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Sample records for oxides lnmo8o14 ln

  1. Ln polyoxocations: yttrium oxide solution speciation & solution deposited thin films.

    PubMed

    Marsh, David A; Goberna-Ferrón, Sara; Baumeister, Mary K; Zakharov, Lev N; Nyman, May; Johnson, Darren W

    2017-01-17

    Rare earth oxide materials, including thin film coatings, are critically important in magnetic, luminescent and microelectric devices, and few substitutes have been discovered with comparable performance. Thin film coatings from solution are almost unknown for rare earth oxides, likely due to their high activity towards hydrolysis which yields poor quality thin films. The hexamer [Ln6(O)(OH)8(H2O)12(NO3)6](2+) is a rare example of a metal-oxo cluster isolated and stabilized without additional supporting organic ligands. Herein we report a new method for both the preparation and stabilization in non-aqueous media, which makes these clusters valuable precursors for solution-processed thin films. Solution characterization (NMR, small-angle X-ray scattering and Raman spectroscopy) in wet organic solvents indicated that the clusters evolve via a fragmentation and reaggregation process. This is especially true for hexamers of the smaller Ln(3+)-ions: the higher charge density yields higher hydration rates. This process produced an entirely new hexadecameric cluster formulated Y16O3(OH)24(NO3)18(OSMe2)16(OCMe2)2(H2O)4. The new structure represents an intermediate hydrolysis product on the pathway from hexanuclear clusters to metal oxyhydroxide bulk solid. DMSO solvent ligands displace aqua ligands on the cluster and likely explain the additional stability observed for these clusters in organic solvents. The enhanced cluster stability in DMF and DMSO also enables solution-processing methods to create high quality thin films.

  2. Polymeric nanocomposites loaded with fluoridated hydroxyapatite Ln3+ (Ln = Eu or Tb)/iron oxide for magnetic targeted cellular imaging

    PubMed Central

    Pan, Jie; Liu, Wei-Jiao; Hua, Chao; Wang, Li-Li; Wan, Dong; Gong, Jun-Bo

    2015-01-01

    Objective To fabricate polymeric nanocomposites with excellent photoluminescence, magnetic properties, and stability in aqueous solutions, in order to improve specificity and sensitivity of cellular imaging under a magnetic field. Methods Fluoridated Ln3+-doped HAP (Ln3+-HAP) NPs and iron oxides (IOs) can be encapsulated with biocompatible polymers via a modified solvent exaction/evaporation technique to prepare polymeric nanocomposites with fluoridated Ln3+-HAP/iron oxide. The nanocomposites were characterized for surface morphology, fluorescence spectra, magnetic properties and in vitro cytotoxicity. Magnetic targeted cellular imaging of such nanocomposites was also evaluated with confocal laser scanning microscope using A549 cells with or without magnetic field. Results The fabricated nanocomposites showed good stability and excellent luminescent properties, as well as low in vitro cytotoxicity, indicating that the nanocomposites are suitable for biological applications. Nanocomposites under magnetic field achieved much higher cellular uptake via an energy-dependent pathway than those without magnetic field. Conclusion The nanocomposites fabricated in this study will be a promising tool for magnetic targeted cellular imaging with improved specificity and enhanced selection. PMID:26487962

  3. Reactions of lanthanide atoms with oxygen difluoride and the role of the Ln oxidation state.

    PubMed

    Mikulas, Tanya; Chen, Mingyang; Dixon, David A; Peterson, Kirk A; Gong, Yu; Andrews, Lester

    2014-01-06

    Laser-ablated lanthanide metal atoms were condensed with OF2 in excess argon or neon at 4 K. New infrared absorption bands were observed and assigned to the oxidative addition products OLnF2 and OLnF on the basis of (18)O isotopic substitution and electronic structure calculations of the vibrational frequencies. The dominant absorptions in the 500 cm(-1) region are identified as Ln-F stretching modes, which follow the lanthanide contraction. The Ln-O stretching frequency is an important measure of the oxidation states of the Ln and oxygen and the spin state of the complex. The OCeF2, OPrF2, and OTbF2 molecules have higher frequency Ln-O stretching modes. The Ce is assigned to the IV oxidation state and the Pr and Tb are assigned to a mixed III/IV oxidation state. The remaining OLnF2 compounds have lower Ln-O stretches, and the Ln is in the III oxidation state and the O is in the -1 oxidation state. For all of the OLnF compounds, the metal is in the III oxidation state, and the Ln-F bonds are ionic. In OCeF2, OLaF, and OLuF, the bonding between the Ln and O is best described as a highly polarized σ bond and two pseudo π bonds formed by donation from the two 2p lone pairs on the O to the Ln. Bonding for the OLnF2 compounds in the III oxidation state is predicted to be fully ionic. The bonding in OLnF2 and OLnF is dominated by the oxidation state on the lanthanide and the spin state of the molecule. The observation of larger neon to argon matrix shifts for Ln-O modes in several OLnF molecules as compared to their OLnF2 analogues is indicative of more ionic character in the OLnF species, consistent with the more formal negative charge on the oxygen in OLnF.

  4. Exploring the effect of the Ln(III)/Ln(II) redox potential on C-F activation and on oxidation of some lanthanoid organoamides.

    PubMed

    Deacon, Glen B; Junk, Peter C; Kelly, Rory P; Wang, Jun

    2016-01-28

    The divalent europium complexes, and (L(Me/Et) = p-HC6F4N(CH2)2NMe2/Et2), have been prepared from redox-transmetallation/protolysis (RTP) reactions between Eu metal, Hg(C6F5)2 and L(Me/Et)H in thf. The complexes exhibit close (C)F-Ln interactions and the amide ligands feature tridentate N,N',F chelation. The complexes are thermally robust but on exposure to light they undergo C-F activation. From exposure of to light, the Eu(III) mixed fluoride/oxide cluster, was isolated, but other well-defined C-F activation products have proven elusive due to the stability of Eu(II). Oxidation of [Ln(L(R))2(thf)2] (Ln = Eu, R = Me; Ln = Yb, R = Et) with I2 afforded the heteroleptic iodo complexes, [Ln(L(R))2I(thf)n] (Ln = Eu, n = 1; Ln = Yb, n = 0), and the homoleptic complexes, [Ln(L(R))3]. The formation of the iodo complexes and the heteroleptic complexes appear to occur by different routes. shows interesting structural differences from reported [Ln(L(Et))3] (Ln = La, Ce, Nd) complexes, and highlights an incomplete shift towards N,N' chelation to the much smaller Yb ion. was prepared from a protolysis reaction between [Sm(CH2C6H4-NMe2-o)3] and L(Me)H. Heating a solution of in toluene at 110 °C for three days did not afford any samarium fluoride complex. An RTP reaction with Sm afforded the heteroleptic samarium complex, , in very low yield. From an attempted protolysis reaction between [Sm(DippForm)2(thf)2] and L(Me)H, the mixed ligand samarium fluoride complex, , was isolated. Overall, the instability of Sm(II) precludes control over the C-F activation reactions.

  5. Magnetic interactions in new fluorite-related rare earth oxides LnLn'2RuO7 (Ln, Ln'=rare earths)

    NASA Astrophysics Data System (ADS)

    Hinatsu, Yukio; Doi, Yoshihiro

    2016-07-01

    New fluorite-related quaternary rare earth oxides Pr2YRuO7 and La2TbRuO7 have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space group Cmcm. Through magnetic susceptibility and specific heat measurements, Pr2YRuO7 shows an antiferromagnetic transition at 27 K, which is considerably lowered compared with that for Pr3RuO7. Analysis of the magnetic specific heat indicates that the magnetic behavior observed at 27 K for Pr2YRuO7 is predominantly due to the magnetic interactions between Ru ions, and that the interactions between the Pr3+ and Ru5+ ions are also important. La2TbRuO7 shows magnetic ordering at 9.0 K, which is ascribed to the magnetic ordering between Ru5+ ions from the analysis of the magnetic specific heat data.

  6. Structures and magnetic properties of new fluorite-related quaternary rare earth oxides LnY2TaO7 and LaLn2RuO7 (Ln=rare earths)

    NASA Astrophysics Data System (ADS)

    Hinatsu, Yukio; Doi, Yoshihiro

    2016-01-01

    New fluorite-related quaternary rare earth oxides LnY2TaO7 (Ln=La-Dy) and LaLn2RuO7 (Ln=Eu-Tb) have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space groups C2221 and Cmcm, respectively. The results of the Rietveld analysis for LnY2TaO7 (Ln=La-Dy) indicate that there exists no structural ordering of the Ln and Y ions at the eight-coordinate 4b site and the seven-coordinate 8c site, but the larger Ln ions occupy the eight-coordinate 4b site rather than the seven-coordinate 8c site, with increasing the Ln ionic radius. On the other hand, the results of the Rietveld analysis for the X-ray diffraction profiles of LaTb2RuO7 showed that La and Tb atoms are almost situated at the eight-coordinated site (4a site) and seven-coordinated site (8g site), respectively, i.e., cation ordering occurs on the 4a and 8g sites. All compounds LnY2TaO7 (Ln=La-Dy) are paramagnetic down to 1.8 K. On the other hand, LaTb2RuO7 shows an antiferromagnetic transition at 17 K. In addition, another magnetic anomaly has been found at 10 K. Analysis of the magnetic specific heat for LaTb2RuO7 indicates that the magnetic transitions at 10 and 17 K are due to the magnetic ordering of Tb3+ and Ru5+ ions, respectively.

  7. Structures and magnetic properties of new fluorite-related quaternary rare earth oxides LnY{sub 2}TaO{sub 7} and LaLn{sub 2}RuO{sub 7} (Ln=rare earths)

    SciTech Connect

    Hinatsu, Yukio Doi, Yoshihiro

    2016-01-15

    New fluorite-related quaternary rare earth oxides LnY{sub 2}TaO{sub 7} (Ln=La–Dy) and LaLn{sub 2}RuO{sub 7} (Ln=Eu–Tb) have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space groups C222{sub 1} and Cmcm, respectively. The results of the Rietveld analysis for LnY{sub 2}TaO{sub 7} (Ln=La–Dy) indicate that there exists no structural ordering of the Ln and Y ions at the eight-coordinate 4b site and the seven-coordinate 8c site, but the larger Ln ions occupy the eight-coordinate 4b site rather than the seven-coordinate 8c site, with increasing the Ln ionic radius. On the other hand, the results of the Rietveld analysis for the X-ray diffraction profiles of LaTb{sub 2}RuO{sub 7} showed that La and Tb atoms are almost situated at the eight-coordinated site (4a site) and seven-coordinated site (8g site), respectively, i.e., cation ordering occurs on the 4a and 8g sites. All compounds LnY{sub 2}TaO{sub 7} (Ln=La–Dy) are paramagnetic down to 1.8 K. On the other hand, LaTb{sub 2}RuO{sub 7} shows an antiferromagnetic transition at 17 K. In addition, another magnetic anomaly has been found at 10 K. Analysis of the magnetic specific heat for LaTb{sub 2}RuO{sub 7} indicates that the magnetic transitions at 10 and 17 K are due to the magnetic ordering of Tb{sup 3+} and Ru{sup 5+} ions, respectively. - Graphical abstract: Two magnetic anomalies have been observed in the temperature dependence of ∂(χT)/∂T for LaTb{sub 2}RuO{sub 7}. It is discussed that the anomalies at 10 and 17 K are due to the magnetic ordering of Tb{sup 3+} and Ru{sup 5+} ions, respectively. - Highlights: • New fluorite-related quaternary rare earth oxides Ln′Ln″{sub 2}MO{sub 7} have been prepared. • All compounds LnY{sub 2}TaO{sub 7} (Ln=La–Dy) are paramagnetic down to 1.8 K. • LaTb{sub 2}RuO{sub 7} shows two magnetic anomalies at 10 and 17 K.

  8. Synthesis of the new layered oxides NaRbLnMO{sub 5} (Ln = La, Nd, Sm, Eu, Gd; M = Nb, Ta)

    SciTech Connect

    Cavazos, Ronaldo J.; Schak, Raymond E

    2004-07-02

    The new layered transition metal oxides NaRbLnMO{sub 5} (Ln = Nd, Sm, Eu, Gd; M = Nb, Ta) were synthesized by direct solid-state reaction. NaRbLaNbO{sub 5} crystallizes with a tetragonal unit cell [a=5.839(6) A, c=8.313(1) A] analogous to that of the related compound NaKLaNbO{sub 5}, while NaRbLaTaO{sub 5} indexes to a larger monoclinic unit cell [a=9.577(2) A, b=5.834(1) A, c=8.323(2) A, {beta}=93.00(2)]. NaRbLnNbO{sub 5} can be prepared for Ln = Nd, Sm, Eu, Gd, and NaRbLnTaO{sub 5} can be prepared for Ln = Nd, Sm. Both series of compounds show the expected decrease in unit cell volume as the size of the lanthanide decreases. NaRbLaNbO{sub 5} is also amenable to ion exchange, forming Li{sub 2-x}Rb{sub x}LaNbO{sub 5} upon reaction with molten lithium nitrate.

  9. Thermochemistry of rare earth doped uranium oxides Ln x U 1-x O 2-0.5x+y (Ln = La, Y, Nd)

    SciTech Connect

    Zhang, Lei; Navrotsky, Alexandra

    2015-10-01

    Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10–50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.

  10. Characterization and evaluation of double perovskites LnBaCoFeO5+δ (Ln = Pr and Nd) as intermediate-temperature solid oxide fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Jin, Fangjun; Xu, Huawei; Long, Wen; Shen, Yu; He, Tianmin

    2013-12-01

    Double perovskites LnBaCoFeO5+δ (Ln = Pr and Nd, PBCF and NBCF) are comparatively investigated as potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). LnBaCoFeO5+δ materials are chemically compatible with La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte at temperatures below 1000 °C. Fe and Co ions in LnBaCoFeO5+δ exist in two oxidation states, 3+ and 4+. Pr ions are found in PBCF mostly as Pr3+. Thermal expansion coefficients (TECs) of PBCF and NBCF are 21.0 × 10-6 and 19.5 × 10-6 K-1, respectively, between 30 and 1000 °C; these are lower than the TECs of undoped LnBaCo2O5+δ. The best electrical conductivity for both materials is observed near 350 °C: 321 and 172 S cm-1 for PBCF and NBCF, respectively. Polarization resistances of PBCF and NBCF cathodes on LSGM electrolyte are 0.049 and 0.062 Ω cm2 at 800 °C, respectively. Maximum power densities of the single-cell with Ni/SDC as anode on a 0.3 mm-thick LSGM electrolyte reach 749 and 669 mW cm-2 for PBCF and NBCF cathodes at 800 °C, respectively. As cathodes for application in IT-SOFCs, the performance of PBCF and NBCF double perovskites is promising.

  11. Nanostructured LnBaCo2O6-𝜹 (Ln = Sm, Gd) with layered structure for intermediate temperature solid oxide fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Mejía Gómez, Augusto E.; Lamas, Diego G.; Leyva, Ana Gabriela; Sacanell, Joaquín

    2017-04-01

    In this work, we present the combination of two characteristics that are beneficial for solid oxide fuel cell (SOFC) cathodic performance in one material. We developed and evaluated for the first time nanostructured layered perovskites of formulae LnBaCo2O6-d with Ln = Sm and Gd (SBCO and GBCO, respectively) as SOFC cathodes, finding promising electrochemical properties in the intermediate temperature range. We obtained those nanostructures by using porous templates to confine the chemical reagents in regions of 200-800 nm. The performance of nanostructured SBCO and GBCO cathodes was analyzed by electrochemical impedance spectroscopy technique under different operating conditions using Gd2O3-doped CeO2 as electrolyte. We found that SBCO cathodes displayed lower area-specific resistance than GBCO ones, because bulk diffusion of oxide ions is enhanced in the former. We also found that cathodes synthesized using smaller template pores exhibited better performance.

  12. 3d-4f {Co(II)3Ln(OR)4} Cubanes as Bio-Inspired Water Oxidation Catalysts.

    PubMed

    Evangelisti, Fabio; Moré, René; Hodel, Florian; Luber, Sandra; Patzke, Greta Ricarda

    2015-09-02

    Although the {CaMn4O5} oxygen evolving complex (OEC) of photosystem II is a major paradigm for water oxidation catalyst (WOC) development, the comprehensive translation of its key features into active molecular WOCs remains challenging. The [Co(II)3Ln(hmp)4(OAc)5H2O] ({Co(II)3Ln(OR)4}; Ln = Ho-Yb, hmp = 2-(hydroxymethyl)pyridine) cubane WOC series is introduced as a new springboard to address crucial design parameters, ranging from nuclearity and redox-inactive promoters to operational stability and ligand exchange properties. The {Co(II)3Ln(OR)4} cubanes promote bioinspired WOC design by newly combining Ln(3+) centers as redox-inactive Ca(2+) analogues with flexible aqua-/acetate ligands into active and stable WOCs (max. TON/TOF values of 211/9 s(-1)). Furthermore, they open up the important family of 3d-4f complexes for photocatalytic applications. The stability of the {Co(II)3Ln(OR)4} WOCs under photocatalytic conditions is demonstrated with a comprehensive analytical strategy including trace metal analyses and solution-based X-ray absorption spectroscopy (XAS) investigations. The productive influence of the Ln(3+) centers is linked to favorable ligand mobility, and the experimental trends are substantiated with Born-Oppenheimer molecular dynamics studies.

  13. Relationship between oxide-ion conductivity and ordering of oxygen vacancy in the Ln2Zr2O7 (Ln = La, Nd, Eu) system having a pyrochlore composition

    NASA Astrophysics Data System (ADS)

    Hagiwara, Takeshi; Yamamura, Hiroshi; Nishino, Hanako

    2011-06-01

    The crystal structures of the Ln2Zr2O7 (Ln = La, Nd, Eu) systems having a pyrochlore-type composition were refined by the Rietveld analyses of the XRD data combined with MEM-based pattern fitting. All the samples showed a single phase of the pyrochlore-type structure. The oxide-ion conductivities of the present samples were discussed on the basis of the ordering of oxygen vacancy in the pyrochlore-type structure. The Rietveld analyses of XRD data showed that the degree of the oxygen 8b site occupancy at R.T. was estimated to be 0.0, 0.27 and 0.48 for La2Zr2O7, Nd2Zr2O7 and Eu2Zr2O7, respectively. The increase in the 8b site occupancy means the increase of incompleteness of the pyrochlore-type structure. The oxide-ion conductivity increased with increase in the 8b site occupancy which can be recognized to be a measure of the incompleteness of the pyrochlore-type structur. The oxide-ion conduction of Eu2Zr2O7 was ascribed to diffusion of oxygen along <100> direction, while the hole conduction of La2Zr2O7 occurred along <110> direction, according to the charge density map estimated by the MEM analysis.

  14. Structure and oxide anion conductivity in Ln{sub 2}(TO{sub 4})O (Ln=La, Nd; T=Ge, Si)

    SciTech Connect

    Leon-Reina, Laura; Porras-Vazquez, Jose M.; Losilla, Enrique R.; Moreno-Real, Laureano; Aranda, Miguel A.G.

    2008-09-15

    Oxy-silicate and oxy-germanate, Ln{sub 2}(TO{sub 4})O (Ln=La and Nd, T=Ge and Si) compounds have been prepared. Oxy-germanates can be readily obtained as highly crystalline single phases, while, the oxy-silicates are difficult to prepare as pure phases. The crystal structure of Nd{sub 2}(SiO{sub 4})O has been studied from a joint Rietveld refinement of neutron and laboratory X-ray powder diffraction data. The electrochemical characterisation indicates that these compounds display oxide anion conductivity with p-type electronic contribution under oxidising conditions. The apparent activation energies under dry flowing nitrogen, where p-type contribution is minimised, are 0.97(1), 1.05(3) and 1.17(4) eV, for Nd{sub 2}(SiO{sub 4})O, La{sub 2}(GeO{sub 4})O and Nd{sub 2}(GeO{sub 4})O, respectively. The overall conductivities at 1173 K range from 1.2x10{sup -4} S cm{sup -1} for Nd{sub 2}(SiO{sub 4})O to 1.3x10{sup -6} S cm{sup -1} for La{sub 2}(GeO{sub 4})O. Finally, the stability of these compounds under very reducing conditions has been studied and partial degradation is reported. - Graphical abstract: Ln{sub 2}(TO{sub 4})O oxy-silicates and oxy-germanates show ionic conductivities {approx}10{sup -4} S cm{sup -1} at 1173 K with p-type electronic contribution under oxidising conditions. Furthermore, the studied materials are not stable under strongly reducing conditions as shown in the attached figure. Display Omitted.

  15. Morphotropy, isomorphism, and polymorphism of Ln{sub 2}M{sub 2}O{sub 7}-based (Ln = La-Lu, Y, Sc; M = Ti, Zr, Hf, Sn) oxides

    SciTech Connect

    Shlyakhtina, A. V.

    2013-07-15

    Structural studies of compounds of variable composition and measurements of their conductivity have made it possible to identify new oxygen-ion-conducting rare-earth pyrochlores, Ln{sub 2}Ti{sub 2}O{sub 7} (Ln = Dy-Lu) and Ln{sub 2}Hf{sub 2}O{sub 7} (Ln = Eu, Gd), with intrinsic high-temperature oxygen ion conductivity (up to 1.4 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C). Twenty six systems have been studied, and more than 50 phases based on the Ln{sub 2}M{sub 2}O{sub 7} (Ln= La-Lu; M = Ti, Zr, Hf) oxides have been synthesized and shown to be potential oxygen ion conductors. The morphotropy and polymorphism of the Ln{sub 2}M{sub 2}O{sub 7} (Ln = La-Lu; M = Ti, Zr, Hf) rare-earth pyrochlores have been analyzed in detail for the first time. Thermodynamic and kinetic (growth-related) phase transitions have been classified with application to the pyrochlore family.

  16. Low temperature synthesis of LnOF rare-earth oxyfluorides through reaction of the oxides with PTFE

    SciTech Connect

    Dutton, S.E.; Hirai, D.; Cava, R.J.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Low temperature synthesis of LnOF rare-earth oxyfluorides from Ln{sub 2}O{sub 3} and PTFE (CF{sub 2}). Black-Right-Pointing-Pointer Rhombohedral LnOF is the major phase and forms as nanocrystals, 29-103 nm. Black-Right-Pointing-Pointer Expected lanthanide contraction observed in lattice parameters and bond lengths. Black-Right-Pointing-Pointer TbOF orders antiferromagnetically at 10 K and has a metamagnetic transition at 1.8 T. Black-Right-Pointing-Pointer GdOF orders antiferromagnetically at 5 K, other LnOF are paramagnetic. -- Abstract: A low temperature solid-state synthesis route, employing polytetrafluoroethylene (PTFE) and the rare-earth oxides, for the formation of the LnOF rare-earth oxyfluorides (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), is reported. With the exception of LaOF, which forms in a tetragonal variant, rhomobohedral LnOF is found to be the major product of the reaction. In the case of PrOF, a transition from the rhombohedral to the cubic fluorite phase is observed on heating in air to 500 Degree-Sign C. X-ray diffraction shows the expected lanthanide contraction in the lattice parameters and bond lengths. Magnetic susceptibility measurements show antiferromagnetic-like ordering in TbOF, T{sub m} = 10 K, with a metamagnetic transition at a field {mu}{sub 0}H{sub t} = 1.8 T at 2 K. An antiferromagnetic transition, T{sub N} = 4 K, is observed in GdOF. Paramagnetic behavior is observed above 2 K in PrOF, NdOF, DyOF, HoOF and ErOF. The magnetic susceptibility of EuOF is characteristic of Van Vleck paramagnetism.

  17. Synthesis and characterization of ultrafine Ln{sub 2}Ti{sub 2}O{sub 7} (Ln = Sm, Gd, Dy, Er) pyrochlore oxides by stearic acid method

    SciTech Connect

    Zhang Weiguang; Zhang Lili; Zhong Hui; Lu Lude; Yang Xujie; Wang Xin

    2010-02-15

    Stearic acid method (SAM) was developed to synthesize series of pyrochlore Ln{sub 2}Ti{sub 2}O{sub 7} (Ln = Sm, Gd, Dy, Er) nanocrystals. The synthesis process was monitored by X-ray diffraction, Thermal-gravimetric-differential thermal analysis and Fourier Transform InfraRed methods. Comparing with traditional solid-state reaction (SSR), Ln{sub 2}Ti{sub 2}O{sub 7} can be synthesized at relatively low temperature (700-800 deg. C) with shortened reaction time (2-4 h). The average particle size of Ln{sub 2}Ti{sub 2}O{sub 7} was greatly reduced (ca. 40 nm) and the BET surface area was increased (ca. 12 m{sup 2}/g) by using SAM. From the X-ray diffraction patterns, we found that Ln has an effect on the crystal structure of Ln{sub 2}Ti{sub 2}O{sub 7}, every lattice peak shifted to larger angle slightly with the increasing atomic number of Ln. Also, the lattice constant of Ln{sub 2}Ti{sub 2}O{sub 7} was calculated by Jade.5 and found it decreased along with the decrease of ionic radius of Ln{sup 3+}. The morphology of obtained Ln{sub 2}Ti{sub 2}O{sub 7} was determined by transmission electron microscopy technique. Results showed that the obtained Ln{sub 2}Ti{sub 2}O{sub 7} were all square-like and the interplanar distance of Ln{sub 2}Ti{sub 2}O{sub 7} (Ln = Sm, Gd, Dy, Er) according to (111) plane was 0.65, 0.64, 0.63, and 0.62 nm respectively, which was measured from High Resolution Transmission Electron Microscopy images. Possible reason for this phenomenon was presented.

  18. Partial oxidation of methane to synthesis gas using LnCoO{sub 3} perovskites as catalyst precursors

    SciTech Connect

    Lago, R.; Pena, M.A.; Fierro, J.L.G.

    1997-04-01

    In this work, a series of cobalt-containing perovskites LnCoO{sub 3} (Ln = La, Pr, Nd, Sm, and Gd) has been studied as catalyst precursors for the partial oxidation of methane to synthesis gas. All the perovskite precursors were prereduced in situ, producing cobalt metal finely dispersed over the rare earth sesquioxide support described here as Ln-Co-O. Of the catalyst tested, the system Gd-Co-O showed exceptionally better performance for CO and H{sub 2} production (with methane conversion of 73% and selectivities of 79 and 81% for CO and H{sub 2}, respectively, at 1009 K). The production of synthesis gas over the other catalysts decreased in the following order: Sm-Co-O {much_gt} Nd-Co-O > Pr-Co-O. The catalyst La-Co-O was active for methane combustion and only traces of CO and H{sub 2} were observed under the reaction conditions. Based on results obtained here, it is proposed that the deactivation of the catalysts Ln-Co-O by reoxidation of cobalt metal is related to the thermodynamic stability of the parent perovskite structure. The authors also present evidence that hydroxyl groups on the rare earth oxide, specially in the La-Co-O system, might make some contribution to the reoxidation of cobalt metal during the reaction via a reverse spillover process. 48 refs., 12 figs., 2 tabs.

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

    SciTech Connect

    Hinatsu, Yukio Doi, Yoshihiro

    2016-07-15

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

  20. Dopant-induced modification of active site structure and surface bonding mode for high-performance nanocatalysts: CO oxidation on capping-free (110)-oriented CeO2:Ln (Ln = La-Lu) nanowires.

    PubMed

    Ke, Jun; Xiao, Jia-Wen; Zhu, Wei; Liu, Haichao; Si, Rui; Zhang, Ya-Wen; Yan, Chun-Hua

    2013-10-09

    Active center engineering at atomic level is a grand challenge for catalyst design and optimization in many industrial catalytic processes. Exploring new strategies to delicately tailor the structures of active centers and bonding modes of surface reactive intermediates for nanocatalysts is crucial to high-efficiency nanocatalysis that bridges heterogeneous and homogeneous catalysis. Here we demonstrate a robust approach to tune the CO oxidation activity over CeO2 nanowires (NWs) through the modulation of the local structure and surface state around Ln(Ce)' defect centers by doping other lanthanides (Ln), based on the continuous variation of the ionic radius of lanthanide dopants caused by the lanthanide contraction. Homogeneously doped (110)-oriented CeO2:Ln NWs with no residual capping agents were synthesized by controlling the redox chemistry of Ce(III)/Ce(IV) in a mild hydrothermal process. The CO oxidation reactivity over CeO2:Ln NWs was dependent on the Ln dopants, and the reactivity reached the maximum in turnover rates over Nd-doped samples. On the basis of the results obtained from combined experimentations and density functional theory simulations, the decisive factors of the modulation effect along the lanthanide dopant series were deduced as surface oxygen release capability and the bonding configuration of the surface adsorbed species (i.e., carbonates and bicarbonates) formed during catalytic process, which resulted in the existence of an optimal doping effect from the lanthanide with moderate ionic radius.

  1. Thermochemistry of rare earth doped uranium oxides LnxU1-xO2-0.5x+y (Ln = La, Y, Nd)

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Navrotsky, Alexandra

    2015-10-01

    Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10-50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.

  2. X-ray photoelectron spectroscopic study of direct reforming catalysts Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln = La, Nd, and Sm) for high temperature-operating solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Kim, Keunsoo; Jeong, Jihoon; Azad, Abul K.; Jin, Sang Beom; Kim, Jung Hyun

    2016-03-01

    Chemical states of lanthanide doped perovskite for direct reforming anode catalysts, Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln = La, Nd, and Sm) have been studied by X-ray Photoelectron Spectroscopy (XPS) in order to determine the effects of various lanthanide substitution in complex perovskites for high temperature-operating solid oxide fuel cells (HT-SOFC). The charge state of lanthanide ions remained at 3+ and the binding energies of the lanthanide ions in Ln0.5Sr0.5Ti0.5Mn0.5O3±d were located in a relatively lower range compared to those of conventional lanthanide oxides. Mn and Ti were regarded as charge compensation components in Ln0.5Sr0.5Ti0.5Mn0.5O3±d; Mn was more influential than Ti. In the cases of substituting Nd and Sm into Ln0.5Sr0.5Ti0.5Mn0.5O3±d, some portion of Ti showed metallic behavior; the specific Mn satellite peak indicating an electro-catalytic effect had occurred. Three types of oxygen species comprised of lattice oxygen, carbonate species, and adsorbed oxygen species were observed in Ln0.5Sr0.5Ti0.5Mn0.5O3±d from the O 1s spectra; a high portion of lattice oxygen was observed in both Nd0.5Sr0.5Ti0.5Mn0.5O3±d (NSTM) and Sm0.5Sr0.5Ti0.5Mn0.5O3±d (SSTM). In various respects, NSTM and SSTM will be desirable reforming catalysts and anode candidates for high temperature solid oxide fuel cell.

  3. Systematic evaluation of cobalt-free Ln0.5Sr0·5Fe0·8Cu0·2O3-δ (Ln = La, Pr, and Nd) as cathode materials for intermediate-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Pang, Shengli; Wang, Wenzhi; Chen, Tao; Shen, Xiangqian; Wang, Yonggang; Xu, Kaijie; Xi, Xiaoming

    2016-09-01

    Cobalt-free perovskites, Ln0.5Sr0·5Fe0·8Cu0·2O3-δ (Ln = La, Pr, and Nd), are systematically evaluated as the cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) using Gd0.1Ce0·9O1.95 as the electrolyte. The samples exhibit an orthorhombic perovskite structures, and their cell volumes decrease as the ionic radius of Ln decreases. Both the oxygen vacancy content and the magnitude of lattice oxygen release per formula unit increase in the temperature range from 370 °C to 850 °C as the ionic radius of Ln decreases. Ln0.5Sr0.5Fe0.8Cu0.2O3-δ is chemically and thermally compatible with the Gd0.1Ce0·9O1.95 electrolyte. In the temperature range of 600 °C-750 °C, Nd0.5Sr0·5Fe0·8Cu0·2O3-δ possesses the highest catalytic activity for the oxygen reduction reaction with area specific resistance values of 0.071 Ω cm2 and 0.141 Ω cm2 at 750 °C and 700 °C, respectively. The maximum power densities of the anode-supported single cells at 800 °C and 700 °C are 1003.7 mW cm-2 and 516.7 mW cm-2 for Pr0.5Sr0·5Fe0·8Cu0·2O3-δ and 944.5 mW cm-2 and 530.2 mW cm-2 for Nd0.5Sr0·5Fe0·8Cu0·2O3-δ, respectively. Ln0.5Sr0.5Fe0.8Cu0.2O3-δ is shown to be a promising cathode material for IT-SOFCs.

  4. Structural, thermal and electrical conductivity characteristics of Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (Ln: La, Nd and Sm) complex perovskites as anode materials for solid oxide fuel cell

    SciTech Connect

    Jeong, Jihoon; Azad, Abul K.; Schlegl, Harald; Kim, Byungjun; Baek, Seung-Wook; Kim, Keunsoo; Kang, Hyunil; Kim, Jung Hyun

    2015-03-15

    The Ti and Mn replaced complex perovskites, Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (Ln: La, Nd and Sm), were reported as potential anode materials for high temperature-operating solid oxide fuel cells (HT-SOFCs). For the present research study, synthesis, crystallographic, thermal and electrical conductivity properties of Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} complex perovskites were investigated using X-ray diffraction (XRD), Rietveld method, thermogravimetric analysis (TGA) and electrical conductivity to apply these oxide materials for the HT-SOFC anode materials. XRD results showed that Ln{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} oxide systems synthesized as single phases did not react with 8 mol% yttria stabilized zirconia (8YSZ) and 10 mol% Gd-doped cerium oxide (CGO91) up to 1500 °C and did not decompose under dry 3.9% hydrogen at 850 °C. The crystal structures of La{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (LSTM), Nd{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (NSTM) and Sm{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d} (SSTM) showed orthorhombic symmetry with the space group Pbnm and SSTM showed a more distorted structure. Thermogravimetric analysis (TGA) proved weight gains in these three sample occurred under oxidizing conditions and weight loss under reducing conditions. Electrical conductivity values of NSTM were higher than those of LSTM and SSTM under oxidizing and reducing conditions. - Graphical abstract: The B-site cations (Ti/Mn) are surrounded by regular octahedra of oxygen in Nd{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Mn{sub 0.5}O{sub 3±d}(NSTM). These octahedra are linked together in a corner sharing three dimensional framework, while Nd/Sr ion occupies 12-coordinated A-site between these octahedra. The Ti/Mn–O{sub 6} octahedra are elongated along the c-axis. The crystal structure distortion was due to the smaller ionic radius of the A-site cations, which force the (Ti

  5. Solvothermal syntheses, crystal structures, and properties of lanthanide(III) thioarsenates [Ln(dien)2(μ-1κ,2κ2-AsS4)]n (Ln==Sm, Eu, Gd) and [Ln(dien)2(1κ2-AsS4)] (Ln==Tb, Dy, Ho)

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Tang, Chunying; Chen, Ruihong; Zhang, Yong; Jia, Dingxian

    2013-10-01

    Solvothermal reactions of Ln2O3, As and S in diethylenetriamine (dien) at 170 °C for 6 days afforded two structural types of lanthanide thioarsenates with the general formulae [Ln(dien)2(μ-1κ,2κ2-AsS4)]n [Ln=Sm(1), Eu(2), Gd(3)] and [Ln(dien)2(1κ2-AsS4)] [Ln=Tb(4), Dy(5), Ho(6)]. The Ln2O3 oxides were converted to [Ln(dien)2]3+ complex units in the solvothermal reactions. The As atom binds four S atoms, forming a tetrahedral AsS4 unit. In 1-3, the AsS4 units interconnect the [Ln(dien)2]3+ cations via Ln-S bonds as tridentate μ-1κ,2κ2-AsS4 bridging ligands, resulting in the neutral coordination polymers [Ln(dien)2(μ-1κ,2κ2-AsS4)]n (Ln1). In 4-6, the AsS4 units coordinate with the Ln3+ ion of [Ln(dien)2]3+ as 1κ2-AsS4 chelating ligands to form neutral coordination compounds [Ln(dien)2(1κ2-AsS4)] (Ln2). The Ln3+ ions are in nine- and eight-coordinated environments in Ln1 and Ln2, respectively. The formation of Ln1 and Ln2 is related with ionic size of the Ln3+ ions. Optical absorption spectra showed that 1-6 have potential use as semiconductors with the band gaps in the range 2.18-3.21 eV.

  6. Magnetic properties of EuLn{sub 2}O{sub 4} (Ln=rare earths)

    SciTech Connect

    Hirose, Keiichi; Doi, Yoshihiro; Hinatsu, Yukio

    2009-07-15

    Ternary rare earth oxides EuLn{sub 2}O{sub 4} (Ln=Gd, Dy-Lu) were prepared. They crystallized in an orthorhombic CaFe{sub 2}O{sub 4}-type structure with space group Pnma. {sup 151}Eu Moessbauer spectroscopic measurements show that the Eu ions are in the divalent state. All these compounds show an antiferromagnetic transition at 4.2-6.3 K. From the positive Weiss constant and the saturation of magnetization for EuLu{sub 2}O{sub 4}, it is considered that ferromagnetic chains of Eu{sup 2+} are aligned along the b-axis of the orthorhombic unit cell, with neighboring Eu{sup 2+} chains antiparallel. When Ln=Gd-Tm, ferromagnetically aligned Eu{sup 2+} ions interact with the Ln{sup 3+} ions, which would overcome the magnetic frustration of triangularly aligned Ln{sup 3+} ions and the EuLn{sub 2}O{sub 4} compounds show a simple antiferromagnetic behavior. - Graphical abstract: Ternary rare earth oxides EuLn{sub 2}O{sub 4} (Ln=Gd, Dy-Lu) crystallized in an orthorhombic CaFe{sub 2}O{sub 4}-type structure with space group Pnma. Moessbauer spectroscopic measurements show that the Eu ions are in the divalent state. All these compounds show an antiferromagnetic transition at 4.2-6.3 K. It is considered that ferromagnetic chains of Eu{sup 2+} are aligned along the b-axis of the orthorhombic unit cell, with neighboring Eu{sup 2+} chains antiparallel.

  7. Ln 0.6Sr 0.4Co 1- yFe yO 3- δ (Ln = La and Nd; y = 0 and 0.5) cathodes with thin yttria-stabilized zirconia electrolytes for intermediate temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Torres-Garibay, Claudia; Kovar, Desiderio; Manthiram, Arumugam

    The electrochemical performances of the solid oxide fuel cells (SOFC) fabricated with Ln 0.6Sr 0.4Co 1- yFe yO 3- δ (Ln = La, Nd; y = 0, 0.5) perovskite cathodes, thin yttria-stabilized zirconia (YSZ) electrolytes, and YSZ-Ni anodes by tape casting, co-firing, and screen printing are evaluated at 600-800 °C. Peak power densities of ∼550 mW cm -2 are achieved at 800 °C with a La 0.6Sr 0.4CoO 3- δ (LSC) cathode that is known to have high electrical conductivity. Substitution of La by Nd (Nd 0.6Sr 0.4CoO 3- δ) to reduce the thermal expansion coefficient (TEC) results in only a slight decrease in power density despite a lower electrical conductivity. Conversely, substitution of Fe for Co (La 0.6Sr 0.4Co 0.5Fe 0.5O 3- δ or Nd 0.6Sr 0.4Co 0.5Fe 0.5O 3- δ) to reduce the TEC further reduces the cell performance greatly due to a significant decrease in electrical conductivity. However, infiltration of the Fe-substituted cathodes with Ag to increase the electrical conductivity increases the cell performance while preserving the low TEC.

  8. Vibrational and excited electronic states of six-coordinate rare earth complexes with 2,6-lutidine n-oxide: [Ln(C 7H 9NO) 6](ClO 4) 3·H 2O (Ln=Pr,Nd,Sm,Eu,Gd,Dy)

    NASA Astrophysics Data System (ADS)

    Ban-Oganowska, H.; Godlewska, P.; Macalik, L.; Hanuza, J.; Oganowski, W.; Hermanowicz, K.

    2002-09-01

    A series of six-coordinate complexes of 2,6-lutidine N-oxide (C 7H 9NO) with praseodymium, neodymium, samarium, europium, gadolinium and dysprosium has been synthesised and chemically characterised. FT-IR and FT-Raman spectra in the range 80-4000 cm -1 as well as electronic absorption and emission spectra in the range 4000-50,000 cm -1 have been measured. The Lorenzian deconvolution of the vibrational contour in the 100-300 cm -1 region has been used in the discussion of the molecular and site symmetries of the Ln 3+ ion situated in the oxygen polyhedron. The sequence of the electronic levels for all RE ions has been obtained and assigned to the respective transitions.

  9. Homoleptic rare earth dipyridylamides [Ln2(N(NC5H4)2)6], Ln = Ce, Nd, Sm, Ho, Er, Tm, Yb, and Sc: metal oxidation by the amine melt and in 1,2,3,4-tetrahydroquinoline with the focus of different metal activation by amalgams, liquid ammonia, and microwaves.

    PubMed

    Müller-Buschbaum, Klaus; Quitmann, Catharina C

    2006-03-20

    Homoleptic dimeric dipyridylamide complexes of the rare earth elements are obtained by solvent-free oxidation reactions of the metals with melts of 2,2'-dipyridylamine. As the thermal stabilities of the ligand as well as the amide complexes are limiting factors in these high-temperature syntheses, several different metal activation procedures have been investigated: the formation of Ln amalgams and dissolution of the metals in liquid ammonia as well as coupling to microwaves. For comparison with a solvent that shows low solubility of the metals and products, reactions in 1,2,3,4-tetrahydroquinoline were also carried out. For all lanthanides and group 3 metals used homoleptic dimers of the formula [Ln(2)(Dpa)(6)], Ln = Ce (1), Nd (2), Sm (3), Ho (4), Er (5), Tm (6), Yb (7), and Sc (8) and Dpa- = (C5H4N)2N-, were obtained, all containing trivalent rare earth ions with a distorted square antiprismatic nitrogen coordination. Due to the large differences in the ionic radii of the metal ions, two different structure types are found that crystallize in the space groups P2(1)/c and P2(1)/n with the border of the two types being between Tm and Yb. The orientations of two 1,3/1,3-double chelating and linking dipyridylamide ligands (Dpa(-) = (C(5)H(4)N)(2)N(-)) result in different overall orientations of the dimers and thus two structure types. All compounds were identified by single-crystal X-ray analysis. Mid-IR, far IR, and Raman spectroscopy, microanalyses, and simultaneous DTA/TG as well as mass spectrometry regarding their thermal behavior were also carried out to characterize the products. Crystal data for the two types follow. Ce (1): P2(1)/n; T = 170(2) K; a = 1063.0(1), b = 1536.0(1), c = 1652.0(2) pm; beta = 101.60(1) degrees ; V = 2642.2(3) x 10(6) pm(3); R(1) for F(o) > 4sigma(F(o)) = 0.046, wR(2) = 0.120. Sc (8): P2(1)/c; T = 170(2) K; a = 1073.0(1), b = 1506.2(2), c = 1619.8(2) pm; beta = 103.16(9) degrees ; V = 2548.9(5) x 10(6) pm(3); R(1) for F(o) > 4sigma

  10. Solvothermal syntheses, crystal structures, and properties of lanthanide(III) thioarsenates [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} (Ln==Sm, Eu, Gd) and [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] (Ln==Tb, Dy, Ho)

    SciTech Connect

    Wang, Fang; Tang, Chunying; Chen, Ruihong; Zhang, Yong; Jia, Dingxian

    2013-10-15

    Solvothermal reactions of Ln{sub 2}O{sub 3}, As and S in diethylenetriamine (dien) at 170 °C for 6 days afforded two structural types of lanthanide thioarsenates with the general formulae [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} [Ln=Sm(1), Eu(2), Gd(3)] and [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] [Ln=Tb(4), Dy(5), Ho(6)]. The Ln{sub 2}O{sub 3} oxides were converted to [Ln(dien){sub 2}]{sup 3+} complex units in the solvothermal reactions. The As atom binds four S atoms, forming a tetrahedral AsS{sub 4} unit. In 1−3, the AsS{sub 4} units interconnect the [Ln(dien){sub 2}]{sup 3+} cations via Ln−S bonds as tridentate μ-1κ,2κ{sup 2}-AsS{sub 4} bridging ligands, resulting in the neutral coordination polymers [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} (Ln1). In 4−6, the AsS{sub 4} units coordinate with the Ln{sup 3+} ion of [Ln(dien){sub 2}]{sup 3+} as 1κ{sup 2}-AsS{sub 4} chelating ligands to form neutral coordination compounds [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] (Ln2). The Ln{sup 3+} ions are in nine- and eight-coordinated environments in Ln1 and Ln2, respectively. The formation of Ln1 and Ln2 is related with ionic size of the Ln{sup 3+} ions. Optical absorption spectra showed that 1−6 have potential use as semiconductors with the band gaps in the range 2.18−3.21 eV. - Graphical abstract: Two types of Ln-thioarsenates [Ln(dien){sub 2}(μ-1κ,2κ{sup 2}-AsS{sub 4})]{sub n} and [Ln(dien){sub 2}(1κ{sup 2}-AsS{sub 4})] were prepared by solvothermal methods and the soft Lewis basic AsS{sub 4}{sup 3–} ligand to Ln(III) centers with polyamine co-ligand was obtained. Display Omitted - Highlights: • Lanthanide thioarsenates were prepared by solvothermal methods. • The soft Lewis basic AsS{sub 4} ligand coordinate Ln{sup 3+} ions with coexistence polyamine ligands. • Two structural types of Ln-thioarsenates with structural turnover at Tb were obtained along Ln series. • The Ln-thioarsenates are potential semiconductors

  11. Ab initio prediction of the electronic, magnetic and topological properties of Ln2O3 clusters

    NASA Astrophysics Data System (ADS)

    Xia, Xiuli; Shao, Yuanzhi

    2017-07-01

    The structural, electronic and magnetic properties of the lanthanide oxide Ln2O3 clusters, where Ln signifies lanthanides from La to Lu, have been calculated using spin-polarized density functional theory with the B3LYP hybrid functional. The intensities of ferromagnetic RKKY interaction are found comparable with that of antiferromagnetic superexchange interaction in Ce2O3 / Pr2O3 / Nd2O3 / Gd2O3 / Tb2O3 / Tm2O3 clusters, while the other Ln2O3 clusters prefer ferromagnetic states to antiferromagnetic states in energy, except nonmagnetic La2O3 and Lu2O3 clusters. The theoretical spin magnetic moments, calculated three-dimensional spin density maps and dipole moments of Ln2O3 clusters suggest that the induced polarizations of oxygen atoms in Sm2O3, Eu2O3 and Yb2O3 clusters remarkably lead to the elongated Ln-O bond lengths in these clusters. The partial density of states of Ln2O3 clusters reveals that Sm3+ /Eu3+ /Yb3+ ions are distinctive from other Ln3+ ions in that their Ln-4f electrons are strongly hybrid with O-2 p electrons. The topological analysis of the electron density was also performed with quantum theory of atoms in molecules, which indicates the ionic Ln-O bonds have partial covalent characteristics.

  12. Magnetic ordering of divalent europium in double perovskites Eu{sub 2}LnTaO{sub 6} (Ln=rare earths)

    SciTech Connect

    Misawa, Yoshitaka; Doi, Yoshihiro; Hinatsu, Yukio

    2011-06-15

    Structures and magnetic properties of double perovskite-type oxides Eu{sub 2}LnTaO{sub 6} (Ln=Eu, Dy-Lu) were investigated. These compounds adopt a distorted double perovskite structure with space group P2{sub 1}/n. Magnetic susceptibility, specific heat, and {sup 151}Eu Moessbauer spectrum measurements show that the Eu{sup 2+} ions at the 12-coordinate sites of the perovskite structure are antiferromagnetically ordered at {approx}4 K, and that Ln{sup 3+} ions at the 6-coordinate site are in the paramagnetic state down to 1.8 K. - Graphical abstract: Magnetic properties of double perovskite-type oxides Eu{sub 2}LnTaO{sub 6} (Ln=Eu, Dy-Lu) were investigated. Magnetic susceptibility, specific heat, and {sup 151}Eu Moessbauer spectrum measurements show that the Eu{sup 2+} ions at the 12-coordinate sites of the perovskite structure are antiferromagnetically ordered at {approx}4 K. Highlights: > Crystal structures of double perovskites Eu{sub 2}LnTaO{sub 6} (Ln=rare earth) were determined. > We found that these compounds show an antiferromagnetic ordering at {approx}4 K. > The magnetic ordering is due to the interactions of Eu{sup 2+} ions. > It was elucidated by specific heat and {sup 151}Eu Moessbauer spectrum measurements.

  13. Normal coordinate analysis and DFT calculations of the vibrational spectra for lanthanide(III) complexes with 3-bromo-4-methoxy-2,6-lutidine N-oxide: LnCl 3(3Br4CH 3OC 7H 7NO) 3 (Ln=Pr, Nd, Sm, Eu, Gd, Dy)

    NASA Astrophysics Data System (ADS)

    Godlewska, P.; Ban-Oganowska, H.; Macalik, L.; Hanuza, J.; Oganowski, W.; Roszak, S.; Lipkowski, P.

    2006-01-01

    The results of the FT-Raman and FT-IR studies of the LnCl 3(LNO) 3 type complexes (where Ln=Pr, Nd, Sm, Eu, Gd, Dy and LNO=3-Br-4-CH 3OC 7H 7NO) are presented. The spectral contours observed in the regions of the lanthanide-oxygen, lanthanide-chlorine and nitrogen-oxygen vibrations are employed in the discussion of the molecular structure of the complex ions and the local symmetry of the LnCl 3(ON) 3 polyhedron. The discussion of the vibrational spectra is based on the classical normal coordinate analysis and its results are compared to the results of DFT quantum chemical calculations performed for complete molecule. The normal coordinate analysis has been performed for PrCl 3(ON) 3 and DyCl 3(ON) 3 molecular systems, which have been treated as a different 'isotopic units'. Basing on the predominant PED contributions of the respective internal coordinates the assignment of the normal vibrations has been proposed.

  14. A determination of the oxygen non-stoichiometry of the oxygen storage materials LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr)

    SciTech Connect

    Jeamjumnunja, Kannika; Gong, Wenquan; Makarenko, Tatyana; Jacobson, Allan J.

    2016-07-15

    The A-site ordered double-perovskite oxides, LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage properties of these materials. The present results are compared with our previous data for YBaMn{sub 2}O{sub 5+δ}. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn{sub 2}O{sub 5+δ}. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln{sup 3+} ions larger than Y{sup 3+}. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn{sub 2}O{sub 5} and fully-oxidized LnBaMn{sub 2}O{sub 6} during changes of the oxygen partial pressure between air and 1.99% H{sub 2}/Ar. In addition, the oxygen non-stoichiometries of GdBaMn{sub 2}O{sub 5+δ} and PrBaMn{sub 2}O{sub 5+δ} were determined as a function of pO{sub 2} at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching ~6. The stabilities of the LnBaMn{sub 2}O{sub 5+δ} phases extend over a wide range of oxygen partial pressures (∼10{sup −25}≤pO{sub 2} (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln{sup 3+} cation the lower pO{sub 2} for phase conversion. At some temperatures and pO{sub 2} conditions, the LnBaMn{sub 2}O{sub 5+δ} compounds are unstable with respect to decomposition to BaMnO{sub 3−δ} and LnMnO{sub 3}. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions. - Graphical abstract: Structure of Ln

  15. Magnetic properties and structural transitions of orthorhombic fluorite-related compounds Ln{sub 3}MO{sub 7} (Ln=rare earths, M=transition metals)

    SciTech Connect

    Wakeshima, Makoto; Hinatsu, Yukio

    2010-11-15

    Magnetic properties and structural transitions of ternary rare-earth transition-metal oxides Ln{sub 3}MO{sub 7} (Ln=rare earths, M=transition metals) were investigated. In this study, we prepared a series of molybdates Ln{sub 3}MoO{sub 7} (Ln=La-Gd). They crystallize in an orthorhombic superstructure of cubic fluorite with space group P2{sub 1}2{sub 1}2{sub 1}, in which Ln{sup 3+} ions occupy two different crystallographic sites (the 8-coordinated and 7-coordinated sites). All of these compounds show a phase transition from the space group P2{sub 1}2{sub 1}2{sub 1} to Pnma in the temperature range between 370 and 710 K. Their magnetic properties were characterized by magnetic susceptibility measurements from 1.8 to 400 K and specific heat measurements from 0.4 to 400 K. Gd{sub 3}MoO{sub 7} shows an antiferromagnetic transition at 1.9 K. Measurements of the specific heat for Sm{sub 3}MoO{sub 7} and the analysis of the magnetic specific heat indicate a 'two-step' antiferromagnetic transition due to the ordering of Sm magnetic moments in different crystallographic sites, i.e., with decreasing temperature, the antiferromagnetic ordering of the 7-coordinated Sm ions occur at 2.5 K, and then the 8-coordinated Sm ions order at 0.8 K. The results of Ln{sub 3}MoO{sub 7} were compared with the magnetic properties and structural transitions of Ln{sub 3}MO{sub 7} (M=Nb, Ru, Sb, Ta, Re, Os, or Ir). -- Graphical Abstract: Magnetic properties and structural transitions of ternary rare-earth transition-metal oxides Ln{sub 3}MO{sub 7} (Ln=rare earths, M=transition metals) were investigated. In this study, we prepared a series of molybdates Ln{sub 3}MoO{sub 7} (Ln=La{approx}Gd). These compounds show a phase transition from the space group P2{sub 1}2{sub 1}2{sub 1} to Pnma in the temperature range between 370 and 710 K. Their magnetic properties were characterized by magnetic susceptibility and specific heat measurements from 0.4 to 400 K. The results of Ln{sub 3}MoO{sub 7} were

  16. A determination of the oxygen non-stoichiometry of the oxygen storage materials LnBaMn2O5+δ (Ln=Gd, Pr)

    NASA Astrophysics Data System (ADS)

    Jeamjumnunja, Kannika; Gong, Wenquan; Makarenko, Tatyana; Jacobson, Allan J.

    2016-07-01

    The A-site ordered double-perovskite oxides, LnBaMn2O5+δ (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage properties of these materials. The present results are compared with our previous data for YBaMn2O5+δ. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn2O5+δ. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln3+ ions larger than Y3+. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn2O5 and fully-oxidized LnBaMn2O6 during changes of the oxygen partial pressure between air and 1.99% H2/Ar. In addition, the oxygen non-stoichiometries of GdBaMn2O5+δ and PrBaMn2O5+δ were determined as a function of pO2 at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching 6. The stabilities of the LnBaMn2O5+δ phases extend over a wide range of oxygen partial pressures (∼10-25≤pO2 (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln3+ cation the lower pO2 for phase conversion. At some temperatures and pO2 conditions, the LnBaMn2O5+δ compounds are unstable with respect to decomposition to BaMnO3-δ and LnMnO3. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions.

  17. Phase transformations during HLnTiO4 (Ln=La, Nd) thermolysis and photocatalytic activity of obtained compounds

    NASA Astrophysics Data System (ADS)

    Silyukov, Oleg I.; Abdulaeva, Liliia D.; Burovikhina, Alena A.; Rodionov, Ivan A.; Zvereva, Irina A.

    2015-03-01

    Layered HLnTiO4 (Ln=La, Nd) compounds belonging to Ruddlesden-Popper phases were found to form partially hydrated compounds Ln2Ti2O7·xH2O during thermal dehydration as well as defect oxides Ln2□Ti2O7 as final products. Further heating of metastable defect Ln2□Ti2O7 substances leads to the formation of pyrochlore-type oxides Ln2Ti2O7 (p), with subsequent transformation under higher temperatures to stable layered 110-type perovskites Ln2Ti2O7. The occurring structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO4<Ln2Ti2O7·yH2O<Ln2□Ti2O7<Ln2Ti2O7 (p)<Ln2Ti2O7 in the reaction of hydrogen evolution from aqueous isopropanol solution.

  18. Syntheses, structure, some band gaps, and electronic structures of CsLnZnTe3 (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y).

    PubMed

    Yao, Jiyong; Deng, Bin; Sherry, Leif J; McFarland, Adam D; Ellis, Donald E; Van Duyne, Richard P; Ibers, James A

    2004-11-29

    Eleven new quaternary rare-earth tellurides, CsLnZnTe3 (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Y), were prepared from solid-state reactions at 1123 K. These isostructural materials crystallize in the layered KZrCuS3 structure type in the orthorhombic space group Cmcm. The structure is composed of LnTe6 octahedra and ZnTe4 tetrahedra that share edges to form [LnZnTe3] layers. These layers stack perpendicular to [010] and are separated by layers of face- and edge-sharing CsTe8 bicapped trigonal prisms. There are no Te-Te bonds in the structure of these CsLnZnTe3 compounds so the formal oxidation states of Cs/Ln/Zn/Te are 1+/3+/2+/2-. Optical band gaps of 2.13 eV for CsGdZnTe3 and 2.12 eV for CsTbZnTe3 were deduced from single-crystal optical absorption measurements. A first-principles calculation of the density of states and the frequency-dependent optical properties was performed on CsGdZnTe3. The calculated band gap of 2.1 eV is in good agreement with the experimental value. A quadratic fit for the lanthanide contraction of the Ln-Te distance is superior to a linear one if the closed-shell atom is included.

  19. Growth of CaLnA10/sub 4/ crystals by the Czochralski method

    SciTech Connect

    Appen, Z.S.; Korovkin, A.M.; Romanov, A.Y.; Udalov, Y.P.; Valtere, A.Y.

    1986-05-01

    The authors grew crystals of CaLnA10/sub 4/ by the Czochralski method at oxygen partial pressures of 10-/sup 5/ to 10-/sup 2/ Pa. The effect of oxygen partial pressure is due to the incongruent volatilization of oxides from CaLnA10/sub 4/ melts, with formation of defects dependent on the excess or deficiency of oxygen in the lattice. Cleavage, observed along the (100) plane, is associated with the cellular growth of CaLnA10/sub 4/ with concentrational supercooling.

  20. Preparation and structure of the light rare-earth copper selenides LnCuSe 2 ( Ln=La, Ce, Pr, Nd, Sm)

    NASA Astrophysics Data System (ADS)

    Ijjaali, Ismail; Mitchell, Kwasi; Ibers, James A.

    2004-03-01

    The ternary selenides LnCuSe 2 ( Ln=La, Ce, Pr, Nd, Sm) have been synthesized by the reaction at 1173 K of Ln, Cu, and Se in a KBr or KI flux. The compounds, which are isostructural with LaCuS 2, crystallize with four formula units in the space group P2 1/ c of the monoclinic system. The structure may be thought of as consisting of layers of CuSe 4 tetrahedra separated by double layers of LnSe 7 monocapped trigonal prisms along the a-axis. Cell constants (Å or deg) at 153 K are: LaCuSe 2, 6.8142(5), 7.5817(6), 7.2052(6), 97.573(1)°; CeCuSe 2, 6.7630(5), 7.5311(6), 7.1650(6), 97.392(1)°; PrCuSe 2, 6.740(1), 7.481(1), 7.141(1), 97.374(2)°; NdCuSe 2, 6.7149(6), 7.4452(7), 7.1192(6), 97.310(1)°; SmCuSe 2, 6.6655(6), 7.3825(7), 7.0724(6), 97.115(1)°. There are no Se-Se bonds in the structure of LnCuSe 2; the formal oxidation states of Ln/Cu/Se are 3+/1+/2-.

  1. Structures and magnetic properties of rare earth double perovskites containing antimony or bismuth Ba{sub 2}LnMO{sub 6} (Ln=rare earths; M=Sb, Bi)

    SciTech Connect

    Otsuka, Shumpei Hinatsu, Yukio

    2015-07-15

    A series of double perovskite-type oxides Ba{sub 2}LnMO{sub 6} (Ln=lanthanides; M=Sb, Bi) were synthesized and their structures were studied. The Ln and M are structurally ordered in the rock-salt type at the B-site of the perovskite ABO{sub 3}. For Ba{sub 2}PrBiO{sub 6} and Ba{sub 2}TbBiO{sub 6}, it has been found that the disordering between Ln ion and Bi ion occurs at the B-site of the double perovskite and both the Pr (Tb) and Bi exist in two oxidation state in the same compound from the analysis of the X-ray diffraction and magnetic susceptibility data. Magnetic susceptibility measurements show that all these compounds are paramagnetic and have no magnetic ordering down to 1.8 K. - Graphical abstract: Tolerance factor for Ba{sub 2}LnMO{sub 6} (M=Sb, Bi) plotted against the ionic radius of Ln{sup 3+}. We have found that there is a clear relation between crystal structures and tolerance factors. - Highlights: • The Ln and M ions are structurally ordered in the rock-salt type at the B-site. • The disordering between Pr (Tb) ion and Bi ion occurs at the B-site. • Ba{sub 2}LnMO{sub 6} (M=Sb, Bi) have no magnetic ordering down to 1.8 K.

  2. Computational study of LnGaO3 (Ln = La Gd) perovskites

    NASA Astrophysics Data System (ADS)

    Senyshyn, A.; Ehrenberg, H.; Vasylechko, L.; Gale, J. D.; Bismayer, U.

    2005-10-01

    Atomistic simulation techniques have been used to study the thermal properties of perovskite-type LnGaO3 (Ln = La-Gd). A set of interatomic potentials describing interatomic interactions in these compounds was developed and tested over a wide temperature range through utilizing free energy minimization. The predicted dielectric constants, thermal expansion coefficients, phonon density of states and its projections, heat capacity and entropy, elastic moduli, Grüneisen parameters, surface energies for main crystallographic directions and Debye temperatures are in good agreement with the limited available experimental data. Perovskite-type LnGaO3 (Ln = La-Gd) compounds have been examined under conditions to which substrate materials are typically subjected. Only a narrow region in the phase diagram of LnGaO3 (Ln = La-Gd) and their solid solutions is recommended for use in substrate applications.

  3. Phase transformations during HLnTiO{sub 4} (Ln=La, Nd) thermolysis and photocatalytic activity of obtained compounds

    SciTech Connect

    Silyukov, Oleg I. Abdulaeva, Liliia D.; Burovikhina, Alena A.; Rodionov, Ivan A.; Zvereva, Irina A.

    2015-03-15

    Layered HLnTiO{sub 4} (Ln=La, Nd) compounds belonging to Ruddlesden–Popper phases were found to form partially hydrated compounds Ln{sub 2}Ti{sub 2}O{sub 7}·xH{sub 2}O during thermal dehydration as well as defect oxides Ln{sub 2}□Ti{sub 2}O{sub 7} as final products. Further heating of metastable defect Ln{sub 2}□Ti{sub 2}O{sub 7} substances leads to the formation of pyrochlore-type oxides Ln{sub 2}Ti{sub 2}O{sub 7} {sub (p)}, with subsequent transformation under higher temperatures to stable layered 110-type perovskites Ln{sub 2}Ti{sub 2}O{sub 7}. The occurring structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO{sub 4}<Ln{sub 2}Ti{sub 2}O{sub 7}·yH{sub 2}O<Ln{sub 2}□Ti{sub 2}O{sub 7}<Ln{sub 2}Ti{sub 2}O{sub 7} {sub (p)}<Ln{sub 2}Ti{sub 2}O{sub 7} in the reaction of hydrogen evolution from aqueous isopropanol solution. - Graphical abstract: Layered HLnTiO{sub 4} (Ln=La, Nd) compounds form partially hydrated Ln{sub 2}Ti{sub 2}O{sub 7}·xH{sub 2}O compounds during thermal dehydration, further heating results to the formation to defect oxides Ln{sub 2}□Ti{sub 2}O{sub 7}, pyrochlor-type oxides Ln{sub 2}Ti{sub 2}O{sub 7} {sub (p)}, with subsequent transformation to layered 110-type perovskites Ln{sub 2}Ti{sub 2}O{sub 7}. Structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO{sub 4}<Ln{sub 2}Ti{sub 2}O{sub 7}·yH{sub 2}O<Ln{sub 2}□Ti{sub 2}O{sub 7}<Ln{sub 2}Ti{sub 2}O{sub 7} {sub (p)}<Ln{sub 2}Ti{sub 2}O{sub 7}. - Highlights: • We studied dehydration and further thermolysis of HLnTiO{sub 4} (Ln=La, Nd) compounds. • XRD, STA and solid state IR studies were carried out. • A new series of metastable Ln{sub 2}Ti{sub 2}O{sub 7}·yH{sub 2}O compounds was obtained. • We examined the photocatalytic activity of all obtained compounds. The hydrogen evolution rate increased in the course of the structure changes during thermolysis.

  4. Hydride-Based Electride Material, LnH2 (Ln = La, Ce, or Y).

    PubMed

    Mizoguchi, Hiroshi; Okunaka, Masaaki; Kitano, Masaaki; Matsuishi, Satoru; Yokoyama, Toshiharu; Hosono, Hideo

    2016-09-06

    In view of the strong electron-donating nature of H(-) and extensive vacancy formation in metals by hydrogen insertion, a series of LnH2+x (Ln = La, Ce, or Y) compounds with fluorite-type structures were verified to be the first hydride-based electride, where itinerant electrons populating the cage are surrounded by H(-) anions. The electron transfer into the cage probably originates from Ln-cage covalent interaction. To the best of our knowledge, anion-rich electrides are extremely rare, and a key requirement for their formation is that the cage site is not occupied by lone pair electrons of the adjacent ions. In the case of LnH2, the cage site is surrounded by eight H(-) anions with isotopic electronic character caused by the lack of mixing of H p-orbital character. Notably, Ru-loaded LnH2+x electride powders synthesized by hydrogen embrittlement (Ln = La or Ce) were found to work as efficient catalysts for ammonia synthesis at ambient pressure, without showing serious signs of hydrogen poisoning. There are several possible origins of the observed high catalytic activity in the hydride promotors: the small work function of LnH2+x derived from the covalent interaction between Ln cation and the H(-) σ donor, and the formation of Ln nitride during catalytic reaction.

  5. Formation enthalpies of LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

    SciTech Connect

    Qi, Jianqi; Guo, Xiaofeng; Mielewczyk-Gryn, Aleksandra

    2015-07-15

    High-temperature oxide melt solution calorimetry using 3Na{sub 2}O·MoO{sub 3} at 802 °C was performed for interlanthanide perovskites LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La{sub 2}O{sub 3}, Ho{sub 2}O{sub 3}, Er{sub 2}O{sub 3}, Tm{sub 2}O{sub 3} and Yb{sub 2}O{sub 3}). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be −8.3±3.4 kJ/mol for LaHoO{sub 3}, −9.9±3.0 kJ/mol for LaErO{sub 3}, −10.8±2.7 kJ/mol for LaTmO{sub 3} and −12.3±2.9 kJ/mol for LaYbO{sub 3}. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds. - Graphical abstract: A linear relationship between the enthalpy of formation and the tolerance factor for interlanthanide LaLn'O{sub 3} (Ln'=Ho, Er, Tm, and Yb) and other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites. - Highlights: • Interlanthanide perovskites were synthesized by solid state reactions. • Their enthalpies of formation were measured by oxide melt solution calorimetry. • ΔH{sub f,ox} shows a linear relationship with tolerance factor.

  6. Ln3Pb3(IO3)13(mu3-O) (Ln = La-Nd): new types of second-order nonlinear optical materials containing two types of lone pair cations.

    PubMed

    Hu, Ting; Qin, Li; Kong, Fang; Zhou, Yong; Mao, Jiang-Gao

    2009-03-02

    Hydrothermal reactions of lanthanide oxide, lead chloride, I(2)O(5), and H(2)O at 200 degrees C led to four novel quaternary compounds, namely, Ln(3)Pb(3)(IO(3))(13)(mu(3)-O) (Ln = La-Nd). They are isostructural, and their structures feature a complicated 3D network composed of LaO(9) and PbO(6) polyhedra interconnected by asymmetric IO(3) groups. Ln(3)Pb(3)(IO(3))(13)(mu(3)-O) (Ln = La, Pr, Nd) display moderate second harmonic generation efficiencies of about 2.0, 1.0, and 0.8 times the value of KH(2)PO(4), respectively. These compounds are thermally stable up to 520 degrees C. Luminescence measurements indicate that Ln(3)Pb(3)(IO(3))(13)(mu(3)-O) (Ln = Ce, Pr, Nd) exhibit strong emission bands in the visible or near IR region. Magnetic studies indicate that there exist significant antiferromagnetic interactions between magnetic centers in Ln(3)Pb(3)(IO(3))(13)(mu(3)-O) (Ln = Pr, Nd).

  7. Formation enthalpies of LaLn'O3 (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

    NASA Astrophysics Data System (ADS)

    Qi, Jianqi; Guo, Xiaofeng; Mielewczyk-Gryn, Aleksandra; Navrotsky, Alexandra

    2015-07-01

    High-temperature oxide melt solution calorimetry using 3Na2O·MoO3 at 802 °C was performed for interlanthanide perovskites LaLn'O3 (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be -8.3±3.4 kJ/mol for LaHoO3, -9.9±3.0 kJ/mol for LaErO3, -10.8±2.7 kJ/mol for LaTmO3 and -12.3±2.9 kJ/mol for LaYbO3. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM3+O3 (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds.

  8. Sonochemical synthesis of highly luminescent Ln2O3:Eu3+ (Y, La, Gd) nanocrystals

    DOE PAGES

    Alammar, Tarek; Cybinska, Joanna; Campbell, Paul S.; ...

    2015-05-12

    In this study, sonication of Ln(CH3COO)3·H2O, Eu(CH3COO)3·H2O and NaOH dissolved in the ionic liquid-butyl-3-methylimidazolium bis(trifluoromethane)sulfonylamide lead to Ln(OH)3:Eu (Ln: Gd, La, Y) nanoparticles. Subsequent calcination at 800 °C for 3 h allowed to obtain Ln2O3:Eu nanopowders. Gd2O3 and Y2O3 were obtained in the C-type lanthanide sequioxide structure, whereas La2O3 crystallized in the A-type. Structure, morphology, and luminescent properties of the nano-oxides were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), dispersive X-ray (EDX), and photoluminescence (PL). SEM studies revealed that the synthesized Gd2O3:Eu, La2O3:Eu, and Y2O3:Eu formed nano-spindle, -sheets, and -rods in shape, respectively. The nanoscale materials showmore » very efficient red emission due to the intraconfigurational f–f transitions of Eu3+. The quantum yields for Ln2O3:Eu (5%) were determined to be 4.2% for Ln=Gd, 13.8% for Ln=Y and 5.2% for Ln=La. The asymmetric ratio I02/I01 of Eu3+ varies from 5.3 for Gd2O3, to 5.6 for Y2O3 to 6.5 for La2O3, which increased the color chromaticity.« less

  9. Structurally characterized luminescent lanthanide zinc carboxylate precursors for Ln-Zn-O nanomaterials.

    PubMed

    Boyle, Timothy J; Raymond, Rebecca; Boye, Daniel M; Ottley, Leigh Anna M; Lu, Ping

    2010-09-14

    A novel family of lanthanide zinc carboxylate compounds was synthesized, characterized (structural determination and luminescent behavior), and investigated for utility as single-source precursors to Ln-Zn-O nanoparticles. Carboxylic acids [H-ORc = H-OPc (H-O(2)CCH(CH(3))(2), H-OBc (H-O(2)CC(CH(3))(3), H-ONc (H-O(2)CCH(2)C(CH(3))(3))] were individually reacted with diethyl zinc (ZnEt(2)) to yield a set of previously unidentified zinc carboxylates: (i) [Zn(mu-ORc)(3)Zn(mu-ORc)](n) [ORc = OPc (1), ONc (2)], (ii) [(py)Zn](2)(mu-ORc)(4) [ORc = OBc (3), ONc (4), and py = pyridine], or (iii) Zn(ORc)(2)(solv)(2) [ORc/solv = OPc/py (5), O(c)Nc/H(2)O (6) (O(c)Rc = chelating)]. Introduction of lanthanide cation [Ln[N(SiMe(3))(2)](3), ZnEt(2), and HOBc in py] yielded the mixed cationic species structurally characterized as: (i) (O(c)Bc)Ln[(mu-OBc)(3)Zn(py)](2) [Ln = Pr (7), Nd (8), Sm (9)] or (ii) (py)(2)Zn(mu-OBc)(3)Ln(O(c)Bc)(2)(py) [Ln = Tb (10), Dy (11), Er (12), Y (13), Yb (14)]. Exploration of alternative starting materials [Ln(NO(3))(3).nH(2)O, Zn(O(2)CCH(3))(2), HOBc in py] led to the isolation of (NO(3)(c))Ln[(mu-OBc)(3)Zn(py)](2) [Ln = La (15), Ce (16), Pr (17), Nd (18), Sm (19), Eu (20), Gd (21), Tb (22) Dy (23), and Er (24); NO(3)(c) = chelating]. The UV-vis spectra of 7-24 revealed standard absorption spectra for the Ln cations. Representative compounds were used to generate nanoparticles from an established 1,4-butanediol-based solution precipitation route. The nanoproducts isolated adopted either a mixed zincite/lanthanum oxide (18n or 22n) or pure zincite (8n or 10n) phase dependent on NO(3) or OBc moiety. Fluorescence was not observed for any of these nanomaterials possibly due to phase separation, low crystallinity, surface traps, and/or quenching based on elevated Ln cation content.

  10. High temperature Aurivillius piezoelectrics: the effect of (Li, Ln) modification on the structure and properties of (Li, Ln)0.06(Na, Bi)0.44Bi(2)Nb2O9 (Ln = Ce, Nd, La and Y).

    PubMed

    Long, Changbai; Fan, Huiqing; Li, Mengmeng

    2013-03-14

    High temperature Aurivillius piezoelectrics, (Li, Ln)(0.06)(Na, Bi)(0.44)Bi(2)Nb(2)O(9) (NBN-LiLn), with Li and Ln (Ce, Nd, La and Y) co-substitution at the A site, were prepared using a solid-state reaction process. Taking cation disordering between A site and the (Bi(2)O(2))(2+) layers into consideration, the crystal structure of (Li, Nd)(0.06)(Na, Bi)(0.44)Bi(2)Nb(2)O(9) (NBN-LiNd) was refined by using the Rietveld method with powder X-ray diffraction, which was confirmed to be a two-layer Aurivillius oxide with an orthorhombic space group, A2(1)am [a = 5.48666(9) Å, b = 5.46046(8) Å, c = 24.9122(4) Å and Z = 4], at room temperature. LiNd substitution induced a decrease in cation disorder and an increase in orthorhombic distortion. The ferroelectric to paraelectric phase transition temperature (T(c)) of the NBN-LiLn (Ln = Ce, Nd, La and Y) ceramics ranged from 751 to 842 °C and the T(c) increased as the radii of the Ln(3+) (Ce(3+), Nd(3+), La(3+) and Y(3+)) was decreased. The NBN-LiCe and NBN-LiNd had a d(33) of 31 and 29 pC N(-1), respectively, which is much higher than the reported d(33) values of other Aurivillius ceramics with a high T(c) (T(c) > 650 °C, d(33) < 20 pC N(-1)). With increasing annealing temperature, a significant degradation in d(33) was observed for NBN-LiCe, while no drop in d(33) was observed up to 650 °C for NBN-LiNd. The inhomogeneous domain structures determined the dissimilar piezoelectric behaviors of NBN-LiCe and NBN-LiNd.

  11. Estimate of the basicity of Ln[sub 2]O[sub 3]-Bi[sub 2]O[sub 3] catalysts for oxidative couping of methane through diffuse reflectance UV-vis experiments

    SciTech Connect

    Centeno, M.A.; Capitan, M.J.; Malet, P.; Carrizosa, I.; Odriozola, J.A. )

    1994-07-01

    The present work is aimed toward estimating the basicity rare earth oxide/bismuth oxide catalysts based in the electronic structure of the solid. The stabilization of the [beta]-Bi[sub 2]O[sub 3] phase due to the presence of rare earth cations allows the separation of the role of the basicity of the catalysts from the influence of the crystalline structure in the activity in the oxidative coupling of methane. 13 refs., 3 figs., 2 tabs.

  12. Pillared-layer cluster organic frameworks constructed from nanoscale Ln10 and Cu16 clusters.

    PubMed

    Fang, Wei-Hui; Yang, Guo-Yu

    2014-06-02

    Two pillared-layer cluster organic frameworks, [Ln5(μ3-OH)4(μ-H2O)Cu8I8L11]·H2O (L = 4-pyridin-4-yl-benzoate; Ln = Dy(1), Eu(2)), have been made by employing lanthanide oxide and copper(I) halide as the source of lanthanide and transitional metal under hydrothermal condition. Compared to the pillared-layer frameworks constructed from heterometallic layers and organic pillars, these two compounds are derived from lanthanide cluster organic layers and copper(I) halide cluster motifs. Thus, there are two distinct types of inorganic metal connectors in the structure, one is hydroxo lanthanide [Ln10(μ3-OH)8](22+) (Ln10) cluster, and the other is copper(I) halide [Cu16I16] (Cu16) cluster. The rational assembly of these two inorganic connectors and organic linear linkers leads to the formation of the two complexes here. To the best of our knowledge, they appear to be the first 3D frameworks constructed from decanuclear hydroxo lanthanide clusters. From the topological point of view, these compounds represent an intriguing example of a binodal (8,14)-connected net considering the Ln10 and Cu16 connectors as the nodes, revealing that they are typical high dimensional frameworks with high connected net based on high nuclearity nodes. Furthermore, elemental analysis, IR, TGA, PXRD, and UV-vis properties are also studied.

  13. Electrochemical and spectroscopic investigation of Ln3+ (Ln = Sm, Eu, and Yb) solvation in bis(trifluoromethylsulfonyl)imide-based ionic liquids and coordination by N,N,N',N'-tetraoctyl-3-oxa-pentane diamide (TODGA) and chloride.

    PubMed

    Pan, Yunfeng; Hussey, Charles L

    2013-03-18

    The electrochemistry and electronic absorption spectroscopy of samarium, europium, and ytterbium were investigated in the 1-(1-butyl)trimethylammonium bis(trifluoromethylsulfonyl)imide (BuMe3NTf2N) and 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyroTf2N) ionic liquids and in these solvents containing the neutral tridentate ligand N,N,N',N'-tetraoctyl-3-oxo-pentane diamide (TODGA) and the anionic hard ligand chloride. Lanthanide ions were introduced into the ionic liquids by controlled potential oxidation of the respective metals to yield solutions containing Eu(2+), Sm(3+), and Yb(3+), and it was possible to cycle between Eu(2+) and Eu(3+) as well as Yb(3+) and Yb(2+) using controlled potential electrolysis. Electronic absorption spectroscopy suggested that the Ln(3+) species are weakly solvated by Tf2N(-) anions as [Ln(Tf2N)x]((x-3)-) in the neat ILs. The quasireversible Ln(3+/2+) couples of all three elements were readily accessible in these ILs, but Sm(2+) was only stable on the voltammetric time scale. Addition of TODGA to [Ln(Tf2N)x]((x-3)-) solutions produces 3:1 complexes with Eu(3+) and Sm(3+) but only a 2:1 complex with the smaller Yb(3+) ion. Depending on the temperature, addition of Cl(-) to solutions of [Ln(Tf2N)x]((x-3)-) induces precipitation of LnCl3(s) when the mole ratio mCl(-)/mLn(3+) ≈ 3. However, when mCl(-)/mLn(3+) > 3, these precipitates redissolve to form the octahedral chloride complexes, [LnCl6](3-).

  14. Enthalpies of melting of LnSF compounds (Ln = La, Ce, Pr, Nd, Sm)

    NASA Astrophysics Data System (ADS)

    Andreev, P. O.; Mikhalkina, O. G.; Andreev, O. V.; Elyshev, A. V.

    2015-05-01

    The melting temperatures and enthalpies of such congruently melting compounds as LaSF ( T m = 1713 ± 7 K, Δ H = 45.7 ± 4.6 kJ/mol), CeSF ( T m = 1683 ± 7 K, Δ H = 40.7 ± 4.1 kJ/mol), PrSF ( T m = 1661 ± 7 K, Δ H = 39.7 ± 4.0 kJ/mol), NdSF ( T m = 1654 ± 7 K, Δ H = 40.2 ± 4.0 kJ/mol), and SmSF ( T m = 1587 ± 7 K, Δ H = 36.1 ± 3.6 kJ/mol) are determined via synchronous thermal analysis. The tetrad effect is evident in the change of the melting temperatures and enthalpies of LnSF compounds (Ln = La, Ce, Pr, Nd, Sm) depending on r(Ln3+).

  15. Two unprecedented decanuclear heterometallic [MnMnLn] (Ln = Dy, Tb) complexes displaying relaxation of magnetization.

    PubMed

    Wang, Hui-Sheng; Yang, Feng-Jun; Long, Qiao-Qiao; Huang, Zhi-Yong; Chen, Wei; Pan, Zhi-Quan; Song, You

    2016-11-15

    We report the syntheses, crystal structures, and magnetic properties of two 3d-4f heterometallic compounds; namely, [Mn8Ln2O2(OH)2{(py)2CO2}4(teaH)4(CH3COO)6]·6CH3CN·2H2O (Ln(III) = Dy (1), Tb (2); (py)2CO2H2 = the gem-diol form of di-2-pyridyl ketone, teaH3 = triethanolamine). Both compounds were prepared by the reaction of Mn(OAc)2·4H2O, Ln(NO3)3·5H2O (Ln = Dy and Tb) with the ligands di-2-pyridyl ketone and triethanolamine in MeCN, and they crystallize in the monoclinic space group C2/c. [Mn8Ln2] complexes have not been reported before, and the metallic cores of both complexes were unprecedented. In these cores, two Dy or Tb and two Mn ions comprised a well-known butterfly topology, with three of the remaining six Mn atoms each being situated on either side of the butterfly, linked through two μ3-O(2-) ions. Six Mn(III) and two Mn(II) were in six-coordinated distorted octahedrons and two Ln(III) ions were in nine-coordinated distorted muffins. Interestingly, the coordination sites of Ln(III) ions are occupied by six O and two N atoms from two teaH(2-) ligands and one μ3-O(2-) atom, without the presence of coordinated solvent molecules such as H2O and small anions such as NO3(-) ions, which is rare in 3d-4f complexes. Remarkably, alternating current (ac) magnetic susceptibility measurements revealed that both complexes displayed dynamic anisotropic magnetic behaviour. The effective energy barrier (Ueff) of complex 2 was estimated to be 18.97 K through high frequency (111-9111 Hz) ac susceptibility measurements. The low symmetry of the coordination configuration of Ln(3+) in 1 and 2 may be responsible for the small energy barriers of these two compounds.

  16. Catalytic combustion of soot particulates over rare-earth substituted Ln2Sn2O7 pyrochlores (Ln=La, Nd and Sm).

    PubMed

    Wang, Zhongpeng; Zhu, Hongjian; Ai, Lijie; Liu, Xuhui; Lv, Min; Wang, Liguo; Ma, Zhenmin; Zhang, Zhaoliang

    2016-09-15

    Catalytic combustion is one of the most promising methods for diesel soot removal. Ln2Sn2O7 pyrochlores substituted with different rare-earth (RE) elements (Ln=La, Nd and Sm) were prepared through co-precipitation method for catalytic combustion of soot particulates. The structural, textural and redox properties, together with the oxygen vacancy of the catalysts were investigated systematically. Their catalytic activities were evaluated by both temperature-programmed oxidation and isothermal reaction techniques. With the increasing in RE ionic radius (r), the SnO bond strength in Ln2Sn2O7 pyrochlores evaluated from the stretching IR band was decreased, resulting in the improved reducibility and enhanced oxygen vacancies of catalysts. The increase of oxygen vacancy concentration was further confirmed by photoluminescence (PL) investigations wherein upon excitation with UV radiation, the pyrochlores nanoparticles exhibited strong and sharp transition at 408nm attributed to oxygen vacancies. Catalytic combustion and isothermal reactions revealed that the ignition activity (ignition temperature, T5) and the intrinsic activity (turnover frequency, TOF) were shown to depend correlatedly on redox properties and oxygen vacancy concentrations, both of which were influenced by the substitution of different RE elements. Among the pyrochlore oxides, the as-synthesized La2Sn2O7 sample displayed relatively the highest ignition activity and the largest intrinsic activity with TOF of 2.33×10(-3)s(-1).

  17. Syntheses, structures, and sensitized lanthanide luminescence by Pt --> Ln (Ln = Eu, Nd, Yb) energy transfer for heteronuclear PtLn2 and Pt2Ln4 complexes with a terpyridyl-functionalized alkynyl ligand.

    PubMed

    Li, Xiu-Ling; Shi, Lin-Xi; Zhang, Li-Yi; Wen, Hui-Min; Chen, Zhong-Ning

    2007-12-10

    Reaction of Pt(dppm-P,P')Cl2 (dppm = 1,2-bis(diphenylphosphino)methane) with HCCPhtpy (HCCPhtpy = 4'-(4-ethynylphenyl)-2,2':6',2"-terpyridine) in the presence of copper(I) iodide and diisopropylamine induced isolation of mononuclear complex cis-Pt(dppm-P,P')(C[triple bond]CPhtpy)2 (1), which can be converted into face-to-face diplatinum(II) species Pt2(mu-dppm)2(C[triple bond]CPhtpy)4 (5) when equivalent dppm is added. Incorporating 1 or 5 to Ln(hfac)3(H2O)2 (Hhfac = hexafluoroacetylacetone) gave PtLn2 (Ln = Nd (2), Eu (3), Yb (4)) or Pt2Ln4 (Ln = Nd (6), Eu (7), Gd (8), Yb (9)) adducts with the lanthanide centers chelated by terdentate terpyridyl in the bridging C[triple bond]CPhtpy. The structures of 1, 6, 7, and 9 were determined by X-ray crystallography. Upon excitation at lambdaex = 360-450 nm (2-4) or 360-500 nm (6-9), where the PtII alkynyl antenna chromophores absorb strongly but the model complexes Ln(hfac)3(HC[triple bond]CPhtpy) lack obvious absorption in this region, these PtLn2 and Pt2Ln4 (Ln = Nd, Eu, Yb) species exhibit band-like lanthanide luminescence that is typical of the corresponding Ln3+ ions, demonstrating unambiguously that efficient Pt --> Ln energy transfer occurs indeed from the PtII alkynyl antenna chromophores to the lanthanide centers across the bridging CCPhtpy with intramolecular Pt...Ln distances being ca. 14.2 A. The Pt --> Ln energy transfer rate (kET) is 6.07 x 10(7) s(-1) for Pt2Nd4 (6) and 2.12 x 10(5) s(-1) for Pt2Yb4 (9) species.

  18. Crystal growth, structure and magnetic properties of the double perovskites Ln{sub 2}MgIrO{sub 6} (Ln=Pr, Nd, Sm-Gd)

    SciTech Connect

    Mugavero, Samuel J. III; Fox, Adam H.; Smith, Mark D.; Loye, Hans-Conrad zur

    2010-02-15

    Single crystals of double-perovskite type lanthanide magnesium iridium oxides, Ln{sub 2}MgIrO{sub 6} (Ln=Pr, Nd, Sm-Gd) have been grown in a molten potassium hydroxide flux. The compounds crystallize in a distorted 1:1 rock salt lattice, space group P2{sub 1}/n, consisting of corner shared MO{sub 6} (M=Mg{sup 2+} and Ir{sup 4+}) octahedra, where the rare earth cations occupy the eight-fold coordination sites formed by the corner shared octahedra. Pr{sub 2}MgIrO{sub 6}, Nd{sub 2}MgIrO{sub 6}, Sm{sub 2}MgIrO{sub 6}, and Eu{sub 2}MgIrO{sub 6} order antiferromagnetically around 10-15 K. - Graphical abstract: A SEM image of a typical crystal of Ln{sub 2}MgIrO{sub 6}, which forms in the monoclinic double perovskite structure, is shown.

  19. Thermoelectric properties of binary LnN (Ln=La and Lu): First principles study

    SciTech Connect

    Sreeparvathy, P. C.; Gudelli, Vijay Kumar; Kanchana, V.; Vaitheeswaran, G.; Svane, A.; Christensen, N. E.

    2015-06-24

    First principles density functional calculations were carried out to study the electronic structure and thermoelectric properties of LnN (Ln = La and Lu) using the full potential linearized augmented plane wave (FP-LAPW) method. The thermoelectric properties were calculated by solving the Boltzmann transport equation within the constant relaxation time approximation. The obtained lattice parameters are in good agreement with the available experimental and other theoretical results. The calculated band gaps using the Tran-Blaha modified Becke-Johnson potential (TB-mBJ), of both compounds are in good agreement with the available experimental values. Thermoelectric properties like thermopower (S), electrical conductivity scaled by relaxation time (σ/τ) and power-factor (S{sup 2}σ/τ) are calculated as functions of the carrier concentration and temperature for both compounds. The calculated thermoelectric properties are compared with the available experimental results of the similar material ScN.

  20. The formation of the complex manganites LnSr{sub 2}Mn{sub 2}O{sub 7} (Ln = La, Nd, Gd)

    SciTech Connect

    Missyul, A.B.; Zvereva, I.A.; Palstra, T.T.M.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Formation of the LnSr{sub 2}Mn{sub 2}O{sub 7} phases proceeds according to two different pathways. ► Cationic composition of the obtained phase depends on the formation pathway. ► Step-by-step synthesis allows obtaining single-phase material. ► Structure and magnetic properties of the single-phase NdSr{sub 2}Mn{sub 2}O{sub 7} were investigated. -- Abstract: The process of formation of the Ruddlesden–Popper phases LnSr{sub 2}Mn{sub 2}O{sub 7} (Ln = La, Nd, Gd) was investigated by means of X-ray diffraction, thermal analysis and microprobe analysis. Two parallel pathways were found for the reaction. The first one includes the formation of the intermediate K{sub 2}NiF{sub 4}-type compound by interaction of Sr{sub 7}Mn{sub 4}O{sub 15} and perovskite-type solid solution (Ln,Sr)MnO{sub 3}, while in the second one the K{sub 2}NiF{sub 4}-type intermediate is formed during the reaction of the same perovskite-type solid solution with the corresponding rare earth oxide. This result gives an explanation for the formation of two phases with slightly different cationic compositions. The kinetics of the reaction was investigated for both mechanisms resulting in determination of their relative contribution to the final composition. Pure NdSr{sub 2}Mn{sub 2}O{sub 7} was obtained using a step-by-step process according to the first mechanism, and the magnetic properties of this phase were investigated.

  1. Molybdate templated assembly of Ln12Mo4-type clusters (Ln = Sm, Eu, Gd) containing a truncated tetrahedron core.

    PubMed

    Zheng, Yong; Zhang, Qian-Chong; Long, La-Sheng; Huang, Rong-Bin; Müller, Achim; Schnack, Jürgen; Zheng, Lan-Sun; Zheng, Zhiping

    2013-01-04

    Three heterometallic cluster complexes {Ln(12)Mo(4)} featuring an Ln(12) core of a distorted truncated tetrahedron were synthesized with the assistance of four MoO(4)(2-) anions as ancillary ligands. Magnetic studies of the {Gd(12)Mo(4)} cluster revealed a large magnetocaloric effect due to the presence of the large number of weakly coupled Gd(III) ions.

  2. Computational study on the complexation behavior of tetrapropyl diglycolamide with Ln3+ (Ln = Nd, Pm, Sm, and Eu) cation series

    NASA Astrophysics Data System (ADS)

    Hosseinnejad, Tayebeh; Nikoo, Sepideh

    2015-09-01

    In the present study, we have focused mainly on the survey of interactions in Ln3+ (Ln = Nd, Pm, Sm, Eu) complexes with tetrapropyl diglycolamide (TPDGA) by means of density functional theory (DFT) methods. In the first step, the interaction of TPDGA ligand with Ln3+ cation series has been assessed thermodynamically in the gas phase and in presence of three solvents: n-hexane, chloroform and toluene, via polarized continuum model (PCM) calculations. The trend of metal-ligand interaction strength has been investigated and compared with the trend of ionic hardness within the series of lanthanide cations. Our results for the gas and solution phases demonstrate a consistency between the increasing trend in the hardness of Ln3+ cation series with the increasing in thermodynamical stability of [Ln(TPDGA)]3+ complex series. Moreover, our PCM calculations show that using n-hexane as a solvent is more favorable thermodynamically than chloroform and toluene for the complexation reaction of all [Ln(TPDGA)]3+ complex series. It should be stated that this issue has been observed in many experimental calculations. Finally the assessment of calculated deformation energies and also the variation in bond order of some selected key bonds in [Ln(TPDGA)]3+ complex series shows a similar trend with increasing in the hardness of Ln3+ cation series.

  3. 2,5-Dioxido-1,4-benzoquinonediimine (H2L2-), a hydrogen-bonding noninnocent bridging ligand related to aminated topaquinone: different oxidation state distributions in complexes [{(bpy)2Ru}2(mu-H2L)]n (n=0,+,2+,3+,4+) and [{(acac)2Ru}2(mu-H2L)]m (m=2-,-,0,+,2+).

    PubMed

    Kar, Sanjib; Sarkar, Biprajit; Ghumaan, Sandeep; Janardanan, Deepa; van Slageren, Joris; Fiedler, Jan; Puranik, Vedavati G; Sunoj, Raghavan B; Kaim, Wolfgang; Lahiri, Goutam Kumar

    2005-08-19

    The symmetrically dinuclear title compounds were isolated as diamagnetic [(bpy)2Ru(mu-H2L)Ru(bpy)2](ClO4)2 (1-(ClO4)2) and as paramagnetic [(acac)2Ru(mu-H2L)Ru(acac)2] (2) complexes (bpy=2,2'-bipyridine; acac- = acetylacetonate = 2,4-pentanedionato; H2L = 2,5-dioxido-1,4-benzoquinonediimine). The crystal structure of 22 H2O reveals an intricate hydrogen-bonding network: Two symmetry-related molecules 2 are closely connected through two NH(H2L2-)O(acac-) interactions, while the oxygen atoms of H2L2- of two such pairs are bridged by an (H2O)8 cluster at half-occupancy. The cluster consists of cyclic (H2O)6 arrangements with the remaining two exo-H2O molecules connecting two opposite sides of the cyclo-(H2O)6 cluster, and oxido oxygen atoms forming hydrogen bonds with the molecules of 2. Weak antiferromagnetic coupling of the two ruthenium(III) centers in 2 was established by using SQUID magnetometry and EPR spectroscopy. Geometry optimization by means of DFT calculations was carried out for 1(2+) and 2 in their singlet and triplet ground states, respectively. The nature of low-energy electronic transitions was explored by using time-dependent DFT methods. Five redox states were reversibly accessible for each of the complexes; all odd-electron intermediates exhibit comproportionation constants K(c)>10(8). UV-visible-NIR spectroelectrochemistry and EPR spectroscopy of the electrogenerated paramagnetic intermediates were used to ascertain the oxidation-state distribution. In general, the complexes 1n+ prefer the ruthenium(II) configuration with electron transfer occurring largely at the bridging ligand (mu-H2Ln-), as evident from radical-type EPR spectra for 13+ and (+. Higher metal oxidation states (iii, iv) appear to be favored by the complexes 2m; intense long-wavelength absorption bands and RuIII-type EPR signals suggest mixed-valent dimetal configurations of the paramagnetic intermediates 2+ and 2-.

  4. On the Crystal Structure of Ln

    SciTech Connect

    Olafsen, Anja; Larsson, Ann-Kristin; Fjellvaag, Helmer; Hauback, Bjoern C.

    2001-04-01

    The crystal structures of La{sub 2}O{sub 2}CO{sub 3} II and Nd{sub 2}O{sub 2}CO{sub 3} II have been shown by means of high-resolution powder neutron (PND) and synchrotron X-ray diffraction (SXRD) combined with selected area electron diffraction (SAED) studies to be far more complex than earlier anticipated, owing to ordering of carbonate groups between (Ln{sub 2}O{sub 2}{sup +2}){sub n} layers. In contrast to earlier descriptions, the carbonate groups appear to be rather regular. Relative to an average model, the SAED patterns show additional scattering in the form of closely distributed, but essentially discrete, spots along < 1/3, 1/3, 1 >. Most of the observed scattering, H, can be described as H=G{+-}m q{sub 1}+n q{sub 2}, where G is the Bragg reflections of the underlying average P6{sub 3}/mmc lattice, q1=[1/3, 1/3, {+-}1/2]*, q2=[1/3, 1/3, {+-}2/3]*, and m and n are integers. The additional scattering reflects ordering of the carbonate groups into trigonal layers between the (Ln{sub 2}O{sub 2}{sup +2}){sub n} layers, but it remains open whether q{sub 1} and q{sub 2} represent two separate structures with different stacking sequences of such layers or whether they correspond to an even more complex stacking sequence. In any case, some disorder and rotational domain twinning are present. Two structure models, one for each modulation wave vector, were constructed. Rietveld-type refinements of PND data of La{sub 2}O{sub 2}CO{sub 3} II were performed, approximating the complex, and at least partly disordered, stacking sequence as a two-phase mixture of the two modulated phases. Satisfactory convergence was achieved with R{sub p}=6.4%, R{sub wp}=8.3%, and {chi}{sup 2}=3.32. The isothermal expansivities, {alpha}{sub p}, for La{sub 2}O{sub 2}CO{sub 3} II and Nd{sub 2}O{sub 2}CO{sub 3} II between 298 and 893 K were determined as 2.92x10{sup {minus}5} and 2.70x10{sup {minus}5} K{sup {minus}1}, respectively.

  5. The Ba 2LnFeNb 4O 15 "tetragonal tungsten bronze": Towards RT composite multiferroics

    NASA Astrophysics Data System (ADS)

    Josse, M.; Bidault, O.; Roulland, F.; Castel, E.; Simon, A.; Michau, D.; Von der Mühll, R.; Nguyen, O.; Maglione, M.

    2009-06-01

    Several Niobium oxides of formula Ba 2LnFeNb 4O 15 (Ln = La, Pr, Nd, Sm, Eu, Gd) with the "tetragonal tungsten bronze" (TTB) structure have been synthesised by conventional solid state methods. The neodymium, samarium and europium compounds are ferroelectric with Curie temperature ranging from 320 to 440 K. The praseodymium and gadolinium compounds behave as relaxors below 170 and 300 K respectively. The praseodymium, neodymium, samarium, europium and gadolinium compounds exhibit magnetic hysteresis loops at room temperature originating from traces of a barium ferrite secondary phase. The presence of both ferroelectric and magnetic hysteresis loops at room temperature allows considering these materials as composites multiferroic. Based on crystal-chemical analysis we propose some relationships between the introduction of Ln 3+ ions in the TTB framework and the chemical, structural and physical properties of these materials.

  6. Effect of A-TIG Welding Process on the Weld Attributes of Type 304LN and 316LN Stainless Steels

    NASA Astrophysics Data System (ADS)

    Vasudevan, M.

    2017-03-01

    The specific activated flux has been developed for enhancing the penetration performance of TIG welding process for autogenous welding of type 304LN and 316LN stainless steels through systematic study. Initially single-component fluxes were used to study their effect on depth of penetration and tensile properties. Then multi-component activated flux was developed which was found to produce a significant increase in penetration of 10-12 mm in single-pass TIG welding of type 304LN and 316LN stainless steels. The significant improvement in penetration achieved using the activated flux developed in the present work has been attributed to the constriction of the arc and as well as reversal of Marangoni flow in the molten weld pool. The use of activated flux has been found to overcome the variable weld penetration observed in 316LN stainless steel with <50 ppm of sulfur. There was no degradation in the microstructure and mechanical properties of the A-TIG welds compared to that of the welds produced by conventional TIG welding on the contrary the transverse strength properties of the 304LN and 316LN stainless steel welds produced by A-TIG welding exceeded the minimum specified strength values of the base metals. Improvement in toughness values were observed in 316LN stainless steel produced by A-TIG welding due to refinement in the weld microstructure in the region close to the weld center. Thus, activated flux developed in the present work has greater potential for use during the TIG welding of structural components made of type 304LN and 316LN stainless steels.

  7. Effect of A-TIG Welding Process on the Weld Attributes of Type 304LN and 316LN Stainless Steels

    NASA Astrophysics Data System (ADS)

    Vasudevan, M.

    2017-02-01

    The specific activated flux has been developed for enhancing the penetration performance of TIG welding process for autogenous welding of type 304LN and 316LN stainless steels through systematic study. Initially single-component fluxes were used to study their effect on depth of penetration and tensile properties. Then multi-component activated flux was developed which was found to produce a significant increase in penetration of 10-12 mm in single-pass TIG welding of type 304LN and 316LN stainless steels. The significant improvement in penetration achieved using the activated flux developed in the present work has been attributed to the constriction of the arc and as well as reversal of Marangoni flow in the molten weld pool. The use of activated flux has been found to overcome the variable weld penetration observed in 316LN stainless steel with <50 ppm of sulfur. There was no degradation in the microstructure and mechanical properties of the A-TIG welds compared to that of the welds produced by conventional TIG welding on the contrary the transverse strength properties of the 304LN and 316LN stainless steel welds produced by A-TIG welding exceeded the minimum specified strength values of the base metals. Improvement in toughness values were observed in 316LN stainless steel produced by A-TIG welding due to refinement in the weld microstructure in the region close to the weld center. Thus, activated flux developed in the present work has greater potential for use during the TIG welding of structural components made of type 304LN and 316LN stainless steels.

  8. Thermodynamic properties of liquid Mg-ln-Cd ternary solutions

    NASA Astrophysics Data System (ADS)

    Moser, Z.; Gasior, W.; Panek, Z.

    1984-09-01

    By means of concentration cells of the following type: Mg(s)∣MgCl2 in (LiCl-KCl)eut( l)∣Mg-In or Mg-ln-Cd( l), the partial thermodynamic data of Mg in Mg-ln and Mg-ln-Cd liquid solutions have been obtained in the composition range 0.1 ≤ XMg ≤ 0.7 for binary while for ternary alloys for t = 0.4, 0.6, and 0.8 (where t = XIn/(XIn + XCd)) and at various mangesium concentrations 0.1≤ XMg ≤ 0.6. Both ternary and binary alloys were investigated at a temperature range 750 to 900 K. Experimental partial excess Gibbs energies of Mg were interpreted by the Pelton and Flengas method. Results for Mg-ln system show a slight difference in comparison with previously published data for the same system also from emf studies. Results of this study for Mg-ln system exhibit negative and positive excess entropies of magnesium and the same is observed in ternary system Mg-ln-Cd at the range of concentration close to Mg-ln.

  9. Uniform hollow Lu2O3:Ln (Ln = Eu3+, Tb3+) spheres: facile synthesis and luminescent properties.

    PubMed

    Yang, Piaoping; Gai, Shili; Liu, Yanchao; Wang, Wenxin; Li, Chunxia; Lin, Jun

    2011-03-21

    Uniform hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) phosphors have been successfully prepared via a urea-assisted homogeneous precipitation method using carbon spheres as templates, followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, kinetic decays, quantum yields (QY), and UV-visible diffuse reflectance spectra were employed to characterize the samples. The results show that hollow Lu(2)O(3):Ln spheres can be indexed to cubic Gd(2)O(3) phase with high purity. The as-prepared hollow Lu(2)O(3):Ln phosphors are confirmed to be uniform in shape and size with diameter of about 300 nm and shell thickness of approximate 20 nm. The possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow Lu(2)O(3):Ln microspheres has been proposed. Upon ultraviolet (UV) and low-voltage electron beams excitation, the hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) spheres exhibit bright red (Eu(3+), (5)D(0)-(7)F(2)) and green (Tb(3+), (5)D(4)-(7)F(5)) luminescence, which may find potential applications in the fields of color display and biomedicine.

  10. Structural, spectroscopic, and theoretical comparison of traditional vs recently discovered Ln(2+) ions in the [K(2.2.2-cryptand)][(C5H4SiMe3)3Ln] complexes: the variable nature of Dy(2+) and Nd(2+).

    PubMed

    Fieser, Megan E; MacDonald, Matthew R; Krull, Brandon T; Bates, Jefferson E; Ziller, Joseph W; Furche, Filipp; Evans, William J

    2015-01-14

    The Ln(3+) and Ln(2+) complexes, Cp'3Ln, 1, (Cp' = C5H4SiMe3) and [K(2.2.2-cryptand)][Cp'3Ln], 2, respectively, have been synthesized for the six lanthanides traditionally known in +2 oxidation states, i.e., Ln = Eu, Yb, Sm, Tm, Dy, and Nd, to allow direct structural and spectroscopic comparison with the recently discovered Ln(2+) ions of Ln = Pr, Gd, Tb, Ho, Y, Er, and Lu in 2. 2-La and 2-Ce were also prepared to allow the first comparison of all the lanthanides in the same coordination environment in both +2 and +3 oxidation states. 2-La and 2-Ce show the same unusual structural feature of the recently discovered +2 complexes, that the Ln-(Cp' ring centroid) distances are only about 0.03 Å longer than in the +3 analogs, 1. The Eu, Yb, Sm, Tm, Dy, and Nd complexes were expected to show much larger differences, but this was observed for only four of these traditional six lanthanides. 2-Dy and 2-Nd are like the new nine ions in this tris(cyclopentadienyl) coordination geometry. A DFT-based model explains the results and shows that a 4f (n)5d(1) electron configuration is appropriate not only for the nine recently discovered Ln(2+) ions in 2 but also for Dy(2+) and Nd(2+), which traditionally have 4f (n+1) electron configurations like Eu(2+), Yb(2+), Sm(2+), and Tm(2+). These results indicate that the ground state of a lanthanide ion in a molecule can be changed by the ligand set, a previously unknown option with these metals due to the limited radial extension of the 4f orbitals.

  11. DETAIL INTERIOR VIEW OF THE CYANAMIDE (LN) OVEN BUILDING LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL INTERIOR VIEW OF THE CYANAMIDE (L-N) OVEN BUILDING LOOKING NORTHEAST AT A C. 1932 CHICAGO PNEUMATIC COMPRESSOR. (NOT ORIGINAL LOCATION). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  12. DETAIL INTERIOR VIEW OF THE CYANAMIDE (LN) OVEN BUILDING LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL INTERIOR VIEW OF THE CYANAMIDE (L-N) OVEN BUILDING LOOKING SOUTHEAST AT INGERSOLL-RAND COMPRESSORS #BE565 & 564. (NOT ORIGINAL LOCATION). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  13. PERSPECTIVE VIEW LOOKING NORTHWEST AT CYANAMIDE (LN) COOLING SHED, MILL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PERSPECTIVE VIEW LOOKING NORTHWEST AT CYANAMIDE (L-N) COOLING SHED, MILL BUILDING AND CONVEYOR BRIDGE. NOTE CORNERSTONE ON THE MILL BUILDING. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  14. DETAIL INTERIOR VIEW OF THE CYANAMIDE (LN) OVEN BUILDING LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL INTERIOR VIEW OF THE CYANAMIDE (L-N) OVEN BUILDING LOOKING WEST AT INGERSOLL-RAND COMPRESSORS #BE565 & 564. (NOT ORIGINAL LOCATION). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  15. DETAIL INTERIOR VIEW OF THE CYANAMIDE (LN) OVEN BUILDING LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL INTERIOR VIEW OF THE CYANAMIDE (L-N) OVEN BUILDING LOOKING NORTHWEST AT A C. 1932 CHICAGO PNEUMATIC COMPRESSOR. (NOT ORIGINAL LOCATION). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  16. PERSPECTIVE VIEW LOOKING SOUTHWEST AT THE CYANAMIDE (LN) OVEN BUILDING, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PERSPECTIVE VIEW LOOKING SOUTHWEST AT THE CYANAMIDE (L-N) OVEN BUILDING, AMMONIA SPHERES IN FOREGROUND. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  17. Heat capacity, entropy of Ln2(MoO4)3 (Ln = La, Sm, and Gd), and the high-temperature enthalpy of Ln2(MoO4)3 (Ln = Eu, Dy, and Ho)

    NASA Astrophysics Data System (ADS)

    Lazarev, V. M.; Suponitskiy, Y. L.; Liashenko, S. E.

    2016-05-01

    The low-temperature heat capacity of Ln2(MoO4)3 (Ln = La, Sm, and Gd) is investigated by means of adiabatic calorimetry within the range of 60-300 K. The temperature dependences of the heat capacity are found and the values of the standard entropy are calculated, based on extrapolations to 0 K. Characteristic temperatures for molybdates are determined from the results of IR spectroscopic studies. The high-temperature enthalpy of Ln2(MoO4)3 (Ln = Eu, Dy, and Ho) is measured via high-temperature microcalorimetry, and the temperature dependence of heat capacity is calculated in the range of 298-1000 K. Since samarium and gadolinium molybdates are of the same structural type as terbium molybdate, we can estimate the anomaly of the heat capacity in the low-temperature region using the data for terbium molybdate and find the entropy of samarium and gadolinium molybdates.

  18. High pressure luminescence spectra of CaMoO4:Ln3+ (Ln = Pr, Tb).

    PubMed

    Mahlik, S; Behrendt, M; Grinberg, M; Cavalli, E; Bettinelli, M

    2013-03-13

    Photoluminescence spectra and luminescence kinetics of pure CaMoO(4) and CaMoO(4) doped with Ln(3+) (Ln = Pr or Tb) are presented. The spectra were obtained at high hydrostatic pressure up to 240 kbar applied in a diamond anvil cell. At ambient pressure undoped and doped samples exhibit a broad band emission extending between 380 and 700 nm with a maximum at 520 nm attributed to the MoO(4)(2-) luminescence. CaMoO(4) doped with Pr(3+) or Tb(3+) additionally yields narrow emission lines related to f-f transitions. The undoped CaMoO(4) crystal was characterized by a strong MoO(4)(2-) emission up to 240 kbar. In the cases of CaMoO(4):Pr(3+) and CaMoO(4):Tb(3+), high hydrostatic pressure caused quenching of Pr(3+) and Tb(3+) emission, and this effect was accompanied by a strong shortening of the luminescence lifetime. In doped samples, CaMoO(4):Pr(3+) and CaMoO(4):Tb(3+), quenching of the emission band attributed to MoO(4)(2-) was also observed, and at pressure above 130 kbar this luminescence was totally quenched. The effects mentioned above were related to the influence of the praseodymium (terbium) trapped exciton PTE (ITE-impurity trapped exciton) on the efficiency of the Pr(3+) (Tb(3+)) and MoO(4)(2-) emissions.

  19. Structure and bulk modulus of Ln-doped UO2 (Ln = La, Nd) at high pressure

    NASA Astrophysics Data System (ADS)

    Rittman, Dylan R.; Park, Sulgiye; Tracy, Cameron L.; Zhang, Lei; Palomares, Raul I.; Lang, Maik; Navrotsky, Alexandra; Mao, Wendy L.; Ewing, Rodney C.

    2017-07-01

    The structure of lanthanide-doped uranium dioxide, LnxU1-xO2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ∼50-55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ∼ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ∼ 0.25-0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. This trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO2, such as Young's modulus.

  20. High pressure luminescence spectra of CaMoO4:Ln3+ (Ln = Pr, Tb)

    NASA Astrophysics Data System (ADS)

    Mahlik, S.; Behrendt, M.; Grinberg, M.; Cavalli, E.; Bettinelli, M.

    2013-03-01

    Photoluminescence spectra and luminescence kinetics of pure CaMoO4 and CaMoO4 doped with Ln3+ (Ln = Pr or Tb) are presented. The spectra were obtained at high hydrostatic pressure up to 240 kbar applied in a diamond anvil cell. At ambient pressure undoped and doped samples exhibit a broad band emission extending between 380 and 700 nm with a maximum at 520 nm attributed to the {{MoO}}_{4}^{2-} luminescence. CaMoO4 doped with Pr3+ or Tb3+ additionally yields narrow emission lines related to f-f transitions. The undoped CaMoO4 crystal was characterized by a strong MoO{}_{4}^{2-} emission up to 240 kbar. In the cases of CaMoO4:Pr3+ and CaMoO4:Tb3+, high hydrostatic pressure caused quenching of Pr3+ and Tb3+ emission, and this effect was accompanied by a strong shortening of the luminescence lifetime. In doped samples, CaMoO4:Pr3+ and CaMoO4:Tb3+, quenching of the emission band attributed to {{MoO}}_{4}^{2-} was also observed, and at pressure above 130 kbar this luminescence was totally quenched. The effects mentioned above were related to the influence of the praseodymium (terbium) trapped exciton PTE (ITE—impurity trapped exciton) on the efficiency of the Pr3+ (Tb3+) and {{MoO}}_{4}^{2-} emissions.

  1. Rare-earth transition-metal chalcogenides Ln{sub 3}MGaS{sub 7} (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln{sub 3}MGaSe{sub 7} (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni)

    SciTech Connect

    Yin, Wenlong; Shi, Youguo; Kang, Bin; Deng, Jianguo; Yao, Jiyong; Wu, Yicheng

    2014-05-01

    Fifteen new rare-earth transition-metal chalcogenides, Ln{sub 3}MGaS{sub 7} (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln{sub 3}MGaSe{sub 7} (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni), have been synthesized by solid state reactions. They are isostructural, adopt Ce{sub 3}Al{sub 1.67}S{sub 7}—related structure type, and crystallize in the non-centrosymmetric hexagonal space group P6{sub 3}. They adopt a three-dimensional framework composed of LnQ{sub 7} monocapped trigonal prisms with the interesting [MQ{sub 3}]{sup 4−} chains and isolated GaQ{sub 4} tetrahedra lying in two sets of channels in the framework. The magnetic susceptibility measurements on Ln{sub 3}CoGaQ{sub 7} (Ln=Dy, Er, Q=S; Ln=Dy, Q=Se) indicate that they are paramagnetic and obey the Curie–Weiss law over the entire experimental temperature, while the magnetic susceptibility of Sm{sub 3}CoGaSe{sub 7} deviates from the Curie–Weiss law as a result of the crystal field splitting. - Graphical abstract: Ln{sub 3}MGaS{sub 7} (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln{sub 3}MGaSe{sub 7} (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni) adopt a three-dimensional framework composed of LnQ{sub 7} monocapped trigonal prisms with interesting [MQ{sub 3}]{sup 4−} chains and isolated GaQ{sub 4} tetrahedra lying in two sets of channels in the framework. - Highlights: • New compounds, Ln{sub 3}MGaQ{sub 7} (Ln=rare-earth; M=Co, Ni; Q=S, Se), were synthesized. • They are isostructural and crystallize in the noncentrosymmetric space group P6{sub 3}. • They adopt a three-dimensional framework built by LnQ{sub 7} monocapped trigonal prisms. • Ln{sub 3}CoGaQ{sub 7} (Ln=Dy, Er; Q=S, Se) are paramagnetic and obey the Curie–Weiss law. • The magnetic susceptibility of Sm{sub 3}CoGaSe{sub 7} deviates from the Curie–Weiss law.

  2. Crystal growth of a series of lithium garnets Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd): Structural properties, Alexandrite effect and unusual ionic conductivity

    SciTech Connect

    Roof, Irina P.; Smith, Mark D.; Cussen, Edmund J.; Loye, Hans-Conrad zur

    2009-02-15

    We report the single crystal structures of a series of lanthanide containing tantalates, Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd) that were obtained out of a reactive lithium hydroxide flux. The structures of Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} were determined by single crystal X-ray diffraction, where the Li{sup +} positions and Li{sup +} site occupancies were fixed based on previously reported neutron diffraction data for isostructural compounds. All three oxides crystallize in the cubic space group Ia3-bard (No. 230) with lattice parameters a=12.7735(1), 12.6527(1), and 12.5967(1) A for La{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, Pr{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, and Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, respectively. A UV-Vis diffuse reflectance spectrum of Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} was collected to explain its unusual Alexandrite-like optical behavior. To evaluate the transport properties of Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, the impedance data were collected in air in the temperature range 300{<=}T(deg. C){<=}500. - Graphical abstract: Crystal structure of garnets Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd). TaO{sub 6} polyhedra are shown in yellow and Ln{sup 3+} are shown as light blue spheres. Octahedrally and tetrahedrally coordinated Li{sup +} ions are shown in green and brown, respectively. Oxygen atoms are omitted for clarity.

  3. High Specific Power Motors in LN2 and LH2

    NASA Technical Reports Server (NTRS)

    Brown, Gerald V.; Jansen, Ralph H.; Trudell, Jeffrey J.

    2007-01-01

    A switched reluctance motor has been operated in liquid nitrogen (LN2) with a power density as high as that reported for any motor or generator. The high performance stems from the low resistivity of Cu at LN2 temperature and from the geometry of the windings, the combination of which permits steady-state rms current density up to 7000 A/cm2, about 10 times that possible in coils cooled by natural convection at room temperature. The Joule heating in the coils is conducted to the end turns for rejection to the LN2 bath. Minimal heat rejection occurs in the motor slots, preserving that region for conductor. In the end turns, the conductor layers are spaced to form a heat-exchanger-like structure that permits nucleate boiling over a large surface area. Although tests were performed in LN2 for convenience, this motor was designed as a prototype for use with liquid hydrogen (LH2) as the coolant. End-cooled coils would perform even better in LH2 because of further increases in copper electrical and thermal conductivities. Thermal analyses comparing LN2 and LH2 cooling are presented verifying that end-cooled coils in LH2 could be either much longer or could operate at higher current density without thermal runaway than in LN2.

  4. High Specific Power Motors in LN2 and LH2

    NASA Technical Reports Server (NTRS)

    Brown, Gerald V.; Jansen, Ralph H.; Trudell, Jeffrey J.

    2007-01-01

    A switched reluctance motor has been operated in liquid nitrogen (LN2) with a power density as high as that reported for any motor or generator. The high performance stems from the low resistivity of Cu at LN2 temperature and from the geometry of the windings, the combination of which permits steady-state rms current density up to 7000 A/sq cm, about 10 times that possible in coils cooled by natural convection at room temperature. The Joule heating in the coils is conducted to the end turns for rejection to the LN2 bath. Minimal heat rejection occurs in the motor slots, preserving that region for conductor. In the end turns, the conductor layers are spaced to form a heat-exchanger-like structure that permits nucleate boiling over a large surface area. Although tests were performed in LN2 for convenience, this motor was designed as a prototype for use with liquid hydrogen (LH2) as the coolant. End-cooled coils would perform even better in LH2 because of further increases in copper electrical and thermal conductivities. Thermal analyses comparing LN2 and LH2 cooling are presented verifying that end-cooled coils in LH2 could be either much longer or could operate at higher current density without thermal runaway than in LN2.

  5. Theoretical aspects of photonic band gap in 1D nano structure of LN: MgLN periodic layer

    SciTech Connect

    Sisodia, Namita

    2015-06-24

    By using the transfer matrix method, we have analyzed the photonic band gap properties in a periodic layer of LN:MgLN medium. The Width of alternate layers of LN and MgLN is in the range of hundred nanometers. The birefringent and ferroelectric properties of the medium (i.e ordinary, extraordinary refractive indices and electric dipole moment) is given due considerations in the formulation of photonic band gap. Effect of electronic transition dipole moment of the medium on photonic band gap is also taken into account. We find that photonic band gap can be modified by the variation in the ratio of the width of two medium. We explain our findings by obtaining numerical values and the effect on the photonic band gap due to variation in the ratio of alternate medium is shown graphically.

  6. Influence of thermal aging on the intergranular corrosion resistance of types 304LN and 316LN stainless steels

    NASA Astrophysics Data System (ADS)

    Mudali, U. Kamachi; Dayal, R. K.; Gnanamoorthy, J. B.; Rodriguez, P.

    1996-10-01

    Intergranular corrosion (IGC) resistance of types 304LN and 316LN stainless steels (SS) thermally aged at 823, 873, and 923 K for various durations was assessed by ASTM A262 practice A test (electrolytic etch test) and electrochemical potentiodynamic reactivation (EPR) test. The results indicated that the type 316LN SS has significantly improved IGC resistance compared to 304LN SS. Based on the results of these tests, time-temperature-sensitization (TTS) diagrams were developed for both alloys. The secondary precipitates formed during thermal aging treatments were electrochemically extracted and analyzed by X-ray diffraction (XRD) to determine the types of precipitates formed during the aging treatments. The results indicated that the precipitates were mostly of M23C6 carbides.

  7. Influence of thermal aging on the intergranular corrosion resistance of types 304LN and 316LN stainless steels

    SciTech Connect

    Mudali, U.K.; Dayal, R.K.; Gnanamoorthy, J.B.; Rodriguez, P.

    1996-10-01

    Intergranular corrosion (IGC) resistance of types 304LN and 316LN stainless steels (SS) thermally aged at 823, 873, and 923 K for various durations was assessed by ASTM A262 practice A test (electrolytic etch test) and electrochemical potentiodynamic reactivation (EPR) test. The results indicated that the type 316LN SS has significantly improved IGC resistance compared to 304LN SS. Based on the results of these tests, time-temperature-sensitization (TTS) diagrams were developed for both alloys. The secondary precipitates formed during thermal aging treatments were electrochemically extracted and analyzed by X-ray diffraction (XRD) to determine the types of precipitates formed during the aging treatments. The results indicated that the precipitates were mostly of M{sub 23}C{sub 6} carbides.

  8. MOLTEN SALT SYNTHESIS OF YF3:Yb3+/Ln3+(Ln = Er3+, Tm3+) MICROSHEETS WITH MULTICOLOR UPCONVERSION LUMINESCENCE

    NASA Astrophysics Data System (ADS)

    Ding, Mingye; Lu, Chunhua; Cao, Linhai; Ni, Yaru; Xu, Zhongzi

    2013-09-01

    In this paper, highly crystalline YF3:Yb3+/Ln3+(Ln = Er3+, Tm3+) microsheets were successfully synthesized by a surfactant-free molten salt method for the first time. The results indicated that the as-obtained samples belonged to orthorhombic system and exhibited microsheets morphology with side lengths of 30 to 80 μm and wall thickness from 1 to 1.5 μm. By changing the dopant's species (Ln3+), multicolor (yellow and blue) upconversion emission can be observed in YF3:Yb3+/Ln3+ microsheets under 980 nm laser diode (LD) excitation. The upconversion mechanisms in co-doping YF3 samples were analyzed in detail based on the emission spectra. Importantly, this approach not only proposes a new alternative in synthesizing such materials, but also opens the possibility to meet the increasing commercial demand.

  9. Luminescence of Bi 3+ in the metaphosphates LnP 3O 9 ( Ln = Sc, Lu, Y, Gd, La)

    NASA Astrophysics Data System (ADS)

    Oomen, E. W. J. L.; Blasse, G.

    1988-07-01

    The luminescence of the Bi 3+ ion (6 s2) is studied in the metaphosphates LnP 3O 9 ( Ln = Sc, Lu, Y, Gd, La). For Ln = Sc, Lu, Y, Gd the metaphosphates have a monoclinic structure with four slightly different sites for the trivalent cations. For Ln = Sc, Lu, Y the Stokes shift of the Bi 3+ luminescence increased with increasing radius of the host lattice cation. Concentration quenching of the Bi 3+ luminescence is observed. In the case of GdP 3O 9-Bi 3+ the excitation energy is transferred to the Gd 3+ ions. LaP 3O 9 adopts an orthorhombic structure with only one site available for the trivalent cations. The different coordination of the Bi 3+ ion leads to a large increase of the Stokes shift of the Bi 3+ luminescence.

  10. New Antimony Lanthanide Disulfide Dibromides LnSbS

    SciTech Connect

    Gout, D.; Jobic, S.; Evain, M.; Brec, R.

    2001-05-01

    CeSbS{sub 2}Br{sub 2} (I), Ce{sub 1/2}La{sub 1/2}SbS{sub 2}Br{sub 2} (II), and LaSbS{sub 2}Br{sub 2} (III) have been synthesized at 700 C from a mixture of LnBr{sub 3}, Ln{sub 2}S{sub 3}, Sb, and S and characterized by single-crystal X-ray diffraction. The three phases are isostructural (space group P2{sub 1}/c, Z=4) and crystallize in a novel, dense, bidimensional structure with cell parameters a=8.709(3) {angstrom}, b=9.187(2) {angstrom}, c=17.397(5) {angstrom} {beta}=104.26(3) for I, a=8.739(7) {angstrom}, b=9.219(7) {angstrom}, c=17.41(2) {angstrom}, =104.3(1) for II, and a=8.785(1) {angstrom}, b=9.236(2) {angstrom}, c=17.372(3) {angstrom}, {beta}=104.09(2) for III. In these compounds, [Ln S{sub 5}Br{sub 4}] and [Ln S{sub 3}Br{sub 6}] (Ln=Ce, La) distorted tricapped trigonal prisms define infinite {sub {infinity}}{sup 2}[LnS{sub 2}Br{sub 2}] layers counterbalanced and capped by antimony cations. In good accordance with the structural features, the charge balance in these materials is to be written Ln{sup III}Sb{sup III}S{sup -II}{sub 2}Br{sup -I}{sub 2}. These compounds exhibit a yellow hue with a measured absorption threshold of 2.42(1), 2.55(1), and 2.72(1) eV for I, II, and III, respectively. In the two cerium containing bromothioantimonates I and II, the origin of the color is assigned to a Ce-4f{yields}Ce-5d electronic transition, which shifts to higher energy from I to II due either to a matrix effect (increase of the mean Ln-S distances under the substitution of Ce for La) or to an atomic ordering between Ce and La cations on the Ln(1) and Ln(2) crystallographic sites. In contrast, the electronic transition at play in III involves a charge transfer from the bromine and sulfur ions to the antimony ions, the latter contributing substantially to the lowermost levels of the conduction band.

  11. Decanuclear Ln10 Wheels and Vertex-Shared Spirocyclic Ln5 Cores: Synthesis, Structure, SMM Behavior, and MCE Properties.

    PubMed

    Das, Sourav; Dey, Atanu; Kundu, Subrata; Biswas, Sourav; Narayanan, Ramakirushnan Suriya; Titos-Padilla, Silvia; Lorusso, Giulia; Evangelisti, Marco; Colacio, Enrique; Chandrasekhar, Vadapalli

    2015-11-16

    The reaction of a Schiff base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln10 (Ln = Dy (1), Tb (2), and Gd (3)) and pentanuclear Ln5 complexes (Ln = Gd (4), Tb (5), and Dy (6)), respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes (1-6) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff) = 16.12(8) K and relaxation time (τo) = 3.3×10(-5) s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out-of-phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: -ΔSm = 26.6 J kg(-1) K(-1) at T = 2.2 K for 3 and -ΔSm = 27.1 J kg(-1) K(-1) at T = 2.4 K for 4, both for an applied field change of 7 T.

  12. On the origin of the anomalous electrical resistivity of LnMo 5O 8 (Ln=TRIVALENT rare earth)

    NASA Astrophysics Data System (ADS)

    Koo, H.-J.; Whangbo, M.-H.; McCarroll, W. H.; Greenblatt, M.; Gautier, R.; Halet, J.-F.; Gougeon, P.

    1998-10-01

    Electronic structures of AMo 5O 8 (A=rare earth, alkaline earth) and the solid solution Sr 1- xLa xMo 5O 8 ( x=0-1) were examined using the extended Hückel tight binding method. AMo 5O 8 phases with divalent A cations (A=Sr, Ca, Eu) are normal semiconductors with small band gap. The Fermi surfaces of Sr 1- xLa xMo 5O 8 (0.0< x≤1.0) and LnMo 5O 8 (Ln=trivalent rare earth) do not exhibit any nesting. In the electronic structures of LnMo 5O 8 (Ln=trivalent rare earth) phases, the Fermi level is dominated by the d-orbitals of the Mo(2) atoms of their Mo 10 clusters. With decreasing x from 1.0 in Sr 1- xLa xMo 5O 8, the dominance of the Mo(2) atoms at the Fermi level sharply diminishes. Based on this observation, we proposed a probable reason for the weakly semiconducting state above 180 K and the metallic state below 180 K in LnMo 5O 8 (Ln=trivalent rare earth).

  13. Characterization and Defect Structure of Anion-Excess Fluorite-Related Phases in LnOF-LnF

    SciTech Connect

    Laval, J. P.; Taoudi, A.; Abaouz, A.

    2001-02-15

    The phases LnO{sub 1-x}F{sub 1+2x}, derived from the fluorite-type structure by anionic excess, form, for medium size Ln cations (Ln=Nd, Sm, Eu, Gd), a homogeneous series of orthorhombic symmetry (space group Pmmn, a{approx}b{approx}a{sub F}{radical}2/2; c=a{sub F}). Structural comparison of these phases by X-ray powder diffraction allows us to make a better determination of their defect structure: O/F order in sheets perpendicular to the [001] axis and formation of 1:0:2 clusters which can be associated in dimer units. For Nd, an orthorhombic-tetragonal transition is explained by a change from 1:0:2 to denser 1:0:3 clusters. Comparison of the structural features of these phases with ''vernier'' modulated phases, isolated for Sm-Lu cations, allows a general classification of LnO{sub 1-x}F{sub 1+2x} phases at low temperature to be proposed. All are characterized by the preservation of an anionic O/F order in sheets perpendicular to the [001]{sub F} axis and by a progressive loss of freedom in the accommodation of the anionic excess (nature and orientation of the clusters, tendency to long-range ordering) from La to Lu, caused by the decrease in Ln size and therefore in Ln coordination.

  14. The luminescence of the Sb 3+ ion in Ln(PO 3) 3 ( Ln = Sc, Lu, Y, Gd, La)

    NASA Astrophysics Data System (ADS)

    Oomen, E. W. J. L.; Peeters, R. C. M.; Smit, W. M. A.; Blasse, G.

    1988-03-01

    The efficient luminescence of the 5 s2 ion Sb 3+ in Ln(PO 3) 3 ( Ln = Sc, Lu, Y, Gd, La) is reported. The compounds Ln(PO 3) 3 ( Ln = Sc, Lu, Y, Gd) adopt the Yb(PO 3) 3 structure in which four slightly different octahedral sites are available for the trivalent cation, while La(PO 3) 3 has the Nd(PO 3) 3 structure in which only one position with eight coordination is available for the cation. The emission and excitation spectra of Ln(PO 3) 3Sb 3+ ( Ln = Sc, Lu, Gd) show broad bands, caused by the strongly overlapping bands of the four Sb 3+ centers. The spectra and decay time measurements show that the differences in luminescence characteristics between the four Sb 3+ centers become more apparent with decreasing radius of the host lattice cation. The luminescence properties of Y(PO 3) 3Sb 3+ are rather complex and lead to the conclusion that the relaxed excited state of some of the Sb 3+ centers is distorted by a Jahn-Teller effect. The luminescence of La(PO 3) 3Sb 3+ originates from one Sb 3+ center and can be described by usual models

  15. Trivalent lanthanide compounds with fluorinated thiolate ligands: Ln-F dative interactions vary with Ln and solvent.

    PubMed

    Melman, Jonathan H; Rohde, Christa; Emge, Thomas J; Brennan, John G

    2002-01-14

    The fluorinated tris-thiolate compounds Ln(SC(6)F(5))(3) can be isolated as THF, pyridine, or DME coordination complexes. In THF, the larger Ce forms dimeric [(THF)(3)Ce(SC(6)F(5))(3)](2) (1) with bridging thiolate ligands, while the smaller lanthanides (Ln = Ho (2), Er (3)) form monometallic (THF)(3)Ln(SC(6)F(5))(3) compounds. There is a tendency for fluoride to coordinate to Ln throughout the lanthanide series (Ce-Er). The cerium compound 1 contains a pair of bridging thiolates connecting two eight-coordinate Ce(III) ions. Of the two terminal thiolates, only one exhibits a distinct Ce-F bond. In contrast, the Ho derivative (THF)(3)Ho(SC(6)F(5))(3) is a molecular compound in the solid state, with two monodentate thiolates and one thiolate that again coordinates through both S and F atoms. Incorporation of a stronger Lewis base reduces but does not necessarily eliminate the tendency to form Ln-F bonds. Structural characterization of the eight-coordinate (pyridine)(4)Sm(SC(6)F(5))(3) (4) reveals a single, clearly defined Ln-F interaction, while in (pyridine)(4)Yb(SC(6)F(5))(3) (5) there are no Yb-F bonds. In the structure of (DME)(2)Er(SC(6)F(5))(3) (6) the DME ligands completely displace F from the Er coordination sphere.

  16. Structure and magnetic properties of LnMnSbO ( Ln=La and Ce)

    DOE PAGES

    Zhang, Qiang; Kumar, C. M. N.; Tian, Wei; ...

    2016-03-11

    Here, a neutron powder diffraction (NPD) study of LnMnSbO (Ln = La or Ce) reveals differences between the magnetic ground state of the two compounds due to the strong Ce-Mn coupling compared to La-Mn. The two compounds adopt the P4/nmm space group down to 2 K, and whereas magnetization measurements do not show obvious anomaly at high temperatures, NPD reveals a C-type antiferromagnetic (AFM) order below TN = 255K for LaMnSbO and 240 K for CeMnSbO. While the magnetic structure of LaMnSbO is preserved to base temperature, a sharp transition at TSR = 4.5K is observed in CeMnSbO due tomore » a spin-reorientation (SR) transition of the Mn2+ magnetic moments from pointing along the c axis to the ab plane. The SR transition in CeMnSbO is accompanied by a simultaneous long-range AFM ordering of the Ce moments, which indicates that the Mn SR transition is driven by the Ce-Mn coupling. The ordered moments are found to be somewhat smaller than those expected for Mn2+ (S = 5/2) in insulators, but large enough to suggest that these compounds belong to the class of local-moment antiferromagnets. The lower TN found in these two compounds compared to the As-based counterparts (TN = 317 for LaMnAsO, TN = 347K for CeMnAsO) indicates that the Mn-Pn (Pn=As or Sb) hybridization that mediates the superexchange Mn-Pn-Mn coupling is weaker for the Sb-based compounds.« less

  17. Structures and Properties of the Products of the Reaction of Lanthanide Atoms with H2O: Dominance of the +II Oxidation State.

    PubMed

    Mikulas, Tanya C; Chen, Mingyang; Fang, Zongtang; Peterson, Kirk A; Andrews, Lester; Dixon, David A

    2016-02-11

    The reactions of lanthanides with H2O have been studied using density functional theory with the B3LYP functional. H2O forms an initial Lewis acid-base complex with the lanthanides exothermically with interaction energies from -2 to -20 kcal/mol. For most of the Ln, formation of HLnOH is more exothermic than formation of H2LnO, HLnO + H, and LnOH + H. The reactions to produce HLnOH are exothermic from -25 to -75 kcal/mol. The formation of LnO + H2 for La and Ce is slightly more exothermic than formation of HLnOH and is less or equally exothermic for the rest of the lanthanides. The Ln in HLnOH and LnOH are in the formal +II and +I oxidation states, respectively. The Ln in H2LnO is mostly in the +III formal oxidation state with either Ln-O(-)/Ln-H(-) or Ln-(H2)(-)/Ln=O(2-) bonding interactions. A few of the H2LnO have the Ln in the +IV or mixed +III/+IV formal oxidation states with Ln=O(2-)/Ln-H(-) bonding interactions. The Ln in HLnO are generally in the +III oxidation state with the exception of Yb in the +II state. The orbital populations calculated within the natural bond orbital (NBO) analysis are consistent with the oxidation states and reaction energies. The more exothermic reactions to produce HLnOH are always associated with more backbonding from the O(H) and H characterized by more population in the 6s and 5d in Ln and the formation of a stronger Ln-O(H) bond. Overall, the calculations are consistent with the experiments in terms of reaction energies and vibrational frequencies.

  18. Crystal growth and magnetic properties of the new iridates Ln 1- xNa 1+ xIrO 4 (Ln = Gd-Er, Y; x = 0.04-0.25)

    NASA Astrophysics Data System (ADS)

    Mugavero, Samuel J.; Smith, Mark D.; zur Loye, Hans-Conrad

    2007-07-01

    We report the single crystal structures and magnetic properties of a series of lanthanide-containing iridates, Ln 1- xNa 1+xIrO 4 (Ln = Gd-Er, Y; x = 0.04-0.26) grown from a mixed sodium and cesium hydroxide flux. The compounds crystallize in the hexagonal space group P-62 m (#189) with lattice parameters ranging from a = 9.3872(2)-9.4596(3) Å and c = 3.1512(1)-3.2030(2) Å and are structurally related to other iridium oxides. The oxidation state of iridium ranges from +4.08 (Gd) to +4.50 (Er). Magnetic susceptibility measurements reveal the existence of antiferromagnetic correlations below 15 K.

  19. Physicochemical properties of rare earth doped ceria Ce0.9Ln0.1O1.95 (Ln = Nd, Sm, Gd) as an electrolyte material for IT-SOFC/SOEC

    NASA Astrophysics Data System (ADS)

    Chaubey, Nityanand; Wani, B. N.; Bharadwaj, S. R.; Chattopadhyaya, M. C.

    2013-06-01

    Nanosized crystallites of rare earth doped ceria Ce0.9Ln0.1O1.95 (Ln = Nd, Sm, Gd) a promising electrolyte material for Intermediate Temperature - Solid Oxide Fuel Cells/electrolysis cells have been synthesized by standard ceramic route. Detection of impurities in the samples was done by FTIR spectroscopy. X-ray diffraction studies were used for the determination of phase purity, crystal structure and average crystallite size of the samples. Kinetics involved in phase formation has been discussed. Raman study showed a major band around 465 cm-1 in all the samples, which is attributed to the cubic fluorite structure of ceria. It was also found that for samples Ce0.9Ln0.1O1.95 (Ln = Nd, Sm, Gd) the frequency of F2g shifts to lower value. Electrochemical impedance spectroscopy has been used to measure the ionic conductivity of the samples at elevated temperatures. The Gd doped sample showed the highest grain boundary and total conductivity in comparison to Sm and Nd doped sample. Bulk thermal expansion behavior, sintered densities and micro structural features of the samples have also been studied.

  20. Nine members of a family of nine-membered cyclic coordination clusters; Fe6Ln3 wheels (Ln = Gd to Lu and Y).

    PubMed

    Kühne, Irina A; Mereacre, Valeriu; Anson, Christopher E; Powell, Annie K

    2016-01-18

    We report a family of isostructural nonanuclear Fe(III)-Ln(III) cyclic coordination clusters [Fe(III)(6)Ln(III)(3)(μ-OMe)9(vanox)6(benz)6]. (Ln = Tb (1), Dy (2), Ho (3), Er (4), Tm (5), Yb (6), Lu (7), Y (8) and Gd (9)), containing an odd number of metal ions. The planar cyclic coordination cluster cores are built up from three [Fe2Ln] subunits.

  1. (BMI)3LnCl6 crystals as models for the coordination environment of LnCl3 (Ln = Sm, Eu, Dy, Er, Yb) in 1-butyl-3-methylimidazolium chloride ionic-liquid solution.

    PubMed

    Han, Yulun; Lin, Cuikun; Meng, Qingguo; Dai, Fengrong; Sykes, Andrew G; Berry, Mary T; May, P Stanley

    2014-06-02

    A series of (BMI)3LnCl6 (Ln = Sm, Eu, Dy, Er, Yb) crystals was prepared from solutions of LnCl3 dissolved in the ionic liquid, 1-butyl-3-methylimidazolium chloride (BMICl). Crystals with Ln = 5% Sm + 95% Gd and with Ln = 5% Dy + 95% Gd were also grown to assess the importance of cross-relaxation in the Sm and Dy samples. The crystals are isostructural, with monoclinic space group P21/c and four formula units per unit cell. The first coordination sphere of Ln(3+) consists of six Cl(-) anions forming a slightly distorted octahedral LnCl6(3-) center. The second coordination sphere is composed of nine BMI(+) cations. The emission spectra and luminescence lifetimes of both (BMI)3LnCl6 crystals and LnCl3 in BMICl solution were measured. The spectroscopic similarities suggest that crystalline (BMI)3LnCl6 provides a good model of the Ln(3+) coordination environment in BMICl solution.

  2. Luminescence of NaGdFPO{sub 4}:Ln {sup 3+} after VUV excitation: A comparison with GdPO{sub 4}:Ln {sup 3+} (Ln=Ce, Tb)

    SciTech Connect

    Tian Zifeng; Liang Hongbin . E-mail: cesbin@mail.sysu.edu.cn; Lin Huihong; Su Qiang; Guo Bei; Zhang Guobin; Fu Yibing

    2006-05-15

    The phosphors NaGdFPO{sub 4}:Ln {sup 3+} and GdPO{sub 4}:Ln {sup 3+} (for Ln{sup 3+}=Ce{sup 3+} and Tb{sup 3+}) were prepared by solid-state reaction technique, the VUV-vis spectroscopic properties of the phosphors were investigated, and we vividly compare the luminescence of Ce{sup 3+} and Tb{sup 3+} in the hosts. For phosphors GdPO{sub 4}:Ln {sup 3+}, the band near 155 nm in VUV excitation spectrum is assumed to be the host-related absorption, and for NaGdFPO{sub 4}:Ln {sup 3+} the absorption is moved to longer wavelength, near 170 nm, showing the P-O bond covalency increased after fluoridation. The f-d transitions of Ce{sup 3+} and Tb{sup 3+} in the host lattices are assigned and corroborated, and it was found that the 5d states are with lower energy in NaGdFPO{sub 4}:Ln {sup 3+} than those in GdPO{sub 4}:Ln {sup 3+}. For fluoridation of GdPO{sub 4}:Ln {sup 3+} to NaGdFPO{sub 4}:Ln {sup 3+}, the energy change of Ln {sup 3+} (Ln=Ce, Tb) 5d states is consistent with that of host-related absorption.

  3. Cationic ordering and role of the B-site lanthanide(III) and molybdenum(V) cations on the structure and magnetism of double perovskites Sr{sub 2}LnMoO{sub 6}

    SciTech Connect

    Pinacca, R.M.; Larrégola, S.A.; López, C.A.; Pedregosa, J.C.; Pomjakushin, Vladimir; Sánchez, R.D.; Alonso, J.A.

    2015-06-15

    Highlights: • Five new double perovskites of formula Sr{sub 2}LnMoO{sub 6} were synthesized. • All the samples crystallize in the monoclinic P2{sub 1}/n space group. • Strong reducing conditions were used in order to stabilized Mo(V) cations. • A complete ordering between the rare earth and molybdenum ions was observed. • Magnetism agrees with the crystal distortions observed from Rietveld analysis. - Abstract: We describe the preparation, crystal structure determination and magnetic properties of a new series of ordered double perovskite oxides Sr{sub 2}LnMoO{sub 6} (Ln = Eu, Gd, Dy, Ho, Er, Yb) with Mo{sup 5+} and Ln{sup 3+} electronic configurations. These compounds have been obtained by solid state reaction under reducing conditions in order to stabilize Mo{sup 5+} cations. Structural characterization by XRPD and NPD was performed when Ln = Ho, Er, Yb and just XRPD for absorbing Ln = Eu, Gd, Dy. At room temperature, an excellent Rietveld fit was obtained for all the samples in a monoclinic symmetry, space group P2{sub 1}/n, with long-range ordering of Ln and Mo atoms. Magnetic susceptibility measurements show that some of these materials present magnetic ordering below 25 K and the determined effective magnetic moments are consistent with those expected for the pair Ln{sup 3+}–Mo{sup 5+}. All the phases have negative values​​ of the Weiss temperature indicating dominance of antiferromagnetic interactions.

  4. A new continuous two-step molecular precursor route to rare-earth oxysulfides Ln{sub 2}O{sub 2}S

    SciTech Connect

    De Crom, N.

    2012-07-15

    A continuous two-step molecular precursor pathway is designed for the preparation of rare-earth oxysulfides Ln{sub 2}O{sub 2}S (Ln=Y, La, Pr, Nd, Sm-Lu). This new route involves a first oxidation step leading to the rare-earth oxysulfate Ln{sub 2}O{sub 2}SO{sub 4} which is subsequently reduced to the rare-earth oxysulfide Ln{sub 2}O{sub 2}S by switching to a H{sub 2}-Ar atmosphere. The whole process occurs at a temperature significantly lower than usual solid state synthesis (T{<=}650 Degree-Sign C) and avoids the use of dangerous sulfur-based gases, providing a convenient route to the synthesis of the entire series of Ln{sub 2}O{sub 2}S. The molecular precursors consist in heteroleptic dithiocarbamate complexes [Ln(Et{sub 2}dtc){sub 3}(phen)] and [Ln(Et{sub 2}dtc){sub 3}(bipy)] (Et{sub 2}dtc=N,N-diethyldithiocarbamate; phen=1,10-phenanthroline; bipy=2,2 Prime -bipyridine) and were synthesized by a new high yield and high purity synthesis route. The nature of the molecular precursor determines the minimum synthesis temperature and influences therefore the purity of the final Ln{sub 2}O{sub 2}S crystalline phase. - Graphical abstract: A continuous two-step molecular precursor pathway was designed for the preparation of rare-earth oxysulfides Ln{sub 2}O{sub 2}S (Ln=Y, La, Pr, Nd, Sm-Lu), starting from heteroleptic dithiocarbamate complexes. The influence of the nature of the molecular precursor on the minimum synthesis temperature and on the purity of the final Ln{sub 2}O{sub 2}S crystalline phase is discussed. Highlights: Black-Right-Pointing-Pointer A new high yield and high purity synthesis route of rare earth dithiocarbamates is described. Black-Right-Pointing-Pointer These compounds are used as precursors in a continuous process leading to rare-earth oxysulfides. Black-Right-Pointing-Pointer The oxysulfides are obtained under much more moderate conditions than previously described.

  5. Sulfate Exchange of the Nitrate-Type Layered Hydroxide Nanosheets of Ln2(OH)5NO3· nH2O for Better Dispersed and Multi-color Luminescent Ln2O3 Nanophosphors (Ln = Y0.98RE0.02, RE = Pr, Sm, Eu, Tb, Dy, Ho, Er, and Tm)

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoli; Liu, Weigang; Li, Ji-Guang; Zhu, Qi; Li, Xiaodong; Sun, Xudong

    2016-07-01

    Through restricting thickness growth by performing coprecipitation at the freezing temperature of ~4 °C, solid-solution nanosheets (up to 5-nm thick) of the Ln2(OH)5NO3· nH2O layered hydroxide (Ln = Y0.98RE0.02; RE = Pr, Sm, Eu, Tb, Dy, Ho, Er, and Tm, respectively) were directly synthesized without performing conventional exfoliation. In situ exchange of the interlayer NO3 - with SO4 2- produced a sulfate derivative [Ln2(OH)5(SO4)0.5· nH2O] of the same layered structure and two-dimensional crystallite morphology but substantially contracted d 002 basal spacing (from ~0.886 to 0.841 nm). The sulfate derivative was systematically compared against its nitrate parent in terms of crystal structure and phase/morphology evolution upon heating. It is shown that the interlayer SO4 2-, owing to its bonding with the hydroxide main layer, significantly raises the decomposition temperature from ~600 to 1000 °C to yield remarkably better dispersed oxide nanopowders via a monoclinic Ln2O2SO4 intermediate. The resultant (Y0.98RE0.02)2O3 nanophosphors were studied for their photoluminescence to show that the emission color, depending on RE3+, spans a wide range in the Commission Internationale de l'Eclairage (CIE) chromaticity diagram, from blue to deep red via green, yellow, orange, and orange red.

  6. Rare-earth transition-metal chalcogenides Ln3MGaS7 (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln3MGaSe7 (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni)

    NASA Astrophysics Data System (ADS)

    Yin, Wenlong; Shi, Youguo; Kang, Bin; Deng, Jianguo; Yao, Jiyong; Wu, Yicheng

    2014-05-01

    Fifteen new rare-earth transition-metal chalcogenides, Ln3MGaS7 (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln3MGaSe7 (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni), have been synthesized by solid state reactions. They are isostructural, adopt Ce3Al1.67S7-related structure type, and crystallize in the non-centrosymmetric hexagonal space group P63. They adopt a three-dimensional framework composed of LnQ7 monocapped trigonal prisms with the interesting [MQ3]4- chains and isolated GaQ4 tetrahedra lying in two sets of channels in the framework. The magnetic susceptibility measurements on Ln3CoGaQ7 (Ln=Dy, Er, Q=S; Ln=Dy, Q=Se) indicate that they are paramagnetic and obey the Curie-Weiss law over the entire experimental temperature, while the magnetic susceptibility of Sm3CoGaSe7 deviates from the Curie-Weiss law as a result of the crystal field splitting.

  7. Studies on supercritical hydrothermal syntheses of uranium and lanthanide oxide particles and their reaction mechanisms

    NASA Astrophysics Data System (ADS)

    Hwang, DongKi; Tsukahara, Takehiko; Tanaka, Kosuke; Osaka, Masahiko; Ikeda, Yasuhisa

    2015-11-01

    In order to develop preparation method of raw metal oxide particles for low decontaminated MOX fuels by supercritical hydrothermal (SH) treatments, we have investigated behavior of aqueous solutions dissolving U(VI), Ln(III) (Ln: lanthanide = Ce, Pr, Nd, Sm, Tb), Cs(I), and Sr(II) nitrate or chloride compounds under SH conditions (temperature = 400-500 °C, pressure = 30-40 MPa). As a result, it was found that Ln(NO3)3 (Ln = Ce, Pr, Tb) compounds produce LnO2, that Ln(NO3)3 (Ln = Nd, Sm) compounds are hardly converted to their oxides, and that LnCl3 (Ln = Ce, Pr, Nd, Sm, Tb), CsNO3, and Sr(NO3)2 do not form their oxide compounds. Furthermore, HNO2 species were detected in the liquid phase obtained after treating HNO3 aqueous solutions containing Ln(NO3)3 (Ln = Ce, Pr, Tb) under SH conditions, and also NO2 and NO compounds were found to be produced by decomposition of HNO3. From these results, it was proposed that the Ln oxide (LnO2) particles are directly formed with oxidation of Ln(III) to Ln(IV) by HNO3 and HNO2 species in the SH systems. Moreover, the uranyl ions were found to form U3O8 and UO3 depending on the concentration of HNO3. From these results, it is expected that the raw metal oxide particles for low decontaminated MOX fuels are efficiently prepared by the SH method.

  8. (Ln = Pr, Nd, M = Nb, Ta)

    NASA Astrophysics Data System (ADS)

    Noked, O.; Melchior, A.; Shuker, R.; Steininger, R.; Kennedy, B. J.; Sterer, E.

    2014-06-01

    High-pressure X-ray diffraction measurements have demonstrated that the cation-deficient perovskites Pr1/3NbO3, Pr1/3TaO3, Nd1/3NbO3, and Nd1/3TaO3 undergo irreversible pressure-induced amorphization (PIA). This occurs near 14.5 GPa for the niobates and 18.5 GPa for the tantalates. The unit cell volumes of the four oxides show an almost linear decrease as the pressure is increased. It is concluded that the PIA transition occurs at higher pressures in the tantalates due to the lower MO6 initial tilting at ambient conditions, which is associated with the larger atomic mass of the tantalum. The behavior of these oxides is compared to that of CaTiO3, and the role of both the weakening of the M-O-M π-bonding and the cation vacancies on the observed structural changes is discussed.

  9. Synthesis and characterization of Ln(B{sub 0.5}Mn{sub 0.5})O{sub 3} (Ln-lanthanoid; B = Ni, Co) perovskites

    SciTech Connect

    Troyanchuk, I.O.; Samsonenko, N.V.; Shapovalova, E.F.; Szymczak, H.; Nabialek, A.

    1997-01-01

    The Ln(B{sub 0.5}Mn{sub 0.5})O{sub 3} (Ln-lanthanoid; B = Ni, Co) compounds with the orthorhombic perovskite structure have been prepared by a solid state reaction. They are ferromagnets with relatively high Curie temperatures. The Curie temperature decreases with decreasing average radii of the Ln-ion. It is shown that the Ln(Co{sub 0.5}Mn{sub 0.5})O{sub 3} (Ln = Gd, Tb, Dy, Y, Ho) are metamagnets.

  10. Water photolysis by the K2Ln2/3Ta2O7 and K2LnTa3O10 (Ln =La, Pr, Nd) tantalates

    NASA Astrophysics Data System (ADS)

    Valencia-Sanchez, Hoover; Negron-Mendoza, Alicia; Acosta-Najarro, Dwight; de La Mora, Pablo; Tavizon, Gustavo

    2014-03-01

    Six compounds of the hydrated phase of K2Ln2/3Ta2O7 and K2LnTa3O10 were prepared by the polymerizable complex method; these compounds were characterized in crystal structure, specific surface area (BET), optical band gap (DRS) and reactivity for water photolysis using a 300 W Hg-lamp. Tantalates containing La, Pr and Nd show a shift in the band gap value, from 3.8, 2.6 and 2.07 eV, respectively. Hydrogen production without co-catalyst has been observed, and no noticeable difference appears when NiOx was impregnated to powders. The hydrogen production notably increases when a sacrificial agent as methanol was used. In this work we compare the hydrogen production efficiencies for the bi-octahedral and three-octahedral tantalum hydrated compounds. This work is partially supported by grants from PAPIIT; IN 214313 and IN 113913.

  11. Synthesis, crystal and electronic structures, and magnetic properties of LiLn9Mo16O35 (Ln = La, Ce, Pr, and Nd) compounds containing the original cluster Mo16O36.

    PubMed

    Gougeon, Patrick; Gall, Philippe; Cuny, Jérôme; Gautier, Régis; Le Pollès, Laurent; Delevoye, Laurent; Trébosc, Julien

    2011-12-02

    The new compounds LiLn(9)Mo(16)O(35) (Ln=La, Ce, Pr, and Nd) were synthesized from stoichiometric mixtures of Li(2)MoO(4), Ln(2)O(3), Pr(6)O(11) or CeO(2), MoO(3), and Mo heated at 1600 °C for 48 h in a molybdenum crucible sealed under a low argon pressure. The crystal structure, determined from a single crystal of the Nd member, showed that the main building block is the Mo(16)O(36) unit, the Mo(16) core of which is totally new and results from the fusion of two bioctahedral Mo(10) clusters. It can also be viewed as a fragment of an infinite twin chain of edge-sharing Mo(6) octahedra. The Mo(16)O(36) cluster units share some oxygen atoms to form infinite chains running parallel to the b axis, which are separated by the rare-earth and lithium cations. (7)Li-NMR experiments, carried out at high field on the nonmagnetic LiLa(9)Mo(16)O(35), provided insights into the local environment of the lithium ions. Magnetic susceptibility measurements confirmed the trivalent oxidation state of the magnetic rare-earth cations and indicated the absence of localized moments on the Mo(16) clusters. The electronic structure of the LiLn(9)Mo(16)O(35) compounds was analyzed using molecular and periodic quantum calculations. The study of the molecular orbital diagrams of isolated Mo(16)O(36) models allowed the understanding of this unique metallic architecture. Periodic density functional theory calculations demonstrated that few interactions occur between the Mo(16) clusters, and predicted semiconducting properties for LiLn(9)Mo(16)O(35) as a band gap of 0.57 eV was computed for the lanthanum phase. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y).

    PubMed

    Liu, Z K; Yang, L X; Wu, S-C; Shekhar, C; Jiang, J; Yang, H F; Zhang, Y; Mo, S-K; Hussain, Z; Yan, B; Felser, C; Chen, Y L

    2016-09-27

    Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.

  13. Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)

    SciTech Connect

    Liu, Z. K.; Yang, L. X.; Wu, S. -C.; Shekhar, C.; Jiang, J.; Yang, H. F.; Zhang, Y.; Mo, S. -K.; Hussain, Z.; Yan, B.; Felser, C.; Chen, Y. L.

    2016-09-27

    Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.

  14. Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)

    NASA Astrophysics Data System (ADS)

    Liu, Z. K.; Yang, L. X.; Wu, S.-C.; Shekhar, C.; Jiang, J.; Yang, H. F.; Zhang, Y.; Mo, S.-K.; Hussain, Z.; Yan, B.; Felser, C.; Chen, Y. L.

    2016-09-01

    Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.

  15. Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)

    PubMed Central

    Liu, Z. K.; Yang, L. X.; Wu, S.-C.; Shekhar, C.; Jiang, J.; Yang, H. F.; Zhang, Y.; Mo, S.-K.; Hussain, Z.; Yan, B.; Felser, C.; Chen, Y. L.

    2016-01-01

    Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors. PMID:27671444

  16. Pressure dependence of Tc in LnFeAsO1-y (Ln = La, Ce, Nd, Tb)

    NASA Astrophysics Data System (ADS)

    Takeshita, N.; Miyazawa, K.; Iyo, A.; Furuta, S.; Mito, M.; Eisaki, H.

    2014-12-01

    We measured the temperature dependence of electrical resistivity of non-fluorine- substituted, oxygen-deficient LnFeAsO1-y (Ln = La, Ce, Nd, Tb) under hydrostatic high pressure up to '8 GPa in order to observe pressure dependence of superconducting transition temperature Tc. In LaFeAsO0.65, onset Tc initially enhances below 4 GPa, then decreases by applying further pressure. However, the zero-resistivity temperature does not show enhancement by applying pressure. In the case of NdFeAsO1-y and TbFeAsO1-y, Tc shows monotonic decrease as increasing pressure. Tc is much more likely to go down faster if Ln with small ionic size was taken. Therefore, the bulk superconductivity is suppressed finally at ~7 GPa in TbFeAsO0.7.

  17. Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)

    DOE PAGES

    Liu, Z. K.; Yang, L. X.; Wu, S. -C.; ...

    2016-09-27

    Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states onmore » these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.« less

  18. Method for synthesizing fine-grained phosphor powders of the type (RE.sub.1- Ln.sub.x)(P.sub.1-y V.sub.y)O.sub.4

    DOEpatents

    Phillips, Mark L. F.

    1998-01-01

    A method for generating well-crystallized photo- and cathodoluminescent oxide phosphor powders. The method of this invention uses hydrothermal synthesis and annealing to produce nearly monosized (RE.sub.1-x Ln.sub.x)(P.sub.1-y V.sub.y)O.sub.4 (Ln.dbd.Ce.fwdarw.Lu) phosphor grains with crystallite sizes from 0.04 to 5 .mu.m. Such phosphors find application in cathode-ray tube, flat-panel, and projection displays.

  19. Structural Studies of Layered Cuprates LnLn'CaBa_2Cu_2Ti_3O_14 (LnLn' = NdY, Tb2, TbY, Dy2 and DyY) by Neutron Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Hu, Z.; Jorgensen, J. D.; Short, S.; Otzschi, K. D.; Poeppelmeier, K. R.; Vander Griend, D.; Kane, M. H.

    1998-03-01

    In this presentation we report the neutron powder diffraction studies on several compounds in a new family of layered cuprates, LnLn'CaBa_2Cu_2Ti_3O_14 (LnLn' = NdY, Tb2, TbY, Dy2 and DyY). All compounds are found to crystallize in space group P 4/mmm. Strong site preferences of B-action (Cu and Ti) are observed in the NdY, Tb2 and TbY systems where Cu atoms strongly prefer 2g (0 0 0.084) sites. Due to the similar neutron scattering length of Nd, Tb, and Y, it is difficult to determine A-cation distributions in the NdY, Tb2 and TbY systems. In the DyY case, however, Dy atoms are found to strongly prefer site the 1 c (0.5 0.5 0) and do not mix with Y atoms on the (0.5 0.5 0.188) sites. The mechanism for these site preferences will be discussed. The oxygen content is found to be slightly different from the theoretical value for all compounds.

  20. Luminescent pillared Ln{sup III}–Zn{sup II} heterometallic coordination frameworks with two kinds of N-heterocyclic carboxylate ligands

    SciTech Connect

    Liu, Sui-Jun; Jia, Ji-Min; Cui, Yu; Han, Song-De; Chang, Ze

    2014-04-01

    In our efforts toward rational design and systematic synthesis of ‘pillar-layer’ structure coordination frameworks, four new Ln{sup III}–Zn{sup II} heterometallic coordination polymers (CPs) based on two kinds of N-heterocyclic carboxylic ligands with formula ([LnZn(L1){sub 2}(L2)(H{sub 2}O){sub m}]·nH{sub 2}O){sub ∞} (Ln=La (1), Eu (2), Gd (3) and Dy (4), m=3 (for 1) and 2 (for 2–4), n=8 (for 1) and 7 (for 2–4), H{sub 2}L1=pyridine-2,3-dicarboxylate acid, HL2=isonicotinic acid), have been synthesized under hydrothermal reaction of Ln{sub 2}O{sub 3}, ZnO, H{sub 2}L1 and HL2. CP 1 has a three-dimensional (3D) structure with a (3,6)-connected sit topology network, while CPs 2–4 are isostructural with 3D single-node pcu alpha-Po topology network. Also, luminescent properties of these CPs have also been investigated. The emission of 1 and 3 should be attributed to the coordination-perturbed ligand-centered luminescence and the emission spectra of 2 and 4 show the characteristic bands of the corresponding Ln{sup III} ions. - Graphical abstract: Four new 3D Ln{sup III}–Zn{sup II} coordination frameworks with “pillar-layer” sit or pcu alpha-Po topology have been successfully obtained. Moreover, the photoluminescent properties of compounds 1–4 have also been investigated. - Highlights: • Four new Ln{sup III}–Zn{sup II} heterometallic coordination frameworks with two types of topologies have been synthesized. • Metal oxides and two kinds of N-heterocyclic carboxylate ligands were used for the construction of targeted coordination polymers. • The luminescent properties of the coordination polymers are investigated.

  1. Luminescent LuVO4:Ln3+ (Ln = Eu, Sm, Dy, Er) hollow porous spheres for encapsulation of biomolecules

    NASA Astrophysics Data System (ADS)

    Li, Dan; Liu, Chunlei; Jiang, Lianzhou

    2015-10-01

    In this study, LuVO4:Ln3+ (Ln = Eu, Sm, Dy, Er) hollow porous spheres, synthesized via self-sacrificing templated route, are developed for enzyme immobilization and protein adsorption. The four LuVO4 hollow spheres with diameter of 180 nm, 280 nm, 370 nm and 480 nm were obtained. The size of LuVO4 hollow sphere is dependent on Lu(OH)CO3 template. Upon excitation by UV light, hollow LuVO4:Ln3+ (Ln = Eu, Sm, Dy, Er) spheres exhibit red (Eu3+), orange (Sm3+), yellow-green (Dy3+), and green (Er3+) emissions. The good biocompatibility of sample is validated by MTT assay. Due to structure feature and size of obtained sample, the rapid encapsulation of biomolecules within samples has been achieved. Furthermore, the hollow spheres show different biomolecules adsorption capacities at different buffer solution pH values. The release behaviors of two kinds of biomolecules (lysozyme and bovine serum albumin) are also investigated. LuVO4 hollow spheres are suitable carriers for biomolecules. The emission intensity of Eu3+ in the LuVO4:Eu3+ varies with the released amount of LYZ. This enables the monitoring of release process by the change in the luminescence intensity.

  2. Antiferromagnetic transitions of osmium-containing rare earth double perovskites Ba{sub 2}LnOsO{sub 6} (Ln=rare earths)

    SciTech Connect

    Hinatsu, Yukio Doi, Yoshihiro; Wakeshima, Makoto

    2013-10-15

    The perovskite-type compounds containing both rare earth and osmium Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm–Lu) have been prepared. Powder X-ray diffraction measurements and Rietveld analysis show that Ln{sup 3+} and Os{sup 5+} ions are structurally ordered at the M site of the perovskite BaMO{sub 3}. Magnetic susceptibility and specific heat measurements show that an antiferromagnetic ordering of Os{sup 5+} ions has been observed for Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm, Eu, Gd, Lu) at 65–71 K. Magnetic ordering of Ln{sup 3+} moments occurs when the temperature is furthermore decreased. - Graphical abstract: The perovskite-type compounds containing both rare earth and osmium Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm–Lu) have been prepared. An antiferromagnetic ordering of Os{sup 5+} ions has been observed for Ba{sub 2}LnOsO{sub 6} (Ln=Pr, Nd, Sm, Eu, Gd, Lu) at 65–71 K. Measurements and analysis of the specific heat for Ba{sub 2}PrOsO{sub 6} show that magnetic ordering of the Pr{sup 3+} moments should have occurred at ∼20 K. Display Omitted.

  3. Geometries, electronic and magnetic properties of dinitrogen adsorbed on lanthanide element LnN2 (Ln = La-Lu) systems: A density functional investigation

    NASA Astrophysics Data System (ADS)

    Zhao, Run-Ning; Chen, Rui; Sun, Shaoping; Zhang, Yan-Jun; Yuan, Yan-Hong

    2017-08-01

    Geometries, highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, and magnetic and electronic properties of LnN2 (Ln = La-Lu) systems are studied by using the density functional method with relativistic effect being taken into accounts. Interestingly, the optimized geometries exhibit that Rare earth Ln atom is favored of adsorptions of N2 with end-on or side-on form. According to the calculated magnetic moments of LnN2 (Ln = La-Lu), it is apparently shown that total magnetic moments mainly depend on the electrons filled in 4f orbitals which generates magnetic properties of LnN2 (Ln = La-Lu) clusters, GdN2 has the biggest magnetic moment. The calculated natural populations of LnN2 (Ln = La-Lu) systems show that the charges are transferred mainly from 6s2 to 5d orbitals. Most of 4f subshell in LnN2 is inert and hardly involves in chemical bonding, surprisingly, 4f orbitals of Pr atom involve in chemical bonding with N2 molecule.

  4. Structure and ionic conductivity of NaLnTiO{sub 4}: Comparison with those of Na{sub 2}Ln{sub 2}Ti{sub 3}O{sub 10} (Ln = La, Nd, Sm, and Gd)

    SciTech Connect

    Byeon, Song-Ho; Park, Kileung; Itoh, Mitsuru

    1996-02-01

    The crystal structures of NaLnTiO{sub 4} (Ln = La, Nd, Sm, and Gd) were determined by Rietveld refinements on their powder X-ray diffraction patterns. They had K{sub 2}NiF{sub 4}-type related superstructure (space group P4/nmm (D{sub 4h}{sup 7})) in which NaO and LnO double layers are 1:1 ordered perpendicular to the c axis. Although the c parameter decreases form Ln-La to Nd, Sm, and Gd, the Na-O distance along the c axis was not proportional to the variation of the unit cell parameter. A strong corrugation parameter was observed, which would be induced by the poor charge compensation between NaO and LnO layers. Due to such a corrugation, the a parameter did not show decreasing tendency despite the fact that the constituting lanthanide ion becomes smaller. Ionic conductivity of NaLnTiO{sub 4} lower than that of Na{sub 2}Ln{sub 2}Ti{sub 3}O{sub 10} (Ln = La, Nd, Sm, and Gd) also resulted from the corrugation of LnO layer with coordination number 9 accompanied by contraction of the NaO layer.

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

    SciTech Connect

    Doi, Yoshihiro Satou, Tatsuya; Hinatsu, Yukio

    2013-10-15

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

  6. Ultrafast Atomic Layer-by-Layer Oxygen Vacancy-Exchange Diffusion in Double-Perovskite LnBaCo2O5.5+δ Thin Films

    PubMed Central

    Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L.; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

    2014-01-01

    Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; −0.5 < δ < 0.5) by carefully monitoring the resistance changes under a switching flow of oxidizing gas (O2) and reducing gas (H2) in the temperature range of 250 ~ 800°C. A giant resistance change ΔR by three to four orders of magnitude in less than 0.1 s was found with a fast oscillation behavior in the resistance change rates in the ΔR vs. t plots, suggesting that the oxygen vacancy exchange diffusion with oxygen/hydrogen atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism. PMID:24751601

  7. Crystal growth, structure, and physical properties of Ln(Cu,Al)12 (Ln = Y, Ce, Pr, Sm, and Yb) and Ln(Cu, Ga)12 (Ln = Y, Gd-Er, and Yb).

    PubMed

    Drake, Brenton L; Capan, C; Cho, Jung Young; Nambu, Y; Kuga, K; Xiong, Y M; Karki, A B; Nakatsuji, S; Adams, P W; Young, D P; Chan, Julia Y

    2010-02-17

    Single crystals of Ln(Cu,Al)12 and Ln(Cu,Ga)12 compounds (Ln = Y, Ce-Nd, Sm, Gd-Ho, and Yb for Al and Ln = Y, Gd-Er, Yb for Ga) have been grown by flux-growth methods and characterized by means of single-crystal x-ray diffraction, complemented with microprobe analysis, magnetic susceptibility, resistivity and heat capacity measurements. Ln(Cu,Ga)12 and Ln(Cu,Al)12 of the ThMn12 structure type crystallize in the tetragonal I4/mmm space group with lattice parameters a approximately 8.59 Å and c approximately 5.15 Å and a approximately 8.75 Å and c approximately 5.13 Å for Ga and Al containing compounds, respectively. For aluminium containing compounds, magnetic susceptibility data show Curie-Weiss paramagnetism in the Ce and Pr analogues down to 50 K with no magnetic ordering down to 3 K, whereas the Yb analogue shows a temperature-independent Pauli paramagnetism. Sm(Cu,Al)12 orders antiferromagnetically at T(N)approximately 5 K and interestingly exhibits Curie-Weiss behaviour down to 10 K with no Van Vleck contribution to the susceptibility. Specific heat data show that Ce(Cu,Al)12 is a heavy fermion antiferromagnet with T(N) approximately 2 K and with an electronic specific heat coefficient γ0 as large as 390 mJ K2 mol(-1). In addition, this is the first report of Pr(Cu,Al)12 and Sm(Cu,Al)12 showing an enhanced mass (approximately 80 and 120 mJ K(2) mol(-1)). For Ga containing analogues, magnetic susceptibility data also show the expected Curie-Weiss behaviour from Gd to Er, with the Yb analogue being once again a Pauli paramagnet. The antiferromagnetic transition temperatures range over 12.5, 13.5, 6.7, and 3.4 K for Gd, Tb, Dy, and Er. Metallic behaviour is observed down to 3 K for all Ga and Al analogues. A large positive magnetoresistance up to 150% at 9 T is also observed for Dy(Cu,Ga)12. The structure, magnetic, and transport properties of these compounds will be discussed.

  8. Linear Dependence of Photoluminescence in Mixed Ln-MOFs for Color Tunability and Barcode Application.

    PubMed

    Yang, Qing-Yuan; Pan, Mei; Wei, Shi-Chao; Li, Kang; Du, Bin-Bin; Su, Cheng-Yong

    2015-06-15

    Multicolored photoluminescence tuning in a single-phase material has invaluable potential in display and security applications. By deliberate design of a multifunctional antenna ligand and precise control of mixed metal ionic compositions in lanthanide metal-organic frameworks (Ln-MOFs), we achieved dichromatic fine-tuning among red, green, or blue primary colors through growth of a series of isomorphous Ln-MOF crystals·solvents of formula [LnnLn'1-n(TTP)2·H2O]Cl3 (Ln = Ln' = Eu, Tb, and Gd, 1-3; Ln = Eu, Ln' = Tb, 4-8; Ln = Gd, Ln' = Eu, 9-11; Ln = Gd, Ln' = Tb, 12-14; 0 < n < 1; TTP = 1',1″-(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)tris(pyridine-4(1H)-one)). The linear dependence of the emissions were analyzed, and the mathematical matrix models were established, which are useful to control the synthetic conditions and to predict the color chromaticity coordinates under varied excitation wavelengths. The potential relevance of these multicolored photoluminescent Ln-MOFs to barcoded materials was demonstrated.

  9. Systematics and anomalies in rare earth/aluminum bromide vapor complexes: thermodynamic properties of the vapor complexes LnAl3Br12 from Ln = Sc to Ln = Lu.

    PubMed

    Wang, Zhi-Chang; Yu, Jin

    2007-05-14

    Systematics and anomalies in the rare earth/aluminum bromide vapor complexes have been investigated by the phase equilibrium-quenching experiments. The measurements suggest that the LnAl3Br12 complexes are the predominant vapor complexes for the 16 rare earth elements Ln = Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu in the temperature range 601-833 K and pressure range 0.01-0.22 MPa, which is different from the rare earth/aluminum chloride systems, where the predominant vapor complexes are LnAl3Cl12 from Ln = La to Ln = Lu, but LnAl2Cl9 for Ln = Sc and Y are roughly in the same ranges, which indicates the importance of the halogen anion radius on the rare earth vapor complex formation. In the temperature and pressure ranges, gaseous Al2Br6 and AlBr3 are dominant species and the molar fraction of LnAl3Br12 is normally less than 0.01. Thermodynamic functions of the reactions LnBr3(s) + (3/2)Al2Br6(g) = LnAl3Br12(g) were calculated from the measurements for the 16 rare earth elements and then smoothly interpolated for the radioelement Ln = Pm. The standard molar enthalpies and standard molar entropies show significant Gd divergences from LaAl3Br12 to LuAl3Br12 when plotted as functions of the rare earth atomic number. They also suggest nearly linear manner for ScAl3Br12, LuAl3Br12, YAl3Br12, and LaAl3Br12 when plotted as functions of the rare earth ionic radius.

  10. Synthesis and Photoluminescent Properties of Nanorod Bundle Ln4O(OH)9NO3:Eu(Ln = Y, Lu) Prepared by Hydrothermal Method.

    PubMed

    Li, Ling; Noh, Hyeon Mi; Liu, Xiaoguang; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun

    2015-07-01

    Well-crystallized nanorod bundles Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) have been successfully prepared by hydrothermal method. The crystalline phase, size and optical properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), infrared (IR) spectrograph and photoluminescent (PL) spectra. Site occupations of Eu3+ in crystals Ln4O(OH)9NO3:Eu(Ln = Y, Lu) were discussed based on excitation spectra and the empirical relationship formula between the charge transfer (CT) energy and the environmental factor. The emission spectra exhibited that the strongest emission peaks with an excitation wavelength of 395 nm were at 617 and 626 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, both of which come from 5D0-7F2 transition of the Eu3+ ions. The broad excitation peaks at about 254 and 255 nm were found when monitored at 617 and 628 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, which were due to O-Eu CT transition. Based on the dielectric theory of complex crystal, the CT bands at about 254 and 255 nm in Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) were assigned to the transition of O-Eu at Ln3(Ln = Y, Lu) site, from which we can conclude that Eu3+ ions occupied the site of Ln3(Ln = Y, Lu) in crystal Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu). It put forward a new route to investigate site occupation of luminescent center ions in rare earth doped complex inorganic luminescence materials.

  11. LN2 Dewar 42 Delivery Overfill Inlet Solution

    SciTech Connect

    Wu, J.; Mulholland, G.T.; /Fermilab

    1991-02-26

    Pressure vessels must be protected against overpressure scenarios. A scenario of particular concern is that from a high pressure LN2 pump, now standard on LN2 delivery trailers. A safety mechanism must be in place to prevent the overfilling, and subsequent overpressure from occurring because these pumps have a higher mass flow output than reasonably sized relief valves provide. The original solution to the problem was to close a valve on the fill line when a certain liquid level in the dewar is reached. The valve remains closed until the level drops below that threshold. The trigger level was about 13,000 gallons for the 20,000 gallon capacity dewar. The solution was in place from 1989 until present, 2004.

  12. The crystal structure and luminescence of Ce3+, Tb3+ and Eu3+ in KBaLn3+(BO3)2 [Ln3+ = Sc, Y, Lu, Gd

    NASA Astrophysics Data System (ADS)

    Camardello, S. J.; Her, J. H.; Toscano, P. J.; Srivastava, A. M.

    2015-11-01

    The structure of KBaLn3+(BO3)2 [Ln3+ = Sc, Lu, Gd] was solved by Rietveld refinement of the powder X-ray diffraction data. The materials crystallize with the mineral Buetschliite [K2Ca(CO3)2] structure. The lattice parameters of KBaLn3+(BO3)2 [Ln3+ = Sc, Lu, Gd] increased with increasing ionic radius of the Ln3+ cation. In this structure, the Ln3+ cations are octahedrally coordinated. The phase formation region is dependent on the ionic radii of the Ln3+ cation. The optical properties of Ce3+, Tb3+ and Eu3+ and their dependence on the host lattice composition are investigated and discussed. It is noteworthy that the optical properties of these ions are independent of the Ln3+ cation in KBaLn3+(BO3)2. It is concluded that in this family of materials, the crystalline field strength and the covalence at the rare earth site is independent of the host lattice composition.

  13. Studies on phase transition temperature of rare earth niobates Ln3NbO7 (Ln = Pr, Sm, Eu) with orthorhombic fluorite-related structure

    NASA Astrophysics Data System (ADS)

    Hinatsu, Yukio; Doi, Yoshihiro

    2017-06-01

    The phase transition of ternary rare earth niobates Ln3NbO7 (Ln = Pr, Sm, Eu) was investigated by the measurements of high-temperature and low-temperature X-ray diffraction, differential scanning calorimetry (DSC) and differential thermal analysis (DTA). These compounds crystallize in an orthorhombic superstructure derived from the structure of cubic fluorite (space group Pnma for Ln = Pr; C2221 for Ln = Sm, Eu). Sm3NbO7 undergoes the phase transition when the temperature is increased through ca. 1080 K and above the transition temperature, its structure is well described with space group Pnma. For Eu3NbO7, the phase transition was not observed up to 1273 K Pr3NbO7 indicates the phase transition when the temperature is increased through ca. 370 K. The change of the phase transition temperature against the Ln ionic radius for Ln3NbO7 is quite different from those for Ln3MO7 (M = Mo, Ru, Re, Os, or Ir), i.e., no systematic relationship between the phase transition temperature and the Ln ionic radius has been observed for Ln3NbO7 compounds.

  14. Dual shell-like magnetic clusters containing Ni(II) and Ln(III) (Ln = La, Pr, and Nd) ions.

    PubMed

    Kong, Xiang-Jian; Ren, Yan-Ping; Long, La-Sheng; Zheng, Zhiping; Nichol, Gary; Huang, Rong-Bin; Zheng, Lan-Sun

    2008-04-07

    Dual shell-like nanoscopic magnetic clusters featuring a polynuclear nickel(II) framework encapsulating that of lanthanide ions (Ln = La, Pr, and Nd) were synthesized using Ni(NO3)(2).6H2O, Ln(NO3)(3).6H2O, and iminodiacetic acid (IDA) under hydrothermal conditions. Structurally established by crystallographic studies, these clusters are [La20Ni30(IDA)30(CO3)6(NO3)6(OH)30(H2O)12](CO3)(6).72H2O (1), [Ln20Ni21(C4H5NO4)21(OH)24(C2H2O3)6(C2O4)3(NO3)9(H2O)12](NO3)9.nH2O [C2H2O3 is the alkoxide form of glycolate; Ln = Pr (2), n = 42; Nd (3), n = 50], and {[La4Ni5Na(IDA)5(CO3)(NO3)4(OH)5(H2O)5][CO3].10H2O} infinity (4). Carbonate, oxalate, and glycolate are products of hydrothermal decomposition of IDA. Compositions of these compounds were confirmed by satisfactory elemental analyses. It has been found that the cluster structure is dependent on the identity of the lanthanide ion as well as the starting Ln/Ni/IDA ratio. The cationic cluster of 1 features a core of the Keplerate type with an outer icosidodecahedron of Ni(II) ions encaging a dodecahedral kernel of La(III). Clusters 2 and 3, distinctly different from 1, are isostructural, possessing a core of an outer shell of 21 Ni(II) ions encapsulating an inner shell of 20 Ln(III) ions. Complex 4 is a three-dimensional assembly of cluster building blocks connected by units of Na(NO3)/La(NO3)3; the structure of the building block resembles closely that of 1, with a hydrated La(III) ion internalized in the decanuclear cage being an extra feature. Magnetic studies indicated ferromagnetic interactions in 1, while overall antiferromagnetic interactions were revealed for 2 and 3. The polymeric, three-dimensional cluster network 4 displayed interesting ferrimagnetic interactions.

  15. Crystal growth of a series of lithium garnets Ln3Li 5Ta 2O 12 ( Ln=La, Pr, Nd): Structural properties, Alexandrite effect and unusual ionic conductivity

    NASA Astrophysics Data System (ADS)

    Roof, Irina P.; Smith, Mark D.; Cussen, Edmund J.; zur Loye, Hans-Conrad

    2009-02-01

    We report the single crystal structures of a series of lanthanide containing tantalates, Ln3Li 5Ta 2O 12 ( Ln=La, Pr, Nd) that were obtained out of a reactive lithium hydroxide flux. The structures of Ln3Li 5Ta 2O 12 were determined by single crystal X-ray diffraction, where the Li + positions and Li + site occupancies were fixed based on previously reported neutron diffraction data for isostructural compounds. All three oxides crystallize in the cubic space group Ia3¯d (No. 230) with lattice parameters a=12.7735(1), 12.6527(1), and 12.5967(1) Å for La 3Li 5Ta 2O 12, Pr 3Li 5Ta 2O 12, and Nd 3Li 5Ta 2O 12, respectively. A UV-Vis diffuse reflectance spectrum of Nd 3Li 5Ta 2O 12 was collected to explain its unusual Alexandrite-like optical behavior. To evaluate the transport properties of Nd 3Li 5Ta 2O 12, the impedance data were collected in air in the temperature range 300⩽ T(°C)⩽500.

  16. Structural chemistry and magnetic properties of LnMnFeGe4O12 (Ln = Y, Eu, Lu)

    NASA Astrophysics Data System (ADS)

    Xu, Diming; Avdeev, Maxim; Battle, Peter D.; Cadogan, J. M.; Lamont, Henry

    2017-10-01

    Polycrystalline samples of LnMnFeGe4O12 (Ln = Y, Eu, Lu) have been prepared using the ceramic method and characterised by a combination of magnetometry, Mössbauer spectroscopy, X-ray diffraction and neutron diffraction. They all adopt the space group P4/nbm with a 9.670, c 4.81 Å and show long-range antiferromagnetic order with transition temperatures 15 ≤ TN/K ≤ 17. The magnetic structure is the same in each case and consists of an A-type ordering of (001) planes; the ordered spins lie in the (001) plane. Comparison with isostructural compounds leads to the conclusion that subtle structural changes play a greater role than the electronic configuration of the cation in determining the magnetic structure.

  17. Single crystal synthesis and magnetism of the BaLn2O4 family (Ln = lanthanide)

    DOE PAGES

    Besara, Tiglet; Lundberg, Matthew S.; Sun, Jifeng; ...

    2014-05-27

    The series of compounds in the BaLn2O4 family (Ln = La–Lu, Y) has been synthesized for the first time in single crystalline form, using a molten metal flux. The series crystallizes in the CaV2O4 structure type with primitive orthorhombic symmetry (space group Pnma, #62), and a complete structural study of atomic positions, bonds, angles, and distortions across the lanthanide series is presented. With the exception of the Y, La, Eu, and Lu members, magnetic susceptibility measurements were performed between 2 K and 300 K. BaCe2O4 and BaYb2O4 display large crystal fields effects and suppression of magnetic ordering. As a result,more » all compounds show signs of magnetic frustration due to the trigonal arrangements of the trivalent lanthanide cations in the structure.« less

  18. Chemical Substitution and High Pressure Effects on Superconductors in the LnOBiS$_2$ (Ln = La-Nd) System

    SciTech Connect

    Fang, Yuankan; Wolowiec, Christian T.; Yazici, Duygu; Maple, M. Brian

    2015-12-14

    A large number of compounds which contain BiS$_2$ layers exhibit enhanced superconductivity upon electron doping. Much interest and research effort has been focused on BiS$_2$-based compounds which provide new opportunities for exploring the nature of superconductivity. Important to the study of BiS2-based superconductors is the relation between structure and superconductivity. By modifying either the superconducting BiS$_2$ layers or the blocking layers in these layered compounds, one can effectively tune the lattice parameters, local atomic environment, electronic structure, and other physical properties of these materials. In this article, we will review some of the recent progress on research of the effects of chemical substitution in BiS$_2$-based compounds, with special attention given to the compounds in the LnOBiSS$_2$ (Ln = La-Nd) system. Strategies which are reported to be essential in optimizing superconductivity of these materials will also be discussed.

  19. Formation and Fragmentation Chemistry of Tripositive Ln(TMGA)3 3+ Complexes in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Chen, Xiuting; Li, Qingnuan; Gong, Yu

    2017-08-01

    Electrospray ionization (ESI) of LnCl3 (Ln = La-Lu except Pm) and TMGA (tetramethyl glutaramide) mixtures resulted in the formation of gas-phase Ln(TMGA)3 3+ complexes, where tripositive lanthanide cation was coordinated by three neutral TMGA ligands. Collision induced dissociation (CID) was employed to investigate the fragmentation chemistry of these tripositive complexes. Ln(TMGA)2(TMGA- 45)3+ resulting from Ccarbonyl-N bond cleavage of TMGA and hydrogen transfer is the major CID product for all Ln(TMGA)3 3+ except Eu(TMGA)3 3+ which predominantly forms divalent EuII(TMGA)2 2+ complex via loss of TMGA+. Analogous YbII(TMGA)2 2+ and SmII(TMGA)2 2+ complexes arising from charge reduction were also observed, in competition with the formation of charge conserving YbIII(TMGA)(TMGA-H)2+ and SmIII(TMGA)(TMGA-H)2+ products. The yield of these charge reducing products follows their reduction potentials in condensed phase. In addition to Ln(TMGA)3 3+, tripositive ions such as Ln(TMGA)4 3+ and Ln(TMGA)2 3+ were experimentally identified as well. While the former was observed along with Ln(TMGA)3 3+ during ESI, the latter was observed upon CID of Ln(TMGA)3 3+, suggesting two TMGA molecules can stabilize Ln3+ in the gas phase.

  20. Anisotropy and hysteresis of transport critical currents in high temperature Ln-Y-Ba-Cu-O superconductors

    NASA Astrophysics Data System (ADS)

    Watanabe, K.; Noto, K.; Morita, H.; Fujimori, H.; Mizuno, K.; Aomine, T.; Ni, B.; Matsushita, T.; Yamafuji, K.; Muto, Y.

    1989-03-01

    Following the measurements of anisotropy and hysteresis in transport critical currents with changing temperature and polarity of magnetic field, a.c. magnetic measurements by the Campbell method were performed for sintered Ln-Y-Ba-Cu-O superconductors. The information derived from them indicated that hysteresis does not occur in the intragrain current but in the intergrain one. The results are interpreted in terms of flux pinning, where the anisotropy originates from the texture structure and hysteresis is associated with the superconducting weak links of the sintered oxide pellets.

  1. Lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals: Synthesis, characterization, and photocatalytic properties

    SciTech Connect

    Wang, Wanjun; Liang, Shijing; Bi, Jinhong; Yu, Jimmy C.; Wong, Po Keung; Wu, Ling

    2014-08-15

    Highlights: • Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) are synthesized by hydrothermal method. • Light absorption edge shows red shift with decreasing Ln{sup 3+} radius from Nd{sup 3+} to Yb{sup 3+}. • Ln{sub 2}Sn{sub 2}O{sub 7} shows increasing photocatalytic activity with the decease of Ln{sup 3+} radius. • Electronic configuration reaches 4f{sup 14} under light irradiation may decrease photocatalytic activity. • Hydroxyl radicals are detected to be the major reactive species. - Abstract: A series of lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals have been successfully synthesized via a facile hydrothermal route. With the decrease of Ln{sup 3+} radius, the light absorption edge of the as-prepared Ln{sub 2}Sn{sub 2}O{sub 7} shows a red shift from Nd{sup 3+} to Yb{sup 3+}. Their photocatalytic activities are found to be improved with the decrease of Ln{sup 3+} radius. However, the photocatalytic activity of Yb{sub 2}Sn{sub 2}O{sub 7} is a little lower than Er{sub 2}Sn{sub 2}O{sub 7}, although the Yb{sup 3+} radius is smaller than Er{sup 3+}, which may be attributed to the full-filled electronic configuration (4f{sup 14}) of surface Yb{sup 2+} intermediates (formed by Yb{sup 3+} trapping a photo-excited electron). The crystallite size and surface area play the most important role in determining the activities. Furthermore, hydroxyl radicals are detected to be the major reactive species during the photo-degradation process. Our findings provide insights in the fabrication of highly efficient stannate photocatalysts, thus enlarging the family of photocatalysts available.

  2. Structure and stability of the low-temperature modification compounds Cs[sub 3]LnCl[sub 6] (Ln = La-Gd)

    SciTech Connect

    Seifert, H.J.; Fink, H. ); Baumgartner, B. )

    1993-11-01

    The crystal structure of the low-temperature modification of Cs[sub 3]LaCl[sub 6] has been determined from X-ray powder diffraction data by the Rietveld method. The monoclinic lattice with a = 27.286(5) [angstrom]; b = 8.291(1) [angstrom]; c = 13.305(2) [angstrom]; [beta] = 99.64(1)[degrees] belongs to the Cs[sub 3]BiCl[sub 6]-type (space group C2/c). All other compounds Cs[sub 3]LnCl[sub 6] (Ln = Gd) and the analogous Rb-compounds are isotypic. Emf measurements in a galvanic cell for solid electrolytes for the reactions CsCl + Cs[sub 2]LnCl[sub 5] = Cs[sub 3]LnCl[sub 6] reveal that the compounds with Ln = La,Ce,Pr,Nd are formed with a loss of lattice enthalpy, compensated by a considerable gain in entropy; they therefore are stable only at temperatures higher than O K. The compounds with Ln = Sm,Eu,Dg are formed with a gain in lattice enthalpy and are stable at T = OK, too. This difference is attributed to the different crystal structures of the neighboring compounds Cs[sub 2]LnCl[sub 5]: they crystallize with the K[sub 2]PrCl[sub 5]-structure (CN = 7 for Ln[sup 3+]) for the compounds with Ln = La-Nd, while the other compounds belong to the Cs[sub 2]DyCl[sub 5]-type with octahedral surroundings for the Ln[sup 3+] ions.

  3. A structural study of the CaLn2CuTi2O9 (Ln = Pr, Nd, Sm) and BaLn2CuTi2O9 (Ln =La, Pr, Nd) triple perovskite series

    NASA Astrophysics Data System (ADS)

    Iturbe-Zabalo, E.; Igartua, J. M.; Aatiq, A.; Pomjakushin, V.

    2013-02-01

    The new ALn2CuTi2O9 (A = Ca, Ba; Ln = La, Pr, Nd, Sm) series have been synthesized and the structures have been characterized by X-ray and neutron powder diffraction techniques. The whole series show a cationic disordered distribution over the A- and B-sites of the perovskite structure. CaLn2CuTi2O9 samples are isostructural, crystallizing at room temperature in an orthorhombic cell with space group Pbnm (ITA No. 62); and BaLn2CuTi2O9 samples in the tetragonal I4/mcm (ITA No. 140) space group. The homovalent substitution of a larger lanthanide cation leads to an increase in the unite-cell volume, but a decrease in the Cu/TiO6 octahedra tilting. By comparing the room temperature symmetry structure with an archetype (Pm3¯m, ITA, No. 221) phase of Pbnm or I4/mcm symmetry, two distortion modes R4+ and M3+ were found to be dominant for the orthorhombic phase; whereas for tetragonal phase there is a unique active mode, R4+. They correspond to Cu/TiO6 octahedron tilt modes, commonly found in many perovskite type materials. The high temperature study for CaLa2CuTi2O9, CaNd2CuTi2O9 and CaSm2CuTi2O9 materials (300-1670 K) showed that the room temperature Pbnm orthorhombic symmetry seems to be stable up to 1475 K; and irreversible phase transition is observed above that temperature.

  4. Nd2K2IrO7 and Sm2K2IrO7: Iridium(VI) Oxides Prepared under Ambient Pressure

    SciTech Connect

    Mugavero, III, S.; Smith, M; Yoon, W; zur Loye, H

    2009-01-01

    The most-oxidized iridium oxides known to date are prepared in a hydroxide flux under normal pressure. They contain iridium centers exclusively in the +VI oxidation state and are characterized crystallographically. The picture shows the structure of the Ln2K2IrO7 (Ln=Nd, Sm) and its structural components: IrO6 octahedra (black), KO10 polyhedra (beige), LnO10 polyhedra (blue).

  5. Sonochemical synthesis of highly luminescent Ln2O3:Eu3+ (Y, La, Gd) nanocrystals

    SciTech Connect

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

    2015-05-12

    In this study, sonication of Ln(CH3COO)3·H2O, Eu(CH3COO)3·H2O and NaOH dissolved in the ionic liquid-butyl-3-methylimidazolium bis(trifluoromethane)sulfonylamide lead to Ln(OH)3:Eu (Ln: Gd, La, Y) nanoparticles. Subsequent calcination at 800 °C for 3 h allowed to obtain Ln2O3:Eu nanopowders. Gd2O3 and Y2O3 were obtained in the C-type lanthanide sequioxide structure, whereas La2O3 crystallized in the A-type. Structure, morphology, and luminescent properties of the nano-oxides were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), dispersive X-ray (EDX), and photoluminescence (PL). SEM studies revealed that the synthesized Gd2O3:Eu, La2O3:Eu, and Y2O3:Eu formed nano-spindle, -sheets, and -rods in shape, respectively. The nanoscale materials show very efficient red emission due to the intraconfigurational f–f transitions of Eu3+. The quantum yields for Ln2O3:Eu (5%) were determined to be 4.2% for Ln=Gd, 13.8% for Ln=Y and 5.2% for Ln=La. The asymmetric ratio I02/I01 of Eu3+ varies from 5.3 for Gd2O3, to 5.6 for Y2O3 to 6.5 for La2O3, which increased the color chromaticity.

  6. Rhombus-shaped tetranuclear [Ln4] complexes [Ln = Dy(III) and Ho(III)]: synthesis, structure, and SMM behavior.

    PubMed

    Chandrasekhar, Vadapalli; Hossain, Sakiat; Das, Sourav; Biswas, Sourav; Sutter, Jean-Pascal

    2013-06-03

    The reaction of a new hexadentate Schiff base hydrazide ligand (LH3) with rare earth(III) chloride salts in the presence of triethylamine as the base afforded two planar tetranuclear neutral complexes: [{(LH)2Dy4}(μ2-O)4](H2O)8·2CH3OH·8H2O (1) and [{(LH)2Ho4}(μ2-O)4](H2O)8·6CH3OH·4H2O (2). These neutral complexes possess a structure in which all of the lanthanide ions and the donor atoms of the ligand remain in a perfect plane. Each doubly deprotonated ligand holds two Ln(III) ions in its two distinct chelating coordination pockets to form [LH(Ln)2](4+) units. Two such units are connected by four [μ2-O](2-) ligands to form a planar tetranuclear assembly with an Ln(III)4 core that possesses a rhombus-shaped structure. Detailed static and dynamic magnetic analysis of 1 and 2 revealed single-molecule magnet (SMM) behavior for complex 1. A peculiar feature of the χM" versus temperature curve is that two peaks that are frequency-dependent are revealed, indicating the occurrence of two relaxation processes that lead to two energy barriers (16.8 and 54.2 K) and time constants (τ0 = 1.4 × 10(-6) s, τ0 = 7.2 × 10(-7) s). This was related to the presence of two distinct geometrical sites for Dy(III) in complex 1.

  7. A Study of the Magnetic and Thermal Properties of Ln

    SciTech Connect

    Harada, Daijitsu; Hinatsu, Yukio

    2001-05-01

    Crystal structures, and magnetic, electric, and thermal properties of fluorite related compounds Ln{sub 3}RuO{sub 7} (Ln=Sm, Eu) have been investigated. For Eu{sub 3}RuO{sub 7}, a magnetic transition due to Ru{sup 5+} ions is found at T{sub N}=22.5 K on the susceptibility-temperature curve. Specific heat measurements also exhibit a {lambda}-type anomaly at the same temperature. The Moessbauer spectrum measured at 10 K shows broadening of the line corresponding to magnetic splitting. For Sm{sub 3}RuO{sub 7}, two magnetic anomalies have been observed at 10.5 and 22.5 K from its magnetic susceptibility measurements. Below 22.5 K Ru{sup 5+} ions are antiferromagnetically coupled, and when the temperature is decreased through 10.5 K the ordering of Sm{sup 3+} ions occurs rapidly. Specific heat measurements show first-order transition peaks at T=280 and 190 K for Eu{sub 3}RuO{sub 7} and Sm{sub 3}RuO{sub 7}, respectively. T he results of magnetic susceptibility and electric resistivity measurements indicate that these transitions are structural phase transitions.

  8. Enhanced visible light-responsive photocatalytic activity of LnFeO{sub 3} (Ln = La, Sm) nanoparticles by synergistic catalysis

    SciTech Connect

    Li, Li; Wang, Xiong; Zhang, Yange

    2014-02-01

    Highlights: • LnFeO{sub 3} (Ln = La, Sm) nanoparticles were prepared by a facile sol–gel method. • The samples exhibit superior visible-light-responsive photocatalytic activity. • Synergistic effect will enhance the photodegradation of RhB under visible light. - Abstract: LnFeO{sub 3} (Ln = La, Sm) nanoparticles were prepared by a facile sol–gel method with assistance of glycol at different calcination temperatures. The as-synthesized LnFeO{sub 3} was characterized by X-ray diffraction, transmission electron microscopy, differential scanning calorimeter and thermogravimetric analysis, and UV–vis absorption spectroscopy. The photocatalytic behaviors of LnFeO{sub 3} nanoparticles were evaluated by photodegradation of rhodamine B under visible light irradiation. The results indicate that the visible light-responsive photocatalytic activity of LnFeO{sub 3} nanoparticles was enhanced remarkably by the synergistic effect between the semiconductor photocatalysis and Fenton-like reaction. And a possible catalytic mechanism was also proposed based on the experimental results.

  9. Superconducting Critical Temperature of Overdoped LnBa2Cu3Oy+Δy (Ln=La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb)

    NASA Astrophysics Data System (ADS)

    Okai, Bin; Ono, Akira

    1999-09-01

    A series of overdoped LnBa2Cu3Oy+Δy (Ln=La˜Yb) was synthesized at high oxygen pressure for investigating the relationship between the superconducting critical temperature Tc, overdoping oxygen content Δy, and Ln. Tc of 1-2-3 compound LnBa2Cu3Oy+Δy remains almost unchanged through various levels of overdoping for small ionic radii of Ln. As the ionic radus of Ln increases, Tc decreases with the level of overdoping. The decrease changes systematically from EuBa2Cu3Oy+Δy to LaBa2Cu3Oy+Δy; the decrease for LaBa2Cu3Oy+Δy is the steepest. Tc is also reduced probably by the mixing of Ln and Ba, as observed in NdBa2Cu3Oy+Δy and LaBa2Cu3Oy+Δy.

  10. Synthesis, structure, magnetic and transport properties of LnFeSb3 (Ln = Pr, Nd, Sm, Gd, and Tb)--tuning of anisotropic long-range magnetic order as a function of Ln.

    PubMed

    Phelan, W Adam; Nguyen, Giang V; Karki, Amar B; Young, David P; Chan, Julia Y

    2010-07-28

    Single crystals of LnFeSb(3) (Ln = Pr, Nd, Sm, Gd, and Tb) have been grown from excess Sb flux. The crystal structure consists of (infinity)(2)[FeSb(2)] octahedra separated by layers of Ln atoms and nearly square planar nets of (infinity)(2)[Sb(2)]. These compounds are metallic and display anisotropic magnetic properties. Long-range antiferromagnetic order is observed in the Sm, Gd, and Tb samples when the magnetic field is applied along the crystallographic a-axis. Evidence of magnetic ordering in all the samples is observed for the field applied parallel to the layers. The magnetic properties are well-described by considering only the magnetic interactions between the Ln 4f moments, with no contribution from the Fe sublattice. Herein, we report the crystal growth, structure, magnetization, transport, and chemical stabilities of the title compounds.

  11. Tetradecanuclearity in 3d-4f chemistry: relaxation and magnetocaloric effects in [NiLn] species.

    PubMed

    Canaj, Angelos B; Kalofolias, Dimitris A; Siczek, Milosz; Lis, Tadeusz; McNab, Robbie; Lorusso, Giulia; Inglis, Ross; Evangelisti, Marco; Milios, Constantinos J

    2017-03-14

    The employment of 2-amino-isobutyric acid, Haib, and 2-hydroxy-1-naphthaldehyde, Hnaphth, in Ni(II)/Ln(III) chemistry has led to the isolation and characterization of two new isostructural 3d-4f tetradecanuclear [NiLn] clusters (Ln = Gd(III), Dy(III)), with the Dy analogue displaying temperature and frequency dependent out-of-phase signals, and the Gd analogue showing interesting magnetocaloric properties.

  12. Synthesis, properties and phase transitions of pyrochlore- and fluorite-like Ln{sub 2}RMO{sub 7} (Ln = Sm, Ho; R = Lu, Sc; M = Nb, Ta)

    SciTech Connect

    Shlyakhtina, A.V.; Belov, D.A.; Pigalskiy, K.S.; Shchegolikhin, A.N.; Kolbanev, I.V.; Karyagina, O.K.

    2014-01-01

    Graphical abstract: Temperature dependences of bulk conductivity for Sm{sub 2}ScTaO{sub 7} pyrochlore prepared at (1) 1400 °C, 20 h; and (2) 1200 °C, 40 h. - Highlights: • The phase formation of Ln{sub 2}RMO{sub 7} (Ln = Sm, Ho; R = Lu, Sc; M = Nb, Ta) at 1200–1600 °C. • The bulk conductivity and magnetic susceptibility were measured. • The bulk conductivity of Sm{sub 2}ScTaO{sub 7} has oxygen ion type at T ≥ 750 °C. • The first-order structural phase transition was observed in Sm{sub 2}ScTaO{sub 7} at ∼650–700 °C. • This phase transformation is not typical for defect fluorites. - Abstract: We have studied the new compounds with fluorite-like (Ho{sub 2}RNbO{sub 7} (R = Lu, Sc)) and pyrochlore-like (Sm{sub 2}ScTaO{sub 7}) structure as potential oxide ion conductors. The phase formation process (from 1200 to 1600 °C) and physical properties (electrical, thermo mechanical, and magnetic) for these compounds were investigated. Among the niobate materials the highest bulk conductivity is offered by the fluorite-like Ho{sub 2}ScNbO{sub 7} synthesized at 1600 °C: 3.8 × 10{sup −5} S/cm at 750 °C, whereas in Sm system the highest bulk conductivity, 7.3 × 10{sup −6} S/cm at 750 °C, is offered by the pyrochlore Sm{sub 2}ScTaO{sub 7} synthesized at 1400 °C. In Sm{sub 2}ScTaO{sub 7} pyrochlore we have observed the first-order phase transformation at ∼650–700 °C is related to rearrangement process in the oxygen sublattice of the pyrochlore structure containing B-site cations in different valence state and actually is absent in the defect fluorites. The two holmium niobates show Curie–Weiss paramagnetic behavior, with the prevalence of antiferromagnetic coupling. The magnetic susceptibility of Sm{sub 2}ScTaO{sub 7} is a weak function of temperature, corresponding to Van Vleck paramagnetism.

  13. A quantum chemistry investigation on the structure of lanthanide triflates Ln(OTf)3 where Ln = La, Ce, Nd, Eu, Gd, Er, Yb and Lu.

    PubMed

    Hannachi, Douniazed; Ouddai, Nadia; Chermette, Henry

    2010-04-21

    Density functional theory has been used to probe the electronic structure, coordination number, optical properties and the vibration spectra of monolanthanide trifluoromethane sulfonate Ln(OTf)(3) complexes where Ln = La, Ce, Nd, Eu, Gd, Er, Yb and Lu. The study reveals that the OTf group is bonded to Ln as a bidentate ligand. TDDFT calculations show that, for La(OTf)(3), MLTC and HOMO-LUMO transitions in the UV-vis are strongly bathochromically shifted compared to those of Lu(OTf)(3.).

  14. Deliverable for FαST project: Ln Resin based PLE

    SciTech Connect

    Peterson, Dominic S.; Armenta, Claudine E.; Rim, Jung H.

    2012-05-03

    This memo describes the fabrication of a polymer ligand extractant based on Eichrom's LN-1 resin. This work has been in support of the Fast Alpha Spectrometry Tool (F{alpha}ST) project. The first part of LANL's role in this project is to evaluate new extractants for use in polymer ligand extractants (PLEs). The first new extractant evaluated is Di(2-ethyl hexyl) phosphoric acid (HDEHP), which is an effective metal extractant. It has very efficient chelating properties for a wide variety of metal ions. HDEHP is an amphiphillic molecule with two long hydrocarbon chains and a polar end with a phosphoryl oxygen (P=O) and an acidic -OH group as shown in Figure 1. HDEHP has shown effectiveness in extracting lanthanides, selective actinides, and other trivalent elements. Several authors have reported that lanthanides and elements with +3 oxidation state have similar extraction behavior in nitric acid. The distribution ratio for lanthanides rapidly decreases at lower nitric concentration then start to increase at higher concentration as shown in. The trivalent americium, curium, and yttrium exhibit similar trend as trivalent lanthanides. This extraction trend can be also observed from hydrogen chloride solution. This work describes the use of this ligand in a PLE to extract plutonium from solution. Polymer ligand films were prepared by dissolving HDEHP ligands and polystyrene beads in THF. The solution was directly deposited onto a 40 mm diameter stainless steel substrate using an automated pipette. HDEHP based PLEs with direct stippling method are shown in Figure 2. The solution was air dried at room temperature overnight to ensure complete evaporation of THF. The plutonium tracer solution was prepared in 0.01, 0.1, 1, and 8M nitric solutions to study the effect of nitric concentration in plutonium extraction. 0.1667 Bq {sup 239}Pu tracer solution was directly stippled on each PLE and was allowed to equilibrate for 3 hours before removing the solution. The plutonium

  15. Structure and bulk modulus of Ln-doped UO2 (Ln = La, Nd) at high pressure

    DOE PAGES

    Rittman, Dylan R.; Park, Sulgiye; Tracy, Cameron L.; ...

    2017-04-10

    The structure of lanthanide-doped uranium dioxide, LnxU1-xO2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ~50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ~ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ~ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius ofmore » the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. As a result, this trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO2, such as Young's modulus.« less

  16. Chemical Substitution and High Pressure Effects on Superconductors in the LnOBiS$$_2$$ (Ln = La-Nd) System

    DOE PAGES

    Fang, Yuankan; Wolowiec, Christian T.; Yazici, Duygu; ...

    2015-12-14

    A large number of compounds which contain BiSmore » $$_2$$ layers exhibit enhanced superconductivity upon electron doping. Much interest and research effort has been focused on BiS$$_2$$-based compounds which provide new opportunities for exploring the nature of superconductivity. Important to the study of BiS2-based superconductors is the relation between structure and superconductivity. By modifying either the superconducting BiS$$_2$$ layers or the blocking layers in these layered compounds, one can effectively tune the lattice parameters, local atomic environment, electronic structure, and other physical properties of these materials. In this article, we will review some of the recent progress on research of the effects of chemical substitution in BiS$$_2$$-based compounds, with special attention given to the compounds in the LnOBiSS$$_2$$ (Ln = La-Nd) system. Strategies which are reported to be essential in optimizing superconductivity of these materials will also be discussed.« less

  17. Effect of LN2 injection station location on the drive fan power and LN2 requirements of a cryogenic wind tunnel

    NASA Technical Reports Server (NTRS)

    Adcock, J. B.

    1977-01-01

    A theoretical analysis comparing the fan power and coolant (LN2) flow rates resulting from injection of the LN2 either upstream or downstream of the drive fan of a closed circuit transonic cryogenic tunnel is presented. The analysis is restricted to steady state tunnel operation and to the condition that the tunnel walls are adiabatic. The stagnation pressure and temperature range of the tunnel is from 1.0 to 8.8 atm and from 300 K to liquefaction temperature, respectively. Calculations are made using real gas properties of nitrogen. Results show that the fan power and LN2 flow rates are lower if the LN2 is injected upstream of the fan. The lower fan inlet temperature resulting from injecting upstream of the fan has a greater influence on the power than does the additional mass flow going through the fan.

  18. Effect of inclining strain on the crystal lattice along an extended series of lanthanide hydroxysulfates Ln(OH)SO4 (Ln = Pr-Yb, except Pm).

    PubMed

    Zehnder, Ralph A; Wilson, Christopher S; Christy, Hunter T; Harris, Kenneth S; Chauhan, Varun; Schutz, Victor; Sullivan, Matthew; Zeller, Matthias; Fronczek, Frank R; Myers, Jacob A; Dammann, Kyle; Duck, James; Smith, Peter M; Okuma, Antony; Johnson, Kristin; Sovesky, Robert; Stroudt, Cameron; Renn, Robert A

    2011-02-07

    A series of trivalent lanthanide hydroxysulfates, Ln(OH)SO(4), (Ln = Pr through Yb, except radioactive Pm) has been synthesized via hydrothermal methods from Ln(2)(SO(4))(3)·8H(2)O by reaction with aqueous NaOH at 170 °C in Teflon lined Parr steel autoclaves, and were characterized by single crystal X-ray diffraction and FT-IR spectroscopy. Two types of arrangements were found in the solid state. The lighter (Ln = Pr-Nd, Sm-Gd) and heavier lanthanide(III) hydroxysulfates (Tb-Yb) are each isostructural. Both structure types exhibit the monoclinic space group P2(1)/n, but the unit cell content is doubled with two crystallographically distinct LnO(8) polyhedra for the heavier lanthanide compounds. The lighter complexes maintain the coordination number 9, forming a three-dimensional extended lattice. The heavier counterparts exhibit the coordination number 8, and arrange as infinite columns of two crystallographically different LnO(8) polyhedra, while extending along the "c" axis. These columns of LnO(8) polyhedra are surrounded and separated by six columns of sulfate ions, also elongating in the "c" direction. The rigid sulfate entities seem to obstruct the closing in of the lighter LnO(9) polyhedra, and show an inclining degree of torsion into the "ac" layers. The crystal lattice of the lighter 4f complexes can sufficiently withstand the tension buildup, caused by the decreasing Ln(3+) radius, up to Gd(OH)SO(4). The energy profile of this structural arrangement then seems to exceed levels at which this structure type is favorable. The lattice arrangement of the heavier Ln-analogues seems to offer a lower energy profile. This appears to be the preferred arrangement for the heavier lanthanide hydroxysulfates, whose crystal lattice exhibits more flexibility, as the coordination sphere of these analogues is less crowded. The IR absorbance frequencies of the hydroxide ligands correlate as a function of the Ln(3+) ionic radius. This corresponds well with the X-ray single

  19. Ultralarge 3d/4f Coordination Wheels: From Carboxylate/Amino Alcohol-Supported {Fe4Ln2} to {Fe18Ln6} Rings

    PubMed Central

    2017-01-01

    A family of wheel-shaped charge-neutral heterometallic {FeIII4LnIII2}- and {FeIII18MIII6}-type coordination clusters demonstrates the intricate interplay of solvent effects and structure-directing roles of semiflexible bridging ligands. The {Fe4Ln2}-type compounds [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(EtOH), Ln = Dy (1a), Er (1b), Ho (1c); [Fe4Tb2(O2CCMe3)6(N3)4(Htea)4] (1d); [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(CH2Cl2), Ln = Dy (2a), Er (2b); [Fe4Ln2(O2CCMe3)4(N3)6(Htea)4]·2(EtOH)·2(CH2Cl2), Ln = Dy (3a), Er (3b) and the {Fe18M6}-type compounds [Fe18M6(O2CCHMe2)12(Htea)18(tea)6(N3)6]·n(solvent), M = Dy (4, 4a), Gd (5), Tb (6), Ho (7), Sm (8), Eu (9), and Y (10) form in ca. 20–40% yields in direct reaction of trinuclear FeIII pivalate or isobutyrate clusters, lanthanide/yttrium nitrates, and bridging triethanolamine (H3tea) and azide ligands in different solvents: EtOH for the smaller {Fe4Ln2} wheels and MeOH/MeCN or MeOH/EtOH for the larger {Fe18M6} wheels. Single-crystal X-ray diffraction analyses revealed that 1–3 consist of planar centrosymmetric hexanuclear clusters built from FeIII and LnIII ions linked by an array of bridging carboxylate, azide, and aminopolyalcoholato-based ligands into a cyclic structure with a cavity, and with distinct sets of crystal solvents (2 EtOH per formula unit in 1a–c, 2 CH2Cl2 in 2, and 2 EtOH and 2 CH2Cl2 in 3). In 4–10, the largest 3d/4f wheels currently known, nearly linear Fe3 fragments are joined via mononuclear Ln/Y units by a set of isobutyrates and amino alcohol ligands into virtually planar rings. The magnetic properties of 1–10 reveal slow magnetization relaxation for {Fe4Tb2} (1d) and slow relaxation for {Fe4Ho2} (1c), {Fe18Dy6} (4), and {Fe18Tb6} (6). PMID:28135085

  20. Ultralarge 3d/4f Coordination Wheels: From Carboxylate/Amino Alcohol-Supported {Fe4Ln2} to {Fe18Ln6} Rings.

    PubMed

    Botezat, Olga; van Leusen, Jan; Kravtsov, Victor Ch; Kögerler, Paul; Baca, Svetlana G

    2017-02-20

    A family of wheel-shaped charge-neutral heterometallic {Fe(III)4Ln(III)2}- and {Fe(III)18M(III)6}-type coordination clusters demonstrates the intricate interplay of solvent effects and structure-directing roles of semiflexible bridging ligands. The {Fe4Ln2}-type compounds [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(EtOH), Ln = Dy (1a), Er (1b), Ho (1c); [Fe4Tb2(O2CCMe3)6(N3)4(Htea)4] (1d); [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(CH2Cl2), Ln = Dy (2a), Er (2b); [Fe4Ln2(O2CCMe3)4(N3)6(Htea)4]·2(EtOH)·2(CH2Cl2), Ln = Dy (3a), Er (3b) and the {Fe18M6}-type compounds [Fe18M6(O2CCHMe2)12(Htea)18(tea)6(N3)6]·n(solvent), M = Dy (4, 4a), Gd (5), Tb (6), Ho (7), Sm (8), Eu (9), and Y (10) form in ca. 20-40% yields in direct reaction of trinuclear Fe(III) pivalate or isobutyrate clusters, lanthanide/yttrium nitrates, and bridging triethanolamine (H3tea) and azide ligands in different solvents: EtOH for the smaller {Fe4Ln2} wheels and MeOH/MeCN or MeOH/EtOH for the larger {Fe18M6} wheels. Single-crystal X-ray diffraction analyses revealed that 1-3 consist of planar centrosymmetric hexanuclear clusters built from Fe(III) and Ln(III) ions linked by an array of bridging carboxylate, azide, and aminopolyalcoholato-based ligands into a cyclic structure with a cavity, and with distinct sets of crystal solvents (2 EtOH per formula unit in 1a-c, 2 CH2Cl2 in 2, and 2 EtOH and 2 CH2Cl2 in 3). In 4-10, the largest 3d/4f wheels currently known, nearly linear Fe3 fragments are joined via mononuclear Ln/Y units by a set of isobutyrates and amino alcohol ligands into virtually planar rings. The magnetic properties of 1-10 reveal slow magnetization relaxation for {Fe4Tb2} (1d) and slow relaxation for {Fe4Ho2} (1c), {Fe18Dy6} (4), and {Fe18Tb6} (6).

  1. Chloride derivatives of lanthanoid(III) ortho-oxidotungstates(VI) with the formula LnCl[WO4] (Ln=Gd-Lu): Syntheses, crystal structures and spectroscopic properties

    NASA Astrophysics Data System (ADS)

    Schustereit, Tanja; Schleid, Thomas; Höppe, Henning A.; Kazmierczak, Karolina; Hartenbach, Ingo

    2015-03-01

    The lanthanoid(III) chloride ortho-oxidotungstates(VI) with the formula LnCl[WO4] crystallize monoclinically in space group C2/m (a=1019-1032, b=721-733, c=682-689 pm and β=107-108°, Z=4) for Ln=Gd-Er and triclinically in space group P1¯ (a=593-596, b=719-721, c=684-686 pm, α=93-94, β≈103 and γ≈122°, Z=2) for Ln=Tm-Lu. The monoclinic structure contains crystallographically unique Ln3+ cations, which are surrounded by two Cl- and six O2- anions forming distorted trigonal dodecahedra. Their fusion via common edges leads to anionic layers ∞ 2 {[ LnCl2/2eO4/2eO2/1t ] 6 - }. The polyhedra around the Ln3+ cations in the triclinic crystal structure are also built up by two Cl-, but only five O2- anions to form distorted monocapped trigonal prisms. Their linkage through edges constitutes anionic strands ∞ 1 {[ LnCl2/2eO2/2eO3/1t ] 6 - } along [100]. The complex anionic entities of both LnCl[WO4] arrangements become interconnected by W6+ cations to complete the structures by generating discrete [WO4]2- tetrahedra. Since the title compounds emerge as pure phases according to X-ray powder diffractometry, spectroscopic measurements such as single crystal Raman as well as diffuse reflectance spectroscopy (DRS) were performed. Furthermore, GdCl[WO4] and LuCl[WO4] are suitable host materials for doping with Eu3+, which leads to materials with a red luminescence upon excitation with UV light for both structures. Moreover, TbCl[WO4] exhibits a Tb3+-typical yellow-green bulk luminescence upon UV excitation, which could be analyzed by luminescence spectroscopy.

  2. Fabrication and luminescence properties of one-dimensional CaMoO(4): Ln(3+) (Ln = Eu, Tb, Dy) nanofibers via electrospinning process.

    PubMed

    Hou, Zhiyao; Chai, Ruitao; Zhang, Milin; Zhang, Cuimiao; Chong, Peng; Xu, Zhenhe; Li, Guogang; Lin, Jun

    2009-10-20

    One-dimensional CaMoO(4):Ln(3+) (Ln = Eu, Tb, Dy) nanofibers have been prepared by a combination method of sol-gel and electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and low voltage cathodoluminescence (CL) as well as kinetic decays were used to characterize the resulting samples. SEM and TEM analyses indicate that the obtained precursor fibers have a uniform size, and the as-formed CaMoO(4):Ln(3+) nanofibers consist of nanoparticles. Under ultraviolet excitation, the CaMoO(4) samples exhibit a blue-green emission band with a maximum at 500 nm originating from the MoO(4)(2-) groups. Due to an efficient energy transfer from molybdate groups to dopants, CaMoO(4):Ln(3+) phosphors show their strong characteristic emission under ultraviolet excitation and low-voltage electron beam excitation. The energy transfer process was further studied by the emission spectra and the kinetic decay curves of Ln(3+) upon excitation into the MoO(4)(2-) groups in the CaMoO(4):x mol % Ln(3+) samples (x = 0-5). Furthermore, the emission colors of CaMoO(4):Ln(3+) nanofibers can be tuned from blue-green to green, yellow, and orange-red easily by changing the doping concentrations (x) of Ln(3+) ions, making the materials have potential applications in fluorescent lamps and field emission displays (FEDs).

  3. B-site disordering in Ba{sub 3}Ln{sub 2}MoO{sub 9} (Ln=Ho, Er) perovskites: A neutron diffraction study

    SciTech Connect

    Larregola, S.A.; Alonso, J.A.; Garcia Hernandez, M.; Fernandez-Diaz, M.T.; Pedregosa, J.C.

    2009-06-15

    We describe the preparation, structure determination and magnetic properties of two Ba perovskites containing rare-earth cations at the B-sublattice. Ba{sub 3}Ln{sub 2}MoO{sub 9} (Ln=Ho{sup 3+} and Er{sup 3+}) were synthesized by ceramic procedures. Joint X-ray (XRPD) and neutron (NPD) powder diffraction refinements were carried out to analyse the crystal structure. At room temperature, both phases are tetragonal, space group I4/mcm, Z=4. Ln and Mo atoms are found to be distributed at random over the octahedral sites of the perovskites. Magnetic measurements at 0.1 T show that both samples are paramagnetic between 3 and 300 K, following a Curie-Weiss law. M vs. H curves show a region of paramagnetic behaviour and above 2.5 T a magnetic saturated system is observed. Finally, the temperature evolution of the NPD patterns of Ba{sub 3}Ho{sub 2}MoO{sub 9} reveals the absence of long-range magnetic ordering down to 2 K. - Graphical Abstract: Preparation, structure and magnetic properties of Ba{sub 3}Ln{sub 2}MoO{sub 9} (Ln=Ho{sup 3+} and Er{sup 3+}) are descripted. Joint XRPD and NPD refinements confirm a tetragonal I4/mcm structure. Ln and Mo atoms are found to be distributed at random over the octahedral sites of the perovskites.

  4. Enhanced near-infrared emission in phase and size controlled NaLnF4: Pr3+-Yb3+ (Ln = Gd3+ and Y3+) nanocrystals

    NASA Astrophysics Data System (ADS)

    Ye, Song; Hu, Rongxuan; Wang, Huiyun; Wang, Deping

    2015-01-01

    NaLnF4 (Ln = Y, Gd): Pr3+, Yb3+ nanocrystals were prepared through a facile modified solvothermal method, in which the cubic to hexagonal phase transformation and size evaluation of NaLnF4 nanocrystals could be well controlled by carefully adjusting Gd3+ content. In this system, the infrared emission associated with Yb3+: 2F5/2 → 2F7/2 transition could be obtained under the excitation of Pr3+: 3P0 energy level as a result of efficient energy transfer from Pr3+ to Yb3+. The structural and spectral measurement indicated that the energy transfer efficiency from Pr3+ to Yb3+ firstly increased with the increase of Gd3+ content due to the formation of a higher percentage of hexagonal phase NaLnF4 in the final production, and then decreased with further increase in Gd3+ content due to the expansion of NaLnF4 unit-cell volume. However, a monotonous increase in Yb3+ infrared emission intensity could be observed with the increasing of Gd3+ content until the radiative emission was suppressed by the nonradiative transition originating from the surface defects in smaller NaLnF4 nanocrystals.

  5. No pyroanions: The representatives of the lanthanoid(III) fluoride oxidodimolybdates(VI) LnFMo2O7 with the Smaller Cations (Ln = Eu - Yb)

    NASA Astrophysics Data System (ADS)

    Müller, Sabine L.; Blaschkowski, Björn; Hartenbach, Ingo

    2017-07-01

    The representatives of lanthanoid(III) fluoride oxidodimolybdates(VI) with the formula LnFMo2O7 (Ln = Eu - Yb) occur during reactions of Ln2O3 and LnF3 with MoO3 in 1: 1: 6 molar ratio after 6 days in evacuated silica ampoules at 850 °C. The title compounds crystallize monoclinically in space group P2/c (a = 421 - 436, b = 651 - 667, c = 1133 - 1140 pm and β = 90.4 - 90.6°, Z =2). The crystal structures contain crystallographically unique Ln3+ cations, which are surrounded by two F- and five O2- anions each, forming distorted pentagonal bypramids with the F- anions as apical vertices by which these bipyramids are fused together to strands according to ∞ 1LnF2/2vO5/1t]8- running parallel to the a axis. The Mo6+ cations show a distorted square-pyramidal coordination environment of five O2- anions. These pyramids are interconnected by common edges and vertices to form chains with the formula <∞1[ MoO2/2eO1/2vO2/1t ]- which are arranged parallel to [001]. Besides the crystal structure determination single crystal Raman spectroscopy was performed and the magnetic behavior of HoFMo2O7 was determined.

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

    SciTech Connect

    Salame, Paresh Hiralal

    2016-05-23

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

  7. Structural and electrical properties of T'-type Ln2CuO4 (Ln = Pr, Nd, Sm, Eu and Gd) ceramics

    NASA Astrophysics Data System (ADS)

    Salame, Paresh Hiralal

    2016-05-01

    T'-type Ln2CuO4 (Ln = Pr, Nd, Sm, Eu and Gd) were successfully synthesized in phase pure form using conventional solid state reaction and sintering route. For all the Ln2CuO4 samples, the solid state reaction temperature was found to be 950 °C and pure phase was realized only after 2-3 intermediate milling and solid state reaction cycles, irrespective of the lanthanide ion radius. Effect of lanthanide ion contraction on the structural properties was clearly revealed by the powder X-ray diffraction, with the XRD peaks observed to be shifting towards higher 2θ values with the decrease in Ln ionic radii. The optimum sintering temperature of these solid state reacted Ln2CuO4 powder was found to be 1100 °C except for Pr2CuO4 powder. The conductivity of these samples were tested over a wide temperature range (-100 to 150 °C), an anomaly was observed in the conductivity of all the Ln2CuO4 samples near the antiferromagnetic ordering temperature of Cu (~ 30 °C), thus suggesting the bearing of ordering of magnetic moments on the electrical properties.

  8. Linking two distinct layered networks of nanosized {Ln18} and {Cu24} wheels through isonicotinate ligands.

    PubMed

    Cheng, Jian-Wen; Zhang, Jie; Zheng, Shou-Tian; Yang, Guo-Yu

    2008-01-01

    A new series of heterolanthanide(III)-copper(I) wheel-cluster complexes [Ln6(micro3-O)2](IN)18-[Cu8(micro4-I)2(micro2-I)3].H3O (IN=isonicotinate; Ln=Y 1, Nd 2, Dy 3, Gd 4, Sm 5, Eu 6, Tb 7) were prepared by hydrothermal reaction at low pH. X-ray crystallographic studies reveal that two unusual trinuclear [Ln3(micro3-O)] and tetranuclear [Cu4(micro4-I)] cores are successfully used as secondary building units to make two different nanosized wheels [Ln18(micro3-O)6(CO2)48](6-), {Ln18}, and [Cu24(micro4-I)6(micro2-I)12]6+, {Cu24}, with 12-rings and a diameter of 26.7 and 26.4 A, respectively. The wheels are further assembled into two-dimensional (2D) {Ln18} and {Cu24} networks, the linkages between two distinct layered networks of {Ln18} and {Cu24} wheels by IN pillars along the c axis giving a series of unprecedented three-dimensional (3D) sandwich frameworks. To our knowledge, compounds 1-7 are the first examples containing two different layered networks of nanosized Ln and transition metal (TM) wheels in wheel-cluster chemistry. The IR, UV/Vis, thermogravimetric analysis (TGA), luminescent, and magnetic properties of these complexes were also studied.

  9. [Theoretical and experimental vibrational spectroscopy study of K3Ln(PO4)2 phosphates].

    PubMed

    Benarafa, L; Rghioui, L; Nejjar, R; Saidi Idrissi, M; Knidiri, M; Lorriaux, A; Wallart, F

    2005-01-14

    The monoclinic phosphates with K3Ln(PO4)2 (Ln=rare earth) formula were synthesized. Their infrared and Raman spectra have been reported and analysed. The results of a force field calculation for K3Nd(PO4)2 are presented.

  10. Intracluster interactions in "butterfly" {Fe3LnO2} molecules

    NASA Astrophysics Data System (ADS)

    Badía-Romano, L.; Rubín, J.; Bartolomé, F.; Bartolomé, J.; Luzón, J.; Prodius, D.; Turta, C.; Mereacre, V.; Wilhelm, F.; Rogalev, A.

    2016-02-01

    The magnetization contributions of the Fe3 and Ln subcluster in the "butterfly" molecule [Fe3Ln(μ3-O)2(CCl3COO)8(H2O)(THF)3], in brief {Fe3LnO2}, with Ln=Lu, Gd, Tb, Dy and Ho, have been determined by a combination of vibrating sample magnetometry and x-ray circular magnetic dichroism at low temperature and magnetic field up to 14 T. These contributions have been explained in terms of an effective spin model where the Fe3 is described by a SFe3 = 5 / 2 spin, Gd by an isotropic J=7/2, Dy by a Kramers doublet, and non-Kramers ions Tb and Ho by a ligand field split doublet. The intracluster interactions JFeLn have been found to amount to a few K.

  11. A family of 12-azametallacrown-4 structural motif with heterometallic Mn(III) -Ln-Mn(III) -Ln (Ln=Dy, Er, Yb, Tb, Y) alternate arrangement and single-molecule magnet behavior.

    PubMed

    Yang, Hua; Cao, Fan; Li, Dacheng; Zeng, Suyuan; Song, You; Dou, Jianmin

    2015-10-05

    Mixed 3d-4f 12-azametallacrown-4 complexes, [Mn2 Ln2 (OH)2 (hppt)4 (OAc)2 (DMF)2 ]⋅2 DMF⋅H2 O [Ln=Dy (1), Er (2), Yb (3), Tb (4) and Y (5), H2 hppt=3-(2-hydroxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole)], were synthesized by reactions of H2 hppt with Mn(OAc)2 ⋅4 H2 O and Ln(NO3 )3 ⋅6 H2 O. This is the first 3d-4f azametallacrown family to incorporate Ln ions into the ring sets. These isostructural complexes exhibit alternating arrangements of two Mn and two Ln ions in the rings with each pair of metal centers bound by an NN group and μ2 -O bridging. Magnetic measurements revealed dominant antiferromagnetic interactions between metal centers, and frequency-dependent out-of-phase (${\\chi {^\\prime}{^\\prime}_{\\rm{M}} }$) signals below 4 K suggest slow relaxation of magnetization. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Method for synthesizing fine-grained phosphor powders of the type (RE{sub 1{minus}x}Ln{sub x})(P{sub 1{minus}y}V{sub y})O{sub 4}

    DOEpatents

    Phillips, M.L.F.

    1998-04-28

    A method for generating well-crystallized photo- and cathodoluminescent oxide phosphor powders is disclosed. The method of this invention uses hydrothermal synthesis and annealing to produce nearly monosized (RE{sub 1{minus}x}Ln{sub x})(P{sub 1{minus}y}V{sub y}O{sub 4}) (Ln{double_bond}Ce{yields}Lu) phosphor grains with crystallite sizes from 0.04 to 5 {micro}m. Such phosphors find application in cathode-ray tube, flat-panel, and projection displays. 4 figs.

  13. Synthesis method dependence of the lattice effects in Ln0.5M0.5FeO3 perovskites (Ln = La and (Nd or Gd); M = Ba and (Ca or Sr))

    NASA Astrophysics Data System (ADS)

    Ortega-San-Martín, L.; Vidal, K.; Roldán-Pozo, B.; Coello, Y.; Larrañaga, A.; Arriortua, M. I.

    2016-05-01

    A new series of cubic iron perovskites with the composition Ln0.5M0.5FeO3 (Ln = La and Nd (or Gd); M = Ba and Sr (or Ca)) with the same average A-site radius ( = 1.3 Å) but different A-site size disorder, σ 2(r A), from 0.0114 to 0.0230 Å2, has been prepared by three different synthesis routes: (a) ceramic method, (b) combustion method and (c) the Pechini method. A strong correlation of the structural parameters with σ 2(r A) and the synthesis method is observed. The unit cell volume increases with σ 2(r A) in all the cases but the overall isotropic displacement factor of the atoms and the lattice microstrain do not show the same trends. Samples synthesised by the low temperature routes show a σ 2(r A)-dependence of the microstrain whereas in the oxides prepared by the ceramic method microstrain seems to be σ 2(r A)-independent.

  14. Monodisperse lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm): morphology controlled synthesis, up-conversion luminescence and in vitro cell imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Li, Xuejiao; Hou, Zhiyao; Lin, Jun

    2014-05-01

    Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb3+, 0.04Er3+ nanospheres is dominated by a single red emission at 660 nm, which falls into the ``optical window'' of biological tissues. The application of YOF: 0.20Yb3+, 0.04Er3+ nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise.Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are

  15. The absence of ferroelectric polarization in layered and rock-salt ordered NaLnMnWO6 (Ln = La, Nd, Tb) perovskites.

    PubMed

    De, Chandan; Kim, Tai Hoon; Kim, Kee Hoon; Sundaresan, A

    2014-03-21

    The ordered perovskites, NaLnMnWO6 (Ln = La, Nd, Tb), are reported to exhibit simultaneous ordering of A-site cations (Na and Ln) in layered arrangement and B-site cations (Mn and W) in rock salt structure. They have been shown to crystallize in a monoclinic structure with the polar space group P21. Based on density functional calculations and group theoretical analysis, it has recently been proposed that NaLaMnWO6 should be ferroelectric with a relatively large polarization (16 μC cm(-2)). Contrary to this prediction, our electrical measurements such as conventional P-E loop, Positive-Up and Negative-Down (PUND), piezoelectric response and Second Harmonic Generation (SHG) reveal the absence of ferroelectric polarization in NaLnMnWO6 (Ln = La, Nd, Tb). A dielectric anomaly is observed just below room temperature (∼270 K) for all the three compounds, which is related to the change in conductivity as revealed by temperature dependent ac and dc resistivity. A pyrocurrent peak is also observed at the same temperature. However, its origin cannot be attributed to a ferroelectric transition.

  16. Synthesis and photoluminescence properties of Ln3+ (Ln3+=Tb3+, Dy3+, Sm3+, Er3+)-doped Ca2Nb2O7 phosphors

    NASA Astrophysics Data System (ADS)

    Xian, Jieqiang; Yi, Shuangping; Deng, Yaomin; Zhang, Lu; Hu, Xiaoxue; Wang, Yinhai

    2016-02-01

    A series of Ln3+ (Ln3+=Tb3+/Dy3+/Sm3+/Er3+) ions doped Ca2Nb2O7 phosphors have been synthesized by high-temperature solid-state reaction. The Ln3+-doped samples are well indexed to the pure Ca2Nb2O7 phase which revealed for the X-ray diffraction (XRD) result. Under the ultraviolet light, the prepared Ca2-xNb2O7:xLn3+ (Ln3+=Tb3+/Dy3+/Sm3+/Er3+) phosphors show the characteristic cyan (Tb3+), green-white (Sm3+), yellowish (Dy3+) and green (Er3+) emissions. The energy transfer mechanisms in Ca2Nb2O7: Tb3+/Dy3+/Sm3+/Er3+ phosphors have been investigated and it deduced to be a resonant type via an electric dipole-dipole interaction. In addition, their critical distances have been calculated by concentration quenching methods. The luminescence properties of Ca2Nb2O7:Tb3+/Dy3+/Sm3+/Er3+ phosphors indicated that the Ca2Nb2O7 is a suitable host for rare earth doped laser crystal and optical materials.

  17. Ce3+ and Ln3+ (Ln = Dy, Eu, Sm, Tb) Codoped SrF2 Nanoparticles: Synthesis and Multicolor Light Emission.

    PubMed

    Su, Yiguo; Liu, Mengqing; Han, Dan; Li, Lv; Wang, Tingting; Wang, Xiaojing

    2016-04-01

    For optically active Ln3+ ions, fluoride is a very good luminescent substrate that has been used in the field of lasers, solid-phase optical transmitters, optical communications, up/down conversion. This work reports a systematic study on bridging between structure and tunable luminescence for SrF2:Ce3+/Ln3+ (Ln = Dy, Eu, Sm, Tb) nanoparticles. Regardless of the dopant level, all nano-crystals crystallized in a single cubic phase with the diameter of ~20-30 nm. It was found that SrF2:Ce3+ exhibited intense ultraviolet emission under 288 nm excitation which can be attributed to the typical 4f-5d transition of Ce3+ ions. After the incorporation of Ln3+ ions, multicolor emission can be achieved when excited by the 4f-5d transition of Ce3+. This result gave an evidence that the excitation energy of Ce3+ can be transferred to Ln3+ leading to multicolor emission. The findings reported in this work may provide useful information in designing novel luminescent materials for tailored performances.

  18. Seven new rare-earth transition-metal oxychalcogenides: Syntheses and characterization of Ln{sub 4}MnOSe{sub 6} (Ln=La, Ce, Nd), Ln{sub 4}FeOSe{sub 6} (Ln=La, Ce, Sm), and La{sub 4}MnOS{sub 6}

    SciTech Connect

    Ijjaali, Ismail; Deng Bin; Ibers, James A. . E-mail: ibers@chem.northwestern.edu

    2005-05-15

    The quaternary oxychalcogenides Ln{sub 4}MnOSe{sub 6} (Ln=La, Ce, Nd), Ln{sub 4}FeOSe{sub 6} (Ln=La, Ce, Sm), and La{sub 4}MnOS{sub 6} have been synthesized by the reactions of Ln (Ln=La, Ce, Nd, Sm), M (M=Mn, Fe), Se, and SeO{sub 2} at 1173K for the selenides or by the reaction of La{sub 2}S{sub 3} and MnO at 1173K for the sulfide. Warning: These reactions frequently end in explosions. These isostructural compounds crystallize with two formula units in space group C{sub 6v}{sup 4}-P6{sub 3}mc of the hexagonal system. The cell constants (a, c in A) at 153K are: La{sub 4}MnOSe{sub 6}, 9.7596(3), 7.0722(4); La{sub 4}FeOSe{sub 6}, 9.7388(4), 7.0512(5); Ce{sub 4}MnOSe{sub 6}, 9.6795(4), 7.0235(5); Ce{sub 4}FeOSe{sub 6}, 9.6405(6), 6.9888(4); Nd{sub 4}MnOSe{sub 6}, 9.5553(5), 6.9516(5); Sm{sub 4}FeOSe{sub 6}, 9.4489(5), 6.8784(5); and La{sub 4}MnOS{sub 6}, 9.4766(6), 6.8246(6). The structure of these Ln{sub 4}MOQ{sub 6} compounds comprises a three-dimensional framework of interconnected LnOQ{sub 7} bicapped trigonal prisms, MQ{sub 6} octahedra, and the unusual LnOQ{sub 6} tricapped tetrahedra.

  19. Synthesis, structures, and luminescent and magnetic properties of Ln-Ag heterometal-organic frameworks.

    PubMed

    Zhao, Xiao-Qing; Zhao, Bin; Wei, Shi; Cheng, Peng

    2009-12-07

    A series of Ln-Ag heterometal-organic frameworks based on 4-hydroxylpyridine-2,6-dicarboxylic acid (H(3)CAM) with formulas {LaAg(2)(CAM)(HCAM)(H(2)O)(2)}(n) (1), {LnAg(HCAM)(2)(H(2)O)(3)}(n) (Ln = Pr, 2; Nd, 3; Sm, 4; Eu, 5), and {LnAg(3)(CAM)(2)(H(2)O)}(n) (Ln = Gd, 6; Tb, 7; Dy, 8; Tm, 9; Yb, 10), have been synthesized with the hydrothermal reaction of Ln(OH)(3), Ag(2)O, and H(3)CAM at 160 degrees C. The single-crystal X-ray diffraction analyses reveal that three kinds of structures are exclusively governed by the size of lanthanide ions and the progression of structures is mainly ascribed to the lanthanide contraction effect. Compound 1 consists of a 3D network with an alpha-polonium-like Ag(+)-homometallic net and helical La(3+) chain. Compounds 2-5 display a 2D honeycomb-like structure with 18-membered Ln(3)Ag(3)O(12) motifs, and compounds 6-10 can be described as a sandwich-like 3D framework built of a 3D Ag(+)-homometallic net and 2D Ln(3+)-4(4) layer. In 4 (Sm), 5 (Eu), 7 (Tb), and 8 (Dy) samples, the efficient energy transfer from CAM to Ln(III) ions was observed, which results in the typical intense emissions of corresponding Ln(III) ions in the visible region, and the strongest emissions are (4)G(5/2) --> (6)H(7/2) (602 nm), (5)D(0) --> (7)F(2) (614 nm), (5)D(4) --> (7)F(5) (548 nm), and (4)F(9/2) --> (6)H(13/2) (576 nm) transitions. Variable-temperature magnetic susceptibility measurements of 6-10 show that the ferromagnetic interaction between gadolinium(III) ions appears in 6, whereas the mu(eff) values of 7-10 smoothly decrease on cooling. For the orbital contribution of Ln(III) ions, it is very difficult to determine the intrinsic magnetic interactions between Ln(III) ions.

  20. Synthesis and characterization of monodisperse spherical SiO{sub 2}-RE{sub 2}O{sub 3} (RE=rare earth elements) and SiO{sub 2}-Gd{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles with core-shell structure

    SciTech Connect

    Wang, H.; Yang, J.; Zhang, C.M.; Lin, J.

    2009-10-15

    Spherical SiO{sub 2} particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO{sub 2}-RE{sub 2}O{sub 3} (RE=rare earth elements) and SiO{sub 2}-Gd{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO{sub 2}-RE{sub 2}O{sub 3} (RE=rare earth elements) and SiO{sub 2}-Gd{sub 2}O{sub 3}:Ln{sup 3+} (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}, Sm{sup 3+}, Er{sup 3+}, Ho{sup 3+}) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln{sup 3+} ion mainly shows its characteristic emissions in the core-shell particles from Gd{sub 2}O{sub 3}:Ln{sup 3+} (Eu{sup 3+}, Tb{sup 3+}, Sm{sup 3+}, Dy{sup 3+}, Er{sup 3+}, Ho{sup 3+}) shells. - Graphical abstract: The advantages of core-shell phosphors are the easy availability of homogeneous spherical morphology in different size, and its corresponding luminescence color can change from red, yellow to green.

  1. Crystal structure of Ln1/3NbO 3 ( Ln=Nd, Pr) and phase transition in Nd 1/3NbO 3

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaoming; Howard, Christopher J.; Kennedy, Brendan J.; Knight, Kevin S.; Zhou, Qingdi

    2007-06-01

    The crystal structure of the A-site deficient perovskite Ln1/3NbO 3 ( Ln=Nd, Pr) at room temperature has been determined, for the first time, as orthorhombic in space group Cmmm using high-resolution neutron powder diffraction. Pertinent features are the alternation of unoccupied layers of A-sites and layers partly occupied by Ln cations, as well as out-of-phase tilting of the NbO 6 octahedra around an axis perpendicular to the direction of the cation/vacancy ordering. The phase transition behaviour of Nd 1/3NbO 3 has also been studied in situ. This compound undergoes a continuous phase transition at around 650 °C to a tetragonal structure in space group P4/ mmm due to the disappearance of the octahedral tilting. The analysis of spontaneous strains shows that this phase transition is tricritical in nature.

  2. PNBE-supported metallopolymer-type optical materials through grafting of Zn-Ln (Ln = Nd, Yb or Er) benzimidazole complex monomers with efficient NIR luminescence

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Li, Hongyan; Feng, Weixu; Fu, Guorui; Lü, Xingqiang; Wong, Wai-Kwok; Jones, Richard A.

    2017-02-01

    Through the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with each of obtained allyl-containing complex monomers [Zn(L)2(Py)Ln(NO3)3] (Ln = La, 1; Nd, 2; Yb, 3; Er, 4 or Gd, 5; HL = 4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol; Py = pyridine), a series of metallopolymers Poly(NBE-co-[Zn(L)2Ln(Py)(NO3)3)]) were obtained, respectively. Especially for Poly(NBE-co-2) and Poly(NBE-co-3), covalently-bonded grafting endows significantly improved physical properties including efficient NIR luminescence (ΦNdL = 0.63% and ΦYbL = 1.43%) in solid state.

  3. Pressure-induced phase transitions in LnTe (Ln=La, Gd, Ho, Yb) and AmTe.

    PubMed

    Zvoriste-Walters, C E; Heathman, S; Klimczuk, T

    2013-07-03

    The structural behaviour under compression of different lanthanide (La, Gd, Ho, Yb) and actinide (Am) monochalcogenides is studied by means of in situ high-pressure x-ray diffraction. All the investigated compounds crystallize at ambient conditions within a cubic (B1) NaCl-type structure but show different behaviours at high pressures. LaTe and AmTe undergo B1 to B2 (CsCl-type structure) phase transitions, starting at 9 GPa and 12 GPa, respectively. The high-pressure phase of AmTe exhibits an electronic transition, identified by an anomaly in the compression curve which is accompanied by a sample colour change. The other three monochalcogenides studied here show clear evidence of decomposition and amorphization under pressure and are, to the best of our knowledge, the first in the LnTe series to show a pressure-induced amorphization. The bulk moduli of all B1-type structure compounds are calculated using the third-order Birch-Murnaghan equation of state.

  4. Surstructures de type fluorine observées dans les systèmes KF LnF 3 ( Ln = Pr … Er)

    NASA Astrophysics Data System (ADS)

    Le Fur, Y.; Aleonard, S.; Perroux, M.; Gorius, M. F.; Roux, M. T.

    1988-02-01

    Phases having fluoride-related superstructures are determined in the system K 0,5- xLn0,5+ xF 2+2 x (0.33 < 2 x < 0.5 and Ln = Pr … Er). The composition range in which they are observed has been studied by X-ray and electron diffraction at high resolution. (i) 2 x = 0,33 ( Ln = Tb … Er, t = 1000°C). A compound K 0,33Ln0,67F 2,33 is observed (monoclinic system, Cm, a ≈ a F√6, b ≈ a F√2, c ≈ {3a F}/{√2}, β = 125°). (ii) 0,33 < 2 x < 0,5 ( Ln = Gd or Eu, t = 900°C); Phase A. An incommensurate modulated structure appears, with a wave vector q = ybq (0,25 < y < 0,33). This incommensurate structure is limited by two commensurate phases with y = 0,33 (2 x ≈ 0.33, orthorhombic system, a ≈ 2 aF, b ≈ aF√2, c ≈ 3 aF√2) and y = 0,25 (2 x > 0,45, orthorhombic system, Immm, a ≈ 2 aF, b ≈ aF√2, c ≈ 4 aF√2). (iii) 0,33 < 2 x < 0,40 ( Ln = Pr … Gd, t ≈ 800°C); Phase B. A new compound is obtained (monoclinic system, Cm, C2 ou {C2}/{m}, a ≈ 2a F√3, b ≈ a F√2, c ≈ {1}/{2}a F√114 , β ≈ 97°).

  5. Hydrothermal synthesis, structure, and property characterization of rare earth silicate compounds: NaBa3Ln3Si6O20 (Ln = Y, Nd, Sm, Eu, Gd)

    NASA Astrophysics Data System (ADS)

    Sanjeewa, Liurukara D.; Fulle, Kyle; McMillen, Colin D.; Wang, Fenglin; Liu, Yufei; He, Jian; Anker, Jeffrey N.; Kolis, Joseph W.

    2015-10-01

    A series of new lanthanide (Ln) silicates have been synthesized using high temperature hydrothermal techniques, and structurally characterized using single crystal and powder X-ray diffraction. The compounds have the general formula NaBa3Ln3Si6O20 (Ln = Y, Nd, Sm, Eu, Gd), and crystallize in the space group Ama2 (No.40). As a representative example, the unit cell parameters of NaBa3Gd3Si6O20 are a = 14.731(3) Å, b = 23.864(5) Å, c = 5.5449(11) Å and Z = 4. The title compounds adopt a three dimensional polar acentric framework made of Ln-O-Si bonding. The framework is comprised of LnO8 and LnO7 units forming edge-sharing infinite chains along the c-axis. These oxy-bridged infinite chains are also linked by [Si4O13] tetrasilicate and [Si2O7] disilicate units to form the three-dimensional framework structure, with Ba2+ and Na+ cations residing inside channels of the framework. The polarity in the structure is imparted by the unusual tetrasilicate arrangement. The luminescence and magnetic properties were investigated on selected compounds. The temperature dependent magnetic susceptibility measurements on the Nd, Sm, and Gd derivatives reveal a Curie-Weiss behavior with an antiferromagnetic coupling parameter. For the Eu-derivative, the temperature dependent magnetic susceptibility deviates significantly from Curie-Weiss behavior. Luminescence properties of NaBa3Eu3Si6O20 and NaBa3Sm3Si6O20 compounds exhibited the characteristic transitions of Eu3+ (5D0 → 7FJ, J = 0-4) and Sm3+ (4G5/2 → 6HJ, J = 5/2, 7/2), respectively, leading to strong visible red and orange emissions, respectively.

  6. Microwave Dielectric Properties of Temperature-Stable BaLn2(MoO4)4-TiO2 (Ln = Ce, Nd, and Sm) Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Wen-Bo; Xi, Hai-Hong; Zhou, Di

    2015-11-01

    A series of temperature-stable microwave dielectric ceramics (1 - x)Ba Ln2(MoO4)4- xTiO2 (Ln = Ce, Nd, and Sm; 0.4 ≤ x ≤0.55) were prepared by solid-state reaction. Sintering behavior, phase composition, microstructure, and microwave dielectric properties were investigated. X-ray powder diffraction and scanning electron microscopy revealed that the main phases of the BaLn2(MoO4)4-TiO2 ceramics were the monoclinic BaLn2(MoO4)4 phase and the rutile TiO2 phase. Study of the materials' microwave dielectric properties revealed that the permittivity ( ɛ r) and the temperature coefficient of the resonant frequency ( τ f) increased gradually with increasing x value whereas quality factors ( Q × f) decreased. For BaLn2(MoO4)4-TiO2 (Ln = Ce and Nd), τ f values could be adjusted to near zero, relative permittivity ( ɛ r) was 13.2-14.3, and Q × f values were between 11,950 and 45,720 GHz (at 9.11-9.83 GHz) when x = 0.45 to 0.55. For BaSm2(MoO4)4-TiO2, excellent microwave dielectric properties were obtained when x = 0.4 to 0.5, τ f values could be adjusted to near zero, ɛ r was 13.1-13.9, and Q × f values were between 25,520 and 63,130 GHz (at 9.31-10.11 GHz).

  7. Predictable self-assembled [2×2] Ln(III)4 square grids (Ln = Dy,Tb)-SMM behaviour in a new lanthanide cluster motif.

    PubMed

    Anwar, Muhammad Usman; Thompson, Laurence Kenneth; Dawe, Louise Nicole; Habib, Fatemah; Murugesu, Muralee

    2012-05-14

    The ditopic carbohydrazone ligand (L1) produces the square, self-assembled [2×2] grids [Dy(4)(L1)(4)(OH)(4)]Cl(2) (1) and [Ln(4)(L1)(4)(μ(4)-O)(μ(2)-1,1-N(3))(4)] (Ln = Dy (2), Tb (3)), with 2 exhibiting SMM behaviour. Two relaxation processes occur with U(eff) = 51 K, 91 K in the absence of an external field, and one with U(eff) = 270 K in the presence of a 1600 Oe optimum field.

  8. Hydrothermal synthesis and luminescent properties of SrF2 and SrF2:Ln3+ (Ln = Eu, Ce, Tb) nano-assembly with controllable morphology.

    PubMed

    Sun, Yuanping; Jia, Peiyun

    2014-05-01

    SrF2 and SrF2:Ln3+ (Ln = Eu, Ce, Tb) nano-assemblies with controllable size and morphology have been successfully prepared via a facile hydrothermal process. X-ray diffraction, scanning electron microscopy, and photoluminescence spectrum were used to characterize the samples. The experimental results indicate that chelating reagent and acidity play important roles in the formation of micro-crystals with uniform size and peculiar morphology. As-obtained SrF2:Eu3+ and SrF2:Ce3+, SrF2:Tb3+ samples show red, ultraviolet and green emission under the irradiation of ultraviolet.

  9. Local Reversion of Cold Formed AISI 301LN

    NASA Astrophysics Data System (ADS)

    Järvenpää, A.; Jaskari, M.; Hietala, M.; Mäntyjärvi, K.

    This study demonstrates applying laser heat treatment for reversion treatments of cold-formed AISI 301LN. Sheets were cold- rolled to final thicknesses of 1.5 and 3 mm (65pct reduction), having martensite fraction of 70-95%. Sheets were heated locally by a laser beam to various peak temperatures to obtain different degrees of martensite reversion to austenite. Mechanical properties and formability of grain-refined and coarse-grained structures were measured by tensile, bending and Erichsen cup tests. In addition to standard Erichsen cup test, additional interrupted tests were carried out, where cups were first stretched close to the critical strain. Drawn cups were then heated locally by a laser beam to revitalize the structure and thereby enhance the formability in the following cupping test until failure. Various structures were produced: completely reverted microstructures (T > 700 °C) with grain sizes 0.9 - 2 μm in addition to partially reverted structure (T < 700 °C) containing nano- and ultrafine-grained austenite (0.6 μm) with some martensite. Results showed that local laser heat treatment is suitable for the reversion treatment to refine the austenite grain size. Refinement of the austenitic structures increased strength properties and the formability was better than with coarse grained structures having the same strength. Especially the yield strength was significantly enhanced, being around 900 MPa in the strongest reverted structure compared to the 300-400 MPa of the coarse grained austenitic structure. It was demonstrated that the local laser treatment restored formability of the drawn cups, allowing stretching to be continued.

  10. Synthesis, structural characterization and magnetic behaviour of a family of [CoLn] butterfly compounds.

    PubMed

    Funes, Alejandro V; Carrella, Luca; Rechkemmer, Yvonne; van Slageren, Joris; Rentschler, Eva; Alborés, Pablo

    2017-03-07

    We have successfully prepared and structurally characterized a family of butterfly-like [CoLn] complexes where all magnetic properties are due to the Ln(iii) ions. The complexes with Ln = Tb(1), Dy(2), Ho(3), Er(4) and Yb(5) are iso-structural. An exception is the complex with Ln = Gd(6) which strings in a one dimensional chain. The structural similarity together with the high tendency of the crystallites to align under an applied magnetic field allowed an overall DC magnetic data treatment to extract phenomenological crystal field parameters and hence to determine the ground state multiplet energy level splitting. The Dy(iii) member is the only one showing slow relaxation of magnetization under zero DC applied field, while all the others need a small DC applied field.

  11. [Overexpression of laminine-5( LN-5) in peritoneal lavage of colorectal cancer patients preliminary results].

    PubMed

    Volpi, A; D'Elia, G; Pannarale, O C; Di Gennaro, F; Guida, P; Martinelli, E; Kavvadias, A; Balducci, G; Ialongo, P; Panebianco, A; De Luca, M; Fabiano, G; Palasciano, N

    2011-01-01

    Recent studies show that interaction between LN (heterotrimeric protein formed by a3/b3/g2 chains) and cancer cells plays an important role in tumor invasion, also in colorectal cancer. The overall survival was significantly worse in patients with free peritoneal cancer cells(FPTCs): detection of FPTCs after curative surgery is a challenge, because could improve staging and prognosis. Peritoneal citology is the current standard procedure with very low sensivity. We aimed to study the expression of LN5 in the peritoneal lavage of colorectal cancer pts and in controls with semiquantitative reverse trancriptase-polymerase chain reaction (RT-PCR). LN-5 overexpression was evaluated observing PCR- products intensity at electrophoresis: high intensity is correlated to overexpression. Pre and post-operative peritoneal lavages of 30 pts with colorectal cancer (13M;17F), with median age of 69 (58-84), and of 10 controls, were analyzed by conventional cytology and a semiquantitative RT-PCR. No cancer pts showed pre/postoperative negative cytology and did not express LN-5. In cancer pts. cytology was positive in 2 pts in pre/postoperative lavage. LN-5 overexpression was observed in 56,6% preoperatively and in 76,6% postoperatively. LN-5 g 2 chain was most frequent chain. Our study suggests a relationship between LN-5 and FPTCs, as shown by the low expression of lamimine in controls. LN-5 could be a useful marker to identify a subgroup of early-stage patients at increased risk of recurrence; moreover, mortality seems to correlated to LAMB3 chain. The diagnostic accuracy could be improved by using a quantitative RT-PCR or western-blot and detecting serum laminine. Finally, to validate these findings a larger number of pts with follow-up study is required.

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

    SciTech Connect

    Kazmierczak, Karolina; Hoeppe, Henning A.

    2011-05-15

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

  13. Rapid microwave-assisted sol-gel preparation of Pd-substituted LnFeO3 (Ln = Y, La): phase formation and catalytic activity

    SciTech Connect

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

    2014-02-13

    We present a rapid microwave-assisted sol–gel approach to Pd-substituted LnFeO3 (Ln = Y, La) for applications in C–C coupling reactions. These materials could be prepared in household microwave ovens in less than 15 minutes of reaction time with the final materials displaying well-defined structure and morphology. Phase evolution was studied using time-dependent microwave heatings and then compared with the results obtained from thermogravimetric analyses. Materials were confirmed to be phase pure by laboratory and synchrotron X-ray diffraction. Substituted Pd is ionic as shown by the binding energy shift from X-ray photoelectron spectroscopy. The short heating periods required for phase purity allow these materials less time for sintering as compared to conventional solid state preparation methods, making relatively high surface areas achievable. These materials have been successfully used as catalyst precursor materials for C–C coupling reactions in which the active species is Pd0. Pd-substituted LnFeO3 (Ln = Y, La) provides Pd0 in solution which can be complexed by the ligand SPhos, allowing for aryl chloride coupling.

  14. Infrared and Raman spectra of tris(dipivaloylmethanato) lanthanides, Ln(thd)3 (Ln = La, Nd, Eu, Gd, Tb, Ho, Er, Tm, Yb, Lu)

    NASA Astrophysics Data System (ADS)

    Belova, Natalya V.; Sliznev, Valery V.; Christen, Dines

    2017-03-01

    The infrared and Raman vibrational spectra of the series of solid tris(dipivaloylmethanato) lanthanides, Ln(thd)3 (Ln = La, Nd, Eu, Gd, Tb, Ho, Er, Tm, Yb, Lu), have been recorded at room temperature over wide ranges (4000-50 cm-1 and 3500-80 cm-1, respectively). The experimental spectra obtained in the present study were successfully assigned based on the quantum chemical calculations (DFT/PBE0) performed for the monomer Ln(thd)3 molecules. The experimental vibrational spectra for all complexes studied are rather similar as are the theoretical simulations. The data analysis shows that the main contributions to vibrational modes arise from the vibrations of the ligand possessing practically the same geometry for all complexes. According to the calculation results the structure of the coordination polyhedron is increasingly distorted in the series from La(thd)3 to Lu(thd)3. Although the contributions of the polyhedron vibrations in vibrational modes are not predominant, there is rise in the frequencies associated with vibrations of the coordination polyhedron LnO6 in this series. This increase has been explained by the concept of lanthanide contraction.

  15. Thermal expansion properties of Ln{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} (Ln = Er and Y)

    SciTech Connect

    Wu, M.M.; Hu, Z.B.; Liu, Y.T.; Chen, D.F.

    2009-10-15

    Structures and thermal expansion properties of Ln{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} (Ln = Er and Y) have been investigated by X-ray powder diffraction. Rietveld analysis results of Ln{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} indicate that compounds Er{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} (0 {<=} x {<=} 0.3) and Y{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} (0 {<=} x {<=} 0.2) crystallize in orthorhombic structure and exhibit negative thermal expansion, while both monoclinic and orthorhombic compounds Er{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} (1.7 {<=} x {<=} 2.0) and Y{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} (1.8 {<=} x {<=} 2.0) possess positive coefficient of thermal expansion. The coefficients of linear thermal expansion of orthorhombic Ln{sub 2-x}Cr{sub x}Mo{sub 3}O{sub 12} change from negative to positive with increasing chromium content. Thermogravimetric and differential scanning calorimetry have been used to study the hygroscopicity and the phase transition temperature.

  16. Interplay of structural chemistry and magnetism in perovskites; A study of CaLn2Ni2WO9; Ln=La, Pr, Nd

    NASA Astrophysics Data System (ADS)

    Chin, Chun-Mann; Paria Sena, Robert; Hunter, Emily C.; Hadermann, Joke; Battle, Peter D.

    2017-07-01

    Polycrystalline samples of CaLn2Ni2WO9 (Ln=La, Pr, Nd) have been synthesized and characterised by a combination of X-ray and neutron diffraction, electron microscopy and magnetometry. Each composition adopts a perovskite-like structure with a 5.50, b 5.56, c 7.78 Å, β 90.1° in space group P21/n. Of the two crystallographically distinct six-coordinate sites, one is occupied entirely (Ln=Pr) or predominantly (Ln=La, Nd) by Ni2+ and the other by Ni2+ and W6+ in a ratio of approximately 1:2. None of the compounds shows long-range magnetic order at 5 K. The magnetometry data show that the magnetic moments of the Ni2+ cations form a spin glass below 30 K in each case. The Pr3+ moments in CaPr2Ni2WO9 also freeze but the Nd3+ moments in CaNd2Ni2WO9 do not. This behaviour is contrasted with that observed in other (A,A')B2B'O9 perovskites.

  17. Magnetic interactions in rhenium-containing rare earth double perovskites Sr2LnReO6 (Ln=rare earths)

    NASA Astrophysics Data System (ADS)

    Nishiyama, Atsuhide; Doi, Yoshihiro; Hinatsu, Yukio

    2017-04-01

    The perovskite-type compounds containing both rare earth and rhenium Sr2LnReO6 (Ln=Y, Tb-Lu) have been prepared. Powder X-ray diffraction measurements and Rietveld analysis show that Ln3+ and Re5+ ions are structurally ordered at the B site of the perovskite SrBO3. Magnetic anomalies are found in their magnetic susceptibility and specific heat measurements at 2.6-20 K for Ln=Y, Tb, Dy, Yb, Lu compounds. They are due to magnetic interactions between Re5+ ions. The results of the magnetic hysteresis and remnant magnetization measurements for Sr2YReO6 and Sr2LuReO6 indicate that the antiferromagnetic interactions between Re5+ ions below transition temperatures have a weak ferromagnetic component. The analysis of the magnetic specific heat data for Sr2YbReO6 shows that both the Yb3+ and Re5+ ions magnetically order at 20 K. For the case of Sr2DyReO6, magnetic ordering of the Re5+ moments occurs at 93 K, and with decreasing temperature, the moments of Dy3+ ferromagnetically order at 5 K from the measurements of magnetic susceptibility and specific heat.

  18. Ln(iii) complexes (Ln = Eu, Gd, Tb, Dy) with a chiral ligand containing 1,10-phenanthroline and (-)-menthol fragments: synthesis, structure, magnetic properties and photoluminescence.

    PubMed

    Larionov, Stanislav V; Bryleva, Yuliya A; Glinskaya, Ludmila A; Plyusnin, Victor F; Kupryakov, Arkady S; Agafontsev, Alexander M; Tkachev, Alexey V; Bogomyakov, Artem S; Piryazev, Dmitry A; Korolkov, Ilya V

    2017-08-29

    A series of lanthanide(iii) complexes based on the new chiral ligand L, which contains 1,10-phenanthroline and (-)-menthol fragments, namely [LnL2(NO3)3] (Ln = Eu (1), Gd (2), Tb (3), Dy (4)), have been synthesized and structurally characterized. Complexes 1-4 are isostructural and crystallize in the non-centrosymmetric space group P41212. The mononuclear complexes comprise a 10-coordinate Ln(3+) ion with two bidentate N,N-donor ligands (L) and three bidentate chelating nitrate groups. The magnetic properties of complexes 1-4 are determined mainly by the Ln(3+) ions. In the case of complexes 3 and 4, significant anisotropy results in nonlinear field dependences of magnetization at low temperature. Complexes 1, 3 and 4 exhibit metal-centered red (Eu(3+)), green (Tb(3+)) and yellow (Dy(3+)) luminescence, respectively, whereas complex 2 displays blue ligand-based luminescence in the solid state at room temperature. The luminescence quantum yield for the solid samples increases in the order 4 < 2 ≈ 3 < 1. The europium(iii) complex shows long luminescence lifetimes (up to 1750 μs) and a very high quantum yield (φf = 0.87); these make this compound promising for application in sensing and optoelectronics.

  19. Fluorescent naphthalene diols as bridging ligands in Ln(III) cluster chemistry: synthetic, structural, magnetic, and photophysical characterization of Ln(III)8 "Christmas stars".

    PubMed

    Alexandropoulos, Dimitris I; Fournet, Adeline; Cunha-Silva, Luís; Mowson, Andrew M; Bekiari, Vlasoula; Christou, George; Stamatatos, Theocharis C

    2014-06-02

    The initial employment of the fluorescent bridging ligand naphthalene-2,3-diol in 4f-metal coordination chemistry has provided access to a new family of Ln(III)8 clusters with a "Christmas-star" topology, single-molecule magnetism behavior, and ligand-centered emissions.

  20. Explanation for the variance of the Ce 3+ emission energy in LnI 3 [Ln = Lu 3+, Y 3+, Gd 3+

    NASA Astrophysics Data System (ADS)

    Srivastava, A. M.; Camardello, S. J.; Comanzo, H. A.; Aycibin, M.; Happek, U.

    2010-07-01

    The experimental result that the energy of the emitted photon increases with decreasing ionic radii of the host lattice is a remarkable feature of the Ce 3+ luminescence in the isostructural LnI 3 [Ln 3+ = Lu 3+, Y 3+, Gd 3+] family of materials. To understand this variation, the optical properties of YI 3:Ce 3+ is measured and compared with those reported for Ce 3+ activated LuI 3 and GdI 3. The results indicate that the crystal field splitting and the centroid shift of the Ce 3+ 5d 1 electronic configuration in these iodides are of the same order of magnitude. The lowest energy Ce 3+ 4f 1 → 5d 1 excitation transition in LnI 3 [Ln 3+ = Lu 3+, Y 3+, Gd 3+] is practically uninfluenced by the ionic radii of the host lattice cation, which the Ce 3+ ion substitutionally replaces. The increase in energy of the emitted photon with decreasing ionic radii of the host lattice is a result of the increasing Stokes shift of the Ce 3+ emission in the sequence LuI 3-YI 3-GdI 3. The quenching temperature of the Ce 3+ emission in YI 3 is high.

  1. Covalently-bonded grafting of [Ln3(Benzimidazole)4]-arrayed (Ln = Tb, Nd, Yb or Er) complex monomers into PNBE (poly(norbornene)) with highly luminous color-purity green-light or efficient NIR luminescence

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Fu, Guorui; Feng, Heini; Guan, Jiaqing; Li, Fengping; Lü, Xingqiang; Wong, Wai-Kwok; Jones, Richard A.

    2017-07-01

    Within series of Ln3-grafted polymers Poly({[Ln3(L)4(NO3)6]·(NO3)·(H3O)2}-co-NBE) (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; Ln = Nd, 4; Ln = Yb, 5; Ln = Er, 6 or Ln = Gd, 7) obtained from ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with each of allyl-functionalized complex monomers {[Ln3(L)4(NO3)6]·(NO3)·(H3O)2} (HL = 4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol), PNBE-assisted effective energy transfer renders Poly(3-co-NBE) Tb3+-centered highly luminous color-purity green-light with an attractive quantum yield of 87% and efficient near-infrared (NIR) luminescence (ΦNdL = 0.61%; ΦYbL = 1.47% and ΦErL = 0.03%) for Nd3+-, Yb3+- or Er3+-grafted polymers.

  2. Influence of Tuned Linker Functionality on Modulation of Magnetic Properties and Relaxation Dynamics in a Family of Six Isotypic Ln2 (Ln = Dy and Gd) Complexes.

    PubMed

    Mukherjee, Soumya; Lu, Jingjing; Velmurugan, Gunasekaran; Singh, Shweta; Rajaraman, Gopalan; Tang, Jinkui; Ghosh, Sujit K

    2016-11-07

    A coordination complex family comprising of six new dinuclear symmetric lanthanide complexes, namely, [Ln2(Lx)2(L')2(CH3OH)2]·yG (H2Lx: three related yet distinct Schiff-base linkers; x = 1-3, according to the nomenclature of the Schiff-base linker employed herein. HL': 2,6-dimethoxyphenol. yG refers to crystallographically assigned guest solvent species in the respective complexes; y = number of solvent molecules; Ln(III) = Dy/Gd) were isolated employing a mixed-ligand strategy stemming out of a strategic variation of the functionalities introduced among the constituent Schiff-base linkers. The purposeful introduction of three diverse auxiliary groups with delicate differences in their electrostatic natures affects the local anisotropy and magnetic coupling of Ln(III) ion-environment in the ensuing Ln2 dinuclear complexes, consequentially resulting into distinctly dynamical magnetic behaviors among the investigated new-fangled family of isotypic Ln2 complexes. Among the entire family, subtle alterations in the chemical moieties render two of the Dy2 analogues to behave as single molecule magnets, while the other Dy2 congener merely exhibits slow relaxation of the magnetization. The current observation marks one of the rare paradigms, wherein magnetic behavior modulation was achieved by virtue of the omnipresent influence of subtly tuned linker functionalities among the constituent motifs of the lanthanide nanomagnets. To rationalize the observed difference in the magnetic coupling, density functional theory and ab initio calculations (CASSCF/RASSI-SO/POLY_ANISO) were performed on all six complexes. Subtle difference in the bond angles leads to difference in the J values observed for Gd2 complexes, while difference in the tunnel splitting associated with the structural alterations lead to variation in the magnetization blockade in the Dy2 complexes.

  3. Hydrazinium lanthanide oxalates: synthesis, structure and thermal reactivity of N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce, Nd.

    PubMed

    De Almeida, Lucie; Grandjean, Stéphane; Rivenet, Murielle; Patisson, Fabrice; Abraham, Francis

    2014-03-28

    New hydrazinium lanthanide oxalates N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce (Ce-HyOx) and Nd (Nd-HyOx), were synthesized by hydrothermal reaction at 150 °C between lanthanide nitrate, oxalic acid and hydrazine solutions. The structure of the Nd compound was determined from single-crystal X-ray diffraction data, space group P2₁/c with a = 16.315(4), b = 12.127(3), c = 11.430(2) Å, β = 116.638(4)°, V = 2021.4(7) Å(3), Z = 4, and R1 = 0.0313 for 4231 independent reflections. Two distinct neodymium polyhedra are formed, NdO9 and NdO8N, an oxygen of one monodentate oxalate in the former being replaced by a nitrogen atom of a coordinated hydrazinium ion in the latter. The infrared absorption band at 1005 cm(-1) confirms the coordination of N2H5(+) to the metal. These polyhedra are connected through μ2 and μ3 oxalate ions to form an anionic three-dimensional neodymium-oxalate arrangement. A non-coordinated charge-compensating hydrazinium ion occupies, with water molecules, the resulting tunnels. The N-N stretching frequencies of the infrared spectra demonstrate the existence of the two types of hydrazine ions. Thermal reactivity of these hydrazinium oxalates and of the mixed isotypic Ce/Nd (CeNd-HyOx) oxalate were studied by using thermogravimetric and differential thermal analyses coupled with gas analyzers, and high temperature X-ray diffraction. Under air, fine particles of CeO2 and Ce(0.5)Nd(0.5)O(1.75) are formed at low temperature from Ce-HyOx and CeNd-HyOx, respectively, thanks to a decomposition/oxidation process. Under argon flow, dioxymonocyanamides Ln2O2CN2 are formed.

  4. Cyanido-Bridged {Ln(III)W(V)} Heterobinuclear Complexes: Synthesis and Magneto-Structural Study.

    PubMed

    Alexandru, Maria-Gabriela; Visinescu, Diana; Shova, Sergiu; Lloret, Francesc; Julve, Miguel

    2017-09-27

    A new series of cyanido-bridged {Ln(III)W(V)} heterobinuclear complexes of formula [Ln(III)(pyim)2(i-PrOH)(H2O)2(μ-CN)W(V)(CN)7]·2H2O [Ln = Gd (1), Tb (2), Dy (3), Ho (4), and Er (5); pyim = 2-(1H-imidazol-2-yl)-pyridine) and i-PrOH = isopropyl alcohol] were synthesized by one-pot reaction between (NH3Bu)3[W(CN)8] and [Ln(pyim)2](2+) complexes (generated in situ by mixing the corresponding Ln(III) ions and the pyim ligand). Compounds 1-5 are isomorphous and crystallize in the monoclinic system P21/n space group. Their crystal structure consists of binuclear units in which the octacyanotungstate(V) anion coordinates to the corresponding Ln(III) ion through a single cyanide ligand. The tungsten(V) and lanthanide(III) ions are eight-coordinated, in distorted square antiprism (W(V)) and distorted trigonal dodecahedron (Ln(III)) geometries, respectively. The direct-current (dc) magnetic properties for 1-5 reveal the occurrence of weak antiferromagnetic interactions between W(V) and Ln(III) cation, with (8)S7/2, (7)F6, (6)H15/2, (5)I8, and (4)I15/2 as ground terms for Gd(III), Tb(III), Dy(III) Ho(III), and Er(III), respectively [JWLn = -1.19(1) (1), -1.02(2) (2), -1.10(2) (3), -1.30(2) (4), and -1.50(3) cm(-1) (5), the spin Hamiltonian being defined as H = -JWLn SW·SLn]. The fit of the χMT data of 2-4 points out a positive value for the energy gap between the ML components (Δ). This feature is corroborated by their Q-band electron paramagnetic resonance spectra at low temperature, which clearly show MJ = 0 (2 and 4) and ±1/2 (3 and 5). Incipient frequency-dependent alternating-current magnetic susceptibility signals are observed for 3 and 5 under applied dc fields supporting the presence of slow magnetic relaxation behavior, the blocking temperatures being below 2.0 K. This new series of {Ln(III)W(V)} heterobinuclear compounds provides more insights into the exchange magnetic interaction between 5d and 4f centers via the cyanide-bridge, for which scarce information

  5. Consideration of sub-cooled LN2 circulation system for HTS power machines

    NASA Astrophysics Data System (ADS)

    Yoshida, Shigeru; Hirai, Hirokazu; Nara, N.; Nagasaka, T.; Hirokawa, M.; Okamoto, H.; Hayashi, H.; Shiohara, Y.

    2012-06-01

    We consider a sub-cooled liquid nitrogen (LN) circulation system for HTS power equipment. The planned circulation system consists of a sub-cool heat exchanger (subcooler) and a circulation pump. The sub-cooler will be connected to a neon turbo- Brayton cycle refrigerator with a cooling power of 2 kW at 65 K. Sub-cooled LN will be delivered into the sub-cooler by the pump and cooled within it. Sub-cooled LN is adequate fluid for cooling HTS power equipment, because its dielectric strength is high and it supports a large critical current. However, a possibility of LN solidification in the sub-cooler is a considerable issue. The refrigerator will produce cold neon gas of about 60 K, which is lower than the nitrogen freezing temperature of 63 K. Therefore, we designed two-stage heat exchangers which are based on a plate-fin type and a tube-intube type. Process simulations of those heat exchangers indicate that sub-cooled LN is not frozen in either sub-cooler. The plate-fin type sub-cooler is consequently adopted for its reliability and compactness. Furthermore, we found that a cooling system with a Brayton refrigerator has the same total cooling efficiency as a cooling system with a Stirling refrigerator.

  6. Fabrication of Ln-MOFs with color-tunable photoluminescence and sensing for small molecules

    NASA Astrophysics Data System (ADS)

    Wang, Shengyan; Shan, Liang; Fan, Yong; Jia, Jia; Xu, Jianing; Wang, Li

    2017-01-01

    Three isomorphic lanthanide metal-organic frameworks (Ln-MOFs) [LnL(H2O)2]·2H2O (Ln=Tb for 1, Eu for 2, Gd for 3) have been constructed from flexible organic ligand 4-(2-carboxyphenoxy)benzene-1,3-dioic acid (H3L). They exhibit two-dimensional (2D) layered structure with the rhombus windows along the b axis. This network can be described as a shubnikov plane net with Schäfli symbol of (43)2(46.66.83). Solid state luminescent studies indicate that 1 and 2 show the characteristic red, and green emissions of the corresponding Ln3+ ions, respectively, while 3 exhibits blue emission arising from the organic ligand. Then by adjusting the relative amounts of different luminescent components into the well-defined host framework, a series of new co-doped Ln-MOF, Tb1-xEuxL (4) (x refers to the molar ratios of Eu3+ and Tb3+), with tunable luminescence have been fabricated. The luminescent color of 4 can be tuned from green to red due to the energy transfer from the Tb3+ to Eu3+ ions by changing the doping concentration of the Eu3+ ions. In addition, 2 exhibits good stability in different solvents and excellent fluorescence sensing for small molecules, especially for CH3CN and nitrobenzene.

  7. Multifunctionality in bimetallic Ln(III)[W(V)(CN)8]3- (Ln = Gd, Nd) coordination helices: optical activity, luminescence, and magnetic coupling.

    PubMed

    Chorazy, Szymon; Nakabayashi, Koji; Arczynski, Mirosław; Pełka, Robert; Ohkoshi, Shin-ichi; Sieklucka, Barbara

    2014-06-02

    Two chiral luminescent derivatives of pyridine bis(oxazoline) (Pybox), (SS/RR)-iPr-Pybox (2,6-bis[4-isopropyl-2-oxazolin-2-yl]pyridine) and (SRSR/RSRS)-Ind-Pybox (2,6-bis[8H-indeno[1,2-d]oxazolin-2-yl]pyridine), have been combined with lanthanide ions (Gd(3+), Nd(3+)) and octacyanotungstate(V) metalloligand to afford a remarkable series of eight bimetallic CN(-)-bridged coordination chains: {[Ln(III)(SS/RR-iPr-Pybox)(dmf)4]3[W(V)(CN)8]3}n ⋅dmf⋅4 H2O (Ln = Gd, 1-SS and 1-RR; Ln = Nd, 2-SS and 2-RR) and {[Ln(III)(SRSR/RSRS-Ind-Pybox)(dmf)4][W(V)(CN)8]}n⋅5 MeCN⋅4 MeOH (Ln = Gd, 3-SRSR and 3-RSRS; Ln = Nd, 4-SRSR and 4-RSRS). These materials display enantiopure structural helicity, which results in strong optical activity in the range 200-450 nm, as confirmed by natural circular dichroism (NCD) spectra and the corresponding UV/Vis absorption spectra. Under irradiation with UV light, the Gd(III)-W(V) chains show dominant ligand-based red phosphorescence, with λmax ≈660 nm for 1-(SS/RR) and 680 nm for 3-(SRSR/RSRS). The Nd(III)-W(V) chains, 2-(SS/RR) and 4-(SRSR/RSRS), exhibit near-infrared luminescence with sharp lines at 986, 1066, and 1340 nm derived from intra-f (4)F3/2 → (4)I9/2,11/2,13/2 transitions of the Nd(III) centers. This emission is realized through efficient ligand-to-metal energy transfer from the Pybox derivative to the lanthanide ion. Due to the presence of paramagnetic lanthanide(III) and [W(V)(CN)8](3-) moieties connected by cyanide bridges, 1-(SS/RR) and 3-(SRSR/RSRS) are ferrimagnetic spin chains originating from antiferromagnetic coupling between Gd(III) (SGd = 7/2) and W(V) (SW = 1/2) centers with J1-(SS) = -0.96(1) cm(-1), J1-(RR) =-0.95(1) cm(-1), J3-(SRSR) = -0.91(1) cm(-1), and J3-(RSRS) =-0.94(1) cm(-1). 2-(SS/RR) and 4-(SRSR/RSRS) display ferromagnetic coupling within their Nd(III)-NC-W(V) linkages.

  8. Characterization and luminescence properties of sol–gel derived M′-type LuTaO{sub 4}:Ln{sup 3+} (Ln = Pr, Sm, Dy) phosphors

    SciTech Connect

    Wu, Mengqiu; Liu, Xiaolin Gu, Mu; Ni, Chen; Liu, Bo; Huang, Shiming

    2014-12-15

    Graphical abstract: Emission spectra of LuTaO{sub 4}:Ln (Ln = Pr, Sm and Dy) phosphors under X-ray excitation. The insets illustrate their SEM micrographs. - Highlights: • M′-type LuTaO{sub 4}:Ln{sup 3+} (Ln = Pr, Sm, Dy) phosphors were synthesized by sol–gel technique. • The phosphors exhibited an efficient energy transfer from the host to activators. • High intensity of activator emission was achieved under X-ray excitation. • The phosphors are encouraging for application in high-spatial-resolution X-ray CT imaging. - Abstract: M′-type Lu{sub 1−x}Ln{sub x}TaO{sub 4} (Ln = Pr, Sm, Dy) phosphors have been successfully synthesized by sol–gel technique, their crystallization, morphology, photoluminescence and X-ray excited luminescence properties were investigated in detail. The phosphors had good crystallization behavior. The optimum doping concentrations of Pr{sup 3+}, Sm{sup 3+} and Dy{sup 3+} in LuTaO{sub 4} were at x = 0.003, 0.025, 0.02, respectively. They exhibited a more efficient host excitation relative to the 4f–4f excitations of the rare-earth ions, and a dominant {sup 1}D{sub 2} → {sup 3}H{sub 4}, {sup 4}G{sub 5/2} → {sup 6}H{sub 7/2} or {sup 4}F{sub 9/2} → {sup 6}H{sub 13/2} emission for Pr{sup 3+}, Sm{sup 3+} or Dy{sup 3+}, respectively, which corresponds to the average decay time of 21.7, 745.7 or 10.0 μs, respectively. It is expected that Pr{sup 3+}- or Dy{sup 3+}-doped LuTaO{sub 4} phosphors with a microsecond level decay time are very encouraging for applications in X-ray computerized tomographic imaging with high spatial resolution.

  9. Crystal chemistry of the orthorhombic Ln{sub 2}TiO{sub 5} compounds with Ln=La, Pr, Nd, Sm, Gd, Tb and Dy

    SciTech Connect

    Aughterson, Robert D.; Lumpkin, Gregory R.; Thorogood, Gordon J.; Zhang, Zhaoming; Gault, Baptiste; Cairney, Julie M.

    2015-07-15

    The crystal structures of seven samples of orthorhombic (Pnma) Ln{sub 2}TiO{sub 5} compounds with Ln=La, Pr, Nd, Sm, Gd, Tb and Dy were refined by Rietveld analysis of synchrotron X-ray powder diffraction (S-XRD) data. With increasing size of the lanthanide cation, the lattice parameters increase systematically: c by only ~1.5% whereas both a and b by ~6% from Dy{sub 2}TiO{sub 5} to La{sub 2}TiO{sub 5}. The mean Ti–O bond length only increases by ~1% with increasing radius of the Ln cation from Gd to La, primarily due to expansion of the pair of Ti–O{sub 3} bonds to opposite corners of the Ti–O{sub 5} square based pyramid polyhedra. For Dy{sub 2}TiO{sub 5} and Tb{sub 2}TiO{sub 5}, a significant variation in Ti–O{sub 1} and Ti–O{sub 4} bond lengths results in an increased deformation of the Ti–O{sub 5} base. The particular configuration consists of large rhombic shaped tunnels and smaller triangular tunnels along the b axis, which have implications for defect formation and migration caused by radiation damage or the ionic conductivity. - Graphical abstract: Figure: The crystallographic study of a systematic series of compounds with nominal stoichiometry Ln{sub 2}TiO{sub 5} (with Ln representing La, Pr, Nd, Sm, Gd, Tb and Dy) and orthorhombic, Pnma, symmetry shows changes in cell parameters which fit a linear trend. However, bond lengths are shown to deviate from trend with compounds containing the smaller, heavier lanthanides. - Highlights: • First fabrication and crystallographic refinement of compound Pr{sub 2}TiO{sub 5}. • First systematic study of the crystallography, using S-XRD, for Ln{sub 2}TiO{sub 5} series. • Cation to anion bonding trends and valence states are investigated. • The densities and band-gaps of the series are experimentally determined.

  10. Towards hybrid biocompatible magnetic rHuman serum albumin-based nanoparticles: use of ultra-small (CeLn)3/4+ cation-doped maghemite nanoparticles as functional shell

    NASA Astrophysics Data System (ADS)

    Israel, Liron L.; Kovalenko, Elena I.; Boyko, Anna A.; Sapozhnikov, Alexander M.; Rosenberger, Ina; Kreuter, Jörg; Passoni, Lorena; Lellouche, Jean-Paul

    2015-01-01

    Human serum albumin (HSA) is a protein found in human blood. Over the last decade, HSA has been evaluated as a promising drug carrier. However, not being magnetic, HSA cannot be used for biomedical applications such as magnetic resonance imaging (MRI) and magnetic drug targeting. Therefore, subsequent composites building on iron oxide nanoparticles that are already used clinically as MRI contrast agents are extensively studied. Recently and in this context, innovative fully hydrophilic ultra-small CAN-stabilized maghemite ((CeLn)3/4+-γ-Fe2O3) nanoparticles have been readily fabricated. The present study discusses the design, fabrication, and characterization of a dual phase hybrid core (rHSA)-shell ((CeLn)3/4+-γ-Fe2O3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeLn)3/4+-γ-Fe2O3 NPs enabled to exploit both rHSA (protein functionalities) and (CeLn)3/4+-γ-Fe2O3 NP surface functionalities (COOH and ligand L coordinative exchange) in addition to very effective MRI contrast capability due to optimal accessibility of H2O molecules with the outer magnetic phase. Resulting hybrid nanoparticles might be used as a platform modular system for therapeutic (drug delivery system) and MR diagnostic purposes.

  11. Two nanosized 3d-4f clusters featuring four Ln6 octahedra encapsulating a Zn4 tetrahedron.

    PubMed

    Zheng, Xiu-Ying; Wang, Shi-Qiang; Tang, Wen; Zhuang, Gui-Lin; Kong, Xiang-Jian; Ren, Yan-Ping; Long, La-Sheng; Zheng, Lan-Sun

    2015-07-07

    Two high-nuclearity 3d-4f clusters Ln24Zn4 (Ln = Gd and Sm) featuring four Ln6 octahedra encapsulating a Zn4 tetrahedron were obtained through the self-assembly of Zn(OAc)2 and Ln(ClO4)3. Quantum Monte Carlo (QMC) simulations show the antiferromagnetic coupling between Gd(3+) ions. Studies of the magnetocaloric effect (MCE) show that the Gd24Zn4 cluster exhibits the entropy change (-ΔSm) of 31.4 J kg(-1) K(-1).

  12. Simple correction for the sample shape and radial offset effects on SQUID magnetometers: Magnetic measurements on Ln2O3 (Ln=Gd, Dy, Er) standards

    NASA Astrophysics Data System (ADS)

    Morrison, Gregory; zur Loye, Hans-Conrad

    2015-01-01

    An increased focus on magnetic measurements of oriented single crystals, thin films, and magnetically dilute systems has led to a demand for the measurement of weak magnetic moments. This level of sensitivity and precision can be achieved on SQUID magnetometers by decreasing the size of the detection coils. However, the smaller detection coils can amplify two errors in the magnitude of the measured moment, the sample shape and radial offset effects, which were small and typically unaccounted for on previous magnetometers. We report a simple method to determine the radial offset of a sample by taking advantage of the two basic scan modes, DC and lock-in, typically used on magnetometers. This technique allows for the correction of the sample shape and radial offset effects in order to obtain the true moment of a sample. To show the efficacy of this technique, we report the magnetic properties of Ln2O3 (Ln=Gd, Dy, Er).

  13. Facile fabrication and upconversion luminescence enhancement of LaF3:Yb3+/Ln3+@SiO2 (Ln = Er, Tm) nanostructures decorated with Ag nanoparticles.

    PubMed

    He, Enjie; Zheng, Hairong; Dong, Jun; Gao, Wei; Han, Qingyan; Li, Junna; Hui, Le; Lu, Ying; Tian, Huani

    2014-01-31

    A novel hybrid nanostructure, that is a Ag nanoparticle decorated LaF(3):Yb(3+)/Ln(3+)@SiO(2) nanosphere (Ln=Er, Tm), was constructed by a facile strategy, and characterized by XRD, TEM, FTIR, XPS and UV-vis-NIR absorption. Obvious spectral broadening and red-shift on the surface plasmon resonance were obtained by adjusting the size and configuration of Ag nanoparticles. Effective upconversion luminescence enhancements for Er(3+) and Tm(3+) containing samples were obtained. It is suggested that the luminescence enhancement results from both the excitation and emission processes, and the configuration of the studied hybrid nanostructure is an efficient system to enhance the luminescence emission of rare earth doped nanomaterials. It is believed that the enhancement from the hybrid nanostructure will find great potential in the development of photovoltaic solar cells.

  14. Synthesis and luminescent properties of spindle-like YVO4:Ln3+ (Ln=Eu, Dy) self-assembled of nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, Lihui; You, Hongpeng; Yang, Mei

    2012-02-01

    Large-scale spindle-like YVO4 particles with an euatorial diameter of 100-150 nm and a length of 300-350 nm were synthesized by utilizing the Y(OH)CO3 colloid spheres as the precursor and NH4VO3 as the vanadium source through a simple solution-based hydrothermal process, for the first time. In the first stage of the reaction, hierarchical flower-like YVO4 spheres were formed. Then, petals of spindle-like YVO4 particles were obtained via a following self-abscission process from these flower spheres. The possible formation mechanism has been discussed in detail. Moreover, the photoluminescent properties of spindle-like YVO4:Ln3+ (Ln=Eu, Dy) nanoparticles were investigated. They might have potential application in advanced flat panel display, minioptoelectronic devices, and biological labeling.

  15. On the energy transfer in (Y,Gd)Al3(BO3)4:Ln3+ (Ln = Tb3+, Dy3+)

    NASA Astrophysics Data System (ADS)

    Dierkes, Tobias; Pues, Patrick; Jüstel, Thomas

    2015-08-01

    Single-phase (Y,Gd)Al3(BO3)4:Ln3+ (Ln = Tb3+, Dy3+) (YAB) samples were synthesized via solid state reactions and spectroscopic investigations were conducted in order to characterise possible energy transfer mechanisms between Gd3+ and the activator ions, Tb3+/Dy3+. Photoluminescence spectra ranging from 120 to 800 nm were recorded which made it possible to assign charge transfer absorption bands of the host structure, 4f → 5d and 4f → 4f excitations of the activators and their respective emission multiplets. Spectroscopic measurements such as reflection spectra, decay curves, emission/excitation spectra and calculations of external quantum efficiencies were presented to support the suggested energy transfer scheme in Gd3+ activated YAB.

  16. Investigation of the structural properties of an extended series of lanthanide bis-hydroxychlorides Ln(OH)(2)Cl (Ln = Nd-Lu, except Pm and Sm).

    PubMed

    Zehnder, Ralph A; Clark, David L; Scott, Brian L; Donohoe, Robert J; Palmer, Phillip D; Runde, Wolfgang H; Hobart, David E

    2010-06-07

    The trivalent lanthanide bis-hydroxychloride compounds, Ln(OH)(2)Cl, (Ln = Nd through Lu, with the exception of Pm and Sm) have been prepared by hydrothermal synthesis starting with LnCl(3).nH(2)O. These compounds were synthesized at temperatures not exceeding the melting point of the Teflon liners in the Parr autoclaves ( approximately 220 degrees C). The compounds obtained were characterized by single crystal X-ray diffraction analysis, diffuse reflectance, FT-IR, and FT-Raman spectroscopies. Most of the lanthanide(III) bis-hydroxychlorides are isostructural and generally crystallize in the monoclinic space group P2(1)/m. The bis-hydroxychlorides of the heavier lanthanide(III) atoms with smaller ionic radii also crystallize in the orthorhombic crystal system. Apparently hydrogen bonds between the OH groups and the Cl atoms connect the layers in the "c" direction. These H-bonds seem to be the driving force for the angle beta of the monoclinic complexes to decrease with decreasing ionic radius of the Ln(III) ion and also for tying the layers together more strongly. As a result of this behavior, the structure of the heavier 4f analogues significantly resembles that of their orthorhombic counterparts. The heavier lanthanide bis-hydroxychlorides preferentially crystallize in the orthorhombic modification. The IR absorbance and Raman frequencies of the hydroxide ligands correlate as a function of the central lanthanide(III) ionic radius. This observation is corroborated by X-ray diffraction (XRD) structural data. These compounds are quite insoluble in near-neutral and basic aqueous solutions, but soluble in acidic solutions. It is expected that the analogue actinide bis-hydroxychlorides exhibit similar behavior and that this may have important implications in the immobilization and safe disposal of nuclear waste.

  17. The extended chain compounds Ln12(C 2) 3I 17 ( Ln=Pr, Nd, Gd, Dy): Synthesis, structure and physical properties

    NASA Astrophysics Data System (ADS)

    Ryazanov, Mikhail; Mattausch, Hansjürgen; Simon, Arndt

    2007-04-01

    The title compounds are obtained in high yield from stoichiometric mixtures of Ln, LnI 3 and graphite, heated at 900-950 °C in welded Ta containers. The crystal structures of new Pr and Nd phases determined by single-crystal X-ray diffraction are related to those of other Ln12(C 2) 3I 17-type compounds ( C 2/ c, a=19.610(1) and 19.574(4) Å, b=12.406(2) and 12.393(3) Å, c=19.062(5) and 19.003(5) Å, β=90.45(3)° and 90.41(3)°, for Pr 12(C 2) 3I 17 and Nd 12(C 2) 3I 17, respectively). All compounds contain infinite zigzag chains of C 2-centered metal atom octahedra condensed by edge-sharing into the [tcc] ∞ sequence (c= cis, t= trans) and surrounded by edge-bridging iodine atoms as well as by apical iodine atoms that bridge between chains. The polycrystalline Gd 12(C 2) 3I 17 sample exhibits semiconducting thermal behavior which is consistent with an ionic formulation ( Ln3+) 12(C 26-) 3(I -) 17(e -) under the assumption that one extra electron is localized in metal-metal bonding. The magnetization measurements on Nd 12(C 2) 3I 17, Gd 12(C 2) 3I 17 and Dy 12(C 2) 3I 17 indicate the coexistence of competing magnetic interactions leading to spin freezing at Tf=5 K for the Gd phase. The Nd and Dy compounds order antiferromagnetically at TN=25 and 29 K, respectively. For Dy 12(C 2) 3I 17, a metamagnetic transition is observed at a critical magnetic field H≈25 kOe.

  18. Increasing Dietary Fat Elicits Similar Changes in Fat Oxidation and Markers of Muscle Oxidative Capacity in Lean and Obese Humans

    PubMed Central

    Bergouignan, Audrey; Gozansky, Wendolyn S.; Barry, Daniel W.; Leitner, Wayne; MacLean, Paul S.; Hill, James O.; Draznin, Boris; Melanson, Edward L.

    2012-01-01

    In lean humans, increasing dietary fat intake causes an increase in whole-body fat oxidation and changes in genes that regulate fat oxidation in skeletal muscle, but whether this occurs in obese humans is not known. We compared changes in whole-body fat oxidation and markers of muscle oxidative capacity differ in lean (LN) and obese (OB) adults exposed to a 2-day high-fat (HF) diet. Ten LN (BMI = 22.5±2.5 kg/m2, age = 30±8 yrs) and nine OB (BMI = 35.9±4.93 kg/m2, 38±5 yrs, Mean±SD) were studied in a room calorimeter for 24hr while consuming isocaloric low-fat (LF, 20% of energy) and HF (50% of energy) diets. A muscle biopsy was obtained the next morning following an overnight fast. 24h respiratory quotient (RQ) did not significantly differ between groups (LN: 0.91±0.01; OB: 0.92±0.01) during LF, and similarly decreased during HF in LN (0.86±0.01) and OB (0.85±0.01). The expression of pyruvate dehydrogenase kinase 4 (PDK4) and the fatty acid transporter CD36 increased in both LN and OB during HF. No other changes in mRNA or protein were observed. However, in both LN and OB, the amounts of acetylated peroxisome proliferator-activated receptor γ coactivator-1-α (PGC1-α) significantly decreased and phosphorylated 5-AMP-activated protein kinase (AMPK) significantly increased. In response to an isoenergetic increase in dietary fat, whole-body fat oxidation similarly increases in LN and OB, in association with a shift towards oxidative metabolism in skeletal muscle, suggesting that the ability to adapt to an acute increase in dietary fat is not impaired in obesity. PMID:22253914

  19. Increasing dietary fat elicits similar changes in fat oxidation and markers of muscle oxidative capacity in lean and obese humans.

    PubMed

    Bergouignan, Audrey; Gozansky, Wendolyn S; Barry, Daniel W; Leitner, Wayne; MacLean, Paul S; Hill, James O; Draznin, Boris; Melanson, Edward L

    2012-01-01

    In lean humans, increasing dietary fat intake causes an increase in whole-body fat oxidation and changes in genes that regulate fat oxidation in skeletal muscle, but whether this occurs in obese humans is not known. We compared changes in whole-body fat oxidation and markers of muscle oxidative capacity differ in lean (LN) and obese (OB) adults exposed to a 2-day high-fat (HF) diet. Ten LN (BMI = 22.5±2.5 kg/m², age = 30±8 yrs) and nine OB (BMI = 35.9±4.93 kg/m², 38±5 yrs, Mean±SD) were studied in a room calorimeter for 24hr while consuming isocaloric low-fat (LF, 20% of energy) and HF (50% of energy) diets. A muscle biopsy was obtained the next morning following an overnight fast. 24h respiratory quotient (RQ) did not significantly differ between groups (LN: 0.91±0.01; OB: 0.92±0.01) during LF, and similarly decreased during HF in LN (0.86±0.01) and OB (0.85±0.01). The expression of pyruvate dehydrogenase kinase 4 (PDK4) and the fatty acid transporter CD36 increased in both LN and OB during HF. No other changes in mRNA or protein were observed. However, in both LN and OB, the amounts of acetylated peroxisome proliferator-activated receptor γ coactivator-1-α (PGC1-α) significantly decreased and phosphorylated 5-AMP-activated protein kinase (AMPK) significantly increased. In response to an isoenergetic increase in dietary fat, whole-body fat oxidation similarly increases in LN and OB, in association with a shift towards oxidative metabolism in skeletal muscle, suggesting that the ability to adapt to an acute increase in dietary fat is not impaired in obesity.

  20. Magnetic structure and electromagnetic properties of LnCrAsO with a ZrCuSiAs-type structure (Ln = La, Ce, Pr, and Nd).

    PubMed

    Park, Sang-Won; Mizoguchi, Hiroshi; Kodama, Katsuaki; Shamoto, Shin-ichi; Otomo, Toshiya; Matsuishi, Satoru; Kamiya, Toshio; Hosono, Hideo

    2013-12-02

    We report the synthesis, structure, and electromagnetic properties of Cr-based layered oxyarsenides LnCrAsO (Ln = La, Ce, Pr, and Nd) with a ZrCuSiAs-type structure. All LnCrAsO samples showed metallic electronic conduction. Electron doping in LaCrAsO by Mn-substitution for the Cr sites gave rise to a metal-insulator transition. Analysis of powder neutron diffraction data revealed that LaCrAsO had G-type antiferromagnetic (AFM) ordering, i.e., a checkerboard-type AFM ordering in the CrAs plane and antiparallel spin coupling between the adjacent CrAs planes, at 300 K with a large spin moment of 1.57 μB along the c axis. The magnetic susceptibility of LaCrAsO was very small (on the order of 10(-3) emu/mol) and showed a broad hump at ∼550 K. First-principles density functional theory calculations of LaCrAsO explained its crystal structure and metallic nature well, but could not replicate the antiparallel spin coupling between the CrAs layers. The electronic structure of LaCrAsO is discussed with regard to those of related compounds LaFeAsO and LaMnAsO.

  1. Band structure and near infrared quantum cutting investigation of GdF3:Yb3+, Ln3+ (Ln = Ho, Tm, Er, Pr, Tb) nanoparticles.

    PubMed

    Guo, Linna; Wang, Yuhua; Zeng, Wei; Zhao, Lei; Han, Lili

    2013-09-14

    A series of GdF3:Yb(3+), Ln(3+) (Ln = Ho, Tm, Er, Pr, Tb) nanoparticles were prepared by a simple and green hydrothermal method without any additives, which exhibited an ellipse-like shape with a diameter of 63 nm and a length of 101 nm on average. To prove the existence (or not) of near infrared quantum cutting for various lanthanide ion couples (Yb/Ho; Yb/Tm; Yb/Er; Yb/Pr; Yb/Tb) in one host lattice (GdF3), the measured luminescence spectra and decay lifetimes of these samples were analysed. Furthermore, the band structures and densities of state of GdF3 were also studied with the help of first-principles calculations, and the direct band gap of GdF3 was estimated to be 7.443 eV wide. Based on this, detailed processes and possible mechanisms of the luminescence phenomena are discussed. GdF3:Yb(3+), Ln(3+) nanoparticles may have potential applications in modifying the solar spectrum to enhance the efficiency of silicon solar cells.

  2. Multi-Enhanced-Phonon Scattering Modes in Ln-Me-A Sites co-substituted LnMeA11O19 Ceramics

    PubMed Central

    Lu, Haoran; Wang, Chang-An; Huang, Yong; Xie, Huimin

    2014-01-01

    Authors reported an effective path to decrease the thermal conductivity while to increase the coefficient of thermal expansion, thus enhancing the thermo-physical properties of the LnMeA11O19-type magnetoplumbite LaMgAl11O19 by simultaneously substituting La3+, Mg2+ and Al3+ ions with large ionic radius Ba2+, Zn2+ and Ti4+, respectively. The mechanism behind the lowered thermal conductivity was mainly due to the multi-enhanced-phonon scattering modes in Ln-Me-A sites co-substituted LnMeA11O19 ceramics. These modes involve the following four aspects, namely, point defect mechanism, the intrinsic scattering in the complex crystal cell and materials with stepped surface to localize phonon vibrational modes, as well as nano-platelet-like structure to incorporate additional grain boundary scattering. This study provides novel thoughts for promising candidate materials of even lower thermal conductivity for the next generation thermal barrier coatings. PMID:25351166

  3. Multi-enhanced-phonon scattering modes in Ln-Me-A sites co-substituted LnMeA11O19 ceramics.

    PubMed

    Lu, Haoran; Wang, Chang-An; Huang, Yong; Xie, Huimin

    2014-10-29

    Authors reported an effective path to decrease the thermal conductivity while to increase the coefficient of thermal expansion, thus enhancing the thermo-physical properties of the LnMeA11O19-type magnetoplumbite LaMgAl11O19 by simultaneously substituting La(3+), Mg(2+) and Al(3+) ions with large ionic radius Ba(2+), Zn(2+) and Ti(4+), respectively. The mechanism behind the lowered thermal conductivity was mainly due to the multi-enhanced-phonon scattering modes in Ln-Me-A sites co-substituted LnMeA11O19 ceramics. These modes involve the following four aspects, namely, point defect mechanism, the intrinsic scattering in the complex crystal cell and materials with stepped surface to localize phonon vibrational modes, as well as nano-platelet-like structure to incorporate additional grain boundary scattering. This study provides novel thoughts for promising candidate materials of even lower thermal conductivity for the next generation thermal barrier coatings.

  4. Monodisperse lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm): morphology controlled synthesis, up-conversion luminescence and in vitro cell imaging.

    PubMed

    Zhang, Yang; Li, Xuejiao; Hou, Zhiyao; Lin, Jun

    2014-06-21

    Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb(3+)/Er(3+), Yb(3+)/Ho(3+) and Yb(3+)/Tm(3+) co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb(3+), 0.04Er(3+) nanospheres is dominated by a single red emission at 660 nm, which falls into the "optical window" of biological tissues. The application of YOF: 0.20Yb(3+), 0.04Er(3+) nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise.

  5. Controllable synthesis and up-conversion properties of tetragonal BaYF5:Yb/Ln (Ln=Er, Tm, and Ho) nanocrystals.

    PubMed

    Niu, Na; Yang, Piaoping; Liu, Yanchao; Li, Chunxia; Wang, Dong; Gai, Shili; He, Fei

    2011-10-15

    The nanocrystals (NCs) of tetragonal barium yttrium fluoride (BaYF(5)) doped 1 mol% Ln(3+) (Ln=Er, Tm, Ho) and 20 mol% Yb(3+) with different morphologies and sizes have been successfully synthesized through a facile hydrothermal method. The influences of pH values of the initial solution and fluorine sources on the final structure and morphology of the products have been well investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the size, structure and morphology of these samples prepared at different conditions. And it is found that BaYF(5):Yb/Ln NCs prepared at pH value of 10 using NaBF(4) as F(-) source have a uniform spherical morphology with average diameter of 25 nm. Additionally, the up-conversion (UC) properties of Yb/Er, Yb/Tm, and Yb/Ho doped BaYF(5) nanoparticles were also discussed. Under 980 nm laser excitation, the BaYF(5):Yb/Er, BaYF(5):Yb/Tm, and BaYF(5):Yb/Ho NCs exhibit green, whitish blue, and yellow green UC luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.

  6. Self-assembled Ln(III)4 (Ln = Eu, Gd, Dy, Ho, Yb) [2 × 2] square grids: a new class of lanthanide cluster.

    PubMed

    Randell, Nicholas M; Anwar, Muhammad U; Drover, Marcus W; Dawe, Louise N; Thompson, Laurence K

    2013-06-03

    Self-assembly of the Ln(III) ions (Ln = Eu, Gd, Dy, Ho, Yb) into square [2 × 2] grid-like arrays has been readily effected using simple, symmetric ditopic ligands based on a carbohydrazone core. The metal ions are connected via single atom bridges (e.g., μ2-O(hydrazone), μ2-OH, μ2-OMe, μ2-1,1-N3(-), μ4-O), depending on reaction conditions. The Gd(III)4 examples exhibit intramolecular antiferromagnetic exchange (-J < 0.11 cm(-1)), and in one Dy(III)4 example, with a combination of μ2-1,1-N3(-), and μ4-O bridges linking adjacent metal ions, SMM behavior is observed. One thermally driven relaxation process is observed in the temperature range 10-25 K (τ0 = 6.5(1) × 10(-7) s, U(eff) = 110(1) K) in the presence of an 1800 Oe external field, employed to suppress a second quantum based relaxation process. The extended group of Ln(III) ions which submit to this controlled self-assembly, typical of the transition metal ions, indicates the general applicability of this approach to the lanthanides. This occurs despite the anticipated limitations based on larger ionic radii and coordination numbers, and is an encouraging sign for extension to larger grids with appropriately chosen polytopic ligands.

  7. The size confinement effect for Ln3+ (Ln = Tm or Eu) concentration quenching and energy transfer in Y2O3 nanocrystals.

    PubMed

    Wang, Changwen; Meng, Qingyu

    2014-05-01

    Y2O3:Ln (Ln = Tm or Eu) nano-powders with different particle sizes and various doping concentrations were prepared by using a combustion method. The bulk powders doped with the same concentrations were obtained by annealing the nano-powders at high temperatures. Emission spectra of the phosphors were measured. The crystal structure and morphology of the phosphors were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy), respectively. The concentration quenching of luminescent centers and energy transfer between luminescent centers in Y2O3:Ln nanocrystal powders were investigated. It is found that the behavior of luminescent concentration quenching for Eu3+ 5D0 --> 7F2 in nano-powders is similar to that in bulk powders. On the contrary, the quenching concentration for Tm3+ 1D2 --> 3H4 is distinctly higher than that in bulk powders. This owes to the size confinement effect which will restrain the electric dipole-dipole interaction as a long-rang interaction (e.g., energy transfer between Tm3+ ions), and will hardly affect the exchange interaction which is a short-rang interaction (e.g., energy transfer between Eu3+ ions).

  8. Structures and crystal chemistry of the double perovskites Ba{sub 2}LnB'O{sub 6} (Ln=lanthanide and B'=Nb, Ta):

    SciTech Connect

    Saines, Paul J.; Spencer, Jarrah R.; Kennedy, Brendan J. Kubota, Yoshiki; Minakata, Chiharu; Hano, Hiroko; Kato, Kenichi; Takata, Masaki

    2007-11-15

    The structures of eight members of the series of double perovskites of the type Ba{sub 2}LnB'O{sub 6} (Ln=La{sup 3+}-Sm{sup 3+} and Y{sup 3+} and B'=Nb{sup 5+} and Ta{sup 5+}) were examined both above and below room temperature using synchrotron X-ray powder diffraction. The La{sup 3+} and Pr{sup 3+} containing compounds had an intermediate rhombohedral phase whereas the other tantalates and niobates studied have a tetragonal intermediate. This difference in symmetry appears to be a consequence of the larger size of the La{sup 3+} and Pr{sup 3+} cations compared to the other lanthanides. The temperature range over which the intermediate symmetry is stable is reduced in those compounds near the point where the preferred intermediate symmetry changes from tetragonal to rhombohedral. In such compounds the transition to the cubic phase involves higher order terms in the Landau expression. This suggests that in this region the stability of the two intermediate phases is similar. - Graphical abstract: Variable temperature structural studies of Ba{sub 2}LaTaO{sub 6} show the presence of a unexpected rhombohedral phase. Other Ba{sub 2}LnB'O{sub 6} (B'=Nb, Ta) have a tetragonal intermediate phase.

  9. Strain-rate dependent fatigue behavior of 316LN stainless steel in high-temperature water

    NASA Astrophysics Data System (ADS)

    Tan, Jibo; Wu, Xinqiang; Han, En-Hou; Ke, Wei; Wang, Xiang; Sun, Haitao

    2017-06-01

    Low cycle fatigue behavior of forged 316LN stainless steel was investigated in high-temperature water. It was found that the fatigue life of 316LN stainless steel decreased with decreasing strain rate from 0.4 to 0.004 %s-1 in 300 °C water. The stress amplitude increased with decreasing strain rate during fatigue tests, which was a typical characteristic of dynamic strain aging. The fatigue cracks mainly initiated at pits and slip bands. The interactive effect between dynamic strain aging and electrochemical factors on fatigue crack initiation is discussed.

  10. Infrared detector Dewars - Increased LN2 hold time and vacuum jacket life spans

    NASA Technical Reports Server (NTRS)

    Jennings, D. E.; Boyd, W. J.; Blass, W. E.

    1976-01-01

    IR detector Dewars commonly suffer from shorter than desired LN2 hold times and insulation jacket vacuum corruption over relatively short time periods. In an attempt to solve this problem for a 9144 detector Dewar, small 1 liter/s appendage ion pumps were selected for continuous pumping of the vacuum jackets. This procedure extended LN2 hold times from 20 to 60 h and virtually eliminated vacuum jacket corruption. Thus the detector systems are usable continuously over periods of 6 months or more.

  11. Infrared detector Dewars - Increased LN2 hold time and vacuum jacket life spans

    NASA Technical Reports Server (NTRS)

    Jennings, D. E.; Boyd, W. J.; Blass, W. E.

    1976-01-01

    IR detector Dewars commonly suffer from shorter than desired LN2 hold times and insulation jacket vacuum corruption over relatively short time periods. In an attempt to solve this problem for a 9144 detector Dewar, small 1 liter/s appendage ion pumps were selected for continuous pumping of the vacuum jackets. This procedure extended LN2 hold times from 20 to 60 h and virtually eliminated vacuum jacket corruption. Thus the detector systems are usable continuously over periods of 6 months or more.

  12. Exploring the Influence of Diamagnetic Ions on the Mechanism of Magnetization Relaxation in {Co(III)2Ln(III)2} (Ln = Dy, Tb, Ho) "Butterfly" Complexes.

    PubMed

    Vignesh, Kuduva R; Langley, Stuart K; Murray, Keith S; Rajaraman, Gopalan

    2017-03-06

    The synthesis and magnetic and theoretical studies of three isostructural heterometallic [Co(III)2Ln(III)2(μ3-OH)2(o-tol)4(mdea)2(NO3)2] (Ln = Dy (1), Tb (2), Ho (3)) "butterfly" complexes are reported (o-tol = o-toluate, (mdea)(2-) = doubly deprotonated N-methyldiethanolamine). The Co(III) ions are diamagnetic in these complexes. Analysis of the dc magnetic susceptibility measurements reveal antiferromagnetic exchange coupling between the two Ln(III) ions for all three complexes. ac magnetic susceptibility measurements reveal single-molecule magnet (SMM) behavior for complex 1, in the absence of an external magnetic field, with an anisotropy barrier Ueff of 81.2 cm(-1), while complexes 2 and 3 exhibit field induced SMM behavior, with a Ueff value of 34.2 cm(-1) for 2. The barrier height for 3 could not be quantified. To understand the experimental observations, we performed DFT and ab initio CASSCF+RASSI-SO calculations to probe the single-ion properties and the nature and magnitude of the Ln(III)-Ln(III) magnetic coupling and to develop an understanding of the role the diamagnetic Co(III) ion plays in the magnetization relaxation. The calculations were able to rationalize the experimental relaxation data for all complexes and strongly suggest that the Co(III) ion is integral to the observation of SMM behavior in these systems. Thus, we explored further the effect that the diamagnetic Co(III) ions have on the magnetization blocking of 1. We did this by modeling a dinuclear {Dy(III)2} complex (1a), with the removal of the diamagnetic ions, and three complexes of the types {K(I)2Dy(III)2} (1b), {Zn(II)2Dy(III)2} (1c), and {Ti(IV)2Dy(III)2} (1d), each containing a different diamagnetic ion. We found that the presence of the diamagnetic ions results in larger negative charges on the bridging hydroxides (1b > 1c > 1 > 1d), in comparison to 1a (no diamagnetic ion), which reduces quantum tunneling of magnetization effects, allowing for more desirable SMM characteristics

  13. The extended chain compounds Ln {sub 12}(C{sub 2}){sub 3}I{sub 17} (Ln=Pr, Nd, Gd, Dy): Synthesis, structure and physical properties

    SciTech Connect

    Ryazanov, Mikhail; Mattausch, Hansjuergen; Simon, Arndt

    2007-04-15

    The title compounds are obtained in high yield from stoichiometric mixtures of Ln, LnI{sub 3} and graphite, heated at 900-950 deg. C in welded Ta containers. The crystal structures of new Pr and Nd phases determined by single-crystal X-ray diffraction are related to those of other Ln {sub 12}(C{sub 2}){sub 3}I{sub 17}-type compounds (C 2/c, a=19.610(1) and 19.574(4) A, b=12.406(2) and 12.393(3) A, c=19.062(5) and 19.003(5) A, {beta}=90.45(3){sup o} and 90.41(3){sup o}, for Pr{sub 12}(C{sub 2}){sub 3}I{sub 17} and Nd{sub 12}(C{sub 2}){sub 3}I{sub 17}, respectively). All compounds contain infinite zigzag chains of C{sub 2}-centered metal atom octahedra condensed by edge-sharing into the [tcc] {sub {infinity}} sequence (c=cis, t=trans) and surrounded by edge-bridging iodine atoms as well as by apical iodine atoms that bridge between chains. The polycrystalline Gd{sub 12}(C{sub 2}){sub 3}I{sub 17} sample exhibits semiconducting thermal behavior which is consistent with an ionic formulation (Ln {sup 3+}){sub 12}(C{sub 2} {sup 6-}){sub 3}(I{sup -}){sub 17}(e{sup -}) under the assumption that one extra electron is localized in metal-metal bonding. The magnetization measurements on Nd{sub 12}(C{sub 2}){sub 3}I{sub 17}, Gd{sub 12}(C{sub 2}){sub 3}I{sub 17} and Dy{sub 12}(C{sub 2}){sub 3}I{sub 17} indicate the coexistence of competing magnetic interactions leading to spin freezing at T {sub f}=5 K for the Gd phase. The Nd and Dy compounds order antiferromagnetically at T {sub N}=25 and 29 K, respectively. For Dy{sub 12}(C{sub 2}){sub 3}I{sub 17}, a metamagnetic transition is observed at a critical magnetic field H{approx}25 kOe. - Graphical abstract: Zigzag chains of edge-sharing metal atom octahedra in Ln {sub 12}(C{sub 2}){sub 3}I{sub 17}.

  14. Crystal structure and properties of complexes [Ln(Gly)4Im·(ClO4)4]n (Ln:Nd, Sm) constructed from eight-coordination containing square antiprism

    NASA Astrophysics Data System (ADS)

    Pan, Lu; Gao, Xiao-han; Lv, Xue-chuan; Tan, Zhi-cheng; Cao, Hui

    2016-08-01

    Two eight-coordination containing square antiprism polyhedra, [Ln(Gly)4Im·(ClO4)4]n (Ln:Nd, Sm) were synthesized through the self-assembly of Ln3+ (Ln:Nd, Sm) ions, glycine and imidazole in aqueous solution and characterized by X-ray single crystal diffraction. Both of the complexes crystallized in the C2/c space group. In the cluster, each Ln3+ ions was eight-coordination by eight oxygen atoms of the glycine. The coordination sphere of each Ln3+ ions could be described as a distorted square antiprism. Two central Ln3+ ions were connected by four bridging carboxyl groups from four glycine molecules. The Ln-O bond distances were related to the coordination geometries of the ligands. The complexes had two special solid-solid phase transitions at 224 K and 248 K, which were interpreted as a freezing-in phenomenon of the reorientational motion of perchlorate ions ClO4- and the orientational order/disorder process of ClO4- ions. The decomposition mechanism of the complexes was deduced to be three stages from 300 to 700 K. The fluorescent excitation and emission spectra showed that the complexes had strong fluorescent property.

  15. Phase relations and crystal structures in the systems (Bi,Ln){sub 2}WO{sub 6} and (Bi,Ln){sub 2}MoO{sub 6} (Ln=lanthanide)

    SciTech Connect

    Berdonosov, Peter S.; Charkin, Dmitri O.; Knight, Kevin S.; Johnston, Karen E.; Goff, Richard J.; Dolgikh, Valeriy A.; Lightfoot, Philip . E-mail: pl@st-and.ac.uk

    2006-11-15

    Several outstanding aspects of phase behaviour in the systems (Bi,Ln){sub 2}WO{sub 6} and (Bi,Ln){sub 2}MoO{sub 6} (Ln=lanthanide) have been clarified. Detailed crystal structures, from Rietveld refinement of powder neutron diffraction data, are provided for Bi{sub 1.8}La{sub 0.2}WO{sub 6} (L-Bi{sub 2}WO{sub 6} type) and BiLaWO{sub 6}, BiNdWO{sub 6}, Bi{sub 0.7}Yb{sub 1.3}WO{sub 6} and Bi{sub 0.7}Yb{sub 1.3}WO{sub 6} (all H-Bi{sub 2}WO{sub 6} type). Phase evolution within the solid solution Bi{sub 2-} {sub x} La {sub x} MoO{sub 6} has been re-examined, and a crossover from {gamma}(H)-Bi{sub 2}MoO{sub 6} type to {gamma}-R{sub 2}MoO{sub 6} type is observed at x{approx}1.2. A preliminary X-ray Rietveld refinement of the line phase BiNdMoO{sub 6} has confirmed the {alpha}-R{sub 2}MoO{sub 6} type structure, with a possible partial ordering of Bi/Nd over the three crystallographically distinct R sites. - Graphical abstract: A summary of phase relations in the lanthanide-doped bismuth tungstate and bismuth molybdate systems is presented, together with some additional structural data on several of these phases.

  16. Syntheses, Structure, Magnetism, and Optical Properties of the Interlanthanide Sulfides delta-Ln2-xLuxS3 (Ln = Ce, Pr, Nd)

    SciTech Connect

    Booth, Corwin H; Jin, Geng Bang; Choi, Eun Sang; Guertin, Robert P.; Brooks, James S.; Bray, Travis H.; Booth, Corwin H.; Albrecht-Schmitt, Thomas E.

    2008-01-11

    {delta}-Ln{sub 2-x}LuxS{sub 3} (Ln = Ce, Pr, Nd; x = 0.67-0.71) compounds have been synthesized through the reaction of elemental rare earth metals and S using Sb{sub 2}S{sub 3} flux at 1000 C. These compounds are isotypic with CeTmS{sub 3}, which has a complex three-dimensional structure. It includes four larger Ln{sup 3+} sites in eight- and nine-coordinate environments, two disordered seven-coordinate Ln{sup 3+}/Lu{sup 3+} positions, and two six-coordinate Lu{sup 3+} ions. The structure is constructed from one-dimensional chains of LnSn (n = 6-9) polyhedra that extend along the b axis. These polyhedra share faces or edges with two neighbors within the chains, while in the [ac] plane they share edges and corners with other chains. Least square refinements gave rise to the formulas of {delta}-Ce{sub 1.30}Lu{sub 0.70}S{sub 3}, {delta}-Pr{sub 1.29}Lu{sub 0.71}S{sub 3} and {delta}-Nd{sub 1.33}Lu{sub 0.67}S{sub 3}, which are consistent with the EDX analysis and magnetic susceptibility data. {delta}-Ln{sub 2-x}LuxS{sub 3} (Ln = Ce, Pr, Nd; x = 0.67-0.71) show no evidence of magnetic ordering down to 5 K. Optical properties measurements show that the band gaps for {delta}-Ce{sub 1.30}Lu{sub 0.70}S{sub 3}, {delta}-Pr{sub 1.29}Lu{sub 0.71}S{sub 3}, and {delta}-Nd{sub 1.33}Lu{sub 0.67}S{sub 3} are 1.25 eV, 1.38 eV, and 1.50 eV, respectively. Crystallographic data: {delta}-Ce{sub 1.30}Lu{sub 0.70}S{sub 3}, monoclinic, space group P2{sub 1}/m, a = 11.0186(7), b = 3.9796(3), c = 21.6562(15) {angstrom}, {beta} = 101.6860(10), V = 929.93(11), Z = 8; {delta}-Pr{sub 1.29}Lu{sub 0.71}S{sub 3}, monoclinic, space group P2{sub 1}/m, a = 10.9623(10), b = 3.9497(4), c = 21.5165(19) {angstrom}, {beta} = 101.579(2), V = 912.66(15), Z = 8; {delta}-Nd{sub 1.33}Lu{sub 0.67}S{sub 3}, monoclinic, space group P2{sub 1}/m, a = 10.9553(7), b = 3.9419(3), c = 21.4920(15) {angstrom}, {beta} = 101.5080(10), V = 909.47(11), Z = 8.

  17. Effect of lanthanide contraction on the mixed polyamine systems Ln/Sb/Se/(en+dien) and Ln/Sb/Se/(en+trien): Syntheses and characterizations of lanthanide complexes with a tetraelenidoantimonate ligand

    SciTech Connect

    Zhao Jing; Liang Jingjing; Pan Yingli; Zhang Yong; Jia Dingxian

    2011-06-15

    Mixed polyamine systems Ln/Sb/Se/(en+dien) and Ln/Sb/Se/(en+trien) (Ln=lanthanide, en=ethylenediamine, dien=diethylenetriamine, trien=triethylenetetramine) were investigated under solvothermal conditions, and novel mixed-coordinated lanthanide(III) complexes [Ln(en){sub 2}(dien)({eta}{sup 2}-SbSe{sub 4})] (Ln=Ce(1a), Nd(1b)), [Ln(en){sub 2}(dien)(SbSe{sub 4})] (Ln=Sm(2a), Gd(2b), Dy(2c)), [Ln(en)(trien)({mu}-{eta}{sup 1},{eta}{sup 2}-SbSe{sub 4})]{sub {infinity}} (Ln=Ce(3a), Nd(3b)) and [Sm(en)(trien)({eta}{sup 2}-SbSe{sub 4})] (4a) were prepared. Two structural types of lanthanide selenidoantimonates were obtained across the lanthanide series in both en+dien and en+trien systems. The tetrahedral anion [SbSe{sub 4}]{sup 3-} acts as a monodentate ligand mono-SbSe{sub 4}, a bidentate chelating ligand {eta}{sup 2}-SbSe{sub 4} or a tridentate bridging ligand {mu}-{eta}{sup 1},{eta}{sup 2}-SbSe{sub 4} to the lanthanide(III) center depending on the Ln{sup 3+} ions and the mixed ethylene polyamines, indicating the effect of lanthanide contraction on the structures of the lanthanide(III) selenidoantimonates. The lanthanide selenidoantimonates exhibit semiconducting properties with E{sub g} between 2.08 and 2.51 eV. - Graphical Abstract: Two structural types of lanthanide(III) selenidoantimonates are formed in both en-dien and en-trien mixed polyamines across lanthanide series, indicating the lanthanide contraction effect on the structures of the lanthanide(III) selenidoantimonates. Highlights: > Two structural types of lanthanide selenidoantimonates are prepared across the lanthanide series in both Ln/Sb/Se/(en+dien) and Ln/Sb/Se/(en+trien) systems. > The [SbSe{sub 4}]{sup 3-} anion acts as a mono-SbSe{sub 4}, a {eta}{sup 2}-SbSe{sub 4} or a {mu}-{eta}{sup 1},{eta}{sup 2}-SbSe{sub 4} ligand to the Ln{sup 3+} ions. > The soft base ligand [SbSe{sub 4}]{sup 3-} can be controlled to coordinate to the Ln{sup 3+} ions with en+dien and en+trien as co-ligands.

  18. Anion dependent self-assembly of 56-metal Cd-Ln nanoclusters with enhanced near-infrared luminescence properties

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoping; Schipper, Desmond; Zhang, Lijie; Yang, Keqin; Huang, Shaoming; Jiang, Jijun; Su, Chengyong; Jones, Richard A.

    2014-08-01

    Two series of Cd-Ln clusters: nano-drum [Ln8Cd24L12(OAc)48] and nano-double-drum [Ln12Cd44L20Cl30(OAc)54] (Ln = Nd and Yb) were prepared using a flexible Schiff base ligand bearing two aryl-Br groups. Chloride (Cl-) ions, together with the interactions of Br with other electronegative atoms, play a key role in the formation of the nano-double-drums. The structures were studied by TEM and photophysical properties were determined.Two series of Cd-Ln clusters: nano-drum [Ln8Cd24L12(OAc)48] and nano-double-drum [Ln12Cd44L20Cl30(OAc)54] (Ln = Nd and Yb) were prepared using a flexible Schiff base ligand bearing two aryl-Br groups. Chloride (Cl-) ions, together with the interactions of Br with other electronegative atoms, play a key role in the formation of the nano-double-drums. The structures were studied by TEM and photophysical properties were determined. Electronic supplementary information (ESI) available: Full experimental and characterization details for 1-4. CCDC 972369-972372. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr03075c

  19. Ln is a key regulator of leaflet shape and number of seeds per pod in soybean.

    PubMed

    Jeong, Namhee; Suh, Su Jeoung; Kim, Min-Hee; Lee, Seukki; Moon, Jung-Kyung; Kim, Hong Sig; Jeong, Soon-Chun

    2012-12-01

    Narrow leaflet soybean (Glycine max) varieties tend to have more seeds per pod than broad leaflet varieties. Narrow leaflet in soybean is conferred by a single recessive gene, ln. Here, we show that the transition from broad (Ln) to narrow leaflet (ln) is associated with an amino acid substitution in the EAR motif encoded by a gene (designated Gm-JAGGED1) homologous to Arabidopsis JAGGED (JAG) that regulates lateral organ development and the variant exerts a pleiotropic effect on fruit patterning. The genomic region that regulates both the traits was mapped to a 12.6-kb region containing only one gene, Gm-JAG1. Introducing the Gm-JAG1 allele into a loss-of-function Arabidopsis jagged mutant partially restored the wild-type JAG phenotypes, including leaf shape, flower opening, and fruit shape, but the Gm-jag1 (ln) and EAR-deleted Gm-JAG1 alleles in the jagged mutant did not result in an apparent phenotypic change. These observations indicate that despite some degree of functional change of Gm-JAG1 due to the divergence from Arabidopsis JAG, Gm-JAG1 complemented the functions of JAG in Arabidopsis thaliana. However, the Gm-JAG1 homoeolog, Gm-JAG2, appears to be sub- or neofunctionalized, as revealed by the differential expression of the two genes in multiple plant tissues, a complementation test, and an allelic analysis at both loci.

  20. O(alpha{sup 3} ln(alpha)) Corrections to Muonium and Positronium Hyperfine Splitting

    SciTech Connect

    Melnikov, Kirill

    2001-07-25

    We compute O({alpha}{sup 3} ln {alpha}) relative corrections to the ground state hyperfine splitting of a QED two body bound state with different masses of constituents. The general result is then applied to muonium and positronium. In particular, a new value of the muon to electron mass ratio is derived from the muonium ground state hyperfine splitting.

  1. O(alpha{sup 3} ln alpha) Corrections to Positronium Decay Rates

    SciTech Connect

    Melnikov, Kirill

    2001-07-25

    We compute O ({alpha}{sup 3} ln {alpha}) corrections to the decay rates of para- and orthopositronium into two and three photons, respectively. For this calculation we employ the nonrelativistic QED regularized dimensionally and we explain how in this framework the logarithms of the fine structure constant can be extracted.

  2. Ball Indentation Studies on the Effect of Nitrogen on the Tensile Properties of 316LN SS

    NASA Astrophysics Data System (ADS)

    Mathew, M. D.; Ganesh Kumar, J.; Ganesan, V.; Laha, K.

    2015-12-01

    Type 316L(N) stainless steel (SS) containing 0.02-0.03 wt% carbon and 0.06-0.08 wt% nitrogen is used as the major structural material for the components of fast reactors. Research is underway to improve the high-temperature mechanical properties of 316LN SS by increasing the nitrogen content in the steel above the level of 0.08 wt%. In this investigation, ball indentation (BI) technique was used to evaluate the effect of nitrogen content on the tensile properties of 316LN SS. BI tests were conducted on four different heats of 316LN SS containing 0.07, 0.11, 0.14 and 0.22 wt% nitrogen in the temperature range 300-923 K. The tensile properties such as yield strength and ultimate tensile strength increased with increase in nitrogen content at all the investigated temperatures. These results were consistent with the corresponding uniaxial tensile test results. These studies showed that BI technique can be used to optimize the chemical composition during alloy development by evaluating tensile properties with minimum volume of material.

  3. Modeling and control of a LN2-GN2 operated closed circuit cryogenic wind tunnel

    NASA Technical Reports Server (NTRS)

    Balakrishna, S.; Thibodeaux, J. J.

    1979-01-01

    An explicit but simple lumped parameter nonlinear multivariable model of a LN2-GN2-operated closed circuit cryogenic wind tunnel has been developed and its basic features have been experimentally validated. The model describes the mass-energy interaction involved in the cryogenic tunnel process and includes the real gas properties of nitrogen gas.

  4. Nanomaterial size distribution analysis via liquid nebulization coupled with ion mobility spectrometry (LN-IMS).

    PubMed

    Jeon, Seongho; Oberreit, Derek R; Van Schooneveld, Gary; Hogan, Christopher J

    2016-02-21

    We apply liquid nebulization (LN) in series with ion mobility spectrometry (IMS, using a differential mobility analyzer coupled to a condensation particle counter) to measure the size distribution functions (the number concentration per unit log diameter) of gold nanospheres in the 5-30 nm range, 70 nm × 11.7 nm gold nanorods, and albumin proteins originally in aqueous suspensions. In prior studies, IMS measurements have only been carried out for colloidal nanoparticles in this size range using electrosprays for aerosolization, as traditional nebulizers produce supermicrometer droplets which leave residue particles from non-volatile species. Residue particles mask the size distribution of the particles of interest. Uniquely, the LN employed in this study uses both online dilution (with dilution factors of up to 10(4)) with ultra-high purity water and a ball-impactor to remove droplets larger than 500 nm in diameter. This combination enables hydrosol-to-aerosol conversion preserving the size and morphology of particles, and also enables higher non-volatile residue tolerance than electrospray based aerosolization. Through LN-IMS measurements we show that the size distribution functions of narrowly distributed but similarly sized particles can be distinguished from one another, which is not possible with Nanoparticle Tracking Analysis in the sub-30 nm size range. Through comparison to electron microscopy measurements, we find that the size distribution functions inferred via LN-IMS measurements correspond to the particle sizes coated by surfactants, i.e. as they persist in colloidal suspensions. Finally, we show that the gas phase particle concentrations inferred from IMS size distribution functions are functions of only of the liquid phase particle concentration, and are independent of particle size, shape, and chemical composition. Therefore LN-IMS enables characterization of the size, yield, and polydispersity of sub-30 nm particles.

  5. AlN/Pt/LN structure for SAW sensors capable of operating at high temperature

    NASA Astrophysics Data System (ADS)

    Naumenko, Natalya; Nicolay, Pascal

    2017-08-01

    There is a need for wireless sensors able to operate in the intermediate temperature range (ITR) between 300 °C and 600 °C. Surface acoustic wave (SAW) sensors are promising candidates to solve this issue. However, existing SAW sensors most often fail in the ITR, due to the quick degradation of the sensor housing in extreme conditions. A promising way to circumvent the issue is to use "package-less" devices, where the acoustic waves are guided in a multilayered structure where they are intrinsically protected from adverse environmental effects. We present here an innovative multilayered structure that fulfills all the basic requirements, to achieve a wireless and "package-less" SAW Sensor for the ITR. The structure is made of a thin AlN layer deposited on top of a Y + 128°LN substrate and equipped with buried Pt electrodes. Numerical simulations of the acoustic waves propagating in SAW resonators built on this structure reveal the existence of a useful Rayleigh-type SAW that propagates at the AlN/LN interface with a velocity up to 4500 m/s and a high electromechanical coupling k2=5.6%, without leakage into the substrate. The existence of this mode is due to specific properties of the Y + 128°LN cut, which are analyzed in detail in this paper. The performances of an optimized AlN/Pt/LN structure are also compared to the ones of previously suggested "package-less" structures, including AlN/ZnO/Sapphire. It is shown that better device characteristics can be expected from the AlN/Pt/LN structure in the ITR.

  6. Vanadium oxide bronzes containing rare-earth elements

    SciTech Connect

    Volkov, V.L.; Zubkov, V.G.; Fedyukov, A.S.; Zainulin, Yu.G.

    1988-05-01

    We attempted to make phases having the general formula Ln/sub x/V/sub 2/O/sub 5/ (Ln = La, Eu, Yb) without success; the specimens usually consisted of three phases: the rare-earth orthovanadate LnVO/sub 4/, vanadium(V) oxide, and VO/sub 2/. To shift the process to give Ln/sub x/V/sub 2/O/sub 5/, heat treatment was applied to mixtures of the initial high-purity substances. The x-ray patterns were recorded with a DRON-UM1 apparatus with Cr K..cap alpha.. radiation and were processed by the Poroshok program. The IR spectra were recorded with UR-20 spectrometer with oil mulls.

  7. Synthesis, crystal and electronic structure of the quaternary sulfides Ln{sub 2}CuMS{sub 5} (Ln=La, Ce; M=Sb, Bi)

    SciTech Connect

    Kussainova, Ardak M.; Akselrud, Lev G.; Suen, Nian-Tzu; Voss, Leonard; Stoyko, Stanislav; Bobev, Svilen

    2016-01-15

    The series of quaternary sulfides with general formula Ln{sub 2}CuMS{sub 5} (Ln=La, Ce; M=Sb, Bi) have been synthesized by solid-state reactions. Three representative members have been structurally characterized by single-crystal X-ray diffraction. La{sub 2}CuSbS{sub 5} crystallizes in a new structure type (space group Ima2 (no. 46), Z=4, a=13.401(2) Å, b=7.592(1) Å, c=7.598(1) Å, V=773.1(3) Å{sup 3}). The bismuth analogs of composition La{sub 2}CuBiS{sub 5} and Ce{sub 2}CuBiS{sub 5} crystallize with the La{sub 2}CuInSe{sub 5} structure type (space group Pnma (no. 62), Z=4). Lattice parameters for La{sub 2}CuBiS{sub 5}: a=11.9213(5) Å, b=3.9967(2) Å, c=17.0537(8) Å, V=812.56(7) Å{sup 3}; lattice parameters for Ce{sub 2}CuBiS{sub 5}: a=11.9179(15) Å, b=3.9596(5) Å, c=16.955(2) Å, V=800.13(17) Å{sup 3}). The similarities and the differences between the two structures are discussed. Electronic structure calculations for La{sub 2}CuSbS{sub 5} and La{sub 2}CuBiS{sub 5} are also presented; they suggest semiconducting behavior with energy gaps exceeding 1.7 eV. - Graphical abstract: La{sub 2}CuSbS{sub 5} crystallizes in a new structure type (space group Ima2 (no. 46). Its bismuth analog La{sub 2}CuBiS{sub 5} crystallizes in the La{sub 2}CuInSe{sub 5} structure type (space group Pnma (no. 62)). Z=4, a=11.9213(5) Å, b=3.9967(2) Å, c=17.0536(10) Å, V=813.53(10) Å{sup 3}). The structures are based on rare-earth metal atoms coordinated by S atoms in a trigonal-prismatic and/or square-antiprismatic fashion, Cu-centered tetrahedra, and pnictogen atoms in pyramidal or distorted octahedral coordination. - Highlights: • Ln{sub 2}CuSbS{sub 5} are complex quarternary phases crystallizing in their own structure type. • Ln{sub 2}CuSbS{sub 5} and Ce{sub 2}CuBiS{sub 5} are new compound in the respective ternary phase diagrams. • Ln{sub 2}CuSbS{sub 5} on one side, and Ln{sub 2}CuBiS{sub 5} on the other are not isotypic.

  8. Aqueous Synthesis and Structural Comparison of Rare Earth Niobates and Tantalates: (La,K,[vacancy])[subscript 2]Nb[subscript 2]O[subscript 7-x](OH)[subscript 2] and Ln2Ta2O7(OH)2 ([vacancy] = vacancy; Ln = La-Sm)

    SciTech Connect

    Nyman, May; Rodriguez, Mark A.; Alam, Todd M.; Anderson, Travis M.; Ambrosini, Andrea

    2009-06-30

    Rare-earth niobates and tantalates are functional materials that are exploited as photocatalysts, host lattices for phosphors, and ion conductors. These phases are extremely challenging to synthesize by methods other than solid-state processing, which limits expansion of this useful class of materials. Hydrothermal processing in particular is hampered by the incompatibility of base-soluble tantalate or niobate with acid-soluble rare-earth oxides. Furthermore, an added challenge with tantalates is they are especially inert and insoluble. We present here a general hydrothermal process that has produced a range of rare-earth niobate/tantalate materials; including new phases, (La,K,{sub {open_square}}){sub 2}Nb{sub 2}O{sub 7-x}(OH){sub 2} (1) and Ln{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} (2) ({open_square} = vacancy, Ln = La-Sm -- excluding radioactive promethium). The structures of 1 and the La-analogue of 2 were determined from powder X-ray diffraction data collected at the APS 11-BM line and corroborated by compositional analyses, infrared spectroscopy, {sup 139}La and {sup 1}H MAS NMR, and thermogravimetric analyses. The synthesis and characterization studies reveal that the tantalate (2) is compositionally pure with no vacancies or dopants, while the niobate (1) formed under identical conditions has both vacancies and potassium dopants. We attribute these features to the greater flexibility of Nb{sup 5+} in oxide lattices to accommodate distorted and lower coordination geometries, whereas Ta{sup 5+} is found predominantly in octahedral environments. Other differences in aqueous niobate and tantalate chemistry are noted by the different phases that form as a function of the Ln{sup 3+} radius.

  9. Ln{sub 2}Sr{sub 2}PtO{sub 7+{delta}} (Ln=La, Pr, and Nd): Three new Pt-containing [A{sub 2}{sup '}O{sub 1+{delta}}] [A{sub n}B{sub n-1}O{sub 3n}]-type hexagonal perovskites

    SciTech Connect

    Ebbinghaus, Stefan G. Erztoument, Chasanoglou; Marozau, Ivan

    2007-12-15

    Polycrystalline samples of Ln{sub 2}Sr{sub 2}PtO{sub 7+{delta}} (Ln=La, Pr, Nd) were prepared by conventional solid state synthesis. The three compounds are new examples for n=2 members of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family of hexagonal perovskites containing platinum as the B-type cation. XRD Rietveld refinements show the platinates to crystallize in space group R3-bar and, in the case of Pr and Nd, revealed a complete ordering of Ln/Sr on the two distinct A-type positions, while for La a partial disorder was observed. By XANES investigations at the Pt-L{sub III} threshold the oxidation state +4 for platinum was found. Thermogravimetry revealed a small oxygen excess for Ln=La and Pr ({delta}=0.13 and 0.07), pointing to the presence of peroxide ions as already observed for isostructural Ru- and Ir-based compounds. UV-Vis measurements were done for the yellow lanthanum and the green neodymium compound. They revealed two optical band gaps of 2.52 and 3.05 eV, respectively. Magnetic measurements showed La{sub 2}Sr{sub 2}PtO{sub 7+{delta}} to be diamagnetic as expected for Pt{sup 4+} with low-spin (t{sub 2g}{sup 6}) configuration. For Ln=Pr and Nd the observed strong paramagnetism can be explained solely by the magnetic moments of the rare earths. - Graphical abstract: Hexagonal perovskites of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family have so far only been known for the transition metals Mn, Nb, Ru, and Ir. In this paper, three new n=2 examples containing platinum as B-type cation are presented. The structure and physical properties of the three title compounds were investigated by XRD Rietveld refinements, thermogravimetry, X-ray absorption spectroscopy, magnetic measurements and optical spectroscopy.

  10. An investigation of structural parameters and magnetic and optical properties of EuLn{sub 2}Q{sub 4} (Ln=Tb-Lu, Q=S, Se)

    SciTech Connect

    Jin Gengbang; Choi, Eun Sang; Guertin, Robert P.; Albrecht-Schmitt, Thomas E.

    2008-01-15

    EuLn{sub 2}Q{sub 4} (Ln=Tb-Lu; Q=S, Se) has been synthesized using Sb{sub 2}Q{sub 3} (Q=S, Se) fluxes at 1000 deg. C. These compounds crystallize in a CaFe{sub 2}O{sub 4}-type three-dimensional channel structure that is built from edge-shared double rutile chains of [LnQ{sub 6}] octahedra running down the b-axis. Each double chain is connected at the vertices to four other double chains to form open channels where bicapped trigonal prismatic Eu{sup 2+} ions reside. All of these compounds show antiferromagnetic ordering with Neel temperatures, T{sub N}{approx}3-4 K. The optical band gaps for EuTb{sub 2}Se{sub 4}, EuDy{sub 2}Se{sub 4}, EuHo{sub 2}Se{sub 4}, EuEr{sub 2}Se{sub 4}, EuTm{sub 2}Se{sub 4}, EuYb{sub 2}Se{sub 4} EuLu{sub 2}Se{sub 4}, and EuYb{sub 2}S{sub 4} are found to be 2.0, 1.8, 1.8, 1.7, 1.8, 1.3, 1.7, and 1.6 eV, respectively. - Graphical abstract: A view of the three-dimensional channel structure of EuYb{sub 2}S{sub 4} down the b-axis.

  11. Synthesis and anisotropic properties of single crystalline Ln{sub 2}Ru{sub 3}Al{sub 15+x} (Ln=Gd, Tb)

    SciTech Connect

    Morrison, Gregory; Prestigiacomo, Joseph; Haldolaarachchige, Neel; Rai, Binod K.; Young, David P.; Stadler, Shane; Morosan, Emilia; Chan, Julia Y.

    2016-04-15

    Single crystals of Ln{sub 2}Ru{sub 3}Al{sub 15+x} (Ln=Gd, Tb) have been grown using the self-flux method under Ru-poor conditions. The structure of the Gd analog is found to be highly dependent on the synthesis method. Gd{sub 2}Ru{sub 3}Al{sub 15.08} orders antiferromagnetically at 17.5 K. Tb{sub 2}Ru{sub 3}Al{sub 15.05} enters an antiferromagnetic state at 16.6 K followed by a likely incommensurate-to-commensurate transition at 14.9 K for crystals oriented with H//ab. For crystals oriented with H//c, a broad maximum is observed in the temperature dependent M/H, indicative of a highly anisotropic magnetic system with the hard axis in the c-direction. The magnetization as a function of field and magnetoresistance along the ab-direction of Tb{sub 2}Ru{sub 3}Al{sub 15.05} display a stepwise behavior and indicate strong crystalline electric field effects. - Graphical abstract: Single crystal, structure, and highly anisotropic magnetoresistance due to strong crystalline electric field effects of Tb{sub 2}Ru{sub 3}Al{sub 15.05}. - Highlights: • Single crystals of Ln{sub 2}Ru{sub 3}Al{sub 15+x} were grown for the first time via flux growth. • The structure of Gd{sub 2}Ru{sub 3}Al{sub 15.09} differs from that of arc melted Gd{sub 2}Ru{sub 3.08}Al{sub 15}. • Tb{sub 2}Ru{sub 3}Al{sub 15.05} exhibits highly anisotropic magnetic and transport properties. • The properties of Tb{sub 2}Ru{sub 3}Al{sub 15.05} arise due to crystalline electric field effects.

  12. Synthesis and photoluminescence characteristics of Ln3+ (Ln = Sm, Er and Dy)-doped BaGd2(MoO4)4 phosphors

    NASA Astrophysics Data System (ADS)

    Deng, Yaomin; Yi, Shuangping; Wang, Yinhai; Xian, Jieqiang

    2014-06-01

    BaGd2(MoO4)4 phosphor powders activated with the trivalent rare-earth Ln3+ (Ln = Sm, Er and Dy) were synthesized by a traditional high temperature solid-state reaction. The resulted phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. XRD results demonstrate that Ln3+-doped samples can be well indexed to the pure monoclinic scheelite-type structure BaGd2(MoO4)4. The photoluminescence investigations revealed that the phosphors exhibit apparent characteristic emissions from the 4G5/2 to 6H5/2, 7/2, 9/2 state for Sm3+, 2H11/2 and 4S3/2 state to the 4I15/2 ground state for Er3+, 4I15/2, 4F9/2 to 6H15/2 and 4F9/2 to 6H13/2 for Dy3+ under near ultraviolet excitation. BaGd1.95(MoO4)4:0.05Sm3+, BaGd1.93(MoO4)4:0.07Er3+ and BaGd1.90(MoO4)4:0.10Dy3+ emit bright orange-red, green and white light with the CIE coordinates of (0.5381, 0.4544), (0.2307, 0.6096) and (0.3314, 0.3853) respectively. The sharp emission peaks and excellent luminescence properties show that BaGd2(MoO4)4 is a suitable host for rare earth doped phosphors, which may be potentially applied in the applications of the optical materials.

  13. Synthesis, structure, and polymorphism of A{sub 3}LnSi{sub 2}O{sub 7} (A=Na, K; Ln=Sm, Ho, Yb)

    SciTech Connect

    Latshaw, Allison M.; Yeon, Jeongho; Smith, Mark D.; Loye, Hans-Conrad zur

    2016-03-15

    Four new members of the A{sub 3}LnSi{sub 2}O{sub 7} family, K{sub 3}SmSi{sub 2}O{sub 7}, Na{sub 3}HoSi{sub 2}O{sub 7}, and two polymorphs of Na{sub 3}YbSi{sub 2}O{sub 7}, are reported. K{sub 3}SmSi{sub 2}O{sub 7} crystallizes in the hexagonal space group P6{sub 3}/mcm, Na{sub 3}HoSi{sub 2}O{sub 7} and Na{sub 3}YbSi{sub 2}O{sub 7} crystallize in the hexagonal space group P6{sub 3}/m, and Na{sub 3}YbSi{sub 2}O{sub 7} crystallizes in the trigonal space group P31c. The Na{sub 3}YbSi{sub 2}O{sub 7} composition that crystallizes in P31c is a new structure type. The magnetic properties for the Ho and Yb analogs are reported. - Graphical abstract: The different structure types and polymorphs of the A{sub 3}LnSi{sub 2}O{sub 7} family reported. - Highlights: • Four new members of the A{sub 3}LnSi{sub 2}O{sub 7} family are presented. • Na{sub 3}YbSi{sub 2}O{sub 7} is reported as two polymorphs, one is a new structure type. • Crystals synthesized out of molten fluoride fluxes.

  14. Syntheses and crystal structures of the quaternary uranium lanthanide oxyselenides UYb2O2Se3 and U2Ln2O4Se3 (Ln=Pr, Sm, Gd)

    NASA Astrophysics Data System (ADS)

    Raw, Adam D.; Ibers, James A.

    2012-02-01

    Single crystals of the new uranium lanthanide oxyselenide compounds UYb2O2Se3 and U2Ln2O4Se3 (Ln=Pr, Sm, Gd) have been synthesized from an Sb2Se3 flux. The structures have been determined from single-crystal X-ray diffraction data. UYb2O2Se3 is isostructural to UYb2O2S3. The structure comprises layers of edge-sharing YbSe6 octahedra and double layers of disordered (U/Ln)O4Se4 square antiprisms. The U2Ln2O4Se3 (Ln=Pr, Sm, Gd) compounds are isostructural to U2Ln2O4S3 (Ln=La-Gd) whose structure had been deduced previously from X-ray powder diffraction data. In the structure a dodecahedron of four O atoms and four Se atoms surrounds a site primarily occupied by U and a distorted bicapped octahedron of five Se atoms and three O atoms surrounds a site primarily occupied by the lanthanide. These compounds represent the first examples of quaternary uranium oxyselenides.

  15. Near-infrared (NIR) luminescent hetero-tetranuclear Zn2Ln2 (Ln = Nd, Yb or Er) complexes self-assembled from the benzimidazole-based HL and two rigid 4,4‧-bipyridine ligands with different spacers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao; Feng, Weixu; Su, Peiyang; Liu, Han; Zhang, Yao; Wang, Zheng; Miao, Tiezheng; Lü, Xingqiang; Fan, Daidi; Wong, Wai-Kwok; Jones, Richard A.

    2013-12-01

    Through the self-assembly of the benzimidazole-based ligand HL (HL = 2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol) with Zn(OAc)2·2H2O, Ln(NO3)3·6H2O (Ln = Nd, Yb, Er or Gd) and 4,4‧-bipyridine ligand (bpy, 4,4‧-bipyridine or bpe, trans-bis(4-pyridyl)ethylene), two series of Zn2Ln2-arrayed complexes [Zn2Ln2(L)4(bpy)(NO3)6] (Ln = Nd, 1; Yb, 2; Er, 3 or Gd, 4) and [Zn2Ln2(L)4(bpe)(NO3)6] (Ln = Nd, 5; Yb, 6; Er, 7 or Gd, 8) were obtained, respectively. The result of their photophysical properties shows that the characteristic near-infrared (NIR) luminescence of Nd3+, Yb3+ or Er3+ ion has been sensitized from the excited state (both 1LC and 3LC) of the mixed HL and bipyridyl ligands in both complexes 1-3 and 5-7. Moreover, the change from bpy to bpe bridging for the fine-tuning of whole molecular conjugations, attributing to the different crossings of the two benzimidazole-based L- ligands, has the important influence on their NIR luminescent properties.

  16. Luminescence properties and energy transfer in the novel red emitting phosphors Ba2Ln(BO3)2Cl:Sm3+, Eu3+ (Ln=Y, Gd)

    NASA Astrophysics Data System (ADS)

    Fan, Yan; Hu, Yihua; Chen, Li; Wang, Xiaojuan; Ju, Guifang

    2014-10-01

    A series of Sm3+/Eu3+ singly and co-doped Ba2Ln(BO3)2Cl (Ln=Y3+, Gd3+) phosphors were prepared via the solid-state method. The XRD results indicate that the as-prepared products keep the monoclinic structure with a P21/m space group of Ba2Ln(BO3)2Cl, which belongs to the isomorphic substitution for Ln3+ sites in the Ba2Yb(BO3)2Cl host. The photoluminescence (PL) spectra demonstrate that Ba2Ln(BO3)2Cl:Sm3+,Eu3+ emits red light centered at 593 nm under the 393 nm excitation which is in good agreement with the emission wavelength from near ultraviolet light-emitting diodes (LEDs). The luminescence decays suggest that the energy transfer from Sm3+ to Eu3+ ions in Ba2Ln(BO3)2Cl:Eu3+, Sm3+ occurs. All results mean that Ba2Ln(BO3)2Cl:Eu3+, Sm3+ phosphors exhibit potential to act as a kind of red phosphor for near ultraviolet white light-emitting diodes (w-LEDs).

  17. Ultralong well-aligned TiO2:Ln(3+) (Ln = Eu, Sm, or Er) fibres prepared by modified electrospinning and their temperature-dependent luminescence.

    PubMed

    Yu, Hongquan; Li, Yue; Song, Yang; Wu, Yanbo; Lan, Xijie; Liu, Shimin; Tang, Yanning; Xu, Shasha; Chen, Baojiu

    2017-03-07

    Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibres in micro-/nano-scale fineness: however, it remains a significant technological challenge to assemble aligned fibre arrays via an conventional electrospinning method due to the inherent whipping instability of the polymeric jet. We herein have first developed a simple modified electrospinning method with which to prepare ultralong (>300 mm) well-aligned inorganic fibre arrays, i.e., using an ultrahigh molecular weight polymer to suppress or eliminate the whipping motion of the electrospun jet, has emerged as a facile approach for the continuous fabrication of well-aligned, ultralong fibres through simply using a rotating cylinder as the collector (it was not found necessary to use a very high rotating speed, extra magnetic, electrical field) in the electrospinning process. As result, the ultralong well-aligned TiO2:Ln(3+) (Ln = Eu, Sm, or Er) fibre arrays can be obtained from ultrahigh molecular weight poly(ethylene oxide), tetra-n-butyl titanate (Ti(OC4H9)4) and lanthanide nitrate in the modified electrospinning approach. The grow mechanism and luminescent properties of these ultralong well-aligned TiO2:Ln(3+) fibre arrays were also investigated.

  18. Ultralong well-aligned TiO2:Ln3+ (Ln = Eu, Sm, or Er) fibres prepared by modified electrospinning and their temperature-dependent luminescence

    PubMed Central

    Yu, Hongquan; Li, Yue; Song, Yang; Wu, Yanbo; Lan, Xijie; Liu, Shimin; Tang, Yanning; Xu, Shasha; Chen, Baojiu

    2017-01-01

    Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibres in micro-/nano-scale fineness: however, it remains a significant technological challenge to assemble aligned fibre arrays via an conventional electrospinning method due to the inherent whipping instability of the polymeric jet. We herein have first developed a simple modified electrospinning method with which to prepare ultralong (>300 mm) well-aligned inorganic fibre arrays, i.e., using an ultrahigh molecular weight polymer to suppress or eliminate the whipping motion of the electrospun jet, has emerged as a facile approach for the continuous fabrication of well-aligned, ultralong fibres through simply using a rotating cylinder as the collector (it was not found necessary to use a very high rotating speed, extra magnetic, electrical field) in the electrospinning process. As result, the ultralong well-aligned TiO2:Ln3+ (Ln = Eu, Sm, or Er) fibre arrays can be obtained from ultrahigh molecular weight poly(ethylene oxide), tetra-n-butyl titanate (Ti(OC4H9)4) and lanthanide nitrate in the modified electrospinning approach. The grow mechanism and luminescent properties of these ultralong well-aligned TiO2:Ln3+ fibre arrays were also investigated. PMID:28266593

  19. Ultralong well-aligned TiO2:Ln3+ (Ln = Eu, Sm, or Er) fibres prepared by modified electrospinning and their temperature-dependent luminescence

    NASA Astrophysics Data System (ADS)

    Yu, Hongquan; Li, Yue; Song, Yang; Wu, Yanbo; Lan, Xijie; Liu, Shimin; Tang, Yanning; Xu, Shasha; Chen, Baojiu

    2017-03-01

    Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibres in micro-/nano-scale fineness: however, it remains a significant technological challenge to assemble aligned fibre arrays via an conventional electrospinning method due to the inherent whipping instability of the polymeric jet. We herein have first developed a simple modified electrospinning method with which to prepare ultralong (>300 mm) well-aligned inorganic fibre arrays, i.e., using an ultrahigh molecular weight polymer to suppress or eliminate the whipping motion of the electrospun jet, has emerged as a facile approach for the continuous fabrication of well-aligned, ultralong fibres through simply using a rotating cylinder as the collector (it was not found necessary to use a very high rotating speed, extra magnetic, electrical field) in the electrospinning process. As result, the ultralong well-aligned TiO2:Ln3+ (Ln = Eu, Sm, or Er) fibre arrays can be obtained from ultrahigh molecular weight poly(ethylene oxide), tetra-n-butyl titanate (Ti(OC4H9)4) and lanthanide nitrate in the modified electrospinning approach. The grow mechanism and luminescent properties of these ultralong well-aligned TiO2:Ln3+ fibre arrays were also investigated.

  20. Assessment of surface relief and short cracks under cyclic creep in a type 316LN austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Sarkar, Aritra; Nagesha, A.; Parameswaran, P.; Sandhya, R.; Laha, K.

    2015-12-01

    Formation of surface relief and short cracks under cyclic creep (stress-controlled fatigue) in type 316LN stainless steel was studied at temperatures ranging from ambient to 923 K using scanning electron microscopy technique. The surface topography and crack distribution behaviour under cyclic creep were found to be strong functions of testing temperature due to the difference in strain accumulation. At 823 K, surface relief mainly consisted of fine slip markings due to negligible accumulation of strain as a consequence of dynamic strain ageing (DSA) which led to an increase in the cyclic life. Persistent slip markings (PSM) with distinct extrusions containing minute cracks were seen to prevail in the temperature range 873-923 K, indicating a higher slip activity causing higher strain accumulation in the absence of DSA. Besides, a large number of secondary cracks (both transgranular and intergranular) which were partially accentuated by severe oxidation, were observed. Extensive cavitation-induced grain boundary cracking took place at 923 K, which coalesced with PSM-induced transgranular cracks resulting in failure dominated by creep that in turn led to a drastic reduction in cyclic life. Investigations on the influence of stress rate were also carried out which underlined the presence of DSA at 823 K. At 923 K, lowering the stress rate caused further strengthening of the contribution from creep damage marked by a shift in the damage mechanism from cyclic slip to diffusion.

  1. Hydrothermal synthesis, structure, and optical properties of two nanosized Ln26 @CO3 (Ln=Dy and Tb) cluster-based lanthanide-transition-metal-organic frameworks (Ln MOFs).

    PubMed

    Zhang, Yu; Huang, Lian; Miao, Hao; Wan, Hong Xiang; Mei, Hua; Liu, Ying; Xu, Yan

    2015-02-16

    Two Ln26 @CO3 (Ln=Dy and Tb) cluster-based lanthanide-transition-metal-organic frameworks (Ln MOFs) formulated as [Dy26 Cu3 (Nic)24 (CH3 COO)8 (CO3 )11 (OH)26 (H2 O)14 ]Cl ⋅3 H2 O (1; HNic=nicotinic acid) and [Tb26 NaAg3 (Nic)27 (CH3 COO)6 (CO3 )11 (OH)26 Cl(H2 O)15 ]⋅7.5 H2 O (2) have been successfully synthesized by hydrothermal methods and characterized by IR, thermogravimetric analysis (TGA), elemental analysis, and single X-ray diffraction. Compound 1 crystallizes in the monoclinic space group Cc with a=35.775(12) Å, b=33.346(11) Å, c=24.424(8) Å, β=93.993(5)°, V=29065(16) Å(3) , whereas 2 crystallizes in the triclinic space group P$\\bar 1$ with a=20.4929(19) Å, b=24.671(2) Å, c=29.727(3) Å, α=81.9990(10)°, β=88.0830(10)°, γ=89.9940(10)°, V=14875(2) Å(3) . Structural analysis indicates the framework of 1 is a 3D perovskite-like structure constructed out of CO3 @Dy26 building units and Cu(+) centers by means of nicotinic acid ligand bridging. In 2, however, nanosized CO3 @Tb26 units and [Ag3 Cl](2+) centers are connected by Nic(-) bridges to give rise to a 2D structure. It is worth mentioning that this kind of 4d-4f cluster-based MOF is quite rare as most of the reported analogous compounds are 3d-4f ones. Additionally, the solid-state emission spectra of pure compound 2 at room temperature suggest an efficient energy transfer from the ligand Nic(-) to Tb(3+) ions, which we called the "antenna effect". Compound 2 shows a good two-photon absorption (TPA) with a TPA coefficient of 0.06947 cm GM(-1) (1 GM=10(-50)  cm(4)  s photon(-1) ), which indicates that compound 2 might be a good choice for third-order nonlinear optical materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Sellmeier equations, group velocity dispersion, and thermo-optic dispersion formulas for CaLnAlO4 (Ln = Y, Gd) laser host crystals.

    PubMed

    Loiko, Pavel; Becker, Petra; Bohatý, Ladislav; Liebald, Christoph; Peltz, Mark; Vernay, Sophie; Rytz, Daniel; Serres, Josep Maria; Mateos, Xavier; Wang, Yicheng; Xu, Xiaodong; Xu, Jun; Major, Arkady; Baranov, Alexander; Griebner, Uwe; Petrov, Valentin

    2017-06-15

    We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, CaLnAlO4 (Ln=Gd or Y). Sellmeier equations were derived for the spectral range of 0.35-2.1 μm. The group velocity dispersion (GVD) in CaGdAlO4 is positive at ∼1  μm, 95  fs2/mm and negative at ∼2  μm, -40  fs2/mm. The GVD values for CaYAlO4 are similar. In addition, thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path were determined for CaYAlO4. dn/dT is negative at ∼1  μm, dno/dT=-7.8, and dne/dT=-8.7×10-6  K-1. Thermo-optic dispersion formulas were constructed. The obtained data are of key importance to the design of high-power mode-locked oscillators at ∼1 and ∼2  μm based on such laser hosts.

  3. Emission Enhancement and Color Tuning for GdVO4:Ln(3+) (Ln = Dy, Eu) by Surface Modification at Single Wavelength Excitation.

    PubMed

    Song, Yan; Shao, Baiqi; Feng, Yang; Lü, Wei; Huo, Jiansheng; Zhao, Shuang; Liu, Man; Liu, Guixia; You, Hongpeng

    2017-01-03

    The surface modification can realize systematically the emission enhancement of GdVO4:Ln(3+) (Ln = Dy, Eu) microstructures and multicolor emission at single component. The structure, morphology, composition, and the surface ligands modification of as-prepared samples were studied in detail. It is found that the surface-modified ligands can act as sensitizer to improve the emission of the Eu(3+) and Dy(3+) ions via the energy transfer besides the VO4(3-)-Eu(3+)/Dy(3+) process. More importantly, under a single wavelength excitation, the emission color can be effectively tuned by manipulating the doping ratio of the Eu(3+) ions in the internal crystal lattice and the Tb(3+) ions in the external surface ligands, simultaneously. And further, multicolor emissions are obtained under single wavelength excitation due to the high overlapping between the VO4(3-) absorption and the π-π* electron transition of the ligands. These findings may open new avenues to design and develop new highly efficient luminescent materials.

  4. Single crystal synthesis and magnetism of the BaLn2O4 family (Ln = lanthanide)

    SciTech Connect

    Besara, Tiglet; Lundberg, Matthew S.; Sun, Jifeng; Ramirez, Daniel; Dong, Lianyang; Whalen, Jeffrey B.; Vasquez, Rafael; Herrera, Felix; Allen, John R.; Davidson, Michael W.; Siegrist, Theo

    2014-05-27

    The series of compounds in the BaLn2O4 family (Ln = La–Lu, Y) has been synthesized for the first time in single crystalline form, using a molten metal flux. The series crystallizes in the CaV2O4 structure type with primitive orthorhombic symmetry (space group Pnma, #62), and a complete structural study of atomic positions, bonds, angles, and distortions across the lanthanide series is presented. With the exception of the Y, La, Eu, and Lu members, magnetic susceptibility measurements were performed between 2 K and 300 K. BaCe2O4 and BaYb2O4 display large crystal fields effects and suppression of magnetic ordering. As a result, all compounds show signs of magnetic frustration due to the trigonal arrangements of the trivalent lanthanide cations in the structure.

  5. Rare-earth metal methylidene complexes with Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 core structure.

    PubMed

    Schädle, Dorothea; Meermann-Zimmermann, Melanie; Maichle-Mössmer, Cäcilia; Schädle, Christoph; Törnroos, Karl W; Anwander, Reiner

    2015-11-07

    Trinuclear rare-earth metal methylidene complexes with a Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 structural motif were synthesized by applying three protocols. Polymeric [LuMe3]n (1-Lu) reacts with the sterically demanding amine H[NSiMe3(Ar)] (Ar = C6H3iPr2-2,6) in tetrahydrofuran via methane elimination to afford isolable monomeric [NSiMe3(Ar)]LuMe2(thf)2 (4-Lu). The formation of trinuclear rare-earth metal tetramethyl methylidene complexes [NSiMe3(Ar)]3Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3(thf)3 (7-Ln; Ln = Y, Ho, Lu) via reaction of [LnMe3]n (1-Ln; Ln = Y, Ho, Lu) with H[NSiMe3(Ar)] is proposed to occur via an "intermediate" species of the type [NSiMe3(Ar)]LnMe2(thf)x and subsequent C-H bond activation. Applying Lappert's concept of Lewis base-induced methylaluminate cleavage, compounds [NSiMe3(Ar)]Ln(AlMe4)2 (5-Ln; Ln = Y, La, Nd, Ho) were converted into methylidene complexes 7-Ln (Ln = Y, Nd, Ho) in the presence of tetrahydrofuran. Similarly, tetramethylgallate complex [NSiMe3(Ar)]Y(GaMe4)2 (6-Y) could be employed as a synthesis precursor for 7-Y. The molecular composition of complexes 4-Ln, 5-Ln, 6-Y and 7-Ln was confirmed by elemental analyses, FTIR spectroscopy, (1)H and (13)C NMR spectroscopy (except for holmium derivatives) and single-crystal X-ray diffraction. The Tebbe-like reactivity of methylidene complex 7-Nd with 9-fluorenone was assessed affording oxo complex [NSiMe3(Ar)]3Nd3(μ3-O)(μ2-Me)4(thf)3 (8-Nd). The synthesis of 5-Ln yielded [NSiMe3(Ar)]2Ln(AlMe4) (9-Ln; Ln = La, Nd) as minor side-products, which could be obtained in moderate yields when homoleptic Ln(AlMe4)3 were treated with two equivalents of K[NSiMe3(Ar)].

  6. Octanuclear [Ni(II)₄Ln(III)₄] complexes. Synthesis, crystal structures and magnetocaloric properties.

    PubMed

    Pasatoiu, Traian D; Ghirri, Alberto; Madalan, Augustin M; Affronte, Marco; Andruh, Marius

    2014-06-28

    Two original heterooctanuclear [Ni(II)4Ln(III)4] complexes (Ln(III) = Sm(III), Gd(III)) have been obtained starting from the [Ni(II)(valpn)(H2O)2] mononuclear precursor [H2valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)] and the corresponding lanthanide nitrates, in the presence of azide anions, through slow capture of atmospheric CO2. Three weak and competitive exchange interactions, J(GdGd), J(GdNi), J(NiNi), make the ground state of this magnetic system degenerate at cryogenic temperature and zero field. This, along with the high spin of Gd(III), lead to a significant magnetocaloric effect spread in the temperature range 1 to 20 K (ΔSm[0-7 T, 3.5 K] = 19 J kg(-1) K(-1)).

  7. Hardness of Carburized Surfaces in 316LN Stainless Steel after Low Temperature Neutron Irradiation

    SciTech Connect

    Byun, TS

    2005-01-31

    A proprietary surface carburization treatment is being considered to minimize possible cavitation pitting of the inner surfaces of the stainless steel target vessel of the SNS. The treatment gives a large supersaturation of carbon in the surface layers and causes substantial hardening of the surface. To answer the question of whether such a hardened layer will remain hard and stable during neutron irradiation, specimens of the candidate materials were irradiated in the High Flux Isotope Reactor (HFIR) to an atomic displacement level of 1 dpa. Considerable radiation hardening occurred in annealed 316LN stainless steel and 20% cold rolled 316LN stainless steel, and lesser radiation hardening in Kolsterised layers on these materials. These observations coupled with optical microscopy examinations indicate that the carbon-supersaturated layers did not suffer radiation-induced decomposition and softening.

  8. Mechanical properties of cold-rolled AISI 304LN steel at low temperatures

    SciTech Connect

    Ilola, R.J.; Haenninen, H.E.; Heinaekari, M.J.

    1996-12-01

    Mechanical properties of 0--70% cold-rolled AISI 304LN steel (0, 16 wt.% N) were investigated by means of tensile and Charpy V-notch impact tests between room temperature and {minus}196 C. Fracture surfaces of the tested specimens were investigated using SEM (scanning electron microscope). Austenite stability against {alpha}{prime}-martensite formation during cooling and during deformation in cold-rolling and mechanical testing was determined using magnetic measurements.

  9. TES/Aura L2 Ozone (O3) Lite Nadir (TL2O3LN)

    Atmospheric Science Data Center

    2015-08-26

    TES/Aura L2 Ozone (O3) Lite Nadir (TL2O3LN) News:  TES News ... Level:  L2 Instrument:  TES/Aura L2 Ozone Spatial Coverage:  5.3 km nadir Spatial ... OPeNDAP Access:  OPeNDAP Parameters:  Ozone Order Data:  Search and Order:   Earthdata Search ...

  10. Equipping an FPGA-Based Mars Rover With an LN-200 IMU

    NASA Technical Reports Server (NTRS)

    Zola, Nicholas J.

    2005-01-01

    The Mars Exploration Rovers (MER) currently navigating the surface of Mars are outfitted with an advanced stereovision correlation algorithm which allows them to "see" three-dimensionally and autonomously avoid obstac'les in their path. A bottleneck of this system is that it is computationally intense and requires 3 minutes of processing for every correlated image and path choice. Taking advantage of the optimization and reprogrammability of FPGAs, the Mobility Avionics lab has reduced this process to under a second. The lab is demonstrating the advancement with a prototype rover, complete with an LN-200 inertial measurement unit (IMU), which is a flight spare from MER. The LN-200 is a space-grade, six degrees-of-freedom IMU using three fiber-optic gyroscopes and three silicon accelerometers and no moving parts. It has particular power-sequencing needs and communicates with a specialized serial protocol (SDLC over RS-422), requiring specific hardware and software for proper functionality and interfacing with an FPGA. The process of incorporating the LN-200 into the system is described herein.

  11. Photogalvanic self-pulsing of electro-wetting of LC droplet on LN-crystal

    NASA Astrophysics Data System (ADS)

    Kukhtarev, N.; Kukhtareva, T.; Geng, J.; Zhang, XZ; Xu, JJ

    2017-06-01

    Photogalvanic current photoinduced by CW laser illumination of Fe-doped LN reveals quasi-periodic pulsing due to microplasmas discharges. This transformation of constant external influence into periodic response is interesting as example of self-excited systems, resembling pulsations of biological systems (including heart beats). Microplasmas is also interesting for potential applications in various fields, such as surface treatment, sterilization, water splitting, light sources, micro jets. Self-pulsing regime of microplasmas discharges in microhollow cathode discharges was observed and modeled in plasmas physics. In this paper, we analyze self-pulsing of photogalvanic current visualized by dynamic electrowetting in a simple LC-cell, formed by a nematic LC droplet placed on Fe-doped LN crystal. We have developed model of self-pulsing regime based on nonlinear discharge resistance. Experimental phase-space plot may be used to find parameters of the nonlinear discharge resistance. In the dynamic modeling contributions from both photogalvanic and pyroelectric effect are included. The analysis of dynamic regime reveals that a current pulse (in microsecond range) have asymmetric shape with extremely sharp rise with longer decay time. These self-pulsations are visualized by reflection of laser light from a LC droplet placed on LN-crystal. Reflected interference patterned was modulated by the dynamic electro-wetting effect.

  12. Syntheses, structures and photophysical properties of a series of Zn-Ln complexes

    NASA Astrophysics Data System (ADS)

    Wang, Yan-Mei; Wang, Yan; Wang, Rui-Xue; Qiu, Ju-Qing; Chi, Yu-Xian; Jin, Jing; Niu, Shu-Yun

    2017-05-01

    Six Zn-Ln coordination complexes, [Nd2Zn2(C6H5COO)10(Imh)2(H2O)2] (1), [Pr2Zn2(C6H5COO)10(Imh)2(H2O)2] (2), [ErZn2(C6H5COO)7(Imh)2] (3), [HoZn2(C6H5COO)7(Imh)2] (4), [EuZn2(C6H5COO)7(Imh)2] (5), [TbZn2(C6H5COO)7(Imh)2] (6) (C6H5COOH=benzoic acid, Imh=imidazole) have been synthesized under hydrothermal conditions and their crystal structures have been characterized by single crystal X-ray diffraction. All complexes are crystallized in triclinic system, with space group Pī. Complexes 1 and 2 are isomorphous with tetranuclear molecular structure and complexes 3-6 are isomorphous and trinuclear molecular complexes. All complexes are characterized by IR, UV-Vis-NIR and luminescent spectra in the visible and near-infrared (NIR) regions at room temperature. The study of luminescent properties indicates that all complexes exhibit the characteristic emission bands of corresponding Ln(III) ions, which should be attributed to sensitization from d-block and ligands after introducing Zn(II) ion and ligands into the system of Ln(III) complexes. Moreover, the NIR emission bands of complexes 1-4 exhibit shift and split, which can be evidenced in their UV-Vis-NIR absorption spectra.

  13. Equipping an FPGA-Based Mars Rover With an LN-200 IMU

    NASA Technical Reports Server (NTRS)

    Zola, Nicholas J.

    2005-01-01

    The Mars Exploration Rovers (MER) currently navigating the surface of Mars are outfitted with an advanced stereovision correlation algorithm which allows them to "see" three-dimensionally and autonomously avoid obstac'les in their path. A bottleneck of this system is that it is computationally intense and requires 3 minutes of processing for every correlated image and path choice. Taking advantage of the optimization and reprogrammability of FPGAs, the Mobility Avionics lab has reduced this process to under a second. The lab is demonstrating the advancement with a prototype rover, complete with an LN-200 inertial measurement unit (IMU), which is a flight spare from MER. The LN-200 is a space-grade, six degrees-of-freedom IMU using three fiber-optic gyroscopes and three silicon accelerometers and no moving parts. It has particular power-sequencing needs and communicates with a specialized serial protocol (SDLC over RS-422), requiring specific hardware and software for proper functionality and interfacing with an FPGA. The process of incorporating the LN-200 into the system is described herein.

  14. Deterioration in Fracture Toughness of 304LN Austenitic Stainless Steel Due to Sensitization

    NASA Astrophysics Data System (ADS)

    Ghosh, Swati; Kain, V.; Ray, A.; Roy, H.; Sivaprasad, S.; Tarafder, S.; Ray, K. K.

    2009-12-01

    The aim of this report is to examine the influence of sensitization on the mechanical properties of AISI grade 304LN stainless steel with special emphasis on its fracture toughness. A series of stainless steel samples has been sensitized by holding at 1023 K for different time periods ranging from 1 to 100 hours followed by water quenching. The degree of sensitization (DOS) for each type of the varyingly heat-treated samples has been measured by an electrochemical potentiodynamic reactivation (EPR) test. The microstructures of these samples have been characterized by optical metallography, scanning electron microscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses, together with measurements of their hardness and tensile properties. The fracture toughness of the samples has been measured by the ball indentation (BI) technique and the results are validated by conducting conventional J-integral tests. It is revealed for the first time that the fracture toughness and ductility of AISI 304LN stainless steel deteriorate significantly with increased DOS, while the tensile strength (TS) values remain almost unaltered. The results have been critically discussed in terms of the depletion of solid solution strengtheners, the nature of the grain boundary precipitations, and the strain-induced martensite formation with the increasing DOS of the 304LN stainless steel.

  15. High-temperature X-ray diffraction measurements of fluorite-related rare earth antimonates Ln{sub 3}SbO{sub 7} (Ln=Nd, Tb) and their magnetic properties

    SciTech Connect

    Hinatsu, Yukio Doi, Yoshihiro

    2014-09-15

    Ternary rare-earth antimonates Ln{sub 3}SbO{sub 7} (Ln=rare earths) were prepared, and their structures were determined by X-ray diffraction measurements. They crystallize in an orthorhombic superstructure of cubic fluorite (space group Cmcm for Ln=La, Pr; Ccmm for Ln=Sm–Dy), in which Ln{sup 3+} ions occupy two different crystallographic sites (the 8-coordinated and 7-coordinated). For Ln=Nd, two phases with the Cmcm and Ccmm space groups coexist at room temperature. When the temperature was increased, the Nd{sub 3}SbO{sub 7} compound transformed into a single phase with the space group Cmcm. Through magnetic susceptibility measurements, an antiferromagnetic transition was observed at 3.0 K (Ln=Nd) and 7.8 K (Ln=Tb). Analysis of the magnetic specific heat for Tb{sub 3}SbO{sub 7} indicates that the 8-coordinated Tb ions magnetically orders at 7.8 K, and with furthermore decreasing temperature, the 7-coordinated Tb ions shows antiferromagnetic ordering at 3.0 K. - Graphical abstract: Temperature dependence of the specific heat divided by temperature (C{sub p}/T) and the magnetic entropy (S{sub mag}) for Tb{sub 3}SbO{sub 7}. Two-step magnetic transition has been observed. - Highlights: • The phase transition of Nd{sub 3}SbO{sub 7} is from the Ccmm space group to the Cmcm one. • Nd{sub 3}SbO{sub 7} shows an antiferromagnetic transition at 3.0 K. • For Tb{sub 3}SbO{sub 7}, two-step magnetic transition has been observed at 7.8 and 3.0 K.

  16. Ab initio study on structure and phase transition of A- and B-type rare-earth sesquioxides Ln{sub 2}O{sub 3} (Ln=La-Lu, Y, and Sc) based on density function theory

    SciTech Connect

    Wu Bo Zinkevich, Matvei Aldinger, Fritz Wen Dingzhong Chen Lu

    2007-11-15

    Ab initio energetic calculations based on the density functional theory (DFT) and projector augmented wave (PAW) pseudo-potentials method were performanced to determine the crystal structural parameters and phase transition data of the polymorphic rare-earth sesquioxides Ln{sub 2}O{sub 3} (where Ln=La-Lu, Y, and Sc) with A-type (hexagonal) and B-type (monoclinic) configurations at ground state. The calculated results agree well with the limited experimental data and the critically assessed results. A set of systematic and self-consistent crystal structural parameters, energies and pressures of the phase transition were established for the whole series of the A- and B-type rare-earth sesquioxides Ln{sub 2}O{sub 3}. With the increase of the atomic number, the ionic radii of rare-earth elements Ln and the volumes of the sesquioxides Ln{sub 2}O{sub 3} reflect the so-called 'lanthanide contraction'. With the increase of the Ln{sup 3+}-cation radius, the bulk modulus of Ln{sub 2}O{sub 3} decreases and the polymorphic structures show a degenerative tendency. - Graphical abstract: This graph shows the calculated transition pressure with respect to the transition of the Ln{sub 2}O{sub 3} from its B- to A-type together with the available experimental data superimposed. The transition pressure was obtained by calculating the common tangent slope of the two fitted E-V curves based on the empirical third-order Birch-Murnaghan equation of state.

  17. Enneanuclear [Ni6Ln3] Cages: [Ln(III)3] Triangles Capping [Ni(II)6] Trigonal Prisms Including a [Ni6Dy3] Single-Molecule Magnet.

    PubMed

    Canaj, Angelos B; Tzimopoulos, Demetrios I; Siczek, Milosz; Lis, Tadeusz; Inglis, Ross; Milios, Constantinos J

    2015-07-20

    The use of (2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) ligand, H3L, in Ni/Ln chemistry has led to the isolation of three new isostructural [Ni(II)6Ln(III)3] metallic cages. More specifically, the reaction of Ni(ClO4)2·6H2O, the corresponding lanthanide nitrate salt, and H3L in MeCN, under solvothermal conditions in the presence of NEt3, led to the isolation of three complexes with the formulas [Ni6Gd3(OH)6(HL)6(NO3)3]·5.75MeCN·2Et2O·1.5H2O (1·5.75MeCN·2Et2O·1.5H2O), [Ni6Dy3(OH)6(HL)6(NO3)3]·2MeCN·2.7Et2O·2.4H2O (2·2MeCN·2.7Et2O·2.4H2O), and [Ni6Er3(OH)6(HL)6(NO3)3]·5.75MeCN·2Et2O·1.5H2O (3·5.75MeCN·2Et2O·1.5H2O). The structure of all three clusters describes a [Ln(III)3] triangle capping a [Ni(II)6] trigonal prism. Direct current magnetic susceptibility studies in the 5-300 K range for complexes 1-3 reveal the different nature of the magnetic interactions within the clusters: dominant antiferromagnetic exchange interactions for the Dy(III) and Er(III) analogues and dominant ferromagnetic interactions for the Gd(III) example. Alternating current magnetic susceptibility measurements under zero external dc field displayed fully formed temperature- and frequency-dependent out-of-phase peaks for the [Ni(II)6Dy(III)3] analogue, establishing its single molecule magnetism behavior with Ueff = 24 K.

  18. A comparative evaluation of low-cycle fatigue behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joint

    NASA Astrophysics Data System (ADS)

    Valsan, M.; Sundararaman, D.; Rao, K. Bhanu Sankara; Mannan, S. L.

    1995-05-01

    A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joints was carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 × 10-3 s-1 with strain amplitudes in the range ±0.20 to ±1.0 pct. Weld pads with single V and double V configuration were prepared by the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation in the number density of slip bands. From TEM, the cyclic softening in weld metal was ascribed to the annihilation of dislocations during LCF. Type 316LN base metal exhibits better fatigue resistance than weld metal at 773 K, whereas the reverse holds true at 873 K. The weld joint shows the lowest life at both temperatures. The better fatigue resistance of weld metal is related to the brittle transformed delta ferrite structure and the high density of dislocations at the interface, which inhibits the growth rate of cracks by deflecting the crack path. The lower fatigue endurance of the weld joint was ascribed to the shortening of the crack initiation phase caused by surface intergranular crack initiation and to the poor

  19. Metallocyclic Ni4Ln2M2 single-molecule magnets.

    PubMed

    Liu, Mei-Jiao; Hu, Kong-Qiu; Liu, Cai-Ming; Cui, Ai-Li; Kou, Hui-Zhong

    2017-05-23

    We herein report the synthesis, crystal structure and magnetic properties of nine new heterotrimetallic complexes. [Ni(Me2valpn)] (H2Me2valpn = N,N'-bis(3-methoxysalicylidene)-2,2-dimethyl-1,3-diaminopropane) was used as the precursor to construct phenoxo-bridged [Ni2Ln](3+) (Ln(3+) = Dy, Tb, Gd and Y) species that were respectively connected by two [M(CN)6](3-) (M = Cr, Fe or Co) anions to form octanuclear cyclic complexes, i.e. {[Ni(Me2valpn)]2Ln(H2O)M(CN)6}2 in which Ln = Y, Gd, Tb and Dy and M = Cr, Fe or Co (1-9). Each of the complexes contains many lattice-bound molecules of solvation. The Ni(ii) ions are penta-coordinate, while the Ln(iii) ions are nine coordinated with a muffin geometry. The fitting to the χmT vs. T curves of complexes 6-9 gave the parameters of JNiCr = 11.82 cm(-1), JNiGd = 0.94 cm(-1) and g = 2.04 for complex 6, JNiFe = 10.58 cm(-1), JNiGd = 1.24 cm(-1) and g = 2.03 for complex 7, JNiCr = 9.4(1) cm(-1), zJ' = -0.050(2) cm(-1) and g = 2.06(1) for complex 8 and JNiFe = 4.9(7) cm(-1), zJ' = -0.35(2) cm(-1) and g = 2.24(1) for complex 9, respectively. The dynamic magnetic investigations demonstrate that complexes 1-5 display single-molecule magnet properties with an effective energy barrier (Ueff) of 38.9 K (1, M1 = Dy, M2 = Cr), 37.2 K (2, M1 = Dy, M2 = Cr), 24.4 K (3, M1 = Dy, M2 = Co), 21.9 K (4, M1 = Tb, M2 = Cr) and 29.6 K (5, M1 = Tb, M2 = Fe), respectively. Complex 1 shows the highest energy barrier among the octanuclear [Ni4LnM2] (Ln = Dy or Tb, M = Fe, Cr, Co or W) system. Although the [Ni4Dy2Cr2] complexes have Ueff higher than that of [Ni4Dy2Fe2], complex [Ni4TbCr2] shows lower Ueff than that of [Ni4TbFe2]. The results indicate that besides the M-C[triple bond, length as m-dash]N-Ni magnetic coupling the lanthanide ions can significantly affect the magnetic performances of heterotrimetallic SMMs as well. Moreover, the SMMs are achieved when diamagnetic Co(iii) was substituted by paramagnetic Cr(iii) or Fe(iii) in the [Ni4Tb2 M2

  20. Oxygen non-stoichiometry of Ln4Ni 2.7Fe 0.3O 10-δ ( Ln=La, Pr)

    NASA Astrophysics Data System (ADS)

    Tsipis, E. V.; Patrakeev, M. V.; Waerenborgh, J. C.; Pivak, Y. V.; Markov, A. A.; Gaczyński, P.; Naumovich, E. N.; Kharton, V. V.

    2007-06-01

    The oxygen deficiency of iron-substituted nickelates Ln4Ni 2.7Fe 0.3O 10-δ ( Ln=La, Pr) with the orthorhombic Ruddlesden-Popper structure was studied by thermogravimetric analysis and coulometric titration in the oxygen partial pressure range 6×10 -5 to 0.7 atm at 973-1223 K. In air, the non-stoichiometry values vary in the relatively narrow ranges (2.4-4.2)×10 -2 for La- and (0.01-2.0)×10 -2 for Pr-containing compositions, increasing with temperature. Due to the smaller size of praseodymium cations, Pr 4Ni 2.7Fe 0.3O 10-δ exhibits a substantially lower thermodynamic stability in comparison with La 4Ni 2.7Fe 0.3O 10-δ and La 4Ni 3O 10-δ, although the oxygen content in Pr 4Ni 2.7Fe 0.3O 10-δ lattice is higher. The partial substitution of iron for nickel has no essential effect on the low- p(O 2) stability limit corresponding to the transition of Pr 4Ni 3O 10-δ into K 2NiF 4-type Pr 2NiO 4+δ. On the contrary, doping of La 4Ni 3O 10-δ with iron decreases the oxygen vacancy concentration and shifts the phase stability boundary towards lower oxygen chemical potentials, suggesting a stabilization of the transition metal-oxygen octahedra in lanthanum nickelate lattice. The Mössbauer spectroscopy showed that the predominant state of iron cations, statistically distributed between the nickel sites, is trivalent.

  1. A Green Route to Hexagonal and Monoclinic BiPO4:Ln3+ (Ln = Sm, Eu, Tb, Dy) Nanocrystallites for Tailoring Luminescent Performance.

    PubMed

    Yang, Errui; Li, Guangshe; Zheng, Yunlong; Li, Liping

    2016-04-01

    Selective synthesis of specific phased nanomaterials via a green route is a promising yet challeng- ing task. In the present work, the hexagonal and monoclinic phases of BiPO4:Ln3+ (Ln = Sm, Eu, Tb, Dy) were prepared via room temperature co-precipitation method. For adjusting the phase of the products, the prepared mediums selected were the most common solvents, i.e., water and ethanol. It was very important that the prepared mediums could be easily recycled and reused by evapo- rating the filtrate. The formation mechanisms of hexagonal in water and monoclinic in ethanol were investigated. Interestingly, the growth behaviors of these phases were quite distinct and thus gave rise to distinct morphology and particle size. The hexagonal phase possesses a rod-like morphol- ogy with diameters of 50-160 nm and lengths of 65-400 nm while the monoclinic phase consists of almost entirely irregular nanoparticles. Also, it was found that the bending and stretching vibrations of O-H and PO4 tetrahedra were quite different for the products prepared in water and ethanol. Moreover, it was found that the luminescence properties, including emission intensity, lifetime, quan- tum efficiency, and color, could be readily tailored through controlling the phase structures and microstructures. The results showed that the monoclinic phase exhibited superior luminescent per- formance to the hexagonal phase. The methodologies reported in this work were fundamentally important, which could be easily extended to large-scale synthesis of other phased nanomaterials for potential applications as electroluminescent devices, optical integrated circuits, or biomarkers.

  2. Host-sensitized luminescence properties in CaNb2O6:Ln(3+) (Ln(3+) = Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+)) phosphors with abundant colors.

    PubMed

    Li, Kai; Liu, Xiaoming; Zhang, Yang; Li, Xuejiao; Lian, Hongzhou; Lin, Jun

    2015-01-05

    A series of Ln(3+) (Ln(3+) = Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+)) ion doped CaNb2O6 (CNO) phosphors have been prepared via the conventional high-temperature solid-state reaction route. The X-ray diffraction (XRD) and structure refinement, diffuse reflection, photoluminescence (PL), and fluorescent decay curves were used to characterize the as-prepared samples. Under UV radiation, the CNO host present a broad emission band from about 355 to 605 nm centered around 460 nm originating from the NbO6 octahedral groups, which has spectral overlaps with the excitation of f-f transitions of Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) in CNO:Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) samples. They show both host emission and respective emission lines derived from the characteristic f-f transitions of activators, which present different emission colors owing to the energy transfer from the NbO6 group in the host to Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) with increasing activator concentrations. The decreases of decay lifetimes of host emissions in CNO:Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+) demonstrate the energy transfer from the hosts to Eu(3+)/Tb(3+)/Dy(3+)/Sm(3+). The energy transfer mechanisms in CNO:Eu(3+)/Tb(3+)/Dy(3+) phosphors have been determined to be a resonant type via dipole-dipole mechanisms. For CNO:Sm(3+), the metal-metal charge transfer transition (MMCT) might contribute to the different variations of decay lifetimes and emission intensity from CNO:Eu(3+)/Tb(3+)/Dy(3+) samples. The best quantum efficiency is 71.2% for CNO:0.01/0.02Dy(3+). The PL properties of as-prepared materials indicate the promising application in UV-pumped white-emitting lighting diodes field.

  3. Triacylglycerols composition, oxidation and oxidation compounds in camellia oil using liquid chromatography-mass spectrometry.

    PubMed

    Zeb, Alam

    2012-07-01

    Camellia seed oil is one of most important edible oil, rich in oleic acid and contains many natural antioxidants with various biological activities. During preparation of foods or storage camellia oil oxidizes by the auto-oxidation and produce oxidized compounds. Traditional analytical techniques like FFA, POV are used for the determination of oxidation and adulteration of oils and fats. These methods were rarely able to detect the oxidized compounds produced and extent of oxidation. This paper presents the uses of liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS) for the analysis of triacylglycerols (TAGs) composition and evaluation of auto-oxidation and oxidation products of camellia seed oil. The camellia oil was auto-oxidized for 12 months at room temperature. The TAGs were identified from their characteristics fragmentations such as protonated molecular ion, ammonium and sodium adducts, diacylglycerols, epoxy-diacylglycerols fragments and mono-acylglycerol fragments in ESI-MS mass spectra. HPLC-ESI-MS data revealed the separation and identification of 15 TAGs. The major TAGs separated and identified in camellia seed oil were POO, OOO, OLO, PLO/POL, OLL, SOO, ALO and OLLn. The auto-oxidation studies revealed a total loss of LnLLn, LnOLn, LLLn and OLLn amounting about 13.5% total oxidation. The auto-oxidation products were epoxy hydroperoxides, epoxy epidioxides, and mono-epoxides. It was observed that these were characteristic compounds produced in high oleic oils.

  4. Ln3M(1-delta)TX7--quasi-isostructural compounds: stereochemistry and silver-ion motion in the Ln3Ag(1-delta)GeS7 (Ln = La-Nd, Sm, Gd-Er and Y; delta = 0.11-0.50) compounds.

    PubMed

    Daszkiewicz, Marek; Gulay, Lubomir D; Lychmanyuk, Olga S

    2009-04-01

    The crystal structures of the Ln3Ag(1-delta)GeS7 (Ln = La-Nd, Sm, Gd-Er, Y; delta = 0.11-0.50, space group P6(3)) compounds were determined by means of X-ray single-crystal diffraction and the similarities among the crystal structures of all Ln3M(1-delta)TX7 (space group P6(3); Ln--lanthanide element, M--monovalent element; T--tetravalent element and X--S, Se) compounds deposited in the Inorganic Crystal Structure Database (ICSD) are discussed. Substitutions of each element in Ln3M(1-delta)TX7 result in a different structural effect. On the basis of the data deposited in the ICSD the large family of the Ln3M(1-delta)TX7 compounds was divided into three groups depending on the position of the monovalent element in the lattice. This position determines what kind of stereoisomer is present in the structure, either the ++ enantiomer or the +- diastereoisomer. Since the silver ions can occupy a different position and the energy barriers between positions are low the ions can move through the channel. It was shown that this movement is not a stochastic process but a correlated one.

  5. Study of Ln{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Mn{sub 0.2}O{sub 3-{delta}} (Ln=La, Gd, Sm or Nd) as the cathode materials for intermediate temperature SOFC

    SciTech Connect

    Chen Wenxia; Wen Tinglian; Nie Huaiwen; Zheng Rui

    2003-07-14

    Perovskite type oxides Ln{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Mn{sub 0.2}O{sub 3-{delta}} (Ln=La, Gd, Sm, or Nd) have been prepared by the solid state reaction of corresponding oxides. The crystal parameters of the compositions were determined by XRD powder diffraction, which revealed that all the compositions have orthorhombic structure. The reaction test of all samples with Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9} was carried out at 1200 deg. C for 48 h, and no reaction product was detected by XRD. The change in mass of La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Mn{sub 0.2}O{sub 3-{delta}} as a function of temperature was determined by thermogravimetric analysis (TGA). The electrical conductivity of the sintered samples were measured as a function of temperature from 200 to 1000 deg. C. The highest conductivity of about 1400 S cm{sup -1} was found in La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Mn{sub 0.2}O{sub 3-{delta}}. The cathodic polarization of these oxides electrodes deposited on Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9} tablet was studied at 500-800 deg. C in air.

  6. Hydrothermal synthesis and luminescence properties of hierarchical SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) micro/nanocomposite architectures

    SciTech Connect

    Peng, Jing; Hou, Suying; Liu, Xianchun; Feng, Jing; Yu, Xiaodan; Xing, Yan; Su, Zhongmin

    2012-02-15

    Graphical abstract: Uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microsphere assembled by numerous nanoplates have been successfully synthesized via a facile hydrothermal process in the presence of chelating reagent. Highlights: Black-Right-Pointing-Pointer Uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microsphere were obtained by a simple hydrothermal method. Black-Right-Pointing-Pointer The reaction time, chelating reagent and F source play important roles for the formation of hierarchical microspheres. Black-Right-Pointing-Pointer The luminescence properties of lanthanide ion-doped SrF{sub 2} hierarchical microstructures were discussed. -- Abstract: Highly uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microspheres assembled by 2D nanoplates have been successfully synthesized by a facile and friendly hydrothermal route. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the samples. The experimental results indicate that reaction time and chelating reagent play a key role in forming the hierarchical microspheres. The formation mechanism was proposed based on the evolution of this morphology as a function of hydrothermal time. The near-infrared luminescence of lanthanide ions (Er, Nd, and Yb) doped SrF{sub 2} microspheres were discussed in detail. In addition, the as-obtained SrF{sub 2}:Eu{sup 3+} sample exhibits orange-red emission centered at 590 nm under excitation at 393 nm, while the SrF{sub 2}:Tb{sup 3+} exhibits a strong green emission at 540 nm. The as-synthesized SrF{sub 2}:Ln{sup 3+} luminescent microspheres might find some potential applications in areas of photoluminescence, telecommunication and laser emission.

  7. Facile synthesis and multicolor luminescent properties of uniform Lu2O3:Ln (Ln=Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanospheres.

    PubMed

    Li, Rumin; Gai, Shili; Wang, Liuzhen; Wang, Jun; Yang, Piaoping

    2012-02-15

    Multicolor Lu(2)O(3):Ln (Ln=Eu(3+), Tb(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) nanocrystals (NCs) with uniform spherical morphology were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize these samples. The XRD results reveal that the as-prepared nanospheres can be well indexed to cubic Lu(2)O(3) phase with high purity. The SEM images show the obtained Lu(2)O(3):Ln samples consist of regular nanospheres with the mean diameter of 95 nm. And the possible formation mechanism is also proposed. Upon ultraviolet (UV) excitation, Lu(2)O(3):Ln (Ln=Eu(3+) and Tb(3+)) NCs exhibit bright red (Eu(3+), (5)D(0)→(7)F(2)), and green (Tb(3+), (5)D(4)→(7)F(5)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu(2)O(3):Ln (Ln=Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) NCs display the typical up-conversion (UC) emissions of green (Er(3+), (4)S(3/2),(2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow-green (Ho(3+), (5)F(4), (5)S(2)→(5)I(8)), respectively.

  8. Laparoscopic extended pelvic lymph node (LN) dissection as validation of the performance of [(11) C]-acetate positron emission tomography/computer tomography in the detection of LN metastasis in intermediate- and high-risk prostate cancer.

    PubMed

    Daouacher, Georgios; von Below, Catrin; Gestblom, Charlotta; Ahlström, Håkan; Grzegorek, Rafael; Wassberg, Cecilia; Sörensen, Jens; Waldén, Mauritz

    2016-07-01

    To evaluate the accuracy of the radiopharmaceutical [(11) C]-acetate combined with positron emission tomography/computer tomography (acetate-PET/CT) in lymph node (LN) staging in newly diagnosed prostate cancer cases. A second aim was to evaluate the potential discriminative properties of acetate-PET/CT in clinical routine. In a prospective comparative study, from July 2010 to June 2013, 53 men with newly histologically diagnosed intermediate- or high-risk prostate cancer underwent acetate-PET/CT investigation at one regional centre before laparoscopic extended pelvic LN dissection (ePLND) at one referral centre. The sensitivity, specificity and accuracy of acetate-PET/CT were calculated. Comparisons were made between true-positive and false-negative PET/CT cases to identify differences in the clinical parameters: PSA level, Gleason status, lymph metastasis burden and size, calculated risk of LN involvement, and curative treatment decisions. In all, 26 patients had surgically/histologically confirmed LN metastasis (LN+). Acetate-PET/CT was true positive in 10 patients, false positive in one, false negative in 16, and true negative in 26. The individual sensitivity was 38%, specificity 96%, and accuracy 68%. The acetate-PET/CT positive cases had significantly more involved LNs (mean 7.9 vs 2.4, P < 0.001) with larger cancer diameters (14.1 vs 4.9 mm, P = 0.001) and fewer eventually had treatment with curative intent (40% vs 94%, P <0.005), although we lack long-term outcome data. Acetate-PET/CT has too low a sensitivity for routine LN staging but the specificity is high. The acetate-PET/CT positive cases have a very high burden of LN spread. © 2015 The Authors BJU International © 2015 BJU International Published by John Wiley & Sons Ltd.

  9. First-principles studies on linear and nonlinear optical effects in Ln{sub 4}GaSbS{sub 9} (Ln=Ce-Nd, Sm, Gd-Tm, Lu)

    SciTech Connect

    Zhou, Liu-Jiang; Chen, Ling; Li, Jun-Qian; Wu, Li-Ming

    2012-11-15

    Density functional theory (DFT) calculations have been performed on electronic structures of 11 middle-infrared (mid-IR) nonlinear optical quaternary sulfides: Ln{sub 4}GaSbS{sub 9} (Ln=Ce-Nd, Sm, Gd-Tm, Lu). Our results show that Ln{sub 4}GaSbS{sub 9} are indirect gap semiconductors with a slight band gap increase from Ce to Lu. Their linear optical properties, including refractive index, absorption coefficient and energy loss function, as well as the nonlinear optical coefficients including static d{sub 31}, d{sub 32}, d{sub 33} and dynamic d{sub 32}, are calculated. More importantly, the strong SHG response of Ln{sub 4}GaSbS{sub 9} can be attributed to the electronic transitions from S 3p states in valence bands (VB) to Sb-S and Ln-S antibonding states (CB). - Graphical Abstract: Density functional theory (DFT) calculations on Ln{sub 4}GaSbS{sub 9} reveal their linear optical properties, including refractive index, adsorption coefficient and energy loss function, the nonlinear optical coefficients including static d{sub 31}, d{sub 32}, d{sub 33} and dynamic d{sub 32}, as well as the origins of the strong SHG response. Highlights: Black-Right-Pointing-Pointer First-principles studies on a newly discovered NLO active family Ln{sub 4}GaSbS{sub 9}. Black-Right-Pointing-Pointer Reports static SHG coefficients (d{sub 31}, d{sub 32}, d{sub 33}) and dynamic d{sub 32}. Black-Right-Pointing-Pointer Reveals the origin of the strong SHG response.

  10. Single crystals of LnFeAsO 1-xF x (Ln = La, Pr, Nd, Sm, Gd) and Ba 1-xRb xFe 2As 2: Growth, structure and superconducting properties

    NASA Astrophysics Data System (ADS)

    Karpinski, J.; Zhigadlo, N. D.; Katrych, S.; Bukowski, Z.; Moll, P.; Weyeneth, S.; Keller, H.; Puzniak, R.; Tortello, M.; Daghero, D.; Gonnelli, R.; Maggio-Aprile, I.; Fasano, Y.; Fischer, Ø.; Rogacki, K.; Batlogg, B.

    2009-05-01

    A review of our investigations on single crystals of LnFeAsO 1-xF x (Ln = La, Pr, Nd, Sm, Gd) and Ba 1-xRb xFe 2As 2 is presented. A high-pressure technique has been applied for the growth of LnFeAsO 1-xF x crystals, while Ba 1-xRb xFe 2As 2 crystals were grown using a quartz ampoule method. Single crystals were used for electrical transport, structure, magnetic torque and spectroscopic studies. Investigations of the crystal structure confirmed high structural perfection and show incomplete occupation of the (O, F) position in superconducting LnFeAsO 1-xF x crystals. Resistivity measurements on LnFeAsO 1-xF x crystals show a significant broadening of the transition in high magnetic fields, whereas the resistive transition in Ba 1-xRb xFe 2As 2 simply shifts to lower temperature. The critical current density for both compounds is relatively high and exceeds 2 × 10 9 A/m 2 at 15 K in 7 T. The anisotropy of magnetic penetration depth, measured on LnFeAsO 1-xF x crystals by torque magnetometry is temperature dependent and apparently larger than the anisotropy of the upper critical field. Ba 1-xRb xFe 2As 2 crystals are electronically significantly less anisotropic. Point-Contact Andreev-Reflection spectroscopy indicates the existence of two energy gaps in LnFeAsO 1-xF x. Scanning Tunneling Spectroscopy reveals in addition to a superconducting gap, also some feature at high energy (∼20 meV).

  11. Synthesis of complex metal oxides using hydroxide, cyanide, and nitrate solid solution precursors

    NASA Astrophysics Data System (ADS)

    Vidyasagar, K.; Gopalakrishnan, J.; Rao, C. N. R.

    1985-06-01

    Precursor solid solutions provide convenient routes for preparing complex metal oxides. Hydroxide solid solutions of the general formula Ln1- xMx(OH) 3 (where Ln = La or Nd and M = Al, Cr, Fe, Co, or Ni) and La 1- x- yM' xM″ y(OH) 3 (where M' = Ni and M″ = Co or Cu) crystallize in the rare earth trihydroxide structure and can be decomposed at relatively low temperatures to yield complex metal oxides. Several oxides of the type LaNiO 3, NdNiO 3, LaNi 1- xCo xO 3, and LaNi 1- xCu xO 3 have been prepared by the hydroxide precursor route. Thermal decomposition of cyanide precursors of the type Ln[ M1- xM' x(CN) 6] · 5H 2O and Ln1- xLn' x[ M(CN) 6] · 5H 2O yields the quaternary oxides which are not readily made by ceramic methods. Nitrate solid solution precursors of the type Ba 1- xPb x(NO 3) 2, Sr 1- xPb x(NO 3) 2, and BaSrPb(NO 3) 6 have been used for preparing several interesting oxides such as BaPbO 3, Ba 2PbO 4, and BaSrPbO 4.

  12. Agreement between a smart-phone pulse sensor application and ECG for determining lnRMSSD.

    PubMed

    Esco, Michael R; Flatt, Andrew A; Nakamura, Fabio Y

    2016-06-27

    The purpose of this study was to determine the agreement between a smartphone pulse finger sensor (SPFS) and electrocardiography (ECG) for determining ultra-short-term heart rate variability (HRV) in three different positions. Thirty college-aged men (n = 15) and women (n = 15) volunteered to participate in this study. Sixty second heart rate measures were simultaneously taken with the SPFS and ECG in supine, seated and standing positions. lnRMSSD was calculated from the SPFS and ECG. The lnRMSSD values were 81.5 ± 11.7 via ECG and 81.6 ± 11.3 via SPFS (p = 0.63, Cohen's d = 0.01) in the supine position, 76.5 ± 8.2 via ECG and 77.5 ± 8.2 via SPFS (p = 0.007, Cohen's d = 0.11) in the seated position, and 66.5 ± 9.2 via ECG and 67.8 ± 9.1 via SPFS (p < 0.001, Cohen's d = 0.15) in the standing positions. The SPFS showed a possibly strong correlation to the ECG in all three positions (r values from 0.98 to 0.99). In addition, the limits of agreement (CE ± 1.98 SD) were -0.13 ± 2.83 for the supine values, -0.94± 3.47 for the seated values, and -1.37 ± 3.56 for the standing values. The results of the study suggest good agreement between the SPFS and ECG for measuring lnRMSSD in supine, seated, and standing positions. Though significant differences were noted between the two methods in the seated and standing positions, the effect sizes were trivial.

  13. D0 Silicon Upgrade: Vapor Pressure Thermometry System Near LN2 Subcooler

    SciTech Connect

    Kuwazaki, Andrew; /Fermilab

    1996-07-01

    Fermi National Accelerator Laboratory (Fermilab) is in the process of upgrading its detectors. Among these upgrades is the need for more transfer lines containing both liquid nitrogen and helium gas. These two fluids are used to provide the necessary operating cryogenic temperatures for the various detectors, such as the Visible Light Photon Counter (VLPC) and the solenoid inside the detector's calorimeter. With additional piping, it is important to monitor the temperatures to assure that the detectors can operate correctly. This can be done two ways. The first method is to use a Resistance Temperature Device, called a RTD, which is made using either a carbon resistor or a platinum resistor and measures the temperature based on resistance. The second method is to use a vapor-pressure thermometry system. This design will focus on the second method. A nitrogen Vapor Pressure Thermometer (VPT) system is designed to determine the temperature of the liquid nitrogen (LN{sub 2}) supply line, after exiting the LN{sub 2} subcooler, inside the D-Zero Assembly Hall. The operating temperature range is designed from 77 to 300 Kelvin with an initial charge pressure of 100 psia. A cylindrical bulb with a 0.1875-inch diameter and 0.625-inch length allows for minimum cold and warm 1/4-inch O.D. SS 304L tubing lengths, 12-inch and 18-inch respectively, and maintains a liquid level of 50% inside the bulb during cold operation. The amount of nitrogen needed to fill the cylindrical bulb approximately half full is 0.149 grams. In order to conform to the conventional cold volume and warm volume VPT systems, we need to enlarge the existing 1/2-inch x 2-inch SCH. 10 LN{sub 2} supply line over a one foot section to 1-inch x 3-inch SCH. 10 piping.

  14. Agreement Between a Smartphone Pulse Sensor Application and Electrocardiography for Determining lnRMSSD.

    PubMed

    Esco, Michael R; Flatt, Andrew A; Nakamura, Fábio Y

    2017-02-01

    Esco, MR, Flatt, AA, and Nakamura, FY. Agreement between a smartphone pulse sensor application and electrocardiography for determining lnRMSSD. J Strength Cond Res 31(2): 380-385, 2017-The purpose of this study was to determine the agreement between a smartphone pulse finger sensor (SPFS) and electrocardiography (ECG) for determining ultra-short-term heart rate variability in 3 different positions. Thirty college-aged men (n = 15) and women (n = 15) volunteered to participate in this study. Sixty-second heart rate measures were simultaneously taken with the SPFS and ECG in supine, seated, and standing positions. The log transformed root mean square of successive R-R interval differences (lnRMSSD) was calculated from the SPFS and ECG. The lnRMSSD values were 81.5 ± 11.7 using ECG and 81.6 ± 11.3 using SPFS (p = 0.63, Cohen's d = 0.01) in the supine position, 76.5 ± 8.2 using ECG and 77.5 ± 8.2 using SPFS (p = 0.007, Cohen's d = 0.11) in the seated position, and 66.5 ± 9.2 using ECG and 67.8 ± 9.1 using SPFS (p < 0.001, Cohen's d = 0.15) in the standing position. The SPFS showed a possibly strong correlation to the ECG in all 3 positions (r values from 0.98 to 0.99). In addition, the limits of agreement (constant error ± 1.98 SD) were -0.13 ± 2.83 for the supine values, -0.94 ± 3.47 for the seated values, and -1.37 ± 3.56 for the standing values. The results of the study suggest good agreement between the SPFS and ECG for measuring lnRMSSD in supine, seated, and standing positions. Although significant differences were noted between the 2 methods in the seated and standing positions, the effect sizes were trivial.

  15. First-order Judd-Ofelt optical characterization of DNA-Ln3+ complexes

    NASA Astrophysics Data System (ADS)

    Paulson, Bjorn; Sauer, Gregor; Cheon, Seungwuk; Dugasani, Sreekantha Reddy; Oh, Kyunghwan

    2016-09-01

    Complexes formed of deoxyribose nucleic acid (DNA) and trivalent lanthanide ions (Ln3+) promise a combination of high optical gain and low optical loss in an organic polymer host matrix. However, there has been some dispute about the binding mechanism between the DNA helix and the positively-charged lanthanide ions. Here we introduce an attempt to resolve the mechanism for binding through Judd-Ofelt analysis on DNA-Eu3+, DNA-Tb3+, and DNA-Sm3+ to first order. From initial Judd-Ofelt parameters extrapolations can be made to the line strengths, Einstein coefficients, and fluorescence lifetimes.

  16. Screening Test Results of Fatigue Properties of type 316LN Stainless Steel in Mercury

    SciTech Connect

    Pawel, S.J.

    1999-05-20

    Fully reversed, load-controlled uniaxial push-pull fatigue tests at room temperature have been performed in air and in mercury on specimens of type 316LN stainless steel. The results indicate a significant influence of mercury on fatigue properties. Compared to specimens tested in air, specimens tested in mercury had reproducibly shorter fatigue lives (by a factor of 2-3), and fracture faces exhibiting intergranular cracking. Preliminary indications are that crack initiation in each environment is similar, but mercury significantly accelerates crack propagation.

  17. Fatigue Properties of Type 316 LN Stainless Steels as a Function of Frequency and Waveform

    SciTech Connect

    DiStefano, J.R.

    2001-01-30

    The low cycle fatigue behavior of type 316LN stainless steel was investigated in air and mercury at frequencies from 0.1 to 10 Hz. Cyclic stress ratios (R) of {minus}1 and 0.1 were used with sinusoidal, triangular and positive sawtooth wave forms. Mercury appears to reduce fatigue life at high stress amplitudes, but the endurance limit may be unaffected. Low frequency and mean stress decreased the fatigue endurance limit, but type of waveform did not appear to affect fatigue life under the conditions of these tests.

  18. Electronic Structure and Magnetic Anisotropy in Lanthanoid Single-Ion Magnets with C3 Symmetry: The Ln(trenovan) Series.

    PubMed

    Lucaccini, Eva; Baldoví, José J; Chelazzi, Laura; Barra, Anne-Laure; Grepioni, Fabrizia; Costes, Jean-Pierre; Sorace, Lorenzo

    2017-04-17

    We report the syntheses and the magnetic characterization of a new series of lanthanide complexes, in which the Ce, Nd, Gd, Dy, Er, and Yb derivatives show single-molecule magnet behavior. These complexes, named Ln(trenovan), where H3trenovan is tris(((3-methoxysalicylidene)amino)ethyl)amine, exhibit trigonal symmetry and the Ln(III) ion is heptacoordinated. Their molecular structure is then very similar to that of the previously reported Ln(trensal) series, where H3trensal is 2,2',2″-tris(salicylideneimino)triethylamine. This prompted us to use the spectroscopic and magnetic properties of the Ln(trensal) family (Ln = Nd, Tb, Dy, Ho, Er, and Tm) to obtain a set of crystal-field parameters to be used as starting point to determine the electronic structures and magnetic anisotropy of the analogous Ln(trenovan) complexes using the CONDON computational package. The obtained results were then used to discuss the electron paramagnetic resonance (EPR) and ac susceptibility results. As a whole, the obtained results indicate for this type of complexes single-molecule magnet behavior is not related to the presence of an anisotropy barrier, due to a charge distribution of the ligand around the lanthanoid, which results in highly mixed ground states in terms of MJ composition of the states. The crucial parameter in determining the slow relaxation of the magnetization is then rather the number of unpaired electrons (only Kramers ions showing in-field slow relaxation) than the shape of the charge distribution for different Ln(III).

  19. Family of defect-dicubane Ni4Ln2 (Ln = Gd, Tb, Dy, Ho) and Ni4Y2 complexes: rare Tb(III) and Ho(III) examples showing SMM behavior.

    PubMed

    Zhao, Lang; Wu, Jianfeng; Ke, Hongshan; Tang, Jinkui

    2014-04-07

    Reactions of Ln(III) perchlorate (Ln = Gd, Tb, Dy, and Ho), NiCl2·6H2O, and a polydentate Schiff base resulted in the assembly of novel isostructural hexanuclear Ni4Ln2 complexes [Ln = Gd (1), Tb (2), Dy (3), Ho (4)] with an unprecedented 3d-4f metal topology consisting of two defect-dicubane units. The corresponding Ni4Y2 (5) complex containing diamagnetic Y(III) atoms was also isolated to assist the magnetic studies. Interestingly, complexes 2 and 3 exhibit SMM characteristics and 4 shows slow relaxation of the magnetization. The absence of frequency-dependent in-phase and out-of-phase signals for the Ni-Y species suggests that the Ln ions' contribution to the slow relaxation must be effectual as previously observed in other Ni-Dy samples. However, the observation of χ″ signals with zero dc field for the Ni-Tb and Ni-Ho derivatives is notable. Indeed, this is the first time that such a behavior is observed in the Ni-Tb and Ni-Ho complexes.

  20. Tuning the Energy Transfer Efficiency between Ce(3+) and Ln(3+) Ions (Ln=Tm, Sm, Tb, Dy) by Controlling the Crystal Phase of NaYF4 Nanocrystals.

    PubMed

    Adusumalli, Venkata N K B; Koppisetti, Heramba V S R M; Ganguli, Sagar; Sarkar, Shyam; Mahalingam, Venkataramanan

    2017-01-23

    NaYF4 is a superior host matrix to study the luminescence properties of lanthanide (Ln(3+) ) ions. Ln(3+) ions in hexagonal-phase NaYF4 (β-phase) nanocrystals (NCs) exhibit strong luminescence via an upconversion process compared to cubic NaYF4 (α-phase) NCs. However, in Ce(3+) /Ln(3+) -doped NaYF4 NCs (Ln=Tm, Tb, Sm, Dy) the α-phase NaYF4 NCs shows strong luminescence compared to their counterpart β-phase NCs despite the latter being much larger in size. This is attributed to comparatively large overlap between Ce(3+) ions emission band with excited energy levels of those Ln(3+) ions in α-phase compared to β-phase NCs. This difference is attributed to different crystal-field splitting of Ce(3+) ions 4f-5d band in different crystal environments of the α-phase (cubic crystal field environment) and β-phase (trigonal prismatic with equatorials crystal field environment) NaYF4 NCs with respect to their barycenter. The enhanced luminescence from α-phase NaYF4 NCs is advantageous as they are prepared at a relatively lower temperature and shorter reaction times compared to β-NaYF4 NCs.

  1. Structural Study of a Doubly Ordered Perovskite Family NaLnCoWO6 (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb): Hybrid Improper Ferroelectricity in Nine New Members.

    PubMed

    Zuo, Peng; Colin, Claire V; Klein, Holger; Bordet, Pierre; Suard, Emmanuelle; Elkaim, Erik; Darie, Céline

    2017-07-17

    The compounds of the doubly ordered perovskite family NaLnCoWO6 (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb) were synthesized by solid-state reaction, nine of which (Ln = Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb) are new phases prepared under high-temperature and high-pressure conditions. Their structural properties were investigated at room temperature by synchrotron X-ray powder diffraction and neutron powder diffraction. All of them crystallize in monoclinic structures, especially the nine new compounds have the polar space group P21 symmetry, as confirmed by second harmonic generation measurements. The P21 polar structures were decomposed and refined in terms of symmetry modes, demonstrating that the polar mode is induced by two nonpolar modes in a manner of Hybrid Improper Ferroelectricity. The amplitudes of these three major modes all increase with decreasing the Ln cation size. The spontaneous ferroelectric polarization is estimated from the neutron diffraction data of three samples (Ln = Y, Tb, and Ho) and can be as large as ∼20 μC/cm(2).

  2. Probing the magnetic and magnetothermal properties of M(II)-Ln(III) complexes (where M(II) = Ni or Zn; Ln(III) = La or Pr or Gd).

    PubMed

    Ahmed, Naushad; Das, Chinmoy; Vaidya, Shefali; Srivastava, Anant Kumar; Langley, Stuart K; Murray, Keith S; Shanmugam, Maheswaran

    2014-12-14

    We establish the coordination potential of the Schiff base ligand (2-methoxy-6-[(E)-2'-hydroxymethyl-phenyliminomethyl]-phenolate (H2L)) via the isolation of various M(II)-Ln(III) complexes (where M(II) = Ni or Zn and Ln(III) = La or Pr or Gd). Single crystals of these five complexes were isolated and their solid state structures were determined by single crystal X-ray diffraction. Structural determination revealed molecular formulae of [NiGd(HL)2(NO3)3] (1), [NiPr(HL)2(NO3)3] (2) and [Ni2La(HL)4(NO3)](NO3)2 (3), [Zn2Gd(HL)4(NO3)](NO3)2 (4), and [Zn2Pr(HL)4(NO3)](NO3)2 (5). Complexes and were found to be neutral heterometallic dinuclear compounds, whereas 3-5 were found to be linear heterometallic trinuclear cationic complexes. Direct current (dc) magnetic susceptibility and magnetization measurements conclusively revealed that complexes 1 and 4 possess a spin ground state of S = 9/2 and 7/2 respectively. Empirically calculated ΔχMT derived from the variable temperature susceptibility data for all complexes undoubtedly indicates that the Ni(II) ion is coupled ferromagnetically with the Gd(III) ion, and antiferromagnetically with the Pr(III) ion in 1 and 2 respectively. The extent of the exchange interaction for was estimated by fitting the magnetic susceptibility data using the parameters (g = 2.028, S = 9/2, J = 1.31 cm(-1) and zJ = +0.007), supporting the phenomenon observed in an empirical approach. Similarly using a HDVV Hamiltonian, the magnetic data of 3 and 4 were fitted, yielding parameters g = 2.177, D = 3.133 cm(-1), J = -0.978 cm(-1), (for 3) and g = 1.985, D = 0.508 cm(-1) (for 4). The maximum change in magnetic entropy (-ΔSm) estimated from the isothermal magnetization data for was found to be 5.7 J kg(-1) K(-1) (ΔB = 7 Tesla) at 7.0 K, which is larger than the -ΔSm value extracted from 4 of 3.5 J kg(-1) K(-1) (ΔB = 7 Tesla) at 15.8 K, revealing the importance of the exchange interaction in increasing the overall ground state of a molecule for

  3. Effect of Lactobacillus buchneri LN4637 and Lactobacillus buchneri LN40177 on the aerobic stability, fermentation products, and microbial populations of corn silage under farm conditions.

    PubMed

    Tabacco, E; Piano, S; Revello-Chion, A; Borreani, G

    2011-11-01

    This study determined the efficacy of the use of 2 commercial inoculants containing Lactobacillus buchneri alone or in combination with homofermentative lactic acid bacteria in improving aerobic stability of corn silage stored in commercial farm silos in northern Italy. In the first survey, samples were collected from 10 farms that did not inoculate their silages and from 10 farms that applied a Pioneer 11A44 inoculant (L. buchneri strain LN4637; Pioneer Hi-Bred International, Des Moines, IA). In the second survey, corn silage samples were collected from 11 farms that did not inoculate their silages and from 11 farms that applied a Pioneer 11CFT inoculant (L. buchneri strain LN40177; Pioneer Hi-Bred International). Inoculants were applied directly through self-propelled forage harvesters, at the recommended rate of 1 g/t of fresh forage, to achieve a final application rate of 1.0 × 10(5) cfu/g of L. buchneri. One corn bunker silo, which had been open for at least 10 d, was examined in detail on each farm. The silages inoculated with L. buchneri had lower concentrations of lactic acid, a lower lactic-to-acetic acid ratio, a lower yeast count, and higher aerobic stability compared with the untreated silages. Unexpectedly, concentrations of acetic acid and 1,2-propanediol, 2 hallmarks of L. buchneri activity, did not differ between treatments and were only numerically higher in the inoculated silages compared with untreated ones, in both surveys. Aerobic stability, on average, was 107 and 121 h in the inoculated silages and 64 and 74 h in the untreated silages, for surveys 1 and 2, respectively, and decreased exponentially as the yeast count in the silage at the time of sampling increased, regardless of treatment. Inoculation with L. buchneri proved to be effective in reducing the yeast count to <2 log cfu/g of silage in 16 of 21 of the studied farm silages, confirming the ability of this inoculum to enhance the aerobic stability of corn silages in farm bunker silos

  4. O-2p holes in tetravalent oxides of Ce and Pr and the Fehrenbacher-Rice hybrid in PrBa2Cu3O7-δ

    NASA Astrophysics Data System (ADS)

    Hu, Z.; Meier, R.; Schüßler-Langeheine, C.; Weschke, E.; Kaindl, G.; Felner, I.; Merz, M.; Nücker, N.; Schuppler, S.; Erb, A.

    1999-07-01

    We report on an x-ray absorption near-edge structure (XANES) study of O-2p holes induced by Ln-4f/O-2p covalence in LnO2 (Ln=Ce,Pr) and BaLnO3 (Ln=Ce,Pr,Tb). The pre-edge peak in the O-1s XANES spectra, associated with O-2p holes, shifts to lower energy from Ce to Pr, in agreement with theoretical expectation, and its intensity scales with the strength of the 4f/2p covalence. In Pr(IV) oxides, the pre-edge peak is at the energy of the ``Fehrenbacher-Rice'' state in PrBa2Cu3O7-δ , supporting the view that the suppression of superconductivity in PrBa2Cu3O7-δ is due to Pr-4f/O-2p hybridization.

  5. The series of rare earth complexes [Ln2Cl6 (μ-4,4'-bipy)(py)6], Ln=Y, Pr, Nd, Sm-Yb: a molecular model system for luminescence properties in MOFs based on LnCl3 and 4,4'-bipyridine.

    PubMed

    Matthes, Philipp R; Nitsch, Jörn; Kuzmanoski, Ana; Feldmann, Claus; Steffen, Andreas; Marder, Todd B; Müller-Buschbaum, Klaus

    2013-12-16

    A series of 12 dinuclear complexes [Ln2Cl6(μ-4,4'-bipy)(py)6], Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, (1-12, respectively) was synthesized by an anhydrous solvothermal reaction in pyridine. The complexes contain a 4,4'-bipyridine bridge and exhibit a coordination sphere closely related to luminescent lanthanide MOFs based on LnCl3 and 4,4-bipyridine. The dinuclear complexes therefore function as a molecular model system to provide a better understanding of the luminescence mechanisms in the Ln-N-MOFs (∞)(2)[Ln2Cl6(4,4'-bipy)3]·2(4,4'-bipy). Accordingly, the luminescence properties of the complexes with Ln=Y, Sm, Eu, Gd, Tb, Dy, (1, 4-8) were determined, showing an antenna effect through a ligand-metal energy transfer. The highest efficiency of luminescence is observed for the terbium-based compound 7 displaying a high quantum yield (QY of 86%). Excitation with UV light reveals typical emission colors of lanthanide-dependent intra 4f-4f-transition emissions in the visible range (Tb(III) : green, Eu(III) : red, Sm(III) : salmon red, Dy(III) : yellow). For the Gd(III)- and Y(III)-containing compounds 6 and 1, blue emission based on triplet phosphorescence is observed. Furthermore, ligand-to-metal charge-transfer (LMCT) states, based on the interaction of Cl(-) with Eu(III), were observed for the Eu(III) compound 5 including energy-transfer processes to the Eu(III) ion. Altogether, the model complexes give further insights into the luminescence of the related MOFs, for example, rationalization of Ln-independent quantum yields in the related MOFs.

  6. Hall Petch Behavior in Ultra-Fine-Grained AISI 301LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Rajasekhara, S.; Ferreira, P. J.; Karjalainen, L. P.; Kyröläinen, A.

    2007-06-01

    An ultra-fine-grained AISI 301LN austenitic stainless steel has been achieved by heavy cold rolling, to induce the formation of martensite, and subsequent annealing at 800 °C, 900 °C, and 1000 °C, from 1 to 100 seconds. The microstructural evolution was analyzed using transmission electron microscopy and the yield strength determined by tension testing. Ultra-fine austenite grains, as small as ˜0.54 μm, were obtained in samples annealed at 800 °C for 1 second. For these samples, tensile tests revealed a very high yield strength of ˜700 MPa, which is twice the typical yield strength of conventional fully annealed AISI 301LN stainless steels. An analysis of the relationship between yield strength and grain size in these submicron-grained stainless steels indicates a classical Hall Petch behavior. Furthermore, when the yield dependence on annealing temperature is considered, the results show that the Hall Petch relation is due to an interplay between fine-grained austenite, solid solution strengthening, precipitate hardening, and strain hardening.

  7. Highly-efficient multi-watt Yb:CaLnAlO4 microchip lasers

    NASA Astrophysics Data System (ADS)

    Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Yumashev, Konstantin; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

    2017-02-01

    Tetragonal rare-earth calcium aluminates, CaLnAlO4 where Ln = Gd or Y (CALGO and CALYO, respectively), are attractive laser crystal hosts due to their locally disordered structure and high thermal conductivity. In the present work, we report on highly-efficient power-scalable microchip lasers based on 8 at.% Yb:CALGO and 3 at.% Yb:CALYO crystals grown by the Czochralski method. Pumped by an InGaAs laser diode at 978 nm, the 6 mm-long Yb:CALGO microchip laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η = 84% (with respect to the absorbed pump power) and an optical-to-optical efficiency of ηopt = 49%. The 3 mm-long Yb:CALYO microchip laser generated 5.06 W at 1048-1056 nm corresponding to η = 91% and ηopt = 32%. Both lasers produced linearly polarized output (σ- polarization) with an almost circular beam profile and beam quality factors M2 x,y <1.1. The output performance of the developed lasers was modeled yielding a loss coefficient as low as 0.004-0.007 cm-1. The results indicate that the Yb3+- doped calcium aluminates are very promising candidates for high-peak-power passively Q-switched microchip lasers.

  8. ln-Timişoara Molecular activity combined models toward interspecies toxicity assessment.

    PubMed

    Chicu, Sergiu A; Putz, Mihai V

    2009-11-20

    Aiming to provide a unified picture of computed activity - quantitative structure activity relationships, the so called Köln (ESIP-ElementSpecificInfluenceParameter) model for activity and Timisoara (Spectral-SAR) formulation of QSAR were pooled in order to assess the toxicity modeling and inter-toxicity correlation maps for aquatic organisms against paradigmatic organic compounds. The Köln ESIP model for estimation of a compound toxicity is based on the experimental measurement expressing the direct action of chemicals on the organism Hydractinia echinata so that the structural influence parameters are reflected by the metamorphosis degree itself. As such, the calculation of the structural parameters is absolutely necessary for correct evaluation and interpretation of the evolution of M(easured) and the C(computed) values. On the other hand, the Timişoara Spectral-SAR analysis offers correlation models and paths for H.e. species as well as for four other different organisms with which the toxicity may be inter-changed by means of the same mechanism of action induced by certain common chemicals.

  9. Damage structure of austenitic stainless steel 316LN irradiated at low temperature in HFIR

    SciTech Connect

    Hashimoto, N.; Robertson, J.P.; Grossbeck, M.L.; Rowcliffe, A.F.; Wakai, E.

    1998-03-01

    TEM disk specimens of austenitic stainless steel 316LN irradiated to damage levels of about 3 dpa at irradiation temperatures of either about 90 C or 250 C have been investigated by using transmission electron microscopy. The irradiation at 90 C and 250 C induced a dislocation loop density of 3.5 {times} 10{sup 22} m{sup {minus}3} and 6.5 {times} 10{sup 22} m{sup {minus}3}, a black dot density of 2.2 {times} 10{sup 23} m{sup {minus}3} and 1.6 {times} 10{sup 23} m{sup {minus}3}, respectively, in the steels, and a high density (<1 {times} 10{sup 22} m{sup {minus}3}) of precipitates in matrix. Cavities could be observed in the specimens after the irradiation. It is suggested that the dislocation loops, the black dots, and the precipitates cause irradiation hardening, an increase in the yield strength and a decrease in the uniform elongation, in the 316LN steel irradiated at low temperature.

  10. Microchip Yb:CaLnAlO4 lasers with up to 91% slope efficiency.

    PubMed

    Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Jambunathan, Venkatesan; Navratil, Petr; Lucianetti, Antonio; Mocek, Tomas; Zhang, Xuzhao; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

    2017-07-01

    Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO4(Ln=Gd,Y)) crystals in plano-plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at. % Yb:CaGdAlO4 laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η=84% (with respect to the absorbed pump power). An even higher η=91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO4 laser, from which 5.06 W were extracted at 1048-1056 nm. Both lasers produced linearly polarized output (σ-polarization) with an almost circular diffraction-limited beam (Mx,y2<1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004-0.007  cm(-1). In addition, their spectroscopic properties were revisited.

  11. Effect of rare earth substitution in the density of electronic states of LnOFeAs

    NASA Astrophysics Data System (ADS)

    García Saravia Ortíz de Montellano, A.; Mustre de León, J.; Saini, N. L.; Bianconi, A.

    2012-06-01

    Measurements of the Fe K-edge x-ray absorption near edge (XANES) spectra of LnOFeAs (Ln being a lanthanide) high Tc superconductors exhibit significant changes in the pre-edge peak region upon rare earth substitution. Ab initio XANES calculations, based on the local structure centered at the Fe site obtained by crystallographic investigations, reproduce the observed changes in the spectra, indicating variations of the Fe d-local unoccupied electronic states. The calculated Fe density of states (DOS) at the Fermi energy shows an increase of the Fe d-density of states with increasing height of the arsenic atomic position with respect to the iron plane, similar to that observed for the superconducting transition temperature, Tc. These calculations show that not only the atomic position variation of the Fe-As layers induced by the rare earth substitution is relevant in the increase of the DOS at the Fermi-level, but the actual change in electronic configuration of the rare earth also plays a role in the increase of Fe d-density of states at the Fermi energy.

  12. Kramers non-magnetic superconductivity in LnNiAsO superconductors.

    PubMed

    Li, Yuke; Luo, Yongkang; Li, Lin; Chen, Bin; Xu, Xiaofeng; Dai, Jianhui; Yang, Xiaojun; Zhang, Li; Cao, Guanghan; Xu, Zhu-an

    2014-10-22

    We investigated a series of nickel-based oxyarsenides LnNiAsO (Ln=La, Ce, Pr, Nd, Sm) compounds. CeNiAsO undergoes two successive anti-ferromagnetic transitions at TN1=9.3 K and TN2=7.3 K; SmNiAsO becomes an anti-ferromagnet below TN≃3.5 K; NdNiAsO keeps paramagnetic down to 2 K but orders anti-ferromagnetically below TN≃1.3 K. Superconductivity was observed only in Kramers non-magnetic LaNiAsO and PrNiAsO with Tc=2.7 K and 0.93 K, respectively. The superconductivity of PrNiAsO is further studied by upper critical field and specific heat measurements, which reveal that PrNiAsO is a weakly coupled Kramers non-magnetic superconductor. Our work confirms that the nickel-based oxyarsenide superconductors are substantially different in mechanism to iron-based ones, and are likely to be described by the conventional superconductivity theory.

  13. On the constitutive model of nitrogen-containing austenitic stainless steel 316LN at elevated temperature.

    PubMed

    Zhang, Lei; Feng, Xiao; Wang, Xin; Liu, Changyong

    2014-01-01

    The nitrogen-containing austenitic stainless steel 316LN has been chosen as the material for nuclear main-pipe, which is one of the key parts in 3rd generation nuclear power plants. In this research, a constitutive model of nitrogen-containing austenitic stainless steel is developed. The true stress-true strain curves obtained from isothermal hot compression tests over a wide range of temperatures (900-1250°C) and strain rates (10(-3)-10 s(-1)), were employed to study the dynamic deformational behavior of and recrystallization in 316LN steels. The constitutive model is developed through multiple linear regressions performed on the experimental data and based on an Arrhenius-type equation and Zener-Hollomon theory. The influence of strain was incorporated in the developed constitutive equation by considering the effect of strain on the various material constants. The reliability and accuracy of the model is verified through the comparison of predicted flow stress curves and experimental curves. Possible reasons for deviation are also discussed based on the characteristics of modeling process.

  14. ln-Timişoara Molecular Activity Combined Models toward Interspecies Toxicity Assessment

    PubMed Central

    Chicu, Sergiu A.; Putz, Mihai V.

    2009-01-01

    Aiming to provide a unified picture of computed activity – quantitative structure activity relationships, the so called Köln (ESIP-ElementSpecificInfluenceParameter) model for activity and Timisoara (Spectral-SAR) formulation of QSAR were pooled in order to assess the toxicity modeling and inter-toxicity correlation maps for aquatic organisms against paradigmatic organic compounds. The Köln ESIP model for estimation of a compound toxicity is based on the experimental measurement expressing the direct action of chemicals on the organism Hydractinia echinata so that the structural influence parameters are reflected by the metamorphosis degree itself. As such, the calculation of the structural parameters is absolutely necessary for correct evaluation and interpretation of the evolution of M(easured) and the C(computed) values. On the other hand, the Timişoara Spectral-SAR analysis offers correlation models and paths for H.e. species as well as for four other different organisms with which the toxicity may be inter-changed by means of the same mechanism of action induced by certain common chemicals. PMID:20057956

  15. FATIGUE PROPERTIES OF MODIFIED 316LN STAINLESS STEEL AT 4 K FOR HIGH FIELD CABLE-IN-CONDUIT APPLICATIONS

    SciTech Connect

    Toplosky, V. J.; Walsh, R. P.; Han, K.

    2010-04-08

    Cable-In-Conduit-Conductor (CICC) alloys, exposed to Nb{sub 3}Sn reaction heat-treatments, such as modified 316LN require a design specific database. A lack of fatigue life data (S-n curves) that could be applied in the design of the ITER CS and the NHMFL Series Connected Hybrid magnets is the impetus for the research presented here. The modified 316LN is distinguished by a lower carbon content and higher nitrogen content when compared to conventional 316LN. Because the interstitial alloying elements affect the mechanical properties significantly, it is necessary to characterize this alloy in a systematic way. In conjunction, to ensure magnet reliability and performance, several criteria and expectations must be met, including: high fatigue life at the operating stresses, optimal stress management at cryogenic temperatures and thin walled conduit to reduce coil mass. Tension-tension load control axial fatigue tests have good applicability to CICC solenoid magnet design, thus a series of 4 K strength versus fatigue life curves have been generated. In-situ samples of 316LN base metal, seam welded, butt welded and seam plus butt welded are removed directly from the conduit in order to address base and weld material fatigue life variability. The more than 30 fatigue tests show good grouping on the fatigue life curve and allow discretionary 4 K fatigue life predictions for conduit made with modified 316LN.

  16. Mature DC from skin and skin-draining LN retain the ability to acquire and efficiently present targeted antigen.

    PubMed

    Henri, Sandrine; Siret, Carole; Machy, Patrick; Kissenpfennig, Adrien; Malissen, Bernard; Leserman, Lee

    2007-05-01

    Skin-draining LN contain several phenotypically distinguishable DC populations, which may be immature or mature. Mature DC are generally considered to have lost the capacity to acquire and present newly encountered Ag. Using antibody-opsonized liposomes as Ag carriers, we show that mature DC purified from skin explants are able to efficiently capture liposomes, process Ag encapsulated within them and activate Ag-specific CD4(+) T cells. Explant DC from mice with Langerhans cells (LC) expressing the primate diphtheria toxin receptor that were exposed to diphtheria toxin in vivo presented Ag as well as explant DC from wild-type mice, indicating that LC are not required and dermal DC are probably responsible for this presentation. We further show that all DC subtypes from LN that capture opsonized Ag are capable of cross-presenting it to CD8(+) T cells. Induction of additional maturation in vivo by LPS or treatment with double-stranded RNA did not alter the Ag presentation capacity of the skin or LN DC subtypes. These results suggest that mature DC present in skin-draining LN may play an important role in the induction of primary and/or secondary immune responses against Ag delivered to the LN that they take up by receptor-mediated endocytosis.

  17. Self-Assembly of Tunable Heterometallic Ln-Ru Coordination Polymers with Near-Infrared Luminescence and Magnetocaloric Effect.

    PubMed

    Wang, Lei; Xie, Zhigang; Dang, Song; Sun, Zhong-Ming

    2017-02-24

    A series of heterometallic lanthanide (Ln)-Ru coordination polymers, denoted Gd-1, Yb-2, and Nd-3, were prepared by solvothermal reaction of a carboxylate derivative of [Ru(bpy)3 ](2+) (Rubpy, bpy=2,2'-bipyridine), oxalic acid, and Ln(OAc)3 by using the metalloligand strategy. Single-crystal X-ray diffraction indicated that the resulting isostructural heterometallic complexes have 1D butterfly-shaped Ln-Ru-based coordination chains but show slight differences in the coordination environments of the Ln centers. The introduced Ru(bpy) metalloligands could act as good light-harvesting antennas to effectively sensitize near-infrared (NIR) luminescence by energy transfer from the triplet metal-to ligand charge transfer state of Rubpy units to Ln (Yb or Nd) under the excitation in the visible-light region. Additionally, dopant-concentration-dependent behavior of the Ru-based emission and sensitized NIR emission was demonstrated in Gd-1. Finally, the magnetocaloric effect of Gd-1 was studied. The preparation of such heterometallic coordination polymers offers a versatile platform to investigate dimensionally controlled properties.

  18. Hydrothermal phase equilibria in Ln 2O 3-H 2O-CO 2 systems . I. The lighter lanthanides

    NASA Astrophysics Data System (ADS)

    Tareen, J. A. K.; Kutty, T. R. N.

    1980-10-01

    Phase diagrams for Nd 2O 3-H 2O-CO 2 and Gd 2O 3-H 2O-CO 2 systems at 1500 atm are given along with the results of selected runs in La, Sm and Eu systems. The stable phases in systems of La and Nd, are Ln(OH)CO 3-B, Ln 2O 2CO 3-II and LnOOH, in addition to the Ln(OH) 3 phase at extremely low partial pressures of CO 2 in the system. The systems become more and more complex with decreasing ionic radi and the number of stable carbonate phases increases. Ln 2(CO 3) 3 · 3H 2O orthorhombic (tengerate-like phase) is stable from Sm to Gd in addition to the other phases. The Gd(OH)CO 3-A (ancylite-like phase) is hydrothermally stable at XCO 2 ⩾ 0.5 while its hexagonal polymorph, Gd(OH)CO 3-B is stable at low partial pressures of CO 2 in the system.

  19. The Uncommon Channel-Based Ln-MOFs for Highly Selective Fe(3+) Detection and Superior Rhodamine B Adsorption.

    PubMed

    Xing, Shanghua; Bing, Qiming; Song, Lifei; Li, Guanghua; Liu, Jingyao; Shi, Zhan; Feng, Shouhua; Xu, Ruren

    2016-11-02

    Two new isostructural 3D lanthanide-organic frameworks [H2 N(Me)2 ] [Ln3 (OH)(bpt)3 (H2 O)3 ] (DMF)2 ⋅(H2 O)4 (1-Ln; Ln=Sm and Eu) with a 1D channel (25 Å) have been successfully assembled from the rare trinuclear [Ln3 (OH)(COO)9 ] clusters and biphenyl-3,4',5-tricarboxylic acid (H3 bpt) and exhibit high stability towards water in the pH range 3-10. MOF 1-Eu is a promising luminescent probe for sensing Fe(3+) in aqueous solution and is also selective towards rhodamine B (RhB) with a superior adsorption capacity of 735 mg g(-1) , which is the highest among the reported Ln-MOFs for RhB removal so far. Periodic DFT calculations further confirmed the selective adsorption of rhodamine B over other dyes. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Thermodynamic modeling of REE behavior in oxidized hydrothermal fluids of high sulfate sulfur concentrations

    NASA Astrophysics Data System (ADS)

    Shironosova, G. P.; Kolonin, G. R.; Borovikov, A. A.; Borisenko, A. S.

    2016-08-01

    Thermodynamic calculations using the HCh software were made for mineral equilibriums including REEs in the fluoride-sulfide-chloride-carbonate-sulfate-system in the presence of Na, Ca, and P with fluids of various acidities-alkalinities [11]. The obtained thermodynamic characteristics of thenardite allowed us to carry out the calculations for this phase under complicated hydrothermal conditions simulating the presence of oxidized fluids at 500-100°C and 2000-125 bar. Among other solid phases, REEs-fluorite, monazite, and REE-F-apatite were formed as CaF2-(Ln,Y)F3, LnPO4, and Ca5(PO4)3F-(Ln,Y)3(PO4)3 ideal solid solutions, respectively, where Ln is La, Ce, Pr, Nd, Sm, Eu, and Gd. Xenotime, anhydrite, elemental sulfur, and calcite were found as well.

  1. A comparative evaluation of low-cycle fatigue behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joint

    SciTech Connect

    Valsan, M.; Sundararaman, D.; Sankara Rao, K.B.; Mannan, S.L.

    1995-05-01

    A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 {times} 10{sup {minus}3} s{sup {minus}1} with strain amplitudes in the range {+-}0.20 to {+-}1.0 pct. Weld pads with single V and double V configuration were prepared by the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation in the number density of slip bands. The 18-8 group of austenitic stainless steels, such as AISI type 316, 304, and their modified grades, finds applications as structural material for various components of the liquid-metal-cooled fast breeder reactor (LMFBR).

  2. Glass Ceramic Waste Forms for Combined CS+LN+TM Fission Products Waste Streams

    SciTech Connect

    Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna; Sickafus, Kurt E.

    2010-09-23

    In this study, glass ceramics were explored as an alternative waste form for glass, the current baseline, to be used for immobilizing alkaline/alkaline earth + lanthanide (CS+LN) or CS+LN+transition metal (TM) fission-product waste streams generated by a uranium extraction (UREX+) aqueous separations type process. Results from past work on a glass waste form for the combined CS+LN waste streams showed that as waste loading increased, large fractions of crystalline phases precipitated upon slow cooling.[1] The crystalline phases had no noticeable impact on the waste form performance by the 7-day product consistency test (PCT). These results point towards the development of a glass ceramic waste form for treating CS+LN or CS+LN+TM combined waste streams. Three main benefits for exploring glass ceramics are: (1) Glass ceramics offer increased solubility of troublesome components in crystalline phases as compared to glass, leading to increased waste loading; (2) The crystalline network formed in the glass ceramic results in higher heat tolerance than glass; and (3) These glass ceramics are designed to be processed by the same melter technology as the current baseline glass waste form. It will only require adding controlled canister cooling for crystallization into a glass ceramic waste form. Highly annealed waste form (essentially crack free) with up to 50X lower surface area than a typical High-Level Waste (HLW) glass canister. Lower surface area translates directly into increased durability. This was the first full year of exploring glass ceramics for the Option 1 and 2 combined waste stream options. This work has shown that dramatic increases in waste loading are achievable by designing a glass ceramic waste form as an alternative to glass. Table S1 shows the upper limits for heat, waste loading (based on solubility), and the decay time needed before treatment can occur for glass and glass ceramic waste forms. The improvements are significant for both combined waste

  3. Equilibrium and formation/dissociation kinetics of some Ln(III)PCTA complexes.

    PubMed

    Tircsó, Gyula; Kovacs, Zoltan; Sherry, A Dean

    2006-11-13

    The protonation constants () of 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA) and stability constants of complexes formed between this pyridine-containing macrocycle and several different metal ions have been determined in 1.0 M KCl at 25 degrees C and compared to previous literature values. The first protonation constant was found to be 0.5-0.6 log units higher than the value reported previously, and a total of five protonation steps were detected (log = 11.36, 7.35, 3.83, 2.12, and 1.29). The stability constants of complexes formed between PCTA and Mg2+, Ca2+, Cu2+, and Zn2+ were also somewhat higher than those previously reported, but this difference could be largely attributed to the higher first protonation constant of the ligand. Stability constants of complexes formed between PCTA and the Ln3+ series of ions and Y3+ were determined by using an "out-of-cell" potentiometric method. These values ranged from log K = 18.15 for Ce(PCTA) to log K = 20.63 for Yb(PCTA), increasing along the Ln series in proportion to decreasing Ln3+ cation size. The rates of complex formation for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA) were followed by conventional UV-vis spectroscopy in the pH range 3.5-4.4. First-order rate constants (saturation kinetics) obtained for different ligand-to-metal ion ratios were consistent with the rapid formation of a diprotonated intermediate, Ln(H(2)PCTA)(2+). The stabilities of the intermediates as determined from the kinetic data were 2.81, 3.12, 2.97, and 2.69 log K units for Ce(H(2)PCTA), Eu(H(2)PCTA), Y(H(2)PCTA), and Yb(H(2)PCTA), respectively. Rearrangement of these intermediates to the fully chelated complexes was the rate-determining step, and the rate constant (k(r)) for this process was found to be inversely proportional to the proton concentration. The formation rates (k(OH)) increased with a decrease in the lanthanide ion size [9.68 x 10(7), 1.74 x 10(8), 1.13 x 10(8), and 1.11 x 10(9) M(-1

  4. Chemical bond properties and charge transfer bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) in Eu(3+)-doped garnet hosts Ln3M5O12 and ABO4 molybdate and tungstate phosphors.

    PubMed

    Liu, Xiaoguang; Li, Ling; Noh, Hyeon Mi; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun

    2014-06-21

    Charge transfer (CT) energy from the ligand to the central ions is an important factor in luminescence properties for rare earth doped inorganic phosphors. The dielectric theory of complex crystals was used to calculate chemical bond properties. Combining the photoluminescence and the dielectric theory of complex crystals, the CT bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) for Eu(3+)-doped inorganic phosphors have been investigated experimentally and theoretically. Taking Eu(3+)-doped Ln3M5O12 (Ln = Y, Lu and M = Al, Ga), Gd3Ga5O12, MMoO4 (M = Ca, Sr, Ba) and MWO4 (M = Ca, Sr, Ba) as typical phosphors, we investigated the effects of the cation size on the CT bands and chemical bond properties including the bond length (d), the covalency (fc), the bond polarizability (αb) and the environmental factor (he) of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+), respectively. For systematic isostructural Ln3M5O12 (Ln = Y, Lu and M = Al, Ga) phosphors, with the increasing M ion radius, the bond length of Ln-O decreases, but fc and αb increase, which is the main reason that the environmental factor increased. For the isostructural MMoO4:Eu, with the increasing M ion radius, the Mo-O bond length increases, but fc and αb decrease, and thus he decreases. However, in the compound system MWO4:Eu (M = Ca, Ba) with the increasing M ion radius, the O-W bond length increases, but fc and αb increase, and thus he increases and the O-W CT energy decreases. Their O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) CT bands as well as their full width at half maximum (FWHM) were directly influenced by he. And with the increasing he, CT bands of O-Eu or O-Mo or O-W decrease and their FWHM increases. These results indicate a promising approach for changing the material properties, searching for new Eu(3+) doped molybdate, tungstate or other oxide phosphors and analyzing the experimental result.

  5. On the crystal structures of Ln{sub 3}MO{sub 7} (Ln=Nd, Sm, Y and M=Sb, Ta)-Rietveld refinement using X-ray powder diffraction data

    SciTech Connect

    Fu, W.T.; IJdo, D.J.W.

    2009-09-15

    We have investigated, using X-ray powder diffraction data, the crystal structures of some fluorite derivatives with the formula Ln{sub 3}MO{sub 7} (Ln=lanthanide or Y and M=Sb and Ta). In these compounds ordering of Ln and M occurs, leading to a parent structure in Cmmm. Tilting of the MO{sub 6} octahedra causes doubling of one of the cubic axes, leading to a number of non-isomorphic subgroups, e.g. Cmcm, Ccmm and Cccm. We have identified an alternative space group Ccmm instead of C222{sub 1} for those compounds containing a medium sized lanthanide or Y and M being Sb or Ta. Interestingly this is an alternative setting for the space group of the structure obtained when Ln is large (Cmcm). However, there tilting of the octahedra is around the a-axis of the parent structure, rather than around the b-axis as it is found in the compounds which we are reporting on here. In one compound, Nd{sub 3}TaO{sub 7}, both tilts occur. The phase transition between the two possible structures is a slow and difficult process above 80 K, allowing both phases to coexist. - Graphical abstract: (a) A projected view of Ln{sub 3}MO{sub 7} along the a-axis showing the ordering of Ln and M cations in the fluoride lattice. Note that the unit cells of the fluorite (dashed line), the parent Cmmm (dashed line) and the Cmcm/Ccmm structures (continuous line) are indicated. (b) Schematic representations of the crystal structures of Y{sub 3}SbO{sub 7} showing SbO{sub 6} octahedra and Y. Oxygens that do not bond to M cations are also shown.

  6. Low-Temperature Sintering and Microwave Dielectric Properties of Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) Ceramics

    NASA Astrophysics Data System (ADS)

    Wang, Zixing; Yuan, Changlai; Yang, Tao; Feng, Qin; Liu, Fei; Chen, Jinman; Zhou, Changrong; Chen, Guohua

    2016-08-01

    Microwave dielectric ceramics of Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) with a low firing temperature were prepared via conventional solid-state reaction. The phases and microstructures of the ceramics were characterized by x-ray diffraction and scanning electron microscopy. The temperature coefficients of resonant frequency in the three compositions increased as sintering temperature increased. It is worth noting that a phase transition of the Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) ceramics from a monoclinic to a tetragonal scheelite structure was found with an increase in sintering temperature. The densification temperatures of all compositions were below 700°C. Excellent microwave dielectric properties were obtained for the Bi0.9Nd0.05Li0.05V0.9Mo0.1O4 ceramic sintered at 650°C, with a dielectric constant of ~72.2, a quality factor of ~6467 GHz and a temperature coefficient of resonant frequency of ~2.6 ppm/°C. The Bi0.9Ln0.05Li0.05V0.9Mo0.1O4 (Ln = Sm, Nd and La) ceramics are chemically compatible with both Ag and Cu powders at their sintering temperatures, and are thus a promising candidate for use in LTCC technology applications.

  7. Enhancement of superconductivity near the pressure-induced semiconductor-metal transition in the BiS₂-based superconductors LnO₀.₅F₀.₅BiS₂ (Ln = La, Ce, Pr, Nd).

    PubMed

    Wolowiec, C T; White, B D; Jeon, I; Yazici, D; Huang, K; Maple, M B

    2013-10-23

    Measurements of electrical resistivity were performed between 3 and 300 K at various pressures up to 2.8 GPa on the BiS2-based superconductors LnO0.5F0.5BiS2 (Ln=Pr, Nd). At lower pressures, PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2 exhibit superconductivity with critical temperatures Tc of 3.5 and 3.9 K, respectively. As pressure is increased, both compounds undergo a transition at a pressure Pt from a low Tc superconducting phase to a high Tc superconducting phase in which Tc reaches maximum values of 7.6 and 6.4 K for PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2, respectively. The pressure-induced transition is characterized by a rapid increase in Tc within a small range in pressure of ∼0.3 GPa for both compounds. In the normal state of PrO0.5F0.5BiS2, the transition pressure Pt correlates with the pressure where the suppression of semiconducting behaviour saturates. In the normal state of NdO0.5F0.5BiS2, Pt is coincident with a semiconductor-metal transition. This behaviour is similar to the results recently reported for the LnO0.5F0.5BiS2 (Ln=La, Ce) compounds. We observe that Pt and the size of the jump in Tc between the two superconducting phases both scale with the lanthanide element in LnO0.5F0.5BiS2 (Ln=La, Ce, Pr, Nd).

  8. High-throughput and microwave investigation of rare earth phosphonatoethanesulfonates-Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) (Ln=Ho, Er, Tm, Yb, Lu, Y)

    SciTech Connect

    Sonnauer, Andreas

    2008-11-15

    Following the strategy of using bifunctional phosphonic acids for the synthesis of new metal phosphonates, the flexible ligand 2-phosphonoethanesulfonic acid, H{sub 2}O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}H (H{sub 3}L), was used in a high-throughput (HT) and microwave investigation of rare earth phosphonatoethanesulfonates. The HT-investigation led to six isotypic compounds Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) with Ln=Ho (1), Er (2), Tm (3), Yb (4), Lu (5) and Y (6). The syntheses were scaled-up in glass reactor tubes in order to obtain larger amounts for a detailed characterization. Based on these results all compounds could be also synthesized by microwave-assisted heating and the influence of reaction time and stirring rate during the synthesis was established. For compound 2 the crystal structure was determined by single-crystal X-ray diffraction. The compounds contain isolated slightly distorted LnO{sub 6} octahedra that are connected by the phosphonate and sulfonate groups into a three-dimensional framework. Thermogravimetric investigations demonstrate the high thermal stability of the compounds up to 460 deg. C. - Graphical abstract: A high-throughput and microwave investigation of the System LnX{sub 3}/H{sub 2}O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}/NaOH/H{sub 2}O led to six new compounds Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) with Ln=Ho, Er, Tm, Yb, Lu, Y.

  9. Solvothermal synthesis of SrMoO{sub 4}:Ln (Ln = Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) nanoparticles and its photoluminescence properties at room temperature

    SciTech Connect

    Niu, Na; Yang, Piaoping; Wang, Wenxin; He, Fei; Gai, Shili; Wang, Dong; Lin, Jun

    2011-03-15

    Research highlights: {yields} A facile hydrothermal process was used to fabricate luminescent nanocrystals. {yields} The PL emissions the nanocrystals can be tuned by doping different rare-earth ions. {yields} A possible formation scheme for the as-synthesized nanocrystals was presented. -- Abstract: Rare-earth ions (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) doped SrMoO{sub 4} nanoparticles were prepared by solvothermal route using oleic acid as surfactant to control the particle shape and size. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), photoluminescence spectra (PL) and the kinetic decay times were applied to characterize the obtained samples. The XRD patterns reveal that all the doped samples are assigned to the scheelite-type tetragonal structure of SrMoO{sub 4} phase. In addition, the as-synthesized SrMoO{sub 4}:Ln (Ln = Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) particles are high purity well crystallized and with the average size of 30-50 nm. The possible formation process of SrMoO{sub 4}:Ln (Ln = Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) nanoparticles have been discussed as well. Upon excitation by ultraviolet radiation, the as-synthesized SrMoO{sub 4}:Ln (Ln = Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) nanoparticles exhibit the characteristic emission lines of corresponding Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}, respectively.

  10. Properties of Lanthanide Hydroxide Molecules Produced in Reactions of Lanthanide Atoms with H2O2 and H2 + O2 Mixtures: Roles of the +I, +II, +III, and +IV Oxidation States.

    PubMed

    Wang, Xuefeng; Andrews, Lester; Fang, Zongtang; Thanthiriwatte, K Sahan; Chen, Mingyang; Dixon, David A

    2017-03-02

    The reactions of laser-ablated lanthanide metal atoms with hydrogen peroxide or hydrogen plus oxygen mixtures have been studied experimentally in a solid argon matrix and theoretically with the ab initio MP2 and CCSD(T) methods. The Ln(OH)3 and Ln(OH)2 molecules and Ln(OH)2(+) cations are the major products, and the reactions to form those hydroxides are predicted to be highly exothermic at the CCSD(T) level. Vibronic interactions are hypothesized to contribute to the abnormalities in deuterium shifts for Ln-OH(D) stretching modes for several hydroxides, consistent with CASSCF calculations. Additional new absorptions were assigned as HLnO or LnOH and OLnOH molecules. The tetrahydroxides of Ce, Pr, and Tb have also been observed. These reactive intermediates were identified from their matrix infrared spectra by using D2O2, HD, D2, (16,18)O2, and (18)O2 isotopic substitution, by matching observed frequencies with values calculated by electronic structure methods, and by following the trends observed in frequencies going through different lanthanide metal hydroxide series across the periodic table. The lanthanides are in the +II oxidation state for Ln(OH)2 and are in the +III oxidation state for Ln(OH)3 and Ln(OH)2(+).

  11. Synthesis, structure and spectroscopy of the complexes tetrakis (. mu. -trichloroacetato)bis(trichloroacetatoethanol-(1,10-phenanthroline-N,N prime )Ln(III)) (Ln = Pr, Nd and Er)

    SciTech Connect

    Nan Dong ); Hong Wang; Barton, R.J.; Robertson, B.E. )

    1990-01-01

    Tetrakis({mu}-trichloroacetato)bis(trichloroacetatoethanol-(1,10-phenanthroline-N,N{prime})Ln(III)) (Ln = Pr, Nd and Er) complexes have been synthesized and their crystal structures have been determined by X-ray diffraction at reduced temperatures. The three structures are isomorphous: monoclinic, P2{sub 1}/c. Each lanthanide ion is coordinated by four bridging bidentate trichloroacetate ligands, one monodentate trichloroacetate ligand, one ethanol ligand and one phenanthroline ligand, yielding a distorted square antiprismatic configuration. The two lanthanide ions are connected by the four bridging bidentate trichloroacetate ligands to form a dimer. The NMR spectra of the complexes confirm the coordination of ethanol ligands to the lanthanide ions.

  12. Lanthanoid single-ion magnets based on polyoxometalates with a 5-fold symmetry: the series [LnP5W30O110]12- (Ln3+ = Tb, Dy, Ho, Er, Tm, and Yb).

    PubMed

    Cardona-Serra, S; Clemente-Juan, J M; Coronado, E; Gaita-Ariño, A; Camón, A; Evangelisti, M; Luis, F; Martínez-Pérez, M J; Sesé, J

    2012-09-12

    A robust, stable and processable family of mononuclear lanthanoid complexes based on polyoxometalates (POMs) that exhibit single-molecule magnetic behavior is described here. Preyssler polyanions of general formula [LnP(5)W(30)O(110)](12-) (Ln(3+) = Tb, Dy, Ho, Er, Tm, and Yb) have been characterized with static and dynamic magnetic measurements and heat capacity experiments. For the Dy and Ho derivatives, slow relaxation of the magnetization has been found. A simple interpretation of these properties is achieved by using crystal field theory.

  13. Ln-Co-based rock-salt-type porous coordination polymers: vapor response controlled by changing the lanthanide ion.

    PubMed

    Kobayashi, Atsushi; Suzuki, Yui; Ohba, Tadashi; Noro, Shin-ichiro; Chang, Ho-Chol; Kato, Masako

    2011-03-21

    We synthesized new porous coordination polymers (PCPs) {Ln(III)[Co(III)(dcbpy)(3)]·nH(2)O} (Ln = La(3+), Nd(3+), Gd(3+); H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and characterized them by X-ray diffraction and vapor-adsorption measurements. These three Ln-Co-based PCPs have similar rock-salt types and highly symmetrical porous structure and show a reversible structural collapse-regeneration accompanied by water-vapor desorption-adsorption. Similar structural regeneration was also observed for the Gd-Co PCP upon exposure to MeOH and CH(3)CN vapors, whereas the remaining two PCPs barely responded to organic vapors.

  14. Evaluation of Bi defect concentration in LnO1-xFxBiCh 2 by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Demura, S.; Ishida, N.; Fujisawa, Y.; Sakata, H.

    2017-07-01

    We examined a concentration of Bi defects in layered BiCh 2 based superconductors LnO1-xFxBiCh 2 (Ln = La, Ce, Nd Ch = S, Se). These materials show superconductivity by electron carrier doping into BiCh 2 layer. Since Bi defects affect the carrier concentration directly, an examination of the concentration is important to evaluate an actual carrier concentration. In this paper, the concentration of Bi defects on the BiCh 2 layers in BiCh 2 based superconductors was evaluated by scanning tunneling microscopy measurements in real space. We found the samples with BiSe2 layers have less Bi defects than those with BiS2 layers. Furthermore, the concentration of Bi defects was found to be almost constant regardless of F concentration and Ln ion.

  15. P-type conductive amorphous oxides of transition metals from solution processing

    NASA Astrophysics Data System (ADS)

    Li, Jinwang; Kaneda, Toshihiko; Tokumitsu, Eisuke; Koyano, Mikio; Mitani, Tadaoki; Shimoda, Tatsuya

    2012-07-01

    We report a series of solution-processed p-type conductive amorphous Ln-M-O (a-Ln-M-O, where M = Ru, Ir, and Ln is a lanthanide element except Ce) having low resistivities (10-3 to 10-2 Ω cm). These oxides are thermally stable to a high degree, being amorphous up to 800 °C, and processable below 400 °C. Their film surfaces are smooth on the atomic scale, and the process allows patterning simply by direct imprinting without distortion of the pattern after annealing. These properties have high potential for use in printed electronics. The electron configurations of these oxides are apparently different from existing p-type oxides.

  16. Stratification and Destratification of Liquid Nitrogen LN2 in a Cryogenic Tank

    NASA Astrophysics Data System (ADS)

    Arndt, Tim

    Interactions between thermodynamic aspects and sloshing propellant occur frequently in cryogenic upper stages, particularly during the lift off phase, where typical rolling and rotation maneuvers are carried out that lead to larger sloshing motions during the first minutes after lift off and during missions including multiple restarts. Experimental investigations of these phenomena are of major importance concerning the next generation of cryogenic upper stages. In order to investigate the coupled phenomena, benchmark analyses are currently being carried out that focus on sloshing of LN2 in a cylindrical container. This paper concerns on the characteristics of sloshing liquid nitrogen LN2 in a closed cylindrical glass Dewar vessel in a 1g environment. The pressure and the temperature are measured inside the vessel, whereas the temperature sensors are located at defined positions in the ullage and the liquid phase. The pressure is measured in the ullage assuming a constant pressure in the vessel. The lateral vessel motion is induced by an electric engine equipped with a crank drive to generate the approximately harmonic oscillation for the excitation. In order to investigate occurring pressure drop phenomena, the vessel in filled with LN2 up to a constant fill level. As a thermal boundary condition, a heater is installed at the top inside of the Dewar vessel. The heat input without heater in a closed system is measured to be 4 W. After closing the vessel, a thermal stratification is developed in the ullage. With increasing pressure the temperature increases assuming that gaseous nitrogen can be considered as ideal gas. Reaching a certain pressure level, sloshing is induced and the pressure as well as the temperature in the ullage decrease in the order of 20 to 50 kPa. For a given liquid, this pressure drop phenomenon is in the first instance a function of the liquid subcooling caused by the selfpressurization but also depended on sloshing parameters such as

  17. Intracluster interactions in butterfly {Fe3LnO2} molecules with the non-Kramers ions Tb(III) and Ho(III)

    NASA Astrophysics Data System (ADS)

    Badía-Romano, L.; Rubín, J.; Bartolomé, F.; Bartolomé, J.; Luzón, J.; Prodius, D.; Turta, C.; Mereacre, V.; Wilhelm, F.; Rogalev, A.

    2015-08-01

    The intracluster exchange interactions within the "butterfly" [Fe3Ln (μ3-O )2(CCl3COO )8(H2O )(THF )3] molecules, where Ln(III) represents a lanthanide cation, have been determined by a combination of x-ray magnetic circular dichroism (XMCD) and vibrating sample magnetometry (VSM) along with an interaction model. We have studied the compounds with Ln =Tb and Ho, both non-Kramers lanthanides and with high uniaxial anisotropy, and Ln =Lu (III) and Y(III) as pseudolanthanides, which supply nonmagnetic Ln reference cases. At low temperature, the three Fe atoms can be considered as a self-unit with total spin SFe 3=5 /2 . Using the element selectivity of the XMCD magnetometry, measured at the Ln L2 ,3 edges, together with the VSM measurements, the local magnetization of the Ln ion and the Fe3 subcluster, as a function of the field and low temperature (T ≈2.5 K ), has been determined separately. These results are described quantitatively in the framework of a theoretical model based on an effective spin Hamiltonian, which considers the competing effects of intracluster interactions and the external applied magnetic field. The Ln -Fe3 exchange interaction within the {Fe3LnO2} cluster has been determined to be antiferromagnetic, in both Tb and Ho compounds, with JFeTb/kB=-0.13 (1 ) K and JFeHo/kB=-0.18 (1 ) K , respectively. In both cases, a field-induced reorientation of the Fe3 and Ln spins from antiparallel to parallel orientation takes place at a threshold field μ0H =1.1 and 2 T, for the {Fe3TbO2} and {Fe3HoO2} compounds, respectively. By comparison with other compounds of the series with uniaxial anisotropy, it is concluded that the polarizability of the Fe3 subcluster magnetic moment decreases in the trend {Fe3YO2}→{Fe3TbO2}→{Fe3HoO2}→{Fe3DyO2} , because of the increasing opposition of the exchange antiferromagnetic field caused by the Ln ion. In the Ln =Tb , Ho, and Dy, the magnetization of the whole molecule is dominated by the anisotropy of the Ln ion

  18. Three-dimensional open-frameworks based on Ln(III) ions and open-/closed-shell PTM ligands: synthesis, structure, luminescence, and magnetic properties.

    PubMed

    Datcu, Angela; Roques, Nans; Jubera, Véronique; Imaz, Inhar; Maspoch, Daniel; Sutter, Jean-Pascal; Rovira, Concepció; Veciana, Jaume

    2011-03-21

    A series of isostructural open-framework coordination polymers formulated as [Ln(dmf)(3)(ptmtc)] (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5); PTMTC = polychlorotriphenylmethyl tricarboxylate) and [Ln(dmf)(2)H(2)O(αH-ptmtc)] (Ln = Sm (1'), Eu (2'), Gd (3'), Tb (4'), Dy (5')) have been obtained by treating Ln(III) ions with PTMTC ligands with a radical (PTMTC(3-)) or a closed-shell character (αH-PTMTC(3-)). X-ray diffraction analyses reveal that these coordination polymers possess 3D architectures that combine large channels and fairly rare lattice complex T connectivity. In addition, these compounds show selective framework dynamic sorption properties. For both classes of ligands, the ability to act as an antenna in Ln sensitization processes has been investigated. No luminescence was observed for compounds 1-5, and 3' because of the PTMTC(3-) ligand and/or Gd(III) ion characteristics. Conversely, photoluminescence measurements show that 1', 2', 4', and 5' emit dark orange, red, green, and dark cyan metal-centered luminescence. The magnetic properties of all of these compounds have been investigated. The nature of the {Ln-radical} exchange interaction in these compounds has been assessed by comparing the behavior of the radical-based coordination polymers 1-5 with those of the compounds with the diamagnetic ligand set. While antiferromagnetic {Sm-radical} interactions are found in 1, ferromagnetic {Ln-radical} interactions propagate in the 3D architectures of 3, 4, and 5 (Ln = Gd, Tb, and Dy, respectively). This procedure also provided access to information on the {Ln-Ln} exchange existing in these magnetic systems.

  19. Giant Hollow Heterometallic Polyoxoniobates with Sodalite-Type Lanthanide-Tungsten-Oxide Cages: Discrete Nanoclusters and Extended Frameworks.

    PubMed

    Jin, Lu; Li, Xin-Xiong; Qi, Yan-Jie; Niu, Ping-Ping; Zheng, Shou-Tian

    2016-10-24

    The first series of niobium-tungsten-lanthanide (Nb-W-Ln) heterometallic polyoxometalates {Ln12 W12 O36 (H2 O)24 (Nb6 O19 )12 } (Ln=Y, La, Sm, Eu, Yb) have been obtained, which are comprised of giant cluster-in-cluster-like ({Ln12 W12 }-in-{Nb72 }) structures built from 12 hexaniobate {Nb6 O19 } clusters gathered together by a rare 24-nuclearity sodalite-type heterometal-oxide cage {Ln12 W12 O36 (H2 O)24 }. The Nb-W-Ln clusters present the largest multi-metal polyoxoniobates and a series of rare high-nuclearity 4d-5d-4f multicomponent clusters. Furthermore, the giant Nb-W-Ln clusters may be isolated as discrete inorganic alkali salts and can be used as building blocks to form high-dimensional inorganic-organic hybrid frameworks. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Generation of Constant Life Diagram under Elevated Temperature Ratcheting of 316LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Sarkar, Aritra; Nagesha, A.; Sandhya, R.; Mathew, M. D.

    2016-04-01

    Combined influence of mean stress and stress amplitude on the cyclic life under elevated temperature (823-923 K) ratcheting of 316LN austenitic stainless steel is discussed. Constant life Haigh diagrams have been generated, using different combinations of stress amplitude and mean stress. In the plastic domain, the allowable stress was found to increase or decrease with mean stress depending on the temperature and combination of mean stress - stress amplitude employed. Strong influence of dynamic strain aging (DSA) was found at 823 K which affected the mode of deformation of the material in comparison with 923 K. Failure mode expressed through a fracture mechanism map was found to change from fatigue to necking depending on the test temperature as well as combinations of mean stress and stress amplitude. Occurrence of DSA at 823 K proved to be beneficial by way of extending the safe zone of operation to higher R-ratios in comparison with 923 K.

  1. Effect of surface polishing and vacuum firing on electron stimulated desorption from 316LN stainless steel

    SciTech Connect

    Malyshev, Oleg B. Hogan, Benjamin T.; Pendleton, Mark

    2014-09-01

    The reduction of thermal outgassing from stainless steel by surface polishing or vacuum firing is well-known in vacuum technology, and the consequent use of both techniques allows an even further reduction of outgassing. The aim of this study was to identify the effectiveness of surface polishing and vacuum firing for reducing electron-stimulated desorption (ESD) from 316LN stainless steel, which is a frequently used material for particle accelerator vacuum chambers and components. It was found that, unlike for thermal outgassing, surface polishing does not reduce the ESD yield and may even increase it, while vacuum firing of nonpolished sample reduces only the H{sub 2} ESD yield by a factor 2.

  2. Evaluation of Cavitation-Erosion Resistance of 316LN Stainless Steel in Mercury Containing Metallic Solutes

    SciTech Connect

    Pawel, Steven J; Mansur, Louis K

    2006-08-01

    Room temperature cavitation tests of vacuum annealed type 316LN stainless steel were performed in pure Hg and in Hg with various amounts of metallic solute to evaluate potential mitigation of erosion/wastage. Tests were performed using an ultrasonic vibratory horn with specimens attached at the tip. All of the solutes examined, which included 5 wt% In, 10 wt% In, 4.4 wt% Cd, 2 wt% Ga, and a mixture that included 1 wt% each of Pb, Sn, and Zn, were found to increase cavitation-erosion as measured by increased weight loss and/or surface profile development compared to exposures for the same conditions in pure Hg. Qualitatively, each solute appeared to increase the post-test wetting tenacity of the Hg solutions and render the Hg mixture susceptible to manipulation of droplet shape.

  3. Influence of Heat Treatment on Mercury Cavitation Resistance of Surface Hardened 316LN Stainless Steel

    SciTech Connect

    Pawel, Steven J; Hsu, Julia

    2010-11-01

    The cavitation-erosion resistance of carburized 316LN stainless steel was significantly degraded but not destroyed by heat treatment in the temperature range 500-800 C. The heat treatments caused rejection of some carbon from the carburized layer into an amorphous film that formed on each specimen surface. Further, the heat treatments encouraged carbide precipitation and reduced hardness within the carburized layer, but the overall change did not reduce surface hardness fully to the level of untreated material. Heat treatments as short as 10 min at 650 C substantially reduced cavitation-erosion resistance in mercury, while heat treatments at 500 and 800 C were found to be somewhat less detrimental. Overall, the results suggest that modest thermal excursions perhaps the result of a weld made at some distance to the carburized material or a brief stress relief treatment will not render the hardened layer completely ineffective but should be avoided to the greatest extent possible.

  4. Fracture Behaviour of Type 304LN Stainless Steel and its Welds

    SciTech Connect

    Dubey, J.S.; Chakravartty, J.K.; Singh, P.K.; Banerjee, S.

    2006-07-01

    SA312 type 304LN stainless steel material, having closer control over impurities and inclusion content, is the intended piping material in the Advanced Heavy Water Reactors. Deformation, fatigue and fracture behaviour of this material and its weldments have been characterized at ambient temperature and at 558 K. The details of the fractographic investigations and stretch zone width measurements are also discussed. The base metals shows high initiation toughness (>500 kJ/m{sup 2}) and large tearing modulus at ambient and operating temperatures. Shielded Metal Arc Welding (SMAW) weld metal shows much much reduced initiation toughness and tearing resistance in comparison to base metal and Gas Tungsten Arc Welding (GTAW) welds. This is attributed to larger density of second phase inclusions in the SMAW weld metal. SZW measurements give a good alternate estimate of the toughness of the materials. Fatigue crack growth rate in SMAW weld metal was found to be comparable to base metal at higher load ratios. (authors)

  5. Aqueous Ln(III) Luminescence Agents Derived from a Tasty Precursor

    SciTech Connect

    Jocher, C.J.; Moore, E.G.; Pierce, J.D.; Raymond, K.N.

    2008-06-02

    The synthesis, aqueous stability and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7 (1)]. A very poor metal centered quantum yield with Eu(III) was observed ({Phi}{sub tot} = 0.04%), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) {sup 5}D{sub 0} emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the Near Infra-Red (NIR).

  6. Thermomechanical and Isothermal Fatigue Behavior of 316LN Stainless Steel with Varying Nitrogen Content

    NASA Astrophysics Data System (ADS)

    Prasad Reddy, G. V.; Nagesha, A.; Sandhya, R.; Sankaran, S.; Mathew, M. D.; Bhanu Sankara Rao, K.

    2015-02-01

    Thermomechanical (TMF) and isothermal (IF) fatigue behavior of 316LN stainless steel alloyed with 0.07, 0.14, and 0.22 wt pct nitrogen is presented in this manuscript. In the TMF tests with temperature cycling in the range of 573 K to 873 K (300 °C to 600 °C), life decreased with increasing nitrogen content for both in-phase (IP) and out-of-phase (OP) cycling, with a peak at 0.07 wt pct N. In contrast, 0.14 wt pct N yielded maximum life under IF cycling carried out at 873 K (600 °C). Cyclic lives are seen to follow the sequence, IP-TMF < IF < OP-TMF cycling, and it remained same irrespective of the nitrogen content in 316LN SS. Lives under IP-TMF are lower than those in OP cycling by a factor of 2 to 2.5, in spite of the higher cyclic stress response in OP cycling. At all the nitrogen contents in the present study, nitrogen and dynamic strain aging induced slip localization in the form of planar slip bands both in IP and OP-TMF, in comparison to IF deformation wherein complete planar slip mode of deformation is evidenced only at 0.22 wt pct N. In TMF studies, increasing nitrogen content promoted strong slip localization ( i.e., increase in slip band density with a decrease in interband spacing) in combination with high tensile cyclic stresses that marred the beneficial effect of nitrogen content on TMF life.

  7. Synthesis and crystal structure of Ln{sub 2}M{sup 2+}Ge{sub 4}O{sub 12}, Ln=rare-earth element or Y; M=Ca, Mn, Zn

    SciTech Connect

    Zubkov, Vladimir G.; Tarakina, Nadezda V.; Leonidov, Ivan I.; Tyutyunnik, Alexander P.; Surat, Ludmila L.; Melkozerova, Marina A.; Zabolotskaya, Elena V.; Kellerman, Dina G.

    2010-05-15

    The crystal structure of the promising optical materials Ln{sub 2}M{sup 2+}Ge{sub 4}O{sub 12}, where Ln=rare-earth element or Y; M=Ca, Mn, Zn and their solid solutions has been studied in detail. The tendency of rare-earth elements to occupy six- or eight-coordinated sites upon iso- and heterovalent substitution has been studied for the Y{sub 2-x}Er{sub x}CaGe{sub 4}O{sub 12} (x=0-2), Y{sub 2-2x}Ce{sub x}Ca{sub 1+x}Ge{sub 4}O{sub 12} (x=0-1), Y{sub 2}Ca{sub 1-x}Mn{sub x}Ge{sub 4}O{sub 12} (x=0-1) and Y{sub 2-x}Pr{sub x}MnGe{sub 4}O{sub 12} (x=0-0.5) solid solutions. A complex heterovalent state of Eu and Mn in Eu{sub 2}MnGe{sub 4}O{sub 12} has been found. - Graphical abstract: Crystal structure of Ln{sub 2}MGe{sub 4}O{sub 12}, where Ln=rare-earth element or Y; M=Ca, Mn, Zn.

  8. Up/down conversion luminescence and charge compensation investigation of Ca0.5Y1-x(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors

    NASA Astrophysics Data System (ADS)

    Mahalingam, Venkatakrishnan; Thirumalai, Jagannathan; Krishnan, Rajagopalan; Mantha, Srinivas

    2016-01-01

    Microstructures of Ca0.5Y(1-x)(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors were prepared via the solid-state reaction method. X-ray diffraction, scanning electron microscopy and photoluminescence were used to characterize the prepared phosphor samples. The results reveal that the phosphor samples have single phase scheelite structures with tetragonal symmetry of I41/a. The down/up conversion photoluminescence of the Ca0.5Y(1-x)(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors properties reveal characteristic visible emissions. The energy transfer process, fluorescence lifetime and color coordinates are discussed in detail. Furthermore, the phosphor Ca0.5Y(1-x)(WO4)2:xPr3+ co-doped with alkali chlorides shows the enhancement of luminescence, which was found in the sodium chloride co-doped powder phosphor. The photometric characteristics indicate the suitability of the inorganic powder phosphors for solid-state lighting and display applications.

  9. Water Exchange on [Ln(DO3A)(H2O)2] and [Ln(DTTA-Me)(H2O)2](-) Studied by Variable Temperature, Pressure, and Magnetic Field NMR.

    PubMed

    Karimi, Shima; Helm, Lothar

    2016-05-02

    Water exchange kinetics of [Ln(L)(H2O)2](x) complexes (Ln = Pr, Nd, Dy, Tm, and Yb; L = DO3A and DTTA-Me) were studied by (17)O NMR spectroscopy as a function of temperature, pressure, and frequency and by (1)H nuclear magnetic relaxation dispersion. Water exchange rate constants of both complexes show a maximum at dysprosium. Water exchange on negatively charged complexes of the acyclic DTTA-Me ligand is much faster than on the neutral complexes of the macrocyclic DO3A. Small activation volumes |ΔV(⧧)| < 1 cm(3) mol(-1) measured for water exchange on [Ln(DO3A)(H2O)2] indicate an interchange type of mechanism (I) for the lanthanide complexes studied. In the case of [Ln(DTTA-Me)(H2O)2](-), a change in mechanism is detected from a dissociative mechanism (D, ΔV(⧧) = 7 cm(3) mol(-1)) for complexes with larger ions (Pr to Gd) to an interchange mechanism (Id, I; ΔV(⧧) = +1.8 and +0.4 cm(3) mol(-1)) for complexes with smaller ions (Dy and Tm).

  10. Rethinking Sensitized Luminescence in Lanthanide Coordination Polymers and MOFs: Band Sensitization and Water Enhanced Eu Luminescence in [Ln(C15H9O5)3(H2O)3]n (Ln = Eu, Tb).

    PubMed

    Einkauf, Jeffrey D; Kelley, Tanya T; Chan, Benny C; de Lill, Daniel T

    2016-08-15

    A coordination polymer [Ln(C15H9O9)3(H2O)3]n (1-Ln = Eu(III), Tb(III)) assembled from benzophenonedicarboxylate was synthesized and characterized. The organic component is shown to sensitize lanthanide-based emission in both compounds, with quantum yields of 36% (Eu) and 6% (Tb). Luminescence of lanthanide coordination polymers is currently described from a molecular approach. This methodology fails to explain the luminescence of this system. It was found that the band structure of the organic component rather than the molecular triplet state was able to explain the observed luminescence. Deuterated (Ln(C15H9O9)3(D2O)3) and dehydrated (Ln(C15H9O9)3) analogues were also studied. When bound H2O was replaced by D2O, lifetime and emission increased as expected. Upon dehydration, lifetimes increased again, but emission of 1-Eu unexpectedly decreased. This reduction is reasoned through an unprecedented enhancement effect of the compound's luminescence by the OH/OD oscillators in the organic-to-Eu(III) energy transfer process.

  11. Ultralow loss visible surface plasmon based waveguides formed in indium-tin-oxide coated Fe-doped LiNbO3 slabs.

    PubMed

    Zhao, Hua; Xue, Tingyu; Li, Liang; Zhang, Jingwen

    2016-09-15

    Visible reconfigurable waveguides were evidenced in a composite system formed with indium-tin-oxide (ITO) films coated on iron-doped lithium noibate (LN) slabs. Surface plasmon polaritions (SPPs) excited at the ITO/LN interface were believed to be behind the observed light guiding, which is inherent with superlow loss for its sub-nanometer modified layer. The forward near-surface-normal scattering and accompanying reduction of the specular reflectivity in the front ITO/LN interface are consistent with SPP excitation.

  12. Perovskite-Like Polar Lanthanide Formate Frameworks of [NH2NH3][Ln(HCOO)4] (Ln = Tb-Lu and Y): Synthesis, Structures, Magnetism, and Anisotropic Thermal Expansion.

    PubMed

    Zhao, Tian-Meng; Chen, Sa; Shang, Ran; Wang, Bing-Wu; Wang, Zhe-Ming; Gao, Song

    2016-10-17

    A series of isostructural hydrazinium lanthanide (Ln) formate framework compounds of [NH2NH3][Ln(HCOO)4] for Ln(3+) ions from Tb(3+) to Lu(3+) and Y(3+) have been successfully prepared by utilizing NH2NH3(+). The compounds crystallize in orthorhombic polar space group Pca21, with cell parameters at 180 K of a = 18.2526(7)-18.1048(5) Å, b = 6.5815(2)-6.5261(2) Å, c = 7.6362(3)-7.5044(2) Å, and V = 917.33(6)-886.67(4) Å(3), showing the effect of lanthanide contraction. The compounds possess polar perovskite-like structures incorporating the hydrazinium cations in the cavities of the NaCl-like framework, in which the Ln(3+) ions in a bicapped trigonal prism are connected by anti-anti and syn-anti formate groups. The N-H···Oformate hydrogen-bonding interactions are between the hydrazinium cations and the anionic framework. One anti-anti formate group is frustrated by the competitive N-H···Oformate hydrogen-bonding interactions. It thus twists or flips upon warming, resulting in large anisotropic thermal expansion and negative thermal expansion below 180 K. A comparison with the transition metal and magnesium analogues revealed that the structural compactness, tighter binding of the hydrazinium cation by the framework, and symmetrically better match between the framework and ammonium cation for Ln compounds could inhibit the occurrence of phase transition in the series. The IR spectroscopic, thermal, and magnetic properties are investigated.

  13. Synthesis, crystal structure and optical investigation of the new phosphates: Na{sub 7}Mg{sub 13}Ln(PO{sub 4}){sub 12} (Ln=La, Eu)

    SciTech Connect

    Jerbi, Hasna; Hidouri, Mourad; Glorieux, Benoit; Darriet, Jacques; Garcia, Alain; Jubera, Veronique; Ben Amara, Mongi

    2010-08-15

    Two new isostructural rare earth phosphates Na{sub 7}Mg{sub 13}Ln(PO{sub 4}){sub 12} (Ln=La, Eu) have been synthesized and investigated by X-ray diffraction and optical measurements. They crystallize in the orthorhombic system with the Cmc2{sub 1} space group (Z=4). The crystal structure exhibits a new type of framework built up from LnO{sub 8} (Ln=La, Eu), MO{sub 6} (M=0.5Mg+0.5Na) and MgO{sub x} (x=5, 6) polyhedra and PO{sub 4} tetrahedra linked by common corner, edge or face. It can be described in terms of [Mg{sub 4}MP{sub 4}O{sub 22}]{sub {infinity}} layers stacked along the a direction. These layers are interconnected by [Mg{sub 4}LnP{sub 4}O{sub 36}]{sub {infinity}} undulating chains spreading along the b direction. This framework delimits 6 distinct cavities occupied by Na{sup +} cations. The results of the optical study of Na{sub 7}Mg{sub 13}La{sub 1-x}Eu{sub x}(PO{sub 4}){sub 12} (x=0, 0.02, 0.1, 1) reveal the presence of two different Eu{sup 3+} ion environments whereas the X-ray study predicts the existence of only one Eu site. This difference can be explained by the possible presence of the europium element in the sodium sites with small occupancies which cannot be detected by the X-ray structural determination. - Graphical abstract: Emission spectra of Na{sub 7}Mg{sub 13}Eu(PO{sub 4}){sub 12} and Na{sub 7}Mg{sub 13}La{sub 0.9}Eu{sub 0.1}(PO{sub 4}){sub 12} compounds for {lambda}{sub exc}=240, 290 and 393.2 nm.

  14. K{sub 3}Ln[OB(OH){sub 2}]{sub 2}[HOPO{sub 3}]{sub 2} (Ln=Yb, Lu): Layered rare-earth dihydrogen borate monohydrogen phosphates

    SciTech Connect

    Zhou Yan; Hoffmann, Stefan; Huang Yaxi; Prots, Yurii; Schnelle, Walter; Menezes, Prashanth W.; Carrillo-Cabrera, Wilder; Sichelschmidt, Joerg; Mi Jinxiao; Kniep, Ruediger

    2011-06-15

    Two isotypic layered rare-earth borate phosphates, K{sub 3}Ln[OB(OH){sub 2}]{sub 2}[HOPO{sub 3}]{sub 2} (Ln=Yb, Lu), were synthesized hydrothermally and the crystal structures were determined by single-crystal X-ray diffraction (R3-bar , Z=3, Yb: a=5.6809(2) A, c=36.594(5) A, V=1022.8(2) A{sup 3}, Lu: a=5.6668(2) A, c=36.692(2) A, V=1020.4(1) A{sup 3}). The crystal structure can be described in terms of stacking of Glaserite-type slabs consisting of LnO{sub 6} octahedra interlinked by phosphate tetrahedra and additional layers of [OB(OH){sub 2}]{sup -} separated by K{sup +} ions. Field and temperature dependent measurements of the magnetic susceptibility of the Yb-compound revealed Curie-Weiss paramagnetic behavior above 120 K ({mu}{sub eff}=4.7 {mu}{sub B}). Magnetic ordering was not observed down to 1.8 K. - Graphical abstract: Two isotypic layered rare-earth borate phosphates, K{sub 3}Ln[OB(OH){sub 2}]{sub 2}[HOPO{sub 3}]{sub 2} (Ln = Yb, Lu), were synthesized hydrothermally and the crystal structures were determined by single-crystal X-ray diffraction. The structure can be described by stacking of Glaserite-type slabs and dihydrogen borate layers separated by potassium cations. Highlights: > First hydrothermal synthesis of rare-earth borate phosphates. > Instead of microcrystalline powders the synthesis of single crystals was achieved. > Successful single-crystal X-ray structure determination. > 2D arrangement of magnetic rare-earth ions. > EPR spectrum of Yb{sup 3+} at 5 K.

  15. High-pressure synthesis and structures of lanthanide germanides of LnGe{sub 5} (Ln=Ce, Pr, Nd, and Sm) isotypic with LaGe{sub 5}

    SciTech Connect

    Fukuoka, Hiroshi; Baba, Kazuya; Yoshikawa, Mayumi; Ohtsu, Fumiko; Yamanaka, Shoji

    2009-08-15

    A series of lanthanide penta-germanides LnGe{sub 5} (Ln=Ce, Pr, Nd and Sm) has been prepared by high-pressure (5-13 GPa) and high-temperature (500-1200 deg. C) reaction. CeGe{sub 5} crystallizes in an orthorhombic unit cell (S.G. Immm (71)) with a=4.000(5) A, b=6.192(5) A, c=9.86(1) A, and V=244.1(5) A{sup 3}. The new germanides are isotypic with LaGe{sub 5} consisting of a Ge covalent network with tunnels where guest ions Ln{sup 3+} are situated. The network is composed of sublayers with edge-sharing Ge six-membered rings with only boat conformation. The sublayers are connected by rare eight-coordinated Ge atoms. The cell volume of the compounds systematically decreases from La to Sm compounds, except for CeGe{sub 5,} owing to the lanthanide contraction. The lattice constants of CeGe{sub 5} are smaller than those of the Pr compound because it contains Ce{sup 4+} ions. CeGe{sub 5} is paramagnetic above 2 K, but does not obey the Curie-Weiss law. PrGe{sub 5} and NdGe{sub 5} are Curie-Weiss type paramagnets with Weiss temperatures of -3.3 and -18.4 K. SmGe{sub 5} shows an antiferromagnetic transition at 10.4 K. - Graphical abstract: A series of lanthanide penta-germanides LnGe{sub 5} (Ln=Ce, Pr, Nd and Sm) has been prepared by high-pressure (5-13 GPa) and high-temperature (500-1200 deg. C) reaction.

  16. Substitution studies of Mn and Fe in Ln{sub 6}W{sub 4}Al{sub 43} (Ln=Gd, Yb) and the structure of Yb{sub 6}Ti{sub 4}Al{sub 43}

    SciTech Connect

    Treadwell, LaRico J.; Watkins-Curry, Pilanda; McAlpin, Jacob D.; Prestigiacomo, Joseph; Stadler, Shane; Chan, Julia Y.

    2014-02-15

    The synthesis and characterization of Mn- and Fe-substituted Ln{sub 6}W{sub 4}Al{sub 43} (Ln=Gd, Yb) and Yb{sub 6}Ti{sub 4}Al{sub 43} are reported. The compounds adopt the Ho{sub 6}Mo{sub 4}Al{sub 43} structure type with lattice parameters of a∼11 Å and c∼17.8 Å with structural site preferences for Mn and Fe. The magnetization of Yb{sub 6}W{sub 4}Al{sub 43} is sensitive to Mn and Fe doping, which is evident by an increase in the field dependent magnetization. Gd{sub 6}W{sub 4}Al{sub 43}, Gd{sub 6}W{sub 4}Al{sub 42.31(11)}Mn{sub 0.69(11)}, and Gd{sub 6}W{sub 4}Al{sub 41.69(12)}Fe{sub 1.30(12)} order antiferromagnetically in the ab- and c-directions at 15, 14, and 13 K, respectively, with positive Weiss constants, suggesting the presence of ferromagnetic exchange interactions. Anisotropic magnetization data of Gd{sub 6}W{sub 4}Al{sub 43−y}T{sub y} (T=Mn, Fe) analogs are discussed. - Graphical abstract: The magnetic susceptibility of Ln{sub 6}W{sub 4−x}Al{sub 43−y}T{sub x+y} (Ln = Gd, Yb; T= Mn, Fe). Display Omitted - Highlights: • Single crystals of Ln{sub 6}W{sub 4−x}Al{sub 43−y}T{sub x+y} were grown with Al-flux. • Anisotropic magnetic behavior were determined on single crystals. • Gd{sub 6}W{sub 4−x}Al{sub 43−y}T{sub x+y} (T=Mn, Fe) analogs order antiferromagnetically.

  17. [W(bipy)(CN)6]-: a suitable metalloligand in the design of heterotrimetallic complexes. The first Cu(II)Ln(III)W(V) trinuclear complexes.

    PubMed

    Alexandru, Maria-Gabriela; Visinescu, Diana; Madalan, Augustin M; Lloret, Francesc; Julve, Miguel; Andruh, Marius

    2012-05-07

    The first 3d-4f-5d heterotrimetallic complexes using [W(V)(bipy)(CN)(6)](-) as a metalloligand were synthesized (bipy = 2,2'-bipyridine). The structural and magnetic properties of three [Cu(II)Ln(III)W(V)] complexes (Ln = Gd, Ho, Tb) are discussed.

  18. Chiroptical Spectra of Tetrakis (+)-3-Heptafluorobutylrylcamphorate Ln(III) Complexes with an Encapsulated Alkali Metal Ion: Solution Structures as Revealed by Chiroptical Spectra

    PubMed Central

    Shirotani, Dai; Yamanari, Kazuaki; Kuroda, Reiko; Harada, Takunori; Lunkley, Jamie L.; Muller, Gilles; Sato, Hisako; Kaizaki, Sumio

    2012-01-01

    The preparation of tetrakis((+)-hfbc) lanthanide(III) complexes with an encapsulated alkali metal and ammonium ions M[Ln((+)-hfbc)4] (hereafter abbreviated as M-Ln : (+)-hfbc, (+)-heptafluorobutyrylcamphorate; M, ammonium or benzyl ammonium ions as well as alkali metal ions) was reported and discussed. The electronic circular dichroism (CD) spectra in the intraligand π–π* transition of M–Ln were examined in view of the solvent effect. Here, the concentration, alkali metal, and ammonium ion dependences are compared with the solid CD, 5D0 ← 7F0(Eu(III)) excitation spectra, circularly polarized luminescence, and vibrational circular dichroism. It has been revealed that the dodecahedral eight coordinate DD-8-M-Ln complexes in crystals are equilibrated between the diastereoselectively formed square antiprism eight coordinate SAPR-8-M-Ln and [Ln((+)-hfbc)3] in EtOH and CH3CN solutions or between the SAPR-8-M-Ln and DD-D2d(mmmm)-8-M-Ln complexes in CHCl3 solution. The observed CD couplets are found to reflect the exciton CD couplets which are useful to determine the four-bladed SAPR-(llll) absolute configuration around the lanthanide(III) ion. PMID:22945448

  19. Long-Term Cyclic Oxidation Behavior of Uncoated and Coated Re-108 and In-939 at 980 and 870 C

    NASA Technical Reports Server (NTRS)

    Lee, K. N.; Barrett, C. A.; Smith, J.

    1999-01-01

    Very long-term cyclic oxidation behavior of Re-108 and ln-939 with and without a protective coating was evaluated at 980 and 870 C, respectively. Re-108 and ln-939 without a protective coating began to show rapid weight loss at 3000 h due to scale spallation, indicating the need for an oxidation protective coating for longer than thousands of hours of oxidative life. NiAl-base coatings of a vapor phase aluminide (VPA), a pack aluminide (CODEP), and a slurry paint aluminide (SERMALOY J) were applied on Re-108 and ln-939. VPA and CODEP on Re-108 and all three coatings on ln-939 showed excellent cyclic oxidation resistance out to 10000 hr. Coated alloys were annealed in an inert atmosphere to determine the loss of Al from the coating into the alloy substrate through diffusion. The Al loss from the coating through diffusion was twice as great as the Al loss through oxidation after 10000 h of cyclic exposure. Oxidation life of VPA-coated Re-108 was estimated by calculating the amount of Al initially available for protective oxidation and the amount of Al lost through oxidation and diffusion.

  20. Boiling phenomenon due to quasi-steadily and rapidly increasing heat inputs in LN 2 and LHe I

    NASA Astrophysics Data System (ADS)

    Sakurai, A.; Shiotsu, M.; Hata, K.

    Dynamic boiling processes, including the transition from a single-phase non-boiling regime to film boiling caused by exponentially increasing heat inputs, Q 0e t/τ for a wide range of periods and pressures on horizontal wires in LN 2 and LHe I were investigated. The main problem is that there are no active cavities on the wire surfaces for initial boiling in the liquids. The heat transfer processes due to increasing heat inputs with increasing rates ranging from quasi-steady to rapidly increasing ones in LN 2 were classified into three types for the pressures. The dynamic boiling processes in LHe I due to rapidly increasing heat inputs at the pressures tested here correspond to Type 3 processes including semi-direct transitions in LN 2 at pressures higher than about 1 MPa. The lower limit temperatures of boiling initiation on the wire surfaces for initial boiling in liquids at pressures due to quasi-steadily increasing heat inputs are clearly lower than the homogeneous spontaneous nucleation temperatures corresponding to these pressures. Liquid superheat close to the solid surface in LHe I was evaluated from the value of the wire surface temperature, taking off the temperature drop due to Kapitza resistance. The initial boiling temperatures due to quasi-steady heat inputs at pressures in saturated LN 2 and LHe I agreed with the values derived from the theoretical model based on the heterogeneous spontaneous nucleation in flooded cavities on the solid surface.

  1. Phthalocyanine supported dinuclear Ln(III) complexes: the solvent-induced change of magnetic properties in dysprosium(iii) analogues.

    PubMed

    Ge, Jing-Yuan; Wang, Hai-Ying; Li, Jing; Xie, Jia-Ze; Song, You; Zuo, Jing-Lin

    2017-02-24

    Three dinuclear lanthanide complexes, [Ln2(thd)4Pc]·2C6H6 (Hthd = 2,2,6,6-tetramethylheptanedione, Ln = Sm (1), Tb (2), Dy (3)), have been synthesized based on phthalocyanine (Pc). They can be reversibly transformed into [Ln2(thd)4Pc] (Ln = Sm (1'), Tb (2'), Dy (3')) via desolvation and resolvation of the lattice benzene molecules. This change generates dramatic influences on the structural and magnetic properties of the dysprosium analogue. In complex 3, one crystallographically independent metal center is observed, and it exhibits a single relaxation process of magnetization with an energy barrier of 55.7 K. Upon desolvation, the resulting complex 3' contains two types of metal centers, and shows the field-induced single-molecule magnetic behavior with two thermally activated magnetic relaxation processes. The anisotropy barriers for 3' are as high as 63.3 K and 109.6 K, respectively. This work confirms that the solvated molecules can finely tune the magnetic relaxation mechanisms.

  2. Evaluation of the photocatalytic activity of Ln3+-TiO2 nanomaterial using fluorescence technique for real wastewater treatment

    NASA Astrophysics Data System (ADS)

    Saif, M.; Aboul-Fotouh, S. M. K.; El-Molla, S. A.; Ibrahim, M. M.; Ismail, L. F. M.

    2014-07-01

    Evaluation the photocatalytic activity of different Ln3+ modified TiO2 nanomaterials using fluorescence based technique has rarely been reported. In the present work, x mol Ln3+ modified TiO2 nanomaterials (Ln = Nd3+, Sm3+, Eu3+, Gd3+, Dy3+ and Er3+ ions; x = 0.005, 0.008, 0.01, 0.02 and 0.03) were synthesized by sol-gel method and characterized using different advanced techniques. The photocatalytic efficiency of the modified TiO2 expressed in the charge carrier separation and rad OH radicals formation were assigned using TiO2 fluorescence quenching and fluorescence probe methods, respectively. The obtained fluorescence measurements confirm that doping treatment significantly decreases the electron-hole recombination probability in the obtained Ln3+/TiO2. Moreover, the rate of rad OH radicals formation is increased by doping. The highly active nanoparticles (0.02Gd3+/TiO2 and 0.01Eu3+/TiO2) were applied for industrial wastewater treatment using solar radiation as a renewable energy source.

  3. Solution structure of Ln(III) complexes with macrocyclic ligands through theoretical evaluation of 1H NMR contact shifts.

    PubMed

    Rodríguez-Rodríguez, Aurora; Esteban-Gómez, David; de Blas, Andrés; Rodríguez-Blas, Teresa; Botta, Mauro; Tripier, Raphaël; Platas-Iglesias, Carlos

    2012-12-17

    Herein, we present a new approach that combines DFT calculations and the analysis of Tb(III)-induced (1)H NMR shifts to quantitatively and accurately account for the contact contribution to the paramagnetic shift in Ln(III) complexes. Geometry optimizations of different Gd(III) complexes with macrocyclic ligands were carried out using the hybrid meta-GGA TPSSh functional and a 46 + 4f(7) effective core potential (ECP) for Gd. The complexes investigated include [Ln(Me-DODPA)](+) (H(2)Me-DODPA = 6,6'-((4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(methylene))dipicolinic acid, [Ln(DOTA)(H(2)O)](-) (H(4)DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate), [Ln(DOTAM)(H(2)O)](3+) (DOTAM = 1,4,7,10- tetrakis[(carbamoyl)methyl]-1,4,7,10-tetraazacyclododecane), and related systems containing pyridyl units (Ln = Gd, Tb). Subsequent all-electron relativistic calculations based on the DKH2 approximation, or small-core ECP calculations, were used to compute the (1)H hyperfine coupling constants (HFCCs) at the ligand nuclei (A(iso) values). The calculated A(iso) values provided direct access to contact contributions to the (1)H NMR shifts of the corresponding Tb(III) complexes under the assumption that Gd and Tb complexes with a given ligand present similar HFCCs. These contact shifts were used to obtain the pseudocontact shifts, which encode structural information as they depend on the position of the nucleus with respect to the lanthanide ion. An excellent agreement was observed between the experimental and calculated pseudocontact shifts using the DFT-optimized geometries as structural models of the complexes in solution, which demonstrates that the computational approach used provides (i) good structural models for the complexes, (ii) accurate HFCCs at the ligand nuclei. The methodology presented in this work can be classified in the context of model-dependent methods, as it relies on the use of a specific molecular structure obtained from DFT

  4. Axially Symmetric U-O-Ln- and U-O-U-Containing Molecules from the Control of Uranyl Reduction with Simple f-Block Halides.

    PubMed

    Arnold, Polly L; Cowie, Bradley E; Suvova, Markéta; Zegke, Markus; Magnani, Nicola; Colineau, Eric; Griveau, Jean-Christophe; Caciuffo, Roberto; Love, Jason B

    2017-08-28

    The reduction of U(VI) uranyl halides or amides with simple Ln(II) or U(III) salts forms highly symmetric, linear, oxo-bridged trinuclear U(V) /Ln(III) /U(V) , Ln(III) /U(IV) /Ln(III) , and U(IV) /U(IV) /U(IV) complexes or linear Ln(III) /U(V) polymers depending on the stoichiometry and solvent. The reactions can be tuned to give the products of one- or two-electron uranyl reduction. The reactivity and magnetism of these compounds are discussed in the context of using a series of strongly oxo-coupled homo- and heterometallic poly(f-block) chains to better understand fundamental electronic structure in the f-block. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Examination of Compatibility of Potentially Cavitation-Resistant Modifications of Type 316LN Stainless Steel with Mercury in a Thermal Convection Loop

    SciTech Connect

    Pawel, SJ

    2002-08-29

    A 316L stainless steel thermal convection loop (TCL) containing a variety of stainless steel coupons circulated mercury for 2000 h. The TCL conditions included a maximum temperature of 307 C, a maximum temperature gradient of 90 C, and a Hg velocity of about 1.4 m/min. In addition to mill-annealed/surface-ground 316LN coupons serving as the baseline material, other coupons included 316LN that was 50% cold-worked, 316LN that was given a proprietary surface hardening treatment termed ''kolsterizing,'' and Nitronic 60. The purpose of this test was to examine Hg compatibility with these modest variations of annealed 31 6LN stainless steel that are considered potential improvements over annealed 31 6LN for cavitation-erosion resistance in the Spallation Neutron Source (SNS) target containment system. The results indicated negligible weight change for each coupon type, no significant indication of attack or surface roughening, and generally no interaction with Hg.

  6. A family of acetato-diphenoxo triply bridged dimetallic Zn(II)Ln(III) complexes: SMM behavior and luminescent properties.

    PubMed

    Oyarzabal, Itziar; Artetxe, Beñat; Rodríguez-Diéguez, Antonio; García, JoséÁngel; Seco, José Manuel; Colacio, Enrique

    2016-06-21

    Eleven dimetallic Zn(II)-Ln(III) complexes of the general formula [Zn(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN (Ln(III) = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7), Ho (8), Er (9), Tm (10), Yb (11)) have been prepared in a one-pot reaction from the compartmental ligand N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromo-benzyl)ethylenediamine (H2L). In all these complexes, the Zn(II) ions occupy the internal N2O2 site whereas the Ln(III) ions show preference for the O4 external site. Both metallic ions are bridged by an acetate bridge, giving rise to triple mixed diphenoxido/acetate bridged Zn(II)Ln(III) compounds. The Nd, Dy, Er and Yb complexes exhibit field induced single-ion magnet (SIM) behaviour, with Ueff values ranging from 14.12 to 41.55 K. The Er complex shows two relaxation processes, but only the second relaxation process with an energy barrier of 21.0 K has been characterized. The chromophoric L(2-) ligand is able to act as an "antenna" group, sensitizing the near-infrared (NIR) Nd(III) and Yb(III)-based luminescence in complexes 2 and 11 and therefore, both compounds can be considered as magneto-luminescent materials. In addition, the Sm(III), Eu(III) and Tb(III) derivatives exhibit characteristic emissions in the visible region.

  7. Synthesis, structure, luminescent, and magnetic properties of carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2] (Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato).

    PubMed

    Ehama, Kiyomi; Ohmichi, Yusuke; Sakamoto, Soichiro; Fujinami, Takeshi; Matsumoto, Naohide; Mochida, Naotaka; Ishida, Takayuki; Sunatsuki, Yukinari; Tsuchimoto, Masanobu; Re, Nazzareno

    2013-11-04

    Carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2]·solvent were synthesized through atmospheric CO2 fixation reaction of [Zn(II)L(n)(H2O)2]·xH2O, Ln(III)(NO3)3·6H2O, and triethylamine, where Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato. Each Zn(II)2Ln(III)2 structure possessing an inversion center can be described as two di-μ-phenoxo-bridged {Zn(II)L(n)Ln(III)(NO3)} binuclear units bridged by two carbonato CO3(2-) ions. The Zn(II) ion has square pyramidal coordination geometry with N2O2 donor atoms of L(n) and one oxygen atom of a bridging carbonato ion at the axial site. Ln(III) ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base L(n), two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9-300 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic susceptibilities under the direct current bias fields of 0 and 1000 Oe were measured. The magnetic properties of the Zn(II)2Ln(III)2 complexes are analyzed on the basis of the dicarbonato-bridged binuclear Ln(III)-Ln(III) structure, as the Zn(II) ion with d(10) electronic configuration is diamagnetic. ZnGd1 (L(1)) and ZnGd2 (L(2)) show a ferromagnetic Gd(III)-Gd(III) interaction with J(Gd-Gd) = +0.042 and +0.028 cm(-1), respectively, on the basis of the Hamiltonian H = -2J(Gd-Gd)ŜGd1·ŜGd2. The magnetic data of the Zn(II)2Ln(III)2 complexes (Ln(III) = Tb(III), Dy(III)) were analyzed by a spin Hamiltonian including the crystal field effect on the Ln(III) ions and the Ln(III)-Ln(III) magnetic interaction. The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy. Luminescence spectra of Zn(II)2Tb(III)2 complexes were observed, while those

  8. Crystal structure and magnetic properties of Ba-ordered manganites Ln{sub 0.70}Ba{sub 0.30}MnO{sub 3-{delta}} (Ln = Pr, Nd)

    SciTech Connect

    Trukhanov, S. V. Khomchenko, V. A.; Lobanovski, L. S.; Bushinsky, M. V.; Karpinsky, D. V.; Fedotova, V. V.; Troyanchuk, I. O.; Trukhanov, A. V.; Stepin, S. G.; Szymczak, R.; Botez, C. E.; Adair, A.

    2006-09-15

    The structure and magnetic properties of the Ba-ordered state in solid solutions of manganites Ln{sub 0.70}Ba{sub 0.30}MnO{sub 3-{delta}} (Ln = Pr, Nd) with a cation ratio Ln{sup 3+}/Ba{sup 2+} >> 1 are studied experimentally. The samples are obtained by two-stage synthesis. The initial stoichiometric Ba-disordered solid solutions Ln{sub 0.70}Ba{sub 0.30}MnO{sub 3} synthesized in air according to traditional ceramic technology are characterized by the orthorhombic (Imma, Z = 4) perovskite-like unit cell and are ferromagnets with Curie temperatures T{sub C} {approx} 173 and {approx} 143 K for Pr and Nd, respectively. The average size of a crystalline in the initial samples is 5 {mu}m. It is found that annealing of the initial samples in a vacuum of P[O{sub 2}] = 10{sup -4} Pa leads to their separation into three phases: (1) the anion-deficient ordered LnBaMn{sub 2}O{sub 5} phase described by a tetragonal (P4/mmm, Z = 2) perovskite-like unit cell, as well as the phases (2) Ln{sub 2}O{sub 3} (P3-barm1, Z = 1) and (3) MnO (Fm3-barm, Z = 2). Reduction leads to the formation of a nanocomposite with an average crystallite size = 100 nm. Anion-deficient Ba-ordered phases of LnBaMn{sub 2}O{sub 5} exhibit ferrimagnetic properties with Neel temperatures T{sub N} {approx} 113 and {approx}123 K for Pr and Nd, respectively. Annealing of anion-deficient samples in air at a moderate temperature of T = 800{sup o}C does not change the average size of the nanocrystallite, but noticeably alters their phase composition. Stoichiometric nanocomposites consist of two perovskite-like phases: (1) the Ba-deficient ordered stoichiometric phase LnBaMn{sub 2}O{sub 6}, which is described by a tetragonal (P4/mmm, Z = 2) unit cell and has the Curie temperatures T{sub C} {approx} 313 (Pr) and {approx}303 K (Nd), and (2) the Ba-disordered superstoichiometric phase Ln{sub 0.90}Ba{sub 0.10}MnO{sub 3+{delta}}, which is described by an orthorhombic (Imma, Z = 4) unit cell and has Curie

  9. Syntheses, structure, and luminescent properties of novel hydrated rare earth borates Ln2B6O10OH4•H2O (Ln = Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Y).

    PubMed

    Cong, Rihong; Yang, Tao; Wang, Zheming; Sun, Junliang; Liao, Fuhui; Wang, Yingxia; Lin, Jianhua

    2011-03-07

    Ln(2)B(6)O(10)(OH)(4)•H(2)O (Ln = Pr, Nd, Sm-Gd, Dy, Ho, and Y), a new series of hydrated rare earth borates, have been synthesized under hydrothermal conditions. A single crystal of Nd analogue was used for the structure determination by X-ray diffraction. It crystallizes in the monoclinic space group C2/c with lattice constants a = 21.756(4), b = 4.3671(9), c = 12.192(2) Å, and β = 108.29(3)°. The other compounds are isostructural to Nd(2)B(6)O(10)(OH)(4)•H(2)O. The fundamental building block (FBB) of the polyborate anion in this structure is a three-membered ring [B(3)O(6)(OH)(2)](5-). The FBBs are connected by sharing oxygen atoms forming an infinite [B(3)O(5)(OH)(2)](3-) chain, and the chains are linked by hydrogen bonds, establishing a two-dimensional (2-D) [B(6)O(10)(OH)(4)•H(2)O](6-) layer. The 2-D borate layers are thus interconnected by Ln(3+) ions to form the complex three-dimensional structure. Ln(2)B(6)O(10)(OH)(4)•H(2)O dehydrates stepwise, giving rise to two new intermediate compounds Ln(2)B(6)O(10)(OH)(4) and Ln(2)B(6)O(11)(OH)(2). The investigation on the luminescent properties of Gd(2-2x)Eu(2x)B(6)O(10)(OH)(4)•H(2)O (x = 0.01-1.00) shows a high efficiency of Eu(3+) f-f transitions and the existence of the energy transfer process from Gd(3+) to Eu(3+). Eu(2)B(6)O(10)(OH)(4)•H(2)O and its two dehydrated products, Eu(2)B(6)O(10)(OH)(4) and Eu(2)B(6)O(11)(OH)(2), present the strongest emission peak at 620 nm ((5)D(0) → (7)F(2) transition), which may be potential red phosphors.

  10. Lower denticity leading to higher stability: structural and solution studies of Ln(III)-OBETA complexes.

    PubMed

    Negri, Roberto; Baranyai, Zsolt; Tei, Lorenzo; Giovenzana, Giovanni B; Platas-Iglesias, Carlos; Bényei, Attila C; Bodnár, Judit; Vágner, Adrienn; Botta, Mauro

    2014-12-01

    The heptadentate ligand OBETA (2,2'-oxybis(ethylamine)-N,N,N',N'-tetraacetic acid) was reported to form complexes with Ln(3+) ions more stable than those formed by the octadentate and more popular congener EGTA (ethylene glycol O,O'-bis(ethylamine)-N,N,N',N'-tetraacetic acid). The structural features leading to this puzzling coordination paradox were investigated by X-ray diffraction, solution state NMR, molecular modeling, and relaxometric studies. The stability constant of Gd(OBETA) (log KGdL = 19.37, 0.1 M KCl) is 2 orders of magnitude higher than that of the higher denticity analogue Gd(EGTA) (log KGdL = 17.66, 0.1 M KCl). The half-lives (t1/2) for the dissociation reactions of Gd(OBETA) and Gd(EGTA) ([Cu(2+)]tot = 0.2 mM, [Cit(3-)]tot = 0.5 mM, [PO4(3-)]tot = 1.0 mM, and [CO3(2-)]tot = 25 mM at pH = 7.4 and 25 °C in 0.1 M KCl solution) are 6.8 and 0.63 h, respectively, reflecting the much higher inertness of Gd(OBETA) near physiological conditions. NMR studies and DFT calculations using the B3LYP functional and a large-core ECP indicate that the [Gd(OBETA)(H2O)2](-) complex most likely exists in solution as the Δ(λλ)(δδδδ)A/Λ(δδ)(λλλλ)A enantiomeric pair, with an activation free energy for the enantiomerization process of ∼40 kJ·mol(-1). The metal ion is nine-coordinate by seven donor atoms of the ligand and two inner-sphere water molecules. The X-ray crystal structure of [C(NH2)3]3[Lu(OBETA)(CO3)]·2H2O is in agreement with the predictions of DFT calculations, the two coordinated water molecules being replaced by a bidentate carbonate anion. The (1)H NMRD and (17)O NMR study revealed that the two inner-sphere water molecules in Gd(OBETA) are endowed with a relatively fast water exchange rate (kex(298) = 13 × 10(6) s(-1)). The higher thermodynamic stability and inertness of Ln(OBETA) complexes, peaking in the center of the 4f series, combined with the presence of two coordinated water molecules suggests that Gd(OBETA) is a promising

  11. lnCeDB: database of human long noncoding RNA acting as competing endogenous RNA.

    PubMed

    Das, Shaoli; Ghosal, Suman; Sen, Rituparno; Chakrabarti, Jayprokas

    2014-01-01

    Long noncoding RNA (lncRNA) influences post-transcriptional regulation by interfering with the microRNA (miRNA) pathways, acting as competing endogenous RNA (ceRNA). These lncRNAs have miRNA responsive elements (MRE) in them, and control endogenous miRNAs available for binding with their target mRNAs, thus reducing the repression of these mRNAs. lnCeDB provides a database of human lncRNAs (from GENCODE 19 version) that can potentially act as ceRNAs. The putative mRNA targets of human miRNAs and the targets mapped to AGO clipped regions are collected from TargetScan and StarBase respectively. The lncRNA targets of human miRNAs (up to GENCODE 11) are downloaded from miRCode database. miRNA targets on the rest of the GENCODE 19 lncRNAs are predicted by our algorithm for finding seed-matched target sites. These putative miRNA-lncRNA interactions are mapped to the Ago interacting regions within lncRNAs. To find out the likelihood of an lncRNA-mRNA pair for actually being ceRNA we take recourse to two methods. First, a ceRNA score is calculated from the ratio of the number of shared MREs between the pair with the total number of MREs of the individual candidate gene. Second, the P-value for each ceRNA pair is determined by hypergeometric test using the number of shared miRNAs between the ceRNA pair against the number of miRNAs interacting with the individual RNAs. Typically, in a pair of RNAs being targeted by common miRNA(s), there should be a correlation of expression so that the increase in level of one ceRNA results in the increased level of the other ceRNA. Near-equimolar concentration of the competing RNAs is associated with more profound ceRNA effect. In lnCeDB one can not only browse for lncRNA-mRNA pairs having common targeting miRNAs, but also compare the expression of the pair in 22 human tissues to estimate the chances of the pair for actually being ceRNAs. Downloadable freely from http://gyanxet-beta.com/lncedb/.

  12. Heptanuclear lanthanide [Ln7] clusters: from blue-emitting solution-stable complexes to hybrid clusters.

    PubMed

    Canaj, Angelos B; Tsikalas, George K; Philippidis, Aggelos; Spyros, Apostolos; Milios, Constantinos J

    2014-09-07

    The use of LH3 (2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) and aibH (2-amino-isobutyric acid) in 4f chemistry has led to the isolation of eight new isostructural lanthanide complexes. More specifically, the reaction of the corresponding lanthanide nitrate salt with LH3 and aibH in MeOH, under solvothermal conditions in the presence of NEt3, led to the isolation and characterization of seven complexes with the general formulae [Ln(III)7(OH)2(L')9(aib)]·4MeOH (Ln = Gd, ·4MeOH; Tb, ·4MeOH; Dy, ·4MeOH; Ho, ·4MeOH; Er, ·4MeOH; Tm, ·4MeOH; Yb, ·4MeOH L' = the dianion of the Schiff base between naphthalene aldehyde and 2-amino-isobutyric acid). Furthermore, the isostructural Y(III) analogue, cluster [Y(III)7(OH)2(L')9(aib)]·4MeOH (·4MeOH), was synthesized in a similar manner to . The structure of all eight clusters describes a distorted [M(III)6] octahedron which encapsulates a seventh M(III) ion in an off-centre fashion. Dc magnetic susceptibility studies in the 5-300 K range for complexes reveal the presence of dominant antiferromagnetic exchange interactions within the metallic clusters as evidenced by the negative Weiss constant, θ, while ac magnetic susceptibility measurements show temperature and frequency dependent out-of-phase signals for the [Dy(III)7] analogue (·4MeOH), suggesting potential single molecule magnetism character. Furthermore, for complex , simulation of its dc magnetic susceptibility data yielded very weak antiferromagnetic interactions within the metallic centres. Solid-state emission studies for all clusters display ligand-based emission, while extended 1D and 2D NMR studies for ·4MeOH reveal that the species retain their structural integrity in solution. In addition, TGA measurements for , and revealed excellent thermal stability up to 340 °C for the clusters.

  13. Observation of Slow Relaxation and Single-Molecule Toroidal Behavior in a Family of Butterfly-Shaped Ln4 Complexes.

    PubMed

    Biswas, Sourav; Das, Sourav; Gupta, Tulika; Singh, Saurabh Kumar; Pissas, Michael; Rajaraman, Gopalan; Chandrasekhar, Vadapalli

    2016-12-19

    A family of five isostructural butterfly complexes with a tetranuclear [Ln4 ] core of the general formula [Ln4 (LH)2 (μ2 -η(1) η(1) Piv)(η(2) -Piv)(μ3 -OH)2 ]⋅x H2 O⋅y MeOH⋅z CHCl3 (1: Ln=Dy(III) , x=2, y=2, z=0; 2: Ln=Tb(III) , x=0, y=0, z=6; 3: Ln=Er(III) , x=2, y=2, z=0; 4: Ln=Ho(III) , x=2, y=2, z=0; 5: Ln=Yb(III) , x=2, y=2, z=0; LH4 =6-{[bis(2-hydroxyethyl)amino]methyl}-N'-(2-hydroxy-3-methoxybenzylidene)picolinohydrazide; PivH=pivalic acid) was isolated and characterized both structurally and magnetically. Complexes 1-5 were probed by direct and alternating current (dc and ac) magnetic susceptibility measurements and, except for 1, they did not display single-molecule magnetism (SMM) behavior. The ac magnetic susceptibility measurements show frequency-dependent out-of-phase signals with one relaxation process for complex 1 and the estimated effective energy barrier for the relaxation process was found to be 49 K. We have carried out extensive ab initio (CASSCF+RASSI-SO+SINGLE_ANISO+POLY_ANISO) calculations on all the five complexes to gain deeper insights into the nature of magnetic anisotropy and the presence and absence of slow relaxation in these complexes. Our calculations yield three different exchange coupling for these Ln4 complexes and all the extracted J values are found to be weakly ferro/antiferromagentic in nature (J1 =+2.35, J2 =-0.58, and J3 =-0.29 cm(-1) for 1; J1 =+0.45, J2 =-0.68, and J3 =-0.29 cm(-1) for 2; J1 =+0.03, J2 =-0.98, and J3 =-0.19 cm(-1) for 3; J1 =+4.15, J2 =-0.23, and J3 =-0.54 cm(-1) for 4 and J1 =+0.15, J2 =-0.28, and J3 =-1.18 cm(-1) for 5). Our calculations reveal the presence of very large mixed toroidal moment in complex 1 and this is essentially due to the specific exchange topology present in this cluster. Our calculations also suggest presence of single-molecule toroics (SMTs) in complex 2. For complexes 3-5 on the other hand, the transverse anisotropy was computed to be large, leading to

  14. Series of isostructural planar lanthanide complexes [Ln(III)4(mu3-OH)2(mdeaH)2(piv)8] with single molecule magnet behavior for the Dy4 analogue.

    PubMed

    Abbas, Ghulam; Lan, Yanhua; Kostakis, George E; Wernsdorfer, Wolfgang; Anson, Christopher E; Powell, Annie K

    2010-09-06

    A series of five isostructural tetranuclear lanthanide complexes of formula [Ln(4)(mu(3)-OH)(2)(mdeaH)(2)(piv)(8)], (mdeaH(2) = N-methyldiethanolamine; piv = pivalate; Ln = Tb (1), Dy (2), Ho (3), Er (4), and Tm (5)) have been synthesized and characterized. These clusters have a planar "butterfly" Ln(4) core. Magnetically, the Ln(III) ions are weakly coupled in all cases; the Dy(4) compound 2 shows Single Molecule Magnet (SMM) behavior.

  15. Electrochemical studies of water insertion and proton - Ceramic interaction in substituted perovskite SrZr0.9Ln0.1O2.95

    NASA Astrophysics Data System (ADS)

    Lacroix, O.; Rahmouni, K.; Sirat, A.; Takenouti, H.; Deslouis, C.; Keddam, M.; Sala, B.

    2014-12-01

    Because of their high ionic conduction even at relatively low temperatures, proton conducting ceramics are one of the most promising electrolytes for fuel cell. In contrast to oxide-ion conductors, proton-conducting systems, especially in an electrolyser plant, could operate below 600 °C, critical temperature for mechanical and hot corrosion resistance of common stainless steels. Proton conduction in perovskite type ceramic was analysed under the water molecules insertion to maximize proton conduction. To this end, the SrZr0.9Ln0.1O2.95 electrolyte and its microstructure, particularly grain size was investigated. The insertion and release of water in the perovskite structure was followed by impedance spectroscopy and by using the so-called Brick Layer Model (BLM) to separate the bulk and grain boundary conductivities. It was found that the conductivity in both zones increases namely with steam pressure. It was also verified that the bulk conductivity is higher than that of grain boundaries. Consequently both the operating steam pressure and the grain size appear as the main parameters that can be tuned to enhance the proton conduction.

  16. Physicochemical Properties of Near-Linear Lanthanide(II) Bis(silylamide) Complexes (Ln = Sm, Eu, Tm, Yb).

    PubMed

    Goodwin, Conrad A P; Chilton, Nicholas F; Vettese, Gianni F; Moreno Pineda, Eufemio; Crowe, Iain F; Ziller, Joseph W; Winpenny, Richard E P; Evans, William J; Mills, David P

    2016-10-17

    Following our report of the first near-linear lanthanide (Ln) complex, [Sm(N(††))2] (1), herein we present the synthesis of [Ln(N(††))2] [N(††) = {N(Si(i)Pr3)2}; Ln = Eu (2), Tm (3), Yb (4)], thus achieving approximate uniaxial geometries for a series of "traditional" Ln(II) ions. Experimental evidence, together with calculations performed on a model of 4, indicates that dispersion forces are important for stabilization of the near-linear geometries of 1-4. The isolation of 3 under a dinitrogen atmosphere is noteworthy, given that "[Tm(N″)(μ-N″)]2" (N″ = {N(SiMe3)2}) has not previously been structurally authenticated and reacts rapidly with N2(g) to give [{Tm(N″)2}2(μ-η(2):η(2)-N2)]. Complexes 1-4 have been characterized as appropriate by single-crystal X-ray diffraction, magnetic measurements, electrochemistry, multinuclear NMR, electron paramagnetic resonance (EPR), and electronic spectroscopy, along with computational methods for 3 and 4. The remarkable geometries of monomeric 1-4 lead to interesting physical properties, which complement and contrast with comparatively well understood dimeric [Ln(N″)(μ-N″)]2 complexes. EPR spectroscopy of 3 shows that the near-linear geometry stabilizes mJ states with oblate spheroid electron density distributions, validating our previous suggestions. Cyclic voltammetry experiments carried out on 1-4 did not yield Ln(II) reduction potentials, so a reactivity study of 1 was performed with selected substrates in order to benchmark the Sm(III) → Sm(II) couple. The separate reactions of 1 with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), azobenzene, and benzophenone gave crystals of [Sm(N(††))2(TEMPO)] (5), [Sm(N(††))2(N2Ph2)] (6), and [Sm(N(††)){μ-OPhC(C6H5)CPh2O-κO,O'}]2 (7), respectively. The isolation of 5-7 shows that the Sm(II) center in 1 is still accessible despite having two bulky N(††) moieties and that the N-donor atoms are able to deviate further from linearity or ligand

  17. An anti CuO2-type metal hydride square net structure in Ln2M2As2H(x) (Ln=La or Sm, M=Ti, V, Cr, or Mn).

    PubMed

    Mizoguchi, Hiroshi; Park, SangWon; Hiraka, Haruhiro; Ikeda, Kazutaka; Otomo, Toshiya; Hosono, Hideo

    2015-03-02

    Using a high pressure technique and the strong donating nature of H(-), a new series of tetragonal La2Fe2Se2O3-type layered mixed-anion arsenides, Ln2M2As2H(x), was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M2H square net, which has anti CuO2 square net structures accompanying two As(3-) ions, is sandwiched by (LaH)2 fluorite layers. Notably, strong metal-metal bonding with a distance of 2.80 Å was confirmed in La2Ti2As2H2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt-like ionic hydrides and transition-metal hydrides with metallic characters.

  18. Effects of Out-of-Plane Disorder on the Nodal Quasiparticle and Superconducting Gap in Single-Layer Bi_2Sr_1.6Ln_0.4CuO_6 delta (Ln = La, Nd, Gd)

    SciTech Connect

    Hashimoto, M.

    2011-01-04

    How out-of-plane disorder affects the electronic structure has been investigated for the single-layer cuprates Bi{sub 2}Sr{sub 1.6}Ln{sub 0.4}CuO{sub 6+{delta}} (Ln = La, Nd, Gd) by angle-resolved photoemission spectroscopy. We have observed that, with increasing disorder, while the Fermi surface shape and band dispersions are not affected, the quasi-particle width increases, the anti-nodal gap is enhanced and the superconducting gap in the nodal region is depressed. The results indicate that the superconductivity is significantly depressed by out-of-plane disorder through the enhancement of the anti-nodal gap and the depression of the superconducting gap in the nodal region.

  19. Ag-LnBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (Ln = Y, Nd, Sm, Eu, and Yb) superconductor coatings on stainless steel

    SciTech Connect

    Yokogawa, Y.; Ansart, F.; Bressolles, J.C.; Roux, P.; Traverse, J.P.

    1997-07-01

    Ag-doped LnBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (Ln = Y, Nd, Sm, Eu, and Yb) films on two kinds of stainless steel substrate were prepared by the method of direct deposition and heat treatment. The critical temperatures of the samples were evaluated at 91--92 K, independent of silver content and thickness of the coating layer. The resistance of the samples decreased with silver addition. The SEM observation showed a border between the coating layer and the substrate. The elemental analysis by EPMA revealed that aluminum aggregated in the border. The diffusion of iron ions in the coating layer was hindered by the existence of the border and affected by the quantity of aluminum. The width of the border increased with increasing heat-treatment time, governed by the diffusion of metals from the metallic substrate to the coating layer. This fairly agreed with the results of impedance measurements.

  20. Raman spectra of 2Ln/sub 2/O/sub 3/ /times/ 9TiO/sub 2/ compounds (Ln = Ce, La, Nd, Pr, Sm, Eu, Gd, Tm, Yb, Tb)

    SciTech Connect

    Mel'nik, N.N.; Tsapenko, L.M.

    1988-03-01

    This work uses Raman and x-ray phase analysis methods to investigate compounds of the type 2Ln/sub 2/O/sub 3/ /times/ 9TiO/sub 2/ (where Ln = Ce, La, Nd, Pr, Sm, Eu, Gd, Tm, and Yb). The compounds were synthesized by melting in an optical beam on a water-cooled substrate (quench rate approx. 10/sup 2/ deg/sec) and by rapid quenching of a melt cupel by slamming with water-cooled blocks quench rate approx. 10/sup 5/ - 10/sup 6/ deg/sec. The x-ray diffraction study was done on a DRON-2 diffractometer. The Raman light spectra were recorded with a DFS-24 double monochromator employing argon laser excitation.

  1. Chiroptical spectra of tetrakis (+)-3-heptafluorobutylrylcamphorate Ln(III) complexes with an encapsulated alkali metal ion: solution structures as revealed by chiroptical spectra.

    PubMed

    Shirotani, Dai; Yamanari, Kazuaki; Kuroda, Reiko; Harada, Takunori; Lunkley, Jamie L; Muller, Gilles; Sato, Hisako; Kaizaki, Sumio

    2012-12-01

    The preparation of tetrakis((+)-hfbc) lanthanide(III) complexes with an encapsulated alkali metal and ammonium ions M[Ln((+)-hfbc)(4)] (hereafter abbreviated as M-Ln : (+)-hfbc, (+)-heptafluorobutyrylcamphorate; M, ammonium or benzyl ammonium ions as well as alkali metal ions) was reported and discussed. The electronic circular dichroism (CD) spectra in the intraligand π-π* transition of M-Ln were examined in view of the solvent effect. Here, the concentration, alkali metal, and ammonium ion dependences are compared with the solid CD, (5)D(0)←(7)F(0) (Eu(III)) excitation spectra, circularly polarized luminescence, and vibrational circular dichroism. It has been revealed that the dodecahedral eight coordinate DD-8-M-Ln complexes in crystals are equilibrated between the diastereoselectively formed square antiprism eight coordinate SAPR-8-M-Ln and [Ln((+)-hfbc)(3)] in EtOH and CH(3) CN solutions or between the SAPR-8-M-Ln and DD-D(2d) (mmmm)-8-M-Ln complexes in CHCl(3) solution. The observed CD couplets are found to reflect the exciton CD couplets which are useful to determine the four-bladed SAPR-(llll) absolute configuration around the lanthanide(III) ion. Copyright © 2012 Wiley Periodicals, Inc.

  2. Corrosion Fatigue Behavior of 316LN SS in Acidified Sodium Chloride Solution at Applied Potential

    NASA Astrophysics Data System (ADS)

    Poonguzhali, A.; Pujar, M. G.; Mallika, C.; Mudali, U. Kamachi

    2015-05-01

    The influence of acidified 1 M NaCl solution by addition of 2 ml/L of HCl on the cyclic plastic deformation of AISI Type 316LN SS containing 0.07 wt.% and 0.22 wt.% N was investigated as a function of the applied potentials. The corrosion fatigue (CF) behavior of stainless steel (SS) was explained vis-a-vis the dislocation behavior, the propensity to form microcracks, and the evolution of the current transients based on the studies carried out at both room-temperature and boiling conditions. CF experiments were conducted using round tensile specimens at a stress ratio of 0.5 and a frequency of 0.1 Hz. Two different kinds of damage mechanisms were observed (I) the damage mechanism in the stable-passive state was correlated with the localization of the anodic dissolution due to a depassivation-repassivation process, whereas (II) the cyclic stress induced pitting corrosion in the metastable pitting state, which resulted in formation of microcracks. The study of the microcracking process and its evolution is a key to the physical mechanism by which the fatigue life of stainless steels would be affected in an aqueous corrosive solution under the applied potential.

  3. Pairing in the BCS and LN approximations using continuum single particle level density

    NASA Astrophysics Data System (ADS)

    Id Betan, R. M.; Repetto, C. E.

    2017-04-01

    Understanding the properties of drip line nuclei requires to take into account the correlations with the continuum spectrum of energy of the system. This paper has the purpose to show that the continuum single particle level density is a convenient way to consider the pairing correlation in the continuum. Isospin mean-field and isospin pairing strength are used to find the Bardeen-Cooper-Schrieffer (BCS) and Lipkin-Nogami (LN) approximate solutions of the pairing Hamiltonian. Several physical properties of the whole chain of the Tin isotope, as gap parameter, Fermi level, binding energy, and one- and two-neutron separation energies, were calculated and compared with other methods and with experimental data when they exist. It is shown that the use of the continuum single particle level density is an economical way to include explicitly the correlations with the continuum spectrum of energy in large scale mass calculation. It is also shown that the computed properties are in good agreement with experimental data and with more sophisticated treatment of the pairing interaction.

  4. Ultrastrong Alkali-Resisting Lanthanide-Zeolites Assembled by [Ln60] Nanocages.

    PubMed

    Dong, Jie; Cui, Ping; Shi, Peng-Fei; Cheng, Peng; Zhao, Bin

    2015-12-30

    Zeolites, as one of the most important porous materials, are most widely utilized in sorbents, catalysis, and ion-exchange fields. However, the multi-functional lanthanide-zeolites constructed exclusively by lanthanide ions and oxygen linkers are to our knowledge unknown hitherto. Herein, we, for the first time, report the unique structure and multifunctions of lanthanide zeolites (1·Gd, 1·Tb, 1·Dy), featuring 60 nuclear [Ln60] nanocages as building blocks and ultrastrong alkali-resisting. These compounds possess extremely high stability and still retain single crystallinity after treatment in boiling water, 0.1 M HCl, and 20 M NaOH aqueous solutions. Magnetic studies revealed 1·Gd has large magnetocaloric effect with -ΔSm(max) = 66.5 J kg(-1) K(-1), falling among the largest values known to date. Importantly, these lanthanide-zeolites themselves can efficiently catalyze the cycloaddition of CO2 with epoxides under mild conditions. Our finding extends the conventional zeolites to lanthanide counterparts, opening a new space for seeking novel and/or multifunctional zeolites.

  5. Cold work study on a 316LN modified alloy for the ITER TF coil conduit

    DOE PAGES

    Walsh, Robert; Toplosky, V. J.; McRae, D. M.; ...

    2012-06-01

    The primary structural component of the cable-in-conduit conductor (CICC) magnets, such as the ITER TF coils is the conduit. This function creates requirements for 4 K strength, toughness, fatigue crack resistance, and ductility after exposure to the superconductor's reaction heat treatment. The tensile ductility of a steel is a quality factor related to fatigue and fracture resistance that can be evaluated more economically with tensile tests rather than fatigue and fracture tests. We subject 316LN modified base metal and welds to a range of cold work from 0% to 20% and a subsequent Nb3Sn reaction heat treatment to evaluate themore » effects on the tensile properties. With the addition of cold work, the 4 K yield strength increases while tensile elongation decreases in both the base metal and weld. Our results are compared to previously published data on the same alloy to evaluate the use of tensile ductility parameters as a materials qualification specification in magnet design.« less

  6. LnPO4 nanoparticles doped with Ac-225 and sequestered daughters for targeted alpha therapy.

    PubMed

    McLaughlin, Mark F; Robertson, David; Pevsner, Paul H; Wall, Jonathan S; Mirzadeh, Saed; Kennel, Stephen J

    2014-02-01

    For targeted alpha therapy (TAT) with 225Ac, daughter radioisotopes from the parent emissions should be controlled. Here, we report on a second-generation layered nanoparticle (NP) with improved daughter retention that can mediate TAT of lung tumor colonies. NPs of La3+, Gd3+, and 225Ac3+ ions were coated with additional layers of GdPO4 and then coated with gold via citrate reduction of NaAuCl4. MAb 201b, targeting thrombomodulin in lung endothelium, was added to a polyethylene glycol (dPEG)-COOH linker. The NPs:mAb ratio was quantified by labeling the mAb with 125I. NPs showed 30% injected dose/organ antibody-mediated uptake in the lung, which increased to 47% in mice pretreated with clodronate liposomes to reduce phagocytosis. Retention of daughter 213Bi in lung tissue was more than 70% at one hour and about 90% at 24 hours postinjection. Treatment of mice with lung-targeted 225Ac NP reduced EMT-6 lung colonies relative to cold antibody competition for targeting or phosphate-buffered saline injected controls. We conclude that LnPO4 NPs represent a viable solution to deliver the 225Ac as an in vivo α generator. The NPs successfully retain a large percentage of the daughter products without compromising the tumoricidal properties of the α-radiation.

  7. Effects of Different Forging Processes on Microstructure Evolution for 316LN Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Sui, Dashan; Zhu, Lingling; Wang, Tao; Zhang, Peipei; Cui, Zhenshan

    2017-10-01

    Forging experiments were designed and carried out on a 3150 kN hydraulic press to investigate the effects of different processes on the microstructure evolution for 316LN steel. The forging processes included single-pass (upsetting) and multipass (stretching) deformations, and the experimental results indicated that the average grain size varied with forging processes. Moreover, the size had distinct differences at different positions in the workpiece. Meanwhile, numerical simulations were implemented to study the influence of temperature, strain, and strain rate on microstructure evolution. The results of experiments and simulations comprehensively demonstrated that dynamic, static, and meta-dynamic recrystallization could coexist in the hot forging process and that the recrystallization process could easily occur under the conditions of higher temperature, larger strain, and higher strain rate. Moreover, the temperature had more significant influence on both recrystallization and grain growth. A higher temperature could not only promote the recrystallization but also speed up the grain growth. Therefore, a lower temperature is beneficial to obtain refinement grains on the premise that the recrystallization can occur completely.

  8. Effects of pre-creep on the dislocations of 316LN Austenite stainless steel

    NASA Astrophysics Data System (ADS)

    Pei, Hai-xiang; Hui, Jun; Hua, Hou; Feng, Zai-xin; Xu, Xiao-long

    2017-09-01

    The 316LN Austenite stainless steels (316LNASS) were pre-creep treated, the evolution of microstructure were investigated. The samples were pre-creep at 593 K and from 500 to 2000 h at 873 K with a stress in the range of 20 to 150 MPa, Then the evolution of microstructure and precipitation were investigated by optical microscope (OM), and transmission electron microscope (TEM). The results show that the crystal surface slipping resulted in dislocations and original dislocations decomposition during the pre-creep process, and generate quadrilateral or hexagonal dislocation network was obviously. The sub-grain boundary gradually became narrow with the increasing of pre-creep treatment time and temperature. When the pre-creep temperature was 593 K and 873 K, dislocation network gradually disappear with the increasing of pre-creep time and load. When the pre-creep temperature was 873 K under 120 MPa, and the treatment time was 2000 h, the hexagonal dislocation network (HDN) would completely disappeared. When the pre-creep temperature was 593 K under 20 MPa, and the treatment time was 500 h, the quadrilateral dislocation network (QDN) would completely disappeared.

  9. Cold work study on a 316LN modified alloy for the ITER TF coil conduit

    SciTech Connect

    Walsh, Robert; Toplosky, V. J.; McRae, D. M.; Han, K.; Martovetsky, N. N.

    2012-06-01

    The primary structural component of the cable-in-conduit conductor (CICC) magnets, such as the ITER TF coils is the conduit. This function creates requirements for 4 K strength, toughness, fatigue crack resistance, and ductility after exposure to the superconductor's reaction heat treatment. The tensile ductility of a steel is a quality factor related to fatigue and fracture resistance that can be evaluated more economically with tensile tests rather than fatigue and fracture tests. We subject 316LN modified base metal and welds to a range of cold work from 0% to 20% and a subsequent Nb3Sn reaction heat treatment to evaluate the effects on the tensile properties. With the addition of cold work, the 4 K yield strength increases while tensile elongation decreases in both the base metal and weld. Our results are compared to previously published data on the same alloy to evaluate the use of tensile ductility parameters as a materials qualification specification in magnet design.

  10. Optimization of hybrid laser - TIG welding of 316LN steel using response surface methodology (RSM)

    NASA Astrophysics Data System (ADS)

    Ragavendran, M.; Chandrasekhar, N.; Ravikumar, R.; Saxena, Rajesh; Vasudevan, M.; Bhaduri, A. K.

    2017-07-01

    In the present study, the hybrid laser - TIG welding parameters for welding of 316LN austenitic stainless steel have been investigated by combining a pulsed laser beam with a TIG welding heat source at the weld pool. Laser power, pulse frequency, pulse duration, TIG current were presumed as the welding process parameters whereas weld bead width, weld cross-sectional area and depth of penetration (DOP) were considered as the process responses. Central composite design was used to complete the design matrix and welding experiments were conducted based on the design matrix. Weld bead measurements were then carried out to generate the dataset. Multiple regression models correlating the process parameters with the responses have been developed. The accuracy of the models were found to be good. Then, the desirability approach optimization technique was employed for determining the optimum process parameters to obtain the desired weld bead profile. Validation experiments were then carried out from the determined optimum process parameters. There was good agreement between the predicted and measured values.

  11. Effects of Different Forging Processes on Microstructure Evolution for 316LN Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Sui, Dashan; Zhu, Lingling; Wang, Tao; Zhang, Peipei; Cui, Zhenshan

    2017-07-01

    Forging experiments were designed and carried out on a 3150 kN hydraulic press to investigate the effects of different processes on the microstructure evolution for 316LN steel. The forging processes included single-pass (upsetting) and multipass (stretching) deformations, and the experimental results indicated that the average grain size varied with forging processes. Moreover, the size had distinct differences at different positions in the workpiece. Meanwhile, numerical simulations were implemented to study the influence of temperature, strain, and strain rate on microstructure evolution. The results of experiments and simulations comprehensively demonstrated that dynamic, static, and meta-dynamic recrystallization could coexist in the hot forging process and that the recrystallization process could easily occur under the conditions of higher temperature, larger strain, and higher strain rate. Moreover, the temperature had more significant influence on both recrystallization and grain growth. A higher temperature could not only promote the recrystallization but also speed up the grain growth. Therefore, a lower temperature is beneficial to obtain refinement grains on the premise that the recrystallization can occur completely.

  12. Antifatigue Effect of Luteolin-6-C-Neohesperidoside on Oxidative Stress Injury Induced by Forced Swimming of Rats through Modulation of Nrf2/ARE Signaling Pathways

    PubMed Central

    Duan, Fang-fang; Guo, Ying; Li, Jing-wan

    2017-01-01

    Luteolin-6-C-neohesperidoside (LN) is a flavonoid isolated from moso bamboo leaf. This study was performed to evaluate the antifatigue effect of LN on a rat model undergoing the weight-loaded forced swimming test (FST). Briefly, male Sprague-Dawley rats (20–22 weeks old) were forced to undertake exhaustive swimming every other day for 3 weeks. Each swimming session was followed by the administration of distilled water, LN (25–75 mg/kg), or ascorbic acid (100 mg/kg) 1 h later. Oral administration of LN significantly improved exercise endurance; normalized alterations in energy metabolic markers; and decreased serum lactic acid, lactate dehydrogenase, and blood urea nitrogen levels of rats that underwent FST. Moreover, LN enhanced the activities of antioxidant enzymes and antioxidant capacity, as measured by enzyme activity assays, RT-PCR, and Western blotting, as well as decreasing the levels of proinflammatory cytokines such as tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6 and increasing the level of anti-inflammatory (IL-10) in the liver and skeletal muscle. These results suggested that LN reduces both physical and mental effects of chronic fatigue, probably by attenuating oxidative stress injury and inflammatory responses in the liver and skeletal muscle. This study thus supports the use of LN in functional foods for antifatigue and antioxidant effects. PMID:28588747

  13. Syntheses, structures, and properties of high-nuclear 3d-4f clusters with amino acid as ligand: {Gd6Cu24}, {Tb6Cu26}, and {(Ln6Cu24)2Cu} (Ln = Sm, Gd).

    PubMed

    Zhang, Jian-Jun; Hu, Sheng-Min; Xiang, Sheng-Chang; Sheng, Tianlu; Wu, Xin-Tao; Li, Ya-Min

    2006-09-04

    Four novel high-nuclear 3d-4f heterometallic clusters were obtained through the self-assembly of Ln(III), Cu(II), and amino acid ligands (2-methylalanine (mAla), glycine (Gly), and L-proline (Pro), respectively). The metal skeleton of cluster 1, [Gd6Cu24(mu3-OH)30(mAla)16(ClO4)(H2O)22].(ClO4)17.(OH)2.(H2O)2(0), may be described as a huge {Gd6Cu12} octahedron connected with 12 additional Cu(II) ions. The structure of cluster 2, Na4[Tb6Cu26(mu3-OH)30(Gly)18(ClO4)(H2O)22].(ClO4)25.(H2O)42, may be described as a {Tb6Cu24} main structure connected with two [Cu(Gly)(H2O)2]+ groups. Compounds {[Ln6Cu24(mu3-OH)30(Pro)12(Ac)6(ClO4)(H2O)13]2Cu(Pro)2}.(ClO4)18.(OH)16.(H2O)55 (Ln= Sm (3), Gd (4)) are 61-nuclear clusters, which represent the largest known 3d-4f clusters so far, the structure can be described as two {Ln6Cu24} octahedral units connected by a trans-Cu(proline)2 bridge. The electrical conductivity measurements reveal that they are temperature-sensitive semiconductors. The magnetic susceptibility measurements display that compound 4 is ferromagnetic.

  14. Hydrothermal synthesis of 4ZnO·B2O3·H2O:Ln(3+) (Ln=Eu, Tb) phosphors: Morphology-tunable and luminescence properties.

    PubMed

    Cao, Shiwei; Jiao, Yang; Han, Weifang; Ge, Chunhua; Song, Bo; Wang, Jie; Zhang, Xiangdong

    2017-09-18

    4ZnO·B2O3·H2O:Ln(3+) (Ln=Eu, Tb) phosphors with different morphologies have been successfully synthesized via one-step hydrothermal method through regulating the molar amount of Eu(3+) and Tb(3+). Comprehensive scanning electron microscopy (SEM), X-ray diffraction (XRD) Fourier transform infrared spectrum (FT-IR) and inductively coupled plasma atomic emission spectrometer (ICP-AES) characterizations all confirm that obtained products are 4ZnO·B2O3·H2O:Ln(3+) (Ln=Eu, Tb). The experimental results displayed that the morphology and photoluminescence of compounds is regularly changed with increased the molar amount of rare earth ions. For the Eu(3+)-doped, Tb(3+)-doped and Eu(3+)/Tb(3+) co-doped 4ZnO·B2O3·H2O phosphors of morphologies, the rod-like structures gradually changed to flower-like structures, fine wire-like structure and hybrid structure, respectively. To their photoluminescence, the Eu(3+) shows a red emission (615nm); the Tb(3+) shows a green emission (545nm); for the Eu(3+)/Tb(3+) co-doped 4ZnO·B2O3·H2O phosphors, a combination of blue (5d-4f of Eu(2+)), green ((5)D4-(7)F5 of Tb(3+)) and red ((5)D0-(7)F2 of Eu(3+)) emissions emerges to achieve white emission. In addition, the energy transfer among Eu(3+), Eu(2+) and Tb(3+) ions was also discussed. Copyright © 2017. Published by Elsevier B.V.

  15. Elucidating the impact of A-site cation change on photocatalytic H2 and O2 evolution activities of perovskite-type LnTaON2 (Ln = La and Pr).

    PubMed

    Hojamberdiev, Mirabbos; Bekheet, Maged F; Hart, Judy N; Vequizo, Junie Jhon M; Yamakata, Akira; Yubuta, Kunio; Gurlo, Aleksander; Hasegawa, Masashi; Domen, Kazunari; Teshima, Katsuya

    2017-08-23

    Transition metal (oxy)nitrides with perovskite-type structures have been regarded as one of the promising classes of inorganic semiconductor materials that can be used in solar water splitting systems for the production of hydrogen as a renewable and storable energy carrier. The performance of transition metal (oxy)nitrides in solar water splitting is strongly influenced by the crystal structure-related dynamics of photogenerated charge carriers. Here, we have systematically assessed the influence of A-site cation exchange on the visible-light-induced photocatalytic H2 and O2 evolution activities, photoanodic response, and dynamics of photogenerated charge carriers of perovskite-type LnTaON2 (Ln = La and Pr). The structural refinement results reveal the orthorhombic Imma and Pnma structures for LaTaON2 and PrTaON2, respectively; the latter has a more distorted crystal structure from the ideal cubic perovskite due to the smaller size of Pr(3+) cations. Compared with LaTaON2, PrTaON2 exhibits lower photocatalytic H2 and O2 gas evolution activities and photoanodic response owing to an excessive amount of intrinsic defects associated with anionic vacancies and reduced tantalum species stemming from a long high-temperature nitridation process under reductive NH3 atmosphere. Transient absorption signals evidence the faster decay of photogenerated electrons (holes) in Pt (CoOx)-loaded LaTaON2 than that in Pt (CoOx)-loaded PrTaON2, consistent with the photocatalytic and photoelectrochemical performance of the two photocatalysts. This study suggests that in addition to selecting a suitable A-site cation, it is prerequisite to synthesize LnTaON2 (Ln = La and Pr) crystals with a low defect density to improve their photo-conversion efficiency for solar water splitting.

  16. Synthesis, Structure, and Physical Properties of Ln(Cu,Al,Ga)13-x (Ln = La-Pr, and Eu) and Eu(Cu,Al)13-x

    SciTech Connect

    Phelan, W Adam; Kangas, Michael J; McCandless, Gregory T; Drake, Brenton L; Haldolaarachchige, Neel; Zhao, Liang L; Wang, Jiakui K; Wang, Xiaoping P; Young, David P; Morosan, Emilia; Hoffmann, Christina; Chan, Julia Y

    2012-09-10

    Ln(Cu,Al,Ga)13–x (Ln = La–Pr, and Eu; x ~ 0.2) were synthesized by a combined Al/Ga flux. Single crystal X-ray and neutron diffraction experiments revealed that these compounds crystallize in the NaZn13 structure-type (space group Fm3⁻c) with lattice parameters of a ~ 12 Å, V ~ 1600 Å, and Z ~ 8. Our final neutron models led us to conclude that Cu is occupationally disordered on the 8b Wyckoff site while Cu, Al, and Ga are substitutionally disordered on the 96i Wyckoff site of this well-known structure-type. The magnetic susceptibility data show that Ce(Cu,Al,Ga)13–x and Pr(Cu,Al,Ga)13–x exhibit paramagnetic behavior down to the lowest temperatures measured while Eu(Cu,Al,Ga)13–x displays ferromagnetic behavior below 6 K. Eu(Cu,Al)13–x was prepared via arc-melting and orders ferromagnetically below 8 K. The magnetocaloric properties of Eu(Cu,Al,Ga)13–x and Eu(Cu,Al)13–x were measured and compared. Additionally, an enhanced value of the Sommerfeld coefficient (γ = 356 mJ/mol-K2) was determined for Pr(Cu,Al,Ga)13–x. Herein, we present the synthesis, structural refinement details, and physical properties of Ln(Cu,Al,Ga)13–x (Ln = La–Pr, and Eu) and Eu(Cu,Al)13–x.

  17. Synthesis, structure, and luminescence property of a series of Ag-Ln coordination polymers with the N-heterocyclic carboxylato ligand

    NASA Astrophysics Data System (ADS)

    Jin, Jing; Chen, Chong; Gao, Yan; Zhao, Ran; Wang, Xiuyan; Lü, Chunxin; Chi, Yuxian; Niu, Shuyun

    2016-03-01

    Six Ln-Ag coordination polymers {[LnAg2(IN)4(H2O)5]·NO3·2H2O}n (Ln=Ho (1) and Tb (2), HIN=isonicotinic acid), {[PrAg2(IN)4(H2O)2]·NO3·H2O}n (3), [LnAg(pdc)2]n (Ln=Eu(4) and Pr (5), H2pdc=3,4-pyridine-dicarboxylic acid) and [NdAg(bidc)2(H2O)4]n (6) (H2bidc=benzimidazole-5,6-dicarboxylic acid) have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR, UV-vis-NIR absorption spectra, fluorescence spectra and thermogravimetric analysis. Structural analyses reveal that the six polymers exhibit 0D (polymer (1)), 1D (polymer (2)), 2D (polymers (3) and (5)) and 3D (polymers (4) and (6)) infinite structures, respectively. Polymers (1)-(6) exhibit the Ln(III) characteristic emission in the near-infrared (NIR) region or in the visible region. Especially, the NIR emission bands of polymers 1, 5 and 6 evidently present shift or splitting due to formation of the Ln-Ag coordination polymers. This can be attributed to the tune of inner levels in Ln-Ag system caused by the interact and influence between the 4d orbital of the Ag(I) ion and the 4f orbital of the Ln(III) ion, which can be confirmed by the UV-vis-NIR absorption spectra of the polymers. In addition, the distortion of coordination geometry as well as difference of the coordination number around the Ag(I) ion affect the structure framework.

  18. Crystal structure of Ln {sub 1/3}NbO{sub 3} (Ln=Nd, Pr) and phase transition in Nd{sub 1/3}NbO{sub 3}

    SciTech Connect

    Zhang Zhaoming Howard, Christopher J.; Kennedy, Brendan J.; Knight, Kevin S.; Zhou Qingdi

    2007-06-15

    The crystal structure of the A-site deficient perovskite Ln {sub 1/3}NbO{sub 3} (Ln=Nd, Pr) at room temperature has been determined, for the first time, as orthorhombic in space group Cmmm using high-resolution neutron powder diffraction. Pertinent features are the alternation of unoccupied layers of A-sites and layers partly occupied by Ln cations, as well as out-of-phase tilting of the NbO{sub 6} octahedra around an axis perpendicular to the direction of the cation/vacancy ordering. The phase transition behaviour of Nd{sub 1/3}NbO{sub 3} has also been studied in situ. This compound undergoes a continuous phase transition at around 650 deg. C to a tetragonal structure in space group P4/mmm due to the disappearance of the octahedral tilting. The analysis of spontaneous strains shows that this phase transition is tricritical in nature. - Graphical abstract: Temperature dependence of the measured lattice parameters through the orthorhombic to tetragonal phase transition in the A-site deficient perovskite Nd{sub 1/3}NbO{sub 3}.

  19. Heterometallic Zn3Ln3 Ensembles Containing (μ6-CO3) Ligand and Triangular Disposition of Ln3+ ions: Single-Molecule Toroic (SMT) and Single-Molecule Magnet (SMM) behavior.

    PubMed

    Chandrasekhar, Vadapalli; Colacio, Enrique; Herrera, J M; Wernsdorfer, W; Lan, Y; Suturina, E; Kuprov, I; Goura, J

    2017-09-11

    Two new heterometallic Zn3Dy3 (Ln3+=Dy, Tb) complexes with a double triangular topology of the metal ions have been assembled from the polytopicMannich base ligand 6,6'-{(2-(dimethylamino) ethyl azanediyl)bis(methylene)}bis(2-methoxy-4-methylphenol) (H2L)with the aidof in situ generated carbonate ligand from atmospheric CO2 fixation. Theoretical calculations indicate axial ground states for the Ln3+ ions in these complexes with their local magnetic moments being almost coplanarand tangential to the Ln3+ atoms defining the equilateral triangle. Therefore, they can be considered as single-molecule toroics (SMTs) with almost zero total magnetic moment.Micro-squid measurements on the Dy3+ counterpart show hysteresis loops below 3 K, which have S-shape with large coercive fields opening upon cooling. This behavior is typical of an SMM with very slow zero field relaxation. At around ±0.35 T, the loops have a broad step, which is due to a direct relaxation process and corresponds to an acceleration of the relaxation of the magnetization also observed at this magnetic field from ac susceptibility measurements. Simulations suggest that the broad step corresponds to two level avoiding crossings points where the spin chiral Kramers doublet meets excited states of the coupled manifold, whose position is defined by exchange and dipole interactions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Simple correction for the sample shape and radial offset effects on SQUID magnetometers: Magnetic measurements on Ln{sub 2}O{sub 3} (Ln=Gd, Dy, Er) standards

    SciTech Connect

    Morrison, Gregory; Loye, Hans-Conrad zur

    2015-01-15

    An increased focus on magnetic measurements of oriented single crystals, thin films, and magnetically dilute systems has led to a demand for the measurement of weak magnetic moments. This level of sensitivity and precision can be achieved on SQUID magnetometers by decreasing the size of the detection coils. However, the smaller detection coils can amplify two errors in the magnitude of the measured moment, the sample shape and radial offset effects, which were small and typically unaccounted for on previous magnetometers. We report a simple method to determine the radial offset of a sample by taking advantage of the two basic scan modes, DC and lock-in, typically used on magnetometers. This technique allows for the correction of the sample shape and radial offset effects in order to obtain the true moment of a sample. To show the efficacy of this technique, we report the magnetic properties of Ln{sub 2}O{sub 3} (Ln=Gd, Dy, Er). - Graphical abstract: Correction for the sample shape and radial offset effects on SQUID magnetometers using a combination of DC and VSM scan data. - Highlights: • Sample shape and radial offset effects alter the moment measured by magnetometers. • We present a simple method to correct for these sample effects on magnetometers. • We measure magnetic susceptibilities of Ln{sub 2}O{sub 3} to show the efficacy of this method.

  1. Structural phase transitions and crystal chemistry of the series Ba{sub 2} LnB'O{sub 6} (Ln=lanthanide and B'=Nb{sup 5+} or Sb{sup 5+})

    SciTech Connect

    Saines, Paul J.; Kennedy, Brendan J. Elcombe, Margaret M.

    2007-02-15

    The structures of 28 compounds in the two series Ba{sub 2} LnSbO{sub 6} and Ba{sub 2} LnNbO{sub 6} have been examined using synchrotron X-ray and in selected cases neutron powder diffraction at, below and above ambient temperature. The antimonate series is found to undergo a sequence of phase transitions from monoclinic to rhombohedral to cubic symmetry with both decreasing ionic radii of the lanthanides and increasing temperature. Compounds in the series Ba{sub 2} LnNbO{sub 6}, on the other hand, feature an intermediate tetragonal structure instead of the rhombohedral structure exhibited by the antimonates. This difference in symmetry is thought to be caused by {pi}-bonding in the niobates that is absent in the antimonates. The bonding environments of the cations in these compounds have also been examined with overbonding of the lanthanide and niobium cations being caused by the unusually large B-site cations. - Graphical abstract: Lattice parameters versus temperature for Ba{sub 2}NdNbO{sub 6}. The formation of the I4/m tetragonal phase contrasts with the antimonate series where a rhombohedral structure occurs instead. This difference is believed to be caused by the presence of {pi}-bonding present in the niobates but absent in the antimonates.

  2. The ionothermal synthesis of metal organic frameworks, Ln(C 9O 6H 3)((CH 3NH) 2CO) 2, using deep eutectic solvents

    NASA Astrophysics Data System (ADS)

    Himeur, Farida; Stein, Irene; Wragg, David S.; Slawin, Alexandra M. Z.; Lightfoot, Philip; Morris, Russell E.

    2010-04-01

    Three new isostructural materials Ln(TMA)(DMU) 2 (Ln(C 9O 6H 3)((CH 3NH) 2CO) 2; Ln: La 1, Nd 2, Eu 3; TMA: trimesate, DMU: dimethylurea) have been synthesised ionothermally using a choline chloride/dimethylurea deep eutectic mixture as the solvent. Normally in ionothermal synthesis the urea portion of the deep eutectic solvent is unstable, breaking down to release ammonium cations that act as templates. In the case of 1- 3, however, the dimethylurea remains intact and is incorporated into the final structure.

  3. The structures and luminescence properties of lanthanide (Ln = Sm, Eu and Tb) metal-organic coordination polymers based on 5-(2-hydroxyethoxy)isophthalate ligand

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Zhang, Yu-Jie; Qin, Jie; Chen, Yong; Zhao, Ying

    2015-03-01

    Three unreported isomorphous Ln-containing metal-organic coordination polymeric complexes {LnL(HL)ṡ(H2O)2}n (Ln = Sm (1), Eu (2) and Tb (3), CCDC 971815-971817) were synthesized based on 5-(2-hydroxyethoxy) isophthalic acid (H2L) under hydrothermal conditions. The obtained coordination polymers were characterized by IR, elemental analysis, thermal analysis and X-ray diffraction In solid state, these polymers featured 3-D supramolecular structures constructed by 2-D sheets through H-bonds. Investigation of photoluminescence properties of H2L and 1-3 showed all of them exhibited intense fluorescent emissions in the solid state at room temperature.

  4. True Tolerance Factor Effects in Ln3+1.85M2+0.15CuO 4 Superconductors

    NASA Astrophysics Data System (ADS)

    McAllister, J. A.; Davies, S.; Attfield, J. P.

    2000-11-01

    A series of seven Ln3+1.85M2+0.15CuO4 samples has been prepared in which mixtures of Ln=La and Nd and M=Ca, Sr, and Ba are used to increase the average radius from 1.180 to 1.223 Å (equivalent to an increase of tolerance factor from 0.856 to 0.871) while the size variance is fixed at a constant value of σ2=0.0020 Å2. X-ray powder diffraction is used to study structural changes, and ac magnetic susceptibility, electrical resistivity, and thermoelectric power measurements show the variation of physical properties as a true function of the tolerance factor.

  5. High-power, narrow-bandwidth mid-infrared PPMgLN optical parametric oscillator with a volume Bragg grating.

    PubMed

    Peng, Yuefeng; Wei, Xingbin; Nie, Zan; Luo, Xingwang; Peng, Jue; Wang, Yong; Shen, Deyuan

    2015-11-30

    We report on a high-power, narrow spectral bandwidth 2.907 µm PPMgLN optical parametric oscillator (OPO) pumped by a 1.064 µm pulsed Nd:YAG MOPA laser source. Free-running operation of the OPO exhibits maximum average output power of 71.6 W at 2.907 µm with a slope efficiency of 26.7%. Broad 2.907 μm spectral bandwidth of the free-running OPO was suppressed from ~9 nm to less than 0.7 nm by using a VBG as one cavity mirror. The maximum average power was 51.7 W at 2907.55 nm for the spectrum-narrowed OPO, corresponding to a slope efficiency of 22.5%. Continuously tunable ranges of ~8 nm around 2.907 µm had been achieved via adjusting the temperatures of the VBG and PPMgLN accordingly.

  6. Luminescent materials derived from the surface-modification of Ln3+-doped zeolite L with a silylated terpyridine

    NASA Astrophysics Data System (ADS)

    Qin, Zhiqiao; Li, Hongshi; Wang, Yige

    2014-11-01

    Herein we report luminescent materials of Ln3+ (Ln = Eu or Tb) doped disc shaped zeolite L crystals (Eu3+/ZLD, Tb3+/ZLD) modified with a silylated terpyridine (Terpy-Si). The modified crystals show bright red emission and green emission under UV-light irradiation due to the energy transfer from the Terpy-Si to the Eu3+ and Tb3+ ions. The obtained materials were characterized with FT-IR, SEM, XRD and elemental analysis. Luminescence spectroscopy was used to study the luminescence properties of the modified Eu3+(Tb3+)/ZLD crystals. The formation of europium(III) and terbium(III) Terpy-Si silicon complexes and energy transfer from Terpy-Si to Eu3+ ions and Tb3+ have been confirmed by luminescence spectroscopy.

  7. Extreme compressibility in LnFe(CN)6 coordination framework materials via molecular gears and torsion springs.

    PubMed

    Duyker, Samuel G; Peterson, Vanessa K; Kearley, Gordon J; Studer, Andrew J; Kepert, Cameron J

    2016-03-01

    The mechanical flexibility of coordination frameworks can lead to a range of highly anomalous structural behaviours. Here, we demonstrate the extreme compressibility of the LnFe(CN)6 frameworks (Ln = Ho, Lu or Y), which reversibly compress by 20% in volume under the relatively low pressure of 1 GPa, one of the largest known pressure responses for any crystalline material. We delineate in detail the mechanism for this high compressibility, where the LnN6 units act like torsion springs synchronized by rigid Fe(CN)6 units performing the role of gears. The materials also show significant negative linear compressibility via a cam-like effect. The torsional mechanism is fundamentally distinct from the deformation mechanisms prevalent in other flexible solids and relies on competition between locally unstable metal coordination geometries and the constraints of the framework connectivity, a discovery that has implications for the strategic design of new materials with exceptional mechanical properties.

  8. LN2-free Operation of the MEG Liquid Xenon Calorimeter by using a High-power Pulse Tube Cryocooler

    SciTech Connect

    Haruyama, T.; Kasami, K.; Nishiguchi, H.; Mihara, S.; Mori, T.; Otani, W.; Sawada, R.; Maruno, Y.; Nishitani, T.

    2006-04-27

    A high-power coaxial pulse tube cryocooler, originally developed in KEK and technology-transferred to Iwatani Industrial Gases Corp (IIGC), has been installed in a large liquid xenon calorimeter to evaluate liquid nitrogen-free (LN2-free) operation of the rare {mu}-particle decay experiment (MEG). Features of this pulse tube cryocooler include the cold-end heat exchanger, designed with sufficient surface area to ensure high-power cooling, and a cylindrical regenerator placed inside the pulse tube giving compact design and ease of fabrication. This production-level cryocooler provides a cooling power of {approx}200 W at 165 K, using a 6 kW Gifford-McMahon (GM)-type compressor. The paper describes the detailed configuration of the cryocooler, and the results of the continuous LN2-free operation of the large prototype liquid xenon calorimeter, which ran for more than 40 days without problems.

  9. High-power and widely tunable mid-infrared optical parametric amplification based on PPMgLN.

    PubMed

    Peng, Yuefeng; Wei, Xingbin; Luo, Xingwang; Nie, Zan; Peng, Jue; Wang, Yong; Shen, Deyuan

    2016-01-01

    We report on a high-power and widely tunable optical parametric amplifier (OPA) based on PPMgLN and pumped by a pulsed 1.064 μm MOPA laser. The operating wavelength of the OPA system is continuously tunable from 2.68 to 3.07 μm by adjusting the temperature of PPMgLN crystals, with average output power varying from 74.6 to 66.7 W for 310 W of pump power, corresponding to an optical-to-optical conversion efficiency of ∼22.8% at 2.68 μm and ∼20.5% at 3.07 μm, respectively. Output beam quality factor (M2) of the OPA was measured to be <4 over the whole tuning range.

  10. Aqueous Binary Lanthanide(III) Nitrate Ln(NO3)3 Electrolytes Revisited: Extended Pitzer and Bromley Treatments

    SciTech Connect

    Chatterjee, Sayandev; Campbell, Emily L.; Neiner, Doinita; Pence, Natasha; Robinson, Troy; Levitskaia, Tatiana G.

    2015-09-11

    To date, only limited thermodynamic models describing activity coefficients of the aqueous solutions of lanthanide ions are available. This work expands the existing experimental osmotic coefficient data obtained by classical isopiestic technique for the aqueous binary trivalent lanthanide nitrate Ln(NO3)3 solutions using a combination of water activity and vapor pressure osmometry measurements. The combined osmotic coefficient database for each aqueous lanthanide nitrate at 25°C, consisting of literature available data as well as data obtained in this work, was used to test the validity of Pitzer and Bromley thermodynamic models for the accurate prediction of mean molal activity coefficients of the Ln(NO3)3 solutions in wide concentration ranges. The new and improved Pitzer and Bromley parameters were calculated. It was established that the Ln(NO3)3 activity coefficients in the solutions with ionic strength up to 12 mol kg-1 can be estimated by both Pitzer and single-parameter Bromley models, even though the latter provides for more accurate prediction, particularly in the lower ionic strength regime (up to 6 mol kg-1). On the other hand for the concentrated solutions, the extended three-parameter Bromley model can be employed to predict the Ln(NO3)3 activity coefficients with remarkable accuracy. The accuracy of the extended Bromley model in predicting the activity coefficients was greater than ~95% and ~90% for all solutions with the ionic strength up to 12 mol kg-1 and and 20 mol kg-1, respectively. This is the first time that the activity coefficients for concentrated lanthanide solutions have been predicted with such a remarkable accuracy.

  11. Energy transfer to Ln 3+ in GaS 1-xSe x(0 ⩽ x ⩽ 1) crystals

    NASA Astrophysics Data System (ADS)

    Tagiev, B. G.; Aidaev, F. Sh.; Abbasova, T. M.

    1988-04-01

    The paper deals with the matrix mechanism of excitation energy transfer to rare-earth centres in GaS xSe 1- x crystals. Energy transfer to Ln 3+ is shown to be radiationless in GaS 1- xSe x (0 ⩽ x ⩽ 1) single crystals and to come about predominantly by resonance, involving local states of the matrix forbidden band.

  12. TES/Aura L2 Ammonia (NH3) Lite Nadir V6 (TL2NH3LN)

    Atmospheric Science Data Center

    2017-07-20

    TES/Aura L2 Ammonia (NH3) Lite Nadir (TL2NH3LN) News:  TES News ... Level:  L2 Instrument:  TES/Aura L2 Ammonia Spatial Coverage:  5.3 km nadir Spatial ... OPeNDAP Access:  OPeNDAP Parameters:  Ammonia Order Data:  Earthdata Search:   Order Data ...

  13. TES/Aura L2 Methane (CH4) Lite Nadir V6 (TL2CH4LN)

    Atmospheric Science Data Center

    2017-07-20

    TES/Aura L2 Methane (CH4) Lite Nadir (TL2CH4LN) News:  TES News ... Level:  L2 Instrument:  TES/Aura L2 Methane Spatial Coverage:  5.3 km nadir Spatial ... OPeNDAP Access:  OPeNDAP Parameters:  Methane Order Data:  Earthdata Search:   Order Data ...

  14. TES/Aura L2 Carbon Dioxide (CO2) Lite Nadir V6 (TL2CO2LN)

    Atmospheric Science Data Center

    2017-07-19

    TES/Aura L2 Carbon Dioxide (CO2) Lite Nadir (TL2CO2LN) News:  TES ... Level:  L2 Instrument:  TES/Aura L2 Carbon Dioxide Spatial Coverage:  5.3 km nadir ... OPeNDAP Access:  OPeNDAP Parameters:  Carbon Dioxide Order Data:  Earthdata Search:   Order Data ...

  15. Systematic and in situ energy dispersive X-ray diffraction investigations on the formation of lanthanide phosphonatobutanesulfonates: Ln(O(3)P-C(4)H(8)-SO(3))(H(2)O) (Ln = La-Gd).

    PubMed

    Feyand, Mark; Näther, Christian; Rothkirch, André; Stock, Norbert

    2010-12-06

    Using the flexible linker H(2)O(3)P-C(4)H(8)-SO(3)H (H(3)L) and rare earth ions Ln(3+) (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) we were able to synthesize the new isostructural inorganic organic hybrid compounds Ln(O(3)P-C(4)H(8)-SO(3))(H(2)O). High-throughput experiments were employed to study the influence of the molar ratios Ln:H(3)L and pH on the product formation. The crystal structure of the compounds Sm(O(3)P-C(4)H(8)-SO(3))(H(2)O) (1) and Pr(O(3)P-C(4)H(8)-SO(3))(H(2)O) (2) were determined by single crystal diffraction. The structures are built up from chains of edge-sharing LnO(8)-polyhedra that are connected by the phosphonate and sulfonate groups into layers. These layers are linked by the -(CH(2))(4)- group to form a three-dimensional framework. The synthesis of compound 1 was scaled up in a conventional oven as well as in a microwave reactor system. A modification of a microwave reactor system allowed its integration into the beamline F3 at HASYLAB, DESY, Hamburg. The crystallization was investigated in situ by means of energy dispersive X-ray diffraction using conventional as well as microwave heating methods applying temperatures varying from 110 to 150 °C. The formation of Sm(O(3)P-C(4)H(8)-SO(3))(H(2)O) takes place in two steps. In the first step a crystalline intermediate was observed, which transforms completely into compound 1. The method by Sharp and Hancock was used to determine the rate constants, reaction exponents, and the Arrhenius activation energy for both reaction steps. Comparing both heating methods, microwave heating leads to fully crystallized reaction product after shorter reaction times, but neither the temperature nor the heating method has significant influence on the induction time.

  16. Research on Flow Stress During Hot Deformation Process and Processing Map for 316LN Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Guo, Baofeng; Ji, Haipeng; Liu, Xingang; Gao, Lu; Dong, Rongmei; Jin, Miao; Zhang, Qinghua

    2012-07-01

    In this study, the hot deformation behavior of austenitic stainless steel was investigated using Gleeble-3500 thermomechanical simulator at deformation temperatures in the range of 900-1200 °C and strain rates in the range of 0.001-10 s-1. The effects of initial austenitic grain size and deformation conditions on hot deformation behavior of 316LN were analyzed through true stress-strain curves under different deformation conditions. Both the constitutive equation and processing map for 316LN were obtained. The results show that, with the increase of the deformation temperature and the decrease of the strain rate, the peak stress decreases, and the initial austenitic grain size has a little influence on the peak stress. The relative error between the peak stress values calculated using the constitutive equation and the values measured is less than 10%. Using the processing map, the best hot-working condition for 316LN in the range of experimental deformation parameters appears when T = 1200 °C and dot{\\upvarepsilon } = 0.001 {{s}}^{-1}.

  17. Spin-communication channels between Ln(III) bis-phthalocyanines molecular nanomagnets and a magnetic substrate

    PubMed Central

    Candini, A.; Klar, D.; Marocchi, S.; Corradini, V.; Biagi, R.; De Renzi, V.; del Pennino, U.; Troiani, F.; Bellini, V.; Klyatskaya, S.; Ruben, M.; Kummer, K.; Brookes, N. B.; Huang, H.; Soncini, A.; Wende, H.; Affronte, M.

    2016-01-01

    Learning the art of exploiting the interplay between different units at the atomic scale is a fundamental step in the realization of functional nano-architectures and interfaces. In this context, understanding and controlling the magnetic coupling between molecular centers and their environment is still a challenging task. Here we present a combined experimental-theoretical work on the prototypical case of the bis(phthalocyaninato)-lanthanide(III) (LnPc2) molecular nanomagnets magnetically coupled to a Ni substrate. By means of X-ray magnetic circular dichroism we show how the coupling strength can be tuned by changing the Ln ion. The microscopic parameters of the system are determined by ab-initio calculations and then used in a spin Hamiltonian approach to interpret the experimental data. By this combined approach we identify the features of the spin communication channel: the spin path is first realized by the mediation of the external (5d) electrons of the Ln ion, keeping the characteristic features of the inner 4 f orbitals unaffected, then through the organic ligand, acting as a bridge to the external world. PMID:26907811

  18. Solution properties of the Ln(III) complexes of a novel octadentate chelator with rigidified iminodiacetate arms.

    PubMed

    Tei, Lorenzo; Baranyai, Zsolt; Cassino, Claudio; Fekete, Marianna; Kálmán, Ferenc K; Botta, Mauro

    2012-11-07

    A novel octadentate ligand derived from the core structure of EGTA (ethyleneglycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid) with two piperidine-cis-dicarboxylic acid moieties spaced by a triethylenedioxy chain (L1) has been synthesised with the aim to assess the effect of the structural rigidity on the thermodynamic and kinetic stabilities of its Ln(III) complexes. The stability constants of [Ln(L1)](-) complexes show a weaker binding affinity for Ln(3+) ions of L1 than EGTA. On the other hand, the selectivity of L1 for Ca(2+) over Mg(2+) is one of the highest ever reported. The kinetic inertness has been also investigated and faster rates of both acid catalysed and metal assisted decomplexation have been measured for [Gd(L1)](-) as compared to [Gd(EGTA)](-). The (1)H- and (13)C NMR spectra of the diamagnetic La(3+), Y(3+) and Lu(3+) complexes in aqueous media show pronounced stereochemical rigidity and the occurrence of a structural change across the lanthanide series. Finally, a complete (1)H and (17)O NMR relaxometric study indicates that [Gd(L1)](-) possesses a nine-coordinate ground state with one inner coordination sphere water molecule characterized by a fast rate of exchange ((298)k(ex) = 59 × 10(6) s(-1)).

  19. A comparative evaluation of welding consumables for dissimilar weids between 316LN austenitic stainless steel and Alloy 800

    NASA Astrophysics Data System (ADS)

    Sireesha, M.; Albert, Shaju K.; Shankar, V.; Sundaresan, S.

    2000-03-01

    Transition joints in power plants between ferritic steels and austenitic stainless steels suffer from a mismatch in coefficients of thermal expansion (CTE) and the migration of carbon during service from the ferritic to the austenitic steel. To overcome these, nickel-based consumables are commonly used. The use of a trimetallic combination with an insert piece of intermediate CTE provides for a more effective lowering of thermal stresses. The current work envisages a trimetallic joint involving modified 9Cr-1Mo steel and 316LN austenitic stainless steel as the base materials and Alloy 800 as the intermediate piece. Of the two joints involved, this paper describes the choice of welding consumables for the joint between Alloy 800 and 316LN. Four consumables were examined: 316, 16-8-2, Inconel 82 and Inconel 182. The comparative evaluation was based on hot cracking tests and estimation of mechanical properties and coefficient of thermal expansion. While 16-8-2 exhibited highest resistance to solidification cracking, the Inconel filler materials also showed adequate resistance; additionally, the latter were superior from the mechanical property and coefficient of thermal expansion view-points. It is therefore concluded that for the joint between Alloy 800 and 316LN the Inconel filler materials offer the best compromise.

  20. Operation of bare HPGe detectors in LAr/LN2 for the GERDA experiment

    NASA Astrophysics Data System (ADS)

    Barnabé Heider, M.; Cattadori, C.; Chkvorets, O.; di Vacri, A.; Gusev, K.; Schönert, S.; Shirchenko, M.

    2008-11-01

    rate of LAr ionization which however is reversible. The radiation induced LC is believed to produce pairs of Ar+/e- that are drifted towards the passivation layer by the diode bias electric field (E) dispersed in LAr. In fact, E, numerically calculated by the Maxwell 2D code, resulted strong enough to drift charges before recombination, in the volume surrounding the passivation layer. Charges collected and trapped at the passivation layer cause a decrease of the its resistivity, i.e. an increase of the surface LC. The increase rate depends on the charge collection rate, on the density of trapped charge and on the starting value of the passivation layer resistivity. To study this mechanism two other detector configurations were tested. They have been irradiated in LAr to investigate the influence of both geometry and extension of the passivation layer and measurements with prototype 1 have been also repeated in LN2: prototype 2 (passivation layer only in the groove) shows a ~30 times lower LC increase rate than the case of prototype 1; prototype 3 (no passivation layer) does not show any increase of LC and prototype 1 operated in LN2 does not show any increase. The observed LC is cured by irradiation without HV, explained either by γ ionization of the passivation layer or by effect of the UV LAr scintillation light.

  1. Analyses of Transient and Tertiary Small Punch Creep Deformation of 316LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Ganesh Kumar, J.; Ganesan, V.; Laha, K.

    2016-09-01

    Creep deformation behavior of 316LN stainless steel (SS) under small punch creep (SPC) and uniaxial creep test has been assessed and compared at 923 K (650 °C). The transient and tertiary creep deformation behaviors have been analyzed according to the equation proposed for SPC deflection, δ = δ0 + δ_{{T}} \\cdot (1 - {{e}}^{ - κ \\cdot t} ) + dot{δ }_{{s}} t + δ3 {{e}}^{{[ {φ ( {t - t_{{r}} } )} ]}} on the basis of Dobes and Cadek equation for uniaxial creep strain. Trends in the variations of (i) rate of exhaustion of transient creep ( κ) with steady-state deflection rate ( dot{δ }_{{s}} ) (ii) ` κ' with time to attain steady-state deflection rate, and (iii) initial creep deflection rate with steady-state deflection rate implied that transient SPC deformation obeyed first-order reaction rate theory. The rate of exhaustion of transient creep ( r') values that were determined from uniaxial creep tests were correlated with those obtained from SPC tests. Master curves representing transient creep deformation in both SPC and uniaxial creep tests have been derived and their near coincidence brings unique equivalence between both the test techniques. The relationships between (i) rate of acceleration of tertiary creep ( φ) and steady-state deflection rate, (ii) ` φ' and time spent in tertiary stage, and (iii) final creep deflection rate and steady-state deflection rate revealed that first-order reaction rate theory governed SPC deformation throughout the tertiary region also. Interrelationship between the transient, secondary, and tertiary creep parameters indicated that the same mechanism prevailed throughout the SPC deformation.

  2. Synthesis of water-soluble luminescent LaVO4:Ln3+ porous nanoparticles

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Labis, Joselito P.; Alrokayan, Salman A. H.

    2012-08-01

    Water-soluble luminescent Eu3+ and Tb3+-doped LaVO4 porous nanoparticles were synthesized by co-precipitation method. X-ray diffraction (XRD), Field emission-transmission electron microscopy (FE-TEM), energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, UV/Vis absorption, and photoluminescence spectroscopic techniques were employed to characterize the structure and morphology of as-prepared products. The results of the XRD confirm the formation of well-crystallized LaVO4 phase with a tetragonal zircon structure. The TEM images illustrate that the as-formed Eu3+ and Tb3+-doped LaVO4 nanoparticles have irregular spherical shape, hairy nanoporous structures with an average particle size 50-130 nm. These nanoparticles were well-dispersed in polar and non-polar organic solvents to form clear colloidal solutions. The colloidal solutions of Eu3+ and Tb3+-doped zircon-type LaVO4 nanoparticles show the most dominant characteristic emissions (hypersensitive transitions) of Eu3+ at 615 nm (5 D 0 → 7 F 2) and Tb3+ at 543 nm (5 D 4 → 7 F 5), respectively, as the result of an energy transfer from the VO4 3- to luminescent metal ions activators. Compared with other-shape nanocrystals, the luminescence intensity of the irregular hairy spherical porous-like nanoparticles are obviously enhanced. It therefore, suggests that we could obtain function-improved materials by tailoring the size and shape of the LaVO4:Ln3+ nanostructures that are very suitable for use in biological applications, such as protein-labeling, drug delivery, and fluorescent bioprobes.

  3. Synthesis, structure, and magnetism of heterobimetallic trinuclear complexes {[L2Co2Ln][X]} [Ln = Eu, X = Cl; Ln = Tb, Dy, Ho, X = NO3; LH3 = (S)P[N(Me)N=CH-C6H3-2-OH-3-OMe]3]: A 3d-4f family of single-molecule magnets.

    PubMed

    Chandrasekhar, Vadapalli; Pandian, Balasubramanian Murugesa; Vittal, Jagadese J; Clérac, Rodolphe

    2009-02-02

    Sequential reaction of LH3 (LH3 = (S)P[N(Me)N=CH-C6H3-2-OH-3-OMe]3) with Co(OAc)2 x 4 H2O followed by reaction with lanthanide salts afforded trinuclear heterobimetalllic compounds {[L2Co2Ln][X]} [Ln = Eu (1), X = Cl; Ln = Tb (2), Dy (3), Ho (4), X = NO3] in excellent yields. These compounds retain their integrity in solution as determined by electrospray ionization mass spectrometry studies. The molecular structures of 1-4 were confirmed by a single-crystal X-ray structural study and reveal that these are isostructural. In all of the compounds, the three metal ions are arranged in a perfectly linear manner and are held together by two trianionic ligands, L3-. The two terminal Co(II) ions contain a facial coordination environment (3N, 3O) comprising three imino nitrogen atoms and three phenolate oxygen atoms. The coordination geometry about the cobalt atom is severely distorted. An all-oxygen coordination environment (12O) is present around the central lanthanide ion, which is present in a distorted icosahedral geometry. The coordination sphere around the lanthanide ion is achieved by utilizing three phenolate oxygen atoms and three methoxy oxygen atoms of each ligand. In all of these trinuclear complexes (1-4), the Co-Ln distances are around 3.3 A, while the Co-Co distances range from 6.54 to 6.60 A. The screw-type coordination mode imposed by the ligand induces chirality in the molecular structure, although all of the complexes crystallize as racemates. Magnetic properties of 1-4 have been studied in detail using dc and ac susceptibility measurements. Dynamic measurements reveal that 2-4 display a single-molecule magnet behavior, while the Co2Eu (1) analogue does not show any out-of-phase ac susceptibility.

  4. Crystal structure and dielectric properties of Ca(0.85)Nd(0.1)TiO(3) - LnAlO(3) ceramics.

    PubMed

    Eung, S; Dong, H; Yang, Jun-Mo; Hyung, S; Nur, I; Ohsato, Hitoshi

    2008-05-01

    The microwave dielectric properties of Ca(0.85)Nd(0.1)TiO(3) - LnAlO(3) (Ln = Sm, Gd, Dy, Er) ceramics are investigated in this paper. The structural characteristics of the specimens were evaluated by Rietveld refinement of Xray diffraction (XRD) patterns and high-resolution transmission electron microscopy (HRTEM). Solid solution limits were dependent on the ionic radius of Ln(3+) ions. With the decrease of the ionic radius of the Ln(3+) ions, the thermal stability of the resonant frequency decreases. This can be attributed to the increased level of oxygen octahedral distortion caused by the increase in the B-site bond valence in the ABO(3) perovskite structure. The dielectric constant (K) and the quality factor (Qf) of the specimens were dependent on the polarizability and grain size, respectively.

  5. Solution and solid state structures and magnetism of a series of linear trinuclear compounds with a hexacoordinate Ln(III) and two terminal Ni(II) centers.

    PubMed

    Comba, Peter; Enders, Markus; Großhauser, Michael; Hiller, Markus; Müller, Dennis; Wadepohl, Hubert

    2016-12-20

    Reported are the syntheses, structures and magnetic properties, also by NMR spectroscopy in solution, of a series of 13 linear trinuclear 3d-4f compounds with a lanthanide(iii) surrounded by two Ni(II) ions, NiLn(III), where the central Ln(III) is hexacoordinate. For three of the crystal structures, an additional H2O molecule is coordinated to the central Ln(III) ion, leading to a monocapped trigonal prismatic structure. However, NMR spectroscopy indicates that in solution, these complexes also have a hexacoordinate Ln(III) center. The solution magnetic anisotropies, determined by NMR spectroscopy, indicate that the axial components of the anisotropies are relatively small and that the Dy(III) derivative might therefore not exhibit single molecule magnetism. The axial anisotropies determined by NMR spectroscopy are in good agreement with the expectations based on the distorted trigonal prismatic ligand field.

  6. Homoleptic lanthanide 1,2,3-triazolates (∞)(2–3)[Ln(Tz*)3] and their diversified photoluminescence properties.

    PubMed

    Rybak, J-Christoph; Meyer, Larissa V; Wagenhöfer, Julian; Sextl, Gerhard; Müller-Buschbaum, Klaus

    2012-12-17

    The series of homoleptic lanthanide 1,2,3-triazolates (∞)(3)[Ln(Tz*)3] (Ln3+ = lanthanide cation, Tz*– = 1,2,3-triazolate anion, C2H2N3(–)) is completed by synthesis of the three-dimensional (3D) frameworks with Ln = La, Ce, Pr, Nd, and Sm, and characterization by X-ray powder diffraction, differential thermal analysis-thermogravimetry (DTA/TG) investigations and molecular vibration analysis. In addition, α-(∞)(2)[Sm(Tz*)3], a two-dimensional polymorph of 3D β-(∞)(3)[Sm(Tz*)3], is presented including the single crystal structure. The 3D lanthanide triazolates form an isotypic series of the formula (∞)(3)[Ln(Tz*)3] ranging from La to Lu, with the exception of Eu, which forms a mixed valent metal organic framework (MOF) of different structure and the constitution (∞)(3)[Eu(Tz*)(6+x)(Tz*H)(2–x)]. The main focus of this work is put on the investigation of the photoluminescence behavior of lanthanide 1,2,3-triazolates (∞)(3)[Ln(Tz*)3] and illuminates that six different luminescence phenomena can be found for one series of isotypic compounds. The luminescence behavior of the majority of these compounds is based on the photoluminescence properties of the organic linker molecules. Differing properties are observed for (∞)(3)[Yb(Tz*)3], which exhibits luminescence properties based on charge transfer transitions between the linker and Yb3+ ions, and for (∞)(3)[Ce(Tz*)3] and (∞)(3)[Tb(Tz*)3], in which the luminescence properties are a combination of the ligand and the lanthanide metal. In addition, strong inner-filter effects are found in the ligand emission bands that are attributed to reabsorption of the emitted light by the trivalent lanthanide ions. Antenna effects of varying efficiency are present indicated by the energy being transferred to the lanthanide ions subsequent to excitation of the ligand. (∞)(3)[Ce(Tz*)3] shows a 5d-4f induced intense blue emission upon excitation with UV light, while (∞)(3)[Tb(Tz*)3] shows emission in the green

  7. Genetic and Proteomic Characterization of rpoB Mutations and Their Effect on Nematicidal Activity in Photorhabdus luminescens LN2

    PubMed Central

    Qiu, Xuehong; Yan, Xun; Liu, Mingxing; Han, Richou

    2012-01-01

    Rifampin resistant (RifR) mutants of the insect pathogenic bacterium Photorhabdus luminescens LN2 from entomopathogenic nematode Heterorhabditis indica LN2 were genetically and proteomically characterized. The RifR mutants showed typical phase one characters of Photorhabdus bacteria, and insecticidal activity against Galleria mellonella larvae, but surprisingly influenced their nematicidal activity against axenic infective juveniles (IJs) of H. bacteriophora H06, an incompatible nematode host. 13 out of 34 RifR mutants lost their nematicidal activity against H06 IJs but supported the reproduction of H06 nematodes. 7 nematicidal-producing and 7 non-nematicidal-producing RifR mutants were respectively selected for rpoB sequence analysis. rpoB mutations were found in all 14 RifR mutants. The rpoB (P564L) mutation was found in all 7 mutants which produced nematicidal activity against H06 nematodes, but not in the mutants which supported H06 nematode production. Allelic exchange assays confirmed that the Rif-resistance and the impact on nematicidal activity of LN2 bacteria were conferred by rpoB mutation(s). The non-nematicidal-producing RifR mutant was unable to colonize in the intestines of H06 IJs, but able to colonize in the intestines of its indigenous LN2 IJs. Proteomic analysis revealed different protein expression between wild-type strain and RifR mutants, or between nematicidal-producing and non nematicidal-producing mutants. At least 7 putative proteins including DsbA, HlpA, RhlE, RplC, NamB (a protein from T3SS), and 2 hypothetical proteins (similar to unknown protein YgdH and YggE of Escherichia coli respectively) were probably involved in the nematicidal activity of LN2 bacteria against H06 nematodes. This hypothesis was further confirmed by creating insertion-deletion mutants of three selected corresponding genes (the downregulated rhlE and namB, and upregualted dsbA). These results indicate that the rpoB mutations greatly influence the symbiotic

  8. Evaluation of the long-lasting insecticidal net Interceptor LN: laboratory and experimental hut studies against anopheline and culicine mosquitoes in northeastern Tanzania

    PubMed Central

    2013-01-01

    Background Long lasting insecticidal nets (LN) are a primary method of malaria prevention. Before new types of LN are approved they need to meet quality and efficacy standards set by the WHO Pesticide Evaluation Scheme. The process of evaluation has three phases. In Phase I the candidate LN must meet threshold bioassay criteria after 20 standardized washes. In Phase II washed and unwashed LNs are evaluated in experimental huts against wild, free flying anopheline mosquitoes. In Phase III the LN are distributed to households in malaria endemic areas, sampled over three years of use and tested for continuing insecticidal efficacy. Interceptor® LN (BASF Corporation, Germany) is made of polyester netting coated with a wash resistant formulation of alpha-cypermethrin. Methods Interceptor LN was subjected to bioassay evaluation and then to experimental hut trial against pyrethroid-susceptible Anopheles gambiae and An. funestus and resistant Culex quinquefasciatus. Mosquito mortality, blood feeding inhibition and personal protection were compared between untreated nets, conventional alpha-cypermethrin treated nets (CTN) washed 20 times and LNs washed 0, 20 and 30 times. Results In Phase I Interceptor LN demonstrated superior wash resistance and efficacy to the CTN. In the Phase II hut trial the LN killed 92% of female An. gambiae when unwashed and 76% when washed 20 times; the CTN washed 20 times killed 44%. The LN out-performed the CTN in personal protection and blood-feeding inhibition. The trend for An. funestus was similar to An. gambiae for all outcomes. Few pyrethroid-resistant Cx. quinquefasciatus were killed and yet the level of personal protection (75-90%) against Culex was similar to that of susceptible An. gambiae (76-80%) even after 20 washes. This protection is relevant because Cx. quinquefasciatus is a vector of lymphatic filariasis in East Africa. After 20 washes and 60 nights’ use the LN retained 27% of its initial insecticide dose. Conclusions

  9. Caspase-activated DNase is necessary and sufficient for oligonucleosomal DNA breakdown, but not for chromatin disassembly during caspase-dependent apoptosis of LN-18 glioblastoma cells.

    PubMed

    Sánchez-Osuna, María; Garcia-Belinchón, Mercè; Iglesias-Guimarais, Victoria; Gil-Guiñón, Estel; Casanelles, Elisenda; Yuste, Victor J

    2014-07-04

    Caspase-dependent apoptosis is a controlled type of cell death characterized by oligonucleosomal DNA breakdown and major nuclear morphological alterations. Other kinds of cell death do not share these highly distinctive traits because caspase-activated DNase (DFF40/CAD) remains inactive. Here, we report that human glioblastoma multiforme-derived LN-18 cells do not hydrolyze DNA into oligonucleosomal fragments after apoptotic insult. Furthermore, their chromatin remains packaged into a single mass, with no signs of nuclear fragmentation. However, ultrastructural analysis reveals that nuclear disassembly occurs, although compacted chromatin does not localize into apoptotic nuclear bodies. Caspases become properly activated, and ICAD, the inhibitor of DFF40/CAD, is correctly processed. Using cell-free in vitro assays, we show that chromatin from isolated nuclei of LN-18 cells is suitable for hydrolysis into oligonuclesomal fragments by staurosporine-pretreated SH-SY5Y cytoplasms. However, staurosporine-pretreated LN-18 cytoplasms do not induce DNA laddering in isolated nuclei from either LN-18 or SH-SY5Y cells because LN-18 cells express lower amounts of DFF40/CAD. DFF40/CAD overexpression makes LN-18 cells fully competent to degrade their DNA into oligonucleosome-sized fragments, and yet they remain unable to arrange their chromatin into nuclear clumps after apoptotic insult. Indeed, isolated nuclei from LN-18 cells were resistant to undergoing apoptotic nuclear morphology in vitro. The use of LN-18 cells has uncovered a previously unsuspected cellular model, whereby a caspase-dependent chromatin package is DFF40/CAD-independent, and DFF40/CAD-mediated double-strand DNA fragmentation does not warrant the distribution of the chromatin into apoptotic nuclear bodies. The studies highlight a not-yet reported DFF40/CAD-independent mechanism driving conformational nuclear changes during caspase-dependent cell death.

  10. Caspase-activated DNase Is Necessary and Sufficient for Oligonucleosomal DNA Breakdown, but Not for Chromatin Disassembly during Caspase-dependent Apoptosis of LN-18 Glioblastoma Cells*

    PubMed Central

    Sánchez-Osuna, María; Garcia-Belinchón, Mercè; Iglesias-Guimarais, Victoria; Gil-Guiñón, Estel; Casanelles, Elisenda; Yuste, Victor J.

    2014-01-01

    Caspase-dependent apoptosis is a controlled type of cell death characterized by oligonucleosomal DNA breakdown and major nuclear morphological alterations. Other kinds of cell death do not share these highly distinctive traits because caspase-activated DNase (DFF40/CAD) remains inactive. Here, we report that human glioblastoma multiforme-derived LN-18 cells do not hydrolyze DNA into oligonucleosomal fragments after apoptotic insult. Furthermore, their chromatin remains packaged into a single mass, with no signs of nuclear fragmentation. However, ultrastructural analysis reveals that nuclear disassembly occurs, although compacted chromatin does not localize into apoptotic nuclear bodies. Caspases become properly activated, and ICAD, the inhibitor of DFF40/CAD, is correctly processed. Using cell-free in vitro assays, we show that chromatin from isolated nuclei of LN-18 cells is suitable for hydrolysis into oligonuclesomal fragments by staurosporine-pretreated SH-SY5Y cytoplasms. However, staurosporine-pretreated LN-18 cytoplasms do not induce DNA laddering in isolated nuclei from either LN-18 or SH-SY5Y cells because LN-18 cells express lower amounts of DFF40/CAD. DFF40/CAD overexpression makes LN-18 cells fully competent to degrade their DNA into oligonucleosome-sized fragments, and yet they remain unable to arrange their chromatin into nuclear clumps after apoptotic insult. Indeed, isolated nuclei from LN-18 cells were resistant to undergoing apoptotic nuclear morphology in vitro. The use of LN-18 cells has uncovered a previously unsuspected cellular model, whereby a caspase-dependent chromatin package is DFF40/CAD-independent, and DFF40/CAD-mediated double-strand DNA fragmentation does not warrant the distribution of the chromatin into apoptotic nuclear bodies. The studies highlight a not-yet reported DFF40/CAD-independent mechanism driving conformational nuclear changes during caspase-dependent cell death. PMID:24838313

  11. Synthesis and Crystal Chemistry of HIGH-Tc Oxide Superconductors

    NASA Astrophysics Data System (ADS)

    Cava, R. J.

    The following sections are included: * INTRODUCTION * THE "123" FAMILY * PHASE EQUILIBRIA IN THE Y-Ba-Cu-O SYSTEM * TRANSITION METAL SUBSTITUTIONS IN CUPRATE SUPERCONDUCTORS * THE T, T', AND T* PHASES * La2-xSrxCaCu2O6+δ * THE INFINITE LAYER PHASE * Pb2Sr2LnCu3O8 * BiO AND TlO BASED COPPER OXIDES * OTHER INTERMEDIARY LAYERS * CONCLUSIONS * REFERENCES

  12. Uniform AMoO{sub 4}:Ln (A=Sr{sup 2+}, Ba{sup 2+}; Ln=Eu{sup 3+}, Tb{sup 3+}) submicron particles: Solvothermal synthesis and luminescent properties

    SciTech Connect

    Yang Piaoping; Li Chunxia; Wang Wenxin; Quan Zewei; Gai Shili; Lin Jun

    2009-09-15

    Rare-earth ions (Eu{sup 3+}, Tb{sup 3+}) doped AMoO{sub 4} (A=Sr, Ba) particles with uniform morphologies were successfully prepared through a facile solvothermal process using ethylene glycol (EG) as protecting agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra and the kinetic decays were performed to characterize these samples. The XRD results reveal that all the doped samples are of high purity and crystallinity and assigned to the tetragonal scheelite-type structure of the AMoO{sub 4} phase. It has been shown that the as-synthesized SrMoO{sub 4}:Ln and BaMoO{sub 4}:Ln samples show respective uniform peanut-like and oval morphologies with narrow size distribution. The possible growth process of the AMoO{sub 4}:Ln has been investigated in detail. The EG/H{sub 2}O volume ratio, reaction temperature and time have obvious effect on the morphologies and sizes of the as-synthesized products. Upon excitation by ultraviolet radiation, the AMoO{sub 4}:Eu{sup 3+} phosphors show the characteristic {sup 5}D{sub 0}-{sup 7}F{sub 1-4} emission lines of Eu{sup 3+}, while the AMoO{sub 4}:Tb{sup 3+} phosphors exhibit the characteristic {sup 5}D{sub 4}-{sup 7}F{sub 3-6} emission lines of Tb{sup 3+}. These phosphors exhibit potential applications in the fields of fluorescent lamps and light emitting diodes (LEDs). - Graphical abstract: Uniform rare-earth ions (Eu{sup 3+}, Tb{sup 3+}) doped AMoO{sub 4} (A=Sr, Ba) submicron phosphors with tetragonal scheelite-type structure have been prepared through a facile solvothermal process using EG as reaction media. Display Omitted

  13. Analysis and simulation of optical and magnetic properties of lanthanide aluminates LnMgAl11O19 (Ln=La/Nd,La/Eu,Pr) with magnetoplumbite-like structure

    NASA Astrophysics Data System (ADS)

    Saber, D.; Dexpert-Ghys, J.; Caro, P.; Lejus, A. M.; Vivien, D.

    1985-06-01

    Single crystals of LnMgAl11O19 aluminates with a magnetoplumbite-like structure, (Ln=La1-xNdx, La1-x Eux, Pr), are grown by the flame fusion (Verneuil) or floating zone methods. Optical absorption or fluorescence spectra of these crystals reveal that Ln3+ ions occupy at least two or three different sites, instead of only one as in the ideal magnetoplumbite structure. Eu3+ fluorescence under dye-laser excitation leads to the identification of two low symmetry (probably c2v) sites labeled A and B. Ab initio crystal field parameters for Eu3+ are calculated from the atomic coordinates deduced from the crystal stucture of LaMgAl11O19. These parameters and the experimental energy levels are used to derive an acceptable set of Bkq parameters for the A site. These Bkq corrected for the Nd3+/Eu3+ radial integrals ratio are used in turn to derive the Nd3+ Racah and spin-orbit coupling parameters which fit the Nd3+ absorption spectrum at 4 K. At least two sets of parameters ``high 2P1/2'' and ``low 2P1/2'' are required, confirming the multisite character of La1-xNdxMgAl11O19. For this compound, the ab initio crystal field parameters are used to calculate the magnetic susceptibility and Nd3+ ESR g values. The fairly good agreement between calculated and experimental magnetic parameters confirms that the real sites of the Lanthanide ion arise from minor perturbations of the normal magnetoplumbite one. These perturbations could arise from Al-Mg site disorder, and/or the presence of oxygen vacancies in the lattice.

  14. Crystal structure of fluorite-related Ln{sub 3}SbO{sub 7} (Ln=La–Dy) ceramics studied by synchrotron X-ray diffraction and Raman scattering

    SciTech Connect

    Siqueira, K.P.F.; Borges, R.M.; Granado, E.; Malard, L.M.; Paula, A.M. de; Moreira, R.L.; Bittar, E.M.; Dias, A.

    2013-07-15

    Ln{sub 3}SbO{sub 7} (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb and Dy) ceramics were synthesized by solid-state reaction in optimized conditions of temperature and time to yield single-phase ceramics. The crystal structures of the obtained ceramics were investigated by synchrotron X-ray diffraction, second harmonic generation (SHG) and Raman scattering. All samples exhibited fluorite-type orthorhombic structures with different oxygen arrangements as a function of the ionic radius of the lanthanide metal. For ceramics with the largest ionic radii (La–Nd), the ceramics crystallized into the Cmcm space group, while the ceramics with intermediate and smallest ionic radii (Sm–Dy) exhibited a different crystal structure belonging to the same space group, described under the Ccmm setting. The results from SHG and Raman scattering confirmed these settings and ruled out any possibility for the non-centrosymmetric C222{sub 1} space group describing the structure of the small ionic radii ceramics, solving a recent controversy in the literature. Besides, the Raman modes for all samples are reported for the first time, showing characteristic features for each group of samples. - Graphical abstract: Raman spectrum for La{sub 3}SbO{sub 7} ceramics showing their 22 phonon modes adjusted through Lorentzian lines. According to synchrotron X-ray diffraction and Raman scattering, this material belongs to the space group Cmcm. - Highlights: • Ln{sub 3}SbO{sub 7} ceramics belonging to the space groups Cmcm and Ccmm are synthesized. • SXRD, SHG and Raman scattering confirmed the orthorhombic structures. • Ccmm instead of C222{sub 1} is the correct one based on SHG and Raman data.

  15. Synchrotron X-ray diffraction and Raman spectroscopy of Ln{sub 3}NbO{sub 7} (Ln=La, Pr, Nd, Sm-Lu) ceramics obtained by molten-salt synthesis

    SciTech Connect

    Siqueira, K.P.F.; Soares, J.C.; Granado, E.; Bittar, E.M.; Paula, A.M. de; Moreira, R.L.; Dias, A.

    2014-01-15

    Ln{sub 3}NbO{sub 7} (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) ceramics were obtained by molten-salt synthesis and their structures were systematically investigated by synchrotron X-ray diffraction (SXRD), second harmonic generation (SHG) and Raman spectroscopy. It was observed that ceramics with the largest ionic radii (La, Pr, Nd) crystallized into the Pmcn space group, while the ceramics with intermediate ionic radii (Sm-Gd) exhibited a different crystal structure belonging to the Ccmm space group. For this last group of ceramics, this result was corroborated by SHG and Raman scattering and ruled out any possibility for the non-centrosymmetric C 222{sub 1} space group, solving a recent controversy in the literature. Finally, according to SXRD, Tb-Lu containing samples exhibited an average defect fluorite structure (Fm3{sup ¯}m space group). Nonetheless, broad scattering at forbidden Bragg reflections indicates the presence of short-range domains with lower symmetry. Vibrational spectroscopy showed the presence of six Raman-active modes, inconsistent with the average cubic fluorite structure, and in line with the existence of lower-symmetry nano-domains immersed in the average fluorite structure of these ceramics. - Graphical abstract: Raman spectrum for Sm{sub 3}NbO{sub 7} ceramics showing their 27 phonon modes adjusted through Lorentzian lines. According to synchrotron X-ray diffraction and Raman scattering, this material belongs to the space group Cmcm. Display Omitted - Highlights: • Ln{sub 3}NbO{sub 7} ceramics were obtained by molten-salt synthesis. • SXRD, SHG and Raman scattering confirmed orthorhombic and cubic structures. • Ccmm instead of C222{sub 1} is the correct structure for Sm–Gd ceramics. • Pmcn space group was confirmed for La-, Pr- and Nd-based ceramics. • For Tb–Lu ceramics, ordered domains of a pyrochlore structure were observed.

  16. Daily mortality and air pollutants: findings from Köln, Germany.

    PubMed Central

    Spix, C; Wichmann, H E

    1996-01-01

    STUDY OBJECTIVE AND DESIGN: For the APHEA study, the short term effects of air pollutants on human health were investigated in a comparable way in various European cities. Daily mortality was used as one of the health effects indicators. This report aims to demonstrate the steps in epidemiological model building in this type of time series analysis aimed at detecting short term effects under a poisson distribution assumption and shows the tools for decision making. In addition, it assesses the impact of these steps on the pollution effect estimates. SETTING: Köln, Germany, is a city of one million inhabitants. It is densely populated with a warm, humid, unfavourable climate and a high traffic density. In previous studies, smog episodes were found to increase mortality and higher sulphur dioxide (SO2) levels were connected with increases in the number of episodes of croup. PARTICIPANTS, MATERIALS AND METHODS: Daily total mortality was obtained for 1975-85. SO2, total suspended particulates, and nitrogen dioxide (NO2) data were available from two to five stations for the city area, and size fractionated PM7 data from a neighbouring city. The main tools were time series plots of the raw data, predicted and residual data, the partial autocorrelation function and periodogram of the residuals, cross correlations of prefiltered series, plots of categorised influences, chi 2 statistics of influences and sensitivity analyses taking overdispersion and autocorrelation into account. RESULTS AND CONCLUSIONS: With regard to model building, it is concluded that seasonal and epidemic correction are the most important steps. The actual model chosen depends very much on the properties of the data set. For the pollution effect estimates, trend, season, and epidemic corrections are important to avoid overestimation of the effect, while an appropriate short term meterology influence correction model may actually prevent underestimation. When the model leaves very little over

  17. Carbonato-bridged Ni(II)2Ln(III)2 (Ln(III) = Gd(III), Tb(III), Dy(III)) complexes generated by atmospheric CO2 fixation and their single-molecule-magnet behavior: [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(MeOH or H2O)Ln(III)(NO3)}2]·solvent [3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato].

    PubMed

    Sakamoto, Soichiro; Fujinami, Takeshi; Nishi, Koshiro; Matsumoto, Naohide; Mochida, Naotaka; Ishida, Takayuki; Sunatsuki, Yukinari; Re, Nazzareno

    2013-06-17

    Atmospheric CO2 fixation of [Ni(II)(3-MeOsaltn)(H2O)2]·2.5H2O [3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato], Ln(III)(NO3)3·6H2O, and triethylamine occurred in methanol/acetone, giving a first series of carbonato-bridged Ni(II)2Ln(III)2 complexes [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(MeOH)Ln(III)(NO3)}2] (1Gd, 1Tb, and 1Dy). When the reaction was carried out in acetonitrile/water, it gave a second series of complexes [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(H2O)Ln(III)(NO3)}2]·2CH3CN·2H2O (2Gd, 2Tb, and 2Dy). For both series, each Ni(II)2Ln(III)2 structure can be described as two di-μ-phenoxo-bridged Ni(II)Ln(III) binuclear units bridged by two carbonato CO3(2-) units to form a carbonato-bridged (μ4-CO3)2{Ni(II)2Ln(III)2} structure. The high-spin Ni(II) ion has octahedral coordination geometry, and the Ln(III) ion is coordinated by O9 donor atoms from Ni(II)(3-MeOsaltn), bidentate NO3(-), and one and two oxygen atoms of two CO3(2-) ions. The NO3(-) ion for the first series roughly lie on Ln-O(methoxy) bonds and are tilted toward the outside, while for the second series, the two oxygen atoms roughly lie on one of the Ln-O(phenoxy) bonds due to the intramolecular hydrogen bond. The temperature-dependent magnetic susceptibilities indicated a ferromagnetic interaction between the Ni(II) and Ln(III) ions (Ln(III) = Gd(III), Tb(III), Dy(III)) for all of the complexes, with a distinctly different magnetic behavior between the two series in the lowest-temperature region due to the Ln(III)-Ln(III) magnetic interaction and/or different magnetic anisotropies of the Tb(III) or Dy(III) ion. Alternating-current susceptibility measurements under the 0 and 1000 Oe direct-current (dc) bias fields showed no magnetic relaxation for the Ni(II)2Gd(III)2 complexes but exhibited an out-of-phase signal for Ni(II)2Tb(III)2 and Ni(II)2Dy(III)2, indicative of slow relaxation of magnetization. The energy barriers, Δ/kB, for the spin flipping were estimated from the Arrhenius

  18. Crystal growth and structures of three new platinates: Ln 3NaPtO 7 (Ln = La, Nd) and La 4PtO 7

    NASA Astrophysics Data System (ADS)

    Hansen, Tara J.; Macquart, René B.; Smith, Mark D.; zur Loye, Hans-Conrad

    2007-09-01

    Single crystals of three lanthanide containing platinates, La 3NaPtO 7, Nd 3NaPtO 7 and La 4PtO 7, were grown from carbonate fluxes. La 3NaPtO 7 and Nd 3NaPtO 7 crystallize in the trigonal space group R3¯c with lattice parameters of a = 5.7458(2) Å and c = 35.650(1) Å, and a = 5.6862(5) Å and c = 34.896(3) Å, respectively. La 4PtO 7 crystallizes in the monoclinic space group I2/ m with lattice parameters of a = 9.799(1) Å, b = 4.0014(5) Å, c = 9.491(1) Å and β = 91.759(5)°. La 3NaPtO 7 and Nd 3NaPtO 7 are the first all-platinum members of the [A nB n-1O 3 n][A 2O] family of oxides. The difference in structure types of the three compounds arises from the size of the alkali metal cations present in the fluxes. Synthetic conditions as well as the structure differences between these platinates are discussed.

  19. Dimensional optimization of nanowire--complementary metal oxide--semiconductor inverter.

    PubMed

    Hashim, Yasir; Sidek, Othman

    2013-01-01

    This study is the first to demonstrate dimensional optimization of nanowire-complementary metal-oxide-semiconductor inverter. Noise margins and inflection voltage of transfer characteristics are used as limiting factors in this optimization. Results indicate that optimization depends on both dimensions ratio and digital voltage level (Vdd). Diameter optimization reveals that when Vdd increases, the optimized value of (Dp/Dn) decreases. Channel length optimization results show that when Vdd increases, the optimized value of Ln decreases and that of (Lp/Ln) increases. Dimension ratio optimization reveals that when Vdd increases, the optimized value of Kp/Kn decreases, and silicon nanowire transistor with suitable dimensions (higher Dp and Ln with lower Lp and Dn) can be fabricated.

  20. Complexations of Ln(III) with SnS4H and Sn2S6: Solvothermal syntheses and characterizations of lanthanide coordination polymers with thiostannate and polyamine mixed ligands

    NASA Astrophysics Data System (ADS)

    Tang, Chunying; Lu, Jialin; Han, Jingyu; Liu, Yun; Shen, Yali; Jia, Dingxian

    2015-10-01

    Polymeric lanthanide complexes with thiostannate and polyamine mixed ligands, [Ln(peha)(μ-SnS4H)]n [Ln=La (1a), Nd (1b)] and [{Ln(tepa)(μ-OH)}2(μ-Sn2S6)]nnH2O [Ln=Nd (2a), Sm (2b), Gd (2c), Dy (2d)] (peha=pentaethylenehexamine, tepa=tetraethylenepentamine) were respectively prepared in peha and tepa coordinative solvents by the solvothermal methods. In 1a and 1b, the Ln3+ ions are coordinated by a hexadentate peha ligand forming [Ln(peha)]3+ units. The [SnS4H]3- anion chelates a [Ln(peha)]3+ unit via two S atoms and coordinates to another [Ln(peha)]3+ unit via the third S atom. As a result, the [Ln(peha)]3+ units are connected into coordination polymers [Ln(peha)(μ-SnS4H)]n by an unprecedented tridentate μ-η1,η2-SnS4H bridging ligands. In 2a-2d, the Ln3+ ions are coordinated by a pentadentate tepa ligand, and two [Ln(tepa)]3+ units are joined by two μ-OH bridges to form a binuclear [{Ln(tepa)(μ-OH)}2]4+ unit. Behaving as a bidentate μ-η1, η1-Sn2S6 bridging ligand, the Sn2S6 unit connects [{Ln(tepa)(μ-OH)}2]4+ units into a neutral coordination polymer [{Ln(tepa)(μ-OH)}2(μ-Sn2S6)]n via the trans S atoms. The Ln3+ ions are in distorted monocapped square antiprismatic and bicapped trigonal prismatic environments in [{Ln(peha)(μ-SnS4H)]n and [{Ln(tepa)(μ-OH)}2(μ-Sn2S6)]n, respectively. The denticities of ethylene polyamine play an important role on the formation and complexation of the thiostannate in the presence of lanthanide ions. Compounds 1a-2d show well-defined absorption edges with band gaps between 2.81 and 3.15 eV.

  1. Co(II)4, Co(II)7, and a Series of Co(II)2Ln(III) (Ln(III) = Nd(III), Sm(III), Gd(III), Tb(III), Dy(III)) Coordination Clusters: Search for Single Molecule Magnets.

    PubMed

    Modak, Ritwik; Sikdar, Yeasin; Thuijs, Annaliese E; Christou, George; Goswami, Sanchita

    2016-10-03

    We report herein the syntheses and investigation of the magnetic properties of a Co(II)4 compound, a series of trinuclear Co(II)2Ln(III) (Ln(III) = Nd(III), Sm(III), Gd(III), Tb(III), Dy(III)) complexes, and a Co(II)7 complex. The homometallic Co(II)4 core was obtained from the reaction of Ln(NO3)3·xH2O/Co(NO3)2·6H2O/H2vab/Et3N in a 0.5:0.5:1:2 ratio in methanol. Variation in synthetic conditions was necessary to get the desired Co(II)-Ln(III) complexes. The Co(II)-Ln(III) assembly was synthesized from Ln(NO3)3·xH2O/Co(OAc)2·4H2O/H2vab/NaOMe in a 0.4:0.5:1:1 ratio in methanol. The isostructural Co(II)2Ln(III) complexes have a core structure with the general formula [Co2Ln(Hvab)4(NO3)](NO3)2·MeOH·H2O, (where H2vab = 2-[(2-hydroxymethyl-phenylimino)-methyl]-6-methoxy-phenol) with simultaneous crystallization of Co(II)7 complex in each reaction. The magnetic investigation of these complexes reveals that both homometallic complexes and four Co(II)-Ln(III) complexes (except Co(II)-Nd(III)) display behavior characteristic of single molecule magnets.

  2. The unexpected structures of ``core-shell'' and ``alloy'' LnF3 nanoparticles as examined by variable energy X-ray photo-electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Dong, Cunhai; Pichaandi, Jothirmayanantham; Regier, Tom; van Veggel, Frank C. J. M.

    2011-08-01

    Lanthanide fluoride nanoparticles were synthesized in aqueous media using procedures intended for a core-shell structure of Ln(1)F3-Ln(2)F3, its reverse architecture, and an alloy structure. Their structures were examined by variable photon energy photo-electron spectroscopy using synchrotron radiation, along with X-ray powder diffractometry, transmission electron microscopy, energy dispersive X-ray spectroscopy, and luminescence spectroscopy. The results show that the nanoparticles intended for a core-shell structure do not have a core-shell structure, and that nanoparticles intended for an alloy structure do not always have an alloy structure. A possible explanation for this is cation exchange, a phenomenon that occurs when LnF3 nanoparticles are exposed to another Ln3+ ion in aqueous media, resulting in Ln3+ ions in nanoparticles being quickly replaced by Ln3+ ions in solution. This cation exchange effectively competes with the precipitation of LnF3, which leads to a concentration gradient in the case of the combination of LaF3 and GdF3, and to nearly an alloy structure (isotropic mixture of all the ions) in the case of the combination of LaF3 and NdF3, regardless of the procedure used. Finally, the intended ``core-shell'' nanoparticles were doped with Eu3+ to show that a non-core-shell structure can also give rise to the improvement of optical properties as compared with the corresponding core nanoparticles. These results suggest that conclusions in the literature that a core-shell structure was obtained as inferred by TEM or enhanced luminescence may not be correct.Lanthanide fluoride nanoparticles were synthesized in aqueous media using procedures intended for a core-shell structure of Ln(1)F3-Ln(2)F3, its reverse architecture, and an alloy structure. Their structures were examined by variable photon energy photo-electron spectroscopy using synchrotron radiation, along with X-ray powder diffractometry, transmission electron microscopy, energy dispersive X

  3. Evaluation of DC electric field distribution of PPLP specimen based on the measurement of electrical conductivity in LN2

    NASA Astrophysics Data System (ADS)

    Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Lee, Jong-Geon; Cho, Jeon-Wook; Ryoo, Hee-Suk; Lee, Bang-Wook

    2013-11-01

    High temperature superconducting (HTS) cable has been paid much attention due to its high efficiency and high current transportation capability, and it is also regarded as eco-friendly power cable for the next generation. Especially for DC HTS cable, it has more sustainable and stable properties compared to AC HTS cable due to the absence of AC loss in DC HTS cable. Recently, DC HTS cable has been investigated competitively all over the world, and one of the key components of DC HTS cable to be developed is a cable joint box considering HVDC environment. In order to achieve the optimum insulation design of the joint box, analysis of DC electric field distribution of the joint box is a fundamental process to develop DC HTS cable. Generally, AC electric field distribution depends on relative permittivity of dielectric materials but in case of DC, electrical conductivity of dielectric material is a dominant factor which determines electric field distribution. In this study, in order to evaluate DC electric field characteristics of the joint box for DC HTS cable, polypropylene laminated paper (PPLP) specimen has been prepared and its DC electric field distribution was analyzed based on the measurement of electrical conductivity of PPLP in liquid nitrogen (LN2). Electrical conductivity of PPLP in LN2 has not been reported yet but it should be measured for DC electric field analysis. The experimental works for measuring electrical conductivity of PPLP in LN2 were presented in this paper. Based on the experimental works, DC electric field distribution of PPLP specimen was fully analyzed considering the steady state and the transient state of DC. Consequently, it was possible to determine the electric field distribution characteristics considering different DC applying stages including DC switching on, DC switching off and polarity reversal conditions.

  4. Sensitization and Intergranular Corrosion Behavior of High Nitrogen Type 304LN Stainless Steels for Reprocessing and Waste Management Applications

    NASA Astrophysics Data System (ADS)

    Parvathavarthini, N.; Kamachi Mudali, U.; Nenova, Lilyana; Andreev, Chavdar; Raj, Baldev

    2012-06-01

    High nitrogen 304LN stainless steels (SS) intended for chloride and nitric acid environments in spent nuclear fuel reprocessing and waste management applications were evaluated for their sensitization and intergranular corrosion (IGC) resistance. For this purpose, high nitrogen (0.132 pct, 0.193 pct and 0.406 pct) containing, impurity-controlled, vanadium-added 304LN SS alloys were developed. For comparison, 304L SS, which is currently used in reprocessing plants, was also studied. These stainless steels were subjected to heat treatment at 948 K (675 °C) for various durations ranging from 1 to 1000 hours and tested for susceptibility to IGC as per ASTM A262 Practice A and E tests. The degree of sensitization was estimated with the double loop electrochemical potentiokinetic reactivation technique. The increase in nitrogen content resulted in higher hardness and finer grain size. Based on the detailed microstructural and corrosion studies, it was determined that an addition of 0.132 pct and 0.193 pct nitrogen showed better IGC resistance and an additional increase in nitrogen resulted in deterioration resulting from chromium nitride precipitation, which was confirmed by electrochemical phase separation and X-ray diffraction studies. The onset of desensitization was faster for the alloy with 0.132 pct nitrogen as well as 0.406 pct nitrogen because of the lower nitrogen content in the former case and the finer grain size in the latter case. The higher hardness and superior IGC resistance of 0.132 pct and 0.193 pct nitrogen containing Type 304LN SS suggests the suitability of this alloy for nitric acid- and chloride-containing environments of reprocessing and waste management plants.

  5. Synthesis and novel luminescence properties of one-dimension BaMoO{sub 4}:Ln{sup 3+} nanostructures

    SciTech Connect

    Wang, Yuping; Li, Mingxia; Pan, Kai; Wang, Guofeng

    2015-12-15

    Highlights: • String BaMoO{sub 4}:Ln{sup 3+} nanobeans were prepared by a hydrothermal method. • The Decay dynamics were performed to study the photoluminescence of the BaMoO{sub 4}:Eu{sup 3+} nanobeans. • For BaMoO{sub 4}:Er{sup 3+}/Eu{sup 3+}, the {sup 2}P{sub 3/2} → {sup 4}I{sub 11/2} and {sup 2}H{sub 11/2}/{sup 4}S{sub 3/2} → {sup 4}I{sub 15/2} transitions were observed. - Abstract: String BaMoO{sub 4}:Ln{sup 3+} (Ln = Eu, Tb, Er, and Gd) nanobeans were prepared by a hydrothermal method. The samples were characterized by transmission electron microscope, scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscope, and Raman spectrometer. Under direct excitation in the charge transfer absorption band, concentration quenching phenomenon occurs and decay dynamics were performed to study the photoluminescence of the string BaMoO{sub 4}:Eu{sup 3+} nanobeans. In the emission spectra of BaMoO{sub 4}:Er{sup 3+}/Eu{sup 3+} under 274 nm excitation, the {sup 2}P{sub 3/2} → {sup 4}I{sub 11/2}, {sup 2}H{sub 11/2} → {sup 4}I{sub 15/2}, and {sup 4}S{sub 3/2} → {sup 4}I{sub 15/2} transitions from Er{sup 3+} ions were observed for the first time. In addition, the photoluminescence properties of BaMoO{sub 4}:Tb{sup 3+}/Eu{sup 3+} and BaMoO{sub 4}:Gd{sup 3+}/Eu{sup 3+} were also investigated.

  6. Valence properties of Cu and Ru in titanium-substituted LnCu3Ru4O12+δ (Ln = La, Pr, Nd) investigated by XANES and TGA.

    PubMed

    Riegg, Stefan; Reller, Armin; Loidl, Alois; Ebbinghaus, Stefan G

    2015-06-21

    In the solid-solution series La(y)Cu(3)RuxTi(4-x)O(12+δ) (0 ≤x≤ 4) the Cu and Ru electronic states are highly correlated. With increasing Ru content x the system properties change from a paramagnetic insulator with colossal dielectric constant to a heavy-fermion metal. To further elucidate the occurring phase transitions, the valences of Cu and Ru have been investigated utilizing XANES measurements at the Cu-K and the Ru-K absorption edges. It was found that the Ru oxidation number is close to +4 in all samples, while the Cu valence linearly decreases from +2 for the titanate (x = 0) to +1.6 for the ruthenate (x = 4). Additional thermogravimetric measurements have been used to determine the oxygen content and rather high oxygen excesses up to δ≈ 0.7 (for x = 0.5) were obtained. The additional oxygen for x < 2 is required to compensate the constant Ru +4 valence. Our findings are in accordance with the reported phase transitions of the magnetic and transport properties. Both the valence shift and the shapes of the absorption edges suggest a change from localized to itinerant character of the Cu electronic states with increasing x, while the Ru electrons remain localized. Analogous results concerning the valences were found for the Pr(y)Cu(3)RuxTi(4-x)O(12+δ) and Nd(y)Cu(3)RuxTi(4-x)O(12+δ) solid-solution series.

  7. A Comparative Evaluation of the Effect of Low Cycle Fatigue and Creep-Fatigue Interaction on Surface Morphology and Tensile Properties of 316L(N) Stainless Steel

    NASA Astrophysics Data System (ADS)

    Mariappan, K.; Shankar, Vani; Sandhya, R.; Bhaduri, A. K.; Laha, Kinkar

    2016-04-01

    In the present work, the deformation and damage evolution in 316L(N) stainless steel during low cycle fatigue (LCF) and creep-fatigue interaction (CFI) loadings have been compared by evaluating the residual tensile properties. Towards this, LCF and CFI experiments were carried out at constant strain amplitude of ±0.6 pct, strain rate of 3 × 10-3 s-1 and temperature of 873 K (600 °C). During CFI tests, 30 minutes hold period was introduced at peak tensile strain. Experiments were interrupted up to various levels of fatigue life viz. 5, 10, 30, 50, and 60 pct of the total fatigue life ( N f) under both LCF and CFI conditions. The specimens subjected to interrupted fatigue loadings were subsequently monotonically strained at the same strain rate and temperature up to fracture. Optical and scanning electron microscopy and profilometry were conducted on the untested and tested samples to elucidate the damage evolution during the fatigue cycling under both LCF and CFI conditions. The yield strength (YS) increased sharply with the progress of fatigue damage and attained saturation within 10 pct of N f under LCF condition. On the contrary, under CFI loading condition, the YS continuously increased up to 50 pct of N f, with a sharp increase of YS up to 5 pct of N f followed by a more gradual increase up to 50 pct of N f. The difference in the evolution of remnant tensile properties was correlated with the synergistic effects of the underlying deformation and damage processes such as cyclic hardening/softening, oxidation, and creep. The evolution of tensile properties with prior fatigue damage has been correlated with the change in surface roughness and other surface features estimated by surface replica technique and fractography.

  8. Alpha Radiolysis of Nuclear Solvent Extraction Ligands Used for An(III) and Ln(III) Separations

    SciTech Connect

    Mezyk, Stephen P.; Mincher, Bruce J.; Nilsson, Mikael

    2016-08-01

    This document is the final report for the Nuclear Energy Universities Program (NEUP) grant 10-910 (DE-AC07-05ID14517) “Alpha Radiolysis of Nuclear Solvent Extraction Ligands used for An(III) and Ln(III) Separations”. The goal of this work was to obtain a quantitative understanding of the impacts of both low Linear Energy Transfer (LET, gamma-rays) and high LET (alpha particles) radiation chemistry occurring in future large-scale separations processes. This quantitative understanding of the major radiation effects on diluents and ligands is essential for optimal process implementation, and could result in significant cost savings in the future.

  9. 2.4-watts second-harmonic generation in ppZnO:LN ridge waveguide for lithium laser cooling.

    PubMed

    Kretzschmar, Norman; Eismann, Ulrich; Sievers, Franz; Chevy, Frédéric; Salomon, Christophe

    2017-06-26

    We present a simple all-solid-state laser source emitting 2.4 W of single-frequency light at 671 nm for laser cooling of lithium atoms. It is based on a diode-pumped solid-state laser, which is frequency doubled in a ppZnO:LN ridge waveguide with an internal doubling efficiency of 54%. We develop a simple theory for the thermal effects we observed at elevated fundamental powers, and compare the setup to a more efficient but more complex one with an external resonant frequency doubling cavity providing 5.2 W at 671 nm.

  10. Syntheses and crystal structures of the quaternary uranium lanthanide oxyselenides UYb{sub 2}O{sub 2}Se{sub 3} and U{sub 2}Ln{sub 2}O{sub 4}Se{sub 3} (Ln=Pr, Sm, Gd)

    SciTech Connect

    Raw, Adam D.; Ibers, James A.

    2012-02-15

    Single crystals of the new uranium lanthanide oxyselenide compounds UYb{sub 2}O{sub 2}Se{sub 3} and U{sub 2}Ln{sub 2}O{sub 4}Se{sub 3} (Ln=Pr, Sm, Gd) have been synthesized from an Sb{sub 2}Se{sub 3} flux. The structures have been determined from single-crystal X-ray diffraction data. UYb{sub 2}O{sub 2}Se{sub 3} is isostructural to UYb{sub 2}O{sub 2}S{sub 3}. The structure comprises layers of edge-sharing YbSe{sub 6} octahedra and double layers of disordered (U/Ln)O{sub 4}Se{sub 4} square antiprisms. The U{sub 2}Ln{sub 2}O{sub 4}Se{sub 3} (Ln=Pr, Sm, Gd) compounds are isostructural to U{sub 2}Ln{sub 2}O{sub 4}S{sub 3} (Ln=La-Gd) whose structure had been deduced previously from X-ray powder diffraction data. In the structure a dodecahedron of four O atoms and four Se atoms surrounds a site primarily occupied by U and a distorted bicapped octahedron of five Se atoms and three O atoms surrounds a site primarily occupied by the lanthanide. These compounds represent the first examples of quaternary uranium oxyselenides. - Graphical abstract: The U{sub 2}Ln{sub 2}O{sub 4}Se{sub 3} (Ln=Pr, Sm, Gd) structure: primarily U sites are in black, primarily Ln sites are in blue, O red, Se orange. Highlights: Black-Right-Pointing-Pointer Single crystals of the new compounds UYb{sub 2}O{sub 2}Se{sub 3} and U{sub 2}Ln{sub 2}O{sub 4}Se{sub 3} (Ln=Pr, Sm, Gd) have been synthesized. Black-Right-Pointing-Pointer These compounds represent the first examples of quaternary uranium oxyselenides. Black-Right-Pointing-Pointer U is surrounded by a dodecahedron or square prism of four O atoms and four Se atoms

  11. Ab initio structure determination of new rare earth fluoride borates Ln{sub 3}(BO{sub 3}){sub 2}F{sub 3} (Ln = Sm, Eu, and Gd)

    SciTech Connect

    Corbel, G.; Retoux, R.; Leblanc, M.

    1998-08-01

    The crystal structures of Ln{sub 3}(BO{sub 3}){sub 2}F{sub 3} (Ln = Sm, Eu, and Gd) are determined ab initio from X-ray powder data. The unit cell is monoclinic, space group C2/c, Z = 4, with a = 12.534(1) {angstrom}, b = 6.237(1) {angstrom}, c = 8.360(1) {angstrom}, {beta} = 97.404(6){degree}, V = 648.1(2) {angstrom}{sup 3} for Gd{sub 3}(BO{sub 3}){sub 2}F{sub 3}. The Rietveld refinement reliability converged to R{sub p} = 0.121, R{sub wp} = 0.147, R{sub exp} = 0.050, {chi}{sup 2} = 8.75. The structure presents a 3D network of Archimedian monocapped antiprisms Gd(1)O{sub 4}F{sub 5} and Gd(2)O{sub 7}F{sub 2}. These polyhedra form trimeric entities Gd{sub 3}O{sub 12}F{sub 9}, which build infinite layers parallel to the (010) plane.

  12. Near-infrared photoluminescence in La{sub 0.98}AlO{sub 3}: {sub 0.02}Ln{sup 3+}(Ln = Nd/Yb) for sensitization of c-Si solar cells

    SciTech Connect

    Sawala, N. S. Koparkar, K. A.; Omanwar, S. K.; Bajaj, N. S.

    2016-05-06

    The host matrix LaAlO{sub 3} was synthesized by conventional solid state reaction method in which the Nd{sup 3+} ions and Yb{sup 3+} ions successfully doped at 2mol% concentrations. The phase purity was confirmed by X ray powder diffraction (XRD) method. The photoluminescence (PL) properties were studied by spectrophotometer in near infra red (NIR) and ultra violet visible (UV-VIS) region. The Nd{sup 3+} ion doped LaAlO{sub 3} converts a visible (VIS) green photon (587 nm) into near infrared (NIR) photon (1070 nm) while Yb{sup 3+} ion doped converts ultra violet (UV) photon (221 nm) into NIR photon (980 nm). The La{sub 0.98}AlO{sub 3}: {sub 0.02}Ln{sup 3+}(Ln = Nd / Yb) can be potentiality used for betterment of photovoltaic (PV) technology. This result further indicates its potential application as a luminescence converter layer for enhancing solar cells performance.

  13. The quantum cutting of Tb(3+) in Ca(6)Ln(2)Na(2)(PO(4))(6)F(2) (Ln = Gd, La) under VUV-UV excitation: with and without Gd(3+).

    PubMed

    Xie, Mubiao; Tao, Ye; Huang, Yan; Liang, Hongbin; Su, Qiang

    2010-12-20

    The VUV-vis spectroscopic properties of Tb(3+) activated fluoro-apatite phosphors Ca(6)Ln(2-x)Tb(x)Na(2)(PO(4))(6)F(2) (Ln = Gd, La) were studied. The results show that phosphors Ca(6)Gd(2-x)Tb(x)Na(2)(PO(4))(6)F(2) with Gd(3+) ions as sensitizers have intense absorption in the VUV range. The emission color of both phosphors can be tuned from blue to green by changing the doping concentration of Tb(3+) under 172 nm excitation. The visible quantum cutting (QC) via cross relaxation between Tb(3+) ions was observed in cases with and without Gd(3+). Though QC can be realized in phosphors Ca(6)La(2-x)Tb(x)Na(2)(PO(4))(6)F(2), we found that Gd(3+)-containg phosphors have a higher QC efficiency, confirming that the Gd(3+) ion indeed plays an important role during the quantum cutting process. In addition, the energy transfer process from Gd(3+) to Tb(3+) as well as (5)D(3)-(5)D(4) cross relaxation was investigated and discussed in terms of luminescence spectra and decay curves.

  14. Effect of lanthanide on the microstructure and structure of LnMn0.5Fe0.5O3 nanoparticles with Ln=La, Pr, Nd, Sm and Gd prepared by the polymer precursor method

    NASA Astrophysics Data System (ADS)

    Romero, Mariano; Faccio, Ricardo; Martínez, Javier; Pardo, Helena; Montenegro, Benjamín; Plá Cid, Cristiani Campos; Pasa, André A.; Mombrú, Álvaro W.

    2015-01-01

    The synthesis of LnMn0.5Fe0.5O3 perovskite nanoparticles by the polymer precursor method showed a strong intrinsic dependence with different lanthanides (Ln=La, Pr, Nd, Sm and Gd). The polymerization level reached in the polymer precursor was proportional to the atomic number of lanthanide with exception of samarium, which showed the formation of a different precursor based in a citrate chelate with ethyleneglycol bonded as adduct. The increasing level of polymerization of the polymer precursors showed the formation of large-size perovskite nanoparticles after its calcination. SAXS and TEM analyses suggested that nanoparticles obtained, using this method, have a squared-like microstructure in connection with the polymer precursor microstructure. Structural analysis showed an orthorhombic structure with a slight decline in the Jahn-Teller distortion when the atomic number of lanthanide increases. Mössbauer spectroscopy showed the presence of a majority site in agreement with the Pbnm orthorhombic structure best fitted with Rietveld refinements and in some cases, a more distorted site attributed to local inhomogeneities and oxygen vacancies.

  15. Grain and grain boundary transport in BaCe0.5Zr0.3Ln0.2O3-δ (Ln - Y or lanthanide) electrolytes attractive for protonic ceramic fuel cells application

    NASA Astrophysics Data System (ADS)

    Danilov, N.; Pikalova, E.; Lyagaeva, J.; Antonov, B.; Medvedev, D.; Demin, A.; Tsiakaras, P.

    2017-10-01

    Protonic ceramic fuel cells (PCFCs) belong to very attractive energy conversion systems, which are able to operate effectively at low- and intermediate temperature ranges. The improvement of their electrochemical characteristics is feasible through the optimization of their functional materials. In the present work, emphasis is given to the highly conductive and stable cerate-zirconate electrolytes of BaCe0.5Zr0.3Ln0.2O3-δ (where Ln = Y, Dy, Sm and Nd). Studying the transport properties of these materials in individual form and in PCFC assembly, it is shown that the Dy-doped sample exhibits higher grain (bulk) and grain boundary conductivity in comparison with the most studied Y-doped ones. The single PCFC based on a rather thick 30 μm electrolyte displays about 160 and 290 mW cm-2 at 600 and 700 °C, respectively. These values are comparative with those obtained for PCFCs fabricated with similar electrolytes and Co-free cathode materials, confirming the perspective of cerate-zirconates doped by other lanthanides.

  16. In-phase alignments of asymmetric building units in Ln4GaSbS9 (Ln = Pr, Nd, Sm, Gd-Ho) and their strong nonlinear optical responses in middle IR.

    PubMed

    Chen, Mei-Chun; Li, Long-Hua; Chen, Yu-Biao; Chen, Ling

    2011-03-30

    New noncentrosymmetric rare-earth metal gallium thioantimonates, Ln(4)GaSbS(9) were synthesized from stoichiometric element mixtures at 950 °C by high-temperature solid-state reactions. These compounds crystallize in orthorhombic space group Aba2 (no.41) with a = 13.799(3)-13.427(5) Å, b = 14.187(3)-13.756(5) Å, c = 14.323(3)-13.954(5) Å, V = 2804(2)-2577 (2) Å(3), and Z = 8 on going from Ln = Pr to Ho. The asymmetric building units, bimetallic polar (Sb(2)S(5)) units, and dimeric (GaS(4))(2) tetrahedra are in-phase aligned as an infinite single anionic chain of {[(Ga(2)S(6))(Sb(2)S(5))](10-)}(∞) that is further packed in a noncentrosymmetric pseudolayer motif perpendicular to the c axis. Three of the title compounds show large powder second harmonic generation (SHG) effects at 2.05 μm, and two of them also exhibit large transparency ranges (1.75 or 0.75 to 25 μm) in the middle-IR region. Significantly, the Sm-member exhibits the strongest SHG response among sulfides to date with intensity approximately 3.8 times that of the benchmark AgGaS(2). The band structures, indirect band gap nature, bonding strengths, and lone pair effects around Sb have also been studied by Vienna ab initio simulation package calculations.

  17. Multi-modal imaging and cancer therapy using lanthanide oxide nanoparticles: current status and perspectives.

    PubMed

    Park, J Y; Chang, Y; Lee, G H

    2015-01-01

    Biomedical imaging is an essential tool for diagnosis and therapy of diseases such as cancers. It is likely true that medicine has developed with biomedical imaging methods. Sensitivity and resolution of biomedical imaging methods can be improved with imaging agents. Furthermore, it will be ideal if imaging agents could be also used as therapeutic agents. Therefore, one dose can be used for both diagnosis and therapy of diseases (i.e., theragnosis). This will simplify medical treatment of diseases, and will be also a benefit to patients. Mixed (Ln(1x)Ln(2y)O3, x + y = 2) or unmixed (Ln2O3) lanthanide (Ln) oxide nanoparticles (Ln = Eu, Gd, Dy, Tb, Ho, Er) are potential multi-modal imaging and cancer therapeutic agents. The lanthanides have a variety of magnetic and optical properties, useful for magnetic resonance imaging (MRI) and fluorescent imaging (FI), respectively. They also highly attenuate X-ray beam, useful for X-ray computed tomography (CT). In addition gadolinium-157 ((157)Gd) has the highest thermal neutron capture cross section among stable radionuclides, useful for gadolinium neutron capture therapy (GdNCT). Therefore, mixed or unmixed lanthanide oxide nanoparticles can be used for multi-modal imaging methods (i.e., MRI-FI, MRI-CT, CT-FI, and MRICT- FI) and cancer therapy (i.e., GdNCT). Since mixed or unmixed lanthanide oxide nanoparticles are single-phase and solid-state, they can be easily synthesized, and are compact and robust, which will be beneficial to biomedical applications. In this review physical properties of the lanthanides, synthesis, characterizations, multi-modal imagings, and cancer therapy of mixed and unmixed lanthanide oxide nanoparticles are discussed.

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

    SciTech Connect

    Flura, Aurélien; Dru, Sophie; Nicollet, Clément; Vibhu, Vaibhav; Fourcade, Sébastien; Lebraud, Eric; Rougier, Aline; Bassat, Jean-Marc; Grenier, Jean-Claude

    2015-08-15

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

  19. Synthesis, structure, and luminescence property of a series of Ag–Ln coordination polymers with the N-heterocyclic carboxylato ligand

    SciTech Connect

    Jin, Jing Chen, Chong; Gao, Yan; Zhao, Ran; Wang, Xiuyan; Lü, Chunxin; Chi, Yuxian; Niu, Shuyun

    2016-03-15

    Six Ln–Ag coordination polymers {[LnAg_2(IN)_4(H_2O)_5]·NO_3·2H_2O}{sub n} (Ln=Ho (1) and Tb (2), HIN=isonicotinic acid), {[PrAg_2(IN)_4(H_2O)_2]·NO_3·H_2O}{sub n} (3), [LnAg(pdc){sub 2}]{sub n} (Ln=Eu(4) and Pr (5), H{sub 2}pdc=3,4-pyridine-dicarboxylic acid) and [NdAg(bidc){sub 2}(H{sub 2}O){sub 4}]{sub n} (6) (H{sub 2}bidc=benzimidazole-5,6-dicarboxylic acid) have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR, UV–vis-NIR absorption spectra, fluorescence spectra and thermogravimetric analysis. Structural analyses reveal that the six polymers exhibit 0D (polymer (1)), 1D (polymer (2)), 2D (polymers (3) and (5)) and 3D (polymers (4) and (6)) infinite structures, respectively. Polymers (1)–(6) exhibit the Ln(III) characteristic emission in the near-infrared (NIR) region or in the visible region. Especially, the NIR emission bands of polymers 1, 5 and 6 evidently present shift or splitting due to formation of the Ln–Ag coordination polymers. This can be attributed to the tune of inner levels in Ln–Ag system caused by the interact and influence between the 4d orbital of the Ag(I) ion and the 4f orbital of the Ln(III) ion, which can be confirmed by the UV–vis-NIR absorption spectra of the polymers. In addition, the distortion of coordination geometry as well as difference of the coordination number around the Ag(I) ion affect the structure framework. - Graphical abstract: Six Ag–Ln coordination polymers have been hydrothermally synthesized and characterized. The photoluminescence properties were studied. The distortion of coordination geometry of Ag(I) ion affect structure framework. Introduction of Ag(I) cause wonderful changes to the NIR emission of Ln(III) ions. - Highlights: • Six Ln–Ag polymers have been synthesized and characterized. • The distortion of coordination geometry of Ag(I) ion affect structure framework. • Introduction of Ag(I) cause wonderful changes to the NIR

  20. Magnetism and transport properties of layered rare-earth cobaltates Ln0.3CoO2

    NASA Astrophysics Data System (ADS)

    Knížek, K.; Novák, P.; Jirák, Z.; Hejtmánek, J.; Maryško, M.; Buršík, J.

    2015-05-01

    The ab-initio (GGA+U) electronic structure calculations of layered cobaltates Ln0.3CoO2 (Ln = La, Pr, Nd) prepared by ionic exchange from Na0.90CoO2 precursors have been performed. The data are used for numerical modeling of Seebeck coefficient within Boltzmann transport theory using BoltzTraP program [G. K. H. Madsen and D. J. Singh, Comput. Phys. Commun. 175, 67 (2006)], as well as for determination of the crystal field split levels of rare-earth ions using a method based on a transformation of Bloch states into the basis of Wannier functions [P. Novák et al., Phys. Rev. B 87, 205139 (2013)]. An overall agreement with observed magnetism and transport properties is obtained. In particular, the high p-type thermopower is well reproduced in a broad temperature range, but instead of theoretical linear decrease down to the lowest temperatures, the real systems exhibit an anomalous change of Seebeck sign, which might be related to the change of bare metallic carriers into the polaronic ones.

  1. Antigenic Protein In Microgravity-Grown Human Mixed Mullerian Tumor (LN1) Cells Preserved In RNA Stabilizing Agent

    NASA Technical Reports Server (NTRS)

    Hammond, Dianne K.; Becker, Jeanne; Holubec, K.; Baker, T. L.; Love, J. E.

    2004-01-01

    Cells treated with RNAlater(TradeMark) have previously been shown to contain antigenic proteins that can be visualized using Western blot analysis. These proteins seem to be stable for several months when stored in RNA stabilizer at 4 C. Antigenic protein can be recovered from cells that have been processed using an Ambion RNAqueous(Registered TradeMark) kit to remove RNA. In this set of experiments, human mixed Mullerian tumor (LN1) cells grown on the International Space Station during Expedition 3 were examined for antigenic stability after removal of RNA. The cells were stored for three months in RNAlater(TradeMark) and RNA was extracted. The RNA filtrate Containing the protein was precipitated, washed, and suspended in buffer containing sodium dodecyl sulfate (SDS). Samples containing equal concentrations of protein were loaded onto SDS-polyacrylamide gels. Proteins were separated by electrophoresis and transferred by Western blot to polyvinylidene fluoride (PVDF) membrane. The Western blots were stained with an enhanced chemiluminescent ECL(Registered TradeMark)Plus detection kit (Amersham) and scanned using a Storm 840 gel image analyzer (Amersham, Molecular Dynamics). ImageQuant(Registered TradeMark)a software was used to quantify the densities of the protein bands. The ground control and flight LN1 cell samples showed a similar staining pattern over time with antibodies to vimentin, glyceraldehyde-3-phosphate dehydrogenase, and epithelial membrane antigens.

  2. Ab initio calculation of excess properties of La1-x(Ln,An)xPO4 solid solutions

    NASA Astrophysics Data System (ADS)

    Li, Yan; Kowalski, Piotr M.; Blanca-Romero, Ariadna; Vinograd, Victor; Bosbach, Dirk

    2014-12-01

    We used ab initio computational approach to predict the excess enthalpy of mixing and the corresponding regular/subregular model parameters for La1-xLnxPO4 (Ln=Ce,…, Tb) and La1-xAnxPO4 (An=Pu, Am and Cm) monazite-type solid solutions. We found that the regular model interaction parameter W computed for La1-xLnxPO4 solid solutions matches the few existing experimental data. Within the lanthanide series W increases quadratically with the volume mismatch between LaPO4 and LnPO4 endmembers (ΔV=VLaPO4-VLnPO4), so that W(kJ/mol)=0.618(. We demonstrate that this relationship also fits the interaction parameters computed for La1-xAnxPO4 solid solutions. This shows that lanthanides can be used as surrogates for investigation of the thermodynamic mixing properties of actinide-bearing solid solutions.

  3. Low Cycle Fatigue Behavior of 316LN Stainless Steel Alloyed with Varying Nitrogen Content. Part I: Cyclic Deformation Behavior

    NASA Astrophysics Data System (ADS)

    Prasad Reddy, G. V.; Sandhya, R.; Sankaran, S.; Mathew, M. D.

    2014-10-01

    In this study, the influence of cyclic strain amplitude on the evolution of cyclic stress-strain response and the associated cyclic deformation mechanisms in 316LN stainless steel with varying nitrogen content (0.07 to 0.22 wt pct) is reported in the temperature range 773 K to 873 K (500 °C to 600 °C). Two mechanisms, namely dynamic strain aging and secondary cyclic hardening, are found to strongly influence the cyclic stress response. Deformation substructures associated with both the mechanisms showed planar mode of deformation. These mechanisms are observed to be operative over certain combinations of temperature and strain amplitude. For strain amplitudes >0.6 pct, wavy or mixed mode of deformation is noticed to suppress both the mechanisms. Cyclic stress-strain curves revealed both single and dual-slope behavior depending on the test temperature. Increase in nitrogen content is found to increase the tendency toward planar mode of deformation, while increase in strain amplitude leads to transition from planar slip bands to dislocation cell/wall structure formation, irrespective of the nitrogen content in 316LN stainless steel.

  4. Synthesis of Multicolor Core/Shell NaLuF₄:Yb(3+)/Ln(3+)@CaF₂ Upconversion Nanocrystals.

    PubMed

    Li, Hui; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

    2017-02-07

    The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF₄:Yb(3+)/Ln(3+)@CaF₂ (Ln = Er, Ho, Tm) upconversion nanocrystals (UCNCs) based on the newly established host lattice of sodium lutetium fluoride (NaLuF₄). We exploited the liquid-solid-solution method to synthesize the NaLuF₄ core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF₂) shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm). We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals.

  5. New Composites LnBDC@AC and CB[6]@AC: From Design toward Selective Adsorption of Methylene Blue or Methyl Orange.

    PubMed

    Santos, Guilherme de C; Barros, Amanda L; de Oliveira, Carlos A F; da Luz, Leonis L; da Silva, Fausthon F; Demets, Grégoire J-F; Alves Júnior, Severino

    2017-01-01

    New porous composites LnBDC@AC (AC = Activated carbon, Ln = Eu and Gd and BDC = 1,4-benzenedicaboxylate) and CB[6]@AC (CB[6] = Cucurbit[6]uril) were obtained using hydrothermal route. The LnBDC and CB[B] are located inside the pore of the carbon materials as was observed in SEM-EDS, XRPD and FT-IR analysis. Porosimetry analysis showed values typically between AC and LnBDC material, with pore size and surface area, respectively, 29,56 Å and 353.98 m2g-1 for LnBDC@AC and 35,53 Å and 353.98 m2g-1 for CB[6]@AC. Both materials showed good absorptive capacity of metil orange (MO) and methylene blue (MB) with selectivity as a function of pH. For acid pH, both materials present selectivity by MB and alkaline pH for MO, with notable performance for CB[6]@AC. Additionally, europium luminescence was used as structural probe to investigate the coordination environment of Eu3+ ions in the EuBDC@AC composite after adsorption experiment.

  6. New Composites LnBDC@AC and CB[6]@AC: From Design toward Selective Adsorption of Methylene Blue or Methyl Orange

    PubMed Central

    Santos, Guilherme de C.; Barros, Amanda L.; de Oliveira, Carlos A. F.; da Luz, Leonis L.; da Silva, Fausthon F.; Demets, Grégoire J.-F.; Alves Júnior, Severino

    2017-01-01

    New porous composites LnBDC@AC (AC = Activated carbon, Ln = Eu and Gd and BDC = 1,4-benzenedicaboxylate) and CB[6]@AC (CB[6] = Cucurbit[6]uril) were obtained using hydrothermal route. The LnBDC and CB[B] are located inside the pore of the carbon materials as was observed in SEM-EDS, XRPD and FT-IR analysis. Porosimetry analysis showed values typically between AC and LnBDC material, with pore size and surface area, respectively, 29,56 Å and 353.98 m2g-1 for LnBDC@AC and 35,53 Å and 353.98 m2g-1 for CB[6]@AC. Both materials showed good absorptive capacity of metil orange (MO) and methylene blue (MB) with selectivity as a function of pH. For acid pH, both materials present selectivity by MB and alkaline pH for MO, with notable performance for CB[6]@AC. Additionally, europium luminescence was used as structural probe to investigate the coordination environment of Eu3+ ions in the EuBDC@AC composite after adsorption experiment. PMID:28107440

  7. Une nouvelle famille de pyrochlores: les oxynitrures Ln2Ta 2O 5N 2. Préparation et étude cristallochimique

    NASA Astrophysics Data System (ADS)

    Pors, F.; Marchand, R.; Laurent, Y.

    1993-11-01

    Par action de l'ammoniac à 900-950°C sur les tantalates de terres rares LnTaO 4, on a mis en évidence une nouvelle famille d'oxynitrures dont la structure est de type pyrochlore. Ces composés Ln2Ta 2O 5N 2 ont été obtenus pour les lanthanides de rayon inférieur ou égal à celui du néodyme, ainsi que pour l'yttrium. La maille cristalline est de symétrie cubique (10,2 Å < a < 10,6 Å). La stoechiométrie anionique impose un désordre oxygène-azote au moins partiel entre les deux sites cristallographiques correspondants. New oxynitrides Ln2 Ta 2O 5N 2 ( Ln = Nd → Yb, Y), belonging to the pyrochlore type structure, have been prepared by heating at 900-950°C the LnTaO 4 corresponding tantalates. The a parameter of the cubic unit cell is comprised between 10.2 and 10.6 Å. Because of the anionic stoichiometry, oxygen and nitrogen atoms are disordered, at least partially.

  8. Ionic-radius-driven selection of the main-group-metal cage for intermetalloid clusters [Ln@Pbx Bi14-x](q-) and [Ln@Pby Bi13-y](q-) (x/q=7/4, 6/3; y/q=4/4, 3/3).

    PubMed

    Ababei, Rodica; Massa, Werner; Weinert, Bastian; Pollak, Patrik; Xie, Xiulan; Clérac, Rodolphe; Weigend, Florian; Dehnen, Stefanie

    2015-01-02

    Reactions of the binary, pseudo-homoatomic Zintl anion (Pb2 Bi2 )(2-) with Ln(C5 Me4 H)3 (Ln=La, Ce, Nd, Gd, Sm, Tb) in the presence of [2.2.2]crypt in ethane-1,2-diamine/toluene yielded ten [K([2.2.2]crypt)](+) salts of lanthanide-doped semimetal clusters with 13 or 14 surface atoms. Single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy indicated the presence of the anions [Ln@Pb6 Bi8 ](3-), [Ln@Pb3 Bi10 ](3-), [Ln@Pb7 Bi7 ](4-), or [Ln@Pb4 Bi9 ](4-) in single or double salts; the latter showed various ratios of the components in the solid state. The anions are the first ternary intermetalloid clusters comprising only elements of the sixth period of the periodic table, namely, Pb, Bi and lanthanides. This study, which was complemented by ESI mass spectrometry and (139) La NMR spectroscopy in solution, rationalizes a continuous development of the ratio of 13:14-atom cages with the ionic radius of the embedded Ln(3+) ion, which seems to select the most suitable cage type. Quantum chemical investigations helped to analyze this situation in more detail and to explain the observed subtle influence of the atomic radii. Magnetic measurements confirmed that the embedded Ln(3+) ions keep their expected paramagnetic or diamagnetic nature. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Hetero-metallic {3d-4f-5d} complexes: preparation and magnetic behavior of trinuclear [(L(Me2)Ni-Ln){W(CN)(8)}] compounds (Ln = Gd, Tb, Dy, Ho, Er, Y; L(Me2) = Schiff base) and variable SMM characteristics for the Tb derivative.

    PubMed

    Sutter, Jean-Pascal; Dhers, Sébastien; Rajamani, Raghunathan; Ramasesha, S; Costes, Jean-Pierre; Duhayon, Carine; Vendier, Laure

    2009-07-06

    Assembling bimetallic {Ni-Ln}(3+) units and {W(CN)(8)}(3-) is shown to be an efficient route toward heteronuclear {3d-4f-5d} compounds. The reaction of either the binuclear [{L(Me2)Ni(H(2)O)(2)}{Ln(NO(3))(3)}] complexes or their mononuclear components [L(Me2)Ni] and Ln(NO(3))(3) with (HNBu(3))(3){W(CN)(8)} in dmf followed by diffusion of tetrahydrofuran yielded the trinuclear [{L(Me2)NiLn}{W(CN)(8)}] compounds 1 (Ln = Y), 2a,b (Gd), 3a,b (Tb), 4 (Dy), 5 (Ho), and 6 (Er) as crystalline materials. All of the derivatives possess the trinuclear core resulting from the linkage of the {W(CN)(8)} to the Ni center of the {Ni-Ln} unit. Differences are found in the solvent molecules acting as ligands and/or in the lattice depending on the crystallization conditions. For all the compounds ferromagnetic {Ni-W} and {Ni-Ln} (Ln = Gd, Tb, Dy, and Er} interactions are operative resulting in high spin ground states. Parameterization of the magnetic behaviors for the Y and Gd derivatives confirmed the strong cyano-mediated {Ni-W} interaction (J(NiW) = 27.1 and 28.5 cm(-1)) compared to the {Ni-Gd} interaction (J(NiGd) = 2.17 cm(-1)). The characteristic features for slow relaxation of the magnetization are observed for two Tb derivatives, but these are modulated by the crystal phase. Analysis of the frequency dependence of the alternating current susceptibility data yielded U(eff)/k(B) = 15.3 K and tau(0) = 4.5 x 10(-7) s for one derivative whereas no maxima of chi(M)'' appear above 2 K for the second one.

  10. Synthesis and Lanthanide Coordination Chemistry of Phosphine Oxide Decorated Dibenzothiophene and Dibenzothiophene Sulfone Platforms

    SciTech Connect

    Rosario-Amorin, Daniel; Ouizem, Sabrina; Dickie, D. A.; Paine, Robert T.; Cramer, Roger E.; Hay, Benjamin; Podair, Julien; Delmau, Laetitia Helene

    2014-01-01

    Syntheses for new ligands based upon dibenzothiophene and dibenzothiophene sulfone platforms, decorated with phosphine oxide and methylphosphine oxide donor groups, are described. Coordination chem. of 4, 6- bis(diphenylphosphinoylmethyl) dibenzothiophene (8) , 4, 6- bis(diphenylphosphinoylmethyl) dibenzothiophene- 5, 5- dioxide (9) and 4, 6- bis(diphenylphosphinoyl) dibenzothiophene- 5, 5- dioxide (10) with lanthanide nitrates, Ln(NO3) 3 (H2O) n is outlined, and crystal structure detns. reveal a range of chelation interactions on Ln(III) ions. The HNO3 dependence of the solvent extn. performance of 9 and 10 in 1, 2- dichloroethane for Eu(III) and Am(III) is described and compared against the extn. behavior of related dibenzofuran ligands (2, 3; R = Ph) and n- octyl(phenyl) - N, N- diisobutylcarbamoylmethyl phosphine oxide (4) measured under identical conditions.

  11. Preparation and spectroscopic properties of rare-earth (RE) (RE = Sm, Eu, Tb, Dy, Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) phosphate in vacuum ultraviolet region

    SciTech Connect

    Zhang, Zhi-Jun; Lin, Xiao; Zhao, Jing-Tai; Zhang, Guo-Bin

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► We report the VUV spectroscopic properties of rare-earth ions in K{sub 2}LnZr(PO{sub 4}){sub 3}. ► The O{sup 2−}-Eu{sup 3+} charge transfer bands at about 220 nm have been observed. ► The 4f–5d spin-allowed and spin-forbidden transitions of Tb{sup 3+} have been observed. ► There is energy transfer between the host and rare-earth activators. -- Abstract: Rare earth (RE = Sm, Eu, Tb, Dy and Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) have been synthesized by solid-state reaction method, and their vacuum ultraviolet (VUV) excitation luminescent characteristics have been investigated. The band in the wavelength range of 130–157 nm and the other one range from 155 to 216 nm with the maximum at about 187 nm in the VUV excitation spectra of these compounds are attributed to the host lattice absorption and O–Zr charge transfer transition, respectively. The charge transfer bands (CTB) of O{sup 2−}-Sm{sup 3+}, O{sup 2−}-Dy{sup 3+} and O{sup 2−}-Tm{sup 3+}, in Sm{sup 3+}, Dy{sup 3+} and Tm{sup 3+}-activated samples, have not been obviously observed probably because the 2p electrons of oxygen are tightly bound to the zirconium ion in the host lattice. For Eu{sup 3+}-activated samples, the relatively weak O{sup 2−}-Eu{sup 3+} CTB at about 220 nm is observed. And for Tb{sup 3+}-activated samples, the bands at 223 and 258 nm are related to the 4f-5d spin-allowed and spin-forbidden transitions of Tb{sup 3+}, respectively. It is observed that there is energy transfer between the host lattice and the luminescent activators (e.g. Eu{sup 3+}, Tb{sup 3+}). From the standpoint of luminescent efficiency, color purity and chemical stability, K{sub 2}GdZr(PO{sub 4}){sub 3}:Sm{sup 3+}, Eu{sup 3+}, Tb{sup 3+} are attractive candidates for novel yellow, red, green-emitting PDP phosphors.

  12. Préparation et caractérisation d'une série de cyclohexaphosphates de terres rares: Ln2P 6O 18 · 10H 2O

    NASA Astrophysics Data System (ADS)

    Elmokhtar, Ould Sidi Mohamed; Rzaigui, Mohamed

    1995-10-01

    Six new cyclohexaphosphates with the general formula Ln2 P 6O 18 · 10H 2O with Ln = La, Ce, Pr, Sm, Er, and Yb are reported. They belong to two different structure types. The first type, common to three compounds, corresponds to Ln = La, Ce, and Pr, with an orthorhombic unit cell, Z = 2, and space group P2 12 12. The second type, common to three compounds also, corresponds to Ln = Sm, Er, and Yb, with a monoclinic unit cell, Z = 4, and space group P2 1/ a. Synthesis and characterization by X-ray diffraction, IR absorption, and TA are given.

  13. Structures and crystal chemistry of the double perovskites Ba{sub 2}LnB'O{sub 6} (Ln=lanthanide B'=Nb{sup 5+} and Ta{sup 5+}): Part I. Investigation of Ba{sub 2}LnTaO{sub 6} using synchrotron X-ray and neutron powder diffraction

    SciTech Connect

    Saines, Paul J.; Spencer, Jarrah R.; Kennedy, Brendan J. Avdeev, Maxim

    2007-11-15

    The structure of 14 compounds in the series Ba{sub 2}LnTaO{sub 6} have been examined using synchrotron X-ray diffraction and found to undergo a sequence of phase transitions from I2/m monoclinic to I4/m tetragonal to Fm3-bar m cubic symmetry with decreasing ionic radii of the lanthanides. Ba{sub 2}LaTaO{sub 6} is an exception to this with variable temperature neutron diffraction being used to establish that the full series of phases adopted over the range of 15-500 K is P2{sub 1}/n monoclinic to I2/m monoclinic to R3-bar rhombohedral. The chemical environments of these compounds have also been investigated and the overbonding to the lanthanide cations is due to the unusually large size for the B-site in these perovskites. - Graphical abstract: The evolution of the structure across the series of double perovskites Ba{sub 2}LnTaO{sub 6} is established using a combination of synchrotron X-ray and neutron diffraction. The symmetry increases from monoclinic to tetragonal and then cubic as the size of the lanthanide decreases.

  14. Chemical Characteristics of Cold-Pressed Blackberry, Black Raspberry, and Blueberry Seed Oils and the Role of the Minor Components in Their Oxidative Stability.

    PubMed

    Li, Quanquan; Wang, Jiankang; Shahidi, Fereidoon

    2016-07-06

    The chemical characteristics of cold-pressed blackberry, black raspberry, and blueberry seed oils were evaluated for their fatty acid composition, positional distribution of fatty acids, triacylglycerol (TAG) profile, and minor component profile. The role of minor components, including tocols and pigments, on the oxidative stability was also investigated using high-temperature- and fluorescent-lighting-induced oxidation before and after tested berry seed oils were stripped of their minor components. The results indicated that all tested berry seed oils contained significant levels of palmitic (C16:0), stearic (C18:0), oleic (18:1), linoleic (C18:2ω-6), and α-linolenic (C18:3ω-3) acids, along with a favorable ratio of ω-6/ω-3 fatty acids (1.49-3.86); palmitic, stearic, oleic, and α-linolenic acids were predominantly distributed on the terminal positions. Six TAGs, namely, LnLnLn, LnLLn, LLLn, LLL, OLL, and OLLn, were the major species detected in the tested berry seed oils. Total tocol contents were 286.3-1302.9 mg/kg, which include α-, γ-, and δ-tocopherols as well as δ-tocotrienol. Oxidative stability of the three berry seed oils was compromised after the removal of tocols under high-temperature-induced oxidation, while the loss of pigments (chlorophylls) led to weak oxidative stability when exposed to fluorescent lights.

  15. Complexation of Ln(3+) Ions with Cyclam Dipicolinates: A Small Bridge that Makes Huge Differences in Structure, Equilibrium, and Kinetic Properties.

    PubMed

    Rodríguez-Rodríguez, Aurora; Regueiro-Figueroa, Martín; Esteban-Gómez, David; Tripier, Raphaël; Tircsó, Gyula; Kálmán, Ferenc Krisztián; Bényei, Attila Csaba; Tóth, Imre; de Blas, Andrés; Rodríguez-Blas, Teresa; Platas-Iglesias, Carlos

    2016-03-07

    The coordination properties toward the lanthanide ions of two macrocyclic ligands based on a cyclam platform containing picolinate pendant arms have been investigated. The synthesis of the ligands was achieved by using the well-known bis-aminal chemistry. One of the cyclam derivatives (cb-tedpa(2-)) is reinforced with a cross-bridge unit, which results in exceptionally inert [Ln(cb-tedpa)](+) complexes. The X-ray structures of the [La(cb-tedpa)Cl], [Gd(cb-tedpa)](+), and [Lu(Me2tedpa)](+) complexes indicate octadentate binding of the ligands to the metal ions. The analysis of the Yb(3+)-induced shifts in [Yb(Me2tedpa)](+) indicates that this complex presents a solution structure very similar to that observed in the solid state for the Lu(3+) analogue. The X-ray structures of [La(H2Me2tedpa)2](3+) and [Yb(H2Me2tedpa)2](3+) complexes confirm the exocyclic coordination of the metal ions, which gives rise to coordination polymers with the metal coordination environment being fulfilled by oxygen atoms of the picolinate groups and water molecules. The X-ray structure of [Gd(Hcb-tedpa)2](+) also indicates exocyclic coordination that in this case results in a discrete structure with an eight-coordinated metal ion. The nonreinforced complexes [Ln(Me2tedpa)](+) were prepared and isolated as chloride salts in nonaqueous media. However, these complexes were found to undergo dissociation in aqueous solution, except in the case of the complexes with the smallest Ln(3+) ions (Ln(3+) = Yb(3+) and Lu(3+)). A DFT investigation shows that the increased stability of the [Ln(Me2tedpa)](+) complexes in solution across the lanthanide series is the result of an increased binding energy of the ligand due to the increased charge density of the Ln(3+) ion.

  16. Long Non-Coding RNA LnRPT is Regulated by PDGF-BB and Modulates Proliferation of Pulmonary Artery Smooth Muscle Cells.

    PubMed

    Chen, Jidong; Guo, Jiao; Cui, Xiaolei; Dai, Yan; Tang, Zhixiong; Qu, Junle; Raj, J Usha; Hu, Qinghua; Gou, Deming

    2017-09-15

    Pulmonary artery hypertension (PAH) is a rare and fatal disorder with extensive remodeling of pulmonary arteries mediated by hyperproliferation of pulmonary artery smooth muscle cell (PASMC). Aberrant platelet-derived growth factor (PDGF) activity can lead to hyperproliferation of PASMC, however, little is known about the role of long noncoding RNA (lncRNA) in this process. Using RNA sequencing (RNA-seq), we identified 725 lncRNAs in rat PASMC (RPASMC), 95 of which were expressed differentially in response to PDGF-BB treatment. Depletion of 4 lncRNAs affected proliferation of RPASMC, as measured by EdU incorporation assay. Among these, one lncRNA named LnRPT (lncRNA regulated by PDGF and TGFβ) was the most potent one to promote proliferation of PASMC when knocked down. Oppositely, proliferation of PASMC was repressed when LnRPT was overexpressed. Mechanistically, lnRPT inhibited the expression of two genes involved in the Notch signaling pathway, notch3 and jag1, as well as the cell cycle regulating genes, ccna2. In addition, downregulation of LnRPT induced by PDGF-BB was abrogated when PI3K activity was inhibited with pictilisib. Downregulation of LnRPT was also observed in the pulmonary arteries of MCT-induced PAH rats. These data provide novel insights into the effects of PDGF-BB on lncRNA expression in PASMC, and identify one lncRNA, LnRPT, which was implied in PAH development, as a regulator of PASMC proliferation through mediating the Notch signaling pathway and cell cycle.

  17. Syntheses, crystal structures and properties of series of 4d–4f ln(III)–Ag(I) heterometallic coordination polymers

    SciTech Connect

    Ran, Xing-Rui; Wang, Ning; Xie, Wei-Ping; Xiong, Yan-Ju; Cheng, Qian; Long, Yi; Yue, Shan-Tang; Liu, Ying-Liang

    2015-05-15

    By control of the experimental parameters such as ligands, pH value and reacting temperature, series of three-dimensional (3D) 4d–4f Ln(III)–Ag(I) porous coordination polymers (PCPs) with interesting chain-layer construction, namely, ([Ln{sup III}Ag{sup I}(na)(ina)(ox)]·2(H{sub 2}O)){sub n} [Ln=Sm(1), Eu(2), Gd(3), Tb(4), Dy(5), Ho(6), Y(7), Yb(8)], have been successfully synthesized under hydrothermal conditions and structurally characterized. All the complexes are characterized by elemental analyses, FT-IR spectroscopy, Powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Furthermore, the luminescence properties of compounds 2 and 4 and the magsnetic properties of complexes 3 and 5 were also investigated in detail. - Graphical abstract: Series of three-dimensional (3D) 4d–4f Ln(III)–Ag(I) porous coordination polymers (PCPs) with interesting chain-layer construction which are featured by tetranuclear Ln{sub 2}Ag{sub 2} and ‘non-linear’ N–Ag–N linkages. - Highlights: • Complexes 1–8 are first built by three kinds of organic ligands based on nicotinic acid and isonicotinic acid. • PCPs 1–8 are featured by tetranuclear Ln{sub 2}Ag{sub 2} and ‘non-linear’ N–Ag–N linkages. • The total solvent-accessible volume of PCP 2 comprises 11.6% of the crystal volume after dislodging the free water molecules. • Complexes 2 and 4 exhibit characteristic lanthanide-centered luminescence, while compounds 3 and 5 show antiferromagnetic behaviors.

  18. Structural requirements for human inducible nitric oxide synthase substrates and substrate analogue inhibitors.

    PubMed

    Grant, S K; Green, B G; Stiffey-Wilusz, J; Durette, P L; Shah, S K; Kozarich, J W

    1998-03-24

    Inducible nitric oxide synthase (iNOS; EC 1.14.13.39) catalyzes the NADPH-dependent oxidation of one of the free guanidino nitrogens of L-Arg to form nitric oxide and L-citrulline. Analogues of L-Arg and the inhibitor, L-N6-(1-iminoethyl)lysine, were used to define structural elements required for the binding and catalysis of compounds. L-Arg analogues with sequentially shorter methylene spacing between the guanidino group and the amino acid portion of the molecule were not iNOS substrates but were reversible inhibitors. L-Arg analogues such as agmatine with a hydroxyl substitution at the 2-amino position were substrates. Desaminoarginine was not a substrate but a reversible inhibitor. Desaminoarginine, agmatine, and argininic acid bound to the enzyme to give type I difference spectra similar to that of L-Arg. The amidino compounds L-N6-(1-iminoethyl)lysine, L-N5-(1-iminoethyl)ornithine, and N5-(1-iminoethyl)cadaverdine, but not N6-(1-iminoethyl)-6-aminocaproic acid, were NADPH-dependent, irreversible inactivators of iNOS. For both the L-Arg and L-N6-(1-iminoethyl)lysine analogues, the 2-amino group appeared to play an important role in catalytic events leading to either substrate turnover or mechanism-based inactivation. Inactivation of iNOS by L-N6-(1-iminoethyl)lysine was NADPH- and dioxygen-dependent, but low incorporation of radiolabel with DL--4, 5-3H]-N6-(1-iminoethyl)lysine indicates that the mechanism of enzyme inactivation is not covalent modification of the protein.

  19. Synthesis of Sr(1-x-y)Al4O7:Eu{x/2+},Ln{y/3+} (Ln = Dy, Y, Pr) nanophosphors using rapid gel combustion process and their down conversion characteristics

    NASA Astrophysics Data System (ADS)

    Singh, Devender; Tanwar, Vijeta; Samantilleke, Anura Priyajith; Mari, Bernabe; Bhagwan, Shri; Singh, Krishan Chander; Kadyan, Pratap Singh; Singh, Ishwar

    2017-03-01

    Eu2+ and Eu2++Ln3+ doped SrAl4O7 nanophosphors were synthesized by rapid gel combustion process. The morphology of prepared phosphors was examined with scanning and transmission electron microscopy. The phase identification and the crystal structures of nanophosphors were studied using X-ray powder diffraction techniques. Luminescence characteristics of the prepared nanophosphors were analyzed on account of excitation, emission and phosphorescence decay analysis. The emission spectra demonstrated the broad green emission attributed to 4f65d1→ 4f7 transition of the Eu2+ ions. The effect of codoping of some trivalent lanthanide (Dy3+, Pr3+ and Y3+) ions were investigated for improving the emission intensity and phosphorescence decay time of the basic lattice of SrAl4O7:Eu2+ phosphors. The synthesized materials had enhanced bright luminescent properties that could suitably be applied for display as well as photovoltaic applications. [Figure not available: see fulltext.

  20. Preparation of overdoped superconducting RBa 2Cu 3O y+ Δy (R=Ln and Y) in a single phase

    NASA Astrophysics Data System (ADS)

    Okai, B.; Ono, A.; Mitsuhashi, T.

    2002-01-01

    Overdoped RBa 2Cu 3O y+ Δy specimens (R=Ln and Y) were prepared in a single phase by heat treatment at 600°C under high oxygen pressure. The relationship between Tc, Δy, and R for these specimens is almost the same as that previously obtained for specimens overdoped at temperatures above 1000°C. For R=light Ln, Tc decreases systematically with increasing Δy. For other R's, Tc remains almost unchanged over the range of Δy⩽0.5. The maximum value of Δy is 0.85 for R=Nd.

  1. Building 1D lanthanide chains and non-symmetrical [Ln2] "triple-decker" clusters using salen-type ligands: magnetic cooling and relaxation phenomena.

    PubMed

    Canaj, Angelos B; Siczek, Milosz; Otręba, Marta; Lis, Tadeusz; Lorusso, Giulia; Evangelisti, Marco; Milios, Constantinos J

    2016-11-22

    A solvothermal reaction between Ln(NO3)3·6H2O (Ln: Gd, Tb and Dy), 2-hydroxy-1-naphthaldehyde, 2-OH-naphth, and ethylenediamine, en, in MeOH in the presence of a base, NEt3, led to the formation of the 1D coordination polymers [Ln(L)(MeO)(MeOH)0.5]n·MeOH (Ln = Gd (1·MeOH), Tb(2), Dy (3·MeOH); H2L = 1,1'-((1E,1'E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-ol), the Schiff-base ligand derived from the condensation of 2-OH-naphth and en), while a similar reaction in an excess of NaN3 yielded 1D coordination polymers [Ln(L)(N3)0.75(MeO)0.25(MeOH)]n (Ln = Gd (4), Tb (5), Dy (6)). Finally, upon replacing ethylenediamine with o-phenylenediamine, o-phen, we managed to isolate the discrete dimers [Dy2(L')3(MeOH)]·2MeOH (7·2MeOH) and [Gd2(L')3(MeOH)]·2MeOH (8·2MeOH) (H2L' = 1,1'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))bis (naphthalen-2-ol), the Schiff-base ligand from the condensation of 2-OH-naphth and o-phen). Polymers 1-3 describe one-dimensional chains, containing alternating seven- and eight-coordinate Ln(III) metal centers, polymers 4-6 contain eight-coordinate lanthanide ions, while in both 7 and 8 the two Ln(III) centers are eight- and seven-coordinate, adopting square antiprismatic and "piano-stool" geometry, respectively. The magnetocaloric properties of the three Gd(III) analogues were determined from magnetic measurements, yielding the magnetic entropy change -ΔSm = 21.8, 23.0 and 16.0 J kg(-1) K(-1) at T = 3.0 K on demagnetization of 7 T to 0, for 1, 4 and 8, respectively. The study of the magnetic properties also revealed that all three Dy(III) analogues (3, 6 and 7) display out-of-phase signals, therefore suggesting slow magnetic relaxation, while such behaviour was not established in the Tb(III) analogues.

  2. Two-dimensional 3d-4f heterometallic coordination polymers: syntheses, crystal structures, and magnetic properties of six new Co(II)-Ln(III) compounds.

    PubMed

    Díaz-Gallifa, Pau; Fabelo, Oscar; Pasán, Jorge; Cañadillas-Delgado, Laura; Lloret, Francesc; Julve, Miguel; Ruiz-Pérez, Catalina

    2014-06-16

    Six new heterometallic cobalt(II)-lanthanide(III) complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O)6]·10H2O [Ln = Nd(III) (1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8]n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized via single-crystal X-ray diffraction. 1 and 2 are isostructural compounds with a structure composed of anionic layers of [Ln(bta)(H2O)2]n(n-) sandwiching mononuclear [Co(H2O)6](2+) cations plus crystallization water molecules, which are interlinked by electrostatic forces and hydrogen bonds, leading to a supramolecular three-dimensional network. 3-6 are also isostructural compounds, and their structure consists of neutral layers of formula [Ln2Co(bta)2(H2O)8]n and crystallization water molecules, which are connected through hydrogen bonds to afford a supramolecular three-dimensional network. Heterometallic chains formed by the regular alternation of two nine-coordinate lanthanide(III) polyhedra [Ln(III)O9] and one compressed cobalt(II) octahedron [Co(II)O6] along the crystallographic c-axis are cross-linked by bta ligands within each layer of 3-6. Magnetic susceptibility measurements on polycrystalline samples for 3-6 have been carried out in the temperature range of 2.0-300 K. The magnetic behavior of these types of Ln(III)-Co(II) complexes, which have been modeled by using matrix dagonalization techniques, reveals the lack of magnetic coupling for 3 and 4, and the occurrence of weak antiferromagnetic interactions within the Gd(III)-Gd(III) (5) and Tb(III)-Tb(III) (6) dinuclear units through the exchange pathway provided by the double oxo(carboxylate) and double syn-syn carboxylate bridges.

  3. Crystal structures of [Ln(NO3)3(μ2-bpydo)2], where Ln = Ce, Pr or Nd, and bpydo = 4,4'-bi-pyridine N,N'-dioxide: layered coordination networks containing 4(4) grids.

    PubMed

    Stromyer, Michael L; Lilly, Cassandra P; Dillner, Adam J; Knaust, Jacqueline M

    2016-01-01

    Three isostructural coordination networks of Ce, Pr, and Nd nitrate with 4,4'-bi-pyridine N,N'-dioxide (bpydo) are reported, namely poly[[tris-(nitrato-κ(2) O,O')cerium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Ce(NO3)3(C10H8N2O2)2], poly[[tris-(nitrato-κ(2) O,O')praeseodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Pr(NO3)3(C10H8N2O2)2], and poly[[tris(nitrato-κ(2) O,O')neodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N'], [Nd(NO3)3(C10H8N2O2)2]. All three compounds are isostructural to the previously reported La analogue. The asymmetric unit of [Ln(NO3)3(μ2-bpydo)2] contains one lanthanide cation, two bpydo ligands, and three nitrate anions. Both bpydo ligands act as end-to-end μ2-bridges and display nearly ideal cis and gauche conformations, respectively. The bpydo ligands link the ten-coordinate Ln (III) cations, forming inter-digitating 4(4) grid-like layers extending parallel to (-101), where inter-digitation of layers is promoted by C-H⋯O inter-actions between nitrate anions and bpydo ligands. The inter-digitated layers are linked to sets of neighboring layers via further C-H⋯O and π-π inter-actions.

  4. Highly uniform and monodisperse beta-NaYF(4):Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: hydrothermal synthesis and luminescent properties.

    PubMed

    Li, Chunxia; Quan, Zewei; Yang, Jun; Yang, Piaoping; Lin, Jun

    2007-08-06

    beta-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu3+ (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to 5D0-3 --> 7FJ (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively. When doped with 5% Tb3+ ions, the strong DC fluorescence corresponding to 5D4 --> 7FJ (J = 6, 5, 4, 3) transitions with 5D4 --> 7F5 (green emission at 544 nm) being the most prominent group that has been observed. In addition, under 980 nm laser excitation, the Yb3+/Er3+- and Yb3+/Tm3+-codoped beta-NaYF4 samples exhibit bright green and whitish blue up-conversion (UC) luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.

  5. Crystal structures of [Ln(NO3)3(μ2-bpydo)2], where Ln = Ce, Pr or Nd, and bpydo = 4,4′-bi­pyridine N,N′-dioxide: layered coordination networks containing 44 grids

    PubMed Central

    Stromyer, Michael L.; Lilly, Cassandra P.; Dillner, Adam J.; Knaust, Jacqueline M.

    2016-01-01

    Three isostructural coordination networks of Ce, Pr, and Nd nitrate with 4,4′-bi­pyridine N,N′-dioxide (bpydo) are reported, namely poly[[tris­(nitrato-κ2 O,O′)cerium(III)]-bis­(μ2-4,4′-bi­pyridine N,N′-dioxide-κ2 N:N′)], [Ce(NO3)3(C10H8N2O2)2], poly[[tris­(nitrato-κ2 O,O′)praeseodymium(III)]-bis­(μ2-4,4′-bi­pyridine N,N′-dioxide-κ2 N:N′)], [Pr(NO3)3(C10H8N2O2)2], and poly[[tris(nitrato-κ2 O,O′)neodymium(III)]-bis­(μ2-4,4′-bi­pyridine N,N′-dioxide-κ2 N:N′], [Nd(NO3)3(C10H8N2O2)2]. All three compounds are isostructural to the previously reported La analogue. The asymmetric unit of [Ln(NO3)3(μ2-bpydo)2] contains one lanthanide cation, two bpydo ligands, and three nitrate anions. Both bpydo ligands act as end-to-end μ2-bridges and display nearly ideal cis and gauche conformations, respectively. The bpydo ligands link the ten-coordinate Ln III cations, forming inter­digitating 44 grid-like layers extending parallel to (-101), where inter­digitation of layers is promoted by C—H⋯O inter­actions between nitrate anions and bpydo ligands. The inter­digitated layers are linked to sets of neighboring layers via further C—H⋯O and π–π inter­actions. PMID:26870578

  6. Circular and Chainlike Copper(II)-Lanthanide(III) Complexes Generated by Assembly Reactions of Racemic and Chiral Copper(II) Cross-Linking Ligand Complexes with Ln(III)(NO3)3·6H2O (Ln(III) = Gd(III), Tb(III), Dy(III)).

    PubMed

    Ueno, Takahiro; Fujinami, Takeshi; Matsumoto, Naohide; Furusawa, Masaki; Irie, Ryo; Re, Nazzareno; Kanetomo, Takuya; Ishida, Takayuki; Sunatsuki, Yukinari

    2017-02-06

    The 1:1 assembly reaction of the racemic form of the cross-linking ligand complex Na[Cu(II)L(dpen(1R2R/1S2S))] with Ln(III)(NO3)3·6H2O gave the centrosymmetric circular (Cu(II)Ln(III))2 complex [Cu(II)L(dpen(1R2R/1S2S))Ln(III)(NO3)2]2 (1Ln: Ln = Gd, Tb, Dy), while the reaction of the enantiopure form Na[Cu(II)L(dpen(1R2R))] with Ln(III)(NO3)3·6H2O gave the chiral chainlike (Cu(II)Ln(III))1∞ complex [Cu(II)L(dpen(1R2R))Ln(III)(NO3)2(CH3CN)]1∞·CH3CN (2Ln: Ln = Gd, Tb, Dy), where {Cu(II)L(dpen(1R2R))}(-) is (N-((1R,2R)-2-(((E)-3-ethoxy-2-oxybenzylidene)amino)-1,2-diphenylethyl)-2-oxybenzamide)copper(II) and {Cu(II)L(dpen(1R2R/1S2S))}(-) is the racemic mixture of {Cu(II)L(dpen(1R2R))}(-) and {Cu(II)L(dpen(1S2S))}(-). The copper(II) component functions as a cross-linking ligand complex and bridges two Ln(III) ions at two phenoxo oxygen atoms and one ethoxy oxygen atom, as well as at an amido oxygen atom. For 1Ln, two binuclear species of [Cu(II)L(dpen(1R2R))Ln(III)(NO3)2] and [Cu(II)L(dpen(1S2S))Ln(III)(NO3)2] with opposite chiralities are linked by two amido oxygen atoms O3 and O3* to form a centrosymmetric circular structure with Gd-Cu = 3.370(1) Å and Gd-Cu* = 5.627(1) Å. For 2Ln, binuclear species with the same chirality are bridged by Gd-O3* = 2.228(5) Å to form a chiral chainlike structure with Gd-Cu = 3.3348(9) Å and Gd-Cu* = 6.2326(9) Å. The bridged angles through the amido group of Gd-O3*═C7* are 133.9(5) and 177.6(4)° for 1Gd and 2Gd, respectively. The magnetic susceptibilities of 1Gd and 2Gd were analyzed by the spin-only Hamiltonian on the basis of the circular tetranuclear (-Cu(II)Gd(III)-)2 and linear chainlike (-Cu(II)Gd(III)-)1∞ structures, respectively. The Cu(II)-Gd(III) magnetic interactions through two phenoxo bridges and a three-a