_point} Rather it is a complex function of several physicochemical-electronic properties of doped titania. Enhanced photocatalytic activity of Mn{sup 2+} (0.06 at.%)-TiO{sub 2} was attributed to the combined factors of high positive reduction potential of Mn{sup 2+}/Mn{sup 3+} pairs, synergistic effects in the mixed polymorphs of anatase and rutile, smaller crystallite size with high intimate contact between two phases and favorable surface structure of the photocatalyst. Despite the intense research devoted to transition metal ion doped TiO{sub 2}, it is rather difficult to make unifying conclusion which is highlighted in this study.

  7. Spectroscopic, Electrochemical and Computational Characterisation of Ru Species Involved in Catalytic Water Oxidation: Evidence for a [Ru(V) (O)(Py2 (Me) tacn)] Intermediate.

    Science.gov (United States)

    Casadevall, Carla; Codolà, Zoel; Costas, Miquel; Lloret-Fillol, Julio

    2016-07-11

    A new family of ruthenium complexes based on the N-pentadentate ligand Py2 (Me) tacn (N-methyl-N',N''-bis(2-picolyl)-1,4,7-triazacyclononane) has been synthesised and its catalytic activity has been studied in the water-oxidation (WO) reaction. We have used chemical oxidants (ceric ammonium nitrate and NaIO4 ) to generate the WO intermediates [Ru(II) (OH2 )(Py2 (Me) tacn)](2+) , [Ru(III) (OH2 )(Py2 (Me) tacn)](3+) , [Ru(III) (OH)(Py2 (Me) tacn)](2+) and [Ru(IV) (O)(Py2 (Me) tacn)](2+) , which have been characterised spectroscopically. Their relative redox and pH stability in water has been studied by using UV/Vis and NMR spectroscopies, HRMS and spectroelectrochemistry. [Ru(IV) (O)(Py2 (Me) tacn)](2+) has a long half-life (>48 h) in water. The catalytic cycle of WO has been elucidated by using kinetic, spectroscopic, (18) O-labelling and theoretical studies, and the conclusion is that the rate-determining step is a single-site water nucleophilic attack on a metal-oxo species. Moreover, [Ru(IV) (O)(Py2 (Me) tacn)](2+) is proposed to be the resting state under catalytic conditions. By monitoring Ce(IV) consumption, we found that the O2 evolution rate is redox-controlled and independent of the initial concentration of Ce(IV) . Based on these facts, we propose herein that [Ru(IV) (O)(Py2 (Me) tacn)](2+) is oxidised to [Ru(V) (O)(Py2 (Me) tacn)](2+) prior to attack by a water molecule to give [Ru(III) (OOH)(Py2 (Me) tacn)](2+) . Finally, it is shown that the difference in WO reactivity between the homologous iron and ruthenium [M(OH2 )(Py2 (Me) tacn)](2+) (M=Ru, Fe) complexes is due to the difference in the redox stability of the key M(V) (O) intermediate. These results contribute to a better understanding of the WO mechanism and the differences between iron and ruthenium complexes in WO reactions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Improved molecular weight control in ring-opening metathesis polymerization (ROMP) reactions with ru-based olefin metathesis catalysts using N donors and acid: a kinetic and mechanistic investigation.

    Science.gov (United States)

    Dunbar, Miles A; Balof, Shawna L; LaBeaud, Lawrence J; Yu, Bing; Lowe, Andrew B; Valente, Edward J; Schanz, Hans-Jörg

    2009-11-16

    The effect of the addition of H(3)PO(4) on the ROMP activity of cyclooctene (COE) with first- [Cl(2)(PCy(3))(2)Ru=CHPh] and second-generation [(H(2)IMes)Cl(2)(PCy(3))Ru=CHPh] Grubbs' catalysts 1 and 4 (Cy=cyclohexyl, Ph=phenyl, Mes=2,4,6-trimethylphenyl (mesityl)), their inhibited mixtures with 1-methylimidazole (MIM), as well as their isolated bis-N,N'-dimethylaminopyridine (DMAP) derivatives [Cl(2)(PCy(3))(DMAP)(2)Ru=CHPh)] (5 b) and [Cl(2)(H(2)IMes)(DMAP)(2)Ru=CHPh] (7 b) (DMAP=dimethylaminopyridine), a novel catalyst, has been investigated. The studies include the determination of their initiation rates, as well as a determination of the molecular weights and molecular weight distributions of the polymers obtained with these catalysts and catalyst mixtures from the exo-7-oxanorbornene derivative 11. The structure of catalyst 7 b was confirmed by means of X-ray diffraction. All N-donor-bearing catalysts or N-donor-containing catalyst mixtures not only exhibited elevated activity in the presence of acid, but also increased initiation rates. Using the reversible inhibition/activation protocol with MIM and H(3)PO(4) enabled us to conduct controlled ROMP with catalyst 4 producing the isolated exo-7-oxanorbornene-based polymer 12 with predetermined molecular weights and narrow molecular weight distributions. This effect was based on fast and efficient catalyst initiation in contrast to the parent catalyst 4. Hexacoordinate complex 5 b also experienced a dramatic increase in initiation rates upon acid-addition and the ROMP reactions became well-controlled in contrast to the acid-free reaction. In contrast, complex 7 b performs well-controlled ROMP in the absence of acid, whereas the polymerization of the same monomer becomes less controlled in the presence of H(3)PO(4). The closer evaluation of catalysts 5 b and 7 b demonstrated that their initiation rates exhibit a linear dependency on the substrate concentration in contrast to catalysts 1 and 4. As a consequence

  9. One-pot synthesis of symmetric and asymmetric p-quinone ligands and unprecedented substituent induced reactivity in their dinuclear ruthenium complexes.

    Science.gov (United States)

    Schweinfurth, David; Das, Hari Sankar; Weisser, Fritz; Bubrin, Denis; Sarkar, Biprajit

    2011-02-07

    unprecedented substituent induced release of the Cym ligand, resulting in complexes of the form [(CH(3)CN)(η(6)-Cym)Ru(μ-L(-2H)(3))Ru(CH(3)CN)(3)][ClO(4)](2) (7[ClO(4)](2)) and [{(CH(3)CN)(3)Ru}(2)(μ-L(-2H)(4))][ClO(4)](2) (8[ClO(4)](2)), where the SMe groups are now coordinated to the metal center. In the case of complex 3, which contains an asymmetric bridging ligand, Cym release is observed only at the side that contains an additional SMe donor, thus proving the necessity of such donor substituents for the observed reactivity. The increase in Lewis acidity at the ruthenium center on chloride abstraction is made responsible for SMe coordination and the rigidity of the ligand systems, and their concomitant failure to coordinate in a "fac" manner as is required for a piano stool configuration results in the eventual Cym release. The bridging ligand which then coordinates in a bis-meridional fashion in 8[ClO(4)](2) results in a bis-pincer type of coordination. These observations were validated by a structural analysis of 8[ClO(4)](2). The results show the potential hemilabile character of ligands such as L(3) and L(4). Electrochemical and spectroscopic investigations are reported on 8[ClO(4)](2), and substitution reactions of the CH(3)CN molecules are presented to show the use of 8[ClO(4)](2) as a versatile precursor for other reactions.

  10. Studies of Novel Quantum Phenomena in Ruthenates

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Zhiqiang

    2011-04-08

    Strongly correlated oxides have been the subject of intense study in contemporary condensed matter physics, and perovskite ruthenates (Sr,Ca)n+1RunO3n+1 have become a new focus in this field. One of important characteristics of ruthenates is that both lattice and orbital degrees of freedom are active and are strongly coupled to charge and spin degrees of freedom. Such a complex interplay of multiple degrees of freedom causes the properties of ruthenates to exhibit a gigantic response to external stimuli under certain circumstances. Magnetic field, pressure, and chemical composition all have been demonstrated to be effective in inducing electronic/magnetic phase transitions in ruthenates. Therefore, ruthenates are ideal candidates for searching for novel quantum phenomena through controlling external parameters. The objective of this project is to search for novel quantum phenomena in ruthenate materials using high-quality single crystals grown by the floating-zone technique, and investigate the underlying physics. The following summarizes our accomplishments. We have focused on trilayered Sr4Ru3O10 and bilayered (Ca1-xSrx)3Ru2O7. We have succeeded in growing high-quality single crystals of these materials using the floating-zone technique and performed systematic studies on their electronic and magnetic properties through a variety of measurements, including resistivity, Hall coefficient, angle-resolved magnetoresistivity, Hall probe microscopy, and specific heat. We have also studied microscopic magnetic properties for some of these materials using neutron scattering in collaboration with Los Alamos National Laboratory. We have observed a number of unusual exotic quantum phenomena through these studies, such as an orbital selective metamagnetic transition, bulk spin valve effect, and a heavy-mass nearly ferromagnetic state with a surprisingly large Wilson ratio. Our work has also revealed underlying physics of these exotic phenomena. Exotic phenomena of correlated

  11. Computational studies of the geometry and electronic structure of an all-inorganic and homogeneous tetra-Ru-polyoxotungstate catalyst for water oxidation and its four subsequent one-electron oxidized forms.

    Science.gov (United States)

    Quiñonero, David; Kaledin, Alexey L; Kuznetsov, Aleksey E; Geletii, Yurii V; Besson, Claire; Hill, Craig L; Musaev, Djamaladdin G

    2010-01-14

    Geometry and electronic structure of five species [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](10-) (1), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](9-) (2), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](8-) (3), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](7-) (4), and [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](6-) (5) with different oxidation states of Ru centers were studied at the density functional and COSMO levels of theory. These species are expected to be among the possible intermediates of the recently reported 1-catalyzed water oxidation (Geletii, Y. V.; Botar, B.; Kogerler, P.; Hillesheim, D. A.; Musaev, D. G.; Hill, C. L. Angew. Chem. Int. Ed. 2008, 47, 3896-3899 and Sartorel, A.; Carraro, M.; Scorrano, G.; Zorzi, R. D.; Geremia, S.; McDaniel, N. D.; Bernhard, S.; Bonchio, M. J. Am. Chem. Soc. 2008, 130, 5006-5007). It was shown that RI-BP86 correctly describes the geometry and energy of the low-lying electronic states of compound 1, whereas the widely used B3LYP approach overestimates the energy of its high-spin states. Including the solvent and/or countercation effects into calculations improves the agreement between the calculated and experimental data. It was found that the several HOMOs and LUMOs of the studied complexes are bonding and antibonding orbitals of the [Ru(4)O(4)(OH)(2)(H(2)O)(4)](6+) core, and four subsequent one-electron oxidations of 1, leading to formation of 2, 3, 4, and 5, respectively, involve only {Ru(4)} core orbitals. In other words, catalyst instability due to ligand oxidation in the widely studied Ru-blue dimer, [(bpy)(2)(O)Ru(V)-(mu-O)-Ru(V)(O)(bpy)(2)](4+), is not operable for 1: the latter all-inorganic catalyst is predicted to be stable under water oxidation turnover conditions. The calculated HOMOs and LUMOs of all the studied species are very close in energy and exhibit a "quasi-continuum" or "nanoparticle-type" electronic structure similar to that of nanosized transition

  12. Phase equilibria in the Sm-{l_brace}Ru,Rh{r_brace}-{l_brace}Si,Ge{r_brace} systems at 870 K

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V. [Moscow Lomonosov State Univ. (Russian Federation). Dept. of Chem.; Seropegin, Yu.D. [Moscow Lomonosov State Univ. (Russian Federation). Dept. of Chem.; Bodak, O.I. [L`viv State Univ. (Ukraine). Dept. of Inorg. Chem.

    1996-02-01

    Physico-chemical analysis techniques, including X-ray phase analysis and electron probe X-ray analysis were employed in constructing the isothermal cross-section of the phase diagrams Sm-{l_brace}Ru,Rh{r_brace}-{l_brace}Si,Ge{r_brace} systems at 870 K. The formation of the new ternary intermetallic compounds, Sm{sub 2}RuGe{sub 2}, Sm{sub 2}RhGe{sub 2} (structure type Zr{sub 2}CoSi{sub 2}); Sm{sub 3}Ru{sub 2}Si{sub 2}, Sm{sub 3}Rh{sub 2}Si{sub 2}, Sm{sub 3}Rh{sub 2}Ge{sub 2} (structure type La{sub 3}Ni{sub 2}Ga{sub 2}); SmRh{sub 5}Si{sub 3}, SmRh{sub 5}Ge{sub 3} (structure type UCo{sub 5}Si{sub 3}); Sm{sub 2}Ru{sub 3}Si{sub 5} (structure type Sc{sub 2}Fe{sub 3}Si{sub 5}); SmRu{sub 3}Si{sub 2} (structure type LaRu{sub 3}Si{sub 2}); SmRuSi{sub 3} (structure type BaAl{sub 4}); Sm{sub 33}Rh{sub 20}Ge{sub 47} (structure type AlB{sub 2}); Sm{sub 25}Rh{sub 19}Ge{sub 56} (structure type CeRh{sub 1-x}Ge{sub 2+x}); Sm{sub 2}RhGe{sub 6} (structure type Ce{sub 2}CuGe{sub 6}) and Sm{sub 62}Ru{sub 28}Ge{sub 10}, SmRu{sub 3}Si, Sm{sub 2}RuSi{sub 2}, Sm{sub 62}Ru{sub 10}Si{sub 28}, Sm{sub 33}Rh{sub 50}Si{sub 17}, Sm{sub 16}Rh{sub 68}Si{sub 16}, SmRh{sub 3}Si{sub 6}, Sm{sub 37}Rh{sub 35}Si{sub 28}, Sm{sub 2}RhSi{sub 2}, Sm{sub 4}Rh{sub 4}Si, Sm{sub 33}Rh{sub 53}Ge{sub 14}, SmRh{sub 2}Ge, Sm{sub 18}Rh{sub 64}Ge{sub 18}, SmRh{sub 3}Ge{sub 6}, were detected in Sm-(Ru,Rh)-(Si,Ge) systems. It was found that compound SmRuSi does not belong to the structure type PbFCl. Ternary compound SmRuGe was not found in Sm-Ru-Ge system at 870 K. (orig.)

  13. Germanium thin film integration on silicon substrates via oxide heterostructure buffers

    Energy Technology Data Exchange (ETDEWEB)

    Giussani, Alessandro

    2010-02-15

    Following the GeOI heteroepitaxial approach, Ge was deposited by molecular beam epitaxy (MBE) on PrO{sub 2}(111)/Si(111) support systems, and the initial growth stages were studied by means of in-situ reflection high energy electron diffraction (RHEED), and X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS, respectively). It was shown that in the first evaporation stages an amorphous GeO{sub 2}-like layer forms as a result of the Ge adatom interaction with the PrO{sub 2} substrate, namely the diffusion of lattice oxygen from the dielectric into the growing semiconductor deposit. In consequence the PrO{sub 2}(111) buffer oxide is fully reduced to an oxygen-deficient cub (cubic) Pr{sub 2}O{sub 3}(111) film structure. Since no oxidizing species are available in the process anymore, the Ge oxide layer converts under continuous Ge evaporation to GeO, which is volatile at the deposition temperature ({proportional_to}550 C). The sublimation of GeO uncovers the cub-Pr{sub 2}O{sub 3}(111) surface, which finally provides a thermodynamically stable template for the heteroepitaxial growth of elemental Ge. A Volmer-Weber growth mode is initially observed, which, by properly tuning the deposition parameters, results after island coalescence in the formation of a closed and flat Ge/cub-Pr{sub 2}O{sub 3}/Si heterostructure. Ge epilayer thickness (in the range 20-1000 nm) and morphology were studied ex-situ by means of X-ray reflectivity (XRR) and secondary electron microscopy (SEM). Dynamic secondary ion mass spectroscopy (D-SIMS) was employed to study the chemical compositions of the Ge films, which turned out to be free from Si and Pr impurities at the sensitivity of some parts-per-billion (ppbs), even after supplying a high thermal budget. Then, laboratory- and synchrotron-based X-ray diffraction (XRD) analyses were performed to assess the epitaxial relationship and the defect structure of the Ge epifilms. It was demonstrated that the Ge layers grow single

  14. Role of Gd{sup 3+} ion on downshifting and upconversion emission properties of Pr{sup 3+}, Yb{sup 3+} co-doped YNbO{sub 4} phosphor and sensitization effect of Bi{sup 3+} ion

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, A.; Rai, S. B., E-mail: sbrai49@yahoo.co.in [Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Mishra, Kavita [Department of Physics, University of Lucknow, Lucknow 226007 (India)

    2016-07-28

    concentration of Pr{sup 3+} and Bi{sup 3+} ions, and the results are explained by the well-known simple band structure model. The study of Gd{sup 3+} co-doping reveals noticeable differences in DS characteristics of Y{sub 1−x}Pr{sub x}NbO{sub 4} phosphors: the overall decrement and increment (except for 612 nm emission) in intensity of DS emission on excitation with λ{sub ex} = 264 nm and 491 nm, respectively. These observations have been thoroughly explained, and the {sup 1}D{sub 2}→{sup 3}H{sub 4} transition (612 nm) of Pr{sup 3+} ion is found to be strongly dependent on surrounding environment of the host matrix. The UC properties of Y{sub 0.95−x}Pr{sub x}Yb{sub 0.05}NbO{sub 4} phosphors have been explored using Near Infra-Red (NIR) excitation. The material gives intense green and relatively weak blue and red UC emissions with λ{sub ex} = 980 nm. Interestingly, the UC emission intensity is further enhanced in the case of Y{sub 0.949−x}Pr{sub 0.001}Yb{sub 0.05}Gd{sub x}NbO{sub 4} phosphors. In addition, the less explored laser induced heating effect with the pump power as well as the irradiation time on the UC emission has been explored in Y{sub 0.949−x}Pr{sub 0.001}Yb{sub 0.05}Gd{sub x}NbO{sub 4} (x = 0, 0.5, and 0.949) phosphor samples, and subsequently, this feature has been found to be superior for Gd{sub 0.949}Pr{sub 0.001}Yb{sub 0.05}NbO{sub 4} phosphor. The comparative study between the two hosts, viz., YNbO{sub 4} and GdNbO{sub 4} shows that GdNbO{sub 4} is better than YNbO{sub 4} for UC emission behavior; however, a reverse is observed as for as DS behavior is concerned only for the particular excitation wavelength (λ{sub ex} = 264 nm).

  15. EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems

    Science.gov (United States)

    Ronning, Filip; Batista, Cristian

    2011-03-01

    during SCES 2010. As we learned, past dogmas about strongly correlated materials and phenomena must be re-examined with an open and inquisitive mind. Invited speakers and respected leaders in the field were invited to contribute to this special issue and we have insisted that they present new data, ideas, or perspectives, as opposed to simply an overview of their past work. As with the conference, this special issue touches upon recent developments of strongly correlated electron systems in d-electron materials, such as Sr3Ru2O7, graphene, and the new Fe-based superconductors, but it is dominated by topics in f-electron compounds. Contributions reflect the growing appreciation for the influence of disorder and frustration, the need for organizing principles, as well as detailed investigations on particular materials of interest and, of course, new materials. As this special issue could not possibly capture the full breadth and depth that the conference had to offer, it is being published simultaneously with an issue of Journal of Physics: Conference Series containing 157 manuscripts in which all poster presenters at SCES 2010 were invited to contribute. Since this special issue grew out of the 2010 SCES conference, we take this opportunity to give thanks. This conference would not have been possible without the hard work of the SCES 2010 Program Committee, International and National Advisory Committees, Local Committee, and conference organizers, the New Mexico Consortium. We thank them as well as those organizations that generously provided financial support: ICAM-I2CAM, Quantum Design, Lakeshore, the National High Magnetic Field Laboratory and the Department of Energy National Laboratories at Argonne, Berkeley, Brookhaven, Los Alamos and Oak Ridge. Of course, we especially thank the participants for bringing new ideas and new results, without which SCES 2010 would not have been possible. Strongly correlated electron systems contents Spin-orbit coupling and k