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1

Optical Properties of Gd, Dy, and Tb.  

National Technical Information Service (NTIS)

Optical constants in the spectral range 1.5-5.5 eV are presented for the heavy rare-earth metals, Gd, Tb, and Dy. The samples are thin films prepared by vacuum evaporation at pressures below 10 to the minus 9th power torr, and are studied in situ using a ...

J. L. Erskine G. A. Blake C. J. Flaten

1974-01-01

2

Influence of Dy3+ coactivator on the luminescence properties of Gd2O2S:Tb3+ phosphor  

NASA Astrophysics Data System (ADS)

Gd2O2S:Tb, Dy phosphor were synthesized by co-precipitation method combined with solid-state reactions. The crystal structure and luminescent properties were investigated in this paper. It was confirmed that no new phase was introduced by the analysis of X-ray diffractions (XRD) and fluorescence spectroscopy. It was also illustrated that the lattice size was decreased by doping Dy3+ ions. The results showed that the Dy3+ coactivator had a remarkable influence on the spectral properties of the Gd2O2S:Tb phosphor and can be taken as rare earth ion detector to determine the micro-structure of phosphors. Especially the cross relaxation between Tb3+ and Dy3+ may take place to form the non-radiative energy transfer. Dy3+ as the coactivator added in Gd2O2S:Tb could enhance the luminescence and not disturb its other primary properties. With Dy3+ concentration increased, the intensity of 4F9/2--H13/2 transition at 578 nm was increased further and the emission of 5D4--7FJ transition was highly improved to cause greener emission.

Wang, Fei; Liu, Dachun; Yang, Bin; Zhang, Jinchao; Dai, Yongnian

2012-01-01

3

A new family of Ln-radical chains (Ln = Nd, Sm, Gd, Tb and Dy): synthesis, structure, and magnetic properties.  

PubMed

Five new one-dimensional rare earth-nitronyl nitroxide radical complexes [Ln(hfac)3(NIT-3BrPhOMe)]n (Ln = Nd (1), Sm (2), Gd (3), Tb (4), Dy (5); hfac = hexafluoroacetylacetonate; NIT-3BrPhOMe = 2-(3'-bromo-4'-methoxyl)-4,4,5,5-tetramethyl-imidazolyl-1-oxyl-3-oxide) have been successfully prepared and structurally characterized. Five complexes possess linear chain structure in which the NIT-3BrPhOMe radical ligands link Ln(hfac)3 units through the oxygen atoms of nitronyl nitroxide groups. DC magnetic studies show that Nd, Sm and Gd complexes are paramagnetic above 2.0 K, whereas Tb and Dy complexes show antiferromagnetic ordering with T(N) = 19.9 K and 6.4 K, respectively. Moreover, Tb and Dy complexes exhibit frequency-dependence of ac magnetic susceptibilities, suggesting the presence of slow magnetic relaxation. This work demonstrated that the substituents of the nitronyl nitroxide radical and the lanthanide ion can play a crucial role in modulating the magnetic behavior for one-dimensional lanthanide-radical systems. PMID:24296642

Hu, Peng; Wang, Xiufeng; Ma, Yue; Wang, Qinglun; Li, Licun; Liao, Daizheng

2014-02-01

4

Study of electric quadrupole interactions at 111Cd on Zn sites in RZn (R = Ce, Gd, Tb, Dy) compounds using the PAC spectroscopy  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole interactions at Zn sites in the intermetallic compounds RZn (R = Ce, Gd, Tb, Dy) have been investigated by perturbed gamma-gamma angular correlation (PAC) spectroscopy using 111In(111Cd) as probe nuclei. Measurements were carried out in the temperature range of 10-295 K. These compounds exhibit CsCl type cubic structure and while CeZn shows antiferromagnetic behaviour, the compounds GdZn, TbZn, DyZn are ferromagnetic. The results show that the EFG in these compounds is sensitive to the distribution of rare-earth 4f-electron charges.

Bosch-Santos, Brianna; Carbonari, Artur W.; Cabrera-Pasca, Gabriel A.; Costa, Messias S.; Saxena, Rajendra N.

2013-05-01

5

Structural characterisation of REBaCo 2O 6- ? phases ( RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho)  

NASA Astrophysics Data System (ADS)

REBaCo 2O 6- ? ( RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho) phases were prepared by solid-state reaction at 1100 °C. Post-reaction heat treatments were carried out to alter the oxygen contents, which were determined by H 2-reduction thermogravimetry. Three closely-related structure types were observed, with the general sequence: tetragonal (??0.6) to orthorhombic (0.6???0.4) to tetragonal (0.4??) with increasing oxygen content. Rietveld refinement of combined X-ray and neutron powder diffraction data of NdBaCo 2O 6- ? was carried out for four values of ?. Oxygen deficiency is accommodated by partial occupancy of two sets of oxygen sites, giving a range of coordination environments for Co. Electron diffraction patterns revealed a superlattice ˜2a×4a×c with Cmmm symmetry, where a and c refer to the (pseudo) tetragonal subcell. Tweed-like ferroelastic domains were routinely observed, suggesting that compositions that appear macroscopically tetragonal by X-ray diffraction are in fact orthorhombic with a?b.

Anderson, P. S.; Kirk, C. A.; Knudsen, J.; Reaney, I. M.; West, A. R.

2005-10-01

6

Family of defect-dicubane Ni4Ln2 (Ln = Gd, Tb, Dy, Ho) and Ni4Y2 complexes: rare Tb(III) and Ho(III) examples showing SMM behavior.  

PubMed

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 ?? 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. PMID:24661008

Zhao, Lang; Wu, Jianfeng; Ke, Hongshan; Tang, Jinkui

2014-04-01

7

High temperature enthalpies and related thermodynamic functions of the trifluorides of Sc, Ce, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb  

Microsoft Academic Search

The high temperature enthalpies of high purity ScF3, CeF3, SmF3, GdF3 (redetermined), TbF3, DyF3, ErF3, TmF3, and YbF3 were measured from 100 to 1600°C and EuF3 from 100 to 975°C. The thermal data for the other fluorides in the rare earth series were reported earlier from this laboratory. The heat capacity, enthalpies of transition and fusion, and related thermodynamic functions

F. H. Spedding; B. J. Beaudry; D. C. Henderson; J. Moorman

1974-01-01

8

Thiacalix[4]arene-supported kite-like heterometallic tetranuclear Zn(II)Ln(III)3 (Ln = Gd, Tb, Dy, Ho) complexes.  

PubMed

Four kite-like tetranuclear Zn(II)Ln(III)3 (Ln= Gd 1, Tb 2, Dy 3, Ho 4) clusters supported by p-tert-butylthiacalix[4]arene (H4BTC4A) have been prepared under solvothermal conditions and structurally characterized by single crystal X-ray diffraction and powder X-ray diffraction (PXRD). In the structures of these four complexes, each of them is capped by two tail-to-tail p-tert-butylthiacalix[4]arene molecules to form a bent sandwich-like unit. The photoluminescent analyses reveal that the H4BTC4A is an efficient sensitizer for Tb(3+) ions in 2. The magnetic properties of complexes 1-4 are also investigated, in which complex 3 exhibits slow magnetization relaxation typical for single molecule magnets. PMID:23485195

Su, Kongzhao; Jiang, Feilong; Qian, Jinjie; Wu, Mingyan; Xiong, Kecai; Gai, Yanli; Hong, Maochun

2013-04-01

9

Electronic structures of hexagonal RMnO3 ( R=Gd , Tb, Dy, and Ho) thin films: Optical spectroscopy and first-principles calculations  

NASA Astrophysics Data System (ADS)

We investigated the electronic structure of multiferroic hexagonal RMnO3 ( R=Gd , Tb, Dy, and Ho) thin films using both optical spectroscopy and first-principles calculations. One of the difficulties in explaining the electronic structures of hexagonal RMnO3 is that they exist in nature with limited rare earth ions (i.e., R=Sc , Y, and Ho-Lu), so a systematic study in terms of the different R ions has been lacking. Recently, our group succeeded in fabricating hexagonal RMnO3 ( R=Gd , Tb, and Dy) using the epitaxial stabilization technique [Adv. Mater. (Weinheim Ger.) 18, 3125 (2006)]. Using artificially stabilized hexagonal RMnO3 , we extended the optical spectroscopic studies on the hexagonal multiferroic manganite system. We observed two optical transitions located near 1.7 and 2.3eV , in addition to the predominant absorption above 5eV . With the help of first-principles calculations, we attributed the low-lying optical absorption peaks to interband transitions from the oxygen states hybridized strongly with different Mn orbital symmetries to the Mn3d3z2-r2 state. As the ionic radius of the rare earth ion increased, we observed a systematic increase of the lowest peak position, which became more evident when compared with previously reported results. We explained this systematic change in terms of a flattening of the MnO5 triangular bipyramid.

Choi, Woo Seok; Kim, Dong Geun; Seo, Sung Seok A.; Moon, Soon Jae; Lee, Daesu; Lee, Jung Hyuk; Lee, Ho Sik; Cho, Deok-Yong; Lee, Yun Sang; Murugavel, Pattukkannu; Yu, Jaejun; Noh, Tae W.

2008-01-01

10

Magnetic structure of R2CoGa8 (R = Gd, Tb and Dy) and evolution of the magnetic structures along the series of intermetallic compounds with R = Gd - Tm  

NASA Astrophysics Data System (ADS)

In this work we have determined the magnetic structure of R2CoGa8 (R = Gd, Tb and Dy) intermetallic compounds using X-ray resonant magnetic scattering in order to study the evolution of the anisotropic magnetic properties along the series for R = Gd-Tm. The three compounds have a commensurate antiferromagnetic structure with a magnetic propagation vector (1/2 1/2 1/2) with Néel temperatures of 21.0, 27.5 and 15.2 K for R = Gd, Tb and Dy, respectively. The critical exponent ? obtained from the temperature dependence of the integrated intensity of the resonant magnetic peaks suggest a 3D magnetism for the three compounds. The energy line shapes at the L2 and L3 edges of the magnetic peaks for these compounds present a purely dipolar character as demonstrated by comparison to first principle calculations. Comparing the simulated and integrated intensities corrected for absorption, we conclude that the magnetic moment direction is in the ab-plane for Gd2CoGa8 compound and parallel to the c-axis for the Tb2CoGa8 and Dy2CoGa8 compounds. This information is used to discuss the evolution of the magnetic structure of R2CoGa8 series for R = Gd-Tm where both the direction of the ordered moment and the ordering temperature evolution along the series can be explained through the competition between the indirect Ruderman-Kittel- Kasuya-Yoshida exchange interaction and crystalline electric field effects.

Giles, Carlos; Madergan, Jose Renato; Adriano, Cris; Vescovi, Rafael; Pagliuso, Pascoal

2013-03-01

11

Tunnel-diode Resonator Spectroscopy of Quantum Levels in Cr12Ln4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) Magnetic Molecules  

NASA Astrophysics Data System (ADS)

The differential magnetic susceptibility for a series of Cr12Ln4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) magnetic molecules was measured in static (up to 16 T) and pulsed (up to 45 T) magnetic fields using a rf tunnel-diode resonator (TDR). At low temperatures, the behavior of these finite spin systems is governed by discrete energy spectra of the individual molecules. In magnetic field, low-energy quantum levels Zeeman-split, crossing at field values where magnetization exhibits a step corresponding to switching between different spin states. In high fields, we detect multiple level crossings which allow for a detailed mapping of the energy diagram. We then perform quantum Monte Carlo (QMC) using a Heisenberg Hamiltonian with three adjustable exchange constants whose values are chosen so as to optimize agreement with the experimental energy spectrum. The variations in results for the studied molecules are correlated to the magnetic properties of the lanthanide ions.

Yeninas, Steven; Luban, Marshall; Prozorov, Ruslan; Coniglio, William A.; Agosta, Charles C.; Engelhardt, Larry; Timco, Grigore A.; Winnpenny, Richard E. P.

2011-03-01

12

Assembling 1D magnetic chain based on octacyanotungstate(V) and [Cu2L2Ln] sub-building units (Ln = Eu, Gd, Tb and Dy).  

PubMed

Reaction of (NBu3H)3[W(CN)8]·H2O and linear trinuclear complexes [Cu(II)2L2Ln(III)(NO3)3] (L = 2,6-di(acetoacetyl)pyridine, Ln = Eu (1), Gd (2), Tb (3) and Dy (4)) leads to the formation of four one-dimensional (1D) complexes. Single crystal X-ray analysis reveals that [W(CN)8](3-) bridges between the [Cu(II)2L2Ln(III)] sub-building units to construct the alternative chains. Magnetic investigation indicates that ferromagnetic interaction occurred between all paramagnetic ions and the slow magnetic relaxation properties were observed in complexes 3 and 4. PMID:23673773

Song, Xiao-Jiao; Zhang, Zai-Chao; Xu, Yong-Lu; Wang, Jun; Zhou, Hong-Bo; Song, You

2013-07-14

13

Syntheses and crystal structures of anhydrous Ln(hfac)3(monoglyme). Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Er, Tm.  

PubMed

The crystal structures of a broad series of anhydrous Ln(hfac)(3)(monoglyme) complexes, prepared in moderate to high yield, are presented: hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-; Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Er, Tm. This study contradicts the general assumption that monoglyme is too small a polyether to act as a partitioning agent displacing coordinated water on the larger lanthanide(III) ions. The structures of an intermediate La(hfac)(3)(monoglyme)(2) species and the hydrated Ce(hfac)(3)(monoglyme)(H(2)O) species are also included. The crystallographic evidence presented herein is supplemented by other characterization techniques (melting point, IR, etc.) and trends are delineated. PMID:22130475

Fatila, Elisabeth M; Hetherington, Erin E; Jennings, Michael; Lough, Alan J; Preuss, Kathryn E

2012-01-28

14

Ferromagnetism in novel compounds of the R3Pt23Si11 series with heavy rare earth: Gd, Tb, Dy, Ho and Er  

NASA Astrophysics Data System (ADS)

We have synthesized new compounds of the R3Pt23Si11 series with R=Gd, Tb, Dy, Ho and Er, and studied their magnetic and thermodynamic properties. X-ray powder diffraction characterization confirms that all these compounds crystallize in the same face-centered cubic structure, space group Fm3¯m, as Ce3Pt23Si11. They all present a ferromagnetic order at low temperatures. The Curie temperatures range between 42±1 K and 3.39±0.05 K for Gd3Pt23Si11 and Er3Pt23Si11 respectively. For all compounds the value of the spontaneous moment at 2 K is far below the value expected for the saturated moment of the R3+ ions, except for the Gd compound. The estimations of the magnetic entropy at TC remain smaller than the full entropy of the fundamental multiplet, Rln(2J+1). Both reductions, of the moment and of the magnetic entropy, are ascribed to the crystal field effects. In the paramagnetic phase the thermal variation of the suceptibilities follows a Curie-Weiss law with Curie constants in good agreement with the theoretical values.

Opagiste, C.; Galéra, R. M.

2014-05-01

15

Synthesis, structures and magnetic properties of a family of nitrate-bridged octanuclear [Na2Ln6] (Ln = Dy, Tb, Gd, Sm) complexes.  

PubMed

A new family of octanuclear lanthanide compounds [Na2Ln6L8(C6H4NH2COO)2(C2H5OH)2(H2O)4(NO3)]·NO3·C2H5OH·nH2O [H2L = 2-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzoic acid; Ln = Dy (1) (n = 15); Tb (2), Gd (3) (n = 14); Sm (4) (n = 16)] have been prepared under hydrothermal conditions. The X-ray crystal structure analysis reveals that complexes 1-4 are isomorphous. The core of the structure is a [4 + 2] combination of an Ln4 cubane and an Ln2 unit. The two units are bridged by a nitrate ion, which is located in the center of the cluster and displays an unusual ?8-?(2):?(2):?(4) tridentate bridging mode. The magnetic studies for complex 1 show that the [Na2Dy6] unit exhibits slow magnetic relaxation behavior. PMID:23715465

She, Shixiong; Chen, Yanmei; Zaworotko, Michael J; Liu, Wei; Cao, Yanyuan; Wu, Jian; Li, Yahong

2013-08-01

16

S-shaped decanuclear heterometallic [Ni8Ln2] complexes [Ln(iii) = Gd, Tb, Dy and Ho]: theoretical modeling of the magnetic properties of the gadolinium analogue.  

PubMed

The reaction of 8-quinolinol-2-carboaldoxime (LH2) with Ni(II) and Ln(III) salts afforded the heterometallic decanuclear compounds [Ni8Dy2(?3-OH)2(L)8(LH)2(H2O)6](ClO4)2·16H2O (1), [Ni8Gd2(?3-OH)2(L)8(LH)2(H2O)4(MeOH)2](NO3)2·12H2O (2), [Ni8Ho2(?3-OH)2(L)8(LH)2(H2O)4(MeOH)2](ClO4)2·2MeOH·12H2O (3) and [Ni8Tb2 (?3-OH)2(L)8(LH)2(MeOH)4(OMe)2]·2CH2Cl2·8H2O (4). While compounds 1-3 are dicationic, compound 4 is neutral. These compounds possess an S-shaped architecture and comprise a long chain of metal ions bound to each other. In all the complexes, the eight Ni(II) and two Ln(III) ions of the multimetallic ensemble are hold together by two ?3-OH, eight dianionic (L(2-)) and two monoanionic oxime ligands (LH(-)) whereas compound 4 has two ?3-OH, eight dianionic (L(2-)), two monoanionic oxime ligands (LH(-)) and two terminal methoxy (MeO(-)) ligands. The central portion of the S-shaped molecular wire is made up of an octanuclear Ni(II) ensemble which has at its two ends the Ln(III) caps. Magnetic studies on 1-4 reveal that the magnetic interactions between neighboring metal ions are negligible at room temperature. On the other hand, at lower temperatures in all the compounds anti-ferromagnetic interactions seem to be dominated. Analysis of the magnetic data for the Gd(III) derivative indicates Ni(II)-Ni(II) anti-ferromagnetic interactions and Gd(III)-Ni(II) ferromagnetic interactions at low temperatures. A theoretical density functional study on the magnetic behavior of the Gd(III) derivative suggests that while the weak ferromagnetic interaction between Gd(III) and Ni(II) is in line with the expectation of the magnetic interactions between orthogonal d and f orbitals, antiferromagnetic Ni(II)-Ni(II) interactions are related to the wide Ni-O-Ni angles (?102°) and quasi-planar conformation of the Ni2O2 core. PMID:24876072

Hossain, Sakiat; Das, Sourav; Chakraborty, Amit; Lloret, Francesc; Cano, Joan; Pardo, Emilio; Chandrasekhar, Vadapalli

2014-07-14

17

Magnetic and dielectric study of R{sub 0.5}Sr{sub 0.5}MnO{sub 3} (R = Gd, Tb and Dy)  

SciTech Connect

Magnetic and dielectric properties of perovskite manganites R{sub 0.5}Sr{sub 0.5}MnO{sub 3} (R = Gd, Tb and Dy) have been investigated. DC and AC magnetic measurements showed short-range glassy magnetic ordering at T{sub g} {approx} 40 K. Such ordering was observed by neutron diffraction and is ascribable to the size mismatch of R{sup 3+} and Sr{sup 3+} settled randomly at the same crystallographic site. Dielectric constants for each material were {approx}1000-10,000 between {approx}50 and {approx}300 K and showed broad maximums above T{sub g}. Dielectric dispersion showed poor coherency of the motion of polar regions, plausibly because of the size-mismatch effect; both the magnetic and dielectric properties of this system are governed by the randomness at the R/Sr site. The tan {delta} and EXAFS data suggest that the dielectric response is rooted in a transfer of the Mn-3d electrons.

Yoshii, Kenji, E-mail: yoshiike@spring8.or.jp [Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148 (Japan)] [Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148 (Japan); Hiramitsu, Yusuke; Okajima, Yuka; Yoneda, Yasuhiro; Nishihata, Yasuo; Mizuki, Jun'ichiro [Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148 (Japan)] [Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148 (Japan); Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu; Morii, Yukio [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan)] [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Ikeda, Naoshi [Department of Physics, Okayama University, Okayama 700-8530 (Japan)] [Department of Physics, Okayama University, Okayama 700-8530 (Japan)

2010-11-15

18

Magnetic hyperfine field in antiferromagnetic RGa2 (R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) studied by perturbed angular correlation spectroscopy using 111Cd  

NASA Astrophysics Data System (ADS)

The magnetic and electric hyperfine interactions of the nuclear probe 111Cd in the hexagonal antiferromagnetic rare earth-gallium RGa2 (R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er) intermetallic compounds have been investigated by perturbed angular correlation (PAC) spectroscopy as a function of temperature. With the exception of R = Nd and Ho, the magnetic hyperfine field Bhf is roughly proportional to the spin projection (g - 1)J of the R constituent. However, in the group of the light rare earths, the variation of Bhf with (g - 1)J is much weaker than that for the heavy R constituents, in contrast to the trend reported for all rare earth intermetallics investigated up to now as well as to the trend of the magnetic ordering temperatures of RGa2. The orientation of the 4f spins relative to the c axis of RGa2 deduced from the angle between Bhf and the symmetry axis of the electric field gradient was found to be temperature independent and in agreement with the results of previous magnetization measurements. Except for SmGa2 where the hyperfine field shows an abrupt decrease near TN, the temperature dependence of Bhf(T) is consistent with second order phase transitions. The magnetic ordering temperatures deduced from Bhf(T) agree with magnetization and neutron diffraction results.

Cavalcante, F. H. M.; Pereira, L. F. D.; Cavalcante, J. T.; Saitovitch, H.; Carbonari, A. W.; Saxena, R. N.; Forker, M.

2013-05-01

19

Crystal growth, structure determination, and optical properties of new potassium-rare-earth silicates K 3RESi 2O 7 ( RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)  

NASA Astrophysics Data System (ADS)

Single crystals of K 3RESi 2O 7 ( RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K 3RESi 2O 7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K 3LuSi 2O 7, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K 3LuSi 2O 7 crystallizes in space group P6 3/ mmc with a=5.71160(10) Å and c=13.8883(6) Å. The structures containing the remaining rare earths crystallize in the space group P6 3/ mcm with the lattice parameters of a=9.9359(2) Å, c=14.4295(4) Å, (K 3GdSi 2O 7); a=9.88730(10) Å, c=14.3856(3) Å, (K 3TbSi 2O 7); a=9.8673(2) Å, c=14.3572(4) Å, (K 3DySi 2O 7); a=9.8408(3) Å, c=14.3206(6) Å, (K 3HoSi 2O 7); a=9.82120(10) Å, c=14.2986(2) Å, (K 3ErSi 2O 7); a=9.80200(10) Å, c=14.2863(4) Å, (K 3TmSi 2O 7); a=9.78190(10) Å, c=14.2401(3) Å, (K 3YbSi 2O 7). The optical properties of the silicates were investigated and K 3TbSi 2O 7 was found to fluoresce in the visible.

Vidican, Ioana; Smith, Mark D.; zur Loye, Hans-Conrad

2003-02-01

20

Pentanuclear Heterometallic {Mn(III)2Ln3} (Ln = Gd, Dy, Tb, Ho) Assemblies in an Open-Book Type Structural Topology: Appearance of Slow Relaxation of Magnetization in the Dy(III) and Ho(III) Analogues.  

PubMed

The reaction of Ln(III) nitrate and Mn(ClO4)2·6H2O salts in the presence of a multidentate sterically unencumbered ligand, (E)-2,2'-(2-hydroxy-3-((2-hydroxyphenylimino)methyl)-5-methylbenzylazanediyl)diethanol (LH4) leads to the isolation of four isostructural pentanuclear hetereometallic complexes [Mn(III)2Gd3(LH)4(NO3)(HOCH3)]ClO4·NO3 (1), [Mn(III)2Dy3(LH)4(NO3)(HOCH3)]ClO4·NO3 (2), [Mn(III)2Tb3(LH)4(NO3)(HOCH3)]ClO4·NO3 (3), and [Mn(III)2Ho3(LH)4(NO3)(HOCH3)]ClO4·NO3 (4) with an open-book type structural topology. 1-4 are dicationic and crystallize in the achiral space group, P21/n. A total of four triply deprotonated ligands, [LH](3-), are involved in holding the pentameric metal framework, {Mn(III)2Ln3}. In these complexes both the lanthanide and the manganese(III) ions are doubly bridged, involving phenolate or ethoxide oxygen atoms. The magnetochemical analysis reveals the presence of global antiferromagnetic interactions among the spin centers at low temperatures in all the four compounds. AC susceptibility measurements show the presence of temperature dependent out-of-phase ac signal for compounds 2 and 4 indicating an SMM behavior. PMID:24902495

Bag, Prasenjit; Chakraborty, Amit; Rogez, Guillaume; Chandrasekhar, Vadapalli

2014-07-01

21

Cross sections of proton-induced reactions on 152Gd, 155Gd and 159Tb with emphasis on the production of selected Tb radionuclides  

NASA Astrophysics Data System (ADS)

Cross sections are presented for various Dy, Tb and Gd radionuclides produced in the proton bombardment of 159Tb as well as for the reactions 152Gd(p,4n)149Tb and 155Gd(p,4n)152Tb up to 66 MeV. The experimental excitation functions are compared with theoretical predictions by means of the geometry-dependent hybrid (GDH) model as implemented in the code ALICE/ASH, as well as with values from the TENDL-2012 library and previous literature experimental data, where available. Physical yields have been derived for the production of some of the medically important radioterbiums, namely 149Tb (radionuclide therapy), 152Tb (PET) and 155Tb (SPECT). The indirect production of high-purity 155Tb via the decay of its precursor 155Dy is reported. The possibility of a large-scale production facility based on a commercial 70 MeV cyclotron is also discussed.

Steyn, G. F.; Vermeulen, C.; Szelecsényi, F.; Kovács, Z.; Hohn, A.; van der Meulen, N. P.; Schibli, R.; van der Walt, T. N.

2014-01-01

22

Family of double-cubane Mn4Ln2 (Ln = Gd, Tb, Dy, Ho) and Mn4Y2 complexes: a new Mn4Tb2 single-molecule magnet.  

PubMed

The synthesis and characterization of a family of Mn(2)(III)Mn(2)(II)Ln(III)(2) complexes (Ln = Gd (1), Tb (2), Dy (3), and Ho (4)) of formula [Mn(4)Ln(2)O(2)(O(2)CBu(t))(6)(edteH(2))(2)(NO(3))(2)] are reported, where edteH(4) is N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine. The analogous Mn(4)Y(2) (5) complex has also been prepared. They were obtained from reaction of Ln(NO(3))(3) or Y(NO(3))(3) with Mn(O(2)CBu(t))(2), edteH(4), and NEt(3) in a 2:3:1:2 molar ratio. The crystal structures of representative 1 and 2 were obtained, and their core consists of a face-fused double-cubane [Mn(4)Ln(2)(?(4)-O(2-))(2)(?(3)-OR)(4)] unit. Such double-cubane units are extremely rare in 3d metal chemistry and unprecedented in 3d-4f chemistry. Variable-temperature, solid-state dc and ac magnetic susceptibility studies on 1-5 were carried out. Fitting of dc ?(M)T vs T data for 5 gave J(bb) (Mn(III)···Mn(III)) = -32.6(9) cm(-1), J(wb) (Mn(II)···Mn(III)) = +0.5(2) cm(-1), and g = 1.96(1), indicating a |n, 0, n> (n = 0-5) 6-fold-degenerate ground state. The data for 1 indicate an S = 12 ground state, confirmed by fitting of magnetization data, which gave S = 12, D = 0.00(1) cm(-1), and g = 1.93(1) (D is the axial zero-field splitting parameter). This ground state identifies the Mn(II)···Gd(III) interactions to be ferromagnetic. The ac susceptibility data independently confirmed the conclusions about 1 and 5 and revealed that 2 displays slow relaxation of the magnetization vector for the Mn(4)Tb(2) analogue 2. The latter was confirmed as a single-molecule magnet by observation of hysteresis below 0.9 K in magnetization vs dc field scans on a single crystal of 2·MeCN on a micro-SQUID apparatus. The hysteresis loops also displayed well-resolved quantum tunneling of magnetization steps, only the second 3d-4f SMM to do so. PMID:21939191

Saha, Arpita; Thompson, Michael; Abboud, Khalil A; Wernsdorfer, Wolfgang; Christou, George

2011-10-17

23

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

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.

Zhang, Zhi-Jun, E-mail: zhangzj@mail.sic.ac.cn [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China)] [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Lin, Xiao [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China) [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Graduate School of Chinese Academy of Science, Beijing, 100039 (China); Zhao, Jing-Tai [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China)] [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Zhang, Guo-Bin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026 (China)] [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026 (China)

2013-02-15

24

Octanuclear {Ln(III)8}(Ln = Gd, Tb, Dy, Ho) macrocyclic complexes in a cyclooctadiene-like conformation: manifestation of slow relaxation of magnetization in the Dy(III) derivative.  

PubMed

The synthesis of a series of macrocyclic, isostructural octanuclear lanthanide complexes [Gd8 (LH2)4 (?-Piv)4 (?(2)-Piv)4 (?-OMe)4]·6CH3OH·2H2O (1), [Tb8 (LH2)4 (?-Piv)4 (?(2)-Piv)4 (?-OMe)4]4CH3OH·4H2O (2), [Dy8(LH2)4 (?-Piv)4 (?(2)-Piv)4 (?-OMe)4]·8CH3OH (3), and [Ho8(LH2)4(?-Piv)4 (?(2)-Piv)4 (?-OMe)4]·CH3OH·4H2O (4) have been achieved, using Ln(III) nitrate salts, pivalic acid, and a new multidentate chelating ligand (2E,N'E)-N'-(3-((bis(2- hydroxyethyl)amino)methyl)-2-hydroxy-5-methylbenzylidene)-2-(hydroxyimino) propane hydrazide (LH5), containing two unsymmetrically disposed arms; one side of the phenol unit is decorated with a diethanolamine group while the other side is a hydrazone that has been built by the condensation reaction involving 2-hydroxyiminopropanehydrazide. All the compounds, 1-4, are neutral and are held by the four [LH2](3-) triply deprotonated chelating ligands. In these complexes all the lanthanide ions are doubly or triply bridged via phenolate, alkoxy, and pivalate oxygens. The metal centers are distributed over the 8 vertices of an octagon, resembling a cyclooctadiene ring core. The details of magnetochemical analysis for complexes 1-4 shows that they exhibit antiferromagnetic interactions between the Ln(3+) ions through the phenoxo, alkoxo, and pivalato bridging groups. None of the compounds exhibits slow relaxation of the magnetization at zero applied direct current (dc) magnetic field, which could be due to the existence of a fast quantum tunneling relaxation of the magnetization (QTM). In the case of 3, the application of a small dc field is enough as to fully or partly suppress the fast and efficient zero-field QTM allowing the observation of slow relaxation above 2 K. PMID:23537281

Chandrasekhar, Vadapalli; Bag, Prasenjit; Colacio, Enrique

2013-04-15

25

Magnetomechanical damping in cryogenic TbDy  

NASA Technical Reports Server (NTRS)

Vibration damping in polycrystalline TbDy alloys was studied at cryogenic temperatures. The material was prepared by cold-rolling to induce crystallographic texture, and was then heat-treated to relieve internal stress. Mechanical hysteretic losses were measured at various strains, frequencies, and loading configurations at 77 K. Some textured TbDy materials demonstrated 22.6% energy dissipation in mechanical measurements at low frequency (0.01 Hz) and a mean logarithmic decrement of 0.23 at a higher frequency (25 kHz). Ultrasonic velocities of longitudinal and shear elastic waves were measured on single and polycrystalline TbDy; little variation in ultrasonic velocities was found evenfor samples with large variation in crystallographic texture and magnetomechanical properties.

Dooley, J.; Good, N.; White, C.; Leland, S.; Fultz, B.

2002-01-01

26

Decay studies of neutron deficient nuclei near the Z=64 subshell: 142Dy, 140,142Tb, 140,142Gd, 140,142Eu, 142Sm, and 142Pm  

NASA Astrophysics Data System (ADS)

The electron-capture and ?+-decay branchings (EC/?+) and delayed proton decays of A=142 isotopes with 61<=Z<=66 and A=140 isotopes with 63<=Z<=65 were investigated with the OASIS facility on-line at the Lawrence Berkeley Laboratory SuperHILAC. Electron capture and positron-decay emission probabilities have been determined for 142Pm and 142Sm decays, and extensive decay schemes have been constructed for 142Eug(2.34+/-0.12 s), 142Gd(70.2+/-0.6 s), 140Eu(1.51+/-0.02 s), and 140Gd(15.8+/-0.4 s). Decay schemes for the new isotopes 142Tbg(597+/-17 ms), 142Tbm(303+/-17 ms), 142Dy(2.3+/-0.3 s), 140Eum(125+/-2 ms), and 140Tb(2.4+/-0.2 s) are also presented. We have assigned ? rays to these isotopes on the basis of ?? and x? coincidences, and from half-life determinations. Electron-capture and ?+-decay branchings were measured for each decay, and ?-delayed proton branchings were determined for 142Dy, 142Tb, and 140Tb decays. QEC values, derived from the measured EC/?+ branchings and the level schemes are compared with those from the Wapstra and Audi mass evaluation and the Liran and Zeldes mass calculation. The systematics of the N=77 isomer decays are discussed, and the intense 0+-->1+ and 1+-->0+ ground-state beta decays are compared with shell-model predictions for simple spin-flip transitions.

Firestone, R. B.; Gilat, J.; Nitschke, J. M.; Wilmarth, P. A.; Vierinen, K. S.

1991-03-01

27

Decay studies of neutron deficient nuclei near the Z =64 subshell: sup 142 Dy, sup 140,142 Tb, sup 140,142 Gd, sup 140,142 Eu, sup 142 Sm, and  

SciTech Connect

The electron-capture and {beta}{sup +}-decay branchings (EC/{beta}{sup +}) and delayed proton decays of {ital A}=142 isotopes with 61{le}{ital Z}{le}66 and {ital A}=140 isotopes with 63{le}{ital Z}{le}65 were investigated with the OASIS facility on-line at the Lawrence Berkeley Laboratory SuperHILAC. Electron capture and positron-decay emission probabilities have been determined for {sup 142}Pm and {sup 142}Sm decays, and extensive decay schemes have been constructed for {sup 142}Eu{sup {ital g}}(2.34{plus minus}0.12 s), {sup 142}Gd(70.2{plus minus}0.6 s), {sup 140}Eu(1.51{plus minus}0.02 s), and {sup 140}Gd(15.8{plus minus}0.4 s). Decay schemes for the new isotopes {sup 142}Tb{sup {ital g}}(597{plus minus}17 ms), {sup 142}Tb{sup {ital m}}(303{plus minus}17 ms), {sup 142}Dy(2.3{plus minus}0.3 s), {sup 140}Eu{sup {ital m}}(125{plus minus}2 ms), and {sup 140}Tb(2.4{plus minus}0.2 s) are also presented. We have assigned {gamma} rays to these isotopes on the basis of {gamma}{gamma} and {ital x}{gamma} coincidences, and from half-life determinations. Electron-capture and {beta}{sup +}-decay branchings were measured for each decay, and {beta}-delayed proton branchings were determined for {sup 142}Dy, {sup 142}Tb, and {sup 140}Tb decays. {ital Q}{sub EC} values, derived from the measured EC/{beta}{sup +} branchings and the level schemes are compared with those from the Wapstra and Audi mass evaluation and the Liran and Zeldes mass calculation. The systematics of the {ital N}=77 isomer decays are discussed, and the intense 0{sup +}{r arrow}1{sup +} and 1{sup +}{r arrow}0{sup +} ground-state beta decays are compared with shell-model predictions for simple spin-flip transitions.

Firestone, R.B.; Gilat, J.; Nitschke, J.M.; Wilmarth, P.A.; Vierinen, K.S. (Lawrence Berkeley Laboratory, Berkeley, California 94720 (US))

1991-03-01

28

A new family of rare earth compounds, the ternary silicides RE 2RhSi 3 (RE = Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Er) - crystal structure electrical and magnetic properties  

NASA Astrophysics Data System (ADS)

New ternary silicides RE 2RhSi 3 (RE = Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Er) have been prepared. They crystallize with a hexagonal symmetry structure which is derived from the AlB 2-type. Si and Rh atoms are inside RE 6 distorted trigonal prisms and are ordered in a two dimensional sublattice perpendicular to the c axis. The a and c parameters are approximately twice those of the corresponding disilicides RESi 2. La 2RhSi 3 and Y 2RhSi 3 are not superconducting down to 1.6 K. Nd 2RhSi 3 is ferromagnetic at 15 K, but the other silicides order antiferromagnetically with metamagnetic phase transitions for certain of them.

Chevalier, B.; Lejay, P.; Etourneau, J.; Hagenmuller, P.

1984-02-01

29

Preparation of a New Phase Having a Cation-Ordered C-Type Rare-Earth Oxide Related Structure in the Systems Bi 2O 3- Ln2O 3 ( Ln = Sm, Eu, Gd, Tb, and Dy)  

NASA Astrophysics Data System (ADS)

A new phase Bi 1- xLnxO 1.5 has been found in the systems Bi 2O 3- Ln2O 3 ( Ln = Sm, Eu, Gd, Tb, and Dy with x = 0.38, 0.375, 0.275-0.40, 0.275-0.35, and 0.30-0.35, respectively). The repetitive long-term solid-state reaction at about 800°C has produced the present phase; this phase crystallizes in the cubic system I2 13 with a ? 11 Å and Z = 32, has a structure closely related to the C-type rare-earth oxide one, and is the low-temperature stable phase. Upon heating, the present phase transforms smoothly into the ?-Bi 2O 3-type high-temperature stable phase around 900°C. Upon cooling, however, a rate of transition of the opposite direction is extraordinarily sluggish. This sluggishness is discussed on the basis of the ordering of cations, Bi 3+ and Ln3+ , in a proposed structure.

Watanabe, Akiteru

1995-11-01

30

Synthesis, structural characterization and Mössbauer study of LnV{sub 0.5}Fe{sub 0.5}O{sub 3} perovskites (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er)  

SciTech Connect

Graphical abstract: Mössbauer spectra taken at 200 K for the Y(V{sub 0.5}Fe{sub 0.5})O{sub 3} orthoferrivanadate synthesized by arc-melting. Highlights: ? LnFe{sub 0.5}V{sub 0.5}O{sub 3} were synthesized by the first time for most of the rare-earth elements. ? These orthoferrivanadates crystallize metastably with the perovskite structure. ? Iron and vanadium are trivalent stabilized in these solid solutions. ? The Mössbauer quadrupolar splitting is correlated with the tolerance factor. ? Below 100 K, these perovskites undergo a crystallographic phase transformation. -- Abstract: Perovskites LnV{sub 0.5}Fe{sub 0.5}O{sub 3} (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er) were synthesized by rapid solidification from arc-melted samples and characterized by the study of their crystal structure and hyperfine properties. These metastable solid solutions crystallized in the Pbnm symmetry, with the iron and vanadium cations randomly distributed in the transition metal octahedral sites. Depending on the lanthanide present at the A site of the perovskite, iron is present with two valences (i.e., Fe{sup 3+} and Fe{sup 2+}). The volume of the unit cell for these perovskites increases linearly with the lanthanide ionic radius, as the perovskite approaches its ideal structure. At room temperature, the quadrupolar splitting of the trivalent paramagnetic Mössbauer component works as an indirect measurement for the Goldshmidt tolerance factor. Close to or below 100 K, these perovskites undergo a crystallographic phase transformation, probably due to orbital ordering of the V{sup 3+} cations, originating two different magnetic iron sites.

Ivashita, Flávio F.; Biondo, Valdecir; Bellini, Jusmar V.; Paesano, Andrea [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, 87.020-900 Maringá, PR (Brazil)] [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, 87.020-900 Maringá, PR (Brazil); Blanco, M. Cecilia; Fuertes, Valeria C.; Pannunzio-Miner, Elisa V. [INFIQC-CONICET, Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA Córdoba (Argentina)] [INFIQC-CONICET, Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA Córdoba (Argentina); Carbonio, Raúl E., E-mail: carbonio@fcq.unc.edu.ar [INFIQC-CONICET, Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA Córdoba (Argentina)

2012-09-15

31

Sensitization of Gd3+ ions by Tb3+ ions in Tb3+ doped (La, Gd)PO4  

NASA Astrophysics Data System (ADS)

The role of Tb3+ ions, with respect to efficient energy transfer, on sensitization of Gd3+ ions in (La,Gd)PO4 has been investigated. A series of Tb3+ doped (La, Gd)PO4 were characterized by steady state spectroscopy and efficient energy transfer from Tb3+ 4f75d to Gd3+ 4f7 states was observed. The decay curves of Gd3+6P7/2 and Tb3+5D3, 5D4 states upon Tb3+ 4f75d and Gd3+6IJ states excitation were also performed to reveal the energy transfer processes. With the increase of Gd3+ concentration, the energy transfer efficiency increase accordingly. Based on steady state spectra, around 73% energy transfer efficiency in Gd0.99Tb0.01PO4 was determined.

Shi, Qiufeng; You, Fangtian; Huang, Shihua; Peng, Hongshang; Huang, Yan; Tao, Ye

2014-05-01

32

ARPES study of the evolution of band structure and charge density wave properties in RTe3 ( R=Y , La, Ce, Sm, Gd, Tb, and Dy)  

SciTech Connect

We present a detailed angle-resolved photoemission spectroscopy (ARPES) investigation of the RTe3 family, which sets this system as an ideal"textbook" example for the formation of a nesting driven charge density wave (CDW). This family indeed exhibits the full range of phenomena that can be associated to CDWinstabilities, from the opening of large gaps on the best nested parts of Fermi surface (up to 0.4 eV), to the existence of residual metallic pockets. ARPES is the best suited technique to characterize these features, thanks to its unique ability to resolve the electronic structure in k space. An additional advantage of RTe3 is that theband structure can be very accurately described by a simple two dimensional tight-binding (TB) model, which allows one to understand and easily reproduce many characteristics of the CDW. In this paper, we first establish the main features of the electronic structure by comparing our ARPES measurements with the linear muffin-tinorbital band calculations. We use this to define the validity and limits of the TB model. We then present a complete description of the CDW properties and of their strong evolution as a function of R. Using simple models, we are able to reproduce perfectly the evolution of gaps in k space, the evolution of the CDW wave vector with R, and the shape of the residual metallic pockets. Finally, we give an estimation of the CDWinteraction parameters and find that the change in the electronic density of states n (EF), due to lattice expansion when different R ions are inserted, has the correct order of magnitude to explain the evolution of the CDW properties.

Hussain, Zahid; Brouet, Veronique; Yang, Wanli; Zhou, Xingjiang; Hussain, Zahid; Moore, R.G.; He, R.; Lu, D. H.; Shen, Z.X.; Laverock, J.; Dugdale, S.B.; Ru, N.; Fisher, R.

2008-01-16

33

Magnetoelastic vibration damping properties of TbDy alloys  

NASA Technical Reports Server (NTRS)

Damping of axial and bending mode vibrations in giant magnetoelastic polycrystalline TbDy alloys was studied at cryogenic temperatures. All specimens of TbDy were arc-melted in the proper composition ratio and dropped into a chilled copper mold. Additional treatments consisted of cold plane-rolling to induce crystallographic texture and then heat-treating to relieve internal stress. Mechanical hysteretic losses were measured at various strains, frequencies, and loading configurations down to 77 K. Both as-cast and textured polycrystalline TbDy samples were tested along with an aluminum specimen for comparison. Loss factors at multiple natural vibration frequencies of the samples were measured for axial modes. Larger damping rates were measured for axial mode vibrations than for bending mode vibrations, possibly reflecting the larger specimen volume contributing to magnetoelastic damping. At LN2 temperatures TbDy materials demonstrated q > 0.05 at 0.01 Hz and q > 0.1 at higher frequencies from 0.6-1.5 kHz.

Dooley, J. A.; Good, N. R.; White, C. V.; Leland, R. S.

2002-01-01

34

Large refrigerant capacity of RGa (R = Tb and Dy) compounds  

NASA Astrophysics Data System (ADS)

The magnetic properties and magnetocaloric effects (MCEs) of RGa (R = Tb and Dy) compounds are investigated. The TbGa compound exhibits two successive magnetic transitions: spin-reorientation (SR) transition at TSR = 31 K and second-order ferromagnetic (FM)-paramagnetic (PM) transition at Curie temperature TC = 154 K, while the DyGa compound undergoes a SR transition with TSR=25 K and a FM-PM transition with TC = 113 K. It is noteworthy that a broad distribution of the magnetic entropy change peak is observed. The values of the refrigerant capacity (RC) for TbGa and DyGa are found to be 620.6 and 381.9 J/kg for a field change of 0-5 T, respectively. And for a field change of 0-7 T, the values are 900 and 584.2 J/kg, respectively. The large value of RC for TbGa and DyGa originates from the combined contribution from SR and FM-PM transitions, which enlarges the temperature span of large MCE.

Zheng, X. Q.; Chen, J.; Shen, J.; Zhang, Hu; Xu, Z. Y.; Gao, W. W.; Wu, J. F.; Hu, F. X.; Sun, J. R.; Shen, B. G.

2012-04-01

35

Antiferromagnetic Coupling of Pr0.9RE0.1Ni (RE = Tb, Dy, Ho) Single Crystals  

NASA Astrophysics Data System (ADS)

Magnetization and specific heat measurements were carried out on Pr0.9RE0.1Ni (RE = Tb, Dy, and Ho) single crystals. Spin rearrangements were observed along the c-axis of single crystals with relatively small critical fields, Bc = 6.8, 4.0, and 2.6 T for RE = Tb, Dy and Ho, respectively. The magnetic phase transition temperatures, TM, were extracted from the specific heat data: TM = 22.7, 19.6, and 18.3 K with RE = Tb, Dy, and Ho, respectively. The observed Bc values were used to estimate the heterogeneous (Pr-RE) exchange strength, and then calculate expected TM values, which were found to be close to the experimental ones. The present results of Bc and TM, together with the previous ones of Pr0.9Gd0.1Ni, were found to be consistent with the de Gennes rule.

Nishimura, Katsuhiko; Hutchison, Wayne D.; Namiki, Takahiro

2013-05-01

36

Anomalies in rare earth distributions in seawater: Gd and Tb  

NASA Astrophysics Data System (ADS)

We have measured profiles of the rare earth elements (REE) in Atlantic and Pacific Ocean waters. The data, normalized versus shales, exhibit a pronounced anomaly in Gd relative to its neighbors Eu and Tb in the REE series such that the Gd concentrations are high by 30-50%. Closer inspection reveals that the anomaly is made up of both elevated Gd and depressed Tb concentrations, likely associated with solution chemistry shifts in the transition from an exactly half filled 4f electron shell. Anomalies in Gd and Tb solution complexation are also indicated by the Turner-Whitfield-Dickson speciation model. The overall trend of heavy REE(III) enrichment in seawater and the Gd/Tb anomaly described here tend to support scavenging as an important removal mechanism for the REE from seawater.

De Baar, Hein J. W.; Brewer, Peter G.; Bacon, Michael P.

1985-09-01

37

Thermoluminescence of Tb doped Gd 2O 2S phosphor  

Microsoft Academic Search

Thermoluminescence (TL) of gadolinium oxysulfide activated with terbium (Gd2O2S:Tb) is investigated. The glow curves of Gd2O2S:Tb phosphor recorded in the temperature range of 93–500K with a heating rate of 0.52Ks?1 shows five prominent glow peaks. Comparison of the glow curves exhibited by different samples prepared with varying firing conditions reveals some interesting results. In this phosphor capture centers are mainly

S Chatterjee; Virendra Shanker; Harish Chander

2003-01-01

38

?-decay half-lives of new neutron-rich isotopes 167,168Tb and levels in 167,168Dy  

NASA Astrophysics Data System (ADS)

?-decay half-lives of new neutron-rich isotopes 167Tb and 168Tb produced in the 20 MeV proton-induced fission of 238U have been determined to be 19.4(27) s and 8.2(13) s, respectively, using a gas-jet coupled on-line isotope separator. The present half-lives and those of the recently identified nuclei 159Pm, 161Sm, 165Gd, 166Tb were compared with theoretical predictions. The recent calculation by the gross theory with the new one-particle strength functions shows quite good agreement with the experimental half-lives. Excited states of the daughter nuclides 167Dy and 168Dy have been established for the first time. Level energies of the first 2+ states in even-even Dy isotopes were found to show an irregular behavior at 164Dy and increasing deformation toward the neutron midshell around N~104.

Asai, M.; Ichikawa, S.; Tsukada, K.; Sakama, M.; Shibata, M.; Kojima, Y.; Osa, A.; Nishinaka, I.; Nagame, Y.; Kawade, K.; Tachibana, T.

1999-06-01

39

Synthesis, structure, and magnetic properties of a new family of tetra-nuclear {Mn2(III)Ln2}(Ln = Dy, Gd, Tb, Ho) clusters with an arch-type topology: single-molecule magnetism behavior in the dysprosium and terbium analogues.  

PubMed

Sequential reaction of Mn(II) and lanthanide(III) salts with a new multidentate ligand, 2,2'-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (LH3), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn2Dy2(LH)4(?-OAc)2](NO3)2·2CH3OH·3H2O (1), [Mn2Gd2(LH)4(?-OAc)2](NO3)2·2CH3OH·3H2O (2), [Mn2Tb2(LH)4(?-OAc)2](NO3)2·2H2O·2CH3OH·Et2O (3), and [Mn2Ho2(LH)4(?-OAc)2]Cl2·5CH3OH (4). All of these dicationic complexes possess an arch-like structural topology containing a central Mn(III)-Ln-Ln-Mn(III) core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn(III) ions. Four doubly deprotonated LH(2-) chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln(3+) ions in 1-4 causes pronounced zero-field splitting for Tb(3+), Dy(3+), and Ho(3+). For 1 and 3, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (1) and 13 K (3) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of ?E = 16.8 cm(-1) (1) and 33.8 cm(-1) (3). PMID:23614464

Chandrasekhar, Vadapalli; Bag, Prasenjit; Speldrich, Manfred; van Leusen, Jan; Kögerler, Paul

2013-05-01

40

Thickness dependence of magnetoelastic properties and of crystallization behavior in Fe-Tb-Dy/Fe and Fe-Tb-Dy/nanocrystalline Fe-Si-B-Nb-Cu multilayers  

NASA Astrophysics Data System (ADS)

Fe-Tb-Dy/Finemet™ and Fe-Tb-Dy/Fe multilayers have been prepared by ion beam sputtering on room temperature sapphire substrates (Finemet is a nanocrystalline Fe-Si-B-Nb-Cu magnetic alloy). After production, the Fe-Tb-Dy and the Finemet layers are amorphous, whereas the Fe layers are polycrystalline. Subsequent annealing leads to relaxation of the amorphous Fe-Tb-Dy layers in both cases and to crystallization of the Finemet layers for the Fe-Tb-Dy/Finemet multilayers. In this regime, the properties of the multilayers can be well described by a mixture rule of the two perfectly coupled components. In an optimum thickness range for both layers, they show very soft magnetic properties and high magnetoelasticity. Furthermore, it has been observed that crystallization of the Fe-Tb-Dy layers within the multilayer is hindered by interface stabilization as recently predicted in U. Herr, H. Geisler, H. Ippach, and K. Samwer, Phys. Rev. B 59, 13719 (1999).

Farber, P.; Kronmüller, H.

2000-09-01

41

Luminescent properties of Tb3+ and Gd3+ ions doped aluminosilicate oxyfluoride glasses.  

PubMed

Tb(3+) and Gd(3+) ions doped lithium-barium-aluminosilicate oxyfluoride glasses have been prepared. The transmission, emission and excitation spectra were measured. It has been found that those Tb(3+)-doped lithium-barium-aluminosilicate oxyfluoride glasses exhibit good UV-excited luminescence. The luminescence intensity of Tb(3+) ion increases for those (Tb(3+), Gd(3+))-codoped glasses. Energy transfer process from Gd(3+) ion to Tb(3+) ion is indicated. PMID:21831699

Zuo, Chenggang; Lu, Anxian; Zhu, Ligang; Zhou, Zhihua; Long, Woyun

2011-11-01

42

Luminescent properties of BaAl12O19:Tb, Dy phosphors prepared by sol-gel method.  

PubMed

BaAl12O19:Tb, Dy phosphor was prepared by the sol-gel technique using citric acid as a complextant. XRD was used to characterize the relevant crystallization behavior of the phosphor. The luminescence properties and energy transfer between Tb3+ and Dy3+ were investigated. The results revealed that energy transfer exists between Dy3+ and Tb3+ at appropriate Tb3+ concentrations. The emission intensity of Tb3+ increases and energy transfer happens from Dy3+ to Tb3+ ions at the higher content of Tb3+ when Tb3+ and Dy3+ ions were co-doped. BaAl12O19 phosphors doped with Tb3+ or Dy3+ ions only were studied to compared with BaAl12O19:Tb, Dy phosphors. The results showed that the maximum excitation peak of BaAl12O19:Tb is 240 nm and the emission spectrum consists of four peaks at 490, 545, 590, and 625 nm, originating from 5D4 --> 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ion, respectively. The excitation peaks of BaAl12O19:Dy are at 291, 324 nm and the emissions of Dy3+ are at 370, 447 and 578 nm, originating from 4F9/2 --> 6P5/2, 4F9/2 --> 6H15/2 and 4F9/2 --> 6H13/2 transitions of Dy3+ ion, respectively. PMID:24738430

Xiao, Lin J; Xie, Ying; He, Ming R; Chen, Yong J; Geng, Xiu J; Li, Wen Z

2014-06-01

43

Effects of heteroepitaxial strain on Laves phases TbFe2 and DyFe2  

Microsoft Academic Search

(110) oriented growth was observed for thin films of the highly magnetostrictive Laves phases TbFe2 and DyFe2 on Ta (110). On Nb (111), TbFe2 nucleates in the (111) orientation. Depending on the substrate temperature during growth, varying degrees of residual tensile strain were observed in the films. For TbFe2 grown on Ta (110) at 680 °C, x-ray diffraction revealed a

M. Huth; C. P. Flynn

1998-01-01

44

Thermoluminescence properties of nanophosphors BaSO?:Dy and BaSO?:Tb.  

PubMed

Nanocrystalline BaSO4:Dy and BaSO4:Tb were prepared by the coprecipitation method. The materials were characterized with X-ray diffractometry, UV-visible spectroscopy, and scanning electron microscopy. The glow curves of the BaSO4:Dy and BaSO4:Tb nanophosphors feature main peaks at 505 K and 480 K, respectively. The responses to the (60)Co dose are linear in the range 0.1-1 kGy for BaSO4:Dy and in the range 0.1-7 kGy for BaSO4:Tb. The energy dependences of the responses were also studied. PMID:24035929

Rezaee Ebrahim Saraee, Kadijeh; Aghay Kharieky, Amin

2013-12-01

45

Optical fiber magnetic field sensors with TbDyFe magnetostrictive thin films as sensing materials.  

PubMed

Different from usually-used bulk magnetostrictive materials, magnetostrictive TbDyFe thin films were firstly proposed as sensing materials for fiber-optic magnetic field sensing characterization. By magnetron sputtering process, TbDyFe thin films were deposited on etched side circle of a fiber Bragg Grating (FBG) as sensing element. There exists more than 45pm change of FBG wavelength when magnet field increase up to 50 mT. The response to magnetic field is reversible, and could be applicable for magnetic and current sensing. PMID:19997310

Yang, Minghong; Dai, Jixiang; Zhou, Ciming; Jiang, Desheng

2009-11-01

46

Mössbauer Effect in Tb159  

Microsoft Academic Search

The linewidth of the Mössbauer resonance of the 58-keV radiation from Tb159m has been measured with Dy159(as Dy2O3) and Gd159(as Gd2O3) sources and Tb4O7, Tb metal, and Tb2(CO3)3 absorbers, all at 80°K. The measured linewidths, extrapolated to zero absorber thickness, are 5.0+\\/-1.4 cm sec-1 for the Dy2O3-Tb4O7 system, 7.9+\\/-1.8 cm sec-1 for the Dy2O3-Tb2(CO3)3 system, and 11.5+\\/-1.0 cm sec-1 for

J. C. Woolum; A. J. Bearden

1966-01-01

47

Photoluminescence properties of Li2SrGeO4:RE3+ (RE = Ce/Tb/Dy) phosphors and enhanced luminescence through energy transfer between Ce3+ and Tb3+/Dy3+  

NASA Astrophysics Data System (ADS)

Li2SrGeO4:RE3+ (RE = Tb/Dy/Ce) phosphors were prepared by the conventional solid-state reaction. X-ray diffraction (XRD), photoluminescence (PL) spectra, and lifetimes were utilized to characterize samples. Under the excitation of ultraviolet (231 nm for Tb3+ and 351 nm for Dy3+), the Li2SrGeO4:Tb3+ and Li2SrGeO4:Dy3+ phosphors show their respective characteristic emissions of Tb3+ (5D3,4 ? 7FJ?, J? = 3, 4, 5, 6) and Dy3+ (4F9/2 ? 6H15/2 and 4F9/2 ? 6H13/2), respectively. Ce3+ activated Li2SrGeO4 phosphors exhibit broad band blue emission due to the 5d-4f transition of Ce3+. Co-doping Ce3+ into the LSG: Ce3+/Dy3+ samples enhances the luminescence intensity of Tb3+ and Dy3+ significantly under the excitation wavelength at 340 nm through energy transfer from Ce3+ to Tb3+/Dy3+. In addition, the energy transfer mechanism between Ce3+ and Tb3+/Dy3+ has been demonstrated to be a resonant type via a dipole-quadrupole interaction.

Huang, Shuai; Li, Guogang

2014-07-01

48

Spin structure and magnetic frustration in multiferroic RMn2O5 (R=Tb,Ho,Dy)  

Microsoft Academic Search

We have studied the crystal and magnetic structures of the magnetoelectric\\u000amaterials RMn2O5 (R = Tb, Ho, Dy) using neutron diffraction as a function of\\u000atemperature. All three materials display incommensurate antiferromagnetic\\u000aordering below 40 K, becoming commensurate on further cooling. For R = Tb, Ho,\\u000aa commensurate-incommensurate transition takes place at low temperatures. The\\u000acommensurate magnetic structures have been

G. R. Blake; L. C. Chapon; P. G. Radaelli; N. Hur; S. W. Cheong; J. Rodríguez-Carvajal

2005-01-01

49

Systematics of low-lying dipole strengths in odd and even Dy and Gd isotopes  

SciTech Connect

Photon scattering experiments on the odd, deformed nuclei {sup 161,163}Dy and {sup 157}Gd provided detailed information on the excitation energies and transition probabilities of low-lying dipole excitations. In the case of the even-even nuclei {sup 162,164}Dy in addition spins and parities of the excited states could be determined model independently by measuring the angular distributions and the linear polarization of the scattered photons using a Compton polarimeter. The results are compared with the systematics obtained for the neighboring even-even isotopes {sup 160}Dy and {sup 156,158,160}Gd in previous photon scattering experiments. Whereas in the odd Dy isotopes a concentration of dipole strength is observed, which fits nicely into the systematics of the orbital {ital M}1 mode, the dipole strength in {sup 157}Gd is completely fragmented into about 90 transitions.

Margraf, J.; Eckert, T.; Rittner, M.; Bauske, I.; Beck, O.; Kneissl, U.; Maser, H.; Pitz, H.H.; Schiller, A. [Institut fuer Strahlenphysik, Universitaet Stuttgart, Allmandring 3, D-70569 Stuttgart (Germany)] [Institut fuer Strahlenphysik, Universitaet Stuttgart, Allmandring 3, D-70569 Stuttgart (Germany); Brentano, P.v.; Fischer, R.; Herzberg, R.; Pietralla, N.; Zilges, A. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicher Str. 77, D-50937 Koeln (Germany)] [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicher Str. 77, D-50937 Koeln (Germany); Friedrichs, H. [Institut fuer Kernphysik, Justus-Liebig-Universitaet Giessen, Leihgesterner Weg 217, D-35392 Giessen (Germany)] [Institut fuer Kernphysik, Justus-Liebig-Universitaet Giessen, Leihgesterner Weg 217, D-35392 Giessen (Germany)

1995-11-01

50

Synthesis, Crystal Structure and Magnetism of Lanthanide (Gd, Dy, Ho, Er, Y) Complexes with Nitronyl Nitroxides  

Microsoft Academic Search

Five novel complexes of the formula [Ln (hfac)3] (NITPhCl)2 · m n-C7H16 (Ln = Gd, Dy, Ho, Er, Y; hfac = hexafluoroacetylacetonate; NITPhCl = 2-(4?-chlorophenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxy1–3-oxide; m = 0.5 for Gd, Ho, Er, Y and m = 0 for Dy) have been synthesized. The complex [Gd (hfac)3] (NITPhCl)2 · 0.5 C7H16 crystallizes in the triclinic, space group P1

Yu-Qing Qi; Zong-Hui Jiang; Dai-Zheng Liao; Geng-Lin Wang; Xin-Kan Yao; Hong-Gen Wang

1997-01-01

51

Spectroscopy and energy transfer in lead borate glasses doubly doped with Dy(3)(+)-Tb(3+) and Tb(3)(+)-Eu(3+) ions.  

PubMed

Lead borate glasses doubly doped with Dy(3)(+)-Tb(3+) and Tb(3+)-Eu(3+) were investigated using optical spectroscopy. Luminescence spectra of rare earths were detected under various excitation wavelengths. The main green emission band due to (5)D4?(7)F5 transition of Tb(3+) is observed under excitation of Dy(3+), whereas the main red emission band related to (5)D0?(7)F2 transition of Eu(3+) is successfully observed under direct excitation of Tb(3+). In both cases, the energy transfer processes from Dy(3+) to Tb(3+) and from Tb(3+) to Eu(3+) in lead borate glasses occur through a nonradiative processes with efficiencies up to 16% and 18%, respectively. The presence of energy transfer process was also confirmed by excitation spectra measurements. PMID:24824577

Pisarska, Joanna; Kos, Agnieszka; Pisarski, Wojciech A

2014-08-14

52

OPTICAL CHARACTERIZATION OF Tb3+-DOPED Gd2O3 BASED SCINTILLATING GLASSES  

NASA Astrophysics Data System (ADS)

We prepared Tb3+-doped Gd2O3-based oxide glasses by high-temperature melting method and presented their density and optical characterization including transmission, emission and excitation spectra. Dependence of density and luminescence properties on the concentration of Tb3+ and Gd2O3 was also analyzed. The results show that rising Tb3+ ions concentrations would lead to the reduction of distance between Tb3+ ions, the increase of probabilities of energy resonate-transfer and a stronger luminous intensity. In addition, a high Gd2O3 concentration was beneficial to improve the glass samples density, but exerting a negative effect on Tb3+ ions and decreasing the luminous intensity of Tb3+ ions.

Lai, Fei; Zhang, Yue-Pin; Xia, Hai-Ping; Wang, Jin-Hao; He, Wei

2013-09-01

53

Magneto-optical properties of (Pr,Nd)-(Tb,Dy)-FeCo amorphous films  

SciTech Connect

The authors discuss a systematic study of magneto-optical properties for four different varieties of the (Pr,Nd)-(Tb,Dy)-FeCo system focusing on temperature and wavelength dependence of Kerr rotation {theta}/sub {kappa}/ for alloy films and multilayered films. The relation between Curie temperature Tc and kerr rotation {theta}/sub {kappa}/ at 830nm wavelength was obtained for films, where Co ratio to FeCo was less than 20at%. It was found that in the range of 500 nm to 900 nm the absolute magnitude of {theta}/sub {kappa}/ for all quaternary systems was always less than that for Dy-FeCo. These results suggest that amorphous rare earth-FeCo alloy films, containing Nd or Pr, are not superior to (Tb,Dy)-FeCo films in regard to recording sensitivity and recording density in magneto-optical disks.

Nakada, M.; Yokota, H.; Yumoto, S.; Okada, O.; Gokan, H. (Microelectronics Research Labs., NEC Corp., Miyazaki, Miyamae-ku, Kawasaki 213 (JP))

1989-09-01

54

The magnetostriction and its ratio to hysteresis for Tb-Dy-Ho-Fe alloys  

NASA Astrophysics Data System (ADS)

The x(Tb0.15Ho0.85Fe2) + (1 - x)(Tb0.3Dy0.7Fe2) alloys were prepared in an arc furnace under high purity argon. The as-cast samples wrapped in Mo foil were sealed in a silica tube filled with high purity argon. The static measurement of magnetostriction (?//, ??) was made by standard strain gauge, and the magnetization M was measured by a vibrating sample magnetometer. It is found that the magnetostriction ?// of x(Tb0.15Ho0.85Fe2) + (1 - x)(Tb0.3Dy0.7Fe2) alloys decreases with increasing x and it does from 880 × 10-6 for x = 0 to 210 × 10-6 for x = 0.9 at the magnetic field of 640 kA/m. The ratio (?///Wh) of magnetostriction to hysteresis exhibits a peak when x = 0.1, and it means that the Tb0.285Dy0.63Ho0.085Fe2 (x = 0.1) alloy possesses both large magnetostriction and small magnetostrictive hysteresis.

Wang, Bowen; Lv, Yan; Li, Guolu; Huang, Wenmei; Sun, Ying; Cui, Baozhi

2014-05-01

55

(Gd,Yb,Tb)PO4 up-conversion nanocrystals for bimodal luminescence-MR imaging  

NASA Astrophysics Data System (ADS)

Up-conversion (Gd,Yb,Tb)PO4 materials and their potential for bimodal imaging have received little attention in the literature. Herein, we report the first study on the up-conversion emission of (Gd,Yb,Tb)PO4 nanocrystals synthesized via a hydrothermal method at 150 °C. These materials exhibit ultraviolet, blue and green up-conversion emissions upon excitation with a 980 nm continuous wave laser diode. The intensity of the blue-emission band at 479 nm, ascribed to the cooperative up-conversion emission of a pair of excited Yb3+ ions, depends on the Yb3+/Tb3+ concentration ratio, calcination temperature and particle size. Strong green up-conversion emission of Tb3+ is observed at 543 nm for the 5D4 --> 7F5 transition. Relaxometry measurements reveal that the nanocrystals are efficient T2-weighted (negative) contrast agents which, combined with visible-light emission generated by infrared excitation, affords them considerable potential for being used in bimodal, photoluminescence-magnetic resonance, imaging.Up-conversion (Gd,Yb,Tb)PO4 materials and their potential for bimodal imaging have received little attention in the literature. Herein, we report the first study on the up-conversion emission of (Gd,Yb,Tb)PO4 nanocrystals synthesized via a hydrothermal method at 150 °C. These materials exhibit ultraviolet, blue and green up-conversion emissions upon excitation with a 980 nm continuous wave laser diode. The intensity of the blue-emission band at 479 nm, ascribed to the cooperative up-conversion emission of a pair of excited Yb3+ ions, depends on the Yb3+/Tb3+ concentration ratio, calcination temperature and particle size. Strong green up-conversion emission of Tb3+ is observed at 543 nm for the 5D4 --> 7F5 transition. Relaxometry measurements reveal that the nanocrystals are efficient T2-weighted (negative) contrast agents which, combined with visible-light emission generated by infrared excitation, affords them considerable potential for being used in bimodal, photoluminescence-magnetic resonance, imaging. Electronic supplementary information (ESI) available: A schematic representation for the synthesis of up-conversion monoclinic (Gd,Yb,Tb)PO4 nanocrystals (Fig. S1); XRD patterns of as-synthesized (Gd,Yb,Tb)PO4.2.5H2O and calcined (Gd,Yb,Tb)PO4 samples (Fig. S2) and of dextran-coated and uncoated Gd0.87Yb0.10Tb0.03PO4 nanocrystals (Fig. S3); TEM images of (Gd,Yb,Tb)PO4.2.5H2O and (Gd,Yb,Tb)PO4 samples (Fig. S5 and S6); FT-IR spectra of (Gd,Yb,Tb)PO4.2.5H2O and (Gd,Yb,Tb)PO4 samples (Fig. S7); pump-power dependence of the up-conversion emission intensities (Fig. S8); comparison of the up-conversion emission for dextran-coated and uncoated monoclinic Gd0.87Yb0.10Tb0.03PO4 nanocrystals (Fig. S9); up-conversion emission spectra of monoclinic Gd0.85Yb0.10Tb0.05PO4 nanocrystals calcined for 3 hours at 900 °C and 1200 °C (Fig. S10); relaxivity measurements (Fig. S11 and S12); UV-visible absorption spectra and calibration curve for the Gd3+ leaching test (Fig. S13); steady-state emission/excitation spectra (Fig. S14). See DOI: 10.1039/c2nr31226c

Debasu, Mengistie L.; Ananias, Duarte; Pinho, Sonia L. C.; Geraldes, Carlos F. G. C.; Carlos, Luís D.; Rocha, João

2012-07-01

56

Single crystal growth of (Dy\\/1-x\\/Gd\\/x\\/)3Al5O12 and (Dy\\/1-x-y\\/Gd\\/x\\/Y\\/y\\/)3Al5O12 garnets  

Microsoft Academic Search

A Dy3Al5O12 (DAG) single crystal is one of the most promising magnetic refrigerants for a helium liquefaction magnetic refrigerator below 10 K. Some rare-earth aluminum garnet single crystals containing Dy and Gd ions with large magnetic moment, such as (Dy\\/1-x\\/Gd\\/x\\/)3Al5O12 (DGAG) and (Dy\\/1-x-y\\/Gd\\/x\\/Y\\/y\\/)3Al5O12 (DGYAG) rare-earth solid solutions, were grown using the Czochralski technique. The solid solution limit of rare-earth ions

Hideo Kimura; Takenori Numazawa; Mitsunori Sato; Hiroshi Maeda; Masaru Sakamoto

1989-01-01

57

Resonant tunnelling in Dy- or Gd-doped Al2O3 magnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

Tunnelling characteristics have been measured for Co-insulator-Py magnetic junctions with Dy- or Gd-doped Al2O3 barriers. The theoretically predicted enhancement of the magneto-resistance due to resonant tunnelling in the presence of paramagnetic impurities is not borne out. However, even a full monolayer of Dy or Gd has no detrimental effect on the junction magneto-resistance (JMR) at low temperature and low bias voltage. With increasing temperature and bias, the JMR of the doped junctions decreases significantly faster than the JMR of the Al2O3 control junctions. Junctions in which the entire barrier has been replaced by Dy2O3 or Gd2O3 show strong non-linear current-voltage characteristics, but display no JMR. It is shown that not direct tunnelling but spin-independent impurity-assisted tunnelling is the primary conductance channel in these junctions.

de Groot, C. H.; Ouyang, Y.; Koo, Sang-Mo; Kendall, E.; Shu, Q. Q.; Moodera, J. S.

2002-05-01

58

Trapping parameters and kinetics in Gd 2O 2S: Tb phosphor  

NASA Astrophysics Data System (ADS)

Thermoluminescence (TL) of gadolinium oxysulfide activated with Tb (Gd 2O 2S: Tb) is investigated. The TL spectrum recorded in the temperature range 93 to 500 K with a heating rate of 0.52 K s -1 shows five glow peaks. An analysis of the trapping parameters and order of kinetics for all of the prominent glow peaks has been done.

Chatterjee, S.; Shanker, V.; Ghosh, P. K.

1991-12-01

59

[Photoluminescence of green phosphors Gd2Ba3B3O12 doped with Tb3+].  

PubMed

The green emitting phosphor, Gd2Ba3B3O12:Tb3+ was synthesized with the method of high-temperature solid-state reaction. The phase structure and photoluminescence (PL) properties of the samples were characterized by The X-ray diffraction (XRD), vacuum ultraviolet spectrum and ultraviolet spectrum (VUV-UV). The results indicate that Tb3+ ion acting as the luminescent center inhabited the site of Gd3+ ion in the host of Gd2Ba3B3O12. The VUV-UV excitation spectrum consists of the two strong broad bands at about 160-200 and 200-250 nm and sharp lines at about 260-280 and 300-320 nm. The two strong broad bands were assigned to the host absorption and f--d transition of Tb3+. The sharp lines were ascribed to the f--f transition of Tb3+ and Gd3+. All the samples of Gd2Ba3B3O12:Tb3+ exhibit strong green emission corresponding to (5)D4-->(7)F5 transition (543 nm) of Tb3+ under VUV-UV light excitation. Under 172 nm excitation, 15 mol% Tb3+ doped Gd2Ba3B3O12 sample exhibits strong green emission with good color purity (x = 0.3136, y = 0.4843) and a fitted a decay time r around 2.98 ms. It can be concluded that this series of phosphors Gd2Ba3B3O12:Tb3+ is a promising green vacuum ultraviolet (VUV) phosphor for plasma display panels (PDPs) and Hg-free fluorescent tubes application. PMID:21595203

Zhao, Wen-yu; Fan, Bin; Li, Song-bo; Zhang, Guo-bin; Dai, Ya-tang

2011-03-01

60

Intense visible fluorescence and energy transfer in Dy 3+, Tb 3+, Sm 3+ and Eu 3+ doped rare-earth borate glasses  

Microsoft Academic Search

Tb3+\\/Dy3+ and Eu3+\\/Sm3+ doped rare-earth borate glasses have been synthesized and characterized. Under UV excitation, Dy3+, Tb3+, Sm3+ and Eu3+ emit intense yellowish white, green, reddish orange and red lights, respectively. In Tb3+\\/Dy3+ co-doped glasses, the enhancement of Tb3+ green emission is observed, and the sensitization is related to the efficient energy transfer from Dy3+ to Tb3+. In Eu3+\\/Sm3+ co-doped

Hai Lin; Edwin Yue-Bun Pun; Xiaojun Wang; Xingren Liu

2005-01-01

61

Hydrogen embrittlement failure of (Sm,Dy,Gd)Co 5 permanent magnets  

Microsoft Academic Search

The effect of long-term hydrogenation of the (Sm,Dy,Gd)Co5 permanent magnet on mechanical degradation and decay of magnetic properties in service is investigated. The application of ?15 ?m Cd-coatings is recommended to prevent the hydrogenation of the permanent magnet.

A. A. Lukin; S. Szymura; Yu. M. Rabinovich; H. Bala; A. A. Zhuravlyev

1998-01-01

62

Electroluminescence in Tb-doped Gd2O2S phosphor  

NASA Astrophysics Data System (ADS)

We report a strong ac green electroluminescence (EL) in powder layers of terbium doped gadolinium oxysulfide (Gd2O2S:Tb) with methyl methacrylate as binder. An intensity of the order of 30 nits (Cd/sq m) has been achieved. The EL emission spectra shows line emissions corresponding to 5D3 and 5D4 fluorescing levels of Tb(3+) ions. A very sharply rising B-V curve normally related to insulator-phosphor interface properties of a thin film electroluminescent device has been observed in these cells. This indicates the possibilities of barrier formation due to the localized space charge region in the absence of any prominent interfaces leading to impact excitation of Tb(3+) ions. This has further been confirmed by the excitation spectrum of Gd2O2S:Tb phosphor, which reveals Tb(3+) impurity absorption bands related to 4f8 shell transitions.

Shanker, V.; Chatterjee, S.; Ghosh, P. K.

1992-12-01

63

Excitation mechanisms and effects of dopant concentration in Gd 2O 2S:Tb 3+ phosphor  

Microsoft Academic Search

Gadolinium oxysulfide powders doped with different Tb3+ concentrations were prepared from sulfur vaporization on rare earths’ basic carbonate precursors. Single-phase Gd2O2S samples were obtained, with Tb3+ doping up to 9at%. The study of the excitation mechanisms revealed that the Tb3+ emission might occur after the direct Tb3+ excitation either by energy transfer from Gd3+ or from the phosphor host. The

Alison Abreu da Silva; Marco Aurélio Cebim; Marian Rosaly Davolos

2008-01-01

64

[Synthesis and fluorescence properties of the Tb(Ln) complexes with trimesic acid (Ln = Y, Gd)].  

PubMed

In the present paper two series of mixed rare earth complexes Tb(1-x)LnxBTC x nH2O (Ln = Y, Gd, x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by hydrothermal method. The contents of rare earth were measured by using EDTA titration method; the element analyses of C and H were performed by using Vario EL III elemental analyzer, and the IR spectra were recorded by FTIR-8900 infrared spectroscopy with KBr pellet. Then the molecular formula of the complexes were determined to be Tb(1-x)LnxBTC x 0.5H2O (Ln = Y, Gd). The fluorescence spectrum of all the complexes were recorded by using a Hitachi F-4500 fluorescence spectrophotometer at room temperature. The results indicated that all the complexes emitted characteristic fluorescence of Tb3+, and the fluorescence intensities of the complexes were obviously enhanced with doping rare earth ion of Y3+ or Gd3+. It was showed that Tb3+ was sensitized by doping rare earth ions. This may be because there was intra molecular energy transfer in the complexes. Being doped with the rare earth ion the emission peak positions did not change. Among the four emission peaks, 5D4 --> 7F5 (544 nm) was the strongest one, and it was found when the proportion is Y3+ : Tb3+ = 0.5 : 0.5 or Gd3+ : Tb3+ = 0.3 : 0.7, the fluorescence intensity of Tb(1-x)YxBTC x 0.5H2O or Tb(1-x)GdxBTC x 0.5H2O was the greatest, meanwhile the sensitization degree was bigger with doping Gd3+ than doping Y3+ at 544 nm. PMID:18306803

Song, Hui-hua; Yang, Fang; Wang, Ji-ye; Shi, Shi-kao

2007-10-01

65

Hydrothermal synthesis and luminescent properties of Y 2O 3:Tb 3+ and Gd 2O 3:Tb 3+ microrods  

Microsoft Academic Search

One-dimensional (1D) Y2O3:Tb3+ and Gd2O3:Tb3+ microrods have been successfully prepared through a large-scale and facile hydrothermal method followed by a subsequent calcination process in N2\\/H2 mixed atmosphere. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectra (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED),

Zhenhe Xu; Jun Yang; Zhiyao Hou; Chunxia Li; Cuimiao Zhang; Shanshan Huang; Jun Lin

2009-01-01

66

Microstructure, mechanical and corrosion properties of Mg-Dy-Gd-Zr alloys for medical applications.  

PubMed

In previous investigations, a Mg-10Dy (wt.%) alloy with a good combination of corrosion resistance and cytocompatibility showed great potential for use as a biodegradable implant material. However, the mechanical properties of Mg-10Dy alloy are not satisfactory. In order to allow the tailoring of mechanical properties required for various medical applications, four Mg-10(Dy+Gd)-0.2Zr (wt.%) alloys were investigated with respect to microstructure, mechanical and corrosion properties. With the increase in Gd content, the number of second-phase particles increased in the as-cast alloys, and the age-hardening response increased at 200°C. The yield strength increased, while the ductility reduced, especially for peak-aged alloys with the addition of Gd. Additionally, with increasing Gd content, the corrosion rate increased in the as-cast condition owing to the galvanic effect, but all the alloys had a similar corrosion rate (~0.5 mm year(-1)) in solution-treated and aged condition. PMID:23523938

Yang, L; Huang, Y; Feyerabend, F; Willumeit, R; Mendis, C; Kainer, K U; Hort, N

2013-11-01

67

Laser-plasma source parameters for Kr, Gd, and Tb ions at 6.6 nm  

NASA Astrophysics Data System (ADS)

There is increasing interest in extreme-ultraviolet (EUV) laser-based lamps for sub-10-nm lithography operating in the region of 6.6 nm. A collisional-radiative model is developed as a post-processor of a hydrodynamic code to investigate emission from resonance lines in Kr, Gd, and Tb ions under conditions typical for mass-limited EUV sources. The analysis reveals that maximum conversion efficiencies of Kr occur at 5×1010W/cm2, while for Gd and Tb it was ~=0.9%/2?sr for laser intensities of (2-5)×1012W/cm2.

Masnavi, Majid; Szilagyi, John; Parchamy, Homaira; Richardson, Martin C.

2013-04-01

68

Electroluminescence in Tb-doped Gd2O2S phosphor  

Microsoft Academic Search

We report a strong ac green electroluminescence (EL) in powder layers of terbium doped gadolinium oxysulfide (Gd2O2S:Tb) with methyl methacrylate as binder. An intensity of the order of 30 nits (Cd\\/sq m) has been achieved. The EL emission spectra shows line emissions corresponding to 5D3 and 5D4 fluorescing levels of Tb(3+) ions. A very sharply rising B-V curve normally related

V. Shanker; S. Chatterjee; P. K. Ghosh

1992-01-01

69

Induced assembly and photoluminescence of lanthanum (Tb, Eu, Dy) complexes/ZnO/polyethylene glycol hybrid phosphors  

NASA Astrophysics Data System (ADS)

Some novel kinds of hybrid phosphors were assembled with lanthanum (Tb, Eu, Dy) complexes (with four kinds of terbium complexes is 2,4-dihydroxybenzonic acid (DHBA), 1,10-phenanthroline (phen), acetylacetone (AA) and nicotinic acid (Nic), respectively) doped ZnO/PEG particles by co-precipitation approach derived from Zn(CH 3COO) 2 (Zn(AC) 2), NaOH, PEG as precursors at room temperature. The characteristic luminescence spectra for f-f transitions of Tb 3+, Eu 3+, Dy 3+ were observed. It is worthy to point out that ZnO is the excellent host for lanthanum ions by the assembly of PEG matrices.

Yan, Bing; Chen, Xi; Wu, Jianhua

2007-08-01

70

Hyperfine interactions in R x Gd1 - x Fe3 intermetallics R = Tb, Y  

NASA Astrophysics Data System (ADS)

The structural and magnetic properties of rare earth iron intermetallic compounds Tb x Gd1- x Fe3 and Y x Gd1- x Fe3 ( x = 0. 0, 0. 1, 0. 2, 0. 4, 0. 5, 0. 6, 0. 8, 1. 0) was studied by X-ray diffraction, the 57Fe Mössbauer effect and SQUID measurements. All investigated compounds crystallize in the rhombohedral PuNi3-type of crystal structure. The investigation of magnetic properties of R x Gd1- x Fe3 proved their ferrimagnetic behavior. The Curie temperature of the investigated compounds decreases with the increase of R concentration from 721K (GdFe3) to 655K (TbFe3) and 533K (YFe3). The saturation magnetic moment MS in the R x Gd 1- x Fe3 system increase with x parameter. The Mössbauer spectra are analyzed using four sextets, corresponding to three crystallographically (b, c, h) and four magnetically (b, c, h1, h2) inequivalent sites for iron. The mean hyperfine magnetic field increases with increase of the Gd concentration

Ka¸dzio?ka-Gawe?, M.; Bajorek, A.

2014-04-01

71

Photoluminescence Properties of Li6Gd(BO3)3:Tb3+ Under VUV / UV Excitation  

NASA Astrophysics Data System (ADS)

A series of phosphors Li6Gd1-x(BO3)3:xTb3+ (0:x:1) was prepared by a conventional solid-state reaction method and their photoluminescence properties under VUV/UV excitation were demonstrated. For the excitation spectrum, the host-related absorption band, f-f and f-d transitions of Gd3+ and Tb3+, charge transfer of O2--Gd3+ and O2--Tb3+ were assigned. In Li6Gd(BO3)3:Tb3+, visible quantum cutting through downconversion was observed upon Tb3+ 4f8-4f75d1 excitation and host excitation. The quantum cutting process was demonstrated combining a possible model.

Zhang, Feng; Wang, Yuhua; Tao, Ye

72

Anion disorder in lanthanoid zirconates Gd(2-x)Tb(x)Zr2O7.  

PubMed

The pyrochlore-defect fluorite order-disorder transition has been studied for a series of oxides of the type Gd(2-x)Tb(x)Zr2O7 by a combination of diffraction and spectroscopy techniques. Synchrotron X-ray diffraction data suggest an abrupt transition from the coexistence of pyrochlore and defect fluorite phases to a single defect fluorite phase with increasing Tb content. However neutron diffraction data, obtained at ? ? 0.497 Å for all Gd-containing samples to minimize absorption, not only provide evidence for independent ordering of the anion and cation sublattices but also suggest that the disorder transition across the pyrochlore-defect fluorite boundary of Ln2Zr2O7 is rather gradual. Such disorder was also evident in X-ray absorption measurements at the Zr L3-edge, which showed a gradual increase in the effective coordination number of the Zr from near 6-coordinate in the pyrochlore rich samples to near 7-coordinate in the Tb rich defect fluorites. These results indicate the presence of ordered domains throughout the defect fluorite region, and demonstrate the gradual nature of the order-disorder transition across the Gd(2-x)Tb(x)Zr2O7 series. PMID:23844979

Reynolds, Emily; Blanchard, Peter E R; Kennedy, Brendan J; Ling, Chris D; Liu, Samuel; Avdeev, Max; Zhang, Zhaoming; Cuello, Gabriel J; Tadich, Anton; Jang, Ling-Yun

2013-08-01

73

Luminescent properties of NaGdF4: Ln3+ (Ln3+ = Ce3+, Tb3+) phosphors.  

PubMed

Ln3+ (Ln3+ = Ce3+, Tb3+) single doped and/or co-doped NaGdF4 phosphors have been synthesized through a solid state reaction method under a weak reducing N2/H2 (95/5) atmosphere. The phosphors were characterized by X-ray diffraction (XRD) patterns, room temperature photoluminescence (PL) excitation and emission spectra, and luminescent dynamics decay curves. XRD analysis indicated that the phosphors were in the hexagonal phase and crystallized well. Under Ce3+ 4f-5d 252 nm excitation, the Ce3+ single doped phosphor emitted near ultraviolet light peaking at 398 nm. Under host Gd3+ 275 nm sensitization and direct Tb3+ 4f-4f 380 nm excitation, the Tb3+ single doped NaGdF4 phosphor gave blue and/or green light. Under sensitizer Ce3+ 4f-5d 252 nm and host Gd3+ 4f-4f 275 nm sensitization and direct Tb3+ 4f-4f 380 nm excitation, the Ce3+/Tb3+ co-doped NaGdF4 phosphors had blue and/or green light. With fixed Ce3+ concentrations in the Ce3+/Tb3+ co-doped phosphors, the blue light of Tb3+ became weaker and the green light of Tb3+ became stronger with the increase of Tb3+ concentrations, which was caused by the cross relaxation process 5D3 --> 5D4:7F6 --> F0. The experimental results suggested that the Ce3+/Tb3+ co-doped and Tb3+ single doped NaGdF4 phosphors might be used as blue and/or green light emitting materials. PMID:24734624

Cao, Chunyan; Guo, Siling; Wu, Aijin; Lu, Guojun

2014-05-01

74

Brilliant Sm, Eu, Tb and Dy chiral lanthanide complexes withstrong circularly polarized luminescence  

SciTech Connect

The synthesis, characterization and luminescent behavior of trivalent Sm, Eu, Dy and Tb complexes of two enantiomeric, octadentate, chiral, 2-hydroxyisophthalamide ligands are reported. These complexes are highly luminescent in solution. Functionalization of the achiral parent ligand with a chiral 1-phenylethylamine substituent on the open face of the complex in close proximity to the metal center yields complexes with strong circularly polarized luminescence (CPL) activity. This appears to be the first example of a system utilizing the same ligand architecture to sensitize four different lanthanide cations and display CPL activity. The luminescence dissymmetry factor, g{sub lum}, recorded for the Eu(III) complex is one of the highest values reported, and this is the first time the CPL effect has been demonstrated for a Sm(III) complex with a chiral ligand. The combination of high luminescence intensity with CPL activity should enable new bioanalytical applications of macromolecules in chiral environments.

Petoud, Stephane; Muller, Gilles; Moore, Evan G.; Xu, Jide; Sokolnicki, Jurek; Riehl, James P.; Le, Uyen; Cohen, Seth M.; Raymond,Kenneth N.

2006-07-10

75

Lattice vibrations of AVO4 crystals (A=Lu, Yb, Dy, Tb, Ce).  

PubMed

A short range force constant model has been applied using normal coordinates to investigate the Raman and the infrared wavenumbers in rare earth AVO4 compounds (A=Lu, Yb, Dy, Tb, Ce) having space group I41/a and symmetry C4h(6). The calculation of zone center phonons has been made by using four stretching and five bending force constants. The calculated Raman and infrared wavenumbers are in very good agreement with the observed ones. The present calculations interpret reasonably the mode assignment of 779 cm(-1) as Eg mode and 853 cm(-1) as Ag mode in case of LuVO4, which were assigned differently in earlier observation. The potential energy distribution has also been investigated for determining the significance of contribution from each force constant toward the Raman and the infrared wavenumbers. PMID:23735207

Jindal, Ruby; Sinha, M M; Gupta, H C

2013-09-01

76

Thermal and Mechanical Properties of ACoO3 (R = Sm, Tb, Dy, Ho, and Er)  

NASA Astrophysics Data System (ADS)

The thermal and mechanical properties of orthocobaltates, ACoO3 (A = Sm, Tb, Dy, Ho, and Er), have been investigated using the modified rigid ion model (MRIM) by incorporating the effect of lattice distortions. We have computed the variations of specific heat and thermal expansion coefficient for these orthocobaltates in wide temperature range of 1 K (-272 °C) ? T ? 1000 K (727 °C). The calculated results of specific heat, thermal expansion, bulk modulus, and other thermal and mechanical properties accord very well with the available experimental data, implying that MRIM represents properly the nature of the perovskite-type rare earth cobaltates. In addition, we have also reported the results on molecular force constant ( f), Reststrahlen frequency ( ?), cohesive energy ( ?), Debye temperature ( ? D), and Gruneisen parameter ( ?).

Gaur, N. K.; Thakur, Rasna

2013-12-01

77

Recombination luminescence of CaSO4:Tb3+ and CaSO4:Gd3+phosphors  

NASA Astrophysics Data System (ADS)

A comparative study of the excitation of luminescence by VUV radiation as well as of thermally and photostimulated luminescence has been carried out for CaSO4:Tb3+ and CaSO4:Gd3+ phosphors, where Na+ or F- ions are used for charge compensation. The distinction in hole processes for the phosphors with Na+ or F- compensators is determined by the differing thermal stability of the holes localized at/near Tb3+Na+ and Gd3+Na+ (up to 100-160 K) or at/near Tb3+F- V Ca and Gd3+F- V Ca centers involving also a cation vacancy (up to 400-550 K). Tunnel luminescence in the pairs of localized electrons and holes nearby Tb3+ or Gd3+ has been detected. The mechanisms of electron-hole, hole-electron and tunnel recombination luminescence as well as a subsequent released energy transfer to RE3+ ions are considered.

Kudryavtseva, Irina; Lushchik, Aleksandr; Maaroos, Aarne; Azmaganbetova, Zhannur; Nurakhmetov, Turlybek; Salikhoja, Zhussupbek

2012-08-01

78

Heat treatments of Gd2O2S:Tb, Y2O2S:Tb phosphors  

NASA Astrophysics Data System (ADS)

It's well known, that some heat treatments improve significantly the light yield of Gd2O2S:Tb, Y202S:Tb phosphors, but processes ofthe energy transfer at excitations need further investigations. We present the new results ofthe synthesis and heat treatments optimization of oxysulfide phosphors. The heat treatments curried out at different ambient atmospheres in temperature range 200-1000°C. To measure kinetic properties of defects formations/annealing at heat treatments we measured the dependencies ofrelative defect concentrations on the duration of isothermal annealing. The investigation of bulk and surface defects in phosphors before and after heat treatments carried out at different excitation with different methods: spectra measurements with direct Tb3+ center excitation (4.9 eV UV excitation), spectra measurements with above gap excitation (X-ray; 1 kV and 10 kV electrons, 8.4 eV VUV excitation), thermo-stimulated luminescence measurements. The results of investigations allow us to increase the light yield of phosphors (20% increase in comparison with commercial samples).

Mikhitaryan, Boris V.; Manashirov, Oshir Y.; Mikhrin, Sergey B.

2007-04-01

79

Luminescence properties of Bi3+ ions co-doped Gd2O3:Eu3+, Tb3+ nanophosphors  

Microsoft Academic Search

Gd2O3:Eu3+, Tb3+ and Bi3+ ions co-doped Gd2O3:Eu3+, Tb3+ powders were synthesized by solvothermal reaction method. The crystalline structure, surface morphologies and phase transitions of these powders were investigated according to annealing process by using X-ray diffraction (XRD), field emission-scanning electron microscopy, photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). The purpose of this study is to compare the luminescence properties

Jong Won Chung; Byung Kee Moon; Jung Hyun Jeong; Jung Hwan Kim

2010-01-01

80

Magnetic properties of NiFe2?xRExO4 (RE=Dy, Gd) using magnetic Compton scattering  

NASA Astrophysics Data System (ADS)

Temperature dependent spin momentum densities of NiFe2?xRExO4 (x=0, 0.05; RE=Dy, Gd) ferrites have been measured using a magnetic Compton spectrometer available at SPring-8, Japan. The experimental profiles of NiFe2O4 (NFO) with doping of Dy and Gd show almost similar spin moment as of undoped NFO. The contribution of different constituents in the formation of total spin moment is also deduced from the analysis of Compton line shape. It is seen that 5% doping of Dy3+ or Gd3+ ions at Fe3+ sites leads to a redistribution of spin moment at Fe3+ and RE3+ sites. The magnetic Compton data when compared with the magnetization data (using a vibrating sample magnetometer) show almost a constant orbital moment (0.21±0.03 µB/f.u.) in the doped and undoped NFO.

Sahariya, Jagrati; Mund, H. S.; Sharma, Arvind; Dashora, Alpa; Itou, M.; Sakurai, Y.; Ahuja, B. L.

2014-06-01

81

Photoluminescence properties of MgY4Si3O13:Gd3+, Tb3+ under vacuum ultraviolet excitation  

NASA Astrophysics Data System (ADS)

Gd3+ and Tb3+ co-doped MgY4Si3O13 green phosphors were prepared by a solid-state reaction. The photoluminescence properties in vacuum ultraviolet-visible (VUV-vis) range and decay properties were investigated in details. The f-d transition of Gd3+ ions and spin-allowed f-d transition of Tb3+ ions locate at about 134 nm and 239 nm, respectively. Two charge transfer bands of O2- ? Gd3+ and O2- ? Tb3+ overlap at about 155 nm. Some f-f transition of Tb3+ and Gd3+ ions are confirmed in VUV-vis range. Upon excitation at 172 nm, the optimal composition of MgY3.3Si3O13:0.5Gd3+, 0.2Tb3+ phosphor exhibits the characteristic transitions of Gd3+ and Tb3+ with chromaticity coordinate of (0.2849, 0.5843). The phosphor has a shorter decay time (2.13 ms) than that of Zn2SiO4:Mn2+ (4.56 ms). The results suggest that this green phosphor is a potential candidate for mercury-free luminescence lamps and plasma display panels (PDPs) application.

Zhao, Wenyu; An, Shengli; Fan, Bin; Li, Songbo

2013-07-01

82

Optical spectra and luminescence dynamics of the Dy-doped Gd2SiO5 single crystal  

NASA Astrophysics Data System (ADS)

Spectroscopic properties of the Dy3+:Gd2SiO5 (GSO) single crystal were investigated. The polarized absorption and unpolarized emission spectra were measured at temperature ranging from 10 K to 300 K. Experimental oscillator strengths were determined from room temperature polarized absorption spectra and phenomenological intensity parameters ? t were calculated by using the standard Judd-Ofelt theory. Low-temperature measurements were used to determine the energy level structure of two nonequivalent Dy3+ sites in the GSO crystalline host. Analysis of spectra and decay curves of the 4F9/2 emission revealed that Dy3+ ions entering nine-coordinated sites with C 3 v symmetry and Dy3+ ions entering the seven-coordinated sites with C s symmetry form two distinct, well-isolated subsystems weakly coupled by the spectral energy migration process. In addition to dissimilar crystal field splitting of multiplets, the two subsystems differ significantly in the efficiency of excitation energy transfer between dysprosium ions, thereby showing dissimilar self-quenching of the 4F9/2 emission. Besides, only one of the two Dy3+ subsystems is coupled to Gd3+ ions by nonradiative Gd3+-Dy3+ energy transfer process. Laser potential related to the 4F9/2?6H13/2 yellow luminescence of dysprosium ions was assessed based on evaluation of the emission cross-section values. It was concluded that the Dy:Gd2SiO5 (Dy:GSO) is a promising material for the visible laser operation.

Lisiecki, R.; Dominiak-Dzik, G.; Solarz, P.; Ryba-Romanowski, W.; Berkowski, M.; G?owacki, M.

2010-02-01

83

Optical properties and Judd-Ofelt parameters of Dy3+ doped K2GdF5 single crystal  

NASA Astrophysics Data System (ADS)

Dy3+-doped K2GdF5 single crystals with 10.0 mol% have been prepared by hydrothermal condition. The spectra are analyzed in term of the Judd-Ofelt theory, the intensity parameters (??, ? = 2, 4, 6) have been evaluated for Dy3+-doped K2GdF5 sample. The electric (Sed), magnetic (Smd) dipole line strength, radiative (A), and total radiative (AT) transition probabilities, lifetime (?R), branching ratios (?R) for the excited levels of Dy3+ doped K2GdF5 crystals were investigated by using the intensity parameters. In addition, the stimulated emission cross-sections (??p) and integrated emission cross-section (?if) have been predicted for the transitions from excited level, 4F9/2, to the 6H15/2, 6H13/2 and 6H11/2 levels. The energy transfer occurs from Gd3+ to Dy3+, resulting in the additional intense excitation UV-narrow bands for the luminescence of the Dy3+ ions.

Van Do, Phan; Tuyen, Vu Phi; Quang, Vu Xuan; Thanh, Nguyen Trong; Ha, Vu Thi Thai; Van Tuyen, Ho; Khaidukov, Nicholas M.; Marcazzó, Julián; Lee, Yong-Ill; Huy, Bui The

2013-07-01

84

Observations of phase transitions in the mixed crystal system Dy pGd 1-pVO 4  

NASA Astrophysics Data System (ADS)

The low temperature crystallographic and magnetic phase transitions in the mixed crystal system Dy pGd 1- pVO 4 (0 ? p ? 1) have been studied using thermal expansion measurements and Mössbauer spectroscopy. The introduction of magnetic Gd 3+ ions into the DyVO 4 host causes an anomalous dip in the Néel temperature T N( p), and a rapid reduction of the distortion temperature T D( p) which differs from results on similar mixed systems. A number of pseudo-spin Hamiltonians that model these observations are discussed.

Bingham, D.; Morgan, M. J.; Cashion, J. D.

1982-10-01

85

Phase diagrams of the Tb-Ag-In and Dy-Ag-In systems at 870 K  

SciTech Connect

The phase equilibria of Tb-Ag-In and Dy-Ag-In ternary systems have been studied at 870 K in the whole concentration range by means of X-ray powder, single crystal X-ray diffraction and EDX analyses. Isothermal sections of Tb-Ag-In and Dy-Ag-In phase diagrams at this temperature have been constructed. Both systems are characterized by formation of three ternary compounds: REAg{sub 3}In{sub 3} (YbAg{sub 2}In{sub 4}-type, space group Im-3), REAg{sub 2}In (MnCu{sub 2}Al-type, space group Fm-3m) and RE{sub 2}AgIn{sub 3} (CaIn{sub 2}-type, space group P6{sub 3}/mmc) RE=Tb, Dy. Homogeneity ranges of the ternary phases with CaIn{sub 2} structure type lies from 35 to 60 at% of In for Tb-containing phase and from 39 to 50 at% of In for Dy-containing phase. The existence of solid solutions based on REAg (CsCl-type, space group Pm-3m) binary compounds up to 30 at% of In and REIn{sub 3} (AuCu{sub 3}-type, space group Pm-3 m) binary compounds up to 5 at% of Ag has been found. - Graphical Abstract: Phase relations in the ternary systems Tb-Ag-In and Dy-Ag-In have been established for the isothermal section at T=870 K based on X-ray powder and single crystal diffraction analyses. The existence of three ternary compounds in each system were observed. Highlights: Black-Right-Pointing-Pointer Isothermal section of Tb-Ag-In system at T=870 K was constructed. Black-Right-Pointing-Pointer Isothermal section of Dy-Ag-In system at T=870 K was constructed. Black-Right-Pointing-Pointer Three ternary compounds and two solid solutions in each system were detected.

Demchyna, M., E-mail: marta.dem.85@gmail.com [Faculty of Chemistry, Ivan Franko National University of Lviv, Kyryla and Mefodiya Str. 6, UA-79005 Lviv (Ukraine); Belan, B.; Manyako, M. [Faculty of Chemistry, Ivan Franko National University of Lviv, Kyryla and Mefodiya Str. 6, UA-79005 Lviv (Ukraine); Pietraszko, A. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wroclaw 2 (Poland); Kalychak, Ya. [Faculty of Chemistry, Ivan Franko National University of Lviv, Kyryla and Mefodiya Str. 6, UA-79005 Lviv (Ukraine)

2012-08-15

86

Effects of heteroepitaxial strain on Laves phases TbFe{sub 2} and DyFe{sub 2}  

SciTech Connect

(110) oriented growth was observed for thin films of the highly magnetostrictive Laves phases TbFe{sub 2} and DyFe{sub 2} on Ta (110). On Nb (111), TbFe{sub 2} nucleates in the (111) orientation. Depending on the substrate temperature during growth, varying degrees of residual tensile strain were observed in the films. For TbFe{sub 2} grown on Ta (110) at 680{degree}C, x-ray diffraction revealed a splitting of the (220) Bragg reflection into a strain free component structurally coherent with the template, and a component with 0.5{percent} biaxial tensile strain at room temperature. This strained component can be attributed to the difference in thermal expansion between the sapphire substrate and the TbFe{sub 2} film. Magnetic hysteresis measurements revealed that the axis of easy magnetization lies in the film plane for both (110) and (111) oriented samples. {copyright} {ital 1998 American Institute of Physics.}

Huth, M.; Flynn, C.P. [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois61801 (United States)] [Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois61801 (United States)

1998-06-01

87

Room temperature synthesis of hydrophilic Ln(3+)-doped KGdF4 (Ln = Ce, Eu, Tb, Dy) nanoparticles with controllable size: energy transfer, size-dependent and color-tunable luminescence properties.  

PubMed

In this paper, we demonstrate a simple, template-free, reproducible and one-step synthesis of hydrophilic KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) nanoparticles (NPs) via a solution-based route at room temperature. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the samples. The results indicate that the use of water-diethyleneglycol (DEG) solvent mixture as the reaction medium not only allows facile particle size control but also endows the as-prepared samples with good water-solubility. In particular, the mean size of NPs is monotonously reduced with the increase of DEG content, from 215 to 40 nm. The luminescence intensity and absolute quantum yields for KGdF(4): Ce(3+), Tb(3+) NPs increase remarkably with particle sizes ranging from 40 to 215 nm. Additionally, we systematically investigate the magnetic and luminescence properties of KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) NPs. They display paramagnetic and superparamagnetic properties with mass magnetic susceptibility values of 1.03 × 10(-4) emu g(-1)·Oe and 3.09 × 10(-3) emu g(-1)·Oe at 300 K and 2 K, respectively, and multicolor emissions due to the energy transfer (ET) process Ce(3+)? Gd(3+)? (Gd(3+))(n)? Ln(3+), in which Gd(3+) ions play an intermediate role in this process. Representatively, it is shown that the energy transfer from Ce(3+) to Tb(3+) occurs mainly via the dipole-quadrupole interaction by comparison of the theoretical calculation and experimental results. This kind of magnetic/luminescent dual-function materials may have promising applications in multiple biolabels and MR imaging. PMID:22539001

Yang, Dongmei; Li, Guogang; Kang, Xiaojiao; Cheng, Ziyong; Ma, Ping'an; Peng, Chong; Lian, Hongzhou; Li, Chunxia; Lin, Jun

2012-06-01

88

Magnetic phase transitions in RMnGe (R=Tb, Dy) compounds induced by high magnetic fields  

NASA Astrophysics Data System (ADS)

Magnetization isotherms for polycrystalline TbMnGe and DyMnGe compounds were measured at the temperature 4.2 K in pulsed magnetic fields (up to 360 kOe). The received isotherms demonstrate the appearance of metamagnetic transitions at low temperatures. Both compounds crystallize in the orthorhombic TiNiSi-type structure. It was found that the magnetic phase transitions with a destruction of ferrimagnetic spiral structure occur in the TbMnGe and DyMnGe compounds in high magnetic fields. An attempt was undertaken to explain the nature of these transitions using the results of the powder neutron diffraction and the qualitative estimation of the exchange interaction values on the basis of the molecular field theory.

Ivanova, T. I.; Nikitin, S. A.; Morozkin, A. V.; Gilewski, A.

2010-07-01

89

Pressure effect on the isostructural transition in RNiAl compounds (R=Tb and Gd)  

NASA Astrophysics Data System (ADS)

We have studied the presence of a gap of forbidden c/a values for the hexagonal crystal structure of TbNiAl and GdNiAl, appearing in the whole family of the RTAl compounds (R-rare earth, T-transition metal). TbNiAl and GdNiAl both exhibit a first-order structural transition at low temperatures around 100 K and 205 K, respectively. We have for the first time studied this structural step upon application of hydrostatic pressure on both compounds. An unusually rapid decrease of the critical temperature with pressure was found. The decrease is furthermore steeper for GdNiAl in which the transition appears at higher temperature at ambient pressure. Common property for both studied compounds is preference of the c/a ratio below the critical forbidden interval after application of pressure, due to weaker interplanar chemical bonding in the layered ZrNiAl-type of crystal structure.

Prchal, J.; Klicpera, M.; Doležal, P.; Kaštil, J.; Míšek, M.; Javorský, P.

2014-05-01

90

Performance of Gd-Tb Oxysulfide Ceramic Regenerator Material for G-M Cryocoolers  

NASA Astrophysics Data System (ADS)

Although many candidate materials have been developed and tested to increase a cooling capacity at 4 K, there are only few materials available for the 4 K regenerator materials. We have developed ceramic oxide magnetic regenerator materials, GAP = GdAlO3 and GOS = Gd2O2S. The cooling tests, using those new materials showed remarkable increases on the cooling performance at 4 K in comparison with conventional magnetic regenerator materials, HoCu2 or Er3Ni [1-6]. However, the materials are effective in the temperatures between 3 K and 5 K, but not above 6 K. Therefore, HoCu2 is still needed to provide the heat capacity from 6 K to 10 K. This paper will describe the properties of a new ceramics material, Gd-Tb oxysulfide = (GdxTb1-x)2O2S in substitution for HoCu2. This study is focused on providing a high heat capacity with a broad peak curve above 6 K. Not only the experimental results on heat capacity, but also those on the cooling test will be shown.

Numazawa, T.; Kamiya, K.; Satoh, T.; Nozawa, H.; Yanagitani, T.

2004-06-01

91

The Photophysical Properties of Quaternary Lanthanide (Eu 3+ , Tb 3+ , Sm 3+ , Dy 3+ ) Functional Molecular Complexes  

Microsoft Academic Search

Summary. In this paper, according to the molecular fragment principle, a series of twelve quaternary luminescent lanthanide complex molecular systems were assembled. Both elemental analysis and infrared spectroscopy allowed to determine the complexes formula: Ln( Nic) 3( L)·H 2O, where Ln=Sm, Eu, Tb, Dy; H Nic=pyridine-3-carboxylic acid; L=N,N-dimethylformamide ( DMF), N,N-dimethylacetamide ( DMA), pyrrolidone ( pyro). The photophysical properties of

Bing Yanand; Qiyou Xie

2004-01-01

92

Luminescent properties of single Dy3+ ions activated Ca3Gd7(PO4)(SiO4)5O2 phosphor  

NASA Astrophysics Data System (ADS)

Single Dy3+ ions activated Ca3Gd7(PO4)(SiO4)5O2: Dy3+ (CGPS: Dy3+) phosphors were successfully synthesized by solid-state reaction method. The X-ray diffraction results confirm that the as-prepared CGPS: Dy3+ samples are pure CGPS hexagonal phase. Moreover, the substitution of Dy3+ for Gd3+ in CGPS host leads to the major diffraction peaks moving towards larger angle due to a smaller ions radius of Dy3+ than Gd3+. Upon excitation of 275 nm and 349 nm ultra violet (UV) that are respectively attributed to 8S ? 6I transitions of Gd3+ and 6H15/2 ? 6P7/2 transition of Dy3+, the characteristic emission of Dy3+ ions such as 4F9/2 ? 6H15/2 (480 nm) and 4F9/2 ? 6H13/2 (572 nm) can be clearly observed. A high ratio of yellow emission to blue emission (Y/B) implies that Dy3+ ions prefer to occupy low-symmetry 6h (Cs) sites in CGPS matrix. Therefore, white light can be obtained from Dy3+ mono-doped CGPS: Dy3+ phosphor with CIE chromaticity coordinates of (x = 0.328, y = 0.343). By calculation, the mechanism of concentration quenching between Dy3+ ions is electric dipole-dipole interaction. In addition, the energy transfer (ET) from Gd3+ to Dy3+ can also be observed. These results suggest that CGPS: Dy3+ phosphors could be a promising candidate for UV-based white light illumination.

Tong, Miaohui; Liang, Yujun; Li, Guogang; Xia, Zhanggen; Zhang, Mengfei; Yang, Fan; Wang, Qiang

2014-07-01

93

Synthesis of Gd2O2S:Tb nanoparticles and optical characterization  

NASA Astrophysics Data System (ADS)

Terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) nanoparticles were synthesized by hydrothermal precipitation of urea. On the reaction, were analyzed variables as the temperature of solutions, the reaction time and the stirring velocities as main factors in the crystal growth. WAXD TEM and FTIR analysis were used to characterize the Crystallographic phase, morphology and chemical vibrations of the materials. Moreover, the photoluminescent properties were evaluated as response at the UV light, obtaining the main emission at 544 nm produced by 5D4 --> 7F5 transition of the Tb3+ ions. Besides, we found that the host lattice and doped-ions concentration is essential to obtain a strong visible photoluminescence evaluated experimentally.

Hernández-Adame, L.; Medellín-Rodríguez, F.; Méndez-Blas, A.; Vega-Acosta, R.; Palestino, G.

2013-03-01

94

Synthesis and Luminescence of BaWO4:Ln3+ (Ln = Eu, Tb, and Dy) Powders  

NASA Astrophysics Data System (ADS)

BaWO4:Ln3+ powders were synthesized by a solid-state reaction method. The BaWO4:Ln3+ samples were characterized by x-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), and luminescence spectroscopy. The XRD patterns reveal that the BaWO4:Ln3+ samples present pure tetragonal scheelite structure. The SEM observations demonstrate that the BaWO4:Ln3+ powders are irregular particles with size in the range of micrometers. The excitation spectra of the BaWO4:Ln3+ samples show the broad absorption band originating from charge transfer between oxygen ligands and the central tungstate ions inside WO{4/2-} groups in the metal tungstate. The emission spectra of the BaWO4:Ln3+ samples display the bands associated to the anion molecular complex (WO{4/2-}) and the f-f transitions of Ln3+. According to the emission spectra and the chromaticity coordinates (Commission internationale de l'éclairage, CIE), one can see that the BaWO4:Eu3+, BaWO4:Tb3+, and BaWO4:Dy3+ samples show emission in the red, green, and yellow region, respectively. The results show that the luminescence color can be altered by changing the Ln3+ doping in BaWO4 material.

Sun, Xiaoyu; Sun, Xiaodan; Li, Xingang; He, Jian; Wang, Binsheng

2014-05-01

95

M (Tm3+, Tb3+, Ho3+, Dy3+, Mn2+)-doped transparent fluorophosphate glasses for white light-emitting-diodes  

NASA Astrophysics Data System (ADS)

M-doped (M=Tm3+, Tb3+, Ho3+, Dy3+, Mn2+) transparent fluorophosphate glasses were prepared by a high temperature melting method. Excitation and emission spectra of the samples were investigated. Under near-ultraviolet excitation, the emission colors of the Tm3+-and Mn2+-doped samples are blue and red, respectively; the emission colors of the Tb3+-, Ho3+-, and Dy3+-doped samples are green; and the emission color of Tb3+/ Mn2+/Tm3+ tridoped fluorophosphate glass is white to the naked eye. Our research will be helpful in developing luminescent materials for white light-emitting-diodes.

Ming, Chengguo; Song, Feng; Qin, Yueting; Ren, Xiaobin; An, Liqun

2014-06-01

96

Specific heat studies of RCu 2Si 2 (R=Tb, Ho) and RCu 2Ge 2 (R=Gd, Tb) compounds  

NASA Astrophysics Data System (ADS)

Magnetic properties of RCu 2Si 2 (R=Tb, Ho) and RCu 2Ge 2 (R=Gd, Tb), crystallizing with the tetragonal ThCr 2Si 2-type crystal structure, were investigated by means of magnetic and calorimetric measurements. All compounds exhibit antiferromagnetic ordering below TN equal to 11.2 K for TbCu 2Si 2, 5.3 K for HoCu 2Si 2, 12.0 K for GdCu 2Ge 2 and 12.5 K for TbCu 2Ge 2. At temperatures of Tt=8.5 K for TbCu 2Si 2 and 9.8 K for TbCu 2Ge 2 additional phase transitions were observed. Apart from the investigation on magnetic phase transitions, magnetic contributions to the specific heat were analyzed in terms of Schottky effect. The corresponding crystal electric field (CEF) level splitting schemes were calculated. Moreover, the phononic characteristic temperatures were estimated.

Szytu?a, A.; Ba?anda, M.; Gondek, ?.; Przewo?nik, J.; Nenkov, K.; Duraj, R.

2012-01-01

97

Family of carboxylate- and nitrate-diphenoxo triply bridged dinuclear Ni(II)Ln(III) complexes (Ln = Eu, Gd, Tb, Ho, Er, Y): synthesis, experimental and theoretical magneto-structural studies, and single-molecule magnet behavior.  

PubMed

Seven acetate-diphenoxo triply bridged M(II)-Ln(III) complexes (M(II) = Ni(II) and Ln(III) = Gd, Tb, Ho, Er, and Y; M(II) = Zn(II) and Ln(III) = Ho(III) and Er(III)) of formula [M(?-L)(?-OAc)Ln(NO(3))(2)], one nitrate-diphenoxo triply bridged Ni(II)-Tb(III) complex, [Ni(?-L)(?-NO(3))Tb(NO(3))(2)]·2CH(3)OH, and two diphenoxo doubly bridged Ni(II)-Ln(III) complexes (Ln(III) = Eu, Gd) of formula [Ni(H(2)O)(?-L)Ln(NO(3))(3)]·2CH(3)OH have been prepared in one pot reaction from the compartmental ligand N,N',N"-trimethyl-N,N"-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H(2)L). Moreover, Ni(II)-Ln(III) complexes bearing benzoate or 9-anthracenecarboxylate bridging groups of formula [Ni(?-L)(?-BzO)Dy(NO(3))(2)] and [Ni(?-L)(?-9-An)Dy(9-An)(NO(3))(2)]·3CH(3)CN have also been successfully synthesized. In acetate-diphenoxo triply bridged complexes, the acetate bridging group forces the structure to be folded with an average hinge angle in the M(?-O(2))Ln bridging fragment of ~22°, whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly bridged complexes exhibit more planar structures with hinge angles of ~13° and ~2°, respectively. All Ni(II)-Ln(III) complexes exhibit ferromagnetic interactions between Ni(II) and Ln(III) ions and, in the case of the Gd(III) complexes, the J(NiGd) coupling increases weakly but significantly with the planarity of the M-(O)(2)-Gd bridging fragment and with the increase of the Ni-O-Gd angle. Density functional theory (DFT) theoretical calculations on the Ni(II)Gd(III) complexes and model compounds support these magneto-structural correlations as well as the experimental J(NiGd) values, which were found to be ~1.38 and ~2.1 cm(-1) for the folded [Ni(?-L)(?-OAc)Gd(NO(3))(2)] and planar [Ni(H(2)O)(?-L)Gd(NO(3))(3)]·2CH(3)OH complexes, respectively. The Ni(II)Dy(III) complexes exhibit slow relaxation of the magnetization with ?/k(B) energy barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for [Ni(?-L)(?-BzO)Dy(NO(3))(2)] and [Ni(?-L)(?-9-An)Dy(9-An)(NO(3))(2)]·3CH(3)CN, respectively. PMID:22564020

Colacio, Enrique; Ruiz, José; Mota, Antonio J; Palacios, María A; Cremades, Eduard; Ruiz, Eliseo; White, Fraser J; Brechin, Euan K

2012-05-21

98

Visible quantum cutting through downconversion in green-emitting K2GdF5:Tb3+ phosphors  

NASA Astrophysics Data System (ADS)

Visible quantum cutting under excitations at 212 and 172 nm in a green-emitting phosphor K2GdF5:Tb3+ (11%) via a downconversion mechanism is investigated. The authors measured the vacuum ultraviolet (VUV) excitation and emission spectra and proposed mechanisms to rationalize the quantum-cutting effect. One short-UV or one VUV photon absorbed by Tb3+ is split into multiple visible photons emitted by Tb3+ through cross relaxation and direct energy transfer. Calculations indicate an optimal quantum efficiency as great as 189% for this phosphor.

Lee, Te-Ju; Luo, Li-Yang; Diau, Eric Wei-Guang; Chen, Teng-Ming; Cheng, Bing-Ming; Tung, Chien-Yueh

2006-09-01

99

Rare-earth-gallium-iron glasses. I. Magnetic ordering and hysteresis in alloys based on Gd, Tb, and Er  

Microsoft Academic Search

Results of magnetic measurements are presented on the new metallic glass systems (R80Ga20)100-xFex and (R80Ga20)90B10, where R denotes the heavy rare earths Gd, Tb, and Er, for x=10, 20, and 30, respectively. High-field magnetization (to 80 kOe) and ac and dc susceptibility measurements were made from 1.4 to 300 K. The Gd-Fe glasses are simple ferrimagnets with opposing Gd and

S. G. Cornelison; D. J. Sellmyer

1984-01-01

100

Multicolor tunable luminescence and paramagnetic properties of NaGdF4:Tb(3+)/Sm(3+) multifunctional nanomaterials.  

PubMed

Tb(3+) and/or Sm(3+) doped NaGdF4 luminescent nanomaterials have been successfully synthesized by an SDS-assisted one-step hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray energy dispersive spectrometer (EDS), photoluminescence (PL) spectra and a vibrating sample magnetometer (VSM). The results show that the synthesized samples are all pure ?-NaGdF4. The as-prepared Tb(3+) or Sm(3+) doped samples show strong green and yellow emission, originating from the allowed (5)D3?(7)FJ (J = 5, 4, 3, 2) and (5)D4?(7)FJ (J = 6, 5, 4, 3) transitions of the Tb(3+) ions and the (4)G5/2?(6)H5/2, (6)H7/2, (6)H9/2 transition of the Sm(3+) ions. Based on the excitation wavelengths, multiple (yellowish green, yellow, white) emissions are obtained by Sm(3+) ion co-activated NaGdF4:Tb(3+) phosphors. Moreover, an energy transfer from Tb(3+) to Sm(3+) is observed, which is justified through the luminescence spectra and the fluorescence decay curves. Furthermore, the resonance-type energy transfer from Tb(3+) to Sm(3+) is demonstrated to occur via the dipole-dipole mechanism. In addition, the obtained samples also exhibit paramagnetic properties at room temperature. It is obvious that these multifunctional Tb(3+), Sm(3+) co-doped ?-NaGdF4 nanomaterials, with tunable multicolors and intrinsic paramagnetic properties, may have potential application in the fields of full-color displays, biological labels, bioseparation and magnetic resonance imaging. PMID:24882267

Guan, Hongxia; Liu, Guixia; Wang, Jinxian; Dong, Xiangting; Yu, Wensheng

2014-06-24

101

Optimization of magnetostriction, coercive field and magnetic transition temperature in nanocrystalline TbDyFe+Zr/Nb multilayers  

NASA Astrophysics Data System (ADS)

The magnetostrictive properties of TbDyFe/Nb multilayers containing 2 at% Zr as an additive have been investigated after different annealing treatments for the (Terfenol-D near) composition of [Tb 0.27Dy 0.73] 0.27Fe 0.73. The multilayer structure has been produced by ion-beam sputtering on a sapphire substrate. After 10 min annealing of the multilayers at temperatures from 873 to 973 K the parallel magnetostriction increased from ??(0.8 T)=265 to 520 ppm accompanied by an increase of the magnetic phase transition temperature from TC=333 to 592 K, while the increase of the coercive fields from ?0Hc<5 to 75 mT lies distinctively below 100 mT. These properties are suitable for applications of giant magnetostrictive films in microsystems where values of ?>500 ppm, TC>500 K and ?0Hc?100 mT are required. Establishing a nanocrystalline microstructure with grain sizes d< dc˜15 nm ( dc is the critical grain diameter) smaller than the exchange length is essential for the combination of intrinsic magnetic properties (increased ? and TC) with soft magnetic properties ( ?0Hc of a few mT) as typical for an amorphous microstructure. It is shown by microstructural XRD and TEM investigations that such a nanocrystalline microstructure can be realized by a suitable heat treatment of TbDyFe+Zr/Nb multilayers. Introducing Nb spacer layers effectively reduces grain growth for certain annealing temperatures while Zr is assumed to play a dominant role in forming nucleation centers of nanograins. In combination, both effects can be well used to optimize the magnetostrictive layer properties.

Fischer, S. F.; Kelsch, M.; Kronmüller, H.

1999-06-01

102

Size-dependent magnetic ordering and spin dynamics in DyPO4 and GdPO4 nanoparticles  

NASA Astrophysics Data System (ADS)

Low-temperature magnetic susceptibility and heat-capacity measurements on nanoparticles (d? 2.6 nm) of the antiferromagnetic compounds DyPO4 (TN=3.4 K) and GdPO4 (TN=0.77 K) provide clear demonstrations of finite-size effects, which limit the divergence of the magnetic correlation lengths, thereby suppressing the bulk long-range magnetic ordering transitions. Instead, the incomplete antiferromagnetic order inside the particles leads to the formation of net magnetic moments on the particles. For the nanoparticles of Ising-type DyPO4 superparamagnetic blocking is found in the ac susceptibility at ?1 K, those of the XY-type GdPO4 analog show a dipolar spin-glass transition at ?0.2 K. Monte Carlo simulations for the magnetic heat capacities of both bulk and nanoparticle samples are in agreement with the experimental data. Strong size effects are also apparent in the Dy3+ and Gd3+ spin dynamics, which were studied by zero-field muon spin rotation (?SR) and high-field 31P-nuclear magnetic resonance (31P-NMR) nuclear relaxation measurements. The freezing transitions observed in the ac susceptibility of the nanoparticles also appear as peaks in the temperature dependence of the zero-field ?SR rates, but at slightly higher temperatures, as to be expected from the higher frequency of the muon probe. For both bulk and nanoparticles of GdPO4, the muon and 31P-NMR rates are for T?5 K dominated by exchange-narrowed hyperfine broadening arising from the electron spin-spin interactions inside the particles. The dipolar hyperfine interactions acting on the muons and the 31P are, however, much reduced in the nanoparticles. For the DyPO4 analogs the high-temperature rates appear to be fully determined by electron spin-lattice relaxation processes.

Evangelisti, Marco; Sorop, Tibi G.; Bakharev, Oleg N.; Visser, Dirk; Hillier, Adrian D.; Alonso, Juan J.; Haase, Markus; Boatner, Lynn A.; Jos de Jongh, L.

2011-09-01

103

Unique nanoscale {Cu(II)36Ln(III)24} (Ln = Dy and Gd) metallo-rings.  

PubMed

Two unprecedented 3d-4f hexagonal metallo-rings {Ln(24)Cu(36)} (Ln = Dy and Gd) with a diagonal dimension of about 4.6 nm were facilely synthesized by self-assembly of Cu(II), Ln(III) nitrates and benzoate in the presence of triethylamine. Magnetic studies show slow relaxation behaviour for the dysprosium analogue and a large magnetocaloric effect (MCE) for the gadolinium analogue. PMID:22428160

Leng, Ji-Dong; Liu, Jun-Liang; Tong, Ming-Liang

2012-05-28

104

Spin structure and magnetic frustration in multiferroic RMn{sub 2}O{sub 5} (R=Tb,Ho,Dy)  

SciTech Connect

We have studied the crystal and magnetic structures of the magnetoelectric materials RMn{sub 2}O{sub 5} (R=Tb,Ho,Dy) using neutron diffraction as a function of temperature. All three materials display incommensurate antiferromagnetic ordering below 40 K, becoming commensurate on further cooling. For R=Tb,Ho, a commensurate-incommensurate transition takes place at low temperatures. The commensurate magnetic structures have been solved and are discussed in terms of competing exchange interactions. The spin configuration within the ab plane is essentially the same for each system, and the radius of R determines the sign of the magnetic exchange between adjacent planes. The inherent magnetic frustration in these materials is lifted by a small lattice distortion, primarily involving shifts of the Mn{sup 3+} cations and giving rise to a canted antiferroelectric phase.

Blake, G.R. [ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Chapon, L.C. [ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Radaelli, P.G. [ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Park, S.; Hur, N.; Cheong, S-W. [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Rodriguez-Carvajal, J. [Laboratoire Leon Brillouin (CEA-CNRS), CEA/Saclay, 91191 Gif-sur-Yvette Cedex (France)

2005-06-01

105

Characteristic and synthesis mechanism of Gd 2O 2S:Tb phosphors prepared by cold isostatic press pretreatment  

NASA Astrophysics Data System (ADS)

Characteristic and synthesis mechanism of Gd 2O 2S:Tb X-ray phosphors prepared by cold isostatic press (CIP) pretreatment have been investigated by photoluminescence (PL) spectra, luminescence spectra under X-ray excitation (XL), X-ray diffraction (XRD) and scanning electric microscope (SEM). It is shown that the pre-pressed technology reduces the sintering temperature with about 100 °C. It also decreases the particle size, influences the particle size distribution and morphology, and enhances the luminescence efficiencies of PL and XL of Gd 2O 2S:Tb phosphors greatly. CIP technique also promotes the formation of Gd 2O 2S by breaking the starting Gd 2O 3 particles down to smaller particles as well as retarding the sulphur volatilization at low temperature. The nucleation site density in CIP process is higher than that of the normal technology; the cumulative contribution of the possible increase of the nucleation site numbers and the closer packing of the green body, results in finer and more uniform Gd 2O 2S:Tb particles.

Luo, Xi-xian; Cao, Wang-he; Tian, Ying

2007-10-01

106

Hydrothermal synthesis and luminescence properties of uniform BaMoO4:Ln3+ (Ln = Eu, Tb, Dy, and Sm) microspheres  

NASA Astrophysics Data System (ADS)

Uniform and well-dispersed BaMoO4:Ln3+ (Ln = Eu, Tb, Dy, and Sm) microspheres have been successfully synthesized through a facile hydrothermal approach by using trisodium citrate as surfactant. XRD results demonstrate that Ln3+-doped samples can be well indexed to the pure tetragonal scheelite-type BaMoO4, indicating that the Eu3+, Tb3+, Dy3+, and Sm3+ have been effectively doped into the BaMoO4 host lattices. SEM and TEM images indicate that the as-obtained BaMoO4 microspheres consist of tiny packed nanocrystallites. The as-synthesized BaMoO4:Ln3+ (Ln = Eu, Tb, Dy, and Sm) phosphors show strong light emissions with different colors coming from different activator ions under ultraviolet light excitation, which may find potential applications in light phosphor powders and advanced flat panel display devices.

Jia, Guang; Huang, Cuimiao; Li, Lanfen; Wang, Chunzheng; Song, Xingbang; Song, Le; Li, Zheng; Ding, Shiwen

2012-12-01

107

Structural frustration and occupational disorder: the rare earth metal polysulfides Tb8S(14.8), Dy8S(14.9), Ho8S(14.9), and Y8S(14.8).  

PubMed

Dark red crystals of Y?S(14.8), Tb?S(14.8), Dy?S(14.9), and Ho?S(14.9) have been obtained following different reaction routes. The isostructural title compounds adopt the Gd?Se?? type, a 24-fold superstructure of the ZrSSi-type and can be described in space group A112 (non standard setting of C121, no. 5) with lattice parameter of a = 11.505(1) Å, b = 15.385(1) Å, c = 15.726(1) Å, and ? = 90.21(2)° for Y?S(15-x); a = 11.660(1) Å, b = 15.468(2) Å, c = 15.844(2) Å, and ? = 90.19(2)° for Tb?S(15-x); a = 11.584(1) Å, b = 15.340(2) Å, c = 15.789(2) Å, and ? = 90.34(2)° for Dy?S(15-x); and a = 11.538(1) Å, b = 15.288(2) Å, c = 15.740(2) Å, and ? = 90.23(1)° for Ho?S(15-x), respectively. The structure consists of an alternating stacking of puckered [RES] (RE, rare-earth metals) double slabs and planar sulfur layers along [001]. The planar sulfur layers have a complex arrangement of S?²? dinuclear dianions, isolated S²? ions, and vacancies. All compounds contain trivalent rare-earth metal ions, for Tb?S(15-x) and Dy?S(15-x) antiferromagnetic order was found at T(N) = 5.4(2) K and 3.8(1) K, respectively. Short wavelength cutoff optical band gaps of 1.6 to 1.7 eV were determined. PMID:22136291

Doert, Thomas; Graf, Christian; Vasilyeva, Inga G; Schnelle, Walter

2012-01-01

108

NMR evidence of a long exchange lifetime for the coordinated water in Ln(III)-bis(methyl amide)-DTPA complexes (Ln = Gd, Dy)  

SciTech Connect

The water proton longitudinal relaxation rate for Gd-BMA-DTPA was studied at various temperatures and under varied magnetic fields. It was found that a correlation exists between the residence lifetime {tau}{sub M} of the coordinated water molecule in the coordination site on the metal chelate. The Gd(III) result was confirmed by related studies for Dy(III).

Aime, S.; Botta, M.; Fasano, M. [Universita di Torino (Italy)] [and others

1994-10-12

109

Efficient three-photon luminescence with strong polarization dependence from a scintillating silicate glass co-doped with Gd3+ and Tb3+.  

PubMed

Efficient three-photon luminescence (3PL) from a scintillating silicate glass co-doped with Gd(3+) and Tb(3+) was generated by using a focused femtosecond laser beam at 800 nm. Four emission bands centered at 496, 541, 583, and 620 nm were identified as the electronic transitions between the energy levels of Tb(3+) followed by three-photon absorption (3PA) in Gd(3+) and Tb(3+) and the resonant energy transfer from Gd(3+) to Tb(3+). More interestingly, a strong polarization dependence of the 3PL was observed and it is ascribed to the polarization dependent 3PA in Gd(3+) and Tb(3+) and/or the angular distribution of photogenerated electrons in the glass. PMID:23482170

Li, Guang-Can; Zhang, Cheng-Yun; Deng, Hai-Dong; Liu, Guang-Yin; Lan, Sheng; Qian, Qi-; Yang, Zhong-Min; Gopal, Achanta Venu

2013-03-11

110

Crystal structure of the R 7Cu 3Te 12 (R = Tb, Dy, Ho, Er and Tm) compounds  

Microsoft Academic Search

The crystal structures of the R7Cu3Te12 (R=Tb, Dy, Ho, Er and Tm) compounds (space group R3¯m, Pearson symbol hR27-5) were determined by means of X-ray single crystal diffraction: a=0.43020(6)nm, c=4.1720(8)nm, RI=0.0498 (Ho7Cu3Te12) and X-ray powder diffraction: a=0.43279(3)nm, c=4.1896(3)nm, RI=0.0932 (Tb7Cu3Te12); a=0.43114(5)nm, c=4.1779(8)nm, RI=0.0891 (Dy7Cu3Te12); a=0.42802(2)nm, c=4.1575(2)nm, RI=0.0849 (Er7Cu3Te12); a=0.42709(3)nm, c=4.1540(3)nm, RI=0.0858 (Tm7Cu3Te12). The close packed Te layers in …hhcc… stacking

L. D. Gulay; I. D. Olekseyuk; A. Pietraszko

2005-01-01

111

Tuning of crystal phase and luminescence properties of Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+} phosphors  

SciTech Connect

Graphical abstract: The optical properties of Dy{sup 3+} were found to be sensitive to the crystal phase of the as-synthesized Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+} phosphors, especially the distinct features of the charge transfer (CT) transition. The mechanism involved was discussed in detail based on the experiments and theoretic calculations. Highlights: ? The crystal phase of Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+} was tuned by changing the pH value of the solution in hydrothermal system. ? The optical properties of Dy{sup 3+} were found to be sensitive to the crystal phase of Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+}. ? The mechanisms of different crystal phases affected on the luminescence properties of Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+} were discussed. -- Abstract: The orthorhombic and monoclinic Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+} were successfully synthesized by a hydrothermal process with a subsequent annealing treatment at 800 °C for 4 h. The crystal phase of Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+} was controlled as a function of the pH value of the solution. The crystallization and microstructures of the samples were characterized by Powder X-ray diffraction (XRD) and scanning electron micrograph (SEM). Furthermore, the optical properties were investigated by the diffuse reflection, excitation and emission spectra. The mechanisms of different crystal phases affected on the luminescence properties of Gd{sub 2}(MoO{sub 4}){sub 3}:Dy{sup 3+} were discussed. The electric dipole–dipole interaction between Dy{sup 3+} ions was identified as the main mechanism for the concentration quenching of the two structures. Finally, the chromatic natures of all the samples were analyzed in detail. The results indicate that the orthorhombic phosphor Gd{sub 1.84}(MoO{sub 4}){sub 3}:Dy{sub 0.16}{sup 3+} can be considered as a suitable candidate for white light emitting diodes (W-LEDs).

Xia, Wanwan; Wang, Xiaojie [State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012 (China) [State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012 (China); Key Lab of Coherent Light, Atomic and Molecular Spectroscopy, Ministry of Education, Changchun 130012 (China); Fu, Zuoling, E-mail: zlfu@jlu.edu.cn [State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012 (China) [State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012 (China); Key Lab of Coherent Light, Atomic and Molecular Spectroscopy, Ministry of Education, Changchun 130012 (China); Zhou, Shihong; Zhang, Siyuan [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)] [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Jeong, Jung Hyun, E-mail: jhjeong@pknu.ac.kr [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of)

2012-09-15

112

Luminescence of Tb3+ and Gd3+ ions in sonolysis under the conditions of a single bubble moving in aqueous solutions of TbCl3 and GdCl3  

NASA Astrophysics Data System (ADS)

Luminescence bands of Tb3+ and Gd3+ ions are detected during sonolysis in the regime of a moving single bubble in aqueous solutions of TbCl3 and GdCl3 salts with concentration 1-2 mol/L. Saturation with argon, low temperatures of solutions (-5°C), and a high concentration of salts are the factors facilitating sonoluminescence of the metal. Comparison with the characteristics of sonoluminescence of lanthanide ions studied earlier in the regimes of multibubble and single-bubble sonolysis with a stationary bubble shows that the electron excitation of metal ions in the given case is associated with translational displacements of the bubble. Our results confirm the validity of the sonochemical model of microdroplet injection, which explains the penetration of nonvolatile salts into cavitation bubbles as a result of their deformation during intense movements.

Sharipov, G. L.; Abdrakhmanov, A. M.; Gareev, B. M.

2013-02-01

113

Luminescence, energy transfer and color perception studies of Na3Gd(PO4)2:Dy3+:Tm3+ phosphors  

NASA Astrophysics Data System (ADS)

The white-light-emitting Na3Gd(PO4)2:Dy3+:Tm3+ phosphors were prepared by high temperature solid-state reaction technique. X-ray diffraction, luminescence excitation, emission, and decay measurements were performed. Upon Gd3+8S7/2 ? 6IJ (275 nm) excitation, the phosphors emit intense blue and yellow luminescence originating from the Dy3+4F9/2 ? 6H15/2 and Dy3+4F9/2 ? 6H13/2 transitions together with the Gd3+6P7/2 ? 8S7/2 transition at 313 nm. The excitation of Tm3+ ions by 352 nm radiation results also in efficient yellow and blue luminescence. The luminescence enhancement of Dy3+ in the presence of Tm3+ is discussed. The energy transfer process of the Tm3+-Dy3+ system is also explored. This study includes the color perception analysis of synthesized phosphors. The pure white-light is observed with Na3Gd(PO4)2:1%Dy3+:1%Tm3+ and is a promising material for white-lighting applications.

Jamalaiah, B. C.; Jo, Misun; Zehan, Jiang; Shim, Jae Jeong; Kim, Sun Il; Chung, Wan-Young; Seo, Hyo Jin

2014-08-01

114

A Single Sensisitizer for the Excitation of Visible and NIR Lanthanide Emitters (Sm, Eu, Tb, Dy and Ho) in Water with High Quantum Yields  

PubMed Central

The versatile octadentate TIAM ligand forms lanthanide (Sm, Eu, Tb, Dy, Ho) complexes with high quantum yields in water. This ligand is an efficient sensitizer, and also shields the metal center from solvent quenching, as shown by an X-ray diffraction study of the Ho complex.

Law, Ga-Lai; Pham, Tiffany A.; Xu, Jide; Raymond, Kenneth N.

2012-01-01

115

Photoluminescence properties of aeschynite-type LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) down-converting phosphors.  

PubMed

In this study, a series of LaNbTiO6:RE(3+) (RE = Tb, Dy, Ho) down-converting phosphors were synthesized using a modified sol-gel combustion method, and their photoluminescence (PL) properties were investigated as a function of activator concentration and annealing temperature. The resultant particles were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, UV/Vis diffuse reflectance spectroscopy and PL spectra. The highly crystalline LaNbTiO6:RE(3+) (RE = Tb, Dy, Ho) phosphors with an average size of 200-300 nm obtained at 1100°C have an orthorhombic aeschynite-type structure and exhibit the highest luminescent intensity in our study range. The emission spectra of LaNbTiO6:RE(3+) (RE = Tb, Dy, Ho) phosphors under excitations at UV/blue sources are mainly composed of characteristic peaks arising from the f-f transitions of RE(3+), including 489 nm ((5) D4 ? (7) F6) and 545 nm ((5) D4 ? (7) F5) for Tb(3+), 476 and 482 nm ((4) F9/2 ? (6) H15/2) and 571 nm ((4) F9/2 ? (6) H13/2) for Dy(3+), and 545 nm ((5) F4 +?(5) S2 ? (5) I8) for Ho(3+), respectively. The luminescent mechanisms were further investigated. It can be expected that these phosphors are of intense interest and potential importance for many optical applications. PMID:23868821

Ma, Qian; Lu, Mengkai; Yang, Ping; Zhang, Aiyu; Cao, Yongqiang

2014-06-01

116

White light emission from spin coated Gd2O3:Dy nano phosphors synthesized using polyol technique.  

PubMed

Water dispersible Gd2O3:Dy3+ (2%) nanophosphors were synthesized through a facile polyol process and characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Dynamic Light Scattering (DLS) and photoluminescence (PL) spectrophotometry. The results of XRD, TEM and DLS show that resultant nanoparticles are single phasic and have spherical shape with 17 to 22% dispersibility. An efficient energy transfer was observed from host to the dopant ions. Characteristic blue and yellow emissions from Dy3+ ions were observed. The CIE coordinates of the nanophosphor lie in the white light region of the chromaticity diagram. Spin coating of the nanophosphor was done on quartz substrate. Bright white luminescence of this film was observed under ultraviolet light with lamda exc = 310 nm. PMID:21121321

Bedekar, Vinila; Dutta, Dimple P; Tyagi, A K

2010-12-01

117

Flexible Gd2O2S:Tb scintillators pixelated with polyethylene microstructures for digital x-ray image sensors  

Microsoft Academic Search

Flexible scintillators for digital x-ray image sensors were designed, fabricated and characterized. In these scintillaotrs, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) scintillator pixels were embedded into a polyethylene (PE) substrate. To evaluate the difference in the spatial resolution according to the pixel size, we designed three scintillators with pixels of different pitch sizes: 50 µm pitch size (P50), 100 µm pitch size

Im Deok Jung; Min Kook Cho; Sang Min Lee; Kong Myeong Bae; Phill Gu Jung; Chi Hoon Lee; Jae Min Lee; Seungman Yun; Ho Kyung Kim; Seong Sik Kim; Jong Soo Ko

2009-01-01

118

Fabrication, photoluminescence, and potential application in white light emitting diode of Dy3+-Tm3+ doped transparent glass ceramics containing GdSr2F7 nanocrystals  

NASA Astrophysics Data System (ADS)

Dy3+-Tm3+ doped transparent glass ceramics containing GdSr2F7 nanocrystals were fabricated successfully by a melt-quenching method and subsequent heating. X-ray diffraction and transmission electron microscopy analyses show that tetragonal GdSr2F7 nanocrystals are homogeneously precipitated among the borosilicate glass matrix. If excited with 354 nm UV light, the photoluminescence spectrum of Dy3+ single-doped transparent glass ceramics shows white-light emission. With doping of Tm3+, the overall emission color of Tm3+-Dy3+ co-doped transparent glass ceramics can be tuned from white to blue through energy transfer between Dy3+ and Tm3+. CIE chromaticity and color temperature measurements show that the resulting TGCS may be a candidate as a white LED material pumped by a UV InGaN chip.

Wang, X. F.; Yan, X. H.; Bu, Y. Y.; Zhen, J.; Xuan, Y.

2013-08-01

119

Anisotropic magnetization and resistivity of single crystalline RNi1-xBi2 ± y (R = La-Nd, Sm, Gd-Dy)  

SciTech Connect

We present a detailed study of RNi1?xBi2±y (R = La–Nd, Sm, Gd–Dy) single crystals by measurements of stoichiometry and temperature dependent magnetic susceptibility, magnetization, and electrical resistivity. This series forms with partial Ni occupancy, 0.72 ? (1?x) ? 0.84, as well as a variable Bi occupancy, 1.76 ? (2±y) ? 2.14. For R = Ce–Nd, Gd–Dy, the RNi1?xBi2±y compounds show local-moment like behavior and order antiferromagnetically at low temperatures. Determination of anisotropies as well as antiferromagnetic ordering temperatures for RNi1?xBi2±y (R = Ce–Nd, Sm, Gd–Dy) have been made. Crystalline samples from this family exhibit minority, second phase superconductivity at low temperatures, which can be associated with Ni–Bi and Bi contamination. No evidence of bulk superconductivity has been observed.

Lin, Xiao [Iowa State University; Straszheum, Warren E. [Ames Laboratory; Budko, Sergey L. [Ames Laboratory; Canfield, Paul C. [Ames Laboratory

2012-11-29

120

Resistivity and anisotropic magnetization of single crystalline RNi1-xBi2±y (R = La--Nd, Sm, Gd--Dy)  

NASA Astrophysics Data System (ADS)

We present a detailed study of RNi1-xBi2±y (R = La--Nd, Sm, Gd--Dy) single crystals by measurements of temperature dependent magnetic susceptibility, magnetization, and electrical resistivity. The isostructural compounds RTBi2 and RTSb2 are known to have widths of formation, except for T = Ag. The RNi1-xBi2±y series forms with partial Ni occupancy as well as a variable Bi occupancy. For R = Ce--Nd, Gd--Dy, the RNi1-xBi2±y compounds show local-moment-like behavior and order antiferromagnetically at low temperatures. Determination of anisotropies as well as antiferromagnetic ordering temperatures for RNi1-xBi2±y (R = Ce--Nd, Sm, Gd--Dy) have been made. Although crystalline samples from this family exhibit minority, second phase, superconductivity at low temperatures associated with Ni-Bi and Bi contamination, no evidence of bulk superconductivity has been observed.

Lin, X.; Straszheim, Warren; Bud'Ko, Sergey; Canfield, Paul

2013-03-01

121

Synthesis, P-T phase diagram, and Tc of R2Ba4Cu7O15 (R= Dy,Y, DyY, GdY )  

NASA Astrophysics Data System (ADS)

The oxygen pressure - temperature phase diagrams of R2Ba4Cu15 (R=Dy,Y, Er, DyY, GdY, and EuY) superconductors have been investigated in the temperature range between 850 and 1025^oC and the pressure range between 1,and 50,tm.O2. The relative fraction of the phases: 123, 124, and 247, was determined by studying the intensity of the xray diffraction peaks of each phase. The condition at which the phase pure 247 exists was determined to be P=10 ;atm and T=1025^o C. Under these conditions samples with larger size R = LaY, NdY, SmY, and Eu fail to form pure 247 phase. Annealing at P=200 ; atm. O2 and 400 ^o C was used to increase oxygen content of the as-synthesized materials and to induce superconductivity. The highest transition temperatures of 70 K were observed for R=Y compositions.

Sabok-Sayr, Seyed Ahmad; Dabrowski, Bogdan; Kolesnik, Stanislaw

2012-02-01

122

Ionic Transport Properties in Nanocrystalline Ce0.8A0.2O2-? (with A = Eu, Gd, Dy, and Ho) Materials  

PubMed Central

The ionic transport properties of nanocrystalline 20 mol% Eu, Gd, Dy, and Ho doped cerias, with average grain size of around 14 nm were studied by correlating electrical, dielectric properties, and various dynamic parameters. Gd-doped nanocrystalline ceria shows higher value of conductivity (i.e., 1.8 × 10?4 S cm?1 at 550°C) and a lower value of association energy of oxygen vacancies with trivalent dopants Gd3+ (i.e., 0.1 eV), compared to others. Mainly the lattice parameters and dielectric constants (??) are found to control the association energy of oxygen vacancies in these nanomaterials, which in turn resulted in the presence of grain and grain boundary conductivity in Gd- and Eu-doped cerias and only significant grain interior conductivity in Dy- and Ho-doped cerias.

2010-01-01

123

Crystalline structure, magnetic response and electronic properties of RE2MgTiO6 (RE = Dy, Gd) double perovskites  

NASA Astrophysics Data System (ADS)

The synthesis, crystal structure, morphology, magnetic properties and electronic calculations of two members of the family of double perovskite materials RE2MgTiO6 (RE = Dy, Gd) are described. X-ray powder diffraction measurements show that these materials crystallize in monoclinic perovskite structures with space group P21/n (#14). Unit cell parameters, atomic positions, tilt angle, inter-atomic distances and site occupancies were calculated by Rietveld through the GSAS code reveal. Lattice parameters for Dy2MgTiO6 were a = 5.3624(4) Å, b = 5.5973(2) Å and c = 7.6794(2) Å, and for Gd2MgTiO6a = 5.3143(5) Å, b = 5.5826(2) Å and c = 7.6324(2) Å. Samples morphology analyzed by scanning electron microscopy reveal strongly coupled grains with mean size 3 ?m. Paramagnetic behavior is evidenced by magnetic susceptibility measurements and Curie-Weiss fitting supplies effective magnetic moments which lay 98% in agreement with the theoretical predictions for the isolated rare earth elements for each compound.

Landínez Téllez, D. A.; Martínez Buitrago, D.; Cardona C, R.; Barrera, E. W.; Roa-Rojas, J.

2014-06-01

124

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)

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.

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

2014-05-01

125

Separating Ag, B, Cd, Dy, Eu, and Sm in a Gd matrix using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester extraction chromatography for ICP-AES analysis.  

PubMed

The separation procedure for Ag, B, Cd, Dy, Eu and Sm as impurities in Gd matrix using ICP-AES technique with an extraction chromatographic column has been developed. The spectral interference of the Gd matrix on the elements was eliminated using a chromatography technique with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as the mobile phase and XAD-16 resin as the stationary phase. Ag(+), B(4)O(7)(2-), and Cd(2+) were eluted with 0.1M HNO(3), while rare earth ions were not. The best eluent for separating Eu and Sm in the Gd matrix was 0.3M HNO(3). The limit of quantitation for these elements was 0.6-3.0ng mL(-1). The recovery of Ag, B, and Cd was 90-104% using 0.1M HNO(3) as the eluent, while that of Eu, Gd, and Sm ranged from 100 to 102% with 0.3M HNO(3). Dy was recovered quantitatively with 4M HNO(3). The relative standard deviation of the methods for a set of three replicates was between 1.0 and 15.4% for the synthetic and standard Gd solutions. The proposed separation procedure was used to measure Ag, B, Cd, Dy, Eu, and Sm in a standard Gd solution. PMID:19071357

Choi, Kwang-Soon; Lee, Chang-Heon; Kim, Jong-Goo; Kim, Won-Ho; Kang, Jun-Gill

2007-02-15

126

Two Isostructural 3D Lanthanide Coordination Networks (Ln = Gd(3+), Dy(3+)) with Squashed Cuboid-Type Nanoscopic Cages Showing Significant Cryogenic Magnetic Refrigeration and Slow Magnetic Relaxation.  

PubMed

Two isostructural lanthanide-based 3D coordination networks [Ln = Gd(3+) (1), Dy(3+)(2)] with densely packed distorted cuboid nanoscopic cages are reported for the first time. Magnetic characterization reveals that complex 1 shows a significant cryogenic magnetocaloric effect (-?Sm = 44 J kg(-1) K(-1)), whereas 2 shows slow relaxation of magnetization. PMID:24689862

Biswas, Soumava; Jena, Himanshu Sekhar; Adhikary, Amit; Konar, Sanjit

2014-04-21

127

Photoluminescence properties of rare earths (Eu 3+, Tb 3+, Dy 3+ and Tm 3+) activated NaInW 2O 8 wolframite host lattice  

NASA Astrophysics Data System (ADS)

The photoluminescence (PL) studies on NaIn 1- xRExW 2O 8, with RE=Eu 3+, Tb 3+, Dy 3+ and Tm 3+ phases have shown that the relative contribution of the host lattice and of the intra- f-f emission of the activators to the PL varies with the nature of the rare earth cation. In the case of Dy 3+ and Tm 3+ activators, with yellow and blue emission, respectively, the energy transfer from host to the activator plays a major role. In contrast for Eu 3+, with intense red emission, the host absorption is less pronounced and the intra- f-f transitions of the Eu 3+ ions play a major role, whereas for Tb 3+ intra- f-f transitions are only observed, giving rise to green emission.

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

2012-01-01

128

Young's Modulus Anisotropy and Magnetomechanical Damping of [110] Oriented Tb0.3Dy0.7Fe1.95 Alloy  

Microsoft Academic Search

The ?E effect and the magnetoelastic or magnetomechanical damping of vibrations in [110] oriented Tb0.3Dy0.7Fe1.95 alloy are experimentally studied by quasi-static stress–strain measurements under various constant magnetic fields between 0 and 3000Oe, where stress ranges are taken from about 0 to -25, -50, -75MPa. The linear stress–strain behaviour is obtained when the magnetic field is high enough (9000Oe). However, the

Yong-Mao Pei; Dai-Ning Fang

2007-01-01

129

Crystal growth of Tb 0.9Dy 0.1BaCo 2O 5+ ? using travelling solvent floating zone method  

Microsoft Academic Search

We report on a crystal growth by the travelling solvent floating zone method and characterization of the layered perovskite Tb0.9Dy0.1BaCo2O5+?. The crystal was grown with a rate of 0.5mm\\/h in a gas mixture of 2% O2 in Ar. X-ray diffraction data, electrical and magnetization measurements of the single crystal are reported.

M. Stingaciu; E. Pomjakushina; H. Grimmer; M. Trottmann; K. Conder

2008-01-01

130

Hydrothermal preparation and low temperature magnetic properties of TbOOH, DyOOH, HoOOH, ErOOH, and YbOOH  

Microsoft Academic Search

The monoclinic modification of the oxide hydroxides of terbium, dysprosium, holmium, erbium, and ytterbium was prepared using hydrothermal techniques. The magnetic properties of the compounds were investigated between 2.4 and 273 K. TbOOH, DyOOH, and ErOOH are antiferromagnetic with Néel temperatures of 10, 9, and 7.2 K, respectively, and have metamagnetic properties in high magnetic fields. HoOOH and YbOOH were

A. Nørlund Christensen

1972-01-01

131

Flexible Gd2O2S:Tb scintillators pixelated with polyethylene microstructures for digital x-ray image sensors  

NASA Astrophysics Data System (ADS)

Flexible scintillators for digital x-ray image sensors were designed, fabricated and characterized. In these scintillaotrs, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) scintillator pixels were embedded into a polyethylene (PE) substrate. To evaluate the difference in the spatial resolution according to the pixel size, we designed three scintillators with pixels of different pitch sizes: 50 µm pitch size (P50), 100 µm pitch size (P100) and 200 µm pitch size (P200). Because of the high flexibility and good formability, polyethylene was used as the substrate of the scintillator. To fabricate nickel micromolds with high-aspect-ratio microstructures, two microfabrication techniques were employed: silicon dry-etching using a deep reactive ion etching (DRIE) process and nickel electroforming. The pixelated PE microstructures were fabricated by a hot embossing process. Because the solution-type Gd2O2S:Tb precursor can be handled at room temperature, Gd2O2S:Tb was used as the scintillator material. The measured sensitivities of the P50 and P100 models were, respectively, about 65% and 97% of that of the P200 model. The lower sensitivity values of the models with a small pitch size were due to two factors, such as the different pixel heights and the different fill factors. Because a scintillator with a small pixel size has a low fill factor, the sensitivity of the scintillator decreases as the pixel size decreases. The fill factors of the P50, P100 and P200 models were 36%, 49% and 56.25%, respectively. On the other hand, the spatial resolution of the scintillator increases as the pixel size decreases. Therefore, P50 gave the best spatial resolution among the designed models. The spatial frequency at 10% of the modulation transfer function (MTF) with P50 was 13.5 mm-1, while that with P200 was 10.0 mm-1. The resolution pattern and the tooth x-ray images obtained from a scintillator with a smaller pixel size was also clearer than that obtained from a scintillator with a larger pixel size. PE-based flexible Gd2O2S:Tb scintillators can be utilized directly in flexible x-ray image sensors.

Jung, Im Deok; Cho, Min Kook; Lee, Sang Min; Bae, Kong Myeong; Jung, Phill Gu; Lee, Chi Hoon; Lee, Jae Min; Yun, Seungman; Kim, Ho Kyung; Kim, Seong Sik; Ko, Jong Soo

2009-01-01

132

Narrow spectral emission CaMoO4: Eu3+, Dy3+, Tb3+ phosphor crystals for white light emitting diodes  

NASA Astrophysics Data System (ADS)

Alkaline earth metal molybdates are promising candidates as a host material for high efficiency narrow spectral emission phosphors. These phosphors could potentially be used for the fabrication of phosphor-converted light emitting diodes (pc-LEDs). Phosphor crystals of calcium molybdate doped with rare earth dopant Ln3+(Ln=Eu, Dy, Tb) grown using flux growth method have been shown to exhibit higher excitation efficiency than the powders synthesized by solid-state reaction process. Molybdenum (VI) oxide has been found to be a suitable flux for growing large size optically transparent high quality crystals at a temperature around 1100 °C. Using the excitation wavelengths of 465 nm, 454 nm and 489 nm for CaMoO4: Eu3+, CaMoO4: Dy3+ and CaMoO4: Tb3+, respectively, intense emission lines at wavelengths of 615 nm, 575 nm and 550 nm were observed. The optimized doping concentrations of 12%, 2% and 5% for Eu3+, Dy3+ and Tb3+, respectively, provided the highest luminescence intensity.

Khanna, A.; Dutta, P. S.

2013-02-01

133

Pressure-induced enhancement of ferroelectricity in multiferroic RMn2O5 (R=Tb,Dy,Ho)  

NASA Astrophysics Data System (ADS)

Measurements of ferroelectric polarization and dielectric constant were done on RMn2O5 (R=Tb,Dy,Ho) with applied hydrostatic pressures of up to 18kbar . At ambient pressure, distinctive anomalies were observed in the temperature profile of both physical properties at critical temperatures marking the onset of long range antiferromegnetic order (TN1) and ferroelectricity (TC1) , as well as at temperatures when anomalous changes in the polarization, dielectric constant, and spin wave commensurability have been previously reported. In particular, the step in the dielectric constant at low temperatures (TC2) , associated with both a drop in the ferroelectric polarization and an incommensurate magnetic structure, was shown to be suddenly quenched upon passing an R -dependent critical pressure. This was shown to correlate with the stabilization of the high ferroelectric polarization state, which is coincident with the commensurate magnetic structure. The observation is suggested to be due to a pressure-induced phase transition into a commensurate magnetic structure, as exemplified by the pressure-temperature (p-T) phase diagrams constructed in this work. The p-T phase diagrams are determined for all three compounds.

Dela Cruz, C. R.; Lorenz, B.; Sun, Y. Y.; Wang, Y.; Park, S.; Cheong, S.-W.; Gospodinov, M. M.; Chu, C. W.

2007-11-01

134

Evaluating x-ray detectors for radiographic applications: a comparison of ZnSCdS:Ag with Gd2O2S:Tb and Y2O2S:Tb screens.  

PubMed

ZnSCdS:Ag was evaluated as a radiographic image receptor and was compared with Gd2O2S:Tb and Y2O2S:Tb phosphors often used in radiography. The evaluation of a radiographic receptor was modelled as a three-step process: (i) determination of light output intensity as related to the input radiation dose, (ii) determination of visible light characteristics with respect to radiographic optical detectors, and (iii) determination of image information transfer efficiency. The light intensity emitted per unit of x-ray exposure rate was measured and theoretically calculated for laboratory prepared screens with coating thicknesses from 20 to 220 mg cm-2 and tube voltages from 50 to 250 kVp. ZnSCdS:Ag light intensity was higher than that of Gd2O2S:Tb or Y2O2S:Tb for tube voltages less than 70 and 80 kVp respectively. ZnSCdS:Ag displayed the highest x-ray to light conversion efficiency (0.207) and had optical properties close to those of Gd2O2S:Tb and Y2O2S:Tb, and its emission spectrum was well matched to optical detectors. The image information transfer properties described by the modulation transfer function, the quantum noise transfer function, and the detective quantum efficiency were calculated for both general radiographic and mammographic conditions and were found to be intermediate between those of Gd2O2S:Tb and Y2O2S:Tb screens. Conclusively, ZnSCdS:Ag is an efficient phosphor well suited to radiography. PMID:9253044

Kandarakis, I; Cavouras, D; Panayiotakis, G S; Nomicos, C D

1997-07-01

135

Entropy changes and the caloric effects in R5Si2Ge2 (R=Gd and Tb)  

NASA Astrophysics Data System (ADS)

It has been experimentally shown that at ambient pressure, the compound Gd5Si2Ge2 undergoes a first order transition with giant magnetocaloric effect around this room temperature. Experimental data also show that an applied pressure increases the critical temperature of this compound and keeps the first order phase transition. On the other hand, experimental data show that the compound Tb5Si2Ge2 undergoes a second order phase transition with a normal magnetocaloric effect around 100 K. It has also been shown that an applied pressure increases its critical temperature without changing the order of the phase transition. In this work, we calculate the magnetocaloric and barocaloric effects in and Gd5Si2Ge2 and Tb5Si2Ge2. For this purpose, we use a model of localized magnetic moments including the magnetoelastic interaction. In the model, the order of the phase transition is controlled by the ratio between the exchange interaction and the magnetoelastic coupling parameter. Our calculations show that these compounds exhibit large values of the entropy changes upon pressure variation in good agreement with the available experimental data.

de Oliveira, Nilson

2013-03-01

136

Synthesis, structure and physical properties of LnNi(Sn,Sb){sub 3} (Ln=Pr, Nd, Sm, Gd, Tb)  

SciTech Connect

Five new analogues of the {beta}-CeNiSb{sub 3} family have been synthesized and found to be LnNi(Sn,Sb){sub 3} and isostructural to the previously reported {beta}-CeNiSb{sub 3}. LnNi(Sn,Sb){sub 3} (Ln=Pr, Nd, Sm, Gd, or Tb) crystallizes in the orthorhombic space group, Pbcm, with lattice parameters of a{approx}12.9 A, b{approx}6.1 A, c{approx}12.0 A. The structure consists of layers of nearly square nets of X (X=Sn/Sb) atoms and highly distorted NiX{sub 6} octahedra. Lanthanide atoms are located between layers of X and NiX{sub 6} octahedra. All analogues are metallic and experimental effective magnetic moments are in agreement with the respective Ln{sup 3+} calculated moments. - Graphical abstract: Five new single crystalline analogues of the {beta}-LnNiSb{sub 3} family (Ln=Pr, Nd, Sm, Gd, or Tb) have been synthesized and determined to be LnNi(Sn,Sb){sub 3}. The structures are compared to the previously reported {beta}-CeNiSb{sub 3}. Magnetic and transport behavior are reported and discussed.

Gautreaux, Dixie P. [Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803 (United States); Capan, Cigdem; DiTusa, John F.; Young, David P. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Chan, Julia Y. [Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803 (United States)], E-mail: jchan@lsu.edu

2008-08-15

137

Blue-white-green tunable luminescence from Ba2Gd2Si4O13:Ce3+,Tb3+ phosphors excited by ultraviolet light.  

PubMed

The novel Ba2Gd2Si4O13:Ce3+,Tb3+ phosphors were systemically investigated by fluorescent method for the first time. Through an efficient energy transfer process, the obtained phosphors exhibit both a blue emission of Ce3+ and a yellowish green emission of Tb3+ with considerable intensity under near-ultraviolet excitation (300-370 nm). Tuning of the content of Tb3+ can generate the varied hues from blue to white and eventually to yellowish green. The quantum efficiency of the white phosphor Ba2(Gd0.88Ce0.02Tb0.1)2Si4O13 is 82.3% of commercial ZnS:Ag+,Cl- phosphor. Our results demonstrate that the potential application of these phosphors in solid-state lighting and (or) other areas. PMID:21197003

Guo, Hai; Zhang, Hao; Li, Jingjing; Li, Fang

2010-12-20

138

Syntheses, structure, magnetism, and optical properties of the partially ordered quaternary interlanthanide sulfides PrLnYb{sub 2}S{sub 6} (Ln=Tb, Dy)  

SciTech Connect

Dark red single crystals of PrLnYb{sub 2}S{sub 6} (Ln=Pr/Yb, Tb, Dy) have been synthesized through the reactions of elemental rare earth metals and S using a Sb{sub 2}S{sub 3} flux at 1000 deg. C. These isotypic compounds adopt the F-Ln{sub 2}S{sub 3} three-dimensional open-channel structure type. Eight-coordinate Pr{sup 3+} ions sit in the channels that are constructed from three different edge-shared double chains running down the b-axis that contain Yb(1)S{sub 6} octahedra, Yb(2)S{sub 6} octahedra, and LnS{sub 7} monocapped trigonal prisms. Each double chain connects to four other neighbors by sharing vertices and edges. Considerable disordering in Ln positions was observed in single X-ray diffraction experiments only in the case of Pr/Yb. Least-squares refinements gave rise to the formulas of Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, of PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6}, which are confirmed by the elemental analysis and magnetic susceptibility measurements. Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6} are paramagnetic down to 2 K, without any indications of long-range magnetic ordering. The optical transitions for Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6} are at approximately 1.6 eV. Crystallographic data are listed as an example for PrTbYb{sub 2}S{sub 6}: monoclinic, space group P2{sub 1}/m, a=10.9496(10) A, b=3.9429(4) A, c=11.2206(10) A, {beta}=108.525(2){sup o}, V=459.33(7) A{sup 3}, Z=2. - Graphical abstract: An illustration of the three-dimensional structure of PrTbYb{sub 2}S{sub 6} viewed along the b-axis.

Jin Gengbang [Department of Chemistry and Biochemistry and the E.C. Leach Nuclear Science Center, Auburn University, Auburn, AL 36849 (United States); Choi, Eun Sang [Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Guertin, Robert P. [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Brooks, James S. [Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Booth, Corwin H. [Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Albrecht-Schmitt, Thomas E. [Department of Chemistry and Biochemistry and the E.C. Leach Nuclear Science Center, Auburn University, Auburn, AL 36849 (United States)], E-mail: albreth@auburn.edu

2007-09-15

139

Narrow spectral emission CaMoO{sub 4}: Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+} phosphor crystals for white light emitting diodes  

SciTech Connect

Alkaline earth metal molybdates are promising candidates as a host material for high efficiency narrow spectral emission phosphors. These phosphors could potentially be used for the fabrication of phosphor-converted light emitting diodes (pc-LEDs). Phosphor crystals of calcium molybdate doped with rare earth dopant Ln{sup 3+}(Ln=Eu, Dy, Tb) grown using flux growth method have been shown to exhibit higher excitation efficiency than the powders synthesized by solid-state reaction process. Molybdenum (VI) oxide has been found to be a suitable flux for growing large size optically transparent high quality crystals at a temperature around 1100 Degree-Sign C. Using the excitation wavelengths of 465 nm, 454 nm and 489 nm for CaMoO{sub 4}: Eu{sup 3+}, CaMoO{sub 4}: Dy{sup 3+} and CaMoO{sub 4}: Tb{sup 3+}, respectively, intense emission lines at wavelengths of 615 nm, 575 nm and 550 nm were observed. The optimized doping concentrations of 12%, 2% and 5% for Eu{sup 3+}, Dy{sup 3+} and Tb{sup 3+}, respectively, provided the highest luminescence intensity. - Graphical Abstract: CaMoO{sub 4}: Eu{sup 3+} phosphor crystals grown using a molybdenum (VI) oxide flux exhibited around 1.5 times the emission intensity of powders obtained from solid-state reaction at the same synthesis temperature. These crystals were found to efficiently emit 615 nm red light when excited by near UV light up to a wavelength of 395 nm. Highlights: Black-Right-Pointing-Pointer CaMoO{sub 4}: Ln{sup 3+} (Ln=Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}) phosphor crystals were successfully grown using high temperature flux (solutions) containing molybdenum (VI) oxide or lithium chloride. Black-Right-Pointing-Pointer Narrow spectral emission at 615 nm, 575 nm and 550 nm, respectively, was observed from CaMoO{sub 4}: Ln{sup 3+} (Ln=Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}) phosphor crystals. Black-Right-Pointing-Pointer The optimized doping concentrations of Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+} in CaMoO{sub 4} for highest emission intensity were determined to be 12%, 2% and 5%, respectively. Black-Right-Pointing-Pointer The CaMoO{sub 4}: Ln{sup 3+} (Ln=Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}) phosphor crystals grown with molybdenum (VI) oxide flux exhibited 50% higher emission intensity compared to the crystals grown with lithium chloride flux and the powders synthesized by solid-state reaction.

Khanna, A. [Smart Lighting Engineering Research Center, 110, 8th Street, Troy, New York, 12180 (United States) [Smart Lighting Engineering Research Center, 110, 8th Street, Troy, New York, 12180 (United States); Electrical, Computer and Systems Engineering Department, Rensselaer Polytechnic Institute, 110, 8th Street, Troy, New York, 12180 (United States); Dutta, P.S., E-mail: duttap@rpi.edu [Smart Lighting Engineering Research Center, 110, 8th Street, Troy, New York, 12180 (United States); Electrical, Computer and Systems Engineering Department, Rensselaer Polytechnic Institute, 110, 8th Street, Troy, New York, 12180 (United States)

2013-02-15

140

Crystal structure and critical temperature of RBa 2Cu 4O 8 (R = Tm, Er, Ho, Y, Dy and Gd)  

NASA Astrophysics Data System (ADS)

Bulk superconductors RBa 2Cu 4O 8 (R = rare earth element; Tm, Er, Ho, Y, Dy and Gd) were synthesized by hot isostatic pressing (HIP) technique. The highest Tc ( = 84 K) was obtained for the substitution of Er. The Tc decreases systematically with the increase of the ionic radius of these rare earth ions, and reaches 77 K for the largest ion Gd. The crystal structure of the compounds with R = Tm, Er, Ho and Y has been refined by Rietveld analysis of neutron powder diffraction data at room temperature. Structural changes due to the substitution of these rare earth elements are compared with those of YBa 2Cu 4O 8 under high pressure, and they are discussed in connection with the variation of Tc. The results indicate that l(Cu(2)-O(2)) and l(Cu(2)-O(3)), the bond lengths between Cu and O in the CuO 2 plane, are the most important parameters to decide the Tc of the present systems.

Mori, K.; Kawaguchi, Y.; Ishigaki, T.; Katano, S.; Funahashi, S.; Hamaguchi, Y.

1994-01-01

141

Thermoluminescence properties of isostructural K 2YF 5 and K 2GdF 5 crystals doped with Tb 3+ in response to ?, ? and X-ray irradiation  

NASA Astrophysics Data System (ADS)

The thermoluminescence (TL) properties of isostructural fluoride K 2YF 5 and K 2GdF 5 crystals doped with Tb 3+ of different concentrations have been studied in the temperature range from 30 to 500 °C after ?, ? and X-ray irradiation. Strongly different structures of TL glow curves following ? or ? irradiation have been found for Tb 3+ doped K 2YF 5 for all studied concentrations of Tb 3+ whereas for K 2GdF 5 crystals the different TL curves after ? or ? irradiation are detected only for heavily doped samples. On the other hand, all the studied materials show similar TL glow curves after ? or X-ray irradiation. It has been discovered that K 2YF 5 doped with 1 at.% Tb 3+ has TL radiation sensitivity to ? irradiation of the same order as that of the well known TLD-100 (LiF:Mg,Ti) phosphor and much higher sensitivity to ? irradiation. The TL mechanism in K 2YF 5 and K 2GdF 5 doped with Tb 3+ is discussed by taking into account the TL emission spectra from irradiated samples, which are identical to the emission spectra of the Tb 3+ ions in these hosts under photo-excitation, and the kinetics parameters obtained with the method of various heating rates.

Hanh, Huynh Ky; Khaidukov, Nicholas M.; Makhov, Vladimir N.; Quang, Vu Xuan; Thanh, Nguyen Trong; Tuyen, Vu Phi

2010-10-01

142

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: A novel Dy3+-doped GdPO4 white-light phosphors under vacuum ultraviolet excitation for Hg-free lamps application  

NASA Astrophysics Data System (ADS)

Novel Dy3+-doped GdPO4 white light phosphors with monoclinic system were successfully synthesised by hydrothermal method at 240 °C. This paper investigates the luminescence properties of white-light Gd1-xPO4:xDy3+ under vacuum ultraviolet (VUV) excitation. The strong absorption at around 147 nm in excitation spectrum energy can be transferred to the energy levels of Dy3+ ion from the host absorption. Additionally, this white light phosphors are activated by a single Dy3+ ion and with a lower preparation temperature, which tend to decrease the consumption of rare earth resource and energy. Therefore, the luminescence of Gd1-xPO4:xDy3+ under VUV excitation is effective, and proves to be promising in application to mercury-free lamp.

Han, Guo-Cai; Wang, Yu-Hua; Wu, Chun-Fang; Zhang, Jia-Chi

2009-10-01

143

Vibrational structure in optical spectra of the Ca 4GdO(BO 3) 3 (GdCOB) single crystal doped with Re 3+ (Eu, Tb, Yb)  

NASA Astrophysics Data System (ADS)

The optical spectra of compounds containing trivalent rare earth (Re 3+) ions often show vibronic features. The intensity of vibronic transitions is determined by the strength of the electron-phonon (ion-lattice) coupling and depends strongly on the rare earth and the host lattice. In this paper we report on electron-phonon coupling in the GdCOB system doped with Eu 3+, Tb 3+ and Yb 3+ ions. According to general theory intense vibronic lines are to be expected for electronic transitions with ? J=0, ±2 and these transitions were mainly considered in this paper for both Eu 3+ and Tb 3+ ions. In the case of Yb 3+ ions, a strong vibronic sideband belongs to the 2F 7/2? 2F 5/2 transition with ? J=1 although it seems to be in contradiction to the general selection rule. The vibronic features observed in absorption, excitation and emission spectra were analysed on the basis of the host lattice modes obtained from Raman and the far infrared spectra of the matrix.

Dominiak-Dzik, G.; Ryba-Romanowski, W.; Go??b, S.; Baba, M.; Paj?czkowska, A.

2002-09-01

144

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

145

A broadband-excited and narrow-line GdBO3: Ce3+, Tb3+, Eu3+ red phosphor with efficient Ce3+ ? (Tb3+)n ? Eu3+ energy transfer for NUV LEDs  

NASA Astrophysics Data System (ADS)

A broadband-excited and narrow-line red phosphor, GdBO3: Ce3+, Tb3+, Eu3+, was synthesized by solid state method. The photoluminescence excitation and emission spectra, concentration effect and decay curves are investigated. The emission color of the phosphors can be tuned from blue (0.168, 0.018) to green (0.291, 0.590) and eventually to red (0.612, 0.372) through efficient Ce3+ ? (Tb3+)n ? Eu3+ energy transfer. The optimal-composition phosphor, GdBO3: 0.01Ce3+, 0.50Tb3+, 0.01Eu3+, gives an intense Eu3+ red 4f–4f sharp emission with a strong 4f–5d absorption band of Ce3+ at 356 nm, which perfectly matches with the dominant emission band of NUV LEDs, and makes it as a potential red phosphor for NUV LEDs.

Zhang, Xinguo; Zhou, Liya; Pang, Qi; Gong, Menglian

2014-05-01

146

Decay of {sup 161m1,m2}Dy isomers under conditions of a resonance environment (Moessbauer Screen)  

SciTech Connect

The half-lives of the isomers {sup 161m1}Dy and {sup 161m2}Dy (E = 25.6 keV and T{sub 1/2} {approx} 30 ns for the former and E = 74.6 keV and T{sub 1/2} {approx} 3 ns for the latter) placed in a {sup 160}Gd{sub 2}O{sub 3} crystal lattice at T = 300 K and surrounded by stable {sup 161}Dy nuclei in the composition of {sup 161}Dy{sub 2}O{sub 3} were measured by the method of ({beta}-{gamma}) coincidences in the beta-decay process {sup 161}Tb {yields} {sup 161}Dy. Nuclei of {sup 161m1,m2}Dy were obtained according to the chain {sup 160}Gd(n, {gamma}){sup 161}Gd {yields} {sup 161}Tb {yields} {sup 161}Dy from {sup 160}Dy{sub 2}O{sub 3} weighted portions irradiated at the PWR-M reactor of the Petersburg Nuclear Physics Institute (PNPI, Gatchina, Russia). The T{sub 1/2} value observed for the isomer {sup 161m1}Dy was found to be correlated with the number of surrounding {sup 161}Dy nuclei. The presence of this correlation in {sup 161m1}Dy can be explained by the multiple resonance scattering of photons from isomer decay within the sample used. No such correlation was observed for {sup 161m2}Dy. The half-lives measured for the isomers {sup 161m1}Dy and {sup 161m2}Dy in the absence of the above environment are 29.2(1) and 3.50(1) ns, respectively.

Loginov, Yu. E., E-mail: yurlo@pnpi.spb.ru; Zinoviev, V. G.; Kabina, L. P.; Lisin, S. S.; Maljutenkov, Ed. I. [Russian Academy of Sciences, Petersburg Nuclear Physics Institute (Russian Federation)

2013-06-15

147

Large magnetocaloric effect with a wide working temperature span in the R2CoGa3 (R = Gd, Dy, and Ho) compounds  

NASA Astrophysics Data System (ADS)

We investigate magnetic properties and magnetocaloric effects of R2CoGa3 (R = Gd, Dy, and Ho) compounds. It is found that all the compounds are ferromagnetic with the Curie temperatures of TC = 50, 17, and 10 K for R = Gd, Dy, and Ho, respectively. The R2CoGa3 have large magnetic entropy change (?S) that arise from the second-order ferromagnetic-to-paramagnetic phase transition. The maximum values of ?S are found to be -12.6, -10.8, and -13.8 J/kg K with corresponding refrigerant capacity values of 382, 252, and 287 J/kg for a magnetic field change of 0-50 kOe, respectively. The large ?S values with little or no hysteresis losses as well as wide working temperature spans imply that the R2CoGa3 compounds may serve as promising candidates for magnetic refrigeration.

Wang, L. C.; Cui, L.; Dong, Q. Y.; Mo, Z. J.; Xu, Z. Y.; Hu, F. X.; Sun, J. R.; Shen, B. G.

2014-06-01

148

Field-induced internal Fe and Ln spin reorientation in butterfly {Fe3LnO2} (Ln = Dy and Gd) single-molecule magnets  

NASA Astrophysics Data System (ADS)

The intramolecular exchange interactions within the single-molecule magnet (SMM) “butterfly” molecule [Fe3Ln(?3-O)2(CCl3COO)8(H2O)(THF)3], where Ln(III) represents a lanthanide cation, are determined in a combined experimental [x-ray magnetic circular dichroism (XMCD) and vibrating sample magnetometer (VSM)] and theoretical work. Compounds with Ln=Gd and Dy, which represent extreme cases where the rare earth presents single-ion isotropic and uniaxial anisotropy, on one hand, and with Ln=Lu and Y(III) as pseudolanthanide substitutions that supply a nonmagnetic Ln reference case, on the other hand, are studied. The Dy single-ion uniaxial anisotropy is estimated from ab initio calculations. Low-temperature (T?2.5 K) hard x-ray XMCD at the Ln L2,3 edges and VSM measurements as a function of the field indicate that the Ln moment dominates the polarization of the molecule by the applied field. Within the {Fe3LnO2} cluster the Ln-Fe3 subcluster interaction is determined to be antiferromagnetic in both Dy and Gd compounds, with values JDy-Fe3=-0.4 K and JGd-Fe3=-0.25 K, by fitting to spin Hamiltonian simulations that consider the competing effects of intracluster interactions and the external applied magnetic field. In the uniaxial anisotropic {Fe3DyO2} case, a field-induced reorientation of the Fe3 and Dy spins from an antiparallel to a parallel orientation takes place at a threshold field (?0H=4 T). In contrast, in isotropic {Fe3GdO2} this reorientation does not occur.

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

2013-05-01

149

Study on the exp 151 Gd Excited States in the exp 151 Tb (Tsub(1/2)=16.4 H) Decay.  

National Technical Information Service (NTIS)

For the purpose to specify the scheme of exp 151 Tb decay, energies, intensities of p-transitions and respectively balance of intensities and energies of exp 151 Gd levels the spectra of e- gamma -coincidences, gamma -rays, and internal conversion electro...

N. B. Badalov A. Budzyak T. Vylov Kim Zaj Te V. V. Kuznetsov

1981-01-01

150

Synthesis, thermogravimetric and 57Fe Mössbauer studies of the oxygen deficient perovskite REBaCuFeO5 + x series (RE = Y, Nd, Sm, Gd, Dy, Tm, Lu)  

Microsoft Academic Search

We present the results of thermogravimetric and 57Fe Mössbauer studies of the oxygen deficient perovskite REBaCuFeO5+x series with RE = Y, Nd, Sm, Gd, Dy, Tm, Lu. The presence of the removable content x of oxygen was determined by analysis of TGA measurements in a stream of Ar gas. The amount of removable oxygen was highest for the Nd compound

M. Pissas; C. Mitros; G. Kallias; V. Psycharis; A. Simopoulos; A. Kostikas; D. Niarchos

1992-01-01

151

Effect of hygroscopic nature on the electrical characteristics of lanthanide oxides (Pr2O3, Sm2O3, Gd2O3, and Dy2O3)  

Microsoft Academic Search

The hygroscopic nature of lanthanide oxides such as Pr2O3, Sm2O3, Gd2O3, and Dy2O3 was characterized by means of x-ray photoelectron spectroscopy and its effect on the electrical characteristics of the compounds was investigated. Among the four samples, Pr2O3 was found to be the most reactive with water which can be attributed to the relatively large ionic radius and lower electronegativity

Sanghun Jeon; Hyunsang Hwang

2003-01-01

152

Wheel-shaped nanoscale 3d-4f {Co(II)16Ln(III)24} clusters (Ln = Dy and Gd).  

PubMed

Two unprecedented wheel-shaped nanoscale clusters {Co(II)16Ln(III)24} (Ln = Dy and Gd), with a diameter and a thickness of 3.0 nm and 2.0 nm, respectively, were obtained from the self-assembly of Co(NO3)2, Ln(NO3)3 and a pyridyl-functionalized ?-diketone ligand. Notably, the gadolinium species exhibited a relatively large magnetocaloric effect. PMID:23912749

Zhang, Ze-Min; Pan, Lu-Yi; Lin, Wei-Quan; Leng, Ji-Dong; Guo, Fu-Sheng; Chen, Yan-Cong; Liu, Jun-Liang; Tong, Ming-Liang

2013-09-21

153

Crystal growth, structures, magnetic and photoluminescent properties of NaLnGeO4 (Ln = Sm, Eu, Gd, Tb)  

NASA Astrophysics Data System (ADS)

Single crystals of NaLnGeO4 (Ln = Sm, Eu, Gd) were grown out of a molten sodium hydroxide flux, and their crystal structures were determined by single crystal X-ray diffraction. The lanthanide containing germanates crystallize in the orthorhombic space group of Pnma, and exhibit a complex three-dimensional structure consisting of corner- or edge-shared LnO6, GeO4, and NaO6 polyhedra. UV-vis diffuse reflectance spectra indicated that the reported oxides are insulating materials with wide band gaps. The magnetic susceptibility data shows paramagnetic behavior. For the NaEuGeO4 and NaTbGeO4 compositions intense room temperature photoluminescence was observed.

Yeon, Jeongho; Hardaway, John B.; Sefat, Athena S.; Latshaw, Allison M.; zur Loye, Hans-Conrad

2014-08-01

154

Optimisation of tube voltage for conventional urography using a Gd2O2S:Tb flat panel detector.  

PubMed

With the increasing use of computed tomography (CT) for urography examinations, the indications for 'conventional' projection urography have changed and are more focused on high-contrast details. The purpose of the present study was to optimise the beam quality for urography examinations performed with a Gd(2)O(2)S:Tb flat-panel detector for the new conditions. Images of an anthropomorphic phantom were collected at different tube voltages with a CXDI-40G detector (Canon Inc., Tokyo, Japan). The images were analysed by radiologists and residents in a visual grading characteristics (VGCs) study. The tube voltage resulting in the best image quality was 55 kV, which therefore was selected for a clinical study. Images from 62 patients exposed with either 55 or 73 kV (original tube voltage) at constant effective doses were included. The 55-kV images underwent simulated dose reduction to represent images collected at 80, 64, 50, 40 and 32 % of the original dose level. All images were included in a VGC study where the observers rated the visibility of important anatomical landmarks. For images collected at 55 kV, an effective dose of approximately 85 % resulted in the same image quality as for images collected at 73 kV at 100 % dose. In conclusion, a low tube voltage should be used for conventional urography focused on high-contrast details. The study indicates that using a tube voltage of 55 kV instead of 73 kV for a Gd(2)O(2)S:Tb flat-panel detector, the effective dose can be reduced by approximately 10-20 % for normal-sized patients while maintaining image quality. PMID:20223848

Zachrisson, Sara; Hansson, Jonny; Cederblad, Ake; Geterud, Kjell; Båth, Magnus

2010-01-01

155

Synthesis, optical properties, and energy transfer of Ce(3+)/Tb(3+) co-doped MyGdFx (M=Li, Na, K).  

PubMed

Through a solid-state reaction method, the Ce(3+)/Tb(3+) co-doped MyGdFx (M=Li, Na, K; x=3, 4, 6; y=0, 1, 3) system samples have been synthesized by controlling the annealing temperatures and the ratios of raw materials. The samples were characterized by X-ray diffraction (XRD) patterns, photoluminescence (PL) excitation and emission spectra as well as luminescent dynamic decay curves. The experimental results suggest that the LiF is more difficult to react with the prepared material compared that of NaF or KF under similar reaction conditions. The samples crystallized in different crystalline phases. The energy transfer from Ce(3+) to Tb(3+) or Ce(3+) to Gd(3+) to Tb(3+) has been observed in all the samples. The Ce(3+) and Tb(3+) present different optical properties for they are sensitive to the local environment. In addition, the deduced lifetime of Tb(3+)(5)D4?(7)F5 transition decreases in the same system samples with the annealing temperature increasing. The deduced lifetime of Tb(3+)(5)D4?(7)F5 also decreases with the increase of the KF concentration in the KF system samples. PMID:24973786

Cao, Chunyan; Luo, Zhiyang; Guo, Siling; Cao, Renping; Noh, Hyeon Mi; Jeong, Jung Hyun; Xie, An

2014-12-10

156

Structural and magnetic properties of RFe[sub 6]Ge[sub 6] (R = Y, Gd, Tb, Er)  

SciTech Connect

A series of RFe[sub 6]Ge[sub 6] (R = Y, Gd, Tb, Er) compounds have been prepared by arc-melting. Structural studies using x-ray diffraction (XRD) show that all four as-cast alloys belong to the hexagonal P6/mmm space group with similar lattice parameters (for YFe[sub 6]Ge[sub 6], a = 5.12[angstrom] and c = 4.07[angstrom]). After annealing at 900 C for two weeks, both YFe[sub 6]Ge[sub 6] and TbFe[sub 6]Ge[sub 6] transform into the orthorhombic Cmcm structure. Moessbauer spectroscopy and magnetization measurements show that all of the alloys are antiferromagnetically ordered at room temperature. The authors find a single Fe crystallographic site, consistent with the RFe[sub 6]Ge[sub 6] structures. Both the room temperature [sup 57]Fe hyperfine field and the Neel temperature (T[sub N]) are largely independent of the rare-earth, being 14.9(1) T and 487 K respectively for YFe[sub 6]Ge[sub 6].

Wang, Y.B.; Wiarda, D.; Ryan, D.H. (McGill Univ., Montreal, Quebec (Canada)); Cadogan, J.M. (Univ. of New South Wales, Sydney (Australia))

1994-11-01

157

Synthesis, structure, and magnetic characterization of La2-xRxRuO5 (R = Pr, Nd, Sm, Gd, Dy)  

NASA Astrophysics Data System (ADS)

Polycrystalline samples of La2-xRxRuO5 (R = Pr, Nd, Sm, Gd, Dy) have been prepared, applying a soft-chemistry route based on the thermal decomposition of citric acid precursors. By powder x-ray and neutron diffraction the crystal structures have been investigated in detail. For the unsubstituted parent compound La2RuO5, synchrotron x-ray diffraction patterns reveal a broad structural phase transition regime around 170 K without any significant hysteresis. This structural transition is linked with a drastic reduction of the magnetic susceptibility. A similar behavior was also observed for the lanthanide-substituted compounds La2-xRxRuO5. Magnetic measurements reveal the coexistence of two weakly interacting magnetic sublattices. The effect of rare-earth substitution on the magnetic phase transition is resulting from structural modifications caused by the smaller radius of the R3+ ions. These ions are predominantly located within the LaO-layers, which are alternating with LaRuO4 layers. The transition temperatures determined by differential scanning calorimetry (DSC) are compared to data derived from the susceptibility measurements.

Riegg, S.; Sazama, U.; Fröba, M.; Reller, A.; Ebbinghaus, S. G.

2011-07-01

158

Magnetic and transport properties of RCr{sub 0.3}Ge{sub 2} (R=Tb, Dy, Ho and Er) compounds  

SciTech Connect

The magnetic and transport properties of ternary rare-earth chromium germanides RCr{sub 0.3}Ge{sub 2} (R=Y and Tb-Er) have been determined. X-ray and neutron diffraction studies indicate that these compounds have the CeNiSi{sub 2}-type structure (space group Cmcm) . Magnetic measurements reveal the antiferromagnetic ordering below T{sub N} equal to 18.5 K (R=Tb), 11.8 K (Dy), 5.8 K (Ho) and 3.4 K (Er). From the neutron diffraction data the magnetic structures have been determined. For TbCr{sub 0.3}Ge{sub 2} and DyCr{sub 0.3}Ge{sub 2} at low temperatures the magnetic ordering can be described by two vectors k{sub 1}=(1/2 ,0,0) and k{sub 2}=(1/4 ,0,1/4), and k{sub 1}'=(1/2 ,0,0) and k{sub 2}'=(1/2 ,0,1/2), respectively. In HoCr{sub 0.3}Ge{sub 2} and ErCr{sub 0.3}Ge{sub 2} the ordering can be described by one propagation vector equal to (1/2 ,1/2 ,0) and (0,0,0.4187(2)), respectively. In DyCr{sub 0.3}Ge{sub 2} some change in the magnetic ordering is observed at T{sub t}=5.1 K. In temperature range from T{sub t} to T{sub N} the magnetic ordering is given by one propagation vector k=(1/2 ,0,0). YCr{sub 0.3}Ge{sub 2} is a Pauli paramagnet down to 1.72 K which suggests that in the entire RCr{sub 0.3}Ge{sub 2} series the Cr atoms do not carry magnetic moments. All compounds studied exhibit metallic character of the electrical conductivity. The temperature dependencies of the lattice parameters reveal strong magnetostriction effect at the respective Neel temperatures. -- Graphical abstract: In the neutron diffraction pattern of TbCr{sub 0.3}Ge{sub 2} compound collected at 1.5 K the additional peaks of magnetic origin form two groups. The first one, with strong intensities, can be indexed by the propagation vector k=(1/2 ,0,0) (a), while the second one, with small intensities, can be described by the propagation vector k=(1/4 ,0,1/4) (b). The analysis of the magnetic peak intensities indicates that the Tb magnetic moments located at the positions Tb1 (0,y,1/4), Tb2 (0,-y,3/4), Tb3 (1/2 ,1/2 +y,1/4) and Tb4 (1/2 ,1/2 -y,3/4) form a collinear structure with the (+ + - -) sequence in the crystallographic unit cell for the first component and (- + + -) for the second. Display Omitted

Gil, A., E-mail: a.gil@ajd.czest.p [Department of Mathematics and Natural Science, J. DLugosz University Czestochowa, Armii Krajowej 13/15, 42-200 Czestochowa (Poland); Kaczorowski, D. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 WrocLaw (Poland); Penc, B. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Hoser, A. [BENSC, Helmholtz-Zentrum Berlin, Glienicker Str. 100, 14-109 Berlin (Germany); SzytuLa, A. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)

2011-02-15

159

Trinuclear [Co(III) 2 -Ln(III) ] (Ln=Tb, Dy) Single-Ion Magnets with Mixed 6-Chloro-2-Hydroxypyridine and Schiff Base Ligands.  

PubMed

The Schiff base ligand N1,N3-bis(3-methoxysalicylidene)diethylenetriamine (H2 valdien) and the co-ligand 6-chloro-2-hydroxypyridine (Hchp) were used to construct two 3d-4f heterometallic single-ion magnets [Co2 Dy(valdien)2 (OCH3 )2 (chp)2 ]?ClO4 ?5?H2 O (1) and [Co2 Tb(valdien)2 (OCH3 )2 (chp)2 ]?ClO4 ?2?H2 O?CH3 OH (2). The two trinuclear [Co(III) 2 Ln(III) ] complexes behave as a mononuclear Ln(III) magnetic system because of the presence of two diamagnetic cobalt(III) ions. Complex?1 has a molecular symmetry center, and it crystallizes in the C2/c space group, whereas complex?2 shows a lower molecular symmetry and crystallizes in the P21 /c space group. Magnetic investigations indicated that both complexes are field-induced single-ion magnets, and the Co(III) 2 -Dy(III) complex possesses a larger energy barrier [74.1(4.2)?K] than the Co(III) 2 -Tb(III) complex [32.3(2.6)?K]. PMID:24807145

Liu, Cai-Ming; Zhang, De-Qing; Hao, Xiang; Zhu, Dao-Ben

2014-07-01

160

Dense assembly of Gd2O3:0.05X3+ (X = Eu, Tb) nanorods into nanoscaled thin-films and their photoluminescence properties.  

PubMed

This paper presents a simple and effective oil-water interfacial self-assembly strategy to fabricate monolayer and bilayer nanofilms of densely packed Gd2O3:0.05X(3+) (X = Eu, Tb) nanorods with characteristic luminescence properties. In this process, Gd2O3:0.05X(3+) (X = Eu, Tb) nanotubes synthesized by a hydrothermal method are dispersed in deionized water; then, a certain amount of n-hexane is added to produce a hexane-water interface. With n-butanol added as initiator, the nanotubes are gradually trapped at the interface to form a densely packed nanofilm. A monolayer nanofilm of densely packed Gd2O3:0.05Eu(3+) nanorods is obtained after annealing. In addition, the bilayer nanofilm composed of Gd2O3:0.05X(3+) (X = Eu, Tb) nanorods still retains the luminescence properties of each monolayer nanofilm. Moreover, the adhesion of the film on the substrate is very strong, which is extremely beneficial for its future applications. PMID:24387245

Huan, Jing; Hu, Linfeng; Fang, Xiaosheng

2014-02-12

161

Tunable white-light emission from mixed lanthanide (Eu(3+), Gd(3+), Tb(3+)) coordination polymers derived from 4-(dipyridin-2-yl)aminobenzoate.  

PubMed

Herein, we have developed a series of isostructural mixed Ln(3+)-4-(dipyridin-2-yl)aminobenzoate coordination polymers [Ln(3+) = Eu(3+) (), Tb(3+) (), and Gd(3+) ()], and characterized and investigated their photophysical properties. The results demonstrated that by gently tuning the excitation wavelength of these mixed lanthanide complexes, white light emission can be realized with the Commission Internationale de I'Eclairage coordinates (0.32, 0.34). Furthermore, by changing the concentration profiles of lanthanide ions stoichiometrically in mixed-lanthanide complexes and exciting at particular wavelengths, various emission colours can also be successfully obtained. The antenna ligand, 4-(dipyridin-2-yl)aminobenzoic acid, provides an efficient energy transfer for the sensitization of Eu(3+) and Tb(3+) complexes and exhibits red and green emissions, respectively. Most importantly, due to the high energy (32?150 cm(-1)) of the Gd(3+) ion lowest-lying emission level, the corresponding Gd(3+) complex displays ligand-centered visible emission in the blue light region, and hence it acts as a blue emitter. Therefore, Eu(3+) and Tb(3+) complexes in conjunction with a Gd(3+) complex is a suitable choice to obtain tunable white-light-emission from Ln(3+) coordination polymers. The morphological analyses of the mixed lanthanide coordination polymers by transmission electron microscopy (TEM) disclose that these compounds exist as unique crystalline nano-rods with an average diameter of 200 nm. The developed mixed lanthanide complexes also exhibit high thermal stability (?420 °C). PMID:24903008

Ramya, A R; Varughese, Sunil; Reddy, M L P

2014-06-24

162

Syntheses, Structure, Magnetism, and Optical Properties of the Partial Ordered Quaternary Interlanthanide Sulfides PrLnYb2S6 (Ln = Tb, Dy)  

SciTech Connect

Dark red single crystals of PrLnYb{sub 2}S{sub 6} (Ln = Pr/Yb, Tb, Dy) have been synthesized through the reaction of elemental rare earth metals and S using a Sb{sub 2}S{sub 3} flux at 1000 C. These isotypic compounds adopt the F-Ln{sub 2}S3 three-dimensional open channel structure type. Eight-coordinate Pr{sup 3+} ions sit in the channels, which are constructed from three different edge-shared double chains running down the b axis, which contain Yb(1)S{sub 6} octahedra, Yb(2)S{sub 6}, octahedra and LnS{sub 7} monocapped trigonal prisms, respectively. Each double chain connects to four other neighbors by sharing vertices and edges. Considerable disordering in Ln positions was observed in single X-ray diffraction experiments only in the case of Pr/Yb. Least square refinements gave rise to the formulas of Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, of PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6}, which are confirmed by the elemental analysis and magnetic susceptibility measurements. Pr1.34Yb2.66S{sub 6}, PrTbYb{sub 2}S{sub 6} and PrDyYb{sub 2}S{sub 6} are paramagnetic down to 2 K without any indications of long range magnetic ordering. The optical transitions for Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6} are at approximately 1.6 eV. Crystallographic data: Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, monoclinic, space group P2{sub 1}/m, a = 10.960(2), b = 3.9501(8), c = 11.220(2) {angstrom}, {beta} = 108.545(3), V = 460.54(16), Z = 2; PrTbYb{sub 2}S{sub 6}, monoclinic, space group P2{sub 1}/m, a = 10.9496(10), b = 3.9429(4), c = 11.2206(10) {angstrom}, {beta} = 108.525(2), V = 459.33(7), Z = 2; PrDyYb{sub 2}S{sub 6}, monoclinic, space group P2{sub 1}/m, a = 10.9384(10), b = 3.9398(4), c = 11.2037(10) {angstrom}, {beta} = 108.612(2), V = 457.57(7), Z = 2.

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

163

Brilliant photoluminescence and triboluminescence from ternary complexes of Dy(III) and Tb(III) with 3-phenyl-4-propanoyl-5-isoxazolonate and a bidentate phosphine oxide coligand.  

PubMed

Three new lanthanide heterocyclic ?-diketonate complexes [Dy(PPI)3(EtOH)2] (1), [Dy(PPI)3(DPEPO)] (2), and [Tb(PPI)3(DPEPO)] (3) [where HPPI = 3-phenyl-4-propanoyl-5-isoxazolone and DPEPO = bis(2-(diphenylphosphino)phenyl)ether oxide] have been synthesized and fully characterized. Single-crystal X-ray diffraction analyses reveal that these complexes are mononuclear and that the central Ln(III) ion is coordinated to eight oxygen atoms that are provided by three bidentate ?-diketonate ligands and ethanol or bidentate DPEPO in a distorted square antiprismatic geometry. These complexes have high molar absorption coefficients (up to 3 × 10(4) M(-1) cm(-1) at 285 nm) and display strong visible and, for Dy(III), NIR luminescence upon irradiation at the ligand-centered band in the range 250-350 nm. The emission quantum yields and the luminescence lifetimes at room temperature are 3 ± 0.5% and 15 ± 1 ?s for 1, 12 ± 2% and 33 ± 1 ?s for 2, and 42 ± 6% and 795 ± 1 ?s for 3. Moreover, the crystals of 2 and 3 exhibit brilliant triboluminescence, visible in daylight. PMID:23848056

Biju, S; Gopakumar, N; Bünzli, J-C G; Scopelliti, R; Kim, H K; Reddy, M L P

2013-08-01

164

Magnetic properties of cubic R(x)Y(1-x)Al2 (R = Dy,Tb) intermetallic random anisotropy magnets  

NASA Astrophysics Data System (ADS)

A short review is made of the key magnetic properties of dilute cubic R(x)Y(1-x)Al2 (R = Tb, Dy) intermetallics, in order to show their main magnetic features. Dilution by Y introduces a weak random magnetic anisotropy (RMA). The rich magnetic phase diagram is described, including paramagnetic (P), spin glass (SG), correlated spin glass (CSG), random ferromagnetic (RFM), and ferromagnetic (F) phases, with a triple point and two multicritical ones. The paper deals with the induced macroscopic magnetic anisotropy cooling in a magnetic field below T(sub SG) or T(sub CSG) transition temperatures, which can be either unidirectional or uniaxial or both. High-field (3 T) magnetostriction in Tb series shows, for x = 0.48, 0.59, 0.87, a decrease of the Callen alpha exponent (lambda(sub t) approx. equal to m(sup alpha), m = reduced magnetization) below 3. The Sompolinsky irreversibility parameter delta has been determined for the Tb series in the SG regime, and a replica model is presented to explain the delta (T) dependence. The character of the p goes to SG or P goes to CSG transitions is addressed, through the scaling of nonlinear susceptibility (SG regime) or a ferromagnetic-like scaling of magnetization, respectively. From quasielastic neutron scattering around Q = (1,1,1) we determine the temperature dependence of the magnetic correlation length in Dy0.8Y0.2Al2, which peaks, but does not diverge at T(sub c). A magnon excitation at 3.5 meV is reported for x = 0.8.

del Moral, A.; Arnaudas, J. I.; de La Fuente, C.; Ciria, M.; Joven, E.; Gehring, P. M.

1994-11-01

165

Synthesis, Luminescence, and Energy-Transfer Properties of ?-Na2Ca4(PO4)2(SiO4):A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) Phosphors.  

PubMed

A series of ?-Na2Ca4(PO4)2(SiO4) (?-NCPS):A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) phosphors were prepared via a high-temperature solid-state reaction route. The X-ray diffraction, Fourier transform infrared, photoluminescence (PL), cathodoluminescence (CL) properties, fluorescent lifetimes, and absolute quantum yield were exploited to characterize the samples. Under UV radiation, the ?-NCPS:Eu(2+) phosphors present bright green emissions, and the ?-NCPS:Ce(3+) phosphors show strong blue emissions, which are attributed to their 4f(6)5d(1) ? 4f(7) and 5d-4f allowed transitions, respectively. The ?-NCPS:Ce(3+), Tb(3+) phosphors display intense tunable color from blue to green and high absolute quantum yields (81% for ?-NCPS:0.12Ce(3+) and 83% for ?-NCPS:0.12Ce(3+), 0.08Tb(3+)) when excited at 365 nm. Simultaneously, the energy transfer from Ce(3+) to Tb(3+) ions is deduced from the spectral overlap between Ce(3+) emission and Tb(3+) excitation spectra and demonstrated by the change of emission spectra and decay lifetimes. Moreover, the energy-transfer mechanism from Ce(3+) to Tb(3+) ions is confirmed to be exchange interaction according to the discussion of expression from Dexter and Reisfeld. Under a low-voltage electron-beam excitation, the ?-NCPS:A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) phosphors exhibit their characteristic emissions, and the emission profiles of ?-NCPS:Ce(3+),Tb(3+) phosphors are obviously different from those of the PL spectra; this difference might be ascribed to their different luminescence mechanisms. These results in PL and CL properties suggest that ?-NCPS:A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) phosphors are potential candidates for solid-state lighting and field-emission displays. PMID:24905817

Li, Kai; Shang, Mengmeng; Geng, Dongling; Lian, Hongzhou; Zhang, Yang; Fan, Jian; Lin, Jun

2014-07-01

166

Effect of hygroscopic nature on the electrical characteristics of lanthanide oxides (Pr2O3, Sm2O3, Gd2O3, and Dy2O3)  

NASA Astrophysics Data System (ADS)

The hygroscopic nature of lanthanide oxides such as Pr2O3, Sm2O3, Gd2O3, and Dy2O3 was characterized by means of x-ray photoelectron spectroscopy and its effect on the electrical characteristics of the compounds was investigated. Among the four samples, Pr2O3 was found to be the most reactive with water which can be attributed to the relatively large ionic radius and lower electronegativity of Pr. In contrast, Dy2O3 was the least reactive with water. A direct correlation between the hygroscopicity and electronegativity of lanthanide elements was found. With increasing hygroscopicity, a significant growth of interfacial oxide with annealing temperature was observed. A clear understanding of the nature of hygroscopic effects and the optimization of process flow will be needed for future high-k gate dielectric application.

Jeon, Sanghun; Hwang, Hyunsang

2003-05-01

167

Studies of structural, magnetic, electrical and thermal properties in layered perovskite cobaltite SrLnCoO4 (Ln = La, Ce, Pr, Nd, Eu, Gd and Tb)  

Microsoft Academic Search

The structural, magnetic, electrical and thermal properties have been investigated in single-layered perovskite compounds of SrLnCoO4 (Ln = La, Ce, Pr, Nd, Eu, Gd and Tb) with a K2NiF4-type structure. The variation of Jahn-Teller distortion of the CoO6 octahedron reflected by two different Co-O bond lengths indicates that all the samples are mostly accommodated in the t2g orbital states keeping

R. Ang; Y. P. Sun; X. Luo; C. Y. Hao; W. H. Song

2008-01-01

168

Studies of structural, magnetic, electrical and thermal properties in layered perovskite cobaltite SrLnCoO4 (Ln = La, Ce, Pr, Nd, Eu, Gd and Tb)  

Microsoft Academic Search

The structural, magnetic, electrical and thermal properties have been investigated in single-layered perovskite compounds of SrLnCoO4 (Ln = La, Ce, Pr, Nd, Eu, Gd and Tb) with a K2NiF4-type structure. The variation of Jahn–Teller distortion of the CoO6 octahedron reflected by two different Co–O bond lengths indicates that all the samples are mostly accommodated in the t2g orbital states keeping

R Ang; Y P Sun; X Luo; C Y Hao; W H Song

2008-01-01

169

Superconductivity and magnetic order in RSr 2Cu 2.7Mo 0.3O 7-? (R = Y, Pr, Gd, and Tb)  

NASA Astrophysics Data System (ADS)

Polycrystalline samples RSr 2Cu 2.7Mo 0.3O 7-? with R = Y, Pr, Gd, and Tb were synthesized and studied by means of powder X-ray diffraction, electrical resistivity, magnetic susceptibility, and specific-heat measurements. All four samples form a perovskite-layer structure with a tetragonal symmetry. The calculated lattice constants using space group P4/mmm indicate that these rare-earth ions are basically in the 3+ valence state. Samples R = Y, Gd, and Tb are superconducting with transitions at around 30 K, while PrSr 2Cu 2,7Mo 0.3O 7-? remains semiconducting down to 2 K. Effective magnetic moments ?eff derived from a Curie-Weiss-behavior susceptibility for R = Gd and Tb are 7.92 ? B and 9.75 ? B, respectively, which are close to those of trivalent free ions. While the ?eff = 3.05 ?B for R = Pr is smaller than that expected for a Pr 3+ free ion. A magnetic ordering transition is observed by a ?-type anomaly in specific-heat measurements at 2.27 K and 5.43 K for R = Gd and Tb, respectively. In contrast, no significant feature was observed in specific heat for PrSr 2Cu 2.7Mo 0.3O 7-? in the temperature range 0.6-40 K. The similarities and differences in superconducting and magnetic properties between RSr 2Cu 2.7Mo 0.3O 7-? and RBa 2Cu 3O 7-? are discussed.

Tsay, H. L.; Shih, C. R.; Chen, Y. C.; Lee, W. H.; Meen, T. H.; Yang, H. D.

1995-02-01

170

Fabrication and imaging characterization of high sensitive CsI(Tl) and Gd 2O 2S(Tb) scintillator screens for X-ray imaging detectors  

Microsoft Academic Search

Indirect-detection methods consisted of an X-ray converter and photodiode arrays are more widely used in medical diagnosis and industrial fields. Two major scintillation materials such as terbium-doped gadolinium oxysulfide(Gd2O2S:Tb, Gadox) and thallium-doped cesium iodide(CsI:Tl) are commonly used. In this work, Gadox screens were manufactured by particle in binder (PIB) layer method and CsI:Tl scintillator films with columnar structure were also

Bo Kyung Cha; Jong Yul Kim; Tae Joo Kim; Cheulmuu Sim; Gyuseong Cho

2010-01-01

171

Fabrication and comparison Gd2O2S(Tb) and CsI(Tl) films for X-ray imaging detector application  

Microsoft Academic Search

During the last decade, digital X-ray imaging systems have been replacing analog X-ray imaging systems of conventional X-ray film-screen combination for radiography applications. Indirect detection methods consisted of an X-ray converter (or a scintillator film) and photodiode arrays are more widely used in medical diagnoses and industrial fields. Two major scintillation materials such as terbium doped gadolinium oxysulfide (Gd2O2S:Tb, GOS)

Bo Kyung Cha; Jeong-Hyun Shin; Jong Yul Kim; Hosang Jeon; Jun Hyung Bae; Cha-hun Lee; Sungho Chang; Hyoungtaek Kim; Byoung-Jik Kim; Gyuseong Cho

2008-01-01

172

Photophysical properties of Eu 3+, Gd 3+ and Tb 3+ complexes with 2-hydroxy-2,4,6-cycloheptatrien-1-one  

Microsoft Academic Search

The spectroscopic properties (excitation and emission spectra at 4.2,77 and 298 K, and temperature dependent lifetime measurements from 20 to 298 K) of the Gd(trop)3 complex, (trop = C7H5O2?) are reported here. This compound is used to elucidate the lack of luminescence in the isostructural complexes Eu(trop)3 and Tb(trop)3. The results show that the ligand triplet states are at lower

B. S. Santos; C. de Mello Donegá; G. F. de Sá

1997-01-01

173

Preparation, characterization, magnetic susceptibility (Eu, Gd and Sm) and XPS studies of Ln{sub 2}ZrTiO{sub 7} (Ln=La, Eu, Dy and Gd)  

SciTech Connect

Bulk and nanosized pyrochlore materials Ln{sub 2}ZrTiO{sub 7} (Ln=La, Eu, Dy, Gd and Sm) have been prepared by the sol-gel method. All the samples were characterized by powder X-ray diffraction, Raman and X-ray photoelectron spectroscopy. Magnetic susceptibility ({chi}) measurements of Gd{sub 2}ZrTiO{sub 7}, Sm{sub 2}ZrTiO{sub 7} and Eu{sub 2}ZrTiO{sub 7} were carried out by vibrating sample magnetometer in the temperature range 2-320 K. The variation of {chi}{sup -1} (or {chi}) with temperature of Gd{sub 2}ZrTiO{sub 7}, Sm{sub 2}ZrTiO{sub 7} and Eu{sub 2}ZrTiO{sub 7} follows the Curie law, intermediate formula and the Curie-Weiss law, respectively. From the linear portion of {chi}T vs. T{sup -1} plot of Eu{sub 2}ZrTiO{sub 7} from 2 to 15 K, the classical nearest neighbor exchange (J{sup cl}) and dipolar interactions (D{sub nn}) are obtained. The XPS of Ln{sub 2}ZrTiO{sub 7} (Ln=La, Eu, Dy and Gd) gave characteristic peaks for Ln, Ti, Zr and O. The satellite peaks are observed only for 3d La of La{sub 2}ZrTiO{sub 7}. -- Graphical abstract: Sm{sub 2}ZrTiO{sub 7} does not follow the Curie or the Curie-Weiss law. The effective magnetic moment is found to be 0.768 BM (at 300 K), which is smaller than the free ion moment 1.3-1.4 BM. Display Omitted Research Highlights: {yields} Bulk and nano Ln{sub 2}ZrTiO{sub 7} (Ln=La, Eu, Dy, Gd and Sm) have been prepared by the sol-gel method. {yields} The broad Raman lines are attributed to cation disorder and small crystallite size. {yields} XPS of Ln{sub 2}ZrTiO{sub 7} exhibit characteristic X-ray photoelectron spectral features. {yields} Magnetic moment of Gd{sub 2}ZrTiO{sub 7} is obtained from magnetic susceptibility and ESR spectra.

Vijaya Kumar, B.; Velchuri, Radha; Rama Devi, V. [Department of Chemistry, Osmania University, Hyderabad 500 007 (India); Sreedhar, B. [Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Hyderabad 500 007 (India); Prasad, G. [Department of Physics, Osmania University, Hyderabad 500 007 (India); Jaya Prakash, D. [College of Technology, Osmania University, Hyderabad 500 007 (India); Kanagaraj, M.; Arumugam, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620 024 (India); Vithal, M., E-mail: muga_vithal@osmania.ac.i [Department of Chemistry, Osmania University, Hyderabad 500 007 (India)

2011-02-15

174

The effect of complexing processes on energy transfer Tl+{r_arrow}Gd{sup 3} and Tl+{r_arrow}Tb{sup 3+} in glass  

SciTech Connect

The authors` studies have shown that three types of Tl{sup +} luminescence centers are formed in Tl{sup +}-activated chlorine-containing sodium-borate glass. These centers differ from one another in the number of Cl{sup -} ions contained in the first coordination sphere of Tl{sup +}. They were identified accordingly as 0-, 1-, and 2-centers of Tl{sup +}. The excitation (ES) and luminescence (LS) spectra of the 1- and 2-centers of Tl{sup +} are shifted into the region with lower energies in comparison with the spectra of 0-centers of Tl{sup +}, the LS of the 0-centers of Tl{sup +} are overlapped by the absorption spectrum (AS) of Gd{sup 3+} ions, and the LS of the 1- and 2-centers of Tl{sup +} overlaps the spectral range containing Tb{sup 3+} absorption lines. In view of the data on the overlapping of LS of Tl{sup +} ions in sodium-borate glasses by AS of REI (Gd{sup 3} and Tb{sup 3+}), one can expect effective radiationless energy transfer (RLET) Tl{sup +} {yields} Gd{sup 3+} and Tl{sup +} {yields} Tb{sup 3+}, which is an object of study in the present work.

Belyi, M.U.; Bartnitskaya, N.E.; Mel`nik, I.F. [Kiev Univ. (Russian Federation)] [and others

1995-11-01

175

Ce(3+) sensitized GdPO4:Tb(3+) with iron oxide nanoparticles: a potential biphasic system for cancer theranostics.  

PubMed

We report a biphasic system (BPS) consisting of PEGylated Tb(3+)-doped GdPO4 nanorice sensitized with Ce(3+) (PEG-NRs) and glutamic acid coated iron oxide nanoparticles (IONPs) with multifunctional capabilities. The mesoporous PEG-NRs exhibit green light luminescence properties and a high degree of aqueous stability. Their drug loading and release capacities were investigated for anti-cancer chemo doxorubicin (DOX). Their mesoporous nature and availability of plenty of negatively charged functional groups (-COO(-)) on the surface of PEG-NRs facilitate approximately 94 wt% DOX loading. In vitro studies carried out for PEG-NRs and their biphasic integrated system with iron oxide using HeLa and MCF-7 cell lines demonstrated their cell killing efficacy. The green luminescence observed under confocal laser scanning microscopy (CLSM) confirms the cellular uptake of PEG-NRs by HeLa cell lines and their accumulation in the cytoplasm. Approximately 50-55% of HeLa and MCF-7 cell death was observed after 24 h of incubation with DOX loaded BPS (2 mg IONPs and 0.25 mg PEG-NRs + DOX), which further increased to about 90% when exposed to an AC magnetic field (ACMF) for 25 min. Our findings demonstrate that the therapeutic efficacy of BPS loaded with DOX could be a powerful multimodal system for imaging and synergistic chemo-thermal cancer therapy. PMID:24954721

Sahu, Niroj Kumar; Singh, Naorem Shanta; Pradhan, Lina; Bahadur, Dhirendra

2014-08-14

176

Magnetic Properties of Rare-Earth Ferro- and Aluminoborates RM3(BO3)4 (M = Fe OR Al and R = Y, Gd, Er, or Dy)  

NASA Astrophysics Data System (ADS)

A temperature dependence of the magnetic susceptibility [?(T)] of rare-earth borates RFe3(BO3)4 and RAl3(BO3)4 (R = Y, Gd, Er, or Dy) is measured by the Faraday method at temperatures 20-850°C. Nonlinear anomalies observed in the dependences ?-1(T) are caused by structural transitions. It is established that the dependences ?-1(T) obey a linear Curie-Weiss law for each phase. The Curie temperatures and the magnetic moments corresponding to the chemical formula unit of crystals are calculated.

Kuvandikov, O. K.; Leonyuk, N. I.; Shakarov, Kh. O.; Shodiev, Z. M.; Amonov, B. U.; Nurimov, U. É.; Sulaimonov, O. A.

2014-04-01

177

Studies on the new superconducting system (RE) Ba 2 Ca 3 Sr 4 Cu 5 O x (RE=Gd, Ho & Dy)  

Microsoft Academic Search

Superconducting studies have been carried out in the new high TC (50–65K) system (RE)Ba2Ca3Sr4Cu5OX [(RE) 12345] with RE=Gd, Ho&Dy. The unit cell dimensions are of the order of a=5.44 °A, b=5.46°A and c=14.62°A. The data\\u000a above the diamagnetic onset and below the upturn temperature due to ordering were analyzed to yield the effective magnetic\\u000a moments (Peff) of the rare earth

S. Arumugam

1996-01-01

178

Studies on the new superconducting system (RE) Ba2Ca3Sr4Cu5Ox (RE=Gd, Ho & Dy)  

NASA Astrophysics Data System (ADS)

Superconducting studies have been carried out in the new high TC (50-65K) system (RE)Ba2Ca3Sr4Cu5OX [(RE) 12345] with RE=Gd, Ho&Dy. The unit cell dimensions are of the order of a=5.44 °A, b=5.46°A and c=14.62°A. The data above the diamagnetic onset and below the upturn temperature due to ordering were analyzed to yield the effective magnetic moments (Peff) of the rare earth ions.

Arumugam, S.

1996-03-01

179

New layered compounds with the general composition (MO) (CuSe), where M = Bi, Nd, Gd, Dy, and BiOCuS: Syntheses and crystal structure  

SciTech Connect

The syntheses of four new copper oxyselenides with the general formula (MO)(CuSe)(M = Bi, Nd, Gd, Dy) and one copper oxysulfide, BiOCuS, are reported. The tetragonal unit cell dimensions of all compounds are given. A new bismuth-copper oxyselenide, BiOCuSe, has been structurally characterized from powder X-ray diffraction data and finally solved by the Rietveld profile method with R{sub 1} = 0.069. The BiCuSeO crystal structure is formed by alternating [Bi{sub 2}O{sub 2}] and [Cu{sub 2}Se{sub 2}] layers.

Kusainova, A.M.; Berdonosov, P.S.; Kholodkovskaya, L.N. [Moscow State Univ. (Russian Federation)] [and others] [Moscow State Univ. (Russian Federation); and others

1994-09-01

180

New Layered Compounds with the General Composition (MO) (CuSe), Where M = Bi, Nd, Gd, Dy, and BiOCuS: Syntheses and Crystal Structure  

NASA Astrophysics Data System (ADS)

The syntheses of four new copper oxyselenides with the general formula (MO)(CuSe) ( M = Bi, Nd, Gd, Dy) and one copper oxysulfide, BiOCuS, are reported. The tetragonal unit cell dimensions of all compounds are given. A new bismuth-copper oxyselenide, BiOCuSe, has been structurally characterized from powder X-ray diffraction data and finally solved by the Rietveld profile method with RI = 0.069. The BiCuSeO crystal structure is formed by alternating [Bi 2O 2] and [Cu 2Se 2] layers.

Kusainova, A. M.; Berdonosov, P. S.; Akselrud, L. G.; Kholodkovskaya, L. N.; Dolgikh, V. A.; Popovkin, B. A.

1994-09-01

181

Effect of the mechanical activation of Ln2O3 Oxides (with Ln = Gd, Dy, Ho, and Lu) on the surface tension and density of borate melts  

NASA Astrophysics Data System (ADS)

Effect of the mechanical activation of Gd2O3, Dy2O3, Ho2O3, and Lu2O3 oxides on surface tension ? and density ? of borate melts is studied. Linear temperature dependences of ? and ? are found, and the temperature coefficients are calculated. The dependence of ? on the lanthanide number in the periodic table is found and exhibits nonmonotonic behavior of the melts. The effect of mechanical activation on ? and ? is explained by the formation of complex lanthanide ions, which have uniform geometry in the borate melts.

Ivanov, A. V.; Istomin, S. A.; Khokhryakov, A. A.; Chentsov, V. P.; Ryabov, V. V.

2012-08-01

182

The luminous and magnetic properties of Tb3+-doped four angle star-like NaGd(WO4)2.  

PubMed

Four angle star-like double tungstates NaGd(WO4)2 have been prepared hydrothermally with cetyl trimethyl ammonium bromide (CTAB) as the chelating agent and ethanol as the mixing solvent. Monodisperse micron-sized four angle star-like NaGd(WO4)2 were fabricated for the first time. The samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetrometer (VSM) techniques. This work emphasizes the luminescence properties of Tb(3+)-doped NaGd(WO4)2 under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation and the magnetic properties. The results demonstrate the phosphors are expected to have potential applications in weak lighting systems and magnetic resonance imaging. PMID:24734626

Xin, Shuangyu; Wang, Yuhua; Lil, Fenghua; Liu, Bitao; Zhang, Jia; Tao, Ye

2014-05-01

183

Spin-Lattice Coupling in Ferroelectric Spiral Magnets: Comparison between the Cases of (Tb,Dy)MnO3 and CoCr2O4  

NASA Astrophysics Data System (ADS)

Lattice modulation expected for various types of spiral magnetic ordering with a propagation vector Qm is discussed in terms of the symmetric (Si\\cdotSj type) and antisymmetric (Si×Sj type) exchange interactions between neighboring spins (Si and Sj). We show that the conical ordering causes the superlattice modulation with Qm via the antisymetric interaction, while the elliptical deformation of spiral induces a 2Qm modulation in lattice, due to the symmetric and antisymmetric interactions. This theoretical prediction was experimentally confirmed for a transverse elliptical antiferromagnet (Tb,Dy)MnO3 and a transverse conical ferrimagnet CoCr2O4, both accompanied by ferroelectricity (lattice deformation with Q=0) as well.

Arima, Taka-hisa; Yamasaki, Yuichi; Goto, Takeshi; Iguchi, Satoshi; Ohgushi, Kenya; Miyasaka, Shigeki; Tokura, Yoshinori

2007-02-01

184

The generalized planar fault energy, ductility, and twinnability of Al and Al—RE (RE = Sc, Y, Dy, Tb, Nd) at different temperatures: A first-principles study  

NASA Astrophysics Data System (ADS)

The genearlized planar fault energies of Al and Al—RE (RE = Sc, Y, Dy, Tb, Nd) alloys have been investigated using first-principles methods combined with a quasiharmonic approach. The stacking fault energies, unstable stacking fault energies, and unstable twinning energies decrease slightly with increasing temperature. The ductility parameter D, the relative barrier difference ?utus, and the twinnability ?a of Al and Al—RE alloys at different temperatures have been determined. It is found that the ductilities of Al and Al alloys are nearly the same and the ductilities increase slightly with increasing temperature. The RE alloying elements make twinning more likely and the twinnabilities of Al and Al alloys decrease with increasing temperature.

Wu, Xiao-Zhi; Liu, Li-Li; Wang, Rui; Liu, Qing

2014-06-01

185

Magnetic-field-dependent microstructure evolution and magnetic properties of Tb0.27Dy0.73Fe1.95 alloy during solidification  

NASA Astrophysics Data System (ADS)

We report on the influence of magnetic field strength on the alloy Tb0.27Dy0.73Fe1.95 during slow-cooling solidification. We examined the effect of magnetic field strength on microstructure, magnetization, and magnetostrictive properties of this giant magnetostrictive alloy. We found that after field-treated solidification, the microstructure of specimens had a distinct grain arrangement and displayed magnetic anisotropy. The crystal orientation changed from random in the field-free treatment to aligned along the <110> direction in flux densities of 1 and 2.2 T, and along the easy magnetization axis <111> at a flux density of 4.4 T. In consequence, the magnetostrictive coefficient of the samples under various stresses improved with increasing magnetic flux density. Both the d33 and k33 values and the energy transformation efficiency of the field-treated specimens showed strong enhancements.

Liu, Yin; Wang, Qiang; Kazuhiko, Iwai; Yuan, Yi; Liu, Tie; He, Jicheng

2014-05-01

186

Anisotropic magnetic properties and giant magnetocaloric effect in antiferromagnetic RMnO3 crystals (R=Dy, Tb, Ho, and Yb)  

NASA Astrophysics Data System (ADS)

We have systematically investigated the magnetic properties and magnetocaloric effect (MCE) in RMnO3 (R=Dy, Tb, Ho, and Yb) single crystals. Above a critical value of applied field (Hc), RMnO3 undergo a first-order antiferromagnetic (AFM) to ferromagnetic (FM) transition below the ordering temperature (TNR) of R3+ moment and a second-order FM to paramagnetic (PM) transition above TNR. Both H and T dependence of M shows that the system is highly anisotropic in the FM as well as PM states and, as a result, the magnetic entropy change (?SM) is extremely sensitive to the direction of applied field and can be negative (normal MCE) or positive (inverse MCE). For hexagonal HoMnO3 and YbMnO3 systems, a very small inverse MCE is observed only for H parallel to c axis and it decreases with increasing H and crosses over to normal one above Hc. On the other hand, for orthorhombic DyMnO3 and TbMnO3, though the inverse MCE disappears above Hc along easy axis of magnetization, it increases rapidly with H along hard axis of magnetization for T?TNR. Except for YbMnO3, the values of ?SM, relative cooling power and adiabatic temperature change along easy axis of magnetization are quite large in the field-induced FM state for a moderate field strength. The large values of these parameters, together with negligible hysteresis, suggest that the multiferroic manganites could be potential materials for magnetic refrigeration in the low-temperature region.

Midya, A.; Das, S. N.; Mandal, P.; Pandya, S.; Ganesan, V.

2011-12-01

187

Triple-layered perovskite niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y): new self-activated oxides.  

PubMed

Niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y) were prepared by conventional high-temperature solid-state reaction. The formation of a single-phase compound with triple-layered perovskite-type structure was verified through X-ray diffraction (XRD) studies. The luminescence characteristics such as photoluminescence excitation and emission spectra, X-ray-excited luminescence (XEL), Stokes shift, decay curves, and color coordinates were investigated. The niobates can be efficiently excited by UV light and present luminescence behaviors with rich luminescence colors. Under excitation by ultraviolet radiation, CaRNb3O10 (R = La, Gd, Yb, or Y) exhibits strong blue luminescence due to the self-activation center of the octahedral NbO6 groups, even at room temperature. For the materials of composition CaRNb3O10 (R = Sm, Eu, Dy, or Er), the excitation at the host band produces a characteristic luminescence of rare earth ions, indicating a host-guest energy transfer process. CaRNb3O10 (R = Eu) has the strongest luminescence intensity, which can be efficiently excitated by near UV wavelength. It could be suggested to be a potential candidate for the application on near-UV excited white LEDs. PMID:23977903

Qin, Lin; Wei, Donglei; Huang, Yanlin; Kim, Sun Il; Yu, Young Moon; Seo, Hyo Jin

2013-09-16

188

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

SciTech Connect

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

Zhang, Z. J.; Yuan, J. L.; Duan, C. J.; Xiong, D. B.; Chen, H. H.; Zhao, J. T.; Zhang, G. B.; Shi, C. S. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China) and Graduate School of Chinese Academy of Science, Beijing 100039 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Heifei 230026 (China)

2007-11-01

189

Decay studies of neutron-deficient nuclei near the Z=64 subshell: 141Dy, 141Tb, 141Gdg+m, and 141Eum  

NASA Astrophysics Data System (ADS)

The ?/? and delayed proton decays of mass separated A=141 isotopes with Z=63-66 were investigated with an on-line mass separator. Branching ratios have been redetermined for the total ? decay of the 2.7(3) s, (11/2- isomer 141Eum at 96.5 keV (13+4-2%), and for the direct ? feeding of the 1.58 keV (3/2+ level of 141Sm in the decay of 40-s 141Eug [73(5)%]. Detailed decay schemes have been constructed for the decays of the (11/2- isomer 141Gdm [11(2)% isomeric transition] and the (1/2+ ground state, 141Gdg. Half-lives of 24.5(5) s and 14(4) s, respectively, have been determined for these isomers. A delayed proton branch of 0.03(1)% was identified in the decay of 141Gdg. A detailed decay scheme was also constructed for 3.5(2)-s 141Tb and a J?=(5/2- was assigned to its ground state, at variance with the systematics of heavier, odd-mass Tb isotopes. All ?-ray assignments to the various isotopes are based on x? and ?? coincidences and on half-life measurements. A 0.9(2)-s half-life for 141Dy was determined from its delayed proton decay. All spin assignments proposed in this paper are discussed in terms of Nilsson level diagrams and nuclear shapes.

Gilat, J.; Nitschke, J. M.; Wilmarth, P. A.; Firestone, R. B.

1989-11-01

190

Systematic studies of the structures and magnetic properties for a family of cubane complexes with the formula: [M2Ln2] (Ln = Dy, Gd; M = Ni, Zn) and [Ni2Y2].  

PubMed

Studies of magnetic properties of a family of tetranuclear M(II)(2)Ln(III)(2) (M = Ni, Zn; Ln = Dy, Gd and Y) complexes with hmp (anion of 2-hydroxymethylpyridine) and benzoate as ligands are reported. In these complexes, metal ions (M or Ln) occupy the four alternative corners of a distorted cubane with oxygen atoms from alkoxyl groups on the others. Complexes 1, 2 and 3 crystallized in P2(1)/c and complexes 4 and 5 in C2/c space groups. Although in different space groups, complexes 1-5 have very similar structures which permit the magnetic interactions to be systematically compared with respect to metal ion pairs. In complex 3 (Ni(2)Y(2)), clear ferromagnetic coupling between Ni(II) ions can be seen, with: g = 2.16, S = 2, D = -0.95 cm(-1), J = +3.77 cm(-1) (or g = 2.20, S = 2, D = +1.51 cm(-1)). In complex 5 (Zn(2)Gd(2)), a very weak antiferromagnetic coupling between the Gd(III) ions was observed: g = 2.08, J = -0.05 cm(-1). Based on these data, we concluded that the decrease in ?(M)T-T upon cooling for complex 2 (Zn(2)Dy(2)) might be partly due to antiferromagnetic coupling between Dy(III) ions. The data from complex 4 (Ni(2)Gd(2)) were analyzed based on the preceding results and gave moderate ferromagnetic coupling between Ni(II) and Gd(III) with J = 0.26 cm(-1). A detailed study of magnetic properties of complex 1 (Ni(2)Dy(2)) was not possible, because of its strong orbital contributions from Dy(III) ions. In addition, frequency-dependent out-of-phase signals were clearly observed for both complexes 1 and 2 which can be attributed to magnetoanisotropy contributions from Dy(III) ions. PMID:23334432

Yu, Wan-Rong; Lee, Gene-Hsian; Yang, En-Che

2013-03-21

191

Ba2LnSbO6 and Sr2LnSbO6 (Ln = Dy, Ho, Gd) double perovskites: Lanthanides in the geometrically frustrating fcc lattice  

PubMed Central

Magnetic ground states in solids often arise as a result of a delicate balance between competing factors. One currently active area of research in magnetic materials involves compounds in which long-range magnetic ordering at low temperatures is frustrated by the geometry of the crystalline lattice, a situation known as geometrical magnetic frustration. The number of systems known to display the effects of such frustration is growing, but those that are sufficiently simple from theoretical, chemical, and physical perspectives to allow for detailed understanding remain very few. A search for model compounds in this family has led us to the double perovskites Ba2LnSbO6 and Sr2LnSbO6 (Ln = Dy, Ho, and Gd) reported here. Ba2DySbO6,Ba2HoSbO6,Sr2DySbO6, and Sr2HoSbO6 are structurally characterized by powder neutron diffraction at ambient temperature. The trivalent lanthanides and pentavalent antimony are found to be fully ordered in the double-perovskite arrangement of alternating octahedra sharing corner oxygens. In such a structure, the lanthanide sublattice displays a classical fcc arrangement, an edge-shared network of tetrahedra known to result in geometric magnetic frustration. No magnetic ordering is observed in any of these compounds down to temperatures of 2 K, and in the case of the Dy-based compounds in particular, frustration of the magnetic ordering is clearly present. Lanthanide-based double perovskites are proposed to be excellent model systems for the detailed study of geometric magnetic frustration.

Karunadasa, H.; Huang, Q.; Ueland, B. G.; Schiffer, P.; Cava, R. J.

2003-01-01

192

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Hydrothermal Synthesis and Vacuum Ultraviolet-Excited Luminescence Properties of Novel Dy3+-doped GdPO4 White Light Phosphors  

NASA Astrophysics Data System (ADS)

Novel Dy3+-doped GdPO4 white light phosphors with a monoclinic system are successfully synthesized by the hydrothermal method at 240°C. The strong absorption at around 147 nm in the excitation spectrum is assigned to the host absorption. It is suggested that the vacuum ultraviolet excited energy is transferred from the host to the Dy3+ ions. The f - d transition of the Dy3+ ion is observed to be located at 182 nm, which is consistent with the calculated value using Dorenbos's expression. Under 147nm excitation, Gd0.92PO4:0.08Dy3+ phosphor exhibits two emission bands located at 572 nm (yellow) and 478 nm (blue), which correspond to the hypersensitive transitions 4F9/2-6H13/2 and 4F9/2-6H15/2. The two emission bands lead to the white light. Because of the strong absorption at about 147nm, Gd0.92PO4:0.08Dy3+ under vacuum ultraviolet excitation is an effective white light phosphor, and has promising applications to mercury-free lamps.

Han, Guo-Cai; Wang, Yu-Hua; Wu, Chun-Fang; Zhang, Jia-Chi; Lu, Yang-Hua

2009-06-01

193

Determination of Some Rare Earth Elements in High Purity Y2O3, Gd2O3 and Dy2O3 by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES).  

National Technical Information Service (NTIS)

A method is described for the determination of four trace rare earth elements in high purity Y/sub 2/O/sub 3/, Gd/sub 2/O/sub 3/ and Dy/sub 2/O/sub 3/ using inductively coupled plasma atomic emission spectrometry (ICP-AES). Due to the complex spectrum of ...

P. Sreerama Murty S. S. Biswas V. R. Nair

1988-01-01

194

Solid solutions in the systems Ln/sub 2/TiO/sub 5/-Lu/sub 2/TiO/sub 5/ (Ln = Gd, Tb, Er)  

SciTech Connect

Depending on the ionic radius of the cation and the temperature, titanates of rare-earth elements with the composition Ln/sub 2/TiO/sub 5/ crystallize in the orthorhombic, hexagonal, or cubic systems. In our work we considered the region of existence of solid solutions between rare-earth titanates of one type. The authors studied the pseudobinary systems Ln/sub 2/TiO/sub 5/-Lu/sub 2/TiO/sub 5/ (Ln = Gd, Tb, Er), and obtained data on the melting point, the polymorphous transformation temperature, and the lattice constants of the compounds Ln/sub 2/TiO/sub 5/ Ln = Ge, Tb, Er, and Lu).

Petrova, M.A.; Novikova, A.S.; Romanov, D.P.; Grebenshchikov, R.G.

1986-12-01

195

Microscopic Evidence of Spin State Order and Spin State Phase Separation in Layered Cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho  

Microsoft Academic Search

We report muon-spin relaxation measurements on the magnetic structures of RBaCo2O5.5 with R=Y, Tb, Dy, and Ho. Three different phases, one ferrimagnetic and two antiferromagnetic, are identified below 300 K. They consist of different ordered spin state arrangements of high-, intermediate-, and low-spin Co3+ of CoO6 octahedra. Phase separation into well separated regions with different spin state order is observed

H. Luetkens; M. Stingaciu; Yu. G. Pashkevich; K. Conder; E. Pomjakushina; A. A. Gusev; K. V. Lamonova; P. Lemmens; H.-H. Klauss

2008-01-01

196

Thermal activation, cathodo- and photoluminescence measurements of rare earth doped (Tm, Tb, Dy, Eu, Sm, Yb) amorphous\\/nanocrystalline AlN thin films prepared by reactive rf-sputtering  

Microsoft Academic Search

We present comprehensive cathodo- and photoluminescence measurements from thin amorphous\\/nanocrystalline (a\\/nc-) AlN films doped with rare earths. The (a\\/nc-) AlN films were prepared by reactive rf-sputtering using a high purity (5N) aluminium disk in high purity nitrogen atmosphere (5N, pressure ca. 1.3mbar). The rare earth doping (Tm,Tb,Dy,Eu,Sm,Yb, concentrations were below 1%) was performed by placing respective rare earth metal pieces

R. Weingärtner; O. Erlenbach; A. Winnacker; A. Welte; I. Brauer; H. Mendel; H. P. Strunk; C. T. M. Ribeiro; A. R. Zanatta

2006-01-01

197

Heat capacities, magnetic properties, and resistivities of ternary RPdBi alloys where R = La, Nd, Gd, Dy, Er, and Lu  

SciTech Connect

Over the past four and a half decades research on the rare earths, their compounds, and their alloys has yielded significant insights into the nature of materials. The rare earths can be used to systematically study a series of alloys or compounds. Magnetic ordering, crystalline fields, spin fluctuations, the magnetocaloric effect, and magnetostriction are a small sample of phenomena studied that are exhibited by the rare earth family. A significant portion of research has been conducted on the abundant RM{sub 2} and RM phases, where R is the rare earth and M is a transition metal. The natural progression of science has led to the study of related RMX ternary phases, where X is either another transition metal or semimetal. There are now over 1,000 known RMX phases. The focus of this study is on RPdBi where R = La, Nd, Gd, Dy, Er, and Lu. Their heat capacities, magnetic properties, and resistivities are studied.

Riedemann, T.M.

1996-05-01

198

Self-assembled 3D sphere-like SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) microarchitectures: Facile sonochemical synthesis and optical properties.  

PubMed

Three-dimensional (3D) well-defined SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures of obvious sphere-like shape have been successfully synthesized using a large-scale and facile sonochemical route without using any catalysts or templates. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of SrMoO4 and external factor, namely the ultrasonic time and the pH value, are responsible for the ultimate shape evolutions of the product. The possible formation mechanism for the product is presented. Additionally, the PL properties of SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures were investigated in detail. The Ln(3+) ions doped SrMoO4 samples exhibit respective bright red-orange, yellow, green and white light of Eu(3+), Sm(3+), Tb(3+) and Dy(3+) under ultraviolet excitation, and have potential application in the field of color display. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating about the properties of molybdate materials. PMID:24746510

Zhang, Junjun; Li, Ruiqing; Liu, Lu; Li, Linlin; Zou, Lianchun; Gan, Shucai; Ji, Guijuan

2014-09-01

199

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

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.

Zhang Weiguang, E-mail: zhangweiguang68@yahoo.com.cn [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, Huaiyin Normal University, Jiangsu Province, 223300 (China); Zhang Lili; Zhong Hui [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, Huaiyin Normal University, Jiangsu Province, 223300 (China); Lu Lude; Yang Xujie [Materials Chemistry Laboratory, Nanjing University of Science and Technology, Nanjing 210094 (China); Wang Xin, E-mail: wangx@mail.njust.edu.cn [Materials Chemistry Laboratory, Nanjing University of Science and Technology, Nanjing 210094 (China)

2010-02-15

200

Sintering, microstructure and microwave dielectric properties of rare earth orthophosphates, RePO{sub 4} (Re = La, Ce, Nd, Sm, Tb, Dy, Y, Yb)  

SciTech Connect

Various rare earth orthophosphates, such as monazite and xenotime RePO{sub 4} (Re = La, Ce, Nd, Sm, Tb, Dy, Y, Yb) were prepared by a conventional solid-state reaction method. The crystal structure and microstructure of the sintered ceramics were investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The dielectric properties were measured in the microwave region using a network analyzer. It was found that the monazite RePO{sub 4} could be sintered near 1400 deg. C, although the xenotime RePO{sub 4}, which had a smaller Re{sup 3+} ionic radius, could be sintered above 1600 deg. C. The permittivity ({epsilon}{sub r}) of the monazite structures was higher than that of the xenotime structures. This difference was explained by the differences in ionic polarizability and bond strength. Both monazite and xenotime rare earth orthophosphates, however, exhibited a high quality factor (Q x f), where Q = 1/tan {delta} and f is the measuring frequency, of greater than 60,000 GHz. The temperature coefficient of resonant frequency ({tau}{sub f}) was a negative value, ranging between -17 and -56 ppm/deg. C.

Cho, In-Sun; Choi, Geun Kyu; An, Jae-Sul [School of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Jeong-Ryeol [168 Materials Research Lab., Pennstate University, University Park, PA 16802 (United States); Hong, Kug Sun [School of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)], E-mail: kshongss@plaza.snu.ac.kr

2009-01-08

201

Large Spin-Relaxation Barriers for the Low-Symmetry Organolanthanide Complexes [Cp*2 Ln(BPh4 )] (Cp*=pentamethylcyclopentadienyl; Ln=Tb, Dy).  

PubMed

Single-molecule magnets comprising one spin center represent a fundamental size limit for spin-based information storage. Such an application hinges upon the realization of molecules possessing substantial barriers to spin inversion. Axially symmetric complexes of lanthanides hold the most promise for this due to their inherently high magnetic anisotropies and low tunneling probabilities. Herein, we demonstrate that strikingly large spin reversal barriers of 216 and 331?cm(-1) can also be realized in low-symmetry lanthanide tetraphenylborate complexes of the type [Cp*2 Ln(BPh4 )] (Cp*=pentamethylcyclopentadienyl; Ln=Tb (1) and Dy (2)). The dysprosium congener showed hysteretic magnetization data up to 5.3?K. Further studies of the magnetic relaxation processes of 1 and 2 under applied dc fields and upon dilution within a matrix of [Cp*2 Y(BPh4 )] revealed considerable suppression of the tunneling pathway, emphasizing the strong influence of dipolar interactions on the low-temperature magnetization dynamics in these systems. PMID:24975126

Demir, Selvan; Zadrozny, Joseph M; Long, Jeffrey R

2014-07-28

202

A Mechanism of the influence of Gd(III) and other Ln(III) ions on sensitized luminescence of Eu(III) and Tb(III) ions in aqueous and ethanol solutions: The role of hydroxyl bridges  

Microsoft Academic Search

We studied sensitization of Eu(III) and Tb(III) ions by molecules of 1,10-phenanthroline and 2,2-bipyridil in D2O and d\\u000a 6-ethanol and the influence of Nd(III), Pr(III), Sm(III), Gd(III), and Ho(III) ions on the luminescence intensity I\\u000a lum and lifetime ?lum of Eu(III) and Tb(III) in solutions. The stability constants of complexes of Eu(III) and Gd(III) with 2,2?-bipyridil are\\u000a measured by spectrophotometric

E. B. Sveshnikova; V. E. Lanin; E. V. Krutineva; V. L. Ermolaev

2000-01-01

203

Syntheses, structures, and properties of high-nuclear 3d-4f clusters with amino acid as ligand: {Gd6Cu24}, {Tb6Cu26}, and {(Ln6Cu24)2Cu} (Ln = Sm, Gd).  

PubMed

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. PMID:16933917

Zhang, Jian-Jun; Hu, Sheng-Min; Xiang, Sheng-Chang; Sheng, Tianlu; Wu, Xin-Tao; Li, Ya-Min

2006-09-01

204

Color tunable emission in Ce3+ and Tb3+ co-doped Ba2Ln(BO3)2Cl (Ln = Gd and Y) phosphors for white light-emitting diodes  

NASA Astrophysics Data System (ADS)

Ce3+ and Tb3+ co-doped Ba2Ln(BO3)2Cl (Ln = Y and Gd) green emitting phosphors were prepared by solid state reaction in reductive atmosphere. The emission and excitation spectra as well as luminescence decays were investigated, showing the occurrence of efficient energy transfer from Ce3+ to Tb3+ in this system. The phosphors exhibit both a blue emission from Ce3+ and a green emission from Tb3+ under near ultraviolet light excitation with 325-375 nm wavelength. Emission colors of phosphors could be tuned from deep blue through cyan to green by adjusting the Tb3+ concentrations. The energy transfer efficiency and emission intensity of Ba2Y(BO3)2Cl:Ce3+, Tb3+ precede those of Ba2Gd(BO3)2Cl:Ce3+, Tb3+, and the sample Ba2Y(BO3)2Cl:0.03Ce3+, 0.10Tb3+ is the best candidate for n-UV LEDs.

Zhang, Niumiao; Guo, Chongfeng; Jing, Heng; Jeong, Jung Hyun

2013-12-01

205

Facile template free synthesis of Gd2O(CO3)2·H2O chrysanthemum-like nanoflowers and luminescence properties of corresponding Gd2O3:RE3+ spheres.  

PubMed

Trivalent rare-earth (RE(3+) = Eu(3+), Tb(3+), Dy(3+), and Sm(3+)) ions activated Gd2O(CO3)2·H2O chrysanthemum-like flowers are prepared by a modified urea-based homogeneous precipitation via a template free hydrothermal synthesis route. Subsequently, Gd2O3 monodispersed spheres were obtained after calcining at 750 °C. The growth mechanism of the Gd2O(CO3)2·H2O:RE(3+) chrysanthemum-like morphology (homogeneous precipitation) and their transformation to monodispersed spheres (heterogeneous nucleation) are established by taking scanning electron microscope and transmission electron microscope images of the intermediate products. The thermogravimetric analysis, Fourier transform infrared analyses confirmed the decomposition of CO2 and OH groups, and the corresponding XRD patterns exhibited the Gd2O(CO3)2·H2O and cubic Gd2O3 phases. The photoluminescence measurements are used to explore the emission behavior of different RE(3+) ions activated Gd2O3 spheres. The Gd2O3:Eu(3+) shows gorgeous red emission with high purity red color as compared to the commercial Y2O3:Eu(3+) phosphors. Gd2O3:Tb(3+), Gd2O3:Dy(3+) and Gd2O3:Sm(3+) exhibit green, yellow and rich orange emissions, respectively. The Tb(3+)/Eu(3+) co-doped sample shows warm white light by controlling the energy transfer. At minimal parameters, the cathodoluminescence intensity of Gd2O3:Eu(3+) is beyond the experimental limit for 5 kV of accelerating voltage. The CIE chromaticity coordinates were also calculated from the PL and CL spectra of RE(3+) ions to establish their color richness. PMID:23817306

Raju, G Seeta Rama; Pavitra, E; Yu, Jae Su

2013-08-28

206

Preparation, patterning and luminescent properties of nanocrystalline Gd 2O 3:A (A=Eu 3+, Dy 3+, Sm 3+, Er 3+) phosphor films via Pechini sol–gel soft lithography  

Microsoft Academic Search

Nanocrystalline Gd2O3:A (A=Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol–gel process combined with a soft lithography. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy, UV\\/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that

M. L Pang; J. Lin; J. Fu; R. B Xing; C. X. Luo; Y. C Han

2003-01-01

207

Collective phase-like mode and the role of lattice distortions at TN ˜ TC in RMn2O5 (R= Pr, Sm, Gd, Tb, Bi)  

NASA Astrophysics Data System (ADS)

We report on electronic collective excitations in RMn2O5 (R =Pr, Sm, Gd, Tb) showing condensation starting at and below ˜ TN ˜ TC ˜ 40-50 K. Their origin is understood as partial delocalized eg electron orbitals in the Jahn-Teller distortion of the pyramid dimer with strong hybridized Mn3+-O bonds. Our local probes, Raman, infrared, and x-ray absorption, back the conclusion that there is no structural phase transition at TN ˜ TC. Ferroelectricity is magnetically assisted by electron localization triggering lattice polarizability by unscreening. We have also found phonon hardening as the rare earth is sequentially replaced. This is understood as a consequence of lanthanide contraction. It is suggested that partially f-electron screened rare earth nuclei might be introducing a perturbation to eg electrons prone to delocalize as the superexchange interaction takes place.

Massa, Néstor E.; García-Flores, Ali F.; De Sousa Meneses, Domingos; del Campo, Leire; Echegut, Patrick; Fabbris, Gilberto F. L.; Jesús Martínez-Lope, María; Alonso, José Antonio

2012-05-01

208

Study on the co-luminescence effect of Tb-Gd-epinephrine system and its application to the sensitive determination of epinephrine at nanomol level.  

PubMed

A new fluorimetric method for the determination of epinephrine is established by rare earth co-luminescence effect of Tb-Gd-E-Tris system. Under optimum conditions, a linear relationship has been obtained between the fluorescence intensity and the concentration of epinephrine in the range of 1.8x10(-8) to 2.5x10(-6)mol/l, and the detection limit is 4.5x10(-9)mol/l (S/N=3). The method is applied for the determination of epinephrine in injection and the recovery test in urine by standard addition method, and the results obtained are satisfactory. The mechanism of the co-luminescence in the system was also discussed. PMID:19073020

Guo, Yumei; Yang, Jinghe; Wu, Xia; Mao, Hongzhi

2007-09-15

209

Magnetic properties of quadruple perovskites Ba{sub 4}LnRu{sub 3}O{sub 12} (Ln=La, Nd, Sm-Gd, Dy-Lu)  

SciTech Connect

Quadruple perovskites Ba{sub 4}LnRu{sub 3}O{sub 12} (Ln=La, Nd, Sm-Gd, Dy-Lu) were prepared and their magnetic properties were investigated. They adopt the 12L-perovskite-type structure consisting of Ru{sub 3}O{sub 12} trimers and LnO{sub 6} octahedra. All of these compounds show an antiferromagnetic transition at 2.5-30 K. For Ba{sub 4}NdRu{sub 3}O{sub 12}, ferrimagnetic ordering has been observed at 11.5 K. The observed magnetic transition is due to the magnetic behavior of the Ru{sup 4.33+}{sub 3}O{sub 12} trimer with S=1/2 . Magnetic properties of Ba{sub 4}LnRu{sub 3}O{sub 12} were compared with those of triple perovskites Ba{sub 3}LnRu{sub 2}O{sub 9} and double perovskites Ba{sub 2}LnRuO{sub 6}. - Graphical abstract: Quadruple perovskites Ba{sub 4}LnRu{sub 3}O{sub 12} (Ln=La, Nd, Sm-Gd, Dy-Lu) were prepared. They adopt the 12L-perovskite-type structure consisting of Ru{sub 3}O{sub 12} trimers and LnO{sub 6} octahedra. All of these compounds show an antiferromagnetic transition at 2.5-30 K. For Ba{sub 4}NdRu{sub 3}O{sub 12}, ferrimagnetic ordering has been observed at 11.5 K. The observed magnetic transition is due to the magnetic behavior of the Ru{sup 4.33+}{sub 3}O{sub 12} trimer with S=1/2 . Magnetic properties of Ba{sub 4}LnRu{sub 3}O{sub 12} were compared with those of triple perovskites Ba{sub 3}LnRu{sub 2}O{sub 9} and double perovskites Ba{sub 2}LnRuO{sub 6}.

Shimoda, Yuki; Doi, Yoshihiro; Wakeshima, Makoto [Division of Chemistry, Hokkaido University, Sapporo 060-0810 (Japan); Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.j [Division of Chemistry, Hokkaido University, Sapporo 060-0810 (Japan)

2010-01-15

210

Suitability of the rare-earth compounds Dy2Ti2O7 and Gd3Al5O12 for low temperature (4K-20K) magnetic refrigeration cycle  

NASA Technical Reports Server (NTRS)

Measurements were made of the magnetic entropy and magnetization of powered samples of the compounds Dy2Ti2O7 and Gd3Al5O12. The magnetization was measured for temperatures at and below 4.2 K, in applied fields ranging to 7.0 tesla. Isothermal changes in magnetic entropy were measured for temperatures from 1.2 to 20 K, in applied fields up to 10 tesla. The results of the measurements are consistent with a doublet ground state for Dy2Ti2O7, and an eight-fold degenerate ground state for Gd3Al5O12. Absolute values of magnetic entropy have been obtained at the lower temperatures, permitting the isotherms to be properly located in the S-H plane with the use of adiabatic magnetization data. The iso-field lines in the S-T plane were determined. The results indicate that Dy2Ti2O7 can absorb a maximum of 71 + or - 4 joules/kg of heat at 4.2 K, while Gd3Al5O12 can absorb 233 + or - joules/kg at the same temperature. The large difference between the two is most likely a result of crystal field interactions in the dysoprosium compound. Both materials can be cycled adiabatically between 4.2 and 20 K.

Flood, D. J.

1973-01-01

211

Octanuclear Mn(III)6Mn(II)Ln (Ln = Gd, Dy and Er) clusters with a novel core topology: syntheses, structures, and magnetic properties.  

PubMed

Reactions of [Mn6O2(piv)10(py)2.5(piv)1.5], Ln(NO3)3·6H2O and N-mdeaH2 in MeCN in the presence of Me3SiCl generated a family of octanuclear Mn/Ln complexes [Mn6(III)Mn(II)Ln(N-mdea)3(N-mdeaH)(piv)8O2(OH)3(NO3)(H2O)]·xCH3CN·xH2O [Ln = Gd (1), Dy (2), Er (3), pivH = pivalic acid, N-mdeaH2 = N-methyl diethanolamine]. Each complex possesses a [Mn6(III)Mn(II)Ln(?3-O)2(?3-OH)3](16+) core containing two butterfly-like subunits of [Mn3Ln(?3-OH)2] and [Mn4(?3-O)2] sharing a common vertex, and an outer Mn atom ligated to one of the subunits through a ?3-OH(-) ligand. The core topology represents a new Mn/Ln core type. The magnetic susceptibility study of 1-3 indicates the presence of dominant antiferromagnetic interactions within the complexes. For complex 1, which contains an isotropic Gd(III) atom, fitting of the obtained M/(N?B) vs. H/T data gave S = 4, g = 1.90, and D = -0.31 cm(-1). The results were further supported by ac data. Complex exhibits out-of-phase ac susceptibility signals, indicating it may be a SMM. PMID:23377042

Chen, Hui; Ma, Cheng-Bing; Hu, Ming-Qiang; Wen, Hui-Min; Cui, Hong-Hua; Liu, Jin-Ying; Song, Xiao-Wei; Chen, Chang-Neng

2013-04-14

212

Preparation and Dielectric Measurements of the Rare Earth Green Phases R2BaCuO(5-x) (R = Y, Sm, Gd, Dy, Ho, Er, Yb)  

NASA Technical Reports Server (NTRS)

It has been demonstrated that R2BaCuO(5-x) (R = Y, Sm, Gd, Dy, Ho, Er, Yb) does not undergo significant densification unless the sintering temperatures are near the incongruent melting point or the sintering times are long. Good quality powders of Y2BaCuO(5-x) have been synthesized by using oxide raw materials or precursors such as acetates and nitrates. The acetates- and the nitrates-derived yttrium green phase resulted in finer particle sizes, acceptable dielectric properties and lower melting temperatures than those processed via oxide raw materials. The hot pressing technique has been employed to produce a dense R2BaCuO(5-x) (R=Y,Gd) substrate with satisfactory dielectric properties. Reactivity to reducing conditions, i.e. graphite die, limited the optimization of the properties. A high sensitivity to the annealing atmosphere has been demonstrated in Y2BaCuO,.,,. Oxygen treatment at 950 OC has been shown to improve the dielectric properties while treatment in nitrogen, at the same temperature, degraded desirable properties. A high sensitivity to the annealing atmosphere has been demonstrated in Y2BaCuO(5-x). Oxygen treatment at 950 C has been shown to improve the dielectric properties while treatment in nitrogen, at the same temperature, degraded desirable properties. The dielectric constants of the rare earth green phases R2BaCuO(5-x) were found to be low. Relaxation peaks were detected at low temperatures (T less than 150 K) and at high temperatures (150 less than T greater than 420 K). The dielectric losses and conductivities at 77 K were measured to be in the range of 10(exp -4) and 10(exp -12) (Omega-cm)(exp -1), respectively. Many parameters were found to exhibit dependencies on the rare earth cation sizes.

Gonzalez-Titman, Carlos

1994-01-01

213

A Mechanism of the Influence of Gd(III) and Other Ln(III) Ions on Sensitized Luminescence of Eu(III) and Tb(III) Ions in Aqueous and Ethanol Solutions: The Role of Hydroxyl Bridges  

NASA Astrophysics Data System (ADS)

We studied sensitization of Eu(III) and Tb(III) ions by molecules of 1,10-phenanthroline and 2,2-bipyridil in D2O and d 6-ethanol and the influence of Nd(III), Pr(III), Sm(III), Gd(III), and Ho(III) ions on the luminescence intensity I lum and lifetime ?lum of Eu(III) and Tb(III) in solutions. The stability constants of complexes of Eu(III) and Gd(III) with 2,2'-bipyridil are measured by spectrophotometric and luminescence methods. It is shown that luminescence of Eu(III) is quenched by Gd(III) ions at the ion concentration equal to 10-2 10-1 M, which is caused by competing between these ions for a sensitizer. At the concentration of Ln(III) ions equal to 10-6-10-3 M, the sensitized luminescence of Eu(III) and Tb(III) was quenched and ?lum decreased in the presence of Nd(III) ions, whereas in the presence of Gd(III) the luminescence intensity increased. It is proved that a bridge that connects the two ions upon energy transfer is formed by hydroxyl groups. The intensity of luminescence of Eu(III) and Tb(III) in aqueous solutions and its lifetime decreased in the presence of hydroxyl groups, while upon addition of Gd(III) to these solutions these quantities were restored. We also found that the addition of Gd(III) to deoxygenated ethanol solutions of 2,2'-bipyridil and Eu(III) slows down photochemical and thermal reactions between bipyridil and Eu(III), resulting in the increase in the luminescence intensity of Eu(III).

Sveshnikova, E. B.; Lanin, V. E.; Krutineva, E. V.; Ermolaev, V. L.

2000-09-01

214

Structure and magnetic properties of sulfides of the type Cd RE2S 4 and Mg(Gd xYb 1- x) 2S 4  

NASA Astrophysics Data System (ADS)

Cd RE2S 4 ( RE = Gd, Tb, Dy, Ho, Er, Tm, and Yb) and Mg(Gd xYb 1- x) 2S 4 were prepared by solid-state reactions. All the cadmium-containing compounds are cubic, i.e., the Th 3P 4 structure for Gd, Tb, and Dy and the spinel type for all the others. The first three compounds were deficient in CdS. In the case of the Mg system, for x = 1 the system is cubic Th 3P 4, for x = 0 cubic spinel, and for 0 < x < 1 orthorhombic MnY 2S 4 (Cmc2 1). All the materials studied are paramagnetic above 77 K. Below 77 K in the magnesium family both cubic materials are paramagnetic down to 4.2 K and the orthorhombic materials show magnetic ordering. In the cadmium family all but CdTm 2S 4 show exchange coupling.

Ben-Dor, L.; Shilo, I.

1980-11-01

215

Synthesis, thermogravimetric and 57Fe Mössbauer studies of the oxygen deficient perovskite REBaCuFeO 5 + x series (RE = Y, Nd, Sm, Gd, Dy, Tm, Lu)  

NASA Astrophysics Data System (ADS)

We present the results of thermogravimetric and 57Fe Mössbauer studies of the oxygen deficient perovskite REBaCuFeO 5+x series with RE = Y, Nd, Sm, Gd, Dy, Tm, Lu. The presence of the removable content x of oxygen was determined by analysis of TGA measurements in a stream of Ar gas. The amount of removable oxygen was highest for the Nd compound and varied between 0.07 and 0.12 for the other compounds. By means of the Rietveld method we performed the refinement of the structure of the compounds, based on the space group P4mm, after taking into consideration that the Fe ion occupies the lb 1 ( z = 0.27) site and Cu the lb 2 ( z = 0.74) site. From the analysis of the Mössbauer spectra we found that the compounds become magnetically ordered with transition temperatures depending on the oxygen content. The values of the hyperfine parameters in all the samples indicate the ferric iron to be in a high spin state.

Pissas, M.; Mitros, C.; Kallias, G.; Psycharis, V.; Simopoulos, A.; Kostikas, A.; Niarchos, D.

1992-03-01

216

Green long-after-glow luminescence of Tb3+ in Sr2SiO4  

NASA Astrophysics Data System (ADS)

The green long-after-glow luminescence from Tb3+-doped Sr2SiO4 phosphors, which are synthesized by the high temperature solid state reaction in a reductive atmosphere, is observed in this paper. The results show that under ultraviolet excitation, the obtained phosphors produce an intense green-lighting-emission from the Tb3+, and the green-lighting long-after-glow luminescence related to Tb3+ can last half an hour after the irradiation source has been removed. Moreover, the effects of co-doping Li+, Dy3+, Er3+, Gd3+, and Yb3+ with Tb3+ on the decay properties and thermoluminescence properties are investigated to confirm the long-after-glow mechanism.

Wang, Qi; Qiu, Jian-Bei; Song, Zhi-Guo; Zhou, Da-Cheng; Xu, Xu-Hui

2014-06-01

217

Corrosion study of single crystal Ni-Mn-Ga alloy and Tb0.27Dy0.73Fe1.95 alloy for the design of new medical microdevices.  

PubMed

Once placed in a magnetic field, smart magnetic materials (SMM) change their shape, which could be use for the development of smaller minimally invasive surgery devices activated by magnetic field. However, the potential degradation and release of cytotoxic ions by SMM corrosion has to be determined. This paper evaluates the corrosion resistance of two SMM: a single crystal Ni-Mn-Ga alloy and Tb(0.27)Dy(0.73)Fe(1.95) alloy. Ni-Mn-Ga alloy displayed a corrosion potential (E (corr)) of -0.58 V/SCE and a corrosion current density (i (corr)) of 0.43 ?A/cm(2). During the corrosion assay, Ni-Mn-Ga sample surface was partially protected; local pits were formed on 20% of the surface and nickel ions were mainly found in the electrolyte. Tb(0.27)Dy(0.73)Fe(1.95) alloy exhibited poor corrosion properties such as E (corr) of -0.87 V/SCE and i (corr) of 5.90 ?A/cm(2). During the corrosion test, this alloy was continuously degraded, its surface was impaired by pits and cracks extensively and a high amount of iron ions was measured in the electrolyte. These alloys exhibited low corrosion parameters and a selective degradation in the electrolyte. They could only be used for medical applications if they are coated with high strain biocompatible materials or embedded in composites to prevent direct contact with physiological fluids. PMID:21222141

Pouponneau, Pierre; Savadogo, Oumarou; Napporn, Teko; Yahia, L'Hocine; Martel, Sylvain

2011-02-01

218

Internal And External Factors in the Structural Organization in Cocrystals of the Mixed-Metal Endohedrals (GdSc2N@I(H)-C(80), Gd(2)ScN@I(H)-C(80), And TbSc(2)N@I(H)C(80) ) And Nickel(II) Octaethylporphyrin  

SciTech Connect

Structural characterizations of three new mixed-metal endohedrals, GdSc{sub 2}N@I{sub h}-C{sub 80}, Gd{sub 2}ScN@I{sub h}-C{sub 80}, and TbSc{sub 2}@I{sub h}-C{sub 80}, have been obtained by single-crystal X-ray diffraction on GdSc{sub 2}N@I{sub h}-C{sub 80}{center_dot}Ni{sup II}(OEP){center_dot}2C{sub 6}H{sub 6}, Gd{sub 2}ScN@I{sub h}-C{sub 80}{center_dot}Ni{sup II}(OEP){center_dot}2C{sub 6}H{sub 6}, and TbSc{sub 2}N@I{sub h}-C{sub 80}{center_dot}Ni{sup II}(OEP){center_dot}2C{sub 6}H{sub 6}. All three have I{sub h}-C{sub 80} cages and planar MM'{sub 2}N units. The central nitride ion is positioned further from the larger Gd{sup 3+} or Tb{sup 3+} ions and closer to the smaller Sc{sup 3+} ions. The MM'{sub 2}N units show a remarkable degree of orientational order in these and related compounds in which the endohedral fullerene is cocrystallized with a metalloporphyrin. The MM'{sub 2}N units are oriented perpendicularly to the porphyrin plane and aligned along one of the N-Ni-N axes of the porphyrin. The smaller Sc{sup 3+} ions show a marked preference to lie near the porphyrin plane. The larger Gd{sup 3+} or Tb{sup 3+} ions assume positions further from the plane of the porphyrin. The roles of dipole forces and electrostatic forces in ordering these cocrystals of endohedral fullerenes and metalloporphyrins are considered.

Stevenson, S.; Chancellor, C.J.; Lee, H.M.; Olmstead, M.M.; Balch, A.L.

2009-05-26

219

Vibrational and electronic properties of the lanthanide trifluorides GdF 3, TbF 3, ErF 3 and YbF 3 studied by Raman spectroscopy  

Microsoft Academic Search

Single crystals of GdF3, TbF3, ErF3, YbF3 have been studied by Raman scattering at 10 K and at room temperature when they exhibit orthorhombic symmetry of the ?-YF3 type. Based on group theory analysis and selection rules, Raman spectra have been fully interpreted with the help of the results obtained for the structural archetype YF3. Among the expected 24 Raman

K. Rotereau; Ph. Daniel; J. Y. Gesland

1998-01-01

220

Use of the ion exchange method for the determination of stability constants of trivalent metal complexes with humic and fulvic acids II. Tb 3+, Yb 3+ and Gd 3+ complexes in weakly alkaline conditions  

Microsoft Academic Search

The conditional stability constants for tracer concentrations of Tb(III), Yb(III), and Gd(III) with three soil humic acids, three soil fulvic acids and a fulvic acid from weathered coal were determined at pH 9.0–9.1 (these values are similar to those in calcareous soils) in the presence of NaHCO3 by using the anion exchange method. It was found that 1:1 and 1:2

Dong Wenming; Li Weijuan; Tao Zuyi

2002-01-01

221

Synthesis and VUV-UV spectroscopic properties of rare earth borosilicate oxyapatite: RE {sub 5}Si{sub 2}BO{sub 13}:Ln {sup 3+} (RE=La, Gd, Y; Ln=Eu, Tb)  

SciTech Connect

Three rare earth borosilicate oxyapatites, RE {sub 5}Si{sub 2}BO{sub 13} (RE=La, Gd, Y), were synthesized via wet chemical method, of which RE {sub 5}Si{sub 2}BO{sub 13} (RE=Gd, Y) were first reported in this work. In the three oxyapatites, [BO{sub 4}] and [SiO{sub 4}] share the [TO{sub 4}] tetrahedral oxyanion site, and RE {sup 3+} ions occupy all metal sites. The differential scanning calorimetry-thermo gravimetry measurements and high temperature powder X-ray diffraction pattern revealed a vitrification process within 300-1200 deg. C, which was due to the glass-forming nature of borosilicates. From the VUV excitation spectra of Eu{sup 3+} and Tb{sup 3+} in RE {sub 5}Si{sub 2}BO{sub 13}, the optical band gaps were found to be 6.31, 6.54 and 6.72 eV for RE {sub 5}Si{sub 2}BO{sub 13} (RE=La, Gd, Y), respectively. The emission and excitation bands of Eu{sup 3+} and Tb{sup 3+} are discussed relating with their coordination environments. Among the three hosts, Y{sub 5}Si{sub 2}BO{sub 13} would be the best for Eu{sup 3+} and Tb{sup 3+}-doped phosphors. - Graphical abstract: The perspective view of RE {sub 5}Si{sub 2}BO{sub 13} (RE=La, Gd, Y) oxyapatite along [001] direction. All non-tetrahedral metal sites are occupied by RE {sup 3+}, and the tetrahedral sites by SiO{sub 4} and BO{sub 4} groups. Y{sub 5}Si{sub 2}BO{sub 13} is a good host for both Eu{sup 3+} and Tb{sup 3+} activated phosphors.

Yuan Junlin [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing (China); Zhang Zhijun [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing (China); Wang Xiaojun [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing (China); Chen Haohong [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhao Jingtai [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)], E-mail: jtzhao@mail.sic.ac.cn; Zhang Guobin [NSRL, University of Science and Technology of China, Hefei 230027 (China); Shi Chaoshu [NSRL, University of Science and Technology of China, Hefei 230027 (China)

2007-04-15

222

Synthesis and VUV-UV spectroscopic properties of rare earth borosilicate oxyapatite: RE5Si 2BO 13: Ln3+ ( RE=La, Gd, Y; Ln=Eu, Tb)  

NASA Astrophysics Data System (ADS)

Three rare earth borosilicate oxyapatites, RE5Si 2BO 13 ( RE=La, Gd, Y), were synthesized via wet chemical method, of which RE5Si 2BO 13 ( RE=Gd, Y) were first reported in this work. In the three oxyapatites, [BO 4] and [SiO 4] share the [TO 4] tetrahedral oxyanion site, and RE3+ ions occupy all metal sites. The differential scanning calorimetry-thermo gravimetry measurements and high temperature powder X-ray diffraction pattern revealed a vitrification process within 300-1200 °C, which was due to the glass-forming nature of borosilicates. From the VUV excitation spectra of Eu 3+ and Tb 3+ in RE5Si 2BO 13, the optical band gaps were found to be 6.31, 6.54 and 6.72 eV for RE5Si 2BO 13 ( RE=La, Gd, Y), respectively. The emission and excitation bands of Eu 3+ and Tb 3+ are discussed relating with their coordination environments. Among the three hosts, Y 5Si 2BO 13 would be the best for Eu 3+ and Tb 3+-doped phosphors.

Yuan, Jun-Lin; Zhang, Zhi-Jun; Wang, Xiao-Jun; Chen, Hao-Hong; Zhao, Jing-Tai; Zhang, Guo-Bin; Shi, Chao-Shu

2007-04-01

223

Studies of structural, magnetic, electrical and thermal properties in layered perovskite cobaltite SrLnCoO4 (Ln = La, Ce, Pr, Nd, Eu, Gd and Tb)  

NASA Astrophysics Data System (ADS)

The structural, magnetic, electrical and thermal properties have been investigated in single-layered perovskite compounds of SrLnCoO4 (Ln = La, Ce, Pr, Nd, Eu, Gd and Tb) with a K2NiF4-type structure. The variation of Jahn-Teller distortion of the CoO6 octahedron reflected by two different Co-O bond lengths indicates that all the samples are mostly accommodated in the t2g orbital states keeping intermediate spin configuration. The detailed comparison of the temperature dependence of magnetization, resistivity, thermoelectric power and thermal conductivity suggests that the tolerance factor t plays a very crucial role in transport behaviour. With decreasing A-site rare earth ionic radius r_Ln^{3+} , the tolerance factor t decreases and the distortion of the CoO6 octahedron enhances, which results in the increased bending of the Co-O-Co bond, the narrowing of the bandwidth and the decrease in the mobility of eg electrons caused by the substitution of smaller Ln3+ ions for a larger Sr2+ ion.

Ang, R.; Sun, Y. P.; Luo, X.; Hao, C. Y.; Song, W. H.

2008-02-01

224

Lattice distortions in layered type arsenides LnTAs{sub 2} (Ln=La-Nd, Sm, Gd, Tb; T=Ag, Au): Crystal structures, electronic and magnetic properties  

SciTech Connect

The lanthanide coinage-metal diarsenides LnTAs{sub 2} (Ln=La, Ce-Nd, Sm; T=Ag, Au) have been reinvestigated and their structures have been refined from single crystal X-ray data. Two different distortion variants of the HfCuSi{sub 2} type are found: PrAgAs{sub 2}, NdAgAs{sub 2}, SmAgAs{sub 2}, GdAgAs{sub 2}, TbAgAs{sub 2}, NdAuAs{sub 2} and SmAuAs{sub 2} crystallize as twofold superstructures in space group Pmcn with the As atoms of their planar layers forming zigzag chains, whereas LaAgAs{sub 2}, CeAgAs{sub 2} and PrAuAs{sub 2} adopt a fourfold superstructure (space group Pmca) with cis-trans chains of As atoms. The respective atomic positions can be derived from the HfCuSi{sub 2} type by group-subgroup relations. The compounds with zigzag chains of As atoms exhibit metallic behaviour while those with cis-trans chains are semiconducting as measured on powder pellets. The majority of the compounds including 4f elements show antiferromagnetic ordering at T{sub N}<20 K. - Text3: Zigzig vs. cis-trans.

Rutzinger, D.; Bartsch, C. [Anorganische Chemie, Fachrichtung Chemie und Lebensmittelchemie, Technische Universitaet Dresden, D-01062 Dresden (Germany); Doerr, M. [Institut fuer Festkoerperphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany); Rosner, H. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Str. 40, D-01187 Dresden (Germany); Neu, V. [IFW Dresden, Institut fuer metallische Werkstoffe, Helmholtzstr. 20, D-01069 Dresden (Germany); Doert, Th., E-mail: thomas.doert@chemie.tu-dresden.d [Anorganische Chemie, Fachrichtung Chemie und Lebensmittelchemie, Technische Universitaet Dresden, D-01062 Dresden (Germany); Ruck, M. [Anorganische Chemie, Fachrichtung Chemie und Lebensmittelchemie, Technische Universitaet Dresden, D-01062 Dresden (Germany)

2010-03-15

225

Collective Phase Mode and the Role of lattice distortions at TN˜TC in XMn2O5 (X= Bi, Pr, Sm, Gd, Tb)  

NASA Astrophysics Data System (ADS)

We report on detailed temperature dependent infrared reflectivity, Raman, local structure, and X-ray diffraction measurements of multiferroic XMn2O5 (X= Bi, Pr, Sm, Gd, Tb). While for BiMn2O5 there are weak but distinct spectroscopic changes that together with high resolution diffraction patterns suggest a lattice role at TN˜TC, for the rare earth (R) replaced infrared spectra have as a main feature a broad band at meV energies in addition to progressive rotation of Mn-O polyhedra. That band, independent of the R^3+ ion size and common to all, suggests hopping of carriers through fluctuations at a local scale. It partially condenses below 40 K, i.e., the collective electronic behavior changes from delocalized to one partially localized. We assimilate that condensate to a CDW-like phase mode. It might indicate induced orbital correlation of charge transfers between Mn sites.Frequency Raman phonon shifts are observed at T˜60 K, due to spin-phonon coupling, and at TN˜TC. Below TN˜TC there is no a Raman soft mode that might be associated to a CDW amplitude mode.

Massa, N. E.; García Flores, A. F.; Granado, E.; Fabbris, G. F. L.; Azevedo, G. De M.; Del Campo, L.; de Sousa Meneses, D.; Echegut, P.; Martínez-Lope, M. J.; Alonso, J. A.

2011-03-01

226

Crystal structures of the R 3CuGeSe 7 (R = Ce, Pr, Nd, Sm, Gd, Tb and Ho) compounds  

Microsoft Academic Search

The crystal structures of the R3CuGeSe7 compounds (R=Ce, Pr, Nd, Sm, Gd, Tb and Ho) (La3CuSiS7 structure type, space group P63, Pearson symbol hP24) were determined by means of X-ray single crystal diffraction (a=1.0643(1)nm, c=0.60973(7)nm, R1=0.0269 for Ce3CuGeSe7; a=1.0559(1)nm, c=0.6084(1)nm, R1=0.0301 for Pr3CuGeSe7; a=1.0519(1)nm, c=0.60707(9)nm, R1=0.0305 for Nd3CuGeSe7) and X-ray powder diffraction (a=1.04216(3)nm, c=0.60447(3)nm, RBragg=0.0862 for Sm3CuGeSe7; a=1.03491(8)nm, c=0.60395(7)nm, RBragg=0.0932

L. D. Gulay; O. S. Lychmanyuk; I. D. Olekseyuk; A. Pietraszko

2006-01-01

227

On the nature of low-lying collective 1+ states in the heavy deformed nuclei 154Sm, 156Gd and 164Dy and in the f7/2 shell nucleus 46Ti  

NASA Astrophysics Data System (ADS)

High resolution inelastic proton scattering at 201 MeV on 154Sm, 156Gd and 164Dy is used to clarify the nature of low-lying magnetic dipole states previously observed in inelastic electron scattering. An upper limit on the spin contribution to these collective magnetic dipole excitations is presented. The roles of spin and convection currents are also studied by inelastic proton and electron scattering to the low-lying 1+ state at 4.319 MeV in the f7/2-shell nucleus 46Ti. A substantial orbital contribution is observed in all cases.

Djalali, C.; Marty, N.; Morlet, M.; Willis, A.; Jourdain, J. C.; Bohle, D.; Hartmann, U.; Küchler, G.; Richter, A.; Caskey, G.; Crawley, G. M.; Galonsky, A.

1985-12-01

228

Magnetic ordering in the pyrochlore Ho2CrSbO7 determined from neutron diffraction, and the magnetic properties of other RE2CrSbO7 phases (RE=Y, Tb, Dy, Er)  

NASA Astrophysics Data System (ADS)

The magnetic structure of the pyrochlore Ho2CrSbO7, which orders magnetically below 13 K, has been studied using neutron powder diffraction. Ho2CrSbO7 is found to form an “ordered spin-ice structure” where the magnetic moments are constrained along the 111 axes, but with a ferromagnetic moment in one direction. The Cr3+ ions order ferromagnetically and this is thought to lift the degeneracy of the x, y and z directions in the cubic structure causing the ferromagnetic component from the Ho3+ ions to align. The pyrochlores RE2CrSbO7 where RE=Y, Tb, Dy and Er have also been prepared and studied using SQUID magnetometry.

Whitaker, Mariana J.; Greaves, Colin

2014-07-01

229

(2)?[Bi2Cl6(pyz)4]: A 2D-Pyrazine Coordination Polymer As Soft Host Lattice for the Luminescence of the Lanthanide Ions Sm(3+), Eu(3+), Tb(3+), and Dy(3+).  

PubMed

The 2D-coordination polymer (2)?[Bi2Cl6(pyz)4] was synthesized from BiCl3 and a self-consuming melt of pyrazine (pyz). It proves to be a suitable soft host lattice for in situ co-doping of the lanthanide ions Sm(3+), Eu(3+), Tb(3+), and Dy(3+) during network formation. The series of luminescent networks (2)?[Bi(2-x)LnxCl6(pyz)4] obtained exhibits an efficient antenna effect on the lanthanide ions. Emission is almost exclusively observed from the lanthanide centers at room temperature, whereas cooling to 77 K reveals a bismuth-pyrazine metal-to-ligand charge transfer related phosphorescence, which is also present without lanthanide participation. All parts of the coordination polymer can function for light uptake. Partial substitution is achieved by statistic replacement of bismuth with lanthanides and can range up to 25 at. % for trivalent europium. PMID:24963536

Heine, Johanna; Wehner, Tobias; Bertermann, Rüdiger; Steffen, Andreas; Müller-Buschbaum, Klaus

2014-07-21

230

Synthesis, magnetism, and 57Fe Mössbauer spectroscopic study of a family of [Ln3Fe7] coordination clusters (Ln = Gd, Tb, and Er).  

PubMed

The reaction of N-methydiethanolamine (mdeaH2), benzoic acid, FeCl3, and Ln(NO3)3·6H2O or LnCl3·xH2O yields a series of decanuclear coordination clusters, [Ln3Fe7(?4-O)2(?3-OH)2(mdea)7(?-benzoate)4(N3)6]·4MeCN·H2O, where Ln = Gd(III) (1) or Tb(III) (2), and [Er3Fe7(?4-O)2(?3-OH)2(mdea)7(?-benzoate)4(N3)5(MeOH)]Cl·7.5H2O·11.5MeOH (3). The isostructural compounds 1-3 all crystallize isotypically in the triclinic space group P1? with Z = 2, as does the previously reported dysprosium analogue 4. Six of the Fe(III) ions are pseudooctahedrally coordinated, whereas the seventh has a trigonal-bipyramidal coordination geometry. Temperature-dependent direct-current magnetic susceptibility studies indicate that intracluster antiferromagnetic interactions are dominant in 1-3. The frequency-dependent out-of-phase (??) alternating-current susceptibility reveals that 2 undergoes a slow relaxation of its magnetization, presumably resulting from anisotropy of the Tb(III) ions. Between 30 and 295 K, the (57)Fe Mössbauer spectra reveal paramagnetic behavior with six partially resolved quadrupole doublets, one for the trigonal-bipyramidal Fe(III) site and five for the six pseudooctahedral Fe(III) sites. The Mössbauer spectra of 2 and 3 obtained between 3 and 30 K are consistent with the presence of Fe(III) intracluster antiferromagnetic coupling with slow magnetic relaxation relative to the Larmor precession time. Further, the observed changes in the effective magnetic field values in the spectra measured at 3 K with increasing applied field are consistent with the effect of the local spin polarization along the applied magnetic field direction, a behavior reminiscent of antiparallel spin-coupled iron molecular paramagnetic systems. PMID:24089701

Abbas, Ghulam; Lan, Yanhua; Mereacre, Valeriu; Buth, Gernot; Sougrati, Moulay T; Grandjean, Fernande; Long, Gary J; Anson, Christopher E; Powell, Annie K

2013-10-21

231

Preparation, crystal structure and optical spectroscopy of the rare earth complexes (RE 3+=Sm, Eu, Gd and Tb) with 2-thiopheneacetate anion  

NASA Astrophysics Data System (ADS)

Rare earth complexes with the formulae Sm(TPAC) 3·3H 2O, Eu 2(TPAC) 6·5.25H 2O and RE(TPAC) 3·3.5H 2O (where RE=Gd and Tb), and TPAC=2-thiopheneacetate) have been synthesized and characterized by complexometric titration, elemental analyses, infrared spectroscopy, and X-ray crystallography. Infrared data suggested the presence of both bridging and chelating TPAC anions. The crystal structure of the [Eu 2(TPAC) 6·(H 2O) 3]·2.25H 2O complex in the solid state, determined by X-ray diffraction, revealed that it crystallizes in the orthorhombic crystal system (space group Aba2), with two crystallographically independent Eu 3+ centers (Eu1 and Eu2). These europium centers are held together by one bidentate bridging and two tridentate bridging carboxylate groups. The existence of two Eu 3+ centers was also supported by the emission spectrum. The luminescence properties of the RE-TPAC complexes were investigated by measuring the excitation and emission spectra, and the intramolecular ligand-to-rare earth energy transfer mechanisms were discussed. The emission spectra of the Eu 3+ and Tb 3+ ions displayed only narrow bands arising from 5D 0? 7F 0 and 5D 0? 7F 0-4 transitions, respectively, indicating an efficient luminescence sensitization of these ions by the TPAC 'antenna'. On the other hand, the emission spectrum of the Sm 3+-complex displayed a broad band from the phosphorescence of the TPAC ligand which overlapped the 4f 5-intraconfigurational transitions. The theoretical intensity parameters ?? ( ?=2 and 4), maximum splitting of the 7F 1 state (? E) and the ratio between the 5D 0? 7F 0 and 5D 0? 7F 2 transition intensities ( R02) were calculated based on the X-ray crystalline structure for the Eu 3+-complex, and a comparison with experimental data were made. The emission quantum efficiency ( ?) of the D5 emitting level of the Eu 3+ ion was also determined.

Teotonio, Ercules E. S.; Brito, Hermi F.; Felinto, Maria Cláudia F. C.; Thompson, Larry C.; Young, Victor G.; Malta, Oscar L.

2005-09-01

232

Scintillating fiber optic screens: a comparison of MTF, light conversion efficiency, and emission angle with Gd2O2S:Tb screens.  

PubMed

The widespread effort in developing digital imaging systems has led to large area high pixel density photodetectors such as charge coupled devices (CCDs), amorphous silicon photodiode arrays, and complementary metal oxide semiconductor (CMOS) imagers. These photodetectors have different capabilities, characteristics, and requirements than conventional silver-halide-based film, and this fact had led to a new generation of exotic scintillators, including fiber optic screens made from scintillating glass. The scintillator performance characteristics of five different scintillating fiber optic screens and two conventional Gd2O2S:Tb screens (one 34 mg/cm2 and the other 60 mg/cm2) were measured and compared. The measurements that were made included the angular dependence of light emission relative to the normal, the modulation transfer function (MTF), and the absolute effective conversion efficiency (light photons per absorbed x-ray photon). It was found that the light emission of scintillating fiber optic screens is markedly forward peaked (depending on the sample) compared to conventional screens or Lambertian emitters. The MTFs of the five scintillating fiber optic screens measured were comparable and fell approximately midway between the two conventional screen MTFs. One of the scintillating fiber optic screens demonstrated light efficiency similar to the thick (60 mg/cm2) conventional screen, another had light output capabilities similar to the thin (34 mg/cm2) conventional screen, and the three others were less efficient than the thin screen. The non-Lambertian characteristics of the fiber optic scintillators will cause errors of up to 75% in lens efficiency calculations if a Lambertian source is assumed. The conventional screens were found to conform within about 5% of an ideal Lambertian emitter. PMID:9048369

Yu, T; Sabol, J M; Seibert, J A; Boone, J M

1997-02-01

233

Spin-phonon coupling in multiferroic manganites RMnO3: comparison of pure (R = Eu, Gd, Tb) and substituted (R = Eu1- x Y x ) compounds  

NASA Astrophysics Data System (ADS)

For rare-earth manganite RMnO3 compounds spin-phonon coupling manifests itself as a phonon softening in the temperature range of the magnetically ordered phases. Within this class of materials, a continuous tuning of the lattice and thus also of the magnetic properties of multiferroic manganites is achieved by Y doping in substituted Eu1- x Y x MnO3. We compare the impact on spin-phonon coupling within this partial-substitution approach in a series of Eu1- x Y x MnO3 samples 0 ? x ? 0.5) with the effect of a complete exchange of the rare earth ions R3+ in a series of pure RMnO3 compounds (R = Eu, Gd, Tb). For this purpose we employ polarized Raman scattering in the 10-300 K temperature range. The low-temperature results show phonon softening in all investigated compounds. For decreasing R3+ radius, i.e. an increasing orthorhombic distortion and magnetic frustration, we observe in both systems a weakening of the spin-phonon coupling. For known sublattice magnetization within the MnO2-plane, quantitative results for the spin-phonon coupling constant are derived for both cases within a molecular field approximation. Our results show, that the spin-phonon coupling strength in the magnetically ordered phases of the various investigated manganites does not correlate with the magnetization pattern. Instead, the pure RMnO3 compounds and the substituted Eu1- x Y x MnO3 fit excellently within a common scheme, in which the weakening of the spin-phonon coupling reflects the degree of tilting of the MnO6 octahedra due to the orthorhombic distortion of the crystal lattice.

Issing, S.; Pimenov, A.; Ivanov, Y. Vu.; Mukhin, A. A.; Geurts, J.

2010-12-01

234

Synthesis, phase composition modification, and optical properties of Ce{sup 3+}/Tb{sup 3+} activated KGdF{sub 4} and GdF{sub 3} submicrocrystals  

SciTech Connect

Ce{sup 3+}/Tb{sup 3+} co-doped series of samples have been synthesized based on a citric acid assisted hydrothermal method. By controlling the hydrothermal treating time, the samples evolve from the Ce{sup 3+}/Tb{sup 3+} co-doped cubic phase KGdF{sub 4} with spherical morphology into the Ce{sup 3+}/Tb{sup 3+} co-doped orthorhombic phase GdF{sub 3} with rhombic shape finally. The X-ray diffraction data illustrate the phase composition modification process of the samples. The field emission scanning electron microscopy and the transmission electron microscopy images suggest the transformation in the morphology of final products. The spectra of the energy-dispersive spectroscopy reveal the constituents of the samples. And the selected area electronic diffraction patterns prove the crystalline phases of the samples. Based on previous studies and the experimental data, one possible phase composition modification process has been summarized. The photoluminescence excitation and emission spectra and the luminescent dynamic decay curves demonstrate the variations in optical properties of the Ce{sup 3+}/Tb{sup 3+} co-doped final products. - Graphical abstract: Schematic illustration for the phase composition modification from the Ce{sup 3+}/Tb{sup 3+} doped KGdF{sub 4} to the Ce{sup 3+}/Tb{sup 3+}doped GdF{sub 3} with multiform morphologies and different sizes. (C presents cubic phase, H presents hexagonal phase, and O presents orthorhombic phase.) Highlights: Black-Right-Pointing-Pointer The samples were synthesized by a hydrothermal method. Black-Right-Pointing-Pointer The samples evolved from the cubic phase KGdF{sub 4} into the orthorhombic phase GdF{sub 3}. Black-Right-Pointing-Pointer The morphology evolved from the spherical shape into the rhombic shape finally. Black-Right-Pointing-Pointer A possible phase composition modification process was summarized. Black-Right-Pointing-Pointer The optical properties of final products were compared and studied.

Cao Chunyan [College of Mathematics and Physics, Jinggangshan University, Ji'an 343009 (China); Yang, Hyun Kyoung; Moon, Byung Kee; Choi, Byung Chun [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of); Jeong, Jung Hyun, E-mail: jhjeong@pknu.ac.kr [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of); Kim, Kwang Ho, E-mail: kwhokim@pusan.ac.kr [School of Materials Science and Engineering, Pusan National University, Busan 609-735 (Korea, Republic of)

2012-03-15

235

The molecular structure of TbI 3, DyI 3, HoI 3 and ErI 3 as determined by synchronous gas-phase electron diffraction and mass spectrometric experiment assisted by quantum chemical calculations  

NASA Astrophysics Data System (ADS)

A first gas electron diffraction study of TbI 3, DyI 3, HoI 3 and ErI 3 has been carried out in combination with mass spectrometric vapour monitoring at 1117(10), 1117(10), 1132(10) and 1102(10) K, respectively. Up to 4 mol.% of dimeric species was observed in addition to the dominating monomeric molecules. The change of the thermal-averaged rg-configuration parameters of the molecules in the series TbI 3 ? ErI 3 reflect the lanthanide contraction. A low value of the shrinkage ?(I…I) even at such a high temperatures may be considered due to vibration effects in molecule whose equilibrium geometric nuclear structure is planar and which correspond to configurationally-averaged 4f n electronic state. B3LYP and ??2 calculations performed in this work with large core potential for lanthanide atoms also resulted in equilibrium geometry of D 3h symmetry. According to the both quantum chemical methods applied the potential function the non-planar vibration is essentially anharmonic, which is therefore to be taken into account to correctly describe nuclear dynamics in molecules such as LnI 3. Different models applied in this study predict the equilibrium distance re(Ln-I) to be shorter than the thermal-averaged rg(Ln-I) distance by 0.002-0.018(1) Å.

Shlykov, Sergey A.; Giricheva, Nina I.; Lapykina, Elena A.; Girichev, Georgiy V.; Oberhammer, Heinz

2010-08-01

236

Low temperature preparation and characterization of In 1? x Ln x BO 3 ( x = 0.0 and 0.05; Ln = Gd, Eu, Dy and Sm): ESR of In 0.95Gd 0.05BO 3 and emission of In 0.95Eu 0.05BO 3  

Microsoft Academic Search

Indium borate and rare earth substituted indium borates (In1?xLnxBO3 (x=0.0 and 0.05; Ln=Gd, Eu, Dy and Sm)) are prepared at low temperature by metathesis reaction using InCl3, LnCl3 and NaBO2. They are characterized by powder XRD and infrared spectroscopy. All the compositions (In1?xLnxBO3) crystallize in hexagonal lattice with calcite structure. These borates gave characteristic IR vibrations of planar BO3 group.

Radha Velchuri; B. Vijaya Kumar; V. Rama Devi; K. Ravi Kumar; G. Prasad; M. Vithal

2009-01-01

237

Development of uniaxial magnetocrystalline anisotropy in SrFe12-x(DyGd)xO19 thin film synthesized by incorporation of high coercivity nanoparticles in sol-gel method  

NASA Astrophysics Data System (ADS)

SrFe12-x(DyGd)xO19 thin films with x=0-2.5 were synthesized by a sol-gel method on thermally oxidized silicon wafer (Si/SiO2). XRD patterns and FE-SEM micrographs demonstrated that single phase c-axis hexagonal ferrite films with rather narrow grain size distribution were obtained. It was found that the grain size is decreased from about 110 nm (for the film with no substitution) to 35 nm (for the film with the highest amount of substitution cations). AFM micrographs exhibited that the surface roughness decreases with an increase in substitution content. It was found from the VSM graphs that with an increase in substitution contents coercivity and saturation of magnetization increase. The maximum saturation of magnetization and coercivity at perpendicular direction were 250 emu/g and 5.5 kOe, respectively.

Ghasemi, Ali

2014-06-01

238

Heterometallic octanuclear RE(III)3Ni(II)5 (RE = Dy(III), Gd(III) and Y(III)) clusters with slow magnetic relaxation for the dysprosium derivative.  

PubMed

Reactions of rare earth benzoate and nickel perchlorate with a Schiff-base ligand, 2-([(2-hydroxyphenyl)imino]methyl) phenol (H2L), in the presence of triethylamine yielded three heterobimetallic octanuclear clusters of general formula [RE3Ni5L5(PhCOO)3(?3-OH)5(?3-OCH3)(CH3OH)4(H2O)]·xCH3OH·yH2O (RE = Dy(III), x = 4, y = 4 (1), RE = Gd(III), x = 5, y = 4 (2), RE = Y(III), x = 5, y = 3 (3)). Single-crystal X-ray diffraction reveals that the metal core of each cluster consists of two distorted [RE2Ni2O4] cubane-like moieties and a heterobimetallic triangular [RE2NiO2] unit, with RE ions arranged in a typical triangular fashion. Variable-temperature solid state magnetic susceptibilities of these complexes were measured in the temperature range 2-300 K and the results indicate that an overall ferromagnetic interaction among the metal ions is operative for compounds 2 and 3. Under zero external field, the Dy3Ni5 compound shows a frequency dependence of the out-of-phase (?'') signals, which indicates slow relaxation of the magnetization. PMID:23403627

Wang, Huiyu; Ke, Hongshan; Lin, Shuang-Yan; Guo, Yang; Zhao, Lang; Tang, Jinkui; Li, Yun-Hui

2013-04-21

239

Magnetocaloric effects in RNiIn (R = Gd-Er) intermetallic compounds  

NASA Astrophysics Data System (ADS)

Magnetic properties and magnetocaloric effects (MCEs) of the intermetallic RNiIn (R = Gd-Er) compounds have been investigated in detail. GdNiIn and ErNiIn compounds exhibit a ferromagnetic (FM) to paramagnetic (PM) transition around the respective Curie temperatures. However, it is found that RNiIn with R = Tb, Dy, and Ho undergo two successive magnetic phase transitions with increasing temperature. In addition, a field-induced metamagnetic transition from antiferromagnetic (AFM) to FM states is observed in RNiIn with R = Tb and Dy below their respective AFM-FM transition temperatures (Tt). The maximal values of magnetic entropy change (?SM) of HoNiIn are -9.5 J/kg K at Tt = 7 K and -21.7 J/kg K at TC = 20 K for a magnetic field change of 5 T, respectively. These two successive ?SM peaks overlap partly, giving rise to a high value of refrigerant capacity (RC = 341 J/kg at 5 T) over a wide temperature span. It is noted that the RC value of GdNiIn is as high as 326 J/kg due to the relatively broad distribution of ?SM peak. Consequently, this RNiIn system shows large reversible ?SM and considerable RC values in the temperature range of 10-100 K.

Zhang, H.; Xu, Z. Y.; Zheng, X. Q.; Shen, J.; Hu, F. X.; Sun, J. R.; Shen, B. G.

2011-06-01

240

Lanthanide-Organic Coordination Frameworks Showing New 5-Connected Network Topology and 3D Ordered Array of Single-Molecular Magnet Behavior in the Dy Case.  

PubMed

Five isostructural lanthanide-organic coordination frameworks with a unique 3-D 5-connected (4(7).6(3))(4(3).6(5).8(2)) network, namely, [Ln(phen)(L)]n (Ln = Dy for 1, Gd for 2, Ho for 3, Er for 4, and Tb for 5), have been prepared based on bridging 5-hydroxyisophthalic acid (H3L) and chelating 1,10-phenanthroline (phen) coligand. Significantly, the Dy(III) complex 1 is an organized array of single-molecular magnets (SMMs), with frequency-dependent out-of-phase ac susceptibility signals and magnetization hysteresis at 4 K. Further analysis of the magnetic results can reveal that the SMM behavior of 1 should arise from the smaller ferromagnetic interaction between the Dy(III) ions. Complex 1 was also characterized by X-ray absorption spectra, which give the clear X-ray magnetic circular dichroism signal. PMID:24937442

Chen, Min; Sañudo, E Carolina; Jiménez, Erika; Fang, Shao-Ming; Liu, Chun-Sen; Du, Miao

2014-07-01

241

Evolution of the crystal and magnetic structure of the R2MnRuO7 (R = Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) family of pyrochlore oxides.  

PubMed

The members of the family of pyrochlore oxides with the formula R(2)MnRuO(7) (R = Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) have been synthesized and characterized. Polycrystalline samples were prepared by a soft chemistry procedure involving citrates of the different metal ions, followed by thermal treatments in air or O(2) pressure. The crystallographic and magnetic structures have been analysed from X-ray diffraction (XRD) and neutron powder diffraction (NPD) data, in complement with magnetic measurements; the evolution along the series of the crystallographic parameters (unit-cell parameters, bond distances and angles) is discussed. In R(2)MnRuO(7) pyrochlores, Mn and Ru ions statistically occupy the 16c sites in a cubic unit cell with space group Fd ?3m, which defines an intrinsic frustrated three-dimensional system. In all the cases, the low-temperature NPD data unveils an antiferromagnetic coupling of two subsets of Mn(4+)/Ru(4+) spins, indicating that the magnetic frustration is partially relieved by the random distribution of Mn and Ru over the 16c sites. At lower temperatures there is a polarization of the R(3+) magnetic moments, which also participate in the magnetic structure, when a magnetic rare earth is present. PMID:22669397

Martínez-Coronado, R; Retuerto, M; Fernández, M T; Alonso, J A

2012-07-28

242

Influence of the concentration in Fe-doped BaTiO 3 on magnetoelectric couping of layered composites BaTi 1-xFe xO 3-Tb 1-yDy yFe 2-z  

NASA Astrophysics Data System (ADS)

Perovskites BaTi 1-xFe xO 3 has been synthesized with the concentration x ranging from 0.01 to 0.02. Their transformation point of ferroelectric to paraelectric and the corresponding latent heat of the phase transformation were observed to decrease with increasing the doping level of Fe 3+. Bonded layered composites BaTi 1-xFe xO 3-Tb 1-yDy yFe 2-z have been fabricated and their magnetoelectric effect has been investigated. The sample containing a layer of perovskite BaTi 0.985Fe 0.015O 3 was found to show the maximum transverse ME voltage coefficient, which is about 1422 mV Oe -1 cm -1 under a magnetic field of 1580 Oe, in these bilayers. Analysis shows that the Fe-doped BaTiO 3 with doping level at about 1.5% should have largest piezoelectric coefficient in these ceramics BaTi 1-xFe xO 3.

Zhang, Ning; Wei, Jianjin

243

Enhanced Ferroelectric Polarization by Induced Dy Spin Order in Multiferroic DyMnO{sub 3}  

SciTech Connect

Neutron powder diffraction and single crystal x-ray resonant magnetic scattering measurements suggest that Dy plays an active role in enhancing the ferroelectric polarization in multiferroic DyMnO{sub 3} above T{sub N}{sup Dy}=6.5 K. We observe the evolution of an incommensurate ordering of Dy moments with the same periodicity as the Mn spiral ordering. It closely tracks the evolution of the ferroelectric polarization. Below T{sub N}{sup Dy}, where Dy spins order commensurately, the polarization decreases to values similar for those of TbMnO{sub 3}. The higher P{sub s} found just above T{sub N}{sup Dy} arises from the contribution of Dy spins so as to effectively increase the amplitude of the Mn spin spiral.

Prokhnenko, O.; Landsgesell, S.; Aliouane, N.; Argyriou, D. N. [Hahn-Meitner-Institut, Glienicker Strasse 100, D-14109 Berlin (Germany); Feyerherm, R.; Dudzik, E. [Hahn-Meitner-Institut, c/o BESSY, D-12489 Berlin (Germany); Chapon, L. C. [ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, OX11, 0QX (United Kingdom)

2007-02-02

244

Tuberculosis (TB)  

MedlinePLUS

... JavaScript on. Read more information on enabling JavaScript. Tuberculosis (TB) Skip Content Marketing Share this: Main Content ... thought to be infected with TB bacteria, Mycobacterium tuberculosis ( Mtb ). TB is a chronic bacterial infection. It ...

245

Blue light emitting SrSn(OH){sub 6} nano-rods doped with lanthanide ions (Eu{sup 3+}, Tb{sup 3+} and Dy{sup 3+})  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Room temperature synthesis of blue light emitting SrSn(OH){sub 6} nano-rods. ? Blue light emission originates from the recombination of self trapped excitons. ? There exists energy transfer from host to lanthanide ions in SrSn(OH){sub 6}:Ln nano-rods. ? Solubility of Eu{sup 3+} ions in SrSn(OH){sub 6} nano-rods is around 1.5 at%. -- Abstract: Blue light emitting SrSn(OH){sub 6} nano-rods were prepared in aqueous medium at room temperature. Presence of lanthanide ions in reaction medium during synthesis of nano-rods, leads to significant changes in the morphology of the nano-rods. Based on luminescence studies emission in the blue region from SrSn(OH){sub 6} nano-rods has been attributed to radiative recombination of self trapped excitons in the lattice. SrSn(OH){sub 6} nano-rods were doped with lanthanide ions like Eu{sup 3+}, Tb{sup 3+} and Dy{sup 3+} and their luminescence studies revealed that there exists energy transfer from host to lanthanide ions. From the luminescence studies on Eu{sup 3+} doped samples, it is confirmed that up to 1.5 at%, Eu{sup 3+} ions get incorporated at Sr{sup 2+} site in SrSn(OH){sub 6} lattice and beyond which a separate Eu{sup 3+} containing phase is formed. Part of the europium ions also exists as Eu{sup 2+} species in the lattice as confirmed by electron paramagnetic resonance (EPR) studies.

Patel, D.K.; Nuwad, J. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Rajeswari, B. [Radio Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Radio Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Vishwanadh, B. [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sudarsan, V.; Vatsa, R.K. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Kadam, R.M. [Radio Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Radio Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Pillai, C.G.S. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)] [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Kulshreshtha, S.K., E-mail: kulshres@gmail.com [Knowledge Management Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2013-02-15

246

Photoluminescence of Pr 3+, Sm 3+ and Dy 3+: SiO 2-Al 2O 3-LiF-GdF 3 glass ceramics and Sm 3+, Dy 3+: GeO 2-B 2O 3-ZnO-LaF 3 glasses  

NASA Astrophysics Data System (ADS)

In this paper, we present the absorption and photoluminescence properties of Pr 3+, Sm 3+ and Dy 3+-doped transparent oxyfluoride alumino-silicate glass ceramics and Sm 3+ and Dy 3+-doped oxyfluoride germanate glasses. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of these glasses have been carried out, to confirm their structure and thermal stability. These glasses or glass ceramics have shown strong emission and absorption bands in visible and near-infrared (NIR) region. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters ( ?2, ?4 and ?6) have been calculated for all the studied ions. Compared to Pr 3+, Sm 3+ and Dy 3+ doped glasses, their respective glass ceramics have shown stronger emissions due to LiGdF 4 crystalline phase in alumino-silicate glass ceramics. For Pr 3+ doped glass and glass ceramic, emission bands centered at 527 nm( 3P 0? 3H 5), 610 nm( 3P 0? 3H 6), 640 nm( 3P 0? 3F 2), 678 nm( 3P 1? 3F 3), 702 nm( 3P 0? 3F 3) and 721 nm( 3P 0? 3F 4) have been observed with 445 nm( 3H 4? 3P 2) excitation wavelength. Of them, 640 nm( 3P 0? 3F 2) has shown bright red emission. Emission bands of 4G 5/2? 6H 5/2 (562 nm), 4G 5/2? 6H 7/2 (598 nm), 4G 5/2? 6H 9/2 (644 nm) and 706 nm( 4G 5/2? 6H 11/2) for the Sm 3+: glass and glass ceramic, with excitation at 6H 5/2? 4F 7/2 (402 nm) have been recorded. Of them, 4G 5/2? 6H 7/2 (598 nm) has shown a bright orange emission. With regard to the Dy 3+: glass and glass ceramic, a bright fluorescent yellow emission at 576 nm( 4F 9/2? 6H 13/2) and blue emission at 485 nm( 4F 9/2? 6H 15/2) have been observed, apart from 4F 9/2? 6H 11/2 (662 nm) emission transition for glass ceramic with an excitation at 388 nm( 6H 15/2? 4I 13/2+ 4F 7/2) wavelength. For germanate glasses, emission bands of 4G 5/2? 6H 5/2 (564 nm), 4G 5/2? 6H 7/2 (601 nm), 4G 5/2? 6H 9/2 (644 nm) and 705 nm( 4G 5/2? 6H 11/2) for the Sm 3+: glass, with an excitation at 6H 5/2? 4F 7/2 (401 nm) have been recorded. Of them, 4G 5/2? 6H 7/2 (601 nm) has shown a bright orange emission. With regard to the Dy 3+: glass, a bright fluorescent yellow emission at 576 nm( 4F 9/2? 6H 13/2) and blue emission at 482 nm( 4F 9/2? 6H 15/2) have been observed, apart from 4F 9/2? 6H 11/2 (661 nm) emission transition with an excitation at 386 nm( 6H 15/2? 4I 13/2+ 4F 7/2) wavelength. The stimulated emission cross-sections of all the emission bands of Pr 3+, Sm 3+ and Dy 3+: glasses and glass ceramics have been computed based on their measured full-width at half maxima (FWHM, ? ?) and measured lifetimes ( ? m).

Lakshminarayana, G.; Qiu, Jianrong

2009-05-01

247

A-site size effect in a family of unfilled ferroelectric tetragonal tungsten bronzes: Ba4R0.67Nb10O30 (R = La, Nd, Sm, Gd, Dy and Y).  

PubMed

The effect of A-cation size on the structural and electrical properties in a family of ferroelectric tetragonal tungsten bronzes (TTBs) Ba4R0.67?1.33Nb10O30 (R = La, Nd, Sm, Gd, Dy and Y; ? = vacancy) was investigated. In each case, the crystal structure, as determined from lab-based ambient powder X-ray diffraction (PXRD), is metrically tetragonal and can be refined in the P4bm space group. XRD data show an increased splitting of hk0 00l reflections with decreasing R cation size indicating an increasing tetragonal distortion (measured by tetragonality c/a). Dielectric data and ferroelectric measurements indicate that the ferroelectric Curie temperature, TC, increases with decreasing R size and so a direct correlation between TC and tetragonality/ionic radius of R is demonstrated. Rietveld refinements show that the large A2-site is fully occupied by Ba(2+) and, in addition to the R cation size, the presence of vacancies at the A1-site (perovskite-like site) is also shown to strongly affect the stability of ferroelectricity in this structure type. PMID:24950736

Gardner, Jonathan; Morrison, Finlay D

2014-08-14

248

Tetranuclear lanthanide (III) complexes containing dimeric subunits: single-molecule magnet behavior for the Dy4 analogue.  

PubMed

The reaction of the lanthanide(III) salts [Dy(III), Tb(III), and Gd (III)] with a hetero donor chelating ligand N'-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide (LH3) and pivalic acid (PivH) in the presence of tetra-n-butylammonium hydroxide (TBAH) afforded the tetranuclear Ln(III) coordination compounds, [Ln4(LH)2(LH2)2(?2-?(1)?(1)Piv)2(?(1)Piv)4]·2CHCl3 [Ln = Dy(1), Tb(2), and Gd(3)]. The molecular structure of these complexes reveals that the tetranuclear derivatives are composed of two dinuclear subunits which are interconnected through the coordination action of the picolinoyl hydrazine ligand. Within each subunit two different types of Ln(III) ions are present. One of these is eight-coordinate in a distorted triangular dodecahedral geometry while the other is nine-coordinate in a distorted spherical capped square antiprism geometry. Alternating current (ac) susceptibility measurements of complex 1 reveal a frequency- and temperature-dependent two step out-of-phase signals under 1kOe DC field which is characteristic of a single-molecule magnet (SMM) behavior. Analysis of the magnetic data afforded the anisotropic barriers and relaxation times: ?/kB = 62.6 K, ?0 = 8.7 × 10(-7) s; ?/kB = 26.3 K, ?0 = 1.26 × 10(-6) s for the slow and fast relaxations respectively. PMID:24111517

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

2013-10-21

249

Metal-insulator transitions, structural and microstructural evolution of RNiO{sub 3} (R = Sm, Eu, Gd, Dy, Ho, Y) perovskites: Evidence for room-temperature charge disproportionation in monoclinic HoNiO{sub 3} and YNiO{sub 3}  

SciTech Connect

RNiO{sub 3} nickelates have been prepared under high oxygen pressure (R = Sm, Eu, Gd) or high hydrostatic pressure (R = Dy, Ho, Y) in the presence of KClO{sub 4}. The samples have been investigated at room temperature (RT) by synchrotron X-ray powder diffraction to follow the evolution of the crystal structures and microstructures along the series. The distortion of the orthorhombic (space group Pbnm) perovskite progressively increases along the series, leading for the smallest Ho{sup 3+} and Y{sup 3+} cations to a subtle monoclinic distortion (space group P2{sub 1}/n) which implies the splitting of the Ni positions in the crystal. This symmetry was confirmed by neutron powder diffraction; the crystal structures for R = Ho and Y were refined simultaneously from RT synchrotron and neutron powder diffraction data. In both perovskites the oxygen octahedra around Ni1 and Ni2 positions are significantly distorted, suggesting the manifestation of Jahn-Teller effect, which is almost absent in the nickelates` of lighter rare earths. The very distinct mean Ni-O bond distances observed for Ni1 and Ni2 atoms at RT, in the insulating regime, suggest the presence of a charge disproportionation effect, considered as driving force for the splitting of the Ni positions. The metal-insulator (MI) transitions for RNiO{sub 3} (R = Gd, Dy, Ho, Y), above room temperature, have been characterized by DSC. The transition temperatures for Gd, Dy, Ho, and Y oxides in the heating runs are 510.7, 563.9, 572.7, and 581.9 K, respectively. The increasing rate of T{sub MI} for Dy, Ho, and Y materials is lower than that expected from the variation of T{sub MI} for the larger rare earth perovskites. This is probably related to the subtle monoclinic distortion found for Ho and Y nickelates. The high-resolution synchrotron X-ray powder patterns have revealed changes in the microstructure along the series. Powder patterns for orthorhombic RNiO{sub 3} (R = Sm, Eu, Gd, Dy) display asymmetric tails for some reflections which are due to structural mistakes such as stacking faults or regular intergrowths. These mistakes are not present in monoclinic RNiO{sub 3} (R = Ho, Y) nickelates.

Alonso, J.A.; Martinez-Lope, M.J.; Casais, M.T.; Arangda, M.A.G.; Fernandez-Diaz, M.T. [C.S.I.C., Madrid (Spain). Inst. de Ciencia de Materiales] [C.S.I.C., Madrid (Spain). Inst. de Ciencia de Materiales; [Univ. de Malaga (Spain). Dept. de Quimica Inorganica, Cristalografia y Mineralogia; [Institut Laue-Langevin, Grenoble (France)

1999-05-26

250

Radio and thermoluminescence and energy transfer processes in Ce 3+(Tb 3+)-doped phosphate scintillating glasses  

Microsoft Academic Search

Ce3+ and Tb3+-doped Na(K)-Gd phosphate glasses were synthesized and their radio-, photo- and thermoluminescence properties were investigated. Increased radioluminescence efficiency with respect to Gd-free glass matrix has been achieved at Gd concentrations above 20mol%. This is explained by efficient capture of thermalised electrons and holes in the Gd3+-sublattice resulting in the formation of Gd3+ excited states followed by Gd3+-Gd3+ energy

M. Nikl; J. A. Mares; E. Mihokova; K. Nitsch; N. Solovieva; V. Babin; A. Krasnikov; S. Zazubovich; M. Martini; A. Vedda; P. Fabeni; G. P. Pazzi; S. Baccaro

2001-01-01

251

Point-charge and induced-dipole model analysis of spin-Hamiltonian parameters for Gd3+ doping single crystals of rare-earth-metal trichloride hexahydrates  

NASA Astrophysics Data System (ADS)

Spin-Hamiltonian parameters are calculated for Gd3+ doping single crystals of rare-earth-metal trichloride hexahydrates R Cl3.6H2O (RTH): R = Nd, Sm, Eu, Tb, Dy, Ho, Er, and Tm, with the use of the point-charge plus induced-dipole model, with variable anisotropic tensor polarizabilities. It is found that the parameters can all be computed to be within experimental error by suitable choices of polarizability tensors. Conclusions about the polarizability values of the various ions in the RTH crystals are drawn.

Lewis, Norman R.; Misra, Sushil K.

1982-04-01

252

Multicolour PEI/NaGdF4:Ce3+,Ln3+ nanocrystals by single-wavelength excitation  

NASA Astrophysics Data System (ADS)

Multicolour colloidal PEI/NaGdF4:Ce3+,Ln3+ (Ln = Tb, Eu, Sm or Dy) nanocrystals were synthesized using a simple one-pot hydrothermal procedure. The nanocrystals consist of well crystallized hexagonal phase and have an elongated spherical shape, with diameters between 25 and 45 nm. Under single-wavelength excitation at 254 nm in the ultraviolet (UV) region, the nanocrystals doped with different lanthanide ions show intense visible (VIS) emissions of different colours. The characteristic luminescence property of the nanocrystals can be attributed to strong absorption of the UV irradiation by the Ce3+, followed by energy transfer to (via Gd3+ sublattice) and emission from the luminescent centres.

Wang, Feng; Fan, Xianping; Wang, Minquan; Zhang, Yong

2007-01-01

253

Modeling the Frequency Dependence of the Complex In-plane Permittivity of Strained Ruddlesden-Popper Series Sr(n+1)Ti(n)O(3n+1) (n = 2, 3, 4, 5, 6) Phases on DyScO3 and GdScO3  

NASA Astrophysics Data System (ADS)

We explore the in-plane complex relative permittivity as a function of frequency of epitaxial thin-films of the Ruddlesden-Popper series Srn+1TinO3n+1 (n = 2, 3, 4, 5, 6) grown on the rare-earth scandate substrates DyScO3 and GdScO3, which correspond to biaxial tensile strain of approximately 1.1% and 1.7%, respectively. The thin films are 50 nm on DyScO3 and 25 nm thick on GdScO3, to ensure uniform strain throughout the film. We characterize the thin films with a set of optimally designed coplanar waveguides from 45 MHz to 40 GHz and with a set of interdigitated electrodes of varying active lengths from 10 Hz to 100 MHz. We then extract the in-plane complex permittivity from 10 Hz to 40 GHz for these thin films. We report the dependence of the Curie temperature, tunability, and loss tangent on series number and strain at 1 MHz. We also present a frequency-dependent model and the corresponding fit parameters for these thin films as a function of temperature. The model assumes a distribution of domains below the Curie temperature and high frequency relaxation that we attribute to the lowest-order phonon

Orloff, N. D.; Lee, C.-H.; Biegalski, M. D.; Takeuchi, Ichiro; Schlom, D. G.; Booth, J. C.

2011-03-01

254

Magnetoelectric coupling in Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 thin films deposited on Pt/TiO2/SiO2/Si substrate  

NASA Astrophysics Data System (ADS)

Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) thin films were sputtered on Pt/TiO2/SiO2/Si substrate. PZT and Terfenol-D layers were chosen for their large piezoelectric and magnetostrictive coefficients, respectively. 4%-5% magnetocapacitance has been measured on a Terfenol-D/Pt/PZT stack at room temperature. A magnetoelectric (ME) voltage coefficient of 150 mV/cm Oe was obtained at low dc magnetic field out of mechanical resonance. This work demonstrates the possibility to achieve ME effect in integrated devices involving Terfenol-D and PZT thin films providing that the diffusion, which may occur between both active layers is reduced using an intermediate layer.

Cibert, C.; Zhu, J.; Poullain, G.; Bouregba, R.; More-Chevalier, J.; Pautrat, A.

2013-01-01

255

Crystal structure and magnetic properties of novel R{sub 3}Co{sub 2.2}Si{sub 1.8} compounds (R=Y, Gd-Tm)  

SciTech Connect

The crystal structure of new ternary Dy{sub 3}Co{sub 2.2}Si{sub 1.8} compound has been established using single crystal X-ray diffraction, and those of R{sub 3}Co{sub 2.2}Si{sub 1.8} phases (R=Y, Gd-Tm) phases have been verified through the powder diffraction techniques. The Dy{sub 3}Co{sub 2.2}Si{sub 1.8} structure is a new structure type, which is obtained from the Er{sub 3}Ge{sub 4} with an ordered Er{sub 3}Ge{sub 4}-type structure (space group Cmcm) one by coloring the two Ge sites, 4a and 4c, with Si and the 8f site with Co atoms. Tb{sub 3}Co{sub 2.2}Si{sub 1.8}, Dy{sub 3}Co{sub 2.2}Si{sub 1.8}, Ho{sub 3}Co{sub 2.2}Si{sub 1.8} and Er{sub 3}Co{sub 2.2}Si{sub 1.8} compounds display ferromagnetic-type ordering. - Graphical abstract: The novel R{sub 3}Co{sub 2.2}Si{sub 1.8} compounds (R=Y, Gd-Tm) adopt the new structure type, the ordered variant of Er{sub 3}Ge{sub 4}-type structure Magnetic studies on {l_brace}Tb, Dy, Ho, Er{r_brace}{sub 3}Co{sub 2.2}Si{sub 1.8} suggest that their magnetic interactions are primarily ferromagnetic in nature. Highlights: Black-Right-Pointing-Pointer The novel {l_brace}Y, Gd-Tm{r_brace}{sub 3}Co{sub 2.2}Si{sub 1.8} compounds adopt the Dy{sub 3}Co{sub 2.2}Si{sub 1.8} structure type, Black-Right-Pointing-Pointer The Dy{sub 3}Co{sub 2.2}Si{sub 1.8} type is ordered variant of Er{sub 3}Ge{sub 4} type structure. Black-Right-Pointing-Pointer {l_brace}Gd-Tm{r_brace}{sub 3}Co{sub 2.2}Si{sub 1.8} compounds are primarily ferromagnetic in nature.

Morozkin, A.V., E-mail: morozkin@general.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Moscow GSP-2 119992 (Russian Federation); Yao, Jinlei; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Canada, Ontario L8S 4M1 (Canada)

2012-08-15

256

Syntheses, Structures, and Physical Properties of the New Quaternary Rare-Earth Chalcogenides RbNd 2CuS 4, RbSm 2CuS 4, CsLa 2CuSe 4, CsSm 2CuSe 4, RbEr 2Cu 3S 5, CsGd 2Ag 3Se 5, CsTb 2Ag 3Se 5, and Rb 2Gd 4Cu 4S 9  

NASA Astrophysics Data System (ADS)

Eight quaternary rare-earth chalcogenides, RbNd 2CuS 4, RbSm 2CuS 4, CsLa 2CuSe 4, CsSm 2CuSe 4, RbEr 2Cu 3S 5, CsGd 2Ag 3Se 5, CsTb 2Ag 3Se 5, and Rb 2Gd 4Cu 4S 9, have been synthesized at 973 K with the use of a reactive flux of A2Q 3 ( A=Rb, Cs; Q=S, Se). All structural data were obtained at 153 K. The isostructural compounds ALn2Cu Q4 ( Ln=rare earth) crystallize with four formula units in the KGd 2CuS 4 structure type in space group Cmcm of the orthorhombic system; the isostructural compounds ALn2M3Q5 ( M=Cu, Ag) crystallize with four formula units in the RbSm 2Ag 3Se 5 structure type in space group Cmcm of the orthorhombic system; and Rb 2Gd 4Cu 4S 9 crystallizes with two formula units in space group C2/ m of the monoclinic system. The cell dimensions of ALn2Cu Q4 ( a, b, c (Å)) are as follows: RbNd 2CuS 4, 4.0762(3), 13.954(1), 13.964(1); RbSm 2CuS 4, 4.0391(3), 13.815(1), 13.860(1); CsLa 2CuSe 4, 4.3129(6), 14.959(2), 14.798(2); CsSm 2CuSe 4, 4.2066(3), 14.6101(9), 14.5164(9). The corresponding R1 indices for the refined structures are 0.0264, 0.0196, 0.0258, and 0.0224. The cell dimensions of ALn2M3Q5 are as follows: RbEr 2Cu 3S 5, 3.9283(3), 13.897(1), 16.348(1); CsGd 2Ag 3Se 5, 4.2943(4), 15.424(1), 17.501(2); CsTb 2Ag 3Se 5, 4.2779(4), 15.429(2), 17.426(2). The R1 indices are 0.0257, 0.0255, and 0.0241. The cell dimensions of Rb 2Gd 4Cu 4S 9 ( a, b, c (Å), ? (°)) is 13.897(1), 3.9883(3), 16.054(1), 109.273(1), and the R1 index is 0.0199. All eight compounds have closely related three-dimensional tunnel structures. All alkali metal atoms in the tunnels are coordinated to eight Q atoms. Their anionic frameworks are built from LnQ6 octahedra and MQ4 tetrahedra. ALn2Cu Q4 contains 1?[Cu Q3] chains of vertex-sharing tetrahedra; Rb 2Gd 4Cu 4S 9 contains 1?[Cu 4S 8] chains of tetrahedra; and ALn2M3Q5 contains 2?[ M3Q5] layers of tetrahedra. Rb 2Gd 4Cu 4S 9 and RbEr 2Cu 3S 5, which are paramagnetic, obey the Curie-Weiss law, and have effective magnetic moments of 7.9(2) ?B for Gd 3+ and 9.43(5) ?B for Er 3+. A band gap of 1.94 eV for Rb 2Gd 4Cu 4S 9 was deduced from its diffuse reflectance spectrum, and the typical 4 f-4 f optical transitions for Er 3+ were found in RbEr 2Cu 3S 5 at about 1.6, 1.9, and 2.5 eV.

Huang, Fu Qiang; Ibers, James A.

2001-05-01

257

Monte Carlo study on the imaging performance of powder Lu{sub 2}SiO{sub 5}:Ce phosphor screens under x-ray excitation: Comparison with Gd{sub 2}O{sub 2}S:Tb screens  

SciTech Connect

Lu{sub 2}SiO{sub 5}:Ce (LSO) scintillator is a relatively new luminescent material which has been successfully applied in positron emission tomography systems. Since it has been recently commercially available in powder form, it could be of value to investigate its performance for use in x-ray projection imaging as both physical and scintillating properties indicate a promising material for such applications. In the present study, a custom and validated Monte Carlo simulation code was used in order to examine the performance of LSO, under diagnostic radiology (mammography and general radiography) conditions. The Monte Carlo code was based on a model using Mie scattering theory for the description of light attenuation. Imaging characteristics, related to image brightness, spatial resolution and noise of LSO screens were predicted using only physical parameters of the phosphor. The overall performance of LSO powder phosphor screens was investigated in terms of the: (i) quantum detection efficiency (ii) emitted K-characteristic radiation (iii) luminescence efficiency (iv) modulation transfer function (v) Swank factor and (vi) zero-frequency detective quantum efficiency [DQE(0)]. Results were compared to the traditional rare-earth Gd{sub 2}O{sub 2}S:Tb (GOS) phosphor material. The relative luminescence efficiency of LSO phosphor was found inferior to that of GOS. This is due to the lower intrinsic conversion efficiency of LSO (0.08 instead of 0.15 of GOS) and the relatively high light extinction coefficient m{sub ext} of this phosphor (0.239 {mu}m{sup -1} instead of 0.218 {mu}m{sup -1} for GOS). However, the property of increased light extinction combined with the rather sharp angular distribution of scattered light photons (anisotropy factor g=0.624 for LSO instead of 0.494 for GOS) reduce lateral light spreading and improve spatial resolution. In addition, LSO screens were found to exhibit better x-ray absorption as well as higher signal to noise transfer properties in the energy range from 18 keV up to 50.2 keV (e.g. DQE(0)=0.62 at 18 keV and for 34 mg/cm{sup 2}, instead of 0.58 for GOS). The results indicate that certain optical properties of LSO (optical extinction coefficient, scattering anisotropy factor) combined with the relatively high x-ray coefficients, make this material a promising phosphor which, under appropriate conditions, could be considered for use in x-ray projection imaging detectors.

Liaparinos, Panagiotis F.; Kandarakis, Ioannis S.; Cavouras, Dionisis A.; Delis, Harry B.; Panayiotakis, George S. [Department of Medical Physics, Faculty of Medicine, University of Patras, 265 00 Patras (Greece); Department of Medical Instruments Technology, Technological Educational Institute, 122 10 Athens (Greece); Department of Medical Physics, Faculty of Medicine, University of Patras, 265 00 Patras (Greece)

2007-05-15

258

Photoluminescence properties of Tb3+-doped heavy scintillating germanate glasses  

Microsoft Academic Search

A group of of heavy germanate glasses containing BaO and\\/or Gd2O3, La2O3, SnO and doped with the scintillating rare earth Tb3+ are presented. Photoluminescence measurements are made on these glasses. The intensity of emission peaks is found proportional to the contents of Tb3+ dopants as well as of Gd3+: the former indicates that no obvious concentration quenching effect is visualized

Guorong Chen; S. Baccaro; A. Cecilia; Shan Wang; Jiaxiang Nie; Yonghui Zhang; Yongjuan Du

2003-01-01

259

Ion size effect of rare earth on T c, T N and ? n in (R 1-xPr x)Ba 2Cu 3O 7-y systems (R?Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, Sm and Nd)  

NASA Astrophysics Data System (ADS)

A detailed study of the superconductivity, magnetic ordering of Pr ions and the normal transport properties is reported for sintered (R 1-xPr x)Ba 2Cu 3O 7 samples (R?Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, Sm and Nd) with x = 0-1.0. We found that at a constant Pr concentration, x, the superconducting transition temperature T c, the antiferromagnetic ordering temperature T N of Pr ions and the normal state resistivity ? n in (R 1-xPr x)Ba 2Cu 3O 7 systems are R ion-size dependent. Observed results were interpreted in terms of the hybridization between the local states of Pr ion and the conduction band states of the CuO 2 planes.

Guan, Weiyan

1994-12-01

260

Investigation of annealed and metamict pyrochlore minerals by x-ray absorption spectroscopy. [Synthetic pyrochlores with general formula (RE)/sub 2/Ti/sub 2/O/sub 7/, RE = Er, Y/sub 2/, Gd/sub 2/, Dy, La  

SciTech Connect

Materials of the pyrochlore structure type exhibit a variety of interesting properties including phases capable of acting as hosts for actinides in radioactive wastes. Studies of curium doped gadolinium titanate phases (Gd/sub 2/Ti/sub 2/O/sub 7/) have been made which showed that the radiation damage ingrowth followed an exponential relationship. For the study reported here a series of synthetic pyrochlores were produced having the titanate phase with the general formula (RE)/sub 2/Ti/sub 2/O/sub 7/, RE = Er, Y/sub 2/, Gd/sub 2/, Dy, La. Additionally a set of metamict (radiation damaged) pyrochlores was examined in both a natural and post temperature annealed state. Experiments were conducted on these samples using the Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) techniques. In summary, these studies show that in pyrochlore structure types the Ti-O cage undergoes changes due to radiation damage. The individual Ti-O bonds become more disordered which leads to a loss of short and long range order and, ultimately, to expansion of the bulk material. 2 refs., 2 figs.

Greegor, R.B.; Lytle, F.W.; Ewing, R.C.; Chakoumakos, B.C.; Lumpkin, G.R.

1984-01-01

261

Tuberculosis Facts - Exposure to TB  

MedlinePLUS

... STD, and TB Prevention Division of Tuberculosis Elimination Tuberculosis (TB) Facts Exposure to TB What is TB? “TB” is short for a disease called tuberculosis. TB is spread through the air from one ...

262

Tuberculosis Facts - Testing for TB  

MedlinePLUS

... STD, and TB Prevention Division of Tuberculosis Elimination Tuberculosis (TB) Facts Testing for TB What is TB? “TB” is short for a disease called tuberculosis. TB is spread through the air from one ...

263

Systematics of x-ray resonant scattering amplitudes in R Ni2 Ge2 ( R=Gd ,Tb,Dy,Ho,Er,Tm): The origin of the branching ratio at the L edges of the heavy rare earths  

NASA Astrophysics Data System (ADS)

An investigation of the x-ray resonant magnetic scattering (XRMS) across the series of heavy rare-earth elements, coupled with first-principles calculations, has revealed that spin-orbit coupling in the 5d band plays a critical role in the systematics of the XRMS and x-ray magnetic circular dichroism branching ratio at the L edges of magnetic rare-earth compounds.

Kim, J. W.; Lee, Y.; Wermeille, D.; Sieve, B.; Tan, L.; Bud'Ko, S. L.; Law, S.; Canfield, P. C.; Harmon, B. N.; Goldman, A. I.

2005-08-01

264

The peculiar magnetic property evolution along RCu3Mn4O12 (R=Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu): A first-principles study  

NASA Astrophysics Data System (ADS)

Within RCu3Mn4O12 (R=Rare earth), besides the expected ferrimagnetic order of Mn and Cu ions below TC1, R magnetic moments also play an important role at lower temperatures TC2, leading to their peculiar magnetic behavior. By first-principles calculation, we found that along the series from La to Lu, TC1 monotonically increased due to the ionic radius (IR) induced chemical pressure, as experimentally observed, while TC2 is closely related to the atomic radius of R. Additionally, the magnetic anisotropy energy (?Eani) along the series is found to be correlated with the total magnetic moment of R ion.

Liu, Xiaojuan; Lv, Shuhui; Li, Hongping; Meng, Jian

2010-12-01

265

TB Screening Tests  

MedlinePLUS

... Release Assays; IGRA; T-Spot®.TB; QuantiFERON®-TB Gold (QFT-G); QuantiFERON®-TB Gold In-Tube (QFT-GIT) Formal name: Tuberculin Skin ... June 2010. (Reviewed 2009 June 1). QuantiFERON®-TB Gold Test, CDC Tuberculosis (TB) Fact Sheet [On-line ...

266

Gadolinium complex and phosphorescent probe-modified NaDyF4 nanorods for T1- and T2-weighted MRI/CT/phosphorescence multimodality imaging.  

PubMed

To compensate for the deficiencies of individual imaging modalities, lanthanide-based nanoparticles are ideal building blocks for multifunctional contrast agents. Herein, oleic acid-coated NaDyF4 nanorods (DyNPs) were synthesized by the hydrothermal method, and then coated with ?-cyclodextrin (?-CD) and modified with gadolinium complex (Gd-DTPA) to obtain hydrophilic and functionalized nanoparticles (DyNPs-Gd). By loading the phosphorescent probe (iridium-complex) within the surface hydrophobic layer, the developed nanophosphors (DyNPs-Gd-Ir) could be further applied in phosphorescent cell labeling. The Dy in the host induces a high X-ray absorption ability for X-ray computed tomography (CT) and negative enhancement for T2-weighted magnetic resonance imaging (MRI), whereas positive contrast for T1-weighted MRI results from the Gd-DTPA. DyNPs-Gd-Ir has been successfully applied to T1- and T2-weighted MRI/CT in vivo. Toxicity studies demonstrated that DyNPs-Gd-Ir exhibited low toxicity to living systems. Therefore, DyNPs-Gd-Ir could be a platform for next-generation contrast agents for T1- and T2-weighted MRI/CT/phosphorescence multimodal imaging. PMID:24119502

Zhou, Jing; Lu, Zhigao; Shan, Guogang; Wang, Sihui; Liao, Yi

2014-01-01

267

Nuclear Resonance Absorption in Dy161 Situated in Dy2O3 and Dysprosium Iron Garnet  

Microsoft Academic Search

The recoil-free resonant absorption of the 26-kev gamma ray (T12~3×10-8 sec) emitted in the decay of Tb161 by absorbers containing Dy161 has been investigated. High Mössbauer efficiencies at room temperatures have been observed for sources and absorbers in the form of oxide and rare earth iron garnet. The line shapes obtained were very broad, of the order of 100 times

S. Ofer; P. Avivi; R. Bauminger; A. Marinov; S. G. Cohen

1960-01-01

268

Mössbauer line-shape parameters for 159Tb in TbAl2 and Tb4O7  

NASA Astrophysics Data System (ADS)

Precise line-shape analyses of Mössbauer spectra using the 58-keV transition in 159Tb have been made using an exact representation of the line shape in transmission. Spectra were made using a Dy2O3 source at liquid-nitrogen temperature and absorbers of Tb4O7 and TbAl2 at several temperatures from 81 to 297 K. We have measured the recoilless fraction as a function of temperature between 115 and 297 K for TbAl2 and at 81 and 294 K in Tb4O7. If the theoretical value of the internal conversion coefficient of 11 is accepted, we cannot fit our results to a Debye model, even in a rough approximation. The mean lifetime of the first excited state of 159Tb was determined to be 77(1) ps. We have found the value of the interference parameter for this transition to be -0.0058(7), which appears larger in magnitude than predicted by theory.

Bullard, B. R.; Mullen, J. G.

1991-04-01

269

119Sn Mössbauer spectroscopy and specific heat studies of the stannides RETSn ( RE=Gd-Er and T=Cu,Ag)  

NASA Astrophysics Data System (ADS)

The stannides RETSn ( RE=Gd-Er and T=Cu,Ag), NdPtSb type structure, space group P63mc, have been investigated by 119Sn Mössbauer spectroscopy and specific heat studies. Small transferred magnetic hyperfine fields are detected at the tin nuclei at 4.2 K in the 119Sn Mössbauer spectra of RECuSn ( RE=Tb,Dy and Ho) which reveal that these compounds undergo magnetic transitions at low temperatures. Heat capacity ( C) measurements show that the title compounds undergo antiferromagnetic ordering. In order to explore the magnetic behaviour below the Néel temperature (TN), the magnetic part of heat capacity (C) was obtained by subtracting the lattice part of heat capacity (C) obtained from the isostructural non-magnetic stannides Y TSn ( T=Cu,Ag). C of GdCuSn exhibits an equal moment (EM) magnetic structure and also exhibits multiple transitions below TN, revealing higher order exchange interactions. Among the REAgSn stannides, the magnetic part of heat capacity (C) for RE=Dy and Er exhibits non- T3 behaviour at low temperatures.

Sebastian, C. Peter; Rayaprol, Sudhindra; Pöttgen, Rainer

2006-11-01

270

Global Tuberculosis (TB)  

MedlinePLUS

... Global Tuberculosis (TB) TB is one of the world’s deadliest diseases: One third of the world’s population are infected with TB. In 2012, 8. ... health problem in many other parts of the world. In 2013, 64% of all TB cases and ...

271

TB and Antibiotic Resistance  

NSDL National Science Digital Library

How does the development of antibiotic resistant strains of TB influence modern healthcare practices? We will consider genetic, environmental, epidemiological, and social perspectives of this renewed threat to public health. The TB simulation allows us to experiment with several TB strains and the antibiotics used to treat TB as we explore antibiotic resistance. * use sequence information to develop a protocol for treating antibiotic resistant TB

Marion Fass (Beloit College;Biology)

2006-05-20

272

Testing for TB Infection  

MedlinePLUS

... Laws Publications & Products Fact Sheets General Fact sheets - Spanish TB - General Information The Difference Between Latent TB ... HIV Coinfection Patient Education Series English Only English/Spanish English/Tagalog Tuberculosis - Get the Facts Tuberculosis - La ...

273

Tuberculosis Facts - TB Can Be Treated  

MedlinePLUS

... STD, and TB Prevention Division of Tuberculosis Elimination Tuberculosis (TB) Facts TB Can Be Treated What is TB? “TB” is short for a disease called tuberculosis. TB is spread through the air from one ...

274

Tuberculosis Facts - TB and HIV/AIDS  

MedlinePLUS

... STD, and TB Prevention Division of Tuberculosis Elimination Tuberculosis (TB) Facts TB and HIV/AIDS What is TB? “TB” is short for a disease called tuberculosis. TB is spread through the air from one ...

275

Tuberculosis Facts - You Can Prevent TB  

MedlinePLUS

... STD, and TB Prevention Division of Tuberculosis Elimination Tuberculosis (TB) Facts You Can Prevent TB What is TB? “TB” is short for a disease called tuberculosis. TB is spread through the air from one ...

276

Gd-DTPA enhanced MR imaging in intracranial tuberculosis  

Microsoft Academic Search

Twenty-six patients with intracranial tuberculosis (Tb) (10 with acute meningitis, 5 with chronic meningitis, 5 with meningitic sequelae and 6 with localized tuberculoma(s) were examined with MR before and after Gd-DTPA enhancement (0.1 mmol\\/kg), using 2.0T superconducting unit, and the images were retrospectively analyzed and compared with CT scans. Without Gd-DTPA enhancement, the MR images were generally insensitive to detection

K.-H. Chang; M.-H. Han; J.-K. Roh; I.-O. Kim; M.-C. Han; K.-S. Choi; C.-W. Kim

1990-01-01

277

Difference Between Latent TB Infection and Active TB Disease  

MedlinePLUS

... Viral Hepatitis, STD, and TB Prevention Division of Tuberculosis Elimination What is TB? Tuberculosis (TB) is a disease caused by a germ called Mycobacterium tuberculosis that is spread from person to person through ...

278

Squaring the cube: a family of octametallic lanthanide complexes including a Dy8 single-molecule magnet.  

PubMed

A series of isostructural octanuclear lanthanide complexes of general formula [Ln8(sao)4(?3-OH)4(NO3)12(DMF)12] (Ln = Nd (), Sm (), Eu (), Gd (), Tb (), Dy (), Ho (), Er (); DMF = dimethylformamide) have been prepared via reactions of salicylaldoxime (saoH2), tetramethylammonium hydroxide (Me4NOH) with the appropriate lanthanide nitrate salt (Ln(NO3)3·6H2O). The metallic skeletons of the complexes describe [Ln4] tetrahedra encapsulated inside a [Ln4] square with the inner core stabilised through ?3-OH(-) ions and the periphery by ?4-sao(2-) ligands. The magnetic properties of compounds were investigated by dc and ac magnetometry. Temperature dependent ac magnetic susceptibility data reveal that the dysprosium analogue () displays an out-of-phase signal in the absence of an applied magnetic field indicative of slow relaxation of the magnetization typical of a Single-Molecule Magnet (SMM). Micro-SQUID measurements reveal temperature and sweep rate dependent hysteresis below 1.0 K. PMID:23943045

Fang, Ming; Zhao, Hanhua; Prosvirin, Andrey V; Pinkowicz, Dawid; Zhao, Bin; Cheng, Peng; Wernsdorfer, Wolfgang; Brechin, Euan K; Dunbar, Kim R

2013-10-01

279

New ternary rare-earth metal boride carbides R15B 4C 14 ( R=Y, Gd-Lu) containing BC 2 units: Crystal and electronic structures, magnetic properties  

NASA Astrophysics Data System (ADS)

The ternary rare-earth boride carbides R15B 4C 14 ( R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. The crystal structures of Tb 15B 4C 14 and Er 15B 4C 14 were determined from single crystal X-ray diffraction data. They crystallize in a new structure type in space group P4/ mnc (Tb 15B 4C 14: a=8.1251(5) Å, c=15.861(1) Å, Z=2, R1=0.041 (w R2=0.088) for 1023 reflections with Io>2 ?( Io); Er 15B 4C 14: a=7.932(1) Å, c=15.685(2) Å, Z=2, R1=0.037 (w R2=0.094) for 1022 reflections with Io>2 ?( Io)). The crystal structure contains discrete carbon atoms and bent CBC units in octahedra and distorted bicapped square antiprisms, respectively. In both structures the same type of disorder exists. One R atom position needs to be refined as split atom position with a ratio 9:1 indicative of a 10% substitution of the neighboring C 4- by C 24-. The actual composition has then to be described as R15B 4C 14.2. The isoelectronic substitution does not change the electron partition of R15B 4C 14 which can be written as ( R3+) 15(C 4-) 6(CBC 5-) 4•e -. The electronic structure was studied with the extended Hückel method. The investigated compounds Tb 15B 4C 14, Dy 15B 4C 14 and Er 15B 4C 14 are hard ferromagnets with Curie temperatures TC=145, 120 and 50 K, respectively. The coercive field BC=3.15 T for Dy 15B 4C 14 is quite remarkable.

Babizhetskyy, Volodymyr; Simon, Arndt; Mattausch, Hansjürgen; Hiebl, Kurt; Zheng, Chong

2010-10-01

280

TB Is Back.  

ERIC Educational Resources Information Center

The reemergence of tuberculosis, particularly of new drug-resistant strains, points up the need for well-coordinated school health programs. Immigration effects, growing populations of HIV-infected persons, and relaxed screening procedures are partly responsible for TB's reemergence. Two sidebars offer advice on coping with TB at school and…

Natale, Jo Anna

1992-01-01

281

Questions and Answers about TB  

MedlinePLUS

... TB Print page ? Listen to audio/Podcast Español (Spanish) Contact Us: Centers for Disease Control and Prevention ... Laws Publications & Products Fact Sheets General Fact sheets - Spanish TB - General Information The Difference Between Latent TB ...

282

Ternary rare-earth ruthenium and iridium germanides RE3M2Ge3 (RE=Y, Gd-Tm, Lu; M=Ru, Ir)  

NASA Astrophysics Data System (ADS)

Through arc-melting reactions of the elements and annealing at 800 °C, the ternary rare-earth germanides RE3Ru2Ge3 and RE3Ir2Ge3 have been prepared for most of the smaller RE components (RE=Y, Gd-Tm, Lu). In the iridium-containing reactions, the new phases RE2IrGe2 were also generally formed as by-products. Powder X-ray diffraction revealed orthorhombic Hf3Ni2Si3-type structures (space group Cmcm, Z=4) for RE3M2Ge3 (M=Ru, Ir) and monoclinic Sc2CoSi2-type structures (space group C2/m, Z=4) for RE2IrGe2. Full crystal structures were determined by single-crystal X-ray diffraction for all members of RE3Ru2Ge3 (a=4.2477(6) Å, b=10.7672(16) Å, c=13.894(2) Å for RE=Y; a=4.2610(3)-4.2045(8) Å, b=10.9103(8)-10.561(2) Å, c=14.0263(10)-13.639(3) Å in the progression of RE from Gd to Lu) and for Tb3Ir2Ge3 (a=4.2937(3) Å, b=10.4868(7) Å, c=14.2373(10) Å). Both structures can be described in terms of CrB- and ThCr2Si2-type slabs built from Ge-centred trigonal prisms. However, band structure calculations on Y3Ru2Ge3 support an alternative description for RE3M2Ge3 based on [M2Ge3] layers built from linked MGe4 tetrahedra, which emphasizes the strong M-Ge covalent bonds present. The temperature dependence of the electrical resistivity of RE3Ru2Ge3 generally indicates metallic behaviour but with low-temperature transitions visible for some members (RE=Gd, Tb, Dy) that are probably associated with magnetic ordering of the RE atoms. Anomalously, Y3Ru2Ge3 exhibits semiconductor-like behaviour of uncertain origin. Magnetic measurements on Dy3Ru2Ge3 reveal antiferromagnetic ordering at 3 K and several unusual field-dependent transitions suggestive of complex spin reorientation processes.

Oliynyk, Anton O.; Stoyko, Stanislav S.; Mar, Arthur

2013-06-01

283

Structures and physical properties of rare-earth zinc antimonides Pr6Zn(1+x)Sb(14+y) and RE6Zn(1+x)Sb14 (RE = Sm, Gd-Ho).  

PubMed

A new series of isostructural ternary rare-earth zinc antimonides RE(6)Zn(1+x)Sb(14+y) (RE = Pr, Sm, Gd-Ho) has been obtained by direct reaction of the elements at 1050-1100 degrees C. Single-crystal X-ray diffraction studies revealed that these compounds adopt an orthorhombic structure type (space group Immm (no. 71), Z = 2, a = 4.28-4.11 A, b = 15.15-14.73 A, c = 19.13-18.56 A in the progression from RE = Pr to Ho) that may be regarded as stuffed variants of a (U(0.5)Ho(0.5))(3)Sb(7)-type host structure. Columns of face-sharing RE(6) trigonal prisms, centered by Sb atoms, occupy channels defined by an extensive polyanionic Sb network. This network is constructed from three-atom-wide and four-atom-wide Sb strips, the latter being linked together by single Sb atoms in RE(6)Zn(1+x)Sb(14) (RE = Sm, Gd-Ho; y = 0), but also by additional Sb-Sb pairs in a disordered fashion in Pr(6)Zn(1+x)Sb(14+y) (y = approximately 0.6). Interstitial Zn atoms then partially fill tetrahedral sites (occupancy of 0.5-0.7) and, to a lesser extent, square pyramidal sites (occupancy of 0.04-0.12), accounting for the observed nonstoichiometry with variable x. Except for the Gd member, these compounds undergo antiferromagnetic ordering below T(N) < 9 K, with the magnetic susceptibilities of the Tb, Dy, and Ho members following the Curie-Weiss law above T(N). For the Ho member, the thermal conductivities are low and the Seebeck coefficients are small and positive, implying p-type character consistent with the occurrence of partial Zn occupancies. At low temperatures (down to 5 K), electrical resistivity measurements for the Tb, Dy, and Ho members indicated metallic behavior, which persists at high temperatures (up to 560 K) for the Ho member. Band structure calculations on an idealized "Gd(6)Zn(2)Sb(14)" model revealed the existence of a pseudogap near the Fermi level. PMID:18998668

Liu, Yi; Chen, Ling; Li, Long-Hua; Wu, Li-Ming; Zelinska, Oksana Ya; Mar, Arthur

2008-12-15

284

Series of edge-sharing bi-triangle Ln4 clusters with a ?4-NO3- bridge: syntheses, structures, luminescence, and the SMM behavior of the Dy4 analogue.  

PubMed

A series of Ln4 clusters, [Ln4L2(?3-OH)2(?4-NO3)(NO3)4(OCH3)(H2O)]·xMeCN·yMeOH (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5), Yb (6), L = 2-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-6-methoxyphenol), have been synthesized by the reaction of Ln(NO)3 and a Schiff-base ligand formed in situ. The six complexes display similar structures, with an overall metal core comprising two edge-sharing triangular Ln3 units linked by a ?4-NO3(-) bridge. The luminescence spectrum of complex 2 shows the characteristic emission of the Tb(III) ions. The magnetic susceptibility studies reveal that the Ln(III) ions are very weakly interacting in all six compounds. Frequency dependence of the ac-susceptibility was found for 3, suggesting a typical single-molecule magnet (SMM) behavior with an anisotropic barrier of 28 K. PMID:24316728

Zou, Hua-Hong; Wang, Rong; Chen, Zi-Lu; Liu, Dong-Cheng; Liang, Fu-Pei

2014-02-14

285

VUV sensitisation of Eu 3+ emission by Tb 3+ in Ba 3Tb(PO 4) 3–Eu  

Microsoft Academic Search

The luminescence properties of Ba3Tb0.9Eu0.1(PO4)3 and Ba3Gd0.9Eu0.1(PO4)3 phosphors were studied for excitation over the 120–300nm wavelength range. It is found that Tb3+, which exhibits a strong vacuum-ultraviolet (VUV) absorption band, provides sensitisation of Eu3+ emission in this host. This effect can be used to develop phosphors with enhanced conversion efficiency of the VUV radiation into visible light.

V. B. Mikhailik; H. Kraus

2009-01-01

286

Tuberculosis (TB): Treatment  

MedlinePLUS

... Iseman, MD Dept. of Medicine View full profile Tuberculosis (TB): Treatment Given the many effective medications available ... Calendar Read the News View Daily Pollen Count Tuberculosis Program National Jewish Health is a world-renowned ...

287

Laser induced effects in the optical properties of Tb 3+-doped phosphate scintillating glasses  

Microsoft Academic Search

Optical absorption, photo- and thermo-luminescence measurements were performed on (NaPO3)x(GdPO4)y(TbPO4)z (x=60–77mol%; y=20–30mol%; z=3–10mol%) glasses. Pronounced changes of photoluminescence intensity of the leading 542nm emission line of Tb3+ were observed during prolonged excitation (irradiation) by 308nm XeCl excimer laser line into the Gd3+6P5\\/2 excited state. Laser irradiation also gave rise also to optical absorption that peaks at around 5.4MeV and to

P. Fabeni; G. P. Pazzi; M. Martini; A. Vedda; M. Nikl; K. Nitsch; S. Baccaro

2001-01-01

288

The Dy-Zn phase diagram  

NASA Astrophysics Data System (ADS)

The dysprosium-zinc phase diagram has been investigated over its entire composition range by using differential thermal analysis, (DTA) metallographic analysis, X-ray powder diffraction, and electron probe microanalysis (EPMA). Seven intermetallic phases have been found and their structures confirmed. DyZn, DyZn2, Dy13Zn58, and Dy2Zn17 melt congruently at 1095 °C, 1050 °C, 930 °C, and 930 °C, respectively. DyZn3, Dy3Zn11, and DyZn12 form through peritectic reactions at 895 °C, about 900 °C and 685 °C, respectively. Four eutectic reactions occur at 850 °C and 30.0 at pct Zn (between (Dy) and DyZn), 990 °C and 60.0 at pct Zn (between DyZn and DyZn2), 885 °C and 76.0 at pct Zn (between DyZn3 and Dy3Zn11), and 875 °C and 85.0 at pct Zn (involving Dy13Zn58 and Dy2Zn17). The Dy-rich end presents a catatectic equilibrium; a degenerate invariant effect has been found in the Zn-rich region. The phase equilibria of the Dy-Zn alloys are discussed and compared with those of the other known RE-Zn systems (RE=rare earth metal) in view of the regular change in the relative stabilities of the phases across the lanthanide series

Saccone, A.; Cardinale, A. M.; Delfino, S.; Ferro, R.

2003-03-01

289

Synthesis, structure, and thermally stable luminescence of Eu(2+)-doped Ba2Ln(BO3)2Cl (Ln = Y, Gd and Lu) host compounds.  

PubMed

A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction. The crystal structure and thermally stable luminescence of chloroborate phosphors Ba(2)Ln(BO(3))(2)Cl:Eu(2+) (Ln = Y, Gd, and Lu) have been reported in this paper. X-ray diffraction studies verify the successful isomorphic substitution for Ln(3+) sites in Ba(2)Ln(BO(3))(2)Cl by other smaller trivalent rare earth ions, such as Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. The detailed structure information for Ba(2)Ln(BO(3))(2)Cl (Ln = Y, Gd, and Lu) by Rietveld analysis reveals that they all crystallize in a monoclinic P2(1)/m space group. These compounds display interesting and tunable photoluminescence (PL) properties after Eu(2+)-doping. Ba(2)Ln(BO(3))(2)Cl:Eu(2+) phosphors exhibit bluish-green/greenish-yellow light with peak wavelengths at 526, 548, and 511 nm under 365 UV light excitation for Ba(2)Y(BO(3))(2)Cl:Eu(2+), Ba(2)Gd(BO(3))(2)Cl:Eu(2+), and Ba(2)Lu(BO(3))(2)Cl:Eu(2+), respectively. Furthermore, they possess a high thermal quenching temperature. With the increase of temperature, the emission bands show blue shifts with broadening bandwidths and slightly decreasing emission intensities. It is expected that this series of chloroborate phosphors can be used in white-light UV-LEDs as a good wavelength-conversion phosphor. PMID:21919480

Xia, Zhiguo; Wang, Xiaoming; Wang, Yingxia; Liao, Libing; Jing, Xiping

2011-10-17

290

Affordable TB treatments. South.  

PubMed

This short article reports the proceedings of a session of the World Health Organization (WHO) on tuberculosis (TB) prevention and management. 15 million persons are infected with both TB and HIV; 11 million of these people are in sub-Saharan Africa. Current TB management relies on finding cases and treating them. According to Paul Nunn of WHO, the role of preventive therapy is unclear. Jensa Bell, of Mt. Sinai Hospital in New York, reported on the cost effectiveness of prevention with isoniazid (INH) in sub-Saharan Africa. Direct medical costs of the drug for 6 months are CHF171/year of life saved. When social costs of TB and prevention of secondary cases are included, INH prophylaxis saves money; initial investment is CHF34.50/person treated, while cost averted is CHF36.24/person treated. Mary Mulindwa, of the Joint Clinical Research Centre in Kampala, Uganda, studied reasons for nonadherence to TB preventive regimens in a clinical trial. Major reasons included the following: 1) transport difficulties; 2) caring for a sick family member; 3) change of address without informing the home visitor; and 4) stigma of being seen with a health worker. Richard Chaisson, of the CP-CRA004/ACTG177 study group, reported results from a trial comparing prevention with INH for 12 months to rifampin plus pyrazinamide (R/P) for 2 months in 1600 tuberculin-positive, HIV-positive people without active disease in the US, Mexico, Brazil, and Haiti. "Effective therapy" with INH was equal to at least 6 months of continuous adherence; 67% of patients met this standard. 80% of R/P patients were adherent. Over 3 years, there were 26 confirmed cases of TB in the INH group and 19 in the R/P group; these results are equivalent. However, Chaisson noted that the cost and feasibility of R/P treatment in resource-poor settings should be considered. PMID:12222196

1998-07-01

291

Treatment: Latent TB Infection (LTBI) and TB Disease  

MedlinePLUS

... Listen to audio/Podcast View page in Español (Spanish) Contact Us: Centers for Disease Control and Prevention ... Laws Publications & Products Fact Sheets General Fact sheets - Spanish TB - General Information The Difference Between Latent TB ...

292

Two C3 -Symmetric Dy3 (III) Complexes with Triple Di-?-methoxo-?-phenoxo Bridges, Magnetic Ground State, and Single-Molecule Magnetic Behavior.  

PubMed

Two series of isostructural C3 -symmetric Ln3 complexes Ln3 ?[BPh4 ] and Ln3 ?0.33[Ln(NO3 )6 ] (in which Ln(III) =Gd and Dy) have been prepared from an amino-bis(phenol) ligand. X-ray studies reveal that Ln(III) ions are connected by one ?2 -phenoxo and two ?3 -methoxo bridges, thus leading to a hexagonal bipyramidal Ln3 O5 bridging core in which Ln(III) ions exhibit a biaugmented trigonal-prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self-consistent field (CASSCF) calculations indicate that the magnetic coupling between the Dy(III) ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest Dy?O distance, the local magnetic moments are oriented almost perpendicular to the Dy3 plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the Dy(III) ions are separated by approximately 150 and 177?cm(-1) , for Dy3 ?[BPh4 ] and Dy3 ?0.33[Dy(NO3 )6 ], respectively. As expected for these large energy gaps, Dy3 ?[BPh4 ] and Dy3 ?0.33[Dy(NO3 )6 ] exhibit, under zero direct-current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied Hdc field of 1000?Oe, Dy3 ?[BPh4 ] exhibits two thermally activated processes with Ueff values of 34.7 and 19.5?cm(-1) , whereas Dy3 ?0.33[Dy(NO3 )6 ] shows only one activated process with Ueff =19.5?cm(-1) . PMID:24890335

Hänninen, Mikko M; Mota, Antonio J; Aravena, Daniel; Ruiz, Eliseo; Sillanpää, Reijo; Camón, Agustín; Evangelisti, Marco; Colacio, Enrique

2014-07-01

293

Atomic structure of Tb(11 2 0)  

SciTech Connect

A low-energy electron-diffraction intensity analysis of a Tb(11{bar 2}0) surface finds that the atomic structure of this surface is different from bulk structure in two ways: The spacing between the first and the second layer, which have two inequivalent atoms in the unit mesh, is contracted by 3.3% (0.06 A), and the two inequivalent atoms in the first layer translate parallel to the surface by equal and opposite amounts of 0.21 A. Thus the change in registration of the composite surface layer preserves both the size and the symmetry of the unit mesh of parallel bulk layers. This kind of surface rearrangement is different from that reported by others for the (11{bar 2}0) surfaces of other rare-earth metals, such as Y, Gd, and Ho.

Li, Y.S.; Quinn, J.; Jona, F. (College of Engineering and Applied Science, State University of New York, Stony Brook, New York 11794 (United States)); Marcus, P.M. (IBM Research Center, Yorktown Heights, New York 10598 (United States))

1992-08-15

294

Decay of 66Dy166  

Microsoft Academic Search

Samples of Dy166 were produced by successive neutron capture in stable Dy164. This isotope decays by beta-ray emission with an 80.2-hr half-life to states in Ho166. This isotopic assignment of previous authors is confirmed. Separations of the parent and daughter activities were carried out by use of an ion-exchange column. Scintillation studies were made with a 256-channel scintillation coincidence spectrometer.

R. G. Helmer; S. B. Burson

1960-01-01

295

Synthesis and luminescent properties of low concentration Dy 3+:GAP nanophosphors  

NASA Astrophysics Data System (ADS)

Dy 3+:GAP (gadolinium aluminum perovskite) powder nanophosphors have been newly synthesized by means of solvothermal process. Spherically shaped particles in the nanometer ranges prepared by this method were evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The synthesis, structural and luminescent properties along with chromaticity coordinates of the nanophosphor samples with the compositions xDy 3+:Gd (1 - x)AlO 3 ( x = 0.005-0.05) are featured in this paper. Furthermore, the yellow to blue intensity ratio of Dy 3+:GAP nanophosphors varies from 1.19 to 1.03. Such luminescent powders are expected to find potential applications such as optical display systems.

Seeta Rama Raju, G.; Park, Jin Young; Jung, Hong Chae; Yang, Hyun Kyoung; Moon, Byung Kee; Jeong, Jung Hyun; Kim, Jung Hwan

2009-06-01

296

Ternary aluminides R{sub 0.67}Ni{sub 2}Al{sub 6} (R=Sc, Y, Gd-Lu) with partly disordered structures  

SciTech Connect

Ten rare-earth nickel aluminides R{sub 0.67}Ni{sub 2}Al{sub 6} (R=Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were synthesized by arc melting and their crystal structures studied by X-ray powder diffraction. They crystallize in the hexagonal structure type Yb{sub 0.67}Ni{sub 2}Al{sub 6}: Pearson symbol hP11-2.33, space group P-6m2, a=4.18904(2), c=9.09816(6) A, which can be decomposed into three kinds of layer. The sequence of layers along [001] is Yb{sub 0.67}Al-NiAl{sub 2}-Al-NiAl{sub 2}, but stacking faults appear due to relative shifts of consecutive Yb{sub 0.67}Al layers containing two rare-earth metal atoms for one Al-atom triangle. An ordered superstructure is the type ErNi{sub 3}Al{sub 9} (Pearson symbol hR78, space group R32, a={radical}(3)a{sub 0}, c=3c{sub 0}), refined on single crystals. The physical properties of the R{sub 0.67}Ni{sub 2}Al{sub 6} (R=Tb, Er, Tm, Yb, and Lu) compounds were determined by means of magnetic and electrical transport measurements. All these materials but Lu{sub 0.67}Ni{sub 2}Al{sub 6} exhibit Curie-Weiss paramagnetic behavior due to the trivalent R ions, and order magnetically at low temperatures. They show good metallic conductivity. The Yb-containing compound is a dense Kondo system with distinct features in the paramagnetic state of the interplay between Kondo and crystalline electric field interactions. - Graphical abstract: Stacking of layers along [001] in the Yb{sub 0.67}Ni{sub 2}Al{sub 6}-type structure. Highlights: Black-Right-Pointing-Pointer The aluminides R{sub 0.67}Ni{sub 2}Al{sub 6} (R=Sc, Y, Gd-Lu) adopt a partly disordered structure. Black-Right-Pointing-Pointer The structure is characterized by R{sub 2}Al{sub 3} layers with two R atoms for one Al{sub 3} triangle. Black-Right-Pointing-Pointer The compounds with R=Tb, Er, Tm are paramagnets at rt and order magnetically at lt. Black-Right-Pointing-Pointer The Yb-compound exhibits a magnetically ordered Kondo lattice with strong CEF effect.

Matselko, Oksana; Pukas, Svitlana; Lutsyshyn, Yuriy [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryla i Mefodiya St. 6, 79005 Lviv (Ukraine)] [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryla i Mefodiya St. 6, 79005 Lviv (Ukraine); Gladyshevskii, Roman, E-mail: Roman.Gladyshevskii@franko.lviv.ua [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryla i Mefodiya St. 6, 79005 Lviv (Ukraine)] [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryla i Mefodiya St. 6, 79005 Lviv (Ukraine); Kaczorowski, Dariusz [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland)] [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland)

2013-02-15

297

(Dy0.5Er0.5)Al2: A large magnetocaloric effect material for low-temperature magnetic refrigeration  

Microsoft Academic Search

The low-temprature heat capacity and ac and dc magnetic properties of (Dy0.5Er0.5)Al2 have been studied as a function of magnetic fields up to ?10 T. The magnetocaloric effect in (Dy0.5Er0.5)Al2 is 30% larger than that of the prototype material, GdPd. Magnetic measurements show that there is no measurable magnetic hysteresis above ?17 K. These results suggest that (Dy0.5Er0.5)Al2 would be

K. A. Gschneidner; H. Takeya; J. O. Moorman; V. K. Pecharsky

1994-01-01

298

Spectroscopic Study of Magnetic Phenomena in DyPO4, DyAsO4, and DyVO4.  

National Technical Information Service (NTIS)

The nearest-neighbor interactions in DyPO4, DyAsO4, and DyVO4 produce a five-line structure in the absorption lines. The relative intensities of the five lines have been measured to obtain the relative populations of the five possible nearest-neighbor spi...

J. C. Wright

1970-01-01

299

Determination of Cellulases with Dyed Substrates.  

National Technical Information Service (NTIS)

Methods for the determination of cellulases are discussed. A new method for determining the solubilizing activity of a cellulase complex was developed. It is based on the release of colored compounds from dyed cellulose. Several dyed celluloses were teste...

M. Leisola M. Linko

1976-01-01

300

Ternary aluminides R0.67Ni2Al6 (R=Sc, Y, Gd-Lu) with partly disordered structures  

NASA Astrophysics Data System (ADS)

Ten rare-earth nickel aluminides R0.67Ni2Al6 (R=Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were synthesized by arc melting and their crystal structures studied by X-ray powder diffraction. They crystallize in the hexagonal structure type Yb0.67Ni2Al6: Pearson symbol hP11-2.33, space group P-6m2, a=4.18904(2), c=9.09816(6) Å, which can be decomposed into three kinds of layer. The sequence of layers along [001] is Yb0.67Al-NiAl2-Al-NiAl2, but stacking faults appear due to relative shifts of consecutive Yb0.67Al layers containing two rare-earth metal atoms for one Al-atom triangle. An ordered superstructure is the type ErNi3Al9 (Pearson symbol hR78, space group R32, a=?{3}a0, c=3c0), refined on single crystals. The physical properties of the R0.67Ni2Al6 (R=Tb, Er, Tm, Yb, and Lu) compounds were determined by means of magnetic and electrical transport measurements. All these materials but Lu0.67Ni2Al6 exhibit Curie-Weiss paramagnetic behavior due to the trivalent R ions, and order magnetically at low temperatures. They show good metallic conductivity. The Yb-containing compound is a dense Kondo system with distinct features in the paramagnetic state of the interplay between Kondo and crystalline electric field interactions.

Matselko, Oksana; Pukas, Svitlana; Lutsyshyn, Yuriy; Gladyshevskii, Roman; Kaczorowski, Dariusz

2013-02-01

301

Extensively Drug-Resistant Tuberculosis (XDR TB)  

MedlinePLUS

... TB Print page ? Listen to audio/Podcast Español (Spanish) ? Contact Us: Centers for Disease Control and Prevention ... Laws Publications & Products Fact Sheets General Fact sheets - Spanish TB - General Information The Difference Between Latent TB ...

302

LiDy(PO3)4  

PubMed Central

Single crystals of lithium dysprosium polyphosphate, LiDy(PO3)4, were prepared by the flux method. The atomic arrangement is built up by infinite (PO3)n chains extending along the b axis. Dy3+ and Li+ cations alternate in the middle of four such chains, with Dy?Li distances of 3.54?(1) and 3.48?(1)?Å. The DyO8 dodeca­hedra and LiO4 tetra­hedra deviate significantly from the ideal geometry. Both Dy and Li occupy special positions (Wyckoff position 4e, site symmetry 2).

Chehimi-Moumen, Fathia; Ferid, Mokhtar

2008-01-01

303

Vapor Pressure of GD.  

National Technical Information Service (NTIS)

The vapor pressure of pinacolyl methyl phosphonofluoridate O-(I ,2, 2-trimethylpropyl)-methyl phosphonofluoridate. GD has been measured between - 20 and 50 C, using vapor saturation methodology. The current data are in good agreement with data previously ...

A. Balboa D. E. Tevault J. H. Buchanan L. C. Buettner T. Sewell

2007-01-01

304

Rare earth (Sm3+ and Dy3+)-doped gadolinium oxide nanomaterials for luminescence thermometry  

NASA Astrophysics Data System (ADS)

The possibility of using Sm3+- and Dy3+-doped Gd2O3 nanopowders as thermographic phosphor materials was studied. Both samples were synthesized by a combustion method. The crystalline structure of synthesized samples was confirmed by x-ray diffraction measurements. Photoluminescence measurements were recorded in the temperature range from 298 to 773 K. The photoluminescence spectrum of Sm3+ showed peaks that originate from 4G5/2 ? 6HJ transitions, while in the case of Dy3+ 4F7/2 ? 6HJ transitions were observed. The fluorescence intensity ratio of the prepared nanomaterials was studied as a function of temperature using the 4G5/2 ? 6H5/2 and 4G5/2 ? 6H7/2 transitions of Sm3+ ions and the 4F7/2 ? 6H13/2 and 4F7/2 ? 6H15/2 transitions of Dy3+ ions. Both doped Gd2O3 samples proved to have good potential for the development of thermographic phosphors. The maximum sensitivity was approximately 1.744 × 10-3 K-1 for the sample with 1 mol% Sm3+ at 701 K and 2.48 × 10-3 K-1 for the sample with 1 mol% Dy3+ at 773 K. The lifetime measurements were recorded in the same temperature region for the 606 and 572 nm lines of samarium and dysprosium, respectively. The lifetime at room temperature was found to be about 0.395 ms for Sm3+ and 0.123 ms for Dy3+ and it decreased as the temperature increased.

Al-Juboori, Ayad Zwayen M.

2013-11-01

305

(Dy[sub 0. 5]Er[sub 0. 5])Al[sub 2]: A large magnetocaloric effect material for low-temperature magnetic refrigeration  

SciTech Connect

The low-temprature heat capacity and ac and dc magnetic properties of (Dy[sub 0.5]Er[sub 0.5])Al[sub 2] have been studied as a function of magnetic fields up to [similar to]10 T. The magnetocaloric effect in (Dy[sub 0.5]Er[sub 0.5])Al[sub 2] is 30% larger than that of the prototype material, GdPd. Magnetic measurements show that there is no measurable magnetic hysteresis above [similar to]17 K. These results suggest that (Dy[sub 0.5]Er[sub 0.5])Al[sub 2] would be a significantly better magnetic refrigerant than GdPd.

Gschneidner, K.A. Jr.; Takeya, H.; Moorman, J.O.; Pecharsky, V.K. (Ames Laboratory and Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011-3020 (United States))

1994-01-10

306

The (Dy{sub 1-x}Er{sub x})Al{sub 2} alloys as active magnetic refrigeration  

SciTech Connect

The low temperature properties (heat capacity from 3 to 350 K in fields up to 10 T, and both ac magnetic susceptibility and dc magnetic susceptibility and magnetization from 4 to 325 K in dc fields up to 5.5 T) of nine (Dy{sub 1-x}Er{sub x})Al{sub 2} alloys have been studied as potential active magnetic regenerator (AMR) materials for hydrogen liquefaction using magnetic refrigeration. These data indicate that the (Dy{sub 1-x}Er{sub x})Al{sub 2} alloys would make excellent AMR materials, especially the combination (Dy{sub 0.4}Er{sub 0.6})Al{sub 2} plus DyAl{sub 2} phase mixture, which is significantly better than the prototype (Dy{sub 0.5}Er{sub 0.5})Al{sub 2} plus GdNi{sub 2} phase mixture currently being tested. In addition, the magnetic phase diagram of the (Dy{sub 1-x}Er{sub x})Al{sub 2} has been determined.

Gschneidner, K.A. Jr.; Pecharsky, V.K.; Malik, S.K. [Ames Lab., IA (United States)

1997-06-01

307

Magnetic properties of Dy nanoparticles and Al 2 O 3 -coated Dy nanocapsules  

Microsoft Academic Search

Dy2O3-coated Dy nanoparticles and Al2O3-coated Dy nanocapsules, with Dy cores with the average size of 3.6 and 17.6 nm, respectively, are synthesized by arc-discharge\\u000a technique. The transition from ferromagnetism to antiferromagnetism absents in the Dy nanoparticles, due to that its average\\u000a core size of 3.6 nm is smaller than the helix period of Dy. The temperature of the superparamagnetism–antiferromagnetism transition\\u000a in

X. G. Liu; S. W; B. Li; Z. Q. Ou; L. Zhang; Q. Zhang; D. Y. Geng; F. Yang; D. Li; E. Brück; Z. D. Zhang

2011-01-01

308

'ZS-MDR-TB' versus 'ZR-MDR-TB': improving treatment of MDR-TB by identifying pyrazinamide susceptibility  

PubMed Central

Indispensable for shortening treatment of drug-susceptible tuberculosis (TB), pyrazinamide (PZA, Z) is also essential in the treatment of multidrug-resistant (MDR)-TB. While resistance to PZA in MDR-TB is associated with poor treatment outcome, bacillary susceptibility to PZA along with the use of fluoroquinolone (FQ) and second-line injectable drugs (SLIDs) may predict improved treatment success in MDR-TB. Despite a high prevalence of PZA resistance among MDR-TB patients (10%–85%), PZA susceptibility testing is seldom performed because of technical challenges. To improve treatment of MDR-TB, we propose to: (i) classify MDR-TB into PZA-susceptible MDR-TB (ZS-MDR-TB) and PZA-resistant MDR-TB (ZR-MDR-TB); (ii) use molecular tests such as DNA sequencing (pncA, gyrA, rrs, etc.) to rapidly identify ZS-MDR-TB versus ZR-MDR-TB and susceptibility profile for FQ and SLID; (iii) refrain from using PZA in ZR-MDR-TB; and (iv) explore the feasibility of shortening the treatment duration of ZS-MDR-TB with a regimen comprising PZA plus at least two bactericidal agents especially new agents like TMC207 or PA-824 or delamanid which the bacilli are susceptible to, with one or two other agents. These measures may potentially shorten therapy, save costs, and reduce side effects of MDR-TB treatment.

Zhang, Ying; Chiu Chang, Kwok; Leung, Chi-Chiu; Wai Yew, Wing; Gicquel, Brigitte; Fallows, Dorothy; Kaplan, Gilla; Chaisson, Richard E; Zhang, Wenhong

2012-01-01

309

Magnetic, Caloric and Crystallographic Properties of Dy5(SixGe1-x)4 Alloys  

SciTech Connect

Polycrystals of the intermetallic compound of the Dy{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} system, where x = 0, 0.25, 0.5, 0.625, 0.675, 0.725, 0.75, 0.775, 0.825, 0.875, and 1, have been prepared by electric-arc-melting on water-cooled copper hearth in an argon atmosphere. A study of phase relationships and crystallography in the pseudobinary system Dy{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} using X-ray powder diffraction data and optical metallography was completed. It revealed that silicides in the composition range from 0.825 to 1 crystallize in the Gd{sub 5}Si{sub 4}-type crystal structure: germanides in the composition range from 0 to 0.625 crystallize in the Sm{sub 5}Ge{sub 4}-type structure, and alloys with intermediate composition range from 0.675 to 0.775 crystallize in the monoclinic Gd{sub 5}Si{sub 2}Ge{sub 2}-type structure. The -{Delta}S{sub m} values were determined from magnetization measurements for 7 alloys. The alloys with a monoclinic crystal structure which belong to an intermediate phase region have large MCE value, which exceeds those observed in the other two phase regions by 300 to 500%. The nature of the observed magnetic and structural transformations in the Dy{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} system seems to be similar with those reported for the Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} system. However, the interval and concentration range of three different phase regions in the Dy{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} system are different from that observed in Gd-based alloys. A non-collinear ordering of magnetic moments at low temperature was observed for the alloys with monoclinic crystal structure. The Dy{sub 5}Si{sub 3}Ge alloy exhibited FM phase transition below Curie temperature. A series of magnetic transitions were observed at low temperature in the Dy{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} alloys. The number of transitions increased and the magnetization decreased with increasing germanium content in the alloys. The -{Delta}S{sub m} and -{Delta}T values were calculated from heat capacity data for Dy{sub 5}Si{sub 3.5}Ge{sub 0.5} and Dy{sub 5}Si{sub 4} alloys only, due to the fragile nature of the germanides-rich samples. Based on the MCe values, the alloys from the orthorhombic Dy{sub 5}Si{sub 4}-based solid solution and the intermediate monoclinic phase regions may be useful magnetic refrigerant materials in the temperature range {approx}50K to -160K.

Vitaliy Vladislavovich Ivchenko

2002-07-19

310

Magnetic properties of Fe{sub 2}P-type R{sub 6}CoTe{sub 2} compounds (R=Gd-Er)  

SciTech Connect

The magnetic structure of the Fe{sub 2}P-type R{sub 6}CoTe{sub 2} phases (R=Gd-Er, space group P6-bar 2m) has been investigated through magnetization measurement and neutron powder diffraction. All phases demonstrate high-temperature ferromagnetic and low-temperature transitions: T{sub C}=220 K and T{sub CN}=180 K for Gd{sub 6}CoTe{sub 2}, T{sub C}=174 K and T{sub CN}=52 K for Tb{sub 6}CoTe{sub 2}, T{sub C}=125 K and T{sub CN}=26 K for Dy{sub 6}CoTe{sub 2}, T{sub CN}=60 K and T{sub N}=22 K for Ho{sub 6}CoTe{sub 2} and T{sub CN{approx}}30 K and T{sub N{approx}}14 K for Er{sub 6}CoTe{sub 2}. Between 174 and 52 K Tb{sub 6}CoTe{sub 2} has a collinear magnetic structure with K{sub 0}=[0, 0, 0] and with magnetic moments along the c-axis, whereas below 52 K it adopts a non-collinear ferromagnetic one. Below 60 K the magnetic structure of Ho{sub 6}CoTe{sub 2} is that of a non-collinear ferromagnet. The holmium magnetic components with a K{sub 0}=[0, 0, 0] wave vector are aligned ferromagneticaly along the c-axis, whereas the magnetic component with a K{sub 1}=[1/2, 1/2, 0] wave vector are arranged in the ab plane. The low-temperature magnetic transition at {approx}22 K coincides with the reorientation of the Ho magnetic component with the K{sub 0} vector from the collinear to the non-collinear state. Below 30 K Er{sub 6}CoTe{sub 2} shows an amplitude-modulate magnetic structure with a collinear arrangement of magnetic components with K{sub 0}=[0, 0, 0] and K{sub 1}=[1/2, 1/2, 0]. The low-temperature magnetic transition at {approx}14 K corresponds to the variation in the magnitudes of the M{sub Er}{sup K0} and M{sub Er}{sup K1} magnetic components. In these phases, no local moment was detected on the cobalt site. The magnetic entropy of Gd{sub 6}CoTe{sub 2} increases from {Delta}S{sub mag}=-4.5 J/kg K at 220 K up to {Delta}S{sub mag}=-6.5 J/kg K at 180 K for the field change {Delta}{mu}{sub 0}H=0-5 T. - Graphical abstract: The novel Fe{sub 2}P-type R{sub 6}CoTe{sub 2} phases (R=Gd-Er, space group P6-bar 2m) show ferromagnetic type ordering in the temperature range 14-220 K.All compounds demonstrate high-temperature ferromagnetic and low-temperature antiferromagnetic ordering.The magnetic entropy of Gd{sub 6}CoTe{sub 2} increases from {Delta}S{sub mag}=-4.5 J/kg K at 220 K up to {Delta}S{sub mag}=-6.5 J/kg K at 180 K for the field change {Delta}{mu}{sub 0}H=0-5 T.The R{sub 6}CoTe{sub 2} compounds exhibit the commensurate magnetic structures with wave vectors K{sub 0}=[0, 0, 0] and K{sub 1}=[1/2, 1/2, 1/2].

Morozkin, A.V., E-mail: morozkin@general.chem.msu.r [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Gsp-2, Moscow 119992 (Russian Federation); Mozharivskyj, Yu; Svitlyk, V. [Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1 (Canada); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600 036 (India); Isnard, O. [Institute Laue-Langevin, 6 Rue J. Horowitz, 38042 Grenoble (France); Institut Neel du CNRS/Universite J.Fourier, BP166X, 38042 Grenoble (France); Manfrinetti, P.; Provino, A. [Dipartimento di Chimica, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); LAMIA Laboratory-CNR-INFM, Corso Perrone 24, 16152 Genova (Italy); Ritter, C. [Institute Laue-Langevin, 6 Rue J. Horowitz, 38042 Grenoble (France)

2010-06-15

311

Specific features of the crystal structure and magnetic properties of the DyFeTi2O7 compound  

NASA Astrophysics Data System (ADS)

Results of studying the specific features of formation of the crystal structure and distribution of iron cations over the sites in the DyFeTi2O7 compound have been presented and the comparison with the GdGaTi2O7 isostructural compound has been performed. The atomic disorder in the distribution of the Fe3+ ions over structural sites in the DyFeTi2O7 compound is confirmed by the Mössbauer spectroscopy and X-ray diffractometry. The results of magnetic measurements in the low-temperature region have revealed an inflection point in the temperature dependence of the magnetic moment and its dependence on the magnetic prehistory of the sample. The obtained experimental data suggest that there is a spin glass state with freezing point T f = 6 K in the DyFeTi2O7 compound.

Drokina, T. V.; Petrakovskii, G. A.; Molokeev, M. S.; Velikanov, D. A.; Pletnev, O. N.; Bayukov, O. A.

2013-10-01

312

Polytypic modifications in heavily Tb and Eu doped gadolinium aluminum borate crystals  

NASA Astrophysics Data System (ADS)

The evidence of a new polytypic phase was demonstrated in double doped gadolinium aluminum borate (GAB) crystals grown by the high temperature top seeded solution growth (HTTSSG) method. The structures of the rhombohedral and the new monoclinic phases in the Eu0.02Tb0.12Gd0.86Al3(BO3)4 and Eu0.18Tb0.19Gd0.63Al3(BO3)4 compositions were determined by single crystal and powder X-ray diffraction methods. The monoclinic crystals with different compositions have identical structures with space group C2/c. It was concluded that the starting crystallization temperature was the dominant factor in formation of the rhombohedral and monoclinic phases. The crystals with non-centrosymmetric rhombohedral structure (R32) may possess similar compositions as the previous ones but their starting crystallization temperature was lower.

Beregi, E.; Sajó, I.; Lengyel, K.; Bombicz, P.; Czugler, M.; Földvári, I.

2012-07-01

313

Radiation Induced Color Centers in TB3+-DOPED Phosphate Scintillation Glasses  

Microsoft Academic Search

Radiation induced optical absorption processes were studied at room temperature for a set of NaPO3-GdPO4 phosphate glasses doped by Tb3+ ions. Closely similar features were found under X-ray and gamma-ray irradiations, while under the intense 308 nm XeCl excimer laser irradiation these effects were further obscured by a possible surface damage. The induced absorption band at 3.3-3.4 eV was ascribed

M. Nikl; S. Baccaro; A. Cecilia; P. Fabeni; M. Martini; E. Mihokova; K. Nitsch; G. P. Pazzi; N. Solovieva; A. Vedda

2002-01-01

314

Optical absorption and thermoluminescence of Tb3+-doped phosphate scintillating glasses  

Microsoft Academic Search

We present a study of the optical properties of Tb3+-doped NaPO3-GdPO4-based glasses by means of optical absorption measurements performed at room temperature both before and after x-ray irradiation. A numerical decomposition of the absorption spectra is performed, and the possible nature of the defects responsible for the observed absorption bands is discussed; namely, it is proposed that both intrinsic defects

A. Vedda; M. Martini; M. Nikl; E. Mihokova; K. Nitsch; N. Solovieva; F. Karagulian

2002-01-01

315

Highly enhanced luminescence of Tb 3+-activated gadolinium oxysulfide phosphor by doping with Zn 2+ ions  

Microsoft Academic Search

Gd2O2S:Tb phosphor were synthesized by co-precipitation method combined with solid-state reactions. The brightness of terbium-activated gadolinium oxysulfide phosphors were enhanced and size distributions were controlled by doping the phosphor with a specific amount of zinc oxide. By the analysis of X-ray diffractions, the excitation spectrum and emission spectrum, it can be confirmed that no new phase was introduced and lattice

Fei Wang; Bin Yang; Jinchao Zhang; Yongnian Dai; Wenhui Ma

2010-01-01

316

Phase formation in the systems Li{sub 2}MoO{sub 4}-K{sub 2}MoO{sub 4}-Ln{sub 2}(MoO{sub 4}){sub 3} (Ln=La, Nd, Dy, Er) and properties of triple molybdates LiKLn{sub 2}(MoO{sub 4}){sub 4}  

SciTech Connect

Subsolidus phase relations in the systems Li{sub 2}MoO{sub 4}-K{sub 2}MoO{sub 4}-Ln{sub 2}(MoO{sub 4}){sub 3} (Ln=La, Nd, Dy, Er) were determined. Formation of LiKLn{sub 2}(MoO{sub 4}){sub 4} was confirmed in the systems with Ln=Nd, Dy, Er at the LiLn(MoO{sub 4}){sub 2}-KLn(MoO{sub 4}){sub 2} joins. No intermediate phases of other compositions were found. No triple molybdates exist in the system Li{sub 2}MoO{sub 4}-K{sub 2}MoO{sub 4}-La{sub 2}(MoO{sub 4}){sub 3}. The join LiLa(MoO{sub 4}){sub 2}-KLa(MoO{sub 4}){sub 2} is characterized by formation of solid solutions. Triple molybdates LiKLn{sub 2}(MoO{sub 4}){sub 4} for Ln=Nd-Lu, Y were synthesized by solid state reactions (single phases with ytterbium and lutetium were not prepared). Crystal and thermal data for these molybdates were determined. Compounds LiKLn{sub 2}(MoO{sub 4}){sub 4} form isostructural series and crystallized in the monoclinic system with the unit cell parameters a=5.315-5.145A, b=12.857-12.437A, c=19.470-19.349A, {beta}=92.26-92.98{sup o}. When heated, the compounds decompose in solid state to give corresponding double molybdates. The dome-shaped curve of the decomposition temperatures of LiMLn{sub 2}(MoO{sub 4}){sub 4} has the maximum in the Gd-Tb-Dy region. While studying the system Li{sub 2}MoO{sub 4}-K{sub 2}MoO{sub 4}-Dy{sub 2}(MoO{sub 4}){sub 3} we revealed a new low-temperature modification of KDy(MoO{sub 4}){sub 2} with the triclinic structure of {alpha}-KEu(MoO{sub 4}){sub 2} (a=11.177(2)A, b=5.249(1)A, c=6.859(1)A, {alpha}=112.33(2){sup o}, {beta}=111.48(1){sup o}, {gamma}=91.30(2){sup o}, space group P1-bar , Z=2)

Basovich, O.M. [Baikal Institute of Nature Management, Siberian Branch, Russian Academy of Sciences, Sakh'yanova Street 6, Ulan-Ude, 670047 Buryat Republic (Russian Federation); Khaikina, E.G. [Baikal Institute of Nature Management, Siberian Branch, Russian Academy of Sciences, Sakh'yanova Street 6, Ulan-Ude, 670047 Buryat Republic (Russian Federation)]. E-mail: ekha@binm.bsc.buryatia.ru; Solodovnikov, S.F. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Akad. Lavrent'ev Ave. 3, Novosibirsk 630090 (Russian Federation); Tsyrenova, G.D. [Baikal Institute of Nature Management, Siberian Branch, Russian Academy of Sciences, Sakh'yanova Street 6, Ulan-Ude, 670047 Buryat Republic (Russian Federation)

2005-05-15

317

Preparation, photo- and electro-luminescent properties of a novel complex of Tb (III) with a tripod ligand  

NASA Astrophysics Data System (ADS)

A novel Tb(III) complex TbL (L = tris[2-(2-carboxyphenoxy)ethyl]amine, H 3L) was synthesized and characterized by means of elemental analyses, IR spectra, thermal analyses, and molar conductivity measurement. The photoluminescent properties of the complex were investigated. In addition, PVK doping Tb(III) complex was fabricated as the emissive layer by spin-coating and its electroluminescent properties were studied, in which the structure of the device was ITO (indium tin oxide)/PVK (polyvinylcarbazole)/PVK: TbL/PBD (2-(4-biphenylyl)-5-(4- tert-butylphenyl)-1,3,4-oxadiazole)/LiF/Al. It was indicated that pure green and narrow bandwidth emission at 545 nm from photoluminescence of TbL complex film and the organic electroluminescent device is the characteristic emission of Tb(III) ion, and the electroluminescence spectrum of the device was very similar to that of the photoluminescence of TbL complex film. The lowest triplet level of the ligand was calculated from the phosphorescence spectrum of GdL in N, N-dimethyl formamide (DMF) dilute solution determined at 77 K, and the energy transfer mechanisms in TbL complex were discussed.

Yu, Tianzhi; Zhao, Yuling; Fan, Duowang; Hong, Ziruo; Su, Wenming

2008-02-01

318

New 3d-4f heterometallic clusters built from mixed glycine and iminodiacetate acid: dioctahedron {La2Ni9} and onion-like {Gd5}?{Ni12} with interesting magnetocaloric effect.  

PubMed

The preparation, structures and properties of 3d-4f compounds, undecanuclear [La2Ni9(Gly)12(IDA)3(?3-OH)3][La(H2O)9][Na3(H2O)7(ClO4)3](ClO4)6·5H2O (1) and isostructural heptadecanuclear [Ln5Ni12(Gly)12(IDA)6(?3-OH)9(H2O)3](ClO4)6·11H2O (Ln = Gd (2); Nd (3); Sm (4); Tb (5); Dy (6); Y (7)) based on mixed glycine (HGly) and iminodiacetate acid (H2IDA) ligands were described. The structure of the [La2Ni9(?3-OH)3(IDA)3(Gly)12](3+) cationic cluster in 1 can be described as a face-shared and La-centered dioctahedron. However, the [Ln5Ni12(Gly)12(IDA)6(?3-OH)9(H2O)3](6+) cationic clusters in 2-7 bear an onion-like {Ln5}?{Ni12} structure, where the trigonal bipyramid {Ln5} core is encapsulated by the outer triangular orthobicupola {Ni12} shell. Magnetic studies have been performed for these compounds, and 2 displays dominant ferromagnetic coupling and has a large magnetocaloric effect (21.8 J kg(-1) K(-1), ?H = 7 T). PMID:23443651

Li, Zhong-Yi; Zhu, Jiang; Wang, Xiao-Qun; Ni, Jun; Zhang, Jian-Jun; Liu, Shu-Qin; Duan, Chun-Ying

2013-04-28

319

4f7-4f7 transitions in Gd, oxidized Gd, and epitaxial Gd silicide  

Microsoft Academic Search

4f-4f transitions in the rare earths are investigated in a detailed study of the 4f7-4f7 excitations of Gd observed by electron-energy-loss spectroscopy in reflection mode. Consistent quasiatomic losses are observed in polycrystalline Gd metal, oxidized Gd, and an epitaxially ordered Gd silicide phase. Sharp 4f7-4f7 transitions, whose positions are independent of environment, are superposed on a broad loss background which

J. A. D. Matthew; W. A. Henle; M. G. Ramsey; F. P. Netzer

1991-01-01

320

Stability of multiferroicity against Dy/Mn off-stoichiometry in DyMnO3  

NASA Astrophysics Data System (ADS)

We investigate the effects of slight Dy/Mn off-stoichiometry on the multiferroic behaviors of DyMnO3 (Dy1-xMn1+xO3). It is revealed that the distorted lattice structure and ferroelectric property exhibit higher stability against the Mn deficiency than the Dy deficiency. Since the electric polarization includes the contributions from the Mn-Mn and Dy-Mn interactions, the measured polarization exhibits different dependence on the Mn deficiency from that on the Dy deficiency. The present work suggests that the Dy/Mn off-stoichiometry is detrimental to the ferroelectricity, owing to the modulated spin interactions and reshuffled spin frustration.

Wang, J. X.; Liu, M. F.; Zhao, Z. Y.; Yan, Z. B.; Liu, J.-M.

2014-05-01

321

Ternary Dy-Er-Al magnetic refrigerants  

DOEpatents

A ternary magnetic refrigerant material comprising (Dy.sub.1-x Er.sub.x)Al.sub.2 for a magnetic refrigerator using the Joule-Brayton thermodynamic cycle spanning a temperature range from about 60K to about 10K, which can be adjusted by changing the Dy to Er ratio of the refrigerant.

Gschneidner, Jr., Karl A. (Ames, IA); Takeya, Hiroyuki (Ibaraki, JP)

1995-07-25

322

Simulation of the magnetocaloric effect in Tb nanofilms  

NASA Astrophysics Data System (ADS)

Rare-earth (RE) metals have different magnetic structures resulting from the competition between the crystal-field and exchange interactions. When a magnetic field is applied it creates a third interaction and the magnetic structures are more complicated. In thin films, it is expected that even the magnetic arrangement itself can be strongly modified. Rare-earth helimagnets such as Terbium (Tb), Holmium (Ho) and Dysprosium (Dy) represent the best candidates to evidence such finite-size effects. This finite-size effect is caused by the reduced number of atoms in the direction perpendicular to the film plane that leads to a decrease of the total magnetic exchange energy. We report this contribution to the investigation of magnetocaloric effect (MCE) of thin Terbium films in the helimagnetic temperature range, from TC = 219 K to TN = 231 K, for external fields of the order of 1 kOe. We find that for strong fields, H = 50 kOe, the adiabatic temperature change ?T near the Néel temperature is around 15 K for any thickness of Tb films. However large thickness effects are found for small values of the magnetic field. For field strength of the order of a few kOe, the thermocaloric efficiency increases significantly for ultrathin (nanomagnetic) films.

Anselmo, Dory Hélio A. L.; Mello, Vamberto D.; Vasconcelos, Manoel S.

2014-03-01

323

Rotational structures and their evolution with spin in {sup 152}Gd  

SciTech Connect

The fusion-evaporation reaction involving a 175 MeV {sup 36}S beam and a {sup 124}Sn target was performed, and the emitted {gamma} rays were observed with the Gammasphere spectrometer. Significant additions to the level scheme of {sup 152}Gd were made in spite of the relative weakness of the {alpha}4n exit channel, being only {approx}2% of the total fusion cross-section. The high-spin behavior of {sup 152}Gd was compared with that of other N=88 nuclei. A striking similarity was observed with {sup 154}Dy and it is therefore suggested that the angular-momentum-induced shape changes that take place in {sup 154}Dy also occur in {sup 152}Gd in the 30-40h spin range. This is supported by Cranked Nilsson-Strutinsky calculations which were used to interpret the high-spin bands. It is found that a better agreement between calculation and experiment is obtained if the Z=64 shell gap increases with a decreasing number of valence particles outside the doubly-closed {sub 64}{sup 146}Gd{sub 82} nucleus.

Campbell, D. B. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Laird, R. W. [Department of Physics, Texas Lutheran University, Seguin, Texas 78023 (United States); Riley, M. A. [Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States); Simpson, J. [CCLRC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD (United Kingdom); Kondev, F. G. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Nuclear Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Hartley, D. J. [Department of Physics, United States Naval Academy, Annapolis, Maryland 21402 (United States); Janssens, R. V. F.; Carpenter, M. P.; Lauritsen, T.; Nisius, D. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Brown, T. B. [Savannah River National Laboratory, Aiken, South Carolina 29802 (United States); Fallon, P. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Fischer, S. M. [Department of Physics, DePaul University, Chicago, Illinois 60614-3504 (United States); Ragnarsson, I. [Division of Mathematical Physics, LTH, Lund University, Box 118, S-221 00, Lund (Sweden)

2007-06-15

324

(Dy[sub 0. 5]Er[sub 0. 5])Al[sub 2]: A large magnetocaloric effect material for low-temperature magnetic refrigeration  

Microsoft Academic Search

The low-temprature heat capacity and ac and dc magnetic properties of (Dy[sub 0.5]Er[sub 0.5])Al[sub 2] have been studied as a function of magnetic fields up to [similar to]10 T. The magnetocaloric effect in (Dy[sub 0.5]Er[sub 0.5])Al[sub 2] is 30% larger than that of the prototype material, GdPd. Magnetic measurements show that there is no measurable magnetic hysteresis above [similar to]17

K. A. Jr. Gschneidner; H. Takeya; J. O. Moorman; V. K. Pecharsky

1994-01-01

325

[166Dy]Dy/166Ho hydroxide macroaggregates: an in vivo generator system for radiation synovectomy.  

PubMed

Radiation synovectomy is an effective treatment in patients suffering from inflammatory-rheumatoid and degenerative joint diseases. The aim of this work was to examine the feasibility of preparing dysprosium-166 (166Dy)/holmium-166(166Ho) hydroxide macroaggregates ([166Dy]Dy/166Ho-HM) as an in vivo generator for radiation synovectomy evaluating whether the stability of 166Dy-HM and 166Ho-HM complexes is maintained when the daughter 166Ho is formed. The Monte Carlo (MCNP4B) theoretical depth dose profile for the in vivo [166Dy]Dy/166Ho generator system in a joint model was calculated and compared with that produced by 90Y, 153Sm and 166Ho. 166Dy was obtained by neutron irradiation of enriched 164Dy2O3 in a Triga Mark III reactor. Macroaggregates were prepared by reaction of [166Dy]DyCl3 with 0.5 M NaOH in an ultrasonic bath. [166Dy]Dy/166Ho-HM was obtained with radiochemical purity >99.5% and with the majority of particles in the 2-5 microm range. In vitro studies demonstrated that the radio-macroaggregates are stable in saline solution and human serum without a significant change in the particle size over 14 d, suggesting that no translocation of the daughter nucleus occurs subsequent to beta- decay of 166Dy. Biological studies in normal rats demonstrated high retention in the knee joint even 7 d after [166Dy]Dy/166Ho-HM administration. The Monte Carlo (MCNP4B) theoretical depth dose profiles in a joint model, showed that the in vivo [166Dy]Dy/166Ho generator system would produce 25% and 50% less radiation dose to the articular cartilage and bone surface, respectively, than that produced by 90Y or pure 166Ho in a treatment with the same therapeutic dose to the synovium surface. Despite that 153Sm showed the best depth dose profile sparing doses to healthy tissues, the use of 166Dy could provide the advantage of being applied in patients that cannot be reached within a few hours from a nuclear reactor and to produce less radiation exposure to the medical personnel during the radiopharmaceutical administration. PMID:15388114

Ferro-Flores, G; Hernández-Oviedo, O; Arteaga de Murphy, C; Tendilla, J I; Monroy-Guzmán, F; Pedraza-López, M; Aldama-Alvarado, K

2004-12-01

326

TB in Children in the United States  

MedlinePLUS

... Laws Publications & Products Fact Sheets General Fact sheets - Spanish TB - General Information The Difference Between Latent TB ... HIV Coinfection Patient Education Series English Only English/Spanish English/Tagalog Tuberculosis - Get the Facts Tuberculosis - La ...

327

Multidrug-Resistant Tuberculosis (MDR TB)  

MedlinePLUS

... or more of the primary drugs (isoniazied and rifampin) used for the treatment of tuberculosis. Extensively drug- ... is TB resistant to at least isoniazid and rifampin among the first-line anti-TB drugs and ...

328

Is TB in Your Curriculum?  

ERIC Educational Resources Information Center

Points out the importance of effective health education to fight against tuberculosis (TB) which is the number one fatal infectious disease around the world. Describes a science curriculum on tuberculosis that includes information on the facts about tuberculosis, a forum on tuberculosis, and evaluation. (Contains 17 references.) (YDS)

Kerr, Joanne; Elwell, Jack

2002-01-01

329

Tuberculosis: Learn the Signs and Symptoms of TB Disease  

MedlinePLUS

... Learn the Signs and Symptoms of TB Disease Tuberculosis (TB) is a disease caused by bacteria that ... to recognize the signs and symptoms of TB. Tuberculosis (TB) is a disease caused by bacteria that ...

330

TB in Correctional Facilities Is a Public Health Concern  

MedlinePLUS

... CDC Features TB in Correctional Facilities is a Public Health Concern Share Compartir Diagnosing and treating TB in ... the community with untreated TB present a serious public health concern. Figure 1 (larger view). TB Control in ...

331

Framework of behavioral indicators for outcome evaluation of TB health promotion: a Delphi study of TB suspects and Tb patients  

PubMed Central

Background Health promotion for prevention and control of Tuberculosis (TB) is implemented worldwide because of its importance, but few reports have evaluated its impact on behavior due to a lack of standard outcome indicators. The objective of this study was to establish a framework of behavioral indicators for outcome evaluation of TB health promotion among TB suspects and patients. Methods A two-round modified Delphi method involving sixteen TB control experts was used to establish a framework of behavioral indicators for outcome evaluation of TB health promotion targeted at TB suspects and patients. Results Sixteen of seventeen invited experts in TB control (authority score of 0.91 on a 1.0 scale) participated in round 1 survey. All sixteen experts also participated in a second round survey. After two rounds of surveys and several iterations among the experts, there was consensus on a framework of indicators for measuring outcomes of TB health promotion for TB suspects and patients. For TB suspects, the experts reached consensus on 2 domains (“Healthcare seeking behavior” and “Transmission prevention”), 3 subdomains (“Seeking care after onset of TB symptoms”, “Pathways of seeking care” and “Interpersonal contact etiquette”), and 8 indicators (including among others, “Length of patient delay”). For TB patients, consensus was reached on 3 domains (“Adherence to treatment”, “Healthy lifestyle” and “Transmission prevention”), 8 subdomains (including among others, “Adherence to their medication”), and 14 indicators (including “Percentage of patients who adhered to their medication”). Operational definitions and data sources were provided for each indicator. Conclusions The findings of this study provide the basis for debate among international experts on a framework for achieving global consensus on outcome indicators for TB health promotion interventions targeted at TB patients and suspects. Such consensus will help to increase effectiveness of TB health promotion, while ensuring international comparability of outcome data.

2014-01-01

332

Vibrating-coil magnetometry of the spin liquid properties of Tb2Ti2O7.  

PubMed

We have explored the spin liquid state in Tb(2)Ti(2)O(7) with vibrating-coil magnetometry down to ~0.04 K under magnetic fields up to 5 T. We observe magnetic history dependence below T*~0.2 K reminiscent of the classical spin ice systems Ho(2)Ti(2)O(7) and Dy(2)TiTi(2)O(7). The magnetic phase diagram inferred from the magnetization is essentially isotropic, without evidence of magnetization plateaus as anticipated for so-called quantum spin ice, predicted theoretically for [111] when quantum fluctuations renormalize the interactions. Instead, the magnetization for T?T* agrees semiquantitatively with the predictions of "all-in-all-out" (AIAO) antiferromagnetism. Taken together, this suggests that the spin liquid state in Tb(2)Ti(2)O(7) is akin to an incipient AIAO antiferromagnet. PMID:23006105

Legl, S; Krey, C; Dunsiger, S R; Dabkowska, H A; Rodriguez, J A; Luke, G M; Pfleiderer, C

2012-07-27

333

Staying on Track with TB Medicine  

MedlinePLUS

Staying on Medicine Track with TUBERCULOSIS TB 2 What’s Inside: Read this brochure to learn about TB and what you can do to get healthy. Put it ... department at __________________________ or visit the CDC Division of Tuberculosis Elimination website at http://www.cdc.gov/tb ...

334

Binary amplitude holograms made from dyed photoresist.  

PubMed

A method for fabricating binary amplitude holograms from a dyed photoresist is described. It is of particular interest for holograms that are used as null optics in the form metrology of aspheric surfaces and wavefronts. A pigment that strongly absorbs light near 633 nm was dissolved in a positive photoresist and the dyed resist was spun onto silica glass substrates. Stable resist layers were obtained that were essentially opaque at 633 nm with little effect on the transmittance of the resist in the UV. A Fresnel zone plate was fabricated from the dyed resist layer using contact lithography, and its performance was demonstrated at 633 nm. PMID:21593928

Wang, Quandou; Griesmann, Ulf; Burnett, John H

2011-05-15

335

Lanthanide-doped NaGdF4 core-shell nanoparticles for non-contact self-referencing temperature sensors.  

PubMed

We report that non-contact self-referencing temperature sensors can be realized with the use of core-shell nanostructures. These lanthanide-based nanothermometers (NaGdF4:Yb(3+)/Tm(3+)@Tb(3+)/Eu(3+)) exhibit higher sensitivity in a wide range from 125 to 300 K based on two emissions of Tb(3+) at 545 nm and Eu(3+) at 615 nm under near-infrared laser excitation. PMID:24769587

Zheng, Shuhong; Chen, Weibo; Tan, Dezhi; Zhou, Jiajia; Guo, Qiangbing; Jiang, Wei; Xu, Cheng; Liu, Xiaofeng; Qiu, Jianrong

2014-06-01

336

Low-lying magnetic dipole strength in {sup 163}Dy  

SciTech Connect

We calculated the {ital M}1 strength distribution in {sup 163}Dy within the quasiparticle-phonon nuclear model using the phonon basis for {sup 162}Dy. We found a strong fragmentation of the magnetic dipole strength in {sup 163}Dy which was in qualitative agreement with the experimental data. The calculated fragmentation of the {ital M}1 strength in {sup 163}Dy is much stronger in comparison with that in {sup 162}Dy. {copyright} {ital 1996 The American Physical Society.}

Soloviev, V.G.; Sushkov, A.V.; Shirikova, N.Y. [Joint Institute for Nuclear Research, Bogolubov Laboratory of Theoretical Physics, 141980 Dubna, Moscow region (Russia)] [Joint Institute for Nuclear Research, Bogolubov Laboratory of Theoretical Physics, 141980 Dubna, Moscow region (Russia)

1996-02-01

337

Crystal structure and magnetic properties of Tb-doped Ru-1222 ruthenocuprates  

NASA Astrophysics Data System (ADS)

The effects of Tb doping on the structural, superconducting, and magnetic properties of (Ru0.9Nb0.1)Sr2(Gd1.34-xTbxCe0.66)Cu2Oz and RuSr2(Eu1.34-xTbxCe0.66)Cu2Oz (x=0, 0.34) systems were investigated. It was found that Tb doping in both systems results in a significant suppression of superconductivity and an enhancement of the magnetic ordering temperature, as well as an enhancement of the weak-ferromagnetic component of field-cooled magnetization. The Rietveld refinements of the X-ray diffraction data at room temperature showed that both a and c lattice parameters decrease and the rotation angle of the RuO6 octahedron around the crystallographic c-axis decreases by Tb doping in both systems. The superconducting and magnetic behaviors induced by the Tb doping are discussed in conjunction with the change in hole concentration and the local structural changes in the Ru sublattice induced by Tb doping.

Lee, H. K.; Kim, K. W.; Lee, M. S.; Kim, Y. I.

2014-09-01

338

Heightened Vulnerability to MDR-TB Epidemics after Controlling Drug-Susceptible TB  

PubMed Central

Background Prior infection with one strain TB has been linked with diminished likelihood of re-infection by a new strain. This paper attempts to determine the role of declining prevalence of drug-susceptible TB in enabling future epidemics of MDR-TB. Methods A computer simulation of MDR-TB epidemics was developed using an agent-based model platform programmed in NetLogo (See http://mdr.tbtools.org/). Eighty-one scenarios were created, varying levels of treatment quality, diagnostic accuracy, microbial fitness cost, and the degree of immunogenicity elicited by drug-susceptible TB. Outcome measures were the number of independent MDR-TB cases per trial and the proportion of trials resulting in MDR-TB epidemics for a 500 year period after drug therapy for TB is introduced. Results MDR-TB epidemics propagated more extensively after TB prevalence had fallen. At a case detection rate of 75%, improving therapeutic compliance from 50% to 75% can reduce the probability of an epidemic from 45% to 15%. Paradoxically, improving the case-detection rate from 50% to 75% when compliance with DOT is constant at 75% increases the probability of MDR-TB epidemics from 3% to 45%. Conclusions The ability of MDR-TB to spread depends on the prevalence of drug-susceptible TB. Immunologic protection conferred by exposure to drug-susceptible TB can be a crucial factor that prevents MDR-TB epidemics when TB treatment is poor. Any single population that successfully reduces its burden of drug-susceptible TB will have reduced herd immunity to externally or internally introduced strains of MDR-TB and can experience heightened vulnerability to an epidemic. Since countries with good TB control may be more vulnerable, their self interest dictates greater promotion of case detection and DOTS implementation in countries with poor control to control their risk of MDR-TB.

Bishai, Jason D.; Bishai, William R.; Bishai, David M.

2010-01-01

339

Immigrant screening for TB: a missed opportunity to improve TB control in the United Kingdom  

PubMed Central

Tuberculosis in the United Kingdom and other high-income countries is primarily a disease of the foreign-born arising from the synergy of migration from high TB burden regions and the reactivation of remotely acquired latent TB infection. UK immigrant screening policy primarily aims to identify active, rather than latent, TB although mounting evidence indicates that implementing latent TB screening for new entrants from intermediate and high incidence countries could cost-effectively reduce TB incidence in the UK.

Lalvani, Ajit; Pareek, Manish

2012-01-01

340

EPR study of Dy 3 + ions in DyBa 2 Cu 3 O 6 + x  

NASA Astrophysics Data System (ADS)

Concentrated polycrystalline DyBa2Cu3O6+x compounds are studied by X-band EPR spectroscopy. A broad resonance line due to the highly anisotropic EPR spectrum of Dy3+ ions is identified on several specimens at low temperatures. Powder simulation of the EPR spectra complies with the ground Kramers doublet predicted by crystal field analysis of Dy3+ ions. Calculations of the second and fourth moments of the resonance lines due to the dipole-dipole interactions of Dy3+ indicate the presence of substantial exchange narrowing of the dipolar-broadened EPR linewidth.

Likodimos, V.; Guskos, N.; Typek, J.; Wabia, M.

2001-11-01

341

161Dy hyperfine parameters for C2 and C3i site symmetries in Dy2O3  

Microsoft Academic Search

Low-temperature Mössbauer spectra of 161Dy in Dy2O3 reveal for the first time a resolved magnetic hyperfine structure (hfs) associated with Dy3+ at sites with C3i(S6) point symmetry. The magnetic hfs parameter is near that expected for a pure |Jxi=+\\/-152> Kramers doublet and is about 10% higher than for Dy3+ ions at sites with C2 point symmetry in Dy2O3. A crystal-field

D. W. Forester; W. A. Ferrando

1976-01-01

342

Magnetocaloric effect in DyCu 2  

NASA Astrophysics Data System (ADS)

The magnetocaloric effect of the rare-earth intermetallic compound DyCu 2 is explored through magnetization measurements. DyCu 2 is paramagnetic at the room temperature but becomes antiferromagnetic below 27 K (Neel temperature). Strong temperature and field dependence of magnetization in DyCu 2 at and around the Neel temperature lead to a large magnetocaloric effect. An appreciable magnetocaloric effect persists well above the Neel temperature probably because of the presence of short-range ferromagnetic correlations in the paramagnetic state of DyCu 2. This along with the absence of magnetic hysteresis lead to a large effective refrigerant capacity of 194 J/kg below 44 K, which makes the material important as a potential magnetic refrigerant for the cryogenic liquefier cycles.

Arora, Parul; Tiwari, Pragya; Sathe, V. G.; Chattopadhyay, M. K.

2009-10-01

343

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

SciTech Connect

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

Liu, Xiaohua, E-mail: xhliuxhliu@tom.com [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China)] [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Xiang, Wendou; Chen, Fengming; Hu, Zhengfa; Zhang, Wei [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China)] [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

2013-02-15

344

Photoluminescence of Ce 3+, Pr 3+ and Tb 3+ activated Sr 3Ln(PO 4) 3 under VUV-UV excitation  

NASA Astrophysics Data System (ADS)

The spectroscopic properties in VUV-Vis range for the eulytite structural phosphors Sr 3Gd(PO 4) 3: Ln3+ ( Ln3+=Ce 3+, Pr 3+, Tb 3+), Sr 3Ce(PO 4) 3, Sr 3Gd(PO 4) 3 and Sr 3Tb(PO 4) 3 were investigated. The bands near 170 nm in VUV excitation spectra are assumed to connect with the host lattices related absorption. The f- d transitions of Ce 3+, Pr 3+ and Tb 3+ in the host lattices are assigned and corroborated. A convenient experiment formulation on the relationship between the lowest f- d transition energies and n value for trivalent 4 fn-series rare earth ions in these host lattices is applied.

Liang, Hongbin; Tao, Ye; Xu, Jianhua; He, Hong; Wu, Hao; Chen, Wenxuan; Wang, Shubin; Su, Qiang

2004-03-01

345

Rare-earth chromium gallides RE4CrGa12 (RE=Tb-Tm)  

NASA Astrophysics Data System (ADS)

The ternary rare-earth-metal chromium gallides RE4CrGa12 (RE=Tb-Tm) have been prepared by reactions of the elements at 1000 °C in the presence of excess gallium used as a self-flux. Their structures are derived by inserting Cr atoms into a quarter of the empty Ga6 octahedral clusters found in the parent binary gallides REGa3 (AuCu3-type), although single-crystal X-ray diffraction studies suggest that complex superstructures may be adopted. An ideal ordered Y4PdGa12-type structure was successfully refined for a crystal of Dy4CrGa12 (Pearson symbol cI34, space group Im3¯m, Z=2, a=8.572(1) Å). Magnetic measurements on single-crystal samples reveal ferromagnetic or possibly ferrimagnetic ordering for the Tb, Dy, and Er members (TC=22, 15, and 2.8 K, respectively) and antiferromagnetic ordering for the Ho member (TN=7.5 K). Band structure calculations on a hypothetical "Y4CrGa12" model suggest that the Cr atoms carry no local magnetic moment.

Slater, Brianna R.; Bie, Haiying; Stoyko, Stanislav S.; Bauer, Eric D.; Thompson, Joe D.; Mar, Arthur

2012-12-01

346

Effect of pressure on the optical absorption of REF centers in Ce and Tb doped CaF2  

Microsoft Academic Search

The effect of pressure to 80 kbar has been measured on the absorption peaks associated with REF centers in Ce and Tb doped CaF2. The results are compared with previous data for Gd doped CaF2. The lowest and highest energy excitations [?(1E) and ?(2E)] are associated with an excited state largely of metal 5d(eg) character. The intermediate peak has predominantly

W. D. Drotning; H. G. Drickamer

1973-01-01

347

Unique Y-shaped lanthanide aggregates and single-molecule magnet behaviour for the Dy4 analogue.  

PubMed

The assembly of N'-(amino-(pyrimidin-2-yl)methylene)-o-vanilloyl hydrazine ligands (H2L, Scheme 1) with different lanthanide perchlorates produces novel Y-shaped tetranuclear complexes, [Ln4(?3-OH)(L(2-))4(H2O)6]·(ClO4)3·6H2O, where Ln = Tb (1), Dy (2) and Ho (3). The formation of this unprecedented Y-shaped topology is largely ascribed to the versatility of the mixed-donor hydrazone ligands in terms of their potential denticity. Analysis of the susceptibility data shows that only the Dy-based molecule features SMM-like behaviour. The synthetic methodology of employing H2L and related ligands has provided a very promising route towards new families of magnetic coordination clusters with novel metal topologies and properties. PMID:24213812

Xue, Shufang; Guo, Yun-Nan; Zhao, Lang; Zhang, Peng; Tang, Jinkui

2014-01-28

348

Synthesis and characterization of Dy(OH)3 and Dy2O3 nanotubes.  

PubMed

Dy(OH)3 nanotubes with high aspect ratios of up to about 50 were synthesized in the presence of poly(ethylene glycol) via a hydrothermal method. Poly(ethylene glycol), as a nonionic surfactant, plays an important role in the formation of morphologies. Subsequent thermal treatment of Dy(OH)3 nanotube precursors at 450 degrees C for 6 h led to Dy2O3 nanotubes, during which the precursor tubular morphology was maintained. Selected-area electron diffraction and high-resolution transmission electron microscopy reveal the single-crystal nature of the Dy(OH)3 and Dy2O3 nanotubes. The morphologies and crystalline structure of the as-obtained products were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, respectively. By this method, we can obtain a mass of products. PMID:15853134

Guo, Caixin; Cao, Minhua; Hu, Changwen

2005-02-01

349

Activation cross-sections of deuteron induced reactions on (nat)Gd up to 50 MeV.  

PubMed

Activation cross-sections are presented for the first time for (nat)Gd(d,xn)(161,160,156(m+)), (154,154m1,154m2,153,152(m+),151(m+))Tb, (nat)Gd(d,x)(159,153,151)Gd and (nat)Gd(d,x)(156)Eu reactions from their respective thresholds up to 50 MeV. The cross-sections were measured by the stacked-foil irradiation technique and by using high resolution ?-ray spectrometry. The measured values were compared with the results of theoretical models calculated by the computer codes ALICE-D, EMPIRE-D and TALYS (data from TENDL library). Integral yields of the reaction products were deduced from the excitation functions. PMID:24215815

Tárkányi, F; Takács, S; Ditrói, F; Csikai, J; Hermanne, A; Ignatyuk, A V

2014-01-01

350

Lifetime measurements and shape coexistence in {sup 144}Dy  

SciTech Connect

The known level scheme of {sup 144}Dy has been extended and lifetime measurements have been made with the recoil-distance Doppler-shift method. Reduced transition probabilities and deformations have been determined for four low-lying transitions. These states form part of the first observed band crossing, giving information on the change in nuclear deformation resulting from the rearrangement of h{sub 11/2} protons in the nucleus. Two bands built upon excited 10{sup +} states have been assigned pi(h{sub 11/2}){sup 2} prolate and nu(h{sub 11/2}){sup -2} oblate configurations with tau=12(2)ps and 0.01Gd.

Procter, M. G.; Cullen, D. M.; Niclasen, B.; Mason, P. J. R.; Rigby, S. V.; Dare, J. A.; Lumley, N. M. [Schuster Laboratory, University of Manchester, Manchester M13 9PL (United Kingdom); Scholey, C.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Puurunen, A.; Rahkila, P.; Ruotsalainen, P.; Saren, J. [Department of Physics, University of Jyvaeskylae, FIN-40014 Jyvaeskylae (Finland)

2010-05-15

351

Magnetic and Moessbauer studies on rare-earth-containing Heusler alloys Pd/sub 2/RSn (R = Tb--Yb)  

SciTech Connect

Magnetic susceptibility and /sup 119/Sn Moessbauer studies have been carried out on a new series of rare-earth-containing Heusler alloys having the formula Pd/sub 2/RSn (R = Tb--Yb). The Tm and Yb compounds in this series along with Lu, Sc, and Y compounds are superconducting. The magnetic susceptibility of Pd/sub 2/TmSn and Pd/sub 2/YbSn deviates from the Curie-Weiss behavior at low temperatures indicating that crystalline electric field effects are appreciable. Analysis of the magnetic susceptibility data in terms of crystalline electric fields shows that the ground state of the Tm/sup 3 +/ ion is nonmagnetic which, therefore, does not affect the superconducting state. The susceptibility of Yb/sup 3 +/ ions at low temperatures is also reduced from the free-ion value due to the crystalline electric field interaction. The Tb- and Dy-containing compounds order antiferromagnetically with Neel temperatures of 9 and 15 K, respectively, while Er- and Ho-containing compounds are paramagnetic down to 1.4 K. The hyperfine field at the Sn site in Pd/sub 2/TbSn is about 50 kOe but is only about 10 kOe in Pd/sub 2/DySn at 4.2 K.

Malik, S.K.; Umarji, A.M.; Shenoy, G.K.

1985-06-01

352

First-Line Treatment for Tuberculosis (TB), Drug Resistant TB -- A Visual Tour  

MedlinePLUS

... of Drug-Resistant TB TB Home Page Photo Credit : The photo of Mycobacterium tuberculosis was obtained from ... Prevention , CDC/ Dr. Ray Butler; Janice Carr. Illustration Credit : This illustration is in the public domain. Please ...

353

Enhancement of malignant properties of human osteosarcoma cells with disialyl gangliosides GD2/GD3.  

PubMed

The expression and implications of gangliosides in human osteosarcomas have not been systematically analyzed. In this study, we showed that gangliosides GD3 and GD2 are highly expressed in the majority of human osteosarcoma cell lines derived from oral cavity regions. Introduction of GD3 synthase cDNA into a GD3/GD2-negative (GD3/GD2-) human osteosarcoma subline resulted in the establishment of GD3/GD2+ transfectant cells. They showed increased cell migration and invasion activities in wound healing and Boyden chamber invasion assays, respectively, compared to the control cells. When treated with serum, GD3/GD2+ cells showed stronger tyrosine phosphorylation of p130Cas, focal adhesion kinase, and paxillin than GD3/GD2- cells. In particular, paxillin underwent much stronger phosphorylation, suggesting its role in cell motility. Furthermore, we tried to dissect the roles of GD3 and GD2 in the malignant properties of the transfectant cells by establishing single ganglioside-expressing cells, that is, either GD3 or GD2. Although GD3/GD2+ cells showed the most malignant properties, GD2+ cells showed almost equivalent levels to GD3/GD2+ cells in invasion and migration activities, and in the intensities of tyrosine phosphorylation of paxillin. Among Src family kinases, Lyn was expressed predominantly, and was involved in the invasion and motility of GD3- and/or GD2-expressing transfectants. Furthermore, it was elucidated by gene silencing that Lyn was located in a different pathway from that of FAK to eventually lead paxillin activation. These results suggested that GD2/GD3 are responsible for the enhancement of the malignant features of osteosarcomas, and might be candidate targets in molecular-targeted therapy. PMID:22632091

Shibuya, Hidenobu; Hamamura, Kazunori; Hotta, Hiroshi; Matsumoto, Yasuyuki; Nishida, Yoshihiro; Hattori, Hisashi; Furukawa, Keiko; Ueda, Minoru; Furukawa, Koichi

2012-09-01

354

{beta} decay of {sup 148}Dy: Study of the Gamow-Teller giant state by means of total absorption spectroscopy  

SciTech Connect

The {gamma}-cascades following the Gamow Teller beta decay of {sup 148}Dy 0{sup +} have been investigated with the total absorption gamma spectrometer at GSI. Our measurements confirm that the Gamow-Teller resonant state is populated with a log ft=3.9 and that there is very little mixing of this state with the background J=1 states. In contrast to previous measurements, the experimental method presented here is sensitive to very small admixtures at high excitation energy. Previously unobserved, weak beta-branches to levels in {sup 148}Tb are also reported.

Algora, A.; Nacher, E.; Rubio, B.; Cano-Ott, D.; Tain, J.L.; Gadea, A.; Agramunt, J.; Karny, M.; Janas, Z.; Rykaczewski, K.; Collatz, R.; Hellstroem, M.; Hu, Z.; Kirchner, R.; Roeckl, E.; Shibata, M.; Batist, L.; Moroz, F.; Wittmann, V. [IFIC, CSIC-University Valencia, Apartado Oficial 22085, 46071 Valencia (Spain); Institute of Experimental Physics, Warsaw University, PL-00-681, Warsaw (Poland); Gessellschaft fuer Schwerionenforschung, D-64220 Darmstadt (Germany); St. Petersburg Nuclear Physics Institute, 188-350 Gatchina (Russian Federation)

2004-12-01

355

A comparative investigation of Lu2SiO5:Ce and Gd2O2S:Eu powder scintillators for use in x-ray mammography detectors  

NASA Astrophysics Data System (ADS)

The dominant powder scintillator in most medical imaging modalities for decades has been Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Apart from Gd2O2S:Tb, there are alternative powder phosphor scintillators such as Lu2SiO5:Ce and Gd2O2S:Eu that have been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital mammography detectors such as CCDs. Lu2SiO5:Ce emits blue light and can be combined with blue sensitivity films, photocathodes and some photodiodes. For the purposes of the present study, two scintillating screens, one from Lu2SiO5:Ce and the other from Gd2O2S:Eu powders, were prepared using the method of sedimentation. The screen coating thicknesses were 25.0 and 33.1 mg cm-2 respectively. The screens were investigated by evaluating the following parameters: the output signal, the modulation transfer function, the noise equivalent passband, the informational efficiency, the quantum detection efficiency and the zero-frequency detective quantum efficiency. Furthermore, the spectral compatibility of those materials with various optical detectors was determined. Results were compared to published data for the commercially employed 'Kodak Min-R film-screen system', based on a 31.7 mg cm-2 thick Gd2O2S:Tb phosphor. For Gd2O2S:Eu, MTF data were found comparable to those of Gd2O2S:Tb, while the MTF of Lu2SiO5:Ce was even higher resulting in better spatial resolution and image sharpness properties. On the other hand, Gd2O2S:Eu was found to exhibit higher output signal and zero-frequency detective quantum efficiency than Lu2SiO5:Ce.

Michail, C. M.; Fountos, G. P.; David, S. L.; Valais, I. G.; Toutountzis, A. E.; Kalyvas, N. E.; Kandarakis, I. S.; Panayiotakis, G. S.

2009-10-01

356

Na3DyCl6  

PubMed Central

Single crystals of the title compound, tris­odium hexa­chloridodysprosate, Na3DyCl6, were obtained as a by-product of synthesis using dysprosium(III) chloride and sodium chloride among others. The monoclinic structure with its typical ? angle close to 90° [90.823 (4)°] is isotypic with the mineral cryolite (Na3AlF6) and the high-temperature structure of the Na3 MCl6 series, with M = Eu–Lu, Y and Sc. The isolated, almost perfect [DyCl6]3? octa­hedra are inter­connected via two crystallographically different Na+ cations: while one Na+ resides on centres of symmetry (as well as Dy3+) and also builds almost perfect, isolated [NaCl6]5? octa­hedra, the other Na+ is surrounded by seven chloride anions forming a distorted [NaCl7]6? trigonal prism with just one cap as close secondary contact.

Schurz, Christian M.; Meyer, Gerd; Schleid, Thomas

2011-01-01

357

Spectroscopy of 159Gd  

NASA Astrophysics Data System (ADS)

The well deformed ( ˜ 0.3) nucleus 159Gd was investigated by means of radiative neutron capture and single neutron transfer reactions. The (n, ?) reaction was studied with thermal and resonance neutrons. Secondary ?-rays were investigated with the GAMS2/3 bent-crystal spectrometers at the Institute Laue-Langevin Grenoble. Primary ?-rays were studied with 2 and 24 keV neutrons using the Average Resonance Capture technique and a pair spectrometer at Brookhaven. The single neutron stripping and pick up reactions (d,p) and (?c{d},t) were investigated at the Tandem van de Graaff accelerator of the University and Technical University Munich with unpolarized 18 MeV and polarized 22 MeV deuteron beams, respectively. All experiments resulted in the combined observation of about 300 levels up to 3 MeV. The decay scheme for this nucleus has been completed and expanded up to 1.2 MeV. Evidence of vibrational phonons coupled to single particle states is reported for the first time in this nucleus. The level density was derived and compared with the Fermi gas constant temperature model formula. A preliminary model calculation based on the quasi-particle-phonon model has been undertaken in an attempt to describe the level scheme and structure of this nucleus.

Granja, C.; Rubá?ek, L.; Aprahamian, A.; Börner, H.; Lehmann, H.; Chrien, R. E.; von Egidy, T.; Wirth, H.-F.; Graw, G.; Hertenberger, R.; Eisermann, Y.; Nosek, D.; Pospíšil, S.; Telezhnikov, S. A.

2003-06-01

358

Tuberculosis: The Connection between TB and HIV (the AIDS Virus)  

MedlinePLUS

... tb Print page ? Listen to audio/Podcast Español (Spanish) Contact Us: Centers for Disease Control and Prevention ... Laws Publications & Products Fact Sheets General Fact sheets - Spanish TB - General Information The Difference Between Latent TB ...

359

The TB Alliance: overcoming challenges to chart the future course of TB drug development.  

PubMed

The Global Alliance for TB Drug Development (TB Alliance) is a not-for-profit organization dedicated to the discovery and development of faster-acting and affordable drugs to fight TB. TB kills nearly 2 million people each year, partly due to the inadequacy of the current treatment. There have been no new drugs registered for TB in more than 40 years, but new partnership models over the past decade have enabled tremendous progress in the pipeline. With 10 clinical compounds now in development globally, the TB Alliance is embarking on a new paradigm of clinical development, one that leverages both new and existing compounds to discover and develop markedly shorter, simpler, faster-acting and less toxic multidrug regimens that can treat both drug-sensitive and multidrug-resistant TB concurrently, dramatically simplifying treatment and facilitating the scale-up of global treatment efforts. PMID:21859299

Ginsberg, Ann

2011-08-01

360

Crystal structures and magnetic properties of novel rare-earth copper sulfides, EuRCuS3 (R = Y, Gd Lu)  

NASA Astrophysics Data System (ADS)

Novel quaternary rare-earth copper sulfides EuRCuS3 (R = Y, Gd-Lu excluding Ho, Er) have been investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, and specific heat measurements. These compounds crystallize in the Eu2CuS3-type structure for R = Y, Gd-Dy and in the KZrCuS3-type structure for R = Tm-Lu. Both EuY CuS3 and EuLuCuS3 show a ferromagnetic transition and the other EuRCuS3 compounds show a ferrimagnetic transition at around 5.0 K.

Wakeshima, Makoto; Furuuchi, Fumito; Hinatsu, Yukio

2004-08-01

361

Inelastic Neutron Scattering on 160Gd  

NASA Astrophysics Data System (ADS)

The nature of low-lying excitations, K?=0+ bands in deformed nuclei remain enigmatic in the field, especially in relationship to quadrupole vibrations. One method of characterizing these states beyond excitation energies is through measurements of absolute transition probabilities. In the rare earth region of deformation, there are five stable Gd isotopes, 154Gd, 156Gd, and 158Gd have been studied to obtain B(E2) values, a fourth, 160Gd is the focus of this work. We have examined 160Gd with the (n, n'?) reaction and neutron energies up to 3.0 MeV to confirm known 0+ states.

Lesher, S. R.; Casarella, C.; Crider, B. P.; Ikeyama, R.; Marsh, I.; Peters, E. E.; Prados-Estévez, F. M.; Smith, M. K.; Tully, Z.; Vanhoy, J. R.; Aprahamian, A.; Yates, S. W.

2014-03-01

362

Visible Cathode Luminescence of Oxidized Dy-Doped Si Films  

NASA Astrophysics Data System (ADS)

Visible cathode luminescence (CL) spectra were observed between the wavelengths of 480 and 750 nm at room temperature from oxidized dysprosium (Dy)-doped silicon films formed by pulsed-jet chemical vapor deposition. The films were deposited using CH3SiH3 and Dy(C11H19O2)3 gases at 600 °C on Si(001) substrates followed by thermal oxidization at 860 °C for 30 min. Since the CL spectra from the film were similar to those from Dy2O3 powder, it seems that Dy2O3 as well as SiO2 were formed after the thermal oxidation. The observed CL spectrum appeared to correspond to that of Dy3+ in Dy2O3 or in SiO2 matrix. Secondary ion mass spectrometry measurements of the deposited film showed that Dy was highly doped up to 2× 1021 atoms/cm3.

Masaki, Takayoshi; Kawai, Shinji; Kato, Yoshimine; Motooka, Teruaki

2007-08-01

363

Confronting TB/HIV in the era of increasing anti-TB drug resistance  

PubMed Central

HIV associated TB is a major public health problem. In 2006, it was estimated that there were over 700,000 people who suffered from HIV associated TB, of whom about 200, 000 have died. The burden of HIV associated TB is greatest in Sub-Saharan Africa where the TB epidemic is primarily driven by HIV. There has been steady progress made in reducing the burden of HIV in TB patients with an increasing number of TB patients tested for HIV and provided with cotrimoxazole preventive therapy (CPT) and anti-retroviral treatment (ART). Less progress is being made to reduce the burden of TB in people living with HIV. The number of HIV infected persons reported to have been screened for TB was less than 1% while Isoniazid preventive therapy was reported to have been provided to less than 0.1% of eligible persons in 2006. A major push is urgently needed to accelerate the implementation of three important interventions. The three are Intensified TB Screening (ICF) among people living with HIV, the provision of Isoniazid Preventive Therapy (IPT) and TB Infection Control(IC). These interventions are best carried out by HIV control programmes which should therefore be encouraged to take greater responsibility in implementing these interventions.

2008-01-01

364

Confronting TB/HIV in the era of increasing anti-TB drug resistance.  

PubMed

HIV associated TB is a major public health problem. In 2006, it was estimated that there were over 700,000 people who suffered from HIV associated TB, of whom about 200, 000 have died. The burden of HIV associated TB is greatest in Sub-Saharan Africa where the TB epidemic is primarily driven by HIV. There has been steady progress made in reducing the burden of HIV in TB patients with an increasing number of TB patients tested for HIV and provided with cotrimoxazole preventive therapy (CPT) and anti-retroviral treatment (ART). Less progress is being made to reduce the burden of TB in people living with HIV. The number of HIV infected persons reported to have been screened for TB was less than 1% while Isoniazid preventive therapy was reported to have been provided to less than 0.1% of eligible persons in 2006. A major push is urgently needed to accelerate the implementation of three important interventions. The three are Intensified TB Screening (ICF) among people living with HIV, the provision of Isoniazid Preventive Therapy (IPT) and TB Infection Control(IC). These interventions are best carried out by HIV control programmes which should therefore be encouraged to take greater responsibility in implementing these interventions. PMID:19014421

Chakaya, Jeremiah; Getahun, Haileyesus; Granich, Reuben; Havlir, Diane

2008-01-01

365

Growth and magnetic properties of LPE-grown (EuTbBi) 3(FeAlGa) 5O 12 garnet films  

Microsoft Academic Search

Using the PbO–B2O3–Bi2O3 flux system, (EuTbBi)3(FeAlGa)5O12 (EuTbIG) films were grown on (GdCa)3(GaMgZr)5O12 (SGGG) substrates for optical devices by the liquid phase epitaxial (LPE) method. The grown films' growth and magnetic domain wall were observed as a function of the Fe2O3\\/(Al2O3+Ga2O3)(R2) molar ratio by magnetic force microscope (MFM). As the grown films decreased the R2 molar ratio, the saturation magnetization of

G. Y. Kim; S. G. Yoon; I. S. Chung; S. B. Park; S. J. Suh; D. H. Yoon

2005-01-01

366

Sonochemical synthesis of Dy2(CO3)3 nanoparticles and their conversion to Dy2O3 and Dy(OH)3: Effects of synthesis parameters  

Microsoft Academic Search

Dysprosium carbonates nanoparticles were synthesized by the reaction of Dy(CH3COO)3·6H2O and sodium hydroxide by a sonochemical method. Dysprosium oxide nanoparticles with average size about 12nm were prepared from calcination of Dy2(CO3)3·xH2O nanoparticles. Dy(OH)3 nanoparticles were synthesized by facial hydrothermal processing from Dy2O3 nanoparticles. The as-synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectrum

Masoud Salavati-Niasari; Jaber Javidi; Fatemeh Davar; Alireza Amini Fazl

2010-01-01

367

Growth and characterization of DyP/GaAs and DyAs/GaAs-based heterostructures and superlattices  

NASA Astrophysics Data System (ADS)

Details of the structural and electrical properties of epitaxial DyP/GaAs and DyAs/GaAs is reported. DyP is lattice matched to GaAs, with a room temperature mismatch of less than 0.01%. DyAs, on the other hand, has a mismatch of nearly 2.4%. Both DyP and DyAs have been grown by solid source MBE using custom designed group V thermal cracker cells and group III high-temperature effusion cells. High-quality DyP and DyAs epilayers, as determined by XRD, TEM, and AFM analysis, were obtained for growth temperatures ranging from 500°C to 600°C with growth rates between 0.5 and 0.7 ?m/h. The DyP epilayers are n-type with measured electron concentrations of the order of 3×10 20 to 4×10 20 cm -3, with room temperature mobilities of 250-300 cm 2/V s, and with a barrier height of 0.75 eV to GaAs. The DyAs epilayers are also n-type with concentration of 1×10 21 to 2×10 21 cm -3, with mobilities between 25 and 40 cm 2/V s. DyP is stable in air with no apparent oxidation taking place, even after months of ambient exposure to untreated air.

Lee, P. P.; Hwu, R. J.; Sadwick, L. P.; Balasubramaniam, H.; Kumar, B. R.; Chern, J. H.; Lareau, R. T.

1998-07-01

368

Application of GD&T  

NSDL National Science Digital Library

Many students that take a Geometric Dimensioning and Tolerancing (GD&T) course complain that they lack confidence in applying the concepts learned. One reason is not enough opportunities during the course to practice with assemblies instead of the simple parts typically shown in introductory textbooks. The specification of GD&T controls on the skateboard is an exercise that demonstrates that many possible correct solutions exist, depending on the intent of the designer. Only the mating between the skateboard deck and the truck base is studied in detail in this lesson. Other design, manufacturing and assembly issues that can be resolved with the use of GD&T can also be studied and some will be introduced in this ALT.

Castro-Cedeno, Mario H.

2009-12-03

369

Synthesis and Characterization of New Germanate Pyrochlores, A2Ge2O7 (A = Tb, Yb, Er)  

NASA Astrophysics Data System (ADS)

The titanate pyrochlores, A2Ti2O7, have yielded some of the most well-studied geometrically frustrated magnetic materials. A new class of pyrochlores with germanium on the B-site is now being investigated. The germanates, which in many cases share ground states with their titanate analogues, are far more highly correlated due to the smaller B-site cation. Two germanate pyrochlores, Ho2Ge2O7 and Dy2Ge2O7, were previously synthesized and characterized as new spin ice compounds [1-3]. We now present the new germanate pyrochlores, A2Ge2O7 with A = Tb, Yb, and Er. Based on the titanates, three distinctly different magnetic ground states can be expected for these materials: Er2Ti2O7 has an ``order-by-disorder'' mechanism, Yb2Ti2O7 is a quantum spin ice and Tb2Ti2O7 is a spin liquid. Preliminary measurements on Tb2Ge2O7 indicate that it too is a spin liquid down to at least 0.35 K. We will present the characterizations of A2Ge2O7 (A = Tb, Yb, Er) and compare them to the titanates.[4pt] [1] H. D. Zhou et al., Nature Communications 2, 478 (2011). [0pt] [2] H. D. Zhou et al., Phys. Rev. Lett. 108, 207206 (2012).[0pt] [3] A. M. Hallas et al., accepted for publication in Phys. Rev. B (2012).

Hallas, Alannah; Zhou, Haidong; Arevalo Lopez, Angel; Silverstein, Harlyn; Attfield, J. Paul; Wiebe, Christopher

2013-03-01

370

Stellar neutron capture cross sections of the Gd isotopes.  

National Technical Information Service (NTIS)

The neutron capture cross sections of (sup 152)Gd, (sup 154)Gd, (sup 155)Gd, (sup 156)Gd, (sup 157)Gd, and (sup 158)Gd were measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the (...

K. Wisshak F. Voss F. Kaeppeler K. Guber L. Kazakov

1995-01-01

371

A comparative study of magnetic behaviors in TbNi2, TbMn2 and TbNi2Mn  

NASA Astrophysics Data System (ADS)

All TbNi2, TbMn2, and TbNi2Mn compounds exhibit the cubic Laves phase with AB2-type structure in spite of the fact that the ratio of the Tb to transition-metal components in TbNi2Mn is 1:3. Rietveld refinement indicates that in TbNi2Mn the Mn atoms are distributed on both the A (8a) and B (16d) sites. The values of the lattice constants were measured to be a = 14.348 Å (space group F-43 m), 7.618 Å, and 7.158 Å (space group Fd-3 m) for TbNi2, TbMn2, and TbNi2Mn, respectively. The magnetic transition temperatures TC were found to be TC = 38 K and TC = 148 K for TbNi2 and TbNi2Mn, respectively, while two magnetic phase transitions are detected for TbMn2 at T1 = 20 K and T2 = 49 K. Clear magnetic history effects in a low magnetic field are observed in TbMn2 and TbNi2Mn. The magnetic entropy changes have been obtained.

Wang, J. L.; Md Din, M. F.; Kennedy, S. J.; Hong, F.; Campbell, S. J.; Studer, A. J.; Wu, G. H.; Cheng, Z. X.; Dou, S. X.

2014-05-01

372

Epitaxial growth and characterization of DyP/GaAs, DyAs/GaAs, and GaAs/DyP/GaAs heterostructures  

NASA Astrophysics Data System (ADS)

There is a significant interest in the area of improving high temperature stable contacts to III-V semiconductors. Two attractive material systems that offer promise in this area are dysprosium phosphide/gallium arsenide (DyP/GaAs) and dysprosium arsenide/gallium arsenide (DyAs/GaAs). Details of epitaxial growth of DyP/GaAs and DyAs/GaAs by molecular beam epitaxy (MBE), and their characterization by x-ray diffraction, transmission electron microscopy, atomic force microscopy, Auger electron spectroscopy, Hall measurements, and high temperature current-voltage measurements is reported. DyP is lattice matched to GaAs, with a room temperature mismatch of less than 0.01% and is stable in air with no sign of oxidation, even after months of ambient exposure. Both DyP and DyAs have been grown by solid source MBE using custom designed group V thermal cracker cells and group III high temperature effusion cells. High quality DyP and DyAs epilayer were consistently obtained for growth temperatures ranging from 500 to 600°C with growth rates between 0.5 and 0.7 µm/h. DyP epilayers are n-type with electron concentrations of 3 × 1020 to 4 × 1020 cm-3, room temperature mobilities of 250 to 300 cm2/V·s, and a barrier height of 0.81 eV to GaAs. DyAs epilayers are also n-type with carrier concentrations of 1 × 1021 to 2 × 1021 cm-3, and mobilities between 25 and 40 cm2/V·s.

Lee, P. P.; Hwu, R. J.; Sadwick, L. P.; Balasubramaniam, H.; Kumar, B. R.; Alvis, R.; Lareau, R. T.; Wood, M. C.

1998-05-01

373

Properties of rare-earth scandate single crystals (Re=Nd-Dy)  

NASA Astrophysics Data System (ADS)

Rare-earth (RE) scandate single crystals ranging from NdScO 3 to DyScO 3 were grown by the conventional Czochralski technique. The crystals were found to have a non-stoichiometric composition caused by RE-deficiency on the A-site of the distorted perovskite structure. Their pseudocubic lattice constants lie between 3.95 and 4.01 Å and their average thermal expansion coefficients are between 8.2×10 -6 and 10.9×10 -6 K -1. The pseudocubic lattice constants of the RE scandates vary in about 0.01 Å steps as the RE series is traversed, enabling the growth of substrates appropriate for the strain engineering of perovskite thin films. The crystalline perfection and homogeneity of the DyScO 3 and GdScO 3 single crystals are characterized by a full-width at half-maximum of the 220 reflection of the substrates of about 20-25 arcsec in ? and a very small fluctuation margin of about ±3 arcsec over the whole wafer surface. The average dislocation density of the RE scandate crystals was 10 3-10 5 cm -2. These characteristics make RE scandate single crystals some of the best available substrates for the epitaxial growth of perovskite thin films.

Uecker, R.; Velickov, B.; Klimm, D.; Bertram, R.; Bernhagen, M.; Rabe, M.; Albrecht, M.; Fornari, R.; Schlom, D. G.

2008-05-01

374

Update on the development of TB Vaccines.  

PubMed

Tuberculosis (TB) is an infectious disease caused mainly by members of Mycobacterium tuberculosis complex. In 2012, the WHO estimated 8.7 million new cases and 1.4 million deaths caused by this disease. Under the Millennium Development Goals, the WHO aims to eradicate TB as a public health problem by 2050. However, reaching this goal will require the development and incorporation of new and more effective vaccines that can replace the current BCG vaccine. Much work is therefore ongoing in terms of the development of TB vaccines and more than 10 candidate vaccines are progressing well through the different development stages. The aim of this mini-review is to describe the characteristics of the most promising vaccines, and to give a brief description of some key elements relating to the current and future development of vaccines against TB. PMID:24372249

Zenteno-Cuevas, Roberto

2014-11-01

375

Immunomodulation by vitamin D: implications for TB  

PubMed Central

TB remains a major cause of mortality throughout the world. Low vitamin D status has been linked to increased risk of TB and other immune disorders. These observations suggest a role for vitamin D as a modulator of normal human immune function. This article will detail the cellular and molecular mechanisms by which vitamin D regulates the immune system and how vitamin D insufficiency may lead to immune dysregulation. The importance of vitamin D bioavailability as a mechanism for defining the immunomodulatory actions of vitamin D and its impact on TB will also be discussed. The overall aim will be to provide a fresh perspective on the potential benefits of vitamin D supplementation in the prevention and treatment of TB.

Chun, Rene F; Adams, John S; Hewison, Martin

2011-01-01

376

Homelessness Is a Risk Factor for TB  

MedlinePLUS

... to... Añadir en... Favorites Delicious Digg Google Bookmarks Homelessness is a risk factor for TB Learn how ... the United States, 1% of the population experiences homelessness in a given year, but 5.8% of ...

377

Strengthening TB surveillance system in India: Way forward for improving estimates of TB incidence.  

PubMed

One of the key indicators used under India's TB control program is the DOTS case detection rate of new sputum smear positive TB whose estimates in India are based on incidence estimates derived from Styblo's rule. Styblo's rule was formulated in an era without well-established tuberculosis control program, effective tuberculosis drugs, and emergence of TB-HIV coinfection, so today it does not reflect the true incidence of TB. Considering various loopholes in different methods of measurement of incidence (prevalence surveys of disease/ infection, vital registration system and Styblo's rule), strengthening of existing surveillance system is the best tool to obtain correct estimates of tuberculosis incidence in India. PMID:21712922

Sharma, Rinku; Jain, Vivek; Singh, Saudan

2011-04-01

378

Tb magnetic moment behaviour in amorphous Tb?Fe alloy: A nuclear orientation study  

NASA Astrophysics Data System (ADS)

Amorphous 160Tb : TbFe 4 has been studied in the temperature range down to 5 mK and in external magnetic fields up to 8.5T using the low-temperature nuclear orientation technique. The Tb magnetic moments are noncollinear with respect to Bext even up to Bext = 8.5 T. The hysteresis loop, which was reconstructed from the experimental data, shows the coercive field to be ? 1 T, which is considerably lower than in amorphous TbFe 2.

Trhlík, M.; De Moor, P.; John, J.; Limbach, T.; Schuurmans, P.; Sedlák, B.; Severijns, N.; Vanderpoorten, W.; Vanneste, L.; Wouters, J.

1993-07-01

379

Magnetic and microstructural modification of the Nd-Fe-B sintered magnet by mixed DyF3/DyHx powder doping  

NASA Astrophysics Data System (ADS)

We investigated the magnetic and microstructural properties of Nd-Fe-B sintered magnets doped with DyF3, DyHx, and a mixture of DyF3 and DyHx powders. In the DyHx-doped magnet, diffusion of Dy occurs predominantly via grain boundary diffusion. However, the proportion of Dy being diffused by lattice diffusion is increased in the DyF3-doped magnet due to the different influences of F- and H+ ions. The detailed mechanism of the microstructural changes in terms of the diffusional behavior of Dy induced by the DyF3 and DyHx powder doping is discussed. The formation of a Dy-segregated Nd-rich oxide phase (RE-rich, Dy-Nd-O) was suppressed only in the DyF3-doped magnet, and the (00L) alignment of Nd2Fe14B grains in the sintered magnet increased when it was doped with the DyHx powder. We obtained the optimum microstructural and magnetic properties of the Nd-Fe-B sintered magnet through doping with a mixture of DyF3 and DyHx powders, which compensated for the drawbacks of using each powder alone.

Kim, Tae-Hoon; Lee, Seong-Rae; Kim, Hyo-Jun; Lee, Min-Woo; Jang, Tae-Suk

2014-05-01

380

?-decay half-lives of new neutron-rich rare-earth isotopes 159Pm,162Sm, and 166Gd  

NASA Astrophysics Data System (ADS)

The new neutron-rich rare-earth isotopes 159Pm, 162Sm, and 166Gd produced in the proton-induced fission of 238U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. The half-lives of 159Pm, 162Sm, and 166Gd were determined to be 1.5 ± 0.2, 2.4 ± 0.5, and 4.8 ± 1.0 s respectively. The partial decay scheme of 166Gd was constructed from ??-coincidence data. A more accurate half-life value of 25.6 ± 2.2 s was obtained for the previously identified isotope 166Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by Audi and Wapstra.

Ichikawa, S.; Asai, M.; Tsukada, K.; Haba, H.; Nagame, Y.; Shibata, M.; Sakama, M.; Kojima, Y.

2005-06-01

381

Magnetic domain pinning in an anisotropy-engineered GdTbFe thin film  

SciTech Connect

Focused ion beam irradiation was used to reduce locally the perpendicular anisotropy of magnetic thin films in rectangular lattices of 50 nm sized dots. The effect of the anisotropy patterns, differing in ion fluence and interdot spacing, on the magnetization reversal process was determined in q space with x-ray resonant magnetic scattering and in real space with magnetic force microscopy. At remanence only a slight alignment of the irregularly shaped domains is observed. In perpendicular magnetic fields, however, the high field bubble domains display a pronounced localization on the dots, showing that this form of local anisotropy reduction is a highly efficient way of domain positioning.

Konings, Stan; Miguel, Jorge; Goedkoop, Jeroen; Camarero, Julio; Vogel, Jan [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands); Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Laboratoire Louis Neel, CNRS, BP 166, F-38042 Grenoble (France)

2006-08-01

382

Labeling of biotin with [166Dy]Dy/166Ho as a stable in vivo generator system.  

PubMed

The aim of this work was to synthesize [166Dy]Dy/166Ho-DTPA-Biotin to evaluate its potential as a new radiopharmaceutical for targeted radiotherapy. Dysprosium-166 (166Dy) was obtained by neutron irradiation of enriched 164Dy(2)O(3) in a Triga Mark III reactor. The labeling was carried out in aqueous media at pH 8.0 by addition of [166Dy]DyCl(3) to diethylenetriaminepentaacetic-alpha,omega-bis(biocytinamide) (DTPA-Biotin). Radiochemical purity was determined by high-performance liquid chromatography (HPLC) and TLC. The biological integrity of labeled biotin was studied evaluating its avidity for avidin in an agarose column and by size-exclusion HPLC analysis of the radiolabeled DTPA-Biotin with and without the addition of avidin. Stability studies against dilution were carried out by diluting the radiocomplex solution with saline solution and with human serum at 37 degrees C for 24 h. The [166Dy]Dy/166Ho-labeled biotin was obtained with a 99.1+/-0.6% radiochemical purity. In vitro studies demonstrated that [166Dy]Dy/166Ho-DTPA-Biotin is stable after dilution in saline and in human serum and no translocation of the daughter nucleus occurs subsequent to beta(-) decay of 166Dy that could produce release of 166Ho(3+). Avidity of labeled biotin for avidin was not affected by the labeling procedure. Biodistribution studies in normal mice showed that the [166Dy]Dy/166Ho-DTPA-Biotin has a high renal clearance. In conclusion, the radiolabeled biotin prepared in this investigation has adequate properties to work as a stable in vivo generator system for targeted radiotherapy. PMID:12672609

Ferro-Flores, G; Arteaga de Murphy, C; Pedraza-López, M; Monroy-Guzmán, F; Meléndez-Alafort, L; Tendilla, J I; Jiménez-Varela, R

2003-04-14

383

Ternary systems {Dy, Er}FeB  

Microsoft Academic Search

Specimens for investigation were prepared from materials with weight fractions of not less than 0.995 Dy or Er (REMs), 0.9996 Fe, and 0.9994 B. After being mixed, the iron and boron, which were in powder form, were pressed into compacts, and these were then melted together with the solid REMs in an electric arc furnace provided with a purified argon

G. V. Chernyak; N. F. Chaban; Yu. B. Kuz'ma

1983-01-01

384

Optical properties of crystals doped with Sm3+ or Dy3+ relevant to potential InGaN/GaN laser diode-pumped visible laser operation: A comparative study  

NASA Astrophysics Data System (ADS)

Results of detailed spectroscopic investigation of Sm3+ and Dy3+ ions incorporated in crystal structures of Yal YAl3(BO3)4, LiNbO3, Gd3Ga5O12, Gd2SiO5, Lu2SiO5 and (Gd, Lu)2SiO5 are reported and discussed. The impact of the hosts on transition intensities and excited state relaxation dynamics of incorporated luminescent ions was examined. Distribution of luminescence intensity among spectral bands in terms of luminescence branching ratios was evaluated based on numerical integration of luminescence bands. Intensities of UV and blue absorption bands potentially useful for optical pumping were determined quantitatively in units of absorption cross section. The most intense luminescence bands related to potential laser transitions 4 G 5/2 ? 6 H 7/2 of Sm3+ around 600 nm and 4 F 9/2 ? 6 H 13/2 of Dy3+ around 580 nm were calibrated in units of emission cross section. Evaluated peak values of emission cross section range from 0.43 × 10-20 cm2 for Sm3+ in (Gd, Lu)2SiO5 to 1.17 × 10-20 cm2 for Sm3+ in LiNbO3. Those for dysprosium-doped crystals range from 0.63 × 10-20 cm2 for LiNbO3:Dy3+ to 2.0 × 10-20 cm2 for Yal YAl3(BO3)4:Dy3+. It follows from these considerations that samarium-doped crystals show promise for laser application owing to the combination of a strong absorption that matches radiation of commercial laser diodes emitting near 405 nm and long luminescence lifetime. Major shortcoming of dysprosium-doped crystals results from a weak intensity of absorption bands available for optical pumping near 450 nm and 385 nm combined with relatively strong self-quenching of luminescence.

Ryba-Romanowski, W.; Strz?p, A.; Lisiecki, R.; Berkowski, M.

2014-05-01

385

RADIOACTIVE DECAY OF Tb¹⁵⁷ AND Tb¹⁵⁸  

Microsoft Academic Search

Dysprosium, enriched to 13.8% in Dy¹⁵⁶ and to 0.9% in Dy¹⁵⁸, ; is irradiated with neutrons, and a terbium chemical fraction is obtained. The ; mass number of 155 is assigned to the gamma activity in the chemical fraction. ; The assignment is confirmed by a comparison of the scintillation spectrum of the ; terbium chemical fraction with that obtained

M. R. Bhat; M. L. Pool

1962-01-01

386

Na(3)DyCl(6).  

PubMed

Single crystals of the title compound, tris-odium hexa-chloridodysprosate, Na(3)DyCl(6), were obtained as a by-product of synthesis using dysprosium(III) chloride and sodium chloride among others. The monoclinic structure with its typical ? angle close to 90° [90.823 (4)°] is isotypic with the mineral cryolite (Na(3)AlF(6)) and the high-temperature structure of the Na(3)MCl(6) series, with M = Eu-Lu, Y and Sc. The isolated, almost perfect [DyCl(6)](3-) octa-hedra are inter-connected via two crystallographically different Na(+) cations: while one Na(+) resides on centres of symmetry (as well as Dy(3+)) and also builds almost perfect, isolated [NaCl(6)](5-) octa-hedra, the other Na(+) is surrounded by seven chloride anions forming a distorted [NaCl(7)](6-) trigonal prism with just one cap as close secondary contact. PMID:21754259

Schurz, Christian M; Meyer, Gerd; Schleid, Thomas

2011-05-01

387

Magnetic structure of Dy[superscript 3+] in hexagonal multiferroic DyMnO[subscript 3  

SciTech Connect

Element specific x-ray resonant magnetic scattering (XRMS) investigations were undertaken to determine the magnetic structure of the multiferroic compound, hexagonal DyMnO{sub 3}. In the temperature range from 68 K down to 8 K the Dy{sup 3+} moments are aligned and antiferromagnetically correlated in the c direction according to the magnetic representation {Gamma}{sub 3}. The temperature dependence of the observed intensity can be modeled assuming the splitting of ground-state doublet crystal-field levels of Dy{sup 3+} by the exchange field of Mn{sup 3+}. XRMS together with magnetization measurements indicate that the magnetic representation is {Gamma}{sub 2} below 8 K.

Nandi, S.; Kreyssig, A.; Yan, J.Q.; Vannette, M.D.; Lang, J.C.; Tan, L.; Kim, J.W.; Prozorov, R.; Lograsso, T.A.; McQueeney, R.J.; Goldman, A.I. (Ames)

2008-09-12

388

Magnetic Structure of Dy3+ in Hexagonal Multiferroic DyMnO3  

SciTech Connect

Element specific x-ray resonant magnetic scattering (XRMS) investigations were undertaken to determine the magnetic structure of the multiferroic compound, hexagonal DyMnO{sub 3}. In the temperature range from 68 K down to 8 K the Dy{sup 3+} moments are aligned and antiferromagnetically correlated in the c direction according to the magnetic representation {Lambda}{sub 3}. The temperature dependence of the observed intensity can be modeled assuming the splitting of ground-state doublet crystal-field levels of Dy{sup 3+} by the exchange field of Mn{sup 3+}. XRMS together with magnetization measurements indicate that the magnetic representation is {Lambda}{sub 2}below 8 K.

S.Nandi; A. Kreyssi; J.Q. Yan; M.D. Vannette; J.C. Lang; L. Tan; J.W. Kim; R. Prozorov; T.A. Lograsso; R.J. McQueeney; A.I. Goldman

2008-08-22

389

Scheelite-type NaDy(WO4)2  

PubMed Central

The title compound sodium dysprosium(III) bis­[tungs­tate(VI)], NaDy(WO4)2, has been synthesized under high temperature solution growth (HTSG) conditions in air. The compound crystallizes with the scheelite structure and is composed of isolated WO4 tetra­hedra ( symmetry) with one set of bond lengths and distorted [(Na/Dy)O8] dodeca­hedra ( symmetry; occupancy ratio Na:Dy = 1:1) with two sets of bond lengths.

Zhao, Dan; Li, Feifei; Cheng, Wendan; Zhang, Hao

2010-01-01

390

Scheelite-type NaDy(WO(4))(2).  

PubMed

The title compound sodium dysprosium(III) bis-[tungs-tate(VI)], NaDy(WO(4))(2), has been synthesized under high temperature solution growth (HTSG) conditions in air. The compound crystallizes with the scheelite structure and is composed of isolated WO(4) tetra-hedra ( symmetry) with one set of bond lengths and distorted [(Na/Dy)O(8)] dodeca-hedra ( symmetry; occupancy ratio Na:Dy = 1:1) with two sets of bond lengths. PMID:21579906

Zhao, Dan; Li, Feifei; Cheng, Wendan; Zhang, Hao

2009-01-01

391

Spin-reorientation in GdGa  

NASA Astrophysics Data System (ADS)

We have determined the magnetic structure of the intermetallic compound GdGa by 155Gd Mössbauer spectroscopy and neutron powder diffraction. This compound crystallizes in the orthorhombic ( Cmcm) CrB-type structure. It orders ferromagnetically at T c = 190(2) K and then undergoes a spin reorientation at T SR = 68(2) K. Between T c and T SR , the magnetic structure is characterized by ferromagnetic order of the Gd moments along the b-axis. On cooling below T SR , the Gd 4 c magnetic moments split into two groups (2:2). At 3.6 K, the Gd moment is 6.7(4) ? B , and the Gd magnetic moments are in the bc-plane, canted by 84(3)° and 46(4)° with respect to the crystallographic b-axis. This splitting into two magnetically inequivalent sites is confirmed by our 5 K 155Gd Mössbauer results.

Susilo, R. A.; Cadogan, J. M.; Ryan, D. H.; Lee-Hone, N. R.; Cobas, R.; Muñoz-Pérez, S.

2014-04-01

392

Effect of the medium and the formation of nanostructures on deexcitation of electronic excitation of Eu(III) and Tb(III) chelates  

NASA Astrophysics Data System (ADS)

The intensity I lum and lifetime ?lum of the luminescence of complexes of Eu(III) and Tb(III) ions with ?-diketones and o-phenanthroline in water-ethanol solutions of these ligands have been analyzed as functions of the concentrations of ligand, luminescing lanthanide ions, and added ions causing columinescence and of the solvent deuteration. It is shown that the formation of nanostructures from Ln complexes and their coarsening leads to an increase in ?lum of Eu(III) and Tb(III) and that this increase is due to the suppression of both photochemical deexcitation of these ions and transfer of their electronic excitation energy to OH vibrations of water molecules. The disappearance of the dependence of I lum of Eu(III) on deuteration of water-ethanol solutions of n-methoxybenzoyltrifluoracetone + o-phenanthroline caused by adding Gd(III) ions is explained by the shift of the equilibrium of formation of complexes of Ln chelates to neutral hydrophoblic forms corresponding to the formation of nanostructures of these chelates in the solution. The differences in effect of La(III) and Gd(III) ions on I lum and ?lum of Eu(III) and Tb(III) complexes are explained. It is shown that the widely discussed effect of columinescence not only results from the energy migration in mixed structures of Eu or Tb complexes and Gd complexes but is also due to a large extent to the decrease in ?lum of Eu(III) or Tb(III) caused by their incorporation into nanostructures.

Sveshnikova, E. B.; Dudar, S. S.; Shablya, A. V.; Ermolaev, V. L.

2006-10-01

393

The performance and limitation of T-SPOT.TB for the diagnosis of TB in a high prevalence setting  

PubMed Central

Background Tuberculosis (TB) diagnosis remains difficulty. The previous reports have shown that the T-SPOT.TB assay may be a more promising diagnostic tool for TB, however, it needs a further study to evaluate the diagnostic value of T-SPOT.TB for the specific populations in a high prevalence setting. Methods In this present study, we conducted stratified and comparable analyses to explore the clinical value and the limitation of T-SPOT.TB assay in TB diagnosis in a high TB prevalence setting, Southern China. A total of 413 subjects including 163 pulmonary TB (PTB), 39 extrapulmonary TB (EPTB), 106 non-TB pulmonary diseases (NTBPDs), 20 medical staff and 85 healthy controls were included in the study. Results According to T-SPOT.TB, there had a high incidence of latent TB infection (LTBI) in general population in Southern China, especially in the NTBPDS and medical staff. The T-SPOT.TB had a high performance in the diagnosis of active TB (ATB) in a lower risk of TB infection population such as the general population, however, the T-SPOT.TB for the diagnosis of ATB in the high risk of TB infection populations involving close contacts such as the patients with pulmonary diseases (PD) or medical staff isn’t reliable due to the interference by LTBI. Under this condition, the value of rule-out of the assay was seemed to be better than that of rule-in. We believed that the T-SPOT.TB is suitable for screening both the EPTB and the ATB combined with diabetes mellitus (DM). However, we found that the sensitivity of T-SPOT.TB in sputum smear-negative population wasn’t as high as that in smear-positive population. Conclusions The T-SPOT.TB testing results should be interpreted with caution combined with subject’s characteristics in a high prevalence setting.

Liu, Zhonghua; Li, Zhiqiang

2014-01-01

394

Gd interactions in (Ce,Gd)Al/sub 3/  

SciTech Connect

The susceptibility of Ce/sub 1/..sqrt../sub x/Gd/sub x/Al/sub 3/ for 0.08less than or equal toxless than or equal to0.9 has an anomaly which resembles that associated with a spin-glass transition. For x greater than the percolation threshold concentration for antiferromagnetism at xapprox. =0.5, the size of the susceptibility anomaly decreases two orders of magnitude and a resistivity anomaly appears

Edelstein, A.S.; Holtz, R.L.; Gillespie, D.J.; Rubinstein, M.; Tyson, J.; Fisher, R.A.; Phillips, N.E.

1988-05-01

395

The combined study of Dy2O3-HfO2 nanocrystallites formation by means of EXAFS, PDF, XRD and SAXS  

NASA Astrophysics Data System (ADS)

The process of double oxide Dy2O3-HfO2 nanocrystallites formation upon annealing to 1600°C was investigated with the combination off few X-ray and synchrotron methods. XRD and PDF show the mean crystal structure to be fluorite typical for the compounds of Ln2O3-MeO2 type. The ordering of structure and the growth of nanocrystallites upon annealing was estimated independently from XRD patterns, PDF functions and SAXS scattering curves. Neither transition to pyrochlore phase, nor signs of recently shown in related Gd2O3-HfO2 compounds pyrochlore-type superstructure is observed. However, EXAFS and the short range order of PDF clearly indicate the discrepancy between Dy and Hf local environment. Such a disorder of local crystal structure cannot be described by the fluorite model.

Yaroslavtsev, A. A.; Menushenkov, A. P.; Leshchev, D. S.; Bednarcik, J.; Chernikov, R. V.; Zubavichus, Y. V.; Popov, V. V.; Petrunin, V. F.; Korovin, S. A.

2013-03-01

396

TB database 2010: overview and update.  

PubMed

The Tuberculosis Database (TBDB) is an online database providing integrated access to genome sequence, expression data and literature curation for TB. TBDB currently houses genome assemblies for numerous strains of Mycobacterium tuberculosis (MTB) as well assemblies for over 20 strains related to MTB and useful for comparative analysis. TBDB stores pre- and post-publication gene-expression data from M. tuberculosis and its close relatives, including over 3000 MTB microarrays, 95 RT-PCR datasets, 2700 microarrays for human and mouse TB related experiments, and 260 arrays for Streptomyces coelicolor. To enable wide use of these data, TBDB provides a suite of tools for searching, browsing, analyzing, and downloading the data. We provide here an overview of TBDB focusing on recent data releases and enhancements. In particular, we describe the recent release of a Global Genetic Diversity dataset for TB, support for short-read re-sequencing data, new tools for exploring gene expression data in the context of gene regulation, and the integration of a metabolic network reconstruction and BioCyc with TBDB. By integrating a wide range of genomic data with tools for their use, TBDB is a unique platform for both basic science research in TB, as well as research into the discovery and development of TB drugs, vaccines and biomarkers. PMID:20488753

Galagan, James E; Sisk, Peter; Stolte, Christian; Weiner, Brian; Koehrsen, Michael; Wymore, Farrell; Reddy, T B K; Zucker, Jeremy D; Engels, Reinhard; Gellesch, Marcel; Hubble, Jeremy; Jin, Heng; Larson, Lisa; Mao, Maria; Nitzberg, Michael; White, Jared; Zachariah, Zachariah K; Sherlock, Gavin; Ball, Catherine A; Schoolnik, Gary K

2010-07-01

397

Nuclear structure of 159 Gd  

NASA Astrophysics Data System (ADS)

The well deformed atomic nucleus 159 Gd was investigated by means of radiative neutron capture and single neutron transfer reactions. Nearly 70 secondary ? rays from the (n,?) reaction studied with high-resultion bent-crystal spectrometers at Grenoble are assigned to 159 Gd . About 200 levels with spin up to 11 /2 are observed in this nucleus below 2.3 MeV in (d,p) and (d,t) reactions investigated at the Tandem Van de Graaff accelerator in Garching using unpolarized (18 MeV) and polarized (22 MeV) deuteron beams, respectively. The proposed level scheme for this nucleus is arranged into 21 rotational bands. Experimentally observed levels are interpreted using predictions obtained within the quasiparticle-phonon model and the quasiparticle-rotor approach for a well deformed nucleus.

Granja, C.; Pospíšil, S.; Aprahamian, A.; Börner, H.; Lehmann, H.; von Egidy, T.; Wirth, H.–F.; Graw, G.; Hertenberger, R.; Eisermann, Y.; Nosek, D.; Rubá?ek, L.; Telezhnikov, S. A.

2004-09-01

398

Sonochemical synthesis of Dy2(CO3)3 nanoparticles, Dy(OH)3 nanotubes and their conversion to Dy2O3 nanoparticles  

Microsoft Academic Search

Dysprosium carbonates nanoparticles were synthesized by the reaction of dysprosium acetate and NaHCO3 by a sonochemical method. Dysprosium oxide nanoparticles with average size about 17nm were prepared from calcination of Dy2(CO3)3·1.7H2O nanoparticles. Dy(OH)3 nanotubes were synthesized by sonication of Dy(OAC)3·6H2O and N2H4. The as-synthesized nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM),

Masoud Salavati-Niasari; Jaber Javidi; Fatemeh Davar

2010-01-01

399

Dy(3+)-doped zinc fluorophosphate glasses for white luminescence applications.  

PubMed

Dysprosium (Dy(3+)) ions doped zinc fluorophosphate (PKAZLFDy: P2O5-K2O-Al2O3-ZnF2-LiF-Dy2O3) glasses have been prepared and investigated their spectroscopic properties using absorption, emission and decay measurements. Judd-Ofelt analysis has been carried out to obtain the intensity parameters and in turn predicted radiative properties for the (4)F9/2 level of 1.0 mol% of Dy2O3 doped glass. Visible luminescence spectra have been obtained due to (4)F9/2?(6)HJ (J=11/2, 13/2, 15/2) transitions of Dy(3+) ions under 385 nm excitation. The yellow-to-blue luminescence intensity ratios and chromaticity coordinates of Dy(3+) ions in these glasses have been analyzed as a function of Dy(3+) ion concentration. The decay profiles for the (4)F9/2 level exhibit perfectly single exponential at lower concentrations (up to 1.0 mol%) and turn into non-exponential for higher concentrations (>1.0 mol%) due to energy transfer between donor (excited state Dy(3+) ion) and acceptor (ground state Dy(3+) ion). The results reveal that these glasses emit bright white light which is suitable for the development of W-LEDs. PMID:23719414

Vijaya, N; Upendra Kumar, K; Jayasankar, C K

2013-09-01

400

Optical properties of Dy 3+-doped phosphate and fluorophosphate glasses  

NASA Astrophysics Data System (ADS)

Optical properties of Dy 3+-doped phosphate (P 2O 5 + K 2O + BaO + Al 2O 3) and fluorophosphate (P 2O 5 + K 2O + BaO + BaF 2 + Al 2O 3) glasses have been investigated. The observed bands in absorption spectra of 1.0 mol% Dy 3+-doped glasses have been assigned and analyzed using the parametric free-ion Hamiltonian model. Judd-Ofelt (JO) intensity parameters have been obtained from the optical absorption spectra. The sensitiveness of the ?2 JO parameter to the hypersensitive transition has been demonstrated. Using these JO parameters radiative properties of some of the excited states of Dy 3+ ions have been calculated. A strong yellow emission was observed from the 4F 9/2 ? 6H 13/2 transition of Dy 3+ ions in these glasses. The peak stimulated emission cross-section for the 4F 9/2 ? 6H 13/2 transition is found to be comparable with those of other Dy 3+: systems. The decay curves of the 4F 9/2 level have been measured and are found to deviate from exponential nature with increase in Dy 3+ ions concentration. The non-exponential decay curves have been fitted with the Inokuti-Hirayama model which revealed that dipole-dipole mechanism is responsible for the energy transfer processes through Dy 3+-Dy 3+ interactions.

Babu, S. Surendra; Babu, P.; Jayasankar, C. K.; Tröster, Th.; Sievers, W.; Wortmann, G.

401

Radiative strength functions in {sup 163,164}Dy  

SciTech Connect

The nuclei {sup 163,164}Dy have been investigated using the Oslo method on data from the pickup reaction {sup 164}Dy({sup 3}He,{alpha}{gamma}){sup 163}Dy and the inelastic scattering {sup 164}Dy({sup 3}He,{sup 3}He{sup '}{gamma}){sup 164}Dy, respectively. The radiative strength functions for both nuclei have been extracted, and a small resonance centered around E{sub {gamma}}approx =3 MeV is observed in both cases. The parameters of this so-called pygmy M1 resonance (the scissors mode) are compared with previous results on {sup 160,161,162}Dy using the Oslo method, and with data on {sup 163}Dy measured by the Prague group using the two-step cascade method. In particular, the integrated reduced transition probability B(M1arrow up) of the pygmy resonance is compared with neighboring dysprosium isotopes. We also observe an enhanced strength in the region above E{sub {gamma}}approx =5 MeV in {sup 164}Dy. Possible origins of this feature are discussed.

Nyhus, H. T.; Siem, S.; Guttormsen, M.; Larsen, A. C.; Buerger, A.; Syed, N. U. H.; Tveten, G. M. [Department of Physics, University of Oslo, N-0316 Oslo (Norway); Voinov, A. [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States)

2010-02-15

402

DY163-Ho163 Branching: An S-Process Barometer.  

National Technical Information Service (NTIS)

The neutron capture cross sections of Dy163 and Er164 have been measured to analyze the s-process branching at Dy163-Ho163. The reproduction of the s-process abundance of Er164 via this branching is sensitive to temperature kT, neutron density, and electr...

H. Beer G. Walter R. L. Macklin

1984-01-01

403

Combination of Cytokine Responses Indicative of Latent TB and Active TB in Malawian Adults  

PubMed Central

Background An IFN-? response to M. tuberculosis-specific antigens is an effective biomarker for M. tuberculosis infection but it cannot discriminate between latent TB infection and active TB disease. Combining a number of cytokine/chemokine responses to M. tuberculosis antigens may enable differentiation of latent TB from active disease. Methods Asymptomatic recently-exposed individuals (spouses of TB patients) were recruited and tuberculin skin tested, bled and followed-up for two years. Culture supernatants, from a six-day culture of diluted whole blood samples stimulated with M. tuberculosis-derived PPD or ESAT-6, were measured for IFN-?, IL-10, IL-13, IL-17, TNF-? and CXCL10 using cytokine ELISAs. In addition, 15 patients with sputum smear-positive pulmonary TB were recruited and tested. Results Spouses with positive IFN-? responses to M. tuberculosis ESAT-6 (>62.5 pg/mL) and TB patients showed high production of IL-17, CXCL10 and TNF-?. Higher production of IL-10 and IL-17 in response to ESAT-6 was observed in the spouses compared with TB patients while the ratios of IFN-?/IL-10 and IFN-?/IL-17 in response to M. tuberculosis-derived PPD were significantly higher in TB patients compared with the spouses. Tuberculin skin test results did not correlate with cytokine responses. Conclusions CXCL10 and TNF-? may be used as adjunct markers alongside an IFN-? release assay to diagnose M. tuberculosis infection, and IL-17 and IL-10 production may differentiate individuals with LTBI from active TB.

Hur, Yun-Gyoung; Gorak-Stolinska, Patricia; Ben-Smith, Anne; Lalor, Maeve K.; Chaguluka, Steven; Dacombe, Russell; Doherty, T. Mark; Ottenhoff, Tom H.; Dockrell, Hazel M.; Crampin, Amelia C.

2013-01-01

404

Experimental branching fractions, transition probabilities and oscillator strengths in Gd I and Gd II  

NASA Astrophysics Data System (ADS)

Branching fractions of 13 levels in Gd I and 12 levels in Gd II were experimentally determined based on the emission spectrum of a hollow cathode lamp. In addition, transition probabilities and oscillator strengths for 66 lines of Gd I and 74 lines of Gd II were derived from a combination of the radiative lifetimes reported in the earlier literature and the branching fractions obtained in the present paper.

Wang, Qian; Yin, Jianrui; Jiang, Liyun; Shang, Xue; Tian, Yanshan; Dai, Zhenwen

2014-02-01

405

TAIMA (Stop) TB: The Impact of a Multifaceted TB Awareness and Door-to-Door Campaign in Residential Areas of High Risk for TB in Iqaluit, Nunavut  

PubMed Central

Background The incidence rate of active tuberculosis (TB) disease in the Canadian Territory of Nunavut has shown a rising trend over the past 10 years. In 2010 it was 60 times greater than the national incidence rate. The objective of the Taima (translates to “stop” in Inuktitut) TB study was to implement and evaluate a public health campaign to enhance existing TB prevention efforts in Nunavut. Methods A TB awareness campaign followed by a door-to-door screening campaign was carried out in Iqaluit, Nunavut. The aim of the campaign was to raise awareness about TB, and to provide in-home screening and treatment for people living in residential areas at high risk for TB. Screening was based on geographic location rather than on individual risk factors. Results During the general awareness campaign an increase in the number of people who requested TB testing at the local public health clinic was observed. However, this increase was not sustained following cessation of the awareness campaign. Targeted TB screening in high risk residential areas in Iqaluit resulted in 224 individuals having TSTs read, and detection of 42 previously unidentified cases of latent TB, (overall yield of 18.8% or number needed to screen?=?5.3). These cases of latent TB infection (LTBI) were extra cases that had not been picked up by traditional screening practices (34% relative increase within the community). This resulted in a 33% relative increase in the completion of LTBI treatment within the community. The program directly and indirectly identified 5/17 new cases of active TB disease in Iqaluit during the study period (29.5% of all incident cases). Conclusions While contact tracing investigations remain a cornerstone of TB prevention, additional awareness, screening, and treatment programs like Taima TB may contribute to the successful control of TB in Aboriginal communities.

Alvarez, Gonzalo G.; VanDyk, Deborah D.; Aaron, Shawn D.; Cameron, D. William; Davies, Naomi; Stephen, Natasha; Mallick, Ranjeeta; Momoli, Franco; Moreau, Katherine; Obed, Natan; Baikie, Maureen; Osborne, Geraldine

2014-01-01

406

If I Had - Recurring Cough and Positive TB Test  

MedlinePLUS Videos and Cool Tools

... If I Had - Recurring Cough and Positive TB Test - Dr. Masae Kawamura, MD, University of California, San ... If I Had - Recurring Cough and Positive TB Test - Dr. Masae Kawamura, MD, University of California, San ...

407

HIV-1 and the immune response to TB  

PubMed Central

TB causes 1.4 million deaths annually. HIV-1 infection is the strongest risk factor for TB. The characteristic immunological effect of HIV is on CD4 cell count. However, the risk of TB is elevated in HIV-1 infected individuals even in the first few years after HIV acquisition and also after CD4 cell counts are restored with antiretroviral therapy. In this review, we examine features of the immune response to TB and how this is affected by HIV-1 infection and vice versa. We discuss how the immunology of HIV–TB coinfection impacts on the clinical presentation and diagnosis of TB, and how antiretroviral therapy affects the immune response to TB, including the development of TB immune reconstitution inflammatory syndrome. We highlight important areas of uncertainty and future research needs.

Walker, Naomi F; Meintjes, Graeme; Wilkinson, Robert J

2013-01-01

408

Effects of DyHx and Dy2O3 powder addition on magnetic and microstructural properties of Nd-Fe-B sintered magnets  

NASA Astrophysics Data System (ADS)

The magnetic and microstructural properties of (Nd27.68Dy4.89)-Febal.B1.0M2.4 (wt. %, M = Cu, Al, Co, and Nb) sintered magnets doped with Dy2O3 and DyHx powders were studied. The coercivity of the DyHx-doped magnet improved, with no change in the remanence. Well-developed core-shell microstructures were seen in the DyHx-doped magnet, as compared to the case of the Dy2O3-doped magnet. Diffusion of Dy was enhanced in the DyHx-doped magnet, probably because dissolution of hydrogen in Nd2Fe14B increased the lattice parameter. The (00L) grain alignment in the DyHx-doped magnet was also improved.

Bae, Kyoung-Hoon; Kim, Tae-Hoon; Lee, Seong-Rae; Namkung, Seok; Jang, Tae-Suk

2012-11-01

409

Boeing TB-29 Superfortress (B-29)  

NASA Technical Reports Server (NTRS)

Boeing TB-29 Superfortress (B-29): Arriving for use with the NACA right at the end of World War II, this Boeing B-29 Superfortress was used for research into hydraulically boosting flight controls. After just over five years of study at Langley, the B-29 was returned to the Air Force.

1945-01-01

410

Strengthening TB surveillance system in India: Way forward for improving estimates of TB incidence  

PubMed Central

One of the key indicators used under India’s TB control program is the DOTS case detection rate of new sputum smear positive TB whose estimates in India are based on incidence estimates derived from Styblo’s rule. Styblo’s rule was formulated in an era without well-established tuberculosis control program, effective tuberculosis drugs, and emergence of TB-HIV coinfection, so today it does not reflect the true incidence of TB. Considering various loopholes in different methods of measurement of incidence (prevalence surveys of disease/ infection, vital registration system and Styblo’s rule), strengthening of existing surveillance system is the best tool to obtain correct estimates of tuberculosis incidence in India.

Sharma, Rinku; Jain, Vivek; Singh, Saudan

2011-01-01

411

Kathodolumineszenz der neuen Selten Erd-aktivierten Granate A2A'Sb 2Zn 3O 12 ( A = Gd, Y; A' = Sr, Ca)  

NASA Astrophysics Data System (ADS)

By activation of the new garnet host lattices A2A'Sb 2Zn 3O 12 ( A = Gd, Y; A' = Sr, Ca) with the trivalent rare earth ions ( Ln3+ = Pr, Eu, Tb, Tm) a cathodoluminescence in the visible region is observed. The influence of the electronic structure and concentration of the activator on the relative intensity as well as the host lattice participation in the energy transfer processes are discussed.

Braun, R.; Kemmler-Sack, S.

1986-08-01

412

Complex antiferromagnetic order in Dy3Ag4Sn4  

NASA Astrophysics Data System (ADS)

We have studied the complex magnetic ordering of the Dy sublattices in orthorhombic Dy3Ag4Sn4 by high-resolution neutron diffraction and 119Sn Mössbauer spectroscopy. Magnetic ordering in this compound occurs over two transitions. At 16 K the Dy(2d) site orders in a doubled commensurate antiferromagnetic structure described by a propagation vector [0~\\frac {1}{2}~0] , with moments aligned along [100]. The Dy(4e) site orders incommensurately with a propagation vector [0 0.628(1) 0] and moments in the (001) plane. Below the second transition at 14 K both Dy site ordering modes are commensurate antiferromagnetic with the propagation vector [0~\\frac {1}{2}~0] and unchanged ordering directions. The 119Sn Mössbauer spectra comprise three magnetically split sextets in the area ratio 50%:25%:25% due to transferred hyperfine fields at the 119Sn nuclei from the surrounding magnetic Dy neighbours. This spectral decomposition deviates from the area ratio 50%:50% expected on the basis of the crystal structure and is in perfect agreement with the magnetic structure of Dy3Ag4Sn4 deduced from neutron diffraction data.

Perry, Laura K.; Cadogan, J. M.; Ryan, D. H.; Canepa, F.; Napoletano, M.; Mazzone, D.; Riani, P.

2006-06-01

413

Pulmonary impairment after tuberculosis and its contribution to TB burden  

PubMed Central

Background The health impacts of pulmonary impairment after tuberculosis (TB) treatment have not been included in assessments of TB burden. Therefore, previous global and national TB burden estimates do not reflect the full consequences of surviving TB. We assessed the burden of TB including pulmonary impairment after tuberculosis in Tarrant County, Texas using Disability-adjusted Life Years (DALYs). Methods TB burden was calculated for all culture-confirmed TB patients treated at Tarrant County Public Health between January 2005 and December 2006 using identical methods and life tables as the Global Burden of Disease Study. Years of life-lost were calculated as the difference between life expectancy using standardized life tables and age-at-death from TB. Years lived-with-disability were calculated from age and gender-specific TB disease incidence using published disability weights. Non-fatal health impacts of TB were divided into years lived-with-disability-acute and years lived-with-disability-chronic. Years lived-with-disability-acute was defined as TB burden resulting from illness prior to completion of treatment including the burden from treatment-related side effects. Years lived-with-disability-chronic was defined as TB burden from disability resulting from pulmonary impairment after tuberculosis. Results There were 224 TB cases in the time period, of these 177 were culture confirmed. These 177 subjects lost a total of 1189 DALYs. Of these 1189 DALYs 23% were from years of life-lost, 2% were from years lived-with-disability-acute and 75% were from years lived-with-disability-chronic. Conclusions Our findings demonstrate that the disease burden from TB is greater than previously estimated. Pulmonary impairment after tuberculosis was responsible for the majority of the burden. These data demonstrate that successful TB control efforts may reduce the health burden more than previously recognized.

2010-01-01

414

Valence photoelectron spectroscopy of Gd silicides  

SciTech Connect

Gd{sub 3}Si{sub 5}, GdSi, and Gd{sub 5}Si{sub 3} were investigated with photoemission spectroscopy in the photon-energy range 40.8--149 eV by exploiting the energy dependence of the photoemission cross sections and the valence resonance at the crossing of the Gd 4{ital d}-4{ital f} threshold. The modification of the spectra versus photon energy, along with their stoichiometry dependence, show the relevance of covalent mixed Gd 5{ital d}--Si 3{ital sp} states in the formation of the chemical bond. In the region close to the Fermi level an increase of the {ital d} contribution is observed. These points are discussed in connection with the existing models of the silicide bond.

Braicovich, L. (Istituto di Fisica, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano, Italy (IT)); Puppin, E.; Lindau, I. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94305 (USA)); Iandelli, A.; Olcese, G.L.; Palenzona, A. (Istituto di Chimica Fisica, Universita di Genova, Corso Europa, Palazzo delle Scienze, 16132 Genova, (Italy))

1990-02-15

415

Visible luminescence from Dy3+ doped tellurite glasses  

NASA Astrophysics Data System (ADS)

This paper reports on luminescence property of the Dy3+-doped tellurite glasses. The samples are studied by absorption and visible emission spectra. The measured emission spectrum of Dy3+ glass has revealed two main bands at 484 nm (4F9/2-->6H15/2) and 574 nm (4F9/2-->6H13/2) when pumping with the wavelength of 325 nm. The concentration quenching occurred as Dy3+ concentration increased beyond 2 mol%. The chromaticity coordinates of these samples are close to white light, which implies that the glasses might be a potential candidate for white lighting through an appropriate combination.

Zhang, Feng; Xiao, Zhisong; Yan, Lu; Zhu, Fang; Huang, Anping

2009-08-01

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