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Sample records for sr2 ru o4

  1. Epitaxial YBa2Cu3O7-δ/Sr2RuO4 heterostructures

    International Nuclear Information System (INIS)

    Schlom, D.G.; Merritt, B.A.; Madhavan, S.

    1997-01-01

    The anisotropic oxide superconductors YBa 2 Cu 3 O 7-δ and Sr 2 RuO 4 have been epitaxially combined in various ways (c-axis on c-axis, c-axis on a-axis, and a-axis on a-axis) though the use of appropriate substrates. Phase-pure a-axis oriented or c-axis oriented epitaxial Sr 2 RuO 4 films were grown by pulsed laser deposition. YBa 2 Cu 3 O 7-δ films were then grown on both orientations of Sr 2 RuO 4 films and the resulting epitaxy was characterized

  2. Vertical Line Nodes in the Superconducting Gap Structure of Sr_{2}RuO_{4}

    Directory of Open Access Journals (Sweden)

    E. Hassinger

    2017-03-01

    Full Text Available There is strong experimental evidence that the superconductor Sr_{2}RuO_{4} has a chiral p-wave order parameter. This symmetry does not require that the associated gap has nodes, yet specific heat, ultrasound, and thermal conductivity measurements indicate the presence of nodes in the superconducting gap structure of Sr_{2}RuO_{4}. Theoretical scenarios have been proposed to account for the existence of deep minima or accidental nodes (minima tuned to zero or below by material parameters within a p-wave state. Other scenarios propose chiral d-wave and f-wave states, with horizontal and vertical line nodes, respectively. To elucidate the nodal structure of the gap, it is essential to know whether the lines of nodes (or minima are vertical (parallel to the tetragonal c axis or horizontal (perpendicular to the c axis. Here, we report thermal conductivity measurements on single crystals of Sr_{2}RuO_{4} down to 50 mK for currents parallel and perpendicular to the c axis. We find that there is substantial quasiparticle transport in the T=0 limit for both current directions. A magnetic field H immediately excites quasiparticles with velocities both in the basal plane and in the c direction. Our data down to T_{c}/30 and down to H_{c2}/100 show no evidence that the nodes are in fact deep minima. Relative to the normal state, the thermal conductivity of the superconducting state is found to be very similar for the two current directions, from H=0 to H=H_{c2}. These findings show that the gap structure of Sr_{2}RuO_{4} consists of vertical line nodes. This rules out a chiral d-wave state. Given that the c-axis dispersion (warping of the Fermi surface in Sr_{2}RuO_{4} varies strongly from sheet to sheet, the small a-c anisotropy suggests that the line nodes are present on all three sheets of the Fermi surface. If imposed by symmetry, vertical line nodes would be inconsistent with a p-wave order parameter for Sr_{2}RuO_{4}. To reconcile the gap structure

  3. Electronic structure of Sr2RuO4 studied by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Iwasawa, H.; Aiura, Y.; Saitoh, T.; Yoshida, Y.; Hase, I.; Ikeda, S.I.; Bando, H.; Kubota, M.; Ono, K.

    2007-01-01

    Electronic structure of the monolayer strontium ruthenate Sr 2 RuO 4 was investigated by high-resolution angle-resolved photoemission spectroscopy. We present photon-energy (hν) dependence of the electronic structure near the Fermi level along the ΓM line. The hν dependence has shown a strong spectral weight modulation of the Ru 4d xy and 4d zx bands

  4. Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms

    Science.gov (United States)

    Nobukane, Hiroyoshi; Matsuyama, Toyoki; Tanda, Satoshi

    2017-01-01

    The quantum anomaly that breaks the symmetry, for example the parity and the chirality, in the quantization leads to a physical quantity with a topological Chern invariant. We report the observation of a Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms by employing electric transport. We observed the superconductor-to-insulator transition by reducing the thickness of Sr2RuO4 single crystals. The appearance of a gap structure in the insulating phase implies local superconductivity. Fractional quantized conductance was observed without an external magnetic field. We found an anomalous induced voltage with temperature and thickness dependence, and the induced voltage exhibited switching behavior when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle Θ = π/6 was determined by observing the topological magneto-electric effect in the Bose-insulating phase of Sr2RuO4 nanofilms.

  5. Unconventional transport characteristics of p-wave superconducting junctions in Sr2RuO4-Ru eutectic system

    International Nuclear Information System (INIS)

    Kambara, H.; Kashiwaya, S.; Yaguchi, H.; Asano, Y.; Tanaka, Y.; Maeno, Y.

    2010-01-01

    We report on novel local transport characteristics of naturally formed p-wave superconducting junctions of Sr 2 RuO 4 -Ru eutectic system by using microfabrication technique. We observed quite anomalous voltage-current (differential resistance-current) characteristics for both I//ab and I//c directions, which are not seen in conventional Josephson junctions. The anomalous features suggest the internal degrees of freedom of the superconducting state, possibly due to chiral p-wave domain. The dc current acts as a driving force to move chiral p-wave domain walls and form larger critical current path to cause the anomalous hysteresis.

  6. Optical conductivity of the triplet superconductor Sr2RuO4

    International Nuclear Information System (INIS)

    Virosztek, Attila; Dora, Balazs; Maki, Kazumi

    2003-10-01

    Now the spin triplet superconductivity in Sr 2 RuO 4 is well established. As to the nodal structures seen in high quality samples, there are two alternative models at present: a. 2D f-wave model with Δ(k) ∼ (k-circumflex x ± ik-circumflex y ) cos(ck z ) and b. the multigap model with Δ 1 (k) ∼ (k-circumflex x ± ik-circumflex y ) and Δ 2 (k) ∼ (k-circumflex x ± ik-circumflex y ) cos(ck z /2). In this paper we calculate the optical conductivity for T e in the 2D f-wave model and show that it differs significantly from those in the multigap model. (author)

  7. Galvanomagnetic properties of atomic-disordered Sr2RuO4 single crystals

    International Nuclear Information System (INIS)

    Kar'kin, A.E.; Naumov, S.V.; Goshchitskij, V.N.; Balbashov, A.M.

    2005-01-01

    The effect of neutron-bombardment-induced atomic disorder on the galvanomagnetic properties of Sr 2 RuO 4 single crystals has been experimentally studied in a broad range of temperatures (1.7-380 K) and magnetic fields (up to 13.6 T). The disorder leads to the appearance of negative temperature coefficients for both the in-plane electric resistivity (ρ a ) and that along the c axis (ρ c ), as well as the negative magnetoresistance Δρ, which is strongly anisotropic to the magnetic field orientation (H || a and H || c), with the easy magnetization direction along the c axis and a weak dependence on the probing current direction in the low-temperature region. The experimental ρ a (T) and ρ c (T) curves obtained for the initial and radiation-disordered samples can be described in the framework of a theoretical model with two conductivity channels. The first channel corresponds to the charge carriers with increased effective masses and predominantly electron-electron scattering, the second channel corresponds to the charge carriers with lower effective masses exhibiting magnetic scattering at low temperatures [ru

  8. Enhanced superconductivity at the interface of W/Sr2RuO4 point contact

    Science.gov (United States)

    Wei, Jian; Wang, He; Lou, Weijian; Luo, Jiawei; Liu, Ying; Ortmann, J. E.; Mao, Z. Q.

    Differential resistance measurements are conducted for point contacts (PCs) between the Sr2RuO4 (SRO) single crystal and the tungsten tip. Since the tungsten tip is hard enough to penetrate through the surface layer, consistent superconducting features are observed. Firstly, with the tip pushed towards the crystal, the zero bias conductance peak (ZBCP) due to Andreev reflection at the normal-superconducting interface increases from 3% to more than 20%, much larger than previously reported, and extends to temperature higher than the bulk transition temperature. Reproducible ZBCP within 0.2 mV may also help determine the gap value of SRO, on which no consensus has been reached. Secondly, the logarithmic background can be fitted with the Altshuler-Aronov theory of electron-electron interaction for tunneling into quasi two dimensional electron system. Feasibility of such fitting confirms that spectroscopic information like density of states is probed, and electronic temperature retrieved from such fitting can be important to analyse the PC spectra. Third, at bias much higher than 0.2 mV there are conductance dips due to the critical current effect and these dips persist up to 6.2 K. For more details see. National Basic Research Program of China (973 Program) through Grant No. 2011CBA00106 and No. 2012CB927400.

  9. Anisotropy of the incommensurate fluctuations in Sr2RuO4: a study with polarized neutrons.

    Science.gov (United States)

    Braden, M; Steffens, P; Sidis, Y; Kulda, J; Bourges, P; Hayden, S; Kikugawa, N; Maeno, Y

    2004-03-05

    The anisotropy of the magnetic incommensurate fluctuations in Sr2RuO4 has been studied by inelastic neutron scattering with polarized neutrons. We find a sizable enhancement of the out-of-plane component by a factor of 2 for intermediate energy transfer, which appears to decrease for higher energies. Our results qualitatively confirm calculations of the spin-orbit coupling, but the experimental anisotropy and its energy dependence are weaker than predicted.

  10. Effect of Cleaving Temperature on the Surface and Bulk Fermi Surface of Sr2RuO4 Investigated by High Resolution Angle-Resolved Photoemission

    International Nuclear Information System (INIS)

    Liu Shan-Yu; Zhang Wen-Tao; Weng Hong-Ming; Zhao Lin; Liu Hai-Yun; Jia Xiao-Wen; Liu Guo-Dong; Dong Xiao-Li; Zhang Jun; Dai Xi; Fang Zhong; Zhou Xing-Jiang; Mao Zhi-Qiang; Chen Chuang-Tian; Xu Zu-Yan

    2012-01-01

    High resolution angle-resolved photoemission measurements are carried out to systematically investigate the effect of cleaving temperature on the electronic structures and Fermi surfaces of Sr 2 RuO 4 . Unlike previous reports, which found that a high cleaving temperature can suppress the surface Fermi surface, we find that the surface Fermi surface remains obvious and strong in Sr 2 RuO 4 cleaved at high temperature, even at room temperature. This indicates that cleaving temperature is not a key effective factor in suppressing surface bands. On the other hand, the bulk bands can be enhanced in an aged surface of Sr 2 RuO 4 that has been cleaved and held for a long time. We have also carried out laser ARPES measurements on Sr 2 RuO 4 by using a vacuum ultra-violet laser (photon energy at 6.994 eV) and found an obvious enhancement of bulk bands even for samples cleaved at low temperature. This information is important for realizing an effective approach to manipulating and detecting the surface and bulk electronic structure of Sr 2 RuO 4 . In particular, the enhancement of bulk sensitivity, along with the super-high instrumental resolution of VUV laser ARPES, will be advantageous in investigating fine electronic structure and superconducting properties of Sr 2 RuO 4 in the future. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  11. Fermi Surface of Sr_{2}RuO_{4}: Spin-Orbit and Anisotropic Coulomb Interaction Effects.

    Science.gov (United States)

    Zhang, Guoren; Gorelov, Evgeny; Sarvestani, Esmaeel; Pavarini, Eva

    2016-03-11

    The topology of the Fermi surface of Sr_{2}RuO_{4} is well described by local-density approximation calculations with spin-orbit interaction, but the relative size of its different sheets is not. By accounting for many-body effects via dynamical mean-field theory, we show that the standard isotropic Coulomb interaction alone worsens or does not correct this discrepancy. In order to reproduce experiments, it is essential to account for the Coulomb anisotropy. The latter is small but has strong effects; it competes with the Coulomb-enhanced spin-orbit coupling and the isotropic Coulomb term in determining the Fermi surface shape. Its effects are likely sizable in other correlated multiorbital systems. In addition, we find that the low-energy self-energy matrix-responsible for the reshaping of the Fermi surface-sizably differs from the static Hartree-Fock limit. Finally, we find a strong spin-orbital entanglement; this supports the view that the conventional description of Cooper pairs via factorized spin and orbital part might not apply to Sr_{2}RuO_{4}.

  12. Probing chiral superconductivity in Sr_2RuO_4 underneath the surface by point contact measurements

    International Nuclear Information System (INIS)

    Wang, He; Luo, Jiawei; Lou, Weijian

    2017-01-01

    Sr2RuO4 (SRO) is the prime candidate for a chiral p-wave superconductor with critical temperature T_c(SRO)∼1.5 K. Chiral domains with opposite chiralities p_x±ip_y have been proposed, but are yet to be confirmed. We measure the field dependence of the point contact (PC) resistance between a tungsten tip and an SRO–Ru eutectic crystal, where micrometer-sized Ru inclusions are embedded in SRO with an atomically sharp interface. Ruthenium is an s-wave superconductor with T_c(Ru)∼0.5 K; flux pinned near the Ru inclusions can suppress its superconductivity, as reflected in the PC resistance and spectra. This flux pinning effect originates from SRO underneath the surface and is very strong once flux is introduced. To fully remove flux pinning, one needs to thermally cycle the sample above T_c(SRO) or apply alternating fields with decreasing amplitude. With alternating fields, the observed hysteresis in magnetoresistance can be explained by domain dynamics, providing support for the existence of chiral domains. The origin of the strong pinning could be the chiral domains themselves.

  13. Hydrostatic Pressure Study on 3-K Phase Superconductivity in Sr2RuO4-Ru Eutectic Crystals by AC Magnetic Susceptibility Measurements

    International Nuclear Information System (INIS)

    Yaguchi, Hiroshi; Watanabe, Hiromichi; Sakaue, Akira

    2012-01-01

    We have investigated the effect of hydrostatic pressure on 3-K phase superconductivity in Sr 2 RuO 4 -Ru eutectic crystals by means of AC magnetic susceptibility measurements. We have found that the application of hydrostatic pressure suppresses the superconducting transition temperature T c of the 3-K phase with a pressure coefficient of dT c /dP ≈ −0.2 K/GPa, similar to the case of the 1.5-K phase. We have also observed that the effect of hydrostatic pressure on the 3-K phase seems to be elastic whilst that of uniaxial pressure is plastic.

  14. Coherence peak in the spin susceptibility from nesting in spin-triplet superconductors: A probe for line nodes in Sr2RuO4

    International Nuclear Information System (INIS)

    Yakiyama, Mayumi; Hasegawa, Yasumasa

    2003-01-01

    We study the dynamical spin susceptibility χ(q,ω) for spin-triplet superconductivity. We show that a large peak at ω=2Δ appears in Imχ zz (Q,ω), where z is the direction of the d vector for triplet pairing, if Fermi surface has a nested part with the nesting vector Q and the order parameters are +Δ and -Δ in this part of the Fermi surface. If there are line nodes in the nested part of the Fermi surface, a peak appears in either Imχ zz (Q,ω) or Imχ +- (Q,ω), or both, depending on the perpendicular component of the nesting vector. The comparison with inelastic neutron-scattering experiments can determine the position of the line nodes in triplet superconductor Sr 2 RuO 4

  15. Resonant Raman scattering in Nd2O3 and the electronic structure of Sr2RuO4 studied by synchrotron radiation excitation

    International Nuclear Information System (INIS)

    Ederer, D. L.

    1998-01-01

    This paper is intended to illustrate two points. The first being the extensive growth of resonant Raman soft x-ray scattering due to the emergence of third-generation x-ray sources. With these sources, the ubiquitous presence of Raman scattering near the 3d and 4d ionization thresholds has been used to elucidate the excitation process in a number of rare earth and transition metal compounds. Such scattering can produce dramatic changes in the emission spectrum, as we show in our example of inelastic scattering at the 3d threshold of Nd 2 O 3 . Photon-in photon-out soft x-ray spectroscopy is adding a new dimension to soft x-ray spectroscopy by providing many opportunities for exciting research, especially at third-generation synchrotrons light sources. Second, it is very effective to use theory and experiment to characterize the electronic properties of materials. In particular we confirmed in-plane oxygen-ruthenium bonding in Sr 2 RuO 4 , this first copperless perovskite superconductor, by analyses using calculations, soft x-ray emission spectroscopy (SXE) and photoelectron spectroscopy (PES). Measurements of this type illustrate the importance of combining SXE and PES measurements with theoretical calculations

  16. Quasi-two-dimensional Fermi-liquid state in Sr2RhO4

    International Nuclear Information System (INIS)

    Nagai, Ichiro; Shirakawa, Naoki; Umeyama, Norio; Ikeda, Shin-ichi

    2010-01-01

    Single crystals of layered perovskite Sr 2 RhO 4-δ (δ=0.0 and 0.1) are successfully grown by the floating-zone method. Stoichiometric single crystals (Sr 2 RhO 4.0 ) are obtained by O 2 -annealing the as-grown crystals (Sr 2 RhO 3.9 ). Sr 2 RhO 4.0 and Sr 2 RhO 3.9 show quasi-two-dimensional Fermi-liquid behavior at low temperatures, whereas there are large differences in the anisotropy of electrical resistivity ρ c (3 K)/ρ ab (3 K) and Wilson ratio R w between Sr 2 RhO 4.0 and Sr 2 RhO 3.9 : ρ c (3 K)/ρ ab (3 K)=2400 (19000) and R w =3.8 (6.4) for Sr 2 RhO 4.0 (Sr 2 RhO 3.9 ). The differences observed between the temperature dependence of the in-plane electrical resistivity (T 2 RhO 4.0 and Sr 2 RhO 3.9 are mainly derived from those between the density of states and band structure near the corresponding Fermi level. This indicates that the changes in these physical properties, which are accompanied by oxygen defects in the Sr 2 RhO 4-δ system, can be explained by the rigid band model. Moreover, these results suggest that t 2g band-filling can be controlled by adjusting the oxygen defect content δ in the Sr 2 RhO 4-δ system. Although many similarities are observed in this study between the physical properties of Sr 2 RhO 4.0 and Sr 2 RuO 4 . Sr 2 RhO 4.0 does not exhibit superconductivity down to 36 mK. (author)

  17. Sr2CeO4: Electronic and structural properties

    International Nuclear Information System (INIS)

    Rocha, Leonardo A.; Schiavon, Marco A.; Nascimento, Clebio S.; Guimarães, Luciana; Góes, Márcio S.; Pires, Ana M.; Paiva-Santos, Carlos O.

    2014-01-01

    Highlights: • Sr 2 CeO 4 it was obtained from the heat treatment of Ce 3+ -doped strontium oxalate. • Rietveld analysis made it possible to obtain information about crystalline structure. • Experimental band gap value was compared with theoretical obtained by Sparkle/PM7. • The materials obtained shows intense photoluminescence and scintillator properties. - Abstract: This work presents on the preparation and photoluminescent properties of Sr 2 CeO 4 obtained from the heat treatment of Ce(III)-doped strontium oxalate (10, 25 and 33 mol%). The oxalate precursors were heat treated at 1100 °C for 12 h. The structure of this photoluminescent material was evaluated by the Rietveld method. The route used in this work to prepare the materials showed to be viable when compared to other synthesis reported in the literature. The Sr 2 CeO 4 material showed a broad and intense band emission with a maximum around 485 nm. The quantitative phase analysis showed that the Sr 2 CeO 4 photoluminescent phase is the majority one compared to the impurity phases of SrCeO 3 and SrCO 3 . From all results it was possible to verify a complete elimination of the CeO 2 phase for the sample obtained from the heat treatment of oxalate precursor containing 33 mol% of cerium(III). The material showed excellent properties for possible candidate as scintillator materials, and in the improvement of efficiency of solar cells when excited in the UV–vis region. The CIE chromaticity diagram it is also reported in this work

  18. Anisotropic Magnetoresistance in Antiferromagnetic Sr_{2}IrO_{4}

    Directory of Open Access Journals (Sweden)

    C. Wang

    2014-11-01

    Full Text Available We report point-contact measurements of anisotropic magnetoresistance (AMR in a single crystal of antiferromagnetic Mott insulator Sr_{2}IrO_{4}. The point-contact technique is used here as a local probe of magnetotransport properties on the nanoscale. The measurements at liquid nitrogen temperature reveal negative magnetoresistances (up to 28% for modest magnetic fields (250 mT applied within the IrO_{2} a-b plane and electric currents flowing perpendicular to the plane. The angular dependence of magnetoresistance shows a crossover from fourfold to twofold symmetry in response to an increasing magnetic field with angular variations in resistance from 1% to 14%. We tentatively attribute the fourfold symmetry to the crystalline component of AMR and the field-induced transition to the effects of applied field on the canting of antiferromagnetic-coupled moments in Sr_{2}IrO_{4}. The observed AMR is very large compared to the crystalline AMRs in 3d transition metal alloys or oxides (0.1%–0.5% and can be associated with the large spin-orbit interactions in this 5d oxide while the transition provides evidence of correlations between electronic transport, magnetic order, and orbital states. The finding of this work opens an entirely new avenue to not only gain a new insight into physics associated with spin-orbit coupling but also to better harness the power of spintronics in a more technically favorable fashion.

  19. Photoluminescent properties of Sr2CeO4: Eu3+ and Sr2CeO4: Eu2+ phosphors suitable for near ultraviolet excitation

    International Nuclear Information System (INIS)

    Suresh, K.; Poornachandra Rao, N.V.; Murthy, K.V.R.

    2014-01-01

    Powder phosphors of 1 mol% Eu 3+ - and Eu 2+ -doped strontium cerium oxide (Sr 2 CeO 4 ) were synthesized by standard solid-state reaction method. Eu 3+ - and Eu 2+ -doped Sr 2 CeO 4 phosphors fired at 1100 ℃ for 2 h were analysed by X-ray diffraction (XRD) and photoluminescence (PL) techniques. The XRD patterns confirm that the obtained phosphors are a single phase of Sr 2 CeO 4 composed of orthorhombic structure. Room temperature PL excitation spectrum of air-heated Sr 2 CeO 4 : Eu phosphor has exhibited bands at 260, 280 and 350 nm. Whereas the excitation spectrum of Sr 2 CeO 4 : Eu phosphor heated under reducing (carbon) atmosphere exhibited single broadband range from 260 to 390 nm. The (PL) emission peaks of both the phosphors at 467 (blue), 537 (green) and 616 nm (red) generate white light under 260, 280 and 350 nm excitation wavelengths. The Commission International de l'Eclairage (CIE) colour coordinates conforms that these phosphors emitting white light. The results reveal that these phosphors are multifunctional phosphors which emit white light under these excitations that they could be used as white components for display and lamp devices and as well as possible good light-conversion phosphor LEDs under near-ultraviolet (nUV) chip. (author)

  20. Systems of OsO4-RuO4 and Re2O7-OsO4

    International Nuclear Information System (INIS)

    Nisel'son, L.A.; Sokolova, T.D.; Orlov, A.M.; Shorikov, Yu.S.

    1981-01-01

    The meltability diagrams of the systems OsO 4 -RuO 4 and Re 2 O 7 -OsO 4 are studied using the visual-polythermal method. The OsO 4 -RuO 4 system forms a continuous series of solid solutions with practically rectilinear line of the liquidus. The Re 2 O 7 -OsO 4 system of the eutectic type has the eutectics degenerated from the side of OsO 4 . For the system OsO 4 (basis)-RuO 4 (admixture) the equilibrium coefficient of distribution is determined using the method of directed crystallization [ru

  1. Synthesis, structural and luminescent aspect of Tb3+ doped Sr2SnO4 phosphor

    International Nuclear Information System (INIS)

    Taikar, Deepak R.

    2016-01-01

    A novel green emitting, Tb 3+ doped Sr 2 SnO 4 phosphor was synthesized by the co-precipitation method and its photoluminescence characterization was performed. Sr 2 SnO 4 has an ordered tetragonal K 2 NiF 4 -type structure with space group I4/mmm. The structure of Sr 2 SnO 4 consists of SnO 6 octahedra. From the structure of Sr 2 SnO 4 , it was observed that the sites of Sn 4+ ions have inverse symmetry while the Sr 2+ ions have the low symmetry. X-ray powder diffraction (XRD) analysis confirmed the formation of Sr 2 SnO 4 :Tb 3+ . Photoluminescence measurements showed that the phosphor exhibited bright green emission at about 543 nm attributed to 5 D 4 à 7 F 5 transition of Tb 3+ ion under UV excitation. The emission spectra did not exhibit conventional blue emission peaks of Tb 3+ ions due to 5 D 3 → 7 F J transitions in the spectral region 350-470 nm. The excitation spectra indicate that this compound may be useful as a lamp phosphor. (author)

  2. An open aperture z-scan study of Sr2CeO4 blue phosphor

    International Nuclear Information System (INIS)

    Seema, R.; Sandeep, C.S. Suchand; Philip, Reji; Kalarikkal, Nandakumar

    2011-01-01

    Highlights: → Sr 2 CeO 4 blue phosphor has been prepared by a solid state reaction method. → The XRD study confirms that the structure of the system is orthorhombic. → The TEM reveals that Sr 2 CeO 4 is composed of elongated spherical structures of length ∼0.2-0.6 μm. → The FFT of TEM, XRD peaks and the JCPDS values are compared, from which the Sr 2 CeO 4 phase is reconfirmed. → A z-scan measurement gives the effective two-photon absorption coefficient to be 3.9 x 10 -11 m/W. - Abstract: Sr 2 CeO 4 blue phosphor has been prepared by the solid-state reaction method. The X-ray diffraction (XRD) study confirms the structure of the system to be orthorhombic. High resolution electron transmission microscopy reveals that Sr 2 CeO 4 prepared by the solid state reaction method is composed of elongated spherical structures of length ∼0.2-0.6 μm and width ∼90-150 nm. The excitation spectrum shows a broad band which peaks at 275 nm. The emission spectrum shows a broad band which peaks at 467 nm when excited at 275 nm. The emission band is assigned to the energy transfer between the molecular orbital of the ligand and charge transfer (CT) state of the Ce 4+ ion. The Commission International de l'Eclairage (CIE) co-ordinates are x = 0.15, and y = 0.23. The nonlinear absorption behavior of Sr 2 CeO 4 has been investigated using the open aperture z-scan technique. The calculated effective two-photon absorption coefficient shows that the Sr 2 CeO 4 blue phosphor is a promising optical limiting material.

  3. Nanocrystalline Sr2CeO4 thin films grown on silicon by laser ablation

    International Nuclear Information System (INIS)

    Perea, Nestor; Hirata, G.A.

    2006-01-01

    Blue-white luminescent Sr 2 CeO 4 thin films were deposited by using pulsed laser ablation (λ = 248 nm wavelength) on 500 deg. C silicon (111) substrates under an oxygen pressure of 55 mTorr. High-resolution electron transmission microscopy, electron diffraction and X-ray diffraction analysis revealed that the films were composed of nanocrystalline Sr 2 CeO 4 grains of the order of 20-30 nm with a preferential orientation in the (130) crystallographic direction. The excitation and photoluminescence spectra measured on the films maintained the characteristic emission of bulk Sr 2 CeO 4 however, the emission peak appeared narrower and blue-shifted as compared to the luminescence spectrum of the target. The blue-shift and a preferential crystallographic orientation during the growth formation of the film is related to the nanocrystalline nature of the grains due to the quantum confinement behavior and surface energy minimization in nanostructured systems

  4. Eu and Sr2CeO4 : Eu phosphors suitable for near ultraviolet excitation

    Indian Academy of Sciences (India)

    Administrator

    The study on white light phosphors suitable for near- ultraviolet (nUV) ... Rare earth ion-doped phosphors have been used in varied fields ... practical applications. .... by naked eyes. ... induced by Sr2CeO4 host matrix (Arunachalam Laxmanan.

  5. Influence of dopant concentration on spectroscopic properties of Sr2CeO4:Yb nanocrystals

    Science.gov (United States)

    Stefanski, M.; Kędziorski, A.; Hreniak, D.; Strek, W.

    2017-12-01

    Optical properties of Sr2CeO4:Yb nanocrystals synthesized via Pechini's method are reported. The samples were characterized by X-ray diffraction data measurements. The unit cell parameters were determined using Rietveld refinement. It was found that they decreased with increasing amount of Yb ions. The absorption, excitation, emission spectra and luminescence decay profiles of the Sr2CeO4:Yb nanocrystals were investigated. It was observed that optical properties were strongly dependent on Yb concentration. It was found that Yb3+-O2- charge transfer transitions have great influence on the absorption spectra. It can be seen in the emission spectra that in addition to standard bands/lines corresponding to Ce-O metal-to-ligand charge transfer of Sr2CeO4 and f-f transitions of Yb3+, there is emission band centered at 744 nm. Its intensity depends on the concentration of the dopant. Recorded decay times become shorter with increasing dopant concentration due to the Yb3+ concentration quenching. Excitation spectra indicate the energy transfer from Ce-O charge transfer states to Yb3+2F5/2 state. The issue of appearance of down-conversion process in Sr2CeO4:Yb nanocrystals is considered.

  6. Topotactic Solid-State Metal Hydride Reductions of Sr2MnO4.

    Science.gov (United States)

    Hernden, Bradley C; Lussier, Joey A; Bieringer, Mario

    2015-05-04

    We report novel details regarding the reactivity and mechanism of the solid-state topotactic reduction of Sr2MnO4 using a series of solid-state metal hydrides. Comprehensive details describing the active reducing species are reported and comments on the reductive mechanism are provided, where it is shown that more than one electron is being donated by H(-). Commonly used solid-state hydrides LiH, NaH, and CaH2, were characterized in terms of reducing power. In addition the unexplored solid-state hydrides MgH2, SrH2, and BaH2 are evaluated as potential solid-state reductants and characterized in terms of their reductive reactivities. These 6 group I and II metal hydrides show the following trend in terms of reactivity: MgH2 < SrH2 < LiH ≈ CaH2 ≈ BaH2 < NaH. The order of the reductants are discussed in terms of metal electronegativity and bond strengths. NaH and the novel use of SrH2 allowed for targeted synthesis of reduced Sr2MnO(4-x) (0 ≤ x ≤ 0.37) phases. The enhanced control during synthesis demonstrated by this soft chemistry approach has allowed for a more comprehensive and systematic evaluation of Sr2MnO(4-x) phases than previously reported phases prepared by high temperature methods. Sr2MnO3.63(1) has for the first time been shown to be monoclinic by powder X-ray diffraction and the oxidative monoclinic to tetragonal transition occurs at 450 °C.

  7. Two crystalline modifications of RuO4

    International Nuclear Information System (INIS)

    Pley, Martin; Wickleder, Mathias S.

    2005-01-01

    RuO 4 was prepared by oxidation of elemental ruthenium. Two different modifications were obtained and investigated by X-ray single crystal diffraction. RuO 4 -I has cubic symmetry (P4; - 3n,Z=8,a=8.509(1)A), and two independent tetrahedral molecules are present in the unit cell. Within the standard uncertainties in both molecules the distances Ru-O are 1.695A. The second modification, RuO 4 -II, is monoclinic (C2/c,Z=4,a=9.302(4)A,b=4.3967(10)A,c=8.454(4)A,β=116.82(3) o ) and isotypic with OsO 4 . There is one independent molecule in the unit cell, which shows distances Ru-O of 1.697 and 1.701A, respectively

  8. Effect of In-Doping on Electronic Structure and Optical Properties of Sr2TiO4

    International Nuclear Information System (INIS)

    Jiang-Ni, Yun; Zhi-Yong, Zhang; Jun-Feng, Yan; Fu-Chun, Zhang

    2009-01-01

    The effect of In doping on the electronic structure and optical properties of Sr 2 TiO 4 is investigated by a first-principles calculation of plane wave ultrasoft pseudopotentials based on density functional theory. The calculated results reveal that corner-shared TiO 6 octahedra dominate the main electronic properties of Sr 2 TiO 4 and the covalency of the Ti–O(1) bond in the ab plane is stronger than that of the Ti–O(2) bond along the c-axis. After In doping, there is a little lattice expansion in Sr 2 In 0.125 Ti 0.875 O 4 , and the interaction between the Ti–O bond near the impurity In atom is weakened. The binding energies of Sr 2 TiO 4 and Sr 2 In 0.125 Ti 0.875 O 4 , estimated from the electronic structure calculations indicate that the crystal structure of Sr 2 In 0.125 Ti 0.875 O 4 is still stable after doping, but its stability is lower than that of undoped Sr 2 TiO 4 . Moreover, the valence bands (VBs) of the Sr 2 In 0.125 Ti 0.875 O 4 , system consist of O 2p and In 4d states, and the mixing of O 2p and In 4d states makes the top VBs shift significantly to high energies, resulting in visible light absorption. The adsorption of visible light is of practical importance for the application of Sr 2 TiO 4 as a photocatalyst. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  9. Synthesis and characterization of Sr2CeO4: Eu3+ phosphor by different forms

    International Nuclear Information System (INIS)

    Murthy, K.V.R.; Rao, Ch. Atchyutha; Suresh, K.; Ratna Kumar, B.W.; Nageswara Rao, B.; Poornachandra Rao, N.V.; Subba Rao, B.

    2011-01-01

    High temperature solid state reaction method was explored to synthesize undoped Sr 2 CeO 4 and Eu 3+ RE doped Sr 2 CeO 4 phosphor using inorganic materials taking in three different forms like, form (i) Strontium Carbonate (SrCO 3 ), Cerium Oxide (CeO 2 ), (ii) Strontium Nitrate (Sr(NO 3 ) 2 ), Cerium Oxide (CeO 2 ) and (iii) Strontium Nitrate (Sr(NO 3 ) 2 ), Cerium Nitrate (Ce(NO 3 ) 3 .6(NH 2 .CO.NH 2 ) in stoichiometric proportions of Sr:Ce as 2:1 and ground into a fine powder using agate mortar and pestle about an hour. The grounded samples were placed in an alumina crucible and fired at 1200 deg C for 3 hours in a muffle furnace with a heating rate of 5 deg C/min. To investigate the crystal structure, phase, morphology and luminescent properties of the synthesized phosphors XRD, SEM, Photoluminescence (PL) spectra, TL and CIE techniques were used. The Photoluminescence (PL) emission and excitation spectra were measured by Spectrofluorophotometer (SHIMADZU, RF-5301 PC) using Xenon lamp as excitation source. To identify the crystal phase, XRD analysis was carried out with a powder diffractometer (Rigaku-D/max 2500) using CuKα radiation. The microstructures of the samples were studied using a scanning electron microscopy (SEM) (XL 30 CP Philips). All the analysis was recorded at room temperature. We have compared the results of the prepared samples by different forms. From the XRD analysis it was found that the prepared phosphors are mostly in single phase of Sr 2 CeO 4 with an orthorhombic structure. From the XRD data, using Scherrer's formula the calculated average crystallite size is (i) ∼ 28 nm (ii) ∼ 9 nm (iii) ∼ 7 nm using FWHM. This indicates that, the prepared phosphors via high temperature solid state reaction method is in nano size. Sr 2 CeO 4 exhibits photoluminescence due to the charge transfer (CT) mechanism. The sample displays a broad excitation spectrum range from ∼ 220 to 400 nm. Under 350 nm excitation, the undoped Sr 2 CeO 4 shows

  10. Relaxor behavior in spin glass perovskite Sr2CoRuO6

    International Nuclear Information System (INIS)

    Phatak, Rohan; Sali, S.K.; Mishra, S.K.; Das, A.

    2014-01-01

    Dielectric properties of Sr 2 CoRuO 6 perovskite have been investigated. The compound crystallizes in monoclinic I2/c space group, with random distribution of Co and Ru ion on B site. From our previous study, we showed this compound to be magnetic spin glass with transition at 95K, and was investigated using neutron diffraction and depolarization, ac magnetization and time dependent magnetization

  11. Possible superconductivity in Sr2IrO4 probed by quasiparticle interference

    Science.gov (United States)

    Gao, Yi; Zhou, Tao; Huang, Huaixiang; Wang, Qiang-Hua

    2015-01-01

    Based on the possible superconducting (SC) pairing symmetries recently proposed, the quasiparticle interference (QPI) patterns in electron- and hole-doped Sr2IrO4 are theoretically investigated. In the electron-doped case, the QPI spectra can be explained based on a model similar to the octet model of the cuprates while in the hole-doped case, both the Fermi surface topology and the sign of the SC order parameter resemble those of the iron pnictides and there exists a QPI vector resulting from the interpocket scattering between the electron and hole pockets. In both cases, the evolution of the QPI vectors with energy and their behaviors in the nonmagnetic and magnetic impurity scattering cases can well be explained based on the evolution of the constant-energy contours and the sign structure of the SC order parameter. The QPI spectra presented in this paper can be compared with future scanning tunneling microscopy experiments to test whether there are SC phases in electron- and hole-doped Sr2IrO4 and what the pairing symmetry is. PMID:25783417

  12. Solid state speciation of uranium and its local structure in Sr2CeO4 using photoluminescence spectroscopy

    Science.gov (United States)

    Sahu, M.; Gupta, Santosh K.; Jain, D.; Saxena, M. K.; Kadam, R. M.

    2018-04-01

    An effort was taken to carry our speciation study of uranium ion in technologically important cerate host Sr2CeO4 using time resolved photoluminescence spectroscopy. Such studies are not relevant only to nuclear industry but can give rich insight into fundamentals of 5f electron chemistry in solid state systems. In this work both undoped and varied amount of uranium doped Sr2CeO4 compound is synthesized using complex polymerization method and is characterized systematically using X-ray diffraction (XRD), Raman spectroscopy, photoluminescence spectroscopy and scanning electron microscopy (SEM). Both XRD and Raman spectroscopy confirmed the formation of pure Sr2CeO4 which has tendency to decompose peritectically to SrCeO3 and SrO at higher temperature. Uranium doping is confirmed by XRD. Uranium exhibits a rich chemistry owing to its variable oxidation state from +3 to +6. Each of them exhibits distinct luminescence properties either due to f-f transitions or ligand to metal charge transfer (LMCT). We have taken Sr2CeO4 as a model host lattice to understand the photophysical characteristics of uranium ion in it. Emission spectroscopy revealed the stabilization of uranium as U (VI) in the form of UO66- (octahedral uranate) in Sr2CeO4. Emission kinetics study reflects that uranate ions are not homogeneously distributed in Sr2CeO4 and it has two different environments due to its stabilization at both Sr2+ as well as Ce4+ site. The lifetime population analysis interestingly pinpointed that majority of uranate ion resided at Ce4+ site. The critical energy-transfer distance between the uranate ion was determined based on which the concentration quenching mechanism was attributed to electric multipolar interaction. These studies are very important in designing Sr2CeO4 based optoelectronic material as well exploring it for actinides studies.

  13. High temperature-induced phase transitions in Sr2GdRuO6 complex perovskite

    International Nuclear Information System (INIS)

    Triana, C.A.; Corredor, L.T.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2011-01-01

    Highlights: ► Crystal structure, thermal expansion and phase transitions at high-temperature of Sr 2 GdRuO 6 perovskite has been investigated. ► X-ray diffraction pattern at 298 K of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with P2 1 /n space group. ► Evolution of X-ray diffraction patterns at high-temperature shows that the Sr 2 GdRuO 6 perovskite suffers two-phase transitions. ► At 573 K the X-ray diffraction pattern of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with I2/m space group. ► At 1273 K the Sr 2 GdRuO 6 perovskite suffers a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87). -- Abstract: The crystal structure behavior of the Sr 2 GdRuO 6 complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K ≤ T ≤ 1273 K. Measurements of X-ray diffraction at room-temperature and Rietveld analysis of the experimental patterns show that this compound crystallizes in a monoclinic perovskite-like structure, which belongs to the P2 1 /n (no. 14) space group and 1:1 ordered arrangement of Ru 5+ and Gd 3+ cations over the six-coordinate M sites. Experimental lattice parameters were obtained to be a =5.8103(5) Å, b =5.8234(1) Å, c =8.2193(9) Å, V = 278.11(2) Å 3 and angle β = 90.310(5)°. The high-temperature analysis shows the occurrence of two-phase transitions on this material. First, at 573 K it adopts a monoclinic perovskite-type structure with I2/m (no. 12) space group with lattice parameters a = 5.8275(6) Å, b = 5.8326(3) Å, c = 8.2449(2) Å, V = 280.31(3) Å 3 and angle β = 90.251(3)°. Close to 1273 K it undergoes a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87), with lattice parameters a = 5.8726(1) Å, c = 8.3051(4) Å, V = 286.39(8) Å 3 and angle β = 90.0°. The high-temperature phase transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87) is characterized

  14. Structural and electronic behavior of Sr2GdRuO6 complex perovskite

    International Nuclear Information System (INIS)

    Corredor, L.T.; Velasco Zarate, J.; Landinez Tellez, D.A.; Fajardo, F.; Arbey Rodriguez M, J.; Roa-Rojas, J.

    2009-01-01

    We report experimental and theoretical study of crystallographic lattice and electronic structure of Sr 2 GdRuO 6 complex perovskite, which is used as precursor in the fabrication process of superconducting ruthenocuprate RuSr 2 GdCu 2 O 8 . Samples were produced by the standard solid state reaction. Rietveld refinement of experimental X-ray diffraction patterns shows that material crystallizes in a monoclinic structure, which belongs to the P2 1 /n (no.14) space group, with lattice parameters a=5.8019(6)A, b=5.8296(5)A, c=8.2223(7)A, and tilt angle β=90.258 deg. Calculations of electronic structure were performed by the density functional theory. The exchange and correlation potentials were included through the LDA+U approximation. Density of states (DOS) study was carried out considering the two spin polarizations. Results show Gd are majority responsible for the magnetic character in this material, but Ru contribution is also relevant because d-orbital is closer to Fermi level. Theoretical results evidence that Sr 2 GdRuO 6 material behaves as a magnetic semiconductor, with 20μ B effective magnetic moment.

  15. Magnetic properties and structural characterization of Sr2RuHoO6 complex perovskite

    International Nuclear Information System (INIS)

    Corredor, L.T.; Landínez Téllez, D.A.; Martínez Buitrago, D.; Albino Aguiar, J.; Roa-Rojas, J.

    2012-01-01

    We report an experimental study of the crystallographic lattice, morphologic characteristics and magnetic feature of Sr 2 RuHoO 6 complex perovskite, which is used as a precursor in the fabrication process of the superconducting ruthenocuprate RuSr 2 HoCu 2 O 8 . The samples were produced through the standard solid state reaction. A Rietveld refinement of experimental X-ray diffraction patterns shows that the material crystallizes in a monoclinic structure, which belongs to the P21/n (no.14) space group, with lattice parameters a=5.7719(6) Å, b=5.8784(5) Å, c=8.1651(9) Å, and tilt angle β=90.200°. Magnetic susceptibility measurements reveal the occurrence of an antiferromagnetic ordering for a Néel temperature T N =10.1 K. From the Curie-Weiss fitting of the paramagnetic regime we obtain an effective magnetic moment of 11.31 μ B .

  16. Metabolism and dosimetry of 106Ru inhaled as 106RuO4 by beagle dogs

    International Nuclear Information System (INIS)

    Snipes, M.B.

    1981-01-01

    This report provides metabolism and dosimetry data for inhaled ruthenium developed from studies in Beagle dogs that were exposed by inhalation to 106 RuO 4 . Twenty-six dogs were exposed nose-only to 106 RuO 4 and sacrificed at times from 2 hr to 512 days after inhalation exposure. Ninety-nine percent of the initial body burden was retained with an effective half-time of 1.2 days, 0.7% with a half-time of 14 days and 0.3% with a half-time of 170 days. Initial deposition was primarily in the nasopharyngeal and tracheobronchial regions. Results for deposition and retention of 106 Ru inhaled as 106 RuO 4 in dogs were similar to what has been observed for humans. The data for dogs were used to develop a model to predict potential radiation exposure patterns for humans after inhalation exposure to 106 RuO 4 . The model indicates that for humans the nasopharyngeal region, lower large intestine, and tracheobronchial epithelium would receive approx. 36, 13 and 10 times, respectively, the dose to 500 days after inhalation exposure to 106 RuO 4 that the lung would receive. The nasopharyngeal region should be considered the critical region for inhalation exposures to 106 RuO 4 . (author)

  17. Effect of oxygen vacancies on magnetic and transport properties of Sr2IrO4

    Science.gov (United States)

    Dwivedi, Vinod Kumar; Mukhopadhyay, Soumik

    2018-05-01

    Iridates have recently attracted growing interest because of their potential for realizing various interesting phases like interaction driven Mott-type insulator and magnetically driven Slater-type. In this paper, we present the magnetic and electrical transport properties of polycrystalline Sr2IrO4 synthesized by solid state reaction route. We find a ferromagnetic transition at 240 K. The Curie-Weiss law behavior hold good above the magnetic transition temperature TMag = 240 K with a small effective paramagnetic magnetic moment μeff = 0.25 µB/f.u. and a Curie-Weiss temperature, θCW = +100 K. Zero field cooled (ZFC) magnetization shows a gradual dcrease below 150 K, while same for field cooled (FC) below 50 K. Interestingly, below temperatures, ⁓ 10 K, a sharp increase in ZFC and FC magnetization can be seen. A temperature dependent resistivity reveals insulating behavior followed by power law mechanism. The sintering of sample in air leads to the very low value of resistivity is likely related to Sr or oxygen vacancies.

  18. [Effect of charge compensation on emission spectrum of Sr2SiO4 : Dy3+ phosphor].

    Science.gov (United States)

    Li, Pan-Lai; Wang, Zhi-Jun; Yang, Zhi-Ping; Guo, Qing-Lin

    2009-01-01

    The Sr2SiO4 : Dy3+ phosphor was synthesized by the high temperature solid-state reaction method in air. Dy2O3 (99.9%), SiO2 (99.9%), SrCO3 (99.9%), Li2CO3 (99.9%), Na2CO3 (99.9%) and K2CO3 (99.9%) were used as starting materials, and the Dy3+ doping concentration was 2 mol%. The emission spectrum was measured by a SPEX1404 spectrophotometer, and all the characterization of the phosphors was conducted at room temperature. The emission spectrum of Sr2 SiO4 : Dy3+ phosphor showed several bands centered at 486, 575 and 665 nm under the 365 nm excitation. The effect of Li+, Na+ and K+ on the emission spectra of Sr2SiO4 : Dy3+ phosphor was studied. The results show that the location of the emission spectrum of Sr2SiO4 : Dy3+ phosphor was not influenced by Li+, Na+ and K+. However, the emission spectrum intensity was greatly influenced by Li+, Na+ and K+, and the evolvement trend was monotone with different charge compensation, i. e. the emission spectrum intensity of Sr2SiO4 : Dy3+ phosphor firstly increased with increasing Li+ concentration, then decreased. However the charge compensation concentration corresponding to the maximum emission intensity was different with different charge compensation, and the concentration is 4, 3 and 3 mol% corresponding to Li+, Na+ and K+, respectively. And the theoretical reason for the above results was analyzed.

  19. Luminescent and morphological study of Sr2CeO4 blue phosphor prepared from oxalate precursors

    International Nuclear Information System (INIS)

    Ferrari, Jefferson L.; Pires, Ana M.; Serra, Osvaldo A.; Davolos, Marian R.

    2011-01-01

    Luminescent and morphological studies of Sr 2 CeO 4 blue phosphor prepared from cerium-doped strontium oxalate precursor are reported. Powder samples were prepared from 5 and 25 mol% Ce 3+ -doped strontium oxalate as well as from a mechanical mixture of strontium oxalate and cerium oxalate at a 4:1 ratio, respectively. All the samples were characterized by XRD, IR, PLS, and SEM. The luminescent and structural properties of the Sr 2 CeO 4 material are little affected by the SrCO 3 remaining from precursors. The Sr 2 CeO 4 material consists in one-dimensional chains of edge-sharing CeO 6 octahedra that are linked together by Sr 2+ ions. The carbonate ion might be associated with oxygen ions of the linear chain, and also with the oxygen atoms located in the equatorial position, which consequently affects the charge transfer bands between O 2- and Ce 4+ . As observed by SEM, the morphological changes are related to each kind of precursor and thermal treatment, along with irregular powder particles within the size range 0.5-2 μm.

  20. Study of effect of co-doping on CIE coordinates of strontium cerium oxide phosphor (Sr_2CeO_4)

    International Nuclear Information System (INIS)

    Zambare, Pradip Z.; Ahirrao, P.B.; Chaudhari, D.B.; Zambare, A.P.; Mahajan, O.H.

    2016-01-01

    The phosphors Sr_2CeO_4 doped europium and gadolinium were synthesized by modified solid state diffusion method. From emission spectra, the CIE coordinates (x, y) of x% Eu"3"+ and 0.5 %Gd"3"+ doped Sr_2CeO_4 phosphors was calculated. In present paper, we investigate luminescence properties and colorimetric study of Sr_2CeO_4 doped 0.5% Gd"3"+, x% Eu"3"+. The phosphors Sr_2CeO_4 doped europium and gadolinium were successfully synthesized by modified solid state diffusion method. X-ray diffraction (XRD) profile confirms the orthorhombic nature of Eu"3"+ and 0.5% Gd"3"+ doped Sr_2CeO_4 phosphors. In addition, scanning electron Microscopy (SEM), Fourier-Transformation IR spectroscopy (FTIR), was also used to study the synthesized phosphors

  1. Concentration Dependence of Luminescent Properties for Sr2TiO4:Eu3+ Red Phosphor and Its Charge Compensation

    Directory of Open Access Journals (Sweden)

    Zhou Lu

    2012-01-01

    Full Text Available Sr2TiO4:Eu3+ phosphors using M+ (M = Li+, Na+, and K+ as charge compensators were prepared by the solid-state reaction. The powders were investigated by powder X-ray diffraction (XRD and photoluminescence spectra (PL to study the phase composition, structure, and luminescent properties. The results showed that Li+ ion was the best charge compensator. The phase was Sr2TiO4 when the doping concentration was small (x≤10.0%. When x reached 15.0%, the phase turned into Sr3Ti3O7 because of the structure damage. The phosphor could be effectively excited by ultraviolet (365, 395 nm and blue light (465 nm, and thenitemitted intense red light that peaked at around 620 nm (5D0→7F2. In addition, the emission of 700 nm (5D0→7F4 enhanced the red light color purity. The CIE chromaticity coordinates of samples with the higher red emission were between (0.650, 0.344 and (0.635, 0.352. Doped layered titanate Sr2TiO4:Eu3+ is a promising candidate red phosphor for white LEDs which can be suited for both near-UV LED chip and blue LED chip.

  2. Mechanical properties of polycrystalline RuSr2GdCu2O8 superconductor

    International Nuclear Information System (INIS)

    Brum Leite Gusmao Pinheiro, Lincoln; Serbena, Francisco Carlos; Foerster, Carlos Eugenio; Rodrigues, Pedro Junior; Jurelo, Alcione Roberto; Chinelatto, Adilson Luiz; Junior, Jorge Luiz Pimentel

    2011-01-01

    Research highlights: → Hardness and elastic modulus of Ru-1212 phase measured by instrumented indentation are reported. → Polycrystalline samples were produced by a solid state reaction technique. → Samples were also characterized by SEM, XRD and electrical resistivity measurements. → Hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. → These values are comparable with those of Y-123. - Abstract: The main objective of this paper is to report the room temperature hardness and elastic modulus of the RuSr 2 GdCu 2 O 8 superconductor phase by instrumented indentation. Polycrystalline samples were produced by a solid state reaction technique. The samples were also characterized by scanning electron microscopy, X-ray diffraction and electrical resistivity measurements. The influence of porosity on the mechanical properties was avoided by considering only those indentations inside the grains. The hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. These values are comparable with those of Y-123. The indentation fracture toughness evaluated after conventional Vickers indentation was 1.9 MPa m 1/2 .

  3. Hall effect and magnetization in the magnetic superconductor RuSr2GdCu2O8

    International Nuclear Information System (INIS)

    Jurelo, A.R.; Pimentel, J.L.; Wolff Fabris, F.; Schaf, J.; Pureur, P.; Vieira, V.N.

    2006-01-01

    We report on Hall effect, longitudinal resistivity and magnetization measurements in the rutheno-cuprate RuSr 2 GdCu 2 O 8 . Combining these results we separate the anomalous contribution to the Hall effect and argue that the occurrence of canting and chirality have to be considered for describing this property

  4. Theory of Josephson effect in Sr2RuO4/diffusive normal metal/Sr2RuO4 junctions

    NARCIS (Netherlands)

    Sawa, Y.; Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch

    2007-01-01

    We derive a generalized Nazarov’s boundary condition for diffusive normal metal (DN)/chiral p-wave superconductor (CP) interface including the macroscopic phase of the superconductor. The Josephson effect is studied in CP/DN/CP junctions solving the Usadel equations under the above boundary

  5. Luminescence properties of LiSr2Y1-xLnxO4 (Ln=Eu,Tb,Tm) (0≤x≤1)

    International Nuclear Information System (INIS)

    Kubota, S.; Suzuyama, Y.; Yamane, H.; Shimada, M.

    1998-01-01

    Investigations of the luminescence properties of LiSr 2 Y 1-x Eu x O 4 , LiSr 2 Y 1-x Tb x O 4 and LiSr 2 Y 1-x Tm x O 4 (0≤x≤1) at room temperature are reported. These samples were synthesized by a solid state reaction. The excitation spectra of Tb 3+ emission in LiSr 2 Y 1-x Tb x O 4 (0≤x≤1) consist of broad bands corresponding to a transition between the 4f 8 and 4f 7 5d 1 states of Tb 3+ . The maximum intensity is situated at about 318 nm. This is at a much longer wavelength than those of other Tb 3+ doped phosphors. This is explained by a large offset of the adiabatic potential curve of the 4f 7 5d 1 state. (orig.)

  6. Locking of iridium magnetic moments to the correlated rotation of oxygen octahedra in Sr2IrO4 revealed by x-ray resonant scattering

    DEFF Research Database (Denmark)

    Boseggia, S.; Walker, H. C.; Vale, J.

    2013-01-01

    Sr2IrO4 is a prototype of the class of Mott insulators in the strong spin–orbit interaction (SOI) limit described by a Jeff = 1/2 ground state. In Sr2IrO4, the strong SOI is predicted to manifest itself in the locking of the canting of the magnetic moments to the correlated rotation by 11.8(1)° o...

  7. Influence of doping on the electronic structure of (La, Sr)2CuO4

    International Nuclear Information System (INIS)

    Howell, R.H.; Fluss, M.J.; Sterne, P.A.; Kaiser, J.H.; Kitazawa, K.; Kojima, H.

    1994-01-01

    High-statistics (>4 x 10 8 counts), room-temperature measurements of the electron positron momentum density of La 2-x Sr x CuO 4 have been performed for samples with Sr concentrations of x = 0.0, 0.1, 0.13, and 0.2. These spectra have been analyzed in conjunction with theoretical calculations of the electron positron momentum density. The metallic samples show features consistent with the presence of a Fermi surface, but its evolution with increasing Sr concentration does not follow the predictions of band theory. These results may indicate the effects of electron-electron correlation on the electron momentum distribution in the Cu-O plane. 12 refs., 2 figs

  8. An overview on the research of Sr2IrO4-based system probed by X-ray absorption spectroscopy

    Science.gov (United States)

    Cheng, Jie; Zhu, Chaomin; Ma, Jingyuan; Wang, Yu; Liu, Shengli

    2018-03-01

    Investigations of materials with 5d transition metal ions have opened up new paradigms in condensed-matter physics because of their large spin-orbit coupling (SOC) interactions. The typical compound is Sr2IrO4, which attracted much attention due to its similarities to the parent compound of high-Tc cuprate superconductor La2CuO4. Theoretical calculations predicted that the unconventional superconductivity can occur in carrier doped-Sr2IrO4 system. Until now, hundreds of experimental methods were devoted to investigate the carrier doping effect on Sr2IrO4. Synchrotron radiation-based X-ray absorption spectroscopy (XAS) made great contributions to the local lattice and electronic structure, and also the intimate relationship between the local structure and physical properties induced by carrier doping. The aim of this review is a short introduction to the progress of research on Sr2IrO4-based system probed by the unique technique — XAS, including the strength of the SOC, valence changes upon doping and even local lattice structure with atomic level for this Sr2IrO4-based family.

  9. Synthesis and characterization of Sr2Ir1−xMxO4 (M=Ti, Fe, Co) solid solutions

    International Nuclear Information System (INIS)

    Gatimu, Alvin J.; Berthelot, Romain; Muir, Sean; Sleight, Arthur W.; Subramanian, M.A.

    2012-01-01

    The effects of Ti, Fe and Co substitutions for Ir on the structure and on the physical properties of Sr 2 IrO 4 are investigated. A complete solid solution Sr 2 Ir 1−x Ti x O 4 is obtained while both Fe and Co doping are relatively limited. In each case however, the c-axis cell parameter and the initial IrO 6 octahedra tilting decreases with substitution. Doping with Ti, Fe and Co results in a decrease of the magnetic susceptibility and in an increase in the paramagnetic effective moment for Co and Fe doped samples and a suppression of the weak ferromagnetic ordering observed for Sr 2 IrO 4 . - Graphical abstract: Solid solutions of Sr 2 Ir 1−x M x O 4 (M=Ti, Fe, Co) have been synthesized and characterized by powder X-ray diffraction, magnetism and electrical measurements. Changes in the a parameter and decreases in both the c-axis cell parameters and the initial IrO 6 octahedra tilting are found to be correlated. Highlights: ► Solid Solutions of Sr 2 Ir 1−x M x O 4 (M=Ti, Fe, Co) are synthesized. ► The Sr 2 Ir 1−x Ti x O 4 solid solution is complete while those of Fe and Co are relatively limited. ► The change in a cell parameter with substitution is much less than that of the c parameter. ► Decreased tilting and the smaller size of the M cation contrastingly affect the a parameter. ► Doping results in a suppression of the weak ferromagnetic ordering in Sr 2 IrO 4 .

  10. Electrical Control of Structural and Physical Properties via Strong Spin-Orbit Interactions in Sr2IrO4

    Science.gov (United States)

    Cao, G.; Terzic, J.; Zhao, H. D.; Zheng, H.; De Long, L. E.; Riseborough, Peter S.

    2018-01-01

    Electrical control of structural and physical properties is a long-sought, but elusive goal of contemporary science and technology. We demonstrate that a combination of strong spin-orbit interactions (SOI) and a canted antiferromagnetic Mott state is sufficient to attain that goal. The antiferromagnetic insulator Sr2IrO4 provides a model system in which strong SOI lock canted Ir magnetic moments to IrO6 octahedra, causing them to rigidly rotate together. A novel coupling between an applied electrical current and the canting angle reduces the Néel temperature and drives a large, nonlinear lattice expansion that closely tracks the magnetization, increases the electron mobility, and precipitates a unique resistive switching effect. Our observations open new avenues for understanding fundamental physics driven by strong SOI in condensed matter, and provide a new paradigm for functional materials and devices.

  11. Structure, magnetism, and transport properties for Ca doping in Sr2IrO4

    Directory of Open Access Journals (Sweden)

    Guotai Zhou

    2017-05-01

    Full Text Available An immediate quenching using liquid N2 is applied for synthesizing the 5d transition-metal oxides (Sr1-xCax2IrO4 (0 ≤ x ≤ 0.15 single phase. X-ray diffraction together with Rietveld refinement shows that the lattice parameters along a and c directions and the bond angle of Ir-O2-Ir decrease with the increase of Ca content. X-ray Absorption Fine Spectroscopy measurements prove that the valence of Ir and the average Ir-O bond-length substantially remain unchanged with Ca content increasing in the phase. The effective magnetic moment μeff and Néel temperature TN decrease simultaneously with increased Ca content. Electrical resistivity shows complex temperature dependence behavior, which follows the three-dimensional variable range hopping behavior at low temperature, Arrhenius-type behavior at middle-temperature, and a weak electronic localization in quasi-two-dimensional at high temperature.

  12. Structural characterization and optical properties of Eu"2"+ and Dy"2"+ doped Sr_2SiO_4 phosphor by solid state reaction method

    International Nuclear Information System (INIS)

    Verma, Durga; Verma, Mohan L.; Upma; Patel, R.P.

    2016-01-01

    Thermoluminescence, SEM, FTIR Divalent dysprosium and europium doped strontium silicate (Sr_2SiO_4) phosphors were synthesized with the high-temperature solid-state reaction technique. The obtained phosphor was well characterized by powder X-ray diffraction, scanning electron microscopy, FTIR, UV-visible spectroscopy and thermoluminescence. The crystal structure of the prepared phosphor has an orthorhombic structure with space group Pnma. From scanning electron microscopy (SEM), agglomerations of particles were observed due to the high temperature synthesis process. The chemical composition of the sintered Sr_2SiO_4:Dy"2"+ and Sr_2SiO_4: Eu"2"+ phosphor was confirmed by energy dispersive X-ray spectroscopy (EDX). The UV-VIS analysis can be thought as a good quality check for the optical behavior of materials. The Fourier transmission infrared spectroscopy (FTIR) confirms the present elements in phosphor. Thermoluminescence study was carried out for the phosphor with UV irradiation show one glow peak. The trapping parameters associated with the prominent glow peak of Sr_2SiO_4:Dy"2"+ and Sr_2SiO_4:Eu"2"+ are calculated using Chen's glow curve method. The release of holes/electrons from defect centers at the characteristic trap site initiates the luminescence process in this material. (author)

  13. Two component butterfly hysteresis in RuSr2EuCeCu2O1 ruthenocuprate

    International Nuclear Information System (INIS)

    Zivkovic, I.; Drobac, D.; Prester, M.

    2006-01-01

    We report detailed studies of the ac susceptibility butterfly hysteresis on the RuSr 2 EuCeCu 2 O 1 (Ru1222) ruthenocuprate compound. Two separate contributions to these hysteresis have been identified and studied. One contribution is ferromagnetic-like and is characterized by the coercive field maximum. Another contribution, represented by the so called inverted maximum, is related to the unusual inverted loops, unique feature of Ru1222 butterfly hysteresis. The different nature of the two identified magnetic contributions is proved by the different temperature dependences involved. By lowering the temperature the inverted peak gradually disappears while the coercive field slowly raises. If the maximum dc field for the hysteresis is increased, the size of the inverted part of the butterfly hysteresis monotonously grows while the position of the peak saturates. In reaching saturation exponential field dependence has been demonstrated to take place. At T = 78 K the saturation field is 42 Oe

  14. Red/blue-shift dual-directional regulation of α-(Ca, Sr)2SiO4:Eu(2+) phosphors resulting from the incorporation content of Eu(2+)/Sr(2+) ions.

    Science.gov (United States)

    Lu, Zhijuan; Mao, Zhiyong; Chen, Jingjing; Wang, Dajian

    2015-09-21

    In this work, tunable emission from green to red and the inverse tuning from red to green in α-(Ca, Sr)2SiO4:Eu(2+) phosphors were demonstrated magically by varying the incorporation content of Eu(2+) and Sr(2+) ions, respectively. The tunable emission properties and the tuning mechanism of red-shift resulting from the Eu(2+) content as well as that of blue-shift induced by the Sr(2+) content were investigated in detail. As a result of fine-controlling the incorporation content of Eu(2+), the emission peak red-shifts from 541 nm to 640 nm. On the other hand, the emission peak inversely blue-shifts from 640 nm to 546 nm through fine-adjusting the incorporation content of Sr(2+). The excellent tuning characteristics for α-(Ca, Sr)2SiO4:Eu(2+) phosphors presented in this work exhibited their various application prospects in solid-state lighting combining with a blue chip or a near-UV chip.

  15. Field-dependent antiferromagnetism and ferromagnetism of the two copper sublattices in Sr2Cu3O4Cl2

    International Nuclear Information System (INIS)

    Kastner, M.A.; Aharony, A.; Birgeneau, R.J.; Chou, F.C.; Entin-Wohlman, O.; Greven, M.; Harris, A.B.; Kim, Y.J.; Lee, Y.S.; Parks, M.E.; Zhu, Q.

    1999-01-01

    The Cu 3 O 4 layer in Sr 2 Cu 3 O 4 Cl 2 is a variant of the square CuO 2 lattice of the high-temperature superconductors, in which the center of every second plaquette contains an extra Cu 2+ ion. The ions that make up the conventional CuO 2 network, called CuI, have CuI-CuI exchange energy ∼130meV, and order antiferromagnetically at about 380 K; the CuII-CuII exchange is only ∼10meV, and the CuII close-quote s order at ∼40K. A study is reported here of the dependence of the magnetization on field, temperature, and crystallographic orientation for this interesting system. We show that the small permanent ferromagnetic moment, that appears when the CuI spins order, and the unusual spin rotation transitions seen most clearly for one particular direction of the magnetic field, are the result of several small bond-dependent anisotropic terms in the spin Hamiltonian that are revealed because of the frustration of the isotropic Heisenberg interaction between CuI and CuII spins. These include a term which favors collinearity of the CuI and CuII spins, which originates from quantum fluctuations, and also the pseudodipolar interaction. Some of these small interactions also come into play in other lamellar cuprates, connected with the high-T c superconductivity materials, and in many spin-chain and spin-ladder compounds. copyright 1999 The American Physical Society

  16. Anomalous High-Energy Waterfall-Like Electronic Structure in 5 d Transition Metal Oxide Sr2IrO4 with a Strong Spin-Orbit Coupling

    Science.gov (United States)

    Liu, Yan; Yu, Li; Jia, Xiaowen; Zhao, Jianzhou; Weng, Hongming; Peng, Yingying; Chen, Chaoyu; Xie, Zhuojin; Mou, Daixiang; He, Junfeng; Liu, Xu; Feng, Ya; Yi, Hemian; Zhao, Lin; Liu, Guodong; He, Shaolong; Dong, Xiaoli; Zhang, Jun; Xu, Zuyan; Chen, Chuangtian; Cao, Gang; Dai, Xi; Fang, Zhong; Zhou, X. J.

    2015-08-01

    The low energy electronic structure of Sr2IrO4 has been well studied and understood in terms of an effective Jeff = 1/2 Mott insulator model. However, little work has been done in studying its high energy electronic behaviors. Here we report a new observation of the anomalous high energy electronic structure in Sr2IrO4. By taking high-resolution angle-resolved photoemission measurements on Sr2IrO4 over a wide energy range, we have revealed for the first time that the high energy electronic structures show unusual nearly-vertical bands that extend over a large energy range. Such anomalous high energy behaviors resemble the high energy waterfall features observed in the cuprate superconductors. While strong electron correlation plays an important role in producing high energy waterfall features in the cuprate superconductors, the revelation of the high energy anomalies in Sr2IrO4, which exhibits strong spin-orbit coupling and a moderate electron correlation, points to an unknown and novel route in generating exotic electronic excitations.

  17. Anomalous High-Energy Waterfall-Like Electronic Structure in 5 d Transition Metal Oxide Sr2IrO4 with a Strong Spin-Orbit Coupling.

    Science.gov (United States)

    Liu, Yan; Yu, Li; Jia, Xiaowen; Zhao, Jianzhou; Weng, Hongming; Peng, Yingying; Chen, Chaoyu; Xie, Zhuojin; Mou, Daixiang; He, Junfeng; Liu, Xu; Feng, Ya; Yi, Hemian; Zhao, Lin; Liu, Guodong; He, Shaolong; Dong, Xiaoli; Zhang, Jun; Xu, Zuyan; Chen, Chuangtian; Cao, Gang; Dai, Xi; Fang, Zhong; Zhou, X J

    2015-08-12

    The low energy electronic structure of Sr2IrO4 has been well studied and understood in terms of an effective Jeff = 1/2 Mott insulator model. However, little work has been done in studying its high energy electronic behaviors. Here we report a new observation of the anomalous high energy electronic structure in Sr2IrO4. By taking high-resolution angle-resolved photoemission measurements on Sr2IrO4 over a wide energy range, we have revealed for the first time that the high energy electronic structures show unusual nearly-vertical bands that extend over a large energy range. Such anomalous high energy behaviors resemble the high energy waterfall features observed in the cuprate superconductors. While strong electron correlation plays an important role in producing high energy waterfall features in the cuprate superconductors, the revelation of the high energy anomalies in Sr2IrO4, which exhibits strong spin-orbit coupling and a moderate electron correlation, points to an unknown and novel route in generating exotic electronic excitations.

  18. Physical properties and characterization of RuSr2GdCu2O8 (Ru-1212) grown by top seeded melt textured technique

    International Nuclear Information System (INIS)

    Uthayakumar, S.; Santhosh, P.; Gombos, M.; Babu, M. Ramesh; Jayavel, R.; Vecchione, A.; Pace, S.

    2009-01-01

    Efforts have been made in optimizing growth conditions for bulk textured growth of RuSr 2 GdCu 2 O 8 (Ru-1212) employing top seeded growth technique (TSG). Thermal stability and peritectic temperature (T p ) have been determined by TG-DTA analysis. The study facilitates appropriate thermal treatments to yield good quality sample. The structural study of the as grown sample has been carried out by X-ray diffraction technique. Morphological study by polarized optical microscope (PLOM) and scanning electron microscope (SEM) reveals the growth mechanism. Subsequently, the stoichiometry has been confirmed by energy dispersive X-ray analysis (EDAX). The observed characterization results show the influence of superconducting property on growth technique and allow one to correlate between the physical properties and experimental technique.

  19. Interactions of RuO4(g) with different surfaces in nuclear reactor containments

    International Nuclear Information System (INIS)

    Holm, J.; Glaenneskog, H.; Ekberg, C.

    2008-07-01

    During a severe nuclear reactor accident with air ingress, ruthenium in the form of RuO4 can be released from the nuclear fuel. Hence, it is important to investigate how the reactor containment is able to reduce the source term of ruthenium. This work has investigated the distribution of RuO4 between an aqueous and gaseous phase in the temperature interval of 20-50 deg. C by on-line measurements with an experimental set-up made of glass. The experiments showed that RuO4 is almost immediately distributed in the aqueous phase after its introduction in the set-up in the entire temperature interval. However, the deposition of ruthenium on the glass surfaces in the system was significant. The speciation of the ruthenium on the glass surfaces was studied by SEM-EDX and ESCA and was determined to be the expected RuO2. Experiments of interactions between gaseous ruthenium tetroxide and the metals aluminium, copper and zinc have been investigated. The metals were treated by RuO4 (g) at room temperature and analyzed with ESCA, SEM and XRD. The analyses show that the black ruthenium deposits on the metal surfaces were RuO2, i.e. the RuO4 (g) has been transformed on the metal surfaces to RuO2(s). The analyses showed also that there was a significant deposition of ruthenium tetroxide especially on the copper and zinc samples. Aluminium has a lower ability to deposit gaseous ruthenium tetroxide than the other metals. The conclusion that can be made from the results is that surfaces in nuclear reactor containments will likely reduce the source term in the case of a severe accident in a nuclear power plant. (au)

  20. Rotational and translational distortions of the crystal structure of the Sr2HrRuO6 (Hr = Ho, Dy, Gd, Eu) complex perovskites

    International Nuclear Information System (INIS)

    Triana, C.A.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2013-01-01

    Sr 2 HrRuO 6 (Hr = Ho, Dy, Gd, Eu) complex perovskites were synthesized through the high-temperature solid-state reaction method, and their crystal structures were analyzed in detail as a function of the Hr-cation ionic radius. Results of powder XRD pattern measurement and Rietveld analysis of the experimental profiles show that the Sr 2 HrRuO 6 compounds crystallize in a monoclinic distorted perovskite-like structure, P2 1 /n (#14) space group, where the unit cell parameters are related to the primitive unit cell a p by a≈√(2)a p , b≈√(2)a p and c ≈ 2a p . The structures show an alternate distribution of the Ru 5+ (2d: 0.5, 0, 0) and Hr 3+ (2c: 0, 0.5, 0) making up RuO 6 and HrO 6 octahedra alternatively arranged in two interleaving fcc sublattices, where the O(1), O(2), and O(3) ions are localized at the corner of the octahedral, while the Sr 2+ is located at the A-site, occupying the cavities built by the corner-sharing octahedra with Wyckoff position 4e. Due to the existence of mismatched ionic sizes between the ionic radii of the Sr 2 HrRuO 6 compounds, the HrO 6 and RuO 6 octahedra are constrained to tilting around the [111] c , [001] c , and [110] c cubic directions so as to optimize the Sr–O inter-atomic bond lengths, tending to rotate the structure in order to fix the Ru 5+ and Hr 3+ ions on the M′ and M″ sites of the complex perovskites. The cell parameters a, b, and c, the inter-atomic bond angles, the inter-atomic bond lengths, and the tilting angles increase as the Hr-cation ionic radius increases. The mismatch that exists in the Sr 2 HrRuO 6 ionic radius produces a large distortion from the ideal cubic symmetry. The pure perovskite-like phase of Sr 2 HrRuO 6 is thermodynamically and kinetically stable at high temperatures above 1420 K, where it is entirely governed by the average size of the Hr 3+ and Ru 5+ cations. Highlights: ► Crystal structure of Sr 2 HrRuO 6 (Hr = Ho, Dy, Gd, Eu) as a function of Hr ionic radius. ► XRD

  1. Adsorption of gaseous RuO4 by various sorbents. II

    International Nuclear Information System (INIS)

    Vujisic, L.; Nikolic, R.

    1983-01-01

    Sorption of gaseous RuO 4 on impregnated Alcoa Alumina H-151, impregnated charcoal, silica gel and HEPA filter was investigated. The results obtained on various sorbents are compared and discussed in connection with possibilities to use the chosen material in air cleaning systems

  2. Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru1−xRexSr2GdCu2Oy

    International Nuclear Information System (INIS)

    Corredor, L.T.; Albino Aguiar, J.; Landínez Téllez, D.A.; Pureur, P.; Mesquita, F.; Roa-Rojas, J.

    2015-01-01

    Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr 2 GdCu 2 O 8 . • We synthesized the doped compound Rui x Re x Sr 2 GdCu 2 O y , for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru 1−x Re x Sr 2 GdCu 2 O y ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr 2 GdRu 1−x Re x O y , which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO 2 (magnetic) and CuO 2 (superconductor) sub-lattices can clearly be observed

  3. Preparation, characterization and luminescence of Sm~(3+) or Eu~(3+) doped Sr_2CeO_4 by a modified sol-gel method

    Institute of Scientific and Technical Information of China (English)

    张春祥; 史建设; 杨绪杰; 陆路德; 汪信

    2010-01-01

    Superfine Sr2CeO4:RE3+ (RE=Eu, Sm) phosphors were synthesized at relatively low temperature by a modified sol-gel method using nitrates as raw materials, ethylenediaminetetraacetic acid (EDTA) as complexing agent. Single phase phosphors could be obtained at calcination temperature above 800 °C and pH value higher than 6.4 of initial solution. The as-prepared powders consisted of uniform crotch-like grains. The preparation process was monitored by thermogravimetric and differential thermal analysis (TG-DTA) ...

  4. Observation of a Slater-type metal-to-insulator transition in Sr$_2$IrO$_4$ from time-resolved photo-carrier dynamics

    OpenAIRE

    Hsieh, D.; Mahmood, F.; Torchinsky, D. H.; Cao, G.; Gedik, N.

    2012-01-01

    We perform a time-resolved optical study of Sr$_2$IrO$_4$ to understand the influence of magnetic ordering on the low energy electronic structure of a strongly spin-orbit coupled $J_{eff}$=1/2 Mott insulator. By studying the recovery dynamics of photo-carriers excited across the Mott gap, we find that upon cooling through the N\\'{e}el temperature $T_N$ the system evolves continuously from a metal-like phase with fast ($\\sim$50 fs) and excitation density independent relaxation dynamics to a ga...

  5. RuO4-mediated oxidation of secondary amines 2. imines as main reaction intermediates

    Directory of Open Access Journals (Sweden)

    Florea Cristina A.

    2017-01-01

    Full Text Available Oxidation by RuO4 (generated in situ from RuO2 and NaIO4 of secondary amines such as Bn–NH–CH2R (1; R=H, Me gave complex reaction mixtures, but mainly amides. In the presence of cyanide, the leading products were α-aminonitriles. Comparison of the oxidation products of 1 with those from the corresponding imines PhCH=N–CH2R and Bn–N=CH–R showed that formation of the indicated imines is the first main step in the oxidation of 1. A detailed mechanism is proposed.

  6. Electronic and Crystalline Structure, Magnetic Response, and Optical Characterization of Rare-Earth Ruthenate Sr2HoRuO6

    Science.gov (United States)

    Velásquez Moya, X. A.; Cardona, R.; Villa Hernández, J. I.; Landínez Téllez, D. A.; Roa-Rojas, J.

    2018-03-01

    Sr2HoRuO6 ceramic has been synthesized and its structural, morphological, magnetic, optical, and electronic properties studied. Rietveld refinement of x-ray diffraction patterns revealed that this oxide material crystallizes in monoclinic perovskite structure in space group P2 1 /n (no. 14). Scanning electron microscopy revealed polycrystalline surface morphology. x-Ray dispersive spectroscopy suggested that Sr2HoRuO6 was obtained with expected stoichiometry. Magnetic susceptibility curves as a function of temperature revealed ferrimagnetic feature of this material below the Néel temperature T N of 14 K. Evidence of magnetic disorder was provided by the irreversibility observed in the zero-field-cooled and field-cooled responses of the susceptibility below T irr = 169 K. Analysis of the diffuse reflectance spectrum suggested that this material behaves as a semiconductor with energy gap E g of 1.38 eV. Results of band structure and density-of-states calculations are in agreement with the interpretation of Sr2HoRuO6 as a semiconductor. The ferrimagnetic behavior is interpreted as due to exchange mechanisms of d-f (Ru-O-Ho) electrons. The effective magnetic moment calculated from density functional theory was 93.5% of the experimental value obtained from Curie-Weiss fitting of the susceptibility curve.

  7. Dose patterns for 106RuO4 inhaled by Fischer-344 rats and Beagle dogs

    International Nuclear Information System (INIS)

    Runkle, G.E.; Snipes, M.B.

    1978-01-01

    Ruthenium-106 is an abundant fission product radionuclide in the nuclear fuel cycle which has potential for release as ruthenium tetroxide. Ruthenium tetroxide is a vapor, diffuses rapidly through air and porous materials, is chemically reactive and is rapidly reduced by any organic material to the dioxide form. Current ICRP recommendations consider the lung and gastrointestinal tract as critical organs for inhaled particles of radioactive ruthenium. This study was designed to provide additional data needed to adequately assess the risk for humans potentially exposed to 106 Ru encountered in this vapor form. Fischer-344 rats and Beagle dogs were given a nose-only exposure to 106 RuO 4 vapor to determine its distribution and retention patterns. The largest percentage of the initial body burden was found in the nasopharyngeal region of the respiratory tract. Less than 1% of the initial body burden was deposited in the pulmonary region. Most of the 106 Ru was cleared via the feces. A biomathematical simulation model was developed to fit the tissue and excreta data from the rat. This model was used to assess the short-term and long-term risks after inhalation of 106 RuO 4 . The observed deposition, retention and dose patterns for ruthenium tetroxide indicate the nasopharyngeal region should be considered as a critical region when considering the consequences of human exposure to this vapor

  8. Characteristic features of the magnetoresistance in the ferrimagnetic (Sr2FeMoO6-δ) - dielectric (SrMoO4) nanocomposite

    Science.gov (United States)

    Demyanov, S.; Kalanda, N.; Yarmolich, M.; Petrov, A.; Lee, S.-H.; Yu, S.-C.; Oh, S. K.; Kim, D.-H.

    2018-05-01

    Magnetic metal-oxide compounds with high values of magnetoresistance (MR) have attracted huge interest for spintronic applications, among which Sr2FeMoO6-δ (SFMO) has been relatively less known compared to the cobaltites and manganites, despite 100% electrons spin-polarization degree and a high Curie temperature. Here, stable fabrication and systematic analysis of nanocomposites based on SFMO with SrMoO4 dielectric sheaths are presented. SFMO-SrMoO4 nanocomposites were fabricated as follows: synthesis of the SFMO single-phase nanopowders by the modified citrate-gel technique; compaction under high pressure; thermal treatment for sheaths formation around grains. The nanocomposite is observed to exhibit a transitional behavior of conductivity from metallic, which is characteristic for the SFMO to semiconductor one in the temperature range 4 - 300K under magnetic fields up to 10T. A negative MR is observed due to the spin-polarized charge carriers tunneling through dielectric sheaths. MR value reaches 43% under 8T at 10κ. The dielectric sheaths thickness was determined to be about 10 nm by electric breakdown voltage value at current-voltage characteristics curves. The breakdown is found to be a reversible process determined by collisional ionization of dielectric atoms in strong electric field depending on knocked-out electrons from the SrMoO4. It was found that MR changes sign in electric breakdown region, revealing the giant magnetoresistive properties.

  9. Enhanced rate performance of mesoporous Co3O4 nanosheet supercapacitor electrodes by hydrous RuO2 nanoparticle decoration

    KAUST Repository

    Baby, Rakhi Raghavan; Ché n, Wěi; Hedhili, Mohamed N.; Cha, Dong Kyu; Alshareef, Husam N.

    2014-01-01

    -dimensional network with exceptional supercapacitor performance in standard two electrode configuration. Dramatic improvement in the rate capacity of the Co3O4 nanosheets is achieved by electrodeposition of nanocrystalline, hydrous RuO 2 nanoparticles dispersed

  10. Probing single magnon excitations in Sr2IrO4 using O K-edge resonant inelastic x-ray scattering

    International Nuclear Information System (INIS)

    Liu, X; Ding, H; Dean, M P M; Yin, W G; Hill, J P; Liu, J; Ramesh, R; Chiuzbăian, S G; Jaouen, N; Nicolaou, A; Serrao, C Rayan

    2015-01-01

    Resonant inelastic x-ray scattering (RIXS) at the L-edge of transition metal elements is now commonly used to probe single magnon excitations. Here we show that single magnon excitations can also be measured with RIXS at the K-edge of the surrounding ligand atoms when the center heavy metal elements have strong spin–orbit coupling. This is demonstrated with oxygen K-edge RIXS experiments on the perovskite Sr 2 IrO 4 , where low energy peaks from single magnon excitations were observed. This new application of RIXS has excellent potential to be applied to a wide range of magnetic systems based on heavy elements, for which the L-edge RIXS energy resolution in the hard x-ray region is usually poor. (fast track communication)

  11. Two-Magnon Raman Scattering and Pseudospin-Lattice Interactions in Sr_{2}IrO_{4} and Sr_{3}Ir_{2}O_{7}.

    Science.gov (United States)

    Gretarsson, H; Sung, N H; Höppner, M; Kim, B J; Keimer, B; Le Tacon, M

    2016-04-01

    We have used Raman scattering to investigate the magnetic excitations and lattice dynamics in the prototypical spin-orbit Mott insulators Sr_{2}IrO_{4} and Sr_{3}Ir_{2}O_{7}. Both compounds exhibit pronounced two-magnon Raman scattering features with different energies, line shapes, and temperature dependencies, which in part reflect the different influence of long-range frustrating exchange interactions. Additionally, we find strong Fano asymmetries in the line shapes of low-energy phonon modes in both compounds, which disappear upon cooling below the antiferromagnetic ordering temperatures. These unusual phonon anomalies indicate that the spin-orbit coupling in Mott-insulating iridates is not sufficiently strong to quench the orbital dynamics in the paramagnetic state.

  12. Oxygen vibrations in the series Bi2Sr2Ca{_{n-1}}Cu{n}O{_{4+2 n+y}}

    Science.gov (United States)

    Faulques, E.; Dupouy, P.; Lefrant, S.

    1991-06-01

    We present a discussion of the oxygen vibrations in the Bi{2}Sr{2}Ca{n-1}Cu{n}O{4+2 n+y} high T_c superconductors with the aim of interpreting Raman spectra in the case of the non-symmorphic Amaa structure. Group theory shows that the oxygen atoms belonging to the central CuO{2} plane generate a Raman activity for the n=1,3 phases. Consequently, we propose a novel assignment for the lines of weak intensity at 297, 316 and 333 cm^{-1}. It is shown that the two components of the 460 cm^{-1} band may be consistent with the Amma structure. Spectra recorded in crossed polarization exhibit weak lines which could be assigned to B {1g} modes expected for the three phases. Nous présentons une discussion sur les vibrations des atomes d'oxygène dans la série des supraconducteurs Bi{2}Sr{2}Ca{n-1}Cu{n}O{4+2 n+y} dans le but d'interpréter les spectres Raman. L'analyse des modes normaux de vibration de la structure Amaa pour les phases n=1 ou 3 montre que les atomes d'oxygène du plan CuO{2} contenant les centres d'inversion donnent lieu à une activité Raman. En conséquence, nous proposons une nouvelle attribution pour les raies de faible intensité à 297, 316 et 333 cm^{-1}. Nous montrons que le dédoublement de la bande à 460 cm^{-1} pourrait être dû à la structure Amaa. Les spectres enregistrés en polarization croisée montrent de faibles bandes qui peuvent être attribuées aux modes B {1g} attendus pour les trois phases.

  13. High-Throughput Synthesis and Characterization of Eu Doped Ba xSr2- xSiO4 Thin Film Phosphors.

    Science.gov (United States)

    Frost, Sara; Guérin, Samuel; Hayden, Brian E; Soulié, Jean-Philippe; Vian, Chris

    2018-06-20

    High-throughput techniques have been employed for the synthesis and characterization of thin film phosphors of Eu-doped Ba x Sr 2- x SiO 4 . Direct synthesis from evaporation of the constituent elements under a flux of atomic oxygen on a sapphire substrate at 850 °C was used to directly produce thin film libraries (415 nm thickness) of the crystalline orthosilicate phase with the desired compositional variation (0.24 > x > 1.86). The orthosilicate phase could be synthesized as a pure, or predominantly pure, phase. Annealing the as synthesized library in a reducing atmosphere resulted in the reduction of the Eu while retaining the orthosilicate phase, and resulted in a materials thin film library where fluorescence excited by blue light (450 nm) was observable by the naked eye. Parallel screening of the fluorescence from the combinatorial libraries of Eu doped Ba x Sr 2- x SiO 4 has been implemented by imaging the fluorescent radiation over the library using a monochrome digital camera using a series of color filters. Informatics tools have been developed to allow the 1931 CIE color coordinates and the relative quantum efficiencies of the materials library to be rapidly assessed and mapped against composition, crystal structure and phase purity. The range of compositions gave values of CIE x between 0.17 and 0.52 and CIE y between 0.48 and 0.69 with relative efficiencies in the range 2.0 × 10 -4 -7.6 × 10 -4 . Good agreement was obtained between the thin film phosphors and the fluorescence characteristics of a number of corresponding bulk phosphor powders. The thermal quenching of fluorescence in the thin film libraries was also measured in the temperature range 25-130 °C: The phase purity of the thin film was found to significantly influence both the relative quantum efficiency and the thermal quenching of the fluorescence.

  14. Red, Green, and Blue Photoluminescence of Ba2SiO4:M (M = Eu3+, Eu2+, Sr2+ Nanophosphors

    Directory of Open Access Journals (Sweden)

    Claudia Wickleder

    2013-07-01

    Full Text Available Divalent europium doped barium orthosilicate is a very important phosphor for the production of light emitting diodes (LEDs, generally associated to the green emission color of micron-sized crystals synthesized by means of solid-state reactions. This work presents the combustion synthesis as an energy and time-saving preparation method for very small nano-sized Ba2SiO4 particles, flexibly doped to acquire different emission energies. The size of the resulting spherical nanoparticles (NPs of the green emitting Ba2SiO4:Eu2+ was estimated to about 35 nm applying the Scherrer equation and further characterized with aid of atomic force microscopy (AFM as well as scanning electron microscopy (SEM. This phosphor is able to build homogeneous luminescent suspensions and was successfully down-sized without changing the optical properties in comparison to the bulk phosphors. Besides the X-ray diffraction (XRD analysis and the different types of microscopy, the samples were characterized by luminescence spectroscopy. Undoped Ba2SiO4 NPs are not luminescent, but show characteristic red emission of the 5D0 → 7FJ (J = 0–4 electronic transitions when doped with Eu3+ ions. Moreover, these orthosilicate nanoparticles generate blue light at low temperatures due to impurity-trapped excitons, introduced by the partial substitution of the Ba2+ with Sr2+ ions in the Ba2SiO4 lattice causing a substantial distortion. A model for the temperature behavior of the defect luminescence as well as for their nature is provided, based on temperature-dependent luminescence spectra and lifetime measurements.

  15. Coupled Electronic and Magnetic Phase Transition in the Infinite-Layer Phase LaSrNiRuO4.

    Science.gov (United States)

    Patino, Midori Amano; Zeng, Dihao; Bower, Ryan; McGrady, John E; Hayward, Michael A

    2016-09-06

    Topochemical reduction of the ordered double perovskite LaSrNiRuO6 with CaH2 yields LaSrNiRuO4, an extended oxide phase containing infinite sheets of apex-linked, square-planar Ni(1+)O4 and Ru(2+)O4 units ordered in a checkerboard arrangement. At room temperature the localized Ni(1+) (d(9), S = (1)/2) and Ru(2+) (d(6), S = 1) centers behave paramagnetically. However, on cooling below 250 K the system undergoes a cooperative phase transition in which the nickel spins align ferromagnetically, while the ruthenium cations appear to undergo a change in spin configuration to a diamagnetic spin state. Features of the low-temperature crystal structure suggest a symmetry lowering Jahn-Teller distortion could be responsible for the observed diamagnetism of the ruthenium centers.

  16. Several novel Ru(II) and Ru(III) complexes formed by reduction of (RuO4bipy) and (RuO3phen)2O with hydroquinone and methanol

    International Nuclear Information System (INIS)

    Ishiyama, Toshio

    1975-01-01

    The geometrical isomers, cis-dichloro-trans-(methanol)(hydroquinone)(2,2'-bipyridine)ruthenium(II) and cis-dichloro-cis-(methanol)(hydroquinone)(2,2'-bipyridine)ruthenium(II), [RuCl 2 (MeOH)(QH 2 )bipy] (complex I and II), were synthesized by reduction and substitution reactions of [RuO 4 bipy] and [RuO 2 (OH) 2 bipy] with hydroquinone in hydrochloric acid solution, and methanol. cis-Chloro(hydroquinonato)bis(2,2'-bipyridine)ruthenium(II), cis-[RuCl(QH)(bipy) 2 ], was obtained from the substitution reaction of complex I or II with 2,2'-bipyridine in methanol, and cis-chloro(hydroquinone)bis(2,2'-bipyridine)ruthenium(II) chloride, cis-[RuCl(QH 2 )(bipy) 2 ]Cl, was also obtained from the substitution of cis-trans-[RuCl 2 (MeOH)(QH 2 )bipy] in methanol containing hydrochloric acid. cis-Dihydroxobis(2,2'-bipyridine)ruthenium(II), cis-[Ru(OH) 2 (bipy) 2 ], was obtained by heating an aqueous solution of cis-[RuCl(QH)(bipy) 2 ]. Trihydroxoaquo(1,10-phenanthroline)ruthenium(III), [Ru(OH) 3 (H 2 O)phen] was also synthesized from [RuO 3 phen] 2 O and [Ru(OH) 3 phen] 2 O by reduction reactions similar to those used for [RuCl 2 (MeOH)(QH 2 )bipy]. These complexes were characterized by the infrared, visible and ultraviolet absorption spectra, and also by polarographic and magnetic measurements. The structures are discussed. (auth.)

  17. Correlation Effects and Hidden Spin-Orbit Entangled Electronic Order in Parent and Electron-Doped Iridates Sr_{2}IrO_{4}

    Directory of Open Access Journals (Sweden)

    Sen Zhou

    2017-10-01

    Full Text Available Analogs of the high-T_{c} cuprates have been long sought after in transition metal oxides. Because of the strong spin-orbit coupling, the 5d perovskite iridates Sr_{2}IrO_{4} exhibit a low-energy electronic structure remarkably similar to the cuprates. Whether a superconducting state exists as in the cuprates requires understanding the correlated spin-orbit entangled electronic states. Recent experiments discovered hidden order in the parent and electron-doped iridates, some with striking analogies to the cuprates, including Fermi surface pockets, Fermi arcs, and pseudogap. Here, we study the correlation and disorder effects in a five-orbital model derived from the band theory. We find that the experimental observations are consistent with a d-wave spin-orbit density wave order that breaks the symmetry of a joint twofold spin-orbital rotation followed by a lattice translation. There is a Berry phase and a plaquette spin flux due to spin procession as electrons hop between Ir atoms, akin to the intersite spin-orbit coupling in quantum spin Hall insulators. The associated staggered circulating J_{eff}=1/2 spin current can be probed by advanced techniques of spin-current detection in spintronics. This electronic order can emerge spontaneously from the intersite Coulomb interactions between the spatially extended iridium 5d orbitals, turning the metallic state into an electron-doped quasi-2D Dirac semimetal with important implications on the possible superconducting state suggested by recent experiments.

  18. RuO4-mediated oxidation of secondary amines: Part 1. Are hydroxylamines main intermediates?

    Directory of Open Access Journals (Sweden)

    Florea Cristina A.

    2016-01-01

    Full Text Available The RuO4-catalyzed oxidation of secondary amines Bn-NH-CH2R (1a-b; R=H, Me gave mainly amides, but minute amounts of nitrones PhCH=N(O-CH2R (9a-b and traces of Bn-N(OH-CH2R (R=H, 4a were also detected. In the presence of cyanide, up to 22 reaction products were identified, but mainly α-aminonitriles. Comparison of the oxidation products of 1a-b with those of 4a-b, 9a-b, and Bn-N(O=CHR (10a-b showed that 4a-b cannot be main reaction intermediates formed from 1a-b.

  19. Blue to bluish-green tunable phosphor Sr2LiSiO4F:Ce3+,Tb3+ and efficient energy transfer for near-ultraviolet light-emitting diodes

    International Nuclear Information System (INIS)

    Xie, Mubiao; Zeng, Lihua; Ye, TingLi; Yang, Xi; Zhu, Xianmei; Peng, Siyun; Lei, Lei

    2014-01-01

    Ce 3+ and Tb 3+ activated Sr 2 LiSiO 4 F phosphors were prepared by a solid state reaction technique at high temperature, and their ultraviolet (UV)-visible spectroscopic properties were investigated. Under ultraviolet light excitation, Ce 3+ -doped Sr 2 LiSiO 4 F phosphors emit blue light (420 nm), while Tb 3+ -doped phosphors show yellowish green emission. Efficient energy transfer from Ce 3+ to Tb 3+ ions in co-doped samples was confirmed in terms of corresponding excitation and emission spectra. The energy transfer mechanism between Ce 3+ and Tb 3+ was discussed and demonstrated to be dipole–dipole interaction in Sr 2 LiSiO 4 F:Ce 3+ ,Tb 3+ phosphors. Due to energy transfer from Ce 3+ to Tb 3+ , Ce 3+ and Tb 3+ co-doped Sr 2 LiSiO 4 F phosphors show intense absorption in near-UV region, and present tunable emission from blue to bluish green under 360 nm light excitation. The results indicate that these phosphors can be considered as candidates for white LEDs pumped by n-UV chips. (paper)

  20. Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

    Science.gov (United States)

    Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

    2018-05-01

    In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

  1. Spin-Orbital Excitations in Ca2RuO4 Revealed by Resonant Inelastic X-Ray Scattering

    DEFF Research Database (Denmark)

    Das, L.; Forte, F.; Fittipaldi, R.

    2018-01-01

    The strongly correlated insulator Ca2RuO4 is considered as a paradigmatic realization of both spin-orbital physics and a band-Mott insulating phase, characterized by orbitally selective coexistence of a band and a Mott gap. We present a high resolution oxygen K-edge resonant inelastic x-ray scatt......-Mott scenario. The high-energy excitations correspond to intra-atomic singlet-triplet transitions at an energy scale set by Hund's coupling. Our findings give a unifying picture of the spin and orbital excitations in the band-Mott insulator Ca2RuO4.......The strongly correlated insulator Ca2RuO4 is considered as a paradigmatic realization of both spin-orbital physics and a band-Mott insulating phase, characterized by orbitally selective coexistence of a band and a Mott gap. We present a high resolution oxygen K-edge resonant inelastic x......-ray scattering study of the antiferromagnetic Mott insulating state of Ca2RuO4. A set of low-energy (about 80 and 400 meV) and high-energy (about 1.3 and 2.2 eV) excitations are reported, which show strong incident light polarization dependence. Our results strongly support a spin-orbit coupled band...

  2. Enhanced rate performance of mesoporous Co3O4 nanosheet supercapacitor electrodes by hydrous RuO2 nanoparticle decoration

    KAUST Repository

    Baby, Rakhi Raghavan

    2014-03-26

    Mesoporous cobalt oxide (Co3O4) nanosheet electrode arrays are directly grown over flexible carbon paper substrates using an economical and scalable two-step process for supercapacitor applications. The interconnected nanosheet arrays form a three-dimensional network with exceptional supercapacitor performance in standard two electrode configuration. Dramatic improvement in the rate capacity of the Co3O4 nanosheets is achieved by electrodeposition of nanocrystalline, hydrous RuO 2 nanoparticles dispersed on the Co3O4 nanosheets. An optimum RuO2 electrodeposition time is found to result in the best supercapacitor performance, where the controlled morphology of the electrode provides a balance between good conductivity and efficient electrolyte access to the RuO2 nanoparticles. An excellent specific capacitance of 905 F/g at 1 A/g is obtained, and a nearly constant rate performance of 78% is achieved at current density ranging from 1 to 40 A/g. The sample could retain more than 96% of its maximum capacitance even after 5000 continuous charge-discharge cycles at a constant high current density of 10 A/g. Thicker RuO2 coating, while maintaining good conductivity, results in agglomeration, decreasing electrolyte access to active material and hence the capacitive performance. © 2014 American Chemical Society.

  3. Anelastic characterization and superconducting properties of RuSr2GdCu2O8+δ

    Directory of Open Access Journals (Sweden)

    Jurelo, A. R.

    2008-08-01

    Full Text Available Since the discovery of the high Tc superconductors, many researches have been carried out on the different properties of these materials, especially on the transition temperature into the superconducting state. The rutheno-cuprates belong to a new class of composites, which were synthesized for the first time by Bauernfeind in 1995. Bernhard and collaborators discovered, in 1999, the coexistence of the ferromagnetism and the superconductivity in this phase, which is known as antagonistic phenomenon in the electromagnetism due to spin-charge interactions established in these states. However, the physical nature of the superconducting and magnetic states is still very obscure. The non-stoichiometric (interstitial oxygen is considered as a possible cause for the non-uniformity of the sample properties. In this paper, results of mechanical spectroscopy in Ru-1212 samples are presented showing complex anelastic spectra, which were attributed to the mobility of the interstitial oxygen atoms in the Ru-1212 lattice.Desde el descubrimiento de los superconductores de alta Tc, muchas investigaciones han sido realizadas sobre las diferentes propiedades de estos materiales, especialmente sobre la temperatura de transición dentro del estado superconductor. Los cupratos de rutenio pertenecen a una nueva clase de compositos, los cuales fueron sintetizados por primera vez por Bauernfeind en 1995. Bernhard y colaboradores descubrieron, en 1999, la coexistencia del ferromagnetismo y la superconductividad en esta fase, lo cual es conocido como un fenómeno antagonistico en el electromagnetismo debido a las interacciones spin-carga establecidas en estos estados. Sin embargo, la naturaleza física de los estados superconductores y magnéticos aun no son muy claros. El oxigeno no-estequiométrico (intersticial es considerado como una causa de la no-uniformidad de las propiedades de la muestra. En este articulo, los resultados de espectroscopia mecánica en muestras

  4. Nonlocal Coulomb correlations in pure and electron-doped Sr2IrO4 : Spectral functions, Fermi surface, and pseudo-gap-like spectral weight distributions from oriented cluster dynamical mean-field theory

    Science.gov (United States)

    Martins, Cyril; Lenz, Benjamin; Perfetti, Luca; Brouet, Veronique; Bertran, François; Biermann, Silke

    2018-03-01

    We address the role of nonlocal Coulomb correlations and short-range magnetic fluctuations in the high-temperature phase of Sr2IrO4 within state-of-the-art spectroscopic and first-principles theoretical methods. Introducing an "oriented-cluster dynamical mean-field scheme", we compute momentum-resolved spectral functions, which we find to be in excellent agreement with angle-resolved photoemission spectra. We show that while short-range antiferromagnetic fluctuations are crucial to accounting for the electronic properties of Sr2IrO4 even in the high-temperature paramagnetic phase, long-range magnetic order is not a necessary ingredient of the insulating state. Upon doping, an exotic metallic state is generated, exhibiting cuprate-like pseudo-gap spectral properties, for which we propose a surprisingly simple theoretical mechanism.

  5. Raman Scattering from Higgs Mode Oscillations in the Two-Dimensional Antiferromagnet Ca_{2}RuO_{4}.

    Science.gov (United States)

    Souliou, Sofia-Michaela; Chaloupka, Jiří; Khaliullin, Giniyat; Ryu, Gihun; Jain, Anil; Kim, B J; Le Tacon, Matthieu; Keimer, Bernhard

    2017-08-11

    We present and analyze Raman spectra of the Mott insulator Ca_{2}RuO_{4}, whose quasi-two-dimensional antiferromagnetic order has been described as a condensate of low-lying spin-orbit excitons with angular momentum J_{eff}=1. In the A_{g} polarization geometry, the amplitude (Higgs) mode of the spin-orbit condensate is directly probed in the scalar channel, thus avoiding infrared-singular magnon contributions. In the B_{1g} geometry, we observe a single-magnon peak as well as two-magnon and two-Higgs excitations. Model calculations using exact diagonalization quantitatively agree with the observations. Together with recent neutron scattering data, our study provides strong evidence for excitonic magnetism in Ca_{2}RuO_{4} and points out new perspectives for research on the Higgs mode in two dimensions.

  6. See Also:physica status solidi (a)physica status solidi (c)Copyright © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimGet Sample CopyFree Online Trial -->Recommend to Your LibrarianSave Title to My ProfileSet E-Mail Alert var homepagelinks = new Array(new Array("Journal Home","/cgi-bin/jhome/40001185",""),new Array("Issues","/cgi-bin/jtoc/40001185/",""),new Array("Early View","/cgi-bin/jeview/40001185/",""),new Array("News","/cgi-bin/jabout/40001185/news/index.html",""),new Array("Reviews","/cgi-bin/jabout/40001185/reviews.html",""),new Array("Read Cover Story","/cgi-bin/jabout/40001185/cover/2232/current.html","e"),new Array("","","s"),new Array("Product Information","/cgi-bin/jabout/40001185/2232_info.html",""),new Array("Editorial Board","/cgi-bin/jabout/40001185/edbd.html",""),new Array("For Authors","/cgi-bin/jabout/40001185/authors.html",""),new Array("For Referees","/cgi-bin/jabout/40001185/refserv.html",""),new Array("Subscribe","http://jws-edcv.wiley.com/jcatalog/JournalsCatalogOrder/JournalOrder?PRINT_ISSN=0370-1972",""),new Array("Contact","/cgi-bin/jabout/40001185/contact.html",""),new Array("","","x"));writeJournalLinks("", "40001185");Volume 241, Issue5 (April 2004)Articles in the Current Issue:Cover PictureHorizontal line nodes in superconducting Sr2RuO4

    Science.gov (United States)

    Litak, G.; Annett, J. F.; Györffy, B. L.; Wysokiski, K. I.

    2004-04-01

    Superconductivity in Sr2RuO4 is one of the most interesting phenomena in current condensed matter physics, since it is revealed to be a triplet-pairing state. Our Editor's Choice [1] considers an important problem related to the type of order parameter in this material.The position of line nodes on the Fermi surface, as evident from recent measurements, has been determined for various scenarios shown in the cover picture. Using these models, the temperature dependence of heat capacity and penetration depth has been calculated for easy comparison with experiments.The first author, Grzegorz Litak, is assistant professor at Technical University of Lublin and visiting scientist at the Max Planck Institute in Dresden. He is working on the effect of disorder on correlated and exotic superconductors, nonlinear dynamics, and superconductivity in strontium ruthenate.

  7. Spin-Orbital Excitations in Ca_{2}RuO_{4} Revealed by Resonant Inelastic X-Ray Scattering

    Directory of Open Access Journals (Sweden)

    L. Das

    2018-03-01

    Full Text Available The strongly correlated insulator Ca_{2}RuO_{4} is considered as a paradigmatic realization of both spin-orbital physics and a band-Mott insulating phase, characterized by orbitally selective coexistence of a band and a Mott gap. We present a high resolution oxygen K-edge resonant inelastic x-ray scattering study of the antiferromagnetic Mott insulating state of Ca_{2}RuO_{4}. A set of low-energy (about 80 and 400 meV and high-energy (about 1.3 and 2.2 eV excitations are reported, which show strong incident light polarization dependence. Our results strongly support a spin-orbit coupled band-Mott scenario and explore in detail the nature of its exotic excitations. Guided by theoretical modeling, we interpret the low-energy excitations as a result of composite spin-orbital excitations. Their nature unveils the intricate interplay of crystal-field splitting and spin-orbit coupling in the band-Mott scenario. The high-energy excitations correspond to intra-atomic singlet-triplet transitions at an energy scale set by Hund’s coupling. Our findings give a unifying picture of the spin and orbital excitations in the band-Mott insulator Ca_{2}RuO_{4}.

  8. Spin orientations of the spin-half Ir(4+) ions in Sr3NiIrO6, Sr2IrO4, and Na2IrO3: Density functional, perturbation theory, and Madelung potential analyses.

    Science.gov (United States)

    Gordon, Elijah E; Xiang, Hongjun; Köhler, Jürgen; Whangbo, Myung-Hwan

    2016-03-21

    The spins of the low-spin Ir(4+) (S = 1/2, d(5)) ions at the octahedral sites of the oxides Sr3NiIrO6, Sr2IrO4, and Na2IrO3 exhibit preferred orientations with respect to their IrO6 octahedra. We evaluated the magnetic anisotropies of these S = 1/2 ions on the basis of density functional theory (DFT) calculations including spin-orbit coupling (SOC), and probed their origin by performing perturbation theory analyses with SOC as perturbation within the LS coupling scheme. The observed spin orientations of Sr3NiIrO6 and Sr2IrO4 are correctly predicted by DFT calculations, and are accounted for by the perturbation theory analysis. As for the spin orientation of Na2IrO3, both experimental studies and DFT calculations have not been unequivocal. Our analysis reveals that the Ir(4+) spin orientation of Na2IrO3 should have nonzero components along the c- and a-axis directions. The spin orientations determined by DFT calculations are sensitive to the accuracy of the crystal structures employed, which is explained by perturbation theory analyses when interactions between adjacent Ir(4+) ions are taken into consideration. There are indications implying that the 5d electrons of Na2IrO3 are less strongly localized compared with those of Sr3NiIrO6 and Sr2IrO4. This implication was confirmed by showing that the Madelung potentials of the Ir(4+) ions are less negative in Na2IrO3 than in Sr3NiIrO6 and Sr2IrO4. Most transition-metal S = 1/2 ions do have magnetic anisotropies because the SOC induces interactions among their crystal-field split d-states, and the associated mixing of the states modifies only the orbital parts of the states. This finding cannot be mimicked by a spin Hamiltonian because this model Hamiltonian lacks the orbital degree of freedom, thereby leading to the spin-half syndrome. The spin-orbital entanglement for the 5d spin-half ions Ir(4+) is not as strong as has been assumed.

  9. Magnetic and conductivity study on Mn0.5Ru0.5Co2O4 spinel

    International Nuclear Information System (INIS)

    Bhowmik, R.N.; Ranganathan, R.

    2003-01-01

    The magnetic measurements suggest that Mn 0.5 Ru 0.5 Co 2 O 4 is a ferrimagnet with T c ≅ 140 K followed by irreversibility between zero field cooled and field cooled magnetization and peak in zero field cooled maximum at T m ≅ 100 K on decreasing the temperature. The scaling analysis of the conductivity (G) as a function of frequency (f) with functional form G p (f)/G o ∼ (f/f c ) n suggests two activated regimes at above and below of 210 K, respectively. The G o vs T shows semi-conducting behaviour of the sample. (author)

  10. Electronic structure of (La,Sr)2CuO4 and Ba0.6K0.4BiO3

    International Nuclear Information System (INIS)

    Howell, R.H.; Sterne, P.A.; Fluss, M.J.; Kaiser, J.H.; Kitazawa, K.; Kojima, H.; Mosley, W.D.; Dykes, J.W.; Shelton, R.N.

    1995-01-01

    We have measured and calculated the electron-positron momentum distribution of La 2-x Sr x CuO 4 samples for Sr concentrations of 0, 0.1,0.13, and 0.2 and Ba 0.6 K 0.4 BiO 3 . The momentum distribution of all samples contained features derived from the overlap of the positron distribution with the valence electrons. In addition, discontinuities typical of a Fermi surface are seen in the superconducting samples. The form and position of these features are in general agreement with band theory for both La 2-x Sr x CuO 4 and Ba 0.6 K 0.4 BiO 3 . However the evolution of the Fermi surface with doping in La 2-x Sr x CuO 4 differed significantly from expectations based on single electron band theories. (orig.)

  11. Highly Anisotropic Magnon Dispersion in Ca_{2}RuO_{4}: Evidence for Strong Spin Orbit Coupling.

    Science.gov (United States)

    Kunkemöller, S; Khomskii, D; Steffens, P; Piovano, A; Nugroho, A A; Braden, M

    2015-12-11

    The magnon dispersion in Ca_{2}RuO_{4} has been determined by inelastic neutron scattering on single crytals containing 1% of Ti. The dispersion is well described by a conventional Heisenberg model suggesting a local moment model with nearest neighbor interaction of J=8  meV. Nearest and next-nearest neighbor interaction as well as interlayer coupling parameters are required to properly describe the entire dispersion. Spin-orbit coupling induces a very large anisotropy gap in the magnetic excitations in apparent contrast with a simple planar magnetic model. Orbital ordering breaking tetragonal symmetry, and strong spin-orbit coupling can thus be identified as important factors in this system.

  12. Non-destructive reversible resistive switching in Cr doped Mott insulator Ca2RuO4: Interface vs bulk effects

    KAUST Repository

    Shen, Shida; Williamson, Morgan; Cao, Gang; Zhou, Jianshi; Goodenough, John; Tsoi, Maxim

    2017-01-01

    A non-destructive reversible resistive switching is demonstrated in single crystals of Cr-doped Mott insulator Ca2RuO4. An applied electrical bias was shown to reduce the DC resistance of the crystal by as much as 75%. The original resistance

  13. 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

    The S = 3/2, quasi-one-dimensional (1D) zig-zag chain Heisenberg antiferromagnet Li3RuO4 has been investigated using heat capacity, inelastic neutron scattering, neutron diffraction, and μSR measurements on a powder sample. Our neutron diffraction and μSR studies confirm a long-range ordering of ...

  14. Soft template synthesis of mesoporous Co3O4/RuO2.xH2O composites for electrochemical capacitors

    International Nuclear Information System (INIS)

    Liu Yang; Zhao Weiwei; Zhang Xiaogang

    2008-01-01

    Co 3 O 4 /RuO 2 .xH 2 O composites with various Ru content (molar content of Ru = 5%, 10%, 20%, 50%) were synthesized by one-step co-precipitation method. The precursors were prepared via adjusting pH of the mixed aqueous solutions of Co(NO 3 ) 2 .6H 2 O and RuCl 3 .0.5H 2 O by using Pluronic123 as a soft template. For the composite with molar ratio of Co:Ru = 1:1 annealed at 200 deg. C, Brunauer-Emmet-Teller (BET) results indicated that the composite showed mesoporous structure, and the specific surface area of the composite was as high as 107 m 2 g -1 . The electrochemical performances of these composites were measured in 1 M KOH electrolyte. Compared with the composite prepared without template, the composite with P123 exhibited a higher specific capacitance. When the molar content of Ru was rising, the specific capacitance of the composites increased significantly. It was also observed that the crystalline structures as well as the electrochemical activities were strongly dependent on the annealing temperature. A capacitance of 642 F/g was obtained for the composite (Co:Ru = 1:1) annealed at 150 deg. C. Meanwhile, the composites also exhibited good cycle stability. Besides, the morphologies and textural characteristic of the samples were also investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM)

  15. Comparing the physical properties of Pr/Gd and Pr/Ce substitutions in Ru(Gd1.5Ce0.5)Sr2Cu2O10- δ

    Science.gov (United States)

    Khajehnezhad, A.; Nikseresht, N.; Hadipour, H.; Akhavan, M.

    2008-06-01

    We have compared the electrical and magnetic properties of Ru(Gd1.5- x Pr x )Ce0.5Sr2Cu2O10- δ (Pr/Gd samples) with x = 0.0, 0.01, 0.03, 0.033, 0.035, 0.04, 0.05, 0.06, 0.1 and RuGd1.5(Ce0.5- x Pr x ) Sr2 Cu2O10- δ (Pr/Ce samples) with x = 0.0, 0.01, 0.03, 0.05, 0.08, 0.1, 0.15, 0.2 prepared by the standard solid-state reaction technique. We obtained the XRD patterns for different samples with various x. The lattice parameters versus x for different substitutions have been obtained from Rietveld analysis. To determine how the magnetic and superconducting properties of these layered cuprate systems can be affected by Pr substitution, the resistivity, and magnetoresistivity, with H ext varying from 0.0 to 15 kOe, have been measured at various temperatures. Superconducting transition temperature T c and magnetic transition T irr , have been obtained through resistivity and ac susceptibility measurements. The T c suppression due to Pr/Gd and Pr/Ce substitutions show competition between pair breaking by magnetic impurities, hole doping due to different valances of ions, difference in ionic radii, and oxygen stoichiometry. Pr/Gd substitution suppresses superconductivity more rapidly than for Pr/Ce, showing that the effect of hole doping and magnetic impurity pair breaking is stronger than the difference in ionic radii. In Pr/Gd substitution, the small difference between the ionic radii of Pr3+,4+ and Gd3+, and absorption of more oxygen due to the higher valence of Pr with respect to Gd, decreases the mean Ru-Ru distance, and as a result, the magnetic exchange interaction becomes stronger with the increase of x. However, Pr/Ce substitution has the opposite effect. The magnetic parameters such as H c , obtained through magnetization measurements versus applied magnetic field isotherm at 77 K and room temperatures, become stronger with x in Pr/Gd and weaker with x in Pr/Ce substitution.

  16. Flexible asymmetric supercapacitors based upon Co9S8 nanorod//Co3O4@RuO2 nanosheet arrays on carbon cloth.

    Science.gov (United States)

    Xu, Jing; Wang, Qiufan; Wang, Xiaowei; Xiang, Qingyi; Liang, Bo; Chen, Di; Shen, Guozhen

    2013-06-25

    We have successfully fabricated flexible asymmetric supercapacitors (ASCs) based on acicular Co9S8 nanorod arrays as positive materials and Co3O4@RuO2 nanosheet arrays as negative materials on woven carbon fabrics. Co9S8 nanorod arrays were synthesized by a hydrothermal sulfuration treatment of acicular Co3O4 nanorod arrays, while the RuO2 was directly deposited on the Co3O4 nanorod arrays. Carbon cloth was selected as both the substrate and the current collector for its good conductivity, high flexibility, good physical strength, and lightweight architecture. Both aqueous KOH solutions and polyvinyl alcohol (PVA)/KOH were employed as electrolyte for electrochemical measurements. The as-fabricated ASCs can be cycled reversibly in the range of 0-1.6 V and exhibit superior electrochemical performance with an energy density of 1.21 mWh/cm(3) at a power density of 13.29 W/cm(3) in aqueous electrolyte and an energy density of 1.44 mWh/cm(3) at the power density of 0.89 W/cm(3) in solid-state electrolyte, which are almost 10-fold higher than those reported in early ASC work. Moreover, they present excellent cycling performance at multirate currents and large currents after thousands of cycles. The high-performance nanostructured ASCs have significant potential applications in portable electronics and electrical vehicles.

  17. Photoluminescence and scintillation properties of Ce-doped Sr2(Gd1-xLux)8(SiO4)6O2 (x = 0.1, 0.2, 0.4, 0.5, 0.6) crystals

    Science.gov (United States)

    Igashira, Takuya; Kawano, Naoki; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

    2018-05-01

    Apatite crystals with chemical compositions of 0.5% Ce-doped Sr2(Gd1-xLux)8(SiO4)6O2 (x = 0.1, 0.2, 0.4, 0.5, 0.6) were synthesized by the Floating Zone method, and then we evaluated their photoluminescence (PL) and scintillation properties. All the Ce-doped samples exhibited PL and scintillation with an intense broad emission in 400-550 nm in which the origin was attributed to the 5d-4f transition of Ce3+, and the emission peak became broader with increasing the concentration of Lu3+. Both PL and scintillation decay time profiles were best-approximated by a sum of two exponential decay functions, and the origin of slower component was attributed to the 5d-4f transition of Ce3+. In the X-ray induced afterglow measurements, the Ce-doped Sr2(Gd0.4Lu0.6)8(SiO4)6O2 sample exhibited the lowest afterglow level. Furthermore, the Ce-doped Sr2(Gd0.5Lu0.5)8(SiO4)6O2 and Sr2(Gd0.4Lu0.6)8(SiO4)6O2 samples showed a clear full energy deposited peak under 5.5 MeV 241Am α-ray irradiation, and the estimated absolute scintillation light yields were around 290 and 1300 ph/5.5 MeV-α, respectively.

  18. Removal of nitrogen oxides, 106RuO4 vapors and radioactive aerosols from the gas originating in radioactive wastes solidification

    International Nuclear Information System (INIS)

    Kepak, F.; Pecak, V.; Uher, E.; Kanka, J.; Koutova, S.; Matous, V.

    1985-01-01

    Procedures and equipment for the disposal of nitrogen oxides, RuO 4 vapors and radioactive aerosols of 90 Sr, 137 Cs, 60 Co and 125 Sb contained in the gas generated in the solidification of high- and intermediate-level radioactive wastes were tested on models. Nitrogen oxides were disposed of by absorption and chemical decomposition in various solutions of which the best results gave solutions of ammonium salts. Absorption in solutions, physical and chemical sorption on inorganic sorbents were tested for the disposal of RuO 4 . Aerosols were disposed of by absorption in absorption media with subsequent filtration. Of fibrous filter materials, Czechoslovak AEROS-2 and RA-2 filter papers were proven in the tests. Attention was also devoted to granular filter materials of which silica gel was chosen. On the basis of laboratory tests a multi-step treatment system was designed which consists of a condenser, a nitrogen oxide absorber, a liquid aerosol separator, absorption columns and aerosol filters. The whole system has been manufactured on pilot plant scale and the different parts are being produced. (Z.M.)

  19. Self-organization in complex oxide thin films: from 2D to 0D nanostructures of SrRuO3 and CoCr2O4

    Science.gov (United States)

    Sánchez, F.; Lüders, U.; Herranz, G.; Infante, I. C.; Fontcuberta, J.; García-Cuenca, M. V.; Ferrater, C.; Varela, M.

    2005-05-01

    We report here on the controlled fabrication of nanostructures of varied dimensionality by self-organization processes in the heteroepitaxial growth of SrRuO3 (SRO) and CoCr2O4 (CCO) films. The surface of SRO films on SrTiO3(001) substrates can show extremely smooth terraces (2D objects) separated by atomic steps, a structure of faceted islands (0D objects), a cross-hatch morphology (1D objects), an array of finger-like units (1D objects), or an array of giant bunched steps (1D objects). The surface can be tailored to a particular structure by controlling the vicinality of the substrate and the growth rate and nominal thickness of the film. In the case of CCO films, grown on (001)-oriented MgAl2O4 or MgO substrates, high aspect ratio {111}-faceted pyramids and hut clusters (0D objects), highly oriented and having a similar size, appear above a critical thickness. The size and spatial density can be tuned by varying deposition temperature, nominal thickness, and substrate. This dependence allows the fabrication of surfaces being fully faceted (2D objects), or having arrays of dislocated pyramids of up to micrometric size, or small coherently lattice strained pyramids having a nanometric size. We discuss the driving forces that originate the peculiar SRO and CCO nanostructures. The findings illustrate that the growth of complex oxides can promote a variety of novel self-organized morphologies, and suggest original strategies to fabricate templates or hybrid structures of oxides combining varied functionalities.

  20. Non-destructive reversible resistive switching in Cr doped Mott insulator Ca2RuO4: Interface vs bulk effects

    Science.gov (United States)

    Shen, Shida; Williamson, Morgan; Cao, Gang; Zhou, Jianshi; Goodenough, John; Tsoi, Maxim

    2017-12-01

    A non-destructive reversible resistive switching is demonstrated in single crystals of Cr-doped Mott insulator Ca2RuO4. An applied electrical bias was shown to reduce the DC resistance of the crystal by as much as 75%. The original resistance of the sample could be restored by applying an electrical bias of opposite polarity. We have studied this resistive switching as a function of the bias strength, applied magnetic field, and temperature. A combination of 2-, 3-, and 4-probe measurements provide a means to distinguish between bulk and interfacial contributions to the switching and suggests that the switching is mostly an interfacial effect. The switching was tentatively attributed to electric-field driven lattice distortions which accompany the impurity-induced Mott transition. This field effect was confirmed by temperature-dependent resistivity measurements which show that the activation energy of this material can be tuned by an applied DC electrical bias. The observed resistance switching can potentially be used for building non-volatile memory devices like resistive random access memory.

  1. Non-destructive reversible resistive switching in Cr doped Mott insulator Ca2RuO4: Interface vs bulk effects

    KAUST Repository

    Shen, Shida

    2017-12-29

    A non-destructive reversible resistive switching is demonstrated in single crystals of Cr-doped Mott insulator Ca2RuO4. An applied electrical bias was shown to reduce the DC resistance of the crystal by as much as 75%. The original resistance of the sample could be restored by applying an electrical bias of opposite polarity. We have studied this resistive switching as a function of the bias strength, applied magnetic field, and temperature. A combination of 2-, 3-, and 4-probe measurements provide a means to distinguish between bulk and interfacial contributions to the switching and suggests that the switching is mostly an interfacial effect. The switching was tentatively attributed to electric-field driven lattice distortions which accompany the impurity-induced Mott transition. This field effect was confirmed by temperature-dependent resistivity measurements which show that the activation energy of this material can be tuned by an applied DC electrical bias. The observed resistance switching can potentially be used for building non-volatile memory devices like resistive random access memory.

  2. Sandwich-Type Electrochemiluminescence Sensor for Detection of NT-proBNP by Using High Efficiency Quench Strategy of Fe3O4@PDA toward Ru(bpy)32+ Coordinated with Silver Oxalate.

    Science.gov (United States)

    Shi, Li; Li, Xiaojian; Zhu, Wenjuan; Wang, Yaoguang; Du, Bin; Cao, Wei; Wei, Qin; Pang, Xuehui

    2017-12-22

    Heart failure (HF) is a burgeoning public health problem trigged by a heart circulation disorder. N-terminal pro-B-type natriuretic peptide (NT-proBNP) has been acknowledged as a prognostic biomarker for cardiac disease. Herein, a sandwich-type electrochemiluminescence (ECL) immunosensor was introduced for sensitive detection of NT-proBNP. Gold nanoparticle modified graphene oxide-Ru(bpy) 3 2+ /Ag 2 C 2 O 4 was used as a luminophore and a desirable platform for immobilization of the captured antibodies. The more stable immobilization of plentiful Ru(bpy) 3 2+ could be implemented by direct covalent bonding chelation with Ag 2 C 2 O 4 . More importantly, significant quenching can be achieved by introducing polydopamine (PDA) coated Fe 3 O 4 onto the electrode via sandwich immunoreactions. The quenching mechanism mainly showed that the excited states of Ru(bpy) 3 2+ could be annihilated by quinone units in PDA via energy transfer. The ECL quenching efficiency was logarithmically related to the concentration of the NT-proBNP in the range from 0.0005 ng/mL to 100.0 ng/mL with a detection limit of 0.28 pg/mL. Furthermore, this specific immunosensor presented good stability and repeatability as well as selectivity, which offers a guiding significance in both fundamental and clinical diagnosis of NT-proBNP.

  3. Structural and electrical properties of room temperature pulsed laser deposited and post-annealed thin SrRuO3 films

    International Nuclear Information System (INIS)

    Gautreau, O.; Harnagea, C.; Normandin, F.; Veres, T.; Pignolet, A.

    2007-01-01

    Good quality strontium ruthenate (SrRuO 3 ) thin continuous films (15 to 125 nm thick) have been synthesized on silicon (100) substrates by room temperature pulsed laser deposition under vacuum followed by a post-deposition annealing, a route unexplored and yet not reported for SrRuO 3 film growth. The presence of an interfacial Sr 2 SiO 4 layer has been identified for films annealed at high temperature, and the properties of this interface layer as well as the properties of the SrRuO 3 film have been analyzed and characterized as a function of the annealing temperature. The room temperature resistivity of the SrRuO 3 films deposited by laser ablation at room temperature and post-annealed is 2000 μΩ.cm. A critical thickness of 120 nm has been determined above which the influence of the interface layer on the resistivity becomes negligible

  4. Phase formation in Na2MoO4 - MgMoO4 - Cr2(MoO4)3 system

    International Nuclear Information System (INIS)

    Kotova, I.Yu.; Kozhevnikova, N.M.

    1998-01-01

    Interaction within Na 2 MoO 4 - MgMoO 4 - Cr 2 (MoO 4 ) 3 ternary system is studied by X ray phase and DTA methods. State diagram of NaCr(MoO 4 ) 2 - MgMoO 4 section is plotted. Production of ternary molybdates of Na 1-x Mg 1-x Cr 1+x (MoO 4 ) 3 , where 0 ≤ x ≤ 0.3, and NaMg 3 Cr(MoO 4 ) 5 composition is ascertained [ru

  5. Multiparticle tunneling in the field electron emission from Bi2CaSr2Cu2O8

    International Nuclear Information System (INIS)

    Maslov, V.I.

    2001-01-01

    The studies results on the statistics of the field electron emission (FEE) from the Bi 2 CaSr 2 Cu 2 O 8 oxide superconductor are considered. The multielectron tunneling by FEE is identified. The analysis of the spectral curves and FEE statistics dependence on the experimental conditions is carried out. The possible mechanism of the multiparticle effect is discussed [ru

  6. Optical anisotropy of Bi2Sr2CaCu2O8

    Science.gov (United States)

    Kim, J. H.; Bozovic, I.; Mitzi, D. B.; Kapitulnik, A.; Harris, J. S., Jr.

    1990-04-01

    The optical anisotropy of Bi2Sr2CaCu2O8 in the 0.08-0.5-eV region is investigated by polarized reflectance measurements on single crystals. A very large anisotropy is found in this spectral region. The in-plane reflectance exhibits metallic behavior, while the c-axis reflectance exhibits insulatorlike behavior. This result is consistent with the large anisotropy found in the resistivity of Bi2Sr2CaCu2O8. Our spectroscopic data suggest that Bi2Sr2CaCu2O8 is a quasi-two-dimensional metal similar to La2-xSrxCuO4.

  7. Isolation of a Bis-Iodurated Tetra-THF as a Trace Product from the Oxidation of Squalene with RuO4 and Its Double Ring Expansion to a Novel bis-THF-bis-THP Compound

    Directory of Open Access Journals (Sweden)

    Nicola Borbone

    2011-06-01

    Full Text Available A novel bis-iodurated polyether compound, based on an unprecedented tetra-THF backbone, has been isolated as a trace by-product of the oxidation of squalene with the catalytic system RuO2(cat./NaIO4. The double erythro configuration of the central portion of the molecule furnishes the first indirect support of the previously postulated pathway operating in the oxidative pentacyclization of the isoprenoid substrate. A bidirectional double oxidative bis-cyclization is invoked to explain the formation of this compound. The isolated substance was successfully subjected to a double rearrangement-ring expansion to give a novel bis-THF-bis-THP compound.

  8. Synthesis and characterization of alkyl-imidazolium-based periodic mesoporous organosilicas: a versatile host for the immobilization of perruthenate (RuO4-) in the aerobic oxidation of alcohols.

    Science.gov (United States)

    Karimi, Babak; Elhamifar, Dawood; Yari, Omolbanin; Khorasani, Mojtaba; Vali, Hojatollah; Clark, James H; Hunt, Andrew J

    2012-10-15

    The preparation and characterization of a set of periodic mesoporous organosilicas (PMOs) that contain different fractions of 1,3-bis(3-trimethoxysilylpropyl)imidazolium chloride (BTMSPI) groups uniformly distributed in the silica mesoporous framework is described. The mesoporous structure of the materials was characterized by powder X-ray diffraction, transmission electron microscopy, and N(2) adsorption-desorption analysis. The presence of propyl imidazolium groups in the silica framework of the materials was also characterized by solid-state NMR spectroscopy and diffuse-reflectance Fourier-transform infrared spectroscopy. The effect of the BTMSPI concentration in the initial solutions on the structural properties (including morphology) of the final materials was also examined. The total organic content of the PMOs was measured by elemental analysis, whereas their thermal stability was determined by thermogravimetric analysis. Among the described materials, it was found that PMO with 10% imidazolium content is an effective host for the immobilization of perruthenate through an ion-exchange protocol. The resulting Ru@PI-10 was then employed as a recyclable catalyst in the highly efficient aerobic oxidation of various types of alcohols. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. RuSr2GdCu2O8 and RuSr2Gd1.5Ce0.5Cu2O10

    Indian Academy of Sciences (India)

    Magnetism and superconductivity in rutheno cuprates. [3] C Bernhard, J L Tallon, Ch Niedermayer, Th Blasius, A Golnik, E Brücher, R K Kremer, D R. Noakes, C E Stronack and E J Asnaldo, Phys. Rev. B59, 14099 (1999). [4] J L Tallon, C Bernhard, M E Bowden, T M Soto, B Walker, P W Gilberd, M R Preseland, J P. Attfield ...

  10. Determination of indole-3-acetic acid and indole-3-butyric acid in mung bean sprouts using high performance liquid chromatography with immobilized Ru(bpy)3(2+)-KMnO4 chemiluminescence detection.

    Science.gov (United States)

    Xi, Zhijun; Zhang, Zhujun; Sun, Yonghua; Shi, Zuolong; Tian, Wei

    2009-07-15

    A novel method for determination of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) in an extract from mung bean sprouts using high performance liquid chromatography (HPLC) with chemiluminescence (CL) detection is described. The method is based on the CL reaction of auxin (indole-3-acetic acid and indole-3-butyric acid) with acidic potassium permanganate (KMnO(4)) and tris(2,2'-bipyridyl)ruthenium(II), which was immobilized on the cationic ion-exchange resin. The chromatographic separation was performed on a Nucleosil RP-C18 column (i.d.: 250 mm x 4.6 mm, particle size: 5 microm, pore size: 100) with an isocratic mobile phase consisting of methanol-water-acetic acid (45:55:1, v/v/v). At a flow rate of 1.0 mL min(-1), the total run time was 20 min. Under the optimal conditions, the linear ranges were 5.0x10(-8) to 5.0x10(-6)g mL(-1) and 5.0x10(-7) to 1.0x10(-5)g mL(-1) for IAA and IBA, respectively. The detection limits were 2.0x10(-8)g mL(-1) and 2.0x10(-7)g mL(-1) for IAA and IBA, respectively. The relative standard deviation (RSD) of intra-day were 3.1% and 2.3% (n=11) for 2x10(-6)g mL(-1) IAA and 2x10(-6)g mL(-1) IBA; The relative standard deviations of inter-day precision were 6.9% and 4.9% for 2x10(-6)g mL(-1) IAA and 2x10(-6)g mL(-1) IBA. The proposed method had been successfully applied to the determination of auxin in mung bean sprouts.

  11. [Exogenous Sr2+ sedimentation on otolith of chum salmon embryos].

    Science.gov (United States)

    Wang, Chen; Liu, Wei; Zhan, Pei-rong; Wang, Ji-long; Li, Pei-lun

    2015-10-01

    To explore the exogenous Sr2+ sedimentation on otolith of chum salmon embryos, chum salmon embryos were exposed to culture water contained Sr2+ at Sr2+ concentration of 50, 100, 200 or 400 mg . L-1 for 48 h to imitate Sr2+ sedimentation. After a culturing period of 12 d and 100 d, the otoliths of the chum salmon were taken to detect exogenous Sr2+ sedimentation with electro-probe microanalyzer (EPMA). The results showed that obvious deep red strontium signatures were produced in the otolith of chum salmon at different concentrations of Sr2+. The mean and extreme values of peak strontium area were not stable for the same Sr2+ dose, but the lowest of all the peak values was 35.1 times as much as that of control. Overall, the strontium value increased with the increase of Sr2+concentration. The strontium peak had no signs of abating after a culture period of 100 d. The results also showed that strontium was gradually deposited in the otolith, and had obvious hysteresis to immersion. Strontium sedimentation could also return to a normal level after the peak. These characteristics accorded exactly with the requirement of discharge tag technology, which indicated that exogenous Sr2+ was suitable in the marking of salmon otolith.

  12. Interplay between HIV Entry and Transportin-SR2 Dependency

    Directory of Open Access Journals (Sweden)

    Gijsbers Rik

    2011-01-01

    Full Text Available Abstract Background Transportin-SR2 (TRN-SR2, TNPO3, transportin 3 was previously identified as an interaction partner of human immunodeficiency virus type 1 (HIV-1 integrase and functions as a nuclear import factor of HIV-1. A possible role of capsid in transportin-SR2-mediated nuclear import was recently suggested by the findings that a chimeric HIV virus, carrying the murine leukemia virus (MLV capsid and matrix proteins, displayed a transportin-SR2 independent phenotype, and that the HIV-1 N74D capsid mutant proved insensitive to transportin-SR2 knockdown. Results Our present analysis of viral specificity reveals that TRN-SR2 is not used to the same extent by all lentiviruses. The DNA flap does not determine the TRN-SR2 requirement of HIV-1. We corroborate the TRN-SR2 independent phenotype of the chimeric HIV virus carrying the MLV capsid and matrix proteins. We reanalyzed the HIV-1 N74D capsid mutant in cells transiently or stably depleted of transportin-SR2 and confirm that the N74D capsid mutant is independent of TRN-SR2 when pseudotyped with the vesicular stomatitis virus glycoprotein (VSV-G. Remarkably, although somewhat less dependent on TRN-SR2 than wild type virus, the N74D capsid mutant carrying the wild type HIV-1 envelope required TRN-SR2 for efficient replication. By pseudotyping with envelopes that mediate pH-independent viral uptake including HIV-1, measles virus and amphotropic MLV envelopes, we demonstrate that HIV-1 N74D capsid mutant viruses retain partial dependency on TRN-SR2. However, this dependency on TRN-SR2 is lost when the HIV N74D capsid mutant is pseudotyped with envelopes mediating pH-dependent endocytosis, such as the VSV-G and Ebola virus envelopes. Conclusion Here we discover a link between the viral entry of HIV and its interaction with TRN-SR2. Our data confirm the importance of TRN-SR2 in HIV-1 replication and argue for careful interpretation of experiments performed with VSV-G pseudotyped viruses in

  13. Interaction in the NaIn(MoO4)2 - AMoO4 (A = Mg, Mn) systems

    International Nuclear Information System (INIS)

    Kotova, I.Yu.; Kozhevnikova, N.M.

    2001-01-01

    The results of investigation into NaIn(MoO 4 ) 2 - AMoO 4 (A = Mg, Mn) quasibinary cross-sections by means of X-ray diffraction and differential thermal analysis are presented. Conducted researches revealed that compounds NaMg 3 In(MoO 4 ) and NaMn 3 In(MoO 4 ) melting incongruently at 990 Deg C and 940 Deg C accordingly were formed in the NaIn(MoO 4 ) - AMoO 4 (A = Mg, Mn) systems. The data of initiation of X-ray diffraction pattern of NaMg 3 In(MoO 4 ) 5 are presented. The temperature dependences of conductivity, dielectric permeability and tangent of dielectric losses indicative on ionic-electronic nature conductivity are determined. Activation energy of conductivity in the Mg - Mn row changes moderately - from 9.91 till 5.71 eV [ru

  14. Phase formation in the Rb2MoO4-Li2MoO4-Hf(MoO4)2 system and the crystal structure of Rb5(Li1/3Hf5/3)(MoO4)6

    International Nuclear Information System (INIS)

    Solodovnikov, S.F.; Zolotova, E.S.; Balsanova, L.V.; Bazarov, B.G.; Bazarova, Zh.G.

    2003-01-01

    Phase formation in the Rb 2 MoO 4 -Li 2 MoO 4 -Hf(MoO 4 ) 2 system is studied in subsolidus region in air by the method of crossing sections. Three ternary molybdates are detected in the system. Compositions of two of them are corroborated by selection of isostructural analogues [ru

  15. Phase relations in the M2MoO4 - Ag2MoO4 - Hf(MoO4)2 (M=Li, Na) systems

    International Nuclear Information System (INIS)

    Bazarova, Zh.G.; Bazarov, B.G.; Balsanova, L.V.

    2002-01-01

    The M 2 MoO 4 - Ag 2 MoO 4 - Hf(MoO 4 ) 2 (M=Li, Na) systems were studied by X-ray diffraction and differential thermal analyses in the subsolidus area (450 - 500 Deg C) for the first time. The formation of the binary compound with the variable composition Li 4-x Hf 1+0.2x (MoO 4 ) 4 (0 ≤ x ≤ 0.6) in the Li 2 MoO 4 - Hf(MoO 4 ) 2 system and the ternary molybdates Li 4 Ag 2 Hf(MoO 4 ) 5 (S 1 ) and Na 2 Ag 2 Hf(MoO 4 ) 4 (S 2 ) was established and the thermal characteristics of the prepared compounds were examined. The new binary molybdate Ag 2 Hf(MoO 4 ) 3 was prepared by the reaction between Ag 2 MoO 4 and Hf(MoO 4 ) 2 [ru

  16. Phase equilibria in the CdMoO4-Gd2(MoO4)3 system

    International Nuclear Information System (INIS)

    Tunik, T.A.; Fedorov, N.F.; Razumovskij, S.N.

    1980-01-01

    The constitutional diagram of the CdMoO 4 -Cd 2 (MoO 4 ) 3 system has been plotted using statistical and dynamic methods as well as a complex of instrumental analysis procedures. Three major phases have been found to occur in the systems, viz.: CdMoO 4 based solid solutions that crystallize in the range from 0 to 25 mol.percent of Cd 2 (MoO 4 ) 3 and pass in transit the two-phase narrow region becoming then solid solutions having a distorted scheelite structure and existing in concentrations from 40 to 65 mol.% of Cd 2 (MoO 4 ) 3 . The entire range, in which the Cd 2 (MoO 4 ) 3 solid solutions can exist, amounts to less than 5 mol.%. Certain crystallochemical constants of the phases that occur in the system have been determined [ru

  17. pH-Dependent isotope exchange and hydrogenation catalysed by water-soluble NiRu complexes as functional models for [NiFe]hydrogenases

    OpenAIRE

    Kure, Bunsho; Matsumoto, Takahiro; Ichikawa, Koji; Fukuzumi, Shunichi; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji

    2008-01-01

    The pH-dependent hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes and hydrogenation of the carbonyl compounds have been investigated with water-soluble bis(mu-thiolate)(mu-hydride)NiRu complexes, Ni(II)(mu-SR)(2)(mu-H)Ru(II) {(mu-SR)(2) = N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)-1,3-propanediamine}, as functional models for [NiFe]hydrogenases. In acidic media (at pH 4-6), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes has H(+) properties, and the c...

  18. A novel ferrimagnetic irido-cuprate: IrSr2GdCu2O8

    International Nuclear Information System (INIS)

    Dos Santos-Garcia, A.J.; Aguirre, Myriam H.; Moran, E.; Saez Puche, R.; Alario-Franco, M.A.

    2006-01-01

    We have performed an investigation of the structural, microstructural and magnetic properties of the new compound IrSr 2 GdCu 2 O 8 . The sample was prepared under high temperature (∼1393K) and high-pressure conditions (∼60Kbars) in a Belt type apparatus. X-ray diffraction (XRD) analysis shows that this irido-cuprate is isostructural with the corresponding Ru-1212 phase. Structurally, this material shows an interesting hierarchy of ordering phenomena, whose observation actually depends on the technique used to analyze the material: from a 'simple' cell a p xa p x3a p which is supported by XRD, through a 'diagonal' one, ∼2a p x2a p x3a p as seen by SAED, to a microdomain texture of this last one cell supported by HREM. A ferrimagnetic Ir IV -Gd III spin ordering is observed below 15K. The iridium oxidation state seems to be +4

  19. Contrasting pressure effects in Sr2VFeAsO3 and Sr2ScFePO3

    International Nuclear Information System (INIS)

    Kotegawa, Hisashi; Kawazoe, Takayuki; Tou, Hideki; Murata, Keizo; Ogino, Hiraku; Kishio, Kohji; Shimoyama, Jun-ichi

    2009-01-01

    We report the resistivity measurements under pressure of two Fe-based superconductors with a thick perovskite oxide layer, Sr 2 VFeAsO 3 and Sr 2 ScFePO 3 . The superconducting transition temperature T c of Sr 2 VFeAsO 3 markedly increases with increasing pressure. Its onset value, which was T c onset =36.4 K at ambient pressure, increases to T c onset =46.0 K at ∼4 GPa, ensuring the potential of the '21113' system as a high-T c material. However, the superconductivity of Sr 2 ScFePO 3 is strongly suppressed under pressure. The T c onset of ∼16 K decreases to ∼5 K at ∼4 GPa, and the zero-resistance state is almost lost. We discuss the factor that induces this contrasting pressure effect. (author)

  20. Angular dependence of the upper critical field in Bi2Sr2CuO6+δ

    International Nuclear Information System (INIS)

    Vedeneev, S.I.; Ovchinnikov, Yu.N.

    2002-01-01

    The angular dependence of the upper critical field has been investigated in a wide range of temperatures in very high-quality Bi 2 Sr 2 CuO 6+δ single crystals with critical temperature ≅ 9 K in magnetic fields up to 28 T. Although the typical value of the normal state resistivity ratio ≅ 10 4 , the anisotropy ratio of the upper critical fields is much smaller. A model is proposed based on a strong anisotropy and a small transparency between superconducting layers [ru

  1. Preparation of Sr2(MgMo)1-xRuxO6 ceramics for use in a solid oxide fuel cell anode

    International Nuclear Information System (INIS)

    Bezerra, Matheus Eiji Ohno; Florio, Daniel Zanetti de; Fonseca, Fabio Coral

    2016-01-01

    Full text: Solid Oxide Fuel Cells are the most efficient devices known for the direct conversion of fuels into electric energy. Such devices have advanced steadily and are already available for specific applications such as portable power and residential stationary generation. The main objective of this work is the development of anodes for SOFC operating directly with renewable fuels, without the addition of water and using strategic fuels such as ethanol and natural gas. Specifically, a family of mixed ionic-electronic compounds has been investigated: the double perovskites with compositions Sr 2 (MgMo) 1-x Ru x O 6 with x = 0; 1; 2; 5; 10 e 20 at.%. This material has been synthesized by polymeric precursor method. The resins were prepared by combining stoichiometric amounts of the starting solutions. The resulting solution was heated treated under magnetic stirring. The thermal decomposition of the polymeric resin was studied by means of simultaneous thermogravimetric and differential scanning calorimetry up to 1500 °C with heating and cooling rates of 10 °/min in Ar. The thermal decomposition result shows mass loss up to, approximately, 900 °C. However X-ray diffraction analyses of the powder heat treated at 900 °C and 1200 °C presents a considerable content of an undesiderate phase (SrMoO 4 ). According to the literature for similar compounds a thermal treatment under reduction conditions could be necessary to obtain the double perovskites single phase. After this treatment the material will be characterized regarding its electrical properties. The expected results will contribute to advance both the understanding of the mixed ionic electronic ceramics and the SOFC technology using renewable fuels. (author)

  2. Phase relations in the systems M2MoO4-Cr2(MoO4)3-Zr(MoO4)2 (M=Li, Na, or Rb)

    International Nuclear Information System (INIS)

    Bazarov, B.G.; Chimitova, O.D.; Bazarova, Ts.T.; Arkhincheeva, S.I.; Bazarova, Zh.G.

    2008-01-01

    Phase equilibria in the systems M 2 MoO 4 -Cr 2 (MoO 4 ) 3 -Zr(MoO 4 ) 2 (M=Li, Na, or Rb) were investigated by X-ray powder diffraction analysis, DTA, and IR spectroscopy. The subsolidus structure of the phase diagrams of the systems under study was established. Two phases are formed in the Rb 2 MoO 4 -Cr 2 (MoO 4 ) 3 -Zr(MoO 4 ) 2 system with the molar ratios of the starting components equal to 5:1:1 (S 2 ) and 1:1:1 (S 1 ). Proceeding from isostructural character of Rb 5 FeHf(MoO 4 ) 6 and S 2 , the unit cell parameters are determined for S 2 [ru

  3. Quaternary reciprocal system Na,K//Cl,Co3,MoO4

    International Nuclear Information System (INIS)

    Kochkarov, Zh.A.; Gasanaliev, A.M.

    2004-01-01

    Quaternary reciprocal system Na,K//Cl,Co 3 ,MoO 4 has been investigated for the first time by differential thermal analysis using the methods of projective and differential geometry. A stable (KCl) 2 -Na 2 CO 3 -K 2 CO 3 -K 2 MoO 4 tetrahedron and (NaCl) 2 -(KCl) 2 -Na 2 CO 3 -K 2 MoO 4 -Na 2 MoO 4 pentatope have been revealed in the system. It has been found that four quadruple invariant points are realized in the Na,K//Cl,Co 3 ,MoO 4 system, including one eutectic and three peritectic points [ru

  4. Processing and characterization of Sr2−xVMoO6−δ double perovskites

    International Nuclear Information System (INIS)

    Weisentein, A.J.; Childs, N.; Amendola, R.; Driscoll, D.; Sofie, S.W.; Gannon, P.; Smith, R.

    2013-01-01

    In this study, the analysis and characterization of the processing and sintering of Sr 2−x VMoO 6−δ perovskites, where x = 0.0, 0.1 and 0.2, was investigated with application potential in high temperature fuel cell electrodes and electro-catalysts. Sr 2−x VMoO 6−δ substrates were sintered in a reducing (5%H 2 95%N 2 ) atmosphere at 1100 °C, 1200 °C, and 1300 °C. The X-ray diffraction patterns indicate that the double perovskite is the primary phase for Sr 2−x VMoO 6−δ pellets sintered at 1200 °C and 1300 °C for 20 h; however, these pellets show a secondary phase of SrMoO 4−δ . X-ray photoelectron spectroscopy revealed a deficiency of vanadium on the pellet surfaces, in which samples yielded surface vanadium concentrations of less than 5%. The vanadium inhomogeneity can be explained by the formation of the SrMoO 4−δ scheelite phase (ABO 4 ) due to oxygen exposure on the surface of the pellets, which indicates inward vanadium migration to the bulk, and was exhibited in redox cycling. Sr 2−x VMoO 6−δ pellets sintered at 1300 °C showed the lowest resistivity at both SOFC operating temperature (800 °C) and room temperature. The resistivity tests also show a semiconductor to metallic transition for all double perovskites, from heating up to 800 °C to cooling down to room temperature in a reducing atmosphere, related to the reduction of Mo 6+ to Mo 4+ . - Highlights: ► Primary Sr 2−x VMoO 6−δ phase only shown to form in excess of 1300 °C in reducing. ► Surface formation of secondary phase SrMoO 4−δ (Mo 6+ ) observed at RT in air. ► Surface vanadium deficiency induced by inward atomic diffusion. ► Semiconductor to metallic transition is related to the reduction of Mo 6+ to Mo 4+

  5. Study on sorption capacity and characterization of Sr2+ on synthetic zeolite

    International Nuclear Information System (INIS)

    Wang Jinming; Yi Facheng

    2010-01-01

    Sr 2+ adsorption capacity of synthetic zeolite(ZF) are studied with the intermittence method, and ZF adsorbed the Sr 2+ is characterized and analyzed by XRD, as a reference for the evaluation of the disposal effectiveness of low and medium radwastes. The results show that Sr 2+ adsorption capacity of ZF is good, and the equilibrium time for ZF to adsorb Sr 2+ is in range of 5-14 days. Sr 2+ concentration has the greatest effect on ZF adsorption capacity,and the medium,temperature and pH value of the solution also have effect on ZF adsorption capacity. With the augment of Sr 2+ concentration,the Sr 2+ equilibrium adsorption quantity of ZF increases,but the equilibrium adsorption rate and equilibrium adsorption ratio decreases. Sr 2+ adsorption capacity of ZF improves with the augment of pH value. Sr 2+ adsorption capacity of ZF is complicate and varies with the different ion, concentration and other components in the medium solution. Sr 2+ adsorption capacity of ZF increases with the augment of temperature. As a whole, when Sr 2+ concentration in the solution is 0.005mol/L, the pH value of the solution, and the temperature of medium and solution have less effect on the Sr 2+ adsorption capacity of ZF, and the unit cell parameter of ZF adsorbed Sr 2+ decreases. (authors)

  6. Iridates and RuCl3 - from Heisenberg antiferromagnets to potential Kitaev spin-liquids

    Science.gov (United States)

    van den Brink, Jeroen

    The observed richness of topological states on the single-electron level prompts the question what kind of topological phases can develop in more strongly correlated, many-body electron systems. Correlation effects, in particular intra- and inter-orbital electron-electron interactions, are very substantial in 3 d transition-metal compounds such as the copper oxides, but the spin-orbit coupling (SOC) is weak. In 5 d transition-metal compounds such as iridates, the interesting situation arises that the SOC and Coulomb interactions meet on the same energy scale. The electronic structure of iridates thus depends on a strong competition between the electronic hopping amplitudes, local energy-level splittings, electron-electron interaction strengths, and the SOC of the Ir 5d electrons. The interplay of these ingredients offers the potential to stabilise relatively well-understood states such as a 2D Heisenberg-like antiferromagnet in Sr2IrO4, but in principle also far more exotic ones, such a topological Kitaev quantum spin liquid, in (hyper)honeycomb iridates. I will discuss the microscopic electronic structures of these iridates, their proximity to idealized Heisenberg and Kitaev models and our contributions to establishing the physical factors that appear to have preempted the realization of quantum spin liquid phases so far and include a discussion on the 4d transition metal chloride RuCl3. Supported by SFB 1143 of the Deutsche Forschungsgemeinschaft.

  7. Characterisation and catalytic properties of Ni, Co, Ce and Ru nanoparticles in mesoporous carbon spheres

    International Nuclear Information System (INIS)

    Barros, Francisco A. A.; Castro, Antonio J. R.; Filho, Josue M.; Viana, Bartolomeu C.; Campos, Adriana; Oliveira, Alcineia C.

    2012-01-01

    Ni, Co, Ce and Ru nanoparticles were inserted into templated carbon using a nanocasting technique and evaluated for the dehydration of glycerol. NiO and CeO 2 preferentially yielded 5 nm uniformly sized particles that filled the mesoporous carbon via a geometric confinement effect. Ru generated Ru o and RuO 2 nanoparticles that selectively migrated towards the carbon surface and did not undergo sintering, whereas Co nanoparticles containing CoO and Co 3 O 4 showed the opposite behaviour. The stabilising effects of the Ce and Ru nanoparticles on the carbon matrix effectively prevented the aggregation of small particles, resulting in superior catalytic performance in glycerol dehydration.

  8. pH-Dependent isotope exchange and hydrogenation catalysed by water-soluble NiRu complexes as functional models for [NiFe]hydrogenases.

    Science.gov (United States)

    Kure, Bunsho; Matsumoto, Takahiro; Ichikawa, Koji; Fukuzumi, Shunichi; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji

    2008-09-21

    The pH-dependent hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes and hydrogenation of the carbonyl compounds have been investigated with water-soluble bis(mu-thiolate)(mu-hydride)NiRu complexes, Ni(II)(mu-SR)(2)(mu-H)Ru(II) {(mu-SR)(2) = N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)-1,3-propanediamine}, as functional models for [NiFe]hydrogenases. In acidic media (at pH 4-6), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes has H(+) properties, and the complexes catalyse the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes. A mechanism of the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes through a low-valent Ni(I)(mu-SR)(2)Ru(I) complex is proposed. In contrast, in neutral-basic media (at pH 7-10), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes acts as H(-), and the complexes catalyse the hydrogenation of carbonyl compounds.

  9. Phase equilibria in the MgMoO4-Ln2(MoO4)3 (Ln=La,Gd) systems

    International Nuclear Information System (INIS)

    Fedorov, N.F.; Ipatov, V.V.; Kvyatkovskij, O.V.

    1980-01-01

    Phase equilibria in the MgMoO 4 -Ln 2 (MoO 4 ) 3 systems (Ln=La, Gd) have been studied by static and dynamic methods of the physico-chemical analysis, using differential thermal, visual-polythermal, crystal-optical, X-ray phase, and infrared spectroscopic methods, and their phase diagrams have been constructed. Phase equilibria in the systems studied are characterized by limited solubility of components in the liquid state, formation of solid solutions on the base of α- and β-forms of Gd 2 (MoO 4 ) 3 . Eutectics in the MgMoO 4 -Ln 2 (MoO 4 ) 3 (Ln=La, Gd) systems corresponds to the composition of 71 mode % La 2 (MoO 4 ) 3 -29 mole % MgMoO 4 , tsub(melt)--935+-5 deg C and 57 mole % Gd 2 (MoO 4 ) 3 -43 mole % MgMoO 4 , tsub(melt)=1020+-5 deg C. The region of glass formation has been established [ru

  10. Phase diagrams of systems of Sr2V2O7-M2V2O7 and of Ba2V2O7-M2V2O7 (M=Ca,Cd)

    International Nuclear Information System (INIS)

    Fotiev, A.A.; Zhuravlev, V.D.; Zhukov, V.P.

    1982-01-01

    Using the methods of X-ray phase and differential thermal anlyses phase equilibria in the systems Sr 2 V 2 O 7 -M 2 V 2 O 7 and Ba 2 V 2 O 7 -M 2 V 2 O 7 , where M--Ca, Cd, are studied, their phase diagrams being built. New double pyrovanadates Mosub(0.5)Srsub(1.5)Vsub(2)Osub(7) and MBaV 2 O 7 are found [ru

  11. Mechanosynthesis and mechanical activation processes to the preparation of the Sr2[Srn-1TinO3n+1] Ruddlesden-Popper family

    International Nuclear Information System (INIS)

    Hungria, Teresa; Hungria, A.-B.; Castro, Alicia

    2004-01-01

    A novel mechanochemical activation route has been applied in order to obtain the n=1-4 and ∞ members of the Sr 2 [Sr n-1 Ti n O 3n+1 ] Ruddlesden-Popper series. The evolution of the (n+1)SrO:nTiO 2 powder mixtures during mechanical treatment was followed by X-ray powder diffraction in all cases. Except for the 2SrO:TiO 2 composition, SrTiO 3 was always mechanosynthesized. High-energy milling of 2SrO:TiO 2 sample resulted in the formation of nanosized Sr 2 TiO 4 , which is the only K 2 NiF 4 -type oxide prepared by mechanical treatment until now. The mechanical treatment was followed by annealing at different temperatures to establish the optimized protocol for synthesis of each member of the series. SrTiO 3 , Sr 2 TiO 4 and Sr 3 Ti 2 O 7 were obtained with very important decreases in the formation temperatures and reaction times as compared with the traditional ceramic method. Final and milled products were studied by X-ray powder diffraction at room and increasing temperatures, and by thermal analysis and scanning and high resolution transmission electron microscopy

  12. Investigation of structural, morphological and electromagnetic properties of Mg0.25Mn0.25Zn0.5-xSrxFe2O4 ferrites

    Science.gov (United States)

    Rahaman, Md. D.; Nusrat, Tania; Maleque, Rumana; Hossain, A. K. M. Akther

    2018-04-01

    Polycrystalline Mg0.25Mn0.25Zn0.5-xSrxFe2O4 (0 ≤ x ≤ 0.20) ferrites were synthesized using the solid state reaction sintering at 1373 K and 1473 K for 4 h. The XRD patterns revealed the formation of single phase cubic spinel with Sr2FeO4 and SrFe12O19 as impurity phases. The decrement in the lattice parameter for Sr2+ substituted samples is attributed to the difference in ionic radii of cations. The crystallite size decreases with increase in Sr2+ content. Low frequency dielectric dispersion is attributed due to the Maxwell-Wagner interfacial polarization. The appearance of the peak in dielectric loss spectrum for x = 0.15 and 0.20 at 1373 K and x = 0.20 at 1473 K suggests the presence of relaxing dipoles. The loss peak shifts towards lower frequency side with Sr2+ content at 1373 K which is due to the strengthening of dipole-dipole interactions. The complex impedance spectra clearly revealed that the both grain and grain boundary effects on the electrical properties. A complex electric modulus spectrum indicates that a non-Debye type of conductivity relaxation exists. The saturation magnetization and remanence gradually decreases with Sr2+ substitution which may be due to the existence of non-magnetic phase in the space between the magnetic particles and the substitution of Zn2+ cation in Mg0.25Mn0.25Zn0.5Fe2O4 ferrite lattice by Sr2+ content. The permeability decreases significantly while the cut-off frequency increases with the Sr2+ content at 1373 K and decreases at 1473 K, obeying the Snoek's law. The decrease in permeability with Sr2+ content is attributed due to the decrease in magnetization because non-magnetic ions weaken the inter-site exchange interaction.

  13. Pressure-induced structural, magnetic and transport transitions in Sr2FeO3 from first-principles

    Directory of Open Access Journals (Sweden)

    Ting Jia

    2017-05-01

    Full Text Available The serial system Srn+1FenO2n+1(n=1,2,3… with the FeO4 square planar motif exhibits abundant phase transitions under pressure. In this work, we investigate the pressure-induced structural, magnetic and transport transitions in Sr2FeO3 from first-principles. Our results show that the system undergoes a structural transition from Immm to Ammm when the volume decreases by 30%, together with a spin-state transition (SST from high-spin (S = 2 to intermediate-spin (S = 1, an antiferromagnetic-to-ferromagnetic transition and an insulator-to-metal transition (IMT. Besides, the IMT here is a bandwidth controlled transition, but little influenced by the SST.

  14. Thermodynamic parameters for the protonation and the interaction of arsenate with Mg2+, Ca2+ and Sr2+: Application to natural waters.

    Science.gov (United States)

    Chillè, Donatella; Foti, Claudia; Giuffrè, Ottavia

    2018-01-01

    Thermodynamic parameters for the protonation of AsO 4 3- and for the interaction with Mg 2+ , Ca 2+ and Sr 2+ were reported, comprehensive also of their dependence on ionic strength, considering the 0.1 ≤ I ≤ 1 M range and using NaCl as background salt. The same speciation models were obtained for Mg 2+ , Ca 2+ and Sr 2+ systems, with the formation of three different species: ML, MLH and MLH 2 (L = AsO 4 3- ). Mono- and di-protonated species were very weak, with formation constant values (log K) ranging from 1.45 to 3.23. In order to have a complete picture of thermodynamic properties of the systems under study and to fill the shortage of thermodynamic data on arsenate complex systems, the ligand protonation and metal complex enthalpies were also determined by calorimetric titrations, at t = 25 °C and in NaCl at I = 0.7 M (for H + -AsO 4 3- species also at I = 0.1 M). On the light of the proposed speciation models, examples of As(V) distribution in some natural waters are reported. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Systems Tl2MoO4-E(MoO4)2, where E=Zr or Hf, and the crystal structure of Tl8Hf(MoO4)6

    International Nuclear Information System (INIS)

    Bazarov, B.G.; Bazarova, Ts.T.; Fedorov, K.N.; Bazarova, Zh.G.; Chimitova, O.D.; Klevtsova, R.F.; Glinskaya, L.A.

    2006-01-01

    Systems Tl 2 MoO 4 -E(MoO 4 ) 2 (E=Zr, Hf) were studied by X-ray diffraction, differential thermal analysis and IR spectroscopy. Formation of Tl 8 E(MoO 4 ) 6 and Tl 2 E(MoO 4 ) 2 compounds was established. Phase T-x diagrams of the Tl 2 MoO 4 -Zr(MoO 4 ) 2 system were constructed. Monocrystals were grown, and structure of Tl 8 Hf(MoO 4 ) 6 was studied. The compound is crystallized in monoclinic syngony with elementary cell parameters a=9.9688(6), b=18.830(1), c=7.8488(5) A, β=108.538(1) Deg, Z=2, sp. gr. C2/m. The isolated group [HfMo 6 O 24 ] 8- is responsible for fundamental fragment of the structure. Three varieties of crystallographically independent Tl-polyhedra fill space evenly between fragments [HfMo 6 O 24 ] 8- forming three-dimensional form [ru

  16. Characterization of stem rust resistance gene Sr2 in Indian wheat ...

    African Journals Online (AJOL)

    SONY

    2013-05-01

    May 1, 2013 ... accelerating wheat production in the last forty years and ensured food security of the Nation. In the present investigation, Sr2 specific molecular markers were used to assess their efficacy for assessing the deployment of Sr2 gene in Indian wheat cultivars of highly productive north-west plains and stem rust ...

  17. The coprecipitation of Sr2+ with calcite at 250C and 1 atm

    International Nuclear Information System (INIS)

    Pingitore, N.E. Jr.; Eastman, M.P.

    1986-01-01

    The incorporation of Sr 2+ into calcite at earth surface aqueous conditions is affected by the absolute concentration of Sr 2+ , the presence of Ba 2+ and NaCl in the solution and the rate of precipitation. At solution ratios (molar) of Sr 2+ to Ca 2+ in the low 10 -3 range, which yield calcites with several hundred ppm Sr 2+ , kappasub(calcite) sup(Sr) typically assumes a value between 0.10 and 0.20. Above these concentrations the value of kappasub(calcite) sup(Sr) drops to approximately 0.06. Furthermore, if minor amounts of Ba 2+ or large amounts of Na + (0.48 M) are added to a dilute Sr 2+ solution, a value around 0.06 for kappasub(calcite)sup(Sr) is found. This 'strontium concentration effect' and the associated 'competitive cation effect' suggest that small amounts of Sr 2+ may be incorporated into a limited number of nonlattice sites in calcite. Incorporation of Sr 2+ into these sites, presumably defects, noticeably affects kappasub(calcite)sup(Sr) only at low Sr 2+ concentrations and in the absence of competition from other large cations. An increase in kappasub(calcite)sup(Sr) with rate of precipitation, qualitatively similar to that found in other studies, was observed only when precipitation times were decreased from days to hours. For many geologic settings a partition coefficient for Sr 2+ into calcite of 0.06 appears appropriate, but there are situations - very low Sr 2+ concentrations, the presence of Mg 2+ , and fast precipitation rates - in which a larger value might better approximate natural partitioning. (author)

  18. 103Ru/103mRh generator

    International Nuclear Information System (INIS)

    Bartos, B.; Kowalska, E.; Bilewicz, A.; Skarnemark, G.

    2009-01-01

    103m Rh is a very promising radionuclide for Auger electron therapy due to its very low photon/electron ratio. The goal of the present work was the elaboration a method for production of large quantities of 103m Rh for generator system. It was found that the combination of solvent extraction with evaporation of 103 RuO 4 followed by decomposition of H 5 IO 6 makes it possible to produce 103m Rh of high radionuclidic and chemical purity. (author)

  19. IrSr2TbCu2O8, a high-pressure metamagnetic cuprate: Structure, microstructure and properties

    International Nuclear Information System (INIS)

    Dos Santos-Garcia, A.J.; Duijn, J. van; Saez-Puche, R.; Heymann, G.; Huppertz, H.; Alario-Franco, M.A.

    2008-01-01

    The synthesis, structure and microstructure of the IrSr 2 TbCu 2 O 8 cuprate showing metamagnetic properties are described. The sample was prepared at high temperatures and pressures up to 9.2 GPa. The structure is tetragonal, showing a 1212 type structure, that derives from the classical YBaCuO superconductor structure, replacing the tetracoordinated square planar copper [Cu-O 4 ] in the 'chains' by octahedral [Ir-O 6 ] groups that form a perovskite-like layer in the basal plane of the unit cell. A 'simple' cell, ∼a p xa p x3a p , where a p is the basic perovskite unit cell parameter (a p ∼3.8 A), is supported by X-ray powder diffraction (XRD) and a so-called 'diagonal' one, ∼√2a p x√2a p x3a p , by SAED; a microdomain texture of latter cell and a series of very interesting extended defects have been observed by HREM. Magnetic susceptibility measurements show a magnetic transition, T N ∼6 K, with negative Weiss temperature, that indicates antiferromagnetic interactions among the Tb moments. The magnetic structure has been determined by neutron diffraction. A detailed magnetic study has revealed a metamagnetic behavior, something not previously observed in this type of cuprates. Specific heat and resistivity measurements have also been performed to characterize the transition. - Graphical abstract: Reconstructed image from the SAED of the long c tetragonal axis (3a p ) of a IrSr 2 TbCu 2 O 8 crystal. A unit cell picture is included for comparison. Display Omitted

  20. Nonstoichiometry, point defects and magnetic properties in Sr2FeMoO6−δ double perovskites

    International Nuclear Information System (INIS)

    Kircheisen, R.; Töpfer, J.

    2012-01-01

    The phase stability, nonstoichiometry and point defect chemistry of polycrystalline Sr 2 FeMoO 6−δ (SFMO) was studied by thermogravimety at 1000, 1100, and 1200 °C. Single-phase SFMO exists between −10.2≤log pO 2 ≤−13.7 at 1200 °C. At lower oxygen partial pressure a mass loss signals reductive decomposition. At higher pO 2 a mass gain indicates oxidative decomposition into SrMoO 4 and SrFeO 3−x . The nonstoichiometry δ at 1000, 1100, and 1200 °C was determined as function of pO 2 . SFMO is almost stoichiometric at the upper phase boundary (e.g. δ=0.006 at 1200 °C and log pO 2 =−10.2) and becomes more defective with decreasing oxygen partial pressure (e.g. δ=0.085 at 1200 °C and log pO 2 =−13.5). Oxygen vacancies are shown to represent majority defects. From the temperature dependence of the oxygen vacancy concentration the defect formation enthalpy was estimated (ΔH OV =253±8 kJ/mol). Samples of different nonstoichiometry δ were prepared by quenching from 1200 °C at various pO 2 . An increase of the unit cell volume with increasing defect concentration δ was found. The saturation magnetization is reduced with increasing nonstoichiometry δ. This demonstrates that in addition to Fe/Mo site disorder, oxygen nonstoichiometry is another source of reduced magnetization values. - Graphical abstract: Nonstoichiometry δ of Sr 2 FeMoO 6−δ as function of oxygen partial pressure at 1000, 1100, and 1200 °C. Highlights: ► Sr 2 FeMoO 6−δ is stable at T=1200 °C at low pO 2 only. ► Nonstoichiometry δ measured at 1200, 1100, and 1000 °C. ► Increase of oxygen vacancy concentration with lower pO 2 . ► Reduction of magnetization with increasing nonstoichiometry δ.

  1. Lanthanide-doped Sr2YF7 nanoparticles: controlled synthesis, optical spectroscopy and biodetection

    Science.gov (United States)

    Yang, Yuhan; Tu, Datao; Zheng, Wei; Liu, Yongsheng; Huang, Ping; Ma, En; Li, Renfu; Chen, Xueyuan

    2014-09-01

    Sr2YF7, as an important matrix for trivalent lanthanide (Ln3+) ions to fabricate upconversion (UC) or downshifting (DS) phosphors, has been rarely reported. Herein, monodisperse and size-controllable tetragonal-phase Ln3+-doped Sr2YF7 nanoparticles (NPs) were synthesized via a facile thermal decomposition method. Upon excitation at 980 nm, UC luminescence properties of Sr2YF7:Ln3+/Yb3+ (Ln = Tm, Er) NPs were systematically surveyed. Particularly, after coating an inert Sr2YF7 shell, the UC luminescence intensities of Sr2YF7:Tm3+/Yb3+ and Sr2YF7:Er3+/Yb3+ NPs were enhanced by ~22 and 4 times, respectively. Furthermore, intense multicolor DS luminescence was also achieved in Ce3+/Tb3+ or Eu3+ doped Sr2YF7 NPs, with absolute quantum yields of 55.1% (Tb3+) and 11.2% (Eu3+). The luminescence lifetimes of 5D4 (Tb3+) and 5D0 (Eu3+) were determined to be 3.7 and 8.1 ms, respectively. By utilizing the long-lived luminescence of Ln3+ in these Sr2YF7 NPs, we demonstrated their application as sensitive heterogeneous time-resolved photoluminescence bioprobes to detect the protein of avidin and the tumor marker of the carcinoembryonic antigen (CEA) with their limits of detection down to 40.6 and 94.9 pM, and thus reveal the great potential of these Sr2YF7:Ln3+ nanoprobes in cancer diagnosis.Sr2YF7, as an important matrix for trivalent lanthanide (Ln3+) ions to fabricate upconversion (UC) or downshifting (DS) phosphors, has been rarely reported. Herein, monodisperse and size-controllable tetragonal-phase Ln3+-doped Sr2YF7 nanoparticles (NPs) were synthesized via a facile thermal decomposition method. Upon excitation at 980 nm, UC luminescence properties of Sr2YF7:Ln3+/Yb3+ (Ln = Tm, Er) NPs were systematically surveyed. Particularly, after coating an inert Sr2YF7 shell, the UC luminescence intensities of Sr2YF7:Tm3+/Yb3+ and Sr2YF7:Er3+/Yb3+ NPs were enhanced by ~22 and 4 times, respectively. Furthermore, intense multicolor DS luminescence was also achieved in Ce3+/Tb3+ or Eu3

  2. Anisotropy and Strong-Coupling Effects on the Collective Mode Spectrum of Chiral Superconductors: Application to Sr2RuO4

    Directory of Open Access Journals (Sweden)

    James Avery Sauls

    2015-06-01

    Full Text Available Recent theories of Sr2RuO4 based on the interplay of strong interactions, spin-orbit coupling and multi-band anisotropy predict chiral or helical ground states with strong anisotropy of the pairing states, with deep minima in the excitation gap, as well as strong phase anisotropy for the chiral ground state. We develop time-dependent mean field theory to calculate the Bosonic spectrum for the class of 2D chiral superconductors spanning 3He-A to chiral superconductors with strong anisotropy. Chiral superconductors support a pair of massive Bosonic excitations of the time-reversed pairs labeled by their parity under charge conjugation. These modes are degenerate for 2D 3He-A. Crystal field anisotropy lifts the degeneracy. Strong anisotropy also leads to low-lying Fermions, and thus to channels for the decay of the Bosonic modes. Selection rules and phase space considerations lead to large asymmetries in the lifetimes and hybridization of the Bosonic modes with the continuum of un-bound Fermion pairs. We also highlight results for the excitation of the Bosonic modes by microwave radiation that provide clear signatures of the Bosonic modes of an anisotropic chiral ground state.

  3. Catalytic hydroprocessing of lignin β-O-4 ether bond model compound phenethyl phenyl ether over ruthenium catalysts

    NARCIS (Netherlands)

    Gomez-Monedero, B.; Faria, J.; Bimbela, F.; Ruiz, M.P.

    2017-01-01

    The catalytic hydroprocessing of phenethyl phenyl ether (PPE), a model compound of one of the most significant ether linkages within lignin structure, β-O-4, has been studied. Reactions were carried out using two ruthenium-based catalysts, supported on different materials: 3.8 wt.% Ru/C and 3.9 wt.%

  4. Quatenary Na//F, Cl, CO3, MoO4 system

    International Nuclear Information System (INIS)

    Kochkarov, Zh.A.; Lok''yaeva, S.M.; Shurdumov, G.K.; Gasanaliev, A.M.; Trunin, A.S.

    1999-01-01

    Perspective in applied respect quatenary system (NaF) 2 -(NaCl)-Na 2 CO 3 -Na 2 MoO 4 being element of narrowing of more complex six-membered mutual Na//F, Cl, CO 3 , MoO 4 (WO 4 ) system is investigated by differential thermal analysis with the use of projection-thermographic method for the first time. Crystallization tree of Na//F, Cl, CO 3 , MoO 4 system is established. It is shown that this system by tetrahedrating (NaF) 2 -Na 2 CO 3 -Na 3 ClMoO 4 section is triangulated on two stable system: (NaF) 2 -Na 3 ClMoO 4 -Na 2 CO 3 -(NaCl) 2 and (NaF) 2 -Na 3 ClMoO 4 -Na 2 CO 3 -Na 2 MoO 4 . Phase single units are determined too. Coordinates of desired quatenary nonvariant points are calculated on analytical models of surfaces by mutual crystallization of two phases and are refined by differential thermal analysis [ru

  5. Inelastic scattering on 100Ru

    International Nuclear Information System (INIS)

    Sirota, S.

    1987-01-01

    Aspects of the nuclear structure of 100 Ru whe investigated by means of the scattering of 100 Ru (p,p') 100 Ru* with 16 MeV protons, where 21 states were investigated. The emergent protons were analysed by a magnetic spectrograph, of the enge type with a typical resolution of ≅ 9 KeV. (A.C.A.S.) [pt

  6. Luminescence enhancement of (Sr1-x Mx )2 SiO4 :Eu2+ phosphors with M (Ca2+ /Zn2+ ) partial substitution for white light-emitting diodes.

    Science.gov (United States)

    Wang, Yulong; Zhang, Wentao; Gao, Yang; Long, Jianping; Li, Junfeng

    2017-02-01

    Eu 2 + -doped Sr 2 SiO 4 phosphor with Ca 2 + /Zn 2 + substitution, (Sr 1-x M x ) 2 SiO 4 :Eu 2 + (M = Ca, Zn), was prepared using a high-temperature solid-state reaction method. The structure and luminescence properties of Ca 2 + /Zn 2 + partially substituted Sr 2 SiO 4 :Eu 2 + phosphors were investigated in detail. With Ca 2 + or Zn 2 + added to the silicate host, the crystal phase could be transformed between the α-form and the β-form of the Sr 2 SiO 4 structure. Under UV excitation at 367 nm, all samples exhibit a broad band emission from 420 to 680 nm due to the 4f 6 5d 1  → 4f 7 transition of Eu 2 + ions. The broad emission band consists of two peaks at 482 and 547 nm, which correspond to Eu 2 + ions occupying the ten-fold oxygen-coordinated Sr.(I) site and the nine-fold oxygen-coordinated Sr.(II) site, respectively. The luminescence properties, including the intensity and lifetime of Sr 2 SiO 4 :Eu 2 + phosphors, improved remarkably on Ca 2 + /Zn 2 + addition, and promote its application in white light-emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Synthesis, crystal structure, and ionic conductivity of a new layered metal phosphate, Li2Sr2Al(PO4)3

    International Nuclear Information System (INIS)

    Kim, Sung-Chul; Kwak, Hyun-Jung; Yoo, Chung-Yul; Yun, Hoseop; Kim, Seung-Joo

    2016-01-01

    A new layered metal phosphate, Li 2 Sr 2 Al(PO 4 ) 3 , was synthesized in the form of either a single-crystal or polycrystalline powder using the molten hydroxide flux method or a solid-state reaction, respectively. Li 2 Sr 2 Al(PO 4 ) 3 crystallizes to the P2 1 /n (Z=4) monoclinic space group with lattice parameters a≈4.95 Å, b≈22.06 Å, c≈8.63 Å, and β≈91.5°. The structure is composed of stacked [LiSrAl(PO 4 ) 2 ] layers alternating regularly with [LiSrPO 4 ] layers. In the [LiSrAl(PO 4 ) 2 ] sublattice, the AlO 6 octahedra and PO 4 tetrahedra are tilted cooperatively to form an anionic, corrugated, two-dimensional [Al(PO 4 ) 2 ] 3− framework that can be regarded as a “distorted-glaserite” structure. The [LiSrPO 4 ] sublattice is that of a layered block containing a six-membered ring formed from alternating linkages of LiO 4 and PO 4 tetrahedra. The six-membered rings show a boat-type arrangement with the up(U) or down(D) pointing sequence, UUDUUD. The interspace between the two sublattices generates a two-dimensional pathway for Li + ion conduction. The impedance measurement indicated that Li 2 Sr 2 Al(PO 4 ) 3 had a moderate ion conductivity (σ≈1.30×10 −4 S cm −1 at 667 K), with an activation energy E a ≈1.02 eV. - Graphical abstract: Polyhedral view of Li 2 Sr 2 Al(PO 4 ) 3 . Li + ions are represented by green spheres, Sr atoms by white spheres, AlO 6 groups by octahedra, and PO 4 groups by tetrahedra. - Highlights: • New compound Li 2 Sr 2 Al(PO 4 ) 3 is reported. • The crystal structure is investigated by single-crystal XRD analysis. • The structure is formed by the alternate stacking of two different sublattices. • Correlation between the crystal structure and ionic conductivity is discussed.

  8. Phase formation in the K2MoO4-Lu2(MoO4)3-Hf(MoO4)2 system and the structural study of triple molybdate K5LuHf(MoO4)6

    International Nuclear Information System (INIS)

    Romanova, E.Yu.; Bazarov, B.G.; Tushinova, Yu.L.; Fedorov, K.N.; Bazarova, Zh.G.; Klevtsova, R.F.; Glinskaya, L.A.

    2007-01-01

    Interactions in the ternary system K 2 MoO 4 -Lu 2 (MoO 4 ) 3 -Hf(MoO 4 ) 2 have been studied by X-ray powder diffraction and differential thermal analysis. A new triple (potassium lutetium hafnium) molybdate with the 5 : 1 : 2 stoichiometry has been found. Monocrystals of this molybdate have been grown. Its X-ray diffraction structure has been refined (an X8 APEX automated diffractometer, MoK α radiation, 1960 F(hkl), R = 0.0166). The trigonal unit cell has the following parameters: a = 10.6536(1) A, c = 37.8434(8) A, V=3719.75(9) A, Z = 6, space group R3-bar c. The mixed 3D framework of the structure is built of Mo tetrahedra sharing corners with two independent (Lu,Hf)O 6 octahedra. Two sorts of potassium atoms occupy large framework voids [ru

  9. Quaternary system LiF-LiCl-LiVO3-Li2MoO4

    International Nuclear Information System (INIS)

    Anipchenko, B.V.; Garkushin, I.K.

    2000-01-01

    Interactions in the LiF-LiCl-LiVO 3 -Li 2 MoO 4 system are studied by differential thermal analysis. Rate of heating/cooling of the samples comprised 15 Grad/min, mass of sample composed 0.2 g. The system was investigated in the 300-650 Deg C range. X-ray diffraction method was used for determination of purity of the reagents. Composition and temperature of quaternary component eutectics are determined: 16.5 mol. % of LiF, 47.0 mol. % of LiCl, 28.8 mol. % of LiVO 3 , 7.6 mol. % of Li 2 MoO 4 ; 387 Deg C. Mean value of melting enthalpy of quaternary eutectics mixture in the LiF-LiCl-LiVO 3 -Li 2 MoO 4 system on the results of the tests was in the range of 222 kJ/kg [ru

  10. Electronic structure, magnetism and thermoelectricity in layered perovskites: Sr2SnMnO6 and Sr2SnFeO6

    Science.gov (United States)

    Khandy, Shakeel Ahmad; Gupta, Dinesh C.

    2017-11-01

    Layered structures especially perovskites have titanic potential for novel device applications and thanks to the multifunctional properties displayed in these materials. We forecast and justify the robust spin-polarized ferromagnetism in half-metallic Sr2SnFeO6 and semiconducting Sr2SnMnO6 perovskite oxides. Different approximation methods have been argued to put forward their physical properties. The intriguingly intricate electronic band structures favor the application of these materials in spintronics. The transport parameters like Seebeck coefficient, electrical and thermal conductivity, have been put together to establish their thermoelectric response. Finally, the layered oxides are found to switch their application as thermoelectric materials and hence, these concepts design the principles of the technologically desired thermoelectric and spin based devices.

  11. Effect of Sr2+AND Mg2+ IONS on electrochemical deposition of calcium phosphates

    Energy Technology Data Exchange (ETDEWEB)

    Correia, M.B.; Gualberto Junior, J.P.; Macedo, M.C.S.S.; Resende, C.X.; Santos, E.A. [Universidade Federal de Sergipe (UFS), SE (Brazil)

    2014-07-01

    The incorporation of Sr2+ and Mg2+ ions into apatite favors the mineralization process of the bone, besides it to prevent the osteoporosis. In this work, it was evaluated the individual effect of Sr2+ and Mg2+ ions in the electrochemical deposition process of calcium phosphate on metallic substrate. The electrodeposition was performed using a conventional three- electrode cell. The titanium sheets were immersed in the electrolyte containing Ca(NO3)2 and NH4H2PO4 and a potential of -0. 8 V was applied. The coatings were characterized by SEM and XRD. By XRD analysis was possible to identify octacalcium phosphate in the control sample. However, after the addition of Mg2+ ions the OCP becomes the secondary phase while the brushite showed as majoritary phase. On the other hand, the incorporation of Sr2+ ions stabilized the OCP phase. (author)

  12. Core level photoemission spectroscopy and chemical bonding in Sr2Ta2O7

    DEFF Research Database (Denmark)

    Atuchin, V. V.; Grivel, Jean-Claude; Zhang, Z. M.

    2009-01-01

    Electronic parameters of constituent element core levels of strontium pyrotantalate (Sr2Ta2O7) were measured with X-ray photoelectron spectroscopy (XPS). The Sr2Ta2O7 powder sample was synthesized using standard solid state method. The valence electron transfer on the formation of the Sr-O and Ta......-O bonds was characterized by the binding energy differences between the O 1s and cation core levels, Delta(O-Sr) = BE(O 1s) - BE(Sr 3d(5/2)) and Delta(O-Ta) = BE(O 1s) - BE(Ta 4f(7/2)). The chemical bonding effects were considered on the basis of our XPS results for Sr2Ta2O7 and earlier published...

  13. Magnetocaloric effect in Sr2CrIrO6 double perovskite: Monte Carlo simulation

    Science.gov (United States)

    El Rhazouani, O.; Slassi, A.; Ziat, Y.; Benyoussef, A.

    2017-05-01

    Monte Carlo simulation (MCS) combined with the Metropolis algorithm has been performed to study the magnetocaloric effect (MCE) in the promising double perovskite (DP) Sr2CrIrO6 that has not so far been synthetized. This paper presents the global magneto-thermodynamic behavior of Sr2CrIrO6 compound in term of MCE and discusses the behavior in comparison to other DPs. Thermal dependence of the magnetization has been investigated for different values of reduced external magnetic field. Thermal magnetic entropy and its change have been obtained. The adiabatic temperature change and the relative cooling power have been established. Through the obtained results, Sr2CrIrO6 DP could have some potential applications for magnetic refrigeration over a wide temperature range above room temperature and at large magnetic fields.

  14. Correlation of Structure, Tunable Colors, and Lifetimes of (Sr, Ca, Ba)Al2O4:Eu2+, Dy3+ Phosphors

    Science.gov (United States)

    Xie, Qidi; Li, Bowen; He, Xin; Zhang, Mei; Chen, Yan; Zeng, Qingguang

    2017-01-01

    (Sr, Ca, Ba)Al2O4:Eu2+, Dy3+ phosphors were prepared via a high temperature solid-state reaction method. The correlation of phase structure, optical properties and lifetimes of the phosphors are investigated in this work. For the (Sr, Ca)Al2O4:Eu2+, Dy3+ phosphors, the different phase formation from monoclinic SrAl2O4 phase to hexagonal SrAl2O4 phase to monoclinic CaAl2O4 phase was observed when the Ca content increased. The emission color of SrAl2O4:Eu2+, Dy3+ phosphors varied from green to blue. For the (Sr, Ba)Al2O4:Eu2+, Dy3+ phosphors, different phase formation from the monoclinic SrAl2O4 phase to the hexagonal BaAl2O4 phase was observed, along with a shift of emission wavelength from 520 nm to 500 nm. More interestingly, the decay time of SrAl2O4:Eu2+, Dy3+ changed due to the different phase formations. Lifetime can be dramatically shortened by the substitution of Sr2+ with Ba2+ cations, resulting in improving the performance of the alternating current light emitting diode (AC-LED). Finally, intense LEDs are successfully obtained by combining these phosphors with Ga(In)N near UV chips. PMID:29057839

  15. Correlation of Structure, Tunable Colors, and Lifetimes of (Sr, Ca, BaAl2O4:Eu2+, Dy3+ Phosphors

    Directory of Open Access Journals (Sweden)

    Qidi Xie

    2017-10-01

    Full Text Available (Sr, Ca, BaAl2O4:Eu2+, Dy3+ phosphors were prepared via a high temperature solid-state reaction method. The correlation of phase structure, optical properties and lifetimes of the phosphors are investigated in this work. For the (Sr, CaAl2O4:Eu2+,Dy3+ phosphors, the different phase formation from monoclinic SrAl2O4 phase to hexagonal SrAl2O4 phase to monoclinic CaAl2O4 phase was observed when the Ca content increased. The emission color of SrAl2O4:Eu2+, Dy3+ phosphors varied from green to blue. For the (Sr, BaAl2O4:Eu2+, Dy3+ phosphors, different phase formation from the monoclinic SrAl2O4 phase to the hexagonal BaAl2O4 phase was observed, along with a shift of emission wavelength from 520 nm to 500 nm. More interestingly, the decay time of SrAl2O4:Eu2+, Dy3+changed due to the different phase formations. Lifetime can be dramatically shortened by the substitution of Sr2+ with Ba2+ cations, resulting in improving the performance of the alternating current light emitting diode (AC-LED. Finally, intense LEDs are successfully obtained by combining these phosphors with Ga(InN near UV chips.

  16. Deposition of RuO 4 on various surfaces in a nuclear reactor containment

    Science.gov (United States)

    Holm, Joachim; Glänneskog, Henrik; Ekberg, Christian

    2009-07-01

    During a severe nuclear reactor accident with air ingress, ruthenium can be released from the nuclear fuel in the form of ruthenium tetroxide. Hence, it is important to investigate how the reactor containment is able to reduce the source term of ruthenium. The aim of this work was to investigate the deposition of gaseous ruthenium tetroxide on aluminium, copper and zinc, which all appear in relatively large amounts in reactor containment. The experiments show that ruthenium tetroxide is deposited on all the metal surfaces, especially on the copper and zinc surfaces. A large deposition of ruthenium tetroxide also appeared on the relatively inert glass surfaces in the experimental set-ups. The analyses of the different surfaces, with several analytical methods, showed that the form of deposited ruthenium was mainly ruthenium dioxide.

  17. Electron tunneling and the energy gap in Bi2Sr2CaCu2Ox

    Science.gov (United States)

    Lee, Mark; Mitzi, D. B.; Kapitulnik, A.; Beasley, M. R.

    1989-01-01

    Results of electron tunneling on single crystals of the Bi2Sr2CaCu2Ox superconductor are reported. The junctions show a gap structure with Δ~=25 meV, whose temperature dependence exhibits a qualitatively Bardeen-Cooper-Schrieffer-like behavior with a gap-closing Tc~=81-85 K. Comparisons of these tunneling spectra to those obtained on YBa2Cu3O7-x are made. Evidence that 2Δ/kTc~7 for both Ba2Sr2CaCu2Ox and YBa2Cu3O7-x is also discussed.

  18. Electron excitations in BeAl2O4, Be2SiO4 and Be3Al2Si6O18 crystals

    International Nuclear Information System (INIS)

    Ivanov, V.Yu.; Pustovarov, V.A.; Shlygin, E.S.; Korotaev, A.V.; Kruzhalov, A.V.

    2005-01-01

    Low-temperature (T = 7 K) time-resolved selectively photoexcited luminescence spectra (2-6 eV) and luminescence excitation spectra (8-35 eV) of wide-bandgap chrysoberyl BeAl 2 O 4 , phenacite Be 2 SiO 4 , and beryl Be 3 Al 2 Si 6 O 18 crystals have been studied using time-resolved VUV spectroscopy. Both the intrinsic luminescence of the crystals and the luminescence associated with structural defects were assigned. Energy transfer to impurity luminescence centers in alexandrite and emerald was investigated. Luminescence characteristics of stable crystal lattice defects were probed by 3.6-MeV accelerated helium ion beams [ru

  19. Highly acid-durable carbon coated Co3O4 nanoarrays as efficient oxygen evolution electrocatalysts

    KAUST Repository

    Yang, Xiulin; Li, Henan; Lu, Ang-Yu; Min, Shixiong; Idriss, Zacharie; Hedhili, Mohamed N.; Huang, Kuo-Wei; Idriss, Hicham; Li, Lain-Jong

    2016-01-01

    Most oxygen evolution reaction (OER) electrocatalysts are not stable in corrosive acids. Even the expensive RuO2 or IrO2, the most acid-resistant oxides, can be dissolved at an oxidative potential. Herein, we realize that the failures of OER catalysts are mostly caused by the weak interface between catalysts and the substrates. Hence, the study of the interface structure between catalysts and substrates is critical. In this work, we observe that the cheap OER catalysts Co3O4 can be more durable than the state-of-the-art RuO2 if the interface quality is good enough. The Co3O4 nanosheets deposited on carbon paper (Co3O4/CP) is prepared by electroplating of Co-species and followed by a two-step calcination process. The 1st step occurs in vacuum in order to maintain the surface integrity of the carbon paper and converts Co-species to Co(II)O. The 2nd step is a calcination in ambient conditions which enables the complete transformation of Co(II)O to Co3O4 without degrading the mechanical strength of the Co3O4-CP interface. Equally important, an in situ formation of a layer of amorphous carbon on top of Co3O4 further enhances the OER catalyst stability. Therefore, these key advances make the Co3O4 catalyst highly active toward the OER in 0.5 M H2SO4 with a small overpotential (370 mV), to reach 10 mA/cm2. The observed long lifetime for 86.8 h at a constant current density of 100 mA/cm2, is among the best of the reported in literature so far, even longer than the state-of-art RuO2 on CP. Overall, our study provides a new insight and methodology for the construction of a high-performance and high stability OER electrocatalysts in corrosive acidic environments.

  20. Highly acid-durable carbon coated Co3O4 nanoarrays as efficient oxygen evolution electrocatalysts

    KAUST Repository

    Yang, Xiulin

    2016-04-21

    Most oxygen evolution reaction (OER) electrocatalysts are not stable in corrosive acids. Even the expensive RuO2 or IrO2, the most acid-resistant oxides, can be dissolved at an oxidative potential. Herein, we realize that the failures of OER catalysts are mostly caused by the weak interface between catalysts and the substrates. Hence, the study of the interface structure between catalysts and substrates is critical. In this work, we observe that the cheap OER catalysts Co3O4 can be more durable than the state-of-the-art RuO2 if the interface quality is good enough. The Co3O4 nanosheets deposited on carbon paper (Co3O4/CP) is prepared by electroplating of Co-species and followed by a two-step calcination process. The 1st step occurs in vacuum in order to maintain the surface integrity of the carbon paper and converts Co-species to Co(II)O. The 2nd step is a calcination in ambient conditions which enables the complete transformation of Co(II)O to Co3O4 without degrading the mechanical strength of the Co3O4-CP interface. Equally important, an in situ formation of a layer of amorphous carbon on top of Co3O4 further enhances the OER catalyst stability. Therefore, these key advances make the Co3O4 catalyst highly active toward the OER in 0.5 M H2SO4 with a small overpotential (370 mV), to reach 10 mA/cm2. The observed long lifetime for 86.8 h at a constant current density of 100 mA/cm2, is among the best of the reported in literature so far, even longer than the state-of-art RuO2 on CP. Overall, our study provides a new insight and methodology for the construction of a high-performance and high stability OER electrocatalysts in corrosive acidic environments.

  1. New structural family of ternary molybdates NaA3R(MoO4)5, where A is Mg, Mn, Co or Ni and R is Al, In, Cr or Fe

    International Nuclear Information System (INIS)

    Kozhevnikova, N.M.; Kotova, I.Yu

    1998-01-01

    Ternary NaA 3 R(MoO 4 ) 5 molybdates belonging to a new structural family are produced by crystallization from melted solution and by solid-phase synthesis method. NaMg 3 In(MoO 4 ) 5 , NaNi 3 Al(MoO 4 ) 5 and NaCo 3 Al(MoO 4 ) 5 single crystals are grown. Crystallographic and thermal characteristics of NaA 3 R(MoO 4 ) 5 are determined. Structural similarities in MgMoO 4 , NaIn(MoO 4 ) 2 , Na 2 Mg(MoO 4 ) 6 and NaA 3 R(MoO 4 ) 5 series are revealed [ru

  2. Electronic structure of the antiferromagnetic phase of Sr2Co2O5

    International Nuclear Information System (INIS)

    Pardo, V.; Botta, P.M.; Baldomir, D.; Rivas, J.; Pineiro, A.; Calle, C. de la; Alonso, J.A.; Arias, J.E.

    2008-01-01

    Ab initio calculations analyze the properties of the G-type antiferromagnetic Sr 2 Co 2 O 5 as a high-spin system. The description of the electronic structure is given; all the Co atoms are in a high-spin state with a small unquenched orbital angular momentum. Thermal analysis on a polycrystalline sample shows a magnetic phase transition at high temperatures

  3. Cooper pair formation dynamics in Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Kaindl, R.A.; Carnahan, M.A.; Orenstein, J.; Chemla, D.S.; Oh, S.; Eckstein, J.N.

    2003-01-01

    We utilize ultrafast terahertz pulses to monitor the carrier dynamics in the high-TC superconductor Bi2Sr2CaCu2O8+delta. The temperature, density and time dependence distinctly exposes a bimolecular recombination process of quasiparticles which underlies formation of Cooper pairs

  4. Study of thermoluminescence in K Cl crystals doped with Sr2+

    International Nuclear Information System (INIS)

    Russo, D.M.B.

    1990-01-01

    An attempt is made to correlate the F and Z 1 (F center modified by the presence of a two-valence impurity pair and and positive ion vacancy) and a V center, with the T L curve peaks observed in pure K Cl crystals doped with Sr 2+ , irradiated at room temperature. (L.C.J.A.)

  5. Synthesis of a new compound - Sr2CuO2CO3

    International Nuclear Information System (INIS)

    Fomichev, D.V.; Khardanov, A.L.; Antipov, E.V.; Kovba, L.M.

    1990-01-01

    A new compound of Sr 2 CuO 2 CO 3 composition, being an intermediate product of solid phase synthesis in air in SrCo 3 -CuO system at T 2 CuO 2 CO 3 have low resistance at room temperature and semiconductor type conductivity

  6. Effect of doping Ca on polaron hopping in LaSr 2 Mn 2 O 7

    Indian Academy of Sciences (India)

    ... Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 5-6. Effect of doping Ca on polaron hopping in LaSr2Mn2O7. S N Bhatia Osama A Yassin. Colossal Magnetoresistance & Other Materials Volume 58 Issue 5-6 May-June 2002 pp 1061- ...

  7. Optimized effective potential model for the double perovskites Sr2-xYxVMoO6 and Sr2-xYxVTcO6

    International Nuclear Information System (INIS)

    Solovyev, I V

    2011-01-01

    In an attempt to explore half-metallic properties of the double perovskites Sr 2-x Y x VMoO 6 and Sr 2-x Y x VTcO 6 , we construct an effective low-energy model, which describes the behavior of the t 2g states of these compounds. All parameters of such a model are derived rigorously on the basis of first-principles electronic structure calculations. In order to solve this model, we employ the optimized effective potential method and treat the correlation interactions in the random phase approximation. Although correlation interactions considerably reduce the intraatomic exchange splitting in comparison with the Hartree-Fock approach, this splitting still substantially exceeds the typical values obtained in the local-spin-density approximation (LSDA), which alters many predictions based on the LSDA. Our main results are summarized as follows. (i) All ferromagnetic states are expected to be half-metallic. However, their energies are generally higher than those of the ferrimagnetic ordering between V and Mo/Tc sites (except Sr 2 VMoO 6 ). (ii) All ferrimagnetic states are metallic (except fully insulating Y 2 VTcO 6 ) and no half-metallic antiferromagnetism has been found. (iii) Moreover, many of the ferrimagnetic structures appear to be unstable with respect to the spin-spiral alignment. Thus, the true magnetic ground state of these systems is expected to be more complex. In addition, we discuss several methodological issues related to nonuniqueness of the effective potential for the half-metallic and magnetic insulating states.

  8. Optimized effective potential model for the double perovskites Sr2 - xYxVMoO6 and Sr2 - xYxVTcO6

    Science.gov (United States)

    Solovyev, I. V.

    2011-08-01

    In an attempt to explore half-metallic properties of the double perovskites Sr2 - xYxVMoO6 and Sr2 - xYxVTcO6, we construct an effective low-energy model, which describes the behavior of the t2g states of these compounds. All parameters of such a model are derived rigorously on the basis of first-principles electronic structure calculations. In order to solve this model, we employ the optimized effective potential method and treat the correlation interactions in the random phase approximation. Although correlation interactions considerably reduce the intraatomic exchange splitting in comparison with the Hartree-Fock approach, this splitting still substantially exceeds the typical values obtained in the local-spin-density approximation (LSDA), which alters many predictions based on the LSDA. Our main results are summarized as follows. (i) All ferromagnetic states are expected to be half-metallic. However, their energies are generally higher than those of the ferrimagnetic ordering between V and Mo/Tc sites (except Sr2VMoO6). (ii) All ferrimagnetic states are metallic (except fully insulating Y2VTcO6) and no half-metallic antiferromagnetism has been found. (iii) Moreover, many of the ferrimagnetic structures appear to be unstable with respect to the spin-spiral alignment. Thus, the true magnetic ground state of these systems is expected to be more complex. In addition, we discuss several methodological issues related to nonuniqueness of the effective potential for the half-metallic and magnetic insulating states.

  9. Decoupling of magnetism and electric transport in single-crystal (Sr1‑x A x )2IrO4 (A  =  Ca or Ba)

    Science.gov (United States)

    Zhao, H. D.; Terzic, J.; Zheng, H.; Ni, Y. F.; Zhang, Y.; Ye, Feng; Schlottmann, P.; Cao, G.

    2018-06-01

    We report a systematical structural, transport and magnetic study of Ca or Ba doped Sr2IrO4 single crystals. Isoelectronically substituting Ca2+ (up to 15%) or Ba2+ (up to 4%) ion for the Sr2+ ion provides no additional charge carriers but effectively changes the lattice parameters in Sr2IrO4. In particular, 15% Ca doping considerably reduces the c-axis and the unit cell by nearly 0.45% and 1.00%, respectively. These significant, anisotropic compressions in the lattice parameters conspicuously cause no change in the Néel temperature which remains at 240 K, but drastically reduces the electrical resistivity by up to five orders of magnitude or even precipitates a sharp insulator-to-metal transition at lower temperatures, i.e. the vanishing insulating state accompanies an unchanged Néel temperature in (Sr1‑x A x )2IrO4. This observation brings to light an intriguing difference between chemical pressure and applied pressure, the latter of which does suppress the long-range magnetic order in Sr2IrO4. This difference reveals the importance of the Ir1–O2–Ir1 bond angle and homogenous volume compression in determining the magnetic ground state. All results, along with a comparison drawn with results of Tb and La doped Sr2IrO4, underscore that the magnetic transition plays a nonessential role in the formation of the charge gap in the spin–orbit-tuned iridate.

  10. Reactions of ethanol on Ru

    NARCIS (Netherlands)

    Sturm, Jacobus Marinus; Liu, Feng; Lee, Christopher James; Bijkerk, Frederik

    2012-01-01

    The adsorption and reactions of ethanol on Ru(0001) were studied with temperatureprogrammed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS). Ethanol was found to adsorb intact onto Ru(0001) below 100 K. Heating to 250 K resulted in formation of ethoxy groups, which undergo

  11. Study on the mechanisms of solidification for Cs+ and Sr2+ in alkali-activated slag cement waste forms

    International Nuclear Information System (INIS)

    Yan Sheng; Shen Xiaodong; Lu Linchao; Wu Xuequan; Wen Yinghui

    1994-09-01

    The mechanisms of adsorption and chemical immobilization in Alkali-Activated Slag Cement (AASC) waste forms were quantitatively studied for Cs + and Sr 2+ . Experimental results show that, hardened AASC paste with zeolite and silica fume possesses strong adsorption ability and anti-desorption ability for Cs + and Sr 2+ . The results and analyzed by XRD show that CS + and SR 2+ could be incorporated into the lattice of C-S-H by replacing Ca 2+ in C-S-H. The d 111 values of C-S-H increase with increasing CsNO 3 and Sr(NO 3 ) 2 dosages in a limited and regular step. After washed out by deionized water in a ultrasonic washer, samples were analyzed by SEM-EDS and a lot of Cs + and Sr 2+ were detected. This means that the hydration products of AASC have a high retaining ability for Cs + and Sr 2+ . (3 tabs., 8 figs.)

  12. Sr(1.7)Zn(0.3)CeO4: Eu3+ novel red-emitting phosphors: synthesis and photoluminescence properties.

    Science.gov (United States)

    Li, Haifeng; Zhao, Ran; Jia, Yonglei; Sun, Wenzhi; Fu, Jipeng; Jiang, Lihong; Zhang, Su; Pang, Ran; Li, Chengyu

    2014-03-12

    A series of novel red-emitting Sr1.7Zn0.3CeO4:Eu(3+) phosphors were synthesized through conventional solid-state reactions. The powder X-ray diffraction patterns and Rietveld refinement verified the similar phase of Sr1.7Zn0.3CeO4:Eu(3+) to that of Sr2CeO4. The photoluminescence spectrum exhibits that peak located at 614 nm ((5)D0-(7)F2) dominates the emission of Sr1.7Zn0.3CeO4:Eu(3+) phosphors. Because there are two regions in the excitation spectrum originating from the overlap of the Ce(4+)-O(2-) and Eu(3+)-O(2-) charge-transfer state band from 200 to 440 nm, and from the intra-4f transitions at 395 and 467 nm, the Sr1.7Zn0.3CeO4:Eu(3+) phosphors can be well excited by the near-UV light. The investigation of the concentration quenching behavior, luminescence decay curves, and lifetime implies that the dominant mechanism type leading to concentration quenching is the energy transfer among the nearest neighbor or next nearest neighbor activators. The discussion about the dependence of photoluminescence spectra on temperature shows the better thermal quenching properties of Sr1.7Zn0.3CeO4:0.3Eu(3+) than that of Sr2CeO4:Eu(3+). The experimental data indicates that Sr1.7Zn0.3CeO4:Eu(3+) phosphors have the potential as red phosphors for white light-emitting diodes.

  13. Fe3O4 epitaxial films

    KAUST Repository

    Liu, Xiang; Mi, Wenbo; Zhang, Qiang; Zhang, Xixiang

    2017-01-01

    fast charge ordering process and a continuous formation process of trimeron, which is comfirmed by the temperature-dependent Raman spectra. Just below T-V, the twofold AMR in Fe3O4(100) film originates from uniaxial magnetic anisotropy. The fourfold AMR

  14. Separation and determination of 103Ru in samples of fission 99Mo

    International Nuclear Information System (INIS)

    Aghazarian, V.P.; Duran, Adrian P.; Mondino, Angel V.

    2003-01-01

    In Argentina 99 Mo is produced in the RA-3 reactor at the Ezeiza Atomic Center (CAE), by irradiation of miniplates of Al/U (90% 235 U) alloy. The 99 Mo separation is carried out at the Fission Radioisotopes Production Plant. Quality control is important to assure the quality of molybdenum that is produced in CAE. A new method to purify and on line quantify 103 Ru as an impurity present in 99 Mo samples was developed. This procedure is based in the RuO 4 volatilization and its dissolution in NaOH 6M. This is necessary due to the fact that 103 Ru cannot be detected in presence of high activities of 99 Mo without previous separation. This method allows a quantitative, specific, efficient, fast and reproducible separation of 103 Ru from 99 Mo. (author)

  15. Renewable hydrogen: carbon formation on Ni and Ru catalysts during ethanol steam-reforming

    DEFF Research Database (Denmark)

    Rass-Hansen, Jeppe; Christensen, Christina Hviid; Sehested, J.

    2007-01-01

    for the production of hydrogen is investigated, along with quantitative and qualitative determinations of carbon formation on the catalysts by TPO and TEM experiments. A Ru/ MgAl2O4 catalyst, a Ni/MgAl2O4 catalyst as well as Ag-and K-promoted Ni/ MgAl2O4 catalysts were studied. The operating temperature was between...... addition was a rapid deactivation of the catalyst due to an enhanced gum carbon formation on the Ni crystals. Contrary to this, the effect of K addition was a prolonged resistance against carbon formation and therefore against deactivation. The Ru catalyst operates better than all the Ni catalysts...

  16. Luminescence properties of Na2Sr2Al2PO4Cl9:Sm3+ phosphor

    Science.gov (United States)

    Tamboli, Sumedha; Shahare, D. I.; Dhoble, S. J.

    2018-04-01

    A series of Sm3+ ions doped Na2Sr2Al2PO4Cl9 phosphors were synthesized via solid state synthesis method. Photoluminescence (PL) emission spectra were obtained by keeping excitation wavelength at 406 nm. Emission spectra show three emission peaks at 563 nm, 595 nm and 644 nm. The CIE chromaticity diagram shows emission colour of the phosphor in the orange-red region of the visible spectrum, indicating that the phosphor may be useful in preparing orange light-emitting diodes. Na2Sr2Al2PO4Cl9:Sm3+ phosphors were irradiated by γ-rays from a 60Co source and β-rays from a 90Sr source. Their thermoluminescence (TL) glow curves were obtained by Nucleonix 1009I TL reader. TL Trapping parameters such as activation energy of trapped electrons and order of kinetics were obtained by using Chen's peak shape method, Glow curve fitting method and initial rise method.

  17. Magnetic Properties of Dy in Pb2Sr2DyCu3O8

    International Nuclear Information System (INIS)

    Skanthakumar, S.; Soderholm, L.; Movshovich, R.

    1999-01-01

    Superconductivity can be induced at high temperatures in Pb 2 Sr 2 RCu 3 O 8 (R - rare earth) by partially doping Ca 2+ for R 3+ . In order to understand the interplay between magnetism and superconductivity, the magnetic properties of the parent compounds, Pb 2 Sr 2 RCu 3 O 8 , have been studied. The work presented here includes magnetic susceptibility and specific heat measurements on R=Dy and extends the previous studies on R=Ce, Pr, Tb, Ho and Er. Specific heat experiments suggest that the Dy ions order antiferromagnetically with an ordering temperature of 1.3K. The magnetic susceptibility data are in good agreement with the susceptibility calculated using crystal field parameters that are extrapolated from previous modeling of the R=Er and Ho analogs of this series

  18. Electronic structure calculation of Sr2CoWO6 double perovskite using DFT+U

    Science.gov (United States)

    Mandal, Golak; Jha, Dhiraj; Himanshu, A. K.; Ray, Rajyavardhan; Mukherjee, P.; Das, Nisith; Singh, B. K.; Sreenivas, K.; Singh, M. N.; Sinha, A. K.

    2018-04-01

    Using the synchrotron and Raman spectroscopy we measured the lattice parameter and Raman modes of the half-metallic (HM) Sr2CoWO6 (SCoW) synthesied by the solid state reaction technique.. The physical properties of SCoW are studies within the framework of density function theory (DFT) under the generalised gradient approximation (GGA) of Perdew, Bruke, and Ernzerhof both by itself and including a coulomb repulsion via the Hubbard approach or GGA+U. Our results states that Sr2CoWO6 material behaves as insulators for the spin-up orientation and spindown orientation as found for the half metallic systems and at U = 0.06eV the ground state of spin up channel being insulating with spin gap of 2.27eV comparable to the experimental Band gap (BG).

  19. Effect of α variation on the vibrational spectrum of Sr2

    International Nuclear Information System (INIS)

    Beloy, K.; Hauser, A. W.; Borschevsky, A.; Schwerdtfeger, P.; Flambaum, V. V.

    2011-01-01

    We consider the effect of α variation on the vibrational spectrum of Sr 2 in the context of a planned experiment to test the stability of μ≡m e /m p using optically trapped Sr 2 molecules [Zelevinsky et al., Phys. Rev. Lett. 100, 043201 (2008); Kotochigova et al., Phys. Rev. A 79, 012504 (2009)]. We find the prospective experiment to be 3 to 4 times less sensitive to fractional variation in α as it is to fractional variation in μ. Depending on the precision ultimately achieved by the experiment, this result may give justification for the neglect of α variation or, alternatively, may call for its explicit consideration in the interpretation of experimental results.

  20. 101Ru NQR study in superconducting CeRu2

    International Nuclear Information System (INIS)

    Matsuda, Kazuyuki; Kohori, Yoh; Kohara, Takao

    1995-01-01

    We present measurements of the NQR spectrum and the nuclear spin lattice relaxation rate, 1/T 1 , of 101 Ru in superconducting CeRu 2 from 1.9 K to 10 K. From the NQR spectrum, the electric quadrupole interaction parameters were determined to be ν Q =13.2 MHz and η=0.1/T 1 varies in proportion to temperature in the normal state, and has the Hebel-Slichter coherence peak just below the superconducting transition temperature, T C , of 6.2 K, and decreases exponentially at low temperatures with the energy gap of 2Δ=4.0k B T C . 101 Ru NQR study indicates that CeRu 2 is an s-wave and strong-coupling superconductor. (author)

  1. Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic

    Indian Academy of Sciences (India)

    Administrator

    Polycrystalline sample of Ba3Sr2DyTi3V7O30 was prepared at 950°C using a high-temperature solid-state ... Introduction. Though a large number of ferroelectric oxides of different .... change in its shape with rise in temperature suggesting a change in the .... Singh K S, Sati R and Choudhary R N P 1992 J. Mater. Sci. Lett.

  2. Flux creep in Bi2Sr2CaCu2O8 epitaxial films

    International Nuclear Information System (INIS)

    Zeldov, E.; Amer, N.M.; Koren, G.; Gupta, A.

    1990-01-01

    We incorporate the experimentally deduced flux line potential well structure into the flux creep model. Application of this approach to the resistive transition in Bi 2 Sr 2 CaCu 2 O 8 epitaxial films explains the power law voltage-current characteristics and the nonlinear current dependence of the activation energy. The results cannot be accounted for by a transition into a superconducting vortex-glass phase

  3. Electronic parameters of Sr2Nb2O7 and chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, V.V.; Grivel, Jean-Claude; Korotkov, A.S.

    2008-01-01

    /2)) and Delta(O-Sr) = BE(O 1s)-BE(Sr 3d(5/2)), were used to characterize the valence electron transfer on the formation of the Nb-O and Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and earlier published structural and XPS data for other Sr- or Nb...

  4. Electronic and structural properties of Sr2YSbO6

    International Nuclear Information System (INIS)

    Ortiz-Diaz, O.; Jairo Arbey Rodriguez, M.; Fajardo, F.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2007-01-01

    The electronic and structural properties of the cubic perovskite Sr 2 YSbO 6 were predicted from ab initio calculations. Such properties were obtained using the density functional theory (DFT). The full-potential (linearized) augmented plane-wave ((L)APW) method was used, as it is implemented in wien2k code. We have optimized the volume of the unitary cell and the internal x parameter. The lattice constant (a) and x determine some length bonds. We have found that a=8.405 A, x=0.26177, and the bond lengths Y-O and Sb-O are 2.20 and 2.00 A, respectively. Additionally, Sr 2 YSbO 6 was prepared experimentally by the solid-state reaction method using stoichiometric mixtures of high purity (99.99%). By means of X-ray and Rietveld analysis, the main structural features were determined. The experimental lattice parameter is a=8.249 A, which differs about 1.9% of the value obtained using DFT. The bulk modulus is ∼133 GPa, which is not measured experimentally. DFT predicts that Sr 2 YSbO 6 is an indirect semiconductor and magnetic behavior does not have to be expected because at Fermi level the dominant orbitals are p-oxygen. The gap of the material is at least 2.5 eV

  5. Evidence of three-body correlation functions in Rb+ and Sr2+ acetonitrile solutions

    Science.gov (United States)

    D'Angelo, P.; Pavel, N. V.

    1999-09-01

    The local structure of Sr2+ and Rb+ ions in acetonitrile has been investigated by x-ray absorption spectroscopy (XAS) and molecular dynamics simulations. The extended x-ray absorption fine structure above the Sr and Rb K edges has been interpreted in the framework of multiple scattering (MS) formalism and, for the first time, clear evidence of MS contributions has been found in noncomplexing ion solutions. Molecular dynamics has been used to generate the partial pair and triangular distribution functions from which model χ(k) signals have been constructed. The Sr2+ and Rb+ acetonitrile pair distribution functions show very sharp and well-defined first peaks indicating the presence of a well organized first solvation shell. Most of the linear acetonitrile molecules have been found to be distributed like hedgehog spines around the Sr2+ and Rb+ ions. The presence of three-body correlations has been singled out by the existence of well-defined peaks in the triangular configurations. Excellent agreement has been found between the theoretical and experimental data enforcing the reliability of the interatomic potentials used in the simulations. These results demonstrate the ability of the XAS technique in probing the higher-order correlation functions in solution.

  6. Magnetoelastic coupling in Sr2(Fe1-xCrx)ReO6 double perovskites

    International Nuclear Information System (INIS)

    Serrate, D; Teresa, J M De; Algarabel, P A; Marquina, C; Blasco, J; Ibarra, M R; Galibert, J

    2007-01-01

    We have investigated magnetoelastic coupling in Sr 2 (Fe 1-x Cr x )ReO 6 polycrystalline double perovskites. The end compound, Sr 2 CrReO 6 , shows a high ferromagnetic transition temperature of 635 K and is thought to exhibit a nearly half-metallic conduction band. We probed the unexpected high orbital moment borne by the Re atom by means of volume and anisotropic magnetostriction measurements in magnetic fields up to 12 T. Our magnetostriction results can be explained by the existence of a large spin-orbit coupling which, in combination with crystal-field effects, produces a single-ion type magnetostrictive response. The Re orbital moment triggers a greatly enhanced magnetocrystalline anisotropy compared to other ferromagnetic double perovskites. From our magnetostriction data, the temperature dependence of the coercive field as a function of Cr-doping is obtained. We discovered that the coercive field increases as Fe is replaced with Cr, which is linked to a strong enhancement of the magnetic anisotropy. This suggests a close relationship between the Fe[Cr]-O-Re coupling and the magnetic anisotropy. We also analysed the impact of the Re orbital moment on the spin-dependent transport across Sr 2 CrReO 6 grain boundaries. The present work opens up the possible use of these compounds for magnetostrictive applications in a wide temperature and magnetic field range

  7. Structural, magnetic and electronic properties of rare earth ternary oxides Li Ln(II) 2 Ln(III)O4

    International Nuclear Information System (INIS)

    Malki, M.

    1987-06-01

    Properties of a new class of rare earth ternary oxides Li Ln(II) 2 Ln(III)O 4 where Ln(II) is a divalent metal (Sr, Eu) and Ln(III) a trivalent rare earth (Eu, Gd, Dy, Er and Y). These orthorhombic compounds (type Li Eu 3 O 4 ) allow the study of many magnetic phenomena and their evolution in function of the nature of Ln(II) and Ln(III): diamagnetic ions Sr 2+ , Y 3+ ; isotrope magnetic ions: Eu 2+ , Gd 3+ and anisotrope magnetic ions Dy 3+ , Er 3+ . Magnetic and electric properties are obtained by classical techniques and from hyperfine interaction by Moessbauer spectroscopy. The possibility to use several Moessbauer resonance (nuclei Eu 151, Gd 155, Dy 161 and Er 166) completes informations obtained by the macroscopic study [fr

  8. Transport of Sr 2+ and SrEDTA 2- in partially-saturated and heterogeneous sediments

    Science.gov (United States)

    Pace, M. N.; Mayes, M. A.; Jardine, P. M.; McKay, L. D.; Yin, X. L.; Mehlhorn, T. L.; Liu, Q.; Gürleyük, H.

    2007-05-01

    Strontium-90 has migrated deep into the unsaturated subsurface beneath leaking storage tanks in the Waste Management Areas (WMA) at the U.S. Department of Energy's (DOE) Hanford Reservation. Faster than expected transport of contaminants in the vadose zone is typically attributed to either physical hydrologic processes such as development of preferential flow pathways, or to geochemical processes such as the formation of stable, anionic complexes with organic chelates, e.g., ethylenediaminetetraacetic acid (EDTA). The goal of this paper is to determine whether hydrological processes in the Hanford sediments can influence the geochemistry of the system and hence control transport of Sr 2+ and SrEDTA 2-. The study used batch isotherms, saturated packed column experiments, and an unsaturated transport experiment in an undisturbed core. Isotherms and repacked column experiments suggested that the SrEDTA 2- complex was unstable in the presence of Hanford sediments, resulting in dissociation and transport of Sr 2+ as a divalent cation. A decrease in sorption with increasing solid:solution ratio for Sr 2+ and SrEDTA 2- suggested mineral dissolution resulted in competition for sorption sites and the formation of stable aqueous complexes. This was confirmed by detection of MgEDTA 2-, MnEDTA 2-, PbEDTA 2-, and unidentified Sr and Ca complexes. Displacement of Sr 2+ through a partially-saturated undisturbed core resulted in less retardation and more irreversible sorption than was observed in the saturated repacked columns, and model results suggested a significant reservoir (49%) of immobile water was present during transport through the heterogeneous layered sediments. The undisturbed core was subsequently disassembled along distinct bedding planes and subjected to sequential extractions. Strontium was unequally distributed between carbonates (49%), ion exchange sites (37%), and the oxide (14%) fraction. An inverse relationship between mass wetness and Sr suggested that

  9. Extraction and Analysis of Strontium in Water Sample Using a Sr2+ Selective Polymer as the Absorbent Phase

    Directory of Open Access Journals (Sweden)

    Rongjian Ying

    2015-01-01

    Full Text Available A kind of Sr2+ selective resin was applied as an absorption phase to extract Sr2+ ion from an aqueous solution, and the amount of Sr2+ was determined using inductively coupled plasma optical emission spectrometer. Factors, including absorption time, temperature, stirring rate, salt-out effect, desorption, and the pH of the aqueous solution, were investigated to optimize the absorption efficiency of Sr2+. Foreign ions were examined to observe their effects on the absorption behavior of Sr2+. The optimum condition was absorption time at 20 min, pH of aqueous solution 7, temperature of 35°C, and 600 rpm stirring rate. A 10 mL solution of 0.1 mol/L HCl is used as the desorption agent. The linear range of Sr2+ concentrations from 50 to 1200 μg/L was investigated with the slope of 183 μg/L. The limit of detection was 21 μg/L with 4.23% relative standard deviation. The correlation coefficient was found to be 0.9947. Under the optimized conditions, the concentrations of Sr2+ in four water samples were detected by the developed method. We propose that this method effectively extracts strontium ion from environmental water samples.

  10. Influence of ruthenium ions on the precipitation of α-FeOOH, α-Fe2O3 and Fe3O4 in highly alkaline media

    International Nuclear Information System (INIS)

    Krehula, Stjepko; Music, Svetozar

    2006-01-01

    The influence of ruthenium ions on the precipitation of goethite (α-FeOOH), α-Fe 2 O 3 and Fe 3 O 4 in highly alkaline media was investigated by 57 Fe Moessbauer and FT-IR spectroscopies, thermal field emission scanning electron microscope (FE SEM) and EDS. The presence of Ru-dopant strongly affected the precipitation of α-FeOOH at highly alkaline pH, i.e. the formation of α-Fe 2 O 3 was also noticed. A decrease of hyperfine magnetic field (HMF) at RT from 35.1 T (undoped α-FeOOH) to 31.3 T for sample with [Ru]/([Ru] + [Fe]) = 0.0196 was assigned to the incorporation of ruthenium ions into the α-FeOOH structure. Moessbauer spectroscopy showed the formation of stoichiometric Fe 3 O 4 for [Ru]/([Ru] + [Fe]) = 0.0291-0.0909. α-Fe 2 O 3 and Fe 3 O 4 did not show a tendency to the formation of solid solutions with ruthenium ions. FE SEM observations of the samples showed that reference α-FeOOH sample contained acicular particles of good uniformity, which increased the length up to ∼5 times with increase of concentration of ruthenium ions. On the other hand, large octahedral Fe 3 O 4 crystals (particles) were associated with small particles of ruthenium (hydrous) oxide with a size in the range ∼100 nm or less. A possible catalytic action of ruthenium that created reduction conditions for Fe 3+ ions and formation of Fe 2+ ions for precipitation of Fe 3 O 4 was discussed

  11. Growth of Ca2MnO4 Ruddlesden-Popper structured thin films using combinatorial substrate epitaxy

    International Nuclear Information System (INIS)

    Lacotte, M.; David, A.; Pravarthana, D.; Prellier, W.; Grygiel, C.; Rohrer, G. S.; Salvador, P. A.; Velazquez, M.; Kloe, R. de

    2014-01-01

    The local epitaxial growth of pulsed laser deposited Ca 2 MnO 4 films on polycrystalline spark plasma sintered Sr 2 TiO 4 substrates was investigated to determine phase formation and preferred epitaxial orientation relationships (ORs) for isostructural Ruddlesden-Popper (RP) heteroepitaxy, further developing the high-throughput synthetic approach called Combinatorial Substrate Epitaxy (CSE). Both grazing incidence X-ray diffraction and electron backscatter diffraction patterns of the film and substrate were indexable as single-phase RP-structured compounds. The optimal growth temperature (between 650 °C and 800 °C) was found to be 750 °C using the maximum value of the average image quality of the backscattered diffraction patterns. Films grew in a grain-over-grain pattern such that each Ca 2 MnO 4 grain had a single OR with the Sr 2 TiO 4 grain on which it grew. Three primary ORs described 47 out of 49 grain pairs that covered nearly all of RP orientation space. The first OR, found for 20 of the 49, was the expected RP unit-cell over RP unit-cell OR, expressed as [100][001] film ||[100][001] sub . The other two ORs were essentially rotated from the first by 90°, with one (observed for 17 of 49 pairs) being rotated about the [100] and the other (observed for 10 of 49 pairs) being rotated about the [110] (and not exactly by 90°). These results indicate that only a small number of ORs are needed to describe isostructural RP heteroepitaxy and further demonstrate the potential of CSE in the design and growth of a wide range of complex functional oxides

  12. Synthesis, structural, magnetic and optical properties of Sr2CoSn based inverse Heusler alloy nanoparticles

    Science.gov (United States)

    Asvini, V.; Saravanan, G.; Kalaiezhily, R. K.; Ravichandran, K.

    2018-05-01

    The peculiar ternary full Heusler alloy Sr2CoSn nanoparticles are synthesized by co-precipitation method. X- ray diffraction pattern confirms the formation of XA or Xα structure of Sr2CoSn. Using Williamson-Hall plot (W-H plot), we are able to use the uniform deformation model and get low value of strain induced broadening. UV-Visible absorption spectrum shows sharp absorption peak at 210 nm and the estimated band gap energy of Sr2CoSn Heusler alloy nanoparticles is Eg = 4.6 eV (from Tauc plot). The presence of Sr2CoSn with the particle size of approximately 90 nm was observed using high resolution scanning electron microscopy. The magnetization measurements were carried out using VSM and studied M verses H hysteresis studies.

  13. Electronic parameters of Sr2M2O7 (M = V, Nb, Ta) and Sr-O chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, Victor V.; Grivel, Jean-Claude; Zhang, Zhaoming

    2010-01-01

    XPS measurements were carried out on Sr2Nb2O7 and Sr2Ta2O7 powder samples, which were synthesized using standard solid state method. The binding energy differences between the O 1s and cation core level, Δ(O-Sr) = BE(O 1s) - BE(Sr 3d5/2), was used to characterize the valence electron transfer...... on the formation of the Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and Sr2Ta2O7 and the previously published structural and XPS data for other Sr-oxide compounds. A new empirical relationship between Δ(O-Sr) and L(Sr-O) was obtained. Possible applications...

  14. The adsorption of Cs+, Sr2+ and Ni2+ on bitumen: a mechanistic model

    International Nuclear Information System (INIS)

    Loon, L.R. Van; Kopajtic, Z.

    1991-01-01

    The adsorption of radionuclides on the waste matrix is a positive effect and contributes to the retardation of released radionuclides migrating to the geo-and biosphere. For the safety assessment studies, it is important to know whether or not radionuclides do adsorb on the waste matrix. In the present work the adsorption of 134 Cs + , 85 Sr 2+ and 63 Ni 2+ on bitumen was studied as a function of the pH and ionic strength of the equilibrium solution. Bitumen emulsions with well defined surfaces were used. The surface of bitumen is negatively charged due to the deprotonation of weak acid carboxyl groups at the interface. The functional group density amounts to 1.37.10 18 groups/m 2 and their deprotonation behaviour can be well described by the 'Ionizable Surface Group' model. Cs + , Sr 2+ and Ni 2+ adsorb on the surface by three different processes, i.e. ion exchange, outer sphere complexation and inner sphere surface complexation respectively. The adsorption depends on the pH and the ionic strength of the contact solution. Under near field conditions, Cs + and Sr 2+ do not adsorb on the bitumen due to the competition with Na + , K + and Ca 2+ present in the cement pore water in contact with the bitumen. Ni 2+ adsorption can also be neglected because the formation of neutral and anionic hydroxo complexes in solution competes strongly with the adsorption reaction. Other hydrolysable radionuclides of interest are expected to behave similarly to Ni 2+ . The main conclusion of the study is that the adsorption of radionuclides under near field conditions is expected to be very low. Consequently, this process need not to be considered in safety assessment studies. (author) figs., tabs., 30 refs

  15. Enhanced antibacterial performance of Fe3O4–Ag and MnFe2O4 ...

    Indian Academy of Sciences (India)

    sity in our daily life. ... enhances the biological activity of Ag NPs, but many stud- ... against Gram-positive and Gram-negative bacteria in this ..... Antimicrobial effects of Fe3O4@Nico@Ag, Fe3O4@His@Ag and Fe3O4@HA@Ag against Fe3O4 ...

  16. Column chromatographic separation of Y3+ from Sr2+ by polymeric ionizable crown ether resins

    International Nuclear Information System (INIS)

    Wood, D.J.; Elshani, S.; Wai, C.M.; Bartsch, R.A.; Huntley, M.; Hartenstein, S.

    1993-01-01

    Condensation polymers containing subunits of crown ether carboxylic acid monomers are effective stationary phases for the chromatographic separation of Y 3+ and Sr 2+ . The pH range and metal loading capacities for the resins have been determined under equilibrium conditions. The resin can be regenerated for repeated use without losing its separation capability. Altering the molecular structure of the monomer (sym-dibenzo-16-crown-5-oxyacetic acid) by an alkyl substitution on the macrocyclic cavity decreases the loading capacity of the resin

  17. Structural and Dielectric Properties of LiSr2Nb5O15 Ceramic

    International Nuclear Information System (INIS)

    Behera, Banarji; Mohanty, N. K.; Satpathy, S. K.; Nayak, P.; Choudhary, R. N. P.

    2011-01-01

    The polycrystalline sample of LiSr 2 Nb 5 O 15 (LSN) was prepared by a high temperature solid-state reaction technique. Studies of structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. X-ray studies reveal that the material has an orthorhombic structure at room temperature. Dielectric properties were measured over a wide range of temperature (28-500 deg. C) and frequency (10 2 -10 6 Hz). Conductivity of the material increases with rise in temperature.

  18. Flux pinning in hot isostatically pressed Bi2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Miller, D.J.; Sengupta, S.; Hettinger, J.D.; Shi, D.; Gray, K.E.; Nash, A.S.; Goretta, K.C.

    1992-01-01

    Magnetic hysteresis data were taken from 4.2 to 35 K on Bi 2 Sr 2 CaCu 2 O x samples that were hot isostatically pressed at 105 MPa in an inert atmosphere at 825 degree C. One set of samples was pressed for only 15 min while the other was pressed for 120 min. The samples pressed for 15 min contained a high density of dislocations and planar faults, while the samples pressed for 120 min contained fewer dislocations and faults, with most dislocations present within subgrain boundaries. The samples with the complex dislocation/planar fault structures exhibited substantially larger hysteresis loops, suggesting enhanced flux pinning

  19. AC losses in (Bi,Pb) 2Sr 2Ca 2Cu 3O x tapes

    Science.gov (United States)

    D'Anna, G.; Indenbom, M. V.; André, M.-O.; Benoit, W.; Grivel, J.-C.; Hensel, B.; Flükiger, R.

    1994-05-01

    A double peak structure is observed in the AC losses of (Bi,Pb) 2Sr 2Ca 2Cu 3O x silver-sheathed tapes using a torsion-pendulum oscillator. The low-temperature peak is associated to the intragrain flux expulsion, while the high-temperature peak results from a macroscopic current path around the whole sample due to a well-coupled fraction of the grains. The flux pinning by the dislocations forming small-angle grain boundaries is suggested to control the transport current.

  20. Morphology of growth of Bi2Sr2CaCu2O8 single crystals

    Science.gov (United States)

    Indenbom, M. V.; van der Beek, C. J.; Berseth, V.; Wolf, Th.; Berger, H.; Benoit, W.

    1996-12-01

    A good correlation of twins on the basal surface of flux-grown Bi2Sr2CaCu2Ox (BSCCO) single crystals with surface. growth steps is observed, the b-axis being perpendicular to the steps and, thus, parallel to the growth direction. It is found that mono-twin BSCCO single crystals produced by the travelling solvent floating zone method also grow preferentially along b, i.e. nearly perpendicularly to the boule axis, contrary to the common belief. This new understanding of the morphology of growth explains the nature of major defects in these crystals, which considerably change their measured superconducting properties, in a different way.

  1. Nd(BrO3)3-Yb(BrO3)3-H2O and Nd2(SeO4)3-Yb2(SeO4)3-H2O systems at 25 deg C

    International Nuclear Information System (INIS)

    Serebrennikov, V.V.; Batyreva, V.A.; Tsybukova, T.N.

    1981-01-01

    Using the methods of isothermal solubility the Nd(BrO 3 ) 3 - Yb(BrO 3 ) 3 -H 2 O and Nd 2 (SeO 4 ) 3 -Yb 2 (SeO 4 ) 3 -H 2 O systems are studied at 25 deg C. The compositions of the solid phases are determined by the method of ''residues''. The formation of two series of solid solutions in both systems is established. Besides, there is a crystallization region of Nd 2 (SeO 4 ) 3 in the system of selenates. The solubility diagrams of the systems are presented [ru

  2. Raman scattering spectra of superconducting Bi2Sr2CaCu2O8 single crystals

    International Nuclear Information System (INIS)

    Kirillov, D.; Bozovic, I.; Geballe, T.H.; Kapitulnik, A.; Mitzi, D.B.

    1988-01-01

    Raman spectra of Bi 2 Sr 2 CaCu 2 O 8 single crystals with superconducting phase-transition temperature of 90 K have been studied. The spectra contained phonon lines and electronic continuum. Phonon energies and polarization selection rules were measured. A gap in the electronic continuum spectrum was observed in a superconducting state. Noticeable similarity between Raman spectra of Bi 2 Sr 2 CaCu 2 O 8 and YBa 2 Cu 3 O 7 was found

  3. Raman scattering spectra of superconducting Bi2Sr2CaCu2O8 single crystals

    Science.gov (United States)

    Kirillov, D.; Bozovic, I.; Geballe, T. H.; Kapitulnik, A.; Mitzi, D. B.

    1988-12-01

    Raman spectra of Bi2Sr2CaCu2O8 single crystals with superconducting phase-transition temperature of 90 K have been studied. The spectra contained phonon lines and electronic continuum. Phonon energies and polarization selection rules were measured. A gap in the electronic continuum spectrum was observed in a superconducting state. Noticeable similarity between Raman spectra of Bi2Sr2CaCu2O8 and YBa2Cu3O7 was found.

  4. Sr2+ and Cs+ ion exchange properties of KLn(PO3)4: Ln = Ce and Eu

    International Nuclear Information System (INIS)

    Samatha, B.; Achary, S.N.; Tyagi, A.K.; Ramkumar, Jayshree; Chandramouleeswaran, S.

    2014-01-01

    With the aim to study the potential of layered phosphates as ion exchangers two stoichiometric compositions as KLn(PO 3 ) 4 with Ln = Ce and Eu were prepared by solid state reaction and characterized by powder X-ray diffraction method. The Cs + and Sr 2+ exchange properties of both materials were investigated using standard solutions of Sr 2 + or Cs + in low acidic aqueous medium

  5. O(4) texture with a cosmological constant

    International Nuclear Information System (INIS)

    Cho, Inyong

    2002-01-01

    We investigate O(4) textures in a background with a positive cosmological constant. We find static solutions which comove with the expanding background. There exists a solution in which the scalar field is regular at the horizon. This solution has a noninteger winding number smaller than 1. There also exist solutions in which scalar-field derivatives are singular at the horizon. Such solutions can complete one winding within the horizon. If the winding number is larger than some critical value, static solutions including the regular one are unstable under perturbations

  6. Porous nanocubic Mn3O4-Co3O4 composites and their application as electrochemical supercapacitors.

    Science.gov (United States)

    Pang, Huan; Deng, Jiawei; Du, Jimin; Li, Sujuan; Li, Juan; Ma, Yahui; Zhang, Jiangshan; Chen, Jing

    2012-09-14

    A simple approach has been developed to fabricate ideal supercapacitors based on porous Mn(3)O(4)-Co(3)O(4) nanocubic composite electrodes. We can easily obtain porous corner-truncated nanocubic Mn(3)O(4)-Co(3)O(4) composite nanomaterials without any subsequent complicated workup procedure for the removal of a hard template, seed or by using a soft template. In such a composite, the porous Mn(3)O(4)-Co(3)O(4) enables a fast and reversible redox reaction to improve the specific capacitance. The porous nanocubic Mn(3)O(4)-Co(3)O(4) composite electrode can effectively transport electrolytes and shorten the ion diffusion path, which offers excellent electrochemical performance. These results suggest that such porous Mn(3)O(4)-Co(3)O(4) composite nanocubes are very promising for next generation high-performance supercapacitors.

  7. Controllable synthesis and upconversion emission of ultrasmall near-monodisperse lanthanide-doped Sr2LaF7 nanocrystals

    International Nuclear Information System (INIS)

    Mao, Yifu; Ma, Mo; Gong, Lunjun; Xu, Changfu; Ren, Guozhong; Yang, Qibin

    2014-01-01

    Highlights: • Apropos NaOH content facilitates the growth of pure phase Sr 2 LaF 7 NCs. • Yb 3+ doping is favorable to the formation of Sr 2 LaF 7 NCs with uniform size. • Ultrasmall near-monodispersed Sr 2 LaF 7 NCs(sub-10 nm) were synthesized for the first time. • Intense multicolor upconversion can be obtained by properly lanthanide doping. - Abstract: Fluorite phase Sr 2 LaF 7 nanocrystals (NCs) were synthesized via solvothermal method using oleic acid as capping ligands. The effects of preparing conditions on the phase structure, crystal size, morphology, and upconversion (UC) emission properties of the products were studied. The results reveal that just apropos NaOH content facilitates the growth of near-monodispersed pure phase Sr 2 LaF 7 NCs, and Yb 3+ doping is favorable to the formation of pure Sr 2 LaF 7 phase with more uniform size distribution. The average crystalline size of the products can be controlled less than 10 nm. Following appropriate lanthanide ions doping, the NCs show intense blue, yellow, and white-color UC emission under the excitation of a 980 nm laser. The energy transfer UC mechanisms for the fluorescent intensity were also investigated

  8. Effects of extra oxygen on the structure and superconductivity of La2-xCaxCuO4+y prepared by chemical oxidation

    DEFF Research Database (Denmark)

    Rial, C.; Moran, E.; Alario Franco, M.A.

    1998-01-01

    are strongly conditioned by the smaller size of Ca2+ with respect to La3+. Indeed, this peculiarity clearly differentiates the oxidized La2-xCaxCuO4+y series from the Sr2+ and the Ba2+ substituted systems, where the size of the dopant is larger than that of La3+. In the present work the analogies...... and the differences concerning the insertion of oxygen and the modifications induced in La2-xMxCuO4+y (M = Ca, Sr, Ba) are presented and discussed. (C) 1998 Elsevier Science B.V....... improve considerably upon oxidation. The oxidized Ca-doped materials with x less than or equal to 0.08 show an almost constant T-c of similar to 38 K, close to that corresponding to the optimum hole-doping in La2-xMxCuO4; however, the oxidized samples with higher Ca contents present slightly lower T...

  9. Interfaces exchange bias and magnetic properties of ordered CoFe_2O_4/Co_3O_4 nanocomposites

    International Nuclear Information System (INIS)

    Zhang, B.B.; Xu, J.C.; Wang, P.F.; Han, Y.B.; Hong, B.; Jin, H.X.; Jin, D.F.; Peng, X.L.; Li, J.; Yang, Y.T.; Gong, J.; Ge, H.L.; Wang, X.Q.

    2015-01-01

    Graphical abstract: - Highlights: • CoFe_2O_4 nanoparticles were well-dispersed anchored in mesopores of Co_3O_4. • The magnetic behavior of nanocomposites changed greatly at low temperature. • CoFe_2O_4 nanoparticles reinforced the interfaces magnetic interaction of nanocomposites. • M increased with the doping of CoFe_2O_4 and the decreasing temperature. • Exchange bias effect was observed at 100 K and increased with the doping of CoFe_2O_4. - Abstract: Cobalt ferrites (CoFe_2O_4) nanoparticles were implanted into the ordered mesoporous cobaltosic oxide (Co_3O_4) nanowires to synthesize magnetic CoFe_2O_4/Co_3O_4 nanocomposites. X-ray diffraction (XRD), N_2 physical absorption–desorption, transmission electron microscope (TEM) and energy disperse spectroscopy (EDS) were used to characterize the microstructure of mesoporous Co_3O_4 and CoFe_2O_4/Co_3O_4 nanocomposites. The percent of pore-volume of mesoporous Co_3O_4 nanowires was calculated to be about 41.99% and CoFe_2O_4 nanoparticles were revealed to exist in the mesopores of Co_3O_4_. The magnetic behavior of both samples were investigated with superconducting quantum interference device (SQUID). Magnetization increased with the doping CoFe_2O_4 and decreasing temperature, while coercivity hardly changed. The exchange bias effect was obviously observed at 100 K and enhanced with the doping CoFe_2O_4. CoFe_2O_4 nanoparticles reinforced the interfaces magnetic interaction between antiferromagnetic Co_3O_4 and ferrimagnetic CoFe_2O_4.

  10. Cu4Pr6(MoO4)11-Pr2(MoO4)3 system

    International Nuclear Information System (INIS)

    Arzumanyan, G.A.

    1982-01-01

    Existence boundaries and Dalton compositions (CuPr(MoO 4 ) 2 , CuPr 3 (MoO 4 ) 5 ) of solid solutions that in the mojority are of shcheelite dsitored structure have been determined in the Cu 4 Pr 6 (MoO 4 ) 11 -Pr 2 (MoO 4 ) 3 system. It has been revealed that regions of homogeneity near the CuPr(MoO 4 ) 2 composition have a horseshoeshaped profile

  11. Thermodynamics of CoAl2O4-CoGa2O4 solid solutions

    International Nuclear Information System (INIS)

    Lilova, Kristina I.; Navrotsky, Alexandra; Melot, Brent C.; Seshadri, Ram

    2010-01-01

    CoAl 2 O 4 , CoGa 2 O 4 , and their solid solution Co(Ga z Al 1-z ) 2 O 4 have been studied using high temperature oxide melt solution calorimetry in molten 2PbO.B 2 O 3 at 973 K. There is an approximately linear correlation between lattice parameters, enthalpy of formation from oxides, and the Ga content. The experimental enthalpy of mixing is zero within experimental error. The cation distribution parameters are calculated using the O'Neill and Navrotsky thermodynamic model. The enthalpies of mixing calculated from these parameters are small and consistent with the calorimetric data. The entropies of mixing are calculated from site occupancies and compared to those for a random mixture of Ga and Al ions on octahedral site with all Co tetrahedral and for a completely random mixture of all cations on both sites. Despite a zero heat of mixing, the solid solution is not ideal in that activities do not obey Raoult's Law because of the more complex entropy of mixing. - Graphical abstract: Measured enthalpies of mixing of CoAl 2 O 4 -CoGa 2 O 4 solid solutions are close to zero but entropies of mixing reflect the complex cation distribution, so the system is not an ideal solution.

  12. Synthesis and Structural Study of Sr2CuO3+δ Superconductor under High Pressure

    International Nuclear Information System (INIS)

    Qing-Qing, Liu; Fu-Ren, Wang; Feng-Ying, Li; Liang-Chen, Chen; Ri-Cheng, Yu; Chang-Qing, Jin; Yan-Chun, Li; Jing, Liu

    2008-01-01

    A single-phase Sr 2 CuO 3+δ superconductor is synthesized under high temperature and high pressure, in which oxygen atoms only partially occupy the apical sites next to the CuO 2 planes and act as hole-dopants. The superconducting transition temperature with T c max = 75 K is achieved in the material. Structure analysis from x-ray powder diffraction data show that this material crystallizes into a K 2 NiF 4 structure with tetragonal unit cell of a = 3. 795(3) Å and c = 12. 507(1) Å. Energy-dispersive synchrotron x-ray-diffraction studies at ambient are performed on powder samples of Sr 2 CuO 3+δ in a diamond-anvil cell at pressure up to 35 GPa. Anisotropic compressibility is found. Pressure-induced isostructural phase transition might exist as revealed by the discontinuous change of crystal cell volume V with pressure. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  13. Cs+ and Sr2+ adsorption selectivity of zeolites in relation to radioactive decontamination

    Directory of Open Access Journals (Sweden)

    M.W. Munthali

    2015-09-01

    Full Text Available Zeolites are used as adsorbents of cationic elements in the radioactive decontamination process of water, soil and others. We determined Cs+ and Sr2+ adsorption selectivity of some zeolites to know effective zeolite species for the decontamination of radioactive Cs and Sr. A 30 mL mixed solution containing up to 15 mg L−1 of non-radioactive Cs+ or Sr+ and up to 0.50 M of Na+ or K+ was mixed with 0.5 g of Linde-type A, Na-P1, faujasite X, faujasite Y and mordenite. Among the zeolites, mordenite had the highest Cs+ adsorption selectivity, and the selectivity had no correlation to the cation exchange capacity (CEC of the zeolites. In contrast, Sr2+ adsorption selectivity of the zeolites positively correlated with the CEC of the zeolites; Linde-type A with the highest CEC showed the highest adsorption selectivity, and its adsorption rate was more than 99.9% even in the presence of 0.5 M K+. A simulated soil decontamination experiment of Cs from a Cs-retaining vermiculite by using mordenite and that of Sr from a Sr-retaining vermiculite by using Linde-type A showed decontamination rates of more than 90%.

  14. Magnetic and structural behavior of Sr2ZrMnO6 double perovskite

    International Nuclear Information System (INIS)

    Llamosa, D.P.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2009-01-01

    We report synthesis and characterization of new Sr 2 ZrMnO 6 manganite-like material. Samples were produced by the solid state reaction method with sinterization temperatures up to 1400 deg. C. X-ray diffraction experiments reveal that structure belongs to the perovskite system, space group Fm3-barm(no. 225). Lattice parameter a=7.86A was obtained by means of Rietveld-type refinement, through the GSAS code. Magnetic properties were studied by using an MPMS Quantum Design SQUID. From measurements of magnetization as a function of temperature, we determine the occurrence of a paramagnetic-antiferromagnetic transition with Neel temperature 50 K. Curie-Weiss fitting permitted to obtain the magnetic characteristic parameters. At temperature regimes below the Neel temperature, strong evidences of frustration and an irreversibility temperature between zero field cooling (ZFC) and field cooling (FC) measurements were observed. Curves of magnetization as a function of applied field were performed at T=4K. Results show a hysteretic feature for Sr 2 ZrMnO 6 magnetic material. This response is attributed to formation of magnetic clusters as a consequence of cationic (magnetic and no magnetic) disorder along the double perovskite structure.

  15. Growth of Sr2CrReO6 epitaxial thin films by pulsed laser deposition

    International Nuclear Information System (INIS)

    Orna, J.; Morellon, L.; Algarabel, P.A.; Pardo, J.A.; Magen, C.; Varela, M.; Pennycook, S.J.; De Teresa, J.M.; Ibarra, M.R.

    2010-01-01

    We report the growth, structural, magnetic, and electrical transport properties of epitaxial Sr 2 CrReO 6 thin films. We have succeeded in depositing films with a high crystallinity and a relatively large cationic order in a narrow window of growth parameters. The epitaxy relationship is Sr 2 CrReO 6 (SCRO) (0 0 1) [1 0 0]-parallel SrTiO 3 (STO) (0 0 1) [1 1 0] as determined by high-resolution X-ray diffraction and scanning transmission electron microscopy (STEM). Typical values of saturation magnetization of M S (300 K)=1 μ B /f.u. and ρ (300 K)=2.8 mΩ cm have been obtained in good agreement with previous published results in sputtered epitaxial thin films. We estimate that the antisite defects concentration in our thin films is of the order of 14%, and the measured Curie temperature is T C =481(2) K. We believe these materials be of interest as electrodes in spintronic devices.

  16. Round table on RU486.

    Science.gov (United States)

    Shallat, L

    1993-01-01

    As a non-invasive means of early abortion, RU-486 has the potential to increase women's reproductive options; at the same time, the "abortion pill" has stimulated debate about the ethics and safety of new medical technologies. When combined with a prostaglandin (PG), the success rate for RU-486 is 96% for pregnancies of up to 9 weeks' gestation. In France, over 120,000 women have used RU-486/PG to terminate pregnancy, and this regimen is now used in about 25% of abortions. Clinical trials of RU-486 are underway in Cuba, China, India, Singapore, and Zambia. The Program for Appropriate Technology has identified four considerations for introducing RU-486 to developing countries: whether abortion or menstrual regulation is legal; whether women find the method acceptable and can comply with the multiple visit treatment regimen; whether the health infrastructure can support safe method use, including prevention of misuse and provision of appropriate medical backup personnel and facilities; and whether the cost of the regimen is affordable to individuals and/or programs --conditions unlikely to be met in most such countries. Ideal would be development of a medical abortifacient that is single dose and the lowest possible dose of each drug, provokes miscarriage within a more predictable time frame with less acute and prolonged bleeding, is safe and effective beyond two months, has minimal side effects, and maximizes short-term safety and minimizes long-term effects. Technological advances are being undermined, however, by political and religious attacks on the method. Even some feminists have expressed concerns about potential long-term effects of RU-486 use.

  17. Synthesis and crystal structure of hydrogen selenates K(HSeO4)(H2SeO4) and Cs(HSeO4)(H2SeO4)

    International Nuclear Information System (INIS)

    Troyanov, S.I.; Morozov, I.V.; Zakharov, M.A.; Kemnitz, E.

    1999-01-01

    Hydrogen selenates of the compositions K(HSeO 4 )(H 2 SeO 4 ) and Cs(HSeO 4 )(H 2 SeO 4 ) are synthesized by the reaction of alkali metal carbonates with an excess of the concentrated selenic acid. The X-ray diffraction study showed that both compounds are isostructural to the corresponding hydrogen sulfates. The difference in the systems of hydrogen bonding are caused by various combinations of the acceptor functions of the oxygen atoms in the HSeO 4 and H 2 SeO 4 groups

  18. 103Ru for tumor scanning, 2

    International Nuclear Information System (INIS)

    Mizukawa, Kiichiro

    1979-01-01

    The mechanism of 103 Ru-uptake in tumors was investigated through the incubation of rat ascites hepatoma cells (AH-130) in vitro with various concentrations of Ru-chloride containing 103 Ru-chloride as a tracer. Quantitative analysis of Ru binding to the cells indicated that ascites hepatoma cells contained high- and low-affinity binding sites for Ru. When ascites hepatoma cells were incubated with Ru after incubation with a low concentration of papain, most of the Ru was not bound to the cells but was found in the medium containing solubilized glycoproteins. However Ru bound mainly to washed cells after the incubation with papain. About 65% of the Ru bound to ascites hepatoma cells was liberated by the papain treatment, and about 45% of the liberated Ru was precipitated by cetyltrimethylammonium bromide, indicating that Ru bound tightly to glycopeptides. These results suggest that the tumor affinity of 103 Ru is related to specific binding to glycopeptides on the tumor cell surface. (author)

  19. Investigation of BaMoO4-Ln2(MoO4)3 systems (Ln = Nd, Sm, Yb)

    International Nuclear Information System (INIS)

    Vakulyuk, V.V.; Evdokimov, A.A.; Khomchenko, G.P.

    1982-01-01

    Using the methods of X-ray phase and differential-thermal analyses phase ratios in the systems BaMoO 4 -Ln 2 (MoO 4 ) 3 (Ln=Nd, Sm, Yb); BaNd 2 (MoO 4 ) 4 -MaGd 2 (MoO 4 ) are studied. Unit cell parameters and the character of melting of the compounds BaLn 2 (MoO 4 ) 4 are specified. Effect of growth conditions on laminated nature of BaGd 2 (MoO 4 ) 4 monocrystals is studied

  20. Ru (amp)(bipy)Cl

    Indian Academy of Sciences (India)

    Administrator

    [RuV(amp)(bipy)O]+ intermediate complex which leads to the high affinity for hydrogen atom/hydride abstraction. Acknowledgement. We gratefully acknowledge the financial support from the Department of Science &. Technology, Government of India. We are thankful to Shri Hardyal Singh for his encouragement. Reference.

  1. Low temperature synthesis of Ru-Cu alloy nanoparticles with the compositions in the miscibility gap

    Science.gov (United States)

    Martynova, S. A.; Filatov, E. Yu.; Korenev, S. V.; Kuratieva, N. V.; Sheludyakova, L. A.; Plusnin, P. E.; Shubin, Yu. V.; Slavinskaya, E. M.; Boronin, A. I.

    2014-04-01

    A complex salt [Ru(NH3)5Cl][Cu(C2O4)2H2O]-the precursor of nanoalloys combining ruthenium and copper was prepared. It crystallizes in the monoclinic space group P21/n. Thermal properties of the prepared salt were examined in different atmospheres (helium, hydrogen, oxygen). Thermal decomposition of the precursor in inert atmosphere was thoroughly examined and the intermediate products were characterized. Experimental conditions for preparation of copper-rich (up to 12 at% of copper) metastable solid solution CuxRu1-x (based on Ru structure) were optimized, what is in sharp contrast to the bimetallic miscibility gap known for the bulk counterparts in a wide composition range. Catalytic properties of copper-ruthenium oxide composite were tested in catalytic oxidation of CO.

  2. Characterization of Sr2+ uptake on natural minerals of kaolinite and magnesite using XRPD, SEM/EDS, XPS, and DRIFT

    International Nuclear Information System (INIS)

    Shahwan, T.; Erten, H.N.

    2005-01-01

    The sorption behavior of Sr 2+ ions on natural minerals rich in kaolinite and magnesite was studied using SEM/EDS, XPS, XRPD, AAS/AES and DRIFT techniques. Quantitative analysis of the XPS data shows that magnesite is more effective in Sr 2+ uptake than kaolinite. DRIFT spectra and XRPD patterns indicate that the structures of both minerals were not affected upon Sr 2+ sorption. Intercalation of DMSO in kaolinite lamellae aiming at increasing the interlayer space did not significantly enhance the sorption capacity of the clay towards Sr 2+ probably due to the lack of a negative charge on the accessible sites. EDS mapping indicated that while the sorbed Sr is equally distributed on surface of natural kaolinite, it was associated - to a larger extent - with the regions richer in Mg in the case of natural magnesite. Comparing the uptake mechanisms of natural magnesite with that of pure MgCO 3 , it was seen that while natural magnesite sorbed Sr 2+ mainly through an ion exchange type mechanism, the formation of SrCO 3 coprecipitate was detected on the surface of the MgCO 3 at higher loadings. (orig.)

  3. Flux line patterns in Bi2Sr2Ca1Cu2Ox

    International Nuclear Information System (INIS)

    Weiss, F.; Hardy, V.; Provost, J.; Ruyter, A.; Simon, C.

    1994-01-01

    Results of the defect influence on the flux line lattice in Bi 2 Sr 2 Ca 1 Cu 2 O x single crystals are presented. These crystals, non irradiated or irradiated at GANIL with heavy ions (Pb 56+ , 6 GeV) have been decorated with Ni particles in the superconducting state using the Bitter technique. The defects involved are columnar defects. Resulting decorated flux line patterns have been characterized using scanning electron microscopy and computer image analysis. Disorder of the decorated flux line networks has been found to be strongly dependent on the defect density, which results from the irradiation. In order to characterize this disorder, a method for determining elastic energy terms in the deformation of flux line patterns has been investigated. This method can be applied if Fourier transforms of the decorated flux line patterns exhibit distinct reflections. (orig.)

  4. Surface phonons on Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Phelps, R.B.; Akavoor, P.; Kesmodel, L.L.; Demuth, J.E.; Mitzi, D.B.

    1993-01-01

    We report measurements of surface optical phonons on Bi 2 Sr 2 CaCu 2 O 8+δ with high-resolution electron-energy-loss spectroscopy (HREELS). In addition to peaks near 50 and 80 meV (403 and 645 cm -1 ), which have been previously observed, our loss spectra exhibit a peak at 26 meV (210 cm -1 ). Loss spectra were measured at temperatures from 45 to 146 K, and the temperature dependence of the peaks was found to be weak. The 50 and 80 meV peaks shift to lower frequency by ∼1.5 meV over this temperature range. All three peaks are attributed to surface optical phonons. The identification of particular bulk modes corresponding to the surface modes observed with HREELS is discussed

  5. Surface phonons on Bi2Sr2CaCu2O8+δ

    Science.gov (United States)

    Phelps, R. B.; Akavoor, P.; Kesmodel, L. L.; Demuth, J. E.; Mitzi, D. B.

    1993-11-01

    We report measurements of surface optical phonons on Bi2Sr2CaCu2O8+δ with high-resolution electron-energy-loss spectroscopy (HREELS). In addition to peaks near 50 and 80 meV (403 and 645 cm-1), which have been previously observed, our loss spectra exhibit a peak at 26 meV (210 cm-1). Loss spectra were measured at temperatures from 45 to 146 K, and the temperature dependence of the peaks was found to be weak. The 50 and 80 meV peaks shift to lower frequency by ~1.5 meV over this temperature range. All three peaks are attributed to surface optical phonons. The identification of particular bulk modes corresponding to the surface modes observed with HREELS is discussed.

  6. Synthesis and electrical properties of (Pb,Co)Sr2(Y,Ca)Cu2Oz

    Science.gov (United States)

    Tashiro, T.; Maeda, T.; Abe, R.; Takechi, S.; Takahashi, T.; Haruta, M.; Horii, S.

    One of related materials to high-temperature superconductors (HTSC's) with nominal compositions of (Pb0.5Co0.5)Sr2(Y1xCax)Cu2Oz (x=0∼0.6) is synthesized and characterized. All samples are nearly single-phase, and its crystal structure is likely to be so-called "1-2-1-2" type which is one of typical structures of HTSC's. Electrical resistivity is decreased as x increases. While superconductivity is not observed at temperatures between room-temperature and 20 K for all samples, temperature dependence of the resistivity exhibits metallic behavior down to 150 K for x=0.5. Phase formation and transport behavior are discussed focusing on mixed valence-state of Co2+ and Co3+.

  7. Solvent extraction of Sr2+ and Cs+ based on hydrophobic protic ionic liquids

    International Nuclear Information System (INIS)

    Luo, Huimin; Yu, Miao; Dai, Sheng

    2007-01-01

    A series of new hydrophobic and protic alkylammonium ionic liquids with bis(trifluoromethylsulfonyl) imide or bis(perfluoroethylsulfonyl)imide as conjugated anions was synthesized in a one-pot reaction with a high yield. In essence our synthesis method involves the combination of neutralization and metathesis reactions. Some of these hydrophobic and protic ionic liquids were liquids at room temperature and therefore investigated as new extraction media for separation of Sr 2+ and Cs + from aqueous solutions. An excellent extraction efficiency was found for some of these ionic liquids using dicyclohexano-18-crown-6 and calix[4]arene-bis(tert-octylbenzo-crown-6) as extractants. The observed enhancement in the extraction efficiency can be attributed to the greater hydrophilicity of the cations of the protic ionic liquids. The application of the protic ionic liquids as new solvent systems for solvent extraction opens up a new avenue in searching for simple and efficient ionic liquids for tailored separation processes. (orig.)

  8. New colour centres in KCl:(Tl+ + Ca2+) and KCl:(Tl+ + Sr2+) crystals

    International Nuclear Information System (INIS)

    Ioan, A.; Topa, V.; Giurgea, M.

    1978-01-01

    Electrolytic colouring under unusual conditions (low temperature and high voltage) gives rise to the appearance of three new absorption bands peaking at 3.2, 2.5, and 1.7 eV and at 2.8, 2.1, and 1.5 eV in KCl:(Tl + + Ca 2+ ) and in KCl:(Tl + + Sr 2+ ) single crystals, respectively. The modifications of the absorption spectra of the coloured crystals induced by the application of a reversed electric field at the colouring temperature or by heat treatment are investigated. It is likely that the colour centre responsible for the new absorption bands is an aggregate centre which, besides an Tl - -complex, contains also at least an Ca(Sr) ion, a trapped electron, and an anionic vacancy. (author)

  9. Retrograde densification in Bi2Sr2CaCu2O8 superconductors

    International Nuclear Information System (INIS)

    Johnson, D.W. Jr.; Rhodes, W.W.

    1989-01-01

    Bi 2 Sr 2 CaCu 2 O 8 was prepared using the mixed oxide-carbonate method and sintered at temperatures ranging from 850 degrees to 911 degrees C. The samples were characterized for density, mechanical strength, phase composition, microstructure, and superconducting transition temperatures. A unique retrograde densification characteristic is demonstrated in the temperature range 850 degrees to 890 degrees C whereby the material first becomes less dense as the sintering temperature is raised, and only in a narrow temperature range from 900 degrees to 905 degrees C does the material densify then with the formation of a liquid phase. This retrograde densification, coupled with a narrow sintering range overlapping the melting temperature, makes this compound a difficult one to process

  10. Exchange-coupled Fe3O4/CoFe2O4 nanoparticles for advanced magnetic hyperthermia

    Science.gov (United States)

    Glassell, M.; Robles, J.; Das, R.; Phan, M. H.; Srikanth, H.

    Iron oxide nanoparticles especially Fe3O4, γ-Fe2O3 have been extensively studied for magnetic hyperthermia because of their tunable magnetic properties and stable suspension in superparamagnetic regime. However, their relatively low heating capacity hindered practical application. Recently, a large improvement in heating efficiency has been reported in exchange-coupled nanoparticles with exchange coupling between soft and hard magnetic phases. Here, we systematically studied the effect of core and shell size on the heating efficiency of the Fe3O4/CoFe2O4 core/shell nanoparticles. The nanoparticles were synthesized using thermal decomposition of organometallic precursors. Transmission electron microscopy (TEM) showed formation of spherical shaped Fe3O4 and Fe3O-/CoFe2O4 nanoparticles. Magnetic measurements showed high magnetization (≅70 emu/g) and superparamagnetic behavior for the nanoparticles at room temperature. Magnetic hyperthermia results showed a large increase in specific absorption rate (SAR) for 8nm Fe3O4/CoFe2O4 compared to Fe3O4 nanoparticles of the same size. The heating efficiency of the Fe3O4/CoFe2O4 with 1 nm CoFe2O4 (shell) increased from 207 to 220 W/g (for 800 Oe) with increase in core size from 6 to 8 nm. The heating efficiency of the Fe3O4/CoFe2O4 with 2 nm CoFe2O4 (shell) and core size of 8 nm increased from 220 to 460 W/g (for 800 Oe). These exchange-coupled Fe3O4/CoFe2O4 core/shell nanoparticles can be a good candidate for advanced hyperthermia application.

  11. Structure, magnetic and superconducting properties of MoSr2HoCu2O8-δ

    International Nuclear Information System (INIS)

    Balchev, N.; Nenkov, K.; Mihova, G.; Kunev, B.; Pirov, J.; Dimitrov, D.A.

    2009-01-01

    Samples with nominal composition MoSr 2 HoCu 2 O 8-δ were synthesized and their magnetic and superconducting (SC) properties were investigated. The obtained samples are Mo-deficient. It was established that the magnetic order is of a long-range type. The coincidence of the experimental value of the Curie constant and the theoretical one of MoSr 2 HoCu 2 O 8-δ shows that the observed magnetic properties of the samples are determined by the highly dominating phase Mo-1212. The two-step resistive SC transition, together with the absence of both diamagnetism and a peak in the specific heat between the two critical temperatures may be associated with the presence of a granular superconductivity. The effect of the Mo-deficiency on the magnetic and SC properties of MoSr 2 HoCu 2 O 8-δ was discussed

  12. Half-metallic behavior and electronic structure of Sr2CrMoO6 magnetic system

    International Nuclear Information System (INIS)

    Bonilla, C.M.; Landinez Tellez, D.A.; Arbey Rodriguez, J.; Vera Lopez, E.; Roa-Rojas, J.

    2007-01-01

    Complex perovskite materials with the A 2 BB'O 6 formula have been recently studied because of their peculiar magnetic and electronic properties. The origin of magnetism in the double perovskite Sr 2 FeMoO 6 brought these properties again into discussion. Recently, a new interaction mechanism was proposed for cases in which the hybridization of 3d and 2p levels of Mo with the 3d Fe levels is responsible for the half-metallic behavior in the Sr 2 FeMoO 6 material. We report on LAPW ab initio calculations within the generalized gradient approximation (GGA) to density functional theory (DFT) for another double perovskite, namely, Sr 2 CrMoO 6 . Our results show that this is also a half-metallic system. We correlate our results with an extension of the recent model proposed by Sarma to explain the conduction mechanism in this compound

  13. Phase formation in the Li2MoO4-Rb2MoO4-Ln2(MoO4)3 systems and the properties of LiRbLn2(MoO4)4

    International Nuclear Information System (INIS)

    Basovich, O.M.; Khajkina, E.G.; Vasil'ev, E.V.; Frolov, A.M.

    1995-01-01

    Phase equilibria within subsolidus range of ternary salt systems Li 2 MoO 4 -Rb 2 MoO 4 -Ln 2 (MoO 4 ) 4 (Ln - Nd, Er) are analyzed. Formation of ternary molybdate LiRbNd 2 (MoO 4 ) 4 is proved along LiNd(MoO 4 ) 2 -RbNd(MoO 4 )-2 cross-section. Phase diagram of this cross-section is plotted. Similar compounds are synthesized for Ln = La-Eu. The parameters of their monoclinic elementary cells are determined. Luminescent properties of LiRbLa 2 (MoO 4 ) 4 -Nd 3+ are studied. 17 refs., 4 figs., 2 tabs

  14. Ferromagnetic interactions in Ru(III)-nitronyl nitroxide radical complex: a potential 2p4d building block for molecular magnets.

    Science.gov (United States)

    Pointillart, Fabrice; Bernot, Kevin; Sorace, Lorenzo; Sessoli, Roberta; Gatteschi, Dante

    2007-07-07

    The reaction between [Ru(salen)(PPh3)Cl] and the 4-pyridyl-substituted nitronyl nitroxide radical (NITpPy) leads to the [Ru(salen)(PPh3)(NITpPy)](ClO4)(H2O)2 complex while the reaction with the azido anion (N3-) leads to the [Ru(salen)(PPh3)(N3)] complex 2 (where salen2- = N,N'-ethan-1,2-diylbis(salicylidenamine) and PPh3 = triphenylphosphine). Both compounds have been characterized by single crystal X-ray diffraction. The two crystal structures are composed by a [Ru(III)(salen)(PPh3)]+ unit where the Ru(III) ion is coordinated to a salen2- ligand and one PPh3 ligand in axial position. In 1 the Ru(III) ion is coordinated to the 4-pyridyl-substituted nitronyl nitroxide radical whereas in 2 the second axial position is occupied by the azido ligand. In both complexes the Ru(III) ions are in the same environment RuO2N3P, in a tetragonally elongated octhaedral geometry. The crystal packing of 1 reveals pi-stacking in pairs. While antiferromagnetic intermolecular interaction (J2 = 5.0 cm(-1)) dominates at low temperatures, ferromagnetic intramolecular interaction (J1 = -9.0 cm(-1)) have been found between the Ru(III) ion and the coordinated NITpPy.

  15. Structures and self-activating photoluminescent properties of Sr3−xAxGaO4F (A=Ba, Ca) materials

    International Nuclear Information System (INIS)

    Green, Robert; Vogt, Thomas

    2012-01-01

    The synthesis, structures and photoluminescent properties of mixed oxyfluorides of the type Sr 3−x A x GaO 4 F are compared to Sr 3−x A x AlO 4 F (A=Ca, Ba) materials. In these compounds the F − and O 2− ions are ordered and located on two distinct crystallographic sites. When substituting Sr 2+ by Ba 2+ and Ca 2+ , we find in Sr 3−x A x GaO 4 F materials an ordering of the alkaline earth cations over the two crystallographic sites. The amount of Ba 2+ ions that can be substituted into Sr 3−x A x GaO 4 F is x≤1.2, which is slightly more than can be incorporated into the previously reported Al-analog Sr 3−x A x AlO 4 F (x=1.0). Conversely, the amount of Ca 2+ ions that can be substituted into Sr 3−x Ca x GaO 4 F (x=0.3) is significantly less than in Sr 3−x Ca x AlO 4 F (x=1.0). A post-synthesis reduction step causes these materials to exhibit self-activating broad band photoluminescence where the emitted colors vary with the amount of ions substituted into the host lattice. - Graphical abstract: TOC Statement The structures of the self-activating phosphors Sr 3−x A x MO 4 F (A=Ba, Ca and M=Al, Ga) can be rationalized as alternating layers of bond compression and elongation, which impact the photoluminescence. Highlights: ► Comparison of the structural changes in Sr 3−x A x AlO 4 F and Sr 3−x A x GaO 4 F (A=Ba, Ca) and its influence on the photoluminescence of these self-activating phosphors. ► Analysis of the Global Instability Index of the Sr 3−x A x AlO 4 F and Sr 3−x A x GaO 4 F (A=Ba, Ca). ► Comparison of the photoluminescence between the self-activating phosphors Sr 3−x A x AlO 4 F and Sr 3−x A x GaO 4 F (A=Ba, Ca).

  16. Kinetic study of methanol oxidation on carbon-supported PtRu electrocatalyst

    International Nuclear Information System (INIS)

    Gojkovic, S.Lj.; Vidakovic, T.R.; Durovic, D.R.

    2003-01-01

    Methanol electrooxidation was investigated on the carbon-supported PtRu electrocatalyst (1:1 atomic ratio) in acid media. X-ray diffraction measurement indicated alloying of Pt and Ru. Cyclic voltammetry of the sample reflects the amount of Ru in the catalyst and its ability to adsorb OH radicals. Tafel plots for the oxidation of 0.02-3 M methanol in the solutions containing 0.05-1 M HClO 4 and in the temperature range 27-40 deg. C showed reasonably well-defined linear region with the slope of about 115 mV dec -1 at the low currents, irrespective of the experimental conditions employed. Reaction order with respect to methanol was found to be 0.5. A correlation between methanol oxidation rate and pseudocapacitive current of OH adsorption on Ru sites was established. It was proposed that bifunctional mechanism is operative with the reaction between methanol residues adsorbed on Pt sites and OH radicals adsorbed on Ru sites as the rate-determining step

  17. Sr_2SmNbO_6 perovskite: Synthesis, characterization and density functional theory calculations

    International Nuclear Information System (INIS)

    Dutta, Alo; Mukhopadhyay, P.K.; Sinha, T.P.; Shannigrahi, Santiranjan; Himanshu, A.K.; Sen, Pintu; Bandyopadhyay, S.K.

    2016-01-01

    The density functional theory (DFT) under the generalized gradient approximation (GGA) has been used to investigate the electronic structure of double perovskite oxide Sr_2SmNbO_6 synthesized by the solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern of the sample shows the monoclinic P2_1/n phase at room temperature. The X-ray photoemission spectrum (XPS) of the material is collected in the energy window of 0–1200 eV. The chemical shift of the constituent elements calculated from the core level XPS spectra is used to analyze the covalency between the O anion and Sm/Nb cations. The valence band (VB) XPS spectrum is compared with the calculated VB spectrum using partial density of states in a standard way. The Raman spectrum is employed to investigate the phonon modes of the material in the monoclinic phase. Lorentzian lines are used to fit the experimental Raman spectrum, which present 24 phonon modes corresponding to the stretching and banding of NbO_6/SmO_6 octahedra and translational motion of Sr along the Sr−O bond. The discrepancy between the measured and calculated band gap values has been removed by applying modified Becke-Johnson (mBJ) potential in the DFT calculations. The experimental optical band gap obtained from the UV–visible reflectance spectrum is found to be 3.42 eV, which is well matched with the DFT calculated value of 3.2 eV, and suggests the semiconducting nature of the material. The real (ε′) and imaginary (ε″) parts of the optical dielectric constant as a function of energy along the x-, y- and z-polarization directions using mBJ potential are calculated. The collective vibrational modes of the atoms, the Born effective charge of the ions and their effect on the static dielectric constant of the material are studied using DFT. The calculated value of static dielectric constant for SSN is found to be 41.3. - Highlights: • Electronic structure and dynamical properties of Sr_2SmNbO_6 (SSN

  18. High-pressure synthesis and crystal structures of the strontium oxogallates Sr2Ga2O5 and Sr5Ga6O14

    Science.gov (United States)

    Kahlenberg, Volker; Goettgens, Valerie; Mair, Philipp; Schmidmair, Daniela

    2015-08-01

    High-pressure synthesis experiments in a piston-cylinder apparatus at 1.5 GPa/3.0 GPa and 1000 °C resulted in the formation of single-crystals of Sr2Ga2O5 and Sr5Ga6O14, respectively. The structures of both compounds have been solved from single-crystal diffraction data sets using direct methods. The first compound is orthorhombic with space group type Pbca (a=10.0021(4) Å, b=9.601(4) Å, c=10.6700(4) Å, V=1024.6(4) Å3, Mr=394.68 u, Z=8, Dx=5.12 g/cm3) and belongs to the group of single layer gallates. Individual sheets are parallel to (0 0 1) and can be built from the condensation of unbranched vierer single chains running along [0 1 0]. The layers are characterized by the presence of four- and strongly elliptical eight-membered rings of corner connected tetrahedra in UUDD and UUUUDDDD conformation. Strontium atoms are sandwiched between the tetrahedral layers for charge compensation and are coordinated by six and seven oxygen ligands, respectively. Sr2Ga2O5 is isotypic with several other double sulfides and selenides. To the best of our knowledge, it is the first example of an oxide with this structure type. From a structural point of view, Sr5Ga6O14 is a phyllogallate as well. The crystal structure adopts the monoclinic space group P21/c (a=8.1426(3) Å, b=8.1803(3) Å, c=10.8755(4) Å, β=91.970(4)° V=723.98(5) Å3, Mr=1080.42 u, Z=2, Dx=4.96 g/cm3). Individual sheets extend along (0 0 1). Basic building units are unbranched dreier single chains parallel to [1 0 0]. The layers contain tertiary (Q3) und quaternary (Q4) connected [GaO4]-tetrahedra in the ratio 2:1 resulting in a Ga:O ratio of 3:7 and the formation of exclusively five-membered rings. Linkage between adjacent tetrahedral sheets is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. The layers in Sr5Ga6O14 are similar to those observed in the melilite structure-type. Crystallochemical relationships between the present phases and other

  19. Metalloradical Reactivity of RuI and Ru0 Stabilized by an Indole-Based Tripodal Tetraphosphine Ligand

    NARCIS (Netherlands)

    van de Watering, F.F.; van der Vlugt, J.I.; Dzik, W.I.; de Bruin, B.; Reek, J.N.H.

    2017-01-01

    The tripodal, tetradentate tris(1-(diphenylphosphanyl)-3-methyl-1H-indol-2-yl)phosphane PP3-ligand 1 stabilizes Ru in the RuII, RuI, and Ru0 oxidation states. The octahedral [(PP3)RuII(Cl)2] ( 2 ), distorted trigonal bipyramidal [(PP3)RuI(Cl)] ( 3 ), and trigonal bipyramidal [(PP3)Ru0(N2)] ( 4 )

  20. pH-induced photocurrent switching based on a highly stable drop-casting film of imidazole moiety-containing dinuclear Ru(II) Complex

    International Nuclear Information System (INIS)

    Xue, Long-Xin; Duan, Zhi-Ming; Jia, Jia; Wang, Ke-Zhi; Haga, Masa-aki

    2014-01-01

    Graphical abstract: > Solvent-casting Ru(II) complex modified electrode. > Positive shifting of half-wave potentials of Ru(III)/Ru(II) by pH decreases. > Greatly enhanced cathodic photocurrents by pH decreases. - Highlights: • Solvent-casting Ru(II) complex modified electrode. • Positive shifting of half-wave potentials of Ru(III)/Ru(II) by pH decreases. • Greatly enhanced cathodic photocurrents by pH decreases. - Abstract: A new dinuclear Ru(II) complex of [(H 2 L 1 )Ru(H 2 L 2 )Ru(H 2 L 1 )](ClO 4 ) 4 {H 2 L 1 = 2,6-bis(2-benzimidazolyl)pyridine; H 2 L 2 = 2,6-bis(4-([2,2′:6′,2″-terpyridin]-4′-yl)phenyl)-1,5- dihydrobenzo[1,2-d:4,5-d’]diimidazole} is synthesized and characterized. The Ru(II) complex modified indium-tin oxide electrode prepared using a drop-casting method, exhibited a couple of stable surface-confined Ru(III)/Ru(II)-based redox waves centered at +0.65 V vs saturated calomel electrode that were almost unchanged after 50 consecutive cyclic voltammetry scanning. The modified electrode showed pH-dependent redox behaviors with the formal potential being decreased by 430 mV due to the occurrance of the proton-coupled redox reactions. The cathodic photocurrent generation of the modified electrode was also found to be highly pH-dependent, switching from an “off” state at pH ∼11.0 to an “on” state at pH = 2.20 with an enhancement factor of 18. The modified electrode was shown to have promising applications as photoelectrochemical pH sensing and switching devices

  1. Growth of nucleation sites on Pb-doped Bi2Sr2Ca1Cu2O8+δ

    International Nuclear Information System (INIS)

    Finnemore, D.K.; Xu, M.; Kouzoudis, D.; Bloomer, T.; Kramer, M.J.; McKernan, S.; Balachandran, U.; Haldar, P.

    1996-01-01

    In the growth of Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ from mixed powders of Pb-doped Bi 2 Sr 2 Ca 1 Cu 2 O 8+δ and other oxides, it has been discovered that a dense array of hillocks or mesas grow at the interface between a Ag overlay and Pb-doped Bi 2 Sr 2 Ca 1 Cu 2 O 8+δ grains during the ramp up to the reaction temperature. As viewed in an environmental scanning electron microscope, the Ag coated grains develop a texture that looks like open-quote open-quote chicken pox close-quote close-quote growing on the grains at about 700 degree C. These hillocks are about 100 nm across and are spaced at about 500 to 1000 nm. If there is no Ag, this texture does not develop. Preliminary measurements indicate that the hillocks are a recrystallization of (Bi,Pb) 2 Sr 2 Ca 1 Cu 2 O 8+δ , and are definitely not a Pb rich phase. copyright 1996 American Institute of Physics

  2. Electronic structure of clean and Ag-covered single-crystalline Bi2Sr2CuO6

    International Nuclear Information System (INIS)

    Lindberg, P.A.P.; Shen, Z.; Wells, B.O.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

    1989-01-01

    Photoemission studies of single-crystalline samples of Bi 2 Sr 2 CuO 6 show clear resemblance to the corresponding data for single crystals of Bi 2 Sr 2 CaCu 2 O 8 . In particular, a sharp Fermi-level cutoff, giving evidence of metallic conductivity at room temperature, as well as single-component O 1s emission and Cu 2p satellites with a strength amounting to about 50% of that of the main Cu 2p line, are observed. An analysis of the relative core-level photoemission intensities shows that the preferential cleavage plane of single-crystalline Bi 2 Sr 2 CuO 6 is between adjacent Bi-O layers. Deposition of Ag adatoms causes only weak reaction with the Bi and O ions of the Bi 2 Sr 2 CuO 6 substrate, while the Cu states rapidly react with the Ag adatoms, as monitored by a continuous reduction of the Cu 2p satellite intensity as the Ag overlayer becomes thicker

  3. High colour purity single-phased full colour emitting white LED phosphor Sr2V2O7:Eu3+

    International Nuclear Information System (INIS)

    Zhou Zhi; Zhou Nan; He Zhangxing; Liu Suqin; Liu Younian; Tian Ziwei; Wang Nanfang; Mao Zhiyong; Hintzen, H T

    2013-01-01

    Single-phased white-light-emitting phosphor Sr 2 V 2 O 7 :Eu 3+ was successfully synthesized by the solid-state method. The result of x-ray diffraction analysis indicated that the obtained phosphor has the same crystal structure as that of Sr 2 V 2 O 7 . The synthesized Sr 2 V 2 O 7 :Eu 3+ was combined with near-UV light (365 nm) chips and then assembled into ligtht-emitting diodes (LED) devices, which generated white light with colour coordinates of (0.324, 0.317). The white light was generated from yellow-green and red emissions, which should be attributed to the host Sr 2 V 2 O 7 and dopant Eu ions, respectively. The effects of the concentration of Eu ions and charge compensation on the emission intensity were carefully investigated. The results show that the energy migrates from the host to the dopant and also that Li 2 CO 3 should be the best charge compensator for this single-phased phosphor. In addition, the colour rendering index and luminescence efficiency of the fabricated LED devices with Sr 1.90 V 2 O 7 :0.10Eu 3+ phosphor were 91 and 32 lm W -1 , respectively, suggesting that Sr 1.90 V 2 O 7 :0.10Eu 3+ phosphor is a potential candidate for the phosphor-converted white-light-emitting diodes with near-UV chips.

  4. Positron lifetime studies of Bi2Sr2CaCu2Oy-xFx superconductors

    International Nuclear Information System (INIS)

    Shi Zhiqiang; Chao Xixu; Wu Lingyun

    1994-01-01

    The positron lifetime was measured as a function of doped F content for Bi 2 Sr 2 CaCu 2 O y-x F x superconductor. Combined with the measurement of critical temperature T c , the sites where F substituted for O and the change of electronic structures caused by local substitution of F in the samples were studied

  5. High temperature phase transition in SOFC anodes based on Sr2MgMoO6-δ

    International Nuclear Information System (INIS)

    Marrero-Lopez, D.; Pena-Martinez, J.; Ruiz-Morales, J.C.; Martin-Sedeno, M.C.; Nunez, P.

    2009-01-01

    The double perovskite Sr 2 MgMoO 6-δ has been recently reported as an efficient anode material for solid oxide fuel cells (SOFCs). In the present work, this material have been investigated by high temperature X-ray diffraction (XRD), differential scanning calorimetry (DSC) and impedance spectroscopy to further characterise its properties as SOFC anode. DSC and XRD measurements indicate that Sr 2 MgMoO 6-δ exhibits a reversible phase transition around 275 deg. C from triclinic (I1-bar) with an octahedral tilting distortion to cubic (Fm3-barm) without octahedral distortion. This phase transition is continuous with increasing temperature without any sudden cell volume change during the phase transformation. The main effect of the phase transformation is observed in the electrical conductivity with a change in the activation energy at low temperature. La 3+ and Fe-substituted Sr 2 MgMoO 6-δ phases were also investigated, however these materials are unstable under oxidising conditions due to phase segregations above 600 deg. C. - Graphical abstract: The double perovskite Sr 2 MgMoO 6 , recently proposed as an efficient SOFC anode for direct hydrocarbon oxidation, exhibits a reversible structural phase transition from triclinic to cubic at 275 deg. C.

  6. Inter- and intragranular properties of bismuth calcium strontium copper oxide (Bi2CaSr2Cu2Oy) superconductors

    NARCIS (Netherlands)

    Emmen, J.H.P.M.; Brabers, V.A.M.; Steen, van der C.; Dalderop, J.H.J.; Lenczowski, S.K.J.; Jonge, de W.J.M.

    1989-01-01

    The granular behaviour of sintered bulk Bi2CaSr2Cu2Oy superconductor is investigated by resistivity and ¿ac measurements. The observed temperature and magnetic field dependence is discussed within the framework of a granular model. The frequency dependence of the intragranular losses leads to a flux

  7. Facile preparation and formation mechanism of Sr2Si5N8:Eu2+ red-emitting phosphors

    Science.gov (United States)

    Wang, Yang; Wang, Yunli; Wang, Ming; Shao, Yiran; Zhu, Yingchun

    2018-05-01

    The red-emitting Sr2Si5N8:Eu2+ phosphors have been synthesized in a new facile process using (oxy)nitride precursors by inductive calcination under N2 atmosphere at ordinary pressure. Different from the prevailing methods, lower cost raw materials, simpler pretreatment, without harsh conditions and a shorter reaction time are achieved. It was found that red-emitting Sr2Si5N8:Eu2+ phosphors were synthesized with high crystallinity and purity after 1 h inductive calcination. The formation mechanism was characterized by XRD, SEM, TEM and Fluorescence microscopy. It was demonstrated that a hexagonal mesophase of Sr-doped α-Si3N4 was primarily formed in the reaction process, which transformed into the final product of the orthorhombic Sr2Si5N8:Eu2+ phosphors. During the reaction process, the color of the samples transforms from greenish-yellow to orange and eventually to red. The as-prepared phosphors have a wide excitation in the range of 250 ∼ 570 nm which matches blue light chips and give a red-light emission peaking at 610 nm. The results indicate a promising prospect for a simple, efficient and inexpensive way to prepare Sr2Si5N8:Eu2+ phosphors for blue/UV-based warm-white LEDs and other fluorescent applications.

  8. Multicolor upconversion emission of dispersed ultrasmall cubic Sr2LuF7 nanocrystals synthesized by a solvothermal process

    International Nuclear Information System (INIS)

    Gong, Lunjun; Ma, Mo; Xu, Changfu; Li, Xujun; Wang, Suiping; Lin, Jianguo; Yang, Qibin

    2013-01-01

    Lanthanide (Ln 3+ ) doped Sr 2 LuF 7 (Ln 3+ =Er 3+ /Tm 3+ /Yb 3+ ) nanocrystals (NCs) were synthesized via a solvothermal process using oleate as stabilizing agent. The as-synthesized NCs with a mean diameter of sub-20 nm can be well dispersed in cyclohexane and show a pure cubic phase structure with space group Fm3 ¯ m. Following appropriate lanthanide ion doping, the NCs show intense red, green, blue and white-color upconversion emission (UC) under the excitation of a 980 nm laser. Predominant near-infrared UC can also be obtained in the Yb 3+ /Tm 3+ doped Sr 2 LuF 7 NCs. The energy transfer UC mechanisms for the fluorescent intensity were also investigated. The desirable property of the ultrasmall dispersed NCs makes them promising materials for the applications in miniaturized solid-state light sources, multicolor three-dimensional display devices and fluorescent labels for biomedical imaging. - Highlights: ► Cubic-structure (Fm3 ¯ m) Sr 2 LuF 7 nanocrystals were synthesized for the first time. ► Nanocrystals (sub-20 nm) with cubic or spherical shape can be well dispersed. ► By doping properly, the nanocrystals show intense multicolor upconversion. ► Predominant near-infrared upconversion can be obtained in Sr 2 LuF 7 nanocrystals. ► Upconversion mechanism for the fluorescent intensity is mainly energy transfer.

  9. First-principles study of intrinsic vacancy defects in Sr2MgSi2O7 phosphorescent host material

    Science.gov (United States)

    Duan, H.; Dong, Y. Z.; Huang, Y.; Hu, Y. H.; Chen, X. S.

    2016-01-01

    Electronic structures of intrinsic vacancy defects in Sr2MgSi2O7 phosphorescent host material are investigated using first-principles calculations. Si vacancies are too high in energy to play any role in the persistent luminescence of Sr2MgSi2O7 phosphor. Mg vacancies form easier than Sr vacancies as a result of strain relief. Among all the vacancies, O1 vacancies stand out as a likely candidate because they are the most favorable in energy and introduce an empty triply degenerate state just below the CBM and a fully-occupied singlet state at ~1 eV above the VBM, constituting in this case effective hole trap level and electron trap levels, respectively. Mg vacancies are unlikely to explain the persistent luminescence because of its too shallow electron trap level but they may compensate the hole trap associated with O1 vacancies. We yield consistent evidence for the defect physics of these vacancy defects on the basis of the equilibrium properties of Sr2MgSi2O7, total-energy calculations, and electronic structures. The persistent luminescence mechanism of Sr2MgSi2O7:Eu2+, Dy3+ phosphor is also discussed based on our results for O1 vacancies trap center. Our results provide a guide to more refined experiments to control intrinsic traps, whereby probing synthetic strategies toward new improved phosphors.

  10. Influence of Ba2+ and Sr2+ ions on the hydration process of portland cement and blended cements

    Directory of Open Access Journals (Sweden)

    Živanović, B. M.

    1987-12-01

    Full Text Available This study concerns the influence of the concentration of Sr2+ and Ba2+ ions in mortar batch waters upon the hydration process of various Portland and additive cements. An increase in the mechanical resistence of said cements is observed, after 28 days, when the concentration of Ba2+ and Sr2+ ions in the mortar batch waters increases. This suggests a possible microstructural explanation of said phenomenon.En el presente trabajo se estudia la influencia de la concentración de los iones Sr2+ y Ba2+ en las aguas de amasado sobre el proceso de hidratación de varios cementos portland y de adición. Se comprueba un incremento de las resistencias mecánicas de dichos cementos, a los 28 días, cuando aumenta la concentración de los iones Ba2+ y Sr2+ en las aguas de amasado, lo cual sugiere una posible explicación microestructural a dicho fenómeno.

  11. Preferential orientation relationships in Ca2MnO4 Ruddlesden-Popper thin films

    International Nuclear Information System (INIS)

    Lacotte, M.; David, A.; Prellier, W.; Rohrer, G. S.; Salvador, P. A.

    2015-01-01

    A high-throughput investigation of local epitaxy (called combinatorial substrate epitaxy) was carried out on Ca 2 MnO 4 Ruddlesden-Popper thin films of six thicknesses (from 20 to 400 nm), all deposited on isostructural polycrystalline Sr 2 TiO 4 substrates. Electron backscatter diffraction revealed grain-over-grain local epitaxial growth for all films, resulting in a single orientation relationship (OR) for each substrate-film grain pair. Two preferred epitaxial ORs accounted for more than 90% of all ORs on 300 different microcrystals, based on analyzing 50 grain pairs for each thickness. The unit cell over unit cell OR ([100][001] film ∥ [100][001] substrate , or OR1) accounted for approximately 30% of each film. The OR that accounted for 60% of each film ([100][001] film ∥ [100][010] substrate , or OR2) corresponds to a rotation from OR1 by 90° about the a-axis. OR2 is strongly favored for substrate orientations in the center of the stereographic triangle, and OR1 is observed for orientations very close to (001) or to those near the edge connecting (100) and (110). While OR1 should be lower in energy, the majority observation of OR2 implies kinetic hindrances decrease the frequency of OR1. Persistent grain over grain growth and the absence of variations of the OR frequencies with thickness implies that the growth competition is finished within the first few nm, and local epitaxy persists thereafter during growth

  12. Synthesis and crystal structure of new uranyl selenite(IV)-selenate(VI) [C5H14N][(UO2)3(SeO4)4(HSeO3)(H2O)](H2SeO3)(HSeO4)

    International Nuclear Information System (INIS)

    Krivovichev, S.V.; Tananaev, I.G.; Myasoedov, B.F.; Kalenberg, V.

    2006-01-01

    Crystals of new uranyl selenite(IV)-selenate(VI) [C 5 H 14 N][(UO 2 ) 3 (SeO 4 ) 4 (HSeO 3 )(H 2 O)](H 2 SeO 3 )(HSeO 4 ) are obtained by the method of evaporation from aqueous solutions. Compound has triclinic lattice, space group P1-bar, a=11.7068(9), b=14.8165(12), c=16.9766(15), α=73.899(6), β=76.221(7), γ=89.361(6) Deg, V=2743.0(4) A 3 , Z=2. Laminated complexes (UO 2 ) 3 (SeO 4 ) 4 (HSeO 3 )(H 2 O)] 3- are the basis of the structure. [HSe(VI)O 4 ] - , [H 2 Se(IV)O 3 ] complexes and protonated methylbutylamine cations are disposed between layers [ru

  13. Metal–semiconductor transition in atomically thin Bi2Sr2Co2O8 nanosheets

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2014-09-01

    Full Text Available Two-dimensional layered materials have attracted considerable attention since the discovery of graphene. Here we demonstrate that the layered Bi2Sr2Co2O8 (BSCO can be mechanically exfoliated into single- or few-layer nanosheets. The BSCO nanosheets with four or more layers display bulk metallic characteristics, while the nanosheets with three or fewer layers have a layer-number-dependent semiconducting characteristics. Charge transport in bilayer or trilayer BSCO nanosheets exhibits Mott 2D variable-range-hopping (VRH conduction throughout 2 K–300 K, while the charge transport in monolayers follows the Mott-VRH law above a crossover temperature of 75 K, and is governed by Efros and Shklovskii-VRH laws below 75 K. Disorder potentials and Coulomb charging both contribute to the transport gap of these nanodevices. Our study reveals a distinct layer number-dependent metal-to-semiconductor transition in a new class of 2D materials, and is of great significance for both fundamental investigations and practical devices.

  14. Electronic and magnetic properties of double perovskite Sr2CoUO6: Heisenberg model

    Science.gov (United States)

    Nid-bahami, A.; Ahmed, S. Sidi; Ait-Tamerd, M.; Zaari, H.; El Kenz, A.; Benyoussef, A.

    2018-01-01

    This work will be focused on the electronic and magnetic properties of Sr2CoUO6 (SCUO) using ab-initio calculations and Monte Carlo Simulation (MCS). Firstly, we calculate the exchange coupling and the crystal field, then, the electronic and magnetic properties will be studied, using the full-potential linearized augmented plane wave (FP-LAPW) method, as implemented in the Wien2k code. This method employing the generalized gradient approximation (GGA) for exchange-correlation term. The half-metallic ferromagnetic nature implies a potential application of this new compound in spintronics devices. Also, we have presented the results of the band structures and densities of states for the two up and down spin polarizations. The exchange coupling and the crystal field calculated are J = 0 . 567 meV and δ = 0 . 559meV, and total spin magnetic moments is 2.96 μB closed to experimental values 3 μB. Secondly, we have presented the results for the magnetization and the susceptibility as a function of temperature. Finally, we obtain the critical temperature T = 9 . 20 K by MCS in good agreement with the experimental value.

  15. Structural phase transitions in the ordered double perovskite Sr2MnTeO6

    International Nuclear Information System (INIS)

    Ortega-San Martin, L; Chapman, J P; Hernandez-Bocanegra, E; Insausti, M; Arriortua, M I; Rojo, T

    2004-01-01

    The crystal structure of the ordered double perovskite Sr 2 MnTeO 6 has been refined at ambient temperature from high resolution neutron and x-ray powder diffraction data in the monoclinic space group P 12 1 /n 1 with a 5.7009(1) A, b = 5.6770(1) A, c = 8.0334(1) A and β = 90.085(1) deg. This represents a combination of in-phase (+) and out-of-phase (-) rotations of virtually undistorted MnO 6 and TeO 6 octahedra in the (-+) sense about the axes of the ideal cubic perovskite. High temperature x-ray powder diffraction shows three structural phase transitions at approximately 250, 550 and 675 deg. C, each corresponding to the disappearance of rotations about one of these axes. The first transition was analysed by differential scanning calorimetry and showed a thermal hysteresis with an enthalpy of 0.55 J g -1 . We propose the (P12 1 /n1 → I12/m1 → I4/m → Fm3barm) sequence of structural transitions which has not been previously reported for a double perovskite oxide

  16. Electronic Raman scattering in Bi2Sr2CaCu2O8=δ

    International Nuclear Information System (INIS)

    Quilty, J.W.; Trodahl, H.J.; Pooke, D.

    1996-01-01

    Full text: High-T c superconductors exhibit a definite Electronic Raman Scattering (ERS) continuum, which most materials do not. Typically, the continuum is relatively flat in the normal state, while below T c the ERS spectrum shows reduced scattering at the lowest Raman shifts and a peak close to the superconducting gap energy. The behaviour below T c is due to the breaking of Cooper pairs and reflects the superconducting density of states, hence revealing the superconducting gap. Through an appropriate choice of incident and scattered polarisation vectors, the electronic Raman continuum of high-T c superconductors may also be used to reveal information on the symmetry of the superconducting gap. Previous studies of the electronic continuum show that a broad peak associated with the superconducting gap forms in the continuum below T c in these materials, when compared to the normal-state. We report temperature and polarisation dependent ERS measurements on differently-doped Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) single crystals, within a temperature range of 300 K to 10 K

  17. Crystal growth, electronic structure and optical properties of Sr2Mg(BO3)2

    Science.gov (United States)

    Lv, Xianshun; Wei, Lei; Wang, Xuping; Xu, Jianhua; Yu, Huajian; Hu, Yanyan; Zhang, Huadi; Zhang, Cong; Wang, Jiyang; Li, Qinggang

    2018-02-01

    Single crystals of Sr2Mg(BO3)2 (SMBO) were grown by Kyropoulos method. X-ray powder diffraction (XRD) analysis, transmission spectrum, thermal properties, band structure, density of states and charge distribution as well as Raman spectra of SMBO were described. The as-grown SMBO crystals show wide transparency range with UV cut-off below 180 nm. A direct band gap of 4.66 eV was obtained from the calculated electronic structure results. The calculated band structure and density of states results indicated the top valence band is determined by O 2p states whereas the low conduction band mainly consists of Sr 5s states. Twelve Raman peaks were observed in the experimental spectrum, fewer than the number predicted by the site group analysis. Raman peaks of SMBO were assigned combining first-principle calculation and site group analysis results. The strongest peak at 917 cm-1 in the experimental spectrum is assigned to symmetric stretching mode A1‧(ν1) of free BO3 units. SMBO is a potential Raman crystal which can be used in deep UV laser frequency conversion.

  18. Structural study of caesium-based britholites Sr7La2Cs(PO4)5(SiO4)F2

    International Nuclear Information System (INIS)

    Boughzala, K.; Gmati, N.; Bouzouita, K.; Ben Cherifa, A.; Gravereau, P.

    2010-01-01

    Several studies demonstrated the ability of britholites to retain radionuclides such as the caesium and actinides. Therefore, three compounds with formulas Sr 8 LaCs(PO 4 ) 6 F 2 , Sr 7 La 2 Cs(PO 4 ) 5 (SiO 4 )F 2 and Sr 2 La 7 Cs(SiO 4 ) 6 F 2 , were prepared by solid state reaction. However, it seems that only the mono-silicated composition was obtained in a pure state. In this present work, the X-ray diffraction and magnetic nuclear resonance have been used to investigate the structure for this composition. The results showed that in fact this phase was not pure, but it was mixed with a secondary phase, SrLaCs(PO 4 ) 2 . The refinement by the Rietveld method allowed also to precise the distribution of La 3+ and Cs + ions between the two cationic sites of the apatite. (authors)

  19. High-pressure synthesis and crystal structures of the strontium oxogallates Sr2Ga2O5 and Sr5Ga6O14

    International Nuclear Information System (INIS)

    Kahlenberg, Volker; Goettgens, Valerie; Mair, Philipp; Schmidmair, Daniela

    2015-01-01

    High-pressure synthesis experiments in a piston–cylinder apparatus at 1.5 GPa/3.0 GPa and 1000 °C resulted in the formation of single-crystals of Sr 2 Ga 2 O 5 and Sr 5 Ga 6 O 14 , respectively. The structures of both compounds have been solved from single-crystal diffraction data sets using direct methods. The first compound is orthorhombic with space group type Pbca (a=10.0021(4) Å, b=9.601(4) Å, c=10.6700(4) Å, V=1024.6(4) Å 3 , M r =394.68 u, Z=8, D x =5.12 g/cm 3 ) and belongs to the group of single layer gallates. Individual sheets are parallel to (0 0 1) and can be built from the condensation of unbranched vierer single chains running along [0 1 0]. The layers are characterized by the presence of four- and strongly elliptical eight-membered rings of corner connected tetrahedra in UUDD and UUUUDDDD conformation. Strontium atoms are sandwiched between the tetrahedral layers for charge compensation and are coordinated by six and seven oxygen ligands, respectively. Sr 2 Ga 2 O 5 is isotypic with several other double sulfides and selenides. To the best of our knowledge, it is the first example of an oxide with this structure type. From a structural point of view, Sr 5 Ga 6 O 14 is a phyllogallate as well. The crystal structure adopts the monoclinic space group P2 1 /c (a=8.1426(3) Å, b=8.1803(3) Å, c=10.8755(4) Å, β=91.970(4)° V=723.98(5) Å 3 , M r =1080.42 u, Z=2, D x =4.96 g/cm 3 ). Individual sheets extend along (0 0 1). Basic building units are unbranched dreier single chains parallel to [1 0 0]. The layers contain tertiary (Q 3 ) und quaternary (Q 4 ) connected [GaO 4 ]-tetrahedra in the ratio 2:1 resulting in a Ga:O ratio of 3:7 and the formation of exclusively five-membered rings. Linkage between adjacent tetrahedral sheets is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. The layers in Sr 5 Ga 6 O 14 are similar to those observed in the melilite structure-type. Crystallochemical

  20. The MgSeO4-UO2SeO4-H2O system at 25 deg C

    International Nuclear Information System (INIS)

    Serezhkina, L.B.; Serezhkin, V.N.

    1984-01-01

    The method of isothermal solubility at 25 deg C has been used to study MgSeO 4 -UO 2 SeO 4 -H 2 O system. Formation of the new compound Mg 2 (UO 2 ) 3 (SeO 4 ) 5 X32H 2 O, congruently soluble in water is stated. Thermographic and X-ray diffraction investigations of the prepared magnesium selenato-uranylate and products of its dehydration are conducted

  1. Hydrogenation of carbon monoxide on Co/MgAl2O4 and Ce-Co/MgAl2O4 catalysts

    International Nuclear Information System (INIS)

    Kondoh, S.; Muraki, H.; Fujitani

    1986-01-01

    It is well known that various hydrocarbons are obtained by hydrogenation of CO on Fischer-Tropsch catalysts, the products depending on the catalyst components such as Co, Ni, Fe and Ru: and the reaction conditions, particularly, temperature, pressure, space velocity and H 2 /CO ratio. Further, both reactivity and selectivity of catalysts may be improved by suitable selection of support and an additive. The main program of the present work is to develop a catalyst for producing C 5 + liquid hydrocarbons, as an automobile fuel, by the Fischer-Tropsch synthesis. The authors have studied unique CO catalyst systems consisting of various supports - such as Al 2 O 3 (γ, β, α), MgAl 2 O 4 (alumina magnesia spinel), MgO and additives selected from the lanthanoid elements (LE). The composition of spinel-based supports was altered in a range from 28 mol % excess Al 2 O 3 to 28 mol % excess MgO. Particularly, they found that a MgAl 2 O 4 support with 15-18 mol % excess Al 2 O 3 is the most preferable for our purpose and CeO 2 as the additive for Co/spinel catalyst remarkably improves C 5 + yield. Further, it was confirmed that the catalytic activity of Co-base catalysts agree with the oxidation state of Co-oxides on Co and Co-Ce/spinel catalysts. The performance of Co-based catalysts for the production of higher hydrocarbons from syn-gas were described elsewhere. The items described in this report include (a) selection of supports, (b) selection of optimum reaction conditions for Co-Ce/spinel catalyst, (c) redox characteristics of Co-oxides on a spinel surface, and (d) experimental observation of TPD profiles, adsorption capacities and IR spectra relating to adsorbed CO

  2. Complexing in (NH4)2SeO4-UO2SeO4 H2O system

    International Nuclear Information System (INIS)

    Serezhkina, L.B.

    1994-01-01

    Isotherm of solubility in the (NH 4 ) 2 SeO 4 -UO 2 SeO 4 -H 2 O system has been constructed at 25 deg C. (NH 4 ) 2 (UO 2 ) 2 (SeO 4 ) 3 x6H 2 O formation is established for the first time and certain its physicochemical properties are determined. Regularities of complexing in the R 2 Se) 4 -UO 2 SeO 4 -H 2 O systems, where R-univalent cation are under discussion. 6 refs.; 3 tabs

  3. Cu"+ luminescence in Na_2Sr_2Al_2PO_4Cl_9 halophosphate phosphor

    International Nuclear Information System (INIS)

    Yerpude, Vrushali; Dhoble, S.J.; Ghormare, K.B.

    2016-01-01

    This article reports the luminescence of copper doped halophosphate Na_2Sr_2Al_2PO_4Cl_9. The phosphor was synthesized by wet chemical method by varying Cu concentrations as 0.02, 0.05, 0.1, 0.2 and 0.5 mole %.The material was further dried in the oven at 80 °C with subsequent quenching at 200°C. Photoluminescence (PL) properties were studied with Shimadzu RF-5301 PC Spectroflurophotometer. PL excitation spectra of monitored at 439 nm emission wavelength, shows a prominent peak around 381 nm from the ground state electronic configuration 3d"1"0.The PL emission spectra of the phosphor monitored at 381 nm excitation wavelength in the blue region shows a broadband band around 412 nm with a shoulder peak at 440 nm, corresponding to the 3d"1"0 ↔ 3d"94s transitions of copper, which are strictly forbidden for the free ion but become partially allowed in crystals or glasses by coupling with lattice vibrations of odd parity resulting in broad excitation and emission bands. The luminescence intensity is found to increase progressively with the doping concentrations of activator and the maximum intensity is observed for 0.1 mole %. The PL spectra is found to be the same for all concentrations with difference only in the intensity. The excited states energies and the Stokes shift are reported to be very sensitive to the size and the symmetry of the copper site, leading to strong modulations of the spectral distribution, depending on the nature of the material. (author)

  4. Monte Carlo simulations for the space radiation superconducting shield project (SR2S).

    Science.gov (United States)

    Vuolo, M; Giraudo, M; Musenich, R; Calvelli, V; Ambroglini, F; Burger, W J; Battiston, R

    2016-02-01

    Astronauts on deep-space long-duration missions will be exposed for long time to galactic cosmic rays (GCR) and Solar Particle Events (SPE). The exposure to space radiation could lead to both acute and late effects in the crew members and well defined countermeasures do not exist nowadays. The simplest solution given by optimized passive shielding is not able to reduce the dose deposited by GCRs below the actual dose limits, therefore other solutions, such as active shielding employing superconducting magnetic fields, are under study. In the framework of the EU FP7 SR2S Project - Space Radiation Superconducting Shield--a toroidal magnetic system based on MgB2 superconductors has been analyzed through detailed Monte Carlo simulations using Geant4 interface GRAS. Spacecraft and magnets were modeled together with a simplified mechanical structure supporting the coils. Radiation transport through magnetic fields and materials was simulated for a deep-space mission scenario, considering for the first time the effect of secondary particles produced in the passage of space radiation through the active shielding and spacecraft structures. When modeling the structures supporting the active shielding systems and the habitat, the radiation protection efficiency of the magnetic field is severely decreasing compared to the one reported in previous studies, when only the magnetic field was modeled around the crew. This is due to the large production of secondary radiation taking place in the material surrounding the habitat. Copyright © 2016 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.

  5. Magnetic properties of nanostructured CuFe2O4

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Goya, G.F.; Rechenberg, H.R.

    1999-01-01

    The structural evolution and magnetic properties of nanostructured copper ferrite, CuFe2O4, have been investigated by X-ray diffraction, Mossbauer spectroscopy, and magnetization measurements. Nanometre-sized CuFe2O4 particles with a partially inverted spinel structure were synthesized by high...

  6. Inner-shell photodetachment from Ru-

    International Nuclear Information System (INIS)

    Dumitriu, I.; Gorczyca, T. W.; Berrah, N.; Bilodeau, R. C.; Pesic, Z. D.; Rolles, D.; Walter, C. W.; Gibson, N. D.

    2010-01-01

    Inner-shell photodetachment from Ru - was studied near and above the 4p excitation region, 29-to-91-eV photon energy range, using a merged ion-photon-beam technique. The absolute photodetachment cross sections of Ru - ([Kr]4d 7 5s 2 ) leading to Ru + , Ru 2+ , and Ru 3+ ion production were measured. In the near-threshold region, a Wigner s-wave law, including estimated postcollision interaction effects, locates the 4p 3/2 detachment threshold between 40.10 and 40.27 eV. Additionally, the Ru 2+ product spectrum provides evidence for simultaneous two-electron photodetachment (likely to the Ru + 4p 5 4d 6 5s 2 state) located near 49 eV. Resonance effects are observed due to interference between transitions of the 4p electrons to the quasibound 4p 5 4d 8 5s 2 states and the 4d→εf continuum. Despite the large number of possible terms resulting from the Ru - 4d open shell, the cross section obtained from a 51-state LS-coupled R-matrix calculation agrees qualitatively well with the experimental data.

  7. Formation of graphene on Ru(0001) surface

    Institute of Scientific and Technical Information of China (English)

    Pan Yi; Shi Dong-Xia; Gao Hong-Jun

    2007-01-01

    We report on the formation of a graphene monolayer on a Ru(0001) surface by annealing the Ru(0001) crystal.The samples are characterized by scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES). STM images show that the Moiré pattern is caused by the graphene layer mismatched with the underlying Ru(0001) surface and has an N × N superlattice. It is further found that the graphene monolayer on a Ru(0001) surface is very stable at high temperatures. Our results provide a simple and convenient method to produce a graphene monolayer on the Ru(0001) surface, which is used as a template for fabricating functional nanostructures needed in future nano devices and catalysis.

  8. Density Functional Study of Structures and Electron Affinities of BrO4F/BrO4F-

    Directory of Open Access Journals (Sweden)

    Wei Li

    2009-07-01

    Full Text Available The structures, electron affinities and bond dissociation energies of BrO4F/BrO4F− species have been investigated with five density functional theory (DFT methods with DZP++ basis sets. The planar F-Br…O2…O2 complexes possess 3A' electronic state for neutral molecule and 4A' state for the corresponding anion. Three types of the neutral-anion energy separations are the adiabatic electron affinity (EAad, the vertical electron affinity (EAvert, and the vertical detachment energy (VDE. The EAad value predicted by B3LYP method is 4.52 eV. The bond dissociation energies De (BrO4F → BrO4-mF + Om (m = 1-4 and De- (BrO4F- → BrO4-mF- + Om and BrO4F- → BrO4-mF + Om- are predicted. The adiabatic electron affinities (EAad were predicted to be 4.52 eV for F-Br…O2…O2 (3A'← 4A' (B3LYP method.

  9. Cs2SeO4-UO2SeO4-H2O system at 25 deg C

    International Nuclear Information System (INIS)

    Serezhkina, L.B.; Serezhkin, V.N.

    1987-01-01

    Using the method of isothermal solubility at 25 deg C the interaction of cesium and uranyl selenates in aqueous solution is studied. Formation of congruently soluble Cs 2 UO 2 (SeO 4 ) 2 x2H 2 O and Cs 2 (UO 2 ) 2 x(SeO 4 ) 3 is ascertained, their crystallographic characteristics being determined

  10. Electron tunneling and the energy gap in Bi2Sr2CaCu2O/sub x/

    International Nuclear Information System (INIS)

    Lee, M.; Mitzi, D.B.; Kapitulnik, A.; Beasley, M.R.

    1989-01-01

    Results of electron tunneling on single crystals of the Bi 2 Sr 2 CaCu 2 O/sub x/ superconductor are reported. The junctions show a gap structure with Δ≅25 meV, whose temperature dependence exhibits a qualitatively Bardeen-Cooper-Schrieffer-like behavior with a gap-closing T/sub c/≅81--85 K. Comparisons of these tunneling spectra to those obtained on YBa 2 Cu 3 O/sub 7-//sub x/ are made. Evidence that 2Δ/kT/sub c/∼7 for both Ba 2 Sr 2 CaCu 2 O/sub x/ and YBa 2 Cu 3 O/sub 7-//sub x/ is also discussed

  11. Nanometre-sized inhomogeneity in high-Jc Bi2Sr2CaCu2O8+δ superconductors

    International Nuclear Information System (INIS)

    Nishiyama, M; Kinoda, G; Zhao, Y; Hasegawa, T; Itoh, Y; Koshizuka, N; Murakami, M

    2004-01-01

    We have performed atomic-scale high-resolution scanning tunnelling microscopy and spectroscopy measurements on the cleaved surface of single crystal Bi 2 Sr 2 CaCuO 8+δ superconductors with high critical current density J c . The samples exhibited rugged structure about 15 nm in period, larger than the modulation of the BiO layer, which corresponded well to the energy gap distribution at 77 K. The presence of inhomogeneity from a nanometre to a micrometre scale, in the energy gap distribution, the structural modulation and the chemical composition fluctuation, may play an important role in improving J c values in the Bi 2 Sr 2 CaCuO 8+δ crystals

  12. Edge-shape barrier irreversibility and decomposition of vortices in Bi 2Sr 2CaCu 2O 8

    Science.gov (United States)

    Indenbom, M. V.; D'Anna, G.; André, M.-O.; Kabanov, V. V.; Benoit, W.

    1994-12-01

    Magnetic flux dynamics is studied in Bi 2Sr 2CaCu 2O 8 single crystals by means of magneto-optical technique. It is clearly demonstrated that the magnetic irreversibility of these crystals in a magnetic field perpendicular to the basal plane at temperatures higher than approximately 35 K is governed by an edge-shape barrier and its disappearance determines the high temperature part of the magnetic irreversibility line which is commonly associated in the literature with vortex lattice melting. We argue that this barrier exists because of the non ellipsoidal shape of the samples and can disappear only when the flux lines lose their rigidity decomposing into pancakes, which is the only true magnetic phase transition on the B-T diagram for Bi 2Sr 2CaCu 2O 8.

  13. Melt processing of the Bi2Sr2CaCu2Oy superconductor in oxygen and argon atmospheres

    International Nuclear Information System (INIS)

    Holesinger, T.G.; Miller, D.J.; Chumbley, L.S.

    1992-08-01

    Solidification and subsequent annealing of Bi 2 Sr 2 CaCu 2 O y (2212) in oxygen and argon atmospheres were investigated in order to identify alternative processing routes for controlling microstructures and superconducting properties. In addition to 2212, several other phases formed on cooling in O 2 and did not disappear upon subsequent annealing. Crystallization in Ar resulted in a divorced eutetic structure of Bi 2 Sr 3-x Ca x O y and Cu 2 O/CuO. The superconductor was formed on subsequent anneals. Samples melted in Ar and then annealed generally possessed a more uniform microstructure compared with samples that were melted in oxygen and annealed. Compositional measurements of the 2212 phase suggest that CaO segregation in the melt may be minimized with an overall composition such as Bi 2.15 Sr 2 Ca 0.85 Cu 2 O y

  14. Growth and superconducting properties of Bi2Sr2Ca2Cu3O10 single crystals

    International Nuclear Information System (INIS)

    Clayton, N; Musolino, N; Giannini, E; Garnier, V; Fluekiger, R

    2004-01-01

    Single crystals of Bi 2 Sr 2 Ca 2 Cu 3 O 10 (Bi-2223) have been grown using the travelling solvent floating zone technique in an image furnace. Annealing the crystals under high pressures of O 2 increased their critical temperature to 109 K, and resulted in sharp superconducting transitions of ΔT c = 1 K. The superconducting anisotropy of Bi-2223 was found to be ∼ 50, from measurements of the lower critical field with the magnetic field applied parallel and perpendicular to the c-axis. The anisotropy of Bi-2223 is significantly reduced compared to that of Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212), and this accounts for the enhanced irreversibility fields in Bi-2223. Furthermore, Bi-2223 has a higher critical current density, and a reduced magnetic relaxation rate compared to Bi-2212, which are both signatures of more effective pinning in Bi-2223 due to its reduced anisotropy

  15. Acetate reduction synthesis of Sr2Si5N8:Eu2+ phosphor and its luminescence properties

    International Nuclear Information System (INIS)

    Piao Xianqing; Machida, Ken-ichi; Horikawa, Takashi; Yun Bonggoo

    2010-01-01

    A novel synthesis method was developed for the efficient red phosphor, Eu 2+ -activated Sr 2 Si 5 N 8 , by employing the strontium acetate as both the reducing agent and strontium source. The phase purity of final product was strongly dependent on the heating rate of the precursors. Sr 2 Si 5 N 8 :Eu 2+ (2 at%) phosphor presented a broadband excitation spectrum in the range 300-500 nm, matching well with the blue emission (400/460 nm) of current InGaN light-emitting diodes (LEDs). The red emission peaking at 619 nm gave the relatively high (about 155%) intensity compared with the Y 3 Al 5 O 12 (YAG) (P46-Y3) standard phosphor. In addition, the saturated chromatic coordinates (0.638, 0.359) allowed it a promising candidate as a red phosphor in white LEDs application for illumination or display.

  16. Growth and properties of oxygen doped Bi2Sr2CaCu2O8+δ single crystals

    International Nuclear Information System (INIS)

    Kapitulnik, A.; Mitzi, D.B.

    1990-01-01

    This paper reports results on oxygen doped single crystals in the Bi 2 Sr 2 CaCu 2 O 8+δ system grown by a directional solidification method. Annealing of as made crystals in increasing partial pressure of oxygen reversibly depresses the superconducting transition temperature from 90K (as made) to 77K (oxygen pressure annealed). Magnetic and photoemission properties of these crystals will be discussed

  17. Effect of Pb and Ag additions on electrical properties Bi2Sr2Ca2Cu3Ox superconductive ceramics

    International Nuclear Information System (INIS)

    Reddi, B.V.; Uskov, E.M.

    1990-01-01

    The influence of Pb and Ag additions on the electrical properties of Bi 2 Sr 2 Ca 2 Cu 3 O x superconducting ceramics has been studied by Hall method. It was found that the Pb additions has more influence on the sample characteristics than Ag. It was found, that Hall EMF at 77 K equal to zero in the samples having some residue resistance

  18. Pb solubility of the high-temperature superconducting phase Bi2Sr2Ca2Cu3O10+d

    International Nuclear Information System (INIS)

    Kaesche, S.; Majewski, P.; Aldinger, F.

    1994-01-01

    For the nominal composition of Bi 2.27x Pb x Sr 2 Ca 2 Cu 3 O 10+d the lead content was varied from x=0.05 to 0.45. The compositions were examined between 830 degrees C and 890 degrees C which is supposed to be the temperature range over which the so-called 2223 phase (Bi 2 Sr 2 Ca 2 Cu 3 O 10+d ) is stable. Only compositions between x=0.18 to 0.36 could be synthesized in a single phase state. For x>0.36 a lead containing phase with a stoichiometry of Pb 4 (Sr,Ca) 5 CuO d is formed, for x 2 Sr 2 CaCu 2 O 8+d and cuprates are the equilibrium phases. The temperature range for the 2223 phase was found to be 830 degrees C to 890 degrees C but the 2223 phase has extremely varying cation ratios over this temperature range. Former single phase 2223 samples turn to multi phase samples when annealed at slightly higher or lower temperatures. A decrease in the Pb solubility with increasing temperature was found for the 2223 phase

  19. Preparation and Photocatalytic Properties of Sr2−xBaxTa3O10−yNz Nanosheets

    Directory of Open Access Journals (Sweden)

    Tatsumi Ishihara

    2013-01-01

    Full Text Available Sr2−xBaxTa3O10−yNz (x = 0.0, 0.5, 1.0 nanosheets were prepared by exfoliating layered perovskite compounds (CsSr2−xBaxTa3O10−yNz. The Sr1.5Ba0.5Ta3O9.7N0.2 nanosheet showed the highest photocatalytic activity for H2 production from the water/methanol system among the Sr2−xBaxTa3O9.7N0.2 nanosheets prepared. In addition, Rh-loaded Sr1.5Ba0.5Ta3O9.6N0.3 nanosheet showed the photocatalytic activity for oxygen and hydrogen production from water. The ratio of hydrogen to oxygen evolved was around two. These results indicate that the Rh-loaded Sr1.5Ba0.5Ta3O9.6N0.3 nanosheet is a potential catalyst for photocatalytic water splitting.

  20. STRUCTURAL, MAGNETIC, MULTIFERROIC, AND ELECTRONIC PROPERTIES OF SR2 TIMNO6 DOUBLE PEROVSKITE

    Directory of Open Access Journals (Sweden)

    DAVID LANDÍNEZ-TÉLLEZ

    2012-01-01

    Full Text Available En este trabajo reportamos el análisis estructural, ordenamiento magnético, carácter ferroeléctrico y estructura electrónica de la perovskite compleja Sr2TiMnO6. Las muestras fueron producidas mediante reacción de estado sólido. El análisis cristalográfico fue realizado a través de refinamiento Rietveld de los patrones experimentales de rayos x. Los resultados muestran que este material cristaliza en una perovskita tetragonal correspondiente al grupo espacial I4/mmm. Hemos obtenido un acuerdo del 99% entre las propiedades estructurales predichas por la teoría del funcional de la densidad y el ordenamiento estructural determinado mediante refinamiento Rietveld. A través de medidas de susceptibilidad en función de la temperatura encontramos ordenamiento magnético para una temperatura crítica de 44.8 K. Por medio del ajuste con la teoría molecular de ferrimagnetismo establecimos que el ordenamiento magnético se relaciona con una transición paramagnético-ferrimagnético, la cual se corrobora por el comportamiento del inverso de la susceptibilidad en función de la temperatura. La constante de Curie permitió determinar un momento magnético efectivo de 3.5 mB. Medidas de magnetización en función del campo aplicado a T = 40 K, muestra un comportamiento histerético. La curva de polarización en función del campo eléctrico evidencia una característica ferroeléctrica. Experimentalmente se demuestra que el material se comporta como un multiferróico. Cálculos Ab initio de la densidad de estados fueron realizados por medio de la teoría de funcional densidad y del método ondas planas aumentadas linealizadas para orientaciones de espín arriba y abajo. Los cálculos de intercambio y potencial de correlación fueron incluidos a través de la aproximación de densidad local LDA+U. Los resultados de la densidad de estados muestran la característica aislante de este material con un momento magnético efectivo de 3.3mB.

  1. Fabrication of shape controlled Fe3O4 nanostructure

    International Nuclear Information System (INIS)

    Zheng, Y.Y.; Wang, X.B.; Shang, L.; Li, C.R.; Cui, C.; Dong, W.J.; Tang, W.H.; Chen, B.Y.

    2010-01-01

    Shape-controlled Fe 3 O 4 nanostructure has been successfully prepared using polyethylene glycol as template in a water system at room temperature. Different morphologies of Fe 3 O 4 nanostructures, including spherical, cubic, rod-like, and dendritic nanostructure, were obtained by carefully controlling the concentration of the Fe 3+ , Fe 2+ , and the molecular weight of the polyethylene glycol. Transmission Electron Microscope images, X-ray powder diffraction patterns and magnetic properties were used to characterize the final product. This easy procedure for Fe 3 O 4 nanostructure fabrication offers the possibility of a generalized approach to the production of single and complex nanocrystalline oxide with tunable morphology.

  2. Synthesis and magnetic properties of carbon-coated FeRu, CoRu, and NiRu nanoalloys

    Energy Technology Data Exchange (ETDEWEB)

    El-Gendy, A.A.; Khavrus, V.O.; Hampel, S.; Leonhardt, A.; Klingeler, R.; Buechner, B. [Leibniz Institute for Solid State and Materials Research (IFW) Dresden (Germany)

    2010-07-01

    Carbon coated FeRu, CoRu and NiRu nanoalloys have been synthesised by high pressure chemical vapour deposition (HPCVD). The formation of the core-shell nanoalloys with a mean diameter around 8 nm has been confirmed by means of high resolution transmission electron microscopy imaging (HRTEM), energy dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD). We show the effect of the synthesis parameters on the actual composition of the nanoalloys and on their magnetic properties and we discuss their feasibility for applications in medical hyperthermia.

  3. Novel Electronic Structures of Ru-pnictides RuPn (Pn = P, As, Sb)

    Science.gov (United States)

    Goto, H.; Toriyama, T.; Konishi, T.; Ohta, Y.

    Density-functional-theory-based electronic structure calculations are made to consider the novel electronic states of Ru-pnictides RuP and RuAs where the intriguing phase transitions and superconductivity under doping of Rh have been reported. We find that there appear nearly degenerate flat bands just at the Fermi level in the high-temperature metallic phase of RuP and RuAs; the flat-band states come mainly from the 4dxy orbitals of Ru ions and the Rh doping shifts the Fermi level just above the flat bands. The splitting of the flat bands caused by their electronic instability may then be responsible for the observed phase transition to the nonmagnetic insulating phase at low temperatures. We also find that the band structure calculated for RuSb resembles that of the doped RuP and RuAs, which is consistent with experiment where superconductivity occurs in RuSb without Rh doping.

  4. Aqueous partial molar heat capacities and volumes for NaReO4 and NaTcO4

    International Nuclear Information System (INIS)

    Lemire, R.J.; Saluja, P.P.S.; Campbell, A.B.

    1989-01-01

    As part of the Canadian Nuclear Fuel Waste Management Program, data are required to model the equilibrium thermodynamic behavior of key radionuclides at temperatures above 25 degree C. A flow microcalorimeter/densimeter system has been commissioned to measure heat capacities and densities of solutions containing radioactive species. Measurements for solutions of aqueous NaReO 4 (a common analogue for NaTcO 4 ) were made at seven temperatures (15 to 100 degree C) over the concentration range 0.05 to 0.2 mol·kg -1 . Subsequently, measurements were made for NaTcO 4 solutions under similar conditions. The heat capacity and density data are analyzed using Pitzer's ion-interaction model, and values of the NaReO 4 partial molar heat capacities are compared to literature values based on integral heats of solution. The agreement between the two sets of NaReO 4 data is good below 75 degree C, but only fair at the higher temperatures. Values of the partial molar volumes have also been derived. The uncertainties introduced by using thermodynamic data for ReO 4 - , in the absence of data for TcO 4 - , are discussed

  5. High Q ceramics in the ACe2(MoO4)4 (A = Ba, Sr and Ca) system for LTCC applications

    International Nuclear Information System (INIS)

    Surjith, A.; Ratheesh, R.

    2013-01-01

    Highlights: ► Solid state synthesis of phase pure ACe 2 (MoO 4 ) 4 (A = Ba, Sr and Ca) ceramics. ► Structural and microstructural evaluation of the synthesized ceramic materials. ► Microwave dielectric property studies of ACe 2 (MoO 4 ) 4 (A = Ba, Sr and Ca) ceramics. ► Structure-property correlation through Laser Raman studies. - Abstract: Novel low temperature sinterable high Q ceramic systems ACe 2 (MoO 4 ) 4 (A = Ba, Sr and Ca) have been prepared through solid state ceramic method. The effect of ionic radii of alkaline earth cations on the structure, microstructure and microwave dielectric properties of these ceramics were studied using powder X-ray diffraction, Laser Raman spectroscopy, scanning electron microscopy and Vector Network Analyzer. A structural change from monoclinic to tetragonal structure was observed while substituting Sr 2+ and Ca 2+ cations in place of Ba 2+ . The Sr and Ca analogues possess better microwave dielectric properties compared to BaCe 2 (MoO 4 ) 4 . All the ceramics were well sintered below 840 °C with dielectric constant in the range 10.2–12.3 together with good quality factor. The SrCe 2 (MoO 4 ) 4 ceramic exhibits an unloaded quality factor of 6762 at 8.080662 GHz with a temperature coefficient of resonant frequency of −46 ppm/°C while the CaCe 2 (MoO 4 ) 4 ceramic shows an unloaded quality factor of 7549 at 6.928868 GHz and a temperature coefficient of resonant frequency of −44 ppm/°C.

  6. Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

    Science.gov (United States)

    Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

    2017-10-01

    We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

  7. Phase equilibrium in Rb2MoO4-AMoO4-Zr(MOO4)2 systems (A - bivalent elements)

    International Nuclear Information System (INIS)

    Ivanova, M.N.; Tsyrenova, G.D.; Bazarova, Zh.G.

    1993-01-01

    The Rb 2 MoO 4 -AMoO 4 -Zr(MoO 4 ) 2 systems, where A - bivalent elements, were investigated by solid phase reactions, x-ray and differntial thermal analysis methods. Formation of new ternary molybdates was determined. Phase relationships in the Rb 2 MoO 4 -MnMoO 4 -Zr(MoO 4 ) 2 system in subsolidus range (550 deg C) were studied using x-ray analysis data

  8. Flotation-spectrophotometric determination of ruthenium in the Ru(IV)-chloride-rhodamine 6G-toluene system

    International Nuclear Information System (INIS)

    Balcerzak, M.

    1985-01-01

    The reduction of RuO 4 in hydrochloric acid has been examined. A sensitive flotation-spectrophotometric method of the determination of ruthenium based on the ion associate formed by the anionic chlorid complex of ruthenium RuCl 2- 6 with the basic dye Rhodamine 6G (R6G) has been developed. The solution of the ion associate obeys Beer's law up to the concentration of 0.25 μg Ru/ml. The ion associate precipitates when the aqueous solution is shaken with toluene. The separated compound is dissolved in acetone. The molar absorptivity (epsilon) at 530 nm is 5.1 x 10 5 l x mole -1 x cm -1 . The relative standard deviation is 3-7%. The mole ratio of Ru:R6G in the complex is 1:5. Osmium reacts similarly. The determination of ruthenium can be selective after the preliminary separation of osmium as OsO 4 . The method was applied to the determination of microgram amounts of ruthenium in crucible platinum. (Author)

  9. Magnetic behavior of biosynthesized Co_3O_4 nanoparticles

    International Nuclear Information System (INIS)

    Diallo, A.; Doyle, T.B.; Mothudi, B.M.; Manikandan, E.

    2017-01-01

    This contribution reports for the 1st time on the magnetic behavior of CO_3O_4 nanoparticles synthesized by a “green” process using an Aspalathus linearis’ leaves natural extract. More accurately magnetic behavior of CO_3O_4 nanoparticles successfully biosynthesized was investigated using vibrating sample magnetometer. The magnetization behavior for the samples manifests a combination of size dependent antiferromagnetic and paramagnetic behaviors, respectively, for the core and shell of the nanoparticles. - Highlights: • 1"s"t report on magnetic behavior of Co3O4 nanoparticles via Aspalathus linearis. • Co_3O_4 nanoparticles manifest size-dependent antiferromagnetic & paramagnetic behaviors. • Antiferromagnetic & paramagnetic behaviors were confirmed by VSM.

  10. Experimental heat capacities, excess entropies, and magnetic properties of bulk and nano Fe3O4-Co3O4 and Fe3O4-Mn3O4 spinel solid solutions

    Science.gov (United States)

    Schliesser, Jacob M.; Huang, Baiyu; Sahu, Sulata K.; Asplund, Megan; Navrotsky, Alexandra; Woodfield, Brian F.

    2018-03-01

    We have measured the heat capacities of several well-characterized bulk and nanophase Fe3O4-Co3O4 and Fe3O4-Mn3O4 spinel solid solution samples from which magnetic properties of transitions and third-law entropies have been determined. The magnetic transitions show several features common to effects of particle and magnetic domain sizes. From the standard molar entropies, excess entropies of mixing have been generated for these solid solutions and compared with configurational entropies determined previously by assuming appropriate cation and valence distributions. The vibrational and magnetic excess entropies for bulk materials are comparable in magnitude to the respective configurational entropies indicating that excess entropies of mixing must be included when analyzing entropies of mixing. The excess entropies for nanophase materials are even larger than the configurational entropies. Changes in valence, cation distribution, bonding and microstructure between the mixing ions are the likely sources of the positive excess entropies of mixing.

  11. Sign system choice influence on the substance formation forecast in A2MoO4-B2(MoO4)3 and A2MoO4-CMoO4 systems

    International Nuclear Information System (INIS)

    Manzanov, Yu.E.; Lutsik, V.I.; Mokhosoev, M.V.

    1987-01-01

    Three sign spaces were used for forecasting compound formation in A 2 MoO 4 -B 2 (MoO 4 ) 3 (5:1 ratio, where A-Li, Na, K, Rb, Cs; B-Al, In, Ga, Sc, Cr, Fe, Bi, La, Nd, Sm-Lu, Y) and A 2 MoO 4 -CMoO 4 (1:2 ratio, where A-Li, Na, K, RB, Cs, Tl; C-Mg, Ca, Sr, Ba, Cu, Zn, Cd, Pd, Mn, Co, Ni) systems: 1-electron distribution on energy shells of cations and their valency; 2-the type of incomplete electron shell, charge of cations, three first ionization potentials, standard heat capacity, ionic radius of cations; 3-standard formation enthalpy and standard entropy, oxide melting points and ionic radius of cations. It is shown that sign space, related with thermodynamic properties of oxides contains data, necessary for forecasting interaction in molybdate systems. This enables to improve reliability of forecasting

  12. Defect kinetics in spinels: Long-time simulations of MgAl2O4, MgGa2O4, and MgIn2O4

    International Nuclear Information System (INIS)

    Uberuaga, B. P.; Voter, A. F.; Sickafus, K. E.; Bacorisen, D.; Smith, Roger; Ball, J. A.; Grimes, R. W.

    2007-01-01

    Building upon work in which we examined defect production and stability in spinels, we now turn to defect kinetics. Using temperature accelerated dynamics (TAD), we characterize the kinetics of defects in three spinel oxides: magnesium aluminate MgAl 2 O 4 , magnesium gallate MgGa 2 O 4 , and magnesium indate MgIn 2 O 4 . These materials have varying tendencies to disorder on the cation sublattices. In order to understand chemical composition effects, we first examine defect kinetics in perfectly ordered, or normal, spinels, focusing on point defects on each sublattice. We then examine the role that cation disorder has on defect mobility. Using TAD, we find that disorder creates local environments which strongly trap point defects, effectively reducing their mobility. We explore the consequences of this trapping via kinetic Monte Carlo (KMC) simulations on the oxygen vacancy (V O ) in MgGa 2 O 4 , finding that V O mobility is directly related to the degree of inversion in the system

  13. High-Pressure Phase Relations and Crystal Structures of Postspinel Phases in MgV2O4, FeV2O4, and MnCr2O4: Crystal Chemistry of AB2O4 Postspinel Compounds.

    Science.gov (United States)

    Ishii, Takayuki; Sakai, Tsubasa; Kojitani, Hiroshi; Mori, Daisuke; Inaguma, Yoshiyuki; Matsushita, Yoshitaka; Yamaura, Kazunari; Akaogi, Masaki

    2018-06-04

    We have investigated high-pressure, high-temperature phase transitions of spinel (Sp)-type MgV 2 O 4 , FeV 2 O 4 , and MnCr 2 O 4 . At 1200-1800 °C, MgV 2 O 4 Sp decomposes at 4-7 GPa into a phase assemblage of MgO periclase + corundum (Cor)-type V 2 O 3 , and they react at 10-15 GPa to form a phase with a calcium titanite (CT)-type structure. FeV 2 O 4 Sp transforms to CT-type FeV 2 O 4 at 12 GPa via decomposition phases of FeO wüstite + Cor-type V 2 O 3 . MnCr 2 O 4 Sp directly transforms to the calcium ferrite (CF)-structured phase at 10 GPa and 1000-1400 °C. Rietveld refinements of CT-type MgV 2 O 4 and FeV 2 O 4 and CF-type MnCr 2 O 4 confirm that both the CT- and CF-type structures have frameworks formed by double chains of edge-shared B 3+ O 6 octahedra (B 3+ = V 3+ and Cr 3+ ) running parallel to one of orthorhombic cell axes. A relatively large A 2+ cation (A 2+ = Mg 2+ , Fe 2+ , and Mn 2+ ) occupies a tunnel-shaped space formed by corner-sharing of four double chains. Effective coordination numbers calculated from eight neighboring oxygen-A 2+ cation distances of CT-type MgV 2 O 4 and FeV 2 O 4 and CF-type MnCr 2 O 4 are 5.50, 5.16, and 7.52, respectively. This implies that the CT- and CF-type structures practically have trigonal prism (six-coordinated) and bicapped trigonal prism (eight-coordinated) sites for the A 2+ cations, respectively. A relationship between cation sizes of VIII A 2+ and VI B 3+ and crystal structures (CF- and CT-types) of A 2+ B 2 3+ O 4 is discussed using the above new data and available previous data of the postspinel phases. We found that CF-type A 2+ B 2 3+ O 4 crystallize in wide ionic radius ranges of 0.9-1.4 Å for VIII A 2+ and 0.55-1.1 Å for VI B 3+ , whereas CT-type phases crystallize in very narrow ionic radius ranges of ∼0.9 Å for VIII A 2+ and 0.6-0.65 Å for VI B 3+ . This would be attributed to the fact that the tunnel space of CT-type structure is geometrically less flexible due to the smaller coordination

  14. Thermodynamic assessment of the Al-Ru system

    CSIR Research Space (South Africa)

    Prins, SN

    2003-03-01

    Full Text Available describes the order disorder transformation with one Gibbs energy function. The RuAl6 phase was described as a stoichiometric phase and the remaining intermetallic phases (Ru4Al13, RuAl2 and Ru2Al3) were modelled with the sublattice model. The solubility...

  15. Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen.

    Science.gov (United States)

    Johnson, Grant E; Colby, Robert; Engelhard, Mark; Moon, Daewon; Laskin, Julia

    2015-08-07

    Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 × 10(4) ions μm(-2) and that their average height is centered at 4.5 nm. Scanning transmission electron microscopy images obtained in the high-angle annular dark field mode (HAADF-STEM) further confirm that the soft-landed PtRu nanoparticles are uniform in size. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in atomic concentrations of ∼9% and ∼33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt 4f and Ru 3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He(+) and O(+) ions. The activity of electrodes containing 7 × 10(4) ions μm(-2) of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the nanoparticles supported on glassy carbon. The reproducibility of the nanoparticle synthesis and deposition was

  16. Pseudogap behavior of RuP probed by photoemission spectroscopy

    OpenAIRE

    Sato, K.; Ootsuki, D.; Wakisaka, Y.; Saini, N. L.; Mizokawa, T.; Arita, M.; Anzai, H.; Namatame, H.; Taniguchi, M.; Hirai, D.; Takagi, H.

    2012-01-01

    We have studied the electronic structure of RuP and related Ru pnictides using photoemission spectroscopy. Ru 3d core-level and valence-band spectra of RuP show that the Ru valence is +3 with t_{2g}^5 configuration. The photoemisson spectral weight near the Fermi level is moderately suppressed in the pseudogap phase of RuP, consistent with the pseudogap opening of 2\\Delta/k_BT_c ~ 3 (gap size \\Delta ~ 50 meV and transition temperature T_c ~ 330 K). The Ru 3d peak remains sharp in the pseudoga...

  17. Magnetocapacidad en nanopartículas de Fe3O4 y NiFe2O4

    Directory of Open Access Journals (Sweden)

    Mira, J.

    2010-02-01

    Full Text Available We have synthesized NiFe2O4 (φ∼ 6 nm and Fe3O4 (φ∼ 30 nm magnetic nanoparticles by solvothermal synthesis; furthermore the Fe3O4 nanoparticles have been coated with a SiO2 shell of approximately 5 nm of thickness by the Stöber method. In the study of the dielectric properties as a function of the frequency, temperature and applied magnetic field, we observe a magnetocapacitive behavior (MC at room temperature and under a moderate magnetic field (H=0.5T, that is specially important in the case of the Fe3O4, nanoparticles (MC≈ 6%. On the other hand, the NiFe2O4 and Fe3O4@SiO2 samples present smaller magnetocapacitive effects: MC≈ 2% y MC≈ 1%, respectively. These MC values, that are higher than those reported in the literature for other related magnetic nanoparticles, corroborate the theoretical model proposed by Catalán in which the combination of Maxwell-Wagner effects and magnetoresistance promote the appearance of stronger magnetocapacitive effects.Hemos preparado nanopartículas magnéticas de NiFe2O4 (φ∼ 6 nm y Fe3O4 (φ∼ 30 nm mediante el método de síntesis solvotermal; además estas últimas han sido recubiertas con una capa de SiO2 de unos 5 nm de espesor mediante el método de Stöber. Al estudiar el comportamiento dieléctrico en función de la frecuencia, temperatura y campo magnético aplicado, observamos un comportamiento magnetocapacitivo (MC a temperatura ambiente y bajo un campo magnético moderado (H= 0.5 T que es especialmente importante en el caso de las nanopartículas de Fe3O4 (MC≈ 6%. Por su parte las muestras de NiFe2O4 y Fe3O4@SiO2 presentan efectos magnetocapacitivos menores: MC≈ 2% y MC≈ 1%, respectivamente. Estos valores de MC, que son considerablemente superiores a los descritos hasta el momento para otras nanopartículas magnéticas, corroboran la predicción teórica de Catalán de que la combinación de efecto Maxwell-Wagner con efectos magnetorresitivos potencian la aparición de fen

  18. Ternary system of Na2MoO4-Cs2MoO4-MoO3

    International Nuclear Information System (INIS)

    Zueva, V.P.; Shabanova, A.N.; Drobasheva, T.I.

    1982-01-01

    Using the methods of thermal analysis interaction of components in ternary system Na 2 MoO 4 -Cs 2 MoO 4 -MoO 3 has been studied. Crystallization surface consists of nine fields belonging to initial components and compounds of lateral sides. Triangulation of the system is carried out and the character of nonvariant points is clarified, the temperature of 360 deg C corresponds to low-melting eutectics

  19. Nanoscale decomposition of Nb-Ru-O

    Science.gov (United States)

    Music, Denis; Geyer, Richard W.; Chen, Yen-Ting

    2016-11-01

    A correlative theoretical and experimental methodology has been employed to explore the decomposition of amorphous Nb-Ru-O at elevated temperatures. Density functional theory based molecular dynamics simulations reveal that amorphous Nb-Ru-O is structurally modified within 10 ps at 800 K giving rise to an increase in the planar metal - oxygen and metal - metal population and hence formation of large clusters, which signifies atomic segregation. The driving force for this atomic segregation process is 0.5 eV/atom. This is validated by diffraction experiments and transmission electron microscopy of sputter-synthesized Nb-Ru-O thin films. Room temperature samples are amorphous, while at 800 K nanoscale rutile RuO2 grains, self-organized in an amorphous Nb-O matrix, are observed, which is consistent with our theoretical predictions. This amorphous/crystalline interplay may be of importance for next generation of thermoelectric devices.

  20. Facile fabrication of composited Mn_3O_4/Fe_3O_4 nanoflowers with high electrochemical performance as anode material for lithium ion batteries

    International Nuclear Information System (INIS)

    Zhao, Dianyun; Hao, Qin; Xu, Caixia

    2015-01-01

    Graphical abstract: Mn_3O_4/Fe_3O_4 nanoflowers are successfully prepared through one step dealloying of Mn_5Fe_5Al_9_0 alloy at room temperature. This hierarchical flower-like structure with consists of a packed array of uniform regular hexagon-like nanoslices. Combined with the specific hierarchical flower-like architecture and the synergistic effect exerted by Mn_3O_4 and Fe_3O_4, the nanocomposite exhibits enhanced performance as anode material for lithium ion batteries than pure Mn_3O_4 and Fe_3O_4 anode. - Highlights: • Mn_3O_4/Fe_3O_4 nanoflowers are easily prepared by one step dealloying method. • The nanoflowers consist of packed regular nanoslices with interconnected voids. • Mn_3O_4/Fe_3O_4 nanoflowers deliver higher discharge capacity than Mn_3O_4 and Fe_3O_4. • Mn_3O_4/Fe_3O_4 nanoflowers show lower initial irreversible loss than Mn_3O_4 anode. - Abstract: Mn_3O_4/Fe_3O_4 nanoflowers with controllable components are simply fabricated through one step etching of the Mn_5Fe_5Al_9_0 ternary alloy. The as-made hierarchical flower-like structure with interconnected voids consists of a packed array of uniform regular hexagon-like nanoslices. Based on the simple dealloying strategy the target metals are directly converted to uniform nanocomposite composed of Mn_3O_4 and Fe_3O_4 species. With the unique hierarchical flower-like structure and the synergistic effects between Mn_3O_4 and Fe_3O_4, the nanocomposite exhibits higher performance as anode material for lithium ion batteries than that of pure Mn_3O_4 and Fe_3O_4 anodes. The Mn_3O_4/Fe_3O_4 nanocomposite deliver much higher discharge capacity and lower initial irreversible loss than Mn_3O_4 anode. The Mn_3O_4/Fe_3O_4 anode material also shows an excellent cycling stability at the high rate of 1500 mA g"−"1 with outstanding rate capability. With the advantages of simple preparation and excellent electrochemical performance, Mn_3O_4/Fe_3O_4 nanoflowers manifest great application potential as

  1. Composition Screening in Blue-Emitting Li4Sr1+xCa0.97-x(SiO4)2:Ce3+ Phosphors for High Quantum Efficiency and Thermally Stable Photoluminescence.

    Science.gov (United States)

    Zhang, Jingchen; Zhang, Jilin; Zhou, Wenli; Ji, Xiaoyu; Ma, Wentao; Qiu, Zhongxian; Yu, Liping; Li, Chengzhi; Xia, Zhiguo; Wang, Zhengliang; Lian, Shixun

    2017-09-13

    Photoluminescence quantum efficiency (QE) and thermal stability are important for phosphors used in phosphor-converted light-emitting diodes (pc-LEDs). Li 4 Sr 1+x Ca 0.97-x (SiO 4 ) 2 :0.03Ce 3+ (-0.7 ≤ x ≤ 1.0) phosphors were designed from the initial model of Li 4 SrCa(SiO 4 ) 2 :Ce 3+ , and their single-phased crystal structures were found to be located in the composition range of -0.4 ≤ x ≤ 0.7. Depending on the substitution of Sr 2+ for Ca 2+ ions, the absolute QE value of blue-emitting composition-optimized Li 4 Sr 1.4 Ca 0.57 (SiO 4 ) 2 :0.03Ce 3+ reaches ∼94%, and the emission intensity at 200 °C remains 95% of that at room temperature. Rietveld refinements and Raman spectral analyses suggest the increase of crystal rigidity, increase of force constant in CeO 6 , and decrease of vibrational frequency by increasing Sr 2+ content, which are responsible for the enhanced quantum efficiency and thermal stability. The present study points to a new strategy for future development of the pc-LEDs phosphors based on local structures correlation via composition screening.

  2. Spatially resolved resistivity near the vortex lattice phase transition in Bi 2Sr 2CaCu 2O 8+δ single crystals

    Science.gov (United States)

    Berseth, V.; Indenbom, M. V.; van der Beek, C. J.; D'Anna, G.; Benoit, W.

    1997-08-01

    Using a multiterminal contact configuration, we investigate the local variations of the resistivity drop near the vortex lattice first order phase transition in a very homogeneous Bi2Sr2CaCu2O8+δ (BSCCO) single crystal.

  3. Photoelectron energy-loss study of the Bi2CaSr2Cu2O8 superconductor

    International Nuclear Information System (INIS)

    Shen, Z.; Lindberg, P.A.P.; Dessau, D.S.; Lindau, I.; Spicer, W.E.; Mitzi, D.B.; Bozovic, I.; Kapitulnik, A.

    1989-01-01

    Using energy-loss spectroscopy of photoelectrons from a single crystal of Bi 2 CaSr 2 Cu 2 O 8 , we show that the electronic structure of the near-surface region is the same as that of the bulk. Utilizing the fact that photoelectrons of different elements are excited at different locations in the unit cell, we identify the energy-loss features as due to valence plasmon excitations, and one-electron excitations by comparing the photoelectron energy-loss spectra of the different elements

  4. Unusual Concentration Induced Antithermal Quenching of the Bi(2+) Emission from Sr2P2O7:Bi(2.).

    Science.gov (United States)

    Li, Liyi; Peng, Mingying; Viana, Bruno; Wang, Jing; Lei, Bingfu; Liu, Yingliang; Zhang, Qinyuan; Qiu, Jianrong

    2015-06-15

    The resistance of a luminescent material to thermal quenching is essential for the application in high power LEDs. Usually, thermal luminescence quenching becomes more and more serious as the activator concentration increases. Conversely, we found here that a red phosphor Sr2P2O7:Bi(2+) is one of the exceptions to this as we studied the luminescence properties at low (10-300 K) and high (300-500 K) temperatures. As Bi(2+) ions are incorporated into Sr2P2O7, they exhibit the emissions at ∼660 and ∼698 nm at room temperature and are encoded, hereafter, as Bi(1) and Bi(2) due to the substitutions for two different crystallographic sites Sr(1) and Sr(2), respectively, in the compound. However, they will not substitute for these sites equally. At lower dopant concentration, they will occupy preferentially Sr(2) sites partially due to size match. As the concentration increases, more Bi(2+) ions start to occupy the Sr(1) sites. This can be verified by the distinct changes of emission intensity ratio of Bi(2) to Bi(1). As environment temperature increases, the thermal quenching happens, but it can be suppressed by the Bi(2+) concentration increase. This becomes even more pronounced in Bi(2+) heavily doped sample as we decompose the broad emission band into separated Bi(1) and Bi(2) Gaussian peaks. For the sample, the Bi(1) emission at ∼660 nm even shows antithermal-quenching particularly at higher temperatures. This phenomenon is accompanied by the blue shift of the overall emission band and almost no changes of lifetimes. A mechanism is proposed due to volume expansion of the unit cell, the increase of Bi(1) content, and temperature dependent energy transfer between Bi(2) and Bi(1). This work helps us better understand the complex luminescent behavior of Bi(2+) doped materials, and it will be helpful to design in the future the heavily doped phosphor for WLEDs with even better resistance to thermal quenching.

  5. Synthesis and study of the triphosphate salt LiSr2P3O10·8H2O

    International Nuclear Information System (INIS)

    Sotnikova-Yuzhik, V.A.; Peslyak, G.V.

    1995-01-01

    Lithium triphosphate interaction with strontium nitrate in aqueous solution at 0.3 mole% concentration and 20 deg C is studied. Formation of crystal hydrate LiSr 2 P 3 O 10 ·8H 2 O and amorphous phase of variable composition Li 2,5-0,5x P 3 O 10 ·6H 2 O (0.20≤x≤0.55) is determined. Data on the stability of binary lithium-strontium triphosphate at storage, sequence of chemical and phase transitions under heating are obtained. 5 refs., 4 figs., 3 tabs

  6. Effect of lead content on nonstoichiometric Bi2-xPbySr2Ca2Cu3Oδ ceramic superconductors

    International Nuclear Information System (INIS)

    Diaz-Valdes, E.; Pacheco-Malagon, G.; Contreras-Puente, G.; Mejia-Garcia, C.; Andrade-Garay, G.; Ortiz-Lopez, J.; Conde-Gallardo, A.; Falcony, C.

    1993-01-01

    Ceramic superconducting samples of the type Bi 2-x Pb y Sr 2 Ca 2 Cu 3 O δ were processed with a nonstoichiometric content of Bi and Pb (x≠y) with respect to the 2223 phase in this system. The resistance vs. temperature characteristics and the presence of the 2223 and 2212 phases as a function of the sample preparation conditions and the lead content (Bi/Pb ratio) are reported. The growth of unwanted phases such as PbO was observed for those samples with a high content of Pb (y=0.9) and Bi (x=0.1). (orig.)

  7. Synthesis and Microstructure Properties of (Bi,Pb2Sr2Ca1Cu2Oy Ceramic Superconductor

    Directory of Open Access Journals (Sweden)

    nurmalita .

    2015-11-01

    Full Text Available Properties of (Bi, Pb2Sr2Ca1Cu2Oy ceramic superconductors were prepared by the melt textured growth methods in order to investigate the effects of the slow cooling time on the microstructur.  Phase analyses of the samples by X-ray diffraction (XRD has been carried out to assess the effects of the slow cooling time. From XRD analyses, the addition to the sample of  the slow cooling time degrades formation of the high-Tc Bi-2212 phase. The possible reasons for the observed degradation in the microstructure properties due to the slow cooling time addition were discussed.

  8. Study of some electronics properties of new superconductor Sr2VO3FeAs in ground state

    Directory of Open Access Journals (Sweden)

    M Majidiyan

    2010-09-01

    Full Text Available In this paper, some electronics properties of new superconductor Sr2VO3FeAs, such as density of states, band structure, density of electron cloud and bound lengths in the ground state have been calculated. According to N(Ef in ground state CV/T value has been estimated. The calculations were performed in the framework of density functional theory (DFT, using the full potential linearized augmented plane wave (FP-LAPW method with the general gradient approximation (GGA.

  9. Flux Creep Investigation in Bi2Sr2CaCu2O8+d High-Temperature Superconductor

    Directory of Open Access Journals (Sweden)

    G. R. Blanca

    2004-12-01

    Full Text Available The flux creep process in a c-axis Bi2Sr2CaCu2O8+d thin film was investigated at different temperatures and applied fields using the Kim-Anderson (KA approach. The peaked behavior shown in the magnetoresistance profile was attributed to the competing mechanisms of flux motion and sample-intrinsic transition near Tc.Within the temperature range where the competition occurs, U increases with temperature and consequently a decrease in the superconducting volume corresponds to a decrease in the flux creep. Moreover, the flux creep potential barrier varies with applied current I at all temperatures consistent with the KA model.

  10. Correlation between magnetic properties and nuclear magnetic resonance observations in Sr2FeMoO6 double perovskite

    International Nuclear Information System (INIS)

    Colis, S.; Pourroy, G.; Panissod, P.; Meny, C.; Dinia, A.

    2004-01-01

    We present the influence of the sintering temperature on the magnetic properties of Sr 2 FeMoO 6 double perovskite, on the basis of magnetization and nuclear magnetic resonance (NMR) measurements. Interestingly, the saturation magnetization originating mainly from the Fe moments is correlated with the amount of Mo magnetic moments observed by NMR measurements. We show that there is an optimum temperature of 1000 deg. C for which the reaction leading to the double perovskite becomes more advanced and/or the number of antisite defects is minimum

  11. Plastic Flow of the Vortex Solid in Bi_2Sr_2CaCu_2O_8+δ Crystals

    Science.gov (United States)

    Keener, C. D.; Ammirata, S. M.; Trawick, M. L.; Hebboul, S. E.; Garland, J. C.

    1997-03-01

    We have recently presented evidence in electrical transport data for a first order vortex lattice melting transition in Bi_2Sr_2CaCu_2O_8+δ single crystals. Below the melting temperature T_m, current-induced motion of the vortex solid causes dissipation for sufficiently high currents. We have measured resistance vs. temperature curves in magnetic fields 50 Oe = 1 mA). Below Tm (≈ 80 K at 100 Oe), we find large temporal resistance fluctuations which are characteristic of vortex plastic flow. This vortex motion seems to be well described as ``intermittently flowing rivers" of vortices.(F. Nori, Science 271, 1373 (1996).)

  12. Electrical transport and magnetic studies of Nd1-xCaxSr2Cu2FeOδ compounds

    International Nuclear Information System (INIS)

    Walia, R.; Banerjee, R.; Grandjean, D.; Lanchester, P.C.; De Groot, P.A.J.; Weller, M.T.

    1994-01-01

    We have measured the temperature dependence of the DC electrical resistivity and susceptibility in the interval 4.2-300 K for Nd 1-x Ca x Sr 2 Cu 2 FeO δ (x=0.0, 0.1, 0.2 and 0.3). Analysis of the results showed the density of states to be a strong function of x, indicating the existence of short range fluctuations near the Fermi level E F . The magnetic susceptibility, however, shows the oxidation state of Fe remains at +3 for x≥0. ((orig.))

  13. Half-integer flux quantum effect in tricrystal Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Kirtley, J.R.; Tsuei, C.C.; Raffy, H.; Sun, J.Z.; Megtert, S.

    1996-01-01

    We have used a scanning SQUID microscope to directly observe the half-integer flux quantum effect, in epitaxial films of Bi 2 Sr 2 CaCu 2 O 8+δ , at the meeting point of a tricrystal substrate of SrTiO 3 in a geometry chosen to show this effect for a d-wave superconductor. This observation, when considered along with recent photoemission results, proves that the in-plane order parameter for this high-T c cuprate superconductor closely follows d x 2 -y 2 symmetry. (orig.)

  14. Antisite disorder-induced low-field magnetoresistance in some frustrated Sr2FeMoO6

    International Nuclear Information System (INIS)

    Cai Tianyi; Ju Sheng; Li Zhenya

    2006-01-01

    Considering the existence of antiferromagnetic patches induced by the antisite disorder in ferrimagnetic Sr 2 FeMoO 6 , we have developed a resistor network model to account for the effects of the antisite disorder on the magnetoresistance in this material. It is proposed that the magnetic disorder resulting from the existence of frustration around the antiferromagnetic patches will be suppressed under the applied magnetic field and low-field magnetoresistance will be observed. For samples with low levels of antisite defects, the magnetoresistive behaviour may be strongly affected by the different degrees of magnetic inhomogeneity. Our calculated results are in agreement with experimental observations

  15. Positron annihilation in Bi1.8Sb0.2Sr2Ca2Cu3Ox superconductor

    International Nuclear Information System (INIS)

    Chen Feng; Zheng Shennan; Zhang Suqun

    1992-01-01

    The positron lifetime and Doppler broadening line-shape parameter are measured as a function of the temperature from 78 K to 300 K for the Bi 1.8 Sb 0.2 Sr 2 Ca 2 Cu 3 O x superconductor. A decrease of both lifetime and S parameter is observed across T c . This can be interpreted by the theory of local charge transferring from the CuO layer to the BiO layer during superconducting transition. In the temperature region of normal state two anomalies are found around 165 K and 235 K. The possible origin of the observed anomalies is discussed

  16. Oxidative and antibacterial activity of Mn3O4

    International Nuclear Information System (INIS)

    Chowdhury, Al-Nakib; Azam, Md. Shafiul; Aktaruzzaman, Md.; Rahim, Abdur

    2009-01-01

    Mn 3 O 4 nanoparticles with diameter ca. 10 nm were synthesized by the forced hydrolysis of Mn(II) acetate at 80 deg. C. The X-ray diffraction (XRD), Fourier transform infra red (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques were employed to study structural features and chemical composition of the nanoparticles. The unique oxidative activity of the Mn 3 O 4 nanoparticles was demonstrated in the polymerization and dye degradation reactions. On adding Mn 3 O 4 suspension to an acidic solution of aniline, yielded immediately green sediment of polyaniline (PANI). The organic dyes, viz., methylene blue (MB) and procion red (PR) were found to be completely decolorized from their aqueous solution on treating the dyes with Mn 3 O 4 suspension in acidic media. The Mn 3 O 4 nanoparticles also showed a clear antibacterial activity against the Vibrio cholerae, Shigella sp., Salmonella sp., and Escherichi coli bacteria that cause cholera, dysentery, typhoid, and diarrhea diseases, respectively.

  17. Preparation and characterization of Bi2Sr2CaCu2O8+δ thin films on MgO single crystal substrates by chemical solution deposition

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Kepa, Katarzyna; Hlásek, T.

    2013-01-01

    Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors. Pyrolysis takes place between 200°C and 450°C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c-axis oriented Bi2Sr2Ca...

  18. Phase stability, oxygen nonstoichiometry, and superconductivity properties of Bi2Sr2CaCu2O8+δ and Bi1.8Pb0.4Sr2Ca2Cu3O10+δ

    International Nuclear Information System (INIS)

    Mozhaev, A.P.; Chernyaev, S.V.; Badun, Y.V.

    1995-01-01

    Phase stability of Bi 2 Sr 2 CaCu 2 O 8+δ (2212) and Bi 1.8 Pb 0.4 Sr 2 Ca 2 Cu 3 O 10+δ (2223) was studied by means of thermogravimetry, dilatometry, high-temperature resistivity, and the powder X-ray methods in the temperature range 700-1000 degrees and at P O2 = 1-10 -4.3 atm. The existence of a high-temperature (peritectic melting) boundary of phase stability was found. The temperatures of low-temperature phase decomposition were determined in air and under an oxygen atmosphere. The change in oxygen content was determined for the 2212 phase in the temperature range 700-860 degrees C and at P O2 = 0.21-10 -3.7 atm by iodometric analysis of quenched samples. It was found that in the single-phase region, the change in oxygen nonstoichiometry had an insignificant influence on T c . It was also shown that the slow cooling of samples led to a significant decrease in T c and transport j c due to partial phase decomposition

  19. Thermal expansion studies on Th(MoO4)2, Na2Th(MoO4)3 and Na4Th(MoO4)4

    International Nuclear Information System (INIS)

    Keskar, Meera; Krishnan, K.; Dahale, N.D.

    2008-01-01

    Thermal expansion behavior of Th(MoO 4 ) 2 , Na 2 Th(MoO 4 ) 3 and Na 4 Th(MoO 4 ) 4 was studied under vacuum in the temperature range of 298-1123 K by high temperature X-ray diffractometer. Th(MoO 4 ) 2 was synthesized by reacting ThO 2 with 2 mol of MoO 3 , at 1073 K in air and Na 2 Th(MoO 4 ) 3 and Na 4 Th(MoO 4 ) 4 were prepared by reacting Th(MoO 4 ) 2 with 1 and 2 mol of Na 2 MoO 4 , respectively at 873 K in air. The XRD data of Th(MoO 4 ) 2 was indexed on orthorhombic system where as XRD data of Na 2 Th(MoO 4 ) 3 and Na 4 Th(MoO 4 ) 4 were indexed on tetragonal system. The lattice parameters and cell volume of all the three compounds, fit into polynomial expression with respect to temperature, showed positive thermal expansion (PTE) up to 1123 K. The average value of thermal expansion coefficients for Th(MoO 4 ) 2 , Na 2 Th(MoO 4 ) 3 and Na 4 Th(MoO 4 ) 4 were determined from the high temperature data

  20. NiCo2O4-Based Supercapacitor Nanomaterials

    Directory of Open Access Journals (Sweden)

    Chenggang Wang

    2017-02-01

    Full Text Available In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo2O4 fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electrochemical activity, together with the low cost and environmental friendliness. Finally, the review will be concluded with the perspectives on the future development of spinel NiCo2O4 utilized as the supercapacitor electrodes.

  1. NiCo2O4-Based Supercapacitor Nanomaterials

    Science.gov (United States)

    Wang, Chenggang; Zhou, E; He, Weidong; Deng, Xiaolong; Huang, Jinzhao; Ding, Meng; Wei, Xianqi; Liu, Xiaojing; Xu, Xijin

    2017-01-01

    In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo2O4 fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electrochemical activity, together with the low cost and environmental friendliness. Finally, the review will be concluded with the perspectives on the future development of spinel NiCo2O4 utilized as the supercapacitor electrodes. PMID:28336875

  2. Study of half-metallic behavior in Sr2CoWO6 perovskite by ab initio DFT calculations

    International Nuclear Information System (INIS)

    Bonilla, M.; Landinez Tellez, D.A.; Arbey Rodriguez, J.; Aguiar, J. Albino; Roa-Rojas, J.

    2008-01-01

    In this work, we report several ab initio calculations performed for Sr 2 CoWO 6 by means of the density functional theory and the linearized augmented plane wave method for both spin orientations. For calculations, the exchange and correlation potential were treated into the generalized gradient approximation, which permits to consider from the beginning the difference between the electronic densities for both up and down spin orientations. The densities of states are calculated by the histogram method and the positions of Fermi levels are found by integrating over the density of states for both spin configurations. Our results reveal that Sr 2 CoWO 6 material behaves as insulators for the spin-up orientation and conductor for the spin down, as expected for the half-metallic systems. Results of partial densities of states permit to conclude that the conduction band has predominant contributions of d x 2 -y 2 and d xz+yz states of Co for the spin-down orientation. A magnetic moment of 3 μ B was calculated. From the Murnaghan equation state, we also calculate the cell dimensions that minimize the total energy for several configurations

  3. Spin-glass-like behaviour in IrSr2RECu2O8 (RE=Sm and Eu)

    International Nuclear Information System (INIS)

    Santos-Garcia, A.J. dos; Duijn, J. van; Alario-Franco, M.A.

    2008-01-01

    We report the results of magnetic and specific heat measurements on the 1212-type compounds IrSr 2 RECu 2 O 8 with RE=Sm and Eu, prepared by high-pressure and high-temperature synthesis. The magnetic susceptibility of these compounds shows a large difference in the temperature dependence of the magnetization measured under zero-field-cooled and field-cooled conditions below 87 and 71 K, respectively, and upon further cooling below ∼10 K substantial maxima are observed too. Further AC susceptibility measurements support a glassy behaviour in lower magnetic transitions whereas the specific heat measurements do not show the typical long-range ordering commonly displayed in ferro, ferri or antiferromagnetic transitions. Hysteresis loops suggest the presence of magnetic clusters in the otherwise paramagnetic zone, indicating that these compounds probably display a reentrant spin-glass transition. Results are presented and discussed. - Graphical abstract: IrSr 2 RECu 2 O 8 with RE=Sm and Eu were prepared by high-pressure and high-temperature synthesis. Both samples adopt a M-1212-type perovskite structure and a microdomain texturing of the long c-axis is observed by TEM. A very interesting magnetic behaviour is observed in these materials. A 'cluster by cluster freezing' model is proposed, instead of the classical individual spin freezing one to explain the spin-glass-like behaviour that seems to coexist with weak ferromagnetism in both compounds

  4. Enhanced thermoelectric properties of nano SiC dispersed Bi2Sr2Co2Oy Ceramics

    Science.gov (United States)

    Hu, Qiujun; Wang, Kunlun; Zhang, Yingjiu; Li, Xinjian; Song, Hongzhang

    2018-04-01

    The thermoelectric properties of Bi2Sr2Co2Oy + x wt% nano SiC (x = 0.00, 0.025, 0.05, 0.1, 0.2, and 0.3) prepared by the solid-state reaction method were investigated from 300 K to 923 K. The resistivity can be reduced effectively by adding a small amount of SiC nano particles, which is attributed to the increase of the carrier concentration. At the same time, the Seebeck coefficients can be improved effectively due to the energy filtering effect that low energy carriers are strongly dispersed at the interface between the SiC nano particles and the matrix. The decrease of thermal conductivity is due to the increase of the scattering ability of the phonons by the SiC nanoparticles distributed at the boundary of the matrix. As a result, the Bi2Sr2Co2Oy + x wt% SiC composites exhibit better thermoelectric properties. The maximum ZT value 0.24 is obtained when x = 0.05 at 923 K. Compared with the sample without SiC nano particles, the ZT value is increased by about 59.7%.

  5. Synthesis, crystal structure, and properties of the ordered double perovskite Sr_2CoOsO_6

    International Nuclear Information System (INIS)

    Kumar Paul, Avijit; Reehuis, Manfred; Felser, Claudia; Abdala, Paula M.; Jansen, Martin

    2013-01-01

    Sr_2CoOsO_6, a new osmium based ordered semiconductor double perovskite was prepared by solid state synthesis from the respective binary oxides. Room temperature PXRD analysis shows the compound to be tetragonal [I4/m; a = 5.5503(1) Aa and c = 7.9320(1) Aa], whereas low temperature synchrotron data refinement has revealed a second monoclinic polymorph [I2/m; a = 5.4969(2) Aa, b = 5.4979(2) Aa, c = 8.0090(1) Aa and γ = 90.527(1) ] with a fully ordered rocksalt arrangement of cobalt and osmium atoms over the perovskite B-sites. Heat capacity and magnetic measurements indicate that Sr_2CoOsO_6 shows antiferromagnetic ordering below T_N = 108 K followed by a second magnetic transition at T_2 = 65 K. It was shown that the change from the tetragonal to the monoclinic phase occurs at T_N. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. The k-space origins of scattering in Bi2Sr2CaCu2O8+x.

    Science.gov (United States)

    Alldredge, Jacob W; Calleja, Eduardo M; Dai, Jixia; Eisaki, H; Uchida, S; McElroy, Kyle

    2013-08-21

    We demonstrate a general, computer automated procedure that inverts the reciprocal space scattering data (q-space) that are measured by spectroscopic imaging scanning tunnelling microscopy (SI-STM) in order to determine the momentum space (k-space) scattering structure. This allows a detailed examination of the k-space origins of the quasiparticle interference (QPI) pattern in Bi2Sr2CaCu2O8+x within the theoretical constraints of the joint density of states (JDOS). Our new method allows measurement of the differences between the positive and negative energy dispersions, the gap structure and an energy dependent scattering length scale. Furthermore, it resolves the transition between the dispersive QPI and the checkerboard ([Formula: see text] excitation). We have measured the k-space scattering structure over a wide range of doping (p ∼ 0.22-0.08), including regions where the octet model is not applicable. Our technique allows the complete mapping of the k-space scattering origins of the spatial excitations in Bi2Sr2CaCu2O8+x, which allows for better comparisons between SI-STM and other experimental probes of the band structure. By applying our new technique to such a heavily studied compound, we can validate our new general approach for determining the k-space scattering origins from SI-STM data.

  7. Batch and flow-through continuous stirred reactor experiments of Sr2+-adsorption onto smectite: influence of pH, concentration and ionic strength

    International Nuclear Information System (INIS)

    Guimaraes, V.; Azenha, M.; Silva, A.F.; Bobos, I.

    2012-01-01

    Document available in extended abstract form only. Strontium-90 (t 1/2 = 29.1 years) resulting from the nuclear fission process is one of the main constituents connected with nuclear waste fuel. Concerning the physical properties and sorption behaviour one of the suitable buffer materials used as a backfill in the geological disposal systems for high-level radioactive wastes is smectite. The 2 μm clay fractions of di-octahedral smectite were used for adsorption experiments in batch and flow-through experiments. Flow-through experiments were carried out at different pH (4 and 8) and concentrations (8.00x10 -2 mmolSr 2+ /L, 2.0x10 -1 mmolSr 2+ /L, 3.3x10 -1 mmolSr 2+ /L and 4.1 x10 -1 mmol Sr 2+ /L). Batch experiments were carried out at different ionic strength ([KNO 3 ]=10 -2 M and [KNO 3 ]=10 -3 M), pH (4 and 8), whereas the concentration ranged between 0.19 mmolSr 2+ /L and 9.60 mmolSr 2+ /L. The adsorption strontium rate in flow-through experiments was found higher at pH 4 than at pH 8, where less of 20% amount of strontium was adsorbed on clay surface after 34 hours. This is explained by the surface charge of smectite layers with a permanent negative charge on the basal planes due essentially to isomorphic substitution. Also additional polar sites are conditionally charged by direct protonation of outer edge surfaces. Therefore, more negative sites become available for the strontium ions sorption, as the pH increasing. After adsorption, the clays were submitted to a desorption process. The rate of desorption at pH 4 is initially too fast due to the elevated amount of strontium released by smectite. After 255 min, the strontium amount desorbed is very low and the rate of desorption approached to zero. By contrast at pH 8 the rate of desorption is practically constant, and after 255 min there is a significant amount of strontium released by clay. Due to these different behaviors in different pH conditions, after 10 hours of desorption, the amount of strontium

  8. Electrodeposited Mn3O4-NiO-Co3O4 as a composite electrode material for electrochemical capacitor

    International Nuclear Information System (INIS)

    Rusi; Majid, S.R.

    2015-01-01

    Highlights: • Composite electrodes were synthesized by in situ electrodeposition method. • The highest specific capacitance of composite electrode is 7404 F g −1 . • The power density of composite electrode is 99 kW kg −1 at current density of 20 A g −1 . • The addition of K 3 Fe(CN) 6 in KOH electrolyte has improved the electrochemical performance. - Abstract: A simple and easy galvanostatic electrodeposition method is used to synthesise a composite electrode consisting of manganese oxide (Mn 3 O 4 ), nickel oxide (NiO) and cobalt oxide (Co 3 O 4 ). The influence of Co 3 O 4 on the morphology of fixed Mn 3 O 4 -NiO particles is investigated with a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The nature and elemental of the composite are examined by means of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The electrochemical performances of an Mn 3 O 4 -NiO-Co 3 O 4 nanostructure/SS composite electrode are studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD) in various electrolytes, i.e. 0.5 M Na 2 SO 4 , 0.5 M KOH, 0.5 M Na 2 SO 4 /0.04 M K 3 Fe(CN) 6 and 0.5 M KOH/0.04 M K 3 Fe(CN) 6 electrolytes. The composite electrode prepared from 0.15 M Co deposition solution exhibits the optimum specific capacitance of 7404 F g −1 with high energy and power density of 1028 Wh kg −1 and 99 kW kg −1 at 20 A g −1 in mix KOH/0.04 M K 3 Fe(CN) 6 electrolyte, respectively. The results show that the incorporation of K 3 Fe(CN) 6 in KOH electrolyte influences the capacitance of Mn 3 O 4 -NiO-Co 3 O 4 composite electrodes

  9. Complexing in the system Rb2SeO4-UO2SeO4-H2O

    International Nuclear Information System (INIS)

    Kuchumova, N.V.; Shtokova, I.P.; Serezhkina, L.B.; Serezhkin, V.N.

    1989-01-01

    Method of isothermal solubility at 25 deg C is used to study interaction of rubidium and uranyl selenates in aqueous solution. Formation of congruently soluble Rb 2 UO 2 (SeO 4 ) 2 x2H 2 O and Rb 2 (UO 2 ) 2 x(SeO 4 ) 3 x6H 2 O is stated. For the last compound crystallographic characteristics (a=10.668; b=14.935(9); c=13.891(7) A; β=104.94(1); Z=4, sp.gr. P2 1 /c) are determined. Thermal decomposition of a compound results in formation of Rb 2 U 2 O 7

  10. On phase transitions in NH_{4HSeO4} and ND{4}DSeO{4}

    Science.gov (United States)

    Dvořák, V.; Quilichini, M.; Le Calvé, N.; Pasquier, B.; Heger, G.; Schweiss, P.

    1991-10-01

    We propose a hypothetical prototype phase (space group Imm) from which all observed phases in NH{4}HSeO{4} and ND{4}DSeO{4} can be deduced by introducing order parameters of definite symmetries. Following this hypothesis the symmetry of the superionic phase should be P2/n in disagreement with recent experimental results. Free energies of Landau type are derived by means of which particular phase transitions could be described. The large dielectric anomaly near 252 K in NH{4}HSeO{4} is discussed in some detail. The first order phase transition in ND{4}DSeO{4} from the room temperature phase P2{1}2121 into commensurate lock-in phase (with the wave-vector k {z}(0,0, frac{π}{c})) has been investigated by neutron elastic scattering and the symmetry of the latter has been found to be P112{1} in agreement with our theoretical prediction. Nous proposons une phase prototype hypothétique (de groupe d'espace Immm) à partir de laquelle on peut déduire toutes les phases observées dans NH{4}HSeO{4} et ND{4}DSeO{4} par l'introduction de paramètres d'ordre ayant une symétrie définie. D'après cette hypothèse le groupe d'espace de la phase superionique doit être P2/n ce qui est en désaccord avec des résultats expérimentaux récents. Pour chaque transition de phase on écrit l'énergie libre de type Landau à partir de laquelle elle peut être décrite. La grande anomalie diélectrique au voisinage de 252 K dans le composé NH{4}HSeO{4} est discutée de façon détaillée. Dans le composé ND{4}DSeO{4}, nous avons étudié par diffusion élastique de neutrons la transition de phase du premier ordre qui transforme le cristal de la structure P2{1}2121 dans la phase commensurable d'accrochage (de vecteur d'onde k {z}(0,0, frac{π}{c})). Nous avons montré que la symétrie de cette phase est P112{1}, ce qui en accord avec nos prévisions théoriques.

  11. Carbon supported nanoparticles Pt Ru (Pt Ru/C electrocatalysts) prepared using electron beam irradiation; Preparacao de nanoparticulas de PtRu suportadas em carbono (eletrocatalisadores PtRu/C) utilizando feixe de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F. da; Oliveira Neto, Almir; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Programa de Celulas a Combustivel], e-mail: espinace@ipen.br, e-mail: dfsilva@ipen.br

    2006-07-01

    Carbon-supported Pt Ru (electrocatalysts PtRu/C nanoparticles) were prepared submitting a water/ethylene glycol mixture containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The PtRu/C electrocatalysts were characterized by EDX, XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C ETEK electrocatalyst at ambient temperature. (author)

  12. Single crystalline Co3O4: Synthesis and optical properties

    International Nuclear Information System (INIS)

    Hosny, Nasser Mohammed

    2014-01-01

    Crystals of Co 3 O 4 have been prepared from thermal decomposition of molecular precursors derived from salicylic acid and cobalt (II) acetate or chloride at 500 °C. A cubic phase Co 3 O 4 micro- and nanocrystals have been obtained. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The images of electron microscopes showed octahedral crystals of Co 3 O 4 . The volume and polarizability of the optimized structures of molecular precursors have been calculated and related to the particle size. The optical band gap of the obtained crystals has been measured. The results indicated two optical band gaps with values 2.65 and 2.95 eV for (E g1 ) (E g2 ), respectively. - Highlights: • Synthesis of Co 3 O 4 nanocrystals by decomposition of cobalt salicylic acid precursor. • Characterization of the isolated nanocrystals by using XRD, SEM and HRTEM. • The optical band gap has been measured

  13. Antifungal activity of multifunctional Fe3O4-Ag nanocolloids

    International Nuclear Information System (INIS)

    Chudasama, Bhupendra; Vala, Anjana K.; Andhariya, Nidhi; Upadhyay, R.V.; Mehta, R.V.

    2011-01-01

    In recent years, rapid increase has been observed in the population of microbes that are resistant to conventionally used antibiotics. Antifungal drug therapy is no exception and now resistance to many of the antifungal agents in use has emerged. Therefore, there is an inevitable and urgent medical need for antibiotics with novel antimicrobial mechanisms. Aspergillus glaucus is the potential cause of fatal brain infections and hypersensitivity pneumonitis in immunocompromised patients and leads to death despite aggressive multidrug antifungal therapy. In the present article, we describe the antifungal activity of multifunctional core-shell Fe 3 O 4 -Ag nanocolloids against A. glaucus isolates. Controlled experiments are also carried out with Ag nanocolloids in order to understand the role of core (Fe 3 O 4 ) in the antifungal action. The minimum inhibitory concentration (MIC) of nanocolloids is determined by the micro-dilution method. MIC of A. glaucus is 2000 μg/mL. The result is quite promising and requires further investigations in order to develop a treatment methodology against this death causing fungus in immunocompromised patients. - Research Highlights: →Synthesis of Fe 3 O 4 -Ag core-shell nanocolloids. →Antifungal activity of Fe 3 O 4 -Ag nanocolloids against Aspergillus glaucus isolates. →The MIC value for A. glaucus is 2000 μg/mL. →Antifungal activity is better or comparable with most prominent antibiotics.

  14. Profound Interfacial Effects in CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4 Core/Shell Nanoparticles

    Science.gov (United States)

    Polishchuk, Dmytro; Nedelko, Natalia; Solopan, Sergii; Ślawska-Waniewska, Anna; Zamorskyi, Vladyslav; Tovstolytkin, Alexandr; Belous, Anatolii

    2018-03-01

    Two sets of core/shell magnetic nanoparticles, CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4, with a fixed diameter of the core ( 4.1 and 6.3 nm for the former and latter sets, respectively) and thickness of shells up to 2.5 nm were synthesized from metal chlorides in a diethylene glycol solution. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and magnetic measurements. The analysis of the results of magnetic measurements shows that coating of magnetic nanoparticles with the shells results in two simultaneous effects: first, it modifies the parameters of the core-shell interface, and second, it makes the particles acquire combined features of the core and the shell. The first effect becomes especially prominent when the parameters of core and shell strongly differ from each other. The results obtained are useful for optimizing and tailoring the parameters of core/shell spinel ferrite magnetic nanoparticles for their use in various technological and biomedical applications.

  15. Oxygen evolution from BF3/MnO4-.

    Science.gov (United States)

    Yiu, Shek-Man; Man, Wai-Lun; Wang, Xin; Lam, William W Y; Ng, Siu-Mui; Kwong, Hoi-Ki; Lau, Kai-Chung; Lau, Tai-Chu

    2011-04-14

    MnO(4)(-) is activated by BF(3) to undergo intramolecular coupling of two oxo ligands to generate O(2). DFT calculations suggest that there should be a spin intercrossing between the singlet and triplet potential energy surfaces on going from the active intermediate [MnO(2)(OBF(3))(2)](-) to the O···O coupling transition state.

  16. Magnetic properties of Heusler alloy Mn2RuGe and Mn2RuGa ribbons

    International Nuclear Information System (INIS)

    Yang, Ling; Liu, Bohua; Meng, Fanbin; Liu, Heyan; Luo, Hongzhi; Liu, Enke; Wang, Wenhong; Wu, Guangheng

    2015-01-01

    Heusler alloys Mn 2 RuGe and Mn 2 RuGa have been prepared by melt-spinning method successfully. Theoretical and experimental studies reveal a ferrimagnetic ground state in the two alloys. The Curie temperatures are 303 K for Mn 2 RuGe and 272 K for Mn 2 RuGa. The calculated total spin moments of Mn 2 RuGe and Mn 2 RuGa are integral values of 2.00 μ B and 1.03 μ B , respectively. And the theoretical spin polarization ratio is also quite high. However, due to the atomic disorder in the ribbons, the saturation moments of them measured at 5 K are smaller than the calculated values, especially that of Mn 2 RuGa. This coincides with the disappearance of the superlattice reflection (111) and (200) peaks in the XRD pattern of Mn 2 RuGa. Annealing Mn 2 RuGa ribbon at 773 K can enhance the atomic ordering. Both saturation magnetic moment and Curie temperature increase obviously after the heat treatment. - Highlights: • Mn 2 RuGe and Mn 2 RuGa have been prepared by melt-spinning successfully. • Ferrimagnetic ground state has been confirmed in Mn 2 RuGe and Mn 2 RuGa. • High spin polarization has been predicted in Mn 2 RuGe. • Melt-spinning can be a possible way to adjust the atomic order of Heusler alloys

  17. Hierarchical Heterostructures of NiCo2O4@XMoO4 (X = Ni, Co) as an Electrode Material for High-Performance Supercapacitors.

    Science.gov (United States)

    Hu, Jiyu; Qian, Feng; Song, Guosheng; Wang, Linlin

    2016-12-01

    Hierarchical heterostructures of NiCo2O4@XMoO4 (X = Ni, Co) were developed as an electrode material for supercapacitor with improved pseudocapacitive performance. Within these hierarchical heterostructures, the mesoporous NiCo2O4 nanosheet arrays directly grown on the Ni foam can not only act as an excellent pseudocapacitive material but also serve as a hierarchical scaffold for growing NiMoO4 or CoMoO4 electroactive materials (nanosheets). The electrode made of NiCo2O4@NiMoO4 presented a highest areal capacitance of 3.74 F/cm(2) at 2 mA/cm(2), which was much higher than the electrodes made of NiCo2O4@CoMoO4 (2.452 F/cm(2)) and NiCo2O4 (0.456 F/cm(2)), respectively. Meanwhile, the NiCo2O4@NiMoO4 electrode exhibited good rate capability. It suggested the potential of the hierarchical heterostructures of NiCo2O4@CoMoO4 as an electrode material in supercapacitors.

  18. Synthesis, characterisation and antibacterial activity of [(p-cym)RuX(L)](+/2+) (X = Cl, H2O; L = bpmo, bpms) complexes.

    Science.gov (United States)

    Tripathy, Suman Kumar; Taviti, Ashoka Chary; Dehury, Niranjan; Sahoo, Anupam; Pal, Satyanaryan; Beuria, Tushar Kant; Patra, Srikanta

    2015-03-21

    Mononuclear half-sandwiched complexes [(p-cym)RuCl(bpmo)](ClO4) {[1](ClO4)} and [(p-cym)RuCl(bpms)](PF6) {[2](PF6)} have been prepared by reacting heteroscorpionate ligands bpmo = 2-methoxyphenyl-bis(3,5-dimethylpyrazol-1-yl)methane and bpms = 2-methylthiophenyl-bis(3,5-dimethylpyrazol-1-yl)methane, respectively, with a dimeric precursor complex [(p-cym)RuCl(μ-Cl)]2 (p-cym = 1-isopropyl-4-methylbenzene) in methanol. The corresponding aqua derivatives [(p-cym)Ru(H2O)(bpmo)](ClO4)2 {[3](ClO4)2} and [(p-cym)Ru(H2O)(bpms)](PF6)2 {[4](PF6)2} are obtained from {[1](ClO4)} and {[2](PF6)}, respectively, via Cl(-)/H2O exchange process in the presence of appropriate equivalents of AgClO4/AgNO3 + KPF6 in a methanol-water mixture. The molecular structures of the complexes {[1]Cl, [3](ClO4)2 and [4](PF6)(NO3)} are authenticated by their single crystal X-ray structures. The complexes show the expected piano-stool geometry with p-cym in the η(6) binding mode. The aqua complexes [3](ClO4)2 and [4](PF6)2 show significantly good antibacterial activity towards E. coli (gram negative) and B. subtilis (gram positive) strains, while chloro derivatives ({[1](ClO4)} and {[2](PF6)} are found to be virtually inactive. The order of antibacterial activity of the complexes according to their MIC values is [1](ClO4) (both 1000 μg mL(-1)) < [2](PF6) (580 μg mL(-1) and 750 μg mL(-1)) < [3](ClO4)2 (both 100 μg mL(-1)) < [4](PF6)2 (30 μg mL(-1) and 60 μg mL(-1)) for E. coli and B. subtilis strains, respectively. Further, the aqua complexes [3](ClO4)2 and [4](PF6)2 show clear zones of inhibition against kanamycin, ampicillin and chloramphenicol resistant E. coli strains. The detailed mechanistic aspects of the aforesaid active aqua complexes [3](ClO4)2 and [4](PF6)2 have been explored, and it reveals that both the complexes inhibit the number of nucleoids per cell in vivo and bind to DNA in vitro. The results indeed demonstrate that both [3](ClO4)2 and [4](PF6)2 facilitate the inhibition of

  19. Humidity sensitive electrical responce of K2CrO4 doped ZnCr2O4 ceramic sensors

    International Nuclear Information System (INIS)

    Kavasoglu, N.

    2005-01-01

    The effects of the addition of various percentages of potassium chromate as a sintering aid on the response to air moisture of ZnCr 2 O 4 ceramic body along with its crystalline structure and surface morphology were studied. The fired ceramic body, which proved to be mainly constructed from about 1μm sized ZnCr 2 O 4 spinel grains, was porous. The humidity sensing behaviour of the sensors reveals that the electrical conduction is due mainly to protonic and is controlled through the thin layers of water, adsorbed on the surface of the grains, with charge transfer to the electrodes. Only the material containing 20% K 2 CrO 4 in ZnCr 2 O 4 exhibited an exponential behaviour to humidity, which shows about three orders change in the d.c. resistance over the relative humidity in the range between 25 and 90%. The addition of CuO resulted in an increase in the conductivity but had a deleterious effect on the humidity. Based on a.c. impedance measurements, an equivalent circuit associated with a net work of RC parallel circuit in series with constant phase elements (CPEs) has been suggested. It can be therefore assumed that such equivalent circuit model of the sensor under moderate moist condition indicates the charge transport processes mediated by proton hopping and diffusion. A homemade prototype of such a humidity sensor has also been successfully demonstrated in door

  20. Complexation in the system K2SeO4-UO2SeO4-H2O

    International Nuclear Information System (INIS)

    Serezhkina, L.B.; Kuchumova, N.V.; Serezhkin, V.N.

    1994-01-01

    Complexation in the system K 2 SeO 4 -UO 2 SeO 4 -H 2 O at 25 degrees C is studied by isothermal solubility. Congruently soluble K 2 UO 2 (SeO 4 ) 2 ·4H 2 O (I) and incongruently soluble K 2 (UO 2 ) 2 (SeO 4 ) 3 ·6H 2 O (II) are observed. The unit-cell constants of I and II are determined from an X-ray diffraction investigation. For I, a = 12,969, b = 11.588, c = 8.533 angstrom, Z = 4, space group Pmmb. For II, a = 23.36, b = 6.784, c = 13.699 angstrom, β = 104.42 degrees, Z = 4, space group P2/m, P2, or Pm. Complexes I and II are representatives of the crystal-chemical groups AB 2 2 M 1 and A 2 T 3 3 M 1 , respectively, of uranyl complexes

  1. Magnetism of Bi2Sr2Can-1CunO2n+4+δ (n = 1,2,3)

    International Nuclear Information System (INIS)

    Ishida, T.; Koga, K.; Kanoda, K.; Takahashi, T.

    1992-01-01

    The normal-state dc susceptibility χ dc of the Bi 2 Sr 2 Ca n-1 Cu n O 2n+4+δ (n=1, 2, 3) pellet is of the order of +10 -7 emu/g. A large Curie-Weiss component is found in χ dc and the ESR spin susceptibility χ ESR of the pulverized 2201, 2212 and 2223 samples but it almost disappears by annealing. The relative magnitudes of χ ESR to χ dc for the annealed powders are dissimilar among the three phases: ESR of the 2201 sample is silent, χ ESR of the 2212 phase has almost the same magnitude as χ dc and χ ESR of the 2223 phase is appreciable but smaller than χ dc . (orig.)

  2. Nuclear relaxation behavior of the superconducting cuprates: Bi2Sr2CaCu2O8

    Science.gov (United States)

    Walstedt, R. E.; Bell, R. F.; Mitzi, D. B.

    1991-10-01

    Nuclear-magnetic-resonance data are presented and analyzed for the high-Tc compound Bi2Sr2CaCu2O8 for two oxygen doping levels. Both sample conditions lead to spin-gap behavior for the NMR shift, with a precursive downturn in the data at T>Tc. In addition, the relaxation times T1 obey the relation (T1T)-1~Ks(T) at low temperatures (T<~100 K), where Ks(T) is the spin paramagnetic shift. This relation, which is also obeyed by other superconductors, is argued to be related to the spin-gap effects and thus incompatible with a Fermi-liquid approach to the understanding of these systems.

  3. Anomalous spectral weight transfer at the superconducting transition of Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Dessau, D.S.; Wells, B.O.; Shen, Z.; Spicer, W.E.; Arko, A.J.; List, R.S.; Mitzi, D.B.; Kapitulnik, A.

    1991-01-01

    Anomalous spectral weight transfer at the superconducting transition of single-crystalline Bi 2 Sr 2 CaCu 2 O 8+δ was observed by high-resolution angle-resolved photoemission spectroscopy. As the sample goes superconducting, not only is there spectral weight transfer from the gap region to the pileup peak as in BCS theory, but along the Γ-bar M direction there is also some spectral weight transfer from higher binding energies in the form of a dip. In addition, we note that at the superconducting transition there is a decrease (increase) in the occupied spectral weight for the spectra taken along Γ-bar M (Γ-X)

  4. O 1s core levels in Bi2Sr2CaCu2O8+δ single crystals

    International Nuclear Information System (INIS)

    Parmigiani, F.; Shen, Z.X.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

    1991-01-01

    High-quality Bi 2 Sr 2 CaCu 2 O 8+δ superconducting single crystals, annealed at different oxygen partial pressures, have been studied using angular-resolved x-ray photoelectron spectroscopy with a resolution higher than that used in any previous study. Two states of the oxygen, separated by ∼0.7 eV, are unambiguously observed. Examining these components at different angles makes it possible to distinguish bulk from surface components. Using this capability we discover that annealing under lower oxygen partial pressure (1 atm) results in oxygen intercalation beneath the Bi-O surface layer of the crystal, whereas for higher-pressure anneals (12 atm) additional oxygen is found on the Bi-O surfaces. This steplike intercalation mechanism is also confirmed by the changes observed in the Cu and Bi core lines as a function of the annealing oxygen partial pressure

  5. Defect dependence of the irreversibility line in Bi2Sr2CaCu2O8 single crystals

    Science.gov (United States)

    Lombardo, L. W.; Mitzi, D. B.; Kapitulnik, A.; Leone, A.

    1992-09-01

    The c-axis irreversibility line (IL) of pristine single-crystal Bi2Sr2CaCu2O8 is shown to exhibit three regimes: For fields less than 0.1 T, it obeys a power law, Hirr=H0(1-Tirr/Tc)μ, where μ and H0 vary with Tc. For fields greater than 2 T, the IL becomes linear with a slope of 0.7 T/K. For intermediate fields, there is a crossover region, which corresponds to the onset of collective vortex behavior. Defects produced by proton irradiation shift the IL in all three regimes: The high-field regime moves to higher temperatures, the low-field regime moves to lower temperatures, and the crossover to collective behavior becomes obscured. A maximal increase in the irreversibility temperature in the high-field regime is found to occur at a defect density of nearly one defect per vortex core disk.

  6. Spin-Glass Transition and Giant Paramagnetism in Heavily Hole-Doped Bi2Sr2Co2Oy

    Science.gov (United States)

    Hsu, Hung Chang; Lee, Wei-Li; Lin, Jiunn-Yuan; Young, Ben-Li; Kung, Hsiang-Hsi; Huang, Jian; Chou, Fang Cheng

    2014-02-01

    Hole-doped single crystals of misfit-layered cobaltate Bi2-xPbxSr2-zCo2Oy (x = 0-0.61, y = 8.28-8.62, and z = 0.01-0.22) have been successfully grown using the optical floating-zone method. Heavier hole doping has been achieved through both Pb substitution in the Bi site and the more effective Sr vacancy formation. The Co4+ : Co3+ ratio can be raised significantly from its original ˜1 : 1 to 4.5 : 1, as confirmed by iodometric titration. A spin-glass transition temperature of Tg ˜ 70 K is confirmed by ac susceptibility measurement when the Co4+ : Co3+ ratio becomes higher than 2 : 1, presumably owing to the significantly increased probability of triangular geometrical frustration among antiferromagnetically coupled localized Co4+ spins.

  7. Oxygen stoichiometry and its influence on superconductivity in Bi2Sr2CaCu2O8+x

    International Nuclear Information System (INIS)

    Krishnaraj, P.; Lelovic, M.; Eror, N.G.; Balachandran, U.

    1994-01-01

    Bi 2 Sr 2 CaCu 2 O 8+x (2212) was synthesized from freeze-dried precursors. The oxygen content of 2212 was determined as a function of temperature and oxygen partial pressure and the variation of Tc with oxygen content was determined. It was found that 2212 without excess oxygen (x = 0) is superconducting. This points to the role of the (Bi-O) ∞ layers as a source for holes in 2212. Four probe resistivity measurements were also performed on 2212. The nature of oxygen intercalation and oxygen removal in 2212 was studied by thermogravimetry and resistivity. It was also found that samples of 2212 with the same oxygen content had different T c 's depending on thermal history. This difference in T c is thought to arise from oxygen occupying different sites in the lattice while maintaining the same total oxygen content

  8. A New Class of Octahedral Molecular Sieve Materials for the Selective Removal and Sequestration of 90Sr2+

    International Nuclear Information System (INIS)

    Nyman, May D.; Nenoff, Tina M.; Tripathi, Akhilesh; Parise, John B.; Maxwell, Robert S.; Harrison, William T.A.

    2000-01-01

    The structure of Na 16 Nb 12.8 Ti 3.2 O 44.8 (OH) 3.2 · 8H 2 O, a member of a new family of Sandia Octahedral Molecular Sieves (SOMS) having a Nb/Na/M IV (M= Ti, Zr) oxide framework and exchangeable Na and water in open channels, was determined from Synchrotron X-ray data. The SOMS phases are isostructural with variable M IV :Nb(1:50--1:4) ratios. The SOMS are extremely selective for sorption of divalent cations, particularly Sr 2+ . The ion-exchanged SOMS undergo direct thermal conversion to a perovskite-type phase, indicating this is a promising new method for removal and sequestration of radioactive Sr-90 from mixed nuclear wastes

  9. Synthesis and characterization of Ruddlesden-Popper (RP) type phase LaSr2MnCrO7

    International Nuclear Information System (INIS)

    Singh, Devinder; Singh, Rajinder

    2010-01-01

    New Ruddlesden-Popper (RP) type phase LaSr 2 MnCrO 7 has been synthesized by ceramic method. Rietveld profile analysis shows that the phase crystallizes with tetragonal unit cell in the space group 14/mmm. The electrical resistivity of the phase has been measured in the temperature range of 10-300 K using Leybold closed cycle helium cryostat. The phase shows insulator-metal (I-M) transition at low temperature, the phenomenon often associated with giant magnetoresistance. 3D variable range hopping governs the electrical conduction in the insulator region above the I-M transition temperature. Magnetic susceptibility of the phase has been measured in the temperature range of 100-300 K. Magnetic studies suggest that the phase is ferromagnetic. (author)

  10. Electrical and percolative behavior of Sr2YSbO6-YBa2Cu3O7-δ composites

    International Nuclear Information System (INIS)

    Ortiz-Diaz, O.; Landinez Tellez, D.A.; Perez, F.; Tovar, H.; Roa-Rojas, J.

    2007-01-01

    We found that a mixture of materials Sr 2 YSbO 6 insulator with YBa 2 Cu 3 O 7-δ superconductor is a system where the particles of superconductor and insulator materials are found coexisting in a composite with two well-defined separate phases. Electrical transport properties and percolation behavior have been studied by electrical resistivity measurements at room temperature on several samples of composites with different vol.% of YBa 2 Cu 3 O 7-δ . Resistivity measurements agree with the equation which describes the conductivity in percolation theory. However, critical exponent t=6.65 is greater than universal value t∼2. Furthermore, there is a non-negligible conductivity below percolation threshold while it is expected to be zero in ideal percolative systems. Nevertheless, percolative behavior in this region was found and, critical exponent value s was determined to be s=0.75 in agreement with universal value

  11. Peltier-effect in the mixed state of (Bi, Pb)2Sr2Ca2Cu3Oδ

    International Nuclear Information System (INIS)

    Galffy, M.; Hohn, C.; Freimuth, A.

    1994-01-01

    We present measurements of the Peltier-effect in the mixed state of Bi 1.76 Pb 0.24 Sr 2 Ca 2 Cu 3 O δ . The Peltier-coefficient broadens in a magnetic field quite similar to the resistivity and the thermopower. Comparison with the thermopower shows that Onsagers relation holds well. The occurrence of the Peltier-heat in the mixed state well below T c implies that the electric current is accompanied by a large heat current. We show that the vortex contribution to the Peltier-heat is negligibly small. Therefore the heat current has to be attributed to normal quasiparticle excitations. Our results indicate that this quasiparticle contribution to the heat current remains large even at temperatures far below T c . (orig.)

  12. Systematic magnetization measurements on single crystalline Bi2Sr2CaCu2O8+δ with columnar defects

    International Nuclear Information System (INIS)

    Kimura, Kazuhiro; Koshida, Ryo; Kwok, W.K.; Crabtree, G.W.; Okayasu, Satoru; Sataka, Masao; Kazumata, Yukio; Kadowaki, Kazuo

    1999-01-01

    The authors have performed systematic magnetization measurements on single crystalline Bi 2 Sr 2 CaCu 2 O 8+δ with columnar defects of B Φ = 0.005 to 1 T by using a SQUID magnetometer. Magnetization hysteresis curves of the pristine sample show a weak irreversible behavior in the vortex liquid state, suggesting the existence of the new vortex state in the vortex liquid state. This weak irreversible region persists systematically in the samples with columnar defects even up to B Φ = 1 T. It is shown that the weak hysteresis of magnetization is sensitive to the disorder level of the sample and shifts systematically to higher temperature and field region with increasing the number of columnar defects. This behavior clearly indicates that effective pinning mechanism exists even in the vortex liquid state and generates a finite critical current

  13. Electronic transitions of Ho in Pb2Sr2HoCu3O8 observed by inelastic neutron scattering

    International Nuclear Information System (INIS)

    Soderholm, L.; Loong, C.; Xue, J.S.; Hammonds, J.P.; Greedan, J.E.; Maric, M.

    1993-01-01

    The electronic behavior of the 5 I 8 Russell Saunders ground multiplet of Ho 3+ in Pb 2 Sr 2 HoCu 3 O 8 has been investigated using inelastic neutron scattering. We observe ten peaks in the excitation spectra that are associated with crystal field transitions. The peaks are only slightly broader than expected from instrument resolution, indicating that there are no strong interactions between the local Ho f states and the CuO conduction states. Comparing the energies and intensities of the experimental peaks with those expected from modeling convinces us that there are at least three states populated at the temperature of our experiment (15 K), making the assignments of transitions very difficult in the absence of further data

  14. Strain tolerance of Bi2Sr2Ca1Cu2O8-δ/Ag composites at high field

    International Nuclear Information System (INIS)

    Li, Q.; Ostenson, J.E.; Finnemore, D.K.

    1991-01-01

    Strain tolerance of Bi 2 Sr 2 Ca 1 Cu 2 O 8-δ /Ag composites have been studied at fields up to 20 T and bending strains up to 2.6% in order to determine the factors that control the critical current density. The goal is to find the best way to distribute Ag such as to give both high strain tolerance and high critical current density. Partial melt processed samples prepared from micromilled mixtures containing 30% Ag by volume show a gradually decreasing critical current all the way out to 2.6% strain. Samples typically show about 1000 A/cm 2 at 4.2 K, 20 T, and 0.75% strain. At 20 K, these values occur at 4 T and 0.75% strain

  15. Reinforced fluropolymer nanocomposites with high-temperature superconducting Bi2Sr2CaCu2Oy

    Science.gov (United States)

    Jayasree, T. K.

    2014-10-01

    Bismuth Strontium Calcium Copper Oxide (Bi2Sr2CaCu2Oy)/Polyvinylidene fluoride (PVDF) nanocomposite was prepared and their thermal properties were analyzed. The composite consists of the polyvinylidene fluoride (PVDF) as an insulating polymer matrix, and homogenously distributed Bismuth strontium calcium copperoxide (2212) nanoparticles. SEM data shows flaky grains of the superconductor coated and linked by polymer. Differential scanning calorimetry (DSC) results indicated that the melting point was not affected significantly by the addition of BSCCO. However, the addition of superconducting ceramic resulted in an extra melting peak at a lower temperature (145°C). Thermogravimetric analysis of the samples shows that the onset decomposition temperature of the PVDF matrix was decreased by the addition of SC filler.

  16. Effect of Ag on the peritectic decomposition of Bi2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Margulies, L.; Dennis, K.W.; Kramer, M.J.; McCallum, R.W.

    1995-01-01

    During the melt processing of superconducting wires and tapes a number of partial liquid phase regions are entered, and the type and amount of second phases that exist in the melt before cooling are critical in determining the microstructure of the final material. Decomposition pathway of Bi 2 Sr 2 CaCu 2 O x (Bi2212) with 0, 2, and 10 wt% Ag added was examined at 1 bar PO 2 by performing SAME/EDS analysis on oil quenched samples. A variety of quaternary phase diagrams were constructed to describe the evolution of the phase assemblage with temperature. At all Ag contents, Bi2212 first undergoes a peritectic reaction producing (Sr 1-x Ca x ) 14 Cu 24 O 41 (14,24), Bi 2 (Sr 1-x Ca x ) 4 O x (24x), and liquid

  17. Superconductivity of individual grains and inter-grain boundaries for polycrystalline FeSr2YCu2O6+y

    International Nuclear Information System (INIS)

    Yamaguchi, K.; Hata, Y.; Mochiku, T.; Yasuoka, H.

    2013-01-01

    Polycrystalline FeSr 2 YCu 2 O 6+y was synthesized and its transport and magnetic properties were studied. Diamagnetism was observed below 60 K. Zero resistivity was observed below 38 K under zero magnetic field and below 10 K under 160 kOe. A two-step transition was observed in resistivity measurement due to the superconductivity in individual grains and across inter-grain boundaries. The critical current density in individual grains, J c intra , at 2 K under 1 kOe was deduced 3.4 × 10 5 A/cm 2 from the Bean model. In contrast, the critical current density in inter-grain boundaries, J c inter , at 2 K was 1.7 A/cm 2 in voltage–current measurement. The two-step transition seems to result from the large difference between J c intra and J c inter

  18. Effect of 14N ion irradiation on Bi2Sr2CaCu2Oy superconductors

    International Nuclear Information System (INIS)

    Sharma, M.L.; Ashwini Kumar, P.K.; Sarkar, S.K.; Virdi, G.S.; Rup, R.

    1993-01-01

    The effect of 14 N ion irradiation on a bulk Bi 2 Sr 2 CaCu 2 O y high-T c superconducting system has been studied. The incident energy was kept at 150 keV and the irradiation dose varied between 1 x 10 11 cm -2 and 1 x 10 16 cm -2 . It has been observed that the resistive transition occurs at lower temperatures for the irradiated specimens and the width (10-90% transition) of the superconducting transition decreases. Scanning transmission electron microscopy and x-ray diffraction (XRD) studies were carried out to evaluate the change in surface microstructure and XRD peak intensities due to irradiation. The results are discussed in the light of the similarity of atomic sizes of N and O atoms. (author)

  19. Synthesis and crystal structure of Na6[(UO2)3O(OH)3(SeO4)2]2·10H2O

    International Nuclear Information System (INIS)

    Baeva, E.Eh.; Serezhkina, L.B.; Virovets, A.V.; Peresypkina, E.V.

    2006-01-01

    The complex Na 6 [(UO 2 ) 3 O(OH) 3 (SeO 4 ) 2 ] 2 ·10H 2 O (I) is synthesized and studied by monocrystal X-ray diffraction. The compound crystallizes in the orthorhombic crystal system with the unit cell parameters: a=14.2225(7) A, b=18.3601(7) A, c=16.5406(6) A, V=4319.2(3) A 3, Z=4, space group Cmcm, R 1 =0.0406. Compound I is found to be a representative of the crystal-chemical group A 3 M 3 M 3 2 T 2 3 (A=UO 2 2+ , M 3 =O 2- , M 2 =OH - , T 3 =SeO 4 2- ) of the uranyl complexes; it contains layer uranium-containing groups [(UO 2 ) 3 O(OH) 3 (SeO 4 ) 2 ] 3- . These layers are linked to form a three-dimensional cage through bonds formed by the sodium atoms with the oxygen atoms of the uranyl ions and SeO 4 groups that belong to different layers [ru

  20. Structural relaxation and colour in the spinel-magnesiochromite (MgAl2O4-MgCr2O4) and gahnite-zincochromite (ZnAl2O4-ZnCr2O4) solid solution series

    Science.gov (United States)

    Hålenius, U.; Andreozzi, G. B.; Skogby, H.

    2009-04-01

    Recent studies on binary mineral solid solution series utilising synchrotron based x-ray absorption spectroscopies have indicated strong structural relaxation. For instance, it has been suggested that the real Cr-O bond distances remain nearly constant (relaxation parameter (ɛ) of 0.85, where ɛ=1 equals full relaxation) over the entire compositional range of the MgAl2O4-MgCr2O4 series (Juhin et al. 2007). In the present study we have measured room temperature optical absorption spectra of synthetic single crystals of the ZnAl2-2xCr2xO4 (0.03?x?1) and MgAl2-2xCr2xO4(0.02?x?1) series with the aim to explore the real architecture of the structure and in particular the Cr-O distance as function of composition. Our crystals were synthesized by means of flux-growth methods under atmospheric pressure and temperature profiles resulting in an estimated cation ordering temperature of ca 850 °C. Crystals close to the spinel (sensu stricto) and gahnite end-member compositions were faintly red in colour. With increasing Cr-content the crystals become more intensely red-coloured and at the higher Cr-contents there is a distinct shift towards a dark greenish colouration. These colour changes are reflected in the measured optical spectra by the position and intensity of the two spin-allowed electronic d-d transitions in octahedrally coordinated Cr3+ at ca 18000 (4A2g -4T2g (4F) transition) and 25000 cm-1(4A2g -4T1g (4F) transition). The energy of the first transition (?1-band) is ca 1200 cm-1 lower in magnesiochromite than in weakly Cr-doped spinel (x=0.02) and ca 1400 cm-1 lower in zincochromite than in gahnite with the lowest Cr-content (x=0.03). Concomitantly the energy of the second transition (?2-band) decreases with increasing Cr-content in both series by ca. 1800 cm-1. From the position of the ?1-band, a decrease in crystal field splitting, 10Dq, for six-coordinated Cr3+ with increasing Cr-content in the MgAl2-2xCr2xO4 and ZnAl2-2xCr2xO4 series of 6.5 and 7

  1. The effect of heat treatment on the properties of (Bi,Pb)2Sr2Ca2Cu3Oδ

    International Nuclear Information System (INIS)

    Fetisov, A.V.; Yasnikov, A.G.; Fotiev, A.A.

    1994-01-01

    In synthesis of (Bi,Pb) 2 Sr 2 Ca 2 Cu 2 O δ (2-2-2-3 phase), which is known to belong to a homologous series of bismuth-based superconductors, several routes have been reported to date to yield materials with a high content, around 95% of the main phase. This phase is characterized by the highest superconducting-transition temperature T c among all known high-T c materials. Based on literature data, heat-treatment conditions are expected to affect strongly the T c of the 2-2-2-3 phase, as they do for other high-T c materials. An optimal oxygen content in 2-2-2-3 was presumed to be the deciding factor for attainment of high T c 's. However, heating below ∼ 870 K in air causes no change in oxygen content in the 2-2-2-3 phase. At the same time, it is oxidizing annealing at T c up to 105-110 K. The conclusions found that changes in oxygen content for (Bi,Pb) 2 Sr 2 Ca 2 Cu 2 O δ (2-2-2-3 phase) do not affect T c , which remains unchanged after shor anneals at 370-1020 Kelvin in different atmospheres. In order to obtain high T c 's, it will suffice to exclude long anneals at 1020-1090 Kelvin from the technology. For the 2-2-2-3 phase, a degradation process, which does not change the composition of the phase, is like that for YBa 2 Cu 3 O 6+delta . Proposed is that different structural planes participate in mass exhanage with an atmosphere: (BiO) planes which do not participate to superconductivity, participate in oxygen exchange; and H 2 O and CO 2 penetrate into the CuO 2 planes, which are responsible for superconductivity in the 2-2-2-3 phase

  2. Raman-scattering results from Y1-xCaxSr2Cu2GaO7

    International Nuclear Information System (INIS)

    Salamon, D.; Liu, R.; Klein, M.V.; Groenke, D.A.; Poeppelmeier, K.R.; Dabrowski, B.; Han, P.D.; Payne, D.A.

    1993-01-01

    We present a Raman-scattering study of Y 1-x Ca x Sr 2 Cu 2 GaO 7 for both the x=0 parent compound and doped compositions with x=0.25 and x=0.40. Extrapolation from YBa 2 Cu 3 O 7-d and other cuprates allows us to assign many of the Raman-active phonon modes in the x=0 material, as well as identify a two-magnon scattering peak, a second-order phonon scattering peak, and a Raman continuum out to 4000 cm -1 . Despite compositional inhomogeneities, the doped superconducting samples show some of the same low-energy phonon features as the x=0 material. There is, however, a doping-dependent shift in the positions of features in the 500--700 cm -1 range, possibly due to Ca locating on Sr sites instead of Y sites. The relative intensities of the phonon peaks in the doped material are also changed from the insulator (x=0), suggesting that a resonant Raman phenomenon is occurring. The temperature-dependent spectra show what appears to be a superconducting dip in the background intensity, but the low superconducting fractions in these samples make this difficult to verify. The doped material also has a Raman continuum out to 4000 cm -1 just as in the x=0 samples, but with the two-magnon and second-order phonon scattering peaks significantly reduced in intensity. This may be a result of changes in the long-range ordering, or another manifestation of the same resonance phenomena occurring at lower energies. Single-crystal samples of the doped material Y 1-x Ca x Sr 2 Cu 2 GaO 7 are necessary for a more conclusive Raman study

  3. Luminescence characteristics of Mg2SiO4:Nd

    International Nuclear Information System (INIS)

    Indira, P.; Subrahmanyam, R.V.; Murthy, K.V.R.

    2011-01-01

    Thermoluminescence (TL) properties of Magnesium Ortho silicate (2:1) Mg 2 SiO 4 doped with various concentrations of rare earth (Nd) have been studied. The phosphor material were prepared using standard solid state reaction technique and heated specimens at 1100 ± 20 deg C for two hours. 4% Ammonium chloride was used as flux. The received material was grinded in an agate mortar and pestle. The TL exhibited by the Mg 2 SiO 4 with varying concentration of Nd is interesting in nature. It is interesting to note but as the concentration of Nd increases the peak around 125 deg C TL peak intensity increases. But the hump around 200 deg C resolved as TL peak at 253 deg C with high intensity. (author)

  4. NiCo2O4-Based Supercapacitor Nanomaterials

    OpenAIRE

    Chenggang Wang; E Zhou; Weidong He; Xiaolong Deng; Jinzhao Huang; Meng Ding; Xianqi Wei; Xiaojing Liu; Xijin Xu

    2017-01-01

    In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo2O4 fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electr...

  5. Magnetic excitations in La2CuO4

    International Nuclear Information System (INIS)

    Singh, R.R.P.

    1989-01-01

    The authors compare the experimentally observed magnetic excitations in La 2 CuO 4 with those calculated for a square lattice spin-1/2 Heisenberg antiferromagnet. They find that the short-wavelength spin-pair excitation spectrum deduced from light scattering, and the long wavelength spin- wave dispersion deduced from neutron scattering are both consistent with a nearest neighbor model with the exchange constant J of about 1500 K

  6. Ni doped Fe3O4 magnetic nanoparticles.

    Science.gov (United States)

    Larumbe, S; Gómez-Polo, C; Pérez-Landazábal, J I; García-Prieto, A; Alonso, J; Fdez-Gubieda, M L; Cordero, D; Gómez, J

    2012-03-01

    In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.

  7. On the superconductivity of doped La2 Cu O4

    International Nuclear Information System (INIS)

    Vasiliu-Doloc, L.; Apostol, M.

    1992-01-01

    The superconducting critical temperature and the oxygen isotope shift are analyzed as functions of the doping level x for both La 2-x Sr x Cu O 4 and La 2-x Ba x Cu O 4 within the framework of the theory of high-temperature superconductivity that assumes a coupling between the charge carriers and the oxygen-displacive modes of the lattice. It is shown that an energy gap in the electronic structure at q = ± π/4 (1,±1,0) would markedly depress the critical temperature around x = 1/8 , as for low-temperature tetragonal phase of La 2-x Ba x Cu O 4 , even in the absence of the Fermi surface nesting. On the other hand, a slight reduction in the coupling strength of the model, which may arise in the narrow range around x = 0.12, implies an increase in the oxygen-mass exponent of the lattice frequencies, a decrease in the isotope shift of the critical temperature and a depression of the critical temperature as observed experimentally for both compounds. (Author)

  8. Magnetic behavior of nanocrystalline CoFe2O4

    International Nuclear Information System (INIS)

    Zhang Kai; Holloway, T.; Pradhan, A.K.

    2011-01-01

    Magnetic nanoparticles of CoFe 2 O 4 have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. One of the nanoparticles demonstrated a constricted magnetic hysteresis loop with no or small coercivity and remanence at low magnetic field. However, the loop opens up at high magnetic field. This magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe 2 O 4 nanoparticles were synthesized under an applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments that produce Co ions and vacancies disorder. - Research highlights: → CoFe 2 O 4 nanoparticles were synthesized by co-precipitation route in a magnetic field. → Smaller nanoparticles present superparamagnetic property above their block temperature. → These nanoparticles show interesting magnetic behavior in the blocking state. → Magnetic behavior is strongly dependent on the annealing temperature.

  9. Heat capacity measurement of CeNbO4(s)

    International Nuclear Information System (INIS)

    Bhojane, S.M.; Kulkarni, Jayanthi; Kulkarni, S.G.

    2012-01-01

    Molar heat capacity of CeNbO 4 (s) was determined using differential scanning calorimeter in the temperature range of 550 to 900 K. The molar heat capacity values were least squares analysed and the dependence of molar heat capacity with temperature for CeNbO 4 (s) can be given as, J K -1 mol -1 = 94.7320 + 0.0852T-1.6073 x 10 6 T -2 (550≤T(K)≤900) Cerium is commonly used as an inactive analogue to plutonium; also it is an important fission product with moderate yield. Various Nb alloys are used as cladding material in nuclear industry. Hosts of thermodynamic data are needed to understand the various phenomena that occur in a nuclear reactor. In the present study, the molar heat capacity of CeNbO 4 (s) has been determined using high temperature differential scanning calorimeter in temperature range 550 to 900 K. This is one of the important compounds in the ternary system of Ce-Nb-O

  10. First-principles investigations of disorder effects on electronic structure and magnetic properties in Sr2CrMoO6

    International Nuclear Information System (INIS)

    Li, Q F; Zhu, X F; Chen, L F

    2008-01-01

    The electronic structures and magnetic properties are reported for ordered and disordered Sr 2 CrMoO 6 presenting oxygen vacancies or/and antisite defects (ASs). We investigate the stability of an antiparallel (AP) magnetic moment on Cr antisites and the calculations show that these solutions are more stable relative to the parallel solution for AS defects with or without oxygen vacancies. Electronic band structure calculations indicate that the perfect Sr 2 CrMoO 6 is half-metallic, and the half-metallic character is preserved for Sr 2 CrMoO 6 containing only oxygen vacancies, while the half-metallic nature is destroyed when 25% ASs (50% ASs) with or without oxygen vacancies is present. For 25% ASs with two oxygen vacancies, the system possibly shows nonmetallic behavior. The experimentally observed reduction of the magnetic moment mainly arises from an antiferromagnetic coupling of Cr-O-Cr (Cr-Cr) bonds in a disordered sample

  11. Chalcogenide oxygen reduction reaction catalysis: X-ray photoelectron spectroscopy with Ru, Ru/Se and Ru/S samples emersed from aqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Lewera, A. [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw (Poland); Inukai, J. [Clean Energy Research Center, University of Yamanashi, 7-32 Miyamae-cho, Kofu 400-0006 (Japan); Zhou, W.P. [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Cao, D. [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China); Duong, H.T. [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Alonso-Vante, N. [Laboratory of Electrocatalysis, UMR-CNRS 6503, University of Poitiers, F-86022 Poitiers (France)]. E-mail: Nicolas.Alonso.Vante@univ-poitiers.fr; Wieckowski, A. [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)]. E-mail: andrzej@scs.uiuc.edu

    2007-05-10

    Oxygen reduction Ru/Se and Ru/S fuel cell surface chalcogenide catalysts were prepared via chemical reaction of reduced Ru nanoparticles with selenium and sulfur in xylenes [D. Cao, A. Wieckowski, J. Inukai, N. Alonso-Vante, J. Electrochem. Soc. 153 (2006) A869]. The chalcogenide samples - as well as the starting chalcogens-free Ru nanoparticle material - were immobilized on a gold disk for X-ray Photoelectron Spectroscopy (XPS) characterization. While we found oxygen in most of the samples, predominantly from Ru oxides, we conclude that the oxygen on Ru/S may be located in subsurface sites: the subsurface oxygen. We also found that the transformation of the oxidized Ru black to metallic Ru required intensive electrochemical treatment, including hydrogen evolution. In contrast, five cyclic voltammetric scans in the potential range from 0.00 and 0.75 V versus RHE were sufficient to remove the oxygen forms from Ru/Se and, to a large extent, from Ru/S. We therefore conclude that Ru metal is protected against oxidation to Ru oxides by the chalcogens additives. The voltammetric treatment in the 0.00 and 0.75 V range also removed the SeO{sub 2} or SO {sub x} forms leaving anionic/elemental Se or S on the surface. Upon larger amplitude voltammetric cycling, from 0.00 to 1.20 V versus RHE, both Se and S were dissolved and the dissolution process was coincidental with the oxygen growth in/on the Ru samples.

  12. Chalcogenide oxygen reduction reaction catalysis: X-ray photoelectron spectroscopy with Ru, Ru/Se and Ru/S samples emersed from aqueous media

    International Nuclear Information System (INIS)

    Lewera, A.; Inukai, J.; Zhou, W.P.; Cao, D.; Duong, H.T.; Alonso-Vante, N.; Wieckowski, A.

    2007-01-01

    Oxygen reduction Ru/Se and Ru/S fuel cell surface chalcogenide catalysts were prepared via chemical reaction of reduced Ru nanoparticles with selenium and sulfur in xylenes [D. Cao, A. Wieckowski, J. Inukai, N. Alonso-Vante, J. Electrochem. Soc. 153 (2006) A869]. The chalcogenide samples - as well as the starting chalcogens-free Ru nanoparticle material - were immobilized on a gold disk for X-ray Photoelectron Spectroscopy (XPS) characterization. While we found oxygen in most of the samples, predominantly from Ru oxides, we conclude that the oxygen on Ru/S may be located in subsurface sites: the subsurface oxygen. We also found that the transformation of the oxidized Ru black to metallic Ru required intensive electrochemical treatment, including hydrogen evolution. In contrast, five cyclic voltammetric scans in the potential range from 0.00 and 0.75 V versus RHE were sufficient to remove the oxygen forms from Ru/Se and, to a large extent, from Ru/S. We therefore conclude that Ru metal is protected against oxidation to Ru oxides by the chalcogens additives. The voltammetric treatment in the 0.00 and 0.75 V range also removed the SeO 2 or SO x forms leaving anionic/elemental Se or S on the surface. Upon larger amplitude voltammetric cycling, from 0.00 to 1.20 V versus RHE, both Se and S were dissolved and the dissolution process was coincidental with the oxygen growth in/on the Ru samples

  13. Comparative study for the removal of Sr2+ and Pb2+ from waste solutions using synthetic and natural cow bone apatite

    International Nuclear Information System (INIS)

    Ezz El-Din, M.R.

    2007-01-01

    The aim of this study is to develop the cow bone derived apatite as a new sorbent for Sr 2+ and Pb 2+ ions from their aqueous waste solutions. In this respect, four different types of apatite (Ca 10 (PO 4 )6(OH) 2 ) were investigated. The first was natural cow bone apatite (raw bone). The second was cow bone derived apatite after treatment at 700 degree C. The third was synthetic apatite and the last was commercial apatite supplied from Bio Rad company, USA. Removal of Sr 2+ and Pb 2+ by the studied samples was investigated using batch experiments. The different parameters affecting sorption process such as contact time, metal ion concentration and hydrogen ion concentration of the aqueous phase were studied. Desorption of the investigated ions from the loaded samples was also studied. The results obtained showed that the raw cow bone was more effective than the other investigated HAP for adsorbing both Sr 2+ and Pb 2+ ions since the removal percentage of Sr 2+ and Pb 2+ by natural cow bone apatite were 85% and 98%, respectively, while the removal of Sr 2+ and Pb 2+ by the synthetic apatite were 71% and 62%, respectively. From the obtained data, it can be concluded that the natural (raw) cow bone apatite can be used as an ion exchanger for removal of some radioactive elements that may present in radioactive waste solutions as well as it could be considered as a new competitor of the other natural absorbents. Therefore, it is recommended that the natural cow bone apatite could be used for removal of both Sr 2+ and Pb 2+ from radioactive waste solutions as well as other wastewater

  14. Synthesis and optical properties of red/blue-emitting Sr2MgSi2O7:Eu3+/Eu2+ phosphors for white LED

    Directory of Open Access Journals (Sweden)

    Tong Thi Hao Tam

    2016-06-01

    Full Text Available Phosphor-converted white light emitting diodes (white LEDs have received great attention in recent years since they have several excellent features such as high lumen output, low power consumption, long lifetime and environmentally friendly. In this work, we report the co-precipitation synthesis of red/blue Sr2MgSi2O7:Eu3+/Eu2+ phosphors with various Eu doping concentration. The results show that the obtained Sr2MgSi2O7:Eu3+/Eu2+ phosphors have good crystallinity and emit strong red (Sr2MgSi2O7:Eu3+ and blue (Sr2MgSi2O7:Eu2+ emissions under near UV light excitation. The sharp emission peaks at 577, 590, 612, 653, and 701 nm corresponded to the typical 5D0 → 7Fj (j = 0,1,2,3,4 transitions of Eu3+, and the blue emission peaking at 460 nm is attributed to the typical 4f65d1-4f7 transition of Eu2+ in the same Sr2MgSi2O7 host lattice. Both phosphors can be well excited in the wavelength range of 260–400 nm where the near UV-LED is well matched. The above results suggest that the Sr2MgSi2O7:Eu3+/Eu2+ phosphors are promising red/blue-emitting phosphors for the application in near UV pumped phosphor-converted white LEDs.

  15. Electrochemiluminescence resonance energy transfer system between GNRs and Ru(bpy)32+: Application in magnetic aptasensor for β-amyloid.

    Science.gov (United States)

    Ke, Hong; Sha, Haifeng; Wang, Yinfang; Guo, Weiwei; Zhang, Xin; Wang, Zhiming; Huang, Chusen; Jia, Nengqin

    2018-02-15

    Electrochemiluminescent (ECL) assay has gradually drawn increasing interest in the biomedical analysis. This paper proposed a new methodology for ultrasensitive and facile detection of Alzheimer's disease marker β-amyloid (Aβ) by fabricating a sandwich-type ECL sensing platform. Herein, electrochemiluminescence resonance energy transfer (ECL-RET) was employed to determine Aβ concentration, which can be attributed to the quenching effect from RET between Ru(bpy) 3 2+ and gold nanorods (GNRs) acting as ECL-RET electron donor and acceptor, respectively. In this protocol, mesoporous carbon nanospheres were adopted to immobilize ECL reactant Ru(bpy) 3 2+ and antibody via nafion to acquire the RET donor nanocomposites (MOCs/nafion/Ru(bpy) 3 2+ /antibody), which were tightly interconnected with epoxy group functionalized Fe 3 O 4 nanoparticles. It is of vital importance that GNRs with exquisite rod shape were synthesized and exhibited a typical absorption peak at 650nm to quench ECL signal of Ru(bpy) 3 2+ effectively. In addition, the ECL emission decreased linearly with the logarithm of Aβ concentration in a wide linear range from 1.0 × 10 -5 to 100ng/mL with a detection limit of 4.2 × 10 -6 ng/mL. Furthermore, distinctive and desirable properties were verified to declare the promise for being applicable to analyze the Aβ content in real Alzheimer's cerebrospinal fluid samples with satisfactory results. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Enhanced high-frequency microwave absorption of Fe3O4 architectures based on porous nanoflake

    DEFF Research Database (Denmark)

    Wang, Xiaoliang; Liu, Yanguo; Han, Hongyan

    2017-01-01

    Hierarchical Fe3O4 architectures assembled with porous nanoplates (p-Fe3O4) were synthesized. Due to the strong shape anisotropy of the nanoplates, the p-Fe3O4 exhibits increased microwave resonance towards high frequency range. The improved microwave absorption properties of the p-Fe3O4, includi...

  17. Enhanced high-frequency microwave absorption of Fe3O4 architectures based on porous nanoflake

    DEFF Research Database (Denmark)

    Wang, Xiaoliang; Liu, Yanguo; Han, Hongyan

    2017-01-01

    Hierarchical Fe3O4 architectures assembled with porous nanoplates (p-Fe3O4) were synthesized. Due to the strong shape anisotropy of the nanoplates, the p-Fe3O4 exhibits increased microwave resonance towards high frequency range. The improved microwave absorption properties of the p-Fe3O4, including...

  18. Crystal structure, intensity luminescence characteristics and stimulated radiation of disordered gallate LaSr2Ga11O20-Nd3+

    International Nuclear Information System (INIS)

    Kaminskij, A.A.; Mill', B.V.; Belokoneva, E.L.; Butashin, A.V.; Sarkisov, S.Eh.; Kurbanov, K.; Khodzhabagyan, G.G.

    1986-01-01

    LnA 2 2+ Ga 11 O 20 and A 3 2+ M 0.5 5+ Ga 10.5 O 20 compounds are synthesized, LaSr 2 Ga 11 O 20 and LaSr 2 Ga 11 O 20 -Nd 3+ monocrystals are grown by Czochralski method. Their X-ray diffraction analysis is conducted, absorption - luminescence characteristics are obtained, stimulated Nd 3+ ion radiation is excited and investigated in two generating channel waves 4 F 3/2 → 4 I 11/2,13/2 at 300 K

  19. Study on the equilibrium in the MBr2-CH3OH-H2O system (M = Sr2+, Ba2+) at 25 0C

    International Nuclear Information System (INIS)

    Zlateva, I.; Stoev, M.

    1985-01-01

    The dehydration processes in the three-component system MBr 2 -CH 3 OH-H 2 O (M = Sr 2+ , Ba 2+ ) have been studied at 25 0 C by physio-chemical analyses. Crystallization fields for the lower crystal hydrates SrBr 2 x H 2 O and BaBr 2 x H 2 O have been found. The solubility curves exhibit complex-formation processes. The dehydration and solvation processes in three-component system such as MBr 2 -CH 3 OH-H 2 O at 25 0 C with M = Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ have been discussed in general terms. (author)

  20. Influencia de los iones Ba2+ y Sr2+ en el proceso de hidratación del cemento portland y de los cementos con adiciones activas

    OpenAIRE

    Živanović, B. M.; Petrašinović, Lj.; Milovanović, T.; Karanović, Lj.; Krstanović, I.

    1987-01-01

    En el presente trabajo se estudia la influencia de la concentración de los iones Sr2+ y Ba2+ en las aguas de amasado sobre el proceso de hidratación de varios cementos portland y de adición. Se comprueba un incremento de las resistencias mecánicas de dichos cementos, a los 28 días, cuando aumenta la concentración de los iones Ba2+ y Sr2+ en las aguas de amasado, lo cual sugiere una posible explicación microestructural a dicho fenómeno.

  1. Three-Dimensional NiCo2O4@MnMoO4 Core-Shell Nanoarrays for High-Performance Asymmetric Supercapacitors.

    Science.gov (United States)

    Yuan, Yuliang; Wang, Weicheng; Yang, Jie; Tang, Haichao; Ye, Zhizhen; Zeng, Yujia; Lu, Jianguo

    2017-10-10

    Design of new materials with sophisticated nanostructure has been proven to be an efficient strategy to improve their properties in many applications. Herein, we demonstrate the successful combination of high electron conductive materials of NiCo 2 O 4 with high capacitance materials of MnMoO 4 by forming a core-shell nanostructure. The NiCo 2 O 4 @MnMoO 4 core-shell nanoarrays (CSNAs) electrode possesses high capacitance of 1169 F g -1 (4.24 F cm -2 ) at a current density of 2.5 mA cm -2 , obviously larger than the pristine NiCo 2 O 4 electrode. The asymmetric supercapacitors (ASCs), assembled with NiCo 2 O 4 @MnMoO 4 CSNAs as binder-free cathode and active carbon (AC) as anode, exhibit high energy density of 15 Wh kg -1 and high power density of 6734 W kg -1 . Cycle performance of NiCo 2 O 4 @MnMoO 4 CSNAs//AC ASCs, conducted at current density of 20 mA cm -2 , remain 96.45% of the initial capacitance after 10,000 cycles, demonstrating its excellent long-term cycle stability. Kinetically decoupled analysis reveals that the capacitive capacitance is dominant in the total capacitance of NiCo 2 O 4 @MnMoO 4 CSNAs electrode, which may be the reason for ultra long cycle stability of ASCs. Our assembled button ASC can easily light up a red LED for 30 min and a green LED for 10 min after being charged for 30 s. The remarkable electrochemical performance of NiCo 2 O 4 @MnMoO 4 CSNAs//AC ASCs is attributed to its enhanced surface area, abundant electroactive sites, facile electrolyte infiltration into the 3D NiCo 2 O 4 @MnMnO 4 nanoarrays and fast electron and ion transport path.

  2. Osmotic and activity coefficients of aqueous NaTcO4 and NaReO4 solutions at 250C

    International Nuclear Information System (INIS)

    Boyd, G.E.

    1978-01-01

    Isopiestic vapor-pressure comparison experiments were performed with aqueous binary sodium perchlorate, pertechnetate, and perrhenate solutions to concentrations of approximately 8.5 m. Osmotic coefficients for these solutions and mean molal ionic activity coefficients for NaTcO 4 and NaReO 4 were derived from the isotonic molalities. Pitzer's treatment was applied to describe the concentration dependence of the osmotic coefficients of NaClO 4 , NaTcO 4 , and NaReO 4 , and the implications of the parameters derived from a least-squares fit are discussed in terms of solvent structure and interionic forces. 4 tables, 1 figure

  3. Lesion Orientation of O4-Alkylthymidine Influences Replication by Human DNA Polymerase η

    OpenAIRE

    O’Flaherty, D. K.; Patra, A.; Su, Y.; Guengerich, F. P.; Egli, M.; Wilds, C. J.

    2016-01-01

    DNA lesions that elude repair may undergo translesion synthesis catalyzed by Y-family DNA polymerases. O4-Alkylthymidines, persistent adducts that can result from carcinogenic agents, may be encountered by DNA polymerases. The influence of lesion orientation around the C4-O4 bond on processing by human DNA polymerase η (hPol η) was studied for oligonucleotides containing O4-methylthymidine, O4-ethylthymidine, and analogs restricting the O4-methylene group in an anti-orientation. Primer extens...

  4. Ru-assisted synthesis of Pd/Ru nanodendrites with high activity for ethanol electrooxidation

    Science.gov (United States)

    Zhang, Ke; Bin, Duan; Yang, Beibei; Wang, Caiqin; Ren, Fangfang; Du, Yukou

    2015-07-01

    Due to the specific physical and chemical properties of a highly branched noble metal, the controllable synthesis has attracted much attention. This article reports the synthesis of Pd/Ru nanodendrites by a facile method using an oil bath in the presence of polyvinyl pyrrolidone, potassium bromide and ascorbic acid. The morphology, structure, and composition of the as-prepared catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In the electrochemical measurement, the as-prepared Pd7/Ru1 bimetallic nanodendrites provide a large electrochemically active surface area and exhibit high peak current density in the forward scan toward ethanol electrooxidation, which is nearly four times higher than those of a pure Pd catalyst. The as-prepared Pd7/Ru1 catalysts also exhibit significantly enhanced cycling stability toward ethanol oxidation in alkaline medium, which are mainly ascribed to the synergetic effect between Pd and Ru. This indicates that the Pd7/Ru1 catalysts should have great potential applications in direct ethanol fuel cells.Due to the specific physical and chemical properties of a highly branched noble metal, the controllable synthesis has attracted much attention. This article reports the synthesis of Pd/Ru nanodendrites by a facile method using an oil bath in the presence of polyvinyl pyrrolidone, potassium bromide and ascorbic acid. The morphology, structure, and composition of the as-prepared catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In the electrochemical measurement, the as-prepared Pd7/Ru1 bimetallic nanodendrites provide a large electrochemically active surface area and exhibit high peak current density in the forward scan toward ethanol electrooxidation, which is nearly four times higher than those of a pure Pd catalyst. The as-prepared Pd7/Ru1 catalysts also exhibit significantly

  5. Carbon monoxide oxidation on bimetallic Ru/Au(111 surfaces

    Directory of Open Access Journals (Sweden)

    ROLF-JÜRGEN BEHM

    2001-02-01

    Full Text Available The electrochemical deposition of Ru on Au(111 was performed in 0.5 M H2SO4+10-4 M RuCl3 . The obtained bimetallic Ru/Au(111 surfaces were character-ised by cyclic voltammetry and in situ STM in 0.5 MH2SO4. The Ru deposit consists of nanoscale islands, which merge with increasing coverage. Two different types of bimetallic Ru/Au(111 surfaces with respect to the distribution of Ru islands over the Au(111 substrate surface were obtained. When the deposition was performed at potentials more positive than the range of Au(111 reconstruction, homogeneous nucleation occured resulting in a random distribution of Ru islands. When the deposition was performed on reconstructed Au(111 at low overpotentials, selective nucleation occured resulting in the replication of the Au(111 reconstruction. Only at higher deposition overpotentials, can multilayer deposits be formed, which exhibit a very rough surface morphology. The electrocatalytic activity of such structurally well defined Ru/Au(111 bimetallic surfaces was studied towards CO oxidation with the Ru coverage ranging from submonolayer to several monolayer. COstripping commences at about 0.2 Vand occurs over a broad potential range. The observed influence of the Ru structure on the CO stripping voltammetry is explained by local variations in the COadsorption energy, caused by differences in the local Ru structure and by effects induced by the Au(111 substrate.

  6. Phase formation in the Ag2O - MgO - MoO3 system and the crystal structure of new double molybdate Ag2Mg2(MoO4)3

    International Nuclear Information System (INIS)

    Tsyrenova, G.D.; Khajkina, E.G.; Khobrakova, Eh.T.; Solodovnikov, S.F.

    2001-01-01

    The phase correlations in subsolidus area of the Ag 2 O - MgO - MoO 3 system were studied, the Ag 2 MoO 4 - MgMoO 4 polythermal cross-section was investigated and its T-x diagram was constructed. X-ray diffraction and thermal analytic researches were conducted. The formation of the new double Ag 2 Mg 2 (MoO 4 ) 3 molybdates relating to the structural group Na 2 Mg 5 (MoO 4 ) 6 was established, and its structure (a=6.978(1), b=8.715(2), c=10.294(2) A, α=107.56(3) Deg, β=105.11(3) Deg, γ=103.68(3) Deg, Z=2, sp. gr. P 1-bar, R=0.038) was determined. The mixed carcass from the twin MgO 6 -octahedrons and MoO 4 -tetrahedrons, in which blankness the Ag atoms are arranged, stand out in the structure.The character of disordering in the part of Ag + is analogous to previously found one in the Ag 2 Zn 2 (MoO 4 ) 3 structure. The possible limits in the fields of homogeneity of silver-magnesium molybdate and its analogs, as well as the differences their structure from the structure of isotopic sodium-containing phases, are discussed [ru

  7. Mass spectrometric determination of stability of gaseous BaMoO2, Ba2MoO4, Ba2MoO5, Ba2Mo2O8 molecules

    International Nuclear Information System (INIS)

    Kudin, L.S.; Balduchchi, Dzh.; Dzhil'i, G.; Gvido, M.

    1982-01-01

    During the mass spectrometric investigation of BaCrO 4 evaporation Cr + , Ba + , BaO + main ions are recorded as well as BaMoO 4 + , BaMoO 3 + , BaMoO 2 + , BaMoO + , BaMoO 4 + , Ba 2 MoO 5 + , BaMo 2 O 8 + ions - the products of ionization of three-component (Ba, Mo, M) molecules, forming as a result of substance chemical interaction with the material of an effusion cell (Mo). Heats of formation of BaMoO 2 , Ba 2 MoO 4 , Ba 2 MoO 5 and Ba 2 Mo 2 O 8 molecules which constituted - 577+-70, -1343+-115, -1464+-70, -2393+-90 k J/mol respectively are determined on the base of the analysis of curves of ionisation efficiency and of reaction heats Ba 2 MoO 5 =BaO+BaMoO 4 , ΔH 0 0 =322+-60 kJ/mol Ba 2 Mo 2 O 8 =2BaMoO 4 , ΔH 0 0 =351+-80 kJ/mol calculated with the use of third low of thermodynamics [ru

  8. The provenance investigation on ancient chinese Ru porcelains by NAA

    International Nuclear Information System (INIS)

    Gao Zhengyao; Wang Jie; Chen Songhua

    1997-01-01

    The 28 samples of glazes and bodies of ancient Chinese Ru porcelains are analyzed by neutron activation. The 36 element contents in each sample are determined. The neutron activation analysis (NAA) data are analyzed by fuzzy cluster. The trend cluster diagram is obtained. The result shows that the ancient Chinese Ru porcelains were most probably from the same raw material source though they were from different time, fired in different kilns and in different colors. The near provenance relation between ancient Jun porcelain and ancient Ru porcelain is preliminarily analyzed. The two modern Ru porcelains approximate to ancient Ru porcelains, one becomes estranged from ancient Ru porcelains. Jingdezhen porcelain is unconcerned with Ru porcelains

  9. High-pressure behavior of CaMo O4

    Science.gov (United States)

    Panchal, V.; Garg, N.; Poswal, H. K.; Errandonea, D.; Rodríguez-Hernández, P.; Muñoz, A.; Cavalli, E.

    2017-09-01

    We report a high-pressure study of tetragonal scheelite-type CaMo O4 up to 29 GPa. In order to characterize its high-pressure behavior, we have combined Raman and optical-absorption measurements with density functional theory calculations. We have found evidence of a pressure-induced phase transition near 15 GPa. Experiments and calculations agree in assigning the high-pressure phase to a monoclinic fergusonite-type structure. The reported results are consistent with previous powder x-ray-diffraction experiments, but are in contradiction with the conclusions obtained from earlier Raman measurements, which support the existence of more than one phase transition in the pressure range covered by our studies. The observed scheelite-fergusonite transition induces significant changes in the electronic band gap and phonon spectrum of CaMo O4 . We have determined the pressure evolution of the band gap for the low- and high-pressure phases as well as the frequencies and pressure dependencies of the Raman-active and infrared-active modes. In addition, based on calculations of the phonon dispersion of the scheelite phase, carried out at a pressure higher than the transition pressure, we propose a possible mechanism for the reported phase transition. Furthermore, from the calculations we determined the pressure dependence of the unit-cell parameters and atomic positions of the different phases and their room-temperature equations of state. These results are compared with previous experiments showing a very good agreement. Finally, information on bond compressibility is reported and correlated with the macroscopic compressibility of CaMo O4 . The reported results are of interest for the many technological applications of this oxide.

  10. Josephson effectss in bicrystalline Bi2Sr2CaCu2O8+δ thin films

    International Nuclear Information System (INIS)

    Amrein, T.

    1994-08-01

    A pulsed laser deposition process is developed for preparing high quality thin films of Bi 2 Sr 2 CaCu 2 O x on different substrates. Both microstructural and electrical properties of the superconducting films are well characterized, e.g. by SEM, TEM and AFM. The high reproducability of the thin film quality facilitated a detailed study of Josephson effects in bicrystalline grain boundary junctions (GBJs). Thin films are deposited on commercially available (001) SrTiO 3 bicrystalls and patterned by standard photolithography using wet-etching or Ar + -ion milling. The width of the micobridges ranges from 2 to 111 μm. The critical current densities across grain boundaries of thin film bicrystals have been measured as a function of the tilt angle Θ. For Θ=0 to 45 , the ratio of the grain boundary critical current density to the bulk critical current density decreases exponentially with increasing tilt angle. Microstructure investigations show a rough grain boundary of the superconductor (roughness 100 nm-1 μm) which is not determined by the roughness of the substrate grain boundary (1-3 nm) but by the island-plus-layer growth of the twin domains. The electrical properties are well described by the resistively shunted junction (RSJ) model. The I c R n -product reaches values of 2.2 mV at 4.2 K and 60 μV at 77 K. An optimized design for dc SQUIDs (Θ=24 ) is developed relating to the results of single GBJs. The values of the transfer function (∂V/∂Φ) run up to 74 μV/Φ o . The equivalent flux noise which is measured in a flux-locked loop mode amounts 4.5 to 25 μPhi o Hz in the white noise region for Φ≥25-50 Hz and 13 to 150 μΦ o Hz at 1 Hz. In conclusion, microstructural as well as electrical properties of bicrystalline Bi 2 Sr 2 CaCu 2 O x and YBa 2 Cu 3 O y GBJs are more or less equal. (orig.)

  11. Electronic structure studies of La2CuO4

    Science.gov (United States)

    Wachs, A. L.; Turchi, P. E. A.; Jean, Y. C.; Wetzler, K. H.; Howell, R. H.; Fluss, M. J.; Harshman, D. R.; Remeika, J. P.; Cooper, A. S.; Fleming, R. M.

    1988-07-01

    We report results of positron-electron momentum-distribution measurements of single-crystal La2CuO4 using two-dimensional angular correlation of positron-annihilation-radiation techniques. The data contain two components: a large (~85%), isotropic corelike electron contribution and a remaining, anisotropic valence-electron contribution modeled using a linear combination of atomic orbitals-molecular orbital method and a localized ion scheme, within the independent-particle model approximation. This work suggests a ligand-field Hamiltonian to be justified for describing the electronic properties of perovskite materials.

  12. Electrolytic 99TcO4- reduction at inert electrodes

    International Nuclear Information System (INIS)

    Kremer, C.; Gambino, D.; Leon, A.; Kremer, E.

    1990-01-01

    Electrolytic pertechnetate reduction at inert electrodes was studied as an alternative procedure for synthesizing Tc complexes. Pertechnetate reduction was carried out in aqueous media using different aminated ligands (en, dien, trien and 1,3-dap) forming [TcO 2 (amine) 2 ] + type complexes. Simultaneously with synthesis of the desired Tc complex, TcO 2 was electrodeposited onto the cathode. Conversion of TcO 4 - to Tc complex and TcO 2 was studied as a function of several variables (kind and concentration of supporting electrolyte, ligand concentration, pH, current and electrolysis time). (author) 9 refs.; 6 figs.; 1 tab

  13. Electronic structure studies of La2CuO4

    International Nuclear Information System (INIS)

    Wachs, A.L.; Turchi, P.E.A.; Jean, Y.C.

    1988-01-01

    We report results of positron-electron momentum-distribution measurements of single-crystal La 2 CuO 4 using two-dimensional angular correlation of positron-annihilation-radiation techniques. The data contain two components: a large (∼85%), isotropic corelike electron contribution and a remaining, anisotropic valence-electron contribution modeled using a linear combination of atomic orbitals--molecular orbital method and a localized ion scheme, within the independent-particle model approximation. This work suggests a ligand-field Hamiltonian to be justified for describing the electronic properties of perovskite materials

  14. Positron annihilation study in La2CuO4

    International Nuclear Information System (INIS)

    Kubo, Y.; Asano, S.

    1992-01-01

    The positron annihilation study for La 2 CuO 4 are performed using the full-potential linearized augmented-plane-wave(FLAPW) calculated electron and positron densities. The electron-positron momentum density(EPMD) is computed, and the well known Lock-Crisp-West(LCW) zone folding of the EPMD is produced. In the LCW analysis, small residual variations of order about 3 % are observed. The calculations show that the relative weights of the Fermi surface discontinuities are substantially altered due to the positron preferentially sampling the Cu-O plane region

  15. Relaxation of photodielectric effect in Pb3O4 layers

    International Nuclear Information System (INIS)

    Avanesyan, V. T.; Baranova, E. P.

    2007-01-01

    Experimental data on the kinetics of the photodielectric effect in layers of red lead (Pb 3 O 4 ) are reported. The photocapacitive properties and dielectric loss under photoexcitation have been studied with the spectral composition of light varied at low frequencies of the measuring field. The dielectric parameters attain steady values long after light is switched on (off). The relationship of the photodielectric phenomena with structural features of the semiconductor and, in particular, with the presence of lone pair electrons of Pb 2+ cations is discussed

  16. Enzymes immobilization on Fe 3O 4-gold nanoparticles

    Science.gov (United States)

    Kalska-Szostko, B.; Rogowska, M.; Dubis, A.; Szymański, K.

    2012-01-01

    In the present study Fe3O4 magnetic nanoparticles were synthesized by coprecipitation of Fe2+ and Fe3+ from chlorides. In the next step magnetite-gold core-shell nanoparticles were synthesized from HAuCl4 using an ethanol as a reducing agent. Finally, magnetic nanoparticles were functionalized by hexadecanethiol. The immobilization of biological molecules (trypsin and glucose oxidase) to the thiol-modified and unmodified magnetite-gold nanoparticles surface was tested. The resulting nanoparticles were characterized by infrared spectroscopy, differential scanning calorimetry, Mössbauer spectroscopy and transmission electron microscopy.

  17. EFFECT OF ALKALINE IONS ON THE PHASE EVOLUTION, PHOTOLUMINESCENCE, AND AFTERGLOW PROPERTIES OF SrAl2O4: Eu2+, Dy3+ PHOSPHOR

    Directory of Open Access Journals (Sweden)

    HYUNHO SHIN

    2012-12-01

    Full Text Available A series of SrAl2O4: Eu2+, Dy3+ long-afterglow (LAG phosphors with varying concentration of Li+, Na+ and K+, has been synthesized. The increased concentration of the three types of alkaline ions does not decrease the quantity of the total luminescent phases (SrAl2O4 plus Sr4Al14O25, but a different set of secondary phases has been evoluted for the K+-added series due to the failure of the incorporation of relatively large K+ (1.38 Å to the Sr2+ (1.18 Å site in the hosts, unlike the cases of smaller Li+ (0.76 Å and Na+ (1.02 Å ions. PL excitation, PL emission, and LAG luminescence, are decreased by all investigated alkaline ions, which would be due to the diminished incorporation of Eu2+ and Dy3+ activators into the luminescent hosts by the alkaline ions. For the cases of the Li+ and Na+-added series, the incorporated Li+ or Na+ to the luminescent hosts would also limit the activation of Eu2+ and charge trapping/detrapping of Dy3+ to yield the diminished PL properties and LAG luminescence. The type of defect complex formed by the addition of Li+ and Na+ ions has been deduced and compared with that formed when no alkaline ion is added.

  18. Effect of compositional variations on charge compensation of AlO4 and BO4 entities and on crystallization tendency of a rare-earth-rich aluminoborosilicate glass

    International Nuclear Information System (INIS)

    Quintas, A.; Caurant, D.; Majerus, O.; Charpentier, T.; Dussossoy, J.-L.

    2009-01-01

    This paper presents the structural and crystallization study of a rare-earth-rich aluminoborosilicate glass that is a simplified version of a new nuclear glass proven to be a potential candidate for the immobilization of highly concentrated radioactive wastes that will be produced in the future. In this work, we studied the impact of changing the nature of alkali (Li + , Na + , K + , Rb + , Cs + ) or alkaline-earth (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ) cations present in glass composition on glass structure (by 27 Al and 11 B nuclear magnetic resonance spectroscopy) and on its crystallization tendency during melt cooling at 1 K/min (average cooling rate during industrial process). From these composition changes, it was established that alkali cations were preferentially involved in charge compensation of (AlO 4 ) - and (BO 4 ) - entities in the glassy network comparatively to alkaline-earth cations. Whatever the nature of alkali cations, glass compositions containing calcium gave way to the crystallization of an apatite silicate phase bearing calcium and rare-earth (RE) cations (Ca 2 RE 8 (SiO 4 ) 6 O 2 , RE = Nd or La) but melt crystallization tendency during cooling strongly varied with the nature of alkaline-earth cations.

  19. Electronic Phase Separation in Pr1x(Ca, Sr)xMnO3δ and Tunneling Magnetoresistance in Sr2FeMoO6

    International Nuclear Information System (INIS)

    Niebieskikwiat, Dario

    2003-01-01

    of the origin of the PS phenomenon. Finally, in the ordered double perovskite Sr 2 FeMoO 6 the studies were mainly oriented to the magnetotransport properties. In this material we have analyzed the influence of the oxidation of the grain boundaries (gb) on the tunneling magnetoresistance (TMR), which is observed in ferromagnetic perovskites at low magnetic fields. We showed that the oxidation of the gb induces the formation of SrMoO 4 impurities that reinforce the intergranular insulating barriers, producing an increase of resistivity and notably improving the TMR without affecting the magnetism.By other way, we found the the effects of the Fe/Mo disorder are important for the TMR only when the gb barriers are small. However, when the gb resistance increases due to the oxidation, the intergranular barriers dominate and determine the value of the tunneling magnetoresistance

  20. Thermally-activated vortex dynamics in bismuth calcium strontium copper oxide (Bi2CaSr2Cu2O8+δ) studied by complex susceptibility measurements

    NARCIS (Netherlands)

    Emmen, J.H.P.M.; Brabers, V.A.M.; Jonge, de W.J.M.

    1991-01-01

    Complex AC magnetic susceptibility has been measured on Bi2CaSr2Cu2O8+d single crystals with hnc, Hdc|c-axis. It will be shown that field, frequency and temperature dependence of both ¿' and ¿¿ in a constant but sufficiently large DC magnetic field can quantitatively be described by

  1. Major haplotype divergence including multiple germin-like protein genes, at the wheat Sr2 adult plant stem rust resistance locus

    Czech Academy of Sciences Publication Activity Database

    Mago, R.; Tabe, L.; Vautrin, S.; Šimková, Hana; Kubaláková, Marie; Upadhyaya, N.; Berges, H.; Kong, X.Y.; Breen, J.; Doležel, Jaroslav; Appels, R.; Ellis, J.G.; Spielmeyer, W.

    2014-01-01

    Roč. 14, č. 379 (2014) ISSN 1471-2229 R&D Projects: GA ČR GBP501/12/G090; GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Adult plant resistance (APR) * Map-based cloning * Sr2 Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.813, year: 2014

  2. Two-step transition towards the reversibility region in Bi2Sr2CaCu2O8-δ single crystals

    Science.gov (United States)

    Pastoriza, H.; de La Cruz, F.; Mitzi, D. B.; Kapitulnik, A.

    1992-10-01

    We have performed magnetization measurements on Bi2Sr2CaCu2O8-δ single crystals in the c^ crystallographic direction for fields from 2 Oe up to 700 Oe. The results strongly suggest that the reversible thermodynamic region is achieved after the vortex flux structure shows an abrupt transition at a temperature lower than that determined by the irreversibility line.

  3. Thermal expansion behaviour in the oxygen deficient perovskites Sr2BSbO5.5 (B=Ca, Sr, Ba). Competing effects of water and oxygen ordering

    International Nuclear Information System (INIS)

    Zhou Qingdi; Kennedy, Brendan J.; Avdeev, Maxim

    2011-01-01

    Neutron diffractions studies reveal the presence of oxygen disorder in the oxygen deficient perovskites Sr 2 BSbO 5.5 (B=Ca, Sr, Ba). Synchrotron X-ray studies demonstrate that these oxides have a double perovskite-type structure with the cell size increasing as the size of the B cation increases from 8.2114(2) A for B=Ca to 8.4408(1) A for B=Ba. It is postulated that a combination of local clustering of the anions and vacancies together with water-water and water-host hydrogen bonds plays a role in defining the volume of the encapsulated water clusters and that changes in the local structure upon heating result in anomalous thermal expansion observed in variable temperature diffraction measurements. - Graphical abstract: The oxides Sr 2 BSbO 5.5 (B=Ca, Sr, Ba) have unusual anion disorder. There is a lag in the contraction in the cell size of Sr 2 CaSbO 5.5 nH 2 O established from X-ray diffraction measurements following the loss of water suggesting changes on the local structure are important. Highlights: → The average structures of the defect perovskites Sr 2 MSbO 5.5 established. → Anion and cation disorder quantified by neutron and synchrotron X-ray diffraction. → Anomalous thermal expansion due to local clustering of anions and vacancies observed.

  4. Synthesis and characterization of La1+xSr2-xCoMnO7-δ (x=0,0.2; δ=0,1)

    International Nuclear Information System (INIS)

    El Shinawi, H.; Bertha, A.; Hadermann, J.; Herranz, T.; Santos, B.; Marco, J.F.; Berry, F.J.; Greaves, C.

    2010-01-01

    The n=2 Ruddlesden-Popper phases LaSr 2 CoMnO 7 and La 1.2 Sr 1.8 CoMnO 7 have been synthesized by a sol-gel method. The O6-type phases LaSr 2 CoMnO 6 and La 1.2 Sr 1.8 CoMnO 6 were produced by reduction of the O7 phases under a hydrogen atmosphere. The materials crystallize in the tetragonal I4/mmm space group with no evidence of long-range cation order in the neutron and electron diffraction data. Oxygen vacancies in the reduced materials are located primarily at the common apex of the double perovskite layers giving rise to square pyramidal coordination around cobalt and manganese ions. The oxidation states Co 3+ /Mn 4+ and Co 2+ /Mn 3+ predominate in the as-prepared and reduced materials, respectively. The materials are spin glasses at low temperature and the dominant magnetic interactions change from ferro- to antiferromagnetic following reduction. - Graphical abstract: The n=2 Ruddlesden-Popper phases LaSr 2 CoMnO 7 , La 1.2 Sr 1.8 CoMnO 7 , LaSr 2 CoMnO 6 and La 1.2 Sr 1.8 CoMnO 6 are synthesized and characterized.

  5. Luminescence of Ce3+ at two different sites in ?-Sr2P2O7 under vacuum ultraviolet-UV and x-ray excitation

    NARCIS (Netherlands)

    Hou, D.; Han, B.; Chen, W.; Liang, H.; Su, Q.; Dorenbos, P.; Huang, Y.; Gao, Z.; Tao, Y.

    2010-01-01

    A series of Ce3+ doped ?-Sr2?2xCexNaxP2O7 phosphor compounds has been prepared using a high-temperature solid-state reaction technique. The luminescence properties under vacuum ultraviolet-UV and x-ray excitation were studied. Luminescence spectra reveal three UV-emitting peaks at about 310, 330,

  6. Migration of NpO2+ and Sr2+ in the Vicinity of a Radioactive Waste Repository Under the Coexistence of Humic Acid

    International Nuclear Information System (INIS)

    Ezz El-Din, M.R.; Sheha, R.R.; El-Naggar, H.A.

    1999-01-01

    The migration of the dispersed radionuclides in the vicinity of a radioactive waste repository with groundwater have a predominant role in confirming the suitability of the disposal site. For such assessment process, the sorption of NpO 2 + and Sr 2+ on different soil samples, collected from the proposed repository site in Inshas area, was studied in batch technique. The uptake percent of NpO 2 + ions increases with a varied sensitivity, with increasing the pH value, giving a sigmoidal shape. While the uptake of Sr 2+ ions shows a slight increase as the pH value increased. The distribution coefficient (K d ) of NpO 2 + decreases by increasing the humic acid concentration but k d value of Sr 2+ displays a constant value. Also, the mean relative migration velocity of NpO 2 + in the studied zone, is 5.53x10 -3 cm/day enhanced by the presence of 100 mg/1 humic acid to 326x10 -3 cm/day, while that of Sr 2+ is 2.19x10 -3 cm/day and is independent of the coexistence of humic acid. The revealed data were mathematically treated using a developed computer model for the dispersion of radionuclides in the geosphere to elucidate the migration behavior of these radioactive species in the selected site and to quantitatively predict their concentration at different distances in both x and z directions over long time scales

  7. Preparation of (Bi,Pb)2Sr2Ca2Cu3Ox precursor powders by a modified polyethylene glycol based sol-gel process

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Andersen, N.H.

    2002-01-01

    A modified sol-gel process based on polyethylene glycol has been developed for preparing (Bi,Pb)(2)Sr2Ca2Cu3Ox precursor powders in view of Ag-sheeted tape manufacture. A careful control of the pH and concentration temperature yields an amorphous gel, which can be converted to a fine and extremely...

  8. High-pressure structural behavior of the double perovskite Sr2CrReO6: an experimental and theoretical study

    DEFF Research Database (Denmark)

    Olsen, J.S.; Gerward, Leif; Vaitheeswaran, G.

    2009-01-01

    The high-pressure structural behavior of Sr2CrReO6 has been studied experimentally using synchrotron radiation and the diamond anvil cell and theoretically using density functional theory. The experimental zero-pressure bulk modulus is B0=1704GPa and the pressure derivative is B0'=4.71.0. These r...

  9. Antifungal activity of multifunctional Fe 3O 4-Ag nanocolloids

    Science.gov (United States)

    Chudasama, Bhupendra; Vala, Anjana K.; Andhariya, Nidhi; Upadhyay, R. V.; Mehta, R. V.

    2011-05-01

    In recent years, rapid increase has been observed in the population of microbes that are resistant to conventionally used antibiotics. Antifungal drug therapy is no exception and now resistance to many of the antifungal agents in use has emerged. Therefore, there is an inevitable and urgent medical need for antibiotics with novel antimicrobial mechanisms. Aspergillus glaucus is the potential cause of fatal brain infections and hypersensitivity pneumonitis in immunocompromised patients and leads to death despite aggressive multidrug antifungal therapy. In the present article, we describe the antifungal activity of multifunctional core-shell Fe 3O 4-Ag nanocolloids against A. glaucus isolates. Controlled experiments are also carried out with Ag nanocolloids in order to understand the role of core (Fe 3O 4) in the antifungal action. The minimum inhibitory concentration (MIC) of nanocolloids is determined by the micro-dilution method. MIC of A. glaucus is 2000 μg/mL. The result is quite promising and requires further investigations in order to develop a treatment methodology against this death causing fungus in immunocompromised patients.

  10. Large tunneling magnetoresistance in octahedral Fe3O4 nanoparticles

    Directory of Open Access Journals (Sweden)

    Arijit Mitra

    2016-05-01

    Full Text Available We have observed large tunneling Magnetoresistance (TMR in amine functionalized octahedral nanoparticle assemblies. Amine monolayer on the surface of nanoparticles acts as an insulating barrier between the semimetal Fe3O4 nanoparticles and provides multiple tunnel junctions where inter-granular tunneling is plausible. The tunneling magnetoresistance recorded at room temperature is 38% which increases to 69% at 180 K. When the temperature drops below 150 K, coulomb staircase is observed in the current versus voltage characteristics as the charging energy exceeds the thermal energy. A similar study is also carried out with spherical nanoparticles. A 24% TMR is recorded at room temperature which increases to 41% at 180 K for spherical particles. Mössbauer spectra reveal better stoichiometry for octahedral particles which is attainable due to lesser surface disorder and strong amine coupling at the facets of octahedral Fe3O4 nanoparticles. Less stoichiometric defect in octahedral nanoparticles leads to a higher value of spin polarization and therefore larger TMR in octahedral nanoparticles.

  11. Ag doped (Bi1.6Pb0.4Sr2CaCu2O8+δ textured rods

    Directory of Open Access Journals (Sweden)

    Díez, J. C.

    2008-06-01

    Full Text Available In this work, superconducting samples of (Bi1.6Pb0.4Sr2CaCu2O8+δ with Ag additions have been studied. (Bi1.6Pb0.4Sr2CaCu2O8+δ + x wt.% Ag (with x = 0, 1 and 3 powders were synthesized using a sol-gel method. The obtained powders were used as precursors to fabricate long textured cylindrical bars through a floating zone melting method. A drastic change on the microstructure has been found when comparing with undoped Bi2Sr2CaCu2O8+δ samples. The results showed that electrical resistivity at room temperature, critical current as well as flexural strength are improved when Ag is added to these Pb doped samples, while critical temperature does not change. On the other hand, it has been found that samples with composition (Bi1.6Pb0.4Sr2CaCu2O8+δ + Ag shown E-I curves with very high sharpness values on the zone of the superconducting to normal transition, reaching n-values (E∼In as high as 45 at 65K.Se han preparado polvos cerámicos de composición (Bi1.6Pb0.4Sr2CaCu2O8+δ + x % Ag en peso (con x = 0, 1 y 3 mediante un proceso sol-gel. Estos polvos se han utilizado para fabricar precursores que se texturaron por medio del método de fusión zonal flotante. Se ha encontrado un gran cambio en la microestructura cuando se compara con muestras de composición pura Bi2Sr2CaCu2O8+δ. Tanto la resistividad eléctrica a temperatura ambiente, como la corriente crítica, así como la resistencia a flexión se mejoran cuando la Ag se adiciona a estas muestras dopadas con Pb, mientras que no se observa cambio en la temperatura crítica. Por otra parte, se ha encontrado que las muestras de composición (Bi1.6Pb0.4Sr2CaCu2O8+δ + Ag presentan una gran pendiente de la curva E-I en la zona de transición entre el estado superconductor y el estado normal. Con estas composiciones, se han encontrado valores de n (E∼In de hasta 45 a 65K.

  12. Effects of low-level Ag doping on Bi2Sr2CaCu2O8+x

    International Nuclear Information System (INIS)

    Deis, T.A.; Eror, N.G.; Krishnaraj, P.; Prorok, B.C.; Lelovic, M.; Balachandran, U.

    1995-07-01

    Bi 2 Sr 2 CaCu 2 O 8 has been doped with silver, up to 10,000 ppm, in three ways: excess additions, substitution of Ag for Bi, and substitution of Ag for Sr. Effects of doping on the c-axis lattice parameter and critical temperature (T c ) were measured. Effects from doing were only observed in slow-cooled [10 degree/hr] oxygen equilibrated samples. Doping by excess additions caused a small decrease in T c and an increase in the c-axis length of the lattice. Doping by substitution, compared to excess Ag additions, caused a larger decrease in T c and higher c-axis values for doping levels up to 1,000 ppm. Doping by substitution at higher levels (1,000--10,000 ppm) caused T c to increase and the c-axis to decrease. Samples with similar substitutional doping levels exhibited comparable T c values and samples with Ag substituted for Sr consistently exhibited higher c-axis values than samples that had equivalent amounts of Ag substituted for Bi

  13. High precision optical spectroscopy and quantum state selected photodissociation of ultracold 88Sr2 molecules in an optical lattice

    Science.gov (United States)

    McDonald, Mickey

    2017-04-01

    Over the past several decades, rapid progress has been made toward the accurate characterization and control of atoms, epitomized by the ever-increasing accuracy and precision of optical atomic lattice clocks. Extending this progress to molecules will have exciting implications for chemistry, condensed matter physics, and precision tests of physics beyond the Standard Model. My thesis describes work performed over the past six years to establish the state of the art in manipulation and quantum control of ultracold molecules. We describe a thorough set of measurements characterizing the rovibrational structure of weakly bound 88Sr2 molecules from several different perspectives, including determinations of binding energies; linear, quadratic, and higher order Zeeman shifts; transition strengths between bound states; and lifetimes of narrow subradiant states. Finally, we discuss measurements of photofragment angular distributions produced by photodissociation of molecules in single quantum states, leading to an exploration of quantum-state-resolved ultracold chemistry. The images of exploding photofragments produced in these studies exhibit dramatic interference effects and strongly violate semiclassical predictions, instead requiring a fully quantum mechanical description.

  14. Enhancement of thermoelectric power factor of Sr2CoMoO6 double perovskite by annealing in reducing atmosphere

    Science.gov (United States)

    Tanwar, Khagesh; Saxena, Mandvi; Maiti, Tanmoy

    2017-10-01

    In general, n-type thermoelectric materials are rather difficult to design. This study particularly pivoted on designing potential environmentally benign oxides based n-type thermoelectric material. We synthesized Sr2CoMoO6 (SCMO) polycrystalline ceramics via the solid-state synthesis route. XRD, SEM, and thermoelectric measurements were carried out for phase constitution, microstructure analysis, and to determine its potential for thermoelectric applications. As-sintered SCMO sample showed an insulator like behavior till 640 °C after which it exhibited an n-type non-degenerate semiconductor behavior followed by a p-n type conduction switching. To stabilize a high temperature n-type behavior, annealing of SCMO in reducing atmosphere (H2) at 1000 °C was carried out. After annealing, the SCMO demonstrated an n-type semiconductor behavior throughout the temperature range of measurement. The electrical conductivity (σ) and the power factor (S2σ) were found to be increased manifold in the annealed SCMO double perovskite.

  15. Tunneling spectroscopy of heavily underdoped crystals of Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Ozyuzer, L.; Zasadzinski, J.F.; Miyakawa, N.; Kendziora, C.; Jian, S.; Hinks, D. G.; Gray, K.E.

    2000-01-01

    Crystals of Bi 2 Sr 2 CaCu 2 O 8+δ with optimal Tc = 95 K have been underdoped using two different methods and the superconducting gaps have been obtained by tunneling. In some cases, three different tunneling geometries have been utilized: point contact, STM and break junctions. The first doping method involves control of the oxygen content by annealing in various partial pressures of oxygen. These crystals exhibit a narrow spread of gap values over a wide doping range from overdoped (Tc = 56 K) to underdoped with Tc = 70 K. However, for underdoped crystals with Tc midpoints in the range 25 K--63 K, there is a dramatic increase in the spread of gap values which may signal the development of static phase separation of either chemical or electronic origin. To avoid possible chemical phase separation, the authors have explored another doping procedure which incorporates Dy substitution on the Ca site. These crystals exhibit a relatively narrow superconducting transition width and some preliminary tunneling spectra will be presented

  16. The critical state stability in textured Bi2Sr2CaCu2O8+δ superconductor

    International Nuclear Information System (INIS)

    Nabialek, A.; Niewczas, M.

    2006-01-01

    The influence of parameters such as temperature, density of the critical current j c , sample dimensions and heat exchange conditions on the critical state stability has been studied in thin samples of textured Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO) superconductor, in an external magnetic field perpendicular to the wide surface of the samples. The results show that stability of the superconductor against flux jumps increases with decreasing sample thickness. A composite-like sample consisting of two superconducting slabs glued together exhibits critical state stability as a bulk sample of the same thickness while it is less stable against flux jumping than the unit slab. The field of the first flux jump H fj1 decreases with increasing magnetic field sweep rate. For a given temperature there exists a critical sweep rate below which flux jumps vanish. These observations are interpreted in terms of the current distribution in thin superconducting samples characterized by a strong demagnetizing factor. The results are compared with a model developed for samples characterized by negligible demagnetizing effects. The critical state stability in BSCCO has been discussed in terms of the diffusion of heat and of the magnetic flux within the superconductor and the influence of heat exchange on these conditions

  17. High temperature superconductivity in Zn and Mn substituted (Tl,Cr)Sr2CaCu2O7

    International Nuclear Information System (INIS)

    Lo, S.V.; Abd Shukor, R.

    1999-01-01

    Samples with nominal starting composition (TICr 0 .15)Sr 2 (Ca 1-x M x )Cu 2 O 7 (TI-1212) for x=0 - 0.7 with M= Zn and Mn have been prepared and investigated by powder X-ray diffraction (XRD) and electrical resistance measurements. All sample showed a mixed phase of 1212 and 1201. Dominant 1212-phase was observed for x=0.0-0.5 and x=0.0-0.4, for Zn and Mn series, respectively. The superconducting transition temperature was suppressed when Zn and Mn are substituted at the Ca site. For the Zn series the normal state behavior is metallic throughout the doping range. For the Mn series the normal state behavior is metallic for 0.1≤x≥0.3 and semiconducting like x>0.3. The suppression of T c and formation of the TI-1212 phase are discussed in terms of the ionic radius and valence state of the substituted elements. (author)

  18. Spin-glass behavior in the S=1/2 fcc ordered perovskite Sr2CaReO6

    International Nuclear Information System (INIS)

    Wiebe, C.R.; Greedan, J.E.; Luke, G.M.; Gardner, J.S.

    2002-01-01

    The ordered perovskite Sr 2 CaReO 6 of monoclinic symmetry [space group P2 1 /n,a=5.7556(3) A,b=5.8534(3) A,c=8.1317(4) A,β=90.276(5) deg. at T=4 K] has been synthesized using standard solid-state chemistry techniques. The difference in the size and charge of the cations induces an ordering of the B site Ca 2+ and Re 6+ ions which leads to a distorted fcc lattice of spin-(1/2) Re 6+ (5d 1 ) moments. dc magnetic susceptibility measurements indicate a maximum at T G ∼14 K and an irreversibility in the field-cooled and zero-field-cooled data at ∼22 K that is believed to be caused by the geometric frustration inherent in the fcc structure. Neutron-scattering measurements confirm the absence of magnetic long-range order, and muon spin relaxation experiments indicate the presence of an abrupt spin freezing at T G . Specific heat measurements reveal a broad anomaly typical of spin glasses and no sharp feature. 65% of the spin entropy is released at low temperatures. The low-temperature data do not show the expected linear temperature dependence, but rather a T 3 relationship, as is observed, typically, for antiferromagnetic spin waves. The material is characterized as an unconventional, essentially disorder-free, spin glass

  19. Effect of Sr2TiMnO6 fillers on mechanical, dielectric and thermal behaviour of PMMA polymer

    Directory of Open Access Journals (Sweden)

    P. Thomas

    2015-09-01

    Full Text Available Composites of poly(methyl methacrylate (PMMA and Sr2TiMnO6 (STMO were fabricated via melt mixing followed by hot pressing technique. These were characterized using X-ray diffraction (XRD, thermo gravimetric analysis (TGA, differential scanning calorimetry (DSC, thermo mechanical analysis (TMA and impedance analyser for their structural, thermal and dielectric properties. The coefficient of thermal expansion (CTE was measured between 40°C and 100°C for pure PMMA is 115.2 ppm/°C, which was decreased to 78.58 ppm/°C when the STMO content was increased to 50 wt.% in PMMA. There was no difference in the glass transition (Tg temperature of the PMMA polymer and their composites. However, the FTIR analysis indicated possible interaction between the PMMA and STMO. The density and the hardness were increased as the STMO content increased in the PMMA matrix. Permittivity was found to be as high as 30.9 at 100 Hz for the PMMA+STMO-50 wt.% composites, indicating the possibility of using these materials for capacitor applications. The thermal stability of polymer was enhanced by incorporation of STMO fillers.

  20. Positron annihilation study of the high-Tc (Bi, Pb)2Sr2Ca2Cu3Ox superconductor

    International Nuclear Information System (INIS)

    Lim, H.J.; Byrne, J.G.

    1997-01-01

    Positron lifetime spectroscopy (PLS) and positron Doppler-broadening spectroscopy (PDBS) were applied to the high-T c lead-doped Bi 2 Sr 2 Ca 2 Cu 3 O x (BPSCCO 2223) superconductor as a function of temperature. Neither positron lifetimes nor Doppler parameters (S, W, and S/W) showed significant change through T c . This may result from having the highest positron density in the open BiO 2 double layers and no significant positron density in the superconducting CuO 2 layers where positrons, if mainly present, are known to be sensitive to the transition in other high-T c superconductors. Doppler parameters showed that the probability of positron annihilations with core electrons in the lattice slightly increased and that the probability of positron annihilations with conduction electrons slightly decreased as temperature decreased from ambient temperature to 20 K. The lifetime associated with positron annihilations in the perfect lattice of the sample (τ 1 ) was 209 ps and, due to the annihilations at internal surfaces or voids in the sample (τ 2 ) was about 540 ps, independent of temperature. Finally, the mean lifetime for BSCCO 2223 was about 307 ps. (orig.)

  1. Effect of Ti doping on magnetic properties and magnetoresistance in LaSr2Mn2O7

    International Nuclear Information System (INIS)

    Feng, J.; Che, P.; Wang, J.P.; Lu, M.F.; Liu, J.F.; Cao, X.Q.; Meng, J.

    2005-01-01

    The effect of Ti substitution for Mn on magnetic and transport properties has been investigated for layered manganese oxides LaSr 2 Mn 2-x Ti x O 7 . Titanium doping hampered the canted antiferromagnetic (AFM) exchange at low temperature and their Neel temperature (T N ) decreased from 138 K (x = 0) to 106 K (x = 0.1). Meanwhile, spin glass, charge ordering and metal-insulator transition are suppressed by Ti addition. This can be attributed to Mn-site disorder caused by random substitution of Ti 4+ . The suppression of charge ordering leads to magntetoresistance (MR) ratio increase and MR reaches maximum at x = 0.3. The resistivity increases obviously with x increasing because of double exchange interaction channel broken by Ti 4+ addition. The resistivity of all samples in low temperature range fits to the Mott's variable range hopping (VRH) model, while it fits to nearest neighbor hopping of small polarons model in high temperature range. We also found that both disorder and distortion in A-site and B-site will induce the similar effect to electrical and magnetic properties

  2. Average resonance capture studies of 102Ru

    International Nuclear Information System (INIS)

    Shi, Z.R.; Casten, R.F.; Stachel, J.; Bruce, A.M.

    1984-01-01

    The 102 Ru nucleus has been investigated via the ARC technique which ensures a complete set of J/sup π/ = 0 + , 1 +- , 2 +- , 3 +- , 4 +- , and 5 + levels up to 2 MeV. The results are discussed in the framework of the IBA-1 with Consistent Q. The calculations show good agreement with the empirical data especially for the O 2 + state, suggesting that it can be described in terms of collective degrees of freedom

  3. Graphene wrapped porous Co_3O_4/NiCo_2O_4 double-shelled nanocages with enhanced electrocatalytic performance for glucose sensor

    International Nuclear Information System (INIS)

    Xue, Bei; Li, Kezhi; Feng, Lei; Lu, Jinhua; Zhang, Leilei

    2017-01-01

    Highlights: • Graphene wrapped Co_3O_4/NiCo_2O_4 DSNCs has been prepared for detection of glucose. • Sensing performance was improved by synergy between electrocatalytic activity and efficient electron transport. • The sensor has excellent sensing performance with high sensitivity and low detection limit. • The developed method was successfully applied to detect glucose in human serum. - Abstract: Graphene (G) wrapped porous Co_3O_4/NiCo_2O_4 double-shelled nanocages (Co_3O_4/NiCo_2O_4 DSNCs@G) were prepared by the formation of Co_3O_4/NiCo_2O_4 DSNCs using zeolite imidazole frameworks-67 as template with the subsequent calcination and package of G by hydrothermal method. The abundant accessible active sites provided by the porous structure of Co_3O_4/NiCo_2O_4 DSNCs and efficient electron transport pathways for electrocatalytic reaction offered by the high conductive G worked very well together in a ferocious synergy, which endowed Co_3O_4/NiCo_2O_4 DSNCs@G with excellent electrocatalytic behaviors for determining glucose. A comparison between Co_3O_4/NiCo_2O_4 DSNCs without G packing and Co_3O_4/NiCo_2O_4 DSNCs@G showed that former had linear response window concentrations of 0.01-3.52 mM (correlation coefficient = 0.999), detection limit of 0.744 μM (S/N = 3) and sensitivity of 0.196 mA mM"−"1 cm"−"2, whereas the latter exhibited linear response window concentrations of 0.01-3.52 mM (correlation coefficient = 0.999), detection limit of 0.384 μM (S/N = 3) and sensitivity of 0.304 mA mM"−"1 cm"−"2. The combination of Co_3O_4/NiCo_2O_4 DSNCs and G was a meaningful strategy to fabricate high-performance non-enzyme glucose sensors with low detection limit, good selectivity and high sensitivity.

  4. Laser Spectroscopy of Ruthenium Containing Diatomic Molecules: RuH/D and RuP.

    Science.gov (United States)

    Adam, Allan G.; Konder, Ricarda M.; Nickerson, Nicole M.; Linton, Colan; Tokaryk, D. W.

    2015-06-01

    In the last few years, the Cheung group in Hong Kong and the Steimle group in Arizona have successfully studied several ruthenium containing diatomic molecules, RuX (X =C, O, N, B, using the laser-ablation molecular jet technique. Based on this success, the UNB spectroscopy group decided to try and find the optical signatures of other RuX molecules. Using CH_3OH and PH_3 as reactant gases, the RuH and RuP diatomic molecules have been detected in surveys of the 420 - 675 nm spectral region. RuD has also been made using fully deuterated methanol as a reactant. Dispersed fluorescence experiments have been performed to determine ground state vibrational frequencies and the presence of any low-lying electronic states. Rotationally resolved spectra for these molecules have also been taken and the analysis is proceeding. The most recent results will be presented. F. Wang et al., Journal of Chemical Physics 139, 174318 (2013). N. Wang et al., Journal of Physical Chemistry A 117, 13279 (2013). T. Steimle et al., Journal of Chemical Physics 119, 12965 (2003). N. Wang et al., Chemical Physics Letters 547, 21 (2012).

  5. Ru nanostructure fabrication using an anodic aluminum oxide nanotemplate and highly conformal Ru atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo-Hee; Park, Sang-Joon; Son, Jong-Yeog; Kim, Hyungjun [Department of Material Science and Engineering, POSTECH Pohang University of Science and Technology, San 31, Hyoja-Dong, Nam-Gu, Pohang 790-784 (Korea, Republic of)

    2008-01-30

    We fabricated metallic nanostructures directly on Si substrates through a hybrid nanoprocess combining atomic layer deposition (ALD) and a self-assembled anodic aluminum oxide (AAO) nanotemplate. ALD Ru films with Ru(DMPD)(EtCp) as a precursor and O{sub 2} as a reactant exhibited high purity and low resistivity with negligible nucleation delay and low roughness. These good growth characteristics resulted in the excellent conformality for nanometer-scale vias and trenches. Additionally, AAO nanotemplates were fabricated directly on Si and Ti/Si substrates through a multiple anodization process. AAO nanotemplates with various hole sizes (30-100 nm) and aspect ratios (2:1-20:1) were fabricated by controlling the anodizing process parameters. The barrier layers between AAO nanotemplates and Si substrates were completely removed by reactive ion etching (RIE) using BCl{sub 3} plasma. By combining the ALD Ru and the AAO nanotemplate, Ru nanostructures with controllable sizes and shapes were prepared on Si and Ti/Si substrates. The Ru nanowire array devices as a platform for sensor devices exhibited befitting properties of good ohmic contact and high surface/volume ratio.

  6. Spectroscopy of {sup 96}Ru and {sup 98}Ru: structures of varied character at N {>=} 52

    Energy Technology Data Exchange (ETDEWEB)

    Reviol, W; Garg, U; Aprahamian, A; Davis, B F; Herr, M C; Naguleswaran, S; Walpe, J C; Ye, D [Notre Dame Univ., IN (United States); Ahmad, I; Carpenter, M P; Janssens, R V.F.; Khoo, T L; Lauritsen, T; Liang, Y [Argonne National Lab., IL (United States)

    1992-08-01

    The authors have investigated the onset of deformation at N {>=} 52 by performing high-spin gamma spectroscopy of {sup 96-98}Ru using the {sup 65}Cu({sup 36}S,pxn) reaction with the Argonne-Notre Dame {gamma}-ray facility. From the coincidence data associated with high multiplicity (k {>=} 8) events, they have established two main band structures in {sup 96-98}Ru which extend the previously-known level schemes significantly (up to > 20 {Dirac_h}). In {sup 96}Ru, one of the newly observed structures consists of five rotation-like E2 transitions and feeds into the known 9{sup (-)} state; the other structure bypasses the first one, and based on the observed level-spacings, is tentatively described as vibration-like. A rotational-like structure above a spin of 8 {Dirac_h}, along with a parallel vibration-like structure, has been observed in {sup 98}Ru as well. The data also contain some evidence for a weak sequence of dipole (presumably M1) transitions in {sup 96}Ru. This structure might be similar to the high-K oblate bands recently observed in {sup 119-123}I and {sup 198-20P}b. 9 refs., 3 figs.

  7. Understanding the role of Co3O4 on stability between active hierarchies and scaffolds: An insight into NiMoO4 composites for supercapacitors

    Science.gov (United States)

    Zhao, Yuanyuan; Zhang, Peng; Fu, Wenbin; Ma, Xiangwen; Zhou, Jinyuan; Zhang, Xiaojuan; Li, Jian; Xie, Erqing; Pan, Xiaojun

    2017-09-01

    It is often reported that pseudocapacitive electrodes' mechanical stability seriously limited their cycling performances in supercapacitors due to their quick fall off the electrode matrix during frequent fast charge/discharge process. In this work, we have demonstrated the mechanical enhancement in hierarchical NiMoO4 nanosheet arrays (NSAs) on free-standing substrates after introducing Co3O4 hierarchies. Under sonication vibration environment, the mechanical stability of Co3O4@NiMoO4 NSAs was enhanced by ∼70% compared to that of the pure NiMoO4 ones. Moreover, the Co3O4@NiMoO4 NSAs can display a high specific capacitance of 1476 F g-1 at the current density of 1 A g-1, and an excellent rate capability (keeping 81% at 20 A g-1). And after 2000 cycles, high capacitance retention of 96% was achieved for the Co3O4@NiMoO4 core/shell NSAs, while only 70% for the pure NiMoO4 ones.

  8. Reduced graphene oxide wrapped Fe3O4-Co3O4 yolk-shell nanostructures for advanced catalytic oxidation based on sulfate radicals

    Science.gov (United States)

    Zhang, Lishu; Yang, Xijia; Han, Erfen; Zhao, Lijun; Lian, Jianshe

    2017-02-01

    In this work, we designed and synthesized a high performance catalyst of reduced graphene oxide (RGO) wrapped Fe3O4-Co3O4 (RGO/Fe3O4-Co3O4) yolk-shell nanostructures for advanced catalytic oxidation based on sulfate radicals. The synergistic catalytic action of the RGO/Fe3O4-Co3O4 yolk-shell nanostructures activate the peroxymonosulfate (PMS) to produce sulfate radicals (SO4rad -) for organic dyes degradation, and the Orange II can be almost completely degradated in 5 min. Meanwhile the RGO wrapping prevents the loss of cobalt in the catalytic process, and the RGO/Fe3O4-Co3O4 can be recycled after catalyzed reaction due to the presence of magnetic iron core. What's more, it can maintain almost the same high catalytic activity even after 10 cycles through repeated NaBH4 reduction treatment. Hence, RGO/Fe3O4-Co3O4 yolk-shell nanostructures possess a great opportunity to become a promising candidate for waste water treatment in industry.

  9. Pb3O4 type antimony oxides MSb2O4 (M = Co, Ni) as anode for Li-ion batteries

    International Nuclear Information System (INIS)

    Jibin, A.K.; Reddy, M.V.; Subba Rao, G.V.; Varadaraju, U.V.; Chowdari, B.V.R.

    2012-01-01

    Graphical abstract: Isostructural Pb 3 O 4 type MSb 2 O 4 (M = Co, Ni) compounds were investigated as possible anodes for lithium ion batteries. The reversible capacity is due to electrochemically active Sb and the transition metal and Li 2 O form an inactive matrix which buffers volume variations associated with alloying-de-alloying of antimony. Highlights: ► Isostructural MSb 2 O 4 (M = Co, Ni) were studied as anode for LIBs for first time. ► Li/MSb 2 O 4 (M = Co, Ni) cells displayed reversibility due to electrochemically active Sb. ► CoSb 2 O 4 showed good reversibility compared to NiSb 2 O 4 . - Abstract: Polycrystalline samples of isostructural MSb 2 O 4 (M = Co, Ni) have been prepared by solid state synthesis and lithium-storage is investigated as possible anode materials for lithium-ion batteries. The reaction mechanism of lithium with MSb 2 O 4 (M = Co, Ni) is explored by galvanostatic cycling, cyclic voltammogram and ex situ studies. Both CoSb 2 O 4 and NiSb 2 O 4 exhibit similar electrochemical behavior and show reversible capacity of 490 and 412 mAh g −1 respectively in the first cycle. Reversible alloying de-alloying of Li x Sb takes place in an amorphous matrix of M (Co, Ni) and Li 2 O during electrochemical cycling.

  10. Magnetic transitions in double perovskite Sr2FeRe1-xSbxO6 (0≤x≤0.9)

    International Nuclear Information System (INIS)

    Jung, Alexandra; Ksenofontov, Vadim; Reiman, Sergey; Therese, Helen Annal; Felser, Claudia; Tremel, Wolfgang; Kolb, Ute

    2006-01-01

    The double perovskites Sr 2 FeMO 6 (M=Re,Mo) belong to the important class of half-metallic magnetic materials. In this study we explore the effect of replacing the electronic 5d buffer element Re with variable valency by the main group element Sb with fixed valency. X-ray diffraction reveals Sr 2 FeRe 1-x Sb x O 6 (0 2 FeReO 6 changes to antiferromagnetic upon Sb substitution as was determined by magnetic susceptibility measurements. Samples up to a doping level of 0.3 are ferrimagnetic, while Sb contents higher than 0.6 result in an overall antiferromagnetic behavior. 57 Fe and 121 Sb Moessbauer spectroscopy specifies the valence state of Sb to be +5 within the whole range of substitution whereas the Fe valence state changes from +2.7 for the parent compound to +2.9 for Sr 2 FeRe 0.1 Sb 0.9 O 6 . Accordingly, Fe adopts the role of an electronic buffer element from Re upon heavy Sb doping. Additionally, 57 Fe Moessbauer results show a coexistence of ferri- and antiferromagnetic clusters within the same perovskite-type crystal structure in the Sb substitution range 0.3 2 FeReO 6 and Sr 2 FeRe 0.9 Sb 0.1 O 6 are ''purely'' ferrimagnetic and Sr 2 FeRe 0.1 Sb 0.9 O 6 contains antiferromagnetically ordered Fe sites only. Consequently, a replacement of the Re atoms by a nonmagnetic main group element such as Sb blocks the superexchange pathways -Fe-O-Re(Sb)-O-Fe- along the crystallographic axis of the perovskite unit cell and destroys the itinerant magnetism of the parent compound

  11. Study of cadmium fixation on nanocomposite Mn3O4 / Fe3O4 used in environmental remediation

    International Nuclear Information System (INIS)

    Brito, Ilderando Freires de; Dinola, Isabel Souza; Stavale, Fernando Loureiro; Silva, Gabriela Cordeiro; Rodrigues, Ana Pacheli Heitmann; Ferreira, Angela de Mello

    2016-01-01

    Full text: Nanotechnology is a multidisciplinary field which knowledge is essential to the development of new materials. It is very important to mention that the size of the material is relevant, since lowering it, new properties can be observed. Clean water, with satisfactory quality standards, becomes extremely important for the life cycle of biotic and abiotic organisms (biogeochemical cycles), essential for the maintenance of human survival, among many multiple uses. Water is used as a raw material in a variety of industries including electronics, pharmaceuticals and foods. One of the main promises of nanotechnology is to be useful for environmental remediation. The use of nanomaterials has become an important tool in remediation environment activities. This present work is devoted to the characterization of iron oxide nanoparticles (magnetite) coated with manganese oxide used in the adsorption of contaminants. Since adsorption is a surface phenomenon, it is important that the adsorbents provide a large external and internal surface area associated with its porous structure. The best adsorbents must be on the nanoscale, because they have high surface area. Therefore, photoelectron spectroscopy measurements excited by X-ray (XPS) were performed, since in practice this is a technique that analyzes the surface. Combined with other measures obtained in previous works, such as magnetization and transmission microscopy, we hope to answer questions about the attachment of Cadmium on the surface of Mn 3 O 4 / Fe 3 O 4 nanocomposite. (author)

  12. Hierarchical core-shell NiCo2O4@NiMoO4 nanowires grown on carbon cloth as integrated electrode for high-performance supercapacitors

    Science.gov (United States)

    Huang, Liang; Zhang, Wei; Xiang, Jinwei; Xu, Henghui; Li, Guolong; Huang, Yunhui

    2016-08-01

    Hierarchical core-shell NiCo2O4@NiMoO4 nanowires were grown on carbon cloth (CC@NiCo2O4@NiMoO4) by a two-step hydrothermal route to fabricate a flexible binder-free electrode. The prepared CC@NiCo2O4@NiMoO4 integrated electrode was directly used as an electrode for faradaic supercapacitor. It shows a high areal capacitance of 2.917 F cm-2 at 2 mA cm-2 and excellent cycling stability with 90.6% retention over 2000 cycles at a high current density of 20 mA cm-2. The superior specific capacitance, rate and cycling performance can be ascribed to the fast transferring path for electrons and ions, synergic effect and the stability of the hierarchical core-shell structure.

  13. Double molybdates in Li2MoO4 - Na2MoO4 - H2O system at 25 grad C

    International Nuclear Information System (INIS)

    Karov, Z.G.; Mirzoev, R.S.; Makitova, D.D.; Zhilova, S.B.; Podnek, A.G.; Urusova, R.Kh.

    1989-01-01

    Solubility in Li 2 MoO 4 - Na 2 MoO 4 - H 2 O system at 25 deg C is first stuied. Formation of two Li 2 MoO 4 · Na 2 MoO 4 · 4H 2 O and Li 2 MoO 4 · 3Na 2 MoO 4 · 12H 2 O compounds in a system is ascertained. Density, refractive index, viscosity, surface tension, electric conductivity and pH of saturated solutions are determined. Isothermes of mole volume, equivalent and reduced electric conductivity and seeming mole volume of salts sum in solutions are calculated. All these properties adequtely confirm the character of components interaction in a system determined by solubility method. Crystallhydrates of binary molybdates are separated, indentified and studied

  14. Absorption spectra of CsNd(MoO4)2 and CsGd(MoO4)2-Nd3+ crystals in strong magnetic fields

    International Nuclear Information System (INIS)

    Gorban', I.S.; Kozeeva, L.P.; Slobodyanyuk, A.V.; Shevchenko, V.A.

    1987-01-01

    The comparison of the electronic structure of Nd 3+ in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 - Nd 3+ crystals is made. It is established that in these crystals the activator centers, mainly, of the certain type with the symmetry of the local environment C 2 are formed. The absorption spectra of self-activated CsNd(MoO 4 ) 2 crystal differ from spectra of CsGd(MoO 4 ) 2 - Nd 3+ by the presence of the vibrating structure. The Stark splittings of energy levels of Nd 3+ in the investigated crystalline matrices are more sensitive to the environment effect than the Zeeman ones. The ground state of Nd 3+ ion in CsNd(MoO 4 ) 2 and CsGd(MoO 4 ) 2 molybdates is characterized by the similar values of g-factors

  15. Substituent-directed structural and physicochemical controls of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

    Science.gov (United States)

    Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

    2005-05-30

    A family of diruthenium complexes with ligand-unsupported Ru-Ru bonds has been systematically synthesized, and their crystal structures and physical properties have been examined. A simple, useful reaction between Ru2(OAc)4Cl (OAc- = acetate) and catechol derivatives in the presence of bases afforded a variety of diruthenium complexes, generally formulated as [Na(n){Ru2(R4Cat)4}] (n = 2 or 3; R4 = -F4, -Cl4, -Br4, -H4, -3,5-di-t-Bu, and -3,6-di-t-Bu; Cat(2-) = catecholate). The most characteristic feature of the complexes is the formation of short ligand-unsupported Ru-Ru bonds (2.140-2.273 A). These comprehensive studies were carried out to evaluate the effects of the oxidation states and the substituents governing the molecular structures and physicochemical properties. The Ru-Ru bond distances, rotational conformations, and bending structures of the complexes were successfully varied. The results presented in this manuscript clearly demonstrate that the complexes with ligand-unsupported Ru-Ru bonds can sensitively respond to redox reactions and ligand substituents on the basis of the greater degree of freedom in their molecular structures.

  16. The role of electrolyte anions (ClO4-, NO3-, and Cl-) in divalent metal (M2+) adsorption on oxide and hydroxide surfaces in salt solutions

    International Nuclear Information System (INIS)

    Criscenti, L.J.; Sverjensky, D.A.

    1999-01-01

    Adsorption of divalent metal ions (M 2+ ) onto oxide and hydroxide surfaces from solutions of strong electrolytes has typically been inferred to take place without the involvement of the electrolyte anion. Only in situations where M 2+ forms a strong enough aqueous complex with the electrolyte anion (for example, CdCl + or PbCl + ) has it been frequently suggested that the metal and the electrolyte anion adsorb simultaneously. A review of experimental data for the adsorption of Cd 2+ , Pb 2+ , Co 2+ , UO 2 2+ , Zn 2+ , Cu 2+ , Ba 2+ , Sr 2+ , and Ca 2+ onto quartz, silica, goethite, hydrous ferric oxide, corundum, γ-alumina, anatase, birnessite, and magnetite, from NaNO 3 , KNO 3 , NaCl, and NaClO 4 solutions over a wide range of ionic strengths (0.0001 M-1.0 M), reveals that transition and heavy metal adsorption behavior with ionic strength is a function of the type of electrolyte. In NaNO 3 solutions, metal adsorption exhibits little or no dependence on the ionic strength of the solution. However, in NaCl solutions, transition and heavy metal adsorption decreases strongly with increasing ionic strength. In NaClO 4 solutions, metal adsorption decreases strongly with increasing ionic strength. In NaClO 4 solutions, metal adsorption exhibits little dependence on ionic strength but is often suggestive of an increase in metal adsorption with increasing ionic strength. Analysis of selected adsorption edges was carried out using the extended triple-layer model and aqueous speciation models that included metal-nitrate, metal-chloride, and metal-hydroxide complexes

  17. Study of the Thermodynamics of Chromium(III) and Chromium(VI) Binding to Fe3O4 and MnFe2O4 nanoparticles

    Science.gov (United States)

    Luther, Steven; Brogfeld, Nathan; Kim, Jisoo; Parsons, J.G.

    2013-01-01

    Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4 ± 0.9 nm (Fe3O4) and 15.5 ± 0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative. PMID:23558081

  18. Polarized neutron reflectivity studies of magnetic oxidic Fe3O4/NiO and Fe3O4/CoO multilayers

    NARCIS (Netherlands)

    Ball, A.R.; Fredrikze, H.; Lind, D.M.; Wolf, R.M.; Bloemen, P.J.H.; Rekveldt, M.Th.; Zaag, van der P.J.

    1996-01-01

    The magnetic properties of [1 0 0] oriented Fe3O4/NiO and Fe3O4/CoO multilayers, MBE-grown on MgO(0 0 1) substrates, have been studied by polarized neutron reflectometry. In both samples, the Fe3O4 layer exhibits a depth-dependent magnetic profile characterized by a reduction in the magnetization

  19. Electron microscopic study on SrGdMnO4

    International Nuclear Information System (INIS)

    Nakano, Hiromi; Ishizawa, Nobuo; Kamegashira, Naoki; Zulhadjri; Shishido, Toetsu

    2006-01-01

    Single crystals of SrGdMnO 4 have been synthesized by the floating zone method. The structure was characterized as the K 2 NiF 4 -type, using X-ray diffraction (XRD) and a transmission electron microscope (TEM). Presence of weak reflections breaking the archetypal tetragonal symmetry was observed from the selected area diffraction (SAD). The compound was found to have an orthorhombic unit cell of a ≅ b = 0.532(4) nm, c = 1.271(6) nm, by taking the a and b axes along the diagonal directions on the basal plane of the tetragonal archetype. Structural change occurred around 1018 K. The weak reflections disappeared in the SAD pattern, suggesting that crystal is of the archetype above 1018 K

  20. Ionizing radiation effects in MgAl2O4

    International Nuclear Information System (INIS)

    Ibarra Sanchez, A.

    1990-01-01

    The effect of ionizing radiation in MgAl2O4 has been studied, paying special interest to the influence of the high concentration of intrinsic dsefects of this material. Optical absorption, ESR, photoluminiscence, radioluminiscence, and thermoluminiscence are the main techniques used. The ionizing radiation induces to formation of V centres. During the work its characteristics (structure, thermal stability, absorption spectra, etc.) has been studied. The thermoluminiscence spectra allowed the discovery of several charge release processes between 85 and 650 K, all of them associated to electron release. The V-centres and several impurities (Cr, Mn,...) appear as recombination centres. The obtained data show that the kinetic of these charge release processes is regulated by the presence of a point defect with a very high concentration. This defect is an electron trap and its structure is an Al ion in a lattice site of tetraedral symmetry. (Author)

  1. Sideward flow of K+ in Ru+Ru and Ni+Ni reactions sat SIS energies

    International Nuclear Information System (INIS)

    Crochet, P.; Herrmann, N.; Wisniewski, K.

    2000-01-01

    Experimental data on K + and proton sideward flow measured with the FOPI detector at SIS/GSI in the reactions Ru+Ru at 1.69 A GeV and Ni+Ni at 1.93 A GeV are presented. The K + sideward flow is found to be anti-correlated (correlated) with the one of protons at low (high) transverse momenta. When compared to the predictions of a transport model, the data favour the existence of an in-medium repulsive K + -nucleon potential. (author)

  2. Electron correlation in CaRuO3 and SrRuO3

    International Nuclear Information System (INIS)

    Singh, Ravi Shankar; Maiti, Kalobaran

    2005-01-01

    We investigate the role of electron correlation in the electronic structure of 4d transition-metal oxides CaRuO 3 and SrRuO 3 . The photoemission spectra collected at different surface sensitivities reveal qualitatively different surface and bulk electronic structures in these systems. Extracted bulk spectra could be simulated using first principle approaches consistently with their thermodynamic parameters within the same model. The estimated electron correlation strength (U/W ∼ 0.2) is significantly weak as expected in 4d systems and resolves the long-standing issue that arose due to the prediction of large U/W similar to 3d systems. (author)

  3. Displacement waves in La2CuO(4-delta) and La(1.85)Sr(0.15)CuO(4-delta)

    Science.gov (United States)

    Kajitani, Tsuyoshi; Onozuka, Takashi; Yamaguchi, Yasuo; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-11-01

    Structural investigation of orthorhombic La2CuO(4-delta) and La(1.85)Sr(0.15)CuO(4-delta) was carried out by means of X-ray and neutron diffraction on the basis of the space group Cmmm. The periodic expansion/contraction type distortion of CuO6 octahedra was found in both orthorhombic compounds. The distortion is nearly one-dimensional in La2CuO(4-delta) but is two-dimensional in La(1.85)Sr(0.15)CuO(4-delta). The existence of a charge-density wave is highly possible in the structures.

  4. Thermal and x-ray studies on Tl2U(MoO4)3 and Tl4U(MoO4)4

    International Nuclear Information System (INIS)

    Dahale, N.D.; Keskar, Meera; Kulkarni, N.K.; Singh Mudher, K.D.

    2006-01-01

    In the quaternary Tl-U(IV)-Mo-O system, two new compounds namely Tl 2 U(MoO 4 ) 3 and Tl 4 U(MoO 4 ) 4 were prepared and characterized by powder X-ray diffraction and thermal methods. These compounds were prepared by solid state reactions of Tl 2 MoO 4 , UMoO 5 and MoO 3 in the required stoichiometric ratio at 500 deg C in evacuated sealed quartz ampoule. The XRD data of Tl 2 U(MoO 4 ) 3 and Tl 4 U(MoO 4 ) 4 were indexed on orthorhombic cell. TG curves of Tl 2 U(MoO 4 ) 3 and Tl 4 U(MoO 4 ) 4 did not show any weight change up to 700 deg C in an inert atmosphere. During heating in an inert atmosphere, Tl 2 U(MoO 4 ) 3 and Tl 4 U(MoO 4 ) 4 showed endothermic Dta peaks due to melting of the compounds at 519 and 565 deg C, respectively. (author)

  5. High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

    Science.gov (United States)

    Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

    2016-04-01

    In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

  6. Electron-energy-loss and optical-transmittance investigation of Bi2Sr2CaCu2O8

    International Nuclear Information System (INIS)

    Wang, Y.; Feng, G.; Ritter, A.L.

    1990-01-01

    The energy-loss function Im(-1/ε) of Bi 2 Sr 2 CaCu 2 O 8 has been measured over the range E loss =0.8 to 80 eV by transmission electron-energy-loss spectroscopy (EELS) (nonimaging). The energy and momentum resolution were 0.1 eV and 0.04 A -1 , respectively. The low-energy spectra (E loss ≤3 eV) were studied as a function of momentum transfer (0.1 A -1 ≤q≤0.3 A -1 ). A well-defined peak in the loss function at E loss ∼1 eV is observed to disperse with momentum proportional to q 2 . This excitation is analyzed in terms of both an intracell, charge-transfer exciton model and the free-carrier (plasmon) model. The derived effective mass of the exciton m tot /m congruent 1.0 is far too small for a localized exciton. Using the free-carrier model and random-phase-approximation expressions for the dispersion coefficient, the carrier density and carrier effective mass can be determined separately. From our data and similar measurements by Nuecker et al. [Phys. Rev. B 39, 12 379 (1989)], it is found that the effective mass roughly scales with carrier density. A heuristic model is introduced based on the assumption that low-energy gaps exist in portions of the Fermi surface due to structural instabilities. The model suggests how the effective mass could appear to scale with carrier density and why a single Drude term (with frequency-independent effective mass) does not describe the mid- to far-infrared optical spectra. Finally, the optical transmittance of the EELS sample was measured and the spectra analyzed in terms of the free-carrier model

  7. Dynamic response of the electronic structure of Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Freutel, Simon

    2015-01-01

    This work investigates the dynamic response of the electronic system of the high critical temperature superconductor Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) due to the optical excitation by ultra short laser pulses. By using time- and angle-resolved photoemission spectroscopy on optimally and underdoped Bi2212 in the pseudogap phase two effects revealed by changes in the electronic structure are being discussed which, due to their different temporal behaviors, can be considered as independent. First, this is an photoinduced change of the effective mass m* around the kink energy of E - E F = -70 meV, that occurs during the experiment's time resolution of ∝100 fs and therefore can be interpreted as perturbation of the underlying electronic interaction caused directly by the pump pulse. Second, a shift of the Fermi surface vector k F is observed, that can be interpreted as an effective change of hole doping that gives rise to new opportunities for possible ultrafast optoelectronic devices based on optically induced phase transitions. Furthermore, the energy- and fluence-dependent dynamics of excited electrons are investigated, which exhibit a biexponential behavior. While the slow component of this decay seems to be independent from the excitation fluence, the fast component shows a pronounced jump in the corresponding decay time above and below the material's characteristic energy of 70 meV. This jump is most pronounced for the low fluences, which will be discussed in the context of an appropriate theoretical model system. Moreover, a major part of this work was the construction and build up of an entirely new experimental setup for photoemission spectroscopy. The main part regarding this issue consists of the design of 6-axis manipulator which is capable of moving the sample at low temperature independently in all 3 rotational and translational degrees of freedom. In the context of this work first tests and characterization measurements has been performed using

  8. Fermi surface investigation in the scanning tunneling microscopy of Bi2Sr2CaCu2O8

    International Nuclear Information System (INIS)

    Voo, K.K.; Wu, W.C.; Chen, H.Y.; Mou, C.Y.

    2004-01-01

    Within the ideal Fermi liquid picture, the impurity-induced spatial modulation of local density of states (LDOS) in the d-wave superconductor Bi 2 Sr 2 CaCu 2 O 8 is investigated at different superconducting (SC) gap sizes. These LDOS spectra are related to the finite-temperature dI/dV spectra in scanning tunneling microscopy (STM), when the Fermi distribution factor is deconvoluted away from dI/dV. We find stripe-like structures even in the zero gap case due to a local-nesting mechanism. This mechanism is different from the octet-scattering mechanism in the d-wave SC (dSC) state proposed by McElroy et al. [K. McElroy, R.W. Simmonds, J.E. Hoffman, D.H. Lee, J. Orenstein, H. Eisaki, S. Uchida, J.C. Davis, Nature 422 (2003) 592]. The zero gap LDOS is related to the normal state dI/dV. The zero gap spectra when Fourier-transformed into the reciprocal space, can reveal the information of the entire Fermi surface at a single measuring bias voltage, in contrast to the point-wise tracing out proposed by McElroy et al. This may serve as another way to check the reality of Landau quasiparticles in the normal state. We have also re-visited the octet-scattering mechanism in the dSC state and pointed out that, due to the Umklapp symmetry, there are additional peaks in the reciprocal space that experimentally yet to be found

  9. Gamma-gamma angular correlation measurement in the 100 Ru

    International Nuclear Information System (INIS)

    Kenchian, G.

    1990-01-01

    An angular correlation automatic spectrometer with two Ge(Li) detectors has been developed. The spectrometer moves automatically, controlled by a microcomputer. The gamma-gamma directional angular correlations of coincidence transitions have been measured in 100 Ru nuclide, following the β + and electron capture of 100 Rh. The 100 Rh source has been produced with 100 Ru(p,n) 100 Rh reaction, using the proton beam of the Cyclotron Accelerator insiding in 100 Ru isotope. (author)

  10. Enhanced anodic Ru(bpy)32+ electrogenerated chemiluminescence by polyphenols

    International Nuclear Information System (INIS)

    Lei Rong; Xu Xiao; Xu Da; Zhu Gang; Li Na; Liu Huwei; Li Kean

    2008-01-01

    Anodic Ru(bpy) 3 2+ electrogenerated chemiluminescence (ECL) can be enhanced by polyphenols in alkaline solution. Spin trapping-electron spin resonance (ESR) experiments verified that reactive oxygen species (ROS) were generated during the electrolysis of Ru(bpy) 3 2+ in alkaline solution, and oxidation of quercetin enhanced Ru(bpy) 3 2+ ECL at anodic potential by producing additional ROS. This ECL enhancement can be used to analyze real sample and evaluate antioxidant activity of polyphenols

  11. Nonalloyed carbon-supported PtRu catalysts for PEMFC applications

    NARCIS (Netherlands)

    Papageorgopoulos, D.C.; De Heer, M.P.; Keijzer, M.; Pieterse, J.A.Z.; de Bruijn, F. A.

    2004-01-01

    PtRu(1:1)/C catalysts were prepared by a process that was claimed previously to lead to non-alloyed Pt and Ru particles, using two different precursors, Ru nitrosyl nitrate and Ru chloride hydrate. Both X-ray diffraction and characterization by cyclic voltammetry point toward Pt and Ru being present

  12. Nonalloyed carbon-supported PtRu catalysts for PEMFC applications

    NARCIS (Netherlands)

    Papageorgopoulos, D.C.; Heer, de M.P.; Keijzer, M.; Pieterse, J.A.Z.; Bruijn, de F.A.

    2004-01-01

    PtRu(1:1)/C catalysts were prepared by a process that was claimed previously to lead to nonalloyed Pt and Ru particles, using twodifferent precursors, Ru nitrosyl nitrate and Ru chloride hydrate. Both X-ray diffraction and characterization by cyclic voltammetrypoint toward Pt and Ru being present as

  13. Phase formation in the Li2MoO4–Rb2MoO4–Fe2(MoO4)3 system and crystal structure of a novel triple molybdate LiRb2Fe(MoO4)3

    International Nuclear Information System (INIS)

    Khal'baeva, Klara M.; Solodovnikov, Sergey F.; Khaikina, Elena G.; Kadyrova, Yuliya M.; Solodovnikova, Zoya A.; Basovich, Olga M.

    2013-01-01

    X-ray investigation of solid state interaction of the components in the Li 2 MoO 4 –Rb 2 MoO 4 –Fe 2 (MoO 4 ) 3 system was carried out, and a subsolidus phase diagram of the said system was constructed. The subsystem Rb 2 MoO 4 –LiRbMoO 4 –RbFe(MoO 4 ) 2 was shown to be non-quasiternary. Formation of a novel triple molybdate LiRb 2 Fe(MoO 4 ) 3 was established, conditions of solid state synthesis and crystallization of the compound were found. Its crystal structure (orthorhombic, space group Pnma, Z=4, a=24.3956(6), b=5.8306(1), c=8.4368(2) Å) represents a new structure type and includes infinite two-row ribbons ([Fe(MoO 4 ) 3 ] 3− ) ∞ parallel to the b axis and composed of FeO 6 octahedra, terminal Mo(3)O 4 tetrahedra, and bridge Mo(1)O 4 and Mo(2)O 4 tetrahedra connecting two or three FeO 6 octahedra. The ribbons are connected to form 3D framework via corner-sharing LiO 4 tetrahedra. Rubidium cations are 11- and 13-coordinated and located in cavities of this heterogeneous polyhedral framework. - Graphical abstract: Exploring the Li 2 MoO 4 –Rb 2 MoO 4 –Fe 2 (MoO 4 ) 3 system showed its partial non-quasiternarity and revealed a new compound LiRb 2 Fe(MoO 4 ) 3 which was structurally studied. - Highlights: • The Li 2 MoO 4 –Rb 2 MoO 4 –Fe 2 (MoO 4 ) 3 system study revealed a new compound LiRb 2 Fe(MoO 4 ) 3 . • Its structure of a new type includes ribbons of FeO 6 octahedra and MoO 4 tetrahedra. • The ribbons are connected into a 3D framework via corner-sharing LiO 4 tetrahedra

  14. SYNTHESIS OF M–Nd DOPED Fe3O4 NANOPARTICLES (M = Co ...

    African Journals Online (AJOL)

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    nanoparticles were spherical shaped with inverse spinel structure. ... To obtain nano sized spinel ferrite particles, various preparation techniques have been ... SEM images of (a) Fe3O4, (b) Fe3O4 doped with Nd3+ and Co2+, (c) Fe3O4 doped with. Nd3+ .... Nayar, S.; Mir, A.; Ashok, A.; Sharma, A. J. Bionic Eng. 2010, 7, 29.

  15. Lesion Orientation of O4-Alkylthymidine Influences Replication by Human DNA Polymerase η.

    Science.gov (United States)

    O'Flaherty, D K; Patra, A; Su, Y; Guengerich, F P; Egli, M; Wilds, C J

    2016-08-01

    DNA lesions that elude repair may undergo translesion synthesis catalyzed by Y-family DNA polymerases. O 4 -Alkylthymidines, persistent adducts that can result from carcinogenic agents, may be encountered by DNA polymerases. The influence of lesion orientation around the C4- O 4 bond on processing by human DNA polymerase η (hPol η ) was studied for oligonucleotides containing O 4 -methylthymidine, O 4 -ethylthymidine, and analogs restricting the O 4 -methylene group in an anti -orientation. Primer extension assays revealed that the O 4 -alkyl orientation influences hPol η bypass. Crystal structures of hPol η •DNA•dNTP ternary complexes with O 4 -methyl- or O 4 -ethylthymidine in the template strand showed the nucleobase of the former lodged near the ceiling of the active site, with the syn - O 4 -methyl group engaged in extensive hydrophobic interactions. This unique arrangement for O 4 -methylthymidine with hPol η , inaccessible for the other analogs due to steric/conformational restriction, is consistent with differences observed for nucleotide incorporation and supports the concept that lesion conformation influences extension across DNA damage. Together, these results provide mechanistic insights on the mutagenicity of O 4 MedT and O 4 EtdT when acted upon by hPol η .

  16. Experimental and first-principles calculation study of the pressure-induced transitions to a metastable phase in GaP O4 and in the solid solution AlP O4-GaP O4

    Science.gov (United States)

    Angot, E.; Huang, B.; Levelut, C.; Le Parc, R.; Hermet, P.; Pereira, A. S.; Aquilanti, G.; Frapper, G.; Cambon, O.; Haines, J.

    2017-08-01

    α -Quartz-type gallium phosphate and representative compositions in the AlP O4-GaP O4 solid solution were studied by x-ray powder diffraction and absorption spectroscopy, Raman scattering, and by first-principles calculations up to pressures of close to 30 GPa. A phase transition to a metastable orthorhombic high-pressure phase along with some of the stable orthorhombic C m c m CrV O4 -type material is found to occur beginning at 9 GPa at 320 ∘C in GaP O4 . In the case of the AlP O4-GaP O4 solid solution at room temperature, only the metastable orthorhombic phase was obtained above 10 GPa. The possible crystal structures of the high-pressure forms of GaP O4 were predicted from first-principles calculations and the evolutionary algorithm USPEX. A predicted orthorhombic structure with a P m n 21 space group with the gallium in sixfold and phosphorus in fourfold coordination was found to be in the best agreement with the combined experimental data from x-ray diffraction and absorption and Raman spectroscopy. This method is found to very powerful to better understand competition between different phase transition pathways at high pressure.

  17. In situ Ru K-edge EXAFS of CO adsorption on a Ru modified Pt/C fuel cell catalyst

    International Nuclear Information System (INIS)

    Rose, Abigail; Bilsborrow, Robert; King, Colin R.; Ravikumar, M.K.; Qian Yangdong; Wiltshire, Richard J.K.; Crabb, Eleanor M.; Russell, Andrea E.

    2009-01-01

    The Ru-CO bond of CO adsorbed on a Ru modified Pt/C fuel cell catalyst has been directly probed by in situ EXAFS at the Ru K-edge, providing evidence of a CO:metal surface atom ratio greater than 1:1 and that CO is adsorbed at bridging sites associated with Ru atoms at the surface of the catalyst nanoparticles. This result illustrates the limitations of single crystal models as representations of the bonding of adsorbed species at nanoparticle surfaces.

  18. Structural phase transformation in K2SeO4

    International Nuclear Information System (INIS)

    Iizumi, M.; Axe, J.D.; Shirane, G.; Shimaoka, K.

    1977-01-01

    Successive phase transformations in K 2 SeO 4 at T 1 = 130 K and T/sub c/ = 93 K were studied by the neutron-scattering technique. The superlattice reflections in the intermediate phase were found to be incommensurate with the lattice periodicity. The wave vector characterizing the reflections is q/sub delta/ = (1-delta) a*/3 with delta = 0.07 at 122.5 K. The deviation delta decreases with decreasing temperature with an apparently discontinuous jump to zero at T/sub c/. Below this temperature, the crystal remains commensurate and is known to be ferroelectric. The incommensurate-commensurate transition and the simultaneous occurrence of the commensurate phase and the spontaneous polarization are discussed using a Landau-type expansion of the free energy in which a term proportional to Q 3 (q/sub delta/) P/sub z/ (q 3 /sub delta/) plays an essential role in driving the incommensurate-commensurate phase transformation and in inducing the spontaneous polarization. Here, Q (q/sub delta/) is the amplitude of the primary atomic displacements with wave vector q/sub delta/ and P/sub z/(q 3 /sub delta/) is the polarization wave with wave vector q 3 /sub delta/ = 3delta (a*/3) and becomes the macroscopic polarization below T/sub c/. Above T/sub i/, a Σ 2 optic-phonon branch along (xi,0,0) shows a striking softening and ω/sub j/(q) for q approx. (1/3,0,0) tends to zero at T/sub i/. The softening results from a temperature-dependent decrease of the interlayer forces with ranges a/2 and a (a is one unit-cell length along the a axis) in the presence of strong and persisting forces with a range 3a/2. The intensities of the soft phonon were measured about different reciprocal-lattice points and were used to determine the nature of the soft-phonon mode and suggest a coupled translation of potassium ions with rotational motion of SeO 4 groups to be the origin of the lattice instability

  19. Electrical transport effects due to oxygen content modifications in a Bi2Sr2CaCu2O8+δ superconducting whisker

    International Nuclear Information System (INIS)

    Cagliero, Stefano; Agostino, Angelo; Bonometti, Elisabetta; Truccato, Marco

    2007-01-01

    We report a set of resistivity measurements along the a-axis of a Bi 2 Sr 2 CaCu 2 O 8+δ microscopic superconducting whisker. The effect of the storage environment on sample ageing has been studied, considering both an air atmosphere at 273 K and a helium atmosphere at about 300 K for an overall storage time of about 100 days. It is clearly shown that the material underwent a remarkable resistivity increase of 26% at 260 K accompanied by a decrease in the critical temperature of 0.6 K during the whole ageing period. The helium atmosphere increased the average process rate by about two orders of magnitude. The present results are in agreement with previous findings on room temperature structural modifications in Bi 2 Sr 2 CaCu 2 O 8+δ whiskers and can be ascribed to oxygen depletion phenomena from the material

  20. Anisotropic Resistivities of Precisely Oxygen Controlled Single-Crystal Bi2Sr2CaCu2O8+δ: Systematic Study on ''Spin Gap'' Effect

    International Nuclear Information System (INIS)

    Watanabe, T.; Matsuda, A.; Fujii, T.; Matsuda, A.

    1997-01-01

    The in-plane resistivity ρ a (T) and the out-of-plane resistivity ρ c (T) have been systematically measured for Bi 2 Sr 2 CaCu 2 O 8+δ single crystals with their oxygen contents precisely controlled. In the underdoped region, deviation from T -linear in-plane resistivity, which evidences the opening of the spin gap, is clearly observed, while the out-of-plane resistivity is well reproduced by the activation-type phenomenological formula ρ c (T)=(a/T)exp (Δ/T)+c . In contrast to the YBa 2 Cu 3 O 7-δ system, we find that the onset of the semiconducting ρ c (T) does not coincide with the opening of the spin gap seen in the ρ a (T) in this Bi 2 Sr 2 CaCu 2 O 8+δ system. copyright 1997 The American Physical Society

  1. Phase chemistry and microstructure evolution in silver-clad (Bi2-xPbx)Sr2Ca2Cu3Oy filaments

    International Nuclear Information System (INIS)

    Luo, J.S.; Merchant, N.; Maroni, V.A.; Escorcia-Aparicio, E.; Gruen, D.M.; Tani, B.S.; Riley, G.N. Jr.; Carter, W.L.

    1992-08-01

    The reaction kinetics and mechanism that control the conversion of (Bi,Pb) 2 Sr 2 CaCu 2 O z (Bi-2212) + alkaline earth cuporates to (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O y (Bi-2223) in silver-clad wires were investigated as a function of equilibration temperature and time at a fixed oxygen partial pressure (7.5% O 2 ). Measured values for the fractional conversion of Bi-2223 versus time have been evaluated based on the Avrami equation. SEM and TEM studies of partially and fully converted wires have revealed that (1) the growth of Bi-2223 is two-dimensional and controlled by a diffusion process, (2) liquid phases are present during part of the Bi-2212 -> Bi-2212 conversion, and (3) segregation of the second phases occurs in early time domains of the reaction

  2. Electronic structure in Bi2Sr2CaCu2O8 studied by two dimensional angular correlation of positron annihilation radiations

    International Nuclear Information System (INIS)

    Kondo, H.; Kubota, T.; Nakashima, N.; Tanigawa, S.; Minami, F.; Takekawa, S.

    1992-01-01

    Electronic structure in one of high-Tc-sperconducting materials, Bi 2 Sr 2 CaCu 2 O 8 , was studied by two dimensional angular correlation of positron annihilation radiations (2D-ACAR). The measurements were performed for Bi 2 Sr 2 CaCu 2 O 8 at room temperature and 24K; in the normal and superconducting states. The three dimensional electron momentum density ρ(p) has been reconstructed by using the image reconstruction technique based on a direct Fourier transportation. The reconstructed electron momentum density ρ(p) has been reduced into the reduced electron momentum density n(k) by using the LCW folding procedure. They are compared with that for Cu and Si. The difference in the density distributions between both states was observed. This may be attributed to the smearing by the reduced thermal momenta of positrons. But there is a possibility that the difference is due to the phase transition

  3. Removal of Cs+, Sr2+, and Co2+ ions from the mixture of organics and suspended solids aqueous solutions by zeolites

    International Nuclear Information System (INIS)

    Fang, Xiang Hong; Fang, Fang; Lu, Chun Hai; Zheng, Lei

    2017-01-01

    Serving as an excellent adsorbent and inorganic ion exchanger in the water purification field, zeolite 4A has in this work presented a strong capability for purifying radioactive waste, such as Sr 2+ , Cs + , and Co 2+ in water. During the processes of decontamination and decommissioning of suspended solids and organics in low-level radioactive wastewater, the purification performance of zeolite 4A has been studied. Under ambient temperature and neutral condition, zeolite 4A absorbed simulated radionuclides such as Sr 2+ , Cs + , and Co 2+ with an absorption rate of almost 90%. Additionally, in alkaline condition, the adsorption percentage even approached 98.7%. After conducting research on suspended solids and organics of zeolite 4A for the treatment of radionuclides, it was found that the suspended clay was conducive to absorption, whereas the absorption of organics in solution was determined by the species of radionuclides and organics. Therefore, zeolite 4A has considerable potential in the treatment of radioactive wastewater

  4. Analysis of discrete and continuous laser induced fluorescence spectra of the A 1Σsub(u)+-X 1Σsub(g)+ band system of Sr2

    International Nuclear Information System (INIS)

    Gerber, G.; Moeller, R.

    1982-01-01

    Laser induced fluorescence spectra of the gaseous Sr 2 excimer molecule have been measured. The spectra contain discrete molecular fluorescence series, regularly modulated continuous fluorescence and an unstructured continuum. Analysis of the molecular line spectra yields for the first time Dunham coefficients for the X 1 Σsub(g) + ground state and the A 1 Σsub(u) + excited state. Using the intensity distribution of the modulated continuum which is associated with bound-free transitions the repulsive potential of the ground state up to 3000 cm -1 above the dissociation limit has been determined. The unstructured continuum can be analyzed as due to two types of continuous fluorescence. The dissociation energy of Sr 2 has been determined to Dsub(e)(X) = 965 +- 45 cm -1 . (Auth.)

  5. Analysis of discrete and continuous laser induced fluorescence spectra of the A 1μ+sub(u) - X 1μ+sub(g) band system of SR2

    International Nuclear Information System (INIS)

    Gerber, G.; Moeller, R.

    1982-01-01

    Laser induced fluorescence spectra of the gaseous Sr 2 excimer molecule have been measured. The spectra contain discrete molecular fluorescence series, regularly modulated continuous fluorescence and an unstructured continuum. Analysis of the molecular line spectra yields for the first time Dunham coefficients for the X 1 μ + sub(g) ground state and the A 1 μ + sub(u) excited state. Using the intensity distribution of the modulated continuum which is associated with bound-free transitions the repulsive potential of the ground state up to 3000 cm - 1 above the dissociation limit has been determined. The unstructured continuum can be analyzed as due to two types of continuous fluorescence. The dissociation energy of Sr 2 has been determined to Dsub(e) (X) = 965 +- 45 cm - 1 . (Author)

  6. Neutron-diffraction study of the crystal structure of the superconductor TiSr2(Eu0.8Ce0.2)2Cu2Oz

    International Nuclear Information System (INIS)

    Ishigaki, T.; Ogasawara, Y.; Oikawa, K.; Hoshikawa, A.; Kamiyama, T.

    2004-01-01

    TiSr 2 (RE 1-x Ce x ) 2 Cu 2 O z superconductors (T c ∼20 K) have a 1222-structure with fluorite blocks. Neutron diffraction has been performed on the Eu-containing compound TiSr 2 (Eu 0.8 Ce 0.2 ) 2 Cu 2 O z , with natural Eu, and its crystal structure was refined. The neutron powder diffraction experiment was carried out on the VEGA diffractometer at KENS. The sample was contained in a thin flat cell of 0.5 mm thickness in order to reduce the large absorption effects of natural Eu. The absorption correction for the flat sample was taken into account in the Rietveld refinement. The results show that the O(1) atom in the Ti-layer is shifted from the 4c-site to the split site (8j), and that the concentration is deficient (g∼0.19)

  7. Ferroelectric and dielectric properties of Sr2-x(Na, K)xBi4Ti5O18 lead-free piezoelectric ceramics

    International Nuclear Information System (INIS)

    Chen Qian; Xu Zhijun; Chu Ruiqing; Hao Jigong; Zhang Yanjie; Li Guorong; Yin Qingrui

    2010-01-01

    (Na, K)-doped Sr 2 Bi 4 Ti 5 O 18 (SBTi) bismuth layer structure ferroelectric ceramics were prepared by the solid-state reaction method. Pure bismuth-layered structural Sr 2-x (Na, K) x Bi 4 Ti 5 O 18 (x=0.1, 0.2, 0.3, and 0.4) ceramics with uniform grain size were obtained in this work. The effects of (Na, K)-doping on the dielectric, ferroelectric and piezoelectric properties of SBTi ceramics were investigated. Results showed that (Na, K)-doping caused the Curie temperature of SBTi ceramics to shift to higher temperature and enhanced the ferroelectric and piezoelectric properties. At x=0.2, the ceramics exhibited optimum properties with d 33 =20 pC/N, P r =10.3 μC/cm 2 , and T c =324 o C.

  8. First-principles study on ferromagnetism in double perovskite Sr2AlTaO6 doped with Cu or Zn at B sites

    Science.gov (United States)

    Li, Y. D.; Wang, C. C.; Guo, Y. M.; Yu, Y.; Lu, Q. L.; Huang, S. G.; Li, Q. J.; Wang, H.; Cheng, R. L.; Liu, C. S.

    2018-05-01

    The possibilities of ferromagnetism induced by nonmagnetic dopants (Cu, Zn) in double perovskite Sr2AlTaO6 at B sites are investigated by density functional theory. Calculations reveal that substitutions at Ta-site tend to form high spin electronic configurations and could induce ferromagnetism which can be attributed to the hole-mediated p- d hybridization between Cu (or Zn) eg states and the neighboring O 2p states. The dopants preferably substitute at Al-site and adopt low spin electronic structures. Due to the smaller hole concentration and weaker covalent intensity, Sr2AlTaO6 with dopants at Al-site exhibits p-type metallic semiconductors without spin polarization.

  9. Interactions among magnetic moments in the double perovskites Sr2Fe1+xMo1−xO6

    International Nuclear Information System (INIS)

    Pilo, J.; Carvajal, E.; Oviedo-Roa, R.; Cruz-Irisson, M.; Navarro, O.

    2014-01-01

    It is well known that every double perovskite shows a characteristic magnetic behavior, as a consequence of the interactions among the magnetic moments associated with the atoms in their cells; at the same time, the electric and magnetic properties of the bulk double perovskite Sr 2 FeMoO 6 are well characterized. In this work we studied the iron rich compounds Sr 2 Fe 1+x Mo 1−x O 6 , using a supercell to model such concentrations that made Fe richer perovskites by ±66.6% and ±200%. Starting from the stoichiometric double perovskite, and modifying the Fe/Mo ratio in the compound, the study of these materials were based on the calculation of the magnetic moment at each atom, as well as the partial density of states

  10. Porous Hollow Superlattice NiMn2O4/NiCo2O4 Mesocrystals as a Highly Reversible Anode Material for Lithium-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Lingjun Li

    2018-05-01

    Full Text Available As a promising high-capacity anode material for Li-ion batteries, NiMn2O4 always suffers from the poor intrinsic conductivity and the architectural collapse originating from the volume expansion during cycle. Herein, a combined structure and architecture modulation is proposed to tackle concurrently the two handicaps, via a facile and well-controlled solvothermal approach to synthesize NiMn2O4/NiCo2O4 mesocrystals with superlattice structure and hollow multi-porous architecture. It is demonstrated that the obtained NiCo1.5Mn0.5O4 sample is made up of a new mixed-phase NiMn2O4/NiCo2O4 compound system, with a high charge capacity of 532.2 mAh g−1 with 90.4% capacity retention after 100 cycles at a current density of 1 A g−1. The enhanced electrochemical performance can be attributed to the synergistic effects of the superlattice structure and the hollow multi-porous architecture of the NiMn2O4/NiCo2O4 compound. The superlattice structure can improve ionic conductivity to enhance charge transport kinetics of the bulk material, while the hollow multi-porous architecture can provide enough void spaces to alleviate the architectural change during cycling, and shorten the lithium ions diffusion and electron-transportation distances.

  11. Photoluminescence analysis of Ce3+:Zn2SiO4 & Li++ Ce3+:Zn2SiO4: phosphors by a sol-gel method

    Science.gov (United States)

    Babu, B. Chandra; Vandana, C. Sai; Guravamma, J.; Rudramadevi, B. Hemalatha; Buddhudu, S.

    2015-06-01

    Here, we report on the development and photoluminescence analysis of Zn2SiO4, Ce3+:Zn2SiO4 & Li+ + Ce3+: Zn2SiO4 novel powder phosphors prepared by a sol-gel technique. The total amount of Ce3+ ions was kept constant in this experiment at 0.05 mol% total doping. The excitation and emission spectra of undoped (Zn2SiO4) and Ce3+ doped Zn2SiO4 and 0.05 mol% Li+ co-doped samples have been investigated. Cerium doped Zn2SiO4 powder phosphors had broad blue emission corresponding to the 2D3/2→2FJ transition at 443nm. Stable green-yellow-red emission has been observed from Zn2SiO4 host matrix and also we have been observed the enhanced luminescence of Li+ co-doped Zn2SiO4:Ce3+. Excitation and emission spectra of these blue luminescent phosphors have been analyzed in evaluating their potential as luminescent screen coating phosphors.

  12. A Novel Ternary CoFe2O4/CuO/CoFe2O4 as a Giant Magnetoresistance Sensor

    Directory of Open Access Journals (Sweden)

    Ramli

    2016-12-01

    Full Text Available This paper reports the results of a study relating to the synthesis of a novel ternary CoFe2O4/CuO/CoFe2O4 thin film as a giant magnetoresistance (GMR sensor. The CoFe2O4/CuO/CoFe2O4 thin film was prepared onto silicon substrate via DC magnetron sputtering with the targets facing each other. X-ray diffraction was used to determine the structure of the thin film and a 4-point method was used to measure the MR ratio. The GMR ratio is highly dependent on the ferrimagnetic (CoFe2O4 and nonmagnetic (CuO layer thickness. The maximum GMR ratio at room temperature obtained in the CoFe2O4/CuO/CoFe2O4 thin film was 70% when the CoFe2O4 and the CuO layer had a thickness of 62.5 nm and 14.4 nm respectively.

  13. Biodistribution of Ru-97-labeled DTPA, DMSA and transferrin

    International Nuclear Information System (INIS)

    Som, P.; Oster, Z.H.; Fairchild, R.G.; Atkins, H.L.; Brill, A.B.; Gil, M.C.; Srivastava, S.C.; Meinken, G.E.; Goldman, A.G.; Richards, P.

    1980-01-01

    Ruthenium-97 is being produced at the Brookhaven Linac Isotope Producer (BLIP). The favorable physical properties of Ru-97 and chemical reactivity of ruthenium offer a potential for using this isotope to label compounds useful for delayed scanning. Diethylenetriamine pentaacetic acid (DTPA), 2,3-Dimercaptosuccinic acid (DMSA), and Transferrin (TF) were labeled with Ru-97-chloride. Ru-97-DTPA and In-111-DTPA, injected intravenously, showed similar organ distribution, kinetics, and more than 80% excretion by 0.5 h. Ru-97-DTPA and In-111-DTPA injected into the cisterna magna of dogs showed similar kinetics in brain, blood, and urinary bladder. The energy deposited by 1 mCi In-111-DTPA is twice that from 1 mCi Ru-97-DTPA. High quality camera images of the CSF space in the dog were obtained with both isotopes. Ru-97-DMSA was prepared with and without the addition of SnCl 2 .2H 2 O. Tin-free DMSA was rapidly excreted via the kidneys, whereas for maximum cortical deposition, the tin-containing preparation was superior. This compound is suitable for delayed imaging of both normal and impaired kidneys. Tissue distribution studies were performed in abscess-bearing rats with Ru-97-transferrin. Although blood levels were higher than with Ga-67-citrate, the abscess had twice as much Ru-97-TF as Ga-67-citrate and the Ru-97 muscle activity was one-third that of Ga-67. Imaging of abscess-bearing rabbits with Ru-97-TF visualized the abscesses as early as 1/2 hr after injection. Since the initial images visualize the abscess so clearly and since the TF portion of the compound binds to the abscess, Tc-99m-TF is being studied for the same purpose. Ru-97-labeled compounds are a promising replacement for In-111 and possibly also for Ga-67 compounds with the advantages of lower radiation dose and high quality image

  14. The effect of doping Mg2+ on structure and properties of Sr(1.992-x)MgxSiO4: 0.008Eu2+ blue phosphor synthesized by co-precipitation method

    Science.gov (United States)

    Yang, Lingxiang; Wang, Jin-shan; Zhu, Da-chuan; Pu, Yong; Zhao, Cong; Han, Tao

    2018-01-01

    In order to improve the luminescence property of silicate phosphors, a series of Sr(1.992-x)MgxSiO4: 0.008Eu2+(x = 0, 0.25, 0.50, 0.75) blue phosphors have been synthesized using one-step calcination of a precursor prepared by chemical co-precipitation. And then the crystal structure and luminescence properties of the phosphors are investigated by means of X-Ray Diffraction and spectrophotometer. The results show that β-phase existed in the mixed phases of Sr2SiO4 (β+α‧) would transform to α‧-phase with Mg2+ ions doping into the silicate host until it disappeared. On the other hand, the introduction of Mg2+ ions can enhance the intensity of the excitation spectrum and promote the excitation sensitivity of Sr(1.992-x)MgxSiO4: 0.008Eu2+ phosphors in NUV region. Under NUV excitation at 350 nm, all samples exhibit a broadband emission in range of 400-550 nm due to the 4f65d1→4f7(8S7/2) transition of Eu2+ ions. According to Multi-peak fitting to emission spectra by Gauss method, the broad emission band consists of two single bands with peaks Em1 and Em2 locating at 460 and 490 nm, which corresponds to Eu2+ ions occupying the ten-fold oxygen-coordinated Sr1 site and the nine-fold oxygen-coordinated Sr2 site, respectively. The luminescence intensity of Sr(1.992-x)MgxSiO4:0.008Eu2+(x = 0, 0.25, 0.50, 0.75) blue phosphors has been enhanced remarkably after Mg2+ ions are added. Meanwhile, the chromaticity coordinates change from the blue-green region to the blue region as x moves from 0 to 0.75. Moreover, the decay curves are measured and can be well fitted with double exponential decay equation. It shows that the average lifetime is extended with the concentration of Mg2+ ions increasing. These results indicate that Sr(1.992-x)MgxSiO4: 0.008Eu2+(x = 0, 0.25, 0.50, 0.75) can be used as a potential blue phosphor in near UV-excited white LEDs.

  15. A new route for the synthesis of graphene oxide–Fe3O4 (GO–Fe3O4) nanocomposites and their Schottky diode applications

    International Nuclear Information System (INIS)

    Metin, Önder; Aydoğan, Şakir; Meral, Kadem

    2014-01-01

    Highlights: • Graphene Oxide (GO)–Fe 3 O 4 nanocomposites were prepared by a novel and facile method. • The successful assembly of Fe 3 O 4 NPs onto GO sheets was displayed by TEM. • The GO–Fe 3 O 4 nanocomposites/p-Si junction showed good rectifying property. -- Abstract: Addressed herein is a facile method for the preparation of magnetic graphene oxide–Fe 3 O 4 (GO–Fe 3 O 4 ) nanocomposites and the rectifying properties of (GO–Fe 3 O 4 )/p-Si junction in a Schottky diode. GO–Fe 3 O 4 nanocomposites were prepared by a novel method in which as-prepared GO sheets were decorated with the monodisperse Fe 3 O 4 nanoparticles (NPs) in dimethylformamide/chloroform mixture via a sonication process. The successful assembly of Fe 3 O 4 NPs onto GO sheets was displayed by transmission electron microscopy (TEM). Inductively couple plasma optical emission spectroscopy (ICP-OES) analysis of the GO–Fe 3 O 4 nanocomposite showed that the nanocomposite consists of 20.1 wt% Fe 3 O 4 NPs which provides a specific saturation magnetization (Ms) as 16 emu/g. The current–voltage (I–V) characteristics of the (GO–Fe 3 O 4 )/p-Si junction in a Schottky diode were studied in the temperature range of 50–350 K in the steps of 25 K. It was determined that the barrier height and ideality factor of the Au/GO–Fe 3 O 4 /p-Si/Al Schottky diode were depended on temperature as the barrier height increased while the ideality factor decreased with increasing temperature. The experimental values of barrier height and ideality factor were varied from 0.12 eV and 11.24 at 50 K to 0.76 eV and 2.49 at 350 K, respectively. The Richardson plot exhibited non-linearity at low temperatures that was attributed to the barrier inhomogeneities prevailing at the GO–Fe 3 O 4 /p-Si junction

  16. Solidification of Bi2Sr2Ca1Cu2Oy and Bi2Sr1.75Ca0.25CuOy

    International Nuclear Information System (INIS)

    Holesinger, T.G.; Miller, D.J.; Viswanathan, H.K.; Chumbley, L.S.

    1993-01-01

    The solidification processes for the compositions Bi 2 Sr 2 CaCu 2 O y (2212) and Bi 2 Sr 1.75 Ca 0.25 CuO y (2201) were determined as a function of oxygen partial pressure. During solidification in argon, the superconducting phases were generally not observed to form for either composition. In both cases, the solidus is lowered to approximately 750 degree C. Solidification of Bi 2 Sr 1.75 Ca 0.25 CuO y in Ar resulted in a divorced eutectic structure of Bi 2 Sr 2-x Ca x O y (22x) and Cu 2 O while solidification of Bi 2 Sr 2 CaCu 2 O y in Ar resulted in a divorced eutectic structure of Bi 2 Sr 3-x Ca x O y (23x) and Cu 2 O. Solidification of Bi 2 Sr 1.75 Ca 0.25 CuO y in O 2 resulted in large grains of 2201 interspersed with small regions containing the eutectic structure of 22x and CuO/Cu 2 O. Solidification of Bi 2 Sr 2 CaCu 2 O y in partial pressures of 1%, 20%, and 100% oxygen resulted in multiphase samples consisting of 2212, 2201, some alkaline-earth cuprates, and both divorced eutectic structures found during solidification in Ar. For both compositions, these latter structures can be attributed to oxygen deficiencies present in the melt regardless of the overpressure of oxygen. These eutectic structures are unstable and convert into the superconducting phases during subsequent anneals in oxygen. The formation process of the 2212 phase during solidification from the melt was determined to proceed through an intermediate state involving the 2201 phase

  17. Electron microscopic in situ study of phase and defect formation in Bi2Sr2CaCu2Oy single crystals in heating

    International Nuclear Information System (INIS)

    Goncharov, V.A.; Ignat'eva, E.Yu.; Osip'yan, Yu.A.; Suvorov, Eh.V.

    1997-01-01

    The nonthermal effect of electron irradiation on generating of new phases and structural defects has been uncovered during the investigation of structural variations of monocrystals Bi 2 Sr 2 CaCu 2 O y on heating in situ. The stability of the modulated structure and the package defects to heating under the electron beam action and in the absence of the irradiation has been studied

  18. Structural relaxation in the magnetically treated glass ceramic Bi1.8Pb0.2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Alekseenko, V.I.; Volkova, G.K.; Konstanminova, T.E.; Nosolev, I.K.; Popova, I.B.

    1994-01-01

    Structure relaxation in Bi 1.8 Pb 0.2 Sr 2 CaCu 2 O x amorphous glass ceramics after the treatment using weak pulse magnetic field is studied using microindentation, X-ray structure analysis and inner friction techniques. Structure relaxation after substance treatment using pulse magnetic field is detected to occur at room temperature and to result in its strengthening (increase of microhardness-H v ) and in reduction of inner microstress level.9 refs., 4 figs

  19. Coulomb-Gas scaling law for a superconducting Bi(2+y)Sr(2-x-y)La(x)CuO(6+delta) thin films in magnetic fields

    Science.gov (United States)

    Zhang; Deltour; Zhao

    2000-10-16

    The electrical transport properties of epitaxial superconducting Bi(2+y)Sr(2-x-y)La(x)CuO(6+delta) thin films have been studied in magnetic fields. Using a modified Coulomb-gas scaling law, we can fit all the magnetic field dependent low resistance data with a universal scaling curve, which allows us to determine a relation between the activation energy of the thermally activated flux flow resistance and the characteristic temperature scaling parameters.

  20. Evidence of chemical-potential shift with hole doping in Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Shen, Z.; Dessau, D.S.; Wells, B.O.; Olson, C.G.; Mitzi, D.B.; Lombado, L.; List, R.S.; Arko, A.J.

    1991-01-01

    We have performed photoemission studies on high-quality Bi 2 Sr 2 CaCu 2 O 8+δ samples with various δ. Our results show a clear chemical-potential shift (0.15--0.2 eV) as a function of doping. This result and the existing angle-resolved-photoemission data give a rather standard doping behavior of this compound in its highly doped regime

  1. Color-tunable and highly thermal stable Sr_2MgAl_2_2O_3_6:Tb"3"+ phosphors

    International Nuclear Information System (INIS)

    Zhang, Haiming; Zhang, Haoran; Liu, Yingliang; Lei, Bingfu; Deng, Jiankun; Liu, Wei-Ren; Zeng, Yuan; Zheng, Lingling; Zhao, Minyi

    2017-01-01

    Tb"3"+ activated Sr_2MgAl_2_2O_3_6 phosphor was prepared by a high-temperature solid-state reaction route. The X-ray diffraction, scanning electron microscopy, and photoluminescence spectroscopy were used to characterize the as-prepared samples. The Sr_2MgAl_2_2O_3_6:Tb"3"+ phosphors show intense green light emission under UV excitation. The phosphor exhibit two groups of emission lines from about 370 to 700 nm, which originating from the characteristic "5D_3-"7F_J and "5D_4-"7F_J transitions of the Tb"3"+ ion, respectively. The cross-relaxation mechanism between the "5D_3 and "5D_4 emission was investigated and discussed. The emission colors of these phosphors can be tuned from bluish-green to green by adjusting the Tb"3"+ doping concentration. Furthermore, the thermal quenching temperature (T_1_/_2) is higher than 500 K. The excellent thermal stability and color-tunable luminescent properties suggest that the developed material is a promising green-emitting phosphor candidate for optical devices. - Highlights: • A Color-tunable emitting phosphor Sr_2MgAl_2_2O_3_6:Tb"3"+ was prepared successfully via high-temperature solid-state reaction. • The photoluminescence of Sr_2MgAl_2_2O_3_6:Tb"3"+ shows highly thermal stable. • The cross-relaxation mechanism between the "5D_3 and "5D_4 emission was investigated and discussed.

  2. Enhancement of encaged electron concentration by Sr(2+) doping and improvement of Gd(3+) emission through controlling encaged anions in conductive C12A7 phosphors.

    Science.gov (United States)

    Zhang, Meng; Liu, Yuxue; Zhu, Hancheng; Yan, Duanting; Yang, Jian; Zhang, Xinyang; Liu, Chunguang; Xu, Changshan

    2016-07-28

    Conductive C12A7:0.1%Gd(3+),y%Sr(2+) powders with different Sr(2+) doping concentrations have been prepared in a H2 atmosphere by a solid state method in combination with subsequent UV-irradiation. The encaged electron concentration could be modulated through tuning Sr(2+) doping and its maximum value reaches 2.3 × 10(19) cm(-3). This is attributed to the competition between enhanced uptake and the release of the encaged anions during their formation and diffusion processes and the suppression of encaged electrons generation due to the increased encaged OH(-) anions and the decreased encaged O(2-) anions. Although there exists encaged electrons and different encaged anions (O(2-), H(-) and OH(-)) in C12A7 conductive powders prepared through the hydrogen route, a dominant local environment around Gd(3+) could be observed using electron spin resonance (ESR) detection. It can be ascribed to the stronger coupling of the encaged OH(-) to the framework of C12A7 than those of the encaged electrons, O(2-) and H(-) anions. In addition, emission of Gd(3+) ions is enhanced under UV or low voltage electron beam excitation and a new local environment around Gd(3+) ions appears through the thermal annealing in air because of the decrease of the encaged OH(-) anions and the increase of the encaged O(2-) anions. Our results suggested that Sr(2+) doping in combination with thermal annealing in air is an effective strategy for increasing the conductive performance and enhancing the emission of rare earth ions doped into C12A7 conductive phosphors for low-voltage field emission displays (FEDs).

  3. Zn2+ and Sr2+ Adsorption at the TiO2 (110)-Electrolyte Interface: Influence of Ionic Strength, Coverage, and Anions

    International Nuclear Information System (INIS)

    Zhang, Z.; Fenter, P.; Cheng, L.; Sturchio, N.; Bedzyk, M.; Machesky, M.; Anovitz, L.; Wesolowski, D.

    2006-01-01

    The X-ray standing wave technique was used to probe the sensitivity of Zn 2+ and Sr 2+ ion adsorption to changes in both the adsorbed ion coverage and the background electrolyte species and concentrations at the rutile (α-TiO 2 ) (110)-aqueous interface. Measurements were made with various background electrolytes (NaCl, NaTr, RbCl, NaBr) at concentrations as high as 1 m. The results demonstrate that Zn 2+ and Sr 2+ reside primarily in the condensed layer and that the ion heights above the Ti-O surface plane are insensitive to ionic strength and the choice of background electrolyte (with - , coupled with the insensitivity of Zn 2+ and Sr 2+ cation heights to changes in the background electrolyte, implies that anions do not play a significant role in the adsorption of these divalent metal ions to the rutile (110) surface. Absolute ion coverage measurements for Zn 2+ and Sr 2+ show a maximum Stern-layer coverage of ∼0.5 monolayer, with no significant variation in height as a function of Stern-layer coverage. These observations are discussed in the context of Gouy-Chapman-Stern models of the electrical double layer developed from macroscopic sorption and pH-titration studies of rutile powder suspensions. Direct comparison between these experimental observations and the MUltiSIte Complexation (MUSIC) model predictions of cation surface coverage as a function of ionic strength revealed good agreement between measured and predicted surface coverages with no adjustable parameters

  4. In-situ synchrotron PXRD study of spinel LiMn2O4 nanocrystal formation

    DEFF Research Database (Denmark)

    Birgisson, Steinar; Jensen, Kirsten Marie Ørnsbjerg; Christiansen, Troels Lindahl

    Many solvothermal reactions have a great potential for environmentally friendly and easily scalable way for producing nanocrystalline materials on an industrial scale. Here we study hydrothermal formation of spinel LiMn2O4 which is a well-known cathode material for Li-ion batteries. The LiMn2O4...... nanoparticles are formed by reducing KMnO4 in an aqueous solution containing Li-ions. The reducing agent is an alcohol (here ethanol) and the reaction takes place under high pressure and temperature. The LiMn2O4 nanocrystals are unstable towards further reduction to Mn3O4 nanocrystals. Possible reaction route...

  5. Leishmanicidal Activity of Biogenic Fe3O4 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Mehrdad Khatami

    2017-11-01

    Full Text Available Abstract: Due to the multiplicity of useful applications of metal oxide nanoparticles (ONPs in medicine are growing exponentially, in this study, Fe3O4 (iron oxide nanoparticles (IONPs were biosynthesized using Rosemary to evaluate the leishmanicidal efficiency of green synthesized IONPs. This is the first report of the leishmanicidal efficiency of green synthesized IONPs against Leishmania major. The resulting biosynthesized IONPs were characterized by ultraviolet-visible spectroscopy (UV-Vis, X-ray diffraction (XRD, transmission electron microscopy (TEM, and Fourier transform infrared spectroscopy (FTIR. The leishmanicidal activity of IONPS was studied via 3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT assay. The results showed the fabrication of the spherical shape of monodisperse IONPs with a size 4 ± 2 nm. The UV-visible spectrophotometer absorption peak was at 334 nm. The leishmanicidal activity of biogenic iron oxide nanoparticles against Leishmania major (promastigote was also studied. The IC50 of IONPs was 350 µg/mL. In this report, IONPs were synthesized via a green method. IONPs are mainly spherical and homogeneous, with an average size of about 4 nm, and were synthesized here using an eco-friendly, simple, and inexpensive method.

  6. Structural chemistry of the cation-ordered perovskites Sr2CaMo1-xTexO6 (0=

    International Nuclear Information System (INIS)

    Prior, Timothy J.; Couper, Victoria J.; Battle, Peter D.

    2005-01-01

    The crystal structures of Sr 2 CaMoO 6 and Sr 2 CaTeO 6 have been determined at room temperature by neutron powder diffraction. Both compounds crystallize in the perovskite structure with a rock-salt ordered array of Ca 2+ and M 6+ cations (M=Mo, Te) on the six-coordinate sites (space group P2 1 /n (no. 14); for M=Mo, a=5.76228(7), b=5.84790(7), c=8.18707(9)A, β=90.194(1) o , for M=Te, a=5.79919(9), b=5.83756(8), c=8.2175(1)A, β=90.194(1) o ). Compositions in the solid solution Sr 2 CaMo 1-x Te x O 6 have been synthesized and shown by X-ray diffraction to adopt the same ordered structure. The results are used in a discussion of the cation oxidation states in Ca 2 FeMoO 6 and to establish the similarity between the structural chemistry of hexavalent Mo and Te

  7. CONSTRUCTION AND REARING OF THE MEDITERRANEAN FRUIT FLY, CERATITIS CAPITATA, GENETIC SEXING STRAINS, VIENNA-8 WITH MALES CARRYING THE MARKER SERGEANT-2 (VIENNA-8/Sr2)

    International Nuclear Information System (INIS)

    SHOMAN, A.A.

    2008-01-01

    A trial on the construction, maintenance and adaptation of the genetic sexing strain Vienna-8/Sr2 of the Mediterranean fruit fly, Ceratitis capitata (Wied.), has been done in the fruit fly laboratories of the Egyptian Atomic Energy Authority (EAEA) in the cooperation with the laboratories of International Atomic Energy Agency, Vienna. This trial was successful and this strain was maintained in the medfly laboratories of the EAEA for more than 10 generations up till now. Vienna-8/ Sr 2 is very stable strain and carries the dominant mutation called sergeant-2 (Sr 2 ) and could be used as a visible marker for the sterile male flies released in the field for controlling the Mediterranean fruit fly. This visible marker simplifies the discrimination between released sterile males and wild males caught in field monitoring traps. Males of this strain have three white stripes on the abdomen while wild males have only two stripes. The use of this genetic marker, as a replacement of the external dye marker, clearly has an immediate positive impact on the efficiency of Mediterranean fruit fly SIT programs (by using gamma radiation)

  8. Microstructure, Mechanical and Tribological Properties of Ag/Bi2Sr2CaCu2O x Self-lubricating Composites

    Science.gov (United States)

    Tang, Hua; Zhang, Du; Wang, Yuqi; Zhang, Yi; Ji, Xiaorui; Song, Haojie; Li, Changsheng

    2014-01-01

    Ag/Bi2Sr2CaCu2O x self-lubricating composites were successfully fabricated by a facile powder metallurgy method. The structure and morphology of the as-synthesized composites and the worn surface after tribometer testing are characterized by using X-ray diffraction and scanning electron microscopy together with energy dispersive spectrometry. The results indicated that self-lubricating composites are composed of superconductor phase and Ag phase. Moreover, the effects of Ag on mechanical and tribological properties of the novel composites were investigated. The friction test results showed that the friction coefficient of the pure Bi2212 against stainless steel is about 0.40 at ambient temperature and abruptly decreases to about 0.17 when the temperature is cooled to 77 K. The friction coefficients of the composites from room temperature to high temperature were lower and more stable than those of pure Bi2Sr2CaCu2O x . When the content of Ag is 10 wt.%, the Ag/Bi2Sr2CaCu2O x composites exhibited excellent tribological performance, the improved tribological properties are attributed to the formation of soft metallic Ag films at the contacted zone of the composites.

  9. Effect of charge compensator ions (R+ = Li+, Na+ and K+) on Sr2MgSi2O7:Dy3+ phosphors by solid-state reaction method

    International Nuclear Information System (INIS)

    Sahu, Ishwar Prasad

    2016-01-01

    The Sr 2 MgSi 2 O 7 :Dy 3+ and Sr 2 MgSi 2 O 7 :Dy 3+ , R + (R + = Li + , Na + and K + ) phosphors were prepared by solid-state reaction method. The crystal structures of sintered phosphors were an akermanite-type structure which belongs to the tetragonal crystallography. The prepared phosphors were excited at 350 nm, and their corresponding emission spectrum were recorded at blue (482 nm) and yellow (575 nm) region due to the 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions, respectively, of Dy 3+ ions. Commission Internationale de L'Eclairage coordinates have been calculated for each sample and its value exhibited that overall emission is near white light. The possible mechanisms of discussed white light emitting phosphors were also investigated. In order to investigate the suitability of the samples as white color light sources for industrial uses, color purity, correlated color temperature (CCT) and color rendering index (CRI) were calculated. Values of color purity, CCT and CRI were found well within the defined acceptable range. With incorporating (R + = Li + , Na + and K + ) as charge compensator ions, the emission intensity of Sr 2 MgSi 2 O 7 :Dy 3+ can be obviously enhanced. The results indicate that prepared phosphors may be a potential application in display devices. (orig.)

  10. Effect of charge compensator ions (R+ = Li+, Na+ and K+) on Sr2MgSi2O7:Dy3+ phosphors by solid-state reaction method

    Science.gov (United States)

    Sahu, Ishwar Prasad

    2016-09-01

    The Sr2MgSi2O7:Dy3+ and Sr2MgSi2O7:Dy3+, R+ (R+ = Li+, Na+ and K+) phosphors were prepared by solid-state reaction method. The crystal structures of sintered phosphors were an akermanite-type structure which belongs to the tetragonal crystallography. The prepared phosphors were excited at 350 nm, and their corresponding emission spectrum were recorded at blue (482 nm) and yellow (575 nm) region due to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively, of Dy3+ ions. Commission Internationale de L'Eclairage coordinates have been calculated for each sample and its value exhibited that overall emission is near white light. The possible mechanisms of discussed white light emitting phosphors were also investigated. In order to investigate the suitability of the samples as white color light sources for industrial uses, color purity, correlated color temperature (CCT) and color rendering index (CRI) were calculated. Values of color purity, CCT and CRI were found well within the defined acceptable range. With incorporating (R+ = Li+, Na+ and K+) as charge compensator ions, the emission intensity of Sr2MgSi2O7:Dy3+ can be obviously enhanced. The results indicate that prepared phosphors may be a potential application in display devices.

  11. Enhanced thermoelectric figure-of-merit in environmentally benign BaxSr2-xTiCoO6 double perovskites

    Science.gov (United States)

    Saxena, Mandvi; Roy, Pinku; Acharya, Megha; Bose, Imon; Tanwar, Khagesh; Maiti, Tanmoy

    2016-12-01

    Environmental friendly, non-toxic double perovskite BaxSr2-xTiCoO6 compositions with 0 ≤ x ≤ 0.2 were synthesized using solid-state reaction route for high temperature thermoelectric (TE) applications. XRD and SEM studies confirmed the presence of single-phase solid solution with highly dense microstructure for all the oxide compositions. Temperature dependent electrical conductivity measurement showed semiconductor to metal (M-S) transition in these double perovskites. Incorporation of barium in Sr2TiCoO6 pushed M-S transition to higher temperature making it a potential candidate for high temperature TE applications. Conductivity behaviors of these oxides were explained by small polaron model. Furthermore, these oxides exhibit a glass like behavior resulting in low thermal conductivity. Low temperature dielectric measurement revealed relaxor ferroelectric behavior in these oxides below room temperature. Transition of these relaxors into a glassy state beyond Burns temperature (TD) was found responsible for having low thermal conductivity in these oxides. Maximum dimensionless TE figure-of-merit ZT = 0.29 at 1223 K was achieved for BaxSr2-xTiCoO6 composition with x = 0.2.

  12. A novel double perovskite tellurate Eu3+-doped Sr2MgTeO6 red-emitting phosphor with high thermal stability

    Science.gov (United States)

    Liang, Jingyun; Zhao, Shancang; Yuan, Xuexia; Li, Zengmei

    2018-05-01

    A series of novel double perovskite tellurate red-emitting phosphors Sr2MgTeO6:xEu3+ (x = 0.05-0.40) were successfully synthesized by a high-temperature solid-state reaction method. The phase structure, photoluminescence properties and thermal stability of the phosphor were investigated in detail. The phosphor shows dominant emission peak at 614 nm belonging to the 5D0 → 7F2 electric dipole transition under 465 nm excitation. The luminescence intensity keeps increasing with increasing the content of Eu3+ to 25 mol%, and the critical transfer distance of Eu3+ was calculated to be 12 Å. The quenching temperature for Sr2MgTeO6:0.25Eu3+ was estimated to be above 500 K. This spectral feature reveals high color purity and excellent chromaticity coordinate characteristics. Therefore, Eu3+-doped Sr2MgTeO6 phosphors are potential red phosphors for blue chip-based white light-emitting diode and display devices.

  13. Core/shell structure NiCo2O4@MnCo2O4 nanofibers fabricated by different temperatures for high-performance supercapacitors

    Science.gov (United States)

    Wang, Qing; Qin, Xuefeng; Jiang, Pengcheng; Dai, Jianfeng; Li, Weixue; Gao, Haoran

    2018-03-01

    Core/shell structure NiCo2O4@MnCo2O4 nanofibers (NiCo2O4@MnCo2O4 NFs) were prepared by a facile co-electrospinning method and heat treatment. The composites annealed at 500 °C have a complete, continuously obvious core/shell structure, and clear interface of composites with good morphology, while annealed at 600 °C were stacked on each other and were unable to sustain three-dimensional network structures and 700 °C calcination have completely lost one-dimensional structure. The core NiCo2O4 is about 70 nm in diameter and the MnCo2O4 shell behaves a thickness about 60 nm. When investigated as an electrode material for supercapacitors, the NiCo2O4@MnCo2O4 NFs annealed at 500 °C exihibited the specific capacitance of 463 F g-1 (0.926 F cm-2) at 1 A g-1, higher than that annealed at 600 °C 362 F g-1, 1 A g-1 (0.724 F cm-2, 1 A g-1) and 700 °C 283 F g-1, 1 A g-1 (0.566 F cm-2, 1 A g-1). These results suggest that core/shell NiCo2O4@MnCo2O4 NFs annealed at 500 °C have formed a good morphology with continuously complete core/shell structure which lead to good properties would be potential electrodes for supercapacitors.

  14. Topotactic synthesis of Co3O4 nanoboxes from Co(OH)2 nanoflakes

    International Nuclear Information System (INIS)

    Tian Li; Huang Kelong; Liu Younian; Liu Suqin

    2011-01-01

    Hollow nanocubes of spinel Co 3 O 4 with the dimension of 20 nm were successfully prepared via a facile and reproducible solvothermal route. The structure and morphology of Co 3 O 4 nanoboxes were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) techniques. And a possible growth mechanism of Co 3 O 4 nanoboxes were suggested that solid Co 3 O 4 nanocubes nucleate in-situ and grow epitaxially from hexagonal β-Co(OH) 2 precursors with the structural matching relationship of [0 0 1] β-Co(OH) 2 //[1 1 1] Co 3 O 4 , and then solid Co 3 O 4 nanocubes gradually hollow and convert to single-crystal nanoboxes owing to Ostwald ripening. - Graphical abstract: The formation mechanism of Co 3 O 4 nanoboxes can be expressed as epitaxial growth of Co 3 O 4 nanocubes from β-Co(OH) 2 nanoflakes due to a topotactic transformation and hollowing process owing to Ostwald ripening. Highlights: → Co 3 O 4 nanoboxes were prepared by a convenient, economical and controllable hydrothermal route. → Morphology and structure of Co 3 O 4 nanoboxes were characterized by XRD, SEM, and TEM techniques. → Co 3 O 4 nanoboxes grow epitaxially from Co(OH) 2 by topotactic transformation was suggested.

  15. Supercapacitive performance of hydrous ruthenium oxide (RuO2 ...

    Indian Academy of Sciences (India)

    2016-08-26

    SO4 electrolyte. RuO2.H2O film showed maximum specific capacitance of 192 F.g-1 at a scan rate of 20 mV.s-1. The charge–discharge studies of RuO2.H2O carried out at 300 A.cm-2 current density revealed the specific ...

  16. NOVEL RU-NI-S ELECTRODE CATALYST FOR PEMFC

    Science.gov (United States)

    The expected results from this project include: a new formula and preparation procedures for Ru-Ni-S catalyst; demonstration of CO and S tolerance of the new catalyst; a small size PEMFC with Ru-Ni-S catalyst and good performance; an...

  17. bond activation and catalysis by Ru -pac complexes

    Indian Academy of Sciences (India)

    and their reactivity towards oxidation of a few organic compounds. Keywords. Kinetics; catalysis; -O–O- bond activation; Ru-pac complex; oxidation. 1. Introduction. Ru-pac complexes exhibit catalytic properties,1 in homogeneous conditions in the presence of oxygen atom donors, that mimic the biological enzymatic oxi-.

  18. High-Density Stacked Ru Nanocrystals for Nonvolatile Memory Application

    International Nuclear Information System (INIS)

    Ping, Mao; Zhi-Gang, Zhang; Li-Yang, Pan; Jun, Xu; Pei-Yi, Chen

    2009-01-01

    Stacked ruthenium (Ru) nanocrystals (NCs) are formed by rapid thermal annealing for the whole gate stacks and embedded in memory structure, which is compatible with conventional CMOS technology. Ru NCs with high density (3 × 10 12 cm −2 ), small size (2–4 nm) and good uniformity both in aerial distribution and morphology are formed. Attributed to the higher surface trap density, a memory window of 5.2 V is obtained with stacked Ru NCs in comparison to that of 3.5 V with single-layer samples. The stacked Ru NCs device also exhibits much better retention performance because of Coulomb blockade and vertical uniformity between stacked Ru NCs

  19. Magnesium Aminoclay-Fe3O4 (MgAC-Fe3O4 Hybrid Composites for Harvesting of Mixed Microalgae

    Directory of Open Access Journals (Sweden)

    Bohwa Kim

    2018-05-01

    Full Text Available In this paper, we describe the synthesis of magnesium aminoclay-iron oxide (MgAC-Fe3O4 hybrid composites for microalgae-harvesting application. MgAC-templated Fe3O4 nanoparticles (NPs were synthesized in different ratios of MgAC and Fe3O4 NPs. The uniform distribution of Fe3O4 NPs in the MgAC matrix was confirmed by transmission electron microscopy (TEM. According to obtained X-ray diffraction (XRD patterns, increased MgAC loading leads to decreased intensity of the composites’ (311 plane of Fe3O4 NPs. For harvesting of Chlorella sp. KR-1, Scenedesmus obliquus and mixed microalgae (Chlorella sp. KR-1/ Scenedesmus obliquus, the optimal pH was 4.0. At higher pHs, the microalgae-harvesting efficiencies fell. Sample #1, which had the highest MgAC concentration, showed the most stability: the harvesting efficiencies for Chlorella sp. KR-1, Scenedesmus obliquus, and mixed microalgae were reduced only to ~50% at pH = 10.0. The electrostatic interaction between MgAC and the Fe3O4 NPs in the hybrid samples by microalgae, as confirmed by zeta potential measurements, were attributed to the harvesting mechanisms. Moreover, the zeta potentials of the MgAC-Fe3O4 hybrid composites were reduced as pH was increased, thus diminishing the microalgae-harvesting efficiencies.

  20. Phase relations in Ca(Sr)MoO4-Ln2(NoO4)3 systems (Ln = Pr-Lu)

    International Nuclear Information System (INIS)

    Vakalyuk, V.V.; Evdokimov, A.A.; Berezina, T.A.

    1982-01-01

    Using the methods of X-ray phase and differential thermal analyses phase ratios in the systems Ca(Sr)MoO 4 -Ln 2 (MoO 4 ) 3 at Ln=Pr-Lu are studied and phase diagrams of the systems CaMoO 4 -Ln 2 (MoO 4 ) 3 , for Ln=Nd, Gd, Yb and SrMoO 4 -Sm 2 (MoO 4 ) 3 are built. It is shown that phase ratios in the systems are similar for the following groups of rare earths: Pr-Sm, Eu-Tb, Ho-Lu. In the first group of systems ordered phase over all subsolidus region are formed, in the second one - ordered phases with scheelite-like structure and wide regions of homogeneity on the basis of Ca(Sr)MoO 4 are formed above the temperature of polymorphous transformation of rare earth molybdates, for the third group of systems intermediate compounds are not detected